JP2016213316A - Composition for organic electroluminescent element, organic electroluminescent element, display device and illuminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an organic electroluminescent element having a high current efficiency, and manufactured by use of a composition for an organic electroluminescent element which is high in storage stability and stability of film forming process; and a display device and an illuminating device, each arranged by use of such an organic electroluminescent element.SOLUTION: A composition for an organic electroluminescent element comprises at least a phosphorescence emission material, a charge-transporting compound and a phosphate compound.SELECTED DRAWING: None

Description

  The present invention relates to a composition for an organic electroluminescence device, a composition for an organic electroluminescence device for providing an organic electroluminescence device having high efficiency, an organic electroluminescence device produced using the composition, and the organic electric field The present invention relates to a display device including a light-emitting element and a lighting device.

  In recent years, various electronic devices using organic electroluminescent elements (hereinafter sometimes referred to as “organic EL elements”) such as organic electroluminescent lighting (organic EL lighting) and organic electroluminescent displays (organic EL display) have been put into practical use. It is becoming. An organic EL panel has a low applied voltage, low power consumption, surface emission, and can emit three primary colors. Therefore, application to lighting and displays has been actively studied. Furthermore, reduction in manufacturing cost and practical application of an electronic device using a large area organic EL panel are required.

  On the other hand, for its practical use, further longer life and higher efficiency are required. In the organic electroluminescent element, charges injected from the anode and the cathode recombine on the light emitting layer to emit light by generating excitons. Therefore, confinement of charges injected into the light emitting layer is effective as a means for improving efficiency. As a typical method, there is a method of preventing diffusion of generated excitons, and an exciton diffusion preventing layer is provided on the cathode side adjacent layer of the light emitting layer (Patent Document 1).

  As a method of confining charges in the light emitting layer for realizing high efficiency inside the light emitting layer, a method using a material having a charge trapping property for the light emitting layer can be considered. As one of means for realizing this, a method of capturing and confining charges by a lone electron pair of a hetero atom is conceivable. Examples of the compound having a hetero atom having a lone electron pair include a compound having a phenolic hydroxyl group. The compound having a phenolic hydroxyl group has been conventionally used as an antioxidant. (Patent Document 2, Patent Document 3) In addition, Patent Document 4 describes the use of an antioxidant that does not remain because the performance of organic EL elements such as external quantum efficiency decreases when the phenolic antioxidant remains. Yes. Patent Document 5 describes that a stabilizer, which is a compound having a phenolic hydroxyl group, is removed because it significantly deteriorates the device performance.

International Publication No. 2012/070226 Japanese Patent Laid-Open No. 10-255981 Japanese Patent Application Laid-Open No. 2004-080894 JP 2013-165089 A JP 2013-060396 A

However, as described in Patent Document 2, when a compound having a phenolic hydroxyl group is allowed to coexist with the material of the light emitting layer, there is a possibility of causing deterioration of characteristics. Therefore, as described in Patent Documents 3, 4, and 5, it is assumed that the compound having a phenolic hydroxyl group is removed in order to avoid an adverse effect on the light emitting material. In other words, it was considered by those skilled in the art that it would be preferable for such a compound having an adverse effect to be removed and not remain. Due to such a technical background, a means of positively using a compound having a phenolic hydroxyl group and further confining electric charge has not been implemented.

  Accordingly, an object of the present invention is to provide a composition used for an organic electroluminescence device having high efficiency.

  As a result of intensive studies in view of the above problems, the present inventors have intensively studied this time, and surprisingly, by adding a phosphite compound, an improvement in current efficiency characteristics is observed. The present invention has been completed. In particular, the inventors have also found that the life characteristics can be further improved by using a compound in which the element substituting oxygen in the phosphite compound is limited to sp3 carbon.

The action mechanism of the present invention is estimated as follows.
The electric charge injected into the light emitting layer is transported by hopping conduction on the charge transporting compound contained in the light emitting layer. The heteroatom of the phosphite structure has a lone pair of electrons and has a high electron density, thereby inhibiting the transport of hopping holes and enhancing the effect of confining holes in the light-emitting layer. Presumed. In addition, when the substituent bonded to the oxygen atom, which is preferably a heteroatom of the phosphite structure, is non-conjugated, such as sp3 carbon, the lone electron pair density of the heteroatom is unlikely to decrease, It is thought that the effect of confining holes is maintained.

That is, the gist of the present invention is as follows.
It exists in the composition for organic electroluminescent elements containing a phosphorescence-emitting material, an electrotransport compound, and a phosphite compound at least.

  According to the composition for organic electroluminescent elements of the present invention, the organic electroluminescent element obtained using the composition exhibits high current efficiency and can have a long life. In addition, the storage stability and film forming process stability of the composition for organic electroluminescent elements is expected, and this is a technique that can achieve both, and is very useful as a composition for organic electroluminescent elements.

It is sectional drawing which shows typically an example of the structure of the organic electroluminescent element of this invention.

  Embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the invention.

<Phosphorescent material>
The phosphorescent material of the present invention refers to a material that emits light from an excited triplet state. For example, a metal complex compound having Ir, Pt, Eu, or the like is a typical example, and a material including a metal complex is preferable as a material structure.
Among metal complexes, a phosphorescent organometallic complex that emits light through a triplet state is a long-period periodic table (hereinafter referred to as a “periodic table” unless otherwise specified). And a Werner complex or an organometallic complex compound containing a metal selected from Groups 7 to 11 as a central metal. Preferable examples include compounds represented by the following formula (I) or formula (II).

ML _(q−j) L ′ _j (I)
(In formula (I), M represents a metal, q represents a valence of the metal, L and L ′ represent a bidentate ligand, and j represents a number of 0, 1 or 2. When there are a plurality of L or L ′, the plurality of L or the plurality of L ′ may be the same or different.

(In the formula (II), M ² represents a metal, T represents a carbon atom or a nitrogen atom. R ^{92 to} R ⁹⁵ each independently represents a substituent. However, when T is a nitrogen atom, R 2 ^{No 94} and R ⁹⁵ )
Hereinafter, the compound represented by formula (I) will be described first.
In the formula (I), M is a metal selected from Groups 7 to 11 of the periodic table, preferably ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, gold and the like, and more preferably. Is iridium or platinum, and is most preferably iridium from the viewpoint of high stability and high luminous efficiency.
Further, in the formula (I), the bidentate ligand L represents a ligand having a partial structure represented by the following formula (III).

In the partial structure of the above formula (III), ring A1 represents an aromatic ring group which may have a substituent. The aromatic ring group in the present invention may be an aromatic hydrocarbon ring group or an aromatic heterocyclic group.
In the partial structure of the above formula (III), ring A2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.
In formula (I), bidentate ligand L ′ represents a ligand having the following partial structure.

  Among these, as L ′, the following ligands are preferable from the viewpoint of the stability of the complex.

  More preferable examples of the compound represented by the formula (I) include compounds represented by the following formulas (Ia), (Ib), and (Ic).

(In formula (Ia), M ⁴ represents the same metal as M, w represents the valence of the metal, ring A 1 represents an aromatic ring group which may have a substituent, and ring A2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent, and when w is 2 or more and there are a plurality of rings A1 and A2, the plurality of rings A1 or A2 are the same. May be different.)

(In formula (Ib), M ⁵ represents the same metal as M, w-1 represents the valence of the metal, and ring A1 represents an aromatic ring group which may have a substituent. Ring A2 represents an optionally substituted nitrogen-containing aromatic heterocyclic group, and when w is 3 or more and there are a plurality of rings A1 and A2, the plurality of rings A1 or ring A2 are the same. It may or may not be.)

(In formula (Ic), M ⁶ represents the same metal as M, w represents the valence of the metal, j represents 0, 1 or 2, and ring A1 and ring A1 ′ each represent Independently, it represents an optionally substituted aromatic ring group, and ring A2 and ring A2 ′ each independently represent a nitrogen-containing aromatic heterocyclic group optionally having a substituent. When j is 2 or more or j is 2 or more and there are a plurality of ring A1, ring A1 ′, ring A2 or ring A2 ′, the plurality of rings A1, ring A1 ′, ring A2 or ring A2 ′ are the same May be different.)

  In the above formulas (Ia) to (Ic) and (III), the aromatic rings of ring A1 and ring A1 ′ are aromatic hydrocarbon groups or aromatic heterocyclic groups, and preferably have two free valences. Benzene ring, naphthalene ring, anthracene ring, triphenylyl ring, acenaphthene ring, fluoranthene ring, fluorene ring, furan ring, benzofuran ring, thiophene ring, benzothiophene ring, more preferably benzene ring, naphthalene ring, most preferably Is a benzene ring. Here, in the present invention, free valence can form bonds with other free valences as described in Organic Chemistry / Biochemical Nomenclature (above) (Revised 2nd edition, Nankodo, 1992). Say things. That is, for example, “a benzene ring having one free valence” refers to a phenyl group, and “a benzene ring having two free valences” refers to a phenylene group.

In the above formulas (Ia) to (Ic) and (III), the nitrogen-containing aromatic heterocyclic group for ring A2 and ring A2 ′ is preferably a pyridyl group, a pyrimidyl group, a pyrazyl group, a triazyl group, a pyrazyl group, an imidazolyl group, An oxazolyl group, a thiazolyl group, a benzothiazolyl group, a benzoxazolyl group, a benzimidazolyl group, a quinolyl group, an isoquinolyl group, a quinoxalyl group, a quinazolyl group, a phenanthridyl group, and a benzothiazole group, and more preferably a pyridine ring, a pyrazine ring, Pyrimidine ring, imidazolyl group, quinolyl group, isoquinolyl group, quinoxalyl group and quinazolyl group are preferable, particularly preferably pyridyl group, imidazolyl group, quinolyl group, isoquinolyl group, quinoxalyl group and quinazolyl group, most preferably pyridyl group and imidazolyl group. Group Noryl group, quinoxalyl group, and quinazolyl group.
In the above formulas (Ia) to (Ic) and (III), the combination structure of ring A1 and ring A2 or the combination structure of ring A1 ′ and ring A2 ′ is most preferably a phenyl which may have a substituent. -A pyridine structure, an optionally substituted phenyl-quinoline structure, an optionally substituted phenyl-quinoxaline structure, an optionally substituted phenyl-imidazole structure, and a substituent. It may be a phenyl-quinazoline structure.

  Examples of the substituent that the ring A1, ring A1 ′, ring A2 and ring A2 ′ in the formulas (Ia) to (Ic) and (III) may have include a halogen atom and an alkyl group having 1 to 12 carbon atoms. Alkenyl group having 1 to 12 carbon atoms, alkoxycarbonyl group having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbon atoms, aralkyl group having 1 to 24 carbon atoms, aryloxy group having 1 to 12 carbon atoms, carbon number 1 to 24 dialkylamino group, 8 to 24 carbon diarylamino group, 5 or 6-membered monocyclic ring or 2 to 4 condensed ring, hydrocarbon hydrocarbon group having 6 to 24 carbon atoms Examples thereof include a hydrogen group, a carbazolyl group, an acyl group, a haloalkyl group, and a cyano group. Preferably, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aralkyl group having 1 to 24 carbon atoms, a diarylamino group having 8 to 24 carbon atoms, a 5- or 6-membered monocyclic ring, or 2 An aromatic hydrocarbon ring group having 4 to 4 condensed rings, an aromatic ring group having 4 to 24 carbon atoms, and a carbazolyl group. A diarylamino group having 8 to 24 carbon atoms, an aromatic hydrocarbon ring group which is a 5- or 6-membered monocyclic ring or a condensed ring having 2 to 4 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 24 carbon atoms, and a carbazolyl group May further have a substituent at the aryl moiety constituting the group, and examples of the substituent include an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, and 1 to 24 carbon atoms. And a monovalent aromatic hydrocarbon group having 6 to 24 carbon atoms which may be substituted with an alkyl group having 1 to 12 carbon atoms. The monovalent aromatic hydrocarbon group having 6 to 24 carbon atoms is preferably a monovalent group in which 1 to 4 benzene rings are linked.

These substituents may be connected to each other to form a ring. As a specific example, a substituent of the ring A1 and a substituent of the ring A2 are bonded, or a substituent of the ring A1 ′ and a substituent of the ring A2 ′ are bonded. A condensed ring may be formed. Examples of such a condensed ring include a 7,8-benzoquinoline group. The ring formed by connecting these substituents to each other may further have the substituent. The substituent is 1
One or two or more substituents which may be the same or different.

Preferred examples of M in formulas (Ia) to (Ic) are the same as M in formula (I).
Next, the compound represented by formula (II) will be described.
Wherein (II), ^{M 2} represents a metal. Specific examples include the metals described above as the metal selected from Groups 7 to 11 of the periodic table. Among these, ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold is preferable, and divalent metals such as platinum and palladium are particularly preferable.

  In the formula (II), R92 and R93 each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, a carboxyl group, or an alkoxy group. Represents an alkylamino group, an aralkylamino group, a haloalkyl group, a hydroxyl group, an aryloxy group, an aromatic hydrocarbon group or an aromatic heterocyclic group.

Further, when T is a carbon atom, R94 and R95 each independently represent a substituent represented by the same examples as R92 and R93. Further, when T is a nitrogen atom, there is no R94 or R95 directly bonded to T.
R92 to R95 may further have a substituent. As a substituent, it can be set as the said substituent.
Further, any two or more groups of R92 to R95 may be connected to each other to form a ring. The phosphorescent organic metal complex is preferably a compound represented by the formula (I).

<Phosphite compound>
The phosphite compound in the present invention is not particularly limited as long as it is a compound having a general phosphite structure, but has, for example, the following structure.

R _{1 to} R ₃ each independently represent a C1 to C60 alkyl group, an alkenyl group, an aralkyl group, or a C6 to 30 aryl group. Moreover, in order to provide functionality, you may substitute the C1-30 alkyl group, aralkyl group, and C6-C18 aryl group by an ester bond or an ether bond.
Preferably, it is a case where the substituent that substitutes oxygen of the phosphite structure has a sp3 hybrid orbital, that is, the oxygen of the phosphite structure substitutes with sp3 carbon, and more preferably, This is the case when it is formed only with an alkyl group. For oxygen having a phosphite structure, substitution with sp3 carbon is desirable. Substitution with sp3 carbon is preferable because it has a non-conjugated structure and is difficult to inhibit excitons of the light-emitting material. Further, in principle, the HOMO-LUMO energy difference is large, so that there is no coloring due to absorption of visible light, which is preferable. Furthermore, since the bond due to the nonconjugated group is difficult to reduce the electron density of the lone pair of oxygen atoms, it is preferable that the hole trapping effect is difficult to decrease. In particular, when the oxygen of the phosphite structure is substituted only with an alkyl group, this effect is remarkable and preferable.

Representative compounds include triphenyl phosphite, trihexyl phosphite, tridecyl phosphite, triisodecyl phosphite, trilauryl phosphite and the like. Other examples include phosphorous esters sold by Johoku Chemical Industry Co., Ltd.
Although a specific structure is shown below, it is not limited to this.

<Charge transporting compound>
As the charge transporting compound that can be contained in the composition of the present invention, those conventionally used as materials for organic electroluminescence devices can be used. For example, pyridine, carbazole, naphthalene, perylene, pyrene, anthracene, chrysene, naphthacene, phenanthrene, coronene, fluoranthene, benzophenanthrene, fluorene, acetonaphthofluoranthene, coumarin, p-bis (2-phenylethenyl) benzene and the like Derivatives, quinacridone derivatives, DCM (4- (dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene, aryl Examples thereof include a condensed aromatic ring compound substituted with an amino group, a styryl derivative substituted with an arylamino group, and the like.

One of these may be used alone, or two or more may be used in any combination and ratio.
The content of the charge transporting compound in the composition of the present invention is usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 50% by mass or less, preferably 30% by mass or less, more preferably. It is 10 mass% or less.

<Composition for light emitting layer formation>
The composition of the present invention contains at least a phosphorescent material, a charge transporting compound, and the phosphite compound. Further, the composition such as ink may contain a solvent. The composition of the present invention is usually used for forming a layer or a film by a wet film forming method, and particularly preferably used for forming a light emitting layer of an organic electroluminescent element.

That is, the composition of the present invention is preferably a composition for organic electroluminescent elements, and more preferably used as a composition for forming a light emitting layer of an organic electroluminescent element.
The content of the phosphorescent material in the composition of the present invention is usually 1% by mass or more, preferably 5% by mass or more, more preferably 15% by mass or more and usually 50% by mass or less, based on the total amount of the charge transporting compound. , Preferably it is 40 mass% or less. By setting the content of the phosphorescent light emitting material in the composition within this range, for example, when a light emitting layer is formed using this composition, from the adjacent layer (for example, hole transport layer or hole blocking layer). Holes and electrons are efficiently injected into the light emitting layer, and the driving voltage can be reduced. In addition, the phosphorescence-emitting material may be contained only 1 type in the composition, and may be contained in combination of 2 or more type.

  The emission color of the luminescent material is not particularly limited, but is preferably a long wavelength. Specifically, the luminescent color (peak wavelength) of the coating film of the composition is longer than green. (500 nm or more), more preferably longer wave (550 nm or more) than yellow-green. Due to the emission principle of the phosphorescent layer, quenching of the triplet excited state by lone pairs occurs, but the excited state of the long wavelength emission has lower energy than the excited state of the short wavelength emission, and the triplet excitation. It is presumed that the state itself is stable and is therefore less susceptible to quenching by lone pairs.

  The content of the phosphite compound relative to the solvent in the composition of the present invention is usually 0.01% by mass or more, preferably 0.1% by mass or more, based on the total amount of the charge transporting compound in the composition. Usually, it is 10 mass% or less, More preferably, it is 5 mass% or less, More preferably, it is 1 mass% or less. If it is above the lower limit, the luminous efficiency is improved by trapping the charge, and if it is below the upper limit, when the film is formed using the composition, high luminous efficiency is maintained without quenching due to the interaction of the lone pair of electrons. It is thought.

<Other ingredients>
When the composition of the present invention is used for an organic electroluminescent device, for example, the composition contains a solvent in addition to the above-described phosphorescent material, phosphite compound and charge transporting compound. be able to.
The solvent that may be contained in the composition of the present invention is a volatile liquid component used for forming a layer containing a metal complex compound by wet film formation.

  The solvent is not particularly limited as long as it is a solvent in which a metal complex compound that is a solute, a charge transporting compound described later, and the phenolic compound of the present invention dissolves satisfactorily. Preferred solvents include, for example, alkanes such as n-decane, cyclohexane, ethylcyclohexane, decalin and bicyclohexane; aromatic hydrocarbons such as toluene, xylene, methicylene, phenylcyclohexane and tetralin; chlorobenzene, dichlorobenzene and trichlorobenzene Halogenated aromatic hydrocarbons such as 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, Aromatic ethers such as 2,4-dimethylanisole and diphenyl ether; aromatics such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate Alicyclic ketones such as esters, cyclohexanone, cyclooctanone, and Fencon; Alicyclic alcohols such as cyclohexanol and cyclooctanol; Aliphatic ketones such as methyl ethyl ketone and dibutyl ketone; Aliphatic alcohols such as butanol and hexanol And aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA). Among these, alkanes and aromatic hydrocarbons are preferable. In particular, phenylcyclohexane has a preferable viscosity and boiling point in a wet film forming process.

One of these solvents may be used alone, or two or more thereof may be used in any combination and ratio.
The boiling point of the solvent is usually 80 ° C. or higher, preferably 90 ° C. or higher, more preferably 100 ° C. or higher, and particularly preferably 110 ° C. or higher. Moreover, the boiling point of a solvent is 300 degrees C or less normally, Preferably it is 280 degrees C or less, More preferably, it is 250 degrees C or less. When the boiling point of the solvent is lower than the lower limit, film formation stability may be reduced due to evaporation of the solvent from the composition during wet film formation.

  The content of the solvent in the composition of the present invention is preferably 20% by mass or more, more preferably 50% by mass or more, still more preferably 80% by mass or more, and preferably 99.95% by mass or less, more preferably 99%. 9.9% by mass or less, more preferably 99.8% by mass or less. For example, although the light emitting layer is usually formed to a thickness of about 3 to 200 nm, when the light emitting layer having such a thickness is formed using the composition of the present invention, if the content of the solvent falls below this lower limit, the composition There is a possibility that the viscosity of the object becomes too high and the film forming workability is lowered. On the other hand, if the upper limit is exceeded, the thickness of the film obtained by removing the solvent after film formation cannot be obtained, so that film formation tends to be difficult.

  The metal complex compound-containing composition of the present invention may further contain other compounds and the like in addition to the above-described compounds as necessary. For example, in addition to the above solvent, another solvent may be contained. Examples of such a solvent include amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and dimethyl sulfoxide. One of these may be used alone, or two or more may be used in any combination and ratio.

<Wet deposition method>
The wet film forming method refers to a method of forming a film by applying a composition containing a solvent on a substrate and drying and removing the solvent. Examples of the application method include, but are not limited to, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, capillary coating method, ink jet method, screen printing method, gravure. Examples thereof include a printing method and a flexographic printing method.

  As a method for removing the solvent by drying, heat drying is usually performed. Examples of the heating means used in the heating step include a clean oven, a hot plate, and infrared heating. As the infrared heating, a halogen heater, a ceramic-coated halogen heater, a ceramic heater, or the like can be used. Heating by infrared rays directly gives thermal energy to the substrate or film, enabling drying in a shorter time compared to heating using an oven or hot plate, the influence of gas (moisture and oxygen) in the heating atmosphere, and minute dust This is preferable because it can minimize the influence of the above, and the productivity is improved.

The heating temperature is usually 70 ° C or higher, preferably 75 ° C or higher, more preferably 80 ° C or higher, and is usually 150 ° C or lower, preferably 140 ° C or lower, more preferably 130 ° C or lower.
The heating time is usually 10 seconds or longer, preferably 60 seconds or longer, more preferably 90 seconds or longer, and is usually 120 minutes or shorter, preferably 60 minutes or shorter, more preferably 30 minutes or shorter.
It is also preferable to perform vacuum drying before heat drying.
The film thickness of the organic layer formed by the wet film forming method of the composition of the present invention is usually 5 nm or more, preferably 10 nm or more, more preferably 20 nm or more, usually 500 nm or less, preferably 300 nm or less, more preferably Is 200 nm or less.

[Organic electroluminescence device]
The organic electroluminescent device according to the present invention is an organic electroluminescent device having an anode, a cathode, and at least one organic layer therebetween, and at least one of the organic layers is the composition of the present invention. It is a layer formed by wet film formation using. This layer is preferably a light emitting layer.
FIG. 1 is a schematic cross-sectional view showing a structure example suitable for an organic electroluminescent device according to the present invention. In FIG. 1, reference numeral 1 is a substrate, reference numeral 2 is an anode, reference numeral 3 is a hole injection layer, reference numeral 4 is A hole transport layer, reference numeral 5 denotes a light emitting layer, reference numeral 6 denotes a hole blocking layer, reference numeral 7 denotes an electron transport layer, reference numeral 8 denotes an electron injection layer, and reference numeral 9 denotes a cathode.

[1] Substrate The substrate 1 serves as a support for the organic electroluminescent element, and quartz or glass plates, metal plates, metal foils, plastic films, sheets, and the like are 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 small, the organic electroluminescent element may be deteriorated by the outside air that has passed 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 at least one surface of the synthetic resin substrate is also a preferable method.

[2] Anode An anode 2 is provided on the substrate 1. The anode 2 plays a role of injecting holes into a layer on the light emitting layer side (hole injection layer 3, hole transport layer 4, or light emitting layer 5).
This anode 2 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. In addition, when forming an anode using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, or conductive polymer fine powder, an appropriate binder resin solution is used. The anode 2 can also be formed by dispersing and coating the substrate 1. Furthermore, 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 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.
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 of the anode is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 is arbitrary, and the anode 2 may be the same as the substrate 1. Furthermore, it is also possible to laminate different conductive materials on the anode 2 described above.
For the purpose of removing impurities adhering to the anode and adjusting the ionization potential to improve the hole injection property, the anode surface is subjected to ultraviolet (UV) / ozone treatment, oxygen plasma treatment or argon plasma treatment. It is preferable to do.

[3] Hole Injection Layer The hole injection layer 3 is a layer that transports holes from the anode 2 to the light emitting layer 5 and is usually formed on the anode 2.
The method for forming the hole injection layer 3 according to the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but the hole injection layer 3 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.
The thickness of the hole injection layer 3 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

<Formation of hole injection layer by wet film formation method>
In the case of forming the hole injection layer 3 by wet film formation, the material for forming the hole injection layer 3 is usually mixed with an appropriate solvent (hole injection layer solvent) to form a coating composition (hole An injection layer forming composition) is prepared, and this hole injection layer forming composition is applied onto a layer corresponding to the lower layer of the hole injection layer 3 (usually an anode) by an appropriate technique and dried. Thereby, the hole injection layer 3 is formed.

(Hole transporting compound)
The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as a constituent material of the hole injection layer. The hole transporting compound is a compound having a hole transporting property that is usually used in a hole injection layer of an organic electroluminescence device, and may be a polymer compound or the like, a monomer or the like. Although it may be a low molecular weight compound, it is preferably a high molecular weight compound.

  The hole transporting compound is preferably a compound having an ionization potential of 4.5 eV to 6.0 eV from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3. Examples of hole transporting compounds include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, compounds in which tertiary amines are linked by a fluorene group, hydrazone derivatives, silazane derivatives, silanamines Derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, carbon and the like.

In the present invention, the derivative includes, for example, an aromatic amine derivative, and includes an aromatic amine itself and a compound having an aromatic amine as a main skeleton. It may be a mer.
Among the above examples, an aromatic amine compound is preferable from the viewpoint of amorphousness and visible light transmittance, and an aromatic tertiary amine compound is particularly preferable. Here, the aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.

  The type of the aromatic tertiary amine compound is not particularly limited, but from the viewpoint of uniform light emission due to the surface smoothing effect, a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less (a polymerizable compound in which repeating units are linked) is further included. preferable.

As a material of such a polymer compound, a compound conventionally used as a compound for a hole injection layer can be used. For example, JP 2009-212510 A, International Publication No. 2012/096352, The compounds disclosed in International Publication No. 2013/191137 and the like can be used.
In addition, as a hole transporting compound, a conductive polymer (PEDOT / PSS) obtained by polymerizing 3,4-ethylenedioxythiophene (3,4-ethylenedioxythiophene), which is a derivative of polythiophene, in high molecular weight polystyrene sulfonic acid. Is also preferred. Moreover, the end of this polymer may be capped with methacrylate or the like.

The concentration of the hole transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by mass or more, preferably in terms of film thickness uniformity. Is 0.1
It is at least mass%, more preferably at least 0.5 mass%, and usually at most 70 mass%, preferably at most 60 mass%, more preferably at most 50 mass%. If this concentration is too high, unevenness in film thickness may occur, and if it is too low, defects may occur in the formed hole injection layer.

(Electron-accepting compound)
The composition for forming a hole injection layer preferably contains an electron accepting compound as a constituent material of the hole injection layer.
The electron-accepting compound is preferably a compound having an oxidizing power and the ability to accept one electron from the above-described hole transporting compound, specifically, a compound having an electron affinity of 4 eV or more is preferable, and 5 eV or more. More preferred is a compound that is

  Examples of such electron-accepting compounds include triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Examples thereof include one or more compounds selected from the group. More specifically, high-valent inorganic compounds such as iron (III) chloride (Japanese Patent Laid-Open No. 11-251067) and ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene, tris (pentafluorophenyl) borane (special Aromatic boron compounds such as Kaikai No. 2003-31365); onium salts substituted with organic groups (WO 2005/089024); fullerene derivatives; iodine; polystyrene sulfonate ions, alkylbenzene sulfonate ions, camphor sulfonate Examples thereof include sulfonate ions such as ions.

These electron accepting compounds can improve the conductivity of the hole injection layer by oxidizing the hole transporting compound.
The content of the electron-accepting compound in the hole-injecting layer or the composition for forming a hole-injecting layer with respect to the hole-transporting compound is usually 0.1 mol% or more, preferably 1 mol% or more. However, it is usually 100 mol% or less, preferably 40 mol% or less.

(solvent)
At least one of the solvents of the composition for forming a hole injection layer used in the wet film formation method is preferably a compound that can dissolve the constituent material of the hole injection layer. The boiling point of this solvent is usually 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 110 ° C. or higher, usually 300 ° C. or lower, preferably 280 ° C. or lower. If the boiling point of the solvent is too low, the drying speed is too high and the film quality may be deteriorated. Further, if the boiling point of the solvent is too high, it is necessary to increase the temperature of the drying process, which may adversely affect other layers and the substrate.

Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and the like.
Examples of the ether solvent include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole , Phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, aromatic ethers such as 2,4-dimethylanisole, and the like.

Examples of the ester solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate.
Examples of the aromatic hydrocarbon solvent include toluene, xylene, cyclohexylbenzene, 3-isopropylpropylphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, and methylnaphthalene. Can be mentioned.

Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide, and the like.
In addition, dimethyl sulfoxide and the like can also be used.
These solvent may use only 1 type and may use 2 or more types by arbitrary combinations and a ratio.

(Film formation method)
After preparing the composition for forming the hole injection layer, this composition is applied onto the layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by wet film formation, and dried by drying. The injection layer 3 is formed.
The temperature in the coating step is preferably 10 ° C. or higher, and preferably 50 ° C. or lower in order to prevent film loss due to the formation of crystals in the composition.

Although the relative humidity in an application | coating process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally, and usually 80% or less.
After coating, if necessary, the solvent is roughly removed by vacuum drying or the like, and then the film of the hole injection layer forming composition is dried by heating. Examples of the heating means used in the heating step include a clean oven, a hot plate, an infrared heater (halogen heater) and the like.

  The heating temperature in the heating step is preferably heated at a temperature equal to or higher than the boiling point of the solvent used in the composition for forming a hole injection layer as long as the effects of the present invention are not significantly impaired. In the case of a mixed solvent containing two or more types of solvents used for the hole injection layer, at least one type is preferably heated at a temperature equal to or higher than the boiling point of the solvent. In consideration of an increase in the boiling point of the solvent, it is preferable to heat at 120 ° C. or higher, preferably 300 ° C. or lower in the heating step.

  In the heating step, the heating time is not limited as long as the heating temperature is equal to or higher than the boiling point of the solvent for the composition for forming a hole injection layer and sufficient insolubilization of the film does not occur. Is less than a minute. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, the hole injection layer tends to be inhomogeneous. Heating may be performed in two steps.

<Formation of hole injection layer by vacuum deposition>
When the hole injection layer 3 is formed by vacuum deposition, one or more of the constituent materials of the hole injection layer 3 (the aforementioned hole transporting compound, electron accepting compound, etc.) are placed in a vacuum vessel. Put in crucibles installed (in case of using two or more materials, put them in each crucible), evacuate the inside of the vacuum vessel to about 10 ⁻⁴ Pa with a suitable vacuum pump, and then heat the crucible (two types When using the above materials, each crucible is heated), and the evaporation amount is controlled to evaporate the constituent material of the hole injection layer 3 (when using two or more materials, the evaporation amount is controlled independently). The hole injection layer 3 is formed on the anode 2 of the substrate placed facing the crucible. In addition, when using 2 or more types of materials, the hole injection layer 3 can also be formed by putting those mixtures into a crucible, heating and evaporating.

The degree of vacuum at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 × 10 ⁻⁷ Torr (1.3 × 10 ⁻⁶ Pa) or more, usually 9.0 × 10 ⁻⁶ Torr. (12.0 × 10 ⁻⁴ Pa) or less.
The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 Å / second or more and usually 5.0 Å / second or less.

[4] Hole transport layer The hole transport layer 4 is formed on the hole injection layer 3 when there is a hole injection layer and on the anode 2 when there is no hole injection layer 3. Can do. The organic electroluminescent device of the present invention may have a configuration in which the hole transport layer is omitted.
The formation method of the hole transport layer 4 may be a vacuum deposition method or a wet film formation method, and is not particularly limited. However, from the viewpoint of reducing dark spots, the hole transport layer 4 is preferably formed by a wet film formation method.

  The material for forming the hole transport layer 4 is preferably a material having high hole transportability and capable of efficiently transporting injected holes. Therefore, it is preferable that the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is high, and impurities that become traps are not easily generated during manufacturing or use. In many cases, it is preferable not to quench the light emitted from the light emitting layer 5 or to form an exciplex with the light emitting layer 5 to reduce the efficiency because it is in contact with the light emitting layer 5.

As a material of such a hole transport layer 4, a material conventionally used as a material for a hole transport layer can be used. For example, JP 2009-212510 A, International Publication No. 2012/096352 , Compounds disclosed in International Publication No. 2013/191137 and the like can be used.
When the hole transport layer 4 is formed by a wet film formation method, a composition for forming a hole transport layer is prepared in the same manner as the formation of the hole injection layer 3, and then applied and dried by heating.

The composition for forming a hole transport layer contains a solvent in addition to the above hole transport compound. The solvent used is the same as that used for the composition for forming a hole injection layer. In addition, the application conditions, the heat drying conditions, and the like are the same as in the case of forming the hole injection layer 3.
In the case where the hole transport layer is formed by the vacuum deposition method, the film forming conditions are the same as those in the case of forming the hole injection layer 3.
The film thickness of the hole transport layer 4 thus formed is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably 500 nm or less.

[5] Light-Emitting Layer The light-emitting layer 5 is usually provided on the hole transport layer 4. The light-emitting layer 5 was excited by recombination of holes injected from the anode 2 through the hole injection layer 3 and electrons injected from the cathode 9 through the electron transport layer 7 between the electrodes to which an electric field was applied. , Which is the main light-emitting layer. The light emitting layer 5 preferably contains a light emitting material (dopant) and one or more host materials. The light emitting material is preferably the metal complex compound according to the present invention, and the host material is preferably the charge transporting compound according to the present invention. The light emitting layer 5 is preferably a layer formed by wet-forming the composition of the present invention. The light emitting layer 5 may further have a layer formed by a vacuum deposition method.

In addition, the light emitting layer 5 may contain materials and components other than the light emitting material (dopant) and the host material as long as the performance of the present invention is not impaired.
The organic electroluminescent element may have two or more light emitting layers. In the case where two or more light emitting layers are provided, any one of the light emitting layers may satisfy the definition of the present invention. In the case of two or more layers, each light emitting layer may be in direct contact, or another layer may be interposed therebetween. Examples of the other layer interposed therebetween include a charge transport layer, a block layer, and a charge generation layer. When there are two or more light emitting layers, it is preferably a structure having a light emitting layer formed by a vapor deposition method on a layer formed by wet deposition of the composition of the present invention, more preferably the present invention. The composition has a fluorescent light emitting layer formed by a vapor deposition method on a layer formed by wet film formation of the above composition. A light emitting layer can be uniformly laminated by forming a light emitting layer on a layer formed by wet deposition of the composition of the present invention, which is preferable. Further, if the light emitting layer formed by the vapor deposition method on the layer formed by wet deposition of the composition of the present invention is a fluorescent light emitting layer, the fluorescent light emitting layer material usually does not contain heavy atoms and has a relatively low temperature. Therefore, the energy when adhering to the layer formed by wet-forming the composition of the present invention in which the fluorescent light-emitting material is the lower layer is low, and there is no damage to the lower layer, which is preferable.

[6] Hole blocking layer The hole blocking layer 6 is laminated on the light emitting layer 5 so as to be in contact with the cathode side interface of the light emitting layer 5. In particular, when a phosphorescent light emitting material is used as the light emitting material of the light emitting layer 5 or a blue light emitting material is used, it is effective to provide the hole blocking layer 6. The hole blocking layer 6 has a function of confining holes and electrons in the light emitting layer 5 and improving luminous efficiency. That is, the hole blocking layer 6 is generated by increasing the recombination probability with electrons in the light emitting layer 5 by blocking the holes moving from the light emitting layer 5 from reaching the electron transport layer 7. There is a role of confining excitons in the light emitting layer 5 and a role of efficiently transporting electrons injected from the electron transport layer 7 in the direction of the light emitting layer 5.

The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility, low hole mobility, a large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). Is high.
Examples of the hole blocking layer material satisfying such conditions include mixed arrangements of bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum, and the like. Ligand complexes, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes, styryl compounds such as distyrylbiphenyl derivatives ( JP-A-11-242996), triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole (JP-A-7-41759) And phenanthroline derivatives such as bathocuproine (Japanese Patent Laid-Open No. 10-79297). Further, a compound having at least one pyridine ring substituted at the 2,4,6-position described in International Publication No. 2005/022962 is also preferable as the hole blocking material.

In addition, the material of the hole-blocking layer 6 may use only 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
The film thickness of the hole blocking layer 6 is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.
The hole blocking layer 6 can also be formed by the same method as the hole injection layer 3, but usually a vacuum deposition method is used.

[7] Electron Transport Layer The electron transport layer 7 is provided between the hole injection layer 6 and an electron injection layer 8 described later for the purpose of further improving the light emission efficiency of the device. The electron transport layer 7 is formed of a compound that can efficiently transport electrons injected from the cathode 9 between electrodes to which an electric field is applied in the direction of the light emitting layer 5. As the electron transporting compound used for the electron transport layer 7, the electron injection efficiency from the cathode 9 or the electron injection layer 8 is high, and the injected electrons can be efficiently transported with high electron mobility. It must be a compound.

Materials satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives, Styryl biphenyl derivatives, silole derivatives, 3- or 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948)
Quinoxaline compound (JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type Examples thereof include hydrogenated amorphous silicon carbide, n-type zinc sulfide, and n-type zinc selenide.

The lower limit of the thickness of the electron transport layer 7 is usually 1 nm, preferably about 5 nm, and the upper limit is usually about 300 nm, preferably about 100 nm.
The electron transport layer 7 is formed by a wet film forming method or a vacuum vapor deposition method in the same manner as the hole injection layer 3, but a vacuum vapor deposition method is usually used.

[8] Electron Injection Layer The electron injection layer 8 serves to efficiently inject electrons injected from the cathode 9 into the light emitting layer 5. In order to perform electron injection efficiently, the material for forming the electron injection layer 8 is preferably a metal having a low work function, and alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium are used.

The thickness of the electron injection layer 8 is preferably 0.1 to 5 nm.
Also, an ultrathin insulating film (film thickness of about 0.1 to 5 nm) such as LiF, MgF ₂ , Li ₂ O, Cs ₂ CO ₃ is inserted as the electron injection layer 8 at the interface between the cathode 9 and the electron transport layer 7. This is also an effective method for improving the efficiency of the device (Appl. Phys. Lett., 70, 152, 1997; Japanese Laid-Open Patent Publication No. 10-74586; IEEE Trans. Electronics. Devices, Vol. 44). , 1245, 1997; SID 04 Digest, 154).

  Furthermore, an organic electron transport material represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, or rubidium ( (As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.), it is possible to improve the electron injection / transport properties and achieve excellent film quality. preferable. The film thickness in this case is usually 5 nm or more, preferably 10 nm or more, and usually 200 nm or less, preferably 100 nm or less.

The electron injection layer 8 is formed by a wet film forming method or a vacuum evaporation method in the same manner as the light emitting layer 5. In the case of the vacuum vapor deposition method, the vapor deposition source is put in a crucible or metal boat installed in a vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with an appropriate vacuum pump, and then the crucible or metal boat is Evaporate by heating to form an electron injection layer on the substrate placed facing the crucible or metal boat.

The alkali metal is deposited using an alkali metal dispenser in which nichrome is filled with an alkali metal chromate and a reducing agent. By heating the dispenser in a vacuum container, the alkali metal chromate is reduced and the alkali metal is evaporated. In the case of co-evaporating the organic electron transport material and the alkali metal, the organic electron transport material is put in a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with a suitable vacuum pump. Each crucible and dispenser are simultaneously heated and evaporated to form an electron injection layer on the substrate placed facing the crucible and dispenser.
At this time, co-evaporation is uniformly performed in the film thickness direction of the electron injection layer 8, but there may be a concentration distribution in the film thickness direction.

[9] Cathode The cathode 9 plays a role of injecting electrons into a layer (such as the electron injection layer 8 or the light emitting layer 5) on the light emitting layer 5 side.
The material used for the cathode 9 can be the material used for the anode 2, but a metal having a low work function is preferable for efficient electron injection, and tin, magnesium, indium, calcium, A suitable metal such as aluminum or silver or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.
The film thickness of the cathode 9 is usually the same as that of the anode 2. For the purpose of protecting the cathode made of a low work function metal, further laminating a metal layer having a high work function and stable to the atmosphere on the cathode increases the stability of the device. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used.

[10] Other Constituent Layers While the description has been given centering on the element having the layer constitution shown in FIG. 1, the performance between the anode 2 and the cathode 9 and the light emitting layer 5 in the organic electroluminescent element of the present invention is described. In addition to the layers described above, any layer may be included, and any layer other than the light emitting layer 5 may be omitted.

  For example, it is also effective to provide an electron blocking layer between the hole transport layer 4 and the light emitting layer 5 for the same purpose as the hole blocking layer 8. The electron blocking layer prevents electrons moving from the light emitting layer 5 from reaching the hole transporting layer 4, thereby increasing the recombination probability with holes in the light emitting layer 5, There is a role of confining in the light emitting layer 5 and a role of efficiently transporting holes injected from the hole transport layer 4 in the direction of the light emitting layer 5.

The characteristics required for the electron blocking layer include high hole transportability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). In addition, when the light emitting layer 5 is formed by a wet film forming method, it is preferable that the electron blocking layer is also formed by a wet film forming method because the device manufacturing becomes easy.
For this reason, it is preferable that the electron blocking layer also has wet film formation compatibility. As a material used for such an electron blocking layer, a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (International Publication No. 2004/084260).

The structure opposite to that shown in FIG. 1, that is, the cathode 9, the electron injection layer 8, the electron transport layer 7, the hole blocking layer 6, the light emitting layer 5, the hole transport layer 4, and the hole injection layer 3 on the substrate 1. The organic electroluminescent element of the present invention can be provided between two substrates, at least one of which is highly transparent.
Further, a structure in which a plurality of layers shown in FIG. 1 are stacked (a structure in which a plurality of light emitting units are stacked) may be employed. In this case, instead of the interface layer between the steps (between the light emitting units) (two layers when the anode is ITO and the cathode is Al), for example, V ₂ O ₅ or the like is used as the charge generation layer to form a barrier between the steps. From the viewpoint of luminous efficiency and driving voltage.
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.

[Display equipment and lighting equipment]
The display device and the illumination device of the present invention use the organic electroluminescent element of the present invention as described above. There is no restriction | limiting in particular about the format and structure of the display apparatus of this invention, and an illuminating device, It can assemble in accordance with a conventional method using the organic electroluminescent element of this invention.

For example, the display device and the illumination device of the present invention can be obtained by the method described in “Organic EL display” (Ohm, August 20, 2004, published by Shizushi Tokito, Chiba Adachi, Hideyuki Murata). Can be formed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded.

[Example 1]
The organic electroluminescent element shown in FIG. 1 was produced.
First, an ITO transparent conductive film is deposited on a glass substrate 1 to a thickness of 150 nm and patterned into a 2 mm-wide stripe to form an ITO anode 2 (manufactured by Sanyo Vacuum Co., Ltd., sputtered film) After cleaning in the order of ultrasonic cleaning with a surfactant aqueous solution, water cleaning with ultrapure water, ultrasonic cleaning with ultrapure water, and water cleaning with ultrapure water, they were dried with compressed air and subjected to ultraviolet ozone cleaning.

  Next, 2.0% by mass of the hole transporting polymer compound having a repeating structure represented by the following (P1) and 4-isopropyl-4′-methyldiphenyliodonium tetrakis represented by the following (A1) ( An ethyl benzoate solution (composition for forming a hole injection layer) containing 0.8% by mass of pentafluorophenyl) borate was prepared.

  This composition for forming a hole injection layer is applied onto the ITO substrate by a spin coating method under the conditions shown below, and further baked under the baking conditions shown below, whereby a hole injection layer 3 having a thickness of 40 nm is formed. Got.

<Film formation conditions>
Spin coat atmosphere Under air atmosphere Bake conditions Under air atmosphere, 230 ° C., 1 hour Thereafter, a 1% by mass cyclohexylbenzene solution of a hole transporting polymer compound represented by the following (H1) (composition for forming a hole transport layer) ) Was applied onto the hole injection layer 3 by spin coating under the conditions shown below, and a hole transport layer 4 having a thickness of 10 nm was formed by performing a crosslinking treatment by baking.

<Film formation conditions>
Spin coating atmosphere Nitrogen atmosphere Bake conditions Nitrogen atmosphere, 230 ° C., 1 hour Next, when forming the light emitting layer 5, the light emitting material (D-1) shown below and the charge transporting compounds (h-1 to h) -3), and triisodecyl phosphite as a phosphite compound, a composition for forming a light emitting layer having the following composition was prepared.

<Composition composition for light emitting layer formation>
Solvent cyclohexylbenzene Component concentration (D-1): 0.3% by mass
(H-1): 2.25% by mass
(H-2): 0.375% by mass
(H-3): 0.375% by mass
Triisodecyl phosphite: 0.01% by mass
On the day of preparing the composition for forming the light emitting layer, using this solution, the coating is performed on the hole transport layer 4 by the spin coating method under the following conditions, and the baking treatment is performed under the following baking conditions. Thus, the light emitting layer 5 having a thickness of 50 nm was formed.

<Film formation conditions>
Spin coating atmosphere Under nitrogen atmosphere Bake conditions Under nitrogen atmosphere, 120 ° C., 10 minutes Next, a substrate on which the hole injection layer 3, the hole transport layer 4, and the light emitting layer 5 are wet-formed is carried into a vacuum deposition apparatus, After performing rough evacuation, evacuation was performed using a cryopump until the degree of vacuum in the apparatus became 3.0 × 10 ⁻⁴ Pa or less. On the light-emitting layer 5, HB1 is deposited as a hole blocking material with a film thickness of 10 nm at a vapor deposition rate of 0.6 to 1.2 Å / sec while maintaining the degree of vacuum at 2.2 × 10 ⁻⁴ Pa or less. Thus, the hole blocking layer 6 was formed.

Next, in a state where the degree of vacuum is maintained at 2.2 × 10 ⁻⁴ Pa or less, tris (8-hydroxyquinolinato) aluminum (Alq3) is heated on the hole blocking layer 6 to achieve a deposition rate of 0. The electron transport layer 7 was formed by laminating | stacking 20-nm-thick film thickness by.
Here, the element which performed vapor deposition to the electron carrying layer 7 was conveyed from the chamber for organic layer vapor deposition to the chamber for metal vapor deposition. A 2 mm wide stripe-shaped shadow mask was placed in close contact with the element so as to be orthogonal to the ITO stripe of the anode 2 as a mask for cathode vapor deposition. The apparatus was evacuated until the degree of vacuum was 1.1 × 10 ⁻⁴ Pa or less in the same manner as in the organic layer deposition.

Thereafter, in a state where the degree of vacuum is kept at 1.0 × 10 ⁻⁴ Pa or less, lithium fluoride (LiF) is heated on the electron transport layer 7 by using a molybdenum boat, whereby the deposition rate is 0.07. The electron injecting layer 8 was formed by laminating 0.5 nm film thickness at ˜0.15 Å / sec. Next, in the same manner, in a state where the degree of vacuum is maintained at 2.0 × 10 ⁻⁴ Pa, aluminum is heated using a molybdenum boat to form a film at a deposition rate of 0.6 to 10.0 mm / sec. A cathode 9 was formed by vapor deposition with a thickness of 80 nm. The substrate temperature during the deposition of the electron injection layer 8 and the cathode 9 was kept at room temperature.

Subsequently, in order to prevent the element from being deteriorated by moisture in the atmosphere during storage, a sealing process was performed by the method described below.
In a nitrogen glove box, a photocurable resin 30Y-437 (manufactured by Three Bond) is applied to the outer periphery of a 23 mm × 23 mm size glass plate with a width of 1 mm, and a moisture getter sheet (manufactured by Dynic) is applied to the center. installed. On top of this, the substrate on which the formation of the cathode had been completed was carried in and bonded so that the deposited surface faced the desiccant sheet. Then, only the area | region where the photocurable resin was apply | coated was irradiated with ultraviolet light, and resin was hardened.
As described above, an organic electroluminescent element having a light emitting area portion of 2 mm × 2 mm in size and emitting light at a peak wavelength of 560 nm was obtained.

[Example 2]
The organic electroluminescent element of Example 2 was obtained by operating in the same manner as in Example 1 except that triphenyl phosphite was used instead of triisodecyl phosphite as the phosphite compound.

[Comparative Example 1]
An organic electroluminescent element of Comparative Example 1 was obtained by operating in the same manner as in Example 1 except that the phosphite compound was not used.

[Comparative Example 2]
An organic electroluminescent device of Comparative Example 2 was obtained by operating in the same manner as in Example 1 except that trilauryl thiophosphite was used as the phosphite compound instead of triisodecyl phosphite.

With respect to Examples 1 and 2 and Comparative Examples 1 and 2, luminance current efficiency evaluation when a current of 10 mA / cm ² was passed and direct current driving using a current value at an initial luminance of 5000 cd / m ² The relative brightness after 50 hours was measured to evaluate the life. Table 1 shows the rates of change when Comparative Example 1 is used as a reference. In Example 2, the relative luminance after 50 hours was almost the same, but the luminance current efficiency was improved. In Example 1 using a phosphite composed only of an alkyl group, the luminance current efficiency was improved and the lifetime was extended. On the other hand, it was found that the thiophosphorous acid system was not effective and rather deteriorated, indicating that the phosphite structure is important.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Electron injection layer 9 Cathode 10 Organic electroluminescent device

Claims (6)

  A composition for an organic electroluminescent device comprising at least a phosphorescent material, a charge transporting compound, and a phosphite compound.   2. The composition for organic electroluminescent elements according to claim 1, wherein the substituent that substitutes for oxygen in the phosphite structure of the phosphite compound is carbon having sp3 hybrid orbitals.   The composition for an organic electroluminescent element according to claim 1 or 2, wherein the substituent substituted for oxygen in the phosphite structure of the phosphite compound is a non-conjugated structure.   It is an organic electroluminescent element which has an anode, a cathode, and the at least 1 layer of light emitting layer between the said anode and the said cathode, Comprising: At least 1 layer of the said light emitting layer is as described in any one of Claims 1-3. An organic electroluminescence device formed by wet film formation using a composition.   The display apparatus which has an organic electroluminescent element of Claim 4.   The illuminating device which has an organic electroluminescent element of Claim 4.