JP2016054331A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which exhibits high efficiency and has a long driving life.SOLUTION: An organic electroluminescent element includes: an anode and a cathode; one or a plurality of organic compound layers sandwiched between the anode and the cathode; and a laminated metal oxide thin-film layer between the anode and the organic compound layers and/or between the cathode and the organic compound layers.SELECTED DRAWING: None

Description

  The present invention relates to an organic electroluminescent device.

Organic electroluminescent elements (organic EL) as new light-emitting elements applicable to display devices and lighting
Element) is expected.

An organic EL element has a structure in which one or a plurality of organic compounds containing a light-emitting organic compound is sandwiched between an anode and a cathode, and holes injected from the anode and electrons injected from the cathode are recombined. The light-emitting organic compound is excited using the energy of time to obtain light emission.
The organic EL element is a current-driven element, and the light emission intensity is proportional to the injected current. In order to utilize the flowing current more efficiently, various element structures have been improved.

The most basic and extensively studied structure of the organic EL element is that of a three-layer structure proposed by Adachi et al. (Non-patent Document 1), in which a hole transport layer and a light emitting layer are provided between an anode and a cathode. The structure is such that the electron transport layer is sandwiched in this order. Since this proposal, the organic EL element has been based on a three-layer structure, and many studies have been made with the aim of improving performance such as efficiency and lifetime.

By the way, organic EL elements are generally easily deteriorated by oxygen and water, and strict sealing is indispensable in order to prevent these intrusions. The cause of the deterioration is that the materials that can be used as the cathode are limited to those with a small work function, such as alkali metals and alkali metal compounds, due to the ease of electron injection into the organic compounds, and the organic compounds used The main reason for this is that it itself easily reacts with oxygen and water. Strict sealing impairs the features such as low cost and flexibility that organic EL elements were considered to have superiority to other light emitting elements in the early stages of development.

Morii et al. Of the present inventor have proposed a light-emitting element that can be used without sealing (
Patent Document 1). In this element, by changing the hole transport layer and the electron transport layer to inorganic oxides, it became possible to use FTO or ITO, which are conductive oxide electrodes, as the cathode, and gold as the anode. Since it is not necessary to use a metal having a small work function such as an alkali metal or an alkali metal compound, it is possible to emit light without strict sealing. That is, the organic-inorganic hybrid type electroluminescent device (HOILED device) is completely different from the conventional organic EL device.

As described in Patent Document 1, the basic structure of the HOILED element is a hole injecting metal oxide layer and an electron injecting metal between the anode and the organic compound layer and between the cathode and the organic compound layer, respectively. It consists of an oxide layer. Preferably, the hole injecting metal oxide layer is made of vanadium oxide or molybdenum oxide, and the electron injecting oxide layer is made of titanium oxide.

Among these, various studies have been made on the electron injecting metal oxide layer, and light emission has been confirmed even in an element using zinc oxide, zirconium oxide, magnesium oxide, hafnium oxide, and the like (Non-Patent Documents 2, 3, and 4). .

In addition, providing a hole blocking metal compound layer between the electron injecting metal oxide layer and the organic compound layer has been studied. Patent Document 2 reports that the efficiency is improved by a method of forming a cesium compound layer as a hole blocking metal compound layer on a titanium oxide layer which is an electron injecting metal oxide layer. In addition, the cesium compound layer described in Patent Document 2 is formed by depositing cesium carbonate by vacuum deposition and then exposed to the atmosphere. The chemical state is unknown, and any of cesium carbonate, cesium hydroxide, cesium oxide, or these It is supposed to be a mixture of Cesium carbonate deliquesces to produce cesium hydroxide, while cesium hydroxide reacts with carbon dioxide to produce cesium carbonate. On the other hand, cesium oxide reacts very violently with water to produce cesium hydroxide. From these facts, it can be inferred that the cesium compound layer described in Patent Document 2 will be mainly composed of a mixture of cesium carbonate and cesium hydroxide. A HOILED element using a cesium compound layer is known to have a problem in that it has excellent initial characteristics but a short driving life.

As the organic compound layer, poly (9,9-dioctylfluorene-alt-) exhibiting green light emission.
Benzothiadiazole) has been mainly studied. As an example of examining other luminescent colors, non-patent document 3 describes an element using zirconium oxide as an electron-injecting metal oxide layer in blue, red,
Although the light emission characteristics of the green polymer are described, only the light emission starting voltage is high and the efficiency is low except for the green color. As described above, the reported HOILED elements (particularly blue light emitting elements) have high driving voltage and low efficiency, and are not practically sufficient.

JP 2007-53286 A JP 2009-70954 A

Japan Journal of Applied Physics, 27 (1988) L269. Applied Physics Letters 91, 223501 (2007). Advanced Materials, 2009, 21, 3475. Journal of Materials Chemistry, 2010, 20, 4047.

An object of the present invention is to provide an organic electroluminescent device exhibiting high efficiency and having a long driving life.

As a result of intensive studies, the present inventors have found that the above-described problems can be solved by using a layer in which an oxide thin film and a magnesium compound thin film are stacked as an electron injection layer of an organic electroluminescent element.
The present invention has been completed.
That is, the present invention provides [1] an anode and a cathode, one or more organic compound layers sandwiched between the anode and the cathode, and between the anode and the organic compound layer and / or the cathode. An organic electroluminescent device comprising a metal oxide thin film layer between the organic compound layer and a magnesium compound layer between at least one metal oxide thin film layer and the organic compound layer. is there. [2] Moreover, the organic electroluminescent element of the present invention comprises an anode and a cathode, one or more organic compound layers sandwiched between the anode and the cathode, and between the cathode and the organic compound layer. It is preferable to have a metal oxide thin film layer and a magnesium compound layer between the metal oxide layer and the organic compound layer. [3] Further, the present invention provides an illumination device, [4] and a display device each including the organic electroluminescence element described above.

According to the present invention, it is possible to provide an organic thin film light emitting element with high efficiency and a long driving life, and an illumination device and a display device including the organic thin film light emitting device.

1 is a cross-sectional view of an embodiment of an organic electroluminescent device according to the present invention having a HOILED structure. 6 is a graph showing voltage-luminance characteristics of organic electroluminescent elements created in Example 1, Comparative Example 1 and Comparative Example 3. It is a graph which shows the current density-power efficiency characteristic of the organic electroluminescent element created in Example 1, Comparative Example 1, and Comparative Example 3. It is a graph which shows the voltage-luminance characteristic of the organic electroluminescent element created in Example 2, Comparative Example 2, and Comparative Example 3. It is a graph which shows the current density-power efficiency characteristic of the organic electroluminescent element created in Example 2, Comparative Example 2, and Comparative Example 3. It is a graph which shows the lifetime characteristic of the organic electroluminescent element created in Example 1 and Comparative Example 4.

  Hereinafter, the organic electroluminescence device of the present invention will be described in detail.

The organic electroluminescent element of the present invention comprises an anode and a cathode, 1 sandwiched between the anode and the cathode.
And a metal oxide thin film layer between the anode and the organic compound layer and / or between the cathode and the organic compound layer, and at least one of the metal oxide layers A magnesium compound layer is provided between the thin film layer and the organic compound layer.

The metal oxide thin film layer used in the present invention is made of a semiconductor or an insulator thin film. Metal elements constituting the metal oxide include magnesium, calcium, strontium, barium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, copper, zinc, and cadmium. , Aluminum and silicon.

In the present invention, a sheet having a sheet resistance lower than 100Ω / □ is a conductor, and the sheet resistance is 10
Objects higher than 0Ω / □ are classified as semiconductors or insulators. Therefore, ITO (tin-doped indium oxide) known as transparent electrodes, ATO (antimony-doped indium oxide), IZO (indium-doped zinc oxide), AZO (aluminum-doped zinc oxide),
A thin film such as FTO (fluorine-doped indium oxide) does not correspond to one layer constituting the laminated metal oxide thin film layer of the present invention because it has high conductivity and is not included in the category of a semiconductor or an insulator.

The thickness of each thin film constituting the laminated metal oxide thin film layer is acceptable from about 1 nanometer to several micrometers, but in order to obtain an organic electroluminescent device that can be driven at a low voltage, it is 1 nanometer to 100 nanometer. The degree is preferred.

A method for producing each thin film layer constituting the laminated metal oxide thin film layer is not particularly limited, and a known method can be used as appropriate, but a sputtering method, a vacuum deposition method, a sol-gel method, a spray pyrolysis (SPD) method can be used. Examples include an atomic layer deposition (ALD) method and a chemical vapor deposition (CVD) method. These methods are preferably selected according to the characteristics of the material of each thin film layer, and the production method may be different for each layer.

Furthermore, a magnesium compound layer is disposed between the metal oxide thin film layer and the organic compound layer. The magnesium compound layer is a layer containing at least one magnesium compound. Examples of the magnesium compound include magnesium oxide, magnesium carbonate, magnesium acetate, magnesium hydroxide, magnesium sulfate, magnesium nitrate, magnesium fluoride, magnesium chloride, odor And magnesium iodide, magnesium iodide, magnesium acetylacetonate, and the like. The magnesium compound layer may be a simple substance, a mixture thereof, or a compound other than these. When a plurality of metal oxide thin film layers are present, a magnesium compound layer may be provided between at least one metal oxide thin film layer and the organic compound layer.

As the anode and cathode used in the present invention, known conductive materials can be used as appropriate, but at least one of them is preferably transparent for light extraction. Examples of known transparent conductive materials include ITO (tin-doped indium oxide), ATO (antimony-doped indium oxide), IZO (indium-doped zinc oxide), AZO (aluminum-doped zinc oxide), and FTO (fluorine-doped indium oxide). Is raised. Examples of opaque conductive materials include calcium, magnesium, aluminum, tin, indium,
Examples thereof include copper, silver, gold, and alloys thereof.

As the organic compound layer used in the present invention, known organic low molecular weight materials, organometallic complexes, polymer materials and the like can be used as appropriate, and they can be used in combination as necessary. At least one of the organic compounds is selected from light emitting materials.

Examples of the polymer light-emitting material include polyacetylene compounds such as trans-type polyacetylene, cis-type polyacetylene, poly (di-phenylacetylene) (PDPA), poly (alkyl, phenylacetylene) (PAPA), and poly (para-para-). Fenvinylene) (P
PV), poly (2,5-dialkoxy-para-phenylene vinylene) (RO-PPV),
Cyano-substituted-poly (para-phenvinylene) (CN-PPV), poly (2-dimethyloctylsilyl-para-phenylenevinylene) (DMOS-PPV), poly (2-methoxy, 5- (2'-ethylhexoxy) -Polyparaphenylene vinylene compounds such as para-phenylene vinylene (MEH-PPV), poly (3-alkylthiophene) (PAT
), Polythiophene compounds such as poly (oxypropylene) triol (POPT), poly (9,9-dialkylfluorene) (PDAF), poly (dioctylfluorene-)
Alt-benzothiadiazole) (F8BT), α, ω-bis [N, N′-di (methylphenyl) aminophenyl] -poly [9,9-bis (2-ethylhexyl) fluorene-2
, 7-diyl] (PF2 / 6am4), polyfluorene-based compounds such as poly (9,9-dioctyl-2,7-divinylenefluorenyl-ortho-co (anthracene-9,10-diyl), poly (Para-phenylene) (PPP), poly (1,5-dialkoxy-para-phenylene) (RO-PPP) and other polyparaphenylene compounds, poly (N-vinylcarbazole) (PVK) Polysilane compounds such as carbazole compounds, poly (methylphenylsilane) (PMPS), poly (naphthylphenylsilane) (PNPS), poly (biphenylylphenylsilane) (PBPS), and Japanese Patent Application No. 2010-2
Examples include boron compound polymer materials described in 30995 and Japanese Patent Application No. 2011-6457.

On the other hand, as a low-molecular light-emitting material, for example, 2,2′-bipyridine-4,4 ′ is used as a ligand.
-Tricoordinate iridium complex with dicarboxylic acid, factory (2-phenylpyridine) iridium (Ir (ppy) 3), 8-hydroxyquinoline aluminum (Alq3)
), Tris (4-methyl-8 quinolinolate) aluminum (III) (Almq3),
8-hydroxyquinoline zinc (Znq2), (1,10-phenanthroline) -tris- (4,4,4-trifluoro-1- (2-thienyl) -butane-1,3-dionate)
Europium (III) (Eu (TTA) 3 (phen)), 2, 3, 7, 8, 12, 13
, 17,18-octaethyl-21H, 23H-porphine Various metal complexes such as platinum (II), distyrylbenzene (DSB), diaminodistyrylbenzene (DADS)
Benzene compounds such as B), naphthalene compounds such as naphthalene and nile red, phenanthrene compounds such as phenanthrene, chrysene, chrysene compounds such as 6-nitrochrysene, perylene, N, N′-bis ( 2,5-di-t-butylphenyl)
-Perylene compounds such as 3,4,9,10-perylene-di-carboximide (BPPC), coronene compounds such as coronene, anthracene compounds such as anthracene and bisstyrylanthracene, and pyrenes such as pyrene Compound, 4- (di-cyanomethylene) -2-methyl-6- (para-dimethylaminostyryl) -4H-pyran (DCM)
Of pyran compounds such as acridine, acridine compounds such as acridine, stilbene compounds such as stilbene, thiophene compounds such as 2,5-dibenzoxazole thiophene, benzoxazole compounds such as benzoxazole, Of benzimidazole compounds such as 2,2 ′-(para-phenylenedivinylene) -bisbenzothiazole, bistyryl (1,4-diphenyl-1,3-butadiene), tetraphenylbutadiene Butadiene compounds such as naphthalimide, naphthalimide compounds such as naphthalimide, coumarin compounds such as coumarin, perinone compounds such as perinone, oxadiazole compounds such as oxadiazole,
Ardazine compounds, cyclopentadiene compounds such as 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP), quinacridone compounds such as quinacridone and quinacridone red, pyrrolopyridine, and thiadia Pyridine compounds such as zolopyridine, spiro compounds such as 2,2 ′, 7,7′-tetraphenyl-9,9′-spirobifluorene, metals such as phthalocyanine (H2Pc), copper phthalocyanine or metal-free Phthalocyanine-based compounds, as well as JP2009-155325A, Japanese Patent Application No. 20
Examples thereof include boron compound materials described in Japanese Patent Application No. 10-230995 and Japanese Patent Application No. 2011-6458.

The method for forming the organic compound layer is not particularly limited, and a known method can be used as appropriate in accordance with the characteristics of the material, but when it can be applied as a solution, a spin coating method, a slit coating method,
Examples include dip coating, spray coating, and casting. Among these, the spin coat method and the slit coat method are preferable because the film thickness can be more easily controlled. When not applied or when the solvent solubility is low, vacuum evaporation or ESDUS (Evaporative)
ve Spray Deposition from Ultra-dilute So
(Lution) method or the like.

For reasons such as further improving the characteristics of the organic electroluminescent element, there may be layers other than the above-described layers as necessary. Examples of such a layer include an electron injection layer, a hole blocking layer, a hole injection layer, and an electronic element layer, and known materials can be appropriately used.

When the organic electroluminescent element to which the present invention is applied is a HOILED element, it is desirable to provide a hole injection layer between the organic compound layer and the anode. Examples of the material used for the hole injection layer include molybdenum oxide, tungsten oxide, vanadium oxide, and rhenium oxide, with molybdenum oxide being most preferred.

The electroluminescent element of the present invention may be sealed if necessary. As the sealing step, a known method can be used as appropriate. For example, a method of adhering a sealing container in an inert gas, or organic EL
Examples thereof include a method of directly forming a sealing film on the element. In addition to these, a method of enclosing a moisture absorbing material may be used in combination.

The electroluminescent element of the present invention can emit light by applying a voltage (usually 15 volts or less) between the anode and the cathode. Normally, a DC voltage is applied, but an AC component may be included.

The electroluminescent element of the present invention can be used as a light emitting site of illumination or a display device. The light emission color can be changed by appropriately selecting the material of the organic compound layer, and a desired light emission color can be obtained by using a color filter or the like together.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, the scope of the present invention is not limited only to these Examples.
(Synthesis of blue light-emitting polymer)
(Synthesis Example 1)
Under a nitrogen atmosphere, 1-bromo-3,5-bis (trifluoromethyl) benzene (14.8 g)
, 50.3 mmol) was added 200 ml of diethyl ether and cooled to −78 ° C., and a normal butyl lithium hexane solution (1.65 M, 30.9 ml, 50.9 mmol) was added dropwise thereto, followed by stirring at −78 ° C. for 1 hour. . Furthermore, zinc chloride in diethyl ether (1M, 2
4.3 ml, 24.3 mmol) was added dropwise with stirring. After completion of dropping, the mixture was stirred at room temperature for 1 hour. Thereto was added a toluene solution (200 mL) containing 5-bromo-2- (4-bromo-2-dibromoborylphenyl) pyridine (5.6 g, 11.6 mmol), and 1 at 85 ° C.
The mixture was stirred with heating for 5 hours. After cooling to room temperature, the reaction solution was added to ice water and extracted with chloroform. The organic phase was washed with saturated brine, dried over sodium sulfate and filtered. The filtrate was concentrated with a rotary evaporator and then purified by silica gel chromatography (hexane: dichloromethane = 1: 2) to obtain the following formula (1);

Was obtained in a yield of 69%.
The obtained boron-containing compound (1) (187.2 mg, 0.25 mmol), the following formula (2)
Fluorene compound (140.2 mg, 0.251 mmol), tetrakistriphenylphosphine palladium (2.9 mg, 0.0025 mmol) in toluene 3 ml
And stirred for 10 minutes at room temperature under a nitrogen flow.

To this, ammonium carbonate (240.4 mg, 0.8 mmol) was added 0.75 ml of distilled water.
An aqueous solution prepared by dissolving in was added, and the mixture was further stirred at room temperature for 20 minutes under a nitrogen flow to complete devolatilization. This was heated and stirred at 115 ° C. for 17 hours under reflux, and bromobenzene (39.3 mg, 0.25 mmol) was added for end-capping, followed by stirring for 1 hour, and phenylboronic acid (30.5 mg, 0.25 mmol) was further added. added. The solution was allowed to cool to room temperature, and the toluene solution was separated and washed once with hydrochloric acid and twice with pure water, and the organic layer was concentrated to about several ml. The concentrated solution was dropped into 300 ml of methanol and stirred for 10 minutes as it was, and the resulting precipitate was collected by filtration. By repeating the same purification process three times in total and drying the solid under reduced pressure, the following formula (3);

The blue light emitting polymer represented by this was obtained. The weight average molecular weight in terms of polystyrene by gel permeation chromatography (tetrahydrofuran solvent) was 71,000.

(Creation of organic electroluminescence device)
(Example 1)
[1] A commercially available transparent glass substrate with an ITO electrode layer having an average thickness of 0.7 mm was prepared. At this time, an ITO electrode patterned to have a width of 2 mm was used. This substrate was subjected to ultrasonic cleaning in acetone and isopropanol for 10 minutes, and then boiled in isopropanol for 5 minutes. This substrate was taken out from isopropanol, dried by nitrogen blowing, and UV ozone cleaning was performed for 20 minutes.
[2] This substrate was fixed to a substrate holder of a Miratron sputtering apparatus having a zinc metal target. After reducing the pressure to about 1 × 10 −4 Pa, sputtering was performed with argon and oxygen introduced, and a zinc oxide layer having a thickness of about 2 nm was formed. At this time, a metal mask was used in combination so that a portion of the ITO electrode was not deposited with zinc oxide for electrode extraction.
[3] A mixed solution of magnesium acetate in 1% water-ethanol (1: 3 by volume) was prepared.
The substrate prepared in step [2] was washed again in the same manner as in step [1]. The cleaned substrate with a zinc oxide thin film was set on a spin coater. A magnesium acetate solution was dropped on the substrate and rotated at 1300 rpm for 60 seconds. The magnesium oxide layer was formed by baking this for 2 hours with the hotplate set to 400 degreeC in air | atmosphere.
[4] Next, 1 mL of a 1.2 wt% tetrahydrofuran solution of the blue light-emitting polymer (3) prepared in Synthesis Example 1 was prepared. The prepared substrate with an oxide thin film layer was set on a spin coater. A blue light emitting polymer solution was dropped on the substrate and rotated at 1600 rpm for 30 seconds to form an organic compound layer having a thickness of about 100 nm. This was moved into a glove box in an argon atmosphere, and heated at 200 ° C. for 1 hour using a hot plate to remove the residual solvent in the organic compound layer.
[5] The substrate formed up to the organic compound layer was fixed to a substrate holder of a vacuum deposition apparatus. Molybdenum trioxide was placed in an alumina crucible and set in the first vapor deposition source. At the same time, gold was put in an alumina crucible and set in the second vapor deposition source. The inside of the vacuum deposition apparatus was depressurized to about 1 × 10 −4 Pa, and molybdenum trioxide was deposited to a thickness of 10 nm. Next, the film thickness of gold is 20 nm.
Then, an organic electroluminescence device (Mg: Zn = 4: 0) was prepared. At this time,
A vapor deposition surface was formed into a strip shape having a width of 2 mm using a stainless steel vapor deposition mask. That is, the light emitting area of the produced organic electroluminescent element was 4 mm 2.
(Example 2)
An organic electroluminescent device having a magnesium compound layer on a titanium oxide thin film layer was prepared in the same manner except that a titanium metal target was used instead of the zinc metal target in the step [2] of Example 1.
(Comparative Example 1)
An organic electroluminescent element having a zinc oxide single layer as an oxide thin film layer was produced in the same manner except that the step [3] in Example 1 was omitted.
(Comparative Example 2)
An organic electroluminescence device having a titanium oxide single layer as an oxide thin film layer was produced in the same manner except that the step [3] of Example 2 was omitted.
(Comparative Example 3)
An organic electroluminescent device having a magnesium oxide single layer as an oxide thin film layer was prepared in the same manner except that the step [2] in Example 1 was omitted.
(Comparative Example 4)
An organic electroluminescence device having a cesium compound layer on a zinc oxide thin film layer was produced in the same manner except that the next step [3 ′] was performed instead of the step [3] in Example 1.
[3 ′] The substrate formed up to the oxide thin film layer was fixed to a substrate holder of a vacuum deposition apparatus. Cesium carbonate was placed in an alumina crucible and set in a vapor deposition source. About 1 × 10− inside the vacuum evaporation system
The pressure was reduced to 4 Pa, and cesium carbonate was deposited to a thickness of 3 nm. This substrate was left in the atmosphere for 12 hours to form a cesium compound layer.

(Created organic electroluminescence device)
The configurations of the organic electroluminescent elements prepared in Examples 1 and 2 and Comparative Examples 1 to 4 are summarized as shown in the following table.

(Measurement of light emission characteristics of organic electroluminescence device)
Voltage application to the device and current measurement were performed using a “2400 type source meter” manufactured by Keithley. Luminance was measured with “BM-7” manufactured by Topcon Corporation. Example 1 Comparative Example 1
2 and FIG. 3 show the voltage-luminance characteristics and current density-power efficiency characteristics of the organic electroluminescent device prepared in Comparative Example 3 when a DC voltage of −4 V to 15 V is applied in an argon atmosphere. .
From FIG. 2, the organic electroluminescent element of Example 1 using the laminated structure of the oxide film and magnesium compound film of the present invention is the organic electroluminescent element of Comparative Example 1 and Comparative Example 3 using a single layer oxide thin film. It is clear that light is emitted from a voltage lower than that of.
Further, from FIG. 3, Example 1 using the laminated structure of the oxide film and the magnesium compound film of the present invention.
It is clear that this organic electroluminescent element exhibits higher power efficiency than the organic electroluminescent elements of Comparative Examples 1 and 3 using a single-layer oxide thin film.
Next, voltage-luminance characteristics, current density-power efficiency when the organic electroluminescent elements prepared in Example 2, Comparative Example 2 and Comparative Example 3 were applied with a DC voltage of −4 V to 15 V in an argon atmosphere. The characteristics are shown in FIGS. 4 and 5, respectively.
From FIG. 4, the organic electroluminescent element of Example 2 using the laminated structure of the oxide film and magnesium compound film of the present invention is the organic electroluminescent element of Comparative Example 2 and Comparative Example 3 using a single layer oxide thin film. It is clear that light is emitted from a voltage lower than that of.
Further, from FIG. 5, Example 2 using the laminated structure of the oxide film and the magnesium compound film of the present invention.
It is clear that the organic electroluminescent element of FIG. 3 shows higher power efficiency than the organic electroluminescent elements of Comparative Example 2 and Comparative Example 3 using a single layer oxide thin film.

(Measurement of lifetime characteristics of organic electroluminescent devices)
Application of voltage to the element and measurement of relative luminance were performed using an “organic EL lifetime measuring device” manufactured by System Giken. While this device automatically adjusts the voltage so that a constant current flows through the element,
Relative luminance can be measured with a photodiode. The current value was set for each element so that the luminance at the start of measurement was 100 cd / m 2. FIG. 6 shows the lifetime characteristics of the organic electroluminescent elements prepared in Example 1 and Comparative Example 4.
From FIG. 6, the organic electroluminescent device of Example 1 using the laminated structure of the oxide film and the magnesium compound film of the present invention is the organic electroluminescent device of Comparative Example 4 having a single-layer oxide thin film and a cesium compound layer. It can be seen that the lifetime is longer.

The electroluminescent device of the present invention is a light-emitting device with high efficiency and a long driving life, and the luminescent color can be changed by appropriately selecting the material of the organic compound layer. Can be obtained, and can be suitably used as a light emitting part of illumination or a display device.

DESCRIPTION OF SYMBOLS 1 ... Board | substrate 2 ... Cathode 3 ... Laminated metal oxide thin film layer 4 ... Organic compound layer 5 ... Hole injection metal oxide layer 6 ... Anode

Claims (4)

An anode and a cathode, one or more organic compound layers sandwiched between the anode and the cathode, and between the anode and the organic compound layer and / or between the cathode and the organic compound layer An organic electroluminescent device comprising a metal oxide thin film layer and having a magnesium compound coating layer between at least one metal oxide thin film layer and the organic compound layer. An anode and a cathode; one or more organic compound layers sandwiched between the anode and the cathode; and a metal oxide thin film layer between the cathode and the organic compound layer, and the metal oxide The organic electroluminescent element according to claim 1, further comprising a magnesium compound layer between the layer and the organic compound layer. An illuminating device comprising the organic electroluminescent element according to claim 1. A display device comprising the organic electroluminescent element according to claim 1.

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