JP2001267080A - Light emission element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a light emission element which has high luminescence efficiency and is excellent in color purity with high luminosity. SOLUTION: In a light emission element which has a luminescence substance existing between a positive pole and a negative pole, and emits light by electric energy, the element is the light emission element containing the organic fluorescent substance which has phenanthroline skeleton expressed with a formula (1). In the formula, R1-R8 which can be same with, or different from one another, are chosen from following substances; hydrogen, alkyl group, cycloalkyl group, aralkyl group, alkenyl group, cycloalkenyl group, alkynil group, hydroxyl group, mercapto group, alkoxy group, alkyl-thio group, arylether group, arylthioether group, aryl group, heterocyclic group, halogen, haloalkane, haloalkene, haloalkine, cyano group, aldehyde group, carbonyl group, carboxyl group, ester group, carbamoyl group, amino group, nitro group, silyl group, and siroxanyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an element capable of converting electric energy into light, and relates to a display element, a flat panel display, a backlight, lighting, an interior, a sign, a sign, an electrophotographic device, an optical signal generator, and the like. The present invention relates to a light emitting element that can be used in the field of (1).

[0002]

2. Description of the Related Art In recent years, studies have been actively conducted on organic laminated thin-film light emitting devices in which electrons injected from a cathode and holes injected from an anode emit light when they recombine in an organic phosphor sandwiched between both electrodes. ing. This device has attracted attention because it is thin, emits light with high luminance under a low driving voltage, and emits multicolor light by selecting a fluorescent material.

[0003] This study was carried out by Kodak Corporation. W. Tan
g. et al. showed that the organic laminated thin film element emits light with high luminance (Appl. Phys. Lett. 51 (12)
21, p. 913, 1987), and many research institutions are conducting studies. A typical configuration of an organic laminated thin film light emitting device presented by a research group of Kodak Company is a diamine compound having a hole transporting property and a light emitting layer on an ITO glass substrate.
Aluminum hydroxyquinoline and M as cathode
g: Ag was sequentially provided, and green light emission of 1000 cd / m ² was possible at a driving voltage of about 10 V.

[0004] The light emitting layer is composed of only a host material,
A host material is doped with a guest material.
The light emitting material is required to have three primary colors, but the research on the green light emitting material has been most advanced so far. At present, intensive studies have been made on red light emitting materials and blue light emitting materials with the aim of improving the characteristics. In particular, a blue light-emitting material that can emit light with high luminance and good color purity is desired.

As the host material, the above-mentioned tris (8-
Metal complexes of quinolinol derivatives including quinolinolato) aluminum, benzoxazole derivatives, stilbene derivatives, benzothiazole derivatives, thiadiazole derivatives, thiophene derivatives, tetraphenylbutadiene derivatives, cyclopentadiene derivatives, oxadiazole derivatives, oxadiazole derivative metal complexes And benzazole derivative metal complexes.

As an example of a blue light-emitting host material having relatively good performance, a metal complex obtained by combining a quinolinol derivative with a different ligand (Japanese Patent Laid-Open No. 5-21)
No. 4332) and bisstyrylbenzene derivatives (JP-A-4-117485), but the color purity is not particularly sufficient. Japanese Patent Application Laid-Open No. 7-82551 discloses an example having a phenanthroline skeleton, which claims to improve durability by increasing the melting point, but does not describe the melting point. Further, the phenanthroline skeleton has a planar structure and high crystallinity, and it is difficult to maintain an amorphous thin film. However, no measures have been taken to avoid this.

On the other hand, as a dopant material as a guest material, coumarin derivatives such as 7-dimethylamino-4-methylcoumarin, perylene, pyrene and anthracene, which are known to be useful as laser dyes, are known. Fused aromatic ring derivatives, stilbene derivatives, oligophenylene derivatives, furan derivatives, quinolone derivatives, oxazole derivatives, oxadiazole derivatives and the like are known.

With respect to the structure of this organic layered thin film light emitting device, it is known that an electron transport layer is appropriately provided in addition to the above anode / hole transport layer / light emitting layer / cathode. The hole transporting layer has a function of transporting holes injected from the anode to the light emitting layer, and one electron transporting layer transports electrons injected from the cathode to the light emitting layer. It is known that luminous efficiency and durability are improved by inserting these layers between the light emitting layer and both electrodes. Examples of device configurations using these are anode / hole transport layer / light-emitting layer / electron transport layer / cathode, anode / light-emitting layer / electron transport layer / cathode, and research on organic compounds suitable for each layer. It is performed mainly on hole transport materials.

[0009]

However, many light-emitting materials (host materials and dopant materials) used in the prior art have low light-emitting efficiency and high power consumption, and have low durability and short element life. Was. In addition, red, green, and blue light emission of three primary colors is required as a full-color display. However, in red and blue light emission, few light emission wavelengths are satisfied, and few light emission peaks have a wide emission peak width and good color purity. In particular, for blue light emission, a material having excellent durability and sufficient luminance and color purity characteristics is required.

Conventionally, electron transport materials have not been studied much more than hole transport materials, and even if a few existing materials are used, they interact with a light emitting material or light emission of the electron transport material itself is mixed. For this reason, there has been a problem that a desired luminescent color cannot be obtained, and high efficiency luminescence can be obtained but durability is short. For example, JP-A-5-3314
Japanese Patent No. 59 uses a specific phenanthroline derivative as an electron transporting material. However, although it exhibits high efficiency light emission, it has a problem that it is crystallized by a long-time energization and its durability is extremely short. In addition, quinolinol metal complexes and benzoquinolinol metal complexes exhibit relatively good properties in terms of luminous efficiency and durability. When used as a transport material, the luminescence of these materials themselves may be mixed and the color purity may be degraded.

An object of the present invention is to solve the problems of the prior art and to provide a light emitting device having high luminous efficiency, high luminance and excellent color purity.

[0012]

SUMMARY OF THE INVENTION The present invention relates to an element which emits light by electric energy, in which a light emitting substance is present between a positive electrode and a negative electrode, wherein the element has a phenanthroline skeleton represented by the following general formula (1). A light-emitting element comprising an organic phosphor having:

[0013]

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Here, R _{1 to} R ₈ may be the same or different, and may be hydrogen, an alkyl group, a cycloalkyl group,
Aralkyl group, alkenyl group, cycloalkenyl group, alkynyl group, hydroxyl group, mercapto group, alkoxy group, alkylthio group, aryl ether group, arylthioether group, aryl group, heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, cyano group, It is selected from aldehyde group, carbonyl group, carboxyl group, ester group, carbamoyl group, amino group, nitro group, silyl group and siloxanyl group. However, at least one of them has a three-dimensional structure by itself, or has a three-dimensional structure by steric repulsion with a phenanthroline skeleton or with an adjacent substituent.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a positive electrode is made of a conductive metal oxide such as tin oxide, indium oxide, indium tin oxide (ITO) or a metal such as gold, silver or chromium if it is transparent to extract light. Although not particularly limited, such as metals, inorganic conductive substances such as copper iodide and copper sulfide, and conductive polymers such as polythiophene, polypyrrole, and polyaniline, it is particularly preferable to use ITO glass or Nesa glass. The resistance of the transparent electrode is not limited as long as a current sufficient for light emission of the element can be supplied, but is preferably low from the viewpoint of power consumption of the element. For example, 3
Although an ITO substrate having a resistance of 00 Ω / □ or less functions as an element electrode, a substrate having a resistance of about 10 Ω / □ can be supplied at present. The thickness of the ITO can be arbitrarily selected according to the resistance value, but is usually used in a range of usually 100 to 300 nm. Further, the glass substrate is made of soda lime glass, non-alkali glass, or the like, and the thickness only needs to be sufficient to maintain the mechanical strength.
mm or more is sufficient. For the glass material,
Alkali-free glass is preferred because less ions elute from the glass is preferred, but soda-lime glass with a barrier coat such as SiO ₂ is also commercially available and can be used. The method of forming the ITO film is not particularly limited, such as an electron beam method, a sputtering method, and a chemical reaction method.

In the present invention, the cathode is not particularly limited as long as it can efficiently inject electrons into the organic material layer. Generally, platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium , Sodium, potassium, calcium, magnesium, etc., and lithium, sodium, potassium, calcium, magnesium or an alloy containing these low work function metals is effective in improving the device characteristics by increasing the electron injection efficiency. . However, these low work function metals are generally unstable in the air in many cases. For example, a very small amount of lithium or magnesium is added to an organic layer (1 or less in a vacuum deposition film thickness meter).
The following method can be cited as a preferable example in which an electrode having a high stability is used by doping (e.g., nm or less). However, the use of an inorganic salt such as lithium fluoride is also possible. Absent. Furthermore, for electrode protection, metals such as platinum, gold, silver, copper, iron, tin, aluminum and indium, or alloys using these metals, and inorganic substances such as silica, titania and silicon nitride, polyvinyl alcohol, vinyl chloride, It is preferable to laminate a hydrocarbon polymer or the like. The method for producing these electrodes is not particularly limited, as long as electrical conduction such as resistance heating, electron beam, sputtering, ion plating, and coating can be achieved.

In the present invention, the structure of the luminescent material is 1) a hole transport layer / a light emitting layer, 2) a hole transport layer / a light emitting layer / an electron transport layer, 3) a light emitting layer / an electron transport layer, and 4) May be in any form in which a combination of the above substances is mixed. That is, as the element configuration, in addition to the multilayer laminated structure of the above 1) to 3), a single layer of a luminescent material alone or a layer containing a luminescent material and a hole transporting material or an electron transporting material may be provided as in 4). Further, the luminescent substance in the present invention corresponds to both a substance which emits light by itself and a substance which assists the light emission, and refers to a compound, a layer, or the like involved in light emission.

In the present invention, the hole transporting layer is formed of a hole transporting substance alone or a mixture of two or more substances or a mixture of a hole transporting substance and a polymer binder.
As a hole transporting substance, it is necessary to efficiently transport holes from the positive electrode between electrodes to which an electric field is applied, and it is desirable to have a high hole injection efficiency and to efficiently transport injected holes. . For that purpose, it is required that the ionization potential be small, the hole mobility be large, the stability be further improved, and impurities serving as traps be hardly generated during production and use. The substance satisfying such conditions is not particularly limited,
N, N′-diphenyl-N, N′-di (3-methylphenyl) -4,4′-diphenyl-1,1′-diamine;
N, N'-dinaphthyl-N, N'-diphenyl-4,
Triphenylamines such as 4'-diphenyl-1,1'-diamine, bis (N-allylcarbazole) or bis (N-alkylcarbazole), pyrazoline derivatives, stilbene compounds, hydrazone compounds, oxadiazole derivatives And a phthalocyanine derivative, a heterocyclic compound represented by a porphyrin derivative, in a polymer system, a polycarbonate or a styrene derivative having the monomer in a side chain, polyvinyl carbazole, polysilane and the like are preferable, but a thin film necessary for element production is formed. The compound is not particularly limited as long as it is a compound capable of injecting holes from the positive electrode and further transporting holes.

In the present invention, the luminescent material may be a host material alone or a combination of a host material and a dopant material.
Any of them may be used. In addition, the dopant material may be included in the entire host material, partially, or may be included. The dopant material may be stacked, dispersed, or the like.

In the present invention, the light emitting material includes an organic phosphor having a phenanthroline skeleton represented by the following general formula (1) or (2).

[0021]

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Here, R _{1 to} R ₈ may be the same or different, and include hydrogen, an alkyl group, a cycloalkyl group,
Aralkyl group, alkenyl group, cycloalkenyl group, alkynyl group, hydroxyl group, mercapto group, alkoxy group, alkylthio group, aryl ether group, arylthioether group, aryl group, heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, cyano group, It is selected from aldehyde group, carbonyl group, carboxyl group, ester group, carbamoyl group, amino group, nitro group, silyl group and siloxanyl group. However, at least one of them has a three-dimensional structure by itself, or has a three-dimensional structure by steric repulsion with a phenanthroline skeleton or with an adjacent substituent.

[0023]

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Here, R _{9 to} R ₁₆ may be the same or different from each other, and include hydrogen, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a mercapto group, an alkoxy group, Alkylthio group, arylether group, arylthioether group, aryl group, heterocyclic group, halogen, haloalkane, haloalkene, haloalkyne, cyano group, aldehyde group, carbonyl group, carboxyl group, ester group, carbamoyl group, amino group, nitro group, Silyl group,
It is selected from siloxanyl groups. However, at least one of R _{9 to} R ₁₆ is used for connection. n represents a natural number of 2 or more. X ₁ is a single bond or a linking unit for linking a plurality of phenanthroline skeletons.

Among these substituents, the alkyl group refers to a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, a propyl group, and a butyl group, which may be unsubstituted or substituted. The cycloalkyl group is, for example, a saturated alicyclic hydrocarbon group such as cyclopropyl, cyclohexyl, norbornyl, and adamantyl, which may be unsubstituted or substituted. The aralkyl group refers to an aromatic hydrocarbon group via an aliphatic hydrocarbon such as a benzyl group and a phenylethyl group, and the aliphatic hydrocarbon and the aromatic hydrocarbon may be unsubstituted or substituted. I don't care. The alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond such as a vinyl group, an allyl group and a butadienyl group, which may be unsubstituted or substituted. The cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond such as a cyclopentenyl group, a cyclopentadienyl group, and a cyclohexene group, which may be unsubstituted or substituted. . The alkynyl group means an unsaturated aliphatic hydrocarbon group containing a triple bond such as an acetylenyl group, which may be unsubstituted or substituted. The alkoxy group refers to an aliphatic hydrocarbon group via an ether bond such as a methoxy group, and the aliphatic hydrocarbon group may be unsubstituted or substituted. The alkylthio group is obtained by substituting the oxygen atom of the ether bond of the alkoxy group with a sulfur atom. Further, the aryl ether group refers to an aromatic hydrocarbon group via an ether bond such as a phenoxy group, and the aromatic hydrocarbon group may be unsubstituted or substituted. Also,
The arylthioether group is a group in which an oxygen atom of an ether bond of the arylether group is substituted with a sulfur atom. The aryl group refers to, for example, an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, a biphenyl group, a phenanthryl group, a terphenyl group, and a pyrenyl group, which may be unsubstituted or substituted. Further, the heterocyclic group is, for example, a furyl group, a thienyl group, an oxazolyl group,
It represents a cyclic structural group having an atom other than carbon, such as a pyridyl group, a quinolyl group, and a carbazolyl group, which may be unsubstituted or substituted. Halogen refers to fluorine, chlorine, bromine and iodine. Haloalkanes, haloalkenes, and haloalkynes are those in which some or all of the aforementioned alkyl, alkenyl, and alkynyl groups, such as trifluoromethyl, have been substituted with the aforementioned halogens, and the rest are unsubstituted. It may be replaced. Aldehyde groups, carbonyl groups, ester groups, carbamoyl groups, and amino groups include those substituted with aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, heterocycles, and the like. The cyclic hydrocarbon, aromatic hydrocarbon and heterocyclic ring may be unsubstituted or substituted. The silyl group means a silicon compound group such as a trimethylsilyl group, which may be unsubstituted or substituted. The siloxanyl group refers to a silicon compound group via an ether bond such as a trimethylsiloxanyl group, which may be unsubstituted or substituted. Further, a ring structure may be formed between adjacent substituents. The ring structure formed may be unsubstituted or substituted.

The substituent itself having a three-dimensional structure refers to a bulky three-dimensional structure that is not a two-dimensional planar structure such as a t-butyl group, an adamantyl group or a norbornyl group. It may be done. Further, a substituent that provides a three-dimensional steric structure by steric repulsion with the phenanthroline skeleton or with an adjacent substituent means that the substituent itself has a planar structure, such as an α-naphthyl group, a phenanthrene group, and a mesityl group. This indicates that the plane of the substituent is on a plane different from the plane of the phenanthroline skeleton due to steric repulsion between the substituent and the phenanthroline skeleton or between the substituent and the adjacent substituent. These can be considered using a molecular model or computer chemistry.

The organic phosphor containing a phenanthroline skeleton has a three-dimensional structure by itself having a three-dimensional structure or by providing a three-dimensional structure by steric repulsion with a phenanthroline skeleton or with an adjacent substituent. And crystallization hardly occurs, and a good amorphous thin film state can be maintained.

Further, by linking a plurality of phenanthroline skeletons, the organic phosphor containing the phenanthroline skeleton becomes high in molecular weight and the glass transition temperature rises, so that crystallization hardly occurs, and a good amorphous thin film state is maintained. I can do it.

In the organic phosphor having a phenanthroline skeleton represented by the general formula (1) in the present invention, it is more preferable to introduce a substituent at the 2, 4, 7, 9-position of the phenanthroline skeleton. These substituents are the same as those described above.

Specific examples of the above-mentioned organic phosphor having a phenanthroline skeleton include the following structures.

[0031]

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[0032]

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[0033]

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[0034]

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An organic phosphor having a phenanthroline skeleton may be used as a dopant material, but is preferably used as a host material because of its excellent electron transporting ability.

The host material of the light-emitting material is not limited to one kind of organic phosphor having a phenanthroline skeleton. A plurality of organic phosphors having a phenanthroline skeleton may be used as a mixture. You may mix and use with the organic fluorescent substance which has a skeleton. Examples of the known host material include, but are not particularly limited to, tris (8-quinolinolato) aluminum, a condensed ring derivative such as anthracene, phenanthrene, pyrene, perylene, and chrysene, which has been known as a light emitter before. Metal complexes of quinolinol derivatives, benzoxazole derivatives, stilbene derivatives, benzothiazole derivatives, thiadiazole derivatives, thiophene derivatives, tetraphenylbutadiene derivatives, cyclopentadiene derivatives, oxadiazole derivatives, bisstyryl derivatives such as bisstyrylanthracene derivatives and distyrylbenzene derivatives Complex, oxadiazole derivative metal complex, benzazole derivative metal complex, coumarin derivative, pyrrolopyridine derivative , Perinone derivatives, thiadiazolopyridine derivatives, the polymer system, polyphenylene vinylene derivatives, polyparaphenylene derivatives, and,
Polythiophene derivatives and the like can be used.

The dopant material to be added to the light emitting material is not particularly limited. Specifically, phenanthrene, anthracene, pyrene, tetracene, pentacene, perylene, naphthopyrene, dibenzopyrene, and rubrene are conventionally known. Condensed ring derivatives such as benzoxazole derivatives, benzothiazole derivatives, benzimidazole derivatives, benzotriazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, imidazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazoline derivatives, stilbene derivatives, thiophene derivatives , Bisphenylyl derivatives such as tetraphenylbutadiene derivatives, cyclopentadiene derivatives, bisstyrylanthracene derivatives and distyrylbenzene derivatives, diaza Ndasen derivatives, furan derivatives,
Benzofuran derivatives, phenylisobenzofuran, dimesitylisobenzofuran, di (2-methylphenyl) isobenzofuran, di (2-trifluoromethylphenyl) isobenzofuran, isobenzofuran derivatives such as phenylisobenzofuran, dibenzofuran derivatives, 7
-Dialkylaminocoumarin derivative, 7-piperidinocoumarin derivative, 7-hydroxycoumarin derivative, 7-methoxycoumarin derivative, 7-acetoxycoumarin derivative, 3-benzthiazolyl coumarin derivative, 3-benzimidazolyl coumarin derivative, 3- Coumarin derivatives such as benzoxazolyl coumarin derivatives, dicyanomethylenepyran derivatives, dicyanomethylenethiopyran derivatives,
Polymethine derivatives, cyanine derivatives, oxobenzanthracene derivatives, xanthene derivatives, rhodamine derivatives, fluorescein derivatives, pyrylium derivatives, carbostyril derivatives, acridine derivatives, bis (styryl)
Benzene derivatives, oxazine derivatives, phenylene oxide derivatives, quinacridone derivatives, quinazoline derivatives,
Pyrrolopyridine derivatives, furopyridine derivatives, 1,2,2
A 5-thiadiazolopyrene derivative, a perinone derivative, a pyrrolopyrrole derivative, a squarylium derivative, a biolanthrone derivative, a phenazine derivative, an acridone derivative, a diazaflavin derivative, and the like can be used as they are, but an isobenzofuran derivative is particularly preferably used.

In the present invention, the electron-transporting material needs to efficiently transport electrons from the negative electrode between the electrodes to which an electric field is applied, has a high electron injection efficiency, and efficiently transports the injected electrons. Is desirable. For this purpose, it is required that the material has a high electron affinity, a high electron mobility, a high stability, and a small amount of impurities serving as traps during production and use.

However, considering the transport balance between holes and electrons, when the role of mainly preventing the holes from the positive electrode from flowing to the negative electrode side without recombination is to play an important role, the electron transport Even if the ability is not so high, the effect of improving the luminous efficiency is equivalent to a material having a high electron transport ability. Therefore, the electron transport layer in the present invention includes a hole blocking layer capable of efficiently blocking the movement of holes as the same thing.

As a substance satisfying such conditions, the organic phosphor having a phenanthroline skeleton according to the present invention can be mentioned. In order to obtain stable light emission over a long period of time, a material having excellent thermal stability and thin film forming properties is desired. Among organic phosphors having a phenanthroline skeleton, whether the substituent itself has a three-dimensional structure, Those having a three-dimensional steric structure due to steric repulsion with a phenanthroline skeleton or with an adjacent substituent, or those having a plurality of phenanthroline skeletons linked are preferred. Further, when a plurality of phenanthroline skeletons are connected, a compound containing a conjugated bond, a substituted or unsubstituted aromatic hydrocarbon, or a substituted or unsubstituted aromatic heterocycle in a connection unit is more preferable. Specific examples of the organic phosphor having a phenanthroline skeleton include structures as in the above specific examples (Formula Nos. 6 to 9), but are not limited thereto.

The electron transporting material need not be limited to one kind of organic phosphor having a phenanthroline skeleton. A plurality of the above compounds may be used as a mixture, or one or more known electron transporting materials may be used as a mixture with the above compound. You may. The known electron transporting material is not particularly limited.
Quinolinol derivative metal complex represented by -hydroxyquinoline aluminum, benzoquinoline metal complex, tropolone metal complex, flavonol metal complex, perylene derivative, perinone derivative, naphthalene, coumarin derivative, oxadiazole derivative, aldazine derivative, bisstyryl derivative, pyrazine derivative , A phenanthroline derivative,
There are quinoline derivatives, benzimidazole derivatives, triazole derivatives, quinoxaline derivatives, benzoquinoline derivatives, and the like, but are not particularly limited. These electron transporting materials may be used alone or may be laminated or mixed with different electron transporting materials.

The materials used for the above-described hole transporting layer, light emitting layer and electron transporting layer can be used alone to form the respective layers. As the polymer binder, polyvinyl chloride, polycarbonate, polystyrene, poly (N- Vinyl carbazole), polymethyl methacrylate, polybutyl methacrylate, polyester, polysulfone, polyphenylene oxide, polybutadiene, hydrocarbon resin, ketone resin, phenoxy resin, polysulfone, polyamide,
Solvent-soluble resins such as ethyl cellulose, vinyl acetate, ABS resin, polyurethane resin, phenolic resin, xylene resin, petroleum resin, urea resin, melamine resin, unsaturated polyester resin, alkyd resin, epoxy resin,
It is also possible to use the resin dispersed in a curable resin such as a silicone resin.

In the present invention, the method for forming the luminescent material is not particularly limited, such as resistance heating evaporation, electron beam evaporation, sputtering, molecular lamination, and coating method. It is preferable in terms of characteristics. The thickness of the layer depends on the resistance of the luminescent material and cannot be limited, but is selected from the range of 1 to 1000 nm.

In the present invention, the electric energy mainly refers to a direct current, but it is also possible to use a pulse current or an alternating current. The current value and voltage value are not particularly limited,
In consideration of the power consumption and the life of the device, the maximum luminance should be obtained with the lowest possible energy.

In the present invention, a matrix refers to a matrix in which pixels for display are arranged in a lattice pattern, and displays a character or an image by a set of pixels. The shape and size of the pixel depend on the application. For example, a square pixel having a side of 300 μm or less is usually used for displaying images and characters on a personal computer, a monitor, and a television. In the case of a large display such as a display panel, a pixel having a side of mm order is used. . For monochrome display, pixels of the same color may be arranged, but for color display, red, red,
Green and blue pixels are displayed side by side. In this case, there are typically a delta type and a stripe type. The matrix may be driven by either a line-sequential driving method or an active matrix. The line-sequential driving has the advantage that the structure is simpler. However, in consideration of the operation characteristics, the active matrix is sometimes superior, and therefore it is necessary to use the same depending on the application.

In the present invention, the segment type refers to a pattern formed so as to display predetermined information,
Light is emitted from the determined area. For example, there are a time display and a temperature display on a digital clock or a thermometer, an operation state display of an audio device, an electromagnetic cooker, or the like, and a panel display of an automobile. The matrix display and the segment display may coexist in the same panel.

In the present invention, the backlight is mainly used for improving the visibility of a display device that does not emit light, and is used for a liquid crystal display device, a clock, an audio device, an automobile panel, a display panel, a sign, and the like. . In particular, as a backlight for a liquid crystal display device, especially a personal computer application in which thinning is an issue, considering that it is difficult to reduce the thickness because the conventional type is made of a fluorescent lamp or a light guide plate, the present invention The backlight is thin and lightweight.

[0048]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 A glass substrate (available from Asahi Glass Co., Ltd., 15 Ω / □, electron beam deposited) on which an ITO transparent conductive film was deposited to a thickness of 150 nm was cut into a size of 30 × 40 mm and etched. The obtained substrate was subjected to ultrasonic cleaning with acetone and "Semicocrine 56" (manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes, and then with ultrapure water. Subsequently, the substrate was subjected to ultrasonic cleaning with isopropyl alcohol for 15 minutes, immersed in hot methanol for 15 minutes, and dried. Immediately before this element is fabricated,
V-ozone treatment was performed, the apparatus was set in a vacuum evaporation apparatus, and the apparatus was evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁵ Pa or less. By the resistance heating method, 4,4'-
Bis (N- (m-tolyl) -N-phenylamino) biphenyl was deposited to a thickness of 100 nm. Next, as a luminescent material,
2,9-di (phenylvinyl) -4,7-diphenyl-
1,10-phenanthroline was laminated to a thickness of 50 nm. Next, as an electron transport material, 2- (4-t-butylphenyl) -5- (4-biphenylyl) -1,3,4-
Oxadiazole was laminated to a thickness of 100 nm. Next, after doping the organic layer with lithium to a thickness of 0.5 nm, aluminum was vapor-deposited to a thickness of 200 nm to form a cathode, thereby producing a 5 × 5 mm square device. The film thickness referred to here is a value indicated by a crystal oscillation type film thickness monitor. Good light emission was obtained from this light emitting device. Example 2 As a light emitting material, 2,9-di (1-naphthyl) -4,7-
A light emitting device was manufactured in exactly the same manner as in Example 1 except that diphenyl-1,10-phenanthroline was used. Good light emission was obtained from this light emitting device.

Example 3 A light emitting device was manufactured in the same manner as in Example 1 except that 2,9-di (1- (2-methylnaphthyl))-1,10-phenanthroline was used as a light emitting material. Good light emission was obtained from this light emitting device.

Example 4 A light emitting device was manufactured in exactly the same manner as in Example 1 except that 2,9-di (2,4,6-trimethylphenyl) -1,10-phenanthroline was used as a light emitting material. Good light emission was obtained from this light emitting device.

Example 5 2,9-di (4-tbutylphenyl)-as a light emitting material
A light emitting device was manufactured in exactly the same manner as in Example 1 except that 1,10-phenanthroline was used. Good light emission was obtained from this light emitting device.

Example 6 The steps up to the deposition of each organic layer were performed in the same manner as in Example 1. First, as a hole transport material, 4,
4′-bis (N- (m-tolyl) -N-phenylamino) biphenyl is deposited to a thickness of 150 nm, and 2,9-di (phenylvinyl) -4,7-diphenyl-1,10-phenanthroline is deposited to a thickness of 50 nm. Was deposited. Next, as an electron transporting material, 2- (4-t-butylphenyl) -5-
(4-Biphenylyl) -1,3,4-oxadiazole was laminated to a thickness of 100 nm. Next, lithium was added to 0.
After doping the 5 nm organic layer, aluminum
An element having a size of 5 × 5 mm was formed by vapor deposition of 0 nm. The film thickness here is a value indicated by a crystal oscillation type film thickness monitor. When the light-emitting element was driven in a vacuum cell by a 1 mA pulse (duty ratio 1/60, current value at the time of pulse 60 mA),
Light emission was confirmed.

Example 7 A glass substrate (15 Ω / □, manufactured by Asahi Glass Co., Ltd., electron beam deposited) on which an ITO transparent conductive film was deposited to a thickness of 150 nm was cut into 30 × 40 mm, and 300 μm pitch (remaining width 270 μm) was obtained by photolithography. ) X 32 stripes were patterned. One side of the ITO stripe in the long side direction is 1.2 in order to facilitate electrical connection with the outside.
It is expanded to a pitch of 7 mm (opening width 800 μm).
The obtained substrate was subjected to ultrasonic cleaning with acetone and "Semicocline" 56 for 15 minutes each, and then with ultrapure water. Subsequently, the substrate was subjected to ultrasonic cleaning with isopropyl alcohol for 15 minutes, immersed in hot methanol for 15 minutes, and dried. This substrate was subjected to UV-ozone treatment for 1 hour immediately before the device was manufactured, and was placed in a vacuum evaporation apparatus, and the degree of vacuum in the apparatus was 5 ×.
Evacuation was performed until the pressure became 10 ⁻⁴ Pa or less. First, 4,4′-bis (N- (m
-Tolyl) -N-phenylamino) biphenyl to 150
2,9-di (phenylvinyl) -4,7-
Diphenyl-1,10-phenanthroline was deposited to a thickness of 50 nm. Next, 2- (4-
t-butylphenyl) -5- (4-biphenylyl)-
1,3,4-oxadiazole was laminated to a thickness of 100 nm. The film thickness referred to here is a value indicated by a crystal oscillation type film thickness monitor. Next, a mask having 16 openings of 250 μm (corresponding to a remaining width of 50 μm and a pitch of 300 μm) provided by wet etching on a Kovar plate having a thickness of 50 μm was used.
The mask was exchanged in a vacuum so as to be orthogonal to the ITO stripe, and the magnet and the ITO substrate were fixed from the back surface so that the mask and the ITO substrate were in close contact with each other. After doping the organic layer with lithium by 0.5 nm, aluminum is vapor-deposited by 200 nm to form
A × 16 dot matrix element was manufactured. When this device was driven in a matrix, characters could be displayed without crosstalk.

Example 8 The steps up to the deposition of each organic layer were performed in the same manner as in Example 1. First, copper phthalocyanine (CuPc) is deposited to a thickness of 10 nm as a first hole injecting and transporting material by a resistance heating method, and subsequently, N, N′-diphenyl-N, N′-bis (1) is used as a second hole injecting and transporting material. -Naphthyl) -1,1 '
-Diphenyl-4,4'-diamine (α-NPD)
0 nm was laminated. Further, subsequently, tris (8-quinolinolato) aluminum (III) (Al
q3) was laminated to a thickness of 15 nm, and then ETL1 shown below as an electron transporting material was laminated to a thickness of 35 nm. Subsequently, lithium was doped to a thickness of 0.2 nm, and finally aluminum was deposited to a thickness of 150 nm to form a cathode, thereby producing a 5 × 5 mm square device. This light-emitting element emits green light based on Alq3 having an emission peak wavelength of 536 nm at an applied voltage of 10 V, and has a light emission luminance of 4000 cd / m ² ,
The luminous efficiency was 2.0 cd / A. The initial luminance retention rate of the light-emitting element after 500 hours from energization was 80%.
And a uniform light emitting surface was maintained.

[0056]

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Comparative Example 1 A light emitting device was produced in the same manner as in Example 8, except that 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline was used as the electron transporting material. From this light-emitting element, at an applied voltage of 10 V, the emission peak wavelength becomes 53
Green light emission based on 6 m of Alq3 was obtained, light emission luminance was 3500 cd / m ² , and light emission efficiency was 1.8 cd / A. However, the initial luminance retention rate of this light-emitting element after 500 hours from energization was 50% or less, and unevenness was observed on the light-emitting surface.

Example 9 A light emitting device was manufactured in the same manner as in Example 8, except that ETL2 shown below was used as the electron transporting material. The light-emitting element emits green light based on Alq3 having an emission peak wavelength of 536 nm at an applied voltage of 10 V, an emission luminance of 3800 cd / m ² , and an emission efficiency of 1.9 cd / A.
Met. The light-emitting element had an initial luminance retention rate of 500% after 500 hours from the current supply, and maintained a uniform light-emitting surface.

[0059]

Embedded image

Example 10 Tris (5,7-diphenyl-8-quinolinolato) aluminum (III) was used as the host material for the light emitting layer portion, and 4,4-difluoro-1,3,5,7 as the dopant material.
A light emitting device was manufactured in the same manner as in Example 8, except that -tetraphenyl-4-bora-3a, 4a-diaza-indacene was co-evaporated to a thickness of 15 nm so that the dopant was 1.0 wt%. Produced. From this light emitting element,
At an applied voltage of 10 V, red light emission based on a dopant material having a light emission peak wavelength of 615 nm was obtained.

Comparative Example 2 Example 10 except that Alq3 was used as the electron transporting material.
A light-emitting element was manufactured in exactly the same manner as described above. This light-emitting element did not emit red light at an applied voltage of 10 V,
It became orange light emission having a shoulder peak near 535 nm together with the emission peak wavelength of nm.

[0062]

According to the present invention, it is possible to provide a light emitting device having high luminous efficiency and excellent color purity.

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 3K007 AB02 AB03 AB04 AB17 BA06 CA01 CB01 DA00 DB03 EB00 FA01 5C094 AA10 AA15 AA22 AA60 BA27 CA14 CA19 EA05 EB02 FB01 HA03 HA05 HA06 HA08

Claims (6)

[Claims] 1. An element which emits light by electric energy in which a light emitting substance is present between a positive electrode and a negative electrode, wherein the element contains an organic phosphor having a phenanthroline skeleton represented by the following general formula (1). A light emitting element characterized by the above-mentioned. Embedded image (Where R _{1 to} R ₈ may be the same or different and each represents a hydrogen, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a mercapto group, an alkoxy group, an alkylthio group , Aryl ether group, aryl thioether group,
It is selected from an aryl group, a heterocyclic group, a halogen, a haloalkane, a haloalkene, a haloalkyne, a cyano group, an aldehyde group, a carbonyl group, a carboxyl group, an ester group, a carbamoyl group, an amino group, a nitro group, a silyl group, and a siloxanyl group. However, at least one of them has a three-dimensional structure by itself, or has a three-dimensional structure by steric repulsion with a phenanthroline skeleton or with an adjacent substituent. ) 2. A device in which a luminescent substance is present between a positive electrode and a negative electrode and emits light by electric energy, wherein the device includes an organic phosphor having a phenanthroline skeleton represented by the following general formula (2). The light emitting device according to claim 1, wherein: Embedded image (Where R _{9 to} R ₁₆ may be the same or different and each represents a hydrogen, an alkyl group, a cycloalkyl group, an aralkyl group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a mercapto group, an alkoxy group, an alkylthio group , Aryl ether group, aryl thioether group,
It is selected from an aryl group, a heterocyclic group, a halogen, a haloalkane, a haloalkene, a haloalkyne, a cyano group, an aldehyde group, a carbonyl group, a carboxyl group, an ester group, a carbamoyl group, an amino group, a nitro group, a silyl group, and a siloxanyl group. However, at least one of R _{9 to} R ₁₆ is used for connection. n represents a natural number of 2 or more.
X ₁ is a single bond or a linking unit for linking a plurality of phenanthroline skeletons. ) 3. A phenanthroline skeleton represented by the general formula (1)
And R₁, R_Three, R ₆, R₈At least one of is itself
Has a three-dimensional structure, or has a phenanthroline skeleton
3D by steric repulsion with
The light emission according to claim 1, wherein the light emission has a three-dimensional structure.
element. 4. The light emitting device according to claim 1, wherein said organic phosphor is a light emitting material. 5. The light emitting device according to claim 1, wherein said organic phosphor is an electron transporting material. 6. The light emitting device according to claim 1, wherein the light emitting device is a display for displaying in a matrix and / or a segment system.