JP2015185728A - organic EL light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL light-emitting device that emits light of a plurality of colors including white and whose life can be prolonged.SOLUTION: In an organic EL light-emitting device 1, an organic light-emitting medium layer is arranged between a transparent electrode and a counter electrode. The organic light-emitting medium layer comprises a first light-emitting layer 5 including at least one or more phosphorescent body, and a second light-emitting layer 6 arranged next to the first light-emitting layer, including a fluorescent emission body, and mainly emitting light in a spectral range on the side shorter in wavelength than the light-emission peak of the first light-emitting layer. The excitation triplet energy level of the fluorescence emission body of the second light-emitting layer 6 is lower than the excitation triplet energy level of at least one phosphorescent body of the first light emission layer 5. The fluorescence emission body of the second light-emitting layer 6 is a substance that exhibits delay fluorescence by the energy movement of triplet exciter from at least one phosphorescent body of the first light emission layer 5 and an up-conversion from a triplet excited state to a single excited state.

Description

  The present invention relates to a light emitting device used for illumination or the like, and more particularly to an organic EL light emitting device.

In the organic EL light emitting device, a voltage is applied to the conductive light emitting medium layer, whereby the injected electrons and holes are recombined in the organic light emitting layer in the light emitting medium layer. The organic light emitting molecules in the organic light emitting layer are once excited by the recombination energy, and then return from the excited state to the ground state. The organic EL light emitting device emits light by taking out the energy released at this time as light.
In order to apply a voltage to the organic light emitting layer, electrodes are provided on both sides of the light emitting medium layer, and at least one of the electrodes has a light transmitting property in order to extract light from the organic light emitting layer to the outside. As an example of the structure of such an organic EL light emitting device, a structure in which a light transmitting electrode, a light emitting medium layer (organic light emitting layer), and a counter electrode are sequentially stacked on a light transmitting substrate can be given. Here, there is an embodiment in which the electrode formed on the substrate is used as an anode, and the counter electrode formed on the light emitting medium layer is used as a cathode.

Further, for the purpose of increasing luminous efficiency, in addition to a hole transport layer and a hole injection layer provided between the anode and the organic light emitting layer, an electron transport layer and an electron injection layer are provided between the organic light emitting layer and the cathode. Are appropriately selected and configured as an organic EL light emitting device in many cases. These hole transport layer, hole injection layer, electron transport layer, and electron injection layer are called carrier transport layers. The carrier transport layer, the organic light emitting layer, the hole blocking layer, the electron blocking layer, and the like are collectively referred to as a light emitting medium layer.
In recent years, technology that emits light of a plurality of colors including white has attracted attention. In particular, a white organic EL light emitting device has great potential to be used in the field of illumination.

When producing an organic EL light emitting device, in order to obtain white light emission, it is necessary to combine a plurality of light emitters having different emission peak wavelengths, and there are several methods. For example, as a combination method, there are a method of mixing light emitters of a plurality of colors in a light emitting layer, a method of stacking light emitting layers including light emitters of a plurality of colors above and below, a method of arranging them in a planar direction, and the like. .
High efficiency can be obtained by using, for example, a phosphorescent light emitter as the light emitter to be combined (see, for example, Patent Document 1). A phosphor that uses only singlet excitons has an internal quantum efficiency of 25%, whereas a phosphor that also uses triplet excitons has an internal quantum efficiency of 100%.

JP2013-55341A

However, there is a need for technical improvements in phosphorescent emitters, particularly with respect to the lifetime of phosphorescent emitters having an emission peak wavelength in blue. Although the lifetimes of phosphorescent emitters and blue fluorescent emitters having spectral peaks in the red, green, and blue-green regions tend to be long, when emitting white light, the blue phosphorescent emitter is considered due to the triplet energy level. Is mainly emitted, and there is a problem that the lifetime is reduced by the influence of the blue phosphorescent emitter.
Accordingly, the present invention has been made paying attention to the above points, and an object of the present invention is to provide an organic EL light emitting device that emits light of a plurality of colors including white and can extend the life. And

  In order to solve the above problems, an organic EL light-emitting device according to one aspect of the present invention includes an organic light-emitting medium layer disposed between a transparent electrode and a counter electrode, and the organic light-emitting medium layer includes at least one phosphorescent light. A first light-emitting layer including a light emitter, and a first light-emitting layer that is disposed adjacent to the first light-emitting layer and includes a fluorescent light emitter and emits light mainly in a spectral region shorter than a light emission peak of the first light-emitting layer. And the excited triplet energy level of the fluorescent light emitter of the second light emitting layer is smaller than the excited triplet energy level of at least one phosphorescent light emitter of the first light emitting layer, The fluorescent light emitter of the second light emitting layer is delayed fluorescence by energy transfer of triplet excitons and upconversion from the triplet excited state to the singlet excited state from at least one phosphorescent light emitter of the first light emitting layer. It is a substance showing And wherein the door.

  According to the present invention, a first light-emitting layer including one or more phosphorescent emitters, and a second light-emitting layer including a fluorescent light-emitting body that mainly emits light in a spectral region shorter than the emission peak of the first light-emitting layer. And the excited triplet energy level of the fluorescent light emitter of the second light emitting layer is made smaller than the excited triplet energy level of at least one phosphorescent light emitter of the first light emitting layer. By transferring energy of triplet excitons from phosphor to fluorescent phosphor and obtaining delayed fluorescence by up-conversion from triplet excited state to singlet excited state, multiple colors including white with high efficiency and long lifetime can be obtained. An organic EL light-emitting device capable of obtaining light emission can be provided.

It is sectional drawing which shows typically an example of a structure of the organic electroluminescent light-emitting device concerning embodiment of this invention.

Next, embodiments of the present invention will be described with reference to the drawings.
An embodiment of the present invention includes a transparent electrode, a hole transport layer having at least one of hole injection and hole transport properties formed on the transparent electrode, and a hole transport layer formed on the transparent electrode. A first light-emitting layer including at least one phosphorescent light emitter formed, and a fluorescent light-emitting material on the first light-emitting layer, the main light-emitting layer being in a shorter spectral range than the light emission peak of the first light-emitting layer. A second light emitting layer that emits light, an electron transport layer formed on the second light emitting layer and having at least one of electron injection and electron transport, and a counter electrode are sequentially formed.

FIG. 1 schematically shows a configuration of an organic EL light emitting device according to this embodiment.
As shown in FIG. 1, the organic EL light emitting device 1 according to this embodiment includes a translucent substrate 2, an anode 3 as a transparent electrode formed on one surface of the translucent substrate 2, and an anode 3. On the stacked hole transport layer 4, the first light emitting layer 5 stacked on the hole transport layer 4, and on the second light emitting layer 6 and the second light emitting layer 6 stacked on the first light emitting layer 5 A cathode 8 as a counter electrode laminated on the electron transport layer 7 and disposed opposite to the anode 3, a resin layer 9 sealed so as to cover the cathode 8, and a resin layer 9 A sealing substrate 10 is disposed so as to cover the sealing substrate 10. The hole transport layer 4, the first light emitting layer 5, the second light emitting layer 6, and the electron transport layer 7 constitute an organic light emitting medium layer. The resin layer 9 and the sealing substrate 10 constitute a sealing material.

The translucent substrate 2 is a substrate that supports the anode 3, the organic light emitting layer, and the cathode 8, and is made of a film or sheet such as metal, glass, or plastic.
As the plastic film, polyethylene terephthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, or polycarbonate can be used.
It should be noted that other gas barrier properties such as a ceramic vapor-deposited film, polyvinylidene chloride, polyvinyl chloride, ethylene-vinyl acetate copolymer saponified product, etc., on both sides of the translucent substrate 2 where the anode 3 is not formed. A film may be laminated.

The anode 3 is produced by forming a layer made of the material of the anode 3 on a substrate (translucent substrate 2). The material of the anode 3 includes metal composite oxides such as ITO (indium tin composite oxide), indium zinc composite oxide and zinc aluminum composite oxide, metal materials such as gold and platinum, and these metal oxides and metals. Either a single layer or a laminate of fine particle dispersion films in which fine particles of a material are dispersed in an epoxy resin or an acrylic resin can be used.
Moreover, for the anode 3, a polymer compound exhibiting conductivity may be used, and the polymer compound may contain a dopant. The conductivity of the polymer compound is usually 10 ⁻⁵ S / cm or more and 10 ⁵ S / cm or less, preferably 10 ⁻³ S / cm or more and 10 ⁵ S / cm or less in ^{terms of} conductivity.
It is preferable to select a material having a high work function such as ITO for the anode 3. If necessary, in order to reduce the wiring resistance of the anode, a conductive surface in which a fine wire structure portion of metal and / or alloy such as uniform mesh, comb shape or grid type is arranged is prepared, and the anode is formed thereon. May be formed.

Examples of the constituent material of the polymer compound exhibiting conductivity include polyaniline and derivatives thereof, polythiophene and derivatives thereof, and the like. As the dopant, a known dopant can be used, and examples thereof include organic sulfonic acids such as polystyrene sulfonic acid and dodecylbenzene sulfonic acid, and Lewis acids such as PF ₅ , AsF ₅ , and SbF ₅ . Further, the polymer compound exhibiting conductivity may be a self-doped polymer compound in which a dopant is directly bonded to the polymer compound. The optimum film thickness of the anode 3 varies depending on the element configuration of the organic EL lighting, but it is 100 to 10000 mm, more preferably 100 to 3000 mm, regardless of single layer or stacked layers.
As a method for forming the anode 3, depending on the material, dry film forming methods such as resistance heating vapor deposition, electron beam vapor deposition, reactive vapor deposition, ion plating, and sputtering, gravure printing, and screen printing are used. A wet film forming method such as can be used.

Next, an organic light emitting medium layer is formed as the organic functional thin film of the present embodiment.
As the organic light emitting medium layer in the present embodiment, the hole transport layer 4 stacked on the anode 3, the first light emitting layer 5 stacked on the hole transport layer 4, and the first light emitting layer 5 are provided. The second light emitting layer 6 is stacked, and the electron transport layer 7 is stacked on the second light emitting layer 6.
The order of stacking the first light emitting layer 5 and the second light emitting layer 6 may be reversed.
The hole transport layer 4 has a function of advancing holes injected from the anode 3 serving as an anode toward the cathode 8 serving as a cathode, and preventing electrons from traveling toward the anode 3 while passing holes. Have. Even when it has one of the function of stabilizing injection of holes from the anode 3 when an electric field is applied and the function of transporting holes injected from the anode 3 into the light emitting layer by the force of the electric field It may have both functions of hole injection and hole transport. The hole transport layer 4 may consist of one layer or a plurality of layers. For example, as shown in FIG. 1, the hole transport layer 4 is formed between various light emitting layers and the anode 3.

Examples of the hole transport material used for the hole transport layer 4 include metal phthalocyanines and metal-free phthalocyanines such as copper phthalocyanine and tetra (t-butyl) copper phthalocyanine, quinacridone compounds, 1,1-bis (4- Di-p-tolylaminophenyl) cyclohexane, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine, N, N′-di Aromatic amine low molecular hole transport materials such as (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine, polyaniline, polythiophene, polyvinylcarbazole, poly (3 , 4-ethylenedioxythiophene) and polystyrene sulfonic acid, polyvinyl carbazole or its derivatives, aromatic amino groups in the side chain or main chain. Polyarylene derivatives having an arylamine derivatives, such as triphenyl diamine derivatives, polymeric hole transport material comprising an aromatic amine, polymers, polythiophene oligomer _{materials, Cu 2 O, Cr 2 O} 3, Mn 2 O 3, FeOx _{(x~0.1), NiO, CoO,} Pr 2 O 3, Ag 2 O, MoO 2, Bi 2 O 3, ZnO, TiO 2, SnO 2, ThO 2, V 2 O 5, Nb 2 O 5, It can be selected from inorganic materials such as Ta ₂ O ₅ , MoO ₃ , WO ₃ and MnO ₂ and other existing hole transport materials.

Solvents for dissolving or dispersing the hole transport material include toluene, xylene, anisole, dimethoxybenzene, tetralin, cyclohexanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, acetic acid. Any of butyl, water and the like, or a mixture thereof may be mentioned.
If necessary, a surfactant, an antioxidant, a viscosity modifier, a UV absorber, or the like may be added to the above-described solution or dispersion of the hole transport material. Examples of the viscosity modifier include polystyrene. Polyvinylcarbazole and the like can be used.

As a method for forming the hole transport layer 4, depending on the material used for the hole transport layer 4, spin coating, bar coating, wire coating, slit coating, die coating, spray coating, curtain coating, flow coating, letterpress printing, Wet methods such as a letterpress reverse offset printing method, an ink jet method, and a nozzle printing method, and vapor deposition methods such as resistance heating vapor deposition, electron beam vapor deposition, reactive vapor deposition, ion plating, and sputtering can be used.
The 1st light emitting layer 5 and the 2nd light emitting layer 6 are functional materials of the organic light emitting layer which light-emits by a different light emission peak wavelength, when a voltage is applied. For example, red, green, and blue-green, or a plurality of mixed organic light emitters may be used for the first light-emitting layer 5, and the light emission peak of the first light-emitting layer such as blue is used for the second light-emitting layer. Alternatively, an organic light emitter that mainly emits light in a shorter spectral range than that may be used. Each of the light emitting materials has a maximum wavelength of about 610 nm to 640 nm for red, a maximum wavelength of about 500 nm to 610 nm for green and blue green, and a maximum wavelength of about 430 nm to 500 nm for blue. It is not particularly limited.

The first light-emitting layer 5 and the second light-emitting layer 6 may use a vacuum evaporation method such as a resistance heating evaporation method, an electron beam evaporation method, a reactive evaporation method, an ion plating method, or a sputtering method depending on the material used. it can. In addition, wet or organic electroluminescent ink (ink) dissolved or dispersed on the hole transport layer 4 can be applied separately by spray coating, letterpress printing, letterpress reverse printing, ink jet printing, nozzle printing, gravure printing, and the like. It can also be formed by attaching using a method and then drying. In addition, the film thickness of each light emitting layer should just be the range of 10 nm or more and 100 nm or less. When the film thickness is out of the range, the luminous efficiency tends to decrease.
As the organic light emitting material for forming the first light emitting layer 5, a phosphorescent material containing a phosphorescent compound that emits phosphorescence is used.

  As the phosphorescent compound, an organometallic complex containing a heavy atom is preferable in that the phosphorescent quantum yield is high and the external quantum efficiency of the light-emitting element can be further improved. Iridium, platinum, rhenium, ruthenium, osmium Among them, iridium complexes are particularly preferable. Examples include those in which at least one of the ligands of these metal complexes has a phenylpyridine skeleton, a bipyridyl skeleton, a porphyrin skeleton, and the like. More specifically, tris (1-phenylisoquinoline) iridium, bis [2- (2′-benzo [4,5-α] thienyl) pyridinate-N, C3 ′] iridium (acetylacetonate) (btp2Ir (acac )), 2,3,7,8,12,13,17,18-octaethyl-12H, 23H-porphyrin-platinum (II), bis [2- (2′-benzo [4,5-α] thienyl) Pyridinate-N, C3 ′] iridium, bis (2-phenylpyridine) iridium (acetylacetonate), fac-tris (2-phenylpyridine) iridium (Ir (ppy) 3), bis (2-phenylpyridinate- N, C2 ′) iridium (acetylacetonate), fac-tris [5-fluoro-2- (5-trifluoromethyl-2-pyridy ) Phenyl-C, N] iridium, iridium (III) tris (2- (2,4-difluorophenyl) pyridine) (Ir (FPPy) 3).

As the organic light emitting material for forming the second light emitting layer 6, a substance exhibiting delayed fluorescence is used.
The fluorescent material containing a substance exhibiting delayed fluorescence is not particularly limited as long as it emits blue fluorescence and expresses delayed fluorescence. For example, 4,4′-bis (2,2′-diphenylvinyl) -Aromatic dimethylidin compounds such as biphenyl (DPVBi), distyrylamine derivatives such as distyryldiamine compounds, pyrene derivatives, fluoranthene derivatives, perylene and perylene derivatives, anthracene derivatives, benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, Examples include chrysene derivatives, phenanthrene derivatives, and distyrylbenzene derivatives. One of these can be used alone, or two or more can be used in combination.

Furthermore, a known substance exhibiting thermally activated delayed fluorescence can also be used. Examples of the substance exhibiting thermally activated delayed fluorescence include fullerene and derivatives thereof, acridine derivatives such as proflavine, and eosin. In addition, metal-containing porphyrins including magnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), palladium (Pd), and the like can be given.
As a substance exhibiting thermally activated delayed fluorescence, 2- (biphenyl-4-yl) -4,6-bis (12-phenylindolo [2,3-a] carbazole-) represented by the following structural formula 11-yl) -1,3,5-triazine (abbreviation: PIC-TRZ), π-excess heteroaromatic ring such as 4,5-di (9H-carbazol-9-yl) phthalonitrile (abbreviation: 2CzPN) and A heterocyclic compound having a π-deficient heteroaromatic ring can be used. Since the heterocyclic compound has a π-excess type heteroaromatic ring and a π-deficient heteroaromatic ring, it has high electron transporting property and hole transporting property, and is preferable. In addition, a substance in which a π-rich heteroaromatic ring and a π-deficient heteroaromatic ring are directly bonded increases both the donor property of the π-rich heteroaromatic ring and the acceptor property of the π-deficient heteroaromatic ring, and singlet excitation. This is particularly preferable because the energy difference between the triplet state and the triplet excited state is small.

Examples of the electron transport material used for the electron transport layer 7 include 2- (4-bifinylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (1- Naphthyl) -1,3,4-oxadiazole, oxadiazole derivatives, bis (10-hydroxybenzo [h] quinolinolato) beryllium complexes, triazole compounds, and the like can be used. Alternatively, these electron transport materials may be used as an electron injection layer by doping a small amount of alkali metal or alkaline earth metal having a low work function such as sodium, barium, or lithium.
As a method for forming the electron transport layer 7, a vacuum evaporation method such as a resistance heating evaporation method, an electron beam evaporation method, a reactive evaporation method, an ion plating method, or a sputtering method can be used depending on the material to be used.

When the cathode 8 is a cathode, a material having a high work injection efficiency and a low work function is used for the cathode 8. Specifically, a single metal such as Mg, Al, or Yb is used, or a compound such as Li, oxidized Li, or LiF is sandwiched by about 1 nm at the interface in contact with the light emitting medium, and Al or Cu having high stability and conductivity is placed. You may use it, laminating | stacking. Alternatively, in order to achieve both electron injection efficiency and stability, one or more metals such as Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, and Yb having a low work function and stable Ag, An alloy system with a metal element such as Al or Cu may be used.
As a method for forming the cathode 8, a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method can be used depending on the material. Although there is no restriction | limiting in particular in the thickness of the cathode 8, 10 nm or more and 1000 nm or less are desirable.

  Another layer may be provided between the cathode 8 and the sealing material. For example, a passivation layer may be formed on the cathode 8. Examples of the material for the passivation layer include metal oxides such as silicon oxide and aluminum oxide, metal fluorides such as aluminum fluoride and magnesium fluoride, metal nitrides such as silicon nitride, aluminum nitride and carbon nitride, and silicon oxynitride. A laminated film of a metal carbide such as metal oxynitride or silicon carbide, and a polymer resin film such as an acrylic resin, an epoxy resin, a silicone resin, or a polyester resin may be used as necessary. In particular, from the viewpoint of barrier properties and transparency, it is preferable to use silicon oxide (SiOx), silicon nitride (SiNx), or silicon oxynitride (SiOxNy). Furthermore, a laminated film in which the film density is variable depending on the film forming conditions. Alternatively, a gradient membrane may be used.

As a method for forming the passivation layer, a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, a sputtering method, or a CVD method can be used depending on the material. It is preferable to use a CVD method in terms of translucency. As the CVD method, a thermal CVD method, a plasma CVD method, a catalytic CVD method, a VUV-CVD method, or the like can be used.
In addition, as a reaction gas in the CVD method, a gas such as N ₂ , O ₂ , NH ₃ , H ₂ , or N ₂ O is added to an organic silicone compound such as monosilane, hexamethyldisilazane (HMDS), or tetraethoxysilane. It may be added as necessary. For example, the density of the film may be changed by changing the flow rate of silane, and hydrogen or carbon may be contained in the film by the reactive gas used. The thickness of the passivation layer varies depending on the electrode step of the organic EL element, the height of the partition wall of the substrate, the required barrier characteristics, and the like, but generally about 0.01 μm to 10 μm is generally used.

Since the organic light emitting material is easily deteriorated by moisture and oxygen in the atmosphere, a sealing material for blocking the organic light emitting medium layer from the outside is provided. The sealing material can be formed by providing, for example, the sealing substrate 10 and the resin layer 9. The sealing substrate 10 needs to be a base material having low moisture and oxygen permeability. Examples of the material include ceramics such as alumina, silicon nitride, and boron nitride, glass such as alkali-free glass and alkali glass, metal foil such as quartz, aluminum, and stainless steel, and moisture-resistant film. Examples of moisture-resistant films include films formed by CVD of SiOx on both sides of plastic substrates, films with low permeability and water-absorbing films, or polymer films coated with a water-absorbing agent. The water vapor transmission rate is preferably 10 ⁻⁶ g / m ² / day or less.

As an example of the material of the resin layer 9, a photocurable adhesive resin, a thermosetting adhesive resin, a two-component curable adhesive resin made of epoxy resin, acrylic resin, silicone resin, or the like, or ethylene ethyl acrylate (EEA) ) Acrylic resins such as polymers, vinyl resins such as ethylene vinyl acetate (EVA), thermoplastic resins such as polyamide and synthetic rubber, and thermoplastic adhesive resins such as acid-modified products of polyethylene and polypropylene. .
Examples of the method for forming the resin layer 9 include a solvent solution method, an extrusion lamination method, a melting / hot melt method, a calendar method, a nozzle coating method, a screen printing method, a vacuum laminating method, and a hot roll laminating method. A material having a hygroscopic property or an oxygen absorbing property may be contained as necessary. Although the thickness of the resin layer formed on a sealing material is arbitrarily determined by the magnitude | size and shape of the organic EL element to seal, 5 micrometers or more and 500 micrometers or less are desirable.
The organic EL element and the sealing substrate 10 are bonded together in a sealing chamber. When the sealing material has a two-layer structure of the sealing substrate 10 and the resin layer 9 and a thermoplastic resin is used for the resin layer 9, it is preferable to perform only the pressure bonding with a heated roll. When a thermosetting adhesive resin or a photocurable adhesive resin is used for the resin layer 9, it is preferable to perform light or heat curing in a state of roll pressing or flat plate pressing.

Next, an outline of a method for manufacturing the organic EL light-emitting device 1 having the above-described configuration by a relief printing method and a vacuum vapor deposition method will be described. In addition, this invention is not restricted to this, As mentioned above, it can change to a relief printing method and can use resistance heating vapor deposition methods, such as a die-coat method and a spray coat.
First, the anode 3 is formed on the translucent substrate 2. For this, an ITO film may be formed on the entire surface of the light-transmitting substrate 2 by using a sputtering method, or a polymer compound showing conductivity by a wet method may be used.

Next, an ink of a hole transporting material is applied onto the anode 3 by a relief printing method to form the hole transport layer 4 uniformly.
After the ink of the hole transporting material is applied on the anode 3 by the letterpress printing method, the hole transporting layer 4 is uniformly formed, and then the first light emitting layer 5 is formed by a vacuum vapor deposition method such as a resistance heating vapor deposition method. It is formed on the hole transport layer 4.
Thus, after forming to the 1st light emitting layer 5, the 2nd light emitting layer 6 is similarly formed on the 1st light emitting layer 5 similarly by vacuum evaporation methods, such as a resistance heating vapor deposition method.

When forming the 2nd light emitting layer 6 by a vacuum evaporation method, a host material and a light emission dopant material are formed by a co-evaporation method. The deposition ratio of each material is adjusted by the deposition rate.
Subsequently, the electron transport layer 7 and the cathode 8 are formed by vapor deposition on the second light emitting layer 6 by a vapor deposition method such as a resistance heating vapor deposition method. Finally, the anode 3, the organic light emitting medium layer, and the cathode 8 are filled with a resin layer 9 in order to protect them from oxygen and moisture in the air, and are covered with a sealing substrate 10, thereby sealing the organic EL. The light emitting device 1 is manufactured.

  According to the organic EL light emitting device 1 configured as described above, the first light emitting layer including one or more phosphorescent emitters and the light emission mainly in the spectral region on the shorter wavelength side than the light emission peak of the first light emitting layer. A second light-emitting layer containing the fluorescent light-emitting body to be adjacent to each other, and the excited triplet energy level of the fluorescent light-emitting body of the second light-emitting layer is determined by the excitation triplet energy of at least one phosphorescent light-emitting body of the first light-emitting layer. By making it smaller than the level, energy transfer of the triplet exciton from the phosphorescent emitter to the fluorescent emitter, and obtaining delayed fluorescence by up-conversion from the triplet excited state to the singlet excited state, high efficiency and It is possible to provide an organic EL light emitting device capable of obtaining light emission of a plurality of colors including long-life white.

In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention. For example, the anode 3 may be made of a polymer compound exhibiting conductivity. If necessary, in order to reduce the wiring resistance of the anode, a uniform mesh, comb or grid type metal and / or the like may be used. Alternatively, a conductive surface on which the fine wire structure portion of the alloy is arranged may be produced, and an anode may be formed thereon.
In addition, a hole blocking layer, an electron injection layer, or an electron blocking layer may be formed. Here, like the hole transport layer 4, the electron blocking layer advances holes from the anode 3, which is the anode, to the cathode 8, which is the counter electrode, and passes the holes. It has a function to prevent progress. The hole blocking layer, the electron transporting layer, and the electron injecting layer advance the electrons from the cathode 8 as the counter electrode toward the anode 3 as the anode and pass the electrons, but the holes advance toward the cathode 8. It has a function to prevent this.
Further, a thin film such as lithium fluoride or sodium fluoride may be provided between the cathode 8 and the organic light emitting medium layer.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following description.
(First embodiment)
[Element creation]
As shown in FIG. 1, an anode 3 having a thickness of 0.15 μm was formed on a translucent substrate 2 (white plate glass: vertical 100 mm × horizontal 100 mm × thickness 0.7 mm) by sputtering. Here, the surface roughness Ra of the anode 3 was 20 nm in an arbitrary plane having an area of 200 μm ² .

The hole transport layer 4 uses a polyarylene derivative as a hole transport material, uniformly dissolves this in xylene to a concentration of 3.0% by weight, and uniformly coats it with a relief printing method. Formed by drying for 10 minutes. For the first light emitting layer 5 formed on the hole transport layer 4, a mixed light emitter of a red light emitter and a blue green light emitter was used, and for the second light emitting layer 6, a blue light emitter was used.
The host material of the first light emitting layer 5 is 4,4′-bis (9H-carbazol-9-yl) biphenyl (CBP), and the doping material is tris (1-phenylisoquinoline) iridium, bis [2- (2 ′ -Benzo [4,5-α] thienyl) pyridinate-N, C3 ′] iridium (acetylacetonate) (btp2Ir (acac)) and iridium (III) tris (2- (2,4-difluorophenyl) pyridine) (Ir (FPPy) 3) is used, the deposition rate is adjusted so that the ratio of host to dopan is 8: 2, and the ratio of btp2Ir (acac) to Ir (FPPy) 3 is 1: 9. As described above, the deposition rate was adjusted to form a thickness of 50 nm.

The host material of the second light emitting layer 6 is 4,4′-bis (9H-carbazol-9-yl) biphenyl (CBP), and the doped material is 4,5-di (9H-carbazol-9-yl) phthalonitrile. (2CzPN) was used, the deposition rate was adjusted so that the ratio of host to dopant was 8: 2, and a thickness of 30 nm was formed.
Further, a thickness of 20 nm was formed on the second light emitting layer 6 by vacuum deposition as Alq3 as the electron transport layer 7 at a film formation rate of 0.01 nm / sec. Thereafter, LiF / Al = 0.5 nm / 150 nm was formed as the cathode 8 by vapor deposition. Then, the sealing substrate 10 was adhere | attached and the organic EL light-emitting device 1 was obtained.
In the peripheral part of the display unit of the organic EL light-emitting device 1 thus obtained, an anode-side extraction electrode and a cathode-side extraction electrode connected to the cathode layer are provided. These extraction electrodes were connected to a power source, the organic EL light emitting device was turned on and displayed, and the lighting state and the display state were confirmed. When the obtained organic EL light-emitting device 1 was driven and display was confirmed, it was highly efficient and the light emission state was favorable.

(Second embodiment)
The first light emitting layer is formed to a thickness of 30 nm by the same method as in the first embodiment, and the host material of the second light emitting layer is 4,4′-bis (9H-carbazole-9- Il) biphenyl (CBP), bis (fluorophenylpyridine) iridium picolinate (FIrpic) as the doping material, the deposition rate is adjusted so that the ratio of host to dopant is 8: 2, and the thickness is 50 nm. Formed. The subsequent electron transport layer was formed by the same method as in the above example, and an organic EL light emitting device was obtained.
When the organic EL light-emitting device thus obtained was driven and the display was confirmed, the life of the second example was reduced compared to the first example.
From the second example, the blue phosphorescent light emitter, which is the second light emitting layer, was mainly made to emit light, so that the lifetime was reduced due to the influence of the blue phosphorescent light emitter. By using the delayed fluorescence of the fluorescent light emitter, an organic EL light emitting device capable of obtaining light emission with high efficiency and long life was obtained.

  INDUSTRIAL APPLICABILITY The present invention is useful in providing an organic EL light emitting device that can emit light of a plurality of colors including white and have a long lifetime.

DESCRIPTION OF SYMBOLS 1 ... Organic EL light-emitting device 2 ... Translucent substrate 3 ... Anode 4 ... Hole transport layer 5 ... 1st light emitting layer 6 ... 2nd light emitting layer 7 ... Electron transport layer 8 ... Cathode 9 ... Resin layer 10 ... Sealing substrate

Claims (6)

An organic light emitting medium layer is disposed between the transparent electrode and the counter electrode,
The organic light emitting medium layer includes a first light emitting layer including at least one phosphorescent light emitter, a fluorescent light emitter disposed adjacent to the first light emitting layer, and an emission peak of the first light emitting layer. And a second light emitting layer that mainly emits light in a short wavelength side spectral range,
The excited triplet energy level of the fluorescent light emitter of the second light emitting layer is smaller than the excited triplet energy level of at least one phosphorescent light emitter of the first light emitting layer,
The fluorescent light emitter of the second light emitting layer is delayed by triplet exciton energy transfer and upconversion from a triplet excited state to a singlet excited state from at least one phosphorescent light emitter of the first light emitting layer. An organic EL light emitting device characterized by being a substance exhibiting fluorescence. A hole transport layer having at least one characteristic of hole injection or hole transport formed on the transparent electrode and the transparent electrode, at least on the substrate;
A first light emitting layer comprising at least one phosphorescent emitter formed on the hole transport layer;
A second light-emitting layer that is formed on the first light-emitting layer, includes a fluorescent light emitter, and mainly emits light in a spectral region shorter than the light emission peak of the first light-emitting layer;
An electron transport layer formed on the second light emitting layer and having at least one characteristic of electron injection or electron transport and a counter electrode are sequentially formed;
The excited triplet energy level of the fluorescent light emitter of the second light emitting layer is smaller than the excited triplet energy level of at least one phosphorescent light emitter of the first light emitting layer, and the fluorescent light emitter of the second light emitting layer. Is a substance that exhibits delayed fluorescence by energy transfer of triplet excitons from at least one phosphorescent emitter of the first light-emitting layer and up-conversion from a triplet excited state to a singlet excited state. An organic EL light emitting device.   The phosphorescent emitter included in the first light emitting layer is a phosphorescent emitter that mainly emits light in the green and blue-green spectral regions. Organic EL light emitting device.   4. The organic EL light-emitting device according to claim 3, wherein one of the phosphorescent emitters included in the first light-emitting layer is a phosphorescent emitter that mainly emits light in a red spectral range.   The organic EL according to any one of claims 1 to 4, wherein the fluorescent light emitter included in the second light emitting layer is a fluorescent light emitter that mainly emits light in a blue spectral range. Light emitting device.   6. The organic EL light emitting device according to claim 1, wherein the fluorescent light emitter of the second light emitting layer is a substance exhibiting thermally activated delayed fluorescence.