JP5511454B2 - Organic electroluminescence device - Google Patents

Description

  The present invention relates to an organic electroluminescent device (hereinafter also referred to as “organic electroluminescence device” or “organic EL device”).

  Organic electroluminescence devices have features such as self-emission and high-speed response, and are expected to be applied to flat panel displays. In particular, organic thin films (hole transport layer) that have a hole transport property and organic materials that have an electron transport property Since a two-layer type (laminated type) in which a thin film (electron transport layer) is laminated is reported, it has attracted attention as a large-area light-emitting element that emits light at a low voltage of 10 V or less. The stacked organic electroluminescent element has a basic configuration of positive electrode / hole transport layer / light emitting layer / electron transport layer / negative electrode.

  In such an organic electroluminescent device, various studies have been made in order to achieve high luminous efficiency, and in order to obtain higher luminous efficiency and driving durability, for example, an electron transport property is provided in the luminous layer. It has been proposed to contain a phosphorescent material (Patent Document 1).

  However, this proposal has a multi-layered element structure, and has a problem that the production is complicated and takes time.

  In order to solve such problems, it has been proposed that the cathode is adjacent to the light emitting layer (positive electrode / hole transport layer / light emitting layer / negative electrode) (Patent Document 2, Patent Document 3). For example, it has been proposed that an iridium complex-based light-emitting material is contained in a light-emitting layer and that the light-emitting layer and the cathode are adjacent to each other so that high light emission efficiency can be obtained at a low voltage (Non-patent Document 1). In addition, by adjoining a light emitting layer containing Ir complex, which is a hole transporting phosphorescent light emitting material, as a phosphorescent light emitting material and a cathode (LiF / Al), the hole blocking layer between the light emitting layer and the cathode is omitted, and durability (stable It has been proposed to improve the performance and simplify the device (Patent Document 4).

  However, although these proposals have realized a simple element configuration, there are problems that the drive voltage is still high, and the voltage and chromaticity change after the element deterioration due to long-time driving are large.

  Therefore, there is a strong demand for the rapid development of an organic electroluminescence device that can reduce the driving voltage with a simple device configuration, and can simultaneously increase the voltage after deterioration of the device due to long-time driving and suppress the change in chromaticity. The current situation is.

JP 2008-218972 A JP 2004-296226 A JP-A-2005-101002 JP 2007-311615 A

Applied Physics Letters, 93, 06603 (2008).

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, an object of the present invention is to provide an organic electroluminescence device capable of reducing a driving voltage with a simple device configuration and suppressing a voltage increase and a chromaticity change after device deterioration due to long-time driving.

Means for solving the problems are as follows. That is,
<1> An anode, a cathode, and a light-emitting layer that is laminated adjacent to the cathode and includes an electron-transporting phosphorescent material. The electron-transporting phosphorescent material has the following formula (1) and It is an organic electroluminescent element characterized by satisfy | filling the relationship of following formula (2).

| LUMO _e |> 1.5 eV (1)
| HOMO _e |> 5.4 eV (2)

However, LUMO _e represents the LUMO level of the electron transporting phosphorescent material, and HOMO _e represents the HOMO level of the electron transporting phosphorescent material.
The organic electroluminescent element of the present invention comprises at least an anode, a cathode, and a light emitting layer laminated adjacent to the cathode. The light emitting layer includes an electron transporting phosphorescent material, and the electron transporting phosphorescent material satisfies the relationship of the formula (1) and the formula (2). Thereby, the drive voltage rise at the time of deterioration and the chromaticity change by an electric current are suppressed, improving a low voltage, high efficiency, and durability.
<2> The organic electroluminescence device according to <1>, wherein the cathode has an insulating thin film on the light emitting layer side.
<3> The organic electroluminescent element according to any one of <1> to <2>, wherein the electron-transporting phosphorescent material includes an electron-withdrawing group.
<4> The organic electroluminescence device according to <3>, wherein the electron-withdrawing group is at least one selected from a fluorine atom, a trifluoromethyl group, and a cyano group.
<5> The organic electroluminescent element according to any one of <1> to <4>, wherein the light emitting layer contains 10% by mass or less of a hole trap material satisfying a relationship of the following formulas (3) and (4): .

| LUMO _h | <2.0 eV (3)
| HOMO _h | <5.4 eV (4)

However, LUMO _h represents the LUMO level of the hole trap material, and HOMO _h represents the HOMO level of the hole trap material.
<6> The organic electroluminescent element according to <5>, wherein the hole trap material is an iridium complex.
<7> The organic electroluminescent element according to any one of <1> to <6>, wherein the electron-transporting phosphorescent material is a platinum complex.

  According to the present invention, the above-mentioned problems can be solved and the object can be achieved, and the drive voltage is reduced with a simple element configuration, and the voltage rise and chromaticity after element deterioration due to long-time driving are reduced. An organic electroluminescence device capable of suppressing the change can be provided.

FIG. 1 is a schematic view showing an example of the layer structure of the organic electroluminescent element of the present invention. FIG. 2 is a schematic view showing an example of the layer structure of the organic electroluminescent element of the present invention.

(Organic electroluminescence device)
The organic electroluminescent element of the present invention comprises an anode, a cathode, and a light emitting layer, and further comprises other layers as necessary.

<Cathode>
The cathode is not particularly limited as long as it has a function as an electrode for injecting electrons into the light emitting layer.
There is no restriction | limiting in particular about the shape, structure, size, etc. as said cathode, According to the use and objective of an organic electroluminescent element, it can select suitably from well-known electrode materials.
Examples of the material constituting the cathode include alkali metals, alkaline earth metals, rare earth metals, other metals, and alloys of these metals. These may be used alone, but from the viewpoint of achieving both stability and electron injection properties, it is preferable to use two or more in combination.
Examples of the alkali metal include lithium and sodium.
Examples of the alkaline earth metal include magnesium and calcium.
Examples of the rare earth metal include indium and ytterbium.
Examples of the other metal include gold, silver, lead, and aluminum.
Examples of the alloy include a sodium-potassium alloy, a lithium-aluminum alloy, and a magnesium-silver alloy.
Among these, an alkali metal and an alkaline earth metal are preferable from the viewpoint of electron injecting property, and a material containing aluminum is particularly preferable from the viewpoint of excellent storage stability. The material containing aluminum is aluminum alone, an alloy of aluminum and 0.01% by mass to 10% by mass of alkali metal or alkaline earth metal, or a mixture thereof (for example, lithium-aluminum alloy, magnesium-aluminum alloy). Etc.)

There is no restriction | limiting in particular as a formation method of the said cathode, According to a well-known method, it can carry out, for example, a wet system, a chemical system, a physical system, etc. are mentioned.
Examples of the wet method include a printing method and a coating method.
Examples of the chemical method include CVD and plasma CVD.
Examples of the physical method include a vacuum deposition method, a sputtering method, and an ion plating method.

  In addition, when patterning is performed when forming the cathode, it may be performed by chemical etching such as photolithography, or may be performed by physical etching using laser or the like. It may be performed by sputtering or the like, or may be performed by a lift-off method or a printing method.

The thickness of the cathode is preferably 5 nm or more, more preferably 10 nm or more, and particularly preferably 20 nm or more.
When the thickness is less than 5 nm, the device may be short-circuited.

  As the cathode, in view of improving electron injection property, an alkali metal halide such as lithium fluoride and lithium acetylacetonate of an alkali metal oxide such as lithium oxide (hereinafter referred to as “Li (acac)”) are provided on the light emitting layer side. And an insulator thin film made of cesium carbonate or an alkali metal complex such as 8-quinolinolato-lithium (hereinafter referred to as “Liq”).

The thickness of the insulator thin film is preferably 0.1 nm to 10 nm, more preferably 0.5 nm to 5 nm, and particularly preferably 1 nm to 3 nm.
When the thickness is less than 0.1 nm, the voltage may not be reduced, and when it exceeds 10 nm, the voltage may be improved.

  Examples of the method for forming the insulator thin film include dry film forming methods such as vapor deposition and sputtering, wet coating methods, transfer methods, printing methods, coating methods, ink jet methods, and spray methods.

<Light emitting layer>
The light emitting layer contains an electron transporting phosphorescent material, and further contains a hole trap material, a host material, and other components as necessary.

-Electron transporting phosphorescent material-
As the electron transporting phosphorescent material, the lowest empty orbit (LUMO level) and the highest occupied orbit (HOMO level) have the following formulas (1) and (2) in order to improve the electron injection property and the electron transport property. ) Is preferably satisfied.

| LUMO _e |> 1.5 eV (1)
| HOMO _e |> 5.4 eV (2)

However, LUMO _e represents the LUMO level of the electron transporting phosphorescent material, and HOMO _e represents the HOMO level of the electron transporting phosphorescent material.

  The highest occupied orbit (HOMO level) and the lowest unoccupied orbit (LUMO level) are all Gaussian 03 (Gaussian 03, Revision D.02, MJ Frisch), which is software for molecular orbit calculation manufactured by Gaussian. , Et al, Gaussian, Inc., Wallingford CT, 2004.) and calculated by performing structural optimization using B3LYP / 6-31G * as a keyword ( eV unit conversion value). The calculated value obtained by this method is highly correlated with the experimental value.

The lowest empty orbit (LUMO level) of the electron-transporting phosphorescent material is preferably −1.5 eV to −3.0 eV, more preferably −1.75 eV to −3.0 eV, and −2.0 eV to −3. 0.0eV is particularly preferred.
If the lowest unoccupied orbit is less than −3.0 eV or exceeds −1.5 eV, the driving voltage may increase and the light emission efficiency may decrease.
Further, the highest occupied orbit (HOMO level) of the electron transporting phosphorescent material is preferably −5.4 eV to −7.0 eV, more preferably −5.5 eV to −7.0 eV, and −5.75 eV. -7.0 eV is particularly preferred.
When the highest occupied trajectory is less than −7.0 eV or exceeds −5.4 eV, the driving voltage may be increased and the light emission efficiency may be lowered.

The content (concentration) of the electron transporting phosphor material is preferably 8% by mass or more, more preferably 8% by mass to 40% by mass, and particularly preferably 8% by mass to 30% by mass in the light emitting layer. .
When the content is less than 8% by mass, it may be impossible to suppress voltage increase and chromaticity change after deterioration. When the content exceeds 40% by mass, the efficiency may be lowered due to association of the light emitting materials.

  The electron transporting phosphorescent material is not particularly limited, and is preferably a metal complex compound, a benzimidazole derivative, an imidazopyridine derivative, a pyridine derivative, a pyrimidine derivative, a triazine derivative, or the like. Among these, in the present invention, a metal complex compound is preferable from the viewpoint of durability. The metal complex compound is more preferably a metal complex compound having a ligand having at least one nitrogen atom, oxygen atom or sulfur atom coordinated to the metal.

  The metal ion in the metal complex compound is not particularly limited and can be appropriately selected depending on the purpose. For example, ruthenium ion, rhodium ion, palladium ion, tungsten ion, rhenium ion, osmium ion, iridium ion, Examples include complexes containing platinum, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium ions. It is done. Among these, complexes containing ruthenium ions, rhodium ions, palladium ions and platinum ions are more preferable, and complexes containing platinum ions having a high electron transporting property (platinum complexes) are particularly preferable.

  The electron transporting phosphor material particularly preferably contains at least one electron withdrawing group such as a fluorine atom, a trifluoromethyl group, and a cyano group in terms of electron transporting property.

  As the ligand contained in the metal complex, there are various known ligands. For example, “Photochemistry and Photophysics of Coordination Compounds”, Springer-Verlag, H. et al. Examples include the ligands described in Yersin, published in 1987, “Organometallic Chemistry: Fundamentals and Applications”, Sakai Hanafusa, Yamamoto Akio, published in 1982, and the like.

As said ligand, a nitrogen-containing heterocyclic ligand is preferable. As said nitrogen-containing heterocyclic ligand, C1-C30 is preferable, C2-C20 is more preferable, C3-C15 is especially preferable, Even if it is a monodentate ligand, it is bidentate or more The ligand may be a bidentate or more and a hexadentate or less.
Examples of the ligand include an azine ligand, a hydroxyphenylazole ligand, an alkoxy ligand, an aryloxy ligand, a heteroaryloxy ligand, an alkylthio ligand, and an arylthio ligand. , Heteroarylthio ligand, siloxy ligand, aromatic hydrocarbon anion ligand, aromatic heterocyclic anion ligand, indolenine anion ligand and the like. Among these, nitrogen-containing heterocyclic ligands, aryloxy ligands, heteroaryloxy groups, and siloxy ligands are preferable, nitrogen-containing heterocyclic ligands, aryloxy ligands, siloxy ligands, aromatics An aromatic hydrocarbon anion ligand and an aromatic heterocyclic anion ligand are more preferred.
Examples of the azine ligand include a pyridine ligand, a bipyridyl ligand, and a terpyridine ligand.
Examples of the hydroxyphenylazole ligand include a hydroxyphenylbenzimidazole ligand, a hydroxyphenylbenzoxazole ligand, a hydroxyphenylimidazole ligand, and a hydroxyphenylimidazopyridine ligand.
The alkoxy ligand is, for example, preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 10 carbon atoms, such as methoxy, ethoxy, phenoxy, butoxy, 2-ethylhexyl. Examples include siloxy.
As said aryloxy ligand, C6-C30 is preferable, C6-C20 is more preferable, C6-C12 is especially preferable, For example, phenyloxy, 1-naphthyloxy, 2-naphthyloxy, Examples include 2,4,6-trimethylphenyloxy and 4-biphenyloxy.
As said heteroaryloxy ligand, C1-C30 is preferable, C1-C20 is more preferable, C1-C12 is especially preferable, for example, pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy, etc., for example. Can be mentioned.
As said alkylthio ligand, C1-C30 is preferable, C1-C20 is more preferable, C1-C12 is especially preferable, For example, methylthio, ethylthio, etc. are mentioned.
As said arylthio ligand, C6-C30 is preferable, C6-C20 is more preferable, C6-C12 is especially preferable, For example, phenylthio etc. are mentioned.
The heteroarylthio ligand preferably has 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 12 carbon atoms, such as pyridylthio, 2-benzimidazolylthio, 2-benz. Examples include oxazolylthio and 2-benzthiazolylthio.
As said siloxy ligand, C1-C30 is preferable, C3-C25 is more preferable, C6-C20 is especially preferable, for example, a triphenylsiloxy group, a triethoxysiloxy group, a triisopropylsiloxy group Etc.
As said aromatic hydrocarbon anion ligand, C6-C30 is preferable, C6-C25 is more preferable, C6-C20 is especially preferable, for example, a phenyl anion, a naphthyl anion, an anthranyl anion etc. Can be mentioned.
As said aromatic heterocyclic anion ligand, C1-C30 is preferable, C2-C25 is more preferable, C2-C20 is especially preferable, For example, a pyrrole anion, a pyrazole anion, a pyrazole anion, a triazole Examples include an anion, an oxazole anion, a benzoxazole anion, a thiazole anion, a benzothiazole anion, a thiophene anion, and a benzothiophene anion.

  Specific examples of such an electron-transporting phosphorescent material include, but are not limited to, the following materials.

-Host material-
The host material is not particularly limited as long as it is a host material, and can be appropriately selected according to the purpose. Examples thereof include an electron transporting host material and a hole transporting host material. Among these, it is preferable to use an electron transporting host material from the viewpoint of voltage.

The lowest unoccupied orbit (LUMO level) of the host material is preferably −1.5 eV to −3.0 eV, more preferably −1.75 eV to −3.0 eV, and −2.0 eV to −3.0 eV. Particularly preferred.
If the lowest unoccupied orbit is less than −3.0 eV or exceeds −1.5 eV, the driving voltage may increase and the light emission efficiency may decrease.

The highest occupied orbit (HOMO level) of the host material is preferably −5.4 eV to −7.0 eV, more preferably −5.5 eV to −7.0 eV, and −5.75 eV to −7.0 eV. Is particularly preferred.
When the highest occupied trajectory is less than −7.0 eV or exceeds −5.4 eV, the driving voltage may be increased and the light emission efficiency may be lowered.

  The highest occupied orbit (HOMO level) and the lowest unoccupied orbit (LUMO level) are all Gaussian 03 (Gaussian 03, Revision D.02, MJ Frisch), which is software for molecular orbit calculation manufactured by Gaussian. , Et al, Gaussian, Inc., Wallingford CT, 2004.) and calculated by performing structural optimization using B3LYP / 6-31G * as a keyword ( eV unit conversion value). The calculated value obtained by this method is highly correlated with the experimental value.

The host material is not particularly limited and may be appropriately selected depending on the intended purpose. For example, pyridine, pyrimidine, triazine, imidazole, pyrazole, triazole, oxazole, oxadiazole, fluorenone, anthraquinodimethane, anthrone , Diphenylquinone, thiopyran dioxide, carbodiimide, fluorenylidenemethane, distyrylpyrazine, fluorine-substituted aromatic compounds, azole derivatives, azine derivatives, metal complexes, and the like.
Examples of the heterocyclic tetracarboxylic acid anhydride include naphthalene perylene.
Examples of the metal complex include phthalocyanine, 8-quinolinol derivative metal complexes, metal phthalocyanine, benzoxazole, and metal complexes having benzothiazole as a ligand.
Examples of the azole derivatives include benzimidazole derivatives and imidazopyridine derivatives.
Examples of the azine derivative include a pyridine derivative, a pyrimidine derivative, and a triazine derivative.
Among these, metal complexes, azole derivatives, and azine derivatives are preferable, and metal complex compounds are more preferable from the viewpoint of durability.

  The metal complex compound is preferably a metal complex having a ligand having at least one nitrogen atom, oxygen atom or sulfur atom coordinated to the metal.

  There is no restriction | limiting in particular as a metal ion contained in the said metal complex, According to the objective, it can select suitably, For example, beryllium ion, magnesium ion, aluminum ion, gallium ion, zinc ion, indium ion, tin ion , Platinum ions, palladium ions and the like. Among these, beryllium ion, aluminum ion, gallium ion, zinc ion, platinum ion and palladium ion are preferable, and aluminum ion, zinc ion and palladium ion are more preferable.

  Examples of the ligand contained in the metal complex include “Photochemistry and Photophysics of Coordination Compounds”, Springer-Verlag, H.C. Examples include the ligands described in Yersin, published in 1987, “Organometallic Chemistry: Fundamentals and Applications”, Sakai Hanafusa, Yamamoto Akio, published in 1982, and the like.

Examples of the ligand include azine ligand, hydroxyphenylazole ligand, alkoxy ligand, aryloxy ligand, heteroaryloxy ligand, alkylthio ligand, arylthio ligand, heteroary Examples include a ruthio ligand, a siloxy ligand, an aromatic hydrocarbon anion ligand, an aromatic heterocyclic anion ligand, and an indolenine anion ligand.
Examples of the azine ligand include a pyridine ligand, a bipyridyl ligand, and a terpyridine ligand.
Examples of the hydroxyphenylazole ligand include a hydroxyphenylbenzimidazole ligand, a hydroxyphenylbenzoxazole ligand, a hydroxyphenylimidazole ligand, and a hydroxyphenylimidazopyridine ligand.
As said alkoxy ligand, C1-C30 is preferable, C1-C20 is more preferable, C1-C10 is especially preferable, for example, methoxy, ethoxy, butoxy, 2-ethylhexyloxy etc. are mentioned. .
As said aryloxy ligand, C6-C30 is preferable, C6-C20 is more preferable, C6-C12 is especially preferable, For example, phenyloxy, 1-naphthyloxy, 2-naphthyloxy, Examples include 2,4,6-trimethylphenyloxy and 4-biphenyloxy.
As said heteroaryloxy ligand, C1-C30 is preferable, C1-C20 is more preferable, C1-C12 is especially preferable, For example, pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy, etc. are mentioned. .
As said alkylthio ligand, C1-C30 is preferable, C1-C20 is more preferable, C1-C12 is especially preferable, For example, methylthio, ethylthio, etc. are mentioned.
As said arylthio ligand, C6-C30 is preferable, C6-C20 is more preferable, C6-C12 is especially preferable, For example, phenylthio etc. are mentioned.
As said heteroarylthio ligand, C1-C30 is preferable, C1-C20 is more preferable, C1-C12 is especially preferable, for example, pyridylthio, 2-benzimidazolylthio, 2- Examples include benzoxazolylthio and 2-benzthiazolylthio.
As said siloxy ligand, C1-C30 is preferable, C3-C25 is more preferable, C6-C20 is especially preferable, for example, a triphenylsiloxy group, a triethoxysiloxy group, a triisopropyl, for example Examples include a siloxy group.
As said aromatic hydrocarbon anion ligand, C6-C30 is preferable, for example, C6-C25 is more preferable, C6-C20 is especially preferable, For example, a phenyl anion, a naphthyl anion, an anthranyl anion Etc.
As said aromatic heterocyclic anion ligand, C1-C30 is preferable, C2-C25 is more preferable, C2-C20 is especially preferable, For example, a pyrrole anion, a pyrazole anion, a triazole anion, oxazole Anion, benzoxazole anion, thiazole anion, benzothiazole anion, thiophene anion, benzothiophene anion and the like can be mentioned.
Among these, azine ligand, hydroxyphenylazole ligand, aryloxy ligand, heteroaryloxy group, siloxy ligand, aromatic hydrocarbon anion ligand, aromatic heterocyclic anion ligand An azine ligand, a hydroxyphenylazole ligand, an aryloxy ligand, a siloxy ligand, an aromatic hydrocarbon anion ligand, and an aromatic heterocyclic anion ligand are more preferable.

  Examples of the host material include, for example, JP-A-2002-23576, JP-A-2004-214179, JP-A-2004-221106, JP-A-2004-221665, JP-A-2004-221068, JP-A-2004-327313, and the like. A metal complex is mentioned.

The host material is not particularly limited and may be appropriately selected depending on the intended purpose.For example, anthracene, triphenylene, pyrrole, indole, carbazole, azaindole, azacarbazole, pyrazole, imidazole, polyarylalkane, Pyrazoline, pyrazolone, phenylenediamine, arylamine, amino-substituted chalcone, styrylanthracene, fluorenone, hydrazone, stilbene, silazane, aromatic tertiary amine compound, styrylamine compound, aromatic dimethylidin compound, porphyrin compound, polysilane compound , Poly (N-vinylcarbazole), aniline copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, organic silanes, carbon films, derivatives thereof, etc. And the like.
Among these, indole derivatives, carbazole derivatives, azaindole derivatives, azacarbazole derivatives, aromatic tertiary amine compounds, and thiophene derivatives are preferable, and indole skeleton, carbazole skeleton, azaindole skeleton, azacarbazole skeleton, or aromatic in the molecule Those having an aromatic group tertiary amine skeleton are more preferred, and compounds having a carbazole skeleton are particularly preferred.
In addition, as the host material, a material obtained by substituting part or all of hydrogen of the host material with deuterium can be used.

  Specific examples of such a host material include, but are not limited to, the following compounds.

The content (concentration) of the host material is preferably 50% by mass to 92% by mass, more preferably 60% by mass to 92% by mass, and particularly preferably 70% by mass to 92% by mass in the light emitting layer. .
If the content is less than 50% by mass, the light emission efficiency may decrease, and if it exceeds 92% by mass, the voltage may increase and the light emission efficiency may decrease.

-Hole trap material-
As the hole trap material, in order to stably capture (trap) holes, the lowest empty orbit (LUMO level) and the highest occupied orbit (HOMO level) have the following formulas (3) and (4): It is preferable to satisfy.

| LUMO _h | <2.0 eV (3)
| HOMO _h | <5.4 eV (4)

However, LUMO _h represents the LUMO level of the hole trap material, and HOMO _h represents the HOMO level of the hole trap material.

  The highest occupied orbit (HOMO level) and the lowest unoccupied orbit (LUMO level) are all Gaussian 03 (Gaussian 03, Revision D.02, MJ Frisch), which is software for molecular orbit calculation manufactured by Gaussian. , Et al, Gaussian, Inc., Wallingford CT, 2004.) and calculated by performing structural optimization using B3LYP / 6-31G * as a keyword ( eV unit conversion value). The calculated value obtained by this method is highly correlated with the experimental value.

The lowest vacant orbit (LUMO level) of the hole trap material is preferably 0 eV to -2.0 eV, more preferably 0 eV to -1.75 eV, and particularly preferably 0 eV to -1.5 eV.
When the lowest unoccupied orbit is less than −2.0 eV or exceeds 0 eV, the driving voltage may increase and the light emission efficiency may decrease.
In addition, the highest occupied orbit (HOMO level) of the hole trap material is preferably −4.0 eV to −5.4 eV, more preferably −4.0 eV to −5.25 eV, and −4.0 eV to -5.0 eV is particularly preferred.
If the highest occupied orbit is less than -5.4 eV or exceeds -4.0 eV, the driving voltage may increase and the light emission efficiency may decrease.

  Examples of the hole trap material include US Pat. No. 6,303,238, US Pat. No. 6,097,147, WO00 / 57676, WO00 / 70655, WO01 / 08230, WO01 / 39234, WO01 / 41512 pamphlet, WO02 / 02714 pamphlet, WO02 / 15645 pamphlet, WO02 / 44189 pamphlet, WO05 / 19373 pamphlet, WO2004 / 108857 pamphlet, WO2005 / 042444 pamphlet, WO2005 / 042550 pamphlet, JP Japanese Patent Laid-Open Nos. 2001-247859, 2002-302671, 2002-117978, 20 No. 3-133044, JP-A No. 2002-235076, JP-A No. 2003-123982, JP-A No. 2002-170684, EP No. 12111257, JP-A No. 2002-226495, JP-A No. 2002-234894 JP-A-2001-247859, JP-A-2001-298470, JP-A-2002-173684, JP-A-2002-203678, JP-A-2002-203679, JP-A-2004-357791, JP 2006-93542, JP-A 2006-261623, JP-A 2006-256999, JP-A 2007-19462, JP-A 2007-84635, JP-A 2007-96259, US 2008 / No. 097033, Special Table 2 06-501144, JP 2005-220136, JP 2007-161673, JP-WO2003 / 084972 pamphlet, and the like phosphorescent compounds described in US 2006/0251923 Publication like.

Among these, the hole trap material is not particularly limited and can be appropriately selected according to the purpose. For example, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum, lanthanum, cerium, Examples of the complex include praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Among these, complexes containing rhenium, iridium, and platinum are more preferable, and complexes containing iridium (iridium-based complexes) are particularly preferable in terms of high luminous efficiency and long durability.
The hole-trapping material preferably does not contain an electron-withdrawing group such as a fluorine atom, a phenyl group, a trifluoromethyl group, a cyano group, or a cyano group in terms of hole-trapping properties.

Examples of the ligand of the complex include G.I. Wilkinson et al., Comprehensive Coordination Chemistry, Pergamon Press, 1987, H.C. Listed by Yersin, "Photochemistry and Photophysics of Coordination Compounds", published by Springer-Verlag, 1987, Akio Yamamoto, "Organic Metal Chemistry-Fundamentals and Applications-" It is done.
Examples of the ligand include a halogen ligand, an aromatic carbocyclic ligand, a nitrogen-containing heterocyclic ligand, a diketone ligand, a carboxylic acid ligand, an alcoholate ligand, and a carbon monoxide ligand. Examples thereof include ligands, isonitrile ligands, and cyano ligands. Among these, a nitrogen-containing heterocyclic ligand is particularly preferable.
As said halogen ligand, a chlorine ligand etc. are mentioned, for example.
Examples of the aromatic carbocyclic ligand include a cyclopentadienyl anion, a benzene anion, and a naphthyl anion.
Examples of the nitrogen-containing heterocyclic ligand include phenylpyridine, benzoquinoline, quinolinol, bipyridyl, phenanthroline, and the like.
Examples of the diketone ligand include acetylacetone.
Examples of the carboxylic acid ligand include an acetic acid ligand.
Examples of the alcoholate ligand include a phenolate ligand.

  The complex may have one transition metal atom in the compound, may be a so-called binuclear complex having two or more, and may contain different metal atoms at the same time. Among these, examples of the hole trap material include the following, but are not limited thereto.

The content (concentration) of the hole trap material is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 0.1% by mass to 5% by mass in the mass of the light emitting layer. .
If the content exceeds 10% by mass, the change in voltage and chromaticity after device deterioration may increase.

The thickness of the light emitting layer is preferably 15 nm to 120 nm, more preferably 30 nm to 100 nm, and particularly preferably 40 nm to 80 nm.
If the thickness is less than 15 nm, the light emission efficiency may decrease due to quenching by the metal electrode, and if it exceeds 120 nm, the driving voltage may be improved.

  As the light emitting layer, if necessary, a second light emitting layer may be further provided on the anode side so as to have a two-layer structure and emit white light.

<Anode>
The anode is not particularly limited as long as it has a function as an electrode for supplying holes to the light emitting layer. In view of the properties of the organic electroluminescent device of the present invention, at least one of the anode and the cathode is preferably transparent.
There is no restriction | limiting in particular about the shape, structure, size, etc. as said anode, According to the use and objective of an organic electroluminescent element, it can select suitably from well-known electrode materials.
Examples of the material constituting the anode include conductive metal oxides, metals, mixtures or laminates of these metals and conductive metal oxides, inorganic conductive substances, organic conductive materials, and these and ITO. Examples include laminates.
Examples of the conductive metal oxide include tin oxide doped with antimony and fluorine (ATO, FTO), tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO). Can be mentioned.
Examples of the metal include gold, silver, chromium, and nickel.
Examples of the inorganic conductive substance include copper iodide and copper sulfide.
Examples of the organic conductive material include polyaniline, polythiophene, and polypyrrole.

There is no restriction | limiting in particular as a formation method of the said anode, According to a well-known method, it can carry out, for example, a wet system, a chemical system, a physical system, etc. are mentioned.
Examples of the wet method include a printing method and a coating method.
Examples of the chemical method include CVD and plasma CVD.
Examples of the physical method include a vacuum deposition method, a sputtering method, and an ion plating method.

  In addition, when patterning is performed when forming the anode, it may be performed by chemical etching such as photolithography, or may be performed by physical etching using a laser or the like. It may be performed by sputtering or the like, or may be performed by a lift-off method or a printing method.

<Other layers>
In the organic electroluminescent device of the present invention, examples of the other layers include a hole transport layer, a hole injection layer, and a substrate.

-Hole injection layer, hole transport layer-
The hole injection layer and the hole transport layer are layers having a function of receiving holes from the anode or the anode side and transporting them to the cathode side. The hole injection layer and the hole transport layer may have a single layer structure or a multilayer structure composed of a plurality of layers having the same composition or different compositions.
The hole injecting material or hole transporting material used for these layers may be a low molecular compound, a high molecular compound, or an inorganic compound.
The hole injection material and the hole transport material are not particularly limited and may be appropriately selected depending on the purpose. For example, pyrrole derivatives, carbazole derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives , Polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styryl Examples include amine compounds, aromatic dimethylidin compounds, phthalocyanine compounds, porphyrin compounds, thiophene derivatives, organosilane derivatives, carbon, molybdenum trioxide, and the like. These may be used individually by 1 type and may use 2 or more types together.

The hole injection layer and the hole transport layer may contain an electron accepting dopant.
The electron-accepting dopant may be an inorganic compound or an organic compound as long as it is electron-accepting and has the property of oxidizing an organic compound.
There is no restriction | limiting in particular as said inorganic compound, According to the objective, it can select suitably, For example, a metal halide, a metal oxide, etc. are mentioned.
Examples of the metal halide include ferric chloride, aluminum chloride, gallium chloride, indium chloride, and antimony pentachloride.
Examples of the metal oxide include vanadium pentoxide and molybdenum trioxide.
The organic compound is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a compound having a nitro group, a halogen, a cyano group, a trifluoromethyl group or the like as a substituent, a quinone compound, an acid anhydride Compounds, fullerenes and the like.
These electron-accepting dopants may be used alone or in combination of two or more.

  The amount of the electron-accepting dopant used varies depending on the type of material, but is preferably 0.01% by mass to 50% by mass, and 0.05% by mass to 50% by mass with respect to the hole transport layer material or the hole injection material. % By mass is more preferable, and 0.1% by mass to 30% by mass is particularly preferable.

  The average thickness of the hole injection layer and the hole transport layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, and particularly preferably 10 nm to 100 nm.

-Board-
The organic electroluminescent element of the present invention is preferably provided on the substrate, and may be provided in such a manner that the anode and the substrate are in direct contact with each other, or provided with an intermediate layer interposed therebetween. Also good.
There is no restriction | limiting in particular as a material of the said board | substrate, According to the objective, it can select suitably, For example, an inorganic material, an organic material, etc. are mentioned.
Examples of the inorganic material include yttria stabilized zirconia (YSZ), alkali-free glass, soda lime glass, and the like.
Examples of the organic material include polyethylene terephthalate, polybutylene phthalate, polyethylene naphthalate, polystyrene, polycarbonate, polyethersulfone, polyarylate, polyimide, polycycloolefin, norbornene resin, and polychlorotrifluoroethylene.

There is no restriction | limiting in particular about the shape of the said board | substrate, a structure, a magnitude | size, It can select suitably according to the use, purpose, etc. of a light emitting element. In general, the shape of the substrate is preferably a plate shape.
The structure of the substrate may be a single layer structure, a laminated structure, may be formed of a single member, or may be formed of two or more members. . The substrate may be transparent or opaque, and if transparent, it may be colorless and transparent or colored and transparent.

The substrate may be provided with a moisture permeation preventing layer (gas barrier layer) on the front surface or the back surface.
Examples of the material of the moisture permeation preventing layer (gas barrier layer) include inorganic substances such as silicon nitride and silicon oxide.
The moisture permeation preventing layer (gas barrier layer) can be formed by, for example, a high frequency sputtering method.

-Protective layer-
The organic electroluminescent element of the present invention may be entirely protected by a protective layer.
The material contained in the protective layer is not particularly limited as long as it has a function of suppressing the entry of elements that promote element deterioration such as moisture and oxygen into the element. For example, In, Sn, Pb, Au, Cu, Ag, Al, Ti, Ni, MgO, SiO, SiO ₂ , Al ₂ O ₃ , GeO, NiO, CaO, BaO, Fe ₂ O ₃ , Y ₂ O ₃ , TiO ₂ , SiNx, SiNxOy, MgF ₂ , LiF, AlF ₃ , CaF ₂ , polyethylene, polypropylene, polymethyl methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoro Copolymer of ethylene, chlorotrifluoroethylene and dichlorodifluoroethylene, A copolymer obtained by copolymerizing a monomer mixture containing fluoroethylene and at least one comonomer; a fluorinated copolymer having a cyclic structure in the copolymer main chain; a water-absorbing substance having a water absorption of 1% or more; Examples include a moisture-proof substance of 0.1% or less.

  There is no restriction | limiting in particular as a formation method of the said protective layer, According to the objective, it can select suitably, For example, a vacuum evaporation method, sputtering method, reactive sputtering method, MBE (molecular beam epitaxy) method, cluster ion beam Examples thereof include an ion plating method, a plasma polymerization method (high frequency excitation ion plating method), a plasma CVD method, a laser CVD method, a thermal CVD method, a gas source CVD method, a coating method, a printing method, and a transfer method.

-Sealing container-
As an organic electroluminescent element of this invention, the whole may be sealed using the sealing container. Furthermore, a moisture absorbent or an inert liquid may be sealed in the space between the sealing container and the organic electroluminescent element.
The moisture absorbent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, barium oxide, sodium oxide, potassium oxide, calcium oxide, sodium sulfate, calcium sulfate, magnesium sulfate, phosphorus pentoxide, chloride Examples thereof include calcium, magnesium chloride, copper chloride, cesium fluoride, niobium fluoride, calcium bromide, vanadium bromide, molecular sieve, zeolite, and magnesium oxide.
There is no restriction | limiting in particular as said inert liquid, According to the objective, it can select suitably, For example, paraffins, liquid paraffins, a fluorine-type solvent, a chlorine-type solvent, silicone oil etc. are mentioned.

-Resin sealing layer-
As the organic electroluminescent device of the present invention, device performance deterioration due to oxygen or moisture from the atmosphere may be suppressed by sealing with a resin sealing layer.
The resin material for the resin sealing layer is not particularly limited and may be appropriately selected depending on the purpose. For example, acrylic resin, epoxy resin, fluorine resin, silicone resin, rubber resin, ester resin, etc. Is mentioned. Among these, an epoxy resin is particularly preferable from the viewpoint of moisture prevention function. Among the epoxy resins, a thermosetting epoxy resin or a photocurable epoxy resin is preferable.

  There is no restriction | limiting in particular as a formation method of the said resin sealing layer, According to the objective, it can select suitably, For example, the method of apply | coating a resin solution, the method of crimping | bonding or thermocompressing a resin sheet, vapor deposition, sputtering, etc. And a dry polymerization method.

(Layer structure of organic electroluminescence device)
FIG. 1 is a schematic view showing an example of the layer structure of the organic electroluminescent element of the present invention. As the organic electroluminescent element 10, an anode 2, a hole injection layer 3, a hole transport layer 4, a light emitting layer 5, and a cathode 6 formed on the substrate 1 are laminated in this order. The anode 2 and the cathode 8 are connected to each other via a power source.

  FIG. 2 is a schematic view showing an example of the layer structure of the organic electroluminescent element of the present invention. As the organic electroluminescent element 10, the anode 2, the hole injection layer 3, the hole transport layer 4, the second light emitting layer 51, the light emitting layer 5 and the cathode 6 formed on the substrate 1 are connected to this. It is laminated in order. The anode 2 and the cathode 8 are connected to each other via a power source.

(Use)
The organic electroluminescent device of the present invention is not particularly limited and may be appropriately selected according to the purpose. Display device, display, backlight, electrophotography, illumination light source, recording light source, exposure light source, reading light source, It can be suitably used for signs, signboards, interiors, optical communications, and the like.
As a method for making the organic EL display of a full color type, as described in, for example, “Monthly Display”, September 2000, pages 33 to 37, the three primary colors (blue (B), green (G), red light (R)), a three-color light emitting method in which organic EL elements that respectively emit light corresponding to red (R) are arranged on a substrate, and white light emission by an organic electroluminescent element for white light emission is divided into three primary colors through a color filter. A white method, a color conversion method that converts blue light emitted by an organic electroluminescent element for blue light emission into red (R) and green (G) through a fluorescent dye layer, and the like are known.
Moreover, as an organic electroluminescent element of this invention, a desired luminescent color can be obtained by using in combination several different luminescent colors obtained with the said hole trap material, the said electron transport phosphorescent material, etc. For example, when an organic electroluminescent element for blue, green, and red is used, a hole trap material having an emission peak near a desired wavelength and an electron transporting phosphorescent material may be contained in the light emitting layer. Note that in the case where the hole trapping material is a main light emission, the triplet excitation level of the hole trapping material may be made smaller than the triplet excitation level of the electron transporting phosphorescent material. In the case of main light emission, the triplet excitation level of the electron-transporting phosphorescent material may be made smaller than the triplet excitation level of the hole trap material.
Further, for example, when an organic electroluminescent element for white is used, as a hole trap material, a blue phosphorescent material having an emission peak at 420 nm to 500 nm, a green light emitting material having an emission peak at 500 nm to 570 nm, and 570 nm to 650 nm. You may make it contain the red luminescent material which has a luminescence peak in this.

  Further, for example, when an organic electroluminescent device for white is used, the concentration of the light emitting material that emits blue light in the light emitting layer may be adjusted to be high to cause the light emission associated with the association in the range of 500 nm to 650 nm. Even in the case of using associative light emission, as a hole trap material, a blue light emitting material having an emission peak at 420 nm to 500 nm, a green light emitting material having an emission peak at 500 nm to 570 nm, and a light emitting material at 570 nm to 650 nm A light emitting material that emits red light having a light emission peak may be included.

  Further, for example, when an organic electroluminescent device for white is used, a second light emitting layer is provided on the anode side of the light emitting layer, and the second light emitting layer emits green light having an emission peak at 500 nm to 570 nm, Alternatively, a light emitting material that emits red light having a light emission peak at 570 nm to 650 nm may be included. In this case, an example is shown in FIG. 2, and the organic electroluminescent element 10 includes an anode 2 formed on the substrate 1, a hole injection layer 3, a hole transport layer 4, and a second light emitting layer 51. The light emitting layer 5 and the cathode 6 are laminated in this order. The anode 2 and the cathode 8 are connected to each other via a power source.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
<Production of organic electroluminescence device>
A glass substrate having a thickness of 0.5 mm and a square of 2.5 cm was placed in a cleaning container, subjected to ultrasonic cleaning in 2-propanol, and then subjected to UV-ozone treatment for 30 minutes. The following layers were deposited on this glass substrate by vacuum deposition. In addition, the vapor deposition rate in the following examples and comparative examples is 0.2 nm / second unless otherwise specified. The deposition rate was measured using a quartz resonator. The thickness of each layer below was measured using a quartz resonator.
First, ITO (Indium Tin Oxide) was sputtered as a positive electrode on a glass substrate to a thickness of 70 nm.
Next, co-evaporation was performed so that the compound (TCTA) represented by the following structural formula was 70% by mass and MoO ₃ was 30% by mass to form a hole injection layer having a thickness of 30 nm on the anode (ITO). Made a film.

On the hole injection layer, a compound (TCTA) represented by the above structural formula was deposited as a hole transport layer so as to have a thickness of 10 nm.
The compound A represented by the following structural formula as the host material, the Pt complex A represented by the following structural formula as the electron transporting phosphorescent material, 80% by mass of the compound A with respect to the mass of the light emitting layer, and the Pt complex A A light emitting layer having a thickness of 60 nm was formed on the hole transport layer by co-evaporation so as to be 20% by mass.

Next, after depositing LiF as a cathode to a thickness of 1 nm on the light-emitting layer, a patterned mask (a mask having a light-emitting region of 2 mm × 2 mm) is placed so that the metal aluminum has a thickness of 100 nm. Vapor deposited.
The laminate produced as described above was put in a glove box substituted with argon gas, and sealed with a stainless steel sealing can and an ultraviolet curable adhesive (XNR5516HV, manufactured by Nagase Ciba Co., Ltd.). As described above, the blue organic electroluminescent element of Example 1 was produced.

(Evaluation)
The driving voltage, external quantum efficiency, voltage increase, and chromaticity change (Δ chromaticity) of the organic electroluminescent device of Example 1 produced were evaluated as follows.

<Drive voltage>
Using a source measure unit type 2400 manufactured by KEITHLEY, the voltage at the time of direct current application was measured.

<Measurement of external quantum efficiency (EQE)>
A direct current was applied to the organic electroluminescence device of Example 1 to emit light using a source measure unit 2400 type manufactured by KEITHLEY. The luminance at the time of light emission was measured using a luminance meter BM-8 manufactured by Topcon Corporation. The emission spectrum and emission wavelength were measured using a spectrum analyzer PMA-11 manufactured by Hamamatsu Photonics. Based on these values, the external quantum efficiency was calculated by the brightness conversion method.

<Voltage increase (ΔV)>
The organic electroluminescent element of Example 1 was driven at a constant current of 20 mA / cm ² until the luminance was reduced by half, and the voltage increase (ΔV) from the initial stage until the luminance was reduced to half was measured.

<Chromaticity change (Δ chromaticity)>
The light emission spectrum at the initial stage and half the luminance of the organic electroluminescence device of Example 1 was measured with an emission spectrum measurement system (ELS1500) manufactured by Shimadzu Corporation, and the x value and the y value were obtained from the obtained spectrum using the CIE color system. Was calculated.
Chromaticity change (delta chromaticity) is, x values in the case of when the brightness half from the initial current density 20 mA / cm ^2, the amount of change in y value ([Delta] x, [Delta] y) from the delta chroma = (Δy ² + Δx ^{2) 0.5} was calculated.

(Example 2)
<Production of organic electroluminescence device>
In Example 1, the blue organic electroluminescent element of Example 2 was obtained in the same manner as in Example 1 except that Pt complex A, which is an electron transporting phosphorescent material, was replaced with Pt complex B represented by the following structural formula. Was made.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 3)
<Production of organic electroluminescence device>
In Example 1, the blue organic electroluminescent element of Example 3 was produced in the same manner as Example 1 except that Compound A as the host material was changed to Compound B represented by the following structural formula.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 4)
<Production of organic electroluminescence device>
In Example 1, the green organic electroluminescent element of Example 4 was produced in the same manner as in Example 1 except that the light emitting layer was replaced with the light emitting layer produced as follows.
-Production of light emitting layer-
Compound A represented by the structural formula as a host material, Pt complex A represented by the structural formula as an electron transporting phosphorescent material, and Pt complex B represented by the structural formula as a hole trapping material, A light emitting layer having a thickness of 60 nm was formed on the hole transport layer by co-evaporation so that Compound A was 77% by mass, Pt complex A was 20% by mass, and Pt complex B was 3% by mass with respect to the mass of the light emitting layer. Filmed.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 5)
<Production of organic electroluminescence device>
In Example 1, the green organic electroluminescent element of Example 5 was produced in the same manner as Example 1 except that the light emitting layer was replaced with the light emitting layer produced as follows.
-Production of light emitting layer-
A compound A represented by the above structural formula as a host material, a Pt complex A represented by the above structural formula as an electron transporting phosphorescent material, and an Ir complex B represented by the following structural formula as a hole trap material, a light emitting layer A light emitting layer having a thickness of 60 nm was formed on the hole transport layer by co-evaporation so that the compound A was 77% by mass, the Pt complex A was 20% by mass, and the Ir complex B was 3% by mass with respect to the mass of .
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 6)
<Production of organic electroluminescence device>
In Example 5, the content of the compound A as the host material was changed from 77% by mass to 70% by mass, and the content of the Ir complex B was changed from 3% by mass to 10% by mass. Thus, a green organic electroluminescent element of Example 6 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 7)
<Production of organic electroluminescence device>
In Example 5, the same procedure as in Example 5 was performed except that Ir complex B represented by the above structural formula was replaced with Ir complex C represented by the following structural formula as the hole trap material. Then, a red organic electroluminescent element of Example 7 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 8)
<Production of organic electroluminescence device>
In Example 1, the content of compound A as the host material was changed from 80% by mass to 95% by mass, and the content of Pt complex A was changed from 20% by mass to 5% by mass. Thus, a blue organic electroluminescent element of Example 8 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

Example 9
<Production of organic electroluminescence device>
In Example 1, the content of the compound A as the host material was changed from 80% by mass to 60% by mass, and the content of the Pt complex B as the electron transporting phosphorescent material was changed from 20% by mass to 40% by mass. In the same manner as in Example 1, the blue organic electroluminescent element of Example 8 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 10)
<Production of organic electroluminescence device>
In Example 3, the green organic electroluminescent element of Example 10 was produced in the same manner as in Example 3, except that Compound B as the host material was changed to Compound D represented by the following structural formula.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 11)
<Production of organic electroluminescence device>
A green organic electroluminescent element of Example 11 was produced in the same manner as in Example 3 except that Compound B as the host material was changed to Compound E represented by the following structural formula.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Comparative Example 1)
<Production of organic electroluminescence device>
In Example 1, a blue organic electroluminescence device of Comparative Example 1 was produced in the same manner as in Example 1 except that the light emitting layer, the electron transport layer and the cathode were produced as follows.
-Production of light emitting layer-
The compound A represented by the above structural formula as the host material, the Pt complex A represented by the above structural formula as the electron transporting phosphorescent material, 80% by mass of the compound A based on the mass of the light emitting layer, and the Pt complex A A light emitting layer having a thickness of 30 nm was formed on the hole transport layer by co-evaporation so as to be 20% by mass.
-Preparation of electron transport layer-
On the light-emitting layer, Alq (tris (8-quinolinol) aluminum complex) was deposited as an electron transport layer so as to have a thickness of 30 nm.
-Production of cathode-
On the electron transport layer, LiF was deposited as a cathode to a thickness of 1 nm, and then a patterned mask (a mask having a light emitting area of 2 mm × 2 mm) was placed, and metal aluminum was deposited to a thickness of 100 nm. did.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Comparative Example 2)
<Production of organic electroluminescence device>
In Example 1, the same procedure as in Example 1 was performed except that the Pt complex A represented by the above structural formula was replaced with a hole transporting Ir complex B represented by the following structural formula as an electron transporting phosphorescent material. The blue organic electroluminescent element of Comparative Example 2 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

Table 1 shows the calculation results of the HOMO levels and LUMO levels of the materials used in Examples 1 to 11 and Comparative Examples 1 and 2. Note that the HOMO level and LUMO level are measured by Gaussian's molecular orbital calculation software (Gaussian 03 (Gaussian 03, Revision D. 02, MJ Frisch, et al, Gaussian, Inc., Wallingford CT, 2004). .)) And calculated by performing structure optimization using B3LYP / 6-31G * as a keyword.

Tables 2 and 3 show the evaluation results of the driving voltage, the external quantum efficiency, ΔV, and the chromaticity change (Δ chromaticity), and the element configurations of the organic electroluminescent elements prepared in Examples 1 to 11 and Comparative Examples 1 and 2. Shown in
(In the table, “wt%” represents mass%. Voltage and EQE (external quantum efficiency) are values at a current density of 10 mA / cm ^2. ΔV and Δ chromaticity are current densities of 20 mA / cm ^2. (The change in performance at a current density of 20 mA / cm ² when the luminance is halved at a constant current of.)
(In the table, “wt%” represents mass%. Voltage and EQE (external quantum efficiency) are values at a current density of 10 mA / cm ^2. ΔV and Δ chromaticity are current densities of 20 mA / cm ^2. (The change in performance at a current density of 20 mA / cm ² when the luminance is halved at a constant current of.)

  Compared with Comparative Examples 1 and 2, Examples 1 to 11 achieve a reduction in drive voltage, a voltage increase after element degradation due to long-time driving, and suppression of chromaticity change. This is presumably because the addition of the electron transporting phosphorescent material stabilizes the electron injection property from the cathode and suppresses the change in the light emission position. It can also be seen that the addition of an electron transporting phosphorescent material or hole trapping material having an electron withdrawing group significantly improves stability and significantly suppresses chromaticity change.

(Example 12)
<Production of organic electroluminescence device>
In Example 1, a blue organic electroluminescent element was produced in the same manner as in Example 1 except that Pt complex A was replaced with Pt complex C represented by the following structural formula as the electron transporting phosphorescent material.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 13)
<Production of organic electroluminescence device>
In Example 12, a blue organic electroluminescent element was produced in the same manner as in Example 12 except that the Pt complex C, which is an electron transporting phosphorescent material, was replaced with a Pt complex D represented by the following structural formula.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 14)
<Production of organic electroluminescence device>
In Example 12, a blue organic electroluminescence device of Example 14 was produced in the same manner as Example 12 except that Compound A as the host material was replaced with Compound B represented by the above structural formula.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 15)
<Production of organic electroluminescence device>
In Example 12, the green organic electroluminescent element of Example 15 was produced in the same manner as Example 12 except that the light emitting layer was replaced with the light emitting layer produced as follows.
-Production of light emitting layer-
Compound A represented by the structural formula as a host material, Pt complex C represented by the structural formula as an electron transporting phosphorescent material, and Pt complex D represented by the structural formula as a hole trapping material, A light emitting layer having a thickness of 60 nm is formed on the hole transport layer by co-evaporation so that Compound A is 77% by mass, Pt complex C is 20% by mass, and Pt complex D is 3% by mass with respect to the mass of the light emitting layer. Filmed.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 16)
<Production of organic electroluminescence device>
In Example 1, the green organic electroluminescent element of Example 16 was produced in the same manner as in Example 1 except that the light emitting layer was replaced with the light emitting layer produced as follows.
-Production of light emitting layer-
A compound A represented by the above structural formula as a host material, a Pt complex C represented by the above structural formula as an electron transporting phosphorescent material, and an Ir complex D represented by the following structural formula as a hole trap material, a light emitting layer A light emitting layer having a thickness of 60 nm was formed on the hole transport layer by co-evaporation so that the compound A was 77% by mass, the Pt complex C was 20% by mass, and the Ir complex D was 3% by mass with respect to the mass of .
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 17)
<Production of organic electroluminescence device>
In Example 16, the content of Compound A as the host material was changed from 77% by mass to 70% by mass, and the content of Ir complex D was changed from 3% by mass to 10% by mass. Thus, a green organic electroluminescent element of Example 17 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 18)
<Production of organic electroluminescence device>
In Example 12, a white organic electroluminescent element of Example 18 was produced in the same manner as Example 12 except that the light emitting layer was replaced with the light emitting layer produced as follows.
-Production of light emitting layer-
Compound A represented by the above structural formula as a host material, Pt complex C represented by the above structural formula as an electron transporting phosphorescent material, and Ir complex A represented by the following structural formula as a hole trap material and the following structural formula The compound A is 79.85% by mass, the Pt complex C is 20% by mass, the Ir complex A is 0.1% by mass, and the Ir complex C is 0.05% by mass. A light emitting layer having a thickness of 60 nm was formed on the hole transport layer by co-evaporation so as to be in mass%.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 19)
<Production of organic electroluminescence device>
In Example 18, the content of the compound A as the host material was changed from 79.85% by mass to 59.85% by mass, and the content of the Pt complex C was changed from 20% by mass to 40% by mass. In the same manner as in Example 18, a white organic electroluminescent element of Example 19 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 20)
<Production of organic electroluminescence device>
In Example 12, the content of the compound A as the host material is 80% by mass to 95% by mass, and the electron transporting phosphorescent material is a Pt complex C having a content of 20% by mass and containing 5% by mass. A blue organic electroluminescent element of Example 20 was produced in the same manner as in Example 1 except that the Pt complex B represented by the structural formula was used.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 21)
<Production of organic electroluminescence device>
In Example 12, the content of the compound A as the host material is 80% by mass to 60% by mass, and the electron transporting phosphorescent material is a Pt complex C having a content of 20% by mass and the content is 40% by mass. A blue organic electroluminescent element of Example 21 was produced in the same manner as in Example 12 except that the Pt complex A represented by the structural formula was used.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Comparative Example 3)
<Production of organic electroluminescence device>
An organic electroluminescent device of Comparative Example 3 was produced in the same manner as in Comparative Example 1, except that Pt complex A as the electron transporting phosphorescent material was replaced with Pt complex C represented by the above structural formula in Comparative Example 1. did.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Comparative Example 4)
<Production of organic electroluminescence device>
In Comparative Example 2, the blue color of Comparative Example 4 was the same as Comparative Example 2 except that the Ir complex B represented by the structural formula was replaced with the hole-transporting Ir complex D represented by the following structural formula. An organic electroluminescent element was prepared.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

Table 4 shows the calculation results of the HOMO levels and LUMO levels of the materials used in Examples 12 to 21 and Comparative Examples 3 to 4. The HOMO level and the LUMO level are calculated by molecular orbital calculation software (Gaussian 03 (Gaussian 03, Revision D.02, MJ Frisch, et al, Gaussian, Inc., Wallingford CT, 2004.) manufactured by Gaussian, USA. Calculated by using B3LYP / 6-31G * as a keyword and calculating the structure.

Tables 5 and 6 show the evaluation results of drive voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity), and the device configurations of the organic electroluminescent devices prepared in Examples 12 to 21 and Comparative Examples 3 to 4. Shown in
(In the table, “wt%” represents mass%. Voltage and EQE (external quantum efficiency) are values at a current density of 10 mA / cm ^2. ΔV and Δ chromaticity are current densities of 20 mA / cm ^2. (This is a change in performance at a current density of 20 mA / cm ² when the luminance is halved at a constant current of.)
(In the table, “wt%” represents mass%. Voltage and EQE (external quantum efficiency) are values at a current density of 10 mA / cm ^2. ΔV and Δ chromaticity are current densities of 20 mA / cm ^2. (This is a change in performance at a current density of 20 mA / cm ² when the luminance is halved at a constant current of.)

  In Examples 12 to 21, as compared with Comparative Examples 3 to 4, the driving voltage is reduced, the voltage is increased after element deterioration due to long-time driving, and the chromaticity change is suppressed. This is presumably because the addition of the electron transporting phosphorescent material stabilizes the electron injection property from the cathode and suppresses the change in the light emission position. It can also be seen that the addition of an electron transporting phosphorescent material or hole trapping material having an electron withdrawing group significantly improves stability and significantly suppresses chromaticity change.

(Example 22)
<Production of organic electroluminescence device>
In Example 1, the blue organic electroluminescent element of Example 22 was produced in the same manner as in Example 1 except that the light emitting layer and the cathode were produced as follows.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.
-Production of light emitting layer-
The compound C represented by the following structural formula as the host material, the Ir complex F represented by the following structural formula as the electron transporting phosphorescent material, 80% by mass of the compound C based on the mass of the light emitting layer, A light emitting layer having a thickness of 60 nm was formed on the hole transport layer by co-evaporation so as to be 20% by mass.
-Production of cathode-
After depositing Cs ₂ CO ₃ as a cathode to a thickness of 1 nm on the light emitting layer, a patterned mask (a mask having a light emitting area of 2 mm × 2 mm) is installed, and metallic aluminum is made to have a thickness of 100 nm. Vapor deposited.

(Example 23)
<Production of organic electroluminescence device>
In Example 22, as the electron-transporting phosphorescent material, except that the Ir complex F represented by the above structural formula was replaced with the electron-transporting Ir complex G represented by the following structural formula, the same procedure as in Example 22 was performed. Then, a blue organic electroluminescent device of Example 23 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 24)
<Production of organic electroluminescence device>
In Example 22, the blue organic electroluminescent element of Example 24 was produced in the same manner as in Example 22 except that the compound C as the host material was replaced with the compound A represented by the above structural formula.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 25)
<Production of organic electroluminescence device>
In Example 22, the blue organic electroluminescent element of Example 25 was produced in the same manner as in Example 22 except that the light emitting layer was replaced with the light emitting layer produced as follows.
-Production of light emitting layer-
A compound C represented by the above structural formula as a host material, an Ir complex F represented by the above structural formula as an electron transporting phosphorescent material, and a Pt complex B represented by the above structural formula as a hole trap material, a light emitting layer A light emitting layer having a thickness of 60 nm was formed on the hole transport layer by co-evaporation so that the compound A was 77% by mass, the Pt complex F was 20% by mass, and the Pt complex B was 3% by mass with respect to the mass of .
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 26)
<Production of organic electroluminescence device>
In Example 25, the content of Compound C as a host material was changed from 77% by mass to 70% by mass, and the content of Ir complex F was changed from 3% by mass to 10% by mass. Thus, a green organic electroluminescent element of Example 26 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 27)
<Production of organic electroluminescence device>
In Example 22, a white organic electroluminescent element of Example 27 was produced in the same manner as in Example 22 except that the light emitting layer was replaced with the light emitting layer produced as follows.
-Production of light emitting layer-
A compound C represented by the above structural formula as a host material, an Ir complex F represented by the above structural formula as an electron transporting phosphorescent material, and an Ir complex B represented by the above structural formula as a hole trap material, a light emitting layer A light emitting layer having a thickness of 60 nm was formed on the hole transport layer by co-evaporation so that Compound C was 70% by mass, Ir Complex F was 20% by mass, and Ir Complex B was 10% by mass with respect to the mass of .
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 28)
<Production of organic electroluminescence device>
In Example 22, the white organic electroluminescent element of Example 28 was produced in the same manner as in Example 22 except that the light emitting layer was replaced with the light emitting layer produced as follows.
-Production of light emitting layer-
Compound C represented by the structural formula as a host material, Ir complex F represented by the structural formula as an electron-transporting phosphorescent material, Ir complex B represented by the structural formula as a hole trap material, and the structural formula In the Ir complex C represented by the formula, the compound C is 79.85% by mass, the Ir complex F is 20% by mass, the Ir complex B is 0.1% by mass, and the Ir complex C is 0.05% by mass of the light emitting layer. A light emitting layer having a thickness of 60 nm was formed on the hole transport layer by co-evaporation so as to be in mass%.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 29)
<Production of organic electroluminescence device>
In Example 28, the content of Compound C as a host material was changed from 79.85% by mass to 59.85% by mass, and the content of Ir complex F was changed from 20% by mass to 40% by mass. In the same manner as in Example 28, a blue organic electroluminescent element of Example 29 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 30)
<Production of organic electroluminescence device>
In Example 22, the content of compound C as a host material was changed from 80% by mass to 95% by mass, and the content of Ir complex F was changed from 20% by mass to 5% by mass. Thus, a blue organic electroluminescent element of Example 30 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 31)
<Production of organic electroluminescence device>
In Example 22, the content of compound C as a host material was changed from 80% by mass to 60% by mass, and the content of Ir complex F was changed from 20% by mass to 40% by mass. Thus, a blue organic electroluminescent element of Example 31 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Example 32)
<Production of organic electroluminescence device>
In Example 22, the blue organic electroluminescent element of Example 32 was produced in the same manner as in Example 22 except that the light emitting layer and the cathode were produced as follows.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.
-Production of light emitting layer-
The compound A represented by the above structural formula as the host material, the Pt complex A represented by the above structural formula as the electron transporting phosphorescent material, 80% by mass of the compound A based on the mass of the light emitting layer, and the Pt complex A A light emitting layer having a thickness of 60 nm was formed on the hole transport layer by co-evaporation so as to be 20% by mass.
-Production of cathode-
On the light emitting layer, a mask patterned as a cathode (a mask having a light emitting area of 2 mm × 2 mm) was placed, and metal aluminum was deposited so as to have a thickness of 100 nm.

(Comparative Example 5)
<Production of organic electroluminescence device>
In Comparative Example 1, the Pt complex A represented by the above structural formula was replaced with the electron transporting Ir complex F represented by the above structural formula as an electron transporting phosphorescent material, and the cathode LiF was replaced with Cs ₂ CO ₃ . Except that, the organic electroluminescent element of Comparative Example 5 was produced in the same manner as Comparative Example 1.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Comparative Example 6)
<Production of organic electroluminescence device>
In Comparative Example 2, the Ir complex B represented by the above structural formula as the hole trapping material is replaced with a hole transporting Ir complex E represented by the above structural formula, and the cathode LiF is replaced with Cs ₂ CO ₃ . A blue organic electroluminescent element of Comparative Example 6 was produced in the same manner as in Comparative Example 2 except that.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

(Comparative Example 7)
<Production of organic electroluminescence device>
In Example 32, the Pt complex A represented by the above structural formula was replaced with the hole transporting Ir complex B represented by the above structural formula as an electron transporting phosphorescent material, in the same manner as in Example 32. A blue organic electroluminescent element of Comparative Example 7 was produced.
In the same manner as in Example 1, the driving voltage, external quantum efficiency, ΔV, and chromaticity change (Δ chromaticity) of the produced organic electroluminescence device were evaluated.

Table 7 shows the calculation results of the HOMO levels and LUMO levels of the materials used in Examples 22 to 32 and Comparative Examples 5 to 7. The HOMO level and the LUMO level are obtained from Gaussian's molecular orbital calculation software (Gaussian 03 (Gaussian 03, Revision D.02, MJ Frisch, et al, Gaussian, Inc., Wallingford CT, 2004.). Calculated by using B3LYP / 6-31G * as a keyword and calculating the structure.

Tables 8 and 9 show the evaluation results of the driving voltage, the external quantum efficiency, ΔV, and the chromaticity change (Δ chromaticity), and the element configurations of the organic electroluminescent devices prepared in Examples 22 to 32 and Comparative Examples 5 to 7. Shown in
(In the table, “wt%” represents mass%. Voltage and EQE (external quantum efficiency) are values at a current density of 10 mA / cm ^2. ΔV and Δ chromaticity are current densities of 20 mA / cm ^2. (This is a change in performance at a current density of 20 mA / cm ² when the luminance is halved at a constant current of.)
(In the table, “wt%” represents mass%. Voltage and EQE (external quantum efficiency) are values at a current density of 10 mA / cm ^2. ΔV and Δ chromaticity are current densities of 20 mA / cm ^2. (This is a change in performance at a current density of 20 mA / cm ² when the luminance is halved at a constant current of.)

  In Examples 22 to 32, as compared with Comparative Examples 5 to 7, a reduction in driving voltage, a voltage increase after device deterioration due to long-time driving, and a suppression of chromaticity change are realized. This is presumably because the addition of the electron transporting phosphorescent material stabilizes the electron injection property from the cathode and suppresses the change in the light emission position. It can also be seen that the addition of an electron transporting phosphorescent material or hole trapping material having an electron withdrawing group significantly improves stability and significantly suppresses chromaticity change.

  The organic electroluminescent device of the present invention has improved durability and light emission efficiency, and has a small change in light emission position and can suppress a change in chromaticity due to an electric current. For example, the display device, display, backlight, electrophotography, illumination It is suitably used for a light source, a recording light source, an exposure light source, a reading light source, a sign, a signboard, interior, optical communication, and the like.

DESCRIPTION OF SYMBOLS 10 Organic electroluminescent element 1 Board | substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 51 2nd light emitting layer 6 Cathode

Claims (6)

An anode, a cathode, and a light-emitting layer that is laminated adjacent to the cathode and includes an electron-transporting phosphorescent material;
The electron transporting phosphorescent material to satisfy the relationship of formula (1) and the following formula (2),
The organic light-emitting device , wherein the light-emitting layer contains 10% by mass or less of a hole trap material that satisfies a relationship of the following formulas (3) and (4) .
| LUMO _e |> 1.5 eV (1)
| HOMO _e |> 5.4 eV (2)
| LUMO _h | <2.0 eV (3)
| HOMO _h | <5.4 eV (4)
However, LUMO _e represents the LUMO level of the electron transporting phosphorescent material, and HOMO _e represents the HOMO level of the electron transporting phosphorescent material. LUMO _h represents the LUMO level of the hole trap material, and HOMO _h represents the HOMO level of the hole trap material.   The organic electroluminescent element according to claim 1, wherein the cathode has an insulating thin film on the light emitting layer side.   The organic electroluminescent element according to claim 1, wherein the electron-transporting phosphorescent material contains an electron-withdrawing group.   The organic electroluminescent element according to claim 3, wherein the electron withdrawing group is at least one selected from a fluorine atom, a trifluoromethyl group, and a cyano group. The organic electroluminescent element according to claim 1, wherein the hole trap material is an iridium-based complex. The organic electroluminescent element according to claim 1, wherein the electron transporting phosphorescent material is a platinum complex.