JP2002275179A - Benzimidazole derivative and organic electroluminescent device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent device material having an excellent effect of blocking holes and an effect of injecting electrons into a light emitting layer and producing a stable amorphous thin film. SOLUTION: The benzimidazole derivative represented by the general formula (1) is used as an organic electroluminescent device material. Embedded image

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 which is a self-luminous device suitable for various display devices.

[0002]

2. Description of the Related Art In an organic electroluminescent device, charges injected from both electrodes are recombined in a light emitting layer to obtain light emission. However, there is a problem that a part of the charges pass through the light emitting layer to lower efficiency. Becomes On the other hand, it has been proposed to insert a hole blocking layer or an electron blocking layer for the purpose of improving the probability of charge recombination in the light emitting layer or for obtaining light emission in an arbitrary organic layer.

[0003] Compounds suitable for the hole blocking layer have hitherto been
A triazole derivative (JP-A-7-41759), an aluminum mixed ligand complex, and an aluminum binuclear complex (JP-A-11-40367) have been proposed. Attempts to make the hole transport layer emit light by using bathocuproine as a hole blocking layer (MRS98 Spring Metting G2.1, 19)
98). However, any of the materials has not been able to obtain satisfactory device characteristics because of insufficient film stability or insufficient hole blocking function.

[0004]

SUMMARY OF THE INVENTION The present invention has the effect of preventing holes and improving the efficiency of injecting electrons into the light emitting layer when applied to an organic electroluminescent device. It is an object of the present invention to provide an organic electroluminescent device material that is formed to form a highly efficient and highly durable organic electroluminescent device.

[0005]

Means for Solving the Problems The present inventors have found that a novel benzimidazole derivative has an effect of blocking holes and an effect of improving the efficiency of electron injection into a light emitting layer, and furthermore, produces a stable amorphous thin film. And completed the present invention. That is, the present invention is a benzimidazole derivative represented by the general formula (1).

[0006]

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Wherein R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aralkyl group, and Ar ₁ represents a substituted or unsubstituted aromatic hydrocarbon group, X represents a substituted aromatic heterocyclic group or a substituted or unsubstituted aliphatic cyclic hydrocarbon group, and X represents a substituted or unsubstituted amino group substituted with two substituted or unsubstituted aromatic hydrocarbon groups. An aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group having an amino group substituted with two substituted or unsubstituted aromatic hydrocarbon groups, or two substituted or unsubstituted aromatic heterocyclic groups; A substituted or unsubstituted aromatic hydrocarbon group having a substituted amino group, or a substituted or unsubstituted aromatic compound having an amino group substituted by two substituted or unsubstituted aromatic heterocyclic groups; An elementary ring group, a substituted or unsubstituted aromatic hydrocarbon group or a substituted or unsubstituted aromatic heterocyclic group (in the case where the general formula (1) becomes a symmetrical form by the substitution of the aromatic heterocyclic group, Excluding). ]

Further, the present invention is a benzimidazole derivative represented by the general formula (2) or (3) having a quinolyl group.

[0009]

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[Wherein, R ₁ represents the same group as defined above, and R ₂ independently of R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aralkyl group. , Ar ₁ represents the same group as defined above, Ar ₂ represents a divalent group represented by the following (A) to (F),

[0011]

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(Wherein R ₃ and R ₄ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aralkyl group;
Represents an integer of to 5, Ar ₄ and Ar ₅ represent a substituted or unsubstituted aromatic hydrocarbon group, and Y represents an oxygen atom, a sulfur atom, a substituted or unsubstituted methylene group, or the following (a) to
It represents a divalent group represented by (g). )

[0013]

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(Where R₅, R₆Are independently hydrogen sources
Atom, halogen atom, alkyl group, alkenyl group, alcohol
Represents a xy group, an aryl group, or an aralkyl group; Ar₆, Ar₇
Are independently substituted or unsubstituted aromatic hydrocarbons
Group, substituted or unsubstituted aromatic heterocyclic group or substituted
Or an unsubstituted aliphatic cyclic hydrocarbon group, Ar₈, Ar
₉Are independently substituted or unsubstituted aromatic hydrocarbons
Represents an elementary group. ) Ar_ThreeIs a substituted or unsubstituted aromatic hydrocarbon group,
Or unsubstituted diphenylaminophenyl group or substitution
Alternatively, it represents an unsubstituted aromatic heterocyclic group. ] Used in the above definition of benzimidazole derivatives
Where the aryl group and aromatic hydrocarbon group are fused polycyclic groups
Needless to say, it contains. Similarly, the aromatic complex
A ring group includes a heterocyclic group in which a plurality of rings are fused.
Not even.

Further, the present invention is characterized in that the benzimidazole derivative represented by the general formula (1) is used as a constituent material of a pair of electrodes and at least one organic layer sandwiched therebetween. An element, wherein a benzimidazole derivative represented by the general formula (2) or (3) is used as a constituent material of a pair of electrodes and at least one organic layer interposed therebetween. An organic electroluminescent device.

In the organic electroluminescent device of the present invention, the pair of electrodes and at least one organic layer interposed therebetween can function as a hole blocking layer. By using a benzimidazole derivative represented by the general formula (1), (2) or (3) as a constituent material of the hole blocking layer, holes are injected into the electron transport layer. Can be suppressed. Therefore, since the hole blocking property and the electron transport property are superior to those of the conventional material, the efficiency of the device is improved and the durability is improved.

In the organic electroluminescent device of the present invention, the pair of electrodes and at least one organic layer interposed therebetween can function as an electron transport layer. By using a benzimidazole derivative represented by the general formula (1), the general formula (2) or the general formula (3) as a constituent material of the electron transporting layer, electrons injected from the electrode can be efficiently transmitted to the light emitting region. Can be transported. Further, by using the material of the present invention having a small energy gap as a constituent material of the electron transport layer, the efficiency of electron injection from the electron transport layer to the light emitting layer is improved.

In the organic electroluminescent device of the present invention, the above-mentioned pair of electrodes and at least one organic layer interposed therebetween can function as a light-emitting layer. When a benzimidazole derivative represented by the general formula (1), the general formula (2) or the general formula (3) is used as a constituent material of the light emitting layer, the light emitting layer also functions as a hole transport layer or an electron transport layer. Thus, an organic electroluminescent device having a simple structure and easy manufacture can be realized.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Specific examples of the benzimidazole derivative of the present invention are as follows. (1) 1- [4 ′-(N-phenyl-N-quinoline-3-
(Ilamino) biphenyl-4-yl] -2-phenylbenzimidazole (2) 1- [4 '-(N-phenyl-N-quinoline-6
(Illamino) biphenyl-4-yl] -2-phenylbenzimidazole (3) 1- [6- (N-phenyl-N-quinoline-3-
(Illamino) pyren-1-yl] -2-phenylbenzimidazole (4) 1- [4- (N-phenyl-N-quinoline-3-
(Ylamino) phenyl] -2-phenylbenzimidazole (5) N- [4- (2-phenylbenzimidazole-
1-yl) biphenyl-1-yl] -N- [4- (N-
Phenyl-N-quinolin-3-ylamino] aniline (6) 1- [5- (N, N-di (1-naphthyl) amino) anthracen-1-yl] -2-phenylbenzimidazole (7) 1-pyrenyl 2- (1-naphthyl) benzimidazole (8) 1- (3-quinolyl) -2- (1-anthranyl) benzimidazole (9) 1- [4 ′-(N-phenyl-N-isoquinoline-
4-ylamino) biphenyl-4-yl] -2-phenylbenzimidazole (10) 1- [4 '-(N-phenyl-N-carbazol-3-ylamino) biphenyl-4-yl] -2-phenylbenzimidazole (11) 1- [4 ′-(N- (4-methylphenyl) -N
-(6-Methylquinolin-3-ylamino) biphenyl-4-yl] -2-phenylbenzimidazole (12) 9- [4- (2-phenylbenzimidazol-1-yl) phenyl] -9- [4- (N-phenyl-
N-quinolin-3-ylamino) phenyl] fluorene (13) 1- [4- (N, N-bis (3-quinolyl) amino) phenyl] -2-phenylbenzimidazole

Hereinafter, embodiments of the present invention will be specifically described with reference to examples.

EXAMPLES (Example 1) 1- [4 '-(N-phenyl-N
-Quinolin-3-ylamino) biphenyl-4-yl]
Synthesis of 2-phenylbenzimidazole (compound (4))

[0021]

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1- [4 '-(N-phenylamino) biphenyl-4-yl] -2-phenylbenzimidazole 3.0 g, 3-bromoquinoline 1.7 g, potassium carbonate 1.5 g, copper powder 0.12 g , N-heptadecane 30 mL
And heated to reflux and stirred for about 40 hours under a nitrogen atmosphere. The reaction product was extracted with 200 mL of toluene, and the insoluble matter was separated by filtration. The crude product obtained by concentrating the filtrate was purified by column chromatography using silica gel. The light yellow powder obtained by purification is 2.4 g,
The yield was 62% and the melting point was 110-130 ° C. When the obtained pale yellow powder was analyzed by mass spectrum, a main peak having a molecular weight of 565 corresponding to the compound (4) was detected. From the results of the above mass spectrum analysis, the structure of the compound (4) was identified.

(Example 2) The work function of the benzimidazole derivative (compound (4)) of the present invention in Example 1 was measured using a surface analyzer AC1 (manufactured by Riken Keiki), and the band gap determined from the absorption spectrum was measured. Was used to determine the electron affinity. Further, these values are shown in [Table 1] in comparison with compound (5) which is a typical hole transport material.

[0024]

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[0025]

[Table 1]

As shown in Table 1, the benzimidazole derivative of the present invention has a clearly higher work function than conventional typical hole transport materials, and is suitable as a hole blocking material. Moreover, since the benzimidazole derivative of the present invention has a high electron affinity, it has an effect that high efficiency can be obtained in injecting electrons into the light emitting layer.

Example 3 The benzimidazole derivative (compound (4)) of the present invention in Example 1 was subjected to DSC
Thermal analysis was performed using a differential scanning calorimeter (manufactured by Mac Science), but no endothermic peak (melting point) due to melting of the crystal was observed. When the deposited film of this compound and the deposited film of α-NPD (compound (6)), which is a general-purpose hole transport material, were stored at 25 ° C., the deposited film of α-NPD became 1
Compound (4), which crystallized within a month and became cloudy
The deposited film was transparent without change after two months. From these results, it was revealed that the benzimidazole derivative of the present invention was able to obtain an extremely stable amorphous thin film.

[0028]

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(Example 4) An ITO transparent electrode film was formed as an anode on a glass substrate, and then a compound (5) of 50 nm as a hole transport layer and a light emitting layer, and a compound of the present invention as a hole blocking layer were formed thereon. Benzimidazole derivative (compound (4))
25 nm, tris (8-hydroxyquinolinato) aluminum as an electron transport layer 25 nm, Al as a cathode
Was formed to a thickness of 100 nm to produce an organic electroluminescent device. The organic layer and the cathode were formed under a vacuum of 10 ⁻⁴ Pa. When a voltage was applied to the manufactured element, a current of 108 mA / cm ² flowed when 10 V was applied, and blue light emission was obtained. Light emission luminance was 72 cd / m ² .

Comparative Example 1 An organic electroluminescent device was manufactured in the same manner as in Example 4, except that bathocuproine was used as the hole blocking layer. When voltage was applied to the fabricated device, it was found to be 94 mA / cm ² when 14 V was applied.
And a blue light emission was obtained. Light emission brightness is 41
cd / m ² .

From the results of Example 4 and Comparative Example 1, Example 4
Of the benzimidazole derivative of the present invention (compound (4))
Both of the voltage-current characteristics and the current-luminance characteristics of the organic electroluminescent device using the same were superior to the organic electroluminescent device of the comparative example, and the efficiency was high.

[0032]

The benzimidazole derivative of the present invention has the effect of blocking holes and the effect of improving the efficiency of electron injection into the light emitting layer, and forms a stable amorphous thin film. Therefore, the use of the benzimidazole derivative of the present invention has an effect that an organic electroluminescent element capable of emitting light with stability and high efficiency can be produced.

Claims (7)

[Claims] 1. A benzimidazole derivative represented by the general formula (1). Embedded image [Wherein, R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aralkyl group, and Ar ₁ represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic group. X represents a substituted or unsubstituted aliphatic hydrocarbon group, or a substituted or unsubstituted aromatic hydrocarbon group having an amino group substituted by two substituted or unsubstituted aromatic hydrocarbon groups. A hydrogen group, a substituted or unsubstituted aromatic heterocyclic group having an amino group substituted by two substituted or unsubstituted aromatic hydrocarbon groups, or a substituted or unsubstituted aromatic heterocyclic group substituted by two substituted or unsubstituted aromatic heterocyclic groups A substituted or unsubstituted aromatic hydrocarbon group having an amino group, a substituted or unsubstituted aromatic heterocyclic group having an amino group substituted by two substituted or unsubstituted aromatic heterocyclic groups, Alternatively, it represents an unsubstituted aromatic hydrocarbon group or a substituted or unsubstituted aromatic heterocyclic group (excluding a case where the whole of the general formula (1) becomes symmetrical due to the substitution of the aromatic heterocyclic group). ] 2. A compound of the general formula (2) having a quinolyl group or
The benzimidazo according to claim 1, which is represented by the general formula (3).
Derivatives. Embedded image[Where R₁Represents the same group as defined above, and R_TwoIs R₁When
Independently hydrogen, halogen, alkyl, alkenyl
Group, an alkoxy group, an aryl group or an aralkyl group
Represents, Ar₁Represents the same group as defined above, and Ar₂Is next
Represents a divalent group represented by (A) to (F),(Where R_Three, R₄Are independently a hydrogen atom and a halogen
Atom, alkyl group, alkenyl group, alkoxy group, ant
Represents an aryl group or an aralkyl group, and n is an integer of 1 to 5.
Represents, Ar_Four, Ar₅Is a substituted or unsubstituted aromatic hydrocarbon
Y represents an oxygen atom, a sulfur atom, substituted or unsubstituted
A substituted methylene group, or represented by the following (a) to (g)
Represents a divalent group. )(Where R₅, R₆Are independently a hydrogen atom and a halogen
Atom, alkyl group, alkenyl group, alkoxy group, ant
Aralkyl group, Ar₆, Ar₇Is German
Standing or unsubstituted aromatic hydrocarbon groups,
Or unsubstituted aromatic heterocyclic group or substituted or unsubstituted
Represents an aliphatic cyclic hydrocarbon group of₈, Ar ₉Are each
Independently substituted or unsubstituted aromatic hydrocarbon groups
You. ) Ar_ThreeIs a substituted or unsubstituted aromatic hydrocarbon group,
Or unsubstituted diphenylaminophenyl group or substitution
Alternatively, it represents an unsubstituted aromatic heterocyclic group. ] 3. An organic electroluminescent device having a pair of electrodes and at least one organic layer sandwiched between the pair of electrodes comprises a benzimidazole derivative represented by the following general formula (1) as a constituent material of at least one organic layer. An organic electroluminescent device, comprising: Embedded image [Wherein, R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aralkyl group, and Ar ₁ represents a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic group. X represents a substituted or unsubstituted aliphatic hydrocarbon group, or a substituted or unsubstituted aromatic hydrocarbon group having an amino group substituted by two substituted or unsubstituted aromatic hydrocarbon groups. A hydrogen group, a substituted or unsubstituted aromatic heterocyclic group having an amino group substituted by two substituted or unsubstituted aromatic hydrocarbon groups, or a substituted or unsubstituted aromatic heterocyclic group substituted by two substituted or unsubstituted aromatic heterocyclic groups A substituted or unsubstituted aromatic hydrocarbon group having an amino group, a substituted or unsubstituted aromatic heterocyclic group having an amino group substituted with two substituted or unsubstituted aromatic heterocyclic groups, Alternatively, it represents an unsubstituted aromatic hydrocarbon group or a substituted or unsubstituted aromatic heterocyclic group (except in the case where the whole of the general formula (1) becomes symmetric due to the substitution of the aromatic heterocyclic group). ] 4. The method according to claim 1, wherein the at least one organic layer is
Having a quinolyl group represented by the general formula (2) or (3)
Characterized by being a benzimidazole derivative
The organic electroluminescent device according to claim 3. Embedded image[Where R₁Represents the same group as defined above, and R_TwoIs R₁When
Independently hydrogen, halogen, alkyl, alkenyl
Group, an alkoxy group, an aryl group or an aralkyl group
Represents, Ar₁Represents the same group as defined above, and Ar₂Is next
Represents a divalent group represented by (A) to (F),(Where R_Three, R₄Are independently a hydrogen atom and a halogen
Atom, alkyl group, alkenyl group, alkoxy group, ant
Represents an aryl group or an aralkyl group, and n is an integer of 1 to 5.
Represents, Ar_Four, Ar₅Is a substituted or unsubstituted aromatic hydrocarbon
Y represents an oxygen atom, a sulfur atom, substituted or unsubstituted
A substituted methylene group, or represented by the following (a) to (g)
Represents a divalent group. )(Where R₅, R₆Are independently a hydrogen atom and a halogen
Atom, alkyl group, alkenyl group, alkoxy group, ant
Aralkyl group, Ar₆, Ar₇Is German
Standing or unsubstituted aromatic hydrocarbon groups,
Or unsubstituted aromatic heterocyclic group or substituted or unsubstituted
Represents an aliphatic cyclic hydrocarbon group of₈, Ar ₉Are each
Independently substituted or unsubstituted aromatic hydrocarbon groups
You. ) Ar_ThreeIs a substituted or unsubstituted aromatic hydrocarbon group,
Or unsubstituted diphenylaminophenyl group or substitution
Alternatively, it represents an unsubstituted aromatic heterocyclic group. ] 5. The organic electroluminescent device according to claim 3, wherein the at least one organic layer is a hole blocking layer.
The organic electroluminescent device according to claim 1. 6. The method according to claim 3, wherein the at least one organic layer is an electron transport layer.
The organic electroluminescent device according to claim 1. 7. The organic electroluminescent device according to claim 3, wherein at least one organic layer is a light emitting layer, and the light emitting layer also functions as a hole transporting layer or an electron transporting layer. .