JP2020172633A - Red phosphor and method for producing the same - Google Patents

Abstract

To provide: a red phosphor excellent in optical characteristics and durability in high-temperature, high-humidity environments; and a method for producing the same.SOLUTION: The red phosphor according to the present invention contains a Mn-activated complex fluoride represented by general formula (1) defined by A2MF6:Mn4+, and bismuth. (In the formula, A represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium and cesium, and M represents at least one tetravalent element selected from the group consisting of silicon, germanium, tin, titanium, zirconium and hafnium.)SELECTED DRAWING: None

Description

The present invention relates to a red phosphor that is excited by excitation light such as ultraviolet light and blue light to emit red light, and a method for producing the same. More specifically, the present invention relates to a red phosphor having excellent optical properties and durability in a high temperature / high humidity environment by containing bismuth in a Mn (manganese) activated compound fluoride, and a method for producing the same.

White LEDs (Light Emitting Diodes) have a longer life and lower power consumption than fluorescent lamps. Therefore, it has rapidly become widespread as a backlight for lighting equipment and displays. A white LED of a commercially available lighting fixture is composed of a combination of a blue LED that emits near-ultraviolet light to blue light and a yellow phosphor that is excited by the light. As a result, the white LED makes it possible to irradiate pseudo-white light by mixing the light emitted by the blue LED and the light emitted by the yellow phosphor. However, since the pseudo white light emitted by the white LED contains little or no light emitting component in the red light region, the pseudo white light has a color rendering property (or sunlight, black body radiation) as compared with natural light (or sunlight, black body radiation). It means the characteristics of the appearance of color under the illumination when the object is visually recognized as compared with natural light. For example, when the object is illuminated by the illumination, the appearance of the color is similar to that when the object is illuminated by the natural light. When it is the one, it shows high color rendering properties.) There is a problem that it is inferior.

Therefore, there is a need for a red phosphor that emits red light by being excited by ultraviolet light emitted by a near-ultraviolet LED or blue light emitted by a blue LED. As such a red phosphor, in recent years, a phosphor composition composed of Mn-activated compound fluoride (K ₂ SiF ₆ : Mn ⁴⁺ (KSF: Mn)) that emits red light centered on the transition metal Mn ⁴⁺ ion. Has been developed (see, for example, Patent Documents 1 and 2 and Non-Patent Document 1), and its adoption is rapidly advancing. KSF: Mn has an excitation band at the wavelength of blue light, and has a red emission peak with a narrow half-value width in a narrow band of 600 to 650 nm.

KSF: Mn is formed by the solid ^dissolution of Mn ⁴⁺ ions at the Si ⁴⁺ position of the hexacoordination-octahedral site formed by the K ₂ SiF ₆ crystals acting as the framework of the phosphor and the SiF ₆ ^2- ions. It forms MnF ₆ ^2- octahedral sites and acts as a light emitting center.

However, it has been pointed out that this red phosphor composed of KSF: Mn has a practical problem that the particle surface is darkened when it comes into contact with water, water vapor or the like in a high temperature and high humidity environment. Specifically, manganese dioxide is generated by the reaction of water with the tetravalent manganese ions constituting the red phosphor on the particle surface of the red phosphor, and this manganese dioxide absorbs and fluoresces the excitation light. The suppression of the optical characteristics is caused, and the optical characteristics are deteriorated and the optical characteristics are deteriorated with time (decrease in durability).

Special Table 2009-528429 WO2015 / 093430

H. D. Nguyen, C.I. C. Lin, R.M. S. Liu, Angew. Chem. Vol. 54, No. 37, p. 10862 (2015)

The present invention has been made in view of the above problems, and an object of the present invention is to provide a red phosphor having excellent optical characteristics and durability in a high temperature / high humidity environment and a method for producing the same.

The red phosphor according to the present invention is characterized by containing Mn-activated compound fluoride represented by the following general formula (1) and bismuth in order to solve the above-mentioned problems.

A ₂ MF ₆ : Mn ⁴⁺ (1)
(In the formula, A represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium and cesium, and M represents from the group consisting of silicon, germanium, tin, titanium, zirconium and hafnium. Represents at least one tetravalent element selected.)

In the above configuration, the Mn-activated compound fluoride is in the form of particles, and the bismuth can be present on at least a part of the surface of the particulate Mn-activated compound fluoride.

Further, in the above configuration, a coating layer may be provided on the surface of the particulate Mn-activated difluoride, and the coating layer may contain the bismuth.

Further, in the above configuration, it is preferable that the coating layer is composed of a bismuth simple substance and / or a bismuth compound.

Further, in the above configuration, the bismuth compound is BiF ₃ , BiCl ₃ , BiBr ₃ , BiI ₃ , Bi ₂ O ₃ , Bi ₂ S ₃ , Bi ₂ Se ₃ , BiSb, Bi ₂ Te ₃ , Bi. (OH) ₃ , (BiO) ₂ CO ₃ , BiOCl, BiPO ₄ , Bi ₂ Ti ₂ O ₇ , Bi (WO ₄ ) ₃ , Bi ₂ (SO ₄ ) ₃ , BiOCH ₃ COO, 4 BiNO ₃ (OH) _2. BiO (OH), C ₃ F ₉ O ₉ S ₃ Bi, C ₇ H ₇ BiO ₇ , C ₉ H ₂₁ BiO ₃ , C ₁₅ H ₃₃ BiO ₃ , C ₃₀ H ₅₇ BiO ₆ , C ₁₂ H ₁₀ BiK ₃ O It is preferably at least one selected from the group consisting of ₁₄ , C ₃ F ₉ O ₉ S ₃ Bi, and C ₆ H ₄ (OH) CO ₂ BiO · H ₂ O.

In the above configuration, the content of the bismuth is preferably in the range of 0.01% by mass to 15% by mass with respect to the total mass of the red phosphor.

In the above configuration, the molar ratio of Mn in the Mn-activated compound fluoride is preferably in the range of 0.005 to 0.15 with respect to the total number of moles of M and Mn.

The method for producing a red phosphor of the present invention includes a step of bringing a treatment liquid containing bismuth into contact with the Mn-activated difluoride represented by the following general formula (1) in order to solve the above-mentioned problems. It is characterized by that.

A ₂ MF ₆ : Mn ⁴⁺ (1)
(In the formula, A represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium and cesium, and M represents from the group consisting of silicon, germanium, tin, titanium, zirconium and hafnium. Represents at least one tetravalent element selected.)

In the above configuration, the content of the bismuth in the treatment liquid is preferably in the range of 0.01% by mass to 15% by mass with respect to the total mass of the treatment liquid.

In the above configuration, it is preferable that the solvent of the treatment liquid is water, an organic solvent, a mixed solvent thereof, or an acidic solvent thereof.

In the above configuration, the acidic solvent is an acidic solvent containing hydrogen fluoride, and the mixing ratio of the acidic solvent containing hydrogen fluoride and the bismuth is 30: 1 to 3500: 1 on a mass basis. It is preferably in the range.

In the above configuration, the concentration of the hydrogen fluoride in the acidic solvent containing hydrogen fluoride is preferably in the range of 1% by mass to 70% by mass with respect to the total mass of the acidic solvent.

In the above configuration, the bismuth is Bi alone, BiF ₃ , BiCl ₃ , BiBr ₃ , BiI ₃ , Bi ₂ O ₃ , Bi ₂ S ₃ , Bi ₂ Se ₃ , BiSb, Bi ₂ Te ₃ , Bi. (OH) ₃ , (BiO) ₂ CO ₃ , BiOCl, BiPO ₄ , Bi ₂ Ti ₂ O ₇ , Bi (WO ₄ ) ₃ , Bi ₂ (SO ₄ ) ₃ , BiOCH ₃ COO, 4 BiNO ₃ (OH) _2. BiO (OH), C ₃ F ₉ O ₉ S ₃ Bi, C ₇ H ₇ BiO ₇ , C ₉ H ₂₁ BiO ₃ , C ₁₅ H ₃₃ BiO ₃ , C ₃₀ H ₅₇ BiO ₆ , C ₁₂ H ₁₀ BiK ₃ O It is preferable that it is contained in the treatment liquid as at least one selected from the group consisting of ₁₄ , C ₃ F ₉ O ₉ S ₃ Bi, and C ₆ H ₄ (OH) CO ₂ BiO · H ₂ O.

The present invention achieves the effects described below by the means described above.
That is, according to the red phosphor of the present invention, the inclusion of bismuth in addition to the Mn-activated difluoride reduces or prevents the reaction of Mn ⁴⁺ with water to produce colored manganese dioxide. As a result, it is possible to prevent the absorption of excitation light and the suppression of fluorescence by manganese dioxide, so that the optical characteristics are good, the deterioration of the optical characteristics due to aging in a high temperature and high humidity environment is reduced, and the red color has excellent durability. A phosphor can be provided.

Further, according to the method for producing a red fluorescent substance of the present invention, a red fluorescent substance containing bismuth can be produced by bringing a treatment liquid containing bismuth into contact with the Mn-activated difluoride. As a result, it is possible to produce a red phosphor having good optical characteristics, reducing the deterioration of the optical characteristics due to aging in a high temperature and high humidity environment, and having excellent durability.

(Red phosphor)
The red phosphor according to the present embodiment will be described below.
The red phosphor according to the present embodiment contains Mn-activated compound fluoride represented by the following general formula (1) (hereinafter, may be referred to as “Mn-activated compound fluoride”) and bismuth.

A ₂ MF ₆ : Mn ⁴⁺ (1)
(In the formula, A represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium and cesium, and M represents from the group consisting of silicon, germanium, tin, titanium, zirconium and hafnium. Represents at least one tetravalent element selected.)

The red phosphor of the present embodiment may be a single red phosphor or a mixture of two or more kinds of red phosphors.

In the general formula A ₂ MF ₆ : Mn ⁴⁺ representing the Mn-activated compound fluoride, “A ₂ MF ₆ ” represents the composition of the parent crystal of the red phosphor. Further, "Mn ⁴⁺ " represents an activated ion that is the center of light emission.

Here, "activation" as used herein means adding Mn ⁴⁺ , which is an activator, to A ₂ MF ₆ , which is a parent crystal, in order to express fluorescence. Examples of the activated form include a form in which Mn ⁴⁺ is partially replaced with an arbitrary atom constituting A ₂ MF ₆ . In the case of this embodiment, it is preferable that Mn ⁴⁺ is replaced with M of the mother crystal.

Specific examples of the Mn-activated compound fluoride represented by the general formula A ₂ MF ₆ : Mn ⁴⁺ include, for example, Li ₂ SiF ₆ : Mn ⁴⁺ , Na ₂ SiF ₆ : Mn ⁴⁺ , and K ₂ SiF ₆ : Mn. ^{_{4+, Rb 2 SiF 6: Mn}} 4+, Cs 2 SiF 6: Mn 4+, Li 2 GeF 6: Mn 4+, Na 2 GeF 6: Mn 4+, K 2 GeF 6: Mn 4+, Rb 2 GeF 6: Mn 4+, ^{_{Cs 2 GeF 6: Mn 4+,}} Li 2 SnF 6: Mn 4+, Na 2 SnF 6: Mn 4+, K 2 SnF 6: Mn 4+, Rb 2 SnF 6: Mn 4+, Cs 2 SnF 6: Mn 4+, Li 2 ^{_{TiF 6: Mn 4+, Na 2}} TiF 6: Mn 4+, K 2 TiF 6: Mn 4+, Rb 2 TiF 6: Mn 4+, Cs 2 TiF 6: Mn 4+, Li 2 ZrF 6: Mn 4+, Na 2 ZrF 6 ^{_{: Mn 4+, K 2 ZrF 6}} : Mn 4+, Rb 2 ZrF 6: Mn 4+, Cs 2 ZrF 6: Mn 4+, Li 2 HfF 6: Mn 4+, Na 2 HfF 6: Mn 4+, K 2 HfF 6: Mn ^Examples thereof include ⁴⁺ , Rb ₂ HfF ₆ : Mn ⁴⁺ , and Cs ₂ HfF ₆ : Mn ⁴⁺ . Of these Mn-activated compound fluorides, K ₂ SiF ₆ : Mn ⁴⁺ , K ₂ TiF ₆ : Mn ⁴⁺ , K ₂ GeF ₆ : Mn ⁴⁺ , Na ₂ from the viewpoint of availability and synthesis. SiF ₆ : Mn ⁴⁺ , Na ₂ TiF ₆ : Mn ⁴⁺ , Na ₂ GeF ₆ : Mn ⁴⁺ are preferable, and K ₂ SiF ₆ : Mn ⁴⁺ , K ₂ TiF ₆ : Mn ⁴⁺ are more preferable. The Mn-activated difluoride can be selected according to the optical characteristics required for various applications. Therefore, it is not particularly limited to the exemplified Mn-activated difluoride.

Here, in the present specification, the "optical property" means the absorption rate of a red phosphor or the like, the internal quantum efficiency, and the like. "Absorption rate" means the efficiency with which the red phosphor absorbs the excitation light. For example, when the peak value of the spectral radiance of the excitation light (wavelength 449 nm) emitted from the blue LED is Ex1 and the peak value of the excitation light not absorbed by the red phosphor is Ex2, the absorption rate α is calculated by the following formula. It is represented by (1).
Absorption rate α (%) = (Ex1-Ex2) / Ex1 × 100 (1)

Further, the "internal quantum efficiency" means the efficiency of converting the excitation light absorbed by the red phosphor into fluorescence. For example, when the peak value of the spectral radiance of the fluorescence of the red phosphor is Ex2 under irradiation with excitation light (wavelength 449 nm) from a blue LED, the internal quantum efficiency η is expressed by the following mathematical formula (2). Will be done.
Internal quantum efficiency η (%) = Em / (Ex1-Ex2) × 100 (2)

The Mn-activated difluoride is preferably solid and more preferably particulate. When the Mn-activated double fluoride is in the form of particles, its average particle size does not scatter too much of the excitation light than it absorbs and converts, and it mixes with the resin for mounting on the LED device. It is not particularly limited as long as it does not cause any inconvenience.

The molar ratio of Mn is preferably in the range of 0.005 to 0.15, preferably 0.01 to 0.15, with respect to the total number of moles of M and Mn in the red phosphor (or Mn-activated compound fluoride). It is more preferably in the range of 0.13, further preferably in the range of 0.02 to 0.12, and particularly preferably in the range of 0.03 to 0.1. By setting the molar ratio to 0.005 or more, good emission intensity of the red phosphor can be maintained. On the other hand, by setting the molar ratio to 0.15 or less, it is possible to prevent the durability of the red phosphor from being excessively lowered in a high temperature and high humidity environment.

In the present specification, "durability" means the degree to which the initial optical characteristics of the red phosphor are maintained when the red phosphor is stored in a high temperature and high humidity environment for a certain period of time. .. The meaning of the optical characteristics is as described above.

The bismuth may be present on at least a part of the surface of the Mn-activated difluoride, and more preferably, it covers at least a part of the surface as a coating layer. Further, bismuth may exist in the form of bismuth alone and / or a bismuth compound.

On the surface of Mn-activated compound fluoride, colored manganese dioxide is produced by the reaction of the tetravalent manganese ions that compose it with water, causing darkening on the particle surface of Mn-activated compound fluoride. It is considered. It is presumed that the occurrence of this darkening accelerates under high temperature and high humidity, leading to deterioration of the optical characteristics of the red phosphor and deterioration of durability. However, in the case of the red phosphor of the present embodiment, the presence of bismuth on at least a part of the surface of the Mn-activated difluoride reduces the contact and reaction of tetravalent manganese ions with water. , Or can be prevented. In particular, when bismuth is present as a coating layer on the surface of Mn-activated compound fluoride, it suppresses the invasion of water and water vapor into the red phosphor, thereby improving durability in a high temperature and high humidity environment. And the optical characteristics can be improved.

From the viewpoint of preventing the formation of manganese dioxide, it is preferable that the entire surface of the Mn-activated difluoride is coated with a coating layer containing bismuth. However, coating the entire surface of the Mn-activated difluoride with the coating layer may not be industrially suitable from the viewpoint of production cost and ease of production. Even if bismuth is present on a part of the surface of Mn-activated difluoride, the entire surface of Mn-activated difluoride is not necessarily covered because the durability and optical characteristics can be improved in a high temperature and high humidity environment. It is not necessary to coat with a coating layer. It is preferable that the degree of coating with the coating layer is appropriately changed according to the application of the red phosphor and the required performance according to the application.

The film thickness of the coating layer is such that at least the optical characteristics due to contact with water and the durability in a high temperature / high humidity environment can be improved in the region of Mn-activated double fluoride coated by the coating layer. If so, it is not particularly limited.

The bismuth compound is not particularly limited as long as it does not adversely affect the optical properties of the red phosphor. Specifically, the bismuth compound is, for example, a halogenated bismuth (III) composed of BiF ₃ , BiCl ₃ , BiBr ₃ and BiI ₃ , Bi ₂ O ₃ , Bi ₂ S ₃ , Bi ₂ Se ₃ , BiSb, Bi _2. Te ₃ , Bi (OH) ₃ , (BiO) ₂ CO ₃ , BiOCl, BiPO ₄ , Bi ₂ Ti ₂ O ₇ , Bi (WO ₄ ) ₃ , Bi ₂ (SO ₄ ) ₃ , BiOCH ₃ COO, 4 BiNO ₃ ( OH) ₂ · BiO (OH), C ₃ F ₉ O ₉ S ₃ Bi, C ₇ H ₇ BiO ₇ , C ₉ H ₂₁ BiO ₃ , C ₁₅ H ₃₃ BiO ₃ , C ₃₀ H ₅₇ BiO ₆ , C ₁₂ H _At least one selected from the group consisting of ₁₀ BiK ₃ O ₁₄ , C ₃ F ₉ O ₉ S ₃ Bi, and C ₆ H ₄ (OH) CO ₂ BiO · H ₂ O can be mentioned. Among these bismuth compounds, halogenated bismuth (III) composed of BiF ₃ , BiCl ₃ , BiBr ₃ and BiI ₃ , Bi ₂ O ₃ , Bi ₂ S ₃ , Bi ₂ Se ₃ , BiSb, Bi ₂ Te ₃ , Bi. (OH) ₃ , (BiO) ₂ CO ₃ , BiOCl, BiPO ₄ , Bi ₂ Ti ₂ O ₇ , Bi (WO ₄ ) ₃ , Bi ₂ (SO ₄ ) ₃ , ₄ BiNO ₃ (OH) ₂ · BiO (OH) , And inorganic bismuth salts such as C ₃ F ₉ O ₉ S ₃ Bi are preferable, and BiF ₃ and Bi (NO ₃ ) ₃ are more preferable. Further, the bismuth compound is particularly preferably BiF ₃ from the viewpoint of improving the durability and optical characteristics of the red phosphor in a high temperature and high humidity environment.

The content of the bismuth is preferably in the range of 0.01% by mass to 15% by mass, more preferably in the range of 0.01% by mass to 10% by mass, based on the total mass of the red phosphor. , 0.05% by mass to 10% by mass, and particularly preferably 0.1% by mass to 5% by mass. By setting the content of the bismuth compound to 0.01% by mass or more, the durability of the red phosphor in a high temperature and high humidity environment can be further improved. On the other hand, by reducing the content of the bismuth compound to 15% by mass or less, the deterioration of the optical characteristics can be further reduced.

The (initial) absorption rate of the red phosphor is preferably in the range of 50% to 100%, more preferably in the range of 55% to 100%, and even more preferably in the range of 60% to 100%. By setting the absorptivity to 50% or more, the optical characteristics of the red phosphor can be maintained well. In particular, in the present invention, good optical characteristics can be maintained because the decrease in absorption of excitation light by the red phosphor is suppressed even after storage in a high temperature and high humidity environment for a certain period of time. The numerical range of the absorption rate applies not only to the initial absorption rate of the red phosphor but also to the absorption rate after the red phosphor is stored in a high temperature and high humidity environment for a certain period of time. The definition of absorption rate is as described above.

The (initial) internal quantum efficiency of the red phosphor is preferably in the range of 70% to 100%, more preferably in the range of 75% to 100%, and even more preferably in the range of 80% to 100%. By setting the internal quantum efficiency to 70% or more, the luminous efficiency of the red phosphor can be maintained well. The numerical range of the internal quantum efficiency applies not only to the initial internal quantum efficiency of the red phosphor, but also to the internal quantum efficiency after the red phosphor is stored in a high temperature and high humidity environment for a certain period of time. The definition of internal quantum efficiency is as described above.

The red phosphor of the present embodiment is suitable as, for example, a red phosphor for a white LED using blue light as a light source. The red phosphor of the present embodiment can be suitably used for a light emitting device such as a lighting fixture and an image display device.

(Manufacturing method of red phosphor)
Next, the method for producing the red phosphor according to the present embodiment will be described below.
The method for producing a red phosphor of the present embodiment includes at least a step of bringing a treatment liquid containing bismuth into contact with the Mn-activated difluoride represented by the general formula (1). In this contact step, the surface of the Mn-activated difluoride is modified (surface treatment) by contacting the Mn-activated difluoride with a treatment liquid containing bismuth. Bismuth is present on at least a portion of the surface, more preferably allowing the formation of a coating layer containing bismuth.

The treatment liquid containing bismuth contains bismuth alone and / or a bismuth compound. In the treatment liquid containing bismuth, the added bismuth alone and / or all of the bismuth compound may be completely dissolved, or a part of the added bismuth may not be dissolved and may exist as an insoluble component.

Examples of the bismuth compound include halogenated bismuth (III) composed of BiF ₃ , BiCl ₃ , BiBr ₃ and BiI ₃ , Bi ₂ O ₃ , Bi ₂ S ₃ , Bi ₂ Se ₃ , BiSb, Bi ₂ Te ₃ , Bi ( OH) ₃ , (BiO) ₂ CO ₃ , BiOCl, BiPO ₄ , Bi ₂ Ti ₂ O ₇ , Bi (WO ₄ ) ₃ , Bi ₂ (SO ₄ ) ₃ , BiOCH ₃ COO, 4 BiNO ₃ (OH) ₂ · BiO (OH), C ₃ F ₉ O ₉ S ₃ Bi, C ₇ H ₇ BiO ₇ , C ₉ H ₂₁ BiO ₃ , C ₁₅ H ₃₃ BiO ₃ , C ₃₀ H ₅₇ BiO ₆ , C ₁₂ H ₁₀ BiK ₃ O ₁₄ , C ₃ F ₉ O ₉ S ₃ Bi, and at least one selected from the group consisting of C ₆ H ₄ (OH) CO ₂ BiO · H ₂ O.

Examples of the solvent of the treatment liquid containing bismuth include water, an organic solvent, a mixed solvent thereof, and an acidic solvent thereof.

The organic solvent is not particularly limited, and examples thereof include methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol, methyl acetate, ethyl acetate, tetrahydrofuran, 1,2-dimethoxyethane and the like. Of these organic solvents, methyl alcohol, ethyl alcohol, isopropyl alcohol and isobutyl alcohol are preferable, and methyl alcohol and ethyl alcohol are particularly preferable, from the viewpoint of easy availability and convenience of working environment.

The acidic solvent means a solvent containing an acid having a proton. The acid having a proton is not particularly limited, and examples thereof include hydrogen fluoride, nitric acid, sulfuric acid, and hydrochloric acid. From the viewpoint of the production process and the characteristics of the red phosphor, hydrogen fluoride and nitric acid are preferable, and hydrogen fluoride is particularly preferable.

The content of bismuth in the treatment liquid is preferably in the range of 0.01% by mass to 15% by mass, more preferably in the range of 0.05% by mass to 10% by mass, based on the total mass of the treatment liquid. , 0.1% by mass to 5% by mass is particularly preferable. By setting the content of bismuth to 15% by mass or less, the optical characteristics of the red phosphor can be maintained well. On the other hand, by setting the content of bismuth to 0.01% by mass or more, the optical characteristics and durability of the red phosphor in a high temperature and high humidity environment can be further improved.

The content of bismuth is measured by using a chemical analyzer such as atomic absorption spectroscopy or ICP emission spectroscopic analysis (high frequency inductively coupled plasma emission spectroscopy) for the filtrate obtained by filtering the treatment liquid containing bismus. be able to. Further, the difference between the mass of bismuth added to the solvent and the mass of the dissolution residue (filter) remaining on the filter paper when the treatment solution containing bismuth is filtered is dissolved in the treatment solution containing bismuth. It can also be calculated as the content (concentration) of bismuth.

When an acidic solvent containing hydrogen fluoride, that is, hydrofluoric acid or a mixed solvent of the hydrofluoric acid and an organic solvent is used as the solvent of the treatment liquid, the mixing ratio of the acidic solvent containing hydrogen fluoride and bismuth is , The range is preferably in the range of 30: 1-3500: 1, more preferably in the range of 100: 1-3500: 1, and particularly preferably in the range of 500: 1-1500: 1. .. By setting the mixing ratio to 3500: 1 or less, the amount of the treatment liquid discharged as waste liquid can be reduced, and the environmental load can be reduced. On the other hand, by setting the mixing ratio to 30: 1 or more, the dispersibility of the bismuth simple substance and / or the bismuth compound in the treatment liquid is improved, and after the surface modification of the Mn-activated compound fluoride, the Mn-activated compound is used. It is possible to prevent bismuth and the like from being unevenly present on the surface of the fluoride.

The concentration of hydrogen fluoride in the acidic solvent containing hydrogen fluoride is preferably in the range of 1% by mass to 70% by mass, and 10% by mass to 50% by mass, based on the total mass of the acidic solvent. It is more preferably in the range of 20% by mass to 40% by mass. By setting the concentration of hydrogen fluoride to 70% by mass or less, it is possible to suppress a decrease in the solubility of the Mn-activated difluoride in an acidic solvent containing hydrogen fluoride. On the other hand, by setting the concentration of hydrogen fluoride to 1% by mass or more, it is possible to suppress an increase in the amount of the treatment liquid used and improve the productivity.

The method of bringing the treatment liquid containing bismuth into contact with the Mn-activated compound fluoride is not particularly limited, and for example, a method of adding (immersing) the Mn-activated compound fluoride to be treated into the treatment liquid or a treatment. Examples thereof include a method of spraying a liquid. From the viewpoint of industrially producing a red phosphor, a method of adding (immersing) Mn-activated difluoride into the treatment liquid is preferable. By adding Mn-activated difluoride, a suspension in which Mn-activated difluoride is dispersed is obtained in the treatment liquid. The number of times of addition is not particularly limited, and Mn-activated difluoride may be added into the treatment liquid at one time, or may be added a plurality of times.

The mass ratio of the Mn-activated difluoride to the treatment liquid when Mn-activated difluoride is added to the treatment liquid is not particularly limited, and may be appropriately adjusted within a range that does not affect the subsequent stirring and filtration. Yes (details of stirring and filtration will be described later). However, from the viewpoint of work efficiency, the mass ratio of the treatment liquid to the Mn-activated difluoride is preferably in the range of 100: 1 to 2: 1 and more preferably in the range of 10: 1-3: 1. By setting the mass ratio to 100: 1 or more, it is possible to prevent the amount of Mn-activated difluoride to be treated from becoming too small and the productivity of the red phosphor from decreasing. On the other hand, by setting the mass ratio to 2: 1 or less, the Mn-activated difluoride dispersibility in the treatment liquid is good, and the bismuth compound can be uniformly applied.

After the contact step between the Mn-activated compound fluoride and the treatment liquid, a stirring step of stirring the obtained suspension, a solid-liquid separation step of the suspension, a solid-liquid separated solid washing step, and after washing. It is preferable to carry out the solid drying step in sequence.

The stirring method in the stirring step is not particularly limited, and a known stirring device or the like can be used. The stirring time of the suspension is not particularly limited, and can be appropriately adjusted in consideration of the efficiency of the manufacturing equipment. The stirring speed is also not particularly limited, and can be appropriately set as needed.

The solid-liquid separation step is a step of separating dispersed solid particles from the suspension after the stirring step. The solid-liquid separation method is not particularly limited, and examples thereof include a method of filtering the suspension and a method of allowing the suspension to stand to precipitate dispersed solid particles and then decanting. Be done. The standing time of the suspension is not particularly limited as long as the solid particles can be sufficiently precipitated.

The washing step is performed to wash the cake obtained by solid-liquid separation. In this cleaning step, water, an organic solvent, a mixed solvent thereof, or an acidic solvent thereof can be used as a cleaning agent. The washing time and the number of washings are not particularly limited and can be set as needed.

The organic solvent used in the washing step is not particularly limited, and examples thereof include methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol, methyl acetate, ethyl acetate, tetrahydrofuran, 1,2-dimethoxyethane, and acetone. From the viewpoint of easy availability and convenience of working environment, methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol and acetone are preferable, and ethyl alcohol, isopropyl alcohol and acetone are particularly preferable.

Further, the acidic solvent used in the washing step means a solution containing an acid having a proton. The acid having a proton is not particularly limited, and examples thereof include hydrogen fluoride, nitric acid, sulfuric acid, and hydrochloric acid. The content of the acid having a proton is preferably in the range of 0.1% by mass to 60% by mass, more preferably in the range of 1% by mass to 55% by mass, and 5% by mass to 50% by mass with respect to the total mass of the acidic solvent. The range of mass% is particularly preferable.

The drying step is performed on the cake after the washing step. As a result, the solvent content of the treatment liquid remaining on the cake and the cleaning agent used in the cleaning step can be distilled off. The drying method is not particularly limited, and examples thereof include heat drying and hot air drying. In the case of heat drying, it is preferable to carry out in an atmosphere of nitrogen gas. The drying temperature is preferably in the range of 60 ° C. to 200 ° C., more preferably in the range of 70 ° C. to 150 ° C., and particularly preferably in the range of 80 ° C. to 110 ° C. By setting the drying temperature to 60 ° C. or higher, the drying efficiency can be maintained well. In addition, it is possible to prevent the residual impurities and suppress the deterioration of the optical characteristics of the red phosphor due to the residual impurities. On the other hand, by setting the drying temperature to 200 ° C. or lower, it is possible to prevent the obtained red phosphor from being deteriorated by heat. Further, in the case of heat drying, the drying time is preferably in the range of 0.5 hour to 20 hours, more preferably in the range of 2 hours to 15 hours. By setting the drying time to 0.5 hours or more, it is possible to prevent impurities from remaining and to suppress deterioration of the optical characteristics of the red phosphor due to the residual impurities. On the other hand, by setting the drying time to 20 hours or less, it is possible to prevent a decrease in the production efficiency of the red phosphor.

From the above, it is possible to produce a red phosphor in which bismuth is present on at least a part of the surface of the Mn-activated compound fluoride. It is presumed that the elemental bismuth and / or the bismuth compound precipitates on the surface of the Mn-activated difluoride in the process of stirring the suspension in the stirring step. Alternatively, the solvent component of the treatment liquid is distilled off in the process of drying the Mn-activated compound fluoride having the treatment liquid attached to the surface in the drying step, so that the bismuth simple substance and / or the bismuth compound can be obtained. It is presumed that it precipitates on the surface of Mn-activated compound fluoride.

Further, when the treatment liquid containing bismuth dissolves only a part of the bismuth and contains an insoluble component of the bismuth, the insoluble bismuth may remain as a simple substance on the surface of the Mn-activated difluoride. However, in the present invention, even in such a case, the insoluble component of bismuth may remain on the surface of the Mn-activated difluoride as long as it does not adversely affect the optical properties of the red phosphor. However, if the residual bismuth insoluble content deteriorates the optical characteristics of the red phosphor, etc., use a treatment solution in which bismuth is completely dissolved, or adjust the bismuth content to remove the insoluble content. It is preferable not to occur.

(Other matters)
In the above description, a preferred embodiment of the present invention has been described. However, the present invention is not limited to this embodiment, and can be implemented in various other embodiments.

For example, in the above description, regarding the method for producing a red phosphor, as a method of bringing the treatment liquid containing bismuth into contact with the Mn-activated compound fluoride, a method of adding the Mn-activated compound fluoride into the treatment liquid is described. I mentioned it. However, the present invention is not limited to this method. For example, a method of spraying the treatment liquid onto the Mn-activated double fluoride which is the object to be treated may be used. The spray amount of the treatment liquid is not particularly limited and can be appropriately set. Further, after the treatment liquid is sprayed on the Mn-activated difluoride, it is preferable to distill off the solvent component of the treatment liquid remaining on the surface of the Mn-activated difluoride. The method of distillation is not particularly limited, and for example, the above-mentioned drying step can be performed.

Further, the method for producing Mn-activated difluoride, which is a raw material for the red phosphor, is not particularly limited, and a known method can be adopted. For example, a method of dissolving a compound containing a constituent element of Mn-activated compound fluoride in a hydrofluoric acid solution, mixing them, and subjecting them to reaction crystallization (HD Nguyen, CC Lin, RS. Liu, Angew. Chem. Vol. 54, No. 37, p. 10862 (2015)), all compounds containing the constituent elements of Mn-activated difluoride are dissolved or dispersed in a hydrofluoric acid solution, and further evaporated and concentrated to precipitate. (Refer to Japanese Patent Application Laid-Open No. 2009-528429), a compound containing a constituent element of Mn-activated difluoride is sequentially dissolved in a hydrofluoric acid solution, and a manganese-free composition of solid Mn-activated difluoride is dissolved therein. It was added one _element, K ₂ SiF 6: to precipitate crystals of ^{Mn 4+,} (. see No. WO2015 / 093430) filtration and dried method for the like.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

(Mn activated compound fluoride formation)
H. D. Nguyen, C.I. C. Lin, R.M. S. Liu, Angew. Chem. Mn-activated difluoride was synthesized by the following method in accordance with the method described in Vol. 54, No. 37, p. 10862 (2015).

First, 35 ml of a 48 mass% hydrofluoric acid solution was placed in a PFA container having an internal volume of 0.1 L. Next, while stirring the hydrofluoric acid solution, 1.2 g of SiO ₂ was added and dissolved. Further, 0.3 g of K ₂ MnF ₆ was added to and dissolved in this solution.

Subsequently, 3.5 g of KF was slowly added to the solution over 15 minutes to obtain crystals. The crystals were washed with a 20 mass% hydrofluoric acid solution and acetone, and then dried at 70 ° C. for 6 hours. As a result, K ₂ SiF ₆ : Mn ⁴⁺ as a Mn-activated difluoride was obtained.

(Example 1)
0.15 g of bismuth fluoride (BiF ₃ ) was added to 16.6 ml of 43 mass% hydrofluoric acid, and the mixture was stirred for 5 minutes to prepare a suspension (hydrofluoric acid: bismuth = 1408: 1 (hydrofluoric acid: bismuth = 1408: 1). Mass-based mixing ratio)). Next, while stirring the suspension, the _K 2 _SiF 6: The ^{Mn 4+} were added 5.3 g, was stirred for another 10 minutes.

After the stirring was completed, the suspension was allowed to stand for 10 minutes to precipitate the dispersed solid. Then, suction filtration was performed to collect the filtrate. Further, after adding ethanol to the filter, suction filtration was performed again to remove the supernatant, and this operation was repeated to wash the filter. The washed filtrate was collected and dried in a nitrogen atmosphere at a drying temperature of 105 ° C. to evaporate ethanol. As a result, the red phosphor according to Example 1 was produced.

(Example 2)
In this example, the amount of bismuth fluoride added was changed from 0.15 g to 0.05 g (hydrofluoric acid: bismuth = 423: 1 (mixing ratio based on mass)). A red phosphor according to Example 2 was produced in the same manner as in Example 1 except for the above.

(Example 3)
In this example, the amount of bismuth fluoride added was changed from 0.15 g to 0.015 g (hydrofluoric acid: bismuth = 141: 1 (mixing ratio based on mass)). A red fluorescent substance according to Example 3 was prepared in the same manner as in Example 1 except for the above.

(Example 4)
In this example, the amount of bismuth fluoride added was changed from 0.15 g to 0.60 g (hydrofluoric acid: bismuth = 35: 1 (mixing ratio based on mass)). A red fluorescent substance according to Example 4 was prepared in the same manner as in Example 1 except for the above.

(Example 5)
In this example, the amount of bismuth fluoride added was changed from 0.15 g to 0.90 g, and the amount of hydrofluoric acid having a concentration of 43% by mass was changed from 16.6 ml to 21.5 ml (hydrofluoric acid: Bismuth = 30: 1 (mass-based mixing ratio)). A red phosphor according to Example 5 was prepared in the same manner as in Example 1 except for the above.

(Example 6)
In this example, bismuth fluoride was changed to an aqueous solution of bismuth nitrate having a concentration of 40% by mass, and the amount added was changed from 0.15 g to 0.56 g (hydrofluoric acid: bismuth = 140: 1 (mass-based mixing ratio). )). A red fluorescent substance according to Example 6 was prepared in the same manner as in Example 1 except for these.

(Example 7)
In this example, the concentration of hydrofluoric acid was changed from 43% by mass to 35% by mass, and the amount of bismuth fluoride added was changed from 0.15 g to 0.015 g (hydrofluoric acid: bismuth = 1408: 1 (Mass-based mixing ratio)). A red fluorescent substance according to Example 7 was prepared in the same manner as in Example 1 except for these.

(Comparative Example 1)
In this comparative example, the above-mentioned K ₂ SiF ₆ : Mn ⁴⁺ was used as the red phosphor.

(Evaluation of red phosphor)
The red phosphors according to Examples 1 to 7 and Comparative Example 1 were evaluated by the methods described below.

<Mol ratio of Mn and content of bismuth>
The manganese concentration and bismuth content of the red phosphors of Examples 1 to 7 and Comparative Example 1 were measured by energy dispersive X-ray spectroscopy (EDX). The EDX measurement is a measurement method in which fluorescent X-rays generated when a sample is irradiated with X-rays are measured, and the elements and concentrations constituting the sample are analyzed.

The red phosphors of Examples 1 to 7 and Comparative Example 1 were placed on the sample table of the EDX measuring device, respectively, and the manganese concentration and the bismuth content were calculated. As the EDX measuring device, a JSF-7800F shotkey field emission scanning electron microscope (trade name, manufactured by JEOL Ltd.) was used. The measurement conditions were an accelerating voltage: 15 kV, an irradiation current: 1.0000 nA, and an energy range: 0-20 keV.

As a result of the measurement, the molar ratio of Mn (Mn / (Si + Mn)) to the total number of moles of Si and Mn in the red phosphor was 0.054 and 0.054, respectively, in the case of the red phosphors of Examples 1 to 7, respectively. , 0.055, 0.054, 0.054, 0.055, 0.055, and in the case of the red phosphor of Comparative Example 1, it was 0.055.

In the case of the red phosphors of Examples 1 to 7, the bismuth content was 4.1 wt%, 1.3 wt%, 0.4 wt%, 10.7 wt%, 14.9 wt% and 4.0 wt%, respectively. , 0.4 wt%, which was below the detection limit (0.01 wt%) in the case of the red phosphor of Comparative Example 1.

<Evaluation of optical characteristics of red phosphor>
In order to evaluate the optical characteristics of each of the red phosphors of Examples 1 to 7 and Comparative Example 1, the absorption rate and the internal quantum efficiency of each were determined.

Absorption rate and internal quantum efficiency were measured using a blue LED spot illumination (trade name: TSPA22X8-57B, manufactured by AS ONE Corporation) and a spectroradiometer (trade name: SR-UL2, manufactured by Topcon Corporation). That is, a white plate (BaSO ₄ , manufactured by JASCO Corporation) that reflects almost 100% of the excitation light is set on the sample stage, the spectral radiance of the excitation light (wavelength: 449 nm) is measured, and the peak value (Ex1) is measured. ) Was calculated.

Subsequently, the red phosphor sample of any of Examples 1 to 7 or Comparative Example 1 is packed in the recess of the sample stage, and the spectral radiance peak value (Em) of fluorescence under excitation light irradiation and the unabsorbed component The excitation light peak value (Ex2) of was measured.

The absorption rate α of each of the red phosphors of Examples 1 to 7 and Comparative Example 1 was calculated using the following mathematical formula (1). The results are shown in Table 1.
Absorption rate α (%) = (Ex1-Ex2) / Ex1 × 100 (1)

Further, the internal quantum efficiency η of each of the red phosphors of Examples 1 to 7 and Comparative Example 1 was calculated using the following mathematical formula (2). The results are shown in Table 1.
Internal quantum efficiency η (%) = Em / (Ex1-Ex2) × 100 (2)

<Evaluation of durability of red phosphor>
The durability test was carried out as follows. First, 0.3 g of the red phosphors of Examples 1 to 7 or Comparative Example 1 were placed in PFA trays, set in a constant temperature and humidity chamber controlled at a temperature of 80 ° C. and a relative humidity of 80%, and stored for 88 hours. .. Then, the absorption rate α and the internal quantum efficiency η were obtained by the above-mentioned methods, respectively. Further, the absorptance α and the internal quantum efficiency η after storing each red phosphor for 168 hours in an environment of a temperature of 80 ° C. and a relative humidity of 80% were also determined.

Furthermore, based on the following mathematical formula (3), an index of the durability of the red phosphor in a high temperature and high humidity environment was calculated from the values of the internal quantum efficiency before and after the durability test of each red phosphor. The results are shown in Table 1.
(Durability index) = (Internal quantum efficiency after endurance test) / (Internal quantum efficiency before endurance test) x 100 (3)
In addition, "after the durability test" in the formula (3) means the case after storing for 88 hours in the environment of the temperature 80 degreeC and the relative humidity 80%, and the case after storing for 168 hours.

(result)
As shown in Table 1, the content of bismuth was confirmed in the red phosphors of Examples 1 to 7 which were surface-treated with the treatment liquid containing bismuth fluoride. Further, it was confirmed that the red phosphors of Examples 1 to 7 had improved durability in a high temperature and high humidity environment as compared with the red phosphors of Comparative Example 1 which had not been surface-treated. ..

Claims (13)

A red phosphor containing Mn-activated compound fluoride represented by the following general formula (1) and bismuth.
A ₂ MF ₆ : Mn ⁴⁺ (1)
(In the formula, A represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium and cesium, and M represents from the group consisting of silicon, germanium, tin, titanium, zirconium and hafnium. Represents at least one tetravalent element selected.) The red fluorescent substance according to claim 1, wherein the Mn-activated compound fluoride is in the form of particles, and the bismuth is present on at least a part of the surface of the particulate Mn-activated compound fluoride. A coating layer is provided on the surface of the particulate Mn-activated difluoride.
The red phosphor according to claim 2, wherein the coating layer contains the bismuth. The red phosphor according to claim 3, wherein the coating layer is composed of a simple substance of bismuth and / or a compound of bismuth. The bismuth compounds are BiF ₃ , BiCl ₃ , BiBr ₃ , BiI ₃ , Bi ₂ O ₃ , Bi ₂ S ₃ , Bi ₂ Se ₃ , BiSb, Bi ₂ Te ₃ , Bi (OH) ₃ , (BiO) ₂ CO. ₃ , BiOCl, BiPO ₄ , Bi ₂ Ti ₂ O ₇ , Bi (WO ₄ ) ₃ , Bi ₂ (SO ₄ ) ₃ , BiOCH ₃ COO, 4 BiNO ₃ (OH) ₂ , BiO (OH), C ₃ F ₉ O ₉ S ₃ Bi, C ₇ H ₇ BiO ₇ , C ₉ H ₂₁ BiO ₃ , C ₁₅ H ₃₃ BiO ₃ , C ₃₀ H ₅₇ BiO ₆ , C ₁₂ H ₁₀ BiK ₃ O ₁₄ , C ₃ F ₉ O ₉ S ₃ The red phosphor according to claim 4, which is at least one selected from the group consisting of Bi and C ₆ H ₄ (OH) CO ₂ BiO · H ₂ O. The red phosphor according to any one of claims 1 to 5, wherein the content of the bismuth is in the range of 0.01% by mass to 15% by mass with respect to the total mass of the red phosphor. The aspect of any one of claims 1 to 6, wherein the molar ratio of Mn in the Mn-activated compound fluoride is in the range of 0.005 to 0.15 with respect to the total number of moles of M and Mn. Red phosphor. A method for producing a red phosphor, which comprises a step of bringing a treatment liquid containing bismuth into contact with the Mn-activated compound fluoride represented by the following general formula (1).
A ₂ MF ₆ : Mn ⁴⁺ (1)
(In the formula, A represents at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium and cesium, and M represents from the group consisting of silicon, germanium, tin, titanium, zirconium and hafnium. Represents at least one tetravalent element selected.) The method for producing a red phosphor according to claim 8, wherein the content of the bismuth in the treatment liquid is in the range of 0.01% by mass to 15% by mass with respect to the total mass of the treatment liquid. The method for producing a red phosphor according to claim 8 or 9, wherein the solvent of the treatment liquid is water, an organic solvent, a mixed solvent thereof, or an acidic solvent thereof. The acidic solvent is an acidic solvent containing hydrogen fluoride,
The method for producing a red phosphor according to claim 10, wherein the mixing ratio of the acidic solvent containing hydrogen fluoride and the bismuth is in the range of 30: 1 to 3500: 1 on a mass basis. The method for producing a red phosphor according to claim 11, wherein the concentration of the hydrogen fluoride in the acidic solvent containing hydrogen fluoride is in the range of 1% by mass to 70% by mass with respect to the total mass of the acidic solvent. The bismuth is Bi alone, BiF ₃ , BiCl ₃ , BiBr ₃ , BiI ₃ , Bi ₂ O ₃ , Bi ₂ S ₃ , Bi ₂ Se ₃ , BiSb, Bi ₂ Te ₃ , Bi (OH) ₃ , (BiO). ₂ CO ₃ , BiOCl, BiPO ₄ , Bi ₂ Ti ₂ O ₇ , Bi (WO ₄ ) ₃ , Bi ₂ (SO ₄ ) ₃ , BiOCH ₃ COO, 4BiNO ₃ (OH) ₂ · BiO (OH), C ₃ F ₉ O ₉ S ₃ Bi, C ₇ H ₇ BiO ₇ , C ₉ H ₂₁ BiO ₃ , C ₁₅ H ₃₃ BiO ₃ , C ₃₀ H ₅₇ BiO ₆ , C ₁₂ H ₁₀ BiK ₃ O ₁₄ , C ₃ F ₉ O ₉ The red fluorescence according to any one of claims 8 to 12, which is contained in the treatment liquid as at least one selected from the group consisting of S ₃ Bi and C ₆ H ₄ (OH) CO ₂ BiO · H ₂ O. How to make a body.