JP2004311404A - Organic electroluminescent element, illumination device and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element, an illumination device and a display device high in light-emitting efficiency. <P>SOLUTION: This is the organic electroluminescent element which has organic layers including at least a light-emitting layer. A compound having at least one biaryl part structure is contained in at least one layer of the organic layers, and as for the compound, a dihedral-angle θ of the biaryl part structure in the minimum excitation triplet state obtained by a non-empirical molecular orbit calculation method is 10° to 90°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an organic electroluminescence element, a lighting device, and a display device, and more particularly, to an organic electroluminescence device having excellent luminous efficiency, a lighting device, and a display device having the same.

  2. Description of the Related Art Conventionally, there is an electroluminescence display (ELD) as a light-emitting electronic display device. ELD includes an inorganic electroluminescence element and an organic electroluminescence element (hereinafter, also referred to as an organic EL element).

  Inorganic electroluminescent devices have been used as flat light sources, but require a high AC voltage to drive the light emitting devices.

  On the other hand, an organic EL element has a configuration in which a light-emitting layer containing a compound that emits light is sandwiched between a cathode and an anode, and electrons and holes are injected into the light-emitting layer and recombined to form excitons. And emits light by utilizing light emission (fluorescence / phosphorescence) when the exciton is deactivated. The element can emit light at a voltage of about several volts to several tens of volts. Since it is a light emitting type, it has a wide viewing angle and high visibility, and because it is a thin-film type solid-state element, it is attracting attention from the viewpoint of space saving and portability.

  As for the development of organic EL elements for practical use in the future, organic EL elements that emit light with high efficiency and low power consumption are desired. For example, stilbene derivatives, distyryl arylene derivatives or tris A technique of doping a styrylarylene derivative with a trace amount of a phosphor to improve emission luminance and extend the life of the device (see, for example, Patent Document 1), and using an 8-hydroxyquinoline aluminum complex as a host compound. A device having an organic light emitting layer doped with a small amount of phosphor (see, for example, Patent Document 2), and a device having an organic light emitting layer doped with a quinacridone-based dye using an 8-hydroxyquinoline aluminum complex as a host compound (for example, And Patent Document 3) are known.

  In the technique disclosed in the above-mentioned patent document, when light emission from an excited singlet is used, the generation ratio of a luminescent excited species is 25% because the generation ratio between a singlet exciton and a triplet exciton is 1: 3. And the light extraction efficiency is about 20%, so that the limit of the external extraction quantum efficiency (ηext) is 5%.

  However, since Princeton University reported an organic EL device using phosphorescence emission from an excited triplet (for example, see Non-Patent Document 1), research on materials exhibiting phosphorescence at room temperature has been active. (For example, see Non-Patent Document 2 and Patent Document 4).

  When the excited triplet is used, the upper limit of the internal quantum efficiency becomes 100%. Therefore, the luminous efficiency is quadrupled in principle as compared with the case of the excited singlet, and the performance almost equal to that of the cold cathode tube is obtained. It is also applicable to and is attracting attention.

  For example, many compounds have been studied for synthesis centering on heavy metal complexes such as iridium complexes (for example, see Non-Patent Document 3).

  Further, studies using tris (2-phenylpyridine) iridium as a dopant have been made (for example, see Non-Patent Document 2).

In addition, as a dopant, L ₂ Ir (acac) (L represents a ligand, acac represents acetylacetonate), for example, (ppy) ₂ Ir (acac) (for example, see Non-Patent Document 4), and a dopant As tris (2- (p-tolyl) pyridine) iridium (Ir (ptpy) ₃ ), tris (benzo [h] quinoline) iridium (Ir (bzq) ₃ ), Ir (bzq) ₂ CLP (Bu) ₃ (For example, see Non-Patent Document 5).

  Further, in order to obtain high luminous efficiency, a hole transporting compound is used as a host of a phosphorescent compound (for example, see Non-Patent Document 6).

  In addition, various electron-transporting materials are used as a host of a phosphorescent compound by doping them with a novel iridium complex (for example, see Non-Patent Document 4). Further, high luminous efficiency is obtained by introducing a hole blocking layer (for example, see Non-Patent Document 5). At present, further enhancement of the efficiency of light emission of the organic EL device using the phosphorescent light emission is being studied.

However, for green light emission, although the external extraction efficiency of about 20%, which is the theoretical limit, is achieved, only the low current region (low luminance region) is reached, and the theoretical limit is still high in the high current region (high luminance region). Not achieved. In addition, sufficient efficiency has not yet been obtained for other luminescent colors, and improvement is necessary. In addition, in the organic EL device for practical use in the future, light emission with high efficiency and low power consumption is required. There is a demand for the development of an organic EL device. In particular, an organic EL device which emits blue phosphorescent light with high efficiency is required.
Patent No. 3093796 JP-A-63-264692 JP-A-3-255190 U.S. Pat. No. 6,097,147 M. A. Baldo et al. , Nature, 395, 151-154 (1998) M. A. Baldo et al. , Nature, Vol. 403, No. 17, pp. 750-753 (2000) S. See Lamansky et al. , J. et al. Am. Chem. Soc. 123, 4304 pages (2001) M. E. FIG. Thompson et al. , The 10th International Works on Inorganic and Organic Electroluminescence (EL'00, Hamamatsu) Moon-Jae Youn. Og, Tetsuo Tsutsui et al. , The 10th International Works on Inorganic and Organic Electroluminescence (EL'00, Hamamatsu) Ikai et al. , The 10th International Works on Inorganic and Organic Electroluminescence (EL'00, Hamamatsu)

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an organic EL element, a lighting device, and a display device having high luminous efficiency.

  The above object of the present invention has been achieved by the following constitutions 1 to 12.

(Claim 1)
In an organic electroluminescence device having an organic layer including at least a light emitting layer,
At least one of the organic layers contains a compound having at least one biaryl partial structure, and the compound has a dihedral angle of the biaryl partial structure in the lowest excited triplet state determined by ab initio molecular orbital calculation. The organic electroluminescence device wherein θ is 10 ° to 90 °.

(Claim 2)
The organic electroluminescent device according to claim 1, wherein the compound is contained in the light emitting layer.

(Claim 3)
3. The organic electroluminescent device according to claim 1, wherein the biaryl partial structure is a partial structure having a biphenyl ring or a partial structure having a ring formed by directly bonding a phenyl group and a carbazolyl group. .

(Claim 4)
The compound has at least one group selected from the group consisting of a carbazolyl group, a triazolyl group, a pyrrolyl group, a diarylamino group, an oxadiazolyl group, a dibenzofuranyl group, a dibenzothienyl group, and an indolyl group. Item 4. The organic electroluminescent device according to any one of items 1 to 3.

(Claim 5)
In an organic electroluminescence device having an organic layer including at least a light emitting layer,
An organic electroluminescent device, wherein at least one of the organic layers contains a compound represented by the following general formula 1.

[In the formula, Ar ₁ and Ar ₂ represent an arylene group or a heteroarylene group, and Z ₁ and Z ₂ each independently represent a diarylamino group or an aromatic heterocyclic group. θ ₁ is the dihedral angle of Ar ₁ and Ar _{2 in} the lowest excited triplet state obtained by the ab initio molecular orbital calculation method and satisfies 10 ° ≦ θ ₁ ≦ 90 °. ]
(Claim 6)
The heteroarylene group is a carbazole ring, a triazole ring, a pyrrole ring, an oxadiazole ring, a dibenzofuran ring, a dibenzothiophene ring, a divalent group derived from a group consisting of an indole ring, and the aromatic heterocyclic group is 6. The organic material according to claim 5, wherein the carbazolyl group, triazolyl group, pyrrolyl group, oxadiazolyl group, dibenzofuranyl group, dibenzothienyl group and indolyl group are selected from the group consisting of: Electroluminescent element.

(Claim 7)
In an organic electroluminescence device having an organic layer including at least a light emitting layer,
An organic electroluminescent device, wherein at least one of the organic layers contains a compound represented by the following general formula 2.

[Wherein, Ar ₃ , Ar ₄ , and Ar ₅ represent an arylene group or a heteroarylene group, and Z ₃ and Z ₄ each independently represent a diarylamino group or an aromatic heterocyclic group. θ ₂ is the dihedral angle of Ar ₃ and Ar _{4 in} the lowest excited triplet state obtained by the ab initio molecular orbital calculation method and satisfies 10 ° ≦ θ ₂ ≦ 90 °. θ ₃ is the dihedral angle of Ar ₃ and Ar _{4 in} the lowest excited triplet state obtained by the ab initio molecular orbital calculation method and satisfies 10 ° ≦ θ ₃ ≦ 90 °. ]
(Claim 8)
The heteroarylene group is a carbazole ring, a triazole ring, a pyrrole ring, an oxadiazole ring, a dibenzofuran ring, a dibenzothiophene ring, a divalent group derived from a group consisting of an indole ring, and the aromatic heterocyclic group is 8. The organic compound according to claim 7, wherein the organic compound is any one selected from the group consisting of carbazolyl, triazolyl, pyrrolyl, oxadiazolyl, dibenzofuranyl, dibenzothienyl, and indolyl. Electroluminescent element.

(Claim 9)
The organic electroluminescent device according to any one of claims 1 to 8, wherein the light emitting layer contains a phosphorescent compound selected from osmium, iridium, rhodium, and a platinum complex compound.

(Claim 10)
A display device comprising the organic electroluminescence device according to claim 1.

(Claim 11)
A lighting device comprising the organic electroluminescent element according to claim 1.

(Claim 12)
A display device comprising: the lighting device according to claim 11; and a liquid crystal element as a display unit.

  According to the present invention, an organic EL element, a lighting device, and a display device having high luminous efficiency can be provided.

  In the organic electroluminescent device of the present invention, by adopting the structure defined in any one of claims 1 to 9, an organic electroluminescent device exhibiting high luminous efficiency can be obtained. Further, by using the organic electroluminescence element, a display device according to claim 10 and a lighting device according to claim 11 exhibiting high luminance can be obtained.

  Hereinafter, details of each component according to the present invention will be sequentially described.

  The present inventors have conducted intensive studies and found that, in an organic electroluminescence device having an organic layer including at least a light emitting layer, at least one of the organic layers contains a compound having at least one biaryl partial structure, When the dihedral angle θ of the biaryl partial structure in the lowest excited triplet state (hereinafter also referred to as T1) of the compound obtained by an ab initio molecular orbital calculation method is 10 ° to 90 °, the organic electroluminescent device Has been found to be able to improve the luminous efficiency.

<< Compound Having Biaryl Partial Structure >>
The compound having a biaryl partial structure according to the present invention will be described.

  In the present invention, a compound having at least one biaryl partial structure refers to a compound having at least one biaryl partial structure in a molecule, and a biaryl partial structure is a compound in which an aryl group and an aryl group are directly bonded. A partial structure having a ring formed, a partial structure having a ring formed by directly bonding the aryl group and the aromatic heterocyclic group, and the like, are preferably used, a partial structure having a biphenyl ring, A partial structure having a ring formed by directly bonding a phenyl group and a carbazolyl group is preferable, and a partial structure having a biphenyl ring is particularly preferable.

(Partial structure having a ring formed by directly bonding an aryl group and an aryl group)
Examples of the aryl group relating to the formation of a partial structure having a ring formed by directly bonding an aryl group and an aryl group include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, a naphthyl group, an anthryl group, a phenanthryl group and the like. Examples of the ring formed by directly bonding the aryl group and the aryl group include a biphenyl ring, terphenyl ring, quaterphenyl ring, kink phenyl ring, sexiphenyl ring, septiphenyl ring, octiphenyl ring, nobiphenyl A ring, a deciphenyl ring and the like are preferred, and among them, a biphenyl ring is preferably used.

  The ring formed by the direct bonding of the aryl group and the aryl group may be unsubstituted or may further have a substituent (the substituent will be described later). Further, a ring may be formed.

(Partial structure having a ring formed by directly bonding an aryl group and an aromatic heterocyclic group)
As the aryl group for forming the partial structure having a ring formed by directly bonding an aryl group and an aromatic heterocyclic group, the above-described moiety having a ring formed by directly bonding an aryl group and an aryl group It has the same meaning as the aryl group related to the formation of the structure.

  Examples of the aromatic heterocyclic group for forming a partial structure having a ring formed by directly bonding the aryl group and the aromatic heterocyclic group include a carbazolyl group, a triazolyl group, a pyrrolyl group, an oxadiazolyl group, and a dibenzofuranyl group. , A dibenzothienyl group, an indolyl group, etc., of which carbazolyl group and triazolyl group are preferably used.

  The ring formed by directly bonding the aryl group and the aromatic heterocyclic group may be unsubstituted or may further have a substituent (substituents will be described later). It may combine to form a ring.

  As the compound according to the present invention having at least one biaryl partial structure in a molecule, a compound represented by Formula 1 or Formula 2 is preferable.

<< Compound represented by Formula 1 or Formula 2 >>
The compound represented by Formula 1 or Formula 2 according to the present invention will be described.

In the general formula 1, Ar ₁ and Ar ₂ each represent an arylene group or a heteroarylene group, and Z ₁ and Z ₂ each independently represent a diarylamino group or an aromatic heterocyclic group.

In the general formula 1, examples of the arylene group represented by Ar ₁ and Ar ₂ include a phenylene group (o, m, p-phenylene group, etc.), a naphthylene group, a biphenyldiyl group, a terphenyldiyl group, and a quaterphenyldiyl group. Group, kinkphenyldiyl group, sexiphenyldiyl group, septiphenyldiyl group, octiphenyldiyl group, nobiphenyldiyl group, deciphenyldiyl group and the like.

In the general formula 1, the heteroarylene group represented by Ar ₁ and Ar ₂ is derived from the group consisting of a carbazole ring, a triazole ring, a pyrrole ring, an oxadiazole ring, a dibenzofuran ring, a dibenzothiophene ring, and an indole ring. And other divalent groups.

In the general formula 1, examples of the diarylamino group represented by Z ₁ and Z ₂ include, for example, a diphenylamino group, a dinaphthylamino group, a ditolylamino group, a dixylylamino group, a dibiphenylamino group, a dianthrylamino group, And a diphenanthrylamino group.

In the general formula 1, examples of the aromatic heterocyclic group represented by Z ₁ and Z ₂ include a carbazolyl group, a triazolyl group, a pyrrolyl group, an oxadiazolyl group, a dibenzofuranyl group, a dibenzothienyl group, and an indolyl group. .

In the general formula 2, Ar ₃ , Ar ₄ , and Ar ₅ each represent an arylene group or a heteroarylene group, and Z ₃ and Z ₄ each independently represent a diarylamino group or an aromatic heterocyclic group. .

In the general formula 2, the arylene groups represented by Ar ₃ , Ar ₄ , and Ar ₅ are the same as the arylene groups represented by Ar ₁ and Ar ₂ in the general formula 1, respectively.

In the general formula 2, the heteroarylene groups represented by Ar ₃ , Ar ₄ , and Ar ₅ have the same meanings as the heteroarylene groups represented by Ar ₁ and Ar ₂ in the general formula 1, respectively.

In Formula 2, the diarylamino groups represented by Ar ₃ , Ar ₄ , and Ar ₅ are the same as the diarylamino groups represented by Z ₁ and Z ₂ in Formula 1, respectively.

In the general formula 2, the aromatic heterocyclic groups represented by Ar ₃ , Ar ₄ and Ar ₅ are the same as the aromatic heterocyclic groups respectively represented by Z ₁ and Z ₂ in the general formula 1. .

  In the present invention, the compound having at least one biaryl partial structure in the molecule, the compound represented by the general formula 1 or the compound represented by the general formula 2 may be any one of organic layers (for example, light-emitting layer). Layer, a hole transport layer, a hole blocking layer, etc.), but from the viewpoint of improving the luminous efficiency of the organic EL device, it is preferable to include the luminescent layer.

  When the compound having at least one biaryl partial structure in the molecule, the compound represented by the general formula 1 or the compound represented by the general formula 2 is contained in the light emitting layer, each compound is a host described later. The compound functions as a compound, and the efficiency of energy transfer to a light-emitting material such as a phosphorescent compound contained in the light-emitting layer is improved, so that the light-emitting efficiency can be increased.

Further, when the organic EL device of the present invention (which will be described in detail later) is used for a blue phosphorescent organic EL device or a white phosphorescent organic EL device containing blue light, the above general formula 1 When the compound represented by the formula 2 is used as a host compound, Ar _{1 to} Ar ₄ and Z _{1 to} Z ₄ are each a group having a minimum excited triplet energy of 2.8 eV or more. Preferably. Thereby, energy transfer to the phosphorescent compound contained in the light emitting layer can be more efficiently performed, and the luminous efficiency can be further improved.

《Substituent》
The substituent which the compound having a biallyl partial structure and the compound represented by the general formula 1 or 2 may have will be described.

  The compound having a biaryl partial structure according to the present invention, and the compound represented by the general formula 1 or the general formula 2, which is a preferable embodiment of the compound, may be unsubstituted or may have a substituent. Examples of the substituent include a halogen atom (eg, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc.), an alkyl group (eg, a methyl group, an ethyl group, an isopropyl group, a hydroxyethyl group, a methoxymethyl group, Trifluoromethyl group, t-butyl group, etc.), alkenyl group (eg, vinyl group, etc.), alkoxycarbonyl group (eg, methoxycarbonyl group, ethoxycarbonyl group, etc.), alkoxyl group (eg, methoxy group, ethoxy group, etc.) An aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), an aralkyloxy group (eg, benzyloxy group, Preferred examples of the substituent include a dialkylamino group (eg, diethylamino group, diisopropylamino group, etc.) and a diarylamino group (eg, diphenylamino group, dinaphthylamino group). Examples of the group include a methyl group, a phenyl group, a methoxy group, and a trifluoromethyl group.

  Hereinafter, specific examples of the compound having at least one biaryl partial structure in the molecule and the compound represented by Formula 1 or Formula 2 are shown, but the present invention is not limited thereto.

<< dihedral angle >>
In order to obtain the organic EL device of the present invention having excellent luminous efficiency, in the compound having a biaryl partial structure according to the present invention, the dihedral angle θ of the biaryl partial structure is generally 10 ° to 90 °. In the compound represented by the formula 1, the dihedral angle θ ₁ of Ar ₁ and Ar ₂ constituting the molecular structure of the compound satisfies 10 ° ≦ θ ₁ ≦ 90 °, or is represented by the general formula 2 In the compound, it is necessary that the dihedral angles θ ₂ of Ar ₃ and Ar ₄ constituting the molecular structure of the compound satisfy 10 ° ≦ θ ₂ ≦ 90 °.

Here, the dihedral angles θ, θ ₁ , and θ ₂ are the dihedral angle of the biaryl partial structure in the lowest excited triplet state determined by the ab initio molecular orbital calculation method, and the ab initio molecular orbital calculation, respectively. Represents the dihedral angles of Ar ₁ and Ar ₂ in the lowest excited triplet state obtained by the method, and the dihedral angles of Ar ₃ and Ar _{4 in} the lowest excited triplet state obtained by the ab initio molecular orbital calculation method.

  In the present invention, the ab initio molecular orbital calculation method is a generally known ab initio molecular orbital calculation method including a calculation from a Hartree-Fock approximation called an ab initio method to a calculation called a density functional (DFT) method. is there.

《Ab initio molecular orbital method》
The ab initio molecular orbital method according to the present invention will be described.

  In the present invention, the ab initio molecular orbital calculation method is preferably a calculation based on a density functional method (DFT method). In this case, for example, keywords such as B3LYP and B3PW91 are used. As a basis function for performing the calculation, 3-21G *, 6-31G, 6-31G *, cc-pVDZ, cc-pVTZ, LanL2DZ, LanL2MB, or the like can be used.

  Software used for these ab initio molecular orbital calculation methods includes, for example, Gaussian 98, QChem, Spartan, and the like.

  In the present invention, as the ab initio molecular orbital calculation method, Gaussian 98 (Gaussian 98, Revision A.11.4, MJ. Frisch, et al. Gaussian, Inc., Pittsburgh PA, 2002.).

The dihedral angle θ of the biaryl partial structure of the compound having at least one biaryl partial structure in the lowest excited triplet state (also referred to as T ₁ ) of the compound is measured using the ab initio molecular orbital calculation method described above. Then, the structure of the compound is optimized at T ₁ , and the result is analyzed and examined.

  For example, using Gaussian 98 and using B3LYP / LanL2DZ which is one of the keywords of the density functional theory, the ground state of three compounds of unsubstituted biphenyl, 2-methylbiphenyl and 2,2′-dimethylbiphenyl The dihedral angle θ of the biaryl partial structure is measured at 34 °, 50 °, and 84 °, respectively.

When the dihedral angle θ of the biaryl partial structure at T ₁ was measured for three compounds of unsubstituted biphenyl, 2-methylbiphenyl, and 2,2′-dimethylbiphenyl, they were 0 °, 16 °, and 30 °, respectively. Is calculated.

From these results, it can be seen that unsubstituted biphenyl has a perfect planar structure (θ = 0 °) at T ₁ while its dihedral angle θ is twisted 34 ° in the ground state. I understand.

FIG. 1 shows the distribution of the unpaired electron density of the level having the highest orbital energy level among the occupied orbits of electrons at T ₁ of unsubstituted biphenyl.

  FIG. 1 shows the calculation result of Gaussian 98 using WinMOPAC 3.5 manufactured by Fujitsu Limited. This orbital shows the electron density distribution of the orbital having the highest orbital energy among the occupied orbitals of biphenyl electrons.

From FIG. 1, it can be seen that a has a conjugate broadening in the binding orbital at T ₁ . Introduction of a substituent at the 2- or 6-position of either phenyl group of unsubstituted biphenyl, or introduction of a substituent at the 2- or 6-position of both phenyl groups can break the conjugation spread of a. it can. 2-methyl-biphenyl, 2,2' that cut off the spread of conjugation of a like dimethyl biphenyl the θ dihedral angle biaryl moiety of by T ₁ can be set to 10 ° to 90 °.

A compound in which the dihedral angle θ of the biaryl partial structure at T ₁ is 10 ° to 90 ° has a large minimum excitation triplet energy, so that it can be used as a light emitting material such as a phosphorescent compound contained in a light emitting layer. Efficient energy transfer becomes possible, and the luminous efficiency can be improved.

  The dependence of the dihedral angles on the basis functions (3-21G *, LanL2DZ, 6-31G, 6-31G *, cc-pVDZ) was observed, but the difference was about ± 2 °, and almost no difference was found. You can go.

In the present invention, the dihedral angle θ of the biaryl partial structure at T ₁ of the compound having at least one biaryl partial structure is 10 ° to 90 °, preferably 20 ° to 90 °. Here, the possible value of the dihedral angle θ is theoretically 0 ° or more and less than 360 °. However, for example, a dihedral angle of 120 ° is synonymous with 60 °, 250 ° is synonymous with 70 °, and 300 ° is synonymous with 60 °. The possible value of the plane angle θ is expressed in a range of 0 ° or more and 90 ° or less.

  When the dihedral angle θ is 0 °, the aryl groups have a completely planar structure with each other, and when the dihedral angle is 90 °, the aryl groups have a non-planar structure that is completely conjugated with each other.

When the compound having at least one biaryl partial structure has two or more biaryl partial structures, the dihedral angle θ of the biaryl partial structure at T ₁ is 10 ° to 90 ° for all of these biaryl partial structures. It is necessary to fulfill something.

For example, when the biaryl partial structure is a terphenyl group, the dihedral angle θ of the two biaryl partial structures at T ₁ needs to be 10 ° to 90 °. Also, when the biaryl partial structure is a quarter phenyl group, the dihedral angle θ of each of the three biaryl partial structures at T ₁ needs to be 10 ° to 90 °.

<< Constituent Layer of Organic EL Element >>
The constituent layers of the organic EL device of the present invention will be described.

Preferred specific examples of the layer structure of the organic EL device of the present invention are shown below, but the present invention is not limited thereto.
(I) anode / light emitting layer / electron transport layer / cathode (ii) anode / hole transport layer / light emitting layer / electron transport layer / cathode (iii) anode / hole transport layer / light emitting layer / hole blocking layer / electron Transport layer / cathode (iv) anode / hole transport layer / emission layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) anode / anode buffer layer / hole transport layer / emission layer / hole Blocking layer / Electron transport layer / Cathode buffer layer / Cathode << Anode >>
As the anode in the organic EL element, a metal, an alloy, an electrically conductive compound, or a mixture thereof having a large work function (4 eV or more) as an electrode material is preferably used. Specific examples of such an electrode material include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, a material such as IDIXO (In ₂ O ₃ —ZnO) that can form an amorphous and transparent conductive film may be used. The anode may form a thin film by depositing these electrode materials by a method such as evaporation or sputtering, and form a pattern of a desired shape by a photolithography method, or when the pattern accuracy is not so required (100 μm or more). Degree), a pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. When light is extracted from the anode, the transmittance is desirably greater than 10%, and the sheet resistance of the anode is preferably several hundred Ω / □ or less. Further, the thickness depends on the material, but is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

"cathode"
On the other hand, as a cathode, a metal having a small work function (4 eV or less) (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof are used as an electrode material. Specific examples of such an electrode material include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O) ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among them, from the viewpoint of electron injecting property and durability against oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a large work function, such as a magnesium / silver mixture, magnesium / Aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, lithium / aluminum mixture, aluminum and the like are preferred. The cathode can be manufactured by forming a thin film from these electrode substances by a method such as vapor deposition or sputtering. Further, the sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, it is convenient that one of the anode and the cathode of the organic EL element is transparent or translucent to improve the light emission luminance.

  Further, after the metal is formed in the cathode in a thickness of 1 nm to 20 nm on the cathode, a transparent or translucent cathode can be manufactured by manufacturing the conductive transparent material described in the description of the anode thereon. By applying this, an element in which both the anode and the cathode have transparency can be manufactured.

  Next, an injection layer, a blocking layer, an electron transport layer, and the like used as constituent layers of the organic EL device of the present invention will be described.

<< Injection Layer >>: Electron Injection Layer, Hole Injection Layer The injection layer is provided as necessary, and there are an electron injection layer and a hole injection layer, as described above, between the anode and the light emitting layer or the hole transport layer, and It may be present between the cathode and the light emitting layer or the electron transport layer.

  The injection layer is a layer provided between an electrode and an organic layer for lowering a driving voltage and improving light emission luminance. “The organic EL element and the forefront of its industrialization (published by NTT Corporation on November 30, 1998) )), Vol. 2, Chapter 2, “Electrode Materials” (pages 123 to 166), which includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer).

  The details of the anode buffer layer (hole injection layer) are described in JP-A-9-45479, JP-A-9-260062, and JP-A-8-288069, and specific examples thereof include copper phthalocyanine. Typical examples include a phthalocyanine buffer layer, an oxide buffer layer represented by vanadium oxide, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.

  The details of the cathode buffer layer (electron injection layer) are also described in JP-A-6-325871, JP-A-9-17574, and JP-A-10-74586, and specifically, strontium and aluminum. A buffer layer such as a metal buffer layer, an alkali metal compound buffer layer such as lithium fluoride, an alkaline earth metal compound buffer layer such as magnesium fluoride, and an oxide buffer layer such as aluminum oxide. . The buffer layer (injection layer) is desirably an extremely thin film, and its thickness is preferably in the range of 0.1 nm to 5 μm, depending on the material.

<< blocking layer >>: hole blocking layer, electron blocking layer As described above, the blocking layer is provided as necessary in addition to the basic constituent layers of the organic compound thin film. For example, it is described in JP-A-11-204258 and JP-A-11-204359, and page 237 of "Organic EL Device and Its Industrialization Frontier (NTS, November 30, 1998)". There is a hole blocking (hole block) layer.

  The hole blocking layer is an electron transporting layer in a broad sense, and is made of a material having a function of transporting electrons and having an extremely small ability to transport holes. And the recombination probability of holes can be improved.

  On the other hand, an electron blocking layer is a hole transporting layer in a broad sense, and is made of a material that has a function of transporting holes and has a very small ability to transport electrons, and it blocks electrons while transporting holes. Thus, the recombination probability of electrons and holes can be improved.

  As the hole blocking material, the above-described compound having at least one biaryl partial structure (the dihedral angle θ of the biaryl partial structure at T1 is 10 ° to 90 °) can also be used.

<< Light-emitting layer >>
The light-emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from an electrode or an electron-transport layer and a hole-transport layer, and has a light-emitting partial structure in the light-emitting layer. Alternatively, it may be the interface between the light emitting layer and the adjacent layer.

  The material (light emitting material) used for the light emitting layer is preferably a phosphorescent compound. In the present invention, the phosphorescent compound is a compound that emits light from an excited triplet and emits phosphorescence at room temperature (25 ° C.), and has a phosphorescence quantum yield of 0.2 at 25 ° C. 01 or more compounds. The phosphorescence quantum yield is preferably 0.1 or more.

  The phosphorescence quantum yield can be measured by the method described in Spectroscopy II, 4th Edition, pp. 398 (1992 edition, Maruzen) of Experimental Chemistry Course 7. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescent compound used in the present invention only needs to achieve the above-mentioned phosphorescence quantum yield in any of the solvents.

  Emission of a phosphorescent compound can be categorized into two types in principle. One is the recombination of carriers on the host compound where the carriers are transported, and the excited state of the host compound is generated. An energy transfer type in which light is emitted from a phosphorescent compound by transferring it to a compound.The other is that the phosphorescent compound becomes a carrier trap, and recombination of carriers occurs on the phosphorescent compound, causing the phosphorescent compound to emit light. Is obtained, in which case the energy of the excited state of the phosphorescent compound is lower than the energy of the excited state of the host compound.

  The phosphorescent compound can be appropriately selected from known compounds used for the light emitting layer of the organic EL device.

  The phosphorescent compound used in the present invention is preferably a complex compound containing a metal belonging to Group 8 of the periodic table of the elements, and more preferably an iridium compound, an osmium compound, a rhodium compound, or a platinum compound ( Platinum complex-based compounds) and rare earth complexes, of which iridium compounds are the most preferable.

  Hereinafter, specific examples of the phosphorescent compound used in the present invention are shown, but the invention is not limited thereto. These compounds are described, for example, in Inorg. Chem. 40, 1704-1711.

  In the present invention, the maximum phosphorescent emission wavelength of the phosphorescent compound is not particularly limited, and in principle, it can be obtained by selecting a central metal, a ligand, a substituent of a ligand, and the like. Although the emission wavelength of the phosphorescent compound can be changed, the phosphorescence emission wavelength of the phosphorescent compound preferably has a maximum wavelength of phosphorescence at 380 to 480 nm. With such an organic EL element emitting blue phosphorescent light or an organic EL element emitting white phosphorescent light, the luminous efficiency can be further improved.

  Further, the light emitting layer may contain a host compound in addition to the phosphorescent compound.

  In the present invention, the host compound is a compound having a phosphorescence quantum yield of phosphorescence at room temperature (25 ° C.) of less than 0.01 among the compounds contained in the light emitting layer.

  The host compound preferably has an excited triplet energy of the host compound larger than that of the phosphorescent compound. That is, by making the excited triplet energy of the host compound larger than the excited triplet energy of the phosphorescent compound, phosphorescence emission of energy transfer type from the host compound to the phosphorescent compound is possible.

  The host compound is preferably an organic compound or a complex. In the present invention, the above-mentioned compound having at least one biaryl partial structure (the dihedral angle θ of the biaryl partial structure at T1 is 10 ° to 90 °) Is preferably used as a host compound. Since these compounds have high excited triplet energy, they have high excited triplet like host compounds used in blue phosphorescent organic EL devices or white phosphorescent organic EL devices including blue. It is also very effective as a host compound requiring energy.

  Further, a plurality of host compounds and phosphorescent compounds may be used. By using a plurality of types of host compounds, it is possible to adjust the transfer of electric charges, and to increase the efficiency of the organic EL device. In addition, by using a plurality of kinds of phosphorescent compounds, different luminescence can be mixed, and thus, an arbitrary luminescent color can be obtained. By adjusting the type and the doping amount of the phosphorescent compound, white light emission is possible, and application to illumination and backlight is also possible.

  In addition, the light emitting layer may further contain a host compound having a maximum fluorescence wavelength as the host compound. In this case, by the energy transfer from the other host compound and the phosphorescent compound to the fluorescent compound, the electroluminescence as the organic EL device can also obtain the light emission from the other host compound having the maximum fluorescence wavelength. Preferred as the host compound having the fluorescence maximum wavelength is one having a high fluorescence quantum yield in a solution state. Here, the fluorescence quantum yield is preferably 10% or more, particularly preferably 30% or more. Specific examples of host compounds having a fluorescence maximum wavelength include coumarin-based dyes, pyran-based dyes, cyanine-based dyes, croconium-based dyes, squarium-based dyes, oxobenzanthracene-based dyes, fluorescein-based dyes, rhodamine-based dyes, and pyrylium-based dyes And perylene dyes, stilbene dyes, and polythiophene dyes. The fluorescence quantum yield can be measured by the method described in Spectroscopy II, p. 362 (1992 edition, Maruzen) of the 4th edition of Experimental Chemistry Course 7.

  The color of light emitted in this specification is measured by a spectral radiance meter CS-1000 (manufactured by Minolta) in FIG. 4.16 on page 108 of “New Color Science Handbook” (edited by The Japan Society of Color Science, University of Tokyo Press, 1985). It is determined by the color when the measured result is applied to the CIE chromaticity coordinates.

  The light-emitting layer can be formed by forming the above compound by a known thinning method such as a vacuum evaporation method, a spin coating method, a casting method, an LB method, and an ink-jet method. The thickness of the light emitting layer is not particularly limited, but is usually selected in the range of 5 nm to 5 μm, preferably 5 to 200 nm. The light-emitting layer may have a single-layer structure composed of one or more of these phosphorescent compounds or host compounds, or a laminated structure composed of a plurality of layers having the same composition or different compositions. Good.

《Hole transport layer》
The hole transport layer is made of a hole transport material having a function of transporting holes. In a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.

  The hole transport material has any of hole injection or transport and electron barrier properties, and may be any of an organic substance and an inorganic substance. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styryl anthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbenes Derivatives, silazane derivatives, aniline-based copolymers, conductive polymer oligomers, especially thiophene oligomers, and the like can be given.

  Further, as the hole transporting material, it is also preferable to use the above-described compound having at least one biaryl partial structure (the dihedral angle θ of the biaryl partial structure at T1 is 10 ° to 90 °) as the host compound. Thereby, the luminous efficiency can be further improved.

  As the hole transporting material, those described above can be used, but it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound.

  Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ', N'-tetraphenyl-4,4'-diaminophenyl; N, N'-diphenyl-N, N'- Bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ', N'-tetra-p-tolyl-4,4'-diaminobiphenyl; 1,1-bis (4-di-p-tolyl Aminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' − (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl; N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbenzene; N-phenylcarbazole, and two of those described in U.S. Pat. No. 5,061,569. Having a condensed aromatic ring in the molecule thereof, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-308 No. 88, 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine (MTDATA) in which three triphenylamine units are linked in a starburst type. ) And the like.

  Further, a polymer material in which these materials are introduced into a polymer chain, or a polymer material in which these materials are used as a polymer main chain can be used. Further, inorganic compounds such as p-type Si and p-type SiC can also be used as the hole injection material and the hole transport material.

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

《Electron transport layer》
The electron transport layer is made of a material having a function of transporting electrons. In a broad sense, the electron transport layer includes an electron injection layer and a hole blocking layer. The electron transport layer can be provided as a single layer or a plurality of layers.

  Conventionally, the following materials are used as an electron transporting material (also serving as a hole blocking material) used for a single layer of an electron transporting layer and an electron transporting layer adjacent to the light emitting layer on the cathode side with respect to the light emitting layer. Are known.

  Further, the electron transporting layer only needs to have a function of transmitting electrons injected from the cathode to the light emitting layer, and as the material thereof, any one of conventionally known compounds can be selected and used. .

  Examples of materials used for the electron transport layer (hereinafter, referred to as electron transport materials) include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethanes, and anthrones. Derivatives, oxadiazole derivatives and the like. Further, in the oxadiazole derivative, a thiadiazole derivative in which an oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as the electron transport material.

  Further, a polymer material in which these materials are introduced into a polymer chain, or a polymer material in which these materials are used as a polymer main chain, can also be used.

  Further, a metal complex of an 8-quinolinol derivative, such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum, Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Cu , Ca, Sn, Ga or Pb can also be used as the electron transport material. In addition, metal-free or metal phthalocyanine, or those whose terminals are substituted with an alkyl group, a sulfonic acid group, or the like can be preferably used as the electron transporting material. Further, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can be used as the electron transporting material, and similarly to the hole injection layer and the hole transport layer, inorganic materials such as n-type Si and n-type SiC can be used. Semiconductors can also be used as electron transport materials.

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

<< Substrate (also referred to as substrate, substrate, support, etc.) >>
The organic EL device of the present invention is preferably formed on a substrate.

  The substrate of the organic EL device of the present invention is not particularly limited in the type of glass, plastic, and the like, and is not particularly limited as long as it is transparent. A light-transmitting resin film can be used. A particularly preferred substrate is a resin film that can provide flexibility to the organic EL element.

  Examples of the resin film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), polyether imide, polyether ether ketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose triacetate. (TAC), cellulose acetate propionate (CAP) and the like. In addition, an inorganic or organic coating or a hybrid coating of both may be formed on the surface of the resin film.

  The external extraction efficiency at room temperature of light emission of the organic electroluminescence device of the present invention is preferably 1% or more, more preferably 5% or more. Here, the external extraction quantum efficiency (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons flowing to the organic EL element × 100.

  Further, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter for converting the emission color of the organic EL element into multiple colors using a phosphor may be used in combination. When a color conversion filter is used, λmax of light emission of the organic EL element is preferably 480 nm or less.

<< Method of manufacturing organic EL element >>
As an example of a method for producing an organic EL device of the present invention, a method for producing an organic EL device comprising an anode / a hole injection layer / a hole transport layer / a light emitting layer / an electron transport layer / an electron injection layer / a cathode will be described.

  First, a thin film made of a desired electrode material, for example, a material for an anode is formed on an appropriate substrate by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably 10 to 200 nm, thereby producing an anode. I do. Next, organic compound thin films of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a hole blocking layer, which are organic EL element materials, are formed thereon.

As a method for thinning the organic compound thin film, there are a vapor deposition method and a wet process (spin coating method, casting method, ink jet method, printing method) as described above, but a uniform film is easily obtained and a pinhole is formed. In particular, a vacuum evaporation method, a spin coating method, an ink jet method, and a printing method are particularly preferable from the viewpoint that hardly occurs. Further, a different film forming method may be applied to each layer. When employing the vapor deposition film, the deposition conditions may vary due to kinds of materials used, generally boat temperature 50 ° C. to 450 ° C., vacuum of 10 ^-6 Pa to 10 ^-2 Pa, deposition rate 0 0.01 nm / sec to 50 nm / sec, substrate temperature −50 ° C. to 300 ° C., film thickness 0.1 nm to 5 μm, preferably 5 nm to 200 nm.

  After these layers are formed, a thin film made of a material for a cathode is formed thereon by a method such as evaporation or sputtering so as to have a thickness of 1 μm or less, preferably in a range of 50 nm to 200 nm, and a cathode is provided. As a result, a desired organic EL device is obtained. In the production of this organic EL element, it is preferable to produce from the hole injection layer to the cathode consistently by one evacuation, but it is also possible to take it out in the middle and apply a different film forming method. At that time, it is necessary to consider that the operation is performed in a dry inert gas atmosphere.

  The multi-color display device of the present invention is provided with a shadow mask only when the light emitting layer is formed, and since the other layers are common, patterning such as a shadow mask is unnecessary. The film can be formed by a method, a printing method, or the like.

  When patterning is performed only on the light emitting layer, the method is not particularly limited, but is preferably an evaporation method, an inkjet method, or a printing method. When using an evaporation method, patterning using a shadow mask is preferable.

  In addition, it is also possible to reverse the manufacturing order and manufacture the cathode, the electron injection layer, the electron transport layer, the light emitting layer, the hole transport layer, the hole injection layer, and the anode in this order. When a DC voltage is applied to the multi-color display device thus obtained, light emission can be observed by applying a voltage of about 2 V to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Alternatively, an AC voltage may be applied. The waveform of the applied AC may be arbitrary.

  The multicolor display device of the present invention can be used as a display device, a display, and various light emission light sources. In a display device and a display, full-color display can be performed by using three types of organic EL elements emitting blue, red, and green light.

  Examples of the display device and display include a television, a personal computer, a mobile device, an AV device, a teletext display, and information display in a car. In particular, it may be used as a display device for reproducing a still image or a moving image, and when used as a display device for reproducing a moving image, the driving method may be either a simple matrix (passive matrix) method or an active matrix method.

  Lighting sources include home lighting, interior lighting, backlights for watches and LCDs, signboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copiers, light sources for optical communication processors, and light sources for optical sensors. But not limited thereto.

  Further, the organic EL device according to the present invention may be used as an organic EL device having a resonator structure. The intended use of the organic EL device having such a resonator structure is, for example, a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processor, a light source of an optical sensor, and the like. Not limited. In addition, laser oscillation may be used for the above purpose.

《Display device》
The organic EL element of the present invention may be used as a kind of lamp such as an illumination light source or an exposure light source, a projection device for projecting an image, or a display for directly viewing a still image or a moving image. It may be used as a device (display). When used as a display device for reproducing moving images, the driving method may be either a simple matrix (passive matrix) method or an active matrix method. Alternatively, a full-color display device can be manufactured by using three or more kinds of the organic EL elements of the present invention having different emission colors. Alternatively, it is also possible to convert one luminescent color, for example, white luminescence, to BGR by using a color filter to achieve full color. Further, it is possible to convert the luminescent color of the organic EL to another color by using a color conversion filter to obtain a full color. In this case, the λmax of the organic EL luminescence is preferably 480 nm or less.

  Hereinafter, an example of a display device having the organic EL element of the present invention will be described with reference to the drawings.

  FIG. 2 is a schematic diagram illustrating an example of a display device including an organic EL element. FIG. 3 is a schematic diagram of a display such as a mobile phone for displaying image information by light emission of an organic EL element.

  The display 1 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, and the like.

  The control unit B is electrically connected to the display unit A, sends a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside, and the pixels for each scanning line are converted into an image data signal by the scanning signal. In response, the light is sequentially emitted, the image is scanned, and the image information is displayed on the display unit A.

  FIG. 3 is a schematic diagram of the display unit A.

  The display section A has a wiring section including a plurality of scanning lines 5 and data lines 6 and a plurality of pixels 3 on a substrate. The main members of the display unit A will be described below. FIG. 3 shows a case where the light emitted from the pixel 3 is extracted in the white arrow direction (downward).

  The scanning lines 5 and the plurality of data lines 6 of the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a grid pattern and are connected to the pixels 3 at orthogonal positions (for details, FIG. Not shown).

  When a scanning signal is applied from the scanning line 5, the pixel 3 receives an image data signal from the data line 6 and emits light according to the received image data. By appropriately arranging pixels in a red region, pixels in a green region, and pixels in a blue region on the same substrate, full-color display becomes possible.

  Next, a light emitting process of the pixel will be described.

  FIG. 4 is a schematic diagram of a pixel.

  Each pixel includes an organic EL element 10, a switching transistor 11, a driving transistor 12, a capacitor 13, and the like. A full-color display can be performed by using red, green, and blue light-emitting organic EL elements as the organic EL elements 10 in a plurality of pixels and juxtaposing them on the same substrate.

  In FIG. 4, an image data signal is applied from the control unit B to the drain of the switching transistor 11 via the data line 6. When a scanning signal is applied to the gate of the switching transistor 11 from the control unit B via the scanning line 5, the driving of the switching transistor 11 is turned on, and the image data signal applied to the drain is transferred to the capacitor 13 and the driving transistor 12. Transmitted to the gate.

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

  When the scanning signal is transferred to the next scanning line 5 by the sequential scanning of the control unit B, the driving of the switching transistor 11 is turned off. However, even when the driving of the switching transistor 11 is turned off, the capacitor 13 holds the potential of the charged image data signal, so that the driving of the driving transistor 12 is kept on and the next scanning signal is applied. The light emission of the organic EL element 10 continues until this. When the next scanning signal is applied by the sequential scanning, the driving transistor 12 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 10 emits light.

  That is, the organic EL element 10 emits light by providing a switching transistor 11 and a driving transistor 12 as active elements to the organic EL elements 10 of each of the plurality of pixels, and emitting light of the organic EL elements 10 of each of the plurality of pixels 3. It is carried out. Such a light emitting method is called an active matrix method.

  Here, the light emission of the organic EL element 10 may be light emission of a plurality of gradations based on a multi-valued image data signal having a plurality of gradation potentials, or ON / OFF of a predetermined light emission amount based on a binary image data signal. May be.

  Further, the holding of the potential of the capacitor 13 may be continued until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.

  The present invention is not limited to the active matrix method described above, but may be a passive matrix light emission drive in which the organic EL element emits light in accordance with a data signal only when a scanning signal is scanned.

  FIG. 5 is a schematic diagram of a display device using a passive matrix method. In FIG. 5, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a lattice shape facing each other with the pixel 3 interposed therebetween.

  When the scanning signal of the scanning line 5 is applied by the sequential scanning, the pixels 3 connected to the applied scanning line 5 emit light according to the image data signal. In the passive matrix system, the pixel 3 has no active element, and the manufacturing cost can be reduced.

  Hereinafter, the present invention will be described with reference to examples, but embodiments of the present invention are not limited thereto.

Example 1
<Measurement of dihedral angle θ of compound>
Using Gaussian98, software of ab initio molecular orbital calculation method manufactured by Gaussian Co., USA, CBP, compound 2-1 and tris (biphenyl) using B3LYP / LanL2DZ which is one of the keywords of density functional theory ) Dihedral angles θ (θ1 to θ16) of the biaryl partial structure of the amine, compound 1-24, compound 2-7, and compound 2-13 in the lowest excited triplet state were calculated.

  The dihedral angle of the biaryl partial structure in the ground state of CBP and compound 2-1 was measured in the same manner. As for CBP, θ1 = 53 °, θ2 = 33 °, θ3 = 53 °, and compound 2 For -1, θ4 = 54 °, θ5 = 84 °, and θ6 = 54 °.

  Further, the 0-0 band of the phosphorescence spectrum of these compounds was measured, and the lowest excited triplet energy was calculated.

  The 0-0 band of the phosphorescence spectrum can be determined by the following measurement method.

<< Method of measuring 0-0 band of phosphorescence spectrum >>
The compound to be measured is dissolved in a well-deoxygenated mixed solvent of ethanol / methanol = 4/1 (vol / vol), placed in a cell for phosphorescence measurement, and then irradiated with excitation light at a liquid nitrogen temperature of 77 K. The emission spectrum at 100 ms after irradiation is measured. Since the phosphorescent light has a longer emission lifetime than the fluorescence, the light remaining after 100 ms can be considered to be almost phosphorescent light. The measurement may be performed with a shorter delay time for a compound having a phosphorescence life shorter than 100 ms. However, if the delay time is so shortened that it cannot be distinguished from fluorescence, phosphorescence and fluorescence cannot be separated. Since it causes a problem, it is necessary to select a delay time capable of separating the delay time.

  For a compound that cannot be dissolved in the above-mentioned solvent system, any solvent that can dissolve the compound may be used (substantially, there is no problem because the solvent effect of the phosphorescence wavelength is very small in the above-mentioned measurement method).

  Next, regarding the method of obtaining the 0-0 band, in the present invention, the 0-0 band is defined as the emission maximum wavelength that appears on the shortest wavelength side in the phosphorescence spectrum chart obtained by the above measurement method.

  Since the intensity of a phosphorescent spectrum is usually low, it is sometimes difficult to distinguish between a noise and a peak when the spectrum is enlarged. In such a case, the emission spectrum during excitation light irradiation (this is referred to as a stationary light spectrum for convenience) is enlarged, and the emission spectrum 100 ms after excitation light irradiation (this is referred to as a phosphorescence spectrum for convenience) is superimposed. It is determined by reading the peak wavelength of the phosphorescence spectrum from the partial structure of the stationary light spectrum derived from the light spectrum. Further, by performing a smoothing process on the phosphorescent spectrum, noise and a peak are separated, and a peak wavelength is read. In addition, as the smoothing processing, a Savitzky & Golay smoothing method or the like is applied.

  Table 1 shows the results.

  From the results in Table 1, it can be seen that when the dihedral angle θ (θ1 to θ16) of the biaryl partial structure in the lowest excited triplet state is 10 ° or more, the lowest excited triplet energy is large.

  A host compound, a hole transporting material, and a hole blocking material used in an organic EL device emitting blue phosphorescent light or an organic EL device emitting white phosphorescent light including blue light emission have a high excited triplet energy of 2.8 eV or more. Since 8 eV or more is required, these compounds are used as a host compound, a hole transport material, and a hole blocking material used in a blue phosphorescent organic EL device or a white phosphorescent organic EL device including blue light emission. It was found to be useful as a material.

Example 2
<Preparation of Organic EL Elements 1-1 to 1-9>
A 100 mm × 100 mm × 1.1 mm glass substrate as an anode is patterned on a substrate (NA45, manufactured by NH Techno Glass Co., Ltd.) on which 100 nm of ITO (indium tin oxide) is formed, and then a transparent support provided with this ITO transparent electrode is provided. The substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and washed with UV ozone for 5 minutes. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum evaporation apparatus, while 200 mg of α-NPD was placed in a molybdenum resistance heating boat, 200 mg of CBP was placed in another molybdenum resistance heating boat, and another molybdenum resistance heating boat was placed. 200 mg of bathocuproin (BCP) was placed in a heating boat, 100 mg of Ir-1 was placed in another molybdenum resistance heating boat, and 200 mg of Alq ₃ was further placed in another molybdenum resistance heating boat, and attached to a vacuum evaporation apparatus.

Then, after the pressure in the vacuum chamber was reduced to 4 × 10 ⁻⁴ Pa, the heating boat containing α-NPD was energized and heated, and was vapor-deposited on a transparent support substrate at a vapor deposition rate of 0.1 nm / sec. Was provided. Further, the heating boat containing the CBP and the phosphorescent compound Ir-1 was energized and heated, and was co-evaporated on the hole transport layer at an evaporation rate of 0.2 nm / sec and 0.012 nm / sec, respectively. A light emitting layer was provided. In addition, the substrate temperature at the time of vapor deposition was room temperature. Further, an electric current is applied to the heating boat containing the BCP, and the heating boat is heated to be deposited on the light emitting layer at a deposition rate of 0.1 nm / sec to provide a 10 nm-thick electron transport layer also serving as a hole blocking layer. Was. On top of that, the heating boat containing Alq ₃ was further energized and heated, and was vapor-deposited on the electron transport layer at a vapor deposition rate of 0.1 nm / sec to further provide an electron injection layer having a thickness of 40 nm. . In addition, the substrate temperature at the time of vapor deposition was room temperature.

  Subsequently, 0.5 nm of lithium fluoride and 110 nm of aluminum were vapor-deposited to form a cathode, thereby producing an organic EL device 1-1. Further, the organic EL elements 1-2 to 1-9 were similar to the organic EL element 1-1 except that the compounds of the light emitting layer and the hole transport layer of the organic EL element 1-1 were changed to the compounds shown in Table 2. Was prepared. The structure of the compound used above is shown below.

<Evaluation of organic EL elements 1-1 to 1-9>
The following luminous efficiencies of the organic EL devices 1-1 to 1-9 produced as described above were evaluated. Table 2 shows the results.

(External quantum efficiency)
With respect to the produced organic EL device, the external extraction quantum efficiency (%) was measured when a constant current of ^2.5 mA / cm ² was applied at 23 ° C. in a dry nitrogen gas atmosphere. The measurement results of the external extraction quantum efficiency are expressed as relative values when the measured value of the organic EL element 1-1 is set to 100 for the organic EL elements 1-1 to 1-4. -9 was represented by a relative value when the organic EL element 1-5 was taken as 100.

  From Table 2, it was found that the organic EL device of the present invention had extremely high luminous efficiency. In particular, a remarkable effect was obtained in the blue phosphorescent device.

  Similar results were obtained by using compound 3-4 or compound 3-5 for the hole blocking layer of an organic EL device having a hole blocking layer.

Example 3
The green and blue light-emitting organic EL devices of the present invention prepared in the above-described examples and the red light-emitting organic EL device prepared in the same manner except that the phosphorescent compound of the green light-emitting organic EL device of the present invention was replaced with Ir-9. Were arranged side by side on the same substrate to produce an active matrix type full-color display device shown in FIG. FIG. 3 shows only a schematic diagram of the display section A of the manufactured full-color display device. That is, on the same substrate, a wiring portion including a plurality of scanning lines 5 and data lines 6 and a plurality of pixels 3 (pixels in a red region, pixels in a green region, pixels in a blue region, and the like) are arranged side by side. The scanning lines 5 and the plurality of data lines 6 of the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a grid and are connected to the pixels 3 at orthogonal positions (details). Is not shown). The plurality of pixels 3 are driven by an active matrix method provided with an organic EL element corresponding to each emission color, and a switching transistor and a driving transistor, which are active elements, and a scanning signal is applied from a scanning line 5. Then, an image data signal is received from the data line 6 and light is emitted according to the received image data. By appropriately arranging the red, green, and blue pixels in this manner, full-color display can be achieved.

  By driving the full-color display device, a clear full-color moving image display with high luminance and good durability was obtained.

FIG. 3 is a diagram showing the distribution of unpaired electron density in the lowest excited triplet state of unsubstituted biphenyl. FIG. 2 is a schematic diagram illustrating an example of a display device including an organic EL element. It is a schematic diagram of a display part. It is a schematic diagram of a pixel. It is a schematic diagram of a passive matrix type full color display device.

Explanation of reference numerals

Reference Signs List 1 display 3 pixel 5 scanning line 6 data line 7 power supply line 10 organic EL element 11 switching transistor 12 drive transistor 13 capacitor A display unit B control unit

Claims (12)

In an organic electroluminescence device having an organic layer including at least a light emitting layer,
At least one of the organic layers contains a compound having at least one biaryl partial structure, and the compound has a dihedral angle of the biaryl partial structure in the lowest excited triplet state determined by ab initio molecular orbital calculation. The organic electroluminescence device wherein θ is 10 ° to 90 °. The organic electroluminescent device according to claim 1, wherein the compound is contained in the light emitting layer. 3. The organic electroluminescent device according to claim 1, wherein the biaryl partial structure is a partial structure having a biphenyl ring or a partial structure having a ring formed by directly bonding a phenyl group and a carbazolyl group. . The compound has at least one group selected from the group consisting of a carbazolyl group, a triazolyl group, a pyrrolyl group, a diarylamino group, an oxadiazolyl group, a dibenzofuranyl group, a dibenzothienyl group, and an indolyl group. Item 4. The organic electroluminescent device according to any one of items 1 to 3. In an organic electroluminescence device having an organic layer including at least a light emitting layer,
An organic electroluminescent device, wherein at least one of the organic layers contains a compound represented by the following general formula 1.

[In the formula, Ar ₁ and Ar ₂ represent an arylene group or a heteroarylene group, and Z ₁ and Z ₂ each independently represent a diarylamino group or an aromatic heterocyclic group. θ ₁ is the dihedral angle of Ar ₁ and Ar _{2 in} the lowest excited triplet state obtained by the ab initio molecular orbital calculation method and satisfies 10 ° ≦ θ ₁ ≦ 90 °. ] The heteroarylene group is a divalent group derived from a group consisting of a carbazole ring, a triazole ring, a pyrrole ring, an oxadiazole ring, a dibenzofuran ring, a dibenzothiophene ring, and an indole ring, and the aromatic heterocyclic group is 6. The organic material according to claim 5, wherein the carbazolyl group, triazolyl group, pyrrolyl group, oxadiazolyl group, dibenzofuranyl group, dibenzothienyl group, and indolyl group. Electroluminescent element. In an organic electroluminescence device having an organic layer including at least a light emitting layer,
An organic electroluminescent device, wherein at least one of the organic layers contains a compound represented by the following general formula 2.

[Wherein, Ar ₃ , Ar ₄ , and Ar ₅ represent an arylene group or a heteroarylene group, and Z ₃ and Z ₄ each independently represent a diarylamino group or an aromatic heterocyclic group. θ ₂ is the dihedral angle of Ar ₃ and Ar _{4 in} the lowest excited triplet state obtained by the ab initio molecular orbital calculation method and satisfies 10 ° ≦ θ ₂ ≦ 90 °. θ ₃ is the dihedral angle of Ar ₃ and Ar _{4 in} the lowest excited triplet state obtained by the ab initio molecular orbital calculation method and satisfies 10 ° ≦ θ ₃ ≦ 90 °. ] The heteroarylene group is a divalent group derived from a group consisting of a carbazole ring, a triazole ring, a pyrrole ring, an oxadiazole ring, a dibenzofuran ring, a dibenzothiophene ring, and an indole ring, and the aromatic heterocyclic group is The organic compound according to claim 7, wherein the organic compound is any one selected from the group consisting of carbazolyl group, triazolyl group, pyrrolyl group, oxadiazolyl group, dibenzofuranyl group, dibenzothienyl group, and indolyl group. Electroluminescent element. The organic electroluminescent device according to any one of claims 1 to 8, wherein the light emitting layer contains a phosphorescent compound selected from osmium, iridium, rhodium, and a platinum complex compound. A display device comprising the organic electroluminescence element according to claim 1. A lighting device comprising the organic electroluminescent element according to claim 1. A display device, comprising: the lighting device according to claim 11; and a liquid crystal element as a display unit.

Images