Abstract:
An organic electroluminescent lighting device includes: a pair of rectangular electrode films stacked to face each other sandwiching an organic light-emitting element, and different from each other in polarity; wherein a first electrode film includes power supply terminal sections which are each of edge sides which face each other at a surface of the first electrode film; and auxiliary electrode film group including at least one of a plurality of first auxiliary electrode films and a plurality of second auxiliary electrode films located away from each other on the surface of the first electrode film. A sectional area viewed where the plurality of first auxiliary electrode films cuts perpendicularly to the edge sides increases relative to increasing distance from the edge sides. A sectional area viewed where the plurality of second auxiliary electrode films cuts parallel to the edge sides increases relative to increasing distance from the edge sides.

Description:
TECHNICAL FIELD 
     The present invention relates to an organic electroluminescent lighting device that uses, as a light source, a light-emitting element including an organic light-emitting film held between a pair of electrode films different from each other in polarity. 
     BACKGROUND ART 
     One of the illumination devices is an organic electroluminescent lighting device that uses, as a light source, a light-emitting element including an organic light-emitting film held between a pair of electrode films different from each other in polarity. In the organic electroluminescent lighting device, the organic light-emitting film emits light when an electric field is generated between the pair of electrode films. The light of the organic light-emitting film is transmitted through one of the electrode films to be applied to the outside. Accordingly, one of the electrode films is made of a transparent metallic material such as ITO (indium tin oxide), ZnO, or SnO2 (NESA glass). 
     However, the aforementioned transparent metallic material has relatively high resistance. Further, in the electrode film, generally, each of the opposite edge sides of its surface is a power supply terminal. Thus, in the electrode film, wiring resistance increases farther away from each edge side. The increase of the wiring resistance is accompanied by the increase of a descending voltage. This disables uniform application of a voltage to the entire organic light-emitting film. The brightness of the organic light-emitting film depends on the voltage. Thus, when the voltage is not uniformly applied to the organic light-emitting film, there is a possibility that the brightness of the organic light-emitting film is not uniform. 
     Patent Literature 1 (JP2004-14128A) has therefore disclosed an organic electroluminescent lighting device for preventing the occurrence of the brightness nonuniformity of the organic light-emitting film. The organic electroluminescent lighting device disclosed in Patent Literature 1 includes auxiliary electrodes made of materials having a lower resistance than a transparent electrode and arranged on a grid pattern in the surface of the transparent electrode. According to this organic electroluminescent lighting device, the resistance value of the entire transparent electrode is reduced by forming, in the transparent electrode, auxiliary electrodes that have a lower resistance than the transparent electrode. The wiring resistance accordingly drops to reduce the value of the descending voltage. As a result, the brightness nonuniformity of the organic light-emitting film can be prevented. 
     CITATION LIST 
     
         
         Patent Literature 1: JP2004-14128A 
       
    
     SUMMARY OF INVENTION 
     Problems to be Solved by Invention 
     However, in the organic electroluminescent lighting device described in Patent Literature 1, the auxiliary electrodes are similar in shape (width and film thickness) and arranged at equal intervals in the surface of the transparent electrode. Thus, when the voltage is applied to the entire transparent electrode from each of the edge sides of the transparent electrode, voltage reduction occurs more away from the edge side (closer to the center from the edge side). As a result, a voltage distribution varies in the transparent electrode, causing variance on a voltage distribution in the organic light-emitting film. Thus, brightness uniformity is insufficient in the organic electroluminescent lighting device described in Patent Literature 1. 
     It is therefore an object of the present invention to provide an organic electroluminescent lighting device that can improve brightness uniformity. 
     Solution to Problem 
     To achieve the object, an organic electroluminescent lighting device according to the present invention includes: an organic light-emitting film; a pair of electrode films that are stacked to face each other sandwiching the organic light-emitting element; wherein the pair of electrode films are formed rectangular and different from each other in polarity; wherein the pair of electrode films comprise power supply terminal sections which are connected to the power source; wherein power supply terminal sections are each of edge sides which face each other at a surface of one of the electrode films; and an auxiliary electrode film group including at least one of a plurality of first belt-like auxiliary electrode films and a plurality of second belt-like auxiliary electrode films; wherein the first auxiliary electrode films extend in a direction parallel to the edge sides and the second auxiliary electrode films extend in a direction perpendicular to the edge sides; wherein the first auxiliary electrode films and the second auxiliary electrode films are located away from each other on the surface of one of the electrode films. A sectional area viewed at a section where the plurality of first auxiliary electrode films is cut in the direction perpendicular to the edge sides becomes larger in relation to increasing distance from the edge sides, and a sectional area viewed at a section where the plurality of second auxiliary electrode films is cut in the direction parallel to the edge sides becomes larger in relation to increasing distance from the edge side. 
     To achieve the object, another organic electroluminescent lighting device according to the present invention includes: an organic light-emitting film; a pair of electrode films that are stacked to face each other sandwiching the organic light-emitting element; wherein the pair of electrode films are formed rectangular and different from each other in polarity; wherein the pair of electrode films comprise power supply terminal sections which are connected to the power source; wherein power supply terminal sections are each of edge sides which face each other at a surface of one of the electrode films; and a plurality of first belt-like auxiliary electrode films which are located away from each other on the surface of one of the electrode films; wherein the first auxiliary electrode films extend in a direction parallel to the edge sides. A wiring density which indicates the number of the plurality of first auxiliary electrode films on the surface of one of the electrode films becomes higher in relation to increasing distance from the edge sides. 
     Effects of Invention 
     According to the present invention, in one of the electrode films, in relation to increasing distance from each of the edge sides, the sectional area of at least one of the first auxiliary electrode film and the second auxiliary electrode film becomes larger, or the wiring density of the first auxiliary electrode film becomes higher. Thus, when a voltage is applied from each of the edge sides to the entire electrode film, it is difficult for voltage drop to occur in a region away from the edge side. As a result, since voltage distribution variance in the electrode film is prevented, voltage distribution variance in the organic light-emitting film can also be prevented. Thus, brightness uniformity is improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  A plan view showing the structure of an organic electroluminescent lighting device according to a first embodiment. 
         FIG. 2  A sectional view cut along line A 1 -A 1  shown in  FIG. 1 . 
         FIG. 3  A plan view showing another arrangement pattern of auxiliary electrode films in the organic electroluminescent lighting device according to the first embodiment. 
         FIG. 4  A plan view showing yet another arrangement pattern of the auxiliary electrode films in the organic electroluminescent lighting device according to the first embodiment. 
         FIG. 5  A plan view showing yet another arrangement pattern of the auxiliary electrode films in the organic electroluminescent lighting device according to the first embodiment. 
         FIG. 6  A plan view showing still yet another arrangement pattern of the auxiliary electrode films in the organic electroluminescent lighting device according to the first embodiment. 
         FIG. 7  A plan view showing the structure of an organic electroluminescent lighting device according to a second embodiment. 
         FIG. 8  A sectional view cut along line A 2 -A 2  shown in  FIG. 7 . 
         FIG. 9  A plan view showing the structure of an organic electroluminescent lighting device according to a third embodiment. 
         FIG. 10  A plan view showing another arrangement pattern of auxiliary electrode films in the organic electroluminescent lighting device according to the third embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       FIG. 1  is a plan view showing the structure of organic electroluminescent lighting device  10  according to this embodiment.  FIG. 2  is a sectional view cut along line A 1 -A 1  shown in  FIG. 1 . In  FIG. 1 , for easier understanding, some (interlayer insulating film  4 , organic light-emitting film  5 , and electrode film  2   b ) of the components of organic electroluminescent lighting device  10  are not shown. 
     In organic electroluminescent lighting device  10 , as shown in  FIG. 2 , rectangular electrode film  2   a  is formed on the surface of transparent substrate  1 . Transparent substrate  1  is a glass substrate or a plastic substrate. Electrode film  2   a  is a positive electrode made of a transparent metallic material such as ITO, ZnO, or SnO2 (NESA glass). Edge sides opposite each other on the surface of electrode film  2   a  are power supply terminal sections  6   a  and  6   b  connected to the positive electrode of a power source. 
     Auxiliary electrode film group  3  including a plurality of belt-like auxiliary electrode films  3   a  (first auxiliary electrode films) and a plurality of belt-like auxiliary electrode films  3   b  (second auxiliary electrode films) are formed on the surface of electrode film  2   a . The plurality of auxiliary electrode films  3   a  are located away from each other to extend in a direction parallel to power supply terminal sections  6   a  and  6   b  (edge sides of auxiliary electrode films  3   a ) as shown in  FIG. 1 . In relation to increasing distance from power supply terminal sections  6   a  and  6   b , the width of auxiliary electrode films  3   a  becomes larger. 
     On the other hand, the plurality of auxiliary electrode films  3   b  are located away from each other to extend in a direction perpendicular to power supply terminal sections  6   a  and  6   b . In relation to increasing distance from power supply terminal sections  6   a  and  6   b , the width of each of auxiliary electrode films  3   b  becomes gradually larger. In relation to increasing distance from power supply terminal sections  6   a  and  6   b , the width of each of auxiliary electrode films  3   b  can become continuously larger. 
     Auxiliary electrode films  3   a  and  3   b  are made of metallic materials whose resistance is lower than electrode film  2   a , such as Cr (chromium), Al—Nd (aluminum-neodymium alloy), or Mo—Nb (molybdenum-niobium alloy). Auxiliary electrode films  3   a  and  3   b  can be two-layer films made of molybdenum and aluminum or three-layer films in which molybdenum sandwiches aluminum. In the present invention, the arrangement pattern of auxiliary electrode film group  3  is not limited to a grid pattern shown in  FIG. 1 . For example, as shown in  FIG. 3 , auxiliary electrode film group  3  can have an arrangement pattern including only a plurality of auxiliary electrode films  3   a . Further, as shown in  FIG. 4 , auxiliary electrode film group  3  can have an arrangement pattern including only a plurality of auxiliary electrode films  3   b . In this embodiment, since the plurality of auxiliary electrode films  3   b  is thought to function as a light shielding part, a pattern of auxiliary electrode film group  3  can be formed by taking design (symmetry) into consideration, as shown in  FIG. 5 . In  FIG. 5 , the plurality of auxiliary electrode films  3   a  is formed to be symmetrical with respect to first axis  1  extending in the direction parallel to power supply terminal sections  6   a  and  6   b  and second axis m extending in the direction perpendicular to power supply terminal sections  6   a  and  6   b , which orthogonally intersect each other at center C of electrode film  2   a . In relation to approaching a second axis m, the width of auxiliary electrode films  3   a  becomes larger. Auxiliary electrode films  3   b  are also formed to be symmetrical with respect to first axis  1  and second axis m, and wider closer to second axis m. In the present invention, the pluralities of auxiliary electrode films  3   a  and  3   b  can be formed on the surface of electrode film  2   a  that is in contacted with transparent substrate  1 . 
     The surfaces of the pluralities of auxiliary electrode films  3   a  and  3   b  are covered with interlayer insulating film  4  (refer to  FIG. 4 ) to prevent insulation degradation of organic light-emitting film  5 . The surface of interlayer insulating film  4  is covered with organic light-emitting film  5  (refer to  FIG. 2 ). In the present invention, there is no particular limitation on materials for interlayer insulating film  4  and organic light-emitting film  5 . Conventional materials can be used. The surface of organic light-emitting film  5  is covered with electrode film  2   b  (refer to  FIG. 2 ) which pairs with electrode film  2   a . In this embodiment, electrode film  2   b  is a negative electrode made of a material whose resistance is lower than electrode film  2   a , such as aluminum. 
     In the organic electroluminescent lighting device which does not comprise auxiliary electrode film group  3 , when a voltage is applied from the light source through power supply terminal sections  6   a  and  6   b  to entire electrode film  2   a , in relation to increasing distance from power supply terminal sections  6   a  and  6   b  (in relation to approaching the center of electrode film  2   a ), a potential becomes lower. However, in this embodiment, in relation to increasing distance from power supply terminal sections  6   a  and  6   b , the width of auxiliary electrode films  3   a  becomes larger. Accordingly, a sectional area viewed at a section where the plurality of auxiliary electrode films  3   a  is cut in the direction perpendicular to power supply terminal sections  6   a  and  6   b  is larger in auxiliary electrode film  3   a  that is separated from the power supply terminal sections  6   a  and  6   b . In this embodiment, in relation to increasing distance from power supply terminal sections  6   a  and  6   b , the width of each of auxiliary electrode films  3   b  becomes larger. Accordingly, a sectional area viewed at a section where the plurality of auxiliary electrode films  3   b  is cut in the direction parallel to power supply terminal sections  6   a  and  6   b  is larger the further away it is from power supply terminal sections  6   a  and  6   b.    
     Because of auxiliary electrode films  3   a  and  3   b  formed as described above, even when the voltage is applied from power supply terminal sections  6   a  and  6   b  to entire electrode film  2   a , it is difficult for a voltage drop to occur in the region separated from power supply terminal sections  6   a  and  6   b . As a result, voltage distribution variance in electrode film  2   a  is prevented. This also prevents voltage distribution variance in organic light-emitting film  5 . Thus, the brightness uniformity of organic light-emitting film  5  is improved. 
     In this embodiment, when width W 1  (refer to  FIG. 2 ) of auxiliary electrode film  3   a  formed closest to the center of electrode film  2   a  is excessively large, a light-emitting area is reduced (light shielding area by auxiliary electrode film  3   a  is increased), consequently lowering illuminance. It is accordingly desirable to set width W 1  to be five times larger, at a maximum, than width W 3  (refer to  FIG. 2 ) of auxiliary electrode film  3   a  that is formed closest to each of power supply terminal sections  6   a  and  6   b . For auxiliary electrode film  3   b , similarly, it is desirable to set the width of auxiliary electrode film  3   b  formed closest to the center of electrode film  2   a  to be five times larger, at a maximum, than the width of auxiliary electrode film  3   b  that is formed closest to each of power supply terminal sections  6   a  and  6   b.    
     In this embodiment, the plurality of auxiliary electrode films  3   a  and  3   b  is formed on the surface of electrode film  2   a . However, they can be formed on the surface of electrode film  2   b , or on the surfaces of both of electrode films  2   a  and  2   b . The surface of electrode film  2   b  on which the auxiliary electrode films are formed can be a surface that is in contacted with organic light-emitting film  5 , or that faces (opposite) the surface of electrode film  2   b.    
       FIG. 6  is a plan view showing an example of electrode film  2   b  in which auxiliary electrode films are formed. In  FIG. 6 , the opposing edge sides of the surface of electrode film  2   b  are power supply terminal sections  6   a  and  6   b  connected to the power source. On the surface of electrode film  2   b , as in the case of electrode film  2   a , a plurality of belt-like auxiliary electrode films  3   c  (third auxiliary electrode films) and a plurality of belt-like auxiliary electrode films  3   d  (fourth auxiliary electrode films) are formed. The plurality of auxiliary electrode films  3   c  extends in a direction parallel to power supply terminal sections  6   c  and  6   d . On the other hand, the plurality of auxiliary electrode films  3   d  extends in a direction perpendicular to power supply terminal sections  6   c  and  6   d . Materials for auxiliary electrode films  3   c  and  3   d  can be similar to those of electrode film  2   b . However, it is desirable to use materials whose resistance is lower than those of electrode film  2   b . This is because the resistance of entire electrode film  2   b  is reduced. Specifically, in the case of forming electrode film  2   b  made of aluminum, Ag, Au, or Cu is used. When Ag or Au is used, auxiliary electrode films  3   c  and  3   d  can be easily formed because they are formed by the same vacuum deposition device (deposition by heating) as that for forming organic light-emitting film  5 . Further, when Cu is used as materials for the auxiliary electrode films, the auxiliary electrode films are formed by sputtering or CVD (chemical vapor deposition). The melting point of Cu is relatively high. Thus, it is difficult for electro migration to occur, and it is also difficult for stress migration to occur. 
     Second Embodiment 
     Organic electroluminescent lighting device  20  according to this embodiment will be described. Components similar to those of organic electroluminescent lighting device  10  according to the first embodiment are denoted by similar reference numerals, and thus detailed description thereof will be omitted. 
       FIG. 7  is a plan view showing the structure of organic electroluminescent lighting device  20  according to this embodiment.  FIG. 8  is a sectional view cut along line A 2 -A 2  shown in  FIG. 2 . In  FIG. 7 , for easier understanding, some (interlayer insulating film  4 , organic light-emitting film  5 , and electrode film  2   b ) of the components of organic electroluminescent lighting device  20  are not shown. 
     In this embodiment, auxiliary electrode films  3   a  are equal in width. However, in relation to increasing distance from power supply terminal sections  6   a  and  6   b , auxiliary electrode films  3   a  become thicker (refer to  FIG. 8 ). Accordingly, as in the case of the first embodiment, in relation to increases in the distance from power supply terminal sections  6   a  and  6   b , the sectional area of each of auxiliary electrode films  3   a  becomes larger. Similarly, auxiliary electrode films  3   b  are equal in width. However, in relation increasing distance from power supply terminal sections  6   a  and  6   b , auxiliary electrode films  3   b  become thicker. Accordingly, as in the case of the first embodiment, in relation to increasing distance from power supply terminal sections  6   a  and  6   b , the sectional area of each of auxiliary electrode films  3   b  becomes larger. 
     Because of auxiliary electrode films  3   a  and  3   b  formed as described above, even when the voltage is applied from power supply terminal sections  6   a  and  6   b  to entire electrode film  2   a , it is difficult for voltage drop to occur in the region that is separated from power supply terminal sections  6   a  and  6   b . As a result, voltage distribution variance in electrode film  2   a  is prevented. This also prevents voltage distribution variance in organic light-emitting film  5 . Thus, the brightness uniformity of organic light-emitting film  5  is improved. 
     In this embodiment, when thickness t 1  (refer to  FIG. 8 ) of auxiliary electrode film  3   a  that is formed closest to the center of electrode film  2   a  is excessively large, the step of auxiliary electrode film  3   a  is increased. Then, forming organic light-emitting film  5  and electrode film  2   b  after auxiliary electrode film  3   a  is easily made to have a non-uniform film thickness, which consequently increases the possibility that a short-circuit will occur between electrode film  2   a  and electrode film  2   b . It is accordingly desirable to set thickness t 1  to be three times larger, at a maximum, than thickness t 3  (refer to  FIG. 8 ) of auxiliary electrode film  3   a  that is formed closest to each of power supply terminal sections  6   a  and  6   b . For auxiliary electrode film  3   b , similarly, it is desirable to set the thickness of auxiliary electrode film  3   b  that is formed closest to the center of electrode film  2   a  to be three times larger, at a maximum, than the thickness of auxiliary electrode film  3   b  that is formed closest to each of power supply terminal sections  6   a  and  6   b.    
     In this embodiment, a plurality of auxiliary electrode films  3   c  and  3   d  can be formed on the surface of electrode film  2   b . The shapes of the plurality of auxiliary electrode films  3   c  and  3   d  can be similar to those of the first embodiment, or to those of auxiliary electrode films  3   a  and  3   b  of this embodiment. 
     Third Embodiment 
     Organic electroluminescent lighting device  30  according to this embodiment will be described. Components similar to those of organic electroluminescent lighting device  10  according to the first embodiment are denoted by similar reference numerals, and thus detailed description thereof will be omitted. 
       FIG. 9  is a plan view showing the structure of organic electroluminescent lighting device  30  according to this embodiment. In  FIG. 9 , for easier understanding, some (interlayer insulating film  4 , organic light-emitting film  5 , and electrode film  2   b ) of the components of organic electroluminescent lighting device  30  are not shown. 
     In organic electroluminescent lighting device  30  according to this embodiment, a plurality of auxiliary electrode films  3   a  are arranged at different intervals to extend in a direction parallel to edge sides of electrode film  2   a . In this embodiment, a pattern of auxiliary electrode films  3   a  and  3   b  can be formed by taking symmetrical design into consideration so that a plurality of auxiliary electrode films  3   a  and  3   b  can be symmetrical with respect to first axis  1  and second axis m as shown in  FIG. 10 . 
     In this embodiment, auxiliary electrode films  3   a  are similar in shape (width and thickness). However, a wiring density indicates that the number of a plurality of auxiliary electrode films  3   a  on the surface of electrode film  2   a  becomes higher in relation to increasing distance from power supply terminal sections  6   a  and  6   b . Accordingly, even when voltage is applied from power supply terminal sections  6   a  and  6   b  to entire electrode film  2   a , it is difficult for voltage drop to occur in a region separated from power supply terminal sections  6   a  and  6   b . As a result, voltage distribution variance in electrode film  2   a  is prevented. This also prevents voltage distribution variance in organic light-emitting film  5 . Thus, the brightness uniformity of organic light-emitting film  5  is improved. 
     In this embodiment, in the case of auxiliary electrode films  3   a  and  3   b  formed with the pattern shown in  FIG. 10 , when the wiring density of auxiliary electrode film  3   a  near center C of electrode film  2   a  is excessively large, the light-emitting area is reduced (light shielding area by auxiliary electrode film  3   a  is larger), consequently lowering illuminance. It is accordingly desirable to set the wiring density of auxiliary electrode film  3   a  to be five times larger, at a maximum, than that of auxiliary electrode films  3   a  and  3   b  that are formed near power supply terminal sections  6   a  and  6   b.    
     In this embodiment, a plurality of auxiliary electrode films  3   c  similar in shape to auxiliary electrode film  3   a  of this embodiment can be formed on the surface of electrode film  2   b . Alternatively, auxiliary electrode films  3   a  and  3   b  that have the shapes described in the first and second embodiments can be formed on the surface of electrode film  2   b.    
     The embodiments of the present invention have been described. However, the present invention is not limited to the embodiments. Various changes understandable to those skilled in the art can be made to the configuration and the specifics of the present invention without departing from the spirit and the scope of the invention. 
     This application claims priority from Japanese Patent Application No. 2010-130009 filed Jun. 7, 2010, which is hereby incorporated by reference herein in its entirety. 
     REFERENCE NUMERALS 
       1  Transparent substrate 
       2   a ,  2   b  Electrode film 
       3  Auxiliary electrode film group 
       3   a ,  3   b ,  3   c ,  3   d  Auxiliary electrode film 
       4  Interlayer insulating film 
       5  Organic light-emitting film 
       6   a ,  6   b ,  6   c ,  6   d  Power supply terminal section 
       10 ,  20 ,  30  Organic electroluminescent lighting device