JP2007234253A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an organic electroluminescent element capable of obtaining nearly equal extraction efficiency in a wide range of a visible area and restraining color drift due to a visual field angle. <P>SOLUTION: In the electroluminescent element laminating in turn a reflective layer 2, a first electrode 3, an organic layer 4 including a light-emitting layer, a second electrode 5, and an optical tuning layer 6 and taking out light from a side of the optical tuning layer 6, provided that an optical distance from a light-emitting position 4a in the light-emitting layer to a reflecting face 2a of the reflecting layer 2 is L<SB>1</SB>, an optical distance from the reflecting face 2a of the reflecting layer 2 to a bottom end 5a of the second electrode 5 is L<SB>2</SB>, an optical distance from the reflecting face 2a of the reflecting layer 2 to a top end 6a of the optical tuning layer 6 is L<SB>3</SB>, and a center wavelength of the wavelength band of emission light to be extracted is λ, L<SB>1</SB>is set at an optical distance with which light of the wavelength λ does not interfere, L<SB>2</SB>is set at an optical distance where light of the wavelength λ reinforces each other by interference, and L<SB>3</SB>is set at an optical distance where light of the wavelength λ weakens each other by interference. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence element (organic EL element).

  The organic EL element generally has a structure in which an organic layer having a thickness of several tens to several hundreds of μm is sandwiched between a reflective electrode and a transmissive electrode. The light emitted from the light emitting layer inside the organic layer interferes in this laminated structure and is extracted outside. Various attempts have been made to increase the light emission efficiency by using this interference. When the light emitted from the light emitting layer is monochromatic light, it may be designed in a structure that only increases the wavelength, but when the light emitted from the light emitting layer is white light, in order to increase the luminous efficiency of the mixed color, Attempts have been made to utilize multiple optical interferences.

  In Patent Document 1, the second half mirror layer, the buffer layer, the first half mirror layer, the organic layer, and the reflective layer are stacked in this order from the substrate side, and the interference between the first half mirror layer and the reflective layer is caused. Blue light emission is structured to enhance orange light emission and white light emission by interference between the second half mirror layer and the reflective layer. In Patent Document 2, the second half mirror layer, the buffer layer, the first half mirror layer, the organic layer, and the reflective layer are stacked in this order from the substrate side, and the interference between the first half mirror layer and the reflective layer is caused. Blue light emission, green light emission due to interference between the first half mirror layer and the second half mirror layer, red light emission is strengthened due to interference between the second half mirror layer and the reflective layer, and white light emission is enhanced. Yes. In Patent Document 3, the distance from the light emitting position to the reflective layer and the distance from the light emitting position to the outer surface of the outer layer of the translucent electrode are defined, and interference is not used, thereby preventing white color without color shift due to the viewing angle. Taking out the light.

According to the organic EL element using the interference by the reflective layer, the first half mirror layer, and the second half mirror layer, the light emission efficiency can be improved, but a plurality of single colors are strengthened by the interference. Since the optical distance to the light emitting position changes depending on the angle, there is a problem that the color shift due to the viewing angle becomes large. Further, when the light emission position and the film thickness of the entire element are limited, the color shift due to the viewing angle is reduced, but the light emission efficiency cannot be improved by interference.
JP 2003-151776 A JP 2004-127588 A JP 2004-79421 A

  An object of the present invention is to provide an organic EL element capable of obtaining substantially uniform extraction efficiency in a wide visible range and suppressing color shift due to a viewing angle.

The present invention is an organic electroluminescence device in which a reflective layer, a first electrode, an organic layer including a light emitting layer, a second electrode, and an optical adjustment layer are sequentially laminated on a substrate, and light is extracted from the optical adjustment layer side. The optical distance from the light emitting position in the light emitting layer to the reflecting surface of the reflecting layer is L ₁ , the optical distance from the reflecting surface of the reflecting layer to the lower end of the second electrode is L ₂ , and from the reflecting surface of the reflecting layer to the upper end of the optical adjustment layer Where L _{3 is} the optical distance, and the center wavelength of the wavelength range of light emission to be extracted is λ, L ₁ is set to an optical distance that does not cause interference of light of wavelength λ, and L ₂ is caused by interference of light of wavelength λ. set optical distance constructive, is characterized in that light of the L ₃ wavelength λ is set to an optical distance destructive by interference.

In the present invention, the optical distance L ₁ is set to an optical distance that the light of wavelength λ does not cause interference, and set to an optical distance that the light of the optical distance L ₂ of wavelength λ is constructive the interference, the optical distance light of the L ₃ wavelength λ is set to an optical distance destructive by interference. Hereinafter, light interference caused by the optical distance L _{1 is referred} to as “first interference”, light interference caused by the optical distance L ₂ is referred to as “second interference”, and light interference caused by the optical distance L ₃ is referred to as “second interference”. This is called “third interference”.

  With reference to FIG.1 and FIG.2, the 1st interference in this invention, 2nd interference, and 3rd interference are demonstrated.

  FIG. 1 is a schematic cross-sectional view showing an example of the organic EL element of the present invention. As shown in FIG. 1, a reflective layer 2, a first electrode 3, an organic layer 4 including a light emitting layer, a second electrode 5, and an optical adjustment layer 6 are sequentially stacked on a substrate 1. The light emitted from the light emitting position 4a of the light emitting layer in the organic layer 4 is extracted from the optical adjustment layer 6 side.

In the present invention, the optical distance from the emission position 4a to the reflecting surface 2a of the reflecting layer 2 and L _1, the optical path length from the reflecting surface 2a of the reflective layer 2 to the lower end 5a of the second electrode 5 and L _2, the reflection It is set to L ₃ the optical distance to the upper end 6a of the optical adjustment layer 6 from the reflecting surface 2a of the layer 2.

  FIG. 2 is a schematic cross-sectional view for explaining the first interference, the second interference, and the third interference in the organic EL element shown in FIG. The light emitted from the light emitting position 4a is emitted toward the optical adjustment layer 6 side and also emitted toward the reflective layer 2 side. The light 31b emitted toward the reflective layer 2 side is reflected by the reflective surface 2a of the reflective layer 2 and travels toward the optical adjustment layer 6 side. The interference generated between the light 31 a emitted directly from the light emitting position 4 a to the optical adjustment layer 6 side and the light 31 b reflected by the reflective layer 2 is the first interference 31.

  The second interference 32 is emitted from the light emission position 4a toward the optical adjustment layer 6, and is emitted through the second electrode 5 and emitted from the light emission position 4a toward the optical adjustment layer 6. The interference between the light 32 b reflected from the lower end 5 a of the second electrode 5 toward the reflective layer 2, reflected from the reflective surface 2 a of the reflective layer 2, and emitted toward the optical adjustment layer 6 again. is there.

  The third interference 33 is emitted from the light emitting position 4a toward the optical adjustment layer 6, is reflected by the light 33a emitted through the optical adjustment layer 6, and the upper end 6a of the optical adjustment layer 6, and is reflected. This is interference generated between the light 33 b that is directed to the layer 2 side and reflected by the reflecting surface 2 a of the reflective layer 2 and again toward the optical adjustment layer 6 side.

The first interference 31 can be controlled by adjusting the optical distance L ₁ between the light emitting position 4 a and the reflecting surface 2 a of the reflecting layer 2. The second interference 32 can be controlled by adjusting the optical distance L ₂ between the lower end 5 a of the second electrode 5 and the reflecting surface 2 a of the reflecting layer 2. In addition, the third interference 33 can be controlled by adjusting the optical distance L ₃ between the upper end 6 a of the optical adjustment layer 6 and the reflection surface 2 a of the reflection layer 2.

In the present invention, to set the optical distance L ₁ to the optical distance of the light of wavelength λ does not cause interference, first interference 31 is set so as not to cause. Also, it is set to an optical distance that the optical distance L ₂ is light of wavelength λ constructive the interference. In other words, the optical distance at which the light with the wavelength λ resonates is set by the second interference 32. Also, it is set to an optical distance that the optical distance L ₃ is light of wavelength λ weakened by interference. That is, the third interference 33 is set so that the light with the wavelength λ becomes non-resonant.

In the present invention, as described above, the optical distance L ₁ is set so that the first interference 31 does not occur, the second interference 32 is set to be resonant, and the third interference 33 is non-resonant. By setting so as to be approximately equal, it is possible to obtain substantially uniform extraction efficiency in a wide range of the visible range, and it is possible to suppress color shift due to viewing angle.

  In a preferred embodiment according to the present invention, the optical adjustment layer is composed of an organic buffer layer provided on the second electrode and a third electrode comprising an inorganic transparent electrode provided on the organic buffer layer. The third electrode functions as an auxiliary electrode by grounding the second electrode and the third electrode at the peripheral portion other than the pixel light emitting portion. In the present invention, the optical adjustment layer can thus be composed of the organic buffer layer and the third electrode. In this case, the third electrode can function as an auxiliary electrode by grounding the third electrode at the peripheral portion other than the pixel light-emitting portion, thereby reducing the increase in resistance of the element due to the second electrode. Can be made.

  Moreover, in this invention, the optical adjustment layer may be comprised only from the organic buffer layer, and may be comprised only from the inorganic transparent electrode.

  The organic buffer layer is not particularly limited as long as it does not absorb light emitted from the light emitting layer. For example, the organic buffer layer is formed of a material used as a hole transporting material or an electron transporting material in an organic EL element. can do. The inorganic transparent electrode can be formed from a conductive metal oxide such as ITO (indium tin oxide) or IZO (indium zinc oxide), which is used as a transparent electrode in an organic EL element, a metal thin film, or the like. .

  In the present invention, an external layer such as a protective film may be further provided outside the optical adjustment layer. The outer layer preferably has a refractive index different by 0.2 or more from the refractive index of the upper end portion of the optical adjustment layer and has a film thickness of 1 μm or more. By providing such an external layer, a part of light from the light emitting layer can be reflected at the upper end of the optical adjustment layer.

  The light emitting layer in the organic EL device of the present invention may emit white light, or may emit single color such as red (R), green (G), and blue (B). . In the case of a light emitting layer that emits white light, for example, a blue light emitting material and an orange light emitting material may be contained in one light emitting layer, or a white light emitting layer in which an orange light emitting layer and a blue light emitting layer are laminated. It may be.

In the organic EL device of the present invention, when the light emitting layer is a white light emitting layer, L ₁ , L ₂ and L ₃ preferably satisfy the following formula. By satisfying the following expression, it is possible to obtain substantially the same extraction efficiency in a wide range of the visible range, and it is possible to more effectively obtain the effect of the present invention that the color shift due to the viewing angle can be suppressed. .

L ₁ = 75 to 125 [nm]
_{L 2 = (m + (φ} 1 + φ 2) / 2π) λ 1/2 [nm]
_{L 3 = (n + 1/2 +} (φ 1 + φ 3) / 2π) λ 2/2 [nm]
500 nm <λ <550 nm
λ -15 <λ ₁ <λ + 15
λ -15 <λ ₂ <λ + 15
L ₁ : Optical distance from the light emitting position to the reflective layer (the light emitting position is the interface between the first light emitting layer made of a hole transporting material and the second light emitting layer made of an electron transporting material)
L ₂ : Optical distance from the reflective layer to the lower end of the second electrode
L ₃ : Optical distance from the reflective layer to the upper end of the optical adjustment layer λ: Center wavelength φ ₁ of the white light emission wavelength region to be extracted: Phase change when light is reflected by the reflective layer. It is given by

Refractive index of the first electrode: n _a, the refractive index of the reflective _{layer: n m, φ 1 = tan} -1 {2 n a when the extinction coefficient k _m of the reflection layer ^{_{k m / (n a 2 -}} n m ² - k _m ^2)}
Where 2 n _a k _m / (n _a ² -n _m ² -k _m ² )> 0, 0 <φ ₁ <π / 2
2 n _a k _m / (n _a ² -n _m ² - k _m ²⁾ <When _{0, π / 2 <φ 1} <π
φ ₂ : Phase change when light is reflected at the lower end of the second electrode. It is given by
When the refractive index of the organic layer is n _o , the refractive index of the second electrode is n _c , and the extinction coefficient k _c of the second electrode is φ ₂ = tan ^-1 (2 n _o k _c / (n _e ² -n _m ² - k _m ^2)}
Where 2 n _o k _c / (n _e ² -n _c ² -k _c ² )> 0, 0 <φ ₁ <π / 2
2 n _o k _c / (n _e ² -n _c ² -k _c ² ) <0, π / 2 <φ ₁ <π
φ ₃ : Phase change when light is reflected at the upper end of the optical adjustment layer. 0 when the refractive index of the optical adjustment layer is larger than the outer layer, and π when it is smaller.
m, n: natural number In the organic EL device of the present invention, when the light emitting layer is a monochromatic light emitting layer, L ₁ , L ₂ and L ₃ preferably satisfy the following formula.

L ₁ = 75 to 125 [nm]
_{L 2 = (m + (φ} 1 + φ 2) / 2π) λ 1/2 [nm]
_{L 3 = (n + 1/2 +} (φ 1 + φ 3) / 2π) λ 2/2 [nm]
λ _f -20 <λ <λ _f + 50
λ -15 <λ ₁ <λ + 15
λ -15 <λ ₂ <λ + 15
L ₁ : Optical distance from the light emitting position to the reflective layer (When the light emitting layer is made of a hole transporting material, it becomes the interface with the electron transporting layer, and the light emitting layer is made of an electron transporting material. Is the interface with the hole transport layer)
L ₂ : Optical distance from the reflective layer to the lower end of the second electrode
L ₃ : Optical distance from the reflective layer to the upper end of the optical adjustment layer λ: Center wavelength of monochromatic light to be extracted λ _f : Fluorescence peak wavelength of monochromatic light to be extracted φ ₁ : Phase when light is reflected by the reflective layer change. It is given by

Refractive index of the first electrode: n _a, the refractive index of the reflective _{layer: n m, φ 1 = tan} -1 {2 n a when the extinction coefficient k _m of the reflection layer ^{_{k m / (n a 2 -}} n m ² - k _m ^2)}
Where 2 n _a k _m / (n _a ² -n _m ² -k _m ² )> 0, 0 <φ ₁ <π / 2
2 n _a k _m / (n _a ² -n _m ² - k _m ²⁾ <When _{0, π / 2 <φ 1} <π
φ ₂ : Phase change when light is reflected at the lower end of the second electrode. It is given by
When the refractive index of the organic layer is n _o , the refractive index of the second electrode is n _c , and the extinction coefficient k _c of the second electrode is φ ₂ = tan ^-1 (2 n _o k _c / (n _e ² -n _m ² - k _m ^2)}
Where 2 n _o k _c / (n _e ² -n _c ² -k _c ² )> 0, 0 <φ ₁ <π / 2
2 n _o k _c / (n _e ² -n _c ² -k _c ² ) <0, π / 2 <φ ₁ <π
φ ₃ : Phase change when light is reflected at the upper end of the optical adjustment layer. 0 when the refractive index of the optical adjustment layer is larger than the outer layer, and π when it is smaller.
m, n: natural number

  According to the present invention, substantially uniform extraction efficiency can be obtained in a wide visible range, and color shift due to viewing angle can be suppressed.

  Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples.

Example 1
FIG. 3 is a schematic cross-sectional view showing the element structure of the organic EL element produced in this example. As shown in FIG. 3, a reflective layer 2 (thickness 100 nm) made of Al is formed on a glass substrate 1, and a first electrode 3 (thickness 20 nm) made of ITO (indium tin oxide) is formed thereon. And the positive hole transport layer 4b (film thickness of 5 nm) was formed on it.

  On the hole transport layer 4b, an orange light emitting layer 4c (film thickness 30 nm) and a blue light emitting layer 4d (film thickness 30 nm) were formed in this order. A white light-emitting layer is composed of the orange light-emitting layer 4c and the blue light-emitting layer 4d, and an electron transport layer 4e (film thickness 10 nm) is formed on the white light-emitting layer. The hole transport layer 4b, the orange light emitting layer 4c, the blue light emitting layer 4d, and the electron transport layer 4e constitute an organic layer. In such an element structure, the interface between the orange light emitting layer 4c and the blue light emitting layer 4d is the light emitting position 4a.

  On the electron transport layer 4e, the 2nd electrode 5 which consists of Li layer (film thickness of 1.5 nm) and Au layer (film thickness of 20 nm) was formed.

  An optical adjustment buffer layer 6b (thickness 350 nm) is formed on the second electrode 5, and an optical adjustment third electrode 6c (thickness 110 nm) made of IZO (indium zinc oxide) is formed thereon. Formed. The buffer layer 6b is made of NPB. The third electrode 6c is grounded to the second electrode 5 in the peripheral part other than the pixel light emitting part. The optical adjustment layer of the present invention is constituted by the buffer layer 6b and the third electrode 6c.

  In this embodiment, the hole transport layer 4b is made of NPB. In the orange light emitting layer 4c, NPB is used as the host material, tBuDPN is used as 20% by weight as the first dopant, and DBzR is used as 3% by weight as the second dopant.

  The blue light emitting layer 4d uses TBADN as a host material, uses NPB as a first dopant at 10% by weight, and uses TBP as a second dopant at 2.5% by weight.

Electron-transporting layer 4e is formed from Alq _3.

  NPB is N, N′-di (1-naphthyl) -N, N′-diphenylbenzidine and has the following structure.

ｔＢｕＤＰＮは、５，１２−ビス（４−ターシャリー−ブチルフェニル）ナフタセンであり、以下の構造を有している。

tBuDPN is 5,12-bis (4-tertiary-butylphenyl) naphthacene and has the following structure.

ＤＢｚＲは、５，１２−ビス｛４−（６−メチルベンゾチアゾール−２−イル）フェニル｝−６，１１−ジフェニルナフタセンであり、以下の構造を有している。

DBzR is 5,12-bis {4- (6-methylbenzothiazol-2-yl) phenyl} -6,11-diphenylnaphthacene and has the following structure.

ＴＢＡＤＮは、２−ターシャリー−ブチル−９，１０−ジ（２−ナフチル）アントラセンであり、以下の構造を有している。

TBADN is 2-tertiary-butyl-9,10-di (2-naphthyl) anthracene and has the following structure.

ＴＢＰは、２，５，８，１１−テトラ−ターシャリー−ブチルペリレンであり、以下の構造を有している。

TBP is 2,5,8,11-tetra-tertiary-butylperylene and has the following structure.

Ａｌｑ_３は、トリス−（８−キノリナト）アルミニウム（III）であり、以下の構造を有している。

Alq ₃ is tris- (8-quinolinato) aluminum (III) and has the following structure.

In the present embodiment, the film thickness of each layer is designed by setting the center wavelength λ of the wavelength range of white light to be extracted to 510 nm. Table 1 shows values of λ ₁ , λ ₂ , L ₁ , L ₂ , and L ₃ in this example. Table 2 shows the refractive index and extinction coefficient of each layer used to calculate them.

(Example 2)
In Example 1, an organic EL element was produced in the same manner as in Example 1 except that the thickness of the buffer layer 6b was changed from 350 nm to 180 nm. Table 1 shows values of λ ₁ , λ ₂ , L ₁ , L ₂ , and L ₃ in this example.

(Comparative Example 1)
In Example 1, the thickness of the orange light emitting layer 4c is changed from 30 nm to 20 nm, the thickness of the blue light emitting layer 4d is changed from 30 nm to 45 nm, and the thickness of the buffer layer 6b for optical adjustment is changed from 350 nm to 320 nm. The organic EL element was fabricated in the same manner as in Example 1 except that the film thickness of the third electrode 6c for optical adjustment was changed from 110 nm to 70 nm.

Table 1 shows values of λ ₁ , λ ₂ , L ₁ , L ₂ , and L ₃ in this comparative example.

(Comparative Example 2)
In Example 1, the thickness of the hole transport layer 4b was changed from 5 nm to 105 nm, and an organic EL device was produced in the same manner as in Example 1 except that. Table 1 shows values of λ ₁ , λ ₂ , L ₁ , L ₂ , and L ₃ in this comparative example.

比較例１においては、光学距離Ｌ_３が本発明の範囲外となっており、比較例２においては、光学距離Ｌ_１及びＬ_２が本発明の範囲外となっている。

In Comparative Example 1, the optical distance L ₃ has become out of the range of the present invention, in Comparative Example 2, the optical distance L ₁ and L ₂ are out of the range of the present invention.

  FIG. 4 is a diagram illustrating a simulation result of the extraction efficiency in the visible range according to the first embodiment. In Example 1, the center wavelength λ of the wavelength range of white light to be extracted is set to 510 nm, and the extraction efficiency is broad over all wavelengths that do not cause interference in the first interference. In the second interference, the extraction efficiency of the green region near 510 nm is large, and in the third interference, the extraction efficiency of the green region near 510 nm is small. It can be seen that the total extraction efficiency is affected by these three interferences, and as a result, the extraction efficiency is substantially uniform over a wide range of the visible range.

  FIG. 5 is a diagram showing emission spectra at viewing angles of 0 °, 30 °, and 60 ° in the element of Example 1. As can be seen from FIG. 5, almost no change in the emission color due to the viewing angle occurs, and white light emission with suppressed color shift due to the viewing angle is obtained.

  FIG. 6 is a diagram showing emission spectra at a viewing angle of 0 °, 30 °, and 60 ° in the element of Example 2. Also in Example 2, white light emission with suppressed color shift at the viewing angle was obtained. ing.

Figure 7 shows a simulation result of the extraction efficiency in the visible region of Comparative Example 1, Comparative Example 1, since the optical distance L ₃ is out of the range of the present invention, the third interference green area It can be seen that there is no weakening interference.

  FIG. 8 is a diagram showing emission spectra at viewing angles of 0 °, 30 °, and 60 ° in the element of Comparative Example 1. As shown in FIG. 8, although white light emission is obtained, it can be seen that the color shift due to the viewing angle is large.

  FIG. 9 is a diagram showing emission spectra at a viewing angle of 0 °, 30 °, and 60 ° in the element of Comparative Example 2. As shown in FIG. 9, only blue emission is seen and white emission is not obtained. I understand.

As described above, by setting the optical distances L ₁ , L ₂ and L ₃ according to the present invention, it is possible to obtain almost uniform extraction efficiency in a wide range of visible light, and to suppress color shift due to viewing angle. I understand.

  FIG. 10 is a cross-sectional view showing an organic EL display device using the organic EL element of the embodiment according to the present invention. In this organic EL display device, light emission in each pixel is driven using a TFT as an active element. A diode or the like can also be used as the active element.

Referring to FIG. 10, a laminated film 21 is provided on a substrate 1 made of a transparent substrate such as glass. The laminated film 21 is made of, for example, SiO ₂ and SiN _x . A channel region 11 made of a polysilicon layer is formed on the laminated film 21. A drain electrode 12 and a source electrode 14 are formed on the channel region 11, and a gate electrode 13 is provided between the drain electrode 12 and the source electrode 14. A gate oxide film 22 is provided between the gate electrode 13 and the channel region 11. Gate oxide film 22 is formed, for example, from SiN _x and SiO _2.

A first interlayer insulating film 23 is formed on the gate oxide film 22, and a second interlayer insulating film 24 is formed on the first interlayer insulating film 23. The first interlayer insulating film 23 is made of, for example, SiO ₂ and SiN _x , and the second interlayer insulating film 24 is made of, for example, SiN _x .

  A planarization film 25 is formed on the second interlayer insulating film 24. The planarizing film 25 is made of, for example, an acrylic resin. A reflective layer 2 made of Al or the like is formed on the region of the pixel light emitting unit 30 of the planarizing film 25. A first electrode 3 made of ITO or the like is formed on the reflective layer 2. The first electrode 3 is connected to the drain electrode 12 through a through hole formed in the planarizing film 25. A pixel separation film 26 made of acrylic resin or the like is formed in a region other than the pixel light emitting unit 30 on the first electrode 3. An organic layer 4 including a light emitting layer is formed on the first electrode 3 and the pixel separation film 26 in the pixel light emitting unit 30.

  A second electrode 5 is formed on the organic layer 4, and a buffer layer 6 b and a third electrode 6 c are formed on the second electrode 5. The optical adjustment layer of the present invention is constituted by the buffer layer 6b and the third electrode 6c. The third electrode 6 c is provided so as to be connected to the second electrode 5 in the peripheral portion other than the pixel light emitting unit 30, and serves as an auxiliary electrode that suppresses an increase in resistance due to the second electrode 5.

  An outer layer 7 made of acrylic resin or the like is formed on the third electrode 6c.

  A transparent sealing substrate 28 made of glass or the like is provided on the outer layer 7 via an adhesive layer 27. A color filter layer 29 is provided in the region of the pixel light emitting unit 30 on the element side of the sealing substrate 28.

In the organic EL display device shown in FIG. 10 configured as described above, light emitted from the light emission position 4 a of the organic layer 4 passes through the color filter layer 29 and is emitted to the side opposite to the substrate 1. The light emitted from the light emitting position 4a is reflected on the reflective surface of the reflective layer 2, the interface between the second electrode 5 and the organic layer 4, and the interface between the third electrode 6c and the external layer 7. In the present invention, as described above, the first interference is set to the optical distance L ₁ that does not cause interference, and the second interference is set to be the optical distance L ₂ that enhances light emission desired to be extracted by the interference. and, for the third interference, it is set to have an optical distance L ₃ destructive luminescence to be extracted by the interference. Thereby, substantially uniform extraction efficiency can be obtained in a wide visible range, and color shift due to viewing angle can be suppressed.

The typical sectional view showing an example of the organic EL element of the present invention. The typical sectional view for explaining the 1st interference in the present invention, the 2nd interference, and the 3rd interference. The typical sectional view showing the organic EL element of one example according to the present invention. The figure which shows the simulation result of the taking-out efficiency of the organic EL element of Example 1. FIG. The figure which shows the change of the emission spectrum by the viewing angle of the organic EL element of Example 1. FIG. The figure which shows the change of the emission spectrum by the viewing angle of the organic EL element of Example 2. FIG. The figure which shows the simulation result of the taking-out efficiency of the organic EL element of the comparative example 1. The figure which shows the change of the emission spectrum by the viewing angle of the organic EL element of the comparative example 1. The figure which shows the change of the emission spectrum by the viewing angle of the organic EL element of the comparative example 2. FIG. Sectional drawing which shows the organic electroluminescent display apparatus using the organic electroluminescent element of the Example according to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Reflection layer 2a ... Reflection surface of reflection layer 3 ... 1st electrode 4 ... Organic layer 4a ... Light emission position 5 ... 2nd electrode 6 ... Optical adjustment layer 31 ... 1st interference 32 ... 2nd interference 33 ... third interference

Claims (9)

An organic electroluminescence device in which a reflective layer, a first electrode, an organic layer including a light emitting layer, a second electrode, and an optical adjustment layer are sequentially laminated on a substrate, and light is extracted from the optical adjustment layer side,
The optical distance from the light emitting position in the light emitting layer to the reflective surface of the reflective layer is L ₁ , the optical distance from the reflective surface of the reflective layer to the lower end of the second electrode is L ₂ , and the reflective surface of the reflective layer is When the optical distance to the upper end of the optical adjustment layer is L ₃ and the center wavelength of the wavelength range of light emission to be extracted is λ,
L ₁ is set to an optical distance at which light of wavelength λ does not cause interference, L ₂ is set to an optical distance at which light of wavelength λ is strengthened by interference, and L ₃ is an optical distance at which light of wavelength λ is weakened by interference. An organic electroluminescence device, characterized in that   The optical adjustment layer is composed of an organic buffer layer provided on the second electrode, and a third electrode made of an inorganic transparent electrode provided on the organic buffer layer, and the second electrode and the The organic electroluminescence element according to claim 1, wherein the third electrode functions as an auxiliary electrode by grounding the third electrode at a peripheral portion other than the pixel light emitting portion.   The organic electroluminescence device according to claim 1, wherein the optical adjustment layer is composed of an organic buffer layer.   The organic electroluminescence element according to claim 1, wherein the optical adjustment layer is composed of an inorganic transparent electrode.   An outer layer having a refractive index different by 0.2 or more from the refractive index of the upper end portion of the optical adjustment layer and having a film thickness of 1 μm or more is provided outside the optical adjustment layer. The organic electroluminescent element according to any one of claims 1 to 4.   The organic electroluminescent element according to claim 1, wherein the light emitting layer emits white light. L _1, L ₂ and L ₃ An organic electroluminescence device according to claim 6, characterized by satisfying the following equation.
L ₁ = 75 to 125 [nm]
_{L 2 = (m + (φ} 1 + φ 2) / 2π) λ 1/2 [nm]
_{L 3 = (n + 1/2 +} (φ 1 + φ 3) / 2π) λ 2/2 [nm]
500 nm <λ <550 nm
λ -15 <λ ₁ <λ + 15
λ -15 <λ ₂ <λ + 15
L ₁ : Optical distance from the light emitting position to the reflective layer (the light emitting position is the interface between the first light emitting layer made of a hole transporting material and the second light emitting layer made of an electron transporting material)
L ₂ : Optical distance from the reflective layer to the lower end of the second electrode
L ₃ : Optical distance from the reflective layer to the upper end of the optical adjustment layer λ: Center wavelength φ ₁ of the white light emission wavelength region to be extracted: Phase change when light is reflected by the reflective layer. It is given by
Refractive index of the first electrode: n _a, the refractive index of the reflective _{layer: n m, φ 1 = tan} -1 {2 n a when the extinction coefficient k _m of the reflection layer ^{_{k m / (n a 2 -}} n m ² - k _m ^2)}
Where 2 n _a k _m / (n _a ² -n _m ² -k _m ² )> 0, 0 <φ ₁ <π / 2
2 n _a k _m / (n _a ² -n _m ² - k _m ²⁾ <When _{0, π / 2 <φ 1} <π
φ ₂ : Phase change when light is reflected at the lower end of the second electrode. It is given by
When the refractive index of the organic layer is n _o , the refractive index of the second electrode is n _c , and the extinction coefficient k _c of the second electrode is φ ₂ = tan ^-1 (2 n _o k _c / (n _e ² -n _m ² - k _m ^2)}
Where 2 n _o k _c / (n _e ² -n _c ² -k _c ² )> 0, 0 <φ ₁ <π / 2
2 n _o k _c / (n _e ² -n _c ² -k _c ² ) <0, π / 2 <φ ₁ <π
φ ₃ : Phase change when light is reflected at the upper end of the optical adjustment layer. 0 when the refractive index of the optical adjustment layer is larger than the outer layer, and π when it is smaller.
m, n: natural number   The organic electroluminescent element according to claim 1, wherein the light emitting layer emits a single color. L _{1, L 2,} L ₃ An organic electroluminescence device according to claim 8, characterized by satisfying the following equation.
L ₁ = 75 to 125 [nm]
_{L 2 = (m + (φ} 1 + φ 2) / 2π) λ 1/2 [nm]
_{L 3 = (n + 1/2 +} (φ 1 + φ 3) / 2π) λ 2/2 [nm]
λ _f -20 <λ <λ _f + 50
λ -15 <λ ₁ <λ + 15
λ -15 <λ ₂ <λ + 15
L ₁ : Optical distance from the light emitting position to the reflective layer (When the light emitting layer is made of a hole transporting material, it becomes the interface with the electron transporting layer, and the light emitting layer is made of an electron transporting material. Is the interface with the hole transport layer)
L ₂ : Optical distance from the reflective layer to the lower end of the second electrode
L ₃ : Optical distance from the reflective layer to the upper end of the optical adjustment layer λ: Center wavelength of monochromatic light to be extracted λ _f : Fluorescence peak wavelength of monochromatic light to be extracted φ ₁ : Phase when light is reflected by the reflective layer change. It is given by
Refractive index of the first electrode: n _a, the refractive index of the reflective _{layer: n m, φ 1 = tan} -1 {2 n a when the extinction coefficient k _m of the reflection layer ^{_{k m / (n a 2 -}} n m ² - k _m ^2)}
Where 2 n _a k _m / (n _a ² -n _m ² -k _m ² )> 0, 0 <φ ₁ <π / 2
2 n _a k _m / (n _a ² -n _m ² - k _m ²⁾ <When _{0, π / 2 <φ 1} <π
φ ₂ : Phase change when light is reflected at the lower end of the second electrode. It is given by
When the refractive index of the organic layer is n _o , the refractive index of the second electrode is n _c , and the extinction coefficient k _c of the second electrode is φ ₂ = tan ^-1 (2 n _o k _c / (n _e ² -n _m ² - k _m ^2)}
Where 2 n _o k _c / (n _e ² -n _c ² -k _c ² )> 0, 0 <φ ₁ <π / 2
2 n _o k _c / (n _e ² -n _c ² -k _c ² ) <0, π / 2 <φ ₁ <π
φ ₃ : Phase change when light is reflected at the upper end of the optical adjustment layer. 0 when the refractive index of the optical adjustment layer is larger than the outer layer, and π when it is smaller.
m, n: natural number

Images