JPH06228552A - Organic electroluminescent device - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To provide an electroluminescence device having high brightness and high light emission efficiency, low emission deterioration, and high reliability. An electroluminescent element having at least a phosphor between a pair of electrodes, wherein at least one organic compound represented by the following general formula is used. (In the formula, R ¹ to R ⁶ are a hydrogen atom, a halogen atom,
Cyano group, nitro group, amino group, ester group, hydroxyl group,
Examples thereof include an alkoxy group, a mercapto group, an aryloxy group, a siloxy group, an acyl group, a cycloalkyl group, a carbamoyl group, a carboxylic acid group, a sulfonic acid group, an aliphatic hydrocarbon group, an aromatic hydrocarbon group and a heterocyclic group. )

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 expected to be used 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 device in which a thin film containing an organic compound having a high fluorescence quantum efficiency that emits light at a low voltage of 10 V or less is stacked has been reported and attracted attention (Applied Physics Letters, 51.
Vol., Page 913, 1987).

According to this method, a metal chelate complex is used for the phosphor 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 devices to date have improved the emission intensity due to the improved structure, they still do not have sufficient emission brightness. Further, it has a big problem that it is inferior in stability when repeatedly used. Therefore, under the present circumstances, it is desired to develop an organic EL device having a larger emission brightness and excellent stability in repeated use.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic EL device having a large emission intensity and excellent stability in repeated use.

[0005]

Means for Solving the Problems As a result of intensive investigations by the present inventors, an organic EL device using an organic compound represented by the general formula [1] has a large emission intensity and is stable in repeated use. The inventors have found that they are excellent and have reached the present invention. That is, the present invention is an organic electroluminescent device having at least one kind of the organic compound represented by the general formula [1] in an electroluminescent device having a layer containing at least a phosphor between a pair of electrodes. .

General formula [1]

[0007]

[Chemical 2]

(In the formula, R ¹ to R ⁶ are each independently a hydrogen atom, a halogen atom, a cyano group, a nitro group, an amino group, an ester group, a mono- or di-substituted amino group, a hydroxyl group, an alkoxy group and a mercapto group. , An aryloxy group,
Siloxy group, acyl group, cycloalkyl group, carbamoyl group, carboxylic acid group, sulfonic acid group, substituted or unsubstituted aliphatic hydrocarbon group, substituted or unsubstituted aromatic hydrocarbon group, substituted or unsubstituted aromatic group It is a heterocyclic group or a substituted or unsubstituted heterocyclic group, and an aromatic ring or a heterocycle may be formed between two substituents. However, R
^At least one of ¹ to R ⁶ is a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted heterocycle, or an aromatic ring containing a substituted or unsubstituted heteroatom. )

The substituent atom or substituent in the present invention is
Hydrogen atom, halogen atom, cyano group, nitro group, carboxy group, sulfone group, or methyl group, ethyl group, propyl group, butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, Octyl group, stearyl group, trichloromethyl group, aminomethyl group, acetoxymethyl group, acetoxyethyl group,
A substituted or unsubstituted acyclic hydrocarbon group such as acetooxypropyl group, acetooxybutyl group, hydroxymethyl group, hydroxylethyl group, hydroxylpropyl group, hydroxylbutyl group, cyclopropyl group, cyclohexyl group, 1,3- Cyclohexadienyl group, 2-cyclopenten-1-yl group, 2,4-cyclopentadiene-1-yridenyl group, phenyl group, biphenylenyl group,
Triphenylenyl group, tetraphenylenyl group, 2-methylphenyl group, 3-nitrophenyl group, 4-methylthiophenyl group, 3,5-dicyanophenyl group, o-, m-
And p-tolyl group, xylyl group, o-, m- and p
-Cumenyl group, a substituted or unsubstituted monocyclic hydrocarbon group such as mesityl group, pentalenyl group, indenyl group, naphthyl group, azulenyl group, heptanenyl group, acenaphthylenyl group, phenalenyl group, fluorenyl group, anthryl group, anthraquinonyl group, 3-methylanthryl group, phenanthryl group, triphenylenyl group, pyrenyl group, chrysenyl group, 2-ethyl-1-chrysenyl group, picenyl group, perylenyl group, 6-chloroperenylenyl group, pentaphenyl group, pentacenyl group, tetraphenylenyl group Group, hexaphenyl group, hexacenyl group, rubicenyl group, coronenyl group, trinaphthylenyl group, heptaphenyl group, heptaenyl group, pyrantrenyl group, substituted or unsubstituted condensed polycyclic hydrocarbon such as ovarenyl group, thienyl group,
Furyl group, pyrrolyl group, imidazolyl group, pyrazolyl group, pyridyl group, pyrazinyl group, pyrimidinyl group, pyridazinyl group, indolyl group, quinolyl group, isoquinolyl group, phthalazinyl group, quinoxalinyl group, quinazolinyl group, carbazolyl group, acridinyl group, phenazinyl group A substituted or unsubstituted heterocyclic group such as a furfuryl group, an isothiazolyl group, an isoxazolyl group, a flazanyl group, a phenoxazinyl group, a benzothiazolyl group, a benzoxazolyl group, a benzimidazolyl group, a 2-methylpyridyl group, and a 3-cyanopyridyl group. , Hydroxyl group, methoxy group,
Ethoxy group, propoxy group, butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, stearyloxy group, phenoxy group,
Methylthio group, ethylthio group, propylthio group, butylthio group, sec-butylthio group, tert-butylthio group, pentylthio group, hexylthio group, heptylthio group, octylthio group, phenylthio group, amino group, methylamino group, dimethylamino group, ethylamino Group, diethylamino group, dipropylamino group, dibutylamino group, diphenylamino group, bis (acetoxymethyl)
Amino group, bis (acetooxyethyl) amino group, bis (acetooxypropyl) amino group, bis (acetooxybutyl) amino group, dibenzylamino group, methylsulfamoyl group, dimethylsulfamoyl group, ethylsulfa group Moyl group, diethylsulfamoyl group, propylsulfamoyl group, butylsulfamoyl group, phenylsulfamoyl group, diphenylsulfamoyl group, methylcarbamoyl group, dimethylcarbamoyl group, ethylcarbamoyl group, diethylcarbamoyl group, propyl Carbamoyl group, butylcarbamoyl group, phenylcarbamoyl group, methylcarbonylamino group, ethylcarbonylamino group, propylcarbonylamino group, butylcarbonylamino group, phenylcarbonylamino group, methoxycarbonylamino group Ethoxycarbonylamino group, propoxycarbonylamino group, butoxycarbonylamino group, phenoxycarbonyl group, 2- (2-ethoxyethoxy) ethoxy group, 2- (2-ethoxyethoxy) ethylthio group, 2- [2- (2-methoxy Ethoxy) ethoxy] ethylthio group and the like, but not limited to these substituents.

As the aromatic ring or hetero ring formed between the substituents, there is a 5-membered ring or 6-membered ring to which a carbon atom may be bonded via a nitrogen atom, an oxygen atom, a sulfur atom or the like. . Hereinafter, representative examples of the compound of the general formula [1] used in the present invention will be specifically shown in Table 1, but the present invention is not limited to the following representative examples.

[0011]

[Table 1]

The kind and position of the substituent of the compound of the general formula [1] used in the present invention are not particularly limited, but at least one of the substituents of R ¹ to R ⁶ is substituted or unsubstituted. Since it is an aromatic heterocyclic group, a substituted or unsubstituted heterocycle, or an aromatic ring containing a substituted or unsubstituted heteroatom, it is possible to obtain light emission with higher brightness.

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. Since the compound of the general formula [1] has both strong light emission and a large carrier transport ability, the hole injection layer 3, the phosphor layer 4,
It is effective to use any of the electron injection layers 5. For the phosphor layer 4 of FIG. 1, if necessary, a light emission auxiliary agent, a hole transport material for carrying carriers, and an electron transport material can be used in addition to the light emitting substance.

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 described above, by forming the organic EL element into a multi-layer structure, it is possible to prevent a decrease in brightness and life due to quenching.

As the conductive material used for the anode of the organic EL device, those having a work function larger than 4 eV are suitable, 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 transparent in order to efficiently emit light. Further, it is desirable that the substrate 1 is also transparent. The transparent electrode is made of the above-mentioned conductive material and is set by a method such as vapor deposition or sputtering so as to ensure a predetermined translucency. The substrate 1 is not limited as long as it has mechanical and thermal strength and is transparent, but for example, a glass substrate, an ITO substrate,
Examples include transparent resins such as NESA substrates, polyethylene plates, polyether sulfone plates, and polypropylene plates.

For forming each layer of the organic EL device according to the present invention, any of dry film forming methods such as vacuum deposition and sputtering and wet film forming methods such as spin coating and dipping can be applied. The film thickness is not particularly limited, but each layer needs to be set 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 is used, and the solvent may be any one. Further, an appropriate resin or additive may be used for improving film-forming property and preventing pinholes in the film. Organic EL shown in FIG.
In the device, high light emission characteristics can be achieved by using the compound of the general formula [1] as the light emitting substance. In addition, this compound can obtain more efficient emission luminance by using an auxiliary agent of a light emitting substance in the same layer.
In the organic EL device of the present invention, if necessary, in addition to the compound of the general formula [1], a known light emitting substance, light emission auxiliary, hole transporting substance, and electron transporting substance can be used.

Examples of such known luminescent materials or auxiliaries of known luminescent materials 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, Examples thereof include, but are not limited to, vinylanthracene, diaminocarbazole, pyran, thiopyran, polymethine, merocyanine, imidazole chelated oxinoid compound and the like, and derivatives thereof.

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 transporting substance, a substance having an appropriate electron accepting property is used. Examples include, but are not limited to, anthraquinodimethane, diphenylquinone, oxadiazole, perylene tetracarboxylic acid, and the like.

It is also possible to sensitize by adding an electron accepting substance to the hole transporting substance and adding an electron donating substance to the electron transporting substance. Organic EL shown in FIGS. 2 and 3
In the device, the compound of the general formula [1] can be used in any layer, and at least one of a light emitting substance, a light emission auxiliary, a hole transporting substance and an electron transporting substance may be contained in the same layer. . As described above, in the present invention, since the compound of the general formula [1] is used for the organic EL device, the luminous efficiency and the luminous 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.

The present invention will be described in more detail based on the following examples.

Example 1 Compound (e) was dissolved in chloroform on a washed glass plate with an ITO electrode, and a phosphor layer was formed by spin coating to obtain a phosphor layer having a thickness of 0.05 μm. . An electrode having a film thickness of 0.2 μm was formed thereon with an alloy in which magnesium and silver were mixed at a ratio of 10: 1 to obtain the organic EL device shown in FIG. This device has a DC voltage of 5 V
Light emission of 0 cd / m ² was obtained.

Example 2 Organic E was prepared in the same manner as in Example 1 except that the phosphor layer was formed by vacuum deposition using the compound (a).
An L element was produced. This device has a DC voltage of 5 V
Light emission of 0 cd / m ² was obtained.

Example 3 N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-on a cleaned glass plate with an ITO electrode
Biphenyl-4,4′-diamine was vacuum-deposited to obtain a hole injection layer having a thickness of 0.03 μm. Then compound (g)
A phosphor layer having a thickness of 0.02 μm was obtained by vacuum evaporation. 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 has about 340
Light emission of cd / m ² was obtained.

Example 4 N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-on a cleaned glass plate with an ITO electrode
Biphenyl-4,4′-diamine was vacuum-deposited to obtain a hole injection layer having a thickness of 0.03 μm. Then compound (j)
Was dissolved in chloroform and spin-coated to obtain a phosphor layer having a thickness of 0.02 μm. Furthermore, perylene was vacuum-deposited to obtain an electron injection layer having a thickness of 0.03 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 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.
Luminescent auxiliary substance, hole transporting substance, electron transporting substance, sensitizer,
The resin, the electrode material and the like and the method for manufacturing the element are not limited.

[0026]

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.

[0027]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a schematic structure of an organic EL element used in Examples 1 and 2.

FIG. 2 is a cross-sectional view showing a schematic structure of an organic EL element used in Example 3.

FIG. 3 is a sectional view showing a schematic structure of an organic EL device used in Example 4.

[Explanation of symbols]

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

Claims (1)

[Claims] 1. An electroluminescent device having a layer containing at least a phosphor between a pair of electrodes, wherein at least one compound represented by the general formula [1] is used. . General formula [1] (In the formula, R ¹ to R ⁶ are each independently a hydrogen atom,
Halogen atom, cyano group, nitro group, amino group, ester group, mono- or di-substituted amino group, hydroxyl group, alkoxy group, mercapto group, aryloxy group, siloxy group, acyl group, cycloalkyl group, carbamoyl group, carboxylic acid group A sulfonic acid group, a substituted or unsubstituted aliphatic hydrocarbon group, a substituted or unsubstituted aromatic hydrocarbon group, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted heterocyclic group, 2 You may form an aromatic ring or a heterocyclic ring between one substituent. However, at least one of R ¹ to R ⁶ is a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted heterocycle, or an aromatic ring containing a substituted or unsubstituted heteroatom. )