JP5946054B2 - Method for producing alumina self-supporting thin film containing luminescent transition metal - Google Patents

Description

  The present invention relates to an alumina self-supporting thin film containing a luminescent transition metal compound and a method for producing the same.

  Electroluminescence (EL) is a phenomenon that emits light when a voltage is applied to a fluorescent element. Since it has the feature of low power and simple structure compared to a cathode ray tube or liquid crystal, next-generation displays that use this phenomenon are attracting attention. Has been. Furthermore, since electroluminescence emits light by itself and does not require a backlight, a very thin and flexible display structure is possible, and its viewing angle is wide. EL light-emitting elements are classified into organic EL elements and inorganic EL elements, and organic EL elements have been developed in the display field, but inorganic EL elements are less susceptible to oxygen and water than organic EL elements. It has the advantage that it is used for device displays and LCD backlights.

  A typical configuration of an inorganic EL light-emitting device is formed by arranging a phosphor layer and a ferroelectric layer between a back electrode and a transparent electrode, and is classified into a dispersion type and a thin film type according to its structural form. . The dispersion type has a structure in which fluorescent powder and ferroelectric powder are each dispersed in an organic binder, and this is laminated between a transparent electrode and a back electrode, and the thin film type has the electrode disposed thereon. It has a structure in which a light emitting layer made of a phosphor and a dielectric layer are laminated on a substrate by vapor deposition or the like.

  Patent Document 1 (Japanese Patent Laid-Open No. 11-293239) relates to a dispersion-type EL device, and controls the particle size of phosphor particles to use spherical phosphor particles having a narrow particle size distribution, thereby providing a highly filled phosphor film. Is described. This dispersion-type EL element manufacturing method is a method in which phosphor powder and ferroelectric powder are heat-treated in advance, and are adhered onto a film body using an organic binder, which is an efficient method in terms of productivity. However, since it is not preferable that a large amount of fine particles and coarse particles are present in the phosphor and ferroelectric powder to be used, a classification operation is required as necessary. For this reason, there are problems such as an increase in work steps and a decrease in yield.

  In addition, since the phosphor and ferroelectric powder itself used in the above method do not have a film-forming property, it is necessary to use an organic binder for the molding. If the filling rate of the amount of particles is increased, the coatability deteriorates and a uniform light emitting film cannot be obtained, and the filling rate of the phosphor particles is limited, so that sufficient luminance cannot be obtained.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2008-251336) describes a thin-film inorganic EL element and a method for manufacturing the same. In this manufacturing method, when a sputtering method or a vapor deposition method is used for forming a light emitting layer, it is necessary to smooth the ferroelectric layer, and this method is not suitable for film formation on a large screen.

  Patent Document 3 (Japanese Patent Laid-Open No. 2008-251313) discloses an inorganic EL element and a method for manufacturing the same, and the inorganic EL element has a back electrode, an insulating layer, a light emitting layer, and a transparent electrode arranged in order. The insulating layer is made of a dielectric material such as barium titanate, barium zirconate titanate, lead zirconate titanate, and the like, and is formed by a sol-gel method and does not contain an organic binder. For example, it includes a second insulating layer (buffer layer) made of alumina. In order to form the second insulating layer by the sol-gel method, it is necessary to perform baking at a temperature of 400 ° C. or higher in order to form a light-emitting layer (phosphor film) on the substrate after coating the sol-gel solution on the substrate. Therefore, the substrate must be able to withstand the firing temperature. Further, if Na is contained in the substrate, Na diffuses into the electrode, the insulating layer, and the light emitting layer during high-temperature firing and contaminates them, causing problems such as a decrease in light emission luminance. When the baking temperature is 1000 ° C. or higher, a substrate having a high softening point such as an alumina plate, a zirconia plate silicon wafer, or quartz glass is required as the substrate. There is a problem of inviting a rise. In addition, the electrode film made of ITO conductive oxide used in this EL element has low thermal stability, and there is a problem that the conductivity is lowered at a temperature of 600 ° C. or higher.

In the conventional dispersion-type inorganic EL element as described above, it is necessary to adjust the particle size of the raw material particles of these films to a predetermined value when preparing the phosphor film and the ferroelectric film. There is a reduction in working efficiency and yield, and furthermore, the use of an organic binder is indispensable because none of the particles has a film-forming property, but the emission point density of an EL device obtained by including an organic binder A number of problems are known, such as causing a decrease in
In addition, the thin film method for manufacturing the inorganic EL element is not suitable for a large-scale industrial manufacturing method, and the sol-gel method has restrictions on the materials and characteristics of the substrate and the electrode, and the preparation conditions of the phosphor and the insulator are limited. There are problems such as severe restrictions, and it has been strongly desired to provide a novel inorganic EL element free from these problems and a method for manufacturing the same.

JP-A-11-293239 JP 2008-251336 A JP 2008-251313

  The present invention intends to provide a luminescent transition metal-containing alumina self-supporting film material having sufficient strength to be used independently without containing an organic binder and having a high-density surface emission, and a method for producing the same. To do.

  In such a situation, the present inventors, in view of the above-mentioned prior art, are the result of intensive studies with the goal of developing a phosphor layer having a surface emission at a high density without using an organic binder. By using a mixed solution of alumina nanofibers having a specific property and structure and a transition metal element that forms a luminescent center, it is molded by a specific manufacturing method and manufacturing conditions, so that it can be used independently without using an organic binder. A self-supporting film material that is sufficiently strong to satisfy the above requirements, is used as an inorganic EL light-emitting element with light-emitting points densely and uniformly filled, and has surface emission, without being restricted by the type of substrate or film formation method Based on this finding, the present inventors have completed the present invention.

The luminescent transition metal-containing alumina self-supporting thin film of the present invention contains at least one luminescent transition metal compound as a light emitting source component and alumina as a self-supporting thin film forming component,
The luminescent transition metal compound is selected from a luminescent transition metal ion-containing compound and a luminescent transition metal oxide,
The alumina is produced by a sol-gel method, has a fiber-like shape having a number average aspect ratio of 30 to 5000, and has a fiber-like nanoparticle shape dimension at least in the nanometer order with a fiber width of 10 nm or less. And
The molar ratio of the transition metal contained in the light emitting source component to the aluminum contained in the self-supporting film forming component is in the range of 1: 0.001 to 1: 1,
The light emitting source component is supported by the fiber-like alumina nanoparticles forming the self-supporting thin film.
In the luminescent transition metal-containing alumina self-supporting thin film of the present invention, the short diameter of the fiber-like nanoparticles of the self-supporting thin film-forming alumina is preferably 2 to 10 nm, and the long diameter is preferably 100 to 10,000 nm.
In the luminescent transition metal-containing alumina self-supporting thin film of the present invention, the transition metal contained in the light-emitting source component is preferably selected from titanium, europium, terbium, cerium, dysprosium, ytterbium, samarium, zinc and chromium.
In the luminescent transition metal-containing alumina self-supporting thin film of the present invention, the alumina constituting the self-supporting thin film forming component is at least one of γ-alumina, δ-alumina, θ-alumina, κ-alumina, and χ-alumina. Is preferred.
The manufacturing method of the luminescent transition metal containing alumina self-supporting thin film of this invention is a fiber shape which has a breadth of 10 nm or less and an aspect ratio in the range of 30-5000 by a sol-gel method from a hydrolyzable aluminum compound. Prepare an aqueous sol of alumina precursor nanoparticles,
An aqueous solution or dispersion of at least one luminescent transition metal compound is mixed in the aqueous sol containing fibrous alumina nanoparticles, and at this time, the luminescent transition metal contained in the aqueous solution or dispersion is mixed. Adjusting the molar ratio of the total amount to the aluminum content contained in the aqueous sol within the range of 1: to 0.001 to 1: 1;
Apply the resulting mixed dispersion on the inner surface of the molding container, dry it, and mold it into a thin film.
The obtained thin film-like molded product is fired to change the fiber-like alumina precursor nanoparticles into fiber-like alumina nanoparticles.
In the production method of the present invention, the aqueous sol of the fibrous alumina precursor nanoparticles is produced by hydrolyzing the hydrolyzable aluminum compound in water and heating and peptizing the alumina precursor. The body is preferably an aluminum hydroxide amorphous, boehmite, or pseudoboehmite structure.
In the production method of the present invention, it is preferable that the thin-film molded product is fired at a temperature of 400 to 1300 ° C.
In the manufacturing method of this invention, it is preferable that the said baking temperature exists in the range of 600-1000 degreeC.

  The alumina self-supporting thin film containing the light-emitting transition metal of the present invention has an intensity capable of being used independently, and has a light-emitting point uniformly distributed with high density, even though it does not contain an organic binder. It has surface light emission and is useful as an inorganic EL device, and the method of the present invention can efficiently produce the light-emitting transition metal-containing alumina self-supporting thin film by an easy and simple method.

FIG. 4 is a transition electron micrograph image of an example of an aqueous sol containing fibrous alumina precursor nanoparticles used as a self-supporting film material forming component in the production of the light-emitting transition metal-containing alumina self-supporting thin film of the present invention described in Example 1. , The emission spectrum of the terbium nitrate-containing alumina free-standing thin film of the present invention produced in Example 1 by applying an alternating voltage with a sine wave of 1 kHz is shown. The emission spectrum by the alternating voltage application of the sinusoidal wave 1kHz of the europium nitrate containing alumina self-supporting thin film of this invention manufactured in Example 3 is shown.

  The luminescent transition metal-containing alumina self-supporting thin film of the present invention contains at least one luminescent transition metal compound as a light-emitting source component and alumina as a self-supporting thin-film forming component.

The luminescent transition metal compound used as the luminescent source component is selected from a luminescent transition metal ion-containing compound and a transition metal oxide. The luminescent transition metal is selected from Group 3-12 elements (including tantanoids and actinoids) of the periodic table, and preferably titanium (Ti), europium (Eu), terbium (Tb), cerium. (Ce), dysprosium (Dy), ytterbium (Yb), samarium (Sm), zinc (Zn), chromium (Cr), and the like.
The luminescent transition metal ion-containing compound is preferably selected from sulfates, nitrates, chlorides and organic carboxylic acid salts (preferably acetates) of the luminescent transition metals, more preferably water-soluble nitrates, Selected from chlorides and acetates.

  The luminescent transition metal oxide is preferably fine particles having an average particle diameter of 1 μm or less, preferably 100 nm or less, when it is water-insoluble.

The alumina constituting the self-supporting thin film forming component is a fiber-like particle produced by a sol-gel method, and at least the fiber width is a fiber-like nanoparticle having a nanometer order of 10 nm or less.
In the present invention, the “fiber shape” includes a shape expressed as a wire shape, a needle shape, a rod shape or a column shape.

  The fiber-like alumina nanoparticles have an aspect ratio of 30 to 5000, preferably 100 to 3000. When the aspect ratio is less than 30, the resulting alumina self-supporting thin film has insufficient mechanical strength, and it takes a lot of time to produce alumina nanoparticles having the aspect ratio exceeding 5000. This is disadvantageous in practice because of the high cost.

  The fiber-like alumina nanoparticles have an average fiber width of 10 nm or less as described above, and the average fiber width is preferably 2 to 10 nm, particularly preferably 3 to 7 nm. When the average fiber width exceeds 10 nm, it becomes difficult to form a self-supporting thin film having high flexibility due to aggregation of fibrous alumina nanoparticles. In addition, the industrial yield of fiber-like alumina particles having an average fiber width of less than 2 nm may be insufficient. The average fiber length of the fibrous alumina nanoparticles is preferably 100 to 10,000 nm, and more preferably 200 to 6,000 nm. If the average fiber length is less than 100 nm, the resulting self-supporting thin film may have insufficient mechanical strength. If the average fiber length exceeds 10,000 nm, it takes a long time to synthesize. There may be a disadvantage of high costs.

  The average fiber width of the fiber-like alumina nanoparticles was observed at a magnification of 710,000 times using a transmission electron microscope (TEM, for example, trade name “FEI-TECNAI-G20”, manufactured by FEI). The thickest part of the fiber-like alumina nanoparticles in the observation visual field is measured as “the width of the fiber-like alumina nanoparticles”. The number of measurements is 300, a number distribution is created, and the number average value is defined as the average fiber width. On the other hand, the average fiber length of the fiber-like alumina nanoparticles is determined by using a scanning electron microscope (SEM, for example, trade name “S-4800”, manufactured by Hitachi High-Technologies Corporation) at a magnification of 2500 times. When observed, the axial length is measured as “fiber length of fibrous alumina nanoparticles”. The number of measurements is 300, and the value calculated from the volume average is the average fiber length. The aspect ratio (average fiber length / average fiber width) of the alumina nanofibers is calculated by dividing the average fiber length thus calculated by the average fiber width.

  In the luminescent transition metal-containing alumina self-supporting thin film of the present invention, the molar ratio of at least one luminescent transition metal contained in the light-emitting source component to aluminum contained in the self-supporting thin-film forming component is 1: 0.001-1. Is in the range of 1: 1, preferably in the range of 1: 0.01 to 1: 0.5. When the molar ratio is less than 1: 0.001, the light emitting luminance (Luminance) in the resulting luminescent transition metal-containing alumina free-standing thin film may be insufficient, and when the molar ratio exceeds 1: 1. In contrast to the increase in the content of the light-emitting transition metal compound, the increase in the emission luminance is saturated, the production cost may be excessive, and the emission luminance may decrease.

In the luminescent transition metal-containing alumina self-supporting thin film of the present invention, the fiber-like alumina nanoparticles forming the self-supporting thin film are distributed substantially parallel to the plane or curved surface of the required shape, and the fiber-like alumina nanoparticles adjacent to each other. A self-supporting thin film having a required shape and size is formed by crossing at random or entangled, and the luminescent transition metal compound is supported by fiber-like alumina nanoparticles forming the self-supporting thin film. . The luminescent transition metal compound supported by the fiber-like alumina nanoparticles may be adsorbed in the form of fine particles, or the luminescent metal atoms are bonded to the skeleton structure of the fiber-like alumina. Also good. For example, when terbium nitrate (Tb (NO ₃ ) ₃ ) is used as the luminescent transition metal ion-containing compound, this compound dissolves in the aqueous sol containing fiber-like alumina nanoparticles, and is deposited on the surface of the fiber-like alumina nanoparticles. Adsorb in a uniformly dispersed state. The Tb ³⁺ ions adsorbed at this time form a state in which six water molecules and three nitrate ions are coordinated around it. When the terbium nitrate-supported fibrous alumina nanoparticles in this state are fired, it is recognized that they bind to the alumina skeleton structure in the form of -Al-O-Tb-O-. In this case, it has been confirmed by wide area X-ray absorption fine structure spectroscopy (EXAFS) that Tb ₂ O ₃ is not formed.

  The film thickness of the luminescent transition metal-containing alumina thin film of the present invention is preferably 0.1 to 500 μm, and more preferably 0.5 to 200 μm. When the film thickness is less than 0.1 μm, the mechanical strength of the obtained self-supporting thin film is insufficient, and handling properties when coating the electrode such as ITO on the self-supporting thin film may be insufficient. In addition, if it exceeds 500 μm, there may be a disadvantage that a required driving voltage for light emission becomes high.

  The fibrous alumina nanoparticles constituting the self-supporting thin film forming component have at least one crystal system of γ-alumina, δ-alumina, θ-alumina, κ-alumina and χ-alumina, preferably γ, θ, δ. -Crystalline system. These crystal systems finally transition to α-alumina.

The self-supporting thin film forming component formed by the fibrous alumina nanoparticles preferably has a high purity. For example, sodium ion (Na ⁺ ), potassium ion (K ⁺ ), chlorine ion (Cl ⁻ ), and sulfate ion ( The allowable content of impurities such as SO ₄ ²⁻ ) is 2 ppm or less, respectively. The content of impurities in the self-supporting thin film forming component is usually affected by the purity of the alumina raw material, the type and purity of the chemical used in each treatment, and the high-purity self-supporting thin film forming component can be selected by appropriately selecting these. Can be manufactured. Here, the content of sodium ion (Na ⁺ ), potassium ion (K ⁺ ) and sulfate ion (SO ₄ ²⁻ ) is about 2.0 g of a self-supporting thin film forming component, and is thermally decomposed with a small amount of hydrochloric acid. A measurement sample solution, which was adjusted to exactly 10 mL by adding purified water later, was measured using an atomic absorption photometer (for example, trade name “Z5300”, manufactured by Hitachi, Ltd.) under the condition of a wavelength of 589.0 nm. Can be determined. On the other hand, the content of chlorine ions (Cl ⁻ ) can be measured by ion chromatography using a measurement sample solution prepared by accurately weighing about 1.0 g of a self-supporting thin film forming component and adjusting it to 10 mL with purified water. Ion chromatography uses, for example, an ion chromatograph manufactured by Tosoh (column “TSKgel IC-Anion-PW 4.6 × 50”), temperature: 40 ° C., eluent: TSK eluent IC- It is performed under the conditions of Anion-A, flow rate: 1.5 mL / min, sample size: 50 μL, detector: CM.

The method for producing a luminescent transition metal-containing alumina self-supporting thin film according to the present invention includes the following steps (1) to (4).
(1) An aqueous sol of nano-particles of fibrous alumina precursor is prepared from a hydrolyzable aluminum compound by a sol-gel method. The fiber-like alumina precursor nanoparticles have a fiber width of 10 nm or less, and an aspect ratio of 30 to 5000, preferably 100 to 3000.
(2) An aqueous solution or an aqueous dispersion of at least one luminescent transition metal compound is mixed in the aqueous sol containing fibrous alumina precursor nanoparticles. At this time, the molar ratio of the content of the luminescent transition metal atom contained in the aqueous solution or dispersion to the content of aluminum atom in the aqueous sol is within the range of 1: 0.001 to 1: 1. Adjust to.
(3) The obtained mixed solution is applied to the inner surface of the molding container, dried and molded into a thin film.
(4) The obtained thin film-like molded product is fired to change the fiber-like alumina precursor nanoparticles into fiber-like alumina nanoparticles.

  In the step (1) of the method of the present invention, an aqueous sol of fibrous alumina precursor nanoparticles is obtained by a method (sol preparation method) in which a hydrolyzable aluminum compound is hydrolyzed in water and heated and peptized. The alumina precursor is an aluminum hydroxide amorphous, gibbsite, vialite, diaspore, boehmite, or pseudoboehmite structure.

The hydrolyzable aluminum compound used in the method of the present invention can be selected from hydrolyzable organic and inorganic aluminum compounds. Examples of hydrolyzable inorganic compounds include inorganic acid salts such as aluminum chloride, aluminum sulfate, and aluminum nitrate, and aluminum. Examples thereof include aluminates such as sodium acid, aluminum hydroxide and the like. Examples of the aluminum compound having an organic group include a water-soluble carbonate of aluminum, such as an aluminum carbonate ammonium salt, a water-soluble carboxylate of aluminum, such as aluminum acetate, an aluminum alkoxide, such as aluminum ethoxide, and an aluminum isopropoxy. Cyclic aluminum oligomers, aluminum chelate compounds such as diisopropoxy (ethyl acetoacetate) aluminum, tris (ethyl acetoacetate) aluminum, and alkyl aluminums such as triethyl Aluminum etc. are mentioned.
Of these, as the hydrolyzable aluminum compound in the sol preparation method, it is preferable to use an aluminum alkoxide having moderate hydrolyzability and easy removal of by-products, and an alkoxy group having 2 to 5 carbon atoms. Particularly preferred are those having

  In the sol preparation method, hydrolysis of the hydrolyzable aluminum compound proceeds in the presence of an acid. As the acid for hydrolysis, monovalent acids such as inorganic acids such as hydrochloric acid and nitric acid, organic acids such as formic acid, acetic acid, propionic acid, and butyric acid are preferable, and inorganic acids tend to remain in alumina even after firing. It is preferable to use an organic acid. As the organic acid, it is particularly preferable to use acetic acid from the viewpoint of operability and economy. The amount of the acid used is preferably 0.2 to 2.0 mol times, particularly preferably 0.3 to 1.8 mol times based on the hydrolyzable aluminum compound. If the amount of acid used is less than 0.2 mol, the aspect ratio of the resulting fiber-like alumina nanoparticles may be too small. If the amount of acid used exceeds 2.0 mol, the fiber-like alumina nanoparticles The aqueous sol is not preferable because the stability over time is lowered, which may cause further economic disadvantages.

The hydrolysis conditions are preferably 100 ° C. or lower and 0.1 to 3 hours. If the hydrolysis temperature exceeds 100 ° C., bumping may occur, and if the hydrolysis time is less than 0.1 hour, temperature control is difficult, and if it exceeds 3 hours, the process time becomes long.
The solid content concentration of the acid aqueous solution of the hydrolyzable aluminum compound in the hydrolysis step is preferably 2 to 15% by mass, particularly preferably 3 to 10% by mass. When the solid content concentration is less than 2% by mass, the aspect ratio of the obtained fiber-like alumina nanoparticles may be too small. When the solid content concentration exceeds 15% by mass, the stirring property of the reaction solution may be reduced during peptization. May decrease.

In the sol preparation method, alcohol obtained as a by-product by hydrolysis of the hydrolyzable aluminum compound is preferably distilled off, and then the resulting reaction mixture is peptized. In the peptization treatment, the reaction mixture after hydrolysis is heated at 100 to 200 ° C. for 0.1 to 10 hours, more preferably at 110 to 180 ° C. for 0.5 to 5 hours. When the heating temperature is less than 100 ° C., the reaction requires a long time, and when it exceeds 200 ° C., a high-pressure container or the like is required, which may be economically disadvantageous. When the heating time is less than 0.1 hour, the size of the obtained fibrous alumina nanoparticles is small, and the storage stability may be lowered. When it exceeds 10 hours, the process time becomes longer.
An aqueous sol of fibrous alumina precursor nanoparticles is obtained by the peptization treatment. The fibrous alumina precursor nanoparticles are preferably an aluminum hydroxide amorphous, boehmite, or pseudoboehmite structure. The amorphous aluminum hydroxide may have any structure of gibbsite, bayerite, and diaspore.

  In the method of the present invention, the size and shape of the target fiber-like alumina nanoparticles and the desired crystal structure thereof are appropriately selected from, for example, the type of hydrolyzable aluminum compound, hydrolysis conditions, peptization treatment conditions, and firing conditions. It can be adjusted by setting.

  The aqueous sol of fiber-like alumina precursor nanoparticles obtained by the step (1) of the production method of the present invention may be neutral or alkaline, but facilitates convergence of the fiber-like alumina precursor nanoparticles. In order to achieve this, the pH is preferably 2.5-4. As the pH adjusting reagent for adjusting the pH, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate or ammonia, or organic amines such as ethylamine, tetramethylammonium hydroxide and urea can be used. Among these, when organic amines are used, it is difficult to remain in the target product obtained, and a high-purity target product can be produced. In the subsequent step, step (4), when a basic substance such as ammonia or organic amine is produced, the produced basic substance functions as a pH adjusting reagent. You don't have to.

  When the aqueous sol of fiber-like alumina precursor nanoparticles prepared in this way has a high viscosity, it often contains bubbles, so it is degassed to remove these bubbles. It is preferable to do. Examples of the method for removing bubbles include various deaeration methods such as a decompression process and a centrifugal process.

  In step (2) of the method of the present invention, at least one aqueous solution or dispersion of the luminescent transition metal compound is mixed in the aqueous sol of the fibrous alumina precursor nanoparticles. At this time, the molar ratio of the content of the luminescent transition metal atom contained in the aqueous solution or dispersion to the content of aluminum atom contained in the aqueous sol is 1: 0.001 to 1: 1. It is important to prepare within the range. The mixing operation is preferably performed at a temperature of 20 to 50 ° C.

  In the step (3) of the present invention, the mixed solution is applied onto the inner surface of the molding solution, dried and molded into a thin film. The inner surface of the molded container is preferably water-repellent, and the drying is preferably performed at a temperature of 30 to 60 ° C. for 1 to 5 hours. The thin film-like molded product after drying is peeled off from the inner surface of the molding container and collected.

In the step (4) of the method of the present invention, the thin film-like molded product is fired at a firing temperature of 400 to 1500 ° C., preferably 600 to 1000 ° C. for 1 to 10 hours. For this firing, a high-temperature heat treatment apparatus such as a firing furnace or an electric furnace can be used. Fibrous alumina nanoparticles can be obtained from the fibrous alumina precursor nanoparticles by the firing. The fired fiber-like alumina nanoparticles include at least a boehmite crystal system or a pseudo-boehmite crystal structure, so that the self-supporting thin film forming component formed by the fiber-like alumina nanoparticles is sufficiently high in practical use. Strength. The boehmite is a crystal of alumina hydrate represented by the composition formula: Al ₂ O ₃ .nH ₂ O.

  In the firing step (4), when the firing temperature is less than 400 ° C., the emission luminance of the resulting luminescent transition metal-containing alumina free-standing thin film may be insufficient, and when it exceeds 1500 ° C., The light emission luminance improvement effect accompanying the increase is saturated, and there may be inconveniences such as an increase in manufacturing cost.

The crystal structures of the fiber-like alumina precursor nanoparticles and the fiber-like alumina nanoparticles are confirmed under the following conditions using an X-ray diffractometer (for example, “Mac. Sci. MXP-18”, manufactured by Mac Science). it can.
<Conditions> Tube: Cu, tube voltage: 40 kV, tube current: 250 mA, goniometer: wide-angle goniometer, sampling width: 0.020 °, scanning speed: 10 ° / min, diverging slit: 0.5 °, scattering Slit: 0.5 °, light receiving slit: 0.30mm

  The invention is further illustrated by the following examples.

Example 1
(Preparation of fiber-like alumina nanoparticles)
In a 500 ml four-necked flask, 300 g of ion-exchanged water and 3.1 g (0.051 mol) of acetic acid were taken, and the liquid temperature was raised to 75 ° C. while stirring. To this, 34 g (0.17 mol) of aluminum isoporoxide was added dropwise over 0.6 hours, and hydrolysis was carried out by raising the liquid temperature to 95 ° C. while distilling off the generated isopropyl alcohol. This reaction solution was transferred to an electromagnetic stirring type autoclave, and a peptization reaction was performed at 150 ° C. for 6 hours while stirring. Thereafter, the liquid temperature was cooled to 40 ° C. or lower to complete the reaction, and a fiber-like alumina precursor nanoparticle aqueous sol was obtained. The solid content concentration of the fibrous alumina precursor nanoparticles in the aqueous sol was 2.8% by mass. As a result of observing the obtained fibrous alumina precursor nanoparticles with a transmission electron microscope (TEM) as described above, the average fiber width was 4 nm, the average fiber length was 2,000 nm, and the average aspect ratio was 500. . A transmission electron microscope image of the fiber-like alumina precursor nanoparticle aqueous sol is shown in FIG. In FIG. 1, a large number of fibrous alumina precursor particles are distributed substantially parallel to the display plane and intersect or entangle with each other.

(Preparation of luminescent transition metal alumina free-standing film)
Terbium nitrate hexahydrate 0.25g (5mol%) was added to 20g of the aqueous sol of fiber-like alumina precursor nanoparticles, stirred for 20 minutes, and then deaerated with a centrifuge to obtain a uniform dispersion. . This dispersion was poured into a Teflon (registered trademark) coated container 80 mm × 80 mm × 10 mm and spread on the bottom substrate of the container, and dried in a blowing oven at 40 ° C. for 3 hours. By peeling from the substrate, a uniform free-standing thin film having a length of 80 mm, a width of 80 mm, and a film thickness of 60 μm was obtained. The self-supporting thin film body was fired at 800 ° C. for 5 hours to obtain a light-emitting transition metal-containing alumina self-supporting thin film.

(EL measurement)
This self-supporting thin film is cut into a 5mm x 5mm square, sandwiched between two glasses deposited with ITO, and applied with an alternating voltage of 1KHz sine wave. As a result, the applied voltage can be confirmed from 350V and green light can be confirmed. It was confirmed that the brightness increased with the increase. The luminance at an AC applied voltage of 500 V was 2.1 cd / m ² . EL emission spectrum at this time ^{(f-f emissions from 5 D} 4 - 7 F J (J.6; 5; 4; 3) transition in Tb 3+) are shown in Figure 2.
In FIG. 2, the emission intensity shows the maximum emission intensity at a wavelength of about 550 nm when the applied voltage is 450V.

Comparative Example 1
In a 500 ml four-necked flask, 300 g of ion-exchanged water and 4.08 g (0.068 mol) of acetic acid were taken, and the liquid temperature was raised to 75 ° C. while stirring. To this, 64 g (0.34 mol) of aluminum isoporoxide was added dropwise, and the hydrolysis was carried out by raising the liquid temperature to 98 ° C. while distilling off the generated isopropyl alcohol. This reaction solution was transferred to an electromagnetic stirring type autoclave, and a peptization reaction was performed at 230 ° C. for 1 hour while stirring. Thereafter, the liquid temperature was cooled to 40 ° C. or lower, the reaction was terminated, and an aqueous sol of fiber-like alumina precursor nanoparticles was obtained. The solid content concentration of the alumina precursor in this aqueous sol was 4.8% by mass. The obtained aqueous sol of fiber-like alumina precursor nanoparticles was observed with a transmission electron microscope (TEM) as described above. As a result, a columnar shape having an average fiber width of 10 nm, an average fiber length of 100 nm, and an average aspect ratio of 10 was obtained. It was a body.
To 11.6 g of this columnar alumina sol, 8.4 g of ion exchange water and 0.25 g (5 mol%) of terbium nitrate hexahydrate were added, stirred for 20 minutes, and then degassed with a centrifuge to obtain a uniform dispersion. It was. This dispersion was subjected to a self-supporting thin film forming step in the same manner as in Example 1. However, the obtained film was cracked and a self-supporting film having a size that could be sufficiently utilized could not be obtained.

Comparative Example 2
The Tb-containing alumina self-supporting thin film obtained in Example 1 was pulverized in a mortar, and 0.056 g of ethyl cellulose and 5 g of ethanol were added and stirred for 20 minutes to obtain a uniform dispersion. The dispersion was poured into a Teflon (registered trademark) coated container 80 mm × 80 mm × 10 mm, dried in an air blowing oven at 40 ° C. for 3 hours and peeled to obtain a white sheet film.
As a result of subjecting this film to EL measurement in the same manner as in Example 1, the luminance at the time of application of 500 V was reduced to 1.1 cd / m ² .

Example 2
In the same manner as in Example 1, a Tb-containing alumina self-supporting thin film was produced. However, fiber-like alumina precursor particles having an average aspect ratio of 150 (average minor axis: 3 nm, average major axis: 450 nm) were obtained. The obtained Tb-containing alumina free-standing thin film is cut to 5 mm x 5 mm, sandwiched between ITO-deposited glass, and applied with an alternating voltage of 1 KHz sine wave. As a result, green light can be confirmed from 320 V, and the luminance increases as the voltage increases. It could be confirmed. The luminance at an AC applied voltage of 500 V was 2.5 cd / m ² .

Example 3
Uniform dispersion by adding 0.24 g (5 mol%) of europium nitrate hexahydrate to 20 g of the aqueous sol of fibrous alumina precursor nanoparticles prepared in Example 1 and stirring for 20 minutes, followed by degassing with a centrifuge. A liquid was obtained. This dispersion is poured into a Teflon (registered trademark) coated container 80 mm x 80 mm x 10 mm, dried in a blown oven at 40 ° C for 3 hours, and peeled off from the substrate to obtain a uniform free-standing thin film of 80 mm in length, 80 mm in width, and 60 µm in thickness. Got. This self-supporting thin film was baked at 800 ° C. for 5 hours to obtain an Eu-containing alumina self-supporting thin film.

(EL measurement)
As a result of cutting this Eu-containing alumina self-supporting thin film to 5 mm x 5 mm, sandwiching it with ITO-deposited glass, and applying an alternating voltage of 1 KHz sine wave, you can confirm red light from 200 V, and you can confirm the increase in brightness as the voltage increases It was. The luminance at this time was 1.5 cd / m ² .
Emission spectrum of the applied AC voltage ^{400V (f-f emissions from 5} D 0 -7F J (J = 0,1,2) transitions in Eu 3+) are shown in Figure 3. In FIG. 3, the emission spectrum when the applied voltage is 400 V shows a peak of emission intensity at a wavelength of about 614 nm.

Example 4
To 20 g of the aqueous alumina nanofiber sol prepared in Example 1, 0.24 g (5 mol%) of samarium nitrate hexahydrate was added, stirred for 20 minutes, and then degassed with a centrifuge to obtain a uniform dispersion. . This dispersion is poured into a Teflon (registered trademark) coated container 80 mm × 80 mm × 10 mm, dried in a blowing oven at 40 ° C. for 3 hours, and the dried thin film is peeled off from the substrate to be 80 mm long, 80 mm wide, film thickness A uniform free-standing film of 60 μm was obtained. This self-supporting film was baked at 800 ° C. for 5 hours to obtain an inorganic EL element self-supporting film.
(EL measurement)
This inorganic EL element free-standing film is cut to 5 mm x 5 mm, sandwiched between ITO-deposited glass, and applied with an alternating voltage of 1 KHz sine wave. As a result, yellow light can be confirmed from 350 V, and an increase in luminance can be confirmed as the voltage increases. It was. The luminance at this time was 1.1 cd / m ² .

  The luminescent transition metal-containing alumina self-supporting thin film of the present invention is useful as an inorganic EL element or a light-emitting display surface component that can be self-supported without containing an organic binder. The thin film can be manufactured efficiently and inexpensively.

Claims (8)

Including at least one luminescent transition metal compound as a luminescent source component and alumina as a self-supporting thin film forming component;
The luminescent transition metal compound is selected from a luminescent transition metal ion-containing compound and a luminescent transition metal oxide,
The alumina is produced by a sol-gel method and has a fiber-like shape having a number average aspect ratio of 30 to 5000, and at least the shape of the fiber-like nanoparticles having an average fiber width in the nanometer order of 10 nm or less. Have
The molar ratio of the transition metal contained in the light emitting source component to the aluminum contained in the self-supporting film forming component is in the range of 1: 0.001 to 1: 1,
The method for producing a luminescent transition metal-containing alumina self-supporting thin film , wherein the light emitting source component is supported by the fiber-like alumina nanoparticles forming the self-supporting thin film. Wherein the width of the fibrous nanoparticles freestanding film forming alumina (thickness) is 1 to 10 nm, and the a length 100～10000Nm, production of luminescent transition metal-containing alumina self-supporting film of claim 1 Way . The method for producing an alumina self-supporting thin film containing a light-emitting transition metal according to claim 1, wherein the transition metal contained in the light-emitting source component is selected from titanium, europium, terbium, cerium, dysprosium, ytterbium, samarium, zinc and chromium. The luminescent transition metal containing of Claim 1 or 2 whose alumina which comprises the said self-supporting thin film formation component is at least 1 sort (s) of (gamma) -alumina, (delta) -alumina, (theta) -alumina, (kappa) -alumina, and (chi) -alumina. A method for producing an alumina self-supporting thin film. An aqueous sol of nano-particles of fibrous alumina precursor having a fiber width of 10 nm or less and an aspect ratio in the range of 30 to 5000 is prepared from a hydrolyzable aluminum compound by a sol-gel method.
An aqueous solution or dispersion of at least one luminescent transition metal compound is mixed in the aqueous sol containing fibrous alumina precursor nanoparticles, and at this time, the luminescent property contained in the aqueous solution or dispersion is mixed. Adjusting the molar ratio of the transition metal content to the aluminum content contained in the aqueous sol in the range of 1: to 0.001 to 1: 1,
Apply the resulting mixture on the inner surface of the molding container, dry it, and mold it into a thin film.
A method for producing a luminescent transition metal-containing alumina self-supporting thin film characterized by firing the obtained thin film-like molded product to change the fiber-like alumina precursor nanoparticles into fiber-like alumina nanoparticles.   The aqueous sol of nano-particles of the fibrous alumina precursor is produced by hydrolyzing the hydrolyzable aluminum compound in water and heating and peptizing, wherein the alumina precursor is an amorphous aluminum hydroxide The manufacturing method of Claim 5 which is a boehmite or a pseudo boehmite structure.   The manufacturing method of Claim 5 with which the baking of the said thin-film shaped molding is performed at the temperature of 400-1300 degreeC.   The manufacturing method of Claim 7 which exists in the range whose said calcination temperature is 600-1000 degreeC.