JP2003142265A - Light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting element with high brightness and excellent durability which can emit light with high light emitting efficiency. SOLUTION: For the light emitting element having organic compound layers including a light emitting layer between a pair of electrodes formed on a substrate, at least one of the organic compound layers contains a compound shown by formula (1) and a phosphorescent compound. In formula (1), Z<1> and Z<2> represent nonmetallic atom group necessary for forming a five-membered ring together with nitrogen atom and the ring may have a substituent or may form a fused ring together with an another ring. L<1> , L<2> , L<3> , and L<4> represent hydrogen atom, alkyl group, aryl group, or nitrogen containing aromatic ring group, and M represents metallic atom.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device material and a light emitting device, and more particularly to a light emitting device having high brightness, high luminous efficiency and excellent durability.

[0002]

2. Description of the Related Art Today, research and development relating to various light-emitting devices are active, and among them, organic electroluminescence (EL) devices are promising as light-emitting devices because they can emit light with high brightness at low voltage. ing. For example, a light emitting device in which an organic thin film is formed by vapor deposition of an organic compound is known (Applied Physics Letters, Vol. 51, 91).
3 pages, 1987). The light-emitting device described in this document uses tris (8-hydroxyquinolinato) aluminum complex (Alq) as an electron-transporting material and is laminated with a hole-transporting material (amine compound) to obtain a conventional single-layer device. Compared with this, the light emission characteristics are greatly improved.

In recent years, application of organic EL elements to color displays has been actively studied, but in order to develop high-performance color displays, characteristics of blue, green, and red light emitting elements have been improved. There is a need to. As a means for improving the characteristics of a light emitting device, a green light emitting device utilizing light emission from an iridium complex described in Applied Physics Letters, Vol. 75, p. 4 (1999) has been reported. This device has reached an external quantum efficiency of 8%, which exceeds the external quantum efficiency of 5%, which was said to be the limit of conventional devices, but there is a problem with durability, and improvement thereof has been desired.
Further, Japanese Patent Laid-Open No. 2000-226573 describes an element containing a compound having a pyrazaball structure.
Its durability is low, and its improvement is desired.

On the other hand, an organic light emitting device that realizes high-luminance light emission is a device in which organic substances are laminated by vacuum vapor deposition, but from the viewpoint of simplification of the manufacturing process, workability, increase in area, etc. It is desirable to manufacture the device by a coating method.
However, the element manufactured by the conventional coating method is inferior to the element manufactured by the vapor deposition method in terms of light emission brightness and light emission efficiency, and high brightness and high efficiency light emission are major problems.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a light emitting device which can emit light with high brightness and high efficiency and is excellent in durability.

[0006]

This object was achieved by the following means. (1) In a light-emitting device in which an organic compound layer including a light-emitting layer is formed between a pair of electrodes provided on a substrate, at least one of the organic compound layers contains a compound represented by the following general formula (I) and phosphorescence. A light emitting device comprising a light emitting compound.

[0007]

[Chemical 2]

In the general formula (I), Z ¹ and Z ² represent a group of non-metal atoms necessary for forming a 5-membered ring with a nitrogen atom, and this ring may have a substituent. It may form a condensed ring with another ring. L ¹ , L ² , L ³ and L ⁴
Each represents a hydrogen atom, an alkyl group, an aryl group or a nitrogen-containing aromatic ring group, and M represents a metal atom. (2) The light emitting device according to (1), wherein the compound represented by the general formula (I) has a pyrazabole structure. (3) The compound having the pyrazaball structure is 4,
The light emitting device according to (2), which is 4,8,8-tetrakis (1H-pyrazol-1-yl) pyrazaball. (4) The light emitting device according to any one of (1) to (3), wherein the phosphorescent compound is an organometallic complex. (5) The light emitting device according to any one of (1) to (4), wherein the phosphorescent compound is an orthometallated complex. (6) The light emitting device according to any one of (1) to (5), wherein the phosphorescent compound is an orthometalated iridium complex. (7) The light emitting device according to any one of (1) to (6), wherein the organic light emitting layer contains a polymer compound.

The compound of formula (I) of the present invention is included in the compounds described in JP 2001-3044 A, JP 2001-43973 A and JP 2000-226573 A. There is no description regarding the light emitting compound, and therefore, it is impossible to predict the light emitting device of the present invention and its performance from the specification.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
To do. In the general formula (I), Z¹And Z²Are the same
May be different, each with 5-membered ring with nitrogen atom
Represents the group of non-metal atoms required to form
It may have a substituent, and may form a condensed ring with another ring.
May be done. Examples of the substituent include a halogen atom and fat
Group, aryl, heterocyclic group, cyano, nitro, -O
R¹⁰¹, -SR¹⁰², -CO₂R¹⁰³, -OCOR¹⁰⁴,-
NR¹⁰⁵ R¹⁰⁶, -CONR¹⁰⁷R¹⁰⁸, -SO₂R¹⁰⁹,
-SO₂NR¹¹⁰R¹¹¹, -NR¹¹²CONR ¹¹³R¹¹⁴,-
NR¹¹⁵CO₂R¹¹⁶, -COR¹¹⁷, -NR¹¹⁸COR¹¹⁹
Or-NR¹²⁰SO₂R¹²¹Is mentioned. here
R¹⁰¹, R¹⁰², R¹⁰³, R¹⁰⁴, R¹⁰⁵, R¹⁰⁶, R
 ¹⁰⁷, R¹⁰⁸, R¹⁰⁹, R¹¹⁰, R¹¹¹, R¹¹², R
¹¹³, R¹¹⁴, R¹¹⁵, R¹¹⁶, R¹¹⁷, R¹¹⁸, R
¹¹⁹, R¹²⁰And R¹²¹Are independent hydrogen
A child, an aliphatic group or an aryl group.

As the substituent, a halogen atom among the above,
Aliphatic group, aryl group, -OR ¹⁰¹ , -SR ¹⁰² , -N
R ¹⁰⁵ R ¹⁰⁶ , -SO ₂ R ¹⁰⁹ , -NR ¹¹² CONR ¹¹³ R
¹¹⁴ , -NR ¹¹⁵ CO ₂ R ¹¹⁶ , -NR ¹¹⁸ COR ¹¹⁹ or -NR ¹²⁰ SO ₂ R ¹²¹ is preferred, and a halogen atom, an aliphatic group, an aryl group, -OR ¹⁰¹ , -S.
R ¹⁰² , —NR ¹⁰⁵ R ¹⁰⁶ or —SO ₂ R ¹⁰⁹ is more preferable, a halogen atom, an alkyl group, an aryl group, an alkoxy group, a phenoxy group and a dialkylamino group are more preferable, a halogen atom and a carbon atom. More preferably, it is an alkyl group having 1 to 10 atoms, an aryl group having 6 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms, and a halogen atom or an alkyl group having 1 to 4 carbon atoms. Is most preferred.

Here, the aliphatic group means an alkyl group, an alkenyl group, an alkynyl group and an aralkyl group.

The 5-membered ring formed by Z ¹ and Z ² is preferably a nitrogen-containing aromatic ring, for example, a pyrazole ring, 1,
There are 2,3-triazole rings, 1,2,4-triazole rings, oxadiazole rings and thiadiazole rings. Z ¹ and Z ² are preferably pyrazole rings, 1,
2,4-triazole ring, oxadiazole ring and thiadiazole ring, more preferably pyrazole ring,
1,2,4-triazole ring and oxadiazole ring, most preferably pyrazole ring.

The number of carbon atoms of Z ¹ and Z ² is preferably 3 to 20, more preferably 3 to 8, and further preferably 3 to 5.

In the general formula (I), L ¹ , L ² , L ³ and L ⁴ may be the same or different and each is a hydrogen atom or an alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 carbon atom). -10, more preferably 1 to 4 carbon atoms, for example, methyl, ethyl, iso-propyl, te
rt-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, trifluoromethyl, pentafluoromethyl and the like), an aryl group (preferably having 6 carbon atoms)
To 20, more preferably 6 to 10 carbon atoms, and examples thereof include phenyl, p-methylphenyl, naphthyl, anthranyl, etc.) or a nitrogen-containing aromatic ring group (preferably 1 to 20 carbon atoms, more preferably carbon number). 1 to 10, more preferably 1 to 5 carbon atoms, and the hetero atom other than nitrogen has, for example, an oxygen atom or a sulfur atom, and specifically includes, for example, imidazolyl, triazolyl, pyrazolyl, benzoxazolyl, benzimidazolyl. , Benzthiazolyl and the like), preferably a hydrogen atom,
An alkyl group having 1 to 4 carbon atoms and a nitrogen-containing aromatic ring group having 1 to 5 carbon atoms, more preferably a hydrogen atom, methyl, ethyl, iso-propyl, n-propyl, iso.
-Butyl, iso-pentyl, 1-pyrazolyl, 1,
2,4-triazol-1-yl, oxadiazole-
1-yl and thiadiazol-1-yl are more preferable, and hydrogen atom, methyl, ethyl, iso-propyl and 1-pyrazolyl are more preferable.

M represents a metal atom, preferably a Group 3 metal atom, and most preferably a boron atom.

Of the compounds represented by the general formula (I), compounds having a pyrazabole structure represented by the following general formula (II) are preferable.

[0018]

[Chemical 3]

In the general formula (II), R ¹ , R ² , R ³ ,
R ⁴ , R ⁵ and R ⁶ represent a hydrogen atom or a substituent, and examples and preferable ranges of the substituent are the same as those mentioned for Z ¹ and Z ² .

In the general formula (II), L ¹ , L ² , L ³ and L ⁴ have the same meanings as those in the general formula (I), and their preferable ranges are also the same.

Of the pyrazabole compounds represented by the general formula (II), 4,4,4 represented by the following formula are more preferable.
It is 8,8-tetrakis (1H-pyrazol-1-yl) pyrazabol.

[0022]

[Chemical 4]

Specific examples of the compound represented by formula (I) used in the present invention are shown below, but the present invention is not limited thereto.

[0024]

[Chemical 5]

[0025]

[Chemical 6]

[0026]

[Chemical 7]

[0027]

[Chemical 8]

[0028]

[Chemical 9]

The phosphorescent compound according to the present invention emits light based on a transition between terms having different multiplicities (eg triplet →
Singlet) is stronger than other substances. The phosphorescence quantum yield at room temperature is preferably 25% or more, more preferably 40% or more, further preferably 60%, particularly preferably 80%.
The above is mentioned, for example, an organic compound containing no metal, a metal complex having a metal-heteroatom bond, an organometallic complex having a metal-carbon bond, and the like, and an orthometallated metal complex described below and the like. To be Next, the organometallic complex will be described. The organometallic complex is defined by, for example, “Organometallic Chemistry—Basics and Applications—” p150, 232, Shokabo Publishing, Akio Yamamoto (published in 1982), page 6, in which the metal and the organic group are metal-carbon. Refers to a compound bound by a direct bond. Next, the orthometallated metal complex used in the present invention will be described. The orthometallated metal complex is, for example, "Organometallic Chemistry-Basics and Applications-", p150, 232 by Sobobo Akio Yamamoto, published in 1982, "Photochemistry and Photophysics of Coordin".
ation Compounds "p71-p77, p135-p146 Springer-Verla
It is a generic term for a group of compounds described in H. Yersin, Company g, published in 1987. Any metal can be used as the central metal of the metal complex as long as it is a transition metal. In the present invention, rhodium, platinum, gold, iridium, ruthenium, palladium and the like can be particularly preferably used. Of these, iridium is particularly preferable.

The valence of the metal of the orthometallated metal complex is not particularly limited, but when iridium is used, it is preferably trivalent. The ligand of the orthometallated metal complex is not particularly limited as long as it can form an orthometalated metal complex. For example, a nitrogen-containing heterocyclic ring substituted with an aryl group (the substitution position of the aryl group is a nitrogen-containing heterocyclic nitrogen). It is on the carbon adjacent to the atom, examples of the aryl group include a phenyl group, naphthyl group, anthryl group, and pyrenyl group, and examples of the nitrogen-containing heterocycle include, for example, pyridine, pyrimidine, pyrazine, pyridazine, quinoline, isoquinoline, Quinoxaline, phthalazine, quinazoline, naphthyridine, cinnoline, phenanthroline, pyrrole, imidazole,
Pyrazole, oxazole, oxadiazole, triazole, thiadiazole, benzimidazole, benzoxazole, benzothiazole, phenanthridine, etc.), heteroaryl group-substituted nitrogen-containing heterocycle (heteroaryl group is substituted with nitrogen-containing heterocycle) It is on the carbon adjacent to the nitrogen atom, and the heteroaryl group includes, for example, a group containing the above nitrogen-containing heterocyclic derivative, a thienyl group, a furyl group and the like), 7,8-benzoquinoline, phosphinoaryl, phosphinoaryl, Examples include phenoheteroaryl, phosphinoxyaryl, phosphinoxyheteroaryl, aminomethylaryl, aminomethylheteroaryl and the like and derivatives thereof. Aryl group-substituted nitrogen-containing aromatic heterocycle, heteroaryl group-substituted nitrogen-containing aromatic heterocycle, 7,8-benzoquinoline and derivatives thereof are preferable, and phenylpyridine, thienylpyridine, 7,8-benzoquinoline and derivatives thereof are preferable. Are more preferable, and thienylpyridine and its derivatives, and 7,8-benzoquinoline and its derivatives are particularly preferable.

The compound of the present invention may have other ligands in addition to the ligand necessary for forming the orthometallated metal complex. There are various known ligands as other ligands, for example, “Photochemistry and Photophysic
s of Coordination Compounds '' Springer-Verlag H.
Examples include ligands described in Yersin, published in 1987, “Organometallic Chemistry: Basics and Applications,” published by Shokabosha Akio Yamamoto, published in 1982, and preferably halogen ligands (preferably chlorine coordination). Child), a nitrogen-containing heterocyclic ligand (for example, bipyridyl, phenanthroline, etc.) and a diketone ligand, more preferably a chlorine ligand and a bipyridyl ligand.

The ligand of the ortho-metallated metal complex of the present invention may be of one kind or plural kinds. The number of ligands in the complex is preferably 1 to 3 types, particularly preferably 1 to 2 types, and further preferably 1 type.

The carbon number of the orthometallated metal complex of the present invention is preferably 5 to 100, more preferably 10 to 8.
It is 0, more preferably 14 to 50.

A preferred form of the ortho-metallated metal complex of the present invention is a compound having a partial structure represented by the following general formula (KI) or a tautomer thereof.

[0035]

[Chemical 10]

In the formula, M represents a transition metal. Q _k1 represents an atomic group necessary for forming a 5- or 6-membered aromatic ring.
Q _k2 represents an atomic group necessary for forming a 5- or 6-membered nitrogen-containing aromatic ring. The transition metal represented by M is preferably rhodium, platinum, gold, iridium, ruthenium or palladium, more preferably rhodium, platinum or iridium, further preferably platinum or iridium, and particularly preferably iridium. is there. The 5- or 6-membered aromatic ring formed by Q _k1 may be either an aromatic hydrocarbon ring or an aromatic heterocycle, and examples thereof include benzene, naphthalene, anthracene, pyrene, pyridine, quinoline,
Isoquinoline, pyridazine, pyrimidine, pyrazine, thiophene, furan, pyrrole, pyrazole, imidazole, thiazole, oxazole, thiadiazole, oxadiazole, triazole, quinoxaline, phthalazine, naphthyridine, cinnoline, phenanthroline, benzothiazole, benzoxazole, benzimidazole, fe Nantrizine and the like are preferable, benzene, naphthalene, pyridine, quinoline, isoquinoline, thiophene and furan are preferable, and more preferably benzene, naphthalene, pyridine, quinoline, isoquinoline,
Thiophene, more preferably benzene, naphthalene, or thiophene.

Examples of the 5- or 6-membered nitrogen-containing aromatic ring formed by Q _k2 include pyridine, quinoline, isoquinoline, pyridazine, pyrimidine, pyrazine, pyrazole, imidazole, thiazole, oxazole, thiadiazole, oxadiazole and triazole. , Quinoxaline, phthalazine, naphthyridine, cinnoline, phenanthroline, benzothiazole, benzoxazole,
Examples thereof include benzimidazole and phenanthridine. Pyridine, quinoline, isoquinoline, pyrazole and pyridazine are preferable, pyridine, quinoline, isoquinoline and pyrazole are more preferable, and pyridine, isoquinoline and pyrazole are more preferable. The ring formed by Q _k1 and Q _k2 may have a substituent, and as the substituent, those mentioned as the substituents of Z ¹ and Z ^{2 in} the general formula (I) can be applied, and the preferable range is also It is the same. Further, the substituents may be connected to each other to form a ring. Further, the compound having a partial structure represented by the general formula (K-I) or a tautomer thereof may have one transition metal in the compound, or a so-called multinuclear complex having two or more transition metals. May be Other metal atoms may be contained at the same time.

Of the compounds having a partial structure represented by the general formula (K-I), more preferably the following general formula (K-I)
A compound represented by I) or (K-III) or a tautomer thereof.

[0039]

[Chemical 11]

[0040] In the formula, it represents a R ^k21, R ^k22, R ^k31 and R ^k32 are each substituents. q ²¹ , q ²² and q ³² each represent an integer of 0 to 4, and q ³¹ represents an integer of 0 to 2. q
^21, q ^22, q ^31, when q ³² is 2 or more, plural ^{R k21, R k22, R k31} , R k32 may differ same or another.

[0041] The substituent represented by ^{R k21, R k22, R k31} , R k32, for example can be applied, those exemplified as the substituent of Z ₁ and Z ₂ in the general formula (I). R ^k21 , R
^k22 , R ^k31 and R ^k32 may be further substituted. Further, the substituents may be bonded to each other to form a condensed ring structure.

[0042] ^{R k21, R k22, R k31} , as R ^k32 is preferably an alkyl group, an aryl group, a heterocyclic group, an alkoxy group, an aryloxy group, a halogen atom, a group forming a condensed ring structure bonded to preferably More preferably, it is an alkyl group, an aryl group, a fluorine atom, or a group which is bonded to form an aromatic condensed ring structure. q ²¹ , q ²² , q ³¹ , and q ³² are preferably 0, 1, and 2, and more preferably q ²¹ + q ²² =
0, 1, 2, q ³¹ + q ³² = 0, 1, 2.

L _k2 and L _k3 each represent a ligand.
Examples of the ligand include the ligand necessary for forming the orthometallated metal complex, and the ligands described for other ligands. L _k2 and L _k3 are preferably a ligand necessary for forming an orthometalated iridium complex, a nitrogen-containing heterocyclic ligand, a diketone ligand or a halogen ligand, more preferably an orthometalated iridium complex. It is a ligand necessary for formation, a diketone ligand, and a bipyridyl ligand.

M^{twenty one}And are m³¹Respectively 1, 2, 3
Represented, preferably 2, 3 and more preferably 3.
It m^{twenty two}And m³²Each represents an integer of 0 to 5,
Preferably 0, 1, 2 and more preferably 0, 1
is there. m^{twenty one}And m^{twenty two}, M³¹And m ³²The number combination of
The metal complex represented by the general formula (K-II) or (K-III) is
The combination of the numbers that give a functional complex is preferable.

The ortho-metallated metal complex of the present invention may be a so-called low molecular weight compound having one repeating unit of the general formula (K-1), and a plurality of repeating units of the general formula (K-1). So-called oligomeric compounds and polymer compounds having an average molecular weight (Mw: polystyrene equivalent) of preferably 1000 to 5000000, more preferably 2000
˜1,000,000, more preferably 3000 to 100,000. )
May be The orthometallated metal complex used in the present invention is preferably a low molecular weight compound.

Next, examples of the phosphorescent organic metal complex compound used in the present invention will be shown, but the present invention is not limited thereto.

[0047]

[Chemical 12]

[0048]

[Chemical 13]

[0049]

[Chemical 14]

[0050]

[Chemical 15]

[0051]

[Chemical 16]

[0052]

[Chemical 17]

[0053]

[Chemical 18]

[0054]

[Chemical 19]

[0055]

[Chemical 20]

[0056]

[Chemical 21]

[0057]

[Chemical formula 22]

The orthometallated metal complex used in the present invention is
Inorg. Chem., 1991, Issue 30, page 1685., ibid., 1988, 27.
No., 3464., 1994, No. 33, 545. Inorg.Chim.Ac.
ta, 1991, 181, 245. J. Organomet. Chem., 1987.
335, 293, J. Am. Chem. Soc., 1985, 107,
P. 1431. and the like can be synthesized by various known methods.

In the present invention, the organic compound layer containing the compound represented by formula (I) and the organic compound layer containing the phosphorescent compound may be the same or different, Preferably, the organic compound layer containing the compound represented by formula (I) and the organic compound layer containing the phosphorescent compound are different. Still more preferably, the compound represented by formula (I) is contained in at least one layer between the light emitting layer and the cathode, and the phosphorescent compound is contained in the light emitting layer.

Next, a light emitting device containing the compound of the present invention will be described. The method for forming the organic layer of the light emitting device containing the compound of the present invention is not particularly limited, but resistance heating vapor deposition, electron beam, sputtering, molecular lamination method, coating method, inkjet method, printing method,
A transfer method, an electrophotographic method, or the like is used, and resistance heating vapor deposition and a coating method are preferable in terms of characteristics and manufacturing.

The light emitting element of the present invention is an element in which a plurality of organic compound layers including a light emitting layer are formed between a pair of electrodes of an anode and a cathode, and in addition to the light emitting layer, a hole injection layer, a hole transport layer, and an electron injection layer. It may have a layer, an electron transport layer, a protective layer, and the like, and each of these layers may have another function. Various materials can be used for forming each layer.

The anode supplies holes to the hole injecting layer, the hole transporting layer, the light emitting layer and the like, and may be a metal, an alloy, a metal oxide, an electrically conductive compound, or a mixture thereof. A material having a work function of 4 eV or more is preferable. Specific examples thereof include conductive metal oxides such as tin oxide, zinc oxide, indium oxide and indium tin oxide (ITO), metals such as gold, silver, chromium and nickel, and these metals and conductive metal oxides. A mixture or laminate of the above, an inorganic conductive material such as copper iodide and copper sulfide, an organic conductive material such as polyaniline, polythiophene, polypyrrole, and a laminate of these and ITO, and preferably a conductive metal. Is an oxide,
In particular, ITO is preferable in terms of productivity, high conductivity, transparency and the like. The film thickness of the anode can be appropriately selected depending on the material, but it is usually preferably in the range of 10 nm to 5 μm, more preferably 50 nm to 1 μm, and further preferably 100 nm to 500 nm.

As the anode, a layer formed on soda lime glass, non-alkali glass, a transparent resin substrate or the like is usually used. When glass is used, it is preferable to use non-alkali glass as the material in order to reduce the amount of ions eluted from the glass. Further, when soda lime glass is used, it is preferable to use a glass coated with a barrier such as silica. The thickness of the substrate is not particularly limited as long as it is sufficient to maintain the mechanical strength, but when glass is used, it is usually 0.2 mm or more, preferably 0.7 mm or more. Although various methods are used for producing the anode depending on the material, for example, in the case of ITO, electron beam method, sputtering method, resistance heating vapor deposition method, chemical reaction method (sol-gel method, etc.), dispersion of indium tin oxide is used. A film is formed by a method such as coating. The anode may be washed or otherwise treated to reduce the drive voltage of the element,
It is also possible to increase the luminous efficiency. For example, in the case of ITO, UV-ozone treatment and plasma treatment are effective.

The cathode supplies electrons to the electron injecting layer, the electron transporting layer, the light emitting layer, etc., and the adhesion between the negative electrode and the adjacent layer such as the electron injecting layer, the electron transporting layer, the light emitting layer and the ionization potential, It is selected in consideration of stability and the like. As a material for the cathode, a metal, an alloy, a metal halide, a metal oxide, an electrically conductive compound, or a mixture thereof can be used. Specific examples thereof include an alkali metal (for example, L
i, Na, K, Cs, etc.) and their fluorides, oxides, alkaline earth metals (eg Mg, Ca, etc.) and their fluorides, oxides, gold, silver, lead, arnium, sodium-potassium alloys or them. Mixed metal, a lithium-aluminum alloy or a mixed metal thereof, a magnesium-silver alloy or a mixed metal thereof, a rare earth metal such as indium or ytterbium, and the like, preferably a work function of 4 eV or less, more preferably Is aluminum, lithium-aluminum alloy or mixed metal thereof, magnesium-silver alloy or mixed metal thereof, and the like. The cathode may have not only a single layer structure of the above compound and mixture but also a laminated structure including the above compound and mixture. The film thickness of the cathode can be appropriately selected depending on the material, but it is usually preferably in the range of 10 nm to 5 μm, more preferably 50 nm to 1 μm, and further preferably 100 nm to 1 μm. A method such as an electron beam method, a sputtering method, a resistance heating vapor deposition method, or a coating method is used for producing the cathode, and the metal can be vapor-deposited alone or two or more components can be vapor-deposited simultaneously. Further, it is possible to vapor-deposit a plurality of metals at the same time to form an alloy electrode, or a previously prepared alloy may be vapor-deposited. The sheet resistance of the anode and the cathode is preferably low, and is preferably several hundred Ω / □ or less.

As a material for the light emitting layer, holes can be injected from the anode or the hole injection layer or the hole transport layer when an electric field is applied, and electrons can be injected from the cathode or the electron injection layer or the electron transport layer. Any material may be used as long as it can form a layer having a function, a function of moving injected charges, and a function of providing a field for recombination of holes and electrons to emit light. The light emitting layer preferably contains the orthometallated metal complex of the present invention, but other light emitting materials can be used in combination. For example, benzoxazole, benzimidazole, benzothiazole, styrylbenzene, polyphenyl, diphenylbutadiene, tetraphenylbutadiene, naphthalimide, coumarin, perylene, perinone, oxadiazole, aldazine, pyraridine, cyclopentadiene, bisstyrylanthracene, quinacridone, pyrrolo. Pyridine, thiadiazolopyridine, cyclopentadiene, styrylamine and their derivatives, aromatic dimethylidin compounds, various metal complexes such as 8-quinolinol and its derivatives such as metal complexes and rare earth complexes, polythiophene, polyphenylene, polyphenylene vinylene, Examples thereof include polymer compounds such as polythienylene vinylene. The thickness of the light emitting layer is not particularly limited, but is preferably in the range of usually 1 nm to 5 μm, more preferably 5 nm to 1 μm.
And more preferably 10 nm to 500 nm.
The method for forming the light emitting layer is not particularly limited,
Methods such as resistance heating vapor deposition, electron beam, sputtering, molecular lamination method, coating method (spin coating method, casting method, dip coating method, etc.), LB method, inkjet method, printing method, transfer method, electrophotographic method, etc. are used. Of these, resistance heating vapor deposition and coating methods are preferable.

The material of the hole injecting layer and the hole transporting layer has any of the function of injecting holes from the anode, the function of transporting holes, and the function of blocking the electrons injected from the cathode. If Specific examples thereof include carbazole,
Triazole, oxazole, oxadiazole, imidazole, polyarylalkane, pyrazoline, pyrazolone, phenylenediamine, arylamine, amino-substituted chalcone, styrylanthracene, fluorenone, hydrazone, stilbene, silazane and their derivatives, aromatic tertiary amine compounds , Styrylamine compounds, aromatic dimethylidyne compounds, porphyrin compounds, polysilane compounds, poly (N-vinylcarbazole) and its derivatives, aniline copolymers, thiophene oligomers, conductive polymer oligomers such as polythiophene, carbon films Etc. The thickness of the hole injection layer and the hole transport layer is not particularly limited, but is usually 1
The range of nm to 5 μm is preferable, the range of 5 nm to 1 μm is more preferable, and the range of 10 nm to 50 is more preferable.
It is 0 nm. The hole injection layer and the hole transport layer may have a single-layer structure composed of one or more of the above-mentioned materials, or may have a multi-layer structure composed of a plurality of layers having the same composition or different compositions. As a method for forming the hole injection layer and the hole transport layer, a vacuum deposition method, an LB method, an inkjet method, a printing method, a transfer method, an electrophotographic method, and a method in which the hole injection transport agent is dissolved or dispersed in a solvent and coated. Method (spin coating method, casting method, dip coating method, etc.) is used. In the case of the coating method, it can be dissolved or dispersed together with the resin component, and as the resin component, for example,
Polyvinyl chloride, polycarbonate, polystyrene, polymethylmethacrylate, polybutylmethacrylate,
Polyester, polysulfone, polyphenylene oxide, polybutadiene, poly (N-vinylcarbazole), hydrocarbon resin, ketone resin, phenoxy resin, polyamide, ethyl cellulose, vinyl acetate, ABS resin, polyurethane, melamine resin, unsaturated polyester resin, alkyd resin, Examples thereof include epoxy resin and silicone resin.

The material for the electron injecting layer and the electron transporting layer is one having any of the function of injecting electrons from the cathode, the function of transporting electrons, and the function of blocking the holes injected from the anode. Good. Specific examples thereof include triazole,
Aromatic ring tetracarboxylic acid anhydrides such as oxazole, oxadiazole, fluorenone, anthraquinodimethane, anthrone, diphenylquinone, thiopyran dioxide, carbodiimide, fluorenylidene methane, distyrylpyrazine, naphthalene and perylene, phthalocyanine and these. Of the above, metal complexes of 8-quinolinol and its derivatives, metal phthalocyanines, various metal complexes represented by metal complexes having benzoxazole or benzothiazole as a ligand, and the like. The thickness of the electron injection layer and the electron transport layer is not particularly limited, but is usually 1
The range of 5 nm to 5 μm is preferable, the range of 5 nm to 1 μm is more preferable, and the range of 10 nm to 50 is more preferable.
It is 0 nm. The electron injection layer and the electron transport layer may have a single-layer structure composed of one or more of the above-mentioned materials, or may have a multi-layer structure composed of a plurality of layers having the same composition or different compositions. Examples of the method for forming the electron injection layer and the electron transport layer include a vacuum deposition method, an LB method, an inkjet method, a printing method, a transfer method, an electrophotographic method, and a method of coating the solvent by dissolving or dispersing the electron injecting and transporting agent ( Spin coating method, casting method, dip coating method, etc.) are used. In the case of the coating method, it can be dissolved or dispersed together with the resin component, and as the resin component, for example,
What was illustrated in the case of a positive hole injection transport layer can be applied.

As the material of the protective layer, any material may be used as long as it has a function of preventing a substance such as moisture or oxygen that promotes element deterioration from entering the element. As a concrete example,
In, Sn, Pb, Au, Cu, Ag, Al, Ti, N
Metals such as i, MgO, SiO, SiO ₂ , Al ₂ O ₃ , G
eO, NiO, CaO, BaO, Fe ₂ O ₃ , Y ₂ O ₃ ,
Metal oxides such as TiO ₂ ; nitrides such as SiNx and SiNxOy; metal fluorides such as MgF ₂ , LiF, AlF ₃ and CaF ₂ ; polyethylene, polypropylene, polymethylmethacrylate, polyimide, polyurea, polytetrafluoroethylene, poly Chlorotrifluoroethylene,
Polydichlorodifluoroethylene, a copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene,
A copolymer obtained by copolymerizing a monomer mixture containing tetrafluoroethylene and at least one comonomer, a fluorine-containing copolymer having a cyclic structure in the copolymer main chain,
Examples thereof include a water-absorbing substance having a water absorption rate of 1% or more and a moisture-proof substance having a water absorption rate of 0.1% or less. The method for forming the protective layer is not particularly limited, and examples thereof include vacuum deposition method, sputtering method, reactive sputtering method, MBE (molecular beam epitaxy) method, cluster ion beam method, ion plating method, plasma polymerization method (high-frequency excited ions). Plating method), plasma CVD method, laser CVD method, thermal C
A VD method, a gas source CVD method, a coating method, an inkjet method, a printing method, or a transfer method can be applied.

[0069]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Example 1 A transparent support substrate was prepared by depositing ITO in a thickness of 150 nm (manufactured by Tokyo Sanyo Vacuum Co., Ltd.) on a washed 25 mm × 25 mm × 0.7 mm glass substrate. After etching and washing this transparent support substrate, tetrakis (4-diphenylaminophenyl) silane about 50 nm, the light emitting layer shown in Table 1 (the mass ratio of the host material and the light emitting material is about 94:
6) of about 36 nm and the following compound A of about 36 nm were deposited in this order in a vacuum of 10 ⁻³ to 10 ⁻⁴ Pa at a substrate temperature of room temperature. A patterned mask (a mask having a light emitting area of 5 mm × 4 mm) is placed on the organic thin film, and magnesium: silver = 10: 1 is co-deposited with 250 nm in the vapor deposition apparatus, and then 300 nm of silver is further vapor deposited to obtain an EL element No. ． 1
01-116 were produced. Toyo Technica Source Measure Unit Model 2400 is used to apply a constant DC voltage to the EL element to cause it to emit light, and the brightness is measured by the Topcon brightness meter BM.
-8, and the emission wavelength was measured using a spectrum analyzer PMA-11 manufactured by Hamamatsu Photonics. The results are shown in Table 1.

[0070]

[Table 1]

[0071]

[Chemical formula 23]

Further, these elements were enclosed in an autoclave substituted with argon gas, and heated under conditions of 85 ° C. for 3 hours.
Table 1 also shows the results of the same luminance measurement and light emitting surface observation after storage for a day. From the results in Table 1, in the comparative devices (device Nos. 101 to 104) using the reference compound CBP as the host material, the brightness immediately after preparation and the external quantum efficiency were low, and the brightness was significantly decreased after storage at high temperature. In contrast to the occurrence of dark spots, an element using the host material of the present invention (element No. 105 to 1)
In 16), the brightness immediately after preparation and the external quantum efficiency are good, the decrease in brightness after storage at high temperature is small, and the luminescent surface state is also good, indicating that both the emission characteristics and storage durability immediately after preparation are excellent. I understand. In addition, the device No.
Element No. 116 from which the phosphorescent compound was removed. 11
In No. 7, sufficient brightness was not obtained and external quantum efficiency was low.

Example 2. 25 mm x 25 mm washed
The transparent support substrate was a 0.7 mm glass substrate on which ITO was formed to a thickness of 150 nm (manufactured by Tokyo Sanyo Vacuum Co., Ltd.). After etching and washing this transparent supporting substrate, tetrakis (4-diphenylaminophenyl) silane about 5
0 nm, the light emitting layer shown in Table 2 consisting of the following compound B and the light emitting material (the mass ratio of the compound B and the light emitting material is about 94:
6) is about 36 nm, and the electron transport material shown in Table 2 is about 18 n
m and compound C 18 nm were vapor-deposited in this order at a substrate temperature of room temperature in a vacuum of 10 ⁻³ to 10 ⁻⁴ Pa. Mask patterned on organic thin film (light emitting area is 5mm x 4mm
A mask will be installed and magnesium in the vapor deposition device:
After co-evaporating 250 nm of silver = 10: 1, silver 300 is further added.
nm of the EL element No. 201-216 were produced.

The same measurement and evaluation as in Example 1 were performed on each of the obtained light emitting devices. The results are shown in Table 2.

[0075]

[Table 2]

[0076]

[Chemical formula 24]

From the results of Table 2, a comparative device (device No. 2) in which the compound C, which is a comparative compound, was used as an electron transport material.
Nos. 01 to 204) have low luminance immediately after formation and external quantum efficiency, and a large reduction in luminance and generation of dark spots are observed after storage at high temperature, whereas an element using the electron transport material of the present invention (Element No. 205 to 216), the brightness and external quantum efficiency immediately after preparation were good, the minimum driving voltage was low, the brightness after storage at high temperature was small, and the emission surface condition was good. It can be seen that the storage durability is excellent.

Example 3. Etching as in Example 1,
On a washed ITO glass substrate, 40 mg of poly (N-
Vinylcarbazole (PVK)), 12 mg of 2- (4-
tert-Butylphenyl) -5- (4-biphenylyl)-
1,3,4-oxadiazole (PBD), 1 mg K-
A solution of 1 in 3 ml of 1,2-dichloroethane was spin-coated. The thickness of the organic layer at this time is about 120 n
It was m. Then, a cathode is vapor-deposited in the same manner as in Example 1, and E
L element 301 was produced. K-1 for element 301
And an EL device 3 having exactly the same composition as 301 except that the compounds shown in Table 3 were added in equal amounts instead of PBD.
02-312 were produced. Toyo Technica Source Measure Unit Model 2400 was used to apply a constant DC voltage to the EL element to cause it to emit light, and the brightness was measured by the Topcon brightness meter BM-
8, and the emission wavelength was measured using a spectrum analyzer PMA-11 manufactured by Hamamatsu Photonics. The results are shown in Table 3.

[0079]

[Table 3]

[0080]

[Chemical 25]

As is clear from the results shown in Table 3, the device of the present invention exhibits high emission brightness and emission efficiency even in the case of a coating type device having a low emission efficiency, and is also excellent in storage durability. .

Example 4. 25 mm x 25 mm washed
The transparent support substrate was a 0.7 mm glass substrate on which ITO was formed to a thickness of 150 nm (manufactured by Tokyo Sanyo Vacuum Co., Ltd.). After etching and cleaning this transparent support substrate,
N, N'-bis (4'-diphenylamino-4-biphenylyl) N, N'-diphenylbenzidine about 50 nm,
P-16 and 4-N, N'-bis (p-methylphenyl)
Amino-α-phenyl stilbene (mass ratio 5: 1) about 5
0 nm was vapor-deposited in this order at a substrate temperature of room temperature in a vacuum of 10 ⁻³ to 10 ⁻⁴ Pa. Mask patterned on organic thin film (mask with light emitting area of 5 mm x 4 mm)
Is installed, a cathode made of AlLi alloy is vapor-deposited, and EL element No. 401 was produced. Next, the element No. 401 4-N, N'-bis (p-methylphenyl) amino-α
-Phenylstilbene was replaced with an equal mass of the phosphorescent compound shown in Table 4 in exactly the same manner as in Device No. 402-405 were produced. Furthermore, N, N'-
Bis (4'-diphenylamino-4-biphenylyl)
After depositing about 50 nm of N, N′-diphenylbenzidine, deposit about 20 nm of Alq and then deposit about 40 nm of P-16.
nm, an anode made of AlLi alloy is vapor-deposited, and the device No.
406 was produced. Next, N, N′-bis (4′-diphenylamino-4-biphenylyl) N, N′-diphenylbenzidine was vapor-deposited with a thickness of about 50 nm, and Alq was added with a concentration of about 50 n.
m vapor deposition, vapor deposition of a cathode made of AlLi alloy, element N
o. 407 was produced. Finally, the element No. 402 P-
No. 16 was replaced with CBP having an equal mass, and the element No. 408 was produced. Example 1 for each light emitting element
The same measurement was performed. The results are shown in Table 4.

[0083]

[Table 4]

As is clear from the results shown in Table 4, the device of the present invention has high luminous efficiency, which can be obtained only by using the compound represented by the general formula (I) and the phosphorescent compound in combination. It is an effect.

[0085]

EFFECT OF THE INVENTION The device of the present invention exhibits high luminous brightness and luminous efficiency. Regarding storage durability, there is little decrease in brightness after storage at high temperature, and the light emitting surface is in good condition. To be improved. Further, the same effect can be obtained even in the case of a coating type element which usually has low luminous efficiency.

Claims (7)

[Claims] 1. A light emitting device having an organic compound layer including a light emitting layer formed between a pair of electrodes provided on a substrate, wherein at least one of the organic compound layers comprises a compound represented by the following general formula (I): A light-emitting device comprising a phosphorescent compound. [Chemical 1] In the general formula (I), Z ¹ and Z ² represent a group of non-metal atoms necessary to form a 5-membered ring with a nitrogen atom, and this ring may have a substituent, and A condensed ring may be formed with the ring. L ¹ , L ² , L ³ and L ⁴ each represent a hydrogen atom, an alkyl group, an aryl group or a nitrogen-containing aromatic ring group, and M represents a metal atom. 2. The light emitting device according to claim 1, wherein the compound represented by the general formula (I) has a pyrazaball structure. 3. The compound having a pyrazabol structure is 4,4,8,8-tetrakis (1H-pyrazole-1-
3. The light emitting device according to claim 2, wherein the light emitting device is a pyraza ball. 4. The light emitting device according to claim 1, wherein the phosphorescent compound is an organometallic complex. 5. The light emitting device according to claim 1, wherein the phosphorescent compound is an orthometallated complex. 6. The light emitting device according to claim 1, wherein the phosphorescent compound is an orthometalated iridium complex. 7. The light emitting device according to claim 1, wherein the organic light emitting layer contains a polymer compound.