JP2009053512A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate luminance unevenness and color unevenness in a liquid crystal display wherein a liquid crystal panel is irradiated with light of a light source including a high luminance LED and a high color rendition LED. <P>SOLUTION: In the liquid crystal display 10, a light guide plate designed so that luminance unevenness is not generated in a second light emitting state for light emitting the high color rendition LED 32 is included in a display unit 20. In the liquid crystal display 10, a conversion table 19 in which values for lowering luminance of parts according to a radiation range of the high luminance LED 33 are regulated is stored in a memory 18, processing for altering luminance of display screen data acquired by a display data acquiring part 11 is performed based on the conversion table 19 in a second signal processing part 14 in a first light emitting state for light emitting both LEDs and the display screen data whose luminance is altered are supplied to a display panel 26 from an interface part 15 to prevent generation of luminance unevenness and color unevenness in the first light emitting state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device in which luminance unevenness and color unevenness do not occur in a liquid crystal panel when a light emission state is switched using a light source unit including two types of LEDs having different light emission characteristics.

  Conventionally, small devices (display devices) such as mobile phones and digital cameras equipped with a liquid crystal panel often use a plurality of white LEDs (Light Emitting Diodes) as a light source for illuminating the liquid crystal panel. In general, a sidelight system is adopted. The sidelight system is a system in which a rectangular light guide plate is disposed on the back surface of a liquid crystal panel, and a light source such as a plurality of white LEDs is provided facing a side surface that is one side of the light guide plate. Since the light guide plate converts light from a point light source such as a white LED into a surface light source and guides the light to the back surface of the liquid crystal panel, the liquid crystal panel is irradiated with light from the light source by the function of such a light guide plate. The In a small display device, a chamfered slope may be formed at the corner of the light guide plate, and a light source may be disposed so as to irradiate the slope.

  A light source (white LED) that is currently mainstream used for illuminating a liquid crystal panel is a combination of a blue LED light-emitting chip and a phosphor. When a blue LED light emitting chip and a yellow phosphor (YAG) are combined, a white LED giving priority to luminance (referred to as a high luminance LED) is obtained. Further, when the blue LED light emitting chip and the red and green phosphors are combined, a white LED giving priority to color rendering (referred to as a high color rendering LED) is obtained. The color rendering property refers to the property of a light source that affects the appearance of the color of an object when a light source such as a lamp is illuminated. As a representative index of color rendering property, the average color rendering index Ra Is used. Ra indicates that the color rendering is better as the reference light source is 100, and the closer to 100.

  A small display device (liquid crystal display device) is usually portable and is used both outdoors and indoors, and display performance according to such changes in the usage environment is required. In other words, when used outdoors, it is exposed to sunlight, so that the sunlight reflects on the liquid crystal panel, making it difficult to see the display content, so that it is necessary to increase the luminance related to the display on the liquid crystal panel. On the other hand, in order to improve image quality under indoor light, it is necessary to improve color rendering for display. Therefore, two types of LEDs, a high-brightness LED and a high-color-rendering LED with different light emission characteristics, are used as the light source, and by illuminating the liquid crystal panel with both LEDs, the brightness is increased to make the display content easier to see, and high-color-rendering indoors. It is conceivable to perform switching control related to light emission of the LED such that display with enhanced color rendering is performed by irradiating only with the LED.

In the following Patent Document 1, a liquid crystal display device including a chromaticity correction LED in the vicinity of the LED is disclosed in order to reduce color unevenness of the liquid crystal panel of the liquid crystal display device. Patent Document 2 below discloses a liquid crystal display device that irradiates a liquid crystal panel using a plurality of light sources such as built-in LEDs and external light. Further, Patent Document 3 below discloses that the light amounts of a plurality of LEDs used as light sources are controlled from light amount fluctuation information detected by a photosensor unit.
JP 2001-209049 A JP 2005-130325 A JP-A-2005-208486

  When the above-described high-brightness LED and high color rendering LED are used as a light source, and the switching control of the LED to emit light is performed, the light guide pattern of the light guide plate must be designed according to the light emission characteristics of each LED. The liquid crystal panel has a problem in that luminance unevenness (and color unevenness associated therewith) occurs.

  The luminance unevenness will be described with reference to FIGS. 11 (a) and 11 (b) show a liquid crystal display device 1 that irradiates a liquid crystal panel 3 with a light source unit 2 in which high brightness LEDs 2a and high color rendering LEDs 2b are alternately arranged on a base 2c. A light guide plate (not shown) having a light guide pattern such that the luminance of the liquid crystal panel 3 is made uniform in accordance with the irradiation of the high color rendering LED 2b is disposed. Therefore, as shown in FIG. 11A, when only the high color rendering LED 2b is used for indoor use, the region including the central portion of the liquid crystal panel 3 (shown by a wavy line in the drawing) is uniformly irradiated. Therefore, luminance unevenness and color unevenness do not occur. On the other hand, as shown in FIG. 11 (b), when both the high luminance LED 2a and the high color rendering LED 2b are irradiated for outdoor use, the overall luminance is increased, but the high luminance LED 2a is irradiated. The light is not uniformly distributed by the light guide plate, and a bright area R1 (area shown by hatching in the drawing) is generated in the portion irradiated with the high-intensity LED 2a, thereby causing uneven brightness in the area R1. .

  Also, the liquid crystal display device 1 'shown in FIGS. 12 (a) and 12 (b) has a high luminance LED 2a' and a high color rendering LED 2b 'as a base 2c', like the liquid crystal display device 1 shown in FIGS. 11 (a) and 11 (b). The liquid crystal panel 3 ′ is irradiated by the light source unit 2 ′ disposed. When the light guide pattern of the light guide plate disposed on the back surface of the liquid crystal panel 3 is irradiated by both the high luminance LED 2 a ′ and the high color rendering LED 2 b ′. In addition, the light from each LED 2a ', 2b' is uniformly distributed. For this reason, as shown in FIG. 12 (a), when the LEDs 2a ′ and 2b ′ are irradiated for outdoor use, an area including the central portion of the liquid crystal panel 3 ′ (shown by a wavy line in the figure) is obtained. Irradiation is uniform and brightness unevenness and color unevenness do not occur. However, as shown in FIG. 12 (b), when irradiation is performed only with the high color rendering LED 2b 'for indoor use, the high color rendering LED 2b' is irradiated. On the other hand, an area R2 (area shown by hatching in the figure) 8 that is dark and falls in the range corresponding to the high-intensity LED 2a 'is generated, resulting in uneven brightness.

  Since the high luminance LED and the high color rendering LED emit white light having different color components, color unevenness occurs in the liquid crystal panel as luminance unevenness occurs. Specifically, the light emitted from the high-intensity LED is pseudo white light composed only of blue and yellow as color components. On the other hand, the light emitted from the high color rendering LED is composed of blue, red, and green color components, and is more natural white light. For this reason, the color tone of the display content is different between the region irradiated with the high luminance LED and the region irradiated with the high color rendering LED, and color unevenness occurs.

  The present invention has been made in view of such a problem, and based on a brightness table that defines values for adjusting brightness according to the shape of a region where brightness unevenness and color unevenness occur, the brightness of display data is reduced. An object of the present invention is to provide a liquid crystal display device in which luminance unevenness and color unevenness do not occur in a state of being displayed on a liquid crystal panel.

  In order to solve the above problems, a liquid crystal display device according to the present invention includes a data acquisition unit that acquires display screen data, a data supply unit that supplies the display screen data acquired by the data acquisition unit to a liquid crystal panel, and a guide. In a liquid crystal display device including a light source unit that irradiates the liquid crystal panel through an optical plate, the light source unit includes a first LED and a second LED having different light emission characteristics, and the first LED is higher than the second LED. Brightness, the second LED has higher color rendering than the first LED, and a first light emitting state in which both the first LED and the second LED emit light, and a second light emitting state in which the second LED emits light Switching means for switching between, a luminance table defining values relating to luminance corresponding to the location of the liquid crystal panel, and the data acquisition means Changing means for changing the luminance related to the display screen data based on the luminance table, and the data supply means supplies the display screen data whose luminance is changed by the changing means to the liquid crystal panel. Features.

  In the present invention, the luminance related to the display screen data displayed on the liquid crystal panel is changed based on the luminance table that defines the value relating to the luminance corresponding to the location of the liquid crystal panel, and the changed display screen data is Since the image is supplied to the liquid crystal panel, a screen corresponding to the display screen data is displayed on the liquid crystal panel in a state where the luminance is changed from the original state. For this reason, the brightness of the screen to be displayed can be changed as appropriate according to the position of the liquid crystal panel based on the specified contents of the brightness table. For example, the contents of the brightness table are changed to the light emission state (for example, the first light emission state). Or, according to the second light emission state), it is possible to eliminate luminance unevenness and color unevenness that have conventionally occurred in a specific region.

  In the liquid crystal display device according to the present invention, the light guide plate includes a light guide pattern in which light emitted from the second LEDs is uniformly distributed corresponding to the second light emission state, and the luminance table includes The value is defined so that the luminance according to the location of the liquid crystal panel irradiated with the light emitted from the first LED is lower than other locations, and the changing means is configured such that the switching means is the first switching means. When switching to the light emission state, the luminance is changed based on the luminance table.

  In the present invention, a light guide plate provided with a light guide pattern as shown in FIG. 11 (a) is applied, and the luminance in the light emission state (first light emission state) shown in FIG. 11 (b) is applied. Since a brightness table in which values are specified so that the brightness corresponding to the position of the liquid crystal panel corresponding to the region R1 where the brightness becomes low is used, display screen data whose brightness has been changed based on this brightness table is supplied to the liquid crystal panel. For example, luminance unevenness does not occur even in the first light emission state, and color unevenness is also eliminated accordingly.

  In the liquid crystal display device according to the present invention, the light guide plate includes a light guide pattern in which light emitted from the first LED and the second LED is uniformly distributed corresponding to the first light emission state, and the luminance The table defines values such that the luminance according to the peripheral portion of the portion of the liquid crystal panel irradiated with the light emitted from the second LED is higher than other portions, and the changing means includes: When the switching unit switches to the second light emission state, the luminance is changed based on the luminance table.

  In the present invention, a light guide plate provided with a light guide pattern as shown in FIG. 12A is applied, and the luminance in the light emission state (second light emission state) shown in FIG. Since a luminance table is used in which values are specified so that the luminance according to the location of the liquid crystal panel corresponding to the region R2 where the brightness becomes darker is increased, display screen data whose luminance has been changed based on this luminance table is supplied to the liquid crystal panel. For example, luminance unevenness does not occur even in the second light emission state, and color unevenness is also eliminated accordingly.

  In the liquid crystal display device according to the present invention, the liquid crystal panel has a rectangular shape around the panel, the light source unit is arranged to face one side of the liquid crystal panel, and the brightness table A value relating to luminance is defined for a range including one side of the liquid crystal panel and not including the other side opposite to the one side.

  In the present invention, the light source unit is arranged by the sidelight method, and the luminance table defines the value relating to the luminance only for the range on the side where the light source unit is arranged. Therefore, the size of the luminance table is reduced and the capacity required for storing the luminance table can be reduced as compared with the case where the value relating to the luminance is defined. Since the side opposite to the side where the light source unit is arranged is far from the light source unit, luminance unevenness or the like is generally unlikely to occur. Therefore, there is no particular problem even if the change based on the luminance table is not performed.

  The liquid crystal display device according to the present invention includes the first LED and the second LED in which the light source unit is arranged symmetrically from the center of the one side to both ends in the direction along the one side of the liquid crystal panel, In the luminance table, a value related to luminance is defined for a range from the center of the one side to one end side in a direction along one side of the liquid crystal panel, and the luminance table relates to the luminance defined by the luminance table. Reversing means for inverting the value with respect to the panel position, the changing means changes the luminance based on the luminance table for a range from the center of the one side to one end side, The luminance is changed based on the contents inverted by the inversion means with respect to the range from the center to the other end side.

  In the present invention, the luminance table defines the luminance value for the range from the center to one end side of one side of the liquid crystal panel where the light source unit is arranged, and for the remaining range. Since the specified contents of the luminance table are inverted and used for processing related to the luminance change, the size of the luminance table can be further reduced.

  In the liquid crystal display device according to the present invention, the light source unit includes a plurality of the first LEDs and the second LEDs, respectively, and the luminance table has a luminance with respect to a range irradiated by one first LED or one second LED. Such a value is defined, and the changing means changes the luminance based on the luminance table for each range irradiated by each first LED or second LED included in the light source unit.

  In the present invention, the luminance table defines a value related to the luminance only for a range irradiated by one LED (first LED or second LED), and each LED is irradiated when the luminance is changed. Since the luminance table is used for a plurality of locations, the size of the luminance table can be minimized. Therefore, even when the size of the liquid crystal panel is large, the size of the luminance table can be reduced, which is particularly suitable for a large screen type liquid crystal panel.

In the present invention, since the brightness related to the display screen data is changed based on the brightness table that defines the value related to the brightness corresponding to the location of the liquid crystal panel, the screen brightness displayed on the liquid crystal panel is the content specified in the brightness table. Can be changed according to
Further, in the present invention, since the specified content of the brightness table is designed to lower the brightness corresponding to the irradiation location of the high brightness LED, conventionally, irradiation is performed with both the high brightness LED and the high color rendering LED. The luminance unevenness and the color unevenness that have occurred when performing the operation can be eliminated.
Furthermore, in the present invention, the specified content of the brightness table is designed to brighten the brightness corresponding to the periphery of the irradiated portion of the high color rendering LED, so that conventionally, only the high color rendering LED is irradiated. In this case, it is possible to eliminate luminance unevenness and color unevenness that have occurred in the case of the above.

In the present invention, the light source unit is arranged by the sidelight method, and the luminance table defines the value related to the luminance only for the range on the side where the light source unit is arranged. Therefore, the size of the luminance table can be reduced.
In the present invention, the LEDs are arranged so as to be symmetrical at the center in the direction in which the light source unit is arranged, and the luminance table defines a range from the center to one end, and from the center to the other. Since the specified contents of the luminance table are inverted up to the end, the size of the luminance table can be further reduced.
Further, according to the present invention, the luminance table defines a value relating to the luminance only for the range irradiated by one LED (first LED or second LED). Since the brightness table is used for each of the plurality of locations to be irradiated, the size of the brightness table can be minimized.

  FIG. 1 is a block diagram showing a main internal configuration of a liquid crystal display device 10 according to an embodiment of the present invention. The liquid crystal display device 10 is applicable to a device (display device that can be used both indoors and outdoors) having a display panel (liquid crystal panel) such as a mobile phone or a digital video camera. For example, the present invention can also be applied as a portable television apparatus compatible with one-segment broadcasting. The liquid crystal display device 10 stores a display data acquisition unit 11, a synchronization signal generation unit 12, a first signal processing unit 13, a second signal processing unit 14, an interface unit 15, an operation unit 16, a control unit 17, and a conversion table 19 in advance. The memory 18 and the display unit 20 are included. Hereinafter, the liquid crystal display device 10 of the present embodiment will be described in detail.

  The display data acquisition unit 11 corresponds to data acquisition means, performs a process of acquiring display screen data corresponding to the screen content displayed on the liquid crystal panel, and obtains display screen data according to a target to which the liquid crystal display device 10 is applied. Is different. For example, when the liquid crystal display device 10 corresponds to a portable television device compatible with one-segment broadcasting, the display data acquisition unit 11 acquires display screen data from the one-segment tuner. When the liquid crystal display device 10 is applied to a digital video camera, the display data acquisition unit 11 acquires display screen data from an image sensor (CCD, CMOS, etc.) that captures an image. The display data acquisition unit 11 sends the acquired display screen data to the first signal processing unit 13 in RGB signal units.

  The synchronization signal generator 12 generates a horizontal synchronization signal and a vertical synchronization signal corresponding to the display on the liquid crystal panel 26 included in the display unit 20, and sends the generated synchronization signal to the first signal processing unit 13. . In addition, the first signal processing unit 13 synchronizes the necessary processing for displaying the display screen data sent from the display data obtaining unit 11 with the display unit 20 with the synchronization signal sent from the synchronization signal generating unit 12. As a necessary process, for example, gamma correction is performed. The first signal processing unit 13 sends the processed display screen data to the second signal processing unit 14.

  The second signal processing unit 14 corresponds to a changing unit, and based on a conversion table 19 stored in the memory 18, a process for changing the luminance related to the display screen data sent from the first signal processing unit 13 is synchronized. This is performed in synchronization with the synchronization signal sent from the signal generation unit 12, and the display screen data whose luminance is changed is sent to the interface unit 15. Details of the processing relating to the second signal processing unit 14 will be described later.

  The interface unit 15 corresponds to a data supply unit, and synchronizes the processed display screen data sent from the second signal processing unit 14 to the liquid crystal panel 26 of the display unit 20 with the synchronization signal sent from the synchronization signal generating unit 12. Process to supply. The interface unit 15 supplies the display screen data to the liquid crystal panel 26, so that a screen corresponding to the liquid crystal screen data is displayed on the liquid crystal panel 26.

  As shown also in FIG. 2, the display unit 20 sequentially arranges the first prism sheet 25, the second prism sheet 24, the diffusion sheet 23, the light guide plate 22, and the reflection sheet 21 on the back side of the liquid crystal panel 26. In addition, the light source unit 30 is disposed on the side facing the one side portion 26a of the liquid crystal panel 26 having a rectangular shape in plan view, and the whole is surrounded by the housing 20a. The first prism sheet 25 and the second prism sheet 24 collect light and improve the front luminance. The diffusion sheet 23 improves the luminance of the liquid crystal panel 26, reduces light diffusion, and luminance unevenness. The reflection sheet 21 reflects light leaking from the light guide plate 22 toward the liquid crystal panel 26.

  The light source unit 30 irradiates the liquid crystal panel 26 through the light guide plate 22, and, as shown in FIG. 1, a total of four high-intensity LEDs (corresponding to the first LED. In the figure, hatched LEDs) 33 and high color rendering LEDs (corresponding to the second LEDs) 32 are alternately arranged on the base 31 at equal intervals. The high luminance LED 33 has higher luminance than the high color rendering LED 32 in terms of light emission characteristics, and the high color rendering LED 32 has higher color rendering properties than the high luminance LEDs 33 in terms of light emission characteristics. These LEDs 32 and 33 are arranged so as to be symmetrical from the center of one side portion 26a in the longitudinal direction of the liquid crystal panel 26 to both the left and right sides in FIG. 1, and as shown in FIG. Irradiation is performed toward a portion (a side view on the same side as the one side portion 26a of the liquid crystal panel 26). In the present embodiment, the LEDs 32 and 33 are arranged at regular intervals to provide regularity, and the conversion table 19 described later is also provided with regularity so as to grasp the light path in the light guide plate 22. Of course, it is possible to arrange the LEDs 32 and 33 at unequal intervals according to the specifications or characteristics of the liquid crystal display device 10.

In the present embodiment, the high-intensity LED 33 is a white LED composed of a blue LED light-emitting chip and a yellow phosphor (Ca-α sialon), and the high color rendering LED 32 is a blue LED. A white LED composed of a light emitting chip, a red phosphor (CaAlSiN ₃ ), and a green phosphor (β sialon) is used. Furthermore, in the present embodiment, a chip-shaped LED is applied to each of the LEDs 32 and 33, but it is of course possible to apply a bullet-type or flat-type LED.

  The display state of each LED 32 and 33 included in the light source unit 30 is controlled by the control unit 17, and the control unit 17 switches the display state of each LED 32 according to the operation state of the changeover switch included in the operation unit 16. Specifically, the operation unit 16 includes a changeover switch for switching between an outdoor display pattern and an indoor display pattern, and when this changeover switch is operated to the outdoor display pattern side by the user, The control unit 17 sets the high luminance LED 33 and the high color rendering LED 32 included in the light source unit 30 to emit light (first light emitting state) as switching means. Further, when the changeover switch of the operation unit 16 is operated to the indoor display pattern side by the user, the control unit 17 causes the high color rendering LED 32 included in the light source unit 30 to emit light (second light emission state) as a switching unit. Switch to.

  In addition, the light guide plate 22 included in the display unit 20 has a light guide pattern that makes the luminance of the liquid crystal panel 26 uniform in the second light emission state described above. Specifically, in the second light emission state, In some cases, a light guide pattern is provided in which light emitted from the high color rendering LED 32 is uniformly distributed. Therefore, in the second light emitting state in which only the high color rendering LED 32 emits light as shown in FIG. 1, the display unit 20 has uniform luminance at the center portion of the liquid crystal panel 26 (indicated by a wavy line in FIG. 1), uneven luminance, Color unevenness does not occur.

  On the other hand, as shown in FIG. 3A, in the first light emitting state in which the process according to the present invention is not performed, the liquid crystal panel 26 has a region R10 corresponding to the location irradiated by the high-intensity LED 33, as in the past. Becomes brighter than other portions (other regions), resulting in luminance unevenness and color unevenness. The shape line L10 of the brightened region R10 has a shape that protrudes sharply so that the opposite portion of the central portion of the high-brightness LED 33 is the apex, and has a concave shape at a portion that faces the high color rendering LED 32. ing. Also, there is a difference in the degree of luminance unevenness and color unevenness at each location in the region R10, and the center of the irradiation direction of the high brightness LED 33 is the brightest, and from that location to the left and right in FIG. Since the brighter the lower the distance is, the brightness unevenness and the color unevenness vary accordingly.

  FIG. 5 is a chart showing the contents of the conversion table 19 (corresponding to the luminance table) stored in the memory 18. The conversion table 19 is displayed at a panel location in the liquid crystal panel 26 (a liquid crystal panel having 320 pixels in the horizontal direction (X direction) and 240 pixels in the vertical direction (Y direction)) corresponding to the region R10 shown in FIG. A value related to the luminance is defined for each pixel included, and in the present embodiment, a value for lowering the luminance of the pixel included in the region R10 than other portions is defined. Specifically, the conversion table 19 corresponds to the brightness difference in the region R10, and the pixel at the brightest panel position facing the central portion of the high-intensity LED 33 (for example, the pixel at X = 5, Y = 233). The value of “−40” is defined in order to decrease the value related to the luminance by “40”. In addition, the conversion table 19 indicates that “−38”, “−36”, “−34”, “−” is applied to pixels at positions where the brightness decreases as the distance from the position facing the central portion of the high-intensity LED 33 increases to the left and right. Values such as “32” and “−30” are defined.

  In the liquid crystal display device 10 of the present embodiment, when the first light emission state is set, the control unit 17 reads the conversion table 19 and sends it to the second signal processing unit 14, and the second signal processing unit 14 controls the control unit 17. Thus, the process of changing the value of the pixel included in the display screen data is performed using the sent conversion table 19. For example, if the luminance value corresponding to the pixel of X = 5 and Y = 233 in the display screen data is “120”, it is defined for the pixel of X = 5 and Y = 233 in the conversion table 19. Based on the obtained “−40” value, the second signal processing unit 14 changes the luminance value corresponding to the pixels of X = 5 and Y = 233 in the display screen data to “80 (120-40)”. Perform the process. If the luminance value corresponding to the pixel of X = 2 and Y = 233 in the display screen data is “120”, it is defined for the pixel of X = 2 and Y = 233 in the conversion table 19. Based on the value of “−30”, the second signal processing unit 14 changes the luminance value corresponding to the pixel of X = 2 and Y = 233 in the display screen data to “90 (120-30)”. Process.

  The graphs of FIG. 4A to FIG. 4C represent contents related to the above-described processing performed by the second signal processing unit 14. FIG. 4A shows the luminance value of the input signal (input data) on the AA line shown in FIG. 3A among the display screen data received by the second signal processing unit 14 from the first signal processing unit 13. The horizontal axis represents the position in the X direction (position in the range of X = 0 to X = 319), and the vertical axis represents the luminance level. FIG. 4A shows that the luminance level of the input signal is constant regardless of the position in the X direction.

  FIG. 4B shows values relating to the luminance defined in the X direction at the position of the AA line (for example, the position of Y = 180) as defined by the conversion table 19 of FIG. It is a graph of the converted signal (converted data). Further, FIG. 4C shows the luminance level of the display signal (display data) actually displayed at the position of the AA line of the liquid crystal panel 26 by the luminance change processing of the second signal processing unit 14 by a solid line. The solid line is the curve of the conversion signal shown in FIG. 4B (shown by the wavy line in FIG. 4C) and the liquid crystal panel 26 along the AA line in FIG. The luminance level (shown by a wavy line in FIG. 4C) is synthesized with the curve L10, and such processing is performed by the second signal processing unit 14.

  FIG. 3B shows a state in which the display screen data processed by the second signal processing unit 14 described above is displayed on the liquid crystal panel 26 in the first light emission state. Thus, according to the present invention, even in the first light emitting state, as in the second light emitting state shown in FIG. 1, the liquid crystal panel 26 does not have uneven luminance, and accordingly, uneven color is eliminated, and a uniform luminance level is secured. Has been. Therefore, as shown in FIG. 3B, the liquid crystal display device 10 of the present embodiment is enhanced without causing luminance unevenness and color unevenness even when both the high brightness LED 33 and the high color rendering LED 32 emit light. With this brightness, good display characteristics can be obtained. Also, indoors, as shown in FIG. 1, display with excellent color rendering characteristics can be performed by light emission of the high color rendering LED 32. Note that the liquid crystal display device 10 does not perform luminance change processing based on the conversion table 19 because no luminance unevenness or the like originally occurs in the second light emission state.

  Further, the liquid crystal display device 10 according to the present invention is not limited to the above description, and there are various modifications. For example, switching between the first light emission state and the second light emission state is performed based on an operation instruction with a change-over switch provided in the operation unit 16, but switching is performed using an illuminance sensor that detects illuminance. Also good. In this case, the illuminance sensor is connected to the control unit 17 and a threshold value related to the illuminance is stored in the memory 18. When the value detected by the illuminance sensor exceeds the threshold value, it is determined that the user is outdoors and the first light emission state When the detected value falls below the threshold value, the control unit 17 performs control to determine that the detected value is indoors and switch to the second light emission state. Further, the number of the high luminance LEDs 33 and the high color rendering LEDs 32 of the light source unit 30 can be appropriately increased or decreased according to the size or specification of the liquid crystal panel 26. Further, the order in which the high luminance LEDs 33 and the high color rendering LEDs 32 are arranged is shown in FIG. It is also possible to reverse the case shown in FIG.

  Further, since the conversion table 19 occupies the storage area of the memory 18, if the size of the conversion table 19 is reduced, the occupation ratio of the memory 18 can be reduced. 6 (a) and 6 (b) and FIG. 7 are conceivable.

  FIG. 6A shows a range 35 defined by the conversion table of the modification. That is, the liquid crystal display device 10 has the light source unit 30 disposed on the one side 26 a side of the liquid crystal panel 26, and therefore the other side 26 b opposite to the one side 26 a is away from the light source unit 30. Does not occur. That is, as shown in FIG. 5, since the value specified by the conversion table 19 in the upper portion in the Y direction is “0”, the liquid crystal panel 26 is in the range of Y = 0 to Y = 119 in the Y direction (the liquid crystal panel 26 In the upper half range in FIG. 6A, the luminance changing process is not performed. Therefore, in the conversion table of the modified example, a value relating to luminance is specified for the range 35 (the lower half range in FIG. 6 (middle) including the side of the one side portion 26a and not including the side of the other side portion 26b). For example, the size of the conversion table of the modification can be made half the size of the conversion table shown in FIG. Note that the range defined by the conversion table of the modification is not limited to the lower half of the liquid crystal panel 26 (not limited to Y = 119), and the position in the Y direction is appropriately changed according to the range in which luminance unevenness occurs. Is possible.

  FIG. 6B shows a range 36 defined by the conversion table of the modification in which the size is further reduced. In this modification, the range 35 in FIG. 6A is a range 36 from the pixel (X = 159) which is the center in the X direction of the liquid crystal panel 26 to the left half (X = 0 to X = 159). Only for this range 36, the conversion table defines values relating to luminance. 6A, in the range 37 corresponding to the right half from X = 160 to X = 319 (indicated by thick wavy lines in the figure), the arrangement of the LEDs 32 and 33 of the light source unit 30 is X = Since it is symmetric with respect to 159, the shape of the shape line L10 related to luminance unevenness is also symmetric. Therefore, in this modification, the control unit 17 reads out the conversion table corresponding to the range 36, creates an inversion table with the contents obtained by inverting the read conversion table with respect to X = 159, and converts the conversion table and the inversion table into It is sent to the second signal processing unit 14. Further, the second signal processing unit 14 performs change processing on the range 36 based on the conversion table, and performs change processing on the range 37 based on the inversion table. In this way, the size of the conversion table can be reduced to a quarter size of the conversion table of FIG.

  Furthermore, FIG. 7 shows a case of a modification in which the conversion table is defined only for the ranges 38a and 39a corresponding to the pixels at the panel position corresponding to the irradiation range of the high-intensity LED 33. That is, the shape line L10 indicating the shape of the luminance unevenness is X in the range 39a irradiated to the high luminance LED 33 arranged at the left end in FIG. 7 and the range 39b irradiated to the high luminance LED 33 arranged at the right end. The shape is symmetrical with respect to the center of the direction. Moreover, the range 38a irradiated to the high-intensity LED 33 arranged second from the left and the range 38b irradiated to the high-intensity LED 33 arranged third from the left have the same shape.

  Therefore, in the modification shown in FIG. 7, the conversion table corresponding to the range 39a and the conversion table corresponding to the range 38a are stored in the memory 18, and the conversion table corresponding to the range 39a is stored in the range 39b. The control unit 17 and the second signal processing unit 14 perform processing so that the inverted table of the inverted contents is applied as in the case of), and the conversion table corresponding to the range 38a is applied as it is to the range 38b. Thus, the storage amount of the conversion table stored in the memory 18 can be further reduced. In the modification shown in FIG. 7, the conversion table is efficiently used only for the irradiation range of each LED, particularly when the number of LEDs included in the light source unit 30 is large or the liquid crystal panel 26 is large in size. Since it can be used, it becomes suitable.

  In the above description, the conversion table defines the value related to the luminance for the display screen data sent from the first signal processing unit, but the R signal, G included in the display screen data. A conversion table may be provided for at least one of the signal and the B signal, and the luminance changing process may be performed on the signal corresponding to the conversion table. For example, it is possible to change the luminance only for the R signal of the display screen data by providing a conversion table for the R signal. Also, the conversion table for the R signal and the conversion table for the G signal are provided. It is also possible to change the luminance of the R signal and the G signal. As described above, if the luminance change process is individually performed for each of the R signal, the G signal, and the B signal, the color unevenness caused by the brightness unevenness can be eliminated in more detail.

  FIG. 8 shows a display unit 20 ′ according to another liquid crystal display device. The light guide plate 22 ′ included in the display unit 20 ′ is emitted from both LEDs in a state where both the high luminance LED 33 ′ and the high color rendering LED 32 ′ included in the light source unit 30 ′ emit light (first light emitting state). The light guide pattern has a uniform distribution of light. Therefore, if only the high color rendering LED 32 'is caused to emit light (second light emitting state) and the process according to the present invention is not performed, as shown in FIG. 8, a region R20 around the portion irradiated with the high color rendering LED 32' is irradiated. The brightness unevenness occurs in the liquid crystal panel 26 'so that the brightness becomes darker. The shape line L20 indicating the shape of the luminance unevenness is sharply recessed in the range irradiated to the high luminance LED 33 'and protrudes in a trapezoidal shape in the range irradiated to the high color rendering LED 32'.

  Therefore, the liquid crystal display device shown in FIG. 8 uses the conversion table that defines a value for increasing the luminance with respect to the region R20 as compared with the other regions (other portions) in the liquid crystal panel 26 ′. By performing the luminance changing process only in the light emitting state, it is possible to increase the luminance of the region R20 and eliminate luminance unevenness and color unevenness. As another conversion table, a conversion table that defines a value for decreasing the brightness corresponding to the area corresponding to the range irradiated to the high color rendering LED 22 'is used. In addition, color unevenness can be eliminated. Note that the liquid crystal display device shown in FIG. 8 can also apply the modification examples shown in FIGS. 6A and 6B and FIG. A conversion table that defines a value for lowering the luminance corresponding to the range irradiated by the color rendering LED 32 'is stored, and a process of changing the luminance based on the conversion table is performed for each portion irradiated by each high color rendering LED 32'. Will do.

  FIGS. 9A and 9B show a display unit 40 of a liquid crystal display device according to another modification. In this display unit 40, an oblique side 46c is formed at a corner where a long side 46a and a short side 46b of a rectangular liquid crystal panel 46 intersect, and a light source unit 50 is disposed so as to face the oblique side 46c. It is a feature. In the light source unit 50, a high luminance LED 53 and a high color rendering LED 52 are arranged on the base 51. The light guide plate 42 disposed on the back side of the liquid crystal panel 46 is formed in the same peripheral shape as the liquid crystal panel 46 and, as shown in FIG. 9B, the second light emitting state (high color rendering LED 52). In the first light-emitting state (the state in which both LEDs 52 and 53 are made to emit light) in FIG. 9A, the light guide pattern is designed so as not to cause uneven brightness. If the processing according to the invention is not performed, the region R30 corresponding to the irradiation position of the high-intensity LED 53 becomes bright, and uneven brightness and uneven color occur.

  For this reason, in the liquid crystal display device including the display unit 40 of FIGS. 9A and 9B, the conversion table defining the value for reducing the luminance of the region R30 of FIG. It is possible to prevent occurrence of luminance unevenness and color unevenness even in one light emitting state.

  FIG. 10 shows a display unit 40 ′ which is a modification of the display unit 40 shown in FIGS. 9A and 9B. The light guide plate 42 ′ included in the display unit 40 ′ has uneven luminance in the first light emission state. In the second light emitting state, the range irradiated to the high color rendering LED 52 ′ included in the light source unit 50 ′ becomes brighter and the surrounding region R40 becomes darker. As a result, luminance unevenness and color unevenness occur in the liquid crystal panel 46 '. Therefore, in this case, by using a conversion table that defines a value for increasing the luminance of the region R40, it is possible to prevent occurrence of luminance unevenness and color unevenness in the second light emission state. Even if a conversion table that defines a value for lowering the luminance in the range irradiated to the high color rendering LED 52 'is used, the occurrence of luminance unevenness and color unevenness can be similarly prevented.

It is a block diagram which shows the principal part of the liquid crystal display device which concerns on embodiment of this invention. It is sectional drawing of a display unit. (A) is the schematic which shows the display state when not performing the process which concerns on this invention in a 1st light emission state, (b) is the schematic which shows the display state when performing the process which concerns on this invention in a 1st light emission state. It is. (A) is a graph showing the luminance level of the input signal, (b) is a graph showing the luminance level of the converted signal, and (c) is a graph showing the luminance level of the display signal after the conversion processing. It is a chart which shows the contents of a conversion table. (A) is the schematic which shows the range which the conversion table concerning a modification corresponds, (b) is the schematic which shows the range which the conversion table concerning another modification corresponds. It is the schematic which shows the range which the conversion table concerning another modification corresponds. It is the schematic which shows the display state when not performing the process which concerns on this invention in a 2nd light emission state. FIG. 2 is a display unit in which a light source unit is arranged opposite to a hypotenuse, (a) is a schematic diagram showing a situation where luminance unevenness occurs in the first light emission state, and (b) is a uniform light distribution in the second light emission state. It is the schematic which shows the display state by which was performed. It is the schematic which shows the condition where the brightness | luminance nonuniformity produced in the display unit which has arrange | positioned the light source unit facing an oblique side part in the 2nd light emission state. It is a conventional display unit, (a) is a schematic diagram showing a second light emission state, (b) is a schematic diagram showing a situation where luminance unevenness has occurred in the first light emission state. It is a conventional display unit, (a) is a schematic diagram showing a first light emission state, (b) is a schematic diagram showing a situation where luminance unevenness has occurred in a second light emission state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 11 Display data acquisition part 14 2nd signal processing part 15 Interface part 16 Operation part 17 Control part 18 Memory 19 Conversion table 20 Display unit 22 Light guide plate 26 Liquid crystal panel 26a One side part 30 Light source unit 32 High color rendering LED (1st color rendering LED) 2LED)
33 High-brightness LED (first LED)

Claims (6)

A liquid crystal display comprising: data acquisition means for acquiring display screen data; data supply means for supplying display screen data acquired by the data acquisition means to a liquid crystal panel; and a light source unit that irradiates the liquid crystal panel via a light guide plate In the device
The light source unit includes a first LED and a second LED having different light emission characteristics,
The first LED has a higher brightness than the second LED,
The second LED has higher color rendering than the first LED,
Switching means for switching between a first light emitting state for emitting both the first LED and the second LED and a second light emitting state for emitting the second LED;
A luminance table defining values relating to luminance corresponding to the location of the liquid crystal panel;
Changing means for changing the luminance of the display screen data acquired by the data acquisition means based on the luminance table;
The liquid crystal display device, wherein the data supply means supplies display screen data whose luminance is changed by the changing means to the liquid crystal panel. The light guide plate includes a light guide pattern in which light emitted from the second LED is uniformly distributed corresponding to the second light emission state,
The brightness table has values defined such that the brightness according to the location of the liquid crystal panel irradiated with the light emitted from the first LED is lower than other locations,
The liquid crystal display device according to claim 1, wherein the changing unit changes the luminance based on the luminance table when the switching unit switches to the first light emission state. The light guide plate includes a light guide pattern in which light emitted from the first LED and the second LED is uniformly distributed corresponding to the first light emission state,
In the brightness table, values are defined such that the brightness according to the peripheral portion of the portion of the liquid crystal panel irradiated with the light emitted from the second LED is higher than other portions,
The liquid crystal display device according to claim 1, wherein the changing unit changes the luminance based on the luminance table when the switching unit switches to the second light emission state. The liquid crystal panel has a rectangular shape around the panel,
The light source unit is arranged to face one side of the liquid crystal panel,
The luminance table defines a value relating to luminance with respect to a range that includes one side of the liquid crystal panel and does not include the other side that is opposite to the one side. Item 4. The liquid crystal display device according to any one of items 3 to 3. The light source unit includes the first LED and the second LED arranged symmetrically from the center of the one side to both end sides in a direction along one side of the liquid crystal panel,
The luminance table defines a value relating to luminance with respect to a range on one end side from the center of the one side portion in a direction along one side portion of the liquid crystal panel,
Reversing means for reversing the value relating to the brightness defined by the brightness table with respect to the panel position;
The changing unit changes the luminance based on the luminance table with respect to a range from the center of the one side to one end, and the inversion unit with respect to a range from the center of the one side to the other end. The liquid crystal display device according to claim 4, wherein the luminance is changed based on the inverted contents. The light source unit includes a plurality of the first LEDs and the second LEDs,
In the luminance table, a value relating to luminance is defined for a range irradiated by one first LED or one second LED,
The liquid crystal display device according to claim 4, wherein the changing unit changes the luminance based on the luminance table for each range irradiated by each first LED or second LED included in the light source unit.

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