JP2001326077A - Organic luminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic luminescent element with high directivity and high luminous efficiency. SOLUTION: The optical resonator organic luminescent element is formed by laminating successively a multi-layered mirror 12 laminating two kind of layers with different refractive index alternately with each other, a transparent electrode (an anode) 14 with the function of an anode, an organic compound layer 16 including a luminous layer illuminating by the impression of voltage, and a back side electrode (a cathode) 18 constituting a light resonator together with the multi-layered mirror, with function of a cathode, successively on a transparent substrate 10. The wave length slant width Δλ(θ), defined as the difference between a wave length λL(θ) and a wave length λA(θ), is made less than 80 nm, where; λL is a peak wave length of an emission spectrum when the multi-layered mirror is not formed, λA(θ)is a wave length by which the index of reflection becomes 30% of RL(θ) when multi-layered mirror 12 is irradiated by the angle of incidence of θ, where; RL(θ) is the index of reflection against the light with wave length of λL(θ) when the light with the wave length of λL is irradiated with the angle of incidence of θ(0 deg.<=θ<=90 deg.) into the multi- layered mirror 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting device, and more particularly, to an organic light emitting device of an optical resonator type having an optical resonator in the device and emitting light of a predetermined wavelength by resonance.

[0002]

2. Description of the Related Art An organic light emitting device using a fluorescent organic substance for a light emitting layer is an organic EL device.
(Electroluminescence) elements, which are easier to manufacture than other light-emitting elements, and have been researched and developed as thin-type display elements because of their advantages such as being thin and light-weight. . in recent years,
Since a high-performance organic EL device comparable to a light-emitting diode (LED) made of an inorganic material has been obtained in terms of emission luminance, luminous efficiency, durability and the like, a photosensitive material such as a silver halide photosensitive material has been used. Application to an exposure head for exposing is also being studied. For example, JP-A-7-22649 discloses that
An optical recording device provided with an optical writing unit using an organic EL element has been proposed.

[0003] However, these organic EL devices are
Since the light source emits light over a wide angle and has low directivity (perfectly diffused light source), there is a problem in that the light loss is large when used as a liquid crystal projector, an optical communication device, and a printer exposure light source. are doing. In order to solve such a problem, Japanese Patent Application Laid-Open No. Hei 9-180883 proposes an organic EL device having a small optical resonator structure (microcavity) having a small half-width of an emission spectrum and excellent directivity. ing. This organic EL element controls the optical length of the micro optical resonator to shift the emission wavelength from the peak wavelength (the peak wavelength of the emission spectrum when no micro optical resonator is provided) to the shorter wavelength side. High directivity is achieved by suppressing light emitted in directions other than the direction perpendicular to the substrate. In other words, paying attention to the fact that the angle dependence differs depending on the wavelength of the resonating light, by selecting a wavelength that emits less light at a large angle and resonating, the light is emitted in a direction other than the direction perpendicular to the substrate. Is prevented. However, this organic EL element cannot emit light at the peak wavelength having the maximum intensity, and therefore has a problem that the luminous efficiency is lower than that of the organic EL element without the micro optical resonator.

An object of the present invention is to provide an organic light emitting device having high directivity and high luminous efficiency. is there.

[0005]

In order to achieve the above object, the organic light emitting device according to the first aspect of the present invention functions as a multilayer mirror in which two types of layers having different refractive indexes are alternately stacked, and as an anode. A transparent first electrode, an organic compound layer including a light-emitting layer that emits light by voltage application, and a second electrode that constitutes an optical resonator together with the multilayer mirror and acts as a cathode are sequentially laminated on a transparent substrate. In an optical resonator type organic light emitting device, the peak wavelength of the emission spectrum of the organic light emitting device when the multilayer mirror is not provided is λ _L ,
The light of wavelength λ _L is incident on the multilayer mirror at an incident angle θ (0 ° ≦ θ
≦ 90 °), the reflectance for light of wavelength λ _L (θ) is R _L (θ), and when the light is incident on the multilayer mirror at an incident angle θ, the reflectance is R _L (θ). When the wavelength of the light that becomes 30% is λ _A (θ), the wavelength λ _L (θ)
And the wavelength gradient width Δ defined by the difference between the wavelength λ _A (θ)
λ (θ) is not more than 80 nm.

The wavelength gradient width Δλ _L (θ) of the multilayer mirror indicates the wavelength dependence of the reflectance. The smaller the wavelength gradient width Δλ _L (θ), the greater the wavelength dependence of the reflectance near the peak wavelength λ _L. Becomes larger. Therefore, as in the present invention, the wavelength gradient width Δλ
By configuring an optical resonator using a multilayer mirror having _L (θ) of 80 nm or less, the confinement coefficient for light having a wavelength shorter than the peak wavelength λ _L is reduced, and light having the peak wavelength λ _L is resonated and emitted. At the same time, light having a wavelength shorter than the peak wavelength λ _L is prevented from being emitted at a predetermined angle with respect to the normal vector of the substrate, and high conversion efficiency and high directivity are realized.

According to a second aspect of the present invention, in the organic light emitting device according to the first aspect, the absolute value | d (λ _A (θ)) / of the first derivative of the wavelength λ _A (θ) with respect to the incident angle θ. dθ | is 2 nm / deg or less.

Since the wavelength dependence of the reflectance of the multilayer mirror decreases as the incident angle θ increases, the wavelength λ _A (θ)
Absolute value | d (λ
_By setting _A (θ)) / dθ | to 2 nm / deg or less, higher directivity can be obtained.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an organic light emitting device of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, an organic EL device according to the present invention comprises a transparent substrate 10 having at least two different refractive indexes.
A multilayer mirror 12 in which different types of layers are alternately stacked, a transparent electrode (anode) 14 as a first electrode, an organic compound layer 16 including a light emitting layer, and a back electrode (cathode) 18 as a second electrode are provided. They are stacked in this order. Less than,
Each component will be described in detail.

As the transparent substrate 10, a plastic substrate can be used in addition to a normal glass substrate. The plastic substrate needs to be excellent in heat resistance, dimensional stability, solvent resistance, electrical insulation, workability, low air permeability, and low moisture absorption. Such materials include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyether sulfone, polyarylate,
Allyl diglycol carbonate, polyimide and the like can be mentioned. It is preferable to provide a moisture permeation prevention layer (gas barrier layer) on the surface of the transparent substrate 14 or on the surface opposite to the transparent electrode 14 (the back surface). It is preferable to use an inorganic substance such as silicon nitride or silicon oxide for the moisture permeation preventing layer (gas barrier layer), and the film can be formed by, for example, a high frequency sputtering method. Further, a hard coat layer or an undercoat layer may be provided as necessary.

The multilayer mirror 12 is connected to a back electrode 1 to be described later.
8 together with an optical resonator, and functions as a resonator by setting the optical length L to an integral multiple of the resonance wavelength. In the present invention, the wavelength tilt width Δλ of the multilayer mirror 12 is used.
_L (θ) is required to be 80 nm or less.

As shown in FIG. 2, the reflection characteristics of the multilayer mirror 12 change according to the wavelength of incident light. That is,
As the wavelength of the incident light decreases, the reflectance decreases. In the present invention, as shown in FIG. 2, the peak wavelength of the emission spectrum of the organic EL element when no multilayer mirror is provided is λ _L, and the light of this wavelength λ _L is incident on the multilayer mirror 12 at an incident angle. The reflectance for light of wavelength λ _L (θ) when incident at θ (0 ° ≦ θ ≦ 90 °) is R _L (θ), and when incident on the multilayer mirror 12 at an incident angle θ, the reflectance is R _L
(Theta) the wavelength of light decreases to 30% of when the λ _A (θ), defined as those wavelength lambda _L and the wavelength λ _A (θ) Wavelength slope width difference between Δλ _L (θ). Here, the incident angle θ is
This is the angle formed by the incident light with respect to the normal vector of the multilayer mirror 12.

The wavelength tilt width Δλ of the multilayer mirror 12
_L (θ) represents the wavelength dependence of the reflectance, and the wavelength gradient width Δλ _L
The smaller (θ), the greater the wavelength dependence of the reflectance near the peak wavelength λ _L. That is, if the wavelength shifts to the short wavelength side even slightly from the peak wavelength λ _L , the reflectance sharply decreases. Therefore, as in the present invention, the wavelength gradient width Δλ
By configuring the optical resonator using the multilayer mirror 12 having a small _L (θ) of 80 nm or less, the confinement coefficient for light having a wavelength shorter than the peak wavelength λ _L is reduced, and the light having the peak wavelength λ _L is resonated. In addition, light having a wavelength shorter than the peak wavelength λ _L is suppressed from being emitted at a predetermined angle with respect to the normal vector of the substrate, and high conversion efficiency and high directivity are realized. On the other hand, the wavelength gradient width Δλ _L (θ)
Exceeds 80 nm, light having a wavelength shorter than the peak wavelength λ _L is also resonated, and the proportion of light emitted at a predetermined angle is sharply increased, and the directivity is reduced. In order to further improve the directivity, the wavelength gradient width Δλ _L (θ) is preferably 50 nm or less, and 30 nm or less.
The following is more preferable, and 10 nm or less is particularly preferable.

The wavelength dependence of the reflectance of the multilayer mirror 12 decreases as the incident angle θ increases. That is, as the incident angle θ increases, the wavelength inclination width Δλ _L (θ) increases and the value of the wavelength λ _A (θ) decreases. Therefore,
In order to improve the directivity, it is preferable that the fluctuation of the wavelength λ _A (θ) with respect to the fluctuation of the incident angle θ is small. Specifically, the absolute value of the first derivative of the incident angle theta of the wavelength _{λ A (θ) | d (} λ A (θ)) / dθ | preferably is 2 nm / deg or less, 1.0 nm / deg or less, more preferably 0.5 nm / deg or less.

The multilayer mirror 12 is usually formed by alternately laminating two kinds of dielectric materials having different refractive indices. As the dielectric materials, SiO ₂ , TiO ₂ , Al ₂ O ₃ ,
MgF ₂ , ZrO _{2, and the} like. Multilayer mirror 12
Can be formed by alternately stacking layers having a quarter of the resonance wavelength (emission wavelength), for example. Also, a layer that is 1/8 times the resonance wavelength, a layer that is 1/4 times the resonance wavelength, and a layer that is 1/8 times the resonance wavelength may be alternately stacked to form a layer. Layer that is 1/4 times, 3 of resonance wavelength
A layer having times and a layer having あ る times the resonance wavelength may be alternately stacked. Note that the optical length L is preferably set to be long so that the reflectance of the multilayer mirror 12 can be adjusted when a higher-order mode appears.

The transparent electrode (anode) 14 has a thickness of 400 nm to 7 nm.
In the wavelength region of visible light of 00 nm, at least 50
%, Preferably 70% or more. Examples of a material for forming the transparent electrode 14 include compounds known as transparent electrode materials such as tin oxide, indium tin oxide (ITO), and indium zinc oxide;
A thin film of a metal having a large work function such as gold or platinum may be used. Further, organic compounds such as polyaniline, polythiophene, polypyrrole, and derivatives thereof may be used. The transparent conductive film is described in detail in “New Development of Transparent Conductive Film”, supervised by Yutaka Sawada, published by CMC (1999), and can be applied to the present invention. Further, the lower the surface resistance of the transparent electrode 14, the more preferable. Specifically, the surface resistance of the transparent electrode is preferably 50Ω / □ or less, more preferably 20Ω / □ or less, and more preferably 10Ω / □ or less.

The transparent electrode 14 can be formed on the entire surface or on one surface of the transparent substrate by a vacuum deposition method, a sputtering method, an ion plating method, or the like, depending on the purpose or the like. The electrode patterning can be performed by chemical etching such as photolithography or physical etching using a laser or the like. The electrodes can also be patterned by performing vacuum evaporation or sputtering using a mask.

The organic compound layer 16 may have a single-layer structure composed of only a light-emitting layer, or may have two or more light-emitting layers.
Alternatively, a layered structure having other layers such as a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer as appropriate in addition to the light emitting layer may be used. Specific configurations of the organic compound layer 16 (including the electrodes) are as follows: anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode;
Anode / light-emitting layer / electron transport layer / cathode; anode / hole transport layer / light-emitting layer / electron transport layer / cathode; Further, a plurality of light emitting layers, hole transport layers, hole injection layers, and electron injection layers may be provided.

The light emitting material of the light emitting layer is not particularly limited as long as it is a compound capable of emitting light (fluorescent compound).
It can be appropriately selected according to the purpose, for example, oxinoid compounds, perylene compounds, coumarin compounds, azacoumarin compounds, oxazole compounds, oxadiazole compounds, perinone compounds, pyrrolopyrrole compounds, naphthalene compounds, anthracene compounds, fluorene compounds, fluoranthene Compounds, tetracene compounds, pyrene compounds, coronene compounds, quinolone compounds and azaquinolone compounds, pyrazoline derivatives and pyrazolone derivatives,
Rhodamine compounds, chrysene compounds, phenanthrene compounds, cyclopentadiene compounds, stilbene compounds,
Diphenylquinone compounds, styryl compounds, distyrylbenzene compounds, butadiene compounds, dicyanomethylenepyran compounds, dicyanomethylenethiopyran compounds, fluorescein compounds, pyrylium compounds, thiapyrylium compounds, selenapyrylium compounds, telluropyrylium compounds, aromatic aldadienes, oligophenylenes Compounds, xanthene compounds and thioxanthene compounds,
Cyanine compounds, acridine compounds, acridone compounds, quinoline compounds, metal complexes of 8-hydroxyquinoline compounds, benzoquinolinol beryllium complexes, 2,
Metal complexes of 2'-bipyridine compounds, complexes of Schiff salts with Group III metals, metal complexes of oxadiazole compounds, rare earth complexes, and the like are used.

In order to improve the luminous efficiency, it is preferable that the luminescent layer contains an orthometalated complex. The orthometalated complex is described in, for example, "Organic Metal Chemistry-Fundamentals and Applications-" by Akio Yamamoto, pp. 150, 232, Shokabosha (published in 1982), and "Photochemistry" by H. Yersin.
and Photophysics of Coordination Compounds '' 71
-77, 135-146, Springer-Verlag (1
987) and the like. There are various ligands that form an orthometalated complex, and these ligands are also described in the above literature. Preferred ligands include 2-phenylpyridine derivatives, 7,
8-benzoquinoline derivative, 2- (2-thienyl) pyridine derivative, 2- (1-naphthyl) pyridine derivative,
-Phenylquinoline derivatives and the like. These derivatives may have a substituent as needed. Metals that form the orthometalated complex include Ir, Pd, P
t and the like, and an iridium (Ir) complex is particularly preferable. The ortho-metalated complex may have other ligands in addition to the ligand necessary for forming the ortho-metalated complex. The orthometalated complex includes a compound emitting light from a triplet exciton, and a compound emitting light from the triplet exciton is contained in the light emitting layer in order to improve luminous efficiency. It is particularly preferred to do so.

The light-emitting materials exemplified above may be used alone or in combination. Alternatively, a polymer light-emitting material can be used. Examples of the polymer light emitting material include poly-
In addition to a π-conjugated system such as a p-phenylenevinylene derivative, a polyfluorene derivative, and a polythiophene derivative, a polymer in which a low-molecular weight dye and tetraphenyldiamine or triphenylamine are introduced into a main chain or a side chain is exemplified. A low molecular light emitting material may be mixed with a high molecular light emitting material.

The electron injection layer is formed of an insulating material. When the thickness of the electron transport layer is within a predetermined range, the probability that holes pass through the electron transport layer increases, and as a result, luminous efficiency decreases. Therefore, in order to prevent the holes from passing through, it is preferable to provide the organic compound layer with an electron injection layer formed of an insulating thin film. Examples of the insulating material include aluminum oxide and lithium fluoride, and a thin film having a thickness of 0.01 to 10 nm is formed using these materials. For the same reason, it is preferable to form a hole injection layer made of an insulating thin film.

Examples of the electron transporting compound used in the electron transporting layer include oxadiazole derivatives, triazole derivatives, triazine derivatives, nitro-substituted fluorenone derivatives, thiopyrandioxide derivatives, diphenylquinone derivatives, perylenetetracarboxyl derivatives, anthraquinodines. Methane derivatives, fluorenylidene methane derivatives,
Anthrone derivatives, perinone derivatives, oxine derivatives,
Compounds such as quinoline complex derivatives are exemplified.

Examples of the hole transporting compound used in the hole transporting layer include polymers such as poly-N-vinylcarbazole and polyphenylenevinylene derivatives, polymers such as polyphenylene, polythiophene, polymethylphenylsilane and polyaniline, triazole derivatives, oxadiazole derivatives, and the like. Porphyrins such as imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, carbazole derivatives, styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, and phthalocyanines Derivatives, aromatic tertiary amine compounds and styrylamine compounds, butadiene compounds, benzidine derivatives, police Ren derivatives, triphenylmethane derivatives, tetraphenyl benzene derivatives, and the like can be used starburst polyamine derivatives.

The organic compound layer 16 has, in addition to these components, a conductive polymer layer in contact with the anode between the anode and the hole transport layer (the light emitting layer when no hole transport layer is provided). It may be provided. By providing this conductive polymer layer, the thickness of the organic compound layer 16 can be increased without substantially increasing the driving voltage, and uneven brightness and short-circuit are improved. As a conductive polymer, WO-
Preferred are polyaniline derivatives, polythiophene derivatives and polypyrrole derivatives described in 98/05187. These derivatives include protonic acids such as camphor sulfonic acid, p-toluene sulfonic acid, styrene sulfonic acid,
(Polystyrene sulfonic acid and the like). These derivatives may optionally be used with other polymers (eg, polymethyl methacrylate (PMMA)
Or poly-N-vinylcarbazole (PVCz) or the like. The surface resistance of the conductive polymer layer is preferably 10,000Ω / □ or less. The thickness of the conductive polymer layer is preferably from 10 nm to 1000 nm,
nm to 200 nm is more preferable.

The constituent layers of the organic compound layer 16 such as a hole transport layer, an electron transport layer, a light emitting layer, and a conductive polymer layer are as follows:
It can be formed by a known method such as a vacuum evaporation method, a sputtering method, a dipping method, a spin coating method, a casting method, a bar coating method, and a roll coating method. Multilayer coating is also possible by using different solvents. Further, the organic compound layer 16 is formed on the entire surface or on one surface of the transparent electrode 14 according to the use, purpose, and the like of the light emitting device.

The back electrode (cathode) 18 is made of an alkali metal such as Li or K having a low work function because of its excellent electron injecting property.
It is preferably formed from a cathode material such as an alkaline earth metal such as Mg or Ca or Al which is hardly oxidized and stable. In addition, two or more kinds of cathode materials may be used in combination in order to achieve both storage stability and electron injection properties. Note that cathode materials described in JP-A-2-15595 and JP-A-5-121172 can also be used. Note that, similarly to the transparent electrode 14, the back electrode 18 can be formed by a known method such as a vacuum evaporation method, a sputtering method, and an ion plating method.

Further, the organic EL device of the present invention may be provided with a sealing layer for preventing moisture and oxygen in the atmosphere from entering the organic EL device. As a sealing material used for the sealing layer, a copolymer containing tetrafluoroethylene and at least one comonomer, a fluorinated copolymer having a cyclic structure in the copolymer main chain, polyethylene, polypropylene, polymethyl methacrylate, Two or more copolymers selected from polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, chlorotrifluoroethylene, and dichlorodifluoroethylene, water absorption 1%
The above water-absorbing substances and moisture-proof substances having a water absorption of 0.1% or less, In, Sn, Pb, Au, Cu, Ag, Al, T
i, metal such as Ni, MgO, SiO, SiO ₂ , Al ₂ O
_{3, GeO, NiO, CaO,} BaO, Fe 2 O 3, Y 2 O
Metal oxide such as ₃ , MgF ₂ , LiF, AlF ₃ , CaF ₂
Liquid fluorides such as metal fluorides such as perfluoroalkanes, perfluoroamines, and perfluoroethers, and those obtained by dispersing an adsorbent for adsorbing moisture and oxygen into these liquid fluorides are used.

In the organic EL device of the present invention described above,
A DC voltage (which may include an AC component if necessary) voltage (usually a pulse voltage in the range of 2 to 30 volts) or a pulse voltage is applied between the transparent electrode (anode) 14 and the back electrode (cathode) 18 As a result, light is emitted from the light emitting layer, and light of a specific wavelength out of the emitted light is resonated between the multilayer mirror 12 and the back electrode 18 to be strengthened. Emitted from the side.

[0031]

[Example] (Reference example) 50 mm x 50 mm x 0.5 mm
A glass transparent substrate is prepared, and ultrasonically cleaned with acetone, Semicoclean (trade name, manufactured by Furuuchi Chemical Co., Ltd.) and isopropanol (IPA), and finally, IPA boiling cleaning is performed, and then ultraviolet (UV) / Ozone (O ₃ ) cleaning was performed. Next, an ITO layer serving as an anode (transparent electrode) having a thickness of 40 nm was formed on the washed transparent glass substrate by sputtering using a mask.

Next, an organic compound layer including a light emitting layer was formed on the ITO layer. That is, first, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD) is deposited on the ITO layer at a deposition rate of 3 to 4 ° / sec to a thickness of 480.
Then, the following compound 1 was deposited on this NPD layer.
And the following compound 2 is co-deposited at a thickness of 240 ° so that the compound 1 is 6% by weight with respect to the compound 2, and the following compound 3 is deposited on the layer composed of the compound 1 and the compound 2 at a deposition rate of 3 to 4 ° / Vapor deposition was performed so as to have a thickness of 72 ° in seconds, and tris (8-quinolylato) aluminum was vapor-deposited on the layer made of compound 3 at a deposition rate of 3 to 6 ° / sec to a thickness of 240 °.

[0033]

Embedded image

[0034]

Embedded image

Next, on this organic compound layer, Mg / Ag
= 10/1 (molar ratio) alloy layer is vapor-deposited with a mask at a thickness of 0.6 µm to form a cathode having a predetermined pattern, and a metal layer of Ag alone is vapor-deposited at a thickness of 0.5 µm on the formed cathode. Thus, an organic EL device was obtained. The peak wavelength λ _L of the emission spectrum of this organic EL device was 515 nm.
(Examples 1 to 9, Comparative Examples 1 and 2) 50 mm × 50 mm ×
Prepare a 0.5 mm glass transparent substrate, acetone,
Ultrasonic cleaning was performed using Semico Clean (trade name, manufactured by Furuuchi Chemical Co., Ltd.) and isopropanol (IPA), and finally, IPA boiling cleaning was performed, followed by ultraviolet (UV) / ozone (O ₃ ) cleaning. On the transparent glass substrate after cleaning,
The layer thickness of each layer, the number of laminations, and the refractive index of the laminated material are appropriately changed to reflect the light of 515 nm, the wavelength gradient width Δλ _L (θ = 0 °), and 0 ° ≦ θ as shown in Table 1 below. ≤
_A multilayer mirror having different absolute values | d (λ _A (θ)) / dθ | of the first derivative of the wavelength λ _A (θ) with respect to the incident angle θ in the range of 50 ° is formed, and the multilayer mirror is provided. Substrates A to K were obtained. As described above, the wavelength λ _A (θ) is such that the light having the wavelength λ _L is incident on the multilayer mirror at an incident angle θ (0 ° ≦ θ).
≦ 90 °), the reflectance for light of wavelength λ _L (θ) is _RL (θ), and when the incident light is also incident at an incident angle θ, the reflectance is 30 _RL (θ). % Is the wavelength of light.

[0036]

[Table 1]

Next, the obtained substrates A to M with a multilayer mirror were prepared.
For each of H, an ITO layer serving as an anode, an organic compound layer, a Mg / Ag alloy layer serving as a cathode, and a metal layer made of Ag alone were formed in the same manner as in the above Reference Example, with an optical length L of 515 nm,
495 nm and 475 nm so as to be an integral multiple of a half wavelength of the three wavelengths (that is, each of the resonance wavelengths is 515 n
m, 495 nm, and 475 nm). The organic EL devices of Examples 1 to 9 and Comparative Examples 1 and 2 were obtained by appropriately adjusting the layer thickness of each layer. (Evaluation of Light Emission Characteristics) For the obtained organic EL device, θ
= 0 °, the input end of the optical fiber is arranged in the direction of θ = 45 °, the intensity of the emitted light emitted in each direction is detected by the photodiode, and the intensity in the direction of θ = 0 ° is measured as the emission spectrum. , The external quantum efficiency (the number of output photons / the number of input photons) at each resonance wavelength is determined, and θ = 4 of the light output in the direction of θ = 0 °.
The intensity ratio with respect to the light output in the direction of 5 ° was obtained. The evaluation results are shown in Table 2 below. The intensity ratio is an index indicating directivity, and the greater the intensity ratio, the more light emitted in a direction that forms a predetermined angle with the direction perpendicular to the substrate, indicating that the directivity is higher.

[0038]

[Table 2]

As described above, no multilayer mirror is provided.
The light emitting device of an organic EL device (reference example) having the same configuration except for
Peak wavelength of the spectrum (peak wavelength λ_L) Is 515 nm
It is. From the results shown in Table 1, the wavelength tilt of the multilayer mirror is shown.
Width Δλ_LOrganic EL with (θ = 0 °) exceeding 80 nm
In the element (Comparative Examples 1 and 2), the resonance wavelength is the peak wavelength.
λ_L515 nm which is the highest external quantum efficiency
Has a small intensity ratio of 1.1 and 1.14 and a resonance wavelength of 49.
When the wavelength is shortened to 5 nm or 475 nm, the intensity ratio increases.
However, it can be seen that the external quantum efficiency decreases. Against this
And the wavelength gradient width Δλ_L(Θ = 0 °) is less than 80 nm
In the device EL element (Examples 1 to 6), the resonance wavelength has a peak wave.
Long λ_LIn the case of 515 nm, which is
It can be seen that an intensity ratio of 1.35 or more can be obtained while holding
You. Note that the resonance wavelength is the peak wavelength λ. _LIs 515 nm
In Comparative Examples 1-2, the external quantum efficiency was highest in the case of
Is the same as Also, | d (λ_A(Θ)) / dθ | is 2
nm / deg or less organic EL device (Examples 7 to 9)
Means that the resonance wavelength is the peak wavelength λ_L515 nm
1.61 or more while maintaining high external quantum efficiency
The ratio is obtained and the directivity is significantly improved.
I understand.

[0040]

According to the present invention, an organic light emitting device having high directivity and high luminous efficiency is provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a layer structure of an organic EL device of the present invention.

FIG. 2 is a diagram showing reflection characteristics of a multilayer mirror.

[Explanation of symbols]

 Reference Signs List 10 transparent substrate 12 multilayer mirror 14 transparent electrode (anode) 16 organic compound layer 18 back electrode (cathode)

Claims (2)

[Claims] 1. A multilayer mirror in which two kinds of layers having different refractive indices are alternately stacked, a transparent first electrode acting as an anode, an organic compound layer including a light emitting layer which emits light by applying a voltage, and the multilayer. In an optical resonator type organic light emitting device in which a second electrode constituting an optical resonator together with a film mirror and acting as a cathode is sequentially laminated on a transparent substrate, an organic light emitting device in a case where the multilayer mirror is not provided The peak wavelength of the emission spectrum of the device is λ _L , and the reflectance for light of wavelength λ _L (θ) when light of wavelength λ _L is incident on the multilayer mirror at an incident angle θ (0 ° ≦ θ ≦ 90 °). To R _L
(Θ) and the wavelength of light at which the reflectance is 30% of _RL (θ) when incident on the multilayer mirror at an incident angle θ is λ
_A (θ) wherein the wavelength gradient width Δλ (θ) defined by the difference between the wavelength λ _L (θ) and the wavelength λ _A (θ) is 80 nm or less. element. 2. The absolute value | d (λ _A (θ)) / dθ | of the first derivative of the wavelength λ _A (θ) with respect to the incident angle θ is 2 nm.
The organic light-emitting device according to claim 1, wherein the ratio is not more than / deg.