JP2002231455A - Organic electroluminescence element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve light emitting luminance, and lengthen the service life in an organic EL element. SOLUTION: This organic electroluminescence element has a structure of successively laminating an anode layer 10, a light emitting area 12, an electron injection area 14, and a cathode layer 16. A glass transition point of the electron injection area is set to a value of 100 deg.C or more. The electron injection are includes an aromatic compound including no nitrogen atom and reducing dopant expressed by M+Ar- (here, M represents alkaline metal, and Ar represents a nonsubstituted or substituted aromatic ring compound having the carbon number of 10 to 40). Electron affinity of the electron injection area is set to a range of 1.8 to 3.6 eV.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device (hereinafter, also referred to as "organic EL device"). More specifically, the present invention relates to an organic EL device suitable for use in consumer and industrial display devices (displays) or light sources of printer heads.

[0002]

2. Description of the Related Art An example of a conventional organic EL device is disclosed in Document 1:
It is disclosed in "JP-A-4-297076".
As shown in FIG. 10, the organic EL element 60 disclosed in Document 1 has three organic films 52, 54 and 56 interposed between a cathode layer 58 and an anode layer 50 as a transparent electrode. It constitutes a film stack. Of the three organic films, the first organic film 52 in contact with the cathode layer 58 is doped with a donor impurity, while the second organic film 54 in contact with the anode layer 50 has an acceptor impurity. Is doped. As the acceptor impurities, a CN-substituted compound and a quinone compound (for example, chloranil) are used. The third organic film sandwiched between the first organic film 52 and the second organic film serves as the light emitting layer 56. The light emitting layer 56 includes first and second organic films 52 and 54.
Confine the carrier. Therefore, the organic EL element 60 can obtain high light emission luminance (light emission efficiency) at a low drive voltage.

Another example of the conventional organic EL device is as follows.
Reference 2: "Digest of Technical"
Papers (Digest of Technical Papers) SID '97, p. 775, 1997 ". In the organic EL device disclosed in Document 2, the electron transport layer is made of a material obtained by adding Li to an 8-hydroxyquinoline Al complex (Alq complex).

[0004]

[0005] However, Document 1
In the organic EL device disclosed in the above, the CN-substituted compound or quinone compound used as an acceptor impurity has excellent electron-transporting properties, but has strong acceptor properties,
The electron affinity is a high value of 3.7 eV or more. Therefore, these acceptor impurities tend to react with a compound constituting the light emitting region to easily form a charge transfer complex or an exciplex. For this reason, there have been problems that the emission luminance of the organic EL element is reduced and the life is short.

In the organic EL device disclosed in Document 1, the difference between the electron affinity of the first organic layer doped with the donor impurity and the electron affinity of the light emitting region is 0.5 e.
The value is as large as V or more. For this reason, the light emitting area and the first
Is a blocking junction, and electron injection from the first organic layer to the light-emitting region is likely to be defective. As a result, the luminous efficiency of the organic EL element is further reduced.

On the other hand, also in the organic EL device disclosed in Document 2, the Alq complex contains a nitrogen atom,
Although the electron transport layer composed of the lq complex and the Li compound has excellent electron transport properties, it tends to easily form a charge transfer complex or exciplex and has a high driving voltage. Therefore, similarly to the organic EL element disclosed in Document 1, there is a problem that the emission luminance of the organic EL element is easily reduced and the life is short.

Therefore, the inventors of the present invention diligently studied the above problem, and found that an aromatic ring compound containing no nitrogen atom was used in the electron injection region, or an aromatic ring compound containing a nitrogen atom was used. It has been found that, even when used, by using a specific reducing dopant in combination, the driving voltage of the organic EL element can be reduced, the emission luminance can be improved, and the life can be prolonged. That is, an object of the present invention is to provide an organic EL element having a low driving voltage, a high emission luminance, and a long life.

[0008]

In order to achieve the above object, an organic EL device (first invention) of the present invention has a structure in which at least an anode layer, a light emitting region, an electron injection region, and a cathode layer are sequentially laminated. Having a glass transition point of 100 in the electron injection region.
° C or higher, and the electron injection region contains an aromatic compound containing no nitrogen atom and a reducing dopant represented by the following formula (1). It is in the range of 1.8 to 3.6 eV. M ⁺ Ar ⁻ (1) (where, M represents an alkali metal, and Ar represents an unsubstituted or substituted aromatic ring compound having 10 to 40 carbon atoms.)

As described above, by using an aromatic ring compound containing no nitrogen atom in the electron injection region, excellent electron injection properties can be obtained, and at the same time, the reaction with constituent materials of the adjacent light emitting region is suppressed. can do. That is,
The aromatic ring compound not containing a nitrogen atom is composed of an aromatic ring compound composed of carbon and hydrogen or an aromatic ring compound composed of carbon, hydrogen and oxygen, and is composed of a nitrogen-containing aromatic ring or an electroattracting group (for example, -CN group, -NO2 group,
It does not contain nitrogen-containing groups such as amide groups and imide groups. Therefore, generation of a charge transfer complex or exciplex having low luminous efficiency at the interface between the electron injection region and the light emitting region can be efficiently suppressed.

Along with an aromatic compound containing no nitrogen atom in the electron injection region, M ⁺ Ar ⁻ (where M represents an alkali metal, and Ar represents an unsubstituted or substituted aromatic ring compound having 10 to 40 carbon atoms). ), The aromatic ring of the aromatic compound not containing a nitrogen atom can be efficiently reduced to an anionic state. Therefore, it is possible to more effectively prevent the generation of a charge transfer complex or exciplex having low luminous efficiency, and to improve the luminous luminance and extend the life of the organic EL element.

Furthermore, by limiting the electron affinity in the electron injection region in this way, excellent electron injection properties can be obtained, and a charge transfer complex or exciplex is generated at the interface between the electron injection region and the light emitting region. In addition, the occurrence of blocking junction between the electron injection region and the light emitting region can be suppressed. Therefore, the organic E
It is possible to further improve the emission luminance and extend the life of the L element.

The glass transition point of the electron injection region is set to 100
℃ or more, the heat-resistant temperature of the organic EL element,
For example, the temperature can be set to 85 ° C. or higher. Therefore, the tendency of the electron injection region to be destroyed in a short time due to Joule heat due to current injection from the current injection layer to the light emission region during light emission is reduced, and the life of the organic EL element can be further extended.

In constituting the organic EL device of the first invention, the reducing dopant is selected from the group consisting of anthracene, naphthalene, diphenylanthracene, terphenyl, quarterphenyl, kinkphenyl and sexiphenyl. It preferably contains a group formed from at least one aromatic ring.

In constituting the organic EL device of the first invention, the aromatic ring compound comprises anthracene, fluorene, perylene, pyrene, phenanthone, chrysene, tetracene, rubrene, terphenylene, quarterphenylene, sexiphenylene and triphenylene. It preferably contains a group formed from at least one aromatic ring selected from the group consisting of

In constituting the organic EL device of the first invention, the work function of the reducing dopant is 3.0 eV.
It is preferable to set the following. As described above, by using a reducing dopant having a work function of 3.0 eV or less, the reducing ability can be sufficiently exhibited, and the driving voltage can be reduced, the emission luminance can be improved, and the life can be extended.

In configuring the organic EL device of the first invention, the energy gap of the electron injection region is set to 2.
It is preferable to be 7 eV or more. As described above, by increasing the energy gap of the electron injection region, it is possible to effectively prevent holes from moving to the electron injection region. Therefore, it is possible to prevent the electron injection region itself from emitting light.

Further, in constituting the organic EL device of the first invention, it is preferable that the addition ratio between the aromatic compound and the reducing dopant is in the range of 1:20 to 20: 1 (molar ratio). If the addition ratio of the aromatic compound to the reducing dopant is out of the range of 1:20 to 20: 1 (molar ratio), the emission luminance of the organic EL device tends to decrease and the life tends to be shortened.

In constituting the organic EL device of the first invention, it is preferable that the light-emitting region and the electron injection region contain the same kind of aromatic compound containing no nitrogen atom. By containing the same kind of aromatic compound in both regions, excellent adhesion can be obtained, electrons can smoothly move from the electron injection region to the light emission region, and the mechanical strength can be improved. it can.

Further, in forming the organic EL device of the first invention, or in forming the organic EL device of the second invention described below, the space between the cathode layer and the electron injection region and the space between the anode layer and the light-emitting region are formed. It is preferable to provide an interface layer during or any one of them. By providing the interface layer in this manner, the values of the emission luminance and the half-life can be significantly improved.

Further, another organic EL device of the present invention (second invention) has a structure in which at least an anode layer, a light emitting region, an electron injection region and a cathode layer are sequentially laminated, and the electron injection region An electron transporting compound, and M ⁺ Ar ⁻ having a work function of 2.9 eV or less (where M represents an alkali metal and Ar represents an unsubstituted or substituted aromatic ring compound having 10 to 40 carbon atoms). It contains a reducing dopant, and has an electron affinity of 1.8 to 3.6 eV in the electron injection region.

As described above, in the electron injection region, the work function is 2.
By containing a reducing dopant of 9 eV or less,
Even when the electron transporting compound is oxidized, it can be efficiently reduced to an anion state. Therefore, the generation of the charge transfer complex or the exciplex can be effectively prevented, and the driving voltage, the emission luminance, and the life of the organic EL element can be reduced. That is, in the second invention, unlike the first invention, a nitrogen-containing group (nitrogen atom) such as a nitrogen-containing aromatic ring or an electron-withdrawing group is added to the electron-transporting compound because the reducing ability of the reducing dopant is high. Even if it is included, there is an advantage that it can be suppressed from reacting with the constituent material in the light emitting region.

Further, by limiting the electron affinity in the electron injection region in this way, it is possible to suppress the generation of a charge transfer complex or exciplex at the interface between the electron injection region and the light emitting region, and to reduce the electron injection region. The occurrence of blocking junction with the light emitting region can also be suppressed. Therefore, it is possible to further improve the emission luminance and extend the life of the organic EL element.

Further, in constituting the organic EL device of the second invention, the reducing dopant is selected from the group consisting of anthracene, naphthalene, diphenylanthracene, terphenyl, quarterphenyl, kinkphenyl and sexiphenyl. It is preferable to contain a group formed from at least one aromatic ring.

In constituting the organic EL device of the second invention, the electron transporting compound preferably contains a nitrogen-containing heterocyclic compound. This is because the nitrogen-containing heterocyclic compound is excellent in electron transportability and further improves electron injectability.

In constituting the organic EL device of the second invention, the nitrogen-containing heterocyclic compound is selected from the group consisting of a nitrogen-containing complex, a quinoxaline derivative, a quinoline derivative, an oxadiazole derivative, a thiadiazole derivative and a triazole derivative. Preferably, at least one compound is used.

In constituting the organic EL device of the second invention, the addition ratio of the electron transporting compound and the reducing dopant is preferably in the range of 1:20 to 20: 1 (molar ratio). When the addition ratio of the electron transporting compound and the reducing dopant is out of the range of 1:20 to 20: 1 (molar ratio), the emission luminance of the organic EL element tends to decrease and the life tends to be shortened.

In constituting the organic EL device of the second invention, the glass transition point of the electron injection region is preferably set to 100 ° C. or higher. By setting the glass transition point of the electron injection region to 100 ° C. or higher as described above, the heat resistance temperature of the organic EL element can be increased, and the life of the organic EL element can be extended.

In constituting the organic EL device of the second invention, it is preferable to use the same type of electron transporting compound in the light emitting region and the electron injection region. By containing the same type of electron transporting compound in both regions, excellent adhesion can be obtained, electrons can smoothly move from the electron injection region to the light emitting region, and the mechanical strength is improved. Can be.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the drawings to be referred to show the size of each component so that the present invention can be understood,
It merely shows the shape and arrangement.
Therefore, the present invention is not limited only to the illustrated example. In the drawings, hatching representing a cross section may be omitted.

<First Embodiment> First, a first embodiment of the organic EL device of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of an organic EL device 100 having a structure in which an anode layer 10, a light emitting region 12, an electron injection region 14, and a cathode layer 16 are sequentially laminated on a substrate (not shown). It represents that it is. Hereinafter, the electron injection region 14 which is a characteristic portion of the first embodiment will be mainly described. Therefore, other components, for example,
The configuration and manufacturing method of the anode layer 10, the light-emitting region 12, the cathode layer 16, and the like shall be briefly described, and the portions not mentioned shall adopt the generally known configuration and manufacturing method in the field of organic EL devices. Can be.

(1) Electron Injection Area (Aromatic Compound) The electron injection area in the first embodiment is an aromatic ring compound containing no nitrogen atom, that is, an aromatic ring compound composed of carbon (C) and hydrogen (H). It contains a ring compound or an aromatic ring compound composed of carbon (C), hydrogen (H) and oxygen (O). The aromatic ring compound composed of carbon and hydrogen and the aromatic ring compound composed of carbon, hydrogen and oxygen may be used alone or in combination.

Here, preferred aromatic ring compounds containing no nitrogen atom include, for example, anthracene, fluorene, perylene, pyrene, phenanthrene, chrysene, tetracene, rubrene, terphenylene, quarterphenylene, sexiphenylene, triphenylene, picene,
Those containing a group formed from at least one aromatic ring selected from the group consisting of coronel, diphenylanthracene, benz [a] anthracene and binaphthalene.

Further, the aromatic compound containing no nitrogen atom more preferably contains an aromatic ring in which three or more rings are condensed, such as anthracene, among these aromatic compounds. By having an aromatic ring in which three or more rings are condensed as described above, electron mobility can be increased, and emission luminance of the organic EL element can be improved and high-speed response can be improved.

Further, the aromatic compound containing no nitrogen atom more preferably contains a group formed from a styryl-substituted aromatic ring, a distyr-substituted aromatic ring or a tristyryl-substituted aromatic ring. By having such a styryl-substituted aromatic ring, an organic EL
The light emission luminance and life of the element can be further improved.

Here, as the aromatic ring compound having a styryl-substituted group, for example, a compound represented by the following structural formula (1) is preferably used.

[0036]

Embedded image

In the above formula (1), n represents a condensation number.
And n = 1 to 4. R is a hydrogen atom or a charcoal
An aromatic group (aromatic ring) having a prime number of 6 to 40. Also,
Ar ¹Is an aromatic group having 6 to 40 carbon atoms, and Ar is²
And Ar³Has a hydrogen atom or a carbon number of 6 to
40 aromatic groups. And Ar¹, Ar²and
Ar³At least one is an aromatic group. further,
This aromatic group has three or more rings fused or linked.
Is desirable.

As the aromatic ring compound containing a distil-substituted group, for example, a compound represented by the following structural formula (2) is preferably used. Ar ⁴ -L-Ar ⁵ (2) In the above formula (2), L is an arylene group having 6 to 30 carbon atoms. As the arylene group, for example,
Phenylene, biphenylene, naphthylene, and anthracendil are preferred, and the structure of the arylene group is preferably a single crystal. Further, as Ar ⁴ and Ar ⁵ , for example, diphenylanthracene,
Diphenylpyrene is preferred.

It is preferable that the compound represented by the above formula (1) or (2) is further substituted with a substituent.
Examples of such a substituent include those having 1 to 30 carbon atoms.
An alkyl group, an alkyloxy group having 1 to 30 carbon atoms,
An arylalkyl group having 6 to 30 carbon atoms, a diarylamino group, an N-alkylcarbazolyl group or an N-phenylcarbazolyl group is desirable. By substitution with these substituents, generation of a complex having low luminous efficiency can be efficiently suppressed.

(Reducing Dopant) The electron injection region in the first embodiment is characterized in that it contains a reducing dopant. Here, the reducing dopant is defined as a substance that can reduce an aromatic compound when it is oxidized. Therefore, the reducing dopant is not particularly limited as long as it has a certain reducing property, but specifically, an alkali metal, an alkaline earth metal, a rare earth metal, an oxide of an alkali metal, and an alkali metal. It is preferably at least one substance selected from the group consisting of halides, alkaline earth metal oxides, alkaline earth metal halides, rare earth metal oxides, and rare earth metal halides.

Preferred alkali metals include, for example,
Li (lithium, work function: 2.93 eV), Na (sodium, work function: 2.36 eV), K (potassium,
Work function: 2.3 eV), Rb (rubidium, work function: 2.16 eV) and Cs (cesium, work function:
1.95 eV). The values of the work functions in parentheses are described in the Chemical Handbook (Basic Edition II, P493, edited by The Chemical Society of Japan), and the same applies hereinafter. Also,
Preferred alkaline earth metals include, for example, Ca (calcium, work function: 2.9 eV), Mg (magnesium, work function: 3.66 eV), Ba (barium, work function: 2.52 eV), and Sr (strontium) ,
Work function: 2.0 to 2.5 eV). In addition,
The value of the work function of strontium is based on the Physics of Semiconductor device (NY Wilo 19
69, p. 366). Preferred rare earth metals include, for example, Yb (ytterbium, work function: 2.6 eV), Eu (eurobium,
Work function: 2.5 eV), Gd (gadnium, work function: 3.1 eV) and En (erbium, work function:
2.5 eV).

Preferred alkali metal oxides include, for example, Li ₂ O, LiO and NaO. Preferred alkaline earth metal oxides include:
For example, CaO, BaO, SrO, BeO and MgO
Is raised.

Preferred alkali metal halides include, for example, fluorides such as LiF, NaF and KF, as well as LiCl, KCl and NaCl.
Is mentioned. Preferred alkaline earth metal halides include, for example, CaF ₂ , BaF ₂ , Sr
Fluorides such as F _2, MgF ₂ and BeF _2, and halides other than fluorides.

Further, as a preferable reducing dopant,
An aromatic compound coordinated with an alkali metal is also included. The aromatic compound to which the alkali metal is coordinated is represented by, for example, the following structural formula (3). M ⁺ Ar ⁻ (3) where M in the above formula (3) represents an alkali metal. Ar ⁻ is an aromatic ring compound having 10 to 40 carbon atoms. Examples of the aromatic ring compound represented by the formula (3) include anthracene, naphthalene, diphenylanthracene, terphenyl, quarterphenyl, kinkphenyl, sexiphenyl and derivatives thereof.

Next, the amount of the reducing dopant added in the electron injection region will be described. The amount of the reducing dopant to be added is preferably in the range of 0.01 to 50% by weight when the entire material constituting the electron injection region is 100% by weight. When the amount of the reducing dopant added is less than 0.01% by weight, the light emission luminance of the organic EL element tends to decrease and the life tends to be shortened. On the other hand, when the addition amount of the reducing dopant exceeds 50% by weight, on the contrary, the emission luminance tends to decrease and the life tends to be shortened. Therefore,
From the viewpoint that the balance of emission luminance and life becomes better,
More preferably, the amount of the reducing dopant added is in the range of 0.2 to 20% by weight.

As for the amount of the reducing dopant to be added, it is preferable that the ratio of the aromatic ring compound to the reducing dopant is in the range of 1:20 to 20: 1 (molar ratio). When the addition ratio of the electron transporting compound and the reducing dopant is out of these ranges, the emission luminance of the organic EL device tends to decrease and the life tends to be shortened. Therefore, the addition ratio of the aromatic ring compound to the reducing dopant is more preferably in the range of 1:10 to 10: 1 (molar ratio), and still more preferably in the range of 1: 5 to 5: 1. .

(Electron Affinity) The electron affinity of the electron injection region in the first embodiment is preferably in the range of 1.8 to 3.6 eV. When the value of the electron affinity is less than 1.8 eV, the electron injecting property tends to decrease, which tends to increase the driving voltage and decrease the luminous efficiency. On the other hand, when the value of the electron affinity exceeds 3.6 eV, the light emission Complexes with low efficiency can be easily generated, and generation of blocking junction can be efficiently suppressed. Therefore, the electron affinity of the electron injection region is more preferably in the range of 1.9 to 3.0 eV, and even more preferably in the range of 2.0 to 2.5 eV.

It is preferable that the difference in electron affinity between the electron injection region and the light emission region be 1.2 eV or less.
More preferably, the value is 5 eV or less. The smaller the difference in electron affinity, the easier the electron injection from the electron injection region to the light emission region, and a high-speed response organic EL device can be obtained.

(Glass Transition Point) The glass transition point (glass transition temperature) of the electron injection region in the first embodiment is expressed as follows:
The temperature is preferably 100 ° C. or higher, more preferably 1 ° C.
0.5 to 200 ° C. By limiting the glass transition point in the electron injection region in this way, the organic E
The heat resistance temperature of the L element 100 can be easily set to 85 ° C. or higher. Therefore, at the time of light emission, even if a current is injected from the current injection layer into the light emitting region and Joule heat is generated,
The tendency of the electron injection region to be destroyed in a short time is reduced, and the life of the organic EL element can be extended. The glass transition point of the electron injection region is determined by heating the components constituting the electron injection region using a differential scanning calorimeter (DSC) in a nitrogen gas stream at a rate of temperature increase of 10 ° C./min. From the obtained specific heat change curve, it can be determined as a specific heat change point. This point is the same in other embodiments and examples.

(Energy Gap) The energy gap (band gap energy) of the electron injection region in the first embodiment is preferably set to 2.7 eV or more, more preferably 3.0 eV or more. As described above, if the value of the energy gap is set to a predetermined value or more, for example, 2.7 eV or more, holes are less likely to move beyond the light emitting region to the electron injection region. Therefore, the efficiency of recombination of holes and electrons is improved, the light emission luminance of the organic EL element is increased, and light emission in the electron injection region itself can be avoided.

(Structure of Electron Injection Area) The structure of the electron injection area in the first embodiment is not particularly limited, and is not limited to a single-layer structure. For example, it may have a two-layer structure or a three-layer structure. May be. Also, the thickness of the electron injection region is not particularly limited, but is preferably in the range of, for example, 0.1 nm to 1 μm.
More preferably, the range is 0 nm.

(Method of Forming Electron Injection Area) Next, a method of forming the electron injection area will be described. The method for forming the electron injection region is not particularly limited as long as it can be formed as a thin film layer having a uniform thickness. For example, a known method such as an evaporation method, a spin coating method, a casting method, and an LB method may be used. Can be applied. Note that it is preferable that the aromatic ring compound containing no nitrogen atom and the reducing dopant are co-evaporated. This evaporation method will be described in detail in the sixth embodiment.

It is preferable that the method for forming the electron injection region and the method for forming the light emitting region are the same. For example, when the light emitting region is formed by a vapor deposition method, the electron injection region is preferably formed by a vapor deposition method. When the film is formed by the same method as described above, the electron injection region and the light emitting region can be continuously formed, which is advantageous in simplifying the equipment and shortening the settlement time. Further, since the chances of oxidizing the electron injection region and the light emitting region are reduced, the light emission luminance of the organic EL element can be improved.

(2) Light-Emitting Region (Constituent Material) The organic light-emitting material used as a constituent material of the light-emitting region preferably has the following three functions. (A) Charge injection function: a function of injecting holes from an anode or a hole injection layer during application of an electric field, while injecting electrons from a cathode layer or an electron injection region. (B) Transport function: a function of moving injected holes and electrons by the force of an electric field. (C) Light-emitting function: a function of providing a field for recombination of electrons and holes and connecting them to light emission. However, it is not always necessary to have all of the above functions (a) to (c). For example, the organic light-emitting material may have a hole injection / transport property larger than an electron injection / transport property. Are suitable. One of the objects of the present invention is to promote the transfer of electrons to a light emitting region and reduce the voltage.

Examples of such organic light emitting materials include benzothiazole-based, benzimidazole-based, benzoxazole-based fluorescent whitening agents, styrylbenzene-based compounds, and the like.
A metal complex having an 8-quinolinol derivative as a ligand is preferably used. Further, an organic light-emitting material having a distyrylarylene skeleton such as 4,4′-bis (2,2-diphenylvinyl) biphenyl) is used as a host, and the host is provided with a strong fluorescent dye ranging from blue to red, such as a coumarin-based or host. Those doped with the same fluorescent dye as described above are also suitable as organic light emitting materials.

In addition, excellent adhesion can be obtained, and electrons can be smoothly moved from the electron injection region to the light emission region.
From the viewpoint that the mechanical strength can be improved, the constituent material of the light emitting region and the constituent material of the electron injection region are partially matched, and the same type of aromatic ring compound containing no nitrogen atom is used in both regions. Is preferred. In the light emitting region and the electron injection region, the same kind of aromatic ring compound is preferably 50% by weight or more, and more preferably 60% by weight or more.

(Forming Method) Next, a method of forming a light emitting area will be described. For example, evaporation method, spin coating method,
Known methods such as a casting method and an LB method can be applied. In addition, as described above, the electron injection region and the light emitting region are preferably formed by the same method. For example, when the electron injection region is formed by a vapor deposition method, the light emitting region is also formed by the vapor deposition method. Is preferred.

The light emitting region is a thin film formed by depositing a material compound in a gaseous state or a film formed by solidifying a material compound in a solution state or a liquid state.
It is preferable to use a molecular deposition film. Usually, this molecular deposition film can be distinguished from a thin film (molecule accumulation film) formed by the LB method by a difference in an aggregated structure or a higher-order structure and a functional difference caused by the difference. Furthermore, a light emitting region can also be formed by dissolving a binder such as a resin and an organic light emitting material in a solvent to form a solution, and then thinning the solution by spin coating or the like.

(Thickness of Light Emitting Region) The thickness of the light emitting region formed in this manner is not particularly limited and can be appropriately selected depending on the situation, but is preferably in the range of 5 nm to 5 μm. preferable. When the film thickness in the light emitting region is less than 5 nm, the light emission luminance tends to decrease. On the other hand, when the film thickness in the light emitting region exceeds 5 μm, the value of the applied voltage tends to increase. Therefore, the thickness of the light emitting region is set to 10 nm to 3 μm.
Is more preferable, and the range is more preferably 20 nm to 1 μm.

(3) Electrode (Anode Layer) As the anode layer, it is preferable to use a metal, an alloy, an electrically conductive compound having a large work function (for example, 4.0 eV or more), or a mixture thereof. Specifically, indium tin oxide (ITO), indium copper, tin, zinc oxide, gold, platinum, palladium and the like can be used alone or in combination of two or more. The thickness of the anode layer is not particularly limited, but is preferably in the range of 10 to 1000 nm, and more preferably in the range of 10 to 200 nm.
Further, the anode layer is preferably substantially transparent, more specifically, has a light transmittance of 10% or more so that light emitted from the light emitting region can be effectively extracted to the outside.

(Cathode Layer) On the other hand, for the cathode layer, it is preferable to use a metal, an alloy, an electrically conductive compound or a mixture thereof having a small work function (for example, less than 4.0 eV). Specifically, one kind of magnesium, aluminum, indium, lithium, sodium, silver, etc. alone,
Alternatively, two or more kinds can be used in combination.
The thickness of the cathode layer is not particularly limited, either.
It is preferably in the range of 0 to 1000 nm,
More preferably, it is in the range of 00 nm.

(4) Others Although not shown in FIG. 1, it is preferable to provide a sealing layer for preventing moisture and oxygen from entering the organic EL element so as to cover the entire element. Preferred materials for the sealing layer include copolymers obtained by copolymerizing a monomer mixture containing tetrafluoroethylene and at least one comonomer; a fluorinated copolymer having a cyclic structure in the copolymer main chain; Polyethylene, polypropylene, polymethyl methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene,
Polydichlorodifluoroethylene or a copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene; a water-absorbing substance having an absorption of 1% or more; a moisture-proof substance having a water absorption of 0.1% or less; In, Sn, Pb, Au, Cu , Ag,
Metals such as Al, Ti, Ni; MgO, SiO, Si
O ₂ , GeO, NiO, CaO, BaO, Fe ₂ O, Y
Metal oxides such as ₂ O ₂ and TiO ₂ ; MgF ₂ , LiF,
Metal fluorides such as AlF ₃ and CaF ₂ ; liquid fluorinated carbon such as perfluoroalkane, perfluoroamine and perfluoropolyether; and a composition in which an adsorbent for adsorbing moisture and oxygen is dispersed in the liquid fluorinated carbon. Objects and the like.

In forming the sealing layer, a vacuum evaporation method, a spin coating method, a sputtering method, a casting method, an MBE (molecular beam epitaxy) method, a cluster ion beam evaporation method, an ion plating method, a plasma polymerization method ( RF excitation super-ion plating method), reactive sputtering method, plasma CVD method, laser CVD
Method, thermal CVD method, gas source CVD method, or the like can be appropriately employed.

<Second Embodiment> Next, the organic E of the present invention
A second embodiment in the L element will be described. In the second embodiment, similarly to the first embodiment, as shown in FIG. 1, an anode layer 10, a light emitting region 12, an electron injection region 14, and a cathode layer 16 are provided on a substrate (not shown). ). The second embodiment is different from the first embodiment in that the electron injection region 14 is composed of an electron transporting compound and a reducing dopant having a work function of 2.9 eV or less. I have. Therefore,
In the following description, the electron transporting compound and the work function are 2.
The description will focus on the reducing dopant of 9 eV or less, and other configurations may be the same as those in the first embodiment and a configuration generally known in the field of the organic EL device.

(Electron-Transporting Compound) In the electron-injecting region in the second embodiment, the same electron-transporting compound as in the first embodiment may contain an aromatic ring compound containing no nitrogen atom. It is also preferable to include an organic compound containing a nitrogen-containing heterocyclic compound (hereinafter, sometimes simply referred to as a nitrogen-containing heterocyclic compound). That is, unlike the first embodiment, the second embodiment has a function of transmitting electrons injected from the cathode to the light emitting region, in particular, because a highly reducing reducing dopant is used. Compounds can be widely used, and even if a nitrogen-containing heterocyclic compound is used as the electron-transporting compound, reaction with a material in a light-emitting region can be efficiently suppressed. Therefore, in the electron injection region, the generation of the charge transfer complex or the exciplex can be effectively prevented, and the emission luminance and the life of the organic EL element can be improved.

Here, the nitrogen-containing heterocyclic compound used in the electron injection region is defined as a compound having a heterocyclic ring having a nitrogen atom, and specific examples include a nitrogen-containing complex and a nitrogen-containing ring compound. A nitrogen-containing complex or a nitrogen-containing ring compound has a large electron affinity of 2.7 eV or more and a charge mobility of 1 eV.
This is because it is as fast as 0 ⁻⁶ cm ² / V · S or more. Among them, as a preferable nitrogen-containing complex, a metal complex having an 8-quinolinol derivative as a ligand, for example, a tris (8-quinolinol) Al complex represented by the following formula (4) and a tris (5,7-dichloro- 8-quinolinol) Al complex, tris (5,7-dibromo-8-quinolinol) Al complex, tris (2-methyl-8-quinolinol) Al complex, tris (5-methyl-8-quinolinol) Al complex, tris ( 8-quinolinol) Zn complex, tris (8
-Quinolinol) In complex, tris (8-quinolinol) Mg complex, tris (8-quinolinol) Cu complex,
Tris (8-quinolinol) Ca complex, Tris (8-quinolinol) Sn complex, Tris (8-quinolinol) G
a single complex or a combination of two or more such as a complex and tris (8-quinolinol) Pb complex.

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Among the nitrogen-containing complexes, preferable phthalocyanine derivatives include, for example, metal-free phthalocyanine, Cu phthalocyanine, Li phthalocyanine, Mg
One kind of phthalocyanine, Pb phthalocyanine, Ti phthalocyanine, Ga phthalocyanine, CuO phthalocyanine and the like may be used alone or in combination of two or more kinds.

Preferred nitrogen-containing ring compounds include:
At least one compound selected from the group consisting of oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, quinoxaline derivatives and quinoline derivatives can be mentioned. Among these, representative examples of preferred oxadiazole derivatives are shown in the following formulas (5) and (6), representative examples of preferred thiadiazole derivatives are shown in the following formula (7), and representative examples of preferred triazole derivatives are shown below. Formula (8) shows a typical example of a quinoxaline derivative in the following formula (9), and a typical example of a quinoline derivative in a formula (10) below.

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[0071]

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[0072]

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[0073]

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[0074]

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[0075]

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Further, heterocyclic tetracarboxylic anhydrides such as anthrone derivatives, fluorenylimethane derivatives, carbodiimides, and naphthalene perylene;
It is also preferable to use an electron-transporting compound described as a light-emitting layer material in JP-A-9-194393.

(Reducing dopant having a work function of 2.9 eV or less) The electron injection region in the second embodiment contains a reducing dopant having a work function of 2.9 eV or less. Here, a reducing dopant having a work function of 2.9 eV or less is defined as a substance having a work function of 2.9 eV or less and capable of reducing a certain amount even when the electron transporting compound is oxidized. You. Therefore, the work function is 2.9.
If it is not more than eV, alkali metals, alkaline earth metals, rare earth metals, oxides of alkali metals, halides of alkali metals, oxides of alkaline earth metals are the reducing dopants exemplified in the first embodiment. And at least one substance selected from the group consisting of alkaline earth metal halides, rare earth metal oxides, and rare earth metal halides.

More specifically, the work function is 2.9e
V is preferably not more than V.
(Work function: 2.36 eV), K (work function: 2.28)
eV), Rb (work function: 2.16 eV) and Cs
(Work function: 1.95 eV) at least one alkali metal selected from the group consisting of Ca and work function:
2.9 eV), Sr (work function: 2.0 to 2.5 e)
V), and at least one alkaline earth metal selected from the group consisting of Ba (work function: 2.52 eV).

Among these, a more preferable reducing dopant is at least one alkali metal selected from the group consisting of K, Rb and Cs, more preferably Rb or Cs, and most preferably Cs It is. These alkali metals have particularly high reducing ability,
By adding a relatively small amount to the electron injection region, the luminance of the organic EL device can be improved and the life thereof can be prolonged.

Further, as the reducing dopant having a work function of 2.9 eV or less, a combination of two or more of these alkali metals is also preferable. In particular, a combination containing Cs,
For example, Cs and Na, Cs and K, Cs and Rb or C
It is preferably a combination of s, Na and K. C
By including s in combination, the reducing ability can be efficiently exhibited, and by adding the compound to the electron injection region, the emission luminance and the life of the organic EL element can be improved.

Next, the addition amount of the reducing dopant having a work function of 2.9 eV or less will be described. As in the first embodiment, the amount of the reducing dopant is preferably in the range of 0.1 to 50% by weight based on the material constituting the electron injection region, and is preferably 1 to 20%. It is more preferable to set the value in the range of% by weight. The work function is 2.
With respect to the addition amount of the reducing dopant of 9 eV or less, the addition ratio of the electron transporting compound to the reducing dopant is 1: 2.
It is preferable to set the range of 0 to 20: 1 (molar ratio).
When the addition ratio of the electron transporting compound and the reducing dopant is out of these ranges, the emission luminance of the organic EL device tends to decrease and the life tends to be shortened. Therefore, the addition ratio of the electron transporting compound to the reducing dopant is 1: 1.
It is more preferably in the range of 0 to 10: 1 (molar ratio), more preferably in the range of 1: 5 to 5: 1, and most preferably in the range of 1: 3 to 3: 1. That is.

(Electron Affinity) The electron affinity of the electron injection region in the second embodiment is preferably in the range of 1.8 to 3.6 eV, as in the first embodiment.
More preferably, the range is from 1.9 to 3.0 eV,
More preferably, the range is 2.0 to 2.5 eV. When the value of the electron affinity is out of these ranges, a complex having low luminous efficiency tends to be generated, and it tends to be difficult to suppress generation of a blocking junction. Note that the electron affinity of the electron injection region can be appropriately adjusted by changing the type or mixing ratio of the electron transporting compound and the reducing dopant constituting the electron injection region.

Also, in the electron injection region in the second embodiment, similarly to the first embodiment, the difference between the electron affinity in the electron injection region and the electron affinity in the light emission region is set to a value of 0.5 eV or less. It is more preferable to set the value to 0.2 eV or less. The smaller the difference in electron affinity, the easier the electron injection from the electron injection region to the light emission region,
This is because an organic EL element capable of high-speed response can be obtained.

(Glass Transition Point) The glass transition point of the electron injection region in the second embodiment is preferably set to a value of 100 ° C. or more, as in the first embodiment, and more preferably, The value is in the range of 105 to 200 ° C.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIG. FIG.
FIG. 3 is a cross-sectional view of an organic EL device 102 according to a third embodiment, in which an anode layer 10, a hole injection transport layer 18,
2. It has a structure in which an electron injection region 14 and a cathode layer 16 are sequentially laminated. Then, the organic EL element 102
Has the same structure as the organic EL device 100 of the first and second embodiments except that a hole injection / transport layer 18 is inserted between the anode layer 10 and the light emitting region 12. are doing. Therefore, the following description is about the hole injection / transport layer 18 which is a characteristic portion of the third embodiment, and the other components, for example, the electron injection region 14, etc. The configuration can be the same as that of the embodiment.

The hole injection transport layer 1 in the third embodiment
8 has a function of smoothly injecting holes substantially in the same manner as the hole injection layer, and also has a function of efficiently transporting injected holes. Therefore, by providing the hole injecting and transporting layer 18, the injection of holes and the movement to the light emitting region are facilitated, and a high-speed response of the organic EL element is possible.

Here, the hole injection / transport layer 18 is formed of an organic material or an inorganic material. Preferred organic materials include, for example, diamine compounds, diamine-containing oligomers and thiophene-containing oligomers. Preferred inorganic materials include, for example, amorphous silicon (α-Si), α-SiC, microcrystal silicon (μC-Si), μC-SiC, II-
Group VI compounds, Group III-V compounds, amorphous carbon, crystalline carbon and diamond.

The hole transport layer 18 is not limited to a single-layer structure, but may have a two-layer structure or a three-layer structure.
The thickness of the hole transport layer 18 is not particularly limited, but is preferably, for example, in the range of 0.5 nm to 5 μm.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG.
Is a cross-sectional view of the organic EL element 104 according to the third embodiment, which includes an anode layer 10, a hole injection / transport layer 18, a light emitting region 1;
2, electron injection area 14, first interface layer 20, and cathode layer 1
6 are sequentially laminated.

This organic EL device is the same as the organic EL device 102 of the third embodiment except that the first interface layer 20 is inserted between the electron injection region 14 and the cathode layer 16. It has the same structure. Therefore, the following description is for the first interface layer, which is a characteristic part of the fourth embodiment, and for the other components,
A configuration similar to the first to third embodiments or a configuration generally known in the field of organic EL elements can be used.

The first interface layer in the fourth embodiment comprises:
It has a function to enhance electron injection properties. Therefore,
By providing one interface layer, electron injection and light emission
Movement to the area is easy, and high-speed response of the organic EL element is possible.
It works. Here, the first interface layer has an electron injecting property.
Materials, for example, alkali metal compounds, alkaline earth gold
Amorphous compounds containing genus compounds and alkali metals
Is a microcrystal containing alkali metal
Preferably. More specifically, preferred alkali gold
As the genus compound, for example, LiF, Li ₂O, LiO
And LiCl. Also preferred alkali
Examples of the earth metal compound include BaO, SrO, M
gO, MgF₂, SrCl₂Is raised.

The first interface layer is not limited to a single-layer structure, but may have a two-layer structure or structure. Further, the thickness of the first interface layer is not particularly limited, but is preferably, for example, in the range of 0.1 nm to 10 μm.

<Fifth Embodiment> Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG.
Is a cross-sectional view of the organic EL element 106 according to the fifth embodiment, which includes an anode layer 10, a second interface layer 20, a hole injection transport layer 18, a light emitting region 12, an electron injection region 14, and a cathode layer 1.
6 are sequentially laminated.

The organic EL device 106 of the third embodiment is the same as the organic EL device of the third embodiment except that a second interface layer 20 is inserted between the anode 16 and the hole injection / transport layer 18. 1
02 has the same structure. Therefore, the following description will focus on the anode 1 which is a characteristic part of the fourth embodiment.
6 and the second interface layer 20 provided between the hole injecting and transporting layer 18. Other components are the same as those in the first to fourth embodiments or the organic E layer.
A configuration generally known in the field of the L element can be used.

Second Interface Layer 20 in Fifth Embodiment
Has a function of improving the hole injection property from the anode 16. Therefore, by providing the second interface layer, injection of holes and movement to the light emitting region are facilitated, and the organic EL
A high-speed response of the device becomes possible.

Here, as the constituent material of the second interface layer, polyaniline, amorphous carbon, phthalocyanines, or the like can be used. Further, the second interface layer is not limited to a single-layer structure, and may have, for example, a two-layer structure or structure. Further, the thickness of the second interface layer is not particularly limited, but is preferably in the range of, for example, 0.5 nm to 5 μm.

<Method of Manufacturing Organic EL Element> Next, FIGS.
9, a method for manufacturing the organic EL device of the present invention will be described. More specifically, even when the electron injection region or the like has a large area, the composition ratio of the constituent materials is made uniform, the variation in the driving voltage of the organic EL element is reduced, the life can be made uniform, and the space can be saved. A method of manufacturing a possible organic EL device will be described.

That is, using a vacuum evaporation apparatus 201 as shown in FIGS. 7 and 8 as an example, different evaporation materials are simultaneously evaporated from a plurality of evaporation sources 212A to 212F arranged opposite to the substrate 203 to form a film. In this method, a rotation axis 213A for rotating the substrate 203 is set on the substrate 203, and the deposition sources 212A to 212F are separated from the rotation axis 213A of the substrate 203, respectively. And the substrate 203
Is deposited while rotating.

Here, the vacuum evaporation apparatus 201 shown in FIGS. 7 and 8 comprises a vacuum chamber 210, a substrate holder 211 for fixing the substrate 203, which is installed in the upper portion of the vacuum chamber 210, It comprises a plurality (six) of evaporation sources 212A to 212F for accommodating an evaporation material, which are arranged below the holder 211 to face each other. The inside of the vacuum chamber 210 can be maintained at a predetermined reduced pressure state by an exhaust means (not shown). In addition,
Although the number of vapor deposition sources is shown in the drawing as six, the number is not limited thereto, and may be five or less, or seven or more.

The substrate holder 211 has a holding portion 212 for supporting the peripheral portion of the substrate 203, and is configured to horizontally hold the substrate 203 in the vacuum chamber 210. At the center of the upper surface of the substrate holder 211, a rotating shaft 213 for rotating (rotating) the substrate 203 is provided upright in the vertical direction. The rotating shaft 213 is connected to a motor 214 serving as a rotation driving means.
4 rotates the substrate 203 held by the substrate holder 211 together with the substrate holder 211 into the rotating shaft 2.
13 rotates around the center of rotation. That is, at the center of the substrate 203, the rotation axis 213A of the rotation shaft 213 is set in the vertical direction.

Next, a method for forming the electron injection region 14 on the substrate 203 by using the vacuum evaporation apparatus 201 having the above-described structure will be specifically described. First, a substrate 203 having a square planar shape as shown in FIGS. 7 and 8 is prepared, and this substrate 203 is attached to the holding portion 212 of the substrate holder 211.
To a horizontal state.

Here, in forming the electron injection region 14, two adjacent evaporation sources 212 B on the virtual circle 221 are formed.
And 212C contain the electron transporting compound and the electron injecting material, respectively, and then the vacuum chamber 21
The pressure inside 0 is reduced to a predetermined degree of vacuum, for example, 1.0 × 10 ⁻⁴ Pa.

Next, the evaporation sources 212B and 212C are heated to simultaneously evaporate the electron-transporting compound and the reducing dopant from the evaporation sources 212B and 212C, respectively, and the motor 214 is driven to rotate to move the substrate 203 to the rotation axis. 213A is rotated at a predetermined speed, for example, 1 to 100 rpm. In this manner, the electron injection region 14 is formed by co-evaporating the electron transporting compound and the reducing dopant while rotating the substrate 203. At this time, as shown in FIG.
2C is provided at a position shifted by a predetermined distance M in the horizontal direction from the rotation axis 213A of the substrate 203, so that the rotation of the substrate 203 reduces the incident angle of the electron transporting compound and the reducing dopant to the substrate 203. Can be changed regularly. Therefore, the deposition material is
To the electron injection region 14
In the film surface of (1), a thin film layer in which the composition ratio of the evaporation material is uniform, for example, the concentration unevenness is ± 10% (in terms of mol) can be surely formed. Further, by performing the vapor deposition as described above, the substrate 203 does not need to revolve, so that space and equipment are not required, and the film can be formed economically with a minimum space. Revolving the substrate means rotating around a rotation axis other than the substrate, and requires a larger space than when rotating.

In implementing this manufacturing method,
The shape of the substrate 203 is not particularly limited.
As shown in FIG. 8 and FIG. 8, when the substrate 203 is in the shape of a rectangular flat plate, a plurality of evaporation sources 212A are formed along the circumference of the virtual circle 221 around the rotation axis 213A of the substrate 203.
To 212E, the radius of the virtual circle 221 is M, the substrate 2
When the length of one side of 03 is L, it is desirable to satisfy M> 1/2 × L. When the lengths of the sides of the substrate 203 are not the same but different, the length of the longest side is set to L. With such a configuration, the incident angles of the deposition material from the plurality of deposition sources 212A to 212F with respect to the substrate 203 can be made equal to each other, so that the composition ratio of the deposition material can be more easily controlled. Also,
With this configuration, the evaporation material can be transferred to the substrate 20.
3 is evaporated at a constant incident angle, so that it does not enter vertically, and the uniformity of the composition ratio in the film plane can be further improved.

In implementing this manufacturing method,
As shown in FIG. 7, a plurality of evaporation sources 212A to 212F
Is disposed on the circumference of the virtual circle 221 centered on the rotation axis 213A of the substrate 203, a mixed region composed of two or more materials such as the electron transporting compound and the reducing dopant of the present invention. In the case of forming with a uniform composition ratio, it is desirable to provide these evaporation sources at positions close to each other. When the composition ratios are different in the thickness direction, it is desirable to provide them at positions separated from each other. For example, when the number of evaporation sources is n, each evaporation source is positioned 360 degrees from the center of the circle.
It may be arranged at an angle of ° / n.

Next, the uniformity of the thin film layer formed by this manufacturing method will be described in more detail. As an example, Alq is used as an electron transporting compound, Cs is used as a reducing dopant, and a thin film layer having a thickness of about 1000 angstroms (set value) is formed under the following conditions while rotating the substrate 203 shown in FIG. 9 at 5 rpm. Co-evaporation. Alq deposition rate: 0.2 nm / s Cs deposition rate: 0.03 nm / s Alq / Cs film thickness: 1000 Å (set value)

Next, the thickness of the thin film layer at the measurement points (4A to 4M) on the glass substrate 203 shown in FIG. 9 was measured using a stylus-type thickness gauge, and the composition ratio of Cs / Al was changed to X. The measurement was performed using a line photoelectron spectrometer (ESCA).
The measurement points (4A to 4A) on the glass substrate 203 shown in FIG.
4M) divides the surface of the substrate 203 into 16 equal parts in advance, sets square sections with a side length P of 50 mm, and sets arbitrary corners (13 places) in these sections. Table 1 shows the obtained results.

[0108]

[Table 1]

On the other hand, a thin film layer having a thickness of about 1000 angstroms (set value) was formed in the same manner as in this manufacturing method except that the 203 was not rotated. Note that the evaporation conditions are as described above. Next, the film thickness and Cs / A of the obtained thin film layer at the measurement points (4A to 4M).
1 was measured. Table 2 shows the results.

[0110]

[Table 2]

As is apparent from these results, when this manufacturing method is used, the measurement points (4A to 4
M), the film thickness is extremely uniform within the range of 1008 to 1091 angstroms, and Cs / Al
It has been confirmed that a thin film layer having a very uniform composition ratio of the composition ratio (molar ratio) of 1.0 to 1.10 (-) was obtained. On the other hand, when a manufacturing method different from this manufacturing method is used, at the measurement points (4A to 4M) on the substrate 203,
It was confirmed that the film thickness was in the range of 884 to 1067 angstroms, and the composition ratio of Cs / Al was in the range of 0.6 to 1.2 (-).

In the embodiments described above, examples in which the present invention is configured under specific conditions have been described. However, various modifications can be made in this embodiment. For example, in the embodiment described above, the light emitting region and the electron injection region are separately provided, but the light emitting region and the electron injection region may be combined into one layer. Also, any suitable layer may be interposed between the cathode layer and the anode layer.

[0113]

[Embodiment 1] Next, Embodiment 1 of the present invention will be described with reference to FIGS. The structure of the organic EL element 102a of Example 1 shown in FIG. 5 corresponds to the structure of the organic EL element 102 in the third embodiment shown in FIG. However, the organic EL element 10 of Example 1
2a is different from the organic EL device 102 according to the third embodiment in that the hole injection / transport layer 18 is constituted by a hole injection layer 18a and a hole transport layer 18b which are sequentially stacked.

(1) Preparation for Manufacturing Organic EL Element In manufacturing the organic EL element 102a of Example 1, first, a thickness of 1.1 mm, a length of 200 mm, and a width of 200 m
m as a positive electrode layer 10 on a transparent glass substrate 22
A transparent electrode film of O was formed. Hereinafter, this glass substrate 10
The substrate 30 (203 in FIGS. 7 and 8) is made up of the substrate and the anode layer 10. Subsequently, the substrate 30 was ultrasonically cleaned with isopropyl alcohol, further dried in an N ₂ (nitrogen gas) atmosphere, and then cleaned for 10 minutes using UV (ultraviolet light) and ozone.

Next, as shown in FIG. 8, the substrate 30 is
It is mounted on the substrate holder 211 of the vacuum chamber 210 of the vacuum evaporation apparatus 201, and the hole injection layer 18a is formed with the hole injecting organic substance (HI-1) as the evaporation source 212A, and the hole transport layer 18b is formed with the holes. Injectable transport organics (HT
-1) to the evaporation source 212B, a nitrogen-free aromatic ring compound (EM-1) constituting the electron injection region and the emission region to the evaporation source 212C, and a reducing dopant (Li) constituting the electron injection region to the evaporation source 212C. Metal (Al) constituting the cathode was housed in the evaporation source 212E in the evaporation source 212D. In addition,
The structural formulas of HI-1 represented by the formula (11), HT-1 represented by the formula (12), and EM-1 represented by the formula (13) are shown below. The glass transition point of EM-1 was 105 ° C., and the electron affinity of the electron injection region including the glass transition point was 2.8 eV.

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(2) Manufacture of Organic EL Device Next, after the pressure in the vacuum chamber 210 was reduced to a degree of vacuum of 5 × 10 ⁻⁵ Pa or less, the hole injection layer 18a was formed on the anode layer 10 of the substrate 30. , Hole transport layer 18b, light emitting region 1
2. The electron injection region 14 and the cathode layer 16 were sequentially laminated in this order to obtain an organic EL device 102a. At this time, during the period from the formation of the hole injection layer 18a to the formation of the cathode layer 16, the organic EL element 1 is not broken once without breaking the vacuum state.
02a was produced.

More specifically, the HI is supplied from the evaporation source 212A.
-1 is evaporated under the following conditions to deposit the hole injection layer 18a on the anode layer 10, and then the HT-1 is evaporated from the evaporation source 212B.
Is evaporated to form a hole transport layer 18 on the hole injection layer 18a.
b was deposited. During these depositions, the substrate 30 was not particularly heated or cooled. Deposition rate of HI-1: 0.1 to 0.3 nm / s Thickness of HI-1: 60 nm Deposition rate of HT-1: 0.1 to 0.3 nm / s Thickness of HT-1: 20 nm

Next, EM-1 as an organic light emitting material is evaporated from the evaporation source 212C under the same conditions as those for forming the hole injection layer 18a, and the organic light emitting region 1 is formed on the hole transport layer 18b.
2 was deposited. EM-1 deposition rate: 0.1 to 0.3 nm / s EM-1 film thickness: 40 nm

Next, the evaporation source 212C and the evaporation source 21
Under 2D conditions, EM-1 and Li were simultaneously evaporated from 2D to form an electron injection region 14 on the organic light emitting region 12. EM-1 deposition rate: 0.1 to 0.3 nm / s Li deposition rate: 0.05 to 0.01 nm / s EM-1 / Li film thickness: 20 nm

The simultaneous vapor deposition was performed by the above-mentioned manufacturing method. That is, the evaporation sources 212C and 212D
The substrates 30 (203) are provided at positions shifted by 30 mm in the horizontal direction from the rotation axis 213A of the substrate 30 (203), and are heated in this state to simultaneously evaporate EM-1 and Li from the evaporation sources 212B and 212C, respectively. Then, the motor 214 was driven to rotate, and the electron injection region 14 was formed while the substrate 203 was rotated at 5 rpm along the rotation axis 213A.

Finally, Al was evaporated from the evaporation source 212D under the following conditions to deposit the cathode layer 16 on the electron injection region 14. Al deposition rate: 1 nm / s Al film thickness: 200 nm

(3) Evaluation of Organic EL Device In the obtained organic EL device 102a, a negative (-) electrode is used as the cathode layer 16 and a positive (+) electrode is used as the anode layer 10, and a DC voltage of 7 V is applied between both electrodes. did. The current density at this time was 1.0 mA / c as shown in Table 1 below.
m ² , the luminance at that time was 40 cd / cm ² , and the light emission color was blue. The half life of the element 102a was 1000 hours. Note that the half life is the time required for the luminance to reach half the maximum luminance. For example, in the first embodiment, the luminance is 40 cd / maximum luminance.
It refers to the time required from cm ² to its half value of 20 cd / cm ² . Table 3 shows the obtained results.

[0126]

[Table 3]

Embodiment 2 Next, Embodiment 2 of the present invention will be described. The structure of the organic EL element of Example 2 was the same as the structure of the organic EL element 102a of Example 1, and was manufactured in the same manner as Example 1. However, in Example 2, Ca (calcium) metal was added to the electron injection region as a reducing dopant instead of Li metal. Then, a DC voltage of 7 V was applied to the organic EL element as in Example 1. The current density at this time was 1.2 mA / cm ² and the luminance was 50 cd / cm ² as shown in Table 1 below.
It was m ^2. The half life of the organic EL device of Example 2 was 1500 hours. Table 3 shows the obtained results.

Third Embodiment Next, a third embodiment of the present invention will be described. The structure of the organic EL element of Example 3 was the same as the structure of the organic EL element 102a of Example 1, and was manufactured in the same manner as Example 1. However, in Example 3, Na (sodium) metal was added to the electron injection region as a reducing dopant instead of Li metal.

Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
As shown in Table 1 below, 1.0 mA / cm ² ,
The luminance was 60 cd / m ² . The half life of the organic EL device of Example 3 was 1600 hours. Table 3 shows the obtained results.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described. The structure of the organic EL element of Example 4 was the same as the structure of the organic EL element 102a of Example 1, and was manufactured in the same manner as Example 1. However, in Example 4, instead of Li metal, 1.3 mol of K (potassium) metal was added to the electron injection region instead of Li metal with respect to 1 mol of EM-11.

Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
As shown in Table 3 below, it was 4.0 mA / cm ² ,
The emission luminance was 146 cd / m ² . Example 4
The half life of the organic EL device was 1800 hours.
Table 3 shows the obtained results.

Embodiments 5 to 7 Next, Embodiments 5 to 7 of the present invention will be described. The structures of the organic EL elements of Examples 5 to 7 were the same as the structure of the organic EL element 102a of Example 1, and were manufactured in the same manner as Example 1. However, in Examples 5 to 7, Cs (cesium) metal was used instead of Li metal as a reducing dopant in the electron injection region.
1 mol per 1 mol of EM-1 (Example 5);
5 mol (Example 5) and 4.0 mol (Example 7) were added.

Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
In Example 5, it was 40 mA / cm ² , and Example 6
Was 38 mA / cm ² and in Example 7, it was 25 mA / cm ² . In the range considered, Cs
As the amount of metal added was smaller, the current density tended to be slightly higher. Further, emission luminance at this time, in Example 5 was 1000 cd / cm ^2, in Example 6 is 1300 cd / cm ^2, in Example 7 was 1100 cd / cm ^2. The half-life of the organic EL device was 2500 hours in Example 5, 3000 hours in Example 6, and 1700 hours in Example 7.

[Eighth Embodiment] Next, an eighth embodiment of the present invention will be described. The structure of the organic EL device of Example 8 was the same as the structure of the organic EL device 102a of Example 1, and was manufactured in the same manner as in Example 1. However, in Example 8, a mixture of Cs and Na was used instead of Li metal as the reducing dopant in the electron injection region, respectively, in EM-1.
1.0 mol and 0.5 mol were added per 1 mol.

Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
Was 40 mA / cm ^2, emission luminance 1000 cd / c
It was m ^2. The half life of the organic EL device of Example 9 was 2500 hours. Table 3 shows the obtained results.

Embodiment 9 Next, Embodiment 9 of the present invention will be described. The structure of the organic EL device of the ninth embodiment is the same as that of the first embodiment. However, in Example 9, instead of EM-1, the following (1) was used as the material for the electron injection region.
4) Diphenylanthracene dimer (DFA) represented by the formula
D) was used. The glass transition point in the electron injection region in this case was measured by DSC, and was found to be 120 ° C. The layers other than the electron injection region were made of the same material and thickness as in Example 1.

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Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
Was 1.5 mA / cm ^2, the luminance was 60 cd / cm ^2. The half life of the organic EL device of Example 9 is
1800 hours. Table 3 shows the obtained results.

[Embodiment 10] Next, Embodiment 1 of the present invention will be described.
0 will be described. The structure of the organic EL device of Example 10 is the same as the structure of the organic EL device of Example 1. However, in Example 10, the material of the electron injection region was EM
Alq shown in the formula (4) is used in place of -1 and C is used as a reducing dopant instead of Li metal.
S (cesium) metal was used and added at a ratio of 1.0 mol to 1 mol of Alq. In this case, the glass transition point in the electron injection region was measured by DSC, and was 180 ° C. The layers other than the electron injection region were made of the same material and the same thickness as in Example 1.

Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
The luminance was 25 mA / cm ² and the luminance was 500 cd / cm ² . The half life of the organic EL device of Example 10 was 2500 hours. Table 3 shows the obtained results.

[Embodiment 11] Next, Embodiment 1 of the present invention will be described.
1 will be described. The structure of the organic EL element of Example 11 is the same as the structure of the organic EL element of Example 1. However, in Example 11, Alq shown in the formula (4) was used instead of EM-1 as the material of the light emitting region and the electron injection region, and Na (sodium) was used as the reducing dopant instead of Li metal. ) Using metal, Alq
It was added at a ratio of 0.5 mole to 1 mole. The layers other than the electron injection region were made of the same material and the same thickness as in Example 1.

Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
It was 3 mA / cm ² and the luminance was 200 cd / cm ² . The half life of the organic EL device of Example 11 is as follows:
3000 hours. Table 3 shows the obtained results.

[Embodiment 12] Next, Embodiment 1 of the present invention will be described.
2 will be described. The structure of the organic EL device of Example 12 is the same as the structure of the organic EL device of Example 1. However, in Example 12, the material of the electron injection region was EM
In place of -1, a quinoxaline compound (H1) represented by the formula (9) is used, and as a reducing dopant,
Instead of Li metal, Cs metal was used, and added at a ratio of 1.0 mol to 1 mol of H1.

In this case, the glass transition point of the electron injection region is represented by D
It was 103 ° C. as measured by SC. Also,
Each layer other than the electron injection region was made of the same material and thickness as in Example 1.

Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
It was 5 mA / cm ² and the luminance was 700 cd / cm ² . Further, the half life of the organic EL element of Example 12 is as follows:
1000 hours. Table 3 shows the obtained results.

Embodiment 13 Next, Embodiment 1 of the present invention will be described.
3 will be described. The structure of the organic EL device of Example 13 is the same as the structure of the organic EL device of Example 1. However, in Example 13, the material of the electron injection region was EM
In place of -1, an oxadiazole compound (H2) represented by the following formula (15) is used, and as a reducing dopant, Sr metal is used instead of Li metal.
It was added at a ratio of 1.0 mole to 1 mole. The glass transition point of the electron injection region measured by DSC was 101 ° C. The layers other than the electron injection region were made of the same material and the same thickness as in Example 1.

[0147]

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Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
Was 1.5 mA / cm ^2, the luminance is 200 cd / cm ²
Met. The half life of the organic EL device of Example 13 was 2,000 hours. Table 3 shows the obtained results.

Fourteenth Embodiment Next, a fourteenth embodiment will be described with reference to FIG. The structure of the organic EL element of Example 14 is the same as that of the organic EL element 104 according to the fourth embodiment.
The structure is almost the same. However, in Example 14, a 5 nm-thick BaO (barium oxide) layer was formed as the first interface layer 20 by vacuum deposition at a deposition rate of 0.1 nm / s. The layers other than the first interface layer 20 were made of the same material and the same thickness as in Example 1.

Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
2.0 mA / cm ² and a luminance of 140 cd / cm ²
Met. The half life of the organic EL device of Example 5 was 2500 hours. Table 4 shows the obtained results. Therefore, it was found that the presence of the first interface layer 20 improved the current density, the brightness, and the half-life from those of Example 1.

[0151]

[Table 4]

[Embodiment 15] Next, Embodiment 1 of the present invention will be described.
5 will be described. The structure of the organic EL device of Example 15 is the same as the structure of Example 14. However, Example 1
In No. 5, a 5 nm-thick LiF (lithium fluoride) layer was formed as the first interface layer 20 by vacuum evaporation instead of the BaO layer. The layers other than the first interface layer 20 were made of the same material and the same thickness as in Example 1.

Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
2.2 mA / cm ² and emission luminance of 150 cd / c
It was m ^2. The half life of the organic EL device of Example 15 was 3000 hours. Table 4 shows the obtained results.

[Embodiment 16] Next, Embodiment 1 of the present invention will be described.
6 will be described. The structure of the organic EL device of Example 16 is the same as the structure of the organic EL device of Example 14. However, in Example 16, Ba was used as the first interface layer 20.
Instead of the O layer, a 5 nm thick SrO (strontium oxide) layer was formed by vacuum evaporation. The layers other than the first interface layer 20 were made of the same material and the same thickness as in Example 1.

Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
2.0 mA / cm ² and a luminance of 100 cd / cm ²
Met. The half life of the organic EL device of Example 16 was 2000 hours. Table 4 shows the obtained results.

[Comparative Example 1] Next, Comparative Example 1 will be described. The structure of the organic EL device of Comparative Example 1 is the same as the structure of Example 1. However, in Comparative Example 1, instead of “EM-1”, trinitrofluorenone (TNF) represented by the following formula (16) was used as the material for the electron injection region. The electron affinity in the electron injection region in this case was 4.1 eV. The layers other than the electron injection region were made of the same material and thickness as in Example 1.

[0157]

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Then, a DC voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is
It was 0.1 mA / cm ² , and no luminance was observed.
In the organic EL device of Comparative Example 1, since the electron affinity in the electron injection region was as high as 4.1 eV, TNF reacted with the material in the light emitting region to form a complex, or the excited state generated in the light emitting region was an electron. It is considered that they moved to the injection area and were inactivated.

[Comparative Example 2] Next, Comparative Example 2 will be described. The structure of the organic EL element of Comparative Example 2 is the same as the structure of Example 1. However, in Comparative Example 2, diphenoquinone represented by the following formula (17) was used instead of “EM-1” as the material of the electron injection region. In this case, the glass transition point of the electron injection region was 50 ° C. The layers other than the electron injection region were made of the same material and thickness as in Example 1.

[0160]

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Then, a voltage of 7 V was applied to the organic EL device in the same manner as in Example 1. The current density at this time is 0.
It was ² mA / cm ² , and the luminance was instantaneously obtained at ² cd / m ² , but was immediately extinguished. Table 3 shows the obtained results. In the organic EL device of Comparative Example 2, since the material of the electron injection region contained nitrogen atoms and the glass transition point was as low as 50 ° C., it is considered that the electron injection region was destroyed by Joule heat.

[Comparative Example 3] Next, Comparative Example 3 will be described. The structure of the organic EL device of Comparative Example 3 is the same as the structure of Example 1. However, in Comparative Example 3, a nitrogen-containing compound represented by the following formula (18) was used instead of “EM-1” as the material for the electron injection region. The glass transition point of the electron injection region in this case was 62 ° C. The layers other than the electron injection region were made of the same material and thickness as in Example 1.

[0163]

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Then, a DC voltage of 6 V was applied to the organic EL device. The current density at this time was 1.0 mA / cm
^2, luminance was obtained 90 cd / ^{m 2.} However, the half life of the organic EL element was only 200 hours. In addition, when the emission spectrum was observed, a spectrum component emitting red light was generated. Table 3 shows the obtained results.

It is considered that the nitrogen-containing compound of the formula (18) used in Comparative Example 3 has a strong acceptor property, and thus has a strong possibility of causing quenching by interacting with a material in the light emitting region. Further, it is considered that a compound having a molecular weight of 300 or less and having a low glass transition point is easily mixed with the light emitting region, and as a result, it has caused quenching by interaction.

[0166]

As described above in detail, according to the first aspect of the present invention, the interface between the electron injection region and the light emission region is
The generation of a charge transfer complex or an exciplex having low luminous efficiency can be suppressed, and the generation of a blocking junction, which is undesirable in injecting electrons from the electron injection region to the light emission region, can also be suppressed. Therefore, according to the present invention, it is possible to improve the luminous efficiency and to provide an organic EL device having a longer life.

According to the second aspect of the present invention, not only the case where an aromatic ring compound containing no nitrogen atom is used but also the case where an aromatic ring compound containing a nitrogen atom is used is used. Also, at the interface between the electron injection region and the light emitting region, it is possible to suppress the generation of a charge transfer complex or exciplex having low luminous efficiency, and it is not preferable to inject electrons from the electron injection region to the light emitting region. Generation can also be suppressed. Therefore, according to the second aspect, it is possible to provide an organic EL device having a higher degree of freedom, an improvement in luminous efficiency, and a longer life.

[Brief description of the drawings]

FIG. 1 is a sectional view of an organic EL device according to first and second embodiments.

FIG. 2 is a cross-sectional view of an organic EL device according to a third embodiment.

FIG. 3 is a cross-sectional view of an organic EL device according to a fourth embodiment.

FIG. 4 is a sectional view of an organic EL device according to a fifth embodiment.

FIG. 5 is a cross-sectional view of the organic EL element in Example 1.

FIG. 6 is a cross-sectional view of the organic EL element in Example 2.

FIG. 7 is a perspective view of an example of a vacuum evaporation apparatus for manufacturing the organic EL device of the present invention.

FIG. 8 is a sectional view of the vacuum deposition apparatus in FIG.

FIG. 9 is a diagram provided for describing measurement points on a substrate.

FIG. 10 is a sectional view of a conventional organic EL element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Cathode layer 12 Emission area 14 Electron injection area 16 Anode layer 18 Hole injection transport layer 18a Hole injection layer 18b Hole transport layer 20 First interface layer 22 Glass substrate 20 Second interface layer 30 Substrate 50 Cathode 52 First One organic film 54 Second organic film 56 Third organic film, light emitting area 58 Anode 60 Organic EL element 100, 102, 102a, 104, 04a, 106
Organic EL element 201 Vacuum evaporation apparatus 203 Substrate 210 Vacuum tank 211 Substrate holder 212 Evaporation source 213 Rotation axis 213A Rotation axis 214 Motor 221 Virtual circle

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K007 AB02 AB03 AB04 AB06 AB11 CA01 CB01 DA01 DB03 EB00

Claims (17)

[Claims] 1. An organic electroluminescence device having a structure in which at least an anode layer, a light emitting region, an electron injection region, and a cathode layer are sequentially laminated, wherein a glass transition point of the electron injection region is set to a value of 100 ° C. or more; The electron injection region contains an aromatic compound containing no nitrogen atom and a reducing dopant represented by the following formula, and further has an electron affinity in the electron injection region of 1.8 to 3.6.
An organic electroluminescent device having an eV range. M ⁺ Ar ⁻ (where M represents an alkali metal and Ar represents an unsubstituted or substituted aromatic ring compound having 10 to 40 carbon atoms) 2. The organic electroluminescence device according to claim 1, wherein the reducing dopant is anthracene, naphthalene,
An organic electroluminescent device comprising a group formed from at least one aromatic ring selected from the group consisting of diphenylanthracene, terphenyl, quarterphenyl, kinkphenyl and sexiphenyl. 3. The organic electroluminescence device according to claim 1, wherein the aromatic compound is anthracene, fluorene, perylene, pyrene, phenanthrene, chrysene, tetracene, rubrene, terphenylene, quarterphenylene, sexifphenylene, and triphenylene. An organic electroluminescence device comprising a group formed from at least one aromatic ring selected from the group consisting of: 4. The organic electroluminescence device according to claim 1, wherein the aromatic compound is selected from the group consisting of a styryl-substituted aromatic ring and a distyl-substituted aromatic ring. An organic electroluminescence device comprising a group formed from at least one aromatic ring. 5. The organic electroluminescence device according to claim 1, wherein the work function of the reducing dopant is set to a value of 3.0 eV or less. 6. The organic electroluminescence device according to claim 1, wherein an energy gap of the electron injection region is 2.7 eV or more. 7. The organic electroluminescence device according to claim 1, wherein an addition ratio between the aromatic compound and the reducing dopant is in a range of 1:20 to 20: 1 (molar ratio). An organic electroluminescence device characterized by the above-mentioned. 8. The organic electroluminescence device according to claim 1, wherein the light emitting region and the electron injection region contain the same type of aromatic compound containing no nitrogen atom. Organic electroluminescent element. 9. The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device is provided between the cathode layer and the electron injection region and / or between the anode layer and the light emitting region. An organic electroluminescence device, comprising an interface layer. 10. An organic electroluminescence device having a structure in which at least an anode layer, a light emitting region, an electron injection region and a cathode layer are sequentially laminated, wherein the electron injection region has an electron transporting compound and a work function of 2.9 eV. It contains a reducing dopant represented by the following formula, and has an electron affinity in the electron injection region of 1.8 to 3.6 eV.
An organic electroluminescent device characterized by having the following range. M ⁺ Ar ⁻ (where M represents an alkali metal and Ar represents an unsubstituted or substituted aromatic compound having 10 to 40 carbon atoms) 11. The organic electroluminescent device according to claim 10, wherein the reducing dopant is anthracene, naphthalene,
An organic electroluminescent device comprising a group formed from at least one aromatic ring selected from the group consisting of diphenylanthracene, terphenyl, quarterphenyl, kinkphenyl and sexiphenyl. 12. The organic electroluminescent device according to claim 10, wherein the electron transporting compound includes a nitrogen-containing heterocyclic compound. 13. The organic electroluminescent device according to claim 12, wherein the nitrogen-containing heterocyclic compound is selected from the group consisting of a nitrogen-containing complex, a quinoline derivative, a quinoxaline derivative, an oxadiazole derivative, a thiadiazole derivative, and a triazole derivative. An organic electroluminescence device, which is at least one compound to be produced. 14. The organic electroluminescence device according to claim 10, wherein an addition ratio between the aromatic compound and the reducing dopant is in a range of 1:20 to 20: 1 (molar ratio). An organic electroluminescence device characterized by the above-mentioned. 15. The organic electroluminescent device according to claim 10, wherein a glass transition point of the electron injection region is set to a value of 100 ° C. or more. 16. The organic electroluminescence device according to claim 10, wherein the light emitting region and the electron injection region contain the same type of electron transporting compound. Luminescent element. 17. The organic electroluminescent device according to claim 10, wherein the cathode layer and the electron injection region and / or the anode layer and the light emission region. On the other hand, an organic electroluminescence device characterized by providing an interface layer.