Surface light source device, lighting device, and backlight device

Abstract

A surface light source device is provided that has high light extraction efficiency and high mechanical strength and can suppress a change in color tone at different viewing angles. To that end, the surface light source device includes: an organic EL element including a luminescent layer; and a light-emitting surface structure layer that is disposed in contact with one of the surfaces of the organic EL element and defines a concave-convex structure on the surface on the device light-emitting surface side. The concave-convex structure includes a plurality of concave portions having oblique surfaces and flat portions disposed around the concave portions. The surface light source device further includes a diffusing member on which the light emitted from the luminescent layer is incident, the diffusing member allowing the incident light to pass therethrough or reflecting the incident light in a diffused manner.

1 . A surface light source device, comprising: an organic electroluminescent element including a luminescent layer; and a light-emitting surface structure layer disposed in contact with at least one of surfaces of the organic electroluminescent element, wherein:
 the light-emitting surface structure layer includes a concave-convex structure provided on a surface thereof on a side toward a light-emitting surface of the device,   the concave-convex structure includes a plurality of concave portions having oblique surfaces and flat portions disposed around the concave portions,   the surface light source device further comprises a diffusing member on which light emitted from the luminescent layer is incident, the diffusing member allowing the incident light to pass therethrough or reflecting the incident light in a diffused manner, and   the surface light source device includes the diffusing member as a member that constitutes at least one of:   a layer constituting all or part of the light-emitting surface structure layer, and   a layer disposed at a position farther from the light-emitting surface structure layer than the organic electroluminescent element.   
     
     
         2 . The surface light source device according to  claim 1 , wherein the diffusing member is a member provided as the layer constituting all or part of the light-emitting surface structure layer, and is a member that allows the incident light to pass therethrough in a diffused manner. 
     
     
         3 . The surface light source device according to  claim 2 , wherein the diffusing member is a bonding layer interposed between two layers included in the light-emitting surface structure layer. 
     
     
         4 . The surface light source device according to  claim 3 , wherein the light-emitting surface structure layer includes:
 a substrate disposed in contact with the organic electroluminescent element,   a concave-convex structure layer disposed at a position closer to the device light-emitting surface than the substrate, the concave-convex structure layer including the concave-convex structure on a surface thereof, the surface being on a side close to the device light-emitting surface, and   a bonding layer for bonding the substrate and the concave-convex structure layer, and wherein:   the surface light source device includes the bonding layer as the diffusing member.   
     
     
         5 . The surface light source device according to  claim 1 , wherein the diffusing member is formed from a material containing particles that impart light diffusibility. 
     
     
         6 . The surface light source device according to  claim 1 , wherein the diffusing member is a member disposed at a position farther from the light-emitting surface structure layer than the organic electroluminescent element, and is a member that reflects the incident light in a diffused manner. 
     
     
         7 . The surface light source device according to  claim 1 , wherein, when the concave-convex structure is observed in a direction perpendicular to the device light-emitting surface, a ratio of an area occupied by the flat portions relative to the sum of the area occupied by the flat portions and an area occupied by the concave portions is 10 to 75%. 
     
     
         8 . The surface light source device according to  claim 1 , wherein the concave portions have a pyramid shape, a conical shape, a shape of part of a sphere, or a shape of a combination thereof,
 the plurality of concave portions are aligned on the device light-emitting surface in two or more directions crossing each other, and   spacings are provided between adjacent concave portions in all of the two or more directions, the spacings constituting the flat portions.   
     
     
         9 . The surface light source device according to  claim 1 , wherein the concave portions have a pyramid shape, a conical shape, a shape of part of a sphere, or a shape of a combination thereof,
 the plurality of concave portions are aligned on the device light-emitting surface in two or more directions crossing each other, and   spacings are provided between adjacent concave portions in only one of the two or more directions, the spacings constituting the flat portions.   
     
     
         10 . The surface light source device according to  claim 1 , wherein the concave portions have a groove shape,
 the plurality of concave portions are aligned in parallel to each other on the device light-emitting surface, and   spacings are provided between adjacent concave portions, the spacings constituting the flat portions.   
     
     
         11 . A surface light source device, comprising: an organic electroluminescent element including, in the following order, a first electrode layer, a luminescent layer, and a second electrode layer; and a light-emitting-side member that is disposed in contact with at least one of surfaces of the organic electroluminescent element and has a light-emitting surface from which light is emitted to the outside, wherein:
 the light-emitting-side member includes:   a light-distribution conversion unit that converts a distribution of light emitted from the organic electroluminescent element so as to reduce a difference between a chromaticity of light emitted from the light-emitting surface in a normal direction with respect to the light-emitting surface and a chromaticity of light emitted from the light-emitting surface in an oblique direction crossing the normal direction, and   a diffusing section that diffuses the light emitted from the organic electroluminescent element.   
     
     
         12 . The surface light source device according to  claim 11 , wherein the diffusing section is a layer that is disposed between the light-distribution conversion unit and the organic electroluminescent element and is formed of a composition containing particles that impart light diffusibility. 
     
     
         13 . The surface light source device according to  claim 11 , wherein the diffusing section is a layer that is disposed on a light-emitting side of the light-distribution conversion unit and is formed of a composition containing particles that impart light diffusibility. 
     
     
         14 . The surface light source device according to  claim 11 , wherein the light-distribution conversion unit includes a concave-convex structure layer having a concave-convex structure formed on a surface thereof. 
     
     
         15 . The surface light source device according to  claim 14 , wherein the concave-convex structure layer is formed of a composition containing particles that impart light diffusibility and serves also as the diffusing section. 
     
     
         16 . The surface light source device according to  claim 11 , wherein the light-distribution conversion unit includes a substrate and a concave-convex structure layer disposed on a surface of the substrate, the concave-convex structure layer having a concave-convex structure formed on a surface thereof on a side opposite to the substrate. 
     
     
         17 . The surface light source device according to  claim 16 , wherein the substrate and/or the concave-convex structure layer is formed of a composition containing particles that impart light diffusibility and serves also as the diffusing section. 
     
     
         18 . The surface light source device according to  claim 11 , wherein the light-distribution conversion unit includes a substrate film and a selective reflecting layer disposed on at least one of surfaces of the substrate film. 
     
     
         19 . The surface light source device according to  claim 18 , wherein the selective reflecting layer includes a layer containing a resin having cholesteric regularity. 
     
     
         20 . The surface light source device according to  claim 18 , wherein the substrate film is formed of a composition containing particles that impart light diffusibility and serves also as the diffusing section. 
     
     
         21 . A lighting device comprising the surface light source device according to  claim 1 . 
     
     
         22 . A backlight device comprising the surface light source device according to  claim 1 . 
     
     
         23 . A lighting device comprising the surface light source device according to  claim 11 . 
     
     
         24 . A backlight device comprising the surface light source device according to  claim 11 .