Patent Publication Number: US-2006017671-A1

Title: Display device and electronic apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priorities to Japanese Patent Application Nos. 2004-215326 and 2004-215328, filed on Jul. 23, 2004, the entire disclosures of which are incorporated herein by reference.  
     BACKGROUND  
      The present invention relates to a display device and to an electronic apparatus.  
      Since a self-emitting display device, such as an organic EL device, does not need to have a backlight, it has drawn attention as a display device having a small size. In the organic EL device, sub-pixels (minimum display units) corresponding to red (R), green (G), and blue (B) are arranged in stripes, and three sub-pixels constitute one pixel to perform full-color display (for example, see Japanese Unexamined Patent Application Publication No. 2002-252083).  
      In the display device disclosed in Japanese Unexamined Patent Application Publication No. 2002-252083, full-color display is performed by a structure common to pixels in a display region. This structure is suitable for a case in which display is performed such that a time integral value of the brightness in the display region is constant in every pixel, as in a television. However, when the time integral value of brightness in the display region is different for every pixel, the following problems arise. That is, 1) in a color pixel having a large time integral value of brightness, the brightness is more easily deteriorated than the other color pixels; 2) in the color pixel having a large time integral value of brightness, the deterioration of brightness occurs relatively rapidly, and the whole white balance collapses. Thus, the color is changed, and image quality is easily deteriorated, and 3) when sub-pixels corresponding to three colors are arranged in a monochrome display region, an aperture ratio is lowered, and thus the brightness of the monochrome display portion is rapidly deteriorated.  
     SUMMARY  
      An advantage of the invention is that it provides a display device capable of improving display quality and of increasing life-span. Further, another advantage of the invention is that it provides an electronic apparatus having a high-quality display device.  
      According to a first aspect of the invention, a display device includes a display region having a first display region that is composed of a first pixel group displaying a first light-emitting wavelength range; and a second display region that is composed of a second pixel group displaying a second light-emitting wavelength range different from the first light-emitting wavelength range. Here, the first light-emitting wavelength range is not equal to the second light-emitting wavelength range. That is, the first light-emitting wavelength range may not be completely equal to the second light-emitting wavelength range, and one light-emitting wavelength range may be included in the other light-emitting wavelength range.  
      In the display device, the first pixel group of the first display region and the second pixel group of the second display region have different light-emitting wavelength ranges. That is, in the first and second display regions, the ranges (kinds) of color light components to be emitted are different from each other.  
      Therefore, the display region which the display device of the invention has is divided into at least the first and second display regions emitting different color light components, so that the flexibility of the design of the display region can be improved.  
      In this case, pixels to emit a light component corresponding to a color necessary for a predetermined region in the display regions are arranged, and pixels to emit a light component corresponding to a color unnecessary for the predetermined region are excluded. As a result, it is possible to increase an aperture ratio. That is, according to the related art, since pixels for full-color display are arranged in the display region for performing monochrome display, pixels to emit the light components corresponding to the unnecessary colors are arranged, which causes the aperture ratio to be lowered. In the invention, since the pixels related to the unnecessary colors are excluded, the problem of the aperture ratio being lowered can be solved.  
      In addition, only the pixels related to the necessary colors constitute a predetermined display region. Therefore, even if brightness per one pixel is deteriorated, compared to a case in which the pixels for full-color display are arranged in the entire display region as in the related art, it is possible to obtain the same surface brightness as that in the related art. Therefore, the deterioration of brightness per one pixel can be prevented, and consumption power can be reduced. In addition, it is possible to prolong the life span of brightness.  
      In addition, in the display device, resolution can increase. That is, as compared to a case in which the pixels for full-color display are arranged in the entire display region, it is possible to increase the number of pixels corresponding to necessary colors in the predetermined region and thus to increase resolution.  
      Preferably, the first pixel group is composed of pixels that can display plural kinds of color light components, and the second pixel group is composed of pixels that can display a color light component. In this case, in the first display region, two-color display or plural color display can be performed, but in the second display region, only monochrome display can be performed. In addition, as compared to a case in which the pixels for the full-color display are arranged, as in the related art, the aperture ratio, the resolution, and the life span of brightness can increase in the second display region. More particularly, it is preferable that the first pixel group be composed of pixels each including at least a first sub-pixel to emit a predetermined color light component and a second sub-pixel to emit another color light component different from the light component emitted by the first sub-pixel, and that the second pixel group be composed of pixels each having one sub-pixel to emit a predetermined color light component.  
      Further, it is preferable that the first pixel group be composed of pixels to perform full-color display and that the second pixel group be composed of pixels to perform monochrome display. More particularly, the first pixel group can be composed of pixels each having a sub-pixel to emit a red light component, a sub-pixel to emit a green light component, and a sub-pixel to emit a blue light component. The second pixel group can be composed of pixels each having two or fewer sub-pixels selected from among the sub-pixel to emit the red light component, a sub-pixel to emit a green light component, and a sub-pixel to emit a blue light component.  
      It is preferable that, when the plural kinds of sub-pixels are provided, various sub-pixels have the same size. In this case, the aperture ratio can be adjusted by the number of sub-pixels formed on the display region, and the design of the aperture ratio can be facilitated. Further, it is preferable that the sub-pixels each have a rectangular shape, and that the pixel includes a plurality of the sub-pixels having the rectangular shape and have a square shape.  
      According to a second aspect of the invention, an electronic apparatus includes the above-mentioned display device. By using this electronic apparatus, it is possible to achieve high-definition display on the display unit.  
      According to a third aspect of the invention, there is provided a display device including a display region composed of a plurality of pixels. The pixel is composed of a laminated structure of a plurality of functional layers. The display region has a first display region that is composed of a first pixel group displaying a first light-emitting wavelength range and a second display region that is composed of a second pixel group displaying a second light-emitting wavelength range different from the first light-emitting wavelength range. The first pixel constituting the first pixel group and the second pixel constituting the second pixel group have different laminated structures of the functional layers. Here, the first light-emitting wavelength range is not equal to the second light-emitting wavelength range. That is, the first light-emitting wavelength range may not be completely equal to the second light-emitting wavelength range, and one light-emitting wavelength range may be included in the other light-emitting wavelength range.  
      In the display device, the first pixel group of the first display region and the second pixel group of the second display region have different light-emitting wavelength ranges. That is, in the first and second display regions, the ranges (kinds) of color light components to be emitted are different from each other.  
      Therefore, the display region which the display device of the invention has is divided into at least the first and second display regions each emitting different color light components, so that the flexibility of the design of the display region can be improved.  
      In this case, pixels to emit a light component corresponding to a color necessary for a predetermined region in the display regions are arranged, and pixels to emit a light component corresponding to a color unnecessary for the predetermined region are excluded. As a result, it is possible to raise an aperture ratio. That is, according to the related art, since pixels for full-color display are arranged in the display region for performing monochrome display, pixels to emit the light components corresponding to the unnecessary colors are arranged, which causes the aperture ratio to be lowered. In the invention, since the pixels related to the unnecessary colors are excluded, the problem of the aperture ratio being lowered can be solved.  
      In addition, only the pixels related to the necessary colors constitute a predetermined display region. Therefore, even if brightness per pixel is reduced, compared to a case in which the pixels for full-color display are arranged in the entire display region as in the related art, it is possible to obtain the same surface brightness as that in the related art. Therefore, the deterioration of brightness per pixel and consumption power can be reduced, and the life span of brightness can be prolonged.  
      In addition, in the display device, resolution can increase. That is, as compared to a case in which the pixels for full-color display are arranged over the entire display region, it is possible to increase the number of pixels corresponding to necessary colors in a predetermined region and thus to increase resolution.  
      In the structure in which the display region is divided for each color light component to be emitted, the laminated structure of the functional layers constituting the pixel is different for every divided display region. When emission colors are different, the energy required for performing the light emission is different, so that each pixel corresponding to each color has the desirable structure. However, when the pixels for full-color display are arranged over the entire display region, as in the related art, it is necessary that the pixel structure be changed according to the pattern of each color. As a result, a workload becomes large. However, in the invention, since the display region is divided, the laminated structure of the functional layers may be different for each display region, and the laminated structure suitable for each color can be achieved.  
      In this way, by making the functional layer different for each region, the laminated structure suitable for the luminescent color of the pixel can be employed, and thus light-emitting efficiency and the life span of brightness can be improved.  
      Preferably, the first pixel group is composed of pixels that can display plural kinds of color light components, and the second pixel group is composed of pixels that can display a color light component. In this case, the two-color display can be performed in the first display region, but the monochrome display can be performed in the second display region. Further, as compared to the case in which the pixels for full-color display are provided, as in the related art, the aperture ratio, the resolution, and the life span of brightness can be improved in the second display region. Particularly, it is preferable that the first pixel group be composed of first pixels each including at least a first sub-pixel to emit a predetermined color light component and a second sub-pixel to emit another color light component different from the color light component emitted by the first sub-pixel, and that the second pixel group be composed of second pixels each having one sub-pixel to emit a predetermined color light.  
      Further, it is preferable that the first pixel group be composed of pixels to perform full-color display, and that the second pixel group be composed of pixels to perform monochrome display. Particularly, it is preferable that the first pixel group be composed of first pixels each having a sub-pixel to emit a red light component, a sub-pixel to emit a green light component, and a sub-pixel to emit a blue light component, and that the second pixel group be composed of second pixels each having two or fewer sub-pixels selected from among the sub-pixel to emit the red light component, the sub-pixel to emit the green light component, and the sub-pixel to emit the blue light component.  
      When the plurality of sub-pixels are provided, the sub-pixels may have the same size. In this case, the aperture ratio can be controlled by the number of the sub-pixels formed on the display region, and the aperture ratio can be easily designed. It is preferable that the sub-pixel have a rectangular shape, and that the pixel have a plurality of the sub-pixels having the rectangular shape and have a square shape.  
      A functional layer included in the display device may have a cathode layer, an anode layer, and an organic EL layer formed between the cathode layer and the cathode layer. In this case, it is preferable that the first pixel group be composed of first pixels each having a sub-pixel to emit a blue light component, that the second pixel group be composed of second pixels each having a sub-pixel to emit a red light component and not having the sub-pixel to emit the blue light component, that a cathode layer constituting the functional layer of the first pixel contain lithium fluoride, and that a cathode layer constituting a functional layer of the second pixel do not contain lithium fluoride.  
      The organic EL layer, serving as a light-emitting functional layer, has different light-emitting efficiency for each light-emitting color. Particularly, in the organic EL layer to emit a red light component and the organic EL layer to emit a blue light component, since the light-emitting efficiencies are greatly different because of the difference in the structure of the cathode layer, it is preferable for the organic EL layers to have a suitable cathode layer structure. More particularly, by containing lithium fluoride in the cathode layer, the light-emitting efficiency of the blue organic EL layer can be improved. However, the light-emitting efficiency of the red organic EL layer is a little lowered. Therefore, when the display region is divided, as in the invention, it is possible to easily make the structures of the cathode layer different from each other for the divided display region. More particularly, in the display region composed of the first pixels including the blue sub-pixels and the display region composed of the second pixels including the red sub-pixels and not including the blue sub-pixels, it is possible to easily make the structures of the cathode layer of each pixel different from each other, and the light-emitting efficiency can be easily improved.  
      As such, when the organic EL layer is included as a functional layer, the first pixel group is composed of first pixels each having a sub-pixel to emit a red light component, a sub-pixel to emit a green light component, and a sub-pixel to emit a blue light component, and the second pixel group is composed of second pixels each having the sub-pixel to emit the red light component. In addition, a cathode layer constituting a functional layer of the first pixel contains lithium fluoride, and a cathode layer constituting a functional layer of the second pixel does not contain lithium fluoride. In this case, it is possible to easily make the structures of the cathode layer of each pixel different from each other, and light-emitting efficiency can be easily improved.  
      As the structure of the cathode layer, it is preferable that the cathode layer constituting the functional layer of the first pixel have a complex structure of lithium fluoride, calcium, and aluminum, and that the cathode layer constituting the functional layer of the second pixel have a complex structure of calcium and aluminum.  
      According to a fourth aspect of the invention, an electronic apparatus includes the above-mentioned display device. By using this electronic apparatus, high-definition display can be performed for a long time in the display unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements, and wherein:  
       FIG. 1  is a circuit diagram of an organic EL device according to a first embodiment of the invention;  
       FIG. 2  is a diagram showing the plan-view structure of the organic EL device shown in  FIG. 1 ;  
       FIG. 3  is a diagram showing the plan-view structure of a pixel in a first display region;  
       FIG. 4  is a diagram showing the plan-view structure of a pixel in a second display region;  
       FIG. 5  is a diagram showing the sectional structure of the first display region;  
       FIG. 6  is a diagram showing the sectional structure of the second display region;  
       FIG. 7  is a graph showing a temporal change of brightness in the first embodiment and a temporal change of brightness in a comparative example;  
       FIG. 8  is a diagram illustrating a method of manufacturing the organic EL display device according to the first embodiment;  
       FIG. 9  is a diagram illustrating the method of manufacturing the organic EL display device according to the first embodiment;  
       FIG. 10  is a diagram illustrating the method of manufacturing the organic EL display device according to the first embodiment;  
       FIG. 11  is a diagram illustrating the method of manufacturing the organic EL display device according to the first embodiment;  
       FIG. 12  is a diagram illustrating the method of manufacturing the organic EL display device according to the first embodiment;  
       FIG. 13  is a diagram illustrating the first display region in the method of manufacturing the organic EL display device according to the first embodiment;  
       FIG. 14  is a diagram illustrating the second display region in the method of manufacturing the organic EL display device according to the second embodiment;  
       FIG. 15  is a diagram illustrating the first display region in the method of manufacturing the organic EL display device according to the first embodiment;  
       FIG. 16  is a diagram illustrating the second display region in the method of manufacturing the organic EL display device according to the second embodiment;  
       FIG. 17  is a diagram showing the plan-view structure of a head according to the first embodiment of the invention;  
       FIG. 18  is a diagram showing the plan-view structure of an inkjet device according to the first embodiment of the invention;  
       FIG. 19  is a plan view showing an example of a substrate constituting a display unit mounted on an electronic apparatus;  
       FIG. 20  is a cross-sectional view showing the structure of a substrate constituting the display unit shown in  FIG. 19 ;  
       FIG. 21  is a plan view showing the structure of a display region in the display unit shown in  FIG. 19 ;  
       FIG. 22  is a plan view showing an example of an electronic apparatus;  
       FIG. 23  is a plan view showing a modification of the substrate constituting the display unit mounted on the electronic apparatus;  
       FIG. 24  is a plan view showing an example of an electronic apparatus;  
       FIG. 25  is a diagram showing the sectional structure of a first display region in an organic EL display device according to a second embodiment of the invention;  
       FIG. 26  is a diagram showing the sectional structure of a second display region in the organic EL display device according to the second embodiment of the invention;  
       FIG. 27  is a graph showing a temporal change of brightness in the second embodiment and a temporal change of brightness in a comparative example;  
       FIG. 28  is a graph showing the difference between a temporal change of brightness when a lithium fluoride layer is provided and a temporal change of brightness when the lithium fluoride layer is not provided;  
       FIG. 29  is a diagram illustrating the first display region in a method of manufacturing the organic EL display device according to the second embodiment; and  
       FIG. 30  is a diagram illustrating the second display region in the method of manufacturing the organic EL display device according to the second embodiment. 
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
      Hereinafter, an organic EL device, which is a display device according to first and second embodiments of the invention, and a method of manufacturing the same will be described in detail with reference to the accompanying drawings. In addition, in the respective drawings, in order for each layer or member to be recognizable, each layer or member is shown with a different scale.  
      Organic EL Device  
       FIG. 1  is an explanatory diagram showing the wiring structure of an organic EL device according to a first embodiment of the invention, and  FIG. 2  is a plan view schematically illustrating the organic EL device according to the first embodiment.  FIGS. 3 and 4  are enlarged plan views schematically showing the structure of a pixel, and  FIGS. 5 and 6  are cross-sectional views schematically illustrating a display region of the organic EL device according to the first embodiment.  
      As shown in  FIG. 1 , the organic EL device according to the present embodiment includes a plurality of scanning lines  101 , a plurality of signal lines  102  extending perpendicular to the plurality of scanning lines  101 , and a plurality of power lines  103  extending parallel to the plurality of signal lines  102 . Here, unit display regions P are respectively provided so as to correspond to intersections of the scanning lines  101  and the signal lines  102 .  
      The signal lines  102  are connected to a data line driving circuit  104  which includes a shift register, a level shifter, video lines and analog switches. In addition, the scanning lines  101  are connected to a scanning line driving circuit  105  which includes a shift register and a level shifter.  
      In addition, each unit display region P is provided with a switching thin film transistor  122  having a gate electrode supplied with a scanning signal through the scanning line  101 , a storage capacitor cap for holding a pixel signal supplied from the signal line  102  through the switching thin film transistor  122 , a driving thin film transistor  123  having a gate electrode supplied with the pixel signal held in the storage capacitor cap, a pixel electrode (electrode)  111  to which a driving current flows from the power line  103  when it is electrically connected to the power line  103  through the driving thin film transistor  123 , and an organic EL layer  110  interposed between the pixel electrode  111  and a cathode layer (counter electrode)  12 . The electrode  111 , the counter electrode  12 , and the organic EL layer  110  constitute a light-emitting element.  
      When the scanning line  101  is driven and the switching thin film transistor  122  is turned on, the potential of the signal line  102  is held in the storage capacitor cap, and the on/off state of the driving thin film transistor  123  is determined in accordance with the state of the storage capacitor cap. In addition, a current flows to the pixel electrode  111  from the power line  103  through a channel of the driving thin film transistor  123 , and then the current flows to the cathode layer  12  through the organic EL layer  110 . In the organic EL layer  110 , light is emitted in accordance with the amount of current flowing.  
      As shown in  FIGS. 5 and 6 , the organic EL device according to the present embodiment includes a transparent substrate  2  made of, for example, glass, a light-emitting element portion  11  formed on the substrate  2  and having light-emitting elements arranged in a matrix, and the cathode layer  12  formed on the light-emitting element portion  11 . Here, the light-emitting element portion  11  and the cathode layer  12  constitute a display element  10 . The substrate  2  is a transparent substrate made of, for example, glass. As shown in  FIG. 2 , the substrate  2  is divided into two regions, that is, a display region  2   a  located at a central portion of the substrate  2  and a non-display region  2   c  located at the periphery of the substrate  2  for surrounding the display region  2   a.    
      The display region  2   a  is a region formed of light-emitting elements arranged in a matrix and has a plurality of dots (sub-pixels) each of which can emit a light component corresponding to any one of red (R), green (G), and blue (B). Here, each dot (sub-pixel) serves as a minimum display unit for display and constitutes the unit display region P shown in  FIG. 1 . In addition, according to the present embodiment, the display region  2   a  has a first display region  21  to perform full-color display and a second display region  22  to perform monochrome display. As shown in  FIG. 3 , the first display region  21  has a plurality of pixels each composed of an R dot A 1  to emit a red (R) light component, a G dot A 2  to emit a green (G) light component, and a B dot A 3  to emit a blue (B) light component arranged therein. On the other hand, as shown in  FIG. 4 , the second display region  22  has a plurality of pixels A′ each including three R dots A 1  to emit the red (R) light component arranged therein.  
      That is, in the display region  2   a , the plurality of pixels A and A′ are disposed in a predetermined arrangement. The pixels A and A′ have different wavelength ranges to emit light. That is, the pixel A can emit light having the wavelength range of full color (approximately, a wavelength of 380 to 780 mn), and the pixel A′ can emit light having the wavelength range of red (approximately, a wavelength of 580 to 780 nm). In addition, a display region in which the plurality of pixels A constitute a first pixel group having a predetermined pattern functions as the first display region  21  capable of performing full-color display. In addition, a display region in which the plurality of pixels A′ constitute a second pixel group having a predetermined pattern functions as the second display region  22  capable of performing red display. As shown in  FIGS. 3 and 4 , the respective dots (sub-pixels) A 1 , A 2 , and A 3  have the same rectangular shape and the same area, and the respective pixels A and A′ have substantially the same square shape.  
      Referring to  FIG. 2  again, the power lines  103  ( 103 R,  103 G, and  103 B) are provided in the non-display region  2   c . The scanning line driving circuits  105  are provided at both sides of the display region  2   a . In addition, control signal wiring lines  105   a  for a driving circuit and power lines  105   b  for a driving circuit  105   b  connected to the scanning line driving circuits  105  are provided at both sides of the scanning line driving circuits  105 . A test circuit  106  is provided at an upper side of the display region  2   a  in the drawing to test the quality and defects of a display device during manufacture and shipment.  
       FIG. 5  is a diagram showing the sectional structure of the first display region  21 . The first display region  21  is composed of three types of dots (sub-pixels) A 1 , A 2 , and A 3 , as described above.  
      In the first display region  21 , a circuit element unit  14  on which circuits, such as TFTs, are formed, the light-emitting element portion  11  on which the organic EL layer  110  is formed, and the cathode layer  12  are sequentially laminated on the substrate  2 . Light emitted from the organic EL layer  110  toward the substrate  2  passes through the circuit element unit  14  and the substrate  2 , and then travels toward a lower side (observer side) of the substrate  2 . In addition, the light emitted from the organic EL layer  110  to the opposing side of the substrate  2  is reflected from the cathode layer  12 , and then travels toward the lower side (observer side) of the substrate  2  through the circuit element unit  14  and the substrate  2 .  
      In addition, when the cathode layer  12  is made of a transparent material, it is possible to reflect the light emitted from the cathode layer. The transparent materials forming the cathode layer may include ITO (indium tin oxide), Pt, Ir, Ni, and Pt.  
      In the circuit element unit  14 , a base protecting film  2   c  composed of a silicon oxide film is formed on the substrate  2 , and an island-shaped semiconductor film  141  made of polycrystalline silicon is formed on the base protecting film  2   c . In the semiconductor film  141 , the source region  141   a  and the drain region  141   b  are formed by a highly concentrated phosphorous ion implanting method. A portion where the phosphorous ions are implanted becomes a channel region  141   c.    
      Then, a gate insulating film  142  is formed so as to cover the base protecting film  2   c  and the semiconductor film  141 . A gate electrode  143  (the scanning line  101 ) made of Al, Mo, Ta, Ti, or W is formed on the gate insulting film  142 , and a first interlayer insulating film  144   a  and a second interlayer insulating film  144   b  which are made of a transparent material are formed on the gate electrode  143  and the gate insulating film  142 . The gate electrode  143  is provided at a position adjacent to the channel region  141   c  of the semiconductor film  141 . In addition, contact holes  145  and  146  are formed such that they pass through the first and second interlayer insulating films  144   a  and  144   b  to reach source and drain regions  141   a  and  141   b  of the semiconductor film  141 , respectively.  
      Further, on the second interlayer insulating film  144   b , transparent pixel electrodes  111  made of, for example, ITO are patterned in a predetermined shape, and the contact hole  145  is connected to the pixel electrode  111 . In addition, the contact hole  146  is connected to the power line  103 . In this way, the driving thin film transistor  123  connected to the pixel electrode  111  is formed in the circuit element unit  14 .  
      The light-emitting element portion  11  is mainly composed of the organic EL layers  110  laminated on the plurality of pixel electrodes  111  and bank portions  112  which are provided between the pixel electrodes  111  and the organic EL layers  110  to partition the respective organic EL layers  110 . The cathode layer  12  is arranged on the organic EL layer  110 . The pixel electrode  111 , the organic EL layer  110 , and the cathode layer  12  constitute a light-emitting element. Here, the pixel electrode  111  is made of, for example, ITO and is patterned substantially in a rectangular shape in plan view. The bank portions  112  are provided to partition the pixel electrodes  111 .  
      As shown in  FIG. 5 , the bank portion  112  has a laminated structure of an inorganic bank layer (first bank layer)  112   a , serving as a first partition wall located at the side of the substrate  2 , and an organic bank layer (second bank layer)  112   b , serving as a second partition wall located away from the substrate  2 . The inorganic bank layer  112   a  is formed of, for example, TiO 2  or SiO 2 , and the organic bank layer  112   b  is formed of, for example, an acrylic resin or a polyimide resin.  
      The inorganic and organic bank layers  112   a  and  112   b  are formed so as to ride on the peripheral edge of the pixel electrode  111 . In plan view, the peripheral edge of the pixel electrode  111  and the inorganic bank layer  112   a  partially overlap each other. In addition, similar to the inorganic bank layer  112   a , the organic bank layer  112   b  overlaps a part of the pixel electrode  111  in plan view. Further, the inorganic bank layer  112   a  protrudes more toward the central portion of the pixel electrode  111  than toward the edge of the organic bank layer  112   b . In this way, a first laminated portion (protruding portion)  112   e  of the inorganic bank layer  112   a  is formed at an inner side of the pixel electrode  111 , so that a lower opening  112   c  is formed at a location adjacent to the pixel electrode  111 .  
      In addition, an upper opening  112   d  is formed in the organic bank layer  112   b . The upper opening  112   d  is formed at a location adjacent to the pixel electrode  111  and the lower opening  112   c . As shown in  FIG. 5 , the upper opening  112   d  is larger than the lower opening  112   c  and is smaller than the pixel electrode  111  in diameter. In addition, a top portion of the upper opening  112   d  may be aligned with the end of the pixel electrode  111 . In this case, as shown in  FIG. 5 , the cross section of the upper opening  112   d  of the organic bank layer  112   b  is inclined. In this way, the lower opening  112   c  and the upper opening  112   d  communicate with each other to form an opening  112   g  in the bank portion  112 .  
      In addition, the bank portion  112  has a region having a lyophilic property and a region having a lyophobic property. The regions having the lyophilic property include the first laminated portion  112   e  of the inorganic bank layer  112   a  and an electrode surface  111  a of the pixel electrode  111 , and these regions are given the lyophilic property by a plasma surface treatment using oxygen as a raw gas. In addition, the regions having the lyophobic property include a wall surface of the upper opening  112   d  and a top surface  112   f  of the organic bank layer  112 , and these regions are given fluoridated surfaces (lyophobic property) by a plasma treatment using methane tetrafluoride, tetrafluoromethane, or carbon tetrafluoride as a raw gas.  
      The organic EL layer  110  includes a hole injection/transportation layer  110   a  laminated on the pixel electrode  111  and a light-emitting layer  110   b  formed adjacent to the hole injection/transportation layer  110   a.    
      The hole injection/transportation layer  110   a  has a function for injecting holes into the light-emitting layer  110   b  and a function for transporting the holes therein. In this way, the hole injection/transportation layer  110   a  is provided between the pixel electrode  111  and the light-emitting layer  110   b , so that it is possible to improve element characteristics, such as the light-emitting efficiency and life span of the light-emitting layer  110   b . In addition, in the light-emitting layer  110   b , the holes injected from the hole injection/transportation layer  110   a  and electrons injected from the cathode layer  12  recombine with each other to emit light.  
      The hole injection/transportation layer  110   a  includes a flat portion  110   a   1  which is located inside the lower opening  112   c  and which is formed on the pixel electrode surface  111   a  and a peripheral portion  110   a   2  which is located inside the upper opening  112   d  and which is formed on the first laminated portion  112   e  of the inorganic bank layer. In addition, the hole injection/transportation layer  110   a  is formed only between the inorganic bank layers  112   a  (between the lower openings  112   c ) formed on the pixel electrode  111  (may be formed on only the above-mentioned flat portion).  
      The light-emitting layer  110   b  is formed over the flat portion  110   a   1  and the peripheral portion  110   a   2  of the hole injection/transportation layer  110   a , and the thickness of the light-emitting layer  110   b  on the flat portion  112   a   1  is within the range of 50 to 80 nm. The light-emitting layer  110   b  has a red light-emitting layer  110   b   1  to emit a red (R) light component, a green light-emitting layer  110   b   2  to emit a light green (G) component, and a blue light-emitting layer  110   b   3  to emit a blue (B) light component. The respective light-emitting layers  110   b   1  to  110   b   3  are arranged in stripes in plan view.  
      In addition, the hole injection/transportation layer can be made of, for example, a mixture of a polythiophene derivative, such as polyethylenedioxothiophene (PEDOT), and polystyrene sulfonic acid.  
      In addition, the light-emitting layer  110   b  can be made of for example, (poly) paraphenylenevinylene derivative, polyphenylene derivative, polyfluorene derivative, polyvinylcarvazole, polythiophene derivative, perylene dye, coumarin dye, rhodamine dye, and materials obtained by doping rubrene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, quinacridone or the like in these high polymer materials.  
      The cathode layer  12  is formed over the entire surface of the light-emitting element portion  11  and causes a current to flow in the organic EL layer  110  formed on the pixel electrode  111 . For example, the cathode layer  12  is composed of a laminated layer of a calcium layer and an aluminum layer. In this case, it is preferable that a work function be small in a part of the cathode layer adjacent to the light-emitting layer. More particularly, according to the present embodiment, the cathode layer directly comes into contact with the light-emitting layer  110   b  to inject electrons into the light-emitting layer  110   b.    
      In addition, LiF may be formed between the light-emitting layer  110   b  and the cathode layer  12  in order to improve the light-emitting efficiency. In addition, the materials forming the red and green light-emitting layers  110   b   1  and  110   b   2  are not limited to lithium fluoride, but may be made of other materials. Therefore, in this case, only the blue (B) light-emitting layer  110   b   3  may be formed of lithium fluoride, the other red and green light-emitting layers  110   b   1  and  110   b   2  may be formed of materials other than lithium fluoride. In addition, only the calcium film may be formed on the red and green light-emitting layers  110   b   1  and  110   b   2  without forming a film made of lithium fluoride.  
      In addition, since aluminum forming the cathode layer  12  reflects light emitted from the light-emitting layer  110   b  toward the substrate  2 , it is preferable that the cathode layer  12  be formed of an Ag film or a laminated film of the Al film and the Ag film, in addition to the Al film. In addition, a protective layer for preventing oxidization, made of SiO, SiO 2 , SiN or the like, may be provided on the aluminum film.  
      In an actual organic EL device, a sealing portion is provided on the light-emitting element portion  11  shown in  FIG. 5 . The sealing portion can be formed by applying a sealing resin around the periphery of the substrate  2  in a ring shape and then by sealing it with a sealing can. The sealing resin is composed of a thermosetting resin or an ultraviolet curable resin. In particular, it is preferable that the sealing resin be composed of an epoxy resin, which is a kind of thermosetting resin. The sealing portion is provided in order to prevent the light-emitting layer formed in the cathode layer  12  or light-emitting element portion  11  from being oxidized. In addition, a getter agent may be provided in the sealing can to absorb water and oxygen permeating the sealing can.  
       FIG. 6  is a diagram showing the cross-sectional structure of a second display region  22  composed of only red dots (sub-pixels) A 1 . In addition, the second display region  22  has the same sectional structure as that of the first display region  21  shown in  FIG. 5 , except for the structure of the light-emitting layer  110   b . Therefore, the detailed description thereof will be omitted.  
      In the second display region  22 , three red dots A 1  constitute one pixel, and each dot A 1  is provided with a red light-emitting layer  110   b   1  for emitting a light red (R) component.  
      Further, in the first display region  21 , LiF may be formed between the light-emitting layer  110   b  and the cathode layer  12  in order to improve the light-emitting efficiency. However, since there is a fear that the light-emitting efficiency is deteriorated in the second display region  22 , it is preferable that the LiF not be provided in the second display region  22 .  
      According to the organic EL device having the above-mentioned structure, the display region  2   a  includes the first display region  21  to perform full-color display and the second display region  22  to perform monochrome display. In this case, the pixels for full-color display are not arranged over the entire region of the display region  2   a . However, the pixels to emit necessary color light components can be arranged on a predetermined region (second display region  22 ), and the pixels to emit unnecessary color light components can be excluded in the second display region  22 . As a result, the aperture ratio can be improved as a whole. In addition, only the pixels corresponding to the necessary colors are arranged in the predetermined region (second display region  22 ). Therefore, even if the brightness per pixel decreases, the same brightness as that in the related art can be obtained, compared to the related art in which the pixels for full-color display are arranged over the entire display region  2   a . Thus, the deterioration of brightness per pixel can be reduced, and it is possible to reduce consumption power and to prolong the life span.  
      More particularly, as shown in  FIG. 7 , the life span increases.  FIG. 7  is a graph showing time variation with respect to the brightness (first embodiment) in the second display region  22  of the organic EL device according to the present embodiment and the brightness (comparative example) in a case in which the entire display region is composed of pixels for full-color display. In addition, the vertical axis indicates brightness per pixel (cd/m 2 ) in the surface, and the horizontal axis indicates time (hour).  
      As shown in  FIG. 7 , according to the organic EL device of the present embodiment, when the pixel is set such that the surface brightness of an initial value of 300 cd/m 2  is obtained in one pixel with respect to the organic EL devices according to the first embodiment and the comparative example, the time when brightness becomes 80% of the initial value is 8000 hours in the comparative example, but is 40000 hours in the first embodiment. That is, by using the structure of the present embodiment, it is possible to lengthen the time for brightness to deteriorate by five times.  
      In addition, in the organic EL device according to the present embodiment, the resolution can be improved. That is, as compared to the case in which the pixels for full-color display are arranged over the entire display region  2   a , it is possible to increase the number of pixels corresponding to necessary colors in the predetermined region (second display region  22 ) and thus to improve resolution.  
      In addition, according to the present embodiment, the first display region  21  is used for full-color display, and the second display region  22  is used for monochrome display. However, the first display region  21  may be used for full-color display, and the second display region  22  may be used for two-color display. Alternatively, the first display region  21  may be used for two-color display, and the second display region  22  may be used for monochrome display. In addition, the display region for monochrome display may be formed of a white light-emitting material to emit a white light component. Therefore, it is possible to constitute the display region  2   a  having large variations.  
      Method of Manufacturing Organic EL Device  
      Next, a method of manufacturing the organic EL device will be described with reference to the accompanying drawings.  
      A method of manufacturing the organic EL device according to the present embodiment includes (1) a process of forming a bank portion, (2) a process of forming a hole injection/transportation layer, (3) a process of forming a light-emitting layer, (4) a process of forming a cathode layer, and (5) a process of performing sealing. Since this method is just an illustrative example, other processes can be added, and some of the above-mentioned processes can be removed, if necessary.  
      In addition, (2) the process of forming the hole injection/transportation layer and (3) the process of forming the light-emitting layer are performed by a liquid ejecting method (inkjet method) using a liquid droplet ejecting device (inkjet device).  
      (1) Process of Forming Bank Portion  
      In the process of forming the bank portion, the bank portion  112  is formed at a predetermined location of the substrate  2 . The bank portion  112  has the inorganic bank layer  112   a , functioning as a first bank layer, and the organic bank layer  112   b , functioning as a second bank layer.  
      (1)-1 Forming Inorganic Bank Layer  112   a    
      As shown in  FIG. 8 , first, the inorganic bank layer  112   a  is formed at a predetermined location of the substrate. The location where the inorganic bank layer  112   a  is formed is on the second interlayer insulating film  144   b  and the pixel electrode  111 . In addition, the second interlayer insulting film  144   b  is formed on the circuit element unit  14  in which the thin film transistors, the scanning lines, the signal lines, and the like are arranged. The inorganic bank layer  112   a  can be made of, an inorganic material, such as SiO 2  or TiO 2 . These materials can be formed by, for example, a CVD method, a coating method, a sputtering method, or a vapor deposition method. In addition, preferably, the thickness of the inorganic bank layer  112   a  is within the range of 50 to 200 nm, and more preferably,  150  nm.  
      The inorganic bank layer  112   a  is formed to have an opening by forming an inorganic film on the entire surface of the interlayer insulating layer  144  and the pixel electrode  111  and then by patterning the inorganic film using a photolithography method. The opening is adjacent to the electrode surface  111   a  of the pixel electrode  111  and is provided as a lower opening  112   c , as shown in  FIG. 8 . In addition, the inorganic bank layer  112   a  is formed so as to partially overlap a peripheral portion of the pixel electrode  111 , so that a two-dimensional light-emitting region of the light-emitting layer  110  is controlled.  
      (1)-2 Forming Organic Bank Layer  112   b    
      Next, the organic bank layer  112   b , functioning as a second bank layer, is formed.  
      Particularly, as shown in  FIG. 8 , the organic bank layer  112   b  is formed on the inorganic bank layer  112   a . The organic bank layer  112   b  is made of a material having heat resistance and solvent resistance, such as an acrylic resin or a polyimide resin. Using these materials, the organic bank layer  112   b  is formed by patterning it using a photography technology. In addition, when it is patterned, the upper opening  112   d  is formed in the organic bank layer  112   b . The upper opening  112   d  is provided at a location adjacent to the electrode surface  111   a  and the lower opening  112   c , and has a pattern common to all pixels.  
      As shown in  FIG. 8 , it is preferable that the upper opening  112   d  be larger than the lower opening  112   c  formed on the inorganic bank layer  112   a  in diameter. In addition, it is preferable that the organic bank layer  112   b  have a taper shape in sectional view. Further, it is preferable that a bottom surface of the organic bank layer  112   b  have a width smaller than that of the pixel electrode  111 , and that a top surface of the organic bank layer  112   b  have a width substantially equal to that of the pixel electrode  111 .  
      Thereby, the first laminated portion  112   e  surrounding the lower opening  112   c  of the inorganic bank layer  112   a  more protrudes to the central side of the pixel electrode  111  than to the organic bank layer  112   b . In this way, the upper opening  112   d  formed on the organic bank layer  112   b  and the lower opening  112   c  formed on the inorganic bank layer  112   a  communicate with each other, so that the opening  112   g  passing through the inorganic bank layer  112   a  and the organic bank layer  112   b  is formed.  
      It is preferable that a suitable surface treatment by a plasma treatment be performed on the surfaces of the bank portion  112  and the pixel electrode  111 . In particular, a lyophobic treatment is performed on the surface of the bank portion  112 , and a lyophilic treatment is performed on the surface of the pixel electrode  111 . The surface treatment of the pixel electrode  111  can be performed by an  02  plasma treatment using oxygen gas. For example, it is possible to make the region including the surface of the pixel electrode  111  have a lyophilic property by performing the plasma treatment under the conditions of a plasma power of 100 to 800 kW, an oxygen gas flow rate of 50 to 100 ml/min, a plate carrying speed of 0.5 to 10 mm/sec, and a substrate temperature of 70 to 90° C. In addition, cleaning the surface of the pixel electrode  111  by the O2 plasma treatment and adjusting the work function are simultaneously performed. Next, the surface treatment of the bank portion  112  can be performed by a CF4 plasma treatment using tetrafluoromethane. For example, it is possible to make the region including the upper opening  112   d  and the top surface  112   f  of the bank portion  112  have a lyophobic property by performing the plasma treatment under the conditions of a plasma power of 100 to 800 kW, a methane tetrafluoride gas flow rate of 50 to 100 ml/min, a substrate carrying speed of 0.5 to 10 mm/sec, and a substrate temperature of 70 to 90° C.  
      (2) Process of Forming Hole Injection/Transportation Layer  
      Next, in the process of forming the light-emitting element, first, the hole injection/transportation layer is formed on the pixel electrode  111 .  
      In the process of forming the hole injection/transportation layer, using an inkjet device as a liquid droplet ejecting device, a liquid composition containing the material for forming the hole injection/transportation layer is ejected onto the electrode surface  111   a . After that, by performing a drying treatment and a heat treatment, the hole injection/ transportation layer  110   a  is formed on the pixel electrode  111  and the inorganic bank layer  112   a . In addition, the hole injection/transportation layer  110   a  may not be formed on the first laminated portion  112   e . That is, the hole injection/transportation layer  110   a  may be formed only on the pixel electrode  111 .  
      A method of forming the hole injection/transportation layer using an inkjet method is as follows. That is, as shown in  FIG. 9 , a liquid composition containing the material for forming the hole injection/transportation layer is ejected from a plurality of nozzles provided in an inkjet head H 1 . Here, by moving the inkjet head, the composition is applied onto every pixel. However, by moving the substrate  2 , the composition can be applied onto every pixel. In addition, by relatively moving the inkjet head and the substrate  2 , the composition can be applied onto every pixel. A method of forming a layer using the inkjet head (inkjet method), which will be described below, is the same as the above.  
      A method of ejecting liquid droplets using the inkjet head is as follows. That is, ejection nozzles H 2  formed in the inkjet head H 1  are arranged so as to face the electrode surface  111   a , and a liquid composition is ejected from the nozzles H 2 . The bank portions  112  for partitioning the lower openings  112   c  are formed around the pixel electrodes  111 , and the inkjet head H 1  faces the pixel electrode surface  111   a  located inside the lower opening  112   c . Then, a liquid droplet  110   c  of the liquid composition whose flow rate is controlled for each liquid droplet is ejected onto the electrode surface  111   a  from the ejection nozzles H 2  while relatively moving the inkjet head H 1  and the substrate  2 .  
      As the liquid composition used in the current process, for example, it is possible to use a composition obtained by dissolving a mixture of a polythiophene derivative, such as polyethylenedioxothiophene (PEDOT), and polystyrene sulfonic acid (PSS) into a polar solvent. The polar solvents may include, for example, isopropyl alcohol (IPA), normal buthanol, gamma-butyrolactone, N-methylpyrrolidone (NMP), 1,3-dimethyl-2-imidazolidinone (DMI) and a derivative thereof, and glycol ethers, such as carbitol acetate and butyl carbitol acetate.  
      More particularly, the following compositions can be used: a PEDOT/PSS mixture (PEDOT/PSS=1:20): 12.52% by weight, IPA: 10% by weight, NMP: 27.48% by weight, and DMI: 50% by weight. In addition, preferably, the liquid composition has a viscosity of about 1 to 20 mPa.s, and more preferably, a viscosity of about 4 to 15 mPa.s.  
      By using the above-mentioned liquid composition, it is possible to stably eject the liquid droplet without generating clogging of the ejection nozzle H 2 . In addition, the materials for forming the hole injection/transportation layer are the same with respect to the red (R), green (G), and blue (B) light-emitting layers  110   b   1  to  110   b   3 . The materials may be changed for each light-emitting layer.  
      The liquid droplets  110   c  of the ejected composition are diffused on the electrode surface  111   a  and the first laminated portion  112   e  having the lyophilic property and are then filled into the lower and upper openings  112   c  and  112   d . Even if the first composition liquid droplet  110   c  is ejected onto the top surface  112   f  of the bank portion, deviating from a predetermined ejection location, the top surface  112   f  is not wet by the first composition liquid droplets  110   c , and the ejected first composition liquid droplets  110   c  flow into the lower and upper openings  112   c  and  112   d.    
      The amount of a composition to be ejected onto the electrode surface  111   a  is determined according to the sizes of the lower and upper openings  112   c  and  112   d , the thickness of the hole injection/transportation layer to be formed, the concentration of a material forming the hole injection/transportation layer in the liquid composition. The liquid droplet  110   c  of the liquid composition may be ejected onto the same electrode surface  111   a  many times as well as being ejected once. In this case, whenever the liquid droplet  110   c  is ejected onto the electrode surface, the amount of the liquid droplet may be always the same, or may be changed. In addition, whenever the liquid droplet  110   c  is ejected onto the electrode surface  111   a , the liquid composition may be ejected onto different locations of the electrode surface  111   a  as well as being ejected at the same location of the electrode surface  
      With respect to the structure of the inkjet head, an inkjet head H shown in  FIG. 17  can be used. In addition, the substrate and the inkjet head are preferably arranged as shown in  FIG. 18 . In  FIG. 17 , reference numeral H 7  indicates a supporting substrate for supporting the inkjet head H 1 , and a plurality of inkjet heads H 1  are provided on the supporting substrate H 7 . On an ink ejection surface of the inkjet head H 1  (surface opposite to the substrate), a plurality of ejection nozzles (for example, 180 nozzles are aligned in a row, and thus a total of 360 nozzles is arranged) are provided along a longitudinal direction of the head in a row and at a gap along a width direction in two rows. In addition, the ejection nozzles of the inkjet head H 1  extend toward the substrate. In addition, the ejection nozzles are arranged along the X-axis direction in a row in a state in which they are inclined at a predetermined angle with respect to the X-axis (or the Y-axis), and are plurally located on a supporting plate  20  having a rectangular shape in plan view (in  FIG. 17 , six in a row, and a total of 12 places) in a state in which they are arranged in two rows at a predetermined gap in the Y direction.  
      In addition, in  FIG. 18 , reference numeral  1115  indicates a stage for mounting the substrate  2 , and reference numeral  1116  indicates a guide rail for guiding the stage  1115  in the x-axis direction (main scanning direction). Further, the head H can be moved by a guide rail  1113  via a supporting member  1111  in the y-axis direction (sub-scanning direction). In addition, the head H can be rotated in the θ-axis direction in  FIG. 18 , and the inkjet head H 1  can be inclined by a predetermined angle with respect to the main scanning direction. In this way, the inkjet head is arranged so as to be inclined with respect to the scanning direction, so that it is possible to make a nozzle pitch equal to a pixel pitch. In addition, by adjusting an inclined angle of the inkjet head, it is possible to make the nozzle pitch to be equal to any pixel pitch.  
      As shown in  FIG. 18 , the substrate  2  has a structure in which a plurality of chips are arranged on a mother substrate, that is, a region occupied by one chip corresponds to one display device. Here, three display regions  2   a  are formed, but the invention is not limited thereto. For example, when the composition is applied onto the display region  2   a  located at the left of the substrate  2 , the head H is moved through the guide rail  1113  toward the left side of the drawing, and the substrate  2  is moved through the guide rail  1116  toward the upper side of the drawing, thereby applying the composition onto the display region  2   a  while scanning the substrate  2 . Next, the head H is moved toward the right side of the drawing, and the composition is applied on the display region  2   a  located at the center of the substrate. In the same manner, the composition is applied on the display region  2   a  located at the right end of the substrate. In addition, the head H shown in  FIG. 17  and the inkjet device shown in  FIG. 18  are used for forming the light-emitting layer as well as forming the hole injection/ transportation layer.  
      Next, as shown in  FIG. 10 , a drying treatment is performed. In other words, after ejecting the first composition, the first composition is dried, so that a solvent contained in the first composition is evaporated, thereby forming the hole injection/transportation layer  110   a.  When the drying treatment is performed, the evaporation of the solvent contained in the liquid composition occurs mainly at a portion adjacent to the inorganic bank layer  112   a  and the organic bank layer  112   b , and at the same time, the material forming the hole injection/transportation layer is concentrated and then deposited. As a result, as shown in  FIG. 10 , the peripheral portion  110   a   2  made of the hole injection/transportation layer forming material is formed on the first laminated portion  12   e . The peripheral portion  110   a   2  adheres closely to the wall surface of the upper opening  112   d  (organic bank layer  112   b ), and has a small thickness at a part near to the electrode surface  111   a  and a large thickness at a part away from the electrode surface  111   a , that is, near to the organic bank layer  112   b.    
      Further, at the same time, the evaporation of the solvent occurs on the electrode surface  111   a  through the drying treatment, so that the flat portion  110   a   1  made of the hole injection/transportation layer forming material is formed on the electrode surface  111   a.  Since the evaporation speed of the solvent is almost constant on the electrode surface  111   a,  the hole injection/transportation layer forming material is uniformly concentrated on the electrode surface  111   a , so that the flat portion  110   a   1  having a uniform thickness is formed. In this way, the hole injection/transportation layer  110   a  composed of the peripheral portion  110   a   2  and the flat portion  110   a   1  is formed. In addition, the hole injection/transportation layer may be formed only on the electrode surface  111   a , not on the peripheral portion  110   a   2 .  
      The drying treatment is performed under a pressure of, for example, 133.3 Pa (1 Torr) at room temperature in nitrogen atmosphere. If the pressure is excessively low, the liquid droplet  110   c  of the composition is bumped, so it is not desirable. In addition, if temperature is higher than room temperature, the evaporation speed increases, so that it is not possible to form a flat film. After the drying treatment, it is preferable that the polarity solvent or water remaining in the hole injection/transportation layer  110   a  be removed by performing a heat treatment for ten minutes at a temperature of 200 ° C. in nitrogen atmosphere, preferably, in vacuum atmosphere.  
      (3) Process of Forming Light-Emitting Layer  
      The process of forming the light-emitting layer includes a process of ejecting a light-emitting layer forming material and a drying treatment process.  
      Similar to the above-mentioned hole injection/transportation layer forming process, a liquid composition for forming the light-emitting layer is ejected onto the hole injection/transportation layer  110   a  by the inkjet method. Then, the ejected liquid composition is dried (and thermally treated), and thus the light-emitting layer  110   b  is formed on the hole injection/transportation layer  110   a.    
       FIG. 11  shows a process of ejecting the liquid composition containing the light-emitting layer forming material using the inkjet method. As shown in  FIG. 11 , the liquid composition containing light-emitting layer forming materials for each color (in this embodiment, for example, blue (B)) is ejected from the ejection nozzles H 6  provided in the inkjet head while relatively moving the inkjet head H 5  and the substrate  2 .  
      At the time when the liquid composition is ejected, with the ejection nozzles facing the hole injection/transportation layer  110   a  located inside the lower and upper openings  112   c  and  112   d , the liquid composition is ejected while relatively moving the inkjet head H 5  and the substrate  2 . The amount of liquid per droplet ejected from the ejection nozzle H 6  is controlled. As such, the liquid droplet whose amount is controlled is ejected onto the hole injection/transportation layer  110   a  from the ejection nozzle.  
      As shown in  FIG. 2 , according to the present embodiment, since dot patterns corresponding to the respective colors are different from each other in the first display region  21  and the second display region  22 , each region has a different ejection aspect.  
      As shown in  FIG. 12 , in the first display region  21 , liquid droplet compositions  110   f  and  110   g  containing different color light-emitting layer forming materials are ejected without drying a liquid droplet composition  110   e  dropped on the substrate  2 . On the other hand, the liquid droplet composition  110   g  containing a red light-emitting layer forming material is ejected in the second display region  22 . That is, according to the present embodiment, since the ejection process is performed by the inkjet method, it is possible to selectively eject compositions having predetermined colors onto predetermined dots.  
      As shown in  FIG. 12 , the ejected liquid compositions  110   e  to  110   g  are diffused on the hole injection/transportation layer  110   a  to fill into the lower and upper openings  112   c  and  112   d . On the top surface  112   f  subjected to the lyophobic treatment, even though the respective liquid compositions  110   e  to  110   g  are ejected onto the top surface  112   f  deviating from predetermined locations, the top surface  112   f  is not wet with the liquid compositions  110   e  to  110   g , and the liquid compositions  110   e  to  110   g  flow into the upper and lower openings  112   c  and  112   d.    
      Further, a dummy pixel is arranged at the interface between the first display region  21  and the second display region  22 . The dummy pixel has an opening surrounded by the bank portions  112 . However, since the liquid droplet is not ejected onto the dummy pixel, the light-emitting layer is not formed.  
      As described above, on the first display region  21 , the liquid composition containing the light-emitting layer forming materials corresponding to red, green and blue is ejected. On the other hand, on the second display region  22 , the liquid composition containing the red light-emitting layer forming material is ejected. In this case, when the first display region  21  and the second display region  22  are consecutively formed, color mixture may occur at the interface between the first display region  21  and the second display region  22 . However, as in the present embodiment, the dummy pixels are arranged, so that it is possible to prevent the generation of a display defect caused by the color mixture. In addition, it is preferable that a light-shielding portion be provided in the dummy region so as to overlap it in plan view.  
      In the present embodiment, materials for forming the light-emitting layer may be a polyfluorene-based polymer derivative, a (poly)paraphenylenevinylene derivative, a polyphenylene derivative, a polyvinylcarvazole, a polythiophene derivative, a perylene dye, a coumarin dye, a rhodamine dye, and materials obtained by doping an organic EL material to the above-mentioned polymer materials. For example, the materials may be obtained by doping rubrene, perylene, 9,10-diphenylanthracene, tetraphenylbutadiene, Nile red, coumarin 6, quinacridone, or the like into these polymer materials. In addition, the same kind of solvent is used for each color light-emitting layer for dissolving or dispersing these light-emitting layer forming materials.  
      Next, the drying treatment is performed. In the first display region  21 , after the liquid compositions  110   e  to  110   g  are arranged at predetermined locations, the drying treatment is performed over the entire region to form light-emitting layers  110   b    1  to  110   b   3 . That is, the solvent contained in the liquid compositions  110   e  to  110   g  is evaporated by the drying treatment, so that a red (R) light-emitting layer  110   b    1 , a green (G) light-emitting layer  110   b   2 , a blue (B) light-emitting layer  110   b   3  are formed, as shown in  FIG. 13 . Further, only three red, green, and blue light-emitting layers are shown in  FIG. 13 . However, as can apparently be seen from  FIG. 2  and other drawings, the light-emitting elements are arranged in a matrix, and a plurality of light-emitting layers (not shown) are formed for each color in the invention.  
      On the other hand, in the second display region  22 , the red liquid composition  110   g  is arranged, and then the light-emitting layer  110   b   1  is formed by the drying treatment. That is, the solvent contained in the liquid composition droplet  110   g  is evaporated to form the red (R) light-emitting layer  110   b   1  shown in  FIG. 14 .  
      It is preferable that the drying of the liquid composition be performed by the vacuum drying. More particularly, the drying treatment can be performed under a pressure of 133.3 Pa (1 Torr) at room temperature in nitrogen atmosphere. If the pressure is excessively low, the liquid composition is bumped, so that it is not desirable. In addition, if the temperature is higher than room temperature, the evaporation speed of the solvent increases. As a result, since a large amount of light-emitting layer forming material is stuck on the wall surface of the upper opening  112   d , it is not desirable.  
      Next, when the drying treatment is completed, preferably, the light-emitting layer  110   b  is annealed by using a heating unit, such as a hot plate. The annealing treatment is performed at the same temperature and time at which the light-emitting characteristics of the respective organic EL layers can be maximally exhibited.  
      In this way, the hole injection/transportation layer  110   a  and the light-emitting layer  110   b  are formed on the pixel electrode  111 .  
      (4) Process of Forming Cathode Layer  
      Next, as shown in  FIGS. 15 and 16 , the cathode layer  12  forming a couple together with the pixel electrode (anode layer)  111  is formed in the first and second display regions  21  and  22 . That is, the cathode layer  12  composed of a laminated structure of an aluminum layer and a calcium layer is formed on the entire surface of the substrate  2  including the respective color light-emitting layers  110   b  and the organic bank layers  112   b . In this way, the cathode layer  12  is deposited on the entire surface of the region for forming the respective color light-emitting layers  110   b , and the organic EL elements corresponding to red, green, and blue are respectively formed.  
      Preferably, the cathode layer  12  is formed by using a vapor deposition method, a sputtering method, or a CVD method. Particularly, it is preferable to use the vapor deposition method because the damage of the light-emitting layer  110   b  due to heat can be prevented. In addition, in order to prevent oxidization, a protective layer made of SiO 2  or SiN may be formed on the cathode layer  12 .  
      (5) Process of Performing Sealing  
      Finally, the substrate  2  having the organic EL element formed thereon and a separately prepared sealing substrate are sealed with a sealing resin. For example, the sealing resin made of a thermosetting resin or an ultraviolet curable resin is applied onto the periphery of the substrate  2 , and then the sealing substrate is arranged on the substrate on which the sealing resin is applied. It is preferable that the sealing process be performed in the atmosphere of an inert gas, such as oxygen, argon, or helium. In a case in which the sealing process is performed in the air, if a defect, such as a pinhole, occurs in the cathode layer  12 , water or oxygen is permeated into the cathode layer  12  through the defective portion, which causes the cathode layer  12  to be oxidized. Therefore, this method is undesirable.  
      Thereafter, the cathode layer  12  is connected to the wiring lines of the substrate  2 , and the wiring lines of the circuit element unit  14  are connected to a driving IC (driving circuit) provided on the substrate  2  or at the outside thereof, thereby completing an organic EL device according to the present embodiment.  
      Electronic Apparatus  
      Next, an electronic apparatus including the display device according to the invention will be described.  
      First, a description will be made with respect to a case in which the display device having the same structure as the organic EL device according to the present embodiment is used for a display unit of an instrument panel.  FIG. 19  is a plan view schematically showing the structure of a substrate for a display unit included in the instrument panel, and  FIG. 20  is a cross-sectional view schematically showing the structure of the substrate for a display unit.  
      The display unit has as a main element a main display unit  31  having a structure in which the organic EL layer is interposed between the substrate  2  having the TFTs thereon and a sealing glass  3 , and a display surface  32  is arranged at a central portion of the main display unit  31 . In addition, an external connecting portion  33  includes a flexible substrate  4  connected to the substrate  2  and a data line driving IC  5  disposed on the flexible substrate  4 . The external connecting portion  33  is connected to the main display unit  31 , and external connecting terminals  6  are provided to one end of the external connecting portion  33 .  
      Further, on the substrate  2 , a transistor array and a data holding circuit are provided. A scan driver is built in the substrate  2 . Furthermore, the data lines, the control lines, and the power lines are provided on the flexible substrate  4 , and the data line driving IC has a function for supplying data to each dot (sub-pixel). In addition, the external connecting terminals  6  are a terminal supplied with a control signal from an external control substrate (not shown) and a terminal supplied with power from a power supply substrate.  
      On the other hand,  FIG. 21  is a diagram illustrating the structure of a display region in the mounted display unit. The organic EL device shown in  FIG. 2  has two display regions having different color display ranges. However, a display region  2   a  of the main display unit has a red display region  22   a  to perform only red display corresponding to, a blue display region  22   b  to perform only blue display, and a full-color display region  21  to perform full-color display. Here, at boundary regions between the respective display regions, dummy pixel regions  23  are formed, and regions in which display is not performed, that is, pixel regions in which the light-emitting layers are not provided are formed. Alternatively, the light-emitting layers may formed in the boundary regions, so that it is possible to make no current flow through the control circuit.  
      Further, in the dummy pixel region  23 , three pixels (that is, nine dots (sub-pixels)) are formed in the width-wise direction thereof. Furthermore, the display region  2   a  of the display unit has pixels of  560  ′  560  in total, and one pixel has three dots (sub-pixels). The dummy pixels  23  are provided in the peripheral portion of the display region  2   a.    
      The display unit having the above-mentioned structure is mounted on an instrument panel portion  500 , as shown in  FIG. 22 . More particularly, the flexible substrate  4  is incorporated into the instrument panel portion  500 . When the red display region  22   a  serves as a meter display unit  71  to perform speed display in an automobile, ON display is normally performed on the red display region  22   a . On the other hand, when the blue display region  22   b  serves as a necessary information display unit  72  to display information necessary for driving, ON display is performed on the blue display region  22   b  in accordance with information output timing. Moreover, the full-color display region  21  serves as an arbitrary information display unit  74  for performing full-color display additionally necessary information, such as external information from a mounted camera or navigation information from a navigation system.  
      Next, a description will be made with respect to a case in which a display device having the same structure as the organic EL device according to the present embodiment is applied to a display unit of an electric home appliance.  FIG. 23  is a plan view schematically showing the structure of a display panel attached to a refrigerator, and  FIG. 24  is a plan view showing the state of use of the refrigerator. In addition, since the structure of the substrate is the same as that used for the instrument panel, a detailed description thereof is omitted.  
      A display region  2   a  of the display panel used for the present embodiment includes a full-color display region  21  to perform full-color display, an orange display region  22   c  to perform only monochrome display corresponding to orange, and a red display region  22   d  to perform only monochrome display corresponding to red. In addition, the orange display region  22   c  is composed of pixels each having two red dots (sub-pixels) and one green dot (sub-pixel). Further, the dummy pixel region  23  is formed in a peripheral portion of the display region  2   a.    
      The display panel having the above-mentioned structure is mounted on a display unit  550  of the refrigerator, as shown in  FIG. 24 . More particularly, the red display region  22   d  serves as an operation state display unit  77  for displaying the operation state of and temperature in the refrigerator, and the orange display region  22   c  serves as a service information display unit  76  for displaying service information. According to the present embodiment, a recipe is displayed on a daily basis. Furthermore, the full-color display region  21  serves as an image display unit  75  for displaying image information accompanying the service information.  
      In the electronic apparatus having the above-mentioned structure, the variation of display increases, and the display device of to the invention is also provided. Therefore, it is possible to achieve an electronic apparatus capable of displaying a high-quality image with a long life span.  
     Second Embodiment  
      Organic EL Device  
       FIG. 1  is a diagram illustrating the wiring structure of an organic EL device according to a second embodiment, and  FIG. 2  is a plan view schematically showing the organic EL device according to the second embodiment.  FIGS. 3 and 4  are enlarged plan views schematically showing the structure of a pixel, and  FIGS. 25 and 26  are cross-sectional views schematically illustrating a display region of the organic EL device according to the second embodiment.  
      Since the wiring structure of the organic EL device, the structure of the pixel, and the display region shown in these drawings are similar to those in the first embodiment, the same constituent elements as those in the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.  
      In a first display region  221 , a cathode layer  212  according to the second embodiment has a laminated structure of a lithium fluoride layer  12   a , a calcium layer  12   b , and an aluminum layer  12   c . In this case, it is preferable that a work function be small in a part of the cathode layer adjacent to the light-emitting layer. More particularly, according to the present embodiment, the cathode layer directly comes into contact with a light-emitting layer  110   b  of an organic EL layer  110  to inject electrons into the light-emitting layer  110   b.    
      The aluminum layer  12   c  forming the cathode layer  212  reflects light emitted from the light-emitting layer  110   b  toward the substrate  2 , and it is preferable that the aluminum layer  12   c  be composed of a silver layer or a laminated layer of the aluminum layer and the silver layer, in addition to the aluminum layer. In addition, a protective film for preventing oxidization, made of SiO, SiO 2 , or SiN, may be formed on the aluminum layer  12   c . In the respective layers constituting the cathode layer  212  in the first display region  221 , the lithium fluoride layer  12   a  quality has a thickness of about 5 nm, the calcium layer  12   b  has a thickness of about 5 nm, and the aluminum layer  12   c  has a thickness of about 200 nm.  
       FIG. 26  is a diagram showing the sectional structure of a second display region  222  composed of only red dots (sub-pixels) A 1 . The second display region  222  is different from the first display region  221  shown in  FIG. 25  in the structures of the light-emitting layer  110   b  and the cathode layer  212 . Since the second display region  222  has the same structure as the first display region  221 , except for the structures of the light-emitting layer  110   b  and the cathode layer  212 , a description thereof will be omitted.  
      In the second display region  222 , three red dots A 1  constitute one pixel, and a red light-emitting layer  110   b   1  to emit a red (R) light component is arranged in each dot A 1 . As shown in  FIG. 25 , the lithium fluoride layer  12   a  is formed in the first display region  221  so as to increase light-emitting efficiency at a part of the cathode layer  212  near to the light-emitting layer  110   b . However, in the second display region  222 , the lithium fluoride layer  12   a  is not formed. This is because the lithium fluoride layer  12   a  is a functional layer provided so as to increase the light-emitting efficiency of the blue light-emitting layer  110   b   3  to emit a blue (B) light component among the light-emitting layers  110   b . Further, in the respective layers constituting the cathode layer  212  in the second display region  222 , the calcium layer  12   b  has a thickness of about 5 nm, and the aluminum layer  12   c  has a thickness of about 200 nm.  
      In the organic EL device according to the second embodiment having the above-mentioned structure, similar to the first embodiment, the life span increases, as shown in  FIG. 27 .  FIG. 27  is a graph showing time variation with respect to brightness (second embodiment) in the second display region  222  of the organic EL device according to the present embodiment and brightness (comparative example) in a case in which the entire display region is composed of pixels for full-color display. In addition, the vertical axis indicates brightness per pixel (cd/m 2 ) in the plane, and the horizontal axis indicates time (hour).  
      As shown in  FIG. 27 , according to the organic EL device of the present embodiment, when the pixel is set such that the surface brightness of an initial value  300  cd/m 2  is obtained in one pixel with respect to the organic EL devices according to the second embodiment and the comparative example, the time when brightness becomes 80% of the initial value is 8000 hours in the comparative example, but is 40000 hours in the second embodiment. That is, by using the structure of the present embodiment, it is possible to lengthen the time for which the brightness becomes deteriorated by five times.  
      In addition, in the organic EL device according to the present embodiment, resolution can be improved. That is, as compared to the case in which the pixels for full-color display are arranged over the entire display region  202   a , it is possible to increase the number of pixels corresponding to necessary colors in the predetermined region (second display region  222 ) and to improve resolution.  
      Further, in the organic EL device according to the present embodiment, the display region  202   a  is divided into the first display region  221  and the second display region  222  each of which has a different laminated structure in the functional layer constituting the pixel. More particularly, the cathode layer  212  has the lithium fluoride layer  12   a  in the first display region  221 , and the cathode layer  212  does not have the lithium fluoride layer  12   a  in the second display region  222 . As a result, the light-emitting efficiency is improved for every pixel. Here, in a case in which the lithium fluoride layer  12   a  is included in the second display region  222 , and in a case in which the lithium fluoride layer  12   a  is not included in the second display region  222 , a temporal change of brightness is measured. The measured result is shown in  FIG. 28 . A curve C 1  indicates the temporal change of brightness when the lithium fluoride layer  12   a  is not included in the second display region, and a curve C 2  indicates the temporal change of brightness when the lithium fluoride layer  12   a  is included in the second display region. As can be seen from  FIG. 28 , the lithium fluoride layer  12   a  is not included in the second display region  222 , so that the life span of brightness can be considerably improved.  
      Furthermore, according to the second embodiment, the first display region  221  functions as a full-color display region, and the second display region  222  serves as a monochrome display region. However, similar to the first embodiment, for example, the first display region  221  can serve as the full-color display region, and the second display region  222  can serve as a two-color display region. Alternatively, the first display region  221  can serve as a two-color display region, and the second display region  222  can serve as a monochrome display region. Also, a white light-emitting material may be used for a display region for monochrome display light to emit white light. As a result, it is possible to constitute the display region  202   a  having a large variation.  
      Method of Manufacturing Organic EL Device  
      Next, a method of manufacturing the organic EL device according to the second embodiment will be described with reference to the accompanying drawings. However, a description of the same components as those in the first embodiment will be omitted.  
      (4) Process of Forming Cathode Layer  
      A process of forming the cathode layer different from that in the first embodiment will be described. As shown in  FIGS. 29 and 30 , the cathode layer  212  which forms a couple together with the pixel electrode (anode layer)  111  is formed on each of the first and second display regions  221  and  222 .  
      That is, in the first display region  221 , first, the lithium fluoride layer  12   a  is formed on the entire surface of the substrate  2  including the respective color light-emitting layers  110   b  and the organic bank layers  112   b  shown in  FIG. 29 , and then the calcium layer  12   b  and the aluminum layer  12   c  are sequentially formed thereon. Preferably, the respective layers made of metallic materials are formed using a vapor deposition method, a sputtering method, or a CVD method. Particularly, it is more preferable to use the vapor deposition method because the damage of the light-emitting layer  110   b  due to heat can be prevented.  
      On the other hand, in the second display region  222 , first, the calcium layer  12   b  is formed on the entire surface of the substrate  2  including the respective color light-emitting layers  110   b  and the organic bank layers  112   b  shown in  FIG. 30 , and then the aluminum layer  12   c  is formed thereon. In this case, preferably, the respective layers are formed using the vapor deposition method, the sputtering method, or the CVD method. Particularly, it is more preferable to use the vapor deposition method because the damage of the light-emitting layer  110   b  due to heat can be prevented.  
      In this way, the cathode layer  212  is deposited on the region for forming the light-emitting layer  110   b  in the first display region  221  and the second display region  222 , and the organic EL elements corresponding to red, green, and blue can be respectively formed. In addition, in order to prevent oxidization, a protective layer made of SiO 2  or SiN may be formed on the cathode layer  212 .  
      (5) Process of Performing Sealing  
      Finally, the substrate  2  having the organic EL element formed thereon and a separately prepared sealing substrate are sealed with a sealing resin. For example, the sealing resin made of a thermosetting resin or an ultraviolet curable resin is applied onto the periphery of the substrate  2 , and then the sealing substrate is arranged on the substrate on which the sealing resin is applied. It is preferable that the sealing process be performed in the atmosphere of an inert gas, such as oxygen, argon or helium. In a case in which the sealing process is performed in the air, if a defect, such as a pinhole, occurs in the cathode layer  212 , water or oxygen is permeated into the cathode layer  212  through the defective portion, which causes the cathode layer  212  to be oxidized. Next, the cathode layer  212  is connected to the wiring lines of the substrate  2 , and the wiring lines of the circuit element unit  14  are connected to a driving IC (driving circuit) provided on the substrate  2  or at the outside thereof, thereby completing the organic EL device according to the present embodiment.  
      Electronic Apparatus  
      Next, an electronic apparatus including the display device according to the invention will be described. The same constituent elements as those in the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted.  
      Similar to the first embodiment, the display unit according to the second embodiment is mounted on an instrument panel portion  500 , as shown in  FIG. 22 . More particularly, the display unit is mounted on the instrument panel portion in a manner that the flexible substrate  4  is assembled into the instrument panel portion  500 . When the red display region  222   a  serves as a meter display unit  71  to perform speed display in an automobile, ON display is normally performed on the red display region  222   a . On the other hand, when the blue display region  222   b  serves as a necessary information display unit  72  to display information necessary for driving, ON display is performed on the blue display region  222   b  in accordance with information output timing. Moreover, the full-color display region  221  can serve as an arbitrary information display unit  74  to perform full-color display of additionally necessary information, such as navigation information from a navigation system or external information from a mounted camera.  
      Next, a description will be made with respect to a case in which a display device having the same structure as the organic EL device according to the second embodiment is applied to a display unit of an electric home appliance.  FIG. 23  is a plan view schematically showing the structure of a display panel attached to a refrigerator, and  FIG. 24  is a plan view showing the state of use of the refrigerator. In addition, since the structure of the substrate is the same as that used for the instrument panel, a detailed description thereof will be omitted.  
      Similar to the first embodiment, a display region  202   a  of the display panel used for the present embodiment includes a full-color display region  221  to perform full-color display, an orange display region  222   c  to perform only monochrome display corresponding to orange and a red display region  222   d  to perform only monochrome display corresponding to red. In addition, the orange display region  222   c  is composed of pixels each having two red dots (sub-pixels) and one green dot (sub-pixel). Further, a dummy pixel region  23  is formed in a peripheral portion of the display region  202   a.    
      The display panel having the above-mentioned structure is mounted on a display unit  550  of the refrigerator, as shown in  FIG. 24 . More particularly, the red display region  222   d  serves as an operation state display unit  77  for displaying the operation state of and temperature in the refrigerator, and the orange display region  222   c  serves as a service information display unit  76  for displaying service information. According to the present embodiment, a recipe is displayed on a daily basis. Furthermore, the full-color display region  221  serves as an image display unit  75  for displaying image information accompanying the service information.  
      In the electronic apparatus having the above-mentioned structure, the variation of display increases, and the display device according to the invention is provided. Therefore, it is possible to achieve an electronic apparatus capable of displaying a high-quality image with a long life span.  
      Until now, the preferred embodiments of the invention have been described, but the invention is not limited to the above-mentioned embodiments. Various changes and modifications can be made without departing from the spirit and scope of the invention. The invention is not limited to the above-mentioned embodiments, but is defined by only the appended claims.