JP5679192B2 - Liquid crystal panel drive device and liquid crystal display device using the same - Google Patents

Description

  The present invention relates to a liquid crystal panel driving device that drives a liquid crystal panel based on image data and displays an image corresponding to the image data on a display screen of the liquid crystal panel, and a liquid crystal display device using the same.

  Conventionally, for example, a liquid crystal display device disclosed in Patent Document 1 is known. In this liquid crystal display device, in order to prevent uneven brightness of the display screen due to uneven brightness of a plurality of light sources such as LEDs constituting a backlight of the liquid crystal panel, brightness adjustment regarding brightness variations of the plurality of light sources is performed. Data is stored in advance, and the image data of the illumination area of each light source is corrected based on the brightness adjustment data. Further, when an image that is difficult to notice brightness unevenness such as a moving image is displayed, the image data is not corrected, so that the deterioration of the image quality due to the correction of the image data can be suppressed as much as possible.

JP 2010-097102 A

  By the way, although the brightness unevenness of the backlight or the liquid crystal panel defect as described above may cause the brightness unevenness on the display screen of the liquid crystal panel, the video signal is interrupted when the image is switched. When black (minimum luminance) display is made on the entire display screen, the brightness unevenness in the display screen becomes conspicuous. The liquid crystal panel used in normally black (NB) by the VA (Vertical Alignment) or IPS (In-Place-Switching) drive system displays black on the entire display screen only when the black luminance is lower (black). In particular, the uneven brightness is noticeable.

  In the conventional liquid crystal display device described above, unevenness in brightness of the display screen that may occur when black (minimum luminance) display is performed on the entire display screen of the liquid crystal panel is not particularly considered, and the display is effectively performed. The brightness unevenness on the screen cannot be made inconspicuous.

  The present invention has been made in view of such circumstances, and a liquid crystal panel driving device capable of making brightness unevenness less noticeable when black (minimum luminance) is displayed on the entire display screen of the liquid crystal panel. And a liquid crystal display device using the same.

The liquid crystal panel driving device according to the present invention controls the driving voltage of the liquid crystal panel based on image data representing the luminance of each part of the image, and displays an image having a luminance distribution according to the image data on the display screen of the liquid crystal panel. In the liquid crystal panel driving device, when the image data represents the lowest luminance corresponding to black in the entire display screen of the liquid crystal panel, the all black detection signal is output by the all black detector to represent the lowest luminance black. Driving voltage for correcting the driving voltage of the liquid crystal panel based on the image data so that the luminance is uniformly increased by a predetermined amount in the entire display screen of the liquid crystal panel by switching from the image data based on the image data to the corrected image data A configuration having correction means is provided.

  With such a configuration, when the liquid crystal panel is driven on the basis of image data representing the minimum luminance corresponding to black in the entire display screen of the liquid crystal panel, the driving voltage for the liquid crystal panel is such that the luminance in the entire display screen is high. Since the correction is performed so as to increase uniformly by a predetermined amount, black display is performed in a state where the brightness of the entire display screen is higher than the brightness at the minimum luminance.

In the liquid crystal panel drive device according to the present invention, the drive voltage correction means converts the image data representing the minimum luminance over the entire display screen of the liquid crystal panel into corrected image data representing a predetermined luminance higher than the minimum luminance. It can be set as the structure which has a data conversion means.

With this configuration, when attempting to drive the liquid crystal panel based on the image data representing the lowest luminance corresponding to black in the entire display screen of the liquid crystal panel, correction in which the image data represents a predetermined high luminance than the lowest luminance Since it is converted into image data, the drive voltage controlled based on the converted image data can be corrected so that the luminance is uniformly increased by a predetermined amount over the entire display screen.

  In the liquid crystal panel drive device according to the present invention, the drive voltage obtained by the correction by the drive voltage correction means can be variable.

  With such a configuration, since the drive voltage obtained by the correction is variable, the luminance that can be uniformly increased over the entire display screen of the liquid crystal panel can be made variable. As a result, by varying the drive voltage obtained by the correction according to the degree of unevenness of the display screen brightness, various degrees of unevenness of the display screen brightness can be made conspicuous.

  Furthermore, in the liquid crystal panel drive device according to the present invention, the liquid crystal panel may be a normally black liquid crystal panel that turns black when a drive voltage based on image data is not applied.

  With such a configuration, in a normally black (NB) liquid crystal panel in which the brightness of black is lower (black) and the unevenness of brightness is particularly noticeable when black display is performed on the entire display screen, the brightness of the display screen The unevenness of the thickness can be made inconspicuous.

  Further, in the liquid crystal panel driving device according to the present invention, when the image data represents the lowest luminance corresponding to black on the entire display screen of the liquid crystal panel, the backlight is irradiated with light from behind the liquid crystal panel. It can be set as the structure which has a backlight control means to reduce quantity.

  With such a configuration, the amount of light emitted from the backlight is reduced, and the brightness of the entire display screen is reduced. Therefore, the amount of increase in brightness that is uniformly increased on the entire display screen of the liquid crystal panel is relatively reduced. However, unevenness in brightness of the display screen can be made inconspicuous.

  The liquid crystal display device according to the present invention includes a liquid crystal panel, or a liquid crystal panel and a backlight that emits light from behind the liquid crystal panel, and any of the liquid crystal panel driving devices described above.

  According to the liquid crystal panel driving device of the present invention, when the liquid crystal panel is driven based on the image data representing the minimum luminance corresponding to black in the entire display screen of the liquid crystal panel, the driving voltage for the liquid crystal panel is By correcting the brightness of the entire display screen so that the brightness is uniformly increased by a predetermined amount, black display is performed with the brightness of the entire display screen increased from the brightness at the minimum brightness. As a whole, unevenness in brightness when displaying black (minimum luminance) can be made inconspicuous.

  Further, according to the liquid crystal display device using the liquid crystal panel driving device, black display can be performed in a state in which the unevenness in brightness of the display screen of the liquid crystal panel is less noticeable.

1 is a block diagram illustrating a liquid crystal display device according to an embodiment of the present invention. It is a figure which shows correction | amendment RGB image data. It is a figure which shows an example in the state which the brightness nonuniformity generate | occur | produced on the display screen of a liquid crystal panel. It is a figure which shows an example of the state which raised the brightness | luminance of the whole display screen of a liquid crystal panel. It is a figure which shows an example of the state which raised the brightness | luminance of the whole display screen of a liquid crystal panel, and reduced the light quantity of the backlight.

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

  A liquid crystal display device according to an embodiment of the present invention is configured as shown in FIG.

  In FIG. 1, the liquid crystal display device 100 includes a control unit 10, a liquid crystal panel drive unit 20 (liquid crystal panel drive device), a liquid crystal panel 30, a backlight 40, a backlight drive circuit 50, and an operation unit 60. The liquid crystal panel driving unit 20 is controlled by the control unit 10 to have a predetermined format (for example, a video source 110 (for example, a video playback device such as a DVD playback device or a video information receiving device such as a TV receiver)) input from a video source 110. MPEG) image data is converted into RGB image data representing the luminance (also referred to as gradation and density) of each color component (R (red), G (green), B (blue)) for each pixel, and the RGB image data The drive voltage of the liquid crystal panel 30 is controlled based on the above, and each color component (R (red), G (green), B (blue)) of each pixel is displayed on the display screen of the liquid crystal panel 30 according to the RGB image data. Display an image with brightness. The backlight 40 disposed behind the liquid crystal panel 30 emits light with a light amount corresponding to the drive voltage from the backlight drive circuit 50 controlled by the control unit 10, and irradiates the liquid crystal panel 30 with light from behind. To do. The liquid crystal panel 30 is a normally black (NB) liquid crystal panel, and displays black (minimum luminance: lowest gradation, maximum density) when a drive voltage based on RGB image data is not applied. The control unit 10 controls the liquid crystal panel drive unit 20 and the backlight drive circuit 50 based on the operation input from the operation unit 60.

  The liquid crystal panel drive unit 20 includes an RGB image data generation circuit 21, a frame memory 22, an image data conversion unit 23 (drive voltage correction means: image data conversion means), a drive circuit 24, and a selector 25. The RGB image data generation circuit 21 converts image data in a predetermined format from the video source 110 into RGB image data representing the luminance of each color component (R (red), G (green), B (blue)) for each pixel. . In the frame memory 22, RGB image data for one frame is set. The drive circuit 24 should be applied to the liquid crystal panel 30 based on one frame of RGB image data from the frame memory 22 or one frame of corrected RBG image data obtained by the image data converter 23 as will be described later. Control drive voltage. Thereby, an image in which each color component (R (red), G (green), B (blue)) of each pixel has a luminance corresponding to the RGB image data or the corrected RGB image data on the display screen of the liquid crystal panel 30. Is displayed.

  The image data converter 23 includes a switch 231, three correction frame memories 232 a, 232 b, 232 c, and an all black detector 233. The all-black detector 233 outputs an all-black detection signal when the RBG image data for all pixels in one frame set in the frame memory 22 represents black with the lowest luminance. When the RBG image data of each pixel is expressed by 18 bits in total with 6 bits (64 gradation representations) assigned to each of R, G, and B, for example, as shown in FIG. For all of the pixels, if all 18 bits of the RGB image data are “0” (representing the lowest luminance), the all-black detector 233 outputs an all-black detection signal. Each of the three correction frame memories 232a, 232b, and 232c stores correction RGB image data for one frame representing a luminance uniformly higher than the minimum luminance for each pixel. As described above, when the RGB image data of each pixel is represented by all 18 bits, for example, as shown in FIG. 2B, each 6 bits of R, G, and B of each pixel is represented by “000001”. Then, the corrected frame memory 232a stores the first corrected RGB image data for one frame representing a luminance that is approximately 2% higher than the lowest luminance “000000”. Further, as shown in FIG. 2C, the 6 bits of R, G, and B of each pixel are represented by “000010”, and the first frame for one frame representing a luminance that is about 3% higher than the lowest luminance “000000”. 2 corrected RGB image data is stored in the corrected frame memory 232b. Further, as shown in FIG. 2D, each of the 6 bits of R, G, and B of each pixel is represented by “000011”, and the minimum luminance “000000”. The third corrected RGB image data for one frame representing a luminance 5% higher than “is stored in the corrected frame 232c. Any one of the three correction frame memories 232a, 232b, and 232c is selected as valid by the selector 25 controlled by the control unit 10.

  The switch 231 is set in any one of the three correction frame memories 232a, 232b, and 232c selected by the RGB image data set in the frame memory 22 and the selector 25 in accordance with the output from the all black detector 233. Any of the corrected RGB image data is supplied to the drive circuit 24. Specifically, normally, when the RGB image data set in the frame memory 22 is supplied to the drive circuit 24 and an all black detection signal is output from the all black detector 233, the switch 231 is sent to the drive circuit 24. The supplied RGB image data is switched to corrected RGB image data set in any of the three correction frame memories 232a, 232b, and 232c.

  The liquid crystal display device 100 configured as described above operates as follows.

  Usually, image data from the video source 110 is converted into RGB image data for each pixel by the RGB image data generation unit 21, and the RGB image data is set in the frame memory 22 for each frame. Then, the drive circuit 24 performs drive control of the liquid crystal panel 30 illuminated from behind by the backlight 40 based on the RGB image data for one frame, so that each color of each pixel is displayed on the display screen of the liquid crystal panel 30. An image is displayed in which the components (R (red), G (green), B (blue)) have a luminance corresponding to the RGB image data.

  By the way, when the image is switched or when substantial image data (video signal) from the video source 110 is interrupted, the RGB image data set in the frame memory 22 has the lowest luminance (for all pixels). (For example, as shown in FIG. 2A, all the 18 bits are “0” for each pixel). In this case, normally, a drive voltage based on RGB image data is not applied to the liquid crystal panel 30 (a substantially zero drive voltage is applied), and the normally black liquid crystal panel 30 has its display screen. As a whole, a black display with the lowest luminance is obtained. However, for example, as shown in FIG. 3, if there is a portion Ed that cannot be completely black due to a partial defect or the like on the display screen 30a, the portion Ed that cannot be completely black is displayed on the display screen 30a. It may be noticeable as luminance unevenness.

  Therefore, in the liquid crystal display device 100 according to the present embodiment, when the RGB image data representing the minimum luminance (black) is set for all the pixels in the frame memory 22, the all black detector 233 outputs the all black detection signal. Based on the all black detection signal, the switch 231 is set in the three correction frame memories 232a, 232b, and 232c in place of the RGB image data (see FIG. 2A) set in the frame memory 22. Any one selected from the first corrected RGB image data (see FIG. 2B), the second corrected RGB image data (see FIG. 2C), and the third corrected RGB image data (see FIG. 2D). Is supplied to the drive circuit 24. As a result, a driving voltage corresponding to any one selected from the first corrected RGB image data, the second corrected RGB image data, and the third corrected RGB image data is applied to the liquid crystal panel 30, and the display screen 30a of the liquid crystal panel 30 is applied. Displays an image having a luminance distribution according to the corrected RGB image data. For example, when a driving voltage corresponding to the first corrected RGB image data as shown in FIG. 2B is applied to the liquid crystal panel 30, the luminance uniformly increases by about 2% in the entire display screen 30a. When a driving voltage corresponding to the second corrected RGB image data as shown in 2 (c) is applied to the liquid crystal panel 30, the luminance increases uniformly by about 3% in the entire display screen 30a, and FIG. When a driving voltage corresponding to the third corrected RGB image data as shown in (d) is applied to the liquid crystal panel 30, the luminance is increased uniformly by about 5% in the entire display screen 30a.

  Thus, when driving the liquid crystal panel 30 based on RGB image data representing the minimum luminance corresponding to black in the entire display screen 30a of the liquid crystal panel 30, instead of the RGB image data representing the minimum luminance, By applying the corrected RGB image data (first corrected RGB image data, second corrected RGB image data, third corrected RGB image data) to the liquid crystal panel 30, the luminance is uniformly increased by a predetermined amount on the entire display screen 30a. Thus, black display is performed in a state where the brightness of the entire display screen 30a is higher than the brightness at the minimum luminance. Thereby, for example, as shown in FIG. 4, the contrast between the black portion and the portion Ed that cannot be completely black on the display screen 30a is reduced, and the portion Ed that cannot be completely black is displayed on the display screen 30a. It can be made inconspicuous as luminance unevenness.

  In the liquid crystal display device 100, the correction frame memory selected as valid by the selector 25 controlled by the control unit 10 can be changed by a predetermined operation input from the operation unit 60. As a result, the corrected RGB image data supplied to the drive circuit 24 in place of the RGB image data representing the minimum luminance becomes variable (the first corrected RGB image data, the second corrected RGB image data, and the third corrected RGB image data). either). As described above, since the driving voltage for the liquid crystal panel 30 based on the corrected RGB image data is variable, the luminance that can be uniformly increased over the entire display screen 30a of the liquid crystal panel 30 can be made variable. As a result, by changing the corrected RGB image data (drive voltage) to be selected according to the degree of brightness unevenness of the display screen 30a, various degrees of unevenness of the display screen 30a can be made inconspicuous. It becomes like this.

  For example, in FIG. 3, the first corrected RGB image data (2%), the second corrected RGB image data (3%), and the third corrected RGB image data (2%) as the contrast between the black portion and the portion Ed that is not completely black becomes larger. The corrected RGB image data (corrected frame memories 232a, 232b, 232c) can be selected in the order of corrected image data (5%).

  Furthermore, the contrast between the black portion and the portion Ed that does not become completely black is relatively large. For example, the entire display screen 30a of the liquid crystal panel 30 using the third corrected RGB image data is uniformly about 5% (maximum level). When the portion Ed that does not become black even when the brightness is increased is conspicuous, the operation unit 60 can be operated to reduce the light irradiation amount of the backlight 40. In this case, for example, as shown in FIG. 5, the brightness of the entire display screen 30a of the liquid crystal panel 30 is reduced, and the brightness is uniformly increased throughout the entire display screen 30a. The non-exposed portion Ed can be made inconspicuous as uneven brightness.

  In the above-described liquid crystal display device 100 (liquid crystal panel drive unit 20), the corrected RGB image data is stored in advance in the correction frame memories 232a, 232b, and 232c, but the minimum luminance (black color) for all pixels. The corrected RGB image data may be generated every time the RGB image data representing) is set in the frame memory 22. In addition, by using the corrected RGB image data, the drive voltage of the liquid crystal panel 30 is corrected so that the luminance is uniformly increased over the entire display screen 30a of the liquid crystal panel 30, but the corrected image RGB data is used. For example, the driving voltage can be corrected by applying a predetermined bias voltage to the liquid crystal panel 30, for example.

  The liquid crystal panel driving device and the liquid crystal display device using the same according to the present invention can make the unevenness of brightness more inconspicuous when black (minimum luminance) is displayed on the entire display screen of the liquid crystal panel. It is useful as a liquid crystal panel driving device that drives a liquid crystal panel based on image data and displays an image corresponding to the image data on a display screen of the liquid crystal panel, and a liquid crystal display device using the same.

10 Control Unit 20 Liquid Crystal Panel Drive Unit (Liquid Crystal Panel Drive Device)
21 RGB image data generation circuit 22 Frame memory 23 Image data conversion unit (drive voltage correction means)
231 switching unit 232a, 232b, 232c correction frame memory 233 full black detector 24 drive circuit 25 selector 30 liquid crystal panel 40 backlight 50 backlight drive circuit 60 operation unit

Claims (7)

A liquid crystal panel driving device that controls a driving voltage of a liquid crystal panel based on image data representing luminance of each part of an image, and displays an image having a luminance distribution according to the image data on a display screen of the liquid crystal panel,
When the image data represents the minimum brightness corresponding to black in the entire display screen of the liquid crystal panel, the corrected image data is corrected from the image data based on the output of the all black detection signal representing the minimum brightness black by the all black detector. A liquid crystal panel drive device having drive voltage correction means for correcting the drive voltage of the liquid crystal panel based on the image data so that the brightness is uniformly increased by a predetermined amount over the entire display screen of the liquid crystal panel by switching to . The said drive voltage correction means has an image data conversion means which converts the image data showing the said minimum brightness | luminance in the whole display screen of the said liquid crystal panel into the correction image data showing the predetermined brightness | luminance higher than the said minimum brightness | luminance. Liquid crystal panel drive device.   3. The liquid crystal panel driving device according to claim 1, wherein the driving voltage obtained by correction by the driving voltage correcting means is variable.   4. The liquid crystal panel drive device according to claim 1, wherein the liquid crystal panel is a normally black liquid crystal panel that becomes black when a drive voltage based on image data is not applied. 5.   The backlight control means which reduces the irradiation amount of the light of the backlight which irradiates light from the back of the said liquid crystal panel, when the said image data represents the minimum brightness | luminance corresponding to black in the whole display screen of the said liquid crystal panel. 5. A liquid crystal panel driving device according to any one of 1 to 4.   A liquid crystal display device comprising a liquid crystal panel and the liquid crystal panel driving device according to claim 1.   A liquid crystal display device comprising: a liquid crystal panel; a backlight that emits light from behind the liquid crystal panel; and the liquid crystal panel driving device according to claim 5.

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