JP6686891B2 - Iridium complex, organic electroluminescent material, organic electroluminescent element, display device and lighting device - Google Patents

Description

  The present invention relates to an iridium complex, an organic electroluminescence material using the iridium complex, an organic electroluminescence element, a display device and a lighting device provided with the organic electroluminescence element. More specifically, the present invention relates to an iridium complex having improved luminous efficiency and durability.

  An organic electroluminescence device (hereinafter, also referred to as an organic EL device) has a structure in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode, and is injected from the anode by applying an electric field. A light emitting element that utilizes the emission of light (fluorescence / phosphorescence) when the excitons (excitons) are generated by recombining holes and electrons injected from the cathode in the light emitting layer. Is. The organic EL element is an all-solid-state element in which a space between electrodes is composed of a film of an organic material having a thickness of about submicron, and can emit light at a voltage of about several V to several tens of V. Therefore, it is expected to be used for next-generation flat panel displays and lighting.

As for the development of an organic EL device for practical use, Princeton University reported an organic EL device that uses phosphorescence emission from excited triplets, and since then, research on materials that exhibit phosphorescence at room temperature has become active. Is coming.
Furthermore, since an organic EL element that utilizes phosphorescence emission can achieve a luminous efficiency that is approximately four times as high as that of an organic EL element that previously used fluorescence emission, it is possible to achieve light emission starting from material development. Research and development of layer structure of elements and electrodes are being carried out all over the world. For example, many compounds have been studied for synthesis centering on heavy metal complexes such as iridium complexes.
As described above, the phosphorescence emission method has a very high potential, but an organic EL element that utilizes phosphorescence emission controls the position of the emission center, which is significantly different from an organic EL element that utilizes fluorescence emission. A method, especially how to achieve stable light emission by recombining inside the light emitting layer is an important technical issue for improving efficiency and life of the device.

  First, it is important to increase the luminous efficiency of the phosphorescent compound. The luminous efficiency is determined by the ratio of the radiant velocity that transitions with light emission to the non-radiative transition that transitions with heat. It is known that there is a close connection between the non-radiative transition and the structural change of the phosphorescent compound. That is, when a large structural change occurs, the transition is accompanied by heat, and the luminous efficiency is reduced (for example, see Non-Patent Document 1).

Usually, the phosphorescent compound is composed of a transition metal and a ligand. As the ligand, for example, a compound in which an aromatic heterocycle and an aromatic ring (or an aromatic heterocycle) are connected by a single bond (hereinafter, also referred to as a biaryl-type ligand) is often used, and there is no radiation. It is considered that the main cause of the increase in transition is the structural change of the biaryl type ligand.
Specifically, since the aromatic ring and the aromatic heterocycle (or two aromatic heterocycles) constituting the biaryl-type ligand coordinated to the transition metal are bonded by a single bond, Structural changes occur and non-radiative transitions increase.
As a means for fixing the structure of the biaryl-type ligand, a general method is "stiffening utilizing steric hindrance" (see, for example, Patent Document 1). In addition, a compound in which two ring structures of a biaryl-type ligand are further linked by a covalent bond is known (see, for example, Patent Document 2).

It has been reported that these compounds have a good light emitting property and are blue phosphorescent compounds having a high potential. However, when an aromatic group is introduced as a means for fixing the structure of the biaryl-type ligand, there is a problem in that dopant quenching causes aggregation or aggregation, and concentration quenching and excimer emission occur simultaneously.
This association / aggregation of the dopants may occur immediately after the film formation, but it is more remarkable when the electroluminescent or local Joule heat is applied to the light emitting layer thin film after the passage of electricity.
As described above, due to the association / aggregation of the dopants with each other over the passage of current, the film state in the light emitting layer changes, and the ease of hole flow and the ease of electron flow change. As a result, the resistance value in the light emitting layer changes, causing an increase in voltage during driving.

International Publication No. 2007/097149 International Publication No. 2007/095118

L. Yang, et. al. Inorg. Chem. , 47 (2008) 7154

  The present invention has been made in view of the above problems and circumstances, and the problem to be solved is an iridium complex having improved luminous efficiency and durability, an organic electroluminescent material and an organic electroluminescent element using the iridium complex, and the organic material. An object of the present invention is to provide a display device and a lighting device each including an electroluminescent element.

In order to solve the above problems, the present inventor, in the process of examining the cause of the above problems, the bidentate ligand of the iridium complex has a hydrogen bond in the ligand and immobilizes the structure. As a result, it was found that the non-radiative transition can be suppressed, which leads to the improvement of luminous efficiency and durability, and the present invention has been completed.
That is, the said subject which concerns on this invention is solved by the following means.

（一般式（１）中、Ａ_１及びＡ_２は、それぞれ、芳香族炭化水素環又は芳香族複素環を表
す。Ａ_３は、芳香族複素環を表す。
Ｘ_１ａ及びＸ_５ａは、それぞれ、窒素原子又は炭素原子を表す。
Ｘ_１は、炭素原子を表し、Ｘ_２及びＸ_５は、窒素原子を表す。Ｘ_１〜Ｘ_５により形成される環は、置換基を有していてもよいイミダゾール環又は置換基を有していてもよいトリアゾール環を表す。
Ｘ_６は、酸素原子又は硫黄原子を表す。Ｒａは、水素原子、芳香族炭化水素環基、芳香族複素環基、複素環基、アルキル基又はシクロアルキル基を表す。ｎは１を表す。ｌは１〜３を表す。ｍは０〜２を表す。ｌ＋ｍ＝３である。） 1. An iridium complex having a bidentate ligand containing an aromatic heterocycle,
The bidentate ligand is a ligand in which the aromatic heterocycle is bonded to another aromatic heterocycle or an aromatic ring by a single bond, and has a hydrogen bond in the ligand. An iridium complex having a structure represented by the following general formula (1).

(In the general formula (1), A ₁ and A ₂ each represent an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle.
X _1a and X _5a each represent a nitrogen atom or a carbon atom.
X ₁ represents a carbon atom, and X ₂ and X ₅ represent a nitrogen atom. The ring formed by X _{1 to} X ₅ represents an imidazole ring which may have a substituent or a triazole ring which may have a substituent.
X ₆ represents an oxygen atom or a sulfur atom. Ra represents a hydrogen atom, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, a heterocyclic group, an alkyl group or a cycloalkyl group. n represents 1 . l represents 1 to 3. m represents 0 to 2. 1 + m = 3. )

2. A ₁ in the iridium complex is a benzene ring, The iridium complex according to item 1 .

（一般式（２）中、Ａ_２は、芳香族炭化水素環又は芳香族複素環を表す。Ａ_３は、Ｘ_１ａ及びＸ_５ａを含む芳香族複素環を表す。Ａ_４は、Ｘ_６を含む芳香族複素環を表す。
Ｘ _１ａ 及びＸ _５ａ は、それぞれ、窒素原子又は炭素原子を表す。
Ｘ _１ は、炭素原子を表し、Ｘ _２ 及びＸ _５ は、窒素原子を表す。Ｘ _１ 〜Ｘ _５ により形成される環は、置換基を有していてもよいイミダゾール環又は置換基を有していてもよいトリアゾール環を表す。
Ｘ_６は、酸素原子、窒素原子、硫黄原子、リン原子又はケイ素原子を表す。Ｘ_７及びＸ_８は、ＣＲｃ、Ｎを表し、Ｒｃは水素原子又は置換基を表す。ｌは１〜３を表す。ｍは０〜２を表す。ｌ＋ｍ＝３である。） 3. An iridium complex having a bidentate ligand containing an aromatic heterocycle,
The bidentate ligand has a single bond between the aromatic heterocycle and another aromatic heterocycle or aromatic ring.
A ligand is attached, and having a hydrogen bond to the inner ligands, features and be Louis Rijiumu complex that has a structure that you express the following general formula (2).

(In the general formula (2), A ₂ represents an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle containing X _1a and X _5a. A ₄ represents X ₆ . Represents an aromatic heterocycle containing.
X _1a and X _5a each represent a nitrogen atom or a carbon atom.
X ₁ represents a carbon atom, and X ₂ and X ₅ represent a nitrogen atom. The ring formed by X _{1 to} X ₅ represents an imidazole ring which may have a substituent or a triazole ring which may have a substituent.
X ₆ represents an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom or a silicon atom. X ₇ and X ₈ represent CRc and N, and Rc represents a hydrogen atom or a substituent . l represents 1 to 3. m represents 0 to 2. 1 + m = 3. )

（一般式（３）中、Ａ_２は、芳香族炭化水素環又は芳香族複素環を表す。Ａ_３は、芳香族複素環を表す。
Ｘ_１ａ及びＸ_５ａは、それぞれ、窒素原子又は炭素原子を表す。
Ｘ_１は、炭素原子を表し、Ｘ_２及びＸ_５は、窒素原子を表す。Ｘ_１〜Ｘ_５により形成される環は、置換基を有していてもよいイミダゾール環又は置換基を有していてもよいトリアゾール環を表す。
Ｘ_６は、酸素原子又は硫黄原子を表す。Ｒａは、水素原子、芳香族炭化水素環基、芳香族複素環基、複素環基、アルキル基又はシクロアルキル基を表す。Ｒ_１は、電子吸引基を表す。ｎは１を表す。ｌは１〜３を表す。ｍは０〜２を表す。ｌ＋ｍ＝３である。） 4. An iridium complex having a bidentate ligand containing an aromatic heterocycle,
The bidentate ligand is a ligand in which the aromatic heterocycle is bonded to another aromatic heterocycle or an aromatic ring by a single bond, and has a hydrogen bond in the ligand. An iridium complex having a structure represented by the following general formula (3).

(In general formula (3), A ₂ represents an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle.
X _1a and X _5a each represent a nitrogen atom or a carbon atom.
X ₁ represents a carbon atom, and X ₂ and X ₅ represent a nitrogen atom. The ring formed by X _{1 to} X ₅ represents an imidazole ring which may have a substituent or a triazole ring which may have a substituent.
X ₆ represents an oxygen atom or a sulfur atom. Ra represents a hydrogen atom, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, a heterocyclic group, an alkyl group or a cycloalkyl group. R ₁ represents an electron-withdrawing group. n represents 1 . l represents 1 to 3. m represents 0 to 2. 1 + m = 3. )

（一般式（４）中、Ａ_２は、芳香族炭化水素環又は芳香族複素環を表す。Ａ_３は、芳香族複素環を表す。
Ｘ_１ａ及びＸ_５ａは、それぞれ、窒素原子又は炭素原子を表す。
Ｘ_１は、炭素原子を表し、Ｘ_２及びＸ_５は、窒素原子を表す。Ｘ_１〜Ｘ_５により形成される環は、置換基を有していてもよいイミダゾール環又は置換基を有していてもよいトリアゾール環を表す。
Ｘ_６は、酸素原子又は硫黄原子を表す。Ｒａは、水素原子、芳香族炭化水素環基、芳香族複素環基、複素環基、アルキル基又はシクロアルキル基を表す。Ｒ_２は、電子供与基を表す。ｎは１を表す。ｌは１〜３を表す。ｍは０〜２を表す。ｌ＋ｍ＝３である。） 5. An iridium complex having a bidentate ligand containing an aromatic heterocycle,
The bidentate ligand is a ligand in which the aromatic heterocycle is bonded to another aromatic heterocycle or an aromatic ring by a single bond, and has a hydrogen bond in the ligand. An iridium complex having a structure represented by the following general formula (4).

(In general formula (4), A ₂ represents an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle.
X _1a and X _5a each represent a nitrogen atom or a carbon atom.
X ₁ represents a carbon atom, and X ₂ and X ₅ represent a nitrogen atom. The ring formed by X _{1 to} X ₅ represents an imidazole ring which may have a substituent or a triazole ring which may have a substituent.
X ₆ represents an oxygen atom or a sulfur atom. Ra represents a hydrogen atom, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, a heterocyclic group, an alkyl group or a cycloalkyl group. R ₂ represents an electron donating group. n represents 1 . l represents 1 to 3. m represents 0 to 2. 1 + m = 3. )

6 . The dissociation energy of the hydrogen atom which forms the said hydrogen bond is 390 kJ / mol or less, The iridium complex as described in any one of the 1st term to the 5th term.
7 . The substituent of the imidazole ring or triazole ring is an alkyl group, an alkoxy group, a halogen atom, a nitro group, a dialkylamino group, a trialkylsilyl group, a triarylsilyl group, a triheteroarylsilyl group, a benzyl group, an aryl group or a hetero group. The iridium complex according to any one of items 1 to 6, which is an aryl group.
8 . 7. The iridium complex according to any one of items 1 to 6 , wherein the substituent on the imidazole ring or the triazole ring is a halogen atom, a cyano group, an alkyl group or an aromatic group.
9 . An organic electroluminescent material comprising the iridium complex according to any one of items 1 to 8 .

10 . Between the anode and the cathode, an organic electroluminescent element having at least a light emitting layer,
The light emitting layer contains the organic electroluminescent material according to item 9 , wherein the organic electroluminescent device is characterized.

11 . A display device comprising the organic electroluminescence device according to item 10 .

12 . An illumination device comprising the organic electroluminescence element according to item 10 .

  According to the present invention, there is provided an iridium complex having improved luminous efficiency and durability, an organic electroluminescent material and an organic electroluminescent element using the iridium complex, and a display device and a lighting device provided with the organic electroluminescent element. be able to.

Although the mechanism of action or mechanism of action of the present invention has not been clarified, it is presumed as follows.
By introducing a hydrogen bond into a commonly used biaryl-type ligand into the iridium complex and fixing the structure of the biaryl-type ligand, the structural change of the entire iridium complex (hereinafter also referred to as Ir complex) is caused. It was possible to suppress, fluctuation in the film forming the light emitting layer could be reduced, and association / aggregation of dopants could be suppressed. It is presumed that, as a result, the non-radiative transition can be reduced, the light emitting property of the organic EL element using the iridium complex is improved, and the voltage rise during driving can be suppressed.

Further, as a method for producing an iridium complex used for an organic EL device, it is general to use iridium chloride to react with a ligand. In this reaction, hydrochloric acid is produced as a by-product. Therefore, when H is present at the N-position of imidazole when the ligand contains, for example, imidazole, charges are exchanged between H and Cl such as forming a hydrochloride. Therefore, it is difficult to synthesize an Ir complex unless a substituent such as a methyl group is introduced at the N position.
Therefore, it was found that even if H is present at the N-position, by introducing an intramolecular hydrogen bond into the ligand, the exchange of charges with the reaction by-product, hydrochloric acid, can be eliminated and an Ir complex can be produced. .

Schematic diagram showing an example of a display device composed of organic EL elements Schematic diagram of display A Pixel circuit diagram Schematic diagram of passive matrix full-color display device Illumination device schematic Illumination device schematic diagram

The iridium complex of the present invention is an iridium complex having a bidentate ligand containing an aromatic heterocycle, wherein the bidentate ligand is the aromatic heterocycle and another aromatic heterocycle or an aromatic ring. There is a ligand are linked by a single bond, and have a hydrogen bond to the the ligands, and having the structure represented by the general formula (1). This feature is a technical feature common to the inventions according to each claim.

  As an embodiment of the present invention, it is preferable that the dissociation energy of the hydrogen atom forming the hydrogen bond is 390 kJ / mol or less because the hydrogen bond can suppress the structural change of the ligand.

  Further, it is preferable that the atom forming a hydrogen bond with the hydrogen atom forming the hydrogen bond is a nitrogen atom, an oxygen atom, a phosphorus atom or a silicon atom because a strong hydrogen bond is formed.

  Further, it is preferable that the iridium complex has a partial structure represented by the general formula (1) from the viewpoint of exhibiting the effect of the present invention.

Further, the ring formed by X _{1 to} X ₅ in the iridium complex is preferably an imidazole ring or a triazole ring. Thereby, the radiation speed can be increased.

Further, A ₁ in the iridium complex is preferably a benzene ring. Thereby, the radiation speed can be increased.

  Further, it is preferable that the iridium complex has a partial structure represented by the general formula (2) from the viewpoint of manifesting the effect of the present invention.

  Further, it is preferable that the iridium complex has a partial structure represented by the general formula (3) from the viewpoint of manifesting the effect of the present invention.

  In addition, it is preferable that the iridium complex has a partial structure represented by the general formula (4) from the viewpoint of exhibiting the effect of the present invention.

  Further, it is preferable that the iridium complex has a partial structure represented by the general formula (5) from the viewpoint of exhibiting the effect of the present invention.

  The organic electroluminescent material of the present invention is characterized by containing the iridium complex of the present invention. Thereby, an organic EL material having improved luminous efficiency and durability can be obtained.

  Further, the organic electroluminescent element of the present invention, between the anode and the cathode, is an organic electroluminescent element having at least a light emitting layer, the light emitting layer, containing the organic electroluminescent material of the present invention, To do. This makes it possible to obtain an organic EL device having improved luminous efficiency and durability.

  The organic electroluminescent element of the present invention can be suitably provided in a display device. Thereby, the light emission efficiency and durability can be improved.

  The organic electroluminescent element of the present invention can be suitably provided in a lighting device. Thereby, the light emission efficiency and durability can be improved.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and after that as a lower limit and an upper limit.
Before going into this thesis, the history of introducing hydrogen bonds into the ligands of iridium complexes and the synthetic problems will be described from the viewpoint of technical ideas.

The emission efficiency of the phosphorescent compound (iridium complex) is determined by the ratio of the radiative transition that transitions with light emission and the non-radiative transition that transitions with heat. It is known that there is a close connection between the non-radiative transition and the structural change of the phosphorescent compound, and when a large structural change occurs, the transition is accompanied by heat and the luminous efficiency is reduced.
Usually, the phosphorescent compound is composed of a transition metal and a ligand. As the ligand, for example, a biaryl-type ligand in which an aromatic heterocycle and an aromatic ring (or an aromatic heterocycle) are connected by a single bond is often used, and the main cause of increase in non-radiative transition is biaryl. It is considered that this is a structural change of the type ligand.
In the present invention, the “biaryl-type ligand” is not a compound in which two aromatic rings are connected by a single bond, but a compound in which an aromatic ring and an aromatic heterocycle are connected by a single bond and two It is a compound in which aromatic heterocycles are connected by a single bond, and these aromatic rings and / or aromatic heterocycles may further have a substituent.

  Specifically, as shown below, the aromatic ring and the aromatic heterocycle (or the two aromatic heterocycles) constituting the biaryl-type ligand coordinated to the transition metal are single bonds. It is considered that the structure changes due to the bonding and the non-radiative transition increases.

Further, it is desired that the means for fixing the structure of the biaryl-type ligand is a means capable of suppressing the association or aggregation of the dopants that cause concentration quenching and excimer emission.
The association / aggregation of the dopants may occur immediately after the film formation, but more significantly occurs when electrolysis or local Joule heat is applied to the light emitting layer thin film after the passage of electricity.
As described above, due to the association / aggregation of the dopants with each other over time, the film state in the light emitting layer is changed, and the ease of hole flow and the flow of electrons are changed. It is necessary to prevent the value from changing and causing a voltage increase during driving.

Further, in a method for producing an iridium complex used for an organic EL element, it is general to use iridium chloride to react with a ligand. In this reaction, hydrochloric acid is produced as a by-product. Therefore, when the ligand includes, for example, an imidazole ring, if H is present at the N-position of imidazole, charges are exchanged between H and Cl such as forming a hydrochloride. Therefore, it is difficult to synthesize an Ir complex unless a substituent such as a methyl group is introduced at the N position.
Therefore, as a method for synthesizing without introducing a substituent even when H is present at the N-position, an intramolecular hydrogen bond is introduced into the ligand to exchange charge with the reaction by-product hydrochloric acid. It has been found that the Ir complex can be produced without it.

<< Organic EL element constituent layers >>
The constituent layers of the organic EL device of the present invention will be described. In the organic EL device of the present invention, preferable specific examples of the layer structure of various organic layers sandwiched between the anode and the cathode are shown below, but the present invention is not limited thereto.
(I) Anode / light emitting layer unit / electron transport layer / cathode (ii) Anode / hole transport layer / light emitting layer unit / electron transport layer / cathode (iii) Anode / hole transport layer / light emitting layer unit / hole blocking Layer / electron transport layer / cathode (iv) anode / hole transport layer / light emitting layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) anode / anode buffer layer / hole transport layer / light emission Layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode

Furthermore, the light emitting layer unit may have a non-light emitting intermediate layer between a plurality of light emitting layers, and may have a multi-photon unit structure in which the intermediate layer is a charge generation layer. In this case, the charge generation layer is formed of ITO (indium tin oxide), IZO (indium zinc oxide), ZnO ₂ , TiN, ZrN, HfN, TiOx, VOx, CuI, InN, GaN, CuAlO ₂ , CuGaO. ₂ , a conductive inorganic compound layer such as SrCu ₂ O ₂ , LaB ₆ and RuO ₂ , a two-layer film such as Au / Bi ₂ O ₃ , SnO ₂ / Ag / SnO ₂ , ZnO / Ag / ZnO and Bi ₂ Multilayer films such as O ₃ / Au / Bi ₂ O ₃ , TiO ₂ / TiN / TiO ₂ , TiO ₂ / ZrN / TiO ₂ , fullerene such as C ₆₀ , conductive organic material layer such as oligothiophene, metal phthalocyanines , Metal-free phthalocyanines, metal porphyrins, metal-free porphyrins and other conductive organic compound layers.
The light emitting layer in the organic EL element of the present invention is preferably a white light emitting layer, and a lighting device using these is preferable.
Each layer constituting the organic EL device of the present invention will be described below.

<Light emitting layer>
The light emitting layer according to the present invention is a layer in which electrons and holes injected from an electrode or an electron transporting layer and a hole transporting layer are recombined to emit light, and a light emitting portion is in the layer of the light emitting layer. May be the interface between the light emitting layer and the adjacent layer.
The total thickness of the light emitting layer is not particularly limited, but the homogeneity of the film and the prevention of applying an unnecessary high voltage during light emission, and from the viewpoint of improving the stability of the emission color with respect to the drive current, It is preferably adjusted to a range of 2 nm to 5 μm, more preferably adjusted to a range of 2 to 200 nm, and particularly preferably adjusted to a range of 5 to 100 nm.

For the production of the light emitting layer, for example, a vacuum deposition method, a wet method (also referred to as a wet process, for example, a spin coating method, a casting method, a die coating method, a blade coating method, a roll coating, using a light emitting dopant or a host compound described later. Method, an inkjet method, a printing method, a spray coating method, a curtain coating method, an LB method (Langmuir Blodgett method), etc.) and the like.
The light emitting layer of the organic EL device of the present invention preferably contains a light emitting dopant (phosphorescent light emitting dopant, fluorescent light emitting dopant, etc.) compound and a host compound.

(1) Luminescent Dopant A luminescent dopant (a luminescent dopant, a dopant compound, or simply a dopant) will be described.
As the light emitting dopant, a fluorescent light emitting dopant (also referred to as a fluorescent dopant, a fluorescent compound, or a fluorescent light emitting compound), a phosphorescent light emitting dopant (a phosphorescent dopant, a phosphorescent compound, a phosphorescent light emitting compound, or the like) is also referred to. .) Can be used.

(1.1) Phosphorescent Dopant A phosphorescent dopant is a compound in which light emission from an excited triplet is observed, specifically, a compound that emits phosphorescent light at room temperature (25 ° C.), and has a phosphorescent quantum yield. Is defined as a compound of 0.01 or more at 25 ° C., but a preferable phosphorescence quantum yield is 0.1 or more.
The above-mentioned phosphorescence quantum yield can be measured by the method described in page 398 of Spectroscopy II of Fourth Edition Experimental Chemistry Course 7 (1992 version, Maruzen). The phosphorescence quantum yield in a solution can be measured using various solvents, but the phosphorescence dopant according to the present invention achieves the phosphorescence quantum yield (0.01 or more) in any of the solvents. Good.

  There are two types of light emission of the phosphorescent dopant in principle. One is that recombination of carriers occurs on the host compound to which the carriers are transported and an excited state of the light-emitting host compound is generated. It is an energy transfer type in which light is emitted from the phosphorescent dopant by moving the phosphor to the phosphor. The other is a carrier trap type in which the phosphorescent dopant serves as a carrier trap, and carriers are recombined on the phosphorescent dopant, and light emission from the phosphorescent dopant is obtained. In any case, the excited state energy of the phosphorescent dopant must be lower than the excited state energy of the host compound.

Here, as a result of the inventors' earnest studies to achieve the above-mentioned object of the present invention, as described above, the iridium complex of the present invention has a bidentate ligand containing an aromatic heterocycle. , The bidentate ligand is a ligand in which the aromatic heterocycle and another aromatic heterocycle or an aromatic ring are bonded by a single bond, and has a hydrogen bond in the ligand. Thus, it was clarified that the luminous efficiency and durability can be improved when used in an organic EL device.
Here, a hydrogen bond is a non-covalent bond in which a hydrogen atom covalently bonded to an atom having a high electronegativity forms a lone electron pair of a nitrogen atom, an oxygen atom or a sulfur atom located at a predetermined distance and angle. It is an attractive interaction of sex.
Further, in the present invention, an atom covalently bonded to a hydrogen atom forming a hydrogen bond can be represented as X-H ... Y, where X is an atom forming a bond by a hydrogen bond and Y can be represented. It is assumed that a hydrogen bond is formed when the distance between them is in the range of 1.4 to 2.5Å and the angle formed by X-H ... Y is in the range of 110 to 125 °.

  Regarding the hydrogen bond formed in the ligand of the iridium complex of the present invention, Gaussian98 (Gaussian98, Revision A.11.4, MJ Frisch, which is software for molecular orbital calculation manufactured by Gaussian in the United States). et al, Gaussian, Inc., Pittsburgh PA, 2002.) and using B3LYP / 6-31G * as a keyword to perform structural optimization, and the structurally optimized iridium complex is subjected to hydrogen based on distance and angle. Determined binding.

The atom forming a hydrogen bond with the hydrogen atom is preferably a nitrogen atom, an oxygen atom, a phosphorus atom or a silicon atom because a strong hydrogen bond is formed.
In addition, in the present invention, since a structural change can be suppressed by having a hydrogen bond in the ligand of the iridium complex, a site involved in light emission can be fixed and a non-radiative transition can be suppressed. can do.
It is also preferable that the iridium complex of the present invention further has an inter-ligand hydrogen bond, an inter-molecular hydrogen bond and other interactions.

[Iridium Complex Represented by General Formula (1)]
Further, the iridium complex of the present invention preferably has a partial structure represented by the following general formula (1).

In general formula (1), A ₁ and A ₂ each represent an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle. X ₁ , X ₅ , X _1a and X _5a each represent a nitrogen atom or a carbon atom. X _{2 to} X ₄ each represent a nitrogen atom, a carbon atom, an oxygen atom or a sulfur atom. X ₆ represents an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom or a silicon atom. Ra represents a hydrogen atom, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, a heterocyclic group, an alkyl group or a cycloalkyl group. n represents 0 or 1. l represents 1 to 3. m represents 0 to 2. 1 + m = 3.

In general formula (1), the ring formed by X _{1 to} X ₅ in the iridium complex is preferably an imidazole ring or a triazole ring.

In addition, in the general formula (1), A ₁ in the iridium complex is preferably a benzene ring.

[Iridium Complex Represented by General Formula (2)]
In addition, the iridium complex of the present invention preferably has a partial structure represented by the following general formula (2).

In general formula (2), A ₂ represents an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle containing X _1a and X _5a . A ₄ represents an aromatic heterocycle containing X ₆ . X ₁ , X ₅ , X _1a and X _5a each represent a nitrogen atom or a carbon atom. X _{2 to} X ₄ represent a nitrogen atom, a carbon atom, an oxygen atom or a sulfur atom. X ₆ represents an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom or a silicon atom. X ₇ and X ₈ represent CRc and N, and Rc represents a hydrogen atom or a substituent. ns represents 0 or 1. l represents 1 to 3. m represents 0 to 2. 1 + m = 3.

[Iridium Complex Represented by General Formula (3)]
Further, the iridium complex of the present invention preferably has a partial structure represented by the following general formula (3).

In general formula (3), A ₂ represents an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle. X ₁ , X ₅ , X _1a and X _5a each represent a nitrogen atom or a carbon atom. X _{2 to} X ₄ each represent a nitrogen atom, a carbon atom, an oxygen atom or a sulfur atom. X ₆ represents an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom or a silicon atom. Ra represents a hydrogen atom, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, a heterocyclic group, an alkyl group or a cycloalkyl group. R ₁ represents an electron-withdrawing group. n represents 0 or 1. l represents 1 to 3. m represents 0 to 2. 1 + m = 3.
Here, as the electron-withdrawing group, in addition to the electron-withdrawing group contained in the structural formulas of the iridium complexes D-1 to D-38 shown in the following specific examples, an alkoxycarbonyl group, an aryloxycarbonyl group, a sulfamoyl group, an acyl group Groups such as amide group, carbamoyl group, sulfinyl group, alkylsulfonyl group, arylsulfonyl group, heteroarylsulfonyl group, cyano group and nitro group are also preferably used.

[Iridium Complex Represented by General Formula (4)]
Further, the iridium complex of the present invention preferably has a partial structure represented by the following general formula (4).

In general formula (4), A ₂ represents an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle. X ₁ , X ₅ , X _1a and X _5a each represent a nitrogen atom or a carbon atom. X _{2 to} X ₄ each represent a nitrogen atom, a carbon atom, an oxygen atom or a sulfur atom. X ₆ represents an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom or a silicon atom. Ra represents a hydrogen atom, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, a heterocyclic group, an alkyl group or a cycloalkyl group. R ₂ represents an electron donating group. n represents 0 or 1. l represents 1 to 3. m represents 0 to 2. 1 + m = 3.
Here, as the electron donating group, in addition to the electron donating group contained in the structural formulas of the iridium complexes D-1 to D-38 shown in the following specific examples, an alkoxy group, a cycloalkoxy group, an aryloxy group, an alkylthio group, Groups such as cycloalkylthio group, arylthio group, amino group, hydroxy group, mercapto group and silyl group are also preferably used.

[Iridium Complex Represented by General Formula (5)]
The iridium complex used as a reference preferably has a structure represented by the following general formula (5).

In general formula (5), V represents a trivalent linking group. It is covalently linked to L ₁ , L ₂ and L ₃ . L _{1 to} L ₃ are each a partial structure represented by the following general formula (6).

In formula (6), X ₁ represents a nitrogen atom or a carbon atom. X _{2 to} X ₄ each represent a nitrogen atom, a carbon atom, an oxygen atom or a sulfur atom. X ₆ represents an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom or a silicon atom. Ra represents a hydrogen atom, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, a heterocyclic group, an alkyl group or a cycloalkyl group. n represents 0 or 1. * Represents a binding site with V.

  The partial structure represented by the general formulas (1) to (6) and the aromatic ring contained in the structure may further have a substituent, and the substituent is bonded to another group to form a condensed ring. It may be formed. Examples of the substituent include an alkyl group (eg, methyl group, ethyl group, trifluoromethyl group, isopropyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, etc.), halogen atom (eg, fluorine atom, etc.) , Nitro group, dialkylamino group (eg, dimethylamino group), trialkylsilyl group (eg, trimethylsilyl group), triarylsilyl group (eg, triphenylsilyl group), triheteroarylsilyl group (eg, trialkylsilyl group) Examples thereof include a pyridylsilyl group), a benzyl group, an aryl group (eg, a phenyl group), and a heteroaryl group (eg, a pyridyl group, a carbazolyl group, etc.).

[Specific examples of iridium complex]
Hereinafter, specific examples of the iridium complex containing at least one of the structures represented by the general formulas (1) to (6) of the present invention and as a reference will be shown, but the present invention is not limited thereto. In addition, "..." of H ... Y represents a hydrogen bond in the ligand. Further, these compound examples may further have a substituent, and the substituent has the same meaning as the substituent used in the general formulas (1) to (6). The iridium complex of the present invention shown in these specific examples preferably further has a substituent to the extent that the function is not impaired.

[Dissociation energy of hydrogen atom]
The iridium complex of the present invention is Gaussian 03 (Gaussian 98, Revision C. 11.4, MJ Frisch, et al, Gaussian, Inc., Pittsburgh PA, 2002.), which is software for molecular orbital calculation manufactured by Gaussian in the United States. , The structural optimization was performed using B3LYP / 6-31G * as a keyword, and using this optimal structure, one-point calculation was performed using 6-311 ++ G (2df, 2p) as a keyword to calculate the dissociation energy of the hydrogen atom. I asked.
Dissociation energy of the hydrogen atoms (ΔG): X-H → X - + H +
Specifically, for “X-H” and “X ⁻ ”, structural optimization is performed using the above Gaussian calculation, and the respective energies are calculated. Using this value, X-H → X ^- was dissociation energy from (energy difference neutral and anionic compounds).
The dissociation energy of hydrogen atoms forming a hydrogen bond in the ligand of the iridium complex of the present invention is preferably 390 kJ / mol or less, more preferably 375 kJ / mol or less, and 360 kJ / mol or less. Is particularly preferred. Table 1 shows the calculated dissociation energy.

  The dissociation energy of the hydrogen atom forming the hydrogen bond is preferably 390 kJ / mol or less because the hydrogen bond can suppress the structural change of the ligand.

[Synthesis Example of Iridium Complex]
Hereinafter, synthetic examples of the iridium complex of the present invention will be described, but the present invention is not limited thereto. A method for synthesizing the iridium complex D-1 among the above specific examples will be described as an example.

(Process 1)
2.0 g of intermediate A, 1.2 g of iridium chloride, 45 ml of ethoxyethanol and 15 ml of water were placed in a three-necked flask, and the mixture was heated with stirring at 100 ° C. for 4 hours under a nitrogen atmosphere.
The precipitated crystals were collected by filtration, and the collected crystals were washed with methanol to obtain 1.9 g of intermediate B.

(Process 2)
In a three-necked flask, 1.8 g of the intermediate B obtained in step 1, 0.52 g of acetylacetone, 1.8 g of potassium carbonate and 50 ml of ethoxyethanol were placed, and the mixture was heated with stirring at 80 ° C. for 5 hours under a nitrogen atmosphere. .
The precipitated crystals were collected by filtration, and the collected crystals were washed with methanol and then with water to obtain Intermediate C (0.96 g).

(Process 3)
0.5 g of the intermediate C obtained in step 2, 0.46 g of the intermediate A and 50 ml of ethylene glycol were placed in a three-necked flask, and heated and stirred at 150 ° C. for 7 hours under a nitrogen atmosphere.
The precipitated crystals were collected by filtration, washed with methanol, and separated and purified by silica gel chromatography to obtain 0.2 g of D-1.

The structure of the iridium complex D-1 was confirmed by mass spectrum and ¹ H-NMR.
MASS spectrum (ESI): m / z = 893 [M ⁺ ]
¹ H-NMR (CD ₂ Cl ₂ , 400 MHz) δ: 7.71 (2 H, d, J = 28.3 Hz)

[General synthesis method]
Further, when a compound having a structure similar to that of the intermediate A was used to synthesize the following iridium complex by the following method, it could not be synthesized.

Into a three-necked flask, 3.8 g (26.3 mmol) of 4-phenylimidazole and 1.96 g (6.6 mmol) of IrCl ₃ hydrate (manufactured by Strem Chemicals) were placed, and the atmosphere was replaced with argon.
Next, 30 ml of 2-ethoxyethanol was placed in a three-necked flask and reacted for 18 hours under reflux. As a result, there was no precipitate, and a uniform dark brown solution was obtained. When the solvent was distilled off and the solution was treated, a black solid was obtained, but the desired Ir complex could not be confirmed.

(1.2) Fluorescent Dopant As the fluorescent dopant, a coumarin dye, a pyran dye, a cyanine dye, a croconium dye, a squarylium dye, an oxobenzanthracene dye, a fluorescein dye, a rhodamine dye, a pyrylium dye, Examples thereof include perylene-based dyes, stilbene-based dyes, polythiophene-based dyes, rare earth complex-based phosphors, and the like, and compounds having a high fluorescence quantum yield typified by laser dyes.

[Combination with a conventionally known dopant]
Further, as the light emitting dopant used in the present invention, a plurality of kinds of compounds may be used in combination, phosphorescent dopants having different structures may be used in combination, or phosphorescent dopant and fluorescent dopant may be used in combination.
Here, as the light emitting dopant, a conventionally known light emitting dopant may be used in combination with the iridium complex of the present invention. Specifically, the compounds described in WO 2013/061850 can be preferably used, but the present invention is not limited thereto.

[Host compound]
The host compound (also referred to as a light-emitting host or a light-emitting host compound) that can be used in the present invention has a mass ratio of 20% or more in the compound contained in the light-emitting layer and at room temperature ( A compound having a phosphorescence quantum yield of phosphorescence emission at 25 ° C. of less than 0.1 is defined. The phosphorescence quantum yield is preferably less than 0.01. Further, among the compounds contained in the light emitting layer, the mass ratio in the layer is preferably 20% or more.

  The host compound that can be used in the present invention is not particularly limited, and compounds conventionally used in organic EL devices can be used. Typically, those having a basic skeleton such as a carbazole derivative, a triarylamine derivative, an aromatic derivative, a nitrogen-containing heterocyclic compound, a thiophene derivative, a furan derivative, an oligoarylene compound, or a carboline derivative or a diazacarbazole derivative (here In addition, the diazacarbazole derivative means that at least one carbon atom of the hydrocarbon ring constituting the carboline ring of the carboline derivative is substituted with a nitrogen atom).

As a known host compound that can be used in the present invention, a compound having a hole transporting ability and an electron transporting ability, preventing a long wavelength emission, and having a high Tg (glass transition temperature) is preferable.
In the present invention, conventionally known host compounds may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the transfer of charges and improve the efficiency of the organic EL device. Further, by using a plurality of kinds of the iridium complex of the present invention used as the phosphorescent dopant and / or a conventionally known compound, it is possible to mix different light emissions, and thereby an arbitrary emission color can be obtained.

  The host compound used in the present invention may be a low molecular compound, a high molecular compound having a repeating unit, or a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (polymerizable host compound). Of course, one or more such compounds may be used.

Specific examples of known host compounds include compounds described in the following documents.
JP-A-2001-257076, JP-A-2002-308855, JP-A-2001-313179, JP-A-2002-319491, JP-A-2001-357977, JP-A-2002-334786, and JP-A-2002-8860, No. 2002-334787, No. 2002-15871, No. 2002-334788, No. 2002-43056, No. 2002-334789, No. 2002-75645, No. 2002-338579, No. No. 2002-105445, No. 2002-343568, No. 2002-141173, No. 2002-352957, No. 2002-203683, No. 2002-363227, No. 2002-231453, No. No. 003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-260861, No. 2002-280183, No. 2002-299060, No. 2002. -302516, 2002-305083, 2002-305084, 2002-308837, etc.

  Hereinafter, specific examples used as the host compound of the light emitting layer of the organic EL device of the present invention will be described, but the present invention is not limited thereto. In addition, it is preferable that the host compounds shown below further have a substituent to the extent that the function is not impaired.

<Electron transport layer>
The electron transport layer is made of a material having a function of transporting electrons, and includes, in a broad sense, an electron injection layer and a hole blocking layer. The electron transport layer may be a single layer or a plurality of layers.
The electron-transporting layer may have a function of transmitting electrons injected from the cathode to the light-emitting layer, and as the constituent material of the electron-transporting layer, any one of conventionally known compounds may be selected and used in combination. It is possible.

Examples of conventionally known materials used for the electron transport layer (hereinafter referred to as electron transport materials) include polycyclic aromatic hydrocarbons such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, and naphthaleneperylene. Heterocyclic tetracarboxylic acid anhydride, carbodiimide, fluorenylidene methane derivative, anthraquinodimethane and anthrone derivative, oxadiazole derivative, carboline derivative, or a carbon atom of the hydrocarbon ring constituting the carboline ring of the carboline derivative Examples thereof include a derivative having a ring structure in which at least one is substituted with a nitrogen atom, and a hexaazatriphenylene derivative.
Furthermore, in the oxadiazole derivative, a thiadiazole derivative in which an oxygen atom of the oxadiazole ring is substituted with a sulfur atom, or a quinoxaline derivative having a quinoxaline ring known as an electron-withdrawing group can be used as an electron transporting material.
It is also possible to use a polymer material in which these materials are introduced into the polymer chain, or where these materials are used as the polymer main chain.

Further, metal complexes of 8-quinolinol derivatives, for example, tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum. , Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and the central metal of these metal complexes is In, Mg, A metal complex in which Cu, Ca, Sn, Ga or Pb is replaced can also be used as the electron transport material.
In addition, metal-free or metal phthalocyanine, or those whose terminal is substituted with an alkyl group, a sulfonic acid group, or the like can be used as the electron transport material.
Further, an inorganic semiconductor such as n-type-Si or n-type-SiC can also be used as the electron transport material.

  The electron transport layer is made of an electron transport material, for example, a vacuum deposition method, a wet method (also called a wet process, for example, a spin coating method, a casting method, a die coating method, a blade coating method, a roll coating method, an inkjet method, a printing method, a spray method. It is preferably formed by forming a thin film by a coating method, a curtain coating method, an LB method (including a Langmuir Blodgett method).

The layer thickness of the electron transport layer is not particularly limited, but is usually about 5 to 5000 nm, preferably 5 to 200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials.
Further, an n-type dopant such as a metal compound such as a metal complex or a metal halide may be doped and used.

  The compounds described in International Publication No. 2013/061850 can be preferably used as an example of a conventionally known electron transport material that is preferably used for forming the electron transport layer of the organic EL device of the present invention. Not limited to.

"cathode"
On the other hand, as the cathode, a material having a low work function (4 eV or less) (referred to as an electron injecting metal), an alloy, an electrically conductive compound, or a mixture thereof as an electrode material is used. Specific examples of such an electrode material include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O 3). ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Of these, a mixture of an electron-injecting metal and a second metal which is a stable metal having a larger work function than that of the electron-injecting metal, such as a magnesium / silver mixture, from the viewpoint of electron injecting property and durability against oxidation and the like. A magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like are suitable.

The cathode can be produced by forming a thin film of these electrode substances by a method such as vapor deposition or sputtering. The sheet resistance of the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.
Since the emitted light is transmitted, if either the anode or the cathode of the organic EL element is transparent or semi-transparent, the emission brightness is improved, which is convenient.
In addition, a transparent or semi-transparent cathode can be produced by producing the above-mentioned metal in a thickness of 1 to 20 nm on the cathode and then producing a conductive transparent material to be mentioned later in the explanation of the anode thereon. By applying this, an element in which both the anode and the cathode are transparent can be manufactured.

<< Injection layer: electron injection layer (cathode buffer layer), hole injection layer >>
The injection layer is provided as necessary, and has an electron injection layer and a hole injection layer, and is present between the anode and the light emitting layer or the hole transport layer and between the cathode and the light emitting layer or the electron transport layer as described above. You may let me.
The injection layer is a layer provided between the electrode and the organic layer for the purpose of lowering the driving voltage and improving the light emission brightness. “The organic EL element and its industrial front line (published on November 30, 1998 by NTS Inc.) ) ”, Chapter 2,“ Electrode Materials ”(Pages 123 to 166), Volume 2, and includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer).

  The details of the anode buffer layer (hole injection layer) are also described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Representative phthalocyanine buffer layer, hexaazatriphenylene derivative buffer layer, oxide buffer layer represented by vanadium oxide, amorphous carbon as described in JP-A-2003-159432 and JP-A-2006-135145. Examples thereof include a buffer layer, a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) and polythiophene, and an orthometallated complex layer represented by a tris (2-phenylpyridine) iridium complex.

  Details of the cathode buffer layer (electron injection layer) are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like, and specifically, strontium, aluminum, and the like. Typified by a metal buffer layer, lithium fluoride, an alkali metal compound buffer layer typified by potassium fluoride, magnesium fluoride, an alkaline earth metal compound buffer layer typified by cesium fluoride, typified by aluminum oxide An oxide buffer layer etc. are mentioned. The buffer layer (injection layer) is preferably a very thin film, and its thickness is preferably in the range of 0.1 nm to 5 μm, although it depends on the material.

<< Blocking layer: hole blocking layer, electron blocking layer >>
The blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film as described above. For example, it is described in JP-A Nos. 11-204258, 11-204359, and "237, etc." of "organic EL element and its frontier of industrialization (published on November 30, 1998, NTS Corporation)". There is a hole blocking (hole blocking) layer.

The hole-blocking layer has a function of an electron-transporting layer in a broad sense, and is made of a hole-blocking material having a function of transporting electrons while having a significantly small ability to transport holes. By blocking the above, the recombination probability of electrons and holes can be improved.
Further, the structure of the electron transport layer described above can be used as a hole blocking layer, if necessary.
The hole blocking layer of the organic EL device of the present invention is preferably provided adjacent to the light emitting layer.
In the hole blocking layer, a carbazole derivative, a carboline derivative, and a diazacarbazole derivative (wherein one of the carbon atoms constituting the carboline ring is a nitrogen atom) mentioned above as the host compound. It means that it is replaced by the above).

On the other hand, the electron blocking layer has a function of a hole transport layer in a broad sense, and is made of a material having a function of transporting holes and a significantly low ability to transport electrons, and transports holes while transporting electrons. By blocking, the recombination probability of electrons and holes can be improved.
Further, the structure of the hole transport layer described later can be used as the electron blocking layer, if necessary. The layer thickness of the hole blocking layer and the electron transport layer according to the present invention is preferably 3 to 100 nm, more preferably 5 to 30 nm.

<< Hole transport layer >>
The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, the hole injection layer and the electron blocking layer are also included in the hole transport layer. The hole transport layer may be a single layer or a plurality of layers.
The hole transport material has any of hole injection or transport and electron barrier properties, and may be an organic substance or an inorganic substance. For example, triazole derivative, oxadiazole derivative, imidazole derivative, polyarylalkane derivative, pyrazoline derivative and pyrazolone derivative, phenylenediamine derivative, arylamine derivative, amino-substituted chalcone derivative, oxazole derivative, styrylanthracene derivative, fluorenone derivative, hydrazone derivative, Examples thereof include stilbene derivatives, silazane derivatives, aniline-based copolymers, conductive polymer oligomers, especially thiophene oligomers.
Further, an azatriphenylene derivative as described in JP-B-2003-515432, JP-A-2006-135145, etc. can also be used as a hole transporting material.

Although the above-mentioned materials can be used as the hole-transporting material, it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound.
Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ', N'-tetraphenyl-4,4'-diaminophenyl; N, N'-diphenyl-N, N'- Bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ', N'-tetra-p-tolyl-4,4'-diaminobiphenyl; 1,1-bis (4-di-p-tolyl) Aminophenyl) -4-phenylcyclohexane; Bis (4-dimethylamino-2-methylphenyl) phenylmethane; Bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' − (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbene; N-phenylcarbazole, and two fused aromatic rings described in US Pat. No. 5,061,569. Those having in the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-308688 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (MTDATA) in which the triphenylamine units described in 3) are linked in a three star burst type. Is mentioned.

Further, it is also possible to use a polymer material in which these materials are introduced into the polymer chain or where these materials are used as the polymer main chain.
Inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injecting material and the hole transporting material.

  Further, JP-A No. 11-251067, J. Huang et. al. It is also possible to use a so-called p-type hole transport material as described in the literature (Applied Physics Letters 80 (2002), p.139). In the present invention, it is preferable to use these materials because a light emitting device with higher efficiency can be obtained.

The hole transport layer can be formed by thinning the above hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an inkjet method, and an LB method. it can.
The thickness of the hole transport layer is not particularly limited, but is usually about 5 nm to 5 μm, preferably 5 to 200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

Further, a hole transport layer having a high p property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140 and JP-A-2001-102175, and J. Appl. Phys. , 95, 5773 (2004) and the like.
In the present invention, it is preferable to use such a hole transporting layer having a high p property because a device with lower power consumption can be manufactured.

"anode"
As the anode in the organic EL element, those having an electrode substance of a metal, an alloy, an electrically conductive compound and a mixture thereof having a large work function (4 eV or more) are preferably used. Specific examples of such an electrode material include a metal such as Au, and a conductive transparent material such as CuI, ITO, SnO ₂ , and ZnO.
Alternatively, a material such as IDIXO (In ₂ O ₃ —ZnO) that can form an amorphous transparent conductive film may be used. The anode may be formed into a thin film by a method such as vapor deposition or sputtering of these electrode substances, and a pattern of a desired shape may be formed by a photolithography method, or when pattern precision is not required so much (about 100 μm or more). Alternatively, a pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode substance.

  Alternatively, when a coatable substance such as an organic conductive compound is used, a wet film forming method such as a printing method or a coating method can be used. When the emitted light is taken out from this anode, it is desirable that the transmittance is greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

《Supporting substrate》
The supporting substrate (hereinafter, also referred to as a substrate, a substrate, a substrate, a support, etc.) that can be used in the organic EL device of the present invention is not particularly limited in the kind of glass, plastic, etc., and is transparent. Or it may be opaque. When extracting light from the supporting substrate side, the supporting substrate is preferably transparent. Examples of transparent support substrates that are preferably used include glass, quartz, and transparent resin films. A particularly preferable support substrate is a resin film that can give flexibility to the organic EL element.

  Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, cellulose acetate propionate ( CAP), cellulose acetate phthalate, cellulose esters such as cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyether sulfone (PES), polyphenylene sulfide, polysulfones, Cycloolefin resins such as polyetherimide, polyetherketone imide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylate, Arton (product name JSR) or Apel (product name Mitsui Chemicals) The film of can be mentioned.

On the surface of the resin film, an inorganic film, an organic film, or a hybrid film of both of them may be formed, and the water vapor permeability (25 ± 0.5 ° C.) measured by the method according to JIS K 7129-1992. , Relative humidity (90 ± 2)%) is preferably a barrier film of 0.01 g / m ² · 24 h or less, and further, the oxygen permeability measured by the method according to JIS K 7126-1987. It is preferable that the film has a high barrier property of 1 × 10 ⁻³ ml / m ² · 24 h · atm or less and a water vapor permeability of 1 × 10 ⁻⁵ g / m ² · 24 h or less.

  As a material for forming the barrier layer, any material may be used as long as it has a function of suppressing entry of moisture or oxygen, which causes deterioration of the element, but may be, for example, silicon oxide, silicon dioxide, silicon nitride or the like. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and a layer made of an organic material. The order of laminating the inorganic layer and the organic layer is not particularly limited, but it is preferable to alternately laminate the both layers a plurality of times.

The method for forming the barrier layer is not particularly limited, and examples thereof include vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma polymerization method. The plasma CVD method, the laser CVD method, the thermal CVD method, the coating method and the like can be used, but the method by the atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.
Examples of the opaque support substrate include metal plates such as aluminum and stainless steel, films and opaque resin substrates, and ceramic substrates.

The external extraction yield of light emission of the organic EL device of the present invention at room temperature is preferably 1% or more, and more preferably 5% or more.
Here, the external extraction quantum yield (%) = the number of photons emitted outside the organic EL element / the number of electrons flown into the organic EL element × 100.
Further, a hue improving filter such as a color filter or the like may be used together, or a color conversion filter for converting the emission color from the organic EL element into multiple colors by using a phosphor may be used together. When a color conversion filter is used, the λmax of light emitted from the organic EL element is preferably 480 nm or less.

<< Method of manufacturing organic EL device >>
As an example of a method for manufacturing an organic EL element, a method for manufacturing an element consisting of anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer (electron injection layer) / cathode Will be described.
First, a thin film made of a desired electrode material, for example, a material for an anode, is formed on a suitable substrate so as to have a film thickness of 1 μm or less, preferably 10 to 200 nm, to manufacture an anode.
Then, a thin film containing an organic compound such as a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron transport layer, a cathode buffer layer, which is a device material, is formed thereon.

As a method of forming the thin film, for example, a vacuum deposition method, a wet method (also referred to as a wet process), or the like can be used to form the film.
Wet methods include spin coating method, casting method, die coating method, blade coating method, roll coating method, ink jet method, printing method, spray coating method, curtain coating method and LB method, but a precise thin film can be formed. From the viewpoint of high productivity, die-coating method, roll-coating method, inkjet method, spray-coating method, and the like, which are highly suitable for roll-to-roll method, are preferable. Further, a different film forming method may be applied for each layer.

As a liquid medium for dissolving or dispersing an organic EL material such as a light emitting dopant used in the present invention, for example, methyl ethyl ketone, ketones such as cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, Aromatic hydrocarbons such as toluene, xylene, mesitylene and cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin and dodecane, organic solvents such as dimethylformamide (DMF) and DMSO can be used.
In addition, as a dispersion method, it is possible to disperse by a dispersion method such as ultrasonic wave, high shearing force dispersion or media dispersion.

After forming these layers, a thin film made of a substance for cathode is formed thereon to have a film thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided to obtain a desired organic EL device. .
Further, it is also possible to reverse the order, and manufacture the cathode, the cathode buffer layer, the electron transport layer, the hole blocking layer, the light emitting layer, the hole transport layer, the hole injection layer, and the anode in this order.
In the production of the organic EL device of the present invention, it is preferable to consistently produce from the hole injection layer to the cathode by one vacuum evacuation, but it is also possible to take out in the middle and apply a different film forming method. At that time, it is preferable to carry out the work in a dry inert gas atmosphere.

《Sealing》
Examples of the sealing means used in the present invention include a method of bonding the sealing member, the electrode, and the supporting substrate with an adhesive.
The sealing member may be arranged so as to cover the display area of the organic EL element, and may have a concave plate shape or a flat plate shape. Further, transparency and electrical insulation are not particularly limited.

Specific examples include a glass plate, a polymer plate / film, a metal plate / film, and the like. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz.
Further, examples of the polymer plate include those formed from polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, polysulfone and the like.
Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium and tantalum.

In the present invention, a polymer film or a metal film can be preferably used because the device can be thinned.
Furthermore, the polymer film is measured by the oxygen permeability measured by the method based on JIS K 7126-1987 is ^{1 × 10 -3 ml / m 2} · 24h · atm or less, in conformity with JIS K 7129-1992 method The water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)%) is preferably 1 × 10 ⁻³ g / m ² · 24 h or less.
Sandblasting, chemical etching or the like is used to process the sealing member into a concave shape.

  Specific examples of the adhesive include photocurable and thermosetting adhesives having a reactive vinyl group of acrylic acid-based oligomer and methacrylic acid-based oligomer, and moisture-curable adhesives such as 2-cyanoacrylic acid ester. be able to. Further, a heat and chemical curing type (two liquid mixture) such as an epoxy type can be used. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Further, a cation-curing type UV-curing type epoxy resin adhesive can be mentioned.

  Since the organic EL element may be deteriorated by heat treatment, a material that can be adhesively cured from room temperature to 80 ° C. is preferable. A desiccant may be dispersed in the adhesive. The adhesive may be applied to the sealing portion using a commercially available dispenser or may be printed by screen printing.

Further, it is also preferable to coat the electrode and the organic layer on the outside of the electrode facing the support substrate with the organic layer sandwiched therebetween, and form a layer of an inorganic material or an organic material in contact with the support substrate to form a sealing film. . In this case, as the material for forming the film, any material may be used as long as it has a function of suppressing entry of water or oxygen, which causes deterioration of the element, and for example, silicon oxide, silicon dioxide, silicon nitride or the like is used. it can.
Further, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of an organic material. The method for forming these films is not particularly limited, and examples thereof include vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma. A polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

In the gap between the sealing member and the display region of the organic EL element, an inert gas such as nitrogen or argon or an inert liquid such as fluorocarbon or silicon oil may be injected in the vapor phase and the liquid phase. preferable. A vacuum can also be used. Also, a hygroscopic compound can be enclosed inside.
Examples of the hygroscopic compound include metal oxides (eg, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide), sulfates (eg, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Etc.), metal halides (eg, calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide, etc.), perchloric acids (eg, perchloric acid) Barium, magnesium perchlorate, etc.) and the like, and anhydrous salts are suitably used for sulfates, metal halides and perchloric acids.

《Protective film, protective plate》
A protective film or a protective plate may be provided outside the encapsulating film or the encapsulating film on the side facing the support substrate with the organic layer sandwiched therebetween in order to enhance the mechanical strength of the device. In particular, when the sealing is performed by the sealing film, the mechanical strength thereof is not necessarily high. Therefore, it is preferable to provide such a protective film or protective plate. As the material that can be used for this, the same glass plate, polymer plate / film, metal plate / film, etc. as those used for the above-mentioned encapsulation can be used, but the polymer film is lightweight and thin. Is preferably used.

<< light extraction >>
The organic EL element emits light inside a layer having a higher refractive index than air (refractive index of about 1.7 to 2.1), and can extract only about 15 to 20% of the light generated in the light emitting layer. Is generally said. This is because light incident on the interface (interface between the transparent substrate and air) at an angle θ equal to or greater than the critical angle causes total reflection and cannot be extracted to the outside of the device. This is because the light undergoes total reflection between them, and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes toward the side surface of the element.

  As a method of improving the efficiency of extracting light, for example, a method of forming irregularities on the surface of a transparent substrate to prevent total reflection at the interface between the transparent substrate and the air (US Pat. No. 4,774,435), and condensing on the substrate To improve efficiency (Japanese Patent Application Laid-Open No. 63-314795), a method of forming a reflective surface on the side surface of the device (Japanese Patent Application Laid-Open No. 1-220394), and between the substrate and the light-emitting body. A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index (Japanese Patent Laid-Open No. 62-172691), and introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter. Method (Japanese Unexamined Patent Publication No. 2001-202827), method of forming a diffraction grating between any one of a substrate, a transparent electrode layer, and a light emitting layer (including between the substrate and the outside) (Japanese Unexamined Patent Publication No. 11-283751). There is.

In the present invention, these methods can be used in combination with the organic EL device of the present invention, but a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitting body, or the substrate, the transparent A method of forming a diffraction grating between any of the electrode layers and the light emitting layer (including between the substrate and the outside) can be preferably used.
In the present invention, by combining these means, it is possible to obtain an element having higher brightness or durability.

When a medium with a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness that is longer than the wavelength of light, the light emitted from the transparent electrode becomes more efficiently extracted to the outside as the refractive index of the medium becomes lower. .
Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and fluoropolymer. Since the transparent substrate generally has a refractive index of about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less. Further, it is preferably 1.35 or less.
Further, it is desirable that the thickness of the low refractive index medium is twice or more the wavelength in the medium. This is because when the thickness of the low-refractive index medium becomes about the wavelength of light and the electromagnetic wave exuded by evanescent enters the substrate, the effect of the low-refractive index layer is diminished.

  The method of introducing a diffraction grating into the interface that causes total reflection or into any medium is characterized by a high effect of improving the light extraction efficiency. This method utilizes the property that the diffraction grating can change the direction of light to a specific direction different from refraction by so-called Bragg diffraction such as first-order diffraction and second-order diffraction, and Light that cannot be emitted due to total internal reflection between layers is diffracted by introducing a diffraction grating into one of the layers or into the medium (in the transparent substrate or transparent electrode), and the light is emitted to the outside. It is the one that is going to be taken out.

The diffraction grating to be introduced preferably has a two-dimensional periodic refractive index. This is because light emitted from the light emitting layer is randomly generated in all directions, so a general one-dimensional diffraction grating that has a periodic refractive index distribution only in a certain direction diffracts only light traveling in a specific direction. Therefore, the light extraction efficiency does not increase so much.
However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and the light extraction efficiency is improved.

As described above, the position where the diffraction grating is introduced may be between any layers or in the medium (in the transparent substrate or in the transparent electrode), but it is desirable to be near the organic light emitting layer where light is generated.
At this time, the period of the diffraction grating is preferably about 1/2 to 3 times the wavelength of the light in the medium.
The array of diffraction gratings is preferably a two-dimensional array such as a square lattice shape, a triangular lattice shape, or a honeycomb lattice shape.

《Condensing sheet》
The organic EL element of the present invention is processed on the light extraction side of the substrate, for example, so as to have a microlens array-like structure, or is combined with a so-called light-condensing sheet, so that the organic EL element has a specific direction, for example, a light-emitting surface of the element. By condensing light in the front direction, the brightness in the specific direction can be increased.
As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. The side is preferably 10 to 100 μm. If it is smaller than this, the effect of diffraction occurs and it is colored.

As the light-condensing sheet, it is possible to use, for example, one that has been put to practical use in an LED backlight of a liquid crystal display device. As such a sheet, for example, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used.
As the shape of the prism sheet, for example, a Δ-shaped stripe having an apex angle of 90 ° and a pitch of 50 μm may be formed on the base material, or the apex angle may be rounded and the pitch may be randomly changed. It may have a different shape or another shape.
Further, in order to control the light emission angle from the light emitting element, a light diffusing plate / film may be used together with the light collecting sheet. For example, a diffusion film (light up) manufactured by Kimoto Co., Ltd. can be used.

<< Use >>
The organic EL element of the present invention can be used as an electronic device, a display device, a display, and various light emitting devices. Examples of the light-emitting device include lighting devices (home lighting, interior lighting), clocks and liquid crystal backlights, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, and light sources. Examples of the light source include a light source of a sensor, but not limited thereto. In particular, it can be effectively used as a backlight of a liquid crystal display device and a light source for illumination.

  In the organic EL device of the present invention, patterning may be performed by a metal mask, an inkjet printing method, or the like at the time of film formation, if necessary. In the case of patterning, only the electrodes may be patterned, the electrodes and the light emitting layer may be patterned, or the entire layers of the element may be patterned. In the production of the element, a conventionally known method may be used. You can

The emission color of the organic EL device of the present invention or the compound of the present invention is shown in Fig. 7.16 on page 108 of "Handbook of New Color Science" (edited by the Japanese Society of Color Science, Tokyo University Press, 1985). It is determined by the color when the result measured by CS-1000 (manufactured by Konica Minolta Co., Ltd.) is applied to CIE chromaticity coordinates.
When the organic EL element of the present invention is a white element, white means that the chromaticity in the CIE1931 color system at 1000 cd / m ² is X when the 2 ° viewing angle front luminance is measured by the above method. = 0.33 ± 0.07, Y = 0.33 ± 0.1.

《Display device》
The display device of the present invention will be described. The display device of the present invention comprises the organic EL element of the present invention. Although the display device of the present invention may be monochromatic or multicolored, a multicolor display device will be described here.
In the case of a multicolor display device, a shadow mask is provided only when the light emitting layer is formed, and a film can be formed on one surface by a vapor deposition method, a casting method, a spin coating method, an inkjet method, a printing method, or the like.
When patterning only the light emitting layer, the method is not limited, but the vapor deposition method, the inkjet method, the spin coating method, and the printing method are preferable.

The configuration of the organic EL element included in the display device is selected from the above-described configuration examples of the organic EL element as needed.
The method of manufacturing the organic EL element is as shown in the above-described one aspect of manufacturing the organic EL element of the present invention.
When a direct current voltage is applied to the thus obtained multicolor display device, light emission can be observed by applying a voltage of about 2 to 40 V with the anode having a positive polarity and the cathode having a negative polarity. Moreover, even if a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the − state. The waveform of the alternating current applied may be arbitrary.

The multicolor display device can be used as a display device, a display, and various light emitting light sources. In the display device and the display, full-color display is possible by using three kinds of organic EL elements of blue, red, and green light emission.
Examples of the display device and display include a television, a personal computer, a mobile device, an AV device, a teletext display, and an information display in a car. In particular, it may be used as a display device for reproducing a still image or a moving image, and a driving system for use as a display device for reproducing a moving image may be either a simple matrix (passive matrix) system or an active matrix system.
Light sources include home lighting, interior lighting, backlights for watches and liquid crystals, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. However, the present invention is not limited thereto.

Hereinafter, an example of a display device having the organic EL element of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an example of a display device including an organic EL element. It is a schematic diagram of a display such as a mobile phone, which displays image information by light emission of an organic EL element.

The display 1 has a display section A having a plurality of pixels, a control section B that performs image scanning of the display section A based on image information, a wiring section C that electrically connects the display section A and the control section B, and the like.
The control unit B is electrically connected to the display unit A via the wiring unit C, sends a scanning signal and an image data signal to each of a plurality of pixels based on image information from the outside, and the pixels for each scanning line by the scanning signal. Emits light sequentially according to the image data signal to perform image scanning and display image information on the display unit A.

FIG. 2 is a schematic diagram of a display device of the active matrix system.
The display section A has a wiring section C including a plurality of scanning lines 5 and data lines 6, a plurality of pixels 3 and the like on a substrate. The main members of the display unit A will be described below.
In FIG. 2, the light emitted from the pixel 3 (emitted light L) is extracted in the direction of the white arrow (downward).

The scanning lines 5 and the plurality of data lines 6 in the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a grid pattern and are connected to the pixels 3 at the orthogonal positions (details are shown in the drawings). Not).
When a scanning signal is applied from the scanning line 5, the pixel 3 receives an image data signal from the data line 6 and emits light according to the received image data.
Full color display is possible by appropriately arranging pixels in the red region, pixels in the green region, and pixels in the blue region in the same color on the same substrate.

Next, the light emitting process of the pixel will be described. FIG. 3 is a schematic diagram showing a pixel circuit.
The pixel includes an organic EL element 10, a switching transistor 11, a drive transistor 12, a capacitor 13 and the like. Full-color display can be performed by using red, green, and blue light-emitting organic EL elements as the organic EL element 10 for a plurality of pixels and arranging them in parallel on the same substrate.

  In FIG. 3, an image data signal is applied from the control unit B to the drain of the switching transistor 11 via the data line 6. When a scanning signal is applied from the control unit B to the gate of the switching transistor 11 via the scanning line 5, the driving of the switching transistor 11 is turned on, and the image data signal applied to the drain of the switching transistor 11 is transferred to the capacitor 13 and the driving transistor 12. Is transmitted to the gate.

  By transmitting the image data signal, the capacitor 13 is charged according to the potential of the image data signal, and the driving of the drive transistor 12 is turned on. The drive transistor 12 has a drain connected to the power supply line 7 and a source connected to the electrode of the organic EL element 10. The drive transistor 12 is connected from the power supply line 7 to the organic EL element 10 according to the potential of the image data signal applied to the gate. Electric current is supplied.

When the scanning signal is transferred to the next scanning line 5 by the sequential scanning of the control unit B, the driving of the switching transistor 11 is turned off. However, even if the driving of the switching transistor 11 is turned off, the capacitor 13 holds the potential of the charged image data signal, so that the driving of the driving transistor 12 is kept on and the next scanning signal is applied. The organic EL element 10 continues to emit light. When a scanning signal is applied next by sequential scanning, the driving transistor 12 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 10 emits light.
That is, the light emission of the organic EL element 10 is such that the switching transistor 11 and the drive transistor 12 which are active elements are provided for the organic EL element 10 of each of the plurality of pixels, and the organic EL element 10 of each of the plurality of pixels 3 emits light. It is carried out. Such a light emitting method is called an active matrix method.

Here, the light emission of the organic EL element 10 may be light emission of a plurality of gradations by a multi-valued image data signal having a plurality of gradation potentials, or may be ON or OFF of a predetermined light emission amount by a binary image data signal. Good. The potential of the capacitor 13 may be held continuously until the next scan signal is applied, or may be discharged immediately before the next scan signal is applied.
The present invention is not limited to the active matrix system described above, but may be a passive matrix system light emission drive in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.

FIG. 4 is a schematic diagram of a display device of a passive matrix system. In FIG. 4, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a lattice pattern so as to face each other with the pixel 3 interposed therebetween.
When the scanning signal of the scanning line 5 is applied by sequential scanning, the pixels 3 connected to the applied scanning line 5 emit light according to the image data signal.
In the passive matrix system, the pixel 3 has no active element, and the manufacturing cost can be reduced.
By using the organic EL element of the present invention, a display device having improved luminous efficiency was obtained.

<Lighting device>
The organic EL element of the present invention can also be used in a lighting device.
The organic EL element of the present invention may be used as an organic EL element having a resonator structure. Examples of the purpose of using the organic EL element having such a resonator structure include a light source for an optical storage medium, a light source for an electrophotographic copying machine, a light source for an optical communication processor, a light source for an optical sensor, and the like. Not limited. Moreover, you may use it for the said use by making a laser oscillation.
Further, the organic EL element of the present invention may be used as a kind of lamp for illumination or as an exposure light source, or may be of a projection device for projecting an image, or of a type for directly visually recognizing a still image or a moving image. It may be used as a display device (display).
When used as a display device for moving image reproduction, either a passive matrix system or an active matrix system may be used as a drive system. Alternatively, a full-color display device can be manufactured by using two or more kinds of organic EL elements of the present invention having different emission colors.

  Further, the luminescent compound of the present invention can be applied to an organic EL element that emits substantially white light as a lighting device. For example, when a plurality of light emitting materials are used, white light emission can be obtained by simultaneously emitting a plurality of light emitting colors and mixing the colors. As a combination of a plurality of emission colors, it may contain three emission maximum wavelengths of three primary colors of red, green and blue, or two emission utilizing the relationship of complementary colors such as blue and yellow, blue green and orange. It may contain a maximum wavelength.

Further, in the method for forming an organic EL element of the present invention, a mask is provided only when the light emitting layer, the hole transporting layer, the electron transporting layer and the like are formed, and it is only necessary to simply arrange the masks such that they are separately coated. Since the other layers are common, patterning such as a mask is unnecessary, and for example, an electrode film can be formed on one surface by a vapor deposition method, a casting method, a spin coating method, an inkjet method, a printing method, or the like, and productivity is improved.
According to this method, unlike a white organic EL device in which light emitting elements of a plurality of colors are arranged in parallel in an array, the element itself emits white light.

[One Embodiment of Lighting Device of the Present Invention]
An aspect of the lighting device of the present invention, which includes the organic EL element of the present invention, will be described.
The non-light-emitting surface of the organic EL device of the present invention is covered with a glass case, a glass substrate having a thickness of 300 μm is used as a sealing substrate, and an epoxy photocurable adhesive (Lux manufactured by Toagosei Co., Ltd. is used as a sealing material around the periphery. Track LC0629B) is applied, this is overlaid on the cathode and brought into close contact with the transparent support substrate, and UV light is irradiated from the glass substrate side to cure and seal the illumination as shown in FIGS. 5 and 6. A device can be formed.
FIG. 5 shows a schematic view of a lighting device. The organic EL element of the present invention (organic EL element 101 in the lighting device) is covered with a glass cover 102 (note that the sealing work with the glass cover is performed by lighting The organic EL element 101 in the apparatus was placed in a glove box (under a high-purity nitrogen gas atmosphere with a purity of 99.999% or more) under a nitrogen atmosphere without contacting the atmosphere.
FIG. 6 shows a cross-sectional view of the lighting device. In FIG. 6, 105 is a cathode, 106 is an organic layer, and 107 is a glass substrate with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108 and is provided with a water catching agent 109.
By using the organic EL element of the present invention, a lighting device having improved luminous efficiency was obtained.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.
After patterning was performed on a substrate (NA45 manufactured by NH Techno Glass Co., Ltd.) in which 100 nm of ITO was formed on a glass substrate of 100 mm × 100 mm × 1.1 mm as an anode, the transparent support substrate provided with this ITO transparent electrode was made of isopropyl alcohol. Ultrasonic cleaning, drying with dry nitrogen gas, and UV ozone cleaning were carried out for 5 minutes.
On this transparent supporting substrate, poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, manufactured by Bayer, Baytron P Al 4083) was diluted to 70% with pure water to obtain 3000 rpm, After forming a thin film by a spin coating method under the condition of 30 seconds, it was dried at 200 ° C. for 1 hour to provide a first hole transport layer having a layer thickness of 20 nm.

This transparent support substrate was fixed to a substrate holder of a commercially available vacuum evaporation system, while α-NPD (N, N'-Diphenyl-N, N'-bis (1-naphthalenyl) -1,1 was placed on a molybdenum resistance heating boat. 200 mg of ′ -biphenyl-4,4′-diamine), 200 mg of the host compound OC-4 in another resistance heating boat made of molybdenum, and 200 mg of the dopant (comparative compound 1) in another resistance heating boat made of molybdenum, In another resistance heating boat made of molybdenum, 200 mg of BCP (2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline) was put and attached to a vacuum vapor deposition apparatus.
Then, the vacuum tank was depressurized to 4 × 10 ⁻⁴ Pa, and the heating boat containing α-NPD was energized and heated, and vapor deposition was performed on the hole injection layer at a vapor deposition rate of 0.1 nm / sec. The hole transport layer of

Further, the heating boat containing the host compound OC-4 and the heating boat containing the comparative compound 1 are energized and heated, and the hole transport layer is formed at vapor deposition rates of 0.1 nm / sec and 0.010 nm / sec, respectively. It was co-deposited on the top to provide a 40 nm light emitting layer.
Further, the heating boat containing BCP was energized and heated, and vapor deposition was performed on the hole blocking layer at a vapor deposition rate of 0.1 nm / sec to provide an electron transport layer of 30 nm.
Subsequently, 0.5 nm of lithium fluoride was vapor-deposited as a cathode buffer layer, and further 110 nm of aluminum was vapor-deposited to form a cathode, thereby producing an organic EL element 1-1.

<< Fabrication of Organic EL Elements 1-2 to 1-20 >>
In the production of the organic EL device 1-1, the host compound and the dopant in the light emitting layer were changed to the compounds shown in Table 2.
Other than that was carried out similarly, and each produced organic EL element 1-2 to 1-20.

<< Evaluation of Organic EL Elements 1-1 to 1-20 >>
Calculation of the internal quantum efficiency (%) of the iridium complex (dopant) was performed based on the following method.

[Calculation of internal quantum efficiency (IQE)]
Specifically, when the organic EL element 1-1 is driven at 5 V, the external extraction efficiency (EQE) at room temperature is measured by an integrating sphere using an external quantum efficiency measuring device C9920-12 (manufactured by Hamamatsu Photonics KK). It was measured.
Then, using the layer thickness information and the optical constants of the light emitting layer of the organic EL element 1-1, a mode analysis is carried out by "analysis software Setfos (manufactured by Cybernet System Co., Ltd.)" to change the inside of the organic EL element to the outside of the element. The ratio of the emitted light, that is, the light extraction efficiency (OC) was calculated.

The external quantum efficiency (EQE) can be expressed by the product of the internal quantum efficiency (IQE) and the light extraction efficiency (OC) (see formula (A)).
Formula (A): EQE = IQE × OC
In the present invention, EQE and OC obtained by measurement and analysis were applied to the formula (A) to calculate the internal quantum efficiency of the light emitting material of the organic EL element 1-1. The internal quantum efficiencies of the organic EL elements 1-2 to 1-20 were calculated in the same manner. Table 2 shows the relative value when the internal quantum efficiency of the organic EL element 1-1 is 100.
Table 2 shows that the organic EL device using the iridium complex of the present invention has higher internal quantum efficiency (light emission efficiency) than the organic EL device of Comparative Example.

[Measurement of Rate of Change of Resistance Value of Light Emitting Layer of Organic EL Element by Impedance Spectroscopy]
The resistance of the light emitting layer of the organic EL element produced by using a Solartron 1260 type impedance analyzer and a 1296 type dielectric interface with reference to the measuring method described in "Thin Film Evaluation Handbook", Techno System Co., Ltd. pp. 423-425. The value was measured.

The organic EL device was driven at room temperature (25 ° C.) under a constant current condition of ^2.5 mA / cm ² for 1000 hours, and the resistance values of the light emitting layer before and after the driving were measured, and the measurement results were calculated using the following formula. Then, the rate of change of the resistance value was calculated. Table 2 shows the relative ratio when the change rate of the resistance value of the organic EL element 1-1 is 100.
Rate of change in resistance value before and after driving = | (resistance value after driving / resistance value before driving) -1 | × 100
The closer the value is to 0, the smaller the change rate before and after driving.
From Table 2, it was found that the organic EL device using the iridium complex of the present invention has a smaller change rate of the resistance value of the light emitting layer and an excellent light emission lifetime than the organic EL device of the comparative example.

  INDUSTRIAL APPLICABILITY The iridium complex of the present invention can be preferably used in the field of organic EL devices, and further, a display device or display equipped with the organic EL device, home lighting, vehicle interior lighting, backlight for watches and liquid crystals. , Signboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, and wide-ranging light sources for general household appliances requiring display devices. Can be suitably used as.

1 Display 3 Pixel 5 Scanning Line 6 Data Line 7 Power Supply Line 10 Organic EL Element 11 Switching Transistor 12 Driving Transistor 13 Capacitor 101 Organic EL Element in Lighting Device 102 Glass Cover 105 Cathode 106 Organic EL Layer 107 Glass Substrate with Transparent Electrode 108 Nitrogen Gas 109 Water catching agent A Display section B Control section C Wiring section L Light emission

Claims (12)

An iridium complex having a bidentate ligand containing an aromatic heterocycle,
The bidentate ligand is a ligand in which the aromatic heterocycle is bonded to another aromatic heterocycle or an aromatic ring by a single bond, and has a hydrogen bond in the ligand. An iridium complex having a structure represented by the following general formula (1).

(In the general formula (1), A ₁ and A ₂ each represent an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle.
X _1a and X _5a each represent a nitrogen atom or a carbon atom.
X ₁ represents a carbon atom, and X ₂ and X ₅ represent a nitrogen atom. The ring formed by X _{1 to} X ₅ represents an imidazole ring which may have a substituent or a triazole ring which may have a substituent.
X ₆ represents an oxygen atom or a sulfur atom. Ra represents a hydrogen atom, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, a heterocyclic group, an alkyl group or a cycloalkyl group. n represents 1 . l represents 1 to 3. m represents 0 to 2. 1 + m = 3. ) The iridium complex according to claim 1, wherein A ₁ in the iridium complex is a benzene ring. An iridium complex having a bidentate ligand containing an aromatic heterocycle,
The bidentate ligand is a ligand in which the aromatic heterocycle is bonded to another aromatic heterocycle or an aromatic ring by a single bond, and has a hydrogen bond in the ligand. An iridium complex having a structure represented by the following general formula (2).

(In the general formula (2), A ₂ represents an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle containing X _1a and X _5a. A ₄ represents X ₆ . Represents an aromatic heterocycle containing.
X _1a and X _5a each represent a nitrogen atom or a carbon atom.
X ₁ represents a carbon atom, and X ₂ and X ₅ represent a nitrogen atom. The ring formed by X _{1 to} X ₅ represents an imidazole ring which may have a substituent or a triazole ring which may have a substituent.
X ₆ represents an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom or a silicon atom. X ₇ and X ₈ represent CRc and N, and Rc represents a hydrogen atom or a substituent. l represents 1 to 3. m represents 0 to 2. 1 + m = 3. ) An iridium complex having a bidentate ligand containing an aromatic heterocycle,
The bidentate ligand is a ligand in which the aromatic heterocycle is bonded to another aromatic heterocycle or an aromatic ring by a single bond, and has a hydrogen bond in the ligand. An iridium complex having a structure represented by the following general formula (3).

(In general formula (3), A ₂ represents an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle.
X _1a and X _5a each represent a nitrogen atom or a carbon atom.
X ₁ represents a carbon atom, and X ₂ and X ₅ represent a nitrogen atom. The ring formed by X _{1 to} X ₅ represents an imidazole ring which may have a substituent or a triazole ring which may have a substituent.
X ₆ represents an oxygen atom or a sulfur atom. Ra represents a hydrogen atom, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, a heterocyclic group, an alkyl group or a cycloalkyl group. R ₁ represents an electron-withdrawing group. n represents 1 . l represents 1 to 3. m represents 0 to 2. 1 + m = 3. ) An iridium complex having a bidentate ligand containing an aromatic heterocycle,
The bidentate ligand is a ligand in which the aromatic heterocycle is bonded to another aromatic heterocycle or an aromatic ring by a single bond, and has a hydrogen bond in the ligand. An iridium complex having a structure represented by the following general formula (4).

(In general formula (4), A ₂ represents an aromatic hydrocarbon ring or an aromatic heterocycle. A ₃ represents an aromatic heterocycle.
X _1a and X _5a each represent a nitrogen atom or a carbon atom.
X ₁ represents a carbon atom, and X ₂ and X ₅ represent a nitrogen atom. The ring formed by X _{1 to} X ₅ represents an imidazole ring which may have a substituent or a triazole ring which may have a substituent.
X ₆ represents an oxygen atom or a sulfur atom. Ra represents a hydrogen atom, an aromatic hydrocarbon ring group, an aromatic heterocyclic group, a heterocyclic group, an alkyl group or a cycloalkyl group. R ₂ represents an electron donating group. n represents 1 . l represents 1 to 3. m represents 0 to 2. 1 + m = 3. ) The dissociation energy of the hydrogen atom which forms the said hydrogen bond is 390 kJ / mol or less, The iridium complex as described in any one of Claim 1- Claim 5 characterized by the above-mentioned. The substituent of the imidazole ring or triazole ring is an alkyl group, an alkoxy group, a halogen atom, a nitro group, a dialkylamino group, a trialkylsilyl group, a triarylsilyl group, a triheteroarylsilyl group, a benzyl group, an aryl group or a hetero group. It is an aryl group, The iridium complex as described in any one of Claim 1 to 6 characterized by the above-mentioned. The iridium complex according to any one of claims 1 to 6 , wherein the substituent of the imidazole ring or the triazole ring is a halogen atom, a cyano group, an alkyl group or an aromatic group. An organic electroluminescent material comprising the iridium complex according to any one of claims 1 to 8 . Between the anode and the cathode, an organic electroluminescent element having at least a light emitting layer,
The said electroluminescent layer contains the organic electroluminescent material of Claim 9 , The organic electroluminescent element characterized by the above-mentioned. A display device comprising the organic electroluminescence element according to claim 10 . An illumination device comprising the organic electroluminescence element according to claim 10 .

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