JP2016050211A - Method for producing sulfide phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a sulfide phosphor with excellent temperature characteristics of emission intensity.SOLUTION: The present invention provides a method for producing an alkaline earth metal thiogallate sulfide phosphor by activating europium, where, in a step of mixing raw materials, mixed crystals and/or mixtures of gallium oxides and gallium nitrides are used as the gallium source.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a sulfide phosphor.

As a white LED used for a light source for indoor and outdoor general lighting or a backlight of a liquid crystal display, a white color is obtained by combining a blue LED or near-ultraviolet LED with one or more kinds of phosphors. A white light emitting element is generally used. As a phosphor combined with a blue LED or a near ultraviolet LED, there is a yellow phosphor or a combination of a red phosphor and a green phosphor.

Europium activated calcium thiogallate phosphors are known as yellow phosphors, and europium activated strontium thiogallate phosphors are known as green phosphors.

Patent Literature 1 is obtained by firing in a hydrogen sulfide atmosphere using an alkaline earth metal source such as calcium carbonate or strontium carbonate, gallium oxide as a gallium source, and europium oxide as a europium source. Sulfide phosphors are disclosed.

In Patent Document 2, an oxide precursor of a composite oxide of Eu-containing Ga ₂ O ₃ and an alkaline earth metal Sr oxide is prepared and calcined under carbon disulfide conditions. A product phosphor is disclosed.

Non-Patent Document 1 discloses a thiogallate phosphor obtained by mixing an alkaline earth metal carbonate and Ga ₂ O ₃ and heating in hydrogen sulfide.

JP 2007-056235 A JP 2013-234247 A

Isamu Yashima and Junichi Ito, “Processing and Functions of Sulfide Phosphors”, Journal of MMIJ, 2010, Vol. 126, 456-459

The sulfide phosphors manufactured by the manufacturing methods disclosed in Patent Documents 1 and 2 and Non-Patent Document 1 have a problem that the emission intensity decreases when the powder temperature increases due to an increase in ambient temperature during use. .
For this reason, there are problems such as lighting with a sulfide phosphor and a light source for a backlight of a liquid crystal display, etc., as the operating time becomes longer, the ambient temperature rises and the luminance decreases accordingly, and the color purity decreases. It was. Therefore, there has been a demand for a phosphor that does not easily deteriorate the light emission characteristics even when the ambient temperature increases (in other words, the temperature characteristics of the light emission intensity are excellent).

In view of the above problems, an object of the present invention is to provide a method for producing a sulfide phosphor excellent in temperature characteristics of emission intensity.

In the process of mixing sulfide phosphor raw materials, the present inventors use a mixed crystal and / or mixture of gallium oxide and gallium nitride as a gallium source, thereby providing a sulfide having excellent temperature characteristics of emission intensity. The inventors have found that a phosphor can be produced and have arrived at the present invention.

That is, the method for producing a sulfide phosphor of the present invention is a method for producing an alkaline earth metal thiogallate sulfide phosphor obtained by activating europium, and in the step of mixing raw materials, gallium oxide is used as a gallium source. A mixed crystal and / or mixture of gallium nitride is used.

By using a mixed crystal and / or mixture of gallium oxide and gallium nitride as a gallium source, an alkaline earth metal thiogallate sulfide phosphor excellent in temperature characteristics of emission intensity can be obtained.
The reason why the temperature characteristic of the emission intensity is improved by using gallium nitride as the gallium source is not clear, but the sulfide phosphor in which nitrogen is incorporated into a part of the sulfide phosphor and the interstitial bond strength is improved. May be generated.

In the method for producing a sulfide phosphor of the present invention, the amount of gallium nitride contained in the mixed crystal and / or the mixture of gallium oxide and gallium nitride is in the range of 0.1 wt% to 95.0 wt%. It is desirable.

In the method for producing a sulfide phosphor of the present invention, it is desirable that the crystal matrix of the sulfide phosphor is calcium thiogallate represented by the chemical formula CaGa ₂ S ₄ .

In the method for producing a sulfide phosphor of the present invention, the amount of europium in the sulfide phosphor is preferably in the range of 0.005 mol to 0.10 mol with respect to 1 mol of the sulfide phosphor.

According to the method for producing a sulfide phosphor of the present invention, a sulfide phosphor excellent in temperature characteristics of emission intensity can be produced.

FIG. 1 is a graph showing the evaluation results of the temperature characteristics of the sulfide phosphors produced in Examples 1 to 5 and Comparative Example 1. FIG. 2 is an emission spectrum of the sulfide phosphor produced in Examples 1 and 2 and Comparative Example 1.

Hereinafter, the method for producing the sulfide phosphor of the present invention will be described.
The method for producing a sulfide phosphor of the present invention is a method for producing an alkaline earth metal thiogallate sulfide phosphor obtained by activating europium, and in the step of mixing raw materials, gallium oxide and gallium nitride are used as a gallium source. It is characterized by using a mixed crystal and / or a mixture thereof.

The alkaline earth metal thiogallate sulfide phosphor is an alkaline earth in which the crystal matrix of the sulfide phosphor is represented by the general formula AGa ₂ S ₄ [where A is an alkaline earth metal (Ca, Sr or Ba)]. It is a similar metal thiogallate, and is a phosphor obtained by activating the crystal base material with europium.
As the alkaline earth metal, Ca and Sr are preferable.
In the case of strontium thiogallate represented by the chemical formula SrGa ₂ S ₄ , the calcium thiogallate represented by the chemical formula CaGa ₂ S ₄ becomes yellow (maximum wavelength 550 to 560 nm) by irradiation with blue excitation light (wavelength 450 to 470 nm). Becomes phosphors that emit light in green (maximum wavelength 530 to 540 nm) by irradiation with blue excitation light (wavelength 450 to 470 nm), respectively.
Further, when both Ca and Sr are included as the alkaline earth metal, the maximum wavelength of the phosphor can be shifted without lowering the emission intensity by adjusting the molar ratio of Ca and Sr. The maximum wavelength can be set.

Europium is added by substituting a part of the atoms of A in the crystal base material represented by the general formula AGa ₂ S ₄ , and the amount of europium in the sulfide phosphor is 0. The range of 005 mol to 0.10 mol is desirable. More desirably, the amount is 0.03 to 0.05 mol.
In addition, 1 mol of sulfide phosphors here means the mol number of the whole sulfide phosphor after activating europium. Specifically, a general formula of a sulfide phosphor obtained by activating a crystal base material represented by the general formula AGa ₂ S ₄ with europium is represented by a general A _1-x Eu _x Ga ₂ S ₄ , The amount of europium contained in 1 mol of the sulfide phosphor is xmol.
If the amount of europium is too small, sufficient light emission intensity cannot be achieved, and if it is too large, the light emission intensity is saturated, while the light emission intensity is reduced due to concentration quenching.

The alkaline earth metal thiogallate sulfide phosphor may further contain a coactivator other than europium. Although it does not specifically limit as a co-activator, The compound or ion of rare earth elements other than europium is mentioned. Examples of rare earth elements other than the above europium are selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. Examples include at least one element. Examples of the rare earth element compounds include carbonates, oxides, chlorides, sulfates, nitrates, and acetates of the above elements.

In the method for producing a sulfide phosphor of the present invention, a mixed crystal and / or a mixture of gallium oxide and gallium nitride is used as a gallium source in the step of mixing raw materials.
In the method for producing a sulfide phosphor of the present invention, the amount of gallium nitride contained in the mixed crystal and / or the mixture of gallium oxide and gallium nitride is in the range of 0.1 wt% to 95.0 wt%. It is desirable.

A mixed crystal of gallium oxide and gallium nitride (also referred to as a solid solution) is a crystal in which part of the oxygen site of gallium oxide (Ga ₂ O ₃ ) is replaced with nitrogen. It is obtained by firing in a gas stream using a mixed gas with gas.
The concentration of ammonia gas in the mixed gas is desirably 10 to 70 vol%, the firing temperature is preferably 1000 to 1400 ° C., and the firing time is desirably 1 to 10 hours.

When the gallium source is a mixed crystal of gallium oxide and gallium nitride, the amount of gallium nitride contained in the mixed crystal of gallium oxide and gallium nitride is calculated from the powder X-ray diffraction pattern by a total pattern fitting method (WPPF method). The
The amount of gallium nitride in the mixed crystal of gallium oxide and gallium nitride calculated by the total pattern fitting method from the powder X-ray diffraction pattern is desirably in the range of 0.1 wt% to 95.0 wt%. More preferably, it is in the range of 9.0 wt% to 30.0 wt%.
The powder X-ray diffraction pattern can be obtained by measurement under the following conditions using a powder X-ray diffractometer (manufactured by Rigaku Corporation, sample horizontal strong X-ray diffractometer RINT-TTRIII).
・ Target: Cu tube ・ Measurement range (2θ): 60 ° to 90 °
・ Step width: 0.02 °
-Counting time: 1.0 sec.
For the quantification by the total pattern fitting method, the powder X-ray diffraction pattern obtained by the above measurement method is analyzed with a powder X-ray diffraction pattern comprehensive analysis software (JADE Version 7.0, manufactured by Materials Data. Inc.). Can be done.

The mixture of gallium oxide and gallium nitride is simply a mixture of gallium oxide particles and gallium nitride particles.
When the gallium source is a mixture of gallium oxide and gallium nitride, the amount of gallium nitride in the mixture is desirably in the range of 0.1 wt% to 95.0 wt%. The amount of gallium nitride in the mixture is determined by the weight ratio at the time of mixing.

When the gallium source is a mixed crystal of gallium oxide and gallium nitride and a mixture of gallium oxide and gallium nitride, the gallium nitride in the mixed crystal is obtained from the powder X-ray diffraction pattern by a full pattern fitting method (WPPF method). Next, calculate the amount of gallium nitride in the mixture from the charged amounts of gallium oxide and gallium nitride, and multiply the calculated amount of gallium nitride by the ratio of the mixed crystal and the mixture, respectively. What is necessary is just to determine the quantity of gallium nitride contained in the whole source.

The europium source is not particularly limited, and examples thereof include europium carbonate, europium oxide, europium chloride, europium sulfate, europium nitrate, and europium acetate.

Examples of calcium compounds as an alkaline earth metal source include, but are not limited to, calcium carbonate, calcium oxide, calcium hydroxide, calcium halide (calcium chloride, etc.), calcium sulfate, calcium nitrate, calcium hydrogen phosphate, etc. Can be mentioned.
Examples of the strontium compound as the alkaline earth metal source include, but are not limited to, strontium carbonate, strontium oxide, strontium hydroxide, strontium halide (such as strontium chloride), strontium sulfate, strontium nitrate, and strontium hydrogen phosphate. Can be mentioned.
Examples of barium compounds as alkaline earth metal sources include, but are not limited to, barium carbonate, barium oxide, barium hydroxide, barium halide (barium chloride, etc.), barium sulfate, barium nitrate, barium hydrogen phosphate, etc. Can be mentioned.

In the step of mixing the raw materials, these gallium source, europium source, and alkaline earth metal source are mixed at a predetermined molar ratio. In this step, a co-activator other than europium, a dispersant, a flux component, and the like may be further added.
The mixing ratio of the gallium source, the alkaline earth metal source, and the europium source is desirably a molar ratio of about gallium: alkaline earth metal = 2: 1, and gallium: europium = 2: 0.005-0. It is desirable that the molar ratio is about 10.

It is desirable to add water to these mixtures and further mix a pulverization medium such as alumina balls to perform wet pulverization (in other words, mixing by a wet method).
The type of the grinding medium is not particularly limited, and examples thereof include alumina balls, zirconia balls, silicon nitride balls, carbon nitride balls, glass beads, nylon-coated iron core balls, and the like. Mainly used. Of these, alumina balls are preferable.

The pulverization can be performed by a known pulverizer, and the kind thereof is not particularly limited. However, in order to efficiently perform the pulverization, it is preferable to use a reaction vessel equipped with a pulverization medium stirring type pulverizer. Here, the pulverization medium stirring type pulverizer refers to the pulverization medium that is put into the pulverization container and stirred together with the object to be pulverized by rotating and rotating (rotating or revolving) the pulverization container. This is a pulverizer that performs pulverization with direct stirring. An example of the pulverization medium stirring type pulverizer is not particularly limited, but is preferably any one selected from the group consisting of a planetary mill, a bead mill, and a vibration mill. Among these, a planetary mill with rotation and revolution is particularly preferable.

After pulverization, it is desirable to separate the pulverization medium and perform a drying process.
The drying is desirably performed at 110 to 150 ° C. for about 1 to 48 hours using any commonly used dryer.

The solid obtained by drying is preferably made into a powder having an average particle diameter of 60 μm or less by pulverization and classification.
The pulverization can be performed by the above-described pulverization medium stirring type pulverizer.
Subsequently, firing is performed in a sulfur-containing gas atmosphere to generate europium-activated alkaline earth metal thiogallate. As the sulfur source, hydrogen sulfide gas, hydrogen sulfide gas, a mixed gas of carbon disulfide and an inert gas, or the like can be used. Note that nitrogen gas or argon gas can be used as the inert gas. When a mixed gas is used, the concentration of a sulfur compound such as hydrogen sulfide gas or carbon disulfide is preferably 10% by volume or more.
The firing conditions are desirably 700 to 900 ° C. and about 2 to 12 hours.
As a baking apparatus, it can carry out using arbitrary baking furnaces, such as a muffle furnace and a tubular furnace.

The solid obtained by firing is desirably classified into powder having an average particle size of about 10 to 60 μm by pulverization to obtain a sulfide phosphor as a final product.

Through the above process, an alkaline earth metal thiogallate sulfide phosphor obtained by activating europium can be produced.
Since this sulfide phosphor is excellent in temperature characteristics of emission intensity, it can be suitably used as an LED phosphor used for lighting such as indoor and outdoor general lighting or a backlight for a liquid crystal display backlight.

In order to illustrate the present invention in detail, the following examples are given. However, the present invention is not limited to these examples.
(Example 1)
The gallium oxide powder is put in an alumina boat, and a mixed gas of nitrogen gas and ammonia gas is used in a synthetic quartz tubular furnace, and the ammonia gas concentration in the mixed gas is 50 vol. The mixed crystal of gallium oxide and gallium nitride was manufactured by firing at 1100 ° C. for 3 hours in a stream of air.
A predetermined amount was sampled from the mixed crystal to prepare a mixed crystal of gallium oxide and gallium nitride as a gallium source.
The amount of gallium oxide in the mixed crystal prepared in Example 1 was 91.0% by weight, and the amount of gallium nitride was 9.0% by weight.
The amounts of gallium oxide and gallium nitride were calculated from the powder X-ray diffraction pattern by a total pattern fitting method.
The apparatus and conditions for the all-pattern fitting method are as described above.
Table 1 shows the form of the prepared gallium source and the ratio of gallium oxide and gallium nitride.
Calcium carbonate, europium oxide, and mixed crystals of gallium oxide and gallium nitride are weighed as raw materials, pure water is added to the mixture of the weighed raw materials, and φ1.5 mm alumina balls are used as grinding media Then, they were mixed for 180 minutes by a wet method using a planetary ball mill.
The mixing ratio was adjusted so that the molar composition ratio of Ca, Ga, and Eu was (Ca: Ga: Eu = 0.9556: 2: 0.0444).

Subsequently, the slurry of the alumina balls and the raw material mixture was separated, and the obtained slurry was put in a dryer having a set temperature of 130 ° C. and dried overnight.

The obtained solid was pulverized and classified to 40 μm or less with a mortar and pestle, and these mixtures were placed in an alumina boat and baked in a synthetic quartz tubular furnace at 800 ° C. for 8 hours in a hydrogen sulfide gas atmosphere. Hydrogen sulfide gas having a purity of 99.9% was injected into a tubular furnace at 200 mL / min.

Next, the obtained solid was pulverized and classified to 40 μm or less with a mortar and pestle to produce a sulfide phosphor. The obtained sulfide phosphor is obtained by activating calcium thiogallate represented by the chemical formula CaGa ₂ S ₄ with europium, and the sulfide phosphor represented by the chemical formula Ca _0.9556 Eu _0.0444 Ga ₂ S _4. It is. The amount of europium in the sulfide phosphor is 0.0444 mol with respect to 1 mol of the sulfide phosphor.

(Examples 2 and 3)
A predetermined amount of sampling was separately performed from the mixed crystal of gallium oxide and gallium nitride manufactured in Example 1 to prepare mixed crystals having different ratios of gallium oxide and gallium nitride.
In the mixed crystal of gallium oxide and gallium nitride manufactured in Example 1, mixed crystals having different ratios of gallium oxide and gallium nitride are mixed. Therefore, the ratio of gallium oxide and gallium nitride for each sampling is Different.
Otherwise, a sulfide phosphor was produced in the same manner as in Example 1.
The ratio of gallium oxide and gallium nitride in the mixed crystal is shown in Table 1.

(Examples 4 and 5)
A sulfide phosphor was produced in the same manner as in Example 1 except that a mixture of gallium oxide and gallium nitride was prepared and used as the gallium source.
The ratio of gallium oxide and gallium nitride in the mixture is shown in Table 1.

(Comparative Example 1)
A sulfide phosphor was produced in the same manner as in Example 1 except that only gallium oxide was prepared and used as the gallium source.

(Temperature characteristics)
The prepared phosphors of Examples 1 to 5 and Comparative Example 1 were filled in the sample holders, respectively, and the phosphors filled in the sample holders were fixed on a cooling and heating stage installed in a dark place outside the spectrofluorometer. Then, the spectrum was measured at every predetermined temperature while the same sample (phosphor) was heated from room temperature to 153 ° C. at a temperature rising rate of 30 ° C./min.
Specifically, a program (step) for holding the phosphor for 5 minutes at the measurement temperatures of 56 ° C., 82 ° C., 102 ° C., and 153 ° C. for the purpose of stabilizing the powder temperature is applied to the phosphor filled in the sample holder. It was introduced, and the spectrum measurement was performed immediately before the end of the holding.
Spectral measurement at each temperature is performed by applying blue light (wavelength 470 nm) from a blue LED to a measurement sample on a cooling and heating stage installed in a dark place outside a spectrofluorometer (manufactured by JASCO Corporation, FP-6500). Irradiation was performed by introducing the reflected light into a fluorescence integrating sphere unit (manufactured by JASCO Corporation, ISF-513 type) attached to the spectrofluorometer using an optical fiber. The blue LED was lit only during measurement.
In Table 2 and FIG. 1, the evaluation result of the temperature characteristic of the sulfide fluorescent substance produced in Examples 1-5 and Comparative Example 1 is shown. The emission intensity measured at a powder temperature of 25 ° C. was taken as 100%, and compared with the emission intensity measured at a powder temperature of 56 ° C. to 153 ° C., it was shown as a relative intensity (%).

(Luminescent characteristics)
For the sulfide phosphors obtained in Examples 1 and 2 and Comparative Example 1, an emission spectrum was measured using a spectrofluorometer at an excitation wavelength of 450 nm.
Table 3 shows the maximum wavelength and the photoluminescence (Photo Luminescence) relative intensity of the sulfide phosphors of Examples 1 and 2 and Comparative Example 1.
The photoluminescence relative intensity is a relative intensity when the emission intensity in Comparative Example 1 is 100%. FIG. 2 shows emission spectra of the sulfide phosphors produced in Examples 1 and 2 and Comparative Example 1. The maximum wavelength of the sulfide phosphors of Examples 3 to 5 was also 558 to 559 nm.

As shown in Table 2 and FIG. 1, the sulfide phosphor of this example has a larger relative intensity at a powder temperature of 56 ° C. to 153 ° C. than that of Comparative Example 1, and the temperature characteristics of the emission intensity are high. It was possible to improve.
In addition, regardless of whether the gallium source is a mixed crystal or a mixture, the same effect of improving temperature characteristics was obtained when a raw material containing a gallium nitride crystal phase was used as the gallium source.

Further, as shown in Table 3 and FIG. 2, the sulfide phosphor of Example 2 was able to improve the photoluminescence relative intensity by 9% compared to Comparative Example 1. The sulfide phosphor of Example 1 was also able to improve the photoluminescence relative intensity by about 2%.

Claims (4)

A method for producing an alkaline earth metal thiogallate sulfide phosphor obtained by activating europium, wherein a mixed crystal and / or mixture of gallium oxide and gallium nitride is used as a gallium source in the step of mixing raw materials. A method for producing a sulfide phosphor characterized by the above. The method for producing a sulfide phosphor according to claim 1, wherein the mixed crystal of gallium oxide and gallium nitride and / or the amount of gallium nitride contained in the mixture is in the range of 0.1 wt% to 95.0 wt%. . The method for producing a sulfide phosphor according to claim 1 or 2, wherein the crystal base material of the sulfide phosphor is calcium thiogallate represented by a chemical formula CaGa ₂ S ₄ . The method for producing a sulfide phosphor according to any one of claims 1 to 3, wherein the amount of europium in the sulfide phosphor is in the range of 0.005 mol to 0.10 mol with respect to 1 mol of the sulfide phosphor.

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