KR20110108271A - Organic electric field light-emitting element and organic electric field light-emitting display using the same - Google Patents

Abstract

As an organic electroluminescent element having at least a first electrode, a light emitting layer, a semi-transmissive second electrode, an intermediate layer, a semi-transmissive layer, and a light transmitting layer in this order,
A first resonator structure for resonating the light emitted from the light emitting layer between the first electrode and the second electrode and emitting the light;
It has a second resonator structure for emitting the light by resonating between the first electrode and the transflective layer,
When the thickness of the light transmitting layer is a length of 1/4 of the peak wavelength of the light emitted from the light emitting layer, and the refractive index of the light transmitting layer is n, the following formula 0.9 × t / n or more 1.1 × t / It is an organic electroluminescent element which satisfy | fills n or less.

Description

ORGANIC ELECTRIC FIELD LIGHT-EMITTING ELEMENT AND ORGANIC ELECTRIC FIELD LIGHT-EMITTING DISPLAY USING THE SAME}

The present invention relates to an organic electroluminescent element (hereinafter sometimes referred to as an "organic EL element") having a multiple resonance structure and an organic electroluminescent display using the same.

An organic electroluminescent element is a self-luminous display device and is used for display or illumination. The organic electroluminescent display has the advantage of display performance which is high in visibility compared with the conventional CRT and LCD, and that there is no viewing angle dependency. In addition, there is an advantage that the display can be reduced in weight and thickness. In addition to the advantages of weight reduction and thinning, organic EL lighting has the possibility of realizing lighting having a shape that has not been realized until now by using a flexible substrate.

As described above, the organic EL device has excellent characteristics, but generally, the refractive index of each layer constituting the display device including the light emitting layer is higher than that of air. For example, in an organic electroluminescent element, the refractive index of organic thin film layers, such as a light emitting layer, is 1.6-2.1. For this reason, the emitted light tends to be totally reflected at the interface, and the light extraction efficiency is sometimes less than 20%, and most of the light is lost.

For example, the organic electroluminescent display part in the generally known organic electroluminescent element is comprised by including the organic compound layer arrange | positioned between a pair of electrode layer on a board | substrate. The organic compound layer includes a light emitting layer, and the organic electroluminescent element emits light emitted from the light emitting layer from the light extraction surface side.

However, in this case, since the total reflection component which is light above a critical angle cannot be taken out in the light extraction surface or the interface of an electrode layer and an organic compound layer, there existed a problem that light extraction efficiency was low.

In this regard, in order to improve the light extraction efficiency, for example, an organic electroluminescence having a microcavity structure having an optical resonant layer for resonating light emitted from the light emitting element and an intermediate layer interposed between the optical resonant layer and the light emitting element. An element is proposed (see Japanese Patent Laid-Open No. 2006-140130). According to the organic electroluminescent device, light extraction efficiency is improved as compared with the organic electroluminescent device which does not have a micro cavity structure.

However, in the organic electroluminescent device, since the reflective surface on the light exit side uses a transparent material having a different refractive index, the amount of reflection near the vertical incidence cannot be sufficiently obtained, so that the light extraction efficiency in the front direction cannot be expected very much. there was. In addition, there is a problem that the color changes (color change) corresponding to the position of the observer with respect to the organic electroluminescent element due to the resonance effect.

In addition, an organic electroluminescent element having a multiple resonant structure has been proposed for an organic electroluminescent element having a micro cavity structure (see Japanese Patent Laid-Open No. 2003-123987). The organic electroluminescent device includes a total reflection mirror, a first half mirror layer that selectively reflects a first wavelength, and a second half mirror layer that selectively reflects a second wavelength different from the first wavelength. The first resonator and the second resonator are configured to resonate with respect to different fundamental wavelengths.

The organic electroluminescent element synthesizes different fundamental wavelengths in the first resonator and the second resonator, and additively mixes the light having a fundamental wavelength representing, for example, blue (λ ₁ ) and orange (λ ₂ ) to white. It emits light.

However, since the organic electroluminescent element realizes white as a complementary color, there is a problem that chromaticity changes in correspondence with the position of the observer with respect to the organic electroluminescent element, for example, when the color selection means using a color filter is used together. .

As described above, the organic electroluminescent device having the microcavity structure is still insufficient in improving light extraction efficiency and suppressing chromaticity change, and new improvement is desired.

The present invention provides an organic electroluminescent device having excellent light extraction efficiency and capable of suppressing chromaticity change generated in response to the position of an observer with respect to the organic electroluminescent device, and an organic electroluminescent display using the organic electroluminescent device. It aims to provide.

Means for solving the above problems are as follows. In other words,

As an organic electroluminescent element having at least a <1> first electrode, a light emitting layer, a semi-transmissive second electrode, an intermediate layer, a semi-transmissive layer, and a light transmitting layer in this order,

A first resonator structure for resonating the light emitted from the light emitting layer between the first electrode and the second electrode and emitting the light;

It has a second resonator structure for emitting the light by resonating between the first electrode and the transflective layer,

When the thickness of the light transmitting layer is a length of 1/4 of the peak wavelength of the light emitted from the light emitting layer, and the refractive index of the light transmitting layer is n, the following formula 0.9 × t / n or more 1.1 × t / An organic electroluminescent device characterized by satisfying n or less.

In the organic electroluminescent element according to the above <1>, electrons are injected into the light emitting layer from the first electrode, holes are injected into the light emitting layer from the second electrode, and the electrons and the holes collide in the light emitting layer. . When the electrons collide with the holes, the light emitting material in the light emitting layer obtains energy and enters an excited state, and light is emitted when it returns to the ground state. A portion of the light is repeatedly resonated between the first electrode and the second electrode to resonate to emit light, and the light is emitted to the outside through the intermediate layer, the semi-transmissive layer, and the light transmitting layer.

The other part of the light is repeatedly resonated between the first electrode and the transflective layer to resonate to emit light, and the light is emitted to the outside through the intermediate layer, the transflective layer and the light transmissive layer. In this configuration, the light extraction efficiency is improved.

Since the thickness of the light transmitting layer is approximately equal to the optical length of the quarter of the peak wavelength of the light emitted from the light emitting layer, the light extraction efficiency is further improved in addition to the improvement of the light extraction efficiency by the above configuration. In addition, the chromaticity change generated corresponding to the position of the observer with respect to the organic electroluminescent element is also suppressed.

<2> The <1> above is an organic electroluminescent element having a refractive index difference of at least 0.1 between a light transmitting layer and a layer adjacent to the light transmitting layer.

<3> In <1> or <2>, the material of a transflective layer is an organic electroluminescent element which is a metal.

<4> In <3>, a metal is an organic electroluminescent element which is at least 1 sort (s) chosen from silver, a magnesium-silver alloy, and aluminum.

<5> The light emitting layer is an organic electroluminescent element according to any one of <1> to <4>, which contains at least one phosphorescent light emitting material.

<6> The organic electroluminescent device according to any one of <1> to <5>, which is a bottom emission type organic electroluminescent device.

<7> The light transmitting layer according to any one of <1> to <6>, further comprising a light transmitting layer between the second electrode and the intermediate layer, wherein the thickness of the light transmitting layer is 1/4 of the peak wavelength of the light emitted from the light emitting layer. When it is set to t and the refractive index of the said light transmitting layer is n, it is an organic electroluminescent element which satisfy | fills following formula 0.9xt / n or more and 1.1xt / n or less.

<8> In any one of <1> to <7>, the front resonance wavelength in the emission spectrum of the light emitting material in the light emitting layer is shorter than the first peak wavelength counting from the short wavelength side of the emission spectrum,

The emission spectrum is an organic electroluminescent device that satisfies Δλ <25 nm represented by the following formula (1).

<Equation 1>

Δλ = λ (I0) -λ (0.2 × I0)

In formula (1), λ (I0) is the front resonance wavelength, I0 is the light emission intensity at the wavelength, and λ (0.2 × I0) is the light emission intensity of 0.2 times the light emission intensity of λ (I0). The wavelength is shown, and lambda (I0)> lambda (0.2 x I0).

<9> It is an organic electroluminescent display characterized by having red, green, and blue each monopixel which used the organic electroluminescent element as described in any one of said <1>-<8> as a sub pixel.

ADVANTAGE OF THE INVENTION According to this invention, the said various conventional problems can be solved, the said objective can be achieved, it has the outstanding light extraction efficiency, and suppresses the chromaticity change which arises corresponding to the position of an observer with respect to an organic electroluminescent element. The organic electroluminescent element which can be performed, and the organic electroluminescent display using this organic electroluminescent element can be provided.

1 is a schematic cross-sectional view showing an example of the organic electroluminescent device of the present invention.
2 is a schematic cross-sectional view showing another example of the organic electroluminescent device of the present invention.
3 is a graph showing an example of the shape of an emission spectrum of light transmitted without being reflected by the second electrode among the light emitted from the light emitting layer.
4 is a graph showing another example of the shape of an emission spectrum of light transmitted without being reflected by the second electrode among the light emitted from the light emitting layer.
5 is a schematic cross-sectional view showing an example of the organic electroluminescent display of the present invention.
6 is a graph showing an example of the angle dependency of chromaticity of Examples 1 to 3 and Comparative Examples 1 to 2;
7 is a graph illustrating an example of a relationship between a Δu ′ v ′ value and a viewing angle.
8 is a graph showing an emission spectrum depending on the viewing angle of Comparative Example 1. FIG.
9 is a graph showing an emission spectrum depending on the viewing angle of Example 1. FIG.

(Organic EL device)

The organic electroluminescent device of the present invention comprises at least a first electrode, a light emitting layer, a semi-transmissive second electrode, an intermediate layer, a semi-transmissive layer, and a light transmitting layer in this order, and includes a hole injection layer and a hole as necessary. It has a functional layer selected from a transport layer, an electron injection layer, and an electron transport layer, and else it has a board | substrate, a barrier layer, another member, etc. as needed.

The organic EL device has a first resonator structure and a second resonator structure.

-First electrode, second electrode-

The first electrode is composed of a reflective electrode, and the second electrode is composed of a transflective electrode.

As said 1st electrode, it is comprised as an electrode which has a function which reflects the light radiate | emitted from the said light emitting layer to the light extraction surface side.

There is no restriction | limiting in particular as average thickness of a said 1st electrode, Although it can select suitably according to the objective, 50 nm or more is preferable.

If the average thickness is less than 50 nm, sufficient light reflectance may not be obtained.

There is no restriction | limiting in particular as average thickness of the said 2nd electrode, Although it can select suitably according to the objective, 10 nm or more is preferable and 20 nm or more is more preferable.

If the average thickness is less than 10 nm, some of the light reflected by the first electrode may be transmitted, and other parts of the light may not be reflected. Moreover, it may become a high resistance electrode and power consumption may increase.

As said average thickness, it is the said 1st using the electron microscope (Hitachi Seisakusho make) photograph of the cross-sectional sample produced by the FIB method of an organic electroluminescent element, for example, a stylus type surface shape measuring instrument (made by Albak, etc.). Ten points of thickness of an electrode or a 2nd electrode are measured, and the average value is made into average thickness.

As said 1st electrode and said 2nd electrode, it is formed as any one of an anode and a cathode, and each electrode comprises the anode and the cathode in the said organic electroluminescent element.

--anode--

The anode supplies holes to the hole injection layer, the hole transport layer, the light emitting layer, and the like, and metals, alloys, metal oxides, and the like may be used, and preferably, the work function is 4 eV or more.

There is no restriction | limiting in particular as a material which forms the said anode, Although it can select suitably according to the objective, For example, aluminum, gold, silver, chromium, nickel, etc. are mentioned.

As the method for forming the anode, various methods are used by the above materials. For example, the anode is formed by an electron beam method, a sputtering method, a resistive heating deposition method, or the like.

--cathode--

The said cathode supplies an electron to an electron injection layer, an electron carrying layer, a light emitting layer, etc., and it selects in consideration of adhesiveness, ionization potential, stability, etc. with layers adjacent to a cathode, such as an electron injection layer, an electron carrying layer, and a light emitting layer.

As the material of the negative electrode, a metal, an alloy, a metal oxide, or the like can be used, and preferably a material having a work function of 4 eV or less.

There is no restriction | limiting in particular as said material, According to the objective, it can select suitably, For example, alkali metal, alkaline earth metal, rare earth metal, gold, silver, lead, aluminum, sodium-potassium alloy, lithium-aluminum alloy, magnesium-silver Alloys, mixed metals thereof, and the like.

As said alkali metal, lithium, sodium, potassium, these fluorides, etc. are mentioned, for example.

As said alkaline earth metal, magnesium, calcium, or these fluorides are mentioned, for example.

As said rare earth metal, indium, ytterbium, etc. are mentioned, for example.

As the method for forming the cathode, various methods are used depending on the material. For example, the cathode is formed by an electron beam method, a sputtering method, a resistive heating deposition method, or the like.

It is preferable that the sheet resistance of the said positive electrode and a negative electrode is low, and several hundred ohm / square or less is preferable.

Light emitting layer

There is no restriction | limiting in particular as a material of the said light emitting layer, According to the objective, it can select suitably, The hole can be inject | poured from an anode or a hole injection layer, a hole transport layer at the time of an electric field application, and an electron is made from a cathode or an electron injection layer, an electron transport layer. It is possible to form a layer having a function capable of injecting, a function of moving an injected charge, and providing a field of recombination of holes and electrons to emit light.

There is no restriction | limiting in particular as an average thickness of the said light emitting layer, According to the objective, it can select suitably, 1 nm-5 micrometers are preferable, 5 nm-1 micrometer are more preferable, 10 nm-500 nm are especially preferable. Here, the said average thickness can measure the thickness of the said light emitting layer 10 points, for example using the electron microscope photograph of a cross section, and can make the average value into an average thickness.

The light emitting layer contains a light emitting material. The light emitting layer may be composed of only a light emitting material, or may be a mixed layer of a host material and a light emitting material (in the latter case, the light emitting material may be referred to as a "light emitting dopant" or a "dopant").

As the light emitting material, a fluorescent light emitting material or a phosphorescent light emitting material may be used, or two or more kinds thereof may be mixed, but it is preferable to use a phosphorescent light emitting material in that high efficiency is obtained.

Generally as said phosphorescence emitting material, the complex containing a transition metal atom or a lanthanoid atom is mentioned.

There is no restriction | limiting in particular as said transition metal atom, According to the objective, it can select suitably, For example, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, gold, silver, copper, platinum, etc. are mentioned, Among these, Rhenium, iridium, and platinum are more preferable, and iridium and platinum are especially preferable.

Examples of ligands for the complex include G. Wilkinson et al., Comprehensive Coordination Chemistry, Pergamon Press, Inc., published in 1987, H. Yersin, Photochemistry and Photophysics of Coordination Compounds, Springer-Verlag, Inc., published in 1987, Akio Yamamoto "Organic metal chemistry-foundation and application-", such as the ligand described in Shokabosa 1982 issue etc. are mentioned.

The complex may have one transition metal atom in the compound, or may be a so-called binuclear complex having two or more transition metal atoms. It may contain a different kind of metal atom at the same time.

Among these, as a specific example of the said phosphorescence emitting material, for example, US6303238B1, US6097147, WO00 / 57676, WO00 / 70655, WO01 / 08230, WO01 / 39234A2, WO01 / 41512A1, WO02 / 02714A2, WO02 / 15645A1, WO02 / 44189A1, WO05 / 19373A2, WO2004 / 108857A1, WO2005 / 042444A2, WO2005 / 042550A1, Japanese Patent Publication 2001-247859, Japanese Patent Publication 2002-302671, Japanese Patent Publication 2002-117978, Japanese Patent Publication 2003-133074, Japanese Patent Publication 2002-235076, Japanese Patent Publication 2003-123982, Japanese Patent Publication 2002-170684, EP1211257, Japanese Patent Publication 2002-226495, Japanese Patent Publication 2002-234894, Japanese Patent Publication 2001-247859, Japanese Patent Publication 2001-298470, Japanese Patent Publication 2002-173674 , Japanese Patent Publication 2002-203678, Japanese Patent Publication 2002-203679, Japanese Patent Publication 2004-357791, Japanese Patent Publication 2006-93542, Japanese Patent Publication 2006-261623, Japanese Patent Publication 2006-256999, Japanese Patent Publication 2007-19462, Japanese Patent Publication 2007-84635, Japanese Patent Publication 2007-96259 And the phosphorescent compound described in each publication. Among these, Ir complex, Pt complex, Cu complex, Re complex, W complex, Rh complex, Ru complex, Pd complex, Os complex, Eu complex, Tb complex, Gd complex, Dy complex, Ce complex are preferable, Ir complex, Pt complexes and Re complexes are more preferable, and Ir complexes, Pt complexes, and Re complexes containing a coordination mode of at least one of metal-carbon bonds, metal-nitrogen bonds, metal-oxygen bonds, and metal-sulfur bonds are more preferable. From the standpoints of luminous efficiency, driving durability, chromaticity, and the like, Ir complexes, Pt complexes, and Re complexes containing three or more multidentate ligands are particularly preferable.

Although the following compounds are mentioned as a specific example of the phosphorescence emitting material which can be used for this invention, It is not limited to these.

As content of the said luminescent material, although 0.1 mass%-50 mass% are contained with respect to the mass of the whole compound which forms a light emitting layer generally in a light emitting layer, 1 mass%-50 mass% are preferable from a viewpoint of durability and external quantum efficiency, It is more preferable to contain 2 mass%-40 mass%.

As the host material, a hole transporting host material excellent in hole transporting properties and an electron transporting host material excellent in electron transporting properties can be used.

Examples of the hole transporting host include pyrrole, indole, carbazole, azaindole, azacarbazole, triazole, oxazole, oxadiazole, pyrazole, imidazole, thiophene, polyarylalkane, pyrazoline, para Zolone, phenylenediamine, arylamine, amino substituted chalcone, styrylanthracene, fluorenone, hydrazone, stilbene, silazane, aromatic tertiary amine compound, styrylamine compound, aromatic dimethylidene compound, porphyrin compound , Polysilane-based compounds, poly (N-vinylcarbazole), aniline copolymers, conductive polymer oligomers such as thiophen oligomers, polythiophenes, organic silanes, carbon films, or derivatives thereof. Among these, indole derivatives, carbazole derivatives, aromatic tertiary amine compounds and thiophene derivatives are preferable, those having a carbazole group in the molecule are more preferred, and compounds having a t-butyl substituted carbazole group are particularly preferred.

As the electron transporting host material, the electron affinity (Ea) is preferably 2.5 eV or more and 3.5 eV or less, more preferably 2.6 eV or more and 3.4 eV or less, particularly 2.8 eV or more and 3.3 eV or less from the viewpoint of durability improvement and lowering of the driving voltage. desirable. Further, from the viewpoint of durability improvement and lowering of the driving voltage, the ionization potential Ip is preferably 5.7 eV or more and 7.5 eV or less, more preferably 5.8 eV or more and 7.0 eV or less, particularly preferably 5.9 eV or more and 6.5 eV or less.

As the electron transporting host material, for example, pyridine, pyrimidine, triazine, imidazole, pyrazole, triazole, oxazole, oxadiazole, fluorenone, anthraquinodimethane, anthrone, diphenylquinone, thi Heterocyclic tetracarboxylic anhydrides, phthalocyanine, or derivatives thereof, such as opiranoxide, carbodiimide, fluorenylimidemethane, distyrylpyrazine, fluorine-substituted aromatic compound, naphthaleneperylene, (condensed ring with other rings And various metal complexes represented by metal complexes of 8-quinolinol derivatives such as BAlq, metal complexes containing metal phthalocyanine, benzoxazole and benzothiazole as ligands.

As the electron transporting host material, metal complexes, azole derivatives (benzimidazole derivatives, imidazopyridine derivatives, and the like) and azine derivatives (pyridine derivatives, pyrimidine derivatives, triazine derivatives, etc.) are preferable, and among them, metals from the durability point The complex compound is more preferable. The metal complex compound (A) is preferably a metal complex having a ligand having at least one of a nitrogen atom, an oxygen atom, and a sulfur atom coordinated to the metal.

There is no restriction | limiting in particular in the metal complex in a metal complex, According to the objective, it can select suitably, For example, a beryllium ion, magnesium ion, aluminum ion, gallium ion, zinc ion, indium ion, tin ion, platinum ion, palladium ion, etc. Can be mentioned. Among these, beryllium ions, aluminum ions, gallium ions, zinc ions, platinum ions, or palladium ions are preferable, and aluminum ions, zinc ions, or palladium ions are particularly preferable.

As the ligand contained in the metal complex, various known ligands may be used, and "Photochemistry and Photophysics of Coordination Compounds", Springer-Verlag, H. Yersin, 1987, "Organic Metal Chemistry-Basics and Applications", Shoka Borsa, listed by Akio Yamamoto, published in 1982, and the like.

As said ligand, a nitrogen-containing heterocyclic ligand (C1-C30 is preferable, C2-C20 is more preferable, C3-C15 is especially preferable). The ligand may be a single seat ligand or a two or more ligand, but a ligand of two or more and six or less seats is preferable. Moreover, the ligand of 2 or more and 6 or less seats, and the mixed ligand of a single seat are also preferable.

Examples of the ligand include azine ligands (e.g., pyridine ligands, bipyridyl ligands, terpyridine ligands, etc.), hydroxyphenylazole ligands (e.g., hydroxyphenylbenzimidazole ligands). , Hydroxyphenylbenzoxazole ligand, hydroxyphenylimidazole ligand, hydroxyphenylimidazopyridine ligand, and the like.), Alkoxy ligand (for example, methoxy, ethoxy, butoxy, 2) -Ethylhexyloxy, etc., C1-C30 is preferable, C1-C20 is more preferable, C1-C10 is especially preferable.), An aryloxy ligand (for example, phenyloxy, 1-naphthyloxy, 2-naphthyloxy, 2,4,6-trimethylphenyloxy, 4-biphenyloxy, etc. are mentioned, C6-C30 is preferable, C6-C20 is more preferable, Particularly preferred is 6 to 12 carbon atoms, heteroaryloxy ligand (for example, Pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy, etc. are mentioned, C1-C30 is preferable, C1-C20 is more preferable, C1-C12 is especially preferable.), Alkyl Thio ligand (for example, methylthio, ethylthio, etc. are mentioned, C1-C30 is preferable, C1-C20 is more preferable, C1-C12 is especially preferable.), Arylthio ligand ( For example, phenylthio etc. are mentioned, C6-C30 is preferable, C6-C20 is more preferable, C6-C12 is especially preferable.) Heteroarylthio ligand (for example, a pyrile) Dithio, 2-benzimizolylthio, 2-benzoxazolylthio, 2-benzthiazolylthio, etc. are mentioned, C1-C30 is preferable, C1-C20 is more preferable, C1-C12 Are particularly preferred.), Siloxy ligands (e.g., triphenylsiloxy groups, Ethoxy siloxy group, a triisopropyl siloxy group, etc. are mentioned, C1-C30 is preferable, C3-C25 is more preferable, C6-C20 is especially preferable.) An aromatic hydrocarbon anion ligand (Example For example, a phenyl anion, a naphthyl anion, an anthranyl anion, etc. are mentioned, C6-C30 is preferable, C6-C25 is more preferable, C6-C20 is especially preferable.), Aromatic hetero Ring anion ligands (for example, pyrrole anion, pyrazole anion, triazole anion, oxazole anion, benzoxazole anion, thiazole anion, benzothiazole anion, thiophene anion, and benzothiophene anion, etc. may be mentioned. C1-C30 is preferable, C2-C25 is more preferable, C2-C20 is especially preferable.) Indolenin anion ligand, etc. are mentioned, A nitrogen-containing heterocyclic ligand, Aryl An oxy ligand, a heteroaryloxy group, a siloxy ligand, etc. are preferable, A nitrogen containing heterocyclic ligand, an aryloxy ligand, a siloxy ligand, an aromatic hydrocarbon anion ligand, an aromatic heterocyclic anion ligand, etc. are more preferable.

Examples of the metal complex electron transporting host include, for example, Japanese Patent Laid-Open Publication No. 2002-235076, Japanese Patent Laid-Open Publication 2004-214179, Japanese Patent Laid-Open Publication 2004-221062, Japanese Patent Laid-Open Publication 2004-221065, Japanese Patent Laid-Open Publication 2004-221068, and Japanese Patent Publication The compound of each publication, such as 2004-327313, is mentioned.

The triplet lowest excitation level T1 of the host material is preferably higher than T1 of the phosphorescent material in terms of color purity, luminous efficiency, and driving durability.

Although it does not restrict | limit especially as content of the said host material, 15 mass% or more and 95 mass% or less are preferable with respect to the mass of the whole compound which forms a light emitting layer from a light emission efficiency and a drive voltage.

There is no restriction | limiting in particular as a formation method of the said light emitting layer, According to the objective, it can select suitably, For example, methods, such as resistance heating vapor deposition, an electron beam, sputtering, a molecular lamination method, a coating method, an LB method, are mentioned. Among these, resistance heating vapor deposition and a coating method are especially preferable.

As said coating method, a spin coating method, the casting method, the dip coating method, etc. are mentioned, for example.

Hole injection layer, hole transport layer

The material of the hole injection layer and the hole transport layer is not particularly limited as long as it has any one of a function of injecting holes from the anode, a function of transporting holes, and a function of blocking electrons injected from the cathode. Can be.

Examples of the material for the hole injection layer and the hole transport layer include carbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, parazolone derivatives and phenylene. Diamine derivatives, arylamine derivatives, amino substituted chalcone derivatives, styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidene compounds, Conductive polymer oligomers such as porphyrin-based compounds, polysilane-based compounds, poly (N-vinylcarbazole) derivatives, aniline copolymers, thiophene oligomers, and polythiophene. These may be used individually by 1 type and may use 2 or more types together.

The hole injection layer and the hole transport layer may be a single layer structure composed of one or two or more kinds of the above materials, or may be a multilayer structure composed of a plurality of layers of the same composition or different compositions.

As the method for forming the hole injection layer and the hole transport layer, for example, a method of coating by dissolving or dispersing a vacuum deposition method, an LB method, a hole injection agent and a hole transport agent in a solvent (spin coating method, cast method, dip coating method, etc.). ) Is used. In the case of a coating method, it can melt | dissolve or disperse | distribute with a resin component.

There is no restriction | limiting in particular as said resin component, According to the objective, it can select suitably, For example, polyvinyl chloride resin, polycarbonate resin, polystyrene resin, polymethyl methacrylate resin, polybutyl methacrylate resin, polyester resin , Polysulfone resin, polyphenylene oxide resin, polybutadiene, poly (N-vinylcarbazole) resin, hydrocarbon resin, ketone resin, phenoxy resin, polyamide resin, ethyl cellulose, vinyl acetate resin, ABS resin, polyurethane Resin, melamine resin, unsaturated polyester resin, alkyd resin, epoxy resin, silicone resin and the like. These may be used individually by 1 type and may use 2 or more types together.

There is no restriction | limiting in particular as thickness of the said hole injection layer and a hole transport layer, According to the objective, it can select suitably, For example, 1 nm-5 micrometers are preferable, 5 nm-1 micrometer are more preferable, 10 nm-500 nm Is particularly preferred. As said average thickness, ten points of the thickness of the said hole injection layer or a hole transport layer are measured, for example using the electron microscope photograph of a cross section, and the average value can be made into an average thickness.

Electron injection layer, electron transport layer

The material of the electron injecting layer and the electron transporting layer is not particularly limited as long as it has any one of a function of injecting electrons to the cathode, a function of transporting electrons, and a function of blocking holes injected from the anode. Can be.

As a material of the said electron injection layer and the electron carrying layer, for example, a triazole derivative, an oxazole derivative, an oxadiazole derivative, a fluorenone derivative, an anthraquinodimethane derivative, an anthrone derivative, a diphenylquinone derivative, and thiopyrandiox Heterocyclic tetracarboxylic anhydrides such as seed derivatives, carbodiimide derivatives, fluorenylidene methane derivatives, distyrylpyrazine derivatives, naphthaleneperylene, phthalocyanine derivatives, and 8-quinolinol derivatives, metal complexes, metalphthalocyanines and benzos Various metal complexes etc. which are represented by the metal complex which uses oxazole and benzothiazole as a ligand are mentioned. These may be used individually by 1 type and may use 2 or more types together.

As said electron injection layer and electron carrying layer, the single layer structure which consists of 1 type, or 2 or more types of the said material may be sufficient, and the multilayer structure which consists of multiple layers of the same composition or a different composition may be sufficient.

As the method for forming the electron injection layer and the electron transporting layer, for example, a vacuum vapor deposition method, an LB method, an electron injection agent and an electron transporting agent are dissolved or dispersed in a solvent and coated (spin coating method, cast method, dip coating method, etc.). ) And the like are used. In the case of a coating method, it can melt | dissolve or disperse | distribute with a resin component, As said resin component, what was illustrated in the case of a hole injection layer and a hole transport layer, for example is applicable.

There is no restriction | limiting in particular as thickness of the said electron injection layer and an electron carrying layer, According to the objective, it can select suitably, 1 nm-5 micrometers are preferable, 5 nm-1 micrometer are more preferable, 10 nm-500 nm are especially preferable. Do. As said average thickness, ten points of the thickness of the said electron injection layer or an electron carrying layer can be measured using the electron microscope photograph of a cross section, for example, and the average value can be made into an average thickness.

Middle layer

As said intermediate | middle layer, it has a function which adjusts the length of the light which advances in the said intermediate | middle layer which is in the light extraction surface side of the said 2nd electrode, and is the optical path length of incident light.

The intermediate layer is not particularly limited as long as it has the above-mentioned function. For example, when the sum of the phase differences when reflecting from the first electrode and the semi-transmissive layer is an integer multiple of 2π, from the first electrode to the transflective layer Adjusting an optical path length so that it may become an integer multiple of (lambda) / 2, when making the light emission peak wavelength in a light emitting layer into (lambda), etc. are mentioned.

If it is such a form as said intermediate | middle layer, there will be no restriction | limiting in particular about a shape, a structure, a size, etc., According to the objective, it can select suitably.

The material of the intermediate layer is not particularly limited as long as it does not significantly affect the wavelength or light intensity of the incident light, and various kinds of optically transparent inorganic and organic materials such as polyacrylate, polymethyl methacrylate, and poly Transparent resins, such as mead, are mentioned.

There is no restriction | limiting in particular as a formation method of the said intermediate | middle layer, According to the objective, it can select suitably, For example, methods, such as an electron beam method, sputtering method, resistance heating vapor deposition method, spin coating method, spray coating method, the inkjet method, are mentioned. .

As thickness of the said intermediate | middle layer, it adjusts so that the change of chromaticity by the angle in which the light of predetermined wavelength is observed can be specifically clamped between the 1st electrode and the intermediate | middle layer from following General formula (1) and General formula (2). It depends on the refractive index of the material, its composition, thickness, and the like.

However, in the general formula (1), n represents the refractive index of each layer, d ₁ represents the distance between the light emitting layer side surface of the first electrode and the light emitting layer side surface of the second electrode, m is the order Φ ₀ represents the reflection phase shift amount at the first electrode, φ ₁ represents the reflection phase shift amount at the second electrode, φ ₂ represents the reflection phase shift amount at the semi-transmissive layer, and λ1 is the light emission. The peak wavelength of the light to be shown is shown.

In the formula (2), n represents a refractive index of each layer, d ₂ represents a distance between the surface of the light emitting layer side of the first electrode and the surface of the light emitting layer side of the intermediate layer, and m represents an order. , φ ₀ represents the reflection phase shift amount at the first electrode, φ ₁ represents the reflection phase shift amount at the second electrode, φ ₂ represents the reflection phase shift amount at the semi-transmissive layer, and λ1 emits light. The peak wavelength of light is shown.

The general formula (1) represents a resonance condition when the light of the wavelength lambda 1 is observed from the front direction (θ = 0 °). The front direction refers to a time when a line is drawn from the substrate to the light emitting layer and the viewing angle θ viewed from this direction is 0 °.

The general formula (2) represents a resonance condition when the light of the wavelength lambda 1 is observed from the 45 ° direction (θ = 45 °). The 45 ° direction refers to the direction when the viewing angle θ is 45 ° when a waterline is drawn from the substrate to the light emitting layer and the viewing angle θ in this direction is 0 °.

By shifting the thickness of the intermediate layer to satisfy the relationship between Formulas (1) and (2), the observer's position with respect to the organic electroluminescent device is shifted (moved) to a high angle side such as 45 ° (view angle 45 °). and even the light of a wavelength (λ1) is radiated also continued by the action of the cavity length of the distance (d ₂₎ for the observation from the angle of the high-angle side.

In the front direction of the substrate, the wavelength λ 1 obtained by the resonator length of the distance d ₁ is drawn, but when the observer's position with respect to the organic EL device shifts to the high angle side, the resonance wavelength shifts to the short wavelength side. Going. As a result, the resonance effect due to the distance d ₁ decreases, so the light intensity decreases.

However, on the high angle side where the position of the observer with respect to the organic electroluminescent element is close to the surface of the organic electroluminescent element, the distance d ₂ in the general formula (2) is the resonator length of the wavelength λ1. Since the light satisfies each other again due to the resonance effect caused by the distance d ₂ , the spectral change can be suppressed even when the position of the observer with respect to the organic EL device is changed.

However, the angle change amount of the peak or chromaticity of the spectrum depends on the form of the emission spectrum of the light emitting material as shown in Figs. 3 and 4. For example, as shown in FIG. 8, the resonant wavelength shifts to the shorter wavelength as the viewing angle increases. Since the light emitting material also emits light from the short wavelength side, the light emission intensities on the short wavelength side are intensified with each other, and the viewing angle dependent characteristic (change in chromaticity corresponding to the viewer's position) changes. Therefore, the front resonance wavelength is preferably adjusted to a wavelength shorter than the first peak wavelength by counting from the short wavelength side of the emission spectrum. The light intensity of the peak wavelength of the luminescent material is set to 1, which is shorter wavelength than the peak wavelength, and the slope of the short wavelength side of the emission spectrum until the light intensity becomes 0.2 can be expressed by the following formula (1).

<Equation 1>

Δλ = λ (I0) -λ (0.2 × I0)

In Equation 1, λ (I0) is the front resonance wavelength, I0 is the light emission intensity at the wavelength, and λ (0.2 × I0) is the wavelength at which the light emission intensity is 0.2 times the light emission intensity of λ (I0). Λ (I0)> λ (0.2 × I0).

The reason why the light intensity is defined as Δλ until the light intensity reaches 0.2 is 0.2 because the SN ratio of the light emitting component worsens and the noise increases.

When Δλ of Equation 1 is small, chromaticity change can be suppressed. Δλ represents an inclination on the shorter wavelength side than the peak wavelength of the emission spectrum, as shown in FIGS. 3 and 4. The smaller the Δλ, the steeper the slope as shown in FIG. 3, and the larger the Δλ, the slower the slope as shown in FIG.

If Δλ is large, there are many light emitting components that can be resonated even when the viewing angle changes (the position of the observer with respect to the organic electroluminescent element), so that the light emission intensities are strengthened on the short wavelength side, and the viewing angle dependence characteristic is changed.

Based on the results of the intensive studies of the present inventors, it has been found that in the organic electroluminescent device of the present invention, when? Is less than 25 nm, the change in color taste is suppressed to satisfy the performance as a display.

As the chromaticity change, as shown in Fig. 7, a? U'v 'value is used. As said chromaticity change, it shows by the change amount for every angle from u'v 'value in a front (viewing angle 0 degree). In a display device such as a display, it is generally known that the value of Δu'v 'exceeds 0.02, which is undesirable.

For example, in red ((DELTA) = 25nm (resonance wavelength is short wavelength side) in FIG. 7,) when the index (DELTA) u'v 'of chromaticity change is measured in (DELTA) <25nm in the range of 0-80 degree of viewing angles, it is 0.02 or less. The amount of chromaticity change was suppressed. In addition, as shown in FIG. 7, the effect is similarly obtained also in blue ((DELTA) = 20 nm in FIG. 7) and green ((DELTA) == 15 nm in FIG. 7). If the resonance wavelength is set on the longer wavelength side than the peak wavelength of the emission spectrum, the? U'v 'value exceeds 0.02 as shown in FIG. Thus, chromaticity change can be suppressed by making resonance wavelength into short wavelength side rather than peak wavelength, and (DELTA) (lambda) to less than 25 nm.

Specifically, the average thickness of the intermediate layer can be changed by the color of light emitted from the light emitting layer. For example, the red color is determined as follows.

When the peak wavelength of the light drawn out in the front direction is 620 nm, the total thickness of the first resonator structure including the light emitting layer and the like is 324 nm according to formula (1), and the refractive index of the intermediate layer is 1.8. The thickness of the second resonator structure is found to be 465 nm according to the general formula (2).

Therefore, the thickness obtained by subtracting the average thickness of the second electrode from the difference becomes the average thickness of the intermediate layer, in which case 130 nm is optimal.

In the intermediate layer, the emission spectrum is wide, so that ± 5 nm is an allowable error range. The angle range for suppressing the peak wavelength shift depending on the viewing angle may be set to the lower angle side than the 45 ° direction, and according to the general formula (2) in the 40 ° direction, the average thickness of the intermediate layer is 90 nm. If the angle is further lowered, the peak wavelength shift becomes larger on the high angle side, resulting in a problem of impairing the color taste of the high viewing angle.

Therefore, in this case, 85-135 nm is preferable and, as for the thickness of an intermediate | middle layer, 125-135 nm is more preferable.

When the average thickness is less than 85 nm or more than 135 nm, the chromaticity change and color shift may be large depending on the position of the observer, or the improvement of efficiency may be small, and the effect of the present invention may not be obtained.

Here, as said average thickness, ten points of the thickness of the said intermediate | middle layer are measured using the electron microscope photograph of a cross section, for example, and the average value can be made into an average thickness.

Also, in the case of green and blue, the average thickness can be obtained on the same principle as in the case of red.

Semi-transmissive layer

The transflective layer is provided between the intermediate layer and the light transmitting layer, and has a function of transmitting a part of the light emitted from the light emitting layer and a part of the light reflected by the first electrode and reflecting another part of the respective light.

There is no restriction | limiting in particular as a material of the said semipermeable layer, Although it can select suitably according to the objective, For example, a metal etc. are mentioned.

As said metal, silver, magnesium-silver alloy, aluminum etc. are mentioned, for example.

There is no restriction | limiting in particular as a formation method of the said semi-transmissive layer, According to the objective, it can select suitably, For example, methods, such as an electron beam method, sputtering method, and resistance heating vapor deposition method, are mentioned.

There is no restriction | limiting in particular as an average thickness of the said semi-transmissive layer, According to the objective, it can select suitably, For example, 3 nm-50 nm are preferable, 5 nm-40 nm are more preferable, 10 nm-30 nm Particularly preferred.

When the said average thickness is less than 3 nm, since the reflectance is low, the effect of this invention may not be acquired, and when it exceeds 10 nm, since the transmittance | permeability is low, the effect of this invention may not be acquired.

Here, as said average thickness, 10 points of the thickness of the said semi-transmissive layer can be measured using the electron microscope photograph of a cross section, for example, and the average value can be made into an average thickness.

As the average thickness of the semi-transmissive layer, it is preferable to make the average thickness thinner than the second electrode in order to increase the resonance effect of the optical distance d ₁ . As ratio (average thickness of semi-transmissive layer / average thickness of 2nd electrode) of the average thickness of the said semi-transmissive layer and the said 2nd electrode, 0.1-2 are preferable, 0.2-1.5 are more preferable, 0.4- 1 is particularly preferred.

If the average thickness ratio is less than 0.1, the reflectance may be insufficient, and the effect of the present invention may not be obtained. If the ratio exceeds 2, the target wavelength is not enhanced or the chromaticity suppression effect when viewed from a high angle side is not obtained. There is a case.

Light transmitting layer

The light transmitting layer has at least a gap between the substrate and the transflective layer, cancels the phase of the reflected light between the transflective layer and the substrate interface, increases the amount of light transmitted to the substrate, and changes the chromaticity by the angle observed. It has a function to suppress.

If it has such a function as said light transmitting layer, there will be no restriction | limiting in particular about a shape, a structure, a size, etc., According to the objective, it can select suitably.

There is no restriction | limiting in particular as a material of the said light transmitting layer, According to the objective, what is necessary is just to select suitably, For example, magnesium fluoride, Alq, Cytop (made by Asahi Glass Corporation), SiNx, etc. are mentioned.

As the light transmitting layer, for example, as shown in FIG. 2, the light transmitting layer may be provided between the second electrode and the intermediate layer in addition to the substrate and the transflective layer. By setting it as such a structure, the reflection prevention effect in the interface of a 2nd electrode can be improved, and light extraction efficiency can be improved more.

As average thickness of the said light transmitting layer, when length of 1/4 of the peak wavelength of the light radiate | emitted from the said light emitting layer is set to t, and the refractive index of the said light transmitting layer is set to n, it is 0.9 * t / n or more and 1.1 * t / n. The following is preferable.

If the average thickness is less than 0.9 x t / n, the light extraction efficiency improvement effect by the effect of the present invention may not be obtained. If the average thickness exceeds 1.1 x t / n, the light extraction efficiency may be reversed by absorption depending on the material. You may fall.

Specifically, for example, when the peak wavelength is set to 620 nm of red and MgF ₂ is used as the material, 101 nm to 123.5 nm are preferable because MgF ₂ has a refractive index of 1.38. If it is optimized as a whole structure, such as phase change by reflection, 10 nm thinner than 101 nm-123.5 nm is preferable, and 91 nm-113.5 nm are preferable.

In the light transmitting layer, since the emission spectrum is wide, about ± 5 nm is allowed as a change in thickness. Therefore, as average thickness of a light transmitting layer, 86 nm-118.5 nm are more preferable.

As said average thickness, ten points of the thickness of the said light transmitting layer are measured using the electron microscope photograph of a cross section, for example, and the average value can be made into an average thickness.

As the difference in refractive index Δn between the layers adjacent to the light transmitting layer, when (Δn) is large, the interfacial reflectivity is improved, so the effect is more emphasized, and therefore at least 0.1 is preferable.

If the refractive index difference is less than 0.1, the reflectance is low, so that the resonant structure intended by the present invention may not be obtained. Here, the adjoining layer means a substrate and a transflective layer in FIG. 1, and a substrate, a transflective layer, an intermediate layer, and a second electrode in FIG. 2. The said refractive index can be measured using an ellipsometer (made by Horiba Seisakusho).

-Board-

As the substrate, a shape, a structure, a size, and the like may be appropriately selected, and generally, a plate shape is preferable as the shape of the substrate. As a structure of a board | substrate, a single layer structure may be sufficient, a laminated structure may be sufficient, may be formed from a single member, and may be formed from two or more members.

The substrate may be colorless transparent or colored transparent, but colorless transparent is preferable because it does not scatter or decay light generated from the light emitting layer.

There is no restriction | limiting in particular as a material of the said board | substrate, According to the objective, it can select suitably, For example, inorganic materials, such as yttria stabilized zirconia (YSZ), glass, polyethylene terephthalate resin, polybutylene phthalate resin, polyethylene naphthalate Resin, polyester resin, polystyrene resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, polyimide resin, polycycloolefin resin, norbornene resin, poly (chlorotrifluoroethylene) resin and the like. have. These may be used individually by 1 type and may use 2 or more types together.

When using glass as the said board | substrate, it is preferable to use an alkali free glass in order to reduce the elution ion from glass about the material. In addition, when using soda-lime glass, it is preferable to use the thing which performed barrier coating, such as a silica (for example, a barrier film substrate). In the case of an organic material, it is preferable that it is excellent in heat resistance, dimensional stability, solvent resistance, electrical insulation, and workability.

When using the said thermoplastic substrate, you may further form a hard-coat layer, an undercoat layer, etc. as needed.

The planarization layer for planarizing the upper surface shape may be disposed on the upper surface of the substrate, and the light transmitting layer or the like may be disposed on the planarization layer.

Especially limited as the material of the flattening layer, but, it may be appropriately changed according to the purpose, for example, there may be mentioned SiO _2, SiON, polyimide or the like.

An example of embodiment of the organic electroluminescent element of this invention comprised as mentioned above is demonstrated using FIG.

The organic electroluminescent device 100 includes a first electrode 9, an electron transport layer 8, a light emitting layer 7, a hole transport layer 6, a second electrode 5, an intermediate layer 4, and a transflective layer 3. ), The light transmitting layer 2 and the substrate 1 in this order.

In this organic electroluminescent element 100, it functions as a first resonator structure composed of a first electrode 9, an electron transport layer 8, a light emitting layer 7, a hole transport layer 6, and a second electrode 5. And a first electrode 9, an electron transport layer 8, a light emitting layer 7, a hole transport layer 6, a second electrode 5, an intermediate layer 4, and a semi-transmissive layer 3. 2 Functions as a resonator structure.

In the organic electroluminescent element 100 configured as described above, light of the wavelength? 1 selected from the resonator length of the optical distance d ₁ is emitted in the front direction (θ = 0 °). On the other hand, in the direction in which the angle to observe from the optical axis direction becomes large, the light of wavelength lambda 1 is also emitted on the high angle side by the action of the resonator length of the optical distance d ₂ with respect to the observation from the high angle. As a result, the chromaticity change which arises corresponding to the position of an observer with respect to an organic electroluminescent element can be suppressed.

As the organic electroluminescent device of the present invention, in consideration of a large area light emitting device, it is preferable to set it as a bottom emission type structure which extracts light from the substrate 1 side in view of electrical characteristics such as sheet resistance of the transparent electrode. .

(Organic electroluminescent display)

The organic electroluminescent display of the present invention comprises the organic electroluminescent element, and other configurations can be applied as necessary. There is no restriction | limiting in particular as said other structure, According to the objective, it can select suitably, The all well-known means can be applied as a matter which is necessary for a display.

As an example of the organic electroluminescent display, light of each color is extracted by changing the thickness of the intermediate layer corresponding to red (R), green (G), and blue (B). With such a configuration, it is possible to suppress the change in chromaticity due to the observation angle with excellent light extraction efficiency and low power consumption.

Example

Hereinafter, although the Example of this invention is described, this invention is not limited to these Examples at all. In addition, the material refractive index in an Example is a measured value by the ellipsometry method unless there is particular notice. Since the ellipsometry method is a measurement method by angular scanning of a polarizer as a monochromatic light source, the refractive index in the light source wavelength is described. The light source used the He-Ne laser of 632.8 nm in wavelength.

(Example 1)

<Production of Organic Electroluminescent Device>

MgF ₂ was formed on a glass substrate having a thickness of 0.7 mm and a refractive index of 1.51 by vacuum deposition so as to have a thickness of 100 nm as a light transmitting layer. The refractive index of the light transmissive layer was measured using an ellipsometer and found to be 1.38.

Silver (Ag) was formed on the light transmissive layer by vacuum deposition so as to have a thickness of 12 nm.

Alq (tris (8-trihydroxyquinolinato) aluminum) as an intermediate layer was formed on the semitransmissive layer by vacuum deposition so as to have a thickness of 130 nm. The refractive index of Alq was measured using an ellipsometer and found to be 1.74.

Subsequently, silver (Ag) was formed as a second electrode (anode) on the intermediate layer by vacuum deposition so as to have a thickness of 20 nm, and the formed silver film was brought into contact with the electrode terminal.

F4-TCNQ (2,3,5,6-tetrafluoro) in 2-TNATA (4,4 ', 4' '-tris (2-naphthylphenylamino) triphenylamine) as a hole transport layer on the second electrode -7,7,8,8-tetracyanoquinodimethane) was doped by 1.0% and formed by vacuum deposition to a thickness of 235 nm, and NPD (N, N'-diphenyl-) on the hole transport layer. N, N'-di (α-naphthyl) -benzidine) was vacuum deposited to a thickness of 10 nm.

Subsequently, BAlq (aluminum (III) bis (2-methyl-8-quinolinato) 4-phenylphenolate) was used as a host material on the NPD, and a light emitting material A represented by the following structural formula as a light emitting material had a mass ratio of 95: It formed by vacuum co-evaporation so that thickness might be set to 30 nm in the ratio of 5. In addition, the ratio which monitored the signal of a crystal oscillator with CRTM9000 (made by Alba Corporation) was made into the mass ratio.

Subsequently, BAlq (aluminum (III) bis (2-methyl-8-quinolinato) 4-phenylphenolate) was formed on the light emitting layer by vacuum deposition so as to have a thickness of 39 nm. In order to improve electron injection property, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) was vacuum-deposited to a thickness of 1 nm and LiF to a thickness of 1 nm. Vacuum deposition.

Subsequently, Al was formed on the LiF as a first electrode (cathode) by vacuum deposition so as to have a thickness of 100 nm, thereby producing the organic electroluminescent element 1.

The obtained organic electroluminescent element 1 had a secondary micro cavity structure, and the produced organic electroluminescent element 1 was optimized for red light emission (about 620 nm).

(Example 2)

<Production of Organic Electroluminescent Device>

In Example 1, the organic electroluminescent element 2 was produced like Example 1 except having formed the light transmitting layer as follows.

Formation of the light transmitting layer

MgF ₂ was formed on a glass substrate having a thickness of 0.7 mm and a refractive index of 1.51 by vacuum deposition so as to have a thickness of 112 nm as a light transmitting layer. The refractive index of the light transmissive layer was measured using an ellipsometer and found to be 1.38.

The obtained organic electroluminescent element 2 had a secondary micro cavity structure, and the produced organic electroluminescent element 2 was optimized for red light emission (about 620 nm).

(Example 3)

<Production of Organic Electroluminescent Device>

In Example 1, the organic electroluminescent element 3 was produced like Example 1 except having formed the intermediate | middle layer as follows.

Formation of intermediate layer

A 30 nm thick MgF ₂ film was deposited on the semitransmissive layer as an intermediate layer, and then ITO was formed by vacuum deposition so as to have a thickness of 100 nm. Each refractive index was measured using an ellipsometer, and the MgF ₂ was 1.38 and the ITO was 1.98.

The obtained organic electroluminescent element 3 had a secondary micro cavity structure, and the produced organic electroluminescent element 3 was optimized for red light emission (about 620 nm).

(Comparative Example 1)

<Production of Organic Electroluminescent Device>

In Example 1, the organic electroluminescent element 4 was produced like Example 1 except having set it as the structure which does not have a light transmissive layer, a semi-transmissive layer, and an intermediate | middle layer.

(Comparative Example 2)

<Production of Organic Electroluminescent Device>

In Example 1, the organic electroluminescent element 5 was produced like Example 1 except having set it as the structure which does not have a light transmissive layer.

(evaluation)

The chromaticity change and light extraction efficiency corresponding to the position of an observer with respect to the organic electroluminescent element of each produced organic electroluminescent element were evaluated as follows. In addition, about Example 1 and the comparative example 1, the emission spectrum was measured as follows.

Chromaticity change corresponding to the position of the observer with respect to the organic electroluminescent element

Each organic electroluminescent element thus produced is placed upright, and each angle (a line is drawn from the substrate to the light emitting layer, and a viewing angle viewed from this direction is 0 °, and is 5 ° to ± 85 ° in the left and right direction based on the water line). Was calculated based on the CIE1976 standard from the x and y chromaticity coordinates obtained by calculating the u 'and v' of the CIE chromaticity coordinates. The results are shown in FIG.

Light extraction efficiency

Each produced organic electroluminescent element was made to emit light, and the light quantity was measured with a photometer (multi-channel spectrometer, the product of Oceanphotonics Co., Ltd.). The light extraction efficiency was calculated based on the measured light quantity. The results are shown in Table 1.

<Measurement of emission spectrum with different viewing angles>

About the produced organic electroluminescent element of Example 1 and Comparative Example 1, the emission spectrum was measured with the spectrophotometer CS2000 (made by Konica Minolta), rotating a sample element in a gonio stage. The result of Example 1 is shown in FIG. 8, and the result of the comparative example 1 is shown in FIG.

However, the efficiency in Table 1 shows the current luminance efficiency at 1,000 cd / m 2.

From Table 1, it turned out that Examples 1-3 have improved the light extraction efficiency compared with Comparative Examples 1-2.

6 shows that the values of Δu'v 'are 0.02 in Examples 1 to 3, and the values of Δu'v' are significantly higher than 0.02 in Comparative Examples 1 to 2. As a result, in Examples 1 to 3, it was found that the chromaticity change corresponding to the position of the observer with respect to the organic electroluminescent element was greatly suppressed.

As shown in FIG. 8, it was found that in the emission spectrum of Comparative Example 1, as the viewing angle became larger, the peak position of the spectrum shifted to the shorter wavelength side and the shape of the spectrum also changed.

As shown in FIG. 9, the emission spectrum of Example 1 was found to have a relatively similar shape even when the peak position of the spectrum was small compared to Comparative Example 1 and the viewing angle was changed. It is known that the change in the shape of the spectrum correlates with the change in the color taste, and the smaller the change in both the shift amount of the peak position and the spectral shape is obtained. That is, it was found that the same configuration as in Example 1 improves the brightness of light extraction due to the effect of the light transmitting layer in addition to the chromaticity change.

Since the organic electroluminescent device of the present invention has excellent light extraction efficiency and can suppress chromaticity change corresponding to the position of the observer with respect to the organic electroluminescent device, for example, a display, a computer, a vehicle display, an outdoor display, It can be used suitably in various fields, such as a household apparatus, a business apparatus, a household appliance, a traffic relation indicator, a clock indicator, a calendar indicator, a luminescent screen, an acoustic apparatus, etc.

Claims (9)

As an organic electroluminescent device having at least a first electrode, a light emitting layer, a semipermeable second electrode, an intermediate layer, a semitransmissive layer, and a light transmitting layer in this order:
A first resonator structure for resonating the light emitted from the light emitting layer between the first electrode and the second electrode and emitting the light;
A second resonator structure for resonating the light between the first electrode and the transflective layer and emitting the light;
When the thickness of the light transmitting layer is a length of 1/4 of the peak wavelength of the light emitted from the light emitting layer, and the refractive index of the light transmitting layer is n, the following formula 0.9 × t / n or more 1.1 × t / An organic electroluminescent element characterized by satisfying n or less. The method of claim 1,
And an index of refraction between the light transmitting layer and a layer adjacent to the light transmitting layer is 0.1 or more. The method of claim 1,
The material of the transflective layer is an organic electroluminescent device, characterized in that the metal. The method of claim 3, wherein
The metal is an organic electroluminescent device, characterized in that at least one selected from silver, magnesium-silver alloy, and aluminum. The method of claim 1,
And the light emitting layer contains at least one phosphorescent material. The method of claim 1,
The organic electroluminescent device is an organic electroluminescent device, characterized in that the bottom emission type. The method of claim 1
A light transmitting layer is further provided between the second electrode and the intermediate layer. The thickness of the light transmitting layer is a length of 1/4 of the peak wavelength of the light emitted from the light emitting layer, and the refractive index of the light transmitting layer is n. The organic electroluminescent element which satisfy | fills following formula 0.9xt / n or more and 1.1xt / n or less when it is set as it is. The method of claim 1,
In the emission spectrum of the light emitting material in the light emitting layer, the front resonance wavelength is shorter than the first peak wavelength counting from the short wavelength side of the light emission spectrum,
The emission spectrum satisfies Δλ <25 nm represented by the following formula and the following formula (1).
<Equation 1>
Δλ = λ (I0) -λ (0.2 × I0)
[Wherein λ (I0) represents the front resonant wavelength, I0 represents the light emission intensity at the wavelength, and λ (0.2 × I0) represents the light emission intensity of 0.2 times the light emission intensity of λ (I0). Wavelength, and? (I0)> λ (0.2 × I0).] As an organic electroluminescent element having at least a first electrode, a light emitting layer, a semi-transmissive second electrode, an intermediate layer, a semi-transmissive layer, and a light transmitting layer in this order,
A first resonator structure for resonating the light emitted from the light emitting layer between the first electrode and the second electrode and emitting the light;
A second resonator structure for resonating the light between the first electrode and the transflective layer and emitting the light;
When the thickness of the light transmitting layer is a length of 1/4 of the peak wavelength of the light emitted from the light emitting layer, and the refractive index of the light transmitting layer is n, the following formula 0.9 × t / n or more 1.1 × t / An organic electroluminescent display comprising red, green, and blue monopixels each having an organic electroluminescent element satisfying n or less as a sub pixel.

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