JP2008288254A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element whose cost is reduced. <P>SOLUTION: The organic EL element has a light-emitting layer between an anode and a cathode, and the light-emitting layer contains an iridium complex represented by general formula (1). In the formula (1), m denotes an integer of 0-3, n denotes an integer of 0-3, and m+n is 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic EL element.

  At present, organic EL elements have been energetically studied as flat light sources and thin display panels. The organic EL element is composed of two electrodes and an organic semiconductor thin film sandwiched between the two electrodes. In addition, an electric field is applied to the two electrodes, both hole and electron carriers are injected from each electrode into the thin film, and both carriers recombine in the thin film. Here, the molecules in the thin film are excited by recombination of both carriers, and the excited molecules are subsequently deactivated. In this deactivation process, the organic EL element emits light.

  At present, organic EL elements have been intensively researched and developed for the purpose of improving the light emission efficiency and life of the elements. However, if practical application is considered, higher efficiency and longer life are required.

  Here, the material used for the organic EL element is generally made to have a high purity by removing impurities as much as possible in order to prevent the element itself from deteriorating. The impurity here refers to a by-product such as a structural isomer that may be generated when the material is synthesized or a raw material that remains without being reacted. If these impurities are contained in an amount of about 0.1 to 10% with respect to the material constituting the organic EL element, the current lowers, the efficiency decreases, the element driving life is shortened, and further, the insulation by local electric field concentration is caused. It also causes destruction (for example, see Patent Document 1).

  Moreover, when the material which comprises an organic EL element is an organometallic complex, stereoisomers, such as a facial body and a meridional body, may exist (for example, refer nonpatent literature 1). It is known that the emission spectrum of the complex itself is different between these stereoisomers, that is, the facial form and the meridional form. Here, when the stereoisomer is mixed in the organic EL element, the spectrum of light emitted from the element may change depending on the mixing ratio of the stereoisomer.

  In addition, it is known that the quantum yield of light emission of the organometallic complex is generally 5 to 10 times higher in the facial body than in the meridional body. For this reason, when many meridional bodies are contained, the luminous efficiency of the element may be lowered.

  Further, it is known that when a stereoisomer is contained as an impurity, the characteristics of the organic EL element are greatly impaired depending on the content thereof (see, for example, Patent Document 2).

  For this reason, in manufacturing an organic EL element, it is necessary to remove impurities in advance or prevent impurities from being generated in the material constituting the element. As a specific means for removing impurities, for example, a method for obtaining a high-purity material by establishing a purification method capable of removing impurities generated in the process of synthesizing a material constituting an element and prescribing the method (For example, refer to Patent Documents 1 and 3). However, since this stereoisomer is difficult to remove, there is a problem that the purification process takes time, resulting in a decrease in yield and an increase in material cost.

  In addition, as a method for preventing the generation of impurities, for example, in the molecular design stage, a compound that does not generate much impurities such as synthetic intermediates and by-products is designed, and the compound is synthesized to produce high purity. The method of obtaining this material is mentioned. However, in this method, although an organometallic complex can be obtained, it has been difficult to design a molecule adapted to the characteristics of the organic EL element such as an emission spectrum, which has been a problem.

JP 2003-095992 A JP 2004-303650 A Japanese Patent Laid-Open No. 11-171801 J. et al. Am. Chem. Soc. 2003, 125, 7377-7387

  An object of the present invention is to provide an organic EL element with reduced cost.

  As a result of intensive studies, the present inventors have reached the present invention. That is, the organic EL device of the present invention has an anode, a cathode, and at least a light emitting layer between the anode and the cathode, and the light emitting layer contains at least 1 iridium complex represented by the following general formula (1). It is characterized by being included.

(In Formula (1), m represents an integer of 0 to 3. n represents an integer of 0 to 3. However, m + n is 3. X ₁ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, Represents an alkoxy group, an aryl group, an aryloxy group or a halogen atom, and X ₂ and X ₃ each represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an aryl group, an aryloxy group or a halogen atom. X ₂ and X ₃ are different substituents, and ring A represents a heterocyclic ring represented by any one of the following general formulas (i) to (iii).

(In formulas (i) to (iii), P ₁ , P ₂ and P ₃ each represent a bond, and X _{4 to} X ₁₉ each represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom.) )

  ADVANTAGE OF THE INVENTION According to this invention, the organic EL element which reduced cost can be provided. That is, the iridium complex used as the constituent material of the organic EL device of the present invention is the same or very similar to the iridium complex whose characteristics are the main component of the impurity, even if a positional isomer is included as the impurity. It is. For this reason, it is possible to omit a part of the purification process (recrystallization or the like) for purifying the iridium complex. Therefore, since the yield of the iridium complex is not lowered by an extra purification step, the cost of the organic EL element can be reduced.

  The organic EL device of the present invention is characterized by having an anode and a cathode, and at least a light emitting layer between the anode and the cathode. Hereinafter, the organic EL device of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an embodiment of the organic EL element of the present invention. The organic EL element 1 of FIG. 1 is laminated | stacked in order of the metal electrode 11, the metal electrode layer 12, the electron carrying layer 13, the light emitting layer 14, the positive hole transport layer 15, the transparent electrode 16, and the transparent substrate 17 from the top. In the organic EL element 1 of FIG. 1, the metal electrode 11 and the metal electrode layer 12 function as a cathode, and the transparent electrode 16 functions as an anode.

  The organic EL element of the present invention is not limited to the embodiment shown in FIG. In addition, the embodiment shown below is also included.

(A) Anode / light-emitting layer / cathode (b) Anode / hole transport layer / light-emitting layer / cathode (c) Anode / light-emitting layer / electron transport layer / cathode (d) Anode / hole transport layer / light-emitting layer / electron Transport layer / cathode (Figure 1)
(E) Anode / hole transport layer / electron / exciton blocking layer / light emitting layer / electron transport layer / cathode (f) Anode / hole transport layer / light emitting layer / hole / exciton blocking layer / electron transport layer / Cathode (g) Anode / hole transport layer / electron / exciton blocking layer / light emitting layer / hole / exciton blocking layer / electron transport layer / cathode

  In the above embodiment, a charge injection layer may be provided between the electrode and the charge transport layer, or an adhesion layer for improving the adhesion of the film may be provided. Moreover, you may provide the interference layer for improving the luminous efficiency in a light emitting layer.

  The organic EL device of the present invention is characterized in that the light emitting layer contains at least one organometallic complex represented by the following general formula (1).

  In the formula (1), m represents an integer of 0 to 3. n represents an integer of 0 to 3. However, m + n is 3. In the organic EL device of the present invention, the combination of m and n is not limited to (m, n) = (3,0) or (m, n) = (0,3), but (m, n) = ( 1, 2) and (m, n) = (2, 1) may be included. That is, the organometallic complex of the formula (1) contained in the light emitting layer may contain a regioisomer. Here, the positional isomers are compounds having the same molecular weight and the same configuration of the ligand (particularly the nitrogen atom of the ring A in the formula (1)) and differing only in the coordination position of the ligand. That means. For example, the following complex β is a positional isomer of the complex α.

In Formula (1), X ₁ represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an alkoxy group, an aryloxy group, or a halogen atom.

Examples of the alkyl group having 1 to 20 carbon atoms represented by X ₁ include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, a tertiary butyl group, a secondary butyl group, an octyl group, a cyclohexyl group, and a cyclopentyl group. However, it is not limited to these.

Examples of the aryl group represented by X ₁ include, but are not limited to, a phenyl group, a naphthyl group, a tolyl group, a xylyl group, a biphenyl group, a terphenyl group, and a fluorenyl group.

Examples of the alkoxy group represented by X ₁ include, but are not limited to, a methoxy group, an ethoxy group, a propoxy group, a 2-ethyloctyloxy group, and a benzyloxy group.

Examples of the aryloxy group represented by X ₁ include, but are not limited to, a phenoxy group and a 4-tertiarybutylphenoxy group.

Examples of the halogen atom represented by X ₁ include fluorine, chlorine, bromine and iodine.

In Formula (1), X ₂ and X ₃ each represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an alkoxy group, an aryloxy group, or a halogen atom.

Specific examples of the alkyl group having 1 to 20 carbon atoms, aryl group, alkoxy group, aryloxy group or halogen atom represented by X ₂ and X ₃ are the same as the specific examples of X ₁ above.

X ₂ and X ₃ are different substituents.

  In the formula (1), the ring A represents a heterocyclic ring represented by any one of the following general formulas (i) to (iii).

In formulas (i) to (iii), P ₁ , P _2, and P ₃ each represent a bond that is bonded to a benzene ring in which X _{1 to} X ₃ are substituted.

In formulas (i) to (iii), X _{4 to} X ₁₉ each represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, or a halogen atom.

Specific examples of the alkyl group, aryl group, alkoxy group, aryloxy group or halogen atom represented by X _{4 to} X ₁₉ are the same as the specific examples of X ₁ described above.

When ring A is (i), X _{4 to} X ₇ may be the same or different.

When ring A is (ii), X _{8 to} X ₁₃ may be the same or different.

When ring A is (iii), X _{14 to} X ₁₉ may be the same or different from each other.

  Next, a method for synthesizing the iridium complex represented by the general formula (1) will be described. The organometallic complex of the general formula (1) is synthesized by, for example, the synthesis scheme shown below.

  A specific method for carrying out the above synthesis scheme will be described. First, a ligand that coordinates to iridium ions is synthesized. Specifically, a phenylisoquinoline derivative (intermediate 1-1) as a ligand can be synthesized by a coupling reaction of a phenylboronic acid derivative and a 1-chloroisoquinoline derivative represented by the following formula.

  Subsequently, a complex of intermediate 1-2 can be obtained by reacting intermediate 1-1 with iridium trichloride trihydrate in an equivalent ratio of 4: 2.

  Next, the intermediate body 1-2 and acetylacetone are reacted to obtain an acetylacetone body (intermediate body 1-3). At this time, three kinds of positional isomers can be generated depending on the combination of a and b in the above formula, that is, the coordination method of the phenylisoquinoline ligand.

  Finally, the target complex represented by the formula (1) can be obtained by replacing the acetylacetone ligand with a phenylisoquinoline ligand by a ligand exchange reaction. Depending on the coordination method of the phenylisoquinoline ligand coordinated third at this time, four kinds of positional isomers can finally be formed.

  Conventionally, regarding the organometallic complex used as a constituent material of an organic EL element, when a positional isomer is included as an impurity, how the presence of the positional isomer affects the characteristics of the organic EL element, etc. Had no knowledge. In addition, the presence of impurities in a compound used as a constituent material of an organic EL element causes deterioration of the element. Therefore, when impurities are mixed in the compound to be used, it is considered necessary to remove the impurities. It was done.

  However, organometallic complexes that generate positional isomers as impurities during synthesis are difficult to remove, and it is difficult to extract high-purity materials. For example, when regioisomers are removed by recrystallization, it is necessary to repeat recrystallization many times. Further, since the positional isomers have the same molecular weight and similar thermal properties (melting point, sublimation point, etc.), it is very difficult to remove the positional isomers by sublimation purification.

  Here, the iridium complex of the general formula (1), which is a material constituting the light emitting layer of the organic EL element of the present invention, has the same or very similar properties shown below among positional isomers.

1. Electrical properties (charge mobility, carrier density, energy level, etc.)
2. Physical and chemical properties (thermal properties, molecular weight, molecular polarity, etc.)

  For example, the charge mobility of a molecule is determined by the overlap of molecular orbitals with neighboring molecules, so it is thought to depend on the intermolecular distance with neighboring molecules, but the intermolecular distance varies greatly between positional isomers. It is hard to think. For this reason, it is thought that the charge mobility of the molecule | numerator of regioisomers is the same or very similar.

  For example, consider a case where the light emitting layer is composed of a host and a guest. Here, when the iridium complex of the formula (1) is used as a guest, the charge trapping performance of the guest depends on the energy level of the guest molecule. By the way, the energy level is considered to have a small difference between positional isomers. For this reason, it can be said that the electrical properties of the positional isomers are very similar. Therefore, even if positional isomers are included, it is considered that there is not much difference in the electrical characteristics (current-voltage characteristics) of the device. .

  For this reason, even if the positional isomer is contained as an impurity, an organic EL device having the same characteristics as those obtained when the positional isomer is completely removed with high purity can be realized without substantially affecting the characteristics of the device. . Thereby, the process accompanying a refinement | purification can be reduced, and the loss of the material by refinement | purification can be suppressed simultaneously. As a result, the cost for producing the organic EL element can be reduced.

  Although the specific example of the organometallic complex shown by General formula (1) below is given, this invention is not limited to this.

  In the organic EL device of the present invention, the light emitting layer may be composed only of the iridium complex represented by the general formula (1), but is preferably composed of a carrier transporting host and a guest. When the light emitting layer is composed of a host and a guest, the process in which the organic EL element emits light is a combination of several processes shown below.

-Transport of electrons or holes on the host-Transport of electrons or holes on the guest-Exciton generation on the host-Exciton generation on the guest-Energy transfer between host molecules-From host molecule to guest molecule By the way, when the guest is a phosphorescent material, there are two types of excitons involved in light emission: singlet excitons and triplet excitons, and each exciton can compete in various deactivation processes. Generated from inside.

  In addition, in order to increase the luminous efficiency of the organic EL element, it is also necessary to generate both excitons efficiently by injecting a large amount of both hole and electron carriers injected from the electrode into the light emitting layer in a balanced manner. .

  In particular, the organic light-emitting device of the present invention uses an iridium complex as a material constituting the light-emitting layer. In addition to the iridium complex, the organic light-emitting device of the present invention may be used together with a known low-molecular-weight and polymer-based hole transport compound, light-emitting compound, electron transport compound, etc. It can also be used. . Below, the name and molecular structure of the compound used as a material which comprises an organic light emitting element are shown.

  Examples of the hole transporting compound include TPD, NPD, TPAC, and the like.

Examples of the luminescent compound include DCM2, Alq ₃ , Ir (ppy) _{3 and the} like in addition to the iridium complex of the formula (1).

Examples of the electron transporting compound include TAZ, BCP, Alq _{3 and the} like.

  Examples of the anode include ITO and IZO.

  Examples of the cathode include Al, Mg, and Ca.

  Although it does not specifically limit as a board | substrate used by this invention, Transparent substrates, such as opaque board | substrates, such as a metal board | substrate and a ceramic board | substrate, glass, quartz, a plastic sheet, are used.

  It is also possible to control the emission color using a color filter film, a color conversion filter film, a dielectric reflection film or the like on the substrate.

  In addition, a thin film transistor can be formed over a substrate, and an element can be manufactured by connecting to the thin film transistor.

  Regarding the method of extracting light from the element, either a bottom emission type in which light is extracted from the substrate side or a top emission type in which light is extracted from the side opposite to the substrate is possible.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[Synthesis Example 1] (Synthesis of Exemplified Compound A1)

(1) The following reagents and solvents were charged into a 200 ml three-necked flask.

4-Fluoro-3-methylphenylboronic acid: 3.80 g (25.0 mmol) (Aldrich)
1-chloroisoquinoline: 4.09 g (25.0 mmol)
Toluene: 25ml
Ethanol: 12.5ml
2M-sodium carbonate aqueous solution: 25 ml

Next, 0.98 g (0.85 mmol) of tetrakis- (triphenylphosphine) palladium (0) was added while stirring at room temperature under a nitrogen stream. Thereafter, the reaction solution was stirred while refluxing for 8 hours under a nitrogen stream. After completion of the reaction, the reaction solution was cooled and cold water and toluene were added to extract the organic layer. Next, this organic layer was washed with brine, dried over magnesium sulfate, and then the solvent was distilled off under reduced pressure. Next, the residue was purified by silica gel column chromatography (developing solvent: chloroform / methanol = 10/1) to obtain 3.01 g (yield) of 1- (4-fluoro-3-methylphenyl) isoquinoline (A1-1). Rate 51.1%).
(2) The following reagents and solvent were charged into a 200 ml three-necked flask.

Iridium chloride (III) trihydrate: 0.58 g (1.64 mmol) (manufactured by Acros)
1- (4-Fluoro-3-methylphenyl) isoquinoline (A1-1): 1.66 g (7.34 mmol)
Ethoxyethanol: 45ml
Water: 15ml

Next, the reaction solution was stirred at room temperature for 30 minutes under a nitrogen stream, and then stirred while refluxing for 24 hours. After completion of the reaction, the reaction solution was cooled to room temperature, and the formed precipitate was collected by filtration, washed with water, and further washed successively with ethanol and acetone. Next, 1.02g of A1-2 which is red powder was obtained by drying under reduced pressure at room temperature. This A1-2 is mainly composed of tetrakis [1- (4-fluoro-5-methylphenyl) isoquinoline-C2, N] (μ-dichloro) diiridium (III) in which a = 2 and b = 0. It is a mixture containing regioisomers.
(3) The following reagents and solvents were charged into a 200 ml three-necked flask.

Ethoxyethanol: 70ml
A1-2: 0.95 g (0.72 mmol)
Acetylacetone: 0.22 g (2.10 mmol)
Sodium carbonate: 1.04 g (9.91 mmol)

Next, the reaction solution was stirred at room temperature for 1 hour under a nitrogen stream, and then stirred while refluxing for 15 hours. After completion of the reaction, the reaction solution was ice-cooled, and the precipitate was collected by filtration and washed with water. The precipitate was purified by silica gel column chromatography (developing solvent: chloroform / methanol = 30/1) to obtain 0.43 g (yield 41.3%) of A1-3 as a red powder. This A1-3 is mainly composed of bis [1- (4-fluoro-5-methylphenyl) isoquinoline-C2, N] (acetylacetonato) iridium (III) in which a = 2 and b = 0. It is a mixture containing isomers.
(4) The following reagents and solvent were charged into a 100 ml three-necked flask.

1- (4-Fluoro-5-methylphenyl) isoquinoline: 0.27 g (1.23 mmol)
A1-3: 0.36 g (0.49 mmol)
Glycerol: 25ml

  Next, the reaction solution was stirred for 8 hours while heating at around 180 ° C. under a nitrogen stream. After completion of the reaction, the reaction solution was cooled to room temperature and then poured into 170 ml of 1N hydrochloric acid. Next, the produced precipitate was collected by filtration, washed with water, and dried under reduced pressure at 100 ° C. for 5 hours. Next, 0.27 g (yield 64.5%) of a red powder was obtained by purifying the precipitate by silica gel column chromatography using chloroform as a developing solvent. This red powder is composed mainly of tris [1- (4-fluoro-5-methylphenyl) isoquinoline-C2, N] iridium (III) (Exemplary Compound A1) in which c = 3 and d = 0. It is a mixture containing regioisomers.

[Example 1]
An organic EL device having the exemplified compound A1 (including positional isomers) purified by the purification process described below and the following compounds as constituent materials was produced.

(Purification of complex)
The red powder (Exemplary Compound A1) obtained in Synthesis Example 1 was recrystallized once with a toluene solvent and then purified by sublimation. The yield after sublimation purification was 80% compared to before the purification process.

Further, the λ _max of the emission spectrum of the purified complex in a toluene solution was 607 nm, and the quantum yield was 0.8 when Ir (ppy) ₃ was used as a reference.

In addition, the structure of the complex purified by ¹ H-NMR was identified.

¹ H-NMR (CDCl ₃ , 400 MHz) σ (ppm): 8.90-8.88 (d, 3H), 8.04-8.02 (d, 3H), 7.73-7.70 (m 3H), 7.67-7.62 (m, 6H), 7.26-7.25 (d, 3H), 7.08-7.07 (d, 3H), 6.57-6.54. (D, 3H), 2.21 (s, 9H)

From the ¹ H-NMR measurement, it was found that the steric structure of the complex obtained by purification was a facial form.

  By the way, when exemplary compound A1 is purified by the above purification process, the complex shown below is obtained.

(A) Complex containing only a ligand in which the methyl group is in the 3-position (b) Complex containing only a ligand in which the methyl group is in the 5-position (c) A ligand in which the methyl group is in the 3-position and the methyl group are in the 5-position Therefore, the structure of the complex obtained by the above-described purification process includes four types of complexes (1) to (4) shown below including the positional isomer.

Here, it was confirmed by ¹ H-NMR measurement that the complex (1) having the least steric hindrance by the substituent was preferentially produced.

  Next, regarding the exemplary compound A1 purified by the above purification process, the mixing ratio of the complex (1) and its positional isomer was evaluated from HPLC / UV measurement. Here, the conditions of HPLC / UV measurement are as shown below.

Sample concentration: 0.1 mg / ml
Dissolving solvent: CHCl ₃
Column: YMC ODS-H80 4.6 mmΦ × 250 mm
Mobile phase: Methanol Flow rate: 1.0 ml / min
Detection wavelength: 254 nm (UV absorption)

  As a result of the measurement, the chromatogram shown in FIG. 2 was obtained. In FIG. 2, in the chromatogram of FIG. 2 (a), only one peak can be confirmed visually, but when a part of it is enlarged (FIG. 2 (b)), it can be confirmed that two peaks exist (peak). A, peak B). From this chromatogram, the mixing ratio of complex (1) and its positional isomer was determined from the ratio of each peak area based on the sum of all peak areas. As a result, the mixing ratio of complex (1), which is the main product, and regioisomer was [complex (1)]: [regioisomer] = 97.0: 3.0.

  Further, in the HPLC / UV measurement, when the mass spectrum was measured for the peak derived from the complex (1) and the peak derived from the positional isomer, respectively, the mass spectra shown in FIGS. 3 (a) and (b) were obtained. It was. As a result, the molecular weights of Peak A and Peak B shown in FIG. 2 (b) coincided with the molecular weight 901.2 of Complex (1). Moreover, since the impurity peak has a higher polarity than the main product, it was found that the contained impurity is not a meridional body.

  From the above, it is considered that the contained impurities are any of the above complexes (2) to (4) which are all positional isomers of the complex (1) and are facial.

(Production of organic EL element)
A three-layer organic EL element having the element configuration shown in FIG. 4 was produced. First, indium tin oxide (ITO) to be the transparent electrode 16 was patterned on a glass substrate (transparent substrate 17) so as to have a film thickness of 100 nm and an electrode area of 3.14 mm ² .

Next, the following organic layer and electrode layer were continuously formed on this ITO patterned substrate using a vacuum evaporation method by resistance heating in a vacuum chamber of 10 ⁻⁴ Pa. First, as the hole transport layer 15, the compound A was formed to a thickness of 40 nm. Next, as the light emitting layer 14, a mixture of the compound B and the exemplary compound A1 was co-deposited so that the exemplary compound A1 was 13% by weight as a weight concentration ratio. At this time, the thickness of the light emitting layer 14 was set to 25 nm. Next, as the electron transport layer 13, Bphen was formed to a film thickness of 50 nm. Next, as the metal electrode layer 12, KF was formed to a thickness of 1 nm. Finally, as the metal electrode layer 11, Al was formed with a film thickness of 100 nm.

  An organic EL device was obtained as described above.

  The characteristics of the obtained organic EL device were measured and evaluated by the following methods.

(1) Current value Measured with a Keithley Model 2000 multimeter. At this time, the luminance was measured using BM7 manufactured by Topcon Corporation. At this time, Advantest R6144 was used as a current voltage source.

(2) Emission spectrum Measured and evaluated using SR1 manufactured by Topcon Corporation.

(3) Lifetime The luminance value when a current of 100 mA / cm ² was supplied to the device was defined as the initial luminance, and the time taken for the value to be halved (unit: hours) was defined as the half life. In measuring and evaluating the half-life of the organic EL element, Advantest R6144 was used as a constant current source, and silicon photodiode S2387-1010R made by Hamamatsu Photonics was used for detection of light emission.

When the characteristics of the organic EL device of this example were evaluated, the current efficiency at a luminance of 600 cd / m ² was 13.4 cd / A, and the power efficiency was 11.7 lm / W. At this time, the driving voltage of the device was 3.6 V, and the current density was 4.4 mA / cm ² . Moreover, about the organic EL element of a present Example, the emission spectrum shown in FIG. 4 was obtained, and the peak of the emission spectrum was 610 nm. The CIE chromaticity coordinates were (0.65, 0.35). Further, when a current of 100 mA / cm ² was supplied to the organic EL device of this example, the luminance value at the initial stage of durability was 8000 cd / m ² and the half life was 460 hours.

[Example 2]
(Purification of complex)
In Example 1, the complex was purified in the same manner as in Example 1 except that the number of recrystallizations with a toluene solvent was set to 8. The yield of the complex after sublimation purification was 18% before purification. The thus-purified complex was subjected to HPLC / UV measurement, and the mixing ratio of the complex (1) and its positional isomer was evaluated. The mixing ratio of the complex (1) and the positional isomer was [complex (1) ]: [Regioisomer] = 98.7%: 1.3%.

(Production of organic EL element)
In Example 1, an organic EL device was obtained in the same manner as in Example 1 except that the purified complex was used as a luminescent material. When the obtained organic EL element was evaluated in the same manner as in Example 1, the current efficiency at a luminance of 600 cd / m ² was 13.7 cd / A, and the power efficiency was 11.7 lm / W. At this time, the driving voltage of the device was 3.6 V, and the current density was 4.4 mA / cm ² . Moreover, about the organic EL element of a present Example, the emission spectrum shown in FIG. 4 was obtained, and the peak of the emission spectrum was 610 nm. The CIE chromaticity coordinates were (0.65, 0.35). Further, when a current of 100 mA / cm ² was supplied to the organic EL device of this example, the luminance value at the initial stage of durability was 8000 cd / m ² and the half life was 420 hours.

[Comparative Example 1]
(Purification of complex)
In Example 1, the complex was purified in the same manner as in Example 1 except that the number of recrystallizations with a toluene solvent was 16 times. The yield of the complex after sublimation purification was 5% before purification. The thus purified complex was subjected to HPLC / UV measurement, and the mixing ratio of the complex (1) and its positional isomer was evaluated. The ratio of the complex (1) exceeded 99.9%, and the positional isomer was The peak derived from was not confirmed.

(Production of organic EL element)
In Example 1, an organic EL device was obtained in the same manner as in Example 1 except that the purified complex was used as a luminescent material. When the obtained organic EL device was evaluated in the same manner as in Example 1, the current efficiency at a luminance of 600 cd / m ² was 13.6 cd / A, and the power efficiency was 11.5 lm / W. At this time, the driving voltage of the device was 3.6 V, and the current density was 4.4 mA / cm ² . Moreover, about the organic EL element of this comparative example, the emission spectrum shown in FIG. 4 was obtained, and the peak of the emission spectrum was 610 nm. The CIE chromaticity coordinates were (0.65, 0.35). Furthermore, when a current of 100 mA / cm ² was supplied to the organic EL device of this comparative example, the luminance value at the initial stage of durability was 8000 cd / m ² and the half life was 430 hours.

  From this table, as in Examples 1 and 2, even when the positional isomer of the organometallic complex, which is the light emitting material, is included, the characteristics of the device are the same as those of Comparative Example 1 that hardly includes the positional isomer. Met. From this, it was found that even if some positional isomers are included, the characteristics of the organic EL element itself are hardly affected.

It is a figure which shows one Embodiment in the organic EL element of this invention. 2 is a diagram showing a HPLC / UV chromatogram of the complex of the formula (A) purified by Example 1. FIG. Here, (b) is a chromatogram obtained by enlarging a part of (a). It is a figure which shows the mass spectrum in the peak which appeared in the chromatogram of HPLC / UV of FIG. Here, (a) is a mass spectrum related to the peak A shown in FIG. 2 (b), and (b) is a mass spectrum related to the peak B shown in FIG. 2 (b). It is a figure which shows the emission spectrum of the organic EL element produced in Example 1, Example 2, and Comparative Example 1, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic EL element 11 Metal electrode 12 Metal electrode layer 13 Electron transport layer 14 Light emitting layer 15 Hole transport layer 16 Transparent electrode 17 Transparent substrate

Claims (1)

An anode and a cathode;
Having at least a light emitting layer between the anode and the cathode;
An organic EL element, wherein the light emitting layer contains at least one iridium complex represented by the following general formula (1).

(In Formula (1), m represents an integer of 0 to 3. n represents an integer of 0 to 3. However, m + n is 3. X ₁ is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, Represents an alkoxy group, an aryl group, an aryloxy group or a halogen atom, and X ₂ and X ₃ each represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group, an aryl group, an aryloxy group or a halogen atom. X ₂ and X ₃ are different substituents, and ring A represents a heterocyclic ring represented by any one of the following general formulas (i) to (iii).

(In formulas (i) to (iii), P ₁ , P ₂ and P ₃ each represent a bond, and X _{4 to} X ₁₉ each represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom.) )

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