JP2014072175A - Method for manufacturing organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an organic electroluminescent element with good performance using a wet coating method.SOLUTION: A method for manufacturing an organic electroluminescent element comprises the steps of: laminating a plurality of coating liquids each containing an organic light emitting material to form a plurality of organic light emitting layers, on a substrate on which a first electrode is formed; and forming a second electrode on the substrate on which the organic light emitting layers are formed. Adjacently laminated coating liquids among the coating liquids are prepared using solvents having permanent dipole moments different from each other.

Description

  The present invention relates to a method for manufacturing an organic electroluminescence element, and more particularly to a method for manufacturing an organic electroluminescence element in which a plurality of organic light emitting layers are formed using a wet coating method.

  In recent years, electronic devices using organic materials have attracted attention, and in particular, research and development of organic electroluminescence elements (organic EL elements), organic thin film transistors (organic TFTs), organic solar cells, etc. are actively conducted. Yes. 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, and injects electrons and holes into the light emitting layer to recombine excitons. It is an element that emits light by utilizing light emission (fluorescence / phosphorescence) when the exciton is deactivated.

  Organic EL elements are self-luminous, have a wide viewing angle, and have high visibility. In addition, they are thin-film, completely solid elements, so they have excellent space saving and portability. It is attracting attention as a useful surface light source element. As an element of the surface light source, there is an inorganic electroluminescence element (inorganic EL element), but in order to drive the inorganic EL element, an alternating high voltage is required. On the other hand, the organic EL element can emit light at a voltage of about several volts to several tens of volts. Utilizing these characteristics, organic EL elements are being applied to light sources for illumination and backlights of various displays as light sources to replace light-emitting diodes and cold cathode tubes that have been put to practical use. Demand is increasing, including backlights for LCD full-color displays. Against this background, to improve the performance and functionality of various lighting sources and full-color displays, the performance of organic EL elements, that is, emission characteristics such as luminance and chromaticity, emission efficiency, and emission lifetime are improved. It has been demanded.

  The performance of the organic EL element depends on the electrical and physical properties of the organic compound layer, so the material of the organic compound layer is improved, the manufacturing process of the organic compound layer is improved, the layer structure of the organic compound layer is improved, From such a viewpoint, a means for improving the performance of the organic EL element is being sought. However, although improvement of the organic compound material can be expected to improve performance, it is not easy to search for an optimal compound, and there is a problem that much labor, cost and time are required. In addition, although the knowledge that the performance of the element fluctuates according to the method of forming the organic compound layer is being obtained, the room for improvement is limited because the method of forming the film has practical limitations. ing. On the other hand, improvement of the layer structure is a means that has a relatively high possibility of realization by forming the light emitting layer as a multilayer structure in which a plurality of light emitting layers are laminated and changing the composition / content of the material in each light emitting layer. .

  The film forming means for forming the element includes a dry method and a wet method. Examples of the dry method include vapor deposition and sputtering. Examples of the wet method (wet coating method) include spin coating, printing, casting, and Langmuir. Blodget (LB) method, blade coating method, ink jet method, slit coating method, dip coating method, roll coating method, spraying method, etc. are used, but conventionally, deposition that mainly enables precise layer formation is possible. The law is used. Regarding the improvement of the layer structure of the light emitting layer by the vapor deposition method, for example, a layer having a concentration distribution is formed in the light emitting dopant doped in the light emitting layer to extend the initial luminance half-life of the organic EL element, or to continuously drive the element. There is an example in which the performance improvement is actually confirmed by controlling the vapor deposition rate, for example, by improving the luminance deterioration due to.

  On the other hand, in the wet coating method, the organic compound as a material is dissolved in a solvent or dispersed in a dispersion medium to form a coating liquid, and the coating liquid is layered on a substrate using a precision coating apparatus to form a film in a liquid phase. However, in order to improve device performance and production yield, it is necessary to uniformly dissolve or disperse each material, to form a coating film with a uniform film thickness, and to laminate a coating solution. Numerous conditions are required to prevent coating failure such as not dissolving the lower layer serving as the coating surface. Therefore, the wet coating method has a number of problems in improving the performance of the manufactured organic EL element, such as control of the layer structure of the thin film and formation of a uniform film as compared with the vapor deposition method. It was a way of holding. However, in recent years, there has been a growing demand for wet coating methods suitable for mass production of devices, and wet coating methods such as printing methods are indispensable particularly in the manufacture of large organic EL devices.

  Conventionally, in film formation by a wet coating method, the light emitting layer is formed as a multilayer structure in which a plurality of layers are laminated so that the composition / content of the material of the layer to be formed has a desired structure. As a technique for improving and improving the performance of the device, a dopant concentration gradient in the thickness direction of the light emitting layer is formed by laminating two or more kinds of coating liquids having different dopant concentrations by a die coating method to form a light emitting layer. There is known a method of manufacturing an organic EL element by forming a film (see Patent Document 1).

JP 2012-84415 A

  In the conventional wet coating method suitable for mass production of organic EL elements and large organic EL elements, the surface of the already coated layer is applied when the coating solution is applied and the light emitting layer is laminated. That is, since the coating surface is dissolved by the coating solution to be laminated to produce spots, or interlayer mixing (interfacial mixing) occurs between the laminated layers, a desired layer configuration corresponding to the composition of the coating solution is used. There is a problem that it is difficult to form a multilayer structure. In particular, when layers are stacked using the same luminescent material composition and the same solvent, such interlayer mixing is a major obstacle, and a multilayer structure with a precise layer structure is formed as compared with film formation by vapor deposition. Is difficult. Therefore, depending on the film formation by the wet coating method, it is difficult to produce an organic EL element having a desired layer structure and excellent properties such as luminance and chromaticity, luminous characteristics, luminous efficiency, and luminous lifetime. was there.

  Therefore, the main object of the present invention is to produce a plurality of organic light emitting layers (also referred to as light emitting layers) by laminating an organic light emitting layer coating solution in the production of an organic EL device using a wet coating method. An object of the present invention is to provide a method for producing an organic EL element with good performance by suppressing interlayer mixing between the formed layers.

  The above object of the present invention is achieved by the following configurations.

(1) A method for producing an organic electroluminescence device having a pair of first and second electrodes and a plurality of organic light emitting layers on a substrate, wherein the first electrode is formed on the substrate, A step of laminating and coating a plurality of organic light emitting layer coating solutions prepared with solvents having different permanent dipole moments to form a plurality of organic light emitting layers, the second electrode on the plurality of organic light emitting layers And a step of forming an organic electroluminescent element.
(2) In the step of forming the plurality of organic light emitting layers, after drying the organic light emitting layer coating solution previously applied until the constant rate drying period shifts to the decreasing rate drying period, The method for producing an organic electroluminescent element according to (1), wherein a plurality of organic light emitting layers are formed by laminating and coating the following organic light emitting layer coating solution on the upper layer side.
(3) In the step of forming the plurality of organic light emitting layers, the plurality of organic light emitting layer coating liquids are simultaneously laminated and applied to form a plurality of organic light emitting layers, and the organic electroluminescence according to (1) Device manufacturing method.
(4) The method for producing an organic electroluminescent element according to any one of (1) to (3), wherein the step of forming the plurality of organic light emitting layers is performed in a reduced pressure atmosphere.
(5) The method for producing an organic electroluminescent device according to (2), wherein the coating rate of the organic light emitting layer coating solution laminated and coated on the upper layer side is 4.0 m / min to 30 m / min. .
(6) The method for producing an organic electroluminescent element according to (2), wherein the coating thickness of the organic light emitting layer coating solution laminated and coated on the upper layer side is 5 μm to 100 μm.

  According to the present invention, in the production of an organic EL device using a wet coating method suitable for mass production of organic EL devices and large organic EL devices, a plurality of light emitting layers are formed by laminating an organic light emitting layer coating solution. In this case, it is possible to produce an organic EL element with good performance by suppressing interlayer mixing between the applied layers.

It is a schematic sectional drawing which shows the structure of an organic EL element. It is a partial schematic sectional drawing which shows the structure of the light emitting layer of the organic EL element manufactured by this invention. (A) is a light emitting layer having a two-layer structure, and (b) is a light emitting layer having a plurality of layers (n layers). It is the schematic which shows the film forming apparatus which forms a light emitting layer with a wet coating method. It is the schematic which expanded the application part of the film forming apparatus which forms a light emitting layer with a wet application method.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

<< Configuration of organic EL element >>
The organic EL device produced according to the present invention includes at least a substrate, a first electrode, a second electrode, and a plurality of light emitting layers as constituent elements. Manufactured in a configuration in which an interelectrode structure including a plurality of light-emitting layers is sandwiched between a first electrode and a second electrode provided on a substrate. The first electrode and the second electrode are a pair of an anode and a cathode. The structure between the electrodes may be any of a structure having only a plurality of light-emitting layers, a plurality of light-emitting layers + 1 layer structure, a plurality of light-emitting layers + two-layer structure, or a multilayer structure having more than that. In addition to the plurality of light-emitting layers, other functional layers such as a carrier transport layer and a carrier injection layer can be included. “Carrier” refers to electrons and holes. An element having a structure with only a plurality of light-emitting layers includes an element having a bipolar charge transport material as a light-emitting layer, and an element having a plurality of light-emitting layers plus one layer includes a light-emitting layer that also functions as an electron transport layer and a positive layer. An element composed of a hole transport layer, an element composed of a light emitting layer that also functions as a hole transport layer and an electron transport layer, and an element having a plurality of light emitting layers + two layers structure include a light emitting layer, an electron transport layer, and a hole transport layer. A device formed separately is representative. Furthermore, in order to improve the light emission efficiency, the potential barrier may be adjusted, and other functional layers that perform the functions of carrier injection and confinement may be provided, and a multilayer structure with these layers interposed may be formed. it can.

Specific examples of the configuration between the electrodes having such a multilayer structure include the following. Note that the light emitting layer referred to here refers to a plurality of light emitting layers.
(I) Anode / hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / cathode (ii) anode / hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron Transport layer / electron injection layer / cathode (iii) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode (iv) anode / hole injection layer / hole transport layer / electron blocking layer / Light emitting layer / hole blocking layer / electron transport layer / cathode (v) anode / hole injection layer / hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / cathode ( vi) Anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode

  FIG. 1 shows an example of an organic EL device produced according to the present invention, and an organic EL device in which an electrode is composed of an anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode. It is a schematic sectional drawing of an element. The organic EL element 1 of FIG. 1 has an anode 110 and a cathode 170 formed on a substrate 100. The interelectrode structure includes an anode 110 / a hole injection layer 120 / a hole transport layer 130 / a light emitting layer 140 /. It has a multilayer structure of electron transport layer 150 / electron injection layer 160 / cathode 170. Further, the anode 110, the interelectrode structure, and the cathode 170 on the substrate 100 are sealed with a sealing member 190 via a sealing adhesive 180.

  FIG. 2 shows an example of an organic EL device manufactured according to the present invention. In the step of forming the light emitting layer 140, a coating solution having a different composition is laminated as an organic light emitting layer coating solution containing an organic light emitting material. It is a partial schematic cross section at the time of forming a several light emitting layer. FIG. 2A shows a two-layered light emitting layer composed of an organic light emitting layer 140A and an organic light emitting layer 140B by laminating coating solutions having two different compositions, and FIG. A case where a plurality of coating liquids are stacked to form a light emitting layer having a plurality of layers (n layers) composed of an organic light emitting layer 1401, an organic light emitting layer 1402,. n is an integer greater than 2.

<< Method for Manufacturing Organic EL Element >>

  The present invention relates to a method for manufacturing an organic electroluminescent element (organic EL element) having at least a pair of first and second electrodes and a plurality of light emitting layers on a substrate. A light emitting layer is formed by a wet coating method, that is, formed by forming a film in a liquid phase using a coating liquid, and includes a plurality of organic light emitting layer coating liquids containing an organic light emitting material and having different compositions. By laminating, it is a method that makes it possible to form an interelectrode structure composed of a plurality of light emitting layers in the film thickness direction. In the present invention, among the plurality of organic light emitting layer coating liquids, the organic light emitting layer coating liquids that form adjacent light emitting layers have different permanent dipole moments from each other. Is selected to prepare an organic light emitting layer coating solution, which is laminated and coated on the substrate.

  In the present invention, the permanent dipole moment is a vector quantity that takes a value inherent to a compound, and refers to an electric dipole moment that is expressed in compound molecule units. The difference in the permanent dipole moment means that the magnitude of the absolute value of the permanent dipole moment, which is a vector quantity, is different from each other. The term “permanent dipole moment possessed by the solvent” refers to the permanent dipole moment possessed by the compound constituting the solvent in molecular units.

  In the present invention, a solvent is a liquid that dissolves a substance, and includes a liquid dispersion medium that disperses a substance.

  As an example of the method for producing an organic electroluminescent 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 / light emitting layer / electron transport layer / electron injection layer / cathode Will be described.

(Formation of anode)
First, an anode is formed on a substrate using a desired anode material. The substrate is appropriately cleaned and used as a pretreatment to form a barrier film. The anode material is formed into an anode by vapor deposition or sputtering so that the film thickness is 1 μm or less, preferably 10 to 300 nm.

(Formation of hole injection layer and hole transport layer)
Next, a hole injection layer and a hole transport layer are sequentially formed on the substrate on which the anode is formed. On the upper surface of the anode, a hole injection material is formed by an appropriate method to form a hole injection layer, and on the hole injection layer, a hole transport material is formed to form a hole transport layer. . A wet coating method (casting method, ink jet method, printing method, die coating method, blade coating method, etc.) is used as a film forming method for each of these layers, but a different method may be applied for each layer. When wet coating is performed, the coating is preferably performed in an inert gas atmosphere such as nitrogen, carbon dioxide, helium, neon, argon, krypton, xenon, radon, and more preferably in an inexpensive nitrogen gas atmosphere. . As for the atmosphere at the time of application | coating, it is preferable that oxygen concentration is 1-1000 ppm, It is more preferable that it is 1-100 ppm, Moreover, it is preferable that water concentration is 1-1000 ppm, and it is 1-100 ppm. Is more preferable.

(Formation of light emitting layer)
Next, two light emitting layers are formed on the substrate on which the hole transport layer is formed. The step of forming the light emitting layer will be described later.

(Formation of electron transport layer)
Next, an electron transport layer is formed on the substrate on which the light emitting layer is formed. An electron transport layer is formed on the upper surface of the light emitting layer by an appropriate method using an electron transport material to form an electron transport layer. As a film forming method, a wet coating method (a casting method, an ink jet method, a printing method, a die coating method, a blade coating method, or the like) is used. Preferable conditions for the atmosphere when performing wet coating are the same as those for forming the hole injection layer and the hole transport layer.

(Formation of electron injection layer)
An electron injection layer is formed on the substrate on which the electron transport layer is formed. An electron injection material such as lithium fluoride is deposited on the upper surface of the electron transport layer to form an electron injection layer.

(Formation of cathode)
Subsequently, a cathode is formed on the upper surface of the substrate on which the electron injection layer is formed. A cathode material is formed on the electron injection layer by vapor deposition or sputtering, and the cathode is formed to have a film thickness of 1 μm or less, preferably 50 to 200 nm, whereby an organic EL device is manufactured.

(Post-processing)
The manufactured organic EL element gives the effect of suppressing high-temperature storage stability and chromaticity fluctuation by heat treatment in the range of 40 to 200 ° C. after forming the cathode. When a resin film is used as the substrate, the heating temperature is 40 to 150 ° C., preferably 40 to 120 ° C., and the heat treatment time is in the range of 10 seconds to 30 minutes. The heat-treated organic EL element is sealed by adhering or by adhering a sealing member to the electrode and the substrate using an adhesive.

  As described above, the organic EL device can be produced by forming a thin film in the order from the anode to the cathode, but the cathode, the electron injection layer, the electron transport layer, the light emitting layer, the light emitting layer, and the holes are reversed. It can also be produced in the order of a transport layer, a hole injection layer, and an anode. Accordingly, the substrate on which the anode is formed can be used as the substrate on which the first electrode on which the organic light emitting layer coating liquid for forming the light emitting layer is laminated. A cathode can be formed as an electrode. Alternatively, an anode is formed as a second electrode after forming a plurality of light emitting layers by laminating an organic light emitting layer coating solution on a substrate on which the cathode is formed. You can also. In the case of applying a DC voltage to the manufactured organic EL element in a multi-color display device, light emission can be observed by applying a voltage of about 2 to 40 V with the anode 2 being positive and the cathode 9 being negative. Moreover, arbitrary waveform alternating voltage can also be applied to an element.

<< Formation process of light emitting layer >>
The step of forming the light emitting layer (organic light emitting layer) in the present invention includes, in detail, (S1) a step of preparing an organic light emitting layer coating solution, (S2) a step of applying an organic light emitting layer coating solution, and (S3) organic The step includes primary drying of the light emitting layer coating solution, and (S4) secondary drying of the organic light emitting layer coating solution. By repeating these steps a plurality of times, a thin film containing an organic light emitting material is laminated to form a plurality of organic light emitting layers. In addition, although the process of (S2)-(S3) may be repeated several times by passing through sequentially, you may carry out several times collectively. For example, as a so-called sequential layer coating method, an organic light emitting layer coating solution is applied (S2), the coating solution is first dried (S3), and then the next organic light emitting layer coating solution is applied (S2). After repeating a series of steps of primary drying (S3) of the coating solution, secondary drying (S4) can be performed to form a plurality of organic light emitting layers. The step of applying the coating liquid (S2) is performed in a plurality of times, that is, a plurality of organic light emitting layer coating liquids are simultaneously laminated and applied, and the plurality of laminated coating liquids are primarily dried (S3), and then secondary. A plurality of organic light emitting layers can also be formed by drying (S4). The simultaneous lamination application is not limited to the case where the application start positions or times of the plurality of organic light emitting layer application liquids coincide with each other, and any application may be used as long as each application is performed continuously without interposing a drying step. The number of coatings performed simultaneously is not particularly limited, but if multiple layers are applied at one time, it is difficult to remove the solvent by drying, and there is a risk that layer formation will be poor. It is preferable to carry out by repeating a series of steps of drying. In the present invention, primary drying refers to drying until the transition from the constant rate drying period to the decreasing rate drying period, and secondary drying refers to drying after the decreasing rate drying period starts.

(S1) Step of preparing an organic light emitting layer coating solution In the step of preparing an organic light emitting layer coating solution, an organic light emitting material (light emitting material) constituting the organic light emitting layer is dissolved in a solvent or dispersed in a dispersion medium. Then, at least two or more organic light emitting layer coating solutions having different compositions are prepared. As the solvent / dispersion medium, two or more organic light-emitting layer coating liquids are prepared using different solvents / dispersion media having different permanent dipole moments. Since the permanent dipole moment of the compound constituting the solvent is different for each organic light emitting layer coating solution, when the organic light emitting layer coating solution is laminated to form a light emitting layer, it is already applied by the laminated coating solution. It is possible to suppress dissolution and removal or inter-layer mixing of layers that have been completed until the primary drying and are still wet, and inter-solution inter-solution mixing occurs between adjacent layers during simultaneous lamination coating. Can be suppressed. As a result, an organic EL device having a plurality of light-emitting layers having a desired precise layer structure and improved device performance, that is, light emission characteristics such as luminance and chromaticity, light emission efficiency, and light emission life can be manufactured. In addition, the performance of the organic EL element can be easily improved by selecting from existing materials without searching for new materials.

  As the light emitting material, a known light emitting material such as a bipolar compound or a host compound and a dopant compound described later can be used. The light emitting material can be prepared by changing the concentration of the light emitting material composition and the concentration of the light emitting material component between a plurality of coating liquids so that the light emitting layer has a desired layer composition / layer structure. In this case, a plurality of organic light emitting layer coating solutions can be prepared so as to provide a gradient in the concentration of the light emitting material component.

Examples of the solvent include ketones such as methylene chloride (1.14D), methyl ethyl ketone (2.76D), tetrahydrofuran (1.63D), cyclohexanone (3.01D), and fatty acid esters such as ethyl acetate (1.82D). , Halogenated hydrocarbons such as o-dichlorobenzene (2.14D), m-dichlorobenzene (1.38D), p-dichlorobenzene (0.00D), toluene (0.40D), o-xylene ( 0.44D), m-xylene (0.35D), p-xylene (0.00D), mesitylene (0.07D), cyclohexylbenzene (0.22D) and other aromatic hydrocarbons, cyclohexane (0.00D ), Aliphatic hydrocarbons such as decalin (0.00D), dodecane (0.00D), DMF (3.86D), DMSO (3.9) 6D), alcohols such as n-butanol (1.75D), s-butanol (1.79D), t-butanol (1.66D), and the like, but it is preferable to use an ester compound. The ester compound refers to a compound formed by dehydration condensation of an organic acid such as a carboxylic acid or an inorganic acid such as sulfuric acid with an alcohol. Examples of the organic acid include formic acid, acetic acid, citric acid, oxalic acid, and sulfonic acid, and examples of the inorganic acid include hydrochloric acid, phosphoric acid, nitric acid, sulfuric acid, boric acid, and hydrofluoric acid. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol and the like. . In particular, ester compounds obtained by dehydration condensation of acetic acid and alcohol are suitable, for example, methyl acetate (1.78D), ethyl acetate (1.82D), n-butyl acetate (1.84D), propyl acetate (1.78D). , Isobutyl acetate, isopropyl acetate (1.87D), and phenyl acetate are preferably used.
Moreover, a solvent may be used by 1 type and may be used in mixture of 2 or more types. In this case, the value of the permanent dipole moment is a value obtained by calculating the permanent dipole moment of each solvent by the mixing ratio of the solvent. That is, the value obtained by multiplying the permanent dipole moment value of the mixed solvent type by the volume fraction of the solvent type in the entire solvent is calculated, and the obtained value is added up for all the solvent types to The value of the permanent dipole moment of the solvent in the organic light emitting layer coating solution prepared with the solvent is calculated.

  The permanent dipole moment of the solvent may be different from each other with respect to the coating liquid laminated adjacently in the step of applying the organic light emitting layer coating liquid, but the difference of the permanent dipole moment is 0.01 to 3.0D. It is preferable that it is a range, and it is more preferable that it is 0.05-2.5D. When the difference in permanent dipole moment is 0.01D or more, mixing between coating solutions can be effectively suppressed, and when it is 3.0D or less, the miscibility between coating solutions is excessively lowered, so that the upper layer It can prevent that the applicability | paintability of the coating liquid laminated | stacked on the side becomes inferior. The theoretical value at a predetermined temperature is used as the value of the permanent dipole moment of the solvent in the present invention. Permanent dipole moment values such as the Solvent Handbook (Kodansha Scientific, 1976), Solvent Pocketbook (Ohm, Showa 42), and Chemical Handbook Basics II-576-577 (1993) Can be used.

(S2) Step of applying organic luminescent layer coating solution In the step of applying organic luminescent layer coating solution, the prepared organic luminescent layer coating solution is applied onto a substrate to form a wet film. The first organic light emitting layer coating solution is applied so that the organic light emitting layer coating solution is layered on the substrate on which the first electrode is formed. The coating surface of the first organic light emitting layer coating solution is on the electrode formed on the substrate, or the manufactured organic EL element has a carrier injection layer or carrier transport layer between the electrode and the light emitting layer. In the case of including other functional layers, the upper surface of those layers formed on the substrate on which the electrodes are formed. In this embodiment, the upper surface of the formed hole transport layer is the first coating surface. The second and subsequent coating liquids subsequently applied are dried until the organic light-emitting layer coating liquid previously applied is transferred from the constant rate drying period to the decremental drying period in the case of sequential layer coating. It is applied to a thin film coating solution from which the solvent has evaporated. In other words, the already applied coating solution is finished until constant rate drying, has lost its fluidity but does not reach a complete dry state, and the upper surface of the thin film in a wet state where a lot of solvent remains inside is used as the coating surface. Laminated. In the case of simultaneous multi-layer coating, the multi-layer coating is performed using the upper surface of the wet film before drying of the previously applied coating liquid as the coating surface.

  A plurality of organic light emitting layer coating liquids prepared with solvents having different permanent dipole moments are arranged in a one-to-one relationship such that one organic light emitting layer coating liquid forms one organic light emitting layer. Although it can apply | coat, when forming the light emitting layer which is not adjacent, an organic light emitting layer can also be formed using one organic light emitting layer coating liquid in multiple times. Therefore, the magnitude of the permanent dipole moment may be larger in either the lower layer or the upper layer for the adjacent coating liquid. Due to the difference in the magnitude of the permanent dipole moment of the solvent of each organic light emitting layer coating solution, the miscibility between the solvents decreases, and the time for mixing the organic light emitting layer formed by the coating solution or coating solution is delayed. Thus, interlayer mixing can be suppressed. Moreover, in sequential lamination | stacking application | coating, it can suppress that the lower layer which has already been applied and becomes a wet state used as a coating surface melt | dissolves with a coating liquid.

  As a coating method, any method can be used as long as it is a wet coating method using a coating solution. For example, a casting method, an ink jet method, a printing method, a die coating method, a blade coating method, and a spray coating method are productive. It is preferable from the viewpoint. Of these, the die coating method is particularly preferably used.

  The coating speed can be adjusted as appropriate according to the properties of the coating solution and the thin film to be formed, or environmental conditions such as temperature and atmospheric pressure. In sequential layer coating, the upper side of the organic light emitting layer coating solution previously applied With respect to the coating of the second and subsequent coating liquids laminated on the substrate, 4.0 m / min to 30 m / min is preferable, and 5.0 m / min to 25 m / min is more preferable. When laminating a light emitting layer using a coating solution having a similar component composition, the coating layer is dissolved and formed by the coating solution because the coating speed is 4.0 m / min or more. It is possible to prevent the film thickness of the light emitting layer from deviating from the set film thickness.

  The coating thickness can be set to an appropriate thickness by adjusting the discharge amount and discharge pressure of the coating solution according to the properties of the coating solution and the thin film to be formed, or the environmental conditions such as temperature and pressure, etc. In the above, for the coating of the second and subsequent coating liquids laminated on the upper layer side of the organic light emitting layer coating liquid previously applied, the coating film thickness is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm, and more preferably 20 μm to 50 μm is more preferable. When the coating film thickness of the coating liquid to be laminated is 5 μm or more in terms of wet film thickness, the degree of dissolution of the light emitting layer material previously coated in the laminated coating liquid is small, and the film thickness after lamination is Generation | occurrence | production of the phenomenon which falls can be suppressed.

  The atmosphere at the time of application can be normal pressure, but is preferably a reduced pressure atmosphere. The degree of decompression is preferably −5% of atmospheric pressure, more preferably −10% of atmospheric pressure. By setting the environment at the time of application under reduced pressure, the occurrence of so-called blown spots can be suppressed, the drying speed can be increased, and an appropriate layered state can be obtained.

(S3) Step of primarily drying the organic light emitting layer coating solution In the step of primary drying of the organic light emitting layer coating solution, the coating solution forming a wet film is transferred from the constant rate drying period to the decreasing rate drying period. Allow to dry. In the primary drying process, the coating liquid tends to dry. During this period, evaporation of the surface layer solvent of the coating solution proceeds while being affected by factors such as the external temperature, the speed determined by the solvent vapor concentration, and the degree of circulation to the surface layer.

  As the primary drying method, it is usually preferable to use blow drying at room temperature.

(S4) The step of secondary drying the organic light emitting layer coating solution In the step of secondary drying of the organic light emitting layer coating solution, the organic light emitting layer coating solution that has undergone the primary drying and shifted to the decreasing rate drying period has a drying rate of approximately Dry until steady state. In the secondary drying step, the solvent separation rate of the coating solution is in a reduced state (decreasing drying period). This is due to penetration at the liquid interface within the material. During this period, since the moving distance between the formed vapor and the liquid interface increases, the drying rate tends to decrease.

  As the secondary drying method, it is usually preferable to use blow drying at room temperature.

<< Emission layer deposition apparatus >>
The process of forming the light emitting layer (organic light emitting layer) in the present invention will be described along the example of the film forming apparatus shown in FIG. FIG. 3 is a schematic view showing an example of a film forming apparatus for forming a light emitting layer by a wet coating method.

  As shown in FIG. 3, the film forming apparatus 2 mainly includes an unwinding unit 21, a coating unit 22, and a drying unit 23. The unwinding unit 21, the coating unit 22, and the drying unit 23 are all in a sealed state isolated from the outside air, and the pressure and circulation of the internal gas are controlled so that a predetermined internal atmosphere can be maintained.

  The unwinding unit 21 includes a substrate original winding roll 200 and a transport roller 250. The flexible substrate 100 is wound around the substrate former winding roll 200. Drive means (not shown) for rotating the transport roller 250 is connected to the transport roller 250. The transport roller 250 is configured to transport the substrate in the transport direction A along with the rotation.

  The coating unit 22 includes two slot die coaters 210a and 210b, back rollers 240a and 240b, and a transport roller 250. The back rollers 240a and 240b are arranged at a predetermined interval in the transport direction of the substrate 100, and are connected to driving means (not shown) for rotating the back rollers 240a and 240b, respectively. The slot die coaters 210a and 210b are arranged at positions facing the back rollers 240a and 240b with the substrate 100 interposed therebetween. Storage tanks 220a and 220b are connected to the slot die coaters 210a and 210b via liquid feed pumps 230a and 230b, respectively. The organic light emitting layer coating solution is stored in the storage tanks 220a and 220b.

  FIG. 4 is an enlarged schematic view of the coating unit 22 of the film forming apparatus. The two slot die coaters 210a and 210b have slits 212a and 212b, respectively, and have lips 213a and 213b at the ends of the slits 212a and 212b. The lips 213a and 213b form discharge ports 211a and 211b each having a linear gap between their end portions. The slits 212a and 212b communicate with liquid feeding pipes connected to the liquid feeding pumps 230a and 230b (see FIG. 3), respectively.

  The drying unit 23 (see FIG. 3) includes a heater 260 and a transport roller 250. A plurality of heaters 260 are provided below the transfer position so as to face the surface opposite to the coating surface of the substrate 100.

<Operation of film forming apparatus>
The operation of the film forming apparatus for forming the light emitting layer by the wet coating method shown in FIG. 3 will be described.

  First, the substrate 100 on which the first electrode is formed is wound to form a substrate original winding roll 200 and installed in the unwinding unit 21. Further, in order to stack the light emitting layers, the first organic light emitting layer coating liquid prepared to contain a desired organic light emitting material is stored in the storage tank 220a, and the second organic light emitting layer coating liquid is stored in the storage tank 220b. Fill each.

  First, the substrate 100 wound around the substrate original winding roll 200 is fed out in the transport direction A by a driving unit (not shown) and transported to the coating unit 22 via the transport roller 250.

  Next, while the substrate 100 transported to the coating unit 22 is transported by the back rollers 240a and 240b, the first slot die coater 210a causes the first organic light emission to the substrate 100 at the first coating position on the back roller 240a. Apply the layer coating solution. The first organic light emitting layer coating solution stored in the storage tank 220a is supplied to the slot die coater 210a by appropriately adjusting the supply amount of the coating solution by the liquid feeding pump 230a. As shown in FIG. 4, the first coating liquid 140a for forming the lower light emitting layer is fed from the storage tank 220a to the slit 212a and applied to the substrate 100 from the discharge port 211a to form a wet layer. To do.

  Subsequently, the second slot is formed at the second coating position on the back roller 240b while the substrate 100 coated with the first organic light emitting layer coating liquid is further transported in the transport direction A by the back rollers 240a and 240b. The second organic light emitting layer coating solution is applied to the substrate 100 by the die coater 210b. The second organic light emitting layer coating solution stored in the storage tank 220b is supplied to the slot die coater 210b by appropriately adjusting the supply amount of the coating solution by the liquid feeding pump 230b. As shown in FIG. 4, the second organic light emitting layer coating liquid 140b for forming the upper light emitting layer is fed from the storage tank 220b to the slit 212b, and the first coating liquid 140a is formed from the discharge port 211b. The film is laminated and applied on the wet film.

  The substrate 100 coated with the second organic light emitting layer coating solution is conveyed to the drying unit 23 via the conveyance roller 250. In the drying unit 23, the conveyed substrate 100 is subjected to a primary drying process and a secondary drying process. At this time, the temperature in the atmosphere on the side coated with the coating liquid (the surface of the substrate 100) is 30 ° C. or less, and the opposite side (the back surface of the substrate 100) is heated to 35 to 60 ° C. with the heater 260. The thin film of the coating liquid in which the coating liquids 140a and 140b are laminated is subjected to a drying process, whereby the solvent is removed, and two laminated light emitting layers are formed.

  The substrate 100 on which the light emitting layer is formed is wound up by a winding roll (not shown), and used for the formation of other functional layers and the formation process of the second electrode. Moreover, it is also possible to cut into a sheet shape and to use for a post process, without winding up to a winding roll.

<Components of organic EL elements>
The materials, characteristics, etc. of the main constituent elements of the organic EL device produced according to the present invention will be described.

<Light emitting layer>
The light-emitting layer is a layer containing a light-emitting material that emits light by combining electrons and holes injected from an electrode. As the light-emitting material, a known bipolar compound can be used, as well as a carrier. It can be configured to contain a host compound responsible for transport of light and a dopant compound responsible for light emission. The light-emitting layer can have a structure in which a plurality of layers having different compositions are stacked, and there may be a plurality of layers having the same emission spectrum or emission maximum wavelength. Further, the light emitting portion may be in the light emitting layer or at the interface between the light emitting layer and the adjacent layer.

  The total thickness of the light emitting layers is not particularly limited, but is preferably in the range of 1 to 100 nm, and more preferably 50 nm or less because a lower driving voltage can be obtained. The film thickness of each light emitting layer is preferably adjusted in the range of 1 to 50 nm. There is no particular limitation on the relationship between the film thicknesses of the blue, green and red light emitting layers.

(Host compound)
As the host compound, a known host compound having a hole transporting ability and an electron transporting ability may be used alone, or a plurality of kinds may be used in combination. 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 luminescent materials, and can thereby obtain arbitrary luminescent colors.

  As the host compound used in the present invention, either a conventionally known low molecular compound or a high molecular compound having a repeating unit can be used, and a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (polymerization) Luminescent host) can also be used.

  As the polymer compound, a material having a molecular weight of 1500 or less at the time of coating is preferable, and a material of 1000 or less is more preferable. By using a material having a molecular weight within this range, it is possible to prevent the host compound from taking in the solvent to cause swelling, gelation, and the like, thereby making it difficult to remove the solvent.

  As the host compound, a compound that has a hole transporting ability and an electron transporting ability, prevents emission of longer wavelengths, and has a high Tg (glass transition temperature) is preferable. Here, the glass transition point (Tg) is a value determined by a method based on JIS K 7121 using DSC (Differential Scanning Colorimetry). Moreover, the compound whose phosphorescence quantum yield of phosphorescence emission in room temperature (25 degreeC) is less than 0.1 is preferable, and the compound whose phosphorescence quantum yield is less than 0.01 is more preferable. The host compound preferably has a weight ratio of 60% or more in the compound contained in the light emitting layer.

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

  Moreover, as a host compound, the dibenzofuran compound represented by the following general formula (A) can be used. These dibenzofuran compounds can be synthesized according to a conventionally known synthesis method.

In the general formula (A), R ^{1 to} R ⁸ each represent a hydrogen atom, an alkyl group, an aryl group, a carbazolyl group, or an azacarbazolyl group, and when there are a plurality of them, they may represent different ones, and any substitution It may have a group. In addition, the above substituents may have a linking group and may be combined in plural. As a preferable mode, the general formula (A) is asymmetrically substituted, and specifically, a 2,6-dibenzofurandiyl group, a 2,4,8-dibenzofurantriyl group, and the like are preferable.

  20-99.0 mass% of the light emitting layer to add is preferable, and, as for content of a dibenzofuran compound, 50-97.5 mass% is more preferable.

  Specific examples of the dibenzofuran compound represented by formula (A) (Exemplary Compound A-1 to Exemplified Compound A-78) are shown below, but the compounds used in the present invention are not limited thereto.

(Dopant compound)
As a dopant compound contained in the light emitting layer, a fluorescent dopant (also referred to as a fluorescent compound, a fluorescent light emitting compound, etc.), a phosphorescent dopant (also referred to as a phosphorescent compound, a phosphorescent light emitting compound, etc.) can be used. Alternatively, these can be used in combination. The phosphorescent dopant is a compound in which light emission from an excited triplet is observed, specifically, a compound that emits phosphorescence at room temperature (25 ° C.), and a phosphorescence quantum yield of 0.01 or more at 25 ° C. However, the phosphorescence quantum yield is preferably 0.1 or more.

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

  There are two types of light emission principles of phosphorescent dopants. One is the recombination of carriers on the host compound to which carriers are transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent dopant. Energy transfer type to obtain light emission from the phosphorescent dopant, and another is the carrier trap that the phosphorescent dopant becomes a carrier trap, and carrier recombination occurs on the phosphorescent dopant, and light emission from the phosphorescent dopant is obtained. 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 host compound.

  As a fluorescent dopant, the well-known thing used for the light emitting layer of an organic EL element can be used. Specifically, coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes, stilbene dyes , Polythiophene dyes, or rare earth complex phosphors.

  As a phosphorescence dopant, the well-known thing used for the light emitting layer of an organic EL element can be used. Specific examples include complex compounds containing 8-10 group metals in the periodic table of elements, such as iridium compounds, osmium compounds, platinum compounds (platinum complex compounds), rare earth complexes, and the like.

  Although the specific example (Exemplary compound D-1-Exemplified compound D-133) of the compound used as a phosphorescence dopant is given to the following, this invention is not limited to these. These compounds are described, for example, in Inorg. Chem. 40, 1704-1711, etc.

  As the dopant compound to be contained in the light emitting layer, one kind may be used alone, or two or more kinds of dopant compounds having different emission maximum wavelengths may be used. When two or more types of dopant compounds are contained, a concentration gradient may be formed in the thickness direction of the light emitting layer for all the dopant compounds, but only one type of dopant compound may be formed. When forming a concentration gradient only for one kind of dopant compound, it is preferable to form a concentration gradient for the dopant compound having the shortest emission maximum wavelength.

"anode"
The anode is formed on a substrate using a high work function (4 eV or more) metal, alloy, electrically conductive compound, and a mixture thereof as an electrode material. 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) that can form a transparent conductive film can be used.

  The anode may be formed as a thin film using a method such as vapor deposition or sputtering, and then a pattern having a desired shape may be formed by a photolithography method, or pattern accuracy is not required. The pattern may be formed by forming the electrode substance as a thin film by a method such as vapor deposition or sputtering through a mask having a desired shape (about 100 μm or more). Or when using the substance which can be apply | coated like an organic electroconductive compound, the wet application | coating method of a printing system or a coating system can also be used.

  When light emission is taken out from the anode side, it is desirable that the transmittance be greater than 10%, and the sheet resistance of the anode is preferably several hundred Ω / □ or less.

  The film thickness of the anode can be appropriately determined according to the electrode substance used as a material, but is about 10 to 1000 nm, preferably 10 to 200 nm.

"cathode"
The cathode is formed on a substrate using 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. 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, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the point of durability against electron injection and oxidation, a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function value 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 formed as a thin film by depositing these electrode materials by a method such as vapor deposition or sputtering.

  The sheet resistance of the cathode is preferably several hundred Ω / □ or less.

  The film thickness of the cathode can be set appropriately depending on the electrode material used, but is about 5 to 10 μm, preferably 50 to 200 nm.

  In order to transmit the light generated in the light emitting layer to the outside of the device, the light emission luminance of the device can be improved by making either the anode or the cathode transparent or translucent. About a cathode, after forming a cathode with a film thickness of 1-20 nm, a transparent or semi-transparent cathode can be manufactured by covering the electroconductive transparent material well-known as an electrode material of an anode on it.

"substrate"
A board | substrate is a support body thru | or base material which supports the components of organic EL elements, such as an electrode and a light emitting layer. In the present invention, in addition to the substrate itself, a substrate in the process of manufacturing an element in which electrodes and other layers are laminated may also be referred to as a “substrate” when it is subjected to a predetermined process. . For example, “to form on a substrate” includes not only the case of being formed directly on the substrate but also the case of being formed on a component formed on the substrate (the same applies to “on the organic light emitting layer”). ). Examples of the substrate include a plate-like substrate, a sheet-like or film-like flexible substrate, and the shape is not particularly limited, and may be a rectangle, a circle, or other complex shape. It's okay. As the material of the substrate, glass, plastic, ceramics, metal or the like can be used, and any of an opaque substrate and a transparent substrate can be used. Examples of the opaque substrate include a metal plate such as aluminum and stainless steel, an opaque resin substrate, and a ceramic substrate. Examples of the transparent substrate include a glass substrate, a quartz substrate, and a transparent resin film. In a substrate that is more flexible than a rigid substrate, the effect of suppressing high-temperature storage stability and chromaticity variation appears greatly, and thus a particularly preferable substrate has flexibility that can give flexibility to an organic EL element. A substrate made of a resin film. Moreover, when taking out light from the board | substrate side, it is preferable that a board | substrate is transparent.

  Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, cellulose acetate propionate ( CAP), cellulose esters such as cellulose acetate phthalate, 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 polyarylates, Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Etc. can be used.

The substrate having flexibility has a tensile strength of 20 to 80 kg / mm ² and an elastic modulus in an arbitrary direction parallel to the substrate surface of 1000 to 2500 kg / mm ^2, which is parallel to the substrate surface. Those having a breaking elongation of 5% or more in any direction are preferred.

A film made of an inorganic material, an organic material, or a hybrid thereof may be formed on the surface of the substrate. As such a film, the water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method according to JIS K 7129-1992 is 1 × 10 ⁻³ g / (M ² · 24h) What is a barrier film of the following, Furthermore, the oxygen permeability measured by the method based on JIS K 7126-1987 is 1 × 10 ⁻³ ml / m ² · 24 h · atm or less A film having a high barrier property with a water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) of 1 × 10 ⁻³ g / (m ² · 24 h) or less is suitable. .

  The material for forming the barrier film may be any material that has a function of suppressing the intrusion of moisture, oxygen, or the like that degrades the element. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Furthermore, in order to improve the brittleness of the coating, it is more preferable to give the coating a laminated structure. The laminated structure can be formed, for example, by alternately laminating inorganic layers and organic layers a plurality of times.

  Examples of the method for forming a barrier film include a vacuum deposition method, a sputtering method, a reactive sputtering method, a molecular beam epitaxy method, a cluster ion beam method, an ion plating method, a plasma polymerization method, an atmospheric pressure plasma polymerization method, Examples thereof include a plasma CVD method, a laser CVD method, a thermal CVD method, and a coating method.

<< carrier injection layer: hole injection layer, electron injection layer >>
In the present invention, the carrier injection layer can be provided as necessary. The carrier injection layer is a layer provided between the electrode and the organic compound layer in order to lower the driving voltage and improve the light emission luminance. “The organic EL element and its forefront of industrialization (November 30, 1998, NTS Corporation) Issue) ”, Chapter 2, Chapter 2,“ Electrode Materials ”(pages 123 to 166), which is described in detail, and includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer). The hole injection layer is interposed between the anode and the light emitting layer, or between the anode and the hole transport layer, and the electron injection layer is interposed between the cathode and the light emitting layer, or between the cathode and the electron transport layer. Can be made.

  The details of the hole injection layer are described, for example, in JP-A-9-45479, JP-A-9-260062, and JP-A-8-288069. Injection materials include triazole derivatives, oxadiazole derivatives, imidazole derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, stilbene derivatives. , Polymers containing silazane derivatives, aniline copolymers, polyarylalkane derivatives, or conductive polymers, preferably polythiophene derivatives, polyaniline derivatives, polypyrrole derivatives, more preferably Thiophene derivatives.

  The thickness of the hole injection layer is not particularly limited, but is about 0.1 nm to 5 μm, preferably 0.1 to 100 nm, more preferably 1 to 100 nm, and most preferably 10 to 60 nm.

  Details of the electron injection layer are described in, for example, JP-A-6-325871, JP-A-9-17574, and JP-A-10-74586, and specifically, strontium, aluminum and the like are representative. A metal buffer layer, an alkali metal compound buffer layer typified by lithium fluoride, an alkaline earth metal compound buffer layer typified by magnesium fluoride, and an oxide buffer layer typified by aluminum oxide.

  The thickness of the electron injection layer is not particularly limited, but is about 0.1 nm to 5 μm, preferably 0.1 to 100 nm, more preferably 0.5 to 10 nm, and most preferably 0.5 to 4 nm. is there.

《Hole transport layer》
In the present invention, the hole transport layer can be provided as necessary. The hole transporting material constituting the hole transporting layer is a material having either hole injection or transport or electron barrier properties, and the same compound as that used for the hole injecting layer is used. In addition, porphyrin compounds, aromatic tertiary amine compounds and styrylamine compounds, in particular aromatic tertiary amine compounds can be used.

  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 ' Di (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 those described in US Pat. No. 5,061,569 Having four condensed aromatic rings in the molecule, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 08688 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 semiconductors 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-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. , 95, 5773 (2004), JP-A-11-251067, J. MoI. Huang et. al. Use of a hole transport material that has a so-called p-type semiconducting property, as described in a book (Applied Physics Letters, 80 (2002), p. 139), JP 2003-519432 A You can also.

  For the hole transport layer, the hole transport material is formed by using, for example, a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, a slot die method, a spray coating method, an LB method, a dip coating method, or a blade method. , And a known method such as a slit coating method.

  The thickness of the hole transport layer is not particularly limited, but is about 5 nm to 5 μm, preferably 5 to 200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

  Hereinafter, preferred specific examples of the compound used as the hole transporting material will be given, but the invention is not limited thereto.

  In addition, n described in the above exemplary compounds represents the degree of polymerization and represents an integer having a weight average molecular weight in the range of 50,000 to 200,000. If the weight average molecular weight is less than this range, there is a concern of mixing with other layers during film formation due to the high solubility in the solvent. Even if a film can be formed, the light emission efficiency does not increase at a low molecular weight. When the weight average molecular weight is larger than this range, problems arise due to difficulty in synthesis and purification. Since the molecular weight distribution increases and the residual amount of impurities also increases, the light emission efficiency, voltage, and life of the organic EL element deteriorate. These polymer compounds are disclosed in Makromol. Chem. , Pages 193, 909 (1992) and the like.

《Electron transport layer》
In the present invention, the electron transport layer can be provided as necessary. 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 a single layer, but a plurality of layers can also be provided.

  The electron transport material constituting the electron transport layer (also serving as a hole blocking material) may have a function of transmitting electrons injected from the cathode to the light-emitting layer. Any one can be selected and used, for example, fluorene derivatives, carbazole derivatives, azacarbazole derivatives, oxadiazole derivatives, thiadiazole derivatives, trizole derivatives, silole derivatives, pyridine derivatives, pyrimidine derivatives, diphenylquinone derivatives, Examples thereof include metal complexes such as thiopyrandioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethanes, anthrone derivatives, and 8-quinolinol derivatives.

  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. Moreover, the said dibenzofuran compound can be used.

  In addition, inorganic semiconductors such as n-type-Si and n-type-SiC 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.

  The electron transport layer is formed by using, for example, a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, a slot die method, a spray coating method, an LB method, a dip coating method, a blade method, and the like. The thin film can be formed by a known method such as a slit coating method.

  The thickness of the electron transport layer is not particularly limited, but is about 5 nm to 5 μm, preferably 5 to 200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials.

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

  The electron transport layer preferably contains an alkali metal salt of an organic substance. There are no particular restrictions on the type of organic substance, but formate, acetate, propionic acid, butyrate, valerate, caproate, enanthate, caprylate, oxalate, malonate, succinate Benzoate, phthalate, isophthalate, terephthalate, salicylate, pyruvate, lactate, malate, adipate, mesylate, tosylate, benzenesulfonate , Preferably formate, acetate, propionate, butyrate, valerate, caprate, enanthate, caprylate, oxalate, malonate, succinate, benzoate, more preferably Is preferably an alkali metal salt of an aliphatic carboxylic acid such as formate, acetate, propionate or butyrate, and the aliphatic carboxylic acid preferably has 4 or less carbon atoms. Most preferred is acetate.

  The type of alkali metal of the alkali metal salt of the organic substance is not particularly limited, and examples thereof include Na, K, and Cs, preferably K, Cs, more preferably Cs. Examples of the alkali metal salt of the organic substance include a combination of the above organic substance and alkali metal, preferably, formic acid Li, formic acid K, Na formate, formic acid Cs, acetic acid Li, acetic acid K, Na acetate, acetic acid Cs, propionic acid Li, Propionic acid Na, propionic acid K, propionic acid Cs, oxalic acid Li, oxalic acid Na, oxalic acid K, oxalic acid Cs, malonic acid Li, malonic acid Na, malonic acid K, malonic acid Cs, succinic acid Li, succinic acid Na, succinic acid K, succinic acid Cs, benzoic acid Li, benzoic acid Na, benzoic acid K, benzoic acid Cs, more preferably Li acetate, K acetate, Na acetate, Cs acetate, most preferably Cs acetate.

  The content of these dope materials is preferably 1.5 to 35% by mass, more preferably 3 to 25% by mass, and most preferably 5 to 15% by mass with respect to the electron transport layer to be added. is there.

<Sealing>
As a sealing means used for sealing the organic EL element, any method such as casing type sealing (can sealing) and close contact type sealing (solid sealing) can be used. When the organic EL element is to be flexible or thin, it is preferable to use solid sealing. Specifically, for example, a method of adhering the sealing member, the electrode, and the base material with an adhesive can be mentioned. When sealing using a sealing member, it is preferable to seal so that the whole several light emitting layer in the surface opposite to the light emission surface of the surface emitting panel which arranged several organic EL elements may be covered.

  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. When processing into a concave shape, it can be performed by sandblasting, chemical etching, or the like. Further, transparency and electrical insulation are not particularly limited. Specifically, a glass plate, a polymer plate, a polymer film, a metal plate, a metal film, etc. are mentioned. Examples of the glass plate include soda lime glass, barium-containing glass, strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate and the polymer film include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, polysulfone and the like. The metal plate or metal film is 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, silicone, germanium, and tantalum. Is mentioned.

  Adhesives include photo-curing and thermosetting adhesives having reactive vinyl groups such as acrylic acid oligomers and methacrylic acid oligomers, moisture-curing adhesives such as 2-cyanoacrylates, epoxy-based adhesives, etc. And heat-curing type (two-component mixed) adhesives, hot-melt type polyamides, polyesters, and polyolefin-based adhesives. 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. Further, a desiccant may be dispersed in the adhesive. Application | coating of the adhesive agent to a sealing part may use commercially available dispenser, and may print it like screen printing.

  In addition, as a sealing means used for sealing an organic EL element, an inorganic layer and an organic layer are formed in such a manner that the electrode and the organic layer are coated on the outer side of the electrode facing the substrate with the organic layer interposed therebetween and in contact with the substrate. To form a sealing film. The material for forming the sealing film may be any material that has a function of suppressing entry of moisture, oxygen, or the like that causes deterioration of the element. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Furthermore, in order to improve brittleness, the layer forming the sealing film can have a laminated structure. Examples of the method for forming the sealing film include a vacuum deposition method, a sputtering method, a reactive sputtering method, a molecular beam epitaxy method, a cluster ion beam method, an ion plating method, a plasma polymerization method, an atmospheric pressure plasma polymerization method, and a plasma CVD method. Method, laser CVD method, thermal CVD method, coating method and the like can be used.

  The gap between the sealing member and the display area of the organic EL element can be sealed as a vacuum state. Further, it can be filled with an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil, and a hygroscopic compound can also be sealed inside. Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide), 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, barium perchlorate, Magnesium perchlorate etc.) can be used, and anhydrous salts are preferably used in sulfates, metal halides and perchloric acids.

《Protective film, protective plate》
The organic EL element can be provided with a protective film or a protective plate for increasing the mechanical strength of the element outside the sealing means. In particular, when sealing is performed with a 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 for the protective film or the protective plate, a glass plate, a polymer plate, a polymer film, a metal plate, a metal film, or the like can be used.

<< light extraction means >>
The organic EL element can improve light extraction efficiency by providing light extraction means. Examples of the light extraction means include a method of providing a light extraction member between the substrate and the anode, or anywhere on the light emission side from the substrate. Examples of the light extraction member include a prism sheet, a lens sheet, and a diffusion member. A sheet or the like can be used. The organic EL element emits light inside a layer having a refractive index higher than that of air (refractive index of about 1.6 to 2.1) and can extract only about 15% to 20% of 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 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 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 (for example, US Pat. No. 4,774,435), collecting on the substrate. A method for improving efficiency by imparting light properties (for example, Japanese Patent Laid-Open No. Sho 63-314795), a method for forming a reflecting surface on the side surface of an element (for example, 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 light emitters (for example, Japanese Patent Application Laid-Open No. 62-172691), and a lower refractive index than the substrate between the substrate and the light emitter. (For example, Japanese Patent Laid-Open No. 2001-202827), a method of forming a diffraction grating between any one of the substrate, the transparent electrode layer, and the light emitting layer (including between the substrate and the outside world) Kaihei 11-2 JP) or the like 3751 and the like. These methods can be used in combination with the organic EL element according to the present invention. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, a transparent electrode layer, and light emission A method of forming a diffraction grating between any of the layers (including between the substrate and the outside) can be suitably used. By combining these means, it is possible to obtain an element having higher brightness or durability.

  Between the transparent electrode and the transparent substrate, a low-refractive index medium can be formed, and a low-refractive index layer having a thickness longer than the wavelength of light can be formed. The lower the is, the higher the extraction efficiency to the outside. Examples of the medium for the low refractive index layer include airgel, 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 refractive index of the low refractive index layer is preferably 1.5 or less, and more preferably 1.35 or less. The thickness of the low refractive index layer 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 that causes total reflection or in any medium has a feature that the effect of improving the light extraction efficiency is high. 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 or second-order diffraction. The light that cannot be emitted due to total internal reflection between layers is diffracted by introducing a diffraction grating into any layer or medium (in the transparent substrate or transparent electrode). , Trying to extract light 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. The light extraction efficiency does not increase so much.

  However, by making the refractive index distribution a two-dimensional distribution, light traveling in all directions is diffracted, and light extraction efficiency is increased.

  The position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or 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 gratings is preferably two-dimensionally repeated, such as a square lattice, a triangular lattice, or a honeycomb lattice.

  An organic EL element can be processed so that the light extraction side of the substrate has a microlens array structure, or combined with a condensing sheet, so that the light emission luminance in a specific direction such as the front direction with respect to the light emitting surface of the element can be increased. Can be increased. Moreover, in order to control the light emission angle from an element, a light-diffusion plate and a light-diffusion film can be used together with a condensing sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

  As a microlens array-like structure, for example, a structure in which a quadrangular pyramid having a side of 30 μm and an apex angle of 90 degrees is arranged two-dimensionally on the light extraction side of the substrate. One side of the quadrangular pyramid shape is preferably 10 to 100 μm, and if it is shorter than this, the effect of diffraction is generated and colored, and if it is longer, the structure becomes thick.

  As the condensing sheet, for example, a sheet that has been put into practical use in an LED backlight of a liquid crystal display device can be used. Specifically, a brightness enhancement film (BEF) manufactured by Sumitomo 3M Limited can be used. As the prism shape on the surface of the condensing sheet, for example, the substrate may have a triangle shape with a vertex angle of 90 degrees and a pitch of 50 μm, or the vertex angle is rounded and the pitch is random. The shape may be changed to other shapes or other shapes.

  The organic EL element can be a white light emitting organic EL element. The white light-emitting organic EL element is used as a kind of lamp such as an illumination light source or an exposure light source, used as a projection device for projecting an image, or as a display device (display) for directly viewing a still image or a moving image. can do. The driving method when used as a display device for moving image reproduction may be either a simple matrix (passive matrix) method or an active matrix method. In this case, as a dopant compound used in the light emitting layer, for example, in the case of a backlight in a liquid crystal display element, a platinum complex or a known dopant compound is used so as to be adapted to a wavelength range corresponding to a CF (color filter) characteristic. Any one can be selected to whiten. Moreover, it can also be whitened by combining light extraction means. By arranging the element and the drive transistor circuit in accordance with the CF (color filter) pattern, the white light extracted from the organic EL element is used as the backlight, and the blue light, the green light, and the red light are transmitted through the blue filter, the green filter, and the red filter. Light can be obtained, and a full-color organic electroluminescence display with a low driving voltage and a long lifetime can be obtained. As described above, the white light-emitting organic EL element can be used as a display device, a display, and various light-emitting light sources. Examples of light sources include 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 sources of optical sensors However, it is not limited to this. In particular, it can be used effectively as a backlight for various display devices combined with a color filter, a light diffusing plate, a light extraction film, or the like, or as a light source for illumination.

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

<< Production of organic EL element >>
(1) Preparation of organic EL element 101-106 The organic EL element was produced using the manufacturing method which concerns on this invention. The light-emitting layer has a two-layer structure in which two types of organic light-emitting layer coating liquids are sequentially laminated to form two types of organic light-emitting layers that respectively form an anode-side light-emitting layer (lower layer) and a cathode-side light-emitting layer (upper layer). About the coating liquid, the following organic EL elements 101-106 used as the combination from which the permanent dipole moment of a solvent differs were produced. Moreover, the organic EL element 101 in which the permanent dipole moment of the solvent of two types of coating liquids is the same was produced as a comparative example. The permanent dipole moment of the solvent used was 1.78D for n-propyl acetate, 0.40D for toluene, 1.35D for anisole, 1.82D for ethyl acetate, 1.82D for acetonitrile, 3.91D.

(1-1) Production of Organic EL Element 101 The permanent dipole moment of the solvent of the two organic light emitting layer coating solutions for forming the anode side light emitting layer (lower layer) and the cathode side light emitting layer (upper layer) is the same. The organic EL element 101 of the comparative example to be produced was manufactured by the following procedure.

(1-1-1) Preparation of Substrate A transparent barrier film having a thickness of about 90 nm was formed on a 50 m × 180 mm × 0.125 mm PEN (polyethylene naphthalate) substrate by an atmospheric pressure plasma polymerization method. As a result of measuring the water vapor transmission rate by a method according to JIS K 7129B, it was 10 ⁻³ g / m ² / day or less. As a result of measuring the oxygen transmission rate by a method based on JIS K 7126B, it was 10 ⁻³ g / m ² / day or less.

(1-1-2) Formation of anode A 120 nm thick ITO (Indium Tin Oxide) film is formed on the prepared gas barrier flexible film by sputtering and patterned by photolithography to form the anode. did. The pattern was such that the light emission area was 400 mm square.

(1-1-3) Formation of Hole Injection Layer The patterned ITO substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes. On this substrate, a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (abbreviated as PEDOT / PSS, manufactured by Bayer, Baytron P Al 4083) to 70% with pure water was applied by a slot die coating method. After film formation at a speed of 1 m / min, it was dried at 200 ° C. for 1 hour as secondary drying. In this way, a hole injection layer having a thickness of 30 nm was formed.

(1-1-4) Formation of Hole Transport Layer This substrate was transferred to a nitrogen atmosphere using nitrogen gas (grade G1) and exemplified compound (60) (Mw = 80,000) as a hole transport material. A solution in which 0.5% was dissolved in chlorobenzene was formed at a coating speed of 1 m / min by the slot die coating method, and then dried at 160 ° C. for 30 minutes as secondary drying. In this way, a hole transport layer having a thickness of 30 nm was formed.

(1-1-5) Formation of Light-Emitting Layer (Lower Layer) Next, a light-emitting layer composition (organic light-emitting layer coating solution) having the following composition was prepared, and this was formed by a slot die coating method at a coating speed of 0.5 m / min. After that, the drying process was continued until the constant rate drying process was completed and the reduced rate drying process was started to obtain a wet state. Coating and drying were performed in a nitrogen atmosphere at room temperature using the film forming apparatus 2 shown in FIG. In this way, a light emitting layer (lower layer) having a thickness of 30 nm was formed.

<Light emitting layer (lower layer) composition>
Exemplified Compound A-67 22.3 parts by mass Exemplified Compound D-67 0.05 parts by mass Exemplified Compound D-80 0.05 parts by mass n-propyl acetate 2,000 parts by mass

(1-1-6) Formation of Light-Emitting Layer (Upper Layer) A light-emitting layer composition (organic light-emitting layer coating solution) having the following composition was prepared by a slot die coating method at a coating speed of 5.0 m / min and a wet film thickness of 20 μm. After film formation, it was dried. Coating and drying were performed using a film forming apparatus 2 shown in FIG. 3 in a nitrogen atmosphere. Then, it was dried for 30 minutes in the drying section. In this way, a light emitting layer (upper layer) having a thickness of 30 nm was formed. During drying, the temperature in the atmosphere on the side of the substrate on which the light emitting layer was coated (coating surface) was 25 ° C., and the temperature on the opposite side (back surface) was 30 ° C.

<Light emitting layer (upper layer) composition>
Illustrative Compound A-67 22.3 parts by mass Illustrative Compound D-66 4.9 parts by mass n-propyl acetate 6,700 parts by mass

(1-1-7) Formation of Electron Transport Layer Subsequently, 30 mg of Compound A-77, which is a compound represented by General Formula (A), was dissolved in 4 ml of tetrafluoropropanol (TFPO). After forming a film at a coating speed of 1 m / min by the slot die coating method, the film was dried at 120 ° C. for 30 minutes as secondary drying. In this way, an electron transport layer having a thickness of 30 nm was formed.

(1-1-8) Formation of Electron Injection Layer Subsequently, the substrate was attached to a vacuum deposition apparatus without being exposed to the atmosphere. In addition, a molybdenum resistance heating boat containing sodium fluoride and potassium fluoride is attached to a vacuum deposition apparatus, and after the vacuum chamber is depressurized to 4 × 10 ⁻⁵ Pa, the boat is energized and heated, Sodium fluoride was formed on the electron transport layer as a thin film having a thickness of 1 nm at a rate of 0.02 nm / second. Subsequently, similarly, potassium fluoride was formed as a thin film with a thickness of 1.5 nm on sodium fluoride at 0.02 nm / second to form an electron injection layer.

(1-1-9) Formation of Cathode Subsequently, aluminum was deposited to a thickness of 100 nm on the electron injection layer using a vacuum deposition apparatus under reduced pressure with a vacuum chamber of 4 × 10 ⁻⁵ Pa. To form a cathode.

(1-1-10) Sealing The vapor deposition surface side of the cathode was covered with 300 μm epoxy resin, further covered with 12 μm aluminum foil, and then cured. Sealing was performed in a glove box (in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more) in a nitrogen atmosphere without being exposed to the air. Thereafter, the sheet was cut into single sheets to form an organic EL element 101.

(1-2) Organic EL element 102
The organic EL element 102 was produced in the same procedure as the organic EL element 101 except that the light emitting layer composition (organic light emitting layer coating solution) for forming the light emitting layer (upper layer) on the cathode side was changed to the following composition. .
<Light emitting layer composition>
Illustrative Compound A-67 22.3 parts by mass Illustrative Compound D-66 4.9 parts by mass Toluene 6,700 parts by mass

(1-3) Organic EL element 103
The organic EL element 103 was produced in the same procedure as the organic EL element 101 except that the light emitting layer composition (organic light emitting layer coating solution) for forming the light emitting layer (lower layer) on the anode side was changed to the following composition. .
<Light emitting layer composition>
Exemplary Compound A-67 22.3 parts by mass Exemplary Compound D-67 0.05 part by mass Exemplary Compound D-80 0.05 part by mass Toluene 2,000 parts by mass

(1-4) Organic EL element 104
The organic EL element 104 was produced in the same procedure as the organic EL element 101 except that the light emitting layer composition (organic light emitting layer coating solution) for forming the light emitting layer (upper layer) on the cathode side was changed to the following composition. .
<Light emitting layer composition>
Exemplary Compound A-67 22.3 parts by mass Exemplary Compound D-66 4.9 parts by mass Anisole 6,700 parts by mass

(1-5) Organic EL element 105
The organic EL element 105 was produced in the same procedure as the organic EL element 101 except that the light emitting layer composition (organic light emitting layer coating liquid) for forming the light emitting layer (upper layer) on the cathode side was changed to the following composition. .
<Light emitting layer composition>
Exemplary Compound A-67 22.3 parts by mass Exemplary Compound D-66 4.9 parts by mass Ethyl acetate 6,700 parts by mass

(1-6) Organic EL element 106
The organic EL element 106 was produced in the same procedure as the organic EL element 101 except that the light emitting layer composition (organic light emitting layer coating liquid) for forming the light emitting layer (upper layer) on the cathode side was changed to the following composition. .
<Light emitting layer composition>
Exemplary Compound A-67 22.3 parts by mass Exemplary Compound D-66 4.9 parts by mass Acetonitrile 6,700 parts by mass

(2) Preparation of organic EL elements 201-209 The solvent of the light emitting layer has the same composition as that of the organic EL element 105, and the coating speed and wetness of the light emitting layer (upper layer) are applied for each of the sequential lamination coating and simultaneous lamination coating methods. The following organic EL elements 201 to 209 having the light emitting layer applied under conditions with different film thicknesses were produced.
In sequential layer coating, the light emitting layer (lower layer) is dried until just before the constant rate drying process ends and the rate-decreasing drying is started, and then the light emitting layer (upper layer) is applied. Dried.
In the simultaneous lamination coating, after the light emitting layer (upper layer) is applied to the light emitting layer (lower layer), the ambient temperature on the side of the substrate on which the light emitting layer is coated (coating surface) is 25 ° C., and the opposite side (back surface) ) Was set to 30 ° C. and dried in a nitrogen atmosphere for 30 minutes.

(2-1) Organic EL element 201
The organic EL element 201 was produced in the same procedure as the organic EL element 105, which is a sequential coating, with a coating speed of 3.0 m / min and a wet film thickness of 20 μm in the formation of the light emitting layer (upper layer).

(2-2) Organic EL element 202
The organic EL element 202 was manufactured in the same procedure as that of the organic EL element 105 by sequential lamination coating, in the formation of the light emitting layer (upper layer), with a coating speed of 4.0 m / min and a wet film thickness of 20 μm.

(2-3) Organic EL element 203
The organic EL element 203 was produced in the same procedure as the organic EL element 105, which is a sequential coating, with a coating speed of 5.0 m / min and a wet film thickness of 20 μm in the formation of the light emitting layer (upper layer).

(2-4) Organic EL element 204
The organic EL element 204 was manufactured in the same procedure as that of the organic EL element 105, which is a sequential coating method, in forming a light emitting layer (upper layer) at a coating speed of 10.0 m / min and a wet film thickness of 20 μm.

(2-5) Organic EL element 205
The organic EL element 205 was manufactured in the same procedure as that of the organic EL element 105 by sequential lamination coating, in the formation of the light emitting layer (upper layer), with a coating speed of 5.0 m / min and a wet film thickness of 5 μm.

(2-6) Organic EL element 206
The organic EL element 206 was produced in the same procedure as the organic EL element 105, which is a sequential coating, with a coating speed of 5.0 m / min and a wet film thickness of 10 μm in the formation of the light emitting layer (upper layer).

(2-7) Organic EL element 207
The organic EL element 207 is formed in the same procedure as the organic EL element 105 except that in the formation of the light emitting layer (upper layer), the coating speed is set to 2.0 m / min, the wet film thickness is set to 20 μm, and the simultaneous lamination coating is changed. Produced.

(2-8) Organic EL element 208
The organic EL element 208 is formed in the same procedure as the organic EL element 105 except that in the formation of the light emitting layer (upper layer), the coating speed is set to 5.0 m / min, the wet film thickness is set to 10 μm, and the simultaneous lamination coating is changed. Produced.

(2-9) Organic EL element 209
The organic EL element 209 is formed in the same procedure as the organic EL element 105 except that in the formation of the light emitting layer (upper layer), the coating speed is set to 5.0 m / min, the wet film thickness is set to 20 μm, and the simultaneous lamination coating is changed. Produced.

(3) Preparation of organic EL elements 301 to 303 The following organic EL elements 301 to 303 having the same light emitting layer solvent composition and the same coating conditions as those of the organic EL element 105 and coated with the light emitting layers under different atmospheric pressures Produced.

(3-1) Organic EL element 301
The organic EL element 301 was coated with a light emitting layer under the condition that the ratio between the atmospheric pressure and the atmospheric pressure during coating was 1.00. That is, it was produced in the same procedure as the organic EL element 105.

(3-2) Organic EL element 302
The organic EL element 302 was produced in the same procedure as the organic EL element 105 except that the light emitting layer was applied under the condition that the ratio of the atmospheric pressure to the atmospheric pressure during application was 0.95.

(3-3) Organic EL element 303
The organic EL element 303 was produced in the same procedure as the organic EL element 105 except that the light emitting layer was applied under the condition that the ratio of the atmospheric pressure to the atmospheric pressure during application was 0.90.

<< Performance Evaluation of Organic EL Element 1 >>
The performance of the organic EL elements 102 to 106 of the examples prepared by combining the permanent dipole moments of the solvent of the coating solution for forming the light emitting layer (lower layer) and the light emitting layer (upper layer) different from each other, and the power efficiency (energy conversion efficiency) ) And emission lifetime were measured and evaluated.

Evaluation of power efficiency is performed by causing an organic EL element to emit light by flowing a constant current of ^2.5 mA / cm ² at 23 ° C., and measuring the luminance to calculate the power efficiency (lm / W) of the element. It was. A spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing Co., Ltd.) was used for the measurement of emission luminance. The power efficiency is expressed as a relative value when the value of the organic EL element 101 of the comparative example is 100. The results are shown in Table 1.

  For the evaluation of the light emission lifetime, the organic EL element was continuously driven at a constant current giving an initial luminance of 10000 cd, the time required for the luminance to be halved was measured, and this was evaluated as the half-life time (τ 0.5). A spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing Co., Ltd.) was used for the measurement of emission luminance. In addition, the light emission lifetime was represented by the relative value when the value of the organic EL element 101 of a comparative example was set to 100. The results are shown in Table 1.

  As shown in Table 1, the organic EL elements 102 to 106 as examples were found to have improved performance in at least one of power efficiency and light emission lifetime as compared with the organic EL element of Comparative Example 101. In particular, when there is a difference in the permanent dipole moment of the solvent of the coating solution for forming each of the light emitting layer (lower layer) and the light emitting layer (upper layer), there is a tendency that performance improvement appears more. Further, as shown by the results of the organic EL elements 102 and 103, even when toluene, which is relatively unsuitable as a solvent for the coating solution according to the present invention, is used as a light emitting layer (upper layer), Improved performance was shown.

<< Performance evaluation of organic EL elements 2 >>
With respect to the organic EL device of the example prepared by combining the permanent dipole moments of the solvent of the coating solution for forming the light emitting layer (lower layer) and the light emitting layer (upper layer), the application speed of the light emitting layer (upper layer) and the wet film The performance of the organic EL elements 201 to 209 manufactured under different thickness conditions was evaluated by measuring the remaining coating amount, power efficiency (energy conversion efficiency), and light emission lifetime of the light emitting layer (lower layer).

  In the case of sequential layer coating, the remaining amount of the coating of the light emitting layer (lower layer) is measured by measuring the film thickness when only the light emitting layer (lower layer) is applied and dried to form a film. The thickness of the light emitting layer (upper layer) applied with only the solvent under the respective coating conditions, dried and formed into a film was measured, and the reduction ratio of the thickness was calculated. For the measurement of the film thickness, a reflection spectral film thickness meter FE-3000 (manufactured by Otsuka Electronics Co., Ltd.) was used. The remaining amount of the coating film is expressed as a relative value when the value of the organic EL element 203 is 100, and the coating film remaining amount is determined to be acceptable if 90% or more remains. In the case of simultaneous lamination coating, it was assumed that there was no loss of the coating film of the light emitting layer (lower layer) and the remaining coating film amount was 100%. The results are shown in Table 2.

  The power efficiency of the organic EL element was performed by the same method as described above. The power efficiency is expressed as a relative value when the value of the organic EL element 203 is 100. The results are shown in Table 2. As for the power efficiency, those having a relative ratio with respect to the organic EL element 203 of 90 or more were regarded as acceptable.

  The light emission lifetime of the organic EL element was performed in the same manner as described above. The light emission lifetime was expressed as a relative value when the value of the organic EL element 203 was 100. The results are shown in Table 2. The light emission lifetime was determined to be 90 or higher in relative ratio with respect to the organic EL element 203.

  In the case of sequential lamination coating, as the results of the organic EL elements 201 to 204 show, the higher the coating speed of the light emitting layer (upper layer), the higher the performance of the manufactured organic EL element is recognized. ) Regarding the remaining amount of the coating film, the loss was reduced. In addition, as the results of the organic EL elements 203, 205, and 206 show, the thicker the wet film thickness of the light emitting layer (upper layer), the higher the performance of the manufactured organic EL element is recognized, and the light emitting layer (lower layer) coating film. Regarding the remaining amount, the loss was reduced. In the case of simultaneous lamination coating, there was no difference in the performance of the organic EL device produced due to the difference in the coating speed of the light emitting layer (upper layer) and the wet film thickness. Therefore, the present embodiment, in which the permanent dipole moment of the solvent of the organic light emitting layer coating solution is different from each other, has a precise layer structure in the simultaneous lamination coating in which the liquid coating solutions are formed in contact with each other. It is considered effective as a method for producing an organic EL element having a light emitting layer. Further, in the sequential lamination coating, the organic light emitting layer coating liquid laminated on the upper layer side is coated at a coating speed of 4.0 m / min or more and a coating film thickness of 5 μm or more, thereby improving the performance. It was confirmed that an organic EL element can be produced.

<< Performance evaluation of organic EL elements 3 >>
Conditions for different atmospheric pressures in the coating environment of the organic EL elements of the examples prepared by combining the permanent dipole moments of the solvents of the organic light emitting layer coating solution for forming the light emitting layer (lower layer) and the light emitting layer (upper layer) with different combinations The performance of the organic EL elements 301 to 303 produced in (1) was evaluated by measuring power efficiency (energy conversion efficiency) and light emission lifetime.

  The power efficiency of the organic EL element was performed by the same method as described above. The power efficiency is expressed as a relative value when the value of the organic EL element 301 is 100. The results are shown in Table 3.

  The light emission lifetime of the organic EL element was performed in the same manner as described above. The light emission lifetime was expressed as a relative value when the value of the organic EL element 301 was 100. The results are shown in Table 3.

  As Table 3 shows, it was recognized that the atmospheric pressure at the time of applying the light emitting layer is a reduced pressure condition as compared with the atmospheric pressure, and the smaller the value of the atmospheric pressure ratio is, the more appropriate the manufacturing condition is.

DESCRIPTION OF SYMBOLS 1 Organic EL element 100 Base material 110 Anode 120 Hole injection layer 130 Hole transport layer 140 Light emitting layer 140A Light emitting layer (lower layer)
140B Light emitting layer (upper layer)
140a Coating liquid (light emitting layer lower layer)
140b Coating liquid (light emitting layer upper layer)
1401 Light emitting layer (first layer)
1402 Light emitting layer (second layer)
140n light emitting layer (nth layer)
150 Electron transport layer 160 Electron injection layer 170 Cathode 180 Adhesive 190 Sealing member 2 Film forming device 21 Unwinding unit 22 Coating unit 23 Drying unit 200 Substrate original winding rolls 210a and 210b Slot die coaters 211a and 211b Discharge ports 212a and 212b Slit 213a, 213b Lip 220a, 220b Reservoir tank 230a, 230b Liquid feed pump 240a, 240b Back roller 250 Transport roller 260 Heater A Transport direction

Claims (6)

A method of manufacturing an organic electroluminescent element having a pair of first and second electrodes and a plurality of organic light emitting layers on a substrate,
A step of forming a plurality of organic light emitting layers by laminating and applying a plurality of organic light emitting layer coating liquids prepared with solvents having different permanent dipole moments on the substrate on which the first electrode is formed;
Forming the second electrode on the plurality of organic light emitting layers;
The manufacturing method of the organic electroluminescent element characterized by having.   In the step of forming the plurality of organic light emitting layers, after drying the previously applied organic light emitting layer coating liquid until shifting from the constant rate drying period to the decreasing rate drying period, The manufacturing method of the organic electroluminescent element according to claim 1, wherein a plurality of organic light emitting layers are formed by laminating and applying the following organic light emitting layer coating solution.   2. The manufacturing of the organic electroluminescence device according to claim 1, wherein in the step of forming the plurality of organic light emitting layers, a plurality of organic light emitting layer coating solutions are simultaneously laminated and applied to form a plurality of organic light emitting layers. Method.   The method for producing an organic electroluminescent element according to claim 1, wherein the step of forming the plurality of organic light emitting layers is performed under a reduced pressure atmosphere.   The method for producing an organic electroluminescent element according to claim 2, wherein the coating speed of the organic light emitting layer coating solution laminated and coated on the upper layer side is 4.0 m / min to 30 m / min.   The method for producing an organic electroluminescent element according to claim 2, wherein the coating thickness of the organic light emitting layer coating solution laminated and coated on the upper layer side is 5 μm to 100 μm.

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