JPH06228545A - Organic electroluminescent element - Google Patents

Abstract

PURPOSE:To obtain a thin-film EL element having a high luminescent intensity and an excellent stability in repeated use by incorporating a specific bisazo compd. into an org. EL element contg. a phosphor. CONSTITUTION:At least one bisazo compd. of the general formula: Cp-N=N-Az- N=N-Cp [wherein Az is an azo component of the formula (wherein X<1> to X<10> are each independently H, O, halogen, alkoxy, cycloalkyl, an aliph. or arom. hydrocarbon group, heterocyclic, etc., provided two of them are bonded to the azo groups); and Cp is a coupler group] is incorporated into an EL element which at least has a phosphor between a pair of electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (EL) element used for a flat light source or a display.

[0002]

2. Description of the Related Art An EL element using an organic substance is promising for use as a solid-state light-emitting type inexpensive large-area full-color display element, and many developments have been made. Generally EL
Is composed of a light emitting layer and a pair of counter electrodes sandwiching the light emitting layer. In light emission, when an electric field is applied between both electrodes, electrons are injected from the cathode side and holes are injected from the anode side. Further, this is a phenomenon in which the electrons are recombined with holes in the light emitting layer, and energy is emitted as light when the energy level returns from the conduction band to the valence band.

A conventional organic EL element has a higher driving voltage and lower emission brightness and emission efficiency than an inorganic EL element.
In addition, the deterioration of the characteristics was remarkable and it was not put to practical use.
In recent years, an organic EL in which thin films containing an organic compound having a high fluorescence quantum efficiency that emits light at a low voltage of 10 V or less are laminated
The device has been reported and is of great interest (see Applied Physics Letters, 51, 913, 1987). In this method, a metal chelate complex is used for the phosphor thin film layer and an amine compound is used for the hole injection layer to obtain high-luminance green light emission, and the luminance is several 1 at a DC voltage of 6 to 7V.
The maximum luminous efficiency is 00 cd / m ² and the maximum luminous efficiency is 1.5 lm / W, which is close to the practical range.

However, although the organic EL device up to the present time has improved the emission intensity due to the improved structure, it has a serious problem that it is inferior in stability during repeated use. Therefore, under the present circumstances, there is a demand for the development of an organic EL element having a larger light emission intensity and excellent stability in repeated use.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film EL device having a large emission intensity and excellent stability in repeated use. As a result of intensive studies by the present inventors, an organic E having at least a phosphor between a pair of electrodes
In the L element, it was found that the organic EL element containing the bisazo compound had a large emission intensity of 0 and the stability during repeated use was excellent, and the present invention was completed.

[0006]

That is, the first invention is an electroluminescence device having a layer containing at least a phosphor between a pair of electrodes, which is an organic electroluminescence device containing a bisazo compound. . A second invention is an electroluminescence device having a layer containing at least a phosphor between a pair of electrodes, which is an organic electroluminescence device containing at least one of the bisazo compounds represented by the general formula [1]. . General formula [1] Cp-N = N-Az-N = N-Cp In the formula, Az is an azo component represented by the general formula [2]. General formula [2]

[0007]

[Chemical 11]

Here, Cp represents a coupler group, and X ¹
To X ¹⁰ are each independently a hydrogen atom, an oxygen atom,
Halogen atom, cyano group, nitro group, amino group, dialkyloamino group, diphenylamino group, hydroxyl group, alkoxy group, mercapto group, siloxy group, acyl group, cycloalkyl group, carboxylic acid group, sulfonic acid group, substituted or unsubstituted It represents an aliphatic hydrocarbon group, a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group. Further, it may be an aromatic ring which may have a substituent, an aromatic ring containing a hetero atom or a hetero ring. X ¹ to X ¹⁰ may have any substituent, may form an aromatic ring or a heterocycle between the substituents, and may form a complex with a metal. Two of X ¹ to X ¹⁰ are bonded to the azo group.

A third aspect of the present invention is an electroluminescent device having a layer having at least a phosphor between a pair of electrodes, wherein the coupler group of the compound represented by the general formula [1] is represented by the general formula [3]. An organic electroluminescence device containing at least one of [11] to [11].

General formula [3]

[Chemical 12]

General formula [4]

[Chemical 13]

General formula [5]

[Chemical 14]

General formula [6]

[Chemical 15]

General formula [7]

[Chemical 16]

General formula [8]

[Chemical 17]

General formula [9]

[Chemical 18]

General formula [10]

[Chemical 19]

General formula [11]

[Chemical 20]

Here, Y ¹ to Y ¹² are each independently a hydrogen atom, an oxygen atom, a halogen atom, a cyano group, a nitro group, an amino group, a dialkylamino group, a diphenylamino group, a hydroxyl group, an alkoxy group, a mercapto group, Siloxy group, acyl group, cycloalkyl group, carboxylic acid group, sulfonic acid group, substituted or unsubstituted aliphatic hydrocarbon group, substituted or unsubstituted aromatic hydrocarbon group, substituted or unsubstituted aromatic heterocyclic group Represents Further, it may be an aromatic ring which may have a substituent, an aromatic ring containing a hetero atom or a hetero ring. Y ¹ to Y ¹² may have any substituent, may form an aromatic ring or a heterocycle between the substituents, and may form a complex with a metal. Also, ^one of Y ¹ to Y ¹² is bonded to an azo group.

The bisazo compound consists of an azo component between two azo groups and a coupler component at the end of the azo group. The combination of the azo component and the coupler component of the bisazo compound used in the present invention may be any combination, and may be different coupler components in one molecule. The substituents of the bisazo compound are each independently a hydrogen atom, a halogen atom, a cyano group, a nitro group, an amino group, a dialkylamino group, a diphenylamino group, a hydroxyl group, an alkoxy group, a mercapto group, a siloxy group, an acyl group, a cycloalkyl group. Group, carboxylic acid group, sulfonic acid group, substituted or unsubstituted aliphatic hydrocarbon group,
The substituted or unsubstituted aromatic hydrocarbon group and the substituted or unsubstituted aromatic heterocyclic group are not limited to these. Further, a ring such as an aromatic ring or a heterocycle may be formed between the substituents.

The substituents contained in the bisazo compound used in the present invention are illustrated in more detail below.
Hydrogen atom, halogen atom such as chlorine atom, bromine atom, iodine atom, cyano group, nitro group amino group, hydroxyl group,
Mercapto group, siloxy group, acyl group, cycloalkyl group, carboxylic acid group, sulfonic acid group, or methyl group, ethyl group, t-butyl group, n-stearyl group, trichloromethyl group, aminomethyl group, hydroxymethyl group, etc. Substituted or unsubstituted aliphatic hydrocarbon group, phenyl group, naphthyl group, anthryl group, 2-methylphenyl group, 4-
Substituted or unsubstituted aromatic hydrocarbon group such as chloromethyl group, 4-dimethylaminonaphthyl group, or substituted or unsubstituted aromatic group such as pyridyl group, carbazolyl group, dibenzofuryl group, benzothiazolyl group, 4-methylpyridyl group Group heterocyclic group, methoxy group, ethoxy group, stearyloxy group, phenoxy group, hexylthio group, t-butylthio group, phenylthio group, amino group, n-butylamino group, dimethylamino group, diphenylamino group, methylphenylamino group , Dibenzylamino group, carbazole group, etc., but the kind and number of these substituents are not limited.

1 to 3 show the organic EL used in the present invention.
A schematic diagram of the device is shown. In the figure, the electrode A is generally 2
Is an anode, and electrode 6 is a cathode. The bisazo compound of the present invention is effective when used in any of the hole injection layer 3, the phosphor layer 4, and the electron injection layer 5. In addition to the light emitting substance, a light emission assisting substance, a hole transporting material for transporting carriers, and an electron transporting material can be used for the phosphor layer 4 of FIG.

The structure shown in FIG. 2 has a phosphor layer 4 and a hole injection layer 3.
Are separated. With this structure, the hole injection efficiency from the hole injection layer 3 to the phosphor layer 4 is improved, and the emission brightness and the emission efficiency can be increased. The structure of FIG. 3 has an electron injection layer 5 in addition to the hole injection layer 3, and improves the efficiency of recombination of holes and electrons in the phosphor layer 4.

As the conductive material used for the anode of the organic EL element, those having a work function larger than 4 eV are preferable, and carbon, aluminum, vanadium, iron, cobalt, nickel, tungsten, silver, gold and the like, and Those alloys and metal oxides such as tin oxide and indium oxide are used. As the conductive material used for the cathode,
Those having a work function smaller than 4 eV are preferable, and magnesium, calcium, titanium, yttrium,
Lithium, ruthenium, manganese and the like and alloys thereof are used, but not limited to these.

In the organic EL device, it is desirable that at least the electrode A represented by 2 or the electrode B represented by 6 is a transparent electrode in order to emit light efficiently. Further, it is desirable that the substrate 1 is also transparent. Transparent electrode A or B
Is set using the above-mentioned conductive material so as to ensure a predetermined light-transmitting property by a method such as vapor deposition or sputtering.

The substrate 1 is not limited as long as it has mechanical and thermal strength and is transparent, but examples thereof include a glass substrate, an ITO glass plate, a NESA glass plate and the like, a polyethylene plate, and a poly plate. Examples include transparent resins such as ether sulfone plates and polypropylene plates. For forming each layer of the organic EL element according to the present invention, any method such as a dry film forming method such as vacuum deposition and sputtering, or a wet film forming method such as spin coating and dipping can be applied. It is necessary to set each layer to an appropriate film thickness. If the film thickness is too thick, a large applied voltage is required to obtain a constant light output, resulting in poor efficiency. If the film thickness is too thin, pinholes and the like will occur, and even if an electric field is applied, sufficient emission brightness cannot be obtained.

In the case of the wet film-forming method, a liquid in which the material forming each layer is dissolved or dispersed in an appropriate solvent such as chloroform, tetrahydrofuran, dioxane, etc. is used, but any solvent may be used. Further, an appropriate resin or additive may be used for improving film-forming property and preventing pinholes in the film. The resin used in the present invention,
Examples thereof include, but are not limited to, polystyrene, polycarbonate, polyester, polyvinyl butyral, polysulfone, polymethylmethacrylate, polymethylacrylate, polyamide, polyvinylcarbazole, and polysilylene.

The bisazo compound used in the organic EL device of the present invention is effective when used in any of layers 3 to 5. In the present organic EL device, a known light emitting substance, hole transporting substance, or electron transporting substance can be used in addition to the bisazo compound if necessary. Such known luminescent substances include anthracene, naphthalene, phenanthrene, pyrene, tetracene, coronene, chrysene, fluorescein, perylene, phthaloperylene, naphthaloperylene, perinone, phthaloperinone, naphthaloperinone, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole. , Aldazine, bisbenzoxazoline, bisstyryl, pyrazine, CPD, oxine,
Aminoquinoline, imine, diphenylethylene, vinylanthracene, diaminocarbazole, pyran, thiopyran, polymethine, merocyanine, imidazole chelated oxinoid compounds and the like, and derivatives thereof, are not limited to these.

As the hole transport material, oxadiazole, triazole, imidazolone, which are electron donating materials,
Imidazolethione, pyrazoline, tetrahydroimidazole, oxazole, hydrazone, acylhydrazone, stilbene, butadiene, benzidine type triphenylamine, styrylamine type triphenylamine, diamine type triphenylamine, and their derivatives, and polyvinylcarbazole, polysilane, There is a polymer material such as a conductive polymer, but the material is not limited to these.

As the electron transport substance, a substance having an appropriate electron accepting property is used. For example, anthraquinodimethane,
Examples thereof include, but are not limited to, diphenylquinone, oxadiazole, and perylene tetracarboxylic acid. Further, an electron accepting substance may be added to the hole transporting substance, and an electron donating substance may be added to the electron transporting substance to sensitize. A sensitizer may be used to sensitize the bisazo compound used in the present invention.

In the organic EL device shown in FIGS. 2 and 3, the bisazo compound can be used in any of the layers, and at least one of the light emitting substance, the hole transporting substance and the electron transporting substance is contained in the same layer. May be. As described above, it is possible to increase the charge injection efficiency by using the bisazo compound for the organic EL element, and as a result, it is considered that the light emission efficiency and the light emission brightness can be increased. Further, this element is very stable against heat and current, and the deterioration, which has been a big problem until now, could be greatly reduced.

The organic EL device of the present invention can be used as various display devices.

[0033]

The present invention will be described in more detail based on the following examples. The structures of compounds (a) to (e) used in this example are shown in Tables 1 and 2. Example 1 (8-Hydroxyquinolinol) aluminum metal complex and compound (a) were vacuum-deposited at a ratio of 1: 1 on a washed glass plate with an ITO electrode to give a film thickness of 0.08 μm.
m phosphor layer was obtained. On top of that, add 1 magnesium and 1 silver
An electrode having a film thickness of 0.2 μm was formed from the alloy mixed at 0: 1 to obtain the organic EL device shown in FIG. The device emitted light of about 150 cd / m ² at a DC voltage of 5 V.

Examples 2 to 6 For the phosphor layer, the compound (b to f), diisopropylphenylperylene and polyvinylcarbazole were used in a ratio of 2: 1: 7.
An organic EL device was produced in the same manner as in Example 1 except that the organic EL device was dissolved in chloroform at a ratio of 1, and formed by spin coating. The device emitted light shown in Table 3 at a DC voltage of 5V.

Example 7 A compound (g) was dissolved in chloroform on a washed glass plate with an ITO electrode, and a hole injection layer having a thickness of 0.03 μm was formed by spin coating. Then (8
-Hydroxyquinolinol) aluminum metal complex was vacuum-deposited to obtain a phosphor layer having a thickness of 0.05 μm. Then, an electrode having a film thickness of 0.2 μm was formed from an alloy in which magnesium and silver were mixed at a ratio of 10: 1 to obtain an organic EL device shown in FIG. This device is approximately 210 cd / d at a DC voltage of 5V.
A light emission of m ² was obtained.

Example 8 The compound (h) was dissolved in chloroform and spin-coated to form a hole injection layer having a thickness of 0.03 μm.
An organic EL device was produced in the same manner as in Example 7, except that perylene was vacuum-deposited thereon and a phosphor layer having a thickness of 0.02 μm was used. With this device, light emission of about 260 cd / m ² was obtained at a DC voltage of 5V.

Example 9 1,1-Diphenyl-4,4-bis (4-diethylaminophenyl) butadiene was vacuum-deposited on a washed glass plate with an ITO electrode to form a hole injection layer having a thickness of 0.03 μm. Obtained. Then, 9,10-diphenylanthracene was vacuum-deposited to obtain a phosphor layer having a thickness of 0.02 μm. Next, the compound (i) was dissolved in chloroform and spin coating was performed to form an electron injection layer having a thickness of 0.02 μm. An electrode having a film thickness of 0.2 μm was formed on it by an alloy in which magnesium and silver were mixed at a ratio of 10: 1 to obtain an organic EL device shown in FIG. This device has a DC voltage of 5 V
Light emission of 90 cd / m ² was obtained.

When all the organic EL devices shown in this embodiment were made to emit light continuously at 1 mA / cm ² , 10
Stable light emission could be observed for 00 hours or more. The organic EL device of the present invention achieves improvement in luminous efficiency, luminous brightness, and long life.
The hole transport material, electron transport material, sensitizer, resin and the like are not limited.

Tables 1 and 2 show the azo component (Az) and the coupler component (Cp) of the bisazo compound used in the present invention. Table 3 shows the emission brightness obtained in Examples 2 to 6.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

According to the present invention, it is possible to obtain an organic EL device having higher luminous efficiency, higher luminance and longer life than ever before.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a schematic structure of an organic EL element used in Examples 1 to 6.

FIG. 2 is a cross-sectional view showing a schematic structure of an organic EL element used in Examples 7 and 8.

FIG. 3 is a sectional view showing a schematic structure of an organic EL device used in Example 9.

[Explanation of symbols]

 1: Substrate 2: Electrode A 3: Hole injection layer 4: Phosphor layer 5: Electron injection layer 6: Electrode B 0

Claims (3)

[Claims] 1. An organic electroluminescence device having at least one of bisazo compounds in an electroluminescence device having a layer containing at least a phosphor between a pair of electrodes. 2. An electroluminescent device having a layer containing at least a phosphor between a pair of electrodes, containing at least one compound represented by the general formula [1]. 1. The organic electroluminescence device according to 1. General formula [1] Cp-N = N-Az-N = N-Cp [In formula, Az is an azo component shown by general formula [2]. General formula [2] Here, Cp represents a coupler group, and X ¹ to X
¹⁰ are each independently a hydrogen atom, an oxygen atom, a halogen atom, a cyano group, a nitro group, an amino group, a dialkylamino group, a diphenylamino group, a hydroxyl group, an alkoxy group, a mercapto group, a siloxy group, an acyl group, a cycloalkyl group, It represents a carboxylic acid group, a sulfonic acid group, a substituted or unsubstituted aliphatic hydrocarbon group, a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group. Further, it may be an aromatic ring which may have a substituent, an aromatic ring containing a hetero atom or a hetero ring. X ¹ to X ¹⁰
May have any substituent, may form an aromatic ring or a heterocycle between the substituents, and may form a complex with a metal. Two of X ¹ to X ¹⁰ are bonded to the azo group. ] 3. In an electroluminescent device having a layer having at least a phosphor between a pair of electrodes, the coupler group of the compound represented by the general formula [1] has a general formula [3] to [11]. 3. The organic electroluminescence device according to claim 1, further comprising at least one of the above. General formula [3] General formula [4] General formula [5] General formula [6] General formula [7] General formula [8] General formula [9] General formula [10] General formula [11] [In the formula, Y ¹ to Y ¹² are each independently a hydrogen atom, an oxygen atom, a halogen atom, a cyano group, a nitro group, an amino group, a dialkylamino group, a diphenylamino group, a hydroxyl group, an alkoxy group, a mercapto group, a siloxy group. Represents an acyl group, a cycloalkyl group, a carboxylic acid group, a sulfonic acid group, a substituted or unsubstituted aliphatic hydrocarbon group, a substituted or unsubstituted aromatic hydrocarbon group, or a substituted or unsubstituted aromatic heterocyclic group. . Further, it may be an aromatic ring which may have a substituent, an aromatic ring containing a hetero atom or a hetero ring. Y ¹ to Y ¹² may have any substituent, may form an aromatic ring or a heterocycle between the substituents, and may form a complex with a metal. Also, ^one of Y ¹ to Y ¹² is bonded to an azo group. ]