KR101148859B1 - Luminescent element material and luminescent element - Google Patents

Abstract

[여기서, R¹～R⁴는 알킬기, 시클로알킬기, 알콕시기 또는 아릴에테르기이며, 각각 동일해도 달라도 좋다. R⁵ 및 R⁶은 할로겐, 수소 또는 알킬기이며, 각각 동일해도 달라도 좋다. R⁷은 아릴기, 헤테로아릴기 또는 알케닐기 중 어느 하나이며, 분자량이 200 이상인 것이다. M은 붕소, 베릴륨, 마그네슘, 알루미늄, 크롬, 철, 코발트, 니켈, 구리, 아연 및 백금으로 이루어지는 군으로부터 선택되는 적어도 1종이다. n은 0～4의 정수이다. m은 1～3의 정수이다. L은 할로겐, 수소, 알킬기, 아릴기 또는 헤테로아릴기로부터 선택되는 1가 또는 0가의 기이며, 분자 내의 1개 또는 2개의 원자를 통해서 M과 결합된다. n이 2～4인 경우, 각 L은 서로 같아도 달라도 좋다. m이 2 또는 3인 경우, 각 피로메텐 골격의 R¹～R⁷은 서로 같아도 달라도 좋다.]By using a light emitting element material having a pyrromethene skeleton represented by the general formula (1) and having a compound having a molecular weight of 450 or more, a green light emitting element having high luminous efficiency, long life and high color purity is provided.

[R <^1> -R <^4> is an alkyl group, a cycloalkyl group, an alkoxy group, or an aryl ether group here, and may be same or different, respectively. R <^5> and R <^6> is halogen, hydrogen, or an alkyl group, and may be same or different, respectively. R <^7> is either an aryl group, heteroaryl group, or alkenyl group, and molecular weight is 200 or more. M is at least one member selected from the group consisting of boron, beryllium, magnesium, aluminum, chromium, iron, cobalt, nickel, copper, zinc and platinum. n is an integer of 0-4. m is an integer of 1-3. L is a monovalent or zero-valent group selected from halogen, hydrogen, alkyl group, aryl group or heteroaryl group, and is bonded to M through one or two atoms in the molecule. When n is 2-4, each L may mutually be same or different. When m is 2 or 3, R ¹ to R ⁷ of each pyrromethene skeleton may be the same as or different from each other.]

Description

LUMINESCENT ELEMENT MATERIAL AND LUMINESCENT ELEMENT

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to light emitting devices that can be used in fields such as display devices, flat panel displays, backlights, lighting, interiors, signs, signs, electronic cameras, optical signal generators, etc. as devices for converting electrical energy into light.

BACKGROUND OF THE INVENTION In recent years, studies have been actively conducted on organic laminated thin film light emitting devices in which electrons injected from the cathode and holes injected from the anode emit light upon recombination in the organic phosphor sandwiched in the anode. This device is attracting attention as it is characterized by high luminance emission under thin, low driving voltage, and multicolor emission by selecting fluorescent materials. This research has been studied by many research institutes since Kodak's C. W. Tang et al. Showed that organic laminated thin film devices emit light with high brightness (see Non-Patent Document 1). A typical configuration of an organic multilayer thin film light emitting device presented by Kodak's research group is a hole-transporting diamine compound, 8-hydroxyquinoline aluminum as a light emitting layer, and Mg: Ag as a cathode, sequentially formed on an ITO glass substrate. Green light emission of 1000 cd / m 2 was possible at a driving voltage of. Although the present organic laminated thin film light emitting element changes the structure, such as forming an electron carrying layer other than the said element component, it basically follows the Kodak Corporation structure.

In the organic thin film light emitting device, various light emitting colors can be obtained by using various fluorescent materials in the light emitting layer. In particular, by using a combination of a host material and a dopant material in the light emitting layer, a light emitting device having three primary colors of high efficiency blue, green, and red can be obtained. A pigment having a high luminescence quantum yield is commonly used as a dopant, but, for example, a complex having a pyrromethene skeleton has high efficiency as a dopant having high luminous efficiency and small peak half width of the Stokes Shift and emission spectrum. It is a compound provided with the requirements required for obtaining, and it is known to show favorable element characteristic (refer patent document 1).

As a conventional pyrromethene compound and a good green compound, 1,3,5,7,8-pentamethyl-4,4-difluoro-4-bora-3a, 4a-diaza-s-indacene, The compound which has two or more pyrromethene frame | skeleton in a molecule | numerator, or the compound which introduce | transduced the condensed ring structure which has a bridge | crosslinking position in a pyrromethene frame | skeleton is known (refer patent document 2-3).

Japanese Patent Laid-Open No. 9-118880 Japanese Patent Publication No. 2002-134274 Japanese Patent Publication No. 2004-311030

 Appl. Phys. Lett. 51 (12) 21, p.913, 1987)

However, 1,3,5,7,8-pentamethyl-4,4-difluoro-4-bora-3a, 4a-diaza-s-indacene and the like have many compounds which sublime at low temperature, and the deposition rate is high. Is difficult to control, and there is a problem that the luminous efficiency is lowered due to aggregation at the time of deposition and contamination of the charge transport layer at the time of device fabrication. In addition, the compounds described in Patent Literatures 2 to 3 have high thermal sublimation temperatures but lack thermal stability, and thus have problems such as thermal decomposition at the time of vapor deposition, shift of the emission peak wavelength, and deterioration of color purity.

As mentioned above, although the pyrromethene compound showed favorable green light emission, it was very difficult for the light emitting element to express the light emission characteristic excellent in both luminous efficiency, color purity, and durability life.

Therefore, an object of the present invention is to solve the problems of the prior art and to stably provide a green light emitting device having high luminous efficiency, long life and high color purity.

That is, this invention is a light emitting element material which has a pyrromethene skeleton represented by General formula (1), and contains the compound whose molecular weight is 450 or more.

(Wherein R ¹ to R ⁴ are an alkyl group, a cycloalkyl group, an alkoxy group, or an arylether group, which may be the same or different, respectively. R ⁵ and R ⁶ may be halogen, hydrogen, or an alkyl group, and each may be the same or different.) R ⁷ is aryl At least one selected from the group consisting of boron, beryllium, magnesium, aluminum, chromium, iron, cobalt, nickel, copper, zinc and platinum. N is an integer from 0 to 4. m is an integer from 1 to 3. L is a monovalent or zero-valent group selected from halogen, hydrogen, alkyl, aryl or heteroaryl group, one in the molecule Or two atoms bonded to M. When n is 2 to 4, each L may be the same as or different from each other. When m is 2 or 3, R ¹ to R ⁷ of each pyrromethene skeleton may be the same or different. .)

(Effects of the Invention)

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

The light emitting element material of this invention is a compound which has a pyrromethene skeleton represented by General formula (1), and whose molecular weight is 450 or more.

R <^1> -R <^4> is an alkyl group, a cycloalkyl group, an alkoxy group, or an aryl ether group here, and may be same or different, respectively. R <^5> and R <^6> is halogen, hydrogen, or an alkyl group, and may be same or different, respectively. R <^7> is either an aryl group, heteroaryl group, or alkenyl group, and molecular weight is 200 or more.

Alkyl group among these substituents represents saturated aliphatic hydrocarbon groups, such as a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, and tert- butyl group, for example, even if it has a substituent You do not have to have it. There is no restriction | limiting in particular in the further substituent in the case of substitution, For example, an alkyl group, an aryl group, heteroaryl group, etc. are mentioned, This point is common also to the following description.

A cycloalkyl group shows saturated alicyclic hydrocarbon groups, such as a cyclopropyl group, a cyclohexyl group, a norbornyl group, and an adamantyl group, for example, and it does not need to have a substituent.

An alkoxy group shows the functional group which the aliphatic hydrocarbon group couple | bonded through ether bonds, such as a methoxy group, an ethoxy group, and a propoxy group, for example, and this aliphatic hydrocarbon group does not need to have a substituent.

An arylether group shows the functional group which the aromatic hydrocarbon group couple | bonded through the ether bond, such as a phenoxy group, for example, and the aromatic hydrocarbon group does not need to have a substituent.

Halogen refers to fluorine, chlorine, bromine and iodine.

The aryl group represents, for example, an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, a biphenyl group, a fluorenyl group, a phenanthryl group, a terphenyl group, an anthracenyl group and a pyrenyl group, or a group in which two or more of them are connected, which is substituted even if unsubstituted. It does not matter. Substituents which may have such an aryl group are alkyl group, cycloalkyl group, alkenyl group, alkynyl group, alkoxy group, arylether group, alkylthio group, halogen, cyano group, amino group, silyl group and boryl group. The alkylthio group is one in which the oxygen atom of the ether bond of the alkoxy group is substituted with sulfur atom. Even if the hydrocarbon group of an alkylthio group has a substituent, it is not necessary to have it. An amino group shows the functional group which has a bond to nitrogen atoms, such as a diphenylamino group, a phenylnaphthylamino group, and a dimethylamino group, for example, and it does not need to have a substituent. The silyl group represents, for example, a functional group having a bond to silicon atoms such as trimethylsilyl group, and this may or may not have a substituent. The boryl group represents, for example, a functional group having a bond to a boron atom, such as a bis (methyl) boryl group, which may or may not have a substituent.

A heteroaryl group is, for example, an aromatic cyclic structural group having an atom other than carbon, such as furanyl group, thienyl group, oxazolyl group, pyridyl group, quinolinyl group and carbazolyl group, or a group in which a plurality of these are linked or aromatic with these The hydrocarbon group is linked to the group, and this may be unsubstituted or substituted. The substituent which this heteroaryl group may have is the same as the substituent which the aryl group may have. Any part may be sufficient as the coupling | bonding position of a heteroaryl group, for example, in the case of a pyridyl group, any of 2-pyridyl group, 3-pyridyl group, or 4-pyridyl group may be sufficient.

An alkenyl group refers to an unsaturated aliphatic hydrocarbon group including a carbon-carbon double bond such as, for example, a vinyl group, an allyl group, and a butadienyl group, but here, an aliphatic hydrocarbon group including an unsaturated aliphatic hydrocarbon group and an aryl group and / or a heteroaryl group are also included. Concept. The unsaturated aliphatic hydrocarbon group may be unsubstituted or substituted, and the substituents which may have an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an arylthioether group, a halogen, a cyano group, an amino group, a silyl group, a boryl group, etc. to be.

Among the substituents, R ¹ to R ⁴ are preferably an alkyl group from the viewpoint of color purity, and a methyl group or t-butyl group is more preferable from the viewpoint of excellent thermal stability among the alkyl groups. In addition, methyl groups are particularly preferably used because of their ease of synthesis.

R ⁵ and R ⁶ are preferably an alkyl group or hydrogen from the viewpoint of thermal stability, and more preferably hydrogen in terms of easily obtaining green light emission with high color purity.

In the compound represented by the general formula (1), M is at least one selected from the group consisting of boron, beryllium, magnesium, aluminum, chromium, iron, cobalt, nickel, copper, zinc and platinum, and boron, Aluminum and zinc are preferable, and boron is especially preferable at the point which gives a sharp emission spectrum and high color purity light emission is obtained. L is a monovalent or zero-valent group selected from halogen, hydrogen, alkyl group, aryl group or heteroaryl group, and is bonded to M through one or two atoms in the molecule. Here, zero valence means the case where a pyridyl group coordinates with respect to M through a lone band, for example. Bonding with M through two atoms is the so-called chelate configuration.

When M is boron, L is preferably fluorine, fluorine-containing aryl group, fluorine-containing heteroaryl group, and fluorine-containing alkyl group, and more preferably fluorine in that higher fluorescence quantum yield is obtained. The fluorine-containing aryl group is aryl containing fluorine, and examples thereof include a fluorophenyl group, trifluoromethylphenyl group, pentafulurophenyl group, and the like. The fluorine-containing heteroaryl group is a heteroaryl group containing fluorine, and examples thereof include a fluoropyridyl group, trifluoromethylpyridyl group, and trifluoropyridyl group. A fluorine-containing alkyl group is an alkyl group containing fluorine, A trifluoromethyl group, a pentafluoroethyl group, etc. are mentioned. In addition, when M is other than boron, it is preferable that L is a chelate ligand.

m is an integer of 1-3, Preferably m = 1 when M is boron, m = 3 when M is aluminum, and m = 2 when M is zinc. n is an integer of 0-4, Preferably n = 2 when M is boron, n = 0 when M is aluminum, and n = 0 when M is zinc. When m is 2 or 3, R <^1> -R <^7> of each pyrromethene frame | skeleton may mutually be same or different. In addition, when n is 2-4, each L may mutually be same or different.

Since the compound represented by General formula (1) has a molecular weight of 450 or more, since sublimation temperature becomes high enough and contamination in a chamber can be prevented, it shows stable high brightness light emission, and high efficiency light emission is easy to be obtained. In particular, when R ⁷ is either an aryl group, a heteroaryl group, or an alkenyl group, and the molecular weight is 200 or more, a compound satisfying the above molecular weight can be easily obtained, and the light emission of the obtained compound can achieve good color purity. Become. In other words, when introducing a substituent such as an aryl group, heteroaryl group, or alkenyl group into the pyrrole ring to obtain a compound having a molecular weight of 450 or more, the color purity is lowered, but the compound represented by the general formula (1) is not lowered in color purity. Luminous efficiency and long life can be obtained. In addition, the molecular weight of R ⁷ is more preferably 300 or more in terms of giving a sufficiently high sublimation temperature to control the deposition rate more stably.

On the other hand, it is preferable that the molecular weight of the compound represented by General formula (1) is 1000 or less, More preferably, it is 800 or less from a viewpoint of depositing stably without thermal decomposition.

Further, R ⁷ is preferably selected from an aryl group or a heteroaryl group in view of imparting higher fluorescence quantum yield and more difficult to thermally decompose, and more preferably an aryl group. In addition, R ⁷ is preferably a substituent having a branched structure or a bulky substituent called 9-anthryl derivative. The branched structure here refers to a structure in which an aryl group or heteroaryl group directly bonded to the pyrromethene ring further has a plurality of substituents. Since R ⁷ is bulky, aggregation of molecules can be prevented, so that the light emission efficiency and lifespan are further improved.

The following general formula (2) is mentioned as a preferable example of a substituent which has a branched structure.

Here, R <^8> and R <^9> may be same or different and is chosen from an aryl group or heteroaryl group.

Description of an aryl group and a heteroaryl group is as above-mentioned. The aryl group is more preferably used in terms of obtaining a higher fluorescence quantum yield, and from the thermal stability, a phenyl group and a naphthyl group are particularly preferred examples.

Further, from the viewpoint of further preventing aggregation of molecules, at least one of R ⁸ or R ⁹ is more preferably substituted with an alkyl group, and particularly preferably at least one of R ⁸ or R ⁹ is an aryl group substituted with an alkyl group. Although description of an alkyl group is as above-mentioned, a methyl group and t-butyl group are mentioned as a especially preferable example from a thermal stability viewpoint. In addition, since the substitution position of an alkyl group exhibits the same effect in any position from a viewpoint of preventing the aggregation of a molecule | numerator more, it is not specifically limited. An example of the compound which has a pyrromethene skeleton represented by General formula (1) is shown below.

The compound represented by General formula (1) can be manufactured, for example by the method of Unexamined-Japanese-Patent No. 8-509471 and Unexamined-Japanese-Patent No. 2000-208262. That is, the target pyrromethene-based metal complex is obtained by reacting a pyrromethene compound and a metal salt in a base coexistence.

In addition, the synthesis of the pyrromethene-boron fluoride complex is described in J. Org. Chem., Vol. 64, No. 21, pp. 7813-7819 (1999), Angew. Chem., Int. Ed. Engl., Vol. 36, pp. 1333-1335 (1997). It can manufacture with reference to the method described in these. That is, the compound represented by following General formula (3) and the compound represented by General formula (4) are made to react in dichloromethane to form a pyrromethene frame | skeleton, and boron trifluoride diethyl ether is added in presence of an amine, A pyrromethene-boron fluoride complex is obtained.

In addition, about the compound represented by General formula (3), for example, brominated benzaldehyde and a boronic acid derivative are made to react by the conditions of a Suzuki coupling (Reference: Chem. Rev., vol. 95 (1995)), and R ^The thing which introduce | transduced various aryl groups and heteroaryl group into ⁷ is obtained.

Next, embodiment of the light emitting element in this invention is described in detail, for example. The light emitting device of the present invention has an anode, a cathode, and an organic layer existing between the anode and the cathode, the organic layer includes at least a light emitting layer, and the light emitting layer emits light by electrical energy.

In addition to the light emitting layer, the organic layer may include 1) a hole transport layer / light emitting layer, 2) a hole transport layer / light emitting layer / electron transport layer, 3) light emitting layer / electron transport layer, 4) hole transport layer / light emitting layer / hole blocking layer, 5) hole transport layer / light emitting layer / hole Any of the forms which mixed the barrier layer / electron carrying layer, 6) light emitting layer / hole blocking layer / electron carrying layer, and 7) or more combination materials in one layer may be sufficient. That is, as the element structure, one layer of the light emitting material alone or the layer containing the light emitting material and the hole transporting material or the electron transporting material may be formed in the same manner as in 7) in addition to the multilayer stack structure of 1) to 6). Each of the above layers may be either a single layer or a plurality of layers. When the hole transporting layer is formed of a plurality of layers, the layer on the side in contact with the electrode may be referred to as a hole injecting layer. In the following description, the hole injecting layer is included in the hole transporting layer. On the other hand, when an electron carrying layer consists of multiple layers, although the layer of the side which contact | connects an electrode may be called an electron injection layer, in the following description, an electron injection layer is contained in an electron carrying layer. In addition, the luminescent substance in this invention corresponds to any of the thing which emits light by itself and helps the emission, and points out the compound, layer, etc. which are involved in light emission.

In the present invention, the anode is not particularly limited as long as it is a material capable of efficiently injecting holes into the organic layer, but it is preferable to use a material having a relatively large work function. Conductive metal oxides such as tin oxide, indium oxide, tin indium oxide (ITO), or metals such as gold and silver chromium, inorganic conductive materials such as copper iodide and copper sulfide, conductive polymers such as polythiophene, polypyrrole, and polyaniline Although it does not specifically limit, When taking out light emission from an anode side, it is especially preferable to use ITO glass. The resistance of the anode is not limited as long as it can supply a sufficient current for light emission of the device, but is preferably low resistance from the viewpoint of power consumption of the device. For example, an ITO substrate of 300 Ω / square or less functions as an element electrode, but it is particularly preferable to use a low resistance article of 100 Ω / square or less. Although the thickness of an anode can be arbitrarily selected according to a resistance value, it is usually used between 100-300 nm. In addition, in order to maintain the mechanical strength of the light emitting element, it is preferable to form an anode on the substrate. Soda-lime glass, an alkali free glass, etc. are used for a board | substrate, and 0.5 mm or more is sufficient, since the thickness should just be thickness enough to maintain mechanical strength. In addition, as long as an anode functions stably, the board | substrate does not need to be glass, For example, you may form an anode on a plastic substrate. The film forming method of the anode is not particularly limited and is not particularly limited, such as an electron beam beam method, a sputtering method, or a chemical reaction method.

The cathode is not particularly limited as long as it is a material capable of efficiently injecting electrons into the organic material layer. However, platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, calcium, Magnesium, cesium, and alloys thereof. In order to improve the electron injection efficiency and improve the device characteristics, an alloy containing lithium, sodium, potassium, calcium, magnesium, cesium or these low work function metals is effective. However, these low work function metals are generally unstable in the atmosphere. For example, a method of using an electrode having high stability by doping a small amount of lithium or magnesium (1 nm or less in the film thickness indication of vacuum deposition) in an organic layer is preferable. Although it may be mentioned as an example, the inorganic salt such as lithium fluoride can also be used, and is not particularly limited thereto. In addition, metals such as platinum, gold, silver, copper, iron, tin, aluminum, indium, or alloys using these metals, and inorganic materials such as silica, titania, silicon nitride, polyvinyl alcohol, vinyl chloride, and hydrocarbons for electrode protection Laminating | stacking a system polymer etc. is mentioned as a preferable example. The production method of these electrodes is not particularly limited as long as it can conduct conduction such as resistance heating, electron beam beam, sputtering, ion plating, and coating.

The hole transporting layer is formed by laminating or mixing a hole transporting material alone or two or more kinds of materials, or a mixture of a hole transporting material and a polymer binder, and as a hole transporting material, N, N'-dinaphthyl-N, N'-di Triphenylamines such as phenyl-4,4'-diphenyl-1,1'-diamine, carbazoles such as bis (N-allylcarbazole), pyrazoline derivatives, stilbene compounds, hydrazone compounds, and phthalocyanine derivatives In the heterocyclic compounds represented by porphyrin derivatives and polymers, polycarbonates, styrene derivatives, polyvinylcarbazoles, polysilanes, etc. having the monomers in the side chains are preferable, but thin films required for device fabrication are formed to form holes from the anode. It will not specifically limit, if it is a compound which can be injected and can transport a hole.

In the case of the hole injection layer in contact with the electrode, an inorganic salt such as iron (III) chloride may be added to the hole transport material to form a hole injection layer. In addition, a metal oxide such as molybdenum oxide or vanadium oxide may be added to form a hole injection layer. Further, a hole injection layer may be formed by adding or laminating a compound having a strong acceptor such as a cyano group-substituted aromatic aza compound.

The light emitting layer may be either a single layer or a plurality of layers, a mixture of a host material and a dopant material, or may be either a host material alone. The host material and the dopant material may be one kind or a plurality of combinations, respectively. The dopant material may be contained in the whole host material, or may be included partially, or any may be sufficient as it. The dopant material may be laminated with the host material, or may be dispersed in the host material. When the amount of the dopant material is too large, concentration quenching occurs, so that the amount of the dopant material is preferably 10% by weight or less, more preferably 2% by weight or less, based on the total of the host material and the dopant material. In the doping method, the dopant material may be formed by the co-deposition method with the host material, or the host material and the dopant material may be mixed beforehand and deposited.

Although the light emitting element material of this invention may be used as a host material, it is used suitably as a dopant material from the point which is high in fluorescence quantum yield and small in the half value width of an emission spectrum. When the light emitting element material of the present invention is used as the dopant material, strong light emission is exhibited in the green region. Since the pyrromethene dopant emits light even in a very small amount, it is also possible to use a small amount of the compound by sandwiching the host material in a sandwich form. In this case, one layer or two or more layers may be laminated with the host material.

In addition, the dopant material added to the light emitting layer need not be limited to one of the above pyrromethene-based dopants, and may be used by mixing a plurality of pyromethene-based dopants, or mixing one or more types of known dopant materials with the pyromethene-based dopant. You may use it. In this case, desired light emission such as white light emission can be obtained by combining dopants which exhibit light emission in different wavelength regions. Specifically, rare earth complexes such as naphthalimide derivatives such as bis (diisopropylphenyl) perylenetetracarboxylic acid imide, perinone derivatives, and Eu complexes, and 4- (dicyanomethylene) -2 -Methyl-6- (p-dimethylaminostyryl) -4H-pyran, its flexible body, metal phthalocyanine derivatives such as magnesium phthalocyanine, deazaflavin derivatives, anthracene, pyrene, naphthacene, chrysene Compounds having a condensed polycyclic aromatic hydrocarbon such as, triphenylene, perylene and indene, derivatives thereof, furan, pyrrole, thiophene, benzothiophene, benzofuran, indole, dibenzothiophene, dibenzofuran, imidazopyridine Compounds having heteroaryl rings such as, pyrazine and thioxanthene, derivatives thereof, distyrylbenzene derivatives, aminostyryls such as 4,4'-bis (2- (4-diphenylaminophenyl) ethenyl) biphenyl Derivatives, diketopyrrolo [3,4-c] pyrrole derivatives, 2,3, Coumarin derivatives such as 5,6-1H, 4H-tetrahydro-9- (2'-benzothiazolyl) quinolidino [9,9a, 1-gh] coumarin, and N, N'-diphenyl-N, Aromatic amine derivatives such as N'-di (3-methylphenyl) -4,4'-diphenyl-1,1'-diamine and the like can coexist, but are not particularly limited thereto.

Although it does not specifically limit as a host material, Metal chelation oxynoid compound, Bissty, including the derivative which has condensation aromatics, such as anthracene and a pyrene, known as a light emitting body as a base skeleton, and tris (8-quinolinolato) aluminum previously, Bisstyryl derivatives, such as a rylanthracene derivative and a distyrylbenzene derivative, an oxadiazole derivative, an oxadiazole derivative, a pyrrolopyrrole derivative, a carbazole derivative, a polymer type polyphenylene vinylene derivative, a polyparaphenylene derivative, Polyfluorene derivatives, polyvinylcarbazole derivatives, polythiophene derivatives and the like can be used.

Especially, when the derivative | guide_body which uses a condensed aromatic hydrocarbon as a base skeleton is used as a host, since the effect of the high light emission efficiency which the compound which has a pyrromethene skeleton of this invention becomes more remarkable, it is preferable. Specifically, when a compound selected from an anthracene compound, a pyrene compound and a distyryl arylene derivative is used as a host material, it becomes more efficient and is preferable. Moreover, since it has high heat resistance and carrier transport ability, when an anthracene compound and a pyrene compound are used for a host, a high efficiency and long lifetime light emitting element is obtained, and therefore it is more preferable.

The electron transport layer needs to transport electrons from the cathode efficiently between the electrodes provided with the electric field, and is preferably formed of an electron transport material having high electron injection efficiency and efficiently transporting the injected electrons. For this purpose, it is required that the electron affinity is high, the electron mobility is high, the stability is excellent, and the impurity which becomes a trap is a substance which is hard to generate | occur | produce at the time of manufacture and use. Examples of the material satisfying these conditions include hydroxyazole complexes such as quinolinol derivative metal complexes represented by 8-hydroxyquinoline aluminum, hydroxyphenyloxazole complexes, perylene derivatives, perylene derivatives, naphthalene and anthracene, and the like. The compound which has a condensed aryl ring, its derivative (s), an oxadiazole derivative, a bisstyryl derivative, a phenanthroline derivative, an inoxide derivative, a benzimidazole derivative, a sirol derivative, a triazine derivative, etc. are mentioned.

Among these, the compound having a pyrromethene skeleton of the present invention has a strong electron acceptability, and in combination with an electron transport layer having excellent electron transport ability, more efficient and longer lifespan light emission is achieved, and thus the electron transport material is carbon, hydrogen, nitrogen, oxygen. It is preferable to use a compound composed of an element selected from silicon, phosphorus and phosphorus and having a heteroaryl ring structure containing an electron-accepting nitrogen.

Electron-accepting nitrogen refers to a nitrogen atom which forms a multiple bond with adjacent atoms. Since the nitrogen atom has a high electronegativity, the multiple bonds have electron accepting properties, have excellent electron transporting ability, and can be used for the electron transporting layer to reduce the driving voltage of the light emitting device. Therefore, the heteroaryl ring containing an electron accepting nitrogen has high electron affinity. Examples of the heteroaryl ring containing an electron-accepting nitrogen include pyridine ring, pyrazine ring, pyrimidine ring, quinoline ring, quinoxaline ring, naphthyridine ring, pyrimidpyrimidine ring, benzoquinoline ring, phenanthroline ring, An imidazole 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 phenanthroimidazole ring, etc. are mentioned.

As the compound having these heteroaryl ring structures, for example, benzimidazole derivatives, benzoxazole derivatives, benzthiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, pyrazine derivatives, phenanthroline derivatives And quinoxaline derivatives, quinoline derivatives, benzoquinoline derivatives, oligopyridine derivatives such as bipyridine and terpyridine, quinoxaline derivatives and naphthyridine derivatives and the like. Among them, imidazole derivatives such as tris (N-phenylbenzimidazol-2-yl) benzene, 1,3-bis [(4-tert-butylphenyl) 1,3,4-oxadiazolyl] phenylene and the like Triazole derivatives such as oxadiazole derivatives and N-naphthyl-2,5-diphenyl-1,3,4-triazole, 1,3-bis (1,10-phenanthroline-9-yl) Phenanthroline derivatives such as benzene, benzoquinoline derivatives such as 2,2'-bis (benzo [h] quinolin-2-yl) -9,9'-spirobifluorene, and 2,5-bis (6'- Bipyridine derivatives such as (2 ', 2 "-bipyridyl))-1,1-dimethyl-3,4-diphenylsilol, and 1,3-bis (4'-(2,2 ': 6' Terpyridine derivatives such as 2 " -terpyridinyl)) benzene and naphthyridine derivatives such as bis (1-naphthyl) -4- (1,8-naphthyridin-2-yl) phenylphosphine oxide It is used preferably at the point of.

Although these electron transport materials are used independently, you may use them by laminating | stacking or mixing with another electron transport material. Moreover, it is also possible to mix and use with metals, such as an alkali metal and alkaline-earth metal, or its metal complex. Although the ionization potential of an electron carrying layer is not specifically limited, Preferably it is 5.8 eV or more and 8.0 eV or less, More preferably, they are 6.0 eV or more and 7.5 eV or less.

The hole blocking layer is a layer for preventing the movement of holes from the anode without recombination with electrons from the cathode between the electrodes provided with an electric field, and inserting the layer depending on the type of material constituting each layer. In some cases, an increase in the recombination probability between holes and electrons can be expected to improve luminous efficiency. Therefore, as the hole blocking material, the highest occupied molecular orbital level is lower in energy than the hole transporting material, and it is difficult to produce an exciplex with the material forming the adjacent layer. Although a phenanthroline derivative, a triazole derivative, etc. can be mentioned specifically, it will not specifically limit, if it is a compound which can form the thin film required for element manufacture, and can effectively prevent the movement of the hole from an anode.

The above hole transporting layer, the light emitting layer, the electron transporting layer, and the hole blocking layer may be laminated or mixed with one or two or more kinds of materials, or dispersed in polycarbonate, polystyrene, poly (N-vinylcarbazole), polymethylmethacrylate, or the like as a polymer binder. It is also possible to use it.

The method for forming each of the layers forming the light emitting layer is not particularly limited, such as resistive heating deposition, electron beam deposition, sputtering, molecular lamination, coating, inkjet, printing, and laser organic thermal transfer. Electron beam deposition is preferred in terms of properties. Since the thickness of the layer is also based on the resistance of the substance responsible for light emission, the thickness is not limited, but is selected between 1 and 1000 nm.

The light emitting device of the present invention has a function capable of converting electrical energy into light. The electric energy mainly refers to a direct current, but it is also possible to use a pulse current or an alternating current. The current value and the voltage value are not particularly limited, but the maximum luminance should be obtained with as low energy as possible considering the power consumption and life of the device.

The light emitting element of this invention is used suitably as a display which displays, for example by a matrix and / or a segment system. The matrix method in the present invention means that pixels for display are arranged in a lattice form, and a character or an image is displayed by a set of pixels. In the segment system in the present invention, a pattern is formed to display predetermined information, and the predetermined area is made to emit light. The matrix display and the segment display may coexist in the same panel.

Example

Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited by these Examples.

¹ H-NMR measurement was carried out with chloroform using a superconducting FT-NMR EX-270 (Nihon Den time (Ltd.)), solution.

Synthesis Example 1

Synthesis of Compound [1]

3,5-dibromobenzaldehyde (3.0 g), 4-t-butylphenylboronic acid (5.3 g), tetrakis (triphenylphosphine) palladium (0) (0.4 g), potassium carbonate (2.0 g) Nitrogen substitution was carried in the flask. Degassed toluene (30 mL) and degassed water (10 mL) were added and refluxed for 4 hours. The reaction solution was cooled to room temperature, and the organic layer was separated, and then washed with saturated brine. The organic layer was dried over magnesium sulfate, and the solvent was distilled off after filtration. The obtained reaction product was purified by silica gel chromatography to obtain 3,5-bis (p-t-butylphenyl) benzaldehyde (3.5 g) as a white solid.

3,5-bis (4-t-butylphenyl) benzaldehyde (1.5 g) and 2,4-dimethylpyrrole (0.7 g) were added to the reaction solution, and dehydrated dichloromethane (200 mL) and trifluoroacetic acid (1 drop). Was added and stirred for 4 hours. A dehydrated dichloromethane solution of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (0.85 g) was added, followed by further stirring for 1 hour. After completion of the reaction, boron trifluoride diethyl ether complex (7.0 mL) and diisopropylethylamine (7.0 mL) were added and stirred for 4 hours, followed by addition and stirring of water (100 mL), and the organic layer was separated. The organic layer was dried over magnesium sulfate, and the solvent was distilled off after filtration. The obtained reaction product was refine | purified by silica gel chromatography, and 0.4g of compound [1] shown below was obtained (yield 18%).

¹ H-NMR (CDCl ₃ , ppm): 7.95 (s, 1H), 7.63-7.48 (m, 10H), 6.00 (s, 2H), 2.58 (s, 6H), 1.50 (s, 6H), 1.37 ( s, 18 H).

Example 1

The light emitting element using the compound [1] was produced as follows. The glass substrate (Asahi Glass Co., Ltd. product, 15 ohms / square, an electron beam vapor deposition product) which deposited 150 nm of ITO transparent conductive films was cut | disconnected and etched at 30x40 mm. The obtained board | substrate was ultrasonically cleaned with acetone and "Semicoclean (registered trademark) 56" (made by Furuchi Kagaku Co., Ltd.) for 15 minutes, and wash | cleaned with ultrapure water. Subsequently, ultrasonic cleaning was performed for 15 minutes with isopropyl alcohol, followed by drying for 15 minutes in hot methanol. This board | substrate was UV-ozone-processed for 1 hour, just before manufacturing an element, was installed in the vacuum evaporation apparatus, and it exhausted until the vacuum degree in an apparatus became 5 * 10 <^-5> Pa or less. By resistive heating, first, 10 nm of copper phthalocyanine was deposited as a hole injection material, and 50 nm of 4,4'-bis (N- (1-naphthyl) -N-phenylamino) biphenyl was deposited as a hole transport material. Next, tris (8-quinolinorate) aluminum (Alq ₃ ) was used as a luminescent material, and compound [1] as a dopant material was deposited at a thickness of 40 nm so that the dope concentration was 1% by weight. Next, 1,3-bis (1,10-phenanthrolin-2-yl) benzene was laminated to a thickness of 25 nm as an electron transporting material. Next, after doping lithium to a 0.5 nm organic layer, aluminum was deposited by 1 micrometer and it was set as the cathode, and the element of 5x5 mm angle was produced. The film thickness here is a crystal oscillation film thickness monitor display value. From this light emitting device, there was obtained (0.24, 0.67) and a high efficiency and high color purity green light emission (EL peak wavelength 524 nm) of luminous efficiency 10 cd / A in CIE chromaticity coordinates. When the light emitting element was continuously driven at a direct current of 5 mA / cm 2, the luminance half life time was 3700 hours.

Example 2

A light emitting device was constructed in exactly the same way as in Example 1 except that the compound shown below was used as the host material. From this light emitting device, high-efficiency green light emission (EL peak wavelength 524 nm) with a light emission efficiency of 12 cd / A was obtained at C.I.E.chromatic coordinates (0.22, 0.72). When the light emitting element was continuously driven at a direct current of 5 mA / cm 2, the luminance half life time was 3900 hours.

Comparative Example 1

A light emitting device was constructed in exactly the same way as in Example 1 except that Compound [2] shown below was used as a dopant. From this light emitting device, high color purity green light emission of (0.24, 0.68) was obtained in the C.I.E.chromatic coordinates, but the light emission efficiency was low at 3cd / A (EL peak wavelength of 520 nm). When the light emitting element was continuously driven at a direct current of 5 mA / cm 2, the luminance half life time was 300 hours.

Comparative Example 2

A light emitting device was constructed in exactly the same way as in Example 1 except that Compound [3] shown below was used as a dopant. From this light emitting device, a high color purity green light emission of (0.25, 0.67) was obtained in the C.I.E.chromatic coordinates, but the light emission efficiency was low at 4 cd / A (EL peak wavelength 523 nm). When the light emitting element was continuously driven at a direct current of 5 mA / cm 2, the luminance half life time was 330 hours.

Examples 3-6

A light emitting device was constructed in exactly the same way as in Example 1 except that the compound shown below was used as the host material. Table 1 shows the C.I.E.chromatic coordinates, luminous efficiency, and luminance half-life time obtained by continuous driving at a direct current of 5 mA / cm 2 obtained from these light emitting elements.

Examples 7-11

Other than the H-6, using the compound shown below, or Alq ₃ as the electron transporting layer as a host material in the same way as in Example 1 to prepare a light-emitting device. Table 2 shows the CIE chromaticity coordinates, the luminous efficiency, and the luminance half time of continuous driving at a direct current of 5 mA / cm 2 obtained from these light emitting elements.

Examples 12-18, Comparative Example 3

A light emitting device was constructed in exactly the same way as in Example 1 except that H-5 was used as the host material and the compound shown below as the dopant material. Table 3 shows the C.I.E. chromaticity coordinates, luminous efficiency, and luminance half-life time when continuously driven at a direct current of 5 mA / cm 2 obtained from these light emitting elements.

(Industrial availability)

The light emitting element material of this invention can be used for a light emitting element etc., and can provide the light emitting element material excellent in thin film stability. The light emitting device of the present invention can be used in fields such as display devices, flat panel displays, backlights, lighting, interiors, signs, signs, electronic cameras and optical signal generators.

Claims (9)

It has a pyrromethene skeleton represented by General formula (1), and has a compound whose molecular weight is 450 or more, The light emitting element material characterized by the above-mentioned.

[Here, R <^1> -R <^4> is an alkyl group and may be same or different, respectively. R ⁵ and R ⁶ are hydrogen. R ⁷ is either an aryl group or a heteroaryl group, and has a molecular weight of 200 or more. M is boron. n is 2. m is 1. L is fluorine] The method of claim 1,
R <^7> of the said General formula (1) is represented by following General formula (2), The light emitting element material characterized by the above-mentioned.

[Wherein R ⁸ and R ⁹ may be the same or different and are selected from an aryl group or a heteroaryl group] The method of claim 2,
R ⁸ and R ⁹ are aryl groups. The method of claim 3, wherein
At least one of said R <^8> and R <^9> is an aryl group substituted by the alkyl group, The light emitting element material characterized by the above-mentioned. The method according to claim 3 or 4,
The molecular weight of the structure represented by the said General formula (2) is 300 or more, The light emitting element material characterized by the above-mentioned. A device in which a light emitting material exists between an anode and a cathode, and emits light by electrical energy, the device comprising a light emitting device material according to any one of claims 1 to 4. The method according to claim 6,
A light emitting element wherein the light emitting layer has a host material and a dopant material, and the compound represented by the general formula (1) is a dopant material. A device in which a light emitting material is present between an anode and a cathode and emits light by electric energy, the device comprising a light emitting device material according to claim 5. The method of claim 8,
A light emitting element wherein the light emitting layer has a host material and a dopant material, and the compound represented by the general formula (1) is a dopant material.