JP2006128715A - Organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long-life and high-efficiency organic electroluminescent element (an orgnic EL element) which has little change in a color of emitted light even in a long-time drive. <P>SOLUTION: The organic EL element is provided with an organic compound case at least having a recombination area where a hole and an electron are recombined and a lumious area emitting light in response to the recombination, and a pair of electrodes pinching the organic compound layer. The organic EL element contains at least a kind selected from a nitrogen-containing compound of a specified structure by a ratio of 0.1 to 8 weight percent as a fluorescent dopant at least in either the recombination area or the luminous area. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic electroluminescence (hereinafter abbreviated as EL) element, and more particularly to an organic EL element having a long life and high efficiency such as little change in emission color even when driven for a long time. It is.

EL elements using electroluminescence are highly visible due to self-emission and are completely solid elements, so they have features such as excellent impact resistance, so they are attracting attention as light emitting elements in various display devices. Has been.
In this EL element, there are an inorganic EL element using an inorganic compound as a light emitting material and an organic EL element using an organic compound. Among these, the organic EL element can greatly reduce the applied voltage. As a next-generation display element, research into practical use has been actively conducted.

By the way, in this organic EL device, in order to develop a long-life and high-efficiency blue light-emitting device, research on blue light-emitting materials has been focused on various blue light-emitting materials such as high luminance and high efficiency. Distyrylarylene-based blue light-emitting materials (Patent Document 1), high-brightness chelate-based blue light-emitting materials (Patent Document 2), and high-brightness diamine-based blue light-emitting materials (Patent Document 3) are disclosed. However, these blue light-emitting materials are usually used in the configuration of anode / hole injection / transport layer / light-emitting layer / electron injection / transport layer / cathode and have been demonstrated in performance, but they are always satisfactory in terms of lifetime. Rather, for example, (1) as the driving time elapses, the color changes to green and the emission color changes. (2) The half-life at an initial luminance of 100 cd / m ² is as short as about 1000 hours (practically several). There are problems such as that more than 1000 hours are required).

On the other hand, an element using a compound having a structure similar to the fluorescent dopant in the present invention as a material of the light emitting layer has been proposed (Patent Document 4), but no mention is made of the function of the fluorescent dopant added in a trace amount. Absent.
Patent Documents 5 and 6 disclose a distyrylarylene-based material that is a charge injection auxiliary agent added to the light emitting layer. Although this material also functions as a fluorescent dopant, the half-life of an element using this material is as short as about 1000 hours (initial luminance 100 cd / m ² ), and improvement has been demanded.
JP-A-2-247278 JP-A-5-198378 JP-A-6-220437 JP-A-6-220437 JP-A-6-9953 International Publication No. 94-6157

  The present invention provides a long-life and high-efficiency organic EL element that improves such drawbacks of the conventional organic EL element and has a small change in emission color even when driven for a long time. It is intended.

As a result of intensive studies to develop a long-life and high-efficiency organic EL device, the present inventors, as a fluorescent dopant, in at least one of a bonding region or a light-emitting region of holes and electrons of the device, It has been found that the purpose can be achieved by containing a specific compound in a predetermined ratio. The present invention has been completed based on such findings.
That is, the present invention includes an organic compound layer having at least a recombination region in which holes and electrons recombine, a light emitting region that emits light in response to the recombination, and a pair of electrodes that hold the organic compound layer. In the organic electroluminescence device provided, in the recombination region and / or the light emitting region, a general formula (I)

[In the formula, Ar ¹ , Ar ² and Ar ³ each represent an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 30 carbon atoms or a heterocyclic group, which may be the same or different. At least one of them is a condensed polycyclic hydrocarbon group having 12 or more carbon atoms. ]
And general formula (II)

[In the formula, Ar ⁴ , Ar ⁵ , Ar ⁶ and Ar ⁷ each represent an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 30 carbon atoms or a heterocyclic group, and they are the same or different. Ar ⁸ represents an arylene group having 6 to 30 carbon atoms or a divalent heterocyclic group, and at least one of Ar ^{4 to} Ar ⁸ is a condensed polycyclic hydrocarbon group having 12 or more carbon atoms. . ]
An organic EL device characterized in that at least one selected from the compounds represented by the formula (1) is contained in a proportion of 0.1 to 8% by weight.

  The organic EL device of the present invention contains a fluorescent dopant having a specific structure in at least one of a recombination region where holes and electrons recombine or a light emitting region which emits light in response to the recombination. However, even if it is driven for a long time, it has a long life, such as little change in emission color, and has a high light emission efficiency, and is suitably used for, for example, displays of information industry equipment.

The fluorescent dopant used in the present invention has the general formula (I)

Or general formula (II)

It is a compound which has a structure represented by these.
In the said general formula (I) and (II), Ar < ¹ > -Ar < ⁷ > shows a C1-C10 alkyl group, a C6-C30 aryl group, or a heterocyclic group, respectively. Here, examples of the alkyl group having 1 to 10 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group and the like. Examples of the aryl group having 6 to 30 carbon atoms include non-condensed hydrocarbon groups such as phenyl group, biphenyl group, and terphenyl group, and condensed polycyclic hydrocarbon groups. The condensed polycyclic hydrocarbon group preferably has 18 or less carbon atoms forming a ring, for example, a pentarenyl group, an indenyl group, a naphthyl group, an azulenyl group, a heptaenyl group, a biphenylenyl group, an as-indacenyl group, a fluorenyl group. , S-indacenyl group, acenaphthylenyl group, preadenyl group, acenaphthenyl group, phenalenyl group, phenanthryl group, anthryl group, fluoranthenyl group, acephenanthrenyl group, aceantrirenyl group, triphenylenyl group, pyrenyl group, chrysenyl group , Naphthacenyl group and the like.

  Examples of the heterocyclic group include pyridyl group, pyrimidyl group, pyrazinyl group, triazinyl group, furanyl group, pyrrolyl group, thiophenyl group, quinolyl group, coumarinyl group, benzofuranyl group, benzimidazolyl group, and benzoxazolyl group. , Dibenzofuranyl, benzothiophenyl, dibenzothiophenyl, indolyl, carbazolyl, pyrazolyl, imidazolyl, oxazolyl, isoxazolyl, thiazolyl, indazolyl, benzothiazolyl, pyridazinyl, cinnolyl, quinazolyl Group, quinoxalyl group, phthalazinyl group, phthalazine dionyl group, phthalamidyl group, chromonyl group, naphtholactamyl group, quinolonyl group, o-sulfobenzoic acid imidyl group, maleic acid imidyl group, naphthalidinyl group, benz Midazolonyl, benzoxazolonyl, benzothiazolonyl, benzothiazothionyl, quinazolonyl, quinoxalonyl, phthalazonyl, dioxopyrimidinyl, pyridonyl, isoquinolinyl, isoquinolinyl, isothiazolyl, benzisoxa Examples include zolyl group, benzisothiazolyl group, indazironyl group, acridinyl group, acridonyl group, quinazoline dionyl group, quinoxaline dionyl group, benzoxazine dionyl group, benzoxazinonyl group, naphthalimidyl group and the like.

On the other hand, Ar ⁸ represents an arylene group having 6 to 30 carbon atoms or a divalent heterocyclic group. Here, as the arylene group having 6 to 30 carbon atoms or the divalent heterocyclic group, for example, a divalent group in which one hydrogen atom is removed from the aryl group or heterocyclic exemplified in the description of Ar ^{1 to} Ar ^7. Can be mentioned. Other arylene groups include diarylene alkane groups such as diphenylenepropane group and diphenylenemethane group, diarylene alkane groups such as diphenylenecyclohexane group and diphenylenecyclopentane group, and diarylene ethers such as diphenylene ether group. Groups, diarylene thioether groups such as diphenylene thioether groups, N-aryl diarylene amine groups such as N-phenyl diphenylene amine groups, N-naphthyl dinaphthylene amine groups, N-phenyl carbazolylene groups, and further diphenyl thiophene A diarylthiophene or diarylbithiophene group such as a divalent group of diphenylbithiophene can also be preferably mentioned.
Ar ¹ , Ar ² and Ar ³ may be the same or different, but at least one of them is required to be a condensed polycyclic hydrocarbon group having 12 or more carbon atoms. Ar ⁴ , Ar ⁵ , Ar ⁶ and Ar ⁷ may be the same or different, but at least one of Ar ^{4 to} Ar ⁸ must be a condensed polycyclic hydrocarbon group having 12 or more carbon atoms. It is.

Further, Ar ^{1 to} Ar ⁸ may be introduced with an appropriate substituent. Examples of the substituent include (1) halogen atom (F, Cl, Br, I), cyano group, nitro group, ( 2) an alkyl group, (3) an alkoxy group, (4) an aryloxy group, (5) an alkyl or aryl mercapto group, (6) -NR ¹ R ² (R ¹ and R ² are a hydrogen atom, an alkyl group or an aryl, respectively) A substituted or unsubstituted amino group represented by (7) an alkylenedioxy group, an alkylenedithio group, and the like. Here, the alkyl group of (2) is preferably a linear or branched group having 1 to 20 carbon atoms, particularly 1 to 12 carbon atoms, and the alkyl group further includes a halogen atom (F, Cl, Br, I), a hydroxyl group, a cyano group, an alkoxy group having 1 to 12 carbon atoms, a phenyl group, or a phenyl group substituted with an alkyl group or alkoxy group having 1 to 12 carbon atoms may be contained. Examples of such alkyl groups include methyl, ethyl, n-propyl, isopropyl, t-butyl, sec-butyl, n-butyl, isobutyl, trifluoromethyl, 2-hydroxy Examples include ethyl group, 2-cyanoethyl group, 2-ethoxyethyl group, 2-methoxyethyl group, benzyl group, 4-chlorobenzyl group, 4-methylbenzyl group, 4-methoxybenzyl group, 4-phenylbenzyl group. .

Examples of the alkoxy group (—OR ³ ) of ( ³ ) include those having the alkyl group exemplified in the above (2) as R ³ , specifically, a methoxy group, an ethoxy group, and an n-propoxy group. , Isopropoxy group, t-butoxy group, n-butoxy group, sec-butoxy group, isobutoxy group, 2-hydroxyethoxy group, 2-cyanoethoxy group, benzyloxy group, 4-methylbenzyloxy group, trifluoromethoxy group Etc. As the aryloxy group (—OAr) in (4), a phenyl group in which Ar is unsubstituted or substituted with a halogen atom (F, Cl, Br, I), an alkyl group having 1 to 4 carbon atoms or an alkoxy group, Preferred examples include those having a naphthyl group, specifically, phenoxy group, 1-naphthyloxy group, 2-naphthyloxy group, 4-methylphenoxy group, 4-methoxyphenoxy group, 4-chlorophenoxy group, 6 -A methyl-2-naphthyloxy group etc. are mentioned. Examples of the alkyl or aryl mercapto group (-SR ⁴ ) in (5) include those having the alkyl group exemplified in (2) above as R ⁴ or the phenyl group or naphthyl group exemplified in (4). Specifically, a methylthio group, an ethylthio group, a phenylthio group, a p-methylphenylthio group, and the like can be given.

Furthermore, examples of the group represented by —NR ¹ R ² in (6) include those in which R ¹ and R ² are each a hydrogen atom, an alkyl group, or an aryl group. Here, examples of the alkyl group include those exemplified in the above (2), and examples of the aryl group include unsubstituted or halogen atoms (F, Cl, Br, I), alkyl having 1 to 4 carbon atoms. And a phenyl group, a biphenyl group, a naphthyl group, a pyrenyl group, an anthranyl group and the like substituted with a group or an alkoxy group. R ¹ and R ² may be the same or different from each other, and may be bonded to each other to form a ring structure. Specifically, amino group, diethylamino group, N-methyl-N-phenylamino group, N, N-diphenylamino group, N, N-di- (p-tolyl) amino group, dibenzylamino group, piperidino group , Morpholino groups, euroridyl groups, and the like. Examples of the alkylenedioxy group and alkylenedithio group in (7) include a methylenedioxy group and a methylenedithio group.

Examples of the compounds represented by the general formulas (I) and (II) include the following structures.

In the present invention, these compounds may be used as a fluorescent dopant, or two or more of them may be used in combination.
The fluorescent dopant in the present invention is a compound that emits light in response to recombination of holes and electrons in the recombination region or light emitting region of the organic EL element. The substance to be formed (host material) contains a trace amount. Here, the recombination region is a place in the device where holes and electrons meet and combine to form an excited state. In addition, the light emitting region is a place where the excited state formed in the recombination region moves and diffuses depending on the case, but specifies the diffusion range.

In the present invention, the fluorescent dopant is at least one of the recombination region and the light-emitting region, that is, only in the recombination region, only in the light-emitting region, or in both regions at a ratio of 0.1 to 8% by weight. It is necessary to contain. When the content is less than 0.1% by weight, the effect of the fluorescent dopant is not sufficiently exhibited, and the object of the present invention cannot be achieved. On the other hand, if it exceeds 8% by weight, the disappearance phenomenon may occur due to the association between the fluorescent dopants, and the effect may not be sufficiently exhibited. From the viewpoint of extending the life and efficiency of the device, the preferred content of the fluorescent dopant is in the range of 0.3 to 4% by weight, and particularly preferably in the range of 0.8 to 3% by weight.
Although there is no restriction | limiting in particular about the method of making this fluorescent dopant contain in a recombination area | region or a light emission area | region, For example, it is preferable to employ | adopt the co-evaporation method with the material (host material) which forms a recombination area | region or a light emission area | region. . In this method, the host material and the fluorescent dopant are vacuum-deposited from separate boats in which the host material and the fluorescent dopant are accommodated to form a recombination region and a light emitting region.
In the organic EL device of the present invention, an organic compound layer having at least a recombination region and a light emitting region is used. Since the recombination region and the light emitting region are usually present in the light emitting layer, in the present invention, only the light emitting layer may be used as the organic compound layer, but if necessary, other than the light emitting layer, for example, a hole injection layer. An electron injection layer, an organic semiconductor layer, an electron barrier layer, an adhesion improving layer, and the like can also be used.

Next, the typical structural example of the organic EL element of this invention is shown. Of course, it is not limited to this.
(1) Anode / hole injection layer / light emitting layer / cathode
(2) Anode / hole injection layer / light emitting layer / electron injection layer / cathode
(3) Anode / light emitting layer / electron injection layer / cathode
(4) Anode / organic semiconductor layer / light emitting layer / cathode
(5) Anode / organic semiconductor layer / electron barrier layer / light emitting layer / cathode
(6) Anode / hole injection layer / light emitting layer / adhesion improving layer / cathode Of these, the configuration of (2) is preferably used.

  As described above, the recombination region and the light emitting region in the element of the present invention are usually present in the light emitting layer. Therefore, the fluorescent dopant is usually contained in the light emitting layer. However, in some cases, other layers such as a hole injection layer, an electron injection layer, an organic semiconductor layer, an electron barrier layer, and an adhesion improving layer may be involved in recombination and light emission. In this case, these layers are also preferably contained.

The organic EL device of the present invention has a structure in which the organic compound layer is sandwiched between a pair of electrodes, that is, an anode and a cathode. The anode has a work function (4 eV or more) metal, alloy, What uses an electroconductive compound and a mixture thereof as an electrode material is preferably used. Specific examples of such electrode materials include metals such as Au, and dielectric transparent materials such as CuI, ITO, SnO ₂ and ZnO. The anode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. When taking out light emission from this electrode, it is desirable to make the transmittance greater than 10%, and the sheet resistance as the electrode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually preferably in the range of 10 nm to 1 μm, particularly 10 to 200 nm.

On the other hand, as the cathode, those using an electrode material of a metal, an alloy, an electrically conductive compound and a mixture thereof having a small work function (4 eV or less) are used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / silver alloy, Al / AlO ₂ , indium, and rare earth metals. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. Further, the sheet resistance as an electrode is preferably several hundred Ω / □ or less, and the film thickness is usually in the range of 10 nm to 1 μm, particularly 50 to 200 nm. In the element of the present invention, although not particularly defined, it is preferable that either one of the anode and the cathode is transparent or translucent because the light can be transmitted and extracted efficiently.

で表されるジスチリルアリーレン系化合物が好ましく用いられる。この化合物は、特開平２−２４７２７８号公報に開示されている。 In the light emitting layer in the element of the present invention, the light emitting material (host material) is represented by the general formula (III)

A distyrylarylene compound represented by the formula is preferably used. This compound is disclosed in JP-A-2-247278.

In the general formula (III), Y ^{1 to} Y ⁴ are each a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, a substituted or unsubstituted group. An aryl group having 6 to 18 carbon atoms, a substituted or unsubstituted cyclohexyl group, a substituted or unsubstituted aryloxy group having 6 to 18 carbon atoms, and an alkoxy group having 1 to 6 carbon atoms are shown. Here, the substituent is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, an aryloxy group having 6 to 18 carbon atoms, or an acyl having 1 to 6 carbon atoms. Group, C1-C6 acyloxy group, carboxyl group, styryl group, C6-C20 arylcarbonyl group, C6-C20 aryloxycarbonyl group, C1-C6 alkoxycarbonyl group, vinyl group , Anilinocarbonyl group, carbamoyl group, phenyl group, nitro group, hydroxyl group or halogen. These substituents may be single or plural. Y ^{1 to} Y ⁴ may be the same or different from each other, and Y ¹ and Y ² and Y ³ and Y ⁴ are bonded to a group that is substituted with each other to form a substituted or unsubstituted saturated five-membered member. A ring or a substituted or unsubstituted saturated six-membered ring may be formed. Ar ⁹ represents a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, which may be single-substituted or multiple-substituted, and the binding site may be any of ortho, para, and meta. However, when Ar ⁹ is an unsubstituted phenylene group, Y ^{1 to} Y ⁴ are each an alkoxy group having 1 to 6 carbon atoms, an aralkyl group having 7 to 8 carbon atoms, a substituted or unsubstituted naphthyl group, biphenyl group, and cyclohexyl group. , Selected from aryloxy groups.

Examples of such distyrylarylene-based compounds include:

などが挙げられる。

Etc.

  Another preferred light-emitting material (host material) is 8-hydroxyquinoline or a metal complex of a derivative thereof. Specifically, it is a metal chelate oxinoid compound containing a chelate of oxine (generally 8-quinolinol or 8-hydroxyquinoline). Such compounds exhibit a high level of performance and are easily formed into thin film forms. Examples of this oxinoid compound satisfy the following structural formula.

(In the formula, Mt represents a metal, n is an integer of 1 to 3, and Z represents an atom necessary for completing at least two condensed aromatic rings, each of which is independent at each position. .)
Here, the metal represented by Mt can be a monovalent, divalent or trivalent metal, for example, an alkali metal such as lithium, sodium or potassium, or an alkaline earth metal such as magnesium or calcium. Or an earth metal such as boron or aluminum.
Any monovalent, divalent, or trivalent metal known to be a generally useful chelate compound can be used.

Z represents an atom that forms a heterocyclic ring in which one of at least two condensed aromatic rings is an azole or an azine. Here, if necessary, it is possible to add another different ring to the condensed aromatic ring. In order to avoid adding bulky molecules without functional improvement, it is preferable to maintain the number of atoms represented by Z at 18 or less.
Furthermore, specific examples of chelated oxinoid compounds include tris (8-quinolinol) aluminum, bis (8-quinolinol) magnesium, bis (benzo-8-quinolinol) zinc, bis (2-methyl-8-quinolylato) aluminum. Oxides, tris (8-quinolinol) indium, tris (5-methyl-8-quinolinol) aluminum, 8-quinolinol lithium, tris (5-chloro-8-quinolinol) gallium, bis (5-chloro-8-quinolinol) calcium 5,7-dichloro-8-quinolinol aluminum, tris (5,7-dibromo-8-hydroxyquinolinol) aluminum, and the like.

Further, a phenolate-substituted 8-hydroxyquinoline metal complex described in JP-A-5-198378 is preferable as a blue light-emitting material. Specific examples of the metal complex of the phenolate-substituted 8-hydroxyquinoline include bis (2-methyl-8-quinolinolato) (phenolate) aluminum (III), bis (2-methyl-8-quinolinolato) (o-cresolate) aluminum. (III), bis (2-methyl-8-quinolinolato) (m-cresolate) aluminum (III), bis (2-methyl-8-quinolinolato) (p-cresolate) aluminum (III), bis (2-methyl- 8-quinolinolato) (o-phenylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (m-phenylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (p -Phenylphenolate) Aluminum (III), Bis (2-methyl-8-quinolinolate) ( 2,3-dimethylphenolate) aluminum (III), bis (2-methyl-8-quinolinolato) (2,6-dimethylphenolate) aluminum (III), bis (2-methyl-8-quinolinolato) (3 4-dimethylphenolate) aluminum (III), bis (2-methyl-8-quinolinolato) (3,5-dimethylphenolate) aluminum (III), bis (2-methyl-8-quinolinolato) (3,5- Di-t-butylphenolate) aluminum (III), bis (2-methyl-8-quinolinolato) (2,6-diphenylphenolate) aluminum (III), bis (2-methyl-8-quinolinolato) (2, 4,6-triphenylphenolate) aluminum (III) and the like.
These light emitting materials may be used alone or in combination of two or more.

As a method for forming the light emitting layer in the element of the present invention, for example, it can be formed by thinning by a known method such as vapor deposition, spin coating, casting, LB, etc., but it is particularly a molecular deposited film. It is preferable. Here, the molecular deposited film is a thin film formed by deposition from the vapor phase state of the compound or a film formed by solidification from the molten state or liquid phase state of the compound. Usually, this molecular deposited film can be distinguished from a thin film (molecular accumulated film) formed by the LB method, a difference in aggregation structure and higher order structure, and a functional difference resulting therefrom.
In addition, the light emitting layer can be formed by dissolving in a solvent together with a binder such as a resin to form a solution, and then reducing the film by a spin coating method or the like.
There is no restriction | limiting in particular about the film thickness of the light emitting layer formed in this way, Although it can select suitably according to a condition, Preferably it is 1 nm-10 micrometers, Especially preferably, the range of 5 nm-5 micrometers is good.

Next, the hole injection layer is not necessarily required for the device of the present invention, but is preferably used for improving the light emitting performance. This hole injection layer is a layer that assists the injection of holes into the light emitting layer, has a high hole mobility, and has a small ionization energy of usually 5.5 eV or less. As such a hole injection layer, a material that transports holes to the light emitting layer with a lower electric field is preferable, and the mobility of holes is, for example, at least 10 when an electric field of 10 ⁴ to 10 ⁶ V / cm is applied. ^-6 cm ² / V · sec is more preferable.
Such a hole injection material is not particularly limited as long as it has the above-mentioned preferable properties, and conventionally used as a charge transport material for a hole in an optical transmission material or a hole of an EL element. Any known material used for the injection layer can be selected and used.

Examples of the hole injection material include triazole derivatives (see, for example, US Pat. No. 3,112,197), oxadiazole derivatives (see, for example, US Pat. No. 3,189,447), and imidazole derivatives (Japanese Patent Publication No. 37-16096). Reference), polyarylalkane derivatives (US Pat. Nos. 3,615,402, 3,820,989, 3,542,544, JP-B-45-555, JP-A-51-10983, JP-A-51-93224) Publication, 55-17105 publication, 56-4148 publication, 55-108667 publication, 55-156953 publication, 56-36656 publication, etc.), pyrazoline derivatives and pyrazolone derivatives (US Pat. No. 3,180,729) No. 4,278,746, JP-A-55-88064, JP-A-55-88065, JP-A-49-10. No. 537, No. 55-51086, No. 56-80051, No. 56-88141, No. 57-45545, No. 54-112737, No. 55-74546, etc.), phenylene Diamine derivatives (U.S. Pat. No. 3,615,404, Japanese Patent Publication No. 51-10105, Japanese Patent Publication No. 46-3712, Japanese Patent Publication 47-25336, Japanese Patent Publication No. 54-53435, Japanese Patent Publication No. 54-110536, 54-119925), arylamine derivatives (US Pat. Nos. 3,567,450, 3,180,703, 3,240,597, 3,658,520, 4,232,103, 4,175,961) No. 4,012,376, JP-B-49-35702, JP-A-39-27577, JP-A-55-144250, JP-A-56-1. 19132, 56-22437, West German Patent 1,110,518, etc.), amino-substituted chalcone derivatives (see US Pat. No. 3,526,501, etc.), oxazole derivatives (US Pat. No. 3,257,203, etc.) Styryl anthracene derivatives (see JP 56-46234 A), fluorenone derivatives (see JP 54-110837 A, etc.), hydrazone derivatives (US Pat. No. 3,717,462, JP A) 54-59143, 55-52063, 55-52064, 55-46760, 55-85495, 57-11350, 57-148749, etc.) , Stilbene derivatives (Japanese Patent Laid-Open Nos. 61-210363, 61-228451, 61-14642) Gazette, 61-72255 gazette, 62-47646 gazette, 62-36674 gazette, 62-10652 gazette, 62-30255 gazette, 60-93445 gazette, 60-94462 gazette. Gazette, 60-174749 gazette, 60-175052 gazette, etc.).
Further, silazane derivatives (US Pat. No. 4,950,950), polysilanes (JP-A-2-204996), aniline-based copolymers (JP-A-2-282263), conductive polymer oligomers (JP-A-1 1992). -2139999), especially thiophene-containing oligomers.

  In the present invention, these compounds can be used as a hole injecting material. The following porphyrin compounds (described in JP-A-63-295965), aromatic tertiary amine compounds and Styrylamine compounds (US Pat. No. 4,127,412, JP-A-53-27033, 54-58445, 54-149634, 54-64299, 55-79450, 55-144250, 56-119132, 61-295558, 61-98353, 63-295695, etc.), especially the use of aromatic tertiary amine compounds. preferable.

  Representative examples of the porphyrin compound include porphine, 1,10,15,20-tetraphenyl-21H, 23H-porphine copper (II); 1,10,15,20-tetraphenyl 21H, 23H-porphine zinc (II ); 5,10,15,20-tetrakis (pentafluorophenyl) -21H, 23H-porphine; silicon phthalocyanine oxide; aluminum phthalocyanine chloride; phthalocyanine (metal free); dilithium phthalocyanine; copper tetramethylphthalocyanine; Examples thereof include phthalocyanine; zinc phthalocyanine; lead phthalocyanine; titanium phthalocyanine oxide; magnesium phthalocyanine; copper octamethylphthalocyanine.

  As typical examples of the aromatic tertiary amine compound and styrylamine compound, N, N, N ′, N′-tetraphenyl-4,4′-diaminophenyl, N, N′-diphenyl-N, N '-Di (3-methylphenyl) -4,4'-diaminobiphenyl, 2,2-bis (4-di-p-tolylaminophenyl) propane, 1,1-bis (4-di-p-tolylamino) Phenyl) cyclohexane, N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl, 1,1-bis (4-di-p-tolylaminophenyl) -4-phenylcyclohexane, Bis (4-dimethylamino-2-methylphenyl) phenylmethane, bis (4-di-p-tolylaminophenyl) phenylmethane, N, N′-diphenyl-N, N′-di (4-methoxypheny ) -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) Examples include benzene, 3-methoxy-4′-N, N-diphenylaminostilbenzene, N-phenylcarbazole, and aromatic dimethylidin compounds.

The hole injection layer in the EL device of the present invention can be formed by forming the above compound by a known thin film method such as a vacuum deposition method, a spin coating method, or an LB method. The thickness of the hole injection layer is not particularly limited, but is usually 5 nm to 5 μm. This hole injection layer may be composed of one or more of the above hole injection materials, or a hole injection layer made of a compound different from the hole injection layer is laminated. It may be a thing.
The organic semiconductor layer is a layer that assists hole injection or electron injection into the light emitting layer, and preferably has a conductivity of 10 ⁻¹⁰ S / cm or more. As a material for such an organic semiconductor layer, a conductive oligomer such as a thiophene-containing oligomer or an arylamine oligomer, a conductive dendrimer such as an arylamine dendrimer, or the like can be used. In particular,

Etc.
Furthermore, the electron barrier layer is a layer having a role of confining electrons in the light emitting layer, and is preferably provided between the light emitting layer and the anode and excellent in hole transportability. As a material for such an electron barrier layer, for example,

などを挙げることができる。

And so on.

On the other hand, the electron injection layer is a layer that assists the injection of electrons into the light emitting layer and has a high electron mobility, and the adhesion improving layer is made of a material that adheres particularly well to the cathode among the electron injection layers. It is a layer. Preferred examples of the material used for the electron injection layer include 8-hydroxyquinoline or a metal complex of a derivative thereof, or an oxadiazole derivative. In addition, as a material used for the adhesion improving layer, 8-hydroxyquinoline or a metal complex thereof is particularly suitable.
Specific examples of the metal complex of 8-hydroxyquinoline or a derivative thereof include metal chelate oxinoid compounds containing a chelate of oxine (generally 8-quinolinol or 8-hydroxyquinoline).

On the other hand, as the oxadiazole derivatives, the general formulas (IV) and (V)

(Each of Ar ¹⁰ to Ar ¹³ has the formula a substituted or unsubstituted aryl group, Ar ¹⁰ and Ar ¹¹ and Ar ¹² and Ar ¹³ may be mutually different, even the same in each, Ar ¹⁴ is Represents a substituted or unsubstituted arylene group.)
The electron transfer compound represented by these is mentioned. Here, examples of the aryl group include a phenyl group, a biphenyl group, an anthranyl group, a perylenyl group, and a pyrenyl group. Examples of the arylene group include a phenylene group, a naphthylene group, a biphenylene group, an anthracenylene group, a peryleneylene group, and a pyrenylene group. It is done. Moreover, as a substituent, a C1-C10 alkyl group, a C1-C10 alkoxy group, a cyano group, etc. are mentioned. The electron transfer compound is preferably a thin film-forming compound.

などが挙げられる。 Specific examples of the electron transfer compound include

Etc.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Production Example 1 Production of K-1 In a 300 ml three-necked flask, 2 g of N, N′-diphenyl-4,4′-benzidine (manufactured by Tokyo Chemical Industry Co., Ltd.); 5 g of 1-iodoanthracene (manufactured by Nard Institute) , 10 g of anhydrous potassium carbonate and 1 g of copper were added, dissolved in 200 ml of dimethyl sulfoxide (DMSO), heated at 200 ° C. for 8 hours, and stirred.
After completion of the reaction, the inorganic substance was filtered off, the solvent was distilled off under reduced pressure, and the residue was purified with a column filled with silica gel (manufactured by Hiroshima Wako) using toluene as a developing solvent to obtain 1.8 g of a yellow powder. It was.
This was measured by NMR and FD-MS (Field Diffusion Mass Spectrum), and determined from N, N′-di- (anthracen-1-yl) -N, N′-diphenyl-4,4′-benzidine (K— 1).

Production Example 2 Production of K-2 In Production Example 1, except that 1-iodopyrene (manufactured by Nard Laboratories) was used instead of 1-iodoanthracene, it was reacted and purified in the same manner as in Production Example 1, but yellow 1.5 g of powder was obtained.
This was identified as N, N′-di- (pyren-1-yl) -N, N′-diphenyl-4,4′-benzidine (K-2) by NMR and FD-MS measurements.

Production Example 3 Production of K-3 In Production Example 1, 1,6-diaminopyrene (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of N, N′-diphenylbenzidine, and iodobenzene (Tokyo, Japan) was used instead of 1-iodoanthracene. The reaction and purification were conducted in the same manner as in Production Example 1 except that 20 g (manufactured by Kasei Co., Ltd.) was used, and 1.4 g of yellow powder was obtained.
This was identified as N, N, N ′, N′-tetraphenyl-1,6-diaminopyrene (K-3) by NMR and FD-MS measurements.

Production Example 4 Production of K-4 In Production Example 1, N, N′-diphenyl-1,3-phenylenediamine (manufactured by Nard Laboratories) was used instead of N, N′-diphenylbenzidine, and 1-iodo The reaction and purification were conducted in the same manner as in Production Example 1 except that 1-iodopyrene (manufactured by Nard Laboratories) was used instead of anthracene, and 1.5 g of yellow powder was obtained.
This was identified as N, N′-di- (pyren-1-yl) -N, N′-diphenyl-1,3-phenylenediamine (K-4) by NMR and FD-MS measurements.

Production Example 5 Production of K-5 In Production Example 1, 1-aminopyrene was used instead of N, N′-diphenylbenzidine, and 10 g of iodobenzene was used instead of 1-iodoanthracene. When the reaction and purification were conducted in the same manner, 1.9 g of yellow powder was obtained.
This was identified as N, N′-diphenyl-1-aminopyrene (K-5) by NMR and FD-MS measurements.

Production Example 6 Production of K-6 In a 300 ml three-necked flask, 2 g of 1-aminoanthracene (manufactured by Aldrich); 2,5-bis- (4-iodophenyl-1-yl) -thiophene (Nard Institute) 2 g, 10 g of anhydrous potassium carbonate and 1 g of copper were added, dissolved in 200 ml of DMSO, and heated and stirred at 200 ° C. for 8 hours.
After completion of the reaction, the inorganic substance was filtered off, the solvent was distilled off under reduced pressure, and the residue was purified on a column packed with silica gel (manufactured by Hiroshima Wako) using toluene as a developing solvent to obtain 1.7 g of a yellow powder. It was.
Next, 1.5 g of this yellow powder, 10 g of iodobenzene, 10 g of anhydrous potassium carbonate and 1 g of copper were placed in a 300 ml three-necked flask, dissolved in DMSO, and heated and stirred at 200 ° C. for 8 hours.
After completion of the reaction, the inorganic substance was filtered off and the solvent was distilled off under reduced pressure. The residue was purified on a column filled with silica gel (manufactured by Hiroshima Wako) using toluene as a developing solvent to obtain 0.68 g of yellow powder. It was.
This was identified as 2,5-bis- (4- [N- (anthracen-1-yl) -N-phenyl] aminophenyl) thiophene (K-6) by NMR and FD-MS measurements.

Examples 1 to 6 and Comparative Example 1
A transparent support substrate was formed by depositing ITO with a thickness of 100 nm on a glass substrate of 25 mm × 75 mm × 1.1 mm by a vapor deposition method (manufactured by Geomatic). This substrate was ultrasonically cleaned in isopropyl alcohol for 5 minutes, dried by blowing nitrogen and UV ozone cleaning (UV300, manufactured by Samco International) for 30 minutes.
This transparent support substrate is fixed to a substrate holder of a commercially available vapor deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.), MTDATA 200 mg is put into a molybdenum resistance heating boat, DPVBi 200 mg is put into another molybdenum resistance heating boat, Put 200 mg of NPD which is a hole transport material into a resistance heating boat made of molybdenum, and further put 200 mg of the fluorescent dopant [compound (A)] shown in Table 1 into another resistance heating boat made of molybdenum, and set the vacuum chamber to 1 × The pressure was reduced to 10 ⁻⁴ Pa. Thereafter, the boat containing MTDATA was heated to 215 to 220 ° C. and deposited on a transparent support substrate at a deposition rate of 0.1 to 0.3 nm / second to form a hole injection layer having a thickness of 60 nm. .
Next, without removing the substrate from the vacuum chamber, the boat containing NPD was heated to form a 20 nm-thick hole transport layer on the hole injection layer. At this time, the temperature of the substrate was room temperature. Without removing this from the vacuum chamber, 40 nm of DPVBi was laminated as a host material on the NPD layer. At the same time, the boat of compound (A) was heated, and compound (A) was mixed in the light emitting layer. At this time, the deposition rate of the compound (A) was (C) (shown in Table 1) with respect to the deposition rate of DPVBi ((B) shown in Table 1). Therefore, the mixing ratio [ratio of compound (A) to host material] was (D) (shown in Table 1).
After that, the vacuum chamber is returned to atmospheric pressure, and an 8-hydroxyquinoline / aluminum complex, which is a material for the electron injection layer, is newly added to a resistance heating boat made of molybdenum, and 1 g of a magnesium ribbon is further added to the resistance heating boat made of molybdenum. 500 mg of silver wire was put in the basket, and the vacuum chamber was depressurized to 1 × 10 ⁻⁴ Pa.
Subsequently, an 8-hydroxyquinoline / aluminum complex was deposited at a deposition rate of 0.01 to 0.03 nm / second to form an electron injection layer of 20 nm. Further, silver was co-evaporated at a deposition rate of 0.1 nm / second and magnesium was deposited at a deposition rate of 1.4 nm / second to form a silver: magnesium mixed electrode as a cathode. The film thickness was 150 nm.
Luminous efficiency was calculated by applying a voltage of 8 V to the resulting device and measuring the amount of current and the luminance of the device. The results obtained are shown in Table 2.
The structures of MTDATA, DPVBi, and NPD are as follows.

As a result of the above, it can be seen that the device of the present invention is superior in luminous efficiency compared to that of Comparative Example 1 using perylene (fluorescent dopant described in JP-A-5-198378) as the fluorescent dopant. .
Next, each element was driven in an atmosphere of dry nitrogen at an initial luminance of 300 cd / m ² to obtain a half life (time for the initial luminance to be halved). The results are shown in Table 3. As a result of testing at an initial luminance of 100 cd / m ² , a life of about 3.5 times that of Table 3 was obtained. Therefore, the device of the present invention can have a lifetime of 2500 hours to 1100 hours under the condition of initial luminance of 100 cd / m ² .

第３表から分かるように、本発明の素子は、比較例１のものに比べて寿命が大幅に改善されている。

As can be seen from Table 3, the lifetime of the element of the present invention is significantly improved compared to that of Comparative Example 1.

Comparative Example 2
A device was prepared in the same manner as in Example 1 except that PAVTP (a fluorescent dopant described in International Patent Publication No. 94-6157) was used as the fluorescent dopant [compound (A)], and an initial luminance of 300 cd / m ^{2 was obtained.} When the half-life was obtained, the half-life was 300 hours, which was shorter and inferior to the device of the present invention. The test result at an initial luminance of 100 cd / m ² was a half life of 1000 hours.
The structure of PAVTP is shown below.

Claims (3)

Organic electroluminescence device comprising an organic compound layer having at least a recombination region in which holes and electrons recombine, a light emitting region that emits light in response to the recombination, and a pair of electrodes that hold the organic compound layer In the recombination region and / or the light emitting region, as a fluorescent dopant, the compound represented by the general formula (I)

[In the formula, Ar ¹ , Ar ² and Ar ³ each represent an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 30 carbon atoms or a heterocyclic group, which may be the same or different. At least one of them is a condensed polycyclic hydrocarbon group having 12 or more carbon atoms. ]
And general formula (II)

[In the formula, Ar ⁴ , Ar ⁵ , Ar ⁶ and Ar ⁷ each represent an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 30 carbon atoms or a heterocyclic group, which are the same or different. Ar ⁸ represents an arylene group having 6 to 30 carbon atoms or a divalent heterocyclic group, and at least one of Ar ^{4 to} Ar ⁸ is a condensed polycyclic hydrocarbon group having 12 or more carbon atoms. . ]
An organic electroluminescence device comprising at least one selected from the compounds represented by the formula (0.1) to 8% by weight.   The organic electroluminescent device according to claim 1, wherein a fluorescent dopant is contained in the light emitting layer. The organic electroluminescence device according to claim 1, wherein the device configuration is anode / hole injection layer / light emitting layer / electron injection layer / cathode.