JP2004281382A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element manufacturable by a wet film forming method, and capable of showing high luminous efficiency even if a metal such as aluminum hard to cause deterioration is used for a negative electrode layer. <P>SOLUTION: In this organic electroluminescent element, a luminescent layer contains a phosphorescence emitting material expressed by the general formula (1), and has an electron transporting layer containing a compound expressed by the general formula (2) between the luminescent layer and a negative electrode layer. In the general formula (1), Y expresses a bidentate ligand; R expresses a hydrogen atom or an alkoxy group having 1-10 of carbon atoms; at least one of them expresses the alkoxy group; n expresses integers of 3-8. In the formula (2), X<SB>1</SB>and X<SB>2</SB>each independently expresses X<SB>3</SB>, or 1, 3, 4 - oxadiazole - 2 - yl group having X<SB>3</SB>at the 5 position; X<SB>3</SB>expresses a hydrogen atom, an alkyl group having 1-5 of carbon atoms, a phenyl group, a naphthyl group, or an anthryl group. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic electroluminescence device using a phosphorescent material.

In recent years, the demand for display elements for portable information terminals such as mobile computers, mobile phones, PDAs and the like has been increasing, and there is a demand for lighter and lower power consumption display elements.
A self-luminous organic electroluminescent element (hereinafter, abbreviated as “organic EL element”) does not require a backlight, can be made thinner and lighter, and has a low driving voltage and high luminance. Since light emission can be obtained, research is being conducted as a next-generation display medium that replaces existing display elements such as a cathode ray tube display device and a liquid crystal display element. Particularly recently, application of red, blue, and green organic EL elements to a full-color display has been studied.

  The organic EL element generally has a structure in which a positive electrode layer, a light emitting layer containing a light emitting substance, and a negative electrode layer are sequentially stacked. When a voltage is applied between the positive and negative electrode layers, electrons are injected from the negative electrode layer and holes are injected from the positive electrode layer into the light emitting layer. The injected electrons and holes recombine in the luminescent material, and the luminescent material generates excitons. Light emission occurs when the exciton is deactivated to the ground state. In some cases, an electron transporting layer is provided between the light emitting layer and the negative electrode layer for the purpose of increasing luminous efficiency.

As the light-emitting substance, a fluorescent compound emitting singlet excitons and a phosphorescent compound emitting triplet excitons are known. At present, a fluorescent compound that is stable to heat is most frequently used as a luminescent material for an organic EL device. However, the theoretical luminous efficiency of an organic EL device using a fluorescent compound is extremely low at a maximum of 5%. On the other hand, the theoretical luminous efficiency of an organic EL device using a phosphorescent compound is up to 20%. From this, it can be expected that an organic EL device using a phosphorescent compound exhibits luminous efficiency four times that of an organic EL device using a fluorescent compound.
However, in the conventionally known phosphorescent compounds, triplet excitons are thermally unstable, and it is difficult to emit light at room temperature. Therefore, an organic EL device using a phosphorescent compound that can emit light at room temperature is desired.

As a phosphorescent compound that emits light at room temperature, an iridium (III) tris (2-phenylpyridine) complex (hereinafter abbreviated as “Ir (ppy) ₃ ”) is known, and Ir (ppy) ₃ and a hole 2. Description of the Related Art An organic EL device having a light-emitting layer obtained by co-evaporating a mixture with 4,4′-N, N′-dicarbazole-biphenyl as a transport material on an electrode layer is known (for example, Patent Document 1). 1). This has a luminous efficiency of 8%, which is higher than that of an organic EL device using a fluorescent compound as a luminescent substance. However, the organic EL device has a problem that the manufacturing efficiency is low because the light emitting layer is manufactured by a co-evaporation method. When the concentration of Ir (ppy) ₃ in the light emitting layer is increased, a multimer is formed, and the triplet exciton is deactivated without emitting light, so that the luminous efficiency is reduced (hereinafter, this is abbreviated as “concentration quenching”). .) There was a problem.

On the other hand, Ir (ppy) ₃ having an aromatic group as a substituent exhibits high luminous efficiency because concentration quenching due to formation of a multimer can be suppressed to some extent (for example, see Patent Document 2), but the compound is also Ir (ppy). ₃ Similarly, it is necessary to be formed by vapor deposition, has a problem of low manufacturing efficiency.

On the other hand, Ir (ppy) ₃ is doped into polyparaphenylene, which is a hole transporting material, so that the complex does not form a multimer, that is, the concentration does not cause concentration quenching. A method for obtaining a light emitting layer on a layer by a wet film forming method such as a printing method is known (for example, see Non-Patent Document 1). By doping Ir (ppy) ₃ into a polymer hole transporting material, a light emitting layer can be manufactured by a wet film forming method with high manufacturing efficiency. However, the organic EL device obtained by this method has a problem that the probability of holes injected from the positive electrode layer into polyparaphenylene being transported to Ir (ppy) ₃ , that is, the hole transport efficiency is low. . In addition, since Ir (ppy) ₃ has high crystallinity, Ir (ppy) ₃ cannot be doped at a high concentration, and the luminous efficiency of the obtained organic EL device is limited.

On the other hand, as a phosphorescent compound capable of wet film formation, a polymer having a metal complex structure exhibiting light emission from a triplet excited state in a main chain or a side chain and having a polystyrene equivalent number average molecular weight of 10 ³ to 10 ⁸ . A luminous body is known (for example, see Patent Document 3). The polymer luminous body is manufactured by copolymerizing a metal complex having 1 to 5 halogen atoms or the like and a monomer having 2 halogen atoms or the like. The polymer light-emitting material exhibits a hole-transporting property by using an aromatic compound as a monomer, and thus can transport holes in a molecule to a metal complex, thereby exhibiting high luminous efficiency. Furthermore, since a phosphorescent metal complex unit is introduced into a polymer having film forming properties, crystallinity is reduced and wet film forming is possible.
However, in the polymer luminescent material, it is necessary to increase the concentration of the metal complex introduced into one molecule in order to emit phosphorescence derived from the metal complex. , The crystallinity increases, and the solubility in a solvent decreases. Further, since the metal complex units are polymerized and adjacent to each other, concentration quenching in the molecule may occur.
On the other hand, when the concentration of the metal complex is reduced to suppress the decrease in solubility and crystallization, the fluorescence of the hole transporting unit forming the main chain of the polymer light-emitting material becomes the main light emission, so that the high luminous efficiency is reduced. A high molecular light emitter cannot be obtained.

  On the other hand, for the negative electrode layer, alkali metals such as lithium and potassium, alkaline earth metals such as calcium and magnesium, gold, silver, aluminum, or alloys such as lithium-aluminum alloy and magnesium-silver alloy are known. Usually, an alkali metal or an alkaline earth metal having a lower work function is used. However, alkali metals and alkaline earth metals are liable to be deteriorated by oxygen or moisture, and have been a major cause of shortening the life of the organic EL element. Materials for the negative electrode layer that are unlikely to deteriorate include gold, silver, aluminum, and the like. However, the organic EL element using these metals for the negative electrode layer has a very low luminous efficiency. Therefore, there is a demand for a device having high luminous efficiency using gold, silver, aluminum, or the like, which hardly deteriorates, for the negative electrode layer.

On the other hand, as the electron transport layer, an electron transport layer made of a compound having an oxadiazole ring is known (for example, see Non-Patent Document 2).
International Publication No. 00/70655 pamphlet JP-A-2002-332291 JP 2003-171659 A Applied Physics Letter, March 2002, No. 80 (2002) 2045-2047. "Applied Physics Letters", August 1990, No. 57, 531-533.

  The problem to be solved by the present invention is to provide an organic EL element which can be manufactured by a wet film forming method and has high luminous efficiency even when a metal such as aluminum which does not easily deteriorate is used for a negative electrode layer. Is to do.

The present inventors have solved the problem by using the following three means as means for solving the above problem. That is, by introducing a polyparaphenylene group into the phenyl group of Ir (ppy) ₃ , the efficiency of hole transport between molecules and between molecules is increased, and holes injected from the positive electrode layer are converted into iridium (III) complex. The efficiency of the iridium (III) complex was increased by increasing the probability that electrons and holes would recombine in the iridium (III) complex. By introducing the polyparaphenylene group into the phenyl group of Ir (ppy) ₃ as described above, the interaction between the iridium (III) complex is suppressed simultaneously with the above-mentioned effect, whereby the concentration quenching is reduced, and The concentration of the iridium (III) complex in the solution can be increased. Further, by providing an electron transport layer containing the compound represented by the general formula (2) between the light emitting layer and the negative electrode layer, injection of electrons from the negative electrode layer to the light emitting layer was promoted. Thus, an organic EL device having high luminance and high luminous efficiency can be obtained.

  In addition, an alkoxy group was introduced as a substituent into the polyparaphenylene group, and the number of phenylene groups was set to 3 to 8 to make the polyparaphenylene group more soluble in a solvent, thereby enabling a wet film formation.

  That is, the present invention provides an organic electroluminescent device having a light emitting layer sandwiched between a positive electrode layer and a negative electrode layer formed on a transparent substrate, wherein the light emitting layer is formed of iridium (III) represented by the general formula (1). A) a phosphorescent material comprising a complex, and an electron transport layer between the light-emitting layer and the negative electrode layer containing a compound represented by the following general formula (2). Provided is a luminescence element.

（１）

(1)

（２）

(2)

(In the general formula (1), Y represents a bidentate ligand, R represents a hydrogen atom or an alkoxy group having 1 to 10 carbon atoms, at least one of which represents an alkoxy group, and n is an integer of 3 to 8. In the general formula (2), X ₁ and X ₂ each independently represent X ₃ or a 1,3,4-oxadiazol-2-yl group having X ₃ at the 5-position. And X ₃ are a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a phenyl group which may have an alkyl group having 1 to 5 carbon atoms in the substituent, or an alkyl group having 1 to 5 carbon atoms. Represents a naphthyl group which the substituent may have, or an anthryl group which may have an alkyl group having 1 to 5 carbon atoms in the substituent.)

  Since the organic EL device of the present invention uses the iridium (III) complex represented by the general formula (1) into which a polyparaphenylene group as a hole transport material is introduced, the organic EL device is injected from the positive electrode layer. Holes can be efficiently transported to the iridium (III) complex. Since the probability that electrons and holes recombine in the iridium (III) complex increases, high luminous efficiency can be obtained.

Further, the iridium (III) complex represented by the general formula (1) has a high solubility in a solvent because a polyparaphenylene group substituted with an alkoxy group is introduced, and crystallization occurs during film formation. Absent. Therefore, the light emitting layer can be easily formed by a wet film forming method.
In addition, since a bulky polyparaphenylene group substituted with an alkoxy group is introduced to reduce the interaction between iridium (III) complexes, it is difficult to form a multimer. As a result, even if the iridium (III) complex concentration in the light emitting layer is increased, concentration quenching does not easily occur, so that the concentration can be increased and an organic EL device with high luminance can be obtained.

  Furthermore, the organic EL device of the present invention has an electron transport layer containing the compound represented by the general formula (2) between the light emitting layer containing the iridium (III) complex used in the present invention and the negative electrode layer. As a result, the exciton generated is confined in the light emitting layer in addition to the excellent electron injecting ability, so that high luminance and high luminous efficiency can be obtained. In particular, even when a negative electrode layer, such as gold, silver, and aluminum, which is generally difficult to obtain sufficient light-emitting characteristics and is relatively hard to deteriorate, is used, an organic EL device having high luminance and high luminous efficiency can be obtained.

  In the present invention, the iridium (III) complex refers to an iridium complex having a coordination number of 6. Hereinafter, in the present invention, the iridium (III) complex of the general formula (1) may be abbreviated as the iridium complex (A).

  In the general formula (1), the substitution position of the polyparaphenylene group is preferably the 2-, 3- or 4-position of the phenyl group of 2-phenylpyridine, and most preferably the 4-position. The number n of the substituted phenylene groups in the polyparaphenylene group is preferably 3 to 8. When n is less than 3, the hole transport property of the polyparaphenylene group is not sufficiently exhibited, and when n is more than 8, the polyparaphenylene group itself also emits fluorescence, so that the phosphorescent light emitting efficiency is reduced. Since the light emission of the EL element is mixed, there is a problem that the color purity is reduced. Therefore, n is more preferably 3 to 4, and most preferably 3, from the balance between the solubility in a solvent and the efficiency of phosphorescence emission.

  Further, the polyparaphenylene group has a C1 to C10 alkoxy group represented by R as a substituent. As a substituent of the polyparaphenylene group, an alkyl group or a cyano group is also known. However, when the substituent R is an alkyl group or a cyano group, the effect of enhancing the solubility of the iridium (III) complex is lower than that of the alkoxy group. Therefore, it is necessary to increase the number of replacements. As a result, the hole transporting property of the polyparaphenylene group decreases, and the luminous efficiency of the obtained iridium (III) complex decreases. Therefore, the substituent R is most preferably an alkoxy group. Among the alkoxy groups, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group and a hexyloxy group are preferred. If the carbon number of the alkoxy group is too large, the hole transporting property of the polyparaphenylene group is reduced, so that the luminous efficiency of the obtained iridium (III) complex tends to decrease. Among the above-mentioned alkoxy groups, a butoxy group is most preferable from the balance between solubility and luminous efficiency.

  It is preferable that the above-mentioned alkoxy group is substituted by two per molecule of the phenylene group. The substitution position of the alkoxy group is not particularly limited, but it is preferable that the 2-position and the 5-position of the 1,4-phenylene group are substituted for ease of production.

  In the general formula (1), Y represents a bidentate ligand. Examples of the bidentate ligand include 2-phenylpyridine, a ligand represented by the general formula (3),

（３）

(3)

(In the formula, R represents a hydrogen atom or an alkoxy group having 1 to 10 carbon atoms, at least one of which represents an alkoxy group, and n represents an integer of 3 to 8.)

2- (2-benzothienyl) pyridine represented by the chemical formula (4),

（４）

(4)

  2-phenylquinoline, 2-thienylquinoline, picolinic acid, acetylacetone and the like. Among them, an iridium (III) complex in which Y is a ligand represented by the general formula (3), that is, an iridium (III) having a ligand represented by the general formula (3) in all ligands The complex emits green light, and the iridium (III) complex in which Y is 2- (2-benzothienyl) pyridine represented by the general formula (4) emits red light, which is preferable.

  In the present invention, the polyparaphenylene group has a role of transporting holes. Since the polyparaphenylene group is bonded to the iridium (III) complex, the polyparaphenylene group transports holes received from the positive electrode layer to the iridium (III) complex, which is a luminescent substance, even in the molecule. Can be. Since holes can be transported within and between molecules, the transport efficiency is high, and thus the obtained organic EL device exhibits high luminous efficiency.

Further, since the polyparaphenylene group has an alkoxy group as a substituent, the iridium complex (A) has high solubility in a solvent and low crystallinity during film formation. Therefore, it is more suitable for forming a light emitting layer by a wet film forming method, and crystallization of the obtained light emitting layer can be suppressed.
Further, since the polyparaphenylene group has an alkoxy group as a substituent and is bulky, the iridium complex (A) hardly forms a polymer between molecules, and concentration quenching hardly occurs.

  Examples of the iridium complex (A) include a compound of the formula (5) or the formula (6).

（５）
（式中、ｎは３〜８の整数を表す。）

(5)
(In the formula, n represents an integer of 3 to 8.)

（６）
（式中、ｎは３〜８の整数を表す。）

(6)
(In the formula, n represents an integer of 3 to 8.)

  The iridium (III) complex represented by the formula (5) can be synthesized by a known and commonly used method described in, for example, Inoganic Chemistry, Vol. 30, p. 1685 (1991). Specifically, 2-phenylpyridine having a polyparaphenylene group and an iridium (III) compound can be easily obtained by simply heating and stirring under an inert gas stream.

A solvent may be used for the reaction between 2-phenylpyridine having a polyparaphenylene group and the iridium (III) compound. Examples of the solvent include water, glycerin, ethoxyethanol and the like. If necessary, a catalyst such as silver trifluoroacetate or silver trifluoromethanesulfonate may be used. The reaction temperature may be within the range of room temperature to 250 ° C.
It is preferable to react 3 to 10 mol of 2-phenylpyridine having a polyparaphenylene group with respect to 1 mol of the iridium (III) compound.

  The iridium (III) complex represented by the formula (6) is described in, for example, WO 01/41512, “Journal of American Chemical Society”, 2001, No. 123, p. The compound can be synthesized by the following reaction formula by the method described in 4304 and the like.

(In the formula, R represents a hydrogen atom or an alkoxy group having 1 to 10 carbon atoms, at least one of which represents an alkoxy group, and n represents an integer of 3 to 8.)

  Specifically, 2-phenylpyridine having a polyparaphenylene group and an iridium (III) compound are mixed in a solvent such as water, 2-ethoxyethanol or glycerin under an inert gas stream such as nitrogen or argon. Stirring is performed within the range of ２３０230 ° C. to obtain a bridged iridium dimer. Next, the iridium dimer, 2- (2-benzothienyl) pyridine, and an alkali such as sodium carbonate and sodium methoxide are mixed in a solvent such as 1,2-dichloroethane, ethanol, or 2-ethoxyethanol. It is obtained by reacting under a flow of an inert gas such as nitrogen or argon within a range of 50 ° C. to a reflux temperature.

  2-Phenylpyridine having a polyparaphenylene group is obtained by converting 2- (halogenated phenyl) pyridine and a boric acid compound of a polyparaphenylene derivative into tetrakis (triphenylphosphine) in a solvent such as tetrahydrofuran, toluene, or acetone. It is obtained by performing a coupling reaction in the range of room temperature to reflux temperature under a metal catalyst such as palladium (0) or tris (dibenzylideneacetone) dipalladium (0).

Examples of 2- (halogenated phenyl) pyridine include 2- (4-bromophenyl) pyridine, 2- (4-chlorophenyl) pyridine, 2- (3-bromophenyl) pyridine, and 2- (3-chlorophenyl) pyridine. , 2- (2-bromophenyl) pyridine, 2- (2-chlorophenyl) pyridine and the like.
Among them, 2- (4-bromophenyl) pyridine or an iridium (III) complex comprising a ligand obtained from 2- (4-chlorophenyl) pyridine is preferable.

  The boric acid compound of the polyparaphenylene derivative is, for example, a boric acid compound having a polyparaphenylene group having a butoxy group as a substituent obtained by coupling reaction of 2,5-dibutoxy-4-bromophenylboric acid. No.

  As the iridium (III) compound, for example, iridium (III) trichloride and its hydrate, iridium (III) triacetylacetonate, potassium hexachloroiridate (III) and the like can be used.

  In the present invention, an electron transport layer containing a compound represented by the following general formula (2) is provided between the light emitting layer containing the iridium complex (A) and the negative electrode layer. By providing the electron transport layer, the light emitting efficiency of the light emitting layer containing the iridium complex (A) can be further increased.

（２）

(2)

In formula (2), X ₁ and X ₂ each independently represent X ₃ or a 1,3,4-oxadiazol-2-yl group having X ₃ at the 5-position, and X ₃ is hydrogen An atom, an alkyl group having 1 to 5 carbon atoms, a phenyl group which may have an alkyl group having 1 to 5 carbon atoms in the substituent, or an alkyl group having 1 to 5 carbon atoms in the substituent. Represents an optionally substituted naphthyl group or an anthryl group which may have an alkyl group having 1 to 5 carbon atoms as a substituent. A bulky structure in which an alkyl group having 1 to 5 carbon atoms is branched is preferable because the effect of preventing crystallization is high. Examples of the branched alkyl group having 1 to 5 carbon atoms include a tert-butyl group, a tert-pentyl group, and a neopentyl group.

  As the compound represented by the general formula (2), specifically, 2- (4-biphenylyl) -5-phenyl-1,3,4-oxadiazole, 2- (4-biphenylyl)- 5- (4-tert-butylphenyl) -1,3,4-oxadiazole, 2,2 ′-(1,3-phenylene) bis [5 [4- (1,1-dimethylethyl) phenyl]] -1,3,4-oxadiazole, 2,2 ′-(4,4′-biphenylene) bis [5 [4- (1,1-dimethylethyl) phenyl]]-1,3,4-oxadi Azole and the like. These compounds are available, for example, from Aldrich or H.E. W. It is available as a commercial product from Sands and others. Those which cannot be obtained as a commercial product can be synthesized by a known and commonly used method as disclosed in, for example, JP-A-05-202011 and JP-A-06-092947.

The compound represented by the general formula (2) tends to be more easily crystallized during film formation as the symmetry of the molecule is higher. Therefore, when _one of X ₁ and X ₂ is an alkyl group, the other is preferably a group having a ring such as a phenyl group or an anthryl group among the aforementioned groups.
The molecular weight of the compound represented by the general formula (2) is preferably in the range of 250 to 800. If the molecular weight is too low, it is easy to crystallize, and if it is too high, it is difficult to evaporate when forming a film by a vacuum deposition method, or it becomes difficult to form a film, or the solubility in a solvent is reduced, so when forming a film by a wet film forming method. It becomes difficult to adjust the liquid composition.

  Since the compound represented by the general formula (2) has a good electron-transporting property, the electron-transporting layer containing the compound promotes injection of electrons from the negative electrode layer to the light-emitting layer, and the It serves to increase the number of excitons generated. Further, since the compound represented by the general formula (2) has a wider band gap than the iridium complex (A), it does not enter an excited state even when it receives energy transfer from excitons in the light emitting layer. Therefore, the generated excitons are efficiently confined in the light emitting layer, so that an organic EL device having excellent light emitting efficiency can be obtained. Here, the band gap refers to an energy level difference between the lowest unoccupied orbit and the highest occupied orbit.

Next, an example of the organic EL device of the present invention and a method of manufacturing the same will be described.
The organic EL device of the present invention comprises at least a transparent positive electrode layer on a substrate, a light emitting layer containing an iridium (III) complex used in the present invention, and an electron containing a compound represented by the general formula (2). It has a structure in which a transport layer and a negative electrode layer are sequentially stacked. The negative electrode layer need not be transparent.

  The substrate may be a transparent material that does not deteriorate when the electrode layer or the light emitting layer is formed, and examples thereof include glass and a polymer film. As the polymer film, a film in which a transparent material such as polyethylene terephthalate, polycarbonate, polycycloolefin, polyether sulfone, or the like is gas-barrier-coated with silicon oxide, silicon nitride, or the like can be used.

The transparent positive electrode layer is formed by sputtering or vacuum depositing indium tin oxide (hereinafter abbreviated as ITO) on a substrate or applying a suspension of ITO fine particles to sinter the fine particles. Obtained. Further, when the surface of the electrode is subjected to a surface treatment such as an ultraviolet-ozone treatment and a plasma treatment in an oxygen atmosphere, the driving voltage of the obtained organic EL element is prevented from lowering, and the effect of improving the luminous efficiency is obtained.
When the thickness of the positive electrode layer is in the range of 10 nm to 5 μm, light is easily transmitted. Among them, the thickness is preferably in the range of 20 nm to 1 μm.

A light emitting layer containing the iridium complex (A) is formed on the positive electrode layer provided on the substrate. The light emitting layer is coated or printed with an organic solvent solution of the iridium complex (A) by a coating method such as spray coating, spin coating, dip coating, a printing method such as gravure printing, flexo printing, screen printing, or an inkjet method. Later, it is obtained by drying. There is no particular limitation on the drying method. Further, in order to adjust the viscosity of the organic solvent solution of the iridium complex (A), a polymer material may be contained. The polymer material to be mixed at this time preferably has a charge transporting property so as not to deteriorate the performance of the device. Examples of the polymer material include solvent-soluble polyphenylene, polyfluorene, polythiophene, polyphenylenevinylene, polyvinylcarbazole, polypyrrole, polyacetylene, polyaniline, and polyoxadiazole. Particularly, polyparaphenylene and polyvinyl carbazole which are made soluble in a solvent are preferable.
The mixing ratio between the iridium complex (A) and the polymer material is such that the iridium (III) atom concentration in the light emitting layer is at least 0.2% or more. Specifically, it is preferably in the range of 2:98 to 99: 1, and more preferably in the range of 4:96 to 90:10.
The thickness of the light emitting layer is not particularly limited, but high luminous efficiency is obtained when the thickness is 1 nm to 1 μm after drying. In particular, it is preferable to manufacture the film so that the film thickness is 10 nm to 500 nm.

  As the organic solvent, any organic solvent can be used as long as it can dissolve the iridium complex (A). For example, cyclohexanone, toluene, xylene, tetrahydrofuran, chloroform, dichloromethane, 1,1,2-trichloroethane, chlorobenzene, o-dichlorobenzene, tetralin, 1,1,2,2-tetrachloroethane, butyl carbitol, N-methylpyrrolidone and the like Can be mentioned. If the volatilization rate of the organic solvent is high, the viscosity of the organic solvent solution of the iridium complex (A) increases, and the iridium complex (A) is easily fixed to the printing plate to be used. It is preferably an organic solvent having a boiling point within a range of 0.01 to 3.0 kPa (0.1 to 22.5 mmHg) and a range of 100 to 300 ° C. Examples of such organic solvents include toluene, xylene, cyclohexanone, chlorobenzene, o-dichlorobenzene, tetralin, 1,1,2-trichloroethane, 1,1,2,2-tetrachloroethane, butyl carbitol, N-methyl And pyrrolidone. These organic solvents may be used alone or as a mixture.

  The concentration of the iridium complex (A) in the organic solvent varies depending on the printing method and the coating method, but is preferably in the range of 0.1% by mass to 15% by mass. If the concentration of the iridium complex (A) is less than 0.1% by mass, the printed or coated film after drying becomes too thin, which may cause a short circuit of the organic EL element. On the other hand, when the concentration of the iridium complex (A) exceeds 15% by mass, the thickness of the printed or coated film after drying becomes large, so that the voltage required for light emission becomes high or the light emission luminance becomes low. Become. From the performance of the obtained organic EL device, the concentration of the iridium complex (A) in the organic solvent solution is particularly preferably in the range of 0.5% by mass to 10% by mass. When the concentration of the iridium complex (A) in the organic solvent solution is within this range, it is easy to control the thickness of the light emitting layer after drying to be 1 nm to 1 μm.

An electron transport layer containing the compound represented by the formula (2) used in the present invention is provided on the light emitting layer. This electron transport layer is provided on the light emitting layer by a wet film forming method or a vacuum evaporation method. When the electron transport layer is obtained by a wet film forming method, an organic solvent solution obtained by dissolving or dispersing the compound represented by the general formula (2) in a solvent is coated by a known coating method, inkjet method, or printing method. After being applied by, for example, drying. There is no particular limitation on the drying method.
As the solvent used at this time, it is preferable to use an alcohol, a hydrocarbon-based organic solvent, or the like so that the light emitting layer is not dissolved. Specifically, alcohols having 1 to 4 carbon atoms such as methanol, ethanol, 1-propanol, 2-propanol and 1-butanol are exemplified. At this time, when the concentration of the compound represented by the general formula (2) is adjusted to be 0.1 to 10% by mass, the thickness of the dried electron transport layer can be easily controlled to be 1 nm to 200 nm.
Further, a polymer material may be contained for the purpose of improving the film-forming property of the electron transport layer. As the polymer material, those having a band gap larger than that of the iridium complex (A) are preferable, and polyester, polyacrylate, polycarbonate, polyvinyl butyral, polyphenylene, polyfluorene, polyoxadiazole, and the like, which are dissolved in a solvent, are used. can do. In particular, polyvinyl butyral, polyparaphenylene, polyfluorene, and polyoxadiazole which are soluble in a solvent are preferable. When a polymer material is contained, the amount of the compound represented by the general formula (2) present in the electron transport layer after coating and drying is adjusted to be 20 to 90% in terms of mass percentage. Is preferred. If it is less than 20%, the electron transport properties of the electron transport layer tend to decrease. Conversely, if the amount exceeds 90%, the electron transport layer tends to crystallize, and good film-forming properties cannot be obtained. Among them, it is preferable to adjust so as to be 30 to 80%.

On the other hand, when the electron transport layer is obtained by a vacuum deposition method, the compound represented by the general formula (2) is put into a deposition boat made of tungsten, molybdenum, or the like, and the general formula is applied under a high vacuum under a resistance heating method. The compound represented by (2) is deposited by heating. The degree of vacuum is preferably performed at a pressure of 1 × 10 ⁻² Pa or less, and more preferably at a pressure of 3 × 10 ⁻³ Pa or less. If the deposition rate is too high, it becomes difficult to obtain a uniform and dense deposited film. Therefore, the deposition is preferably performed at a rate of 1 nm / sec or less, and more preferably 0.5 nm / sec or less. However, if the deposition rate is too low, the production efficiency will be low, so the deposition rate is most preferably in the range of 0.01 to 0.5 nm.

  The thickness of the electron transporting layer is preferably as thin as possible within a range where a uniform continuous film can be formed, specifically, in the range of 1 nm to 200 nm, and particularly preferably in the range of 5 nm to 100 nm. If the electron transport layer is too thin, the effect of confining excitons generated in the light emitting layer is reduced, and if the electron transport layer is too thick, the current density flowing through the organic EL element is reduced, and as a result, higher voltage and lower brightness may occur. There is.

  In the electron transport layer, a known electron transport material such as a known oxadiazole derivative, naphthoquinone derivative, or polyquinoxaline derivative other than the compound represented by the general formula (2) is mixed for the purpose of adjusting the electron transport ability. You can also. In this case, the compound represented by the general formula (2) may be dissolved in an organic solvent together with a known electron transport material, and an electron transport layer may be formed by a wet film forming method. The compound represented and a known electron transport material may be co-evaporated to form an electron transport layer.

  A negative electrode layer is provided on the electron transport layer. The negative electrode layer, for example, on the light emitting layer, an alkali metal such as lithium or potassium, an alkaline earth metal such as calcium or magnesium, gold, silver, aluminum, or an alloy such as a lithium-aluminum alloy or a magnesium-silver alloy Can be obtained by vacuum evaporation, sputtering or coating with a paint containing these metal powders. The thickness of the negative electrode layer is preferably from 20 to 500 nm, particularly preferably from 50 to 300 nm.

  In the present invention, an organic EL element which is less likely to be degraded by oxygen or moisture than an alkali metal or an alkaline earth metal or the like, but has sufficiently high luminous efficiency even when aluminum or the like having a low work function is used for the negative electrode layer. Obtainable.

  In the organic EL device of the present invention, a protective layer such as silicon oxide, silicon nitride, silicon dioxide, germanium oxide, or germanium dioxide is formed on the negative electrode layer by sputtering, vacuum deposition, or a paint containing these powders. By providing a protective layer by coating on the substrate, moisture and oxygen, which are factors that deteriorate the organic EL element, can be blocked to further improve the stability of the element.

  In the organic EL device of the present invention, the iridium complex (A) has a π-conjugated chain for efficient charge transport, and the hole transport function or the electron transport function is enhanced. Although high luminous efficiency can be obtained only with the layer, a hole transport layer may be provided between the positive electrode layer and the luminescent layer containing the iridium complex (A) in order to further improve the charge transport property. Similarly, in order to further improve the charge transporting property, a light emitting layer can be formed by mixing a hole transporting material or an electron transporting material with the iridium complex (A). Further, a polymer material other than the iridium (III) complex may be contained in the light emitting layer containing the iridium complex (A) for the purpose of adjusting the viscosity of the coating solution and the like. In addition, in the organic EL device of the present invention, a barrier layer is provided between the light emitting layer and the electron transport layer, and the electron transport layer and the negative electrode layer are formed in order to further increase the efficiency of electron injection from the negative electrode layer to the electron transport layer. An electron injection layer may be provided therebetween, or a buffer layer may be provided on the positive electrode layer.

The hole transport layer is a layer provided for moving holes injected from the anode. Examples of the hole transport material used for the hole transport layer include a triphenylamine derivative, a polyvinyl carbazole derivative, a polyaniline derivative, and a polythiophene derivative.
The hole transport layer is formed on the positive electrode layer. When the hole transporting material is a low molecular compound such as a triphenylamine derivative, or by vacuum deposition on the positive electrode layer, or after dissolving the hole transporting material in an organic solvent, on the positive electrode layer, It is produced by various coating methods, inkjet methods, printing methods, and the like. When the hole transporting material is a polymer compound such as a polyvinyl carbazole derivative or a polythiophene derivative, it may be dissolved in an organic solvent as needed, and then coated on the positive electrode layer by various coating methods, inkjet methods, printing methods. It is produced by, for example.
The hole transport layer is generally formed to have a thickness of 5 nm to 500 nm.

When a hole-transporting material or an electron-transporting material is mixed with the iridium complex (A) to form a light-emitting layer, the above-described hole-transporting material or electron-transporting material and the iridium complex (A) are previously added to cyclohexanone and toluene. , Xylene, tetrahydrofuran, chloroform, dichloromethane, 1,1,2-trichloroethane, chlorobenzene, o-dichlorobenzene, tetralin, 1,1,2,2-tetrachloroethane, butyl carbitol, N-methylpyrrolidone, etc. It is obtained by dissolving, applying the solution on the positive electrode by various coating methods, inkjet methods, printing methods, and the like, and then drying. There is no particular limitation on the drying method.
On the other hand, if the amount of the hole transport material or the electron transport material is too small, sufficient charge transport performance cannot be obtained. On the other hand, if the amount of the hole transport material or the electron transport material is too large, the concentration of the iridium (III) complex is low. The mixture ratio of the iridium (III) complex to the hole transporting material or the electron transporting material is preferably in the range of 2:98 to 99: 1, since the emission ratio becomes too large to obtain a sufficient emission luminance. Particularly preferably, it is in the range of 2:98 to 90:10.

When the iridium (III) complex used in the present invention is mixed with another polymer material, the mixture ratio of the iridium (III) complex and the other polymer material is in the range of 2:98 to 99: 1. It is preferable that Particularly preferably, it is in the range of 2:98 to 90:10. Polymer materials other than the iridium (III) complex used include those having a charge transporting ability, such as solvent-soluble polyphenylene, polyfluorenone, polythiophene, polyphenylenevinylene, polyvinylcarbazole, polypyrrole, polyacetylene, polyaniline, and polyoxadiazole. It is preferable to use a polymer material. Particularly, polyparaphenylene, polypyrrole, and polyvinylcarbazole which are soluble in a solvent are preferable.
The thickness of the light emitting layer is not particularly limited. However, when the light emitting layer is formed to have a thickness of 1 nm to 1 μm after drying, the luminous efficiency can be further increased. In particular, it is preferable to manufacture the film so that the film thickness is 10 nm to 500 nm.

The barrier layer is obtained by, for example, vacuum-depositing a phenanthroline derivative on the light-emitting layer so as to have a thickness of 5 to 100 nm, or applying a paint containing these powders. By providing the barrier layer, the effect of confining excitons is improved, and luminous efficiency can be further increased.
Between the electron transporting layer and the negative electrode, a fluoride layer of an alkali metal such as lithium, potassium or cesium, or a fluoride layer of an alkaline earth metal such as calcium or magnesium as an electron injection layer is formed by a vacuum evaporation method or a sputtering method. It can also be manufactured by a coating method or the like so as to have a thickness of 0.1 to 10 nm.
The buffer layer is obtained, for example, by vacuum-depositing a phthalocyanine derivative on the positive electrode layer so as to have a thickness of 50 nm or less. By providing the buffer layer, the influence of unevenness on the surface of the positive electrode layer can be reduced.

Since the organic EL device of the present invention uses an iridium (III) complex into which a π-conjugated chain, which is a charge transporting material, is introduced, holes injected from the positive electrode layer and electrons injected from the electron injection layer are used. Recombines efficiently on the iridium (III) complex, and high luminous efficiency is obtained.
Further, since an iridium (III) complex having low crystallinity and hardly forming an aggregate is used, a light-emitting layer in which concentration quenching hardly occurs can be obtained. Further, since the iridium (III) complex is easily dissolved in a solvent, a light emitting layer can be easily obtained by a wet film forming method. Due to the low crystallinity of the iridium (III) complex, the organic EL device of the present invention does not crystallize and precipitate out of the iridium (III) complex in the light emitting layer even after a lapse of time, and Hard to deteriorate.
Further, the organic EL device of the present invention has an electron transport layer containing the compound represented by the general formula (2) between the light emitting layer and the negative electrode layer. Higher luminous efficiency can be obtained by the effect of the electron transport layer having the effect of promoting electron injection from the negative electrode layer to the light emitting layer and the effect of confining generated excitons in the light emitting layer. In the present invention, even when a stable metal such as aluminum is used for the negative electrode layer, an organic EL device having sufficiently high luminous efficiency can be obtained.

  The organic EL device of the present invention can be suitably used for applications such as display devices, displays, backlights, illumination light sources, recording light sources, exposure light sources, reading light sources, signs, signboards, interiors, and optical communications.

  Hereinafter, the present invention will be described more specifically with reference to examples. In the following examples, “%” is based on mass unless otherwise specified.

<Synthesis Reference Example 1> Synthesis of 2- (4-bromophenyl) pyridine In a reaction vessel, 11 g of 2-bromopyridine and 200 ml of tetrahydrofuran (hereinafter abbreviated as "THF") were charged, and acetone-dry was performed under a stream of argon. While cooling in an ice bath, 92 ml of a 1.5 mol / l pentane solution of tertiary butyllithium was added dropwise. Immediately after completion of the dropwise addition, 70 ml of a 1.0 mol / l zinc chloride diethyl ether solution was added dropwise. After reacting in an acetone-dry ice bath for 1 hour, at 0 ° C. for 2 hours, and at room temperature for 3 hours, 800 mg of tetrakis (triphenylphosphine) palladium (0) was added, and 19.6 g of 1-bromo-4-iodobenzene was added. Of THF solution was added dropwise. After reacting at room temperature for about 68 hours, 200 ml of ethyl acetate was added to the reaction solution, and the mixture was washed once with 100 ml of 10% aqueous ammonia and twice with 100 ml of distilled water, and the organic layer was concentrated. The residue was separated by silica gel column chromatography (developing solvent: ethyl acetate / hexane), and the solvent was distilled off to obtain 9.6 g of 2- (4-bromophenyl) pyridine.

<Synthesis Reference Example 2> Synthesis of boric acid compound having poly (2,5-dibutoxy-1,4-phenylene) group having Mw of 1300 In a reaction vessel, 2,5-dibutoxy-1-bromo-4-phenylborane was added. 13.8 g of an acid, 80 ml of a 1 mol / l potassium carbonate aqueous solution, 200 ml of THF, and 400 mg of tetrakis (triphenylphosphine) palladium (0) were charged, and the mixture was stirred at 60 ° C. in an argon stream, and after 7 minutes, 4.88 g of phenylboric acid was added. The mixture was further stirred at the same temperature for 8 hours to complete the reaction. The reaction solution was added dropwise to 400 ml of 1 mol / l hydrochloric acid, and the formed precipitate was collected by filtration and washed with 400 ml of distilled water. This precipitate was dissolved in 30 ml of dichloromethane, dried over anhydrous magnesium sulfate, and filtered with a 0.5 μm filter. The dichloromethane was concentrated to obtain 3.3 g of a boric acid compound having poly (2,5-dibutoxy-1,4-phenylene) (hereinafter abbreviated as “boric acid compound (A)”). The boric acid compound (A) was measured for molecular weight distribution in terms of polystyrene using gel permeation chromatography (hereinafter abbreviated as “GPC”), and found to have a weight average molecular weight (hereinafter abbreviated as “Mw”). 1300, the number average molecular weight (hereinafter abbreviated as “Mn”) is 900, Mw / Mn is 1.44, and the number of repetitions n of 2,5-dibutoxy-1,4-phenylene unit calculated from Mw is 5.6. And the average of the number of repetitions n is estimated to be 5-6.

<Synthesis Reference Example 3> Synthesis of boric acid compound having a poly (2,5-dibutoxy-1,4-phenylene) group having Mw of 1600 In a reaction vessel, 2,5-dibutoxy-1-bromo-4-phenylborane was added. 13.8 g of an acid, 80 ml of a 1 mol / l potassium carbonate aqueous solution, 200 ml of toluene and 400 mg of tetrakis (triphenylphosphine) palladium (0) were charged, and the mixture was stirred at 95 ° C. under an argon stream, and after 42 hours, 4.88 g of phenylboric acid was added. In addition, the mixture was further stirred at the same temperature for 8 hours to complete the reaction. Thereafter, the same post-treatment process as in Synthesis Reference Example 2 was performed, and boric acid containing poly (2,5-dibutoxy-1,4-phenylene) having Mw of 1600, Mn of 1400, and Mw / Mn of 1.14 was obtained. 3.3 g of a compound (hereinafter abbreviated as "boric acid compound (B)") was obtained. The number of repetitions n of the 2,5-dibutoxy-1,4-phenylene unit calculated from Mw is 6.9, and the average of the number of repetitions n is estimated to be 6 to 7.

<Synthesis Reference Example 4> Synthesis of 2-phenylpyridine having a polyparaphenylene group In a reaction vessel, 0.7 g of 2- (4-bromophenyl) pyridine obtained in Synthesis Reference Example 1 was obtained in Synthesis Reference Example 2. 1.6 g of the boric acid compound (A), 200 ml of THF, 40 ml of a 1 mol / l potassium carbonate aqueous solution, and 35 mg of tetrakis (triphenylphosphine) palladium (0) were charged, and the mixture was stirred at 60 to 65 ° C. for 24 hours under an argon stream. The organic layer and the aqueous layer of the reaction solution are separated, the organic layer is dried and concentrated, and then purified by silica gel column chromatography (developing solvent: dichloromethane / hexane) to obtain a 2-phenylpyridine derivative having a polyparaphenylene group (hereinafter, referred to as a “polyphenylene derivative”). , Abbreviated as “pyridine derivative (C)”). When the molecular weight distribution of this compound in terms of polystyrene was measured using GPC, Mw was 1,400 and Mn was 1,000.

( ¹ H-NMR spectrum data: CDCl ₃ , 300 MHz)
8.7 ppm (d, 1H, N- CH =), 8.1 ppm (d, 2H),
7.8 ppm (m, 4H), 7.6 ppm (d, 2H),
7.4 ppm (m, 2H), 7.3 ppm (d, 1H),
7.2 ppm (m, 1H), 7.0-7.1 ppm (m, 8H),
_{3.9ppm (t, 12H, O- CH} 2 -),
_{1.6-1.7ppm (m, 12H, - CH} 2 -),
_{1.4-1.5ppm (m, 12H, - CH} 2 -),
_{0.9-1.0ppm (t, 18H, - CH} 3)

<Synthesis Reference Example 5> Synthesis of 2-phenylpyridine having a polyparaphenylene group Except that 1.9 g of boric acid compound (B) was used instead of 1.6 g of boric acid compound (A) in Synthesis Reference Example 4. Is a 2-phenylpyridine derivative having a polyparaphenylene group (hereinafter, referred to as "pyridine derivative (D)") having an Mw of 1,900, an Mn of 1600, and an Mw / Mn of 1.18. 1.4 g was obtained.

(1H-NMR spectrum data: CDCl ₃ , 300 MHz)
8.7 ppm (d, 1H, N- CH =), 8.1 ppm (d, 2H),
7.8 ppm (m, 4H), 7.6 ppm (d, 2H),
7.4 ppm (m, 2H),
7.3 ppm (d, 1H), 7.2 ppm (m, 1H),
7.0-7.1 ppm (m, 6H),
_{3.9ppm (t, 16H, O- CH} 2 -),
_{6-1.7ppm (m, 16H, - CH} 2 -),
_{-1.5ppm (m, 16H, - CH} 2 -),
_{0.9-1.0ppm (t, 24H, - CH} 3)

<Synthesis Reference Example 6> Synthesis of 2,5-dibutoxyphenylboric acid Into a reaction vessel, 110 g of hydroquinone, 140 g of potassium hydroxide, and 800 ml of ethanol were charged, and 412 g of 1-bromobutane was added dropwise while refluxing under a nitrogen stream. After 5 hours, the reaction was terminated, 800 ml of hexane was added to the reaction solution, and the mixture was washed three times with 100 ml of distilled water. The organic layer was concentrated and then recrystallized from water / methanol to obtain 136 g of 1,4-dibutoxybenzene.

  136 g of the obtained 1,4-dibutoxybenzene, 109 g of N-bromosuccinimide, 600 ml of dichloromethane and 300 ml of acetic acid were stirred at 35 ° C. After 7 hours, the reaction was terminated. Most of dichloromethane was distilled off from the reaction solution, 800 ml of hexane was added, 300 ml of distilled water, 250 ml of 3% sodium hydrogen carbonate solution, 100 ml of 10% sodium hydroxide solution and 300 ml of distilled water were added. Washing was performed twice in order, and hexane was finally distilled off. The residue was purified by column chromatography (ethyl acetate / hexane) to obtain 155 g of 2-bromo-1,4-dibutoxybenzene.

  Next, while stirring 155 g of 2-bromo-1,4-dibutoxybenzene and 700 ml of diethyl ether in an acetone / dry ice bath under an argon stream, 200 ml of a 2.6 mol / L hexane solution of N-butyllithium was added dropwise. . After the reaction solution was stirred in the same bath for 2 hours and at room temperature for 2 hours, it was cooled again in an acetone / dry ice bath, and a 200 ml solution of 78 g of trimethoxyborane in diethyl ether was added dropwise. After stirring the reaction solution at room temperature for 10 hours, 500 ml of 2 mol / L hydrochloric acid was added to the reaction solution, and the mixture was stirred for 3 hours. The ether layer was concentrated, and 700 ml of hexane was added to the residue. The resulting precipitate was collected by filtration, dissolved in 500 ml of acetone, and the insoluble material was filtered. Then, acetone was distilled off to obtain 58 g of 2,5-dibutoxyphenylboric acid.

<Synthesis Reference Example 7> Synthesis of 4-bromo-2,5-dibutoxybiphenyl A reaction vessel was charged with 55.8 g of phenylhydroquinone, 44.8 g of potassium hydroxide, and 500 ml of ethanol, and refluxed under a stream of nitrogen under a nitrogen atmosphere. 164 g of bromobutane were added dropwise. After 6 hours, the reaction was completed, 300 ml of hexane was added to the reaction solution, and the mixture was washed three times with 100 ml of distilled water. After concentrating the organic layer, the residue was purified by column chromatography (ethyl acetate / hexane) to obtain 7,3.6 g of 2,5-dibutoxybiphenyl.

  71.2 g of the obtained 2,5-dibutoxybiphenyl was dissolved in 150 ml of acetic acid, and a mixed solution of 25 g of bromine and 35 ml of acetic acid was added dropwise with stirring at room temperature. Stirring was continued, and after 3 hours, 8 g of bromine was added, and the mixture was further stirred for 4 hours. 300 ml of hexane was added to the solution after the reaction, and the mixture was washed twice with 100 ml of distilled water, 100 ml of a 2% aqueous solution of sodium hydrogen carbonate and 100 ml of distilled water, and finally hexane was distilled off. The residue was purified by column chromatography using column chromatography (ethyl acetate / hexane) to obtain 60.6 g of 4-bromo-2,5-dibutoxybiphenyl.

<Synthesis Reference Example 8> 2,5,2 ', 5', 2 '', 5 ''-hexabutoxy [1,1 ', 4', 1 ", 4", 1 '"] quarterphenyl Synthesis of boric acid In a reaction vessel, 18.4 g of 2,5-dibutoxyphenylboric acid obtained in Synthesis Reference Example 6, 20.7 g of 4-bromo-2,5-dibutoxybiphenyl obtained in Synthesis Reference Example 7, 250 ml of THF, 50 ml of a 2 mol / L aqueous potassium carbonate solution, and 600 mg of tetrakis (triphenylphosphine) palladium (0) were charged, and reacted under reflux in an argon stream for 24 hours. 300 ml of hexane was added to the reaction solution, the aqueous layer was separated, and the organic layer was concentrated. The residue was purified by column chromatography (hexane / ethyl acetate) to obtain 25.3 g of 2,5,2 ′, 5′-tetrabutoxy [1,1 ′, 4 ′, 1 ″] terphenyl. .

  25.3 g of the obtained 2,5,2 ', 5'-tetrabutoxy [1,1', 4 ', 1 "] terphenyl was dissolved in 200 ml of acetic acid, and 9 g of bromine and acetic acid were stirred at room temperature. 10 ml of the mixed solution was added dropwise. After 3 hours, the reaction was terminated, 250 ml of hexane was added to the reaction solution, and the organic layer was washed twice with 100 ml of distilled water, 100 ml of a 2% aqueous sodium hydrogen carbonate solution, and 100 ml of distilled water in this order. After concentrating the organic layer, it was purified by column chromatography (hexane / ethyl acetate), and 4-bromo-2,5,2 ', 5'-tetrabutoxy [1,1', 4 ', 1 "] Phenyl was obtained.

  20.8 g of the obtained 4-bromo-2,5,2 ′, 5′-tetrabutoxy [1,1 ′, 4 ′, 1 ″] terphenyl, 2,5-dibutoxy obtained in Reference Example 6 13 g of phenylboric acid, 150 ml of THF, 30 ml of a 2 mol / L aqueous potassium carbonate solution, and 380 mg of tetrakis (triphenylphosphine) palladium were reacted under an argon stream while refluxing for 24 hours. 300 ml of hexane was added to the reaction solution, the aqueous layer was separated, and the organic layer was concentrated. The residue was purified by column chromatography (hexane / ethyl acetate) to give 2,5,2 ′, 5 ′, 2 ″, 5 ″ -hexabutoxy [1,1 ′, 4 ′, 1 ″, 4 ″, 1 ′ ″] quarter phenyl was obtained in an amount of 22.5 g.

  22.5 g of the obtained 2,5,2 ′, 5 ′, 2 ″, 5 ″ -hexabutoxy [1,1 ′, 4 ′, 1 ″, 4 ″, 1 ′ ″] quarterphenyl Was dissolved in a mixed solvent of 100 ml of acetic acid and 50 ml of hexane, and a mixed solution of 5.0 g of bromine and 10 ml of acetic acid was added dropwise with stirring at room temperature. After 3 hours, the reaction was terminated, 300 ml of ethyl acetate was added to the reaction solution, and the organic layer was washed twice with 100 ml of distilled water, 100 ml of a 2% aqueous sodium hydrogen carbonate solution, and 100 ml of distilled water in this order. After concentrating the organic layer, it was purified by column chromatography (hexane / ethyl acetate), and 4-bromo-2,5,2 ′, 5 ′, 2 ″, 5 ″ -hexabutoxy [1,1 ′, [4 ', 1 ", 4", 1' "] quarterphenyl 18.8 g was obtained.

  Next, 4-bromo-2,5,2 ′, 5 ′, 2 ″, 5 ″ -hexabutoxy [1,1 ′, 4 ′, 1 ″, 4 ″, 1 ′ ″] quarter While stirring 18.8 g of phenyl and 200 ml of diethyl ether in an acetone / dry ice bath under an argon stream, 18 ml of a 1.56 mol / L hexane solution of n-butyllithium was added dropwise. After the reaction solution was stirred in the same bath for 2 hours and at room temperature for 2 hours, it was cooled again in an acetone / dry ice bath, and a solution of 5 g of trimethoxyborane in 10 ml of diethyl ether was added dropwise. After stirring the reaction solution at room temperature for 10 hours, 50 ml of 2 mol / L hydrochloric acid was added to the reaction solution, and the mixture was stirred for 3 hours. The organic layer was separated from the reaction solution, the solvent was distilled off, and the residue was purified by column chromatography (ethyl acetate / hexane) to give 2,5,2 ′, 5 ′, 2 ″, 5 ″ -hexabutoxy [4, 1 ′, 4 ′, 1 ″, 4 ″, 1 ′ ″] quarterphenylboric acid 10.4 g was obtained.

<Synthesis Reference Example 9> Synthesis of 2- (2 ′, 5 ′, 2 ″, 5 ″, 2 ′ ″, 5 ′ ″-hexabutoxyquinkephenyl-4-yl) pyridine 9. The obtained 2,5,2 ', 5', 2 '', 5 ''-hexabutoxy [4,1 ', 4', 1 ", 4", 1 '"] quarterphenylboric acid. 4 g, 2.5 g of 2- (4-bromophenyl) pyridine, 200 ml of THF, 15 ml of a 2 mol / L aqueous potassium carbonate solution and 220 mg of tetrakis (triphenylphosphine) palladium were reacted under an argon stream while refluxing for 24 hours. 200 ml of ethyl acetate was added to the reaction solution, the aqueous layer was separated, and the organic layer was concentrated. The residue was purified by column chromatography (hexane / ethyl acetate) to give 2- (2 ', 5', 2 ", 5", 2 '", 5'"-hexabutoxyquinkephenyl-4. -Yl) pyridine (hereinafter abbreviated as "pyridine derivative (E)") 13.9 g was obtained.

<Synthesis Reference Example 10> Synthesis of 2- (2-benzothienyl) pyridine 1.78 g of tianaphthene-2-boric acid, 1.55 g of 2-bromopyridine, 50 ml of THF, 10 ml of 1 mol / l potassium carbonate aqueous solution in a reaction vessel. And 12 mg of tetrakis (triphenylphosphine) palladium (0), and stirred at 60 to 65 ° C. for 24 hours under an argon stream. The organic layer and the aqueous layer of the reaction solution are separated, and the organic layer is dried and concentrated, and then purified by silica gel column chromatography (developing solvent: ethyl acetate / hexane) to obtain 1.92 g of 2- (2-benzothienyl) pyridine. Got.

(1H-NMR spectrum data: CDCl ₃ , 300 MHz)
8.6 ppm (d, 1H, N- CH =),
7.8-7.9 ppm (m, 4H,),
7.7 ppm (t, 1H, -CH =), 7.3-7.4 ppm (m, 2H),
7.2 ppm (t, 1H, -CH =)

<Synthesis Example 1> Synthesis of iridium (III) complex (A-1) having a 2-phenylpyridine derivative having a polyparaphenylene group as a ligand In a reaction vessel, Mw1400, Mn1000 obtained in Synthesis Reference Example 4 were added. 1.2 g of a pyridine derivative (C) having an n number of 5.6, 440 mg of iridium tris (acetylacetonate), and 20 ml of glycerin were charged, and the mixture was stirred under a nitrogen stream at 220 ° C. for 8 hours while refluxing. The reaction solution was added with 200 ml of dichloromethane, and washed three times with 50 ml of distilled water. After concentrating dichloromethane, it is purified by silica gel column chromatography (developing solvent: dichloromethane / hexane), and iridium (III) having a 2-phenylpyridine derivative having a polyparaphenylene group represented by the formula (8) as a ligand 320 mg of complex (A-1) was obtained. When the molecular weight distribution of this compound in terms of polystyrene was measured using GPC, Mw was 4,500 and Mn was 3,100.

( ¹ H-NMR spectrum data: CDCl ₃ , 300 MHz)
7.9 ppm (d, 3H, N- CH =),
7.6-7,8 ppm (m, 15H),
7.4-7.5 ppm (m, 9H,), 7.3 ppm (d, 3H),
6.9-7.1 ppm (m, 40H),
_{3.9ppm (m, 60H, O- CH} 2 -),
_{1.6-1.7ppm (m, 60H, - CH} 2 -),
_{1.4-1.5ppm (m, 60H, - CH} 2 -),
_{0.9-1.0ppm (m, 90H, - CH} 3)

（８）
（式（８）中、ｎは５〜６を表す。）

(8)
(In the formula (8), n represents 5 to 6.)

<Synthesis Example 2> Iridium (2- (2 ′, 5 ′, 2 ″, 5 ″, 2 ′ ″, 5 ′ ″-hexabutoxyquinkephenyl-4-yl) pyridine) as a ligand III) Synthesis of complex (A-2) In a reaction vessel, 8 g of the pyridine derivative (E) obtained in Synthesis Reference Example 9, 1.57 g of silver trifluoroacetate, 1.13 g of iridium tris (acetylacetonate), Glycerin (30 ml) was charged, and the mixture was stirred for 8 hours while being refluxed at 220 ° C. under an argon stream. After cooling the reaction solution, 200 ml of dichloromethane was added to the reaction solution, and the mixture was washed three times with 50 ml of distilled water. After concentrating the dichloromethane, it is purified by silica gel column chromatography (ethyl acetate / hexane) to give 2- (2 ′, 5 ′, 2 ″, 5 ″, 2 ′ ″, 5) represented by the formula (9). 3.98 g of an iridium (III) complex (A-2) having '''-hexabutoxyquinkephenyl-4-yl) pyridine as a ligand was obtained.

(1H-NMR spectrum data: CDCl3, 300 MHz)
7.9 ppm (d, 3H), 7.7 ppm (d, 3H),
7.7 ppm (d, 3H), 7.6 ppm (d, 9H),
7.4 ppm (t, 9H), 7.3 ppm (t, 3H),
7.0 ppm (s, 3H), 7.0 ppm (s, s, 12H),
6.9 ppm (s, 3H), 3.9 ppm (m, 36H),
1.6-1.7 ppm (m, 36H), 1.4-1.5 ppm (m, 36H),
8-0.9 ppm (m, 54H)

（９）

(9)

<Synthesis Example 3> Synthesis of iridium (III) complex (A-3) having 2-phenylpyridine derivative having a polyparaphenylene group and 2- (2-benzothienyl) pyridine as a ligand Obtained in Synthesis Reference Example 5 0.7 g of pyridine derivative (D) having Mw of 1900, Mn of 1600, and n number of 6.9, 71 mg of iridium trichloride trihydrate, 20 ml of 2-ethoxyethanol, and 5 ml of water, and 120 ° C. under a nitrogen stream. For 6 hours. After cooling to room temperature, 50 ml of 1 mol / l hydrochloric acid was added, and the precipitated solid was separated by filtration. Purification by silica gel column chromatography (developing solvent: dichloromethane) gave a yellow solid of a tetrakis (2-phenylpyridine-C ² , N ′) (μ-dichloro) diiridium (III) derivative.

  Next, 500 mg of the obtained yellow solid, 55 mg of 2- (2-benzothienyl) pyridine obtained in Synthesis Reference Example 10, 0.05 ml of a sodium methoxide methanol solution (28 wt%), and 20 ml of chloroform were mixed and heated for 3 hours. Refluxed. After cooling to room temperature, the reaction solution is purified by silica gel column chromatography (developing solvent: dichloromethane / hexane), and the pyridine derivative (D) represented by the formula (10) and 2- (2-benzothienyl) pyridine are coordinated. 140 mg of iridium (III) complex (A-3) as a child was obtained. When the molecular weight distribution of this compound in terms of polystyrene was measured using GPC, Mw was 2,800 and Mn was 2,300.

( ¹ H-NMR spectrum data: CDCl ₃ , 300 MHz)
8.1 ppm (d, 1H, N- CH =),
7.9 ppm (d, 1H, N- CH =),
7.6-7,8 ppm (m, 13H),
7.3-7.5 ppm (m, 11H),
6.9-7.1 ppm (m, 30H),
6.6-6.9 ppm (m, 7H)
_{3.9ppm (m, 60H, O- CH} 2 -),
_{1.6-1.7ppm (m, 60H, - CH} 2 -),
_{1.4-1.5ppm (m, 60H, - CH} 2 -),
_{0.9-1.0ppm (m, 90H, - CH} 3)

（１０）
（式（１０）中、ｎは６〜７を表す。）

(10)
(In the formula (10), n represents 6 to 7.)

<Synthesis Example 4> 2- (2 ′, 5 ′, 2 ″, 5 ″, 2 ′ ″, 5 ′ ″-hexabutoxyquinkephenyl-4-yl) pyridine and 2- (2-benzothienyl) ) Synthesis of iridium (III) complex (A-4) having pyridine as ligand Ligand obtained in Synthesis Reference Example 9 in Synthesis Example 3 instead of 0.7 g of pyridine derivative (D) obtained in Synthesis Reference Example 5. The same operation as in Synthesis Example 3 was carried out except that 142 mg of the pyridine derivative (E) and iridium trichloride trihydrate were used instead of 71 mg of the pyridine derivative (E), and the pyridine derivatives (E) and 2 160 mg of an iridium (III) complex (A-4) having-(2-benzothienyl) pyridine as a ligand was obtained. When the molecular weight distribution of this compound in terms of polystyrene was measured using GPC, Mw was 2,200 and Mn was 2,000.

( ¹ H-NMR spectrum data: CDCl ₃ , 300 MHz)
8.1 ppm (d, 1H, N- CH =),
7.9 ppm (d, 1H, N- CH =),
7.6-7,8 ppm (m, 13H),
7.3-7.5 ppm (m, 11H),
6.9-7.1 ppm (m, 13H),
6.6-6.9 ppm (m, 7H)
_{3.9ppm (m, 24H, O- CH} 2 -),
_{1.6-1.7ppm (m, 24H, - CH} 2 -),
_{1.4-1.5ppm (m, 24H, - CH} 2 -),
_{0.9-1.0ppm (m, 36H, - CH} 3)

（１１）

(11)

<Comparative Synthesis Example 1> Synthesis of polyparaphenylene derivative (B-1) having an iridium (III) complex unit in the main chain 0.642 g of iridium trisacetylacetonate, 2- ( 0.41 g of 4-bromophenyl) pyridine, 0.54 g of 2- (phenyl) pyridine and 30 ml of glycerin were charged, and the mixture was stirred while being refluxed for 10 hours in a 220 ° C. oil bath. After cooling the reaction solution, 200 ml of dichloromethane was added to the reaction solution, and the mixture was washed three times with 50 ml of distilled water. After concentration of the dichloromethane, purification was carried out by silica gel column chromatography (dichloromethane), and the obtained fraction was concentrated to about 3 ml. 100 ml of methanol was added to this concentrated liquid, and 0.3 g of a yellow solid precipitated was collected by filtration. The yellow solid is a tris (2- (phenyl) pyridine) iridium (III) complex (complex 1), a bis (2- (phenyl) pyridine) mono (2- (4-bromophenyl) pyridine) iridium (III) complex (Complex 2), mono (2- (phenyl) pyridine) bis (2- (4-bromophenyl) pyridine) iridium (III) complex (complex 3), tris (2- (4-bromophenyl) pyridine) iridium ( III) A mixture of complexes (complex 4) (hereinafter abbreviated as complex mixture A). The respective ratios obtained from GPC were as follows.

182 mg of 1,4-dibromo-2,5-dibutoxybenzene, 186 mg of 2,5-dibutoxy-1,4-phenyldiboronic acid, and a complex mixture so that the iridium concentration of the reaction product becomes 4.3%. A44 mg (at the time of preparation, the molecular weight of bis (2- (phenyl) pyridine) mono (2- (4-bromophenyl) pyridine) iridium (III) was 733), tetrakis (triphenylphosphine) palladium (0) 10 mg, 10 ml of THF, and 2 ml of a 2 mol / L aqueous potassium carbonate solution were charged, and the mixture was stirred at 60 to 65 ° C. for 24 hours under an argon stream. The organic layer and the aqueous layer of the reaction solution were separated, and the organic layer was concentrated and purified by silica gel column chromatography (developing solvent: ethyl acetate / hexane). After concentrating the fraction of the target substance to about 1 ml, 30 ml of methanol was added to the residue, and the resulting yellow precipitate was collected by filtration, and 130 mg of a polyparaphenylene derivative (B-1) having an iridium (III) complex unit in the main chain. Got. This compound has a structure in which an iridium (III) complex unit and a phenylene unit are randomly copolymerized. When the molecular weight distribution of this compound in terms of polystyrene was measured using GPC, Mw was 4,200 and Mn was 2,900.

<Example 1>
(Preparation of coating liquid)
Iridium complex (A-1) obtained in Synthesis Example 1 and poly (2- (6-cyano-6-methylheptyloxy) -1,4-phenylene (hereinafter, CN-PPP) having a Mw of 100,000 as a charge transporting material. Is dissolved in 1,1,2-trichloroethane at a mass ratio of 14:86 to a solid content of 2% to prepare a coating solution for forming a light emitting layer. Aldrich 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, one of the compounds represented, and polyvinyl made by Wako Pure Chemical Industries, Ltd. A mixture of butyral (polymerization degree: 700) at a mass ratio of 75:25 was dissolved in 1-butanol so as to have a solid content concentration of 1% to prepare a coating liquid for forming an electron transport layer.

(Production of organic EL element)
An ITO electrode layer of a glass plate “1737” manufactured by Corning Co., Ltd. having an area of 20 mm × 20 mm and a thickness of 1.1 mm having an ITO electrode layer having a thickness of 100 nm on one surface is provided with an excimer light irradiation device UES20- manufactured by Ushio Inc. At 172, an ozone excimer treatment was performed for 10 minutes.
A light emitting layer was formed on the ITO electrode layer as follows. The coating solution for forming a light emitting layer was formed into a film with a thickness of 100 nm by a spin coater, and dried at 110 ° C. for 1 hour under vacuum using a vacuum dryer. The iridium atom concentration in the light emitting layer was 0.59%.
After the drying of the light emitting layer is completed, the coating is cooled to room temperature, and then the coating liquid for forming an electron transport layer is formed on the light emitting layer so as to have a thickness of 10 nm by a spin coater. It dried at 30 degreeC for 30 minutes, and obtained the electron transport layer.
The obtained glass plate on which the ITO, the light emitting layer, and the electron transporting layer are laminated in this order is subjected to a shadow mask so that the light emitting area is 2 mm × 2 mm, and then put into a vacuum evaporator to deposit aluminum. An organic EL element A was obtained by forming a negative electrode layer having a thickness of 200 nm.

After a lead wire is drawn from the negative electrode and the positive electrode of the organic EL element A, the lead wire is connected to a Keithley 237 high voltage source measuring unit, and a voltage is applied. Current density and voltage characteristics were measured. Further, the luminance of the organic EL element A was measured using a color luminance meter “BM-7” manufactured by Topcon, and the emission spectrum of the organic EL element A was measured using a fluorometer “F-4500” manufactured by Hitachi. did. The emission wavelength λmax and the external quantum efficiency were calculated from the current density / voltage / luminance characteristics and the emission spectrum. Note that the external quantum efficiency was expressed as a percentage by dividing the number of photons emitted from the organic EL device by the number of charges injected into the organic EL device.
As a result, the organic EL device A had an emission wavelength λmax of 540 nm and an external quantum efficiency of 5.6% when emitting 100 cd / m ² .

<Example 2>
Instead of the light emitting layer in Example 1, the iridium complex (A-1) obtained in Synthesis Example 1 and CN-PPP were mixed at a mass ratio of 35:65 in 1,1,2-trichloroethane at a solid content of 2%. An organic EL device B was obtained in the same manner as in Example 1, except that a light-emitting layer was provided using a solution dissolved so as to be as follows. The concentration of iridium atoms in the light emitting layer was 1.5%. As a result of evaluating the organic EL device B in the same manner as in Example 1, the organic EL device B had an emission wavelength λmax of 540 nm and an external quantum efficiency at the time of emitting 100 cd / m ² of 5.5%.

<Example 3>
Instead of the light emitting layer in Example 1, the iridium complex (A-1) obtained in Synthesis Example 1 and CN-PPP were added to 1,1,2-trichloroethane at a mass ratio of 70:30 at a solid content of 3%. An organic EL device C was obtained in the same manner as in Example 1, except that a light-emitting layer was provided using a solution in which the solution was dissolved. The iridium atom concentration in the light emitting layer was 3.0%. As a result of evaluating the organic EL device C in the same manner as in Example 1, the organic EL device C had an emission wavelength λmax of 540 nm and an external quantum efficiency at the time of emitting 100 cd / m ² of 5.6%.
<Example 4>

Instead of the light emitting layer in Example 1, light was emitted using a solution in which only the iridium complex (A-1) obtained in Synthesis Example 1 was dissolved in 1,1,2-trichloroethane so as to have a solid content of 3%. An organic EL device D was obtained in the same manner as in Example 1, except that the layer was provided. The iridium atom concentration in the light emitting layer was 4.3%. As a result of evaluating the organic EL device D in the same manner as in Example 1, the organic EL device D had an emission wavelength λmax of 540 nm and an external quantum efficiency of 100 cd / m ² at an emission of 5.4%.

<Example 5>
Instead of the light emitting layer in Example 1, light was emitted using a solution in which only the iridium complex (A-2) obtained in Synthesis Example 2 was dissolved in 1,1,2-trichloroethane so as to have a solid content of 3%. An organic EL device E was obtained in the same manner as in Example 1, except that the layer was provided. The iridium atom concentration in the light emitting layer was 6.7%. The organic EL device E was evaluated in the same manner as in Example 1. As a result, the organic EL device E had an emission wavelength λmax of 540 nm and an external quantum efficiency at the time of emission of 100 cd / m ² of 5.6%.

<Example 6>
Instead of the light emitting layer in Example 1, the iridium complex (A-3) obtained in Synthesis Example 3 and poly (N-vinylcarbazole) (hereinafter abbreviated as PVCz) whose charge transport material has Mw of 20,000 are masses. The same operation as in Example 1 was performed, except that the light emitting layer was provided using a solution dissolved in 1,1,2-trichloroethane so as to have a solid content of 3% at a ratio of 20:80. Thus, an organic EL device F was obtained. The concentration of iridium atoms in the light emitting layer was 1.4%. As a result of evaluating the organic EL device F in the same manner as in Example 1, the organic EL device F had an emission wavelength λmax of 587 nm and an external quantum efficiency at the time of emission of 100 cd / m ² of 3.6%.

<Example 7>
Instead of the light-emitting layer in Example 1, the iridium complex (A-3) obtained in Synthesis Example 3 and PVCz were mixed in a mass ratio of 40:60 to give a 1,1,2- An organic EL device G was obtained in the same manner as in Example 1, except that the light emitting layer was provided using a solution dissolved in trichloroethane. The concentration of iridium atoms in the light emitting layer was 2.8%. As a result of evaluating the organic EL element G in the same manner as in Example 1, the organic EL element G had an emission wavelength λmax of 587 nm and an external quantum efficiency of 3.7% when emitting 100 cd / m ² .

Example 8
Instead of the light emitting layer in Example 1, a solution in which only the iridium complex (A-3) obtained in Synthesis Example 3 was dissolved in 1,1,2-trichloroethane so as to have a solid content of 3% was used. An organic EL device H was obtained in the same manner as in Example 1, except that the light emitting layer was provided. The iridium atom concentration in the light emitting layer was 6.9%. As a result of evaluating the organic EL device H in the same manner as in Example 1, the organic EL device H had an emission wavelength λmax of 587 nm and an external quantum efficiency of 3.5% when emitting 100 cd / m ² .

<Example 9>
Instead of the light emitting layer in Example 1, a solution obtained by dissolving only the iridium complex (A-4) obtained in Synthesis Example 4 in 1,1,2-trichloroethane so as to have a solid content of 3% was used. An organic EL device I was obtained by performing the same operation as in Example 1 except that the light emitting layer was provided. The iridium atom concentration in the light emitting layer was 8.8%. As a result of evaluating the organic EL device I in the same manner as in Example 1, the organic EL device I had an emission wavelength λmax of 587 nm and an external quantum efficiency at the time of emitting 100 cd / m ² of 3.7%.

<Comparative Example 1>
Instead of the light emitting layer in Example 1, iridium tris (2-phenylpyridine) and CN-PPP were dissolved in 1,1,2-trichloroethane so as to have a mass ratio of 2:98 and a solid content of 2%. An organic EL device J was obtained in the same manner as in Example 1, except that the light emitting layer was provided using the solution thus obtained. The concentration of iridium atoms in the light emitting layer was 0.59%. As a result of evaluating the organic EL device J in the same manner as in Example 1, the organic EL device J had an emission wavelength λmax of 513 nm, an external quantum efficiency at the time of emitting 100 cd / m ² of 2.6%, and the external quantum efficiency was 2.6%. The values were lower than those of the organic EL devices A to E obtained in Examples 1 to 5.

<Comparative Example 2>
Instead of the light emitting layer in Example 1, iridium tris (2-phenylpyridine) and CN-PPP were dissolved in 1,1,2-trichloroethane at a ratio of 5:95 to a concentration of 2% solids. An organic EL device K was obtained in the same manner as in Example 1, except that the light-emitting layer was provided using the obtained solution. The concentration of iridium atoms in the light emitting layer was 1.5%. As a result of evaluating the organic EL device K in the same manner as in Example 1, the organic EL device K had an emission wavelength λmax of 513 nm. However, since the maximum luminance of the organic EL device K did not reach 100 cd / m ² , the external quantum efficiency at the time of emitting 100 cd / m ² could not be measured. The maximum external quantum efficiency of this device was 1.3%, and the luminance at this time was 70 cd / m ² . The external quantum efficiency was lower than those of the organic EL devices A to E obtained in Examples 1 to 5. Further, the external quantum efficiency of the organic EL device K was lower than that of the organic EL device J of Comparative Example 1, and the effect of concentration quenching was recognized.

<Comparative Example 3>
Instead of the light-emitting layer in Example 1, iridium tris (2-phenylpyridine) and CN-PPP were mixed at a mass ratio of 14.8: 85.2 in a ratio of 1,1, so that the solid content was 2%. An organic EL device L was obtained in the same manner as in Example 1, except that the light emitting layer was provided using a solution dissolved in 2-trichloroethane. The concentration of iridium atoms in the light emitting layer was 4.3%. As a result of visually observing the organic EL device L, crystals of iridium tris (2-phenylpyridine) were precipitated and a uniform light emitting layer was not formed. The organic EL device L was evaluated in the same manner as in Example 1. However, when a voltage was applied, the device was short-circuited, and the luminance and external quantum efficiency could not be measured.

<Comparative Example 4>
Instead of the light emitting layer in Example 1, the polyparaphenylene derivative (B-1) having an iridium (III) complex unit obtained in Comparative Synthesis Example 1 was added to 1,1,2 so as to have a solid content of 2%. -An organic EL device M was obtained in the same manner as in Example 1, except that the light-emitting layer was provided using a solution dissolved in trichloroethane. The concentration of iridium atoms in the light emitting layer was 4.3%. As a result of evaluating the organic EL device M in the same manner as in Example 1, the organic EL device M had an emission wavelength λmax of 535 nm and an external quantum efficiency of 0.8% when emitting 100 cd / m ^2. The value was significantly lower than that of the organic EL device D obtained in Example 4. This is considered to be due to the irregularity of the structure, since the compound (B-1) of Comparative Synthesis Example 1 is a random copolymer of an iridium complex unit and a phenylene unit.

<Comparative Example 5>
In Example 1, aluminum was directly provided on the light emitting layer without providing the electron transporting layer containing 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole. An organic EL device N was obtained by performing the same operation as in Example 1 except that the deposition was performed as the negative electrode layer. The concentration of iridium atoms in the light emitting layer was 0.59%. As a result of evaluating the organic EL device N in the same manner as in Example 1, the organic EL device N had an emission wavelength λmax of 540 nm and an external quantum efficiency of 0.2% when emitting 100 cd / m ^2. The value was significantly lower than that of the organic EL device A obtained in Example 1.

<Comparative Example 6>
In Comparative Example 1, aluminum was directly provided on the light emitting layer without providing the electron transporting layer containing 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole. An organic EL device O was obtained by performing the same operation as in Comparative Example 1 except that the negative electrode layer was deposited. The concentration of iridium atoms in the light emitting layer was 0.59%. Result of the organic EL element O was evaluated in the same manner as in Example 1, the organic EL element O, the emission wavelength λmax external quantum of 100 cd / ^{m 2} light emission time for was the 513nm maximum brightness does not reach the 100 cd / ^{m 2} Efficiency could not be evaluated. The maximum external quantum efficiency of the organic EL element O was 0.05%, and the luminance at this time was 40 cd / m ² . The external quantum efficiency of the organic EL device O was significantly lower than that of the organic EL device J of Comparative Example 1 having the electron transport layer of the present invention. Further, the external quantum efficiency of the organic EL element O was lower than that of the organic EL element N of Comparative Example 5 using the iridium complex (A) as the light emitting material.

<Comparative Example 7>
Instead of the light emitting layer in Example 1, bis (2- (2-benzothienyl) pyridinate-N, C ^{3 ′} ) iridium (III) acetylacetonate (hereinafter abbreviated as BtpIr) and PVCz in a ratio of 5:95 were used. An organic EL device P was obtained in the same manner as in Example 1, except that the light emitting layer was provided using a solution dissolved in tetrahydrofuran so that the solid content concentration became 2%. The concentration of iridium atoms in the light emitting layer was 1.4%. As a result of evaluating the organic EL device P in the same manner as in Example 1, the organic EL device P had an emission wavelength λmax of 614 nm and an external quantum efficiency of 1.2% when emitting 100 cd / m ^2. The values were lower than those of the organic EL devices F to I obtained in Examples 6 to 9.

<Comparative Example 8>
In place of the light emitting layer in Example 1, a light emitting layer was provided by using a solution in which BtpIr and PVCz were dissolved in tetrahydrofuran at a ratio of 10:90 to a solid content of 2% to provide a light emitting layer. The same operation as in Example 1 was performed to obtain an organic EL device Q. The concentration of iridium atoms in the light emitting layer was 2.8%. The organic EL element Q Example 1 Results of evaluation in the same manner as the organic EL element Q is emitting a wavelength λmax was 614 nm, the maximum brightness is outside at 100 cd / ^{m 2} light emission because it did not reach the 100 cd / ^{m 2} The quantum efficiency could not be evaluated. The maximum external quantum efficiency of the organic EL device Q was 0.7%, and the luminance at this time was 60 cd / m ² . The external quantum efficiency of the organic EL device Q was lower than those of the organic EL devices F to I obtained in Examples 6 to 8. Further, the external quantum efficiency of the organic EL element Q was lower than that of the organic EL element P of Comparative Example 7, and the effect of concentration quenching was recognized.

<Comparative Example 9>
The procedure was performed in the same manner as in Example 1 except that the light emitting layer was provided using a solution in which BtpIr and PVCz were dissolved in tetrahydrofuran at a ratio of 25:75 to a solid content of 2% in place of the light emitting layer in Example 1. The same operation as in Example 1 was performed to obtain an organic EL device R. The concentration of iridium atoms in the light emitting layer was 6.9%. As a result of visual observation of the organic EL device R, BtpIr crystals were precipitated and a uniform light emitting layer was not formed. The organic EL device R was evaluated in the same manner as in Example 1. However, when a voltage was applied, the device was short-circuited, and the luminance and external quantum efficiency could not be measured.

１）：７０ｃｄ／ｍ^２発光時 ２）４０ｃｄ／ｍ^２発光時 ３）６０ｃｄ／ｍ^２発光時

1): At 70 cd / m ² light emission 2) At 40 cd / m ² light emission 3) At 60 cd / m ² light emission

In the table, Ir represents iridium. Ir (ppy) ₃ represents iridium (III) tris (2-phenylpyridine). BtpIr represents bis (2- (2-benzothienyl) pyridinate-N, C ³ ′) iridium (III) acetylacetonate.

The organic EL device of the present invention can be suitably used for applications such as display devices, displays, backlights, illumination light sources, recording light sources, exposure light sources, reading light sources, signs, signboards, interiors, and optical communications.

Claims (6)

In an organic electroluminescent device in which a light emitting layer is sandwiched between a positive electrode layer and a negative electrode layer formed on a transparent substrate, the light emitting layer is made of an iridium (III) complex represented by the general formula (1). An organic electroluminescent device comprising a light emitting material and having an electron transport layer containing a compound represented by the following general formula (2) between the light emitting layer and the negative electrode layer.

(1)

(2)
(In the general formula (1), Y represents a bidentate ligand, R represents a hydrogen atom or an alkoxy group having 1 to 10 carbon atoms, at least one of which represents an alkoxy group, and n is an integer of 3 to 8. In the general formula (2), X ₁ and X ₂ each independently represent X ₃ or a 1,3,4-oxadiazol-2-yl group having X ₃ at the 5-position. And X ₃ are a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a phenyl group which may have an alkyl group having 1 to 5 carbon atoms in the substituent, or an alkyl group having 1 to 5 carbon atoms. Represents a naphthyl group which the substituent may have, or an anthryl group which may have an alkyl group having 1 to 5 carbon atoms in the substituent.) The organic electroluminescence device according to claim 1, wherein R in the general formula (1) is a butoxy group. The organic electroluminescence device according to claim 1, wherein n is 3 or 4 in the general formula (1). 4. The method according to claim 1, wherein in the general formula (1), Y is a ligand represented by the general formula (3) or a ligand represented by the general formula (4). 5. Organic electroluminescent element.

(3)
(In the formula (3), R represents a hydrogen atom or an alkoxy group having 1 to 10 carbon atoms, at least one of which represents an alkoxy group, and n represents an integer of 3 to 8.)

(4) The organic electroluminescent device according to claim 1, wherein the compound represented by the general formula (1) is an iridium (III) complex represented by the formula (5).

(5)
The organic electroluminescent device according to claim 1, wherein the compound represented by the general formula (1) is an iridium (III) complex represented by the formula (6).

(6)