JP2010184876A - Organometallic complex, composition for organic electroluminescent device and organic electroluminescent device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organometallic complex having high durability, useful for an organic layer of an organic electroluminescent device formed by a wet film-forming method, having excellent solubility in a solvent, and providing the organic electroluminescent device having high efficiency and long life by the wet film-forming method. <P>SOLUTION: The organometallic complex usable for the organic electroluminescent device has ≤1 wt.% of the content of a compound having a molecular weight larger by 14 than that of the organic metallic complex. The organic electroluminescent device having the long life, high brightness and high efficiency can stably be provided by using the organometallic complex having the reduced content of the specific impurity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organometallic complex used for an organic electroluminescent device, and more specifically, for an organic electroluminescent device having excellent durability, solubility in a solvent, and excellent film formability and wet process suitability. To organometallic complexes of The present invention also provides a composition for an organic electroluminescent device comprising the organometallic complex, a high-efficiency, long-life organic electroluminescent device using the organometallic complex, and an organic EL display using the organic electroluminescent device. And organic EL lighting.

  In recent years, as a thin film type electroluminescent element, an organic electroluminescent element using an organic thin film has been developed instead of using an inorganic material. Organic electroluminescent elements usually have a hole injection layer, a hole transport layer, an organic light emitting layer, an electron transport layer, etc. between the anode and the cathode, and in particular, the light emitting layer has red, green, blue, etc. Luminescent materials are included.

  Such an organic electroluminescent element is required to be improved in efficiency and life for practical use, and in particular, a highly durable phosphorescent light emitting material is required as a material for the light emitting layer.

  Conventionally, as phosphorescent materials, organometallic complexes having a metal such as Ir as a central metal are considered promising, and the following iridium complexes have been proposed (for example, Patent Document 1), but the synthesis process is still unknown. There were many parts and had problems such as unstable performance during production.

  On the other hand, as a method for forming each layer of the organic electroluminescent element, there are a vapor deposition film forming method and a wet film forming method. The vapor deposition method has a problem in terms of yield when manufacturing a medium or large full color panel for a television or a monitor. Therefore, the wet film forming method is suitable for these large-area applications, but in order to form each layer of the organic electroluminescent element by the wet film forming method, the material forming each layer is dissolved in a solvent, and It is necessary that the material has high performance as an element even after wet film formation.

International Publication No. 2002-44189 Pamphlet

The present invention has been made in view of the above problems.
That is, the present invention is an organometallic complex that is highly durable and useful for an organic layer formed by a wet film-forming method of an organic electroluminescent element, has excellent solvent solubility, and is highly efficient by a wet film-forming method. Another object of the present invention is to provide an organometallic complex and a composition for an organic electroluminescence device that can provide a long-life organic electroluminescence device.
Another object of the present invention is to provide a high-efficiency, long-life organic electroluminescence device using the organometallic complex, and an organic EL display and organic EL illumination using the organic electroluminescence device.

  As a result of intensive studies by the present inventors, it has been found that by using an organometallic complex in which specific impurities are reduced, an organic electroluminescence device having a long life, high luminance and high efficiency can be provided stably. Reached.

  The organometallic complex of the present invention (Claim 1) is an organometallic complex used in an organic electroluminescent device, and the content of a compound having a molecular weight 14 larger than that of the organometallic complex is 1% by weight or less. Features.

  The organometallic complex according to claim 2 is selected from the group consisting of Ir, Pt, Pd, Cu, Zn, Ag, Rh, Ru, Os, Au, and Re in claim 1, wherein the metal contained in the organometallic complex is It is characterized by being a metal.

  The organometallic complex according to claim 3 is characterized in that, in claim 1 or 2, the organometallic complex has an alkyl group which may have a substituent in the molecule.

  The composition for organic electroluminescent elements of the present invention (invention 4) is characterized by containing the organometallic complex according to any one of claims 1 to 3 and a solvent.

  The organic electroluminescent element of the present invention (invention 5) is an organic electroluminescent element having an anode, a cathode, and a light emitting layer provided between both electrodes, and is described in any one of claims 1 to 3. It has a layer containing the organometallic complex.

  The organic EL display of the present invention (Claim 6) and the organic EL illumination of the present invention (Claim 7) use this organic electroluminescent element.

  The organometallic complex of the present invention has high durability, high solubility in a solvent, and is suitable for an organic layer of an organic electroluminescent element formed by a wet film-forming method. It is possible to provide an organic electroluminescent device with high efficiency and long life.

  Therefore, the organic electroluminescent element using the organometallic complex of the present invention is a light source that makes use of the characteristics as a flat panel display (for example, for OA computers and wall-mounted televisions), in-vehicle display elements, mobile phone displays, and surface light emitters. (For example, a light source of a copying machine, a backlight light source of a liquid crystal display or an instrument), a display board, and a marker lamp can be considered, and its technical value is high.

It is a schematic diagram of the cross section which shows embodiment of the organic electroluminescent element of this invention. It is a figure which shows the HPLC analysis chart of each iridium complex obtained by the synthesis examples 2-3.

  Embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention does not exceed the gist thereof. Not specific to the content.

[Organic metal complex]
The organometallic complex of the present invention is an organometallic complex used for an organic electroluminescence device, and is characterized in that the content of a compound having a molecular weight 14 larger than that of the organometallic complex is 1% by weight or less.

  First, the action mechanism of the effect by prescribing the content of a compound having a molecular weight of 14 larger than the target organometallic complex compound in the present invention will be described.

  In general, there are isomers such as facial, meridional, E, and Z isomers in metal complexes, and depending on the substituents, various isomers are produced. Although it is difficult, even a slight difference in the structure greatly affects the stability as a complex. When a complex containing such an isomer is used in an organic electroluminescence device, the lifetime of the device is short. It will be a thing. However, it becomes more difficult to analyze and detect the presence of such isomers as the complex structure becomes more complex.

In addition, the situation is further complicated for metal complexes used for wet film formation.
That is, the complex used in the vapor deposition method is generally simple in structure and good in crystallinity. For example, in an Ir complex, when heated in a solution in the manufacturing process, it is isomerized to the most stable facial structure, Since a crystal is generated in the reaction system with the structure, a complex having a high purity and a stable structure can be easily obtained by separating the structure.
On the other hand, the metal complex used for wet film formation is intentionally designed with a highly soluble structure in solvents, so it may be isomerized into a thermally stable structure. Since such crystals have poor crystallinity, impurities are easily mixed even if crystals are formed. Further, it may have a long-chain alkyl group for the purpose of improving solvent solubility and the like, and a ligand in which a part of this alkyl group is oxidized to form a ketone is easily mixed.

  In consideration of such a situation, the present inventors include a compound having a molecular weight of 14 larger than that of the organometallic complex (target compound) as an impurity that can be mixed into the organometallic complex for organic electroluminescent elements. By suppressing the content of the compound (hereinafter sometimes referred to as “impurity (+14)”) to 1% by weight or less, the durability of the organometallic complex is improved, and as a result, the organometallic complex is used. The present inventors have found that an organic electroluminescent device with high efficiency and long life can be produced.

  In general, a compound having a molecular weight of 14 larger than that of the organometallic complex as the target compound means that two hydrogen atoms bonded to one carbon atom of the target compound are replaced with oxygen atoms to form a ketone group. As a result, the molecular weight of the target compound was −2 (molecular weight of 2 hydrogen atoms) +16 (molecular weight of 1 oxygen atom), resulting in a compound having a large molecular weight of 14. Such impurities are usually produced as a reaction by-product in the production process of the target compound and are mixed in the target compound, but may be mixed in the raw material used. Since such an impurity (+14) has a molecular weight close to that of the target compound, it is usually difficult to separate the target compound from the target compound.

  In the present invention, when the content of the impurity (+14) in the organometallic complex exceeds 1% by weight, the durability of the organometallic complex is lowered. Using this organometallic complex, organic electroluminescence with high efficiency and long life is obtained. The device cannot be manufactured. The content of impurities (+14) is preferably as small as possible, and is preferably 0.8% by weight or less, particularly preferably 0.5% by weight or less. However, excessively suppressing this content is industrial in terms of purification cost. The lower limit is usually about 0.0001% by weight.

  The presence of the impurity (+14) in the organometallic complex can be detected by analysis by HPLC (high performance liquid chromatography) or the like. Moreover, content of the impurity (+14) in an organometallic complex can be calculated | required from calculation from the peak area of this HPLC analysis chart.

  As described above, this impurity (+14) is usually formed by oxidizing two hydrogen atoms bonded to the carbon atom of the target compound into oxygen atoms. Therefore, the organometallic complex of the present invention is , A compound that easily undergoes oxidation, in particular, a long-chain alkyl group having 3 or more carbon atoms, for example 3 to 12 carbon atoms, which may have a substituent, on an aromatic ring or a heteroaromatic ring. Compounds having substituents are listed as compounds that can meet the purpose of the present invention.

  The method for reducing the content of such impurities (+14) in the organometallic complex is not particularly limited. In the production process of the target compound, the reaction vessel is replaced with a method for controlling the reaction temperature or an inert gas. Examples thereof include a method and a method of separating and removing impurities (+14) by purifying an organometallic complex obtained by synthesis by a column chromatography method, a recrystallization method, or the like.

  In addition to the impurity (+14), the organometallic complex may contain a compound having a molecular weight higher than that of the target compound, such as a compound having a molecular weight of 30 or 32, as impurities, in addition to the impurity (+14). There is sex. For example, in Synthesis Examples 1 to 3 described later, in addition to the impurity (+14), a compound having a molecular weight 32 larger than the target compound (hereinafter sometimes referred to as “impurity (+32)”) is contained. The content of these compounds is also desired to be low, but in general, the content of impurities other than the impurity (+14) in the organometallic complex is small, and the impurities (+14) in the organometallic complex are purified by purification. Since impurities other than impurities (+14) are also reduced in the removing step, the upper limit of the content of these impurities is not particularly limited, but other than impurities (+14) such as impurities (+32) described later. The total content of impurities in the organometallic complex with impurities different in molecular weight from the target compound similar to the target compound is preferably 5% by weight or less, particularly preferably 1% by weight or less. In particular, the content of impurities (+32) is preferably 0.04% by weight or less, and more preferably 0.02% by weight or less. These impurities having different molecular weights can also be detected and quantified by HPLC analysis.

  Although there is no restriction | limiting in particular about the metal contained in the organometallic complex of this invention, Since it is used as a luminescent material of an organic electroluminescent element, it is preferable that it is a metal chosen from the periodic table 7 thru | or 11 group, and has luminescent property. More preferable is a metal selected from the group consisting of high Ir, Pt, Pd, Cu, Zn, Ag, Rh, Ru, Os, Au, and Re, and among these, Ir, Pt, and particularly Ir is preferable. .

  The organometallic complex applied to the present invention is preferably a compound represented by the following formulas (4) and (5), or described in International Publication No. 2005/011370 and International Publication No. 2005/019373. Compounds.

MG _(qj) G ' _j (4)
(In formula (4), M represents a metal, q represents a valence of the metal M. G and G ′ represent a bidentate ligand. J represents 0, 1 or 2.)

（式（５）中、Ｍ⁵は金属を表し、Ｔは炭素又は窒素を表す。Ｒ⁹²〜Ｒ⁹⁵は、それぞれ独立に置換基を表す。ただし、Ｔが窒素の場合は、Ｒ⁹⁴及びＲ⁹⁵は無い。）

(In the formula (5), M ⁵ represents a metal, T is .R ⁹² to R ⁹⁵ that represents a carbon or nitrogen, each independently represent a substituent. However, when T is nitrogen, R ⁹⁴ and R ^There is no ^95. )

Hereinafter, the compound represented by formula (4) will be described first.
In Formula (4), M represents an arbitrary metal, and specific examples of preferable ones include the metals described above as the metal selected from Groups 7 to 11 of the periodic table.
Moreover, the bidentate ligands G and G ′ in the formula (4) each represent a ligand having the following partial structure.

である。 G ′ is particularly preferably from the viewpoint of the stability of the complex,

It is.

In the partial structures G and G ′, the ring Q1 represents an aromatic hydrocarbon group or an aromatic heterocyclic group, and these may have a substituent. Ring Q2 represents a nitrogen-containing aromatic heterocyclic group, and these may have a substituent.
In the present invention, “may have a substituent” means that it may have one or more substituents.

  Preferred substituents for the rings Q1 and Q2 include: a halogen atom such as a fluorine atom; an alkyl group such as a methyl group and an ethyl group; an alkenyl group such as a vinyl group; an alkoxycarbonyl group such as a methoxycarbonyl group and an ethoxycarbonyl group; Alkoxy groups such as ethoxy groups; aryloxy groups such as phenoxy groups and benzyloxy groups; dialkylamino groups such as dimethylamino groups and diethylamino groups; diarylamino groups such as diphenylamino groups; carbazolyl groups; acyl groups such as acetyl groups A haloalkyl group such as a trifluoromethyl group; a cyano group; an aromatic hydrocarbon group such as a phenyl group, a naphthyl group, and a phenanthyl group;

  More preferred examples of the compound represented by the formula (4) include compounds represented by the following formulas (4a), (4b), and (4c).

（式（４ａ）中、Ｍ^aはＭと同様の金属を表し、ｑ^aは金属Ｍ^aの価数を表す。環Ｑ１は置換基を有していても良い芳香族炭化水素基又は芳香族複素環基を表し、環Ｑ２は置換基を有していても良い含窒素芳香族複素環基を表す。）

(In the formula (4a), M ^a represents the same metal as M, q ^a represents the valence of the metal M ^a. Ring Q1 is aromatic optionally substituted hydrocarbon group or an aromatic Represents a heterocyclic group, and ring Q2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.

（式（４ｂ）中、Ｍ^bはＭと同様の金属を表し、ｑ^bは金属Ｍ^bの価数を表す。環Ｑ１は置換基を有していても良い芳香族炭化水素基又は芳香族複素環基を表し、環Ｑ２は置換基を有していても良い含窒素芳香族複素環基を表す。）

(In formula (4b), M ^b represents the same metal as M, q ^b represents the valence of metal M ^b , and ring Q1 is an aromatic hydrocarbon group or aromatic which may have a substituent. Represents a heterocyclic group, and ring Q2 represents a nitrogen-containing aromatic heterocyclic group which may have a substituent.

（式（４ｃ）中、Ｍ^cはＭと同様の金属を表し、ｑ^cは金属Ｍ^cの価数を表す。ｊは０、１又は２を表す。環Ｑ１及び環Ｑ１’は、それぞれ独立に、置換基を有していても良い芳香族炭化水素基又は芳香族複素環基を表す。環Ｑ２及び環Ｑ２’は、それぞれ独立に、置換基を有していても良い含窒素芳香族複素環基を表す。）

(In formula (4c), M ^c represents the same metal as M, q ^c represents the valence of metal M ^c , j represents 0, 1 or 2. Ring Q1 and ring Q1 ′ are each independent. Represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and ring Q2 and ring Q2 ′ are each independently a nitrogen-containing aromatic which may have a substituent. Represents a heterocyclic group.)

In the above formulas (4a), (4b) and (4c), the ring Q1 and the ring Q1 ′ are preferably, for example, a phenyl group, a biphenyl group, a naphthyl group, an anthryl group, a thienyl group, a furyl group, a benzothienyl group, A benzofuryl group, a pyridyl group, a quinolyl group, an isoquinolyl group, a carbazolyl group, and the like can be given.
The ring Q2 and ring Q2 ′ are preferably, for example, pyridyl group, pyrimidyl group, pyrazyl group, triazyl group, benzothiazole group, benzoxazole group, benzimidazole group, quinolyl group, isoquinolyl group, quinoxalyl group, phenane. A tridyl group etc. are mentioned.

  Substituents that the compounds represented by formulas (4a), (4b), and (4c) may have include halogen atoms such as fluorine atoms; alkyl groups such as methyl groups and ethyl groups; vinyl groups and the like Alkenyl group; alkoxycarbonyl group such as methoxycarbonyl group and ethoxycarbonyl group; alkoxy group such as methoxy group and ethoxy group; aryloxy group such as phenoxy group and benzyloxy group; dialkylamino group such as dimethylamino group and diethylamino group; A diarylamino group such as a diphenylamino group; a carbazolyl group; an acyl group such as an acetyl group; a haloalkyl group such as a trifluoromethyl group; and a cyano group.

  When the said substituent is an alkyl group, the carbon number is 1 or more and 6 or less normally. When the said substituent is an alkenyl group, the carbon number is 2 or more and 6 or less normally. When the substituent is an alkoxycarbonyl group, the carbon number is usually 2 or more and 6 or less. When the said substituent is an alkoxy group, the carbon number is 1 or more and 6 or less normally. When the said substituent is an aryloxy group, the carbon number is 6 or more and 14 or less normally. When the substituent is a dialkylamino group, the carbon number is usually 2 or more and 24 or less. When the substituent is a diarylamino group, the carbon number is usually 12 or more and 28 or less. When the said substituent is an acyl group, the carbon number is 1 or more and 14 or less normally. When the said substituent is a haloalkyl group, the carbon number is 1 or more and 12 or less normally.

These substituents may be connected to each other to form a ring. As a specific example, a substituent of the ring Q1 and a substituent of the ring Q2 are bonded, or a substituent of the ring Q1 ′ and a substituent of the ring Q2 ′ are bonded. Two condensed rings may be formed. Examples of such a condensed ring include a 7,8-benzoquinoline group.
Among them, as a substituent for ring Q1, ring Q1 ′, ring Q2 and ring Q2 ′, more preferably an alkyl group, an alkoxy group, an aromatic hydrocarbon group, a cyano group, a halogen atom, a haloalkyl group, a diarylamino group, a carbazolyl group Is mentioned.

Further, the formula (4a), (4b), preferably as M ^a, M ^b, M ^c in (4c), ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold.

  Specific examples of the organometallic complex represented by the above formula (4), (4a), (4b) or (4c) are shown below, but are not limited to the following compounds. In the following, Ph represents a phenyl group.

  Furthermore, among the organometallic complexes represented by the above formulas (4), (4a), (4b), and (4c), in particular, as the ligand G and / or G ′, a 2-arylpyridine-based ligand, That is, a compound having 2-arylpyridine, a compound in which an arbitrary substituent is bonded thereto, and a compound in which an arbitrary group is condensed to this is preferable.

Next, the compound represented by formula (5) will be described.
In formula (5), M ⁵ represents a metal, and specific examples thereof include the metals described above as the metal selected from Groups 7 to 11 of the periodic table. Among these, ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold is preferable, and divalent metals such as platinum and palladium are particularly preferable.

In the formula (5), R ⁹² and R ⁹³ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, a carboxyl group, Represents an alkoxy group, an alkylamino group, an aralkylamino group, a haloalkyl group, a hydroxyl group, an aryloxy group, an aromatic hydrocarbon group or an aromatic heterocyclic group;

Further, when T is carbon, R ⁹⁴ and R ⁹⁵ each independently represent a substituent represented by the same examples as R ⁹² and R ⁹³ . Further, when T is nitrogen, there is no R ^{94 or} R ⁹⁵ .
R ^{92 to} R ⁹⁵ may further have a substituent. Furthermore, there is no restriction | limiting in the substituent which you may have and arbitrary groups can be used as a substituent.
Further, R ^{92 to} R ⁹⁵ may be connected to adjacent groups to form a ring.

  Specific examples (5-a to 5-g) of the organometallic complex represented by the formula (5) are shown below, but are not limited to the following examples. In the following, Me represents a methyl group, and Et represents an ethyl group.

  The molecular weight of the organometallic complex applied to the present invention is usually 10,000 or less, preferably 5000 or less, more preferably 4000 or less, still more preferably 3000 or less, and usually 100 or more, preferably 200 or more, more preferably 300 or more. More preferably, it is 400 or more. When the molecular weight is less than 100, the heat resistance is remarkably reduced, gas is generated, the film quality is deteriorated when the film is formed, or the morphology of the organic electroluminescent element is changed due to migration or the like. This is not preferable. If the molecular weight exceeds 10,000, it is not preferable because it is difficult to purify the organic compound or it takes time to dissolve the organic compound in a solvent.

[Composition for organic electroluminescence device]
The composition for an organic electroluminescence device of the present invention is a composition used for an organic layer of an organic electroluminescence device preferably formed by a wet film-forming method, and is one kind of the aforementioned organometallic complex of the present invention or It contains two or more, and usually further contains a solvent.

<Solvent>
It is preferable that the composition for organic electroluminescent elements of the present invention contains a solvent.
The solvent contained in the composition for organic electroluminescent elements of the present invention is not particularly limited as long as the solute such as the organometallic complex of the present invention dissolves well, and examples thereof include toluene, xylene, methicylene, Aromatic hydrocarbons such as cyclohexylbenzene and tetralin; halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene and trichlorobenzene; 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole, phenetole, 2-methoxytoluene, Aromatic ethers such as 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, 2,4-dimethylanisole; phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, benzoic acid Aromatic esters such as n-butyl; cyclohex Non-, cyclooctanone and other alicyclic ketones; methyl ethyl ketone and dibutyl ketone and other aliphatic ketones; methyl ethyl ketone, cyclohexanol and cyclooctanol and other alicyclic alcohols; butanol and hexanol and other aliphatic alcohols; ethylene glycol dimethyl ether Aliphatic ethers such as ethylene glycol diethyl ether and propylene glycol-1-monomethyl ether acetate (PGMEA); aliphatic esters such as ethyl acetate, n-butyl acetate, ethyl lactate and n-butyl lactate can be used. Of these, aromatic hydrocarbons such as toluene, xylene, methicylene, cyclohexylbenzene, tetralin and the like are preferable in that they have low water solubility and are not easily altered.

  Since organic electroluminescent devices use many materials such as cathodes that deteriorate significantly due to moisture, the presence of moisture in the composition causes moisture to remain in the dried film, degrading the device characteristics. The possibility is considered and it is not preferable.

  Examples of the method for reducing the amount of water in the composition include dehydration of the solvent in advance by distillation or use of a desiccant, nitrogen gas sealing, use of a solvent with low water solubility, and the like. In particular, it is preferable to use a solvent having low water solubility because the solution film can prevent whitening by absorbing moisture in the atmosphere during the wet film forming process. From such a viewpoint, the composition for organic electroluminescent elements to which the present embodiment is applied includes, for example, a solvent having a water solubility at 25 ° C. of 1% by weight or less, preferably 0.1% by weight or less. It is preferable to contain 10% by weight or more in the composition.

  Further, in order to reduce a decrease in film formation stability due to evaporation of the solvent from the composition during wet film formation, the solvent of the composition for organic electroluminescent elements has a boiling point of 100 ° C. or higher, preferably a boiling point of 150. It is effective to use a solvent having a boiling point of 200 ° C. or higher, more preferably 200 ° C. or higher. In order to obtain a more uniform film, it is necessary for the solvent to evaporate from the liquid film immediately after the film formation at an appropriate rate. For this purpose, the boiling point is usually 80 ° C. or higher, preferably the boiling point is 100 ° C. or higher. It is effective to use a solvent having a boiling point of 120 ° C. or more, usually less than 270 ° C., preferably less than 250 ° C., more preferably less than 230 ° C.

  A solvent that satisfies the above-mentioned conditions, ie, solute solubility, evaporation rate, and water solubility conditions, may be used alone. However, if a solvent that satisfies all the conditions cannot be selected, two or more solvents may be mixed. It can also be used.

<Light emitting material>
The composition for an organic electroluminescent device of the present invention is a composition preferably used for an organic layer of an organic electroluminescent device formed by a wet film forming method, and the above-described organometallic complex of the present invention is used as a luminescent material. In general, it is used as a composition for forming a light emitting layer.
A luminescent material refers to the component which mainly light-emits in the composition for organic electroluminescent elements of this invention, and corresponds to the dopant component in an organic EL device. Of the amount of light (unit: cd / m ² ) emitted from the composition for organic electroluminescent elements, it is usually 10 to 100%, preferably 20 to 100%, more preferably 50 to 100%, and most preferably 80 to 100%. If% is identified as luminescence from a component material, it is defined as the luminescent material.

  In the present invention, the wet film forming method refers to, for example, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, capillary coating method, ink jet method, screen printing. This method is a wet film formation method such as a method, a gravure printing method, or a flexographic printing method. Among these film forming methods, a spin coating method, a spray coating method, and an ink jet method are preferable because they are suitable for the liquid property specific to the composition for organic electroluminescence devices of the present invention used for organic electroluminescence devices.

<Charge transport material>
The composition for organic electroluminescent elements of the present invention preferably further contains a charge transport material, and this charge transport material functions as a host material for the organometallic complex of the present invention which is a light-emitting material. Preferably there is. Examples of the charge transport material include the following hole transport compounds and electron transport compounds.

(Hole transporting compound)
Among the hole transporting compounds, examples of the low molecular weight hole transporting compound include various compounds exemplified as the hole transporting compound in the hole injection layer 3 to be described later, for example, 4,4′- An aromatic diamine represented by bis [N- (1-naphthyl) -N-phenylamino] biphenyl containing two or more tertiary amines and having two or more condensed aromatic rings substituted with nitrogen atoms No. 5-234681, an aromatic amine compound having a starburst structure such as 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine (Journal of Luminescence, 1997, Vol. 72-74). , Pp. 985), an aromatic amine compound consisting of a tetramer of triphenylamine (Chemical Communications, 199). Pp. 2175), 2,2 ′, 7,7′-tetrakis- (diphenylamino) -9,9′-spirobifluorene (Synthetic Metals, 1997, Vol. 91, pp. 209). Only one type of hole transporting compound may be used, or two or more types of hole transporting compounds may be used in any combination and ratio.

(Electron transporting compound)
Among electron transporting compounds, examples of low molecular weight electron transporting compounds include 2,5-bis (1-naphthyl) -1,3,4-oxadiazole (BND) and 2,5-bis ( 6 ′-(2 ′, 2 ″ -bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy), bathophenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl- 1,10-phenanthroline (BCP, bathocuproine), 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 4,4 ′ -Bis (9-carbazole) -biphenyl (CBP) etc. Only 1 type may be used for an electron transport compound, and 2 or more types may be used together by arbitrary combinations and a ratio.

<Other ingredients>
In the composition for organic electroluminescent elements of the present invention, various other solvents may be contained as necessary in addition to the above-mentioned solvent, the organometallic complex as the light emitting material, and the charge transport material. Examples of such other solvents include amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and dimethyl sulfoxide.
Moreover, various additives, such as a leveling agent and an antifoamer, may be included.

  In addition, when two or more layers are laminated by a wet film formation method, in order to prevent these layers from being compatible with each other, a photocurable resin or a thermosetting resin is used for the purpose of curing and insolubilizing after film formation. Can also be contained.

<Material concentration and compounding ratio in the composition for organic electroluminescent elements>
The solid content concentration of the organometallic complex of the present invention, which is a luminescent material in the composition for organic electroluminescent elements of the present invention, a charge transport material, and components (leveling agents, etc.) that can be added as necessary is usually 0. 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, further preferably 0.5% by weight or more, most preferably 1% by weight or more, and usually 80% by weight or less. It is preferably 50% by weight or less, more preferably 40% by weight or less, further preferably 30% by weight or less, and most preferably 20% by weight or less. When this concentration is below the lower limit, it is difficult to form a thick film when forming a thin film, and when it exceeds the upper limit, it is difficult to form a thin film.

  In the composition for organic electroluminescent elements of the present invention, the weight mixing ratio of the light emitting material / charge transporting material is usually 0.1 / 99.9 or more, more preferably 0.5 / 99.5 or more. More preferably, it is 1/99 or more, most preferably 2/98 or more, usually 50/50 or less, more preferably 40/60 or less, and further preferably 30/70 or less. Most preferably, it is 20/80 or less. If this ratio falls below the lower limit or exceeds the upper limit, the luminous efficiency may be significantly reduced.

<Method for Preparing Composition for Organic Electroluminescent Device>
The composition for an organic electroluminescent device of the present invention is generally suitable for a solute comprising the organometallic complex of the present invention, a charge transport material, and various additives such as a leveling agent and an antifoaming agent that can be added as necessary. It is prepared by dissolving in an appropriate solvent. In order to shorten the time required for the dissolution step and to keep the solute concentration in the composition uniform, the solute is usually dissolved while stirring the liquid. The dissolution step may be performed at room temperature, but when the dissolution rate is slow, it can be heated and dissolved. After completion of the dissolution step, a filtration step such as filtering may be performed as necessary.

[Organic electroluminescence device]
The organic electroluminescent element of the present invention is characterized by having an anode and a light emitting layer between the anode and the cathode on the substrate, and a layer containing the organometallic complex of the present invention. The layer containing the organometallic complex of the present invention may be any of the following hole injection layer, hole transport layer, light emitting layer, hole blocking layer, electron transport layer, etc., but the organometallic complex of the present invention. The layer containing is preferably a light emitting layer.

  Below, the layer structure of the organic electroluminescent element of this invention, its general formation method, etc. are demonstrated with reference to FIG.

  FIG. 1 is a schematic cross-sectional view showing a structural example of an organic electroluminescent element 10 of the present invention. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 Represents a light-emitting layer, 6 represents a hole blocking layer, 7 represents an electron transport layer, 8 represents an electron injection layer, and 9 represents a cathode.

  In the present invention, the wet film forming method is, for example, a spin coating method, a dip coating method, a die coating method, a bar coating method, a blade coating method, a roll coating method, a spray coating method, a capillary coating method, and an inkjet as described above. This method is a wet film formation method such as a printing method, a screen printing method, a gravure printing method, or a flexographic printing method. Among these film forming methods, a spin coating method, a spray coating method, and an ink jet method are preferable because they are suitable for the liquid property specific to the composition for organic electroluminescence devices of the present invention used for organic electroluminescence devices.

{substrate}
The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film, a sheet, or the like is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, polysulfone or the like is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too small, the organic electroluminescent element may be deteriorated by the outside air that has passed through the substrate, which is not preferable. For this reason, a method of providing a gas barrier property by providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate is also a preferable method.

{anode}
The anode 2 serves to inject holes into the layer on the light emitting layer side.

  This anode 2 is usually a metal such as aluminum, gold, silver, nickel, palladium, platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide, carbon black, or It is composed of a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline.

  In general, the anode 2 is often formed by a sputtering method, a vacuum deposition method, or the like. In addition, when forming the anode 2 using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, an appropriate binder resin solution It is also possible to form the anode 2 by dispersing it and applying it onto the substrate 1. Furthermore, in the case of a conductive polymer, a thin film can be directly formed on the substrate 1 by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett. 60, 2711, 1992).

  The anode 2 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.

  The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode 2 is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 is arbitrary, and the anode 2 may be the same as the substrate 1. Furthermore, it is also possible to laminate different conductive materials on the anode 2 described above.

  For the purpose of removing impurities adhering to the anode 2 and adjusting the ionization potential to improve the hole injection property, the surface of the anode 2 is treated with ultraviolet (UV) / ozone, or with oxygen plasma or argon plasma. It is preferable to do.

{Hole injection layer}
The hole injection layer 3 is a layer that transports holes from the anode 2 to the light emitting layer 5, and is usually formed on the anode 2.

  The method for forming the hole injection layer 3 according to the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but the hole injection layer 3 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.

  The thickness of the hole injection layer 3 is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably 500 nm or less.

<Formation of hole injection layer by wet film formation method>
When forming the hole injection layer 3 by wet film formation, the material for forming the hole injection layer 3 is usually mixed with an appropriate solvent (hole injection layer solvent) to form a film-forming composition (positive A composition for forming a hole injection layer), and applying the composition for forming a hole injection layer on a layer (usually an anode) corresponding to the lower layer of the hole injection layer 3 by an appropriate technique. The hole injection layer 3 is formed by coating and drying.

(Hole transporting compound)
The composition for forming a hole injection layer usually contains a hole transporting compound and a solvent as constituent materials of the hole injection layer.

  The hole transporting compound is a compound having a hole transporting property that is usually used in a hole injection layer of an organic electroluminescence device, and may be a polymer compound or the like, a monomer or the like. Although it may be a low molecular weight compound, it is preferably a high molecular weight compound.

  The hole transporting compound is preferably a compound having an ionization potential of 4.5 eV to 6.0 eV from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3. Examples of hole transporting compounds include aromatic amine derivatives, phthalocyanine derivatives, porphyrin derivatives, oligothiophene derivatives, polythiophene derivatives, benzylphenyl derivatives, compounds in which tertiary amines are linked by a fluorene group, hydrazone derivatives, silazane derivatives, silanamines Derivatives, phosphamine derivatives, quinacridone derivatives, polyaniline derivatives, polypyrrole derivatives, polyphenylene vinylene derivatives, polythienylene vinylene derivatives, polyquinoline derivatives, polyquinoxaline derivatives, carbon and the like.

  In the present invention, a derivative includes, for example, an aromatic amine derivative, and includes an aromatic amine itself and a compound having an aromatic amine as a main skeleton. It may be a mer.

  The hole transporting compound used as the material for the hole injection layer 3 may contain any one of these compounds alone, or may contain two or more. When two or more hole transporting compounds are contained, the combination thereof is arbitrary, but one or more aromatic tertiary amine polymer compounds and one or two other hole transporting compounds are used. It is preferable to use the above in combination.

  Among the above examples, an aromatic amine compound is preferable from the viewpoint of amorphousness and visible light transmittance, and an aromatic tertiary amine compound is particularly preferable. Here, the aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.

  The type of the aromatic tertiary amine compound is not particularly limited, but from the viewpoint of uniform light emission due to the surface smoothing effect, a polymer compound having a weight average molecular weight of 1,000 or more and 1,000,000 or less (a polymerizable compound in which repeating units are linked) is further included. preferable. Preferable examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (I).

（上記各式中、Ａｒ^６〜Ａｒ^１６は、それぞれ独立して、置換基を有していてもよい芳香族炭化水素基または置換基を有していてもよい芳香族複素環基を表す。Ｒ^１およびＲ^２は、それぞれ独立して、水素原子または任意の置換基を表す。）） (In Formula (I), Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Ar ^{3 to} Ar ⁵ each independently represents an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent. Represents a linking group selected from the group of linking groups, and among Ar ^{1 to} Ar ⁵ , two groups bonded to the same N atom may be bonded to each other to form a ring.

(In said each formula, Ar < ⁶ > -Ar < ¹⁶ > represents each independently the aromatic hydrocarbon group which may have a substituent, or the aromatic heterocyclic group which may have a substituent. R ¹ and R ² each independently represents a hydrogen atom or an arbitrary substituent.))

As the aromatic hydrocarbon group and the aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ , a benzene ring, a naphthalene ring, a phenanthrene ring, a thiophene from the viewpoint of the solubility, heat resistance, hole injection / transport property of the polymer compound A group derived from a ring or a pyridine ring is preferred, and a group derived from a benzene ring or a naphthalene ring is more preferred.

The aromatic hydrocarbon group and aromatic heterocyclic group of Ar ^{1 to} Ar ¹⁶ may further have a substituent. The molecular weight of the substituent is usually 400 or less, preferably about 250 or less. As the substituent, an alkyl group, an alkenyl group, an alkoxy group, an aromatic hydrocarbon group, an aromatic heterocyclic group and the like are preferable.

When R ¹ and R ² are optional substituents, examples of the substituent include an alkyl group, an alkenyl group, an alkoxy group, a silyl group, a siloxy group, an aromatic hydrocarbon group, and an aromatic heterocyclic group. .

  Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the formula (I) include those described in International Publication No. 2005/089024.

  In addition, as a hole transporting compound, a conductive polymer (PEDOT / PSS) obtained by polymerizing 3,4-ethylenedioxythiophene (3,4-ethylenedioxythiophene), a polythiophene derivative, in a high molecular weight polystyrene sulfonic acid. Is also preferred. Moreover, the end of this polymer may be capped with methacrylate or the like.

  The concentration of the hole transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.01% by weight or more, preferably in terms of film thickness uniformity. Is 0.1% by weight or more, more preferably 0.5% by weight or more, and usually 70% by weight or less, preferably 60% by weight or less, more preferably 50% by weight or less. If this concentration is too high, film thickness unevenness may occur, and if it is too low, defects may occur in the formed hole injection layer.

(Electron-accepting compound)
The composition for forming a hole injection layer preferably contains an electron accepting compound as a constituent material of the hole injection layer.

  The electron-accepting compound is preferably a compound having an oxidizing power and the ability to accept one electron from the above-described hole transporting compound, specifically, a compound having an electron affinity of 4 eV or more is preferable, and 5 eV or more. The compound which is the compound of these is further more preferable.

  Examples of such electron-accepting compounds include triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Examples thereof include one or more compounds selected from the group. More specifically, an onium salt substituted with an organic group such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate, triphenylsulfonium tetrafluoroborate (International Publication No. WO 2005/089024); High-valent inorganic compounds such as iron (III) chloride (Japanese Patent Laid-Open No. 11-251067), ammonium peroxodisulfate; cyano compounds such as tetracyanoethylene, tris (pendafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365) Aromatic boron compounds such as); fullerene derivatives; iodine; sulfonate ions such as polystyrene sulfonate ions, alkylbenzene sulfonate ions, camphor sulfonate ions, and the like.

  These electron accepting compounds can improve the conductivity of the hole injection layer by oxidizing the hole transporting compound.

  The content of the electron-accepting compound in the hole-injecting layer or the composition for forming a hole-injecting layer with respect to the hole-transporting compound is usually 0.1 mol% or more, preferably 1 mol% or more. However, it is usually 100 mol% or less, preferably 40 mol% or less.

(Other components)
As a material for the hole injection layer, other components may be further contained in addition to the above-described hole transporting compound and electron accepting compound as long as the effects of the present invention are not significantly impaired. Examples of other components include various light emitting materials, electron transporting compounds, binder resins, and coating property improving agents. In addition, only 1 type may be used for another component and it may use 2 or more types together by arbitrary combinations and a ratio.

(solvent)
At least one of the solvents of the composition for forming a hole injection layer used in the wet film formation method is preferably a compound that can dissolve the constituent material of the hole injection layer. The boiling point of this solvent is usually 110 ° C. or higher, preferably 140 ° C. or higher, particularly 200 ° C. or higher, usually 400 ° C. or lower, and preferably 300 ° C. or lower. If the boiling point of the solvent is too low, the drying speed is too high and the film quality may be deteriorated. Further, if the boiling point of the solvent is too high, it is necessary to increase the temperature of the drying step, which may adversely affect other layers and the substrate.

  Examples of the solvent include ether solvents, ester solvents, aromatic hydrocarbon solvents, amide solvents, and the like.

  Examples of ether solvents include aliphatic ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and propylene glycol-1-monomethyl ether acetate (PGMEA); 1,2-dimethoxybenzene, 1,3-dimethoxybenzene, anisole , Phenetole, 2-methoxytoluene, 3-methoxytoluene, 4-methoxytoluene, 2,3-dimethylanisole, aromatic ethers such as 2,4-dimethylanisole, and the like.

  Examples of the ester solvent include aromatic esters such as phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, propyl benzoate, and n-butyl benzoate.

  As the aromatic hydrocarbon solvent, for example, toluene, xylene, cyclohexylbenzene, 3-isopropylpropylphenyl, 1,2,3,4-tetramethylbenzene, 1,4-diisopropylbenzene, cyclohexylbenzene, methylnaphthalene, etc. Can be mentioned.

  Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide, and the like.

  In addition, dimethyl sulfoxide and the like can also be used.

  These solvent may use only 1 type and may use 2 or more types by arbitrary combinations and a ratio.

(Film formation method)
After preparing the composition for forming the hole injection layer, the composition is applied on the layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by wet film formation, and dried. The hole injection layer 3 is formed.

  The temperature in the film forming step is preferably 10 ° C. or higher, and preferably 50 ° C. or lower, in order to prevent film loss due to the formation of crystals in the composition.

  Although the relative humidity in a film-forming process is not limited unless the effect of this invention is impaired remarkably, it is 0.01 ppm or more normally and 80% or less normally.

  After the film formation, the film of the composition for forming a hole injection layer is usually dried by heating or the like. Examples of the heating means used in the heating step include a clean oven, a hot plate, infrared rays, a halogen heater, microwave irradiation and the like. Among them, a clean oven and a hot plate are preferable in order to uniformly apply heat to the entire film.

  The heating temperature in the heating step is preferably heated at a temperature equal to or higher than the boiling point of the solvent used in the composition for forming a hole injection layer as long as the effects of the present invention are not significantly impaired. In the case of a mixed solvent containing two or more types of solvents used in the hole injection layer, at least one type is preferably heated at a temperature equal to or higher than the boiling point of the solvent. In consideration of an increase in the boiling point of the solvent, the heating step is preferably performed at 120 ° C. or higher, preferably 410 ° C. or lower.

  In the heating step, the heating time is not limited as long as the heating temperature is not lower than the boiling point of the solvent of the composition for forming a hole injection layer and sufficient insolubilization of the coating film does not occur. Is less than a minute. If the heating time is too long, the components of the other layers tend to diffuse, and if it is too short, the hole injection layer tends to be inhomogeneous. Heating may be performed in two steps.

<Formation of hole injection layer by vacuum deposition>
When the hole injection layer 3 is formed by vacuum deposition, one or more of the constituent materials of the hole injection layer 3 (the aforementioned hole transporting compound, electron accepting compound, etc.) are placed in a vacuum container. Put in crucibles installed (in case of using two or more materials, put them in each crucible), evacuate the inside of the vacuum vessel to about 10 ⁻⁴ Pa with a suitable vacuum pump, and then heat the crucible (two types When using the above materials, heat each crucible) and evaporate by controlling the amount of evaporation (when using two or more materials, evaporate by independently controlling the amount of evaporation) and face the crucible Then, the hole injection layer 3 is formed on the anode 2 of the substrate placed on the substrate. In addition, when using 2 or more types of materials, the hole injection layer 3 can also be formed by putting those mixtures into a crucible, heating and evaporating.

The degree of vacuum at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) or more, usually 9.0 × 10 ⁻⁶ Torr. (12.0 × 10 ⁻⁴ Pa) or less. The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 Å / second or more and usually 5.0 Å / second or less. The film forming temperature at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is preferably 10 ° C. or higher, preferably 50 ° C. or lower.

{Hole transport layer}
The hole transport layer 4 can be formed on the hole injection layer 3 when there is a hole injection layer and on the anode 2 when there is no hole injection layer 3. The organic electroluminescent device of the present invention may have a configuration in which the hole transport layer is omitted.

  The method for forming the hole transport layer 4 according to the present invention may be a vacuum deposition method or a wet film formation method, and is not particularly limited, but the hole transport layer 4 is formed by a wet film formation method from the viewpoint of reducing dark spots. It is preferable.

  The material for forming the hole transport layer 4 is preferably a material having high hole transportability and capable of efficiently transporting injected holes. Therefore, it is preferable that the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is high, and impurities that become traps are not easily generated during manufacturing or use. In many cases, it is preferable not to quench the light emitted from the light emitting layer 5 or to form an exciplex with the light emitting layer 5 to reduce the efficiency because it is in contact with the light emitting layer 5.

  The material for the hole transport layer 4 may be any material conventionally used as a constituent material for the hole transport layer. For example, the hole transport property used for the hole injection layer 3 described above. What was illustrated as a compound is mentioned. In addition, arylamine derivatives, fluorene derivatives, spiro derivatives, carbazole derivatives, pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, phthalocyanine derivatives, porphyrin derivatives, silole derivatives, oligothiophene derivatives, condensed polycyclic aromatics Group derivatives, metal complexes and the like.

Also, for example, polyvinylcarbazole derivatives, polyarylamine derivatives, polyvinyltriphenylamine derivatives, polyfluorene derivatives, polyarylene derivatives, polyarylene ether sulfone derivatives containing tetraphenylbenzidine, polyarylene vinylene derivatives, polysiloxane derivatives, polythiophenes Derivatives, poly (p-phenylene vinylene) derivatives, and the like. These may be any of an alternating copolymer, a random polymer, a block polymer, or a graft copolymer. Further, it may be a polymer having a branched main chain and three or more terminal portions, or a so-called dendrimer.
Of these, polyarylamine derivatives and polyarylene derivatives are preferred.

The polyarylamine derivative is preferably a polymer containing a repeating unit represented by the following formula (II). In particular, a polymer composed of a repeating unit represented by the following formula (II) is preferable. In this case, Ar ^a or Ar ^b may be different in each repeating unit.

(In formula (II), Ar ^a and Ar ^b each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.)

  Examples of the aromatic hydrocarbon group which may have a substituent include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a perylene ring, a tetracene ring, a pyrene ring, a benzpyrene ring, a chrysene ring, a triphenylene ring, and an acenaphthene. Examples thereof include a group derived from a 6-membered monocyclic ring or a 2-5 condensed ring, such as a ring, a fluoranthene ring, and a fluorene ring, and a group in which two or more of these rings are linked by a direct bond.

  Examples of the aromatic heterocyclic group which may have a substituent include a furan ring, a benzofuran ring, a thiophene ring, a benzothiophene ring, a pyrrole ring, a pyrazole ring, an imidazole ring, an oxadiazole ring, an indole ring, and a carbazole ring. , Pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine Ring, pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, phenanthridine ring, benzimidazole ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc. Or a group and the rings of from 2-4 fused rings include groups formed by connecting a direct bond or two or more rings.

In view of solubility and heat resistance, Ar ^a and Ar ^b are each independently selected from the group consisting of a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, triphenylene ring, pyrene ring, thiophene ring, pyridine ring, and fluorene ring. A group derived from a selected ring or a group formed by linking two or more benzene rings (for example, a biphenyl group or a terphenyl group) is preferable.
Among these, a group derived from a benzene ring (phenyl group), a group formed by connecting two benzene rings (biphenyl group), and a group derived from a fluorene ring (fluorenyl group) are preferable.

Examples of the substituent that the aromatic hydrocarbon group and aromatic heterocyclic group in Ar ^a and Ar ^b may have include an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, and a dialkyl. Examples thereof include an amino group, a diarylamino group, an acyl group, a halogen atom, a haloalkyl group, an alkylthio group, an arylthio group, a silyl group, a siloxy group, a cyano group, an aromatic hydrocarbon ring group, and an aromatic heterocyclic group.

As the polyarylene derivative, an arylene group such as an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent exemplified as Ar ^a or Ar ^b in the formula (II) is used as its repeating unit. The polymer which has is mentioned.
As the polyarylene derivative, a polymer having a repeating unit composed of the following formula (III-1) and / or the following formula (III-2) is preferable.

(In formula (III-1), R ^a , R ^b , R ^c and R ^d are each independently an alkyl group, an alkoxy group, a phenylalkyl group, a phenylalkoxy group, a phenyl group, a phenoxy group, an alkylphenyl group, Represents an alkoxyphenyl group, an alkylcarbonyl group, an alkoxycarbonyl group, or a carboxy group, and t and s each independently represent an integer of 0 to 3. When t or s is 2 or more, they are contained in one molecule. A plurality of R ^a or R ^b may be the same or different, and adjacent R ^a or R ^b may form a ring.)

(In formula (III-2), R ^e and R ^f are each independently synonymous with R ^a , R ^b , R ^c or R ^d in formula (III-1). Independently, it represents an integer of 0 to 3. When r or u is 2 or more, a plurality of R ^e and R ^f contained in one molecule may be the same or different, and adjacent R ^e or R ^f may form a ring, and X represents an atom or a group of atoms constituting a 5-membered ring or a 6-membered ring.)

  Specific examples of X include an oxygen atom, a boron atom which may have a substituent, a nitrogen atom which may have a substituent, a silicon atom which may have a substituent, and a substituent. A phosphorus atom which may be substituted, a sulfur atom which may have a substituent, a carbon atom which may have a substituent, or a group formed by bonding these.

  Further, the polyarylene derivative has a repeating unit represented by the following formula (III-3) in addition to the repeating unit represented by the following formula (III-1) and / or the following formula (III-2). Is preferred.

(In formula (III-3), Ar ^{c to} Ar ^j each independently represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent. Independently represents 0 or 1.)

Specific examples of Ar ^{c to} Ar ^j are the same as Ar ^a and Ar ^b in the formula (II).

  Specific examples of the above formulas (III-1) to (III-3) and specific examples of polyarylene derivatives include those described in JP-A-2008-98619.

  In the case of forming the hole transport layer 4 by a wet film formation method, a composition for forming a hole transport layer is prepared in the same manner as the formation of the hole injection layer 3 and then heated and dried after the wet film formation. .

  The composition for forming a hole transport layer contains a solvent in addition to the above hole transport compound. The solvent used is the same as that used for the composition for forming a hole injection layer. The film forming conditions, heat drying conditions, and the like are the same as in the case of forming the hole injection layer 3.

  In the case where the hole transport layer is formed by the vacuum deposition method, the film forming conditions are the same as those in the case of forming the hole injection layer 3.

  The hole transport layer 4 may contain various light emitting materials, electron transport compounds, binder resins, coating property improving agents, and the like in addition to the hole transport compound.

  The hole transport layer 4 may also be a layer formed by crosslinking a crosslinkable compound. The crosslinkable compound is a compound having a crosslinkable group, and forms a network polymer compound by crosslinking.

  Examples of this crosslinkable group include groups derived from cyclic ethers such as oxetane and epoxy; groups derived from unsaturated double bonds such as vinyl, trifluorovinyl, styryl, acrylic, methacryloyl and cinnamoyl; benzo Examples include groups derived from cyclobutene.

  The crosslinkable compound may be any of a monomer, an oligomer, and a polymer. The crosslinkable compound may have only 1 type, and may have 2 or more types by arbitrary combinations and ratios.

  As the crosslinkable compound, a hole transporting compound having a crosslinkable group is preferably used. Examples of the hole transporting compound include those exemplified above, and those having a crosslinkable group bonded to the main chain or side chain with respect to these hole transporting compounds. In particular, the crosslinkable group is preferably bonded to the main chain via a linking group such as an alkylene group. In particular, the hole transporting compound is preferably a polymer containing a repeating unit having a crosslinkable group, and the above formula (II) and formulas (III-1) to (III-3) can be used as a crosslinkable group. Is preferably a polymer having a repeating unit bonded directly or via a linking group.

  As the crosslinkable compound, a hole transporting compound having a crosslinkable group is preferably used. Examples of hole transporting compounds include nitrogen-containing aromatic compound derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives, phthalocyanine derivatives, porphyrin derivatives; triphenylamine derivatives Silole derivatives; oligothiophene derivatives, condensed polycyclic aromatic derivatives, metal complexes and the like. Among them, nitrogen-containing aromatic derivatives such as pyridine derivatives, pyrazine derivatives, pyrimidine derivatives, triazine derivatives, quinoline derivatives, phenanthroline derivatives, carbazole derivatives; triphenylamine derivatives, silole derivatives, condensed polycyclic aromatic derivatives, metal complexes, etc. Particularly preferred are triphenylamine derivatives.

  In order to form the hole transport layer 4 by crosslinking the crosslinkable compound, a composition for forming a hole transport layer in which the crosslinkable compound is dissolved or dispersed in a solvent is usually prepared and deposited by wet film formation. To crosslink.

The composition for forming a hole transport layer may contain an additive for promoting a crosslinking reaction in addition to the crosslinking compound. Examples of additives that accelerate the crosslinking reaction include polymerization initiators and polymerization accelerators such as alkylphenone compounds, acylphosphine oxide compounds, metallocene compounds, oxime ester compounds, azo compounds, onium salts; condensed polycyclic hydrocarbons, And photosensitizers such as porphyrin compounds and diaryl ketone compounds.
Further, it may contain a coating property improving agent such as a leveling agent and an antifoaming agent; an electron accepting compound; a binder resin;

  In the composition for forming a hole transport layer, the crosslinkable compound is usually 0.01% by weight or more, preferably 0.05% by weight or more, more preferably 0.1% by weight or more, usually 50% by weight or less, preferably 20%. It is contained in an amount of not more than wt%, more preferably not more than 10 wt%.

  After forming a composition for forming a hole transport layer containing a crosslinkable compound at such a concentration on the lower layer (usually the hole injection layer 3), the composition is crosslinked by heating and / or irradiation with electromagnetic energy such as light. Are crosslinked to form a network polymer compound.

Conditions such as temperature and humidity during film formation are the same as those during the wet film formation of the hole injection layer 3.
The heating method after film formation is not particularly limited. As heating temperature conditions, it is 120 degreeC or more normally, Preferably it is 400 degrees C or less.
The heating time is usually 1 minute or longer, preferably 24 hours or shorter. The heating means is not particularly limited, and means such as placing a laminated body having a deposited layer on a hot plate or heating in an oven is used. For example, conditions such as heating on a hot plate at 120 ° C. or more for 1 minute or more can be used.

  In the case of irradiation with electromagnetic energy such as light, a method of irradiating directly using an ultraviolet / visible / infrared light source such as an ultra-high pressure mercury lamp, a high-pressure mercury lamp, a halogen lamp, an infrared lamp, etc. Examples include a mask aligner and a method of irradiation using a conveyor type light irradiation device. In electromagnetic energy irradiation other than light, for example, there is a method of irradiation using a device that irradiates a microwave generated by a magnetron, a so-called microwave oven. As the irradiation time, it is preferable to set conditions necessary for reducing the solubility of the film, but irradiation is usually performed for 0.1 seconds or longer, preferably 10 hours or shorter.

  Heating and irradiation of electromagnetic energy such as light may be performed individually or in combination. When combined, the order of implementation is not particularly limited.

  The film thickness of the hole transport layer 4 thus formed is usually 5 nm or more, preferably 10 nm or more, and usually 300 nm or less, preferably 100 nm or less.

{Light emitting layer}
When the hole injection layer 3 or the hole transport layer 4 is provided, the light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 is a layer that is excited by recombination of holes injected from the anode 2 and electrons injected from the cathode 9 between electrodes to which an electric field is applied, and becomes a main light emitting source.

<Light emitting layer material>
The light emitting layer 5 contains at least a material having a light emitting property (light emitting material) as a constituent material, and preferably a compound having a hole transporting property (hole transporting compound) or an electron transport. A charge transporting material such as a compound having the following properties (electron transporting compound). A light-emitting material may be used as a dopant material, and a charge transport material such as a hole transport compound or an electron transport compound may be used as a host material. As the light emitting material, those exemplified in the description of the organometallic complex of the present invention can be used. Moreover, as a charge transport material, what was described as what may be contained in the composition for organic electroluminescent elements of the above-mentioned this invention can be used.

  In particular, in the organic electroluminescent element of the present invention, the light emitting layer is preferably formed by a wet film forming method using the composition for organic electroluminescent element of the present invention.

  Furthermore, the light emitting layer 5 may contain other components as long as the effects of the present invention are not significantly impaired. In addition, when forming the light emitting layer 5 with a wet film-forming method, it is preferable to use a low molecular weight material (molecular weight is usually 10,000 or less, preferably 5000 or less).

<Formation of light emitting layer>
When forming the light emitting layer 5 by the wet film-forming method, the material used for a light emitting layer is dissolved in a suitable solvent, and the composition for light emitting layer formation (for example, composition for organic electroluminescent elements of this invention) is prepared. The film is formed by using this film.

  As the solvent for the light emitting layer to be contained in the composition for forming the light emitting layer for forming the light emitting layer 5 by the wet film forming method according to the present invention, The same as described.

  The solid content concentration of the light emitting material, charge transporting compound, etc. in the composition for forming a light emitting layer is usually 0.01% by weight or more and usually 70% by weight or less. If this concentration is too large, film thickness unevenness may occur, and if it is too small, defects may occur in the film.

  After wet-deposition of the composition for forming a light emitting layer, the resulting coating film is dried and the solvent is removed to form a light emitting layer. Specifically, it is the same as the method described in the formation of the hole injection layer. The method of the wet film forming method is not limited as long as the effect of the present invention is not significantly impaired, and any of the methods described above can be used.

  The thickness of the light emitting layer 5 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less. If the thickness of the light emitting layer 5 is too thin, defects may occur in the film, and if it is too thick, the driving voltage may increase.

{Hole blocking layer}
A hole blocking layer 6 may be provided between the light emitting layer 5 and an electron injection layer 8 described later. The hole blocking layer 6 is a layer laminated on the light emitting layer 5 so as to be in contact with the interface of the light emitting layer 5 on the cathode 9 side.

  The hole blocking layer 6 has a role of blocking holes moving from the anode 2 from reaching the cathode 9 and a role of efficiently transporting electrons injected from the cathode 9 toward the light emitting layer 5. Have

  The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility, low hole mobility, a large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). Is high. Examples of the material for the hole blocking layer that satisfies such conditions include bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum, and the like. Mixed-ligand complexes, metal complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum binuclear metal complexes, distyrylbiphenyl derivatives, etc. Triazole derivatives such as styryl compounds (JP-A-11-242996), 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole (JP-A-7 -41759), phenanthroline derivatives such as bathocuproine (JP-A-10-79297), and the like. That. Further, a compound having at least one pyridine ring substituted at positions 2, 4, and 6 described in International Publication No. 2005-022962 is also preferable as a material for the hole blocking layer 6.

  In addition, the material of the hole-blocking layer 6 may use only 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  There is no restriction | limiting in the formation method of the hole-blocking layer 6. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.

  The thickness of the hole blocking layer 6 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less.

  A hole relaxation layer may be provided in place of the hole blocking layer.

{Electron transport layer}
An electron transport layer 7 may be provided between the light emitting layer 5 and an electron injection layer 8 described later.

  The electron transport layer 7 is provided for the purpose of further improving the light emission efficiency of the device, and efficiently transports electrons injected from the cathode 9 between the electrodes to which an electric field is applied in the direction of the light emitting layer 5. Formed from a compound capable of

  As an electron transport compound used for the electron transport layer 7, usually, the electron injection efficiency from the cathode 9 or the electron injection layer 8 is high, and the injected electrons are transported efficiently with high electron mobility. The compound which can be used is used. Examples of the compound satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives , Distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compounds ( JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide , N-type zinc sulfide, n-type zinc Such as emissions of zinc, and the like.

  In addition, the material of the electron carrying layer 7 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  There is no restriction | limiting in the formation method of the electron carrying layer 7. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.

  The thickness of the electron transport layer 7 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 nm or more, preferably 5 nm or more, and usually 300 nm or less, preferably 100 nm or less.

{Electron injection layer}
The electron injection layer 8 plays a role of efficiently injecting electrons injected from the cathode 9 into the light emitting layer 5. In order to perform electron injection efficiently, the material for forming the electron injection layer 8 is preferably a metal having a low work function. Examples include alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium. Examples include lithium fluoride (LiF), magnesium fluoride (MgF ₂ ), lithium oxide (Li ₂ O), cesium carbonate (II) (CsCO ₃ ), and the like (Applied Physics Letters, 1997, Vol. 70, pp. 152; Japanese Patent Laid-Open No. 10-74586; see I Organic EL Display and Organic EL Lighting Transactions on Electron Devices, 1997, Vol. 44, pp. 1245; SID 04 Digest, pp. 154, etc.). The film thickness is usually preferably from 0.1 nm to 5 nm.

  Furthermore, an organic electron transport compound represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, or rubidium ( (As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.), it is possible to improve the electron injection / transport properties and achieve excellent film quality. preferable. In this case, the film thickness is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.

  In addition, the material of the electron injection layer 8 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  There is no restriction | limiting in the formation method of the electron injection layer 8. FIG. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.

{cathode}
The cathode 9 plays a role of injecting electrons into a layer (such as the electron injection layer 8 or the light emitting layer 5) on the light emitting layer 5 side.

  As the material of the cathode 9, the material used for the anode 2 can be used. However, in order to perform electron injection efficiently, a metal having a low work function is preferable. For example, tin, magnesium, indium, A suitable metal such as calcium, aluminum, silver, or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.

  In addition, the material of the cathode 9 may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The film thickness of the cathode 9 is usually the same as that of the anode 2.

  Further, for the purpose of protecting the cathode 9 made of a low work function metal, it is preferable to further stack a metal layer having a high work function and stable to the atmosphere because the stability of the device is increased. For this purpose, for example, metals such as aluminum, silver, copper, nickel, chromium, gold and platinum are used. In addition, these materials may be used only by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

{Other layers}
The organic electroluminescent element of the present invention may have another configuration without departing from the gist thereof. For example, as long as the performance is not impaired, an arbitrary layer may be provided between the anode 2 and the cathode 9 in addition to the layers described above, and an arbitrary layer may be omitted. .

Examples of the layer that may be included include an electron blocking layer.
The electron blocking layer is provided between the hole injection layer 3 or the hole transport layer 4 and the light emitting layer 5 and prevents electrons moving from the light emitting layer 5 from reaching the hole injection layer 3. Thus, the probability of recombination of holes and electrons in the light emitting layer 5 is increased, the excitons generated are confined in the light emitting layer 5, and the holes injected from the hole injection layer 3 are efficiently collected. There is a role to transport in the direction of. In particular, when a phosphorescent material or a blue light emitting material is used as the light emitting material, it is effective to provide an electron blocking layer.

  The characteristics required for the electron blocking layer include high hole transportability, a large energy gap (difference between HOMO and LUMO), and a high excited triplet level (T1). Furthermore, in the present invention, when the light emitting layer 5 is formed as an organic layer according to the present invention by a wet film formation method, the electron blocking layer is also required to be compatible with the wet film formation. Examples of the material used for such an electron blocking layer include a copolymer of dioctylfluorene and triphenylamine typified by F8-TFB (International Publication No. 2004/084260).

  In addition, the material of an electron blocking layer may use only 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  There is no restriction | limiting in the formation method of an electron blocking layer. Therefore, it can be formed by a wet film forming method, a vapor deposition method, or other methods.

  Moreover, a hole relaxation layer can be formed instead of the hole blocking layer 6.

  Moreover, in the layer structure demonstrated above, it is also possible to laminate | stack components other than a board | substrate in reverse order. For example, in the case of the layer configuration of FIG. 1, the other components on the substrate 1 are the cathode 9, the electron injection layer 8, the electron transport layer 7, the hole blocking layer 6, the light emitting layer 5, the hole transport layer 4, the positive layer. The hole injection layer 3 and the anode 2 may be provided in this order.

  Furthermore, it is also possible to constitute the organic electroluminescent element according to the present invention by laminating components other than the substrate between two substrates, at least one of which is transparent.

Further, a structure in which a plurality of components (light emitting units) other than the substrate are stacked in a plurality of layers (a structure in which a plurality of light emitting units are stacked) may be employed. In that case, (when the anode is ITO, the cathode is Al, these two layers) interfacial layer between the respective stages (between emission units) Alternatively, for example, a charge consisting of five vanadium oxide (V 2 _{O 5),} etc. When a generation layer (Carrier Generation Layer: CGL) is provided, a barrier between steps is reduced, which is more preferable from the viewpoint of light emission efficiency and driving voltage.

  Furthermore, the organic electroluminescent device according to the present invention may be configured as a single organic electroluminescent device, or may be applied to a configuration in which a plurality of organic electroluminescent devices are arranged in an array. You may apply to the structure by which the cathode is arrange | positioned at XY matrix form.

  Each layer described above may contain components other than those described as materials unless the effects of the present invention are significantly impaired.

[Organic EL display and organic EL lighting]
The organic electroluminescent element of the present invention is used for organic EL displays and organic EL lighting. The organic electroluminescent device obtained by the present invention is described in, for example, “Organic EL Display” (Ohm, August 20, 2004, written by Shizushi Tokito, Chiba Adachi, and Hideyuki Murata). An organic EL display and organic EL illumination can be formed by the method.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.

[Synthesis Example 1: Synthesis of Ir complex (D-2)]
An organometallic complex represented by the following formula was synthesized by the following method.

  44 ml of dry ether was added to 7.37 g (30.7 mmol) of p-bromohexylbenzene, and the mixture was cooled to -78 ° C. To this solution, 23 ml (36.7 mmol) of a 1.6M n-BuLi hexane solution was dropped, and then the temperature was gradually raised to room temperature over about 2 hours. The disappearance of the raw material was confirmed by thin layer chromatography, and then cooled again to -78 ° C. To that solution, a solution of 5.0 g (30.7 mmol) of 1-chloroisoquinoline in 65 ml of dry ether was added dropwise. The reaction mixture was gradually warmed to room temperature and stirred as it was (about 4 hours). A saturated aqueous ammonium chloride solution was added to the reaction solution, and the mixture was separated, and the organic layer was concentrated. The resulting pale yellow oily crude product was purified by silica gel column chromatography (once with methylene chloride / ethanol system, once with methylene chloride / ethyl acetate system) to give a pale yellow oily intermediate. 6.83 g (yield: 77%) of 1- (4-n-hexylphenyl) isoquinoline was obtained.

3.67 g (12.7 mmol) of this intermediate and 35 ml of glycerin were charged and dehydrated and degassed at 120 ° C. for about 30 minutes. After allowing to cool, Ir (acac) ₃ (acac: acetylacetone) 2.08 g (4.2 mmol) was added, and the mixture was heated to 200 ° C. and reacted for 18 hours (confirmation of distillation of acetylacetone). The temperature was lowered to about 60 ° C., methanol was added, and the crystallized crystals were collected by filtration. The obtained crude crystals were washed with methanol and recrystallized with dimethyl ether to obtain 1.19 g (yield: 27%) of an Ir complex (D-2) which is a target product of dark red crystals.

[Synthesis Example 2: Synthesis of Ir Complex (D-2-I) of the Present Invention]
The Ir complex (D-2) obtained in Synthesis Example 1 was subjected to column chromatography with basic silica gel, then concentrated and dried, and then recrystallized using dimethothietane. The obtained crystals were heated using a sublimation purification apparatus under high vacuum (1 × 10 ⁻⁵ Pa) at 220 ° C. for 1.5 hours to remove low-boiling components, whereby an Ir complex (D-2- I) was obtained.

[Synthesis Example 3: Synthesis of Ir Complex (D-2-G) of Comparative Example]
The Ir complex D-2 obtained in Synthesis Example 1 was subjected to column chromatography with basic silica gel, concentrated and dried, and then sublimated and purified under high vacuum (1 × 10 ^{− 5} Pa) and heating at 220 ° C. for 2 hours to remove low-boiling components, thereby obtaining an Ir complex (D-2-G).

[HPLC analysis]
About each Ir complex obtained by the synthesis examples 2-3, the HPLC analysis was performed with the following method, and the result was shown in FIG.

Using Inertsil ODS-3 (4.6 × 100 mm, 3 μm) as a HPLC column, water / acetonitrile = 15/85 (v / v) as liquid (A) and isopropanol as liquid (B) at 40 ° C. Use (A) / (B) = 60/40, flow at 0.8 mL / min, prepare 500 μg / mL toluene solution of each Ir complex, inject 5 μL of each, peak area at UV254 nm Was measured.
As a result of HPLC analysis, a peak of +14 (impurity (+14) peak having a molecular weight 14 larger than that of the target compound) was significantly observed at 26.9 minutes in any Ir complex, and this was caused by partial oxidation of the alkyl group. It is considered a compound (losing two H atoms and adding one oxygen atom).
Further, a +32 peak (impurity (+32) peak having a molecular weight 32 larger than that of the target compound) is observed at 14.5 minutes, which is considered to be due to the addition of water.
The estimated structure of this impurity (+14) and impurity (+32) is shown below.

  The impurity content of each Ir complex was as shown in Table 1.

[Example 1: Production of organic electroluminescent device]
The organic electroluminescent element shown in FIG. 1 was produced.

  An indium tin oxide (ITO) transparent conductive film deposited on a glass substrate 1 with a thickness of 120 nm (manufactured by Sanyo Vacuum Co., Ltd., sputtered film product) using ordinary photolithography technology and hydrochloric acid etching Then, the anode 2 was formed by patterning into stripes having a width of 2 mm. The patterned ITO substrate is cleaned in the order of ultrasonic cleaning with an aqueous surfactant solution, water cleaning with ultrapure water, ultrasonic cleaning with ultrapure water, and water cleaning with ultrapure water, followed by drying with compressed air, and finally UV irradiation. Ozone cleaning was performed.

  First, a hole-transporting polymer compound having a repeating structure represented by the structural formula (P1) as a hole-transporting compound (weight average molecular weight: 26500, number-average molecular weight: 12000), and a structural formula (A1) as an electron-accepting compound A composition for forming a hole injection layer containing 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and ethyl benzoate shown in FIG. In this composition, the hole transporting polymer compound (P1) was 2.0% by weight, and the electron accepting compound (A1) was 0.8% by weight. This composition was formed by spin coating on the anode in the air at a spinner rotation speed of 1500 rpm and a spinner rotation time of 30 seconds. Then, the hole injection layer 3 with a film thickness of 30 nm was obtained by heating and drying in the atmosphere at 230 ° C. for 3 hours.

  Subsequently, a crosslinkable compound (polymer) H1 (weight average molecular weight: 95000) represented by the following structural formula as a hole transporting compound and toluene as a solvent were prepared. The solid content concentration of the crosslinkable compound in the composition was 0.4% by weight. This composition was formed on the hole injection layer 3 formed as described above by spin coating in a spinner rotation speed of 1500 rpm and a spinner rotation time of 30 seconds and in nitrogen, and crosslinked by heating at 230 ° C. for 1 hour in nitrogen. Thus, a crosslinked film (hole transport layer 4) having a thickness of 20 nm was formed.

  Next, in forming the light emitting layer, the charge transport material (E-1), the charge transport material (E-2) represented by the following structural formula, the Ir complex of the present invention synthesized in Synthesis Example 2 (D-2) A composition for forming a light emitting layer (composition for an organic electroluminescence device of the present invention) containing -I) and cyclohexylbenzene as a solvent was prepared. In the composition, the charge transport material (E-1) is 2.5% by weight, the charge transport material (E-2) is 2.5% by weight, and the Ir complex (D-2-I) is 0.25% by weight. did. This composition was formed on the hole transport layer 4 formed as described above by spin coating at a spinner rotation speed of 1500 rpm, a spinner rotation time of 30 seconds and in nitrogen, and then at 130 ° C. under reduced pressure (0.1 MPa). And dried for 1 hour to obtain a light emitting layer 5 with a film thickness of 50 nm.

Here, after the substrate on which the hole injection layer 3, the hole transport layer 4 and the light emitting layer 5 are formed is transferred into a vacuum vapor deposition apparatus and the apparatus is roughly evacuated by an oil rotary pump, the degree of vacuum in the apparatus is increased. After evacuating with a cryopump until the pressure became 5.1 × 10 ⁻⁴ Pa or less, a compound represented by the following structural formula (C-3) was formed on the light emitting layer 5 by vacuum deposition, A hole blocking layer 6 having a thickness of 5 nm was obtained. The deposition rate was controlled in the range of 0.7 to 1.0 kg / second, and the degree of vacuum during the deposition was 1.9 to 2.0 × 10 ⁻⁴ Pa.

Subsequently, tris (8-hydroxyquinolinato) aluminum was heated and evaporated on the hole blocking layer 6 to form an electron transport layer 7 having a thickness of 30 nm. The degree of vacuum during vapor deposition was 1.3 × 10 ⁻⁴ Pa, and the vapor deposition rate was controlled in the range of 0.6 to 1.0 kg / second.

Here, the element on which the electron transport layer 7 has been vapor-deposited is once taken out from the vacuum vapor deposition apparatus into the atmosphere, and a 2 mm-wide stripe shadow mask is orthogonal to the ITO stripe of the anode 2 as a mask for cathode vapor deposition. Then, the device was brought into close contact with the device, installed in another vacuum vapor deposition apparatus, and evacuated until the degree of vacuum in the apparatus was 2.1 × 10 ⁻⁴ Pa or less in the same manner as the electron transport layer 7. As the electron injection layer 8, lithium fluoride (LiF) was controlled at a deposition rate of 0.07 to 0.17 liters / second and a degree of vacuum of 2.3 to 2.4 × 10 ⁻⁴ Pa using a molybdenum boat, A film having a thickness of 0.5 nm was formed on the electron transport layer 7.

Next, aluminum is similarly heated by a molybdenum boat as the cathode 9 and controlled at a deposition rate of 0.7 to 6.1 liters / second and a degree of vacuum of 2.3 to 2.7 × 10 ⁻⁴ Pa to a film thickness of 80 nm. An aluminum layer was formed. The substrate temperature during the above two-layer deposition was kept at room temperature.

  Subsequently, a sealing process was performed to prevent the element from being deteriorated by moisture in the atmosphere during storage. As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained.

The maximum wavelength of the emission spectrum of the device was 520 nm, which was identified as being from the Ir complex (D-2-I). The chromaticity was CIE (x, y) = (0.65, 0.35).
When this element was driven at 2000 cd / m ² , the time until the initial luminance decreased to 50% (half life) was measured.

[Comparative Example 1]
An organic electroluminescent device was produced in the same manner as in Example 1 except that the Ir complex (D-2-G) of Comparative Example obtained in Synthesis Example 3 was used instead of the Ir complex (D-2-I). In the same manner, the half-life was measured.

In Table 2, the half life of each organic electroluminescent element is shown as a relative value when the half life of the organic electroluminescent element of Comparative Example 1 is used.
Table 2 also shows the impurity content of the Ir complex used.

  Table 2 shows that a long-life organic electroluminescent element can be obtained using the organometallic complex of the present invention.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Electron injection layer 9 Cathode 10 Organic electroluminescent device

Claims (7)

An organometallic complex used in an organic electroluminescent device,
The organometallic complex is characterized in that the content of a compound having a molecular weight 14 larger than that of the organometallic complex is 1% by weight or less.   The metal contained in the organometallic complex is a metal selected from the group consisting of Ir, Pt, Pd, Cu, Zn, Ag, Rh, Ru, Os, Au, and Re. The organometallic complex described.   The organometallic complex according to claim 1 or 2, wherein the organometallic complex has an alkyl group which may have a substituent in the molecule.   An organic electroluminescent element composition comprising the organometallic complex according to any one of claims 1 to 3 and a solvent.   An organic electroluminescent device having an anode, a cathode, and a light emitting layer provided between the two electrodes, wherein the organic electroluminescent element has a layer containing the organometallic complex according to any one of claims 1 to 3. An organic electroluminescent device.   An organic EL display comprising the organic electroluminescent element according to claim 5.   An organic EL illumination comprising the organic electroluminescent element according to claim 5.

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