KR20010030115A - Organic Electroluminescent Device - Google Patents

Abstract

PURPOSE: 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. CONSTITUTION: 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

Organic Electroluminescent Device

The present invention relates to an organic electroluminescent device (hereinafter referred to as an "organic EL device"), and more particularly to an organic EL device containing a novel coumarin derivative.

In today's information age, innovative demands on information display elements have not ceased to display as much information as accurately and comfortably as possible. Currently, brown tubes are mainly used in relatively large information display devices such as computer terminals and television receivers, but CRTs are not suitable for consumer devices or small devices that emphasize portability because of their large volume, weight, and high operating voltage. Smaller devices require thinner, lighter weight plates, lower operating voltages, and lower power consumption. Currently, it is recognized that liquid crystal devices have a low operating voltage and relatively low power consumption, and thus are widely used in various fields. However, the information display device using the liquid crystal element has a problem that the contrast varies depending on the viewing angle, so that a clear display is not obtained unless it is read in a certain angle range, and there is a problem that the power consumption is not reduced that much because it usually requires a backlight. . Organic EL elements have emerged as display elements that solve these problems.

The organic EL device usually has a thin film containing a light emitting agent between the anode and the cathode, and injects holes and electrons into the thin film by applying a DC voltage between the anode and the cathode, and they are recombined with each other to excite the light emitting agent. It is a light emitting element that makes a state and uses light emission such as fluorescence or phosphorescence emitted when the excited state returns to the ground state. The organic EL device is characterized in that the color tone of the light emission can be appropriately changed by selecting an appropriate host light emitting agent and at the same time changing the guest light emitting agent (dopant) combined with the host light emitting agent. In addition, when the host light emitting agent and the guest light emitting agent are combined, there is a possibility that the luminance and lifetime of light emission can be significantly improved. Since the organic EL element spontaneously emits light from the beginning, an information display device using the organic EL element has an advantage that the power consumption can be reduced because there is no dependence on the viewing angle and no backlight is required.

Until now, it has been reported that the organic EL device emitting light in the green region improves the luminous efficiency by incorporating the guest light emitting agent. It has a short lifespan and insufficient durability and reliability. For example, the organic EL devices disclosed in Japanese Patent Application Laid-open No. Hei 10-60427 and U.S. Patent No. 47,9292 have problems in realizing full color because the luminance is not sufficient and the light emission is not completely red.

In order to supply organic EL devices inexpensively, it is essential to simply find a light emitting agent that simplifies the structure of the entire device or facilitates the deposition operation during manufacturing and does not essentially require doping with a guest light emitting agent. There have been various proposals for the light emitting agent used in the organic EL device, but a compound satisfying the various requirements as described above has not yet been found.

In view of such a situation, an object of the present invention is to provide an organic EL device having a good color purity of light emission in a visible region, particularly a red region, and excellent in luminous efficiency and durability, and its use.

In order to solve the above problems, the present inventors conducted research and search, and found that the monovalent group of a hydrogen atom, cyano group, nitro group, carboxyl group, aryl group, alkyl group, alkoxy group, heterocyclic group or polycyclic aromatic hydrocarbon at position 3 It has been found that a series of 4-cyanocoumarin derivatives containing carbon at positions 6 to 8, forming a euroridine ring, have a significant luminous ability in the visible region and are very useful as a light emitting agent in organic EL devices. . It was confirmed that the organic EL device containing such a coumarin derivative efficiently emits light with excellent color purity when a direct current voltage is applied. The present invention is based on the discovery of the production of novel coumarin derivatives and their industrially useful properties.

1 is a schematic diagram of an organic EL device according to the present invention;

2 is a schematic view of a display panel according to the present invention;

3 is a block diagram of an information display apparatus according to the present invention;

(Explanation of the sign)

1, 10 substrate 2, 14 anode 3, 16: hole injection / transport layer

4, 18: light emitting layer 5: electron injection / transport layer 6, 20: cathode

30: DC power supply 32, 34: booster circuit 36, 46: driver circuit

38: microcomputer 40: clock generation circuit 42, 44: oscillation circuit

48: display panel

The organic EL device of the present invention contains a 4-cyanocoumarin derivative represented by the formula (1).

In formula (1), R ₁ to R ₄ each represent an alkyl group or an alkoxy group. When R <_1> -R <_4> is an alkyl group, chain length is selected from a methyl group and an ethyl group which are 3 or less carbon atoms, and usually 1 or 2 carbon atoms. As the alkoxy group, a methoxy group and an ethoxy group having 3 or less carbon atoms, usually 1 or 2 carbon atoms are selected.

In Formula 1, X represents a monovalent group of 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, and the heterocyclic group may have one or more substituents. As each aryl group, a phenyl group, a diphenyl group, a terphenyl group, etc. are mentioned, for example, As an alkyl group, it is chosen from a methyl group and an ethyl group of 3 or less carbon atoms, and usually 1 or 2 carbon atoms. The alkoxy group is selected from methoxy and ethoxy groups having 3 or less carbon atoms, usually 1 or 2 carbon atoms. The heterocyclic group preferably contains one or more oxygen atoms, sulfur atoms and / or nitrogen atoms, and each heterocyclic group may be, for example, a benzothiazolyl group, a naphthothiazolyl group, a benzoxazolyl group and a benzoimide. And a dazolyl group. Moreover, as a monovalent group of polycyclic aromatic hydrocarbon, a naphthyl group, anthracenyl group, a phenanthryl group, etc. are mentioned, for example. Moreover, as a substituent of a heterocyclic group, an alkoxy group, such as a methoxy group and an ethoxy group, or an aryl group, such as a phenyl group, a diphenyl group, and a terphenyl group, is mentioned, for example.

Specific examples of the 4-cyanocoumarin derivatives represented by Formula 1 include compounds represented by Formulas 2 to 10. Since these 4-cyanocoumarin derivatives have remarkable luminescence in the visible region, they are very useful as guest luminescent agents for improving the luminous efficiency or luminescence spectrum by dope a small amount of the host luminescent agent or other host luminescent agents in organic EL devices.

The 4-cyanocoumarin derivatives used in the present invention can be prepared by various methods. When an emphasis on economic efficiency, for example N, N- dimethylformamide, N, N- diethylacetamide, dimethyl sulfoxide with the compound represented by formula (11) having a R ₁ ~R ₄ and X corresponding to Formula 1, N -The method of carrying out 4-cyanoation by acting cyanide compounds, such as sodium cyanide and potassium cyanide, to hydrophilic solvents, such as methylpyrrolidone and hexamethyl phosphate triamide, or a mixture liquid of these hydrophilic solvents and water is suitable. Do. All 4-cyanocoumarin derivatives represented by the formulas (2) to (10) can be easily produced by this method. The compound represented by general formula (11) can be manufactured, for example by the method of Unexamined-Japanese-Patent No. 6-9892. The 4-cyanocoumarin derivatives thus obtained are, for example, separated, decanted, filtered, extracted, concentrated, thin layer chromatography, column chromatography, gas chromatography, high performance liquid chromatography, distillation, sublimation, prior to normal use. It refine | purifies by the conventional method used for refine | purifying related compounds, such as crystallization, and can apply combining these methods as needed.

Most of the 4-cyanocoumarin derivatives represented by the general formula (1) have the maximum emission in the visible region having a wavelength longer than the wavelength of 600 nm, especially the red region having the wavelength of 620 to 650 nm, and form a stable thin film in the glass state. Very useful as a zero. An organic EL device obtained by advantageously applying such coumarin derivatives is an EL device containing an organic compound having inherently luminous ability, and is usually recombined with a positive electrode for applying a constant voltage, a negative electrode for applying a negative voltage, and a hole and an electron. Single-layer and stacked organic EL devices, including a light emitting layer emitting light emission, a hole injection / transport layer for injecting and transporting holes from an anode, and an electron injection / transport layer for injecting and transporting electrons from a cathode, are important applications. . In addition, the 4-cyanocoumarin derivative represented by Formula 1 functions as a guest light emitting agent to improve light emission efficiency and light emission spectrum by a small amount of doping into the hole injection / transport layer material, the electron injection / transport layer material, and other host light emitting agents. Therefore, in the organic EL device in which one or more of these materials are indispensable elements, it can be very advantageously used alone or in combination with other light emitting agents, materials for hole injection / transport layers and / or materials for electron injection / transport layers. . In the case where the light emitting agent combines hole injection / transport or electron injection / transport in the organic EL device, the hole injection / transport layer or the electron injection / transport layer is omitted, respectively, and the hole injection / transport layer material and the electron injection layer material When one side has the other function, the electron injection / transport layer or the hole injection / transport layer is omitted, respectively.

As described above, the organic EL device of the present invention can be configured in a single layer type or a stacked type. The operation of the organic EL device is essentially a process of injecting electrons and holes from the electrode, the process of moving the electrons and holes in the solid, the process of recombination of the electrons and holes and generating singlet or triplet excitons, the exciton light emission These processes are essentially different in the single layer organic EL device or the stacked organic EL device. However, in the single layer organic EL device, the characteristics of the above four processes can be improved simply by changing the molecular structure of the light emitting agent, whereas in the stacked organic EL device, functions required in each process are shared by a plurality of materials. Since each material can be optimized independently, it is generally easier to achieve the desired performance than to form a single layer rather than a single layer.

Referring to the organic EL device of the present invention with reference to the stacked organic EL device, for example, Figure 1 is a schematic diagram of the stacked organic EL device according to the present invention, the number 1 in the drawing is a substrate, usually soda glass, barium silicate glass Glass, such as aluminosilicate glass, or general-purpose substrate materials, such as plastic and a ceramic, are used. Preferred substrate materials are transparent glass and plastic, and opaque ceramics such as silicon are used in combination with transparent electrodes.

No. 2 is an anode, which is usually adhered to one side of the substrate 1 by vacuum deposition, chemical vapor deposition (CVD), sputtering, or the like, and has a low resistivity and a high light transmittance in the entire visible region. It is formed by forming a film at 10 to 1000 nm. As the conductive material, metal oxides such as metals such as gold, platinum, nickel, tin oxide, indium oxide, a mixed system of tin oxide and indium oxide (hereinafter referred to as "ITO"), or aniline, thiophene, Conductive oligomers and polymers having pyrrole and the like as repeating units are used. Among them, ITO is easy to obtain a low resistivity, there is a feature that can easily form a fine pattern by etching with acid.

No. 3 is a hole injection / transport layer, which is usually in close contact with the anode 2 as in the anode 2 to form, for example, an aromatic tertiary amine, hydrazone, carbazole or derivatives thereof in a thickness of 1 to 1000 nm. It is formed by. Aromatic tertiary amines are, for example, N, N'-bis (3-methylphenyl) -N, N'-diphenyl- (1,1'-biphenyl) -4,4'-diamine; Tree such as N, N'-di (1-naphthyl) -N, N'-diphenyl- [1,1'-biphenyl] -4,4'-diamine (hereinafter referred to as "NPB") It may be a phenylamine and its monomers, and may have a spiro center in a molecule, or a so-called "π-electron starburst molecule" such as triarylamine.

No. 4 is a light emitting layer, which is usually formed by bringing the light emitting layer into a thickness of 10 to 1000 nm, preferably 10 to 200 nm by bringing it into close contact with the hole injection / transport layer 3 in the same manner as in the anode 2. Examples of the light emitter include a 4-cyanocoumarin derivative represented by Formula 1 or general purpose oxathiazole, phenanthrene, triazole derivative, quinacridone, rubrene, or derivatives thereof which exhibit high fluorescence quantum yield in a thin film state; Or quinoline derivatives, such as 8-hydroxyquinoline, and metal complexes, such as aluminum, zinc, and beryllium, are used individually or in combination. When the 4-cyanocoumarin derivative represented by the formula (1) is used as a guest light emitting agent, it is usually 0.01 mol% or more, preferably 0.1 to 10 mol relative to the host light emitting agent, depending on the type of host light emitting agent used in combination. Blend in%.

No. 5 is an electron injection / transport layer, which is usually adhered to the light emitting layer 4 in the same manner as in the anode 2, and the same compound as in the light emitting layer 4, or a cyclic ketone such as benzoquinone, anthraquinone, fluorenone, or the like. The derivative is formed by thinning the film with a thickness of 10 to 500 nm.

No. 6 is a cathode, which is usually in close contact with the electron injection / transport layer 5 and has a lower work function than the compound used in the electron injection / transport layer 5 (typically 6 eV or less), for example lithium, magnesium, calcium, Metals such as sodium, silver, aluminum, indium, and the like are deposited alone or in combination, or a buffer layer made of copper phthalocyanine or the like and an ITO electrode are combined to form a cathode. The thickness of the cathode 6 is not particularly limited, and is usually set to 100 nm or more in consideration of conductivity, manufacturing cost, thickness of the entire device, light transmittance, and the like. Further, in order to improve the electron injection efficiency, for example, a thin film of alkali metal or alkaline earth metal may be set between the electron injection / transport layer 5 and the cathode 6.

As described above, the organic EL device of the present invention adjoins the anode 2, the cathode 6, the light emitting layer 4, the hole injection / transport layer 3 and the electron injection / transport layer 5 as necessary on the substrate 1. It can be obtained by integrally forming while being in close contact with each other. As each layer is formed, it is preferable to work collectively under high vacuum, specifically 10 ^-5 Torr, in order to minimize the oxidation, decomposition, or adsorption of oxygen or moisture of organic compounds. Also, by forming a light emitting layer using a combination of a host light emitting agent and a guest light emitting agent, the light emitting layer may be mixed with both light emitting agents in a predetermined ratio in advance, or the heating temperature of both light emitting agents in vacuum deposition may be independently controlled. Adjust the proportion of the light emitter. In addition, the organic EL device thus manufactured may be partially or entirely encapsulated with, for example, an encapsulating gas or a metal cap under an inert gas atmosphere, or a protective film such as an ultraviolet curable resin in order to minimize deterioration in the use environment. It is preferable to coat it.

In the case of the organic EL device shown in FIG. 1, when a direct current 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. (4), electrons injected from the cathode 6 reach the light emitting layer 4 via the electron injection / transport layer 5. As a result, recombination of holes and electrons occurs in the light emitting layer 4, so that light of a predetermined wavelength is emitted through the anode 2 and the substrate 1 from the light emitting agent in an excited state. At this time, white light emission can also be obtained by coexisting light emission from both the host light emitting agent and the guest light emitting agent.

The use of the organic EL device according to the present invention will be described. According to the application, the organic EL device of the present invention may intermittently apply a relatively high voltage pulsed DC voltage or a relatively low voltage non-pulse DC voltage (usually, 3 to 3). 10V) is applied continuously to drive. The organic EL device of the present invention has good color purity of light emission in the visible region, especially in the red region, and has excellent luminous efficiency and durability, and thus has various uses in a device for visually displaying a light emitting body or information. Since the light emitting body using the organic EL element as a light source of the present invention has a low power consumption and can be configured in a lightweight flat plate form, for example, a liquid crystal element, a copying apparatus, a printing apparatus, an electrophotographic apparatus, Computer and its application equipment, industrial control equipment, electronic measuring equipment, general instruments, communication equipment, medical electronic measuring equipment, wheel-mounted equipment such as automobiles, shipboard equipment, aircraft control equipment, spacecraft equipment, interiors, signs, signs It is useful as an energy and space saving light source. When used in computers, televisions, videos, games, watches, car navigation systems, oscilloscopes, radars and sonar information displays, single or combined organic EL elements emitting light in the red, green or blue region, For example, it is processed in the form of a display panel and then driven by applying a general simple matrix method and an active matrix method.

Hereinafter, the preparation of the 4-cyano coumarin derivative used in the present invention in Reference Examples 1 to 4 with reference to Examples of the present invention, and then the 4-cyano in Examples 1 to 3 An organic EL device using a coumarin derivative, a display panel using such an organic EL device, and a government display device using such a display panel will be described.

(Reference Example 1: 4-cyanocoumarin derivative)

5 g of a formyl compound (9-formyl-8-hydroxy-1,1,7,7-tetramethyluroridine) and 1.7 g of cyanoacetamide represented by the formula (12) were dissolved in methanol, and piperidine 0.38 ml was added and reacted under heating and reflux for 3 hours, and then cooled to room temperature. 4.1 g of the crystal of the amidate represented by the formula (13) was filtered out, 2.9 g of o-aminothiophenol and 10 ml of N, N-dimethylformamide were added thereto, and the reactant was reacted at 110 DEG C for 6 hours to give room temperature. After cooling to 30 ml of isopyrophyll ether was added. 4.1 g of the precipitated crystals were filtered, dissolved in 300 ml of acetone, filtered, and half of the acetone was removed. The concentrated solution was cooled, the newly precipitated crystals were filtered out, washed with isopyrophyll ether and dried to obtain 3.5 g of a compound represented by the formula (14) having a benzothiazolyl group bonded at the 3rd position.

2.3 g of the compound represented by the formula (14) was taken and dispersed in 33 ml of N, N-dimethylformamide, and 2.53 ml of an aqueous 30% (w / w) sodium cyanide solution was added dropwise at room temperature, followed by reaction for 1 hour, followed by 0 to 0.44 mL of bromine was added dropwise while cooling to 10 ° C. and stirred for 2 hours. The precipitated crystals were filtered, washed with water and dried, and then purified by silica gel column chromatography using chloroform as a developing agent, to thereby obtain 2.1 g of whitish green crystals of the 4-cyanocoumarin derivative represented by the formula (2).

The melting point of the 4-cyanocoumarin derivative of this example was 266 to 269 ° C., and the absorption maximum fluorescence maximum was exhibited at wavelengths of 564 nm and 614 nm, respectively, when measured in methylene chloride. In addition, ¹ H-nuclear magnetic resonance spectrum (hereinafter referred to as " ¹ H-NMR") in heavy chloroform was measured. ), 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 ( Peaks were observed at the positions of 1H, s), 7.96 (1H, d) and 8.18 (1H, d), respectively.

(Reference Example 2: 4-cyanocoumarin derivative)

To 19 g of the amide represented by the formula (13) obtained by the method of Reference Example 1, 9.2 g of 1-amino-2-thionaphthol and 50 ml of N, N-dimethylformamide were respectively added and reacted at 110 ° C. for 4 hours. The mixture was cooled to room temperature, and the precipitated crystals were filtered out. The crystals were dissolved and filtered in 60 ml of chloroform, and crystallized using 140 ml of methanol. Then, the newly precipitated crystals were filtered and dried to obtain 18.2 g of a compound represented by the formula (15).

5 g of the compound represented by the formula (15) was dispersed in 50 ml of N, N-dimethylformamide, and 3.4 ml of an aqueous 30% (w / w) sodium cyanide solution was added dropwise at room temperature, followed by reaction for 1 hour, and then the reaction product was zero. 0.59 ml bromine was added dropwise while cooling to -10 [deg.] C. and stirred for 2 hours. 4.9 g of the precipitated crystals were washed with water, dried, and recrystallized with N, N-dimethylformamide to give 2.6 g of a whitish green crystal of the 4-cyanocoumarin derivative represented by the formula (5).

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

(Reference Example 3: 4-cyanocoumarin derivative)

To 3.4 g of the amidate represented by the formula (13) obtained by the method of Reference Example 1, 3.0 g of 2-amino-4-phenylthiophenol and 30 ml of N, N-dimethylformamide were respectively added and reacted at 140 ° C. for 4 hours. After making it cool, it cooled to room temperature and the precipitated crystal | crystallization was filtered. The crystals were dissolved in 30 ml of chloroform and filtered, and newly precipitated crystals were filtered out using 70 ml of methanol to obtain 2.5 g of a compound represented by the formula (16).

2.5 g of the compound represented by the formula (16) was dispersed in 25 ml of N, N-dimethylformamide, and 1.6 ml of 30% (w / w) sodium cyanide solution was added dropwise at room temperature, followed by reaction for 1 hour. 0.31 ml of bromine was added dropwise while cooling to 0-10 ° C. and stirred for 2 hours. The precipitated crystals were filtered, washed with water and dried, and then purified by silica gel column chromatography using chloroform as a developing agent to obtain 1.9 g of whitish green crystals of the 4-cyanocoumarin derivative represented by the formula (8).

The melting point of the 4-coumarin derivative of the present example was 261 to 263 DEG C as measured according to a conventional method. When measured in methylene chloride, absorption maximum and fluorescence maximum were shown at wavelengths 569 nm and 617 nm, respectively. In addition, ¹ H-NMR measurement in heavy chloroform showed that the chemical shift δ (ppm, TMS) was 1.38 (6H, s), 1.58 (6H, s), 1.81 (2H, t), 1.85 (2H, t), 3.36. (2H, t), 3.45 (2H, t), 7.26 to 7.41 (1H, m), 7.46 to 7.51 (2H, m), 7.66 to 7.69 (1H, dd), 7.71 to 7.75 (3H, m), 8.01 Peaks were observed at the positions of (1H, d) and 8.39 (1H, d), respectively.

(Reference Example 4: 4-cyanocoumarin derivative)

Take 3.0 g of the amidate represented by the formula (13) obtained by the method of Reference Example 1, add 3.0 g of 2-amino-4,5-dimethoxythiophenol and 15 ml of N, N-dimethylformamide, respectively, at 140 ° C. After reacting for 4 hours, the mixture was cooled to room temperature and the precipitated crystals were filtered out. This crystal was dissolved in chloroform and purified by silica gel column chromatography using a chloroform / ethyl acetate mixture as a developing agent to obtain 2.5 g of a compound represented by the formula (17).

2.5 g of the compound represented by the formula (17) was dispersed in 50 ml of N, N-dimethylformamide, and 2.0 l of 30% (w / w) sodium cyanide solution was added dropwise at room temperature, followed by reaction for 1 hour. 0.25 ml bromine was added dropwise while cooling to 0-10 ° C. and stirred for 2 hours. The precipitated crystals were filtered, washed with water, dried, dissolved in chloroform, and purified by silica gel column chromatography using a chloroform / ethyl acetate mixture as a developing agent to obtain the 4-cyanocoumarin derivative represented by the formula (4). 1.1 g of green crystals were obtained.

The melting point of the 4-cyanocoumarin derivative of this example was 308 to 312 ° C, and the absorption maximum and fluorescence maximum were shown at wavelengths of 576 nm and 629 nm, respectively. In addition, when measured by ¹ H-NMR in heavy chloroform, the chemical shift δ (ppm, TMS) was 1.32 (6H, s), 1.60 (6H, s), 1.77 (2H, t), 1.83 (2H, t), 3.29. Peaks were observed at positions (2H, t), 3.37 (2H, t), 3.98 (6H, s), 7.36 (1H, s), 7.49 (1H, s), and 7.61 (1H, s), respectively.

The physical properties are shown in Table 1 with respect to the 4-cyanocoumarin derivatives obtained by the methods of Reference Examples 1 to 4. 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. In addition, the 4-cyanocoumarin derivatives used in the present invention have a slight difference in structure, raw materials, reaction conditions and quantities, but the methods described in Reference Examples 1 to 4, including those represented by Formulas 2 to 10, or these It can prepare according to the method.

compound Absorption maximum wavelength (nm) Fluorescence maximum wavelength (nm) Melting Point (℃) Formula 2 564 614 266-269 Formula 4 576 629 308-312 Formula 5 580 627 322-326 Formula 8 569 617 261-263

Example 1: Organic EL Device

A glass substrate having a 100 nm thick transparent ITO electrode patterned with aqua regia vapor was ultrasonically cleaned using a neutral detergent, pure water, and isopropyl alcohol, raised with boiled isopropyl alcohol, dried, and washed with ultraviolet ozone. After fixing to the deposition apparatus, the pressure was reduced to 10 ^-7 Torr. Subsequently, NPB was deposited on the surface having the ITO transparent electrode as the anode in the glass substrate until the thickness was 60 nm to form a hole injection / transport layer. Thereafter, 4-cyanocoumarin derivatives represented by the formulas (2), (4), (5) or (8) obtained by the methods of Reference Examples 1 to 4 while being monitored by a film thickness sensor and tris (8-hydroxyquinoline) aluminum (Hereinafter referred to as " Alq3 &quot;) to form a light emitting layer by co-depositing up to 20 nm in thickness so as to have a weight ratio of 0.8: 100, and again depositing Alq3 to 40 nm in thickness to form an electron injection / transport layer, followed by lithium fluoride Were deposited in order to thickness 0.5nm and 150nm, 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 organic EL device thus obtained was tested for light emission characteristics in the usual manner. The organic EL device was prepared in the same manner as above except that the compound represented by the formula (18) was used instead of the 4-cyanocoumarin derivative, and this was treated by the same treatment as the organic EL device using the 4-cyano coumarin derivative. It was. The results are shown in Table 2.

compound Emission wavelength (nm) Luminance (cd / ㎡) ^{* 1} Life (hr) ^{* 2} Remarks Formula 2 625 11 90 The present invention Formula 4 643 85 50 The present invention Formula 5 640 141 512 The present invention Formula 8 630 120 544 The present invention Formula 18 600 80 16 contrast

* 1: Measured value when driven with current 11 mA / cm 2

* 2: Half-life when constant current driving at initial luminance of 300 cd / m2

It is shown in Table 2 that the organic EL device of this embodiment causes red light emission having a maximum emission in a visible region exceeding a wavelength of 600 nm, especially a wavelength of 620 to 650 nm when a direct current voltage is applied. Light emission was confirmed around 4V and reached the highest luminance (6000cd / m 2) at around 15V. The half-life of the luminance when the constant current was driven at the initial luminance of 300 cd / m 2 was the same or significantly exceeded the control (more than 100 hours). Even when 100 hours had elapsed since the start of light emission, a dark part (dark spot) was not observed. On the contrary, as shown in the results of Table 2, the organic EL device of contrast had a shorter maximum wavelength (600 nm), and according to visual observation, the emission color was near orange.

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

Example 2: Display Panel

2 shows a simple matrix display panel (20 electrode rows in the horizontal direction and 30 electrode rows in the vertical direction) mainly composed of the organic EL device of the present invention. Such display panels can be manufactured as follows.

First, according to the method of Example 1, the anode 14 by the ITO transparent electrode is formed on one side of the glass substrate 10, and then the anode 14 is processed into a stripe by the wet etching method. Subsequently, the hole injection / transport layer 16 and the light emitting layer 18 were sequentially formed according to the method of Example 1, and the cathode 20 was formed in a stripe shape using a mechanical mask, and then a glass plate (not shown) and ultraviolet light were formed. The organic EL element is sealed with a cured resin. In addition, in the display panel of the present embodiment, a heat sink or a cooling fan may be mounted on the back side of the cathode 20 as necessary to suppress the temperature rise during use.

Example 3: Information Display Equipment

3 shows an information display apparatus using the display panel manufactured by the method of Example 2. FIG. In Fig. 3, 30 is a DC power supply having an output voltage of 4.5 V, and two boost circuits 32 and 34 are connected to the output terminal thereof. The booster circuit 32 can supply a DC voltage of 5-12V, and its output terminal is connected to the driver circuit 36. The booster circuit 34 is for supplying a constant voltage of 5V 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, a RAM 38c for storing various data, and a CPU 38d for performing various operations. Include. The microcomputer 38 is connected to a clock generating circuit 40 for supplying a clock signal of 8 MHz to the microcomputer 38 and two oscillating circuits 42 and 44, respectively. The two oscillating circuits 42 and 44 are connected to each other. Is supplied to the microcomputer 38 for a signal of 5 to 50 Hz for controlling the display speed and for a signal of 0.2 to 2 KHz for controlling the scanning frequency.

48 is a display panel mainly composed of the organic EL element of the present invention, and is connected to the microcomputer 38 via the driver circuits 36 and 46. The driver circuit 36 is a circuit for suppressing the DC voltage from the booster circuit 32 from being applied to the display panel, and includes a plurality of transistors individually connected to the vertical electrode columns in the display panel 48. Therefore, when any of the transistors in the driver circuit 36 is turned on, the voltage from the boosting circuit 32 is applied to the vertical electrode column connected to the transistor. On the other hand, the driver circuit 46 includes a plurality of transistors which are individually connected to the horizontal electrode columns of the display panel 48. The electrode string of is grounded.

Since the information display device of this embodiment is constituted as described above, when the transistors in the driver circuits 36 and 46 are turned on according to the instructions of the microcomputer 38, the electrodes corresponding to the vertical and horizontal directions of the display panel 48 are turned on. A predetermined voltage is applied between the columns, and the organic EL elements located at their intersections emit light. Thus, for example, by appropriately controlling the driver circuit 46, one column of horizontal electrodes is selected, and the transistor connected to the vertical electrode rows is controlled by appropriately controlling the driver circuit 36 while grounding the electrode rows. When turned on in sequence, the entire horizontal electrode column is scanned in the horizontal direction, and a given pixel is displayed. The entirety of one screen can be displayed by repeating such scanning in the vertical direction in order. In the present embodiment, since the driver circuit 36 has a data register of one column of electrodes, it is preferable to drive the transistor in accordance with the stored data.

The information to be displayed is supplied from the outside in accordance with the display speed and the period, or the information can be stored in the ROM 38b in advance for information having a certain pattern such as, for example, character information and the like. In the case of displaying a TV broadcast using a normal NTSC system, first, the received signal is divided into a horizontal synchronous signal, a horizontal synchronous signal and a vertical synchronous signal according to a horizontal frequency and a vertical frequency according to a broadcast standard, and a video signal is displayed on the display panel. A digital signal corresponding to the number of pixels 48 is converted. By appropriately synchronizing these signals to the microcomputer 38, television broadcasting can be displayed on the display panel 48.

As mentioned above, the present invention is based on the production of novel 4-cyanocoumarin derivatives and the discovery of their industrially useful properties. The organic EL device of the present invention containing such a 4-cyanocoumarin derivative has good light emission color purity in the visible region, especially in the red region, and excellent luminous efficiency and durability. It is very useful for various information display devices.

The present invention having such a remarkable working effect is very large and meaningful invention.

Claims (6)

An organic electroluminescent device containing a 4-cyanocoumarin derivative represented by Formula 1: (Formula 1) In formula (1), R ₁ to R ₄ each represent an alkyl group or an alkoxy group. X represents a monovalent group of a hydrogen atom, cyano group, nitro group, carboxyl group, aryl group, alkyl group, alkoxy group, heterocyclic group or polycyclic aromatic hydrocarbon, and the heterocyclic group may have a substituent. The organic electroluminescent device according to claim 1, comprising a 4-cyanocoumarin derivative represented by the formula (1) as a light emitting agent. The organic light emitting device according to claim 1 or 2, wherein the organic light emitting diode has a maximum light emission in a visible region exceeding a wavelength of 600 nm. The organic electroluminescent device according to claim 1, 2 or 3, which is a single layer type or a stacked type. The light emitting body using the organic electroluminescent element of any one of Claims 1-4. An information display apparatus using the organic light emitting display device according to any one of claims 1 to 4.