Organic electroluminescent device and illumination device
An organic electroluminescent device wherein, among the distribution characteristics of light emitted inside a substrate: the brightness of white light has a maximum value within an angle range of 20-60° from an axis perpendicular to the planar direction of the substrate; the spectral radiance of red light at the maximum emission wavelength and the spectral radiance of green light at the maximum emission wavelength have maximum values within the angle range of 30-70° from the axis perpendicular to the planar direction of the substrate; and the maximum values are greater than the value for spectral radiance of red light at the maximum emission wavelength and the value for the spectral radiance of green light at the maximum emission wavelength, in the axial direction perpendicular to the planar direction of the substrate.
1. An organic electroluminescent device having a structure in which a plurality of light emitting units each including a light emitting layer made of at least an organic compound are stacked one on top of another between a first electrode and a second electrode with a charge generating layer sandwiched between each pair of the adjacent light emitting units, the organic electroluminescent device capable of providing white light through a substrate adjacent to the first electrode or the second electrode by causing the plurality of light emitting units to emit light, wherein
the white light produced by light emission of the plurality of light emitting units is formed of red light, green light, and blue light,
distribution characteristics of light emitted into the substrate are such that a luminance of the white light takes a maximum in an angle range of 20 to 60 degrees with respect to an axis perpendicular to a plane direction of the substrate, and
a spectral radiance at a maximum emission wavelength of the red light and a spectral radiance at a maximum emission wavelength of the green light each take a maximum in an angle range of 30 to 70 degrees with respect to the axis perpendicular to the plane direction of the substrate and the maxima are higher than a value of the spectral radiance in an axial direction perpendicular to the plane direction of the substrate at the maximum emission wavelength of the red light and a value of the spectral radiance in the axial direction perpendicular to the plane direction of the substrate at the maximum emission wavelength of the green light, respectively.
2. The organic electroluminescent device according to claim 1 , wherein the distribution characteristics of light emitted into the substrate are such that, when: an angle at which the luminance of the white light is maximum is (A); an angle at which the spectral radiance at the maximum emission wavelength of the red light is maximum is (B); and an angle at which the spectral radiance at the maximum emission wavelength of the green light is maximum is (C) with the axis perpendicular to the plane direction of the substrate being a reference, the angle (A), the angle (B), and the angle (C) satisfy a relationship of (C)≥(A)≥(B).
3. The organic electroluminescent device according to claim 1 , wherein the distribution characteristics of light emitted into the substrate are such that, when the maximum of the spectral radiance at the maximum emission wavelength of the red light or the green light is (D) and the value of the spectral radiance in the axial direction perpendicular to the plane direction of the substrate at the maximum emission wavelength of the red light or the green light is (E), a ratio of the value (E) to the maximum (D) ((E)/(D)) is 0.7 or smaller.
4. The organic electroluminescent device according to claim 1 , comprising:
a first light emitting unit formed of a red light emitting unit including a red light emitting layer which emits the red light;
a second light emitting unit formed of a blue light emitting unit including a blue light emitting layer which emits the blue light; and
a third light emitting unit formed of a green light emitting unit including a green light emitting layer which emits the green light, wherein
the first light emitting unit and the second light emitting unit are stacked one on top of the other with a first charge generating layer sandwiched therebetween,
the second light emitting unit and the third light emitting unit are stacked one on top of the other with a second charge generating layer sandwiched therebetween, and
the organic electroluminescent device has a structure in which the second electrode, the third light emitting unit, the second charge generating layer, the second light emitting unit, the first charge generating layer, the first light emitting unit, and the first electrode are stacked one on top of another in this order.
5. The organic electroluminescent device according to claim 1 , wherein
the charge generating layer is formed of an electrically insulating layer made of an electron accepting material and an electron donating material, and
a specific resistance of the electrically insulating layer is 1.0×10 2 Ω·cm or more.
6. The organic electroluminescent device according to claim 5 , wherein the specific resistance of the electrically insulating layer is 1.0×10 5 Ω·cm or more.
7. The organic electroluminescent device according to claim 1 , characterized in that
each of the charge generating layers is formed of a mixed layer of different materials and one component of the mixed layer forms a charge transfer complex by redox, and
when voltage is applied between the first electrode and the second electrode, charges in the charge transfer complex move to the first electrode side and the second electrode side to cause holes to be injected into one light emitting unit located on the first electrode side of the charge generating layer and cause electrons to be injected into another light emitting unit located on the second electrode side of the charge generating layer.
8. The organic electroluminescent device according to claim 1 , characterized in that
each of the charge generating layers is formed of a laminate of an electron accepting material and an electron donating material, and
when voltage is applied between the first electrode and the second electrode, in an interface between the electron accepting material and the electron donating material, charges generated by reaction involving electron transfer between the electron accepting material and the electron donating material move to the first electrode side and the second electrode side to cause holes to be injected into one light emitting unit located on the first electrode side of the charge generating layer and cause electrons to be injected into another light emitting unit located on the second electrode side of the charge generating layer.
9. The organic electroluminescent device according to claim 1 , characterized in that the charge generating layers contain a compound having a structure expressed by formula (1):
where R represents an electron withdrawing group of F, Cl, Br, I, CN, or CF 3 .
10. The organic electroluminescent device according to claim 1 , wherein the first electrode is made of silver.
11. A lighting device comprising the organic electroluminescent device according to claim 1 .
12. The lighting device according to claim 11 , comprising an optical film on a light extraction surface side of the organic electroluminescent device.
13. The lighting device according to claim 11 , wherein an average color rendering index (Ra) of the white light is 80 or more.
14. The lighting device according to claim 11 , wherein
the substrate is a base substrate or a sealing substrate,
the base substrate or the sealing substrate is formed of a flexible substrate, and
the lighting device is flexible.