JP2012244060A - Organic electroluminescent element and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which can prevent decrease in emission efficiency due to penetration of electrons and holes through a luminous layer caused by irregularities of a metallic member, and drastically enhances luminous efficiency and durability, and to provide a manufacturing method of an organic electroluminescent element.SOLUTION: The organic electroluminescent element having a pair of electrodes consisting of a positive electrode and a negative electrode, and a luminous layer between the pair of electrodes is further provided with a metallic member having an average height of 20 nm or more contiguously to at least one electrode on the luminous layer side, and an adjacent layer having an average height of 15 nm or less between the metallic member and the luminous layer.

Description

  The present invention relates to an organic electroluminescent device and a method for manufacturing the organic electroluminescent device.

By introducing a metal member such as metal fine particles between the light emitting layer and the electrode of the organic electroluminescent element, the emission from the light emitting layer is promoted by the surface plasmon resonance of the metal member, and the luminous efficiency and durability of the organic electroluminescent element. It is known that can be improved. For example, it has been reported that the EL emission of tris (8-quinolinolato) aluminum (Alq3) is improved 20 times by introducing gold nanoparticles in the vicinity of the light emitting layer (see Non-Patent Document 1).
Such a plasmon effect is achieved by arranging a metal member in the vicinity of the light emitting layer of the organic electroluminescent element, inducing plasmon on the surface of the metal member, adding new light emission that is re-radiated after absorbing energy, and organic An emission transition due to a new plasmon resonance is added to the light emission process of the electroluminescent element, and the effect of shortening the exciton lifetime can be exhibited. By utilizing this plasmon resonance, the luminous efficiency is improved and the durability is improved by shortening the exciton lifetime.

However, the introduction of the metal member in the vicinity of the light emitting layer may additionally have a negative effect on the characteristics of the organic electroluminescent element and may reduce the light emission efficiency. As a negative effect, when a thin portion of the light emitting layer is formed due to the introduction of irregularities by the metal member, electrons or holes penetrate the light emitting layer and recombine at portions other than the light emitting layer, resulting in a decrease in luminous efficiency. May end up. Such a decrease in light emission efficiency is considered to be particularly remarkable in a phosphorescent material having a high internal quantum efficiency.
In order to solve the above problem, for example, Patent Document 1 discloses that an ultrathin film is formed using metal fine particles having a particle diameter of 0.1 nm to 10 nm, thereby suppressing unevenness of the metal fine particles and improving luminous efficiency. It has been proposed.
However, Non-Patent Document 2 suggests that the metal plasmon having a particle size of 0.1 nm to 10 nm is strongly quenched by a non-radiating Forster process, and thus the plasmon effect cannot be obtained effectively.

  Therefore, it is possible to prevent a decrease in light emission efficiency due to penetration of electrons and holes in the light emitting layer due to unevenness of the metal member, and to improve the organic light emitting element and the organic electroluminescent element in which the light emission efficiency and the durability are dramatically improved. At present, the provision of manufacturing methods is strongly demanded.

JP-T 2009-510746

Appl. Phys. Lett. 96,043307 (2010) Anal. Biochem. , 337: 171-194, 2005.

  This invention is made | formed in view of this present condition, and makes it a subject to solve the said various problems in the past and to achieve the following objectives. That is, according to the present invention, by providing an adjacent layer between the metal member and the light emitting layer, it is possible to prevent a decrease in light emission efficiency due to penetration of electrons and holes in the light emitting layer due to unevenness of the metal member. It is possible to provide an organic electroluminescent device and a method for manufacturing the organic electroluminescent device, which are capable of dramatically improving luminous efficiency and durability.

  As a result of intensive studies by the inventor in order to solve the above problems, the metal member is disposed on the light emitting layer side adjacent to at least one electrode of a pair of electrodes composed of an anode and a cathode. It has been found that the effect of shortening the upper level lifetime (exciton lifetime) can be obtained by the luminescence transition due to plasmon resonance, improving the emission efficiency and improving the durability by shortening the exciton lifetime. Further, an adjacent layer having an average height of 15 nm or less is provided between the metal member and the light emitting layer, and the average height of the metal member is set to 20 nm or more, whereby electrons in the light emitting layer due to the unevenness of the metal member. In addition, it is possible to suppress a decrease in light emission efficiency due to penetration of holes and holes, and preferably, by setting the dispersion 2σ of the average height of the metal member to 30 nm or less, the distance between the metal member and the light emitting layer is optimized, and plasmon It has been found that the effect of improving the luminous efficiency and durability by resonance increases.

This invention is based on the said knowledge by this inventor, and as a means for solving the said subject, it is as follows. That is,
<1> An organic electroluminescent device having a pair of electrodes composed of an anode and a cathode, and a light emitting layer between the pair of electrodes,
A metal member having an average height of 20 nm or more on the light emitting layer side adjacent to at least one of the electrodes;
An adjacent layer having an average height of 15 nm or less between the metal member and the light emitting layer;
It is an organic electroluminescent element characterized by having.
<2> The organic electroluminescent element according to <1>, wherein the metal member causes plasmon resonance due to light emitted from the light emitting layer.
<3> The organic electroluminescence device according to any one of <1> to <2>, wherein the dispersion 2σ of the average height of the metal member is 30 nm or less.
<4> The organic electroluminescence device according to any one of <1> to <3>, wherein the metal member is disposed in at least one of a pattern shape and a dot shape.
<5> The organic electroluminescent element according to any one of <1> to <4>, wherein the area ratio of the metal member is 5% or more.
<6> The organic electroluminescent element according to any one of <1> to <5>, wherein the electrode adjacent to the metal member is an ITO electrode.
<7> The organic electroluminescent element according to any one of <1> to <6>, wherein the adjacent layer is produced by a liquid phase film forming method.
<8> The organic electroluminescent element according to any one of <1> to <7>, wherein the light emitting layer contains a phosphorescent material.
<9> A method for producing the organic electroluminescent element according to any one of <1> to <8>,
A metal member forming step of forming a metal member on the electrode;
An adjacent layer forming step of forming an adjacent layer on the metal member by a liquid phase film forming method;
It is the manufacturing method of the organic electroluminescent element characterized by including.

  According to the present invention, various problems in the prior art can be solved, and by providing an adjacent layer between the metal member and the light emitting layer, luminous efficiency due to penetration of electrons and holes in the light emitting layer due to the unevenness of the metal member, etc. Can be prevented, and the organic electroluminescence device and the method for manufacturing the organic electroluminescence device can be provided in which the luminous efficiency and durability are remarkably improved.

FIG. 1 is a diagram for explaining how to obtain the average height of adjacent layers. FIG. 2 is an electron micrograph showing an arrangement state of metal members produced by a method of lifting off a metal material after EB lithography. FIG. 3 is a schematic diagram showing a positional relationship between the metal member of FIG. 2 and the light emitting layer. FIG. 4 is an electron micrograph showing the arrangement of metal members prepared by a method of annealing after depositing a metal material. FIG. 5 is a schematic diagram showing the positional relationship between the metal member of FIG. 4 and the light emitting layer.

(Organic electroluminescent device and organic electroluminescent device manufacturing method)
The organic electroluminescent element of the present invention comprises a pair of electrodes comprising an anode and a cathode, and a light emitting layer between the pair of electrodes, and a metal member on the light emitting layer side adjacent to at least one of the electrodes. And an adjacent layer between the metal member and the light emitting layer, and another layer as necessary.
The method for producing an organic electroluminescent element of the present invention is a method for producing the organic electroluminescent element of the present invention,
A metal member forming step of forming a metal member on the electrode;
An adjacent layer forming step of forming an adjacent layer on the metal member by a liquid phase film forming method, and further including other steps as necessary.
Hereinafter, through the description of the organic electroluminescent element of the present invention, details of the method for producing the organic electroluminescent element of the present invention will be clarified.

<Metal member>
The metal member is disposed adjacent to at least one of the electrodes. That is, the electrode may be adjacent to either of the pair of electrodes including the anode and the cathode, but is preferably an electrode on the light emission side, and more preferably an anode.
The metal member is preferably one that causes plasmon resonance due to light emitted from the light emitting layer. It can be confirmed by measuring the exciton lifetime of the light emitting layer that the metal member has plasmon resonance caused by the light emitted from the light emitting layer.

There is no restriction | limiting in particular about the structure of the said metal member, a shape, a magnitude | size, etc., It can select suitably according to the objective. The metal member is preferably a metal film made of fine metal particles. The metal film may be a solid film or a granular film (a film having a concavo-convex structure smaller than the wavelength of emitted light), but metal fine particles having an average particle diameter of 5 nm or more are randomly selected. Or the island-shaped structure film | membrane disperse | distributed to a periodic-arrangement pattern at a film | membrane form is preferable. Here, the average particle diameter means an average value of the maximum length of the metal fine particles. That is, when the metal fine particles are spherical, the average value of the diameter thereof, and when the metal fine particles are elongated (rod-shaped) metal particles whose aspect ratio of the long diameter and the short diameter perpendicular to the metal fine particles is greater than 1, Mean value.
The average particle diameter of the metal fine particles is preferably 5 nm or more, and more preferably 20 nm to 500 nm.
The average particle diameter of the metal fine particles can be measured, for example, by observing the surface with a scanning electron microscope (S4100, manufactured by Hitachi, Ltd.).

The average height of the metal member is 20 nm or more, preferably 20 nm to 100 nm, and more preferably 20 nm to 60 nm. If the average height is less than 20 nm, metal quenching due to a non-radiative Forster process may occur strongly, which is not preferable.
The average height of the metal members is, for example, the height of 100 metal members measured by measuring the height of the metal members using an atomic force microscope (SPA-400, manufactured by Seiko Instruments Inc.). Was the average height of the metal members.

The average height dispersion 2σ of the metal member is preferably 30 nm or less, more preferably 10 nm or less, and still more preferably 5 nm or less. If the dispersion 2σ of the average height of the metal member exceeds 30 nm, the distance between the light emitting layer and the metal member may not be optimal, and the exciton lifetime may be shortened by plasmon resonance.
The average height variance 2σ of the metal members can be calculated from the measured height values of 100 metal members.
The area ratio (density) of the metal member is preferably 5% or more, more preferably 10% or more, and further preferably 15% to 60%. When the area ratio is less than 5%, the effect of plasmon resonance is small, and the exciton lifetime change may be small.
The area ratio is obtained by, for example, observing the surface of a sample in which a metal member is formed on a substrate with an electrode with a scanning electron microscope (manufactured by Hitachi, S4100). The area B of the non-existing portion is obtained, and the area ratio of the metal member can be obtained from the following formula [A / (A + B)] × 100%.

  The metal material constituting the metal member is not particularly limited as long as plasmon resonance is generated by light emitted from the light emitting layer, and can be appropriately selected according to the purpose. For example, Ag (silver), Au Examples thereof include metals such as (gold), Cu (copper), Al (aluminum), Pt (platinum), and alloys containing these metals as main components. Here, the “main component” is defined as a component having a content of 80% by mass or more. Among these, Ag or Au is particularly preferable. In particular, Ag is preferable if the emitted light is a visible wavelength. This is because Ag can cause surface plasmon resonance in the visible range from the plasma frequency. In addition, if the emitted light has a wavelength other than the visible range, for example, infrared, Au and Ag are preferable.

  There is no restriction | limiting in particular as a formation method of the said metal member, According to the objective, it can select suitably, For example, (1) The method by EB lithography, (2) The method of annealing after forming a metal material into a film, (3) A method of forming a film of a metal material can be used. Among these, the method by (1) EB lithography is particularly preferable from the viewpoint that the distance between the metal member and the light emitting layer can be controlled uniformly and the light emission efficiency can be improved.

According to the method of (1) EB lithography, regularly arranged metal members are formed as shown in FIG. 2, and the distance d1 between the metal member 4 and the light emitting layer 3 is uniformly controlled as shown in FIG. it can.
Here, the distance d1 between the metal member 4 and the light emitting layer means a distance between the maximum height of the metal member and the light emitting layer, and is preferably 5 nm to 30 nm. If the distance d1 is less than 5 nm, charge transfer may occur directly from the light emitting layer and light emission may be attenuated. If the distance d1 exceeds 30 nm, plasmon resonance due to emitted light does not occur and an emission enhancement effect is obtained. It may not be possible.

  The method by (1) EB lithography is not particularly limited and can be appropriately selected according to the purpose. For example, an electron beam (EB) positive chemically amplified resist is applied onto a glass substrate with an ITO electrode. . Next, a predetermined pattern is drawn by the electron beam drawing apparatus. Development is performed after drawing. After development, a metal material having a purity of 99.99% is vapor-deposited with an electron beam vapor deposition apparatus. Next, the resist and metal material in unnecessary portions are removed by immersing the whole substrate in an acetone solution, thereby obtaining regularly arranged metal members as shown in FIG.

(2) According to the method of annealing after forming the metal material, a metal member having a random size and arrangement as shown in FIG. 4 is formed. As shown in FIG. 5, the metal member 4 and the light emitting layer are formed. The distances d2, d3, d4 with respect to 3 are not uniform.
As a method for forming the metal material, electron beam evaporation or thermal evaporation is preferable.
The annealing temperature is preferably 200 ° C to 500 ° C, more preferably 250 ° C to 350 ° C.
The method of annealing after forming the metal material is not particularly limited and can be appropriately selected according to the purpose. For example, the metal material is deposited on an electrode-attached glass substrate by an electron beam deposition apparatus. To do. Thereafter, annealing is performed at 300 ° C. using the substrate heating mechanism of the electron beam evaporation apparatus, thereby obtaining a metal member having a structure with a random size and arrangement as shown in FIG.

  According to the method of (3) depositing a metal material, a metal member having a random size and arrangement is formed. Compared with the method of annealing after (2) depositing the metal material, the size dispersion becomes larger. The film formation is preferably performed by the same method as in (2).

<Adjacent layer>
The adjacent layer is provided between the metal member and the light emitting layer, and has an average height of 15 nm or less, preferably 10 nm or less. When the average height exceeds 15 nm, a thin portion is generated in the light emitting layer, and electrons or holes may penetrate through the light emitting layer and recombine at portions other than the light emitting layer, resulting in a reduction in light emission efficiency.
Here, the average height of the adjacent layer is an average value of the “maximum height” measured at 20 locations, and the “maximum height” is the highest on the surface of the adjacent layer as shown in FIG. The height is the difference between the position and the lowest position, and Ry in FIG. 1 is the maximum height. It shows that an adjacent layer is flat, so that the average height of the said adjacent layer is small.
Specifically, for example, the surface shape of the adjacent layer is observed in an area of 1 μm × 1 μm with an atomic force microscope (SPA-400, manufactured by Seiko Instruments Inc.), and the difference between the maximum value and the minimum value is determined. The maximum height in this area. The measurement was performed in 20 regions, and the arithmetic average value of the maximum height in each region was defined as the average height of the adjacent layer.

The adjacent layer is preferably manufactured by a liquid phase film forming method. Thereby, the unevenness | corrugation by the said metal member can be planarized efficiently.
In the case of the liquid phase film forming method, the adjacent layer material can be formed by dissolving or dispersing the adjacent layer material in a solvent to form a coating solution, applying the coating solution by a known coating method, and drying. .
The solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include aromatic solvents, halogen solvents, ether solvents, ester solvents, alcohol solvents, ketone solvents, paraffin solvents. Examples thereof include a solvent, an alkyl-substituted aromatic solvent having 4 or more carbon atoms, and an amide solvent. These may be used individually by 1 type and may use 2 or more types together.
Examples of the aromatic solvent include benzene, toluene, xylene, ethylbenzene, diethylbenzene, anisole, chlorobenzene, dichlorobenzene, chlorotoluene and the like.
Examples of the halogen solvent include dichloromethane, dichloroethane, chloroform, carbon tetrachloride, tetrachloroethane, and trichloroethane.
Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like.
Examples of the alcohol solvent include methanol, ethanol, propanol, isopropyl alcohol, butanol, pentanol, hexanol, octanol, nonanol, cyclohexanol, methyl cellosolve, ethyl cellosolve, ethylene glycol, and benzyl alcohol.
Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone.
Examples of the paraffinic solvent include n-decane, n-dodecane, n-tetradecane, n-hexadecane and the like.
Examples of the ester solvent include ethyl acetate, butyl acetate, isobutyl acetate, methyl ethanoate, and methyl propanoate.
Examples of the alkyl-substituted aromatic solution having 4 or more carbon atoms include n-butylbenzene, cyclohexylbenzene, butylbenzene, and dodecylbenzene.
Examples of the amide solvent include N, N-dimethylformamide (DMF), dimethyl sulfoxide, N-methyl-2-pyrrolidone and the like.

  The coating method is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the inkjet method, spin coating method, kneader coating method, bar coating method, blade coating method, casting method, dip method, curtain Examples include a coating method. Among these, the spin coat method is particularly preferable.

  When the metal member is provided on the anode (when light is extracted from the anode side), the adjacent layer is preferably a hole injection layer or a hole transport layer.

-Hole injection layer or hole transport layer-
The hole injection layer or hole transport layer is a layer having a function of receiving holes from the anode or anode side and transporting them to the cathode side. The hole injection layer and the hole transport layer may have a single layer structure or a multilayer structure composed of a plurality of layers having the same composition or different compositions.

  There is no restriction | limiting in particular as a material of the said positive hole injection layer, According to the objective, it can select suitably, For example, a starburst amine (4,4 ', 4 "-tris [3-methylphenyl (phenyl) amino) ] Triphenylamine: m-MTDATA), 2-TNATA (4,4 ′, 4 ″ -tris (2-naphthylphenylamino) triphenylamine), copper phthalocyanine, polyaniline and the like.

  The material for the hole transport layer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include aromatic amine compounds, carbazole, imidazole, triazole, oxazole, oxadiazole, polyarylalkane, and pyrazoline. , Pyrazolone, phenylenediamine, arylamine, amino-substituted chalcone, styrylanthracene, fluorenone, hydrazone, stilbene, silazane, styrylamine, aromatic dimethylidin compounds, porphyrin compounds, polysilane compounds, poly (N-vinylcarbazole), aniline compounds Examples thereof include conductive polymer oligomers and polymers such as copolymers, thiophene oligomers, thiophene polymers, and polythiophenes, and carbon films.

The hole injection layer and the hole transport layer may contain an electron accepting dopant.
As the electron-accepting dopant, an inorganic compound or an organic compound can be used as long as it has an electron-accepting property and oxidizes an organic compound.
The inorganic compound is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include metal halides such as ferric chloride, aluminum chloride, gallium chloride, indium chloride and antimony pentachloride; vanadium pentoxide And metal oxides such as molybdenum trioxide.
The organic compound is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a compound having a nitro group, a halogen, a cyano group, a trifluoromethyl group or the like as a substituent; a quinone compound, an acid anhydride Physical compounds, fullerenes, F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) and the like. These may be used individually by 1 type and may use 2 or more types together.
The amount of the electron-accepting dopant used is not particularly limited and varies depending on the type of material, but is preferably 0.01% by mass to 50% by mass with respect to the hole transport layer material or the hole injection material, 0.05 The mass% to 30 mass% is more preferable, and 0.1 mass% to 30 mass% is still more preferable.

  As the material of the hole injection layer, 2-TNATA (4,4 ′, 4 ″ -tris (2-naphthylphenylamino) triphenylamine) and F4TCNQ (2,3,5,6-tetrafluor-7,7 , 8,8-tetracyanoquinodimethane) is particularly preferable.

  The average thickness of the hole injection layer and the hole transport layer is preferably 1 nm to 500 nm, more preferably 5 nm to 250 nm, and still more preferably 10 nm to 200 nm.

  When the metal member is provided on the cathode (when light is extracted from the cathode side), the adjacent layer is preferably an electron injection layer or an electron transport layer.

-Electron injection layer or electron transport layer-
The electron injection layer and the electron transport layer are layers having a function of receiving electrons from the cathode or the cathode side and transporting them to the anode side.
The material for the electron transport layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (basocuproin; BCP), Quinoline derivatives such as organometallic complexes using tris (8-quinolinolato) aluminum (Alq3), BAlq and the like as their ligands, oxadiazole derivatives, triazole derivatives, phenanthroline derivatives, perylene derivatives, pyridine derivatives , Pyrimidine derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives, compound 2 represented by the following structural formula, and the like.
The material of the electron injection layer is not particularly limited and may be appropriately selected depending on the purpose, for example, lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF _2), such as Examples thereof include a thin layer (thickness: 0.1 nm to 10 nm) of an alkali metal or alkaline earth metal fluoride.

There is no restriction | limiting in particular as average thickness of the said electron injection layer and an electron carrying layer, According to the objective, it can select suitably, From a viewpoint of reducing a drive voltage, 500 nm or less is respectively preferable.
The average thickness of the electron transport layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, and still more preferably 10 nm to 100 nm. The average thickness of the electron injection layer is preferably 0.1 nm to 200 nm, more preferably 0.2 nm to 100 nm, and still more preferably 0.5 nm to 50 nm.
The electron injection layer and the electron transport layer may have a single layer structure made of one or two or more materials, or may have a multilayer structure made of a plurality of layers having the same composition or different compositions.

The organic electroluminescent element of the present invention has an organic layer including at least a light emitting layer between an anode and a cathode, and further has other layers appropriately selected as necessary.
The organic layer may include at least the light emitting layer, and may include an electron transport layer, an electron injection layer, a hole injection layer, a hole transport layer, a hole block layer, an electron block layer, and the like as necessary. It is preferable to have at least one layer selected from an electron transport layer, an electron injection layer, a hole injection layer, a hole transport layer, a hole block layer, and an electron block layer.
In addition, about the said electron carrying layer, the said electron injection layer, the said positive hole injection layer, and the said positive hole transport layer, what was mentioned above can be used.

<A pair of electrodes>
The pair of electrodes includes an anode and a cathode, and at least one of the pair of electrodes is preferably transparent.

<< Anode >>
The anode usually has a function as an electrode for supplying holes to the organic compound layer, and the shape, structure, size and the like are not particularly limited, and the use and purpose of the organic electroluminescence device Depending on the case, it can be appropriately selected from known electrode materials. The anode is usually provided as a transparent anode.

  Suitable examples of the material for the anode include metals, alloys, metal oxides, conductive compounds, and mixtures thereof. Specific examples of anode materials include conductive metals such as antimony, fluorine-doped tin oxide (ATO, FTO), tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), etc. Metals such as oxides, gold, silver, chromium, nickel, and mixtures or laminates of these metals and conductive metal oxides, inorganic conductive materials such as copper iodide and copper sulfide, polyaniline, polythiophene, polypyrrole, etc. Or a laminate of these and ITO. Among these, a conductive metal oxide is preferable, and ITO is particularly preferable in terms of productivity, high conductivity, transparency, and the like.

  Examples of the anode include a printing method, a wet method such as a coating method, a physical method such as a vacuum deposition method, a sputtering method, and an ion plating method, and a chemical method such as a CVD method and a plasma CVD method. It can be formed on the substrate in accordance with a method appropriately selected in consideration of suitability with the constituent material. For example, when ITO is selected as the anode material, the anode can be formed according to a direct current or high frequency sputtering method, a vacuum deposition method, an ion plating method, or the like.

  In the organic electroluminescent element of the present invention, the formation position of the anode is not particularly limited and can be appropriately selected according to the use and purpose of the light emitting element, but it is preferably formed on the substrate. In this case, the anode may be formed on the entire one surface of the substrate, or may be formed on a part thereof.

  The patterning for forming the anode may be performed by chemical etching such as photolithography, or may be performed by physical etching such as a laser, or vacuum deposition or sputtering with a mask overlapped. It may be performed by a lift-off method or a printing method.

  The average thickness of the anode can be appropriately selected depending on the material constituting the anode, and cannot be generally defined, but is preferably 10 nm to 50 μm, and more preferably 50 nm to 20 μm.

The resistance value of the anode is preferably 10 ³ Ω / □ or less, and more preferably 10 ² Ω / □ or less. When the anode is transparent, it may be colorless and transparent or colored and transparent. In order to take out light emission from the transparent anode side, the transmittance is preferably 60% or more, and more preferably 70% or more.

  The transparent anode is described in detail in the book “New Development of Transparent Electrode Films” published by CMC (1999), supervised by Yutaka Sawada, and the matters described here can be applied to the present invention. When using a plastic substrate with low heat resistance, a transparent anode formed using ITO or IZO at a low temperature of 150 ° C. or lower is preferable.

<< Cathode >>
The cathode usually has a function as an electrode for injecting electrons into the organic layer, and there is no particular limitation on the shape, structure, size, etc., depending on the use and purpose of the organic electroluminescence device. Thus, it can be appropriately selected from known electrode materials.

  Examples of the material constituting the cathode include metals, alloys, metal oxides, electrically conductive compounds, and mixtures thereof. Specific examples include alkali metals (eg, Li, Na, K, Cs, etc.), alkaline earth metals (eg, Mg, Ca, etc.), gold, silver, lead, aluminum, sodium-potassium alloy, lithium-aluminum alloy, Examples include magnesium-silver alloys, rare earth metals such as indium and ytterbium. These may be used alone, but two or more can be suitably used in combination from the viewpoint of achieving both stability and electron injection.

  Among these, as the material constituting the cathode, alkali metals and alkaline earth metals are preferable from the viewpoint of electron injection, and materials mainly composed of aluminum are more preferable from the viewpoint of excellent storage stability. The material mainly composed of aluminum is aluminum alone, an alloy of aluminum and 0.01% by mass to 10% by mass of alkali metal or alkaline earth metal, or a mixture thereof (for example, lithium-aluminum alloy, magnesium-aluminum). Alloy).

  The materials for the cathode are described in detail in JP-A-2-15595 and JP-A-5-121172, and the materials described in these publications can also be applied to the present invention.

  There is no restriction | limiting in particular about the formation method of the said cathode, According to a well-known method, it can carry out. For example, the cathode described above is configured from a wet method such as a printing method or a coating method, a physical method such as a vacuum deposition method, a sputtering method, or an ion plating method, or a chemical method such as CVD or plasma CVD method. It can be formed according to a method appropriately selected in consideration of suitability with the material. For example, when a metal or the like is selected as the cathode material, one or more of them can be simultaneously or sequentially performed according to a sputtering method or the like.

  The patterning for forming the cathode may be performed by chemical etching such as photolithography, or may be performed by physical etching using a laser or the like. Alternatively, it may be performed by a lift-off method or a printing method.

In the present invention, the cathode formation position is not particularly limited, and may be formed on the entire organic layer or a part thereof.
Further, a dielectric layer made of an alkali metal or alkaline earth metal fluoride or oxide may be inserted between the cathode and the organic layer in a thickness of 0.1 nm to 5 nm. This dielectric layer can also be regarded as a kind of electron injection layer. The dielectric layer can be formed by, for example, a vacuum deposition method, a sputtering method, an ion plating method, or the like.

The average thickness of the cathode can be appropriately selected depending on the material constituting the cathode and cannot be generally defined, but is preferably 10 nm to 5 μm, more preferably 50 nm to 1 μm.
Further, the cathode may be transparent or opaque. The transparent cathode can be formed by depositing a thin cathode material to a thickness of 1 nm to 10 nm and further laminating a transparent conductive material such as ITO or IZO.

<Light emitting layer>
The light-emitting layer receives holes from an anode, a hole injection layer, or a hole transport layer when an electric field is applied, receives electrons from a cathode, an electron injection layer, or an electron transport layer, and recombines holes and electrons. It is a layer having a function of providing a field to emit light.

The light emitting layer contains a light emitting dopant and a host compound, and further contains other components as necessary.
As the luminescent dopant and the host compound, a phosphorescent light emitting material capable of obtaining light emission (phosphorescence) from triplet excitons even in a combination of a fluorescent light emitting material capable of obtaining light emission (fluorescence) from singlet excitons and the host compound. Of these, a combination of a phosphorescent material and a host compound is particularly preferable from the viewpoint of luminous efficiency.
In addition, the said light emitting layer can contain 2 or more types of luminescent dopants in order to improve color purity and to expand the light emission wavelength range.

-Luminescent dopant-
As the luminescent dopant, either a phosphorescent material or a fluorescent material can be used.

--Phosphorescent material--
There is no restriction | limiting in particular as said phosphorescence-emitting material, According to the objective, it can select suitably, For example, the complex etc. which contain a transition metal atom and a lanthanoid atom are mentioned.
Examples of the transition metal atom include ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum, and the like. Among these, rhenium, iridium, and platinum are preferable, and iridium and platinum are particularly preferable.

Examples of the lanthanoid atom include lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Among these, neodymium, europium, and gadolinium are particularly preferable.
Examples of the ligand of the complex include G.I. Wilkinson et al., Comprehensive Coordination Chemistry, Pergamon Press, 1987, H.C. The ligands described in Yersin's "Photochemistry and Photophysics of Coordination Compounds" Springer-Verlag, published in 1987, Akio Yamamoto, "Organic Metal Chemistry-Fundamentals and Applications-" Can be mentioned.
Specific ligands include halogen ligands (preferably chlorine ligands), aromatic carbocyclic ligands (eg, cyclopentadienyl anion, benzene anion, naphthyl anion, etc.), nitrogen-containing hetero Ring ligands (eg, phenylpyridine, benzoquinoline, quinolinol, bipyridyl, or phenanthroline), diketone ligands (eg, acetylacetone, etc.), carboxylic acid ligands (eg, acetate ligands, etc.), alcoholates Examples include ligands (eg, phenolate ligands), carbon monoxide ligands, isonitrile ligands, cyano ligands, and the like. Among these, a nitrogen-containing heterocyclic ligand is particularly preferable.

  The complex may have one transition metal atom in the compound, or may be a so-called binuclear complex having two or more. Different metal atoms may be contained at the same time. Among these, examples of the phosphorescent light emitting material include the following, but are not limited thereto.

  The content of the phosphorescent material is preferably 0.5% by mass to 40% by mass, more preferably 1% by mass to 30% by mass, and more preferably 3% by mass to the total mass of the compound forming the light emitting layer. 20 mass% is still more preferable. When the content is less than 0.5% by mass, the light emission efficiency may be reduced, and when it exceeds 40% by mass, the light emission efficiency may be reduced due to association of the phosphorescent material itself.

--Fluorescent material--
The fluorescent material is not particularly limited and can be appropriately selected according to the purpose. For example, benzoxazole, benzimidazole, benzothiazole, styrylbenzene, polyphenyl, diphenylbutadiene, tetraphenylbutadiene, naphthalimide, Coumarin, pyran, perinone, oxadiazole, aldazine, pyralidine, cyclopentadiene, bisstyrylanthracene, quinacridone, pyrrolopyridine, thiadiazolopyridine, cyclopentadiene, styrylamine, aromatic dimethylidin compound, condensed polycyclic aromatic compound (anthracene) , Phenanthroline, pyrene, perylene, rubrene, pentacene, etc.), metal complexes of 8-quinolinol, various metal complexes represented by pyromethene complexes and rare earth complexes, polythiophene Polyphenylene, polyphenylene vinylene polymer compound, and an organic silane or a derivative thereof.

Among these, specific examples of the fluorescent light emitting material include the following, but are not limited thereto.

  The content of the fluorescent light emitting material is preferably 0.1% by mass to 30% by mass with respect to the total mass of the compound forming the light emitting layer, and 0.5% by mass to 20% from the viewpoint of durability and light emission efficiency. % By mass is more preferable, and 1% by mass to 15% by mass is even more preferable.

-Host compound-
As the host compound, a hole transporting host compound having excellent hole transportability and an electron transporting host compound having excellent electron transportability can be used.

--Hole transporting host compound--
The hole transporting host compound is not particularly limited and may be appropriately selected depending on the intended purpose.For example, pyrrole, indole, carbazole, azaindole, azacarbazole, pyrazole, imidazole, polyarylalkane, pyrazoline, Pyrazolone, phenylenediamine, arylamine, amino-substituted chalcone, styrylanthracene, fluorenone, hydrazone, stilbene, silazane, aromatic tertiary amine compound, styrylamine compound, aromatic dimethylidin compound, porphyrin compound, polysilane compound, poly Examples thereof include (N-vinylcarbazole), aniline-based copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, organic silanes, carbon films, or derivatives thereof.
Among these, indole derivatives, carbazole derivatives, azaindole derivatives, azacarbazole derivatives, aromatic tertiary amine compounds, and thiophene derivatives are preferable, and indole skeleton, carbazole skeleton, azaindole skeleton, azacarbazole skeleton, or aromatic in the molecule Those having an aromatic group tertiary amine skeleton are more preferred, and compounds having a carbazole skeleton are particularly preferred.
Alternatively, a host material in which part or all of the hydrogen in the host compound is substituted with deuterium can be used (Japanese Patent Laid-Open No. 2009-277790, Japanese Translation of PCT International Publication No. 2004-515506).

Specific examples of such a hole transporting host compound include, but are not limited to, the following compounds.

  The content of the hole transporting host compound is preferably 10% by mass to 99.9% by mass, and more preferably 20% by mass to 99.5% by mass with respect to the total mass of the compound forming the light emitting layer. 30 mass% to 99 mass% is more preferable.

--Electron transporting host compound--
The electron transporting host compound is not particularly limited and may be appropriately selected depending on the intended purpose. For example, pyridine, pyrimidine, triazine, imidazole, pyrazole, triazole, oxal, oxadiazole, fluorenone, anthraquinodi Heterocyclic tetracarboxylic acid anhydrides such as methane, anthrone, diphenylquinone, thiopyran dioxide, carbodiimide, fluorenylidenemethane, distyrylpyrazine, fluorine-substituted aromatic compounds, naphthaleneperylene, phthalocyanine, or derivatives thereof (others And a metal ring of a 8-quinolinol derivative, metal phthalocyanine, benzoxazole, and various metal complexes represented by metal complexes having benzothiazole as a ligand.

Examples of the electron transporting host compound include metal complexes, azole derivatives (such as benzimidazole derivatives and imidazopyridine derivatives), and azine derivatives (such as pyridine derivatives, pyrimidine derivatives, and triazine derivatives). Among these, a metal complex compound is preferable from the viewpoint of durability. The metal complex compound is more preferably a metal complex having a ligand having at least one nitrogen atom, oxygen atom or sulfur atom coordinated to a metal.
There is no restriction | limiting in particular as a metal ion in the said metal complex, According to the objective, it can select suitably, For example, beryllium ion, magnesium ion, aluminum ion, gallium ion, zinc ion, indium ion, tin ion, platinum Ion or palladium ion, more preferably beryllium ion, aluminum ion, gallium ion, zinc ion, platinum ion, or palladium ion. Among these, aluminum ion, zinc ion, or palladium ion is particularly preferable.

  As the ligand contained in the metal complex, there are various known ligands. For example, “Photochemistry and Photophysics of Coordination Compounds”, Springer-Verlag, H.C. Examples include the ligands described in Yersin, published in 1987, “Organometallic Chemistry: Fundamentals and Applications”, Sakai Hanafusa, Yamamoto Akio, published in 1982, and the like.

  Examples of the ligand include a nitrogen-containing heterocyclic ligand (preferably having 1 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, and particularly preferably 3 to 15 carbon atoms. Or a bidentate or higher ligand, preferably a bidentate or higher and hexadentate or lower ligand, or a bidentate or higher and lower 6 or lower ligand and a monodentate mixed ligand. Are also preferred), azine ligands (eg, pyridine ligands, bipyridyl ligands, terpyridine ligands, etc.), hydroxyphenylazole ligands (eg, hydroxyphenylbenzimidazole ligands, hydroxyphenyl). Benzoxazole ligands, hydroxyphenylimidazole ligands, hydroxyphenylimidazopyridine ligands, etc.), alkoxy ligands (preferably having 1 to 30 carbon atoms) Preferably it is C1-C20, Most preferably, it is C1-C10, for example, a methoxy, an ethoxy, butoxy, 2-ethylhexyloxy etc. are mentioned, An aryloxy ligand (preferably C6-C30) More preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenyloxy, 1-naphthyloxy, 2-naphthyloxy, 2,4,6-trimethylphenyloxy, 4-biphenyloxy, etc. A heteroaryloxy ligand (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as pyridyloxy, pyrazyloxy, pyrimidyloxy, and Quinolyloxy, etc.), alkylthio ligands (preferably having 1 to 30 carbon atoms, more preferred) Or having 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methylthio and ethylthio, and arylthio ligands (preferably having 6 to 30 carbon atoms, more preferably 6 to 6 carbon atoms). 20, particularly preferably 6 to 12 carbon atoms, for example, phenylthio and the like, a heteroarylthio ligand (preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably carbon numbers). 1 to 12, for example, pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio, 2-benzthiazolylthio and the like, siloxy ligand (preferably having 1 to 30 carbon atoms, and more). Preferably it has 3 to 25 carbon atoms, particularly preferably 6 to 20 carbon atoms. For example, triphenylsiloxy group, triethoxysiloxy group, triiso Examples thereof include a propylsiloxy group. ), An aromatic hydrocarbon anion ligand (preferably having 6 to 30 carbon atoms, more preferably 6 to 25 carbon atoms, particularly preferably 6 to 20 carbon atoms, such as a phenyl anion, a naphthyl anion, an anthranyl anion, etc. Aromatic heterocyclic anion ligands (preferably having 1 to 30 carbon atoms, more preferably 2 to 25 carbon atoms, particularly preferably 2 to 20 carbon atoms, such as pyrrole anion, pyrazole anion, Pyrazole anion, triazole anion, oxazole anion, benzoxazole anion, thiazole anion, benzothiazole anion, thiophene anion, benzothiophene anion, etc.) and indolenine anion ligand. Among these, a nitrogen-containing heterocyclic ligand, an aryloxy ligand, a heteroaryloxy group, or a siloxy ligand is preferable, a nitrogen-containing heterocyclic ligand, an aryloxy ligand, a siloxy ligand, Aromatic hydrocarbon anion ligands or aromatic heterocyclic anion ligands are particularly preferred.

  Examples of the metal complex electron transporting host compound include Japanese Patent Application Laid-Open No. 2002-235076, Japanese Patent Application Laid-Open No. 2004-214179, Japanese Patent Application Laid-Open No. 2004-221106, Japanese Patent Application Laid-Open No. 2004-221105, and Japanese Patent Application Laid-Open No. 2004-221068. And the compounds described in JP-A No. 2004-327313 and the like.

Examples of such an electron transporting host compound include, but are not limited to, the following materials.

  The content of the electron transporting host compound is preferably 10% by mass to 99.9% by mass, more preferably 20% by mass to 99.5% by mass with respect to the total mass of the compound forming the light emitting layer. 30 mass%-99 mass% is still more preferable.

The light-emitting layer receives holes from an anode, a hole injection layer, or a hole transport layer when an electric field is applied, receives electrons from a cathode, an electron injection layer, or an electron transport layer, and recombines holes and electrons. It is a layer having a function of providing a field to emit light.
The light emitting layer is not particularly limited and can be formed according to a known method. For example, by a dry film forming method such as a vapor deposition method or a sputtering method, a wet coating method, a transfer method, a printing method, an ink jet method, or the like. It can form suitably.

  There is no restriction | limiting in particular in the average thickness of the said light emitting layer, According to the objective, it can select suitably, 2 nm-500 nm are preferable, 3 nm-200 nm are more preferable from a viewpoint of luminous efficiency, and 10 nm-200 nm are still more preferable. The light emitting layer may be a single layer or two or more layers.

-Hole blocking layer, electron blocking layer-
The hole blocking layer is a layer having a function of preventing holes transported from the anode side to the light emitting layer from passing through to the cathode side, and is usually provided as an organic compound layer adjacent to the light emitting layer on the cathode side. .
The electron blocking layer is a layer having a function of preventing electrons transported from the cathode side to the light emitting layer from passing through to the anode side, and is usually provided as an organic compound layer adjacent to the light emitting layer on the anode side.
Examples of the compound constituting the hole blocking layer include aluminum complexes such as BAlq3, triazole derivatives, and phenanthroline derivatives such as BCP.
As a compound which comprises the said electron block layer, what was mentioned as the above-mentioned hole transport material can be utilized, for example.

The electron block layer and the hole block layer are not particularly limited and can be formed according to a known method. For example, a vapor deposition method, a dry film forming method such as a sputtering method, a wet coating method, a transfer method, a printing method, It can be suitably formed by an inkjet method or the like.
The average thickness of the hole blocking layer and the electron blocking layer is preferably 1 nm to 200 nm, more preferably 1 nm to 50 nm, and still more preferably 3 nm to 10 nm. The hole blocking layer and the electron blocking layer may have a single-layer structure made of one or more of the materials described above, or a multilayer structure made up of a plurality of layers having the same composition or different compositions. Also good.

-Board-
The organic electroluminescent element of the present invention is preferably provided on a substrate, and may be provided in such a manner that the electrode and the substrate are in direct contact with each other, or may be provided in an intermediate 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 a yttria stabilized zirconia (YSZ) and glass (an alkali free glass, soda-lime glass, etc.); Polyethylene Examples thereof include polyesters such as terephthalate, polybutylene phthalate, and polyethylene naphthalate; organic materials such as polystyrene, polycarbonate, polyethersulfone, polyarylate, polyimide, polycycloolefin, norbornene resin, and poly (chlorotrifluoroethylene).

  There is no restriction | limiting in particular about the shape of the said board | substrate, a structure, a magnitude | size, It can select suitably according to the use, purpose, etc. of a light emitting element. In general, the shape of the substrate is preferably a plate shape. The structure of the substrate may be a single layer structure, a laminated structure, may be formed of a single member, or may be formed of two or more members. . The substrate may be transparent or opaque, and if transparent, it may be colorless and transparent or colored and transparent.

The substrate may be provided with a moisture permeation preventing layer (gas barrier layer) on the front surface or the back surface.
Examples of the material of the moisture permeation preventing layer (gas barrier layer) include inorganic substances such as silicon nitride and silicon oxide.
The moisture permeation preventing layer (gas barrier layer) can be formed by, for example, a high frequency sputtering method.

-Other configurations-
There is no restriction | limiting in particular as said other structure, According to the objective, it can select suitably, For example, a protective layer, a sealing container, a resin sealing layer, a sealing adhesive etc. are mentioned.
There is no restriction | limiting in particular as contents, such as the said protective layer, the said sealing container, the said resin sealing layer, and the said sealing adhesive agent, According to the objective, it can select suitably, for example, Unexamined-Japanese-Patent No. 2009-152572. The matters described in the gazette can be applied.

  There is no restriction | limiting in particular as a structure of the organic electroluminescent element of this invention, Although it can select suitably according to the objective, As its layer structure, the following (1)-(13) layer structure, That is, (1) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode, (2) anode / hole injection layer / hole transport layer / light emitting layer / electron transport Layer / cathode, (3) anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode, (4) anode / hole transport layer / light emitting layer / electron transport layer / cathode, (5) anode / Hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode, (6) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode, (7 ) Anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode, (8) Anode / hole transport layer / light emitting layer / electron transport layer / cathode, (9) positive / Hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode, (10) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode, (11 ) Anode / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode, (12) Anode / hole transport layer / light emitting layer / electron transport layer / cathode, (13) Anode / hole transport layer combined A light emitting layer / electron transport layer / cathode and the like are preferable.

-Drive-
The organic electroluminescence device of the present invention emits light by applying a direct current (which may include an alternating current component as necessary) voltage (usually 2 to 15 volts) or a direct current between the anode and the cathode. Can be obtained.
The organic electroluminescent element of the present invention can be applied to an active matrix by a thin film transistor (TFT). As the active layer of the thin film transistor, amorphous silicon, high temperature polysilicon, low temperature polysilicon, microcrystalline silicon, oxide semiconductor, organic semiconductor, carbon nanotube, or the like can be used.
For example, the thin film transistors described in International Publication No. 2005/088726, Japanese Patent Application Laid-Open No. 2006-165529, US Patent Application Publication No. 2008/0237598, and the like can be applied to the organic electroluminescent device of the present invention.

There is no restriction | limiting in particular in the organic electroluminescent element of this invention, Light extraction efficiency can be improved by various well-known devices. For example, by processing the substrate surface shape (for example, forming a fine concavo-convex pattern), controlling the refractive index of the substrate, ITO layer, organic layer, controlling the thickness of the substrate, ITO layer, organic layer, etc. It is possible to improve the external quantum efficiency.
The light extraction method from the organic electroluminescence device of the present invention may be a top emission method or a bottom emission method.

The organic electroluminescent element of the present invention may have a resonator structure. For example, in the first aspect, a multilayer mirror composed of a plurality of laminated films having different refractive indexes, a transparent or translucent electrode, a light emitting layer, and a metal electrode are superimposed on a transparent substrate. The light generated in the light emitting layer resonates by repeatedly reflecting between the multilayer mirror and the metal electrode as a reflector.
In the second aspect, the transparent or translucent electrode and the metal electrode each function as a reflector on the transparent substrate, and the light generated in the light emitting layer repeats reflection between them and resonates.
In order to form a resonant structure, the optical path length determined from the effective refractive index of the two reflectors and the refractive index and thickness of each layer between the reflectors is adjusted to the optimum value to obtain the desired resonant wavelength. Is done.
The calculation formula in the case of the first aspect is described in, for example, JP-A-9-180883.
The calculation formula in the case of the second aspect is described in, for example, Japanese Patent Application Laid-Open No. 2004-127795.

-Application-
The organic electroluminescent element of the present invention is not particularly limited and may be appropriately selected depending on the intended purpose. However, the display element, display, backlight, electrophotography, illumination light source, recording light source, exposure light source, reading light source, label It can be suitably used for signboards, interiors, optical communications, and the like.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
In the following examples and comparative examples, the average height dispersion 2σ of metal members, the average height of metal members, and the average height of adjacent layers were measured as follows.

<Measuring method of dispersion 2σ of average height of metal member>
The height of the metal member was measured with an atomic force microscope (SPA-400, manufactured by Seiko Instruments Inc.). The dispersion 2σ of the average height of the metal fine particles was calculated from the measured heights of 100 metal members.

<Measuring method of average height of metal member>
The height of the metal member was measured with an atomic force microscope (SPA-400, manufactured by Seiko Instruments Inc.). The average height of the 100 metal members measured was defined as the average height of the metal members.

<Measuring method of average height of adjacent layer>
With an atomic force microscope (SPA-400, manufactured by Seiko Instruments Inc.), the surface shape of the adjacent layer is observed in a 1 μm × 1 μm region, and the difference between the maximum value and the minimum value is determined as the maximum height in this region. (Ry in FIG. 1). The measurement was performed in 20 regions, and the arithmetic average value of the maximum height in each region was defined as the average height of the adjacent layer.

Example 1
<Preparation of substrate>
A 0.5 mm thick, 2.5 cm square glass substrate with an ITO electrode deposited with indium tin oxide (hereinafter abbreviated as ITO) to a thickness of 100 nm was placed in a cleaning container, and ultrasonically cleaned in 2-propanol. UV-ozone treatment was performed for 30 minutes.

<Production of metal member>
-Production of metal member (1) (EB lithography method)-
An electron beam (EB) positive chemically amplified resist (FEP171, manufactured by FUJIFILM Electronics Materials Co., Ltd.) is spin-coated at 1,200 rpm for 1 minute on the prepared glass substrate with ITO electrode at 120 ° C. Heat treatment for 1 minute was performed.
Next, a circular shape having a diameter (φ) of 100 nm was drawn with a period of 400 nm using an electron beam drawing apparatus (JBX-6000FS / E, manufactured by JEOL Ltd.). Following drawing, a heat treatment was performed at 120 ° C. for 1 minute, and then development was performed with a developer (FHD-5, manufactured by Fuji Film Electronics Materials Co., Ltd.).
After development, Ag having a purity of 99.99% was vapor-deposited with an electron beam vapor deposition device (EBX-8C, manufactured by ULVAC TECHNO). The deposition rate was 0.1 nm / second.
Next, the resist and Ag in unnecessary portions were removed by immersing the whole substrate in an acetone solution to obtain regularly arranged metal members as shown in FIG. The average height of the obtained metal member was 60 nm, the average height dispersion 2σ of the metal member was 5.2 nm, the dot diameter was 126 nm, and the interval (pitch) was 400 nm.

<Formation of adjacent layer>
In a glove box substituted with nitrogen gas, 40 mg of 2-TNATA (4,4 ′, 4 ″ -tris (2-naphthylphenylamino) triphenylamine) represented by the following structural formula and the following structural formula 1 mg of F4TCNQ (2,3,5,6-tetrafluor-7,7,8,8-tetracyanoquinodimethane) dissolved in 4 mL of toluene (manufactured by Kanto Chemical Co., Inc.) On the formed glass substrate with an ITO electrode, spin coating was performed at 1,000 rpm for 1 minute to form an adjacent layer having an average height of 10 nm.

<Production of organic electroluminescence device>
On the prepared adjacent layer, an organic layer and a metal layer were vacuum-deposited as follows. The vapor deposition rate was 0.2 nm / second unless otherwise specified, and the vapor deposition rate was measured using a quartz resonator.
Next, an NPD represented by the following structural formula was formed on the formed adjacent layer by a vacuum deposition method to form a hole transport layer having an average thickness of 5 nm.
Next, on the hole transport layer, a light emitting material obtained by doping 10% by mass of the compound 1 represented by the following structural formula into BAlq represented by the following structural formula is formed by a vacuum deposition method, and the average thickness is 10 nm. A light emitting layer was formed.
Next, on the light emitting layer, the compound 2 represented by the following structural formula was formed into a film by a vacuum deposition method to form an electron transport layer having an average thickness of 80 nm.
Next, lithium fluoride (LiF) was vacuum-deposited on the electron transport layer so as to have an average thickness of 0.5 nm to form an electron injection layer.

Next, a mask patterned as a cathode (a mask having a light emitting area of 2 mm × 2 mm) was placed on the electron injection layer, and metal aluminum (Al) was vacuum deposited so as to have an average thickness of 100 nm.
The configuration of the organic electroluminescent element of Example 1 is as follows.
<ITO (100 nm) / metal member / 2-TNATA + 1 mass% F4TCNQ (adjacent layer) / NPD (5 nm) / BAlq + 10 mass% Compound 1 (10 nm) / Compound 2 (80 nm) / LiF (0.5 nm) / Al (100 nm )>
Numbers in () represent average thickness.

(Comparative Example 1)
-Fabrication of organic electroluminescence device-
In Example 1, similar to Example 1 except that spin coating was performed for 1 minute at a rotational speed of 2,000 rpm on the glass substrate with an ITO electrode on which the metal member was prepared, and an adjacent layer having an average height of 27 nm was formed. Thus, an organic electroluminescent element of Comparative Example 1 was produced.

(Comparative Example 2)
-Fabrication of organic electroluminescence device-
Example 1 is the same as Example 1 except that an ITO electrode-attached glass substrate on which a metal member is formed is spin-coated at 3,000 rpm for 1 minute to form an adjacent layer having an average height of 41 nm. Thus, an organic electroluminescent element of Comparative Example 2 was produced.

(Comparative Example 3)
-Fabrication of organic electroluminescence device-
In Example 1, the organic electroluminescence of Comparative Example 3 was made in the same manner as in Example 1 except that an adjacent layer having an average height of 57 nm was formed on the glass substrate with an ITO electrode on which the metal member was formed by vacuum deposition. An element was produced.

(Comparative Example 4)
-Fabrication of organic electroluminescence device-
In Example 1, the organic electroluminescent element of the comparative example 4 was produced like Example 1 except not having provided a metal member on the glass substrate with an ITO electrode.

(Example 2)
<Production of organic electroluminescence device>
Example 1 Example 1 was carried out in the same manner as Example 1 except that production (1) of the metal member was replaced with production (2) of the metal member shown below (self-organization by Ag vapor deposition and annealing). 2 organic electroluminescent elements were produced.
-Production of metal member (2) (Self-organization by Ag deposition and annealing)-
On the glass substrate with an ITO electrode, Ag having a purity of 99.9% was vapor-deposited with an electron beam vapor deposition apparatus (EBX-8C, manufactured by ULVAC TECHNO). Thereafter, annealing was performed at 300 ° C. for 60 minutes using the substrate heating mechanism of the electron beam evaporation apparatus, and a metal member having a random size and arrangement as shown in FIG. 4 was produced.

(Example 3)
<Production of organic electroluminescence device>
In Example 1, the organic electroluminescent element of Example 3 was prepared in the same manner as in Example 1 except that the production (1) of the metal member was replaced with the production (3) (Ag vapor deposition) of the metal member shown below. Was made.
-Production of metal member (3) (Ag vapor deposition)-
On a glass substrate with an ITO electrode, Ag having a purity of 99.9% was vapor-deposited with an electron beam vapor deposition apparatus (EBX-8C, manufactured by ULVAC TECHNO) to produce a metal member having a structure with a random size and arrangement.

  Next, about each sample which formed the metal member on the glass substrate with an ITO electrode, the area ratio of the metal member was calculated | required as follows. The results are shown in Table 1. Moreover, about each produced organic electroluminescent element, the external quantum efficiency and durability were measured as follows. The results are shown in Table 1.

<Area ratio (density) of metal member>
About the sample which formed the metal member on the glass substrate with an ITO electrode, surface observation is performed with a scanning electron microscope (manufactured by Hitachi, Ltd., S4100), and the area A where the metal member is present and the area B where the metal member is not present And the area ratio of the metal member was determined from the following formula [A / (A + B)] × 100%.

<Method for measuring external quantum efficiency (EQE)>
Using a source measure unit 2400 manufactured by Toyo Technica Co., Ltd., a direct current was applied to each organic electroluminescent element to emit light. The emission spectrum at that time was measured using a spectral radiance meter SR-3 manufactured by Topcon Corporation. Based on the obtained spectrum, the external quantum efficiency (EQE) at a current density of the organic electroluminescent element of 0.25 mA / cm ² was calculated by an intensity conversion method for each wavelength.

<Durability measurement method>
Each organic electroluminescent device measures the DC current becomes the luminance 2,000 cd / ^{m 2,} the time until the respective organic electroluminescent device in its current continuous driving to the luminance becomes 1,000 cd / ^{m 2} It was measured.

In each of the organic electroluminescent elements of Examples 1 to 3 and Comparative Examples 1 to 3, the exciton lifetime of the light emitting layer is measured by the fact that the metal member generates plasmon resonance by the light emitted from the light emitting layer. It was confirmed by.

(Examples 4-6 and Comparative Examples 5-7)
In Examples 1 to 3 and Comparative Examples 1 to 3, the average height of the metal member, the dispersion 2σ of the average height of the metal member, and the average height of the adjacent layer by changing the metal deposition time in the production of the metal member Except having changed as shown in Table 2, it carried out similarly to Examples 1-3 and Comparative Examples 1-3, and produced the organic electroluminescent element of Examples 4-6 and Comparative Examples 5-7. In addition, Example 4 is in Example 1, Comparative Example 5 is in Comparative Example 1, Comparative Example 6 is in Comparative Example 2, Comparative Example 7 is in Comparative Example 3, Example 5 is in Example 2, and Example 6 is. Corresponds to Example 3, respectively.
About each produced organic electroluminescent element, it carried out similarly to Examples 1-3 and Comparative Examples 1-4, and measured the area rate, the external quantum efficiency, and durability. The results are shown in Table 2.

In each of the organic electroluminescent elements of Examples 4 to 6 and Comparative Examples 5 to 7, the exciton lifetime of the light emitting layer is measured that the metal member has caused plasmon resonance by the light emitted from the light emitting layer. It was confirmed by.

(Examples 7 to 11 and Comparative Examples 8 to 11)
In Examples 1 to 3 and Comparative Examples 1 to 3, the average height of the metal member, the dispersion 2σ of the average height of the metal member, and the average height of the adjacent layer by changing the metal deposition time in the production of the metal member Except having changed as shown in Table 3, it carried out similarly to Examples 1-3 and Comparative Examples 1-3, and produced the organic electroluminescent element of Examples 7-11 and Comparative Examples 8-11. In addition, Example 7 is in Example 1, Example 8 is in Comparative Example 1, Example 9 is in Comparative Example 2, Comparative Example 8 is in Comparative Example 3, Example 10 is in Example 2, and Example 11 is. Corresponds to Example 3, Comparative Example 9 corresponds to Comparative Example 4, Comparative Example 10 corresponds to Comparative Example 8, and Comparative Example 11 corresponds to Comparative Example 8.
About each produced organic electroluminescent element, it carried out similarly to Examples 1-3 and Comparative Examples 1-4, and measured the area rate, the external quantum efficiency, and durability. The results are shown in Table 3.

In each of the organic electroluminescent elements of Examples 7 to 11 and Comparative Examples 8 and 10 to 11, the exciton lifetime of the light emitting layer was measured by the fact that the metal member caused plasmon resonance by the emitted light from the light emitting layer. It was confirmed by doing.

  The organic electroluminescent element of the present invention can be suitably used for display elements, displays, backlights, electrophotography, illumination light sources, recording light sources, exposure light sources, reading light sources, signs, signboards, interiors, optical communications, and the like. it can.

1 Electrode 2 Adjacent layer 3 Light emitting layer 4 Metal member

Claims (9)

An organic electroluminescent device having a pair of electrodes consisting of an anode and a cathode, and a light emitting layer between the pair of electrodes,
A metal member having an average height of 20 nm or more on the light emitting layer side adjacent to at least one of the electrodes;
An adjacent layer having an average height of 15 nm or less between the metal member and the light emitting layer;
An organic electroluminescent device comprising:   The organic electroluminescent element according to claim 1, wherein the metal member generates plasmon resonance due to light emitted from the light emitting layer.   The organic electroluminescent element according to claim 1, wherein the average height dispersion 2σ of the metal member is 30 nm or less.   The organic electroluminescent element according to claim 1, wherein the metal member is disposed in at least one of a pattern shape and a dot shape.   The organic electroluminescent element according to any one of claims 1 to 4, wherein the metal member has an area ratio of 5% or more.   6. The organic electroluminescent element according to claim 1, wherein the electrode adjacent to the metal member is an ITO electrode.   The organic electroluminescent element according to claim 1, wherein the adjacent layer is produced by a liquid phase film forming method.   The organic electroluminescent element according to claim 1, wherein the light emitting layer contains a phosphorescent material. A method for producing the organic electroluminescent device according to claim 1,
A metal member forming step of forming a metal member on the electrode;
An adjacent layer forming step of forming an adjacent layer on the metal member by a liquid phase film forming method;
The manufacturing method of the organic electroluminescent element characterized by including.