JP2010177338A - Organic electroluminescent element, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which can be manufactured inexpensive wet process and is superior in light emission lifetime and high-temperature preservability, and to provide a method of manufacturing the same. <P>SOLUTION: The organic electroluminescent element includes an anode, a cathode, and a host/dopant emission type light-emitting layer held between them, and the light emitting layer has therein a dopant depletion region, which spreads from an interface between the light emitting layer and an adjacent layer to a range of 10 to 30% of a layer thickness of the entire light emitting layer, and the organic electroluminescent element is manufactured by one-time wet film formation process. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence element and a method for manufacturing the same. Specifically, the present invention relates to an organic electroluminescence element that has a long life, is excellent in high-temperature storage stability and can be produced at low cost, and a method for producing the same.

  As a light-emitting electronic device, there is an electroluminescence element (hereinafter, abbreviated as “ELD” as appropriate). As a constituent element of ELD, an inorganic electroluminescence element (hereinafter also referred to as “inorganic EL element”) and an organic electroluminescence element (hereinafter also referred to as “organic EL element”) can be given. Inorganic EL 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 injected by injecting electrons and holes into the light emitting layer and recombining them. ) And emits light by using light emission (fluorescence / phosphorescence) when the exciton is deactivated, and can emit light at a voltage of several V to several tens V, and further self-emission. Since it is a type, it has a wide viewing angle, high visibility, and since it is a thin-film type completely solid element, it has attracted attention from the viewpoints of space saving, portability, and the like.

  The organic electroluminescence element is also a major feature because it is a surface light source, unlike main light sources that have been put to practical use, such as light emitting diodes and cold cathode tubes. Applications that can effectively utilize this characteristic include illumination light sources and various display backlights. In particular, it is also suitable to be used as a backlight of a liquid crystal full color display whose demand has been increasing in recent years.

  Improvement of luminous efficiency is mentioned as a subject for putting an organic electroluminescent element into practical use as such a light source for illumination, or a backlight of a display. In order to improve the luminous efficiency, it is becoming common to incorporate a so-called host / dopant structure in which a part of the organic functional layer constituting the organic electroluminescence element is composed of a mixture of materials having different functions. is there.

  As a means for further improving the performance, a method for producing a light emitting layer has been developed in which the distribution of the dopant material of the light emitting layer is devised. For example, Patent Document 1 discloses a device having a concentration gradient in which the dopant material of the light-emitting layer continuously changes in the thickness direction, but clearly shows a means for continuously changing the concentration of the light-emitting dopant. This is only the control of the deposition rate in the vacuum deposition method, and cannot be said to be a proposal of means suitable for productivity. In Patent Document 2, a contrivance is made such that an intermediate layer made only of a host compound is formed in a hole transport layer or an electron transport layer, but only the vacuum deposition method is clearly shown as a means for preparing the intermediate layer. Therefore, it cannot be produced unless the intermediate layer and the light emitting layer are subjected to two film formation processes, and it cannot be said that the method is suitable for productivity.

  As a method for producing an organic electroluminescence element, there are a vapor deposition method, a wet process (spin coating method, casting method, ink jet method, spray method, printing method) and the like, but a vacuum process is not required and continuous production is simple. For this reason, in recent years, a manufacturing method in a wet process has attracted attention. For example, in Patent Document 3, a light emitting layer having a host / dopant structure has been devised to be manufactured in a wet process. It is generally known that the organic EL element does not exhibit sufficient performance in terms of element performance, particularly in terms of life, as compared with the vapor deposition type element.

Japanese Patent Laid-Open No. 2005-1000076 JP 2007-42875 A JP 2008-112875 A

  The present invention has been made in view of the above-described problems and circumstances, and a solution to the problem is to provide an organic electroluminescence element that can be produced by a low-cost wet process and that has excellent emission lifetime and high-temperature storage stability. And a method of manufacturing the same.

  The above-mentioned problem according to the present invention is solved by the following means.

  1. An organic electroluminescence device comprising an anode, a cathode, and a host / dopant-type light emitting layer sandwiched between them, wherein the light emitting layer is formed from the interface between the light emitting layer and the adjacent layer, and the entire light emitting layer An organic electroluminescence device having a dopant-deficient region in a range of 10 to 30% of the layer thickness in the light emitting layer and produced by a single wet film forming process.

  2. 2. The organic electroluminescence device according to 1 above, wherein the light emitting dopant of the light emitting layer is a phosphorescent compound.

  3. 3. The organic electroluminescence device according to 1 or 2 above, wherein the light emitting host compound of the light emitting layer has a molecular weight of 1500 or less.

  4). 4. The organic electroluminescence device according to any one of 1 to 3, wherein the adjacent layer is a hole transport layer.

  5. 4. The organic electroluminescent element according to any one of 1 to 3, wherein the adjacent layer is an electron transport layer.

  6). 6. The method for producing an organic electroluminescent element according to any one of 1 to 5, wherein the organic electroluminescent element comprises a step of producing a light emitting layer by a single wet film forming process using a solvent. Manufacturing method of electroluminescent element.

  By the above means of the present invention, it is possible to provide an organic electroluminescence device which can be produced by a low-cost wet process and which has an excellent emission lifetime and high temperature storage stability, and a method for producing the same.

  Although the reason why the light emission lifetime and high-temperature storage stability are improved is not clear with regard to the manifestation mechanism of the effects of the present invention, the host / dopant-type light-emitting layer emits dopant over time, and the adjacent layer It is considered that the stability of device performance is impaired by quenching in the light. By creating a dopant-deficient region, most of the dopant stays in the light-emitting layer even when dopant diffusion begins, and suppresses the diffusion and deterioration of the dopant to the adjacent layer, resulting in excellent emission lifetime and high-temperature storage stability It discovered that an organic EL element was obtained. In addition, when a layer such as a structure close to a deficient region or an intermediate layer is manufactured, it is necessary to form a film by a film forming process twice or more, or by a dry process such as vapor deposition. Since a light-emitting layer having a dopant-deficient region can be formed by the process, it is considered that an interface is not generated when a plurality of light-emitting layers are formed, and carrier traps are hardly generated. In addition, it has been clarified that accompanying effects such as improvement in production efficiency can be obtained by shortening the stroke.

The figure which shows an example of the organic EL element of this invention The figure which shows an example of the result of dynamic SIMS of the organic EL element of this invention

  The organic electroluminescent device of the present invention is an organic electroluminescent device comprising an anode, a cathode, and a host / dopant-type light emitting layer sandwiched between them, and the light emitting layer includes the light emitting layer and the light emitting layer. It has a dopant-deficient region in the light emitting layer ranging from 10 to 30% of the total thickness of the light emitting layer from the interface with the adjacent layer, and is produced by a single wet film forming process. To do.

  In the present application, the “host / dopant light-emitting layer” refers to a light-emitting layer containing a light-emitting host compound and a light-emitting dopant as a compound that contributes to light emission.

  As an embodiment of the present invention, from the viewpoint of the effect of the present invention, the light emitting dopant of the light emitting layer is preferably a phosphorescent compound. Moreover, it is preferable that the molecular weight of the light emitting host compound of the said light emitting layer is 1500 or less.

  In the present invention, the adjacent layer is preferably a hole transport layer, or the adjacent layer is preferably an electron transport layer.

  The method for producing the organic electroluminescent element of the present invention is preferably a production method having an embodiment having a step of producing a light emitting layer by a single wet film forming process using a solvent.

  Hereinafter, the present invention, its components, and modes for carrying out the invention will be described in detail.

≪Dopant deficient region≫
The light-emitting layer of the organic EL device of the present invention emits the dopant-deficient region ranging from 10 to 30%, preferably 10 to 20% of the total thickness of the light-emitting layer from the interface between the light-emitting layer and the adjacent layer. It is characterized by having in the layer.

  In the organic EL device of the present invention, a host / dopant-type light emitting layer produced by a wet process has a dopant-deficient region with respect to an adjacent layer, but the dopant-deficient region is included in a light-emitting layer other than the deficient region. It refers to a region of less than 50% with respect to the average doping concentration of the dopant, and includes a region where no dopant is present. The light emitting layer including the dopant-deficient region is manufactured through a single wet film formation process.

  There are several methods for measuring the dopant-deficient region. Secondary ion mass spectrometry (SIMS) is possible because the amount of element in the film can be analyzed with high sensitivity and the concentration change of the element in the depth direction can be tracked. Is preferably used. As for secondary ion mass spectrometry, for example, Japanese Society for Surface Science “Secondary ion mass spectrometry (Surface Science and Technology Selection)” (Maruzen) can be referred to.

In the secondary ion mass spectrometry, a sample surface is irradiated with an ion beam called primary ions under a high vacuum of about 10 ⁻⁸ Pa to perform sputtering. This is a method of analyzing elements present on the surface by mass spectrometry of secondary ions in the constituent particles released thereby. Although the surface is sputtered and scraped off, it is possible to analyze the change in element concentration from the surface to a depth of μm or more, although it is a destructive analysis.

The primary ion, e.g. Cs ^+, an In ^+, but Ga ⁺ or the like of the metal ionic species is preferred, whether employed which ion species are preferred used for different measurement target elements.

In the present invention, specifically, ADEPT 1010 manufactured by Physical Electronics is used, the primary ion species is Cs ⁺ , and the acceleration voltage of the primary ions is 2 kV. The distribution amounts of various elements in the depth direction in the organic EL element Was measured.

≪Adjacent layer≫
The adjacent layer refers to a layer having a function different from that of the light emitting layer adjacent to the host / dopant type light emitting layer, and the layer may be between the anode and the light emitting layer or between the cathode and the light emitting layer. The adjacent layer is not particularly limited, but the adjacent layer is preferably an electron transport layer or a hole transport layer in order to facilitate the movement of carriers to the light emitting layer.

≪Layer structure of organic EL element≫
Next, 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 / electron transport layer / cathode (ii) Anode / hole transport layer / light emitting layer / electron transport layer / cathode (iii) Anode / hole transport layer / light emitting layer / hole blocking layer / electron Transport layer / cathode (iv) anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) anode / anode buffer layer / hole transport layer / light emitting layer / hole Blocking layer / electron transport layer / cathode buffer layer / cathode Each component will be described below.

≪Luminescent layer≫
The light-emitting layer 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. May be an interface between the light emitting layer and the adjacent layer, but is preferably within the layer of the light emitting layer because of deactivation of excitons between layers.

  The thickness of the light emitting layer is not particularly limited, but from the viewpoint of the uniformity of the film to be formed, the application of unnecessary high voltage during light emission, and the improvement of the stability of the emission color with respect to the drive current. It is preferable to adjust to the range of 2-200 nm, More preferably, it adjusts to the range of 5-100 nm.

  The light-emitting layer of the organic EL device of the present invention is characterized by containing a light-emitting host compound and at least one light-emitting dopant, and has a thickness of 10 to 10 from the interface between the light-emitting layer and the adjacent layer. It is characterized by having a dopant-deficient region ranging from 30%, preferably 10-20%.

  When the light emitting layer according to the present invention was formed, the above-described improvement in the light emission life and improvement in the high temperature storage stability were observed. The reason for this is not clear, but when the light-emitting layer is formed by a wet process, the dopant diffuses to the adjacent layer over time due to heat or light emission due to the change in the morphology of the dry process and the film. While energy deactivation of the protons occurs and the emission lifetime is reduced, the amount of dopant in the region close to the adjacent layer is first reduced to suppress diffusion of the dopant into the adjacent layer and prevent exciton energy deactivation. It is presumed to be because of this. Further, since a light emitting layer having a dopant-deficient region can be formed by a wet process and a single film formation process, an accompanying effect such as excellent productivity can be considered.

  Hereinafter, a host compound (also referred to as a light-emitting host) and a light-emitting dopant (also referred to as a “light-emitting dopant compound”) included in the light-emitting layer will be described.

≪Luminescent host compound≫
A light-emitting host compound (also simply referred to as “host compound”) is a compound having a mass ratio of 20% or more in a light-emitting layer and phosphorescence at room temperature (25 ° C.). A compound having a phosphorescence quantum yield of luminescence of less than 0.1 is defined. The phosphorescence quantum yield is preferably 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 host compound 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 (polymerizable light emission). Host).

  As the known host compound that may be used in combination, a compound that has a hole transporting ability and an electron transporting ability, prevents the emission of light from becoming longer, and has a high Tg (glass transition temperature) is preferable. Specific examples of known host compounds include compounds described in the following documents.

  JP-A-2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445 gazette, 2002-343568 gazette, 2002-141173 gazette, 2002-352957 gazette, 2002-203683 gazette, 2002-363227 gazette, 2002-231453 gazette, No. 003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-286061, No. 2002-280183, No. 2002-299060, No. 2002. -302516, 2002-305083, 2002-305084, 2002-308837, and the like.

≪Luminescent dopant≫
As the light-emitting dopant (also simply referred to as “dopant”) according to the present invention, a fluorescent dopant (also referred to as a fluorescent compound), a phosphorescent dopant (phosphorescent material, phosphorescent compound, phosphorescent compound, etc.) However, from the viewpoint of obtaining an organic EL element with higher luminous efficiency, a light-emitting dopant (also simply referred to as “light-emitting material”) used in the light-emitting layer or light-emitting unit of the organic EL element. It is preferable to contain a phosphorescent dopant at the same time as containing the host compound.

  The phosphorescent 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 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.

≪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, 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. You may let them.

  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 made of a hole blocking material that has a function of transporting electrons and has a remarkably small ability to transport holes. The probability of recombination of electrons and holes can be improved by blocking. 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 according to the present invention is preferably provided adjacent to the light emitting layer.

  The hole blocking layer preferably contains the azacarbazole derivative mentioned as the host compound.

  On the other hand, 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 transports electrons while transporting holes. By blocking, the recombination probability 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.

  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, as well as 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-4-308 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.

  JP-A-11-251067, J. Org. Huang et. al. A so-called p-type hole transport material as described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, these materials are preferably used 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. Pat. 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. In addition, the distyrylpyrazine derivative exemplified as the material of the light emitting layer can also be used as an electron transport material, and an inorganic semiconductor such as n-type-Si, n-type-SiC, etc. as in the case of the hole injection layer and the hole transport layer Can also be used as an electron transporting 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.

  In the inventions according to the seventh and eighth aspects, an electron transport layer having a high n property doped with an impurity as a guest material is 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.

≪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 pattern accuracy is not so high (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. 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≫
As the cathode, a material having a 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₎ mixture, indium, a lithium / aluminum mixture, and rare earth metals. 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, Magnesium / 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 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 light emission luminance is improved, which is convenient.

  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.

<< Board >>
As a substrate (hereinafter also referred to as a base, a base material, a support substrate, a support, etc.) that can be used in the organic EL device according to the present invention, there is no particular limitation on the type of glass, plastic, etc., and it is transparent. Or opaque. When extracting light from the substrate side, the substrate is preferably transparent. Examples of the transparent substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable 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 a barrier film having a water vapor permeability of 0.01 g / m ² / day · atm or less is preferable. Further, it is preferably a high barrier film having an oxygen permeability of 10 ⁻³ g / m ² / day or less and a water vapor permeability of 10 ⁻⁵ g / m ² / day or less.

  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. In order to further 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.

  The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma weight A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, and 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 substrate include a metal plate such as aluminum and stainless steel, a film, an opaque resin substrate, a ceramic substrate, and the like.

  The external extraction efficiency at room temperature of light emission of the organic EL device according to the present invention is preferably 1% or more, more preferably 5% or more.

here,
External extraction quantum efficiency (%) = (number of photons emitted to the outside of the organic EL element) / (number of electrons sent to the organic EL element) × 100
It is.

  In addition, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter that converts the emission color from the organic EL element into multiple colors using a phosphor. In the case of using a color conversion filter, the λmax of light emission of the organic EL element is preferably 480 nm or less.

≪Sealing≫
As a sealing means of the organic EL element used for this invention, the method of adhere | attaching a sealing member, an electrode, and a support substrate with an adhesive agent can be mentioned, for example.

  As a sealing member, it should just be arrange | positioned so that the display area | region of an organic EL element may be covered, and concave plate shape or flat plate shape may be sufficient. Further, transparency and electrical insulation are not particularly limited.

  Specific examples include a glass plate, a polymer plate / film, and a metal plate / film. 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 organic EL element can be thinned. Further, the polymer film, the oxygen permeability was measured by the method based on JIS K 7126-1987 is ^{1 × 10 -3 ml / m 2} / 24h or less, as measured by the method based on JIS K 7129-1992 water vapor transmission rate (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) is preferably that of ^{1 × 10 -3 g / (m} 2 / 24h) or less.

  For processing the sealing member into a concave shape, sandblasting, chemical etching, or the like is used.

  Specific examples of adhesives 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. Can be mentioned. 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 like screen printing.

  In addition, it is also possible to suitably form an inorganic or organic layer as a sealing film by covering the electrode and the organic layer on the outer side of the electrode facing the substrate with the organic layer interposed therebetween, and in contact with the substrate. 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. Further, 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, ion plating, plasma polymerization, atmospheric pressure plasma A combination 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, an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil can be injected in the gas phase and liquid phase. preferable. A vacuum is also possible. 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.

≪Method for manufacturing organic EL element≫
The method for producing an organic EL device according to the present invention is characterized in that a part or all of an organic layer sandwiched between an anode and a cathode is formed by a wet process, and at least a light emitting layer is formed by a wet process. The wet process referred to in the present invention is to form a layer by supplying a layer forming material in the form of a solution when forming a layer.

  As an example of a method for producing an organic EL device according to 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 desired electrode material, for example, a thin film made of 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 to 200 nm, thereby producing an anode.

  Next, organic compound thin films (organic layers) such as a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a hole blocking layer, which are organic EL element materials, are formed thereon.

  As a method for forming each of these layers, there are a vapor deposition method, a wet process (spin coating method, casting method, ink jet method, spray method, printing method) and the like as described above. Furthermore, in the present invention, film formation by a coating method such as a spin coating method, an ink jet method, a spray method, or a printing method is preferable from the viewpoint that a homogeneous film is easily obtained and pinholes are hardly generated.

  Examples of the liquid medium for dissolving or dispersing the organic EL material according to the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, and mesitylene. Aromatic hydrocarbons such as cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as DMF and DMSO can be used.

  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. By providing, a desired organic EL element can be obtained.

  Further, it is possible to reverse the production order, and to 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. An alternating voltage may be applied. The alternating current waveform to be applied may be arbitrary.

≪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 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, etc. used for the sealing can be used, but the polymer film is light and thin. Is preferably used.

≪Light extraction≫
The organic EL element emits light inside a layer having a refractive index higher than that of air (refractive index is about 1.7 to 2.1) and can extract only about 15% to 20% of the light generated in the light emitting layer. It is generally 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 taken out of 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 of improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate and preventing total reflection at the transparent substrate and the air interface (US Pat. No. 4,774,435), A method for improving efficiency by giving light condensing property to a substrate (Japanese Patent Laid-Open No. 63-314795), a method for forming a reflective surface on the side surface of an organic EL element (Japanese Patent Laid-Open No. 1-220394), a substrate A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the substrate and the light emitter (Japanese Patent Laid-Open No. 62-172691), and lowering the refractive index than the substrate between the substrate and the light emitter. A method of introducing a flat layer having a structure (Japanese Patent Laid-Open No. 2001-202827), a method of forming a diffraction grating between any one of a substrate, a transparent electrode layer, and a light emitting layer (including between the substrate and the outside) No. 283751) .

  In the present invention, these methods can be used in combination with the organic EL device according to the present invention, but 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, A method of forming a diffraction grating between any layers of the transparent 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 organic EL device having further high 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. Further, it is preferably 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 diminished when the thickness of the low refractive index medium is about the wavelength of light and the electromagnetic wave that has 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. Light that cannot be emitted due to total internal reflection between layers is diffracted by introducing a diffraction grating in any layer or medium (in a transparent substrate or transparent electrode), and the light is removed. I want to take it out.

  The introduced diffraction grating desirably 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. Therefore, 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.

  As described above, the position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or in the transparent electrode), 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.

≪Condenser sheet≫
The organic EL device according to the present invention is processed to provide, for example, a microlens array-like structure on the light extraction side of the substrate, or combined with a so-called condensing sheet, for example, in a specific direction, for example, device light emission Condensing light in the front direction with respect to the surface can increase the luminance in a specific direction.

  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 is put into practical use in 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.

≪Usage≫
The organic EL element according to the present invention can be used as a display device, a display, and various light sources. For example, lighting devices (home lighting, interior lighting), clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources of optical storage media, light sources of electrophotographic copying machines, light sources of optical communication processors, light Although the light source of a sensor etc. are mentioned, It is not limited to this, It can use effectively for the use as a backlight of a liquid crystal display device, and an illumination light source especially.

  In the organic EL device according to the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like as needed during film formation. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire layer of the element may be patterned. In the fabrication of the element, a conventionally known method is used. Can do.

  The light emission color of the organic EL device according to the present invention and the compound according to the present invention is shown in FIG. 4.16 on page 108 of “New Color Science Handbook” (Edited by the Japan Color Society, University of Tokyo Press, 1985). It is determined by the color when the result measured with a luminance meter CS-1000 (manufactured by Konica Minolta Sensing) is applied to the CIE chromaticity coordinates.

Further, when the organic EL element according to the present invention is a white element, white means that the chromaticity in the CIE1931 color system at 1000 cd / m ² is measured when the front luminance at 2 ° viewing angle is measured by the above method. It means that it is in the region of X = 0.33 ± 0.07 and Y = 0.33 ± 0.1. The light emitting layer of the organic EL device according to the present invention preferably contains at least one of a light emitting host compound and a light emitting dopant as a guest material.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these. The structures of the compounds used in the examples are shown below.

<< Production of Organic EL Element 101 >>
After patterning a 100 mm × 100 mm × 1.1 mm glass substrate made of ITO (Indium Tin Oxide) 100 nm as an anode, the transparent support substrate provided with the ITO transparent electrode was superposed with normal propyl alcohol. Sonic cleaning, drying with dry nitrogen gas, and UV ozone cleaning were performed for 5 minutes.

  On this transparent support substrate, a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) to 70% with pure water at 3000 rpm for 30 seconds. After forming the film by spin coating, the film was dried at 200 ° C. for 1 hour to provide a 30 nm-thick hole injection layer (HIL).

  Next, the substrate was moved to a glove box under a nitrogen atmosphere and spin-coated under a condition of 1500 rpm for 30 seconds using a solution in which compound HT-1 (weight average molecular weight 50000; 50 mg) was dissolved in 10 ml of monochlorobenzene ( And dried at 160 ° C. for 30 minutes under nitrogen to obtain a hole transport layer (HTL).

Next, the substrate is attached to a vacuum deposition apparatus, the vacuum chamber is decompressed to 4 × 10 ⁻⁴ Pa, and the compound H-1 and the compound D-1 are co-deposited so that the compound D-1 has a film thickness ratio of 16%. Then, a light emitting layer (EML) having a thickness of 40 nm was formed.

  The substrate was moved again to the glove box, and spin coating (film) was performed under conditions of 1500 rpm and 30 seconds using a solution in which compound ET-1 (50 mg) was dissolved in 10 ml of 2,2,3,3-tetrafluoropropanol. And dried at 120 ° C. under nitrogen for 30 minutes to form an electron transport layer (ETL).

The substrate is attached to a vacuum deposition apparatus, the vacuum chamber is depressurized to 4 × 10 ⁻⁴ Pa, LiF is deposited as an electron injection layer at 1 nm, then aluminum 110 nm is deposited to form a cathode, and the organic EL element 101 is formed. Produced.

<< Production of Organic EL Element 102 >>
In the preparation of the organic EL element 101, after forming the hole transport layer, the substrate is attached to a vacuum deposition apparatus, the vacuum chamber is decompressed to 4 × 10 ⁻⁴ Pa, and then the compound H-1 is formed at 5 nm as an intermediate layer. The organic EL element 102 is formed in the same manner except that the compound H-1 and the compound D-1 are co-deposited so that the compound D-1 has a film thickness ratio of 16% to obtain a light emitting layer having a thickness of 35 nm. Was made.

<< Production of Organic EL Element 103 >>
In the production of the organic EL element 101, when forming the light emitting layer, the concentration of the guest compound D-1 is 32 vol% at the interface between the hole transport layer and the light emitting layer, and the concentration of the guest compound is at the interface between the light emitting layer and the electron transport layer. An organic EL device 103 was produced in the same manner except that the deposition rate of the compound D-1 was continuously changed so as to be 0 vol%.

<< Production of Organic EL Element 104 >>
In the production of the organic EL element 101, when forming the light emitting layer, the concentration of the guest compound D-1 is 0 vol% at the interface between the hole transport layer and the light emitting layer, and the concentration of the guest compound is at the interface between the light emitting layer and the electron transport layer. The organic EL element 104 was produced in the same manner except that the deposition rate of the compound D-1 was continuously changed so as to be 32 vol%.

<< Production of Organic EL Element 105 >>
In the production of the organic EL device 101, 1500 gm for 30 seconds using a solution prepared by dissolving compound H-2 (weight average molecular weight 50000; 73 mg) and compound D-1 (14 mg) in 10 ml normalpropyl acetate in a glove box. The organic EL element 105 was produced in the same manner except that spin coating was performed under conditions (film thickness: about 40 nm), drying was performed at 120 ° C. for 30 minutes under nitrogen, and the light emitting layer was formed.

<< Production of Organic EL Element 106 >>
An organic EL element 106 was produced in the same manner as in the production of the organic EL element 105 except that the compound H-2 was changed to H-1.

<< Production of Organic EL Element 107 >>
In the production of the organic EL element 105, spin coating (film thickness of about 40 nm) was performed under conditions of 1500 rpm and 30 seconds using a solution in which Compound H-2 (128 mg) and Compound D-1 (24 mg) were dissolved in 10 ml of butyl acetate. The organic EL element 107 was produced in the same manner except that a light emitting layer was formed.

<< Production of Organic EL Element 108 >>
An organic EL element 108 was produced in the same manner as in the production of the organic EL element 107, except that the compound H-2 was changed to H-1.

<< Evaluation of organic EL elements >>
About the produced organic EL element, the light emission lifetime and the high temperature storage property were evaluated as follows.

  For each sample, the distribution of iridium and carbon in the element was measured by dynamic SIMS. For 107 and 108, it has been confirmed that a dopant-deficient region exists. An example is shown in FIG.

[Half life]
The produced organic EL element was continuously driven by applying a current that would give a front luminance of 1000 cd / m ² . The time required for the front luminance to reach the initial half value (500 cd / m ² ) is obtained as the half life, and the half lives of the organic EL elements 101 to 105 and 107 and 108 are the values of the organic EL element 106 (comparative example). It was expressed as a relative value with the measured value as 100.

[Evaluation of high temperature storage stability]
After each organic EL element was stored for 100 hours in an environment of 60 ° C. and 90% relative humidity, whether or not dark spots occurred when each organic EL element was driven at a constant current of 10 mA / cm ² , The emission area was reduced and the change in emission luminance was measured, compared with the characteristics of each untreated organic EL element, and the high temperature storage stability was evaluated according to the following criteria. The emission luminance was measured using CS-1000 manufactured by Konica Minolta Sensing.

  A: The reduction rate of the light emitting area including the dark spot is less than 5% with respect to the untreated product, and the luminance fluctuation when the current density is constant is less than 5%.

  (Triangle | delta): The reduction rate of the light emission area containing a dark spot is 5% or more and less than 10% with respect to an untreated product, or the luminance fluctuation | variation at the time of constant current density is 5% or more and less than 10%.

  X: The reduction rate of the light emitting area including the dark spot is 10% or more with respect to the untreated product, or the luminance fluctuation when the current density is constant is 10% or more.

  The obtained results are shown in Table 1.

  As is apparent from the results shown in Table 1, it can be seen that an organic EL device having a configuration having a dopant-deficient region defined in the present invention can provide an organic EL device having a long lifetime and excellent high-temperature storage stability. . It has also been revealed that the formation of the light-emitting layer having the dopant-deficient region is generated by a single film formation by a wet process, so that the production efficiency is also high.

<< Production of Organic EL Element 201 >>
In the production of the organic EL element 106, the organic EL element 201 was produced in the same manner except that the substrate was cooled at 0 ° C. for 10 minutes before spin-coating the light emitting layer.

<< Production of Organic EL Element 202 >>
In the production of the organic EL element 106, the organic EL element 202 was produced in the same manner except that the pressure in the glove box was applied under a pressure higher than the atmospheric pressure when spin-coating the light emitting layer.

<< Production of organic EL element 203 >>
In the production of the organic EL element 106, the organic EL element 203 was produced in the same manner except that the solvent used for the light emitting layer was changed from normal propyl acetate to mesitylene.

<< Evaluation of organic EL elements >>
About each organic EL element obtained by the above, it carried out similarly to the method as described in Example 1, and evaluated the external extraction efficiency, the drive voltage, and the half life. Each evaluation result of the organic EL elements 201 to 203 was expressed as a relative value with the measured value of the organic EL element 106 as 100.

  The obtained results are shown in Table 2.

  As is clear from the results shown in Table 2, the organic EL device having the dopant-deficient region defined in the present invention has a dopant-deficient region like the organic EL device 108, and has a long life and high-temperature storage stability. It can be seen that an organic EL element excellent in the above can be obtained.

DESCRIPTION OF SYMBOLS 10 Substrate 20 Anode 30 Hole injection layer 40 Hole transport layer 50 Light emitting layer 51 Dopant deficient region 60 Electron transport layer 70 Electron injection layer 80 Cathode

Claims (6)

  An organic electroluminescence device comprising an anode, a cathode, and a host / dopant-type light emitting layer sandwiched between them, wherein the light emitting layer is formed from the interface between the light emitting layer and the adjacent layer, and the entire light emitting layer An organic electroluminescence device having a dopant-deficient region in a range of 10 to 30% of the layer thickness in the light emitting layer and produced by a single wet film forming process.   The organic electroluminescent device according to claim 1, wherein the light emitting dopant of the light emitting layer is a phosphorescent compound.   3. The organic electroluminescence device according to claim 1, wherein the light emitting host compound in the light emitting layer has a molecular weight of 1500 or less.   The organic electroluminescence device according to any one of claims 1 to 3, wherein the adjacent layer is a hole transport layer.   The said adjacent layer is an electron carrying layer, The organic electroluminescent element as described in any one of Claims 1-3 characterized by the above-mentioned.   It is a manufacturing method of the organic electroluminescent element as described in any one of Claims 1-5, Comprising: It has the process of producing a light emitting layer by one wet film-forming process using a solvent, It is characterized by the above-mentioned. A method for manufacturing an organic electroluminescence element.

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