Abstract:
A light-emitting element display device includes a light-emitting element display panel that displays an image by light emission of light-emitting regions of a plurality of sub-pixels. Each of the pixels includes a first R sub-pixel, a second R sub-pixel, a first G sub-pixel, a second G sub-pixel, a first B sub-pixel and a second B sub-pixel. The second R sub-pixel, the second G sub-pixel, and the second B sub-pixel include a W electrode as a common electrode that causes the second R sub-pixel, the second G sub-pixel, and the second B sub-pixel to simultaneously emit lights in response to the application of a potential. The driver circuit includes a sub-pixel control unit that calculates a peak luminance in a screen based on the video signal and controls the plurality of sub-pixels based on the peak luminance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority from Japanese application JP2013-155375 filed on Jul. 26, 2013, the content of which is hereby incorporated by reference into this application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a light-emitting element display device, and more particularly to a light-emitting element display device that performs display by causing a light-emitting element as a self-luminous body arranged in each of pixels to emit light. 
     2. Description of the Related Art 
     In recent years, an image display device (hereinafter referred to as an “organic EL (Electro-luminescent) display device”) using a self-luminous body called an organic light-emitting diode (OLED) has been put to practical use. Since the self-luminous body is used, the organic EL display device is superior in terms of visibility and response speed compared to a related-art liquid crystal display device, and in addition, a further reduction in thickness is possible in the organic EL display device because an auxiliary lighting device such as a backlight is not necessary. 
     For color display in such an organic EL display device, mainly, the organic EL display device includes light-emitting elements that respectively emit lights of three colors of R (red), G (green), and B (blue) in respective pixels in some cases, while, in other cases, the organic EL display device causes a light-emitting element to emit only white light and allows the light to transmit respective wavelength ranges of three colors of R, G, and B through color filters of respective pixels. Moreover, for increasing a contrast ratio without increasing power consumption in the liquid crystal display device, it has been known to further provide a W (white) pixel in addition to R, G, and B pixels to increase luminance. 
     JP 2007-531062 A discloses a display device including a light-emitting layer that emits Y (yellow) light in addition to light-emitting layers that respectively emit R, G, and B lights. 
     SUMMARY OF THE INVENTION 
     Also in the light-emitting element display device including light-emitting elements that individually emit lights of respective colors of R, G, and B, it is desired for expanding a color reproduction range and improving color purity to further add a light-emitting element of W, Y or the like to the R, G, and B light-emitting elements to have four colors. However, such a configuration increases the number of times of deposition process, which is not favorable from the viewpoint of manufacturing cost. Moreover, since the accuracy of a deposition process is rougher than the accuracy of a photolithography process, an increase in the number of times of deposition process leads to an obstruction in higher definition or a deterioration in aperture ratio. 
     The invention has been made in view of the circumstances described above, and it is an object of the invention to provide a light-emitting element display device whose manufacturing cost is suppressed and that has an expanded color reproduction range and improved color purity. 
     A light-emitting element display device according to an aspect of the invention includes: a light-emitting element display panel that displays an image by light emission of light-emitting regions of a plurality of sub-pixels arranged in each of pixels in a display region, controlled by a driver circuit, wherein each of the pixels includes a first R (red) sub-pixel and a second R sub-pixel each of which emits light in a red wavelength range, a first G (green) sub-pixel and a second G sub-pixel each of which emits light in a green wavelength range, and a first B (blue) sub-pixel and a second B sub-pixel each of which emits light in a blue wavelength range, the first R sub-pixel, the first G sub-pixel, and the first B sub-pixel respectively include an R electrode, a G electrode, and a B electrode that control light emission independently of one another in response to the application of potentials, the second R sub-pixel, the second G sub-pixel, and the second B sub-pixel include a W (white) electrode as a common electrode that causes the second R sub-pixel, the second G sub-pixel, and the second B sub-pixel to simultaneously emit lights in response to the application of a potential, and the driver circuit includes a sub-pixel control unit that acquires a video signal to calculate a peak luminance in a screen based on the video signal and controls the plurality of sub-pixels based on the peak luminance. 
     In the light-emitting element display device according to the aspect of the invention, the sub-pixel control unit may include a peak luminance calculating unit that calculates the peak luminance, an area luminance determining unit that determines, based on the peak luminance calculated by the peak luminance calculating unit, the luminance of a W sub-pixel including the W electrode arranged in the pixel in each of areas obtained by dividing the display region into a plurality of regions, and a W sub-pixel control unit that applies, using the luminance of the W sub-pixel, a potential to the W electrode arranged in the pixel in each of the areas. 
     In the light-emitting element display device according to the aspect of the invention, the area luminance determining unit may further determine a light emission time period as a time period in which the potential is applied. 
     In the light-emitting element display device according to the aspect of the invention, the area luminance determining unit may further determine the division of areas based on the peak luminance. 
     In the light-emitting element display device according to the aspect of the invention, the sub-pixel control unit may further include an RGB sub-pixel control unit that determines, based on determination of the area luminance determining unit, the luminances of the first R sub-pixel, the first G sub-pixel, and the first B sub-pixel and applies, based on the respective determined luminances, potentials to the R electrode, the G electrode, and the B electrode. 
     In the light-emitting element display device according to the aspect of the invention, a scanning signal line to which respective transistors for applying potentials to the R electrode, the G electrode, the B electrode, and the W electrode are connected may be common to the R electrode, the G electrode, the B electrode, and the W electrode, and a scanning signal line to which respective transistors for applying potentials to the R electrode, the G electrode, and the B electrode are connected may be common to the R electrode, the G electrode, and the B electrode, and may be different from a scanning signal line to which a transistor for applying a potential to the W electrode is connected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram schematically showing an organic 
       EL display device according to a first embodiment of the invention. 
         FIG. 2  is a diagram showing the configuration of an organic EL panel in  FIG. 1 . 
         FIG. 3  is a diagram showing pixels arranged in a TFT substrate. 
         FIG. 4  is a diagram schematically showing circuits arranged in the pixel. 
         FIG. 5  is a block diagram showing the configuration of a sub-pixel control unit. 
         FIG. 6  is a diagram showing an example of an area arrangement for luminance determined by an area luminance determining unit. 
         FIG. 7  is a diagram showing an example of an area arrangement for luminance determined by the area luminance determining unit. 
         FIG. 8  is a diagram showing pixels arranged in a TFT substrate according to a second embodiment of the invention. 
         FIG. 9  is a diagram schematically showing circuits arranged in the pixel of the TFT substrate according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, first and second embodiments of the invention will be described with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals and signs, and a redundant description is omitted. 
     [First Embodiment] 
       FIG. 1  schematically shows an organic EL display device  100  according to a first embodiment of the invention. As shown in the drawing, the organic EL display device  100  is composed of an organic EL panel  200  fixed between an upper frame  110  and a lower frame  120 . 
       FIG. 2  shows the configuration of the organic EL panel  200  in  FIG. 1 . The organic EL panel  200  includes two substrates, a TFT (Thin Film Transistor) substrate  220  and a sealing substrate  230 . A space between the substrates is filled with a transparent resin (not shown). The TFT substrate  220  includes pixels  280  arranged in a matrix in a display region  202 . Moreover, the TFT substrate  220  includes a driver IC (Integrated Circuit)  260  as a driver circuit that applies, to a scanning signal line (not shown) of a pixel transistor arranged in each of later-described sub-pixels arranged in the pixel, a potential for providing electrical continuity between the source and drain of the pixel transistor, and applies, to a data signal line of each of the pixel transistors, a voltage corresponding to the gray-scale value of the pixel. The driver IC  260  includes therein a sub-pixel control unit  350  for controlling light emission of each of the later-described sub-pixels. 
       FIG. 3  is a diagram showing the pixels  280  arranged in the TFT substrate  220 . As shown in the drawing, the pixel  280  includes a first R (red) sub-pixel  281  and a second R sub-pixel  284  each of which includes a light-emitting portion that emits light in an R wavelength range, a first G (green) sub-pixel  282  and a second G sub-pixel  285  each of which includes a light-emitting portion that emits light in a G wavelength range, and a first B (blue) sub-pixel  283  and a second B sub-pixel  286  each of which includes a light-emitting portion that emits light in a B wavelength range. A scanning signal line  261  is arranged between the first R sub-pixel  281 , the first G sub-pixel  282 , and the first B sub-pixel  283 , and the second R sub-pixel  284 , the second G sub-pixel  285 , and the second B sub-pixel  286 . A light-emitting region of each of the first R sub-pixel  281 , the first G sub-pixel  282 , and the first B sub-pixel  283  is formed larger in size than a light-emitting region of each of the second R sub-pixel  284 , the second G sub-pixel  285 , and the second B sub-pixel  286 . As will be described later, the second R sub-pixel  284 , the second G sub-pixel  285 , and the second B sub-pixel  286  are combined together to constitute a W sub-pixel  287 . 
       FIG. 4  is a diagram schematically showing circuits arranged in the pixel  280 . As shown in the drawing, in the first R sub-pixel  281 , an R anode electrode  291  and an R pixel circuit  301  that correspond to the first R sub-pixel  281  are arranged. In the first G sub-pixel  282 , a G anode electrode  292  and a G pixel circuit  302  that correspond to the first G sub-pixel  282  are arranged. In the first B sub-pixel  283 , a B anode electrode  293  and a B pixel circuit  303  that correspond to the first B sub-pixel  283  are arranged. In the W sub-pixel  287 , a W anode electrode  294  and a W pixel circuit  304  that correspond to the W sub-pixel  287  are arranged. Potentials based on gray-scale values are respectively applied to the pixel circuits, and also, an R signal line  262 , a G signal line  263 , a B signal line  264 , and a W signal line  265  that control light emission are wired in the pixel circuits so as to cross the scanning signal line  261 . Further, a power line  269  that bears substantial power supply at the time of light emission is also wired so as to cross the scanning signal line  261 . 
     That is, the W sub-pixel  287  is configured such that the respective R, G, and B light-emitting regions of the second R sub-pixel  284 , the second G sub-pixel  285 , and the second B sub-pixel  286  as constituent elements of the W sub-pixel  287  are controlled by one W anode electrode  294  and one W pixel circuit  304 . With this configuration, in the second R sub-pixel  284 , the second G sub-pixel  285 , and the second B sub-pixel  286  that constitute the W sub-pixel  287 , all of the R, G, and B light-emitting regions simultaneously emit lights. The circuit shown in each of the sub-pixels is illustrative only, and the circuit may have any form as long as the circuit performs control so as to flow current based on a gray-scale value into an anode electrode. 
       FIG. 5  is a block diagram showing the configuration of the sub-pixel control unit  350 . As shown in the drawing, the sub-pixel control unit  350  includes a peak luminance calculating unit  351 , an area luminance determining unit  352 , a W sub-pixel control unit  353 , and an RGB sub-pixel control unit  354 . The peak luminance calculating unit  351  calculates the peak luminance of a received video signal of one screen and a position on the screen. The area luminance determining unit  352  divides, based on the peak luminance and the position on the screen determined by the peak luminance calculating unit  351 , the screen to determine areas, or previously determines areas, and determines, for each of the areas, the luminance of the W sub-pixel  287  included in the area. The W sub-pixel control unit  353  applies, to the corresponding W signal line  265 , a voltage corresponding to the luminance determined by the area luminance determining unit  352 . The RGB sub-pixel control unit  354  determines, from the video signal and the luminance determined by the area luminance determining unit  352 , the luminances of the first R sub-pixel  281 , the first G sub-pixel  282 , and the first B sub-pixel  283  in each of the pixels  280 , and applies voltages corresponding to the luminances to the R signal line  262 , the G signal line  263 , and the B signal line  264 . 
     The area luminance determining unit  352  may determine the respective luminances of, for example, rectangular areas previously determined as shown in  FIG. 6 . Alternatively, the area luminance determining unit  352  may determine areas having similar luminance as shown in  FIG. 7 , and determine the respective luminances of the determined areas. Further, areas may be set in pixel units, and the luminance of the W sub-pixel may be determined in pixel units. 
     Moreover, the W sub-pixel control unit  353  may set a light emission time period of the W sub-pixel to be shorter than that of the R, G, and B sub-pixels, for example, the W sub-pixel control unit  353  may cause the W sub-pixel to emit light for ½ or ⅓ the time period of the R, G, and B sub-pixels with luminance being doubled or tripled, respectively. When such control is employed, it is especially possible to eliminate motion blur occurring in so-called hold-type display devices. 
     In the embodiment as has been described above, since a region to emit light in a W wavelength range is provided in the organic EL display device, a color reproduction range can be expanded, and also, an improvement in color purity can be achieved. 
     Moreover, since the region to emit light in the W wavelength range is adjacent to the R, G, and B sub-pixels, more natural luminance can be expressed in each of the pixels. Moreover, since the scanning signal line  261  is commonly used, layout can be simplified, and the aperture ratio can be improved. Moreover, with the use of display that the W sub-pixel bears luminance, motion blur can be eliminated. 
     [Second Embodiment] 
     An organic EL display device according to a second embodiment will be described. The entire configuration of the organic EL display device and the configuration of an organic EL panel according to the second embodiment are similar to those in  FIGS. 1 and 2  of the first embodiment, and therefore, a description is omitted.  FIG. 8  is an enlarged view showing the pixels  280  arranged in the TFT substrate  220  according to the second embodiment of the invention.  FIG. 8  differs from  FIG. 3  of the first embodiment in that a W scanning signal line  361  is included in addition to the scanning signal line  261 . In other respects,  FIG. 8  is similar to  FIG. 3 , and therefore, a description is omitted. 
       FIG. 9  is a diagram schematically showing circuits arranged in the pixel  280  of the TFT substrate  220  according to the second embodiment. As shown in the drawing, the embodiment including the W scanning signal line  361  has a configuration including, not the W pixel circuit  304 , but a W pixel circuit  364  connected to the W scanning signal line  361 . By providing the independent scanning signal line for the independent W sub-pixel  287  as described above, the luminance of the W sub-pixel  287  can be controlled independently of the timing of updating a screen, so that lower power consumption can be achieved. 
     Even when the configuration according to the second embodiment is employed, since the region to emit light in the W wavelength range is provided similarly to the first embodiment, a color reproduction range can be expanded, and also, an improvement in color purity can be achieved. Moreover, with the use of display that the W sub-pixel bears luminance, motion blur can be eliminated. 
     In the embodiments described above, a stripe arrangement is employed in which the regions to emit lights of respective colors of R, G, and B are arranged such that the same color is formed in one direction. However, the invention can be applied also to a dot arrangement in which different colors are arranged in each column. Especially, a so-called delta arrangement may be used. 
     Moreover, in the embodiments described above, it is assumed that emission of light in the W wavelength range is performed by emitting lights of respective colors of R, G, and B. However, a pixel maybe configured to bear another wavelength range such as a pixel to emit light in, for example, a Y (yellow) wavelength range. 
     For deposition of light-emitting layers in the embodiments described above, an ink jet method can be used in addition to a method of separately depositing R, G, and B light-emitting layers. When the ink jet is used, material cost can be lowered by using polymeric materials, and manufacturing facility cost can be suppressed. 
     Moreover, in the embodiments described above, the driver circuit is incorporated into the driver IC. However, a portion or the whole of the driver circuit may be directly formed on the TFT substrate. 
     While there have been described what are at present considered to be certain embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claim cover all such modifications as fall within the true spirit and scope of the invention.