TWI396168B - Liquid crystal display device - Google Patents

Description

Liquid crystal display device

The present invention relates to a liquid crystal display device.

In the past, in a liquid crystal display device for improving the high-speed response of animation visibility, it is conceivable to apply backlight brightness control to enhance contrast. For this reason, the brightness of the backlight can be changed according to the image, and even if the range of the brightness is switched, the displayed gamma characteristic can be maintained in an ideal state. Horse characteristics.

In the liquid crystal display device which is characterized by such a high-speed response, for example, an OCB (optically compensated bend) type liquid crystal display device is mounted on a liquid crystal television or a liquid crystal monitor (see, for example, Japanese special). Japanese Patent Publication No. 2004-185027). This OCB type liquid crystal display device proposes a so-called "flashingless" driving method in order to prevent reverse transfer from a wave alignment to a bend alignment. The flicker-free driving method includes a black writing period in which a black image signal is written to each pixel during a frame period, a video writing period in which a video signal is written to each pixel, and a writing to be held to The image signal of each pixel, during which the image of the backlight is held during the period. By using such a flicker-free driving method, it is possible to display a sharp image without causing a reverse transfer.

However, in the above liquid crystal display device, when it is determined that the image is bright, the backlight brightness is raised, and the gamma characteristic is switched to From the dark to the slanting direction of the slanting, and in the case of being judged to be dark in the image, the brightness of the backlight is lowered, and the gamma characteristic is switched to a direction in which the tilt from dark to bright is raised, thereby Gamma characteristics in a wider range of ranges to represent images.

The method for judging the brightness of the image is, for example, a method of judging the gray level of the gray scale of each pixel in the image frame, or by a histogram. The method of judging the gray scale of each pixel and having the most gray level.

The brightness of the backlight is made variable according to the gray level level determined by the judgment method. In this variable method, a method of making a pulse width variable by PWM (Pulse Width Modulation) and a method of making a voltage or a current variable are proposed. .

Switching the brightness of the backlight by interlocking with the image as described above, from the maximum gray level, and from the maximum backlight brightness to the lowest gray level, and to a wide range of minimum backlight brightness, from the liquid crystal The brightness of the display is variable, so a large contrast increase can be achieved.

In addition, in terms of backlight brightness, in addition to the conditions for maximizing lighting, the brightness is lowered, so that the backlight is always lit compared to the conventional method, and the power can be reduced.

However, in order to switch the timing of the image output and the timing of the brightness of the backlight, first, the image of a certain frame time (for example, the "a frame period") is taken in, at (a+1) The above-described averaging processing or gray scale distribution processing is performed during the frame period to calculate the backlight luminance or gamma characteristics.

Therefore, in fact, switching the brightness of the backlight becomes the (a+2) frame period. Between, and delay 2 frames for control. Because of this, the deviation between the output image and the brightness of the backlight is generated, so there is a problem of seeing an abnormal image due to the unevenness of the backlight brightness or the delay of the luminance change.

Therefore, the image signal input from the image signal source is taken in during the a frame and stored in the frame memory. Furthermore, after the backlight luminance and gamma characteristics are calculated during the (a+1)th frame period, the backlight luminance and gamma characteristics are switched during the (a+2)th frame, and the image stored in the frame memory is output.

By using such a frame memory, the brightness and gamma control of the backlight corresponding to the image can be applied.

However, in this method, as described above, it is necessary to have a frame memory for memorizing the image of the frame, and there is a problem that the cost increases and the installation space of the circuit board connected to the liquid crystal panel increases.

Accordingly, the present invention has been made in view of the above problems, and provides a liquid crystal display device which can reduce the capacity of a memory and can clearly display an image.

The present invention relates to a liquid crystal display device comprising: a liquid crystal panel comprising: m signal lines extending in a longitudinal direction; n scanning lines extending in a lateral direction; and a plurality of pixels arranged in the display region a matrix; a backlight for illuminating the liquid crystal panel; a source driver for outputting image signals and non-image signals to the respective signal lines; and a gate driver for outputting the gate signals To each of the scan lines; the first control unit is controlled to write the non-image signal to a non-image signal writing period of each of the pixels, an image writing period in which the video signal is written in each pixel, and an image holding period in which the video signal written in each pixel is held; and a second a control unit configured to control the backlight of the backlight; the display area is divided into a first block to an Lth block extending from the horizontal direction (only 1<L<n); the second control unit Each of the foregoing blocks is disposed, and the backlight is turned on during the image holding period of each of the blocks.

Furthermore, the present invention is a liquid crystal display device comprising: a liquid crystal panel comprising: m signal lines extending in a longitudinal direction; n scanning lines extending in a lateral direction; and a plurality of pixels in the display region Configuring a matrix; a backlight for illuminating the liquid crystal panel; a source driver for outputting image signals and non-image signals to the respective signal lines; and a gate driver for outputting the gate signals to Each of the scan lines is controlled by a first control unit configured to write the non-image signal to a non-image signal write period of each of the pixels, and to write the video signal to a video write period of each of the pixels. a sequence of image holding periods in which the image signals of the respective pixels are held; and a second control unit for controlling the backlight of the backlight; the display area is divided into a horizontal direction From the first block to the Lth block (where 1<L<n); the first control unit is controlled by each of the aforementioned blocks to become the aforementioned non-shadow The order of the image writing period, the image writing period, and the image holding period.

The present invention relates to a liquid crystal display device comprising: a liquid crystal panel comprising: m signal lines extending in a longitudinal direction; n scanning lines extending in a lateral direction; and a plurality of pixels arranged in the display region a matrix; a backlight for illuminating the liquid crystal panel; a source driver for outputting image signals and non-image signals to the respective signal lines; and a gate driver for outputting the gate signals to the foregoing a scanning line; the first control unit is configured to write the non-image signal into the non-image signal writing period of each of the pixels during a frame period, and write the image signal to the image writing of each pixel a sequence in which an image holding period in which the image signals of the respective pixels are held is held; and a second control unit for controlling the backlight of the backlight; the display area is divided into The first block to the Lth block extending in the direction (only 1<L<n); the first control unit (1) is controlled for each of the blocks to be the non-image signal writing period and the image writing. Entry period The order of the image holding period; (2) controls so that the k-th block (provided that 1 <k <L) of the image block of the image writing period is written during a particular time delay than the first (k-1).

Furthermore, the present invention is a liquid crystal display device comprising: a liquid crystal panel comprising: m signal lines in the display region, extending in the longitudinal direction; a scanning line extending in a lateral direction; and a plurality of pixels arranged in a matrix; a backlight for illuminating the liquid crystal panel; and a source driver for outputting the image signal and the non-image signal to each of the foregoing a signal line; a gate driver for outputting a pulse-like gate signal to each of the scan lines; and a first control unit configured to write the non-image signal to each of the pixels a video signal writing period, an image writing period in which the video signal is written to each pixel, an image holding period in which the video signal written in each pixel is held, and a second control unit Turning off the light to control the backlight; the display area is divided into the first block to the Lth block extending from the horizontal direction (where 1<L<n); the backlight is according to each of the foregoing blocks The first control unit (1) controls the order of the non-image signal writing period, the image writing period, and the image holding period in accordance with each of the blocks; (2) controlling to make the kth Block (only 1<k≦L The image writing period is delayed by a specific time from the image writing period of the (k-1)th block; the second control unit (1) corrects the brightness of the light source of the kth block to the aforementioned Within a specific range of the brightness of the light source of the (k-1)th block, (2) lighting the respective light sources with the corrected brightness during each of the image holding periods of each of the blocks, and Out of time light.

Furthermore, the present invention is a liquid crystal display device comprising: a liquid crystal panel comprising: m signal lines extending in a longitudinal direction; n scanning lines extending in a lateral direction; and a plurality of pixels in the display region Configuring a matrix; a backlight for illuminating the liquid crystal panel; a source driver for outputting image signals and non-image signals to the respective signal lines; and a gate driver for pulsing the gate The signal is output to each of the scan lines; the first control unit controls the non-image signal writing period to write the non-image signal to the non-image signal during the frame period, and writes the image signal a sequence of image holding periods in which the image signals written to the respective pixels are held during the image writing period of the pixels; and a second control unit for controlling the backlighting of the backlight; the display The region is divided into a first block to a Lth block extending in the horizontal direction (where 1<L<n); the backlight includes a light source according to each of the blocks; the first control unit is each The foregoing The block control is performed in the order of the non-image signal writing period, the image writing period, and the image holding period, and the second control unit (1) calculates the brightness of each of the light sources based on the image signal for each frame period. (2) the aforementioned light sources during the current frame The brightness is corrected to be within a specific range of the average of the brightness of each of the foregoing light sources in the previous frame period of the current frame period; (3) only during each of the foregoing image holding periods of each of the aforementioned blocks The corrected brightness causes the respective light sources to be lit and extinguished during other periods.

In summary, the present invention can reduce the memory capacity as long as the memory for storing the image signal of each block is prepared.

Hereinafter, an OCB type liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)

An OCB type liquid crystal display device according to a first embodiment of the present invention will be described with reference to Figs.

(1) Composition of liquid crystal display device

The configuration of the liquid crystal display device of this embodiment will be described with reference to Fig. 1 . Fig. 1 is a block diagram showing the configuration of an OCB type liquid crystal display device.

The OCB type liquid crystal display device includes, for example, a liquid crystal panel 10 of 7 to 9 inches, a backlight 11, a source driver 12, a gate driver 13, a controller 14, a block memory 15, an input power source 16, The liquid crystal drive voltage generating circuit 17.

The liquid crystal panel 10 includes an array substrate and a counter substrate, wherein the array substrate is wired with a signal line and a scanning line, and a TFT (Thin Film Transistor) is disposed at the intersection. In addition, the OCB mode liquid crystal is held between the array substrate and the counter substrate. Further, the liquid crystal panel 10 of the present embodiment is formed to be formed in the longitudinal direction. A signal line of 1 to m lines, and a scan line of 1 to n lines is formed in the lateral direction. For example, in the case of WVGA (Wide Video Graphics Array), since it is 800 (×RGB)×480, it becomes n=480.

The backlight 11 is disposed on the back surface of the liquid crystal panel 10. This backlight 11 will be described later.

The block memory 15 is used to temporarily store the data of the input image signal. This block memory 15 will also be described later.

The input power source 16 supplies power to the backlight 11, the controller 14, and the liquid crystal driving voltage generating circuit 17, and the liquid crystal driving voltage generating circuit 17 adjusts the supply to the source driver in accordance with the timing at which the display material is displayed on the liquid crystal panel 10. 12 and the voltage of the gate driver 13.

The gate driver 13 supplies a gate signal to the scanning line of the liquid crystal panel 10, and the source driver 12 supplies a voltage corresponding to a video signal or the like to the signal line of the liquid crystal panel 10.

The source driver 12 includes a D/A converter 23 and a shift register 24.

The controller 14 will be described later.

(2) Structure of backlight 11

Next, the structure of the backlight 11 will be described based on FIG.

The backlight 11 of the present embodiment includes a light guide plate 111 and ten LEDs (light-emitting diodes) 112.

In FIG. 3, five LEDs 112 are embedded in each of the left end portion and the right end portion of the light guide plate 111 at predetermined intervals. In addition, it is fitted to the left and right ends. The LEDs 112 are disposed at opposite positions.

The light guide plate 111 is divided into the first block 111a to the fifth block 111e extending in the lateral direction by the arrangement of the LEDs 112 described above.

When the two LEDs 112 corresponding to the first block 111a are turned on, only the first block 111a of the light guide plate 111 is turned on, and the liquid crystal panel 10 corresponding to the first block 111a of the lighting is displayed. Image.

Since the backlight 11 is divided into five blocks as described above, the block of the display area thus displayed is also divided into five. For example, since the present embodiment is WVGA as described above, the following relationship is obtained.

In the first block, the display area corresponding to the first to 96th scanning lines is the first block.

The display area corresponding to the 97th scanning line to the 192th scanning line in the second block system becomes the second block.

The display area corresponding to the 193th scanning line to the 288th scanning line of the third block system becomes the third block.

The display area corresponding to the 4th block system and the 289th scanning line to the 384th scanning line becomes the 4th block.

The display area corresponding to the fifth block line from the 385th scanning line to the 480th scanning line becomes the fifth block.

In addition, although the division of this block divides 480 scan lines equally into five, it is not limited to this, and can also be set as a division of 100, 100, 80, 100, 100, or Repeat the scan line in the area of the boundary.

(3) Structure of block memory 15

The block memory 15 is not as conventionally known as the image signal during the storage of the frame. The image is composed of three memories, and the image signals of one block are stored in each memory. The image signal of the 1 block is stored as an image signal for performing display of each of the above blocks.

In addition, in the following description, the period in which the image of the 1 block is stored and displayed is referred to as a 1-block period.

(4) Display action in the liquid crystal display device

Next, the display operation of the controller 14 in the liquid crystal display device will be described using FIG.

The video signal belonging to the RGB data is temporarily accumulated in the block memory 15.

The controller 14 reads in the data stored in each of the blocks before the block memory 15, and performs gamma correction processing on the image signal. This correction processing will be described later. Further, according to the start pluse, the data for displaying the correction processing is transmitted to the shift register 24 of the source driver 12 for each column of pixels.

In addition, the controller 14 is configured to prevent the data of the black image of the reverse transfer from being transmitted to the displacement register 24 every 1 column of pixels according to the start pulse.

Furthermore, the controller 14 outputs a load pulse to the D/A converter 23 of the source driver 12. The D/A conversion unit 23 acquires one column of pixels simultaneously with the data stored in the shift register 24, and performs D/A conversion and outputs a voltage corresponding to each display material to the timing at which the load pulse is input. The signal line of the liquid crystal panel 10.

Further, at this time, the controller 14 controls the output timing of the pulse-like gate signals outputted from the gate driver 13 to the respective scanning lines, and causes the backlight 11 at the timing of response of the TFTs of the liquid crystal panel 10 and the display data. Each The LED 112 is turned on, and the display material is displayed on the liquid crystal panel 10.

(5) The composition of the controller 14

Next, the detailed configuration of the signal processing in the controller 14 will be described based on Fig. 2 . 2 is a block diagram of signal processing with respect to controller 14.

As shown in FIG. 2, the controller 14 includes a gray scale distribution detecting unit 30, a block memory control unit 32, a backlight luminance calculating unit 34, a backlight control unit 36, a gamma conversion value calculating unit 38, and a gamma conversion. The unit 40, the RGB independent gamma unit 42, the FRC (Frame Rate Control) processing unit 44, and the source driver output conversion unit 46.

The gray scale distribution detecting unit 30 counts the number of pixels included in each of the ten gradation ranges divided in advance, based on the input video signal, in the image signal of the input frame period. A gray scale distribution is established corresponding to the number of pixels included in each gray scale range (the number of pixels is an example of the frequency of the pixels). This detected gray scale distribution is output to the backlight luminance calculation unit 34 and the gamma conversion value calculation unit 38.

The block memory control unit 32 stores the video signal during the 1-frame period in the block memory 15.

The backlight luminance calculation unit 34 calculates the luminance of the backlight 11 based on the gray scale distribution input from the gray scale distribution detecting unit 30. For example, in the case where the frequency of the lower gray scale range in the gray scale distribution is relatively high, the brightness of the backlight 11 along the gray scale range of the multi-frequency is also small, and even if the brightness is smaller than usual, and is higher In the case where the frequency of the gray scale range is large, the brightness of the backlight 11 is controlled to be high. The backlight luminance calculated as described above is output to the backlight control unit 36.

The backlight control unit 36 adjusts the brightness of the backlight 11 in accordance with the input backlight brightness. The adjustment is a PWM (Pulse Width Modulation) control method in which the brightness is modulated by switching the period of the light emission and the non-light emission at a high speed. Therefore, the backlight control unit 36 generates a PWM control signal based on the light source luminance signal and outputs it to the backlight 11. Regarding the adjustment of the brightness of the backlight 11, in addition to the above, it is also possible to control the amount of current itself.

The gamma conversion value calculation unit 38 calculates a gamma conversion value for correcting the gamma value of the input video signal from the gray scale distribution and the backlight luminance.

The gamma conversion unit 40 changes the gamma of the video signal based on the video signal input from the block memory control unit 32 and the gamma conversion value input from the gamma conversion value calculation unit 38. For example, if the brightness of the backlight 11 is set to be smaller than usual according to the gray scale distribution, the brightness is lowered compared to the original gray level brightness. Therefore, the image signal is converted into a gray scale that is brighter than the original gray scale. This conversion is converted in a manner close to an ideal gamma curve, such as a 2.2 square gamma curve.

The RGB independent gamma unit 42 RGB independently corrects the gamma value of the video signal based on the changed gamma conversion. This correction is, for example, an OCB type liquid crystal, and is effectively applied to a case where gamma setting is preferably performed in accordance with each of R, G, and B.

The FRC (Frame Rate Control) processing unit 44 performs FRC processing on the video signals of the respective RGB. The FRC processing unit 44 is used to drive an 8-bit source, for example, in a 10-bit input video signal. The device performs a grayscale display equivalent to 10 bits, and the like.

The source driver output conversion unit 46 outputs the RGB image signal subjected to the FRC processing to the source driver 12.

(6) Flicker-free driving method

Next, the flicker-free driving method in the liquid crystal panel 10 of the present embodiment will be described.

The flicker-free driving method writes the image signal to the next one during the black frame period during the first 1/4 frame period by, for example, writing the black image signal as a non-image signal during the 1-frame period. The image writing period during the /4 frame period and the image holding period during which the written image signal is held across the 2/4 frame are sequentially constructed. Further, during the image holding period, the backlight 11 and the LEDs 112 corresponding to the respective blocks are turned on to display the image.

If there is no flicker driving method for this, the reverse shift from the curved alignment to the wave alignment can be prevented by writing the black image to the beginning of the 1-frame period, and a sharp image can be obtained. Further, since the backlight 11 is turned on during the image holding period, there is no possibility that the image is uneven or the like.

Further, the "black image signal" is a signal corresponding to black insertion, and in the black writing period, since the backlight 11 is not lit, it is not displayed as an image. In addition, the black color in the black image signal is not limited to the black of the gray scale 0, as long as it is close to the gray scale (color).

In addition, instead of the black image signal, it is also possible to use a non-image signal having a higher voltage value than the black image signal. In this case, it is shown that since the backlight 11 which is grayed out is turned off, there is almost no adverse effect on the contrast, and the reverse transfer can be effectively prevented. For example, by using a non-image signal corresponding to a higher voltage value than a darker image signal, the insertion of the non-image signal can be further shortened. rate. Thereby, a higher display brightness can be obtained even in a high temperature environment where reverse transfer is likely to occur. Further, the insertion rate of the non-image signal can be configured to be appropriately changed according to the environmental temperature.

(7) Specific driving method

Next, a specific driving method of the liquid crystal display device of FIG. 4 will be described with reference to FIG.

Figure 4 is a diagram for explaining the specific display method, showing the flow of processing time for each frame unit. The horizontal axis indicates the flow of each frame period, and the 1-frame period is divided into five divided periods for explanation. Further, the horizontal axis indicates the flow of signals for each block, and the state of turning on or off the LEDs 112 of the backlight 111, which is indicated by "BL" in FIG.

A in Fig. 4 indicates the storage period of the image signal and the storage period of the memory of each of the memories 151 to 153 in the block memory 15. B shows the data calculation period used for the backlight luminance calculation processing and the gamma value calculation processing described above. The C system indicates the image writing period. D is the image holding period. E is a black write period.

(7-1) Block 1

First, the first block will be explained.

In the first division period of the first frame period, the video signal displayed in the first block is taken in and stored in the first memory 151. This saving is performed until the third division period (refer to A in FIG. 4).

Further, in the first division period and the second division period of the first frame period, the black write signal is sent to the pixel corresponding to the first block to perform black writing (see E in FIG. 4).

Next, in the second division period of the first frame period, the backlight luminance and the gamma value are calculated from the video signals displayed in the first block (see B in FIG. 4).

Next, in the third division period of the first frame period, the image signal subjected to the data processing described above is written to each pixel. The pixel to be written is written to each pixel belonging to the range of the first block (refer to C in FIG. 4).

Then, in the fourth division period of the first frame period, the image signal written in the above manner is held, and the LED 112 of the backlight 111 corresponding to the first block is turned on to display an image. (Refer to D in Figure 4).

Finally, in the fifth division period of the first frame period, the black write signal is sent to the pixel corresponding to the first block to perform black writing (see E in FIG. 4).

Next, in the second division period of the first frame period, the backlight luminance and the gamma value are calculated from the video signals displayed in the first block (see B in FIG. 4).

Next, in the third division period of the first frame period, the image signal subjected to the data processing described above is written to each pixel. The pixel to be written is written to each pixel belonging to the range of the first block (refer to C in FIG. 4).

Then, in the fourth division period of the first frame period, the image signal written in the above manner is held, and the LED 112 of the backlight 111 corresponding to the first block is turned on to display an image. (Refer to D in Figure 4).

Finally, in the fifth division period of the first frame period, the first block is made The LED 112 of the corresponding backlight 111 is turned off, and black writing is again performed to the pixel corresponding to the first block (refer to E in FIG. 4).

(7-2) Block 2

Next, the second block will be described.

The second block performs the same processing as the first block by delaying the first divided period from the first block.

That is, in the second division period of the first frame period, the video signal is stored in the second memory 152 (see A in FIG. 4).

Further, in the first division period to the third division period from the first frame period, the black write signal is sent to the pixel corresponding to the second block to perform black writing (see E in FIG. 4).

In the third division period of the first frame period, data processing is performed in the same manner (see B in Fig. 4).

In the fourth division period of the first frame period, the video signal is written to the pixel of the second block (see C in FIG. 4).

In the fifth division period of the first frame period, the written image is held, and the LED 112 of the backlight 111 corresponding to the second block is turned on.

(7-3) Blocks 3~5

Next, in the third block, the same processing is performed while the second block is delayed by one division period. The memory system saved in this case is stored in the third memory 153.

Next, in the fourth block, the same processing is performed while the third block is delayed by one division period. However, in this case, the memory of the video signal corresponding to the fourth block is stored in the first memory 151. That is, the storage in the 4th block The period in which the video signal is stored is the fourth divided period in the first frame period. Therefore, the video signal stored in the first memory 151 in the first block is data-processed and written in the first block. It is not needed, so the image signal of the 4th block is stored.

Next, in the fifth block, the same processing is performed by delaying the division of the fourth block by one division period. However, the memory system stored in this case has finished the data processing for the video signal of the second block, and thus is stored in the second memory 152.

(8) Effect

If the above driving method is performed, it is no longer necessary to store the frame memory of the image signal during the frame period as in the conventional manner, and only three memory blocks for storing the image signals in each block are prepared. Significantly reduce memory capacity.

In addition, since it is divided into five blocks during the 1-frame period and the flicker-free driving method is performed for each block, there is no occurrence of flicker or the like due to the delay of the frame. That is, since the image signal displayed during the 1-frame period coincides with the brightness of the backlight, there is no case where an abnormal image is displayed which is uneven due to the brightness of the backlight or delayed in brightness variation.

(Second embodiment)

Next, a second liquid crystal display device will be described with reference to FIGS. 5 and 6.

(1) Different from the first embodiment

Further, in the first block, the video signal is written from the first divided period to the third divided period, and the image is held after the fourth divided period.

Next, in the second block, the second division period to the fourth division are similarly performed. The video signal is written until the time period, and the image holding period is set after the fifth division period.

Next, in the third block, the video signal is written from the third divided period to the fifth divided period, and the sixth divided period is set as the image holding period.

Next, in the fourth block, the video signal is written from the fourth divided period to the sixth divided period, and the seventh divided period and the subsequent period are set as the image holding period.

Next, in the fifth block, the video signal is written from the fifth divided period to the seventh divided period, and the eighth divided period and thereafter are set as the image holding period.

Finally, the backlight 11 described above is terminated after the eighth division period and the lighting is reached until the frame period.

(3) Effect

Thereby, the backlight 11 can be turned on after the eighth division period, and the backlight brightness can be made bright.

Further, the memory capacity can be reduced in the same manner as in the first embodiment.

In addition, there is no case where an abnormal image is displayed which is uneven due to the brightness of the backlight or delayed in brightness variation.

(Third embodiment)

A liquid crystal display device according to a third embodiment of the present invention will be described with reference to Figs. 7 and 8 .

(1) Comparison with the first embodiment

In the liquid crystal display device of the first embodiment, it is determined by each block. The brightness and gamma value of LED 112. In the method of controlling the brightness of the backlight 11, in the case where the difference in luminance becomes larger in the adjacent block, there is a case where streaks are seen in the boundary of the adjacent block.

Therefore, in the liquid crystal display device of the third embodiment, the method of controlling the brightness of the backlight 11 is provided so that no streaks are generated in the boundary between adjacent blocks.

(2) The concept of brightness adjustment

The method of controlling the brightness of the second embodiment will be described with reference to Fig. 7 in comparison with the control method of the first embodiment.

Fig. 7(a) shows the state of the input of the image signal in the 1-frame period, where the vertical axis is the position of the line and the horizontal axis is the time axis.

Fig. 7(b) is a method of adjusting the brightness of the first embodiment, and each brightness is determined in five blocks. However, if the brightness of each block is controlled, the difference in luminance between the blocks as described above becomes large, for example, in FIG. 7(b), the first block and the second block are The difference in luminance between the two blocks becomes large, and there is a case where streaks are seen in the boundary portion between the first block and the second block in the liquid crystal panel 10.

Fig. 7(c) shows the luminance of each block in the present embodiment.

Focusing on the description of the second block, when the brightness of the second block is calculated in the calculation method of the first embodiment, it is as shown by the value of Fig. 7(b). However, if it is such a value, the difference with the brightness of the first block will become large, and thus streaks will be observed. Therefore, in the present embodiment, the luminance of the second block is corrected within the range of ±10% centering on the luminance of the first block.

In this way, the difference in luminance between adjacent blocks is reduced, and there is no possibility of streaking between the above blocks.

(3) Control method of the embodiment

Next, a method of controlling the brightness of the backlight 11 of the present embodiment will be described with reference to FIG.

In step 1, the luminance P _{k-1 of} the (k-1)th block is input. This luminance P _k-1 is calculated using the one calculated in the previous block.

The luminance P _{k of} the kth block is calculated in step 2. This calculation method is the same as that of the first embodiment.

In step 3, the luminance P _k of the kth block and the luminance P _k-1 of the (k-1)th block are compared with each other, and if the luminance P _{k of} the kth block is 0.9×brightness P _{If k-1 is} large, proceed to step 4. If it is small, proceed to step 5.

In step 4, since the brightness of the k-th block of the one block previous P _k P _k-1 of the luminance of 90% less, and therefore the correction of the brightness (k-1) of block 90 of P _k-1 Light up the brightness of %. Use this corrected brightness to correct the gamma value. Furthermore, proceed to step 8.

In step 5, the comparison of the (k-1) blocks of luminance values P _k-1 and 110% of the k-th block of P _k-1, when the brightness of the k-th block P _k than 1.1 × P _{If k-1 is} small, proceed to step 6. If it is large, proceed to step 7.

In step 6, the luminance P _k of the kth block is within ±10% of the luminance P _k-1 of the (k-1)th block, and thus is lit by the luminance P _{k of} the kth block. Use this brightness to correct the gamma value. Furthermore, proceed to step 8.

In step 7, since the luminance P _{k of} the kth block is larger than 110% of the luminance P _k-1 of the (k-1)th block, the luminance P _k- of the (k-1)th block is corrected. ₁ 110% of the luminance of the lighting. Use this corrected brightness to correct the gamma value. Furthermore, proceed to step 8.

In step 8, it is judged whether or not k = 5, that is, if the last block is not ended, the process proceeds to step 9. If it is over, proceed to step 10.

In step 9, it is assumed that k=k+1 and the process returns to step 1.

In step 10, the process proceeds to the next frame, and in step 11, it is set to k=1 and returns to step 1. In addition, in the case of advancing to the next frame, the brightness of the last block of the previous frame is used in terms of the brightness P _k-1 of the (k-1)th block in step 1.

(4) Brightness

Since the brightness of the next block is within ±10% of the luminance as compared with the brightness of the previous block as described above, there is no case where streaks are generated between adjacent blocks.

(5) Change example

In the above embodiment, although the brightness of the previous block is set to ±10%, the value of ±10% is not included as long as the stripe between the adjacent blocks is not seen. It can also be a larger value or a smaller value.

(Fourth embodiment)

Next, a fourth embodiment will be described based on Fig. 9 .

In the third embodiment, in order to prevent the stripes of the boundary between adjacent blocks from being seen, the determination is made based on the brightness of the previous block. However, in the present embodiment, the current frame is used. The average of the brightness of each block in a frame is the reference.

Figure 9(a) shows the input and line position of the image signal for each frame.

Fig. 9(b) shows the state of the brightness of each frame described in the first embodiment. If it is this state, as described in the second embodiment, streaks may occur at the boundary between adjacent blocks.

Therefore, as shown in FIG. 9(c), the average value of the luminance of each block of the previous frame (hereinafter referred to as "brightness candidate" in the present embodiment) calculated by the backlight luminance calculation unit 34 is obtained. . Furthermore, the brightness of each block of the following frame is within ±10% of the average value of the brightness candidates, and each block of the next frame is calculated by the backlight brightness calculation unit 34. The brightness candidates are corrected and the corrected brightness is illuminated.

By such control, there is no possibility of streaking of the boundary between the blocks.

In addition, it is not limited to ±10% of the average brightness of each block of the full frame, as long as the stripes are not seen at the boundary between adjacent blocks, it may be greater than ±10%. The value, or smaller value.

(change example)

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit and scope of the invention.

(1) Change example 1

In each of the above embodiments, the area extending in the lateral direction has been described as being divided into five blocks, but it may be divided into two or more blocks, or may be divided into 10 blocks or more, for example, 15 or 20 blocks.

(2) Change example 2

In the above embodiment, the OCB type liquid crystal display device is described. However, the present embodiment is a TN (Twisted Nematic) type, a VA (Vertical Alignment) type, an IPS (In Plane Switch) type, a ferroelectric type, or an anti-strong dielectric type. It can also be applied to a liquid crystal display device.

Further, in the case of the response speed of the liquid crystal, for example, in the case of performing 5 msec or less, particularly in the case of non-image signal writing, it is preferable to use an OCB type liquid crystal.

(3) Change example 3

In the first and second embodiments, the flicker-free driving is performed sequentially for each block from the top, but not limited thereto, and the blocks are sequentially ordered from the bottom, and each block is used. Random flicker-free driving is also possible.

10‧‧‧LCD panel

11‧‧‧ Backlight

12‧‧‧Source Driver

13‧‧ ‧ gate driver

14‧‧‧ Controller

15‧‧‧ Block Memory

16‧‧‧Input power supply

17‧‧‧LCD drive voltage generating circuit

23‧‧‧D/A conversion department

24‧‧‧Displacement register

30‧‧‧ Grayscale Distribution Detection Department

32‧‧‧ Block Memory Control Department

34‧‧‧Backlight brightness calculation unit

36‧‧‧Backlight Control Department

38‧‧‧Gamma conversion value calculation unit

40‧‧‧Gama Conversion Department

42‧‧‧RGB independent gamma

44‧‧‧FRC Processing Department

46‧‧‧Source Driver Output Conversion

111‧‧‧Light guide plate, backlight

111a~111e‧‧‧1st block~5th block

112‧‧‧LED

151‧‧‧1st memory

152‧‧‧2nd memory

153‧‧‧3rd memory

A‧‧‧Storage period of memory

B‧‧‧Data calculation period

C‧‧‧Image writing period

D‧‧‧Image retention period

E‧‧‧Black writing period

P _k , P _k-1 ‧‧‧ brightness

Fig. 1 is a block diagram of a liquid crystal display device of a first embodiment.

Figure 2 is a block diagram of a controller.

Fig. 3 is an explanatory view of a backlight, (a) is a plan view, and (b) is a side view.

Fig. 4 is a timing chart showing the flow of processing in a 1-frame unit.

Fig. 5 is an explanatory view of a backlight according to a second embodiment, wherein (a) is a plan view and (b) is a side view.

Fig. 6 is a timing chart showing the flow of processing in a 1-frame unit.

7(a) to 7(c) are explanatory views showing changes in luminance of respective blocks in the first frame of the third embodiment.

Fig. 8 is a flow chart showing a method of controlling the brightness of the third embodiment.

9(a) to 9(c) are diagrams showing each block of each frame of the fourth embodiment. An illustration of the value of the brightness.

10‧‧‧LCD panel

11‧‧‧ Backlight

12‧‧‧Source Driver

13‧‧ ‧ gate driver

14‧‧‧ Controller

15‧‧‧ Block Memory

16‧‧‧Input power supply

17‧‧‧LCD drive voltage generating circuit

23‧‧‧D/A conversion department

24‧‧‧Displacement register

151‧‧‧1st memory

152‧‧‧2nd memory

153‧‧‧3rd memory

Claims (9)

A liquid crystal display device comprising: a liquid crystal panel comprising: m signal lines extending in a longitudinal direction; n scanning lines extending in a lateral direction; and a plurality of pixels arranged in a matrix a backlight for illuminating the liquid crystal panel, a source driver for outputting image signals and non-image signals to the respective signal lines, and a gate driver for outputting the gate signals to the foregoing scans a first control unit configured to write the non-image signal to the non-image signal writing period of each of the pixels during a frame period, and to write the image signal to the image writing of each of the pixels a period in which an image holding period in which the image signals of the respective pixels are held is maintained; and a second control unit for controlling the backlight of the backlight; the display area is divided into a horizontal direction The first block to the Lth block (where 1<L<n) are extended; the first control unit (1) is controlled by each of the blocks to be the non-image signal writing period and the image writing. period, Holding period of said video sequence; the image period (2) of the first control block k (provided that 1 <k <L) of the writing than the first (k-1) of the image block is written during a particular time delay. The liquid crystal display device of claim 1, wherein The backlight includes a light source for each of the blocks, and the second control unit lights the respective light sources only during each of the image holding periods of the respective blocks, and turns off the lights during the other periods. The liquid crystal display device of claim 1, wherein the first frame period includes a video writing period and a lighting period of the backlight; and the first control unit is from the first block to the Lth block The non-image signal and the video signal are written in the signal writing period, and the second control unit causes the display area to be the same as the start of the image holding period of the L-th block in the lighting period The light source is lit and the aforementioned light source is turned off at the same time as the end of the aforementioned frame period. A liquid crystal display device comprising: a liquid crystal panel comprising: m signal lines extending in a longitudinal direction; n scanning lines extending in a lateral direction; and a plurality of pixels arranged in a matrix a backlight for illuminating the liquid crystal panel, a source driver for outputting image signals and non-image signals to the respective signal lines, and a gate driver for outputting a pulsed gate signal to Each of the scan lines; the first control unit is configured to write the non-image signal into the non-image signal writing period of each of the pixels, and to display the image signal a step of writing to the image writing period of each of the pixels, an image holding period in which the image signals written to the pixels are held, and a second control unit for controlling the backlight of the backlight; The display area is divided into a first block to an Lth block extending in the lateral direction (where 1<L<n); the backlight includes a light source according to each of the blocks; the first control unit is 1) controlling each of the blocks to be in the order of the non-image signal writing period, the image writing period, and the image holding period; (2) controlling the kth block (only 1 < k ≦ L) The image writing period is delayed by a specific time from the image writing period of the (k-1)th block; and the second control unit (1) corrects the brightness of the light source of the kth block to the first ( K-1) within a specific range of the brightness of the light source of the block, (2) lighting the respective light sources with the corrected brightness only during each of the image holding periods of each of the blocks, and The light is turned off during the period. The liquid crystal display device of claim 4, wherein the second control unit corrects the brightness of the light source of the kth block to within ±10% of the brightness of the light source of the (k-1)th block . A liquid crystal display device comprising: a liquid crystal panel comprising: m signal lines extending in a longitudinal direction; n scanning lines extending in a lateral direction; and a plurality of pixels arranged in a matrix shape; a backlight for illuminating the liquid crystal panel, a source driver for outputting image signals and non-image signals to the signal lines, and a gate driver for outputting pulsed gate signals to the foregoing a scanning line; the first control unit controls, during the frame period, to write the non-image signal to the non-image signal writing period of each of the pixels, and write the image signal to each of the pixels a video writing period, an order of image holding periods in which the image signals written to the pixels are held; and a second control unit for controlling the backlight of the backlight; the display area is divided into slaves a first block to an Lth block extending in the horizontal direction (where 1<L<n); the backlight includes a light source according to each of the blocks; the first control unit is controlled by each of the foregoing blocks a sequence of the non-image signal writing period, the image writing period, and the image holding period; wherein the second control unit (1) calculates the brightness of each of the light sources based on the image signal for each frame period; ) The aforementioned brightness of each of the foregoing light sources during the current frame is corrected to be within a specific range of the average of the brightness of the foregoing light sources in the previous frame period of the current frame period; (3) only in each of the aforementioned areas Each of the light sources is turned on by the corrected brightness in each of the image holding periods of the block, and is turned off during the other periods. The liquid crystal display device of any one of 4 or 6, which comprises S (in which 1<S<L) block memory for storing image signals of each of the blocks; and is stored in the block memory. The image signal is output to the first control unit. The liquid crystal display device of any of 4, wherein the non-image signal is a signal corresponding to the black display. The liquid crystal display device according to any one of the items 4, wherein the liquid crystal panel is an OCB type liquid crystal.