JP2005255986A - Material for forming emitter layer and organic electroluminescence element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphorescence dopant material-using organic electroluminescence element which retains a high light emitting efficiency, typical of phosphorescence, and has a long life showing little luminosity-decrease when it is used continuously. <P>SOLUTION: A material for forming an emitter layer is obtained by combining a host material comprising two or more different charge transfer compounds with a dopant material comprising an organic metal complex containing at least one metal selected from groups 7-11 of the periodic table, and is characterized in that the excited triplet level (T1) of the two or more different charge transfer compounds is not less than 2.2 eV. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light emitting layer forming material and an organic electroluminescent device, and more particularly to an organic electroluminescent device having high light emission efficiency and little reduction in luminance during continuous driving.

Conventionally, as a thin film type electroluminescent (EL) element, there are ZnS, CaS, SrS, etc. which are inorganic material II-VI compound semiconductors, Mn which is an emission center, rare earth elements (Eu, Ce, Tb, Sm, etc.) ) Is generally used, but an EL element made from the above inorganic material is
1) AC drive is required (50-1000Hz),
2) High drive voltage (~ 200V),
3) Full color is difficult (especially blue),
4) There is a problem that the cost of the peripheral drive circuit is high.

However, in recent years, EL devices using organic thin films have been developed to improve the above problems. In particular, in order to improve luminous efficiency, the type of electrode is optimized for the purpose of improving the efficiency of carrier injection from the electrode, and a hole transporting layer made of aromatic diamine and a light emitting layer made of 8-hydroxyquinoline aluminum complex, Development of an organic electroluminescent device provided with an organic electroluminescent device (see Non-Patent Document 1: Appl. Phys. Lett., 51, 913, 1987), compared with a conventional EL device using a single crystal such as anthracene. There has been a significant improvement in luminous efficiency. In addition, for example, 8-hydroxyquinoline aluminum complex is used as a host material, and a laser fluorescent dye such as coumarin is doped (see Non-Patent Document 2: J. Appl. Phys., 65, 3610, 1989). Therefore, improvement of luminous efficiency, conversion of emission wavelength, and the like have also been performed, which are close to practical characteristics.

  In addition to the electroluminescent device using the low molecular weight material as described above, as a material of the light emitting layer, poly (p-phenylene vinylene), poly [2-methoxy-5- (2-ethylhexyloxy) -1,4 Development of electroluminescent devices using polymer materials such as -phenylenevinylene] and poly (3-alkylthiophene), and devices that combine low molecular light emitting materials and electron transfer materials with polymers such as polyvinylcarbazole. Has been done.

  As an attempt to increase the luminous efficiency of the device, the use of phosphorescence instead of fluorescence has been studied. If phosphorescence is used, that is, light emission from a triplet excited state is used, an efficiency improvement of up to 4 times is expected as compared with a conventional device using fluorescence (singlet). For this purpose, it has been studied to use a coumarin derivative or a benzophenone derivative as a light emitting layer (see Non-Patent Document 3: 51th Japan Society of Applied Physics, 28a-PB-7, 1990), but very low. Only brightness was obtained. Thereafter, the use of a europium complex has been studied as an attempt to utilize the triplet state, but this also did not lead to highly efficient light emission.

Recently, it has been reported that high-efficiency red light emission is possible by using the platinum complex (T-1) shown below (Non-patent Document 4: Nature, 395, 151, 1998). Thereafter, the iridium complex (T-2) shown below is doped into the light emitting layer, and the efficiency is further greatly improved by green light emission (Non-Patent Document 5: Appl. Phys. Lett., Vol. 75, page 4). 1999).

In order to apply the organic electroluminescence device to a display device such as a flat panel display, it is necessary to improve the light emission efficiency of the device and at the same time to ensure sufficient stability during driving.
However, the organic electroluminescence device using the phosphorescent molecule (T-2) described in the above-mentioned document has high efficiency light emission but has insufficient driving stability for practical use (see Non-Patent Document 6: Jpn). .J.
Appl. Phys., 38, L1502, 1999), it is difficult to realize a highly efficient display device.

  For the purpose of improving the lifetime of these phosphorescent devices, Balq (aluminum (III) bis (2-methyl-8-quinolinato) 4-phenylphenolate) and SAlq (aluminum (III) bis (2-methyl-8-quinolinato) Aluminum complex-based hole blocking materials such as triphenylsilanolate have been actively used to achieve a certain long life (see Non-Patent Document 7: Appl. Phys. Lett., 81, 162, 2002). .

However, since the above compound does not have sufficient hole blocking ability, the light emission efficiency of the device is insufficient, or some of the holes pass through the hole blocking material and escape to the electron transport layer. There was a problem that oxidation deterioration of the transport layer material occurred.
In addition, Patent Document 1 (US2002 / 0074935 A1) describes another technique for improving the lifetime of a phosphorescent device. NPD (N, N'-diphenyl-N, N'-bis-alpha-napthylbenzidine) And Alq3 (8-hydroxyquinoline aluminum complex) mixed with host material and PtOEP (2,3,7,8,12,12,17,18-octaethyl-21H, 23H-porphineplatinum II), or BTPIr (bis (2- (2'-benzo [4,5-a] thienylpyridinato-N, C3 ') iridium (III)-
Acetylateton) is described as a phosphorescent dopant.

However, in the above-mentioned Patent Document 1, it can be applied only to a red dopant material, and it has not been possible to extend the life of a green phosphor element or a blue phosphor element necessary for full color display. This is presumably because NPD and Alq3 have a low excited triplet level (T1).
For the reasons described above, rapid charge recombination in the light emitting layer and high emission efficiency of the dopant, or prevention of holes passing through the light emitting layer from escaping to the electron transport layer, and hole blocking material It is necessary for itself to have electrical oxidation-reduction durability, and further improvement studies have been desired for materials and device structures for producing devices with high luminous efficiency and stability.
US Patent Application Publication No. 2002/0074935 Appl. Phys. Lett., 51, 913, 1987 J. Appl. Phys., 65, 3610, 1989 The 51st Japan Society of Applied Physics, 28a-PB-7, 1990 Nature, 395, 151, 1998 Appl. Phys. Lett., 75, 4 pages, 1999 Jpn. J.Appl. Phys., 38, L1502, 1999 Appl. Phys. Lett., 81, 162, 2002

  An object of the present invention is to provide an organic electroluminescent device using a phosphorescent dopant material, and to provide a device having a long lifetime with little reduction in luminance during continuous driving while maintaining high luminous efficiency peculiar to phosphorescence.

As a result of intensive studies by the present inventors, an organic compound using a phosphorescent dopant material by using a host material composed of two or more different charge transporting compounds having an excited triplet level (T1) of 2.2 eV or more is used. It was found that the electroluminescent device can extend the life while maintaining high-efficiency light emission, and reached the present invention.
The “two or more different types of charge transporting compounds” referred to here are at least one material having a hole transporting property, and at least one is a material having an electron transporting property.

  By using such a host material composed of two or more different charge transporting compounds, the hole transporting compound or the electron transporting compound is responsible for transporting holes or electrons in the light emitting layer, respectively. Compared to the case where a carbazole compound such as CBP that has been used alone is used as a host, the light emitting site (or recombination site) can be moved from the vicinity of the interface between the light emitting layer and the adjacent layer to the center. . This makes it possible to suppress deterioration due to oxidation or reduction of the layer adjacent to the light emitting layer (hole blocking layer or hole transporting layer), and to extend the life of the organic electroluminescent device using the phosphorescent dopant material. It is guessed.

Further, by using a material having an excited triplet level (T1) of 2.2 eV or higher as a host, phosphorescent dopants that emit light at shorter wavelengths such as green and blue can be efficiently emitted as well as red. It becomes possible.
That is, the present invention relates to a host material composed of two or more different charge transporting compounds having an excited triplet level (T1) of 2.2 eV or more, and at least one metal selected from Groups 7 to 11 of the periodic table In an organic electroluminescent device having a light emitting layer forming material formed by combining a dopant material composed of an organometallic complex containing, and a substrate, at least an anode, a cathode, and a light emitting layer provided between both electrodes, the light emission The layer includes an organic material including a host material composed of two or more different charge transporting compounds having an excited triplet level (T1) of 2.2 eV or more, and at least one metal selected from Groups 7 to 11 of the periodic table An organic electroluminescent element characterized by containing a dopant material made of a metal complex.

According to the organic electroluminescent element using the light emitting layer forming material of the present invention, it is possible to realize an element having high efficiency and a long lifetime with little decrease in luminance during continuous driving. In particular, even a green phosphor element and a blue phosphor element, which have been difficult until now, can be realized with high efficiency and a long lifetime.
Therefore, the organic electroluminescent device according to the present invention is a flat panel display (for example, for OA computers and wall-mounted televisions), an in-vehicle display device, a light source utilizing characteristics of a mobile phone display or a surface light emitter (for example, a light source of a copying machine, It can be applied to liquid crystal displays and back light sources for instruments, display panels, and indicator lights, and its technical value is great.

The description of the constituent requirements described below is an example (representative example) of the embodiment of the present invention, and the contents are not specified.
The present invention includes a host material composed of two or more different charge transporting compounds having an excited triplet level (T1) of 2.2 eV or more and at least one metal selected from Groups 7 to 11 of the periodic table. It is a light emitting layer formation material which combines the dopant material which consists of organometallic complexes.

As the form of the light emitting layer forming material, two or more kinds of charge transporting compounds (host materials), an organometallic complex (dopant material) containing at least one metal selected from Groups 7 to 11 of the periodic table,
a) Form that is a single composition that is all mixed b) Combination (set) form that is partly mixed and the rest is a single material, or multiple, mixed A combination (set) form of the composition;
c) Although each compound is enclosed individually, the form supplied as a set as a combination material is mentioned.

As a), for example, two or more kinds of charge transporting compounds constituting the host material, and an organometallic complex containing at least one metal selected from Groups 7 to 11 of the periodic table may be appropriately combined with a medium such as chloroform. Mixed. Examples of the medium include halogen solvents such as chloroform, dichloromethane, 1,2-dichloroethane and chlorobenzene, ether solvents such as tetrahydrofuran, ethylene glycol dimethyl ether and anisole, N, N-dimethylformamide, N, N-dimethylacetamide, N Examples include amide solvents such as methylpyrrolidone, ester solvents such as γ-butrolactone and methyl benzoate, ketone solvents such as cyclohexanone and acetophenone, and aromatic solvents such as benzene, xylene and pyridine.

  As for b), in consideration of stability and handleability (sublimation, solubility in a solvent used as a medium, etc.), the medium described in a) is appropriately coexisted, and a plurality of charge transporting compounds and a periodic rule are combined. The organometallic complex containing at least one metal selected from Tables 7 to 11 can be divided into arbitrary compositions to form a combined (set) form. Among these, a mode in which a host material and a dopant material are divided and enclosed and supplied as a set as a combination material is preferable.

c) is a form in which the host material and the dopant material to be used are individually sealed together with the medium.
The host material and the dopant material in the medium are each generally 0.01% by weight or more, preferably 0.1% by weight or more, usually 50% by weight or less, preferably 10% by weight or less as a total concentration. It is better to select by range. If the upper limit is exceeded, the host material and dopant material in the medium are likely to precipitate, and if the lower limit is not reached, it is difficult to form a uniform coating film.
(Host material) Two or more different types of charge transporting compounds In the present invention, "two or more different types of charge transporting compounds" are compounds having at least one hole transporting property, and at least one of them being electron transporting. It is preferable that it is a compound which has property.

Since these charge transport compounds are mainly responsible for charge transport, stability against the charge is required. That is, oxidation stability is required for the hole transporting compound, and reduction stability is required for the electron transporting compound.
In addition, since both holes and electrons are present in the light emitting layer, it is more preferable that the charge transporting compound in the light emitting layer has good stability against charges opposite to the charges to be transported. Specifically, it is more preferable that the hole transporting compound has good reduction stability and the electron transporting compound has good oxidation stability.

  In addition, these charge transport compounds efficiently transfer charges (in this case, holes and electrons, respectively) transferred from the layer adjacent to the light emitting layer, specifically, the hole transport layer and the hole blocking layer, into the light emitting layer. To move to. Therefore, the charge transporting compound in the light emitting layer, that is, the hole transporting compound and the electron transporting compound, each have a small energy barrier between the light emitting layer and the adjacent hole transporting layer and hole blocking layer. preferable.

Furthermore, when the mobility for each charge (hole mobility in the case of a hole transporting compound, electron mobility in the case of an electron transporting compound) is high, light emission from the hole transporting layer, the hole blocking layer, etc. It is preferable because charges transferred from a layer adjacent to the layer can be efficiently taken into the light emitting layer and the driving voltage of the element can be lowered.
In addition, these charge transporting compounds are required to have an excited triplet level of 2.2 eV or higher. The excited triplet level correlates with the emission color and the light emission efficiency, and in particular, a higher excited triplet level is required to efficiently emit a dopant material that exhibits phosphorescence at a short wavelength such as blue. The excited triplet level of the charge transporting compound used in the light emitting layer of the present invention is usually 2.2 eV or more, preferably 2.4 eV or more, more preferably 2.6 eV or more. Moreover, it is preferably 3.4 eV or less, more preferably 3.2 eV or less.

Note that phosphorescence is light emission generated by transition from the excited triplet state to the ground state, and the excited triplet level (T1) can be obtained by experimentally measuring the phosphorescence spectrum of the substance. Usually, it is calculated from the peak wavelength (λ _T1 [nm]) having the highest energy (short wavelength) in the obtained phosphorescence spectrum. The excited triplet level used in the present invention was determined from the following relational expression using λ _{T1 of} the phosphorescence spectrum measured by cooling to about 5 to 10K.

T1 [eV] = 1240 / λ _T1 [nm]
The two or more different charge transporting compounds used in the present invention are preferably at least one or more hole transporting compounds and at least one or more electron transporting compounds. However, in the case of forming a thin film by vapor deposition, when combined with the dopant material, there are a total of three or more types, and the formation of the thin film becomes complicated, so two types of charge transporting compounds are preferable. In the case of forming a thin film by coating, two or more types can be used, but the number is preferably 4 or less, more preferably 2 types.

  In the present invention, by using two or more different charge transporting compounds, the light emitting position (or recombination position) existing in the vicinity of the interface between the light emitting layer and the adjacent layer in the conventional device is changed from the vicinity of the light emitting layer to It is possible to move to the vicinity of the center. As a result, deterioration due to oxidation or reduction of the layer adjacent to the light emitting layer (hole blocking layer or hole transporting layer) can be suppressed, and the lifetime of the organic electroluminescent element using the phosphorescent dopant material can be extended. Is.

In other words, the mixing ratio (compounding ratio) of the charge transporting compounds (hole transporting material and electron transporting material) used in the present invention can be appropriately selected so as to realize adjustment of the light emitting position (or recombination position). Good. This is because it depends on the charge mobility of the hole transporting compound and the electron transporting compound used, the energy barrier (energy gap) between adjacent layers, and the like.
The molecular weight of such a charge transporting compound is usually 4000 or less, preferably 3000 or less, more preferably 2000 or less, and usually 200 or more, preferably 300 or more, more preferably 400 or more. If the molecular weight exceeds the upper limit, the sublimation property is significantly reduced, which may cause trouble in the case of using an evaporation method when manufacturing an electroluminescent device, or decrease in solubility in an organic solvent, or in a synthesis process. As the amount of impurity components increases, it may be difficult to increase the purity of the material (that is, to remove the deterioration-causing substances). When the molecular weight is below the lower limit, the glass transition temperature, melting point, vaporization temperature, etc. Since it falls, there exists a possibility that heat resistance may be impaired remarkably.

The glass transition temperature required for the host material of the light emitting layer depends on the use of the organic electroluminescent device using the same, but is usually 80 ° C. or higher, more preferably 100 ° C. or higher. In the present invention, two or more kinds of charge transporting compounds are used as the host material of the light emitting layer, and the glass transition temperature (Tg _host ) of the host material at that time can be expressed by the following formula.
1 / Tg _host = (W _A / Tg _A + W _B / Tg _B + ...)
Tg _host : Glass transition temperature Tg _{A of the} entire host material of the light emitting layer Tg _A : Glass transition temperature Tg _{B of the} used charge transporting compound _A T: Glass transition temperature W _{A of the} used charge transporting compound B: Charge transporting compound used Weight ratio A _{B of A} : Weight ratio of charge transporting compound _B used When two types of charge transporting compounds are used, the charge transporting compound B is represented by the following formula.
1 / Tg _host = (W _A / Tg _A + W _B / Tg _B )
Therefore, it is required to select the type and blending ratio of the charge transporting compound used so that Tg _host is usually 80 ° C. or higher, more preferably 100 ° C. or higher.
(Specific examples of charge transporting compounds)
(Compound with electron transport property)
Among the charge transporting compounds used in the present invention, compounds having an electron transporting property include oxadiazole derivatives, triazole derivatives, distyrylbiphenyl derivatives, silole derivatives, benzoxazole metal complexes, benzothiazole metal complexes, and trisbenzimidazolylbenzene. (US Pat. No. 5,645,948), quinoxaline compound (JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), boron-containing compound (WO 00/40586), pyridine-containing A ring compound etc. are mentioned.

Among the above compounds, a compound having a pyridine ring has a high excited triplet level (T1) and is more preferable.
Of the compounds having a pyridine ring, a compound represented by the following general formula (1) is more preferable.

In general formula (1), R < ¹ > -R < ³ > represents an arbitrary substituent each independently.
The 3rd and 5th positions of the pyridine ring may be substituted.
n is an integer of 1-8.
When n is 1, Q ¹ is a substituent of the pyridine ring or a hydrogen atom.
Q ¹ is an n-valent linking group when n is 2 or more.
Q ¹ is directly bonded to any one of positions 2 to 6 of the pyridine ring. However, when Q ¹ is bonded to any of the 2, 4 and 6 positions of the pyridine ring, any one of R ^{1 to} R ^{3 at} the bonding position is Q ¹ .
When n is 2 or more, a plurality of R ^{1 to} R ³ contained in the compound may be the same or different.
When n is 2 or more, the position at which the pyridine ring is bonded to Q ¹ may be the same position or different.
(N)
The value of n that can be taken by the compound represented by the general formula (1) is an integer of 1 to 8, but can exhibit excellent durability when it has two or more pyridine rings in the molecule. As a result, it exhibits excellent electron transport properties and a wide redox potential difference. On the other hand, if there are too many pyridine ring groups, the basicity of the compound becomes too strong, and when it is contained in the light emitting layer or a layer in contact with it, it is distributed between the complex contained in the light emitting layer by applying a long electric field. There is a risk of a potential exchange. From such a viewpoint, n representing the number of pyridine rings bonded to Q ¹ is preferably 2 or more, preferably 8 or less, more preferably 6 or less, still more preferably 4 or less, and most preferably 3 or less.
(Molecular weight of general formula (1), etc.)
The molecular weight of the compound represented by the general formula (1) is usually 4000 or less, preferably 3000 or less, more preferably 2000 or less, and usually 200 or more, preferably 300 or more, more preferably 400 or more. . If the molecular weight exceeds the upper limit, the sublimation property is significantly reduced, which may cause trouble in the case of using an evaporation method when manufacturing an electroluminescent device, or decrease in solubility in an organic solvent, or in a synthesis process. As the amount of impurity components increases, it may be difficult to increase the purity of the material (that is, to remove the deterioration-causing substances). When the molecular weight is below the lower limit, the glass transition temperature, melting point, vaporization temperature, etc. Since it falls, there exists a possibility that heat resistance may be impaired remarkably.

Further, the preferred total carbon number of the compound represented by the general formula (1) is usually 300 or less, preferably 200 or less, more preferably 100 or less, and usually 15 or more, preferably 20 or more, more preferably. Is 30 or more.
(Q ¹ )
The linking group Q ¹ in the present invention is not particularly limited as long as it is basically a group linked to a pyridine ring.

That is, when n is 1, Q ¹ is a substituent of the pyridine ring or a hydrogen atom, and n is 2
In the above, Q ¹ is an n-valent linking group.
Q ¹ is directly bonded to any one of the 2 to 6 positions of the pyridine ring, but when Q ¹ is bonded to any of the 2, 4 and 6 positions of the pyridine ring, R ^{1 in the} bonding position thereof. one of the ~R ³ is Q ^1.

When n is 2 or more, the position at which the pyridine ring is bonded to Q ¹ may be the same position or different.
When n representing the number of pyridine rings is 2 or more, the linking group Q ¹ described in the present invention is applicable to a direct bond that connects pyridine rings to each other or any linking group (having no diarylamine skeleton). is there.

Preferably,
Direct bond,
Alkene group (group derived from alkene) which may have a substituent,
Alkyne group (group derived from alkyne) which may have a substituent,
An aromatic hydrocarbon group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene, etc. n-valent group is included)
Or an aromatic heterocyclic group which may have a substituent (eg, furan ring, thiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine Ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc.)
Or a group formed by connecting two or more of these,
Etc.

From the viewpoint of electrical redox durability, a compound in which two or more pyridine rings contained in one molecule are conjugated with each other via a linking group Q ¹ is preferable. In order to make such a compound, a direct bond between pyridine rings,

Or the case where it connects with the partial structure which combines these is preferable. (G ¹ to G ³ each independently represent a hydrogen atom or an arbitrary substituent, or constitute a part of the aromatic hydrocarbon or aromatic heterocyclic ring described above as an example of Q ¹ . G ¹ to G ³ contained in the Q ¹ group may be the same or different.)
Among these, the space between the pyridine rings

Is more preferable, and it is particularly preferable that G ¹ and G ² constitute a part of the aromatic hydrocarbon group in the Q ¹ group.
Preferred examples of the linking group Q ¹ are shown below (Z-1 to Z-173).

Above all, from the viewpoint of sufficiently widening the redox potential difference and the repeated redox durability,
Z-1 (direct bond), Z-2 to 69, 79, 82, 84, 89, 96, 103, 105, 108, 109, 111 to 114, 117, 118, 121, 124, 167, 170 are preferred,
Z-2, 8, 11-13, 15, 17, 19, 20, 22, 23-25, 27-30, 34, 37, 44, 47-61, 63-69, 89, 105, 109, 114, 124, 167, 170 are more preferable,
Z-2, 8, 12, 13, 15, 17, 19, 20, 22, 23, 25, 27-30, 34, 37, 44, 47-50, 63, 64, 66, 67, 89, 109, 114, 124, 167 are more preferred,
Z-2, 8, 12, 13, 15, 17, 19, 20, 23, 28 to 30, 34, 66 are most preferable.

The linking group Q ^{1 in the} above specific example may have an arbitrary substituent (having no diarylamine skeleton, aryloxide skeleton and arylsulfide skeleton),
For example,
Halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom),
An alkyl group which may have a substituent (preferably a linear or branched alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, 2-propyl, n-butyl, isobutyl, tert -Butyl group, etc.)
An alkenyl group which may have a substituent (for example, an alkenyl group having 1 to 8 carbon atoms, such as vinyl, allyl, 1-butenyl group, etc.),
An alkynyl group which may have a substituent (for example, an alkynyl group having 1 to 8 carbon atoms, such as ethynyl, propargyl group, etc.),
An aralkyl group which may have a substituent (for example, an aralkyl group having 1 to 8 carbon atoms, such as a benzyl group);
An acyl group which may have a substituent (preferably an acyl group having 1 to 8 carbon atoms which may have a substituent, for example, formyl, acetyl, benzoyl group, etc.),
An alkoxycarbonyl group which may have a substituent (preferably an alkoxycarbonyl group having 2 to 13 carbon atoms which may have a substituent, including, for example, methoxycarbonyl, ethoxycarbonyl group, etc.),
An aryloxycarbonyl group which may have a substituent (preferably an aryloxycarbonyl group having 2 to 13 carbon atoms which may have a substituent, including, for example, an acetoxy group),
Carboxyl group,

Group (Ra is an optional substituent, preferably an alkyl group having 1 to 8 carbon atoms, an aralkyl group or an aryl group which may have a substituent. Rb is a hydrogen atom or an optional substituent. A group, preferably an alkyl group having 1 to 8 carbon atoms which may have a substituent, an aralkyl group, or an aryl group).

A group (Rc, Rd is a hydrogen atom or an arbitrary substituent, and preferably represents an optionally substituted alkyl group having 1 to 8 carbon atoms, an aralkyl group, or an aryl group),
A cyano group,
A silyl group which may have a substituent (for example, a trimethylsilyl group, a triphenylsilyl group, etc.),
An optionally substituted boryl group (for example, a dimesitylboryl group),
A phosphino group which may have a substituent (for example, a diphenylphosphino group and the like are included),
An aromatic hydrocarbon group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, etc. included)
Or an aromatic heterocyclic group which may have a substituent (eg, furan ring, thiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine Ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring and the like))
From the viewpoint of limiting molecular vibration, a hydrogen atom, a methyl group, or a phenyl group is more preferable, and a hydrogen atom is most preferable.
(R ¹ ~R ³⁾
R ¹ to R ³ in the general formula (1) each independently represents an arbitrary substituent. When n is 2 or more, R ¹ to R ³ contained in the compound may be the same or different. Specific examples of the optional group that can be used for R ¹ to R ³ include an alkyl group which may have a substituent (preferably a linear or branched alkyl group having 1 to 8 carbon atoms, for example, Methyl, ethyl, n-propyl, 2-propyl, n-butyl, isobutyl, tert-butyl group, etc.),
An alkenyl group which may have a substituent (preferably an alkenyl group having 2 to 9 carbon atoms, such as vinyl, allyl, 1-butenyl and the like),
An alkynyl group which may have a substituent (preferably an alkynyl group having 2 to 9 carbon atoms, such as ethynyl and propargyl groups);
An aralkyl group which may have a substituent (preferably an aralkyl group having 7 to 15 carbon atoms, such as a benzyl group);
An amino group which may have a substituent [preferably, an alkylamino group having one or more alkyl groups having 1 to 8 carbon atoms which may have a substituent (for example, methylamino, dimethylamino, diethylamino, Dibenzylamino group, etc.),
An arylamino group having an aromatic hydrocarbon group having 6 to 12 carbon atoms which may have a substituent (for example, phenylamino, diphenylamino, ditolylamino group, etc.);
A heteroarylamino group having a 5- or 6-membered aromatic heterocyclic ring which may have a substituent (for example, pyridylamino, thienylamino, dithienylamino group, etc.);
An acylamino group having an acyl group having 2 to 10 carbon atoms which may have a substituent (for example, acetylamino, benzoylamino group and the like are included)],
An alkoxy group which may have a substituent (preferably an alkoxy group having 1 to 8 carbon atoms which may have a substituent, including methoxy, ethoxy, butoxy groups, etc.),
An aryloxy group which may have a substituent (preferably an aromatic hydrocarbon group having 6 to 12 carbon atoms, such as phenyloxy, 1-naphthyloxy, 2-naphthyloxy group, etc. ),
An optionally substituted heteroaryloxy group (preferably having a 5- or 6-membered aromatic heterocyclic group, including, for example, pyridyloxy, thienyloxy groups),
An acyl group which may have a substituent (preferably an acyl group having 2 to 10 carbon atoms which may have a substituent, for example, a formyl, acetyl, benzoyl group, etc.),
An alkoxycarbonyl group which may have a substituent (preferably an alkoxycarbonyl group having 2 to 10 carbon atoms which may have a substituent, including, for example, a methoxycarbonyl, ethoxycarbonyl group, etc.),
An aryloxycarbonyl group which may have a substituent (preferably an aryloxycarbonyl group having 7 to 13 carbon atoms which may have a substituent, such as a phenoxycarbonyl group);
An alkylcarbonyloxy group which may have a substituent (preferably an alkylcarbonyloxy group having 2 to 10 carbon atoms which may have a substituent, such as an acetoxy group);
Halogen atom (especially fluorine atom or chlorine atom)
Carboxyl group,
A cyano group,
Hydroxyl group,
Mercapto group,
An alkylthio group which may have a substituent (preferably an alkylthio group having 1 to 8 carbon atoms, including, for example, a methylthio group, an ethylthio group, etc.);
An arylthio group which may have a substituent (preferably an arylthio group having 6 to 12 carbon atoms, including, for example, a phenylthio group, a 1-naphthylthio group, etc.);
A sulfonyl group which may have a substituent (for example, mesyl group, tosyl group and the like are included),
A silyl group which may have a substituent (for example, a trimethylsilyl group, a triphenylsilyl group, etc.),
An optionally substituted boryl group (for example, a dimesitylboryl group),
Phosphino group which may have a substituent (for example, diphenylphosphino group and the like are included),
An aromatic hydrocarbon group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, etc. A monovalent group derived from a 5- or 6-membered monocyclic ring or a 2-5 condensed ring is included)
Or an aromatic heterocyclic group which may have a substituent (for example, furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, Pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring , Pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, benzimidazole ring, perimidine ring, quinazoline ring, etc. Group is included) And the like.

The substituent that these may have is not particularly limited as long as the performance of the compound of the present invention is not impaired, but preferably represents an alkyl group, an aromatic hydrocarbon group, or an alkyl-substituted aromatic hydrocarbon group. Specific examples thereof include alkyl groups having about 1 to 6 carbon atoms such as methyl, ethyl, isopropyl and tert-butyl groups; about 6 to 18 carbon atoms such as phenyl, naphthyl and fluorenyl groups. An alkyl-substituted aromatic hydrocarbon group having a total carbon number of about 7 to 30 such as a tolyl group, a mesityl group, and a 2,6-dimethylphenyl group.

Specific examples where R ¹ to R ³ are aromatic hydrocarbon groups or aromatic heterocyclic groups are shown below.

(In the above structures, L ₁ to L ₃ each independently represents an alkyl group, an aromatic hydrocarbon group, or an alkyl-substituted aromatic hydrocarbon group. L ₄ and L ₅ each independently represent a hydrogen atom, an alkyl Represents a group, an aromatic hydrocarbon group, or an alkyl-substituted aromatic hydrocarbon group.
As the alkyl group, aromatic hydrocarbon group, or alkyl-substituted aromatic hydrocarbon group, specifically, an alkyl group having about 1 to 6 carbon atoms such as methyl group, ethyl group, isopropyl group, tert-butyl group; Aromatic hydrocarbon groups having about 6 to 18 carbon atoms such as phenyl group, naphthyl group and fluorenyl group; alkyl substitution having about 7 to 30 total carbon atoms such as tolyl group, mesityl group and 2,6-dimethylphenyl group An aromatic hydrocarbon group, and the like.

Any of the above structures may have a substituent in addition to L ₁ to L ₅ , but if it strongly affects the electronic state on pyridine or the like to which it is bonded, Since the reduction potential difference may be narrowed, it is preferable to select a group that has both a small electron donating property and an electron withdrawing property and that does not easily cause an increase in intramolecular conjugated length. Specific examples of such groups also include alkyl groups, aromatic hydrocarbon groups, alkyl-substituted aromatic hydrocarbon groups, and the like.

In the case of a compound having two or more of the above structures in one molecule, two or more L _{1 to} L ₅ contained in one molecule may be the same or different. )
Among the above exemplary structures, R-1 to 6, 10 to 13, 33, 34, 38, 45, and 48 are preferable, R-1 to 6, and 48 are more preferable, and R- 1-3, 48 are most preferred.

R ¹ to R ³ are, for example, substituted from the viewpoint of limiting the molecular vibration and not impairing the luminous efficiency when the charge transporting compound characterized in the present invention is applied to the light emitting layer of the organic electroluminescent device. An alkyl group which may have a group or an aromatic hydrocarbon group which may have a substituent (especially an aromatic hydrocarbon group having about 6 to 12 carbon atoms) is preferable, and has a large oxidation potential. From the viewpoint, a hydrogen atom or a phenyl group is particularly preferable.
(Substituent of pyridine ring)
The 3-position and 5-position of the pyridine ring may be substituted with any group specifically exemplified as an arbitrary group that can be used for R ¹ to R ³ , but the viewpoint of improving electrical redox durability In order to improve heat resistance, an aromatic hydrocarbon group or an aromatic heterocyclic group is preferable. (Specific example of general formula (1))
Specific preferred examples of the compound represented by the general formula (1) of the present invention are shown below, but the present invention is not limited thereto.

Among these, the compounds shown below are more preferable because of high excitation triplet level (T1).

(Compound with hole transport property)
Moreover, as a compound which has a hole transportability among the charge transportable compounds used by this invention, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl is represented. Aromatic diamine containing two or more tertiary amines and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1-naphthyl) Aromatic amine compounds having a starburst structure such as (phenylamino) triphenylamine (J. Lumin., 72-74, 985, 1997), aromatic amine compounds comprising a tetramer of triphenylamine (Chem) Commun., 2175, 1996), spiro compounds such as 2,2 ′, 7,7′-tetrakis- (diphenylamino) -9,9′-spirobifluorene (Syn) th. Metals, 91, 209, 1997), carbazole derivatives such as 4,4′-N, N′-dicarbazolebiphenyl (WO 00/70655), and the like.

In addition to the above compounds, polyvinyl carbazole (Japanese Patent Laid-Open No. 2001-257076), polyvinyl triphenylamine (Japanese Patent Laid-Open No. 7-53953), and polyarylene ether sulfone (Polym. Adv. Tech.) Containing tetraphenylbenzidine. , 7, p. 33, 1996).
Among the above compounds, a compound having a carbazole ring (such as a carbazole derivative or polyvinyl carbazole) has a high excited triplet level (T1) and is more preferable.

  Of the compounds having a carbazole ring, a compound represented by the following general formula (2) is more preferred.

In general formula (2),
R ⁴ each independently represents an arbitrary substituent or Q ² .
The carbazole ring may have a substituent other than R ⁴ .
m is an integer of 1-6.
When m is 1, Q ² is a carbazole ring substituent or a hydrogen atom.
Q ² is an m-valent linking group when m is 2 or more.
Q ² is directly bonded to any one of the 1 to 9 positions of the carbazole ring or R ⁴ . However, when Q ² is bonded to the 9-position of the carbazole ring, R ⁴ is Q ² .
When m is 2 or more, a plurality of R ⁴ contained in the compound may be the same or different.
When m is 2 or more, the position at which the carbazole ring is bonded to Q ² may be the same position or different.
(M)
The value of m that can be taken by the compound represented by the general formula (2) is an integer of 1 to 6, but can exhibit excellent durability when it has two or more carbazole rings in the molecule. Thus, an excellent hole transport property and a wide oxidation-reduction potential difference are exhibited. On the other hand, when there are too many carbazole rings, the acidity of the compound becomes too strong, and when it is contained in the light emitting layer or a layer in contact with it, there is a risk of reduction and deterioration due to the application of an electric field for a long time. From such a viewpoint, m representing the number of carbazole rings bonded to Q ² is preferably 2 or more, preferably 6 or less, more preferably 4 or less, and most preferably 3 or less.
(Molecular weight of general formula (2), etc.)
The molecular weight of the compound represented by the general formula (2) is usually 4000 or less, preferably 3000 or less, more preferably 2000 or less, and usually 200 or more, preferably 300 or more, more preferably 400 or more. . If the molecular weight exceeds the upper limit, the sublimation property is significantly reduced, which may cause trouble in the case of using an evaporation method when manufacturing an electroluminescent device, or decrease in solubility in an organic solvent, or in a synthesis process. As the amount of impurity components increases, it may be difficult to increase the purity of the material (that is, to remove the deterioration-causing substances). When the molecular weight is below the lower limit, the glass transition temperature, melting point, vaporization temperature, etc. Since it falls, there exists a possibility that heat resistance may be impaired remarkably.

Further, the preferred total carbon number of the compound represented by the general formula (2) is usually 300 or less, preferably 200 or less, more preferably 100 or less, and usually 15 or more, preferably 20 or more, more preferably. Is 30 or more.
(Q ² )
The linking group Q ² in the present invention is not particularly limited as long as it is basically a group linked to a carbazole ring. That is, when m is 1, Q ² is a carbazole ring substituent or a hydrogen atom, and when m is 2 or more, Q ² is an m-valent linking group.

Q ² is directly bonded to any one of the 1 to 9 positions of the carbazole ring or R ⁴ . However, when Q ² is bonded to the 9-position of the carbazole ring, R ⁴ is Q ² .
When m is 2 or more, the position at which the carbazole ring is bonded to Q ² may be the same position or different.
When m representing the number of carbazole rings is 2 or more, any linking group can be applied to the linking group Q ² described in the present invention.

Preferably,
An amino group which may have a substituent,
An alkene group which may have a substituent,
An alkyne group which may have a substituent,
An aromatic hydrocarbon group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene, etc. m-valent groups are included)
Or an aromatic heterocyclic group which may have a substituent (eg, furan ring, thiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine Ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring, etc.)
Or a group formed by connecting two or more of these,
Etc.

Preferred examples of the linking group Q ² are shown below. (ZZ-2 to ZZ-184)

Above all, from the viewpoint of sufficiently widening the redox potential difference and the repeated redox durability,
ZZ-2 to 69, 79, 82, 84, 89, 96, 103, 105, 108, 109, 111 to 114, 117, 118, 121, 124, 167, 170, 174 to 183 are preferred,
ZZ-2, 8, 11-13, 15, 17, 19, 20, 22, 23-25, 27-30, 34, 37, 44, 47-61, 63-69, 89, 105, 109, 114, 124, 167, 170, 174 to 183 are more preferable,
ZZ-2, 8, 12, 13, 15, 17, 19, 20, 22, 23, 25, 27-30, 34, 37, 44, 47-50, 63, 64, 66, 67, 89, 109, 114, 124, 167, 174 to 183 are more preferable,
ZZ-2, 8, 12, 13, 15, 17, 19, 20, 23, 28-30, 34, 66, 174-178, 182-183 are most preferred.

The linking group Q ^{2 in the} above specific example may have an arbitrary substituent,
For example,
Halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom),
An alkyl group which may have a substituent (preferably a linear or branched alkyl group having 1 to 8 carbon atoms, such as methyl, ethyl, n-propyl, 2-propyl, n-butyl, isobutyl, tert -Butyl group, etc.)
An alkenyl group which may have a substituent (for example, an alkenyl group having 1 to 8 carbon atoms, such as vinyl, allyl, 1-butenyl group, etc.),
An alkynyl group which may have a substituent (for example, an alkynyl group having 1 to 8 carbon atoms, such as ethynyl, propargyl group, etc.),
An aralkyl group which may have a substituent (for example, an aralkyl group having 1 to 8 carbon atoms, such as a benzyl group);
An acyl group which may have a substituent (preferably an acyl group having 1 to 8 carbon atoms which may have a substituent, for example, formyl, acetyl, benzoyl group, etc.),
An alkoxycarbonyl group which may have a substituent (preferably an alkoxycarbonyl group having 2 to 13 carbon atoms which may have a substituent, including, for example, methoxycarbonyl, ethoxycarbonyl group, etc.),
An aryloxycarbonyl group which may have a substituent (preferably an aryloxycarbonyl group having 2 to 13 carbon atoms which may have a substituent, including, for example, an acetoxy group),
Carboxyl group,

Group (R ^a is an arbitrary substituent, preferably an alkyl group having 1 to 8 carbon atoms, an aralkyl group or an aryl group which may have a substituent. R ^b is a hydrogen atom or an arbitrary group Which is preferably an alkyl group having 1 to 8 carbon atoms, an aralkyl group or an aryl group which may have a substituent.

Group ( ^Rc , ^Rd is a hydrogen atom or an arbitrary substituent, and preferably represents an alkyl group having 1 to 8 carbon atoms, an aralkyl group or an aryl group, which may have a substituent),
A cyano group,
A silyl group which may have a substituent (for example, a trimethylsilyl group, a triphenylsilyl group, etc.),
An optionally substituted boryl group (for example, a dimesitylboryl group),
A phosphino group which may have a substituent (for example, a diphenylphosphino group, etc.),
An aromatic hydrocarbon ring group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, etc. Included)
Or an aromatic heterocyclic group which may have a substituent (eg furan ring, thiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine Ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, perimidine ring, quinazoline ring, quinazolinone ring, azulene ring and the like))
From the viewpoint of limiting molecular vibration, a hydrogen atom, a methyl group, or a phenyl group is more preferable, and a hydrogen atom is most preferable.
(R ⁴ )
R ⁴ in the general formula (2) represents an arbitrary substituent or Q ² described above. When m is 2 or more, a plurality of R ⁴ contained in the compound may be the same or different. Specific examples of the optional group that can be used for R ⁴ include an optionally substituted alkyl group (preferably a linear or branched alkyl group having 1 to 8 carbon atoms such as methyl, ethyl, and the like. , N-propyl, 2-propyl, n-butyl, isobutyl, tert-butyl group, etc.),
An alkenyl group which may have a substituent (preferably an alkenyl group having 2 to 9 carbon atoms, such as vinyl, allyl, 1-butenyl and the like),
An alkynyl group which may have a substituent (preferably an alkynyl group having 2 to 9 carbon atoms, such as ethynyl and propargyl groups);
An aralkyl group which may have a substituent (preferably an aralkyl group having 7 to 15 carbon atoms, such as a benzyl group);
An amino group which may have a substituent [preferably, an alkylamino group having one or more alkyl groups having 1 to 8 carbon atoms which may have a substituent (for example, methylamino, dimethylamino, diethylamino, Dibenzylamino group, etc.),
An arylamino group having an aromatic hydrocarbon group having 6 to 12 carbon atoms which may have a substituent (for example, phenylamino, diphenylamino, ditolylamino group, etc.);
A heteroarylamino group having a 5- or 6-membered aromatic heterocyclic ring which may have a substituent (for example, pyridylamino, thienylamino, dithienylamino group, etc.);
An acylamino group having an acyl group having 2 to 10 carbon atoms which may have a substituent (for example, acetylamino, benzoylamino group and the like are included)],
An alkoxy group which may have a substituent (preferably an alkoxy group having 1 to 8 carbon atoms which may have a substituent, including methoxy, ethoxy, butoxy groups, etc.),
An aryloxy group which may have a substituent (preferably an aromatic hydrocarbon group having 6 to 12 carbon atoms, such as phenyloxy, 1-naphthyloxy, 2-naphthyloxy group, etc. ),
An optionally substituted heteroaryloxy group (preferably having a 5- or 6-membered aromatic heterocyclic group, including, for example, pyridyloxy, thienyloxy groups),
An acyl group which may have a substituent (preferably an acyl group having 2 to 10 carbon atoms which may have a substituent, for example, a formyl, acetyl, benzoyl group, etc.),
An alkoxycarbonyl group which may have a substituent (preferably an alkoxycarbonyl group having 2 to 10 carbon atoms which may have a substituent, including, for example, a methoxycarbonyl, ethoxycarbonyl group, etc.),
An aryloxycarbonyl group which may have a substituent (preferably an aryloxycarbonyl group having 7 to 13 carbon atoms which may have a substituent, such as a phenoxycarbonyl group);
An alkylcarbonyloxy group which may have a substituent (preferably an alkylcarbonyloxy group having 2 to 10 carbon atoms which may have a substituent, such as an acetoxy group);
Halogen atom (especially fluorine atom or chlorine atom)
Carboxyl group,
A cyano group,
Hydroxyl group,
Mercapto group,
An alkylthio group which may have a substituent (preferably an alkylthio group having 1 to 8 carbon atoms, including, for example, a methylthio group, an ethylthio group, etc.);
An arylthio group which may have a substituent (preferably an arylthio group having 6 to 12 carbon atoms, including, for example, a phenylthio group, a 1-naphthylthio group, etc.);
A sulfonyl group which may have a substituent (for example, mesyl group, tosyl group and the like are included),
A silyl group which may have a substituent (for example, a trimethylsilyl group, a triphenylsilyl group, etc.),
An optionally substituted boryl group (for example, a dimesitylboryl group),
Phosphino group which may have a substituent (for example, diphenylphosphino group and the like are included),
An aromatic hydrocarbon group which may have a substituent (for example, benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzpyrene ring, chrysene ring, triphenylene ring, fluoranthene ring, etc. A monovalent group derived from a 5- or 6-membered monocyclic ring or a 2-5 condensed ring is included)
Or an aromatic heterocyclic group which may have a substituent (for example, furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, Pyrroloimidazole ring, pyrrolopyrazole ring, pyrrolopyrrole ring, thienopyrrole ring, thienothiophene ring, furopyrrole ring, furofuran ring, thienofuran ring, benzoisoxazole ring, benzoisothiazole ring, benzimidazole ring, pyridine ring, pyrazine ring, pyridazine ring , Pyrimidine ring, triazine ring, quinoline ring, isoquinoline ring, sinoline ring, quinoxaline ring, benzimidazole ring, perimidine ring, quinazoline ring, etc. Group is included) And the like.

The substituent that these may have is not particularly limited as long as the performance of the compound of the present invention is not impaired, but preferably represents an alkyl group, an aromatic hydrocarbon group, or an alkyl-substituted aromatic hydrocarbon group. Specific examples thereof include alkyl groups having about 1 to 6 carbon atoms such as methyl, ethyl, isopropyl and tert-butyl groups; about 6 to 18 carbon atoms such as phenyl, naphthyl and fluorenyl groups. An alkyl-substituted aromatic hydrocarbon group having a total carbon number of about 7 to 30 such as a tolyl group, a mesityl group, and a 2,6-dimethylphenyl group.

Specific examples when R ⁴ is an aromatic hydrocarbon group or an aromatic heterocyclic group are shown below.

(In the above structures, L ₁ to L ₃ each independently represents an alkyl group, an aromatic hydrocarbon group, or an alkyl-substituted aromatic hydrocarbon group. L ₄ and L ₅ each independently represent a hydrogen atom, an alkyl Represents a group, an aromatic hydrocarbon group, or an alkyl-substituted aromatic hydrocarbon group.
As the alkyl group, aromatic hydrocarbon group, or alkyl-substituted aromatic hydrocarbon group, specifically, an alkyl group having about 1 to 6 carbon atoms such as methyl group, ethyl group, isopropyl group, tert-butyl group; Aromatic hydrocarbon groups having about 6 to 18 carbon atoms such as phenyl group, naphthyl group and fluorenyl group; alkyl substitution having about 7 to 30 total carbon atoms such as tolyl group, mesityl group and 2,6-dimethylphenyl group An aromatic hydrocarbon group, and the like.

Any of the above structures may have a substituent in addition to L ₁ to L ₅ , but if it strongly affects the electronic state on the carbazole or the like to which it is bonded, oxidation will occur. Since the reduction potential difference may be narrowed, it is preferable to select a group that has both a small electron donating property and an electron withdrawing property and that does not easily cause an increase in intramolecular conjugated length. Specific examples of such groups also include alkyl groups, aromatic hydrocarbon groups, alkyl-substituted aromatic hydrocarbon groups, and the like.

In the case of a compound having two or more of the above structures in one molecule, two or more L _{1 to} L ₅ contained in one molecule may be the same or different. )
Among the above exemplary structures, R-1 to 6, 10 to 13, 33, 34, 38, 45, and 48 are preferable, R-1 to 6, and 48 are more preferable, and R- 1-3, 48 are most preferred.

R ⁴ is an alkyl group which may have a substituent or an aromatic hydrocarbon group which may have a substituent (especially carbon An aromatic hydrocarbon group of about 6 to 12) or Q ² is preferable, and Q ² , a hydrogen atom or a phenyl group is particularly preferable from the viewpoint of giving a large reduction potential.
(Substituent of carbazole ring)
The substituent that may be present in addition to R ^{4 of the} carbazole ring may be substituted with any group specifically exemplified as an arbitrary group that can be used for R ⁴ . From the viewpoint of improving heat resistance and heat resistance, an aromatic hydrocarbon group or an aromatic heterocyclic group is preferable.
(Specific example of general formula (2))
Specific preferred examples of the compound represented by the general formula (2) of the present invention are shown below, but the present invention is not limited thereto.

Among these, the compound having no condensed ring shown below has a high excited triplet level (T1) and is more preferable.

(Combination of two different types of charge transporting compounds)
In the present invention, it is particularly preferable to use a compound having a pyridine ring and a compound having a carbazole ring in combination as two different kinds of charge transporting compounds used for the light emitting layer host. The following five points are raised as the reason.
1) Each of a compound having a carbazole ring and a compound having a pyridine ring
2) HOMO (highest unoccupied molecular orbital) of a compound having a high excited triplet level (T1) 2) a carbazole ring
It is close to the HOMO of the hole transport layer adjacent to the hole, and holes are easily injected. 3) The LUMO (lowest empty molecular orbital) of the compound having a pyridine ring is adjacent to the light emitting layer
It is close to the LUMO of the electron transport layer or hole blocking layer, and electrons are easily injected. 4) Each of the compound having a carbazole ring and the compound having a pyridine ring
High charge mobility (hole mobility and electron mobility, respectively) 5) Each is stable against charge (high stability against redox)
In conventional phosphorescent devices, a charge transporting compound having a high T1 and excellent oxidation-reduction stability was not applied, so it was speculated that high-efficiency and long-life devices could not be realized especially with green and blue devices. Is done.

The combination is not particularly limited as long as it is a combination of a compound having a pyridine ring and a compound having a carbazole ring that satisfies the above five points, but the emission is higher than T1 of the organometallic complex used as the dopant material. It is preferable from the viewpoint of efficiency.
The compound having a pyridine ring is more preferably a combination of the compound represented by the general formula (1), and the compound having a carbazole ring is a combination of the compound represented by the general formula (2).
(Dopant material)
In the present invention, as the dopant material used for the light emitting layer, an organometallic complex containing a metal selected from Groups 7 to 11 of the periodic table is used. The T1 (excited triplet level) of the metal complex is preferably lower than T1 of the charge transporting compound used as the host material from the viewpoint of light emission efficiency. Furthermore, since light emission occurs in the dopant material, chemical stability such as redox is also required.

Preferred examples of the metal in the phosphorescent organometallic complex containing a metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. Preferred examples of these organometallic complexes include compounds represented by the following general formula (II) or general formula (VI).
MLn-jL'j (II)
(In the formula, M represents a metal, n represents a valence of the metal, L and L ′ represent a bidentate ligand, and j represents 0, 1 or 2.)

(Wherein M ⁷ represents a metal, T represents carbon or nitrogen. When T is nitrogen, there is no R ¹⁴ or R ¹⁵ , and when T is carbon, R ¹⁴ or R ¹⁵ represents a hydrogen atom, a halogen atom, or an alkyl. Group, aralkyl group, alkenyl group, cyano group, amino group, acyl group, alkoxycarbonyl group, carboxyl group, alkoxy group, alkylamino group, aralkylamino group, haloalkyl group, hydroxyl group,
An aryloxy group, an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent.

R ¹² and R ¹³ are hydrogen atom, halogen atom, alkyl group, aralkyl group, alkenyl group, cyano group, amino group, acyl group, alkoxycarbonyl group, carboxyl group, alkoxy group, alkylamino group, aralkylamino group, haloalkyl group , A hydroxyl group, an aryloxy group, an aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and may be linked to each other to form a ring. )
In the general formula (II), the bidentate ligands L and L ′ each represent a ligand having the following partial structure.

(Ring A1 and Ring A1 ′ each independently represents an aromatic hydrocarbon group or an aromatic heterocyclic group, which may have a substituent. Ring A2 and Ring A2 ′ are nitrogen-containing aromatic heterocyclic groups. R ′, R ″, and R ′ ″ each represent a halogen atom; an alkyl group; an alkenyl group; an alkoxycarbonyl group; a methoxy group; an alkoxy group; an aryloxy group; (Amino group; diarylamino group; carbazolyl group; acyl group; haloalkyl group or cyano group)
More preferable examples of the compound represented by the general formula (II) include compounds represented by the following general formulas (Va), (Vb) and (Vc).

  (Wherein M4 represents a metal, n represents a valence of the metal, ring A1 represents an aromatic hydrocarbon group which may have a substituent, and ring A2 may have a substituent. Represents a nitrogen-containing aromatic heterocyclic group.)

(In the formula, M ⁵ represents a metal, and n represents a valence of the metal. Ring A1 represents an aromatic hydrocarbon group or aromatic heterocyclic group which may have a substituent, and ring A2 represents a substituent. Represents a nitrogen-containing aromatic heterocyclic group which may have

(In the formula, M ⁶ represents a metal, n represents a valence of the metal, and j represents 0, 1 or 2. Ring A
1 and ring A1 ′ each independently represent an optionally substituted aromatic hydrocarbon group or aromatic heterocyclic group, and ring A2 and ring A2 ′ each independently have a substituent. A nitrogen-containing aromatic heterocyclic group which may be )
As the ring A1 and ring A1 ′ of the compounds represented by the general formulas (Va), (Vb), (Vc), preferably a phenyl group, a biphenyl group, a naphthyl group, an anthryl group, a thienyl group, a furyl group, a benzothienyl Group, benzofuryl group, pyridyl group, quinolyl group, isoquinolyl group, or carbazolyl group.

Ring A2 and ring A2 ′ are preferably a pyridyl group, pyrimidyl group, pyrazyl group, triazyl group, benzothiazole group, benzoxazole group, benzimidazole group, quinolyl group, isoquinolyl group, quinoxalyl group, or phenanthridyl group. Can be mentioned.
Examples of the substituent that the compounds represented by the general formulas (Va), (Vb) and (Vc) may have include a halogen atom such as a fluorine atom; a C 1-6 carbon atom such as a methyl group and an ethyl group An alkyl group; an alkenyl group having 2 to 6 carbon atoms such as a vinyl group; an alkoxycarbonyl group having 2 to 6 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group; an alkoxy group having 1 to 6 carbon atoms such as a methoxy group and an ethoxy group; An aryloxy group such as a phenoxy group and a benzyloxy group; a dialkylamino group such as a dimethylamino group and a diethylamino group; a diarylamino group such as a diphenylamino group; a carbazolyl group; an acyl group such as an acetyl group; A haloalkyl group; a cyano group, and the like, which may be linked to each other to form a ring.

In addition, the substituent which ring A1 and the substituent which ring A2 has may combine, or the substituent which ring A1 'and the substituent which ring A2' may combine may form one condensed ring, Examples of such a condensed ring include a 7,8-benzoquinoline group.
As the substituent for ring A1, ring A1 ′, ring A2 and ring A2 ′, an alkyl group, an alkoxy group, an aromatic hydrocarbon group, a cyano group, a halogen atom, a haloalkyl group, a diarylamino group, or a carbazolyl group is more preferable. Can be mentioned.

M ⁴ to M ⁵ in the formulas (Va) and (Vb) are preferably ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold. M ⁷ in the formula (VI) is preferably ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold, and particularly preferably a divalent metal such as platinum or palladium.

  Specific examples of the organometallic complexes represented by the general formulas (II), (Va), (Vb) and (Vc) are shown below, but are not limited to the following compounds.

Among the organometallic complexes represented by the general formulas (II), (Va), (Vb), and (Vc), a 2-arylpyridine-based ligand (2- A compound having an aryl pyridine, a compound in which an arbitrary substituent is bonded to the aryl pyridine, or a compound in which an arbitrary group is condensed to the aryl pyridine is preferable.
Specific examples of the organometallic complex represented by the general formula (VI) are shown below, but are not limited to the following compounds.

  Furthermore, the light emitting layer or the light emitting layer forming material in the organic electroluminescent element of the present invention may contain a fluorescent dye together with the host material and the dopant material. Examples of fluorescent dyes that emit blue light include perylene, pyrene, anthracene, coumarin, and derivatives thereof. Examples of the green fluorescent dye include quinacridone derivatives and coumarin derivatives. Examples of yellow fluorescent dyes include rubrene and perimidone derivatives. Examples of red fluorescent dyes include DCM compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene and the like.

In addition to the above-mentioned fluorescent dyes for doping, fluorescent dyes listed in Laser Research, Vol. 8, 694, 803, 958 (1980); Vol. 9, p. 85 (1981) emit light. It can be used as a dope material for the layer.
The amount of the organometallic complex contained as a dopant material in the light emitting layer forming material or the light emitting layer is preferably 0.1% by weight or more, and more preferably 30% by weight or less. If the lower limit is not reached, it may not be possible to contribute to improving the luminous efficiency of the device. If the upper limit is exceeded, concentration quenching may occur due to the formation of a dimer between organometallic complexes, etc. There is.

The amount of the dopant material in the light emitting layer exhibiting phosphorescence tends to be preferably slightly larger than the amount of the fluorescent dye (dopant) contained in the light emitting layer in the conventional element using fluorescence (singlet). is there. Moreover, when a fluorescent pigment | dye is contained in a light emitting layer with a phosphorescent dopant material, 0.05 weight% or more is preferable and 0.1 weight% or more is more preferable. Moreover, 10 weight% or less is preferable and 3 weight% or less is more preferable.

The molecular weight of such a phosphorescent dopant material is usually 4000 or less, preferably 3000 or less, more preferably 2000 or less, and usually 200 or more, preferably 300 or more, more preferably 400 or more. If the molecular weight exceeds the upper limit, the sublimation property is significantly reduced, which may cause trouble in the case of using an evaporation method when manufacturing an electroluminescent device, or decrease in solubility in an organic solvent, or in a synthesis process. As the amount of impurity components increases, it may be difficult to increase the purity of the material (that is, to remove the deterioration-causing substances). When the molecular weight is below the lower limit, the glass transition temperature, melting point, vaporization temperature, etc. Since it falls, there exists a possibility that heat resistance may be impaired remarkably.
(element)
Next, the organic electroluminescent element of the present invention will be described.

  The organic electroluminescent element (EL element) of the present invention has an anode, a cathode, and a light emitting layer provided between these two electrodes, and the light emitting layer comprises a host material composed of two or more different types of charge transporting compounds. And a dopant material composed of an organometallic complex containing at least one metal selected from Groups 7 to 11 of the periodic table, wherein the excited triplet level (T1) of the charge transporting compound is 2.2 eV or more. It is characterized by that.

Hereinafter, an example of the structure of the EL element of the present invention will be described with reference to the drawings. However, the structure of the EL element of the present invention is not limited to the one illustrated below.
FIG. 1 is a cross-sectional view schematically showing a structural example of a general organic electroluminescence device used in the present invention. 1 is a substrate, 2 is an anode, 4 is a hole transport layer, 5 is a light emitting layer, and 6 is a light emitting layer. A hole blocking layer, 8 represents a cathode.

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

  An anode 2 is provided on the substrate 1, and the anode 2 plays a role of hole injection into the hole transport layer 4. The anode 2 is usually made of metal such as aluminum, gold, silver, nickel, palladium, platinum, metal oxide such as oxide of indium and / or tin, metal halide such as copper iodide, carbon black, or poly It is composed of conductive polymers such as (3-methylthiophene), polypyrrole, and polyaniline. In general, the anode 2 is often formed by a sputtering method, a vacuum deposition method, or the like. Further, when the anode 2 is formed of metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, It can also be formed by dispersing and coating on the substrate 1. Further, when the anode 2 is formed of a conductive polymer, a polymerized thin film can be directly formed on the substrate 1 by electrolytic polymerization, or a conductive polymer can be applied to the substrate 1 (Appl). Phys. Lett., 60, 2711, 1992).

The anode 2 usually has a single-layer structure, but it can also have a laminated structure made of a plurality of materials if desired.
The thickness of the anode 2 varies depending on the required transparency. When transparency is required, the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness of the anode is usually 5 nm or more, preferably 10 nm or more, and usually 1000 nm or less, preferably about 500 nm or less. When it may be opaque, the thickness of the anode 2 is arbitrary, and if desired, it may be formed of metal to serve as the substrate 1.

  In the element having the configuration shown in FIG. 1, a hole transport layer 4 is provided on the anode 2. As conditions required for the material of the hole transport layer, it is necessary that the material has a high hole injection efficiency from the anode and can efficiently transport the injected holes. For this purpose, the ionization potential is small, the transparency to visible light is high, the hole mobility is high, the stability is high, and impurities that become traps are less likely to be generated during manufacturing and use. Required. Further, in order to contact the light emitting layer 5, it is required not to quench the light emitted from the light emitting layer or to form an exciplex with the light emitting layer to reduce the efficiency. In addition to the above general requirements, when the application for in-vehicle display is considered, the element is further required to have heat resistance. Therefore, a material having a Tg value of 85 ° C. or higher is desirable.

  As such a hole transporting material, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl is representative as in the hole transporting material used for the host material of the light emitting layer. Aromatic diamine containing two or more tertiary amines and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1 -Aromatic amine compound having a starburst structure such as naphthylphenylamino) triphenylamine (J. Lumin., 72-74, 985, 1997), an aromatic amine compound comprising a tetramer of triphenylamine (Chem. Commun., 2175, 1996), spiro compounds such as 2,2 ′, 7,7′-tetrakis- (diphenylamino) -9,9′-spirobifluorene. Synth. Metals, 91, pp. 209 pp., 1997), 4,4'-N, such as a carbazole derivative such as N'- dicarbazole biphenyl. These compounds may be used alone or in combination as necessary.

In addition to the above compounds, polyarylene ether sulfone (Polym. Adv. Tech.) Containing polyvinyl carbazole, polyvinyl triphenylamine (Japanese Patent Laid-Open No. 7-53953), and tetraphenylbenzidine as the material of the hole transport layer 4 is used. , 7, p. 33, 1996).
The hole transport layer 4 may be formed by a normal coating method such as a spray method, a printing method, a spin coating method, a dip coating method, or a die coating method, a wet film forming method such as various printing methods such as an ink jet method or a screen printing method, or a vacuum. It can be formed by a dry film formation method such as a vapor deposition method.

  In the case of the coating method, one or more hole transport materials are added, and if necessary, additives such as binder resins and coating property improving agents that do not trap holes are added and dissolved in a suitable solvent. A solution is prepared, applied onto the anode 2 by a method such as spin coating, and dried to form the hole transport layer 4. Examples of the binder resin include polycarbonate, polyarylate, and polyester. When the binder resin is added in a large amount, the hole mobility is lowered.

In the case of the vacuum evaporation method, the hole transport material is put in a crucible installed in a vacuum vessel, the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with a suitable vacuum pump, and then the crucible is heated, The hole transport material is evaporated and a hole transport layer 4 is formed on the substrate 1 on which the anode 2 is formed, which is placed facing the crucible.
The thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and usually 3
00 nm or less, preferably 100 nm or less. In order to uniformly form such a thin film, a vacuum deposition method is generally used.

  In the element shown in FIG. 1, a light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 is excited by recombination of holes injected from the anode and moving through the hole transport layer and electrons injected from the cathode and moved through the hole blocking layer 6 between the electrodes to which an electric field is applied. And formed from a luminescent compound that exhibits strong luminescence. In this invention, it forms with the dopant material which consists of a host material which consists of 2 or more types of different charge transportable compounds, and the organometallic complex containing at least 1 metal chosen from periodic table group 7-11.

As described above, the light-emitting layer may be one in which the light-emitting layer forming material of the present invention is used, a host material composed of two or more different types of charge transporting compounds, and groups 7 to 11 of the periodic table. If the dopant material which consists of an organometallic complex containing at least 1 metal chosen from these is included, the effect of this invention can be show | played.
Specifically, as described above, at least one is a material having an electron transporting property, and at least one is a material having a hole transporting property. Preferred are a compound having a pyridine ring and a compound having a carbazole ring, and more preferred are a compound represented by general formula (1) and a compound represented by general formula (2), respectively.

  In addition, it is formed with a dopant material composed of a host material composed of two or more different charge transporting compounds of the present invention and an organometallic complex containing at least one metal selected from Groups 7 to 11 of the periodic table. The details of the organometallic complex containing two or more different charge transporting compounds and at least one metal selected from Groups 7 to 11 of the periodic table used for the light emitting layer are the same as those for the light emitting layer forming material described above. It is.

The light-emitting compound used for the light-emitting layer 5 has a stable thin film shape, exhibits high emission (fluorescence or phosphorescence) quantum yield in the solid state, and can efficiently transport holes and / or electrons. It must be a compound. Further, it is required to be a compound that is electrochemically and chemically stable and does not easily generate impurities as traps during production or use.
The thickness of the light emitting layer 5 is usually 3 nm or more, preferably 5 nm or more, and is usually 200 nm or less, preferably 100 nm or less.

The light emitting layer can also be formed by the same method as the hole transport layer. A method for doping the above-described fluorescent dye and / or phosphorescent dye (phosphorescent dopant material) into the host material of the light emitting layer will be described below.
In the case of coating, the above light emitting layer host material, dope dye, and if necessary, additives such as a binder resin that does not become an electron trap or a light quenching quencher, and a coating property improving agent such as a leveling agent are added and dissolved. The applied coating solution is prepared, applied onto the hole transport layer 4 by a method such as spin coating, and dried to form the light emitting layer 5. Examples of the binder resin include polycarbonate, polyarylate, and polyester. When the amount of the binder resin added is large, the hole / electron mobility is lowered. Therefore, the smaller amount is desirable, and 50% by weight or less is preferable.

In the case of the vacuum deposition method, the host material (two or more kinds of charge transporting compounds) is put in separate crucibles set in the vacuum vessel, the dye to be doped is put in another crucible, and the inside of the vacuum vessel is appropriately set. After evacuating to about 1.0 × 10 ⁻⁴ Pa with a vacuum pump, each crucible is heated and evaporated at the same time to form a layer on the substrate placed facing the crucible. As another method, a mixture of the above materials in a predetermined ratio may be evaporated using the same crucible.

When each said dopant is doped in a light emitting layer, although doped uniformly in the film thickness direction of a light emitting layer, there may exist concentration distribution in a film thickness direction. For example, it may be doped only in the vicinity of the interface with the hole transport layer, or conversely, it may be doped in the vicinity of the interface of the hole blocking layer.
As for the host material, as in the dopant material, the mixing ratio (mixing ratio) of the hole transporting compound and the electron transporting compound may be uniform in the film thickness direction of the light emitting layer, or the mixing ratio ( (Mixing ratio) distribution may be present. For example, the ratio of the hole transporting compound may be increased near the interface with the hole transport layer, or the ratio of the electron transporting compound may be increased near the interface with the hole blocking layer.

The light emitting layer can also be formed by the same method as the hole transport layer, but usually a vacuum deposition method is used.
In addition, the light emitting layer 5 may contain components other than the above in the range which does not impair the performance of this invention. In the element shown in FIG. 1, the hole blocking layer 6 is laminated on the light emitting layer 5 so as to be in contact with the cathode side interface of the light emitting layer 5.

  The hole blocking layer has a role of blocking the holes moving from the hole transport layer from reaching the cathode, and a compound that can efficiently transport the electrons injected from the cathode toward the light emitting layer. Preferably it is formed. The physical properties required for the material constituting the hole blocking layer are required to have high electron mobility and low hole mobility. The hole blocking layer 6 has a function of confining holes and electrons in the light emitting layer and improving luminous efficiency.

  As a hole blocking material satisfying such conditions, a mixed ligand complex represented by the following general formula 4 is preferably exemplified.

In General Formula 4, R ^{81 to} R ⁸⁶ each independently represents a hydrogen atom or an arbitrary substituent. Q3 represents a metal atom selected from aluminum, gallium and indium. Y1 represents a group represented by any one of the following formulas 4-1, 4-2, and 4-3.

In General Formula 4-1, General Formula 4-2, and General Formula 4-3, Ar21 to Ar25 may have an aromatic hydrocarbon ring group or a substituent which may have a substituent. Represents a good aromatic heterocyclic group, Y2 represents silicon or germanium.
Furthermore, in the general formula 4, R ^{81 to} R ⁸⁶ each independently represent a hydrogen atom or an arbitrary substituent. Specific examples include a hydrogen atom; a halogen atom such as chlorine or bromine; an alkyl group having 1 to 6 carbon atoms such as a methyl group or an ethyl group; an aralkyl group such as a benzyl group; an alkenyl having 2 to 6 carbon atoms such as a vinyl group. Group; cyano group; amino group; acyl group; alkoxy group having 1 to 6 carbon atoms such as methoxy group and ethoxy group; alkoxycarbonyl group having 2 to 6 carbon atoms such as methoxycarbonyl group and ethoxycarbonyl group; carboxyl group; phenoxy Group, aryloxy group such as benzyloxy group; alkylamino group such as diethylamino group and diisopropylamino group; aralkylamino group such as dibenzylamino group and diphenethylamino group; haloalkyl group such as trifluoromethyl group; hydroxyl group; Groups, aromatic hydrocarbon ring groups such as naphthyl groups; aromatic heterocycles such as thienyl groups and pyridyl groups Group, and the like.

  The above aromatic hydrocarbon ring group and aromatic heterocyclic group may further have a substituent. Examples of the substituent that the aromatic hydrocarbon ring group and the aromatic heterocyclic group may have include, for example, a halogen atom such as a fluorine atom; an alkyl group having 1 to 6 carbon atoms such as a methyl group and an ethyl group; An alkenyl group having 2 to 6 carbon atoms; an alkoxycarbonyl group having 2 to 6 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group; an alkoxy group having 1 to 6 carbon atoms such as a methoxy group and an ethoxy group; a phenoxy group and a benzyloxy group Aryloxy groups such as: alkylamino groups such as dimethylamino group and diethylamino group; acyl groups such as acetyl group; haloalkyl groups such as trifluoromethyl group; cyano groups and the like.

Among these, R ^{81 to} R ⁸⁶ are preferably a hydrogen atom, an alkyl group, a halogen atom or a cyano group. R ⁸⁴ is particularly preferably a cyano group.
Furthermore, in the general formula 4, Ar ^{21 to} Ar ²⁵ specifically include aromatic hydrocarbon ring groups such as phenyl group, biphenyl group and naphthyl group, or aromatic heterocyclic groups such as thienyl group and pyridyl group. It is done. Of these, a 5-membered ring, a 6-membered ring, a 5-membered ring and / or a condensed 6-membered ring, or a structure in which two or three of these are directly bonded are preferable. Of the aromatic hydrocarbon ring group and the aromatic heterocyclic group, an aromatic hydrocarbon ring group is preferable.

Ar ^{21 to} Ar ²⁵ may further have a substituent. Examples of the substituent that Ar ^{21 to} Ar ²⁵ may have include, for example, the same groups as those described above as the substituent that R ^{81 to} R ⁸⁶ may have in the case of an aromatic hydrocarbon ring group or an aromatic heterocyclic group. Is mentioned.
Specific preferred examples of the compound represented by the general formula 4 are shown below, but are not limited thereto.

  Further, as the hole blocking material, in addition to the mixed ligand complex of the general formula 4, a compound having at least one 1,2,4-triazole ring residue represented by the following structural formula may be used. it can.

  Specific examples of the compound having at least one 1,2,4-triazole ring residue represented by the above structural formula are shown below, but are not limited thereto. In the following structural formula, t-Bu- represents a tertiary butyl group, and Et- represents an ethyl group.

Although not described in the above structural formula, the benzene ring and naphthalene ring in the compound having at least one 1,2,4-triazole ring residue may further have a substituent. . Examples of the substituent include, for example, the same groups as described above as substituents that may be possessed when R ^{81 to} R ⁸⁶ in General Formula 4 are an aromatic hydrocarbon ring group or an aromatic heterocyclic group. .

  Furthermore, a compound having at least one phenanthroline ring represented by the following structural formula can also be used as the hole blocking material.

  Specific examples of the compound having at least one phenanthroline ring represented by the above structural formula are shown below, but are not limited thereto.

  As for these compounds having at least one phenanthroline ring, the benzene ring and naphthalene ring may further have a substituent as in the case of the compound having a 1,2,4-triazole ring residue. Examples of the substituent include the same groups as those described above as the substituent that may be possessed when R11 to R16 in the general formula 4 are an aromatic hydrocarbon ring group or an aromatic heterocyclic group.

  Moreover, the compound which has a pyridine ring represented by General formula (1) can also be used as a hole blocking material. In particular, since the compound having a pyridine ring represented by the general formula (1) has a high excited triplet level (T1), it has a high effect of confining excitons in the light emitting layer. Is more preferable. The compound represented by the general formula (1) may be used alone or in combination in the hole blocking layer. Furthermore, you may use together the compound which has a well-known hole-blocking function in the range which does not impair the performance of the compound of this invention.

  The ionization potential of the hole blocking layer used in the present invention is preferably 0.1 eV or more larger than the ionization potential of the light emitting layer. In the case of the present invention in which the light emitting layer includes a host material and a dopant material, it is preferably 0.1 eV or more higher than the ionization potential of the dopant material, and more preferably 0.1 eV or more higher than the ionization potential of the host material. That is, the compound having a pyridine ring represented by the general formula (1) used in the light emitting layer can be used in the hole blocking layer.

The ionization potential is defined by the energy required to emit electrons at the HOMO (highest occupied molecular orbital) level of the material to the vacuum level. The ionization potential can be defined directly by photoelectron spectroscopy or can be determined by correcting the electrochemically measured oxidation potential relative to the reference electrode. In the case of the latter method, for example, when a saturated sweet potato electrode (SCE) is used as a reference electrode,
Ionization potential = oxidation potential (vs. SCE) + 4.3 eV
Defined by ("Molecular Semiconductors", Springer-Verlag, 1985, page 98).

  Further, the electron affinity (EA) of the hole blocking layer used in the present invention is compared with the electron affinity of the light emitting layer (in the case of the present invention, the electron affinity of the electron transporting compound among the host materials in the light emitting layer). It is preferable that it is equal to or higher. Similar to the ionization potential, the electron affinity is also defined by the energy at which the electrons in the vacuum level fall to the LUMO (lowest unoccupied molecular orbital) level of the material and stabilize, with the vacuum level as a reference. The electron affinity can be obtained by subtracting the optical band gap from the above-mentioned ionization potential, or similarly obtained from the electrochemical reduction potential by the following formula.

Electron affinity = reduction potential (vs. SCE) +4.3 eV
Therefore, the hole blocking layer used in the present invention uses an oxidation potential and a reduction potential,
(Oxidation potential of hole blocking material) − (oxidation potential of light emitting material) ≧ 0.1V
(Reduction potential of hole blocking material) ≧ (Reduction potential of light emitting material)
It can also be expressed.

Further, in the case of an element having an electron transport layer described later, the electron affinity of the hole blocking layer is preferably equal to or less than that of the electron transport layer.
(Reduction potential of electron transport material) ≧ (Reduction potential of hole blocking material) ≧ (Reduction potential of light emitting material)
The film thickness of the hole blocking layer 6 is usually 0.3 or more, preferably 0.5 nm or more, and is usually 100 nm or less, preferably 50 nm or less. The hole blocking layer can also be formed by the same method as the hole transporting layer, but usually a vacuum deposition method is used.

  The cathode 8 serves to inject electrons into the light emitting layer 5 through the hole blocking layer 6. The material used for the cathode 8 can be the material used for the anode 2, but a metal having a low work function is preferable for efficient electron injection, such as tin, magnesium, indium, calcium, A suitable metal such as aluminum or silver or an alloy thereof is used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy. Furthermore, inserting an ultrathin insulating film (0.1 to 5 nm) such as LiF, MgF2, or Li2O at the interface between the cathode and the light emitting layer or the electron transporting layer is also an effective method for improving the efficiency of the device (Appl Phys., Lett., 70, 152, 1997; JP-A-10-74586; IEEE Trans. Electron. Devices, 44, 1245, 1997). The film thickness of the cathode 8 is usually the same as that of the anode 2. For the purpose of protecting the cathode made of a low work function metal, further laminating a metal layer having a high work function and stable to the atmosphere on the cathode increases the stability of the device. For this purpose, metals such as aluminum, silver, copper, nickel, chromium, gold, platinum are used.

For the purpose of further improving the luminous efficiency of the device, an electron transport layer 7 may be provided between the hole blocking layer 6 and the cathode 8 as shown in FIGS. The electron transport layer 7 is formed of a compound that can efficiently transport electrons injected from the cathode between the electrodes to which an electric field is applied in the direction of the hole blocking layer 6.
Materials satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives, Styryl biphenyl derivative, silole derivative, 3- or 5-hydroxyflavone metal complex, benzoxazole metal complex, benzothiazole metal complex, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compound No. 207169), phenanthroline derivatives (Japanese Patent Laid-Open No. 5-331459), 2-t-butyl-9,10-N, N′-dicyanoanthraquinonediimine, n-type hydrogenated amorphous silicon carbide, n-type sulfide Examples include zinc and n-type zinc selenide.

Further, the electron transport material is doped with an alkali metal (described in Japanese Patent Application Laid-Open No. 10-270171, Japanese Patent Application No. 2000-285656, Japanese Patent Application No. 2000-285657, etc.), thereby improving the electron transport property. Therefore, it is preferable.
The electron transport layer 7 is formed by laminating on the hole blocking layer 6 by a coating method or a vacuum deposition method in the same manner as the hole transport layer 4. Usually, a vacuum deposition method is used.

In addition, you may use the compound of this invention for this electron carrying layer 7. FIG. In that case, the electron transport layer 7 may be formed using only the compound of the present invention, or may be used in combination with the various known materials described above.
When the compound of the present invention is used for the electron transport layer 7, the compound of the present invention may be used for the hole blocking layer 6 described above, or the compound of the present invention is used only for the electron transport layer 7, Other known hole blocking materials may be used for the hole blocking layer 6.

The thickness of the electron transport layer 6 is usually 5 nm or more, preferably 10 nm or more, and is usually 200 nm or less, preferably 100 nm or less.
The electron transport layer 7 is formed by laminating on the hole blocking layer 6 by a coating method or a vacuum deposition method in the same manner as the hole transport layer 4. Usually, a vacuum deposition method is used.
An anode buffer layer 3 is also inserted between the hole transport layer 4 and the anode 2 for the purpose of further improving the efficiency of hole injection and improving the adhesion of the entire organic layer to the anode. (See FIG. 3). By inserting the anode buffer layer 3, the driving voltage of the initial element is lowered, and at the same time, an increase in voltage when the element is continuously driven with a constant current is suppressed. As conditions required for the material used for the anode buffer layer, a uniform thin film can be formed with good contact with the anode, and it is thermally stable, that is, the melting point and the glass transition temperature are high. The glass transition temperature is preferably 100 ° C. or higher. Furthermore, the ionization potential is low, hole injection from the anode is easy, and the hole mobility is high.

For this purpose, porphyrin derivatives, phthalocyanine compounds (JP-A 63-295695), hydrazone compounds, alkoxy-substituted aromatic diamine derivatives, p- (9-anthryl) have been used as materials for the anode buffer layer 3 so far. ) -N, N'-di-p-tolylaniline, polythienylene vinylene, poly-p-phenylene vinylene, polyaniline (Appl. Phys. Lett., 64, 1245, 1994), polythiophene (OpticalMaterials, 9 Vol. 125, 1998), organic compounds such as starbust aromatic triamine (JP-A-4-308688), sputtered carbon film (Synth. Met. 91, 73, 1997) , Vanadium oxide, ruthenium oxide,
Metal oxides such as molybdenum oxide (J. Phys. D, 29, 2750, 1996) have been reported.

In addition, a layer containing a hole injection / transporting low molecular organic compound and an electron accepting compound (described in JP-A-11-251067, JP-A-2000-159221, etc.), an aromatic amino group, etc. A layer obtained by doping the contained non-conjugated polymer compound with an electron-accepting compound as necessary (JP-A-11-135262, JP-A-11-283750, JP-A-2)
No. 000-36390, JP-A 2000-150168, JP-A 2001-223084, and WO 97/33193), or a layer containing a conductive polymer such as polythiophene (JP-A 10-92584) However, it is not limited to these.

As the anode buffer layer material, either a low molecular compound or a high molecular compound can be used.
Of the low molecular weight compounds, those often used include porphine compounds and phthalocyanine compounds. These compounds may have a central metal or may be metal-free. Preferred examples of these compounds include the following compounds:
Porphin,
5,10,15,20-tetraphenyl-21H, 23H-porphine,
5,10,15,20-tetraphenyl-21H, 23H-porphine cobalt (II),
5,10,15,20-tetraphenyl-21H, 23H-porphine copper (II),
5,10,15,20-tetraphenyl-21H, 23H-porphine zinc (II),
5,10,15,20-tetraphenyl-21H, 23H-porphine vanadium (IV) oxide,
5,10,15,20-tetra (4-pyridyl) -21H, 23H-porphine,
29H, 31H-phthalocyanine,
Copper (II) phthalocyanine,
Zinc (II) phthalocyanine,
Titanium phthalocyanine oxide,
Magnesium phthalocyanine,
Lead phthalocyanine,
Copper (II) 4,4'4 '', 4 '''-tetraaza-29H, 31H-phthalocyanine In the case of an anode buffer layer, a thin film can be formed in the same manner as the hole transport layer. Further, sputtering, electron beam evaporation, or plasma CVD is used.

When the anode buffer layer 3 formed as described above is formed using a low molecular weight compound, the lower limit is usually 3 nm, preferably about 10 nm, and the upper limit is usually 100 nm, preferably about 50 nm. is there.
When using a polymer compound, for example, the polymer compound or the electron-accepting compound, and if necessary, additives such as a binder resin and a coating agent such as a leveling agent that do not trap holes are added and dissolved. A coating solution is prepared, applied to the anode 2 by a normal coating method such as a spray method, a printing method, a spin coating method, a dip coating method, a die coating method, an ink jet method or the like, and dried to form the anode buffer layer 3. A thin film can be formed. Examples of the binder resin include polycarbonate, polyarylate, and polyester. Since the binder resin may reduce hole mobility when the content of the binder resin is large, it is desirable that the content of the binder resin in the anode buffer layer 3 is 50% by weight or less.

Alternatively, a thin film may be formed in advance on a medium such as a film, a support substrate, or a roll by the above-described thin film forming method, and the thin film on the medium is thermally or pressure transferred onto the anode 2. it can.
As described above, the lower limit of the film thickness of the anode buffer layer 3 formed using the polymer compound is usually 5 nm, preferably about 10 nm, and the upper limit is usually about 1000 nm, preferably about 500 nm.

The organic electroluminescence device of the present invention has a structure opposite to that shown in FIG. 1, that is, a cathode 8, a hole blocking layer 6, a light emitting layer 5, a hole transport layer 4 and an anode 2 can be laminated on a substrate in this order. As described above, it is also possible to provide the organic electroluminescence device of the present invention between two substrates, at least one of which is highly transparent. Similarly, the layers can be stacked in the reverse order of the layer configuration shown in FIG. 2 or FIG. Moreover, in any layer structure of FIGS. 1-3, in the range which does not deviate from the meaning of this invention, it may have arbitrary layers other than the above-mentioned, and the layer which has the function of several said layers together By providing, it is possible to appropriately modify the layer structure, for example.

Alternatively, a top emission structure or a transmission type using a transparent electrode for both the cathode and anode, and a structure in which the layer configuration shown in FIG. 1 is stacked in multiple layers (a structure in which a plurality of light emitting units are stacked) is used. Is also possible. In this case, instead of the interfacial layer (between the light emitting units) (when the anode is ITO and the cathode is Al, the two layers) V2O5 or the like is used as the charge generation layer (CGL) as a barrier between the steps. From the viewpoint of luminous efficiency and driving voltage.

  The present invention can be applied to any of an organic electroluminescent element having a single element, an element having a structure arranged in an array, and a structure having an anode and a cathode arranged in an XY matrix.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.
(Example 1)

An organic electroluminescent element having the structure shown in FIG. 3 was produced by the following method.
An indium tin oxide (ITO) transparent conductive film 2 deposited on a glass substrate 1 with a thickness of 150 nm (sputtered film; sheet resistance: 15Ω) is formed into a 2 mm wide stripe using ordinary photolithography and hydrochloric acid etching. An anode was formed by patterning. The patterned ITO substrate was cleaned in the order of ultrasonic cleaning with acetone, water with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally subjected to ultraviolet ozone cleaning.

  As a material for the anode buffer layer 3, a non-conjugated polymer compound (PB-1) having an aromatic amino group having the structural formula shown below

An electron-accepting compound (A-1)

In addition, spin coating was performed under the following conditions.
Solvent Ethyl benzoate Coating solution concentration 2 [wt%]
PB-1: A-1 10: 1
Spinner speed 1500 [rpm]
Spinner rotation time 30 [seconds]
Drying conditions 100 ° C. for 1 hour A uniform thin film having a thickness of 30 nm was formed by the above spin coating.
Next, the substrate on which the anode buffer layer was formed was placed in a vacuum evaporation apparatus. After roughly exhausting the apparatus with an oil rotary pump, the apparatus was exhausted with a cryopump until the vacuum in the apparatus was 1.4 × 10 ⁻⁴ Pa or less. Arylamine compound (H-1) shown below, placed in a ceramic crucible placed in the above apparatus

Vapor deposition was performed by heating with a tantalum wire heater around the crucible. At this time, the temperature of the crucible was controlled in the range of 236 to 261 ° C. A hole transport layer 4 having a thickness of 60 nm was obtained at a vacuum degree of 8.0 × 10 ⁻⁵ Pa and a deposition rate of 0.20 nm / second during the deposition.
Subsequently, pyridine derivative (EMP-1) and carbazole derivative (EMC-1) as main components (host material) of light-emitting layer 5 and organic iridium complex (EMD-1) as separate components (dopant) in separate ceramic crucibles. It installed and formed into a film by the ternary simultaneous vapor deposition method.

The crucible temperature of the compound (EMP-1) was controlled at 271 to 274 ° C, the crucible temperature of the compound (EMC-1) was controlled at 285 ° C, and the crucible temperature of the compound (EMD-1) was controlled at 235 ° C, respectively.
The light emitting layer 5 was laminated on the hole transport layer 4 at a ratio of EMC-1: EMD-1 = 15: 15: 1.8. The degree of vacuum during the deposition was 7.3 × 10 ⁻⁵ Pa.
The excited triplet level of the host material used at this time is from the peak wavelength (λ _T1 [nm]) having the highest energy (short wavelength) in the phosphorescence spectrum of the thin film,
T1 _EMP-1 = 2.7 eV
T1 _EMC-1 = 2.6eV
Met.
Further, as the hole blocking layer 6, pyridine derivative (EMP-1)

The crucible temperature was 286 to 294 ° C., and the film was laminated with a film thickness of 10 nm at a deposition rate of 0.15 nm / second. The degree of vacuum during the deposition was 6.6 × 10 ⁻⁵ Pa.
An aluminum 8-hydroxyquinoline complex (ET-1) shown below as an electron transport layer 7 on the hole blocking layer 6

Was deposited in the same manner. At this time, the crucible temperature of the aluminum 8-hydroxyquinoline complex was controlled in the range of 276 to 285 ° C., the vacuum during deposition was 6.0 × 10 ⁻⁵ Pa, the deposition rate was 0.22 nm / sec, and the film thickness was 35 nm. .
The substrate temperature when vacuum-depositing the hole transport layer, the light emitting layer, and the electron transport layer was maintained at room temperature.

Here, the element on which the electron transport layer 6 has been deposited is once taken out from the vacuum deposition apparatus into the atmosphere, and a 2 mm wide striped shadow mask is used as the cathode deposition mask.
In close contact with the ITO stripe perpendicular to the ITO stripe, it is placed in a separate vacuum deposition apparatus and the degree of vacuum in the apparatus is 2.0x10 ^-6 Torr (about 2.7x10 ^-4 Pa) in the same way as the organic layer Exhaust until below. As the cathode 8, first, lithium fluoride (LiF) is deposited at a deposition rate of 0.01 nm / second, a degree of vacuum of 2.1 × 10 ⁻⁶ Torr (about 2.8 × 10 ⁻⁴ Pa), and a film thickness of 0.5 nm using a molybdenum boat. A film was formed on the transport layer 7. Next, aluminum was heated in the same molybdenum boat, deposition rate 0.40 nm / sec, thickness 80nm in vacuum of 3.4x10 ^-6 ~9.0x10 ^-6 Torr (about 4.5x10 ^-4 ~12.0x10 ^-4 Pa) The aluminum layer was formed to complete the cathode 8. The substrate temperature at the time of vapor deposition of the above two-layer cathode 8 was kept at room temperature.

As described above, an organic electroluminescent element having a light emitting area portion having a size of 2 mm × 2 mm was obtained. The light emission characteristics of this element are shown in Table-1. In Table 1, the maximum light emission luminance is a value at a current density of 0.25 A / cm ² , and the light emission efficiency, luminance / current, and voltage are values at a luminance of 100 cd / m ² . The maximum wavelength of the emission spectrum of the device was 510 nm, and the chromaticity was CIE (x, y) = (0.29, 0.61), which was identified as that from the compound (EMD-1).
(Comparative Example 1)
A device was fabricated in the same manner as in Example 1 except that only the carbazole derivative (EMC-1) was used as the main component (host material) of the light emitting layer 5. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 510 nm, and the chromaticity was CIE (x, y) = (0.28,0.61), which was identified as that from an organic iridium complex (EMD-1).
(Example 2)

A device was fabricated in the same manner as in Example 1 except that the organic iridium complex (EMD-2) was used instead of the organic iridium complex (EMD-1) as a subcomponent (dopant) of the light emitting layer 5. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 624 nm, and the chromaticity was CIE (x, y) = (0.67, 0.32), which was identified as that from an organic iridium complex (EMD-2).

(Comparative Example 2)
A device was fabricated in the same manner as in Example 2 except that only the carbazole derivative (EMC-1) was used as the main component (host material) of the light emitting layer 5. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 624 nm, and the chromaticity was CIE (x, y) = (0.67, 0.32), which was identified as that from an organic iridium complex (EMD-2).
(Example 3)

A device was fabricated in the same manner as in Example 2 except that the carbazole derivative (EMC-2) was used instead of the carbazole derivative (EMC-1) as the main component (host material) of the light emitting layer 5. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 624 nm, and the chromaticity was CIE (x, y) = (0.67, 0.32), which was identified as that from an organic iridium complex (EMD-2).

The excited triplet level of the carbazole derivative (EMC-2) used at this time is from the peak wavelength (λ _T1 [nm]) having the highest energy (short wavelength) of the phosphorescence spectrum of the thin film.
T1 _EMC-2 = 2.9 eV
Met.
(Comparative Example 3)
A device was fabricated in the same manner as in Example 3 except that only the carbazole derivative (EMC-2) was used as the main component (host material) of the light emitting layer 5. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 624 nm, and the chromaticity was CIE (x, y) = (0.67, 0.33), which was identified as that from an organic iridium complex (EMD-2).
Example 4

A device was fabricated in the same manner as in Example 1 except that the organic iridium complex (EMD-3) was used in place of the organic iridium complex (EMD-1) as a subcomponent (dopant) of the light emitting layer 5. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 483 nm, and the chromaticity was CIE (x, y) = (0.17, 0.38), which was identified as that from an organic iridium complex (EMD-3).

(Comparative Example 4)
A device was fabricated in the same manner as in Example 4 except that only the pyridine derivative (EMP-1) was used as the main component (host material) of the light emitting layer 5. The light emission characteristics of this element are shown in Table-1. The maximum wavelength of the emission spectrum of the device was 484 nm and the chromaticity was CIE (x, y) = (0.17, 0.38), which was identified as that from an organic iridium complex (EMD-3).

（駆動寿命試験）
実施例１〜４、比較例１〜４で作製した素子を、下記条件の下、駆動寿命試験を行った。

(Driving life test)
The drive life test was done on the element produced in Examples 1-4 and Comparative Examples 1-4 under the following conditions.

Temperature Room temperature Drive method DC drive (DC drive)
The time until the luminance was reduced by 20% (L / L0 = 0.8) or by 50% (L / L0 = 0.5) was compared. Table 2 shows the relative time of each example when the time of the comparative example element is 1.00. The example has a longer lifetime (time until the luminance is reduced by 50%) than the comparative example, and a long-life organic phosphorescent device is realized by using a mixed host composed of two or more different charge transporting compounds. It was done.

(Example 5)
Instead of using a pyridine derivative (EMP-1) and a carbazole derivative (EMC-1) as the main component (host material) of the light emitting layer 5, a pyridine derivative (EMP-2) and a carbazole derivative (EMC-1) are used. A device was fabricated in the same manner as in Example 1 except that a pyridine derivative (EMP-2) was used instead of the pyridine derivative (EMP-1) as the hole blocking layer 6. The light emission characteristics of this element are shown in Table-3. The maximum wavelength of the emission spectrum of the device was 510 nm, and the chromaticity was CIE (x, y) = (0.28,0.61), which was identified as that from an organic iridium complex (EMD-1).

(Comparative Example 5)
A device was fabricated in the same manner as in Example 5 except that only the carbazole derivative (EMC-1) was used as the main component (host material) of the light emitting layer 5. The light emission characteristics of this element are shown in Table-3. The maximum wavelength of the emission spectrum of the device was 510 nm, and the chromaticity was CIE (x, y) = (0.28,0.61), which was identified as that from an organic iridium complex (EMD-1).

(Driving life test)
The device produced in Example 5 and Comparative Example 5 was subjected to a driving life test under the following conditions.
Temperature Room temperature Drive method DC drive (DC drive)
The time until the luminance was reduced by 40% (L / L0 = 0.6) was compared with continuous light emission at a constant current. Table 4 shows the relative time of the element of Example 5 when the time of the element of Comparative Example 5 is 1.00. The lifetime of the example is longer than that of the comparative example (the time during which the luminance is reduced to a constant luminance), and by using a mixed host composed of two or more specific types of charge transporting compounds, a long-life organic phosphorescent device can be obtained. Realized.

(Example 6)
Other than using pyridine derivative (EMP-1) and carbazole derivative (EMC-3) instead of using pyridine derivative (EMP-1) and carbazole derivative (EMC-1) as the main component (host material) of light emitting layer 5 Were fabricated in the same manner as in Example 1. The light emission characteristics of this device are shown in Table-5. The maximum wavelength of the emission spectrum of the device was 513 nm, and the chromaticity was CIE (x, y) = (0.29, 0.61), which was identified as that from an organic iridium complex (EMD-1).

(Comparative Example 6)
A device was fabricated in the same manner as in Example 6 except that only the carbazole derivative (EMC-3) was used as the main component (host material) of the light emitting layer 5. The light emission characteristics of this device are shown in Table-5. The maximum wavelength of the emission spectrum of the device was 513 nm, and the chromaticity was CIE (x, y) = (0.29,0.63), which was identified as that from an organic iridium complex (EMD-1).

(Example 7)
Instead of using a pyridine derivative (EMP-1) and a carbazole derivative (EMC-1) as the main component (host material) of the light-emitting layer 5, other than using a pyridine derivative (EMP-1) and a carbazole derivative (EMC-4) Were fabricated in the same manner as in Example 1. The light emission characteristics of this device are shown in Table-5. The maximum wavelength of the emission spectrum of the device was 513 nm, and the chromaticity was CIE (x, y) = (0.30,0.62), which was identified as that from the organic iridium complex (EMD-1).

(Comparative Example 7)
A device was fabricated in the same manner as in Example 7 except that only the carbazole derivative (EMC-4) was used as the main component (host material) of the light emitting layer 5. The light emission characteristics of this device are shown in Table-5. The maximum wavelength of the emission spectrum of the device was 514 nm, and the chromaticity was CIE (x, y) = (0.31,0.62), which was identified as that from an organic iridium complex (EMD-1).

(Driving life test)
The drive life test was done on the element produced in Examples 6-7 and Comparative Examples 6-7 under the following conditions.
Temperature Room temperature Drive method DC drive (DC drive)
The time until the luminance was reduced by 40% (L / L0 = 0.6) or 50% (L / L0 = 0.5) was compared by continuously emitting light at a constant current. Table 6 shows the relative times of the element of Example 6 and the element of Example 7 when the time of the element of Comparative Example 6 and the element of Comparative Example 7 is 1.00, respectively. The lifetime of the example is longer than that of the comparative example (the time during which the luminance is reduced to a constant luminance), and by using a mixed host composed of two or more specific types of charge transporting compounds, a long-life organic phosphorescent device can be obtained. Realized.

(Example 8)
As in Example 1, except that the mixing ratio of the pyridine derivative (EMP-1) and the carbazole derivative (EMC-1) as the main component (host material) of the light-emitting layer 5 was set to 10:20 instead of 15:15. Thus, an element was produced. The light emission characteristics of this device are shown in Table 7. The maximum wavelength of the emission spectrum of the device was 512 nm, and the chromaticity was CIE (x, y) = (0.29, 0.62), which was identified as that from the organic iridium complex (EMD-1).

Example 9
As in Example 1, except that the mixing ratio of the pyridine derivative (EMP-1) and the carbazole derivative (EMC-1) as the main component (host material) of the light-emitting layer 5 was set to 20:10 instead of 15:15. Thus, an element was produced. The light emission characteristics of this device are shown in Table 7. The maximum wavelength of the emission spectrum of the device was 512 nm and the chromaticity was CIE (x, y) = (0.30,0.62), which was identified as that from the organic iridium complex (EMD-1).

(Example 10)
As in Example 1, except that the mixing ratio of the pyridine derivative (EMP-1) and the carbazole derivative (EMC-1) as the main component (host material) of the light-emitting layer 5 was 3:27 instead of 15:15. Thus, an element was produced. The light emission characteristics of this device are shown in Table 7. The maximum wavelength of the emission spectrum of the device was 512 nm, and the chromaticity was CIE (x, y) = (0.29, 0.62), which was identified as that from the organic iridium complex (EMD-1).

(Comparative Example 8)
A device was fabricated in the same manner as in Example 10 except that only the carbazole derivative (EMC-1) was used as the main component (host material) of the light emitting layer 5. The light emission characteristics of this device are shown in Table 7. The maximum wavelength of the emission spectrum of the device was 513 nm, and the chromaticity was CIE (x, y) = (0.30,0.62), which was identified as that from the organic iridium complex (EMD-1).

(Driving life test)
The driving life test was performed on the devices manufactured in Examples 8 to 10 and Comparative Example 8 under the following conditions.
Temperature Room temperature Drive method DC drive (DC drive)
Table 8 shows the time required for continuous light emission at a constant current until the brightness decreases by 50% (L / L0 = 0.5). The lifetime of the example is longer than that of the comparative example (the time during which the luminance is reduced to a constant luminance), and by using a mixed host composed of two or more specific types of charge transporting compounds, a long-life organic phosphorescent device can be obtained. Realized. The range of the mixing ratio in which the effect of extending the life by mixing is wide, and even if a small amount of EMP-1 is mixed as in EMP-1: EMC-1 = 3: 27 (Example 10), the long life can be effectively increased. Is realized.

The schematic cross section which showed an example of the organic electroluminescent element. The schematic cross section which showed another example of the organic electroluminescent element. The schematic cross section which showed another example of the organic electroluminescent element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Anode buffer layer 4 Hole transport layer 5 Light emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Cathode

Claims (20)

In the light emitting layer forming material, comprising a combination of a host material composed of two or more different charge transporting compounds and a dopant material composed of an organometallic complex containing at least one metal selected from Groups 7 to 11 of the periodic table.
A light emitting layer forming material, wherein the excited triplet level (T1) of the two or more different charge transporting compounds is 2.2 eV or more.   2. The light emitting layer forming material according to claim 1, wherein at least one of the two or more different types of charge transporting compounds is a compound having a pyridine ring. The light emitting layer forming material according to claim 2, wherein the compound having a pyridine ring is a compound represented by the following general formula (1).

(In general formula (1),
R ^{1 to} R ³ each independently represents an arbitrary substituent.
The 3rd and 5th positions of the pyridine ring may be substituted.
n is an integer of 1-8.
When n is 1, Q ¹ is a substituent of the pyridine ring or a hydrogen atom.
Q ¹ is an n-valent linking group when n is 2 or more.
Q ¹ is directly bonded to any one of positions 2 to 6 of the pyridine ring. However, when Q ¹ is bonded to any of the 2, 4 and 6 positions of the pyridine ring, any one of R ^{1 to} R ^{3 at} the bonding position is Q ¹ .
When n is 2 or more, a plurality of R ^{1 to} R ³ contained in the compound may be the same or different.
When n is 2 or more, the position at which the pyridine ring is bonded to Q ¹ may be the same position or different. )   The light emitting layer forming material according to any one of claims 1 to 3, wherein at least one of the two or more different charge transporting compounds is a compound having a carbazole ring. The light emitting layer forming material according to claim 4, wherein the compound having a carbazole ring is a compound represented by the following general formula (2).

(In general formula (2),
R ⁴ represents a hydrogen atom, an arbitrary substituent, or Q ² .
The carbazole ring may have a substituent other than R ⁴ .
m is an integer of 1-6.
When m is 1, Q ² is a carbazole ring substituent or a hydrogen atom.
Q ² is an m-valent linking group when m is 2 or more.
Q ² is directly bonded to any one of the 1 to 9 positions of the carbazole ring or R ⁴ . However, when Q ² is bonded to the 9-position of the carbazole ring, R ⁴ is Q ² .
When m is 2 or more, a plurality of R ⁴ contained in the compound may be the same or different.
When m is 2 or more, the position at which the carbazole ring is bonded to Q ² may be the same position or different. )   The host material is composed of two different types of charge transporting compounds, and the two different types of charge transporting compounds are a compound having the pyridine ring and a compound having the carbazole ring, respectively. The light emitting layer forming material according to any one of the above.   The host material is composed of two different types of charge transporting compounds, and the two different types of charge transporting compounds are represented by the compound represented by the general formula (1) and the general formula (2), respectively. The light emitting layer forming material according to claim 6 which is a compound.   The at least one metal selected from groups 7 to 11 of the periodic table is selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. The light emitting layer forming material according to any one of the above. On the substrate, at least an anode, a cathode, and an organic electroluminescent element having a light emitting layer provided between both electrodes,
A host material in which the light emitting layer is composed of two or more different charge transporting compounds;
1. A dopant material comprising an organometallic complex containing at least one metal selected from Groups 7 to 11 of the periodic table is contained, and the excited triplet level (T1) of the two or more different charge transporting compounds is 2. An organic electroluminescent element characterized by being 2 eV or more.   The organic electroluminescent element according to claim 9, wherein one of the two or more different charge transporting compounds is a compound having a pyridine ring.   The organic electroluminescent element according to claim 10, wherein the compound having a pyridine ring is a compound represented by the general formula (1).   The organic electroluminescent element according to any one of claims 9 to 11, wherein one of the two or more different charge transporting compounds is a compound having a carbazole ring.   The organic electroluminescent element according to claim 12, wherein the compound having a carbazole ring is a compound represented by the general formula (2).   The host material is composed of two different types of charge transporting compounds, and the two different types of charge transporting compounds are a compound having a pyridine ring and a compound having a carbazole ring, respectively. The organic electroluminescent element according to claim 1.   The host material is composed of two different types of charge transporting compounds, and the two different types of charge transporting compounds are represented by the compound represented by the general formula (1) and the general formula (2), respectively. The organic electroluminescent element according to claim 14, which is a compound.   The at least one metal selected from groups 7 to 11 of the periodic table is selected from ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. Organic electroluminescent element as described in any one of these.   The organic electroluminescent element according to claim 9, further comprising an electron transport layer between the light emitting layer and the cathode.   The organic electroluminescent element according to claim 9, further comprising a hole blocking layer in contact with a cathode side interface of the light emitting layer.   The organic electroluminescent element according to claim 18, wherein the hole blocking layer contains a charge transporting compound represented by the general formula (1).   The organic electroluminescent element according to claim 9, further comprising a hole transport layer between the light emitting layer and the anode.

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