JP2013120704A - Method for manufacturing organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an organic electroluminescent element having favorable emission lifetime, by which interface mixing can be prevented without being limited to a compound to be used.SOLUTION: In a method for manufacturing an organic electroluminescent element including a plurality of organic functional layers sequentially laminated on a base material, at least one layer of a second and subsequent organic functional layers laminated on a base material is formed by a coating step. In the coating step, when temperature of a coating liquid of the organic functional layers formed through the coating step is denoted as A, and temperature of a surface of the organic functional layer which is a just-under layer of the organic functional layers formed through the coating step is denoted as B, a relationship between A and B satisfies A>B.

Description

  The present invention relates to a method for manufacturing an organic electroluminescence element. In detail, it is related with the manufacturing method of the organic electroluminescent element which forms an organic functional layer by an application | coating process.

In recent years, as a light-emitting electronic display device, there is an electroluminescence display (hereinafter abbreviated as ELD). Electroluminescent elements that are one of the constituent elements of ELD include inorganic electroluminescent elements (hereinafter also referred to as inorganic EL elements) and organic electroluminescent elements (hereinafter also referred to as organic EL elements).
Among these, the inorganic EL element is used as a planar light source, and an alternating high voltage is required to drive the light emitting element.

  On the other hand, an organic EL element has a structure in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode. By injecting electrons and holes into the light emitting layer and recombining them, excitons (exciton) are obtained. The light is emitted using the emission of light (fluorescence / phosphorescence) when the exciton is deactivated, and light emission is possible at a voltage of several V to several tens V.

  As described above, the organic EL element can be driven at a lower voltage than the inorganic EL element, and further, since it is a self-luminous type, has a wide viewing angle, high visibility, and is a thin-film type completely solid element. In addition, it has attracted attention from the viewpoint of space saving and portability.

  In addition, the organic EL element has a major feature that it is a surface light source unlike main light sources that have been put to practical use in the past, such as light-emitting diodes and cold-cathode tubes, and can be used effectively. Illumination light sources and various display backlights.

Improvement of luminous efficiency is mentioned as a problem for putting an organic EL element into practical use as such a light source for illumination or a backlight of a display.
In order to improve luminous efficiency, it is becoming common to incorporate a so-called host / guest structure in which a plurality of materials having different functions are mixed in a part of the organic functional layer constituting the organic EL element. is there. For example, a combination of host material / luminescent dopant in the light-emitting layer and a combination of electron transport material / alkali metal material in the electron transport layer correspond to the host / guest structure.

  By the way, as a method for forming the organic functional layer of the organic EL element as described above, there are, for example, a vapor deposition method and a coating method (spin coating method, casting method, ink jet method, spray method, printing method, etc.), but a vacuum process. In recent years, the manufacturing method in the coating method has attracted attention because it is easy to carry out continuous production without the need for a coating.

  However, this coating method has a big problem. In general, an organic EL element is formed by laminating a plurality of organic functional layers. When a coating method is used for laminating the organic functional layers, the organic functional layer is applied to an organic functional layer in which a coating solution has already been formed. There is a problem in that it permeates, a clear interface between layers is not formed, and interfacial mixing occurs. It has been found that such interfacial mixing results from deterioration of the performance of the organic EL element.

Various patent documents have been disclosed as techniques for solving the above problems.
For example, in Patent Document 1, when a device is manufactured by a coating method, phase dissolution (interface mixing) does not occur between adjacent organic layers, and the light emission efficiency and durability of the finally obtained device are improved. In order to obtain an excellent organic EL device, the use of a specific polymerizable aromatic amine compound in the hole transport layer is disclosed.

JP 2009-176964 A

  However, in Patent Document 1 described above, interfacial mixing such as a solvent is prevented by applying and curing a coating solution for a hole transport layer containing a specific polymerizable aromatic amine compound. Necessary things and compounds that can be used in the organic functional layer are limited, and are not suitable for general use.

  The present invention has been made in view of the above-described problems, and is intended to provide a method for producing an organic electroluminescence device that is not limited to a compound to be used, can prevent interfacial mixing, and has a good emission lifetime. To do.

  In order to solve the above problem, the method for producing an organic electroluminescent element of the present invention has the following configuration.

1.
In the method for producing an organic electroluminescence element in which a plurality of organic functional layers are sequentially laminated on a substrate,
Forming at least one of the second and subsequent organic functional layers laminated on the substrate by a coating process;
In the application step,
A and B, where A is the temperature of the coating solution for the organic functional layer formed by the coating step, and B is the surface temperature of the organic functional layer immediately below the organic functional layer formed by the coating step. The relationship is A> B, The manufacturing method of the organic electroluminescent element characterized by the above-mentioned.

2.
2. The method for producing an organic electroluminescent element according to 1 above, wherein a difference AB between the temperature A of the coating solution and the temperature B of the surface is 20 ° C. <A−B <50 ° C.

3.
3. The method for producing an organic electroluminescent element according to 1 or 2, wherein the organic functional layer formed by the coating step is a light emitting layer and / or an electron transport layer.

4).
4. The method for producing an organic electroluminescent element according to 3 above, wherein the organic functional layer formed by the coating step is a light emitting layer.

5.
The method for producing an organic electroluminescent element according to any one of 1 to 4, wherein the coating liquid is heated to satisfy A> B.

6).
The method for producing an organic electroluminescent element according to any one of 1 to 4, wherein the surface is cooled to satisfy A> B.

7.
The method for producing an organic electroluminescent element according to any one of 1 to 6, wherein the coating step is performed using a die coating method, a spin coating method, an ink jet method, or a spray method.

  According to the method for producing an organic electroluminescent element of the present invention, it is possible to provide a method for producing an organic electroluminescent element which is not limited to a compound to be used, can prevent interfacial mixing and has a good emission lifetime.

  Hereinafter, the manufacturing method of the organic EL element according to the present invention will be described using specific embodiments.

(Coating process)
The coating process according to the present embodiment refers to a process in which a coating solution in which an organic functional layer material is dissolved or dispersed in a solvent is coated on the organic functional layer, the solvent is dried and solidified as a film, and is fixed to a substrate. .

  And in the application process according to the present embodiment, when the application temperature A of the organic functional layer formed by the application process and the surface temperature B of the organic functional layer immediately below the organic functional layer formed by the application process, The relationship between A and B is A> B. The relationship between A and B is not particularly limited as long as A> B, but preferably A is 20 ° C. to 80 ° C. and B is 0 ° C. to 60 ° C. .

  In the organic EL device in which a plurality of organic functional layers are laminated on a substrate, the coating process according to the present embodiment is applied to the second and subsequent layers from the substrate side among the plurality of organic functional layers laminated on the substrate. This is applied to at least one organic functional layer to be laminated. The method for forming the first organic functional layer on the substrate may be a coating step or may be formed by another method. As another method, for example, there is a vapor deposition method.

  By applying the above-described coating process to at least one of the second and subsequent organic functional layers stacked in this manner, it is possible to prevent mixing at the interface between the organic functional layer and another organic functional layer. Become. In the organic EL element coating process, the temperature state at the interface immediately after coating is particularly important. By controlling the temperature A and temperature B immediately before coating so as to satisfy the relationship of A> B, interfacial mixing after coating is performed. As a result, an organic EL element showing a good light emission lifetime can be obtained.

  The coating liquid temperature A of the organic functional layer described above is higher than the surface temperature B in the coating process. As a method for measuring the coating liquid temperature A, for example, a non-contact thermometer (KS-8140 manufactured by Sato Keiki Seisakusho) Can be measured.

  On the other hand, the surface temperature B of the organic functional layer immediately below the organic functional layer is lower than the coating solution temperature A in the coating process. As a method for measuring this surface temperature, the above-described non-contact thermometer (Sato meter) It can be measured using a KS-8140) manufactured by Seisakusho.

  The relationship between the coating liquid temperature A of the organic functional layer and the surface temperature B of the organic functional layer immediately below the organic functional layer is such that the difference (A−B) is 20 ° C. <A−B <50 ° C. It is preferable to be in the range. It is preferable that AB is in this range because interfacial mixing can be further suppressed.

  Any method may be used as the above-described relation of A> B, but the organic functional layer immediately below the organic functional layer formed by heating the coating liquid of the organic functional layer and / or in the coating step may be used. It is preferable to satisfy the relationship of A> B by cooling the surface temperature.

  As a method for heating the coating liquid for the organic functional layer described above, a method for heating the container itself containing the coating liquid on a hot plate, a method for directly heating the coating liquid by blowing warm air, and a heated liquid feeding pipe Examples thereof include a method in which the coating liquid is passed through and heated, and a method in which the coating liquid is heated with infrared rays. These methods may be used alone or in combination, and there are no particular restrictions on the combination. be able to.

  In addition, as a method of cooling the surface temperature of the organic functional layer immediately below the organic functional layer formed in the above-described coating process, a method of cooling the surface temperature by placing the substrate on which the organic functional layer is formed in a thermostatic bath, Examples include a method of cooling by contacting a transport roll in which cooling water is circulated, a method of cooling by applying cold air to the surface of the organic functional layer, a method of cooling the organic functional layer by cooling the coating environment itself, and the like. These methods may be used singly or in combination, and there are no particular restrictions on the combination.

Even after the coating solution is applied, the solvent is likely to remain in the coating film even after it is solidified as a film and fixed to the substrate. In the organic EL element, the element performance, particularly the light emission life, may be deteriorated due to the influence of the remaining solvent.
Therefore, in order to remove the solvent remaining in the coating film, it is preferable to heat dry the coating film.

  Examples of such heating methods include a method in which a substrate having an organic functional layer formed on a hot plate is brought into contact and heated, a method in which the substrate is heated in a thermostatic bath, a method in which heating is performed by irradiating infrared rays, and hot air is applied. The method of making it heat by spraying etc. can be mentioned, These methods may be used individually or in combination of two or more, and there can be used especially without restriction of combination etc.

  Moreover, as a coating process according to the present embodiment, for example, a casting method, a printing method, a die coating method, a spin coating method, an ink jet method, a dip coating method, a blade method, a slit coating method, or a spray method can be used. Among these, a die coating method, a spin coating method, an ink jet method or a spray method is particularly preferably used.

Furthermore, in the coating process according to the present embodiment, it is preferable to form a light emitting layer and / or an electron transport layer, which will be described later, and more preferably to form a light emitting layer.
In general, in the organic EL element, the light emitting layer and / or the electron transport layer is a layer that requires more precision of coating and stability because more types of materials are used than other layers. It is preferable to apply the coating process according to the present embodiment to these layers.

(solvent)
Examples of the solvent for dissolving or dispersing the organic functional layer material according to this embodiment include aqueous solvents, esters, ketones, alcohols, aromatic hydrocarbons, and halogenated hydrocarbons.

  As the esters, linear or cyclic esters having 2 to 19 carbon atoms are preferable. Specifically, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, acetic acid Pentyl, methoxybutyl acetate, sec-hexyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, benzyl acetate, methyl propionate, ethyl propionate, butyl propionate, ethyl 2-hydroxy-2-methylpropionate, Examples include diethyl phthalate and dibutyl phthalate.

  As the ketones, chain or cyclic ketones having 3 to 9 carbon atoms are preferable. Specifically, acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, 2-hexanone, methyl isobutyl ketone, 2-heptanone, Examples include 3-heptanone, 4-heptanone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, acetophenone, and the like.

  As the alcohol, a linear or cyclic alcohol having 3 to 16 carbon atoms is preferable, and n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentyl. Alcohol, 2-pentyl alcohol, 1-ethyl-1-propyl alcohol, 2-methyl-1-butyl alcohol, 3-methyl-1-butyl alcohol, 3-methyl-2-butyl alcohol, neopentyl alcohol, 1-hexyl Alcohol, 2-methyl-1-pentyl alcohol, 4-methyl-2-pentyl alcohol, 2-ethyl-1-butyl alcohol, 1-heptyl alcohol, 2-heptyl alcohol, 3-heptyl alcohol, 1-octyl alcohol, 2 - Til alcohol, 2-ethyl-1-hexyl alcohol, 1-nonyl alcohol, 3,5,5-trimethyl-1-hexyl alcohol, 1-decyl alcohol, 1-undealkyl alcohol, 1-dodecyl alcohol, cyclohexyl alcohol, Examples thereof include 1-methylcyclohexyl alcohol, 2-methylcyclohexyl alcohol, 3-methylcyclohexyl alcohol, 4-methylcyclohexyl alcohol, α-terpineol, 2,6-dimethyl-4-heptyl alcohol, nonyl alcohol, tetradecyl alcohol and the like.

  Aromatic hydrocarbons include toluene, xylene, solvent # 100, solvent # 150, benzene and the like.

  Examples of the halogenated hydrocarbons include 1,1-dichloroethane, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, carbon tetrachloride, ethylene trichloride, ethylene tetrachloride and the like.

(Organic EL device)
The organic EL device according to this embodiment has a configuration in which an anode, a cathode, and a plurality of organic functional layers are formed on a substrate and the substrate.
An organic functional layer means each layer which comprises the organic electroluminescence provided between the anode and the cathode.
Examples of the organic functional layer include a hole injection layer (anode buffer layer), a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer (cathode buffer layer), a hole blocking layer, an electron blocking layer, and an intermediate layer. Etc. are included.

Although the preferable specific example of the layer structure of the organic EL element which concerns on this embodiment is shown below, this embodiment is not limited to these.
(I) Anode / hole transport layer / intermediate layer / light emitting layer / electron transport layer / cathode (ii) Anode / hole transport layer / intermediate layer / light emitting layer / hole blocking layer / electron transport layer / cathode (iii) Anode / hole transport layer / intermediate layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode (iv) Anode / anode buffer layer / hole transport layer / intermediate 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

(Light emitting layer)
The light emitting layer according to this embodiment 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 within the layer of the light emitting layer. Alternatively, it may be the interface between the light emitting layer and the adjacent layer.

  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 nm-200 nm, More preferably, it adjusts to the range of 5 nm or more and 100 nm or less.

  The formation method of the light emitting layer of the organic EL device according to the present embodiment is not particularly limited, and can be formed by, for example, a vapor deposition method, a coating method, or the like. Examples include a coating method, an ink jet method, a dip coating method, a blade method, a slit coating method, and a spray method. In the present embodiment, film formation by a coating process of a die coating method, a spin coating method, an ink jet method, or a spray method is preferable from the viewpoint that a homogeneous film is easily obtained and pinholes are hardly generated.

  Hereinafter, the light emitting host and the light emitting dopant contained in the light emitting layer will be described.

(1) Light-Emitting Host A light-emitting host used in this embodiment will be described.
Here, in this embodiment, the light-emitting host has a mass ratio of 20% or more of the compounds contained in the light-emitting layer, and a phosphorescence quantum yield of phosphorescence emission at room temperature (25 ° C.) is 0. Defined as less than 1 compound. 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 such a light emitting host, a known light emitting host may be used alone, or a plurality of kinds may be used in combination. By using a plurality of types of light-emitting hosts, the movement of charges can be adjusted, 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 this embodiment 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 polymerization). Luminescent host).

  As the known light-emitting host 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 light-emitting hosts 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.

(2) Luminescent dopant The luminescent dopant which concerns on this embodiment is demonstrated.
From the viewpoint of obtaining an organic EL element with higher luminous efficiency, the light emitting layer of the organic EL element of the present invention contains the above light emitting host and simultaneously contains a light emitting dopant (phosphorescent dopant). A phosphorescent dopant 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, a preferable phosphorescence quantum yield is 0.1 or more.

  The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence dopant according to the present embodiment achieves the phosphorescence quantum yield (0.01 or more) in any solvent. Just do it.

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

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 this embodiment 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, and most preferred are iridium compounds.

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

  Next, an injection layer, a blocking layer, a transport layer, and the like used as the layer of the organic EL element of this embodiment will be described.

(Injection layer: electron injection layer, hole injection layer)
The injection layer is provided as necessary, and includes an electron injection layer and a hole injection layer. As described above, it can be present between the anode and the light emitting layer or hole transport layer and between the cathode and the light emitting layer or electron transport layer.

  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) ) ", Chapter 2, Chapter 2," Electrode Materials "(pp. 123-166).

  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.

  Further, ferrocene compounds described in JP-A-6-025658, starburst type compounds described in JP-A-10-233287, etc., JP-A 2000-068058, JP-A 2004-6321 Triarylamine type compounds, sulfur-containing ring-containing compounds described in JP-A No. 2002-117879, hexaazatriphenylene described in US 2002/0158242, US 2006/0251922, JP-A 2006-49393, etc. A compound etc. are also mentioned as a positive hole injection layer.

  On the other hand, the details of the cathode buffer layer (electron injection layer) are also described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Metal buffer layer typified by aluminum, etc., 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. Can be mentioned.

  The injection layer as described above is desirably 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 needed in addition to the constituent layers of the organic functional layer 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 embodiment as needed.

  The hole blocking layer of the organic EL element according to this embodiment is preferably provided adjacent to the light emitting layer. The hole blocking layer preferably contains the azacarbazole derivative mentioned as the light emitting host.

  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 having a function of transporting holes while having a very small ability to transport electrons, and transporting 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 thickness of the hole blocking layer and the electron blocking layer according to this embodiment is preferably 3 nm to 100 nm, and more preferably 5 nm 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 as described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In this embodiment, 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 vapor deposition method or a coating method. 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 nm-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.

(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.

  Also, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum, Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and the central metals of these metal complexes are In, Mg, Cu , Ca, Sn, Ga, or Pb can also be used as an 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 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 vapor deposition method or a coating 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 nm-200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials.

(anode)
As the anode in the organic EL device according to the present embodiment, an anode using a metal, an alloy, an electrically conductive compound, and a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such an electrode material include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO2, and ZnO. Alternatively, an amorphous material such as IDIXO (In2O3-ZnO) that can form 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)
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 (Al2O3) mixture. , 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, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al2O3) 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.

(Base material)
As a base material that can be used in the organic EL device according to this embodiment, there is no particular limitation on the type of glass, plastic, and the like, and it may be transparent or opaque. When taking out light from the base material side, it is preferable that the base material is transparent. Examples of the transparent substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable substrate is a resin film that can give 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 Polyetherimide, polyether ketone imide, polyamide, fluorine resin, nylon, polymethyl methacrylate, acrylic or polyarylates, and cycloolefin resins such as ARTON (manufactured by JSR) or APEL (manufactured by Mitsui Chemicals).

  On the surface of the resin film, an inorganic film, an organic film or a hybrid film of both may be formed, and it is preferably a barrier film having a water vapor permeability of 0.01 g / m 2 / day · atm or less, Further, it is preferably a high barrier film having an oxygen permeability of 10-3 g / m2 / day or less and a water vapor permeability of 10-5 g / m2 / 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. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and organic material layers. 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 base material include metal plates such as aluminum and stainless steel, films, opaque resin substrates, ceramic base materials, and the like.

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

  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 used for this embodiment, the method of adhere | attaching a sealing member, an electrode, and a base material 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 embodiment, a polymer film and a metal film can be preferably used because the element can be thinned.
Further, the polymer film has an oxygen transmission rate measured by a method according to JIS K 7126-1987 of 1 × 10 −3 ml / m 2/24 h or less, a water vapor transmission rate measured by a method according to JIS K 7129-1992. The degree (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) is preferably 1 × 10 −3 g / (m 2/24 h) 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 like screen printing.

(Protective film, protective plate)
In order to increase the mechanical strength of the device, 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 functional layer interposed therebetween, or 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. It is preferable to use a film.

(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 (transparent substrate-air interface) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the element, or a transparent electrode or light emitting layer and the transparent substrate. This is because the light undergoes total reflection between the light and the light, 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 side surface of the device.

  As a technique 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 (US Pat. No. 4,774,435). ), A method for improving the efficiency by imparting a light collecting property to the substrate (Japanese Patent Laid-Open No. 63-314795), a method for forming a reflective surface on the side surface of the element (Japanese Patent Laid-Open No. 1-220394), A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the base material and the light emitter (Japanese Patent Laid-Open No. 62-172691), and from the base material between the base material and the light emitting layer In addition, a method of introducing a flat layer having a low refractive index (Japanese Patent Laid-Open No. 2001-202827), a diffraction grating is formed between any one of the base material, the transparent electrode layer and the light emitting layer (including between the substrate and the outside). Method (Japanese Patent Laid-Open No. 11-283951).

  In this embodiment, these methods can be used in combination with the organic EL device of this embodiment, but a method of introducing a flat layer having a lower refractive index than the base material between the base material and the light emitting layer, Alternatively, a method of forming a diffraction grating between any of the base material, the transparent electrode layer, and the light emitting layer (including between the substrate and the outside) can be suitably used.

  In the present embodiment, by combining these means, it is possible to obtain an element having higher luminance or durability.

  If a medium with a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of the 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. Become.

  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. Of these, light that cannot be emitted due to total reflection between layers, etc. is diffracted by introducing a diffraction grating into any layer or medium (inside a transparent substrate or transparent electrode). It is intended to be taken 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 one of the layers or in the medium (in the transparent base material or in the transparent electrode), but is preferably in the vicinity of the 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.

(Condensing sheet)
The organic EL element according to the present embodiment is processed to provide a microlens array-like structure on the light extraction side of the base material, or combined with a so-called condensing sheet, for example, in a specific direction, for example, By condensing in the front direction with respect to the element light emitting surface, 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 is put into practical use in an LED backlight of a liquid crystal display device can be used. As such a sheet, for example, Sumitomo 3M brightness enhancement film (BEF) 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 layer, 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.

(Manufacturing method of organic EL element)
As an example of the method for producing an organic EL device of the present invention, a method for producing an organic EL device comprising an anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode on a substrate is provided. explain.

  First, for example, a desired electrode material, for example, ITO, which is a material for an anode, is formed on a 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, and an anode is manufactured. . Next, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer, which are organic functional layers, are formed and laminated in this order on the anode.

Although it does not specifically limit as a formation method of each said organic functional layer, At least 1 layer after the 2nd layer is formed by the application | coating process which concerns on this embodiment.
In the present embodiment, for example, the light emitting layer and the electron transport layer are formed by the coating process, and the other organic functional layers are formed by using a vapor deposition process. The other organic functional layers are not limited to vapor deposition, and may be formed by a known coating process.

In the coating process according to this embodiment,
(I) A step of applying a coating solution obtained by dissolving or dispersing a predetermined constituent material in a solvent onto the organic functional layer (II) A step of drying the coating solution after coating (I), the processing of (II), It carries out for each layer of the light emitting layer and the electron transport layer.
At that time, in the above (I) and (II), the temperature of the coating solution of the organic functional layer formed by the coating step is A, and the surface of the organic functional layer immediately below the organic functional layer formed by the coating step Is set to B, and the relationship between A and B satisfies A> B.

  Specifically, when the organic functional layer formed in the coating process according to the present embodiment is a light emitting layer, the temperature of the coating liquid of the light emitting layer is A and the surface temperature of the hole transport layer is B, When the organic functional layer formed in the coating process is an electron transport layer, the temperature of the coating liquid for the electron transport layer is A, and the surface temperature of the light emitting layer is B.

  Any method may be used as A> B. For example, a method of heating the coating solution for the light emitting layer and the coating solution for the electron transport layer to A> B, the surface of the hole transport layer, light emission There is a method of cooling the surface of the layer so that A> B.

In the present embodiment, for example, when the light emitting layer is formed, the container containing the coating liquid for the light emitting layer is placed on the hot plate and heated to satisfy A> B.
For example, when forming the electron transport layer, the surface of the light emitting layer is cooled by applying cold air to the surface of the light emitting layer that has already been formed, and A> B is satisfied.

In the step (I), for example, a casting method, a printing method, a die coating method, a spin coating method, an ink jet method, a dip coating method, a blade method, a slit coating method, or a spray method can be used. The light emitting layer and the electron transport layer are formed using a spin coating method.
Each of these organic functional layers has a thickness in the range of 5 nm to 5 μm, for example.

  After these organic functional layers are formed, for example, aluminum, which is a cathode material, is formed thereon so as to have a film thickness of 1 μm or less, preferably in the range of 50 to 200 nm. A cathode is formed by the method. Once the cathode is provided, for example, a sealing member is formed through an adhesive made of a resin to manufacture an organic EL element.

  It is also possible to reverse the manufacturing order and manufacture the cathode, organic functional layer (electron injection layer, electron transport layer, light emitting layer, hole transport layer, hole injection layer), and anode in this order from the base material. is there.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

(Production of organic EL element)
Organic ELNo. Preparation of 1 After depositing 100 nm of ITO (indium tin oxide) on a 100 mm × 100 mm × 1.1 mm glass substrate (NH45 made of NH technoglass) and patterning it as an anode, this ITO transparent electrode was provided The substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.

  A solution of poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) dissolved in isopropyl alcohol (IPA) on this substrate at 3000 rpm for 30 seconds. After film formation by the spin coating method, the substrate was dried at a substrate surface temperature of 100 ° C. for 1 hour to provide a 30 nm-thick hole injection layer.

  This base material was transferred to a glove box in accordance with JIS B 9920 under a nitrogen atmosphere, the measured cleanliness was class 100, the dew point temperature was −80 ° C. or lower, and the oxygen concentration was 0.8 ppm. A hole transport layer coating solution was prepared as follows in a glove box, and applied with a spin coater at 1500 rpm for 30 seconds to provide a hole transport layer. The thickness of the hole transport layer was 20 nm. The substrate temperature on which the hole injection layer was provided was adjusted as follows.

The coating liquid for the hole transport layer was prepared as follows.
Pour cold water at 23 ° C. on the cooling plate CDB-1MP manufactured by ASONE Co., Ltd., adjust the temperature of the substrate provided with a 30 nm-thick hole injection layer, and apply the coating liquid for the hole transport layer to hot manufactured by ASONE Co., Ltd. The solution was placed on a plate stirrer RCTbasic, and the temperature of the hole transport layer coating solution was adjusted to 23 ° C.

  A non-contact thermometer KS-8140 manufactured by Sato Meters Co., Ltd. is used to measure the temperature of the hole transport layer coating solution immediately before the hole transport layer coating solution is applied onto the hole injection layer and the temperature of the hole injection layer surface. As a result, the hole transport layer coating solution was 23 ° C., and the hole injection layer surface temperature was 23 ° C.

  Then, the base material provided with the hole injection layer and the hole transport layer after coating was dried by heating at 120 ° C. for 30 minutes on a hot plate stirrer RCTbasic manufactured by AS ONE.

(Coating liquid for hole transport layer)
Monochlorobenzene 100g
Poly- (N, N′-bis (4-butylphenyl) -N, N′-bis (phenyl) benzidine) (ADS254BE: manufactured by American Die Source) 0.5 g

  Next, a light-emitting layer coating solution was prepared as follows, and a light-emitting layer was provided on the previously formed hole transport layer using a spin coater under the conditions of 2000 rpm and 30 seconds. The thickness of the light emitting layer was 40 nm. In addition, the base-material temperature provided to the positive hole transport layer was adjusted as follows.

The light emitting layer coating solution was prepared as follows.
Cooling plate CDB-1MP manufactured by ASONE Co., Ltd. was allowed to flow cold water at 23 ° C., the substrate temperature formed up to the hole transport layer was controlled, and the coating solution for the light emitting layer was placed on the hot plate stirrer RCTbasic manufactured by ASONE Co., Ltd. The temperature of the coating solution was adjusted to 38 degrees.

  When the luminescent layer coating liquid just before applying the luminescent layer coating liquid on the hole transport layer and the temperature of the surface of the hole transport layer were measured using a non-contact thermometer KS-8140 manufactured by Sato Keiki Seisakusho, The coating solution for the light emitting layer was 38 ° C., and the surface temperature of the hole transport layer was 23 ° C.

  Then, the base material provided to the light emitting layer after application | coating was heat-dried at 120 degreeC for 30 minute (s) on the hot plate stirrer RCTbasic made from ASONE.

(Light emitting layer coating solution)
Butyl acetate 100g
HA 1g
D-28 0.11g
Ir-1 0.002g
Ir-14 0.002g

  Subsequently, the coating liquid for electron carrying layers was prepared as follows, and it apply | coated on the conditions of 1500 rpm and 30 seconds with the spin coater, and provided the electron carrying layer. The film thickness of the electron transport layer was 30 nm. In addition, the base-material temperature provided to the light emitting layer was adjusted as follows.

The electron transport layer coating solution was prepared as follows.
Pour cold water at 23 ° C into the cooling plate CDB-1MP manufactured by ASONE Co., Ltd., adjust the temperature of the substrate formed up to the light emitting layer, and apply the coating solution for the electron transport layer on the hot plate stirrer RCTbasic manufactured by ASONE Co., Ltd. The liquid temperature was adjusted to 23 ° C.

  When the electron transport layer coating solution temperature just before applying the electron transport layer coating solution on the light emitting layer and the temperature of the light emitting layer surface were measured using a KS-8140 made by Sato Keiki Seisakusho, The coating solution temperature for the electron transport layer was 23 ° C., and the surface temperature of the light emitting layer was 23 ° C.

  Then, the base material provided to the electron carrying layer after application | coating was heat-dried at 120 degreeC for 30 minute (s) on the hot plate stirrer RCTbasic by ASONE CORPORATION.

(Coating liquid for electron transport layer)
2,2,3,3-tetrafluoro-1-propanol 100 g
ET-A 0.75g

Next, the substrate provided up to the electron transport layer was moved to a vapor deposition machine without being exposed to the atmosphere, and the pressure was reduced to 4 × 10 ⁻⁴ Pa. Note that potassium fluoride and aluminum were each placed in a tantalum resistance heating boat and attached to a vapor deposition machine.

  First, a resistance heating boat containing potassium fluoride was energized and heated, and an electron injection layer made of potassium fluoride was provided to 3 nm on the substrate. Subsequently, a resistance heating boat containing aluminum was energized and heated, and a cathode having a film thickness of 100 nm made of aluminum was provided at a deposition rate of 1 to 2 nm / second.

The substrate provided up to the cathode is moved to a glove box with a cleanness measured in accordance with JIS B9920, class 100, dew point temperature of -80 ° C or less, and oxygen concentration of 0.8 ppm without exposing it to the atmosphere in a nitrogen atmosphere. And sealing with a glass sealing can attached with barium oxide which is a water catching agent. 1 was obtained.
Barium oxide, a water-absorbing agent, is a high-purity barium oxide powder manufactured by Aldrich, and is attached to a glass sealing can with a fluorine-based semipermeable membrane (Microtex S-NTF8031Q manufactured by Nitto Denko) with an adhesive. Were prepared and used in advance. An ultraviolet curable adhesive was used for bonding the sealing can and the organic EL element, and both were bonded to each other by irradiating ultraviolet rays to produce a sealing element.

Organic EL element No. Preparation of 2-15 The above-mentioned organic EL element No. 1 was prepared in the same manner except that the temperature control of the surface temperature of the hole transport layer provided up to the hole transport layer and the temperature control of the coating solution for the light emitting layer were controlled as shown in Table 1. .
The temperature control of the surface temperature of the hole transport layer was changed by changing the water temperature to the cooling plate CDB-1MP manufactured by AS ONE Corporation.

(Evaluation of organic EL elements)
(Luminescent life)
The produced organic EL element No. 1 to 15 was continuously driven by applying a current that gave a front luminance of 1000 cd / m ^2, and the time taken for the front luminance to reach the initial half value (500 cd / m ² ) was determined. The results are shown in Table 1. Larger values indicate better device performance and better results.

Summary As shown in Table 1, No. in the temperature relationship of A> B. Nos. 1 to 12 have the light emission lifetimes of It turns out that it is favorable compared with 13-15. No. A-B is in the range of 20 ° C. or more and 50 ° C. or less. It can be seen that 2 to 4 and 8 to 10 have better emission lifetimes. This is considered to be because interfacial mixing could be further suppressed because the range of AB was in the above-described range.

  The organic EL element No. 1 prepared in Example 1 was used. 2 was prepared in the same manner except that the temperature control of the surface temperature of the light emitting layer provided up to the light emitting layer and the temperature control of the coating liquid for the electron transport layer were shown in Table 2 below. 16-26 were created.

(Evaluation of organic EL elements)
(Luminescent life)
The light emission life was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Summary As shown in Table 2, it can be seen that the emission lifetime is further improved by applying the coating process according to the present invention when the electron transport layer is formed.

Claims (7)

In the method for producing an organic electroluminescence element in which a plurality of organic functional layers are sequentially laminated on a substrate,
Forming at least one of the second and subsequent organic functional layers laminated on the substrate by a coating process;
In the application step,
A and B, where A is the temperature of the coating solution for the organic functional layer formed by the coating step, and B is the surface temperature of the organic functional layer immediately below the organic functional layer formed by the coating step. The relationship is A> B, The manufacturing method of the organic electroluminescent element characterized by the above-mentioned.   2. The method of manufacturing an organic electroluminescence element according to claim 1, wherein a difference A−B between a temperature A of the coating solution and a temperature B of the surface is 20 ° C. <A−B <50 ° C. 3.   The method for producing an organic electroluminescent element according to claim 1, wherein the organic functional layer formed by the coating step is a light emitting layer and / or an electron transport layer.   The method for producing an organic electroluminescent element according to claim 3, wherein the organic functional layer formed by the coating step is a light emitting layer.   The method for producing an organic electroluminescent element according to claim 1, wherein the coating liquid is heated to satisfy A> B.   The method for producing an organic electroluminescent element according to claim 1, wherein the surface is cooled to satisfy A> B.   The said application | coating process is performed using the die-coating method, a spin coat method, the inkjet method, or the spray method, The manufacturing method of the organic electroluminescent element as described in any one of Claims 1-6 characterized by the above-mentioned.