KR20210150475A - Surface-coated phosphor particles, method for producing surface-coated phosphor particles, and light-emitting device - Google Patents

Abstract

The surface-coated phosphor particle of the present invention comprises a particle containing a phosphor and a coating portion covering the surface of the particle, wherein the phosphor has the general formula M ¹ _a M ² _b M ³ _c Al ₃ N _4-d O _d (provided that M ¹ is at least one element selected from Sr, Mg, Ca and Ba, M ² is at least one element selected from Li and Na, and M ³ is at least one element selected from Eu and Ce and above.), wherein a, b, c and d are each of the following formulas, 0.850≤a≤1.150, 0.850≤b≤1.150, 0.001≤c≤0.015, 0≤d≤0.40, 0 ≤ d/(a+d) < 0.30, the content of elemental fluorine is 15% by mass or more and 30% by mass or less with respect to the entire surface-coated phosphor particle, and the mass increase rate obtained by measurement under predetermined conditions is 15% is below.

Description

Surface-coated phosphor particles, method for producing surface-coated phosphor particles, and light-emitting device

The present invention relates to surface-coated phosphor particles, a method for producing surface-coated phosphor particles, and a light emitting device.

BACKGROUND ART Light emitting devices formed by combining light emitting diodes (LEDs) and phosphors are actively used in lighting devices, backlights of liquid crystal display devices, and the like. In particular, when a light emitting device is used for a liquid crystal display device, since high color reproducibility is required, the use of a phosphor having a narrow full width at half maximum (hereinafter simply referred to as "half width") of the fluorescence spectrum is desired.

A nitride phosphor or oxynitride phosphor activated by ^{Eu 2+} is known as a conventionally used red phosphor with a narrow half width. As representative pure nitride phosphors, Sr ₂ Si ₅ N ₈ :Eu ²⁺ , CaAlSiN ₃ :Eu ²⁺ (abbreviated as CASN), (Ca, Sr)AlSiN ₃ :Eu ²⁺ (abbreviated as SCASN), etc. There is this. CASN phosphors and SCASN phosphors have a peak wavelength in the range of 610 to 680 nm, and the half width is relatively narrow at 75 nm or more and 90 nm or less. However, when these phosphors are used as a light emitting device for liquid crystal display, further expansion of the color reproduction range is desired, and a phosphor having a narrower half width is desired.

_{In recent years, SrLiAl 3} N ₄ :Eu ²⁺ (abbreviated as SLAN) phosphor has been known as a narrow-band red phosphor with a half width of 70 nm or less, and a light-emitting device to which this phosphor is applied is expected to have excellent color rendering and color reproducibility. can

Patent Document 1 discloses a SLAN phosphor having a specific composition.

Japanese Patent Laid-Open No. 2017-088881

SLAN phosphors have a property of being easily decomposed when in contact with water. This property is a factor that the light emission intensity decreases with the passage of time. In recent years, further improvement in the reliability of light emitting devices using SLAN phosphors has been demanded, and further improvement in moisture resistance of SLAN phosphors is also required.

As a result of investigation by the present inventors, for particles containing SLAN phosphor or a nitride phosphor having a similar crystal structure to it, the detailed mechanism is not clear, but the content of elemental fluorine in the entire particle and the mass before and after the high-temperature, high-humidity test By using the increase rate as an index, moisture resistance in particles can be stably evaluated, and by setting the content of the element fluorine to a predetermined value or more and the mass increase rate to a predetermined value or less, the decrease in fluorescence intensity under water exposure environment It was found that it is possible to suppress the moisture resistance, that is, to improve the moisture resistance.

According to the present invention, there is provided a surface-coated phosphor particle comprising a particle including a phosphor and a coating portion covering the surface of the particle, wherein the phosphor has the general formula M ¹ _a M ² _b M ³ _c Al ₃ N _4-d O _d (provided that M ¹ is at least one element selected from Sr, Mg, Ca and Ba, M ² is at least one element selected from Li and Na, and M ³ is at least one element selected from Eu and Ce It is the above element.) has a composition represented by, wherein a, b, c and d are each of the following formulas

to meet,

With respect to the whole said surface-coated fluorescent substance particle, the content rate of a fluorine element is 15 mass % or more and 30 mass % or less,

The surface-coated phosphor particles having a mass increase rate of 15% or less obtained by measurement under the following conditions are provided.

(Conditions for measuring mass increase rate)

Let the initial mass of the powder containing the surface-coated phosphor particles be W1, the mass of the powder after the lapse of 50 hours under the conditions of a temperature of 60°C and a humidity of 90% RH is denoted as W2, and the mass increase rate is (W2-W1)/ It is calculated as W1 x 100 (%).

Further, according to the present invention, there is provided a method for producing the surface-coated phosphor particles described above, comprising a mixing step of mixing raw materials, a firing step of firing the mixture obtained by the mixing step, and an acidity with the fired product obtained by the firing step an acid treatment process of mixing the solution;

In the mixing step, when the molar ratio of Al is 3, ^{the amount of M 1 added} is 1.10 or more and 1.20 or less, and there is provided a surface-coated phosphor particle.

Further, according to the present invention, there is provided a light-emitting device having the above-described surface-coated phosphor particles and a light-emitting element.

According to the present invention, it is possible to provide a technology related to nitride phosphor particles having improved moisture resistance.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail.

The surface-coated fluorescent substance particle which concerns on embodiment contains the particle|grains containing a fluorescent substance, and the coating part which coat|covers the surface of the said particle|grain. Hereinafter, the detail of surface-coated fluorescent substance particle is demonstrated.

The phosphor constituting the particles of the present embodiment is represented by the general formula M ¹ _a M ² _b M ³ _c Al ₃ N _4-d O _d . a, b, c, 4-d and d represent the molar ratio of each element.

In the above general formula, M ¹ is at least one element selected from Sr, Mg, Ca and Ba. Preferably, M ¹ contains at least Sr. 0.850 or more are preferable and, as for the minimum of the molar ratio a of M<^{1>, 0.950 or more are more preferable.} On the other hand, ^{1.150 or less are preferable, as for the upper limit of the molar ratio a of M<1>} , 1.100 or less are more preferable, and its 1.050 or less are still more preferable. Crystal structure stability can be improved by making the molar ratio a of M<^{1> into the said range.}

In the above general formula, M ² is at least one element selected from Li and Na. Preferably, M ² contains at least Li. The lower limit of the molar ratio of M ² b is 0.850 or more is preferable, and is more preferably not less than 0.950. On the other hand, the upper limit of the molar ratio b of M ² is less than 1.150, and preferably, 1.100 or less is more preferred, and even more preferably 1.050 or less. , It is possible to improve the crystal structure stability by the molar ratio b of M ² in the above-described range.

In the above general formula, M ³ is an activator added to the parent crystal, that is, an element constituting the luminescence center ion of the phosphor, and is at least one element selected from Eu and Ce. M ³ can be selected depending on the obtained emission wavelength, and preferably contains at least Eu.

The lower limit of the molar ratio c of M ³ is preferably 0.001 or more, and more preferably 0.005 or more. On the other hand, the upper limit of the molar ratio of M ³ c is 0.015 or less is preferred, and more preferred is 0.010 or less. When ^{the lower limit of the molar ratio c of M 3} falls within the above range, sufficient light emission intensity can be obtained. In addition, ^{by making the upper limit of the molar ratio c of M 3} into the above range, concentration quenching can be suppressed and the light emission intensity can be maintained at a sufficient value.

In the above general formula, the lower limit of the molar ratio d of oxygen is preferably 0 or more, and more preferably 0.05 or more. On the other hand, 0.40 or less is preferable and, as for the upper limit of the molar ratio d of oxygen, 0.35 or less is more preferable. By making the molar ratio d of oxygen into the above range, the crystalline state of the phosphor can be stabilized and the luminescence intensity can be maintained at a sufficient value.

Moreover, less than 2 mass % is preferable and, as for content of the oxygen element in a fluorescent substance, 1.8 mass % or less is more preferable. When the content of the oxygen element is less than 2% by mass, the crystalline state of the phosphor can be stabilized and the luminescence intensity can be maintained at a sufficient value.

0 or more are preferable and, as for the lower limit of the molar ratio of M<^1> and oxygen, ie, the value of d/(a+d) calculated from a and d, 0.05 or more is more preferable. On the other hand, less than 0.30 is preferable and, as for the upper limit of the value of d/(a+d), 0.25 or less are more preferable. By making d/(a+d) into the above range, the crystalline state of the phosphor can be stabilized and the luminescence intensity can be maintained at a sufficient value.

As for the surface-coated fluorescent substance particle|grains of this embodiment, the mass increase rate obtained by measuring on the following conditions is 15 % or less.

(Measurement conditions for mass increase rate)

Let the initial mass of the powder containing the surface-coated phosphor particles be W1, and the mass of the powder containing the surface-coated phosphor particles after the lapse of 50 hours under the conditions of a temperature of 60°C and a humidity of 90% RH is W2. The mass increase rate is calculated from the formula (W2-W1)/W1 x 100 (%).

In addition, it is preferable to store the surface-coated phosphor particles before measurement in an ultra-low humidity dry box with a high humidity of 1% RH or less for a predetermined period of time.

The mass increase rate can be controlled by controlling the component or coating shape of the coating portion formed on the surface of the phosphor particles.

The surface-coated phosphor particles of the present embodiment include the coating portion described above, and by setting the mass increase rate before and after the endurance test to 15% or less, the moisture resistance of the phosphor can be improved, and further, the luminescence intensity can be maintained over a long period of time. have. Incidentally, it is considered that the increase in the mass of the surface-coated phosphor particles is caused by hydrolysis and hydroxylation of the uncoated portion.

In the surface-coated phosphor particle of this embodiment, 12 % or less is preferable and, as for the mass increase rate before and behind an endurance test, 5 % or less is more preferable. By making the mass increase rate before and after the endurance test into the above range, the moisture resistance of the phosphor can be further improved, and further, the luminescence intensity can be maintained for a longer period of time.

In this embodiment, the content rate of the fluorine element with respect to the whole surface-coated fluorescent substance particle is 15 mass % or more and 30 mass % or less. Moisture resistance can be improved by making the content rate of the fluorine element with respect to the whole surface-coated fluorescent substance particle|grains into 15 mass % or more. When the content rate of the element fluorine with respect to the whole surface-coated phosphor particle is 30 mass % or less, luminescence intensity can be maintained at a sufficient value, improving moisture resistance.

18 mass % or more is more preferable, and, as for the minimum of the content rate of the fluorine element with respect to the whole surface-coated fluorescent substance particle, 20 mass % or more is still more preferable. Moreover, as for the upper limit of the content rate of the fluorine element with respect to the whole surface-coated fluorescent substance particle, 27 mass % or less is more preferable, and its 25 mass % or less is still more preferable. Moisture resistance can be further improved by making the minimum of the content rate of a fluorine element into the said range. Moreover, by making the upper limit of the content rate of a fluorine element into the said range, luminescence intensity can be maintained at a sufficient value, further improving moisture resistance.

In addition, elemental fluorine originates in the fluoride of the metal element which can be used as a raw material mentioned later, or is added by the fluorine treatment process mentioned later, and does not comprise the crystal structure of a phosphor.

In the present embodiment, the type of acid and solvent in the acid treatment step, the acid concentration, the hydrofluoric acid concentration in the hydrofluoric acid treatment step, the time of the hydrofluoric acid treatment, the heating temperature and the heating time in the heating step performed after the hydrofluoric acid treatment, etc. By adjusting suitably, the content rate and mass increase rate of the fluorine element in particle|grains can be controlled within desired ranges.

According to the surface-coated phosphor particles of the present embodiment, it is possible to suppress the fluorescence intensity in a water exposure environment, preferably it is possible to suppress a decrease in the fluorescence intensity in a high humidity environment such as 90% RH or more, and more Preferably, the fall of the fluorescence intensity in a high-temperature, high-humidity environment can be suppressed.

It is preferable that the coating part constitutes at least a part of the surface of the particle containing the above-mentioned phosphor. Moreover, it is preferable that the said coating part contains the fluorine compound containing elemental fluorine, and it is more preferable that the fluorine-containing compound containing elemental fluorine and an aluminum element is contained.

In the fluorine-containing compound, it is preferable that fluorine and an aluminum element are directly covalently bonded, and more specifically, the fluorine-containing compound preferably contains either or both of _{(NH 4} ) ₃ AlF ₆ or AlF _{3 .} do. In addition, the fluorine-containing compound may be constituted by a single compound containing elemental fluorine and elemental aluminum.

When the above-described coating portion constitutes at least a part of the outermost surface of the particle containing the phosphor, the moisture resistance of the phosphor constituting the particle can be improved. Further, from the viewpoint of further improving the moisture resistance of the phosphor, it is more preferable that the _{coating portion contains AlF 3 .}

Although the aspect in particular of a coating part is not restrict|limited, The coating part may be comprised so that it may cover at least a part of particle|grain surface, and may be comprised so that the whole particle|grain surface may be covered. Examples of the embodiment of the coating portion include an embodiment in which a large number of particulate fluorine-containing compounds are distributed on the surface of particles containing a phosphor, and an embodiment in which the fluorine-containing compound continuously coats the surface of particles containing a phosphor. .

The diffuse reflectance with respect to light irradiation with a wavelength of 300 nm in the surface-coated phosphor particle|grains of this embodiment is 56 % or more, More preferably, it is 58 % or more, More preferably, it is 60 % or more.

Moreover, the diffuse reflectance with respect to light irradiation in the peak wavelength of a fluorescence spectrum in surface-coated fluorescent substance particle is 85 % or more, for example, Preferably, it is 86 % or more. By providing such a characteristic, the luminous efficiency is further increased, and the luminous intensity is improved.

An example of the surface-coated phosphor particles of the present embodiment, when excited with blue light having a wavelength of 455 nm, preferably has a peak wavelength in a range of 640 nm or more and 670 nm or less, and a half width of 45 nm or more and 60 nm or less. By providing these characteristics, excellent color rendering and color reproducibility can be expected.

In an example of the surface-coated phosphor particles of the present embodiment, when excited by blue light having a wavelength of 455 nm, the color purity of the emitted color preferably satisfies 0.680≤x<0.735 in the CIE-xy chromaticity diagram. By providing these characteristics, excellent color rendering and color reproducibility can be expected. When the x value is 0.680 or more, red light emission with good color purity can be further expected, and since the value of x value of 0.735 or more exceeds the maximum value in the CIE-xy chromaticity diagram, it is preferable to satisfy the above range.

(Method for producing surface-coated phosphor particles)

The surface-coated phosphor particles of the present embodiment are manufactured by a mixing step of mixing raw materials, a firing step of firing the mixture obtained by the mixing step, and an acid treatment step of mixing the fired product obtained by the firing step and an acidic solution can do. In addition to the above steps, it is preferable to add a fluorine treatment step of mixing the calcined product that has undergone the acid treatment step with a compound containing elemental fluorine, and a heating step of subjecting the resultant obtained by the fluorine treatment step to heat treatment.

(mixing process)

A mixing process is a process of mixing each raw material weighed so that the target surface-coated fluorescent substance particle|grains may be obtained, and obtaining a powdery raw material mixture. Although the method of mixing a raw material is not specifically limited, For example, there exists a method of fully mixing using mixing apparatuses, such as a mortar, a ball mill, a V-type mixer, and a planetary mill. In addition, it is appropriate to handle strontium nitride, lithium nitride, etc., which react violently with moisture or oxygen in the air, in a glove box in which the inside is substituted with an inert atmosphere or using a mixing device.

Mixing process WHEREIN: When the molar ratio of Al is 3, it ^{is preferable that the input amount of M<1} > is 1.10 or more in molar ratio. By setting the M ¹ input amount to 1.10 or more in a molar ratio, a shortage of M ^{1 in the} phosphor is suppressed due to ^{volatilization of M 1 during the firing step, etc., defects are less likely to occur in M 1} , and the crystallinity of the crystal structure is maintained well. . As a result, a narrow band fluorescence spectrum is obtained, and it is estimated that the luminescence intensity can be raised. Moreover, in a mixing process, when the molar ratio of Al is 3, it ^{is preferable that the input amount of M<1>} is 1.20 or less in molar ratio. By setting ^{the input amount of M 1} to 1.20 or less in molar ratio, ^{an increase in the abnormality containing M 1} is suppressed, the removal of the abnormality is facilitated by the acid treatment step, and the luminescence intensity can be increased.

Each raw material used in the mixing step may contain at least one selected from the group consisting of a single metal metal element of a metal element included in the composition of the phosphor, and a metal compound containing the metal element. As a metal compound, a nitride, a hydride, a fluoride, an oxide, a carbonate, a chloride, etc. are mentioned. Among them, from the viewpoint of improving the emission intensity of the phosphor, a nitride is preferably used as the metal compound containing ^{M 1} and M ^{2 .} Specific examples of the metal compound containing ^{M 1} _{include Sr 3} N ₂ , SrN ₂ , and SrN. Examples of the metal compound containing ^{M 2} _{include Li 3} N and LiN ₃ . Examples of the metal compound containing M ³ _{include Eu 2} O ₃ , EuN, and EuF ₃ . Examples of metal compounds containing Al, and the like can be _{AlN, AlH 3, AlF 3,} LiAlH 4. In addition, you may add a flux as needed. Examples of the flux include LiF, SrF _{2 , BaF 2} , AlF ₃ , and the like.

(Firing process)

In the firing step, the mixture of the above-mentioned raw materials is filled in the inside of the firing container and fired. It is preferable that the said firing container is equipped with the structure which improves airtightness, and it is preferable that the inside of a firing container is filled with the atmospheric gas of non-oxidizing gas, such as argon, helium, hydrogen, nitrogen. The firing vessel is preferably made of a material that is stable in a high-temperature atmosphere gas and does not easily react with a mixture of raw materials and a reaction product thereof, for example, a vessel made of boron nitride, carbon, molybdenum, tantalum, or tungsten. It is preferable to use a container made of high melting point metal, such as these.

[Firing temperature]

900 degreeC or more is preferable, as for the minimum of the baking temperature in a baking process, 1000 degreeC or more is more preferable, 1100 degreeC or more is still more preferable. On the other hand, 1500 degrees C or less is preferable, as for the upper limit of calcination temperature, 1400 degrees C or less is more preferable, and 1300 degrees C or less is still more preferable. By making the calcination temperature into the above range, the amount of unreacted raw materials after completion of the calcination process can be reduced, and decomposition of the main crystal phase can be suppressed.

[Type of firing atmosphere gas]

As the kind of the firing atmosphere gas in the firing step, for example, a gas containing nitrogen as an element can be preferably used. Specifically, nitrogen and/or ammonia are mentioned, and nitrogen is especially preferable. Similarly, an inert gas such as argon or helium can also be preferably used. The firing atmosphere gas may be composed of one type of gas or may be a plurality of types of gas mixture gas.

[Pressure of Firing Atmosphere Gas]

Although the pressure of the firing atmosphere gas is selected depending on the firing temperature, it is usually in a pressurized state in the range of 0.1 MPa·G or more and 10 MPa·G or less. The higher the pressure of the firing atmosphere gas, the higher the decomposition temperature of the phosphor. However, in consideration of industrial productivity, it is preferably set to 0.5 MPa·G or more and 1 MPa·G or less.

[Firing time]

The firing time in the firing step is selected in a time range in which problems such as a large number of unreacted substances, insufficient growth of phosphor particles, or a decrease in productivity occur. In the manufacturing method of the surface-coated fluorescent substance particle which concerns on embodiment, 0.5 hour or more is preferable, as for the minimum of a baking time, 1 hour or more is more preferable, and 2 hours or more are still more preferable. Moreover, 48 hours or less are preferable, as for the upper limit of calcination time, 36 hours or less are more preferable, and 24 hours or less are still more preferable.

The state of the calcined product obtained by the calcination step varies in powder form and bulk form depending on the raw material mixing and calcination conditions. In the case of actual use as surface-coated phosphor particles, a pulverization/pulverization step and/or a classification operation step of turning the obtained fired product into a powder having a predetermined size may be provided. The average particle diameter of the surface-coated phosphor particles is 5 µm or more and 30 µm when used as the surface-coated phosphor particles for LEDs from the viewpoint of obtaining excitation light absorption efficiency and sufficient luminous efficiency. It is preferable to adjust so that it may become the following. In addition, in the above-mentioned pulverization/pulverization step, in order to prevent mixing of impurities resulting from the treatment, it is preferable that the member of the device in contact with the fired product is made of high toughness ceramics such as silicon nitride, alumina, and sialon.

(acid treatment process)

The acidic solution used in the acid treatment step is preferably an aqueous solution, and the contact with the acidic solution is carried out in an acidic aqueous solution containing at least one of, for example, nitric acid, hydrochloric acid, acetic acid, sulfuric acid, formic acid and phosphoric acid. A method of dispersing the fired material and stirring for several minutes to several hours is common.

Specifically, the above-mentioned calcined product is dispersed in a mixed solution of an organic solvent and an acidic solution, stirred for several hours from a few minutes, and then washed using an organic solvent. The acid treatment can dissolve and remove impurity elements contained in the raw material, impurity elements originating in the calcination vessel, and impurity elements mixed in the pulverization process as a result of abnormalities generated in the calcination process. Since it is also possible to remove the fine powder at the same time, scattering of light can be suppressed, and the light absorptivity of the phosphor is also improved.

Moreover, alcohols, such as methanol, ethanol, 2-propanol, and ketones, such as acetone, can be used as an organic solvent. The acidic solution is one or more of nitric acid, hydrochloric acid, acetic acid, sulfuric acid, formic acid and phosphoric acid. As a mixing ratio of these solutions, it prepares so that an acidic solution may become a density|concentration of 0.1 volume% or more and 3 volume% or less with respect to an organic solvent, for example.

(fluorine treatment process)

In the fluorine treatment step, an aqueous hydrofluoric acid solution is preferably used as the compound containing elemental fluorine to be mixed into the fired product that has undergone the acid treatment step. The lower limit of the concentration of the aqueous hydrofluoric acid solution is preferably 25% or more, more preferably 27% or more, and still more preferably 30% or more. On the other hand, the upper limit of the concentration of the aqueous hydrofluoric acid solution is preferably 38% or less, more preferably 36% or less, and still more preferably 34% or less. By setting the concentration of the aqueous hydrofluoric acid solution to 25% or more, the coating portion containing _{(NH 4} ) ₃ AlF _{6 can be formed on at least a part of the outermost surface of the particles containing the phosphor.} On the other hand, by setting the concentration of the aqueous hydrofluoric acid solution to 38% or less, it is possible to suppress excessively intense reaction between the particles and hydrofluoric acid.

Mixing of the calcined product that has passed through the acid treatment step and the aqueous hydrofluoric acid solution can be performed by a stirring means such as a stirrer. The lower limit of the mixing time of the calcined product and the aqueous hydrofluoric acid solution is preferably 5 minutes or longer, more preferably 10 minutes or longer, and still more preferably 15 minutes or longer. On the other hand, the upper limit of the mixing time of the calcined product and the aqueous hydrofluoric acid solution is preferably 30 minutes or less, more preferably 25 minutes or less, and still more preferably 20 minutes or less. By setting the mixing time of the fired product and the aqueous hydrofluoric acid solution within the above range, the coating portion containing _{(NH 4} ) ₃ AlF _{6 can be stably formed on at least a part of the outermost surface of the particles including the phosphor.}

(heating process)

When the resultant obtained by the fluorine treatment contains (NH ₄ ) ₃ AlF ₆ as a coating part, you may implement a heating process after the above process. 220 degreeC or more is preferable and, as for the minimum of the heating temperature in a heating process, 250 degreeC or more is more preferable. On the other hand, 500 degrees C or less is preferable, as for the upper limit of the said heating temperature, 450 degrees C or less is more preferable, and 400 degrees C or less is still more preferable.

By setting the heating temperature to 220°C or higher, by advancing the following Reaction Formula (1), (NH ₄ ) ₃ AlF ₆ can be changed to AlF _{3 .}

On the other hand, by setting the heating temperature to 500°C or less, the crystal structure of the phosphor can be maintained favorably and the luminescence intensity can be increased.

1 hour or more is preferable, as for the minimum of a heating time, 1.5 hours or more are more preferable, and 2 hours or more are still more preferable. On the other hand, the upper limit of the heating time is preferably 6 hours or less, more preferably 5.5 hours or less, and still more preferably 5 hours or less. By setting the heating time within the above range, (NH ₄ ) ₃ AlF ₆ can be reliably replaced with _{AlF 3} having higher moisture resistance.

In addition, it is preferable to perform a heating process in air|atmosphere or nitrogen atmosphere. According to this, the target substance can be produced|generated without the substance itself in a heating atmosphere inhibiting the said reaction formula (1).

In the present embodiment, the type of acid and solvent in the acid treatment step, the acid concentration, the hydrofluoric acid concentration in the fluorine treatment step, the time of the fluorine treatment, the heating temperature and the heating time in the heating step performed after the fluorine treatment, etc. is appropriately adjusted to form a coating portion covering the surface of the particles containing the phosphor, and the content of the element fluorine with respect to the entire surface-coated phosphor particles is 15% by mass or more and 30% by mass or less, under the conditions described above. Surface-coated phosphor particles having a mass increase rate of 15% or less obtained by measurement can be obtained.

According to the method for producing the surface-coated phosphor particles described above, it is possible to produce nitride phosphor particles having improved moisture resistance and capable of maintaining luminescence intensity over a long period of time.

(light emitting device)

The light-emitting device according to the embodiment includes the surface-coated phosphor particles and the light-emitting element of the above-described embodiment.

As the light emitting element, an ultraviolet LED, a blue LED, or a fluorescent lamp alone or a combination thereof can be used. It is preferable that a light emitting element emits light with a wavelength of 250 nm or more and 550 nm or less, and among these, a blue LED light emitting element of 420 nm or more and 500 nm or less is preferable.

As the phosphor particles used in the light emitting device, other than the surface-coated phosphor particles of the above-described embodiment, phosphor particles having other luminescent colors can be used in combination. Examples of the phosphor particles of other luminescent colors include blue light-emitting phosphor particles, green light-emitting phosphor particles, yellow light-emitting phosphor particles, orange light-emitting phosphor particles, and red phosphor particles, for example, Ca ₃ Sc ₂ Si ₃ O ₁₂ :Ce, CaSc ₂ O _{4 .} :Ce, β-SiAlON:Eu, Y ₃ Al ₅ O ₁₂ :Ce, Tb ₃ Al ₅ O ₁₂ :Ce, (Sr, Ca, Ba) ₂ SiO ₄ :Eu, La ₃ Si ₆ N ₁₁ :Ce, α _{-SiAlON: Eu, Sr 2 Si 5} N 8: Eu, etc. may be mentioned. The phosphor particles that can be used together with the surface-coated phosphor particles of the above-described embodiment are not particularly limited, and can be appropriately selected depending on the luminance, color rendering properties, etc. required for the light emitting device. By mixing the surface-coated phosphor particles of the above-described embodiment with phosphor particles of a different luminous color, white of various color temperatures, such as main white and electric bulb color, can be realized.

As the light emitting device, there are a lighting device, a backlight device, an image display device, and a signal device.

The light emitting device of this embodiment can improve reliability while realizing high light emission intensity by employing the surface-coated phosphor particles of the above-described embodiment.

As mentioned above, although embodiment of this invention was described, these are illustrations of this invention, and you may employ|adopt various structures other than the above.

Example

Hereinafter, although an Example and a comparative example demonstrate this invention, this invention is not limited to these.

(Example 1)

To obtain a phosphor having a composition represented by ^{M 1} _a M ² _b M ³ _c Al ₃ N _4-d O _d ^{and satisfy M 1} =Sr, M ² =Li, M ³ =Eu, Sr ₃ N ₂ (Taiheiyo Cement _{Co., Ltd.), Li 3} N (Materion Co., Ltd.), AlN (Tokuyama Co., Ltd.), Eu ₂ O ₃ (Shin-Etsu Chemical Co., Ltd.) were used as each raw material, and LiF (manufactured by Wako Pure Chemical Industries, Ltd.) as a flux. ) was used. When the molar ratio of Al was set to 3, the input amount of Sr was set to 1.15 by the molar ratio, and the input amount of Eu was set to 0.0115 by the molar ratio. 5 mass % of LiF was added with respect to 100 mass % of the total amount of the said raw material mixture and flux. Incidentally, as described above, when the molar ratio of Al is 3, the input amount of Eu is 0.0115 in the molar ratio.

Hereinafter, the manufacturing method of the surface-coated fluorescent substance particle of Example 1 is specifically described.

In the air, AlN, Eu ₂ O ₃ and LiF were weighed and mixed, and the agglomerates were disintegrated through a nylon sieve having an eye size of 150 μm to obtain a free mixture.

The free mixture was moved into a glove box holding an inert atmosphere containing 1 ppm or less of moisture and 1 ppm or less of oxygen. _{After that, the above-mentioned Sr 3} N ₂ and Li ₃ N are weighed and further blended so that the value of a is 15% excess and the value of b is 20% excess in the stoichiometric ratio (a=1, b=1). After mixing, the agglomeration was disintegrated with a nylon sieve having an eye size of 150 μm to obtain a raw material mixture of a phosphor. Since Sr and Li are easily scattered during firing, more than the theoretical values were blended.

Next, the raw material mixture was filled into a cylindrical BN container with a lid (manufactured by Denka Corporation).

Next, after taking out the said container filled with the raw material mixture of a phosphor from the glove box, it set in the electric furnace (made by Fuji Denpa Kogyo Co., Ltd.) provided with the carbon heater provided with graphite heat insulating material, and performed the baking process.

At the start of the firing step, after degassing the inside of the electric furnace to a vacuum state, firing was started from room temperature in a pressurized nitrogen atmosphere of 0.8 MPa·G. After the temperature in the electric furnace reached 1100°C, firing was continued while maintaining the temperature for 8 hours, and then cooled to room temperature. The obtained calcined material was pulverized with a mortar, classified through a nylon sieve having an eye size of 75 µm, and recovered.

As an acid treatment step, powder of the calcined product was added to a mixed solution in which MeOH (99%) (manufactured by Kokusan Chemical Co., Ltd.) and HNO _{3 (60%) (manufactured by Wako Pure Chemical Industries, Ltd.) was added, followed by stirring for 3 hours,} It classified and obtained phosphor powder.

The fluorine treatment process was implemented by adding the obtained fluorescent substance powder in 30% hydrofluoric acid aqueous solution, and stirring for 15 minutes. After the fluorine treatment process, washing with MeOH until the solution becomes neutral in decantation, performing solid-liquid separation by filtration, drying the solid content, and passing it through a sieve with an eye size of 45 µm to dissolve agglomeration, The surface-coated phosphor particles of Example 1 were obtained.

(Example 2)

After fluorine treatment, the phosphor powder agglomerated by passing through a sieve having an eye size of 45 μm was subjected to heat treatment at 300° C. for 4 hours in an atmospheric atmosphere, except that the same amount of raw materials as in Example 1 and the procedure to obtain the surface-coated phosphor particles of Example 2.

(Example 3)

After the fluorine treatment was performed, the phosphor powder agglomerated by passing through a sieve having an eye size of 45 µm was subjected to heat treatment at 400° C. for 4 hours in an atmospheric atmosphere, except that the same amount of raw materials as in Example 1 and the procedure to obtain the surface-coated phosphor particles of Example 3.

(Comparative Example 1)

Phosphor particles of Comparative Example 1 were obtained in the same manner as in Example 1, except that a 20% aqueous hydrofluoric acid solution was used in the fluorine treatment.

(Comparative Example 2)

A 20% aqueous hydrofluoric acid solution was used in the fluorine treatment, and after the fluorine treatment was performed, the phosphor powder, which was agglomerated by passing through a sieve having an eye size of 45 μm, was subjected to heat treatment at 400° C. for 4 hours in an atmospheric atmosphere, except that Then, the phosphor particles of Comparative Example 2 were obtained in the same amount and procedure as in Example 1.

^{Each element of the chemical composition (ie, general formula: M 1} _a M ² _b M ³ _c Al ₃ N _4-d O _d ) in which all crystal phases were summed for the surface-coated phosphor particles of each Example and the phosphor particles of each comparative example Subscripts a to d were obtained.

In obtaining the said subscripts a to d, it was calculated|required by analyzing the obtained fluorescent substance particle by the following method. That is, analysis results using an ICP emission spectrometer (CIROS-120, manufactured by SPECTRO) for Sr, Li, Al, and Eu, and an oxygen nitrogen analyzer (EMGA-920, manufactured by Horiba Seisakusho) for O and N was calculated using . Table 1 shows the numerical values of a to d for the phosphors of Examples and Comparative Examples.

(The content of elemental fluorine)

The content of elemental fluorine in the entire surface-coated phosphor particles of each Example and the content of elemental fluorine in the entire phosphor particles of each comparative example were measured by a sample combustion apparatus (manufactured by Mitsubishi Chemical Analytech, AQF-2100H) and ion chromatography (Japan). It calculated using the analysis result using the Dionex company make, ICS1500).

(Analysis by X-ray diffraction method)

The crystal structure of the surface-coated phosphor particles of each Example and the phosphor particles of each comparative example was confirmed by a powder X-ray diffraction pattern using CuKα rays using an X-ray diffraction apparatus (UltimaIV, manufactured by Rigaku Corporation). In Example 1, a peak corresponding _{to (NH 4} ) ₃ AlF ₆ was confirmed in the range of 2θ of 16.5° or more to 17.5° or less. In Examples 2 and 3, a peak corresponding _{to AlF 3} was confirmed in the range of 2θ of 14° or more and 15° or less.

In Comparative Example 1, _{a small peak corresponding to (NH 4} ) ₃ AlF ₆ was observed, but compared with Example 1, it is weak and it is thought that the production amount is quite small. Moreover, in Comparative Example 2, _{a peak corresponding to AlF 3} was observed, but compared with Examples 2 and 3, it is weak and it is thought that the amount of production is considerably small.

(Surface analysis by XPS)

The surface-coated phosphor particles of each Example and the phosphor particles of each comparative example were subjected to surface analysis by XPS. In the surface-coated phosphor particles of each Example, it was confirmed that Al and F were present on the outermost surface of the phosphor particles, and that Al and F were covalently bonded. According to the surface analysis result by XPS and the analysis by X-ray diffraction method, in the surface-coated phosphor particles of Example 1, (NH ₄ ) ₃ AlF ₆ constitutes at least a part of the outermost surface of the phosphor particles, In the surface-coated phosphor particles of Examples 2 and 3, it can be said that _{AlF 3 constitutes at least a part of the outermost surface of the phosphor particles.}

(diffuse reflectance)

The diffuse reflectance was measured by attaching an integrating sphere device (ISV-469) to an ultraviolet-visible spectrophotometer (V-550) manufactured by Bunko Corporation. Baseline correction was performed with a standard reflector (spectralon), and a solid sample holder filled with the surface-coated phosphor particles of each example or the phosphor particles of each comparative example was mounted, and the diffuse reflectance and peak wavelength of light with a wavelength of 300 nm were set. The diffuse reflectance with respect to light was measured.

(Luminous properties)

Chromaticity x was measured with a spectrophotometer (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.), and calculated by the following procedure.

The surface-coated phosphor particles of each example or the phosphor particles of each comparative example were filled so that the surface of the concave cell was smooth, and an integrating sphere was mounted. Into this integrating sphere, blue monochromatic light, which was split at a wavelength of 455 nm from a light emitting light source (Xe lamp), was introduced using an optical fiber. Using this blue monochromatic light as an excitation source, the sample of the phosphor was irradiated, and the fluorescence spectrum of the sample was measured.

From the obtained fluorescence spectral data, the peak wavelength and the half-width of the peak were calculated|required.

In addition, the chromaticity x is the CIE chromaticity coordinate x value ( Chromaticity x) was calculated.

(Measurement of mass increase rate)

The prepared powder containing the surface-coated phosphor particles of each Example was stored in an ultra-low humidity dry box with a high internal humidity of 1% RH or less in which deterioration of the powder did not proceed. 1 g of the powder containing the surface-coated phosphor particles of each example was taken and uniformly expanded in a 40 mm phi petri dish. The initial mass W1 of the powder in the dish was measured by measuring the mass of each dish on which the powder was loaded, and subtracting the mass of the dish measured in advance from the measured mass.

Then, using a constant temperature and humidity machine (manufactured by Yamato Chemical Co., Ltd., IW-222), a high-temperature, high-humidity test held under conditions of a temperature of 60°C and a humidity of 90% RH for 50 hours was performed. Thereafter, the petri dish was taken out with a constant temperature and humidity machine, and the mass of each dish loaded with powder was measured within 10 minutes, and the pre-measured mass of the dish was subtracted from the measured mass, thereby initial mass W2 of the powder in the dish. was measured.

Using the obtained W1 and W2, the mass increase rate was computed by Formula (W2-W1)/W1x100 (%). In addition, the mass increase rate was computed by the method similar to the above also about the fluorescent substance particle of a comparative example. The obtained result is shown in Table 1.

(luminescence intensity ratio)

For the surface-coated phosphor particles of each Example and the phosphor particles of each comparative example, the luminescence intensity I ₀ before starting the high-temperature, high-humidity test was measured. Next, the luminescence intensity I after the high-temperature, high-humidity test loaded in the environment of 60 degreeC and 90%RH for 50 hours was measured. The luminescence intensity ratio I/I ₀ (%) was calculated from the obtained measured values. Table 1 shows the results obtained with respect to the emission intensity ratio I/I _{0 .}

In addition, the measurement of luminescence intensity was measured using the spectrofluorescence photometer (Hitachi High-Technologies company make, F-7000) corrected with rhodamine B and an auxiliary standard light source. That is, the fluorescence spectrum at an excitation wavelength of 455 nm was measured using the attached solid sample holder for the photometer.

The peak wavelength of the fluorescence spectrum of the surface-coated phosphor particles of each Example and the phosphor particles of each comparative example was 656 nm. The intensity value at the peak wavelength of the fluorescence spectrum was defined as the emission intensity of the surface-coated phosphor particles or phosphor particles.

As shown in Table 1, in the surface-coated phosphor particles of Examples 1 to 3 in which the mass increase rate can be suppressed to 15% or less, as compared with Comparative Examples 1 and 2, the decrease in luminescence intensity after the high temperature, high humidity test was suppression was confirmed. In Examples 1 to 3, it is thought that moisture resistance is improved by providing the coating portion in which the mass increase rate is 15% or less, and further, the luminescence intensity can be maintained over a long period of time. On the other hand, in the fluorescent substance particles of Comparative Examples 1 and 2, the mass increase rate exceeded 15 %, and it was confirmed that the light emission intensity after a high temperature, high humidity test fell significantly.

This application claims priority on the basis of Japanese Patent Application No. 2019-074460 for which it applied on April 9, 2019, and takes in all the indications here.

Claims (10)

Particles comprising a phosphor;
The coating part which coats the surface of the said particle|grain
It is a surface-coated phosphor particle comprising a,
The phosphor is
General formula M ¹ _a M ² _b M ³ _c Al ₃ N _4-d O _d (provided that M ¹ is at least one element selected from Sr, Mg, Ca and Ba, and M ² is selected from Li and Na at least one element, and M ³ is at least one element selected from Eu and Ce.)

to meet,
With respect to the whole said surface-coated fluorescent substance particle, the content rate of the element fluorine is 15 mass % or more and 30 mass % or less,
The surface-coated fluorescent substance particle whose mass increase rate obtained by measuring on the following conditions is 15 % or less.
(Conditions for measuring mass increase rate)
Let the initial mass of the powder containing the surface-coated phosphor particles be W1, the mass of the powder after 50 hours under the conditions of a temperature of 60°C and a humidity of 90% RH is denoted as W2, and the mass increase rate is (W2-W1)/ It is calculated as W1 x 100 (%). The surface-coated fluorescent substance particle of Claim 1 in which the said coating part comprises the fluorine compound containing the fluorine element while constituting at least a part of the outermost surface of the said particle|grain. The surface-coated phosphor particle according to claim 1 or 2, wherein the coating portion contains a fluorine compound containing elemental fluorine and elemental aluminum. The surface-coated phosphor according to any one of claims 1 to 3, wherein M ¹ contains at least Sr, M ² contains at least Li, and M ³ contains at least Eu. particle. The surface according to any one of claims 1 to 4, wherein the diffuse reflectance with respect to light irradiation with a wavelength of 300 nm is 56% or more, and the diffuse reflectance with respect to light irradiation at the peak wavelength of the fluorescence spectrum is 85% or more. coated phosphor particles. The surface according to any one of claims 1 to 5, wherein when excited with blue light having a wavelength of 455 nm, the peak wavelength is in the range of 640 nm or more and 670 nm or less, and the half width is 45 nm or more and 60 nm or less. coated phosphor particles. The surface according to any one of claims 1 to 6, wherein, when excited with blue light having a wavelength of 455 nm, the color purity of the emitted color satisfies 0.680≤x<0.735 in the CIE-xy chromaticity diagram. coated phosphor particles. A method for producing the surface-coated phosphor particles according to any one of claims 1 to 7,
A mixing process of mixing the raw materials;
a firing step of firing the mixture obtained by the mixing step;
Acid treatment process of mixing the calcined product obtained by the calcination process and an acidic solution
including,
In the mixing step, when the molar ratio of Al is 3, ^{the amount of M 1 added} is 1.10 or more and 1.20 or less in a molar ratio. A method for producing surface-coated phosphor particles. The method for producing surface-coated phosphor particles according to claim 8, wherein in the acid treatment step, an aqueous hydrofluoric acid solution having a fluorine concentration of 25% or more is used in the acidic solution. A light emitting device comprising the surface-coated phosphor particles according to any one of claims 1 to 7 and a light emitting element.