KR101434292B1 - Light-emitting device - Google Patents

Abstract

The present invention relates to a light emitting device having high luminous efficiency and excellent durability.

The light-emitting layer of the device is characterized by including a pyrene compound represented by the general formula (1) and an organic type mineral substance having a peak fluorescence wavelength of 500 nm or more and 680 nm or less, wherein at least a light-emitting layer exists between the anode and the cathode and emits light by electrical energy .

[R ¹ to R ¹⁵ may be the same or different and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl ether group, A heterocyclic group, a heteroaryl group, an amino group, a silyl group, -P (= O) R ¹⁶ R ^17, and adjacent substituents. R ¹⁶ and R ¹⁷ are selected from an aryl group and a heteroaryl group. R ¹ to R ¹⁰ Lt; / RTI > is used for linking with a bicyclic benzoheterocycle. n is an integer of 1 to 4; X is an oxygen atom, a sulfur atom, or -NR ¹⁸ -. R ¹⁸ is selected from hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an aryl group, and a heteroaryl group. And R ¹⁸ may combine with R ¹⁵ to form a ring.]

Light emitting element

Description

[0001] LIGHT-EMITTING DEVICE [0002]

The present invention relates to a pyrene compound useful as a fluorescent coloring matter or a charge transporting material and a light emitting device using the pyrene compound as a light emitting device usable in fields such as a display device, a flat panel display, a backlight, a lighting, an interior, a mark, a signboard, .

Research has been actively conducted on organic thin film light emitting devices in which electrons injected from a cathode and holes injected from an anode emit light when recombined in an organic light emitting element sandwiched between both electrodes. This light-emitting device is thin and characterized in that it emits multicolor light by selecting a high-luminance light emitting material and a light emitting material under a low driving voltage, and has been attracting attention.

Since the organic thin-film light-emitting device has been shown to emit light at a high luminance by CW Tang et al. Of Eastman Kodak Company, the present invention has been studied by many research institutes. A representative structure of the organic thin film light-emitting device proposed by Kodak's research group is a hole-transporting diamine compound, a tris (8-quinolinolate) aluminum (III) light emitting layer, and a Mg: Ag (alloy) , And green light emission of 1,000 cd / m ² was possible at a drive voltage of about 10 V (see Non-Patent Document 1).

Further, the organic thin film light emitting device can obtain various luminescent colors by using various kinds of fluorescent materials in the light emitting layer, and therefore, research for practical use in displays has been prospering. Particularly, research on the three primary colors of red, green, and blue light emitting materials has been actively studied, and studies have been carried out with the aim of improving the characteristics.

One of the biggest problems in the organic thin-film light-emitting device is improvement of durability and luminous efficiency of the device. As means for obtaining a highly efficient light emitting device, a method of forming a light emitting layer by doping a host material with a dopant material (fluorescent material) in an amount of several percent is known (see Patent Document 1). The host material is required to have high carrier mobility and uniform film forming property, and a high fluorescent quantum yield and uniform dispersibility are required for the dopant material. For example, as a blue material, a technique using a styrylamine derivative (see Patent Document 2), a perylene derivative (see Patent Document 3), and a pyrene compound is disclosed (see Patent Documents 4 to 6). Examples of the green material include stilbene compounds (see Patent Document 7), quinoline derivatives and quinacridone compounds (see Patent Document 8), aminostyryl compounds as red materials (see Patent Document 9), diketopyrrolopyrrole derivatives and pyromethene compounds (See Patent Document 10), a coumarin compound and a dicyanomethylene compound (see Patent Document 11), but there was no indication of sufficient luminescence efficiency and durability. The number of host materials and dopant materials for forming the light emitting material are numerous, and the number of the host material and the dopant material becomes large if they are combined. As a guide for ease of energy transfer from a host material to a dopant material in general, the fluorescence spectrum of the host material and the degree of overlap of the absorption spectrum of the dopant material and the distance between molecules are known (refer to Non-Patent Document 2) There are a lot of trial and error parts that are not explained. That is, in order to obtain a light emitting device having better light emission characteristics, it is very important to find not only a novel host material and a dopant material but also a combination of an optimal host material and a dopant material.

Patent Document 1: Japanese Patent No. 2814435

Patent Document 2: JP-A-5-17765

Patent Document 3: JP-A-2003-86380

Patent Document 4: JP-A-2001-118682

Patent Document 5: JP-A-2004-75567

Patent Document 6: Japanese Unexamined Patent Application Publication No. 2002-63988

Patent Document 7: JP-A-2-247278

Patent Document 8: JP-A-3-255190

Patent Document 9: JP-A-2002-134276

Patent Document 10: JP-A-2003-86379

Patent Document 11: JP-A-5-202356

Non-Patent Document 1: Applied Physics letters (USA) 1987, Vol. 51, No. 12, 913-915

Non-Patent Document 2: "Organic EL device and its industrial frontline ", entesis, 1998, pp. 66

An object of the present invention is to provide a light emitting device having high light emitting efficiency and excellent durability by optimizing a combination of a host material and a dopant material.

The present invention relates to a device comprising at least a light-emitting layer between an anode and a cathode, which emits light by electric energy, wherein the light-emitting layer of the device comprises a pyrene compound represented by the general formula (1) and an organic type mineral substance having a fluorescence peak wavelength of 500 nm or more and 680 nm or less Emitting device.

R ¹ to R ¹⁵ may be the same or different and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl ether group, an arylthioether group, , A heteroaryl group, an amino group, a silyl group, -P (= O) R ¹⁶ R ^17, and adjacent substituents. R ¹⁶ and R ¹⁷ are selected from an aryl group and a heteroaryl group. R ¹ to R ¹⁰ Lt; / RTI > is used for linking with a bicyclic benzoheterocycle. n is an integer of 1 to 4; X is an oxygen atom, a sulfur atom, or -NR ¹⁸ -. R ¹⁸ is selected from hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an aryl group, and a heteroaryl group. R ¹⁸ may combine with R ¹⁵ to form a ring.

(Effects of the Invention)

According to the present invention, a light emitting device having high light emitting efficiency and excellent durability can be obtained.

The light emitting device of the present invention is composed of at least an anode and a cathode, and an organic layer composed of a light emitting element material interposed between the anode and the cathode.

The anode used in the present invention is not particularly limited as long as it is a material capable of efficiently injecting holes into the organic layer. However, it is preferable to use a material having a relatively large work function. Examples thereof include tin oxide, Conductive metal oxides such as zinc indium and indium tin oxide (ITO), metals such as gold, silver and chromium, inorganic conductive substances such as copper iodide and copper sulfide, and conductive polymers such as polythiophene, polypyrrole and polyaniline . These electrode materials may be used alone, but a plurality of materials may be laminated or mixed.

The resistance of the electrode may be such that a sufficient current can be supplied for light emission of the light emitting element and is preferably low in terms of power consumption of the light emitting element. For example, an ITO substrate of 300 OMEGA / & squ & or less functions as an element electrode, but currently, a substrate of about 10 OMEGA / & squ & can be supplied. Thickness of ITO can be arbitrarily selected depending on the resistance value, but it is often used between 100 and 300 nm.

Further, in order to maintain the mechanical strength of the light emitting element, it is preferable to form the light emitting element on the substrate. As the substrate, a glass substrate such as soda glass or non-alkali glass is suitably used. Since the thickness of the glass substrate may be sufficient to maintain the mechanical strength, 0.5 mm or more is sufficient. The material of the glass is preferably an alkali-free glass because it is preferable that the elution ions from the glass be small. Alternatively, a soda lime glass on which a barrier coating such as SiO ₂ has been made is also commercially available, so that it may be used. In addition, if the anode functions stably, the substrate need not be glass, and for example, a positive electrode may be formed on a plastic substrate. The ITO film formation method is not particularly limited, such as an electron beam method, a sputtering method, and a chemical reaction method.

The material used for the negative electrode used in the present invention is not particularly limited as long as it is a material capable of efficiently injecting electrons into the organic layer. In general, platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, Lithium, sodium, potassium, cesium, calcium and magnesium, and alloys thereof. In order to increase the electron injection efficiency and improve the device characteristics, alloys including lithium, sodium, potassium, cesium, calcium, magnesium, or their low work function metals are effective. However, their low work function metals are generally unstable in the atmosphere. Therefore, a preferable example is a method of obtaining an electrode with high stability by doping a small amount of lithium or magnesium (1 nm or less in terms of film thickness of vacuum deposition) into the organic layer. It is also possible to use inorganic salts such as lithium fluoride. Particularly, in order to protect the electrodes, metals such as platinum, gold, silver, copper, iron, tin, aluminum and indium or alloys using these metals, inorganic substances such as silica, titania and silicon nitride, polyvinyl alcohol, Organic polymer compounds such as a hydrocarbon-based polymer compound are laminated. The method of manufacturing these electrodes is not particularly limited as long as it can take conduction such as resistance heating, electron beam beam, sputtering, ion plating and coating.

The organic layer constituting the light emitting element of the present invention is composed of at least a light emitting layer made of a light emitting element material. Examples of the structure of the organic layer include a layered structure of 1) a hole transporting layer / a light emitting layer / an electron transporting layer, 2) a light emitting layer / electron transporting layer, and 3) a hole transporting layer / light emitting layer. Each of the layers may be a single layer or a plurality of layers. In the following description, the hole injecting material and the electron injecting material are referred to as a hole transporting material and an electron injecting material, respectively. Respectively.

The hole transporting layer is formed by a method of laminating or mixing one or more of the hole transporting materials, or a method of using a mixture of a hole transporting material and a polymer binder. Further, an inorganic salt such as iron (III) chloride may be added to the hole transporting material to form the hole transporting layer. The hole transporting material is not particularly limited as long as it is a compound capable of forming a thin film necessary for manufacturing a light emitting device and injecting holes from the anode and transporting holes. For example, 4,4'-bis (N- (3-methylphenyl) -N-phenylamino) biphenyl, 4,4'-bis , Triphenylamine derivatives such as 4 ', 4 "-tris (3-methylphenyl (phenyl) amino) triphenylamine and the like, biscarbazole derivatives such as bis (N-allylcarbazole) , Heterocyclic compounds such as pyrazoline derivatives, stilbene compounds, hydrazine compounds, benzofuran derivatives and thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives and porphyrin derivatives, A carbonate, a styrene derivative, a polythiophene, a polyaniline, a polyfluorene, a polyvinylcarbazole and a polysilane are preferable.

In the present invention, the light-emitting layer may be a single layer or a plurality of layers, and each may be formed of a light-emitting material (host material, dopant material), and they may be a mixture of a host material and a dopant material, . That is, in the light emitting device of the present invention, in each light emitting layer, only the host material or the dopant material may emit light, or the host material and the dopant material may emit light together. Each of the host material and the dopant material may be one type or a combination of a plurality of types. The dopant material may be included in the entire host material or partially included. The dopant materials may be laminated or dispersed. If the amount of the dopant material is excessively large, the concentration quenching phenomenon occurs. Therefore, it is preferably 20 wt% or less, more preferably 10 wt% or less, based on the host material. The doping method may be formed by a co-evaporation method with a host material, but may be vapor-deposited at the same time after mixing with the host material in advance.

In the present invention, the light emitting layer contains a pyrene compound represented by the general formula (1) and an organic type mineral substance having a fluorescent peak wavelength of 500 nm or more and 680 nm or less. The pyrene compound represented by the general formula (1) can also be used as a dopant material, but it is preferable to use the pyrene compound as a host material in consideration of the high carrier mobility of the pyrene compound. Organic type minerals having a fluorescent peak wavelength of 500 nm or more and 680 nm or less are preferably used as a dopant material. Here, the fluorescence peak wavelength is a value in a dichloromethane lean solution state. If the fluorescent peak wavelength is larger than 680 nm, the visibility becomes worse, and it is difficult to obtain high-efficiency red light emission.

The host material contained in the light emitting material is not limited to only one kind of the above-mentioned pyrene compounds, and a plurality of pyrene compounds may be used in combination or at least one of known host materials may be mixed with the pyrene compound. Specific examples thereof include compounds having a condensed aryl ring such as anthracene or derivatives thereof, aromatic amine derivatives such as 4,4'-bis (N- (1-naphthyl) -N-phenylamino) biphenyl, tris Metal chelated oxylate compounds including aluminum (III), bisstyryl derivatives such as distyrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, A polyphenylenevinylene derivative, a polyparaphenylene derivative, a polyfluorene derivative, a polyvinylcarbazole derivative, and a poly (vinylpyrrolidone) derivative, a cyclopentadiene derivative, an oxadiazole derivative, a carbazole derivative, a pyrrolopyrrole derivative, Thiophene derivatives are preferably used.

The pyrene compound represented by the general formula (1) contained in the light emitting layer used in the present invention has the structure shown below.

R ¹ to R ¹⁵ may be the same or different and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl ether group, an arylthioether group, , it is selected from a ring structure formed between a heteroaryl group, an amino group, a silyl ^{group, -P (= O) R 16} R 17 and an adjacent substituent. R ¹⁶ and R ¹⁷ are selected from an aryl group and a heteroaryl group. R ¹ to R ¹⁰ Lt; / RTI > is used for linking with a bicyclic benzoheterocycle. n is an integer of 1 to 4; X is an oxygen atom, a sulfur atom, or -NR ¹⁸ -. R ¹⁸ is selected from hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an aryl group, and a heteroaryl group. R ¹⁸ may combine with R ¹⁵ to form a ring.

The alkyl group in these substituents represents, for example, a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, a propyl group, or a butyl group, which may be unsubstituted or substituted. The substituent when it is substituted is not particularly limited, and examples thereof include an alkyl group, an aryl group, and a heteroaryl group, and this point is common to the following description. The number of carbon atoms of the alkyl group is not particularly limited, but is usually in the range of 1 to 20, from the viewpoint of availability and cost.

The cycloalkyl group refers to a saturated alicyclic hydrocarbon group such as cyclopropyl, cyclohexyl, norbornyl, adamantyl, etc., which may be unsubstituted or substituted. The number of carbon atoms in the alkyl group moiety is not particularly limited, but is generally in the range of 3 to 20 carbon atoms.

The heterocyclic group means a group formed of an aliphatic ring having a ring other than carbon, such as a pyran ring, a piperidine ring, and a cyclic amide, which may be unsubstituted or substituted. The number of carbon atoms of the heterocyclic group is not particularly limited, but usually ranges from 2 to 20 carbon atoms.

Also, the alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond such as a vinyl group, an allyl group, a butadienyl group and the like, which may be unsubstituted or substituted. The number of carbon atoms of the alkenyl group is not particularly limited, but usually ranges from 2 to 20, inclusive.

Further, the cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group including a double bond such as a cyclopentenyl group, a cyclopentadienyl group, and a cyclohexenyl group, which may be unsubstituted or substituted.

Furthermore, the alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond such as an ethynyl group, which may be unsubstituted or substituted. The carbon number of the alkynyl group is not particularly limited, but usually ranges from 2 to 20.

The alkoxy group refers to, for example, an aliphatic hydrocarbon group having an ether bond such as a methoxy group, and the aliphatic hydrocarbon group may be unsubstituted or substituted. The number of carbon atoms of the alkoxy group is not particularly limited, but usually ranges from 2 to 20.

The alkylthio group is an oxygen atom of an ether bond of an alkoxy group substituted with a sulfur atom.

The aryl ether group is, for example, an aromatic hydrocarbon group having an ether bond such as a phenoxy group, and the aromatic hydrocarbon group may be unsubstituted or substituted. The number of carbon atoms of the aryl ether group is not particularly limited, but is usually in the range of 6 to 40, inclusive.

The arylthioether group is an oxygen atom of an ether bond of an aryl ether group substituted by a sulfur atom.

The aryl group represents 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. The aryl group may be unsubstituted or substituted. The number of carbon atoms of the aryl group is not particularly limited, but is generally in the range of 6 to 40, inclusive.

The heteroaryl group refers to an aromatic group containing in the ring other atoms than carbon, such as a furanyl group, a thiophenyl group, an oxazolyl group, a pyridyl group, or a quinolinyl group, which may be unsubstituted or substituted. The number of carbon atoms of the heteroaryl group is not particularly limited, but usually ranges from 2 to 30.

The amino group may be unsubstituted or substituted, and examples of the substituent include an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group, and these substituents may be further substituted.

The silyl group refers to a functional group containing a bond to a silicon atom such as a trimethylsilyl group, and these groups may or may not have a substituent. The number of carbon atoms of the silyl group is not particularly limited, but usually ranges from 3 to 20. The number of silicon atoms is in the range of 1 to 6, inclusive.

The cyclic structure formed in the adjacent group is represented by the general formula (1), and any adjacent two substituents selected from R ¹ to R ¹⁰ (for example, R ¹ and R ² ) may be bonded to each other to form a conjugated or non- To form a ring. These condensed rings may contain nitrogen, oxygen and sulfur atoms in the ring structure, and may be condensed with other rings. However, when the atoms constituting these condensed rings are only carbon atoms and hydrogen atoms, excellent heat resistance is obtained, which is preferable.

The pyrene compound represented by the general formula (1) has 1 to 4 pyrene skeletons and 2-cyclic benzoheterocyclic rings (benzofuran ring, benzothiophene ring, and indole ring) in the molecule. This makes it possible to achieve high carrier mobility and heat resistance at the same time, to improve the luminous efficiency of the device and to improve the durability. In addition, since the pyrene compound has a fluorescent peak wavelength of 500 nm or more in a thin film state, it can be suitably used as a host material in a cyan to red region (500 to 680 nm region).

R ¹ to R ¹⁰ R &^lt; ³ >, R < ⁶ >, R < ⁸ > Is used for the linkage with the dicyclic benzoheterocycle. Also, R ¹ to R ¹⁰ Is an aryl group or a heteroaryl group, it is preferable that the pyrene compounds are prevented from associating with each other to form a stable thin film. When X in the general formula (1) is an oxygen atom, higher luminous efficiency can be obtained, which is preferable.

A known method can be used for the synthesis of the pyrene compound represented by the general formula (1). The method of introducing a bicyclic benzoheterocycle into the pyrene skeleton can be carried out, for example, by a coupling reaction using a halogenated pyrene derivative and a bicyclic benzoheterocyclic metal reagent under a palladium or nickel catalyst, or a method in which a halogenated dicyclic benzoheterocycle and a pyrene derivative boron And a method of using a coupling reaction in the presence of palladium or nickel catalyst of an acid, but the present invention is not limited thereto.

The pyrene compound having a group containing a bicyclic benzoheterocycle represented by the above general formula (1) is specifically exemplified below.

Examples of organic minerals having a fluorescent peak wavelength of 500 nm or more and 680 nm or less include a compound having a condensed aromatic ring such as naphthalene, rubrene, perylene, and terylene, a derivative thereof, thiophene, imidazole pyridine, pyridine, naphthyridine , Compounds having a heteroaryl ring such as quinoxaline, pyrrolopyridine, thioxanthene, pyridinothiadiazole and pyrazolopyridine, derivatives thereof, distyrylbenzene derivatives, aminostyryl derivatives, aldazine derivatives, diketopyrrolopyrroles [3,4-c] pyrrole derivatives such as 2,3,5,6-1H, 4H-tetrahydro-9- (2'-benzothiazolyl) quinolizine [9,9a, 1- Azole derivatives such as coumarin derivatives, imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole and triazole, metal complexes thereof, aromatic amine derivatives, bis (diisopropylphenyl) perylene tetracarboxylate A naphthalimide derivative such as an imide, a perinone derivative, A rare earth complex such as cetyl acetone, a Eu complex in which benzoyl acetone and phenanthroline are ligands, and a rare earth complex such as 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H- Derivatives, metal phthalocyanine derivatives such as magnesium phthalocyanine and aluminum chlorophthalocyanine, metal porphyrin derivatives such as zinc porphyrin, rhodamine compounds, deazaplain derivatives, oxazine compounds, phenoxazine derivatives, phenoxazone derivatives, quinacridone derivatives, A dicyanoethenyl arene derivative and the like can be used. However, a compound having a high fluorescent quantum yield in a solution state is preferably used from the viewpoint of obtaining high-efficiency light emission. When combined with the pyrene compound represented by the general formula (1), an organic type mineral having a fluorescence peak wavelength of 500 nm or more and 650 nm or less is more preferable from the viewpoint of energy transfer efficiency.

Among the organic minerals, a compound having a pyromethene skeleton represented by the general formula (2) has a high fluorescence quantum yield and a narrow half width of a fluorescence spectrum, so that light emission with high efficiency and high color purity can be obtained.

R ¹⁹ to R ²⁵ may be the same or different and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl ether group, an arylthioether group, , A heteroaryl group, a cyano group, an amino group, a silyl group, -P (= O) R ²⁸ R ^29, and adjacent substituents. R ²⁸ and R ²⁹ are selected from an aryl group and a heteroaryl group. R ²⁶ and R ^{27, which} may be the same or different, are selected from halogen, hydrogen, alkyl, aryl, and heterocyclic group. Y is a carbon atom or a nitrogen atom, but in the case of a nitrogen atom, the R ²⁵ is not present. The description of these substituents is the same as described above.

Since the compound having the pyromethene skeleton is excellent in phase affinity with the pyrene compound in the present invention, the energy transfer between the host material and the dopant material occurs efficiently. Therefore, it is possible to obtain a light emitting device having high durability with high luminous efficiency.

R ¹⁹ , R ²¹ , R ²² and R ²⁴ may be the same or different, and an aryl group or a heteroaryl group is preferable because concentration quenching by association of dopants can be suppressed.

The following specific examples of the pyromethene metal complex represented by the above general formula (2) may be mentioned.

The dopant material contained in the light emitting material is not limited to only one kind of the compound having the pyrromethene skeleton, and a plurality of pyromethene compounds may be used in combination, or at least one of the above dopant materials may be mixed with a pyromethene compound It is also good.

In the present invention, the electron transporting layer is a layer that injects electrons from a cathode and transports electrons. The electron-transporting layer preferably has a high electron-injecting efficiency and efficiently transports injected electrons. Therefore, it is preferable that the electron transporting layer is made of a substance which is large in electron affinity, has a large electron mobility, is excellent in stability, and impurities which are trapped are hardly generated at the time of production and use. However, when considering the transport balance of holes and electrons, the electron transport layer mainly plays a role of effectively preventing the holes from the anode from flowing to the cathode side without recombination, The effect of improving the light emitting efficiency is equivalent to that of the case of being made of a material having a high electron transporting ability. Therefore, the electron transporting layer in the present invention includes a hole blocking layer capable of efficiently blocking the movement of holes.

Examples of the electron transporting material used in the electron transporting layer include condensed polycyclic aromatic derivatives such as naphthalene and anthracene, styryl aromatic ring derivatives represented by 4,4'-bis (diphenylethenyl) biphenyl, anthraquinone and diphenoquinone Quinolinol complexes such as quinone derivatives, phosphorus oxide derivatives, tris (8-quinolinolate) aluminum (III), benzoquinolinol complexes, hydroxyazole complexes, azomethine complexes, troporon metal complexes and furavanol metal But it is preferable to use a heteroaryl ring which is composed of an element selected from carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus, and which contains electron-accepting nitrogen, from the viewpoint of reducing driving voltage and achieving high- It is preferable to use a compound having a structure.

The electron-accepting nitrogen in the present invention represents a nitrogen atom forming multiple bonds between adjacent atoms. Since the nitrogen source has a high electron affinity, the multiple bonds have electron accepting properties. Hence, the heteroaryl ring containing electron-accepting nitrogen has high electron affinity and is excellent in electron transporting ability, and can be used in an electron transporting layer to reduce the driving voltage of the light emitting element. The heteroaryl ring containing an electron-accepting nitrogen is, for example, a pyridine ring, a pyrazine ring, a pyrimidine ring, a quinoline ring, a quinoxaline ring, a naphthyridine ring, a pyrimidopyrimidine ring, a benzoquinoline ring, a phenanthroline ring, An oxazole ring, an oxadiazole ring, a triazole ring, a thiazole ring, a thiadiazole ring, a benzoxazole ring, a benzothiazole ring, a benzimidazole ring, a phenanthroididazole ring, and the like.

Examples of the compound having a heteroaryl ring structure include a benzimidazole derivative, a benzoxazole derivative, a benzothiazole derivative, an oxadiazole derivative, a thiadiazole derivative, a triazole derivative, a pyrazine derivative, a phenanthroline derivative, Quinoline derivatives, benzoquinoline derivatives, oligopyridine derivatives such as bipyridine and terpyridine, quinoxaline derivatives and naphthyridine derivatives, and the like are listed as preferred compounds. Among these, imidazole derivatives such as tris (N-phenylbenzimidazol-2-yl) benzene and the like, 1,3-bis [(4-tert- butylphenyl) 1,3,4-oxadiazolyl] Oxadiazole derivatives, triazole derivatives such as N-naphthyl-2,5-diphenyl-1,3,4-triazole, bathocuproin, 1,3-bis (1,10- Benzoquinoline derivatives such as 2,2'-bis (benzo [h] quinolin-2-yl) -9,9'-spirobifluorene, benzoquinoline derivatives such as 2,2'- Bipyridine derivatives such as 5-bis (6 '- (2', 2 "-bipyridyl)) - 1,1-dimethyl- (1-naphthyl) -4- (1,8-naphthyridin-2-yl) phenylphosphine oxide, and the like, Is preferably used in terms of electron transporting ability.

The electron transporting material may be used alone, but two or more kinds of the electron transporting materials may be used in combination, or one or more of other electron transporting materials may be mixed with the above electron transporting material.

The electron transporting layer may be composed of a first electron transporting layer in contact with the light emitting layer and a second electron transporting layer composed of the electron transporting material present between the cathode and the first electron transporting layer. As the constituent material of the first electron transporting layer and the second electron transporting layer, any two types of the electron transporting material can be selected, but from the viewpoint of both long life and low driving voltage, the first electron transporting layer does not contain electron- It is preferable to use a polycyclic aromatic compound as the second electron transporting layer and a compound having a heteroaryl ring structure composed of an element selected from carbon, hydrogen, nitrogen, oxygen, silicon and phosphorus and containing electron-accepting nitrogen . From the viewpoint of high efficiency, the polycyclic aromatic compound is more preferably a compound comprising an anthracene or pyrene skeleton.

It is also possible to use them in combination with metals such as alkali metals and alkaline earth metals. The ionization potential of the electron transporting layer is not particularly limited, but is preferably 5.8 eV or more and 8.0 eV or less, and more preferably 6.0 eV or more and 7.5 eV or less.

The method of forming the respective layers constituting the light emitting element is not particularly limited, such as resistance heating deposition, electron beam deposition, sputtering, molecular lamination, coating, etc. Usually, resistance heating deposition or electron beam deposition is preferable from the viewpoint of device characteristics Do.

The thickness of the organic layer is not limited because it depends on the resistance value of the light emitting material, but is selected between 1 and 1000 nm. The film thicknesses of the light emitting layer, the electron transporting layer, and the hole transporting layer are preferably 1 nm or more and 200 nm or less, and more preferably 5 nm or more and 100 nm or less.

The light emitting device of the present invention has a function of converting electric energy into light. Here, a direct current is mainly used as electric energy, but it is also possible to use a pulse current or an alternating current. The current value and the voltage value are not particularly limited, but in consideration of the power consumption and lifetime of the device, it is necessary to select such that the maximum luminance can be obtained with as low energy as possible.

The light emitting element of the present invention is suitably used as a display for displaying in a matrix and / or segment manner, for example.

The matrix method is a method in which pixels for display are arranged two-dimensionally, such as a lattice image or a mosaic image, to display a character or an image as a set of pixels. The shape and size of the pixel are determined by the application. For example, in a personal computer, a monitor, a television image, and a character display, a quadrangle pixel having one side of 300 mu m or less is usually used. In the case of a large display such as a display panel, In the case of a monochrome display, pixels of the same color may be arranged, but in the case of a color display, red, green, and blue pixels are displayed in a line. In this case, there are typically a delta type and a stripe type. The driving method of the matrix may be either a line-sequential driving method or an active matrix. Although the structure of the line-sequential driving is simple, considering the operating characteristics, the active matrix may be superior to the line-sequential driving.

The segment system in the present invention is a system in which a pattern is formed so as to display predetermined information and a region determined by the arrangement of the pattern is emitted. For example, a time or temperature display in a digital clock or a thermometer, an operation status display of an audio device or an electromagnetic cooker, and a panel display of an automobile are listed. The matrix display and the segment display may coexist in the same panel.

The light emitting device of the present invention is also preferably used as a backlight for various devices. The backlight is used mainly for the purpose of improving the visibility of a display device which does not emit light, and is used for a liquid crystal display device, a clock, an audio device, an automobile panel, a display panel and a marking. Particularly, among the liquid crystal display devices, a light-emitting element of the present invention can be preferably used for a backlight for personal computer use, which has been studied to be thinner, so that a thin and lightweight backlight can be provided.

(Example)

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples. In addition, the numbers of the compounds in the following respective Examples refer to the numbers of the compounds described in the above formulas. The evaluation method for structural analysis is shown below.

Synthesis Example 1

Synthesis of Compound [13]

15 g of 1-bromoprene was dissolved in 400 ml of carbon tetrachloride, 100 ml of a carbon tetrachloride solution of 2.7 ml of bromine was added dropwise under a nitrogen atmosphere, and the mixture was stirred at room temperature for 12 hours. The precipitated solid was collected by filtration and washed with methanol. The obtained solid was recrystallized with toluene to obtain 5.7 g of 1,6-dibromopyrene.

2.3 g of p-methylphenylboronic acid, 5.9 g of tripotassium phosphate, 0.90 g of tetra n-butylammonium bromide and 60 ml of N, N-dimethylformamide were added to 2.0 g of the obtained 1,6-dibromophenylene, After that, it was put under a nitrogen atmosphere. 64 mg of palladium acetate was added to the mixed solution, and the mixture was stirred at 130 캜 for 6 hours. After cooling at room temperature, the solution was poured into 500 ml of water and the precipitated solid was collected by filtration. The obtained solid was dissolved in hot toluene, filtered using celite while heating, and concentrated. The obtained solid was washed with ethyl acetate and further recrystallized with toluene to obtain 1.8 g of 1,6-bis (4-methylphenyl) pyrene.

1.3 g of the resulting 1,6-bis (4-methylphenyl) pyrene was dissolved in 30 ml of N, N-dimethylformamide, 0.6 g of N-bromosuccinimide was added under a nitrogen stream and stirred at 60 ° C for 5 hours Respectively. After cooling at room temperature, 30 ml of water was added and extracted with 100 ml of dichloromethane. The organic layer was washed twice with 50 ml of water, dried over magnesium sulfate and concentrated. Recrystallization from toluene gave 1.0 g of 3-bromo-1,6-bis (4-methylphenyl) pyrene.

To 1.0 g of 3-bromo-1,6-bis (4-methylphenyl) pyrene was added a solution of 2- (4,4,5,5-tetramethyl-1,3,2-dioxaborolan- 1.6 g of [b] furan, 2.8 g of tripotassium phosphate, 57 mg of PdCl ₂ (dppf) .CH ₂ Cl ₂ and 25 ml of degassed dimethylformamide were added and the mixture was stirred at 100 ° C for 4 hours under a nitrogen stream. After cooling at room temperature, 30 ml of water was injected and filtered. Washed with 30 ml of methanol, and then purified by silica gel column chromatography to obtain 0.34 g of compound [13].

Synthesis Example 2

Synthesis of Compound [26]

To 1.0 g of 1,6-dibromopyrene obtained in the same manner as described above, 1.4 g of 2-benzofuranboronic acid, 3.0 g of tripotassium phosphate, 0.45 g of tetra n-butylammonium bromide, 30 ml of N, N-dimethylformamide And the reaction was carried out in a nitrogen atmosphere after the vacuum degassing. 42 mg of palladium acetate was added to the mixed solution, and the mixture was stirred at 130 캜 for 5 hours. After cooling at room temperature, the solution was poured into 200 ml of water, and the precipitated solid was collected by filtration. The obtained solid was dissolved in heat 1,3-dimethyl-2-imidazolidinone and filtered while using Celite. After cooling at room temperature, the precipitated solid was collected by filtration. The resulting solid was washed with N, N-dimethylformamide to obtain 0.71 g of compound [26].

Synthesis Example 3

Synthesis of Compound [157]

Was synthesized according to the method described in JP-A-2005-53900. 4.7 g of 2- (4-methoxybenzoyl) -3,5-bis (4-t-butylphenyl) pyrrole and 3.3 g of 2,4-bis (4-t-butylphenyl) pyrrole were dissolved in 1,2- , 1.5 g of phosphorus oxychloride was added, and the mixture was reacted under heating and refluxing for 12 hours. After cooling at room temperature, 5.2 g of diisopropylethylamine and 5.6 g of boron trifluoride diethyl ether complex were added and stirred for 6 hours. 50 ml of water was added, dichloromethane was added, and then the organic layer was extracted and concentrated. The product was purified by silica gel column chromatography to obtain 5.0 g of the compound [157].

Synthesis Example 4

Synthesis of compound [158]

(4-t-butylphenyl) pyrrole in place of 2- (2-methoxybenzoyl) -3,5-bis Was used to synthesize the compound [158].

Synthesis Example 5

Synthesis of Compound [36]

Except that 4-methylphenylboronic acid was used in place of 2- (3-t-butylphenyl) -4,4,5,5-tetramethyl 1,3,2-dioxaborolane. The compound [36] was synthesized.

Example 1

A light emitting device using the compound [13] and the compound [158] was prepared as follows. A glass substrate (manufactured by Asahi Glass Co., Ltd., 15 Ω / □, electron beam evaporation product) in which an ITO transparent conductive film was deposited to 125 nm was cut into 30 × 40 mm, and the ITO conductive film was patterned by photolithography And an electrode withdrawing portion were produced. The obtained substrate was ultrasonically washed with acetone, "Semicocurin 56" (manufactured by Furuuchi Chemical Corporation) for 15 minutes, and then washed with ultrapure water. Subsequently, it was ultrasonically washed with isopropyl alcohol for 15 minutes, then immersed in hot methanol for 15 minutes, and dried. The substrate was subjected to UV-ozone treatment for 1 hour immediately before fabricating the device, and further placed in a vacuum deposition apparatus, and evacuated until the degree of vacuum in the apparatus became 5 × 10 ^-5 Pa or less. First, copper phthalocyanine was deposited to a thickness of 10 nm as a hole injecting material and 4,4'-bis (N- (1-naphthyl) -N-phenylamino) biphenyl as a hole transporting material to a thickness of 50 nm. Subsequently, a compound [13] was used as a host material and a compound [158] (fluorescent peak wavelength in a diluted dichloromethane solution: 612 nm) was deposited as a host material at a thickness of 40 nm so as to have a doping concentration of 1% . Subsequently, as the electron transporting material, E-1 shown below was laminated to a thickness of 35 nm. Subsequently, lithium fluoride was vapor-deposited at a thickness of 0.5 nm, and aluminum was vapor-deposited at a thickness of 1000 nm to form a cathode. The film thickness referred to here is a crystal oscillation type film thickness monitor display value. From this light emitting device, high-efficiency red light emission with a light emission efficiency of 3.0 lm / W was obtained. When this light emitting device was driven by direct current at 40 mA / cm ² , the brightness half-life time was 2,500 hours.

Comparative Example 1

A light emitting device was fabricated in the same manner as in Example 1 except that H-1 shown below was used as a host material. From this device, colored light emission with a luminous efficiency of 0.8 lm / W was obtained. This light emitting device was driven by direct current at 40 mA / cm < ² >, and the brightness half-life time was 400 hours.

Comparative Example 2

(4-methylphenyl) pyrrolo [3,4-c] pyrrole (hereinafter, referred to as H-2 (3,5-dimethylbenzyl) Quot;) was used as a light-emitting element. From this device, red luminescence with a luminous efficiency of 2.5 lm / W was obtained. This light emitting device was driven by direct current at 40 mA / cm ² , and the luminance half-life time was 500 hours.

Examples 2 to 18

A light emitting device was fabricated in the same manner as in Example 1 except that the material shown in Table 1 was used as a host material, a dopant material, and an electron transporting material. The results of the respective examples are shown in Table 1. In Table 1, the compound [128] was Pyrromethene 546 (manufactured by Exciton Inc.). In Table 1, D-1 to D-4 and E-2 to E-6 are compounds represented by the following formulas.

Example 19

A light emitting device was fabricated in the same manner as in Example 3 except that D-5 (fluorescent peak wavelength in the state of a diluted dichloromethane solution: 553 nm) shown below was used as a dopant material so that the doping concentration was 5%. From this device, an orange light emission with a luminous efficiency of 2.1 m / W was obtained. This light emitting device was driven by direct current at 40 mA / cm ² , and the luminance half-life time was 2,000 hours.

Comparative Example 3

A light emitting device was fabricated in the same manner as in Example 3 except that D-6 (fluorescence peak wavelength in the state of a diluted dichloromethane solution: 686 nm) shown below was used as a dopant material. From this device, red light emission with a luminous efficiency of 0.5 m / W was obtained. This light emitting device was driven by direct current at 40 mA / cm ² , and the luminance half-life time was 950 hours.

Example 20

E-7 shown below was laminated as a first electron transporting material to a thickness of 25 nm instead of laminating the E-1 shown above as a electron transporting material in a thickness of 35 nm, and then E-1 Was laminated to a thickness of 10 nm, a light emitting device was fabricated in the same manner as in Example 3. From this device, high-efficiency red light emission with a luminous efficiency of 5.2 lm / W was obtained. This light emitting device was driven by direct current at 40 mA / cm < ² >, and the luminance half-life time was 6000 hours.

The light emitting device of the present invention has high luminous efficiency and excellent durability and can be used in fields such as a display device, a flat panel display, a backlight, a lighting, an interior, a mark, a signboard, an electronic camera and an optical signal generator.

Claims (6)

At least the light-emitting layer exists between the anode and the cathode, and the light-emitting element emits light by electric energy: Wherein the light emitting layer of the device comprises a pyrene compound represented by the general formula (1) and an organic type mineral substance represented by the following general formula (2) and having a peak fluorescence wavelength of 500 nm or more and 680 nm or less.

[R ¹ to R ¹⁵ may be the same or different and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl ether group, A heterocyclic group, a heteroaryl group, an amino group, a silyl group, -P (= O) R ¹⁶ R ^17, and adjacent substituents. R ¹⁶ and R ¹⁷ are selected from an aryl group and a heteroaryl group. Among R ¹ to R ¹⁰ , n is used for linking with a bicyclic benzoheterocycle. n is an integer of 1 to 2; X is an oxygen atom.]

[R ¹⁹ to R ²⁵ may be the same or different and each represents hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an aryl ether group, an arylthioether group, (= O) R ²⁸ R ^29, and adjacent substituents. The ring structure is preferably selected from the group consisting of a hydrogen atom, a cyano group, a cyano group, an amino group, a silyl group, -P (= O) R ²⁸ and R ²⁹ are selected from an aryl group and a heteroaryl group. R ²⁶ and R ²⁷ are fluorine atoms. Y is a carbon atom.] delete The method according to claim 1, R ¹ , R ³ , R ⁶ , R ⁸ Wherein at least one of R 1 and R 2 is bonded to a bicyclic benzoheterocycle. The method according to claim 1, R ¹ to R ¹⁰ Is an aryl group or a heteroaryl group. delete The method according to claim 1, Wherein at least an electron transporting layer exists between the light emitting layer and the cathode and the electron transporting layer contains a compound comprising a heteroaryl ring having electron-accepting nitrogen, and the compound comprising a heteroaryl ring is an element selected from carbon, hydrogen, nitrogen, oxygen, Emitting element.