JP5145490B2 - Method for manufacturing phosphor for inorganic EL - Google Patents

Description

  The present invention relates to a method for manufacturing a phosphor for inorganic EL, which is a light-emitting material for thin film electroluminescence (EL) used for a display for displaying various information and images, and more specifically, blue light-emitting barium thioaluminum for inorganic EL. The present invention relates to a method for producing an nate-based phosphor.

In recent years, development of inorganic EL elements, which are light-emitting materials for thin film electroluminescence (EL), used for displays for displaying various information and images, has been actively promoted. As the technology, for example, a method of performing full color display using a phosphor containing a high-brightness rare earth-added alkaline earth thioaluminate phosphor (structural formula AB ₂ C ₄ : Re) is known (patent). Reference 1).
This method is, for example, a reactive sputtering method in which a hydride gas having an element constituting C is contained in a sputtering gas, or a plurality of vapor gases having one or more kinds of elements constituting A, B, C, and Re. Is a method of manufacturing a multi-color display thin-film EL panel using several kinds of phosphor thin films formed by a film-forming method in which a thin film is formed by independently controlling the above.

As rare earth-added alkaline earth thioaluminate phosphors, for example, EL materials having high luminance and blue light emission with excellent color purity and thin film EL elements using such materials as light emitting layers are known (Patent Document 2). reference). This EL material uses an alkaline earth thioaluminate as a base material and a lanthanoid element such as cerium as an activator.
Among such thin film EL materials, the Eu-added BaAl ₂ S ₄ sulfide phosphor is the most expected material because of its high luminance and good color purity. These phosphors can be obtained by mixing and baking sulfide powders such as aluminum sulfide. In this case, the finer the raw material powder, the more uniform the phosphor. In particular, in order to produce a high-luminance phosphor, it is important that Eu, which is a light-emitting element, is uniformly dispersed and the element position of Ba is replaced.

Such Eu-added BaAl ₂ S ₄ sulfide phosphors can be prepared by using, for example, an alkaline earth element compound, an aluminum raw material, and a rare earth element compound in a sulfur-containing gas atmosphere such as hydrogen sulfide at a temperature of 700 ° C. or higher. A synthesis method has also been proposed (see Patent Document 3).

However, sulfides such as aluminum sulfide, which are starting materials for the above-described Eu-added BaAl ₂ S ₄ sulfide phosphor, easily react with moisture in the air and deteriorate in quality, and are toxic hydrogen sulfide during pulverization and mixing. There is a problem of generating gas. In addition, the use of sulfides with deteriorated quality has the disadvantage that the crystallinity of the sulfide phosphor is deteriorated and the fluorescence intensity is lowered. In particular, when the powder is refined, the quality of the sulfide is significantly deteriorated. Furthermore, BaS and EuS have a low purity of 98 to 99%, and there is a problem that impurities are not easily managed.
In addition, a method of synthesizing sulfides such as barium sulfide and europium sulfide uniformly by using an alkaline earth element compound, an aluminum raw material, and a rare earth element compound in a sulfur-containing gas atmosphere such as hydrogen sulfide at a temperature of 700 ° C. or higher. Since it is difficult to disperse, it is necessary to treat toxic gas in order to synthesize in a gas atmosphere such as hydrogen sulfide.
Further, the above-described conventional synthesis method has a problem that it is difficult to completely sulfidize Al and luminance is insufficient.
JP-A-7-122364 JP-A-8-134440 JP 2005-344094 A

The present invention has been made in view of the present situation, and particularly suppresses the generation of toxic gas during pulverization / mixing of sulfides such as aluminum sulfide, and does not use toxic gas such as hydrogen sulfide during synthesis. is intended to propose a novel process for producing inorganic EL phosphor capable of producing a Eu added BaAl ₂ S ₄ sulfide phosphor.

The first method for producing an inorganic EL phosphor according to the present invention is a method for producing an inorganic EL phosphor by synthesizing Eu-added barium thioaluminate, wherein the Eu-added barium thioaluminate comprises Eu. Is mixed with Eu-added BaS uniformly dispersed, and the sulfur powder is melted by heating at a temperature of 750 ° C. to 1100 ° C. in a sulfur vapor pressure of 1 atm or higher. Addition of Eu in which liquid phase sulfur is formed, and after the formation of aluminum powder having aluminum sulfided on the outer periphery by contact between the liquid phase sulfur and the aluminum powder, the Eu is uniformly dispersed under sulfur vapor It is a method for producing a phosphor for inorganic EL, which is obtained by contact with BaS .
The second method for producing a phosphor for inorganic EL according to the present invention is a method for producing a phosphor for inorganic EL by synthesizing Eu-added barium thioaluminate , wherein the Eu-added barium thioaluminate is Aluminum powder and sulfur powder are mixed with Eu-added BaS in which Eu is uniformly dispersed, and heat treatment is performed at a temperature of 850 ° C. to 1100 ° C. for 30 minutes to 12 hours in a sulfur vapor pressure of 1 to 10 atm. After the sulfur powder is melted to form liquid-phase sulfur, an aluminum powder having aluminum sulfided on the outer periphery by contact between the liquid-phase sulfur and the aluminum powder is formed, and then the Eu is applied under sulfur vapor. Is obtained by contact with uniformly added Eu-added BaS .
Furthermore, the first phosphor for inorganic EL of the present invention comprises Eu-added barium thioaluminate having a particle diameter of 1 μm or more and 100 μm or less obtained by the first and second production methods. The second inorganic EL phosphor is characterized in that the Eu concentration obtained by the first and second manufacturing methods is 3% or more and 10% or less with respect to Ba.

In the present invention, Eu-added BaS in which Eu is uniformly dispersed is mixed with aluminum and sulfur, and heated at a temperature of 750 ° C. or higher and 1100 ° C. or lower in a sulfur vapor pressure of 1 atm or higher to obtain Eu-added barium thioaluminate. Since this is a method of synthesizing this and producing a phosphor for inorganic EL, a toxic gas atmosphere such as hydrogen sulfide is used even during synthesis without generating a toxic gas when pulverizing and mixing sulfides such as aluminum sulfide. There is no need to do.
Furthermore, a high-luminance Eu-added BaAl ₂ S ₄ sulfide phosphor is produced by making the Eu concentration of the inorganic EL phosphor not less than 3% and not more than 10% by the method for producing the phosphor for inorganic EL. Can do.
Further, according to this method, since the Eu-added BaAl ₂ S ₄ sulfide phosphor is free from residues such as raw material compounds and by-products, Eu-added BaAl ₂ S ₄ that emits light with high crystallinity and high brightness. A sulfide phosphor thin film can be obtained.

The manufacturing method of the phosphor for inorganic EL of the present invention will be described below.
The manufacturing method of the phosphor for inorganic EL according to the present invention includes 1) a step of synthesizing Eu-added BaS in which Eu is uniformly dispersed, 2) mixing aluminum and sulfur with Eu-added BaS obtained in 1), and heat treatment. And a step of synthesizing barium thioaluminate.

1) Step of synthesizing Eu-added BaS in which Eu is uniformly dispersed Eu-added BaS is preferably prepared by a complex polymerization method using barium carbonate and europium oxide, but has good dispersibility. You may use what heat-mixed europium.
More specifically, A.I. Eu oxide is dissolved in acid, alcohol, oxycarboxylic acid, and barium carbonate are sequentially added. After further obtaining a gel at 120 to 250 ° C., the precursor obtained by heat-treating the gel at 400 to 500 ° C. is again used. A step of heat treatment at 650 to 1000 ° C .; Eu-added BaS in which Eu is uniformly dispersed by, for example, a step of heat-treating Eu-added BaS obtained by this process at 850 to 1100 ° C. under a flow of H ₂ S—N ₂ gas of 10% or more. Can be synthesized.
Here, in order to obtain a high-luminance phosphor, the Eu concentration is preferably 3% or more and 10% or less with respect to Ba. If it is less than 3%, the Eu emission center is small and luminance does not appear. If it exceeds 10%, the probability that Eu atoms are adjacent to each other increases, and the crystallinity is deteriorated to cause a decrease in luminance.
From the viewpoint of reactivity, the particle size of Eu-added BaS is preferably 100 μm or less, but less than 1 μm is not preferable because it tends to float.

2) Step of synthesizing barium thioaluminate by mixing aluminum and sulfur in Eu-added BaS and heat-treating Sulfur and aluminum are melted by heat-treatment, so the particle size is not limited, but to mix uniformly with Eu-added BaS Preferably, sulfur and aluminum powder are mixed and pelletized.
Here, among sulfur, aluminum, and Eu-added BaS, it is preferable that aluminum and Eu-added BaS are brought into close contact with each other because synthesis of barium thioaluminate proceeds uniformly. In addition, since the surface of the aluminum powder is easily sulfided when covered with a sulfur melt, it is desirable to mix sulfur and aluminum powder.
Since the boiling point of sulfur is 447 ° C., a temperature higher than that has a vapor pressure of 1 atm or higher. Since the sulfidation reaction of aluminum proceeds rapidly, care must be taken not to damage the reaction vessel. Therefore, it is possible to take a method of controlling the vapor pressure by providing a low temperature part and a high temperature part in the reaction vessel, placing sufficient sulfur in the low temperature part and transporting sulfur vapor to the reaction part.
Al reacts with S in sulfur vapor to become Al ₂ S ₃ , and further Al ₂ S ₃ reacts with Eu-added BaS at 750 ° C. or higher to synthesize barium thioaluminate (compositional formula Eu: BaAl ₂ S ₄ ). Is done.
Here, the reason why the Eu-added barium thioaluminate produced by the above process exhibits excellent high brightness as described later is that Al is completely sulfided in sulfur vapor, so _{This is because 2} S ₃ always has no Al present in the commercially available Al ₂ S ₃ . In addition, in the synthesis of Eu-added barium thioaluminate, S evaporation is suppressed and S defects are reduced, which is considered to contribute to excellent high luminance.
Furthermore, in order to obtain a barium thioaluminate phosphor with high brightness, the following treatment may be performed. After the synthesis of barium thioaluminate, if the heat treatment is performed at 850 ° C. to 1100 ° C. and a sulfur vapor pressure of 1 to 10 atm for 30 minutes to 12 hours, the luminance of the resulting barium thioaluminate phosphor increases. This is thought to be because Eu is substituted at the atomic position of Ba and activated as divalent.
In order to increase the luminance when the Eu concentration is 3% or more and 10% or less, the heat treatment temperature is preferably 800 ° C. or more and 1100 ° C. or less, more preferably 850 ° C. or more and 1100 ° C. or less. When the temperature is lower than 800 ° C., the synthesis temperature of the barium thioaluminate sulfide is insufficient and the crystallinity is poor. Further, in order to replace Eu with 3% or more and 10% or less with respect to Ba to contribute to light emission, the temperature is preferably set to 850 ° C. or more.
On the other hand, when the temperature is higher than 1100 ° C., the aluminum sulfide is melted and evaporated, so that the composition changes. Moreover, since it is hard to remove | eliminate sulfur from the surface up to 1100 degreeC, it is preferable.
The synthesis of the Eu-added BaAl ₂ S ₄ powder is preferably vacuum-encapsulated, because when oxygen or moisture is mixed, sulfate or oxide is formed and becomes unstable due to lack of reproducibility.
After vacuum sealing, the heat treatment is performed in a uniform heat treatment furnace or using two or more heat treatment furnaces capable of independently controlling the temperature.
Beside synthesized in the vacuum-sealed is possible for example to use a high pressure vessel to synthesize the compound semiconductor such as G AAS.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(1) Synthesis of Eu-added BaS 0.26 g of europium oxide (3N manufactured by Furuuchi Chemical Co., Ltd.) was dissolved in nitric acid having a concentration of 15% (60% manufactured by Kanto Chemical Co., Ltd.), and after 5 minutes 0.01 liter of water And stirred for 1 hour for complete dissolution. After stirring, 21 g of ethylene glycol (99.5%, manufactured by Kanto Chemical Co., Ltd.) and 20 g of citric acid (98%, manufactured by Wako Pure Chemical Industries, Ltd.) were added to this solution. Further, 5.5 g of barium carbonate (BaCO ₃ ) was added to 40 ° C., and the mixture was stirred for 8 hours to completely dissolve the carbonate. Subsequently, the liquid temperature of the mixed solution in which the carbonate was completely dissolved was increased to 200 ° C. and stirred until a viscous gel was formed. After stirring, the obtained gel was heated to 450 ° C. with a mantle heater, the gel was pyrolyzed to prepare a precursor powder, the precursor powder was lightly pulverized with an agate mortar, and then placed in an alumina crucible and a tubular furnace The carbonic acid salt was prepared by annealing at 850 ° C. for 10 hours.
2.0 g of this Eu-added BaCO ₃ powder was heated in a nitrogen-hydrogen sulfide mixed gas having an H ₂ S concentration of 10.5%, and annealed at 950 ° C. for 24 hours to obtain 1.7 g of Eu-added BaS powder.
The Eu concentration of the obtained Eu-added BaS was 5.1% with respect to Ba.
(2) Synthesis of barium thioaluminate 0.5 g of the Eu-added BaS powder, 0.1585 g of commercially available Al powder (4N made by high purity chemical) and 0.2825 g of sulfur (99.5% made by Kanto Chemical Co., Ltd.) were used in an agate mortar. The mixture was mixed for 20 minutes, and this mixture was pressurized to 200 MPa with a hand press to prepare a molded body (pellet). The molded body was vacuum-sealed in a quartz ampule, and the quartz ampule was heated to 1000 ° C. and kept for 1 hour for heat treatment. The X-ray diffraction pattern of the obtained powder is shown in FIG.

  A barium thioaluminate powder was prepared in the same manner as in Example 1 except that the temperature of the quartz ampule was 900 ° C., and XRD measurement was performed. The results are shown in FIG.

  Using a quartz ampule with an internal volume of 5.45 ml, 0.058 g of sulfur and the powder of Example 1 were vacuum-sealed and heat-treated at 1000 ° C. for 12 hours. At 1000 ° C., the heat treatment was performed in a sulfur vapor pressure of 1.74 atm. The XRD pattern of the obtained powder is shown in FIG. A pattern similar to that of FIG. 1 was obtained.

  A powder was prepared in the same manner as in Example 3 except that 0.095 g of sulfur was used using a quartz ampule with an internal volume of 3.80 ml. At 1000 ° C., heat treatment was performed in a sulfur vapor pressure of 4.08 atm. The XRD pattern of the obtained powder was the same as in Example 3.

(Comparative Example 1)
Pellets were prepared in the same manner as in Example 1, and were prepared in the same manner as in Example 1 except that heat treatment was performed at 650 ° C. Barium thioaluminate could not be observed by XRD measurement.

(Comparative Example 2)
A powder was prepared in the same manner as in Example 1, and was prepared in the same manner as in Example 1 except that it was heat-treated at 650 ° C. Barium thioaluminate could not be observed by XRD measurement.

(Conventional example)
10.7 g of commercially available BaS (manufactured by Alfa AeSar), 0.5 g of EuS (manufactured by Furuuchi Chemical Co., Ltd.) and 9.9 g of Al ₂ S ₃ were weighed, and the agate in the nitrogen-substituted glove box with a humidity of 0.02% or less The mixture was mixed in a mortar for 20 minutes, and a powder was prepared in the same manner as in Example 1. The X-ray diffraction pattern of the obtained powder is shown in FIG. As apparent from FIG. 3, Al ₂ O ₃ was detected in addition to BaAl ₂ S ₄ in the obtained powder.

Further, the dark spots on the pellet surfaces prepared in Examples 1, 2, 3, 4 and Comparative Example 2 and the conventional example were removed with abrasive paper, and each pellet was excited by irradiation with light of 254 nm to obtain fluorescence intensity. Was measured. The strength measurement results are shown in FIG. The fluorescence spectra of Example 3 and Comparative Example 2 are shown in FIG.
As apparent from FIG. 4, the powder obtained by the method of the present invention showed a fluorescence intensity 1.7 to 2 times that of the conventional example and 1.4 to 1.8 times that of the comparative example. Further, as is clear from FIG. 5, it was confirmed that strong fluorescence having a peak at 476 nm was emitted.

[Phosphor according to the present invention]
As described above, it has been found that the phosphor obtained in the present invention is a BaAl ₂ S ₄ : Eu single phase, and the fluorescence intensity is stronger than that of the conventional example.
Since sputter targets for phosphor films for television use about 1 to ₃ kg of Al ₂ S ₃ , it is essential to use a lobe box after vacuum in order not to generate hydrogen sulfide. It was necessary to devise such as using a fluorinated liquid. Since this method does not use Al ₂ S ₃ , there is no fear of generation of hydrogen sulfide, and since a vacuum glove box is not required, it is an extremely useful method in which workability is remarkably improved.

According to the method of the present invention, it is possible to produce a high-quality Eu-added BaAl ₂ S ₄ sulfide phosphor in which Eu is uniformly dispersed without generating a toxic gas during the pulverization and mixing of sulfides such as aluminum sulfide. can also Eu added BaAl ₂ S ₄ from the sulfide material compound phosphor and residue byproducts like is eliminated, Eu added BaAl ₂ S ₄ sulfide phosphor thin film for emitting the crystallinity of good high intensity Therefore, the industrial value is extremely large.

It is a figure which shows the XRD pattern of the powder of Example 1 and Example 2. FIG. FIG. 6 is a diagram showing an XRD pattern of Example 3. It is a figure which shows the XRD pattern of a prior art example. It is a figure which shows the comparison result of the fluorescence intensity of each Example, the comparative example 2, and a prior art example. It is a figure which shows the fluorescence spectrum of Example 3 and Comparative Example 2.

Claims (4)

A method for producing a phosphor for inorganic EL by synthesizing Eu-added barium thioaluminate,
The Eu-added barium thioaluminate is mixed with Eu-added BaS in which Eu is uniformly dispersed, mixed with aluminum powder and sulfur powder, and heated at a temperature of 750 ° C. to 1100 ° C. in a sulfur vapor pressure of 1 atm or higher. The sulfur powder melts to form liquid phase sulfur, and after forming the aluminum powder having aluminum sulfided on the outer periphery by contact between the liquid phase sulfur and the aluminum powder, A method for producing a phosphor for inorganic EL, which is obtained by contact with Eu-added BaS in which Eu is uniformly dispersed . A method for producing a phosphor for inorganic EL by synthesizing Eu-added barium thioaluminate,
The Eu-added barium thioaluminate is mixed with Eu-added BaS in which Eu is uniformly dispersed and mixed with aluminum powder and sulfur powder at a temperature of 850 ° C. to 1100 ° C. in a sulfur vapor pressure of 1 to 10 atm. The sulfur powder melts to form liquid phase sulfur by heat treatment for 30 minutes to 12 hours, and aluminum powder having aluminum sulfided on the outer periphery is formed by contact between the liquid phase sulfur and the aluminum powder. Then, a method for producing a phosphor for inorganic EL, which is obtained by contact with Eu-added BaS in which Eu is uniformly dispersed under sulfur vapor .   An inorganic EL phosphor comprising an Eu-added barium thioaluminate having a particle diameter of 1 μm or more and 100 μm or less obtained by the production method according to claim 1.   A phosphor for inorganic EL, wherein the Eu concentration obtained by the production method according to claim 1 or 2 is 3% or more and 10% or less with respect to Ba.