JP2018116782A - Manufacturing method of organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an organic electroluminescent element of low drive voltage, and to provide a suitable manufacturing method of organic electroluminescent element.SOLUTION: A manufacturing method of organic electroluminescent element having at least between a positive electrode and a negative electrode, a hole injection layer adjacent to the positive electrode, a hole transport layer and a luminous layer in this order, includes a step of forming the hole injection layer by wet deposition of a composition for forming the hole injection layer, a step of forming the hole transport layer by wet deposition of a composition for forming the hole transport layer, and a step of forming the luminous layer by wet deposition of a composition for forming the luminous layer. The composition for forming the hole injection layer, the composition for forming the hole transport layer and the composition for forming the luminous layer each contains, independently, an organic solvent, and one kind or more of charge transport material or luminous material dissolved into the organic solvent, and 95 wt.% or more of the organic solvent contained, respectively, in the three types of composition is a benzoic ester-based solvent or an aromatic ether-based solvent.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing an organic electroluminescent element.

Development of organic EL displays and organic EL lighting has been actively conducted since the announcement of Kodak's stacked organic electroluminescence (EL) elements. It is being put into practical use.
In such a stacked organic electroluminescent device, a plurality of organic layers (light emitting layer, hole injection layer, hole transport film, electron transport layer, etc.) are stacked between the anode and the cathode. . In many cases, these organic layers are formed by vacuum-depositing organic layer materials such as low molecular weight dyes. However, it is difficult to obtain a thin film that is homogeneous and free of defects by vacuum deposition. In addition, since the vacuum deposition method requires a long time to form a plurality of organic layers, there is a problem in terms of device manufacturing efficiency.

  On the other hand, a technique for forming a plurality of organic layers of a stacked organic electroluminescent element by a wet film forming method has been reported. For example, Patent Document 1 discloses an organic electroluminescent device having a charge transport film and a light emitting layer containing a crosslinkable polymer obtained by applying a composition containing a compound having a crosslinking group and crosslinking with light or heat. Have been described. When a charge transport film containing a crosslinkable polymer is used, another layer can be easily formed on the charge transport film by a wet film formation method.

  The manufacturing process of an organic electroluminescent element by such a wet film-forming method is expected to enable simplification, efficiency, and cost reduction of manufacturing a large area organic EL device, and various studies have been made. . Moreover, the manufacturing process of the organic electroluminescent element by such a wet film-forming method forms a wet film using an inkjet system, a nozzle coat system, etc., for example as described in patent document 2 and patent document 3. Therefore, it is considered that a large-area organic EL device can be realized at low cost.

  In the manufacturing process of an organic electroluminescent element by a wet film forming method, an ink in which a material for forming a layer having various functions is dissolved or dispersed in a solvent is manufactured, and a coating film is manufactured using the ink. Specifically, the layer structure of a typical organic electroluminescent element is a laminate of anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / electron injection layer / cathode. Among them, it has been proposed to form three layers of a hole injection layer, a hole transport layer, and a light emitting layer by a wet film formation method (for example, Patent Document 4).

  At this time, since the hole injection layer and the hole transport layer are formed by a wet film formation method on the upper layer after the film formation, the organic solvent of the upper layer is included by performing a crosslinking treatment after the film formation. A device has been devised to prevent the components from eluting when the composition is applied. However, it is difficult to completely suppress such elution, and there are many adverse effects on the characteristics of the organic electroluminescent element due to this phenomenon.

Japanese Unexamined Patent Publication No. 7-114987 JP 2004-127919 A JP 2004-41943 A International Publication WO2010 / 013780 Pamphlet

  In view of the above circumstances, the present invention provides an organic electroluminescent device manufacturing method capable of reducing driving voltage in an organic electroluminescent device in which a hole injection layer, a hole transport layer, and a light emitting layer are formed by a wet film forming method. The task is to do.

As a result of intensive studies to solve the above-mentioned problems, the present inventors use the composition for forming the above three layers when forming a hole injection layer, a hole transport layer, and a light-emitting layer by a wet film formation method. It has been found that by unifying the organic solvent with a specific organic solvent, the driving voltage of the organic electroluminescent element can be reduced, and the present invention has been achieved.
[1] A method of manufacturing an organic electroluminescent device having a hole injection layer, a hole transport layer, and a light emitting layer adjacent to the anode in this order between at least the anode and the cathode, the manufacturing method comprising: Forming the hole injection layer by wet-forming the injection layer forming composition, forming the hole transport layer by wet-forming the hole transport layer forming composition, and forming the light-emitting layer A step of forming the light emitting layer by wet-depositing the composition for forming the hole injection layer, the hole injection layer forming composition, the hole transport layer forming composition, and the light emitting layer forming composition are each independently An organic solvent and one or more charge transporting materials or light emitting materials dissolved in the organic solvent, the hole injection layer forming composition, the hole transport layer forming composition, and the light emitting layer 95% by weight or more of the organic solvent contained in each forming composition is all benzoic acid ester Or 95% by weight or more of the organic solvent contained in each of the composition for forming a hole injection layer, the composition for forming a hole transport layer, and the composition for forming a light emitting layer is aromatic. A method for producing an organic electroluminescent device, which is an ether solvent.
[2] The method for producing an organic electroluminescent element according to [1], wherein all of the organic solvents contained in the respective compositions are benzoate solvents.
[3] The method for producing an organic electroluminescent element according to [1] or [2], wherein all the organic solvents contained in the respective compositions have boiling points of 150 ° C. or higher.
[4] The method for producing an organic electroluminescent element according to any one of [1] to [3], wherein the composition for forming a hole injection layer contains a polymer compound as a charge transport material.
[5] The method for producing an organic electroluminescent element according to any one of [1] to [4], wherein the composition for forming a hole transport layer contains a polymer compound as a charge transport material.
[6] The method for producing an organic electroluminescent element according to any one of [1] to [5], wherein all of the organic solvents contained in the respective compositions have the same composition.

According to the method for producing an organic electroluminescent element of the present invention, an organic electroluminescent element having a low driving voltage can be obtained by a wet film forming method.
Since the organic electroluminescence device manufactured by the method of the present invention has a low driving voltage, a light source (for example, a copying machine) utilizing a feature as a flat panel display (for example, for OA computers or wall-mounted televisions) or a surface light emitter. It can be applied to light sources, back light sources for liquid crystal displays and instruments), display boards, and sign lamps, and its technical value is high.

It is sectional drawing which shows typically an example of the structure of the organic electroluminescent element of this invention.

Hereinafter, the manufacturing method of the organic electroluminescent element of this invention is demonstrated in detail. However, the description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not specified by these contents unless it exceeds the gist.
The method for producing an organic electroluminescent element of the present invention comprises a step of forming a hole injection layer forming composition by wet film formation, and a step of forming the hole injection layer forming composition. A step of forming the hole transport layer, and a step of forming the light emitting layer by wet-depositing the composition for forming a light emitting layer. In this production method, formation of a hole injection layer for forming a hole injection layer, a hole transport layer, and a light emitting layer (hereinafter sometimes simply referred to as three layers) by a wet film formation method. To prepare each of the composition for forming a hole, the composition for forming a hole transport layer, and the composition for forming a light emitting layer (hereinafter collectively referred to simply as a total composition, each of which may be simply referred to as each composition) is important. That is, each of the composition for forming a hole injection layer, the composition for forming a hole transport layer, and the composition for forming a light emitting layer according to the present invention is independently an organic solvent and one type dissolved in the organic solvent. 95% by weight or more of the organic solvent contained in each of the compositions including the above charge transporting material or light-emitting material is all a benzoate solvent or an aromatic ether solvent. It is necessary. First, the composition will be described in detail.

(Essential composition in each composition)
<Organic solvent>
In the present invention, 95% by weight or more of the organic solvent contained in each composition is a benzoate solvent or an aromatic ether solvent.
The benzoate solvent in the present invention is a compound having an ester bond with benzoic acid, such as methyl benzoate, ethyl benzoate, N-propyl benzoate, isopropyl benzoate, butyl benzoate, isobutyl benzoate, benzoate. Organic solvents such as acid N-pentyl, isoamyl benzoate, N-hexyl benzoate, and benzyl benzoate. The boiling point of the benzoate solvent is usually 150 ° C. or higher, preferably 240 ° C. or higher, more preferably 248 ° C. or higher, and further preferably 260 ° C. or higher. When the boiling point of the organic solvent is equal to or higher than the above lower limit, coating unevenness is unlikely to occur, and a trace amount remains in the film even after drying, so that it is considered that the effect by the action mechanism described later is easily obtained.

  The aromatic ether solvent in the present invention is an aromatic compound and a compound having an ether bond, such as benzyl methyl ether, phenetole, diphenyl ether, dibenzyl ether, o-methyl diphenyl ether, m-methyl diphenyl ether, p-methyl diphenyl ether. Organic solvents such as The boiling point of the aromatic ether solvent is usually 150 ° C. or higher, preferably 240 ° C. or higher, more preferably 250 ° C. or higher, and further preferably 270 ° C. or higher. When the boiling point of the organic solvent is equal to or higher than the above lower limit, coating unevenness is unlikely to occur, and a trace amount remains in the film even after drying, so that it is considered that the effect by the action mechanism described later can be easily obtained.

  The content of the benzoate solvent or aromatic ether solvent in the organic solvent of each composition is 95% by weight or more, preferably 97% by weight or more, more preferably 99% by weight or more, and 100% by weight. More preferably it is. 100% by weight means substantially 100% by weight, and this does not exclude the inclusion of other solvents as trace amounts of impurities. Here, the organic solvent in each composition may be a mixed solvent of a benzoate solvent and an aromatic ester solvent, but the boiling point of all organic solvents is preferably 150 ° C. or higher, and benzoic acid. More preferably, only ester solvents or aromatic ether solvents are used.

As long as the composition of the organic solvent in each composition is within the above range, it is not necessary that all the three layers have the same composition, and they may be different from each other, but all three layers are preferably the same.
Moreover, it is preferable that all the organic solvents in each composition are benzoic acid ester system.
The content of the organic solvent in each composition is usually 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more. When the content of the organic solvent is not less than the above lower limit, the flatness and uniformity of the formed layer can be improved.

(Action mechanism of the present invention)
The solvent contained in the composition for forming a hole injection layer is considered to remain in a very small amount in the hole injection layer when the hole injection layer is formed by drying after wet film formation. When the hole transport layer forming composition is wet-film-formed and then dried to form a hole transport layer in contact with the hole injection layer, the trace amount of the organic solvent remaining in the hole injection layer is 95. % By weight and 95% by weight or more of the organic solvent contained in the composition for forming a hole transport layer are both the same solvent system, that is, both are benzoate solvents or both are aromatic ether solvents. And a composition for forming a hole transport layer on the surface of the hole injection layer by an interaction between the organic solvent present in a trace amount in the hole injection layer and an organic solvent contained in the composition for forming a hole transport layer. It is thought that the wettability of an object improves. Further, at this time, the charge transporting material is dissolved in the composition for forming the hole injection layer, whereby a hole injection layer having a uniform surface is formed. As a result, the composition applied on the hole injection layer It is thought that wettability is improved. Furthermore, since the charge transport material is dissolved in the composition for forming a hole transport layer wet-formed on the hole injection layer, the adhesion is further improved and the hole transport having a uniform surface is achieved. It is considered that the wettability of the composition for forming a light-emitting layer, in which a layer is formed and a wet film is formed thereon, is improved. This improves the adhesion between the films, reduces the hole injection barrier at the film interface, and enables smooth hole movement. Therefore, it becomes possible to flow a current at a low potential, and the voltage of the element can be reduced. Further, since the same phenomenon occurs at the interface between the hole transport layer and the light emitting layer, further low voltage driving is possible.

In particular, a benzoate solvent has high wettability to all surfaces including electrode surfaces such as ITO, and spreads evenly to form a uniform coating film, thereby realizing a stable low voltage.
Since the charge transport material and the light-emitting material usually contain a compound having an aromatic ring and a hetero atom, a benzoate solvent or an aromatic ether solvent containing an aromatic ring and a hetero atom is preferable because of high solubility. Further, from the viewpoint of the stability of the solvent that remains in a very small amount in the film, a benzoate solvent is preferable.

<Charge transport material>
The charge transport material according to the present invention is a material capable of efficiently injecting and transporting charges (holes, electrons) from the electrode, and from the conventionally known materials for organic electroluminescence devices, A material that can be dissolved in the organic solvent can be appropriately selected and used.
The charge transport material is mainly used in the charge injection layer, the charge transport layer, and the light emitting layer in the organic electroluminescent device. In addition, these materials are often used alone in each of the above layers, but a plurality of types may be used in combination in order to control charge transport. Furthermore, a low molecular material or a polymer material may be used.

  Such charge transport materials are classified into hole transport compounds and electron transport compounds, hole transport compounds are mainly used for the hole injection layer and the hole transport layer, and holes are used for the light emitting layer. Both transporting compounds and electron transporting compounds are often used. Specific compound materials will be described later.

<Light emitting material>
The light-emitting material according to the present invention is a material that emits light at a desired light emission wavelength and has good light emission efficiency. A material that can be dissolved in the organic solvent according to the present invention from a conventionally known material for an organic electroluminescent element. It can be appropriately selected and used.
The light emitting material is mainly used for the light emitting layer in the organic electroluminescent element. In addition, these materials are often used alone in the light emitting layer, but may be used as a mixture of plural kinds in order to adjust to a desired light emission wavelength. Furthermore, a low molecular material or a polymer material may be used. Specific materials will be described later.

(Layer structure and manufacturing method of organic electroluminescence device according to the present invention)
Hereinafter, an example of an embodiment of a general layer configuration of an organic electroluminescent element according to the present invention and a manufacturing method thereof will be described with reference to FIG.
FIG. 1 is a schematic cross-sectional view showing a structural example of an organic electroluminescent device 10 according to the present invention. In FIG. 1, 1 is a substrate, 2 is an anode, 3 is a hole injection layer, 4 is a hole transport layer, Reference numeral 5 denotes a light emitting layer, 6 denotes a hole blocking layer, 7 denotes an electron transport layer, 8 denotes an electron injection layer, and 9 denotes a cathode. In the present invention, the anode 2, the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, and the cathode 9 are essential components.
As materials and manufacturing methods applied to these structures, known materials and manufacturing methods can be applied, and there is no particular limitation, but typical materials and manufacturing methods for each layer are described below as an example. In addition, when citing publications and papers, the relevant contents can be applied and applied as appropriate within the scope of common knowledge of those skilled in the art.

<Substrate 1>
The substrate 1 serves as a support for the organic electroluminescent element, and a quartz or glass plate, a metal plate or a metal foil, a plastic film or a sheet is usually used. Of these, glass plates and transparent synthetic resin plates such as polyester, polymethacrylate, polycarbonate, and polysulfone are preferable. The substrate 1 is preferably made of a material having a high gas barrier property because the organic electroluminescence element is hardly deteriorated by the outside air. For this reason, when using a material having a low gas barrier property, such as a synthetic resin substrate, it is preferable to provide a dense silicon oxide film or the like on at least one surface of the substrate 1 to improve the gas barrier property.

<Anode 2>
The anode 2 has a function of injecting holes into the layer on the light emitting layer side. The anode 2 is usually made of a metal such as aluminum, gold, silver, nickel, palladium, or platinum; a metal oxide such as an oxide of indium and / or tin; a metal halide such as copper iodide; a carbon black and a poly (3 -Methylthiophene), polypyrrole, polyaniline and other conductive polymers. In general, the anode 2 is often formed by a dry method such as a sputtering method or a vacuum deposition method. In addition, when forming the anode 2 using fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, an appropriate binder resin solution It can also be formed by being dispersed in and coated on a substrate. In the case of a conductive polymer, a thin film can be directly formed on the substrate by electrolytic polymerization, or the anode 2 can be formed by applying a conductive polymer on the substrate (Appl. Phys. Lett., 60, 2711, 1992).

The anode 2 usually has a single layer structure, but may have a laminated structure as appropriate. When the anode 2 has a laminated structure, different conductive materials may be laminated on the first anode. The thickness of the anode 2 may be determined according to required transparency and material. In particular, when high transparency is required, a thickness at which visible light transmittance is 60% or more is preferable, and a thickness at which 80% or more is more preferable. The thickness of the anode 2 is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably 500 nm or less. On the other hand, when transparency is not required, the thickness of the anode 2 may be an arbitrary thickness depending on the required strength, and in this case, the anode 2 may have the same thickness as the substrate 1.
When film formation is performed on the surface of the anode 2, impurities on the anode are removed and the ionization potential thereof is adjusted by performing treatment such as ultraviolet ray + ozone, oxygen plasma, argon plasma before film formation. It is preferable to improve the hole injection property.

<Hole injection layer 3>
There are a hole injection layer 3 and a hole transport layer 4 as layers responsible for transporting holes from the anode side to the light emitting layer side, and the layer closer to the anode side is called the hole injection layer 3. The hole injection layer 3 is formed on the anode.
The thickness of the hole injection layer 3 is usually 1 nm or more, preferably 5 nm or more, and usually 1000 nm or less, preferably 500 nm or less.
The hole injection layer 3 includes a hole transporting compound, and more preferably includes a hole transporting compound and an electron accepting compound. Further, the hole injection layer preferably contains a cation radical compound, and particularly preferably contains a cation radical compound and a hole transporting compound.

  The composition for forming a hole injection layer contains a hole transporting compound to be the hole injection layer 3 and the organic solvent according to the present invention. It is preferable that the composition for forming a hole injection layer has high hole transportability and can efficiently transport injected holes. For this reason, it is preferable that the hole mobility is high and impurities that become traps are less likely to be generated during production or use. Moreover, it is preferable that it is excellent in stability, has a small ionization potential, and has high transparency to visible light.

<< Hole Transporting Compound >>
The hole transporting compound is preferably a compound having an ionization potential of 4.5 eV to 6.0 eV from the viewpoint of a charge injection barrier from the anode 2 to the hole injection layer 3. A low molecular compound or a high molecular compound may be used, but a high molecular compound is preferable. Examples of hole transporting compounds include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, compounds in which tertiary amines are linked by a fluorene group, hydrazones Compound, silazane compound compound, quinacridone compound and the like.

Of the above-described exemplary compounds, an aromatic amine compound is preferable and an aromatic tertiary amine compound is particularly preferable from the viewpoint of amorphousness and visible light transmittance. Here, the aromatic tertiary amine compound is a compound having an aromatic tertiary amine structure, and includes a compound having a group derived from an aromatic tertiary amine.
The type of the aromatic tertiary amine compound is not particularly limited, but is a polymer compound having a weight average molecular weight of 1,000 to 1,000,000 (polymerization compound in which repeating units are linked) from the viewpoint of easily obtaining uniform light emission due to the surface smoothing effect. Is preferably used. Preferable examples of the aromatic tertiary amine polymer compound include a polymer compound having a repeating unit represented by the following formula (I).

(In Formula (I), Ar ¹ and Ar ² each independently represent an aromatic group which may have a substituent or a heteroaromatic group which may have a substituent. Ar ³ -Ar ⁵ each independently represents an aromatic group which may have a substituent or a heteroaromatic group which may have a substituent, and Y is selected from the following group of linking groups. Represents a selected linking group, and among Ar ^{1 to} Ar ⁵ , two groups bonded to the same N atom may be bonded to each other to form a ring.
The linking group is shown below.

(In said each formula, Ar < ⁶ > -Ar < ¹⁶ > respectively independently represents the aromatic group which may have a substituent, or the heteroaromatic group which may have a substituent. R < ⁵ >->. R ⁶ independently represents a hydrogen atom or an arbitrary substituent.) As the aromatic group and heteroaromatic group of Ar ^{1 to} Ar ¹⁶ , the solubility, heat resistance, and hole injection of the polymer compound From the viewpoint of transportability, a group derived from a benzene ring, naphthalene ring, phenanthrene ring, thiophene ring or pyridine ring is preferred, and a group derived from a benzene ring or naphthalene ring is more preferred.
Specific examples of the aromatic tertiary amine polymer compound having a repeating unit represented by the formula (I) include those described in International Publication No. 2005/089024.

<< Electron-accepting compound >>
The hole injection layer 3 preferably contains an electron accepting compound because the conductivity of the hole injection layer 3 can be improved by oxidation of the hole transporting compound.
As the electron-accepting compound, a compound having an oxidizing power and the ability to accept one electron from the above-described hole-transporting compound is preferable, and specifically, a compound having an electron affinity of 4 eV or more is preferable. More preferably, the compound is 5 eV or more.

  Examples of such electron-accepting compounds include triarylboron compounds, metal halides, Lewis acids, organic acids, onium salts, salts of arylamines and metal halides, and salts of arylamines and Lewis acids. Examples thereof include one or more compounds selected from the group. Specifically, onium salts substituted with organic groups such as 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) borate and triphenylsulfonium tetrafluoroborate (WO 2005/089024 pamphlet); High valence inorganic compounds such as iron (III) (Japanese Patent Laid-Open No. 11-251067) and ammonium peroxodisulfate; Cyano compounds such as tetracyanoethylene; Tris (pentafluorophenyl) borane (Japanese Patent Laid-Open No. 2003-31365) Aromatic boron compounds such as: fullerene derivatives and iodine.

<< Cation Radical Compound >>
As the cation radical compound, an ionic compound composed of a cation radical which is a chemical species obtained by removing one electron from a hole transporting compound and a counter anion is preferable. However, when the cation radical is derived from a hole transporting polymer compound, the cation radical has a structure in which one electron is removed from the repeating unit of the polymer compound.

The cation radical is preferably a chemical species obtained by removing one electron from the compound described above as the hole transporting compound. A chemical species obtained by removing one electron from a compound preferable as a hole transporting compound is preferable in terms of amorphousness, visible light transmittance, heat resistance, solubility, and the like.
Here, the cation radical compound can be generated by mixing the hole transporting compound and the electron accepting compound. That is, by mixing the hole transporting compound and the electron accepting compound, electron transfer occurs from the hole transporting compound to the electron accepting compound, and the cation radical and the counter anion of the hole transporting compound A cation ion compound consisting of

Cationic radical compounds derived from polymer compounds such as PEDOT / PSS (Adv. Mater., 2000, 12, 481) and emeraldine hydrochloride (J. Phys. Chem., 1990, 94, 7716) It is also produced by oxidative polymerization (dehydrogenation polymerization).
Oxidative polymerization here refers to oxidation of a monomer chemically or electrochemically with peroxodisulfate in an acidic solution. In the case of this oxidative polymerization (dehydrogenation polymerization), the monomer is polymerized by oxidation, and a cation radical that is removed from the polymer repeating unit by using an anion derived from an acidic solution as a counter anion is removed. Generate.

<< Formation of Hole Injection Layer 3 by Wet Film Formation Method >>
In the method for manufacturing an organic electroluminescent element of the present invention, the hole injection layer 3 is formed by a wet film forming method. In the present invention, the wet film forming method is a film forming method, that is, a coating method, for example, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, capillary It refers to a method of forming a film by adopting a wet film forming method such as a coating method, an ink jet method, a nozzle printing method, a screen printing method, a gravure printing method, or a flexographic printing method, and drying the coating film. The above-described composition for forming a hole injection layer is prepared, and this composition for forming a hole injection layer is formed on the layer corresponding to the lower layer of the hole injection layer 3 (usually the anode 2) by using the above-described method. It is formed by coating, forming a film, and drying.

  The concentration of the hole transporting compound in the composition for forming a hole injection layer is arbitrary as long as the effects of the present invention are not significantly impaired, but in terms of film thickness uniformity, the lower one is preferable. From the viewpoint that defects are unlikely to occur in the hole injection layer 3, a higher value is preferable. Specifically, it is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, particularly preferably 0.5% by mass or more, and on the other hand, 70% by mass. The content is preferably less than 60% by mass, more preferably 60% by mass or less, and particularly preferably 50% by mass or less.

<Hole transport layer 4>
The hole transport layer 4 is formed between the hole injection layer 3 and the light emitting layer 5.
The film thickness of the hole transport layer 4 is usually 5 nm or more, preferably 10 nm or more, and is usually 300 nm or less, preferably 100 nm or less.
The composition for forming a hole transport layer contains a hole transport compound that becomes the hole transport layer 4 and the organic solvent according to the present invention.

<< Hole Transporting Compound >>
Examples of the hole transporting compound contained in the hole transporting layer 4 include the hole transporting compound contained in the hole injection layer 3 described above, and in particular, 4,4′-bis [N- (1- (Naphthyl) -N-phenylamino] biphenyl, an aromatic diamine containing two or more tertiary amines and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Laid-Open No. 5-234681), Aromatic amine compounds having a starburst structure such as 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine (J. Lumin., 72-74, 985, 1997), tri Aromatic amine compounds consisting of tetramers of phenylamine (Chem. Commun., 2175, 1996), 2,2 ′, 7,7′-tetrakis- (diphenylamino) -9,9′-spirobifluore Spiro compounds (Synth. Metals, 91, 209, 1997), carbazole derivatives such as 4,4′-N, N′-dicarbazole biphenyl, and the like. Also, for example, polyvinyl carbazole, polyvinyl triphenylamine (Japanese Patent Laid-Open No. 7-53953), polyarylene ether sulfone (Polym. Adv. Tech., 7, 33, 1996) containing tetraphenylbenzidine, etc. It can be preferably used.

<Formation of hole transport layer 4 by wet film formation method>
In the method for producing an organic electroluminescent element of the present invention, the hole transport layer 4 is formed by a wet film forming method.
The above-described composition for forming a hole transport layer is prepared, and this composition for forming a hole transport layer is applied onto the hole injection layer 3 by using a wet film formation method, and then dried. To form.
The concentration of the hole transporting compound in the composition for forming a hole transport layer can be in the same range as the concentration of the hole transporting compound in the composition for forming a hole injection layer.

<Light emitting layer 5>
The light emitting layer 5 is a layer having a function of emitting light when excited by recombination of holes injected from the anode 2 and electrons injected from the cathode 9 when an electric field is applied between a pair of electrodes. . The light emitting layer 5 is a layer formed between the anode 2 and the cathode 9, and the light emitting layer 5 is formed between the hole transport layer 4 and the cathode 9.

The thickness of the light-emitting layer 5 is arbitrary as long as the effects of the present invention are not significantly impaired. However, it is preferable that the thickness of the light-emitting layer 5 is small in that it is difficult to cause defects in the film. Is preferred. Specifically, the thickness is usually 3 nm or more, preferably 5 nm or more, and usually 200 nm or less, preferably 100 nm or less.
The organic electroluminescent device according to the present invention may be provided with two or more light emitting layers.
The composition for forming a light emitting layer contains a light emitting material to be the light emitting layer 5 and the organic solvent according to the present invention. In addition, it is preferable to include a charge transporting material.

<< Luminescent Material >>
The light emitting material according to the present invention may be a fluorescent light emitting material or a phosphorescent light emitting material, but is preferably a phosphorescent light emitting material from the viewpoint of internal quantum efficiency.
Examples of the fluorescent light emitting material include the following materials.
Examples of the fluorescent light-emitting material that gives blue light emission (blue fluorescent light-emitting material) include naphthalene, perylene, pyrene, anthracene, coumarin, chrysene, p-bis (2-phenylethenyl) benzene, and derivatives thereof.

Examples of the fluorescent light-emitting material that gives green light emission (green fluorescent light-emitting material) include quinacridone derivatives, coumarin derivatives, aluminum complexes such as Al (C ₉ H ₆ NO) _{3, and the} like.
Examples of the fluorescent light-emitting material that gives yellow light (yellow fluorescent light-emitting material) include rubrene and perimidone derivatives.
Examples of fluorescent light emitting materials that give red light emission (red fluorescent light emitting materials) include DCM (4-
(Dicyanomethylene) -2-methyl-6- (p-dimethylaminostyryl) -4H-pyran) compounds, benzopyran derivatives, rhodamine derivatives, benzothioxanthene derivatives, azabenzothioxanthene and the like.

Examples of the phosphorescent material include organometallic complexes containing a metal selected from Groups 7 to 11 of the long-period periodic table. Preferred examples of the metal selected from Groups 7 to 11 of the periodic table include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold.
As the ligand of the organometallic complex, a ligand in which a (hetero) aryl group such as a (hetero) arylpyridine ligand or (hetero) arylpyrazole ligand and a pyridine, pyrazole, phenanthroline, or the like is connected is preferable. In particular, a phenylpyridine ligand and a phenylpyrazole ligand are preferable. Here, (hetero) aryl represents an aryl group or a heteroaryl group.

  Specific examples of preferred phosphorescent materials include tris (2-phenylpyridine) iridium, tris (2-phenylpyridine) ruthenium, tris (2-phenylpyridine) palladium, bis (2-phenylpyridine) platinum, and tris. Examples thereof include phenylpyridine complexes such as (2-phenylpyridine) osmium and tris (2-phenylpyridine) rhenium, and porphyrin complexes such as octaethylplatinum porphyrin, octaphenylplatinum porphyrin, octaethyl palladium porphyrin, and octaphenyl palladium porphyrin.

  Polymeric light-emitting materials include poly (9,9-dioctylfluorene-2,7-diyl), poly [(9,9-dioctylfluorene-2,7-diyl) -co- (4,4′- (N- (4-sec-butylphenyl)) diphenylamine)], poly [(9,9-dioctylfluorene-2,7-diyl) -co- (1,4-benzo-2 {2,1'-3 } -Triazole)] and the like, and polyphenylene vinylene materials such as poly [2-methoxy-5- (2-hexylhexyloxy) -1,4-phenylenevinylene].

<< Charge-transporting material >>
Specific examples of charge transporting materials include aromatic amine compounds, phthalocyanine compounds, porphyrin compounds, oligothiophene compounds, polythiophene compounds, benzylphenyl compounds, and compounds in which tertiary amines are linked by a fluorene group. , Hydrazone compounds, silazane compounds, silanamin compounds, phosphamine compounds, quinacridone compounds, and the like as examples of hole transporting compounds in the hole injection layer, anthracene compounds, pyrene compounds, Examples thereof include electron transporting compounds such as carbazole compounds, pyridine compounds, phenanthroline compounds, oxadiazole compounds and silole compounds.

In addition, for example, two or more condensed aromatic rings including two or more tertiary amines typified by 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl have nitrogen atoms. Aromatic amine compounds having a starburst structure such as substituted aromatic diamines (Japanese Patent Laid-Open No. 5-234681), 4,4 ′, 4 ″ -tris (1-naphthylphenylamino) triphenylamine (J. Lumin., 72-74, 985, 1997), an aromatic amine compound comprising a tetramer of triphenylamine (Chem. Commun., 2175, 1996), 2, 2 ′, 7, 7 Fluorene compounds such as' -tetrakis- (diphenylamino) -9,9'-spirobifluorene (Synth. Metals, 91, 209, 1997), 4,4'-N, '- compounds exemplified as the hole-transporting compound of the hole transport layer of the carbazole-based compounds such as di-biphenyl, or the like can be preferably used.

  In addition, 2- (4-biphenylyl) -5- (p-tertiarybutylphenyl) -1,3,4-oxadiazole (tBu-PBD), 2,5-bis (1-naphthyl)- Oxadiazole compounds such as 1,3,4-oxadiazole (BND), 2,5-bis (6 ′-(2 ′, 2 ″ -bipyridyl))-1,1-dimethyl-3,4 Examples thereof include silole compounds such as diphenylsilole (PyPySPyPy) and phenanthroline compounds such as bathophenanthroline (BPhen) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP, bathocuproin).

<Formation of Light-Emitting Layer 5 by Wet Film Formation Method>
In the manufacturing method of the organic electroluminescent element of the present invention, the light emitting layer 5 is formed by a wet film forming method.
The light emitting layer forming composition described above is prepared, and this light emitting layer forming composition is formed on the hole transport layer 4 by coating using a wet film forming method and then dried.
The content of the light emitting material in the composition for forming a light emitting layer is usually 0.01% by weight or more, preferably 0.1% by weight or more, usually 50% by weight or less, preferably 40% by weight or less.
The content of the charge transporting material in the composition for forming a light emitting layer is usually 0.01% by weight or more, preferably 0.1% by weight or more, usually 50% by weight or less, preferably 30% by weight or less.

<Hole blocking layer 6>
A hole blocking layer 6 may be provided between the light emitting layer 5 and an electron injection layer 8 described later. The hole blocking layer 6 is a layer stacked on the light emitting layer 5 so as to be in contact with the cathode side interface of the light emitting layer 5.
The hole blocking layer 6 has a role of blocking holes moving from the anode 2 from reaching the cathode 9 and a role of efficiently transporting electrons injected from the cathode 9 toward the light emitting layer 5. Have The physical properties required for the material constituting the hole blocking layer 6 include high electron mobility, low hole mobility, a large energy gap (difference between HOMO and LUMO), and excited triplet level (T1). Is high.

Examples of the material of the hole blocking layer 6 satisfying such conditions include, for example, bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum. Mixed ligand complexes such as bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinolato) aluminum binuclear metal complexes, distyrylbiphenyl derivatives, etc. Of styryl compounds (JP-A-11-242996), triazole derivatives such as 3- (4-biphenylyl) -4-phenyl-5 (4-tert-butylphenyl) -1,2,4-triazole 7-41759) and phenanthroline derivatives such as bathocuproine (Japanese Patent Laid-Open No. 10-79297). It is. Further, a compound having at least one pyridine ring substituted at the 2,4,6-positions described in International Publication No. 2005/022962 is also preferable as the material of the hole blocking layer 6.
The method for forming the hole blocking layer 6 is not limited, and it may be formed by a wet film formation method similar to the method for forming the light emitting layer 5 described above, but it is usually preferable to use the following vacuum deposition method.

<< Formation of Hole Blocking Layer 6 by Vacuum Deposition >>>>
When the hole blocking layer 6 is formed by a vacuum deposition method, one or more of the above-described constituent materials of the hole blocking layer 6 are usually placed in a crucible installed in a vacuum vessel (two or more types). Are usually put in separate crucibles), the inside of the vacuum vessel is evacuated to about 10 ⁻⁴ Pa with a vacuum pump, and then the crucible is heated (when using two or more kinds of materials, Usually, each crucible is heated) and evaporated while controlling the evaporation amount of the material in the crucible (when two or more materials are used, evaporation is usually performed while independently controlling the evaporation amount). A hole blocking layer is formed on the light emitting layer 5 on the substrate placed face to face. When two or more kinds of materials are used, the hole blocking layer 6 can be formed by putting a mixture of them into a crucible, heating and evaporating the mixture.

The degree of vacuum at the time of vapor deposition is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 × 10 ⁻⁶ Torr (0.13 × 10 ⁻⁴ Pa) or more and 9.0 × 10 ⁻⁶ Torr ( 12.0 × 10 ⁻⁴ Pa) or less. The deposition rate is not limited as long as the effect of the present invention is not significantly impaired, but is usually 0.1 to 5.0 liters / second or more. The film forming temperature at the time of vapor deposition is not limited as long as the effects of the present invention are not significantly impaired, but it is preferably performed at 10 ° C. or higher and 50 ° C. or lower.
The thickness of the hole blocking layer 6 is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 0.3 nm or more, preferably 0.5 nm or more, and usually 100 nm or less, preferably 50 nm or less. is there.

<Electron transport layer 7>
For the purpose of further improving the current efficiency of the organic electroluminescence device, an electron transport layer 7 may be provided between the light emitting layer 5 and an electron injection layer 8 described later.
The electron transport layer 7 is formed of a compound that can efficiently transport electrons injected from the cathode 9 between electrodes to which an electric field is applied in the direction of the light emitting layer 5. As the electron transporting compound used for the electron transport layer 7, the electron injection efficiency from the cathode 9 or the electron injection layer 8 is high, and the injected electrons can be efficiently transported with high electron mobility. It must be a compound.

  The electron transporting compound used for the electron transporting layer 7 is generally preferably a compound that has high electron injection efficiency from the cathode 9 or the electron injection layer 8 and can efficiently transport injected electrons. Specific examples of the electron transporting compound include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadi Azole derivatives, distyrylbiphenyl derivatives, silole derivatives, 3-hydroxyflavone metal complexes, 5-hydroxyflavone metal complexes, benzoxazole metal complexes, benzothiazole metal complexes, trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline Compound (JP-A-6-207169), phenanthroline derivative (JP-A-5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinonediimine, n-type hydrogenated amorphous Silicon carbide, n-type zinc sulfide, n-type cell Such as emissions of zinc, and the like.

The thickness of the electron transport layer 7 is usually 1 nm or more, preferably 5 nm or more, and is usually 300 nm or less, preferably 100 nm or less.
The electron transport layer 7 is formed by laminating on the hole blocking layer by a wet film formation method or a vacuum deposition method in the same manner as described above. Usually, a vacuum deposition method is used.

<Electron injection layer 8>
An electron injection layer 8 may be provided between the electron transport layer 7 and the cathode 9 as a layer that plays a role of efficiently injecting electrons injected from the cathode 9 into the electron transport layer 7 or the light emitting layer 5.
In order to perform electron injection efficiently, the material for forming the electron injection layer 8 is preferably a metal having a low work function. Examples include alkali metals such as sodium and cesium, and alkaline earth metals such as barium and calcium. The film thickness is usually preferably from 0.1 nm to 5 nm.

Furthermore, an organic electron transport material represented by a metal complex such as a nitrogen-containing heterocyclic compound such as bathophenanthroline or an aluminum complex of 8-hydroxyquinoline is doped with an alkali metal such as sodium, potassium, cesium, lithium, or rubidium ( (As described in JP-A-10-270171, JP-A-2002-1000047, JP-A-2002-1000048, etc.) also improves electron injection / transport and makes it possible to achieve both excellent film quality. preferable.
The film thickness is usually in the range of 5 nm or more, preferably 10 nm or more, and usually 200 nm or less, preferably 100 nm or less.
The electron injection layer 8 is formed by laminating on the electron transport layer by a wet film formation method or a vacuum deposition method in the same manner as described above. Usually, a vacuum deposition method is used.

<Cathode 9>
The cathode 9 plays a role of injecting electrons into a layer on the light emitting layer side (such as the electron injection layer 8 or the light emitting layer 5). As the material of the cathode 9, the material used for the anode 2 can be used. However, in order to perform electron injection efficiently, it is preferable to use a metal having a low work function. , Metals such as indium, calcium, aluminum, silver, or alloys thereof are used. Specific examples include low work function alloy electrodes such as magnesium-silver alloy, magnesium-indium alloy, and aluminum-lithium alloy.

In terms of device stability, it is preferable to protect the cathode 9 made of a metal having a low work function by laminating a metal layer having a high work function and stable to the atmosphere on the cathode 9. Examples of the metal to be laminated include metals such as aluminum, silver, copper, nickel, chromium, gold, and platinum.
The thickness of the cathode is usually the same as that of the anode 2.

<Other layers>
The organic electroluminescent element of the present invention may further have other layers as long as the effects of the present invention are not significantly impaired. In other words, any other layer described above may be provided between the anode 2 and the cathode 9.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of a following example, unless the summary is exceeded.

(Preparation of composition for forming hole injection layer)
As a charge transporting material, 2.0 weight percent of a hole transporting polymer compound having a repeating structure of the following formula P1, and 4-isopropyl-4′-methyldiphenyliodonium tetrakis (pentafluorophenyl) as an electron accepting compound 0.4% by weight of borate is dissolved in butyl benzoate, isoamyl benzoate and toluene as organic solvents and heated in a vial on a 110 ° C. hot plate for 3 hours to form three types of hole injection layers A composition was prepared. The ink prepared with toluene was diluted four times by adding a toluene solvent again after cooling. A composition using butyl benzoate is a composition for forming a hole injection layer 1, a composition using isoamyl benzoate is a composition for forming a hole injection layer 2, and a composition using toluene is forming a hole injection layer. Composition 3 was obtained.

(Preparation of composition for forming hole transport layer)
As a charge transporting material, 1.5% by weight of a hole transporting polymer compound having a repeating structure of the following formula P2 is dissolved in butyl benzoate, isoamyl benzoate and phenylcyclohexane as organic solvents, respectively, and heated at 80 ° C. It heated for 30 minutes within the vial bottle on a plate, and prepared 3 types of compositions for hole transport layer formation. A composition using butyl benzoate is a composition for forming a hole transport layer 1, a composition using isoamyl benzoate is a composition for forming a hole transport layer 2, and a composition using phenylcyclohexane is a hole transport layer. Forming composition 3 was designated.

(Preparation of composition for forming light emitting layer)
A material having the structure of the following formula D1 as the light-emitting material and the following formulas H1 and H2 as the charge transporting material is weighed at a ratio of H1: H2: D1 = 37.5: 45.8: 16.7, and 5 as a whole. .94% by weight dissolved in butyl benzoate, isoamyl benzoate, and phenylcyclohexane, and heated in a vial on an 80 ° C. hot plate for 30 minutes to prepare three types of light emitting layer forming compositions. Prepared. A composition using butyl benzoate is a composition for forming a light-emitting layer 1, a composition using isoamyl benzoate is a composition for forming a light-emitting layer 2, and a composition using phenylcyclohexane is a composition for forming a light-emitting layer 3. did.

(Preparation of substrate 1 and anode 2)
An indium tin oxide (ITO) film having a thickness of 50 nm was formed on a glass substrate having a thickness of 0.7 mm by sputtering, and the anode was formed by patterning ITO in a stripe shape by an ordinary photolithography method. The finished pattern substrate was cut into 37.5 mm × 25.0 mm pieces, and the surface was rubbed with a wiper, then ultrasonically washed with an alkaline detergent, and then ultrasonically washed with pure water. The substrate after cleaning was subjected to hot air drying at 120 ° C. for 15 minutes after air droplets on the surface were blown off. The surface of the substrate on the ITO film side was further subjected to ultraviolet ozone cleaning treatment.

Example 1
An organic electroluminescent element having the structure shown in FIG. 1 was prepared according to the following procedure.
<Formation of hole injection layer 3>
On the substrate 1 on which the anode 2 is formed, the hole injection layer forming composition 1 is rotated by a spin coater at a spinner rotation speed of 500 rpm and a spinner rotation time of 2 seconds, and then a spinner rotation speed of 2350 rpm and a spinner rotation. The coating was performed by rotating for 30 seconds. The coating environment was in the atmosphere, and the environmental temperature was 26.4 to 26.6 ° C. The spin-coated coating film was vacuum-dried at a vacuum of 10 Pa or less for 2 minutes and then heated on a hot plate at 120 ° C. for 20 seconds to obtain a hole injection layer 3 of 30 to 34 nm. The hole injection layer 3 was further heated on a hot plate at 220 ° C. for 30 minutes to accelerate the P1 cross-linking reaction and thermoset.

<Formation of hole transport layer 4>
On the substrate 1 on which the hole injection layer 3 is formed, the hole transport layer forming composition 1 is rotated at a spinner rotation speed of 500 rpm and a spinner rotation time of 2 seconds by a spin coater (MS-A100 manufactured by MIKASA). Then, the spinner was rotated at 1750 rpm and the spinner rotation time was 50 seconds. The coating environment was in nitrogen and the environmental temperature was 34.4-35.2 ° C. The spin-coated coating film was vacuum-dried at a vacuum of 10 Pa or less for 1 minute and then heated on a hot plate at 120 ° C. for 20 seconds to obtain a 20 to 23 nm hole transport layer 4. The hole transport layer 4 was further heated on a hot plate at 230 ° C. for 30 minutes, thereby promoting the P2 crosslinking reaction and thermosetting.

<Formation of light emitting layer>
On the substrate 1 on which the hole transport layer 4 was formed, the composition 1 for light emitting layer formation was rotated at a spinner rotation speed of 500 rpm and a spinner rotation time of 2 seconds by a spin coater (MS-A100 manufactured by MIKASA). Thereafter, the coating was carried out by spinning at a spinner rotation speed of 1950 rpm and a spinner rotation time of 50 seconds. The coating environment was in nitrogen, and the environmental temperature was 35.5-35.9 ° C. The spin-coated coating film was vacuum-dried at a vacuum of 10 Pa or less for 1 minute, and then heated on a hot plate at 120 ° C. for 20 seconds to obtain a light-emitting layer 5 having a wavelength of 52 to 53 nm. The light emitting layer 5 was further heated on a hot plate at 120 ° C. for 20 minutes.

<Hole blocking layer 6>
A compound represented by the following structural formula (HB-1) was formed as a hole blocking layer 6 on the substrate 1 on which the light emitting layer 5 was formed, using a vacuum heating vapor deposition apparatus. The hole blocking layer 6 was formed with a film thickness of 10 nm, the film thickness of which was controlled by a crystal resonator.

<Electron transport layer 7>
A compound represented by the following structural formula (ET-1) was formed as the electron transport layer 7 on the substrate 1 on which the hole blocking layer 6 was formed, using a vacuum heating vapor deposition apparatus. The thickness of the electron transport layer 7 was controlled by a crystal resonator, and was formed to a thickness of 20 nm.

<Electron injection layer 8 and cathode 9>
Lithium fluoride was formed as the electron injection layer 8 on the substrate 1 on which the electron transport layer 7 was formed, using a vacuum heating vapor deposition apparatus. The thickness of the electron injection layer was controlled by a crystal resonator, and was formed to a thickness of 0.5 nm.
Next, aluminum was formed as a cathode 9 on the substrate 1 on which the electron injection layer 8 was formed, using a vacuum heating vapor deposition apparatus. The thickness of the cathode 9 was controlled by a crystal resonator, and was formed to a thickness of 80 nm. The electron injection layer 8 and the cathode 9 have a film formation area defined by a shadow mask, and are formed in a 2 mm wide region orthogonal to the 2 mm wide ITO pattern, thereby crossing the ITO pattern and the cathode pattern. An organic electroluminescent element 10 of 2 mm × 2 mm was formed in the section.

<Sealing>
Sealing was performed by the following method so that the organic electroluminescent device 10 obtained as described above was not deteriorated by oxygen, moisture, etc. in the atmosphere.
First, leaving a 2 mm wide portion of the outer periphery of a 23.0 mm × 23.0 mm × 1.1 mm glass plate, one side was cut out by general wet etching to prepare a sealing glass having a hollow structure. An ultraviolet curable resin was applied to the outer peripheral 2 mm width portion of the glass digging surface side, and a getter material that absorbs moisture was bonded to the central portion. The getter material is bonded to the sealing glass and the substrate 1 so as to face the organic electroluminescent element 10, and the ultraviolet curable resin portion on the outer periphery is cured by irradiating with ultraviolet rays, whereby the organic electroluminescent element 10 and Shielded from outside atmosphere.

(Example 2)
In Example 1, the organic electroluminescent element 10 was formed in the same manner as in Example 1 except that the hole transport layer 4 was formed by changing the spin coat conditions using the composition 2 for forming a hole transport layer. Produced. The spin coating conditions for the hole transport layer 4 were a spinner rotation speed of 500 rpm and a spinner rotation time of 2 seconds, and then a spinner rotation speed of 1750 rpm and a spinner rotation time of 60 seconds.

(Comparative Example 1)
In Example 1, the hole injection layer 3 is formed using the hole injection layer forming composition 2 while changing the spin coating conditions, and the hole transport layer 4 is formed using the hole transport layer forming composition 3. An organic electric field was formed in the same manner as in Example 1 except that the light emitting layer 5 was formed by changing the spin coating conditions using the light emitting layer forming composition 2. A light-emitting element 10 was manufactured. The spin coating conditions for the hole injection layer 3 were a spinner rotation speed of 500 rpm and a spinner rotation time of 2 seconds, and then a spinner rotation speed of 2200 rpm and a spinner rotation time of 30 seconds. The spin coating conditions for the hole transport layer 4 were a spinner rotation speed of 500 rpm and a spinner rotation time of 2 seconds, and then a spinner rotation speed of 1800 rpm and a spinner rotation time of 120 seconds. The spin coating conditions for the light-emitting layer 5 were a spinner rotation speed of 500 rpm and a spinner rotation time of 2 seconds, and then a spinner rotation speed of 1800 rpm and a spinner rotation time of 60 seconds.

(Comparative Example 2)
In Example 1, the hole injection layer 3 is formed using the hole injection layer forming composition 3 while changing the spin coating conditions, and the hole transport layer 4 is formed using the hole transport layer forming composition 3. In the same manner as in Example 1, except that the light-emitting layer 5 was formed by changing the spin-coat conditions using the composition 3 for forming a light-emitting layer. A light-emitting element 10 was manufactured. The spin coating conditions for the hole injection layer 3 were a spinner rotation speed of 500 rpm and a spinner rotation time of 2 seconds, and then a spinner rotation speed of 4000 rpm and a spinner rotation time of 30 seconds. The spin coating conditions for the hole transport layer 4 were a spinner rotation speed of 500 rpm and a spinner rotation time of 2 seconds, and then a spinner rotation speed of 1800 rpm and a spinner rotation time of 120 seconds. The spin coating conditions for the light-emitting layer 5 were a spinner rotation speed of 500 rpm and a spinner rotation time of 2 seconds, and then a spinner rotation speed of 2550 rpm and a spinner rotation time of 120 seconds.

(Evaluation results)
The obtained organic electroluminescent elements of Examples 1 and 2 and Comparative Examples 1 and 2 were all confirmed to be uniform and good light emission. With respect to these organic electroluminescent elements, a driving voltage for passing a current of 10 mA / cm ² was measured, and a relative driving voltage value obtained by subtracting the value of Example 1 was obtained. The results are shown in Table 1.

  Example 1 is butyl benzoate in which all the organic solvents contained in each of the three layers of the composition are benzoate esters, and Example 2 is that all the organic solvent contained in each of the three layers of the compositions is benzoic acid. The ester series is butyl benzoate or isoamyl benzoate. The boiling point of butyl benzoate is 249 ° C., and the boiling point of isoamyl benzoate is 261-262 ° C. (From Aldrich)

On the other hand, in Comparative Example 1, the organic solvent contained in the composition for forming a hole transport layer is phenylcyclohexane which is neither benzoate nor aromatic ether, and Comparative Example 2 further forms a hole injection layer. The organic solvent contained in the composition for use is toluene which is neither benzoic acid ester nor aromatic ether, and the organic solvent contained in the light emitting layer forming composition is either benzoic acid ester or aromatic ether. There is no phenylcyclohexane.
From the above results, it can be seen that according to the method for producing an organic electroluminescent element of the present invention, an organic electroluminescent element having a low driving voltage can be obtained.

The present invention, as a method for producing an organic electroluminescent element, takes advantage of the characteristics of various fields in which the organic electroluminescent element is used, for example, a flat panel display (for example, for OA computers and wall-mounted televisions) and a surface light emitter. It can be suitably used in the fields of a light source (for example, a light source of a copying machine, a backlight light source of a liquid crystal display or an instrument), a display panel, a marker lamp, and an illumination device.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Electron injection layer 9 Cathode 10 Organic electroluminescent device

Claims (6)

A method for producing an organic electroluminescent device having a hole injection layer, a hole transport layer and a light emitting layer adjacent to the anode in this order between at least the anode and the cathode,
The manufacturing method is as follows:
Forming the hole injection layer by wet-forming a composition for forming a hole injection layer;
Including a step of forming a hole transport layer by wet-forming a composition for forming a hole transport layer, and a step of forming a light-emitting layer by wet-forming a composition for forming a light-emitting layer,
The hole injection layer forming composition, the hole transport layer forming composition and the light emitting layer forming composition are each independently
An organic solvent,
Including one or more charge transporting materials or light emitting materials dissolved in the organic solvent,
95% by weight or more of the organic solvent contained in each of the composition for forming a hole injection layer, the composition for forming a hole transport layer, and the composition for forming a light emitting layer is a benzoate solvent, Or
95% by weight or more of the organic solvent contained in each of the composition for forming a hole injection layer, the composition for forming a hole transport layer, and the composition for forming a light emitting layer is an aromatic ether solvent. Features
Manufacturing method of organic electroluminescent element.   The method for producing an organic electroluminescent element according to claim 1, wherein all the organic solvents contained in the respective compositions are benzoate solvents.   The manufacturing method of the organic electroluminescent element of Claim 1 or 2 whose boiling point of all the said organic solvents contained in each said composition is 150 degreeC or more.   The manufacturing method of the organic electroluminescent element of any one of Claim 1 thru | or 3 in which the said composition for positive hole injection layer formation contains a high molecular compound as a charge transport material.   The manufacturing method of the organic electroluminescent element of any one of Claims 1 thru | or 4 in which the said composition for positive hole transport layer formation contains a high molecular compound as a charge transport material.   The method for producing an organic electroluminescent element according to claim 1, wherein all of the organic solvents contained in the respective compositions have the same composition.

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