JPH11162647A - Organic electroluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the electron implanting characteristics, heighten the brightness in light emission, and exert a stable performance even through repetitive uses by furnishing at least a positive electrode, light emission layer, an electron implantation layer consisting of electron conveying material and metal oxide or metal halide, and a negative electrode. SOLUTION: On a glass board, a positive electrode 1 having a work function of 4 eV or more is provided, such as ITO, and thereon if necessary a hole injection conveying layer 2 is provided, whereon an organic light emission layer 3 is formed, and thereon a negative electrode 5 having a work function of 4 eV or less such as Al is formed with an electron implantation layer 4 interposed. Thus an intended organic electroluminescence element is accomplished, wherein the electron implantation layer 4 consists of a mixture substance of an electron conveying material such as chelated oxynoid compound and metal oxide or metal halide, with a preferable film thickness of 0.1-20 nm. The metal oxide or metal halide should preferably have a work function of 4.2 eV or less such as MgO, LiF, etc., and its mix proportion should preferably lie from 100:1 to 1:1.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an organic electroluminescence device.

[0002]

2. Description of the Related Art An organic electroluminescence element is an element which emits light in response to an electric signal and is constituted by using an organic compound as a light emitting substance.

[0003] The organic electroluminescent element basically comprises an organic light emitting layer and a pair of opposing electrodes sandwiching the layer. In the light emission, electrons are injected from one of the electrodes and holes are injected from the other electrode, so that the luminescent material in the luminescent layer is excited to a higher energy level, and the excited luminescent material is returned to its original base. When returning to the state, the extra energy is emitted as light.

In order to increase the luminous efficiency, in addition to the above basic structure, a hole injection layer is further provided on the electrode for injecting holes, and an electron transport layer is provided on the electrode for injecting electrons. Configuration has been taken.

US Pat. No. 3,530,325 describes an example of an organic electroluminescent device in which single crystal anthracene or the like is used as a luminous body. Japanese Patent Application Laid-Open No. Sho 59-194393 proposes a combination of a hole injection layer and an organic light emitting layer. JP-A-63-295695 proposes a combination of an organic hole injection / transport layer and an organic electron injection / transport layer.

The electroluminescent device having such a laminated structure has a structure in which an organic phosphor, a charge transporting organic substance (charge transporting material) and an electrode are laminated, and holes and electrons injected from each electrode are charged. Light is emitted as they move through the transport material and recombine. As an organic phosphor, 8
-Organic dyes that emit fluorescence such as quinolinol aluminum complex and coumarin compounds are used. As the charge transporting material, for example, N, N'-di (m-tolyl)
Diamino compounds such as N, N'-diphenylbenzidine and 1,1-bis [N, N-di (p-tolyl) aminophenyl] cyclohexane, and 4- (N, N-diphenyl) aminobenzaldehyde-N, N- And diphenylhydrazone compounds. Further, porphyrin compounds such as copper phthalocyanine have been proposed.

[0007] Incidentally, although the organic electroluminescence device has high light emission characteristics, it is not sufficient in terms of stability during light emission and storage stability, and has not been put to practical use. It has been pointed out that the stability of the charge transporting material is one of the problems in the light emission stability and storage stability of the device.
A layer formed of an organic material of an electroluminescent device is very thin, several tens to several hundreds of nanometers, and a voltage applied per unit thickness is very high. In addition, heat is generated by light emission and energization. Therefore, the charge transporting material is required to have electrical, thermal or chemical stability.

Japanese Unexamined Patent Publications Nos. Hei 2-15595 and Hei-3-1595 use a cathode other than aluminum in order to reduce the light emission starting voltage of the organic electroluminescent element.
No. 37994, JP-A-4-132191, JP-A-5-121172 and the like.

Japanese Patent Application Laid-Open No. 4-132189 discloses an electron injection layer using a film in which an electron transport material and a metal are mixed.
And JP-A-7-268317.

[0010] However, those using metals other than aluminum have problems such as difficult film formation conditions and easy oxidation, and similar problems have arisen when an electron transport material and a metal are mixed.

If the metal used as the electron injection layer is oxidized during vapor deposition, a powdery substance is formed and a uniform film cannot be formed, or it becomes cloudy and a metal-colored film cannot be formed and cannot be used as an electrode. There is a problem that the element cannot emit light. At present, an electron injection layer having good characteristics has not yet been obtained.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organic electroluminescent device having a high emission intensity and exhibiting stable performance even when used repeatedly. An object of the present invention is to provide a luminescence element.

[0013]

According to the present invention, there is provided an organic electroluminescence device provided with at least an anode, a light emitting layer, an electron injection layer and a cathode, wherein the electron injection layer comprises an electron transporting material and a metal oxide or a metal halide. The present invention relates to an organic electroluminescence device characterized by being a mixed film.

The organic electroluminescent device of the present invention comprises at least a light emitting layer and an electron injection layer between the anode (1) and the cathode (5). The present invention is fundamentally characterized in that the electron injection layer of the organic electroluminescence element is a mixed film of an electron transport material and a metal oxide or a metal halide. Hereinafter, the present invention will be described with reference to FIG. FIG. 1 shows a configuration example of an organic electroluminescence element to which the present invention can be applied. In the figure, (1) is an anode, on which a hole injection transport layer (2), an organic light emitting layer (3), an electron injection layer (4) and a cathode (5) are sequentially laminated.

As the conductive substance used as the anode (1) of the organic electroluminescence element, those having a work function of more than 4 eV are preferable, and carbon, aluminum, vanadium, iron, cobalt, nickel, copper, zinc,
Tungsten, silver, tin, gold, and alloys thereof, and conductive metal compounds such as tin oxide, indium oxide, antimony oxide, zinc oxide, and zirconium oxide are used.

As the metal forming the cathode (5), aluminum, silver or those having a work function smaller than 4 eV,
For example, magnesium, calcium, titanium, yttrium, lithium, gadolinium, ytterbium, ruthenium, manganese, and alloys thereof are used.

In the organic electroluminescence element, at least the anode (1) or the cathode (5) needs to be a transparent electrode so that light emission can be seen. On this occasion,
If a transparent electrode is used for the cathode, the transparency is likely to be impaired.

When forming a transparent electrode, on a transparent substrate,
Using a conductive material as described above, a device such as vapor deposition, sputtering, or a method such as a sol-gel method or a method of dispersing and applying in a resin or the like is used to secure desired translucency and conductivity. I just need.

The transparent substrate is not particularly limited as long as it has an appropriate strength, is not adversely affected by heat due to vapor deposition or the like when producing an organic electroluminescent element, and is transparent. It is also possible to use a glass substrate, a transparent resin such as polyethylene, polypropylene, polyethersulfone, polyetheretherketone, and the like. As a transparent electrode formed on a glass substrate, commercially available products such as ITO and NESA are known, but these may be used.

FIG. 1 shows a structure in which a hole injection / transport layer (2) is formed on the above-mentioned anode (1). The hole injection transport layer (2) may be formed by vapor deposition of a compound, or may be formed by dip coating or spin coating a solution in which the compound is dissolved or a solution in which a suitable resin is dissolved.

When the hole injection transport layer is formed by a vapor deposition method,
Its thickness is usually 1 to 200 nm, preferably 5 to 10 nm.
0 nm, and when formed by a coating method, 5 to 500 n
m may be formed. As the film thickness is larger, the applied voltage for emitting light needs to be higher, and the luminous efficiency is poor, and the organic electroluminescent element is likely to be deteriorated. When the film thickness is small, the luminous efficiency is improved, but the breakdown is easy and the life of the organic electroluminescent element is shortened.

As the hole injecting and transporting material used for the hole injecting and transporting layer, known materials can be used, for example, N, N '.
-Diphenyl-N, N'-bis (3-methylphenyl)
-1,1'-diphenyl-4,4'-diamine, N, N '
-Diphenyl-N, N'-bis (4-methylphenyl)
-1,1'-diphenyl-4,4'-diamine, N, N '
-Diphenyl-N, N'-bis (1-naphthyl) -1,
1'-diphenyl-4,4'-diamine, N, N'-diphenyl-N, N'-bis (2-naphthyl) -1,1'-diphenyl-4,4'-diamine, N, N'- Tetra (4-
Methylphenyl) -1,1′-diphenyl-4,4′-diamine, N, N′-tetra (4-methylphenyl)-
1,1′-bis (3-methylphenyl) -4,4′-diamine, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-bis (3-methyl Phenyl)
-4,4′-diamine, N, N′-bis (N-carbazolyl) -1,1′-diphenyl-4,4′-diamine,
4 ', 4 "-tris (N-carbazolyl) triphenylamine, N, N', N" -triphenyl-N, N ', N "-tris (3-methylphenyl) -1,3,5-tri (4-
Aminophenyl) benzene, 4,4 ', 4 "-tris [N, N', N" -triphenyl-N, N ', N "-tris (3-methylphenyl)] triphenylamine and the like. These may be used as a mixture of two or more.

An organic light emitting layer (3) is formed on the hole injection transport layer (2). As the organic light emitting material used for the organic light emitting layer (3), known organic light emitting materials can be used, for example, epidolidine, 2,5-bis [5,7-di-t-pentyl-2-benzoxazolyl] thiophene. , 2, 2 '
-(1,4-phenylenedivinylene) bisbenzothiazole, 2,2 ′-(4,4′-biphenylene) bisbenzothiazole, 5-methyl-2- {2- [4- (5-methyl-2- Benzoxazolyl) phenyl] vinyl} benzoxazole, 2,5-bis (5-methyl-2-benzooxazolyl) thiophene, anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene, perinone, 1,4-diphenyl Butadiene, tetraphenylbutadiene, coumarin, acridine, stilbene, 2
-(4-biphenyl) -6-phenylbenzoxazole, aluminum trisoxine, magnesium bisoxin, bis (benzo-8-quinolinol) zinc, bis (2-methyl-8-quinolinolate) aluminum oxide, indium trisoxin, aluminum tris (5-methyloxin), lithium oxine, gallium trisoxin, calcium bis (5-chlorooxin), polyzinc-bis (8-hydroxy-5-quinolinolyl) methane, dilithium epindridione, zinc bisoxin, Examples thereof include 2-phthaloperinone and 1,2-naphthaloperinone.

In addition, general fluorescent dyes such as fluorescent coumarin dyes, fluorescent perylene dyes, fluorescent pyran dyes, fluorescent thiopyran dyes, fluorescent polymethine dyes, fluorescent methyanine dyes, fluorescent imidazole dyes, etc. Can be used. Among them, particularly preferred are chelated oxinoid compounds.

The organic light-emitting layer may have a single-layer structure of the above-described light-emitting substance, or may have a multi-layer structure in order to adjust characteristics such as light emission color and light emission intensity. Further, two or more kinds of light emitting substances may be mixed, or the light emitting layer may be doped with another generating substance.

When formed by a vapor deposition method, the thickness of the light emitting layer is
The thickness is usually 1 to 200 nm, preferably 1 to 100 nm, and when formed by a coating method, the thickness may be about 5 to 500 nm. As the film thickness is larger, the applied voltage for emitting light needs to be higher, and the luminous efficiency is poor, and the organic electroluminescent element is likely to be deteriorated. When the film thickness is small, the luminous efficiency is improved, but the breakdown is easy and the life of the organic electroluminescent element is shortened.

On the organic light emitting layer (3), a mixed film of an electron transporting material and a metal oxide or metal halide is formed as an electron injection layer (4).

Examples of the electron transporting material used for the electron injection layer (4) include nitro-substituted fluorenone derivatives, anthraquinodimethane derivatives, diphenoquinone derivatives, thiopyran dioxide derivatives, oxadiazole derivatives, triazole derivatives, thiadiazole derivatives, and coumarin. Derivatives, chelated oxinoid compounds and the like can be mentioned. Among these, chelated oxinoid compounds are particularly favorable from the viewpoint of heat resistance.

When the above-mentioned organic luminous substance has an electron transporting function, the organic luminous substance may be used as an electron transporting material for the electron injection layer. At this time, it is preferable that the organic light emitting material and the electron transporting material used for the electron injection layer configuration are the same. As such a material, a chelated oxinoid compound, a benzoxazole complex, a benzothiazole complex or the like can be used, and among them, a chelated oxinoid compound is preferable.

A metal oxide mixed with the electron injection layer and / or
Alternatively, a metal halide having a work function smaller than 4.2 eV is preferable, and magnesium oxide, magnesium fluoride, calcium fluoride, strontium fluoride, yttrium oxide, strontium oxide, yttrium fluoride, lithium fluoride, lithium fluoride, Lithium oxide, lithium oxide, magnesium bromide and the like are used. In particular, magnesium fluoride, calcium fluoride, lithium fluoride, and lithium oxide are preferable from the viewpoint of light-emitting characteristics and film-forming properties.

The mixing ratio of the electron transporting material and the metal oxide or metal halide (electron transporting material: metal oxide and / or metal halide) is 100: 1 to 1: 1:
2, preferably 20: 1 to 1: 1.

The electron injection layer (4) is formed by a vacuum evaporation method, and has a thickness of 0.1 to 20 nm. As the film thickness is larger, the applied voltage for emitting light needs to be higher, and the luminous efficiency is poor, and the organic electroluminescent element is likely to be deteriorated. In addition, when the film thickness is small, it is difficult to form a uniform film, and defects tend to occur. As a result, the luminous efficiency is deteriorated and the life of the organic electroluminescent element is shortened. The thickness of each of the above layers such as the electron injection layer can be measured using a quartz oscillation type thickness gauge.

The mixed film of the electron transporting material and the metal oxide or metal halide used for the electron injection layer may be formed by various known deposition methods such as a normal resistance heating method, a sputtering method, an EB evaporation method, an ion plating method, and an ionization evaporation method. It can be formed by a method.

FIGS. 2 to 4 show an organic electroluminescence device having another structure. In FIG. 2, (1) is an anode, on which a hole injection / transport layer (2), an organic light emitting layer (3), an electron transport layer (6), an electron injection layer (4), and a cathode (5). ) Are sequentially laminated, and the electron injection layer is a mixed film of an electron transport material and a metal oxide or a metal halide.

In FIG. 3, (1) is an anode, on which a hole injection layer (7) and a hole transport layer (8), an organic light emitting layer (3), an electron transport layer (6), an electron It has a configuration in which an injection layer (4) and a cathode (5) are sequentially laminated, and the electron injection layer is a mixed film of an electron transporting material and a metal oxide or a metal halide.

In FIG. 4, (1) is an anode, on which a hole injection layer (7), a hole transport layer (8), an organic light emitting layer (3), an electron injection layer (4) and a cathode are provided. (5) A configuration in which a sealing film (9) is sequentially laminated is adopted, and the electron injection layer is a mixed film of an electron transporting material and a metal oxide or a metal halide.

As shown in FIG. 2 or FIG. 3, when forming the electron transporting layer (6), it is formed to have a thickness of about 1 to 200 nm, preferably about 1 to 100 nm. As the electron transport material, the electron injection layer described earlier,
The same material as the electron transporting material can be used. When the electron transporting layer (6) is formed by utilizing the electron transporting function of the above-mentioned organic light emitting material as the electron transporting material, the same substance can be applied to the light emitting layer to form a doped light emitting layer. . For example, the electron transporting layer can be formed of aluminum trisoxine, and in this case, the light emitting layer is preferably formed of a layer obtained by doping aluminum trisoxin with a light emitting body. The electron transport layer, like the light emitting layer,
It can be formed by a conventionally known method such as an evaporation method or a coating method.

In the organic electroluminescent device shown in FIGS. 3 and 4, the hole injection / transport layer of FIG. 1 is functionally separated into two layers, a hole injection layer (7) and a hole transport layer (8). It has a configuration. The hole injection layer (7) is formed to a thickness of about 1 to 30 nm using a known material, for example, a phthalocyanine compound, a conductive polymer compound, an arylamine compound, or the like, by means of vapor deposition or the like. The hole transport layer (8)
Is formed using a known material, for example, a benzidine compound, an arylamine compound, a styryl compound, or the like, to a thickness of about 10 to 200 nm by means such as vapor deposition.

When the sealing layer (9) is formed as shown in FIG. 4, a thin film is formed by a vacuum evaporation method using a compound such as silicon oxide, zinc oxide, magnesium fluoride, and magnesium oxide. The thickness is about 5 to 1000 nm.

A pair of transparent electrodes, a cathode (5) and an anode (1), is connected to a suitable lead wire (10) such as a nichrome wire, a gold wire, a copper wire, a platinum wire, etc. The sense element emits light by applying an appropriate voltage (Vs) to both electrodes.

According to the present invention, the electron injecting property is improved by using a mixed film of an electron transporting material and a metal oxide or a metal halide for the electron injecting layer, and the thickness is 0.1 to 20 nm.
By reducing the thickness, the flow of electrons becomes extremely smooth by increasing the electric field strength, and the light emission starting voltage required for causing the organic electroluminescent device of the present invention to emit light may be low, and therefore, the voltage is stable. It is thought that light emission for a long time is possible.

The organic electroluminescent device of the present invention is applicable to various display devices, display devices, and the like.

Hereinafter, the present invention will be described by way of examples.
The organic electroluminescent device of the present invention achieves an improvement in luminous efficiency, luminous brightness and a long life. The following examples describe the luminescent substance, luminescent auxiliary material, charge transport material, The invention is not intended to be limited to agents, resins, electrode materials, and the like, and element manufacturing methods.

Example 1 N, N'-diphenyl-N, N'-bis (3-N-N-diphenyl-N, N'-bis
A thin film having a thickness of 60 nm was formed by vapor deposition of (methylphenyl) -1,1′-diphenyl-4,4′-diamine.

A thin film was formed thereon as an organic light emitting layer by vapor deposition of aluminum trisoxine to a thickness of 60 nm. A thin film of lithium fluoride and aluminum trisoxin was formed thereon as an electron injection layer by a co-evaporation method using resistance heating so as to have a volume ratio of 1:10 and a thickness of 5 nm.

Next, a thin film was formed to a thickness of 200 nm by vapor deposition of aluminum as a cathode. Thus, an organic electroluminescence device was manufactured.

EXAMPLE 2 N, N'-diphenyl-N, N'-bis (3-N-N-diphenyl-N, N'-bis
A thin film having a thickness of 60 nm was formed by vapor deposition of (methylphenyl) -1,1′-diphenyl-4,4′-diamine.

A thin film was formed thereon as an organic light emitting layer by vapor deposition of aluminum trisoxine to a thickness of 60 nm. A thin film of lithium fluoride and aluminum trisoxine was formed thereon as an electron injection layer by a co-evaporation method using resistance heating so as to have a volume ratio of 1:10 and a thickness of 2 nm.

Next, a thin film was formed to a thickness of 200 nm by vapor deposition of aluminum as a cathode. Thus, an organic electroluminescence device was manufactured.

Example 3 An N, N'-diphenyl-N, N'-bis (3-N-N-diphenyl-N, N'-bis
A thin film having a thickness of 60 nm was formed by vapor deposition of (methylphenyl) -1,1′-diphenyl-4,4′-diamine.

A thin film having a thickness of 60 nm was formed thereon as an organic light emitting layer by vapor deposition of aluminum trisoxine by vapor deposition. A thin film of lithium fluoride and aluminum trisoxine was formed thereon as an electron injection layer by a co-evaporation method using resistance heating so as to have a volume ratio of 1: 5 and a thickness of 1 nm.

Next, a thin film was formed to a thickness of 200 nm by vapor deposition of aluminum as a cathode. Thus, an organic electroluminescence device was manufactured.

Example 4 An N, N'-diphenyl-N, N'-bis (3-N-N-diphenyl-N, N'-bis
A thin film having a thickness of 60 nm was formed by vapor deposition of (methylphenyl) -1,1′-diphenyl-4,4′-diamine.

A thin film was formed thereon as an organic light emitting layer by vapor deposition of aluminum trisoxine to a thickness of 60 nm. A thin film of lithium fluoride and aluminum trisoxine was formed thereon as an electron injection layer by a co-evaporation method using resistance heating so as to have a thickness of 0.5 nm at a volume ratio of 1: 1.

Next, a thin film was formed to a thickness of 200 nm by vapor deposition of aluminum as a cathode. Thus, an organic electroluminescence device was manufactured.

Comparative Example 1 An organic electroluminescent device was produced in the same manner as in Example 1 except that the electron injection layer was not provided.

Example 5 N, N′-diphenyl-N, N′-bis (1) was formed as a hole injecting and transporting layer on a substrate of indium tin oxide coated glass.
-Naphthyl) -1,1'-diphenyl-4,4'-diamine was deposited to form a thin film having a thickness of 55 nm.

A thin film having a thickness of 10 nm was formed thereon as an organic light emitting layer by co-evaporation of aluminum trisoxin doped with 5% by weight of rubrene. Next, a thin film having a thickness of 45 nm was formed by vapor deposition of aluminum trisoxine as an electron transporting layer.

A thin film of magnesium fluoride and aluminum trisoxine was formed thereon as an electron injection layer at a volume ratio of 1: 5 to a thickness of 2 nm by a co-evaporation method using resistance heating.

Finally, a thin film was formed to a thickness of 200 nm by vapor deposition of aluminum as a cathode. Thus, an organic electroluminescence device was manufactured.

Comparative Example 2 An organic electroluminescent device was prepared in exactly the same manner as in Example 5, except that magnesium was formed to a thickness of 2 nm by resistance heating to form an electron injection layer. Was prepared.

COMPARATIVE EXAMPLE 3 In Example 5, a thin film was formed as an electron injecting layer so as to have a thickness of 2 nm with a volume ratio of 1: 5 by co-evaporation of magnesium and aluminum trisoxine by resistance heating. Next, aluminum is deposited as a cathode by vapor deposition.
A thin film was formed to a thickness of 00 nm. Thus, an organic electroluminescence device was manufactured.

Comparative Example 4 In Example 5, an oxadiazole compound (A) represented by the following formula was used as an electron injection layer by evaporation of 2 n by resistance heating.
A thin film was formed to have a thickness of m. Next, a thin film was formed to a thickness of 200 nm by vapor deposition of aluminum as a cathode. Thus, an organic electroluminescence device was manufactured.

[0064]

Embedded image

Example 6 An N, N′-diphenyl-N, N′-bis (1) was formed on a substrate of indium tin oxide coated glass as a hole injecting and transporting layer.
-Naphthyl) -1,1'-diphenyl-4,4'-diamine was deposited to form a thin film having a thickness of 55 nm. An organic light-emitting layer was formed by co-evaporation of aluminum trisoxine doped with 5% by weight of rubrene by co-evaporation.
A thin film was formed so as to have a thickness of 0 nm.

Next, a thin film having a thickness of 45 nm was formed by vapor deposition of aluminum trisoxine as an electron transporting layer. A thin film of yttrium fluoride and aluminum trisoxine was formed thereon as an electron injection layer by a co-evaporation method using resistance heating so as to have a thickness of 1 nm at a volume ratio of 1: 1.

Finally, a thin film was formed to a thickness of 200 nm by vapor deposition of aluminum as a cathode. Thus, an organic electroluminescence device was manufactured.

Example 7 On a substrate of indium tin oxide coated glass, 4,4 ', 4 "-tris [N, N', N" -triphenyl-N, N ', N "was formed as a hole injection layer. [Tris (3-methylphenyl)]] triphenylamine was deposited to form a thin film having a thickness of 15 nm.

Next, on the hole injection layer, N, N'-diphenyl-N, N'-bis (4-methylphenyl) -1,1'-bis (3-methylphenyl) was formed as a hole transport layer. )-
A thin film having a thickness of 45 nm was formed by vapor deposition of 4,4′-diamine.

A thin film having a thickness of 30 nm was formed thereon as an organic light emitting layer by co-evaporation of aluminum trisoxine doped with 5% by weight of rubrene. Next, a thin film having a thickness of 30 nm was formed by vapor deposition of aluminum trisoxine as an electron transporting layer.

A thin film of magnesium fluoride and aluminum trisoxine was formed thereon as an electron injection layer by a co-evaporation method using resistance heating so as to have a thickness of 2 nm at a volume ratio of 1: 3. Finally, a thin film was formed as a cathode by vapor deposition of Mg and Ag at an atomic ratio of 10: 1 to a thickness of 200 nm. Thus, an organic electroluminescence device was manufactured.

Example 8 N, N′-diphenyl-N, N′-bis (1) was formed as a hole injecting and transporting layer on a glass substrate coated with indium tin oxide.
-Naphthyl) -1,1'-diphenyl-4,4'-diamine was deposited to form a thin film having a thickness of 55 nm. An organic light-emitting layer was formed by co-evaporation of aluminum trisoxine doped with 5% by weight of rubrene by co-evaporation.
A thin film was formed so as to have a thickness of 0 nm.

Next, a thin film having a thickness of 45 nm was formed by vapor deposition of aluminum trisoxine as an electron transporting layer. A thin film of lithium bromide and aluminum trisoxine was formed thereon as an electron injection layer by a co-evaporation method using resistance heating so as to have a thickness of 2 nm at a volume ratio of 1: 1. Finally, a thin film was formed by vapor deposition of aluminum as a cathode so as to have a thickness of 200 nm. Thus, an organic electroluminescence device was manufactured.

Example 9 N, N′-diphenyl-N, N′-bis (1-naphthyl) -1,1′-diphenyl-4 was used as a hole injecting and transporting layer on a glass substrate coated with indium tin oxide. , 4'-
A thin film having a thickness of 55 nm was formed by diamine evaporation. An organic light emitting layer was formed thereon by co-evaporation of aluminum trisoxin doped with 5% by weight of rubrene to form a thin film having a thickness of 10 nm.

Next, a thin film having a thickness of 45 nm was formed by vapor deposition of aluminum trisoxine as an electron transporting layer. A thin film of lithium oxide and aluminum trisoxine was formed thereon as an electron injection layer by a co-evaporation method using resistance heating so as to have a thickness of 2 nm at a volume ratio of 1: 1. Finally, a thin film was formed by vapor deposition of aluminum as a cathode so as to have a thickness of 200 nm. Thus, an organic electroluminescence device was manufactured.

Example 10 N, N'-diphenyl-N, N'-bis (1-naphthyl) -1,1'-diphenyl-4 was used as a hole injecting and transporting layer on a glass substrate coated with indium tin oxide. , 4'-
A thin film having a thickness of 55 nm was formed by diamine evaporation. An organic light emitting layer was formed thereon by co-evaporation of aluminum trisoxin doped with 5% by weight of rubrene to form a thin film having a thickness of 10 nm.

Next, a thin film having a thickness of 45 nm was formed by vapor deposition of aluminum trisoxine as an electron transport layer. A thin film of yttrium oxide and aluminum trisoxine was formed thereon as an electron injection layer by a co-evaporation method using resistance heating so as to have a thickness of 1 nm at a volume ratio of 1: 3. Finally, a thin film was formed by vapor deposition of aluminum as a cathode so as to have a thickness of 200 nm.
Thus, an organic electroluminescence device was manufactured.

Comparative Example 5 An organic electroluminescent device was produced in the same manner as in Example 7 except that the electron injection layer was not provided.

Evaluation The organic electroluminescent devices obtained in Examples 1 to 10 and Comparative Examples 1 to 5 were applied with a glass electrode as an anode and a voltage (V) at which light emission was started when a DC voltage was gradually applied. ) and luminance (cd / cm ² when applying a DC voltage of 5V), to measure the emission luminance when applying a direct current voltage of 10V (cd / cm ^2). Further, the maintenance rate (%) of the initial output when operated at a current density of 5 mA / cm ² for 5 hours [output after 5 hours (mW / cm ² ) / initial output (mW / cm ² ) × 10
0]. Table 1 summarizes the measurement results.

[0080]

[Table 1]

As can be seen from Table 1, the organic electroluminescent device of the present invention started emitting light at a low potential, and exhibited good emission luminance. In addition, the organic electroluminescent device of the present invention was able to observe stable light emission having a small output and a long lifetime.

[0082]

According to the present invention, it is possible to obtain an organic electroluminescence device having a high light emission intensity, a low light emission starting voltage and excellent durability by including a specific compound in the electron injection layer of the organic electroluminescence device. it can.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of one configuration example of an organic electroluminescence element of the present invention.

FIG. 2 is a schematic cross-sectional view of one configuration example of the organic electroluminescence element of the present invention.

FIG. 3 is a schematic cross-sectional view of one configuration example of the organic electroluminescence element of the present invention.

FIG. 4 is a schematic cross-sectional view of one configuration example of the organic electroluminescence element of the present invention.

[Explanation of symbols]

1: anode, 2: hole injection / transport layer, 3: organic light emitting layer, 4:
Electron injection layer, 5: cathode, 6: electron transport layer, 7: hole injection layer, 8: hole transport layer, 9: sealing film, 10: lead wire

Claims (3)

[Claims] 1. An organic electroluminescence device provided with at least an anode, a light emitting layer, an electron injection layer and a cathode, wherein the electron injection layer is a mixed film of an electron transport material and a metal oxide or a metal halide. Organic electroluminescent element. 2. The electron injection layer having a thickness of 0.1 to 20 nm.
The organic electroluminescent device according to claim 1, wherein: 3. The organic electroluminescent device according to claim 1, wherein the work function of the metal oxide or metal halide mixed in the electron injection layer is 4.2 eV or less.