JP5267123B2 - Light emitting element - Google Patents

Description

  The present invention relates to a pyrene compound useful as a fluorescent dye or a charge transport material, and a light emitting device using the same, and includes a display device, a flat panel display, a backlight, illumination, an interior, a sign, a signboard, an electrophotographic machine, and an optical signal The present invention relates to a light-emitting element that can be used in fields such as a generator.

  In recent years, research on organic thin-film light-emitting devices that emit light when electrons injected from a cathode and holes injected from an anode are recombined in an organic light-emitting body sandwiched between both electrodes has been actively conducted. This light-emitting element is characterized by thin light emission with high luminance under a low driving voltage and multicolor light emission by selecting a light-emitting material.

This study was conducted by Eastman Kodak's C.I. W. Since Tang et al. Have shown that organic thin-film light-emitting elements emit light with high brightness, many research institutions have studied. The representative structure of the organic thin film light emitting device presented by the Kodak research group is a hole transporting diamine compound on an ITO glass substrate, tris (8-quinolinolato) aluminum (III) as a light emitting layer, and a cathode. Mg: Ag (alloy) was sequentially provided, and green light emission of 1,000 cd / m ² was possible with a driving voltage of about 10 V (see Non-Patent Document 1).

  In addition, organic thin-film light-emitting elements can be obtained in various emission colors by using various fluorescent materials for the light-emitting layer, and therefore, researches for practical application to displays and the like are actively conducted. In particular, research on light emitting materials of the three primary colors of red, green, and blue is the most active, and intensive research has been conducted with the aim of improving characteristics.

One of the biggest problems in organic thin film light emitting devices is the improvement of the durability and luminous efficiency of the devices. As a means for obtaining a highly efficient light emitting element, a method of forming a light emitting layer by doping a host material with a dopant material (fluorescent material) by several percent is known. (See Patent Document 1) The host material is required to have high carrier mobility and uniform film formability, and the dopant material is required to have high fluorescence quantum yield and uniform dispersibility. For example, as a blue material, a technique using a styrylamine derivative (see Patent Document 2), a perylene derivative (see Patent Document 3), or a pyrene compound is disclosed (see Patent Documents 4 to 6). Examples of green materials include stilbene compounds (see Patent Document 7), quinoline derivatives and quinacridone compounds (see Patent Document 8), and examples of red materials include aminostyryl compounds (see Patent Document 9), diketopyrrolopyrrole derivatives and pyromethene compounds. (See Patent Document 10), coumarin compounds and dicyanomethylenepyran compounds (see Patent Document 11), but none showed sufficient luminous efficiency and durability. In addition to the above, there are a large number of host materials and dopant materials that form a light emitting material, and the combination of these materials becomes enormous. In general, the degree of overlap between the fluorescence spectrum of the host material and the absorption spectrum of the dopant material and the intermolecular distance are known as guidelines for the ease of energy transfer from the host material to the dopant material (non-patented). However, not all light emission mechanisms have been elucidated, and there are many trial and error parts. That is, in order to obtain a light-emitting element having better light emission characteristics, it is very important not only to discover a new host material and dopant material, but also to find an optimal combination of host material and dopant material.
Japanese Patent No. 2814435 JP-A-5-17765 JP 2003-86380 A JP 2001-118682 A JP 2004-75567 A JP 2002-63988 A JP-A-2-247278 JP-A-3-255190 JP 2002-134276 A JP 2003-86379 A JP-A-5-202356 Applied Physics Letters (USA) 1987, 51, 12, p. 913-915 “Organic EL elements and the forefront of industrialization”, NTS, 1998, p. 66

  An object of the present invention is to provide a light-emitting element that optimizes the combination of a host material and a dopant material and has high luminous efficiency and excellent durability.

The present invention is an element in which at least a light emitting layer exists between an anode and a cathode and emits light by electric energy. The light emitting layer of the element has a pyrene compound represented by the general formula (1) and a fluorescence peak wavelength. look including the 680nm following organic fluorescent substance or 500nm, the light emitting device, wherein the fluorescent peak wavelength of a compound having a pyrromethene skeleton 680nm following organic fluorescent substance or 500nm is represented by the general formula (2) is there.

R ^{1 to} R ¹⁵ may be the same as or different from each other, and are hydrogen, alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, aryl thioether group, an aryl group, a heteroaryl group, an amino group, a silyl group, -P (= O) R 16 R 17, and selected from the ring structure formed between adjacent substituents. R ¹⁶ and R ¹⁷ are selected from aryl groups and heteroaryl groups. Here, n is 2, ^{R 1} and R ⁶ are, used for linking the benzofuran ring or indole ring of the group represented by the general formula (3) in the general formula (1), ^{R 3} and ^{R 8} are each may be the same or different, Ru hydrogen or an aryl group der. X is selected from an oxygen atom and —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 be bonded to R ¹⁵ to form a ring .
R ^{19 to} R ²⁵ may be the same as or different from each other, and hydrogen, alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, aryl thioether The ring structure is selected from a group, an aryl 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 aryl groups and heteroaryl groups. R ²⁶ and R ²⁷ may be the same or different and are selected from halogen, hydrogen, alkyl, aryl, and a heterocyclic group. Y is a carbon atom or a nitrogen atom. In the case of a nitrogen atom, R ²⁵ does not exist.

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

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

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

  The resistance of the electrode is sufficient if a current sufficient for light emission of the light emitting element can be supplied, and it is desirable that the resistance is low from the viewpoint of power consumption of the light emitting element. For example, an ITO substrate of 300Ω / □ or less will function as a device electrode, but since it is now possible to supply a substrate of about 10Ω / □, use a low-resistance product of 100Ω / □ or less. Is particularly desirable. The thickness of ITO can be arbitrarily selected according to the resistance value, but is usually used in a range of 100 to 300 nm.

In order to maintain the mechanical strength of the light emitting element, the light emitting element is preferably formed over a substrate. As the substrate, a glass substrate such as soda glass or non-alkali glass is preferably used. As the thickness of the glass substrate, it is sufficient that the thickness is sufficient to maintain the mechanical strength. As for the glass material, alkali-free glass is preferred because it is better that there are fewer ions eluted from the glass. Alternatively, soda lime glass provided with a barrier coat such as SiO ₂ is also commercially available and can be used. Furthermore, if the anode functions stably, the substrate does not have to be glass. For example, the anode may be formed on a plastic substrate. The ITO film forming method is not particularly limited, such as an electron beam method, a sputtering method, and a chemical reaction method.

  The material used for the cathode used in the present invention is not particularly limited as long as it is a substance that can efficiently inject electrons into the organic layer, but is generally platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium. Lithium, sodium, potassium, cesium, calcium and magnesium, and alloys thereof. Lithium, sodium, potassium, cesium, calcium, magnesium, or alloys containing these low work function metals are effective for increasing the electron injection efficiency and improving device characteristics. However, these low work function metals are often often unstable in the atmosphere. Therefore, a preferable example is a method in which a highly stable electrode is obtained by doping a small amount of lithium or magnesium (1 nm or less in vacuum vapor deposition thickness display) into the organic layer. Also, an inorganic salt such as lithium fluoride can be used. Furthermore, for electrode protection, 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, polyvinyl chloride Lamination of organic polymer compounds such as hydrocarbon polymer compounds is a preferred example. The method for producing these electrodes is not particularly limited as long as conduction can be achieved, such as resistance heating, electron beam, sputtering, ion plating, and coating.

  The organic layer constituting the light emitting device of the present invention is composed of at least a light emitting layer made of a light emitting device material. As an example of the organic layer configuration, in addition to the configuration consisting of only the light emitting layer, 1) hole transport layer / light emitting layer / electron transport layer and 2) light emitting layer / electron transport layer, 3) hole transport layer / light emission A laminated structure such as a layer can be mentioned. Moreover, each said layer may consist of a single layer, respectively, and may consist of multiple layers. When the hole transport layer and the electron transport layer are composed of a plurality of layers, the layers in contact with the electrode may be referred to as the hole injection layer and the electron injection layer, respectively. In the material, the electron injection material is included in the electron transport material.

  The hole transport layer is formed by a method of laminating or mixing one or more hole transport materials or a method using a mixture of a hole transport material and a polymer binder. Alternatively, the hole transport layer may be formed by adding an inorganic salt such as iron (III) chloride to the hole transport material. The hole transport material is not particularly limited as long as it is a compound that forms a thin film necessary for manufacturing a light emitting element, can inject holes from the anode, and can further transport holes. For example, 4,4′-bis (N- (3-methylphenyl) -N-phenylamino) biphenyl, 4,4′-bis (N- (1-naphthyl) -N-phenylamino) biphenyl, 4,4 Triphenylamine derivatives such as', 4 "-tris (3-methylphenyl (phenyl) amino) triphenylamine, biscarbazole derivatives such as bis (N-allylcarbazole) or bis (N-alkylcarbazole), pyrazoline derivatives, Heterocyclic compounds such as stilbene compounds, hydrazone compounds, benzofuran derivatives and thiophene derivatives, oxadiazole derivatives, phthalocyanine derivatives, porphyrin derivatives, and polymer systems such as polycarbonates, styrene derivatives, polythiophene, polyaniline , Polyfluorene, poly Such alkenyl carbazole and polysilane are preferred.

  In the present invention, the light emitting layer may be either a single layer or a plurality of layers, each formed of a light emitting material (host material, dopant material), which may be a mixture of a host material and a dopant material, Either the material alone or the material may be used. That is, in the light emitting element of the present invention, only the host material or the dopant material may emit light in each light emitting layer, or both the host material and the dopant material may emit light. Each of the host material and the dopant material may be one kind or a plurality of combinations. The dopant material may be included in the entire host material or may be partially included. The dopant material may be laminated or dispersed. If the amount of the dopant material is too large, a concentration quenching phenomenon occurs, so that it is preferably used at 20% by weight or less, more preferably 10% by weight or less with respect to the host material. As a doping method, it can be formed by a co-evaporation method with a host material, but it may be pre-mixed with the host material and then simultaneously deposited.

  In the present invention, the light emitting layer contains a pyrene compound represented by the general formula (1) and an organic fluorescent material having a fluorescence peak wavelength of 500 nm or more and 680 nm or less. Although the pyrene compound represented by the general formula (1) can be used as a dopant material, it is preferable to use it as a host material in consideration of the high carrier transfer property of the pyrene compound. An organic fluorescent material having a fluorescence peak wavelength of 500 nm or more and 680 nm or less is preferably used as a dopant material. Here, the fluorescence peak wavelength is a value in a dilute solution of dichloromethane. When the fluorescence peak wavelength is larger than 680 nm, the visibility is deteriorated and it is difficult to obtain highly efficient red light emission.

  The host material contained in the light emitting material need not be limited to only one pyrene compound, and may be used by mixing a plurality of pyrene compounds or by mixing one or more known host materials with a pyrene compound. Good. Specifically, compounds having condensed aryl rings such as anthracene and derivatives thereof, aromatic amine derivatives such as 4,4′-bis (N- (1-naphthyl) -N-phenylamino) biphenyl, tris (8-quinolinolate) ) Metal chelated oxinoid compounds such as aluminum (III), bisstyryl derivatives such as distyrylbenzene derivatives, tetraphenylbutadiene derivatives, indene derivatives, coumarin derivatives, oxadiazole derivatives, pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives , Oxadiazole derivatives, carbazole derivatives, pyrrolopyrrole derivatives, in polymer systems, polyphenylene vinylene derivatives, polyparaphenylene derivatives, polyfluorene derivatives, polyvinyl carbazole derivatives and polythiol Down derivative is preferably used.

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

R ^{1 to} R ¹⁵ may be the same as or different from each other, and are hydrogen, alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, aryl thioether group, an aryl group, a heteroaryl group, an amino group, a silyl group, -P (= O) R 16 R 17, and selected from the ring structure formed between adjacent substituents. R ¹⁶ and R ¹⁷ are selected from aryl groups and heteroaryl groups. Any n of R ^{1 to} R ¹⁰ are used for linking with a bicyclic benzoheterocycle. n is an integer of 1-4. X is selected from an oxygen atom, a sulfur atom, and —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 be bonded to R ¹⁵ to form a ring.

  Among these substituents, the alkyl group 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 in the case of being substituted is not particularly limited, and examples thereof include an alkyl group, an aryl group, a heteroaryl group, and the like, and this point is common to the following description. Moreover, the number of carbon atoms of the alkyl group is not particularly limited, but is usually in the range of 1 or more and 20 or less from the viewpoint of availability and cost.

  The cycloalkyl group represents a saturated alicyclic hydrocarbon group such as cyclopropyl, cyclohexyl, norbornyl, adamantyl, and the like, which may be unsubstituted or substituted. Although carbon number of an alkyl group part is not specifically limited, Usually, it is the range of 3-20.

  The heterocyclic group refers to a group consisting of an aliphatic ring having atoms other than carbon, such as a pyran ring, piperidine ring and cyclic amide, in the ring, which may be unsubstituted or substituted. . Although carbon number of a heterocyclic group is not specifically limited, Usually, it is the range of 2-20.

  Moreover, an alkenyl group shows the unsaturated aliphatic hydrocarbon group containing double bonds, such as a vinyl group, an allyl group, and a butadienyl group, for example, and this may be unsubstituted or substituted. Although carbon number of an alkenyl group is not specifically limited, Usually, it is the range of 2-20.

  The cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond such as a cyclopentenyl group, a cyclopentadienyl group, or a cyclohexenyl group, which is unsubstituted or substituted. It doesn't matter.

  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. Although carbon number of an alkynyl group is not specifically limited, Usually, it is the range of 2-20.

  The alkoxy group refers to, for example, an aliphatic hydrocarbon group via an ether bond such as a methoxy group, and the aliphatic hydrocarbon group may be unsubstituted or substituted. Although carbon number of an alkoxy group is not specifically limited, Usually, it is the range of 2-20.

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

  The aryl ether group refers to, for example, an aromatic hydrocarbon group via an ether bond such as a phenoxy group, and the aromatic hydrocarbon group may be unsubstituted or substituted. Although carbon number of an aryl ether group is not specifically limited, Usually, it is the range of 6-40.

  The arylthioether group is a group in which the oxygen atom of the ether bond of the arylether group is substituted with a sulfur atom.

  Moreover, an aryl group shows aromatic hydrocarbon groups, such as a phenyl group, a naphthyl group, a biphenyl group, a phenanthryl group, a terphenyl group, a pyrenyl group, for example. The aryl group may be unsubstituted or substituted. Although carbon number of an aryl group is not specifically limited, Usually, it is the range of 6-40.

  The heteroaryl group refers to an aromatic group having an atom other than carbon, such as a furanyl group, a thiophenyl group, an oxazolyl group, a pyridyl group, or a quinolinyl group, which is unsubstituted or substituted. It doesn't matter. Although carbon number of heteroaryl group is not specifically limited, Usually, it is the range of 2-30.

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

  A silyl group refers to, for example, a functional group having a bond to a silicon atom, such as a trimethylsilyl group, which may or may not have a substituent. Although carbon number of a silyl group is not specifically limited, Usually, it is the range of 3-20. The number of silicon is usually in the range of 1 to 6.

When the ring structure formed between adjacent groups is described in the general formula (1), any two adjacent substituents selected from R ^{1 to} R ¹⁰ (for example, R ¹ and R ² ) are mutually bonded. Bonded to form a conjugated or non-serving fused ring. These condensed rings may contain nitrogen, oxygen, or sulfur atoms in the ring structure, or may be condensed with another ring, but the atoms constituting these condensed rings are only carbon atoms and hydrogen atoms. It is preferable because excellent heat resistance can be obtained.

  The pyrene compound represented by the general formula (1) has a pyrene skeleton and 1 to 4 bicyclic benzoheterocycles (benzofuran ring, benzothiophene ring, indole ring) in the molecule. As a result, both high carrier mobility and heat resistance can be achieved, and the light emission efficiency of the device can be improved and the durability can be improved. Moreover, since this pyrene compound has a fluorescence peak wavelength of 500 nm or more in a thin film state, it can be suitably used as a host material in a blue-green to red region (500 to 680 nm region).

Any n of R ^{1 to} R ¹⁰ are used for linking to a bicyclic benzoheterocycle, but at least ^one of R ¹ , R ³ , R ⁶ , and R ⁸ is used because of availability of raw materials and ease of synthesis. One is preferably used for linking to a bicyclic benzoheterocycle. Moreover, it is preferable that at least one of R ¹ to R ¹⁰ is an aryl group or a heteroaryl group, because association between pyrene compounds is suppressed and a stable thin film is formed. Moreover, since X of General formula (1) is an oxygen atom, since higher luminous efficiency is obtained, it is preferable.

  A known method can be used for the synthesis of the pyrene compound represented by the general formula (1). Examples of the method for introducing a bicyclic benzoheterocycle into a pyrene skeleton include a method using a coupling reaction under a palladium or nickel catalyst with a halogenated pyrene derivative and a bicyclic benzoheterocyclic metal reagent, or a halogenated bicyclic benzoheterocycle. And a method using a coupling reaction of a pyrene derivative boronic acid with a palladium or nickel catalyst, but is not limited thereto.

  Specific examples of the pyrene compound having a group containing a bicyclic benzoheterocycle represented by the general formula (1) include the following.

  Examples of the organic fluorescent substance having a fluorescence peak wavelength of 500 nm to 680 nm used in the present invention include compounds having a condensed aromatic ring such as naphthacene, rubrene, perylene, and terylene, and derivatives thereof, thiophene, imidazopyridine, pyrazine, naphthyridine, quinoxaline, Compounds having heteroaryl rings such as pyrrolopyridine, thioxanthene, pyridinothiadiazole, pyrazolopyridine and derivatives thereof, distyrylbenzene derivatives, aminostyryl derivatives, aldazine derivatives, diketopyrrolo [3,4-c] pyrrole derivatives, 2, Coumarin derivatives such as 3,5,6-1H, 4H-tetrahydro-9- (2'-benzothiazolyl) quinolidino [9,9a, 1-gh] coumarin, imidazole, thiazole, thiadiazole, carbazole, oxazo Coordination of azole derivatives such as ru, oxadiazole and triazole and their metal complexes, aromatic amine derivatives, naphthalimide derivatives such as bis (diisopropylphenyl) perylenetetracarboxylic imide, perinone derivatives, acetylacetone, benzoylacetone and phenanthroline Rare earth complexes such as Eu complex, pyran derivatives such as 4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran, metal phthalocyanine derivatives such as magnesium phthalocyanine and aluminum chlorophthalocyanine , Metalloporphyrin derivatives such as zinc porphyrin, rhodamine compounds, deazaflavin derivatives, oxazine compounds, phenoxazine derivatives, phenoxazone derivatives, quinacridone derivatives, di Can be used as the anode ethenyl arene derivatives, those having a high fluorescence quantum yield in solution is preferably used from the viewpoint of obtaining a high efficiency light emission. When combined with the pyrene compound represented by the general formula (1), an organic fluorescent material 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 organic fluorescent substance, a compound having a pyrromethene skeleton represented by the general formula (2), since the narrow half width of the high fluorescence spectrum fluorescent quantum yield, high efficiency and high color purity light emission can be obtained.

R ^{19 to} R ²⁵ may be the same as or different from each other, and hydrogen, alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, aryl thioether The ring structure is selected from a group, an aryl 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 aryl groups and heteroaryl groups. R ²⁶ and R ²⁷ may be the same or different and are selected from halogen, hydrogen, alkyl, aryl, and a heterocyclic group. Y is a carbon atom or a nitrogen atom. In the case of a nitrogen atom, R ²⁵ does not exist. The explanation of these substituents is the same as described above.

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

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

  Examples of the pyromethene metal complex represented by the general formula (2) can include the following specific examples.

  The dopant material contained in the light-emitting material need not be limited to only one compound having the pyromethene skeleton, and a mixture of a plurality of pyromethene compounds may be used, or one or more of the above-described dopant materials may be mixed with a pyromethene compound. May be used.

  In the present invention, the electron transport layer is a layer in which electrons are injected from the cathode and further transports electrons. The electron transport layer has high electron injection efficiency, and it is desired to efficiently transport injected electrons. Therefore, it is desirable that the electron transport layer is made of a material having a high electron affinity, a high electron mobility, excellent stability, and a trapping impurity that is unlikely to be generated during manufacture and use. However, considering the transport balance between holes and electrons, if the electron transport layer mainly plays a role of effectively preventing the holes from the anode from recombining and flowing to the cathode side, the electron transport Even if it is made of a material that does not have a high capability, the effect of improving the luminous efficiency is equivalent to that of a material that has a high electron transport capability. Therefore, the electron transport layer in the present invention includes a hole blocking layer that can efficiently block the movement of holes as the same meaning.

  Examples of the electron transport material used in the electron transport layer include condensed polycyclic aromatic derivatives such as naphthalene and anthracene, styryl aromatic ring derivatives represented by 4,4′-bis (diphenylethenyl) biphenyl, anthraquinone, diphenoquinone, and the like. Quinoline derivatives, phosphorus oxide derivatives, quinolinol complexes such as tris (8-quinolinolato) aluminum (III), benzoquinolinol complexes, hydroxyazole complexes, azomethine complexes, tropolone metal complexes, and flavonol metal complexes. 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, because driving voltage is reduced and high-efficiency light emission is obtained. Is preferably used.

  The electron-accepting nitrogen in the present invention represents a nitrogen atom that forms a multiple bond with an adjacent atom. Since the nitrogen atom has a high electronegativity, the multiple bond has an electron accepting property. Therefore, a heteroaryl ring containing electron-accepting nitrogen has high electron affinity, excellent electron transport ability, and can be used for an electron transport layer to reduce the driving voltage of a light-emitting element. Heteroaryl rings containing electron-accepting nitrogen include, for example, pyridine ring, pyrazine ring, pyrimidine ring, quinoline ring, quinoxaline ring, naphthyridine ring, pyrimidopyrimidine ring, benzoquinoline ring, phenanthroline ring, imidazole ring, oxazole ring, oxalate ring, Examples include a diazole ring, a triazole ring, a thiazole ring, a thiadiazole ring, a benzoxazole ring, a benzothiazole ring, a benzimidazole ring, and a phenanthrimidazole ring.

  Examples of these compounds having a heteroaryl ring structure include benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, quinoline derivatives, benzoins. Preferred compounds include quinoline derivatives, oligopyridine derivatives such as bipyridine and terpyridine, quinoxaline derivatives and naphthyridine derivatives. Among them, imidazole derivatives such as tris (N-phenylbenzimidazol-2-yl) benzene, oxadiazole derivatives such as 1,3-bis [(4-tert-butylphenyl) 1,3,4-oxadiazolyl] phenylene, Triazole derivatives such as N-naphthyl-2,5-diphenyl-1,3,4-triazole, phenanthroline derivatives such as bathocuproine and 1,3-bis (1,10-phenanthroline-9-yl) benzene, 2,2 ′ A benzoquinoline derivative such as bis (benzo [h] quinolin-2-yl) -9,9′-spirobifluorene, 2,5-bis (6 ′-(2 ′, 2 ″ -bipyridyl))-1, Bipyridine derivatives such as 1-dimethyl-3,4-diphenylsilole, 1,3-bis (4 ′-(2,2 ′: 6′2 ″ -ta Terpyridine derivatives such as pyridinyl)) benzene, naphthyridine derivatives such as bis (1-naphthyl) -4- (1,8-naphthyridin-2-yl) phenylphosphine oxide are preferably used from the viewpoint of electron transporting capability.

  The electron transport material may be used alone, but two or more of the electron transport materials may be mixed and used, or one or more of the other electron transport materials may be mixed with the electron transport material.

Further, the electron transport layer may be composed of a first electron transport layer in contact with the light emitting layer and a second electron transport layer composed of the electron transport material existing between the cathode and the first electron transport layer. As a constituent material of the first electron transport layer and the second electron transport layer, any two kinds of the above electron transport materials can be selected. From the viewpoint of achieving both a long life and a low driving voltage, A polycyclic aromatic compound that does not contain electron-accepting nitrogen is used as a second electron-transporting layer that is composed of an element selected from carbon, hydrogen, nitrogen, oxygen, silicon, and phosphorus, and includes heteroaryl containing electron-accepting nitrogen. It is preferable to use a “compound having a ring structure”. Further, 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 a mixture with a metal such as an alkali metal or an alkaline earth metal. The ionization potential of the electron transport 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 each layer constituting the light emitting element is not particularly limited, such as resistance heating vapor deposition, electron beam vapor deposition, sputtering, molecular lamination method, coating method, etc., but resistance heating vapor deposition or electron beam vapor deposition is usually used in terms of element characteristics. preferable.

  The thickness of the organic layer depends on the resistance value of the luminescent material and cannot be limited, but is selected from 1 to 1000 nm. The film thicknesses of the light emitting layer, the electron transport layer, and the hole transport layer are each preferably 1 nm to 200 nm, and more preferably 5 nm to 100 nm.

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

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

  In the matrix method, pixels for display are two-dimensionally arranged such as a lattice shape or a mosaic shape, and a character or an image is displayed by a set of pixels. The shape and size of the pixel are determined by the application. For example, a square pixel with a side of 300 μm or less is usually used for displaying images and characters on a personal computer, monitor, TV, and a pixel with a side of mm order for a large display such as a display panel. become. In monochrome display, pixels of the same color may be arranged. However, in color display, 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 driving method may be either a line sequential driving method or an active matrix. Although the structure of the line sequential drive is simple, the active matrix may be superior in consideration of the operation characteristics, and it is necessary to use it depending on the application.

  The segment system in the present invention is a system in which a pattern is formed so as to display predetermined information and an area determined by the arrangement of the pattern is caused to emit light. For example, the time and temperature display in a digital clock or a thermometer, the operation state display of an audio device or an electromagnetic cooker, the panel display of an automobile, etc. 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 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, the light-emitting element of the present invention is preferably used for a backlight for a liquid crystal display device, particularly a personal computer for which a reduction in thickness is being considered, and a backlight that is thinner and lighter than conventional ones can be provided.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited by these Examples. In addition, the number of the compound in each following Example points out the number of the compound described in the above chemical formula. The evaluation method for structural analysis is shown below.

Synthesis example 1
Synthesis of Compound [13] 15 g of 1-bromopyrene 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.

  To 2.0 g of the obtained 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. After degassing under reduced pressure, a nitrogen atmosphere was set. To the mixed solution, 64 mg of palladium acetate was added and stirred at 130 ° C. for 6 hours. After cooling to room temperature, it was poured into 500 mL of water, and the precipitated solid was collected by filtration. The obtained solid was dissolved in hot toluene, filtered hot using Celite, and concentrated. The obtained solid was washed with ethyl acetate and recrystallized with toluene to obtain 1.8 g of 1,6-bis (4-methylphenyl) pyrene.

  1.3 g of the obtained 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 the mixture was stirred at 60 ° C. for 5 hours. did. After cooling to room temperature, 30 ml of water was poured 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.

2- (4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) benzo [b] is added to 1.0 g of 3-bromo-1,6-bis (4-methylphenyl) pyrene. 1.6 g of 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 heated and stirred at 100 ° C. for 4 hours under a nitrogen stream. After cooling to room temperature, 30 ml of water was poured and filtered. After washing with 30 ml of methanol, purification by silica gel column chromatography gave 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 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 was added, and after degassing under reduced pressure, a nitrogen atmosphere was established. To the mixed solution was added 42 mg of palladium acetate, and the mixture was stirred at 130 ° C. for 5 hours. After cooling to room temperature, it was poured into 200 mL of water, and the precipitated solid was collected by filtration. The resulting solid was dissolved in hot 1,3-dimethyl-2-imidazolidinone and filtered hot with celite. After cooling to room temperature, the precipitated solid was collected by filtration. The obtained solid was washed with N, N-dimethylformamide to obtain 0.71 g of compound [26].

Synthesis example 3
Synthesis of Compound [157] The compound [157] was synthesized according to the method described in JP-A-2005-53900. 2- (4-Methoxybenzoyl) -3,5-bis (4-tert-butylphenyl) pyrrole (4.7 g) and 2,4-bis (4-tert-butylphenyl) pyrrole (3.3 g) were converted into 1,2-dichloroethane. It melt | dissolved in 30 mL, 1.5 g of phosphorus oxychloride was added, and it was made to react under heating reflux for 12 hours. After cooling to room temperature, 5.2 g of diisopropylethylamine and 5.6 g of boron trifluoride diethyl ether complex were added and stirred for 6 hours. After adding 50 ml of water and adding dichloromethane, the organic layer was extracted and concentrated. The crude product was purified by silica gel column chromatography to obtain 5.0 g of compound [157].

Synthesis example 4
Synthesis of Compound [158] 2- (2-methoxybenzoyl) -3,5-bis (4-t) instead of 2- (4-methoxybenzoyl) -3,5-bis (4-t-butylphenyl) pyrrole Synthesis was performed in the same manner as in Synthesis Example 3 except that -butylphenyl) pyrrole was used to obtain Compound [158].

Synthesis example 5
Synthesis of Compound [36] Synthesis Example except that 4-methylphenylboronic acid was used in place of 2- (3-t-butylphenyl) -4,4,5,5-tetramethyl-1,3,2-dioxaborolane 5 was synthesized in the same manner as in Example 5 to obtain compound [36].

Comparative Example 1
A light emitting device using the compound [13] and the compound [158] was produced as follows. A glass substrate (manufactured by Asahi Glass Co., Ltd., 15Ω / □, electron beam vapor-deposited product) on which an ITO transparent conductive film is deposited to 125 nm is cut to 30 × 40 mm, and the ITO conductive film is patterned by a photolithography method to produce a light emitting portion And the electrode extraction part was produced. The obtained substrate was ultrasonically cleaned with acetone, “Semicocrine 56” (manufactured by Furuuchi Chemical Co., Ltd.) for 15 minutes and then with ultrapure water. Subsequently, it was ultrasonically cleaned with isopropyl alcohol for 15 minutes and then immersed in hot methanol for 15 minutes and dried. Immediately before the device was fabricated, this substrate was subjected to UV-ozone treatment for 1 hour, further placed in a vacuum vapor deposition apparatus, and evacuated until the degree of vacuum in the apparatus became 5 × 10 ⁻⁵ Pa or less. By the resistance heating method, first, copper phthalocyanine was deposited as a hole injecting material at 10 nm, and 4,4′-bis (N- (1-naphthyl) -N-phenylamino) biphenyl was deposited as a hole transporting material at 50 nm. Next, the compound [13] is used as the light emitting material, the compound [13] is used as the host material, and the compound [158] (fluorescence peak wavelength in a diluted dichloromethane solution state: 612 nm) is used as the dopant material. Vapor deposited. Next, as an electron transport material, E-1 shown below was laminated to a thickness of 35 nm. Next, after depositing 0.5 nm of lithium fluoride, 1000 nm of aluminum was vapor-deposited to form a cathode, and a 5 × 5 mm square device was fabricated. The film thickness referred to here is a crystal oscillation type film thickness monitor display value. From this light-emitting element, high-efficiency red light emission with a light emission efficiency of 3.0 lm / W was obtained. When this light emitting device was DC-driven at 40 mA / cm ² , the luminance half time was 2,500 hours.

Comparative Example 2
A light emitting device was produced in the same manner as in Comparative Example 1 except that H-1 shown below was used as the host material. From this device, pink light emission with a light emission efficiency of 0.8 lm / W was obtained. When this light emitting device was DC-driven at 40 mA / cm ² , the luminance half time was 400 hours.

Comparative Example 3
As a host material, 1,4-diketo-2,5-bis (3,5-dimethylbenzyl) -3,6-bis (4-methylphenyl) pyrrolo [3,4-c] pyrrole (hereinafter referred to as H-2) A light emitting device was fabricated in the same manner as in Comparative Example 1 except that was used. From this device, red light emission with a luminous efficiency of 2.5 lm / W was obtained. When this light emitting device was DC-driven at 40 mA / cm ² , the luminance half time was 500 hours.

Examples 1 to 12 , Comparative Examples 4 to 8
A light emitting device was fabricated in the same manner as in Comparative Example 1 except that the materials shown in Table 1 were used as the host material, the dopant material, and the electron transport material. The results of each example are shown in Table 1. In Table 1, Pyrromethene 546 (Exciton Inc.) was used as the compound [128]. Moreover, in Table 1, D-1 to D-4 and E-2 to E-6 are compounds represented by the following formula.

Comparative Example 9
A light emitting device was produced in the same manner as in Example 2 except that D-5 shown below (fluorescence peak wavelength in a dilute solution of dichloromethane: 553 nm) was used as the dopant material so that the doping concentration was 5%. From this device, orange light emission with a luminous efficiency of 2.1 m / W was obtained. When this light emitting device was DC-driven at 40 mA / cm ² , the luminance half time was 2,000 hours.

Comparative Example 10
A light emitting device was produced in the same manner as in Example 2 except that D-6 shown below (fluorescence peak wavelength in dilute solution of dichloromethane: 686 nm) was used as the dopant material. From this device, red light emission with a luminous efficiency of 0.5 m / W was obtained. When this light emitting device was DC-driven at 40 mA / cm ² , the luminance half time was 950 hours.

Example 13
As an electron transport material, instead of laminating E-1 shown above to a thickness of 35 nm, E-7 shown below as a first electron transport material is laminated to a thickness of 25 nm, followed by a second electron transport material. As described in Example 2 , a light-emitting element was fabricated except that E-1 was laminated to a thickness of 10 nm. From this device, high-efficiency red light emission with a light emission efficiency of 5.2 lm / W was obtained. This light emitting device was galvanically driven at 40 mA / cm ² , and the luminance half 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 display devices, flat panel displays, backlights, lighting, interiors, signs, signboards, electrophotographic machines, and optical signal generators. .

Claims (4)

An element that has at least a light emitting layer between an anode and a cathode and emits light by electric energy. The light emitting layer of the element has a pyrene compound represented by the general formula (1) and a fluorescence peak wavelength of 500 nm or more and 680 nm or less And a fluorescent peak wavelength of 500 nm to 680 nm is a compound having a pyromethene skeleton represented by the general formula (2).

(R ^{1 to} R ¹⁵ may be the same as or different from each other, hydrogen, alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, aryl R ¹⁶ and R are selected from a ring structure formed between a thioether group, an aryl group, a heteroaryl group, an amino group, a silyl group, —P (═O) R ¹⁶ R ¹⁷ , and adjacent substituents. ¹⁷ is selected from an aryl group and a heteroaryl group, provided that n is 2, and R ¹ and R ⁶ are a benzofuran ring of a group represented by the general formula (3) in the general formula (1) or used in connection with the indole ring may be R ³ and R ⁸ are either the same or different, respectively, Ru hydrogen or an aryl group der .X oxygen atom, NR ¹⁸ - is ^{.R 18} selected from among hydrogen, an alkyl group, a cycloalkyl group, a heterocyclic group, an aryl group, ^{.R 18} selected from heteroaryl groups joined to form a ring with ^{R 15} May be .
R ^{19 to} R ²⁵ may be the same as or different from each other, and hydrogen, alkyl group, cycloalkyl group, heterocyclic group, alkenyl group, cycloalkenyl group, alkynyl group, alkoxy group, alkylthio group, aryl ether group, aryl thioether The ring structure is selected from a group, an aryl 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 aryl groups and heteroaryl groups. R ²⁶ and R ²⁷ may be the same or different and are selected from halogen, hydrogen, alkyl, aryl, and a heterocyclic group. Y is a carbon atom or a nitrogen atom. In the case of a nitrogen atom, R ²⁵ does not exist. ) X is Ri Oh oxygen atom, R ¹ and R ⁶ has the general formula (1) in the general formula (3) used in connection with the benzofuran ring of the group represented by claim 1 Symbol, wherein Rukoto The light-emitting element. 3. The light emitting device according to claim 1, wherein at least one of R ^{1 to} R ¹⁰ is an aryl group or a heteroaryl group. There is at least an electron transport layer between the light emitting layer and the cathode, and the electron transport layer contains a compound composed of a heteroaryl ring having electron-accepting nitrogen, and the compound composed of a heteroaryl ring is carbon, hydrogen, nitrogen, oxygen The light emitting device according to claim 1, wherein the light emitting device is composed of an element selected from silicon, silicon, and phosphorus.