JP2007221028A - Organic electroluminescence element, display, and illumination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescence element having an excellent power efficiency and excellent driving resistance, and to provide a display and an illumination device. <P>SOLUTION: The organic electroluminescence element includes a luminescent layer and an electronic transport layer composed of an organic compound between opposing positive and negative electrodes. A thin layer with the thickness of not more than 3 nm is formed of only metal or metal salt including elements with the work function of not more than 2.9 eV, and is formed in an area interposed between the luminescent layer and the negative electrode and also at a position which contacts neither the luminescent layer nor the negative electrode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence element, a display device using the same, and an illumination device.

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

  An organic EL 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 (excitons) are generated by injecting electrons and holes into the light-emitting layer and recombining them. The device emits light using the emission of light (fluorescence / phosphorescence) when the exciton is deactivated, and can emit light at a voltage of about several V to several tens of V, and is self-luminous. Therefore, it has a wide viewing angle, high visibility, and since it is a thin-film type complete solid-state device, it has attracted attention from the viewpoints of space saving and portability.

  Another major feature of the organic EL element is that it is a surface light source, unlike main light sources that have been conventionally used in practice, such as light-emitting diodes and cold-cathode tubes. Applications that can make effective use of this characteristic include illumination light sources and backlights for various displays. In particular, it can be suitably used as a backlight of a liquid crystal full-color display whose demand has been increasing in recent years.

  In recent years, since organic EL elements with higher luminance can be obtained, phosphorescent materials have been developed in recent years (see, for example, Non-Patent Documents 1 to 3 and Patent Document 1). This is because the emission from the conventional phosphor is emission from the excited singlet, and the generation ratio of the singlet exciton and triplet exciton is 1: 3, so the generation probability of the luminescent excited species is 25%. On the other hand, in the case of a phosphorescent material using light emission from an excited triplet, the upper limit of internal quantum efficiency is 100% due to the exciton generation ratio and internal conversion from singlet excitons to triplet excitons. Therefore, in principle, the luminous efficiency is up to four times that of a fluorescent material.

  In phosphorescent organic electroluminescence devices, it is known that a hole blocking layer is preferably provided between the light emitting layer and the cathode in order to increase the light emission efficiency.

  However, when a hole blocking layer is provided, the driving voltage increases for the following reasons, and in some cases, the driving voltage becomes higher than the increase in luminous efficiency, which may be disadvantageous in terms of power efficiency. have.

On the other hand, a technique for doping an electron transport layer with a low work function metal is known as means for improving power efficiency. Although there is a description of an organic electroluminescence device having an electron transport layer made of an organic compound and a low work function metal (see, for example, Patent Documents 2 and 3), doping is performed so that the metal distribution in the electron transport layer is uniform. Has been. An organic electroluminescence device having a layer doped with an organic compound and a metal oxide or metal salt at the interface with the cathode is disclosed (see, for example, Patent Document 4), but is not in contact with the cathode of the present invention. There is no description suggesting the effect of having a metal layer.
US Pat. No. 6,097,147 WO2005 / 109543 specification Japanese Patent No. 3266573 JP-A-10-270172 M.M. A. Baldo et al. , Nature, 395, 151-154 (1998) M.M. A. Baldo et al. , Nature, 403, 17, 750-753 (2000) B. W. D'andrade et al. , Advanced Materials, Vol. 14, pp. 147-151 (2002)

  An object of the present invention is to provide an organic electroluminescence element, a display device, and a lighting device that are excellent in power efficiency and excellent in driving durability.

  The above object of the present invention can be achieved by the following configuration.

  1. In an organic electroluminescence device having a light emitting layer composed of an organic compound and an electron transport layer between an anode and a cathode facing each other, the region sandwiched between the light emitting layer and the cathode, and the light emitting layer An organic electroluminescence device, wherein a thin layer having a thickness of 3 nm or less of only a metal or a metal salt made of an element having a work function of 2.9 eV or less is formed at a position not in contact with the cathode.

  2. 2. The organic electroluminescent element according to 1 above, wherein the electron transport layer has a thin layer made of only the metal or metal salt.

  3. 3. The organic electroluminescence device according to 2 above, wherein the electron transport layer has a layer made of a metal or metal salt composed of an element having a work function of 2.9 eV or less and an organic compound.

  4). 4. The organic electroluminescence device as described in 2 or 3 above, wherein the triplet energy of the organic compound contained in the electron transport layer is 3 to 4 eV.

  5. 5. The organic electroluminescence device according to any one of 1 to 4, wherein the metal or metal salt is Cs or a Cs compound.

  6). The organic electroluminescent element of any one of said 1-5 is used, The display apparatus characterized by the above-mentioned.

  7). The organic electroluminescent element of any one of said 1-5 is used, The illuminating device characterized by the above-mentioned.

  According to the present invention, an organic electroluminescence element, a display device, and a lighting device that are excellent in power efficiency and excellent in driving durability can be provided.

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

<< Organic EL element >>
The organic EL element of the present invention will be described.

  Although the preferable specific example of the layer structure of the organic EL element of this invention is shown below, this invention is not limited to these.

(I) Anode / light emitting layer unit / electron transport layer / cathode (ii) Anode / hole transport layer / light emitting layer unit / electron transport layer / cathode (iii) Anode / hole transport layer / light emitting layer unit / hole blocking Layer / C / cathode (iv) anode / hole transport layer / light emitting layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) anode / anode buffer layer / hole transport layer / light emitting layer unit / Hole blocking layer / electron transport layer / cathode buffer layer / cathode Here, the light emitting layer unit may include a plurality of light emitting layers or a single light emitting layer. When a plurality of light emitting layers are included, it is preferable to have a non-light emitting intermediate layer between the light emitting layers. The electron transport layer of the present invention may be composed of a plurality of layers.

<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 be the interface between the light emitting layer and the adjacent layer.

  In the present invention, the main light emitter contained in the light emitting layer is preferably a phosphorescent dopant.

  The main light emitter included in the light emitting layer refers to a light emitter that bears the largest part in the light emission intensity generated from the light emitting layer, and the light emitted by the main light emitter is preferably 50% or more of the light emission of the light emitting layer. .

  The total thickness of the light emitting layers in the present invention is preferably in the range of 2 to 100 nm, and more preferably 30 nm or less because a lower driving voltage can be obtained. In addition, the sum total of the film thickness of the light emitting layer said by this invention is a film thickness also including this intermediate | middle layer, when a nonluminous intermediate | middle layer exists between light emitting layers.

  When it has a some light emitting layer, it is preferable to adjust to the range of 2-50 nm as a film thickness of each light emitting layer, More preferably, it is adjusting to the range of 2-20 nm.

  For the production of the light-emitting layer, a light-emitting dopant or a host compound, which will be described later, is formed and formed by a known thinning method such as a vacuum deposition method, a spin coating method, a casting method, an LB method, or an ink-jet method. it can.

  In the present invention, a plurality of light emitting compounds may be mixed in each light emitting layer, and a phosphorescent dopant and a fluorescent light emitter may be mixed and used in the same light emitting layer.

  In the present invention, it is preferable that the light emitting layer contains a host compound and a light emitting dopant (also referred to as a light emitting dopant compound) and emits light from the dopant.

  As the host compound contained in the light emitting layer of the organic EL device of the present invention, a compound having a phosphorescence quantum yield of phosphorescence emission at room temperature (25 ° C.) of less than 0.1 is preferable. More preferably, the phosphorescence quantum yield is less than 0.01. Moreover, it is preferable that the mass ratio in the layer is 20% or more among the compounds contained in a light emitting layer.

  As the host compound, known host compounds may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient. Moreover, it becomes possible to mix different light emission by using multiple types of light emission dopants mentioned later, and, thereby, arbitrary luminescent colors can be obtained.

  The light emitting host used in the present invention may be a conventionally known low molecular compound or a high molecular compound having a repeating unit, and a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (evaporation polymerizable light emitting host). )But it is good.

  As the known host compound, a compound that has a hole transporting ability and an electron transporting ability, prevents the emission of light from being increased in wavelength, and has a high Tg (glass transition temperature) is preferable. Here, the glass transition point (Tg) is a value obtained by a method based on JIS-K-7121 using DSC (Differential Scanning Colorimetry).

  Specific examples of known host compounds include compounds described in the following documents. For example, Japanese Patent Application Laid-Open Nos. 2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860 Gazette, 2002-334787 gazette, 2002-15871 gazette, 2002-334788 gazette, 2002-43056 gazette, 2002-334789 gazette, 2002-75645 gazette, 2002-338579 gazette. No. 2002-105445, No. 2002-343568, No. 2002-141173, No. 2002-352957, No. 2002-203683, No. 2002-363227, No. 2002-231453. No. 2003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-286061, No. 2002-280183, No. 2002-299060. 2002-302516, 2002-305083, 2002-305084, 2002-308837, and the like.

  Next, the light emitting dopant according to the present invention will be described.

  As the light-emitting dopant according to the present invention, a fluorescent compound or a phosphorescent dopant (also referred to as a phosphorescent compound or a phosphorescent compound) is used.

  The phosphorescent dopant according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, it is a compound that emits phosphorescence at room temperature (25 ° C.). Although defined as being a compound of 01 or more, the preferred phosphorescence quantum yield is 0.1 or more.

  The phosphorescent 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 emission dopant according to the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. That's fine.

  There are two types of light emission of the phosphorescent dopant in principle. One is the recombination of carriers on the host compound to which carriers are transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent dopant. Energy transfer type to obtain light emission from the phosphorescent light emitting dopant, and the other is that the phosphorescent light emitting dopant becomes a carrier trap, carrier recombination occurs on the phosphorescent light emitting dopant, and light emission from the phosphorescent light emitting dopant is obtained. Although it is a trap type, in any case, the excited state energy of the phosphorescent dopant is required to be lower than the excited state energy of the host compound.

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

  The phosphorescent dopant according to the present invention is preferably a complex compound containing a group 8-10 metal in the periodic table of elements, more preferably an iridium compound, an osmium compound, or a platinum compound (platinum complex compound). Rare earth complexes, most preferably iridium compounds.

  Although the specific example of the compound used as a phosphorescence emission dopant below is shown, this invention is not limited to these. These compounds are described, for example, in Inorg. Chem. 40, 1704-1711, and the like.

  A fluorescent substance can also be used for the organic electroluminescent element of the present invention. Representative examples of fluorescent emitters (fluorescent dopants) 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.

  Conventionally known dopants can also be used in the present invention. For example, International Publication No. 00/70655 pamphlet, JP-A Nos. 2002-280178, 2001-181616, 2002-280179, 2001 181617, 2002-280180, 2001-247859, 2002-299060, 2001-313178, 2002-302671, 2001-345183, 2002. No. 324679, International Publication No. 02/15645, JP 2002-332291 A, 2002-50484, 2002-332292, 2002-83684, JP 2002-540572, JP 2 No. 02-117978, No. 2002-338588, No. 2002-170684, No. 2002-352960, Pamphlet of International Publication No. 01/93642, JP 2002-50483, No. 2002-1000047. No. 2002-173684, No. 2002-359082, No. 2002-17584, No. 2002-363552, No. 2002-184582, No. 2003-7469, No. 2002-525808. JP-A 2003-7471, JP-T 2002-525833, JP-A 2003-31366, JP-A 2002-226495, JP-A 2002-234894, JP-A 2002-2335076, JP-A 2002-24175 Gazette, 2001-319779, 2001-319780, 2002-62824, 2002-1000047, 2002-203679, 2002-343572, 2002-203678. A gazette etc. are mentioned.

  A non-light emitting intermediate layer (also referred to as an undoped region or the like) used in the present invention will be described.

  The non-light emitting intermediate layer is a layer provided between the light emitting layers in the case of having a plurality of light emitting layers.

  The film thickness of the non-light emitting intermediate layer is preferably in the range of 1 to 20 nm, and further in the range of 3 to 10 nm suppresses interaction such as energy transfer between adjacent light emitting layers, and the current of the device This is preferable because a large load is not applied to the voltage characteristics.

  The material used for the non-light emitting intermediate layer may be the same as or different from the host compound of the light emitting layer, but may be the same as the host material of at least one of the adjacent light emitting layers. preferable.

  The non-light-emitting intermediate layer may contain a non-light-emitting layer, a compound common to each light-emitting layer (for example, a host compound), and each common host material (where a common host material is used) In the case where the physicochemical characteristics such as phosphorescence emission energy and glass transition point are the same, or the molecular structure of the host compound is the same, etc.) The barrier is reduced, and the effect of easily maintaining the injection balance of holes and electrons even when the voltage (current) is changed can be obtained. Furthermore, by using a host material having the same physical characteristics or the same molecular structure as the host compound contained in each light-emitting layer in the undoped light-emitting layer, device fabrication, which is a major problem in conventional organic EL device fabrication, is achieved. Complexity can also be eliminated.

  In the organic EL device of the present invention, since the host material is responsible for carrier transport, a material having carrier transport capability is preferable. Carrier mobility is used as a physical property representing carrier transport ability, but the carrier mobility of an organic material generally depends on the electric field strength. Since a material having a high electric field strength dependency easily breaks the balance between injection and transport of holes and electrons, it is preferable to use a material having a low electric field strength dependency of mobility for the intermediate layer material and the host material.

  On the other hand, in order to optimally adjust the injection balance of holes and electrons, it is also preferable that the non-light emitting intermediate layer functions as a blocking layer described later, that is, a hole blocking layer and an electron blocking layer. It is done.

<< 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, it exists between the anode and the light emitting layer or the hole transport layer and between the cathode and the light emitting layer or the electron transport layer. May be.

  An injection layer is a layer provided between an electrode and an organic layer in order to reduce drive voltage and improve light emission luminance. “Organic EL element and its forefront of industrialization (issued by NTT Corporation on November 30, 1998) 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 the film thickness is preferably in the range of 0.1 nm to 5 μm although it depends on the material.

<Blocking layer: hole blocking layer, electron blocking layer>
The blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film as described above. For example, it is described in JP-A Nos. 11-204258, 11-204359, and “Organic EL elements and their forefront of industrialization” (issued by NTT, Inc. on November 30, 1998). There is a hole blocking (hole blocking) layer.

  The hole blocking layer has a function of an electron transport layer in a broad sense, and is composed of a hole blocking material that has a function of transporting electrons and has a very small ability to transport holes, and transports holes while transporting electrons. By blocking this, the recombination probability of electrons and holes can be improved. Moreover, the structure of the electron carrying layer mentioned later can be used as a hole-blocking layer concerning this invention as needed.

  The hole blocking layer of the organic EL device of the present invention is preferably provided adjacent to the light emitting layer.

  The organic hole blocking material used for the hole blocking layer of the present invention has a triplet transition energy of 2.8 eV or more.

  The hole blocking layer of the present invention may contain a metal atom or metal ion having a work function of 2.9 eV or less. The metal atom or metal ion used in the present invention is preferably Cs or Cs ion.

  In the case of containing the metal or metal ion, a triplet transition equal to or more than the triplet transition energy of the light emitting layer host compound between the light emitting layer and the hole blocking layer containing the metal or metal ion. It is preferable to have an intermediate layer made of a compound having energy. The thickness of the intermediate layer is 5 nm or less, and preferably 3 nm or less. By having the intermediate layer, the drive life characteristics of the element are improved.

  The electron blocking layer has a function of a hole transport layer in a broad sense, and is made of a material that has a function of transporting holes and has an extremely small ability to transport electrons, and blocks electrons while transporting holes. Thus, the probability of recombination of electrons and holes can be improved. Moreover, the structure of the positive hole transport layer mentioned later can be used as an electron blocking layer as needed. The film thickness of the hole blocking layer and the electron transport layer according to the present invention is preferably 3 to 100 nm, and more preferably 5 to 30 nm.

《Hole transport layer》
The hole transport layer is made of a hole transport 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 has any 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, Examples thereof include stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

  The above-mentioned materials can be used as the hole transport material, 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 also two of those described in US Pat. No. 5,061,569. Having a condensed aromatic ring in the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-3086 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 8 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.

  JP-A-11-251067, J. Org. Huang et. al. A so-called p-type hole transport material described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, it is preferable to use these materials because a light-emitting element with higher efficiency can be obtained.

  The hole transport layer can be formed by thinning the hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. it can. Although there is no restriction | limiting in particular about the film thickness of a positive hole transport layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

  Alternatively, a hole transport layer having a high p property doped with impurities can be used. Examples thereof include JP-A-4-297076, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

  In the present invention, it is preferable to use a hole transport layer having such a high p property because a device with lower power consumption can be produced.

《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 electron transport layer and a plurality of layers, an electron transport material (also serving as a hole blocking material) used for an electron transport layer adjacent to the light emitting layer on the cathode side is injected from the cathode. As long as it has a function of transferring electrons to the light-emitting layer, any material can be selected and used from among conventionally known compounds. For example, nitro-substituted fluorene derivatives, diphenylquinone derivatives Thiopyrandioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives and the like. 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), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material. 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 transporting material. Further, the distyrylpyrazine derivatives exemplified as the material of the light emitting layer can also be used as the electron transport material, and inorganic semiconductors such as n-type-Si and n-type-SiC can be used as well as the hole injection layer and the hole transport layer. It can be used as an electron transport material.

  The electron transport layer can be formed by thinning the electron transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. Although there is no restriction | limiting in particular about the film thickness of an electron carrying layer, Usually, 5 nm-about 5 micrometers, Preferably it is 5-200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials.

  Further, an electron transport layer having a high n property doped with impurities can also be used. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

  In the present invention, it is preferable to use an electron transport layer having such a high n property because an element with lower power consumption can be manufactured.

  In the present invention, the electron transport layer preferably contains an organic compound and a metal or metal salt composed of an element having a work function of 2.9 eV or less. More preferably, the metal or metal salt compound is a Cs or Cs salt compound. In the electron transport layer containing a metal or metal salt compound, the triplet energy of the organic compound is preferably 3 eV or more.

  In the present invention, in the organic compound in the region sandwiched between the light emitting layer and the cathode, the thickness of 5 nm comprising only the metal or metal salt composed of an element having a work function of 2.9 eV or less at a position not in contact with the light emitting layer and the cathode. Although the following thin layers are formed, it is preferable that the layer forming portion is in the electron transport layer.

  When the thickness is 3 nm or more, unexpected side effects such as light reflection and light scattering on the thin layer surface occur, and in the case of a metal salt compound, an increase in voltage is undesirable.

  When the thin layer consisting only of the metal or metal salt is in contact with the cathode, it is the same mode as the cathode buffer layer and does not exhibit a new effect.

  When the thin layer consisting only of the metal or metal salt is in contact with the light emitting layer, it contributes to the improvement of power efficiency, but the deterioration in driving durability is extremely undesirable.

  In the present invention, the metal or metal salt compound is preferably Cs or a Cs salt compound.

  In the present invention, it can be preferably used in combination with the cathode buffer layer.

《Support substrate》
There are no particular limitations on the type of glass, plastic, etc., as the support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) according to the organic EL device of the present invention. It may be. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of giving flexibility to the organic EL element.

  Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), Cellulose esters such as cellulose acetate phthalate (TAC) and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfones Cycloolefin resins such as polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylate, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Can be mentioned.

An inorganic or organic film or a hybrid film of both may be formed on the surface of the resin film, and the water vapor permeability measured by a method in accordance with JIS K 7129-1992 is 0.01 g / m ^2. The film is preferably a barrier film of day · atm (1 atm is 1.01325 × 10 ⁵ Pa) or less, and the oxygen permeability measured by a method based on JIS K 7126-1992 is 10 ^−3. g / m ² / day or less, preferably water vapor permeability is 10 ^-3 g / m ² / day or less of the high barrier film, wherein the water vapor transmission rate, also oxygen permeability any 10 ^-5 g / More preferably, it is not more than m ² / day.

  As a material for forming the barrier film, any material may be used as long as it has a function of suppressing entry of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and layers made of organic materials. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.

<Method for forming barrier film>
The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, the sputtering method, the reactive sputtering method, the molecular beam epitaxy method, the cluster ion beam method, the ion plating method, the plasma polymerization method, the atmospheric pressure plasma A polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used, but an atmospheric pressure plasma polymerization method as described in JP-A-2004-68143 is particularly preferable.

  Examples of the opaque support substrate include metal plates / films such as aluminum and stainless steel, opaque resin substrates, ceramic substrates, and the like.

<Sealing>
Examples of the sealing means used for sealing the organic EL element of the present invention include a method of bonding a sealing member, an electrode, and a support substrate with an adhesive.

  The sealing member may be disposed so as to cover the display area of the organic EL element, and may be concave or flat. Moreover, transparency and electrical insulation are not particularly limited.

  Specifically, a glass plate, a polymer plate, a film, a metal plate, a film, etc. are mentioned. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, a polymer film and a metal film can be preferably used because the element can be thinned. Furthermore, the polymer film preferably has an oxygen permeability of 10 ⁻³ g / m ² / day or less and a water vapor permeability of 10 ⁻³ g / m ² / day or less. The water vapor permeability and oxygen permeability are more preferably 10 ⁻⁵ g / m ² / day or less.

  For processing the sealing member into a concave shape, sandblasting, chemical etching, or the like is used. Specific examples of the adhesive include photocuring and thermosetting adhesives having reactive vinyl groups such as acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylates. be able to. Moreover, heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.

  In addition, since an organic EL element may deteriorate by heat processing, what can be adhesive-hardened from room temperature to 80 degreeC is preferable. A desiccant may be dispersed in the adhesive. Application | coating of the adhesive agent to a sealing part may use commercially available dispenser, and may print it like screen printing.

  In addition, it is also preferable to coat the electrode and the organic layer on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and form an inorganic or organic layer in contact with the support substrate to form a sealing film. it can. In this case, the material for forming the film may be any material that has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like may be used. it can. Furthermore, in order to improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials. The method for forming these films is not particularly limited. For example, vacuum deposition, sputtering, reactive sputtering, molecular beam epitaxy, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure A plasma polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

  In the gap between the sealing member and the display area of the organic EL element, it is preferable to inject an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil in the gas phase and the liquid phase. . A vacuum can also be used. Moreover, a hygroscopic compound can also be enclosed inside.

  Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide) and sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Etc.), metal halides (eg calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide etc.), perchloric acids (eg perchloric acid) Barium, magnesium perchlorate, and the like), and anhydrous salts are preferably used in sulfates, metal halides, and perchloric acids.

《Protective film, protective plate》
In order to increase the mechanical strength of the element, a protective film or a protective plate may be provided on the outer side of the sealing film on the side facing the support substrate with the organic layer interposed therebetween or on the sealing film. In particular, when the sealing is performed by the sealing film, the mechanical strength is not necessarily high, and thus it is preferable to provide such a protective film and a protective plate. As a material that can be used for this, the same glass plate, polymer plate / film, metal plate / film, and the like used for the sealing can be used, but the polymer film is light and thin. Is preferably used.

"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, these electrode materials may be formed into a thin film 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 (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered. Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film forming methods, such as a printing system and a coating system, can also be used. When light emission is extracted from the anode, it is desirable that the transmittance be 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, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like. 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 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the emission luminance is advantageously improved.

  Moreover, after producing the said metal with a film thickness of 1-20 nm on a cathode, a transparent or semi-transparent cathode can be produced by producing the electroconductive transparent material quoted by description of the anode on it, By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

<< 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 / hole blocking layer / electron transport layer / cathode will be described.

  First, a thin film made of a desired electrode material, for example, a material for an anode is formed on a suitable support substrate by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 10 to 200 nm to produce an anode. . Next, an organic compound thin film of a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, and an electron transport layer, which are organic EL element materials, is formed thereon. A thin film layer of the metal or metal salt compound of the present invention is formed in the hole blocking layer or the electron transport layer at a position where it does not contact the light emitting layer and the cathode.

As a method for thinning the organic compound thin film, there are a vapor deposition method and a wet process (spin coating method, casting method, ink jet method, printing method) as described above, but it is easy to obtain a uniform film and a pinhole. From the point of being difficult to form, a vacuum deposition method, a spin coating method, an ink jet method, and a printing method are particularly preferable. Further, different film forming methods may be applied for each layer. When employing a vapor deposition method 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 degree of vacuum of 10 ⁻⁶ to 10 ⁻² Pa, and a vapor deposition rate of 0.01 to It is desirable to select appropriately within the range of 50 nm / second, substrate temperature −50 to 300 ° C., film thickness 0.1 nm to 5 μm, preferably 5 to 200 nm.

  After these layers are formed, 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 thickness of 1 μm or less, preferably in the range of 50 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.

  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 liquid crystal 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. An alternating voltage may be applied. The alternating current waveform to be applied may be arbitrary.

  An organic EL element generally emits light within a layer having a refractive index higher than that of air (refractive index of about 1.6 to 2.1) and can extract only about 15 to 20% of light generated in the light emitting layer. It has been said. This is because light incident on the interface (interface between the transparent substrate and air) at an angle θ greater than the critical angle causes total reflection and cannot be extracted outside the device, or between the transparent electrode or light emitting layer and the transparent substrate. This is because the light is totally reflected between the light and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the direction of the element side surface.

  As a method for improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate to prevent total reflection at the interface between the transparent substrate and the air (for example, US Pat. No. 4,774,435). ), A method of improving the efficiency by giving the substrate a light condensing property (for example, JP-A-63-314795), a method of forming a reflective surface on the side surface of the element (for example, JP-A-1-220394) Gazette), a method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the substrate and the light emitter (for example, Japanese Patent Application Laid-Open No. 62-172691), and a substrate between the substrate and the light emitter. A method of introducing a flat layer having a lower refractive index than that (for example, Japanese Patent Application Laid-Open No. 2001-202827), a diffraction grating between any one of the substrate, the transparent electrode layer and the light emitting layer (including between the substrate and the outside). Method of forming There is 1-283751 JP), and the like.

  In the present invention, these methods can be used in combination with the organic EL device of the present invention. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, transparent A method of forming a diffraction grating between any layers of the electrode layer and the light emitting layer (including between the substrate and the outside) can be suitably used. In the present invention, by combining these means, it is possible to obtain an element having higher luminance or durability.

  When a medium having a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the light extracted from the transparent electrode has a higher extraction efficiency to the outside as the refractive index of the medium is lower.

  Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and a fluorine-based polymer. Since the refractive index of the transparent substrate is generally about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less. Furthermore, it is preferable that it is 1.35 or less.

  The thickness of the low refractive index medium is preferably at least twice the wavelength in the medium. This is because the effect of the low-refractive index layer is reduced when the thickness of the low-refractive index medium is about the wavelength of light and the electromagnetic wave exuded by evanescent enters the substrate.

  The method of introducing a diffraction grating into an interface or any medium that causes total reflection is characterized by a high effect of improving light extraction efficiency. This method uses the property that the diffraction grating can change the direction of light to a specific direction different from refraction by so-called Bragg diffraction, such as first-order diffraction and second-order diffraction. Among them, light that cannot be emitted due to total reflection between layers, etc. is diffracted by introducing a diffraction grating into any layer or medium (in a transparent substrate or transparent electrode), and the light is emitted outside. I want to take it out.

  It is desirable that the diffraction grating to be introduced has a two-dimensional periodic refractive index. This is because light emitted from the light-emitting layer is randomly generated in all directions, so in a general one-dimensional diffraction grating having a periodic refractive index distribution only in a certain direction, only light traveling in a specific direction is diffracted. The light extraction efficiency does not increase so much. However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and light extraction efficiency is increased.

  The position where the diffraction grating is introduced may be in any one of the layers or in the medium (in the transparent substrate or the transparent electrode) as described above, but is preferably in the vicinity of the organic light emitting layer where light is generated.

  At this time, the period of the diffraction grating is preferably about 1/2 to 3 times the wavelength of light in the medium. The arrangement of the diffraction grating is preferably two-dimensionally repeated, such as a square lattice, a triangular lattice, or a honeycomb lattice.

  The organic EL device of the present invention is processed on the light extraction side of the support substrate to provide, for example, a structure on a microlens array, or in combination with a so-called condensing sheet, for example, with respect to a specific direction, for example, the device light emitting surface. By condensing in the front direction, the luminance in a specific direction can be increased.

  As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

  As the condensing sheet, for example, a sheet that has been put into practical use for an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the shape of the prism sheet, for example, the base material may be formed by forming a △ -shaped stripe having a vertex angle of 90 degrees and a pitch of 50 μm, or the vertex angle is rounded and the pitch is changed randomly. Other shapes may be used.

  Moreover, in order to control the light emission angle from a light emitting element, you may use together a light diffusing plate and a film with a condensing sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

<Application>
The organic EL element of the present invention can be used as a display device, a display, and various light emission sources. Examples of 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, and light sources for optical sensors. Although it is not limited to this, it can be effectively used particularly as a backlight of a liquid crystal liquid crystal display device combined with a color filter and a light source for illumination.

  When used as a backlight of a display in combination with a color filter, it is preferably used in combination with the light collecting sheet in order to further increase the luminance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.

Example 1
<< Production of Organic EL Element 1-1 >>
After patterning a support substrate in which 120 nm of ITO (indium tin oxide) was formed on a glass substrate having a thickness of 30 mm × 30 mm and a thickness of 0.7 mm as an anode, the transparent support substrate to which this ITO transparent electrode was attached was isopropyl alcohol. Was subjected to ultrasonic cleaning, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes. This transparent support substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus.

  Each of the vapor deposition crucibles in the vacuum vapor deposition apparatus was filled with the constituent material of each layer in an optimum amount for device fabrication. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.

Then, after reducing the vacuum to 4 × 10 ⁻⁴ Pa, the vapor deposition crucible containing m-MTDATA was energized and heated, and deposited on the transparent support substrate at a deposition rate of 0.1 nm / second. A hole injection layer was provided. Next, α-NPD was deposited in the same manner to provide a 30 nm hole transport layer. Subsequently, each light emitting layer and its intermediate | middle layer were provided in the following procedures.

  CBP and the compound (A-1) were co-evaporated at a deposition rate of 0.1 nm / second so that the film thickness ratio was 95: 5 to form a 30-nm green phosphorescent light-emitting layer.

  Next, 5 nm of BAlq is deposited at a deposition rate of 0.1 nm / second to form a hole blocking layer adjacent to the cathode side on the green light-emitting layer, and then 40 nm of BCP is deposited at a deposition rate of 0.1 nm / second to transport electrons. After providing the layer, LiF was deposited to 0.5 nm at a deposition rate of 0.05 nm / second to provide an electron injection layer.

  Furthermore, aluminum 110nm was vapor-deposited, the cathode was formed, and the organic EL element 1-1 was produced.

<< Production of Organic EL Element 1-2 >>
An organic EL element 1-2 was produced in the same manner as the organic EL element 1-1 except that the electron transport layer was changed as follows.

  BCP was deposited at a deposition rate of 0.1 nm / second to 20 nm, and then CsF was deposited at a deposition rate of 0.1 nm / second for 2 nm. Next, BCP was again evaporated at a deposition rate of 0.1 nm / second to 18 nm to form an electron transport layer having a thickness of 40 nm as a whole.

<< Evaluation of sealing process, current efficiency, and power efficiency of organic EL elements >>
The non-light emitting surface of each of the organic EL elements 1-1 to 1-2 is covered with a glass case (in addition, the sealing operation with the glass cover is a glove box under a nitrogen atmosphere (purity) without bringing the organic EL element into contact with the atmosphere. 99.999% or more in a high purity nitrogen gas atmosphere)). Next, the power efficiency of each organic EL element was evaluated using a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing). The evaluation results are shown in Table 1. In Table 1, the power efficiency is shown as a relative value with the power efficiency of the organic EL element 1-1 at 2 ° viewing angle front luminance of 300 cd / m ² as 100.

  The organic EL device of the present invention showed excellent performance in current efficiency and power efficiency.

Example 2
<< Preparation of Organic EL Element 2-1 >>
An organic EL element 2-1 was produced in the same manner as the organic EL element 1-1 in Example 1, except that the electron transport layer was changed as follows.

  BCP and CsF were deposited to a thickness of 80:20 at a deposition rate of 0.1 nm / second to 40 nm to provide an electron transport layer.

<< Production of Organic EL Element 2-2 >>
An organic EL element 2-2 was produced in the same manner as the organic EL element 1-1 except that the electron transport layer was changed as follows.

  BCP and CsF were deposited at a deposition rate of 0.1 nm / second to 20 nm so that the film thickness ratio was 80:20, and then CsF was deposited at a deposition rate of 0.1 nm / second for 2 nm. Next, BCP and CsF were again deposited at 18 nm at a deposition rate of 0.1 nm / second so that the film thickness ratio was 80:20, and an electron transport layer having a thickness of 40 nm was formed as a whole.

<< Production of Organic EL Element 2-3 >>
An organic EL element 2-3 was produced in the same manner as the organic EL element 1-1 except that the electron transport layer was changed as follows.

  Compound (A-2) and CsF were vapor-deposited at 40 nm at a vapor deposition rate of 0.1 nm / second so that the film thickness ratio was 80:20, and an electron transport layer was provided.

<< Production of Organic EL Element 2-4 >>
Organic EL element 2-4 was produced in the same manner as organic EL element 1-1 except that the electron transport layer was changed as described below.

  Compound (A-2) and CsF were deposited at a deposition rate of 0.1 nm / second to 20 nm so that the film thickness ratio was 80:20, and then CsF was deposited at a deposition rate of 0.1 nm / second for 2 nm. Next, the compound (A-2) and CsF were again vapor-deposited at a deposition rate of 0.1 nm / second for 18 nm so that the film thickness ratio was 80:20, and an electron transport layer having a thickness of 40 nm was formed as a whole.

<< Preparation of organic EL element 2-5 >>
An organic EL element 2-5 was produced in the same manner as the organic EL element 1-1 except that the electron transport layer was changed as follows.

  Compound (A-2) and CsF were deposited at a deposition rate of 0.1 nm / second to 20 nm so that the film thickness ratio was 80:20, and then CsF was deposited at a deposition rate of 0.1 nm / second for 5 nm. Next, the compound (A-2) and CsF were again evaporated at a deposition rate of 0.1 nm / second by 15 nm so that the film thickness ratio was 80:20, and an electron transport layer having a thickness of 40 nm was formed as a whole.

<< Preparation of organic EL element 2-6 >>
Organic EL element 2-6 was produced in the same manner as organic EL element 1-1 except that the electron transport layer was changed as described below.

  The compound (A-3) and CsF were deposited to a thickness ratio of 80:20 at a deposition rate of 0.1 nm / second to 20 nm, and then CsF was deposited to a thickness of 2 nm at a deposition rate of 0.1 nm / second. Next, the compound (A-3) and CsF were again vapor-deposited at a deposition rate of 0.1 nm / second for 18 nm so that the film thickness ratio was 80:20, and an electron transport layer having a thickness of 40 nm was formed as a whole.

  The triplet energy of BCP, compound (A-2), and compound (A-3) used in this example was the following value. BCP 2.6 eV, compound (A-2) 3.1 eV, compound (A-3) 3.1 eV.

<< Evaluation of sealing process, current efficiency, and power efficiency of organic EL elements >>
In the same manner as in Example 1, each non-light emitting surface of the organic EL elements 2-1 to 2-6 is covered with a glass case (in addition, the sealing operation with the glass cover is performed without bringing the organic EL element into contact with the atmosphere. This was performed in a glove box under a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more). Next, the power efficiency of each organic EL element was evaluated using a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing). The evaluation results are shown in Table 2. In Table 1, the power efficiency is shown as a relative value with the power efficiency of the organic EL element 2-1 at 2 ° viewing angle front luminance of 300 cd / m ² as 100.

  The organic EL device 2-2 of the present invention showed excellent performance in current efficiency and power efficiency.

  Further, the organic EL elements 2-4 and 2-6 of the present invention in which the triplet energy of the organic compound constituting the electron transport layer is 3 eV or more are 3Ev in the organic compound constituting the electron transport layer. Compared with the element 2-2 which does not satisfy the above, the performance is more excellent.

Example 3
<< Production of Organic EL Element 3-1 >>
An organic EL element 3-1 was produced in the same manner as the organic EL element 2-3 except that the hole blocking layer and the electron transport layer were changed as follows.

  After the formation of the light emitting layer, a hole blocking layer was formed by depositing CsF at a deposition rate of 0.1 nm / second at 2 nm and then depositing BAlq at a deposition rate of 0.1 nm / second at 5 nm. Compound (A-2) and CsF were vapor-deposited at 38 nm at a vapor deposition rate of 0.1 nm / second so as to have a film thickness ratio of 80:20 to form an electron transport layer.

<< Evaluation of sealing process, current efficiency, and power efficiency of organic EL elements >>
After performing the sealing process in the same manner as in Example 1, the power efficiency was evaluated in the same manner as in Example 1. Furthermore, the continuous drive characteristics at a 2 ° viewing angle front luminance of 300 cd / m ² were evaluated.

  Although the organic EL element 3-1 in which the CsF single vapor deposition layer was adjacent to the light emitting layer was superior in power efficiency to the comparative example 2-3, the driving life was short and overall was inferior. On the other hand, the element 2-4 of the present invention had a driving life equivalent to that of the element 2-3, and showed a comprehensively excellent performance.

Example 4
<< Preparation of Organic EL Element 4-1 >>
An organic EL element 4-1 was produced in the same manner as the organic EL element 2-4 except that the metal thin film layer in the electron transport layer was changed to Li 2 nm.

  When the power efficiency was determined in the same manner as in Example 2, the power efficiency of the organic EL element was higher than that of the element 2-3 in which the metal thin film layer was not provided in the electron transport layer, but CsF was used as the metal salt compound. It was inferior to the organic EL element 2-4 used.

Claims (7)

In an organic electroluminescence device having a light emitting layer composed of an organic compound and an electron transport layer between an anode and a cathode facing each other, the region sandwiched between the light emitting layer and the cathode, and the light emitting layer An organic electroluminescence device, wherein a thin layer having a thickness of 3 nm or less of only a metal or a metal salt made of an element having a work function of 2.9 eV or less is formed at a position not in contact with the cathode. The organic electroluminescence element according to claim 1, wherein the electron transport layer has a thin layer made of only the metal or metal salt. 3. The organic electroluminescence device according to claim 2, wherein the electron transport layer has a layer made of a metal or metal salt made of an element having a work function of 2.9 eV or less and an organic compound. The organic electroluminescence device according to claim 2 or 3, wherein the triplet energy of the organic compound contained in the electron transport layer is 3 to 4 eV. The organic electroluminescence device according to any one of claims 1 to 4, wherein the metal or metal salt is Cs or a Cs compound. The organic electroluminescent element of any one of Claims 1-5 is used, The display apparatus characterized by the above-mentioned. An illuminating device using the organic electroluminescent element according to claim 1.