Organic electroluminescent element

An organic electroluminescent element with a structure in which a plurality of light-emitting layers are stacked between a first electrode with light reflectivity and a second electrode with optical transparency while one or more interlayers with a light transmissive property are interposed between the plurality of light-emitting layers,

• wherein:
• the one or more interlayers includes a first interlayer closest to the first electrode;
• a first light-emitting unit is formed between the first electrode and the first interlayer to include a first light-emitting layer which is one of the plurality of light-emitting layers and has a first light-emitting source;
• a second light-emitting unit is formed on a side of the first interlayer close to the second electrode to include a second light-emitting layer which is one of the plurality of light-emitting layers and has a second light-emitting source;
• and
• the first interlayer is a semi-transmissive layer which has both of optical transparency and light reflectivity and has a total light absorption ratio of 10% or less,
• wherein
• the organic electroluminescent element has a characteristic which satisfies relations of:
• 0.9*X≦D1(λ1)≦1.1*X;
• 0.1*Y≦D3(λ2)≦2.0*Y;
• and
• 0.8*Z≦D1(λ1)+D2(λ1)≦1.2*Z,
• wherein:
• λ1 represents a weighted-averaged emission wavelength of the first light-emitting source;
• λ2 represents a weighted-averaged emission wavelength of the second light-emitting source;
• D1(λ1) represents an optical path length defined as a product of a refractive index at the wavelength λ1 and a thickness with regard to a medium situated between the first light-emitting source and the first electrode;
• D2(λ1) represents an optical path length defined as a product of a refractive index at the wavelength λ1 and a thickness with regard to a medium situated between the first light-emitting source and the semi-transmissive layer;
• D3(λ2) represents an optical path length defined as a product of a refractive index at the wavelength λ2 and a thickness with regard to a medium situated between the second light-emitting source and the semi-transmissive layer;
• and
• X, Y, and Z satisfy equations of X=φ1(λ1)*(λ1/4π)+λ1*l/2, Y=(φ2(λ2)*(λ2/4π)+λ2*m/2, and Z=φ1(λ1)+φ2(λ1)*(λ1/4π)+λ1*n/2, respectively,
• wherein:
• l, m, and n are integers of 0 or more, respectively;
• φ1 represents a phase shift expressed by a following formula (I) which occurs at the first electrode;
• φ2 represents a phase shift expressed by the following formula (I) which occurs at the semi-transmissive layer;
• φ1(λ1) represents a phase shift of light emitted from the first light-emitting source which arises from reflection at the first electrode;
• φ2(λ1) represents a phase shift of light emitted from the first light-emitting source which arises from reflection at the semi-transmissive layer;
• φ2(λ2) represents a phase shift of light emitted from the second light-emitting source which arises from reflection at the semi-transmissive layer;
• and
• the formula (1) is:
• ϕ
• =
• tan
• -
• 1
• 
• {
• 2
• 
• (
• n
• 1
• 
• k
• 2
• -
• n
• 2
• 
• k
• 1
• )
• n
• 1
• 2
• -
• n
• 2
• 2
• +
• k
• 1
• 2
• -
• k
• 2
• 2
• }
• ,
• (
• 1
• )
• wherein:
• n1 and k1 representing a refractive index and an extinction coefficient of a layer in contact with a reflection layer, respectively;
• n2 and k2 representing a refractive index and an extinction coefficient of the reflection layer, respectively;
• and
• n1, n2, k1, and k2 are functions of λ.