WO2013047230A1

WO2013047230A1 - Liquid crystal display device

Info

Publication number: WO2013047230A1
Application number: PCT/JP2012/073580
Authority: WO
Inventors: 井上　尚人; 弘之鍋澤; 暎冨吉
Original assignee: シャープ株式会社
Priority date: 2011-09-30
Filing date: 2012-09-14
Publication date: 2013-04-04

Abstract

In order to suppress the generation of cross talk and to dim a backlight, a backlight drive means (6): determines a drive timing for a backlight (2) such that the cross talk detected by a liquid crystal panel (1) is minimized, on the basis of an obtained pulse width; and lights the backlight (2) using the drive timing and the pulse width.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device used for a flat-screen television receiver or the like.

In recent years, it has become possible to display 3D video (stereoscopic video) on a liquid crystal display device, displaying right-eye video and left-eye video alternately, observing right-eye video with the right eye and left-eye video with the left eye. By doing so, the observer synthesizes each image in the brain and recognizes it as a three-dimensional image.

In addition, when displaying a three-dimensional image on the liquid crystal display device, the right-eye image is written twice and the left-eye image is written twice, and the backlight is turned on at the second writing time of the right-eye image and the left-eye image. ing. This is because the response speed of the liquid crystal is slow, and at the time of the first writing, rewriting from the previous video is insufficient, and so-called crosstalk may occur, in which the video for the right eye and the video for the left eye are mixed. It is. In this way, the occurrence of crosstalk is suppressed by turning on the backlight at the time of the second video rewriting.

Further, in the liquid crystal display device, images are written line-sequentially from the upper stage to the lower stage (scanning driving). That is, the video to be written on the liquid crystal panel differs in the stage of writing (the writing position is different), so that the writing start timing is different. For example, when displaying the left-eye video, the upper part is written in the first half of the period and the lower video is written in the second half of the period. For this reason, the liquid crystal panel has a different timing for writing video depending on the position. In order to suppress the influence of the previous image due to the writing timing shift due to the scanning drive of the liquid crystal panel, a backlight that sequentially drives the light source in synchronization with the scanning driving timing of the liquid crystal panel is employed (for example, Japanese Patent Application Laid-Open No. 2005-260707). 2010-276728, JP-A-2011-112745, JP-A-2011-128587, etc.). As a result, it is possible to suppress the occurrence of crosstalk due to a shift in the scanning timing of the liquid crystal panel.

As described above, most of the backlights of liquid crystal display devices are PWM-controlled, and are adjusted (PWM dimming) to have an arbitrary brightness at the ratio of lighting and extinguishing (width of lighting period). ing. In the liquid crystal display device, the backlight has a specific brightness, and the drive timing of the backlight is synchronized with the drive timing of the liquid crystal panel so that the crosstalk is minimized at the brightness.

JP 2011-112745 A JP 2010-276828 A JP 2011-125887 A

However, in the case where the liquid crystal panel and the backlight are synchronized so that the crosstalk is minimized when the backlight has a specific brightness as described above, the backlight is used to change the brightness. If the width of the lighting period is changed, the leakage light increases due to the difference between the rising characteristics (response speed when the transmittance increases) and the falling characteristics (response speed when the transmittance decreases) of the liquid crystal. In particular, in the case of a liquid crystal display device capable of three-dimensional display, the liquid crystal panel is driven at a high frequency of 240 Hz, and an increase in leakage light due to a difference in response characteristics becomes significant, that is, crosstalk increases.

In addition, as described above, the liquid crystal panel writes the left-eye video and the left-eye video once, for simplification, from the current configuration in which the left-eye video and the right-eye video are written twice. In such a case, the influence of the response speed of the liquid crystal panel becomes large, and there is a concern that more crosstalk will occur.

Furthermore, for simplification of the apparatus, when using a backlight with a small number of divisions (the number of scans is small) or a light that is turned on simultaneously (cannot be scanned), the backlight cannot be driven in synchronization with the scanning of the liquid crystal panel. It is difficult for the driving of the backlight to be accurately synchronized with the scanning of the liquid crystal panel. In such a state, there is a concern that crosstalk increases when dimming is performed by changing the width of the backlight lighting period.

Therefore, an object of the present invention is to provide a liquid crystal display device capable of dimming a backlight while suppressing the occurrence of crosstalk.

To achieve the above object, the present invention provides a liquid crystal panel capable of displaying a three-dimensional image, a backlight for supplying light to the liquid crystal panel, and a pulse width such that the backlight has a determined brightness. Dimming means for determining the light intensity, and backlight driving means for obtaining the pulse width from the dimming means and controlling the driving of the backlight, wherein the backlight driving means is based on the obtained pulse width. And determining a driving timing of the backlight that minimizes the crosstalk detected by the liquid crystal panel, and lighting the backlight with the driving timing and the pulse width. it can.

According to this configuration, it is possible to suppress the occurrence of crosstalk by lighting the backlight at an appropriate timing according to the pulse width. Thereby, it is possible to suppress the occurrence of crosstalk due to the dimming of the backlight.

In the above configuration, the backlight may be an illumination that is turned on simultaneously on one surface. At this time, the liquid crystal panel scans line-sequentially and writes an image, and the backlight driving means writes the image with scanning lines at an arbitrary stage among the plurality of scanning lines of the liquid crystal panel. The backlight drive timing at which the detected crosstalk is minimized may be determined. Thereby, even when the backlight is dimmed by pulse width modulation, the occurrence of crosstalk can be suppressed. Note that the backlight drive timing may be determined so as to be synchronized with writing of any of the plurality of scanning lines.

In the above configuration, the backlight driving unit alternately displays the black image and the white image, and the transmitted light in the black display period and the transmitted light in the white display period are equal in a portion where the black display is switched to the white display. The drive timing may be determined as described above. Thereby, even when the backlight is dimmed by pulse width modulation, the occurrence of crosstalk can be suppressed.

In the above configuration, the backlight may be divided into at least two regions in the scanning direction of the liquid crystal panel, and each region may be lit independently. At this time, the liquid crystal panel scans line-sequentially and writes an image, and the backlight driving means reduces crosstalk when writing an image with a scanning line at the center of each area of the backlight, The drive timing adjusted so as to reduce the crosstalk when the video is written by the scanning line in the central portion of the entire liquid crystal panel may be determined. Thereby, even when the backlight is dimmed by pulse width modulation, the occurrence of crosstalk can be suppressed.

In the above-described configuration, the backlight driving means may determine the timing at which the backlight is turned off as the backlight driving timing. Thereby, even when the backlight is dimmed by pulse width modulation, the occurrence of crosstalk can be suppressed.

In the above-described configuration, the backlight driving unit may determine that the timing of turning off the light is shifted later in time series when the pulse width increases. Thereby, even when the backlight is dimmed by pulse width modulation, the occurrence of crosstalk can be suppressed.

In the above configuration, the backlight driving means may determine a midpoint position of the backlight lighting period as the backlight driving timing. Thereby, even when the backlight is dimmed by pulse width modulation, the occurrence of crosstalk can be suppressed.

In the above configuration, the backlight driving means may determine that the midpoint position of the lighting period of the backlight is shifted forward in time series when the pulse width is increased. Thereby, even when the backlight is dimmed by pulse width modulation, the occurrence of crosstalk can be suppressed.

In the above configuration, a database in which a pulse width and a driving timing are associated with each other is provided, and the backlight driving unit may acquire a driving timing corresponding to the pulse width acquired by accessing the database. .

In the above configuration, the backlight driving unit includes an arithmetic expression that associates a pulse width with a driving timing, and determines the driving timing of the backlight by applying the acquired pulse width to the arithmetic expression. You may do it.

In the above configuration, the backlight may be a direct type in which light sources are arranged on the back surface of the liquid crystal panel, or may be an edge light type that guides light to the liquid crystal panel using a light guide plate. In addition, although it is possible to employ | adopt LED as a light source, it is not limited to this, What can irradiate the said surface uniform light to the said liquid crystal panel can be employ | adopted widely.

According to the present invention, a liquid crystal display device capable of dimming the backlight while suppressing the occurrence of crosstalk can be provided.

It is a disassembled perspective view of the liquid crystal display device concerning this invention. It is a block diagram which shows the electrical connection of the liquid crystal display device concerning this invention. It is a figure which shows the relationship between the response waveform of a liquid crystal in the part which switches from the image for left eyes to the image for right eyes, and leak light. It is a figure which shows the backlight period when crosstalk becomes the minimum when changing the lighting period of a backlight. It is a figure which shows operation | movement of the liquid crystal display device concerning this invention. It is a figure which shows operation | movement of the other example of the liquid crystal display device concerning this invention. It is a block diagram which shows the electrical connection of the liquid crystal display device concerning another example of this invention. 8 is a timing chart showing the operation of the liquid crystal display device shown in FIG. It is a figure which shows the response of the liquid crystal of the liquid crystal display device concerning this invention, lighting of a backlight, and leakage light. 6 is a timing chart when the lighting period is fixed and the drive timing is shifted in the liquid crystal display device according to the present invention. It is a figure which shows the relationship between the lighting deviation | shift amount of a backlight, and a crosstalk value. It is a figure which shows the crosstalk when a backlight is light-modulated with the liquid crystal display device concerning this invention.

Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is an exploded perspective view of a liquid crystal display device according to the present invention. The liquid crystal display device A is a liquid crystal display device capable of displaying a three-dimensional image. As shown in FIG. 1, the liquid crystal display device A includes a liquid crystal panel 1 and a backlight 2. In the following description, although it may be referred to as a vertical direction or a horizontal direction, or up and down or left and right, the direction in a state where an image displayed on the liquid crystal display device is viewed is shown.

As shown in FIG. 1, the liquid crystal panel 1 is arranged with an array substrate 11 having pixel electrodes and TFTs (switching elements) (both not shown) arranged in an array on the surface, and facing the array substrate 11. The counter substrate 12 is provided with a common electrode and a color filter for coloring transmitted light (both not shown), and a liquid crystal layer 13 between the array substrate 11 and the counter substrate 12. The liquid crystal layer 13 is sealed with a sealing member so that liquid crystals having fluidity do not leak. A polarizing film (not shown) is attached to the light receiving surface side of the array substrate 11 and the light emitting surface side of the counter substrate 12. Details of the liquid crystal panel 1 will be described later.

The backlight 2 is an illuminating device that is disposed on the back surface of the liquid crystal panel 1 that displays an image, and includes a plurality of LED lamps 21 including white LED lamps or RGB three-color LEDs as light sources. In the liquid crystal display device A, the backlight 2 is a direct type, and the LED lamps 21 are two-dimensionally arranged on the surface facing the liquid crystal panel 1. The LEDs 2 arranged in the backlight 2 are controlled so as to repeatedly turn on and off simultaneously.

The backlight 2 includes an optical sheet 22. The optical sheet 22 has a configuration in which a plurality of optical sheet members are stacked. For example, in the optical sheet group 22, as an optical sheet member, a diffusion sheet 221 that diffuses light emitted from the backlight 2, a brightness enhancement sheet (DBEF) 222 that improves luminance, and light emitted from the backlight 2 A prism sheet 223 that aligns the directions, that is, changes the direction so that light that has entered obliquely enters the liquid crystal panel 1 is provided. An optical sheet member having optical characteristics other than these may be used.

The liquid crystal display device A displays the right-eye video and the left-eye video alternately. Then, by observing the right-eye video with the right eye and the left-eye video with the left eye, the observer synthesizes each video in the brain and recognizes it as a three-dimensional video. At this time, active shutter glasses 8 described later are used so that the observer can accurately observe the right-eye image with the right eye and the left-eye image with the left eye. The active shutter glasses 8 operate in synchronization with the liquid crystal display device A, and block the left eye view when the right eye image is displayed, and change the right eye view when the left eye image is displayed. Operates to shut off.

Next, the electrical connection of the liquid crystal display device A will be described with reference to a new drawing. FIG. 2 is a block diagram showing electrical connection of the liquid crystal display device according to the present invention. As shown in FIG. 2, the liquid crystal display device A includes a liquid crystal panel 1, a backlight 2, a video signal processing circuit 3, a PWM dimming circuit (dimming means) 4, a timing control circuit 5, and a backlight. A controller (backlight driving means) 6 and a shutter controller 7 are provided. Further, when observing a three-dimensional image with the liquid crystal display device A, active shutter glasses 8 that alternately block the field of view of the right eye and the left eye of the viewer who wears it are used.

On the array substrate 11 of the liquid crystal panel 1, a plurality of source lines 111 (also referred to as data lines) formed in the vertical direction as video signal lines and arranged in parallel in the horizontal direction, and a vertical extension as scanning signal lines in the horizontal direction. And a plurality of gate lines 112 formed in parallel to the direction. That is, the source line 111 and the gate line 112 are formed side by side in a lattice pattern, and a TFT is disposed at the intersection of the source line 111 and the gate line 112. The source line 111 is connected to the source of the TFT, and the gate line 112 is connected to the gate of the TFT. The drain of the TFT is connected to the pixel electrode. When a voltage is applied to the source of the TFT and a signal (voltage) is input to the gate, a current flows between the source and the drain, and charge is accumulated (charged) in the pixel electrode.

A plurality of source lines 111 are connected to the source driver 14, and a plurality of gate lines 112 are connected to the gate driver 15. The source driver 14 converts the liquid crystal drive signal Lcs received from the timing control circuit 5 into a voltage (referred to as a video voltage), and applies the video voltage to the source line 111 based on the source timing signal Sts received from the timing control circuit 5. Supply. Further, the gate driver 15 supplies pulse voltages (gate drive signals) for operating the TFTs to the plurality of gate lines 112 in order from the upper stage based on the gate timing signal Gts from the timing control circuit 5.

In the liquid crystal panel 1, as described above, a pulse-like gate drive signal for driving is applied to the TFT by the gate line 112 extending in the horizontal direction, so that all the TFTs in the horizontal row are simultaneously turned on / off. In accordance with the on / off timing, a video voltage is applied from the source line 111, and a video is simultaneously written to all the pixels in a horizontal row. This operation is repeated a number of times corresponding to the number of pixels in the vertical direction to complete one frame of video. That is, the liquid crystal panel 1 is operated in a line sequential manner. Note that writing an image to a pixel means accumulating charge in the pixel electrode, and this charge is held until the next image is written. The liquid crystal display device A is a liquid crystal display device capable of full HD display, and the number of pixels in the vertical direction of the liquid crystal panel 1 is 1080. That is, the liquid crystal panel 1 has 1080 gate lines 112.

In such a liquid crystal panel 1, liquid crystal molecules are rotated by an electric field generated between the pixel electrode and the common electrode. The liquid crystal panel 1 displays an image using the change in transmittance caused by the inclination of the liquid crystal molecules. In other words, video display based on the liquid crystal drive signal Lcs is performed by modulating the light supplied from the backlight 2.

The LEDs 21 provided in the backlight 2 are each controlled to be turned on by pulse width modulation (PWM) control. Further, the LEDs 21 of the backlight 2 are driven by the backlight controller 6 and are all turned on simultaneously. The backlight controller 6 supplies a pulse current to the LED 21 based on a timing signal from the timing control circuit 5 and a PWM value (described later) from the PWM dimming circuit 4.

The video signal processing circuit 3 generates (separates) left-eye video data Lid and right-eye video data Rid based on a video signal Ims from an external device such as a tuner, a BD, or a DVD, for example, and left-eye video data Lid. And right-eye video data Rid are alternately transmitted to the timing control circuit 5. In addition, timing data Tmd indicating timing for writing the left-eye video and the right-eye video is transmitted to the timing control circuit 5.

Timing control circuit 5 drives source driver 14 and gate driver 15. More specifically, the timing control circuit 5 transmits to the source driver 14 a liquid crystal drive signal Lcs including information on transmittance in each pixel based on the left-eye video data Lid and the right-eye video data Rid. As described above, the source driver 14 converts the liquid crystal drive signal Lcs into a voltage to be applied to the liquid crystal in each pixel. The timing control circuit 5 generates a source timing signal Sts indicating the driving timing of the source driver 14 and a gate timing signal Gts indicating the driving timing of the gate driver 15 from the timing data Tmd, and the source driver 14 and the gate driver 15. Send to each of the.

In the liquid crystal display device A, the left-eye video and the right-eye video are alternately written on the liquid crystal panel 1. Therefore, the timing control circuit 5 may include a storage unit that stores the left-eye video data Lid, the right-eye video data Rid, and the timing data Tmd sent from the video processing circuit 3 in time series. Then, the left-eye video data Lid and the right-eye video data Rid are extracted from the storage unit in time series, converted into the liquid crystal drive signal Lcs in accordance with the writing timing of the left-eye video and the right-eye video, and the source timing signal Sts and the source. The gate timing signal Gts synchronized with the source timing signal Sts may be sent to the driver 14 and sent to the gate driver 15.

Also, the timing control circuit 5 converts the timing data Tmd and sends a write timing signal Rts indicating the write timing of the left-eye video and the right-eye video to the shutter controller 7. The shutter controller 7 performs opening / closing control of the left eye shutter 81 and the right eye shutter 82 of the active shutter glasses 8 based on the write timing signal Rts. More specifically, the shutter controller 7 calculates a period for writing the left-eye video (left-eye video period) and a period for writing the right-eye video (right-eye video period) on the liquid crystal panel 1 based on the write timing signal Rts. Then, the shutter controller 7 controls the active shutter glasses 8 so that the right eye shutter 82 is closed during the left eye video period and the left eye shutter 81 is closed during the right eye video period.

The shutter controller 7 may be arranged in the main body of the liquid crystal display device A, and may be configured to control the active shutter glasses 8 wirelessly or by wire, or may be mounted on the active shutter glasses 8 and from the timing control circuit 5. The write timing signal Rts may be received wirelessly or by wire. Further, the active shutter glasses 8 may be those provided with a member that blocks the field of view such as a liquid crystal shutter in the lens portion. In addition to the liquid crystal shutter, those capable of switching light transmission / blocking at high speed can be widely employed.

In the liquid crystal display device A, the brightness of the LED 21 of the backlight 2 is dimmed by PWM control (PWM dimming). PWM dimming is a dimming that adjusts the brightness by changing the ratio of lighting time (referred to as pulse width or PWM value, and the ratio at which the LED 21 is turned on in%) while supplying a constant current to the LED 21. Is the method. For example, when the PWM value is small, the LED 21 is dark, and when it is large, the LED 21 is lit bright. Since the liquid crystal display device A is configured to alternately display the right-eye video and the left-eye video, the PWM value is 50% or less.

In the liquid crystal display device A, the brightness of the backlight 2 can be adjusted and the brightness of the image can be adjusted according to a user instruction. The PWM dimming circuit 4 that adjusts the brightness of the LED 21 is inputted with a luminance instruction by the user using an input device such as a remote controller (not shown).

The PWM dimming circuit 4 determines the luminance of the backlight 2 based on a user instruction. Then, based on the determined luminance of the backlight 2, the current value supplied to the LED 21 and the PWM value for supplying the current are determined. Then, the PWM dimming circuit 4 transmits backlight drive data (PWM value) including the current value and the PWM value to the backlight controller 6. In this embodiment, the PWM dimming circuit 4 determines the brightness of the backlight 2 according to a user's instruction. However, the present invention is not limited to this, and the brightness around the liquid crystal display device A is detected. However, the backlight 2 may be automatically determined to have the optimum brightness for viewing the video in accordance with the brightness. In this case, the storage unit provided inside or outside of the PWM dimming circuit 4 is provided with a database in which ambient brightness and PWM values are associated, and the database is accessed to determine the PWM value corresponding to ambient brightness. You may make it do.

The backlight controller 6 is a control circuit that controls the brightness of the backlight 2 by controlling the current value supplied to the LED 21 provided in the backlight 2 and the timing of supplying the current. The backlight controller 6 is supplied with the write timing signal Rts indicating the timing for writing the left-eye video and the right-eye video from the timing control circuit 5, and the current value and PWM value from the PWM dimming circuit 4. . Then, the backlight controller 6 determines the drive timing of the LED 21 based on the PWM value and the write timing signal Rts, and supplies a pulse current to the LED 21 with an appropriate timing and PWM value.

As described above, the source timing signal Sts, the gate timing signal Gts, and the write timing signal Rts output from the timing control circuit 5 are all based on the timing data Tmd transmitted from the video signal processing circuit 3 to the timing control circuit 5. All signals are accurately synchronized. For this reason, the liquid crystal panel 1, the backlight 2, and the active shutter glasses 8 are accurately driven synchronously.

In the liquid crystal display device A, since the left-eye video is written twice and the right-eye video is written twice in succession, the scan frequency of the liquid crystal panel 1 is 240 Hz. That is, the liquid crystal panel 1 is driven at 240 Hz. Here, the scan frequency of 240 Hz indicates that 240 frames are displayed per second, that is, 240 times of video writing is performed per second. One frame is 1/240 seconds (about 4 ms). Written. When the liquid crystal panel 1 is driven at such a high speed, the liquid crystal panel 1 cannot respond completely, that is, the transmittance of the liquid crystal panel 1 does not completely correspond to an image.

For example, when the left-eye image is a black image, the transmittance of the liquid crystal does not become 0%. When the backlight 2 is turned on in this state, the light emitted from the backlight 2 is transmitted through the liquid crystal panel 1 ( Leaks). This leaked light (leakage light) causes so-called crosstalk in which left-eye video and right-eye video are mixed.

Next, crosstalk necessary for explaining the operation of the liquid crystal display device according to the present invention will be described with reference to the drawings. FIG. 3 is a diagram showing the relationship between the response waveform of the liquid crystal and the leakage light at the portion where the video for the left eye is switched to the video for the right eye. Note that FIG. 3 shows a period for displaying a black-color image (left-eye video period) to a white-color image display period (right-eye video period) in a predetermined one-stage scanning line (gate line) of the liquid crystal panel 1. The part which switches to is shown. In FIG. 3, the horizontal axis represents the time axis, and the response waveform of the liquid crystal panel 1, the lighting waveform of the backlight 1, and the waveform of leaked light leaking from the liquid crystal panel 1 are displayed.

As shown in FIG. 3, the transmittance of the liquid crystal panel 1 responds after the start of video writing (response delay). That is, the video is not written (previous video is held) for a certain time from the start of video writing. Since such a liquid crystal response delay occurs in the liquid crystal panel 1, the response characteristic of the liquid crystal panel 1 has a low transmittance at the switching portion between the left-eye video period and the right-eye video period. Therefore, the leakage light is minimized by turning on the backlight 2 across the switching portion between the left-eye video period and the right-eye video period, that is, crosstalk is minimized.

In FIG. 3, when the backlight 2 is turned on, the area of leakage light in the left-eye video period is Sc1, and the leakage light area Sc2 in the right-eye video period. As shown in FIG. 3, when the lighting period of the backlight 2 deviates (advances) forward, the leakage light area Sc1 increases and the leakage light area Sc2 decreases. Further, when the lighting period of the backlight 2 is shifted backward (delayed), the leakage light area Sc1 decreases and the leakage light area Sc2 increases. Therefore, in order to minimize the crosstalk, the backlight 2 may be turned on at the timing when the leaked light area Sc1 and the leaked light area Sc2 become equal.

Note that, as shown in FIG. 3, the time from the start of lighting of the backlight to the end of the video period for the left eye is not equal to the time from the start of the video period for the right eye to the extinguishing of the backlight. This is because, as shown in FIG. 3, the falling characteristic (ratio of decrease in transmittance) and the rising characteristic (ratio of increase in transmittance) of the liquid crystal panel 1 are different.

Also, an example of changing the width of the backlight lighting period will be described. FIG. 4 is a diagram illustrating a backlight period in which crosstalk is minimized when the backlight lighting period is changed. FIG. 4 shows the lighting start position, the backlight extinguishing position, and the center position of the lighting period when the PWM value (lighting period) of the backlight 2 is changed from 0% to 50%.

As shown in FIG. 4, when the PWM value is small, the lighting position and the non-lighting position of the backlight are close to the switching portion between the left-eye video period and the right-eye video period. Further, as the PWM value increases, the lighting start shifts forward and the lighting end shifts backward. As described above, this is a result of adjusting the backlight drive timing so that the crosstalk is minimized.

As shown in FIG. 4, when the PWM value for driving the backlight 2 is increased, the lighting end position is shifted backward and the center of the lighting period is shifted forward. This is because the response characteristics (falling characteristics and rising characteristics) of the liquid crystal panel 1 are different as described above.

Control of the backlight 2 as described above is performed by the backlight controller 6. Based on the input of the PWM value from the PWM dimming circuit 4, the backlight controller 6 determines the backlight drive timing in accordance with the conditions shown in FIG. 3 (Sc1 = Sc2). Note that the backlight controller 6 determines the backlight lighting timing by providing a table including the PWM value and the lighting start or extinguishing timing inside or outside, and starting the lighting of the backlight 2 corresponding to the PWM value or You may make it take out a light extinction timing.

Further, an arithmetic expression for calculating the center position or the extinction position of the lighting period determined linearly or by a predetermined function is determined from the graph as shown in FIG. 4, and the lighting period of the backlight 2 is determined from the PWM value and the arithmetic expression. The shift amount of the center position or the extinguishing position may be determined. In the example shown in FIG. 4, the lighting start position of the backlight, the center position of the lighting period, and the extinguishing position are all arranged in a straight line, and the arithmetic expression is a linear arithmetic expression, but is not limited thereto. Absent. If the conditions shown in FIG. 3 (Sc1 = Sc2) are met, there may be a different arrangement (for example, a curve is obtained by connecting the center positions of the lighting periods with different PWM values). It can be calculated by using an arithmetic expression including a function or a function that approximately represents a curve.

Note that the deviation amount of the backlight start position, the center position of the lighting period, or the extinguishing position may be calculated as the time from the point at which the left-eye video period and the right-eye video period are switched. In addition, as for this time, the liquid crystal panel 1 is a system in which video is written in a line-sequential manner, and since there are 1080 gate lines 112, the amount of deviation is determined by taking the time required for one frame divided by 1080 as a reference time. Has been decided.

Based on these facts, the operation of the liquid crystal display device of the present invention will be described with reference to a new drawing. FIG. 5 is a diagram showing the operation of the liquid crystal display device according to the present invention. In FIG. 5, the horizontal axis represents time, the uppermost stage represents the driving timing of the liquid crystal panel, and the lower three stages represent the driving timing of the backlight with different PWM values. In FIG. 5, the PWM values are 25%, 15%, and 5%.

FIG. 5 shows an operation when three-dimensional display is performed on the liquid crystal display device A, and the scan frequency of the liquid crystal panel 1 is 240 Hz. As shown in FIG. 5, the liquid crystal display device A is configured to write the left-eye video and the right-eye video twice (every two frames). Note that (left 1) and (left 2) shown in FIG. 5 indicate the first and second written images of the left-eye video, respectively, and (right 1) and (right 2) are also the right eye. The first and second writing images of the video for use are shown.

Specifically, as shown in FIG. 5, in the liquid crystal display device A, the source driver 14 and the gate driver 15 are driven based on the signal from the timing control circuit 5, and the liquid crystal panel 1 is driven for the first time. After the left-eye video (left 1) is written in 1/240 seconds, the same video is written as the second left-eye video (left 2) in 1/240 seconds. Accordingly, the left-eye video is held on the liquid crystal panel 1, and the left-eye video is displayed on the liquid crystal panel 1 by turning on the backlight 2 at the timing when the left-eye video is held. During the first and second left-eye video writing time (left-eye video period), the active shutter glasses 8 open the left-eye shutter 81 and close the right-eye shutter 82, so that the user is displayed on the liquid crystal panel 1. The left eye image is observed with the left eye.

Next, after the first right-eye video (right 1) is written in 1/240 seconds, the same video is written as the second right-eye video (right 2) in 1/240 seconds. Similarly, the right-eye video is displayed on the liquid crystal panel 1 by turning on the backlight at the timing when the right-eye video is held. At this time, the active shutter glasses 8 close the left-eye shutter 81 and open the right-eye shutter 82 during the first and second right-eye video writing time (right-eye video period). The right-eye image displayed on the liquid crystal panel 1 is observed with the right eye.

As shown in FIG. 5, when the 3D image is displayed on the liquid crystal panel 1, the left-eye image is displayed once by writing the left-eye image twice, and the right-eye image is displayed by writing the right-eye image twice. Display once. That is, in the liquid crystal display device A, the operation of the liquid crystal panel 1 is 240 Hz, but the video switching is 120 Hz. The backlight 2 is lit at the boundary between the second writing of the left-eye video and the first writing of the right-eye video, and the switching between the second writing of the right-eye video and the first writing of the left-eye video is performed. Since the lighting is performed at the boundary, the lighting frequency of the backlight 2 is 120 Hz.

The drive timing of the backlight 2 in the liquid crystal display device A will be described with reference to FIG. As described above, the backlight 2 is turned on at the timing before the second left-eye video (left 2) is written. This is because the liquid crystal panel 1 is written in line-sequential manner and the LED 21 in which the backlight 2 is arranged is turned on simultaneously.

In addition, as described above, the liquid crystal panel 1 is sequentially supplied with gate drive signals from the upper stage to the lower stage from the gate driver 15 and writes video in line sequential order, and writing start and end of the liquid crystal panel 1 are in the lower stage. I'm late. That is, in the liquid crystal display device A, when the writing time of the second left-eye video frame (left 2) and the second right-eye video frame (right 2) in FIG. Ends.

On the other hand, since the LED 21 in which the backlight 2 is arranged is lit at the same time, it is impossible to illuminate so that crosstalk is minimized in all the upper, middle and lower stages. Therefore, the backlight 2 is turned on so that the change of the video is most easily confirmed by the user, in other words, the crosstalk is most easily recognized at the center portion.

That is, as shown in FIG. 5, the backlight 2 is turned on when the writing time of the second left-eye video frame (left 2) and the second right-eye video frame (right 2) is halfway. Yes. Alternatively, in the liquid crystal display device A, it can be said that the backlight 2 is turned on when approximately 3/4 of the left-eye video period and the right-eye video period have elapsed.

The driving timing of the backlight 2 is determined by the width of the lighting period (PWM value), as shown in FIG. 5, and the longer the lighting period width, the more the center position of the lighting period is. The sequence shifts forward, and the timing of turning off the light shifts backward. Details of the drive timing are as shown in FIG.

In the above-described embodiment, the backlight 2 is turned on so that the crosstalk is minimized when the video is written in the central portion of the liquid crystal panel 1. However, the present invention is not limited to this. For example, based on the response characteristics of the liquid crystal panel 1, the liquid crystal panel 1 may be lit at a timing such that the crosstalk is reduced as a whole.

Since the liquid crystal panel 1 includes 1080 gate lines 112, the backlight controller 6 causes the crosstalk to occur at any stage by shifting the driving timing of the backlight 2 back and forth by 1/1080 frames. The drive timing of the backlight 2 can be minimized. As described above, the liquid crystal panel 1 and the backlight 2 can be accurately synchronized by adjusting the lighting timing of the backlight 2 in accordance with the number of the gate lines 112.

As described above, in the liquid crystal display device A, the liquid crystal panel 1 is driven at 240 Hz, the backlight 2 is turned off when writing the first frame, and the backlight 2 is turned on when writing the second frame. Then, when writing in the central stage of the liquid crystal panel 1 during writing of the second frame, the backlight 2 is turned on so that crosstalk is minimized, and further, according to the width of the lighting period of the backlight 2. The drive timing is shifted.

Thereby, even if the brightness of the backlight 2 is changed by PWM dimming in accordance with the user's instruction and the ambient brightness, an increase in crosstalk is suppressed, and a clean and easy-to-see liquid crystal display device is provided. Is possible.

(Second Embodiment)
Another example of the liquid crystal display device according to the present invention will be described with reference to the drawings. The basic configuration of the liquid crystal display device according to the present embodiment is the same as that of the liquid crystal display device according to the first embodiment, and a detailed description thereof is omitted. FIG. 6 is a diagram showing another example of the operation of the liquid crystal display device according to the present invention. As shown in FIG. 6, in the liquid crystal display device A, driving for writing the left-eye video and the right-eye video once is performed. The lower three stages show the driving timing of the backlight with different PWM values. In FIG. 6, the PWM value is 25%, 15%, and 5%.

More specifically, the liquid crystal display device A is controlled to write the left-eye video once in the left-eye video period and write the right-eye video once in the right-eye video period, and the scan frequency of the liquid crystal panel 1 is set to the left-eye video period. This is half of when the video for the right eye and the video for the right eye are written twice, that is, 120 Hz. That is, writing is performed in 1/120 second (about 8 ms) per frame.

As shown in FIG. 6, in the liquid crystal display device A, the source driver 14 and the gate driver 15 are driven based on the signal from the timing control circuit 5, and the left-eye video is displayed on the liquid crystal panel 1 for 1/120 seconds. Write in. Accordingly, the left-eye video is held on the liquid crystal panel 1, and the backlight 2 is turned on at the timing when the left-eye video is held, and the left-eye video is displayed on the liquid crystal panel 1. During the left-eye video writing time (left-eye video period), the active shutter glasses 8 open the left-eye shutter 81 and close the right-eye shutter 82, so the user can view the left-eye video displayed on the liquid crystal panel 1 with the left-eye video. Observe at.

When the left-eye video period ends, the right-eye video is written to the liquid crystal panel 1 in 1/120 seconds. Similarly, the right-eye video is displayed on the liquid crystal panel 1 by turning on the backlight at the timing when the right-eye video is held. At this time, the active shutter glasses 8 close the left-eye shutter 81 and open the right-eye shutter 82 during the first and second right-eye video writing time (right-eye video period). The right-eye image displayed on the liquid crystal panel 1 is observed with the right eye.

The drive timing of the backlight 2 in the liquid crystal display device A will be described with reference to FIG. As shown in FIG. 6, the backlight 2 has a configuration in which the arranged LEDs 21 are simultaneously lit, so it is impossible to light up so that crosstalk is minimized in all the upper, middle, and lower stages. . Therefore, the backlight 2 is turned on so that the change of the video is most easily confirmed by the user, in other words, the crosstalk is most easily recognized at the center portion.

In addition, as described above, the liquid crystal panel 1 is sequentially supplied with gate drive signals from the upper stage to the lower stage from the gate driver 15 and writes video in line sequential order, and writing start and end of the liquid crystal panel 1 are in the lower stage. I'm late. That is, when the liquid crystal display device A is driven as shown in FIG. 6, the writing in the center portion is completed when the left-eye video period and the right-eye video period have passed by half.

The drive timing of the backlight 2 is determined by the width of the lighting period (PWM value), and as shown in FIG. 6, the longer the width of the lighting period (the larger the PWM value), the more the lighting time The center position of the period is shifted forward in time series, and the turn-off timing is shifted backward. The details of the drive timing are as shown in FIG.

As described above, in the liquid crystal display device A, the liquid crystal panel 1 is driven at 120 Hz, and the drive timing is shifted in accordance with the width of the lighting period of the backlight 2. Thereby, even if the brightness of the backlight 2 is changed in accordance with the user's instruction and the ambient brightness, it is possible to provide a liquid crystal display device that suppresses an increase in crosstalk and is clean and easy to see.

(Third embodiment)
Another example of the liquid crystal display device according to the present invention will be described with reference to the drawings. FIG. 7 is a block diagram showing electrical connection of still another example of the liquid crystal display device according to the present invention. The liquid crystal display device C shown in FIG. 7 has the same configuration as the liquid crystal display device A shown in FIG. 2 except that the backlight 2c and the backlight controller 6c are different. Detailed description of substantially the same parts is omitted.

When the liquid crystal panel 1 is driven at 120 Hz, one frame is about 8 ms, which is about twice as long as when driven at 240 Hz (4 ms). Therefore, in the case of 120 Hz driving, there is a large shift in the optimal driving timing of the backlight 2 (driving timing of the backlight 2 that minimizes crosstalk) due to the difference in the stage. Cross talk becomes larger than the case.

Therefore, in the liquid crystal display device C, a backlight 2c divided into an upper part 201 and a lower part 202 is adopted. In the backlight 2c, the LED 21 arranged in the upper part 201 and the LED 21 arranged in the lower part 202 are connected to the backlight controller 6c by different wirings. And the backlight controller 6c is provided with the control circuit which can light the LED21 arrange | positioned at the upper part 201 of the backlight 2c, and LED21 arrange | positioned at the lower part 202 at a different timing.

The upper part 201 of the backlight 2c is disposed so as to face the upper half of the liquid crystal panel 1, that is, the first to 540th scanning lines (pixels), and the lower part 202 is the lower half of the liquid crystal panel 1, that is, , 541-th to 1080-th scanning lines (pixels).

The operation of the liquid crystal display device C will be described with reference to the drawings. FIG. 8 is a timing chart showing the operation of the liquid crystal display device shown in FIG. In FIG. 8, for the sake of convenience, the first half of the left-eye video period is displayed as (upper left) because the upper side of the left-eye video is written, and the second half is displayed (lower left). Similarly, in the right-eye video period, the first half is displayed as (upper right) and the second half is displayed as (lower right).

As shown in FIG. 8, in the liquid crystal display device C, the liquid crystal panel 1 is driven at 120 Hz, and the left-eye video and the right-eye video are written in 1/120 seconds (about 8 ms). Note that writing to the liquid crystal panel 1 is the same as in the second embodiment, and details thereof are omitted. In FIG. 8, writing of the upper half of the left-eye video is displayed as (upper left). Similarly, writing in the lower half of the left-eye video is denoted as (lower left). Similarly, writing of the right-eye video is described as (upper right) and (lower right).

As shown in FIG. 8, when the left-eye video is written, the upper part 201 of the backlight 2c is turned on when the upper half (from the first stage to the 540th stage) video is written (upper left), and the lower half (541st stage). The lower part 202 of the backlight 2c is lit when writing video (from the first to the 1080th stage) (lower left).

More specifically, in the liquid crystal display device C, the upper part 201 of the backlight 2c is turned on at the timing when the crosstalk is minimized when the video is written in the central part of the upper half of the liquid crystal panel 1. That is, since there are 1080 gate lines 112 in the liquid crystal panel 1, the upper part 201 of the backlight 2c is lit so that the crosstalk is minimized when writing a video of the 1/4 level (270th level) from above. To do. Note that when the upper part 201 of the backlight 2c is lit, the lower part 202 of the backlight 2c is turned off. In other words, in the liquid crystal display device C, the upper part 201 of the backlight 2c is turned on at the timing when a quarter of the left-eye video period of the liquid crystal display panel 1 has passed.

Then, the lower part 202 of the backlight 2c is turned on at the timing when the crosstalk is minimized when the video is written in the central part of the lower half of the liquid crystal panel 1. In other words, in the liquid crystal panel 1, the lower portion 202 of the backlight 2c is lit so that the crosstalk is minimized when the video is written in the 1/4 (3/4 from the top) level (810th level) from the bottom. In addition, when the lower part 202 of the backlight 2c is lit, the upper part 201 of the backlight 2c is in an extinguished state. In other words, in the liquid crystal display device C, the lower part 202 of the backlight 2c is turned on at the timing when 3/4 of the video period for the left eye of the liquid crystal display panel 1 has elapsed.

On the other hand, the same applies when writing the video for the right eye. That is, as shown in FIG. 8, when the right-eye video is written, the upper portion 201 of the backlight 2c is turned on when the upper half (first to 540th) video is written (upper right), and the lower half ( The lower part 202 of the backlight 2c is lit when writing the video (from the 541st stage to the 1080th stage) (lower right).

More specifically, in the liquid crystal display device C, the upper part 201 of the backlight 2c is turned on at the timing when the crosstalk is minimized when the video is written in the central part of the upper half of the liquid crystal panel 1. That is, since there are 1080 gate lines 112 in the liquid crystal panel 1, the upper part 201 of the backlight 2c is lit so that the crosstalk is minimized when writing a video of the 1/4 level (270th level) from above. To do. Note that when the upper part 201 of the backlight 2c is lit, the lower part 202 of the backlight 2c is turned off. In other words, in the liquid crystal display device C, the upper part 201 of the backlight 2c is turned on at the timing when the 1/4 video period for the right eye of the liquid crystal display panel 1 has elapsed.

Then, the lower part 202 of the backlight 2c is turned on at the timing when the crosstalk is minimized when the video is written in the central part of the lower half of the liquid crystal panel 1. In other words, in the liquid crystal panel 1, the lower portion 202 of the backlight 2c is lit so that the crosstalk is minimized when the video is written in the 1/4 (3/4 from the top) level (810th level) from the bottom. In addition, when the lower part 202 of the backlight 2c is lit, the upper part 201 of the backlight 2c is in an extinguished state. In other words, in the liquid crystal display device C, the lower part 202 of the backlight 2c is turned on when 3/4 of the right-eye video period of the liquid crystal display panel 1 has elapsed.

In this way, when the backlight 2c is driven separately up and down to write an image on the liquid crystal panel 1, the upper part 201 of the backlight 2c is written once by writing the upper half and the lower part 202 of the backlight 2c is written by writing the lower half. By turning on the liquid crystal panel 1 once, even if the liquid crystal panel 1 is driven at 120 Hz, it is possible to suppress leakage light due to a response shift of the liquid crystal panel 1 when the upper part 201 and the lower part 202 of the backlight 2c are turned on. As described above, even when the liquid crystal panel and the backlight are driven at 120 Hz, by dividing and lighting the backlight 2c, the upper end and the lower end are compared with the case where the backlight 2c is turned on simultaneously. Crosstalk in the section is reduced.

The backlight drive timing according to the present embodiment will be described with reference to the drawings. FIG. 9 is a diagram showing the response of the liquid crystal, the lighting of the backlight, and the leakage light of the liquid crystal display device according to the present invention. In FIG. 9, the horizontal axis is the time axis, the driving waveform at the stage of the central portion of the liquid crystal panel 1, and the lighting of the upper part 201 and the lower part 202 of the backlight 2 c is shown below.

The central part of the liquid crystal panel 1 is located at the boundary between the upper part 201 and the lower part 202 of the backlight 2c. For this reason, when an image is written to the central stage of the liquid crystal panel 1, light leaks when the upper part 201 is lit and light leaks when the lower part 202 is lit.

As shown in FIG. 9, the luminance (area) of the leaked light when the upper part 201 of the backlight 2c is lit is Scc1, and the luminance (area) of the leaked light when the lower part 202 of the backlight 2c is lit is Scc2. The luminance of the leaked light at the central portion of the liquid crystal panel 1 is the sum of Scc1 and Scc2. If the lighting of the backlight 2c is shifted forward, the leakage light luminance Scc1 increases and the leakage light luminance Scc2 decreases. Further, if the lighting of the backlight 2c is shifted backward, the leakage light luminance Scc1 decreases and the leakage light luminance Scc2 increases.

From the above, in order to minimize the crosstalk when the video is written at the center portion of the liquid crystal panel 1, the leakage light luminance Scc1 and the leakage light luminance Scc2 may be adjusted to be equal. In this way, by adjusting the driving timing of the backlight 2c, it is possible to reduce crosstalk in the upper, middle, and lower stages on the liquid crystal display device C.

In the present embodiment, the upper part 201 of the backlight 2c is placed in the central part of the lower half so that the crosstalk is minimized when video is written to the central part of the upper half of the liquid crystal panel 1. Each of the lower portions 202 of the backlight 2c is turned on so that the crosstalk is minimized when the video is written. However, the present invention is not limited to this. For example, the total (or average) crosstalk of the central portion (1/4 portion from the top) of the liquid crystal panel 1, the central portion of the liquid crystal panel 1, and the central portion of the lower half (3/4 portion from the top) ) May be determined so that the backlight driving timing is minimized.

Since the liquid crystal panel 1 is provided with 1080 gate lines 112, the backlight controller 6 can shift either the driving timing of the upper part 201 and the lower part 202 of the backlight 2c back and forth by 1/1080 frames. In this stage, it is possible to set the driving timing of the backlight 2 at which the crosstalk is minimized. That is, according to the number of gate lines 112, the amount of shift in driving timing can be determined by (number of gate lines to be shifted × 1/1080 frames). As described above, the lighting timing of the backlight 2 is adjusted according to the number of the gate lines 112, and the lighting timing of the backlight 2 is accurately synchronized with the scanning of any of the gate lines 112 (scanning lines).

Therefore, even if the PWM value is changed for dimming the backlight 2c, the occurrence of crosstalk can be suppressed. In this embodiment, the backlight 2c is divided into upper and lower parts. However, the present invention is not limited to this, and the direction is not particularly limited as long as the backlight 2c is divided in the gate line arrangement direction. Is not limited to two.

In each of the embodiments described above, an LED is used as the light source of the backlight. However, the present invention is not limited to this, and a discharge arc tube such as a cold cathode fluorescent tube may be used. In the case of using a fluorescent tube and lighting the backlight in two parts, the cold cathode fluorescent tube may be lit in two groups as in the case of using the LED. Further, in each of the above-described embodiments, a direct type backlight is adopted, but a so-called edge light type backlight using a light guide plate may be used. It is also possible to divide and illuminate such an edge light type backlight. In that case, a plurality of light guide plates may be used, and a single light guide plate and light sources arranged at the top and bottom May be lit separately.

(Example)
The reduction of the crosstalk of the liquid crystal display device according to the present invention will be described with reference to the drawings. First, crosstalk was calculated when the backlight driving timing during a certain lighting period was shifted. FIG. 10 is a timing chart when the lighting period is fixed and the drive timing is shifted in the liquid crystal display device according to the present invention, and FIG. 11 is a diagram showing the relationship between the backlight lighting deviation amount and the crosstalk value.

The crosstalk was detected by shifting the drive timing of the backlight 2 that was lit at a PWM value (lighting period width) of 30% (lighting width of about 2.5 ms) by 0.6 ms. The liquid crystal panel 1 is 240 Hz drive that writes black left-eye video twice and white right-eye video twice.

10 is the drive waveform of the liquid crystal panel 1, that is, the transmittance of the liquid crystal panel 1. Also, (1) to (5) above the driving waveform of the liquid crystal panel 1 are standardized light transmitted through the liquid crystal panel unit 1 when the backlight 2 is turned on by shifting the lighting timing by 0.6 ms. It shows the light intensity. In addition, what integrated this luminous intensity is handled as a brightness | luminance.

As shown in FIG. 10, in the state of (1), the back is almost at the center of the left eye video writing period (left eye video period) and the right eye video writing period (right eye video period). Light 2 is on. (2), (3), (4), and (5) are shifted backward by 0.6 ms. According to this figure, in (1), in the left-eye video period, the area Sa of the leaked light portion is large immediately after lighting and starting. On the contrary, in (5), it can be seen that the area Sa of the leaked light portion is large just before the end of lighting.

In the right-eye video period, the area Sb of the light transmittance (here, white light) increases from (1) to (3). In (4) and (5), the liquid crystal Due to the decrease in the transmittance of the panel 1, the area Sb of white light is reduced just before the light is turned off.

Here, a crosstalk value for comparing crosstalk will be described. In order to evaluate the crosstalk observed when mixed with the right-eye video (white video) due to light leakage when displaying the left-eye video (black video), the crosstalk value was defined as follows.
Crosstalk value = (leakage light area Sa / white light area Sb) × 100

The crosstalk values (1) to (5) are calculated from the above results, and the relationship with the delay time of the drive timing of the backlight 2 with respect to (1) is shown in FIG. In the graph of FIG. 11, the horizontal axis represents the backlight drive timing delay time (ms), and the vertical axis represents the crosstalk value (%).

As shown in FIG. 11, at (1), the crosstalk value of about 7.0% decreases to (2) and (3), and at (4), it is substantially the minimum value (about 3.1%). ), And the crosstalk value increases toward (5). That is, when the PWM value is 30%, the crosstalk is minimized by turning on the backlight 2 at the timing (4). That is, the backlight drive timing that minimizes the crosstalk is determined by the PWM value of the backlight 2.

Then, in the liquid crystal display device A according to the present invention, the crosstalk value was calculated by changing the PWM value to 5%, 20%, 30%, 40%, and 50%. The result is shown in FIG. FIG. 12 is a diagram showing crosstalk when the backlight is dimmed in the liquid crystal display device according to the present invention. Note that the driving condition of the liquid crystal display device uses a 240 Hz driving liquid crystal panel, and the backlight is PWM-modulated. In FIG. 12, the vertical axis represents the crosstalk value (%), and the horizontal axis represents the PWM value (%) at the time of PWM dimming of the backlight.

In addition, in order to show the effect of the present invention, three conventional comparative examples were prepared using a conventional 240 Hz drive three-dimensional image display liquid crystal display device. A comparative example is as follows. Using the liquid crystal display devices P1, P2, and P3 having backlights adjusted so that the crosstalk is minimized when the PWM values are 5%, 30%, and 50%, the backlight PWM values are 5%, 20%, and 30%. %, 40%, and 50%, and crosstalk was detected. Note that the crosstalk value described above is used as a crosstalk comparison.

12, the crosstalk value in the liquid crystal display device P1 is plotted as a circle, the crosstalk value in the liquid crystal display device P2 is triangular, and the crosstalk value in the liquid crystal display device P3 is plotted as a square. The crosstalk value in the liquid crystal display device A according to the present invention is indicated by a broken line.

As shown in FIG. 12, in the liquid crystal display device P1, when the PWM value is 5%, the crosstalk value is as small as about 1%, but as the PWM value increases (the backlight becomes brighter). Therefore, the crosstalk value is large, and when the PWM value is 50%, the crosstalk value exceeds 10%. Similarly, in the liquid crystal display device P3, when the PWM value is 50%, the crosstalk value is minimum, but as the PWM value becomes smaller (as the backlight becomes darker), the crosstalk value becomes larger. When the PWM value is 5%, the crosstalk value is larger than 10%. Further, in the liquid crystal display device P2, since the crosstalk is adjusted to be minimum when the PWM value is 30%, the crosstalk value is minimum, but both the PWM value becomes small or large. The crosstalk value is large. For the above reasons, when the backlight is PWM-modulated in a conventional liquid crystal display device, crosstalk increases, and the video is disturbed, making it difficult to see.

On the other hand, when the liquid crystal display device A according to the present invention is used, the crosstalk value is small even if the PWM value of the backlight changes. Therefore, in the liquid crystal display device of the present invention, it is possible to suppress the occurrence of crosstalk due to the PWM dimming of the backlight even when the driving frequency of the liquid crystal panel is high, such as when displaying a three-dimensional image. It is. As a result, the liquid crystal display device of the present invention can adjust the brightness of the image and can display a clear image that is easy to view.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this content. The embodiments of the present invention can be variously modified without departing from the spirit of the invention.

The liquid crystal display device of the present invention can be used as a display device for devices that display three-dimensional images, such as thin television devices, thin display devices, and mobile phones.

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 11 Array substrate 111 Source electrode 112 Gate electrode 12 Opposite substrate 13 Liquid crystal layer 14 Source driver 15 Gate driver 2 Backlight 21 LED
3 Video processing circuit 4 PWM dimming circuit 5 Timing control circuit 6 Backlight controller 7 Shutter controller 8 Active shutter glasses

Claims

A liquid crystal panel capable of displaying 3D images;
A backlight for supplying light to the liquid crystal panel;
Dimming means for determining a pulse width such that the backlight has a determined brightness;
A backlight driving means for obtaining the pulse width from the dimming means and controlling the driving of the backlight, and
The backlight driving means determines the backlight driving timing that minimizes the crosstalk detected by the liquid crystal panel based on the acquired pulse width, and lights the backlight with the driving timing and pulse width. A liquid crystal display device.
The backlight is a light that is turned on simultaneously on one side,
The liquid crystal panel scans line-sequentially and writes an image,
The backlight drive means determines a drive timing of the backlight that minimizes crosstalk detected when an image is written with a scanning line of an arbitrary stage among a plurality of scanning lines of the liquid crystal panel. Item 2. A liquid crystal display device according to item 1.
The backlight driving means displays black video and white video alternately, and drives so that the transmitted light in the black display period is equal to the transmitted light in the white display period in the portion where the black display is switched to the white display. The liquid crystal display device according to claim 1, wherein timing is determined.
The backlight is divided into at least two areas in the scanning direction of the liquid crystal panel, and each area is lit independently.
The liquid crystal panel scans line-sequentially and writes an image,
The backlight driving means reduces crosstalk when writing video with the central scanning line of each area of the backlight and reduces crosstalk when writing video with the central scanning line of the entire liquid crystal panel. The liquid crystal display device according to claim 1, wherein the drive timing adjusted to be small is determined.
The backlight driving means alternately displays a black image and a white image, and transmits the transmitted light and the white display in a black display period in a scanning line of a portion of the liquid crystal panel facing a boundary portion of the plurality of regions of the backlight. The liquid crystal display device according to claim 4, wherein the drive timing is determined so that the transmitted light in the period becomes equal.
6. The liquid crystal display device according to claim 1, wherein the backlight driving means determines a timing at which the backlight is turned off as a driving timing of the backlight.
The liquid crystal display device according to claim 6, wherein when the pulse width is increased, the backlight driving unit adjusts the timing of turning off so as to shift later in time series.
8. The liquid crystal display device according to claim 1, wherein the backlight driving means determines a midpoint position of a lighting period of the backlight as the driving timing of the backlight.
The liquid crystal display device according to claim 8, wherein the backlight driving means adjusts so that a midpoint position of a lighting period of the backlight is shifted forward in time series when the pulse width is increased.
10. The liquid crystal display device according to claim 7, wherein the backlight driving means determines an amount of shifting the backlight driving timing in accordance with the number of scanning lines.
There is a database that correlates pulse width and drive timing,
11. The liquid crystal display device according to claim 1, wherein the backlight driving unit acquires a driving timing corresponding to the pulse width acquired by accessing the database.
The backlight driving means includes an arithmetic expression that associates a pulse width with a driving timing, and determines the driving timing of the backlight by applying the acquired pulse width to the arithmetic expression. The liquid crystal display device according to claim 11.