WO2009084413A1

WO2009084413A1 - Organic electroluminescent device and method for manufacturing organic electroluminescent device

Info

Publication number: WO2009084413A1
Application number: PCT/JP2008/072756
Authority: WO
Inventors: Kunimasa Hiyama; Yoshiyuki Suzuri
Original assignee: Konica Minolta Holdings, Inc.
Priority date: 2007-12-28
Filing date: 2008-12-15
Publication date: 2009-07-09
Also published as: JPWO2009084413A1

Abstract

Disclosed is a method for manufacturing an organic electroluminescent device having high luminous efficiency and long life, wherein an organic electroluminescent device can be stably produced by a wet process. Specifically disclosed is a method for manufacturing an organic electroluminescent device which at least comprises, on a substrate, an anode, a cathode and a light-emitting layer interposed between the anode and the cathode and containing a luminescent host and a luminescent dopant. This method for manufacturing an organic electroluminescent device is characterized in that the light-emitting layer is formed by a wet process and the concentration of the luminescent dopant contained in the light-emitting layer is continuously varied from the anode side toward the cathode side.

Description

ORGANIC ELECTROLUMINESCENT ELEMENT AND METHOD FOR PRODUCING ORGANIC ELECTROLUMINESCENT ELEMENT

The present invention relates to an organic electroluminescence element and a method for producing the organic electroluminescence element. Specifically, the present invention relates to an organic electroluminescent element that can be manufactured by a simple process and has improved light emission efficiency and lifetime, and a method for manufacturing the organic electroluminescent element.

There is an electroluminescence display (hereinafter abbreviated as ELD) as a light-emitting electronic display device. As an ELD component, an inorganic electroluminescence element (hereinafter also referred to as an inorganic EL element) and an organic electroluminescence element (hereinafter also referred to as an organic EL element) can be given. Inorganic EL elements have been used as planar light sources, but an alternating high voltage is required to drive the light emitting elements.

On the other hand, an organic electroluminescence device has a structure in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode, and excitons (excitons) by injecting electrons and holes into the light emitting layer and recombining them. Is generated. It is an element that emits light using the emission of light (fluorescence / phosphorescence) when this exciton is deactivated, and can emit light at a voltage of several V to several tens V, and it is self-luminous. In addition, it is attracting attention from the viewpoints of space saving, portability and the like because it is a thin film type complete solid element with a wide viewing angle and high visibility.

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

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

Specifically, a combination of a host material / a light emitting dopant in the light emitting layer may be mentioned. The ratio of the light-emitting dopant to the light-emitting host in the light-emitting layer is continuously changed in the light-emitting layer, indicating that the lifetime is improved (for example, see Patent Documents 1 and 2). What is clearly shown as the means for changing to is only the control of the deposition rate in the vacuum deposition method, and cannot be said to be a proposal of means suitable for productivity.

On the other hand, as a manufacturing method of these organic electroluminescent elements, there are a vapor deposition method, a wet process (spin coating method, die coating method, casting method, ink jet method, spray method, printing method), but a vacuum process is not required, In recent years, a manufacturing method in a wet process has been attracting attention because continuous production is simple.

Means for continuously mixing components between two adjacent layers is disclosed (see, for example, Patent Documents 3 and 4), but in this case, a difference in solubility between adjacent two layers is utilized, There is a problem that it cannot be applied as means for continuously changing the dopant concentration in a single layer using the same material. Moreover, the barrier of the interface between a positive hole transport layer and a light emitting layer can be relieve | moderated by mixing the components of two adjacent layers, for example, a positive hole transport layer, and a light emitting layer continuously, and to the light emitting layer. Although the efficiency of hole injection can be improved, on the other hand, the function of the electronic block is lowered, and it is difficult to increase the light emission efficiency only by this technique.
Japanese Patent Laid-Open No. 2004-6102 JP 2005-38672 A Japanese Patent Laid-Open No. 11-74083 JP 2007-42312 A

The present invention has been made in view of the above problems, and an object of the present invention is to provide an organic electroluminescence element that has high luminous efficiency and long life and can be stably produced by a wet process, and a method for producing the organic electroluminescence element Is to provide.

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

1. In a method for producing an organic electroluminescence device having at least an anode, a cathode, and a light emitting host containing at least an anode, a cathode, and a light emitting host and a light emitting dopant sandwiched between the anode and the cathode, the light emitting layer is formed by a wet process, And the manufacturing method of the organic electroluminescent element characterized by changing continuously the density | concentration of the light emission dopant contained in this light emitting layer toward the cathode side from an anode side.

2. 2. The method for producing an organic electroluminescent element according to 1 above, wherein the concentration of the luminescent dopant decreases from the anode side toward the cathode side.

3. 3. The method for producing an organic electroluminescent element according to 1 or 2, wherein the light-emitting dopant is represented by the following general formula (1).

(In the formula, R ₁ represents a substituent. Z represents a group of nonmetallic atoms necessary to form a 5- to 7-membered ring. N1 represents an integer of 0 to 5. B ₁ to B ₅ represent carbon. Represents an atom, a nitrogen atom, an oxygen atom or a sulfur atom, at least one of B ₁ to B ₅ represents a nitrogen atom, M ₁ represents a group 8 to group 10 metal in the periodic table, and X ₁ and X ₂ Represents a carbon atom, a nitrogen atom or an oxygen atom, L ₁ represents an atomic group forming a bidentate ligand with X ₁ and X ₂ , m1 represents an integer of 1, 2 or 3, and m2 represents 0 Represents an integer of 1 or 2, and m1 + m2 is 2 or 3.)
4). 4. The method for producing an organic electroluminescent element according to any one of 1 to 3, wherein the light emitting host is a compound having a molecular weight of 700 or more represented by the following general formula (2).

(In General Formula (2), Y ₁ and Y ₂ represent O, S or NR ₀ , and R ₀ , R ₁₁ to R ₁₈ and R ₂₁ to R ₂₈ represent a hydrogen atom or a substituent, provided that R ₁₁ At least one of ~ R ₁₈ and R ₀ is used in connection with X _1, R ₂₁ ~ R ₂₈ and at least one .X ₁ which is used for connection with the X ₁ represented by the following general formula R ₀ (3 ) or (4 .n1 that represents a divalent linking group represented by) represents an integer of 1 or more, when n1 is 2 or more, X ₁ is may be the same or different.)

(Wherein Y ₃ represents O, S or NR ₃₀ , and R ₃₀ to R ₃₈ and R ₄₁ to R ₄₆ represent a hydrogen atom or a substituent, provided that R ₃₀ to R ₃₈ and R ₄₁ to R ₄₆ represent At least two of each are used for linking, and when R ₄₁ and R ₄₄ are used for linking, at least one of R ₄₂ , R ₄₃ , R ₄₅ and R ₄₆ has a substituent other than a hydrogen atom.)
5. 5. The method for producing an organic electroluminescence device according to any one of 1 to 4, wherein the light emitting layer is dried by controlling the atmospheric temperature in contact with the back side of the coating film to be lower than the atmospheric temperature in contact with the front side of the coating film. A method for producing an organic electroluminescence element, comprising forming the organic electroluminescence element.

6. 6. The method for producing an organic electroluminescence device as described in 5 above, wherein the atmospheric temperature on the back side of the coating film is controlled to be 10 ° C. lower than the atmospheric temperature on the front side of the coating film.

7. 5. The method for producing an organic electroluminescence device according to any one of 1 to 4, wherein a layer coating of two or more types of light emitting layer solutions having different light emitting dopant concentrations is applied, and the light emitting dopant / light emission of the solution to be applied to the most anode side A method for producing an organic electroluminescent device, wherein a light emitting layer is formed by performing a host ratio higher than a light emitting dopant / light emitting host ratio of a solution coated on the most cathode side and then drying.

8. Among the two or more kinds of light emitting layer solutions having different light emitting dopant concentrations, the light emitting dopant / light emitting host ratio of the solution coated on the most anode side is 100 to 10% by mass, and the light emitting dopant / light emitting host of the solution coated on the most cathode side. 8. The method for producing an organic electroluminescent element as described in 7 above, wherein the ratio is 5 to 0% by mass.

9. 5. The method of manufacturing an organic electroluminescence device according to any one of 1 to 4, wherein the solvent of the light emitting layer solution is a two-component mixed solvent having a boiling point and a light emitting dopant solubility, and has a higher light emitting dopant solubility. A method for producing an organic electroluminescent device, wherein the solvent has a boiling point higher than that of the solvent having the lower emission dopant solubility.

10. 10. An organic electroluminescence device manufactured by the method for manufacturing an organic electroluminescence device according to any one of 1 to 9 above.

According to the present invention, it is possible to provide an organic electroluminescence element that has high luminous efficiency and long life and can be stably produced by a wet process, and a method for producing the organic electroluminescence element.

Hereinafter, the present invention will be described in detail.

The present invention provides an organic electroluminescent device having at least an anode, a cathode, and a light emitting layer containing a light emitting host and a light emitting dopant sandwiched between the anode and the cathode on a substrate, wherein the light emitting layer is formed by a wet process. And the density | concentration of the light emission dopant contained in this light emitting layer changes continuously toward the cathode side from an anode side, It is characterized by the above-mentioned. In particular, it is preferable that the concentration of the luminescent dopant decreases from the anode side toward the cathode side.

Hereinafter, details of each component of the organic electroluminescence element of the present invention (hereinafter also referred to as the organic EL element of the present invention) will be sequentially described.

<< Layer structure of organic EL element >>
Next, although the preferable specific example of the layer structure of the organic EL element of this invention is shown below, this invention is not limited to these.

(I) Anode / light emitting layer unit / electron transport layer / cathode (ii) Anode / hole transport layer / light emitting layer unit / electron transport layer / cathode (iii) Anode / hole transport layer / light emitting layer unit / hole blocking Layer / electron transport layer / cathode (iv) anode / hole transport layer / light emitting layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode (v) anode / anode buffer layer / hole transport layer / light emission Layer unit / hole blocking layer / electron transport layer / cathode buffer layer / cathode << light emitting layer >>
The light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May be the interface between the light emitting layer and the adjacent layer.

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

The light emitting layer of the organic electroluminescence device of the present invention is formed by a wet process. Known wet process coating methods include spin coating, die coating, casting, inkjet, spraying, printing, etc., but it is easy to obtain a homogeneous film and it is difficult to generate pinholes. From the viewpoint, in the present invention, film formation by a coating method such as a spin coating method, a die coating method, an ink jet method, a spray method, or a printing method is preferable.

The light emitting layer of the organic electroluminescence device of the present invention contains a light emitting host and at least one light emitting dopant, and the concentration of the light emitting dopant in the light emitting layer is continuously changed from the anode side to the cathode side. Features.

As a means for continuously changing the concentration, one of the following means or a combination of a plurality of means is used.

1) When drying after applying the light emitting layer solution, drying is performed while controlling the atmospheric temperature in contact with the back side of the coating film to be lower than the atmospheric temperature in contact with the front side of the coating film, and the drying speed in the thickness direction of the coating film is controlled. Using the concentration gradient generated in In order to decrease the concentration of the luminescent dopant from the anode side toward the cathode side, the atmospheric temperature in contact with the back side of the coating film may be lowered by 10 ° C. or more from the atmospheric temperature in contact with the front side of the coating film and dried. As a method of controlling the atmospheric temperature of the front and back of the coating film, a method of separately controlling the temperature of the drying air sent to the front side and the drying air sent to the back side using an isolated drying box for each of the coated samples, coating Although there is a method of bringing a temperature-controlled heater into contact with the front side and the back side of the sample, respectively, a method of controlling the drying air temperature on the front side and the back side is preferable in order to avoid damage to the coating film due to contact.

2) A method in which two or more kinds of light emitting layer solutions having different ratios of light emitting host light emitting dopants are prepared in advance, and these are sequentially laminated and coated so that the light emitting host and the light emitting dopant diffuse to each other and cause a continuous concentration change. . In order to decrease the concentration of the light-emitting dopant from the anode side toward the cathode side, the light-emitting dopant / light-emitting host ratio of the solution to be applied to the anode side is the highest when two or more types of light-emitting layer solutions having different light-emitting dopant concentrations are applied. What is necessary is just to make it higher than the light emission dopant / light emission host ratio of the solution apply | coated to the cathode side, and to dry after that.

3) A method in which two or more mixed solvents having different boiling points and different solubilities with respect to the luminescent dopant are used as the solvent of the luminescent layer solution, and the difference between the supersaturation points of the luminescent host and the luminescent dopant in the drying process is used. In order to decrease the concentration of the luminescent dopant from the anode side toward the cathode side, the solvent of the luminescent layer solution has a boiling point of the solvent with the higher luminescent dopant solubility for the mixed solvent of two liquids having different boiling point and luminescent dopant solubility. The dopant solubility is higher than the boiling point of the lower solvent.

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

(Light emitting host)
In the present invention, the light-emitting host has a mass ratio of 20% or more in a compound contained in a light-emitting layer, and a phosphorescence quantum yield of phosphorescence emission is 0 at room temperature (25 ° C.). Less than 1 compound. The phosphorescence quantum yield is preferably less than 0.01. Moreover, it is preferable that the mass ratio in the layer is 20% or more among the compounds contained in a light emitting layer.

In the present invention, it is preferable to use a compound having a molecular weight of 700 or more represented by the general formula (2) as a luminescent host. The light emitting host according to the present invention has a molecular weight of 700 or more, preferably a molecular weight of 800 or more and 3,000 or less, 800 or more and 2,000 or less, 800 or more and 1,500 or less, and most preferably a molecular weight of 1,000 or more and 1,500 or less. .

In general formula (2), Y ₁ and Y ₂ represent O, S or NR ₀ , and R ₀ , R ₁₁ to R ₁₈ and R ₂₁ to R ₂₈ represent a hydrogen atom or a substituent. However, at least one of R ₁₁ to R ₁₈ and R ₀ is used for connection with X _1, and at least one of R ₂₁ to R ₂₈ and R ₀ is used for connection with X ₁ . X ₁ represents a divalent linking group represented by the following general formula (3) or (4). n1 represents an integer of 1 or more, and when n1 is 2 or more, X ₁ may be the same or different.

In general formulas (3) and (4), Y ₃ represents O, S or NR ₃₀ , and R ₃₀ to R ₃₈ and R ₄₁ to R ₄₆ represent a hydrogen atom or a substituent. However, at least two of each of R ₃₀ to R ₃₈ and R ₄₁ to R ₄₆ are used for connection, and when R ₄₁ and R ₄₄ are used for connection, at least R ₄₂ , R ₄₃ , R ₄₅ , R ₄₆ are used. One has a substituent other than a hydrogen atom.

The substituents represented by R ₀ , R ₁₁ to R ₁₈ and R ₂₁ to R ₂₈ , and R ₃₀ to R ₃₈ and R ₄₁ to R ₄₆ have the same meaning as the substituent represented by R ₁ in the general formula (1). is there.

Hereinafter, examples of a compound having a molecular weight of 700 or more represented by the general formula (2) are shown below, but are not limited thereto.

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

In addition, the light emitting host used in the present invention may be a conventionally known low molecular compound or a high molecular compound having a repeating unit, and a low molecular compound having a polymerizable group such as a vinyl group or an epoxy group (deposition polymerization property). Light emitting host).

As the known light-emitting host that may be used in combination, a compound that has a hole transporting ability and an electron transporting ability, prevents the emission of longer wavelengths, and has a high Tg (glass transition temperature) is preferable.

Specific examples of known light-emitting hosts include compounds described in the following documents.

JP-A-2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002 -302516, 2002-305083, 2002-305084, 2002-308837, and the like.

(Luminescent dopant)
The light emitting dopant according to the present invention will be described.

As the light-emitting dopant according to the present invention, a fluorescent dopant or a phosphorescent dopant can be used. From the viewpoint of obtaining an organic EL element with higher luminous efficiency, it is used for the light-emitting layer and the light-emitting unit of the organic EL element of the present invention. As the light emitting dopant, it is preferable to contain a phosphorescent dopant at the same time as containing the above light emitting host.

(Phosphorescent dopant)
The phosphorescent dopant according to the present invention will be described.

The phosphorescent dopant according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, the phosphorescent dopant is a compound that emits phosphorescence at room temperature (25 ° C.) and has a phosphorescence quantum yield of 25. It is a compound of 0.01 or more at ° C., and a preferable phosphorescence quantum yield is 0.1 or more.

The phosphorescent quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of the Fourth Edition Experimental Chemistry Course 7. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence dopant according to the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. That's fine.

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

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

In the present invention, it is preferable to use a phosphorescent dopant represented by the general formula (1) as a light emitting dopant.

In the light-emitting dopant represented by the general formula (1) according to the present invention, examples of the substituent represented by R ₁ include an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, t- Butyl group, pentyl group, hexyl group, octyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (eg, vinyl group, allyl group) Etc.), alkynyl groups (for example, ethynyl group, propargyl group, etc.), aromatic hydrocarbon ring groups (aromatic carbocyclic group, aryl group, etc.), for example, phenyl group, p-chlorophenyl group, mesityl group, tolyl group , Xylyl, naphthyl, anthryl, azulenyl, acenaphthenyl, fluorenyl, phenanthri Group, indenyl group, pyrenyl group, biphenylyl group, etc.), aromatic heterocyclic group (for example, pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, imidazolyl group, benzoimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (for example, 1,2,4-triazol-1-yl group, 1,2,3-triazol-1-yl group, etc.), oxazolyl group, benzoxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, furazanyl group, thienyl Group, quinolyl group, benzofuryl group, dibenzofuryl group, benzothienyl group, dibenzothienyl group, indolyl group, carbazolyl group, carbolinyl group, diazacarbazolyl group (one of the carbon atoms constituting the carboline ring of the carbolinyl group is (Represented by nitrogen atom substitution), quinoxari Nyl group, pyridazinyl group, triazinyl group, quinazolinyl group, phthalazinyl group, etc.), heterocyclic group (eg, pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propyloxy) Group, pentyloxy group, hexyloxy group, octyloxy group, dodecyloxy group, etc.), cycloalkoxy group (eg, cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.) , Alkylthio groups (for example, methylthio group, ethylthio group, propylthio group, pentylthio group, hexylthio group, octylthio group, dodecylthio group, etc.), cycloalkylthio groups (for example, cyclopentylthio group, cyclohexylthio group, etc.), aryl O group (eg, phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (eg, methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, dodecyloxycarbonyl group, etc.), aryloxycarbonyl group (Eg, phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (eg, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octyl) Aminosulfonyl groups, dodecylaminosulfonyl groups, phenylaminosulfonyl groups, naphthylaminosulfonyl groups, 2-pyridylaminosulfonyl groups, etc.), acyl groups (eg Acetyl, ethylcarbonyl, propylcarbonyl, pentylcarbonyl, cyclohexylcarbonyl, octylcarbonyl, 2-ethylhexylcarbonyl, dodecylcarbonyl, phenylcarbonyl, naphthylcarbonyl, pyridylcarbonyl, etc.), acyloxy Groups (for example, acetyloxy group, ethylcarbonyloxy group, butylcarbonyloxy group, octylcarbonyloxy group, dodecylcarbonyloxy group, phenylcarbonyloxy group, etc.), amide groups (for example, methylcarbonylamino group, ethylcarbonylamino group, Dimethylcarbonylamino group, propylcarbonylamino group, pentylcarbonylamino group, cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, octyl Tilcarbonylamino group, dodecylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group) Cyclohexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (for example, methylureido group, An ethylureido group, a pentylureido group, a cyclohexylureido group, an octylureido group, a dodecylureido group, a phenylureido group, a naphthylureido group, -Pyridylaminoureido group, etc.), sulfinyl groups (for example, methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, 2-ethylhexylsulfinyl group, dodecylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group) Group), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group, etc.), arylsulfonyl group or heteroarylsulfonyl group (for example, phenyl) Sulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (for example, amino group, ethylamino group, dimethylamino group, Tilamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, naphthylamino group, 2-pyridylamino group, etc., cyano group, nitro group, hydroxy group, mercapto group, silyl group (for example, trimethylsilyl group) , Triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.).

Of these substituents, preferred are an alkyl group and an aryl group.

Z represents a nonmetallic atom group necessary for forming a 5- to 7-membered ring. Examples of the 5- to 7-membered ring formed by Z include a benzene ring, naphthalene ring, pyridine ring, pyrimidine ring, pyrrole ring, thiophene ring, pyrazole ring, imidazole ring, oxazole ring and thiazole ring. Of these, a benzene ring is preferred.

B ₁ to B _{5 each} represent a carbon atom, a nitrogen atom, an oxygen atom or a sulfur atom, and at least one represents a nitrogen atom. The aromatic nitrogen-containing heterocycle formed by these five atoms is preferably a monocycle. Examples include pyrrole ring, pyrazole ring, imidazole ring, triazole ring, tetrazole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, oxadiazole ring, and thiadiazole ring.

Of these, a pyrazole ring and an imidazole ring are preferable, and an imidazole ring is more preferable. These rings may be further substituted with the above substituents. Preferred as the substituent are an alkyl group and an aryl group, and more preferably an aryl group.

L ₁ represents an atomic group that forms a bidentate ligand together with X ₁ and X ₂ . Specific examples of the bidentate ligand represented by X ₁ -L ₁ -X ₂ include, for example, substituted or unsubstituted phenylpyridine, phenylpyrazole, phenylimidazole, phenyltriazole, phenyltetrazole, pyrazabol, picolinic acid And acetylacetone. These groups may be further substituted with the above substituents.

M1 represents an integer of 1, 2 or 3, m2 represents an integer of 0, 1 or 2, but m1 + m2 is 2 or 3. Especially, the case where m2 is 0 is preferable.

As the metal represented by M ₁ , a transition metal element of Group 8 to Group 10 (also referred to simply as a transition metal) in the periodic table of elements is used. Among them, iridium and platinum are preferable, and iridium is more preferable.

Note that the light-emitting dopant represented by the general formula (1) according to the present invention may or may not have a polymerizable group or a reactive group.

Specific examples of the compound used as the light emitting dopant are shown below, but the present invention is not limited thereto.

These metal complexes are described in, for example, Organic Letter, vol. 16, 2579-2581 (2001), Inorganic Chemistry, Vol. 30, No. 8, pp. 1685-1687 (1991), J. Am. Am. Chem. Soc. , 123, 4304 (2001), Inorganic Chemistry, Vol. 40, No. 7, pages 1704-1711 (2001), Inorganic Chemistry, Vol. 41, No. 12, pages 3055-3066 (2002) , New Journal of Chemistry. 26, 1171 (2002), European Journal of Organic Chemistry, Vol. 4, pages 695-709 (2004), and further synthesized by applying methods such as references described in these documents. it can.

(Fluorescent dopant)
As fluorescent dopants, 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.

Next, an injection layer, a blocking layer, an electron transport layer, and the like used as a constituent layer of the organic EL element of the present invention will be described.

<< Injection layer: electron injection layer, hole injection layer >>
The injection layer is provided as necessary, and there are an electron injection layer and a hole injection layer, and as described above, it exists between the anode and the light emitting layer or the hole transport layer and between the cathode and the light emitting layer or the electron transport layer. May be.

An injection layer is a layer provided between an electrode and an organic layer in order to reduce drive voltage and improve light emission luminance. “Organic EL element and its forefront of industrialization (issued by NTT Corporation on November 30, 1998) 2), Chapter 2, “Electrode Materials” (pages 123 to 166) in detail, and includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer).

The details of the anode buffer layer (hole injection layer) are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Examples thereof include a phthalocyanine buffer layer represented by an oxide, an oxide buffer layer represented by vanadium oxide, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.

The details of the cathode buffer layer (electron injection layer) are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, strontium, aluminum, etc. Metal buffer layer typified by lithium, alkali metal compound buffer layer typified by lithium fluoride, alkaline earth metal compound buffer layer typified by magnesium fluoride, oxide buffer layer typified by aluminum oxide, etc. . The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 nm to 5 μm, although it depends on the material.

<Blocking layer: hole blocking layer, electron blocking layer>
The blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film as described above. For example, it is described in JP-A Nos. 11-204258 and 11-204359, and “Organic EL elements and the forefront of industrialization (published by NTT Corporation on November 30, 1998)” on page 237. There is a hole blocking (hole blocking) layer.

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

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

It is preferable that the hole blocking layer contains the carbazole derivative mentioned as the light emitting host.

In the present invention, when a plurality of light emitting layers having different light emission colors are provided, the light emitting layer having the shortest wavelength of light emission is preferably closest to the anode among all the light emitting layers. In this case, it is preferable to additionally provide a hole blocking layer between the shortest wave layer and the light emitting layer next to the anode next to the anode. Further, it is preferable that 50% by mass or more of the compound contained in the hole blocking layer provided at the position has an ionization potential of 0.3 eV or more larger than the light emitting host of the shortest wave emitting layer.

The ionization potential is defined by the energy required to emit electrons at the HOMO (highest occupied molecular orbital) level of the compound to the vacuum level, and can be obtained by, for example, the following method.

(1) Gaussian 98 (Gaussian 98, Revision A.11.4, MJ Frisch, et al, Gaussian, Inc., Pittsburgh PA, 2002.), a molecular orbital calculation software manufactured by Gaussian, USA, is used as a keyword. The ionization potential can be obtained as a value obtained by rounding off the second decimal place of a value (eV unit converted value) calculated by performing structural optimization using B3LYP / 6-31G *. This calculation value is effective because the correlation between the calculation value obtained by this method and the experimental value is high.

(2) The ionization potential can also be obtained by a method of directly measuring by photoelectron spectroscopy. For example, a low energy electron spectrometer “Model AC-1” manufactured by Riken Keiki Co., Ltd. or a method known as ultraviolet photoelectron spectroscopy can be suitably used.

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

《Hole transport layer》
The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.

The hole transport material has either hole injection or transport or electron barrier properties, and may be either organic or inorganic. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, Examples thereof include stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

The above-mentioned materials can be used as the hole transport material, but it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound.

Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ′, N′-tetraphenyl-4,4′-diaminophenyl; N, N′-diphenyl-N, N′— Bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p-tolyl) Aminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' 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, and also two described in US Pat. No. 5,061,569 Having a condensed aromatic ring of, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-308 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 88 are linked in a starburst type ( MTDATA) and the like.

Further, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used. In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material and the hole transport material. JP-A-11-251067, J. Org. Huang et. al. A so-called p-type hole transport material described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, these materials are preferably used because a light-emitting element with higher efficiency can be obtained.

The hole transport layer can be formed by thinning the hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. it can. The thickness of the hole transport layer is not particularly limited, but is usually 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.

It is also possible to use a hole transport layer having a high p property doped with impurities. Examples thereof include JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like.

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

《Electron transport layer》
The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

Conventionally, in the case of a single electron transport layer and a plurality of layers, an electron transport material (also serving as a hole blocking material) used for an electron transport layer adjacent to the light emitting layer on the cathode side is injected from the cathode. Any material may be used as long as it has a function of transferring electrons to the light-emitting layer, and any material can be selected from conventionally known compounds. Examples include nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives, and the like. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material.

In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. In addition, the distyrylpyrazine derivative exemplified as the material for the light emitting layer can also be used as an electron transport material, and an inorganic semiconductor such as n-type-Si, n-type-SiC, etc. as in the case of the hole injection layer and the hole transport layer. Can also be used as an electron transporting material.

The electron transport layer can be formed by thinning the electron transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. The thickness of the electron transport layer is not particularly limited, but is usually 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.

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

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

《Reactive organic compound》
In the present invention, an organic compound having a reactive group (reactive organic compound) may be used. There is no restriction | limiting in particular as a layer using a reactive organic compound, It can use for each layer.

Reactive organic compounds can be reacted on a substrate to form a network polymer with organic molecules. Generation | occurrence | production of a network polymer can suppress element deterioration by Tg (glass transition point) adjustment of a structure layer. It is also possible to change the emission wavelength of the organic EL element, suppress deterioration of the specific wavelength, etc. by adjusting the reaction accompanied by the cleavage or generation of the conjugated system of the molecule using the active radical in use. is there.

On the other hand, on the manufacturing side, for example, in the case of a step of laminating by coating, it is preferable that the lower layer is not dissolved in the upper layer coating solution, and upper layer coating can be made possible by resinating the lower layer and degrading solvent solubility. .

An example of a reactive group that can be used in the present invention is shown below.

Moreover, an example of a reactive organic compound is shown.

"anode"
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode substances 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 may be used.

For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when pattern accuracy is not so high (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material. Or when using the substance which can be apply | coated like an organic electroconductivity compound, wet film-forming methods, such as a printing system and a coating system, can also be used.

When light emission is taken out from the anode, it is desirable that the transmittance is greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

"cathode"
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like.

Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Suitable are a magnesium / aluminum mixture, a magnesium / indium mixture, an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture, a lithium / aluminum mixture, aluminum and the like.

The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either one of the anode or the cathode of the organic EL element is transparent or translucent, the light emission luminance is improved, which is convenient.

In addition, a transparent or semi-transparent cathode can be produced by producing the conductive transparent material mentioned in the description of the anode on the cathode after producing the metal with a film thickness of 1 to 20 nm. By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

《Support substrate》
As a support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) that can be used in the organic EL device of the present invention, there is no particular limitation on the type of glass, plastic, etc., and it is transparent. May be opaque. When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of giving flexibility to the organic EL element.

Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), Cellulose esters such as cellulose acetate phthalate (TAC) and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfone , Polyetherimide, polyether ketone imide, polyamide, fluorine resin, nylon, polymethyl methacrylate, acrylic or polyarylates, and cycloolefin resins such as ARTON (manufactured by JSR) or APEL (manufactured by Mitsui Chemicals).

An inorganic or organic film or a hybrid film of both may be formed on the surface of the resin film, and it is preferably a barrier film having a water vapor permeability of 0.01 g / m ² / day · atm or less. Furthermore, a high barrier film having an oxygen permeability of 10 ⁻³ g / m ² / day or less and a water vapor permeability of 10 ⁻⁵ g / m ² / day or less is preferable.

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

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

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

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

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

<Sealing>
As a sealing means used for this invention, the method of adhere | attaching a sealing member, an electrode, and a support substrate with an adhesive agent can be mentioned, for example. As a sealing member, it should just be arrange | positioned so that the display area | region of an organic EL element may be covered, and concave plate shape or flat plate shape may be sufficient. Further, transparency and electrical insulation are not particularly limited.

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

In the present invention, a polymer film and a metal film can be preferably used because the element can be thinned.

Furthermore, the polymer film oxygen permeability measured by the method based on JIS K 7126-1987 is ^{^{1 × 10 -3 ml / m 2}} / 24h or less, as measured by the method based on JIS K 7129-1992, water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)%) is preferably that of ^{1 × 10 -3 g / (m} 2 / 24h) or less.

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

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

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

In addition, it is also preferable that the electrode and the organic layer are coated on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and an inorganic or organic layer is formed in contact with the support substrate to form a sealing film. . In this case, the material for forming the film may be a material having a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like may be used. it can.

In order to further improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials. The method for forming these films is not particularly limited. For example, vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma A polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

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

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

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

《Light extraction》
The organic EL element emits light inside a layer having a refractive index higher than that of air (refractive index is about 1.7 to 2.1) and can extract only about 15% to 20% of the light generated in the light emitting layer. It is generally said. This is because light incident on the interface (interface between the transparent substrate and air) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the device, or between the transparent electrode or light emitting layer and the transparent substrate. This is because the light is totally reflected between the light and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the side surface direction of the element.

As a method of improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate and preventing total reflection at the transparent substrate and the air interface (US Pat. No. 4,774,435), A method for improving efficiency by giving light condensing property to a substrate (Japanese Patent Laid-Open No. 63-314795), a method of forming a reflective surface on the side surface of an element (Japanese Patent Laid-Open No. 1-220394), and light emission from the substrate A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the bodies (Japanese Patent Laid-Open No. 62-172691), a flat having a lower refractive index between the substrate and the light emitter than the substrate A method of introducing a layer (Japanese Patent Laid-Open No. 2001-202827), a method of forming a diffraction grating between any one of a substrate, a transparent electrode layer and a light emitting layer (including between the substrate and the outside) (Japanese Patent Laid-Open No. 11-283951) Gazette).

In the present invention, these methods can be used in combination with the organic EL device of the present invention. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, transparent A method of forming a diffraction grating between any layers of the electrode layer and the light emitting layer (including between the substrate and the outside) can be suitably used.

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

When a medium having a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the efficiency of taking out the light from the transparent electrode to the outside increases as the refractive index of the medium decreases.

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

Also, the thickness of the low refractive index medium is preferably at least twice the wavelength in the medium. This is because the effect of the low refractive index layer is diminished when the thickness of the low refractive index medium is about the wavelength of light and the electromagnetic wave that has exuded by evanescent enters the substrate.

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

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

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

At this time, the period of the diffraction grating is preferably about 1/2 to 3 times the wavelength of light in the medium.

The arrangement of the diffraction grating is preferably two-dimensionally repeated such as a square lattice, a triangular lattice, or a honeycomb lattice.

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

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

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

Further, in order to control the light emission angle from the light emitting element, a light diffusion plate / film may be used in combination with the light collecting sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

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

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

Next, an organic compound thin film of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a hole blocking layer, which are organic EL element materials, is formed thereon.

The light emitting layer of the organic EL device of the present invention is formed by a wet process as described above. As a method for forming an organic layer other than the light emitting layer, there are a vapor deposition method, a wet process (spin coating method, die coating method, casting method, ink jet method, spray method, printing method), etc., but a homogeneous film is easily obtained. Further, in the present invention, film formation by a coating method such as a spin coating method, a die coating method, an ink jet method, a spray method, a printing method, or the like is preferable for part or all of the organic layer in view of the difficulty of generating pinholes.

Examples of the liquid medium for dissolving or dispersing the organic EL material according to the present invention include ketones such as methyl ethyl ketone and cyclohexanone, fatty acid esters such as ethyl acetate, halogenated hydrocarbons such as dichlorobenzene, toluene, xylene, and mesitylene. Aromatic hydrocarbons such as cyclohexylbenzene, aliphatic hydrocarbons such as cyclohexane, decalin, and dodecane, and organic solvents such as DMF and DMSO can be used. Moreover, as a dispersion method, it can disperse | distribute by dispersion methods, such as an ultrasonic wave, high shear force dispersion | distribution, and media dispersion | distribution.

After these layers are formed, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided. Thus, a desired organic EL element can be obtained.

It is also possible to reverse the production order to produce a cathode, an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, a hole injection layer, and an anode in this order. When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. An alternating voltage may be applied. The alternating current waveform to be applied may be arbitrary.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<< Production of organic EL element >>
[Production of Organic EL Element 111]
After patterning a substrate (NH technoglass NA45) formed by depositing 100 nm of ITO (indium tin oxide) on a 100 mm × 100 mm × 1.1 mm glass substrate as an anode, a substrate provided with this ITO transparent electrode was formed. Ultrasonic cleaning with isopropyl alcohol, drying with dry nitrogen gas, and UV ozone cleaning were performed for 5 minutes. A solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) to 70% with pure water on this substrate was spin-coated at 3000 rpm for 30 seconds. After film formation by the method, the film was dried at 200 ° C. for 1 hour to provide a first hole transport layer having a thickness of 30 nm.

This substrate was transferred to a nitrogen atmosphere, and a solution obtained by dissolving 60 mg of Exemplified Compound 4-1 in 10 ml of toluene on the first hole transport layer was formed into a film (film thickness) by spin coating under conditions of 1000 rpm and 30 seconds. About 40 nm) and irradiated with ultraviolet light for 30 seconds, followed by heat drying at 120 ° C. for 30 minutes to form a second hole transport layer.

Furthermore, the light emitting layer composition 1 having the following composition was discharged and injected using an inkjet head (manufactured by Epson; MJ800C) so that the wet film thickness was 4 μm. This substrate was fixed to a substrate holder of a drying box provided with upper and lower partition walls and provided with an independent drying air temperature controller at the upper and lower portions of the partition wall, and heating controlled to 120 ° C. on the upper surface of the substrate (light emitting layer coating surface). Dry nitrogen was circulated, and heated dry nitrogen circulated at 80 ° C. on the back side of the substrate. In this state, the light emitting layer was dried by performing a drying process for 10 minutes. It was confirmed that the temperature of dry nitrogen circulated on both sides of the substrate was controlled within ± 1 ° C. from the start to the end of drying.

This corresponds to lowering the temperature on the anode side in claims 5 and 6 further by 10 ° C. (in this case, 40 ° C.) lower than the temperature on the cathode side.

(Light emitting layer composition 1)
(2) -37 1.0 part by mass (1) -79 0.1 part by mass Toluene 100 parts by mass This substrate was fixed to the substrate holder of the vacuum evaporation apparatus, while 200 mg of ET-A was added to the resistance heating boat made of molybdenum. Then, 100 mg of CsF was put into another resistance heating boat made of molybdenum, and attached to a vacuum deposition apparatus. The vacuum chamber was depressurized to 4 × 10 ⁻⁴ Pa, and then heated by energizing the heating boat containing ET-A and CsF, and the light emitting layer was deposited at a deposition rate of 0.2 nm / second and 0.03 nm / second, respectively. An electron transport layer having a film thickness of 40 nm was further provided. Subsequently, 110 nm of aluminum was deposited to form a cathode, and an organic EL element 111 was produced.

[Production of organic EL elements 112 to 114]
In the production of the organic EL element 111, the organic EL element 111 was formed in the same manner except that the temperature of nitrogen to be circulated to the substrate upper surface side and the substrate rear surface side in the drying step after the discharge injection of the light emitting layer composition 1 was changed as shown in Table 1. EL elements 112 to 114 were produced.

[Production of Organic EL Elements 121-123, 131-133, 141-142]
In the production of the organic EL element 111, the material constituting the light emitting layer composition 1 is changed as shown in Table 1, and nitrogen circulated between the substrate upper surface side and the substrate back surface side in the drying step after the discharge injection of the light emitting layer composition. Organic EL elements 121 to 123, 131 to 133, and 141 to 142 were fabricated in the same manner except that the temperature was changed as shown in Table 1.

The concentration distribution of the light-emitting dopant contained in the light-emitting layer of the obtained organic EL element is detected by analyzing the Ir distribution in the film thickness direction by TOF-SIMS (time-of-flight secondary ion mass spectrometry). Can do. Table 1 shows the concentration distribution from the anode side to the cathode side in the light emitting layers of the organic EL devices 111 to 114, 121 to 123, 131 to 133, and 141 to 142.

<< Evaluation of organic EL elements >>
About the produced organic EL element, the external extraction quantum efficiency and the light emission lifetime were evaluated as follows.

[External extraction quantum efficiency]
External quantum efficiency (%) was measured when a ^2.5 mA / cm ² constant current was applied to the produced organic EL element. For the measurement, a spectral radiance meter CS-1000 (manufactured by Konica Minolta Sensing) was used. The external extraction quantum efficiencies of the organic EL elements 111 to 116 were expressed as relative values with the measured value of the organic EL element 116 (comparative) as 100.

The external extraction quantum efficiency of the organic EL elements 121 to 123 is a relative value with the measured value of the organic EL element 123 (comparative) as 100, and the external extraction efficiency of the organic EL elements 131 to 133 is a measurement of the organic EL element 133 (comparative). The relative value with the value of 100, the external extraction quantum efficiency of the organic EL elements 141 to 143 is the relative value with the measured value of the organic EL element 143 (comparison) as 100, and the external extraction efficiency of the organic EL elements 151 to 153 is the organic EL The relative value when the measured value of the element 153 (comparison) is 100 and the external extraction efficiency of the organic EL elements 161 to 162 are expressed as relative values when the measured value of the organic EL element 162 (comparative) is 100. .

[Luminescence life]
The produced organic EL element was continuously driven by applying a current that would give a front luminance of 1000 cd / m ² . The time required for the front luminance to reach the initial half value (500 cd / m ² ) is obtained, and the light emission lifetimes of the organic EL elements 111 to 116 are relative values with the measured value of the organic EL element 116 (comparative) as 100. expressed.

The light emission lifetimes of the organic EL elements 121 to 123 are relative values with the measured value of the organic EL element 123 (comparative) as 100, and the light emission lifetimes of the organic EL elements 131 to 133 are the measured value of the organic EL element 133 (comparative) as 100. The relative lifetimes of the organic EL elements 141 to 143 are relative values with the measured value of the organic EL element 143 (comparison) as 100, and the emission lifetimes of the organic EL elements 151 to 153 are those of the organic EL element 153 (comparative). The relative value when the measured value is 100, and the light emission lifetimes of the organic EL elements 161 to 162 are expressed as relative values when the measured value of the organic EL element 162 (comparative) is 100.

The results obtained are shown in Table 1.

From Table 1, the organic EL device of the present invention can continuously change the concentration of the light-emitting dopant in the light-emitting layer even in the manufacturing method using the wet process. As a result, the external extraction quantum efficiency and the light emission lifetime are improved. It can be seen that it has improved.

Example 2
<< Production of organic EL element >>
[Production of Organic EL Element 211]
After patterning a substrate (NH technoglass NA45) formed by depositing 100 nm of ITO (indium tin oxide) on a 100 mm × 100 mm × 1.1 mm glass substrate as an anode, a substrate provided with this ITO transparent electrode was formed. Ultrasonic cleaning with isopropyl alcohol, drying with dry nitrogen gas, and UV ozone cleaning were performed for 5 minutes. On this substrate, poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer, Baytron P Al 4083) diluted to 70% with pure water was spin-coated at 3000 rpm for 30 seconds. After film formation by the method, the film was dried at 200 ° C. for 1 hour to provide a first hole transport layer having a thickness of 30 nm.

Further, the light emitting layer composition 1 having the following composition was discharged and injected using an inkjet head (manufactured by Epson; MJ800C) so that the wet film thickness was 4 μm. The substrate was subjected to a drying treatment for 10 minutes in a 120 ° C. drying box to form the light emitting layer 1.

(Light emitting layer composition 1)
(2) -16 1.0 part by mass (1) -79 0.18 part by mass Toluene 100 parts by mass Subsequently, a light emitting layer composition 2 having the following composition was wet filmed using an inkjet head (manufactured by Epson; MJ800C). The discharge was injected so that the thickness was 2 μm. This substrate was subjected to a drying treatment for 10 minutes in a drying box at 120 ° C. to form a 20 nm light emitting layer 2.

(Light emitting layer composition 2)
(2) -16 1.0 part by mass (1) -79 0.02 part by mass Toluene 100 parts by mass This substrate was fixed to the substrate holder of the vacuum evaporation apparatus, while 200 mg of ET-A was added to a molybdenum resistance heating boat. Then, 100 mg of CsF was put into another resistance heating boat made of molybdenum, and attached to a vacuum deposition apparatus. The vacuum chamber was depressurized to 4 × 10 ⁻⁴ Pa, and then heated by energizing the heating boat containing ET-A and CsF, and the light emitting layer was deposited at a deposition rate of 0.2 nm / second and 0.03 nm / second, respectively. An electron transport layer having a film thickness of 40 nm was further provided. Subsequently, 110 nm of aluminum was deposited to form a cathode, and an organic EL element 211 was produced.

Regarding the organic EL element 211, the light emitting dopant / light emitting host ratio of the solution coated on the most anode side among the two or more kinds of light emitting layer solutions having different light emitting dopant concentrations of claim 7 and claim 8 is 100. This corresponds to an emission dopant / emission host ratio of 5 to 0% by mass of the solution coated on the cathode side, and in this case, the emission dopant / emission host ratio of the solution applied on the anode side is 18%. The light emitting dopant / light emitting host ratio of the solution applied on the most cathode side is 2% by mass.

[Production of organic EL elements 212 to 218]
In the production of the organic EL element 211, organic EL elements 211 to 218 were produced in the same manner except that the compositions and film thicknesses of the light emitting layer compositions 1 and 2 were changed as shown in Table 2.

The organic EL elements 212 and 213 are also equivalent to claims 7 and 8, respectively, and the emission dopant / emission host ratio of the solution coated on the most anode side is 20% by mass, 40% by mass, and most on the cathode side, respectively. The ratio of the luminescent dopant / luminescent host of the solution applied to is 0% by mass and 0% by mass, respectively.

The organic EL element 214 is claimed in claim 7, but the light emitting dopant / light emitting host ratio of the solution coated on the most anode side is 14% by mass, and the light emitting dopant / light emitting host ratio of the solution coated on the most cathode side is mass. Since it is 6%, it does not correspond to Claim 8.

Regarding the organic EL element 217, the solubility of the luminescent dopant ((1) -79) in chlorobenzene is higher than that of toluene, and the boiling point of chlorobenzene is higher. That is, it corresponds to claim 9. On the other hand, the organic EL element 218 has a higher solubility in the luminescent dopant ((1) -79) in chlorobenzene than p-xylene, and conversely, the boiling point of p-xylene is equal to or higher than that of chlorobenzene. Does not correspond to 9.

<< Evaluation of organic EL elements 211 to 218 >>
The produced organic EL elements 211 to 218 were evaluated for external extraction quantum efficiency and light emission lifetime in the same manner as in Example 1. The results obtained are shown in Table 2. The external extraction quantum efficiency and the emission lifetime were expressed as relative values when the measured value of the organic EL element 216 (comparison) was 100.

From Table 2, the organic EL device of the present invention can continuously change the concentration of the light-emitting dopant in the light-emitting layer even in the manufacturing method using the wet process, and as a result, the external extraction quantum efficiency and the light emission lifetime are improved. It can be seen that it has improved.

Claims

In a method for producing an organic electroluminescence device having at least an anode, a cathode, and a light emitting host containing at least an anode, a cathode, and a light emitting host and a light emitting dopant sandwiched between the anode and the cathode, the light emitting layer is formed by a wet process, And the manufacturing method of the organic electroluminescent element characterized by changing continuously the density | concentration of the light emission dopant contained in this light emitting layer toward the cathode side from an anode side.
2. The method of manufacturing an organic electroluminescence element according to claim 1, wherein the concentration of the luminescent dopant decreases from the anode side toward the cathode side.
The method for producing an organic electroluminescent element according to claim 1 or 2, wherein the light-emitting dopant is represented by the following general formula (1).

(In the formula, R 1 represents a substituent. Z represents a group of nonmetallic atoms necessary to form a 5- to 7-membered ring. N1 represents an integer of 0 to 5. B 1 to B 5 represent carbon. Represents an atom, a nitrogen atom, an oxygen atom or a sulfur atom, at least one of B 1 to B 5 represents a nitrogen atom, M 1 represents a metal of Group 8 to Group 10 in the periodic table, X 1 and X 2 represents a carbon atom, a nitrogen atom or an oxygen atom, L 1 represents an atomic group forming a bidentate ligand with X 1 and X 2 , m1 represents an integer of 1, 2 or 3; m2 represents an integer of 0, 1 or 2, and m1 + m2 is 2 or 3.)
The organic electroluminescence device according to any one of claims 1 to 3, wherein the luminescent host is a compound having a molecular weight of 700 or more represented by the following general formula (2). Method.

(In General Formula (2), Y 1 and Y 2 represent O, S or NR 0 , and R 0 , R 11 to R 18 and R 21 to R 28 represent a hydrogen atom or a substituent, provided that R 11 At least one of ~ R 18 and R 0 is used in connection with X 1, R 21 ~ R 28 and at least one .X 1 which is used for connection with the X 1 represented by the following general formula R 0 (3 ) or (4 .n1 that represents a divalent linking group represented by) represents an integer of 1 or more, when n1 is 2 or more, X 1 is may be the same or different.)

(Wherein Y 3 represents O, S or NR 30 , and R 30 to R 38 and R 41 to R 46 represent a hydrogen atom or a substituent, provided that R 30 to R 38 and R 41 to R 46 represent At least two of each are used for linking, and when R 41 and R 44 are used for linking, at least one of R 42 , R 43 , R 45 and R 46 has a substituent other than a hydrogen atom.)
5. The method of manufacturing an organic electroluminescence device according to claim 1, wherein the drying is performed while controlling the atmospheric temperature in contact with the back side of the coating film to be lower than the atmospheric temperature in contact with the front side of the coating film. A light emitting layer is formed by doing so, The manufacturing method of the organic electroluminescent element characterized by the above-mentioned.
The method for producing an organic electroluminescent element according to claim 5, wherein the atmospheric temperature on the back side of the coating film is controlled to be lower by 10 ° C or more than the atmospheric temperature on the front side of the coating film.
5. The method of manufacturing an organic electroluminescence device according to claim 1, wherein the lamination coating of two or more light emitting layer solutions having different light emitting dopant concentrations is applied to the most anode side. Production of an organic electroluminescent device characterized in that the emission dopant / emission host ratio of the solution is higher than the emission dopant / emission host ratio of the solution coated on the cathode side, and then dried to form the emission layer Method.
Among the two or more kinds of light emitting layer solutions having different light emitting dopant concentrations, the light emitting dopant / light emitting host ratio of the solution coated on the most anode side is 100 to 10% by mass, and the light emitting dopant / light emitting host of the solution coated on the most cathode side. The method for producing an organic electroluminescent element according to claim 7, wherein the ratio is 5 to 0% by mass.
The method for producing an organic electroluminescent element according to any one of claims 1 to 4, wherein the solvent of the solution of the light emitting layer is a mixed solvent of two liquids having different boiling points and luminescent dopant solubilitys, The manufacturing method of the organic electroluminescent element characterized by the boiling point of the solvent with higher luminescent dopant solubility being higher than the boiling point of the solvent with lower luminescent dopant solubility.
An organic electroluminescent device manufactured by the method for manufacturing an organic electroluminescent device according to any one of claims 1 to 9.