JP3223632B2 - 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. Generally EL
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 and holes are injected from the anode side. Further, 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.

[0003] Conventional organic EL devices have a higher driving voltage and lower luminous brightness and luminous efficiency than inorganic EL devices.
In addition, the characteristic deterioration was remarkable, and it had not been put to practical use.

In recent years, an organic EL device in which a thin film containing an organic compound having high fluorescence quantum efficiency which emits light at a low voltage of 10 V or less has been reported and attracted attention (Applied Physics Letters, vol. , 913, 1987). In this method, a high-luminance green light emission is obtained by using a metal chelate complex for the phosphor layer and an amine compound for the hole injection layer, and the luminance is several hundred cd / m ² at a DC voltage of 6 to 7 V. Maximum luminous efficiency is 1.5l
m / W, and has performance close to the 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 a higher light emission luminance and excellent stability when repeatedly used.

[0006]

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. As a result of intensive studies by the present inventors, they have found that an organic EL device using an organic compound represented by the general formula [1] has high emission intensity and excellent stability during repeated use. Reached.

[0007]

That is, a first aspect of the present invention is an organic electroluminescent device having a light-emitting layer composed of one or more organic compound thin films between a pair of electrodes, wherein at least one layer has the following general formula: An organic electroluminescence device which is a layer containing the compound represented by [1]. General formula [1]

[0008]

Embedded image

Wherein X and Y 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,
Alkoxy group, mercapto group, alkyloxy group, alkylthio group, aryloxy group, arylthio group, siloxy group, acyl group, cycloalkyl group, carbamoyl group, carboxylic acid group, sulfonic acid group, substituted or unsubstituted aliphatic group, It represents a substituted or unsubstituted aliphatic ring group, a substituted or unsubstituted carbocyclic aromatic ring group, a substituted or unsubstituted heterocyclic aromatic ring group, or a substituted or unsubstituted heterocyclic group. Z is a divalent residue represented by the general formula [2], and A and B are each independently O, S, N
^{R 13, C = O, C} = S, (C = O) - (C = O), (C
= S) - (C = S ), SO 2, CH 2, CH 2 -CH 2, C
H = CH or C = C (CN) ₂ . General formula [2]

[0010]

Embedded image

R ¹ to R ¹³ each independently represent a hydrogen atom, a halogen atom, a cyano group, a nitro group, an amino group,
Ester group, mono- or di-substituted amino group, hydroxyl group, alkoxy group, mercapto group, alkyloxy group, alkylthio group, aryloxy group, arylthio group, siloxy group, acyl group, cycloalkyl group, carbamoyl group, carboxylic acid group, sulfone Acid group, substituted or unsubstituted aliphatic group, substituted or unsubstituted aliphatic ring group, substituted or unsubstituted carbocyclic aromatic ring group, substituted or unsubstituted heterocyclic aromatic ring group, substituted Alternatively, it represents an unsubstituted heterocyclic group, and one of R ⁵ to R ⁸ and R ⁹ to R ¹² is bonded to a carbon atom of an adjacent vinyl bond.
R ⁵ to R ⁸ or R ⁹ to R ¹² each represent a substituted or unsubstituted aliphatic ring, substituted or unsubstituted carbocyclic aromatic ring, substituted or unsubstituted heterocyclic group, It may form a cyclic aromatic ring or a substituted or unsubstituted heterocyclic ring. ]

According to a second aspect of the present invention, there is provided an organic electroluminescent device having a light emitting layer composed of one or more organic compound thin films between a pair of electrodes, wherein the light emitting layer contains a compound represented by the general formula [1]. The organic electroluminescence device is characterized in that the organic electroluminescence device is a layer to be formed.

According to a third aspect of the present invention, there is provided an organic electroluminescence device having a light emitting layer comprising one or more organic compound thin films between a pair of electrodes, wherein the hole injection layer is a compound represented by the general formula [1]: An organic electroluminescence device characterized in that it is a layer containing

According to a fourth aspect of the present invention, there is provided an organic electroluminescence device having a light emitting layer comprising one or more organic compound thin films between a pair of electrodes, wherein the electron injection layer comprises a compound represented by the general formula [1]. An organic electroluminescence device characterized by being a layer containing.

Examples of the group in the present invention and a substituent atom or a substituent added to the group include a hydrogen atom, a halogen atom, a cyano group, a nitro group, a carboxy group, a sulfone group, a methyl group, an ethyl group, Propyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, stearyl, trichloromethyl, aminomethyl, acetooxymethyl, acetooxyethyl, acetooxyethyl Oxypropyl group, acetooxybutyl group, hydroxymethyl group, hydroxylethyl group, hydroxylpropyl group,
A substituted or unsubstituted acyclic hydrocarbon group such as a hydroxylbutyl group, a vinyl group, a styryl group, and an acetylene group, a cyclopropyl group, a cyclohexyl group, a 1,3-cyclohexadienyl group, and a 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-dicyano A substituted or unsubstituted monocyclic hydrocarbon group such as phenyl group, o-, m- and p-tolyl group, xylyl group, o-, m- and p-cumenyl group, 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 group, hexaphenyl group, hexacenyl group, ruvicenyl group, colonenyl group, trinaphthenyl group, heptaphenyl group, heptaphenyl Group, pyranthrenyl group, substituted or unsubstituted condensed polycyclic hydrocarbon such as ovalenyl group, thienyl group, furyl group, pyrrolyl group,
Imidazolyl, pyrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolyl, quinolyl, isoquinolyl, phthalazinyl, quinoxalinyl, quinazolinyl, carbazolyl, acridinyl, phenazinyl, furfuryl, isothiazolyl , Isoxazolyl group, furazanyl group, phenoxazinyl group, benzothiazolyl group, benzoxazolyl group, benzimidazolyl group, 2-methylpyridyl group,
A substituted or unsubstituted heterocyclic group such as a 3-cyanopyridyl group, a hydroxyl group, a methoxy group, an ethoxy group, a 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, hexylthio, heptylthio, octylthio, phenylthio, amino, methylamino, dimethylamino, ethylamino, diethylamino, dipropylamino, dibutylamino, diphenylamino, bis (acetooxy Methyl) amino group, bis (acetooxyethyl) amino group, bis (acetooxypropyl) amino group, bis (acetooxybutyl) amino group, dibenzylamino group, methylsulfamoyl group, dimethylsulfamoyl group, ethyl Rufamoyl, diethylsulfamoyl, propylsulfamoyl, butylsulfamoyl, phenylsulfamoyl, diphenylsulfamoyl, methylcarbamoyl, dimethylcarbamoyl, ethylcarbamoyl, diethylcarbamoyl, propyl Carbamoyl, butylcarbamoyl, phenylcarbamoyl, methylcarbonylamino, ethylcarbonylamino, propylcarbonylamino, butylcarbonylamino, phenylcarbonylamino, methoxycarbonylamino, ethoxycarbonylamino, propoxycarbonylamino , Butoxycarbonylamino group, phenoxycarbonyl group,
2- (2-ethoxyethoxy) ethoxy group, 2- (2-
An ethoxyethoxy) ethylthio group, a 2- [2- (2-methoxyethoxy) ethoxy] ethylthio group,
It is not limited to these substituents.

The type, number and position of the substituent atoms or substituents of the compound of the general formula [1] used in the present invention are not particularly limited. The compound of the general formula [1] is generally synthesized by a Wittig reaction using a phosphorus compound. Hereinafter, typical examples of the compound of the general formula [1] used in the present invention will be specifically illustrated, but the present invention is not limited to the following typical examples.

[0017]

[0018]

[0019]

[0020]

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 luminescence due to fluorescence and a large carrier transporting ability, it is effective to be used in any of the hole injection layer 3, the light emitting layer 4, and the electron injection layer 5. . In the light emitting layer 4 in FIG. 1, if necessary, a light emitting substance, a light emission auxiliary, a hole transporting material for transporting carriers, or an electron transporting material can be used in addition to the compound of the general formula [1]. . The structure of FIG. 2 includes the light emitting 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 light emitting layer 4 is improved, and the light emission luminance and the light emission efficiency can be increased.

The structure shown 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 light emitting 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. Also in the devices of FIGS. 2 and 3, if necessary, in addition to the compound of the general formula [1], a luminescent agent, a luminescent auxiliary agent, and a hole transport material or an electron transport material for transporting carriers are combined in each layer. Can be used.

As the conductive substance used for the anode of the organic EL element, those having a work function of more than 4 eV are preferable, and carbon, aluminum, vanadium, iron, cobalt, nickel, tungsten, silver, gold, platinum , Palladium and the like, alloys thereof, metal oxides such as tin oxide and indium oxide called ITO substrates and NESA substrates, and organic conductive resins such as polythiophene and polypyrrole are used. As the conductive material used for the cathode, those having a work function of less than 4 eV are preferable, and magnesium, calcium, tin, lead, titanium,
Yttrium, lithium, ruthenium, manganese, and the like and alloys thereof are used, but are not limited thereto.

In the organic EL device, at least one of the electrode A 2 and the electrode B 6 is desirably sufficiently transparent in the emission wavelength region of the device 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 electrode that extracts light emission
It is desirable that the light transmittance be 10% or more. Substrate 1
Is not limited as long as it has mechanical and thermal strength and is transparent, but examples thereof include transparent resins such as a glass substrate, a polyethylene plate, a polyether sulfone plate, and a polypropylene plate. .

Each layer of the organic EL device according to the present invention can be formed by any of a dry film forming method such as vacuum evaporation and sputtering and a wet film forming method 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. Normal film thickness is from 10 nm to 10
μm, preferably in the range of 100 Angstroms to 2000 Angstroms.

In the case of the wet film forming method, a thin film is formed by using a solution in which the material for forming each layer is dissolved or dispersed in an appropriate solvent such as chloroform, tetrahydrofuran, dioxane or the like. May be. Further, in any of the organic layers, an appropriate resin or additive may be used for improving film forming properties, preventing pinholes in the film, and the like. Examples of such a resin include insulating resins such as polystyrene, polycarbonate, polyarylate, polyester, polyamide, polysulfone, polymethyl methacrylate, and polymethyl acrylate; photoconductive resins such as poly-N-vinylcarbazole and polysilane; and polythiophene. And a conductive resin such as polypyrrole.

This organic EL device has a light emitting layer, a hole injection layer,
In the electron injection layer, if necessary, a known luminescent substance, luminescent auxiliary agent, hole transport substance, or electron transport 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, fluorescein, perylene, phthaloperylene, naphthaloperylene, perinone,
Phthaloperinone, naphthaloperinone, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, aldazine, bisbenzoxazoline, bisstyryl, pyrazine, cyclopentadiene, oxine, aminoquinoline, imine, diphenylethylene, vinylanthracene, diaminocarbazole, pyran, thiopyran , Polymethine, merocyanine, imidazole chelated oxinoid compounds, quinacridone, and the like, and derivatives thereof, but are not limited thereto. Further, the compound of the general formula [1] of the present invention can be used not only as a luminescent substance but also in combination with a suitable luminescent substance as a luminescence auxiliary.

The hole transporting material has the ability to transport holes, has an excellent hole injection effect on the light emitting layer or the luminescent agent, and has an electron transporting layer or an electron transporting exciton generated in the light emitting layer. Compounds which prevent transfer to a transport agent and have excellent thin film forming ability are exemplified. Specifically, oxadiazole, triazole, imidazole, imidazolone, imidazolethione, pyrazoline, pyrazolone, tetrahydroimidazole, oxazole, oxadiazole, hydrazone, acylhydrazone, polyarylalkane,
Stilbene, butadiene, benzidine-type triphenylamine, styrylamine-type triphenylamine, diamine-type triphenylamine and the like, and derivatives thereof, and polymer materials such as polyvinylcarbazole, polysilane, and a conductive polymer. However, the present invention is not limited to this.

The electron transporting substance has the ability to transport electrons, has an excellent electron injecting effect on a light emitting layer or a light emitting agent, and has a hole transporting layer or a hole transporting function for excitons generated in the light emitting layer. Compounds that prevent transfer to the agent and have excellent thin film forming ability. For example, fluorenone, anthraquinodimethane, diphenylquinone, thiopyran dioxide, oxadiazole, perylenetetracarboxylic acid,
Examples include, but are not limited to, fluorenylidenemethane, anthraquinodimethane, anthrone, and the like, and their derivatives.

The sensitization can also be carried out 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. . In order to improve the stability of the organic EL device obtained by the present invention, it is also possible to provide a protective layer on the surface of the device, or to protect the entire device by encapsulating silicon oil or the like. With these methods, temperature, humidity,
The element can be protected against the atmosphere and the like.

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. 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.

[0032]

The present invention will be described in more detail with reference to the following examples. Parts described in examples are parts by weight. (Synthesis example) 2,7-dimethylanthrone-bis (triphenylphosphonium chloride) 8.3 in a flask
And 2.1 parts of benzaldehyde were dissolved in 150 ml of absolute ethanol. To this, 1.9 parts of sodium ethoxide was added at room temperature, and the mixture was stirred for 10 hours. Thereafter, the precipitate was filtered and washed to obtain 8.7 parts of a yellowish white powder. This powder was recrystallized from toluene to obtain yellow crystals. As a result of mass analysis of the crystals, chemical analysis such as infrared absorption spectrum, etc., it was confirmed that the crystals were the compound described in Compound (4).

Example 1 A compound (4) was dissolved in chloroform on a washed glass plate with an ITO electrode, and a light emitting layer was formed by spin coating to obtain a phosphor layer having a thickness of 500 angstroms. Add magnesium and silver 10:
An electrode having a thickness of 2000 angstroms was formed from the alloy mixed in Step 1 to obtain the organic EL device shown in FIG. This device emitted light of about 80 cd / m ² at a DC voltage of 10 V.

Example 2 An organic EL device was manufactured in the same manner as in Example 1, except that the compound (4) was used to form a light-emitting layer by a vacuum evaporation method. This element is approximately 110 cd / m at a DC voltage of 10 V.
² luminescence 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 is vacuum deposited to obtain 50
A hole injection layer having a thickness of 0 Å was obtained. Next, a light emitting layer of compound (4) having a thickness of 500 angstroms was formed by a vacuum evaporation method, and an electrode having a thickness of 2000 angstroms was formed thereon by using an alloy of magnesium and silver mixed at a ratio of 10: 1. An organic EL device shown in FIG. 2 was obtained. This element is approximately 200 cd / m at a DC voltage of 10 V.
² luminescence was obtained.

Example 4 Compound (7) was used in place of N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-biphenyl-4,4'-diamine. An organic EL device was manufactured in the same manner as in Example 3, except that the hole injection layer was formed by a vacuum evaporation method. This device emitted light of about 280 cd / m ² at a DC voltage of 10 V.

Example 5 N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'- was placed on a washed glass plate with an ITO electrode.
Biphenyl-4,4'-diamine is vacuum deposited to obtain 50
A hole injection layer having a thickness of 0 Å was obtained. Next, a light emitting layer having a thickness of 300 Å of the compound (17) was formed by a vacuum evaporation method, and an electron injection layer having a thickness of 200 Å of the compound (29) was obtained by a vacuum evaporation method. On top of that, 10: 1 magnesium and silver
An electrode having a film thickness of 2,000 Å was formed from the alloy mixed in the step (1) to obtain the organic EL device shown in FIG. This device emitted light of about 420 cd / m ² at a DC voltage of 10 V.

When continuous light emission was performed at 1 mA / cm ² for all the organic EL devices shown in this example, 10
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.

[0039]

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.

[0040]

[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 Examples 3 and 4.

FIG. 3 is a cross-sectional view illustrating a schematic structure of an organic EL device used in Example 5.

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C09K 11/06 655 C09K 11/06 655

Claims (4)

(57) [Claims] 1. An organic electroluminescence device comprising a light emitting layer comprising one or more organic compound thin films between a pair of electrodes, wherein at least one layer is a layer containing a compound represented by the following general formula [1]. An organic electroluminescent device, comprising: General formula [1] [In the formula, X and Y 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, a mercapto group, an alkyloxy group, an alkylthio group. Group, aryloxy group, arylthio group, siloxy group,
Acyl group, cycloalkyl group, carbamoyl group, carboxylic acid group, sulfonic acid group, substituted or unsubstituted aliphatic group, substituted or unsubstituted aliphatic ring group, substituted or unsubstituted carbocyclic aromatic ring group Represents a substituted or unsubstituted heterocyclic aromatic ring group or a substituted or unsubstituted heterocyclic group. Z is a divalent residue represented by the general formula [2];
And B are each independently O, S, NR ¹³ , C = O,
C = S, (C = O)-(C = O), (C = S)-(C =
S), shows the _{SO 2, CH 2, CH 2} -CH 2, CH = CH or C = C (CN) _2. General formula [2] R ¹ to R ¹³ each independently represent a hydrogen atom, a halogen atom, a cyano group, a nitro group, an amino group, an ester group,
Mono- or di-substituted amino group, hydroxyl group, alkoxy group, mercapto group, alkyloxy group, alkylthio group, aryloxy group, arylthio group, siloxy group, acyl group, cycloalkyl group, carbamoyl group, carboxylic acid group, sulfonic acid group, A substituted or unsubstituted aliphatic group,
A substituted or unsubstituted aliphatic type ring group represents a substituted or unsubstituted carbocyclic aromatic ring group, a substituted or unsubstituted heterocyclic aromatic ring group, a substituted or unsubstituted heterocyclic group, R ⁵ And R ⁸ and R ⁹ to R ¹² each represent 1
One bond to a carbon atom of an adjacent vinyl bond. Also,
R ⁵ to R ⁸ or R ⁹ to R ¹² each represent a substituted or unsubstituted aliphatic ring, substituted or unsubstituted carbocyclic aromatic ring, substituted or unsubstituted heterocyclic An aromatic ring or a substituted or unsubstituted heterocyclic ring may be formed. ] 2. An organic electroluminescence device having a light-emitting layer comprising one or more organic compound thin films between a pair of electrodes, wherein the light-emitting layer is a layer containing a compound represented by the general formula [1]. The organic electroluminescence device according to claim 1, wherein: 3. An organic electroluminescence device having a light emitting layer composed of one or more organic compound thin films between a pair of electrodes, wherein the hole injection layer has a general formula [1].
The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device is a layer containing a compound represented by the following formula: 4. An organic electroluminescence device having a light emitting layer composed of one or more organic compound thin films between a pair of electrodes, wherein the electron injection layer has a general formula [1].
The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device is a layer containing a compound represented by the following formula: