JP2012256503A - Light-emitting device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the light extraction efficiency from lowering, in a top emission light-emitting device having a resonance structure and using a white light-emitting element of tandem structure.SOLUTION: In a red light-emitting element U1 and a green light-emitting element U2, a second luminous layer 23 provided at a position closer to a counter electrode 30 than a charge separation layer 20 is used, and a pixel electrode 13 is provided between a first luminous layer 16 provided at a position closer to a reflective layer 11 than a charge separation layer 20 and the reflective layer 11. In a blue light-emitting element U3, a first luminous portion provided at a position closer to the reflective layer 10 than the charge separation layer 20 is used, and the reflective layer 10 also serves as the pixel electrode.

Description

  The present invention relates to a light emitting device using various light emitting elements and an electronic apparatus including the light emitting device.

  In recent years, a top emission type light-emitting device in which an organic EL (electroluminescence) element is formed as a light-emitting element on a substrate and light emitted from the light-emitting element is extracted on the side opposite to the substrate has been widely used as a display device for electronic devices. In the top emission method, a reflective layer is formed between one of the first electrodes (for example, an anode) formed on the substrate side and the substrate, with the light emitting element interposed therebetween, and the other second electrode (for example, a cathode) that sandwiches the light emitting element. This is a method of taking out light from the side, and is a method with high light utilization efficiency.

In a top emission type light emitting device, a technology is disclosed in which a white organic EL element is used to resonate light having a predetermined wavelength between the second electrode and the reflective layer, thereby increasing light extraction efficiency ( For example, Non-Patent Document 1). In this technique, the peak wavelength in the resonance structure is λ, the optical distance from the reflective layer to the second electrode is D, the phase shift in reflection at the reflective layer is φ _L , and the phase shift in reflection at the second electrode is An optical structure that satisfies the following formula is proposed, where φ _{U is} an integer m.
D = {(2πm + φ _L + φ _U ) / 4π} λ (1)

  In addition to having the above-mentioned resonance structure, a red organic EL element, a green organic EL element, and a blue organic EL element are stacked via an intermediate layer to form a white light emitting element having a tandem structure, and a full color using a color filter. A light emitting device that realizes the above has been proposed.

  Furthermore, the light-emitting device has such a tandem white light-emitting element, and the optical path lengths of the two organic EL elements are the same among the red organic EL element, the green organic EL element, and the blue organic EL element. In addition, a light emitting device with a simplified manufacturing process has been proposed (Patent Document 1).

  This light emitting device has a resonance structure in which the value of m is 2 or more in the equation (1) so that a plurality of peaks appear at the same optical distance. In the case of adopting the tandem structure, it is preferable to secure a film thickness of 200 or more because the characteristics deteriorate when the film thickness of the light emitting element is reduced. In addition, if the optical distance is changed so that a peak appears for each color, the number of manufacturing steps increases. Therefore, in the case of adopting the tandem structure, in order to prevent the deterioration of the characteristics and simplify the manufacturing process, as described above, the resonance structure in which the value of m is 2 or more in the equation (1) is provided. It can be said that it is preferable.

JP 2006-30250 A

  However, as the value of m in the equation (1) increases, the emission spectrum of the peak wavelength obtained by the resonance structure becomes narrower. As a result, the light energy is reduced, so that the light extraction efficiency is lowered and the power consumption is increased.

  Against this backdrop, the present invention prevents a decrease in light extraction efficiency in a top emission type light emitting device having a resonance structure that satisfies the above formula (1) and using a tandem white light emitting element. The purpose is to solve the problem of suppressing the increase in power consumption.

  In order to solve the above problems, a light emitting device according to the present invention includes a plurality of pixels, and each of the plurality of pixels includes a reflective layer, a light transmission semi-reflective layer, and the reflective layer. A plurality of light emitting portions formed between the light transmitting and semi-reflective layer, at least one charge separation layer formed between the light emitting portions, and a counter electrode. Among these, for a pixel that extracts light emitted from the light emitting portion provided at a position closer to the reflective layer than the charge separation layer, the reflective layer also serves as the pixel electrode, and among the plurality of pixels, A pixel electrode is provided between the charge separation layer and the reflective layer for a pixel that extracts light emitted from the light emitting unit provided at a position closer to the light transmissive semi-reflective layer than the charge separation layer. And among the plurality of pixels, the charge separation layer For pixels to extract light emitted from the the remote said provided at a position closer to the reflective layer emitting portion, wherein the reflective layer is characterized in that functions as a pixel electrode.

  In the present invention, a plurality of light emitting portions formed between the reflective layer and the light transmissive semi-reflective layer, at least one charge separation layer formed between the plurality of light emitting portions, and a counter electrode are provided. Since it has the structure provided, it has a structure that is substantially common to the pixels of each color, and the manufacturing process can be simplified. In addition, with respect to a pixel that extracts light emitted from the light emitting unit provided at a position closer to the light transmission semi-reflective layer than the charge separation layer, light emission provided at a position closer to the reflection layer than the charge separation layer. The pixel electrode is provided between the portion and the reflective layer. Therefore, an optical structure with high light extraction efficiency can be realized by adjusting the layer thickness of the pixel electrode. In addition, for a pixel that extracts light emitted from a light emitting portion provided at a position closer to the reflective layer than the charge separation layer, the reflective layer also serves as the pixel electrode. Therefore, the interlayer distance from the reflective layer serving also as the pixel electrode to the light emitting portion provided at a position close to the reflective layer can be shortened, and an optical structure with high light extraction efficiency can be realized. As a result, power consumption can be reduced.

In the light emitting device according to the present invention, the optical distance between the reflective layer and the light transmissive semi-reflective layer is D, the phase shift in reflection at the reflective layer is φ _L , and the phase shift in reflection at the light transmissive semi-reflective layer Is φ _U , the peak wavelength is λ, and m ₁ is an integer, the following formula (2) for any color pixel: D = {(2πm ₁ + φ _L + φ _U ) / 4π} λ (2 )
In this case, m ₁ ≧ 1 may be satisfied.

According to the present invention, a plurality of light emitting portions formed between the reflective layer and the light transmissive semi-reflective layer, at least one charge separation layer formed between the plurality of light emitting portions, a counter electrode, In the above equation (2), m ₁ ≧ 1 is satisfied, so that the emission spectrum has a wide width, and the light extraction efficiency can be increased by increasing the light energy. it can. As a result, power consumption can be reduced.

As a light-emitting device according to the present invention, for a pixel that extracts light emitted from the light-emitting portion provided at a position closer to the reflective layer than the charge separation layer, the reflective layer that also serves as the pixel electrode; When the optical distance between the light emitting portion provided at a position close to the reflective layer is L, the phase shift at the interface of the reflective layer is φ, and the peak wavelength is λ, the following equation (3):
2L = (φ / 2π) λ (3)
You may make it satisfy | fill.

  According to the present invention, a plurality of light emitting portions formed between the reflective layer and the light transmissive semi-reflective layer, at least one charge separation layer formed between the plurality of light emitting portions, a counter electrode, In addition, since the above formula (3) is satisfied, the positional relationship between the reflective layer and the light emitting portion is a positional relationship that increases the light extraction efficiency, and the light extraction efficiency is increased. As a result, power consumption can be reduced.

  As a light-emitting device according to the present invention, for a pixel that extracts light emitted from the light-emitting unit provided at a position closer to the reflective layer than the charge separation layer, the reflective layer that also serves as the pixel electrode; A metal oxide layer may be formed between the light emitting portion provided at a position close to the reflective layer. According to the present invention, since the metal oxide layer is formed between the reflective layer and the light emitting portion provided at a position close to the reflective layer, the reflective layer has a function as a pixel electrode. Is possible.

  In the light emitting device according to the present invention, the reflective layer may be formed of Al, Ag, or an alloy containing these as a main component. According to the present invention, the reflectance in the reflective layer is high, and high light extraction efficiency can be obtained.

  As the light-emitting device according to the present invention, a color filter may be provided on the side from which light is emitted from the counter electrode. In the light emitting device according to the present invention, the light extraction efficiency can be improved and the power consumption can be reduced while realizing a simple structure in which a color filter is provided on the upper layer of the electrode.

  An electronic apparatus according to the present invention includes the light emitting device. Since the electronic apparatus according to the present invention includes the light emitting device, power consumption can be reduced.

It is typical sectional drawing which shows the outline | summary of the light-emitting device which concerns on one Embodiment of this invention. Materials used in the hole transport layer, the first light emitting layer, the electron transport layer, the charge generation layer, the charge separation layer, the red organic EL element, the green organic EL element, the second light emitting layer, and the hole block in FIG. FIG. The optical distance between the reflective layer and the counter electrode is D, the phase shift in reflection at the reflective layer is φ _L , the phase shift in reflection at the counter electrode is φ _U , the peak wavelength of the standing wave is λ, and an integer is Assuming m, when the optical structure is represented by D = {(2πm ₁ + φ _L + φ _U ) / 4π} λ, the relationship between the integer m ₁ and the film thickness from the reflective layer to the counter electrode with respect to the peak wavelength of each color FIG. It is a figure which shows the simulation model for calculating the relationship between a light emission position and light extraction efficiency. It is a figure which shows the relationship between the wavelength, the distance from a reflective layer to a light emitting layer, and light extraction efficiency in case the interlayer distance of a reflective layer and a counter electrode is 220 nm. The optical distance between the reflective layer and the counter electrode is D, the phase shift in reflection at the reflective layer is φ _L , the phase shift in reflection at the counter electrode is φ _U , the peak wavelength of the standing wave is λ, and an integer is FIG. 5 is a diagram showing the relationship between the value of the integer m ₁ and the light extraction efficiency when the peak wavelength is 490 nm when the optical structure is represented by D = {(2πm ₁ + φ _L + φ _U ) / 4π} λ. It is. It is a figure which shows the transmittance | permeability of the color filter used for the panel simulation of this embodiment. It is the figure which showed the material and film thickness of each layer of Example 1 and Example 2 of this invention. It is the figure which showed the material and film thickness of each layer of the comparative example 1 and the comparative example 2. FIG. It is the figure which showed the color filter and each element structure of the comparative example 1, the comparative example 2, Example 1, and Example 2. FIG. It is the figure which showed the power consumption of the comparative example 1, the comparative example 2, Example 1, and Example 2. FIG. It is the figure which showed the NTSC area ratio of the comparative example 1, the comparative example 2, Example 1, and Example 2. FIG. It is a figure which shows the light extraction efficiency of the red area | region and blue area | region of a comparative example and an Example. It is a figure which shows the light extraction efficiency of the green area | region of a comparative example and an Example. It is a perspective view which shows the structure of the mobile personal computer which employ | adopted the light-emitting device which concerns on embodiment of FIG. 1 as a display apparatus. It is a perspective view which shows the structure of the mobile telephone which employ | adopted the light-emitting device which concerns on embodiment of FIG. 1 as a display apparatus. It is a perspective view which shows the structure of the portable information terminal which employ | adopted the light-emitting device which concerns on embodiment of FIG. 1 as a display apparatus.

Hereinafter, various embodiments according to the present invention will be described with reference to the accompanying drawings. In the drawings, the ratio of dimensions of each part is appropriately changed from the actual one.
<A: Structure of light emitting device>
FIG. 1 is a schematic cross-sectional view showing an outline of a light emitting device E1 according to an embodiment of the present invention. The light-emitting device E1 has a configuration in which a plurality of red light-emitting elements U1, green light-emitting elements U2, and blue light-emitting elements U3 are arranged on the surface of the first substrate. In FIG. Are illustrated one by one.
The light emitting device E1 of the present embodiment is a top emission type, and the light generated by the red light emitting element U1, the green light emitting element U2, and the blue light emitting element U3 is opposite to the first substrate, that is, from the bottom of FIG. Proceed upward. Although not shown in FIG. 1, an opaque plate material such as a ceramic or metal sheet can be used for the first substrate in addition to a light-transmitting plate material such as glass.
In addition, although wiring for supplying power to the red light emitting element U1, the green light emitting element U2, and the blue light emitting element U3 to emit light is arranged on the first substrate, illustration of the wiring is omitted. Further, although a circuit for supplying power to the red light emitting element U1, the green light emitting element U2, and the blue light emitting element U3 is disposed on the first substrate, illustration of the circuit is omitted.

  The red light emitting element U1, the green light emitting element U2, and the blue light emitting element U3 are the reflective layer 11 or the reflective layer / pixel electrode 10 formed on the first substrate, the pixel electrode 14 (anode), and the light extraction side translucent. A counter electrode 30 (cathode) as a reflective layer, a first light emitting layer 16 and a second light emitting layer 23 are provided. Details will be described below.

  In the red light emitting element U1 and the green light emitting element U2, as shown in FIG. 1, the reflective layer 11 is formed on the first substrate. The reflective layer 11 is formed of a material having light reflectivity. As this type of material, for example, a single metal such as Al (aluminum) or Ag (silver), or an alloy containing Al or Ag as a main component is preferably employed. In the present embodiment, the reflective layers 11 of the red light emitting element U1 and the green light emitting element U2 are made of Al.

  On the other hand, in the blue light emitting element U3, as shown in FIG. 1, the reflective layer / pixel electrode 10 is formed on the first substrate. The reflective layer / pixel electrode 10 functions as a reflective layer and also functions as a pixel electrode (anode). The reflective layer / pixel electrode 10 is made of a material in which MoOx (molybdenum oxide) and Al (aluminum) are laminated, or a material in which a-ITO (amorphous ITO) and Ag (silver) are laminated. In the present embodiment, the reflective layer / pixel electrode 10 is formed of Al, and a hole injection layer 14 made of MoOx is laminated on the reflective layer / pixel electrode 10 as will be described later.

A transparent layer 12 is formed on the reflective layer 11 of the red light emitting element U1 and the green light emitting element U2, and a pixel electrode (anode) 13 is formed on the transparent layer 12. As described above, in the blue light emitting element U3, since the reflective layer / pixel electrode 10 has a function as a pixel electrode (anode), the blue light emitting element U3 includes the transparent layer 12 and the pixel electrode (anode) 13. Is not formed.
The transparent layer 12 of the red light emitting element U1 and the green light emitting element U2 is formed of SiO ₂ or SiN. In the present embodiment, the transparent layer 12 is formed of SiN.
A pixel electrode (anode) 13 is formed on the transparent layer 12 of the red light emitting element U1 and the green light emitting element U2. In the present embodiment, the pixel electrodes 13 of the red light emitting element U1 and the green light emitting element U2 are formed from an ITO transparent conductive film.
In the present embodiment, the distance between the reflective layer 11 of the red light emitting element U1 and the green light emitting element U2 and the counter electrode 30 is adjusted by the film thickness of the pixel electrode 13. In the present embodiment, the film thickness of the pixel electrode 13 of the red light emitting element U1 is set to be larger than the film thickness of the pixel electrode 13 of the green light emitting element U2. Details will be described later.

A hole injection layer 14 is formed on the pixel electrode 13 of the red light emitting element U1 and the green light emitting element U2 and on the reflective layer / pixel electrode 10 of the blue light emitting element U3. In the present embodiment, the hole injection layer 14 is made of MoOx (molybdenum oxide).
In particular, the hole injection layer 14 made of MoOx (molybdenum oxide) is used as a reflective layer and pixel in order to cause the reflective layer and pixel electrode 10 of the blue light emitting element U3 to function as a reflective layer and as a pixel electrode. It is preferable to laminate on the electrode 10.

  The layer structure above the hole injection layer 14 and the materials used for each layer are common to the red light emitting element U1, the green light emitting element U2, and the blue light emitting element U3.

  A hole transport layer (HTL) 15 is formed in the hole injection layer 14. As shown in FIG. 2, α-NPD ((N- (1-naphthyl) -N-phenyl) benzidine) is used for the hole transport layer 15. In FIG. 2, the hole transport layer 15 is indicated as “HTL1”.

  A first light emitting layer 16 is formed on the hole transport layer 15. The first light emitting layer 16 is formed of a fluorescent B unit. The fluorescent B unit is formed of an organic EL material that emits light by combining holes and electrons. In this embodiment, the organic EL material is a low molecular material, and the blue host material (B-Host) is 10,10′-di (biphenyl-2-yl) -9 as shown in FIG. 9'-bianthracene is used. As the blue dopant material (B-Dopant), 4,4′-bis [2- {4- (N, N-diphenylamino) phenyl} vinyl] biphenyl is used as shown in FIG.

A charge separation layer (CGL: Carrier Generation Layer) 20 is formed on the first light emitting layer 16. The charge separation layer 20 includes an electron transport layer (ETL) 17, a charge generation layer 18, and a hole transport layer (HTL) 19.
As shown in FIG. 2, Alq3 (tris (8-quinolinolato) aluminum) is used for the electron transport layer 17. In FIG. 2, the electron transport layer 17 is indicated as “ETL1”.
For the charge generation layer 18, LG101 (hexaazatriphenylenehexacarbonitrile) is used as shown in FIG.
As shown in FIG. 2, α-NPD ((N- (1-naphthyl) -N-phenyl) benzidine) is used for the hole transport layer 19. In FIG. 2, the hole transport layer 19 is indicated as “HTL2”.

A second light emitting layer 23 is formed on the charge separation layer 20. In the present embodiment, a phosphorescent RG unit is used as the second light emitting layer. The phosphorescent RG unit 23 is formed of an organic EL material that emits light by combining holes and electrons. In the present embodiment, the organic EL material is a low molecular material, and includes a red organic EL element 21 and a green organic EL element 22. As shown in FIG. 2, the red organic EL element 21 includes a red host material (TCTA: 1,4,7-triazacyclononane-N, N ′, N ″ -triacetate) and a red dopant (Ir ( MDQ) ₂ (acac): consists of bis (2-methyl-dibenzo [f.h] quinoxaline) (acetylacetonate) iridium (III)).
As shown in FIG. 2, the green organic EL element 22 includes a green host material (TPBi: 1,3,5-tris (N-phenylbenzimidazol-2-yl) benzene) and a green dopant material ( Ir (ppy) ₃ : Tris (2-phenylpyridinate) iridium (III)).

  On the second light emitting layer 23, a hole block layer (HBL) 24 is formed. For the hole blocking layer 24, TPBi (1,3,5-tris (N-phenylbenzimidazol-2-yl) benzene) is used.

  An electron transport layer 25 is formed on the hole block layer 24. As shown in FIG. 2, Alq3 (tris (8-quinolinolato) aluminum) is used for the electron transport layer 25. In FIG. 2, the electron transport layer 25 is shown as “ETL2”.

  On the electron transport layer 25, a counter electrode (cathode) 30 is formed as a light extraction side translucent reflective layer. In the present embodiment, the counter electrode 30 is made of MgAg (magnesium silver alloy).

A sealing layer 31 is formed on the counter electrode 30. For the sealing layer 31, a transparent resin material, for example, SiO ₂ or SiN is used. In the present embodiment, the sealing layer 31 is made of SiN. A second substrate is disposed on the sealing layer 31. Although illustration of the 2nd board | substrate is abbreviate | omitted in FIG. 1, the 2nd board | substrate is formed with the material which has light transmittances, such as glass. A color filter and a light shielding film (not shown) are formed on the surface of the second substrate facing the first substrate. The light shielding film is a film body of a light shielding body in which an opening is formed to face each light emitting element U1, U2, U3. A color filter is formed in the opening. The second substrate on which the color filter and the light shielding film are formed is bonded to the first substrate through the sealing layer 31.

  In the present embodiment, a red color filter that selectively transmits red light is formed in the opening corresponding to the red light emitting element U1, and the blue light is selectively transmitted in the opening corresponding to the blue light emitting element U2. A blue color filter is formed, and a green color filter that selectively transmits green light is formed in the opening corresponding to the green light emitting element U3. The above is the structure of the light-emitting device of this embodiment.

<B: Optical structure>
Next, the optical structure in the light emitting device E1 of the present embodiment will be described. The light emitting device E1 in this embodiment includes a counter electrode 30 as a light extraction side translucent reflective layer from the reflective layer 11 of the red light emitting element U1 and the green light emitting element U2 and the reflective layer / pixel electrode 10 of the blue light emitting element U3. By adopting a resonance structure in which a standing wave is generated in the counter electrode 30 from the reflective layer 11 and the reflective layer / pixel electrode 10 by setting the optical distance to a predetermined value.

Specifically, the optical distance between the reflective layer 11 and the reflective layer / pixel electrode 10 and the counter electrode 30 is D, the phase shift in reflection at the reflective layer 11 and the reflective layer / pixel electrode 10 is φ _L , When the phase shift in reflection at the electrode 30 is φ _U , the peak wavelength of the standing wave is λ, and the integer is m ₁ , the structure satisfies the following formula.
D = {(2πm ₁ + φ _L + φ _U ) / 4π} λ (4)

In the above formula (4), the refractive index n of the reflective layer 11 between the Al reflective layer 11 and the reflective layer / pixel electrode 10 and the MgAg counter electrode 30 is 1.8, and the reflection layer 11 and the reflective layer / pixel electrode 10 FIG. 3 is a diagram in which the peak wavelength is plotted assuming the optical distance D between the counter electrodes 30, the integer m ₁ , and the colors red, green, and blue.

As shown in the area surrounded by an ellipse in FIG. 3, the red peak wavelength when m ₁ = 2 in the above equation (4) and the blue peak wavelength when m ₁ = 3 in the above equation (3) are It can be seen that a peak is obtained at the same distance between Al and MgAg.

Further, between the reflective layer 11 and the reflective layer / pixel electrode 10 and the counter electrode 30, a place where the light extraction efficiency is high at a place of several minutes obtained by adding ₁ to the integer m ₁ used in the equation (4). Exists. This can be calculated from the interference effect from the reflection interface to the light emission position, and is characterized by the following equation (5).
L = {(2πm ₂ + φ) / 4π} λ (5)
Here, L is the optical distance from the reflective layer to the light emitting layer (where D> L), φ is the phase shift at the interface of the reflective layer, λ is the peak wavelength, and m ₂ is an integer.

  For reference, the result of calculating the relationship between the light emission position and the light extraction efficiency using a simulation model as shown in FIG. 4 will be described. As shown in FIG. 4, in this simulation model, the interlayer distance from the reflective layer (Al) to the counter electrode (MgAg) is 220 nm, and the refractive index of the intermediate layer from the reflective layer (Al) to the light emitting layer is 1.8. In addition, the light extraction efficiency was calculated by setting the refractive index of the intermediate layer from the light emitting layer to the counter electrode (MgAg) as 1.8, and the interlayer distance from the reflective layer (Al) to the light emitting layer as a variable x.

  FIG. 5 shows a calculation result of the light extraction efficiency based on the simulation model of FIG. As shown in FIG. 5, it can be seen that there are two places where the light extraction efficiency is 1.6 to 1.8, that is, two places where the light extraction efficiency is the highest. That is, it can be seen that there are two light emitting positions satisfying the above formula (5).

The peak wavelength obtained when the interlayer distance from the reflective layer (Al) to the counter electrode (MgAg) is 220 nm corresponds to the blue peak wavelength (460 nm) when m ₁ = 1 in FIG.

When N = 1.8, the optical constant of Al = 460 nm is n ₂ = 0.5, and the extinction coefficient is k ₂ = 4.5, the phase shift is given by the following equation.
φ = tan ⁻¹ {2Nk ₂ / (N ² −n ₂ ² −k ₂ ² )}
Substituting the optical constant into this results in φ≈2.4 [rad]. Substituting this into equation (5) gives L as equation (6).
L = {(2πm ₂ +2.4) / 4π} * 460
= {(M ₂ /2)+0.19}*460 (6)
If m ₂ = 0 in the above equation (6),
L = 0.19 * 460 = 87.9 nm
Since d = L / N, where d is the distance from the reflective interface to the light emitting point,
d = 87.9 / 1.8≈48.8 nm
Thus, it can be seen that the result agrees with the result shown in FIG.

Therefore, in the present embodiment, in the light emitting device E1 having the tandem structure, the fluorescent B unit is disposed in the first light emitting layer 16 on the side close to the reflective layer / pixel electrode (cathode) 10 of the blue light emitting element U3, and the above (4) In the equation, parameters such as the optical distance D were set so as to obtain an optical structure in the case of m ₁ = 1. In addition, in the blue light emitting element U3, in order to set the interlayer distance between the reflective layer and the first light emitting layer 16 to about 40 nm as described above, the reflective layer / pixel electrode which can be used as the reflective layer and the pixel electrode (cathode). 10 and this reflective layer / pixel electrode 10 was formed of Al.

Next, the position of the light emitting layer that can increase the light extraction efficiency in the tandem light emitting device will be described. A tandem light-emitting device has a structure in which a charge generation layer is disposed between two light-emitting layers. When a resonant structure is used, the light-emitting layer is placed at a position where the light extraction efficiency is high for each color pixel. By arranging, power consumption can be reduced.
When realizing a full-color display, the light-emitting layer is formed to have the same layer thickness for each color pixel, and the optical path length is adjusted by adjusting the layer thickness of the transparent layer or transparent conductive layer formed on the substrate. By doing so, light of a desired peak wavelength is emitted with high light extraction efficiency.
In this case, as a material used for the reflective layer on the substrate side, Al or Ag having a high reflectance in the entire visible light region is often used.

When Al is used as the reflective layer, if the ITO used for the pixel electrode and the Al reflective layer are brought into direct contact with each other, electrocorrosion occurs, so a transparent layer needs to be inserted between the Al reflective layer and the ITO. . Therefore, the distance from the reflective layer to the light emitting layer is increased by the thickness of the transparent layer. For example, when the blue peak wavelength is to be extracted by the optical structure when m ₁ = 1 in the above equation (4), the distance from the reflective layer to the light emitting layer is set to a short interlayer distance of about 40 nm as described above. However, when Al is used for the reflective layer and ITO is used for the pixel electrode, such setting is difficult.

  Although Ag may be used as the reflective layer, Ag is a material that is difficult to etch, and it is difficult to form a transparent conductive film such as ITO on Ag. When the light emitting layer is formed to have the same layer thickness in each color pixel, it is necessary to adjust the optical path length by adjusting the layer thickness of the transparent layer or transparent conductive layer formed on the substrate. However, it is difficult to adjust the interlayer distance by forming a transparent layer or a transparent conductive film on Ag.

In the conventional tandem light emitting device, for this reason, the thickness of each layer is so large that m ₁ = 2 or more in the above equation (4), and the optical distance between the reflective layer and the transflective layer is small. In many cases, a long optical structure was adopted.

However, in the case of the resonance structure having a large value of m ₁ in the above formula (4), the light extraction efficiency is lowered as compared with the resonance structure having a small value of m ₁ . Here, the relationship between the value of m ₁ in the above equation (4) and the light extraction efficiency is shown in FIG. As shown in FIG. 6, the peak height does not change even if the value of m ₁ changes. However, as the value of m ₁ increases, the light extraction efficiency becomes steep and the area becomes smaller. Therefore, it can be seen that the light energy is weak and the light extraction efficiency is reduced.

Therefore, in this embodiment, the pixels of any color are configured to have an optical structure in which the value of m ₁ in the above equation (4) is 1. First, in the blue light emitting element U3, as described above, the reflective layer / pixel electrode 10 that serves as the reflective layer and the pixel electrode is formed of Al, and the interlayer from the reflective layer / pixel electrode 10 to the first light emitting layer 16 is formed. The distance was set to about 40 nm.
Further, in the red light emitting element U1 and the green light emitting element U2, red is formed by using Al as the reflective layer 11, forming the transparent layer 12 and the ITO pixel electrode 13, and adjusting the layer thickness of the ITO pixel electrode 13. Each of the light emitting element U1 and the green light emitting element U2 is configured such that an optimum optical path length is obtained with an optical structure in which the value of m ₁ in the above equation (4) is 1.

<C: Panel simulation>
Next, a panel simulation performed using the light emitting device of this embodiment and the device of the comparative example will be described.
In this simulation, Example 1 and Example 2 having the same configuration as the light emitting device E1 shown in FIG. 1 and Comparative Example 1 and Comparative Example 2 prepared for comparison were used. The comparative example has substantially the same configuration as the light-emitting device E1 shown in FIG. 1, but has an optical structure in which each color pixel has m ₁ = 2 or 3 in the above equation (4).

In this simulation, as shown in FIG. 7, two types of color filters, CF1 which is a thin color filter and CF2 which is a thick color filter, were used. As shown in FIG. 7, CF1, which is a thin color filter, used a color filter having a transmittance of 95% for light of 600 nm or more as a red color filter CF1-R. As the green color filter CF1-G, a color filter having a transmittance of 85 to 90% for light of 520 to 560 nm was used. As the blue color filter CF1-B, a color filter having a transmittance of 80 to 85% for light of 430 to 470 nm was used.
As the thick color filter CF2, a color filter having a transmittance of 90% for light of 600 nm or more is used as the red color filter CF2-R. As the green color filter CF2-G, a color filter having a transmittance of 65 to 70% for light of 520 to 560 nm was used. As the blue color filter CF2-B, a color filter having a transmittance of 60 to 65% for light of 430 to 470 nm was used.

<C-1: Structure of Example 1>
The light-emitting device of Example 1 has substantially the same structure as the light-emitting device E1 shown in FIG. 1, and the light-emitting device shown in FIG. Different from the device E1. The film thickness of each layer is shown in FIG. Al was used for the reflective layer 11 of the red light emitting element U1 and the green light emitting element U2, and the film thickness was 100 nm. Both the red light emitting element U1 and the green light emitting element U2 have a transparent layer 12 and a pixel electrode 14 on the reflective layer 11, and the transparent layer 12 is made of SiN, and the pixel electrode 14 is made of ITO. The layer thickness of the transparent layer 12 is 25 nm for both the red light emitting element U1 and the green light emitting element U2, the pixel electrode 14 of the red light emitting element U1 is set to 20 nm, and the pixel electrode 14 of the green light emitting element U2 is set to 70 nm.
For the blue light emitting element U3, the reflective layer / pixel electrode 10 was made of Al, and the film thickness was 100 nm. A hole injection layer 14 was formed of MoO ₃ on the reflective layer / pixel electrode 10 and the film thickness was 2 nm. The interlayer distance from the reflective layer / pixel electrode 10 to the first light emitting layer 16 was set to 42 nm.
Thick color filters CF2-R, CF2-G, and CF2-B were used as the color filters.
<C-2: Structure of Example 2>
The light emitting device of Example 2 is the same as the light emitting device of Example 1 in the thickness of each layer, and is different from Example 1 in that thin color filters CF1-R, CF1-G, and CF1-B are used as color filters. ing.
<C-3: Structure of Comparative Example 1>
The light emitting device of Comparative Example 1 has substantially the same structure as the light emitting device of Example 1, but differs from Example 1 and Example 2 in that all the pixels include ITO as a pixel electrode and a transparent layer. ing. The light-emitting device of Comparative Example 1 has an optical structure in which the red light-emitting element and the green light-emitting element have an optical structure in which the value of m ₁ in the above formula (4) is 2, and the blue light-emitting element has The optical structure in the case where the value of ₁ is 3 is different from those of Example 1 and Example 2.
The structure and film thickness of each layer are shown in FIG. As shown in FIG. 9, the reflective layers of the red light emitting element and the blue light emitting element were made of Al, and the layer thickness was 150 nm. For the green light emitting element, the reflective layer was made of Al and the layer thickness was 100 nm. The transparent layer was 50 nm in any light emitting element.
ITO pixel electrodes were 200 nm for red and blue light emitting elements and 140 nm for green light emitting elements.
Thick color filters CF2-R, CF2-G, and CF2-B were used as the color filters.
<C-4: Structure of Comparative Example 2>
The light emitting device of Comparative Example 2 has the same thickness as each of the light emitting devices of Comparative Example 1, and differs from Comparative Example 1 in that thin color filters CF1-R, CF1-G, and CF1-B are used as color filters. ing.
FIG. 10 shows the color filter and each element structure in each example.

<C-5: Results of panel simulation>
As shown in FIG. 11, when the power consumption of Comparative Example 1 was normalized to 1.00, the power consumption of Example 1 was 0.71, and the power consumption could be reduced by about 30%. The power consumption of Comparative Example 2 was 0.61, while the power consumption of Example 2 was 0.45, and the power consumption could be reduced by about 20%.

Also, as shown in FIG. 12, the color gamut (NTSC area ratio) was 103.9% in Comparative Example 1 and 101.9% in Comparative Example 1. Further, Comparative Example 2 was 92.51%, while Example 2 was 92.7%. Thus, Example 1 using a thick color filter was almost the same as Comparative Example 1 using the same color filter, although the color gamut was slightly reduced. In addition, Example 2 using a thin color filter was almost the same as Comparative Example 2 using the same color filter.
Thus, the color gamut was almost the same as that of the comparative example in both Example 1 and Example 2.

  Further, FIG. 13 and FIG. 14 show the light extraction efficiency. As shown in FIG. 13, for the blue light emitting device, the peak heights of the comparative example and the example are almost the same, but the emission spectrum of the example is broader. Therefore, it can be seen that the area is large, the light energy is larger in the example, and the light extraction efficiency is higher.

  Further, as shown in FIG. 13, for the red light emitting element, the peak heights of the comparative example and the example are almost the same, but the emission spectrum of the example is broader. Therefore, it can be seen that the area is large, the light energy is larger in the example, and the light extraction efficiency is higher.

  Further, as shown in FIG. 14, for the green light emitting element, the comparative example and the example had almost the same peak height and light extraction efficiency.

  As described above, in the present embodiment, in the top emission type light emitting device using the white light emitting element of the tandem structure, the resonance structure in which the value of m is 1 in the equation (4) for any color pixel. Therefore, the light extraction efficiency could be increased while adopting a tandem structure to simplify the manufacturing process.

<D: Application example>
Next, an electronic apparatus using the light emitting device according to the present invention will be described. FIG. 15 is a perspective view showing a configuration of a mobile personal computer adopting the light emitting device E1 according to the above-described embodiment as a display device. The personal computer 2000 includes a light emitting device E1 as a display device and a main body 2010. The main body 2010 is provided with a power switch 2001 and a keyboard 2002. Since the light emitting device E1 uses an organic EL element, it is possible to display an easy-to-see screen with a wide viewing angle.

  FIG. 16 shows a configuration of a mobile phone to which the light emitting device E1 according to the above-described embodiment is applied. The cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and a light emitting device E1 as a display device. By operating the scroll button 3002, the screen displayed on the light emitting device E1 is scrolled.

  FIG. 17 shows a configuration of a portable information terminal (PDA: Personal Digital Assistant) to which the light emitting device E1 according to the above-described embodiment is applied. The information portable terminal 4000 includes a plurality of operation buttons 4001, a power switch 4002, and a light emitting device E1 as a display device. When the power switch 4002 is operated, various kinds of information such as an address book and a schedule book are displayed on the light emitting device E1.

  Electronic devices to which the light-emitting device according to the present invention is applied include those shown in FIGS. 15 to 17, digital still cameras, televisions, video cameras, car navigation devices, pagers, electronic notebooks, electronic papers, calculators. , Word processors, workstations, videophones, POS terminals, printers, scanners, copiers, video players, devices equipped with touch panels, and the like.

In the above-described embodiment, the case where the integer m ₁ is 1 in all the color pixels in the formula (4) has been described, but the present invention is not limited to this, and the integer m _The present invention is also applicable when ₁ is 2 or more.

  Furthermore, in the embodiment described above, an example using Al as an example of the reflective layer and the reflective layer / pixel electrode has been described. However, the present invention is not limited to this, and a single metal of Ag, or An alloy mainly containing at least one of Al and Ag may be used.

  In the above-described embodiment, the example in which the reflective layer of the green light emitting element and the blue light emitting element are formed of the same material and the reflective layer of the red light emitting element is formed of different materials has been described. The configuration is not limited. For example, the reflective layer of the red light emitting element and the green light emitting element may be formed of the same material, and the reflective layer of the blue light emitting element may be formed of different materials.

DESCRIPTION OF SYMBOLS 10 ... Reflective layer and pixel electrode, 11 ... Reflective layer, 12 ... Transparent layer, 13 ... Pixel electrode, 14 ... Hole injection layer, 15 ... Hole transport layer, 16 ... 1st light emitting layer , 17... Electron transport layer, 18... Charge generation layer, 19... Hole transport layer, 20... Charge separation layer, 21. Light emitting layer, 24 ... hole block layer, 25 ... electron transport layer, 30 ... counter electrode, 31 ... sealing layer, E1 ... light emitting device, U1 ... red light emitting element, U2 ... green light emitting element, U3 ... blue light emitting element

Claims (7)

A light emitting device in which a plurality of pixels are formed,
Each of the plurality of pixels is
A reflective layer;
A light transmissive semi-reflective layer;
A plurality of light emitting portions formed between the reflective layer and the light transmissive semi-reflective layer;
At least one charge separation layer formed between the plurality of light emitting units;
A counter electrode,
Among the plurality of pixels, a pixel for extracting light emitted from the light emitting unit provided at a position closer to the light transmission semi-reflective layer than the charge separation layer is provided between the charge separation layer and the reflection layer. Is provided with a pixel electrode,
Of the plurality of pixels, for a pixel that extracts light emitted from the light emitting unit provided closer to the reflective layer than the charge separation layer, the reflective layer functions as a pixel electrode.
A light emitting device characterized by that. The optical distance between the reflection layer and the light transmission semi-reflection layer is D, the phase shift in reflection at the reflection layer is φ _L , the phase shift in reflection at the light transmission semi-reflection layer is φ _U , and the peak wavelength is λ , M ₁ is an integer, for each of the plurality of pixels,
D = {(2πm ₁ + φ _L + φ _U ) / 4π} λ
The light emitting device according to claim 1, wherein m ₁ ≧ 1 is satisfied. The pixel for extracting light emitted from the light emitting unit provided at a position closer to the reflective layer than the charge separation layer is provided at the reflective layer that also serves as the pixel electrode and at a position close to the reflective layer. Further, when the optical distance between the light emitting part is L, the phase shift at the interface of the reflective layer is φ, and the peak wavelength is λ,
2L = (φ / 2π) λ
The light-emitting device according to claim 1, wherein:   The pixel for extracting light emitted from the light emitting unit provided at a position closer to the reflective layer than the charge separation layer is provided at the reflective layer that also serves as the pixel electrode and at a position close to the reflective layer. 4. The light emitting device according to claim 1, wherein a metal oxide layer is formed between the light emitting portion and the light emitting portion.   5. The light emitting device according to claim 1, wherein the reflective layer is made of Al, Ag, or an alloy containing these as a main component.   The light-emitting device according to claim 1, wherein a color filter is formed on a side from which light is emitted from the counter electrode. An electronic apparatus comprising the light emitting device according to claim 1.

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