JP2001076875A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve color purity of the emitting light particularly in a red color area, and to improve light emitting efficiency and durability by including a 4-cyanocoumarin derivative. SOLUTION: A 4-cyanocoumarin derivative included in an organic EL element is expressed by the formula. In the formula, R1 to R4 respectively independently represent an alkyl group or an alkoxy group, X represents a hydrogen atom, a cyano group, a nitro group, a carboxyl group, an aryl group, an alkyl group, an alkoxy group, a heterocyclic group or a monovalent group of polycyclic aromatic hydrocarbon, and the heterocyclic group may have one or plural substituents. The 4-cyanocoumarin derivative is excellent as a light emitting agent since it has remarkable light emitting capacity in a visible area. Many of these have an emission maximum in the visible area having a wavelength longer than a wavelength of 600 nm, particularly, a red color area of a wavelength of 620 to 650 nm, and can form a stable thin film in a glass state.

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 (hereinafter abbreviated as "organic EL device"), and more particularly to an organic EL device containing a novel coumarin derivative. is there.

[0002]

2. Description of the Related Art In recent years, which can be described as the information age, innovative demands on information display elements are constantly ending in order to display as much information as possible accurately and comfortably. At present, CRTs are mainly used in relatively large information display devices such as computer terminals and television receivers.However, CRTs are large in volume and weight, and have high operating voltages. It is not suitable for small devices that emphasize portability. Smaller devices are required to be thinner, lighter, flat, low in operating voltage and low in power consumption. At present, liquid crystal elements have been used frequently in various fields, because of their low operating voltage and relatively low power consumption. However, information display devices using liquid crystal elements are:
Since the contrast changes depending on the viewing angle, a clear display cannot be obtained unless the image is read within a certain angle range. In addition, since a backlight is usually required, there is a problem that power consumption is not so reduced. An organic EL element has emerged as a display element that solves these problems.

[0003] The organic EL element is usually formed by interposing a thin film containing a luminescent agent between an anode and a cathode, and applying a DC voltage between the anode and the cathode to generate holes and electrons in the thin film. A light-emitting element that emits light such as fluorescence or phosphorescence emitted when the excited state returns to the ground state by creating an excited state of the luminescent agent by injecting each of them and recombining them. The organic EL element has a feature that the color tone of light emission can be appropriately changed by selecting an appropriate host light emitting agent and changing a guest light emitting agent (dopant) to be combined with the host light emitting agent. Also,
Depending on the combination of the host luminescent agent and the guest luminescent agent, there is a possibility that the luminance and the lifetime of light emission can be significantly improved. In the first place, an organic EL element emits light by itself, and an information display device using the organic EL element has an advantage that it has no viewing angle dependence and does not require a backlight, so that power consumption can be reduced. Is said to be.

[0004] In organic EL devices that emit light in the green range, improvement in luminous efficiency by the addition of a guest luminescent agent has been reported.
An effective guest luminescent agent has not yet been found, and is still far from complete red emission, has a short emission life,
The situation is insufficient in both durability and reliability. For example, the organic EL devices disclosed in Japanese Patent Application Laid-Open No. 10-6042 and U.S. Pat. No. 4,769,292 do not have sufficient luminance and light emission is not completely red. I have to say that there is a problem.

Further, in order to supply an organic EL device at a low cost, it is necessary not only to simplify the structure of the entire device and to facilitate the vapor deposition operation during the manufacture, but also to dope with a guest luminescent agent. It is important to find a luminescent agent that is not required for the above. Although various proposals have been made for luminescent agents used in organic EL devices, compounds satisfying the above requirements have not been found yet.

[0006]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an organic electroluminescent (E) filter having a high color purity of light emission in a visible region, particularly, a red region, and excellent luminous efficiency and durability.
It is an object to provide an L element and its use.

[0007]

Means for Solving the Problems In order to solve this problem,
As a result of extensive research and search conducted by the present inventors, a hydrogen atom, a cyano group, a nitro group, a carboxyl group, an aryl group, an alkyl group, an alkoxy group, a heterocyclic group or a polycyclic aromatic hydrocarbon is substituted at the 3-position. A series of 4-cyanocoumarin derivatives having any of the valent groups and comprising a 6- to 8-position carbon to form a urolidine ring have a remarkable luminous ability in a visible region, and have an organic EL device. Has been found to be extremely useful as a luminescent agent. Further, the organic EL device containing such a coumarin derivative, when a DC voltage is applied,
It was confirmed that light emission with excellent color purity was efficiently achieved and that it was maintained for a long period of time. The present invention is based on the creation of a novel coumarin derivative and the discovery of its industrially useful properties.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The organic EL device of the present invention is
And a 4-cyanocoumarin derivative represented by the formula:

[0009]

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In the formula 1, R _{1 to} R ₄ each independently represent an alkyl group or an alkoxy group. R _{1 to} R ₄
Is an alkyl group, the chain length is selected from methyl groups and ethyl groups having up to 3 carbon atoms, usually having 1 or 2 carbon atoms. As the alkoxy group, a methoxy group and an ethoxy group having up to 3 carbon atoms and usually 1 or 2 carbon atoms are selected.

Further, in the chemical formula 1, X represents a hydrogen atom, a cyano group, a nitro group, a carboxyl group, an aryl group, an alkyl group, an alkoxy group, a heterocyclic group or a monovalent group of a polycyclic aromatic hydrocarbon; The heterocyclic group may have one or more substituents. Individual aryl groups include, for example, phenyl, diphenyl and terphenyl groups, and alkyl groups are selected from methyl groups and ethyl groups having up to 3 carbon atoms, usually 1 or 2 carbon atoms. Is done. The alkoxy group is selected from methoxy groups and ethoxy groups having up to 3 carbon atoms, usually 1 or 2 carbon atoms. As the heterocyclic group, those containing at least one oxygen atom, sulfur atom and / or nitrogen atom are desirable. As the individual heterocyclic groups, for example, benzothiazolyl group, naphthothiazolyl group, benzoxazolyl group and benzimidazolyl group Is mentioned. Examples of the monovalent group of the polycyclic aromatic hydrocarbon include a naphthyl group, an anthracenyl group, a phenanthryl group, and the like. In addition,
Examples of the substituent of the heterocyclic group include an alkoxy group such as a methoxy group and an ethoxy group, and an aryl group such as a phenyl group, a diphenyl group, and a terphenyl group.

Specific examples of the 4-cyanocoumarin derivative represented by Chemical Formula 1 include compounds represented by Chemical Formulas 2 to 10. Since these 4-cyanocoumarin derivatives have remarkable luminous ability in the visible region, they are used for improving the luminous efficiency and luminous spectrum by doping a host luminous agent or another host luminous agent in an organic EL device in a small amount. Very useful as a guest luminescent agent.

[0013]

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[0014]

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[0015]

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[0016]

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[0017]

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[0018]

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[0019]

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[0020]

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[0021]

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The 4-cyanocoumarin derivative used in the present invention can be prepared by various methods. If emphasis is placed on economy, the compounds represented by Chemical Formula 11 having R _{1 to} R ₄ and X corresponding to Chemical Formula ₁ include, for example, N, N-dimethylformamide, N, N-diethylacetamide, dimethyl sulfoxide. , N-methylpyrrolidone, hexamethylphosphoric acid triamide or the like, or a cyanide compound such as sodium cyanide or potassium cyanide in a mixed solution of these hydrophilic solvents and water to perform 4-cyanoation. Is preferred. The 4-cyanocoumarin derivatives represented by Chemical Formulas 2 to 10 are:
All can be easily prepared by this method. Incidentally, the compound represented by Chemical formula 11 can be prepared, for example, by the method described in JP-A-6-9892. The 4-cyanocoumarin derivative thus obtained is usually used prior to use, for example, for separation, gradient, filtration, extraction, concentration, thin-layer chromatography, column chromatography, gas chromatography, high-performance liquid chromatography, Purification is performed by general-purpose methods used for purification of analogous compounds such as distillation, sublimation, and crystallization, and these methods are applied in combination as necessary.

[0023]

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Many of the 4-cyanocoumarin derivatives represented by Chemical Formula 1 have a light emission maximum in a visible region having a wavelength longer than 600 nm, particularly a red region having a wavelength of 620 to 650 nm, and have a thin film which is stable in a glassy state. Is extremely useful as a luminescent agent for an organic EL device. An organic EL device to which such a coumarin derivative can be advantageously applied is essentially an EL device containing an organic compound having a luminous ability, and usually has an anode to which a positive voltage is applied, and an anode to which a negative voltage is applied. A cathode, a light emitting layer for recombining holes and electrons to extract light emission, a hole injecting / transporting layer for injecting and transporting holes from the anode, if necessary, and an electron injecting and transporting for electrons from the cathode Single-layer and stacked organic EL elements provided with an electron injection / transport layer are important applications. Further, the 4-cyanocoumarin derivative represented by Chemical Formula 1 is doped with a small amount of a material for a hole injection / transport layer, a material for an electron injection / transport layer, and another host luminescent agent to improve the luminous efficiency and the luminescent spectrum. In an organic EL device in which one or more of such materials is an indispensable element because it also functions as a guest luminescent agent for improvement, a single or other luminescent agent, a material for a hole injection / transport layer, and / or an electron It can be used very advantageously in combination with a material for the injection / transport layer. In the stacked organic EL device, the luminescent agent was injected with holes /
In the case of having both the transporting ability and the electron injecting / transporting ability, the hole injecting / transporting layer or the electron injecting / transporting layer may be omitted, respectively. When one of them has the other function, the electron injection / transport layer or the hole injection / transport layer may be omitted.

As described above, the organic EL device of the present invention can be configured as a single layer type or a stacked type. The operation of an organic EL element is essentially a process of injecting electrons and holes from an electrode, a process of moving electrons and holes through a solid,
Electrons and holes are recombined to generate singlet or triplet excitons, and the exciton emits light. These processes are performed in a single-layer organic EL device and a stacked organic EL device. There is essentially no difference. However, in the single-layer organic EL device, the characteristics of the above four processes can be improved only by changing the molecular structure of the luminescent agent, whereas in the stacked organic EL device, the functions required in each process are improved. Can be shared among multiple materials, and each material can be optimized independently.In general, it is better to configure a stacked type rather than a single layer type to achieve the expected performance. easy.

Therefore, the organic EL device of the present invention
To further explain, taking a stacked organic EL element as an example, FIG. 1 is a schematic view of a stacked organic EL element according to the present invention, in which 1 is a substrate, usually soda glass, barium silicate glass, Glass such as aluminosilicate glass, or a general-purpose substrate material such as plastic or ceramic is used. Preferred substrate materials are transparent glass and plastic, and opaque ceramics such as silicon are used in combination with transparent electrodes.

Reference numeral 2 denotes an anode, which is usually brought into close contact with one side of the substrate 1 by a method such as vacuum evaporation, chemical vapor deposition (CVD), or sputtering, and has an electrically low resistivity and is completely visible. It is formed by depositing a conductive material having high light transmittance over a region to a thickness of 10 to 1,000 nm. As the conductive material, usually, metals such as gold, platinum, and nickel, tin oxide, indium oxide, and a mixed system of tin oxide and indium oxide (hereinafter abbreviated as “ITO”).
Such as metal oxides, or aniline, thiophene,
Conductive oligomers and polymers having pyrrole or the like as a repeating unit are used. Among them, ITO is characterized in that a low-resistivity one can be easily obtained and a fine pattern can be easily formed by etching with an acid.

Reference numeral 3 denotes a hole injecting / transporting layer, which is usually brought into close contact with the anode 2 in the same manner as in the anode 2,
For example, it is formed by forming a film of an aromatic tertiary amine, hydrazone, carbazole, or a derivative thereof to a thickness of 1 to 1,000 nm. The aromatic tertiary amine is, for example, N, N'-bis (3-methylphenyl)-
N, N'-diphenyl- (1,1'-biphenyl)-
4,4'-diamine, N, N'-di (1-naphthyl)-
N, N'-diphenyl- [1,1'-biphenyl]-
4,4'-diamine (hereinafter abbreviated as "NPB")
Or a multimer thereof, or a so-called “π-electron star burst molecule” such as a compound having a spiro center in the molecule or a triarylamine.

Reference numeral 4 denotes a light-emitting layer, which is usually brought into close contact with the hole injecting / transporting layer 3 by the same method as that for the anode 2 so that the light-emitting agent has a thickness of 10 to 1,000 nm, preferably 10 to 200 nm. It is formed by forming a film. As the luminescent agent, it gives a high fluorescence quantum yield in a thin film state, for example, a 4-cyanocoumarin derivative represented by Chemical Formula 1, or a general-purpose oxathiazole, phenanthrene, triazole derivative, quinacridone, rubrene or a derivative thereof, or And a metal complex of a quinoline derivative such as 8-hydroxyquinoline and aluminum, zinc, beryllium or the like is used alone or in combination.
When the 4-cyanocoumarin derivative represented by Chemical Formula 1 is used as a guest luminescent agent, it is usually at least 0.01 mol% based on the host luminescent agent, although it depends on the type of the host luminescent agent used in combination. Is blended in the range of 0.1 to 10 mol%.

Reference numeral 5 denotes an electron injecting / transporting layer, which is usually brought into close contact with the light emitting layer 4 in the same manner as in the anode 2, and is made of the same compound as in the light emitting layer 4, or benzoquinone, anthraquinone, fluorenone, or the like. By forming a thin film of a cyclic ketone or a derivative thereof to a thickness of 10 to 500 nm.

Reference numeral 6 denotes a cathode which is usually in close contact with the electron injecting / transporting layer 5 and has a work function lower than that of the compound used in the electron injecting / transporting layer 5 (usually 6 eV or less), for example, lithium, magnesium, A metal such as calcium, sodium, silver, aluminum and indium is used alone or in combination, or a buffer layer of copper phthalocyanine or the like and an ITO electrode are combined to form a cathode. There is no particular limitation on the thickness of the cathode 6, while taking into account the conductivity, the manufacturing cost, the thickness of the entire device, the light transmittance,
Usually, the thickness is set to 100 nm or more. In order to improve the efficiency of electron injection, for example, a thin film of an alkali metal or an alkaline earth metal may be provided between the electron injection / transport layer 5 and the cathode 6.

As described above, the organic EL device of the present invention
An anode 2, a cathode 6, a light emitting layer 4 and, if necessary, a hole injection / transport layer 3 and an electron injection / transport layer 5 on a substrate 1.
Can be obtained by forming them integrally while adhering to adjacent layers. In forming each layer, in order to minimize oxidation and decomposition of organic compounds and further adsorption of oxygen and moisture, under high vacuum, in detail,
It is desirable to work consistently at 10 ^-5 Torr or less. In addition, in forming a light emitting layer using a combination of a host light emitting agent and a guest light emitting agent, both light emitting agents are mixed in a predetermined ratio in advance, or the heating temperature of both light emitting agents in vacuum deposition. Are controlled independently of each other to adjust the ratio of both luminescent agents in the luminescent layer. In addition, in order to minimize the deterioration in the use environment, a part or the whole of the organic EL device thus constructed
For example, it is desirable to seal with a sealing glass or a metal cap in an inert gas atmosphere, or to cover with a protective film made of an ultraviolet curable resin or the like.

In the case of the organic EL device shown in FIG. 1, when a DC voltage is applied between the anode 2 and the cathode 6, holes injected from the anode 2 pass through the hole injection / transport layer 3 to the light emitting layer 4. In addition, electrons injected from the cathode 6 reach the light emitting layer 4 via the electron injection / transport layer 5, respectively. As a result, the light emitting layer 4
In the above, recombination of holes and electrons occurs, and light of a predetermined wavelength is emitted from the excited luminescent agent through the anode 2 and the substrate 1. At this time, white light emission can be obtained by causing light emission from both the host light emitting agent and the guest light emitting agent to coexist.

The application of the organic EL device according to the present invention will be described. The organic EL device according to the present invention applies a relatively high voltage pulse DC voltage intermittently or a relatively low voltage depending on the application. Driving is performed by continuously applying a non-pulse DC voltage (usually 3 to 10 V).
INDUSTRIAL APPLICABILITY The organic EL device of the present invention has good color purity of light emission in the visible region, particularly in the red region, and also has excellent luminous efficiency and durability. Has a variety of uses. Since the light-emitting body using the organic EL element of the present invention as a light source has low power consumption and can be formed into a light-weight flat plate, in addition to a light source for general illumination, for example, a liquid crystal element, a copying apparatus,
Printing equipment, electrophotographic equipment, computers and their applied equipment, industrial control equipment, electronic measurement equipment, general instruments, communication equipment, medical electronic measurement equipment, on-vehicle equipment such as automobiles,
It is useful as an energy-saving and space-saving light source for on-board equipment in ships, aircraft control equipment, on-board equipment for spacecraft, interiors, signs, and signs. When used for information display devices in computers, televisions, videos, games, clocks, car navigation systems, oscilloscopes, radars, and sonars, they need to be used alone or in combination with organic EL elements that emit light in the red, green, or blue regions. Accordingly, for example, after processing into the form of a display panel, driving is performed by applying a general-purpose simple matrix method and an active matrix method.

In the following, the preparation of the 4-cyanocoumarin derivative used in the present invention will be described first in Reference Examples 1 to 4 according to the embodiment of the present invention, and then in Examples 1 to 3, An organic EL element using the 4-cyanocoumarin derivative, a display panel using the organic EL element, and an information display device using the display panel will be described.

[0036]

Reference Example 1 <4-cyanocoumarin derivative> 5 g of a formyl compound (9-formyl-8-hydroxy-1,1,7,7-tetramethylurolidine) and 1.7 g of cyanoacetamide represented by the formula (12) were obtained. The mixture was dissolved by heating in methanol, 0.38 ml of piperidine was added, and the mixture was reacted under heating and reflux for 3 hours, and then cooled to room temperature. 4.1 g of the crystal of the amidated compound represented by the formula (13) was collected by filtration, 2.9 g of o-aminothiophenol and 10 ml of N, N-dimethylformamide were added, and reacted at 110 ° C. for 6 hours. After cooling to room temperature, 30 ml of isopropyl ether was added. 4.1 g of the precipitated crystals were collected by filtration, dissolved by heating in 300 ml of acetone, filtered, and half of the acetone was distilled off. The concentrated solution was cooled, and the newly precipitated crystals were collected by filtration, washed with isopropyl ether,
After drying, 3.5 g of a crystal of the compound represented by Chemical Formula 14 having a benzothiazolyl group bonded at the 3-position was obtained.

[0037]

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[0038]

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[0039]

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2.3 g of a compound represented by the following formula:
Dispersed in 33 ml of N, N-dimethylformamide, 2.53 ml of a 30% (w / w) aqueous solution of sodium cyanide was added dropwise at room temperature, and the mixture was allowed to react for 1 hour. 0.44 ml of bromine was added dropwise,
Stir for 2 hours. The precipitated crystals were collected by filtration, washed with water and dried, and then purified by silica gel column chromatography using chloroform as a developing agent. As a result, 2.1 g of a bright green crystal of a 4-cyanocoumarin derivative represented by Chemical Formula 2 was obtained. Obtained.

The melting point of the 4-cyanocoumarin derivative of this example was 266 to 269 ° C. as measured by a conventional method. When measured in methylene chloride, it showed an absorption maximum and a fluorescence maximum at wavelengths of 564 nm and 614 nm, respectively.
When ¹ H-nuclear magnetic resonance spectrum (hereinafter abbreviated as “ ¹ H-NMR”) was measured in deuterated chloroform, the chemical shift δ (ppm, TMS) was 1.37 (6
H, s), 1.59 (6H, s), 1.80 (2H,
t), 1.85 (2H, t), 3.36 (2H, t),
3.45 (2H, t), 7.39 to 7.44 (1H,
m), 7.52 to 7.61 (1H, m), 7.72
(1H, s), 7.96 (1H, d) and 8.18 (1
Peaks were observed at the positions of H and d).

[0042]

Reference Example 2 <4-cyanocoumarin derivative> One 19 g of the amidated compound represented by Chemical Formula 13 obtained by the method of Reference Example 1 was added.
-Amino-2-thionaphthol (9.2 g) and N, N-dimethylformamide (50 ml) were added,
For 4 hours, cooled to room temperature, and the precipitated crystals were collected by filtration. The crystals were dissolved in 60 ml of chloroform, filtered, crystallized using 140 ml of methanol, and the newly precipitated crystals were collected by filtration and dried.
18.2 g of crystals of the compound represented by Chemical Formula 15 were obtained.

[0043]

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5 g of the compound represented by the formula
Dispersed in 50 ml of N-dimethylformamide, 3.4% aqueous 30% (w / w) sodium cyanide solution at room temperature
After reacting for 1 hour, 0.59 ml of bromine was added dropwise while cooling the reaction mixture to 0 to 10 ° C.
Stir for 2 hours. The precipitated crystals (4.9 g) were collected by filtration, washed with water, dried, and recrystallized from N, N-dimethylformamide. As a result, a bright green crystal of the 4-cyanocoumarin derivative represented by Chemical Formula 5 was obtained. 0.6 g was obtained.

The melting point of the 4-cyanocoumarin derivative of this example was 322 to 326 ° C. as measured by a conventional method. When measured in methylene chloride, it showed an absorption maximum and a fluorescence maximum at wavelengths of 580 nm and 627 nm, respectively.
¹ H-NMR measurement in deuterated chloroform revealed that the chemical shift δ (ppm, TMS) was 1.40 (6
H, s), 1.60 (6H, s), 1.81 (2H,
t), 1.87 (2H, t), 3.36 (2H, t),
3.45 (2H, t), 7.58 to 7.63 (1H,
m), 7.71 to 7.76 (1H, m), 7.79
(1H, s), 7.81 to 7.84 (1H, m),
7.94 to 7.99 (2H, m) and 9.01 (1
Peaks were observed at the positions of H and d).

[0046]

Reference Example 3 <4-cyanocoumarin derivative> To 3.4 g of the amidated compound represented by Chemical Formula 13 obtained by the method of Reference Example 1, 3.0 g of 2-amino-4-phenylthiophenol and N, N-dimethyl were added. After adding 30 ml of formamide and reacting at 140 ° C. for 4 hours, the mixture was cooled to room temperature,
The precipitated crystals were collected by filtration. The crystals are treated with chloroform 30
The crystals were dissolved in the crystals, filtered, 70 ml of methanol was added, and the newly precipitated crystals were collected by filtration and dried to obtain 2.5 g of the crystals of the compound represented by the formula (16).

[0047]

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2.5 g of a compound represented by the following formula:
The mixture was dispersed in 25 ml of N, N-dimethylformamide, 1.6 ml of a 30% (w / w) aqueous sodium cyanide solution was added dropwise at room temperature, and the mixture was reacted for 1 hour. Then, the reaction product was cooled to 0 to 10 ° C. While adding 0.31 ml of bromine dropwise, the mixture was stirred for 2 hours. The precipitated crystals were collected by filtration, washed with water, and dried, and then purified by silica gel column chromatography using chloroform as a developing agent. As a result, 1.9 g of a bright green crystal of a 4-cyanocoumarin derivative represented by Chemical Formula 8 was obtained. Obtained.

The melting point of the 4-coumarin derivative of this example was 261 to 263 ° C. as measured by a conventional method, and the wavelength was 569 nm and 617 nm when measured in methylene chloride.
m shows the absorption maximum and the fluorescence maximum, respectively. ¹ H-NMR measurement in deuterated chloroform revealed that the chemical shift δ (ppm, TMS) was 1.38 (6H, s),
1.58 (6H, s), 1.81 (2H, t), 1.8
5 (2H, t), 3.36 (2H, t), 3.45 (2
H, t), 7.26 to 7.41 (1H, m), 7.4
6 to 7.51 (2H, m), 7.66 to 7.69
(1H, dd), 7.71 to 7.75 (3H, m),
Peaks were observed at the positions of 8.01 (1H, d) and 8.39 (1H, d), respectively.

[0050]

Reference Example 4 <4-cyanocoumarin derivative> 3.0 g of the amidated compound represented by Chemical Formula 13 obtained by the method of Reference Example 1
Then, 3.0 g of 2-amino-4,5-dimethoxythiophenol and 15 ml of N, N-dimethylformamide were added, and the mixture was reacted at 140 ° C. for 4 hours. After cooling to room temperature, the precipitated crystals were collected by filtration. . The crystals were dissolved in chloroform and purified by silica gel column chromatography using a chloroform / ethyl acetate mixed solution as a developing agent.
g were obtained.

[0051]

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2.5 g of the compound represented by the formula
The mixture was dispersed in 50 ml of N, N-dimethylformamide, 2.0 l of a 30% (w / w) aqueous sodium cyanide solution was added dropwise at room temperature, and the mixture was reacted for 1 hour.
While cooling to １０10 ° C., 0.25 ml of bromine was added dropwise and stirred for 2 hours. The precipitated crystals are collected by filtration, washed with water,
After drying, it was dissolved in chloroform and purified by silica gel column chromatography using a mixed solution of chloroform / ethyl acetate as a developing agent. As a result, 1.1 g of a bright green crystal of a 4-cyanocoumarin derivative represented by Chemical Formula 4 was obtained.
Obtained.

The melting point of the 4-cyanocoumarin derivative of this example was 308 to 312 ° C. as measured by a conventional method. When measured in methylene chloride, it showed an absorption maximum and a fluorescence maximum at wavelengths of 576 nm and 629 nm, respectively.
¹ H-NMR measurement in deuterated chloroform revealed that the chemical shift δ (ppm, TMS) was 1.32 (6
H, s), 1.60 (6H, s), 1.77 (2H,
t), 1.83 (2H, t), 3.29 (2H, t),
3.37 (2H, t), 3.98 (6H, s), 7.3
6 (1H, s), 7.49 (1H, s) and 7.61
A peak was observed at the position (1H, s).

4 obtained by the methods of Reference Examples 1 to 4.
Table 1 summarizes various physical properties of the cyanocoumarin derivative. In Table 1, the absorption maximum wavelength was measured by dissolving in methylene chloride, and the fluorescence maximum wavelength was measured at a concentration of 10 ^-7 M in methylene chloride. Although the 4-cyanocoumarin derivative used in the present invention has some differences in raw materials, reaction conditions, and yields depending on the structure, it includes Reference Examples 1 to 10 including those represented by Chemical Formulas 2 to 10. It can be easily prepared by the method described in No. 4 or according to those methods.

[0055]

[Table 1]

[0056]

Example 1 <Organic EL device> A glass substrate having a transparent ITO electrode with a thickness of 100 nm patterned with steam was washed with a neutral detergent, pure water and isopropyl alcohol by ultrasonic cleaning, and boiled isopropyl alcohol. After being pulled up, dried, washed with ultraviolet ozone, and fixed to a vapor deposition device, the pressure was reduced to 10 ^-7 Torr. Next, NPB was evaporated to a thickness of 60 nm on the surface of the glass substrate having the ITO transparent electrode as an anode to form a hole injection / transport layer. Thereafter, while monitoring with a film thickness sensor, any of the 4-cyanocoumarin derivatives represented by Chemical Formula 2, Chemical Formula 4, Chemical Formula 5, and Chemical Formula 8 obtained by the methods of Reference Examples 1 to 4 and tris (8-hydroxy Quinoline) aluminum (hereinafter abbreviated as “Alq3”) having a thickness of 20 to give a weight ratio of 0.8: 100.
nm to form a light emitting layer.
Was deposited to a thickness of 40 nm to form an electron injection / transport layer, and then lithium fluoride and aluminum were deposited in this order to a thickness of 0.5 nm and 150 nm, respectively, to form a cathode. Thereafter, the entire device was sealed with a glass plate and an ultraviolet curable resin under a nitrogen atmosphere to obtain four types of organic EL devices.

The luminescence characteristics of the thus obtained organic EL device were tested according to a conventional method. Simultaneously, an organic EL device was prepared in the same manner as described above except that the compound represented by Chemical Formula 18 was used instead of the 4-cyanocoumarin derivative.
This was treated in the same manner as in the case of the organic EL device using the 4-cyanocoumarin derivative to serve as a control. Table 2 shows the results.

[0058]

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[0059]

[Table 2]

As can be seen from the results in Table 2, the organic EL device of this example, when applied with a DC voltage, has a visible region exceeding a wavelength of 600 nm, especially a wavelength of 620 to 650 nm.
Gave a red emission with a maximum emission. Light emission is 4V
It was confirmed from the front and rear, and the maximum brightness (6,000
cd / m ² ). The half-life of the luminance when driven at a constant current at an initial luminance of 300 cd / m ² was equal to or significantly greater than that of the control (100 hours or more). No partial dark spot (dark spot) was observed even after 100 hours from the start of light emission. On the other hand, as can be seen from the results in Table 2, the control organic EL element had a shorter emission maximum wavelength (600 nm), and the luminescent color was close to orange according to visual observation.

These results indicate that the organic EL device of this example is a red light emitting device having good color purity.

[0062]

Embodiment 2 <Display Panel> FIG. 2 shows a simple matrix type display panel (20 electrode rows in the horizontal direction and 30 electrode rows in the vertical direction) mainly comprising the organic EL element of the present invention. Such a display panel can be manufactured as follows.

That is, first, according to the method of the first embodiment, the anode 14 made of an ITO transparent electrode is
Is formed, the anode 14 is processed into a stripe shape by a wet etching method. Next, a hole injection / transport layer 16 and a light emitting layer 18 are sequentially formed according to the method of Example 1, and a cathode 20 is formed in a stripe shape using a mechanical mask. The organic EL element is sealed with a resin. In the display panel of this example, a heat radiating plate or a cooling fan may be mounted on the back side of the cathode 20 as needed in order to suppress a rise in temperature during use.

[0064]

Third Embodiment <Information Display Apparatus> FIG. 3 shows an information display apparatus using a display panel manufactured by the method of the second embodiment. In FIG. 3, reference numeral 30 denotes a DC power supply having an output voltage of 4.5 V, and two booster circuits 32, 3
4 are connected. The booster circuit 32 can supply a DC voltage in the range of 5 to 12 V, and its output terminal is connected to the driver circuit 36. The other booster circuit 3
Reference numeral 4 is for supplying a constant voltage of 5 V to the microcomputer 38.

The microcomputer 38 includes an I / O interface 38a for exchanging signals with the outside, a ROM 38b for storing programs and the like, a RAM 38c for storing various data, and a CP for executing various operations.
U38d. The microcomputer 38 is connected to a clock generation circuit 40 for supplying a clock signal of 8 MHz to the microcomputer 38 and two oscillation circuits 42 and 44. The two oscillation circuits 42 and 44 are connected to the microcomputer 38. To
Each is for supplying a signal of 5 to 50 Hz for controlling the display speed and a signal of 0.2 to 2 kHz for controlling the scanning frequency.

Reference numeral 48 denotes a display panel mainly including the organic EL element of the present invention, which is connected to the microcomputer 38 via driver circuits 36 and 46. The driver circuit 36 is a circuit that controls the application of the DC voltage from the booster circuit 32 to the display panel, and includes a plurality of transistors individually connected to a vertical electrode row in the display panel 48. . Therefore, when one of the transistors in the driver circuit 36 is turned on, the voltage from the booster circuit 32 is applied to the vertical electrode row connected to the transistor.
On the other hand, the driver circuit 46 includes a plurality of transistors individually connected to a horizontal electrode row of the display panel 48. When any of the transistors in the driver circuit 46 is turned on, the horizontal circuit connected to the transistor is turned off. The electrode rows in the directions are grounded.

Since the information display device of this embodiment is configured as described above, when the transistors in the driver circuits 36 and 46 are turned on in accordance with the instruction of the microcomputer 38, the gap between the corresponding electrode rows in the vertical and horizontal directions of the display panel 48 is obtained. Is applied, and the organic EL element located at the intersection thereof emits light. Therefore, for example, one horizontal electrode row is selected by appropriately controlling the driver circuit 46, and the electrode row is connected to the vertical electrode row by appropriately controlling the driver circuit 36 while grounding the electrode row. When the transistors are sequentially turned on, the entire selected horizontal electrode row is scanned in the horizontal direction, and a given pixel is displayed. By repeating such scanning sequentially in the vertical direction, an entire screen can be displayed. Note that the driver circuit 3 in this example is
6 has a data register for one row of electrodes,
It is preferable to drive the transistor based on the stored data.

The information to be displayed is supplied from the outside in accordance with the display speed and cycle, or the information having a fixed pattern such as character information is stored in the ROM 38b in advance. In advance, this may be used as data. Also, normal NT
When displaying a television broadcast by the SC system,
First, a received signal is separated into a horizontal synchronization signal and a vertical synchronization signal according to a horizontal frequency and a vertical frequency based on a broadcast standard, and a video signal is converted into a digital signal corresponding to the number of pixels of the display panel 48. By appropriately synchronizing and supplying these signals to the microcomputer 38, a television broadcast can be displayed on the display panel 48.

[0069]

As described above, the present invention is based on the creation of a novel 4-cyanocoumarin derivative and the discovery of its industrially useful properties. The organic EL device of the present invention containing such a 4-cyanocoumarin derivative has good color purity of light emission in the visible region, particularly in the red region, and also has excellent luminous efficiency and durability. It can be very advantageously used in a light-emitting body as a light source in the above-mentioned and various kinds of information display devices for visually displaying information.

The present invention having such remarkable functions and effects can be said to be a significant invention which greatly contributes to the art.

[Brief description of the drawings]

FIG. 1 is a schematic view of an organic EL device according to the present invention.

FIG. 2 is a schematic diagram of a display panel according to the present invention.

FIG. 3 is a block diagram of an information display device according to the present invention.

[Description of sign]

 DESCRIPTION OF SYMBOLS 1, 10 Substrate 2, 14 Anode 3, 16 Hole injection / transport layer 4, 18 Emission layer 5 Electron injection / transport layer 6, 20 Cathode 30 DC power supply 32, 34 Boost circuit 36, 46 Driver circuit 38 Microcomputer 40 Clock Generation circuit 42, 44 Oscillation circuit 48 Display panel

Continued on the front page (72) Inventor Sadaharu Suga 8-7-1, Uno 8-chome, Tamano-shi, Okayama Prefecture (72) Inventor Shizushi Tokito 41 Chiku-jimichi, Nagakute-cho, Aichi-gun, Aichi Prefecture 1 Toyota Central Research Laboratory Co., Ltd. 72) Inventor Kuki Fujikawa 41 Toyota Chuo R & D Co., Ltd., at 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture (72) Inventor Koji Koji 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi, 1 Toyota Chuo Kenkyu Co., Ltd. In-house (72) Inventor Atsushi Miura 1 at 41-Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. (72) Inventor Yasukun Taga 41-41 Yokomichi, Nagakute-cho, Aichi-gun, Aichi Central Research Laboratory F term (reference) 3K007 AB00 AB03 AB04 BA06 CA01 CA02 CA05 CB01 DA00 DB03 EB00 FA01

Claims (6)

[Claims] 1. An organic electroluminescent device comprising a 4-cyanocoumarin derivative represented by the following chemical formula 1. Embedded image In Chemical Formula 1, R _{1 to} R ₄ each independently represent an alkyl group or an alkoxy group. X represents a hydrogen atom, a cyano group, a nitro group, a carboxyl group, an aryl group, an alkyl group, an alkoxy group, a heterocyclic group or a monovalent group of a polycyclic aromatic hydrocarbon, and the heterocyclic group has a substituent. It may be. 2. The organic electroluminescent device according to claim 1, comprising a 4-cyanocoumarin derivative represented by Chemical Formula 1 as a luminescent agent. 3. The organic electroluminescent device according to claim 1, wherein the organic electroluminescent device has an emission maximum in a visible region exceeding a wavelength of 600 nm. 4. The organic electroluminescent device according to claim 1, wherein the device is a single-layer type or a laminated type. 5. A luminous body using the organic electroluminescent device according to claim 1. 6. An information display device using the organic electroluminescent device according to claim 1.