JP2009076511A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element with high light emission efficiency and excellent durability. <P>SOLUTION: The organic electroluminescent element includes at least one organic layer having a luminescent layer between a pair of electrodes. A layer containing an organic compound in which two or more nitrogenous heterocycles, aromatic hydrocarbon rings or heterocycles are bonded through linking groups, is formed between the luminescent layer and a negative electrode, and the luminescent layer contains at least one kind of electron transport material, and at least one kind of hole transport material. At least one of the electron transport material and hole transport material is a luminescent material. Concentration of the hole transport material in the luminescent layer is reduced in a direction from a positive electrode to the negative electrode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent device. In particular, the present invention relates to an organic electroluminescent device having high luminous efficiency and excellent durability.

  An organic electroluminescent element (hereinafter abbreviated as an organic EL element) is composed of a light emitting layer or a plurality of organic functional layers including a light emitting layer, and a counter electrode sandwiching these layers. In the organic EL element, electrons injected from the cathode and holes injected from the anode are recombined in the light emitting layer, and the generated light from the excitons and energy transferred from at least one of the excitons are generated. It is an element for obtaining light emission utilizing light emission from excitons of molecules.

  Until now, organic EL elements have been developed with greatly improved brightness and element efficiency by using a laminated structure with separated functions. For example, a two-layer stacked device in which a hole transport layer and a light-emitting / electron transport layer are stacked, a three-layer stacked device in which a hole transport layer, a light-emitting layer, and an electron transport layer are stacked, a hole transport layer, and a light-emitting layer A four-layer stacked element in which a hole blocking layer and an electron transport layer are stacked is often used (see Non-Patent Document 1, for example).

  However, many problems still remain in practical use of organic EL elements. The first is to achieve high luminous efficiency, and the second is to achieve high driving durability. In particular, quality degradation during continuous driving is the biggest problem.

  For example, an interface layer of 0.1 nm to 5 nm is provided as a barrier layer between the light emitting layer and the hole transport layer, and the external quantum efficiency is adjusted by adjusting the movement balance of holes and electrons by slowing the movement of holes. Attempts have been made to improve the above (for example, see Patent Document 1). However, with this means, since the movement of the carrier as a whole is reduced, the luminance is lowered, the drive voltage is increased, and the dwell time in the element of the carrier is increased, so that there is a concern that the drive durability is lowered.

  In addition, a configuration in which a single light emitting unit including a light emitting layer called a multiphoton and a functional layer is stacked in multiple layers is known. For example, a configuration is disclosed in which light emitting units of a plurality of organic electroluminescent elements (hereinafter also referred to as organic EL elements) are separated by an insulating layer and electrodes facing each light emitting unit are arranged (for example, patents). Reference 2). However, in this configuration, since the insulating layer and the electrode between the light emitting units hinder the extraction of the light emission, the light emission from each light emitting unit cannot substantially be utilized sufficiently. In addition, it is not a means for improving the low external quantum efficiency inherent to each light emitting unit. In an inorganic light-emitting element (hereinafter also referred to as an inorganic EL element), a structure in which light-emitting units are similarly stacked and each light-emitting unit is separated by an insulating layer is also disclosed (for example, see Patent Document 3). However, even in this configuration, a plurality of light emitting units are simply stacked, and it is not a means for improving the low external quantum efficiency inherent to each light emitting unit.

  In addition, a hole blocking layer containing an azole compound or an azine compound having a large ionization potential as an electron transport material is disclosed (for example, see Patent Document 4). These azole compounds and azine compounds are excellent in electron transport properties and have the effect of lowering the driving voltage and improving the light emission efficiency. On the other hand, since the Ip (ionization potential) is high and the holes are blocked, the anode side interface As a result, holes are easily collected, and resistance to holes is weak. Therefore, the holes are likely to be deteriorated by holes leaking from the light emitting layer to the electron transport layer, resulting in poor driving durability.

  Further, when the organic EL element has a laminated structure, there is a problem that the carrier injection property is lowered due to the barrier between the respective layers, the driving voltage is increased, and the durability is lowered. As a means for reducing such a barrier between layers, it is proposed to provide a gradient in the concentration of each layer of the hole injection material, the electron injection material, or the hole transport material and the electron transport material contained in each layer (for example, , See Patent Document 5). In this configuration, the light emitting material in the light emitting layer is disposed in a limited region in the light emitting layer formed from the bipolar mixed layer. Even in this configuration, light is emitted only in a limited region where the light emitting material is disposed.

  Further, it has been proposed that the concentrations of the light emitting material and the charge transport material in the light emitting layer are both low on the anode side, high on the cathode side, and concentrated to cause light emission in the cathode side region (for example, Patent Document 6). reference.). This means is effective for problems specific to polymer-dispersed light-emitting elements, but the light-emitting region is only a partial region on the cathode side, and the entire light-emitting layer is not effectively used for light emission. It cannot be said that it is an improvement.

To achieve both high external quantum efficiency and high driving durability is an extremely important issue in designing a practically useful organic EL device, and has always been a demand for improvement.
Science, 267, 3, 1995, p. 1332 JP 2003-123984 A JP-A-6-310275 JP-A-8-162273 JP 2006-310778 A JP 2002-313583 A JP 2001-189193 A

  An object of the present invention is to provide an organic EL device having high luminous efficiency and excellent durability.

It has been found that the above-mentioned problems of the present invention can be solved by the following means.
<1> An organic electroluminescent device having at least one organic layer including a light emitting layer between a pair of electrodes, wherein the following general formula (A-1) or (B-1) is provided between the light emitting layer and the cathode: And the light emitting layer contains at least one electron transport material and at least one hole transport material, and at least one of the electron transport material and the hole transport material. Is an emissive material, wherein the concentration of the hole transport material in the emissive layer decreases from the anode toward the cathode.

(In General Formula (A-1), Z ^A1 represents an atomic group necessary for forming a nitrogen-containing heterocycle. L ^A1 represents a linking group. N ^A1 represents an integer of 2 or more);

(In the general formula (B-1), Z ^B1 represents an atomic group necessary for forming an aromatic hydrocarbon ring or a heterocycle. L ^B1 represents a linking group. N ^B1 represents an integer of 2 or more.) .
<2> The concentration of the hole transport material in a region near the cathode side interface of the light emitting layer is 0% or more and 50% with respect to the concentration of the hole transport material in a region near the anode side interface of the light emitting layer. The organic electroluminescent element as described in <1>, which is as follows.
<3> The organic layer according to <1> or <2>, wherein the layer containing the organic compound represented by the general formula (A-1) or (B-1) is in contact with the light emitting layer. Electroluminescent element <4> The organic electroluminescent element according to any one of <1> to <3>, wherein the hole transporting material is a hole transporting luminescent material.
<5> The organic electroluminescent element according to any one of <1> to <3>, wherein the hole transporting material is a hole transporting host material.
<6> The organic electroluminescent element according to any one of <1> to <3> and <5>, wherein the electron transporting material is an electron transporting light emitting material.
<7> The organic electroluminescent element according to any one of <1> to <4>, wherein the electron transporting material is an electron transporting host material.
<8> The organic electroluminescent element according to any one of <4> to <6>, wherein the light emitting material is a metal complex having a tridentate or higher ligand.
<9> The organic electroluminescent element according to <8>, wherein the metal complex is a metal complex represented by the following general formula (I):

(In General Formula (I), M ¹¹ represents a metal ion, and L ^{11 to} L ¹⁵ each represents a ligand coordinated to M ^{11. An} atomic group further exists between L ¹¹ and L ^14. L ¹⁵ may be bonded to both L ¹¹ and L ¹⁴ to form a cyclic ligand, Y ¹¹ , Y ¹² and Y ¹³ are each a linking group, Represents a single bond or a double bond, and when Y ¹¹ , Y ¹² , or Y ¹³ is a linking group, L ¹¹ and Y ¹² , Y ¹² and L ¹² , L ¹² and Y ¹¹ , Y ¹¹ and L ¹³ , L ¹³ and Y ¹³ , and the bond between Y ¹³ and L ¹⁴ each independently represents a single bond or a double bond, n ¹¹ represents 0 to 4. M ¹¹ and L ^{11 to} L ¹⁵ These bonds may be any of coordination bond, ionic bond, and covalent bond.)
<10> The organic electroluminescent element according to <8> or <9>, wherein the metal complex having a tridentate or higher ligand is a platinum complex.

According to the present invention, an organic EL device having high luminous efficiency and excellent durability is provided.
In particular, an organic EL element having excellent driving durability with high luminous efficiency using a phosphorescent material is provided.

  The organic EL device of the present invention is an organic electroluminescent device having at least one organic layer including a light emitting layer between a pair of electrodes, and is formed of the general formula (A-1) or between the light emitting layer and the cathode. A layer containing an organic compound represented by (B-1), wherein the light emitting layer contains at least one electron transport material and at least one hole transport material, and the electron transport material and the holes. At least one of the transport materials is a light emitting material, and the concentration of the hole transport material in the light emitting layer decreases from the anode side toward the cathode side. In the present invention, the phrase “the concentration decreases from the anode side toward the cathode side” means that the overall decrease is from the anode side toward the cathode side. The main point is that it may change continuously or stepwise. Alternatively, even if there is a region that is partially increased or decreased, it is within the intended scope of the present application if it is generally decreased. In the present application, a pattern in which the density continuously changes is preferable.

  Preferably, the concentration of the hole transport material contained in the light emitting layer in the light emitting layer gradually decreases from the anode side toward the cathode side, and the hole transport material in the region near the cathode side interface of the light emitting layer The concentration is 0% or more and 50% or less with respect to the concentration of the hole transport material in a region near the anode side interface of the light emitting layer. More preferably, it is 0% or more and 25% or less.

  In the specification of the present application, the “region near the cathode side interface of the light emitting layer” is defined as a region having a thickness of 10% of the thickness of the entire light emitting layer from the cathode side interface of the light emitting layer. The “region near the anode side interface” is defined as a region having a thickness of 10% of the thickness of the entire light emitting layer from the anode side interface of the light emitting layer. Further, the density in the region is defined as indicating the average density in the region. Furthermore, the concentration of each material in the “region near the cathode side (anode side) interface of the light-emitting layer” is the time of flight secondary ion mass spectrometry (TOF-SIMS), etching X-ray photoelectron spectroscopy (XPS / ESCA), etc. It can be measured by the method.

Preferably, the layer containing the organic compound represented by the general formula (A-1) or (B-1) is in contact with the light emitting layer.
Preferably, the light emitting layer contains a phosphorescent material.

  The light emitting layer in the present invention has a structure in which the concentration of the hole transporting material in the light emitting layer is inclined as described above and gradually decreases from the anode side toward the cathode side. The organic compound-containing layer represented by formula (A-1) or (B-1) in the present invention is preferably arranged adjacent to the cathode side of the light emitting layer. A region near the cathode side interface of the light emitting layer adjacent to the organic compound-containing layer represented by the general formula (A-1) or (B-1) is a region having the lowest hole transporting material concentration. In the light emitting layer having a tilted structure in the present invention, the movement balance of electrons and holes in the light emitting layer is preferably adjusted, and electrons and holes can be efficiently recombined across the entire light emitting layer. Efficiency is improved. Furthermore, since holes injected from the anode are efficiently recombined in the light emitting layer, holes do not leak from the light emitting layer to the cathode side. Therefore, the layer containing the organic compound represented by the general formula (A-1) or (B-1) is not deteriorated by holes, and all of reduction in driving voltage, improvement in driving durability, and improvement in luminous efficiency are achieved. It can be improved dramatically.

1. Organic EL Element Structure The organic EL element of the present invention has a cathode and an anode on a substrate, and an organic compound layer including an organic light emitting layer (hereinafter sometimes simply referred to as “light emitting layer”) between both electrodes. . In view of the properties of the light emitting element, at least one of the anode and the cathode is preferably transparent.
As a form of lamination of the organic compound layer of the present invention, an aspect in which a hole transport layer, a light emitting layer and an electron transport layer are laminated in this order from the anode side is preferable. Further, a hole injection layer may be provided between the hole transport layer and the anode, and an electron injection layer may be provided between the electron transport layer and the cathode.
The organic compound-containing layer represented by formula (A-1) or (B-1) in the present invention is between the cathode and the light emitting layer, preferably between the electron injection layer or the electron transport layer and the light emitting layer. Arranged.

  A preferred embodiment of the organic compound layer in the organic electroluminescence device of the present invention is, in order from the anode side, at least (1) a hole injection layer, a hole transport layer (the hole injection layer and the hole transport layer may serve as both). Good), light-emitting layer, organic compound-containing layer represented by formula (A-1) or (B-1), electron transport layer, and electron injection layer (the electron transport layer and the electron injection layer may be combined). ), (2) hole injection layer, hole transport layer (hole injection layer and hole transport layer may serve both), hole transport intermediate layer, light emitting layer, general formula (A- 1) In a mode having an organic compound-containing layer represented by 1) or (B-1), an electron transport layer, an electron transporting intermediate layer, and an electron injection layer (the electron transport layer and the electron injection layer may serve both). is there.

  The hole transporting intermediate layer preferably has at least one of a function of accelerating hole injection into the light emitting layer and a function of blocking electrons.

  Each layer constituting the organic compound layer can be suitably formed by any of dry film forming methods such as vapor deposition and sputtering, transfer methods, printing methods, coating methods, ink jet methods, and spray methods.

  Next, the element which comprises the organic EL element of this invention is demonstrated in detail.

2. Light-emitting layer The light-emitting layer receives holes from the anode, hole injection layer, hole transport layer, or hole transport intermediate layer when an electric field is applied, and from the cathode, electron injection layer, electron transport layer, or electron transport intermediate layer. It is a layer having a function of receiving electrons and providing a field for recombination of holes and electrons to emit light.
The light emitting layer in the present invention includes at least one electron transport material and at least one hole transport material, and at least one of the electron transport material and the hole transport material is a light emitting material, The concentration of the hole transport material decreases from the anode side toward the cathode side.
As the electron transporting material, an electron transporting light emitting material or an electron transporting host material is used. As the hole transporting material, a hole transporting light emitting material or a hole transporting host material is used.

The concentration of the hole transport material in the region in the vicinity of the anode side interface of the light emitting layer is preferably 10% by mass or more and 100% by mass or less, more preferably 20% by mass or more and 100% by mass or less of the previous light emitting layer composition. Preferably they are 30 mass% or more and 100 mass% or less.
The concentration of the hole transport material in a region near the cathode side interface of the light emitting layer is preferably 0% by mass or more and 50% by mass or less, more preferably 0% by mass or more and 25% by mass or less of the previous light emitting layer composition.

  When the concentration of the hole transport material exceeds 50% by mass of the concentration of the light emitting layer composition in the region near the cathode side interface, the amount of holes that escape from the light emitting layer to the cathode side increases, and the luminous efficiency and durability are improved. It is not preferable in terms of reduction. In addition, if the concentration of the hole transport material is less than 10% by mass of the concentration of the light emitting layer composition in the region near the anode side interface, the amount of holes injected into the light emitting layer is reduced, and the light emission efficiency is lowered. It is not preferable.

(Electron transporting luminescent material)
The light emitting material in the light emitting layer according to the present invention may be a fluorescent light emitting material or a phosphorescent light emitting material as long as it has an electron transporting property.

(A) Phosphorescent material The phosphorescent material generally includes complexes containing transition metal atoms or lanthanoid atoms.
The transition metal atom is preferably ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, and platinum, more preferably rhenium, iridium, and platinum, and more preferably iridium, platinum. .
Examples of the lanthanoid atom include lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Among these lanthanoid atoms, neodymium, europium, and gadolinium are preferable.

Examples of the ligand of the complex include G.I. Wilkinson et al., Comprehensive Coordination Chemistry, Pergamon Press, 1987, H.C. Examples include ligands described in Yersin's "Photochemistry and Photophysics of Coordination Compounds" published by Springer-Verlag 1987, Akio Yamamoto "Organic Metal Chemistry-Fundamentals and Applications-" .
Specific ligands are preferably halogen ligands (preferably chlorine ligands), aromatic carbocyclic ligands (eg, cyclopentadienyl anion, benzene anion, or naphthyl anion), Nitrogen-containing heterocyclic ligand (eg, phenylpyridine, benzoquinoline, quinolinol, bipyridyl, or phenanthroline), diketone ligand (eg, acetylacetone), carboxylic acid ligand (eg, acetic acid ligand) , Alcoholate ligands (eg, phenolate ligands), carbon monoxide ligands, isonitrile ligands, and cyano ligands, more preferably nitrogen-containing heterocyclic ligands.
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, specific examples of the light emitting material include, for example, US6303238B1, US6097147, WO00 / 57676, WO00 / 70655, WO01 / 08230, WO01 / 39234A2, WO01 / 41512A1, WO02 / 02714A2, WO02 / 15645A1, WO02 / 44189A1, Japanese Patent Application Laid-Open No. 2001-247859, Japanese Patent Application No. 2000-33561, Japanese Patent Application No. 2002-117978, Japanese Patent Application Laid-Open No. 2002-225352, Japanese Patent Application No. 2002-233501, Japanese Patent Application No. 2001-239281, Japanese Patent Application Laid-Open No. 2002-170684, Japanese Patent Application No. JP, 2002-234894, JP, 2001-247859, JP, 2001-298470, JP, 2002-173673, JP, 2002-203. 78, JP 2002-203679, JP 2004-357791, Japanese Patent Application No. 2005-75340, and the like phosphorescent compounds described in patent documents such as JP-2006-256999.

(B) Fluorescent luminescent materials Fluorescent luminescent dopants generally include benzoxazole, benzimidazole, benzothiazole, styrylbenzene, polyphenyl, diphenylbutadiene, tetraphenylbutadiene, naphthalimide, coumarin, pyran, perinone, oxa Diazole, aldazine, pyralidine, cyclopentadiene, bisstyrylanthracene, quinacridone, pyrrolopyridine, thiadiazolopyridine, cyclopentadiene, styrylamine, aromatic dimethylidin compounds, condensed polycyclic aromatic compounds (anthracene, phenanthroline, pyrene, perylene, Rubrene, pentacene, etc.), 8-quinolinol metal complexes, pyromethene complexes and various metal complexes represented by rare earth complexes, polythiophene, polyphenylene, poly Examples thereof include polymer compounds such as rephenylene vinylene, organic silanes, and derivatives thereof.

In addition, the electron-transporting light-emitting material preferably has an electron-transport property having an electron affinity (Ea) of 2.5 eV to 3.5 eV and an ionization potential (Ip) of 5.7 eV to 7.0 eV. It is a luminescent material.
Specifically, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium complex More preferred is a ruthenium, rhodium, palladium, or platinum complex, and most preferred is a platinum complex.
Examples of platinum complexes are shown below, but the present invention is not limited thereto.

  The electron-transporting phosphorescent material used in the present invention is particularly preferably a metal complex having a tridentate or higher ligand.

(Multidentate metal complex)
The metal complex having a tridentate or higher ligand in the present invention will be described.
1) Metal ion The atom coordinated to the metal ion in the metal complex is not particularly limited, but is preferably an oxygen atom, a nitrogen atom, a carbon atom, a sulfur atom or a phosphorus atom, more preferably an oxygen atom, a nitrogen atom or a carbon atom, More preferred are nitrogen or carbon atoms.

  The metal ion in the metal complex is not particularly limited, but is preferably a transition metal ion or a rare earth metal ion from the viewpoint of improving luminous efficiency, improving durability, and lowering driving voltage, iridium ion, platinum ion, gold ion, Rhenium ion, tungsten ion, rhodium ion, ruthenium ion, osmium ion, palladium ion, silver ion, copper ion, cobalt ion, zinc ion, nickel ion, lead ion, aluminum ion, gallium ion, or rare earth metal ion (for example, europium) An iridium ion, a platinum ion, a gold ion, a rhenium ion, a tungsten ion, a palladium ion, a zinc ion, an aluminum ion, a gallium ion, and the like. , Europium, cadmium, or terbium, more preferably iridium, platinum, rhenium, tungsten, europium, cadmium, or terbium, and more preferably iridium. Platinum ion, palladium ion, zinc ion, aluminum ion, or gallium ion, and most preferably platinum ion.

2) Coordination number The metal complex having a tridentate or higher ligand in the present invention is preferably a metal complex having a tridentate or higher and a hexadentate or lower ligand from the viewpoint of improving luminous efficiency and durability. In the case of a metal ion that easily forms a hexacoordinate complex represented by iridium ion, a metal complex having a tridentate, tetradentate, or hexadentate ligand is more preferable, and platinum ion is representative. In the case of a metal ion that easily forms a tetracoordinate complex, a metal complex having a tridentate or tetradentate ligand is more preferable, and a metal complex having a tetradentate ligand is more preferable.

3) Ligand From the viewpoint of improving luminous efficiency and durability, the ligand of the metal complex in the present invention is preferably a chain or a ring, and a central metal (for example, the general formula (I) described later) In the case of a compound represented by the formula, N ¹¹ represents a nitrogen-containing heterocycle coordinated with nitrogen (for example, pyridine ring, quinoline ring, pyrimidine ring, pyrazine ring, pyrrole ring, imidazole ring, pyrazole ring). Oxazole ring, thiazole ring, oxadiazole ring, thiadiazole ring, or triazole ring). The nitrogen-containing heterocycle is more preferably a nitrogen-containing 6-membered heterocycle or a nitrogen-containing 5-membered heterocycle. These heterocycles may form condensed rings with other rings.

  That the ligand of the metal complex is a chain means that the ligand of the metal complex does not have a cyclic structure (for example, a terpyridyl ligand). Further, that the ligand of the metal complex is cyclic means that a plurality of ligands in the metal complex are bonded to each other to form a closed structure (for example, phthalocyanine ligand, crown ether coordination). Etc.).

4) Preferred Metal Complex Structure The metal complex in the present invention is preferably an organic compound represented by the general formula (I) described in detail below.

<Metal Complex Represented by General Formula (I)>
First, the organic compound represented by the general formula (I) will be described.

In the general formula ^{(I), M 11} represents a metal ^ion, L 11 ^{~L 15} represents a ligand coordinated to ^{M 11,} respectively. An atomic group may further exist between L ¹¹ and L ¹⁴ to form a cyclic ligand. L ¹⁵ may combine with both L ¹¹ and L ¹⁴ to form a cyclic ligand.
Y ¹¹ , Y ¹² and Y ¹³ each represent a linking group, a single bond or a double bond. When Y ¹¹ , Y ¹² , or Y ¹³ is a linking group, L ¹¹ and Y ¹² , Y ¹² and L ¹² , L ¹² and Y ¹¹ , Y ¹¹ and L ¹³ , L ¹³ and Y ¹³ , Y ¹³ And the bond between L ¹⁴ each independently represents a single bond or a double bond. n ¹¹ represents the 0-4. The bond between M ¹¹ and L ^{11 to} L ¹⁵ may be any of a coordination bond, an ionic bond, and a covalent bond.

The organic compound represented by the general formula (I) will be described in detail.
In the general formula (I), M ¹¹ represents a metal ion. Although it does not specifically limit as a metal ion, A bivalent or trivalent metal ion is preferable. As the divalent or trivalent metal ion, platinum ion, iridium ion, rhenium ion, palladium ion, rhodium ion, ruthenium ion, copper ion, europium ion, gadolinium ion, terbium ion are preferable, platinum ion, iridium ion, or Europium ions are more preferred, platinum ions and iridium ions are more preferred, and platinum ions are particularly preferred.

In general formula (I), L ¹¹ , L ¹² , L ¹³ , and L ¹⁴ each independently represent a ligand that coordinates to M ¹¹ . The atoms contained in L ¹¹ , L ¹² , L ¹³ , and L ¹⁴ and coordinated to M ¹¹ are preferably a nitrogen atom, an oxygen atom, a sulfur atom, a carbon atom, or a phosphorus atom. An atom, a sulfur atom, or a carbon atom is more preferable, and a nitrogen atom, an oxygen atom, or a carbon atom is still more preferable.

The bonds formed by M ¹¹ and L ¹¹ , L ¹² , L ¹³ , and L ¹⁴ may each independently be a covalent bond, an ionic bond, or a coordinate bond. For convenience of explanation, the ligand in the present invention shall be used not only in the case of a coordination bond but also in the case of being formed by other ionic bonds or covalent bonds.
The ligand consisting of L ¹¹ , Y ¹² , L ¹² , Y ¹¹ , L ¹³ , Y ¹³ , and L ¹⁴ is an anionic ligand (a ligand in which at least one anion binds to a metal). Is preferred. 1-3 are preferable, as for the number of anions in an anionic ligand, 1 and 2 are more preferable, and 2 is further more preferable.

L ¹¹ , L ¹² , L ¹³ , and L ¹⁴ coordinated to M ¹¹ by a carbon atom are not particularly limited, but are each independently an imino ligand, an aromatic carbocyclic ligand (for example, a benzene ligand). , Naphthalene, anthracene, or phenanthracene ligands), heterocyclic ligands (eg, thiophene ligands, pyridine ligands, pyrazine ligands, pyrimidine ligands, thiazole ligands) Ligands, oxazole ligands, pyrrole ligands, imidazole ligands, pyrazole ligands, and condensed rings containing them (eg, quinoline ligands, benzothiazole ligands, etc.) and their tautomers Sex body).

L ¹¹ , L ¹² , L ¹³ , and L ¹⁴ coordinated to M ¹¹ by a nitrogen atom are not particularly limited, but each independently includes a nitrogen-containing heterocyclic ligand (eg, pyridine ligand, pyrazine coordination). Ligand, pyrimidine ligand, pyridazine ligand, triazine ligand, thiazole ligand, oxazole ligand, pyrrole ligand, imidazole ligand, pyrazole ligand, triazole ligand, oxadi Azole ligands, thiadiazole ligands, and condensed rings containing them (for example, quinoline ligands, benzoxazole ligands, benzimidazole ligands, etc.) and tautomers thereof (note that In the present invention, in addition to the usual isomers, the following examples are also defined as tautomers, for example, the 5-membered heterocyclic ligand of the compound (24) described later and the 5-membered terminal of the compound (64). Arocyclic ligands, 5-membered heterocyclic ligands of the compound (145) are also defined as pyrrole tautomers, etc.) amino ligands (alkylamino ligands (preferably having 2 to 30 carbon atoms, More preferably, it has 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, and examples thereof include methylamino.), Arylamino ligands (for example, phenylamino), acylamino ligands (Preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, and examples thereof include acetylamino and benzoylamino), alkoxycarbonylamino ligands (preferably Has 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, and particularly preferably 2 to 12 carbon atoms, and examples thereof include methoxycarbonylamino. ), An aryloxycarbonylamino ligand (preferably having 7 to 30 carbon atoms, more preferably 7 to 20 carbon atoms, particularly preferably 7 to 12 carbon atoms, and examples thereof include phenyloxycarbonylamino). Sulfonylamino ligands (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methanesulfonylamino, benzenesulfonylamino, etc.), imino. These ligands may be further substituted.

L ¹¹ , L ¹² , L ¹³ , and L ¹⁴ coordinated to M ¹¹ with an oxygen atom are not particularly limited, but are independently an alkoxy ligand (preferably having 1 to 30 carbon atoms, more preferably having carbon atoms). 1 to 20, particularly preferably 1 to 10 carbon atoms, such as methoxy, ethoxy, butoxy, 2-ethylhexyloxy), aryloxy ligands (preferably 6 to 30 carbon atoms, more preferably Has 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyloxy, 1-naphthyloxy, 2-naphthyloxy and the like, and a heterocyclic oxy ligand (preferably having 1 carbon atom). To 30, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as pyridyloxy, pyrazyloxy, pyrimidyloxy, Noryloxy, etc.), acyloxy ligands (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, such as acetoxy, benzoyloxy and the like. ), A silyloxy ligand (preferably having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, and examples thereof include trimethylsilyloxy and triphenylsilyloxy). , Carbonyl ligands (eg, ketone ligands, ester ligands, amide ligands, etc.), ether ligands (eg, dialkyl ether ligands, diaryl ether ligands, furyl ligands, etc.) Can be mentioned.

Although it does not specifically limit as L < ¹¹ >, L < ¹² >, L <^13> , and L < ¹⁴ > coordinated to M < ¹¹ > by a sulfur atom, Each is independently alkylthio ligand (preferably C1-C30, More preferably, carbon number. 1 to 20, particularly preferably 1 to 12 carbon atoms, for example, methylthio, ethylthio, etc.), an arylthio ligand (preferably 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably Has 6 to 12 carbon atoms, for example, phenylthio and the like, and a heterocyclic thio ligand (preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms). And examples thereof include pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio, 2-benzthiazolylthio), and thiocarbo. Le ligands (e.g. thioketone ligand, etc. thioester ligands), or thioether ligands (e.g. dialkyl thioether ligands, diaryl thioether ligands, etc. thiofuryl ligand), and the like. These substituted ligands may be further substituted.

L ¹¹ , L ¹² , L ¹³ , and L ¹⁴ coordinated to M ¹¹ with a phosphorus atom are not particularly limited, but each independently includes a dialkylphosphino group, a diarylphosphino group, a trialkylphosphine, a triarylphosphine, And a phosphinin group. These groups may be further substituted.

L ¹¹ and L ¹⁴ are each independently an aromatic carbocyclic ligand, alkyloxy ligand, aryloxy ligand, ether ligand, alkylthio ligand, arylthio ligand, alkylamino coordination Ligand, arylamino ligand, acylamino ligand, nitrogen-containing heterocyclic ligand (eg pyridine ligand, pyrazine ligand, pyrimidine ligand, pyridazine ligand, triazine ligand, thiazole ligand) Ligands, oxazole ligands, pyrrole ligands, imidazole ligands, pyrazole ligands, triazole ligands, oxadiazole ligands, thiadiazole ligands, or condensed ligand bodies containing them (For example, a quinoline ligand, a benzoxazole ligand, a benzimidazole ligand, or the like, or a tautomer thereof) is preferable, and an aromatic carbocyclic ligand Aryloxy ligands, arylthio ligands, arylamino ligands, and pyridine ligands, pyrazine ligands, imidazole ligands, or condensed ligand bodies containing them (for example, quinoline ligands) Quinoxaline ligand, benzimidazole ligand, etc.), or tautomers thereof, more preferably aromatic carbocyclic ligand, aryloxy ligand, arylthio ligand, or arylamino coordination A child is further preferred, and an aromatic carbocyclic ligand or an aryloxy ligand is particularly preferred.

L ¹² and ^{L 13} each ^{independently} ligands preferably form a coordinate bond with ^{M 11,} as ligands forming a coordination bond with ^{M 11,} a pyridine ring, a pyrazine ring, a pyrimidine ring, Triazine ring, thiazole ring, oxazole ring, pyrrole ring, triazole ring, and condensed ring containing them (for example, quinoline ring, benzoxazole ring, benzimidazole ring, or indolenine ring) and their tautomerism Pyridine ring, pyrazine ring, pyrimidine ring, pyrrole ring, and condensed ring containing them (for example, quinoline ring, benzpyrrole, etc.) and tautomers thereof are more preferable, pyridine ring, More preferred are a pyrazine ring, a pyrimidine ring, and a condensed ring containing them (for example, a quinoline ring, etc.), a pyridine ring, and A condensed ring containing a pyridine ring (for example, a quinoline ring) is particularly preferable.

In the general formula (I), L ¹⁵ represents a ligand coordinated to M ¹¹ . L ¹⁵ is preferably a 1-4-dentate ligand, more preferably a 1-4-dentate anionic ligand. Although it does not specifically limit as an anionic ligand of 1-4 tetradentate, The monoanionic property containing a halogen ligand, a 1, 3- diketone ligand (for example, acetylacetone ligand etc.), and a pyridine ligand Bidentate ligand (eg, picolinic acid ligand, 2- (2-hydroxyphenyl) -pyridine ligand, etc.), L ¹¹ , Y ¹² , L ¹² , Y ¹¹ , L ¹³ , Y ¹³ , L ¹⁴ And a monoanionic bidentate ligand containing a 1,3-diketone ligand (for example, an acetylacetone ligand) or a pyridine ligand (for example, a picolinic acid ligand). A tetradentate ligand formed by L ¹¹ , Y ¹² , L ¹² , Y ¹¹ , L ¹³ , Y ¹³ , L ¹⁴ , and the like. Preferably, 1,3-diketone Ligands (eg, acetylacetone ligand), monoanionic bidentate ligands containing pyridine ligand (eg, picolinic acid ligand, 2- (2-hydroxyphenyl) -pyridine ligand, etc.) Are more preferable, and a 1,3-diketone ligand (for example, an acetylacetone ligand) is particularly preferable. The number of coordination sites and the number of ligands do not exceed the coordination number of the metal. However, L ¹⁵ does not combine with both L ¹¹ and L ¹⁴ to form a cyclic ligand.

In general formula (I), Y ¹¹ , Y ¹² , and Y ¹³ each independently represent a linking group, a single bond, or a double bond. Although it does not specifically limit as a coupling group, For example, the coupling group comprised including the atom selected from a carbon atom, a nitrogen atom, an oxygen atom, a sulfur atom, a silicon atom, and a phosphorus atom is preferable. Specific examples of such a linking group include the following.

When Y ¹¹ , Y ¹² , or Y ¹³ is a linking group, L ¹¹ and Y ¹² , Y ¹² and L ¹² , L ¹² and Y ¹¹ , Y ¹¹ and L ¹³ , L ¹³ and Y ¹³ , Y ¹³ And the bond between L ¹⁴ each independently represents a single bond or a double bond.

Y ¹¹ , Y ¹² , and Y ¹³ are each independently preferably a single bond, a double bond, a carbonyl linking group, an alkylene linking group, or an alkenylene group. Y ¹¹ is more preferably a single bond or an alkylene group, and still more preferably an alkylene group. Y ¹² and Y ¹³ are more preferably a single bond or an alkenylene group, and even more preferably a single bond.

Ring formed by Y ¹² , L ¹¹ , L ¹² , and M ¹¹ , Ring formed by Y ¹¹ , L ¹² , L ¹³ , and M ¹¹ , Formed by Y ¹³ , L ¹³ , L ¹⁴ , and M ¹¹ The ring to be formed preferably has 4 to 10 ring members, more preferably 5 to 7 ring members, and further preferably 5 or 6 ring members.

In the general formula ^{(I), n 11} represents 0 to 4. If M ¹¹ is a metal coordination number ^{4, n 11} is ^0, when ^{M 11} is a metal coordination number ^{6, n 11} is 1, 2 is preferable, and more preferably 1. When M ¹¹ is coordination number 6 and n ¹¹ is 1, L ¹⁵ represents a bidentate ligand, and when M ¹¹ is coordination number 6 and n ¹¹ is 2, L ¹⁵ represents a monodentate ligand. When M ¹¹ is a metal having a coordination number of 8, n ¹¹ is preferably 1 to 4, more preferably 1, 2, and more preferably 1. When M ¹¹ is coordination number 8 and n ¹¹ is 1, L ¹⁵ represents a tetradentate ligand, and when M ¹¹ is coordination number 8 and n ¹¹ is 2, L ¹⁵ represents a bidentate ligand. When n ¹¹ is plural, a plurality of L ¹⁵ may be different even in the same.

(Hole-transporting light-emitting material)
As the hole transporting light emitting material used in the present invention, a hole transporting fluorescent light emitting material or a hole transporting phosphorescent light emitting material can be used, and a hole transporting phosphorescent light emitting material is preferable.
The hole transporting luminescent material in the present invention will be described.

  The hole transporting light emitting material used for the light emitting layer of the present invention preferably has an ionization potential (Ip) of 5.1 eV or more and 6.4 eV or less from the viewpoint of improving durability and lowering driving voltage. It is more preferably 4 eV or more and 6.2 eV or less, and further preferably 5.6 eV or more and 6.0 eV or less. Further, from the viewpoint of improving durability and lowering driving voltage, the electron affinity (Ea) is preferably 1.2 eV or more and 3.1 eV or less, more preferably 1.4 eV or more and 3.0 eV or less. More preferably, it is 8 eV or more and 2.8 eV or less.

  Specific examples of such hole transporting light emitting materials include, for example, pyrrole compounds, indole compounds, carbazole compounds, imidazole compounds, polyarylalkane compounds, arylamine compounds, styryl compounds, In addition to styrylamine compounds, thiophene compounds, aromatic polycyclic condensation compounds, metal complexes, and the like can be given.

  The metal ion in the metal complex is not particularly limited, but is preferably a transition metal ion or a rare earth metal ion, more preferably an iridium ion or platinum, from the viewpoints of improving luminous efficiency, durability, and driving voltage. Ion, gold ion, rhenium ion, tungsten ion, rhodium ion, ruthenium ion, osmium ion, palladium ion, silver ion, copper ion, cobalt ion, nickel ion, lead ion, rare earth metal ion (for example, europium ion, gadolinium ion, Or terbium ions, and the like, more preferably iridium ions, platinum ions, gold ions, rhenium ions, tungsten ions, europium ions, cadolinium ions, or terbium ions, and particularly preferably iridium Ion, platinum ion, a rhenium ion, europium ion, a gadolinium ion, or terbium ions, most preferably iridium ion. Among metal complexes having iridium ions, particularly preferred are metal complexes having a carbon-Ir bond and a nitrogen-Ir bond (in this case, the bond may be a coordination bond, an ionic bond or a covalent bond). is there.

Specific examples of such hole-transporting light-emitting materials include, but are not limited to, the following materials.

(Electron transporting host material)
The electron transporting host material used in the present invention preferably has an electron affinity Ea of 2.5 eV or more and 3.5 eV or less, from the viewpoint of improving durability and lowering driving voltage, and 2.6 eV or more and 3.4 eV or less. It is more preferable that it is 2.8 eV or more and 3.3 eV or less. Further, from the viewpoint of improving durability and reducing driving voltage, the ionization potential Ip is preferably 5.7 eV or more and 7.5 eV or less, more preferably 5.8 eV or more and 7.0 eV or less, and 5.9 eV or more. More preferably, it is 6.5 eV or less.

  Specific examples of such an electron transporting host include, for example, pyridine, pyrimidine, triazine, imidazole, pyrazole, triazole, oxazole, oxadiazol, fluorenone, anthraquinodimethane, anthrone, and diphenylquinone. , Thiopyran dioxide, carbodiimide, fluorenylidenemethane, distyrylpyrazine, fluorine-substituted aromatic compounds, heterocyclic tetracarboxylic anhydrides such as naphthaleneperylene, phthalocyanines, and their derivatives (form condensed rings with other rings) Or metal complexes of 8-quinolinol derivatives, metal phthalocyanines, various metal complexes typified by metal complexes having benzoxazole or benzothiazole as a ligand, and the like.

The electron transporting host material is preferably a metal complex, an azole derivative (benzimidazole derivative, imidazopyridine derivative, etc.), or an azine derivative (pyridine derivative, pyrimidine derivative, triazine derivative, etc.). From the viewpoint, a metal complex compound is preferable. 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 the metal.
The metal ion in the metal complex is not particularly limited, but is preferably beryllium ion, magnesium ion, aluminum ion, gallium ion, zinc ion, indium ion, tin ion, platinum ion, or palladium ion, more preferably beryllium ion, Aluminum ion, gallium ion, zinc ion, platinum ion, or palladium ion, and more preferably aluminum ion, zinc ion, platinum ion, or palladium ion.

  There are various known ligands contained in the metal complex. For example, “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.

The ligand is preferably a nitrogen-containing heterocyclic ligand (preferably having 1 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 3 to 15 carbon atoms, and a monodentate ligand. Alternatively, 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 lower 6 or lower 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). And a hydroxyphenyl benzoxazole ligand, a hydroxyphenyl imidazole ligand, a hydroxyphenylimidazopyridine ligand, etc.), an alkoxy ligand (preferably having 1 to 30 carbon atoms, more preferably 1 carbon atom). To 20, particularly preferably 1 to 10 carbon atoms, such as methoxy, ethoxy, butoxy, 2-ethylhexyloxy), aryloxy ligands (preferably 6 to 30 carbon atoms, more preferably 6-20 carbon atoms, particularly preferably 6-12 carbon atoms, for example phenyl Carboxymethyl, 1-naphthyloxy, 2-naphthyloxy, 2,4,6-trimethylphenyl oxy, and 4-biphenyloxy and the like.),

Heteroaryloxy ligand (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include pyridyloxy, pyrazyloxy, pyrimidyloxy, and quinolyloxy. ), An alkylthio ligand (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methylthio and ethylthio), 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 ligand (preferably 1 carbon atom) To 30, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as pyridylthio , 2-benzimidazolylthio, 2-benzoxazolylthio, 2-benzthiazolylthio, etc.), a siloxy ligand (preferably having 1 to 30 carbon atoms, more preferably 3 to 25 carbon atoms). Particularly preferably, it has 6 to 20 carbon atoms, and examples thereof include a triphenylsiloxy group, a triethoxysiloxy group, and a triisopropylsiloxy group.), An aromatic hydrocarbon anion ligand (preferably having 6 carbon atoms) To 30, more preferably 6 to 25 carbon atoms, particularly preferably 6 to 20 carbon atoms, such as a phenyl anion, a naphthyl anion, an anthranyl anion, etc.), an aromatic heterocyclic anion ligand (preferably Has 1 to 30 carbon atoms, more preferably 2 to 25 carbon atoms, and particularly preferably 2 to 20 carbon atoms. Pyrrole anion, pyrazole anion, pyrazole anion, triazole anion, oxazole anion, benzoxazole anion, thiazole anion, benzothiazole anion, thiophene anion, benzothiophene anion, etc.), indolenine anion ligand, etc. , Preferably a nitrogen-containing heterocyclic ligand, aryloxy ligand, heteroaryloxy group, or siloxy ligand, more preferably a nitrogen-containing heterocyclic ligand, aryloxy ligand, siloxy coordination Or an aromatic hydrocarbon anion ligand or an aromatic heterocyclic anion ligand.

  Examples of the metal complex electron transporting host are described in, for example, JP-A No. 2002-235076, JP-A No. 2004-214179, JP-A No. 2004-221106, JP-A No. 2004-221665, JP-A No. 2004-221068, JP-A No. 2004-327313, and the like. The compound of this is mentioned.

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

  The electron transport layer host material is preferably E-1 to E-6, E-8, E-9, E-10, E-21, or E-22, and E-3, E-4, E-6. E-8, E-9, E-10, E-21, or E-22 are more preferred, and E-3, E-4, E-8, E-9, E-21, or E-22 are preferred. Further preferred.

  In the light emitting layer of the present invention, when a phosphorescent dopant is used as the luminescent dopant, the lowest triplet excitation energy T1 (D) of the phosphorescent dopant and the lowest excited triplet energy of the plurality of host compounds. It is preferable in terms of color purity, external quantum efficiency, and driving durability that the above T1 (H) min satisfies the relationship of T1 (H) min> T1 (D).

(Hole-transporting host material)
The hole transporting host material used in the light emitting layer of the present invention preferably has an ionization potential Ip of 5.1 eV or more and 6.4 eV or less from the viewpoint of improving durability and lowering driving voltage. It is more preferably 6.2 eV or less, and further preferably 5.6 eV or more and 6.0 eV or less. Further, from the viewpoint of improving durability and lowering driving voltage, the electron affinity Ea is preferably 1.2 eV or more and 3.1 eV or less, more preferably 1.4 eV or more and 3.0 eV or less, and 1.8 eV or more. More preferably, it is 2.8 eV or less.

Specific examples of such hole transporting host materials include 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 Examples include copolymers, thiophene oligomer thiophene oligomers, conductive polymer oligomers such as polythiophene, organic silanes, carbon films, and derivatives thereof.
Among them, indole derivatives, carbazole derivatives, azaindole derivatives, azacarbazole derivatives, aromatic tertiary amine compounds, and thiophene derivatives are preferable. Those having a plurality of at least one of tertiary amine skeletons are preferred.
Specific examples of such a hole transporting host material include, but are not limited to, the following compounds.

<Mixing ratio of luminescent material and host material>
In the present invention, the mixing ratio of the hole-transporting host material and the electron-transporting light-emitting material is associative light emission or concentration quenching while obtaining a sufficient light emission intensity, from the viewpoint of suppressing leakage of holes from the light-emitting layer, The total of the light emitting layers is preferably a95: 5 to 50:50 by mass ratio, and more preferably b90: 10 to 70:30.
-Mixing ratio of electron transporting host material and hole transporting light emitting material-
In the present invention, the mixing ratio of the electron transporting host material and the hole transporting light-emitting material is associative light emission or concentration quenching while obtaining a sufficient light emission intensity, from the viewpoint of suppressing leakage of holes from the light emitting layer, The total amount of the light emitting layers is preferably c5: 95 to 50:50, more preferably d10: 90 to 30:70 in terms of mass ratio.

<Film thickness>
The thickness of the light emitting layer is preferably 0.03 μm or more and 0.5 μm or less, and more preferably 0.06 μm or more and 0.4 μm or less from the viewpoint of luminance unevenness, driving voltage, and luminance. If the light-emitting layer is thin, it can be driven with high brightness and low voltage, but the device resistance becomes small, so it is more susceptible to changes in brightness due to voltage drop, resulting in increased brightness unevenness. It becomes. If the thickness of the light emitting layer is large, the drive voltage increases, leading to a decrease in light emission efficiency and limiting the application.

<Layer structure>
The light emitting layer may be one layer or two or more layers, and each layer may emit light in different emission colors. In the case where the light emitting layer has a laminated structure, the film thickness of each layer constituting the laminated structure is not particularly limited, but it is preferable that the total film thickness of each light emitting layer is in the above-described range.

3. Layer containing organic compound represented by general formula (A-1) or (B-1) The organic compound-containing layer represented by general formula (A-1) or (B-1) in the present invention is a cathode. Between the light emitting layer and the light emitting layer, preferably between the electron injecting layer or the electron transporting layer and the light emitting layer.
The organic compound-containing layer represented by the general formula (A-1) or (B-1) in the present invention is disposed adjacent to the light emitting layer containing the hole transporting material in the present invention with a concentration gradient. As a result, it has high electron transport properties, lowers the driving voltage, improves the light emission efficiency, and realizes high driving durability.

  The organic compound-containing layer represented by the general formula (A-1) or (B-1) in the present invention is preferably in direct contact with the light emitting layer.

(Organic compound represented by general formula (A-1) or (B-1))
The organic compound represented by formula (A-1) or (B-1) according to the present invention will be described.

In General Formula (A-1), Z ^A1 represents an atomic group necessary for forming a nitrogen-containing heterocycle. L ^A1 represents a linking group. n ^A1 represents an integer of 2 or more.

In General Formula (B-1), Z ^B1 represents an atomic group necessary for forming an aromatic hydrocarbon ring or a heterocycle. L ^B1 represents a linking group. n ^B1 represents an integer of 2 or more.

Next, the organic compound represented by the general formula (A-1) will be described.
L ^A1 in the general formula (A-1) represents a linking group. The linking group represented by L ^A1 is preferably a linking group formed of, in addition to a single bond, a carbon atom, a silicon atom, a nitrogen atom, a phosphorus atom, a sulfur atom, an oxygen atom, a boron atom, or a germanium atom. More preferably a single bond, a carbon atom, a silicon atom, a boron atom, an oxygen atom, a sulfur atom, a germanium atom, an aromatic hydrocarbon ring, or an aromatic heterocycle, more preferably a carbon atom, a silicon atom, An aromatic hydrocarbon ring or an aromatic heterocycle, more preferably a divalent or higher aromatic hydrocarbon ring, a divalent or higher aromatic heterocycle, or a carbon atom, more preferably a divalent or higher valence. An aromatic hydrocarbon ring and a divalent or higher aromatic heterocycle, particularly preferably 1,3,5-benzenetriyl group, 1,2,5,6-benzenetetrayl group, 1,2,3. , 4 , 5,6-Benzenehexyl group, 2,2′-dimethyl-4,4′-biphenylene group, 2,4,6-pyridinetriyl group, 2,3,4,5,6-pyridinepentyl group 2,4,6-pyrimidinetriyl group, 2,4,6-triazinetriyl group, or 2,3,4,5-thiophenetetrayl group. Specific examples of the linking group represented by L ^A1 include the following.

L ^A1 may have a substituent, and examples of the substituent include an alkyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms; For example, methyl, ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc.), an alkenyl group (preferably having 2 to 30 carbon atoms) Preferably it is C2-C20, Most preferably, it is C2-C10, for example, vinyl, allyl, 2-butenyl, 3-pentenyl etc.), an alkynyl group (preferably C2-C30, more) Preferably it is C2-C20, Most preferably, it is C2-C10, for example, a propargyl, 3-pentynyl, etc. are mentioned. ), An aryl group (preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyl, p-methylphenyl, naphthyl, and anthranyl). An amino group (preferably having 0 to 30 carbon atoms, more preferably 0 to 20 carbon atoms, particularly preferably 0 to 10 carbon atoms, such as amino, methylamino, dimethylamino, diethylamino, dibenzylamino, diphenylamino, ), Alkoxy groups (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, butoxy, 2-ethylhexyl). And siloxy).

An aryloxy group (preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include phenyloxy, 1-naphthyloxy, 2-naphthyloxy and the like. ), A heterocyclic oxy group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include pyridyloxy, pyrazyloxy, pyrimidyloxy, quinolyloxy and the like.) An acyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as acetyl, benzoyl, formyl, pivaloyl, etc.), an alkoxycarbonyl group (Preferably 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably carbon number. For example, methoxycarbonyl, ethoxycarbonyl, etc.), aryloxycarbonyl group (preferably having 7 to 30 carbon atoms, more preferably having 7 to 20 carbon atoms, particularly preferably having 7 to 12 carbon atoms). , For example, phenyloxycarbonyl, etc.), an acyloxy group (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, such as acetoxy, benzoyloxy and the like. An acylamino group (preferably having 2 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 2 to 10 carbon atoms, such as acetylamino and benzoylamino), alkoxy Carbonylamino group (preferably having 2 to 30 carbon atoms, more preferably 2 to 2 carbon atoms) 0, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonylamino, and the like, aryloxycarbonylamino group (preferably 7 to 30 carbon atoms, more preferably 7 to 20 carbon atoms, particularly preferably 7 to 12 carbon atoms such as phenyloxycarbonylamino), sulfonylamino group (preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms). For example, methanesulfonylamino, benzenesulfonylamino, etc.), sulfamoyl groups (preferably having 0 to 30 carbon atoms, more preferably 0 to 20 carbon atoms, particularly preferably 0 to 12 carbon atoms, for example, sulfamoyl Methylsmethylsulfamoyl, dimethylsulfamoyl, phenylsulfa For example, moile. ),

A carbamoyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl and the like), alkylthio. A group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methylthio and ethylthio), an arylthio group (preferably having 6 to 6 carbon atoms). 30, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenylthio, and the like, and a heterocyclic thio group (preferably 1 to 30 carbon atoms, more preferably 1 carbon atom). To 20, particularly preferably 1 to 12 carbon atoms, for example pyridylthio, 2-benzimidazolyl E, 2-benzoxazolylthio, 2-benzthiazolylthio, etc.), sulfonyl group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms). For example, mesyl, tosyl, etc.), sulfinyl groups (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methanesulfinyl, benzene And ureido groups (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably 1 to 12 carbon atoms. Examples thereof include ureido, methylureido, and phenylureido. Phosphoric acid amide group (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, and particularly preferably carbon 1 to 12, for example, diethyl phosphate amide, phenyl phosphate amide, etc.), hydroxy group, mercapto group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, Sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms, Examples thereof include a nitrogen atom, an oxygen atom, and a sulfur atom, and specific examples include imidazolyl, pyridyl, quinolyl, furyl, thienyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl, carbazolyl group, azepinyl group, and the like. ),

A silyl group (preferably having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, such as trimethylsilyl, triphenylsilyl, etc.), a silyloxy group (preferably carbon 3 to 40, more preferably 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, and examples thereof include trimethylsilyloxy, triphenylsilyloxy, and the like.

These substituents may be further substituted. The substituent is preferably an alkyl group, an aryl group, a heterocyclic group, a halogen atom or a silyl group, more preferably an alkyl group, an aryl group, a heterocyclic group or a halogen atom, still more preferably an alkyl group or an aryl group. , An aromatic heterocyclic group atom. As these substituents, those which may be possessed by L ^A1 can be applied, and preferred ranges thereof are also the same.

Z ^A1 represents an atomic group necessary for forming a nitrogen-containing heterocycle, and the nitrogen-containing heterocycle formed by Z ^A1 may be a single ring or a condensed ring in which two or more rings are condensed. The nitrogen-containing heterocycle formed by Z ^A1 is preferably a 5-membered to 8-membered nitrogen-containing heterocycle, more preferably a 5-membered to 7-membered nitrogen-containing heterocycle, still more preferably 5-membered or 6-membered. A nitrogen-containing aromatic heterocycle, particularly preferably a 5-membered aromatic heterocycle. A plurality of nitrogen-containing heterocycles formed by Z ^A1 connected to L ^A1 may be the same or different.

Specific examples of the nitrogen-containing heterocycle formed by Z ^A1 include, for example, a pyrrole ring, an indole ring, an oxazole ring, an oxadiazole ring, a thiazole ring, a thiazizole ring, an azaindole ring, a carbazole ring, a carboline ring (norharman ring), Imidazole ring, benzimidazole ring, imidazopyridine ring, purine ring, pyrazole ring, indazole ring, azaindazole ring, triazole ring, tetrazole ring, azepine ring, iminostilbene ring (dibenzoazepine ring), tribenzazepine ring, phenothiazine Ring, phenoxazine ring and the like, preferably oxadiazole ring, triazole ring, imidazole ring, benzimidazole ring or imidazopyridine ring, more preferably benzimidazole ring and imidazopyridine ring. .

Z ^A1 may further form a condensed ring with another ring, if possible, and may have a substituent. As the substituent for Z ^A1 , for example, those mentioned as the substituent that L ^A1 in formula (A-1) may have can be applied, and the preferred range is also the same.
n ^A1 represents an integer of 2 or more, preferably 2 to 8, more preferably 2 to 6.

Next, the organic compound represented by the general formula (B-1) will be described.
L ^B1 in the general formula (B-1) represents a linking group. As the linking group represented by L ^B1 , those exemplified as specific examples of the linking group L ^A1 in formula (A-1) can be applied, and L ^B1 is preferably a single bond or a divalent or higher aromatic carbonization. A hydrogen ring, a divalent or higher aromatic heterocycle, a carbon atom, a nitrogen atom, or a silicon atom, more preferably a divalent or higher aromatic hydrocarbon ring, a divalent or higher aromatic heterocycle, Preferably, 1,3,5-benzenetriyl group, 1,2,5,6-benzenetetrayl group, 1,2,3,4,5,6-benzenehexyl group, 2,2′-dimethyl- 4,4′-biphenylene group, 2,4,6-pyridinetriyl group, 2,3,4,5,6-pyridinepentyl group, 2,4,6-pyrimidinetriyl group, 2,4,6 -Triazine triyl group, 2,3,4,5-thiophenetetrayl group Carbon atom, a nitrogen atom, or a silicon atom.
L ^B1 may further have a substituent. As the substituent, for example, those exemplified as the substituent for L ^A1 in formula (A-1) can be applied, and the preferred range is also the same.

Z ^B1 represents an atomic group necessary for forming an aromatic hydrocarbon ring or an aromatic heterocycle, and the aromatic hydrocarbon ring and aromatic heterocycle formed by Z ^B1 are monocyclic or bicyclic or more. A condensed ring having condensed rings may be used. A plurality of aromatic hydrocarbon rings or aromatic heterocycles formed by Z ^B1 connected to L ^B1 may be the same or different.

The aromatic hydrocarbon ring formed by Z ^B1 preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as a benzene ring, a naphthalene ring, an anthracene ring, Examples thereof include a phenanthrene ring, a pyrene ring, and a triphenylene ring, and a benzene ring, a naphthalene ring, a phenanthrene ring, and a triphenylene ring are preferable.
The aromatic heterocycle formed by Z ^B1 is a heterocycle of a condensed ring in which a single ring or two or more rings are condensed, preferably 1 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, still more preferably It is an aromatic heterocycle having 2 to 10 carbon atoms. The heterocycle is preferably an aromatic heterocycle containing at least one of a nitrogen atom, an oxygen atom and a sulfur atom.

Specific examples of the heterocycle formed by Z ^B1 include, for example, pyridine ring, quinoline ring, isoquinoline ring, acridine ring, phenanthridine ring, pteridine ring, pyrazine ring, quinoxaline ring, pyrimidine ring, quinazoline ring, pyridazine ring, cinnoline Ring, phthalazine ring, triazine ring, oxazole ring, benzoxazole ring, thiazole ring, benzothiazole ring, imidazole ring, benzimidazole ring, pyrazole ring, indazole ring, isoxazole ring, benzoisoxazole ring, isothiazole ring, benzoiso Thiazole ring, oxadiazole ring, thiadiazole ring, triazole ring, tetrazole ring, furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, indole ring, imidazopyridine ring, carbazole ring And phenanthroline ring, preferably pyridine ring, quinoline ring, isoquinoline ring, acridine ring, phenanthridine ring, pyrazine ring, quinoxaline ring, pyrimidine ring, quinazoline ring, pyridazine ring, phthalazine ring, triazine ring, imidazole Ring, benzimidazole ring, pyrazole ring, indazole ring, oxadiazole ring, triazole ring, imidazopyridine ring, carbazole ring or phenanthroline ring, more preferably pyridine ring, quinoline ring, isoquinoline ring, pyrazine ring, quinoxaline ring A pyrimidine ring, a quinazoline ring, a pyridazine ring, a phthalazine ring, a triazine ring, an imidazole ring, a benzimidazole ring, an oxadiazole ring, a triazole ring, an imidazopyridine ring, or a phenanthroline ring, The preferably a benzimidazole ring, an oxadiazole ring, a triazole ring, an imidazopyridine ring, or phenanthroline ring, particularly preferably a benzimidazole ring, imidazopyridine ring.

The aromatic hydrocarbon ring and aromatic heterocycle formed by Z ^B1 may further form a condensed ring with another ring, and may have a substituent. As the substituent, for example, those exemplified as the substituent for L ^A1 in formula (A-1) can be applied, and preferred ranges are also the same.
n ^B1 represents an integer of 2 or more, preferably 2 to 8, more preferably 2 to 6.

  The compound, general formula (A-1) and general formula (B-1) in the present invention may be low molecular compounds, and oligomer compounds and polymer compounds (weight average molecular weight (polystyrene conversion) is preferably 1000 to 1000. 5000000, more preferably 2000 to 1000000, and still more preferably 3000 to 100,000. The compound in the present invention is preferably a low molecular compound.

  Specific examples of the general formula (A-1) and the general formula (B-1) in the present invention are listed below, but the present invention is not limited to these organic compounds.

  The compound represented by the general formula (A-1) or (B-1) contained in the layer containing the compound represented by the general formula (A-1) or (B-1) in the present invention is 50 The content is preferably from 100% by mass to 100% by mass, more preferably from 70% by mass to 100% by mass, and particularly preferably from 80% by mass to 100% by mass.

  As materials other than the organic compound represented by the general formula (A-1) or (B-1) contained in the organic compound-containing layer represented by the general formula (A-1) or (B-1), There are electron transporting materials, for example, materials described in an electron injection layer and an electron transport layer described later, and electron transport materials in a light emitting layer described above.

Electron transfer of the organic compound represented by the general formula (A-1) or (B-1) used for the layer containing the organic compound represented by the general formula (A-1) or (B-1) in the present invention. The degree is preferably 1 × 10 ⁻⁵ cm ² / Vs or more from the viewpoint of sufficient electron injection into the light emitting layer, and more preferably 1 × 10 ⁻⁴ cm ² / Vs or more.
The electron mobility can be obtained from a TOF (Time of Flight) method.

  The organic compound-containing layer represented by the general formula (A-1) or (B-1) of the present invention is a dry film forming method such as a vapor deposition method or a sputtering method, a transfer method, a printing method, a coating method, an ink jet method, It can be suitably formed by any of the spray method and the like.

4). 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 material and the hole transport material used for these layers may be a low molecular compound or a high molecular compound.
Specifically, pyrrole derivatives, carbazole derivatives, azacarbazole derivatives, indole derivatives, azaindole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, styryl Anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives, silazane derivatives, aromatic tertiary amine compounds, styrylamine compounds, aromatic dimethylidin compounds, phthalocyanine compounds, porphyrin compounds, thiophene derivatives, organosilane derivatives, carbon, And the like.

  An electron-accepting dopant can be contained in the hole injection layer or the hole transport layer of the organic EL device of the present invention. As the electron-accepting dopant introduced into the hole-injecting layer or the hole-transporting layer, an inorganic compound or an organic compound can be used as long as it has an electron-accepting property and oxidizes an organic compound.

  Specifically, examples of the inorganic compound include metal halides such as ferric chloride, aluminum chloride, gallium chloride, indium chloride, and antimony pentachloride, metal oxides such as vanadium pentoxide, and molybdenum trioxide.

In the case of an organic compound, a compound having a nitro group, halogen, cyano group, trifluoromethyl group or the like as a substituent, a quinone compound, an acid anhydride compound, fullerene, or the like can be preferably used.
In addition, JP-A-6-212153, JP-A-11-111463, JP-A-11-251067, JP-A-2000-196140, JP-A-2000-286054, JP-A-2000-315580, JP-A-2001-102175, JP-A-2001-2001. -160493, JP2002-252085, JP2002-56985, JP2003-157981, JP2003-217862, JP2003-229278, JP2004-342614, JP2005-72012, JP20051666667 The compounds described in JP-A-2005-209643 and the like can be preferably used.

  Among these, hexacyanobutadiene, hexacyanobenzene, tetracyanoethylene, tetracyanoquinodimethane, tetrafluorotetracyanoquinodimethane, p-fluoranyl, p-chloranil, p-bromanyl, p-benzoquinone, 2,6-dichlorobenzoquinone, 2 , 5-dichlorobenzoquinone, 1,2,4,5-tetracyanobenzene, 1,4-dicyanotetrafluorobenzene, 2,3-dichloro-5,6-dicyanobenzoquinone, p-dinitrobenzene, m-dinitrobenzene, o-dinitrobenzene, 1,4-naphthoquinone, 2,3-dichloronaphthoquinone, 1,3-dinitronaphthalene, 1,5-dinitronaphthalene, 9,10-anthraquinone, 1,3,6,8-tetranitrocarbazole, 2,4,7-trinitro-9- Luenone, 2,3,5,6-tetracyanopyridine or fullerene C60 is preferred, and hexacyanobutadiene, hexacyanobenzene, tetracyanoethylene, tetracyanoquinodimethane, tetrafluorotetracyanoquinodimethane, p-fluoranyl, p- Chloranil, p-bromanyl, 2,6-dichlorobenzoquinone, 2,5-dichlorobenzoquinone, 2,3-dichloronaphthoquinone, 1,2,4,5-tetracyanobenzene, 2,3-dichloro-5,6-dicyano Benzoquinone or 2,3,5,6-tetracyanopyridine is more preferred, and tetrafluorotetracyanoquinodimethane is particularly preferred.

These electron-accepting dopants may be used alone or in combination of two or more.
Although the usage-amount of an electron-accepting dopant changes with kinds of material, it is preferable that it is 0.01 mass%-50 mass% with respect to hole transport layer material, and it is 0.05 mass%-20 mass%. It is further more preferable and it is especially preferable that it is 0.1 mass%-10 mass%.

The thicknesses of the hole injection layer and the hole transport layer are each preferably 500 nm or less from the viewpoint of lowering the driving voltage.
The thickness of the hole transport layer is preferably 1 nm to 200 nm, more preferably 5 nm to 100 nm, and still more preferably 10 nm to 60 nm. In addition, the thickness of the hole injection layer is preferably 0.1 nm to 500 nm, more preferably 0.5 nm to 300 nm, and still more preferably 1 nm to 200 nm.
The hole injection layer and the hole transport layer may have a single-layer structure composed of one or more of the materials described above, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions. .

5). 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 injection material and the electron transport material used for these layers may be a low molecular compound or a high molecular compound.
Specifically, pyridine derivatives, quinoline derivatives, pyrimidine derivatives, pyrazine derivatives, phthalazine derivatives, phenanthroline derivatives, triazine derivatives, triazole derivatives, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, fluorenone derivatives, anthraquinodimethane derivatives, anthrone Derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimide derivatives, fluorenylidenemethane derivatives, distyrylpyrazine derivatives, naphthalene, perylene and other aromatic ring tetracarboxylic acid anhydrides, phthalocyanine derivatives, 8-quinolinol derivative metal complexes, Metal phthalocyanines, various metal complexes represented by metal complexes with benzoxazole and benzothiazole as ligands, organosilane derivatives represented by siloles Body, or the like is preferably a layer containing.

The electron injection layer or the electron transport layer of the organic EL device of the present invention can contain an electron donating dopant. The electron donating dopant introduced into the electron injecting layer or the electron transporting layer only needs to have an electron donating property and a property of reducing an organic compound, such as an alkali metal such as Li or an alkaline earth metal such as Mg. Transition metals including rare earth metals and reducing organic compounds are preferably used. As the metal, a metal having a work function of 4.2 eV or less can be preferably used. Specifically, Li, Na, K, Be, Mg, Ca, Sr, Ba, Y, Cs, La, Sm, Gd , And Yb. Examples of the reducing organic compound include nitrogen-containing compounds, sulfur-containing compounds, and phosphorus-containing compounds.
In addition, materials described in JP-A-6-212153, JP-A-2000-196140, JP-A-2003-68468, JP-A-2003-229278, JP-A-2004-342614, and the like can be used.

These electron donating dopants may be used alone or in combination of two or more.
Although the usage-amount of an electron donating dopant changes with kinds of material, it is preferable that it is 0.1 mass%-99 mass% with respect to electron transport layer material, and it is 1.0 mass%-80 mass%. Is more preferable, and 2.0 mass% to 70 mass% is particularly preferable.

The thicknesses of the electron injection layer and the electron transport layer are each preferably 500 nm or less from the viewpoint of lowering the driving voltage.
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. In addition, the thickness of the electron injection layer is preferably 0.1 nm to 200 nm, more preferably 0.1 nm to 50 nm, and still more preferably 0.5 nm to 20 nm.
The electron injection layer and the electron transport layer may have a single layer structure composed of one or more of the above-described materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions.

7). Substrate The substrate used in the present invention is preferably a substrate that does not scatter or attenuate light emitted from the organic compound layer. Specific examples include zirconia-stabilized yttrium (YSZ), inorganic materials such as glass, polyesters such as polyethylene terephthalate, polybutylene phthalate, and polyethylene naphthalate, polystyrene, polycarbonate, polyethersulfone, polyarylate, polyimide, and polycycloolefin. , Organic materials such as norbornene resin and poly (chlorotrifluoroethylene).
For example, when glass is used as the substrate, alkali-free glass is preferably used as the material in order to reduce ions eluted from the glass. Moreover, when using soda-lime glass, it is preferable to use what gave barrier coatings, such as a silica. In the case of an organic material, it is preferable that it is excellent in heat resistance, dimensional stability, solvent resistance, electrical insulation, and workability.

  There is no restriction | limiting in particular about the shape of a 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 substrate structure 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 colorless and transparent or colored and transparent, but is preferably colorless and transparent in that it does not scatter or attenuate light emitted from the organic light emitting layer.

The substrate can be provided with a moisture permeation preventing layer (gas barrier layer) on the front surface or the back surface.
As a material for the moisture permeation preventive layer (gas barrier layer), inorganic materials such as silicon nitride and silicon oxide are preferably used. The moisture permeation preventing layer (gas barrier layer) can be formed by, for example, a high frequency sputtering method.
When a thermoplastic substrate is used, a hard coat layer, an undercoat layer, or the like may be further provided as necessary.

8). Electrode (Anode)
The anode usually has a function as an electrode for supplying holes to the organic compound layer, and there is no particular limitation on the shape, structure, size, etc., depending on the use and purpose of the light-emitting element. , Can be appropriately selected from known electrode materials. As described above, the anode is usually provided as a transparent anode.

  As a material of the anode, for example, a metal, an alloy, a metal oxide, a conductive compound, or a mixture thereof can be suitably cited, and a material having a work function of 4.0 eV or more is preferable. Specific examples of the anode material include conductive metals such as tin oxide doped with antimony and fluorine (ATO, FTO), tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO). Metals such as oxides, gold, silver, chromium, nickel, and mixtures or laminates of these metals and conductive metal oxides, inorganic conductive materials such as copper iodide and copper sulfide, polyaniline, polythiophene, polypyrrole, etc. Organic conductive materials, and a laminate of these and ITO. Among these, conductive metal oxides are preferable, and ITO is particularly preferable from the viewpoints of productivity, high conductivity, transparency, and the like.

  The anode is composed of, for example, a wet method such as a printing method and a coating method, a physical method such as a vacuum deposition method, a sputtering method, and an ion plating method, and a chemical method such as a CVD and a plasma CVD method. It can be formed on the substrate according to a method appropriately selected in consideration of suitability with the material to be processed. For example, when ITO is selected as the anode material, the anode can be formed according to a direct current or high frequency sputtering method, a vacuum deposition method, an ion plating method, or the like.

  In the organic electroluminescent element of the present invention, the formation position of the anode is not particularly limited and can be appropriately selected according to the use and purpose of the light emitting element. Is preferably formed on the substrate. In this case, the anode may be formed on the entire one surface of the substrate, or may be formed on a part thereof.

  The patterning for forming the anode may be performed by chemical etching such as photolithography, or may be performed by physical etching such as laser, or vacuum deposition or sputtering with a mask overlapped. It may be performed by a lift-off method or a printing method.

  The thickness of the anode can be appropriately selected depending on the material constituting the anode and cannot be generally defined, but is usually about 10 nm to 50 μm, and preferably 50 nm to 20 μm.

The resistance value of the anode is preferably 10 ³ Ω / □ or less, and more preferably 10 ² Ω / □ or less. When the anode is transparent, it may be colorless and transparent or colored and transparent. In order to take out light emission from the transparent anode side, the transmittance is preferably 60% or more, and more preferably 70% or more.

  Note that the transparent anode is described in detail in Yutaka Sawada's “New Development of Transparent Electrode Film” published by CMC (1999), and the matters described here can be applied to the present invention. In the case of using a plastic substrate having low heat resistance, a transparent anode formed using ITO or IZO at a low temperature of 150 ° C. or lower is preferable.

(cathode)
The cathode usually has a function as an electrode for injecting electrons into the organic compound layer, and there is no particular limitation on the shape, structure, size, etc., depending on the use and purpose of the light-emitting element, It can select suitably from well-known electrode materials.

  Examples of the material constituting the cathode include metals, alloys, metal oxides, electrically conductive compounds, and mixtures thereof, and those having a work function of 4.5 eV or less are preferable. Specific examples include alkali metals (eg, Li, Na, K, Cs, etc.), alkaline earth metals (eg, Mg, Ca, etc.), gold, silver, lead, aluminum, sodium-potassium alloys, lithium-aluminum alloys, magnesium. -Rare earth metals such as silver alloys, indium, ytterbium, and the like. 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, as a material constituting the cathode, an alkali metal or an alkaline earth metal is preferable from the viewpoint of electron injecting property, and a material mainly composed of aluminum is preferable from the viewpoint of excellent storage stability.
The material mainly composed of aluminum is aluminum alone, an alloy of aluminum and 0.01 to 10% by mass of alkali metal or alkaline earth metal, or a mixture thereof (for example, lithium-aluminum alloy, magnesium-aluminum alloy, etc.) Say.

  The materials for the cathode are described in detail in JP-A-2-15595 and JP-A-5-121172, and the materials described in these public relations can also be applied in the present invention.

  There is no restriction | limiting in particular about the formation method of a cathode, According to a well-known method, it can carry out. For example, the cathode described above is configured from 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, or a chemical method such as CVD or plasma CVD method. It can be formed according to a method appropriately selected in consideration of suitability with the material. For example, when a metal or the like is selected as the cathode material, one or more of them can be simultaneously or sequentially performed according to a sputtering method or the like.

  Patterning when forming the cathode may be performed by chemical etching such as photolithography, physical etching by laser, or the like, or by vacuum deposition or sputtering with the mask overlaid. It may be performed by a lift-off method or a printing method.

In the present invention, the cathode formation position is not particularly limited, and may be formed on the entire organic compound layer or a part thereof.
Further, a dielectric layer made of an alkali metal or alkaline earth metal fluoride or oxide may be inserted between the cathode and the organic compound layer with a thickness of 0.1 nm to 5 nm. This dielectric layer can also be regarded as a kind of electron injection layer. The dielectric layer can be formed by, for example, a vacuum deposition method, a sputtering method, an ion plating method, or the like.

The thickness of the cathode can be appropriately selected depending on the material constituting the cathode and cannot be generally defined, but is usually about 10 nm to 5 μm, and preferably 50 nm to 1 μm.
Further, the cathode may be transparent or opaque. The transparent cathode can be formed by depositing a thin cathode material to a thickness of 1 nm to 10 nm and further laminating a transparent conductive material such as ITO or IZO.

9. Protective layer In the present invention, the entire organic EL device may be protected by a protective layer.
As a material contained in the protective layer, any material may be used as long as it has a function of preventing materials that promote device deterioration such as moisture and oxygen from entering the device.
Specific examples thereof include metals such as In, Sn, Pb, Au, Cu, Ag, Al, Ti, and Ni, MgO, SiO, SiO ₂ , Al ₂ O ₃ , GeO, NiO, CaO, BaO, and Fe ₂ O. ₃ , metal oxides such as Y ₂ O ₃ , TiO ₂ , metal nitrides such as SiN _x , SiN _x O _y , metal fluorides such as MgF ₂ , LiF, AlF ₃ , CaF ₂ , polyethylene, polypropylene, polymethyl Monomer mixture containing methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene, tetrafluoroethylene and at least one comonomer Copolymer obtained by copolymerization, cyclic in the copolymer main chain Examples thereof include a fluorine-containing copolymer having a structure, a water-absorbing substance having a water absorption of 1% or more, and a moisture-proof substance having a water absorption of 0.1% or less.

  The method for forming the protective layer is not particularly limited. For example, vacuum deposition, sputtering, reactive sputtering, MBE (molecular beam epitaxy), cluster ion beam, ion plating, plasma polymerization (high frequency) Excited ion plating method), plasma CVD method, laser CVD method, thermal CVD method, gas source CVD method, coating method, printing method, transfer method can be applied.

10. Sealing Furthermore, the organic electroluminescent element of this invention may seal the whole element using a sealing container.
Further, a moisture absorbent or an inert liquid may be sealed in a space between the sealing container and the light emitting element. Although it does not specifically limit as a moisture absorber, For example, barium oxide, sodium oxide, potassium oxide, calcium oxide, sodium sulfate, calcium sulfate, magnesium sulfate, phosphorus pentoxide, calcium chloride, magnesium chloride, copper chloride Cesium fluoride, niobium fluoride, calcium bromide, vanadium bromide, molecular sieve, zeolite, magnesium oxide and the like. The inert liquid is not particularly limited, and examples thereof include fluorinated solvents such as paraffins, liquid paraffins, perfluoroalkanes, perfluoroamines, perfluoroethers, chlorinated solvents, and silicone oils. It is done.

11. Driving 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 driving method of the organic electroluminescence device of the present invention is described in JP-A-2-148687, JP-A-6-301355, JP-A-5-29080, JP-A-7-134558, JP-A-8-234658, and JP-A-8-2441047. The driving method described in each publication, Japanese Patent No. 2784615, US Pat. Nos. 5,828,429, 6023308, and the like can be applied.

12 Resonant Structure The organic EL element in the present invention may have a resonator structure. For example, a multilayer mirror made 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 another preferred embodiment, a transparent or translucent electrode and a metal electrode each function as a reflector on a transparent substrate, 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 embodiment 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.

13. Applications Applications of the organic EL device of the present invention are not particularly limited, but can be applied to a wide range of fields such as mobile phone displays, personal digital assistants (PDAs), computer displays, automobile information displays, TV monitors, or general lighting.

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

Example 1
1. Production of organic EL element (production of organic EL element 1 of the present invention)
A glass substrate (manufactured by Geomatic Co., Ltd., surface resistance 10Ω / □) on which 0.5 mm thick and 2.5 cm square indium tin oxide (denoted as ITO) is vapor-deposited is placed in a cleaning container and ultrasonically cleaned in 2-propanol. Then, UV-ozone treatment was performed for 30 minutes. The following layers were deposited on this transparent anode by vacuum deposition. The vapor deposition rate in the examples of the present invention is 0.2 nm / second unless otherwise specified. The deposition rate was measured using a quartz resonator. The film thicknesses described below were also measured using a crystal resonator.

Hole injection layer: 4,4 ′, 4 ″ -tris (2-naphthylphenylamino) triphenylamine (abbreviated as 2-TNATA) and 2,3,5,6-tetrafluoro-7,7,8, 8-tetracyanoquinodimethane (abbreviated as F4-TCNQ) was co-deposited so that F4-TCNQ was 1.0 mass% with respect to 2-TNATA, and the thickness was 160 nm.
Hole transport layer: N, N′-dinaphthyl-N, N′-diphenyl- [1,1′-biphenyl] -4,4′-diamine (abbreviated as α-NPD), thickness 10 nm.

  Light emitting layer: hole transporting host material N, N′-dicarbazolyl-1,3-benzene (abbreviated as mCP) and electron transporting light emitting material Pt-1 are co-evaporated, and the co-evaporation ratio is increased as the deposition proceeds. Changed. The deposition rate of each component is adjusted so that the mixing ratio of mCP is 100% by mass in the region close to the hole transporting layer at the initial stage of vapor deposition, and the mixing ratio is 25% by weight in the region near the electron transporting layer at the end of the deposition. did. The mixing ratio of each component was continuously changed between these regions. The film thickness of the light emitting layer was 60 nm.

Subsequently, the following electron transport layer and electron injection layer were provided on the light emitting layer.
Electron transport layer: The organic compound ETA-1 of the general formula (A-1) of the present invention was deposited to a thickness of 40 nm.
Electron injection layer: LiF, thickness 1 nm.

Furthermore, patterning was performed using a shadow mask to provide Al having a thickness of 100 nm as a cathode.
Each layer was provided by resistance heating vacuum deposition.

  The produced laminate was put in a glove box substituted with nitrogen gas, and sealed using a stainless steel sealing can and an ultraviolet curable adhesive (XNR5516HV, manufactured by CHI Nagase).

(Preparation of the organic EL element 2 of the present invention)
In the organic EL element 1, the organic compound ETA-1 in the electron transport layer was changed to ETA-2, and the others were produced in the same manner as the organic EL element 1 to produce an organic EL element 2.

(Preparation of the organic EL device 3 of the present invention)
In the organic EL element 1, the organic compound ETA-1 in the electron transport layer was changed to ETA-3, and the others were produced in the same manner as the organic EL element 1 to produce an organic EL element 2.

(Preparation of the organic EL element 4 of the present invention)
In the organic EL element 1, the organic compound ETA-1 of the electron transport layer was changed to ETA-4, and the others were the same as the organic EL element 1, and the organic EL element 4 was produced.

(Preparation of the organic EL element 5 of the present invention)
In the organic EL element 1, the organic compound ETA-1 in the electron transport layer was changed to ETA-5, and the others were the same as the organic EL element 1, and the organic EL element 5 was produced.

(Preparation of the organic EL element 6 of the present invention)
In the organic EL element 1, the organic compound ETA-1 of the electron transport layer was changed to ETA-6, and the others were the same as the organic EL element 1, and the organic EL element 6 was produced.

(Preparation of the organic EL element 7 of the present invention)
In the organic EL element 1, the light emitting layer was changed to the following, and the others were the same as the organic EL element 1, and the organic EL element 7 was produced.
Light-emitting layer: hole-transporting host material mCP and electron-transporting light-emitting material Pt-1 are co-deposited, and the co-evaporation ratio is 100% by mass of mCP at the anode-side interface at the initial stage of vapor deposition. In the region close to the electron transport layer, the deposition rate of each component was adjusted so that the mixing ratio was 10% by mass. The mixing ratio of each component was continuously changed between these interfaces. The film thickness of the light emitting layer was 60 nm.

(Preparation of the organic EL element 8 of the present invention)
In the organic EL element 1, the light emitting layer was changed to the following, and the others were the same as the organic EL element 1, and the organic EL element 8 was produced.
Light-emitting layer: hole-transporting host material mCP and electron-transporting light-emitting material Pt-1 are co-deposited, and the co-evaporation ratio is 100% by mass of mCP at the anode-side interface at the initial stage of vapor deposition. In the region adjacent to the electron transport layer, the deposition rate of each component was adjusted so that the mixing ratio was 50% by mass. The mixing ratio of each component was continuously changed between these interfaces. The film thickness of the light emitting layer was 60 nm.

(Preparation of the organic EL element 9 of the present invention)
In the organic EL element 1, the light emitting layer was changed to the following, and the others were the same as the organic EL element 1, and the organic EL element 9 was produced.
Light-emitting layer: hole-transporting host material mCP and electron-transporting light-emitting material Pt-1 are co-deposited, and the co-evaporation ratio is 100% by mass of mCP at the anode-side interface at the initial stage of vapor deposition. The vapor deposition rate of each component was adjusted so that the mixing ratio was 75% by mass in the region adjacent to the electron transport layer. The mixing ratio of each component was continuously changed between these interfaces. The film thickness of the light emitting layer was 60 nm.

(Preparation of the organic EL device 10 of the present invention)
In the organic EL element 1, the light emitting layer was changed to the following, and the others were the same as the organic EL element 1, and the organic EL element 10 was produced.

Light-emitting layer: Aluminum (III) bis (2-methyl-8-quinolinato) 4-phenylphenolate (abbreviated as BAlq) as an electron transporting host material and Ir (piq) ₃ as a hole transporting light-emitting material were co-evaporated. These co-deposition ratios were changed as the deposition progressed. The mixing ratio of Ir (piq) ₃ 1 is 100% by mass in the region close to the hole transport layer in the initial stage of vapor deposition, and the mixing ratio of Ir (piq) ₃ is 8% by mass in the region near the electron transport layer at the end of the vapor deposition. The deposition rate of each component was adjusted so that The mixing ratio of each component was continuously changed between these regions. The film thickness of the light emitting layer was 60 nm.

(Production of Comparative Organic EL Element A)
In the organic EL element 1, the light emitting layer was changed to the following. Others were the same as the organic EL element 1, and the comparative organic EL element A was produced.

  Light emitting layer: mCP and light emitting material Pt-1 were co-evaporated. The deposition rate of each component was adjusted so that the mixing ratio of the light emitting material Pt-1 to mCP was uniformly 15% by mass throughout the light emitting layer. The film thickness of the light emitting layer was 60 nm.

(Production of Comparative Organic EL Element B)
In the organic EL device 1 of the present invention, the electron transport layer was changed to the following, and the following hole blocking layer was provided between the light emitting layer and the electron transport layer. Other than that, the organic EL element B for comparison was produced in the same manner as the organic EL element 1 of the present invention.

Hole blocking layer: Bathocuproine (abbreviated as BCP) was deposited to a thickness of 10 nm.
Electron transport layer: tris (8-hydroxyquinolinate) aluminum (abbreviated as Alq ₃ ), thickness 40 nm.

(Production of comparative organic EL element C)
In the organic EL element 10, the electron transport layer was changed to the following, and the following hole blocking layer was further provided between the light emitting layer and the electron transport layer. Others were the same as the organic EL element 2, and the comparative organic EL element C was produced.

Hole blocking layer: Bathocuproine (abbreviated as BCP) was deposited to a thickness of 10 nm.
Electron transport layer: Tris (8-hydroxyquinolinate) aluminum (abbreviated as Alq ₃ ), thickness 60 nm.

  The structure of the organic compound used in the examples is shown below.

2. Performance Evaluation Results External quantum efficiency and driving durability of the obtained comparative organic EL device and the organic EL device of the present invention were measured under the same conditions by the following means.

<Drive voltage>
A DC voltage reaching a luminance of 360 cd / m ² was used as a driving voltage.

<Method for measuring external quantum efficiency>
The produced light emitting element was made to emit light by applying a DC voltage to the light emitting element using a source measure unit 2400 type manufactured by KEITHLEY. Elements A and B in comparison with elements 1 to 9 of the present invention emitted blue light. The device 10 of the present invention and the device C for comparison showed red light emission.
The voltage is adjusted to emit light so that the luminance is 360 cd / m ² , the emission spectrum and the amount of light are measured using a luminance meter SR-3 manufactured by Topcon Corporation, and the external quantum is calculated from the emission spectrum, the amount of light, and the current at the time of measurement. Efficiency was calculated.

<< Measurement method of driving durability ratio >>
A direct current voltage was applied to each element so as to have a luminance of 360 cd / m ^2, and the device was continuously driven to measure the luminance half time until the luminance reached 180 cd / m ² . This luminance half time was used as an index of driving durability.

The obtained results are shown in Table 1.
Both the elements A and B in comparison with the elements 1 to 9 of the present invention use the electron transporting light emitting material Pt-1 as the light emitting material, but the driving durability of the element 1 of the present invention is remarkably improved. The driving voltage of the comparative device A was lower than that of the comparative device B, but the driving durability was deteriorated. On the other hand, the elements 1 to 9 of the present invention exhibited extremely high driving durability at a low driving voltage equivalent to that of the comparative element A.
On the other hand, when the device 10 of the present invention using the hole transporting light emitting material Ir (piq) ₃ is compared with the device C of the present invention, the drive voltage of the device 10 of the present invention is reduced to about ½ or less. Was also greatly improved.
From the above results, it has been found that according to the present invention, it is possible to obtain an extremely excellent light emitting device in which the driving voltage is significantly reduced and the light emission efficiency and durability are greatly improved.

Claims (10)

An organic electroluminescent element having at least one organic layer including a light emitting layer between a pair of electrodes, and represented by the following general formula (A-1) or (B-1) between the light emitting layer and the cathode. And the light emitting layer contains at least one electron transport material and at least one hole transport material, and at least one of the electron transport material and the hole transport material is a light emitting material. The concentration of the hole transport material in the light emitting layer decreases from the anode toward the cathode.

(In General Formula (A-1), Z ^A1 represents an atomic group necessary for forming a nitrogen-containing heterocycle. L ^A1 represents a linking group. N ^A1 represents an integer of 2 or more);

(In the general formula (B-1), Z ^B1 represents an atomic group necessary for forming an aromatic hydrocarbon ring or a heterocycle. L ^B1 represents a linking group. N ^B1 represents an integer of 2 or more.) .   The concentration of the hole transport material in a region near the cathode side interface of the light emitting layer is 0% or more and 50% or less with respect to the concentration of the hole transport material in a region near the anode side interface of the light emitting layer. The organic electroluminescent element according to claim 1.   The organic electroluminescent element according to claim 1 or 2, wherein a layer containing the organic compound represented by the general formula (A-1) or (B-1) is in contact with the light emitting layer.   The organic electroluminescent element according to any one of claims 1 to 3, wherein the hole transport material is a hole transportable light emitting material.   The organic electroluminescent element according to any one of claims 1 to 3, wherein the hole transport material is a hole transportable host material.   The organic electroluminescent element according to claim 1, wherein the electron transporting material is an electron transporting light emitting material. The organic electroluminescent element according to claim 1, wherein the electron transporting material is an electron transporting host material.   The organic light-emitting device according to claim 4, wherein the light-emitting material is a metal complex having a tridentate or higher ligand. The organic electroluminescent device according to claim 8, wherein the metal complex is a metal complex represented by the following general formula (I):

(In General Formula (I), M ¹¹ represents a metal ion, and L ^{11 to} L ¹⁵ each represents a ligand coordinated to M ^{11. An} atomic group further exists between L ¹¹ and L ^14. L ¹⁵ may be bonded to both L ¹¹ and L ¹⁴ to form a cyclic ligand, Y ¹¹ , Y ¹² and Y ¹³ are each a linking group, Represents a single bond or a double bond, and when Y ¹¹ , Y ¹² , or Y ¹³ is a linking group, L ¹¹ and Y ¹² , Y ¹² and L ¹² , L ¹² and Y ¹¹ , Y ¹¹ and L ¹³ , L ¹³ and Y ¹³ , and the bond between Y ¹³ and L ¹⁴ each independently represents a single bond or a double bond, n ¹¹ represents 0 to 4. M ¹¹ and L ^{11 to} L ¹⁵ These bonds may be any of coordination bond, ionic bond, and covalent bond.)   The organic electroluminescent element according to claim 8 or 9, wherein the metal complex having a tridentate or higher ligand is a platinum complex.