JP2007119481A - Compound for forming organic layer of organic electric field light-emitting element, and organic electric field light-emitting element by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compound for forming an organic layer of an organic electric field light-emitting element, consisting of a phenoxazone-based compound useful as a new red color-based fluorescent pigment having a high brightness of the emitted light and excellent in characteristics such as solidity, light-emitting efficiency, etc., and an organic electric field light-emitting element by using the same. <P>SOLUTION: This compound for forming the organic layer of the organic electric field light-emitting element is provided by consisting of the phenoxazone-based compound expressed by general formula (II) [wherein, a ring Z is a heterocyclic aromatic 6-membered ring which may have a substituent and contains one nitrogen atom], and the organic electric field light-emitting element of which organic layer contains the phenoxazone-based compound, having the organic layer between opposing anode and cathode is also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a compound for forming an organic layer of an organic electroluminescent element, which is composed of a phenoxazone compound useful as a red fluorescent dye, and an organic electroluminescent element using the same.

Conventionally, fluorescent pigments have been used for coloring various materials such as resins, dyes, and inks. Recently, applications in the field of electronic devices such as thin-film light-emitting elements have been developed using the fluorescence efficiency. Yes. As fluorescent dyes, dyes having various structures and luminescent colors are known. However, there are few compounds that emit light with high brightness in red and are particularly excellent in fastness, particularly required in the field of electronic equipment.
Patent Document 1 relating to an organic electroluminescent device (organic EL device) using a phenoxazone compound has an example in which red light emission is obtained using a phenoxazone compound having a julolidine structure represented by the following formula (D-1). It is disclosed.

However, an organic EL device using such a compound has low light emission luminance and light emission efficiency as will be apparent from Comparative Examples described later, and is not satisfactory as a dye for the organic EL device.
Japanese Patent Laid-Open No. 7-21457

In view of such circumstances, with respect to fluorescent dye compounds, the development of new dyes is constantly required in order to further expand the diversity, functionality, and the like.
The present invention relates to a compound for forming an organic layer of an organic electroluminescence device, comprising a phenoxazone compound useful as a novel red fluorescent dye having high emission luminance, fastness, and excellent characteristics such as light emission efficiency, and the like. The object is to provide an organic electroluminescent device.

As a result of extensive studies, the present inventors have found that a novel phenoxazone compound further having a heteroaromatic 6-membered ring containing one nitrogen atom is a red fluorescent dye having excellent performance. Achieved.
That is, the gist of the present invention resides in a compound for forming an organic layer of an organic electroluminescence device, characterized by comprising a phenoxazone compound represented by the following general formula (II).

(In the formula, ring Z represents a heteroaromatic 6-membered ring containing one nitrogen atom which may have a substituent, R ₁ and R ₂ are an alkyl group which may be substituted, Represents an optionally substituted phenyl group or an optionally substituted acyl group, and R _{3 to} R ₆ are each independently hydrogen, a halogen atom, a cyano group, a nitro group, an optionally substituted alkyl group, Represents an optionally substituted phenyl group, an optionally substituted alkoxy group, an optionally substituted amino group, an optionally substituted alkoxycarbonyl group, or an optionally substituted acyl group, and R ₁ and R ₂ may form the same ring, or R ₃ and R ₄ , R ₄ and R ₁ , or R ₂ and R ₅ may combine to form a ring.)

  The gist of the present invention also resides in an organic electroluminescent device characterized by having an organic layer between an anode and a cathode facing each other, and the organic layer contains the phenoxazone-based compound.

  The phenoxazone compound of the present invention is a novel red fluorescent dye compound having high emission brightness and good fastness, and the organic electroluminescent device obtained by the present invention is a specific phenoxazone compound (of the present invention). By including the dye, the light emission starting voltage, the light emission luminance, the light emission efficiency, etc. are superior in performance to the element containing a conventionally known phenoxazone compound.

  Hereinafter, the present invention will be described in detail. The compound of the present invention has a structure represented by the following general formula (I), wherein Z is a heteroaromatic 6-membered ring containing one nitrogen atom, and among the general formula (I) Particularly preferred is a compound of the following general formula (II).

(In the formula, rings A and B may further have a substituent, and ring Z may have a substituent, and represents a heteroaromatic 6-membered ring containing one nitrogen atom)

(In the formula, ring Z represents a heteroaromatic 6-membered ring containing one nitrogen atom which may have a substituent, R ₁ and R ₂ are an alkyl group which may be substituted, Represents an optionally substituted phenyl group or an optionally substituted acyl group, and R _{3 to} R ₆ are each independently hydrogen, a halogen atom, a cyano group, a nitro group, an optionally substituted alkyl group, Represents an optionally substituted phenyl group, an optionally substituted alkoxy group, an optionally substituted amino group, an optionally substituted alkoxycarbonyl group, or an optionally substituted acyl group, and R ₁ and R ₂ may form the same ring, or R ₃ and R ₄ , R ₄ and R ₁ , or R ₂ and R ₅ may combine to form a ring.)
“R ₁ and R ₂ form the same ring” means that R ₁ and R ₂ combine to form a ring.

In the general formula (II), when R ₁ to R ₆ represent an alkyl group, for example, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl A linear or branched alkyl group having about 1 to 8 carbon atoms, preferably 1 to 3 carbon atoms, such as a group, t-butyl group, n-pentyl group, and 2-ethylhexyl group. These alkyl groups may be substituted, and examples of the substituent include a hydroxy group, an aryl group, an alkoxy group, an aralkyloxy group, an acyloxy group, a heterocyclic group, and an aryloxy group. The total number of carbon atoms is preferably 1 to 20, particularly 1 to 8.

When R ₁ to R ₆ represent a substituted phenyl group, examples of the substituent include an alkyl group, a hydroxy group, and an alkoxy group, and the substituted phenyl group preferably has a total carbon number of 1 to 20, particularly 1 to 8.
When R ₁ to R ₆ represent a substituted amino group, examples of the substituent include an alkyl group, a hydroxy group, an alkoxy group, an aryl group, and the like. The total number of carbon atoms of the substituted amino group is 1 to 20, particularly 1 to 8. Is preferred.
The same applies to the substituent and the total number of carbon atoms when R ₁ to R ₆ represent a substituted alkoxycarbonyl group or a substituted acyl group.
R ₁ to R ₆ are preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. R ₃ to R ₆ are more preferably a hydrogen atom, and R ₁ and R ₂ are alkyl groups, particularly an alkyl group having 1 to 3 carbon atoms, or R ₁ and R ₂ are bonded to R ₄ and R ₅ , respectively. Thus, a compound forming a ring is preferably used.

  Among the general formula (II), a compound represented by the following general formula (III) is particularly preferable.

In the formula (III), R ₇ is a hydrogen atom or a methyl group, and a methyl group is particularly preferable.
In the formula (III), R ₃ and R ₆ are preferably hydrogen atoms.
In the general formula (I) ~ (III), Examples of the substituent substituent which be substituted in the pyridine ring for ring Z, may be mentioned those similar to the substituents of R ₁ to R ₆ described above, the ring Z is preferably unsubstituted. Further, the position of the nitrogen atom in the ring Z is not particularly limited. Those having a nitrogen atom at the 6-position, such as 1 to 5, are particularly preferable.
Representative examples of such compounds of the present invention are shown in Table 1 below, but the compounds of the present invention are not limited thereto.

  The compound of the present invention represented by the general formula (II) can be produced, for example, according to the following formula.

(In the formula, ring Z is the same as Z in formula (I), and R ₁ and R ₂ are an optionally substituted alkyl group, an optionally substituted phenyl group, or a substituted group. It represents an acyl group which may, R ₃ to R ₆ are each independently hydrogen, a halogen atom, a cyano group, a nitro group, an optionally substituted alkyl group, a phenyl group which may be substituted, substituted Represents an alkoxy group which may be substituted, an amino group which may be substituted, an alkoxycarbonyl group which may be substituted, or an acyl group which may be substituted, and R ₁ and R ₂ form the same ring. R ₃ and R ₄ , R ₄ and R ₁ , or R ₂ and R ₅ may be bonded to each other to form a ring.)

A compound of the general formula (II) is obtained by reacting a nitrosophenol derivative represented by the formula (IV) or a hydrochloride thereof with a quinolinol represented by the formula (V).
The quinolinol represented by the formula (V) may be any one of the 5-position, 6-position, 7-position and 8-position of the nitrogen in the ring Z, but it is produced from the 6-position. The phenoxazone compounds of the general formulas (I) to (III) are particularly useful as dyes.
The reaction is usually carried out in an inert solvent. Examples of the inert solvent used include N, N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, chlorobenzene, dichlorobenzene, chlorobenzene, trichlorobenzene, nitrobenzene, toluene, xylene, methyl cellosolve, ethyl cellosolve, and water. Among these, N, N-dimethylformamide and N-methylpyrrolidone are preferable. The amount of the solvent to be used is usually 5 to 50 times by weight, preferably about 10 to 20 times by weight, relative to the above compound (IV).
The reaction temperature is in the range of 50 ° C to 300 ° C, preferably 100 ° C to 200 ° C, and the reaction time is about 0.5 to 48 hours.

After completion of the reaction, the reaction solution is cooled, and the precipitated crystals are filtered, washed with methanol or water and dried to obtain the desired product. In addition, in the case where crystallization does not occur even after cooling, the reaction solution is discharged into methanol or water, the precipitated crystals are filtered, washed with methanol or water and dried to obtain the desired product. If it does not precipitate even when released into methanol or water, it can be extracted with ethyl acetate, dichloromethane, etc., washed, dried and concentrated. The product may be purified by recrystallization or column chromatography as necessary. In this case, chlorobenzene, dichlorobenzene, toluene, ethyl acetate, chloroform, methylene chloride, n-hexane and the like are suitable as the purification solvent.
The phenoxazone compound of the present invention thus produced is preferably used as a water-insoluble dye. In addition to coloring of various resins, paints, inks, and dyeing of fibers, dye laser, organic E (organic electric field) Suitable for dyes such as light-emitting elements, fluorescent labeling reagents, fluorescent collectors, fluorescent sensors, scintillators, optical fiber amplifiers, etc., especially as red fluorescent dyes used for resin coloring or organic EL elements Very useful.

Below, the organic electroluminescent element using the pigment | dye which consists of a compound shown by general formula (I) is demonstrated, referring drawings.
The organic electroluminescent element of the present invention has an organic layer between an anode and a cathode facing each other, and the organic layer contains a dye composed of the compound of the general formula (I).
FIG. 1 is a schematic cross-sectional view showing a basic embodiment of an organic electroluminescence device of the present invention. 1 is a substrate, 2 is an anode, 4 is a hole transport layer, 5 is an electron transport layer, 7 Represents each cathode.

The “organic layer” in the present invention means a layer substantially consisting of an organic substance located between the anode and the cathode, and these layers are inorganic substances within a range not impairing the performance of the organic electroluminescent device of the present invention. May be included. Specifically, for example, the hole transport layer 4 and the electron transport layer 5 in the element having the structure shown in FIG. 1 correspond to the “organic layer”.
The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film, a sheet, or the like is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, or polysulfone is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too low, the organic electroluminescence device may be deteriorated by the outside air passing through the substrate, which is not preferable. For this reason, a method of providing a gas barrier property by providing a dense silicon oxide film or the like on one side or both sides of the synthetic resin substrate is also a preferable method.

  An anode 2 is provided on the substrate 1, and the anode 2 plays a role of hole injection into the hole transport layer 4. This anode is usually a metal such as aluminum, gold, silver, nickel, palladium, platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide, carbon black, or A conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline is used.

In general, the anode 2 is often formed by sputtering, vacuum deposition, or the like. Further, in the case of metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powders, they are dispersed in an appropriate binder resin solution and placed on the substrate 1. It is also possible to form the anode 2 by applying to. Further, in the case of a conductive polymer, a thin film can be directly formed on the substrate 1 by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett. 60, 2711, 1992). The anode 2 can be formed by laminating two or more different materials. The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness is usually 5 to 1000 nm, preferably 10 to 10%. It is about 500 nm. If it may be opaque, the anode 2 may be approximately the same as the thickness of the substrate 1. Furthermore, it is also possible to laminate different conductive materials on the anode 2 described above.
A hole transport layer 4 is provided on the anode 2. The hole transport material used for the hole transport layer 4 needs to have a high hole injection efficiency from the anode and be able to efficiently transport the injected holes. For this purpose, the ionization potential is small, the transparency to visible light is high, the hole mobility is high, the stability is high, and impurities that become traps are less likely to be generated during manufacturing and use. Required. In addition to the above general requirements, when the application for in-vehicle display is considered, the element is further required to have heat resistance. Therefore, a material having a Tg value of 70 ° C. or higher is desirable.

  As such a hole transport material, for example, an aromatic diamine compound in which a tertiary aromatic amine unit such as 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane is linked (Japanese Patent Laid-Open No. 59-86). No. 194393), including two or more tertiary amines represented by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl, and two or more condensed aromatic rings are nitrogen atoms Aromatic amines substituted with the above (Japanese Patent Laid-Open No. 5-234681), triphenylbenzene derivatives and aromatic triamines having a starburst structure (US Pat. No. 4,923,774), N, N′-diphenyl-N , N′-bis (3-methylphenyl) biphenyl-4,4′-diamine and the like (US Pat. No. 4,764,625), α, α, α ′, α′-tetramethyl-α , α'-bis (4-di-p-tolylaminophenyl) -p-xylene (JP-A-3-2699084), sterically asymmetric triphenylamine derivative as a whole molecule (JP-A-4-129271) , A compound in which a plurality of aromatic diamino groups are substituted on a pyrenyl group (Japanese Patent Laid-Open No. 4-175395), an aromatic diamine in which a tertiary aromatic amine unit is linked with an ethylene group (Japanese Patent Laid-Open No. 4-264189), styryl Aromatic diamines having a structure (Japanese Patent Laid-Open No. 4-290851), those obtained by connecting aromatic tertiary amine units with a thiophene group (Japanese Patent Laid-Open No. 4-304466), starburst aromatic triamines (Japanese Patent Laid-Open 308688), a benzylphenyl compound (Japanese Patent Laid-Open No. 4-364153), and a tertiary amine linked by a fluorene group (JP-A-5-25473), triamine compounds (JP-A-5-239455), bisdipyridylaminobiphenyl (JP-A-5-320634), N, N, N-triphenylamine derivatives (special Kaihei 6-1972), aromatic diamines having a phenoxazine structure (JP-A-7-138562), diaminophenylphenanthridine derivatives (JP-A-7-252474), hydrazone compounds (JP-A-2-311591). No. 4), silazane compounds (US Pat. No. 4,950,950), silanamine derivatives (JP-A-6-49079), phosphamine derivatives (JP-A-6-25659), quinacridone compounds, and the like. These compounds may be used alone or in combination as necessary.

  In addition to the above compounds, as the material for the hole transport layer 4, polyvinyl carbazole and polysilane (Appl. Phys. Lett., 59, 2760, 1991), polyphosphazene (Japanese Patent Laid-Open No. 5-3109949), Polyamide (JP-A-5-310949), polyvinyltriphenylamine (JP-A-7-53953), a polymer having a triphenylamine skeleton (JP-A-4-133055), and a triphenylamine unit as a methylene group Polymers linked by the same method (Synthetic Metals, 55-57, 4163, 1993), polymethacrylate containing aromatic amine (J. Polym. Sci., Polym. Chem. Ed., 21, 969) , 1983).

The hole transport layer 4 is formed by laminating the above hole transport material on the anode 2 by a coating method or a vacuum deposition method.
In the case of the coating method, one or more hole transport materials and, if necessary, additives such as a binder resin and a coating property improving agent that do not trap holes are added and dissolved to prepare a coating solution. Then, it is applied on the anode 2 by a method such as spin coating, and dried to form the hole transport layer 4. Examples of the binder resin include polycarbonate, polyarylate, and polyester. When the binder resin is added in a large amount, the hole mobility is lowered.

In the case of the vacuum evaporation method, the hole transport material is put in a crucible installed in a vacuum vessel, the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with a suitable vacuum pump, and then the crucible is heated, The hole transport material is evaporated and a hole transport layer 4 is formed on the anode 2 on the substrate 1 placed facing the crucible.
The film thickness of the hole transport layer 4 is usually 10 to 300 nm, preferably 30 to 100 nm. In order to uniformly form such a thin film, a vacuum deposition method is generally used. An electron transport layer 5 is provided on the hole transport layer 4. As an electron transport material used for the electron transport layer 5, it is necessary that the electron injection efficiency from the cathode 7 is high and the injected electrons can be efficiently transported toward the hole transport layer 4. For this purpose, it is required that the material has a high electron affinity, a high electron mobility, and a material that is excellent in stability and hardly generates impurities that become traps at the time of manufacture or use.

Materials satisfying such conditions include aromatic compounds such as tetraphenylbutadiene (Japanese Patent Laid-Open No. 57-51781) and metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393). Metal complexes of 10-hydroxybenzo [h] quinoline (JP-A-6-322362), mixed ligand aluminum chelate complexes (JP-A-5-198377, JP-A-5-198378, JP-A-5-1993) No. 214332, JP-A-6-172751), cyclopentadiene derivative (JP-A-2-289675), perinone derivative (JP-A-2-289676), oxadiazole derivative (JP-A-2-216791) ), Bisstyrylbenzene derivatives (JP-A-1-245087, 2- 22484), perylene derivatives (JP-A-2-189890, JP-A-3-791), coumarin compounds (JP-A-2-191694, JP-A-3-792), rare earth complexes (JP-A-1- 256584), distyrylpyrazine derivatives (JP-A-2-252793), p-phenylene compounds (JP-A-3-33183), thiadiazolopyridine derivatives (JP-A-3-37292), pyrrolopyridine. Derivatives (JP-A-3-37293), naphthyridine derivatives (JP-A-3-203982), silole derivatives (The Chemical Society of Japan 70th Spring Annual Meeting, 2D10 02 and 2D1 03, 1996) and the like.
The film thickness of the electron transport layer 5 is usually 10 to 200 nm, preferably 30 to 100 nm.
The electron transport layer can also be formed by the same method as the hole transport layer, but a vacuum deposition method is usually used.

The compound represented by the general formula (I) is doped into the hole transport layer 4 and / or the electron transport layer 5 to emit light. For example, when the electron transport layer 5 is doped, the above-described electron transport material serves as a host material, and when the hole transport layer 4 is doped, the above-described aromatic amine compound, hydrazone compound, or the like is used. The hole transport material serves as the host material.
The region doped with the phenoxazone derivative represented by the general formula (I) may be the whole layer or a part of the hole transport layer 4 and / or the electron transport layer 5. Even if it is doped uniformly in the thickness direction, the concentration may be appropriate in the thickness direction. For example, the electron transport layer 5 may be doped only in the vicinity of the interface with the hole transport layer 4, or conversely, in the vicinity of the cathode interface. The doped amount of the compound represented by the general formula (I) is preferably 10 ⁻³ to 10% by weight with respect to the host material.

The phenoxazone derivative represented by the general formula (I) exhibits strong fluorescence in a solution state, and when the host material is doped, the light emission efficiency of the device is improved. In particular, the phenoxazone derivative is preferable because visible light having a wavelength longer than 600 nm can be efficiently obtained when the host material is doped.
The doping of the phenoxazone derivative represented by the general formula (I) into the electron transport layer 5 and / or the hole transport layer 4 is performed by a coating method or a vacuum deposition method in accordance with a method of forming a host layer. Performed during layer formation.

  In the case of a coating method, for example, an electron transport material, a phenoxazone derivative represented by the above general formula (I), and if necessary, a binder resin that does not serve as an electron trap or light emission quencher, or a leveling agent is improved. A coating solution in which an additive such as an agent is added and dissolved is prepared, applied onto the hole transport layer 4 by a method such as spin coating, and dried to form the electron transport layer 5. Examples of the binder resin include polycarbonate, polyarylate, and polyester. When the amount of the binder resin added is large, the electron mobility is lowered.

In the case of the vacuum vapor deposition method, for example, the electron transport material is put in a crucible installed in a vacuum vessel, the phenoxazone derivative represented by the general formula (I) is put in another crucible, and the inside of the vacuum vessel is appropriately placed. After evacuating to about 10 ⁻⁶ Torr with a vacuum pump, each crucible is heated and evaporated simultaneously to form a layer on the substrate placed facing the crucible. As another method, a mixture of the above materials in a predetermined ratio may be evaporated using the same crucible.
The same applies when doping the hole transport layer 4.

The cathode 7 serves to inject electrons into the electron transport layer 5. The material used for the cathode 7 can be the material used for the anode 2, but a metal having a low work function is preferable for efficient electron injection, such as tin, magnesium, indium, calcium, A suitable metal such as aluminum or silver or an alloy thereof is used. The film thickness of the cathode 7 is usually the same as that of the anode 2.
In addition, for the purpose of protecting the cathode made of a low work function metal, when a metal layer having a high work function and stable to the atmosphere, such as aluminum, silver, nickel, chromium, gold, platinum, is further laminated thereon, This is preferable because the stability of the element is increased.

Further, in order to improve the contact between the cathode 7 and the adjacent organic layer (for example, the electron transport layer 5 and the electron injection layer 6 described later), a field cathode surface layer may be provided between them. Examples of the compound used in the cathode interface layer include aromatic diamine compounds (JP-A-6-267658), quinacridone compounds (JP-A-6-330031), naphthacene derivatives (JP-A-6-330032), and organic compounds. Silicon compounds (JP-A-6-325871), organophosphorus compounds (JP-A-5-325872), compounds having an N-phenylcarbazole skeleton (JP-A-8-60144), N-vinylcarbazole polymers ( Examples thereof include a layer composed of JP-A-8-60145).
The thickness of the interface layer is usually 2 to 100 nm, preferably 5 to 30 nm.
Instead of providing the interface layer, a region containing 50% by weight or more of the material of the interface layer may be provided in the vicinity of the cathode interface of the electron transport layer and the electron injection layer.

1, the hole transport layer 4 has a function of receiving holes from the anode 2 (hole injection) and a function of transporting the received holes to the electron transport layer 5 (hole transport). The electron transport layer 5 also functions to carry electrons received from the cathode 7 to the hole transport layer 4 (electron transport).
However, in order to further improve the light emission characteristics and driving stability of the device of the present invention, an electron injection layer 6 is provided between the electron transport layer 5 and the cathode 7 as shown in FIG. As shown, an anode buffer layer 3 is provided between the anode 2 and the hole transport layer 4, and a structure in which the layers are divided for each function, that is, a function-separated element can be obtained.

As shown in FIGS. 2 and 3, by providing the electron injection layer 6 between the electron transport layer 5 and the cathode 7, it is possible to further improve the light emission efficiency of the device. The material used for the electron injection layer 6 is required to be easy to inject electrons from the cathode and to have a larger electron transport capability. Examples of such electron transport materials include 8-hydroxyquinoline aluminum complexes and oxadiazole derivatives (Appl. Phys. Lett., 55, 1489, 1989, etc.) already mentioned as electron transport layer materials, System dispersed in a resin such as polymethyl methacrylate (PMMA) (Appl. Phys. Lett., 61, 2793, 1992), phenanthroline derivative (JP-A-5-331459), 2-t-butyl- 9,10-N, N′-dicyanoanthraquinone diimine (Phys. Stat. Sol. (A), 142, 489, 1994), n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n Type zinc selenide and the like.
The thickness of the electron injection layer 6 is usually 5 to 200 nm, preferably 10 to 100 nm.

Further, in order to improve the contact between the anode 2 and the hole transport layer 4, it is conceivable to provide the anode buffer layer 3 as shown in FIG. As conditions required for the material used for the anode buffer layer, it is possible to form a uniform thin film with good contact with the anode and thermally stable, that is, the melting point and the glass transition temperature are high, and the melting point is 300 ° C. or higher. The glass transition temperature is required to be 100 ° C. or higher. Furthermore, the ionization potential is low, hole injection from the anode is easy, and the hole mobility is high. For this purpose, porphyrin derivatives and phthalocyanine compounds (JP-A 63-295695), starbust aromatic triamines (JP-A 4-308688), and hydrazone compounds (JP-A 4-330483) Gazette), alkoxy-substituted aromatic diamine derivatives (JP-A-4-220995), p- (9-anthryl) -N, N-di-p-tolylaniline (JP-A-3-111485), polythieny Organic compounds such as lenvylene, poly-p-phenylene vinylene (JP-A-4-145192), polyaniline (Appl. Phys. Lett., 64, 1245, 1994), sputtered carbon films (special Kaihei 8-31573) and metal oxides such as vanadium oxide, ruthenium oxide, molybdenum oxide (the 43rd applied physics) Academic conference on academic relations, 27a-SY-9, 1996) has been reported.
Examples of compounds often used as the anode buffer layer material include porphyrin compounds and phthalocyanine compounds. These compounds may have a central metal or may be metal-free.

Specific examples of preferred these compounds include the following compounds:
Porphine 5,10,15,20-tetraphenyl-21H, 23H-porphine 5,10,15,20-tetraphenyl-21H, 23H-porphine cobalt (II)
5,10,15,20-tetraphenyl-21H, 23H-porphine copper (II)
5,10,15,20-tetraphenyl-21H, 23H-porphine zinc (II)
5,10,15,20-tetraphenyl-21H, 23H-porphine vanadium (IV) oxide 5,10,15,20-tetra (4-pyridyl) -21H, 23H-porphine 29H, 31H-phthalocyanine copper (II) Phthalocyanine Zinc (II) phthalocyanine Titanium phthalocyanine oxide Magnesium phthalocyanine Lead phthalocyanine Copper (II) 4,4 ', 4'',4'''-Tetraaza-29H, 31H-phthalocyanine

In the case of the anode buffer layer, a thin film can be formed in the same manner as the hole transport layer, but in the case of an inorganic material, a sputtering method, an electron beam evaporation method, or a plasma CVD method is further used.
The film thickness of the anode buffer layer 3 formed as described above is usually 3 to 100 nm, preferably 10 to 50 nm.

1 to 3 show an example of an element structure employed in the present invention, and the present invention is not limited to the illustrated one. For example, the structure opposite to that shown in FIG. 1, that is, the cathode 7, the electron transport layer 5, the hole transport layer 4, and the anode 2 can be laminated in this order on the substrate, and at least one of them is transparent as described above. It is also possible to provide the organic electroluminescent element of the present invention between two highly functional substrates. Similarly, it is also possible to laminate in a structure opposite to that of each of the layers shown in FIGS.
The present invention can be applied to any of an organic electroluminescent element having a single element, an element having a structure arranged in an array, and a structure having an anode and a cathode arranged in an XY matrix.

  EXAMPLES The present invention will be specifically described below with reference to examples and test examples, but the present invention is not limited to these unless it exceeds the gist. In addition, the compound No. in the following examples. No. of the compounds in Table-1. Corresponding to

[Example 1] Table 1 Compound No. 1 Synthesis of 1 To 100 g of DMF was added to 3.4 g (14.7 mmol) of 2-Nitroso-5-diethylaminophenol hydrochloride and 1.95 g (13.4 mmol) of 5-hydroxyisoquinoline, and the mixture was reacted for 4 hours while heating under reflux. Water was added to the reaction solution, followed by extraction with ethyl acetate. The organic layer was washed with water, dried over sodium sulfate and then concentrated to obtain 4 g as crude crystals. The obtained crude product was purified by column chromatography to obtain about 2 g. In order to remove 5-Hydroxyisoquinoline mixed therein, it was washed with a sodium bicarbonate water-methanol solution, and compound No. 5 was washed. 0.17 g of compound 1 was obtained.
The analysis results of the obtained solid are as follows. It was confirmed to be a compound having a structure of 1.

MS: m / z 319
¹ H-NMR (CDCl ₃ (δ = ppm)):
1.29 (t, 3H), 3.51 (dd, 2H), 6.48 (s, 1H), 6.52 (d, 1H), 6.76 (dd, 1H), 7.69 (d, 1H), 8.13 (d, 1H), 8.89 (d, 1H), 9.94 (s, 1H)
Absorption spectrum: λmax 559 nm (solvent: methylene chloride)
Fluorescence spectrum: λmax 619 nm (solvent: methylene chloride)

Example 2 Table 1 Compound No. Synthesis of 4 DMF 150 ml was added to 1,1,7,7-tetramethyl-8-hydroxy-9-nitrosojulolidine 8.9 g (32.4 mmol) and 5-hydroxyisoquinoline 4.28 g (29.5 mmol) and heated under reflux for 7 hours. Reacted. Water was added to the reaction solution, extracted with ethyl acetate, the organic layer was washed with water, dried over sodium sulfate and concentrated, and the resulting crude product was purified by column chromatography to obtain about 1 g. .
In order to remove the contaminating 5-hydroxyisoquinoline, it was washed with an aqueous solution of sodium bicarbonate-methanol and further purified by column chromatography. 4 mg of compound 4 was obtained.
The analysis results of the obtained solid are as follows. It was confirmed to be a compound having a structure of 4.

MS: m / z 399
¹ H-NMR (CDCl ₃ (δ = ppm)):
1.38 (s, 6H), 1.55 (s, 6H), 1.82 (dt, 4H), 3.40 (dt, 4H), 6.53 (s, 1H), 7.56 (s, 1H), 8.11 (d, 1H), 8.85 (d, 1H), 9.94 (s, 1H)
Absorption spectrum: λmax 594 nm (solvent: methylene chloride)
Fluorescence spectrum: λmax 645 nm (solvent: methylene chloride)

[Example 3] Table 1 Compound No. Synthesis of 7 20 ml of DMF was added to 0.68 g (2.95 mmol) of 2-Nitroso-5-diethylaminophenol hydrochloride and 0.39 g (2.68 mmol) of 5-quinoline, and the mixture was reacted for 4 hours with heating under reflux. Water was added to the reaction solution, extraction was performed with ethyl acetate, the organic layer was washed with water, dried over sodium sulfate and concentrated, and the resulting crude product was purified by column chromatography to obtain about 40 mg. .
The analysis results of the obtained solid are as follows. It was confirmed to be a compound having a structure of 7.

¹ H-NMR (CDCl ₃ (δ = ppm)):
1.28 (t, 3H), 3.49 (dd, 2H), 6.44 (s, 1H), 6.50 (s, 1H), 6.76 (d, 1H), 7.60 (dd, 1H), 7.87 (d, 1H), 8.64 (d, 1H), 9.09 (d, 1H)
Absorption spectrum: λmax 554 nm (solvent: methylene chloride)
Fluorescence spectrum: λmax 609 nm (solvent: methylene chloride)

Example 4 Table 1 Compound No. 4. Coloring of resin by 4 0.05 g of the compound produced in Example 2 was mixed with 100 g of polymethyl methacrylate (“Acrypet MD” manufactured by Mitsubishi Rayon Co., Ltd.), treated at 200 ° C. using an extruder, and colored pellets. It was created. The pellets were molded by an injection molding machine at 200 ° C. for 5 minutes to prepare a colored molded plate.
The resulting colored plate showed a very strong fluorescent red color and was excellent in light resistance and migration resistance.
Further, the color tone of the colored plate molded in the same manner as described above except that it was kept at 250 ° C. for 10 minutes at the time of injection molding showed the same color tone as that of the colored plate molded at 200 ° C. for 5 minutes. There was no change.

[Example 5] Table 1 Compound Nos. Example 7 Coloring of Resin with No. 7 0.05 g of the produced compound was mixed with 100 g of polymethylmethacrylate (“Acrypet MD” manufactured by Mitsubishi Rayon Co., Ltd.) and treated at 200 ° C. using an extruder to give colored pellets. Created. The pellets were molded by an injection molding machine at 200 ° C. for 5 minutes to prepare a colored molded plate. The resulting colored plate showed a very strong fluorescent red color and was excellent in light resistance and migration resistance.
Further, the color tone of the colored plate molded in the same manner as described above except that it was kept at 250 ° C. for 10 minutes at the time of injection molding showed the same color tone as that of the colored plate molded at 200 ° C. for 5 minutes. There was no change.

[Example 6] Table 1 Compound Nos. Production of an organic electroluminescent device having 1 An organic electroluminescent device having the structure shown in FIG. 2 was produced by the following method.
An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate 1 having a thickness of 120 nm (manufactured by Geomat Corp .; electron beam film-formed product; sheet resistance 15 Ω) is 2 mm wide using ordinary photolithography and hydrochloric acid etching. The anode 2 was formed by patterning into a stripe. The patterned ITO substrate is cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, then dried with nitrogen blow, and finally with UV ozone cleaning, and installed in a vacuum evaporation system. did. After the apparatus was roughly evacuated with an oil rotary pump, the apparatus was evacuated with an oil diffusion pump equipped with a liquid nitrogen trap until the degree of vacuum in the apparatus was 2 × 10 ⁻⁶ Torr or less.
The aromatic amine compound represented by the following structural formula (H1) placed in a ceramic crucible arranged in the apparatus was heated by a Ta wire heater around the crucible and evaporated in a vacuum vessel. The temperature of the crucible was in the range of 220 to 240 ° C., and the degree of vacuum during evaporation was 2.8 × 10 ⁻⁶ Torr. In this manner, a hole transport layer 4 having a thickness of 60 nm was deposited. The deposition time was 3 minutes.

Subsequently, as a material for the electron transport layer 5 (light emitting layer), 8-hydroxyquinoline complex (E1) of aluminum shown in the following structural formula, and Table 1 No. 1 as a compound to be doped. One compound was deposited by heating at the same time using separate crucibles. The temperature of each crucible at this time was controlled in the range of 275 to 285 ° C. for the compound (E1) and in the range of 160 to 170 ° C. for the compound No. 1 in Table 1. The degree of vacuum during the deposition was 2.5 × 10 ⁻⁶ Torr, the deposition rate was 0.3 to 0.4 nm / sec, and the deposition time was 3 minutes. As a result, Table 1 No. As a result, an electron transport layer 5 in which 1 compound was doped by 1 wt% with respect to the compound (E1) was obtained.

Subsequently, an 8-hydroxyquinoline complex (E1) of aluminum was deposited as a material for the electron injection layer 6. The temperature of the crucible at this time was controlled in the range of 315 to 350 ° C. The degree of vacuum during the deposition was 1.2 × 10 ⁻⁶ Torr, and the deposition time was 3 minutes. As a result, an electron injection layer 6 having a film thickness of 45 nm was obtained.
The substrate temperature during vacuum deposition of the hole transport layer 4, the electron transport layer 5, and the electron injection layer 6 was kept at room temperature.
Here, the element on which the electron injection layer 6 has been deposited is once taken out from the vacuum deposition apparatus into the atmosphere, and a 2 mm wide striped shadow mask is orthogonal to the ITO stripe of the anode 1 as a mask for cathode deposition. The elements were brought into close contact with each other and placed in another vacuum vapor deposition apparatus, and evacuated until the degree of vacuum in the apparatus was 2 × 10 ⁻⁶ Torr or less in the same manner as the organic layer. Subsequently, magnesium fluoride was deposited as a cathode interface layer using a molybdenum board so as to have a film pressure of 0.5 nm. The degree of vacuum during vapor deposition was 5 × 10 ⁻⁶ Torr.
Subsequently, aluminum was vapor-deposited with the film thickness of 40 nm as the cathode 7 using the molybdenum board.
The degree of vacuum during aluminum deposition was 1.5 × 10 ⁻⁵ Torr, and the deposition time was 1 minute 30 seconds. Furthermore, copper was vapor-deposited with a film thickness of 40 nm using a molybdenum board. The degree of vacuum during copper deposition was 1.5 × 10 ⁻⁶ Torr, and the deposition time was 1 minute 10 seconds.
As described above, an organic electroluminescent element having a light emitting area portion of 2 mm × 2 mm size was obtained. The light emission characteristics of this element are shown in Table-2. In Table 2, the emission start voltage is a voltage at which the luminance is 1 cd / m ² , the emission luminance is a value at a current density of 250 mA / cm ² , the luminous efficiency is a value at 100 cd / m ² , and the luminance / current is luminance − The drive voltage indicates the value of 100 cd / m ² for the slope of the current density characteristic. This device showed uniform red light emission, and the peak wavelength of light emission was 634 nm. The peak wavelength of light emission of the host material is 530 nm.

Example 7 Table 1 Compound No. Preparation of an organic electroluminescent device having 4 No. 1 The structure shown in FIG. 2 is the same as that of Example 6 except that the compound No. 4 is used, and the hole transport layer 4, the electron transport layer 5 (light emitting layer), and the electron injection layer 6 are formed under the following conditions. An organic electroluminescent element was prepared.
On the anode 2 formed in the same manner as in Example 6, the aromatic amine compound represented by the structural formula (H1) was deposited to form the hole transport layer 4. The temperature of the crucible is 289 to 293 ° C., the degree of vacuum during deposition is 2.8 × 10 ⁻⁶ Torr, the deposition rate is 0.1 to 0.7 nm / second, the deposition time is 2 minutes and 50 seconds, and the film thickness is 60. A 1 nm hole transport layer 4 was formed.

Subsequently, as the material for the electron transport layer 5 (light emitting layer), the 8-hydroxyquinoline complex of aluminum represented by the structural formula (E1) and the compound No. 1 in Table 1 were used. 4 were heated and deposited simultaneously using separate crucibles. The temperature of each crucible at this time is in the range of 288 to 304 ° C. with respect to compound (E1). 4 was controlled in the range of 227 to 232 ° C. The degree of vacuum during the deposition was 2.5 × 10 ⁻⁶ Torr, the deposition rate was 0.1 to 0.2 nm / second, and the deposition time was 2 minutes and 10 seconds. As a result, the film thickness was 30.3 nm and Table 1 No. As a result, an electron transport layer 5 in which the compound 4 was 0.8% doped with respect to (E1) was obtained. Subsequently, an 8-hydroxyquinoline complex of aluminum represented by the structural formula (E1) was deposited as the electron injection layer 6. At this time, the temperature of the crucible was in the range of 293 to 329 ° C., the degree of vacuum during the deposition was 1.2 × 10 ⁻⁶ Torr, and the deposition time was 1 minute 50 seconds. As a result, an electron injection layer 6 having a film thickness of 45.1 nm was obtained.
Thereafter, a cathode interface layer, a cathode and the like were provided in the same manner as in Example 6 to complete the organic electroluminescence device.
The light emission characteristics of this element are shown in Table-2. This device showed uniform red light emission, the light emission peak was 650 nm, and the CIE chromaticity coordinate values were x = 0.68 and y = 0.31.

[Comparative Example 1]
In the light emitting layer, Compound No. An organic electroluminescent element was produced in the same manner as in Example 5 except that 1% by weight of the compound of the formula (D-1) was doped instead of 1. The light emission characteristics of this element are shown in Table-2. This device had a light emission peak at 630 nm, a high light emission start voltage and a high drive voltage, and low light emission luminance.

It is the schematic cross section which showed an example of embodiment of an organic electroluminescent element. It is the schematic cross section which showed another example of embodiment of an organic electroluminescent element. It is the schematic cross section which showed another example of embodiment of an organic electroluminescent element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Anode 3 Anode buffer layer 4 Hole transport layer 5 Electron transport layer 6 Electron injection layer 7 Cathode

Claims (8)

A compound for forming an organic layer of an organic electroluminescence device, comprising a phenoxazone compound represented by the following general formula (II).

(In the formula, ring Z represents a heteroaromatic 6-membered ring containing one nitrogen atom which may have a substituent, R ₁ and R ₂ are an alkyl group which may be substituted, Represents an optionally substituted phenyl group or an optionally substituted acyl group, and R _{3 to} R ₆ are each independently hydrogen, a halogen atom, a cyano group, a nitro group, an optionally substituted alkyl group, Represents an optionally substituted phenyl group, an optionally substituted alkoxy group, an optionally substituted amino group, an optionally substituted alkoxycarbonyl group, or an optionally substituted acyl group, and R ₁ and R ₂ may form the same ring, or R ₃ and R ₄ , R ₄ and R ₁ , or R ₂ and R ₅ may combine to form a ring.)   In the general formula (II), the substituent in the ring Z is selected from a halogen atom, a cyano group, a nitro group, an alkyl group, a hydroxyl group, an alkoxy group, a formyl group, a carboxylic acid group, an alkoxycarbonyl group, an amino group, and an aryl group. The compound for forming an organic layer of an organic electroluminescence device according to claim 1, which is a group. The compound for forming an organic layer of an organic electroluminescence device according to claim ₁ , wherein R ₁ and R ₂ in the general formula (II) are alkyl groups having 1 to 8 carbon atoms. The compound for forming an organic layer of an organic electroluminescence device according to any one of claims 1 to 3, wherein in the general formula (II), R ₄ and R ₅ are hydrogen atoms. The compound for forming an organic layer of an organic electroluminescent element according to any one of claims 1 to 4, wherein in the general formula (II), R ₃ and R ₆ are hydrogen atoms.     The compound for forming an organic layer of an organic electroluminescence device according to any one of claims 1 to 5, wherein in the general formula (II), Z is an unsubstituted pyridine ring.     An organic electroluminescent device comprising an organic layer between an anode and a cathode facing each other, wherein the organic layer contains the compound according to any one of claims 1 to 6. The organic electroluminescent element according to claim 7, wherein the organic layer is a hole transport layer and / or an electron transport layer.

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