JP4517673B2 - Organic electroluminescence element, display device and lighting device - Google Patents

Description

  The present invention relates to an organic electroluminescence element (hereinafter also referred to as an organic EL element), a display device, and a lighting device, and in particular, has an emission luminance and luminous efficiency, and an organic electroluminescence element having particularly excellent durability, and the same The present invention relates to a display device or a lighting device.

  Conventionally, as a light-emitting electronic display device, there is an electroluminescence display (hereinafter also referred to as ELD). As a component of ELD, an inorganic electroluminescent element and an organic electroluminescent element are mentioned. Inorganic electroluminescent elements have been used as planar light sources, but an alternating high voltage is required to drive the light emitting elements.

  On the other hand, an organic electroluminescence device has a structure in which a light emitting layer containing a light emitting compound is sandwiched between a cathode and an anode, and excitons (exciton) are formed by injecting electrons and holes into the light emitting layer and recombining them. ), And light is emitted using light (fluorescence, phosphorescence) emitted when the exciton is deactivated. And it is possible to emit light at a voltage of several volts to several tens of volts, it is self-luminous, has a wide viewing angle and high visibility, and is a thin-film completely solid element, saving space. It is currently attracting attention because it has advantages such as excellent portability.

  For the development of organic electroluminescent elements for practical use in the future, organic electroluminescent elements that emit light with higher luminance and lower power consumption are desired. Specifically, a technique for improving light emission luminance and extending the lifetime of a device by doping a stilbene derivative, a distyrylarylene derivative or a tristyrylarylene derivative with a small amount of a phosphor (see, for example, Patent Document 1). ), 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 8-hydroxyquinoline aluminum complex as a host compound. A device having an organic light emitting layer doped with a quinacridone dye (for example, see Patent Document 3) is known.

  In the techniques disclosed in these documents, when light emission from excited singlet is used, the generation ratio of singlet excitons and triplet excitons is 1: 3, so that the generation probability of luminescent excited species is 25%. And the light extraction efficiency is about 20%, the limit of the external extraction quantum efficiency (ηext) is set to 5%.

  However, since research on organic electroluminescence devices using phosphorescence emission from excited triplets by Princeton University (see, for example, Non-Patent Document 1), research on materials that exhibit phosphorescence at room temperature has been actively conducted. (For example, refer nonpatent literature 2 and patent literature 4.).

  When excited triplets are used, the upper limit of internal quantum efficiency is 100%, so that in principle, the luminous efficiency is four times that of excited singlets, so that almost the same performance as a cold cathode tube can be obtained. It is also attracting attention as it can be applied to.

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

Further, studies have been made using tris (2-phenylpyridine) iridium (Ir (ppy) ₃ ) as a dopant (see, for example, Non-Patent Document 2).

In addition, as a dopant, L ₂ Ir (acac) (wherein L represents a bidentate ligand and acac represents acetylacetone), for example, (ppy) ₂ Ir (acac) (see, for example, Non-Patent Document 4) ) And as a dopant, tris (2- (p-tolyl) pyridine) iridium (Ir (ptpy) ₃ ), tris (benzo [h] quinoline) iridium (Ir (bzq) ₃ ), Ir (bzq) Studies using ₂ ClP (Bu) ₃ or the like (for example, see Non-Patent Document 5) have been made.

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

  Further, as a technique for using various electron transporting materials as a host of a phosphorescent compound, a method of doping and using a novel iridium complex can be given (for example, see Non-Patent Document 4). Furthermore, it is known that high luminous efficiency can be obtained by introducing a hole blocking layer (see, for example, Non-Patent Document 5).

  However, although the external extraction efficiency of nearly 20%, which is the theoretical limit, is achieved for green light emission, sufficient external extraction efficiency is not yet obtained for other colored light, and improvements are being urged.

  Thus, in the organic electroluminescent element for future practical use, development of the organic electroluminescent element which can light-emit with high brightness with further low power consumption is desired.

  In addition, there is a strong demand for element durability having a sufficient light emission lifetime that can be practically used for display applications and illumination applications. In this regard, studies have been made from various directions so far. For example, Patent Documents 5, 6, and 7 describe an approach from the viewpoint of element sealing, and Patent Document 8 describes an appropriate energy level. Patent Document 9 discloses an approach for improving durability by adding a dopant having an element, and discloses a method of enclosing a hygroscopic agent in an airtight space formed by a substrate material, an element, and a sealing agent constituting the element. Has been. Further, studies have been made to further improve the durability of the charge transporting material constituting the element and the material itself used for the light emitting layer, and many of these are disclosed in Patent Documents 10 to 13 and the like.

  Furthermore, the influence on the durability of the organic electroluminescent element which the impurity which the organic compound layer in the element which these organic materials comprise contains gives is examined. For example, Patent Document 14 describes the amount of impurities contained in the organic compound layer constituting the element, and Patent Document 15 describes the amount of impurities derived from the cross-coupling reaction when synthesizing the organic electroluminescent material. Patent Document 16 discloses that impurities containing halogen atoms affect the durability of the device.

These various approaches can be used together as long as they do not cancel each other. Therefore, a technical approach for further enhancing the durability of the organic electroluminescence device continues to be sought, and a new technology for improving the durability is still awaited.
Japanese Patent No. 3093796 Japanese Unexamined Patent Publication No. 63-264692 JP-A-3-255190 US Pat. No. 6,097,147 JP 2002-31559 A Japanese Patent Laid-Open No. 08-236271 JP 2002-367771 A Japanese Patent Application Laid-Open No. 07-065958 JP 2002-198170 A JP 2002-363227 A Japanese Patent Laid-Open No. 2002-352961 JP 2002-356462 A JP 2002-363550 A JP 2002-373785 A JP 2002-373786 A International Publication No. 00/41443 Pamphlet M.M. A. Baldo et al. , Nature, 395, 151-154 (1998) M.M. A. Baldo et al. , Nature, 403, 17, 750-753 (2000) S. Lamansky et al. , J .; Am. Chem. Soc. 123, 4304 (2001) M.M. E. Thompson et al. , The 10th International Works on Organic and Organic Electroluminescence (EL'00, Hamamatsu) Moon-Jae Youn. 0 g, Tetsuo Tsutsui et al. , The 10th International Works on Organic and Organic Electroluminescence (EL'00, Hamamatsu) Ikai et al. , The 10th International Works on Organic and Organic Electroluminescence (EL'00, Hamamatsu)

  The object of the present invention has been made in view of the above circumstances, and has an organic electroluminescence device having high emission luminance and excellent quantum efficiency, and at the same time, particularly excellent durability, and the same. A display device and a lighting device are provided.

The above object of the present invention is achieved by the configuration 1-7 below.

1. In an organic electroluminescence device having at least one organic layer on a substrate, a carbazole derivative represented by the following general formula (1) obtained by a condensed heterocycle formation reaction of 2,2′-dihalogeno-biphenyl and an amine And a compound represented by the following general formula (2), wherein an amino group is bonded to a structural part that is bonded to the carbazole ring, which is a reaction intermediate compound when the compound represented by the general formula (1) is synthesized. DOO well as contained in the organic layer, the content of the compound is Ru represented by organic layers definitive the general formula (2) is organic electroluminescent device you and less than 0.33 wt%.

(In the formula, m is an integer of 1 to 6, A is a monovalent organic group when m = 1, and m is a linking group when m is not _1. R ₁ and R ₂ are substituents. , N1 and n2 represent an integer of 0 to 4.)

(In the formula, A, R ₁ , R ₂ , n1, and n2 have the same meanings as in the general formula (1). X represents a bromine atom or an iodine atom, m1, m2, and m3 are integers from 0 to 6, (The sum of m1, m2, and m3 is an integer of 1 to 6, and neither m2 nor m3 is 0.)
2. 2. The organic electroluminescence device according to 1 above, wherein the content of the compound represented by the general formula (2) in the organic layer is less than 0.1% by mass.

3. 3. The organic electroluminescent element according to 1 or 2 above, wherein light emission generated when an electric field is applied to the organic electroluminescent element includes phosphorescent light emission.

4). 4. The organic electroluminescent element according to any one of 1 to 3 , wherein light emission generated when an electric field is applied to the organic electroluminescent element emits white light.

5. 5. A display device comprising the organic electroluminescence element according to any one of 1 to 4 above .

6). The organic electroluminescent element of any one of said 1-4 is comprised, The illuminating device characterized by the above-mentioned.

7). 6. The display device according to 5 above , comprising the illumination device according to 6 and a liquid crystal element as display means.

  The object of the present invention has been made in view of the above circumstances, and has an organic electroluminescence device having high emission luminance and excellent quantum efficiency, and at the same time, particularly excellent durability, and the same. Provided display device and lighting device

In the organic electroluminescent element of the present invention, by adopting the configuration according to any one of claims 1 to 4 , the organic electroluminescent element has high emission luminance and excellent quantum efficiency, and particularly has excellent durability. It was possible to find an electroluminescence element.

Furthermore, the display apparatus of each of Claims 5 and 6 which has the organic electroluminescent element of any one of Claims 1-4 , and the illuminating device of Claim 7 were able to be obtained.

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

  As a result of repeated studies, the inventors have found that when a compound containing an organic electroluminescent material having a specific structural unit is mixed as an impurity with a compound derived from the structural unit, the durability of the manufactured device is improved. The present inventors have found that it has a very great influence and have completed the present invention.

  Hereinafter, the present invention will be described in more detail.

  The organic electroluminescence device of the present invention comprises an organic layer containing a substituted carbazole compound, an anode and a cathode.

  In the substituted carbazole compound contained in the organic layer, the compound formed by bonding a substituted or unsubstituted amino group to the structural portion bonded to the carbazole ring is less than 0.5% by mass, preferably less than 0.3% by mass, More preferably, when the content is less than 0.1% by mass, the organic electroluminescence element is driven as an element having very high durability as well as high emission luminance and excellent quantum efficiency.

  A preferred embodiment of the present invention contains the substituted carbazole compound represented by the general formula (1) in the organic layer and is represented by the general formula (2) existing as an impurity in the organic layer containing the substituted carbazole compound. In the organic electroluminescence device, the content of the compound is less than 0.5% by mass, preferably less than 0.3% by mass, and more preferably less than 0.1% by mass. The present invention includes a case where a plurality of types of impurities represented by the general formula (2) are simultaneously contained in the organic layer.

  Hereinafter, the substituted carbazole compound represented by the general formula (1) and the compound represented by the general formula (2) present as impurities will be described in detail.

  The compound represented by the general formula (1) which is an organic electroluminescence material is a compound having a structure in which m substituted or unsubstituted carbazole rings are connected to the organic group A. Here, m represents an integer of 1 to 6, and a compound in which m hydrogen atoms are bonded to A, that is, as a compound derived from A, methane, ethene, acetylene, benzene, naphthalene, azulene, anthracene, In addition to hydrocarbon compounds such as phenanthrene, fluorene, pyrene, and tetracene, borane, ammonia, silane, hydrogen sulfide, water and other compounds in which a heteroatom is bonded to hydrogen, furan, thiophene, selenophene, pyrrole, pyridine, pyrazine, pyrimidine, Heteroaromatic compounds such as pyrazole, imidazole, triazole, triazine, thiazole, oxadiazole, thiadiazole, benzofuran, dibenzothiophene, indole, isoindole, carbazole, benzthiazole, benzimidazole, pyrazoloimidazo , Pyrazolotriazole, quinoline, quinoline, acridine, pyridoindole, dipyridopyrrole, condensed polycyclic aromatic compounds such as purine, sinoline, phenoxazine, phenothiazine, etc., and any organic group derived from these compounds These combinations are also included in the example of A.

  A may have a substituent, and examples thereof include an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, octyl group, dodecyl group). Group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (eg, vinyl group, allyl group, etc.), alkynyl group (eg, ethynyl group, propargyl group, etc.) Etc.), aryl groups (eg phenyl group, naphthyl group etc.), aromatic heterocyclic groups (eg furyl group, thienyl group, pyridyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group, pyrazolyl group) , Thiazolyl group, quinazolinyl group, phthalazinyl group, etc.), heterocyclic group (for example, Pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxyl group (for example, methoxy group, ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxyl group (Eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group) , Dodecylthio group, etc.), cycloalkylthio group (eg, cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyl) Oxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (eg, Aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2 -Pyridylaminosulfonyl group, etc.), acyl group (for example, acetyl group, ethylcarbonyl group, propylcarbonyl group, pentylcarbonyl group, cyclohexane) Xylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (for example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group) Octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide group (for example, methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonyl) Amino group, 2-ethylhexylcarbonylamino group, octylcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthyl Carbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl) Group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, Dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group, etc.), sulfinyl group (for example, methylsulfinyl group, ethyl) Rufinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group) , Butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group (phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group etc.), amino group (for example, amino group, ethyl group) Amino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, diphenylamino group, anilino group, ethyltri Ruamino group, naphthylamino group, 2-pyridylamino group, etc.), fluorinated hydrocarbon group (eg, fluoromethyl group, trifluoromethyl group, pentafluoroethyl group, pentafluorophenyl group, etc.), cyano group, mercapto group, silyl group Examples include a group (for example, trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group), a fluorine atom, and the like.

  These substituents may be further substituted with the above substituents. Further, these substituents may be bonded together to form a ring. When there are a plurality of substituted or unsubstituted carbazole ring moieties bonded to A, the carbazole ring moieties may be the same as or different from each other.

  Examples of substituted or unsubstituted carbazole residues bonded to A and A are shown below, but the structure of the compound represented by the general formula (1) according to the present invention is not limited by these examples.

In the general formula (1), R ₁ and R ₂ independently represent a monovalent substituent, and examples thereof include the substituents in which A in the general formula (1) is listed above. N1 and n2 independently represent an integer of 0 to 4.

In the general formula (2), A, R ₁ , R ₂ , n1, and n2 are all the same as those in the general formula (1), and X represents a bromine atom or an iodine atom. m1, m2 and m3 represent integers from 0 to 6, and the sum of m1, m2 and m3 is an integer from 1 to 6. Further, m2 and m3 are not 0 at all, which means that the impurity is a compound having a structure having a substituted or unsubstituted amino group.

  Moreover, it is preferable that the molecular weight of the compound represented by General formula (1) is 600-2000. When the molecular weight is 600 to 2000, Tg (glass transition temperature) increases, thermal stability is improved, and device lifetime is improved. A more preferred molecular weight is 800-2000.

  The organic electroluminescence device according to the present invention contains a substituted carbazole compound in an organic layer, and binds a substituted or unsubstituted amino group to a structural portion that binds to a carbazole ring present in the organic layer as an impurity. The content of the compound having the structure is at least less than 0.5% by mass, preferably less than 0.3% by mass, and more preferably less than 0.1% by mass with respect to the substituted carbazole compound in the organic layer. By suppressing the above, high luminous efficiency, luminous luminance, and high durability are exhibited.

  The mechanism that reduces the light emission efficiency, light emission luminance, and durability of the device by the presence of a compound having a structure in which a substituted or unsubstituted amino group is bonded to the structure portion bonded to the carbazole ring in the organic layer as an impurity. Although it is not necessarily clear, it is presumably that trap levels are formed in the organic electroluminescence device, the impurity and the substituted carbazole compound react to promote decomposition of the substituted carbazole compound, or an electrode adjacent to the organic layer. Adhesion with other organic layers, and if it is adjacent to other organic layers, it may adversely affect the characteristics of the organic electroluminescent element by inhibiting the adhesion with the adjacent organic layer. It is estimated that the durability is lowered.

  In particular, regarding the durability, the impurities are poorer in electrical and thermal stability than the substituted carbazole compound, so that it decomposes in a relatively short time during electroluminescence, and the resulting decomposition products are produced by the mechanism described above. This is presumed to deteriorate the element.

  The cause of the impurities being mixed into the organic layer is presumed to be due to various conditions such as the production method and purification method of the substituted carbazole compound, the production method of the organic electroluminescence device, and one of them is an amine compound and dihalogenation. When a substituted carbazole compound is synthesized by a coupling reaction of a biphenyl derivative, the reaction intermediate may be mixed as an impurity in the target product. In addition, these impurities can be removed by ordinary purification methods, but in reality they are not completely removed, but are brought into the organic electroluminescence device manufacturing process and mixed into the organic layer of the device as impurities. It is guessed.

  The substituted carbazole compound represented by the general formula (1) according to the present invention can be used for any of a hole transport layer, an electron transport layer, and a light emitting layer that constitute an organic layer of an organic electroluminescence element described later. However, it is preferable to use for an electron carrying layer thru | or a light emitting layer.

  In addition, the substituted carbazole compound represented by the general formula (1) transfers a luminescent or phosphorescent compound in the light emitting layer, and does not emit light by itself. It can also be preferably used as a material known as “host compound”. The organic electroluminescence device according to the present invention is a phosphorescent organic electroluminescence device comprising a light emitting layer together with a phosphorescent compound using the above substituted carbazole compound as a host compound from the viewpoint of the luminous efficiency described above. It is particularly preferred.

  Substituted carbazole compounds used in the present invention are disclosed in Tetrahedron Lett. 39 (1998), 2367-2370, Japanese Patent No. 3161360, Angew. Chem. Int. Ed. 37 (1998), 2046-2067, Tetrahedron Lett. , 41 (2000), pages 481-484, Synth. Commun. 11 (7) (1981), pp. 513-519, and Chem. Rev. , 2002, 102, pages 1359 to 1469 and the like, and the like, etc., can be produced by a synthesis method well known to those skilled in the art.

<< Constituent layers of organic EL elements >>
The constituent layers of the organic EL element of the present invention will be described.

In this invention, although the preferable specific example of the layer structure of an organic EL element is shown below, this invention is not limited to these.
(1) Anode / light emitting layer / electron transport layer / cathode (2) Anode / hole transport layer / light emitting layer / electron transport layer / cathode (3) Anode / hole transport layer / light emitting layer / hole blocking layer / electron Transport layer / cathode (4) anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode (5) anode / anode buffer layer / hole transport layer / light emitting layer / hole Blocking layer / electron transport layer / cathode buffer layer / cathode << Anode >>
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used. For the anode, a thin film may be formed by depositing these electrode materials by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when the pattern accuracy is not required (100 μm or more) Degree), a pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. When light emission is extracted from the anode, it is desirable that the transmittance is greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

"cathode"
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials 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 these, a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value than this, such as a magnesium / silver mixture, magnesium, from the viewpoint of electron injectability and durability against oxidation, etc. / Aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. 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 1000 nm, preferably 50 nm to 200 nm. In order to transmit light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the light emission luminance is improved, which is convenient.

  Next, an injection layer, a hole transport layer, an electron transport layer, etc. used as a constituent layer of the organic EL element 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, and as described above, between the anode and the light emitting layer or the hole transport layer, and You may exist between a cathode, a light emitting layer, or an electron carrying layer.

  An injection layer is a layer provided between an electrode and an organic layer in order to lower drive voltage or improve light emission luminance. “Organic EL element and its forefront of industrialization (issued on November 30, 1998 by NTS Corporation) 2), Chapter 2, “Electrode Materials” (pages 123 to 166) in detail, and 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, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Examples thereof include a phthalocyanine buffer layer represented by an oxide, 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 described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, strontium, aluminum, etc. Metal buffer layer typified by lithium, alkali metal compound buffer layer typified by lithium fluoride, alkaline earth metal compound buffer layer typified by magnesium fluoride, oxide buffer layer typified by aluminum oxide, etc. .

  The buffer layer (injection layer) is preferably a very thin film, and although it depends on the material, the film thickness is preferably in the range of 0.1 nm to 100 nm.

  As described above, the blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film. For example, JP-A-11-204258, JP-A-11-204359, and “Organic EL devices and their forefront of industrialization” (issued on November 30, 1998 by NTS, Inc.), page 237, etc. There is a hole blocking layer.

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

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

  The hole transport layer is made of a material having a function of transporting holes, and 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 and the electron transport layer can be provided as a single layer or a plurality of layers.

  In the organic EL device of the present invention, it is preferable that the fluorescence maximum wavelength of all the materials of the host of the light emitting layer, the hole transport layer adjacent to the light emitting layer, and the electron transport layer adjacent to the light emitting layer is 415 nm or less.

<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 the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May also be the interface between the light emitting layer and the adjacent layer.

  The material used for the light emitting layer (hereinafter referred to as the light emitting material) is preferably an organic compound or complex that emits fluorescence or phosphorescence, and is appropriately selected from known materials used for the light emitting layer of the organic EL device. Can be used. Such a light-emitting material is mainly an organic compound, and has a desired color tone, for example, Macromol. Synth. 125, pages 17-25, etc. can be used.

  The light emitting material may have a hole transport function and an electron transport function in addition to the light emitting performance, and most of the hole transport material and the electron transport material can be used as the light emitting material.

  The light-emitting material may be a polymer material such as p-polyphenylene vinylene or polyfluorene, and a polymer material in which the light-emitting material is introduced into a polymer chain or the light-emitting material is a polymer main chain is used. May be.

  This light emitting layer can be formed by forming the above compound by a known thinning method such as a vacuum deposition method, a spin coating method, a casting method, or an LB method. Although the film thickness as a light emitting layer does not have a restriction | limiting in particular, Usually, it selects in the range of 5 nm-5 micrometers. This light emitting layer may have a single layer structure composed of one or two or more of these light emitting materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions. A preferred embodiment of the organic EL device of the present invention is when the light emitting layer is composed of two or more materials, and one of them is the compound of the present invention.

  Further, as described in JP-A-57-51781, this light emitting layer is prepared by dissolving the above light emitting material in a solvent together with a binder such as a resin, and then using a spin coating method or the like. It can be formed as a thin film. 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, Usually, it is the range of 5 nm-5 micrometers.

  In another embodiment of the present invention, the light emitting layer contains at least one fluorescent compound having a fluorescence maximum wavelength that is longer than the emission maximum wavelength in addition to the organic compound that is the main component. You may let them. Thus, in the case where any compound is contained in the light emitting layer in addition to the main constituent component, the main constituent component is called a host compound or simply a host, and the added compound is called a dopant. The above-mentioned organic compound which is the main constituent of is a host compound, and the added fluorescent compound is a dopant, particularly in this case, a fluorescent dopant. The fluorescent dopant is excited by the host compound to emit fluorescence, and as a result, light emission from the fluorescent compound is taken out from the organic EL device thus configured. Fluorescent compounds that can be used in such applications include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes. Examples thereof include dyes, perylene dyes, stilbene dyes, polythiophene dyes, and rare earth complex phosphors. As the fluorescent compound to be used, those having a high fluorescence quantum yield in a solution state are preferable, and the fluorescence quantum yield is preferably 10% or more, particularly preferably 30% or more. The fluorescence quantum yield can be measured by the method described in Spectroscopic II, page 362 (1992 version, Maruzen) of the Fourth Edition Experimental Chemistry Course 7.

  In another embodiment of the present invention, phosphorescence having a light emission maximum wavelength longer than the light emission maximum wavelength of the compound constituting the light emitting layer is the same as that in the case where the fluorescent dopant is added in the above embodiment. A functional compound may be added as a dopant. When a phosphorescent dopant is added to the light emitting layer, phosphorescence emission is extracted from the organic EL element by energy transfer from the host compound to the phosphorescent dopant. As already described, the form using phosphorescence emission is preferable from the viewpoint of light emission efficiency as the organic EL element. Similarly, in the present invention, an organic EL element in which at least a part of the light emitting component is due to phosphorescence emission is also used. preferable.

  The “phosphorescent compound” in the present invention is a compound in which light emission from an excited triplet is observed, and is a compound having a phosphorescence quantum yield of 0.001 or more at 25 ° C. The phosphorescence quantum yield is preferably 0.01 or more, more preferably 0.1 or more.

  The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence quantum yield used in the present invention is only required to achieve the phosphorescence quantum yield in any solvent.

  The phosphorescent compound used in the present invention is preferably a complex compound containing a group 8 metal in the periodic table of elements, more preferably an iridium compound, an osmium compound, or a platinum compound (platinum complex system). Compound), and most preferred is an iridium compound.

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

  In yet another embodiment, in addition to the host compound and the phosphorescent compound, at least one fluorescent compound having a fluorescence maximum wavelength may be contained in a region longer than the maximum wavelength of light emission from the phosphorescent compound. . In this case, electroluminescence as an organic EL element can be emitted from the fluorescent compound by energy transfer from the host compound and the phosphorescent dopant.

  Further, by using a plurality of fluorescent or phosphorescent dopants and simultaneously taking out light emitted from these dopants, a light emitting element having a plurality of light emission maximum wavelengths can be formed. For example, by using polyvinyl carbazole as a luminescent compound that also serves as a host compound and coumarin 6 and Nile red as fluorescent dopants, blue luminescence from polyvinyl carbazole, green luminescence from coumarin 6 and red luminescence from Nile red can be simultaneously used. An element that emits white light can be formed. Similarly, in the phosphorescent organic EL element, light emission can be mixed by using a plurality of types of phosphorescent dopants.

  Taking advantage of the characteristics of the organic EL element that it is thin and can be formed on a resin substrate, a white light-emitting element is constructed considering the case of using it for a panel or other lighting device It is practically useful to do. At present, there is no single light emitting material that exhibits white light emission, and therefore, a plurality of light emitting colors are simultaneously emitted by a plurality of light emitting materials to obtain white light emission by color mixing. The combination of a plurality of emission colors may include three emission maximum wavelengths of three primary colors of blue, green, and blue, or two using a complementary color relationship such as blue and yellow, blue green and orange, etc. The thing containing the light emission maximum wavelength may be used. As described above, the light emission of these mixed colors can be performed by using a dopant, and the color tone of the emission color can be controlled by changing the kind and amount of the dopant.

《Hole transport layer》
The hole transport layer is made of a material having a function of transporting holes, and 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 is not particularly limited, and is conventionally used as a hole charge injection / transport material in an optical transmission material or a well-known material used for a hole injection layer or a hole transport layer of an EL element. Any one can be selected and used.

  The hole transport material has one of hole injection or transport and electron barrier properties, and may be either organic or inorganic. 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, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbenes Derivatives, silazane derivatives, aniline copolymers, conductive polymer oligomers, particularly thiophene oligomers, and the like can be given.

  As the hole transport 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 more described in US Pat. No. 5,061,569 Having a condensed aromatic ring of, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-308 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 88 are linked in a starburst type ( MTDATA) and the like.

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

  In addition, 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.

  In the present invention, the hole transport material of the hole transport layer preferably has a fluorescence maximum wavelength at 415 nm or less. That is, the hole transport material is preferably a compound that has a hole transport ability, prevents the emission of light from becoming longer, and has a high Tg.

  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, an ink jet method, or an LB method. Although there is no restriction | limiting in particular about the film thickness of a positive hole transport layer, Usually, it is about 5-5000 nm. The hole transport layer may have a single layer structure composed 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, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

  Conventionally, in the case of a single-layer electron transport layer and a plurality of layers, the following materials are used as the electron transport material (also serving as a hole blocking material) used for the electron transport layer adjacent to the cathode side with respect to the light emitting layer. Are known.

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

  Examples of materials used for this electron transport layer (hereinafter referred to as electron transport materials) include heterocyclic tetracarboxylic acid anhydrides such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, carbodiimides, Examples include fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, and oxadiazole derivatives. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the 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 an electron transport material.

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

  In addition, metal complexes of 8-quinolinol derivatives 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), etc., and the central metals of these metal complexes are In, Mg, Cu Metal complexes replaced with Ca, Sn, Ga, or Pb can also be used as electron transport materials. In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transport material. In addition, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transport material, and similarly to the hole injection layer and the hole transport layer, inorganic such as n-type-Si and n-type-SiC. A semiconductor can also be used as an electron transport material.

  It is preferable that the preferable compound used for an electron carrying layer has a fluorescence maximum wavelength in 415 nm or less. That is, the compound used for the electron transport layer is preferably a compound that has an electron transport ability, prevents emission of longer wavelengths, and has a high Tg.

<< Substrate (also referred to as substrate, substrate, support, etc.) >>
The substrate of the organic EL device of the present invention is not particularly limited to the type of glass, plastic, etc., and is not particularly limited as long as it is transparent. Examples of substrates that are preferably used include glass, quartz, A light transmissive resin film can be mentioned. A particularly preferable substrate is a resin film that can give flexibility to the organic EL element.

  Examples of the resin film include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose triacetate. Examples thereof include films made of (TAC), cellulose acetate propionate (CAP) and the like.

  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 EL device of the present invention is preferably 1% or more, more preferably 2% 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 sent to the organic EL element × 100.

  Further, a hue improving filter such as a color filter may be used in combination.

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

  First, a thin film made of a desired electrode material, for example, an anode material is formed on a suitable substrate by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 10 nm to 200 nm, thereby producing an anode. To do. Next, an organic compound thin film 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 element materials, is formed thereon.

As described above, there are spin coating methods, casting methods, ink jet methods, vapor deposition methods, printing methods, and the like as methods for thinning the organic compound thin films, but it is easy to obtain a uniform film and pinholes are not easily generated. In view of the above, the vacuum deposition method or the spin coating method is particularly preferable. Further, different film forming methods may be applied for each layer. When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 to 450 ° C., a vacuum degree of 10 ⁻⁶ Pa to 10 ⁻² Pa, a vapor deposition rate of 0. It is desirable to select appropriately within the range of 01 nm to 50 nm / second, substrate temperature of −50 ° C. to 300 ° C., and film thickness of 0.1 nm to 5 μm.

  After forming these layers, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably in the range of 50 nm to 200 nm, and a cathode is provided. Thus, a desired organic EL element can be obtained. The organic EL element is preferably produced from the hole injection layer to the cathode consistently by a single evacuation, but may be taken out halfway and subjected to different film forming methods. At that time, it is necessary to consider that the work is performed in a dry inert gas atmosphere.

  The multicolor display device of the present invention is provided with a shadow mask only at the time of forming a light emitting layer, and the other layers are common, so that patterning of the shadow mask or the like is unnecessary, and the evaporation method, the casting method, the spin coating method, the ink jet method on one side. A film can be formed by a printing method or the like.

  When patterning is performed only on the light-emitting layer, the method is not limited, but a vapor deposition method, an inkjet method, and a printing method are preferable. In the case of using a vapor deposition method, patterning using a shadow mask is preferable.

  In addition, it is also possible to reverse the production order and produce 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 multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Further, even when a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The alternating current waveform to be applied may be arbitrary.

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

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

  Light sources include home lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. For example, but not limited to.

  Further, the organic EL element according to the present invention may be used as an organic EL element having a resonator structure.

  Examples of the purpose of use of the organic EL element having such a resonator structure include a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processor, and a light source of an optical sensor. Not. Moreover, you may use for the said use by making a laser oscillation.

<Display device>
The organic EL element of the present invention may be used as a kind of lamp such as an illumination or exposure light source, or a projection device that projects an image, or a display device that directly recognizes a still image or a moving image. (Display) may be used. 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 two or more organic EL elements of the present invention having different emission colors.

  An example of a display device composed of the organic EL element of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram illustrating an example of a display device including organic EL elements. It is a schematic diagram of a display such as a mobile phone that displays 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, and sends a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside. The pixels for each scanning line are converted into image data signals by the scanning signal. In response to this, light is sequentially emitted and image scanning is performed to display image information on the display unit A.

  FIG. 2 is a schematic diagram of the display unit A.

  The display unit A includes a wiring unit including a plurality of scanning lines 5 and data lines 6, a plurality of pixels 3 and the like on a substrate. The main members of the display unit A will be described below.

  In the figure, the light emitted from the pixel 3 is extracted in the direction of the white arrow (downward).

  The scanning lines 5 and the plurality of data lines 6 in 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 lattice shape and are connected to the pixels 3 at the orthogonal positions (details are shown in 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. Full color display is possible by appropriately arranging pixels in the red region, the green region, and the blue region that emit light on the same substrate.

  Next, the light emission process of the pixel will be described.

  FIG. 3 is a schematic diagram of a pixel.

  The pixel includes an organic EL element 10, a switching transistor 11, a driving transistor 12, a capacitor 13, and the like. 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. 3, an image data signal is applied from the control unit B to the drain of the switching transistor 11 through the data line 6. When a scanning signal is applied from the control unit B to the gate of the switching transistor 11 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 supplied to the capacitor 13 and the driving transistor 12. Is 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 drive of the drive transistor 12 is turned on. The drive transistor 12 has a drain connected to the power supply line 7 and a source connected to the electrode of the organic EL element 10, and the power supply line 7 connects 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 moved 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 if the driving of the switching transistor 11 is turned off, the capacitor 13 maintains 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. Until then, the light emission of the organic EL element 10 continues. When the scanning signal is next applied by 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 the switching transistor 11 and the drive transistor 12 that are active elements for the organic EL element 10 of each of the plurality of pixels, and the light emission of the organic EL element 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 by a multi-value image data signal having a plurality of gradation potentials, or on / off of a predetermined light emission amount by a binary image data signal. But you can.

  The potential of the capacitor 13 may be held continuously until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.

  In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.

  FIG. 4 is a schematic view of a passive matrix display device. In FIG. 4, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a lattice shape so as to face each other with the pixel 3 interposed therebetween.

  When the scanning signal of the scanning line 5 is applied by 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.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
<Synthesis of Compound 1, Samples 1A to 1D>
Under a nitrogen atmosphere, 4,4'-diamino-biphenyl 1 g, 2, 2 '- dibromo biphenyl 3.5 g, bis (dibenzylideneacetone) palladium 0.4 g, tri -tert- butylphosphine 0.6 ml, sodium -tert- butoxide 2.5 g was stirred at reflux temperature in 60 ml of toluene for 4 hours. After allowing the reaction mixture to cool, ethyl acetate, tetrahydrofuran and water were added, the organic layer was extracted, purified by silica gel column chromatography and recrystallized to give 4,4-dicarbazolylbiphenyl (Compound 1) as 1 0.8 g was obtained (yield 69%). The structure of the obtained compound was identified by NMR spectrum and mass spectrometry spectrum.

  Furthermore, from the results of high performance liquid chromatography analysis and liquid chromatography mass spectrometry of the sample and reaction intermediate obtained by sublimation purification of the obtained compound, impurities a and b were 0.24 in the obtained sample, respectively. It was found that 0.57% by mass of impurities having an amino group was contained in an amount of 0.33% by mass and 0.33% by mass. This compound is designated as sample 1A.

  Furthermore, synthesis was performed in the same manner, but after refining by repeating silica gel column chromatography, samples 1B, 1C and 1D obtained by recrystallization and sublimation purification were also analyzed in the same manner as sample 1A. Was found to contain 0.42 mass%, 1C 0.19 mass%, and 1D 0.08 mass% impurities having amino groups. That is, these samples all have the same main components but different impurity contents.

<Synthesis of Compound 2>
Under a nitrogen atmosphere, 2.5 g of 2,2 -bis (4-aminophenyl) hexafluoropropane, 4.9 g of 2,2′-dibromobiphenyl, 0.5 g of bis (dibenzylideneacetone) palladium, tri-tert-butylphosphine 0.9 ml of sodium-tert-butoxide (3.0 g) was stirred in refluxing temperature for 6 hours in 60 ml of toluene. After allowing the reaction mixture to cool, toluene and water are added to extract the organic layer, which is purified by silica gel column chromatography and recrystallized to give 2,2-bis (4-carbazolylphenyl) hexafluoropropane (compound 2 g of 2) was obtained (34% yield). The structure of the obtained compound was identified by NMR spectrum and mass spectrometry spectrum. Analysis was conducted in the same manner as in the case of Compound 1, and it was found that the sample obtained by sublimation purification of the obtained compound contained 0.56% by mass of impurities having an amino group. This compound is designated as sample 2A.

  Further, samples 2B, 2C, and 2D having different degrees of purification as in the case of Compound 1 were prepared and analyzed. Samples 2B and 2C contained 0.28% by mass and 0.09% by mass of impurities, respectively. Turned out to be. In sample 2D, the presence of impurities could not be detected, and it was found that the content of impurities was reduced to at least 0.01% by mass or less.

<Synthesis of Compounds 3-8 and Samples 3A-8D>
In addition, compounds 3 to 8, which are substituted carbazole compounds, were synthesized by a known synthesis method, and samples 3A to 8D were obtained by the same purification method as compounds 1 and 2.

<Measurement of impurity content in the deposited film>
Samples 1A, 1B, 1C, and 1D obtained by the above synthesis method were vacuum deposited on glass substrates, respectively, and this vacuum deposited film was dissolved in toluene. When this solution was analyzed by high performance liquid chromatography, it was found that the deposited film contained impurities having amino groups as follows.

Sample Impurity content (% by mass)
1A 0.59
1B 0.40
1C 0.13
1D not detected Similarly, the deposited films of Samples 2A, 2B, 2C, and 2D obtained by the above synthesis method were analyzed, and the results were as follows.

Sample Impurity content (% by mass)
2A 0.53
2B 0.16
2C not detected 2D not detected Example 2
<Production of organic EL element>
An organic EL element was produced as follows.

  After patterning on a substrate (NA-45 manufactured by NH Techno Glass Co., Ltd.) having a film of 150 nm of ITO (indium tin oxide) formed on a glass substrate of 100 mm × 100 mm × 1.1 mm as an anode, this ITO transparent electrode was provided. The transparent support substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.

This transparent support substrate is fixed to a substrate holder of a commercially available vacuum vapor deposition apparatus, while 200 mg of α-NPD is placed in a molybdenum resistance heating boat, and sample 1A synthesized by the above synthesis method is placed in another molybdenum resistance heating boat. 200 mg was put in, 200 mg of bathocuproin (BCP) was put in another resistance heating boat made of molybdenum, and 200 mg of Alq ₃ was put in another resistance heating boat made of molybdenum, and attached to a vacuum deposition apparatus.

Next, 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 deposited on the transparent support substrate at a deposition rate of 0.1 nm / sec. The hole transport layer was provided. Further, the heating boat containing the sample 1A of the compound 1 of the present invention was energized and heated, and was deposited on the hole transport layer at a deposition rate of 0.2 nm / sec to provide a light emitting layer having a thickness of 20 nm. . In addition, the substrate temperature at the time of vapor deposition was room temperature. In addition, an electron transport layer that also serves as a hole blocking function with a film thickness of 10 nm is provided by energizing and heating the heating boat containing BCP and depositing on the light emitting layer at a deposition rate of 0.1 nm / sec. It was. Furthermore, the heating boat containing Alq ₃ was further energized and heated, and was deposited on the electron transport layer at a deposition rate of 0.1 nm / sec to 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, and an organic EL element 2-1 was produced.

  The structure of the compound used above is shown below.

  Organic EL elements 2-2 to 2-4 were produced in the same manner except that sample 1A in organic EL element 2-1 was replaced with 1B, 1C, and 1D, respectively.

The light emission luminance (cd / m ² ) and light emission efficiency (lm / W) were measured when a 10 V DC voltage was applied at a temperature of 23 ° C. and a nitrogen atmosphere of the organic EL element 2-1. The light emission luminance was measured using CS-1000 (Minolta). Further, when it was driven at a constant current of 10 mA / cm ² , the time required for the initial luminance to drop to half of the original was measured, and this was used as the durability index as the half-life time.

  The same measurement was performed on the organic EL elements 2-2, 2-3, and 2-4. The results are shown in Table 1 as relative values with the result for an element having the highest content of an impurity having an amino group in the vapor deposition film among organic EL elements using the same compound as 100.

As apparent from Table 1, when the content of the impurity b having an amino group contained in the organic compound layer containing the substituted carbazole compound is less than 0.33% by mass, the organic EL device having the organic compound layer Performance is greatly improved. In particular, this effect is remarkable in terms of durability. In particular, an organic EL element having an organic compound layer in which the content of impurities is suppressed to 0.1% by mass or less has a significant improvement effect.

  In the same manner as the compounds 1A, 1B, 1C, and 1D and the organic EL elements 2-1 to 4 using these, the organic EL elements 2-5 to 32 obtained from the compounds 2 to 8 are included in the deposited film. The content of impurities having amino groups was evaluated. The results are shown in Table 2.

  As is apparent from Table 2, it was confirmed that suppressing the incorporation of impurities having an amino group in any compound has a significant improvement effect on the characteristics, particularly durability, of the organic EL device using the compound. It was done.

Reference example 3
About organic EL elements 3-1 to 16 produced in exactly the same manner as the elements except that BCP in the electron transport layer of organic EL element 2-3 of Example 2 was replaced with compounds 2 to 5 shown in Table 3, respectively. The light emission luminance, light emission efficiency, and half-life time (durability) were measured in the same manner as in Example 2. The obtained results are shown in Table 3 together with the element number, the compound used for the electron transport layer and the impurity content of the deposited film.

  As is clear from Table 3, for any compound, suppression of the incorporation of impurities having an amino group is a characteristic of the organic EL device even when the organic compound layer using the compound functions as an electron transport layer, In particular, it has a significant improvement effect on durability.

Reference example 4
In the production of the organic EL device 2-1 of Example 2, instead of vapor-depositing the sample 1A on the hole transport layer to form a light-emitting layer, a co-deposited film of 1A and the phosphorescent compound Ir-1 was emitted. As a layer, a phosphorescent organic EL element 4-1 was produced.

  When installing the light emitting layer, 100 mg of phosphorescent compound Ir-1 was put in a heating boat different from 1A, and each heating boat containing 1A and Ir-1 was energized, and 1A was 0.2 nm. / Sec, Ir-1 was co-deposited at a deposition rate of 0.012 nm / sec.

  Further, organic EL elements 4-2 to 32 using the compound of the present invention instead of sample 1A were prepared in the same manner, and the obtained phosphorescent organic EL element was subjected to emission luminance and light emission in the same manner as in Example 2. The results of evaluating the efficiency and durability are shown in Table 4.

  As is apparent from Table 4, even when a phosphorescent organic EL device is produced, mixing of impurities having an amino group is suppressed even when any compound is used as a host compound. It has a significant improvement effect on properties, especially durability.

Reference Example 5
A two-wavelength light-emitting organic EL element 5-1 was produced in the same manner as in the production of the phosphorescent organic EL element of Reference Example 4, except that Ir-6 and Ir-12 were used as phosphorescent dopants. At this time, the light emitting layer uses 1A as a host compound, Ir-6 and Ir-12 as phosphorescent dopants, and the deposition rates are 0.5 nm / sec, 0.005 nm / sec, and 0.02 nm / sec, respectively. And co-evaporated to form an organic compound layer having a thickness of 30 nm. The phosphorescence emission of Ir-6 is red and the phosphorescence emission of Ir-12 is blue. Therefore, the emission from the organic EL element has two emission maximum wavelengths, and is white for human vision. It is recognized as luminescence.

  In the same manner, phosphorescent white light emitting organic EL elements 5-2 to 5-16 were produced using the compounds shown in Table 5 instead of 1A as the host compound, and light emission was performed in the same manner as in Example 2. Luminance, luminous efficiency and durability were evaluated. The results are shown in Table 5.

  As is apparent from the results in Table 5, even when a phosphorescent white light emitting organic EL device is produced, it is possible to suppress the incorporation of impurities having an amino group even when any compound is used as a host compound. This brings about a remarkable improvement effect on the characteristics of the EL element, particularly the durability.

Example 6
Red, green, and blue light emitting organic EL devices prepared with Ir-6, Ir-1, and Ir-12, respectively, as phosphorescent dopants by the same method as in Example 2, were prepared, and these were juxtaposed on the same substrate. The active matrix type full-color display device shown in FIG. 1 was produced. FIG. 2 shows only a schematic diagram of the display portion A of the produced full-color display device. That is, a wiring portion including a plurality of scanning lines 5 and data lines 6 and a plurality of juxtaposed pixels 3 (light emission color is a red region pixel, a green region pixel, a blue region pixel, etc.) on the same substrate. Each of the scanning lines 5 and the plurality of data lines 6 in the wiring portion is made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a lattice shape and are connected to the pixels 3 at the orthogonal positions (details). Is not shown).

  The plurality of pixels 3 are driven by an active matrix system provided with an organic EL element corresponding to each emission color, a switching transistor as an active element, and a driving transistor, 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. In this way, full-color display is possible by appropriately juxtaposing the red, green, and blue pixels.

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

It is the schematic diagram which showed an example of the display apparatus comprised from an organic EL element. 4 is a schematic diagram of a display unit A. FIG. It is a schematic diagram of a pixel. It is a schematic diagram of the display apparatus by a passive matrix system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Display 3 Pixel 5 Scan line 6 Data line 7 Power supply line 10 Organic EL element 11 Switching transistor 12 Drive transistor 13 Capacitor A Display part B Control part

Claims (7)

In an organic electroluminescence device having at least one organic layer on a substrate,
When synthesizing a carbazole derivative represented by the following general formula (1) obtained by the condensation heterocycle formation reaction of 2,2′-dihalogeno-biphenyl and an amine and the compound represented by the general formula (1) The organic layer contains a compound represented by the following general formula (2) formed by bonding an amino group to a structural portion bonded to the carbazole ring which is a reaction intermediate compound of the general formula in the organic layer. (2) content of the represented Ru compound is organic electroluminescent device you and less than 0.33 wt%.

[Wherein, m represents an integer of 1 to 6, A represents a monovalent organic group when m = 1, and represents an m-valent linking group when m is not 1. R ₁ and R ₂ represent substituents, and n 1 and n 2 represent an integer of 0 to 4. ]

[Wherein, A, R ₁ , R ₂ , n1, and n2 have the same meanings as in general formula (1). X represents a bromine atom or an iodine atom, m1, m2 and m3 are integers from 0 to 6, the sum of m1, m2 and m3 is an integer from 1 to 6, and both m2 and m3 are 0. There is no. ] The content rate in the said organic layer of the compound represented by the said General formula (2) is less than 0.1 mass%, The organic electroluminescent element of Claim 1 characterized by the above-mentioned. 3. The organic electroluminescent element according to claim 1, wherein light emitted when an electric field is applied to the organic electroluminescent element includes phosphorescent light emission. 4. The organic electroluminescence device according to any one of claims 1 to 3, wherein light emission generated when an electric field is applied to the organic electroluminescence device emits white light. A display device comprising the organic electroluminescence element according to claim 1. An illuminating device comprising the organic electroluminescence element according to claim 1. The display device according to claim 5, comprising a lighting device according to claim 6 and a liquid crystal element as display means.

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