JP2006134666A - Dispersion liquid, thin film and organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inorganic fine particle dispersion wherein inorganic fine particles such as titanium oxides are stably dispersed without causing aggregation, having low viscosity and excellent application suitability, and capable of forming a thin film having a high content of inorganic fine particles. <P>SOLUTION: In this dispersion formed by dispersing the inorganic fine particles in a dispersion medium with a dispersing agent, the dispersing agent is an organic material having arboroid branch structure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a dispersion obtained by dispersing inorganic fine particles with a specific dispersant, a thin film comprising the dispersion, and an organic electroluminescence (hereinafter abbreviated as “EL”) element.

  The organic EL element is configured by sandwiching an organic light emitting layer between a pair of counter electrodes, and electrons injected from one electrode and holes injected from the other electrode are recombined in the light emitting layer. Sometimes the light emitting layer emits light. Since such a device was found in 1963 to emit light when a DC voltage was applied to an anthracene single crystal by M. Pope, HP Kallmann, etc., research and development began in earnest. KODAK's TWTang et al. First announced an organic EL device using an organic thin-film stack structure.

  After that, based on this announcement model, research and development of organic EL elements aiming at improving functions from various aspects such as materials, layer configuration, layer configuration method, and elementization method have been promoted. A layer configuration of a general organic EL element is shown in FIG. Among these layers, titanium oxide has been proposed as a material for forming a hole transport layer that greatly affects light emission characteristics and color characteristics (Patent Document 1). The hole transport layer made of titanium oxide described in Patent Document 1 is formed by a sputtering method. Such a sputtering method has an advantage that a homogeneous and thin hole transport layer can be formed. However, there is a problem that an expensive apparatus is required for film formation and it is difficult to form a large-area film.

As a method for solving the above problems, titanium dioxide nanoparticles are prepared by a sol-gel method, and the particles are dispersed in a liquid medium containing polyvinyl alcohol (PVA) to obtain a dispersion liquid. A method for forming a hole transport layer made of titanium oxide has been proposed (Patent Document 2). According to such a coating method, although the above-mentioned problems are solved, in order to maintain the dispersion stability of the titanium dioxide fine particles in the dispersion, it is essential to use a large amount of a binder such as PVA. When a large amount of binder is used, the viscosity of the dispersion becomes extremely high, and not only the coating suitability is lost, but also the titanium dioxide concentration in the formed film is low, and the function as a hole transport layer is insufficient. . Further, when the ratio of the binder is decreased, the dispersion stability of the titanium dioxide fine particles is deteriorated, and the homogeneity and strength of the formed film are decreased.
JP-A-5-343183 JP-A-9-148071

  Accordingly, an object of the present invention is to form an inorganic film in which inorganic fine particles such as titanium oxide are stably dispersed without causing aggregation, have a low viscosity, have excellent coating suitability, and can form a thin film having a large content of inorganic fine particles. It is to provide a fine particle dispersion.

The above object is achieved by the present invention described below. That is, the present invention has the following configuration.
1. A dispersion obtained by dispersing inorganic fine particles in a dispersion medium with a dispersant, wherein the dispersant is an organic material having a dendritic structure.
2. 2. The dispersion according to 1 above, wherein the dispersant is a dendrimer or a dendron (hereinafter collectively referred to as “dendrimer”).
3. 2. The dispersion according to 1 above, wherein the dendrimer has a functional group that interacts with the surface of the conductive fine particle at the terminal.

4). 2. The dispersion liquid as described in 1 above, wherein the inorganic fine particles are metal fine particles or metal compound fine particles.
5. 2. The dispersion according to 1 above, wherein the inorganic fine particles are fine titanium oxide particles having a hole transporting property.
6). 2. The dispersion according to 1 above, wherein the 50% average particle size of the inorganic fine particles in the dispersion is 100 nm or less.
7). 7. Dispersion liquid of any one of said 1-6 whose mass ratio of an inorganic fine particle (A) and a dispersing agent (B) is A: B = 100: 50-5.

8). A thin film formed by applying the dispersion according to any one of 1 to 7 above to form a film.
9. An organic EL device having at least a pair of counter electrodes, a hole transport layer sandwiched between them, and an organic light emitting layer, wherein the hole transport layer is formed of the thin film described in 8 above. element.

  The organic material having a dendritic branch structure used as a dispersant for inorganic fine particles in the present invention is a compound called a dendrimer, which is a compound in which a large number of branch structures are developed around the core structure. Unlike conventional dispersants composed of linear polymers, the compound has a large steric hindrance effect, and is disposed between inorganic fine particles dispersed in a dispersion medium, so that it does not excessively increase the viscosity of the dispersion. The dispersion stability of the fine particles can be maintained for a long time.

  Further, although the dendrimer is a relatively high molecular weight material, it is a single molecular weight material, and its performance is hardly changed by the molecular weight distribution. Furthermore, these materials have high storage stability and high solubility in dispersion media such as water and organic solvents, and are suitable for dispersing inorganic fine particles in various dispersion media. Further, since these materials have a certain number of generations, they themselves have film-forming properties, and thus have a function as a dispersant and a function as a binder (film-forming material).

  Therefore, by using the above dendrimer or the like as a dispersant for inorganic fine particles such as titanium oxide, a dispersion having a low viscosity and good dispersion stability of the inorganic fine particles can be obtained. By using the dispersion, a thin film suitable as a hole transport layer of the organic EL device can be formed.

Next, the present invention will be described in more detail with reference to the best mode for carrying out the invention. The organic material having a dendritic branch structure used in the present invention is a dendritic macromolecule having a highly regulated structure, and is a nano-sized molecule having a substantially spherical shape. These dendrimers are known per se, and as PAMAM (polyanidoamine) dendrimers, for example, DAB-Am-4 (polypropyleneimine tetraamine dendrimer generation number 1)
DAB-Am-8 (polypropyleneimine octaamine dendrimer generation number 2)
DAB-Am-16 (polypropyleneimine hexadecaamine dendrimer generation number 3)
DAB-Am-32 (polypropyleneimine dotriacontamine dendrimer generation number 4)
DAB-Am-64 (polypropyleneimine tetrahexacontamine dendrimer generation number 5) is known. The basic structure of the AMAM dendrimer is as follows.

  Other dendrimers include cyclotriphosphazene-PMMH (phenoxymethyl (methylhydrazono)) dendrimers (generations 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3. 5, 4.0, 4.5, 5.0, 5.5, etc.), thiophosphoryl-PMMH dendrimers (generations 0.5, 1.0, 1.5, 2.0, 2.5, 3. 0, 3.5, 4.0, 4.5, 5.0, 5.5, etc.) are known. These dendrimers are also commercially available as solutions of various concentrations such as methanol.

  Any of the above-described dendrimers and other known dendrimers can be used in the present invention. However, if the number of generations is too low, the dispersibility and film forming performance with respect to inorganic fine particles are low, while if the number of generations is too high, water and organic Since the solubility with respect to a solvent falls and the viscosity of a solution becomes high, the generation number of the preferable dendrimer used by this invention is 3-4. In addition, when the dendrimer has a functional group that interacts with the surface of the conductive fine particles, such as an amino group, a hydroxyl group, or a carboxyl group, at the terminal, these groups interact with the inorganic fine particles to disperse the inorganic fine particles. This is preferable because the properties and dispersion stability are improved.

  The inorganic fine particles used in the present invention are metal fine particles such as gold, silver and copper, metal oxides such as titanium oxide, silicon oxide, tin oxide, zinc oxide, tungsten oxide, aluminum oxide and iron oxide, zinc selenide. And selenides and sulfides of metals such as cadmium selenide and cadmium sulfide. These inorganic fine particles can be produced by various methods, and those having various particle diameters are commercially available. The inorganic fine particles useful in the present invention have an average particle diameter of 30 to 70 nm. Particularly preferred inorganic fine particles are titanium oxide fine particles having excellent photocatalytic activity and hole transportability.

  The dispersion of the present invention can be obtained by dispersing the inorganic fine particles in a dispersion medium such as water or an organic solvent using the dendrimer as a dispersant / film-forming material. Dispersion media include alcohol solvents such as water, methyl alcohol, ethyl alcohol and propyl alcohol, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate, and aromatic solvents such as toluene and xylene. A solvent and those mixed solvents are mentioned.

  As a method of dispersing the inorganic fine particles in the dispersion medium using the dendrimer, any conventionally known method may be used. The amount of the dendrimer used for dispersion is preferably 50 to 5 parts by mass per 100 parts by mass of the inorganic fine particles. If the amount of dendrimer used is less than 5 parts by mass, the inorganic fine particles cannot be dispersed sufficiently and stably. On the other hand, when the amount of the dendrimer used exceeds 50 parts by mass, it is not economical and the amount of inorganic fine particles in the formed thin film is insufficient, and a desired function, for example, sufficient hole transportability cannot be exhibited. Moreover, it is preferable that the 50% average particle diameter of the inorganic fine particles in the dispersion is 100 nm or less. If the 50% average particle diameter of the inorganic fine particles exceeds 100 nm, it becomes difficult to form a thin film layer for a thin film electronic device such as an organic EL element, and necessary electrical properties such as conductivity cannot be secured. This is not preferable. In addition, you may use the conventionally well-known thermoplastic resin and thermosetting resin soluble in a dispersion medium in the said dispersion liquid in the range which does not prevent achievement of the objective of this invention. In addition to the dendrimer, a known dispersant can be used in combination.

  The thin film of this invention is obtained by apply | coating and drying the said dispersion liquid on the base-material surface. When the inorganic fine particles in the dispersion are metal fine particles, the dispersion is useful for forming a conductive layer, an electrode, a conductive pattern, and the like. When the inorganic fine particles have a hole transporting property, the organic EL element is used. When the inorganic fine particles are insulative, it is useful for forming an insulating layer for various electronic devices. Although the thickness of such a thin film changes with uses, when using as a positive hole transport layer of an organic EL element, it is preferable that it is a thickness of 50-80 nm, for example.

  The organic EL device of the present invention includes a pair of counter electrodes and at least a hole transport layer and a light emitting layer sandwiched between them, and the hole transport layer is formed of the thin film of the present invention. As long as it is formed, there is no restriction | limiting in particular about another structure, A well-known structure is employable.

  For example, a structure having a pair of electrodes on both sides of a light emitting layer made of the mixture of the dispersion of the present invention and a light emitting material, and an electron transport layer and / or anode containing an electron transport material between the cathode and the light emitting layer And the light-emitting layer are laminated with the thin film of the present invention as a hole transport layer. Further, the present invention includes a case where the light emitting layer and the hole transport layer are a single layer and a combination of a plurality of layers.

  Next, a typical method for producing the organic EL element of the present invention will be described. In order to obtain a planar light-emitting organic EL device, it is desirable that at least one of the electrodes is transparent or translucent and that light is extracted from the transparent or translucent electrode side. However, this does not apply to the case where light emission is extracted from the end face of the element.

  As the substrate of the organic EL element, a glass plate such as quartz or soda glass, a metal plate or a metal foil, a plastic such as an acrylic resin, a styrene resin, or a polycarbonate resin is used. When the light emission extraction direction of the organic EL element is the substrate side, it is desirable that the electrode provided on the substrate among the electrodes of the substrate and the organic EL element is transparent or translucent.

  For the electrode, a conductive metal oxide film, a metal thin film, or the like is used. Specifically, conductive metal oxides such as tin oxide, zinc oxide, indium oxide and indium tin oxide (ITO), metals such as gold, silver, chromium and nickel, organic conductive materials such as polyaniline, polythiophene and polypyrrole In addition, a mixture or a laminate of these may be used. In particular, ITO can be preferably used as the anode from the viewpoint of high conductivity and transparency.

  Next, a hole transport layer comprising the thin film of the present invention is formed on the electrode, and a light emitting layer is formed on the hole transport layer. Examples of the light-emitting material include organometallic complexes such as aluminum quinoline complexes, derivatives thereof, π-conjugated polymer materials typified by polyparaphenylene vinylene naphthalene derivatives, anthracene or derivatives thereof, perylene or derivatives thereof, polymethines, Examples thereof include xanthene-based, coumarin-based and cyanine-based pigments, aromatic amines, tetraphenylcyclopentadiene or derivatives thereof, and tetraphenylbutadiene or derivatives thereof.

  In the present invention, it is particularly preferable to use a phosphorescent iridium compound as the light emitting material. Examples of phosphorescent iridium compounds useful in the present invention include iridium, phenylpyridine, phenylpyrimidine, bipyridyl, 1-phenylpyrazole, 2-phenylquinoline, 2-phenylbenzothiazole, 2-phenyl-2-oxazoline, 2,4-diphenyl-1,3,4-oxadiazole, 5-phenyl-2- (4-pyridyl) -1,3-oxadiazole, 2- (2-pyridyl-thiophene) -2-phenyl- And a complex compound with a nitrogen atom-containing aromatic compound such as 4H-3,1-benzoxazine-4 or a derivative thereof.

  As the method for forming the hole transport layer and the light emitting layer, a spin coating method, a cast coating method, a dip coating using the dispersion liquid of the present invention, a molten liquid, a solution, a dispersion liquid, or a mixed liquid of the above-described materials. It is particularly preferable to form a film by a coating method such as a method, a die coating method, a bead coating method, a bar coating method, a roll coating method, a spray coating method, a gravure coating method, a flexographic printing method, a screen printing method, or an offset printing method.

  The preferable thickness of the hole transport layer is 50 to 80 nm as described above. If the thickness of the hole transport layer is less than 50 nm, the probability of occurrence of shorts from defects and defects increases, and as a result, the stability of the organic EL element characteristics is improved. However, there is a problem in that the reliability cannot be obtained. On the other hand, when the thickness of the hole transport layer exceeds 80 nm, there is a problem in that the electric resistance value is increased and the current luminous efficiency of the organic EL element is lowered. The thickness of the light emitting layer is 1 nm to 1 μm, preferably 2 nm to 500 nm, and more preferably 5 nm to 100 nm. In addition, when forming a positive hole transport layer and a light emitting layer by the apply | coating method, in order to remove a solvent, Preferably it is 30-300 degreeC under reduced pressure or inert atmosphere, Preferably it is 60-200 degreeC. It is desirable to heat and dry at a temperature. In addition, when laminating the light emitting layer and another charge transporting material, a hole transporting layer is formed on the anode before the light emitting layer is provided by the above film forming method, or electron transport is performed after the light emitting layer is provided. It is desirable to form a layer.

  The method for forming the charge transport layer is not particularly limited, but a vacuum deposition method from a solid state, or a spin coating method from a molten state, a solution state, a dispersion state, a mixed liquid state, a cast coating method, a dip coating method, A die coating method, a bead coating method, a bar coating method, a roll coating method, a spray coating method, a gravure coating method, a flexographic printing method, a screen printing method, and an offset printing method can be used. The thickness of the charge transport layer is 1 nm to 1 μm, preferably 2 nm to 500 nm, more preferably 5 nm to 100 nm.

  Next, an electrode is provided on the light emitting layer or the charge transport layer. This electrode becomes the cathode. The cathode preferably has a work function of less than 4 eV so that electrons can be easily injected. Alkali metals (eg, lithium, sodium, cesium, etc.) and halides thereof (eg, lithium fluoride, cesium fluoride, lithium chloride) , Cesium chloride, etc.), alkaline earth metals (calcium, magnesium, etc.) and their halides (calcium fluoride, magnesium fluoride, etc.), metals such as aluminum and silver, conductive metal oxides and alloys or mixtures thereof. Is mentioned.

  As a method for producing the cathode, a vacuum deposition method, a sputtering method, a laminating method for press-bonding a metal thin film, or the like is used. A protective layer for protecting the organic EL element may be mounted after the cathode is produced. In order to use this organic EL element stably for a long period of time, it is desirable to attach a protective layer or a protective cover in order to protect the element from the outside. As the protective layer, a polymer compound, metal oxide, metal fluoride, metal boride, silicon oxide, silicon nitride, or the like can be used. Further, as the protective cover, a glass plate, a plastic plate having a low water permeability treatment on the surface, or the like can be used, and a method of sealing the cover by bonding it to the element substrate with a thermosetting resin or a photocurable resin is preferable. Used for.

  FIG. 1 shows an example of a cross-sectional view of the organic EL device of the present invention. For example, an electron injection layer containing an electron transporting compound is provided between the light emitting layer and the cathode as shown in FIG. 1A, or the light emitting layer and the hole transport layer are used as shown in FIG. Or a hole injection layer containing a hole-transporting compound (not shown) is provided between the light-emitting layer and the anode, and further, as shown in FIG. Or an electron injection layer containing an electron transporting compound (not shown) adjacent to the light emitting layer and the cathode, or a hole transporting compound adjacent to the light emitting layer and the anode. By providing the hole injection layer containing, it becomes possible to easily inject electrons or holes or both electrons and holes into the organic EL element.

  In order to obtain a planar element using the organic EL element of the present invention, the planar anode and cathode may be arranged so as to overlap each other. Further, in order to obtain pattern-like light emission, a method of installing a mask provided with a pattern-like window on the surface of the planar light-emitting element, substantially forming an organic layer of a non-light-emitting part extremely thick Examples thereof include a non-light emitting method and a method of forming either one of the anode or the cathode or both electrodes in a pattern.

  By doing as described above, a highly efficient organic EL element can be easily obtained as compared with the case of using a conventional CBP. In addition, since the organic EL element according to the present invention can be manufactured by coating film formation, it can be an element having a large display area. The organic EL device according to the present invention thus manufactured is thermocompression-bonded with a module obtained through the module process and an anisotropic conductive film (ACF), etc., so that the organic EL device according to the present invention is obtained. can get.

  Further, in order to obtain a dot matrix element, there are a method in which both the anode and the cathode are formed in a stripe shape and arranged so as to be orthogonal, and a method in which one electrode can be selectively driven by a TFT. Further, by arranging a plurality of organic EL elements having different emission colors on the same surface, partial color display, multi-color display, and full-color display are possible.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

[Example 1; Dispersion]
(Preparation of dendrimer dispersion (1))
Completely 0.16 g of amino group-terminated dendrimer material (DAB-Am-32 made by Sigma-Aldrich) in a mixed solvent of Kanto Chemical Co., Ltd. special grade methyl alcohol 80 g, the company special grade 2-propyl alcohol 40 g, and pure water 40 g Dissolved. This dispersant solution and 1.6 g of titanium oxide fine particles having high photocatalytic activity (ST-01, manufactured by Ishihara Sangyo Co., Ltd.) are mixed, 0.3 mm zirconia beads are added as a dispersion medium, and then shaken for 3 hours with a paint shaker. Finally dispersed. After shaking dispersion, the dispersion medium was removed with a mesh filter to obtain a titanium oxide dispersion (1).

(Preparation of dendrimer dispersion (2); Evaluation of dispersion aid effect)
The dispersion in the dispersion (1) was changed from 0.16 g of dendrimer to 0.06 g of the same dendrimer and 0.1 g of Disperbyk-180 manufactured by Byk Chemie. It was set as the liquid (2).

(Preparation of dendrimer dispersion (3); addition amount inhibition evaluation)
The amount of the dispersant in the dispersion (1) was changed from 0.16 g of dendrimer to 0.13 g of the dendrimer, and a titanium oxide dispersion (3) was obtained by the same procedure.

[Comparative Example 1; Dispersion]
(Preparation of dispersion using dispersant)
The dispersant in the dispersion liquid (1) was changed from dendrimer to Disperbyk-180 manufactured by Byk Chemie, and a titanium oxide dispersion liquid was obtained by the same procedure.

[Dispersion viscosity and particle size measurement results]

From the results shown in Table 1 above, no. 1 and No. Comparison of 4 shows that by using a dendrimer material as a dispersant, the initial viscosity of the dispersion and the particle size of the inorganic fine particles can be kept small, and the stability of the dispersion over time can be secured.
No. 1 and No. Compared with 2 and 3, the dendrimer material can be used in combination with a general dispersing agent (as a dispersion aid) to further improve the dispersion performance, and the amount added to the object to be dispersed is also suppressed in fine particles. It can be seen that it is possible.
Although the dendrimer material depends on its skeletal structure, the molecular weight is preferably in the range of Mw = 5,000 to 15,000. For the dendrimer, the fourth generation product (Mw = 11,450) within the range is used. (If the molecular weight is below the above range, there is a problem with thermal stability, and if it exceeds, the solubility is problematic.)

[Example 2; coating film]
(Dendrimer coating film formation (1))
After stirring and mixing 1 g of amino group-terminated dendrimer material (Sigma Aldrich DAB-Am-32) to 20 g of dispersion (1) (immediately after dispersion), dust was removed by a 0.5 μm mesh disk filter and washed. It apply | coated by spin coating on the already alkali-free glass. After leaving still at room temperature for 30 minutes, it was made to heat-dry on a 150 degreeC hotplate for 30 minutes, and the titanium oxide coating film | membrane with a film thickness of about 80 nm was obtained.

[Comparative Example 2; coating film]
(General inorganic binder coating film formation)
After stirring and mixing 2 g of organoalkoxysilane (TSL8113 manufactured by Toshiba Silicone Co., Ltd.), an inorganic binder monomer, with 20 g of the comparative dispersion (immediately after dispersion), dust was removed with a 0.5 μm mesh disk filter and washed. On the non-alkali glass, it was applied by spin coating. By the same drying method as the coating film (1), the inorganic binder was hydrolyzed and polymerized to obtain a titanium oxide coating film. The amount of monomer was set to the minimum amount necessary to form a uniform coating film.

[Surface smoothness of coating film and titanium oxide concentration]

The measurement conditions of the atomic force microscope (AFM) are as follows.
Measuring device: Nano Scope IIIa Dimension300 manufactured by Digital Instruments
Measurement conditions: Measurement mode Tapping Mode
Scanning range: 30μm
Scanning speed: 0.3Hz

  According to the present example, it was found that a film equivalent to or higher than a low-concentration product can be formed from the viewpoint of atomization of particles in the film, although the solid content of the titanium oxide particles is large. In the future, by further optimizing the dendrimer structure, further improvement of solid content and formation of fine particles in the film can be expected.

[Example 3; Preparation and evaluation of organic EL element]
After the glass substrate on which the ITO transparent conductive film was formed was subjected to cleaning and UV / ozone treatment, a titanium oxide coating film having a film thickness of 80 nm was formed according to the methods of Example 1 and Example 2, and holes were formed. It was set as the transport layer. Subsequently, a red light emitting layer ink (ADS100TS manufactured by American Dye Source) was dropped onto the hole transport layer, spin-coated, and heated and dried on a hot plate at 100 ° C., thereby emitting red light with a thickness of 80 nm. A layer was formed. Subsequently, a calcium thin film having a thickness of 10 nm was vacuum-deposited at a deposition rate of 0.2 nm / s, and a silver thin film having a thickness of 100 nm was further vacuum-deposited thereon at a deposition rate of 2 nm / s to form an electrode. An organic EL device was obtained.
When the ITO electrode of the obtained organic EL element was connected to the positive electrode of the variable DC power source, the silver electrode was connected to the negative electrode, and a DC voltage was applied, a good red color with a maximum luminous efficiency of 0.4 cd / A was obtained from the light emitting layer. Luminescence was confirmed.

  According to the present invention, the organic material having a dendritic structure used as a dispersant for inorganic fine particles in the present invention is a compound called a dendrimer, which is a compound in which a large number of branch structures are developed around the core structure. is there. Unlike conventional dispersants composed of linear polymers, the compound has a large steric hindrance effect, and is disposed between inorganic fine particles dispersed in a dispersion medium, so that it does not excessively increase the viscosity of the dispersion. The dispersion stability of the fine particles can be maintained for a long time.

The figure which shows the structural example of an organic EL element.

Claims (9)

  A dispersion obtained by dispersing inorganic fine particles in a dispersion medium with a dispersant, wherein the dispersant is an organic material having a dendritic structure.   The dispersion liquid according to claim 1, wherein the dispersant is a dendrimer or a dendron.   The dispersion according to claim 1, wherein the dendrimer or dendron has a functional group that interacts with the surface of the conductive fine particle at the terminal.   The dispersion according to claim 1, wherein the inorganic fine particles are metal fine particles or metal compound fine particles.   The dispersion according to claim 1, wherein the inorganic fine particles are fine titanium oxide particles having a hole transport property.   The dispersion according to claim 1, wherein the 50% average particle size of the inorganic fine particles in the dispersion is 100 nm or less.   The dispersion according to any one of claims 1 to 6, wherein the mass ratio of the inorganic fine particles (A) to the dispersant (B) is A: B = 100: 50-5.   A thin film formed by applying the dispersion according to any one of claims 1 to 7 to form a film.   An organic electroluminescence device having at least a pair of counter electrodes, a hole transport layer sandwiched between them and an organic light emitting layer, wherein the hole transport layer is made of the thin film according to claim 8. Electroluminescence element.

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