JP4565985B2 - Amorphous composite oxide particles, method for producing the same, fluorescent material and phosphor - Google Patents

Description

  The present invention relates to an amorphous composite oxide particle, a method for producing the same, a fluorescent material and a phosphor, and more specifically, an amorphous composite oxide particle having a spherical shape with a small maximum diameter and a narrow particle size distribution, and the production thereof. The present invention relates to a method, a fluorescent material comprising the amorphous composite oxide particles, and a red phosphor having high luminous efficiency.

Among the fluorescent materials used for phosphors such as color cathode ray tubes and fluorescent lamps, materials that develop a red color include yttrium oxide (Y ₂ O ₃ : Eu) activated with europium (Eu), Y ₂ O ₂ S: Eu. The thing which consists of etc. is known. These materials have been produced by placing a mixture of raw material powders in a firing container such as a crucible, causing a solid-phase reaction by heating at a high temperature for a long time, and pulverizing it with a ball mill or the like. . However, the fluorescent material manufactured by this method is composed of irregularly shaped particles. When this is used for the above-mentioned applications, the fluorescent film obtained by coating is non-homogeneous. The variation was large.
On the other hand, materials that replace the Y-based compounds as described above have been studied. For example, Non-Patent Document 1 discloses a method of using SiO ₂ : Eu using alkaline silica sol and europium nitrate. .

F. Iskandar et al. Nanoparticle Res. 3 (2001), p. 263-270

According to the method disclosed in Non-Patent Document 1, when the total amount of Si and Eu is 100 mol%, the precipitate is precipitated in a mixed solution of silica sol and europium nitrate even though Eu is as small as 10 mol%. The resulting phosphor has a non-uniform composition, and stable light emission characteristics cannot be obtained.
An object of the present invention is to solve the above-described problems, and is spherical, has a small maximum diameter and a narrow particle size distribution, a method for producing the same, and the above non- An object of the present invention is to provide a fluorescent material composed of crystalline composite oxide particles and capable of easily forming a homogeneous and dense fluorescent film, and a fluorescent material which is a red structure having a high luminous efficiency.

As a result of intensive studies aimed at achieving the above object, the present inventors have completed the present invention.
The present invention is shown below.
1. An amorphous material comprising: a step of atomizing a mixed solution containing a compound containing a rare earth element and an acidic silica sol to form droplets; and a step of heat-treating the droplets at 600 to 1500 ° C. A method for producing composite oxide particles.
2. The composition ratios of Si and rare earth elements in the mixed solution are 99 to 50 mol% and 1 to 50 mol%, respectively, of the amorphous composite oxide particles according to 1 above, when the total of these is 100 mol%. Production method.
3. 3. The method for producing amorphous composite oxide particles according to 1 or 2 above, wherein the rare earth element is at least one selected from Eu, Tm, Er, Pr, Tb, and Ce.
4). An amorphous composite oxide obtained by the production method according to any one of 1 to 3 above, comprising Si, O, and a rare earth element, having a spherical shape and a maximum diameter of 2 μm or less. particle.
5). 5. A fluorescent material comprising the amorphous composite oxide particles as described in 4 above.
6). 6. A structure using the fluorescent material according to 5 above, comprising a base and a fluorescent layer formed on at least a part of the base and including the fluorescent material.

The method for producing amorphous composite oxide particles according to the present invention comprises a step of atomizing a mixed solution containing a compound containing a rare earth element and an acidic silica sol to form droplets, and the droplets at 600 to 1500 ° C. In this case, it is possible to produce one solid particle from one droplet, and thus it is possible to easily produce amorphous composite oxide particles having a narrow particle size distribution.
Since the amorphous composite oxide particles of the present invention are spherical and have a small maximum diameter, when this is used as a fluorescent material, a homogeneous and dense fluorescent film can be easily and thinly formed with little variation. Red light emission is obtained. Further, by setting the constituent ratios of Si and rare earth elements to predetermined ones, higher luminous efficiency can be obtained.
In addition, the phosphor of the present invention can be a red structure having high luminous efficiency.

The present invention will be described in detail below.
1. Method for Producing Amorphous Composite Oxide Particles The method for producing an amorphous composite oxide particle of the present invention is a mixed solution containing a compound containing a rare earth element and an acidic silica sol (hereinafter also referred to as “raw material solution”). .) Is atomized into droplets (hereinafter referred to as “atomization step”) and a step of heat-treating the droplets at 900 to 1500 ° C. (hereinafter referred to as “heat treatment step”).

The rare earth element is not particularly limited as long as it is selected from Sc, Y, La, Ac, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. . Of these, Eu, Tm, Er, Pr, Tb and Ce are preferred.
As the compound containing these rare earth elements (hereinafter also referred to as “compound (A)”), it is preferable to use a water-soluble substance. For example, nitrate, sulfate, phosphate, borate, carbonate, Oxides, chlorides, organometallic salts, and the like can be used. Moreover, the compound which melt | dissolves in the aqueous medium containing alcohol can also be used. The said compound (A) can be used individually by 1 type or in combination of 2 or more types.
The compound (A) may be used as it is when preparing a mixed solution, or may be used as a solution formed by dissolving in water or the like.

If the said silica sol is acidic, it can be used without limiting the pH. The preferred pH is 1-5, more preferably 2-5, still more preferably 2-4.
Although the density | concentration of the silica sol at the time of preparing a mixed solution is not specifically limited, Usually, 0.1-6 mass%, Preferably it is 0.5-6 mass%, More preferably, it is 1-6 mass%.

  Although the said mixed solution contains a compound (A) and a silica sol, these content rates are not specifically limited. In the present invention, it is preferable that the content ratios of Si and rare earth elements derived from the respective components are as follows. That is, when the total of these Si and rare earth elements is 100 mol%, it is preferably 99 to 50 mol% and 1 to 50 mol%, more preferably 90 to 70 mol% and 10 to 30 mol%, still more preferably 85, respectively. -75 mol% and 15-25 mol%. If the constituent ratio of the rare earth element is too large, the luminous efficiency tends to decrease.

Next, the “atomization process” will be described. The method for atomizing the mixed solution (raw material solution) containing the compound (A) and silica sol is not particularly limited, but there are an ultrasonic spray method, a spray method using a nozzle, a spray, a direct dropping method, a charging method, and the like. Can be mentioned. Of these, ultrasonic spraying is preferred.
In the case of atomization by the ultrasonic spray method, the diameter of the droplet can be adjusted by properly combining the ultrasonic oscillation conditions, the concentration of the raw material solution, etc., thereby producing particles having a desired particle diameter. can do. In addition, particles having a narrow particle size distribution can be produced.

The droplets formed by the atomization step evaporate a medium such as water and sinter inorganic components by a “heat treatment step”. In this heat treatment step, heat treatment is performed on the mist droplets. This method is sometimes called a “spray pyrolysis method”.
The heat treatment can be performed by an electric furnace, an infrared condensing heating furnace, plasma induction heating, or the like. The heating temperature of the droplet is 600-1500 ° C, preferably 800-1300 ° C, more preferably 900-1100 ° C. When the heating temperature of the droplet is too high, the emission intensity tends to decrease with the crystallization of amorphous silica. On the other hand, if the heating temperature is too low, the light emitting efficiency tends to be low because the amorphous structure is unstable. The heating time is preferably 5 to 60 seconds, more preferably 5 to 30 seconds, and still more preferably 10 to 20 seconds. When the heating time of the droplets is too long, the particles aggregate and the particle size distribution tends to be widened. On the other hand, if the heating time is too short, the luminous efficiency tends to be low.
The heat treatment of the droplets may be performed at a constant temperature between 600 and 1500 ° C., but is set so that the temperature gradually increases in the moving direction of the droplets in the furnace. The heat treatment may be performed at a temperature. In the latter case, for example, inside the electric furnace or the like, the temperature can be set such that the temperature is gradually increased by 100 ° C. from the droplet introduction side and the maximum temperature is 1200 ° C.

Moreover, the atmosphere at the time of heat-processing the said droplet is not specifically limited, For example, air, nitrogen, argon, oxygen, hydrogen etc. are mentioned.
The introduction of droplets into an electric furnace or the like may be from one place or from a plurality of places. The method for introducing droplets is not particularly limited, but an atomizer is disposed above an electric furnace or the like, and a method of introducing droplets into the furnace by the natural fall of the droplets, using an atomizer and a device connected to the furnace, A method of introducing droplets into the furnace by using a carrier gas can be used.

When a carrier gas is used, any of an inert gas, a reducing gas, and an oxidizing gas may be used, but usually air, nitrogen, argon, or the like is used.
The flow rate of the carrier gas is usually 0.1 to 10 liters / minute, preferably 1 to 5 liters / minute, more preferably 1 to 3 liters / minute, depending on the type of carrier gas.

  After the heat treatment step, a filtration step using a filter or the like, a dust collection device, a fine particle classifier, a recovery step using a cyclone or the like can be further provided.

  Since the particles obtained by the production method of the present invention are heat-treated in the form of droplets, they do not aggregate and are spherical and have a particle diameter of 3 μm or less, preferably 0.3 to 2 μm.

2. Fluorescent material The fluorescent material of the present invention is characterized by comprising the above amorphous composite oxide particles. This fluorescent material may be used as it is, or may be used after performing a heat treatment such as reheating. In the latter case, the heating temperature is preferably 700 to 1300 ° C, more preferably 800 to 1200 ° C. If the heating temperature is too high, the emission intensity tends to decrease. The heating time is preferably 2 to 48 hours, more preferably 2 to 24 hours, and further preferably 3 to 12 hours. When the heating time is too long, the particles tend to aggregate.
Moreover, although the atmosphere at the time of heat-processing the said fluorescent material is not specifically limited, For example, oxygen, nitrogen, argon etc. are mentioned.

  The fluorescent material of the present invention is suitable for each application requiring red light emission because it exhibits red fluorescence with high luminance by ultraviolet excitation, vacuum ultraviolet excitation, or the like. Since the particle size distribution is narrow, a homogeneous and dense fluorescent film can be easily and thinly formed.

3. Phosphor The phosphor of the present invention is a structure using the above-described phosphor material, and includes a substrate and a phosphor layer formed on at least a part of the substrate and containing the phosphor material. This fluorescent layer may be formed on the entire surface (both sides) of the substrate.
A schematic diagram of the phosphor of the present invention is shown in FIG. The phosphor 1 in FIG. 6 includes a base 11 and a fluorescent layer 12 formed on the surface of the base 11 and including a fluorescent material 13. Depending on the purpose and application, a layer made of another constituent material such as a glass layer may be provided on the surface of the fluorescent layer 12.

  The substrate may have a shape according to the purpose, application, etc., and may be a plate shape such as a plane or a curved surface, a block shape such as a cube or a rectangular parallelepiped, a solid lattice shape, or the like. These sizes are not particularly limited. Moreover, this base | substrate may consist of what kind of material, Organic materials, such as inorganic materials, such as a metal and ceramics, resin, rubber | gum, etc. are mentioned.

  The fluorescent layer may be composed of only the fluorescent material, or may be a layer including an adhesive, a pressure-sensitive adhesive, and the like for bonding to the substrate and the fluorescent material. The thickness of the fluorescent layer may be selected depending on the purpose, application, etc., but is usually 0.1 to 20 μm, preferably 2 to 10 μm.

In forming the fluorescent layer on the surface of the substrate, a known method may be applied, and examples thereof include a method of applying a raw material constituting the fluorescent layer, a spraying method, and a transferring method.
In the case of application, a method using a coating apparatus, a method of immersing the substrate in a raw material solution containing a fluorescent material, and the like can be used. In the case of spraying, a method of spraying a material gas obtained by atomizing a suspension containing a fluorescent material onto the substrate, a method of spraying a carrier gas containing the fluorescent material onto the substrate, and the like can be mentioned.
The fluorescent layer obtained by the above method is a more uniform and dense film because the particle size of the fluorescent material is almost uniform. As a result, a phosphor with less uneven emission can be obtained.
Therefore, the phosphor of the present invention is suitable for a color cathode ray tube, a fluorescent lamp, and the like.

  Hereinafter, the present invention will be specifically described with reference to examples. In addition, this invention is not restrict | limited at all by these Examples. Further, “%” and “part” in the examples are based on mass unless otherwise specified.

1. Production of amorphous composite oxide particles Silica sol having pH 2.5 (trade name “Snowtex O”, manufactured by Nissan Chemical Industries, Ltd., solid content, 20%) and 15% europium nitrate aqueous solution were mixed (Si and The molar ratio of Eu was 80/20) to prepare a raw material solution. Thereafter, a spray pyrolysis apparatus (model name “LPS97-1”, manufactured by ONEN General Electric Co., Ltd.) is used as an apparatus for producing amorphous composite oxide particles, and air flows as a carrier gas at a flow rate of 1.0 liter / min. A four-stage heating type electric furnace (heat treatment section, each heating source is 30 cm in length, which is disposed in the apparatus (refer to FIG. 1) and is set at a stepwise increase of 200 ° C., 400 ° C., 800 ° C. and 1000 ° C. ), The raw material solution was introduced in the form of a mist by using ultrasonic vibration. The residence time at 800 ° C. and 1000 ° C. is about 15 to 18 seconds. Subsequently, collection was performed using a membrane filter having a pore size of 0.5 μm (trade name “TO50A142C”, manufactured by Advantech Co., Ltd.) to obtain amorphous composite oxide particles.
The amorphous composite oxide particles were observed with a scanning electron microscope (model name “S-800”, manufactured by Hitachi, Ltd.) and the particle diameter was measured to be 0.8 to 2 μm (see FIG. 2). ). FIG. 2 shows that the particle size distribution is narrow.
An X-ray diffraction diagram is shown in FIG. FIG. 3 also shows the case where no Eu is contained at all and the case where the molar ratio of Si and Eu is 50/50. In the latter case, a peak derived from a crystal component that is considered to be an oxide of Eu is observed.

2. Evaluation of Amorphous Composite Oxide Particles The fluorescence characteristics of the amorphous composite oxide particles obtained above were measured using a fluorescence characteristic measuring apparatus. As the excitation light, an Ar laser having a wavelength of 351 nm was used. The result is shown in FIG. As shown in FIG. 4, a strong peak was observed at a wavelength of 614 nm, indicating a red color.
The same measurement was performed on composite oxide particles produced by changing the Eu content, and the results are shown in FIG. FIG. 5 shows that the fluorescence intensity shows a maximum value when Eu is 20 mol%. In FIG. 5, the fluorescence intensity decreases as the constituent ratio of Eu increases. This is due to concentration quenching of Eu ³⁺ .
In the conventional method using alkaline silica sol, even if Eu is 10 mol%, the fluorescence intensity is about 0.7, and the amorphous composite oxide particles obtained by the method of the present invention have a constituent ratio of Eu. It is clear that the fluorescence intensity is high and high.

  Since the amorphous composite oxide particles of the present invention are spherical and have a substantially uniform particle size, they are useful as fluorescent materials with high red light emission efficiency, and are suitably used for phosphors such as color cathode ray tubes and fluorescent lamps. It is done.

It is a schematic explanatory drawing of the spray pyrolysis apparatus used in the Example. It is an image which shows the amorphous complex oxide particle obtained in the Example. It is an X-ray diffraction pattern of the non-crystalline composite oxide particles obtained in the examples. It is a graph which shows the fluorescence characteristic of the amorphous | non-crystalline complex oxide particle obtained in the Example. It is a graph which shows the fluorescence characteristic in 614 nm of the amorphous complex oxide particle obtained in the Example, and the amorphous complex oxide particle from which Eu content rate differs. It is a schematic sectional drawing which shows an example of the fluorescent substance of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1; Phosphor, 11; Base | substrate, 12; Fluorescent layer, 13: Fluorescent material.

Claims (6)

  An amorphous material comprising: a step of atomizing a mixed solution containing a compound containing a rare earth element and an acidic silica sol to form droplets; and a step of heat-treating the droplets at 600 to 1500 ° C. A method for producing composite oxide particles.   2. The amorphous composite oxide particles according to claim 1, wherein the constituent ratios of Si and rare earth elements in the mixed solution are 99 to 50 mol% and 1 to 50 mol%, respectively, when the total of these is 100 mol%. Manufacturing method.   The method for producing an amorphous composite oxide particle according to claim 1, wherein the rare earth element is at least one selected from Eu, Tm, Er, Pr, Tb, and Ce.   An amorphous composite oxidation obtained by the production method according to claim 1, comprising Si, O, and a rare earth element, having a spherical shape and a maximum diameter of 2 μm or less. Particle.   A fluorescent material comprising the amorphous composite oxide particles according to claim 4.   A structure using the fluorescent material according to claim 5, comprising a base and a fluorescent layer formed on at least a part of the surface of the base and containing the fluorescent material. .