JP3211450B2 - Organic electroluminescence device - Google Patents

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) device used for a flat light source and a display.

[0002]

2. Description of the Related Art An EL device using an organic substance is expected to be used as an inexpensive, large-area, full-color display device of a solid light emitting type, and many developments have been made. In general EL element
The element is composed of a light emitting layer and a pair of opposed electrodes sandwiching the layer. In light emission, when an electric field is applied between both electrodes, electrons are injected from the cathode side, holes are injected from the anode side , and the electrons recombine with holes in the light emitting layer, and the energy level is changed to the conduction band. This is a phenomenon in which energy is emitted as light when returning to the valence band from. The conventional organic EL element has a higher driving voltage and lower light emission luminance and light emission efficiency than the inorganic EL element. In addition, the characteristic deterioration was remarkable, and it had not been put to practical use. In recent years, an organic EL device formed by laminating a thin film containing an organic compound having a high fluorescence quantum efficiency and emitting light at a low voltage of 10 V or less has been reported, and has attracted attention (Applied Physics Letters, Vol. 51, 91).
3 pages, 1987).

In this method, high-luminance green light is obtained by using a metal chelate complex for a phosphor layer and an amine compound for a hole injection layer.
00 cd / m ² and a maximum luminous efficiency of 1.5 lm / W, which is a performance close to a practical range. However, organic EL devices up to now have improved light emission intensity due to the improved structure, but do not yet have sufficient light emission luminance. In addition, there is a major problem that the stability upon repeated use is poor. Therefore, at present, it is desired to develop an organic EL device having higher emission luminance and excellent stability when repeatedly used.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic EL device having a high luminous intensity and excellent stability when used repeatedly.

[0005]

As a result of diligent studies by the present inventors, an organic EL device using an organic compound represented by the general formula [1] has a large luminous intensity and a high stability when used repeatedly. It was found to be excellent and led to the present invention. That is, the present invention relates to an electroluminescent element having at least a layer containing a phosphor between a pair of electrodes, the organic electroluminescent element using at least one of the organic compounds represented by the general formula [1]. .

The general formula [1]

[0007]

Embedded image

(Wherein R ¹ to R ⁶ each independently represent 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, 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 heterocyclic group, or
Others, a heterocyclic group other than the aromatic heterocyclic ring substituted or unsubstituted, may form an aromatic ring or a heterocyclic ring between the two substituents. Provided that at least one of from R ¹ R ⁶ is a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted non-aromatic heterocyclic group or the two,
It is an aromatic hydrocarbon group that forms a heterocyclic ring between substituents . )

[0009] In the present invention, the substituent atom or substituent 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, stearyl, trichloromethyl, aminomethyl, acetooxymethyl, acetooxyethyl,
A substituted or unsubstituted acyclic hydrocarbon group such as an acetooxypropyl group, an acetooxybutyl group, a hydroxymethyl group, a hydroxylethyl group, a hydroxylpropyl group, a hydroxylbutyl group, a cyclopropyl group, a cyclohexyl group, a 1,3- Cyclohexadienyl group, 2-cyclopenten-1-yl group, 2,4-cyclopentadiene-1-ylenyl 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, substituted or unsubstituted monocyclic hydrocarbon group such as mesityl group, pentalenyl group, indenyl group, naphthyl group, azulenyl group, heptalenyl 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-chloroperylenyl group, pentaphenyl group, pentacenyl group, tetraphenylenyl A substituted or unsubstituted fused polycyclic hydrocarbon such as a group, a hexaphenyl group, a hexacenyl group, a ruvicenyl group, a coronenyl group, a trinaphthylenyl group, a heptaphenyl group, a heptacenyl group, a pyranthrenyl group, an ovalenyl group, a thienyl group,
Furyl, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolyl, quinolyl, isoquinolyl, phthalazinyl, quinoxalinyl, quinazolinyl, carbazolyl, acridinyl, phenazinyl Substituted or unsubstituted heterocyclic groups such as, furfuryl, isothiazolyl, isoxazolyl, furazanyl, phenoxazinyl, benzothiazolyl, benzoxazolyl, benzimidazolyl, 2-methylpyridyl and 3-cyanopyridyl , Hydroxyl group, methoxy group,
Ethoxy, propoxy, butoxy, sec-butoxy, tert-butoxy, pentyloxy, hexyloxy, stearyloxy, phenoxy,
Methylthio, ethylthio, propylthio, butylthio, sec-butylthio, tert-butylthio, pentylthio, hexylthio, heptylthio, octylthio, phenylthio, amino, methylamino, dimethylamino, ethylamino Group, diethylamino group, dipropylamino group, dibutylamino group, diphenylamino group, bis (acetooxymethyl)
Amino group, bis (acetooxyethyl) amino group, bis (acetooxypropyl) amino group, bis (acetooxybutyl) amino group, dibenzylamino group, methylsulfamoyl group, dimethylsulfamoyl group, ethylsulfa Moyl, diethylsulfamoyl, propylsulfamoyl, butylsulfamoyl, phenylsulfamoyl, diphenylsulfamoyl, methylcarbamoyl, dimethylcarbamoyl, ethylcarbamoyl, diethylcarbamoyl, propyl Carbamoyl, butylcarbamoyl, phenylcarbamoyl, methylcarbonylamino, ethylcarbonylamino, propylcarbonylamino, butylcarbonylamino, phenylcarbonylamino, methoxycarbonylamino 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 are not limited to these substituents.

The aromatic ring or hetero ring formed between the substituents includes a 5-membered ring or a 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, typical examples of the compound of the general formula [1] used in the present invention are specifically shown in Table 1, but the present invention is not limited to the following typical examples.

[0011]

[Table 1]

The type and position of the substituents of the compound of the general formula [1] used in the present invention are not particularly limited, but at least one of the substituents R ¹ to R ⁶ is substituted or unsubstituted. An aromatic heterocyclic group, a heterocyclic group other than a substituted or unsubstituted aromatic heterocyclic group , or the two
Since the aromatic hydrocarbon group formed a heterocyclic ring between the substituents, higher-luminance light emission could be obtained.

FIGS. 1 to 3 show an organic EL used in the present invention.
A schematic diagram of the device is shown. In the figure, generally, electrode A 2
Is an anode, and 6 which is an electrode B is a cathode. Since the compound of the general formula [1] has both strong light emission and 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 in FIG. 1, if necessary, a light-emitting auxiliary agent, a hole transport material for transporting carriers, or an electron transport material can be used in addition to the light-emitting substance.

FIG. 2 shows the structure of the phosphor layer 4 and the 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 light emission luminance and the light emission efficiency can be increased. The structure in FIG. 3 has an electron injection layer 5 in addition to the hole injection layer 3 to improve the efficiency of recombination of holes and electrons in the phosphor layer 4. In this manner, by making the organic EL element have a multilayer structure, it is possible to prevent a decrease in luminance and life due to quenching.

As the conductive material used for the anode of the organic EL device, those having a work function of more than 4 eV are preferable, and carbon, aluminum, vanadium, iron, cobalt, nickel, tungsten, silver, gold, etc. Alloys thereof 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 preferred, and magnesium, calcium, titanium, yttrium,
Lithium, ruthenium, manganese and the like and alloys thereof are used, but not limited thereto.

In the organic EL device, it is desirable that at least the electrode A indicated by 2 or the electrode B indicated by 6 be transparent in order to emit light efficiently. Further, it is desirable that the substrate 1 is also transparent. The transparent electrode is set so as to secure a predetermined light transmittance by a method such as vapor deposition or sputtering using the above-described conductive substance. 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 substrate,
Transparent resins such as a NESA substrate, a polyethylene plate, a polyethersulfone plate, and a polypropylene plate can be used.

Each layer of the organic EL device according to the present invention can be formed by any of dry film forming methods such as vacuum evaporation and sputtering and wet film forming methods such as spin coating and dipping. The thickness is not particularly limited, but each layer needs to be set to an appropriate thickness. If the film thickness is too large, a large applied voltage is required to obtain a constant light output, resulting in poor efficiency. If the film thickness is too small, pinholes and the like are generated, and sufficient light emission luminance cannot be obtained even when an electric field is applied. In the case of the wet film formation method, a liquid in which a material for forming each layer is dissolved or dispersed in an appropriate solvent such as chloroform, tetrahydrofuran, dioxane or the like is used, and the solvent may be any one. Further, an appropriate resin or additive may be used for improving the film forming property, preventing pinholes in the film, and the like. Organic EL shown in FIG.
In the device, high emission characteristics can be achieved by using the compound of the general formula [1] as a light emitting substance. In addition, this compound can obtain more efficient light emission luminance by using a light emitting substance auxiliary agent in the same layer.
In the present organic EL device, if necessary, a known luminescent substance, luminescent auxiliary agent, hole transporting substance, and electron transporting substance can be used in addition to the compound of the general formula [1].

Examples of such known luminescent substances or luminescent auxiliary substances include anthracene, naphthalene, phenanthrene, pyrene, tetracene, coronene, chrysene and the like.
Fluorescein, perylene, phthaloperylene, naphthaloperylene, perinone, phthaloperinone, naphthaloperinone, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, aldazine, bisbenzoxazoline, bisstyryl, pyrazine, CPD, oxine, aminoquinoline, imine, diphenylethylene, Examples include, but are not limited to, vinylanthracene, diaminocarbazole, pyran, thiopyran, polymethine, merocyanine, imidazole chelated oxinoid compounds, and the like.

As the hole transporting substance, oxadiazole, triazole, imidazolone,
Imidazolethione, pyrazoline, tetrahydroimidazole, oxazole, hydrazone, acylhydrazone, stilbene, butadiene, benzidine-type triphenylamine, styrylamine-type triphenylamine, diamine-type triphenylamine, and the like, and derivatives thereof, and polyvinyl carbazole, polysilane, There is a polymer material such as a conductive polymer, but it is not limited thereto. As the electron transporting substance, an appropriate substance having an electron accepting property is used. Examples include, but are not limited to, anthraquinodimethane, diphenylquinone, oxadiazole, perylenetetracarboxylic acid, and the like.

It is also possible to sensitize by adding an electron accepting substance to the hole transporting substance and 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 luminescent material, a luminescent auxiliary, a hole transport material, and an electron transport material may be contained in the same layer. . As described above, in the present invention, since the compound of the general formula [1] was used for the organic EL device, the luminous efficiency and the luminous brightness could be increased. In addition, this element was extremely stable against heat and current, and the degradation, which had been a major 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 with reference to the following examples.

Example 1 A 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 thickness of 0.2 μm was formed thereon using 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 element has a DC voltage of 5 V and
Light emission of 0 cd / m ² was obtained.

Example 2 The same procedure as in Example 1 was repeated except that the compound (a) was used to form a phosphor layer by a vacuum evaporation method.
An L element was produced. This element has a DC voltage of 5 V and
Light emission of 0 cd / m ² was obtained.

Example 3 N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'- was placed on a washed 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)
Was obtained by a vacuum evaporation method to obtain a phosphor layer having a thickness of 0.02 μm. An electrode having a thickness of 0.2 μm was formed thereon using 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 element has a DC voltage of 5 V and is about 340.
Light emission of cd / m ² was obtained.

Example 4 N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'- was placed on a washed 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 the compound (j)
Was dissolved in chloroform, and a 0.02 μm-thick phosphor layer was obtained by spin coating. Further, perylene was vacuum-deposited to obtain an electron injection layer having a thickness of 0.03 μm. An electrode having a thickness of 0.2 μm was formed thereon using 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 element has about 380
Light emission of cd / m ² was obtained.

When all the organic EL elements shown in this embodiment were continuously emitted at 1 mA / cm ² ,
Stable light emission could be observed for 00 hours or more. The organic EL device of the present invention achieves luminous efficiency, improved luminous brightness and longer life, and a luminescent material used in combination therewith,
Luminescence auxiliary substances, hole transport substances, electron transport substances, sensitizers,
It does not limit the resin, the electrode material and the like, and the element manufacturing method.

[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 the conventional one.

[0027]

[Brief description of the drawings]

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

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

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

[Explanation of symbols]

 1. Substrate 2. Electrode A3. 3. Hole injection layer Phosphor layer 5. Electron injection layer 6. Electrode B

Claims (1)

(57) [Claims] 1. An organic electroluminescent device having at least one 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] (Wherein, 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, or a substituted or unsubstituted non-aromatic heterocyclic group And may form an aromatic ring or a heterocyclic ring between the two substituents. However,
At least one of R ¹ to R ⁶ is a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted aromatic complex.
A heterocyclic group other than an elementary ring, or a heterocyclic group between the two substituents
It is an aromatic hydrocarbon group forming a ring . )