Patent Publication Number: US-2016225332-A1

Title: Self-power feeding type display device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2015-020233 filed in Japan on Feb. 4, 2015; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a self-power feeding type display device. 
     BACKGROUND 
     In recent years, improvement of various devices with the object of reducing energy consumption quantity has been regarded as serious. Under the circumstances, reduction of power consumption is also demanded for a display device used as, for example, an electronic poster that always displays a predetermined picture. 
     However, there is a limit in reduction of power consumption. It is becoming difficult to further reduce a supply quantity of power generated outside of the display device while demanded performance for the display device is maintained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view schematically illustrating a self-power feeding type display device according to a first embodiment; 
         FIG. 2  is an enlarged top view illustrating a portion of the self-power feeding type display device illustrated in  FIG. 1 ; 
         FIG. 3A  is a sectional view of one pixel group along a dot-dash line Xa-Xa′ illustrated in  FIG. 2 ; 
         FIG. 3B  is a sectional view of one pixel group along a dot-dash line Xb-Xb′ illustrated in  FIG. 2 ; 
         FIG. 4  is a schematic perspective view for explaining a manufacturing method of the self-power feeding type display device according to the first embodiment; 
         FIG. 5A  is a sectional view corresponding to  FIG. 3A , for explaining moves of light incident on the self-power feeding type display device according to the first embodiment; 
         FIG. 5B  is a sectional view corresponding to  FIG. 3B , for explaining moves of light incident on the self-power feeding type display device according to the first embodiment; 
         FIG. 6  is a functional block diagram illustrating the self-power feeding type display device according to the first embodiment; 
         FIG. 7A  is a sectional view corresponding to  FIG. 3A , of one pixel group included in a self-power feeding type display device according to a modification of the first embodiment; 
         FIG. 7B  is a sectional view corresponding to  FIG. 3B , of one pixel group included in the self-power feeding type display device according to the modification of the first embodiment; 
         FIG. 8  is a schematic perspective view for explaining a manufacturing method of the self-power feeding type display device according to the modification of the first embodiment; 
         FIG. 9A  is a sectional view corresponding to  FIG. 7A , for explaining moves of light incident on the self-power feeding type display device according to the modification of the embodiment of the first embodiment; 
         FIG. 9B  is a sectional view corresponding to  FIG. 7B , for explaining moves of light incident on the self-power feeding type display device according to the modification of the first embodiment; 
         FIG. 10  is a functional block diagram illustrating the self-power feeding type display device according to the modification of the first embodiment; 
         FIG. 11  is an enlarged top view corresponding to  FIG. 2 , illustrating a portion of the self-power feeding type display device according to a second embodiment; 
         FIG. 12A  is a sectional view of one pixel group along a dot-dash line Xa-Xa′ illustrated in  FIG. 11 ; 
         FIG. 12B  is a sectional view of one pixel group along a dot-dash line Xb-Xb′ illustrated in  FIG. 11 ; 
         FIG. 13A  is a sectional view corresponding to  FIG. 12A , illustrating an example of a structure of a reflection layer in a self-power feeding type display device according to the second embodiment; 
         FIG. 13B  is a sectional view corresponding to  FIG. 12B , illustrating an example of a structure of a reflection layer in a self-power feeding type display device according to the second embodiment; 
         FIG. 14  is a schematic perspective view for explaining a manufacturing method of the self-power feeding type display device according to the second embodiment; 
         FIG. 15A  is a sectional view corresponding to  FIG. 12A , for explaining moves of light incident on the self-power feeding type display device according to the second embodiment; 
         FIG. 15B  is a sectional view corresponding to  FIG. 12B , for explaining moves of light incident on the self-power feeding type display device according to the second embodiment; 
         FIG. 16  is a functional block diagram illustrating the self-power feeding type display device according to the second embodiment; 
         FIG. 17A  is a sectional view corresponding to  FIG. 12A , of one pixel group included in a self-power feeding type display device according to a modification of the second embodiment; 
         FIG. 17B  is a sectional view corresponding to  FIG. 12B , of one pixel group included in the self-power feeding type display device according to the modification of the second embodiment; 
         FIG. 18  is a schematic perspective view for explaining a manufacturing method of the self-power feeding type display device according to the modification of the second embodiment; 
         FIG. 19A  is a sectional view corresponding to  FIG. 17A , for explaining moves of light incident on the self-power feeding type display device according to the modification of the embodiment of the second embodiment; 
         FIG. 19B  is a sectional view corresponding to  FIG. 17B , for explaining moves of light incident on the self-power feeding type display device according to the modification of the second embodiment; and 
         FIG. 20  is a functional block diagram illustrating the self-power feeding type display device according to the modification of the second embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Certain embodiments provide a self-power feeding type display device including a reflection unit, a power generation unit, and a power storage unit. The reflection unit reflects light in a first band. The power generation unit absorbs light in a second band different from the first band and generates power. The power storage unit stores electricity generated in the power generation unit. The self-power feeding type display device is a display device configured by arranging a plurality of reflection pixels each formed by laminating the reflection unit and the power generation unit. 
     The self-power feeding type display device described hereafter is a display device capable of displaying a desired picture by reflecting light which is included in incident light and has waveforms in a predetermined band and capable of generating power by absorbing light which is included in the incident light and has waveforms outside the predetermined band. The display device absorbs light that are unnecessary for display of the picture in the display device and generates power. Therefore, it is possible to reduce a supply quantity of power generated outside the display device to the display device. Hereafter, embodiments of such a display device will be described with reference to the drawings. 
     First Embodiment 
       FIG. 1  is a top view schematically illustrating a self-power feeding type display device according to a first embodiment. A self-power feeding type display device illustrated in  FIG. 1  is an electronic poster that displays a desired picture by two-dimensionally arranging reflection pixels that reflect light which is included in incident light and has wavelengths in a predetermined band. By the way, the incident light may be natural light such as sunlight, or may be light emitted from a white-colored light source or the like provided separately to irradiate the self-supply type display device  10 . 
       FIG. 2  is an enlarged top view illustrating a portion (an area T surrounded by a dash line circle in  FIG. 1 ) of the self-power feeding type display device illustrated in  FIG. 1 . As illustrated in  FIG. 2 , the self-power supply feeding device  10  is configured by arranging a plurality of reflection pixels two-dimensionally. Each of the plurality of reflection pixels is, for example, one of a red color reflection pixel  11 R, which reflects red color light, a green color reflection pixel  11 G, which reflects green color light, and a blue color reflection pixel  11 B, which reflects blue color light. In the self-power feeding type display device  10 , such a plurality of reflection pixels  11 R,  11 G and  11 B are selected suitably according to a displayed picture and arranged. In the self-power feeding type display device  10  according to the present embodiment, nine reflection pixels each of which is one of a red color reflection pixel  11 R, a green color reflection pixel  11 G, and a blue color reflection pixel  11 B form a pixel group  12 . In the pixel group  12 , nine reflection pixels is arranged so that reflection pixels of the same color are not adjacent to each other. The self-power feeding type display device  10  according to the present embodiment is configured by arranging such a plurality of pixel groups  12  two-dimensionally. 
       FIG. 3A  is a sectional view of one pixel group  12  along a dot-dash line Xa-Xa′ illustrated in  FIG. 2 , and  FIG. 3B  is a sectional view of one pixel group  12  along a dot-dash line Xb-Xb′ illustrated in  FIG. 2 . Hereafter, structure of respective reflection pixels  11 R,  11 G and  11 B will is described in detail with reference to  FIG. 3A  and  FIG. 3B . 
     As illustrated in  FIG. 3A  and  FIG. 3B , the red color reflection pixel  11 R includes a red color reflection unit  13 R, which reflects red color light and transmits light other than red color light (light of cyan (Cy) color). In addition, the red color reflection pixel  11 R includes a cyan color power generation unit  14 Cy, which absorbs cyan color light and generates power, and a power storage unit  15 , which stores power generated in the cyan color power generation unit  14 Cy. In the red color reflection pixel  11 R, the cyan color power generation unit  14 Cy and the red color reflection unit  13 R are laminated on the power storage unit  15  in the cited order. 
     In the same way, as illustrated in  FIG. 3A , the green color reflection pixel  11 G includes a green color reflection unit  13 G, which reflects green color light and transmits light other than green color light (light of the magenta (Mg) color). In addition, the green color reflection pixel  11 G includes a magenta color power generation unit  14 Mg, which absorbs magenta color light and generates power, and the power storage unit  15 , which stores power generated in the magenta color power generation unit  14 Mg. In the green color reflection pixel  11 G, the magenta color power generation unit  14 Mg and green color reflection unit  13 G are laminated on the power storage unit  15  in the cited order. 
     As illustrated in  FIG. 3B , the blue color reflection pixel  11 B includes a blue color reflection unit  13 B, which reflects blue color light and transmits light other than blue color light (yellow (Ye) color light). In addition, the blue color reflection pixel  11 B includes a yellow color power generation unit  14 Ye, which absorbs yellow color light and generates power, and the power storage unit  15 , which stores power generated in the yellow color power generation unit  14 Ye. In the blue color reflection pixel  11 B, the yellow color power generation unit  14 Ye and the blue color reflection unit  13 B are laminated on the power storage unit  15  in the cited order. 
     As illustrated in  FIG. 3A  and  FIG. 3B , a plurality of reflection units  13 R,  13 G and  13 B configure a reflection layer  13  of a single layer in the pixel group  12 . The reflection layer  13  of the single layer is, for example, a cholesteric liquid crystal layer of a single layer capable of varying a reflection band every predetermined region. 
     Cholesteric liquid crystal that configures the cholesteric liquid crystal layer has a property of reflecting light of an arbitrary wavelength according to an orientation state of the cholesteric liquid crystal. The orientation state of the cholesteric liquid crystal can be controlled arbitrarily by applying a strong electric field temporarily. In addition, the cholesteric liquid crystal has a property of maintaining the orientation state of the cholesteric liquid crystal if application of the electric field is stopped after the cholesteric liquid crystal is brought into a desired orientation state by applying the electric field. The above-described reflection layer  13  of the single layer is a cholesteric liquid crystal layer configured by cholesteric liquid crystal having such a property. 
     By the way, it suffices that each of the reflection units  13 R,  13 G, and  13 B of respective colors is capable of reflecting light having a wavelength in a predetermined band and transmitting light outside the band. Therefore, materials configuring the reflection units  13 R,  13 G, and  13 B and structures such as film thicknesses may be different from each other. That is, the plurality of reflection units  13 R,  13 G, and  13 B maybe reflection layers that are independent from each other. 
     The plurality of power generation units  14 Cy,  14 Mg, and  14 Ye are configured by organic solar batteries, which absorb light transmitted by the reflection units  13 R,  13 G, and  13 B respectively that is unnecessary for display of the picture and generate power. That is, for example, the cyan color power generation unit  14 Cy has a structure in which an electrolyte layer  17 Cy including titanium dioxide with a cyan color pigment adsorbed is filled between one pair of opposed transparent electrodes  16 . In the same way, the magenta color power generation unit  14 Mg has a structure in which an electrolyte layer  17 Mg including titanium dioxide with a magenta color pigment adsorbed is filled between one pair of opposed transparent electrodes  16 . The yellow color power generation unit  14 Ye has a structure in which an electrolyte layer l 7 Ye including titanium dioxide with a yellow color pigment adsorbed is filled between one pair of opposed transparent electrodes  16 . 
     By the way, each of the plurality of power generation units  14 Cy,  14 Mg, and  14 Ye having the configuration described heretofore has a reflection reducing film  18  on the transparent electrode  16  of an upper layer and has a reflection film  19  under the transparent electrode  16 . As a result, the power generation efficiency in each of the power generation units  14 Cy,  14 Mg, and  14 Ye is improved. 
     If light is incident on each of such power generation units  14 Cy,  14 Mg, and  14 Ye which are configured by organic solar batteries, the light excites electrons in the pigment. The excited electrons are led to the transparent electrode  16  (cathode) via titanium dioxide and taken out as a direct current. The electrons sent out return to the opposed transparent electrode  16  (anode) via an external circuit, and return to the pigment again via ions in the electrolyte layers l 7 Cy,  17 Mg, and  17 Ye sandwiched between the transparent electrodes  16 . In this way, the light is absorbed and power is generated. 
     The plurality of power generation units  14 Cy,  14 Mg, and  14 Ye each of which is configured by the organic solar battery configure a power generation layer  14  in one pixel group  12 . 
     The power storage unit  15  included in the reflection pixels  11 R,  11 G and  11 B of respective colors is configured by a capacitor layer of a single layer or a battery layer of a single layer, and is capable of store power generated in the power generation units  14 Cy,  14 Mg, and  14 Ye. 
     As illustrated in  FIG. 4 , the self-power feeding type display device  10  configured by the reflection pixels  11 R,  11 G, and  11 B having such structures can be manufactured by forming each of the reflection layer  13 , the power generation layer  14 , and the power storage layer  15  in a sheet form and sticking the sheet-like layers  13 ,  14 , and  15  together. Therefore, for example, a self-feeding type display device having a large screen can be manufactured easily. 
     Operation of such a self-power feeding type display device will now be described with reference to  FIG. 5A ,  FIG. 5B , and  FIG. 6 .  FIG. 5A  is a sectional view corresponding to  FIG. 3A , for explaining moves of light incident on the self-power feeding type display device  10  according to the first embodiment.  FIG. 5B  is a sectional view corresponding to  FIG. 3B , for explaining moves of light incident on the self-power feeding type display device  10  according to the first embodiment.  FIG. 6  is a functional block diagram illustrating the self-power feeding type display device  10  according to the first embodiment. 
     First, if the incident light L is incident on the self-power feeding type display device  10 , light having a wavelength in a predetermined band is reflected in the reflection layer  13 . As illustrated in  FIG. 5A  and  FIG. 5B , if the incident light L is incident on, for example, the red color reflection pixel  11 R, the red color reflection unit  13 R reflects red color light L R  included in the incident light L. In the same way, if the incident light L is incident on the green color reflection pixel  11 G, the green color reflection unit  13 G reflects green color light L G  included in the incident light L. If the incident light L is incident on the blue color reflection pixel  11 B, the blue color reflection unit  13 B reflects blue color light L B  included in the incident light L. In this way, the reflection layer  13  reflects light in a predetermined band. As a result, the self-power feeding type display device  10  is capable of displaying a picture according to a pixel arrangement. 
     Light L cy , L Mg , and L ye  which is included in the incident light L incident on the self-power feeding type display device  10  and other than light reflected in the reflection layer  13  is transmitted by the reflection layer  13  and arrives at the power generation layer  14 . The light L cy , L Mg , and L ye  that arrives at the power generation layer  14  is absorbed in the power generation layer  14 , and power is generated. As illustrated in  FIG. 5A  and  FIG. 5B , for example, the cyan (Cy) color light L cy  which is transmitted through the red color reflection unit  13 R arrives at the cyan color power generation unit  14 Cy included in the red color reflection pixel  11 R. The cyan color power generation unit  14 Cy absorbs the light L cy  which arrives at the layer  14 Cy, and generates power. In the same way, the magenta (Mg) color light L Mg  which is transmitted through the green color reflection unit  13 G arrives at the magenta color power generation unit  14 Mg included in the green color reflection pixel  11 G. The magenta color power generation unit  14 Mg absorbs the light L Mg  which arrives at the layer  14 Mg, and generates power. The yellow (Ye) color light L Ye  which is transmitted through the blue color reflection unit  13 B arrives at the yellow color power generation unit  14 Ye included in the blue color reflection pixel  11 B. The yellow color power generation unit  14 Ye absorbs the light L Ye  arriving at the layer  14 Ye, and generates power. In this way, the light L cy , L Mg , and L ye  other than light reflected in the reflection layer  13  is absorbed in the power generation layer  14 . As a result, the self-power feeding type display device  10  can absorb the light L cy , L Mg , and L ye  that is unnecessary for display of the picture, and generate power. 
     As illustrated in  FIG. 6 , the power generation layer  14  and the power storage unit  15  are connected electrically by wiring, which is not illustrated. Power generated in the power generation layer  14  can be stored in the power storage unit  15 . The power stored in the power storage unit  15  can be taken out as occasion demands. Power required when the self-power feeding type display device  10  operates can be taken out from the power storage unit and used. 
     In the self-power feeding type display device  10  according to the first embodiment described heretofore, it is possible to absorb the light L cy , L Mg , and L ye  that is unnecessary for display of the picture in the power generation layer  14 , generate power, and store the power in the power storage unit  15 . The self-power feeding type display device  10  can operate by taking out the power stored in the power storage unit  15  and using the power. Therefore, the supply quantity of power generated outside the self-power feeding type display device  10  to the self-power feeding type display device  10  can be reduced. 
     Furthermore, in the self-power feeding type display device  10  according to the first embodiment, the reflection layer  13  is disposed on the power generation layer  14 . Therefore, it is possible to suppress attenuation of the incident light which is incident on the self-power feeding type display device  10 , in the power generation layer  14 . In addition, it is also possible to suppress attenuation of light which is reflected in the reflection layer  13 , in the power generation layer  14 . Even if the light quantity of the incident light which is incident on the self-power feeding type display device  10  is small, therefore, a desired picture can be displayed normally. 
     &lt;Modification&gt; 
       FIG. 7A  is a sectional view corresponding to  FIG. 3A , illustrating one pixel group in a self-power feeding type display device according to a modification of the first embodiment.  FIG. 7B  is a sectional view corresponding to  FIG. 3B , illustrating one pixel group in the self-power feeding type display device according to the modification of the first embodiment. As illustrated in  FIG. 7A  and  FIG. 7B , the reflection layer  13  and the power generation layer  14  may be laminated on the power storage unit  15  of the single layer in the cited order. That is, it is also possible to configure a red color reflection pixel  11 R′ by laminating the red color reflection color reflection unit  13 R and the cyan color power generation unit  14 Cy on the power storage unit  15  in the cited order, configure a green color reflection pixel  11 G′ by laminating the green color reflection color reflection unit  13 G and the magenta color power generation unit  14 Mg on the power storage unit in the cited order, and configure a blue color reflection pixel  11 B′ by laminating the blue color reflection color reflection unit  13 B and the yellow color power generation unit  14 Ye on the power storage unit  15  in the cited order. 
     A self-power feeding type display device configured by the reflection pixels  11 R′ ,  11 G′ , and  11 B′ having such structures can be manufactured in the same way as the self-power feeding type display device  10 . That is, as illustrated in  FIG. 8 , the self-power feeding type display device can be manufactured by forming each of the reflection layer  13 , the power generation layer  14 , and the power storage layer  15  in a sheet form and sticking the sheet-like layers  13 ,  14 , and  15  together. 
     Operation of such a self-power feeding type display device will now be described with reference to  FIG. 9A ,  FIG. 9B , and  FIG. 10 .  FIG. 9A  is a sectional view corresponding to  FIG. 7A , for explaining moves of light incident on the self-power feeding type display device according to the modification of the first embodiment.  FIG. 9B  is a sectional view corresponding to  FIG. 7B , for explaining moves of light incident on the self-power feeding type display device according to the modification of the first embodiment.  FIG. 10  is a functional block diagram illustrating the self-power feeding type display device according to the modification of the first embodiment. 
     First, if the incident light L is incident on the self-power feeding type display device according to the modification, light having a wavelength in a predetermined band is absorbed in the power generation layer  14  and power is generated. As illustrated in  FIG. 9A  and  FIG. 9B , in the cyan color power generation unit  14 Cy, cyan color light L Cy  which is included in the incident light L arriving at the layer  14 Cy is absorbed and power is generated. In the same way, in the magenta color power generation unit  14 Mg, magenta color light L Mg , which is included in the incident light L arriving at the layer  14 Mg is absorbed and power is generated. In the yellow color power generation unit  14 Ye, yellow color light L Ye  which is included in the incident light L arriving at the layer  14 Ye is absorbed and power is generated. 
     Light that is not absorbed in the power generation layer  14  is transmitted by the power generation layer  14  and arrives at the reflection layer  13 . The light arriving at the reflection layer  13  is reflected in the reflection layer  13 , transmitted by the power generation layer  14 , and emitted to the outside of the self-power feeding type display device according to the modification. As illustrated in  FIG. 9A  and  FIG. 9B , light L Mg+Ye  of magenta color+yellow color, which is not absorbed in the cyan color power generation unit  14 Cy, i.e., the red color light L R  is transmitted by the cyan color power generation unit  14 Cy and arrives at the red color reflection unit  13 R. The light arriving at the red color reflection unit  13 R is reflected in the red color reflection unit  13 R, transmitted by the cyan color power generation unit  14 Cy, and emitted to the outside of the self-power feeding type display device according to the modification. In the same way, light L Cy+Ye  of cyan color+yellow color, which is not absorbed in the magenta color power generation unit  14 Mg, i.e., the green color light L G  is transmitted by the magenta color power generation unit  14 Mg and arrives at the green color reflection unit  13 G. The light arriving at the green color reflection unit  13 G is reflected in the green color reflection unit  13 G, transmitted by the magenta color power generation unit  14 Mg, and emitted to the outside of the self-power feeding type display device according to the modification. Light L Cy−Mg  of cyan color+magenta color, which is not absorbed in the yellow color power generation unit  14 Ye, i.e., the blue color light L B  is transmitted by the yellow color power generation unit  14 Ye and arrives at the blue color reflection unit  13 B. The light arriving at the blue color reflection unit  13 B is reflected in the blue color reflection unit  13 B, transmitted by the yellow color power generation unit  14 Ye, and emitted to the outside of the self-power feeding type display device according to the modification. In this way, the reflection layer  13  reflects light having a wavelength in a predetermined band. As a result, the self-power feeding type display device according to the modification can display a picture according to a pixel arrangement. In addition, the self-power feeding type display device according to the modification can absorb the light L cy , L Mg , and L ye , which is unnecessary for display of the picture, and generate power. 
     As illustrated in  FIG. 10 , the power generation layer  14  and the power storage unit  15  are connected electrically by wiring, which is not illustrated. Power generated in the power generation layer  14  can be stored in the power storage unit  15 . The power stored in the power storage unit  15  can be taken out as occasion demands. Power required when the self-power feeding type display device according to the modification operates can be taken out from the power storage unit  15  and used. 
     In the self-power feeding type display device according to the modification of the first embodiment described heretofore, it is also possible to reduce the supply quantity of power generated outside the self-power feeding type display device to the self-power feeding type display device by a reason similar to that of the self-power feeding type display device  10  according to the first embodiment. 
     Furthermore, in the self-power feeding type display device according to the modification of the first embodiment, the reflection layer  13  is disposed on the power generation layer  14 . Therefore, it is possible to increase the absorption quantity of light in the power generation layer  14  as compared with the self-power feeding type display device  10  according to the first embodiment. Accordingly, the power generation quantity can be increased. 
     Second Embodiment 
     A self-power feeding type display device according to a second embodiment differs from the self-power feeding type display device  10  according to the first embodiment in that a displayed picture can be changed without changing the pixel arrangement. A change only in color is also included in change of a picture referred to herein. That is, a change of a letter “P” illustrated in  FIG. 1  to, for example, a letter “Q” is included in the picture change. In addition, a case where the letter “P” illustrated in  FIG. 1  is not changed, but the color of the letter “P” is changed is also included in the picture change. Hereafter, such a self-power feeding type display device will be described with reference to the drawings. 
       FIG. 11  is an enlarged top view corresponding to  FIG. 2 , illustrating a portion of the self-power feeding type display device according to the second embodiment. The self-power feeding type display device has a plurality of pixel groups  22 , each of which includes a plurality of reflection pixels and at least one sensor pixel  31 . The self-power feeding type display device according to the second embodiment is configured by arranging such a plurality of pixel groups  22  two-dimensionally. 
     Each of the plurality of reflection pixels included in each pixel group  22  is any one of a red color reflection pixel  21 R, which reflects red color light, a green color reflection pixel  21 G, which reflects green color light, and a blue color reflection pixel  21 B, which reflects blue color light, in the same way as, for example, the self-power feeding type display device  10  according to the first embodiment. In the self-power feeding type display device according to the second embodiment, such a plurality of reflection pixels  21 R,  21 G, and  21 B are selected suitably according to a displayed picture and arranged. 
     The sensor  31  included in each pixel group is a pixel that detects a light quantity of the incident light L. The sensor  31  includes a light reception unit configured by, for example, a photodiode or the like. 
     In the self-power feeding type display device according to the present embodiment, eight reflection pixels each of which is one of the red color reflection pixel  21 R, the green color reflection pixel  21 G, and the blue color reflection pixel  21 B form a pixel group  22 . In the pixel group  22 , eight reflection pixels is arranged in a ring form so that reflection pixels  21 R,  21 G, and  21 B of the same color are not adjacent to each other. In addition, in the pixel group  22 , the sensor pixel  31  is disposed in a center surrounded by a plurality of reflection pixels  21 R,  21 G, and  21 B. The self-power feeding type display device according to the present embodiment is configured by arranging such a plurality of pixel groups  22  two-dimensionally. 
     By the way, the self-power feeding type display device according to the present embodiment has a structure in which one sensor pixel  31  is always included in each pixel group  22 . However, the pixel group  22  including the sensor pixel  31  and a pixel group that does not include the sensor pixel  31  (a pixel group configured by only reflection pixels) may be mixedly present. That is, it suffices that the self-power feeding type display device according to the present embodiment has at least one sensor pixel  31 . 
       FIG. 12A  is a sectional view of one pixel group  22  along a dot-dash line Xa-Xa′ illustrated in  FIG. 11 , and  FIG. 12B  is a sectional view of one pixel group  22  along a dot-dash line Xb-Xb′ illustrated in  FIG. 11 . Hereafter, structures of respective reflection pixels  21 R,  21 G and  21 B and a structure of the sensor pixel  31  will be described in detail with reference to  FIG. 12A  and  FIG. 12B . As illustrated in  FIG. 12A  and  FIG. 12B , the reflective pixels  21 R,  21 G, and  21 B of respective colors are configured by laminating a power generation layer  24  including a cyan color power generation unit  24 Cy, a magenta color power generation unit  24 Mg, and a yellow color power generation unit  24 Ye, and a reflection layer  23  including a red color reflection unit  23 R, a green color reflection unit  23 G, and a blue color reflection unit  23 B over a power storage unit  25  in the cited order in the same way as the reflection pixels  11 R,  11 G, and  11 B in the self-power type display device  10 , respectively. 
     Meanwhile, the sensor pixel  31  is configured by laminating the cyan color power generation unit  24 Cy and a reflection unit  33  on a sensor unit  32  provided on a power storage unit  25  in the cited order. 
     The sensor unit  32  includes a light reception unit which receives the incident light L, and a gate which reads out signal charge generated in the light reception unit by receiving the incident light L. The light reception unit is configured by a photodiode provided on a surface of a semiconductor substrate such as, for example, a silicon substrate. The gate is configured by, for example, a transistor provided on the surface of the semiconductor substrate. By the way, it suffices that the sensor unit is provided in at least the sensor pixel  31 . As illustrated, however, the sensor unit  32  may extend into the reflection pixels  21 R,  21 G, and  21 B. 
     In the sensor pixel  31 , for example, the cyan color power generation unit  24 Cy is provided on the sensor unit as a power generation unit. However, the power generation unit provided in the sensor pixel  31  is not restricted to the cyan color power generation unit  24 Cy, but may be a power generation unit that absorbs light in another wavelength band and generates power (for example, the magenta color power generation unit  24 Mg or the yellow color power generation unit  24 Ye). Furthermore, the sensor pixel  31  does not always need the power generation unit, and the power generation unit may not be provided in the sensor pixel  31 . 
     In the sensor pixel  31 , the reflection unit  33  is laminated on the cyan color power generation unit  24 Cy. The reflection unit  33  is configured to transmit substantially all of the incident light L. The reflection unit  33  may be configured to be capable of reflecting the incident light outside a band for which light can be received in the light reception unit in the sensor unit  32  and a cyan color band for which light is absorbed in the cyan color power generation unit  24 Cy. However, the reflection unit  33  is not a portion that is always needed, but may not be provided. 
     In the pixel group  22 , the reflection units  23 R,  23 G,  23 B, and  33  included in the plurality of reflection pixels  21 R,  21 G, and  21 B and the sensor pixel  31  described heretofore configure the reflection layer  23  of the single layer.  FIG. 13A  and  FIG. 13B  are sectional views illustrating an example of a structure of the reflection layer  23 .  FIG. 13A  is a sectional view corresponding to  FIG. 12A , of the reflection layer  23 .  FIG. 13B  is a sectional view corresponding to  FIG. 12B , of the reflection layer  23 . 
     As illustrated in  FIG. 13A  and  FIG. 13B , the reflection layer  23  is configured by sandwiching a cholesteric liquid crystal layer  41  of a single layer which is formed to have reflection bands that are different from each other every pixel between one pair of transparent electrodes  43   a  and  43   b  via orientation films  42 . In the present embodiment, one transparent electrode  43   a  is provided on a top surface side of the cholesteric liquid crystal layer  41  every pixel group  22 . One transparent electrode  43   b  is provided on a bottom surface side of the cholesteric liquid crystal layer  41  every pixel group  22 . In each pixel group  22 , however, transparent electrodes  43   a  and  43   b  divided, for example, every pixel may be provided. 
     If a voltage is applied to the pair of transparent electrodes  43   a  and  43   b  in the reflection layer  23  having the above-described configuration, an electric field is generated in the cholesteric liquid crystal layer  41 . The electric filed changes the orientation state of the cholesteric liquid crystal. In this way, the reflection wavelength band of the reflection layer  23  can be changed every pixel. 
     By the way, it suffices that the reflection band of the reflection layer  23  can be changed by an arbitrary reflection band change means including the transparent electrodes  43   a  and  43   b . Therefore, the reflection layer  23  may be configured by a material that can be changed in refractive index, such as a photonic interlayer film or a plasmon layer. 
     Referring back to  FIG. 12A  and  FIG. 12B , each of the cyan color power generation unit  24 Cy, the magenta color power generation unit  24 Mg and the yellow color power generation unit  24 Ye included in the above-described plurality of reflection pixels  21 R,  21 G, and  21 B and the sensor pixel  31  is configured by an organic solar battery in the same way as, for example, the self-power feeding type display device  10  according to the first embodiment. Such plurality of power generation units  24 Cy,  24 Mg and  24 Ye configure the power generation layer  24 . 
     As illustrated in  FIG. 14 , the self-power feeding type display device described heretofore can also be manufactured by forming each of the reflection layer  23 , the power generation layer  24 , the sensor unit  32 , and the power storage unit  25  in a sheet form and sticking together the reflection layer  23 , the power generation layer  24 , the sensor unit  32 , and the power storage unit  25  each formed in a sheet form. Therefore, it is facilitated to, for example, make the screen large. 
     Operation of the self-power feeding type display device will now be described with reference to  FIG. 15A ,  FIG. 15B , and  FIG. 16 .  FIG. 15A  is a sectional view corresponding to  FIG. 12A , for explaining moves of light incident on the self-power feeding type display device according to the second embodiment.  FIG. 15B  is a sectional view corresponding to  FIG. 12B , for explaining moves of light incident on the self-power feeding type display device according to the second embodiment.  FIG. 16  is a functional block diagram illustrating the self-power feeding type display device according to the second embodiment. 
     First, if the incident light L is incident on the reflection pixels  21 R,  21 G, and  21 B in the self-power feeding type display device, light having a wavelength in a predetermined band is reflected in the reflection layer  23  of each of the pixels  21 R,  21 G, and  21 B. As illustrated in  FIG. 15A  and  FIG. 15B , if the incident light L is incident on, for example, the red color reflection pixel  21 R, the red color reflection unit  23 R reflects red color light L R . If the incident light L is incident on the green color reflection pixel  21 G, the green color reflection unit  23 G reflects green color light L G . If the incident light L is incident on the blue color reflection pixel  21 B, the blue color reflection unit  23 B reflects blue color light L B . In this way, the reflection layer  23  reflects light having a wavelength in a predetermined band. As a result, the self-power feeding type display device can display a picture according to the pixel arrangement. Light L Cy , L Mg , and L ye  that is included in the incident light L incident on the reflection pixels  21 R,  21 G, and  21 B in the self-power feeding type display device and that is not reflected in the reflection layer  23  of the pixels  21 R,  21 G, and  21 B is transmitted by the reflection layer  23  and arrives at the power generation layer  24 . The light L Cy , L Mg , and L ye  arriving at the power generation layer  24  is absorbed in the layer  24  and power is generated. As illustrated in  FIG. 15A  and  FIG. 15B , for example, cyan (Cy) color light L Cy  which is transmitted through the red color reflection unit  23 R arrives at the cyan color power generation unit  24 Cy and is absorbed in the cyan color power generation unit  24 Cy and power is generated. In the same way, magenta (Mg) color light L Mg  which is transmitted through the green color reflection unit  23 G arrives at the magenta color power generation unit  24 Mg and is absorbed in the magenta color power generation unit  24 Mg and power is generated. Yellow (Ye) color light L Ye  which is transmitted through the blue color reflection unit  23 B arrives at the yellow color power generation unit  24 Ye and is absorbed in the yellow color power generation unit  24 Ye and power is generated. In this way, the light L Cy , L Mg , and L ye  that is not reflected in the reflection layer  23  is absorbed in the power generation layer  24 . As a result, the self-power feeding type display device can absorb the light L Cy , L Mg , and L ye  that is unnecessary for picture display and generate power. 
     As illustrated in  FIG. 16 , power generated in the power generation layer  24  can be stored in the power storage unit  25 . It is possible to take out the power stored in the power storage unit  25  according to, for example, a command from a control unit  51 , which controls the power storage unit  25  and supply the power to a place specified by the control unit  51 . 
     In contrast, if the incident light L is incident on the sensor pixel  31  as illustrated in  FIG. 15A , the reflection unit  33  included in the pixel  31  does not substantially reflect the incident light L and the incident light L is transmitted. 
     The incident light L transmitted by the reflection unit  33  in the sensor pixel  31  arrives at the cyan color power generation unit  24 Cy included in the sensor pixel  31  and is absorbed in the power generation unit  24 Cy, and power is generated. Power generated in the cyan color power generation unit  24 Cy is stored in the power storage unit  25  as illustrated in  FIG. 15A . 
     Light that is not absorbed in the cyan color power generation unit  24 Cy (for example, the red color light L R ) is transmitted through the cyan color power generation unit  24 Cy and arrives at a light reception unit (not illustrated) in the sensor unit  32 . The light reception unit generates an electric signal depending upon the light quantity of light L R  arriving at the light reception unit. The electric signal generated in the light reception unit is taken out by a gate, which is provided separately in the sensor unit  32 , and is supplied to the control unit as illustrated in  FIG. 16 . 
     A method for changing a picture displayed by the self-power feeding type display device will now be described. 
     For example, if a portion of the self-power feeding type display device is touched with a hand, a light quantity of light incident on the sensor pixel  31  that is present in an area touched with the hand lowers. Therefore, alight quantity of light arriving at the light reception unit in the sensor pixel  31  also lowers and a voltage of the electric signal generated in the light reception unit also lowers. Accordingly, an electric signal having a low voltage arrives at the control unit  51 . 
     If the voltage of the electric signal supplied from the light reception unit changes in this way, the control unit  51  detects the change, takes out power from the power storage unit  25 , and supplies the power taken out to the reflection layer  23  (for example, one pair of transparent electrodes  43   a  and  43   b  having the cholesteric liquid crystal layer  41  sandwiched between them). 
     If power is supplied to the transparent electrodes  43   a  and  43   b , an electric field is generated in the cholesteric liquid crystal layer  41  sandwiched between the transparent electrodes  43   a  and  43   b . The orientation state of the cholesteric liquid crystal changes according to the electric field. As a result, the wavelength band of light reflected in the reflection layer  23  is changed. Accordingly, the displayed picture is also changed. 
     That is, in the self-power feeding type display device according to the present embodiment, the displayed picture can be changed by, for example, touching a portion of the self-power feeding type display device and consequently changing the light reception quantity in the sensor pixel  31 . 
     In the self-power feeding type display device described heretofore, it is also possible to reduce the supply quantity of power generated outside the self-power feeding type display device to the self-power feeding type display device by a reason similar to that of the self-power feeding type display device  10  according to the first embodiment. 
     In addition, in the self-power feeding type display device according to the second embodiment as well, a desired picture can be displayed normally even if the light quantity of light incident on the self-power feeding type display device according to the second embodiment is small, by a reason similar to that of the self-power feeding type display device  10  according to the first embodiment. 
     In addition, in the self-power feeding type display device according to the second embodiment, the reflection wavelength band of the reflection layer  23  is changed by supplying stored power to the transparent electrodes  43   a  and  43   b  having the cholesteric liquid crystal layer  41  sandwiched between them. Therefore, the displayed picture can be changed without using power supplied from the outside of the self-power feeding type display device or by using only slightly power supplied from the outside of the self-power feeding type display device. 
     &lt;Modification&gt; 
       FIG. 17A  is a sectional view corresponding to  FIG. 12A , of one pixel group included in a self-power feeding type display device according to a modification of the second embodiment.  FIG. 17B  is a sectional view corresponding to  FIG. 12B , of one pixel group included in the self-power feeding type display device according to the modification of the second embodiment. As illustrated in  FIG. 17A  and  FIG. 17B , the reflection layer  23  and the power generation layer  24  may be laminated over the power storage unit  25  of the single layer in the cited order. That is, a red color reflection pixel  21 R′ may be configured by laminating the red color reflection unit  23 R and the cyan color power generation unit  24 Cy over the power storage unit  25  in the cited order. A green color reflection pixel  21 G′ may be configured by laminating the green color reflection unit  23 G and the magenta color power generation unit  24 Mg over the power storage unit  25  in the cited order. A blue color reflection pixel  21 B′ may be configured by laminating the blue color reflection unit  23 B and the yellow color power generation unit  24 Ye over the power storage unit  25  in the cited order. In addition, a sensor pixel  31 ′ may be configured by laminating the reflection unit  33  and the cyan color power generation unit  24 Cy over the power storage unit  25  in the cited order. 
     The self-power feeding type display device configured by the reflection pixels  21 R′,  21 G′, and  21 B′ and the sensor pixel  31 ′ having such structures can be manufactured in the same way as the self-power feeding type display device according to the second embodiment. That is, as illustrated in  FIG. 18 , the self-power feeding type display device can be manufactured by forming each of the reflection layer  23 , the power generation layer  24 , the sensor unit  32  and the power storage layer  25  in a sheet form and sticking together the reflection layer  23 , the power generation layer  24 , the sensor unit  32  and the power storage layer  25  each formed in a sheet form. Therefore, it is facilitated to, for example, make the screen large. 
     Operation of the self-power feeding type display device will now be described with reference to  FIG. 19A ,  FIG. 19B , and  FIG. 20 .  FIG. 19A  is a sectional view corresponding to  FIG. 17A , for explaining moves of light incident on the self-power feeding type display device according to the modification of the second embodiment.  FIG. 19B  is a sectional view corresponding to  FIG. 17B , for explaining moves of light incident on the self-power feeding type display device according to the modification of the second embodiment.  FIG. 20  is a functional block diagram illustrating the self-power feeding type display device according to the modification of the second embodiment. 
     First, if the incident light L is incident on the self-power feeding type display device according to the modification, light having a wavelength in a predetermined band is absorbed in the power generation layer  24  and power is generated. As illustrated in  FIG. 19A  and  FIG. 19B , cyan color light L cy  included in the incident light L arriving at the layer  24 Cy is absorbed in the cyan color power generation unit  24 Cy and power is generated. In the same way, magenta color light L Mg  included in the incident light L arriving at the layer  24 Mg is absorbed in the magenta color power generation unit  24 Mg and power is generated. Yellow color light L Ye  included in the incident light L arriving at the layer  24 Ye is absorbed in the magenta color power generation unit  24 Ye and power is generated. 
     Light that is not absorbed in the power generation layer  24  is transmitted through the power generation layer and arrives at the reflection layer  23 . The light arriving at the reflection layer  23  is reflected in the reflection layer  23 , transmitted through the power generation layer  24 , and emitted to the outside of the self-power feeding type display device according to the modification. As illustrated in  FIG. 19A  and  FIG. 19B , light L Mg+Ye  of magenta color+yellow color, which is not absorbed in the cyan color power generation unit  24 Cy, i.e., the red color light L R  is transmitted through the cyan color power generation unit  24 Cy and arrives at the red color reflection unit  23 R. The light arriving at the red color reflection unit  23 R is reflected in the red color reflection unit  23 R, transmitted through the cyan color power generation unit  24 Cy, and emitted to the outside of the self-power feeding type display device according to the modification. In the same way, light L Cy+Ye  of cyan color+yellow color, which is not absorbed in the magenta color power generation unit  24 Mg, i.e., the green color light L G  is transmitted through the magenta color power generation unit  24 Mg and arrives at the green color reflection unit  23 G. The light arriving at the green color reflection unit  23 G is reflected in the green color reflection unit  23 G, transmitted through the magenta color power generation unit  24 Mg, and emitted to the outside of the self-power feeding type display device according to the modification. Light L Cy|Mg  of cyan color+magenta color, which is not absorbed in the yellow color power generation unit  24 Ye, i.e., the blue color light L B  is transmitted through the yellow color power generation unit  24 Ye and arrives at the blue color reflection unit  23 B. The light arriving at the blue color reflection unit  23 B is reflected in the blue color reflection unit  23 B, transmitted through the yellow color power generation unit  24 Ye, and emitted to the outside of the self-power feeding type display device according to the modification. In this way, the reflection layer  23  reflects light having a wavelength in a predetermined band. As a result, the self-power feeding type display device according to the modification can display a picture according to a pixel arrangement. In addition, the self-power feeding type display device according to the modification can absorb the light L cy , L Mg , and L ye , which is unnecessary for display of the picture, and generate power. 
     As illustrated in  FIG. 20 , the power generation layer  24  and the power storage unit  25  are connected electrically by wiring, which is not illustrated. Power generated in the power generation layer  24  can be stored in the power storage unit  25 . The power stored in the power storage unit  25  can be taken out as occasion demands. Power required when the self-power feeding type display device according to the modification operates can be taken out from the power storage unit  25  and used. 
     In contrast, if the incident light L is incident on the sensor pixel  31 ′ as illustrated in  FIG. 19A , the cyan color power generation unit  24 Cy included in the pixel  31 ′ absorbs cyan color light L Cy  out of the incident light L and generates power. The generated power is stored in the stored in the power storage unit  25  as illustrated in  FIG. 20 . 
     Light that is not absorbed in the cyan color power generation unit  24 Cy (red color light L R ) is transmitted through the cyan color power generation unit  24 Cy, further transmitted through the reflection unit  33  as well, and arrives at the light reception unit (not illustrated) in the sensor unit  32 . The light reception unit generates an electric signal depending upon a light quantity of the light L R  arriving at the light reception unit. The electric signal generated in the light reception unit is taken out by a gate provided separately in the sensor unit  32  and supplied to the control unit  51  as illustrated in  FIG. 20 . 
     For example, if a light quantity of light incident on the sensor pixel  31 ′ lowers by touching a portion of the self-power feeding type display device according to the modification with a hand, a voltage of the electric signal supplied to the control unit  51  lowers. If the voltage of the electric signal supplied from the light reception unit changes in this way, the control unit  51  detects the change, takes out power from the power storage unit  25 , and supplies the power taken out to the reflection layer  23  (for example, one pair of transparent electrodes  43   a  and  43   b  having the cholesteric liquid crystal layer sandwiched between them). 
     If power is supplied to the transparent electrodes  43   a  and  43   b , an electric field is generated in the cholesteric liquid crystal layer  41  sandwiched between the transparent electrodes  43   a  and  43   b . The orientation state of the cholesteric liquid crystal changes according to the electric field. As a result, the wavelength band of light reflected in the reflection layer  23  is changed. Accordingly, the displayed picture is also changed. In the self-power feeding type display device according to the modification of the second embodiment as well, the displayed picture can be changed by changing the light reception quantity in the sensor pixel  31 ′ in this way. 
     In the self-power feeding type display device according to the modification of the second embodiment described heretofore as well, it is also possible to reduce the supply quantity of power generated outside the self-power feeding type display device to the self-power feeding type display device by a reason similar to that in the self-power feeding type display device according to the second embodiment. 
     In addition, in the self-power feeding type display device according to the modification of the second embodiment as well, the displayed picture can be changed without using power supplied from the outside of the self-power feeding type display device or by using only slightly power supplied from the outside of the self-power feeding type display device, in the same way as the self-power feeding type display device according to the second embodiment. 
     Furthermore, in the self-power feeding type display device according to the modification of the second embodiment, the power generation layer  24  is disposed on the reflection layer  23 . As compared with the self-power feeding type display device according to the second embodiment, therefore, the absorption quantity of light in the power generation layer  24  can be increased. Accordingly, the power generation quantity can be increased. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. 
     For example, in each of the above-described embodiments, the power storage units  15  and  25  are included within the self-power feeding type display device. As a result, wiring connecting the power generation layers  14  and  24  to the power storage units  15  and  25 , and wiring connecting the power storage units  15  and  25  to each unit in the self-power feeding type display device can be shortened. Therefore, it is possible to suppress power consumption caused by wiring and utilize power efficiently. However, it is not always necessary to include the power storage units  15  and  25  within the self-power feeding type display device, but the power storage units  15  and  25  may be disposed outside the self-power feeding type display device.