JP7242368B2 - Manufacturing method of fluoride phosphor - Google Patents

Description

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

2. Description of the Related Art In recent years, as a white light source, a white light emitting diode (LED), which is a combination of a light emitting diode (LED) as an excitation source and a phosphor, has been applied to a backlight source of a display and a lighting device. Among them, a white LED using an InGaN-based blue LED as an excitation source is widely used.

A phosphor used in a white LED is, for example, a phosphor that emits fluorescence in the visible light region that is efficiently excited by the light emitted by the blue LED and that mixes with the blue light emitted by the blue LED itself to produce white light. is desirable. A typical example of a phosphor for a white LED is a Ce-activated yttrium aluminum garnet (YAG) phosphor, which is efficiently excited by blue light and emits broad yellow light. A pseudo-white color can be obtained by combining a YAG phosphor alone with a blue LED. For this reason, white LEDs containing YAG phosphors are used for illumination and backlight sources. There is a problem that the color rendering property is low and the color reproduction range is narrow for backlight applications.

For the purpose of improving color rendering properties and color reproducibility, white LEDs have also been developed in which a red phosphor that can be excited by a blue LED is combined with a green phosphor such as Eu-activated β-sialon or orthosilicate.

As the red phosphor that can be excited by the blue LED, a nitride or an oxynitride having Eu ²⁺ as a luminescence center has a high fluorescence conversion efficiency, a small decrease in luminance at high temperatures, and excellent chemical stability. Phosphors are widely used, and representative ones are those represented by the chemical formulas _Sr2Si5N8Eu2 ⁺ , _CaAlSiN3 :Eu2 ⁺ , and _{( Ca} ,Sr) _AlSiN3 :Eu2 ⁺ . mentioned. However, the emission spectrum of the phosphor using Eu ²⁺ is broad and contains many emission wavelength components with low luminosity. and the YAG phosphor are greatly reduced compared to the phosphor combined with the YAG phosphor. In particular, phosphors used for displays must be compatible with color filters, so phosphors with broad emission spectra are not preferable. has been desired.

Eu ³⁺ and Mn ⁴⁺ are examples of emission centers of red phosphors having sharp emission spectra. Among them, a red phosphor obtained by dissolving Mn ⁴⁺ in a fluoride crystal such as K ₂ SiF ₆ as a solid solution and activating it is also called a KSF phosphor, and is a representative fluoride phosphor (the general formula is , for example K ₂ SiF ₆ :Mn ⁴⁺ ). The KSF phosphor is efficiently excited by blue light and has a sharp emission spectrum with a narrow half width. Therefore, excellent color rendering properties and color reproducibility can be achieved without lowering the brightness of white LEDs, and thus application of K ₂ SiF ₆ :Mn ⁴⁺ phosphors to white LEDs has been actively studied. (See Non-Patent Document 1)

On the other hand, light-emitting devices using white LEDs are required to have high moisture resistance, and phosphors used therein are also required to have similar characteristics. Various methods have been investigated for imparting moisture resistance to the fluoride phosphor itself, and Patent Document 1 discloses a fluoride phosphor in which the surface of fluoride phosphor particles is coated with a fluoride that does not contain Mn. is disclosed.

In the fluoride phosphor disclosed in Patent Document 1, the surface of the fluoride phosphor particles is coated with a fluoride that does not contain Mn, thereby improving its moisture resistance. However, this method is not necessarily sufficient in terms of reducing the dissolution of the fluoride phosphor in water, and cannot be said to be satisfactory depending on the severity of the environment in which it is used and the setting of the limit time for which it can be used. In addition, the members constituting the white LED, which is a general application of this fluoride phosphor, may include silicone resin and metal parts, which are generated by contact between the fluoride phosphor and water. Deterioration such as corrosion and embrittlement occurs due to the influence of hydrogen fluoride and fluorine. Therefore, there remains an improvement point that suppression of such deterioration is required separately.

Moreover, Patent Document 2 discloses a manufacturing method in which the surface of a fluoride phosphor is treated with a compound having a hydrophobic molecule or a hydrophobic functional group.

The fluoride phosphor disclosed in Patent Document 2 is treated with a hydrophobic molecule or a compound having a hydrophobic functional group to improve moisture resistance. However, the operating temperature tends to rise as the output of the white LED increases, and there is a problem that the treatment of only organic substances may not be practical.

Further, Patent Document 3 discloses a method of forming a new surface layer on the surface of a fluoride phosphor by coating treatment.

The fluoride phosphor disclosed in Patent Document 3 is moisture-proof by forming a surface layer through surface coating treatment. However, simply immersing the phosphor particles in a dispersion or solution and heating them lowers the luminescence characteristics, and further improvement has been desired in terms of moisture resistance as well.

Patent Document 4 discloses a method for producing a fluoride phosphor represented by the general formula: A ₂ SiF ₆ :Mn (element A is an alkali metal element containing at least potassium), wherein the solvent contains element A and fluorine. A step of preparing a dissolved aqueous solution, and a step of adding to the aqueous solution a manganese compound that supplies solid silicon dioxide and manganese other than +7 valent manganese, and the amount of the manganese compound added is such that the Mn content in the fluoride phosphor A method for producing a fluoride phosphor in which the amount is in the range of 0.1% by mass or more and 1.5% by mass or less, and the fluoride phosphor is deposited in parallel with the dissolution of silicon dioxide in the aqueous solution. is disclosed.

However, even the phosphor disclosed in Patent Document 4 does not mention that the surface treatment of the phosphor is necessarily necessary, and even if the surface treatment is performed, the method is disclosed in the application of Patent Document 4. In order to remain within the range of publicly known technology at the time, further improvement was sought with respect to improvement of the moisture resistance of the phosphor produced by the method of Patent Document 4.

Japanese Patent Publication No. 2013-533363 JP 2014-141684 A JP 2015-113362 A WO2017/057671

A. G. Paulusz, Journal of The Electrochemical Society, 1973, Vol. 120, No. 7, p. 942-947

An object of the present invention is to provide a method for producing a fluoride phosphor that has improved moisture resistance without impairing light emission properties.

As a result of various studies aimed at solving the above problems, the present inventors have solved the problems by means of the following [1] to [4], and completed the present invention.

[1] The present invention comprises a step of preparing a fluoride phosphor intermediate represented by the following general formula (1), treating the prepared fluoride phosphor intermediate and a silicon-containing compound with a treatment solution containing a manganese reducing agent A method for producing a fluoride phosphor, comprising the step of contacting through
General formula: _{K2SiF6 :} Mn4 ⁺ (1)

[2] The present invention is also preferably the method for producing a fluoride phosphor according to [1], wherein the silicon-containing compound is a compound represented by the following general formula (2).
General formula: Si(OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ ) (2)
(R ¹ , R ² , R ³ and R ⁴ are monovalent hydrocarbon groups.)

[3] In the present invention, it is preferable that the method for producing a fluoride phosphor according to [1] or [2], wherein the treatment solution containing the manganese reducing agent is a solution containing water.

[4] Further, in the present invention, it is preferable that the method for producing a fluoride phosphor according to any one of [1] to [3], wherein the manganese reducing agent is hydrogen peroxide.

[5] Further, the step of preparing the fluoride phosphor intermediate represented by the general formula (1) is
A step of preparing a fluoride phosphor intermediate represented by general formula (1);
and a step of separating and recovering the prepared fluoride phosphor intermediate.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing a fluoride phosphor having better moisture resistance than conventional ones without impairing light emission properties.

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

(Fluoride phosphor)
The present invention is a method for producing a fluoride phosphor. In the present specification, the fluoride phosphor has a tetravalent element site of the fluoride represented by K ₂ SiF ₆ partially substituted with manganese. Fluoride phosphors represented by the general formula K ₂ SiF ₆ :Mn ⁴⁺ , which emit red light when exposed to light, are not included. In this specification, for convenience, the fluoride phosphor represented by the general formula K ₂ SiF ₆ :Mn ⁴⁺ is referred to as "fluoride phosphor intermediate". The fluoride phosphor produced by the production method according to the present invention is obtained by further chemically treating the surface of the above fluoride phosphor intermediate.

As long as the gist of the present invention is not deviated from the gist of the present invention, the fluoride phosphor intermediate may contain a portion of its constituent elements potassium, silicon, fluorine, and manganese in addition to other elements such as sodium, germanium, titanium, and oxygen. Other elements or compounds are included as impurities, elements with different valences partially penetrate or substitute, or some elements in the crystal are missing. . Moreover, as a result, the number indicating the number of atoms in the general formula (1) may change. In addition, the fluoride phosphor intermediate is previously subjected to a treatment other than the treatment performed in the steps included in the method for producing a fluoride phosphor of the present invention, unless it deviates from the gist of the present invention. may be

A fluoride phosphor intermediate used in the method for producing a fluoride phosphor according to the present invention can be prepared using the same production method as for conventional K ₂ SiF ₆ :Mn ⁴⁺ . It is also possible to purchase a commercially available KSF phosphor and prepare it as a fluoride phosphor intermediate as referred to herein without departing from the gist of the present invention. When manufacturing and preparing a fluoride phosphor intermediate, for example, a potassium compound, a silicon compound, a manganese compound is dissolved in hydrofluoric acid and heated to evaporate to dryness, or hydrogen fluoride It is also possible to use a solution obtained by cooling a liquid obtained by dissolving a potassium compound, a silicon compound, or a manganese compound in an acid, or by adding a poor solvent for the fluoride phosphor to lower the solubility and deposit it. The production method disclosed in WO2017/057671 (Patent Document 4) will be exemplified below as one method for producing a fluoride phosphor intermediate.

(Exemplification of methods for manufacturing and preparing fluoride phosphor intermediates)
The fluoride phosphor intermediate used in carrying out the method for producing a fluoride phosphor of the present invention is, for example, (a) a part of a compound (raw material compound) containing an element constituting the fluoride phosphor intermediate is dissolved in the raw material aqueous solution, and (b) another raw material compound is added to the raw material aqueous solution, and the precipitate generated in the raw material aqueous solution (i.e., the fluoride phosphor intermediate) is appropriately removed. It can be collected and further (c) washed, dried, and classified as necessary for preparation. A series of procedures in this method are shown below in (a), (b), and (c).

(B) <Procedure for preparing a raw material aqueous solution in which a part of a compound (raw material compound) containing an element constituting a fluoride phosphor intermediate is dissolved>
The raw material aqueous solution in which a part of the raw material compound is dissolved can be prepared by dissolving, for example, a potassium-containing compound or a fluorine-containing compound in, for example, an aqueous hydrofluoric acid solution or an aqueous hydrosilicofluoric acid solution. Examples of the potassium-containing compound include potassium hydrogen fluoride compounds (KHF ₂ etc.) and potassium fluorides (KF etc.). These can be preferably used because they act both as a source of potassium and as a source of fluorine. In addition, an aqueous hydrofluoric acid solution and an aqueous hydrosilicofluoric acid solution are preferable because they dissolve the potassium-containing compound and at the same time act as a fluorine supply source. When using an aqueous hydrofluoric acid solution, the concentration of hydrogen fluoride is preferably 40 to 70% by mass. Since hydrofluoric acid dissolves many substances, the utensils and containers for handling it are preferably made of chemically stable fluororesin so as not to be contaminated with impurities.

In addition, it is necessary to exceed the lower limit of the potassium concentration in the raw material aqueous solution so that at least the fluoride phosphor intermediate precipitates in the raw material aqueous solution. That is, in the equilibrium relationship between potassium and the fluoride phosphor intermediate in the raw material aqueous solution, it is necessary to exceed the minimum potassium addition concentration at which the fluoride phosphor intermediate becomes at least the saturated concentration or higher in the raw material aqueous solution. . Moreover, the upper limit of the concentration of potassium to be added is the concentration that gives the saturated solubility of the potassium-containing compound to be added to the raw material aqueous solution. Since the upper/lower limits vary depending on the temperature of the aqueous solution of hydrofluoric acid or the like used, the range cannot be uniquely defined.

In addition, a silicon-containing compound may be dissolved in advance in the raw material aqueous solution so as to contain silicon within a concentration range in which K ₂ SiF ₆ crystals are not precipitated. Preferred silicon-containing compounds as silicon sources include silicon dioxide (SiO ₂ ), hydrogen silicofluoride (H ₂ SiF ₆ ), and potassium silicofluoride (K ₂ SiF ₆ ). In particular, hydrogen silicofluoride and potassium fluorosilicofluoride are preferable because they act as a source of silicon and also as a source of potassium and fluorine.

Potassium, fluorine, and silicon contained in the raw material aqueous solution are generally assumed to be ionized, but they do not necessarily have to be free ions. no.

(b) <Procedure for adding another raw material compound to the raw material aqueous solution and appropriately recovering precipitates generated in the raw material solution>
Here, by adding, for example, silicon dioxide and a manganese compound to the raw material aqueous solution obtained in (a), a precipitate, which is a fluoride phosphor intermediate, is obtained in the solution. At this time, the silicon dioxide or manganese compound may be added either in the form of a solution or in the form of a solid. The method for separating and recovering the fluoride phosphor intermediate precipitated in the raw material aqueous solution is not particularly limited, and a known method can be used. By separating and recovering the fluoride phosphor intermediate in this way, it is possible to remove the influence of excess impurities (potassium hydrofluoride, etc.) remaining in the raw material aqueous solution, and the finally obtained fluoride phosphor It is preferable because it can improve the quality of

If solid silicon dioxide is used, it may be crystalline, amorphous, or a mixture thereof. Solid silicon dioxide is not limited in its form, such as bulk or powder, but its dissolution rate in the raw material aqueous solution affects the particle form and size of the precipitated fluoride phosphor intermediate. In consideration of facilitating control of the dissolution rate, the silicon dioxide is preferably powdered. That is, since the dissolution rate of silicon dioxide is largely governed by the area of the contact interface between the added powder and the raw material aqueous solution, the particle size range of the fluoride phosphor intermediate can be adjusted by adjusting the specific surface area of the silicon dioxide powder. can be adjusted. The dissolution rate of silicon dioxide can also be adjusted by the temperature of the liquid in the system, the concentration of hydrofluoric acid, and the like.

The manganese compound is preferably a manganese compound capable of supplying manganese with a valence other than +7, especially manganese with a valence of +4 or less, more preferably manganese with a valence of +4. Manganese with a valence of +7 is difficult to form a solid solution in the mother crystal of the fluoride phosphor according to the present invention, and there is a tendency that a fluoride phosphor with good characteristics cannot be obtained. A preferable manganese compound is a compound that is easily dissolved in a solvent such as hydrofluoric acid, forms MnF ₆ ^2- complex ions in an aqueous solution, and adds +4 valent manganese to a fluoride crystal represented by the general formula: K ₂ SiF ₆ . K ₂ MnF ₆ that can be solid-dissolved is preferred.

The order of adding the silicon dioxide and the manganese compound is not particularly limited as long as it does not interfere with obtaining the fluoride phosphor intermediate used in the present invention. That is, the manganese compound may be added before adding silicon dioxide, at the same time as adding silicon dioxide, or after adding silicon dioxide. Further, the addition operation of each raw material is not limited to one time, and may be divided into multiple times.

In the procedure for precipitating the fluoride phosphor intermediate, the temperature is not particularly limited, but cooling or heating may be carried out as necessary to adjust the dissolution rate of silicon dioxide. For example, the aqueous solution may be cooled, if necessary, because dissolution of silicon dioxide generates heat. Moreover, there is no particular restriction on the pressure to be applied.

(C) <Procedures for further washing, drying, and classifying the collected precipitate as necessary>
The fluoride phosphor intermediate precipitated and recovered in the raw material aqueous solution can be further subjected to post-treatments such as washing, drying and classification, if necessary. As a washing method, a method of washing the recovered fluoride phosphor intermediate using an organic solvent can be employed. In washing, when the fluoride phosphor intermediate is washed with water, part of the phosphor is hydrolyzed to generate a brown manganese compound, which may deteriorate the properties of the resulting phosphor. Therefore, for washing, for example, methanol, ethanol, acetone, etc. are preferably used. Further, by washing several times with hydrofluoric acid before washing with an organic solvent, impurities generated in trace amounts can be dissolved and removed more reliably. The concentration of hydrofluoric acid used for washing is preferably 15% by mass or more from the viewpoint of suppressing hydrolysis of the fluoride phosphor intermediate. Furthermore, it is preferable to dry so as to completely evaporate the washing liquid following washing. Classification is an operation to suppress variation in particle size of the fluoride phosphor intermediate and adjust it within a certain range, and there is no particular limitation on the classification method, and classification can be performed using known methods, tools, and devices. Specifically, a method of sorting using a sieve having a predetermined mesh size is preferably employed.

In this case, the particle size range of the fluoride phosphor intermediate is not particularly limited. Alternatively, D50 can be 5 μm or less (for example, 0.1 μm or more and 5 μm or less, 1 μm or more and 5 μm or less, etc.) for the purpose of obtaining the final fluoride phosphor as a small particle size product. If D50 is larger than 30 μm, the mixture of the phosphor and the resin may cause inconvenience such as clogging of the potting nozzle when manufacturing an LED light emitting device. The particle size can be measured, for example, according to the laser diffraction/scattering method described in JIS Z8825 (2013).

(Example of treatment solution containing manganese reducing agent)
The treatment solution containing the manganese reducing agent, which is prepared when carrying out the method for producing a fluoride phosphor according to the present invention, is obtained by dissolving the manganese reducing agent in a predetermined liquid. When the fluoride phosphor intermediate comes into contact with water or moisture in the air, it may be partially hydrolyzed to produce a brown manganese compound, which may deteriorate its phosphor properties. Therefore, the treatment solution must contain a manganese reducing agent in order to suppress the generation reaction of the manganese compound, which causes deterioration of the properties. Without wishing to be bound by any particular theory herein, the final fluoride It is assumed that a phosphor is obtained.

(manganese reducing agent)
The manganese reducing agent is not particularly limited as long as it can reduce manganese. In a preferred embodiment, the manganese reducing agent is preferably capable of reducing manganese with a valence of +4 or less (eg, Mn ²⁺ , Mn ³⁺ , Mn ⁴⁺ ). Also, it is preferred that the manganese reducing agent is different from the silicon-containing compound (does not contain silicon). More preferably, the manganese reducing agent is capable of reducing manganese with a valence of +4 or less and is not a silicon-containing compound. Specific manganese reducing agents include, for example, hydroxyl radical sources such as hydrogen peroxide, and weak acids such as oxalic acid. Among these, hydrogen peroxide is preferable because it can reduce manganese with a valence of +4 or less without adversely affecting the fluoride phosphor.

Note that the concentration of the manganese reducing agent in the treatment solution is not particularly limited. The concentration of the manganese reducing agent can be appropriately selected according to the total amount of manganese contained in the fluoride phosphor intermediate used in the present invention. Preferably.

In the prior art, when a solution is brought into contact with a _K2SiF6 : ^Mn4+ fluoride phosphor for post-treatment, avoiding the water content of _the solution is necessary to improve the luminescence properties of _K2SiF6 :Mn4 ⁺ _. Although it was one method of preventing deterioration, in the method for producing a fluoride phosphor of the present invention, the treatment solution containing the manganese reducing agent accelerates the reaction between the fluoride phosphor intermediate and the silicon-containing compound. Thus, it is preferable that the material contains moisture, and even if it contains moisture, it has little effect on the light emission characteristics of the fluoride phosphor. Moisture may be directly added or indirectly added to the processing solution from other manganese reducing agents, pH adjusters, etc. Moisture in the atmosphere may be gradually incorporated into the processing solution. may be

A dispersant may also be added to the treatment solution to control the reaction rate between the fluoride phosphor intermediate and the silicon-containing compound. The compound that functions as a dispersant preferably does not contain an element that adversely affects the properties of the phosphor. Specific examples include organic solvents such as alcohol, and from the viewpoint of ease of handling and purchase, methanol and ethanol. is preferred.

Furthermore, a pH adjuster may be added to the treatment solution to control the reaction rate between the fluoride phosphor intermediate and the silicon-containing compound. The pH adjuster preferably does not contain an element that adversely affects the properties of the phosphor, and specifically includes aqueous ammonia, ammonium acetate, acetic acid, hydrochloric acid, and the like.

A surfactant that is positively charged in the treatment solution may be added to the treatment solution in order to adjust the surface properties of the fluoride phosphor intermediate. Specific examples include cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, polyvinylpyrrolidone, and the like. Since the surface state of the fluoride phosphor intermediate may change depending on the synthesis method and post-treatment method, it is possible to obtain the effect of improving moisture resistance by using a surfactant in this way. .

(Exemplification of step of contacting fluoride phosphor intermediate and silicon-containing compound via treatment solution containing manganese reducing agent)
Hereinafter, the method will be described with respect to the step of contacting the fluoride phosphor intermediate and the silicon-containing compound via a treatment solution containing a manganese reducing agent. However, the present invention is not limited to the method of dispersing the fluoride phosphor intermediate in a treatment solution containing a manganese reducing agent and further adding a silicon-containing compound. That is, any method can be adopted as long as it is a method of contacting the treatment solution containing the manganese reducing agent, the fluoride phosphor intermediate, and the silicon-containing compound. A silicon-containing compound is also included in advance in a treatment solution containing a manganese reducing agent, and a fluoride phosphor intermediate is dispersed in this solution, or the particles of the fluoride phosphor intermediate are preliminarily added with silicon in a treatment solution containing a manganese reducing agent. A method of contacting by spraying a solution of the contained compound can also be applied.

(Silicon-containing compound)
The silicon-containing compound is preferably a compound represented by the following general formula (2).
General formula: Si(OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ ) (2)
R ¹ , R ² , R ³ and R ⁴ are symbols representing monovalent hydrocarbon groups. These may be collectively described as R ^{1 to 4} . R ^{1 to R 4} may each be different hydrocarbon groups, or part or all of R ^{1 to 4} may be the same hydrocarbon group.

The number of carbon atoms contained in R ^{1 to 4} is not particularly limited, and from the viewpoint of reactivity, the total number of carbon atoms contained in R ^{1 to 4} is the concentration of the fluoride phosphor intermediate contained in the treatment solution , the temperature of the treatment solution, the pH of the treatment solution, etc., the number of carbon atoms can be appropriately selected. In addition, the number of carbon atoms is preferably 12 or less.

Specific examples of the silicon-containing compound used in the production method of the present invention include tetramethyl orthosilicate, tetraethyl orthosilicate, and tetrapropyl orthosilicate. Tetraethyl orthosilicate is preferred from the viewpoints of availability of the compound and ease of reaction control.

The concentration of the silicon-containing compound in the treatment solution depends on the volume median diameter (D50) of the particles of the fluoride phosphor intermediate used in the present invention, the treatment amount, the temperature of the treatment solution, the pH of the treatment solution, and the like. , can be selected as appropriate. Specifically, for 100.0 g of fluoride phosphor particles (D50: 5 μm) used in the present invention, it is preferable to use, for example, 0.02 to 3.0 mol. For example, it is preferable to use 0.004 to 0.3 mol with respect to 0 g. If the concentration of the silicon-containing compound is low, the moisture resistance of the fluoride phosphor may be insufficiently improved. On the other hand, when the concentration of the silicon-containing compound is too high, the ratio of the fluoride phosphor is relatively decreased, which may deteriorate the light emission characteristics.

In the method of dispersing the fluoride phosphor intermediate in the treatment solution containing the manganese reducing agent and adding the silicon-containing compound, the particles of the fluoride phosphor intermediate are immersed in the treatment solution containing the manganese reducing agent. Further, a silicon-containing compound is added and dispersed by stirring for about 1 minute to 72 hours, and then allowed to stand still for about 1 minute to 30 minutes to obtain a precipitate, ie, a fluoride phosphor. The stirring time can be appropriately adjusted depending on the pH of the treatment solution and the type and amount of the silicon-containing compound used, but it is more preferably 3 to 24 hours from the viewpoint of reactivity and productivity. Furthermore, this precipitate can be collected by solid-liquid separation by filtration, centrifugation, decantation, or the like, and dried by heating at 100° C. to 250° C. for about 1 minute to 24 hours. The heating temperature is preferably 100° C. to 200° C. from the influence on the particles of the fluoride phosphor. The heating time is preferably 2 hours to 10 hours from the viewpoint of the dry state of the powder, productivity, and the like.

In the method for producing a fluoride phosphor of the present invention, a fluoride phosphor intermediate whose chemical composition is represented by the following general formula (1) is brought into contact with a silicon-containing compound via a treatment solution containing a manganese reducing agent. However, after the above steps, another step may be performed as necessary.
General formula: _{K2SiF6 :} Mn4 ⁺ (1)

EXAMPLES Hereinafter, the present invention will be described more specifically by showing examples and comparative examples of the present invention, but the present invention is not limited by the contents of the following examples as long as it does not depart from the gist of the present invention. The fluoride phosphor intermediate K ₂ SiF ₆ :Mn ⁴⁺ was precipitated by adding silicon dioxide and separately prepared K ₂ MnF ₆ powder to a hydrofluoric acid solution containing potassium hydrogen fluoride. It can be prepared by a procedure to recover the precipitate (K ₂ SiF ₆ :Mn ⁴⁺ ).

<Preparation _{of K2MnF6} >
K ₂ MnF ₆ used for preparing the fluoride phosphor intermediate K ₂ SiF ₆ :Mn ⁴⁺ was prepared according to the method described in Non-Patent Document 1. Specifically, 800 ml of hydrofluoric acid with a concentration of 40% by mass was placed in a fluororesin beaker with a capacity of 2000 ml, and 260.00 g of potassium hydrogen fluoride powder (manufactured by Kanto Chemical Co., Ltd.) and potassium permanganate powder (manufactured by Kanto Chemical Co., Ltd.) ) 12.00 g was dissolved. While stirring this hydrofluoric acid solution with a magnetic stirrer, 8 ml of 30% hydrogen peroxide solution (manufactured by Kanto Kagaku Co., Ltd.) was added dropwise little by little. When the dropwise amount of the hydrogen peroxide solution exceeded a certain amount, yellow powder began to precipitate, and the color of the reaction solution began to change from purple. After a certain amount of hydrogen peroxide solution was added dropwise, stirring was continued for a while, and then the stirring was stopped to precipitate precipitated powder. After precipitation, the supernatant was removed, methanol (manufactured by Kanto Kagaku Co., Ltd.) was added, the mixture was stirred, the mixture was allowed to stand, the supernatant was removed, and methanol was further added. This procedure was repeated until the liquid became neutral. After that, the precipitated powder was collected by filtration, dried, and methanol was completely removed by evaporation to obtain 19.00 g of K ₂ MnF ₆ powder. All these operations were performed at room temperature.

<Comparative Example 1>
A method for producing a fluoride phosphor intermediate represented by K ₂ SiF ₆ :Mn ⁴⁺ of Comparative Example 1 is shown below. That is, at room temperature, put 200 ml of 55% by mass hydrofluoric acid (manufactured by Stella Chemifa) in a fluororesin beaker with a capacity of 500 ml, and dissolve 25.6 g of potassium hydrogen fluoride powder (manufactured by Wako Pure Chemical Industries, Ltd.). An aqueous solution was prepared. While stirring this aqueous solution, 6.9 g of silicon dioxide (manufactured by Denka, trade name FB-50R) and 1.2 g of the prepared K ₂ MnF ₆ powder were added. It was visually confirmed that yellow powder (K ₂ SiF ₆ :Mn ⁴⁺ ) began to form in the aqueous solution immediately after adding the silicon dioxide powder. When the silicon dioxide powder was added to the aqueous solution, the temperature of the aqueous solution began to rise due to the generation of heat of dissolution. was completed, the solution temperature dropped.

After the silicon dioxide powder was completely dissolved, stirring of the aqueous solution was continued for a while to complete precipitation of yellow powder, and then the aqueous solution was allowed to stand to precipitate a solid content. After confirming the precipitation, the supernatant is removed, the yellow powder is washed with hydrofluoric acid and methanol (manufactured by Kanto Kagaku Co., Ltd.) having a concentration of 24% by mass, and this is filtered to separate and recover the solid portion. Residual methanol was evaporated off by a drying process. After the drying treatment, using a nylon sieve with an opening of 75 μm, only the yellow powder that passed through this sieve was classified and recovered, and finally 20.3 g of a yellow powdery fluoride phosphor intermediate was obtained.

<Example 1>
A method for producing the fluoride phosphor of Example 1 is shown below. The fluoride phosphor of Example 1 was produced by further subjecting the fluoride phosphor intermediate obtained in Comparative Example 1 to a step of contacting a manganese reducing agent and a silicon-containing compound in a treatment solution. be.

That is, 239.9 g of ion-exchanged water, 146.6 g of ethanol (manufactured by Kanto Chemical Co., Ltd.), 4.0 g of 30% hydrogen peroxide water (manufactured by Kanto Chemical Co., Ltd.), and 40.5 g of ammonia water (manufactured by Wako Pure Chemical Industries, Ltd.) were Stir for 1 minute to mix. This aqueous solution was used as a treatment solution containing a manganese reducing agent, and 10.0 g of the K ₂ SiF ₆ :Mn ⁴⁺ fluoride phosphor intermediate of Comparative Example 1 was put thereinto and stirred for 5 minutes. Next, 6.8 g of tetraethoxysilane (manufactured by Kanto Kagaku Co., Ltd.) was added. After stirring for 3 hours, the aqueous solution was allowed to settle to precipitate solids. After confirming the precipitation, the supernatant was removed and filtered to separate and recover the solid portion, followed by drying (100° C.-3 hours). After the drying treatment, using a nylon sieve with an opening of 75 μm, only the yellow powder that passed through this sieve was classified and recovered, and finally 8.75 g of a yellow powdery fluoride phosphor was obtained.

<Example 2>
A fluoride phosphor of Example 2 was obtained in the same manner as in Example 1, except that the drying treatment conditions were changed to 200° C.-5 hours.

<Example 3>
245.0 g of ion-exchanged water, 1.0 g of 30% hydrogen peroxide solution (manufactured by Kanto Chemical Co., Ltd.), and 0.2 ml of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd.) were stirred and mixed for 5 minutes. This aqueous solution was used as a treatment solution containing a manganese reducing agent, and 10.0 g of the K ₂ SiF ₆ :Mn ⁴⁺ fluoride phosphor intermediate of Comparative Example 1 was added and stirred for 5 minutes. Next, 6.8 g of tetraethoxysilane (manufactured by Kanto Kagaku Co., Ltd.) was added. After stirring for 15 hours, the aqueous solution was allowed to settle to precipitate solids. After confirming the precipitation, the supernatant was removed and filtered to separate and recover the solid portion, followed by drying (100° C.-3 hours). After the drying treatment, using a nylon sieve with an opening of 75 μm, only the yellow powder that passed through this sieve was classified and recovered, and finally 8.70 g of a yellow powdery fluoride phosphor was obtained.

<Reference example 1>
A fluoride phosphor of Reference Example 1 was obtained in the same manner as in Example 3, except that the amount of ion-exchanged water was changed to 470.0 g and the amount of acetic acid was changed to 0.8 ml.

<Example 4>
A fluoride phosphor of Example 4 was obtained by carrying out the treatment in the same manner as in Example 3 except that the drying treatment conditions were changed to 200° C. for 5 hours.

<Example 5>
245.0 g of ion-exchanged water, 1.0 g of 30% hydrogen peroxide solution (manufactured by Kanto Chemical Co., Ltd.), 0.2 ml of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd.), and 0.08 g of cetyltrimethylammonium bromide (manufactured by Tokyo Kasei Co., Ltd.) Stir for 1 minute to mix. This aqueous solution was used as a treatment solution containing a manganese reducing agent, and 10.0 g of the K ₂ SiF ₆ :Mn ⁴⁺ fluoride phosphor intermediate of Comparative Example 1 was added and stirred for 5 minutes. Next, 6.8 g of tetraethoxysilane (manufactured by Kanto Kagaku Co., Ltd.) was added. After stirring for 15 hours, the aqueous solution was allowed to settle to precipitate solids. After confirming the precipitation, the supernatant was removed and filtered to separate and recover the solid portion, followed by drying (100° C.-3 hours). After the drying treatment, using a nylon sieve with an opening of 75 μm, only the yellow powder that passed through this sieve was classified and recovered, and finally 8.72 g of a yellow powdery fluoride phosphor was obtained.

<Comparative Example 2>
50 cm ³ of tetraethoxysilane (manufactured by Kanto Kagaku Co., Ltd.) was prepared. To this, 25.0 g of the fluoride phosphor intermediate of Comparative Example 1 was added, stirred for 10 minutes, and then allowed to stand for 10 minutes. Next, the solid content is separated and recovered by filtration, acetone (manufactured by Kanto Kagaku Co., Ltd.) is sprinkled and washed, filtered again to separate and recover the solid content, and then vacuum dried, finally 22.5 g of yellow color. A powdery fluoride phosphor was obtained.

<Comparative Example 3>
To 10.0 g of the fluoride phosphor intermediate of Comparative Example 1, 0.2 g of tetraethoxysilane (manufactured by Kanto Kagaku Co., Ltd.) was added and mixed. Next, a drying treatment (at 100° C. for 3 hours) was performed. After the drying treatment, using a nylon sieve with an opening of 75 μm, only the yellow powder that passed through this sieve was classified and recovered, and finally 9.4 g of a yellow powdery fluoride phosphor was obtained.

<Comparative Example 4>
To 50 ml of methanol, 0.8 g of silicon dioxide (manufactured by Denka, trade name UFP-80) was added and stirred for 10 minutes, then 10.0 g of the fluoride phosphor intermediate of Comparative Example 1 was added and further stirred for 1 hour. Next, this solution was evaporated to dryness in a drier at 100° C. to obtain 10.4 g of a yellow powdery fluoride phosphor.

<Comparative Example 5>
From the treatment solution containing the manganese reducing agent used in Example 1, 30% hydrogen peroxide solution was removed and the excess was supplemented with ion-exchanged water. ) and 40.5 g of aqueous ammonia (manufactured by Wako Pure Chemical Industries, Ltd.) were mixed to prepare a treatment solution containing no manganese reducing agent, and treatment was carried out in the same manner as in Example 1 except that this solution was used. . However, the fluoride phosphor of Comparative Example 5 uniformly discolored to brown, and hardly exhibited its function as a phosphor.

<Evaluation of moisture resistance of fluoride phosphor>
The moisture resistance of each of the fluoride phosphors of Examples 1 to 5 and Comparative Examples 1 to 4 was evaluated by the following method. excluded from the evaluation). That is, a standard reflector (product name: Spectralon, manufactured by Labsphere) with a reflectance of 99% was set in the side opening (φ10 mm) of an integrating sphere (φ60 mm). A monochromatic light having a wavelength of 455 nm from a light emitting source (Xe lamp) was introduced into this integrating sphere through an optical fiber, and the spectrum of the reflected light was measured with a spectrophotometer (product name: MCPD-7000, manufactured by Otsuka Electronics Co., Ltd.). . At that time, the number of excitation light photons (Qex) was calculated from the spectrum in the wavelength range of 450 to 465 nm. Next, a recessed cell filled with a phosphor so that the surface is smooth is set in the opening of the integrating sphere, irradiated with monochromatic light with a wavelength of 455 nm, and the reflected light of excitation and the spectrum of fluorescence are measured spectrophotometrically. measured by a meter. The number of fluorescence photons (Qem) was calculated from the obtained spectrum data. The number of reflected excitation light photons was calculated in the same wavelength range as the number of excitation light photons, and the number of fluorescence photons was calculated in the range of 465 to 800 nm. The external quantum efficiency (=Qem/Qex×100) was obtained from the obtained three types of photon numbers, and was defined as the emission characteristic Q1. Next, 3 g of phosphor was weighed on a watch glass made of Teflon (registered trademark) and spread thinly. The watch glass was set in a thermo-hygrostat (product name: IW222, manufactured by Yamato Kagaku Co., Ltd.) at 60° C.-90% RH. After reaching 60° C.-90% RH, it was left for 25 hours, and the phosphor was taken out. The emission characteristics of the extracted phosphor were determined by the same measurement method as described above, and were defined as emission characteristics Q2. The retention rate (Q2/Q1×100(%)) of the emission characteristics was calculated from the values of Q1 and Q2 and used as an index of moisture resistance. As shown in Table 1, the retention values of Examples 1 to 5 all exceeded 95%, whereas none of the retention values of Comparative Examples 1 to 4 exceeded 87%. .

From the results of Examples 1 to 5 and Comparative Examples 1 to 4 shown in Table 1, it can be seen that the fluoride phosphors produced by the production method of the present invention have improved moisture resistance.

Although the present invention has been described with reference to the embodiments, the present invention is not limited to these embodiments, and other embodiments, additions, changes, deletions, etc. can be conceived by those skilled in the art. It is included in the scope of the present invention as long as it can be changed within the scope and the effects of the present invention can be exhibited in any aspect.

By carrying out the present invention, it is possible to produce a fluoride phosphor with improved moisture resistance without impairing its light emission (fluorescence) properties.

Claims (4)

A step of preparing a fluoride phosphor intermediate represented by the following general formula (1);
placing the prepared fluoride phosphor intermediate in a treatment solution containing a manganese reducing agent ;
a step of contacting a silicon-containing compound represented by the following general formula (2) with the fluoride phosphor intermediate in the treatment solution containing the manganese reducing agent;
A method for producing a fluoride phosphor, comprising:
General formula: _{K2SiF6 :} Mn4 ⁺ (1)
General formula: Si(OR ¹ ) (OR ² ) (OR ³ ) (OR ⁴ ) (2)
(R ¹ , R ² , R ³ and R ⁴ are monovalent hydrocarbon groups.) 2. The method for producing a fluoride phosphor according to claim 1 , wherein the treatment solution containing the manganese reducing agent is a solution containing water. 3. The method for producing a fluoride phosphor according to claim 1 , wherein said manganese reducing agent is hydrogen peroxide. The step of preparing a fluoride phosphor intermediate represented by general formula (1) includes
A step of preparing a fluoride phosphor intermediate represented by general formula (1);
and separating and recovering the prepared fluoride phosphor intermediate.