JP2001326079A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which can illuminate with high brightness at low voltage. SOLUTION: An organic compound layer 20 is arranged between the first electrode 12 and the second electrode 18, and the layer 20 has a hole carrying luminous layer 22 including an organic compound shown by the formula (1), (in the formula (1); R1-R4 are substituents, [A] is an alternative of either (1) composition of more than two carbon atoms, (2) a combined composition of one or more of carbon atom and requested substituent or the atom other than carbon, or (3) composition of two biphenyl derivatives bound at plural points without interposing atom.) and an electron transfer layer 24 including an organic compound shown by the formula (2), (in the formula (2); Ar1, Ar2, and Ar3 are aryl group or aromatic heterocycle group, X1, X2 and X3 are substituents, n1, n2 and n3 are integer of 0-3.). For the hole transferable luminous layer 22, a prescribed doping material may be doped in a host material like the material shown by the formula (1).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device (hereinafter, referred to as an organic EL device), and particularly to a structure of an organic compound layer.

[0002]

2. Description of the Related Art Since the announcement of an electroluminescent device in which two kinds of fluorescent organic ultra-thin films are laminated by Eastman Kodak Company in 1987, display devices using organic EL devices have been vigorously developed. I have. As the organic electroluminescent device, four configurations shown in FIG. 1 are known as typical ones.

The configuration shown in FIG. 1A is a single-layer type having an emission layer (EML) between a cathode and an anode, and has been studied since the 1960's. The configuration in FIG. 1B includes a light emitting layer also serving as an electron transport layer (ETL) between a cathode and an anode, and a hole transport layer (HTL), and holes are supplied from the hole transport layer to the light emitting layer. Light emission occurs. The configuration in FIG. 1C includes a light emitting layer also serving as a hole transport layer, and an electron transport layer, and electrons are supplied from the electron transport layer to the light emitting layer to emit light. FIG.
The configuration (d) includes a hole transporting layer, a light emitting layer, and an electron transporting layer. In the light emitting layer, holes are supplied through the hole transporting layer, and electrons are supplied through the electron transporting layer. Holes and electrons are recombined in the layer to emit light.

In the three-layer device shown in FIG. 1D, the luminous efficiency is currently the highest and several hundred cd.
A half life of 10,000 hours or more is achieved at a luminance level of / m ² . This three-layer device is disclosed in US Pat.
69292 (Eastman Kodak Company) and the like, in which an electron-transporting light-emitting layer is used. Also,
Even in the two-layered device, a device using an electron-transporting light-emitting layer as shown in FIG.

[0005]

However, the organic E
At this stage, the characteristics of the L element are still insufficient in terms of element efficiency, stability, color adjustment, etc., and further improvement and development are required. One of them is the hole transport property. It is also necessary to develop a device using the light-emitting layer.

As a device using a light-emitting layer having a hole-transporting property, in 1995, a device having a hole-transporting layer doped with rubrene at an initial luminance of 500 cd / m ² was used.
It has been reported that a half life of 0 hours or more was obtained (Ha
mada, et al., Jpn.J. Appl.Phys. 34 (1995) L824-L8
26).

Further, Japanese Patent Application Laid-Open No. 7-65958, US Pat.
Japanese Patent No. 273862 and the like also disclose an element utilizing light emission in a hole transport layer, a hole transporting light emitting layer, and the like.

An object of the present invention is to realize an organic EL device using such a light-emitting layer having a hole-transporting property, which has higher device efficiency, higher luminance and higher stability. .

[0009]

To achieve the above object, the present invention has the following features.

An organic EL device comprising a plurality of organic compound layers between first and second electrodes, wherein the organic compound layer has the following chemical formula (1)

Embedded image (Wherein, in the formula (1), R1 to R4
Is a substituent, and [A] is (i) a carbon atom 2
(Ii) a combination of one or more carbon atoms and a desired substituent or a non-carbon atom (atom other than carbon), or (iii) two biphenyl derivatives directly connected at a plurality of positions without intervening atoms A light-emitting layer having any of the following structures:

Embedded image An organic compound represented by the formula (wherein, Ar ₁ , A
r ₂ and Ar ₃ are each an aryl group or an aromatic heterocyclic group, X ₁ , X ₂ and X ₃ are each a substituent, and n ₁ , n ₂ and n ₃ are each 0 to 3 An electron transport layer containing an integer).

Another feature of the present invention is that the hole transporting light emitting layer is formed by doping a predetermined doping material in a host material, and using the organic compound represented by the chemical formula (1) as the host material. It is to include.

In the present invention, the organic compound represented by the above chemical formula (1) is represented by the following chemical formula (3) or (4):

Embedded image

Embedded image Another feature is that the compound is represented by any one of the above.

As described above, the organic compound represented by the chemical formula (1), (3) or (4) used for the hole transporting light emitting layer is as follows:
It has high hole-transporting property and light-emitting property, and enables highly efficient light emission. Further, since the energy barrier with the electron transporting layer is small, electrons are easily injected from the electron transporting layer, and the organic compound layer of the organic EL device can have a two-layer structure with the electron transporting layer. Further, it has a high glass transition temperature (Tg) and is chemically stable.

Further, the organic compound represented by the chemical formula (2) used for the electron transport layer has a high electron transport property and a high Tg. In addition, since the difference between the highest occupied molecular orbital (HOMO) level and the lowest unoccupied molecular orbital (LUMO) is large, holes are less likely to pass through the layer by using it as an electron transport layer. Have.

As described above, the novel organic compound represented by the chemical formula (1), (3) or (4) is used for the hole transporting light emitting layer, and the novel organic compound represented by the chemical formula (2) is used. Is used for the electron transporting layer, the light emitting layer and the first or second
An electron transporting layer having a high hole blocking ability and a very high electron transporting property is present between the electrode and the electrode to which a negative voltage is applied. Therefore, it is necessary to reduce the possibility that excitons generated by recombination of electrons and holes in the light-emitting layer move through the electron transport layer and reach the cathode, where they disappear without contributing to light emission. Can be. As a result, higher luminous efficiency can be achieved than in the case where light is emitted from the light emitting layer that also serves as the electron transport layer, and electrons can be efficiently injected into the light emitting layer. Becomes In addition, since both the hole-transporting light-emitting layer and the electron-transporting layer are chemically stable, an organic EL device having high luminance and a long lifetime can be obtained by using these materials. .

Another feature of the present invention is that, in the above-mentioned organic EL device, between the first and second electrodes to which a positive voltage is applied and the hole transporting light emitting layer.
Further, a hole injection layer is provided.

By providing such a hole injecting layer, it is possible to improve the adhesion between the electrode to which a positive voltage is applied, that is, the anode and the light emitting layer having a hole transporting property, and to stabilize the element structure. Can be achieved. Further, since the barrier to the anode is small, holes can be more efficiently injected from the anode into the light emitting layer via the hole injection layer.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter, referred to as embodiments) will be described below with reference to the drawings.

FIG. 2 shows an organic EL according to an embodiment of the present invention.
1 shows a schematic sectional configuration of an element. The organic EL device has a structure in which a first electrode 12, an organic compound layer 20 that emits light by application of an electric field, and a second electrode 18 are sequentially stacked on a transparent substrate 10. In the device shown in FIG.
The organic compound layer 20 has a two-layer structure and includes a hole-transporting light-emitting layer 22 containing an organic compound represented by the general formula (1) and an electron transport layer 24 containing an organic compound represented by the general formula (2). It has. However, the organic compound layer 20 is not limited to the two-layer structure of the hole transporting light emitting layer 22 and the electron transporting layer 24, and may have, for example, a configuration further including a hole injection layer as described later.

As the transparent substrate 10, a glass substrate, a transparent substrate
Use of ceramic substrates, diamond substrates, etc.
it can. The first electrode 12 has high light transmittance and conductivity.
Is used, for example, ITO (Indium T
in Oxide), SnO_Two, In _TwoO_Three, Polyaniline, etc.
Thin film materials can be used.

The second electrode 18 is generally a metal electrode, and may be a metal such as Mg, Ag, Ca, Li, Al, In, or an alloy thereof. Further, an extremely thin fluoride of an alkali metal or an alkaline earth metal or an oxide thereof may be inserted between the metal layer functioning as a cathode and the organic compound layer, and a multilayer structure of these may be used as the metal electrode.

In this embodiment, the hole-transporting light-emitting layer of the organic compound layer 20 has a chemical formula (1) in which two biphenyl derivatives are bonded via the structure substituted by [A].

Embedded image And an organic compound represented by the formula: [A] in equation (1) is
It does not include a structure consisting of only a single carbon atom, that is, a structure in which two biphenyl derivatives are directly spiro-bonded. That is, [A] is a combination of (i) two or more carbon atoms, or (ii) one or more carbon atoms and a desired substituent or an atom other than carbon;
Or (iii) a configuration in which two biphenyl derivatives are directly connected at a plurality of positions without intervening atoms. Specifically, the structure of the chemical formula (3) in which the [A] portion has a double bond,
Alternatively, it is an organic compound having the structure of the chemical formula (4) having a ketone and a spiro bond.

In the structure in which the [A] portion is composed of a double bond of carbon and the two biphenyl derivatives are bonded in a conjugated system as in the compound of the chemical formula (3), π electrons are spread throughout the molecule. It is suitable because it exhibits extremely excellent fluorescence. In addition, chemical stability is high because the molecular structure is twisted. In the compound of the chemical formula (4), [A]
Is a single bond of carbon, the π electrons are localized in each of the two biphenyl derivative moieties, but the asymmetry of the molecular structure is high, and the presence of the carbonyl group causes the adhesion of the ITO to the first electrode 12. Is improved, and the durability of the organic EL element can be improved.

In the organic compounds represented by the chemical formulas (1), (3) and (4), R ₁ , R ₂ , R ₃ and R ₄ represent substituents. These substituents R ₁ , R ₂ , R ₃ , R ₄
Thereby, the electronic properties (e.g., luminous efficiency, luminescent color, hole transportability) of the organic compound can be improved. When large (bulky) substituents are used as the substituents R _{1 to} R ₄ , the substituents interfere with each other, causing steric hindrance.
The compound will have a twisted conformation. Such a twisted structure can suppress crystallization of the organic compound, and can provide a compound having a high glass transition temperature Tg and a high melting point Tm. By using such a compound, the heat resistance of the element can be improved. It becomes possible.

As R _{1 to} R ₄ , for example, the following Tables 1 and 2

[Table 1]

[Table 2] The following combinations can be adopted. For example,
The following chemical formulas (5), (6), (7)

Embedded image And the like are examples of specific configurations.

The organic compound represented by the formula (1), (3) or (4) described above can be used as a main light emitting material of the light emitting layer 22 also serving as a hole transport layer. Further, an organic compound of any of the above formulas (1), (3) and (4) is used as a host material of the hole transporting light emitting layer 22, and another light emitting material is doped into the host material as a doping material. It is also possible to form the light emitting layer 22.

Further, as shown in FIG.
It is also possible to set 2 to be a laminated structure of a single layer containing the organic compound of the above formulas (1), (3) and (4) as a main material and a doped layer into which the above-mentioned doping material is injected. Examples of the doping material include methylated quinacridone (Qd) represented by the following chemical formula (8) and a compound (DCM1) represented by the following chemical formula (9).

Embedded image Etc. can be used.

The organic compound represented by the chemical formula (1), (3) or (4) has a high hole-transporting property and a light-emitting property and has a small energy barrier with the electron-transporting layer. It is easy to inject, and by using this compound as the main light emitting material or host material of the light emitting layer, high efficiency,
High-brightness light emission can be realized. In addition, since the glass transition temperature Tg is high, a thin film state can be stably maintained for a long time even with high luminance light emission, which contributes to a longer life of the organic EL element.

Next, the hole transporting light emitting layer 22 and the second
The electron transport layer 24 provided between the electrode (cathode) 18 will be described. In the present embodiment, the electron transport layer 24
Has the general formula (2)

Embedded image Is used.

The organic compound represented by the chemical formula (2) has a high electron transporting property and a high Tg. In addition, the highest occupied molecular orbital (HOMO) level and the lowest unoccupied molecular orbital (LU
MO), the use of the layer as an electron transport layer makes it difficult for holes to pass through the layer, that is, exhibits a high hole blocking ability. Therefore, as described above, the hole transporting light emitting layer 22 using the compound of the general formula (1) capable of emitting light with high efficiency and high luminance, and the electron transporting layer 24 using the compound of the chemical formula (2) are used. In addition, an electron and a hole can be injected into the light emitting layer 22 very efficiently, and an organic EL device capable of emitting light with high luminance and high efficiency can be realized.

Here, in the general formula (2), Ar ₁ , A
r ₂ and Ar ₃ each represent an aryl group or an aromatic heterocyclic group. X ₁ , X ₂ and X ₃ each represent a substituent. n ₁ , n ₂ and n ₃ each represent an integer of 0 to 3.

The aryl groups represented by Ar ₁ , Ar ₂ and Ar ₃ may be the same or different from each other, and preferably have 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and still more preferably 6 to 6 carbon atoms. And 18 aryl groups, for example, phenyl, naphthyl, anthryl, phenanthryl, pyrenyl and the like.

The aromatic heterocyclic groups represented by Ar ₁ , Ar ₂ and Ar ₃ may be the same or different from each other, and are preferably 5- or 6-membered aromatic heterocycles, more preferably A heteroatom containing at least one of N, O, and S atoms, more preferably containing at least one N atom, and particularly preferably an aromatic having 2 to 12 carbon atoms containing at least one N atom. Group azole group.

Specific examples of the aromatic heterocycle include furyl, thienyl, imidazolyl, pyridyl, pyrimidyl, quinolyl, isoquinolyl, phthalazyl, naphthyridyl, quinoxalyl and the like, and preferably pyridyl, quinolyl and isoquinolyl. And more preferably quinolyl.

The aryl group or the aromatic heterocyclic group represented by Ar ₁ , Ar ₂ or Ar ₃ may be further condensed with another ring or may have a substituent. As this substituent, for example, an alkyl group (preferably having 1 to 30 carbon atoms, more preferably having 1 to 20 carbon atoms, and particularly preferably having 1 carbon atoms)
And for example, methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n
-Hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc.), alkenyl group (preferably having 2 to 30 carbon atoms, more preferably having 2 to 2 carbon atoms)
0, particularly preferably 2 to 10 carbon atoms, for example, vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), alkynyl group (preferably 2 to 30 carbon atoms,
More preferably, it has 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, for example, propargyl, 3-pentynyl and the like, and an aryl group (preferably 6 carbon atoms).
-30, more preferably 6-20 carbon atoms, particularly preferably 6-12 carbon atoms, for example, phenyl, p-methylphenyl, naphthyl, etc.), amino group (preferably 0-30 carbon atoms, Preferably 0 to 2 carbon atoms
0, particularly preferably 0 to 10 carbon atoms, such as amino, methylamino, dimethylamino, diethylamino,
Dibenzylamino, diphenylamino, ditolylamino and the like), an alkoxy group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 10 carbon atoms, for example, methoxy, ethoxy, Butoxy, 2-ethylhexyloxy and the like), an aryloxy group (preferably having 6 to 30 carbon atoms,
More preferably, it has 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, for example, phenyloxy, 1-naphthyloxy, 2-naphthyloxy, etc.), an acyl group (preferably 1 to 30 carbon atoms, More preferably, it has 1 to 20 carbon atoms, particularly preferably 2 to 12 carbon atoms, for example, acetyl, benzoyl, formyl, pivaloyl and the like, and an alkoxycarbonyl group (preferably 2 to 30 carbon atoms, more preferably 2 to 20, particularly preferably 2 to 12 carbon atoms, for example, methoxycarbonyl, ethoxycarbonyl and the like), aryloxycarbonyl group (preferably 7 to 30 carbon atoms,
More preferably, it has 7 to 20 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonyl and the like, and an acyloxy group (preferably 2 carbon atoms).
-30, more preferably 2-20 carbon atoms, particularly preferably 2-10 carbon atoms, for example, acetoxy, benzoyloxy, etc.), acylamino group (preferably 2-30 carbon atoms, more preferably carbon number). 2-20,
Particularly preferably, it has 2 to 10 carbon atoms, for example, acetylamino, benzoylamino, etc.), an alkoxycarbonylamino group (preferably having 2 to 30 carbon atoms,
More preferably, it has 2 to 20 carbon atoms, particularly preferably 2 to 12 carbon atoms, for example, methoxycarbonylamino and the like), aryloxycarbonylamino group (preferably 7 to 30 carbon atoms, more preferably 7 carbon atoms)
-20, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonylamino).
A sulfonylamino group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably
12, for example, methanesulfonylamino, benzenesulfonylamino, etc.), and a sulfamoyl group (preferably having 0 to 30, more preferably 0 to 20, and particularly preferably 0 to 12 carbon atoms. Sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl, etc.), a carbamoyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 carbon atom).
To 12, for example, carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl and the like), an alkylthio group (preferably having 1 carbon atom).
To 30, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, for example, methylthio, ethylthio and the like, and an arylthio group (preferably 6 to 30 carbon atoms, more preferably 6 carbon atoms). -20, particularly preferably 6 to 12 carbon atoms, such as phenylthio, etc.) and a sulfonyl group (preferably 1 carbon atom).
-30, more preferably 1-20 carbon atoms, particularly preferably 1-12 carbon atoms, for example, mesyl, tosyl, etc.), sulfinyl group (preferably 1-carbon
30, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methanesulfinyl and benzenesulfinyl, and a ureido group (preferably 1 to 30 carbon atoms, more preferably 1 to 30 carbon atoms). 1
To 20, particularly preferably 1 to 12 carbon atoms, for example, ureido, methylureide, phenylureide and the like, a phosphoric amide group (preferably 1 to 3 carbon atoms)
0, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as diethylphosphoramide, phenylphosphoramide, etc., a hydroxy group, a mercapto group, a halogen atom (for example, a fluorine atom ,
Chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably 1 to 1 carbon atoms
2, and examples of the hetero atom include, for example, a nitrogen atom, an oxygen atom, a sulfur atom, and specifically include, for example, imidazolyl, pyridyl, quinolyl, furyl, thienyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzothiazolyl, and the like. ), A silyl group (preferably having 3 to 40 carbon atoms, more preferably having 3 to 30 carbon atoms,
Particularly preferably, it has 3 to 24 carbon atoms, and examples thereof include trimethylsilyl and triphenylsilyl. These substituents may be further substituted. When there are two or more substituents, they may be the same or different. If possible, they may be linked to form a ring.

The substituents of Ar ₁ , Ar ₂ and Ar ₃ are preferably an alkyl group, alkenyl group, alkynyl group, aryl group, amino group, alkoxy group, aryloxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl Group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group,
A carbamoyl group, an alkylthio group, an arylthio group, a sulfonyl group, a halogen atom, a cyano group, or a heterocyclic group, more preferably an alkyl group, an alkenyl group, an aryl group, an alkoxy group, an aryloxy group, a halogen atom, a cyano group, or a heterocyclic group. It is a ring group, more preferably an alkyl group, an aryl group, an alkoxy group, an aryloxy group, or an aromatic heterocyclic group, and particularly preferably an alkyl group, an aryl group, an alkoxy group, or an aromatic heterocyclic group.

X ₁ , X ₂ and X ₃ each represent a substituent and may be the same or different from each other. X ₁ , X ₂ ,
Examples of the substituent represented by X ₃ include Ar ₁ , Ar ₂ ,
The substituents for Ar ₃ can be applied, and the preferred range is also the same.

N₁, N_TwoAnd n_ThreeAre 0 to
Represents an integer of 3, preferably 0, 1, or 2, more preferably
It is preferably 0 or 1, and more preferably 0. Ma
N ₁, N_Two, N_ThreeIs 2 or 3, a plurality of X₁, X
_Two, X_ThreeMay be the same or different from each other.

The structures of specific examples of the compound represented by formula (2) are shown below (chemical formulas (ii-1) to (ii-10)). Among these organic compounds, each has a glass transition temperature of 1
Chemical formulas (ii-1) and (ii-2) and (ii-8), which are as high as 35 ° C. and 180 ° C., are particularly preferred, but the organic compound of formula (2) is not limited to the following structure. Absent.

[0040]

Embedded image

Embedded image

Embedded image The general formula (2) is described above, and as specific examples, the above (ii-1) to (ii-10)
Organic compounds such as JP-B-44-23025, JP-B-48-8842, JP-A-53-6331, JP-A-10-92578, U.S. Pat.
9, 255, 5,766, 779; Am. C
hem. Soc. , 94, 2414 (1972), He.
lv. Chim. Acta, 63, 413 (198
0), Liebigs Ann. Chem. , 1423
(1982).

FIG. 4 shows an organic compound layer 20 similar to FIG.
2 shows a configuration of an organic EL device further provided with a hole injection layer 26. The hole injection layer 26 is a first hole of the organic EL element.
Of the second electrode and the second electrode, the positive electrode is formed between an electrode (anode) 12 to which a positive voltage is applied and the hole transporting light emitting layer 22 containing the organic compound of the general formula (1). As the hole injection layer 26, for example, the following chemical formula (10)

Embedded image Organic compounds such as starburst amine (m-MTDATA) shown in (1) can be used. By forming the hole injection layer 26 using such an organic compound, the adhesion between the first electrode (anode) 12 and the light-emitting layer 22 having a hole-transport property can be improved. Can be stabilized. In addition, the hole injection layer 26 using the above formula (10) has a small barrier with respect to the anode, so that the hole transporting light emitting layer can be more efficiently formed from the first electrode 12 through the hole injection layer 26. It becomes possible to inject holes into 22.
As shown in FIG. 3, the hole transporting light emitting layer 22 may have a laminated structure of a single layer and a doped layer.

[0042]

Next, an embodiment of the present invention will be described.

[Example 1: Organic EL device having a single hole-transporting luminescent layer: FIG. 2] (Example 1-1) In Example 1-1, an organic EL device having the structure shown in FIG. Was prepared. Organic EL according to the present embodiment
The element has a structure in which an anode 12, a hole transporting light emitting layer 22, an electron transporting layer 24, and a cathode 18 are sequentially formed on a glass substrate 10 from the glass substrate 10 side. A lead 30 is connected to each of the cathode 18 and the cathode 18 so that a voltage can be applied between the anode 12 and the cathode 18.

The anode 12 is an ITO film, and the glass substrate 1
0. The light-emitting layer 22 having a hole-transport property has a chemical formula (5)

Embedded image Was formed on the anode 12 with a thickness of 60 nm by a vacuum evaporation method. The electron transport layer 24 has a chemical formula (11)

Embedded image An organic compound represented by the following formula (same as the above chemical formula (ii-1)) was formed to a thickness of 60 nm by a vacuum evaporation method.

The cathode 18 is arranged in order from the electron transport layer 24 side.
It was composed of a laminate in which LiF was formed to 0.5 nm and Al was formed to 160 nm. The degree of vacuum when vacuum-depositing the organic compound layer and each layer of the cathode of the organic EL device according to Example 1 was 8 × 10 ⁻⁵ Pa.

The anode 12 of the obtained organic EL device (IT
When a positive voltage was applied to the O) side and a negative voltage was applied to the cathode 18 (Al) side, luminance-voltage characteristics as shown in FIG. 5 were obtained. In FIG. 5, the vertical axis represents luminance (cd / m
² ), the horizontal axis is the applied voltage (V). As shown in FIG. 5, in the obtained device, stable light emission was confirmed from a very low voltage. Also, 500c with only 4V applied voltage
A very high luminance of d / m ² was achieved, and blue-green light emission (emission peak wavelength: 490 nm) caused by the organic compound of the chemical formula (5) used for the light-emitting layer 22 was obtained.

When the change in light emission luminance with respect to the driving time was examined, it was found that the device of Example 1-1 had a luminance of 300 cd / cm.
It has been found that a half life of about 1000 hours can be achieved by continuous driving of m ² .

(Example 1-2) In Example 1-2, as in Example 1, the material for forming the electron transport layer 24 in the element configuration shown in FIG.

Embedded image An organic EL device was produced by using the same organic compound (same as the above formula (ii-2)), and using the same materials as in Example 1 except for the above.

A positive electrode is provided on the anode 12 side of the organic EL device.
When a negative voltage was applied to the cathode 18 side, a luminance-voltage characteristic as shown in FIG. 6 was obtained. In FIG. 6, the vertical axis represents luminance (cd / m ² ), and the horizontal axis represents applied voltage (V). As shown in FIG. 6, in the organic EL device according to Example 1-2, stable light emission was confirmed from a very low voltage. 513 cd with only 4 V applied voltage
/ M ^2, a very high luminance was achieved.
Similarly to the above, blue-green light emission (emission peak wavelength: 490 nm) resulting from the organic compound represented by the chemical formula (5) was obtained.

When the change in light emission luminance with respect to the driving time was examined, the device of Example 1-2 was found to be 300 cd / m 2.
It has been found that a half life of about 1200 hours can be achieved by the continuous driving of ² .

Example 1-3 In Example 1-3, the material of the hole transporting light emitting layer 22 was the same as that of Example 1-1, and the chemical formula (6) was used.

Embedded image Are used for the electron transport layer 24, and the organic compound represented by the same chemical formula (12) as in Example 1-2 is used, and the other steps are the same as those in Example 1-1.
An element was manufactured.

A plus electrode is provided on the anode 12 side of the organic EL device.
When a negative voltage was applied to the cathode 18 side, a luminance-voltage characteristic as shown in FIG. 7 was obtained. In FIG. 7, the vertical axis represents luminance (cd / m ² ), and the horizontal axis represents applied voltage (V).
It is. As shown in FIG. 7, also in the organic EL device according to Example 1-3, stable light emission was confirmed from a very low voltage. 445c with only 4V applied voltage
Light was emitted at an extremely high luminance of d / m ² , and blue-green light emission (emission peak wavelength: 500 nm) caused by the organic compound represented by the chemical formula (6) was obtained.

When the change in light emission luminance with respect to the driving time was examined, the device of Example 1-3 was found to be 300 cd / m 2.
It was found that a half life of about 1800 hours can be achieved by the continuous driving of No. ² .

(Comparative Example 1-1) As Comparative Example 1, an organic compound represented by the above chemical formula (5) was used as a material of the hole transporting light emitting layer 22 in the configuration shown in FIG. The electron transport material of the electron transport layer 24 is represented by a chemical formula (13)

Embedded image The widely used tris (8-quinolinol) aluminum (Alq) as shown in
The electron transport layer 24 was formed to a thickness of 60 nm. Other configurations are the same as those of the embodiment 1-1.

When a positive voltage was applied to the anode 12 and a negative voltage was applied to the cathode 18 of the obtained organic EL device of Comparative Example 1-1, the luminance-voltage characteristics as shown in FIG. 8 were obtained. In FIG. 8, the vertical axis represents luminance (cd / m ² ), and the horizontal axis represents applied voltage (V). The device according to Comparative Example 1-1 is:
At an applied voltage of 4 V, the emission colors were as in Examples 1-1 and 1-1-1.
Blue-green light emission (emission peak wavelength: 490 nm) as in 2.
However, with continuous driving of 300 cd / m ² , 50 cd / m ²
Only a brightness of m ² was obtained. Also, in Comparative Example 1-
The organic EL device according to No. 1 had a half life of 1500 hours when continuously driven at 300 cd / m ² .

Comparative Example 1-2 In Comparative Example 1-2, a chemical formula (1) was used as a hole transport material on ITO serving as the anode 12.
4)

Embedded image 60 nm using a diamine derivative (NPD) represented by
The thickness of the hole transport layer was formed. Next, using Alq (chemical formula (13)) as a light emitting material, a light emitting layer having a thickness of 20 nm, and an electron transporting material having the same chemical formula (1) as in Example 1-1.
An electron transport layer having a thickness of 40 nm was formed in this order by using the organic compound shown in 1), and an organic EL device having the same configuration as that of Example 1-1 was manufactured.

When a positive voltage was applied to the anode and a negative voltage was applied to the cathode of the organic EL device according to Comparative Example 1-2,
FIG. 9 shows the luminance-voltage characteristics. In FIG. 9, the vertical axis represents luminance (cd / m ² ), and the horizontal axis represents applied voltage (V).
It is. Under an applied voltage of 4 V, the emission color was green emission (emission peak wavelength: 520 nm) due to Alq, but only a luminance of 60 cd / m ² was obtained. In the organic EL device according to Comparative Example 1-2, 300
A half life of 1350 hours was shown by continuous driving at cd / m ² .

(Comparison between Example 1 and Comparative Example 1) The following Table 3 shows the results of Examples 1-1, 1-2, and 1--1.
3 and the characteristics of the organic EL device produced in Comparative Example 1-1, and Table 4 shows the characteristics of the organic EL device corresponding to Comparative Example 1-2.

[0059]

[Table 3]

[Table 4] As shown in Tables 3 and 4, a hole-transporting light-emitting layer using an organic compound represented by Formulas (5) and (6) having a chemical formula (3) as a basic structure, and a chemical formula (2) having a basic structure. Equation (1)
Comparative Examples 1-1 and 1-2 by providing both 1) and an electron transport layer using an organic compound represented by the formula (12).
It can be seen that high-luminance light emission can be obtained at an extremely low voltage even when compared with the other element as shown in FIG.

The reason why high-luminance light emission is produced at a low voltage is that the difference between the LUMO level of the hole-transporting light-emitting layer and the LUMO level of the electron-transporting layer is as described in Comparative Example 1-1. 1-
This is considered to be due to the fact that the electron injection from the electron transport layer to the light emitting layer is facilitated. In the device of Example 1, the difference between the HOMO level of the hole transporting light emitting layer and the HOMO level of the electron transporting layer is considered to be larger than the devices of Comparative Examples 1-1 and 1-2. This also hinders the injection of holes into the electron transporting layer, and the more efficient recombination of electrons and holes in the hole transporting light emitting layer is also considered to be a factor of higher efficiency.

Example 2: Organic EL device in which the hole-transporting luminescent layer has a doped layer: FIG. 3. Organic EL device according to Example 2
The device of Example 1 was similar to Example 1 in that the organic compound layer between the anode 12 and the cathode 18 had a layered structure of a hole transporting light emitting layer 22 and an electron transporting layer 24 from the anode side. Same as each element. However, in Example 2, as shown in FIG. 3, the light-emitting layer 22 is constituted by a single layer and a laminated structure having a dye-doped layer on the contact side with the electron transport layer 24. The organic compound of the general formula (1) is used as a host material, and another luminescent material (dye) is doped as a doping material.

Example 2-1 In Example 2-1
The anode 12 is an ITO film formed on the glass substrate 10, and a hole transporting light emitting layer 22 is formed on the anode 12. In forming the light emitting layer 22, first, a single layer of the organic compound represented by the chemical formula (5) is formed to a thickness of 40 nm by a vacuum evaporation method. Next, a doped layer was formed to a thickness of 20 nm so that the compound of the above formula (5) contained 1% of methylated quinacridone (Qd) shown in the above formula (8). That is, the layer containing the host material is 60 nm, and the doped layer containing the doped material is 20 nm.

On the doped layer, an organic compound represented by the above chemical formula (12) is used as an electron transporting material.
This was deposited to a thickness of 60 nm by a vacuum evaporation method to form an electron transport layer 24.

The cathode 18 is provided with Li from the electron transport layer 24 side.
A laminate obtained by laminating F with a thickness of 0.5 nm and Al with a thickness of 160 nm was used. The degree of vacuum when vacuum-depositing the organic layer and each layer of the cathode of this organic EL element is 8 × 10 ^−5.
Pa.

When a positive voltage was applied to the anode 12 and a negative voltage was applied to the cathode 18 of the obtained organic EL device according to Example 2-1, the luminance-voltage characteristics as shown in FIG. 10 were obtained. In FIG. 10, the vertical axis represents luminance (cd / m ² ),
The horizontal axis is the applied voltage (V). As shown in FIG. 10, it was confirmed that the device according to Example 2-1 emitted stable light from a very low voltage. Further, with an applied voltage of only 4 V, 622 cd / m ² higher than that of the device of Example 1 described above.
High brightness was achieved. In addition, light emission (emission peak wavelength: 530 nm) attributed to the methylated quinacridone of the above chemical formula (8) used as the doping material was obtained.

Further, when the change of the light emission luminance with respect to the driving time of the organic EL device of Example 2-1 was examined, the device of Example 2-1 was about 5000 hours by continuous driving of 300 cd / m ^2. It was also found that a very long half-life was achieved as compared with each element of Example 1.

Embodiment 2-2 In Embodiment 2-2, FIG.
In the configuration of Example 2-,
In place of Qd of 1, DCM represented by the above chemical formula (9)
1 was used. Other configurations and procedures were the same as those in Example 2-1.

When a positive voltage was applied to the anode 12 and a negative voltage was applied to the cathode 18 of the obtained organic EL device according to Example 2-2, the luminance-voltage characteristics as shown in FIG. 11 were obtained. In FIG. 11, the vertical axis represents luminance (cd / m ² ),
The horizontal axis is the applied voltage (V). As shown in FIG. 11, also in the device according to Example 2-2, stable light emission was confirmed from a very low voltage, and further, with a very high luminance of 572 cd / m ² at an applied voltage of only 4 V. Light emission was achieved. In addition, orange light emission (emission peak wavelength: 575 nm) resulting from DCM1 of Chemical Formula (9) used as the dope material was obtained.

When the change in light emission luminance with respect to the driving time was examined, the device of Example 2-2 was found to be 300 cd /
In Example 2, the continuous driving of m ² was about 4600 hours.
As in the case of No. 1, it was found that a very long half-life was achieved even when compared with the devices of Example 1.

(Comparative Example 2) As Comparative Example 2, a structure similar to that of Example 2 was used, and the electron transporting material represented by the chemical formula (13) was used.
Was manufactured using Alq shown in (1) and a layer formed to a thickness of 60 nm.

When a positive voltage was applied to the anode 12 and a negative voltage was applied to the cathode 18 of the organic EL device, the luminance-voltage characteristics as shown in FIG. 12 were obtained. In FIG. 12, the vertical axis represents luminance (cd / m ² ), and the horizontal axis represents applied voltage (V). As shown in FIG. 12, the obtained device emits light (peak emission wavelength: 530 nm) from methylated quinacridone (Qd) represented by the chemical formula (8) at a luminance of 231 cd / m ² when a voltage of 4 V is applied. Obtained.

When the change in light emission luminance with respect to the driving time was examined, the device of Comparative Example 2 achieved a half life of about 5,400 hours by continuous driving at 300 cd / m ² .

(Comparison between Example 2 and Comparative Example 2)
13 shows the characteristics of the organic EL elements according to Example 2 (2-1 and 2-2) and Comparative Example 2.

[0074]

[Table 5] From Table 5, it can be seen that the organic compound of the formula (5) represented by the general formula (3) is used as a host material, and the host material is doped with a dye. It can be seen that the emission color can be adjusted. Also, in the element structure doped with a dye, by using an organic compound represented by the general formula (2) as an electron transport material to constitute an organic EL element, Alq is used as an electron transport material as in Comparative Example 2. It can be seen that low-voltage and high-luminance light emission can be obtained as compared with the element which was used.

Example 3 As Example 3, a synthesis example of the organic compounds of the above-mentioned chemical formulas (7), (5) and (6) will be described.

The method of synthesizing the compounds of the formulas (7) and (5) will be described according to the following reaction formula (X).

[0077]

Embedded image A spiro ketone having a tetraamino group represented by the formula (7) is
It can be prepared by the method shown in the upper part of the reaction formula (X).

(Compound A to Compound B) Palladium acetate and this tri-t-butylphosphine (1: 4 molar ratio) are previously mixed in xylene to prepare a catalyst solution. 2,7-dibromo-9-fluorenone (4.
06 g: 12 mmol) and 2 equivalents of 1-
Naphthyl phenylamine and 2.4 equivalents of sodium t
A xylene mixture of butoxide was added under a nitrogen atmosphere in an amount corresponding to 1 mol% of the above catalyst solution, and the mixture was kept at 120 ° C. for 3 hours. After benzene extraction, the product was subjected to a conventional treatment and the product was purified by column chromatography to obtain 2,7-bis (diphenylamino) -9-fluorenone shown in Compound B. The melting point of the obtained compound B was 217 ° C to 218 ° C.

(Compound B to Compound C of Chemical Formula (7))
2,7-bis (diphenylamino) shown in compound B
3.60 g (7 mmol) of -9-fluorenone and 1
Mix 5 g of triethyl phosphite [P (OEt) ₃ ]
When heated at 140 ° C. for 24 hours in a nitrogen atmosphere, the raw materials almost disappeared. The reaction mixture is concentrated under reduced pressure, separated and dried with benzene or chloroform, and the obtained crude product is purified by column chromatography to obtain a compound represented by the chemical formula (7).
3.8 g (75% yield) of the compound C shown in the above was obtained. The melting point of the obtained compound represented by the chemical formula (7) is
It was 300 ° C or higher. A glass transition temperature was observed at about 140 ° C.

(Compound C of Chemical Formula (7) to Compound of Chemical Formula (5)) 0.30 mmol of spiro ketone (C) represented by chemical formula (7) is added to excess (4.0 mmol) of lithium aluminum hydride (LiAlH ₄ ). At room temperature for 20 minutes in anhydrous tetrahydrofuran (THF) to give the corresponding compound (C-1) shown in Reaction Formula (X).
A dimeric alcohol was produced. The yield was 76%. Next, the crude product of the compound represented by (C-1) was treated with acetic acid (A
cOH) in small amounts of methanesulfonic acid (MeSO ₃ H)
At the same time, the mixture was heated at 40 ° C. for 45 minutes. As a result, the desired compound represented by the chemical formula (5) was obtained at a yield of 96%. The compound of formula (5) was purified by silica gel column chromatography to obtain pale yellow crystals (yield after purification: 70%). Glass transition temperature T
g was 152 ° C., and the melting point was 313 ° C. to 314 ° C., but it melted once at 186 ° C. to 187 ° C., and then showed a property of crystallization. In addition, a large amount of CHCl
It was not soluble unless it was ₃ or PhH, and was insoluble in acetone.

(Compound of Chemical Formula (6)) A method of synthesizing the compound represented by the chemical formula (6) will be described according to the following chemical reaction formula (Y).

[0082]

Embedded image The compound of the chemical formula (6) is represented by the following formula (X):
A compound obtained by substituting one phenyl group of the diphenylamino group of the spiro ketone shown by (C) with a naphthyl group is reacted in the same manner as in the middle part of the reaction formula (X) to obtain a dimer alcohol (C-1) (C-2) of the compound (Reaction formula (Y)) corresponding to

Next, in this reaction formula (Y), 0.6 mmol of the dimer alcohol represented by (C-2) was added to acetic acid (Ac
OH) with a small excess of methanol (MeOH) at 60 ° -70 ° C. for 1 hour. As a result, the desired compound represented by the chemical formula (6) was obtained in a yield of 74%. The obtained chemical substance was a yellow crystal, had a glass transition temperature Tg of 154 ° C, and a melting point of 199 ° C to 204 ° C. Unlike the chemical formula (5), the compound of the chemical formula (6)
There was no crystallization after melting at ° C.

[0084]

As described above, according to the present invention, a hole-transporting luminescent material represented by the general formula (1):
By using the electron transporting material represented by the general formula (2), an organic EL device capable of emitting light at a low voltage and high luminance is realized as compared with a device having a conventional hole transporting light emitting layer. can do.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of an organic EL element.

FIG. 2 is a diagram showing a configuration of an organic EL device of the present invention.

FIG. 3 is a diagram showing another configuration of the organic EL device of the present invention, which is different from FIG.

FIG. 4 is a view showing another structure of the organic EL device of the present invention, which is different from FIGS. 2 and 3.

FIG. 5 is a diagram showing a luminance-voltage characteristic of the organic EL element of Example 1-1.

FIG. 6 is a diagram showing a luminance-voltage characteristic of the organic EL element of Example 1-2.

FIG. 7 is a diagram showing a luminance-voltage characteristic of the organic EL element of Example 1-3.

FIG. 8 is a diagram showing a luminance-voltage characteristic of the organic EL element of Comparative Example 1-1.

FIG. 9 is a diagram showing luminance-voltage characteristics of the organic EL element of Comparative Example 1-2.

FIG. 10 is a diagram showing a luminance-voltage characteristic of the organic EL element of Example 2-1.

FIG. 11 is a graph showing the luminance-voltage characteristics of the organic EL device of Example 2-2.

FIG. 12 is a diagram showing a luminance-voltage characteristic of the organic EL element of Comparative Example 2.

[Explanation of symbols]

Reference Signs List 10 glass substrate, 12 first electrode (transparent electrode, anode), 18 second electrode (metal electrode, cathode), 20 organic compound layer, 22 hole transporting light emitting layer, 24 electron transporting layer.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05B 33/22 H05B 33/22 DB // C07C 211/61 C07C 211/61 C07D 471/04 112 C07D 471 / 04 112X 519/00 311 519/00 311 (72) Inventor Shizuki Tokito 41 No. 1 Yokomichi Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Institute, Inc. (72) Inventor Koji Noda Aichi, Aichi (41) Inside the Toyota Central Research Institute, Inc. (72) Inventor Yasunori Taga 41, Toyoda Central Research Institute Co., Ltd. Person Hisashi Okada 210 Nakanuma, Minamiashigara, Kanagawa Prefecture Inside Fuji Photo Film Co., Ltd. (72) Inventor Makoto Kimura Hachi, Minato-ku, Nagoya-shi, Aichi Prefecture Shima 2-401 (72) Inventor Yasuhiko Sawaki 56-404 Ishikane, Iwasaki-cho, Nisshin-shi, Aichi F-term (reference) 3K007 AB02 AB03 AB04 CA01 CA02 CB01 DA01 DB03 EB00 4C065 AA04 BB09 CC09 DD02 EE02 HH01 JJ04 LL04 PP01 4C072 MM02 UU05 4H006 AB92 BJ50 BR70 BU48

Claims (4)

[Claims] 1. An organic electroluminescent device comprising a plurality of organic compound layers between a first electrode and a second electrode, wherein the organic compound layer has the following chemical formula (1): (In the formula (1), R _{1 to} R
₄ is a substituent, [A] is a configuration having 2 or more carbon atoms, or a combination configuration of 1 or more carbon atoms and a desired substituent or a non-carbon atom, or two biphenyl derivatives without intervening atoms Is one of the configurations in which the compound is directly connected at a plurality of positions), and a light-emitting layer having a hole-transporting property, and the following chemical formula (2): An organic compound represented by the formula (wherein, Ar ₁ , A
r ₂ and Ar ₃ are each an aryl group or an aromatic heterocyclic group, X ₁ , X ₂ and X ₃ are each a substituent, and n ₁ , n ₂ and n ₃ are each an integer of 0 to 3 An organic electroluminescent device comprising: an electron transport layer comprising: 2. The organic electroluminescent device according to claim 1, wherein the hole transporting light emitting layer has a predetermined doping material doped in a host material, and the host material is represented by the following chemical formula (1). An organic electroluminescent device comprising the organic compound shown in the following. 3. The organic electroluminescent device according to claim 1, wherein the organic compound represented by the formula (1) is represented by the following chemical formula (3) or (4): Embedded image An organic electroluminescent device, which is a compound represented by any one of the above. 4. The organic electroluminescent device according to claim 1, wherein an electrode to which a positive voltage is applied among the first and second electrodes, and the hole transporting property. An organic electroluminescent device comprising a hole injection layer between the organic electroluminescent device and the light emitting layer.