JP2002194344A - Luminous material, luminous element and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a blue luminous material having excellent thermal stability and long-term stability and a luminous element using the material, to provide a device using the luminous element and to obtain further the luminous element having good color purity without lowering electric current efficiency in a high brightness region and without lowering life characteristics. SOLUTION: This luminous material is a polynuclear metal complex compound having a pyrazabole structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting material, a light emitting element, and an apparatus using the light emitting element.

[0002]

2. Description of the Related Art Organic electroluminescent devices are
The charges (holes and electrons) injected from both the anode and cathode electrodes recombine in the luminous body to generate excitons, and the generated excitons excite the molecules of the luminescent material to emit light. This is a so-called injection type light emitting element, and can be driven at low voltage.

In an organic electroluminescence device, first, an organic thin film has a two-layer structure of a thin film made of a hole transporting material and a thin film made of an electron transporting material. element having an element structure that emits light by where the electrons recombine was developed (Applied Physics Letters, 51, 1987, P.91
3.)

[0004] The hole-transporting material, light emitting material, element having a three-layer structure of the electron transport material has been developed (Japanese J
ournal of Applied Physics, Vol.27, No.2, P.26
9.). In addition, there has been a report of a device in which a light emitting layer is doped with a fluorescent dye to improve the function of the device (Journal of App.
lied Physics, 65, 1989, P.3610., JP-A-63-26
No. 4692). In these reports, a device was prepared in which an organic luminescent layer made of aluminum quinoline was doped with a fluorescent dye such as a coumarin derivative or DCM1, and it was found that the luminescent color was changed by appropriately selecting the dye. further,
It was revealed that the luminous efficiency was also increased as compared with the case of undoping.

[0005] The organic compounds used for the light-emitting material have the advantage that the emission color can be arbitrarily changed by changing the molecular structure theoretically due to the diversity.
Therefore, by performing molecular design, R (red), G (green),
It can be said that it is easy to arrange three colors of B (blue).

The doping method of doping a light emitting layer with a fluorescent pigment or a laser dye as a guest material is a useful method for improving luminous efficiency and improving color purity. However, in the doping method, the guest material emits light by absorbing energy from the host material. The light emission obtained is low in energy, that is, light emission with a long emission wavelength is obtained. In this regard, the doping method is an effective method for obtaining light having a long wavelength such as green or red. However, in order to obtain light having a short wavelength such as blue light emission, there are problems such as a decrease in color purity. Further, the optimum doping concentration in the doping method is usually as low as 0.1% to 1%, and there is a problem that it is difficult to control the concentration.

Furthermore, the blue emission energetically higher,
The load applied to the light emitting material is large. For this reason, the light-emitting material deteriorates quickly and there is a problem in durability.

Further, development of a material having both a charge transport function and a light emitting function as a light emitting material not using a doping method is desired. However, in the materials developed so far, when a fluorescent dye is used at a high concentration, there is a problem that the luminance is reduced due to association of the fluorescent dyes.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a blue light-emitting material having excellent thermal stability and long-term stability, a light-emitting element using the same, and a light-emitting element using the same. An object of the present invention is to provide a device using an element.

It is another object of the present invention to provide a light emitting device which has good color purity, does not decrease current efficiency in a high luminance region, and does not deteriorate its life characteristics.

[0011]

(A) The present invention is based on the finding of a novel blue light emitting material having excellent thermal stability.

The luminescent material of the present invention is a polynuclear metal complex compound having a plurality of boron atoms as central metals. Boron atoms have a small atomic radius. Therefore, the boron atom is strongly bonded to the ligand, and a complex compound that is extremely stable thermally is formed. In particular, even when a polynuclear metal complex compound is deposited on a substrate at a high temperature, the polynuclear metal complex compound of the present invention is stably present. For this reason, the polynuclear metal complex compound of the present invention is particularly preferable as a light emitting material used for an organic EL device.

The present inventors have found that, as a polynuclear metal complex compound having a plurality of boron atoms as central metals, a polynuclear metal complex compound having a pyrazaball structure has excellent electron transporting properties (Japanese Patent Laid-Open No. 2000-3044). No.). The pyrazaball structure refers to a structure in which a conjugated electron is delocalized and a pyrazole ring having strong aromaticity is bonded to a boron atom. By making the nitrogen atom a coordination atom for the boron atom, the pyrazole ring acts as a ligand forming a strong covalent metal chelate bond. As a result, a stable polynuclear metal complex compound is obtained. In addition, polynuclear metal complex compounds such as pyrazaboles often have a complex conformational structure. As a result, the form of polynuclear metal complex compound obtained is often variously molecule is a form aggregated collectively. Therefore, the polynuclear metal complex compound of the present invention is particularly preferable as a constituent material of an organic EL device requiring amorphousness.

As a material having a pyraza ball structure used as an electron transporting material, for example, the following materials are known.

A-1: Pilaza ball

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A-2: 1,3,5,7-tetramethylpyrazaball

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A-3: 4,4,8,8-tetraethylpyrazaball

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A-4: 4,4,8,8-tetrakis (1
H-pyrazol-1-yl) pyrazaball

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These pyrazaball structures emit purple light due to the pyrazole ring. The light emission of the Pilaza ball structure is stable and strong light emission. Generally, the part that participates in light emission in a molecule is a part where π electrons are conjugated. The ligand in the polynuclear metal complex compound includes a bridging ligand bridging and coordinating to a plurality of boron atoms, and a normal ligand coordinating to one boron atom. In the pyrazaball structures A-1 to A-3, the bridging ligand portion serves as a light emitting site.
On the other hand, in the pyrazaball structure of A-4, both the bridging ligand and the ligand have π-conjugated electrons. The absorption and emission of light in organic molecules are mainly HOMO-LU
Caused by electron transition between MO. The molecular orbital calculation was performed on the pyrazaball structure of A-4 in order to determine which of the bridging ligand and the ligand caused the electron transition involved in the light absorption / emission process. A-
In the Pilaza ball structure No. 4, electrons were localized in the bridging ligand portion in both HOMO and LUMO. From this, it was found that the pyrazole ring as the bridging ligand was the light emitting site.

The present inventors have studied the substituents to be introduced into the pyrazole ring, which is a bridging ligand, and have obtained a stable light emitting material which emits strong blue light. That is, the present invention is as follows.

The light emitting material of the present invention is a polynuclear metal complex compound represented by the following general formula (1).

[0022]

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Where R¹, R^Two, R^Three, And R^FourIs the same
May be one or different, each
Having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms,
Good aryl group or nitrogen-containing group which may have substituents
R represents a heterocyclic group;¹And R^TwoAnd / or R^ThreeAnd R^FourIs
Each may bond to form a ring, R^Five, R⁶,
R ⁷, And R⁸Can be the same or different
Each of which has hydrogen and 1 carbon atom which may have a substituent.
-3 alkyl group or a carbon which may have a substituent
It represents an alkylene group of prime 2 or 3, X¹, And X^Two
May be the same, be different well, each location
Aryl group which may have a substituent, or
Represents a nitrogen-containing heterocyclic group which may be substituted. )

Alternatively, a luminescent material is a polynuclear metal complex compound represented by the following general formula (2).

[0025]

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(Wherein R ¹ , R ² , R ³ and R ⁴ may be the same or different and each have a hydrogen atom, an alkyl group having 1 to 5 carbon atoms and a substituent. Represents an aryl group which may be substituted or a nitrogen-containing heterocyclic group which may have a substituent, wherein R ¹ and R ² and / or R ³ and R ⁴ may be bonded to each other to form a ring; R ⁹ and R ¹⁰ may be the same or different, and each has hydrogen, an alkyl group having 1 to 3 carbon atoms which may have a substituent, or a substituent. Represents an alkylene group having 2 or 3 carbon atoms, and X ³ , X ⁴ , X ⁵ , and X ⁶ may be the same or different, and each may have a substituent. It may have an aryl group or a substituted group, a nitrogen-containing heterocyclic group.)

A luminescent material characterized by being a polynuclear metal complex compound represented by the following general formula (3).

[0028]

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Where R¹, R^Two, R^Three, And R^FourIs the same
May be one or different, each
Having 1 to 5 carbon atoms, an alkyl group having 1 to 5 carbon atoms,
Good aryl group or nitrogen-containing group which may have substituents
R represents a heterocyclic group;¹And R^TwoAnd / or R^ThreeAnd R^FourIs
X may be bonded to each other to form a ring;⁷, X⁸,
X ⁹, X^Ten, X¹¹And X¹²Are the same, but different
Each having a hydrogen atom and a substituent.
An alkyl group having 1-3 carbon atoms which may be substituted or substituted
An alkylene group having 2 or 3 carbon atoms which may have a group
And X⁷And X⁸And / or X⁸And X⁹Or X^Ten
And X¹¹And / or X¹¹And X¹²Are each alone,
Or they may be bonded together to form an aromatic ring.
Ku, be further substituent are bonded to each other to form a ring good
No. )

According to these constitutions, a group having π electrons is introduced into the pyrazole ring which is a bridging ligand. As a result, the conjugation of π electrons in the pyrazole ring extends to the substituent, so that the polynuclear metal complex compound of the present invention emits blue light. Furthermore, polynuclear metal complex compound of the present invention has the pyrazabole structure has excellent electron transport ability.

(B) The light-emitting material is, for example, a light-emitting element in which a layer having a light-emitting region is provided between an anode and a cathode, and the layer has the general formula (1) to (3). A light emitting material which is a compound represented may be included.

In the layer having a light emitting region, the above general formula (1)
When the light emitting material is a compound represented by - (3) are included, the light emitting device is obtained which emits blue light excellent in color purity.

The light emitting device is a light emitting device in which a hole transport layer and an electron transport layer are laminated between a cathode and an anode,
The electron transport layer may be a layer having the above-described light emitting region.

Further, the light emitting element may be a light emitting element including a light emitting layer between an anode and a cathode, and the light emitting layer may be a layer having the above light emitting region.

According to such a configuration, the function of the luminescent material of the present invention having an electron transporting ability can be more effectively utilized.

An apparatus using the light emitting element described above is
It can be configured as follows.

An image signal output section for generating an image signal, a drive section for generating a current based on the image signal from the image signal output section, and a light emitting section for emitting light based on the current generated from the drive section. A display device comprising: the light-emitting unit includes at least one light-emitting element;
A light-emitting element including a light-emitting layer between the anode and the cathode,
A display device, wherein the light-emitting layer includes the light-emitting material according to any one of the general formulas (1) to (3).

In this display device, a plurality of light emitting elements may be arranged in a matrix on the substrate.

In this display device, the light emitting element may be formed by laminating on a substrate provided with a thin film transistor for controlling driving of the light emitting element.

[0040] A lighting device comprising: a driving section for generating a current; and a light emitting section for emitting light based on the current generated from the driving section, wherein the light emitting section has at least one light emitting element. emitting element, between an anode and a cathode, a light emitting device including a light-emitting layer, wherein the luminescent layer has a luminescent material according to any one of the above general formula (1) to (3) Lighting equipment.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the drawings.

The light emitting material of the present invention is a polynuclear metal complex compound represented by the following general formula (1).

[0043]

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Where R¹, R^Two, R^Three, And R^FourAre the same
Or may be different, each being a hydrogen atom,
It may have an alkyl group having 1 to 5 carbon atoms and a substituent.
An aryl group or a nitrogen-containing hetero be substituted
A ring group;¹And R^TwoAnd / or R^ThreeAnd R^FourIs it
Each may be bonded to form a ring;^Five, R⁶,
R ⁷, And R⁸Can be the same or different
Each of which has hydrogen and 1 carbon atom which may have a substituent.
-3 alkyl group or a carbon which may have a substituent
It represents an alkylene group of prime 2 or 3, X¹, And X^Two
May be the same, be different well, each location
Aryl group which may have a substituent, or
Represents a nitrogen-containing heterocyclic group which may be substituted.

The alkyl group having 1 to 5 carbon atoms represented by R ¹ , R ² , R ³ and R ⁴ may be linear, branched or cyclic. Specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a tert-butyl group, a pentyl group, a cyclopropyl group, and a cyclopentyl group.

The optionally substituted aryl group represented by R ¹ , R ² , R ³ and R ⁴ is preferably an aryl group having 6 to 20 carbon atoms, particularly preferably an aryl group having 6 to 20 carbon atoms.
To 14 aryl groups. Specifically, a phenyl group, 3
-Methylphenyl group, naphthyl group and the like.

The optionally substituted nitrogen-containing heterocyclic group represented by R ¹ , R ² , R ³ and R ⁴ is preferably a 5- to 10-membered ring containing at least one nitrogen atom. an aromatic heterocyclic group, particularly preferably a 5-membered ring or 6
It is a membered aromatic heterocyclic group. Specific examples of the aromatic heterocycle include those containing one nitrogen atom, such as pyrrole, pyridine, and oxazole, and imidazole, pyrazole, pyridazine, pyrazine, pyrimidine, oxadiazole, triazole, triazine, tetrazine, and tetrazole. And those containing two or more nitrogen atoms.

These aryl groups or nitrogen-containing heterocyclic groups may have a substituent. When the aryl group or the nitrogen-containing heterocyclic group has a substituent, the substituents may be bonded to each other to form a ring.

In the above nitrogen-containing heterocyclic group, when the substituents are bonded to each other to form a ring, another part of the ring may contain another boron atom. Further, this ring may have a pyrazaball structure with a boron atom as a central metal. That is, the light emitting material of the present invention may include two or more pyraza ball structures in one molecule.

The alkyl group having 1 to 3 carbon atoms represented by R ⁵ , R ⁶ , R ⁷ and R ⁸ includes a methyl group, an ethyl group,
Examples thereof include a propyl group and an isopropyl group, and preferably a methyl group and an ethyl group. These alkyl groups may have a substituent. As the substituent, R ¹ ,
R ^2, R ^3, and used in R ^4, include nitrogen-containing heterocyclic group optionally having an optionally substituted aryl group or a substituted group.

Examples of the optionally substituted alkylene group having 2 or 3 carbon atoms represented by R ⁵ , R ⁶ , R ⁷ and R ⁸ include a vinyl group, a 1-propenyl group, an allyl group, An isopropenyl group is mentioned, and a vinyl group is preferable. These alkenyl groups may have a substituent. Examples of the substituent, the ^{R 1, R 2, R 3} , and used in R ^4, include nitrogen-containing heterocyclic group optionally also have an aryl group or a substituent substituted Can be

An aryl group which may have a substituent, an alkylene group which may have a substituent or a nitrogen-containing hetero ring which may have a substituent represented by X ¹ and X ² Examples of the group include aryl groups, alkylene groups, or nitrogen-containing heterocyclic aryl groups represented by R ¹ , R ² , R ³ , and R ⁴ or a nitrogen-containing heterocyclic group which may have a substituent. Can be mentioned.

[0053] X ^1, and as the aryl group which may have a substituent represented by X ^2, preferably 6 carbon atoms
It is an aryl group having 20 and particularly preferably an aryl group having 6 to 14 carbon atoms. Specifically, a phenyl group, a naphthyl group,
And an anthryl group.

In the light emitting material of the present invention, the X group plays an important role for obtaining blue light emission. That is, since the conjugation of the π electron from the pyrazole ring to the X group is widened, the emission wavelength becomes longer. Therefore, the light emitting material of the present invention emits blue light.

When the substituent of the pyrazole ring other than R ¹ , R ² , R ³ and R ⁴ is an alkenyl group, π electrons are easily spread from the pyrazole ring to the alkenyl group.
Easy to emit blue light.

[0056] Another light emitting material of the present invention is a light-emitting material, which is a polynuclear metal complex compound represented by the following general formula (2).

[0057]

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In the formula, R ¹ , R ² , R ³ and R ⁴ may be the same or different and each represents a hydrogen atom,
Represents an alkyl group having 1 to 5 carbon atoms, an aryl group which may have a substituent or a nitrogen-containing heterocyclic group which may have a substituent, and R ¹ and R ² and / or R ³ and R ⁴ may be combined with each other to form a ring, and R ⁹ and R
¹⁰ may be the same or different, and each may be hydrogen, an alkyl group having 1 to 3 carbon atoms which may have a substituent, or 2 carbon atoms which may have a substituent or X ³ , X ⁴ , X ⁵ , and X
⁶ are identical, represent different even if well, which may have a substituent aryl group, or may have a substituent nitrogen-containing heterocyclic group.

R ¹ , R ² , R ³ and R ⁴ are as defined above.

R ⁹ and R ¹⁰ are the same as R ⁵ , R ⁶ , R ⁷ ,
And R ⁸ are synonymous.

X ³ , X ⁴ , X ⁵ , and X ⁶ are the same as X ¹ ,
And X ² .

Still another light emitting material of the present invention is a light emitting material characterized by being a polynuclear metal complex compound represented by the following general formula (3).

[0063]

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Where R¹, R^Two, R^Three, And R^FourAre the same
Or may be different, each being a hydrogen atom,
It may have an alkyl group having 1 to 5 carbon atoms and a substituent.
An aryl group or a nitrogen-containing hetero be substituted
A ring group;¹And R^TwoAnd / or R^ThreeAnd R^FourIs it
X may be bonded to each other to form a ring;⁷, X⁸,
X ⁹, X^Ten, X¹¹And X¹²Are the same, but different
Each having a hydrogen atom and a substituent
Having an alkyl group having 1-3 carbon atoms or a substituent
Also represents an alkylene group, X⁷And X⁸And / or
Or X⁸And X⁹Or X^TenAnd X¹¹And / or X¹¹When
X¹²Each alone or combined with simultaneous aromatic
May form an aromatic ring, and further the substituents are bonded to each other.
To form a ring.

R ¹ , R ² , R ³ and R ⁴ are as defined above.

The alkyl group or alkylene group represented by X ⁷ , X ⁸ , X ⁹ , X ¹⁰ , X ¹¹ and X ¹² is the same as that of R ⁵ ,
It has the same meaning as the alkyl group or alkylene group for R ⁶ , R ⁷ and R ⁸ . Incidentally, X ⁷ and X ⁸ and / or X
⁸ and X ⁹ or X ¹⁰ and X ¹¹ and / or X ¹¹ and X
¹² may be independently or simultaneously bonded to form an aromatic ring, which means that X ⁷ and X ⁸ and / or X ⁸ and X ⁹ or X ¹⁰ and X ¹¹ and / or X ¹¹ X ¹²
Include a pyrazole ring and form a monocyclic or bicyclic aromatic ring. Specifically, it means forming an aromatic ring such as a benzene ring or a naphthalene ring.

Further, that the substituents may be bonded to each other to form a ring means that a monocyclic or bicyclic aromatic ring containing a pyrazole ring has another condensed ring. .
Specifically, there is a case where a phenalene ring, a phenanthrene ring, an anthracene ring, a pyrene ring, or the like is formed containing the above monocyclic or bicyclic aromatic rings.

As specific examples of the light emitting material, the following structural formulas (4) to (12) are exemplified.

[0069]

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[0070]

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[0071]

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[0072]

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[0073]

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[0074]

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[0075]

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[0076]

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[0077]

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[0078] The light-emitting device of the present invention, between an anode and a cathode, a light emitting element including a layer having a light emitting region. The layer having the light emitting region contains the above light emitting material.

The light emitting device of the present invention may include another functional layer in addition to the layer having the light emitting region. FIG. 1 is a schematic diagram illustrating an example of a light emitting element that can be used in the present invention. For example, as shown in FIG. 1, an anode 2, a hole transport layer 3, a light-emitting layer 4, an electron transport layer 5, and a cathode 6 may be laminated on a transparent substrate 1 in this order. This configuration is commonly called a DH structure.

In addition to the above structure, the SH-A structure in which the light emitting layer 4 also has the function of the electron transporting layer 5, the hole transporting layer 3
The light-emitting device according to the present invention may be any of the SH-B structure in which the light-emitting layer 4 has the function of the light-emitting layer 4 and the single-layer structure in which the light-emitting layer 4 also has the functions of both the hole transport layer 3 and the electron transport layer 5 Can be used as Since the light emitting material of the present invention has an electron transporting property, the SH-A structure is preferable.

In this specification, a light emitting device means a device having at least a functional layer such as a light emitting layer between a hole transport electrode and an electron injection electrode. The functional layer may be configured such that all of the functional layers are composed of a layer made of an organic material, or may be composed of a layer composed of an inorganic material. For example, the electron transport layer may be a layer composed of an inorganic material, the hole transport layer may be a layer composed of an organic material, and conversely, the electron transport layer may be a layer composed of an organic material, and the hole transport layer may be a layer composed of an inorganic material. good. Alternatively, any one or more of the hole transport layer, the light emitting layer, and the electron transport layer may be a layer containing an inorganic material.

The light emitting device having the structure shown in FIG. 1 can be manufactured, for example, as follows. Transparent substrate 1, has a proper strength, when the element created, without being adversely affected by heat, such as during deposition are not particularly limited as long as transparent. As a material of the transparent substrate 1, for example, glass (for example, Corning 17)
37) and transparent resins such as polyethylene, polypropylene, polyethersulfone, polycarbonate,
And polyether ether ketone. In addition to the display element of this embodiment, the display element according to the present invention can be formed by sequentially laminating on the transparent substrate 1 described above.

As can be said for the entire display device according to the present invention, the illustrated anode 2 is usually formed of a transparent conductive film. As a material for such a transparent conductive film, it is preferable to use a conductive substance having a work function greater than about 4 eV. Examples of such a substance include metals such as carbon, aluminum, vanadium, iron, cobalt, nickel, copper, zinc, tungsten, silver, tin, gold, and alloys thereof, tin oxide, indium oxide, antimony oxide, zinc oxide, Metal oxides such as zirconium oxide and their solid solutions and mixtures (eg, ITO (indium tin oxide) etc.)
And a conductive compound such as a conductive metal compound. When the anode 2 is formed, a method such as vapor deposition and sputtering, a sol-gel method, or a method in which such a substance is dispersed in a resin or the like and applied using a conductive substance as described above on the transparent substrate 1 is used. The anode may be formed so that desired translucency and conductivity are ensured. In particular, an ITO film is formed by a method such as sputtering, electron beam evaporation, or ion plating for the purpose of improving its transparency or reducing its resistivity.

The thickness of the anode 2 is determined from the required sheet resistance and visible light transmittance. In the case of a light emitting element, since the driving current density is relatively high, it is necessary to reduce the sheet resistance. Therefore, the film thickness is often 100 nm or more.

Next, a hole transport layer 3 is formed on the anode 2. In the light emitting device according to the present invention including the illustrated hole transport layer 3, as the hole transport material that can be used for forming the hole transport layer, known materials can be used. it is a derivative having triphenylamine having excellent sex as a basic skeleton.

Specifically, the tetraphenylbenzidine compound, triphenylamine trimer and benzidine dimer described in JP-A-7-126615,
Various tetraphenyldiamine derivatives described in JP-A-48656, N, and N, described in JP-A-7-65958.
N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine (MTPD (commonly called TPD)) and the like. The triphenylamine tetramer described in JP-A-10-228982 is more preferred. In addition, diphenylamino-α-phenylstilbene, diphenylaminophenyl-α-phenylstilbene and the like can also be used.
Further, an inorganic material such as amorphous silicon for forming the p-layer may be used.

The thickness of the hole transport layer 3 is 10 nm to 10 nm.
The thickness may be about 00 nm. The thickness of the hole transport layer 3 is 1
When the thickness is less than 0 nm, the luminous efficiency is good, but dielectric breakdown and the like are liable to occur, and the life of the element is shortened. On the other hand, if the thickness of the hole transport layer 3 is thicker than 1000 nm, in order to emit light at a predetermined luminance must be increased applied voltage, with luminous efficiency is low, tends to cause deterioration of the element.

Next, the light emitting layer 4 is formed on the hole transport layer 3. A light-emitting layer 4 of the light-emitting device according to FIG. 1 is configured to include a luminescent material described above.

The thickness of the light emitting layer 4 is 5 nm to 1000 nm.
It should just be about. When the thickness of the light emitting layer is less than 5 nm, the light emitting efficiency is good, but the dielectric breakdown and the like are apt to occur, and the life of the element is shortened. On the other hand, the thickness of the light emitting layer is 1000 nm.
When the thickness is larger, it is necessary to increase the applied voltage in order to emit light with a predetermined luminance, and the luminous efficiency is poor,
It is easy to cause deterioration of the element. Usually 5 nm to 100 nm
It is sufficient if the film thickness is about the same.

The light emitting layer 4 may further contain a hole transporting material or an electron transporting material for the purpose of improving the charge transporting ability in addition to the above light emitting material. Further, the light emitting material may be dispersed in a polymer matrix.

Next, the electron transport layer 5 is formed on the light emitting layer 4. As the electron transporting material that can be used for forming the electron transporting layer in the light emitting device according to the present invention, including the electron transporting layer 5 shown in the drawings, known materials can be used. Preferably, it is tris (8-quinolilat) aluminum (aluminum quinoline, hereinafter referred to as Alq). Other electron transporting materials include metal complexes such as tris (4-methyl-8-quinolylato) aluminum, 3- (2′-benzothiazolyl) -7-diethylaminocoumarin, and the like.

The thickness of the electron transport layer 5 is from 10 nm to 100
It may be about 0 nm. The thickness of the electron transport layer is 10 nm
When the thickness is smaller, the luminous efficiency is good, but dielectric breakdown and the like are apt to occur, and the life of the element is shortened. On the other hand, when the thickness of the electron transporting layer is more than 1000 nm, it is necessary to increase the applied voltage in order to emit light with a predetermined luminance, and the luminous efficiency is poor and the device is liable to be deteriorated.

The hole transport layer 3 and the electron transport layer 5
Each may be a single layer, but may be formed from a plurality of layers in consideration of the ionization potential and the like.

[0094] hole transport layer 3, the light-emitting layer 4, the electron transport layer 5
May be formed by a vapor deposition method, respectively, using a solution in which the materials forming these layers are dissolved or a solution in which the materials forming these layers are dissolved together with an appropriate resin, using a dip coating method or a spin coating method. Or the like. The Langmuir-Blodgett (LB) method may be used. A preferred film forming method is a vacuum evaporation method. This is because, according to the vacuum deposition method, a homogeneous layer in an amorphous state can be formed in each of the above layers. In particular, since the luminescent material of the present invention forms a complex compound that is extremely stable thermally, it can exist stably even at a high temperature during vapor deposition.

The hole transport layer 3, the light emitting layer 4, and the electron transport layer 5
May be formed independently, but it is preferable to form each layer continuously in a vacuum. If formed continuously, impurities can be prevented from adhering to the interface of each layer,
A decrease in operating voltage can be prevented, and characteristics such as improvement in luminous efficiency and extension of life can be improved.

[0096] hole transport layer 3, the light-emitting layer 4, the electron transport layer 5
Wherein any one of the layers comprises a plurality of compounds,
When a layer is formed using a vacuum deposition method, it is preferable to co-deposit a plurality of boats containing a single compound by individually controlling the temperature, but to deposit a mixture of a plurality of compounds in advance. it may be.

Although not shown, an electron injection layer for improving electron injection / transport characteristics may be formed on the electron transport layer 5. As the electron injecting material for forming the electron injecting layer, various conventionally known electron injecting materials can be used, and preferably, an alkali metal (such as lithium and sodium), an alkaline earth metal (such as beryllium and magnesium), or These salts and oxides can be used.

The electron injection layer can be formed by a method such as vapor deposition or sputtering. The thickness is 0.1 nm to 2 nm.
It is about 0 nm.

Next, the cathode 6 is formed on the electron transport layer 5. In the light emitting device according to the present invention, including the cathode 6 shown in FIG. 1, it is desirable to use a metal alloy having a low low work function. When the electron injection layer is formed, a metal having a large work function, such as aluminum or silver, can be stacked. When the cathode is formed of a transparent or translucent material, surface light emission can be obtained from the cathode side.

When the cathode 6 is formed, the above-described metal material is used to form the cathode by a technique such as vapor deposition or sputtering. The thickness of the cathode, 10nm~500n
m, more preferably in the range of 50 nm to 500 nm, from the viewpoints of conductivity and production stability.

The light emitting material used in the light emitting device of the present invention includes a blue light emitting substance having high color purity. Accordingly, a white balance is improved, and a high-quality display device and a lighting device can be provided. The display device may include a plurality of light-emitting elements of the present invention arranged in matrix on a substrate, and the light-emitting elements of the present invention are stacked over a substrate provided with a thin film transistor for driving control of the light-emitting element. It may be formed.
The lighting device can create a new lighting space as a new surface-emitting light source. Further, it can be applied to other optical uses.

[0102]

EXAMPLES (Synthesis Example 1) The synthesis method of the compound of the present invention is specifically described below.

Synthesis of Compound (12) Equal amounts of 1H-indazole and triphenylborane were dissolved in toluene, and reacted under heating and reflux until benzene was no longer generated. After pouring the reaction solution into cold water,
The precipitated solid was collected by filtration. A mixture of the product and pyrazole, 4 times the molar amount of the product, was heated with stirring to remove hydrogen. The reaction was recrystallized in boiling toluene to give compound (12). The yield was 75%.

Other polynuclear metal complex compounds having different bridging ligands could be synthesized by replacing 1H-indazole with pyrazole having a desired substituent. Further, regarding other polynuclear metal complex compounds having different ligands,
The compound was synthesized by replacing twice the molar amount of pyrazole with a compound having a desired skeleton.

Hereinafter, the contents of the present invention will be specifically described based on examples.

(Embodiment 1) In this embodiment, an embodiment of the element configuration shown in FIG. 1 will be described. N, N'-bis (4'-diphenylamino-4-) was formed on a glass substrate on which ITO was formed.
A hole transport layer having a thickness of 50 nm and made of (biphenylyl) -N, N'-diphenylbenzidine was formed. next,
A material shown in Structural Formula (4) was deposited to a thickness of 20 nm to form a light-emitting layer. Next, an electron transport layer having a thickness of 20 nm and made of tris (8-quinolinolato) aluminum (hereinafter referred to as Alq) was formed. Lithium was deposited to a thickness of 1 nm on the electron transport layer. Next, 100n made of aluminum
A cathode having a thickness of m was formed to produce the light emitting device shown in FIG.

A DC voltage was applied to this light emitting device, and the characteristics of the light emitting device were evaluated. Blue light emission with a luminous efficiency of 2.5 cd / A was obtained.

Example 2 A light emitting device was manufactured in the same manner as in Example 1 except that the compound represented by the structural formula 5 was used as the light emitting material. When a DC voltage was applied to these elements to emit light, blue light emission with a luminous efficiency of 2.9 cd / A was obtained.

[0109] except for using (Example 3) compound of structure 6 as a light emitting material, light emitting devices were manufactured in the same manner as in Example 1. When a DC voltage was applied to these elements to emit light, blue light emission with a luminous efficiency of 3.6 cd / A was obtained.

Example 4 A compound of structural formula 7 was used as a light emitting material, and 20 wt% of 4-N,
A light-emitting element was manufactured in the same manner as in Example 1, except that N′-bis (p-methylphenyl) amino-α-phenylstilbene was co-evaporated. When a DC voltage was applied to these elements to emit light, blue light emission with a luminous efficiency of 3.5 cd / A was obtained.

Example 5 A light emitting device was manufactured in the same manner as in Example 1 except that the compound represented by the structural formula 8 was used as the light emitting material. When a DC voltage was applied to these elements to emit light, blue light emission with a luminous efficiency of 3.0 cd / A was obtained.

Example 6 A light emitting device was manufactured in the same manner as in Example 1, except that the compound of Structural Formula 9 was used as the light emitting material, and the compound of Structural Formula 9 and 30 wt% of tristriamine were co-deposited. did. When a DC voltage was applied to these elements to emit light, blue light emission having a light emission efficiency of 2.8 cd / A was obtained.

Example 7 A light emitting device was manufactured in the same manner as in Example 1 except that the compound represented by the structural formula 10 was used as the light emitting material. When a DC voltage was applied to these elements to emit light, blue light emission with a luminous efficiency of 4.7 cd / A was obtained.

Example 8 A light emitting device was manufactured in the same manner as in Example 1 except that the compound represented by the structural formula 11 was used as the light emitting material. When a DC voltage was applied to these elements to emit light, blue light emission having a light emission efficiency of 2.8 cd / A was obtained.

[0115] except for using the compound of Example 9 Structural Formula 12 as the luminescent material, light emitting devices were manufactured in the same manner as in Example 1. When a DC voltage was applied to these elements to emit light, blue light emission with a luminous efficiency of 4.5 cd / A was obtained.

(Example 10) When the light emitting device obtained in each of the above examples was subjected to a constant current lighting test at an initial luminance of 500 cd / m ² , light emission was stably continued for 1000 hours or more.

(Embodiment 11) FIG. 2 is a schematic diagram for explaining an example of a display device using the light emitting device of the present invention. In this example, the display device includes an image signal output unit 30 that generates an image signal, a drive unit 33 that includes a scan electrode drive circuit 31 that generates an image signal from the image signal output unit, and a signal drive circuit 32, and 100 × And a light emitting section 35 having 100 light emitting elements 34 arranged in a matrix. Each of the light emitting devices prepared in Examples 1 to 10
The electroluminescent display device shown in FIG. 2 arranged in a matrix of 0 × 100 was prepared, and a moving image was displayed. In each of the display devices, good images with high color purity were obtained. In addition, even when a repetitive electroluminescent display device was produced, there was no variation between the devices, and a device having excellent in-plane uniformity was obtained.

[0118] (Example 12) FIG 3 is a schematic diagram for explaining an example of a lighting device using the light-emitting device of the present invention. In this example, the display device includes a driving unit 4 that generates a current.
0 and based on the current generated from the driving unit and a light emitting portion 41 including a light-emitting element emits light. In this example, the lighting device was used as a backlight of the liquid crystal display panel 42. When the light-emitting elements prepared in Examples 1 to 10 were formed on a film substrate and lit by applying a voltage, without using indirect lighting leading to a loss of luminance, a planar uniform surface light-emitting lighting device was obtained. Was.

[0119]

As described above, the luminescent material of the present invention is a blue luminescent material having excellent color purity, and has high thermal stability,
Excellent long-term stability. In addition, when such a light-emitting material is used for a light-emitting element, a light-emitting element with high color purity, low current efficiency in a high luminance region, and long life characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating one embodiment of a light emitting element of the present invention.

FIG. 2 is a schematic diagram for explaining an example of a display device using the light emitting element of the present invention.

FIG. 3 is a schematic diagram for explaining an example of a lighting device using the light emitting element of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Anode 3 Hole transport layer 4 Light emitting layer 5 Electron transport layer 6 Cathode 30 Image signal output unit 31 Scan electrode drive circuit 32 Signal drive circuit 33 Drive unit 34 Light emitting element 35 Light emitting unit 40 Drive unit 41 Light emitting unit 42 Liquid crystal display panel

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisanori Sugiura 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Terms (reference) 3K007 AB02 AB04 AB11 BA06 CA01 CB01 DA01 DB03 EB00 4H048 AA03 AB92 VA32 VA75 VB10

Claims (10)

[Claims] 1. A light-emitting material, which is a polynuclear metal complex compound represented by the following general formula (1). Embedded image (In the formula, R ¹ , R ² , R ³ , and R ^{4 each} represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group which may have a substituent, or a A good nitrogen-containing heterocyclic group, wherein R ¹ and R ² and / or R ³ and R ⁴ may be bonded to each other to form a ring, and R ⁵ , R ⁶ , R ⁷ , and R ⁸ are Hydrogen, carbon atom 1 which may have a substituent
-3 represents an alkyl group having 3 or an alkylene group having 2 or 3 carbon atoms which may have a substituent, and X ¹ and X ²
It is an optionally substituted aryl group, a nitrogen-containing heterocyclic group which may have a substituent. ) 2. A light-emitting material, which is a polynuclear metal complex compound represented by the following general formula (2). Embedded image (In the formula, R ¹ , R ² , R ³ , and R ^{4 each} represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group which may have a substituent, or a group which may have a substituent. It represents a nitrogen-containing heterocyclic group, which may be the R ¹ and R ² and / or R ³ and R ⁴ are bonded to each other to form a ring, R ^9, and R
¹⁰ is hydrogen, an alkyl group having 1 to 3 carbon atoms which may have a substituent, or 2 carbon atoms which may have a substituent.
Or X ³ represents an alkylene group, and X ³ , X ⁴ , X ⁵ , and X ⁶ represent an aryl group which may have a substituent, or a nitrogen-containing heterocyclic group which may have a substituent. Represent. ) 3. A light-emitting material which is a polynuclear metal complex compound represented by the following general formula (3). Embedded image (Wherein, R ¹ , R ² , R ³ , and R ⁴ represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkylene group substituent having 2 or 3 carbon atoms which may have a substituent. Represents an aryl group which may have a substituent or a nitrogen-containing heterocyclic group which may have a substituent, wherein R ¹ and R ² and / or R ³ and R ⁴
May be bonded to each other to form a ring, X ⁷ ,
X ⁸ , X ⁹ , X ¹⁰ , X ¹¹ and X ¹² each represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms which may have a substituent or 2 carbon atoms which may have a substituent. Or 3 alkylene groups, and X ⁷ and X ⁸ and / or X ⁸ and X ⁹
Alternatively, X ¹⁰ and X ¹¹ and / or X ¹¹ and X ¹² may be independently or simultaneously bonded to form an aromatic ring, and further, the substituents may be bonded to each other to form a ring. Is also good. ) 4. A light emitting element layer having a light-emitting region is provided between an anode and a cathode, the light emitting material is included in the layer is a compound represented by the following general formula (1) A light-emitting element. Embedded image (In the formula, R ¹ , R ² , R ³ , and R ^{4 each} represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group which may have a substituent, or a A good nitrogen-containing heterocyclic group, wherein R ¹ and R ² and / or R ³ and R ⁴ may be bonded to each other to form a ring, and R ⁵ , R ⁶ , R ⁷ , and R ⁸ are Hydrogen, carbon atom 1 which may have a substituent
-3 represents an alkyl group having 3 or an alkylene group having 2 or 3 carbon atoms which may have a substituent, and X ¹ and X ²
It is an optionally substituted aryl group, a nitrogen-containing heterocyclic group which may have a substituent. ) 5. A light-emitting element in which a layer having a light-emitting region is provided between an anode and a cathode, wherein the layer contains a light-emitting material which is a compound represented by the following general formula (2). A light-emitting element. Embedded image (In the formula, R ¹ , R ² , R ³ , and R ^{4 each} represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an aryl group which may have a substituent, or a group which may have a substituent. It represents a nitrogen-containing heterocyclic group, which may be the R ¹ and R ² and / or R ³ and R ⁴ are bonded to each other to form a ring, R ^9, and R
¹⁰ is hydrogen, an alkyl group having 1 to 3 carbon atoms which may have a substituent, or 2 carbon atoms which may have a substituent.
Or X ³ represents an alkylene group, and X ³ , X ⁴ , X ⁵ , and X ⁶ represent an aryl group which may have a substituent, or a nitrogen-containing heterocyclic group which may have a substituent. Represent. ) 6. A light-emitting element in which a layer having a light-emitting region is provided between an anode and a cathode, wherein the layer contains a light-emitting material that is a compound represented by the following general formula (3). A light-emitting element. Embedded image (Wherein, R ^1, R ^2, R ^3, and R ⁴ is a hydrogen atom, an alkyl group or may have a substituent group alkylene group substituent having 2 or 3 carbon atoms, 1-5 carbon atoms the represents a nitrogen-containing heterocyclic group which may have an aryl group or a substituted group may have, R ¹ and R ² and / or R ³ and R ⁴
May be bonded to each other to form a ring, X ⁷ ,
X ⁸ , X ⁹ , X ¹⁰ , X ¹¹ and X ¹² each represent a hydrogen atom, an alkyl group having 1 to 3 carbon atoms which may have a substituent or 2 carbon atoms which may have a substituent. or an alkylene group having 3, X ⁷ and X ⁸ and / or X ⁸ and X ⁹
Alternatively, X ¹⁰ and X ¹¹ and / or X ¹¹ and X ¹² may be independently or simultaneously bonded to form an aromatic ring, and further, the substituents may be bonded to each other to form a ring. Is also good. ) 7. The light-emitting device according to claim 4, wherein the hole-transport layer and the electron-transport layer are stacked between a cathode and an anode. A light-emitting element, which is a layer having a light-emitting region according to any of the above items. Wherein said light emitting element is a light-emitting element including a light-emitting layer between an anode and a cathode, the luminescent layer has a light-emitting region of any one of paragraph 4 to 6 claims A light-emitting element, which is a layer. 9. An image signal output unit for generating an image signal, a drive unit for generating a current based on the image signal from the image signal output unit, and a light emitting unit for emitting light based on the current generated from the drive unit A light-emitting element including a light-emitting layer between an anode and a cathode, wherein the light-emitting section includes at least one light-emitting element. A display device comprising the light emitting material according to any one of claims 1 to 3. 10. A lighting device comprising: a driving unit that generates a current; and a light emitting unit that emits light based on the current generated by the driving unit, wherein the light emitting unit has at least one light emitting element. The light-emitting element is a light-emitting element including a light-emitting layer between an anode and a cathode, wherein the light-emitting layer has the light-emitting material according to any one of claims 1 to 3. Lighting device characterized by the following.