JP5890504B2 - Organic electroluminescence device - Google Patents

Description

  The present invention relates to an organic electroluminescent element (hereinafter also referred to as “organic electroluminescence element”, “organic EL element”, etc.).

  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. A stacked organic electroluminescent element has an anode, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode as a basic configuration, and the light-emitting layer functions as the hole transport layer or the electron transport layer. May also be used.

Such an organic electroluminescent device has a problem that when the current density is changed, the balance of carriers is lost, the luminous efficiency and durability are lowered, and the chromaticity is changed. Among them, the main factor causing the change in chromaticity is the influence of optical interference due to the change in the light emission position. Due to optical interference, the closer to the electrode, the bluer the color, and the farther away from the electrode, the stronger the red color. This effect becomes more prominent as the thickness of the light emitting layer increases.
In order to solve the above-mentioned problem, for example, Patent Document 1 discloses an organic electroluminescent element in which an organic layer including a light emitting layer is sandwiched between a pair of electrodes, and the light emitting layer has at least an Ea value (electron affinity) or an Ip value. 2 types of light emitting materials having different (ionization potentials) and at least one type of host material, and the concentration of the light emitting material having the larger Ea value or Ip value of the two types of light emitting materials in the light emitting layer. The concentration of the light emitting material of the light emitting layer that gradually decreases from the cathode side to the anode side of the light emitting layer and has the smaller Ea value or Ip value of the two types of light emitting materials from the anode side to the cathode. An organic electroluminescent element that gradually decreases toward the side is proposed.
Patent Document 2 discloses a light emitting element having a light emitting region between an anode and a cathode, wherein the light emitting region includes a substance that contributes to light emission and a medium containing the substance, and the light emitting element. There has been proposed a light-emitting element having a structure in which the substance contributing to the above has a concentration distribution substantially continuously from the anode side to the cathode side of the light-emitting region.
However, the concentration control of the luminescent material described in the prior art document is intended to improve the light emission efficiency and durability by carrier balance control, and does not consider suppression of chromaticity change due to current density change. It was.

  Therefore, the suppression of color shift due to optical interference due to a change in doping concentration can suppress a change in chromaticity when a current density changes, and it is desired to provide an organic electroluminescent device with improved luminous efficiency and durability. Currently.

JP 2009-55010 A JP 2001-189193 A

  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 suppressing a change in chromaticity when a current density is changed and having improved luminous efficiency and durability.

  As a result of intensive studies by the present inventors in order to solve the above problems, the present invention includes two or more kinds of light emitting materials having different concentration ratios, that is, light emission wavelength peaks, which are different in emission spectrum, and has a short wavelength side peak light emitting material. By changing the concentration ratio of the concentration B of the light emitting material at the peak of the long wavelength with respect to the concentration A of the above, or the concentration ratio of the aggregate to the monomer in the light emitting layer, the change in the emission spectrum due to optical interference can be suppressed. It has been found that an organic electroluminescent device can be obtained in which the change in chromaticity when the current density changes can be suppressed and the luminous efficiency and durability are improved.

The present invention is based on the above findings by the present inventors, and means for solving the above problems are as follows. That is,
<1> An organic electroluminescent device comprising at least a light emitting layer between an anode and a cathode,
The light emitting layer includes two or more kinds of light emitting materials having different light emission wavelength peaks, and the concentration ratio of the concentration B of the light emitting material of the long wavelength side peak to the concentration A of the light emitting material of the short wavelength side peak [(B / A) × 100 Is gradually increased as it approaches the cathode,
The organic electroluminescence device, wherein the concentration ratio [(B / A) × 100] is 10% or less.
<2> The organic electroluminescence device according to <1>, wherein the concentration of the light emitting material having a long wavelength side peak is constant, and the concentration of the light emitting material having a short wavelength side peak decreases as it approaches the cathode.
<3> The organic electroluminescence device according to <1>, wherein the concentration of the light emitting material having a long wavelength side peak increases as the cathode approaches the cathode, and the concentration of the light emitting material having a short wavelength side peak is constant.
<4> The organic electroluminescence device according to <1>, wherein the concentration of the light emitting material having a long wavelength side peak increases as it approaches the cathode, and the concentration of the light emitting material having a short wavelength side peak decreases as it approaches the cathode.
<5> When the ratio of the concentration of the light emitting material of the long wavelength side peak to the concentration of the light emitting material of the short wavelength side peak is a on the cathode side of the light emitting layer and b on the anode side of the light emitting layer, It is an organic electroluminescent element in any one of said <1> to <4> which satisfy | fills b> 1.05.
<6> An organic electroluminescent device comprising at least a light emitting layer between an anode and a cathode,
The light-emitting layer contains a light-emitting material, and the light-emitting material has a different emission wavelength peak between the monomer and the aggregate,
The concentration ratio of the aggregate to the monomer concentration (aggregate concentration / monomer concentration) gradually increases as the cathode approaches.
The organic electroluminescent element is characterized in that an intensity ratio [(D / C) × 100] of the integrated spectral intensity D of the aggregate to the integrated spectral intensity C of the monomer is 20% or more.
<7> The organic electroluminescence device according to <6>, wherein the concentration of the aggregate of the long wavelength side peak is constant, and the concentration of the monomer of the short wavelength side peak decreases as it approaches the cathode.
<8> The organic electroluminescence device according to <6>, wherein the concentration of the aggregate of the long wavelength side peak increases as it approaches the cathode, and the concentration of the monomer of the short wavelength side peak is constant.
<9> The organic electroluminescence device according to <6>, wherein the concentration of the aggregate of the long wavelength side peak increases as it approaches the cathode, and the concentration of the monomer of the short wavelength side peak decreases as it approaches the cathode. .
<10> When the ratio of the concentration of the long wavelength side peak aggregate to the concentration of the short wavelength side peak monomer is a on the cathode side of the light emitting layer and b on the anode side of the light emitting layer, The organic electroluminescence device according to any one of <6> to <9>, wherein /b>1.05 is satisfied.
<11> The organic electroluminescent element according to any one of <1> to <10>, wherein the light emitting layer has a thickness of 20 nm or more.
<12> The organic electroluminescent element according to any one of <1> to <11>, wherein the cathode is a reflective electrode and the anode is a transparent electrode.
<13> The organic electroluminescent element according to any one of <1> to <11>, wherein the cathode is a reflective electrode and the anode is a transflective electrode.
<14> The organic electroluminescent element according to any one of <1> to <13>, wherein the light emitting material is a phosphorescent material.

  According to the present invention, it is an object to provide an organic electroluminescent device that can solve the conventional problems, can suppress a change in chromaticity when a current density changes, and has improved luminous efficiency and durability.

FIG. 1 is a schematic view showing an example of the organic electroluminescent element of the present invention. 2 is a diagram showing an emission spectrum of Example 1. FIG. FIG. 3 is a diagram showing an emission spectrum of Comparative Example 1. FIG. 4 is a diagram showing an emission spectrum of Example 2. FIG. 5 is a diagram showing an emission spectrum of Comparative Example 2. 6 shows the emission spectrum of Example 3. FIG. FIG. 7 is a graph showing an emission spectrum of Example 4. FIG. 8 is a graph showing an emission spectrum of Example 5. FIG. 9 is a diagram showing an emission spectrum of Comparative Example 5. 10 shows the emission spectrum of Example 6. FIG. FIG. 11 is a diagram showing an emission spectrum of Comparative Example 6. 12 shows the emission spectrum of Example 7. FIG. FIG. 13 is a diagram showing an emission spectrum of Comparative Example 7. FIG. 14 is a graph showing an emission spectrum of Example 8. FIG. 15 is a diagram showing an emission spectrum of Comparative Example 8. FIG. 16 is a diagram showing an emission spectrum of Example 9. FIG. 17 is a diagram showing an emission spectrum of Comparative Example 9.

(Organic electroluminescence device)
It preferably has at least a light emitting layer between the anode and the cathode, and preferably has an electron transport layer, an electron injection layer, a hole injection layer, a hole transport layer, a hole block layer, and an electron block layer. Depending on the, other configurations may be provided.

  In the organic electroluminescence device of the present invention, in the first embodiment, the light emitting layer contains two or more kinds of light emitting materials having different light emission wavelength peaks, and the light emission of the long wavelength side peak with respect to the concentration A of the light emitting material of the short wavelength side peak The concentration ratio [(B / A) × 100] of the concentration B of the material gradually increases as it approaches the cathode (reflection electrode), and the concentration ratio [(B / A) × 100] is 10% or less. .

The light emitting layer includes two or more light emitting materials having different emission wavelength peaks. Thereby, the change in the emission spectrum due to optical interference can be suppressed by changing the concentration ratio of two or more kinds of light emitting materials having different emission spectra in the light emitting layer.
As the two or more kinds of light emitting materials having different emission wavelength peaks, those that become white by mixing light emitting materials of a plurality of colors are preferable, and three colors of red (R), green (G), and blue (B) are used. It is more preferable to use the light emitting material.

The concentration ratio [(B / A) × 100] of the concentration B of the light emitting material of the long wavelength side peak to the concentration A of the light emitting material of the short wavelength side peak gradually increases as the cathode (reflecting electrode) is approached. Thereby, the position dependence of the influence of optical interference is reduced, and the chromaticity change at the time of a current density change can be suppressed.
Examples of the method of gradually increasing the concentration ratio [(B / A) × 100] as it approaches the cathode include a method of changing the deposition rate ratio of each component as it approaches the cathode.

The concentration ratio [(B / A) × 100] is 10% or less, preferably 0.1% to 2%.
When the concentration ratio [(B / A) × 100] exceeds 10%, only the long wavelength peak component may be emitted.
Here, the concentration A of the light emitting material having the short wavelength side peak and the concentration B of the light emitting material having the long wavelength side peak can be measured by, for example, the deposition rate of each material relative to the deposition rate of the host material.

The concentration of the light emitting material of the long wavelength side peak is constant, and the concentration of the light emitting material of the short wavelength side peak decreases as it approaches the cathode (reflecting electrode). Modulation is preferable in that the position dependency of the influence of optical interference is reduced, and the change in chromaticity when the current density changes can be suppressed.
The concentration of the light emitting material at the long wavelength side peak increases as it approaches the cathode (reflecting electrode), and the concentration of the light emitting material at the short wavelength side peak is constant. This is preferable in that the position dependency of the influence of optical interference is reduced by this modulation, and the change in chromaticity when the current density changes can be suppressed.
It is more precise that the concentration of the light emitting material at the long wavelength side peak increases as it approaches the cathode (reflecting electrode) and decreases as the concentration of the light emitting material at the short wavelength side peak approaches the cathode (reflecting electrode). This is preferable in that the position dependency of the influence of interference can be reduced, and the change in chromaticity when the current density changes can be suppressed.
When the ratio of the concentration of the light emitting material of the long wavelength side peak to the concentration of the light emitting material of the short wavelength side peak is a on the cathode side of the light emitting layer and b on the anode side of the light emitting layer, It is preferable to satisfy> 1.05 in that the change in chromaticity when the current density changes can be effectively suppressed. The ratio (a / b) is more preferably 1.1 to 2.0.

In the organic electroluminescence device of the present invention, in the second embodiment, the light emitting layer contains a light emitting material, the light emitting material has a different emission wavelength peak between the monomer and the aggregate, and the concentration of the monomer The concentration ratio of the concentration of the aggregate (aggregate concentration / monomer concentration) gradually increases as the cathode (reflecting electrode) approaches.
The intensity ratio [(D / C) × 100] of the integral spectrum intensity D of the aggregate to the integral spectrum intensity C of the monomer is 20% or more.

The light emitting layer contains a light emitting material, and the light emitting material has a light emission wavelength peak different between the monomer and the aggregate. Thereby, the emission spectrum change by optical interference can be suppressed by changing the density | concentration ratio of 1 type of luminescent material from which an emission spectrum differs in a light emitting layer.
As the light-emitting material, a phosphorescent light-emitting material that exhibits associative light emission and emits white light alone is suitable.
In the second embodiment, since the aggregate is more energetically more stable than the monomer, the emission wavelength peak from the monomer is a short wavelength peak, and the emission wavelength peak from the aggregate is a long wavelength peak. It becomes.

The concentration ratio of the aggregate to the monomer concentration (aggregate concentration / monomer concentration) gradually increases as the cathode (reflecting electrode) is approached. Thereby, the position dependence of the influence of optical interference is reduced, and the chromaticity change at the time of a current density change can be suppressed.
Examples of the method of gradually increasing the concentration ratio (concentration of the aggregate / monomer concentration) as it approaches the cathode include a method of increasing the deposition rate of the luminescent material with respect to the host material as it approaches the cathode. .

The concentration of the association of the long wavelength side peak is constant, and the concentration of the monomer of the short wavelength side peak decreases as it approaches the cathode (reflecting electrode). This is preferable in that the position dependency of the influence of optical interference is reduced by the modulation of the density, and the change in chromaticity when the current density changes can be suppressed.
The concentration of the aggregate of the long wavelength side peak increases as it approaches the cathode (reflecting electrode), and the concentration of the monomer of the short wavelength side peak is constant. Density modulation is preferable in that the position dependency of the influence of optical interference is reduced, and the change in chromaticity when the current density changes can be suppressed.
The effect of optical interference is more precisely that the concentration of the aggregate of the long wavelength side peak increases as it approaches the cathode (reflecting electrode) and decreases as the monomer concentration of the short wavelength side peak approaches the cathode. It is preferable in that it can reduce the position dependency of the chromaticity and can suppress a change in chromaticity when the current density changes.
When the ratio of the concentration of the aggregate of the long wavelength side peak to the concentration of the monomer of the short wavelength side peak is a on the cathode side of the light emitting layer and b on the anode side of the light emitting layer, It is preferable that b> 1.05 is satisfied in that the chromaticity change at the time of the current density change can be effectively suppressed. The ratio (a / b) is more preferably 1.1 to 2.0.

The intensity ratio [(D / C) × 100] of the integrated spectral intensity D of the aggregate to the integrated spectral intensity C of the monomer is 20% or more, preferably 25% to 400%, preferably 50% to 200% is more preferable. If the intensity ratio [(D / C) × 100] is less than 20%, emission of the aggregate may not be observed.
Here, the integral spectral intensity of the monomer and the integral spectral intensity of the aggregate are measured by, for example, measuring the EL emission spectrum, and then separating the spectrum of the monomer and the aggregate by fitting to integrate each component. It can be measured by determining the strength.

<Light emitting layer>
The light emitting layer contains a light emitting material and a host material, and further contains other components as necessary.
The light emitting layer is preferably one of the following two aspects.
(1) A mode in which the light-emitting layer contains one kind of light-emitting material and the light-emitting material has different emission wavelength peaks between the monomer and the aggregate (a material that exhibits associated light emission and emits white light by one type)
(2) A mode in which the light emitting layer contains two or more kinds of light emitting materials having different emission wavelength peaks (a material that contains at least two kinds of light emitting materials and the at least two kinds of light emitting materials emit light in different colors)

<< Luminescent Material >>
As the light emitting material, either a phosphorescent light emitting material or a fluorescent light emitting material can be used, but a phosphorescent light emitting material is particularly preferable in terms of high luminous efficiency.

-(1) A material that exhibits associative luminescence and emits white light of one kind-
A phosphorescent material is preferable as the material that exhibits associative light emission and emits platinum alone, and a platinum complex is more preferable.

Examples of the ligand of the platinum 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.
Specific ligands include halogen ligands (preferably chlorine ligands), aromatic carbocyclic ligands (eg, cyclopentadienyl anion, benzene anion, naphthyl anion, etc.), nitrogen-containing hetero Ring ligands (eg, phenylpyridine, benzoquinoline, quinolinol, bipyridyl, or phenanthroline), diketone ligands (eg, acetylacetone, etc.), carboxylic acid ligands (eg, acetic acid ligands, etc.), alcoholates Examples include ligands (eg, phenolate ligands), carbon monoxide ligands, isonitrile ligands, cyano ligands, and the like. Among these, a nitrogen-containing heterocyclic ligand is particularly preferable.

  The complex may have one transition metal atom in the compound, or may be a so-called binuclear complex having two or more. Different metal atoms may be contained at the same time. Among these, examples of the phosphorescent light emitting material include the following, but are not limited thereto.

  The dope concentration of the platinum complex is preferably 10% by mass to 90% by mass, more preferably 20% by mass to 60% by mass, and still more preferably 30% by mass to 50% by mass with respect to the host material.

-(2) A material containing at least two kinds of light emitting materials, and the at least two kinds of light emitting materials emit light in different colors-
As the light-emitting material (2), either a phosphorescent material or a fluorescent material can be used, and a phosphorescent material is particularly preferable.

-Phosphorescent material-
There is no restriction | limiting in particular as said phosphorescence-emitting material, According to the objective, it can select suitably, For example, the complex etc. which contain a transition metal atom and a lanthanoid atom are mentioned.
Examples of the transition metal atom include ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum, and the like. Among these, rhenium, iridium, and platinum are preferable, and iridium is particularly preferable.

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.
Specific ligands include halogen ligands (preferably chlorine ligands), aromatic carbocyclic ligands (eg, cyclopentadienyl anion, benzene anion, naphthyl anion, etc.), nitrogen-containing hetero Ring ligands (eg, phenylpyridine, benzoquinoline, quinolinol, bipyridyl, or phenanthroline), diketone ligands (eg, acetylacetone, etc.), carboxylic acid ligands (eg, acetic acid ligands, etc.), alcoholates Examples include ligands (eg, phenolate ligands), carbon monoxide ligands, isonitrile ligands, cyano ligands, and the like. Among these, a nitrogen-containing heterocyclic ligand is particularly preferable.

  The complex may have one transition metal atom in the compound, or may be a so-called binuclear complex having two or more. Different metal atoms may be contained at the same time. Among these, examples of the phosphorescent light emitting material include the following, but are not limited thereto.

There is no restriction | limiting in particular as a phosphorescence-emitting material which is the said complex containing iridium, Although it can select suitably according to the objective, It is represented by either of following General formula (1), (2) and (3). Are preferred.
However, in said general formula (1), (2) and (3), n represents the integer of 1-3. XY represents a bidentate ligand. Ring A represents a ring structure that may contain any of a nitrogen atom, a sulfur atom, and an oxygen atom. R ¹¹ represents a substituent, and m1 represents an integer of 0 to 6. When m1 is 2 or more, adjacent R ¹¹ may be bonded to form a ring which may contain any of a nitrogen atom, a sulfur atom and an oxygen atom, and the ring is further substituted with a substituent. May be. R ¹² represents a substituent, and m2 represents an integer of 0 to 4. When m2 is 2 or more, adjacent R ¹² may be bonded to form a ring which may contain any of a nitrogen atom, a sulfur atom and an oxygen atom, and the ring is further substituted with a substituent. May be. R ¹¹ and R ¹² may combine to form a ring that may contain any of a nitrogen atom, a sulfur atom, and an oxygen atom, and the ring may be further substituted with a substituent. .

  The ring A represents a ring structure that may contain any of a nitrogen atom, a sulfur atom, and an oxygen atom, and examples thereof include a 5-membered ring and a 6-membered ring. The ring may be substituted with a substituent.

XY represents a bidentate ligand, and a bidentate monoanionic ligand is preferably exemplified.
Examples of the bidentate monoanionic ligand include picolinate (pic), acetylacetonate (acac), dipivaloylmethanate (t-butyl acac), and the like.
Examples of ligands other than the above include the ligands described in pages 89 to 91 of Lamansky et al., International Publication No. 2002/15645 pamphlet.

The substituent for R ¹¹ and R ¹² is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a halogen atom, an alkoxy group, an amino group, an alkyl group, a cycloalkyl group, a nitrogen atom or sulfur It represents an aryl group which may contain an atom, an aryloxy group which may contain a nitrogen atom or a sulfur atom, and these may be further substituted.
R ¹¹ and R ¹² may be bonded to each other adjacent to each other to form a ring that may contain a nitrogen atom, a sulfur atom, or an oxygen atom, and a 5-membered ring, a 6-membered ring, and the like are preferable. It is mentioned in. The ring may be further substituted with a substituent.

Specific examples of the compound represented by any one of the general formulas (1), (2), and (3) include, but are not limited to, the following compounds.

Other examples of the phosphorescent material include the following compounds.

  The total content of the phosphorescent material is preferably 0.5% by mass to 30% by mass, more preferably 0.5% by mass to 20% by mass, and more preferably 3% by mass to 10% by mass with respect to the total amount of the light emitting layer. Further preferred.

--Fluorescent material--
The fluorescent light emitting material is not particularly limited and may be appropriately selected depending on the purpose. For example, benzoxazole, benzimidazole, benzothiazole, styrylbenzene, polyphenyl, diphenylbutadiene, tetraphenylbutadiene, naphthalimide, coumarin , Pyran, perinone, oxadiazole, aldazine, pyralidine, bisstyrylanthracene, quinacridone, pyrrolopyridine, thiadiazolopyridine, cyclopentadiene, styrylamine, aromatic dimethylidin compounds, condensed polycyclic aromatic compounds (anthracene, phenanthroline, pyrene) , Perylene, rubrene, pentacene, etc.), metal complexes of 8-quinolinol, pyromethene complexes, various metal complexes represented by rare earth complexes, polythiophene, polyphenylene, poly Polymeric compounds such as Enirenbiniren, organic silanes or derivatives, and the like.

Among these, specific examples of the fluorescent light emitting material include the following, but are not limited thereto.

  The total content of the fluorescent light emitting material is preferably 0.1% by mass to 30% by mass, more preferably 0.2% by mass to 15% by mass, and more preferably 0.5% by mass to 12% by mass with respect to the total amount of the light emitting layer. % Is more preferable.

<< Host material >>
The host material is not particularly limited and may be appropriately selected depending on the purpose. For example, a hole transporting host material having excellent hole transportability and an electron transporting host material having excellent electron transportability may be used. it can.

-Hole-transporting host material-
The hole transporting host material is not particularly limited and may be appropriately selected depending on the intended purpose.For example, 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 Examples thereof include (N-vinylcarbazole), aniline-based copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, organic silanes, carbon films, or derivatives thereof.
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 the present invention, a host material obtained by substituting part or all of hydrogen of the host material with deuterium can be used (JP 2009-277790 A, JP 2004-515506 A).

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

  The content of the hole transporting host material is preferably 10% by mass to 99.9% by mass, more preferably 20% by mass to 99.5% by mass with respect to the total amount of the light emitting layer, and 30% by mass to 99%. More preferred is mass%.

-Electron transporting host material-
The electron transporting 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, naphthaleneperylene, and other heterocyclic tetracarboxylic anhydrides, phthalocyanines, or derivatives thereof (other rings And a metal ring of an 8-quinolinol derivative, metal phthalocyanine, benzoxazole, various metal complexes represented by metal complexes having benzothiazole as a ligand, and the like.

Examples of the electron transporting host material include metal complexes, azole derivatives (such as benzimidazole derivatives and imidazopyridine derivatives), and azine derivatives (such as pyridine derivatives, pyrimidine derivatives, and triazine derivatives). 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 having a ligand having at least one nitrogen atom, oxygen atom or sulfur atom coordinated to a metal.
The metal ion in the metal complex is not particularly limited and may be appropriately selected depending on the purpose. For example, beryllium ion, magnesium ion, aluminum ion, gallium ion, zinc ion, indium ion, tin ion, platinum ion And palladium ions. Among these, beryllium ions, aluminum ions, gallium ions, zinc ions, platinum ions, or palladium ions are preferable, and aluminum ions, zinc ions, or palladium ions are more preferable.

  There are no particular limitations on the ligand contained in the metal complex, and there are various known ligands. For example, “Photochemistry and Photophysics of Coordination Compounds”, Springer-Verlag, H .; 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 a nitrogen-containing heterocyclic ligand (preferably having 1 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, and particularly preferably 3 to 15 carbon atoms). It may be a bidentate or higher ligand, preferably a bidentate or higher and a hexadentate or lower ligand, or a bidentate or higher and a hexadentate ligand and a monodentate mixed ligand. preferable.
Examples of the ligand include an azine ligand (for example, pyridine ligand, bipyridyl ligand, terpyridine ligand, etc.), a hydroxyphenylazole ligand (for example, hydroxyphenylbenzimidazole coordination). , A hydroxyphenylbenzoxazole ligand, a hydroxyphenylimidazole ligand, a hydroxyphenylimidazopyridine ligand, etc.), an alkoxy ligand (preferably having 1 to 30 carbon atoms, more preferably 1 to 1 carbon atoms). 20, particularly preferably 1 to 10 carbon atoms, such as methoxy, ethoxy, butoxy, 2-ethylhexyloxy and the like, aryloxy ligands (preferably 6 to 30 carbon atoms, more preferably carbon numbers) 6 to 20, particularly preferably 6 to 12 carbon atoms, for example phenylo , 1-naphthyloxy, 2-naphthyloxy, 2,4,6-trimethylphenyloxy, 4-biphenyloxy, etc.), heteroaryloxy ligands (preferably having 1 to 30 carbon atoms, more preferably C1-C20, Most preferably, it is C1-C12, for example, pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy etc. are mentioned, alkylthio ligand (preferably C1-C30, more preferably carbon number) 1 to 20, particularly preferably 1 to 12 carbon atoms, such as methylthio and ethylthio, and arylthio ligands (preferably 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms such as phenylthio), heteroarylthio coordination (Preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 12 carbon atoms. For example, pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio, and 2-benz Thiazolylthio, etc.), siloxy ligands (preferably having 1 to 30 carbon atoms, more preferably 3 to 25 carbon atoms, particularly preferably 6 to 20 carbon atoms, such as triphenylsiloxy group, Ethoxysiloxy group, triisopropylsiloxy group, etc.), aromatic hydrocarbon anion ligand (preferably having 6 to 30 carbon atoms, more preferably 6 to 25 carbon atoms, and particularly preferably 6 to 20 carbon atoms). For example, phenyl anion, naphthyl anion, anthranyl anion, etc.), aromatic heterocyclic anion coordination (Preferably having 1 to 30 carbon atoms, more preferably 2 to 25 carbon atoms, particularly preferably 2 to 20 carbon atoms, such as pyrrole anion, pyrazole anion, triazole anion, oxazole anion, benzoxazole anion, thiazole anion, Benzothiazole anion, thiophene anion, benzothiophene anion, etc.), indolenine anion ligand, etc., preferably nitrogen-containing heterocyclic ligand, aryloxy ligand, heteroaryloxy group, or Siloxy ligands, more preferably nitrogen-containing heterocyclic ligands, aryloxy ligands, siloxy ligands, aromatic hydrocarbon anion ligands, or aromatic heterocyclic anion ligands.

  Examples of the metal complex electron transporting host material include Japanese Patent Application Laid-Open No. 2002-235076, Japanese Patent Application Laid-Open No. 2004-214179, Japanese Patent Application Laid-Open No. 2004-221106, Japanese Patent Application Laid-Open No. 2004-221665, and Japanese Patent Application Laid-Open No. 2004-221068. And compounds described in JP-A No. 2004-327313.

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

  10 mass%-99.9 mass% are preferable with respect to the said light emitting layer whole quantity, as for content of the said electron transport host material, 20 mass%-99.5 mass% are more preferable, 30 mass%-99 mass%. % Is more preferable.

  There is no restriction | limiting in particular as a formation method of the said light emitting layer, According to the objective, it can select suitably, For example, resistance heating vapor deposition method, vacuum vapor deposition method, electron beam method, sputtering method, molecular lamination method, coating method (spin A coating method, a casting method, a dip coating method, etc.). Among these, the vacuum evaporation method is particularly preferable.

  There is no restriction | limiting in particular in the thickness of the said light emitting layer, Although it can select suitably according to the objective, 20 nm or more is preferable and 25 nm-100 nm are more preferable. If the thickness is less than 20 nm, charge leakage may occur, leading to a decrease in luminous efficiency.

<Electron injection layer, electron transport layer>
The electron injection layer and the electron transport layer are layers having a function of receiving electrons from the cathode or the cathode side and transporting them to the anode side.
The electron transport layer includes a material such as the electron transport host material and the electron donating dopant.

There is no restriction | limiting in particular as thickness of the said electron injection layer and an electron carrying layer, According to the objective, it can select suitably, From a viewpoint of reducing a drive voltage, 500 nm or less is respectively preferable.
The thickness of the electron transport layer is preferably 1 nm to 500 nm, more preferably 5 nm to 200 nm, and still more preferably 10 nm to 100 nm.
The thickness of the electron injection layer is preferably 0.1 nm to 200 nm, more preferably 0.2 nm to 100 nm, and still more preferably 0.5 nm to 50 nm.
The electron injection layer and the electron transport layer may have a single layer structure made of one or more materials, or may have a multilayer structure made of a plurality of layers having the same composition or different compositions.

<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 injection material or hole transport material used for these layers may be a low molecular compound or a high molecular compound.
The hole injection material or hole transport material is not particularly limited and may be appropriately selected depending on the purpose. For example, a pyrrole derivative, a carbazole derivative, a triazole derivative, an oxazole derivative, an oxadiazole derivative, an imidazole derivative, 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, styrylamine Examples thereof include compounds, aromatic dimethylidin compounds, phthalocyanine compounds, porphyrin compounds, thiophene derivatives, organosilane derivatives, and carbon. 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.
As the electron-accepting dopant, an inorganic compound or an organic compound can be used as long as it has an electron-accepting property and oxidizes an organic compound.
The inorganic compound is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include metal halides such as ferric chloride, aluminum chloride, gallium chloride, indium chloride, and antimony pentachloride; vanadium pentoxide, And metal oxides such as 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 may be used individually by 1 type and may use 2 or more types together.
The amount of the electron-accepting dopant used is not particularly limited and varies depending on the type of material, but is preferably 0.01% by mass to 50% by mass with respect to the hole transport material or the hole injection material, and 0.05% by mass. % To 30% by mass is more preferable, and 0.1% to 30% by mass is even more preferable.

The hole injection layer and the hole transport layer are not particularly limited and can be formed according to a known method. For example, a dry film forming method such as a vapor deposition method and a sputtering method, a wet coating method, a transfer method, and a printing method. It can be suitably formed by a method, an ink jet method, or the like.
The thickness of the hole injection layer and the hole transport layer is preferably 1 nm to 500 nm, more preferably 5 nm to 250 nm, and still more preferably 10 nm to 200 nm.

<Hole blocking layer, electron blocking layer>
The hole blocking layer is a layer having a function of preventing holes transported from the anode side to the light emitting layer from passing through to the cathode side, and is usually provided as an organic compound layer adjacent to the light emitting layer on the cathode side. .
The electron blocking layer is a layer having a function of preventing electrons transported from the cathode side to the light emitting layer from passing through to the anode side, and is usually provided as an organic compound layer adjacent to the light emitting layer on the anode side.
Examples of the compound constituting the hole blocking layer include aluminum complexes such as BAlq, triazole derivatives, and phenanthroline derivatives such as BCP.
As a compound which comprises the said electronic block layer, what was mentioned, for example as the above-mentioned hole transport material can be utilized.

The electron block layer and the hole block layer are not particularly limited and can be formed according to a known method, for example, a dry film forming method such as a vapor deposition method and a sputtering method, a wet coating method, a transfer method, and a printing method. It can be suitably formed by an inkjet method or the like.
The thickness of the hole blocking layer and the electron blocking layer is preferably 1 nm to 200 nm, more preferably 1 nm to 50 nm, and still more preferably 3 nm to 10 nm. In addition, the hole blocking layer and the electron blocking layer may have a single-layer structure made of one or more of the materials described above, or may have a multilayer structure made up of a plurality of layers having the same composition or different compositions. Good.

<Electrode>
The organic electroluminescent element of the present invention includes a pair of electrodes, that is, an anode and a cathode. From the nature of the organic electroluminescent device, at least one of the anode and the cathode is preferably transparent, the anode is a transparent electrode or a semitransparent electrode, and the cathode is more preferably a reflective electrode. Usually, the anode only needs to have a function as an electrode for supplying holes to the organic compound layer, and the cathode only needs to have a function as an electrode for injecting electrons into the organic compound layer.
There is no restriction | limiting in particular about the shape, a structure, a magnitude | size, etc. as said electrode, According to the use and objective of an organic electroluminescent element, it can select suitably from well-known electrode materials.
As a material which comprises the said electrode, a metal, an alloy, a metal oxide, a conductive compound, or a mixture thereof etc. are mentioned suitably, for example.

-Anode-
Examples of the material constituting the anode 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). Conductive metal oxides; metals such as gold, silver, chromium and nickel; mixtures or laminates of these metals and conductive metal oxides; inorganic conductive materials such as copper iodide and copper sulfide; polyaniline, polythiophene, Examples thereof include organic conductive materials such as polypyrrole, and laminates of these with ITO. Among these, conductive metal oxides are preferable, and ITO is particularly preferable in terms of productivity, high conductivity, transparency, and the like.

-Cathode-
Examples of the material constituting the cathode include alkali metals (eg, Li, Na, K, Cs, etc.), alkaline earth metals (eg, Mg, Ca, etc.), gold, silver, lead, aluminum, sodium-potassium alloys, Examples thereof include lithium-aluminum alloys, magnesium-silver alloys, rare earth metals such as indium and ytterbium. These may be used alone, but two or more can be suitably used in combination from the viewpoint of achieving both stability and electron injection.
Among these, alkali metals and alkaline earth metals are preferable from the viewpoint of electron injecting property, and materials mainly composed of aluminum are more preferable from the viewpoint of excellent storage stability.
Examples of the material mainly composed of aluminum include 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). Alloys).

  The method for forming the electrode is not particularly limited and can be performed according to a known method. For example, a wet method such as a printing method or a coating method; a physical method such as a vacuum deposition method, a sputtering method, or an ion plating method; Examples include chemical methods such as CVD and plasma CVD. Among these, it can be formed on the substrate in accordance with an appropriately selected method in consideration of suitability with the material constituting the electrode. For example, when ITO is selected as the anode material, it can be formed according to a direct current or high frequency sputtering method, a vacuum deposition method, an ion plating method, or the like. When a metal or the like is selected as the cathode material, one or more of them can be formed simultaneously or sequentially according to a sputtering method or the like.

  In addition, when performing patterning when forming the electrode, 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.

<Board>
The organic electroluminescent element of the present invention is preferably provided on a substrate, and may be provided in such a manner that the electrode and the substrate are in direct contact with each other, or may be provided in an intermediate layer. .
The material for the substrate is not particularly limited and may be appropriately selected depending on the intended purpose. For example, inorganic materials such as yttria-stabilized zirconia (YSZ) and glass (such as alkali-free glass and soda lime glass); polyethylene terephthalate And polyesters such as polybutylene phthalate and polyethylene naphthalate; organic materials such as polystyrene, polycarbonate, polyethersulfone, polyarylate, polyimide, polycycloolefin, norbornene resin, and poly (chlorotrifluoroethylene).

  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 preventive 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.

-Other configurations-
There is no restriction | limiting in particular as said other structure, According to the objective, it can select suitably, For example, a protective layer, a sealing container, a resin sealing layer, a sealing adhesive etc. can be mentioned.
There is no restriction | limiting in particular as contents, such as the said protective layer, the said sealing container, the said resin sealing layer, and the said sealing adhesive agent, According to the objective, it can select suitably, for example, Unexamined-Japanese-Patent No. 2009-152572. The matters described in the gazette can be applied.

  FIG. 1 is a schematic view showing an example of the layer structure of the organic electroluminescent element of the present invention. The organic electroluminescent element 10 includes an anode 2 (for example, an ITO electrode) formed on the glass substrate 1, a hole injection layer 3, a hole transport layer 4, a light emitting layer 5, and a first electron transport layer 6. The second electron transport layer 7, an electron injection layer (not shown), and a cathode 8 (for example, an Al—Li electrode) are stacked in this order. The anode 2 (for example, ITO electrode) and the cathode 8 (for example, Al-Li electrode) are connected to each other via a power source.

-Drive-
The organic electroluminescence device of the present invention emits light by applying a direct current (which may include an alternating current component as necessary) voltage (usually 2 to 15 volts) or a direct current between the anode and the cathode. Can be obtained.
The organic electroluminescent element of the present invention can be applied to an active matrix by a thin film transistor (TFT). As the active layer of the thin film transistor, amorphous silicon, high temperature polysilicon, low temperature polysilicon, microcrystalline silicon, oxide semiconductor, organic semiconductor, carbon nanotube, or the like can be used.
The organic electroluminescent element of the present invention can be applied with the thin film transistor described in, for example, International Publication No. 2005/088726 pamphlet, Japanese Patent Application Laid-Open No. 2006-165529, US Patent Application Publication No. 2008/0237598.

There is no restriction | limiting in particular in the organic electroluminescent element of this invention, Light extraction efficiency can be improved by various well-known devices. For example, by processing the substrate surface shape (for example, forming a fine concavo-convex pattern), controlling the refractive index of the substrate, ITO layer, organic layer, controlling the thickness of the substrate, ITO layer, organic layer, etc. It is possible to improve the external quantum efficiency.
The light extraction method from the organic electroluminescence device of the present invention may be a top emission method or a bottom emission method.

The organic electroluminescent element of the present invention may have a resonator structure. For example, in the first aspect, a multilayer mirror composed of a plurality of laminated films having different refractive indexes, a transparent or translucent electrode, a light emitting layer, and a metal electrode are superimposed on a transparent substrate. The light generated in the light emitting layer resonates repeatedly with the multilayer mirror and the metal electrode as a reflection plate.
In the second aspect, a transparent or translucent electrode and a metal electrode function as a reflecting plate on the transparent substrate, respectively, and light generated in the light emitting layer repeats reflection and resonates between them.
In order to form a resonant structure, the optical path length determined from the effective refractive index of the two reflectors and the refractive index and thickness of each layer between the reflectors is adjusted to the optimum value to obtain the desired resonant wavelength. Is done.
The calculation formula in the case of the first aspect is described in JP-A-9-180883.
The calculation formula in the case of the second aspect is described in Japanese Patent Application Laid-Open No. 2004-127795.

-Application-
The organic electroluminescent element of the present invention is not particularly limited and may be appropriately selected depending on the intended purpose. However, the display element, display, backlight, electrophotography, illumination light source, recording light source, exposure light source, reading light source, label It can be suitably used for signboards, interiors, optical communications, and the like.
As a method for making the organic electroluminescent display of a full color type, for example, as described in “Monthly Display”, September 2000, pages 33 to 37, the three primary colors (blue (B), Three-color light emission method in which organic electroluminescent elements that emit light corresponding to green (G) and red (R) are arranged on a substrate, and white light emitted by an organic electroluminescent element for white light emission through a color filter. There are known a white method, a color conversion method for converting 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.

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

<Method for producing organic electroluminescent element>
A 0.5 mm thick, 2.5 cm square glass substrate with an ITO electrode deposited with indium tin oxide (hereinafter abbreviated as ITO) to a thickness of 100 nm was placed in a cleaning container, and ultrasonically cleaned in 2-propanol. UV-ozone treatment was performed for 30 minutes. The organic layer and metal layer of each example were vapor-deposited on this transparent anode using the vacuum vapor deposition apparatus. In addition, all the vacuum evaporation methods in a following example and a comparative example are performed on the same conditions, and a vapor deposition rate is 0.2 nm / sec unless there is particular notice. The deposition rate was measured using a quartz resonator. The pressure is 1 × 10 ⁻⁴ Pa.
In the layer in which two or more kinds of substances are co-deposited, the deposition rate of the substance having a low concentration is adjusted so as to obtain a desired concentration.
In addition, the substance whose concentration in the light emitting layer was changed was adjusted by linearly changing the deposition rate to obtain a light emitting layer having a desired concentration distribution.

Example 1
-Fabrication of white associative light emitting device-
A glass substrate having a thickness of 0.5 mm and a square of 2.5 cm was placed in a cleaning container, ultrasonically cleaned in a neutral detergent, then ultrasonically cleaned in pure water, and heat-treated at 120 ° C. for 120 minutes. Thereafter, UV-ozone treatment was performed 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) as a positive electrode was sputter-deposited on a glass substrate to a thickness of 100 nm.
Next, on the anode (ITO), 4,4 ′, 4 ″ -tris (N, N- (2-naphthyl) -phenylamino) triphenylamine (2-TNATA) represented by the following structural formula A hole injection layer doped with 1% by mass of F4-TCNQ represented by the following structural formula was formed by a vacuum deposition method so as to have a thickness of 45 nm.

Next, α-NPD (Bis [N- (1-naphthyl) -N-phenyl] benzidine)) is formed on the hole injection layer as a hole transport layer by a vacuum deposition method so as to have a thickness of 7 nm. did.
Next, the compound 1 represented by the following structural formula was vacuum deposited on the hole transport layer to form a second hole transport layer having a thickness of 3 nm.

Next, on the second hole transport layer, mCP (1,3-bis (carbazol-9-yl) benzene) is used as a host material, and 40% by mass (compound 1 side) to 50% with respect to the mCP. A light-emitting layer doped with compound 2 represented by the following structural formula, which is a phosphorescent material, was continuously vacuum-deposited to a thickness of 30 nm while continuously changing to mass% (Balq side).

Next, Balq (Bis- (2-methyl-8-quinolinolato) -4- (phenyl-phenolate) -aluminum (III)) is formed as a first electron transporting layer on the light emitting layer so as to have a thickness of 39 nm. Vacuum deposited.

Next, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) as a second electron transport layer was vacuum deposited on the first electron transport layer so as to have a thickness of 1 nm.
Next, LiF was vacuum-deposited as an electron injection layer on the second electron transport layer so as to have a thickness of 0.5 nm.
Next, a patterned mask (a mask having a light emitting region of 2 mm × 2 mm) was placed on the electron injection layer, and metal aluminum was vacuum evaporated to a thickness of 100 nm to form a cathode.
The produced laminate was put in a glove box substituted with nitrogen gas, and sealed with a glass sealing can and an ultraviolet curable adhesive (XNR5516HV, manufactured by Nagase Ciba Co., Ltd.). Thus, the organic electroluminescent element of Example 1 was produced.
The layer structure of the organic electroluminescent element of Example 1 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + XX mass% Compound 2 (30 nm) / Balq (39 nm) / BCP (1 nm) / LiF ( 0.5 nm) / Al (100 nm)>

(Comparative Example 1)
In Example 1, the organic material of Comparative Example 1 was prepared in the same manner as in Example 1 except that the compound 2 represented by the above structural formula, which is a phosphorescent material of 40% by mass, was doped with respect to mCP as the host material. An electroluminescent element was produced.
The layer structure of the organic electroluminescent element of Comparative Example 1 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + 40 mass% Compound 2 (30 nm) / Balq (39 nm) / BCP (1 nm) / LiF ( 0.5 nm) / Al (100 nm)>

  Next, for the produced Example 1 and Comparative Example 1, the integral spectral intensity C of the monomer, the integral spectral intensity D of the aggregate, the external quantum efficiency, durability (relative luminance half time), CIEx, CIEy, and chromaticity change (ΔE) were evaluated. The results are shown in Table 1.

<Measurement of Monomer Integral Spectral Strength C and Aggregate Integral Spectral Strength D>
Using a source measure unit 2400 manufactured by Toyo Technica Co., Ltd., a direct current was applied to each element to emit light. The emission spectrum at that time was measured using a spectral radiance meter SR-3 manufactured by Topcon Corporation. The obtained emission spectrum was fitted by the least square method using the monomer spectrum and the aggregate emission spectrum, and the integral spectral intensity C of the monomer and the integral spectrum intensity D of the aggregate were calculated. The emission spectrum of Example 1 when energized at 0.25 mA / cm ² is shown in FIG. 2, and the emission spectrum of Comparative Example 1 is shown in FIG.

<External quantum efficiency>
The external quantum efficiency when the current density of each organic electroluminescent element is 0.25 mA / cm ² was calculated by an intensity conversion method for each wavelength.

<Durability>
The durability of each organic electroluminescent element was determined by measuring the luminance half time at a constant current of 1,000 cd / m ² and deriving the relative luminance half time with respect to the corresponding Comparative Example 1.

<Evaluation of color difference>
Using a source measure unit 2400 manufactured by Toyo Technica Co., Ltd., a direct current was applied to each element to emit light. The emission spectrum at that time was measured using a spectral radiance meter SR-3 manufactured by Topcon Corporation. Based on the obtained emission spectrum, the CIE chromaticity coordinates (x, y) at the current density of the organic electroluminescence device of 0.25 mA / cm ² and 25 mA / cm ² were obtained by converting the spectrum. . Furthermore, the color difference (ΔE) in the Lab color solid was obtained by converting the chromaticity coordinates.

(Example 2)
-Production of white single layer light emitting element-
In Example 1, 15 mass% of the compound 3 represented by the following structural formula with respect to mCP, 0.13 mass% of the compound 4 represented by the following structural formula with respect to mCP, and 0 with respect to mCP. In the same manner as in Example 1, except that the compound 5 represented by the following structural formula was doped by continuously changing from 13% by mass (compound 1 side) to 0.2% by mass (Balq side). The organic electroluminescent element of Example 2 was produced.

The layer structure of the organic electroluminescent element of Example 2 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + xx mass% Compound 3 + yy mass% Compound 4 + zz mass% Compound 5 (30 nm) / Balq (39 nm) / BCP (1 nm) / LiF (0.5 nm) / Al (100 nm)>

(Comparative Example 2)
In Example 1, 15% by mass of the compound 3 represented by the above structural formula with respect to mCP, 0.13% by mass of the compound 4 represented by the above structural formula with respect to mCP, and 0 with respect to mCP. An organic electroluminescent element of Comparative Example 2 was produced in the same manner as in Example 1 except that the compound 5 represented by the above structural formula was doped with 13% by mass.
The layer structure of the organic electroluminescent element of Comparative Example 2 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + 15 mass% Compound 3 + 0.13 mass% Compound 4 + 0.13 mass% Compound 5 (30 nm) / Balq (39 nm) / BCP (1 nm) / LiF (0.5 nm) / Al (100 nm)>

  Next, for Example 2 and Comparative Example 2, the concentration A of the light emitting material having a short wavelength peak and the concentration B of the light emitting material having a long wavelength peak were measured as follows. Further, in the same manner as in Example 1 and Comparative Example 1, external quantum efficiency, durability (relative luminance half time), CIEx, CIEy, and chromaticity change (ΔE) were evaluated. The results are shown in Table 1. The emission spectrum of Example 2 measured in the same manner as Example 1 and Comparative Example 1 is shown in FIG. 4, and the emission spectrum of Comparative Example 2 is shown in FIG.

<Measurement of concentration A of the light emitting material having a short wavelength peak and concentration B of the light emitting material having a long wavelength peak>
The concentration A of the light emitting material having the short wavelength peak and the concentration B of the light emitting material having the long wavelength peak were measured from the value of the crystal resonator during the deposition.

(Example 3)
-Production of white single layer light emitting element-
In Example 1, the compound 3 represented by the above structural formula was continuously changed from 15% by mass (compound 1 side) to 13% by mass (Balq side) with respect to mCP, and 0. Example 1 was carried out in the same manner as in Example 1 except that 13% by mass of Compound 4 represented by the above structural formula and 0.13% by mass of Compound 5 represented by the above structural formula with respect to mCP were doped. 3 organic electroluminescent elements were produced.
The layer structure of the organic electroluminescent element of Example 3 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + xx mass% Compound 3 + yy mass% Compound 4 + zz mass% Compound 5 (30 nm) / Balq (39 nm) / BCP (1 nm) / LiF (0.5 nm) / Al (100 nm)>

(Comparative Example 3)
The same organic electroluminescent element as Comparative Example 2 was used as Comparative Example 3.

  Next, for Example 3 and Comparative Example 3, as in Example 2 and Comparative Example 2, the concentration A of the light emitting material having the short wavelength peak, the concentration B of the light emitting material having the long wavelength peak, the external quantum efficiency, and the durability (Relative luminance half-life), CIEx, CIEy, and chromaticity change (ΔE) were evaluated. The results are shown in Table 1. The emission spectrum of Example 3 measured in the same manner as Example 1 and Comparative Example 1 is shown in FIG. The emission spectrum of Comparative Example 3 is the same as FIG.

Example 4
-Production of white single layer light emitting element-
In Example 1, the compound 3 represented by the above structural formula was continuously changed from 15% by mass (compound 1 side) to 14% by mass (Balq side) with respect to mCP, and 0. 13% by mass of the compound 4 represented by the above structural formula and 0.13% by mass (compound 1 side) to 0.18% by mass (Balq side) with respect to mCP An organic electroluminescent element of Example 4 was produced in the same manner as in Example 1 except that the compound 5 represented by
The layer structure of the organic electroluminescent element of Example 4 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + xx mass% Compound 3 + yy mass% Compound 4 + zz mass% Compound 5 (30 nm) / Balq (39 nm) / BCP (1 nm) / LiF (0.5 nm) / Al (100 nm)>

(Comparative Example 4)
The same organic electroluminescent element as Comparative Example 2 was used as Comparative Example 4.

  Next, for Example 4 and Comparative Example 4, as in Example 2 and Comparative Example 2, the concentration A of the light emitting material having the short wavelength peak, the concentration B of the light emitting material having the long wavelength peak, the external quantum efficiency, and the durability (Relative luminance half-life), CIEx, CIEy, and chromaticity change (ΔE) were evaluated. The results are shown in Table 1. The emission spectrum of Example 4 measured in the same manner as in Example 1 and Comparative Example 1 is shown in FIG. The emission spectrum of Comparative Example 4 is the same as FIG.

(Example 5)
-Fabrication of iridium-based single layer light emitting devices-
A glass substrate having a thickness of 0.5 mm and a square of 2.5 cm was placed in a cleaning container, ultrasonically cleaned in a neutral detergent, then ultrasonically cleaned in pure water, and heat-treated at 120 ° C. for 120 minutes. Thereafter, UV-ozone treatment was performed 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) as a positive electrode was sputter-deposited on a glass substrate to a thickness of 100 nm.
Next, the 4,4 ′, 4 ″ -tris (N, N- (2-naphthyl) -phenylamino) triphenylamine (2-TNATA) represented by the above structural formula is formed on the anode (ITO). A hole injection layer doped with 1% by mass of F4-TCNQ represented by the above structural formula was formed by vacuum deposition so that the thickness was 160 nm.

  Next, α-NPD (Bis [N- (1-naphthyl) -N-phenyl] benzidine) is formed as a hole transport layer on the hole injection layer by a vacuum deposition method so as to have a thickness of 10 nm. did.

Next, on the hole transport layer, 10% by mass of the compound 6 represented by the following structural formula with respect to the compound 11 represented by the following structural formula as a host material, and the compound represented by the following structural formula The compound 7 represented by the following structural formula of 0.10% by mass with respect to 11 and the compound 11 represented by the following structural formula with 0.10% by mass (NPD side) to 0.16% by mass (Balq The light emitting layer doped continuously with the compound 8 represented by the following structural formula was vacuum-deposited to a thickness of 30 nm.

On the light emitting layer, Balq was vacuum-deposited as a first electron transport layer so as to have a thickness of 39 nm.
Next, BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) as a second electron transport layer was vacuum deposited on the first electron transport layer so as to have a thickness of 1 nm.
Next, LiF was vacuum-deposited as an electron injection layer on the second electron transport layer so as to have a thickness of 1 nm.
Next, a patterned mask (a mask having a light emitting region of 2 mm × 2 mm) was placed on the electron injection layer, and metal aluminum was vacuum evaporated to a thickness of 100 nm to form a cathode.
The produced laminate was put in a glove box substituted with nitrogen gas, and sealed with a glass sealing can and an ultraviolet curable adhesive (XNR5516HV, manufactured by Nagase Ciba Co., Ltd.). Thus, an organic electroluminescent element of Example 5 was produced.
The layer structure of the organic electroluminescent element of Example 5 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (160 nm) / NPD (10 nm) / Compound 11 + xx mass% Compound 6 + yy mass% Compound 7 + zz mass% Compound 8 (30 nm) / Balq (39 nm) / BCP (1 nm) / LiF (1 nm) / Al (100 nm)>

(Comparative Example 5)
In Example 5, 10 mass% of the compound 6 represented by the above structural formula with respect to the compound 11 represented by the above structural formula as a host material, and 0.10 with respect to the compound 11 represented by the above structural formula. Example 5 except that 7% by mass of the compound 7 represented by the above structural formula and 0.10% by mass of the compound 8 represented by the above structural formula were doped with respect to the compound 11 represented by the above structural formula. In the same manner, an organic electroluminescent element of Comparative Example 5 was produced.
The layer structure of the organic electroluminescent element of Comparative Example 5 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (160 nm) / NPD (10 nm) / Compound 11 + 10 mass% Compound 6 + 0.10 mass% Compound 7 + 0.10 mass% Compound 8 (30 nm) / Balq (39 nm) / BCP (1 nm) / LiF (1 nm) / Al (100 nm)>

  Next, for Example 5 and Comparative Example 5, as in Example 2 and Comparative Example 2, the concentration A of the light emitting material having the short wavelength peak, the concentration B of the light emitting material having the long wavelength peak, the external quantum efficiency, and the durability (Relative luminance half-life), CIEx, CIEy, and chromaticity change (ΔE) were evaluated. The results are shown in Table 1. The emission spectrum of Example 5 measured in the same manner as Example 1 and Comparative Example 1 is shown in FIG. 8, and the emission spectrum of Comparative Example 5 is shown in FIG.

(Example 6)
In Example 5, 10% by mass of the compound 9 represented by the following structural formula with respect to the compound 11 represented by the above structural formula as a host material, and 0.10 with respect to the compound 11 represented by the above structural formula. Continuously from 0.10% by mass (NPD side) to 0.16% by mass (Balq side) with respect to 10% by mass of the compound 10 represented by the following structural formula and the compound 11 represented by the above structural formula. An organic electroluminescent element of Example 6 was produced in the same manner as in Example 5 except that the compound 5 represented by the above structural formula was doped.

(Comparative Example 6)
In Example 6, 10% by mass of the compound 9 represented by the structural formula with respect to the compound 11 represented by the structural formula as a host material, and 0.10 with respect to the compound 11 represented by the structural formula. Example 6 except that 10% by mass of the compound 10 represented by the above structural formula and 0.10% by mass of the compound 5 represented by the above structural formula were doped with respect to the compound 11 represented by the above structural formula. In the same manner, an organic electroluminescent element of Comparative Example 6 was produced.

  Next, for Example 6 and Comparative Example 6, as in Example 2 and Comparative Example 2, the concentration A of the light emitting material having the short wavelength peak, the concentration B of the light emitting material having the long wavelength peak, the external quantum efficiency, and the durability (Relative luminance half-life), CIEx, CIEy, and chromaticity change (ΔE) were evaluated. The results are shown in Table 1. The emission spectrum of Example 6 measured in the same manner as Example 1 and Comparative Example 1 is shown in FIG. 10, and the emission spectrum of Comparative Example 6 is shown in FIG.

(Example 7)
A glass substrate having a thickness of 0.5 mm and a square of 2.5 cm was placed in a cleaning container, ultrasonically cleaned in a neutral detergent, then ultrasonically cleaned in pure water, and heat-treated at 120 ° C. for 120 minutes. Thereafter, UV-ozone treatment was performed 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) as a positive electrode was sputter-deposited on a glass substrate to a thickness of 100 nm.
Next, the 4,4 ′, 4 ″ -tris (N, N- (2-naphthyl) -phenylamino) triphenylamine (2-TNATA) represented by the above structural formula is formed on the anode (ITO). A hole injection layer doped with 1% by mass of F4-TCNQ represented by the above structural formula was formed by a vacuum deposition method so as to have a thickness of 45 nm.

Next, α-NPD (Bis [N- (1-naphthyl) -N-phenyl] benzidine)) is formed on the hole injection layer as a hole transport layer by a vacuum deposition method so as to have a thickness of 7 nm. did.
Next, the compound 1 represented by the above structural formula was vacuum deposited on the hole transport layer to form a second hole transport layer having a thickness of 3 nm.

  Next, on the second hole transport layer, mCP (1,3-bis (carbazol-9-yl) benzene) is used as a host material, and 40% by mass (compound 1 side) to 50% with respect to the mCP. A light-emitting layer doped with the compound 2 represented by the above structural formula, which is a phosphorescent material, was continuously vacuum-deposited to a thickness of 30 nm while continuously changing to mass% (Balq side).

Balq was vacuum-deposited as a first electron transport layer on the light emitting layer so as to have a thickness of 10 nm.
Next, a second electron transport layer doped with 1% by mass of Li with respect to BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) is formed on the first electron transport layer. Vacuum deposition was performed so that the thickness was 230 nm.
Next, a patterned mask (a mask having a light emitting region of 2 mm × 2 mm) was placed on the electron injection layer, and metal aluminum was vacuum evaporated to a thickness of 100 nm to form a cathode.
The produced laminate was put in a glove box substituted with nitrogen gas, and sealed with a glass sealing can and an ultraviolet curable adhesive (XNR5516HV, manufactured by Nagase Ciba Co., Ltd.). Thus, an organic electroluminescent element of Example 7 was produced.
The layer structure of the organic electroluminescent element of Example 7 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + XX mass% Compound 2 (30 nm) / Balq (10 nm) / BCP + 1 mass% Li (230 nm) / Al (100 nm)>

(Comparative Example 7)
In Example 7, an organic electroluminescent element of Comparative Example 7 was produced in the same manner as in Example 7 except that 40% by mass of Compound 2 represented by the above structural formula was doped with respect to mCP.
The layer structure of the organic electroluminescent element of Comparative Example 7 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + 40 mass% Compound 2 (30 nm) / Balq (10 nm) / BCP + 1 mass% Li (230 nm) / Al (100 nm)>

  Next, for Example 7 and Comparative Example 7, as in Example 1 and Comparative Example 1, the integrated spectral intensity C of the monomer, the integrated spectral intensity D of the aggregate, the external quantum efficiency, and the durability (relative luminance) Half time), CIEx, CIEy, and chromaticity change (ΔE) were evaluated. The results are shown in Table 1. The emission spectrum of Example 7 measured in the same manner as Example 1 and Comparative Example 1 is shown in FIG. 12, and the emission spectrum of Comparative Example 7 is shown in FIG.

(Example 8)
In Example 1, the light emitting layer doped with the compound 2 represented by the above structural formula by changing continuously from 30% by mass (compound 1 side) to 50% by mass (Balq side) with respect to mCP is 60 nm. An organic electroluminescent device of Example 8 was produced in the same manner as Example 1 except that the thickness was vacuum deposited.
The layer structure of the organic electroluminescent element of Example 8 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + XX mass% Compound 2 (60 nm) / Balq (39 nm) / BCP (1 nm) / LiF ( 0.5 nm) / Al (100 nm)>

(Comparative Example 8)
In Example 8, except that the light emitting layer doped with the compound 2 represented by the above structural formula at 40% by mass with respect to mCP as the host material was vacuum-deposited to a thickness of 60 nm, the same as in Example 1, An organic electroluminescent element of Comparative Example 8 was produced.
The layer structure of the organic electroluminescent element of Comparative Example 8 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + 40 mass% Compound 2 (60 nm) / Balq (39 nm) / BCP (1 nm) / LiF ( 0.5 nm) / Al (100 nm)>

  Next, for Example 8 and Comparative Example 8, as in Example 1 and Comparative Example 1, the integral spectral intensity C of the monomer, the integral spectral intensity D of the aggregate, the external quantum efficiency, and durability (relative luminance) Half time), CIEx, CIEy, and chromaticity change (ΔE) were evaluated. The results are shown in Table 1. The emission spectrum of Example 8 measured in the same manner as Example 1 and Comparative Example 1 is shown in FIG. 14, and the emission spectrum of Comparative Example 8 is shown in FIG.

Example 9
In Example 1, the emission layer doped with the compound 2 represented by the above structural formula by changing continuously from 40% by mass (compound 1 side) to 50% by mass (Balq side) with respect to mCP is 15 nm. An organic electroluminescent element of Example 9 was produced in the same manner as Example 1 except that the thickness was vacuum deposited.
The layer structure of the organic electroluminescent element of Example 9 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + XX mass% Compound 2 (15 nm) / Balq (39 nm) / BCP (1 nm) / LiF ( 0.5 nm) / Al (100 nm)>

(Comparative Example 9)
In Example 9, except that the light emitting layer doped with the compound 2 represented by the above structural formula in 40% by mass with respect to mCP as the host material was vacuum-deposited to a thickness of 15 nm, the same as in Example 9, An organic electroluminescent element of Comparative Example 9 was produced.
The layer structure of the organic electroluminescent element of Comparative Example 9 is as shown below. () Represents thickness.
<ITO (100 nm) / 2-TNATA + 1 mass% F4-TCNQ (45 nm) / NPD (7 nm) / Compound 1 (3 nm) / mCP + 40 mass% Compound 2 (15 nm) / Balq (39 nm) / BCP (1 nm) / LiF ( 0.5 nm) / Al (100 nm)>

  Next, for Example 9 and Comparative Example 9, as in Example 1 and Comparative Example 1, the integrated spectral intensity C of the monomer, the integrated spectral intensity D of the aggregate, the external quantum efficiency, and the durability (relative luminance) Half time), CIEx, CIEy, and chromaticity change (ΔE) were evaluated. The results are shown in Table 1. The emission spectrum of Example 9 measured in the same manner as Example 1 and Comparative Example 1 is shown in FIG. 16, and the emission spectrum of Comparative Example 9 is shown in FIG.

* Spectral intensity is 0.25 mA / cm ² and is the value when energized.
* Concentration is the concentration on the anode (transparent electrode) side in the light emitting layer.

From the results of Table 1, in Examples 1 to 9, the chromaticity change (ΔE) at the time of current change was smaller than in Comparative Examples 1 to 9. Moreover, the improvement effect was recognized also in luminous efficiency and durability.

  The organic electroluminescent element of the present invention is suitably used for display elements, displays, backlights, electrophotography, illumination light sources, recording light sources, exposure light sources, reading light sources, signs, signboards, interiors, optical communications, and the like.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 First electron transport layer 7 Second electron transport layer 8 Cathode 10 Organic electroluminescent element

Claims (5)

An organic electroluminescent element including at least a light emitting layer between an anode and a cathode,
The light emitting layer contains a light emitting material, the light emitting material has a different emission wavelength peak between the monomer and the aggregate, the monomer has a short wavelength side emission wavelength peak, and the aggregate is on the long wavelength side. Has an emission wavelength peak,
The concentration ratio of the aggregate to the monomer concentration (aggregate concentration / monomer concentration) gradually increases as the cathode approaches.
An organic electroluminescence device, wherein an intensity ratio [(D / C) × 100] of an integral spectrum intensity D of the aggregate to an integral spectrum intensity C of the monomer is 20% or more.   2. The organic electroluminescence device according to claim 1, wherein the concentration of the aggregate of the long wavelength side peak is constant, and the concentration of the monomer of the short wavelength side peak decreases as it approaches the cathode.   2. The organic electroluminescent device according to claim 1, wherein the concentration of the long-wavelength-side peak aggregate increases as it approaches the cathode, and the monomer concentration of the short-wavelength-side peak is constant.   2. The organic electroluminescence device according to claim 1, wherein the concentration of the aggregate of the long wavelength side peak increases as it approaches the cathode, and the concentration of the monomer of the short wavelength side peak decreases as it approaches the cathode.   When the ratio of the concentration of the long wavelength side peak to the concentration of the short wavelength side peak monomer is a on the cathode side of the light emitting layer and b on the anode side of the light emitting layer, the following equation is given: a / b> The organic electroluminescent element according to claim 1, which satisfies 1.05.