JP2010008871A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of flicker by performing more suitable impulse emission in a liquid crystal display device including an impulse type backlight. <P>SOLUTION: In a liquid crystal display device 100, a display area of a liquid crystal panel 4 is divided into a plurality of display sub-areas, and a backlight 7 is constituted of a plurality of light sources L corresponding to the plurality of display sub-areas. A determination means compares prescribed flicker determination calculation values calculated from pixel values of pixels within display sub-areas with a preset determination value to determine flicker occurrence levels in each display sub-area, and a decision means decides frequencies in light emission of corresponding light sources in each display sub-area in accordance with flicker occurrence levels in each display sub-area determined by the determination means, and a light emission control means causes corresponding light sources L to emit light in each one-frame period in accordance with the frequencies in light emission in each display sub-area decided by the decision means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device.

The liquid crystal display device displays an image by passing or blocking light by applying a voltage to the liquid crystal sandwiched between two electrodes to change the alignment direction of the liquid crystal.
The liquid crystal display device is a hold-type display device in which the voltage applied to the liquid crystal is held for one frame period from the switching of the image to the next switching of the image. However, such a hold-type display device has a problem of image quality deterioration due to motion blur. In motion blur, the human eye watching a movie moves so as to follow a moving object, whereas the actually displayed image is stationary for one frame period. It is a phenomenon that is perceived as if the moving image is blurred due to the perception of an image that is doubled and shifted.

  On the other hand, there is known a liquid crystal display device that performs impulse-type display in which the backlight is turned on only during a part of one frame period and the backlight is turned off during the remaining period. In the impulse-type liquid crystal display device, an image display period and an image non-display period are included in one frame period, so that it is possible to suppress an operational blur that is a problem in the hold-type display device. On the other hand, the impulse-type display device has a drawback that flicker is likely to occur.

Therefore, for example, in Patent Document 1, by detecting the motion vectors of the current frame image and the previous frame image for each frame block, the current frame image is distinguished into a moving image and a still image for each frame block, There has been proposed a liquid crystal display device that blinks a corresponding light source block in a determined frame block and constantly lights a corresponding light source block in a frame block determined to be a still image.
JP 2005-99367 A

The liquid crystal display device of Patent Document 1 controls the light emission time of the backlight depending on whether the display image is a moving image or a still image. However, the ease of occurrence of flicker is not constant, and the closer to a still image, the more prominent the flicker is.
Therefore, as in Patent Document 1, simply controlling the backlight by distinguishing the display image into two, that is, a moving image and a still image, makes it impossible to sufficiently suppress flicker by shortening the light emission time, or vice versa. In addition, the light emission time may be too long, causing motion blur.

  An object of the present invention is to suppress the occurrence of flicker by performing more optimal impulse light emission in a liquid crystal display device including an impulse-type backlight.

In order to solve the above-described problem, the invention described in claim 1 is a liquid crystal display device including a liquid crystal panel and a backlight that irradiates the liquid crystal panel with impulse-type light.
The display area of the liquid crystal panel is divided into a plurality of sub display areas,
The backlight comprises a plurality of light sources corresponding to the plurality of sub display areas,
A determination unit that determines a flicker occurrence level by comparing a predetermined flicker determination calculation value calculated from a pixel value of a pixel in the sub display region with a predetermined determination value for each sub display region; ,
Determination for determining, for each sub display area, the number of times of light emission of the corresponding light source increases as the flicker generation level increases, according to the flicker generation level for each sub display area determined by the determination unit. Means,
In one frame period, light emission control means for causing the corresponding light source to emit light according to the number of times of light emission for each sub display area determined by the determination means;
It is characterized by providing.

  According to a second aspect of the present invention, in the liquid crystal display device according to the first aspect, the light emission control unit causes the light source to be spaced at a predetermined time interval when the number of times of light emission determined by the determination unit is two or more. It is characterized by emitting light.

  According to a third aspect of the present invention, in the liquid crystal display device according to the first or second aspect, the predetermined flicker determination calculation value is a difference between image signals in consecutive frames.

The invention according to claim 4 is a liquid crystal display device comprising a liquid crystal panel and a backlight for irradiating the liquid crystal panel with impulse-type light.
The display area of the liquid crystal panel is divided into a plurality of sub display areas,
The backlight comprises a plurality of light sources corresponding to the plurality of sub display areas,
In each frame period, for each of the sub display areas, a predetermined flicker determination calculation value calculated from the pixel values of the pixels in the sub display area is compared with a predetermined determination value to determine the flicker occurrence level. Determination means for determining;
Determination for determining, for each sub display area, the number of times of light emission of the corresponding light source increases as the flicker generation level increases, according to the flicker generation level for each sub display area determined by the determination unit. Means,
In one frame period, light emission control means for causing the corresponding light source to emit light according to the number of times of light emission for each sub display area determined by the determination means;
With
The predetermined flicker determination calculation value is a difference between image signals in successive frames,
The light emission control unit causes the light source to emit light at a predetermined time interval when the number of times of light emission determined by the determination unit is 2 or more,
The light source includes two substrates disposed to face each other at a predetermined interval, and an excitation source connected to a cathode electrode is connected to a facing surface of one substrate, and an anode electrode is connected to the facing surface of one substrate. A surface light source comprising a phosphor layer,
The electron emission layer is made of carbon nanotubes.

According to the present invention, the display area of the liquid crystal panel is divided into a plurality of sub-display areas, and the backlight includes a plurality of light sources corresponding to the plurality of sub-display areas. A predetermined flicker determination calculated value calculated from the pixel values of the pixels in the sub display area is compared with a predetermined determination value to determine the flicker occurrence level. In accordance with the flicker generation level for each sub-display area determined by the determination unit, the number of times of light emission of the corresponding light source is determined so as to increase as the flicker generation level increases, and the light emission control unit determines in one frame period. The corresponding light source emits light according to the number of times of light emission for each sub display area determined by the determining means.
That is, for each sub display area obtained by dividing the display area of the liquid crystal panel, a flicker occurrence level is determined based on a predetermined flicker determination calculation value and a predetermined determination value, and a light source corresponding to each sub display area However, light is emitted for the number of times of light emission corresponding to the determined flicker occurrence level. Further, the number of times of light emission of the light source within one frame period increases as the flicker generation level in the corresponding sub display area increases, and decreases as the flicker generation level decreases. Therefore, as compared with the case where the display image is simply distinguished into a moving image and a still image and the light emission time of the backlight is variably controlled, more appropriate light emission is possible, and the occurrence of flicker can be further suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The scope of the invention is not limited to the illustrated example.

  As shown in FIG. 1, for example, the liquid crystal display device 100 according to the present embodiment includes a signal input unit 1, a video processing unit 2, a timing control unit 3, a liquid crystal panel 4, a scanning line driving unit 5, and a signal line driving unit 6. A backlight 7, a backlight control unit 8, a frame memory 9, a frame memory 10, a difference calculation unit 11, a control unit 12, and the like are provided.

  The signal input unit 1 includes, for example, an antenna and tuner that receives a television broadcast signal, various video terminals that receive an image signal from an external device, and receives the input image signal to perform video processing. Output to part 2.

  The video processing unit 2 generates an RGB image signal based on the image signal supplied from the signal input unit 1, performs a scaling process according to the number of pixels of the liquid crystal panel 4, and outputs an image signal for one frame. Generate. Further, after various image quality corrections are performed on the image signal for one frame, the image signal is output to the frame memory 9.

  The timing control unit 3 generates a timing signal indicating one line period and a timing signal indicating one frame period based on the image signal supplied from the signal input unit 1, and supplies the timing signal to each unit of the liquid crystal display device 100. .

The liquid crystal panel 4 is, for example, the liquid crystal panel 4 based on the active matrix driving method, and is formed by sealing liquid crystal between a pair of substrates disposed at a predetermined interval. The pair of substrates is sandwiched between two polarizing plates whose polarization axes are orthogonal to each other, and a backlight 7 is disposed on the back side.
On the upper surface of the substrate, p rows of scanning lines X (X _{1 to} X _p ) and q columns of signal lines Y (Y _{1 to} Y _q ) are arranged so as to be orthogonal to each other. At each intersection, pixels provided with thin film transistors (TFTs) as active elements are arranged in a matrix. A pixel electrode is formed in each pixel, and a counter electrode is formed on the opposing substrate so as to face the pixel electrode. An alignment film is formed on the opposing surfaces of the pixel electrode and the counter electrode.

The scanning line driving unit 5 is provided corresponding to each of the scanning lines X (X _{1 to} X _p ) in the liquid crystal panel 4, and sequentially selects each scanning line X according to the timing signal from the timing control unit 3. Thus, the TFTs connected on the same scanning line X are turned on / off.
The signal line driving unit 6 is provided corresponding to each of the signal lines Y (Y _{1 to} Y _q ) in the liquid crystal panel 4, and in synchronization with the scanning of each scanning line X by the scanning line driving unit 5, A voltage corresponding to the image signal input from the processing unit 2 is applied to the signal line Y.
When the scanning line X and the signal line Y are driven by the scanning line driving unit 5 and the signal line driving unit 6, the TFTs of the pixels at the intersections thereof are turned on and charges are accumulated in the pixel electrodes. The alignment direction of the liquid crystal sandwiched between the counter electrode and the counter electrode changes, and the light irradiated from the backlight 7 is allowed to pass or block in units of pixels together with the alignment film and the polarizing plate.

Here, as shown in FIG. 2A, the display area of the liquid crystal panel 4 according to the present embodiment is divided into a matrix of n vertical display areas and m horizontal display areas.
For example, when the liquid crystal panel 4 of the present embodiment is composed of pixels of 768 rows (p rows) × 1024 columns (q columns), a region including pixels of 64 rows × 64 columns is used as a display region as one sub display region. Is divided, the entire display area of the liquid crystal panel 4 is composed of 12 vertical (n) vertical x 16 horizontal (m) sub-display areas.

  The backlight 7 is an impulse type backlight provided on the back side of the liquid crystal panel 4 and capable of emitting pulses in a short period. As shown in FIG. 2B, the backlight 7 is composed of n vertical x m horizontal light sources L corresponding one-to-one to the vertical n × horizontal sub display areas in the liquid crystal panel 4. In response to driving by the backlight control unit 8, each light source L can be made to emit impulse light individually.

Each light source L constituting the backlight 7 is, for example, a surface light source that emits light by irradiating a phosphor with an excitation source such as electrons. As shown in FIG. 3, the two substrates 71 are spaced apart from each other by a predetermined interval. , 72 are arranged opposite to each other in parallel, and an electron emission layer 74 connected to the cathode electrode 73 is formed on the opposite surface of one substrate 71. The electron emission layer 74 is made of, for example, carbon nanotubes (CNT: Carbon Nanotube) having a single-layer structure or a multi-layer structure, and is applied on the substrate 71 via the cathode electrode 73.
Further, a phosphor layer 76 connected to the anode electrode 75 is formed on the opposite surface of the other substrate 72.
In such a backlight 7, when a driving voltage is applied to the cathode electrode 73 and the anode electrode 75, electrons are emitted from the electron emission layer 74 and collide with the phosphor layer 76 to cause the phosphor layer 76 to emit light. .

Further, mercury particles or the like may be enclosed in an electron emission region between the electron emission layer 74 and the phosphor layer 76. Thereby, the electrons emitted from the electron emission layer 74 collide with the mercury particles to generate ultraviolet rays from the mercury particles, and the ultraviolet rays cause the phosphor layer 76 to emit light.
Moreover, you may use ultraviolet LED etc. which light-emit ultraviolet light as an excitation source.

  In the following description, among the display areas of the liquid crystal panel 4, the upper left sub display area is S (1, 1), the upper right sub display area is S (m, 1), and the lower left sub display area is S (1). 1, n), and the lower right sub display area is S (m, n). Further, among the light sources L of the backlight 7 provided corresponding to the respective sub display areas of the liquid crystal panel 4, the upper left light source corresponding to the sub display area S (1, 1) is represented by L (1, 1), The upper right light source corresponding to the sub display area S (m, 1) is L (m, 1), the lower left light source corresponding to the sub display area S (1, n) is L (1, n), and the sub display area S is displayed. The lower right light source corresponding to (m, n) will be described as L (m, n).

  The frame memory 9 accumulates input image signals in units of frames and outputs them to the frame memory 10 and the difference calculation unit 11. The frame memory 10 delays the image signal input from the frame memory 9 by one frame and outputs the delayed image signal to the difference calculation unit 11.

The difference calculation unit 11 is configured by, for example, a subtracter, and is based on image signals input from the frame memory 9 and the frame memory 10 for each of n vertical and m horizontal sub display areas obtained by equally dividing one frame. Then, the difference between the image signals between successive frames is calculated.
For example, when the frame fetched from the frame memory 9 is the current frame and the frame fetched from the frame memory 10 is the previous frame, the difference calculation unit 11 is the same position in the same sub-display area of the current frame and the previous frame. The absolute value of the difference between the pixel values corresponding to each other is obtained. Then, an average value of the absolute difference values of the pixel values is calculated for each sub display area. The difference absolute value between the current frame and the previous frame for each sub display area detected by the difference calculation unit 11 is used as a predetermined flicker determination calculation value C, which will be described later, for determining the flicker occurrence level in the sub display area. .
Note that the predetermined flicker determination calculation value C is arbitrary, and for example, a deviation in luminance level difference between adjacent pixels in the sub display area may be used. Further, for example, statistics of difference values between consecutive frames in a frame within a certain period may be used.

  The control unit 12 includes, for example, a CPU (Central Processing Unit) 121, a RAM (Random Access Memory) 122 used as a work area of the CPU 121, an EEPROM (Electrically Erasable Programmable ROM) capable of rewriting and erasing data, and the like. 123, and a ROM (Read Only Memory) 124 for storing various programs executed by the CPU 121.

  The CPU 121 executes various programs stored in the ROM 124 in accordance with input signals input from the respective units of the liquid crystal display device 100, and outputs output signals to the respective units based on the execution programs. Overall control of the operation of the apparatus 100 is performed.

The reference table 123 stores in advance determination values (for example, determination values J1 and J2) for determining the flicker occurrence level. When the flicker occurrence level is determined in the execution of the determination program 124b described later. Referenced.
FIG. 4 shows an example of the reference table 123. As shown in FIG. 4, the reference table 123 stores determination values J1 and J2 as determination values for determining the occurrence level of flicker, and predetermined flicker determination calculation values calculated by the difference calculation unit 11 are stored. By comparing with C, the flicker occurrence level is determined in three stages. For example, in the reference table 123 of FIG. 4, when the predetermined flicker determination calculation value C is equal to or greater than the determination value J2, the flicker occurrence level is determined to be “1 (low)”, and the determination value J1 is equal to or greater than the determination value J2. If it is less than the threshold value, the flicker occurrence level is determined to be “2 (medium)”, and if it is less than the determination value J1, the flicker occurrence level is determined to be “3 (high)”.
Here, the flicker occurrence level “1” indicates an image having the largest moving image area, that is, an image having a low flicker occurrence frequency, and the flicker occurrence level “3” indicates an image having the most still area, that is, occurrence of flicker. A frequently-used image is shown. Further, the flicker occurrence level “2” indicates an image with a moderate flicker occurrence frequency.

Further, the reference table 123 stores the number N of times of light emission of the light source L corresponding to each flicker occurrence level 1 to 3, and the number of times of light emission N according to the determined flicker occurrence level in the execution of the determination program 124c described later. Referenced when determining.
According to the reference table 123 of FIG. 4, when the flicker occurrence level determined in the execution of the determination program 124b is “1”, the number of times of light emission N is determined as “1”, and the flicker occurrence level is “2”. ”Is determined to be“ 2 times ”, and when the flicker occurrence level is“ 3 ”, the number of times N is determined to be“ 3 ”.
As described above, the number of times of light emission N associated with the flicker occurrence level increases as the flicker occurrence level increases.

  The ROM 124 stores a calculation program 124a, a determination program 124b, a determination program 124c, a light emission control program 124d, and the like in a program storage area.

The calculation program 124a is, for example, a program for causing the CPU 121 to realize a function of calculating a predetermined flicker determination calculation value C from the pixel value of the pixel in the sub display area for each sub display area.
Specifically, for each of the sub display areas, the CPU 121 determines the current frame image signal input from the frame memory 9 and the previous frame that is the previous frame image signal input from the frame memory 10. The absolute value of the difference from the image signal is calculated.
For example, when the display area of the liquid crystal panel 4 is composed of vertical (n) × 16 horizontal (m) sub-display areas, the current frame is displayed for each of the 192 sub-display areas. The difference absolute value of the image signal between the previous frame and the previous frame is calculated. This absolute difference value is used as a predetermined flicker determination calculation value C to determine the flicker occurrence level.

For example, the determination program 124b compares the CPU 121 with a predetermined flicker determination calculation value C calculated from the pixel values of the pixels in the sub display area for each sub display area, and a predetermined determination value. This is a program for realizing a function of determining a flicker occurrence level.
Specifically, the CPU 121 calculates the predetermined flicker determination calculation value C (the absolute difference between the image signals of the current frame and the previous frame) by executing the calculation program 124a. The flicker determination calculation value C is compared with the determination values J1 and J2 stored in the reference table 123 to determine the flicker occurrence level.
As described above, for example, when the absolute value of the difference between the image signals of the current frame and the previous frame is equal to or greater than the determination value J2, the flicker occurrence level is “1”, that is, the area where the moving image area is large and flicker is not conspicuous. It is determined that there is. Further, for example, when the absolute value of the difference between the image signals of the current frame and the previous frame is less than the determination value J1, it is determined that the flicker occurrence level is “3”, that is, the area where there are many still areas and the flicker is conspicuous. The
The CPU 121 functions as a determination unit by executing the determination program 124b.

The determination program 124c, for example, causes the CPU 121 to set the flicker occurrence number N of the corresponding light source L according to the flicker occurrence level for each sub display area determined by the execution of the determination program 124b for each sub display area. This is a program for realizing a function of determining an increase as the generation level increases.
Specifically, when the occurrence level of flicker is determined by executing the determination program 124b, the CPU 121 reads the number of times of light emission N associated with the determined flicker occurrence level from the reference table 123, and handles this. This is determined as the number N of light emission of the light source L to be performed.
For example, when the flicker generation level is “1”, the number of times of light emission N of the corresponding light source L is determined to be “1”. Further, for example, when the flicker occurrence level is “3”, the number of times of light emission N of the corresponding light source L is determined to be “3 times”.
The CPU 121 functions as a determination unit by executing the determination program 124c.

The light emission control program 124d is a program for causing the CPU 121 to realize a function of causing the corresponding light source L to emit light in accordance with the number of times of light emission N for each sub display area determined by executing the determination program 124c in one frame period. is there.
The CPU 121 functions as a light emission control unit together with the backlight control unit 8 by executing the light emission control program 124d.

  Here, the light emission control processing of the light source L by the light emission control program 124d will be described more specifically.

When the light emission number N of the light source L corresponding to the sub display area is determined, the CPU 121 determines the light emission amount of the light source L according to the determined light emission number N.
The light emission amount of the light source L is adjusted according to the number of times of light emission N so that the luminance level according to the image signal is obtained over the entire period T by the time integration effect. For example, when it is determined that the light emission number N of the light source L is “3 times”, the light emission amount per light emission of the light source L is 1 / of the case where the light emission number N is “1”. The light emission amount is 3.

When the CPU 121 determines the number of times N and the amount of light emission of the light source L according to the flicker occurrence level, the image signal is sent to each sub display area in the liquid crystal panel 4 by driving the scanning line driving unit 5 and the signal line driving unit 6. And the light source L corresponding to each sub-display area in the backlight 7 is caused to emit light with the determined light emission amount for the determined number of times N.
As a result, the light source L corresponding to each sub display area emits light at the most effective number of times N for suppressing flicker according to the ease of occurrence of flicker obtained from the image signal of each sub display area. It becomes.

In the present embodiment, it is assumed that the light emission time t of the light source L (that is, the light emission time t ₁ per light emission and the total light emission time t2 at each light emission number N) is determined in advance. This light emission time t is shorter than the period T required for displaying an image in one sub-display area, and both flicker and motion blur are taken into account in consideration of power consumption, member life, device differences, and the like. Is set to be an optimum value for reducing.
For example, when the time required for accumulating charges corresponding to the image signal to the pixels in the sub-display area in the period T (loading time of image data) is Td and the response time of the liquid crystal is Ts, The light emission time t of L is set in the range of 0 <t <T− (Td + Ts).
In consideration of the visual characteristics of the user, the flicker and the motion blur may be set to a value that can preferentially reduce flicker that has a large influence on the image quality.

Here, with reference to FIG. 5, the timing of image loading, liquid crystal response, and light source emission in the period T for displaying an image in one sub display area will be described.
For example, when the flicker occurrence level “1” and the light emission number N “1” of the light source L are determined for the sub display area S (1, 1), the CPU 121 determines the timing as shown in FIG. In accordance with the timing signal from the control unit 3, the scanning line X and the signal line corresponding to the pixel in the sub display area S (1,1) are scanned by the scanning line driving unit 5 and the signal line driving unit 6 at the load time Td of the image data. A voltage corresponding to the image signal is applied to Y to set the image signal from the frame memory 9 to the pixel in the sub display area S (1, 1).
Then, in the liquid crystal response time Ts, the liquid crystal of the pixels in the sub display area S (1, 1) changes the alignment direction.
Next, the CPU 121 sets the light source L corresponding to the sub display area S (1, 1) according to the timing signal indicating the stable timing of the liquid crystal in the sub display area S (1, 1) sent from the timing signal. once the determined light emission amount is emitted, the light source L is turned off when the light emission time t ₁ has elapsed.

For example, when the flicker occurrence level “3” and the light emission number N “3 times” of the light source L are determined for the sub display area S (n, m), the CPU 121, as shown in FIG. In accordance with the timing signal from the timing control unit 3, the scanning line X and the scanning line X corresponding to the pixels in the sub display area S (n, m) are loaded by the scanning line driving unit 5 and the signal line driving unit 6 at the load time Td of the image data. A voltage corresponding to the image signal is applied to the signal line Y, and the image signal from the frame memory 9 is set to the pixel of the sub display area S (n, m).
Then, in the liquid crystal response time Ts, the liquid crystal of the pixels in the sub display area S (n, m) changes the alignment direction.
Next, the CPU 121 sets the light source L corresponding to the sub display area (n, m) to 1 according to the timing signal indicating the stable timing of the liquid crystal in the sub display area S (n, m) sent from the timing signal. between t ₁ per time, light is emitted at the determined light emission amount, the light emission at a predetermined time interval, repeated intermittently 3 times. Further, the third light emission time t ₁ has elapsed the emission, the total emission time turns off the light source L when the t _2.

  As a result, in the sub display area S (1, 1) where flicker is not noticeable, it is not necessary to increase the number of times of light emission of the light source, and control becomes easy. In addition, in the sub display area S (n, m) where flicker is conspicuous, the number of times of light emission can be increased to cause the light source L to emit light intermittently, and flicker can be more effectively suppressed.

  The CPU 121 performs the above-described processing in 12 frame (n) × 16 (m) sub display regions S (1, 1) to S (n, n) included in the display region of the liquid crystal panel 4 within one frame period. for each of m). Therefore, the light source L of each sub display area emits light an optimum number of times, and an image for one screen with reduced flicker is displayed on the liquid crystal panel 4 in units of sub display areas.

  Note that the order of scanning and the order in which the light sources L emit light are arbitrary, and are not limited to the method of sequentially performing scanning and light emission for each sub-display area. For example, a plurality of sub display areas (for example, S (1, 1) to S (m, 1)) arranged in the horizontal direction are scanned, and the corresponding light sources L (for example, L (1, 1) to L (m) are scanned. 1)) may be used at the same time, or all light sources L may be simultaneously emitted after scanning of the entire screen is completed.

  Next, the flow of the flicker occurrence level and the flow of the image display process based on the determined flicker occurrence level will be described with reference to the flowchart of FIG.

First, in step S1, an absolute difference value of image signals of consecutive frames (for example, the current frame and the previous frame) is calculated as a predetermined flicker determination calculation value C for one sub display area. Next, in step S2, the calculated predetermined flicker determination calculated value C is compared with the determination values J1 and J2 read from the reference table 123 to determine the flicker occurrence level in the sub display area. Further, in step S3, the number N of times of light emission and the light emission amount of the light source L corresponding to the sub display area are determined according to the determined flicker occurrence level.
In step S <b> 4, the scanning line driving unit 5 and the signal line driving unit 6 load the corresponding scanning line X and signal line Y onto the pixels in the sub display area with image data. Then, in step S5, the liquid crystal of the pixel in the sub display area responds according to the loaded image data.
When the liquid crystal responds, in step S6, the light source L corresponding to the sub display area is caused to emit light according to the determined number of times of light emission N and the amount of light emission, and this processing is terminated.

According to the liquid crystal display device 100 in the present embodiment described above, the display area of the liquid crystal panel 4 is divided into a plurality of sub display areas, and the backlight 7 includes a plurality of light sources L corresponding to the plurality of sub display areas. The predetermined flicker determination calculation value C calculated from the pixel value of the pixel in the sub display area is compared with the predetermined determination values J1 and J2 for each sub display area by the determination means (determination program 124b). The flicker occurrence level is determined, and the determination unit (determination program 124c) determines the flicker generation level for each sub display area and the sub display area determined by the determination unit (determination program 124b). The number of times of light emission N of the corresponding light source L is determined and determined by the light emission control means (light emission control program 124d) in one frame period. Accordance with the light emission number N of the sub-display for each area determined by the (determination program 124c), the corresponding light source L is emitted.
That is, for each sub display area obtained by dividing the display area of the liquid crystal panel 4, the flicker occurrence level is determined based on a predetermined flicker determination calculation value C and a predetermined determination value, and each sub display area corresponds to each sub display area. The light source L that emits light is emitted for the number N of times of light emission corresponding to the determined flicker generation level. Further, the number N of light emission times of the light source L within one frame period increases as the flicker generation level in the corresponding sub display area increases, and decreases as the flicker generation level decreases. Therefore, as compared with the case where the display image is simply distinguished into a moving image and a still image and the light emission time of the backlight 7 is variably controlled, appropriate light emission is possible, and the occurrence of flicker can be further suppressed.

That is, the light source corresponding to the sub display area where flicker is conspicuous can be emitted intermittently by increasing the number of times of light emission, while the light source corresponding to the sub display area where flicker is not conspicuous is emitted without increasing the number of times of light emission. Flicker can be more effectively and efficiently suppressed.
In addition, since flicker can be reduced in units of sub display areas, flicker on the entire screen is further reduced.

  Further, when the number of times of light emission N determined by the determining means (decision program 124c) is 2 or more by the light emission control means (light emission control program 124d, backlight control unit 8), the light source L is emitted at predetermined time intervals. The Therefore, the light source L corresponding to the sub display area where flicker is conspicuous emits light intermittently, and flicker can be more effectively suppressed.

  Further, since the predetermined flicker determination calculation value C is a difference between image signals in consecutive frames, a value for determining the flicker occurrence level can be calculated by a simple method.

Further, the light source L includes two substrates 71 and 72 arranged to face each other at a predetermined interval, and an electron emission layer 74 connected to the cathode electrode 73 is provided on the opposite surface of the one substrate 71. 72 is a surface light source provided with a phosphor layer 76 connected to an anode electrode 75 on the opposite surface of 72, and the electron emission layer 74 is made of carbon nanotubes.
Therefore, more uniform light can be irradiated toward the display area. In addition, since carbon nanotubes are easy to emit in a field, power can be reduced.

  The scope of the present invention is not limited to the above embodiment, and various improvements and design changes may be made without departing from the spirit of the present invention.

For example, the division method of the sub display area is arbitrary, and may not be equally divided.
Further, the flicker occurrence level may be determined more finely. Conversely, binary determination for determining whether flicker occurs or not may be used.
In the above-described embodiment, an electron emission type backlight is used as the backlight. In addition, an organic EL, LED (Light Emitting Diode), CCFL (Cold Cathode Fluorescent Lamp), EEFL (Hot Cathode) are used. A tube (external electrode fluorescent lamp) or the like may be used. Further, the backlight is not limited to the direct type, but may be a side edge type.
Also, any method can be used as a method for determining the flicker occurrence level. For example, the temporal fluctuation of the luminance level may be measured by a measuring device such as an optical sensor provided on the liquid crystal panel side, and the flicker occurrence level may be determined using this as a predetermined flicker determination calculation value.
In the above embodiment, the light emission time of the light source is set in advance, and the case where a desired luminance is obtained by adjusting the light emission amount according to the number of times of light emission has been described. However, the light emission time is variable for each frame period. It may be adjusted. In this case, the light emission amount may be fixed or variable for each frame period.

It is a block diagram which illustrates the principal part structure of the liquid crystal display device in this embodiment. FIG. 2A is a diagram for explaining sub display areas constituting the display area of the liquid crystal panel, and FIG. 2B is a diagram for explaining light sources provided corresponding to the sub display areas. . It is side surface sectional drawing of a light source. It is a figure which illustrates a reference table. It is a figure explaining the timing of the image load in the period required for the image display of 1 sub display area, a liquid crystal response, and light source light emission. FIG. 6 is a diagram for explaining a flow of image display processing based on determination of flicker occurrence level and the determined flicker occurrence level.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Liquid crystal display device 4 Liquid crystal panel 7 Backlight 71, 72 Substrate 73 Cathode electrode 74 Electron emission layer 75 Anode electrode 76 Phosphor layer 121 CPU (determination means, determination means, light emission control means)
124a determination program (determination means)
124b Determination program (determination means)
124c Light emission control program (light emission control means)
L Light source N Number of flashes

Claims (4)

In a liquid crystal display device comprising a liquid crystal panel and a backlight that irradiates the liquid crystal panel with impulse-type light,
The display area of the liquid crystal panel is divided into a plurality of sub display areas,
The backlight comprises a plurality of light sources corresponding to the plurality of sub display areas,
A determination unit that determines a flicker occurrence level by comparing a predetermined flicker determination calculation value calculated from a pixel value of a pixel in the sub display region with a predetermined determination value for each sub display region; ,
Determination for determining, for each sub display area, the number of times of light emission of the corresponding light source increases as the flicker generation level increases, according to the flicker generation level for each sub display area determined by the determination unit. Means,
In one frame period, light emission control means for causing the corresponding light source to emit light according to the number of times of light emission for each sub display area determined by the determination means;
A liquid crystal display device comprising:   The liquid crystal display device according to claim 1, wherein the light emission control unit causes the light source to emit light at a predetermined time interval when the number of times of light emission determined by the determination unit is 2 or more.   The liquid crystal display device according to claim 1, wherein the predetermined flicker determination calculation value is a difference between image signals in consecutive frames. In a liquid crystal display device comprising a liquid crystal panel and a backlight that irradiates the liquid crystal panel with impulse-type light,
The display area of the liquid crystal panel is divided into a plurality of sub display areas,
The backlight comprises a plurality of light sources corresponding to the plurality of sub display areas,
In each frame period, for each of the sub display areas, a predetermined flicker determination calculation value calculated from the pixel values of the pixels in the sub display area is compared with a predetermined determination value to determine the flicker occurrence level. Determination means for determining;
Determination for determining, for each sub display area, the number of times of light emission of the corresponding light source increases as the flicker generation level increases, according to the flicker generation level for each sub display area determined by the determination unit. Means,
In one frame period, light emission control means for causing the corresponding light source to emit light according to the number of times of light emission for each sub display area determined by the determination means;
With
The predetermined flicker determination calculation value is a difference between image signals in successive frames,
The light emission control unit causes the light source to emit light at a predetermined time interval when the number of times of light emission determined by the determination unit is 2 or more,
The light source includes two substrates disposed to face each other at a predetermined interval, and an excitation source connected to a cathode electrode is connected to a facing surface of one substrate, and an anode electrode is connected to the facing surface of one substrate. A surface light source comprising a phosphor layer,
The liquid crystal display device, wherein the electron emission layer is made of carbon nanotubes.

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