TW201529802A - Method for producing fluorescent substance - Google Patents

Abstract

The present invention pertains to a method for producing a fluorescent substance, the method making it possible to produce a composite fluoride-based fluorescent substance represented by the general formula: A2MF6:Mn4+ (in the formula, element A is an alkali metal element including at least K; element M is a metal element of one or more selected from Si, Ge, Sn, Ti, Zr, and Hf, including at least Si; F is fluorine; and Mn is manganese) safely and at high yield, and also making it possible to obtain a fluorescent substance having high external quantum efficiency. The present invention is characterized in including: a step for preparing a reaction solution by dissolving element A, element M, F, and Mn in a solvent comprising hydrofluoric acid so that the molar ratio of element A to element M ([number of mols of element A in reaction solution]/[number of mols of element M in reaction solution]) is within a range of 0.04-1.3; and a step for adding a solid compound of element A to the reaction solution so that the molar ratio of element A in the solid compound to element A in the reaction solution ([number of mols of element A in solid compound]/[number of mols of element A in reaction solution]) is within a range of 1-50 while maintaining the maximum temperature of the reaction solution at 35 DEG C or below, and causing a reaction.

Description

Method of manufacturing phosphor

The present invention relates to a method of producing a phosphor that emits red light when excited by blue light. More specifically, the formula: A ₂ MF ₆ : Mn ⁴⁺ can be obtained safely and with high productivity (the element A contains at least the alkali metal element of K, and the element M contains at least Si selected from Si, Ge, Sn. A composite fluoride phosphor represented by one or more metal elements of Ti, Zr, and Hf), and a method for producing a phosphor having high external quantum efficiency and excellent luminous efficiency can be obtained.

In order to obtain white light for illumination and display, the blue LED chip as a light source is combined with a green phosphor that emits blue to emit green light and a red phosphor that emits blue to emit red light, and the addition of light is utilized. The way of mixing principles is widely used.

For the red phosphor, a nitride phosphor such as CaAlSiN ₃ :Eu, (Sr,Ca)AlSiN ₃ :Eu, or a sulfide phosphor such as (Ca,Sr)S:Eu or the like is known. Formula: A ₂ [MF ₆ ]: Mn ⁴⁺ (Element A is Li, Na, K, Rb, Cs, NH _4, etc., element M is Ge, Si, Sn, Ti, Zr, etc.) The fluorescence spectrum of the fluorescent system is very sharp, and the red phosphor having a deep red color and high brightness is attracting attention (Non-Patent Documents 1 and 2). This phosphor has a structure in which a part of the tetravalent element M has a Mn ⁴⁺ substituted solid solution, and a luminescence spectrum of a plurality of linear light-emitting combinations is exhibited by electron transfer of Mn ⁴⁺ .

With respect to the method for producing a composite fluoride phosphor represented by A ₂ [MF ₆ ]: Mn ⁴⁺ , Patent Document 1 discloses a crystal of A ₂ [MF ₆ ] prepared and contained as a precursor of a phosphor. A method for producing a crystal of K ₂ MnF ₆ of Mn at the center of luminescence, dissolving the crystal of the same in hydrofluoric acid, and evaporating and drying it.

Further, Patent Document 2 discloses a method in which a monomer metal such as hydrazine is immersed in a mixed liquid of hydrofluoric acid and potassium permanganate.

Further, Patent Documents 3 and 4 disclose a method of producing a reaction product in a reaction liquid or a solid state in a reaction liquid in a part of constituent elements in which a fluoride phosphor is dissolved. .

However, in the production method described in Patent Document 1, in order to evaporate hydrofluoric acid, it is a reaction apparatus which is excellent in heat resistance and corrosion resistance, and a device which removes hydrogen fluoride gas which is harmful to human body due to evaporation, and is mass-produced. Underneath, high manufacturing equipment is required.

Further, in the production method described in Patent Document 2, it is difficult to control the amount of manganese in the phosphor to be produced, and the characteristics of the produced phosphor are not uniform, and the produced fluorescent light is left unreacted during production. The luminescence intensity of the body is insufficient, and the productivity is low due to the slow reaction rate of the phosphor.

Further, in the production methods described in Patent Document 3 and Patent Document 4, it is difficult to control the particle size of the precipitated phosphor, and sufficient luminescence characteristics cannot be obtained.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] US Patent Application Publication No. 2006/0169998

[Patent Document 2] International Publication No. 2009/119486

[Patent Document 3] JP-A-2010-209311

[Patent Document 4] JP-A-2012-224536

[Non-patent literature]

[Non-Patent Document 1] A. G. PAulusz, Journal of The Electrochemical Society, 1973, No. 12, No. 7, p. 942-947

[Non-Patent Document 2] A. A. Setlur, et al., Chemistry of Materials, 2010, p. 22, p. 4076-4082

The inventors of the present invention added a compound of a specific element among the constituent elements of the phosphor in a solid state to a raw material having a composition different from that of the phosphor, and dissolved the raw material of the phosphor in hydrofluoric acid. The reaction liquid is further reacted in a specified temperature range and at a specified composition ratio, whereby a phosphor represented by the general formula: A ₂ MF ₆ :Mn ⁴⁺ can be produced safely and with high productivity, and an external quantum can be produced. The highly efficient phosphors, and even the completion of the present invention.

That is, an object of the present invention is to provide a phosphor represented by the general formula: A ₂ MF ₆ : Mn ⁴⁺ (wherein element A is an alkali metal element containing at least K, and element M is at least containing Si). A method for producing one or more metal elements selected from the group consisting of Si, Ge, Sn, Ti, Zr, and Hf, F-based fluorine, and Mn-based manganese, comprising: a molar ratio of element A to element M ([reaction liquid The molar number of the element A in the medium / / [the number of moles of the element M in the reaction liquid] is in a range of 0.04 or more and 1.3 or less, and the element A, the elements M, F and Mn are dissolved in hydrofluoric acid. a step of preparing a reaction liquid by a solvent; and maintaining a maximum temperature of the reaction liquid at 35 ° C or lower, and a molar ratio of the element A in the solid compound to the element A in the reaction liquid (in the solid compound) The molar number of the element A] / [the number of moles of the element A in the reaction liquid) is in the range of 1 or more and 50 or less, and the solid compound of the element A is added to the reaction liquid to carry out the reaction.

The solid compound of the element A is preferably a hydrogen fluoride salt of the element A.

Further, the element A is preferably potassium (K), and the element M is preferably lanthanum (Si).

According to the method for producing a phosphor of the present invention, a phosphor represented by the general formula: A ₂ MF ₆ : Mn ⁴⁺ can be produced safely and with high productivity, and a phosphor having high external quantum efficiency can be obtained.

Fig. 1 is a view showing an X-ray diffraction pattern of the phosphor obtained in Example 1.

[Fig. 2] shows the excitation/fluorescence of the phosphor obtained in Example 1. spectrum.

The present invention is a method for producing a phosphor represented by the general formula: A ₂ MF ₆ : Mn ⁴⁺ .

The element A contains at least an alkali metal element of K, and specifically, in addition to K, it may be Na or Li. In the case of containing an alkali metal element other than K, the K content is preferably from the viewpoint of chemical stability, and it is preferable to have K alone.

The element M is at least one metal element selected from the group consisting of Si, Ge, Sn, Ti, Zr, and Hf, and is preferably Si having excellent chemical stability alone. The excitation band of the phosphor of the present invention is affected by the constituent elements, and particularly has a large influence due to the type of the element M.

In the method for producing a phosphor of the present invention, the starting material is a solid compound in which the reaction liquid and the element A which are dissolved in a specific composition ratio of the element A, the elements M, F and Mn are prepared.

<reaction solution>

The reaction liquid is prepared by dissolving a raw material compound of the supply element A, elements M, Mn, and F in a solvent composed of hydrofluoric acid.

The higher the concentration of hydrogen fluoride of hydrofluoric acid as a solvent, the lower the Mn impurity which is not related to the phosphor. However, when the vapor pressure is too high, the risk of treatment is greatly increased. Therefore, the mass is 50% by mass or more and 70% by mass. % is better.

The element A source, for example, has a fluoride of the element A, a hydrogen fluoride salt, a nitrate salt, a carbonate salt, an acetate salt, and a chloride.

In terms of the element M source, it is preferable to use an oxide, a hydroxide or a carbonate of the element M without using the element M monomer from the viewpoint of stability.

As the Mn source, K ₂ MnF ₆ , KMnO ₄ or the like can be used, but K ₂ MnF _{6 is} preferably used. In the case of K ₂ MnF ₆ , in addition to Mn, F and K (corresponding to element A) constituting the phosphor can be simultaneously supplied, which is preferable.

When the molar ratio of the element A in the reaction liquid to the element M ([the number of moles of the element A in the reaction liquid] / [the number of moles of the element M in the reaction liquid]) is too small, the absorption rate becomes low. There is a tendency that the external quantum efficiency is lowered, and if it is too large, there is a tendency that the amount of heterogeneous formation other than the target phosphor increases. Therefore, the blending amount of the raw material compound is adjusted so that the molar ratio of the element A in the reaction liquid to the element M is in the range of 0.04 or more and 1.3 or less.

<Solid compound of element A>

In the case of the solid compound of the element A, specifically, a fluoride, a hydrogen fluoride, a nitrate, a carbonate, an acetate or a chloride of the element A can be used. Among them, those which do not generate heat when dissolved in the hydrofluoric acid reaction solution are preferred, and a hydrogen fluoride salt is preferred.

The solid compound may be in the form of a granule such as a powder or a granule, or a lumpy form obtained by press molding the granules. The difference in these forms affects the dissolution and the precipitation reaction of the phosphor when added to the reaction solution, and affects the particle size and distribution of the available phosphor. When the solid compound of the element A is added to the reaction liquid in a fine state, the particle size of the phosphor which can be obtained becomes fine, and when it is added in a large block state, the particle size of the phosphor which can be obtained becomes large.

The solid compound of the element A is prepared so that the element A in the solid solution can be a specific molar ratio in order to precipitate the phosphor having a high purity with a high productivity and to prepare the element A in the reaction liquid.

That is, the element A in the solid compound is relative to the reaction liquid. When the amount of the element A is too small, the external quantum efficiency of the available phosphor tends to be low, and if there is too much, the characteristic variation of the obtained phosphor tends to be large. Therefore, the molar ratio of the element A in the solid compound to the element A in the reaction liquid ([the number of moles of the element A in the solid compound] / [the number of moles of the element A in the reaction liquid]) Adjustment is made in a range of 1 or more and 50 or less.

<Reaction Step of Reaction Liquid with Solid Compound of Element A>

The method for producing a phosphor of the present invention is a reaction of a reaction liquid with a solid compound of the element A at a constant temperature or lower.

When the solid compound of the element A is added to the reaction liquid, the temperature of the reaction liquid rises. As the temperature in the reaction liquid rises, Mn dissolved in the reaction liquid also becomes a compound other than the fluoride phosphor, and this compound becomes an impurity. Since this impurity has a color, it interferes with the fluorescent light when it coexists with the phosphor. In order to avoid the generation of such impurities, the maximum temperature of the reaction liquid in the reaction step is maintained at 35 ° C or lower.

When the solid compound of the element A is dissolved in the reaction liquid, the phosphor is partially supersaturated to precipitate the phosphor.

<post processing>

In the method for producing a phosphor of the present invention, in the post-treatment, it is preferred to carry out a washing step and a classification step for the phosphor produced in the above-described reaction step.

In the case of washing, the phosphor is separated by solid-liquid separation by filtration or the like, and washed with an organic solvent such as methanol, ethanol or acetone. When the phosphor is washed with water, a part of the phosphor is hydrolyzed to form a brown color. The manganese compound reduces the characteristics of the phosphor. Therefore, in the washing step, it is necessary to use an organic solvent. Further, when washing with a hydrofluoric acid reaction solution several times before washing with an organic solvent, impurities generated in a small amount can be dissolved and removed. From the viewpoint of suppressing hydrolysis of the fluoride phosphor, the concentration of the hydrofluoric acid used for washing is preferably 15% by mass or more. Preferably, after the washing step, the phosphor is dried to completely evaporate the washing liquid.

Further, by classifying using a sieve having an opening of a predetermined size, it is possible to suppress unevenness in particle size of the phosphor and to adjust it within a certain range.

[Examples]

The invention is illustrated in more detail by the examples shown below. Table 1 shows the composition ratio of the starting materials and specific elements used in the production methods of the respective Examples and Comparative Examples, the maximum temperature of the reaction liquid, and various evaluation results.

In Table 1, the composition ratio [the number of moles of K in the solid compound] / [the number of moles of K in the reaction liquid] is contained in the K ₂ MnF ₆ and KHF ₂ raw materials dissolved in the reaction liquid. The molar number of K is calculated from the number of moles of K contained in the KHF ₂ raw material added as a solid compound.

In addition, the composition ratio [the number of moles of K in the reaction liquid] / [the number of moles of Si in the reaction liquid] is the K contained in the K ₂ MnF ₆ and KHF ₂ raw materials dissolved in the reaction liquid. The number of ears and the number of moles of Si contained in the SiO ₂ raw material dissolved in the reaction liquid were calculated.

The maximum temperature (° C.) of the reaction liquid was measured using a Sheath thermocouple (K type) coated with a fluororesin.

The productivity (unit: %), the crystal phase (x-ray diffraction), the external quantum efficiency at the excitation wavelength of 455 nm, and the emission peak wavelength in the method for producing a phosphor of the examples and the comparative examples were measured in the following manner.

The productivity is a ratio of the mass of the actually obtained phosphor with respect to the theoretical mass in the case where all of Si and Mn of the SiO ₂ and K ₂ MnF ₆ raw materials are K ₂ SiF ₆ :Mn. The preferred productivity is 60% or more, and the more preferable productivity is 70% or more.

The crystal phase (X-ray diffraction) was judged by an X-ray diffraction pattern and measured by an X-ray diffraction apparatus (Ultima IV, manufactured by Rigaku Corporation). This assay uses a CuK alpha tube. Specifically, it is judged whether or not the crystal is the same pattern as the K ₂ SiF ₆ crystal, and whether it is the same pattern as the KHF ₂ crystal.

The external quantum efficiency was measured by using a spectrofluorometer (F-7000, manufactured by Hitachi High-Technologies Co., Ltd.) to measure the excitation/fluorescence spectrum of the phosphor. The excitation spectrum of the fluorescence spectrum is 455 nm, and the excitation spectrum of the excitation spectrum is 632 nm. The integrating sphere is used for the phosphor. Full beam luminescence spectroscopy was performed.

This measurement was carried out in accordance with the quantum efficiency measurement of the NBS standard phosphor of Okubo and Akira et al. (Lighting Society, Heisei 11, Vol. 83, No. 2, p. 87-93). The split Xe light source is split for use as excitation light.

A preferred external quantum efficiency is 0.35 or more, and a more preferable external quantum efficiency is 0.45 or more.

The emission peak wavelength was obtained by performing fluorescence/luminescence spectrometry of a phosphor using a spectrofluorometer (F-7000, manufactured by Hitachi High-Technologies Co., Ltd.). The excitation wavelength of the fluorescence spectrum was set to 455 nm, and the excitation wavelength of the excitation spectrum was set to 632 nm.

Example 1

<preparation step>

Reaction solution

K ₂ MnF ₆ powder was produced by the method described in Non-Patent Document 1. Specifically, 800 ml of hydrofluoric acid having a concentration of 40% by mass is placed in a fluororesin beaker having a capacity of 1 liter, and KHF ₂ powder (manufactured by Wako Pure Chemical Industries, Ltd., special grade test) 260 g and potassium permanganate powder are placed. (produced by Wako Pure Chemical Industries Co., Ltd., reagent grade 1) 12 g dissolved. The hydrofluoric acid reaction solution was stirred with a magnetic stirrer, and 8 ml of 30% hydrogen peroxide water (special grade reagent) was dropped little by little. When the amount of the hydrogen peroxide water dropped exceeds a certain amount, the yellow particles start to precipitate, and the color of the reaction liquid changes from purple. After a predetermined amount of hydrogen peroxide water was dropped, stirring was continued, and the stirring was stopped to precipitate precipitated particles. After the precipitation is repeated, the upper clear liquid is removed, methanol is added, and the mixture is stirred/rested, and the upper clear liquid is removed, and methanol is added until the liquid becomes neutral. Thereafter, the precipitated particles were collected by filtration, dried, and completely evaporated by methanol to obtain 19 g of K ₂ MnF ₆ powder. These operations are all carried out at room temperature.

Next, 28.8 g of SiO ₂ powder (purity: 99%, manufactured by High Purity Chemical Research Laboratory Co., Ltd.) was dissolved in 840 ml of a hydrofluoric acid having a concentration of 55% by mass in the blending amount shown in Table 1. Since it is heated due to dissolution, it is left to cool to room temperature. After sufficiently cooling, 7.2 g of K ₂ MnF ₆ powder prepared as described above and 36 g of KHF ₂ powder (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent) were sequentially dissolved to prepare a reaction liquid. The K ₂ MnF ₆ powder and the KHF ₂ powder system were completely dissolved, and the temperature of the solution at that time was slightly increased. The K present in the reaction liquid was 0.519 mol, and Si was 0.48 mol. The composition ratio in the reaction liquid [the number of moles of K in the reaction liquid] / [the number of moles of Si in the reaction liquid] was 1.08.

2. Solid shape compound

The KHF ₂ powder (manufactured by Wako Pure Chemical Industries, Ltd., special grade reagent) of 76.56 g which is a solid form compound which is different from the above reaction liquid was prepared. The K of the solid-form compound is 0.980 mol, and therefore, the composition ratio of K in the solid solution compound to K in the above reaction liquid [molar number of K in the solid compound] / [in the reaction liquid The molar number of K is 1.89.

<Reaction step>

The above solid solution compound was added little by little to the above reaction liquid. With the addition, the formation of yellow powder was visually confirmed. After the KHF ₂ powder was added in its entirety, it was stirred for 10 minutes, and then allowed to stand to precipitate a solid portion. The maximum temperature of the reaction solution was 28 °C.

After the precipitation was confirmed, the upper clear liquid was removed, and 20% by mass of hydrofluorocarbon was used. The acid and methanol were washed, and the solid portion was separated and recovered by filtration, and the residual methanol was removed by evaporation.

For the dried phosphor, a sieve made of 75 μm mesh was used, and the sieve was passed through only the sieve to obtain 87 g of a yellow powder.

When it is assumed that all of Si and Mn of the SiO ₂ and K ₂ MnF ₆ raw materials are K ₂ SiF ₆ :Mn, the productivity with respect to the theoretical yield of 108 g is 81%.

The X-ray diffraction pattern of the phosphor obtained in the method for producing a phosphor of Example 1 was measured by an X-ray diffraction apparatus (Ultima IV, manufactured by Rigaku Corporation). The measurement system used CuKα tube balls. The measurement results are shown in Fig. 1.

It was confirmed that the fluorescent system produced by the method for producing a phosphor of Example 1 has the same pattern as the K ₂ SiF ₆ crystal, and does not contain another crystal phase.

The excitation/fluorescence spectrum of this phosphor was measured by a spectrofluorometer (F-7000, manufactured by Hitachi High-Technologies Co., Ltd.). The measurement results are shown in Fig. 2. The excitation spectrum of the fluorescence spectrum in this measurement was 455 nm, and the excitation fluorescence wavelength of the excitation spectrum was 632 nm.

It was confirmed that the fluorescent system has two excitation bands of ultraviolet light having a peak wavelength of around 350 nm and blue light having a peak wavelength of around 450 nm, and a plurality of bands of light emission in a red region of 600 to 700 nm.

The external quantum efficiency of this phosphor when excited by blue light having a wavelength of 455 nm is 0.512. The method of measuring the external quantum efficiency uses the aforementioned method.

Fluorescence spectrum excitation using a spectrofluorometer (F-7000, manufactured by Hitachi High-Technologies) The wavelength was set to 455 nm, and the emission peak wavelength was measured, and it was confirmed that it had a peak at 632 nm.

<Examples 2 to 4, Comparative Examples 1 to 3>

In Examples 2 to 4 and Comparative Examples 1 to 3, the amounts of SiO ₂ powder, K ₂ MnF ₆ powder, and KHF ₂ powder in the reaction liquid and the solid form compound were set to values shown in Table 1, and Example 1 was used. Made in exactly the same way.

As shown in Comparative Example 1 and Comparative Example 3, the molar ratio of K to Si in the reaction liquid ([molar number of K in the reaction liquid] / [molar number of Si in the reaction liquid]) and solid When K in the compound is deviated upward with respect to K molar ratio in the reaction liquid ([molar number of K in the solid compound] / [molar number of K in the reaction liquid)), in addition to K ₂ In addition to SiF ₆ : Mn, KHF ₂ is present in a heterogeneous phase, and the external quantum efficiency is remarkably lowered.

Further, as shown in Comparative Example 2, the molar ratio of K in the solid compound to K in the reaction liquid ([the number of moles of K in the solid compound] / [the number of moles of K in the reaction liquid) ]) When the deviation is downward, productivity is significantly reduced.

<Comparative Example 4>

In the same manner as in Example 1, except that the KHF ₂ powder added in a solid state was changed to KF powder (a special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.), the comparative example 4 was produced. The KF addition amount was set to 56.9 g, and the enthalpy became the same molar number as the solid KHF ₂ powder added in Example 1. After the addition of the KF powder, the temperature of the reaction liquid was raised to 60 ° C due to the heat of dissolution of KF. After completion of the reaction, the mixture was allowed to cool to room temperature, and the precipitate was collected in the same manner as in Example 1.

The productivity of the phosphor in Comparative Example 4 was 75%, and the crystal phase confirmed by X-ray diffraction measurement was only K ₂ SiF ₆ phase, and the average particle diameter was 13 μm. However, as a result of quantum efficiency measurement, the absorption rate was 0.752, and the external quantum efficiency was 0.340. It was confirmed that the external quantum efficiency of the obtained phosphor was remarkably lowered because the reaction step in the precipitation of the phosphor exceeded 35 °C.

Claims (3)

A method for producing a phosphor, which is a phosphor represented by the general formula: A ₂ MF ₆ : Mn ⁴⁺ (wherein element A contains at least an alkali metal element of K, and element M contains at least Si). A method for producing one or more metal elements selected from the group consisting of Si, Ge, Sn, Ti, Zr, and Hf, F-based fluorine, and Mn-based manganese, comprising: a molar ratio of element A to element M ([reaction liquid The molar number of the element A in the medium / / [the number of moles of the element M in the reaction liquid] is in a range of 0.04 or more and 1.3 or less, and the element A, the elements M, F and Mn are dissolved in hydrofluoric acid. a step of preparing a reaction liquid by a solvent; and maintaining a molar ratio of the element A in the solid compound to the element A in the reaction liquid while maintaining the maximum temperature of the reaction liquid at 35 ° C or lower (in the solid compound) The molar number of the element A] / [the number of moles of the element A in the reaction liquid] is in the range of 1 or more and 50 or less, and the solid compound of the element A is added to the reaction liquid to carry out the steps of the reaction. The method for producing a phosphor according to claim 1, wherein the solid compound of the element A is a hydrogen fluoride salt of the element A. A method of producing a phosphor according to claim 1 or 2, wherein the element A is potassium and the element M is ruthenium.