Patent Publication Number: US-2016233275-A1

Title: Organic el display device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims the benefit of priority from the prior Japanese Patent Application No. 2015-023885, filed on 10 Feb. 2015, the entire contents of which are incorporate herein by reference. 
     FIELD 
     The present invention relates to an organic EL display device. In particular, the present invention relates to technology of an organic EL element in which a photochromic layer is arranged. 
     BACKGROUND 
     Recently, it has been strongly demanded to increase resolution and decrease power consumption of light-emitting display devices for mobile use. As the display devices for mobile use, liquid crystal display devices (LCD), display devices utilizing self-emitting elements such as organic EL display devices (OLED), electronic paper, and the like are represented. 
     Among them, the organic EL display devices have been developed for the purpose of reducing thickness, increasing luminance, and improving response speed of display panels. The organic EL display devices are display devices having pixels composed of OLED and characterized by high response speed due to the absence of mechanical operation. The organic EL display devices do not require a backlight source and a polarizing plate because each pixel undergoes self-emission, which allows for the reduction in thickness of the display devices. Therefore, the organic EL display devices are expected as next generation display devices. 
     The OLED element decreases in emission efficiency while a current flows, and it has been known that a phenomenon called “burning” takes place due to the reduction in luminance at a certain current. In particular, in the case of a white-emissive OLED element having a tandem structure including a blue-emissive (B) OLED element and a yellow-emissive (Y) OLED element, a change of the balance of the emission intensity of B and Y causes a variation of the chromaticity, which may result in the burning phenomenon. 
     An organic EL display device arranged with a photochromic layer was proposed in order to sufficiently demonstrate a function of the organic EL display as a transparent display (e.g., Japanese laid- open publication No. 2014-72126). 
     SUMMARY 
     An organic EL display device according to an embodiment of the present invention includes an insulating surface; an anode electrode provided over the insulating surface; an organic layer provided over the anode electrode; and a cathode electrode over the organic layer. The organic EL display device further includes a photochromic layer which is provided so as to be in contact with the cathode electrode or the anode electrode and which has a light-absorption property with respect to a specific wavelength region. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a drawing showing the whole structure of an organic EL display device according to Embodiment 1 of the present invention; 
         FIG. 2  is a drawing showing a structure of a pixel portion of an organic EL display device according to Embodiment 1 of the present invention; 
         FIG. 3  is a cross-sectional view of an organic EL display device according to Embodiment 1 of the present invention; 
         FIG. 4  is a schematic view of a cross section of an organic EL display device according to Embodiment 1 of the present invention; 
         FIG. 5A  is a graph explaining a characteristic of a photochromic layer of an organic EL display device according to Embodiment 1 of the present invention; 
         FIGS. 5B  and  FIG. 5C  are graphs explaining a change in relative luminance of an organic EL display device according to Embodiment 1 of the present invention; 
         FIG. 6A  to  FIG. 6C  are drawings explaining a driving method of an organic EL display device according to Embodiment 1 of the present invention; 
         FIG. 7  is a cross-sectional view of an organic EL display device according to Embodiment 2 of the present invention; 
         FIG. 8  is a schematic view of a cross section of an organic EL display device according to Embodiment 2 of the present invention; 
         FIG. 9  is a schematic view of a cross section of an organic EL display device according to Embodiment 3 of the present invention; and 
         FIG. 10  is a schematic view of a layout of a light-emitting layer and a photochromic layer of an organic EL display device according to Embodiment 4 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An object of the present invention is to suppress the variation of chromaticity when a current flows in an organic EL element in order to prevent burning of an organic EL display device. 
     Hereinafter, the embodiments of the present invention are explained with reference to the drawings. Note that the disclosure is only an example of the embodiments, and those readily conceived by persons skilled in the art through an appropriate change of the embodiments within the concept of the invention should be considered to be included in the scope of the present invention. Further, the width, thickness, shape, and the like of each component may be schematically illustrated and different from those of an actual mode in the drawings in order to provide a more clear explanation. However, the drawings simply give an example and do not limit the interpretation of the present invention. Moreover, in the specification and each of the drawings, elements which are the same as those explained in the preceding drawings are denoted with the same reference numbers, and there detailed explanation may be omitted appropriately. 
     Embodiment 1 
     A structure of an organic EL display device according to Embodiment 1 is explained using  FIG. 1  to  FIG. 4 ,  FIG. 5A  to  FIG. 5C , and  FIG. 6A  to  FIG. 6C . 
     &lt;Whole Structure of Organic EL Display Device&gt; 
       FIG. 1  is a drawing showing the whole structure of the organic EL display device  100  according to Embodiment 1 of the present invention. The organic EL display device  100  has a pixel portion (display region)  102 , a scanning line driving circuit  103 , a data line driving circuit  104 , and a driver IC  105  formed over a substrate  20 . 
     The driver IC  105  functions as a control portion giving signals to the scanning line driving circuit  103  and the data line driving circuit  104 . 
     Note that the data line driving circuit  104  may also be included in the driver IC  105 . In  FIG. 1 , an example in which the driver IC  105  is integrated over the substrate  20  is shown. However, the driver IC  105  may also be separately arranged over another substrate in a form of an IC chip. Additionally, a mode in which the driver IC  105  is mounted to an FPC (Flexible Printed Circuit) and attached to the substrate may be employed. 
     A plurality of pixels are arranged in a matrix form in the pixel portion  102  shown in  FIG. 1 . Data signals corresponding to image data are provided to each of the pixels from the data line driving circuit  104 . The data signals are provided to pixel electrodes through transistors formed in each of the pixels, by which display can be performed according to the image data. Typically, a thin film transistor (TFT) can be used as the transistors. However, the transistors are not limited to a TFT, and any kind of element can be used as long as a current flow can be controlled. 
       FIG. 2  is a drawing showing a structure of the pixel portion  102  of the organic EL display device  100  illustrated in  FIG. 1 . In this embodiment, the pixel  201  includes a sub-pixel  201 R corresponding to red (R), a sub-pixel  201 G corresponding to green (G), a sub-pixel  201 B corresponding to blue (B), and a sub-pixel  201 W corresponding to white (W). A thin film transistor  202  is provided as a switching element in each of the sub-pixels. On/off control of each of the sub-pixels  201 R,  201 G,  201 B, and  201 W by using the thin film transistor  202  allows light emission in an arbitrary color corresponding to each of the sub-pixels, by which a variety of colors can be reproduced in one pixel. 
     A structure using sub-pixels of 4 colors of RGBW is shown in  FIG. 2 . However, this embodiment is not limited to this structure and may employ a structure in which a sub-pixel corresponding to yellow (Y) is used instead of the sub-pixel corresponding to W or a structure in which only 3 sub-pixels corresponding to the primary colors RGB are used in the absence of the sub-pixel corresponding to W. Additionally, although an example in which the sub-pixels corresponding to the same color are arranged in a stripe layout is shown, another layout which achieves the delta layout, the Bayer layout, or the PenTile layout can be adopted. 
     &lt;Cross-Sectional Structure of Organic EL Display Device&gt; 
     Next, a cross-sectional structure of the organic EL display device according to Embodiment 1 is explained using  FIG. 3 . 
       FIG. 3  shows a cross-sectional view of the pixel of the organic EL display device according to Embodiment 1 and corresponds to the cross-section obtained by cutting the pixel illustrated in  FIG. 2  along the A-A′ line. The substrate  20  is formed using glass, a resin, and the like. A pixel circuit layer  21  composed of a control TFT, a driving TFT, a storage capacitor, and the like is arranged over the substrate  20 . The pixel circuit layer  21  includes an interlayer insulating film in which a plurality of layers formed with an inorganic material such as silicon nitride and silicon oxide are stacked. Further, in addition to the pixel circuit layer  21 , a scanning signal line, an image signal line, a driving power source line, an auxiliary capacitor electrode, and the like are appropriately arranged over the substrate  20 . A planarizing film  22  formed with an organic material such as an acrylic resin and a polyimide is formed on an upper side of the interlayer insulating film for planarization, resulting in an insulating surface  23  at an upper surface of the planarization film  22 . 
     An anode electrode  24  corresponding to an anode is arranged over the insulating surface  23 . The anode electrode  24  is also arranged in a contact hole formed in the planarization film  22 , thereby electrically connecting the anode electrode  24  to the pixel circuit. A material with a light-transmitting property may be used for the anode electrode  24 . For example, ITO (indium tin oxide), ZnO (zinc oxide), SnO 2  (tin oxide), In 2 O 3  (indium oxide), IZO (zinc oxide added with indium as a dopant), GZO (zinc oxide added with gallium as a dopant), AZO (zinc oxide added with aluminum as a dopant), titanium oxide added with an impurity such as niobium as a dopant, and the like can be used. A reflective metal  26  having a light-reflecting property such as Al, Ti, Mo, Ni, Ag, and their alloys is arranged in a portion corresponding to the pixel under the anode electrode  24  (on a side of the substrate  20 ). In the case of the top-emission type organic EL display device shown in Embodiment 1, because the reflective metal  26  having a light-reflecting property and the anode electrode  24  having a light-transmitting property are stacked in this order, the reflective metal  26  functions as a light-reflecting electrode to reflect light, which is generated in an organic layer  30  and which is emitted downwards, upwards. Note that the aforementioned layer structure of the reflective metal  26  and the anode electrode  24  is only an example, and a three-layer structure in which an anode electrode, a reflective metal, and an anode electrode are stacked in this order over the insulating surface  23  (e.g., ITO/AG/ITO) may be used. 
     A pixel separation film (i.e., bank)  28  is arranged so that an edge portion of the anode electrode  24  and a contact hole formed in the planarization film  22  are covered. A common resin material can be used for the pixel separation film  28 , and a photo-sensitive resin material can be also used. As a photo-sensitive resin, a photo-sensitive acrylic resin, a photo-sensitive polyimide, and the like can be used. The portion which is defined by the pixel separation film  28  of the anode electrode  24  serves as the pixel. 
     The organic layer  30 , a cathode electrode  40 , a photochromic layer  51 , and a passivation layer  42  are stacked in this order over the anode electrode  24  and the pixel separation film  28 . Additionally, an opposing substrate  46  is bonded to the substrate  20 , and a region between the passivation layer  42  and the opposing substrate  46  is filled with a filling material  44 . The organic layer  30  and the photochromic layer  51  are explained below. The cathode electrode  40  corresponds to a cathode and is a common electrode formed as a single film to supply electric power to the organic layer  30  in association with the anode electrode  24 . A material having a light-transmitting property can be used for the cathode electrode  40 . Similar to the anode electrode  24 , ITO, ZnO, SnO 2 , In 2 O 3 , IGO, GZO, AZO, titanium oxide added with an impurity such as Nb as a dopant, and the like can be used as a material having a light-transmitting property. 
     The passivation layer  42  is arranged so that at least the organic layer  30  is covered, and the passivation layer  42  can be formed using a material having a high ability to block an impurity such as water. For example, a SiN x  film, a SiO x  film, a SiN x O y  film, a SiO x N y  film, an AlN x  film, an AlO x  film, an AlO x N y  film, and the like can be used (x and y are arbitrary). Further, a structure in which these films are stacked can be employed. 
     A common transparent resin is used for the filling material  44 . The filling material  44  relieves the steps resulted from the structures formed over the substrate  20  and the opposing substrate  46  which is bonded to the substrate  20  so as to face each other. The region between the substrate  20  and the opposing substrate  46  is filled with the filling material  44  so that these substrates are arranged to be substantially parallel to each other. 
     &lt;Structure of Organic Layer&gt; 
     Next, the organic layer  30  of Embodiment 1 is explained using  FIG. 4 .  FIG. 4  is a schematic view of a cross section of the organic EL display device of Embodiment 1 of the present invention and is an expanded view of a portion showing the organic layer  30  at the center. 
     As shown in  FIG. 4 , the organic layer  30  in Embodiment 1 has a tandem structure in which a Y light-emitting layer  31  that is yellow emissive and a B light-emitting layer  32  that is blue emissive are stacked. The organic layer  30  displays white color as whole by combining the yellow emission obtained from the Y light-emitting layer  31  and the blue emission obtained from the B light-emitting layer  32 . 
     A carrier transport layer (hole transport layers  81  and  82  and electron transport layers  83  and  84 ), an charge generation layer  85 , and the like are arranged in the organic layer  30  in addition to the Y light-emitting layer  31  and the B light-emitting layer  32 . The organic layer  30  is prepared using a low molecular-weight material or a high molecular-weight material. For example, when a low molecular-weight organic material is used for organic layer  30 , the carrier transport layers such as the hole transport layers  81  and  82  and the electron transport layers  83  and  84  are added in addition to the light-emitting layer including an emissive organic material, so as to sandwich the light-emitting layer. Moreover, a unit (Y unit) composed of the hole transport layer  81 , the Y light-emitting layer  31 , and the electron transport layer  83  and a unit (B unit) composed of the hole transport layer  82 , the B light-emitting layer  32 , and the electron transport layer  84  are stacked with the charge generation layer  85  interposed therebetween. The charge generation layer  85  injects electrons and holes to the Y and B units, respectively. 
     &lt;Photochromic Layer&gt; 
     Next, the photochromic layer  51  in Embodiment 1 is explained with reference to  FIG. 5A  to  FIG. 5C . 
     The photochromic layer  51  of Embodiment 1 is arranged over and in contact with the cathode electrode  40 . An inorganic compound or an organic compound which has a light-absorbing property with respect to a specific wavelength region is used for the photochromic layer  51 . 
     As an inorganic compound used for the photochromic layer  51 , a metal oxide and the like including at least one of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), niobium (Nb), molybdenum (Mo), ruthenium (Ru), indium (In), tin (Sn), antimony (Sb), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), and biomass (Bi) is given, for example. These metal oxides are able to attain a characteristic to absorb light of a specific wavelength region due to the localized surface plasmon resonance. The wavelength of the light absorbed by the photochromic layer  51  can be adjusted according to the kind of metal, size of particle, distance between the particles, and anisotropy. 
     A material including any of a diarylethene compound such as stilbene, a spiropyran compound, a spiroperimidine compound, a viologen compound, and an azobenzene compound may be used as an organic compound used for the photochromic layer  51 . The wavelength of the light absorbed by the photochromic layer  51  can be adjusted by adding a functional group to these organic compounds. 
     Moreover, the photochromic layer  51  has a property whereby its absorption increases with an increasing amount of light irradiated to the photochromic layer  51 . As a result, light transmittance of the photochromic layer  51  decreases with increasing luminance of the organic EL display device.  FIG. 5A  is a graph showing the relationship between the luminance (w/sr) of light irradiated to the photochromic layer  51  and the light transmittance of the photochromic layer  51 . Referring to  FIG. 5A , it is understood that an increase in luminance leads to a decrease in transmittance and a decrease in luminance results in a decrease in transmittance. 
     &lt;Effect of Photochromic Layer&gt; 
       FIG. 5B  is a drawing showing the change in relative luminance of the B emission and Y emission with respect to the current flow time in the organic EL element having the B light-emitting layer and the Y light-emitting layer. In  FIG. 5B , B and Y represent the changes in relative luminance of the B emission and Y emission, respectively. Here, it is assumed that the time-depending deterioration of the B light-emitting layer is larger than that of the Y light-emitting layer. In this case, after a certain current flow time, the reduction of the relative luminance of the B light-emitting layer is larger than that of the Y light-emitting layer. Accordingly, in the case of the tandem structure having the B light-emitting layer and the Y light-emitting layer arranged in the organic layer, the chromaticity shifts to the yellow side after a certain current flow time. The yellow shift of the chromaticity is likely to cause the burning phenomenon due to the chromaticity variation. 
     In Embodiment 1, the photochromic layer  51  which has a property to selectively absorb light in a B wavelength region (400 nm to 500 nm) is arranged over the cathode electrode  40 . Because the photochromic layer  51  has a light-absorbing property in the B wavelength region, the B emission irradiated to the photochromic layer  51  is absorbed, while the Y emission is not absorbed. Furthermore, the photochromic layer  51  has a property whereby its transmittance decreases with increasing amount of light irradiated thereto and increases with a decreasing amount of light irradiated thereto. That is, the photochromic layer  51  reduces the amount of B emission passing therethrough when the luminance of the B emission is high, while increasing the amount of B emission passing therethrough when the luminance of the B emission is low. Thus, it is possible to suppress the reduction of the relative luminance of B emission passing through the photochromic layer  51  which occurs in the current flow time compared with the case where the photochromic layer  51  is not arranged. 
       FIG. 5C  is a drawing showing the change in relative luminance of the B emission (B′ in the figure) after passing through the photochromic layer  51 , in addition to the change in relative luminance of the B emission and Y emission with respect to the current flow time. Comparison of B and B′ in  FIG. 5C  reveals that the reduction of the relative luminance can be suppressed by allowing the emission from the light-emitting layer to pass through the photochromic layer  51  and that the variation of the property which occurs as the current flow time elapses can be decreased. As described above, the arrangement of the photochromic layer  51  enables it to suppress the variation of the balance between the B emission color and the Y emission color, prevent the burning problem caused by the chromaticity shift, and improve the reliability. 
     &lt;Driving Method&gt; 
     Next, a driving method of the pixel circuit of Embodiment 1 is explained with reference to  FIG. 6A  to  FIG. 6C . 
     As described above, the photochromic layer  51  in Embodiment 1 has a property whereby its transmittance decreases with an increasing amount of light irradiated thereto and increases with a decreasing amount of light irradiated thereto. Therefore, when a driving method is employed where current flowing in the organic layer is changed according to the gray scale of the emission, it is considered to be difficult to correctly reproduce the gray scale because the photochromic layer  51  changes in transmittance with the change of the emission intensity of the organic layer. 
     Therefore, the gray scale may be controlled by the mode in which the emission duty ratio is varied in Embodiment 1.  FIG. 6A  is a graph showing the relationship between the operation time and the current density when display is performed at a full gray scale. Referring to  FIG. 6A , the operation is carried out at a constant current density (50 (a. u.)) in one frame.  FIG. 6B  and  FIG. 6C  are graphs showing the relationship between the operation time and the current density when display is performed at ½ and ⅓ gray scales, respectively. Comparison of  FIG. 6B  with  FIG. 6C  proves that the operation is carried out at the same current density regardless of the gray scale. Note that in the case of displaying at a ½ gray scale as shown in  FIG. 6B , the operation time is a ½ frame period, and the display is controlled in an operation period that is ½ the case of displaying at a full gray scale as shown in  FIG. 6A . Similarly, in the case of displaying at a ⅓ gray scale as shown in  FIG. 6C , the display is controlled in an operation period that is ⅓ the case of displaying at a full gray scale. 
     As explained above, in Embodiment 1, the display is controlled by the driving method in which the emission duty ratio is varied while keeping the current density constant, by which the gray scale can be relatively easily represented. 
     &lt;Variation of Embodiment 1&gt; 
     In Embodiment 1, explanation is given using the photochromic layer  51  having a property of selectively absorbing light in the B wavelength region (400 nm to 500 nm). However, the wavelength region of the absorbed light is not limited to the B wavelength region. For example, the time-depending change in luminance of the Y light-emitting layer  31  may be larger than that of the B light-emitting layer  32 , depending on the materials of the Y light-emitting layer  31  and the B light-emitting layer  32  which constitute the organic layer  30 . In this case, the photochromic layer  51  having a property of selectively absorbing light in a Y wavelength region may be arranged. 
     Embodiment 2 
     Next, the structure of the organic EL display device according to Embodiment 2 is explained using  FIG. 7  and  FIG. 8 . Note that the portions which are not particularly specified are regarded as common to Embodiments 1 and 2. 
       FIG. 7  shows a cross-sectional view of the pixel of the organic EL display device according to Embodiment 2. Referring to  FIG. 7 , it is understood that the photochromic layer  52  is arranged between the reflective metal  26  and the anode electrode  24 . Light generated in the organic layer  30  and emitted downward (to the side of the substrate  20 ) passes through the anode electrode  24  having a light-transmitting property and reflects upward on the reflective metal  26  having a light-reflecting property (to the side of a display surface of the display device). In Embodiment 2, part of the light generated in the light-emitting layer  30  passes through the photochromic layer  52  because the photochromic layer  52  is interposed between the anode electrode  24  and the reflective metal  26 . 
       FIG. 8  is a schematic view of the cross section of the organic EL display device according to Embodiment 2 and is an expanded view showing the organic layer  30  at the center. In  FIG. 8 , B 1  represents light generated in the B light-emitting layer  32  and emitted upward, B 2  represents light emitted downward from the B light-emitting layer, and B 3  represents light formed by the reflection of B 2  on the reflective metal  26 . B 2  passes the photochromic layer  52  immediately before the reflection on the reflective metal  26 . Further, B 3  is light which passes the photochromic layer  52  immediately after the reflection on the reflective metal  26 . As described above, the photochromic layer  52  has a property whereby its transmittance decreases with an increasing amount of light irradiated thereto and increases with a decreasing amount of light irradiated thereto. Thus, B 3  is light which is subjected to the luminance adjustment by the photochromic layer  52 . 
     Thus, in the organic EL display device according to Embodiment  2 , the blue light passing through the passivation layer  42  from the side of the substrate  20  includes the blue light B 1  that does not pass through the photochromic layer  52  and the blue light B 3  that is reflected on the reflective metal  26  and then passes through the photochromic layer  52 . Therefore, the arrangement of the photochromic layer  52  enables the control of the luminance of the blue light reflected on the reflective metal  26 , which allows the adjustment of the luminance of the blue light component of the organic EL display device. 
     &lt;Variation of Embodiment 2&gt; 
     Embodiment 2 may be an embodiment combined with Embodiment 1. That is, the photochromic layer  52  may be arranged between the reflective metal  26  and the anode electrode  24 , and the photochromic layer  51  may be further arranged between the cathode electrode  40  and the passivation layer  42 . In this case, the photochromic layers  51  and  52  may have a property of selectively absorbing light of the same wavelength region and also may have a property of selectively absorbing light of different wavelength regions. 
     Embodiment 3 
     Next, the structure of the organic EL display device according to Embodiment 3 is explained using  FIG. 9 . 
       FIG. 9  is a schematic view of a cross section of the organic EL display device according to Embodiment 3 and is an expanded view of a portion with the organic layer  30  at the center. Unlike Embodiment 1, Embodiment 3 is characterized in that the red (R) light-emitting layer  33  and the green (G) light-emitting layer  34  are arranged instead of the Y light-emitting layer. Note that although the R light-emitting layer  33  and the G light-emitting layer  34  are arranged so as to be in contact with each other, some kind of organic material may be arranged between the R light-emitting layer  33  and the G light-emitting layer  34 . 
     &lt;Variation of Embodiment 3&gt; 
     In  FIG. 9 , a structure is illustrated in which the R light-emitting layer  33 , the G light-emitting layer  34 , and the B light-emitting layer  32  are arranged in this order from the side of the anode electrode. However, the order of the light-emitting layers may be different from this order. Further, although  FIG. 9  shows a structure in which the photochromic layer  51  is arranged between the cathode electrode  40  and the passivation layer  42 , the photochromic layer  52  (not shown) may be arranged between the anode electrode  24  and the reflective metal  26  as explained in Embodiment 2. Additionally, although the aforementioned photochromic layer  51  of Embodiment 1 has a property of selectively absorbing light of the B wavelength region, the photochromic layer  51  (or photochromic layer  52 ) may have a property of selectively absorbing light of the R wavelength region or the B wavelength region. Moreover, similar to the variation of Embodiment 2, both the photochromic layer  51  and the photochromic layer  52  may be included, and they may have a property of selectively absorbing light of different wavelength regions. 
     Embodiment 4 
     Next, the structure of the organic EL display device according to Embodiment 4 is explained with reference to  FIG. 10 . 
       FIG. 10  is a schematic view showing the layout of the light-emitting layer and the photochromic layer  53  of the organic EL display device according to Embodiment 4.  FIG. 10  is a schematic view of adjacent three sub-pixels of R, G, and B, and the anode electrode  24 R corresponding to the R sub-pixel, the anode electrode  24 G corresponding to the G sub-pixel, the anode electrode  24 B corresponding to the B sub-pixel are arranged. In Embodiment 4, the tandem structure explained in Embodiments 1 to 3 is not employed, but a structure of a SBS (side-by-side) mode is used in which the R light-emitting layer  35 , the G light-emitting layer  36 , and the B light-emitting layer  37  are arranged along a surface parallel to the substrate  20  (not shown). The photochromic layer  53  is arranged between the cathode electrode  40  and the passivation layer  42 . Further, the photochromic layer  53  is formed on the whole surface so as to be substantially parallel to the substrate  20  similar to the cathode electrode  40 . 
     Here, similar to the photochromic layer  51  explained in Embodiment 1, the photochromic layer  53  of Embodiment 4 selectively absorbs light of the B wavelength region (400 nm to 500 nm) and has a property whereby its transmittance decreases with an increasing amount of light irradiated thereto and increases with a decreasing amount of light irradiated thereto. Therefore, although the photochromic layer  53  is arranged on the upper side of the R light-emitting layer  35 , the G light-emitting layer  36 , and the B light-emitting layer  37 , the photochromic layer  53  changes in transmittance only with respect to the light generated in the B light-emitting layer  37 , but does not influence the light generated in the R light-emitting layer  35  and the G light-emitting layer  36 . Thus, arrangement of the photochromic layer  53  in the organic EL display device having the SBS mode also provides the same effects explained in Embodiment 1. 
     In the aforementioned Embodiments, although the cases of the organic EL display device are described as exemplified disclosure, the embodiments can be applied to any kind of display devices of the flat panel type such as other self-emission type display devices, liquid crystal display devices, and electronic paper type display device having electrophoretic elements and the like. In addition, it is apparent that the size of the display device is not limited, and the embodiment can be applied to display devices having any size from medium to large. 
     The persons ordinarily skilled in the art are able to conceive of a variety of changes and modifications within the scope of the concept of the present invention, and the examples of such changes and modifications are also included in the scope of the invention. For example, a mode realized by the persons ordinarily skilled in the art through the appropriate addition, deletion, and design change of elements is included in the scope of the present invention as long as it possesses the concept of the present invention.