JP5164618B2 - Method for manufacturing phosphor for inorganic EL - Google Patents

Description

The present invention relates to a method for producing 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 particularly, for barium thioaluminum for inorganic EL that emits blue light. The present invention relates to a method for producing an nate-based phosphor.
Furthermore, since the phosphor according to the present invention emits high-luminance fluorescence in the near ultraviolet, it can be used as an ultraviolet-excited blue 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. For example, a method of performing full color display using a phosphor containing a high-brightness rare earth-added alkaline earth thioaluminate phosphor is known (see Patent Document 1).
In this method, for example, in a phosphor in which A is an alkaline earth element, B is a Group III metal element, C is sulfur, RE is a rare earth element, and RE is added to a compound having the chemical formula AxByCz, a pure metal target, AB, or ABRE is used. A reactive sputtering method in which hydrogen sulfide is contained in a sputtering gas using an alloy target or a sulfide target (see Patent Document 2), or a plurality of elements each including one or more elements constituting A, B, C, and RE In a method of manufacturing a multicolor display thin-film EL panel using several kinds of phosphor thin films formed by a film forming technique in which vapor gas is independently controlled and supplied to the substrate surface to form a thin film (see Patent Document 3). is there.

  Further, 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 the materials as light emitting layers are known (Patent Document 4). 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, Eu-added barium thioaluminate sulfide (BaAl ₂ S ₄ ) phosphor is the most expected material because of its high luminance and good color purity.
This phosphor can be obtained by mixing and baking sulfide powders such as aluminum sulfide, barium sulfide, and europium 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 substituted.
JP-A-7-122364 WO 2005/085493 JP 2001-294852 A JP-A-8-134440

However, to produce sulfides such as aluminum sulfide, barium sulfide, and europium sulfide, which are raw materials for Eu-added barium thioaluminate sulfide (BaAl ₂ S ₄ ) phosphor, toxic hydrogen sulfide gas must be used. It has a big problem in terms of safety. Furthermore, since this hydrogen sulfide is not only toxic but also a malodorous substance and an unstable substance, strict management is required even in a trace amount, leading to a decrease in manufacturing cost and production efficiency. There are also problems such as.

The present invention has been made in view of the present situation. Eu-added BaAl ₂ O ₄ is heat-treated in an inert gas containing carbon disulfide and subjected to reduction sulfidation, whereby Eu-added barium thioaluminum having high fluorescence brightness. The present invention provides a method for producing a phosphor for inorganic EL, which produces a nate sulfide (BaAl ₂ S ₄ ) phosphor.

The method for producing an inorganic EL phosphor according to the present invention is a method for producing Eu-added barium thioaluminate sulfide for inorganic EL, and is a first method for synthesizing Eu-added BaAl ₂ O _{4 in} which Eu is uniformly dispersed. And a second step in which the Eu-added BaAl ₂ O ₄ obtained in the first step is heat-treated in an inert gas containing carbon disulfide and subjected to reduction sulfidation. It is a manufacturing method of fluorescent substance.

In the first step in this method, Eu nitrate is dissolved in water, aluminum nitrate, oxycarboxylic acid, glycol or water and barium carbonate are sequentially added, and further heated to 120 to 250 ° C. A carbonate precursor is prepared by heat treatment at 500 ° C., and heat treatment is performed at 700 to 1100 ° C. to obtain Eu-added BaAl ₂ O _{4 in} which Eu is uniformly dispersed. In the second step, The Eu-added BaAl ₂ O _{4 in} which Eu is uniformly dispersed obtained in the above step is heat-treated at 800 to 1150 ° C. under an inert gas flow containing carbon disulfide, and is reduced and sulfided. is there.

  Further, the fired product obtained in the second step is pulverized, heat treated at 800 to 1150 ° C. under an inert gas flow containing carbon disulfide, and the step of reducing and sulfiding is repeated twice or more. To do.

The present invention, Eu is a first step of uniformly synthesize dispersed Eu added BaAl ₂ O _4, and Eu added BaAl ₂ O ₄ obtained in the above step, in an inert gas containing carbon disulfide A method for producing a phosphor for inorganic EL characterized by comprising a second step of heat treatment and reductive sulfidation, and sulfides such as aluminum sulfide, barium sulfide, and europium sulfide that are easy to react with moisture in the air as a raw material High-quality crystals can be obtained without using toxic hydrogen, and a high-luminance Eu-added barium thioaluminate sulfide (BaAl ₂ S ₄ ) phosphor can be produced without using toxic hydrogen sulfide. is there.

1. First step of synthesizing Eu-added BaAl ₂ O _{4 in} which Eu is uniformly dispersed:
First, the Eu source to be added is preferably prepared by dissolving europium oxide (Eu ₂ O ₃ ) as a raw material in nitric acid having a concentration of 40 to 60% by mass. In order to completely dissolve the raw material Eu ₂ O ₃ , stirring is performed for about 1 hour. Thereafter, this Eu solution is dried to obtain Eu nitrate.

Next, Eu nitrate is redissolved with water, and aluminum nitrate, glycol and oxycarboxylic acid are added to the solution. Here, water can be used instead of glycol. When the added oxycarboxylic acid is completely dissolved, the liquid temperature is increased to 55 to 65 ° C., and barium carbonate (BaCO ₃ ) is added to obtain a carbonate in which Eu is uniformly dispersed.
Here, the amounts of aluminum nitrate, oxycarboxylic acid and glycol to be added are adjusted to about 1: 3.5: 12 by volume ratio.
In addition, as glycol to add, although ethylene glycol or propylene glycol is especially suitable, polyethyleneglycol can also be used. Citric acid is particularly suitable for the oxycarboxylic acid used, but malic acid, tartaric acid, and the like may be used.

Next, after the carbonate is completely dissolved, the liquid temperature is set to 120 to 250 ° C., more preferably 180 to 220 ° C. for polymerization, and the mixture is stirred until a viscous gel is formed. The stirring time is preferably 4 to 16 hours. Thereby, a polymerized gel containing Eu uniformly is obtained.
Subsequently, the obtained gel is heated to 400 to 500 ° C., more preferably 440 to 460 ° C., and the gel is thermally decomposed to produce an oxide precursor powder.

The obtained oxide precursor powder was lightly pulverized in a mortar and then heat treated to produce Eu-added BaAl ₂ O ₄ in which Eu was uniformly dispersed.
This heat treatment is performed at a heat treatment temperature of 700 to 1100 ° C. Incidentally, the analysis of TG-DTA, occur fired residual organics 600 ° C. Although the BaAl ₂ O ₄ at 890 ° C. or higher, than the BaAl ₂ O ₄ which was completely oxide, low crystallinity Since BaAl ₂ O ₄ is more easily reduced and sulfided, 750 to 890 ° C. at which residual organic matter is eliminated is more preferable. The heat treatment time is 3 to 8 hours, more preferably 4 to 6 hours.

2. Second step of producing Eu-added barium thioaluminate sulfide (BaAl ₂ S ₄ ) phosphor by heat-treating Eu-added BaAl ₂ O ₄ in an inert gas containing carbon disulfide and reducing and sulfidizing it.
In this second step, the Eu-added BaAl ₂ O ₄ powder obtained in the first step is heated in an inert gas containing carbon disulfide (CS ₂ ) at 800 to 1150 ° C. for 5 to 12 hours. Heat treatment is performed to obtain a fired product of Eu-added barium thioaluminate sulfide (BaAl ₂ S ₄ ) phosphor powder.
The temperature of this heat treatment is particularly preferably 950 to 1100 ° C., and if it is less than 800 ° C., reduction sulfidation becomes insufficient, which is not preferable. This is not preferable because it may cause unevenness of the fired product. Further, the sulfur vapor pressure is increased, and sulfur is volatilized from the surface of the reduced and sulfurized Eu-added barium thioaluminate sulfide (BaAl ₂ S ₄ ) phosphor powder, which is not preferable.
As the inert gas used here, Ar gas is preferable, and as a method of including carbon disulfide in the Ar gas, a method of passing Ar gas through liquid carbon disulfide as shown in FIG. 1 can be used. The temperature of carbon disulfide or Ar gas is preferably 15 ° C. or higher and lower than 46 ° C., particularly preferably 20 ° C. or higher and 25 ° C. or lower. If it is less than 15 ° C, the concentration of carbon disulfide contained in the Ar gas is low and reduction sulfidation does not proceed. Is not preferable because it becomes difficult. Note that it is not preferable to use nitrogen as the inert gas because aluminum nitride is formed.

When the fired product of the obtained powder was subjected to X-ray diffraction, an X-ray diffraction pattern including a BaAl ₂ S ₄ phase and a small amount of a different phase was observed. Note that a gas containing carbon disulfide is required during the heat treatment, and it is preferable to continue flowing the gas containing carbon disulfide until the cooling is completed and the temperature reaches room temperature.
Since carbon adheres to the surface of the obtained powder fired product, the luminance is low as it is. Therefore, the luminance can be improved by pulverizing this to make the surface a new surface.

Further, the crushed Eu-added barium thioaluminate sulfide (BaAl ₂ S ₄ ) is again heat-treated at a temperature of 800 to 1150 ° C. under an inert gas flow containing carbon disulfide, and crystallized by repeating reductive sulfidation. Thus, high brightness Eu-added barium thioaluminate sulfide (BaAl ₂ S ₄ ) can be obtained. Even if the number of repetitions is 4 or more times, no further improvement in luminance can be expected, and 2 or 3 times is preferable.

[Preparation of oxide precursor in the first step]
Europium oxide (3N: Eu ₂ O ₃ manufactured by Furuuchi Chemical Co., Ltd.) 0.2454 g was completely dissolved in 1 ml of nitric acid (60% manufactured by Kanto Chemical Co., Ltd.) having a concentration of 15%, and then dried. The obtained nitric acid Eu was redissolved in water, 100 ml of aluminum nitrate solution (0.5589M) was added, and then 66 g of citric acid and 65 g of propylene glycol were added to completely dissolve the citric acid. The temperature was raised to 60 ° C., and 5.2409 g of barium carbonate (BaCO ₃ ) was added and stirred for 12 hours to completely dissolve the barium carbonate. The liquid temperature at that time was 120 ° C.

Next, it was held at 210 ° C. for 5 hours to obtain a polymerized gel. This gel was heated to 450 ° C. using a mantle heater to produce a carbonate.
The obtained carbonate was fired by heat treatment at 700 ° C., 800 ° C., and 1000 ° C. for 5 hours to prepare an oxide precursor.
The oxide precursor calcined at 700 ° C. is considered to be gray and organic matter remains, but the X-ray diffraction pattern of the oxide precursor calcined at 800 ° C. and 1000 ° C. is 800 as shown in FIG. In the oxide precursor calcined at 0 ° C., the peak of BaAl ₂ O ₄ can be seen but the strength is low and the crystallinity is poor, whereas the oxide precursor calcined at 1000 ° C. is good in crystallinity.

[Reduction sulfurization in the second step]
0.3 g of the oxide precursor calcined at 800 ° C. is put in an alumina crucible and heat treated at 1045 ° C. for 6 hours under Ar flowing through liquid carbon disulfide by the method shown in FIG. Then, Eu-added BaAl ₂ S ₄ sulfide was produced. The Ar flow rate was 40 ml / min.
The measurement result of the X-ray diffraction pattern of this fired product is shown in FIG. The peak indicated by the arrow in FIG. 3 is a heterogeneous peak.
Since the surface of Eu-added BaAl ₂ S ₄ sulfide was gray, it was ground in a mortar for 3 minutes to obtain a new surface. The fluorescence measurement results before and after grinding are shown in FIG. Before pulverization is represented by As-prepared, and after pulverization is represented by 3 min ground. It can be seen that the brightness is increased by grinding.

[Repeated sulfurization: 2 times]
The same first step as in Example 1, through the second step, was calcined by reduction sulfurized Eu added BaAl ₂ S ₄ sulfides 0.3 g, in an agate mortar, and the hexane solvent was ground for 5 minutes Into an alumina boat, using the same method as in the second step of Example 1, a second reduction sulfidation was performed under the conditions of 1045 ° C. and 4.5 hours to produce Eu-added BaAl ₂ S ₄ sulfide. did.

[Repeated sulfurization: 3 times]
In the same manner as in Example 2, was repeated reducing sulfide twice Eu added BaAl ₂ S ₄ sulfides 0.3 g, in an agate mortar, and the hexane solvent was ground for 5 minutes, placed in an alumina boat, carried Using the same method as in the second step of Example 1, a third reduction sulfidation was performed at 1045 ° C. for 3 hours to produce Eu-added BaAl ₂ S ₄ sulfide.
The measurement result of the X-ray diffraction pattern of this sulfide is shown in FIG. FIG. 5 shows that almost no heterogeneous peaks appear.

Next, in order to measure the fluorescence of this sulfide, this sulfide was pulverized in the same manner as in Example 1, and the fluorescence before and after pulverization was measured. The result is shown in FIG.
In FIG. 6, the pre-grinding is shown as prepared and the ground is shown as ground. Even after pulverization, the strength comparable to that of the sample after pulverization of Example 1 with only one reduction sulfide is obtained, and after pulverization, the strength obtained is 1.5 times higher than that of the sample after pulverization of Example 1. You can see that

Ar flow through which 0.3 g of the oxide precursor (BaAl ₂ O ₄ : Eu) fired at 1000 ° C. prepared in Example 1 was put in an alumina crucible and passed through liquid carbon disulfide by the method shown in FIG. Then, heat treatment was performed at 1045 ° C. for 3.5 hours, and reduction sulfidation was performed to produce Eu-added BaAl ₂ S ₄ sulfide. The Ar flow rate was 50 ml / min.

[Repeated sulfurization: 2 times]
Through the same steps as in Example 4, 0.3 g of Eu-added BaAl ₂ S ₄ sulfide reduced and sulfided and calcined was pulverized for 5 minutes in an agate mortar using hexane as a solvent and placed in an alumina boat. Using the same method as in the second step 1, a second reduction sulfidation was performed under the conditions of 1045 ° C. and 3.5 hours to produce Eu-added BaAl ₂ S ₄ sulfide.

The measurement results of the X-ray diffraction pattern of the calcined product prepared in Example 4 and 5 (Eu added BaAl ₂ S ₄ sulfides) shown in FIG. 8. In the figure, ● represents the peak position of BaAl ₂ S ₄ . It can be seen from this that reductive sulfidation can be performed even with an oxide precursor fired at 1000 ° C. Moreover, it turns out that the different phase remains in the baked product produced in Example 4 and 5 compared with FIG.

[Conventional example]
10.7 g of commercially available barium sulfide (BaS, manufactured by Alfa AeSar), 0.5 g of europium sulfide (EuS, manufactured by Furuuchi Chemical Co., Ltd.) and 9.9 g of aluminum sulfide (Al ₂ S ₃ ) were weighed, and the humidity was 0.02%. Eu-added BaAl ₂ S ₄ sulfide was prepared in the same manner as in Example 1 except that mixing was performed for 20 minutes using an agate mortar in the following glove box substituted with nitrogen.
The X-ray diffraction pattern of the prepared sample is shown in FIG. As is apparent from FIG. 7, Al ₂ O ₃ is detected in addition to BaAl ₂ S ₄ .

[Brightness evaluation]
In order to compare the luminance, BaMgAl ₁₀ O ₁₇ : Eu (BAM phosphor: manufactured by Kasei Opto), which is well known as a blue phosphor for PDP, and the first, second, third, and conventional examples are used. Comparison was made with the produced Eu-added BaAl ₂ S ₄ phosphor.
The BAM phosphor was excited with excitation light having a wavelength of 305 nm, and the luminance of the obtained fluorescence spectrum was integrated from 400 nm to 600 nm to obtain the integrated intensity of fluorescence. Similarly, the Eu-added BaAl ₂ S ₄ phosphor is also excited with excitation light having a wavelength of 355 nm, the luminance of the fluorescence spectrum is integrated from 400 nm to 600 nm to obtain the integrated intensity of the fluorescence, and the obtained integrated intensity is integrated with the BAM phosphor. The value divided by the intensity was used as the intensity ratio for comparison. The results are shown in Table 1.
Here, from the result of the excitation spectrum, the excitation light 305 nm is the excitation wavelength at which the BAM phosphor is most fluorescent, and the wavelength of 355 nm is the excitation wavelength at which the Eu-added BaAl ₂ S ₄ phosphor is most fluorescent.

According to the method of the present invention, it is possible to produce a high-intensity barium thioaluminate sulfide (BaAl ₂ S ₄ ) phosphor for inorganic EL without using hydrogen sulfide. A phosphor having an intensity of 16% to 28%, and particularly a reductively reduced and sulfurized phosphor, can obtain a much larger intensity, nearly twice as much as that of a phosphor by a conventional method. Further, the excitation light has a practical luminance up to a wavelength of about 400 nm, and thus can be used as a phosphor emitting blue light with a near-ultraviolet LED in the vicinity of a wavelength of 400 nm.

The Ar gas in Embodiment 1 of the present invention is a diagram showing a method to include carbon disulfide (CS _2). In the method of the present invention, showing the X-ray diffraction measurement results of BaAl ₂ O ₄ powder calcined at 800 ° C. and 1000 ° C.. Is a diagram showing an X-ray diffraction measurement results of Eu added BaAl ₂ S ₄ powder in Example 1 of the present invention. It shows the fluorescence spectra before and after grinding of Eu added BaAl ₂ S ₄ powder in Example 1 of the present invention. Is a diagram showing an X-ray diffraction measurement results of Eu added BaAl ₂ S ₄ powder in Example 3 of the present invention. It shows the fluorescence spectra before and after grinding of Eu added BaAl ₂ S ₄ powder in Example 3 of the present invention. It is a figure which shows the X-ray-diffraction measurement result in the prior art example of this invention. It is a figure which shows the X-ray-diffraction measurement result in Example 4 and Example 5 of this invention.

Claims (3)

A method for producing Eu-added barium thioaluminate sulfide for inorganic EL,
Eu nitrate is dissolved in water, aluminum nitrate, oxycarboxylic acid, glycol or water and barium carbonate are sequentially added, and further heated to 120 to 250 ° C. to obtain a gel, and then the gel is heat-treated at 400 to 500 ° C. Then, a carbonate precursor is prepared, and the obtained carbonate precursor is heat-treated at 700 to 1100 ° C. to obtain Eu-added BaAl ₂ O ₄ in which Eu is uniformly dispersed, whereby Eu added BaAl in which Eu is uniformly dispersed. _A first step of synthesizing ₂ O ₄ ;
An inorganic EL phosphor comprising a second step of heat-treating and reducing and sulfiding the Eu-added BaAl ₂ O ₄ obtained in the first step in an inert gas containing carbon disulfide. Production method. In the second step, Eu-added BaAl ₂ O ₄ in which Eu obtained in the first step is uniformly dispersed is heat-treated at 800 to 1150 ° C. under an inert gas flow containing carbon disulfide. The method for producing a phosphor for inorganic EL according to claim 1, wherein the fired product is reduced and sulfided. The fired product obtained in the second step is pulverized, subjected to heat treatment at 800 to 1150 ° C. under an inert gas flow containing carbon disulfide, and reduced and sulfided twice or more. The manufacturing method of the fluorescent substance for inorganic EL of Claim 2 .