WO2013058260A1

WO2013058260A1 - Display device

Info

Publication number: WO2013058260A1
Application number: PCT/JP2012/076775
Authority: WO
Inventors: 山川亮
Original assignee: シャープ株式会社
Priority date: 2011-10-18
Filing date: 2012-10-17
Publication date: 2013-04-25

Abstract

A liquid crystal display device (display device) (1), which is provided with a backlight device (backlight) (3) and a liquid crystal panel (display) (2), wherein a gradation voltage instruction unit (25) is provided to a control unit (16). Based on a temperature distribution when light-emitting diodes (light source) (4) of the backlight device (3) are lit up, the gradation voltage instruction unit (25) determines, for each of a plurality of display areas, a correction value for a gradation value for each pixel contained in an inputted video signal, and drives and controls the liquid crystal panel (2).

Description

Display device

The present invention relates to a display device, particularly a non-light-emitting display device such as a liquid crystal display device.

In recent years, for example, liquid crystal display devices have been widely used in liquid crystal televisions, monitors, mobile phones and the like as flat panel displays having features such as thinness and light weight compared to conventional cathode ray tubes. Such a liquid crystal display device includes a backlight device that emits light, and a liquid crystal panel that displays a desired image by acting as a shutter for light from a light source provided in the backlight device. Yes.

Further, in the liquid crystal display device as described above, normally, gradation correction processing (gamma correction) using a predetermined gamma curve is performed on luminance information (gradation value) for each pixel included in an external video signal. Processing) is performed.

Further, as described in Patent Document 1 below, for example, a plurality of gamma curves are used for a conventional liquid crystal display device according to the combination of the brightness of the backlight device and the environmental illuminance at the installation location of the liquid crystal panel. Has been proposed. In this conventional liquid crystal display device, even when the luminance of the backlight device is changed based on the luminance information for each pixel included in the video signal from the outside, the visibility in the low gradation region is improved. It was possible.

JP 2011-53264 A

However, the conventional liquid crystal display device as described above may not be able to improve the display quality. In particular, in the conventional liquid crystal display device, when the screen of the liquid crystal panel (display panel, display unit) is enlarged, there is a problem that it is difficult to improve the display quality.

Here, the problems in the conventional liquid crystal display device will be described in detail with reference to FIGS.

FIG. 18 is a diagram for explaining a main configuration of a conventional liquid crystal display device. FIG. 19A to FIG. 19H are timing charts showing an operation example in each part of the liquid crystal panel shown in FIG. FIGS. 20A and 20B are graphs showing examples of target gamma curves and measurement results at the center BC and the end BE shown in FIG. 18, respectively.

In FIG. 18, as is well known, an active matrix substrate is used for a liquid crystal panel LP included in a conventional liquid crystal display device, and a plurality of data lines (source lines) and a plurality of data lines (source lines) are provided on the active matrix substrate. A plurality of scanning wirings (gate wirings) are provided in a matrix (not shown). Further, the plurality of source wirings are equally distributed and connected to a plurality of, for example, eight source drivers 51. The plurality of gate wirings are equally distributed and connected to a plurality of, for example, four gate drivers (not shown) provided on the left end side and the right end side of the liquid crystal panel LP, respectively. That is, in the liquid crystal panel LP, the left end portion and the right end portion of each gate wiring are connected to the gate drivers on the left end portion side and the right end portion side, respectively.

In this liquid crystal display device, as shown in FIG. 18, light emitting diodes 53 as light sources are provided outside the gate drivers on the left end side and the right end side (that is, on the left end side and the right end side of the liquid crystal panel LP). Are provided. That is, as shown in FIG. 18, in the conventional liquid crystal display device, a plurality of, for example, eight light emitting diodes 53 mounted LED substrates 54 are provided on the left end side and the right end side of the liquid crystal panel LP. Illumination light from the light emitting diode 53 is irradiated to the entire surface of the liquid crystal panel LP through a light guide plate (not shown).

Further, in the liquid crystal panel LP, a plurality of pixels are provided at the intersection of the source wiring and the gate wiring. The source driver 51 also applies the gradation voltage after the gradation correction processing using a predetermined gamma curve is performed on the luminance information (gradation value) for each pixel included in the video signal from the outside. Is supplied to the corresponding source wiring as a gradation signal. Further, in the liquid crystal panel LP, the scanning signal is supplied from the gate driver to the left end portion and the right end portion of the gate wiring, respectively. Thus, in the liquid crystal panel LP, the grayscale voltage is set to the pixel in the liquid crystal layer (not shown). Charged to the unit. Thereby, in the liquid crystal panel LP, the transmittance is controlled in units of pixels, and a desired image is displayed.

However, in the conventional liquid crystal display device, due to heat from the light emitting diode (light source) 53, the grayscale voltage at the pixel at the central portion BC of the liquid crystal panel LP is higher than that at the end BE of the liquid crystal panel LP. The battery has become insufficiently charged. For this reason, in conventional liquid crystal display devices, the entire screen may not be displayed with a desired luminance when an image is displayed.

More specifically, in any pixel P included in the end BE of the liquid crystal panel LP, as illustrated in FIG. 19A, when the gate clock GLK is turned on at time T1, the gate driver is The scanning signal Goutge is supplied to the corresponding gate wiring. Subsequently, when the control signal LS to the source driver 51 is turned on at a time point T2, a gradation signal (gradation voltage) Sout se is supplied from the source driver 51 to the corresponding source wiring. That is, in the pixel P, charging of the gradation voltage starts from the time point T2.

Further, since the arbitrary pixel P included in the end portion BE is located in the vicinity of the light emitting diode (light source) 53, the ambient temperature of the pixel P is high due to the heat from the light emitting diode 53. The waveform dullness of the gradation signal Soutse at is small. That is, as shown in FIG. 19D, the gradation signal Soutse rises almost simultaneously when the control signal LS is turned on at time T2, and the charge rate in the liquid crystal layer of the pixel P decreases. Instead, the charging is appropriately started from time T2.

Thereafter, when the gate clock GLK is turned on at time T3, the supply of the scanning signal Goutge to the corresponding gate wiring is stopped. Subsequently, when the control signal LS to the source driver 51 is turned on at time T4, the supply of the gradation signal Soutse to the corresponding source wiring is stopped. In the pixel P, charging of the gradation voltage is stopped at time T3. That is, in the pixel P, the period between the time point T2 and the time point T3 is the grayscale voltage charging period.

On the other hand, in the arbitrary pixel P ′ included in the central portion BC of the liquid crystal panel LP, as illustrated in FIG. 19E, when the gate clock GLK is turned on at the time T1, the gate driver corresponds to the corresponding gate. A scanning signal Gout gc is supplied to the wiring. Thereafter, the control signal LS to the source driver 51 is turned on at time T2, and the gradation signal (gradation voltage) Sout sc is supplied from the source driver 51 to the corresponding source wiring.

However, since the pixel P ′ is away from the light emitting diode 53, it is not heated by the heat from the light emitting diode 53. For this reason, the ambient temperature of the pixel P ′ is lower than the ambient temperature of the pixel P, and the waveform of the gradation signal Sout sc in the source wiring is greatly dull. That is, as shown in FIG. 19 (h), the gradation signal Sout sc does not rise almost simultaneously even when the control signal LS is turned on at time T2, and becomes a predetermined value at time T5. For this reason, in the pixel P ′, charging of the gradation voltage is insufficient from the time point T2 to the time point T5, and is started from the time point T5. As a result, the charging rate in the liquid crystal layer of the pixel P ′ is reduced.

Thereafter, when the gate clock GLK is turned on at time T3, the supply of the scanning signal Gout gc to the corresponding gate wiring is stopped. Subsequently, when the control signal LS to the source driver 51 is turned on at time T4, the supply of the gradation signal Sout sc to the corresponding source wiring is stopped. In the pixel P ′, the charging of the gradation voltage is stopped at time T3. That is, in the pixel P ′, the period from the time point T5 to the time point T3 is the gradation voltage charging period, which is shorter than the charging period of the pixel P.

As a result, as shown in FIGS. 20 (a) and 20 (b), at the central portion BC and the end portion BE of the liquid crystal panel LP, gradation values (for example, 8 bits = 256 gradations) and output light are output. The relationship between the brightness and the brightness was not the same, and the display quality could not be improved.

More specifically, in the central portion BC of the liquid crystal panel LP, the measurement result curve 60 indicated by the solid line in FIG. 20A is substantially the same as the target gamma curve 61 indicated by the dotted line in FIG. Match.

On the other hand, at the end BE of the liquid crystal panel LP, a curve 62 as a measurement result indicated by a solid line in FIG. 20B is a curve 61 corresponding to a target gamma curve 61 indicated by a dotted line in FIG. Compared with

As described above, in the central part BC and the end part BE of the liquid crystal panel LP, the relationship between the gradation value and the luminance of the output light is not the same, and the display quality may not be improved. In particular, in the conventional liquid crystal display device, when the screen of the liquid crystal panel (display unit) is enlarged, it is difficult to improve display quality. In the central part BC, the gamma curve 61 and the curve 60 substantially coincide with each other in consideration of the influence of the ambient temperature due to the heat from the light emitting diode 53 (reduction of the charging period of the gradation voltage). This is because the voltage is set large.

In view of the above problems, an object of the present invention is to provide a display device capable of improving the display quality even when the display section is enlarged.

In order to achieve the above object, a display device according to the present invention includes a backlight unit having a light source, and a plurality of pixels, and displays information using illumination light from the backlight unit. A display device comprising:
A control unit that performs drive control of at least the display unit using the input video signal,
The display unit is provided with a plurality of display areas,
Based on the temperature distribution when the light source of the backlight unit is driven to turn on, the control unit applies a gradation value for each pixel included in the input video signal for each of the plurality of display areas. A gradation voltage instruction unit that determines a correction value and performs drive control of the display unit is provided.

In the display device configured as described above, the control unit performs drive control of at least the display unit using the input video signal. Further, the control unit corrects the gradation value for each pixel included in the input video signal for each of the plurality of display areas based on the temperature distribution when the light source of the backlight unit is driven to turn on. And a gradation voltage instruction unit for controlling the driving of the display unit is provided. Thus, unlike the conventional example, it is possible to configure a display device that can improve display quality even when the screen of the display unit is enlarged.

In the above display device, the gradation voltage instruction unit may correspond to a corresponding level included in the video signal from the outside so that the luminance of the output light output from the pixel to the outside becomes a desired value. It is preferable to correct the tone value to a predetermined tone value.

In this case, the characteristics of the brightness and gradation value of the output light can be improved, and the display quality can be reliably improved even when the display screen is enlarged.

Further, in the above display device, the gradation voltage instruction unit uses an arithmetic unit that obtains a predetermined gradation value by calculation using a gradation value for each pixel included in an external video signal. May be.

In this case, the predetermined gradation value is appropriately obtained by the calculation unit.

In the display device, the gradation voltage instruction unit uses a lookup table that associates a gradation value for each pixel included in an external video signal with a predetermined gradation value. May be.

In this case, the predetermined gradation value is appropriately obtained by the lookup table.

In the display device, the gradation voltage instruction unit may determine a corrected gradation value by using predetermined different gamma curves according to the plurality of display areas. preferable.

In this case, even when the screen of the display unit is enlarged, the corrected gradation value can be appropriately determined according to the display area, and the display quality can be improved reliably.

In the display device, the backlight unit is provided with a temperature sensor,
The gradation voltage instruction unit may determine a correction value for a gradation value for each pixel included in the input video signal using a detection result of the temperature sensor.

In this case, the temperature distribution when the light source of the backlight unit is turned on by the temperature sensor can be grasped more accurately, and the correction value for the gradation value for each pixel can be determined more appropriately. . As a result, the display quality can be improved more reliably even when the screen of the display unit is enlarged.

Further, in the display device, the backlight unit is provided with a plurality of light emitting areas that allow the light of the light source to enter the plurality of display areas, respectively.
The control unit is configured to perform drive control of the display unit and the backlight unit using an input video signal,
The gradation voltage instruction unit may determine a correction value for a gradation value for each pixel included in the input video signal using lighting states of light sources corresponding to the plurality of light emitting areas.

In this case, the correction value for the gradation value for each pixel can be determined more appropriately while determining the lighting state of the light source in each of the plurality of light emitting areas, that is, the temperature state in the corresponding light emitting area. As a result, the display quality can be improved more reliably even when the screen of the display unit is enlarged.

In the display device, a liquid crystal panel is used as the display unit.
In the liquid crystal panel, a gate driver and a plurality of source drivers provided at different positions from the gate driver are provided,
In the plurality of source drivers, it is preferable that gradation voltages using different gamma curves are input from the gradation voltage instruction unit according to the plurality of display areas.

In this case, a liquid crystal display device excellent in display quality can be easily configured.

According to the present invention, it is possible to provide a display device capable of improving the display quality even when the screen of the display unit is enlarged.

FIG. 1 is a diagram for explaining a liquid crystal display device according to a first embodiment of the present invention. FIG. 2 is a diagram for explaining a main configuration of the liquid crystal panel shown in FIG. FIG. 3 is a block diagram illustrating a configuration example of the panel control unit illustrated in FIG. 2. FIG. 4 is a block diagram illustrating a configuration example of the backlight control unit illustrated in FIG. FIG. 5 is a diagram for explaining a source driver and a display area provided in the liquid crystal panel and the light emitting diode shown in FIG. FIGS. 6A and 6B are graphs for explaining specific examples of correction values determined by the gradation voltage instruction unit shown in FIG. 3 for different display areas. FIG. 7 is a diagram for explaining a liquid crystal display device according to a second embodiment of the present invention. FIG. 8 is a diagram for explaining a main configuration of the backlight device shown in FIG. FIG. 9 is a diagram for explaining a main configuration of the liquid crystal panel shown in FIG. FIG. 10 is a block diagram illustrating a configuration example of the panel control unit illustrated in FIG. 9. FIG. 11 is a diagram illustrating a liquid crystal display device according to the third embodiment of the present invention. FIG. 12 is a diagram for explaining a main configuration of the backlight device shown in FIG. FIG. 13 is a diagram illustrating a specific example of a plurality of light emitting areas provided in the backlight device illustrated in FIG. 11 and a plurality of display areas irradiated with light from these light emitting areas. FIG. 14 is a diagram for explaining a main configuration of the liquid crystal panel shown in FIG. FIG. 15 is a block diagram illustrating a configuration example of the panel control unit illustrated in FIG. 13. FIG. 16 is a block diagram illustrating a configuration example of the backlight control unit illustrated in FIG. 13. FIGS. 17A and 17B are graphs for explaining specific examples of correction values determined by the gradation voltage instruction unit shown in FIG. 14 for different display areas. FIG. 18 is a diagram for explaining a main configuration of a conventional liquid crystal display device. FIG. 19A to FIG. 19H are timing charts showing an operation example in each part of the liquid crystal panel shown in FIG. FIGS. 20A and 20B are graphs showing examples of target gamma curves and measurement results at the center BC and the end BE shown in FIG. 18, respectively.

Hereinafter, preferred embodiments of the display device of the present invention will be described with reference to the drawings. In the following description, the case where the present invention is applied to a transmissive liquid crystal display device will be described as an example. Moreover, the dimension of the structural member in each figure does not faithfully represent the actual dimension of the structural member, the dimensional ratio of each structural member, or the like.

[First Embodiment]
FIG. 1 is a diagram for explaining a liquid crystal display device according to a first embodiment of the present invention. In FIG. 1, the liquid crystal display device 1 of the present embodiment is provided with a liquid crystal panel 2 as a display unit for displaying information and a backlight device 3 as a backlight unit. In the liquid crystal display device 1, the liquid crystal panel 2 displays information using illumination light from the backlight device 3, and the liquid crystal panel 2 and the backlight device 3 are transmissive liquid crystal displays. The device 1 is integrated.

The liquid crystal panel 2 includes a liquid crystal layer and an active matrix substrate and a color filter substrate as a pair of substrates that sandwich the liquid crystal layer (not shown). In the active matrix substrate, as will be described in detail later, a pixel electrode, a thin film transistor (TFT), or the like is formed between the liquid crystal layer in accordance with a plurality of pixels included in the display surface of the liquid crystal panel 2. ing. On the other hand, on the color filter substrate, a color filter, a common electrode, and the like are formed between the liquid crystal layer (not shown).

Further, the liquid crystal panel 2 is provided with a control device (not shown) that controls the driving of the liquid crystal panel 2, and operates the liquid crystal layer in units of pixels to drive the display surface in units of pixels. A desired image is displayed on the display surface.

For the liquid crystal panel 2 of the present embodiment, a normally black mode, for example, is used. That is, the liquid crystal panel 2 of the present embodiment is configured such that when no voltage is applied to the liquid crystal layer, black display is performed and the transmittance in the liquid crystal layer increases according to the applied voltage. Has been.

Further, the backlight device 3 includes a light emitting diode 4 as a light source, an LED substrate 5 as a light source substrate on which the light emitting diode 4 is mounted, and light from the light emitting diode 4 in a predetermined propagation direction (the horizontal direction in FIG. 1). ) And a light guide plate 6 for emitting the light on the liquid crystal panel (object to be irradiated) 2 side is provided. The light guide plate 6 is made of, for example, a synthetic resin such as a transparent acrylic resin having a rectangular cross section. The light guide plate 6 is disposed so as to face the light emitting diode 4, and light from the light emitting diode 4 is used. A light incident surface 6a, a light emitting surface 6b that emits light toward the liquid crystal panel 2, and a facing surface 6c that faces the light emitting surface 6b.

The backlight device 3 is provided below the light-emitting diode 4 and the light guide plate 6, a reflection plate 8 that reflects light from the light-emitting diode 4 and the light guide plate 6, and the liquid crystal panel 2 side of the light-emitting diode 4. A reflection plate 9 is provided as a reflection part that is provided and reflects light from the light emitting diode 4. In the backlight device 3, for example, a diffusion sheet 10, a prism sheet 11, and a reflective polarizing sheet 12 are sequentially provided from the light guide plate 6 side as optical members provided between the light guide plate 6 and the liquid crystal panel 2. Thus, the light from the light emitting surface 6b of the light guide plate 6 is changed to the above-mentioned planar illumination light having a uniform luminance and given to the liquid crystal panel 2.

Furthermore, the backlight device 3 includes a bottomed chassis 13 that houses the light-emitting diode 4, the light guide plate 6, the diffusion sheet 10, the prism sheet 11, and the reflective polarizing sheet 12, and an L-shaped cross section having an opening. And a bezel 14 which is assembled to the chassis 13 and constitutes an outer container of the backlight device 3 is provided. In the liquid crystal display device 1 of the present embodiment, a P (plastic) chassis 15 is installed on the bezel 14, and the liquid crystal panel 2 is placed on the P chassis 15. The device 3 is assembled with each other.

In addition to the above description, instead of the reflector plate 8, a light-emitting diode is applied by applying a paint having a high light reflectance such as silver or white on the bottom surface of the chassis 13 facing the light-emitting diode 4 and the light guide plate 6. It is good also as a structure which reflects the light from 4 and the light from the light-guide plate 6. FIG.

Next, the liquid crystal panel 2 of the present embodiment will be specifically described with reference to FIGS.

FIG. 2 is a diagram for explaining a main configuration of the liquid crystal panel shown in FIG. FIG. 3 is a block diagram illustrating a configuration example of the panel control unit illustrated in FIG. 2. FIG. 4 is a block diagram illustrating a configuration example of the backlight control unit illustrated in FIG.

In FIG. 2, a video signal is input to the control unit 16 from the outside of the liquid crystal display device 1 via a signal source (not shown) such as a TV (receiver) or a PC. Further, the control unit 16 substantially performs drive control of the liquid crystal panel 2 using the input video signal. Further, the control unit 16 is configured to substantially perform drive control of the backlight device 3 using the input video signal.

More specifically, the control unit 16 uses the video signal to drive and control the liquid crystal panel 2 in units of pixels. The video signal is used to control the light emitting diodes 4 of the backlight device 3. A backlight control unit 18 that performs drive control and a frame memory 19 configured to be able to store display data in units of frames included in the video signal are provided. For example, an ASIC (Application 制御 Specific Integrated Circuit) is used for each of the panel control unit 17 and the backlight control unit 18, and the panel control unit 17 and the backlight control unit 18 are sequentially stored in the frame memory 19. Predetermined arithmetic processing can be performed on display data at high speed. In addition, since the panel control unit 17 and the backlight control unit 18 are provided as described above, in the liquid crystal display device 1 of the present embodiment, the panel control unit 17 and the backlight control unit 18 are each provided with a liquid crystal panel (display). Part) 2 and the backlight device (backlight part) 3 can be appropriately driven, and high-quality display can be easily performed. That is, in the liquid crystal display device 1 of the present embodiment, the dark portion of the image on the display surface of the liquid crystal panel 2 lowers the luminance of the illumination light from the corresponding light emitting area, and the bright portion of the image is illuminated from the corresponding light emitting area. The dynamic contrast can be improved by increasing the luminance of light.

In addition to the above description, the backlight control unit 18 is configured to perform drive control of the light emitting diode 4 using only the dimming instruction signal from the outside without using the input video signal. Also good.

As shown in FIG. 3, the panel control unit 17 is provided with an image processing unit 25 that generates each instruction signal to the source driver 20 and the gate driver 21 shown in FIG. 2 based on the video signal. ing. Further, the panel control unit 17 is provided with a gradation voltage instruction unit 26. As will be described in detail later, an instruction signal to the source driver 20 generated by the image processing unit 25 is a gradation voltage instruction unit 26. After being corrected at, it is output to the source driver 20.

As shown in FIG. 4, the backlight control unit 18 is provided with an LED drive control unit 27 that substantially controls the drive of each light-emitting diode 4 using a video signal. That is, the LED drive control unit 27 generates an instruction signal for each light emitting diode 4 using the video signal, and controls lighting driving of each light emitting diode 4.

In FIG. 2, a source driver 20 and a gate driver 21 are drive circuits that drive a plurality of pixels P provided in the liquid crystal panel 2 in units of pixels, and the source driver 20 and the gate driver 21 include a plurality of sources. Wirings S1 to SM (M is an integer of 2 or more, hereinafter collectively referred to as “S”) and a plurality of gate wirings G1 to GN (N is an integer of 2 or more, hereinafter collectively referred to as “G”) .) Are connected to each other. The source lines S1 to SM and the gate lines G1 to GN are arranged in a matrix, and the areas of the plurality of pixels P are formed in the areas partitioned in the matrix. The plurality of pixels P include red, green, and blue pixels P. Further, the red, green, and blue pixels P are sequentially arranged in parallel with each of the gate wirings G1 to GN, for example, in this order.

Further, a plurality of source drivers 20 and gate drivers 21 are provided, and are sequentially arranged along the horizontal direction and the vertical direction of the liquid crystal panel 2. The plurality of source drivers 20 and the plurality of gate drivers 21 are installed in accordance with a plurality of display areas provided on the display surface of the liquid crystal panel 2, and the pixels P included in the corresponding display areas are arranged. It is driven appropriately.

Here, with reference to FIG. 5, the plurality of light emitting diodes 4, the plurality of source drivers 17, and the plurality of display areas in the liquid crystal panel 2 of the present embodiment will be specifically described.

FIG. 5 is a diagram illustrating the source driver and display area provided in the liquid crystal panel and the light emitting diode shown in FIG.

As shown in FIG. 5, in the liquid crystal panel 2 of the present embodiment, a plurality of, for example, eight source drivers 20-1 to 20-8 (hereinafter collectively referred to as “20”) include eight flexible printed circuit boards. (SOF) 28, respectively. One end of each flexible printed circuit board 28 is connected to the source wiring S on the active matrix substrate outside the effective display area A. Further, the same number of source lines S, that is, (M / 8) source lines S are connected to each of the source drivers 20-1 to 20-8.

The other end side of each flexible printed circuit board 28 is connected to one of the two printed circuit boards 29. In the liquid crystal panel 2, an instruction signal corresponding to information displayed on the display unit of the liquid crystal panel 2 is input from the panel control unit 17 to each of the source drivers 20-1 to 20-8. Yes. Thereafter, each of the source drivers 20-1 to 20-8 outputs a gradation signal to the corresponding source line S.

Also, in the liquid crystal panel 2, a plurality of, for example, four gate drivers are provided on the left end side and the right end side of the liquid crystal panel 2 (not shown). These gate drivers are each mounted on a flexible printed circuit board (SOF) (not shown), like the source driver. One end of each flexible printed circuit board is connected to the gate wiring G on the active matrix substrate outside the effective display area A. Further, the left end and the right end of each gate line G are connected to the gate drivers on the left end side and the right end side, respectively, and the same number of gate lines G are connected to each gate driver on the left end side and the right end side. That is, (N / 4) gate wirings G are connected (not shown).

Further, each gate driver is connected to the panel control unit 17 (not shown) via a corresponding flexible printed circuit board and wiring (not shown) provided on the active matrix substrate. Each gate driver receives an instruction signal from the panel control unit 17 and outputs a scanning signal to be described later to the corresponding gate wiring G.

Also, in the liquid crystal panel 2, as shown in FIG. 5, a plurality of, for example, eight light emitting diodes 4 mounted on the LED substrate 5 are arranged on each of the left end side and the right end side.

In the liquid crystal panel 2, as shown in FIG. 5, a plurality of, for example, eight display areas A1 to A8 are set in the effective display area A. Each display area A1 to A8 includes a plurality of pixels P provided at the intersections of the source lines S and the gate lines G arranged in a matrix. These display areas A1 to A8 are respectively set according to the source drivers 20-1 to 20-8 connected to the internal source lines S, and the left and right end portions of the liquid crystal panel 2 are set. Display areas are formed at different distances from the light emitting diode (light source) 4 provided on the side.

Furthermore, the liquid crystal panel 2 is provided with a plurality of source drivers 20-1 to 20-8 arranged at different positions from the light emitting diode 4 as shown in FIG. Further, in the plurality of source drivers 20-1 to 20-8, as will be described in detail later, the gradation voltages using different gamma curves according to the distance from the light emitting diode 4 are converted into the gradation voltage instructions. It is input from the unit 26.

Returning to FIG. 2, the gate of the switching element 22 provided for each pixel P is connected to each of the gate wirings G1 to GN. On the other hand, the source of the switching element 22 is connected to each of the source lines S1 to SM. Further, a pixel electrode 23 provided for each pixel P is connected to the drain of each switching element 22. In each pixel P, the common electrode 24 is configured to face the pixel electrode 23 with the liquid crystal layer provided on the liquid crystal panel 2 interposed therebetween. The gate driver 21 sequentially outputs gate signals (scanning signals) for turning on the gates of the corresponding switching elements 22 to the gate wirings G1 to GN based on the instruction signal from the image processing unit 25. . On the other hand, the source driver 20 outputs a gradation signal (gradation voltage) corresponding to the luminance (gradation) of the display image to the corresponding source lines S1 to SM based on the instruction signal from the gradation voltage instruction unit 26. To do.

In FIG. 3, the gradation voltage instruction unit 26 includes a plurality of display areas A1 to A8 based on the temperature distribution when the light emitting diode (light source) 4 of the backlight device (backlight unit) is driven to light. Every time, a correction value (corrected gradation value) for the gradation value for each pixel included in the input video signal is determined, and the drive control of the liquid crystal panel (display unit) 2 is substantially performed. It is configured.

In addition, the gradation voltage instruction unit 26 sets the corresponding gradation value included in the external video signal so that the luminance of the output light output from the pixel P toward the outside becomes a desired value. The gradation value is corrected to a predetermined gradation value (corrected gradation value). Further, the gradation voltage instruction unit 26 determines a corrected gradation value by using predetermined different gamma curves in accordance with a plurality of display areas A1 to A8 of the liquid crystal panel 2. (Details will be described later).

More specifically, as shown in FIG. 3, the gradation voltage instruction unit 26 uses a gradation value for each pixel P included in an external video signal to set a predetermined gradation value. A calculation unit 26a obtained by calculation and a memory 26b in which data necessary for calculation processing such as mathematical formulas and parameters used in the calculation unit 26a are stored in advance are provided.

And the gradation voltage instruction | indication part 26 correct | amends the instruction | indication signal (gradation signal) to the source driver 20 which the image process part 25 produced | generated using the corrected gradation value determined in the calculating part 26a. To the source driver 20.

In addition to the above description, the gradation voltage instruction unit 26 outputs the corrected gradation value determined by the calculation unit 26a to the image processing unit 25, and the image processing unit 25 corrects the gradation value after correction. , The instruction signal (gradation signal) to the source driver 20 may be corrected and output to the source driver 20 (the same applies to the embodiments described later).

Hereinafter, the operation of the liquid crystal display device 1 of the present embodiment configured as described above will be described. In the following description, the operation of the gradation voltage instruction unit 26 of this embodiment will be mainly described with reference to FIG.

6 (a) and 6 (b) are graphs for explaining specific examples of correction values determined by the gradation voltage instruction unit shown in FIG. 3 for different display areas.

The gradation voltage instruction unit 26 of the present embodiment divides the plurality of display areas A1 to A8 into, for example, two sets, and uses a predetermined gamma curve that is different from each other in advance and corrects the display areas A1 to A8. The gradation value is determined. Specifically, the gradation voltage instruction unit 26 is divided into display areas A1, A2, A7, A8 closer to the light emitting diode 4 and display areas A3, A4, A5, A6 farther from the light emitting diode 4. , The gamma curves used for the source drivers 20-1, 20-2, 20-7, 20-8 assigned to the closer display areas A1, A2, A7, A8 and the farther display areas A3, A4, The gamma curves used for the source drivers 20-3, 20-4, 20-5, and 20-6 assigned to A5 and A6 are configured to have different values.

That is, in the gradation voltage instruction unit 26, the calculation unit 26a is farther from the source driver 20-, 20-2, 20-7, 20-8 closer to the light-emitting diode 4 than the source driver 20- 3. A predetermined gradation value (corrected gradation value) is obtained using a value larger than the value of the gamma curve used for 3, 20-4, 20-5, and 20-6. Yes.

In other words, in the gradation voltage instruction unit 26, since the heat from the light emitting diode (light source) 4 is difficult to be transmitted and the ambient temperature is relatively low, the gradation voltage is likely to be insufficiently charged, and the charging rate of the liquid crystal layer for each pixel P For the source drivers 20-3, 20-4, 20-5 and 20-6 assigned to the distant display areas A3, A4, A5 and A6, the light emitting diode (light source) 4 Since the ambient temperature is relatively high, it is difficult for the grayscale voltage to be insufficiently charged, the charge rate of the liquid crystal layer for each pixel P is unlikely to decrease, and the closer source drivers 20-1, 20-2, By using a value smaller than the value of the gamma curve used for 20-7 and 20-8, a predetermined gradation value (corrected gradation value) is obtained.

More specifically, in the liquid crystal panel 2, when the value of the gamma curve is set as a desired value, for example, a value of “2.2”, the calculation unit 26 a has a source closer to the light emitting diode 4. For the drivers 20-1, 20-2, 20-7, and 20-8, for example, a gamma curve having a value of “2.3” is used. Specifically, in FIG. 6A, when the horizontal axis and the vertical axis are the x axis and the y axis, respectively, and the gradation value is, for example, 8 bits = 256 gradations, the curve 70 and the curve 71 Are both expressed by the equation y = ^xγ , and the value of the gamma curve, that is, the value of γ is “2.2” and “2.3” in the curve 70 and the curve 71, respectively. In the present embodiment, the calculation unit 26a uses the gamma curve shown in the curve 71 for the source drivers 20-1, 20-2, 20-7, and 20-8, so that the light emitting diode 4 In the display areas A1, A2, A7, and A8 where adverse effects due to heat (that is, the reduction in the charging rate) are unlikely to occur, the value of the gamma curve can be set to the desired value of “2.2”.

On the other hand, in the arithmetic unit 26a, for example, a gamma curve having a value of “2.1” is used for the source drivers 20-3, 20-4, 20-5, and 20-6 farther from the light emitting diode 4. It has become. Specifically, in FIG. 6B, when the horizontal axis and the vertical axis are the x axis and the y axis, respectively, and the gradation value is, for example, 8 bits = 256 gradations, the curve 70 and the curve 72 Are both expressed by the equation y = ^xγ , and the value of the gamma curve, that is, the value of γ is “2.2” and “2.1” in the curve 70 and the curve 72, respectively. In this embodiment, the calculation unit 26a uses the gamma curve shown by the curve 72 for the source drivers 20-3, 20-4, 20-5, and 20-6, so that the light emitting diode 4 In the display areas A3, A4, A5, and A6 that are likely to be adversely affected by heat (that is, the reduction in the charging rate), the value of the gamma curve can be set to the desired value of “2.2”.

Further, the gradation voltage instruction unit 26 according to the present embodiment performs a verification test or simulation using an actual product to perform gradation values (input gradations) for a plurality of pixels P included in an external video signal. In other words, a corrected gradation value (output gradation data) is obtained in advance so that the luminance of the output light output from the pixel P toward the outside becomes a desired value. Also, based on the relationship between the obtained input gradation data and output gradation data, data such as mathematical formulas and parameters necessary for calculation processing for calculating output gradation data from these input gradation data are obtained. It is determined and stored in the memory 26b in advance. In the gradation voltage instruction unit 26, the calculation unit 26a calculates a predetermined gradation value by using the gradation value included in the video signal from the outside and the data stored in the memory 26b. After the determination, the gradation voltage instruction unit 26 corrects the instruction signal (gradation signal) to the source driver 20 generated by the image processing unit 25 using the corrected gradation value calculated by the calculation unit 26a. To the source driver 20. Thereby, in the present embodiment, as described above, the corrected gradation value is determined using predetermined different gamma curves in accordance with the display areas A1 to A8.

In addition to the above description, for example, the data stored in the memory 26b may be appropriately calculated when the arithmetic unit 26a performs arithmetic processing, or the data may be dynamically received from the outside. . Thus, in the case of the configuration, the installation of the memory 26b can be omitted.

In the liquid crystal display device 1 of the present embodiment configured as described above, drive control of the liquid crystal panel (display unit) 2 and the backlight device (backlight unit) 3 using the video signal input by the control unit 16. I do. In addition, the control unit 16 includes each of the display areas A1 to A8 in the input video signal based on the temperature distribution when the light emitting diode (light source) 4 of the backlight device 3 is turned on. A gradation voltage instruction unit 26 that determines a correction value for the gradation value for each pixel and performs drive control of the liquid crystal panel 2 is provided. Thus, in the present embodiment, unlike the conventional example, a liquid crystal display device (display device) 1 that can improve display quality even when the screen of the liquid crystal panel 2 is enlarged can be configured.

In the present embodiment, the gradation voltage instruction unit 26 corresponds to a corresponding level included in the video signal from the outside so that the luminance of the output light output from the pixel P toward the outside has a desired value. The tone value is corrected to a predetermined tone value. Thereby, in this embodiment, the characteristic of the brightness | luminance and gradation value of the said output light can be improved, and even when the liquid crystal panel 2 enlarges a screen, display quality can be improved reliably. .

In the present embodiment, the gradation voltage instruction unit 26 uses the gradation value for each pixel P included in the external video signal to calculate a predetermined gradation value by calculation. Is used, the above-described predetermined gradation value is appropriately obtained by the calculation unit 26a.

In the present embodiment, the gradation voltage instruction unit 26 determines a corrected gradation value using predetermined different gamma curves according to the plurality of display areas A1 to A8. ing. Thereby, in this embodiment, even when the screen of the liquid crystal panel 2 is enlarged, the corrected gradation value can be appropriately determined according to the display areas A1 to A8, and the display quality is ensured. Can be improved.

Further, in the present embodiment, even when the liquid crystal panel (display panel) 2 has a large screen, the gradation voltage instruction unit 26 that can improve the display quality is used, so that the display quality is excellent. The liquid crystal display device 1 can be easily configured.

In this embodiment, the liquid crystal panel 2 is used as the display panel. In the liquid crystal panel 2, the gate driver 21 and a plurality of source drivers 20-1 to 20- provided at different positions from the gate driver 21 are used. 8 are provided. In the plurality of source drivers 20-1 to 20-8, gradation voltages using different gamma curves are input from the gradation voltage instruction unit 26 in accordance with the plurality of display areas A1 to A8. Thereby, in this embodiment, the liquid crystal display device 1 excellent in display quality can be configured easily.

In the above description, in the gradation voltage instruction unit 26, the source drivers 20-1, 20-2, 20-7, and 20-8 closer to the light emitting diode 4 and the farther source drivers 20-3, 20-8. -4, 20-5, and 20-6 have been described using gamma curves having different values. However, the present embodiment is not limited to this, and for example, each of the eight source drivers 20- For 1 to 20-8, gamma curves having mutually different values may be used. Further, when the liquid crystal display device 1 is in use, that is, when the liquid crystal panel 2 is erected (for example, when the source driver 20 side shown in FIG. 5 is arranged on the upper side in the vertical direction), a plurality of display areas A1 to A8. Is divided into two upper and lower display areas, and in these two upper and lower display areas, gamma curves having different values may be used on the assumption that the influence of heat from the light emitting diode 4 is different.

[Second Embodiment]
FIG. 7 is a diagram for explaining a liquid crystal display device according to a second embodiment of the present invention. FIG. 8 is a diagram for explaining a main configuration of the backlight device shown in FIG. FIG. 9 is a diagram for explaining a main configuration of the liquid crystal panel shown in FIG. FIG. 10 is a block diagram illustrating a configuration example of the panel control unit illustrated in FIG. 9.

In the figure, the main difference between the present embodiment and the first embodiment is that a LUT (Look Up Table) is used in place of the calculation unit, a temperature sensor is provided in the backlight unit, and a gradation voltage instruction is provided. The unit is to determine a correction value for the gradation value for each pixel included in the input video signal using the detection result of the temperature sensor. In addition, about the element which is common in the said 1st Embodiment, the same code | symbol is attached | subjected and the duplicate description is abbreviate | omitted.

That is, as shown in FIG. 7, in the liquid crystal display device 1 of the present embodiment, a direct type backlight device 3 is used as a backlight unit. The backlight device 3 has an opening on the liquid crystal panel 2 side, a housing 31 that houses the light emitting diode 4, and a diffusion plate 30 that is provided so as to cover the opening of the housing 31.

Further, as illustrated in FIG. 8, the backlight device 3 includes a total of 32 light-emitting diodes 4 installed in the housing 31. Further, in the backlight device 3, as shown by a one-dot chain line in FIG. 8, four light emitting diodes 4 are assigned to the display areas A1 to A8. Furthermore, in the backlight device 3, as shown in FIG. 8, a total of 35 temperature sensors 32 are installed at the boundary between two adjacent display areas.

As shown in FIG. 9, in the present embodiment, the detection result of the temperature sensor 32 is input to the control unit 16, and the panel control unit 33 provided in the control unit 16 is operated at the temperature. Using the detection result of the sensor 32, the drive control of the liquid crystal panel 2 is performed.

That is, as shown in FIG. 10, the panel control unit 33 of the present embodiment uses the image processing unit 25 and the detection result of the temperature sensor to generate a floor for each pixel P included in the input video signal. A gradation voltage instruction unit 34 for determining a correction value (corrected gradation value) for the tone value is provided. The gradation voltage instruction unit 34 uses an LUT 34a. In this LUT 34a, gradation values before and after the correction processing are stored in association with each other for each predetermined temperature unit. That is, in the LUT 34a, the gradation value (input gradation data) for each of the plurality of pixels P included in the external video signal and the luminance of the output light output from the pixel P to the outside are desired. The corrected gradation value (output gradation data) as a value is associated with each other for each predetermined temperature unit. Then, when the input gradation data for the pixel P included in the video signal from the outside is input, the gradation voltage instruction unit 34 also uses the detection result of the temperature sensor 32 at the position corresponding to the pixel P. The corresponding output gradation data is obtained from the LUT 34a, and is used as the corrected gradation value. Then, the gradation voltage instruction unit 34 corrects the instruction signal (gradation signal) to the source driver 20 generated by the image processing unit 25 using the corrected gradation value, and outputs it to the source driver 20. To do. Thus, in the present embodiment, the corrected gradation value is determined using predetermined different gamma curves in accordance with the detection results of the display areas A1 to A8 and the temperature sensor 32.

With the above configuration, the present embodiment can achieve the same operations and effects as the first embodiment. In the present embodiment, the gradation voltage instruction unit 34 uses the detection result of the temperature sensor 32 to determine a correction value for the gradation value for each pixel included in the input video signal. Thereby, in this embodiment, the temperature distribution when the light emitting diode (light source) 4 of the backlight device (backlight unit) is driven to be turned on by the temperature sensor 32 can be grasped more accurately. It becomes possible to determine a correction value for the gradation value more appropriately. As a result, in this embodiment, even when the liquid crystal panel (display unit) 2 has a large screen, the display quality can be improved more reliably.

In the present embodiment, the gradation voltage instruction unit 34 uses the LUT 34a in which the gradation value for each pixel P included in the external video signal is associated with a predetermined gradation value. Therefore, the predetermined gradation value is appropriately obtained by the LUT 34a.

[Third Embodiment]
FIG. 11 is a diagram illustrating a liquid crystal display device according to the third embodiment of the present invention. FIG. 12 is a diagram for explaining a main configuration of the backlight device shown in FIG. FIG. 13 is a diagram illustrating a specific example of a plurality of light emitting areas provided in the backlight device illustrated in FIG. 11 and a plurality of display areas irradiated with light from these light emitting areas. FIG. 14 is a diagram for explaining a main configuration of the liquid crystal panel shown in FIG. FIG. 15 is a block diagram illustrating a configuration example of the panel control unit illustrated in FIG. 13. FIG. 16 is a block diagram illustrating a configuration example of the backlight control unit illustrated in FIG. 13.

In the figure, the main difference between the present embodiment and the second embodiment is that the backlight unit is provided with a plurality of light emitting areas that allow the light of the light source to enter the plurality of display areas. The input video signal is used to control the driving of the display unit and the backlight unit, and the gradation voltage instruction unit uses the lighting state of the light source corresponding to the plurality of light emitting areas to input the video. This is a point for determining a correction value for the gradation value for each pixel included in the signal. In addition, about the element which is common in the said 2nd Embodiment, the same code | symbol is attached | subjected and the duplicate description is abbreviate | omitted.

That is, as shown in FIG. 11, in the liquid crystal display device 1 of the present embodiment, a direct type backlight device 3 is used as a backlight unit, as in the second embodiment. The backlight device 3 has an opening on the liquid crystal panel 2 side, a housing 31 that houses the light emitting diode 4, and a diffusion plate 30 that is provided so as to cover the opening of the housing 31.

Further, as illustrated in FIG. 12, the backlight device 3 includes a total of 32 light-emitting diodes 4 installed in the housing 31.

Further, as shown in FIG. 13, the backlight device 3 of the present embodiment has a light emitting diode (light source) for a plurality of display areas A-1 to A-32 set in the liquid crystal panel (display unit) 2. A plurality of light emitting areas (1) to (32) through which the four lights are respectively incident are provided. That is, one light emitting diode 4 is assigned to each light emitting area (1) to (32), and illumination light is irradiated to the corresponding display areas A-1 to A-32. Yes. Further, in the plurality of display areas A-1 to A-32, each of the four display areas arranged in the vertical direction in FIG. 13 includes the source line S connected to one source driver 20.

That is, the source driver 20-1 is assigned to the display areas A-1, A-9, A-17, and A-25, and the display areas A-2, A-10, A-18, and A-26 are assigned. Is assigned a source driver 20-2. Further, the source driver 20-3 is assigned to the display areas A-3, A-11, A-19, and A-27, and the display areas A-4, A-12, A-20, and A-28 are allocated. Is assigned the source driver 20-4. The source driver 20-5 is assigned to the display areas A-5, A-13, A-21, and A-29, and the display areas A-6, A-14, A-22, and A-30 are assigned. Is assigned the source driver 20-6. The source driver 20-7 is assigned to the display areas A-7, A-15, A-23, and A-31, and the display areas A-8, A-16, A-24, and A-32 are assigned. Is assigned a source driver 20-8.

Further, in the liquid crystal display device 1 of the present embodiment, the matrix light emitting areas (1) to (32) and the matrix display areas A-1 to A-32 are set in a one-to-one relationship. For one display area, an area active (local dimming) backlight that is appropriately irradiated according to information to be displayed by illumination light from one light emitting area is configured.

Specifically, as shown in FIG. 14, the control unit 16 of the present embodiment is provided with a panel control unit 35 and a backlight control unit 36. The panel control unit 35 and the backlight control unit 36 perform drive control of the liquid crystal panel (display unit) 2 and the backlight device (backlight unit) 3 using the video signal input to the control unit 16, respectively. It is configured as follows.

As shown in FIG. 15, the panel control unit 35 of the present embodiment includes the image processing unit 25 and the lighting state of the light emitting diodes (light sources) 4 corresponding to the plurality of light emitting areas (1) to (32). Is used to determine a correction value for the gradation value for each pixel P included in the input video signal.

Further, in the panel control unit 35, the luminance value of each light emitting area is notified from an area luminance calculation unit described later provided in the backlight control unit 36, and an instruction signal to the source driver 20 is notified. After being corrected to a signal reflecting the luminance value of each light emitting area, the signal is output from the panel control unit 35 to the source driver 20 (details will be described later).

The gradation voltage instruction unit 37 uses an LUT 37a. The gradation voltage instruction unit 37 receives the luminance value of each light emitting area from the area luminance calculation unit. The luminance value of each light emitting area is a luminance value after being corrected using the luminance value of the surrounding light emitting area, and is a value that takes into account the influence of light crosstalk from the surrounding light emitting area.

The LUT 37a holds the gradation values before and after the correction processing in association with each other for each luminance value of the light emitting area. In other words, in the LUT 37a, the gradation value (input gradation data) for each of the plurality of pixels P included in the external video signal and the luminance of the output light output from the pixel P to the outside are desired. The corrected gradation value (output gradation data) as a value is associated with each other for each luminance value of the light emitting area. Then, when input gradation data for the pixel P included in the video signal from the outside is input, the gradation voltage instruction unit 37 also uses the luminance value of the light emitting area at the position corresponding to the pixel P to use the LUT 37a. The corresponding output gradation data is obtained from the above and used as the corrected gradation value. Then, the gradation voltage instruction unit 37 corrects the instruction signal (gradation signal) to the source driver 20 generated by the image processing unit 25 using the corrected gradation value, and outputs it to the source driver 20. To do. Thereby, in the present embodiment, predetermined different gamma curves different from each other in accordance with the lighting states of the light emitting diodes 4 corresponding to the display areas A-1 to A-32 and the light emitting areas (1) to (32). Is used to determine the corrected gradation value.

In addition, as shown in FIG. 16, the backlight control unit 36 is provided with a region luminance calculation unit 38 and an LED drive control unit 39. The area luminance calculation unit 38 acquires the luminance information of the pixels P included in the corresponding display area from the input video signal for each light emitting area. In addition, the area luminance calculation unit 38 performs luminance calculation processing that is obtained by calculating the luminance values of red, green, and blue colors in each light emitting area using the acquired luminance information of the pixel P. (Details will be described later).

Further, the area luminance calculation unit 38 performs an area crosstalk correction process described later on the luminance value of each color obtained by performing the luminance calculation process, thereby affecting the influence of crosstalk of light from the surrounding light emitting areas. Thus, the corrected luminance value of each color is obtained. Then, the area luminance calculation unit 38 outputs the calculated luminance value of each color after correction of each light emitting area to the gradation voltage instruction unit 37 and the LED drive control unit 39.

Here, the luminance calculation processing and the region crosstalk correction processing in the region luminance calculation unit 38 will be described. In the following description, among the nine light emitting areas (1), (2), (3), (9), (10), (11), (17), (18), (19), A case where the luminance value of the light emitting area (10) located at the center is obtained will be described as an example.

In the area

luminance calculation unit

38, 9 corresponding to the light emitting areas (1), (2), (3), (9), (10), (11), (17), (18), and (19), respectively. Luminance calculation processing is performed on the video signals in the display areas A-1, A-2, A-3, A-9, A-10, A-11, A-17, A-18, and A-19, respectively. Accordingly, red, blue, and green in the corresponding light emitting areas (1), (2), (3), (9), (10), (11), (17), (18), and (19) The luminance value of each color is obtained.

Specifically, the area luminance calculation unit 38 acquires luminance information of a plurality of pixels P (for example, 640 × 360 pixels P) included in the display area A-1 from the frame memory 19. Then, the area luminance calculation unit 38 performs luminance calculation processing on the acquired luminance information, thereby extracting, for example, data of the maximum luminance value for each color of red, blue, and green, and displaying the display area A−. The luminance value of each color in the light emitting area (1) corresponding to 1. That is, when the area luminance calculation unit 38 executes the luminance calculation process, the luminance value of the pixel P to be displayed in red at the highest luminance among the plurality of pixels P included in the display area A-1 is emitted. It is selected as the red luminance value in area (1).

Also, in this luminance calculation process, a filtering process for removing noise is performed, so that adverse effects of noise can be surely eliminated. In other words, the area luminance calculation unit 38 can prevent the luminance value from being extracted as the maximum luminance value when there is a pixel P having an abnormally high luminance value compared to the surrounding pixels P due to noise mixing. It is configured as follows.

Similarly, in a plurality of pixels P included in the display area A-1, the luminance value of the pixel P to be displayed in green with the highest luminance is selected as the green luminance value in the light emitting area (1). Similarly, in the plurality of pixels P included in the display area A-1, the luminance value of the pixel P to be displayed in blue with the highest luminance is selected as the blue luminance value in the light emitting area (1). Then, the area luminance calculation unit 38 determines the luminance values of the selected red, blue, and green colors as the luminance values of the light emitting area (1).

Similarly, the area luminance calculation unit 38 is configured to display red and blue in the light emitting areas (2), (3), (9), (10), (11), (17), (18), and (19). The luminance value of each color of green and green is obtained. Then, in the area luminance calculation unit 38, the luminance values of the light emitting area (10), for each of red, blue, and green colors, the surrounding light emitting areas (1), (2), (3), (9) , (11), (17), (18), and (19) region crosstalk correction processing using the luminance values is performed.

In this area crosstalk correction process, the area luminance calculation unit 38 corrects the obtained luminance value by using a correction coefficient stored in a memory (not shown), thereby red, blue, and green colors. In addition, the luminance value after correction of each light emitting area is calculated.

That is, for example, in the light emitting area (10), by the light from the surrounding light emitting areas (1), (2), (3), (9), (11), (17), (18), (19) For each of red, blue, and green colors, the brightness of each color light increases. Therefore, by performing a test or simulation result using an actual product, a correction coefficient that cancels out the luminance increase in each of the red, blue, and green colors is obtained in advance and stored in the memory. Then, the area luminance calculation unit 38 corrects each color of the light emitting area (10) by using the luminance value of each color of the light emitting area (10) obtained by the luminance calculation processing and the correction coefficient held in the memory. Later luminance values are calculated. Then, the area luminance calculation unit 38 outputs the calculated luminance value of each color after correction of each light emitting area to the gradation voltage instruction unit 37 and the LED drive control unit 39.

Further, since the above-described correction coefficient is determined based on the result of a test or simulation using an actual product, the change in luminance due to the internal structure of the liquid crystal panel 2 and the presence / absence of a diffusion plate or an optical sheet is taken into consideration. In addition, the influence of crosstalk in the liquid crystal display device 1 can be more reliably eliminated, and the display quality can be improved more easily.

Returning to FIG. 16, the LED drive control unit 39 constitutes a drive control unit that drives and turns on the light source, and responds based on the corrected luminance values of the plurality of light emitting areas from the region luminance calculation unit 38. The lighting period of the light emitting diode 4 is determined, and the light emitting diode 4 is driven to be lit by PWM dimming according to the determined lighting period. That is, the LED drive control unit 39 determines the on / off duty in the PWM dimming according to the luminance value determined by the region luminance calculation unit 38, and a signal that indicates the determined on / off duty. Is output to the lighting drive circuit (not shown) as an instruction signal. Then, the lighting drive circuit supplies the power to each light emitting diode 4 based on the instruction signal, thereby driving each of the light emitting diodes 4 to light.

On the other hand, when the luminance value of each color of red, green, and blue in each light emitting area (1) to (32) is transmitted from the area luminance calculation unit 38 to the gradation voltage instruction unit 37, the gradation voltage instruction unit 37. Acquires the corrected gradation value from the LUT 37a using these luminance values. Then, using the acquired corrected gradation value, the gradation voltage instruction unit 37 corrects the instruction signal to the source driver 20 input from the image processing unit 25, and the source driver as a new instruction signal. 20 is output.

Hereinafter, the operation of the liquid crystal display device 1 of the present embodiment configured as described above will be described. In the following description, the operation of the gradation voltage instruction unit 37 of this embodiment will be mainly described with reference to FIG.

FIGS. 17A and 17B are graphs for explaining specific examples of correction values determined by the gradation voltage instruction unit shown in FIG. 14 for different display areas.

The gradation voltage instruction unit 37 according to the present embodiment has a luminance value (that is, a light emitting diode in the light emitting area) of the corresponding light emitting areas (1) to (32) for each of the plurality of display areas A-1 to A-32. 4), the corrected gradation value is obtained from the LUT 37a.

Specifically, in the liquid crystal panel 2, when the value of the gamma curve is set as a desired value, for example, a value of “2.2”, the gradation voltage instruction unit 37 determines the luminance value of the light emitting area. Is equal to or greater than a predetermined value (that is, when the light-emitting diode 4 in the light emitting area is turned on with a predetermined brightness or higher), for example, “2.3” for the source driver corresponding to the light emitting area. The gamma curve of the value of is used. Specifically, in FIG. 17A, when the horizontal axis and the vertical axis are the x axis and the y axis, respectively, and the gradation value is, for example, 8 bits = 256 gradations, the curve 80 and the curve 81 Are both expressed by the equation y = ^xγ , and the value of the gamma curve, that is, the value of γ is “2.2” and “2.3” in the curve 80 and the curve 81, respectively. In the present embodiment, the gradation voltage instruction unit 37 applies the gamma indicated by the curve 81 to the source driver 20 assigned to the display area corresponding to the light emitting area that is turned on at a predetermined brightness or higher. By using the curve, the value of the gamma curve can be set to the desired value of “2.2” in the display area where the adverse effect due to heat from the light emitting diode 4 (that is, the reduction in the charging rate) is unlikely to occur. it can.

On the other hand, in the gradation voltage instruction unit 37, when the luminance value of the light emitting area is less than the predetermined value (that is, when the light emitting diode 4 in the light emitting area is turned on with less than the predetermined brightness (turned off). In this case, for example, a gamma curve having a value of “2.1” is used for the source driver corresponding to the light emitting area. Specifically, in FIG. 17B, when the horizontal axis and the vertical axis are the x axis and the y axis, respectively, and the gradation value is, for example, 8 bits = 256 gradations, the

curves

80 and 82 are obtained. Are both expressed by the equation y = ^xγ , and the value of the gamma curve, that is, the value of γ is “2.2” and “2.1” in the curve 80 and the curve 82, respectively. In the present embodiment, the gradation voltage instruction unit 37 applies the gamma indicated by the curve 82 to the source driver 20 assigned to the display area corresponding to the light emitting area that is turned on with less than a predetermined brightness. By using the curve, in the display areas A3, A4, A5, and A6 where the adverse effect due to the heat from the light emitting diode 4 (that is, the reduction in the charging rate) is likely to occur, the value of the gamma curve is set to “2.2” Value.

With the above configuration, the present embodiment can achieve the same operations and effects as those of the second embodiment. Further, in the present embodiment, the backlight device (backlight unit) 3 has a plurality of light emitting areas (light emitting diodes (light sources) 4) respectively incident on the plurality of display areas A-1 to A-32. 1) to (32) are provided. The control unit 16 is configured to perform drive control of the liquid crystal panel (display unit) 2 and the backlight device 3 using the input video signal. Further, the gradation voltage instruction unit 37 uses the lighting states of the light emitting diodes 4 corresponding to the plurality of light emitting areas (1) to (32) to perform the gradation value for each pixel included in the input video signal. The correction value is determined. Thereby, in this embodiment, while determining the lighting state of the light emitting diode 4 in each of the plurality of light emitting areas (1) to (32), that is, the temperature state in the corresponding light emitting areas (1) to (32), The correction value for the gradation value for each pixel P can be determined more appropriately. As a result, in the present embodiment, even when the liquid crystal panel 2 is enlarged, the display quality can be improved more reliably.

It should be noted that all of the above embodiments are illustrative and not restrictive. The technical scope of the present invention is defined by the claims, and all modifications within the scope equivalent to the configurations described therein are also included in the technical scope of the present invention.

For example, in the above description, the case where the present invention is applied to a transmissive liquid crystal display device has been described. However, the display device of the present invention is not limited to this, and a transflective liquid crystal display device or a liquid crystal display device is not limited thereto. The present invention can be applied to various display devices such as a projection display device using a panel as a light valve.

In the above description, the light emitting diode is used as the light source. However, the light source of the present invention is not limited to this, and a discharge tube such as a cold cathode fluorescent tube or a hot cathode fluorescent tube is used. You can also.

In addition to the above description, the gradation voltage instruction unit is configured to display red (R), green (G), and green in a plurality of display areas based on the temperature distribution when the light source of the backlight unit is driven to turn on. For each blue (B) pixel, a correction value for the gradation value for each pixel included in the input video signal may be determined to control the display unit.

In addition to the above description, the gradation voltage instruction unit of the present invention may be applied to a normally white mode liquid crystal panel.

In the above description, the case where the gradation voltage instruction unit determines a corrected gradation value using predetermined different gamma curves according to a plurality of display areas has been described. However, the gradation voltage instruction unit according to the present invention is configured such that, based on the temperature distribution when the light source of the backlight unit is turned on, the level of each pixel included in the input video signal is displayed for each of the plurality of display areas. Any method may be used as long as a correction value for the tone value is determined and drive control of the display unit is performed, and a predetermined gamma curve may not be used.

However, as in the above embodiments, when the predetermined gamma curve is used, the corrected gradation value is appropriately determined according to the display area even when the screen of the display unit is enlarged. This is preferable in that the display quality can be improved with certainty.

Besides the above description, the first to third embodiments may be appropriately combined.

The present invention is useful for a display device that can improve display quality even when the screen of the display unit is enlarged.

1 Liquid crystal display device 2 Liquid crystal panel (display unit)
3 Backlight device (backlight part)
4 Light emitting diode (light source)
16 Control unit 20, 20-1 to 20-8 Source driver 21

Gate driver

26, 34, 37 Gradation voltage instruction unit 26a

Arithmetic unit

34a, 37a LUT
32 Temperature sensors A1 to A8, A1 to A32 Display area (1) to (32) Light emission area

Claims

A display device including a backlight unit having a light source and a display unit that includes a plurality of pixels and displays information using illumination light from the backlight unit,
A control unit that performs drive control of at least the display unit using the input video signal,
The display unit is provided with a plurality of display areas,
Based on the temperature distribution when the light source of the backlight unit is driven to turn on, the control unit applies a gradation value for each pixel included in the input video signal for each of the plurality of display areas. A gradation voltage instruction unit that determines a correction value and performs drive control of the display unit is provided.
A display device characterized by that.
The gradation voltage instruction unit determines a corresponding gradation value included in an external video signal so that the luminance of output light output from the pixel toward the outside becomes a desired value. The display device according to claim 1, wherein the display device corrects the gradation value.
The calculation unit for calculating a predetermined gradation value by using the gradation value for each pixel included in the video signal from the outside is used for the gradation voltage instruction unit. 2. The display device according to 2.
The lookup table that associates a gradation value for each pixel included in an external video signal with a predetermined gradation value is used for the gradation voltage instruction unit. The display device described in 1.
The gradation voltage instruction unit determines a corrected gradation value using predetermined gamma curves that are different from each other in advance according to the plurality of display areas. The display device according to item.
The backlight unit is provided with a temperature sensor,
6. The gradation voltage instructing unit according to claim 1, wherein the gradation voltage instruction unit determines a correction value for a gradation value for each pixel included in the input video signal using a detection result of the temperature sensor. The display device described.
The backlight unit is provided with a plurality of light emitting areas for allowing light from the light sources to enter the plurality of display areas,
The control unit is configured to perform drive control of the display unit and the backlight unit using an input video signal,
The gradation voltage instruction unit determines a correction value for a gradation value for each pixel included in an input video signal using lighting states of light sources corresponding to the plurality of light emitting areas. The display device according to any one of the above.
As the display unit, a liquid crystal panel is used,
In the liquid crystal panel, a gate driver and a plurality of source drivers provided at different positions from the gate driver are provided,
The gradation voltage using different gamma curves is input from the gradation voltage instruction unit to the plurality of source drivers according to the plurality of display areas. Display device.