Light-emitting element and organic electroluminescent display device

Abstract

Provided is a light-emitting element in the structure and configuration of causing no possibility of a short circuit between first and second electrodes even if there is any foreign substance or a protrusion on the first electrode. Such a light-emitting element is configured to include, in order, a first electrode 21 , an organic layer 23 including a light-emitting layer made of an organic light-emitting material, a semi-transmissive/reflective film 40 , a resistance layer 50 , and a second electrode 22 . The first electrode 21 reflects a light coming from the light-emitting layer, and the second electrode 22 passes through a light coming from the semi-transmissive/reflective film 40 after passing therethrough. The semi-transmissive/reflective film on the organic layer 23 has an average film thickness of 1 nm to 6 nm both inclusive.

1 . A light-emitting element, comprising:
 (A) a first electrode;   (B) an organic layer including a light-emitting layer made of an organic light-emitting material;   (C) a semi-transmissive/reflective film;   (D) a resistance layer; and   (E) a second electrode,   
       wherein, 
       the first electrode is configured to reflect light coming from the light-emitting layer, 
       the second electrode is configured to allow light coming from the semi-transmissive/reflective film to be transmitted therethrough, 
       the semi-transmissive/reflective film on the organic layer has an average film thickness of 1 nm to 6 nm both inclusive, 
       the light from the light-emitting layer is made to resonate between (i) a first interface between the first electrode and the organic layer, and (ii) a second interface between the semi-transmissive/reflective film and the organic layer, and 
       a part of the light is emitted from the semi-transmissive/reflective film. 
     
     
         2 . The light-emitting element according to  claim 1 , wherein
 the semi-transmissive/reflective film is made of alloys of magnesium-silver, aluminum, or silver.   
     
     
         3 . The light-emitting element according to  claim 1 , 
       wherein,
 a material configuring the resistance layer has an electrical resistivity of 1×106 Ωm to 1×1010 Ωm both inclusive, and 
 
       the resistance layer above the organic layer has a thickness of 0.1 μm to 2 μm both inclusive. 
     
     
         4 . The light-emitting element according to  claim 1 , 
       wherein,
 the first electrode includes a foreign substance or a protrusion, 
 
       the semi-transmissive/reflective film is not formed to a region proximal to the foreign substance or the protrusion, and 
       the resistance layer is in a region between (i) a portion of the semi-transmissive/reflective film in the periphery of the foreign substance or the protrusion, and (ii) a portion of the first electrode under the foreign substance or beneath the protrusion. 
     
     
         5 . The light-emitting element according to  claim 1 , 
       wherein,
 when a distance from the first interface being an interface between the first electrode and the organic layer to a position on the light-emitting layer where a level of light emission is maximum is L1, an optical distance thereof is OL1, a distance from the second interface being an interface between the semi-transmissive/reflective film and the organic layer to the position on the light-emitting layer where a level of light emission is maximum is L2, and an optical distance thereof is OL2, expressions (1-1) and (1-2) below are satisfied,
   0.7{−Φ1/(2π)+ m 1}≦2 ×OL 1/λ≦1.2{−Φ1/(2π)+ m 1}  (1-1)
 
   0.7{−Φ2/(2π)+ m 2}≦2 ×OL 2/λ≦1.2{−Φ2/(2π)+ m 2}  (1-2)
 
 
 
       where λ is a maximum peak wavelength in a spectrum of the light generated in the light-emitting layer,
 Φ1 is an amount of phase shift (unit: radian) of a reflected light generated on the first interface (where −2π<Φ1<0) 
 Φ2 is an amount of phase shift (unit: radian) of a reflected light generated on the second interface (where −2π<Φ2<0, and 
 
       a value of (m1, m2) is (0, 0), (1, 0), or (0, 1). 
     
     
         6 . The light-emitting element according to  claim 1 , 
       wherein,
 when an optical distance between the first interface being an interface between the first electrode and the organic layer and the second interface being an interface between the semi-transmissive/reflective film and the organic layer is L, a sum of phase shift to be observed when the light generated in the light-emitting layer is reflected on the first and second interfaces is Φ radian, and a maximum peak wavelength in a spectrum of the light generated in the light-emitting layer is λ, an expression of
   0.7<{(2 L )/λ+Φ/(2π)}<1.3
 
   or 
   −0.3<{(2 L )/λ+Φ/(2π)}<0.3
 
 
 
       is satisfied. 
     
     
         7 . A light-emitting element, comprising:
 (A) a first electrode;   (B) an organic layer including a light-emitting layer made of an organic light-emitting material;   (C) a semi-transmissive/reflective film;   (D) a resistance layer; and   (E) a second electrode,   
       wherein, 
       the first electrode is configured to reflect light coming from the light-emitting layer,
 the second electrode is configured to transmit light coming from the semi-transmissive/reflective film after passing through the semi-transmissive/reflective film, and 
 when a distance from a first interface between the first electrode and the organic layer to a position on the light-emitting layer where a level of light emission is maximum is L1, an optical distance thereof is OL1, a distance from a second interface between the semi-transmissive/reflective film and the organic layer to a position on the light-emitting layer where a level of light emission is maximum is L2, and an optical distance thereof is OL2, expressions (1-1) and (1-2) below are satisfied,
   0.7{−Φ1/(2π)+ m 1}≦2 ×OL 1/λ≦1.2{−Φ1/(2π)+ m 1}  (1-1)
 
   0.7{−Φ2/(2π)+ m 2}≦2 ×OL 2/λ≦1.2{−Φ2/(2π)+ m 2}  (1-2)
 
 
 
       where λ is a maximum peak wavelength in a spectrum of a light generated in the light-emitting layer,
 Φ1 is an amount of phase shift (unit: radian) of a reflected light generated on the first interface (where −2π<φ1<0) 
 Φ2 is an amount of phase shift (unit: radian) of a reflected light generated on the second interface (where −2π<Φ2<0), and 
 
       a value of (m1, m2) is (0, 0), (1, 0), or (0, 1). 
     
     
         8 . A light-emitting element, comprising:
 (A) a first electrode;   (B) an organic layer including a light-emitting layer made of an organic light-emitting material;   (C) a semi-transmissive/reflective film;   (D) a resistance layer; and   (E) a second electrode,   
       wherein, 
       the first electrode is configured to reflect light coming from the light-emitting layer,
 the second electrode is configured to transmit light coming from the semi-transmissive/reflective film after passing through the semi-transmissive/reflective film, and 
 when an optical distance between a first interface between the first electrode and the organic layer and a second interface between the semi-transmissive/reflective film and the organic layer is L, a sum of phase shift to be observed when a light generated in the light-emitting layer is reflected on the first and second interfaces is 4 radian, and a maximum peak wavelength in a spectrum of the light generated in the light-emitting layer is λ, 
 an expression of
   0.7<{(2 L )/λ+Φ/(2π)}<1.3
 
   or 
   −0.3<{(2 L )/λ+Φ/(2π)}<0.3
 
 
 
       is satisfied. 
     
     
         9 . An organic electroluminescent display device, including a plurality of organic electroluminescent elements each comprising:
 (a) a first electrode;   (b) an insulation layer including an aperture, and from a bottom portion of the aperture, the first electrode is exposed;   (c) an organic layer disposed from the above of a portion of the first electrode exposed from the bottom portion of the aperture to a portion of the insulation layer around the aperture, and includes a light-emitting layer made of an organic light-emitting material;   (d) a semi-transmissive/reflective film formed at least on the organic layer;   (e) a resistance layer covering the semi-transmissive/reflective film; and   (f) a second electrode formed on the resistance layer,   
       wherein,
 the first electrode reflects a light coming from the light-emitting layer, 
 the second electrode passes through a light coming from the semi-transmissive/reflective film after passing therethrough, and 
 a portion of the semi-transmissive/reflective film on the insulation layer is at least partially discontinuous. 
 
     
     
         10 . The organic electroluminescent display device according to  claim 9 , wherein
 the semi-transmissive/reflective film on the organic layer has an average film thickness of 1 nm to 6 nm both inclusive.   
     
     
         11 . The organic electroluminescent display device according to  claim 9 , wherein
 the semi-transmissive/reflective film is made of alloys of magnesium-silver, aluminum, or silver.   
     
     
         12 . The organic electroluminescent display device according to  claim 9 , 
       wherein,
 a material configuring the resistance layer has an electrical resistivity of 1×106 Ωm to 1×1010 Ωm both inclusive, and 
 
       the resistance layer above the organic layer has a thickness of 0.1 μm to 2 μm both inclusive. 
     
     
         13 . The organic electroluminescent display device according to  claim 9 , 
       wherein,
 the first electrode includes a foreign substance or a protrusion, 
 
       the semi-transmissive/reflective film is not formed to a region proximal to the foreign substance or the protrusion, and 
       the resistance layer is in a region between (i) a portion of the semi-transmissive/reflective film in the periphery of the foreign substance or the protrusion, and (ii) a portion of the first electrode under the foreign substance or beneath the protrusion. 
     
     
         14 . The organic electroluminescent display device according to  claim 9 , 
       wherein,
 a light generated in the light-emitting layer is made to resonate between a first interface between the first electrode and the organic layer and a second interface between the semi-transmissive/reflective film and the organic layer, and 
 
       a part of the resulting light is emitted from the semi-transmissive/reflective film. 
     
     
         15 . The organic electroluminescent display device according to  claim 14 , 
       wherein,
 when a distance from the first interface between the first electrode and the organic layer to a position on the light-emitting layer where a level of light emission is maximum is L1, an optical distance thereof is OL1, a distance from the second between the semi-transmissive/reflective film and the organic layer to a position on the light-emitting layer where a level of light emission is maximum is L2, and an optical distance thereof is OL2, expressions (1-1) and (1-2) below are satisfied,
   0.7{−Φ1/(2π)+ m 1}≦2 ×OL 1/λ≦1.2{−Φ1/(2π)+ m 1}  (1-1)
 
   0.7{−Φ2/(2π)+ m 2}≦2 ×OL 2/λ≦1.2{−Φ2/(2π)+ m 2}  (1-2)
 
 
 
       where λ is a maximum peak wavelength in a spectrum of the light generated in the light-emitting layer,
 Φ1 is an amount of phase shift (unit: radian) of a reflected light generated on the first interface (where −2π<Φ1<0) 
 Φ2 is an amount of phase shift (unit: radian) of a reflected light generated on the second interface (where −2π<Φ2<0), and 
 
       a value of (m1, m2) is (0, 0), (1, 0), or (0, 1). 
     
     
         16 . The organic electroluminescent display device according to  claim 14 , 
       wherein,
 when an optical distance between the first interface between the first electrode and the organic layer and the second interface between the semi-transmissive/reflective film and the organic layer is L, a sum of phase shift to be observed when the light generated in the light-emitting layer is reflected on the first and second interfaces is Φ radian, and a maximum peak wavelength in a spectrum of the light generated in the light-emitting layer is λ, an expression of
   0.7<{(2 L )/λ+Φ/(2π)}<1.3
 
   or 
   −0.3<{(2 L )/λ+Φ/(2π)}<0.3
 
 
 
       is satisfied.