JP2003229277A - Material for light emitting element, light emitting element and light emitting device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for a light emitting element made of an organic compound having sufficient electron transporting property which hardly deteriorates the light emitting element, and to provide a light emitting element using the same. <P>SOLUTION: The material for the light emitting element is a compound shown by the general formula (1). In the formula, R<SP>1</SP>and R<SP>2</SP>represent aryl group or heterocyclic group which may or may not have substituent, R<SP>3</SP>, R<SP>4</SP>, R<SP>5</SP>, R<SP>6</SP>represent substituent of which, at least one represents polycyclic condensed ring group or the same linked by the one group or atom chosen from vinyl group, ethynyl group, phenyl group, oxygen atom or sulfur atom, and M represents a central metal. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a light emitting element material, a light emitting element using the same, and an apparatus using the light emitting element.

[0002]

2. Description of the Related Art In recent years, with the diversification of information equipment, CR
There is an increasing need for a flat display element that consumes less power than T. In particular, the electroluminescence element is of a self-luminous type, and has attracted attention because of its clear display and wide viewing angle. In particular, in an organic electroluminescence device, the charges (holes and electrons) injected from both the anode and cathode electrodes recombine in the luminescent material to generate excitons, which excite molecules of the luminescent material to emit light. To do,
Since it is a so-called injection type light emitting element, it can be driven at a low voltage. Moreover, since the light-emitting material is an organic compound, the molecular structure of the light-emitting material can be easily changed, and thus an arbitrary emission color can be obtained.

As an organic electroluminescence device, first, an organic thin film is formed into a two-layer structure of a thin film made of a hole transporting material and a thin film made of an electron transporting material, and holes injected from the respective electrodes into the organic thin film. A device structure that emits light when electrons recombine has been developed (Ap
plied Physics Letters, 51, 1987, P.913.).

As an electron transporting material used in such a layered device, a tris (8-quinolinolato) aluminum complex (hereinafter
Alq) is used. After that, electron transport materials centering on organometallic complexes such as beryllium benzoquinoline and gallium complexes have been developed.

On the other hand, electron transport materials using organic compounds have been developed. Examples of the electron transport material using an organic compound include 2- (4-biphenylyl) -5- (4-
Examples include oxadiazol derivatives such as t-butylphenyl) -1,3,4-oxadiazol (PBD) and π-electron deficient aromatic compounds such as triazole derivatives. This is because the heterocycle has a π-electron deficiency and thus has excellent electron affinity.

However, when the organometallic complex is used as an electron transport material, the organometallic complex has a weak bond between the ligand and the central metal. Therefore, there is a problem that the cleavage of the coordination bond is likely to occur when the electrons are given and received, that is, when the redox reaction is performed, and the device is likely to deteriorate.

On the other hand, electron transport materials using organic compounds have the following problems. For example, a triazole derivative such as PBD has a problem that it is easily crystallized and cannot be put to practical use. Therefore, it has been attempted to suppress crystallization by dimerizing or introducing a bulky functional group. However, since these organic compounds do not have the effect of reducing the electron injection obstacle, there is a problem that the driving voltage becomes high, and the electron transporting property is not sufficient only by utilizing the π electron deficiency of the organic compound.

[0008]

The present invention has been made in view of the above, and an object thereof is to provide a light emitting device material using an organic compound having a sufficient electron transporting ability and a light emitting device using the same. Especially. Another object of the present invention is to provide a light emitting element material in which the element does not easily deteriorate and a light emitting element using the same.

[0009]

In developing a new light emitting device, improving the luminous efficiency is one of the important points. To improve luminous efficiency,
This is done by developing a light emitting material with high quantum efficiency or by improving the probability of recombination of electrons and holes. Generally, an organic material exhibits a property that electrons easily enter an empty orbital in a cation radical state, that is, a property of excellent hole transport property. On the other hand, as an organic material having an excellent electron transporting property, only a compound in which a π-electron-deficient heterocycle such as triazole or triazine is introduced is known. This is because the π-electron-deficient compound has an insufficient electron-transporting ability, so that holes are excessively present inside the light-emitting device and sufficient recombination of holes and electrons cannot be performed.

In order for the organic compound to be an excellent electron-transporting material, 1) the molecule has a large electron affinity because electrons are easily injected from the cathode and is easily a radical anion. 2) The injected electron. Is a molecule having a high electron mobility in order to quickly move in the electron transport layer and reach the light emitting layer, and 3) holes are efficiently recombined with electrons in the light emitting layer. It is desired that the molecule be a molecule that is difficult to become a radical cation.

As a result of intensive studies on the above problems, the present inventors have completed the present invention by discovering an organic compound which is easy to inject electrons from the cathode and has high electron mobility. That is,
The present invention is as follows.

The light emitting device material of the present invention is characterized by being a compound represented by the following general formula (1).

[Chemical 5] (In the formula, R ¹ and R ² each represent an aryl group which may or may not have a substituent, or a heterocyclic group, and R ³ , R ⁴ and R ⁵ And R ⁶ represents a substituent, and at least one of R ³ , R ⁴ , R ^{5 and} R ⁶ is a polycyclic fused ring group, or a vinyl group, an ethynyl group, a phenyl group, an oxygen atom and a sulfur atom. It is a polycyclic fused ring group in which one is selected from the group consisting of and M is a central metal.)

The compound represented by the general formula (1) may be a compound represented by the following general formula (2).

[Chemical 6] (In the formula, R ⁷ , R ⁸ , R ⁹ and R ¹⁰ represent a substituent,
At least one of R ⁷ , R ⁸ , R ⁹ or R ¹⁰ is linked by a polycyclic condensed ring group or one selected from the group consisting of a vinyl group, an ethynyl group, a phenyl group, an oxygen atom and a sulfur atom. Is a condensed polycyclic ring group. )

The compound represented by the general formula (1) may be a compound represented by the following general formula (3).

[Chemical 7] (In the formula, R ¹¹ , R ¹² , R ¹³ and R ¹⁴ represent a substituent, and R ¹¹ and R ¹⁴ , or R ¹² and R ¹³ may be the same or different from each other; It is a condensed ring group or a polycyclic condensed ring group linked by one selected from the group consisting of a vinyl group, an ethynyl group, a phenyl group, an oxygen atom, and a sulfur atom.)

The compound represented by the general formula (1) may be a compound represented by the following general formula (4).

[Chemical 8] (In the formula, R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ are each a polycyclic condensed ring group, or a vinyl group, an ethynyl group, a phenyl group,
It represents a polycyclic fused ring group linked by one selected from the group consisting of an oxygen atom and a sulfur atom. )

The light emitting device of the present invention is a light emitting device in which at least a light emitting layer is provided between an anode and a cathode, and contains the above light emitting device material.

The light emitting device of the present invention is a light emitting device in which at least a light emitting layer and an electron transport layer are provided between an anode and a cathode, and at least one layer of the light emitting layer and the electron transport layer is provided. It is characterized in that the above-mentioned light emitting element material is contained.

The light emitting device of the present invention is a light emitting device in which at least a light emitting layer and an electron transport layer are provided between an anode and a cathode, and the electron transport layer contains the above light emitting device material. It is characterized by

In the light emitting device of the present invention, the light emitting device material may be uniformly dispersed in the electron transport layer or in the light emitting layer.

Alternatively, in the light emitting device of the present invention, the light emitting device material has a concentration gradient in the light emitting layer or in the electron transport layer in the thickness direction of the light emitting layer or in the thickness direction of the electron transport layer. It may be dispersed and has a gradient such that the concentration becomes higher as it gets closer to the cathode.

The light emitting device may be one in which a hole transport layer and a light emitting layer are laminated in this order from the anode side.

The display device of the present invention comprises 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 current based on the current generated by the drive section. And a light emitting section that emits light, wherein the light emitting section has at least one light emitting element, and the light emitting element is the above light emitting element.

The illuminating device of the present invention is a illuminating device comprising a drive section for generating an electric current and a light emitting section for emitting light based on the electric current generated by the drive section, wherein the light emitting section is at least one. A light emitting element is included, and the light emitting element is the above light emitting element.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The light emitting device material of the present invention is a compound represented by the following formula (1).

[Chemical 9]

In the formula, R ¹ and R ² each represent an aryl group which may or may not have a substituent, or a heterocyclic group, and R ³ , R ⁴ , R ⁵ and R ⁶ represent a substituent, and at least one of R ³ , R ⁴ , R ⁵ or R ⁶ is a polycyclic condensed ring group, or a vinyl group, an ethynyl group, a phenyl group, an oxygen atom, and sulfur. It is a polycyclic fused ring group in which one is selected from the group consisting of atoms, and M represents a central metal.

The light-emitting device material of the present invention comprises a novel electron-injection function part in which electrons are easily injected from the cathode to form radical anions, and an electron-transportation function part in which injected electrons are transported to the light-emitting material. It is an electron transport material.

First, the electron injection function section will be described.
The electron transport material is required to be a molecule that facilitates injection of electrons from the cathode. In the light emitting element,
As the cathode material, a metal having a small work function such as an alkali metal or an alkaline earth metal is generally used to facilitate injection of electrons into the organic material. The work function of an alkali metal is 2.93 eV of Li to 1.95 e of Cs.
It is in the range up to V. The work function of alkaline earth metals is
It is in the range from 3.66 eV of Mg to 2.52 eV of Ba (Chemical Handbook, 4th revised edition, Maruzen, 1993, Basic Edition II). That is, the electron-transporting material that is easily injected with electrons is a substance whose LUMO energy level of the molecule is in the range of 3.66 eV to 1.95 eV depending on the work function of the above-mentioned alkali metal or alkaline earth metal. . As a method of lowering the LUMO energy level of a molecule to the above range, there are a method of introducing an electron withdrawing group into a molecule and a method of using a molecule having a large electron affinity.

In the light emitting device material of the present invention, a method of using a molecule having a large electron affinity is adopted as a means for introducing an electron injecting function portion into the molecule. Examples of the molecule having a large electron affinity include compounds represented by the following general formula (5).

[Chemical 10]

In the formula, R ¹ and R ² are represented by the above general formula (1).
It has the same meaning as R ¹ and R ² in the compound represented by.
M is a central metal.

As the central metal represented by M, Be, M
Examples thereof include metal elements or metalloid elements selected from the atomic group consisting of g, Ca, B, Al and Ga. Since these central metals have empty orbits in the valence band,
The central metal acts as a Lewis acid. Therefore, these central metals are easily coordinated by the basic compound. Since the compound represented by the general formula (1) is an electron-deficient compound having a smaller number of valence electrons than the number of valence orbitals, it is a molecule having a large electron affinity. That is, the compound represented by the general formula (1) is a molecule having a low LUMO energy level and having a function of injecting electrons from the cathode.
As a result, electrons are filled in the light emitting element material, and the number of molecules in the radical anion state increases, so that hopping movement of electrons is promoted. As a result, the recombination probability of electrons and holes can be improved.

R ¹ and R ^{2 which} can be used are an aryl group which may or may not have a substituent, or a heterocyclic group. Specifically, an aryl group (preferably having 6 to 20 carbon atoms. For example, phenyl group, 1-naphthyl group, 2-naphthyl group, 4-methoxyphenyl group, 3-methylphenyl group, 9-phenanthryl group, 9 Anthryl group, 1-pyrenyl group, benzyl group, etc.), heterocyclic group (preferably having 1 to 20 carbon atoms. Examples of preferable heterocyclic group are pyrrole, thiophene, furan, imidazole, pyrazole, Thiazole, oxazole, triazole, oxadiazol,
Examples thereof include a 5-membered aromatic ring such as thiadiazole or a condensed ring thereof, a 6-membered aromatic ring such as pyridine, pyridazine, pyrimidine, pyrazine and triazine, or a condensed ring thereof. Further, it may be a non-aromatic heterocycle such as piperidine, tetrahydrofuran, or tetrahydrothiophene. ) And the like.

Among the compounds represented by the above general formula (1), a preferable compound is a polynuclear metal complex compound having a plurality of boron atoms as a central metal. Boron atoms have a small atomic radius. Therefore, the boron atom is firmly bonded to the ligand, and a complex compound that is extremely stable thermally is formed. In particular, even when the polynuclear metal complex compound is vapor-deposited on the substrate at a high temperature, the polynuclear metal complex compound of the present invention exists stably.
Since super conjugation works effectively between the boron atom and the carbon atom of the aryl group, a double bond is formed between B and C, and the anion radical state is stable. Further, in the case of a heterocyclic group, pπ-n conjugation between a boron atom and an unshared electron pair works effectively, so that a double bond is generated between the heteroatom and
Stable in the anion radical state.

Among the polynuclear metal complex compounds having a plurality of boron atoms as a central metal, a polynuclear metal complex compound having a pyrazabole structure is particularly preferable. The pyrazabol 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 with respect to the boron atom, the pyrazole ring acts as a ligand that forms 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 pirazaboles often have a complicated conformational structure. As a result, the resulting polynuclear metal complex compound is often in the form of aggregated and aggregated molecules. Therefore, the polynuclear metal complex compound of the present invention is particularly preferable as a constituent material of an organic EL device which is required to be amorphous.

Next, the electron transport function section will be described.
In order for the light emitting device material to have an excellent electron transporting ability, it is necessary that injected electrons move quickly through the electron transporting layer and reach the light emitting layer. Therefore, the light emitting device material of the present invention is
It is required that the molecule has high electron mobility. The inventors of the present application have already found that a compound having a pyrazabole structure has an excellent electron transporting ability (Japanese Patent Application Laid-Open No. 20-29200).
01-3044). However, when the electron-transporting functional part is a polycyclic fused ring group, a more excellent electron-transporting ability can be added to the electron-transporting material. In the present invention, the electron transporting functional part is a polycyclic condensed ring and has high planarity. That is, the polycyclic condensed ring has a large overlap of π electron orbits between molecules. As a result, a π network is formed between molecules, and electrons can move through this π network, resulting in high electron mobility. Furthermore, the hopping electrons are π
It is electronic. Even considering the hopping movement of electrons, the electrons can move through the π network. In this respect, when the aromatic ring or the heterocyclic ring is connected without forming a condensed ring, the rings are twisted and connected, so that the planarity is poor and the above effect cannot be obtained. Further, the polycyclic condensed ring used in the present invention,
Two-ring condensed ring and three-ring condensed ring. Preferably, the flatness is excellent and the electron mobility can be further increased. 3
It is a condensed ring. On the other hand, the 4-ring condensed ring has a problem that it is difficult to handle because the solubility is lowered when the light emitting device material of the present invention is synthesized.

Examples of the polycyclic condensed ring used for the polycyclic condensed ring group constituting the electron transporting functional part include, for example, naphthalene and
Two-ring condensed hydrocarbon rings such as azulene and two-ring condensed heterocycles such as isobenzofuran, chromene, indolizine, indole, isoindole, indazole, purine, quinolidine, isoquinolidine, phthalazine, naphtholidine, quinoxaline, quinazoline, cinoline, Tricyclic condensed hydrocarbon rings such as biphenylene, indacene, acenaphthylene, fluorene, phenalene, phenanthrene, anthracene, carbazole, carboline, phenanthridine, acridine, phenanthroline, pericidine, benzoquinoline, benzocinnoline, phenothiazine,
Phenoxazine, phenothiazine, phenoxathine,
Known tricyclic condensed heterocycles such as cyanensulene can be used. These groups may further have a substituent. As the substituent, the substituents used in the following R ³ , R ⁴ , R ⁵ and R ⁶ other than the group used in the electron transporting functional part can be used.

That is, the light emitting device material represented by the general formula (1) of the present invention has an electron injection function part in which electrons are easily injected from the cathode to form radical anions, and the injected electrons are used as the light emitting material. Since it is composed of an electron transporting functional part for transporting, it is an extremely stable compound in the anion radical state. For this reason, the movement of electrons from the cathode to the light emitting layer is performed extremely smoothly. As a result, since the driving voltage can be lowered, it is possible to suppress the chemical deterioration of the metal cations that have emitted electrons at the cathode and contribute to the long-term stabilization of the light emitting element.

In the light emitting device material of the present invention, the electron injection part and the electron transport part are connected by one selected from the group consisting of vinyl group, ethynyl group, phenyl group, oxygen atom and sulfur atom. It may have been done. By connecting the electron injection part and the electron transport part with these groups or atoms,
This is because a film having an amorphous structure that is more excellent in electron transportability can be formed. Even if the electron injection part and the electron transport part are connected by these groups or atoms, the movement of the electron from the electron injection part to the electron transport part is not affected.

The group in which the substituent has an electron transporting function is as described above.
R of the compound represented by the general formula (1) ³, R^Four, R^Fiveand
R⁶Of these, at least one substituent may be used. Electric
Substituents other than the child transport function part are not particularly limited,
Is halogen (eg fluorine, chlorine, bromine, iodine),
Substituted or unsubstituted alkyl group (preferably having 1 carbon atom)
~ 20. For example, methyl group, ethyl group, n-propy
Group, i-propyl group, n-butyl group, i-butyl group,
t-butyl group, n-pentyl group, n-hexyl group, octyl
Cyl group, dodecyl group, cyclopropyl group, cyclobutyl group
Group, cyclopentyl group, cyclohexyl group, etc.
It ), An alkenyl group (preferably having 2 to 20 carbon atoms).
It For example, ethynyl group, propenyl group, butenyl group, etc.
Is. ), An alkynyl group (preferably having 2 to 20 carbon atoms).
Is. For example, ethynyl group, propynyl group, butynyl group
And so on. ), An alkoxy group (preferably having a carbon number of 1 to
30 and more preferably 1 to 15 carbon atoms. For example
Toxyl group, ethoxy group, cyclohexyloxy group, etc.
is there. ), An aryl group (preferably having 6 to 20 carbon atoms)
It For example, phenyl group, 1-naphthyl group, 2-naphthyl group
Group, 4-methoxyphenyl group, 3-methylphenyl group,
9-phenanthryl group, 9-anthryl group, 1-pyreny
Group, benzyl group and the like. ), A heterocyclic group (preferably
Has 1 to 20 carbon atoms. Examples of preferred heterocyclic groups
Is pyrrole, thiophene, furan, imidazole, pyrrole
Razole, thiazole, oxazole, triazole,
5-membered aromatics such as oxadiazol and thiadiazole
A ring, or a condensed ring thereof, pyridine, pyrida
6-membered products such as gin, pyrimidine, pyrazine, and triazine
An incense ring or a condensed ring thereof can be mentioned.
It Furthermore, piperidine, tetrahydrofuran, tet
A non-aromatic heterocycle such as lahydrothiophene
Good. ) And the like.

A preferred embodiment of the light emitting device material of the present invention is
It is a compound represented by the following general formula (2).

[Chemical 11]

In the formula, at least one of R ⁷ , R ⁸ , R ⁹ and R ¹⁰ is selected from the group consisting of polycyclic condensed ring groups, vinyl groups, ethynyl groups, phenyl groups, oxygen atoms and sulfur atoms. It is a polycyclic fused ring group connected by one other. R
⁷ , R ⁸ , R ⁹ and R ¹⁰ have the same meanings as R ³ , R ⁴ , R ⁵ or R ⁶ represented by the general formula (1). If at least one of the substituents has an electron transporting function, it can be used as the light emitting device material of the present invention.

A preferred embodiment of the light emitting device material of the present invention is
It is a compound represented by the following general formula (3).

[Chemical 12]

In the formula, R ¹¹ , R ¹² , R ¹³ and R ¹⁴ represent a substituent, and R ¹¹ and R ¹⁴ or R ¹² and R ^14
15 are polycyclic fused ring groups which may be the same or different, or are linked by one selected from the group consisting of a vinyl group, an ethynyl group, a phenyl group, an oxygen atom, and a sulfur atom. It is a polycyclic fused ring group. It is preferable that R ¹¹ and R ¹⁴ , or R ¹² and R ¹⁵ are the same group, because the production is easier. ^{Incidentally, R 11, R 12, R} 13 and R ^14, R ^3, R ⁴ represented by the general formula (1), R
It is synonymous with ⁵ or R ⁶ .

A preferred embodiment of the light emitting device material of the present invention is
It is a compound represented by the following general formula (4).

[Chemical 13]

In the formula, R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ are each one selected from the group consisting of polycyclic condensed ring groups, vinyl groups, ethynyl groups, phenyl groups, oxygen atoms and sulfur atoms. Represents a polycyclic fused ring group connected by two. These substituents may be the same or different. It is preferable that all the substituents are the same group, because production is easy. In addition, R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ have the same meaning as R ³ , R ⁴ , R ⁵ or R ⁶ represented by the above general formula (1).

Specific examples of the compound represented by the above general formula (1) are compounds represented by the following chemical formulas (6) and (7).

[Chemical 14]

[Chemical 15]

The light emitting device material of the present invention is, for example, 1 to 3.
It can be produced by reacting a borohydride compound having 4 substituents with an aromatic compound or a heterocyclic compound which may or may not have a substituent.

The light emitting device of the present invention is a light emitting device in which at least a light emitting layer is provided between an anode and a cathode. The organic compound layer contains the above light emitting element material.

In the light emitting device of the present invention, as the above light emitting layer,
It may be configured to include a functional layer. FIG. 1 is a schematic view showing 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 in this order on a transparent substrate 1. This structure 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 transport layer 5, the hole transport layer 3
The SH-B structure in which the light emitting layer 4 also has the above function, and the single-layer structure in which the light emitting layer 4 has both the functions of the hole transporting layer 3 and the electron transporting layer 5, both of which are the light emitting element of the present invention. Can be used as

In the present specification, the light emitting element means an element having at least a functional layer such as a light emitting layer between the hole transport electrode and the electron injecting electrode. In the functional layer, all the functional layers may be composed of a layer made of an organic material, or may be composed of a layer made of an inorganic material. For example, the electron transport layer may be a layer made of an organic material and the hole transport layer may be a layer made of an inorganic material. Alternatively, any one layer or a plurality of layers of the hole transport layer, the light emitting layer, and the electron transport layer may be a layer containing an inorganic material.

In one embodiment of the light emitting device of the present invention, as shown in FIG. 1, the electron transport layer 5 is a layer made of the light emitting device material of the present invention.

The light emitting device having the structure of FIG. 1 can be manufactured, for example, as follows. The transparent substrate 1 is not particularly limited as long as it has a proper strength, is not adversely affected by heat during vapor deposition, etc., in producing an element, and is transparent. As a material of the transparent substrate 1, for example, glass (for example, Corning 17
37) and transparent resins such as polyethylene, polypropylene, polyether sulfone, polycarbonate,
Examples thereof include polyether ether ketone. Not only the display element of this embodiment but also the display element according to the present invention can be formed by sequentially stacking on the transparent substrate 1.

Not only in the display element of this embodiment but also in the display elements according to the present invention in general, the anodes including the illustrated anode 2 are usually formed of a transparent conductive film.
As a material of such a transparent conductive film, it is preferable to use a conductive substance having a work function larger than about 4 eV. Such substances include carbon, aluminum, vanadium, iron, cobalt, nickel, copper, zinc, tungsten, silver, tin, gold, and other metals such as alloys thereof, as well as tin oxide, indium oxide, antimony oxide, zinc oxide, Metal oxides such as zirconium oxide and solid solutions or mixtures thereof (eg ITO (indium tin oxide))
A conductive compound such as a conductive metal compound can be exemplified.

When forming the anode 2, on the transparent substrate 1,
A desired light-transmitting property and conductivity are ensured by using a method such as vapor deposition, sputtering, or a sol-gel method or a method of applying such a substance by dispersing such a substance in a resin or the like by using the above-mentioned conductive substance. It may be formed as follows. In particular, the 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 film thickness of the anode 2 is determined from the required sheet resistance value 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 value. Therefore, the film thickness is often 100 nm or more.

Next, the hole transport layer 3 is formed on the anode 2. In the light emitting device according to the present invention including the hole transporting layer 3 shown in the figure, known hole transporting materials can be used for forming the hole transporting layer. It is a derivative having triphenylamine as a basic skeleton, which has excellent properties.

Specifically, the tetraphenylbenzidine compound, triphenylamine trimer and benzidine dimer described in JP-A-7-126615,
-48656, various tetraphenyldiamine derivatives described in JP-A-7-69558, N,
Examples thereof include N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine (MTPD (common name TPD)). The triphenylamine tetramer described in JP-A-10-228982 is more preferable. In addition, diphenylamino-α-phenylstilbene, diphenylaminophenyl-α-phenylstilbene and the like can be used.
Further, an inorganic material such as amorphous silicon forming the p layer may be used.

The thickness of the hole transport layer 3 is 10 nm to 10 nm.
It may be about 00 nm. The hole transport layer thickness is 10
When the thickness is less than nm, the light emission efficiency is good, but dielectric breakdown is likely to occur and the life of the device is shortened. On the other hand, when the thickness of the hole transport layer 3 is more than 1000 nm, it is necessary to increase the applied voltage in order to emit light with a predetermined brightness.
The luminous efficiency is poor and the element is easily deteriorated.

Next, the light emitting layer 4 is formed on the hole transport layer 3. The light emitting material used in the light emitting layer of the light emitting device according to FIG. 1 is not particularly limited, and in addition to Alq described above, tris (4-methyl-8-quinolinolato) aluminum which is a derivative thereof, 4, Distyrylarylene derivatives such as 4′-bis (2,2-diphenylvinyl) biphenyl, porphyrin derivatives such as tetraphenylporphyrin, anthracene, pyrene, bisstyrylanthracene derivatives, tetraphenylbutadiene derivatives, coumarin derivatives, oxadiazole derivatives,
Known low-molecular light emitting materials such as pyrrolopyridine derivatives, perinone derivatives, cyclopentadiene derivatives, and thiadiazolopyridine derivatives, and poly (p-phenylene vinylene)
Known polymer light emitting materials such as polyphenylene vinylene derivatives, polythiophene derivatives, polyfluorene and the like can be mentioned. In addition, a light emitting material such as a laser dye, for the purpose of improving the light emitting efficiency or changing the light emitting color,
Dope rubrene, tris (2-phenylpyridine) iridium, 2,3,7,8,12,13,1
7,18-Octaethylporphyrin platinum (II)
You may use the phosphorescent heavy metal complex such as.

In order to improve the hole transporting ability and electron transporting ability in the light emitting layer, the light emitting layer may contain the above hole transporting material or the light emitting element material of the present invention in its layer structure. Further, an inorganic light emitting material may be used as the light emitting material. Further, the light emitting material may be dispersed in the polymer matrix.

The thickness of the light emitting layer 4 is 5 nm to 1000 nm.
It should be about. When the thickness of the light emitting layer is thinner than 5 nm, the light emitting efficiency is good, but dielectric breakdown is likely to occur, and the life of the device is shortened. On the other hand, the thickness of the light emitting layer is 1000 nm
If the thickness becomes thicker, it is necessary to increase the applied voltage in order to emit light with a predetermined brightness, and the luminous efficiency is poor, and
Deterioration of the element is likely to occur. Usually 5 nm to 100 nm
It is preferable that the film thickness is about the same.

The light emitting layer may be made of only a single material which emits each color such as red, green and blue independently, or a plurality of light emitting materials may be contained in the same layer to extract a mixed color.
Further, a structure in which red, green, and blue light emitting materials are separately coated for each subpixel may be used. Furthermore, a layered structure in which light emission colors are different for each layer may be stacked and the light emission colors from the respective layers may be stacked.

Next, the electron transport layer 5 is formed on the light emitting layer 4. The electron transport material that can be used for forming the electron transport layer in the light emitting device according to the present invention, including the electron transport layer 5 shown in the figure, is the above light emitting device material.

When there is an electron injection obstacle between the cathode or the light emitting layer, in consideration of the electron affinity, the light emitting device of the present invention uses another electron transport material in addition to the above light emitting device material. Good. Other electron transport materials include 2,9-
Known electron transport materials such as dimethyl-4,7-diphenyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, 3- (2'-benzothiazolyl) -7-diethylaminocoumarin can be used. When another electron transporting material is used in combination, the light emitting device material of the present invention is dispersed with a concentration gradient in the thickness direction of the electron transporting layer 5 even if it is uniformly dispersed in the electron transporting layer 5. May be.

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

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

Hole transport layer 3, light emitting layer 4, electron transport layer 5
May be formed by a vapor deposition method, or by using a solution in which the material forming these layers is dissolved or a solution in which the material forming these layers is dissolved with an appropriate resin, a dip coating method or a spin coating method. You may form by coating methods, such as. The Langmuir-Blodgett (LB) method may be used. A preferred film forming method is a vacuum vapor deposition method. This is because according to the vacuum vapor deposition method, a homogeneous layer in an amorphous state can be formed in each of the above layers.

The light emitting layer may contain an electron transporting substance. In this case, the electron transport material may be dispersed uniformly throughout the light emitting layer. Further, the electron transport material may be dispersed in the thickness direction of the light emitting layer from the cathode side to a range of about ½ of the light emitting layer. Further, in the light emitting layer, when the electron transporting substance in the light emitting layer has a concentration gradient, the light emitting layer having the concentration gradient can be formed by controlling the temperature and controlling the concentration. If the number of moles of the electron transporting substance contained in the light emitting layer is equal to or less than the number of moles of the light emitting substance,
Number of moles of electron transporting substance: Number of moles of light emitting substance = 10: 90
You may form a light emitting layer in the range of -99: 1. In particular, the light emitting device material of the present invention not only has excellent electron injecting property and electron transporting property, but also has good light emitting properties. Therefore, it functions effectively as an electron transporting light emitting layer.

Hole transport layer 3, light emitting layer 4, electron transport layer 5
May be formed individually, but it is preferable to form each layer continuously in a vacuum. If formed continuously, it is possible to prevent impurities from adhering to the interface of each layer,
It is possible to prevent a decrease in operating voltage and improve characteristics such as improved luminous efficiency and a longer life.

Hole transport layer 3, light emitting layer 4, electron transport layer 5
One of the layers contains a plurality of compounds,
When the layer is formed using a vacuum vapor deposition method, it is preferable to co-evaporate by controlling the temperature of a plurality of boats containing a single compound individually, but by vapor depositing a mixture of a plurality of compounds in advance. Is also good.

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, but preferably, an alkali metal (lithium, sodium, etc.), an alkaline earth metal (beryllium, magnesium, etc.), 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
It is about 0 nm.

Next, the cathode 6 is formed on the electron transport layer 5. For the cathodes in the light emitting device according to the present invention, including the cathode 6 shown in FIG. 3, it is desirable to use an alloy of a metal having a low work function. When the electron injection layer is formed, a metal having a high work function such as aluminum or silver can be stacked. Further, even if the cathode is made of a transparent or translucent material, surface emission can be taken out.

When forming the cathode 6, the metal material as described above is used to form the cathode by a method such as vapor deposition and sputtering. The thickness of the cathode 6 is 10 nm to 500 n
m, more preferably in the range of 50 nm to 500 nm is preferable in terms of conductivity and manufacturing stability.

The light emitting device material of the present invention has excellent electron injecting property and electron transporting property. Therefore, the luminous efficiency can be improved regardless of whether the luminescent color of the luminescent material is red, green, or blue, so that a high-quality display device and a lighting device can be provided. In the display device, a plurality of light emitting elements of the present invention may be arranged in matrix over a substrate, and the light emitting element of the present invention is stacked on 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 type light source. Further, in a display device such as a liquid crystal display, it can be used as a backlight for a white light source or a monochromatic light source, and thus can be applied to other optical applications.

[0076]

EXAMPLES The contents of the present invention will be specifically described below based on examples. Example 1 In this example, a compound represented by the chemical formula (6) was synthesized. 0.1 mol of trinaphthylborane and 1.0 mol of pyrazole were refluxed and reacted with heating. Then, the reaction product was poured into 800 ml of water and reacted for 2 days under stirring. Then, the solid precipitated from the reaction solution was filtered off, and this solid was air-dried. Next, this solid was recrystallized from boiling toluene. The recrystallized product was washed with ether and air-dried to obtain 16.2 g of the compound of formula (6). The yield was 48.9%. The compounds represented by the general formula (1) including the compound of the chemical formula (6) can be synthesized by the same method.

(Embodiment 2) In this embodiment, an embodiment of the element structure shown in FIG. 1 will be described. N, N′-diphenyl-N, N′-bis (3-
Methylphenyl) -1,1'-biphenyl-4,4'-
A 50 nm-thick hole transport layer made of diamine was formed. Next, tris (8-quinolinolato) aluminum was vapor deposited to form a light emitting layer having a film thickness of 30 nm. next,
An electron transport layer having a film thickness of 20 nm represented by the chemical formula (6) was formed. Lithium was evaporated to a thickness of 1 nm on the electron transport layer. Next, a cathode of aluminum having a film thickness of 100 nm was formed to manufacture the light emitting device shown in FIG.

A direct current voltage was applied to the present light emitting device to evaluate the characteristics of the light emitting device. The luminous efficiency was 4.5 cd / A, and stable green light emission was obtained with high luminous efficiency. When this device was subjected to a constant current lighting test at an initial luminance of 1000 cd / m ² , the luminance half-life was about 800 hours.

Further, the electron transport layer is formed of the compound of the chemical formula (6) and 2,9-dimethyl-4,7-diphenyl-1,10.
-Phenanthroline was formed such that the compound of formula (6) was uniformly dispersed. In this case as well, a light emitting device having a high luminous efficiency and a long luminance half-life was obtained as in this example. Further, when the compound of the chemical formula (6) is dispersed with a concentration gradient in the thickness direction of the electron transport layer, and the electron transport layer is formed so that the concentration becomes higher toward the cathode, the same is true. A light emitting device having high luminous efficiency and a long luminance half-life was obtained.

Example 3 A light emitting device of Example 3 was prepared in the same manner as in Example 1, except that the chemical formula (7) was used in place of the chemical formula (6) as the electron transport material. .

A direct current voltage was applied to the present light emitting device to evaluate the characteristics of the light emitting device. The luminous efficiency was 4.3 cd / A, and stable green light emission was obtained with high luminous efficiency. When this device was subjected to a constant current lighting test at an initial luminance of 1000 cd / m ² , the luminance half-life was about 800 hours.

In this embodiment, the DH structure was used as shown in FIG. 1. However, even in the device structures such as SH-A and SH-B, the luminous efficiency is high and the luminance is reduced to half as in this embodiment. A light emitting device having a long period was obtained. Further, when the compound of the chemical formula (7) is dispersed with a concentration gradient in the thickness direction of the light emitting layer and the light emitting layer is formed such that the concentration becomes higher toward the cathode, the same light emission is performed. A light emitting device having high efficiency and a long luminance half-life was obtained.

(Embodiment 4) In this example, an image signal output section for generating an image signal, a drive section having a scan electrode drive circuit and a signal drive circuit for generating an image signal from the image signal output section, and 100 × A display device including 100 light emitting portions having light emitting elements arranged in a matrix was manufactured. Each of the light emitting devices prepared in Examples 2 and 3 was 100
An electroluminescent display device arranged in a matrix of × 100 was prepared and a moving image was displayed. In each display device, a good image with high color purity was obtained. Further, even when the electroluminescent display device was repeatedly manufactured, there was no variation among the devices, and a device having excellent in-plane uniformity was obtained.

An illuminating device having a driving section for generating a current and a light emitting section having a light emitting element for emitting light based on the current generated by the driving section was prepared. Further, in this example, the lighting device was used as a backlight of the liquid crystal display panel. When the light emitting device produced in Examples 2 and 3 was produced on a film substrate and was turned on by applying a voltage, a curved surface-uniform surface emitting illumination device was obtained without using indirect illumination leading to a loss of brightness. It was

Comparative Example 1 In the light emitting device of Example 1, the electron transport layer was formed of 2- (4-biphenyl) -5- (4-t-butylphenyl) 1,3,4-oxadiazo-containing film having a thickness of 30 nm. A light emitting device was produced in the same manner as in Example 1 except that the layer was made of a ruthenium.

A direct current voltage was applied to the present light emitting device to evaluate the characteristics of the light emitting device. The luminous efficiency was 3.0 cd / A. When this element was subjected to a constant current lighting test at an initial luminance of 1000 cd / m ² , the luminance half-life was about 350 hours.

[0087]

As described above, according to the present invention, it is possible to obtain a light emitting device material using an organic compound having a sufficient electron transporting ability and a light emitting device using the same. Further, it is possible to obtain a light emitting element material which does not easily deteriorate the element and a light emitting element using the same.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing one embodiment of a light emitting device of the present invention.

[Explanation of symbols]

1 transparent substrate 2 anode 3 hole transport layer 4 Light emitting layer 5 Electron transport layer 6 cathode

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hisanori Sugiura             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 3K007 AB03 AB12 DB03                 4H048 AA01 AB91 VA32 VA75 VB10

Claims (12)

[Claims] 1. A light emitting device material, which is a compound represented by the following general formula (1). [Chemical 1] (In the formula, R ¹ and R ² each represent an aryl group which may or may not have a substituent, or a heterocyclic group, and R ³ , R ⁴ and R ⁵ And R ⁶ represents a substituent, and at least one of R ³ , R ⁴ , R ^{5 and} R ⁶ is a polycyclic fused ring group, or a vinyl group, an ethynyl group, a phenyl group, an oxygen atom and a sulfur atom. It is a polycyclic fused ring group in which one is selected from the group consisting of and M is a central metal.) 2. The light emitting device material according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2). [Chemical 2] (In the formula, R ⁷ , R ⁸ , R ⁹ and R ¹⁰ represent a substituent,
At least one of R ⁷ , R ⁸ , R ⁹ or R ¹⁰ is linked by a polycyclic condensed ring group or one selected from the group consisting of a vinyl group, an ethynyl group, a phenyl group, an oxygen atom and a sulfur atom. Is a condensed polycyclic ring group. ) 3. The light emitting device material according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (3). [Chemical 3] (In the formula, R ¹¹ , R ¹² , R ¹³ and R ¹⁴ represent a substituent, and R ¹¹ and R ¹² , or R ¹³ and R ¹⁴ may be the same or different from each other. It is a condensed ring group or a polycyclic condensed ring group linked by one selected from the group consisting of a vinyl group, an ethynyl group, a phenyl group, an oxygen atom, and a sulfur atom.) 4. The light emitting device material according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (4). [Chemical 4] (In the formula, R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ are each a polycyclic condensed ring group, or a vinyl group, an ethynyl group, a phenyl group,
It represents a polycyclic fused ring group linked by one selected from the group consisting of an oxygen atom and a sulfur atom. ) 5. A light emitting device having at least a light emitting layer provided between an anode and a cathode, wherein the light emitting layer contains the light emitting device material according to any one of claims 1 to 4. A light-emitting element characterized in that. 6. A light emitting device comprising at least a light emitting layer and an electron transport layer provided between an anode and a cathode,
A light emitting device comprising the light emitting device material according to any one of claims 1 to 4 in at least one of the light emitting layer and the electron transporting layer. 7. A light emitting device comprising at least a light emitting layer and an electron transport layer provided between an anode and a cathode, comprising:
A light emitting device, wherein the electron transport layer contains the light emitting device material according to any one of claims 1 to 4. 8. The light emitting device according to claim 5, wherein the light emitting device material is uniformly dispersed in the electron transport layer or in the light emitting layer. 9. The light-emitting device material is dispersed in the light-emitting layer or in the electron-transporting layer with a concentration gradient in the thickness direction of the light-emitting layer or in the thickness direction of the electron-transporting layer, and as it approaches the cathode. The light emitting device according to claim 5, wherein the light emitting device has a gradient so as to have a high concentration. 10. The light emitting device according to claim 5, wherein the light emitting device is formed by laminating a hole transport layer and a light emitting layer in this order from the anode side. 11. 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 by the drive section. 11. A display device comprising: and the light emitting unit having at least one light emitting element, wherein the light emitting element is the light emitting element according to any one of claims 5 to 10. Display device. 12. A lighting device comprising: a drive unit that generates an electric current; and a light emitting unit that emits light based on a current generated by the drive unit, wherein the light emitting unit has at least one light emitting element. The light emitting device is a device according to any one of claims 5 to 10.
An illumination device comprising the light-emitting element according to any one of 1.