WO2020209147A1

WO2020209147A1 - Surface-coated fluorescent particles, production method for surface-coated fluorescent particles, and light-emitting device

Info

Publication number: WO2020209147A1
Application number: PCT/JP2020/014910
Authority: WO
Inventors: 雅斗赤羽; 秀幸江本
Original assignee: デンカ株式会社
Priority date: 2019-04-09
Filing date: 2020-03-31
Publication date: 2020-10-15
Also published as: CN113785030A; KR20210150474A; TWI829912B; JPWO2020209147A1; TW202104549A; CN113785030B

Abstract

A surface-coated fluorescent particle according to the present invention is composed of a particle that includes a fluorophore, and a coating part that coats the surface of the particle, wherein: the fluorophore has a composition expressed by the general formula M¹ _aM² _bM³ _cAl₃N_4-dO_d (therein, M¹ is one or more elements selected from among Sr, Mg, Ca and Ba, M² is one or more elements selected from among Li and Na, and M³ is one or more elements selected from among Eu and Ce); a, b, c and d satisfy the formulae 0.850≤a≤1.150, 0.850≤b≤1.150, 0.001≤c≤0.015, 0≤d≤0.40 and 0≤d/(a+d)<0.30; the coating part constitutes at least a part of the outermost surface of the particle, and includes a fluorinated compound that contains elemental fluorine and elemental aluminum; and the elemental fluorine constitutes 15-30 mass%, inclusive, of the entire surface-coated fluorescent particle.

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.

Light emitting devices formed by combining light emitting diodes (LEDs) and phosphors are widely 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, high color reproducibility is required. Therefore, it is desired to use a phosphor having a narrow full width at half maximum (hereinafter, simply referred to as "full width at half maximum") of the fluorescence spectrum. ..

As a red phosphor having a narrow half-value width that has been conventionally used, a nitride phosphor or an oxynitride phosphor activated by Eu ²⁺ is known. Typical pure nitride phosphors include Sr ₂ Si ₅ N ₈ : Eu ²⁺ , CaAlSiN ₃ : Eu ²⁺ (abbreviated as CASN), (Ca, Sr) AlSiN ₃ : Eu ²⁺ (abbreviated as SCANSN). )and so on. The CASN phosphor and the SCASN phosphor have a peak wavelength in the range of 610 to 680 nm, and the half width thereof is relatively narrow as 75 nm or more and 90 nm or less. However, when these phosphors are used as a light emitting device for a liquid crystal display, further expansion of the color reproduction range is desired, and a phosphor having a narrower half-value width is desired.

In recent years, an SrLiAl ₃ N ₄ : Eu ²⁺ (abbreviated as SLAN) phosphor has been known as a narrow band red phosphor having a half-value width of 70 nm or less, and a light emitting device applying this phosphor has excellent color rendering properties. And color reproducibility can be expected.

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

JP-A-2017-088881

The SLAN phosphor has the property of being easily decomposed when it comes into contact with water. This property causes the emission intensity to decrease with the passage of time. In recent years, further improvement in reliability of a light emitting device using an SLAN phosphor has been required, and further improvement in moisture resistance of the SLAN phosphor has also been required.

As a result of the examination by the present inventor, in the particles containing the SLAN phosphor and the nitride phosphor having a similar crystal structure, the detailed mechanism is not clear, but the particle surface is composed of at least a fluorine-containing compound and the particle surface is composed of at least a fluorine-containing compound. It has been found that the decrease in fluorescence intensity in a water-exposed environment can be suppressed, that is, the moisture resistance can be improved by setting the content of the fluorine element with respect to the entire particles to a predetermined value or more.

According to the present invention, the surface-coated phosphor particles include particles containing a phosphor and a coating portion that covers the surface of the particles, and the phosphor is a general formula M ¹ _a M ² _b M ³ _c Al ₃ N _4-d _Od (where M ¹ is one or more elements selected from Sr, Mg, Ca and Ba, and M ² is one or more elements selected from Li and Na. , M ³ is one or more elements selected from Eu and Ce), and the a, b, c, and d satisfy 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 coating portion comprises at least a part of the outermost surface of the particles and contains a fluorine-containing compound containing a fluorine element and an aluminum element.
Provided are surface-coated phosphor particles having a fluorine element content of 15% by mass or more and 30% by mass or less with respect to the entire surface-coated phosphor particles.

Further, according to the present invention, in the above-mentioned method for producing surface-coated phosphor particles, a mixing step of mixing raw materials, a firing step of firing the mixture obtained by the mixing step, and a firing step of firing the mixture obtained by the mixing step are obtained. In the mixing step, Al includes an acid treatment step of mixing the fired product and an acidic solution, and a fluorine treatment step of mixing the fired product that has undergone the acid treatment step with a compound containing a fluorine element. Provided is a method for producing surface-coated phosphor particles in which the amount of M ¹ charged is 1.10 or more and 1.20 or less when the molar ratio is 3.

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

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

Hereinafter, embodiments of the present invention will be described in detail.

The surface-coated phosphor particles according to the embodiment include particles containing a phosphor and a coating portion that covers the surface of the particles. The details of the surface-coated phosphor particles will be described below.

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 _Od . a, b, c, 4-d, and d indicate the molar ratio of each element.

In the above general formula, M ¹ is one or more elements selected from Sr, Mg, Ca and Ba. Preferably, M ¹ comprises at least Sr. The lower limit of the molar ratio a of M ¹ is preferably 0.850 or more, more preferably 0.950 or more. On the other hand, the upper limit of the molar ratio a of M ¹ is preferably 1.150 or less, more preferably 1.100 or less, and even more preferably 1.050 or less. By setting the molar ratio a of M ¹ to the above range, the crystal structure stability can be improved.

In the above general formula, M ² is one or more elements selected from Li and Na. Preferably, M ² contains at least Li. Molar ratio lower limit of b of M ² is preferably not less than 0.850, more preferably not less than 0.950. On the other hand, the upper limit of the molar ratio b of ^{M 2} is preferably 1.150 or less, more preferably 1.100 or less, more preferably 1.050 or less. The molar ratio a of M ² is in the above range, it is possible to improve the crystal structure stability.

In the above general formula, M ³ is an activator added to the mother crystal, that is, an element constituting the emission center ion of the phosphor, and is one or more elements selected from Eu and Ce. M ³ can be selected according to the required 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 c of ^{M 3} is preferably 0.015 or less, more preferably 0.010 or less. By setting the lower limit of the molar ratio c of M ³ to the above range, sufficient emission intensity can be obtained. Further, by setting the upper limit of the molar ratio c of M ³ to the above range, concentration quenching can be suppressed and the 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, more preferably 0.05 or more. On the other hand, the upper limit of the molar ratio d of oxygen is preferably 0.40 or less, more preferably 0.35 or less. By setting the molar ratio d of oxygen in the above range, the crystalline state of the phosphor can be stabilized and the emission intensity can be maintained at a sufficient value.
Further, the content of the oxygen element in the phosphor is preferably less than 2% by mass, more preferably 1.8% by mass or less. By setting the content of the oxygen element to less than 2% by mass, the crystalline state of the phosphor can be stabilized and the emission intensity can be maintained at a sufficient value.

The lower limit of the molar ratio of M ¹ and oxygen, that is, the value of d / (a + d) calculated from a and d is preferably 0 or more, and more preferably 0.05 or more. On the other hand, the upper limit of the value of d / (a + d) is preferably less than 0.30, more preferably 0.25 or less. By setting d / (a + d) in the above range, the crystal state of the phosphor can be stabilized and the emission intensity can be maintained at a sufficient value.

The covering portion constitutes at least a part of the outermost surface of the particles containing the above-mentioned phosphor. The coating contains a fluorine-containing compound containing a fluorine element and an aluminum element.
In the fluorine-containing compound, it is preferable that the fluorine element and the aluminum element are directly covalently bonded, and more specifically, the fluorine-containing compound is one or both of (NH ₄ ) ₃ AlF _{6 and} AlF _3. Is preferably included. The fluorine-containing compound may be composed of a single compound containing a fluorine element and an aluminum element.
By forming at least a part of the surface of the particles containing the phosphor in the above-mentioned coating portion, the moisture resistance of the phosphor constituting the particles can be improved. From the viewpoint of further improving the moisture resistance of the phosphor, it is more preferable that the coating portion contains AlF ₃ .

The mode of the covering portion is not particularly limited, but the covering portion may be configured to cover at least a part of the particle surface, and may be configured to cover the entire particle surface. Examples of the mode of the coating portion include a mode in which a large number of particulate fluorine-containing compounds are distributed on the surface of the particles containing the phosphor, and a mode in which the fluorine-containing compound continuously covers the surface of the particles containing the phosphor. Can be mentioned.

In the present embodiment, the content of the fluorine element with respect to the entire surface-coated phosphor particles is 15% by mass or more and 30% by mass or less. Moisture resistance can be enhanced by setting the content of the fluorine element to the entire surface-coated phosphor particles to be 15% by mass or more. By setting the content of the fluorine element with respect to the entire surface-coated phosphor particles to 30% by mass or less, it is possible to maintain the emission intensity at a sufficient value while increasing the moisture resistance.
The lower limit of the content of the fluorine element with respect to the entire surface-coated phosphor particles is more preferably 18% by mass or more, further preferably 20% by mass or more. Further, the upper limit of the content of the fluorine element with respect to the entire surface-coated phosphor particles is more preferably 27% by mass or less, further preferably 25% by mass or less. By setting the lower limit of the content of the fluorine element in the above range, the moisture resistance can be further enhanced. Further, by setting the upper limit of the content of the fluorine element in the above range, it is possible to further improve the moisture resistance and maintain the emission intensity at a sufficient value.
The fluorine element is derived from the fluoride of the metal element used as a raw material, which will be described later, or is added by the fluorine treatment step described later, and does not constitute the crystal structure of the phosphor.

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

The diffuse reflectance of the surface-coated phosphor particles of the present embodiment with respect to light irradiation at a wavelength of 300 nm is, for example, 56% or more, more preferably 58% or more, and more preferably 60% or more.
Further, the diffuse reflectance of the surface-coated phosphor particles with respect to light irradiation at the peak wavelength of the fluorescence spectrum is, for example, 85% or more, preferably 86% or more. By providing such characteristics, the luminous efficiency is further increased and the luminous intensity is improved.

An example of the surface-coated phosphor particles of the present embodiment preferably has a peak wavelength in the 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 when excited by blue light having a wavelength of 455 nm. By providing such characteristics, excellent color rendering and color reproducibility can be expected.

An example of the surface-coated phosphor particles of the present embodiment has a color purity of emission color of 0.680 ≦ x <0.735 in the CIE-xy chromaticity diagram when excited by blue light having a wavelength of 455 nm. It is preferable to meet. By providing such characteristics, excellent color rendering and color reproducibility can be expected. If the x value is 0.680 or more, red light emission with good color purity can be further expected, and if the x value is 0.735 or more, it exceeds the maximum value in the CIE-xy chromaticity diagram, so the above range is satisfied. Is preferable.

In the present embodiment, the type of acid and solvent in the acid treatment step, the concentration of the acid, the concentration of hydrofluoric acid 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. By appropriately adjusting the above, a fluorine-containing compound containing a fluorine element and an aluminum element can be formed on the surface of the particles containing a phosphor, and the content of the fluorine element in the particles can be controlled within a desired range. Can be done.

According to the surface-coated phosphor particles described above, the moisture resistance of the nitride phosphor can be enhanced by coating the surface of the phosphor particles with a coating portion containing a fluorine-containing compound containing a fluorine element and an aluminum element. As a result, the emission intensity can be maintained for a long period of time.

(Manufacturing method of surface-coated phosphor particles)
The surface-coated phosphor particles of the present embodiment are 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. It can be produced by a fluorine treatment step of mixing a fired product that has undergone the acid treatment step and a compound containing a fluorine element. In addition to the above steps, it is preferable to add a heating step of applying a heat treatment to the result product obtained by the fluorine treatment step.

(Mixing process)
The mixing step is a step of mixing each of the raw materials weighed so as to obtain the desired surface-coated phosphor particles to obtain a powdered raw material mixture. The method of mixing the raw materials is not particularly limited, but for example, there is a method of sufficiently mixing using a mixing device such as a mortar, a ball mill, a V-type mixer, and a planetary mill. Strontium nitride, lithium nitride, etc., which react violently with moisture and oxygen in the air, should be handled in a glove box in which the inside is replaced with an inert atmosphere or by using a mixing device.

In the mixing step, it is preferable that the amount of M ¹ charged when the molar ratio of Al is 3 is 1.10 or more in terms of molar ratio. By setting the amount of M ¹ charged to 1.10 or more in terms of molar ratio, it is possible to prevent the shortage of M ¹ in the phosphor due to volatilization of M ¹ during the firing process, and it is difficult for defects to occur in M ^1. , The crystallinity of the crystal structure is kept good. As a result, a narrow-band fluorescence spectrum can be obtained, and it is presumed that the emission intensity can be increased. Further, in the mixing step, it is preferable that the amount of M ¹ charged when the molar ratio of Al is 3 is 1.20 or less in terms of molar ratio. By setting the charge amount of M ¹ to 1.20 or less in terms of molar ratio, the increase of the different phase containing M ¹ can be suppressed, the removal of the different phase can be facilitated by the acid treatment step, and the emission intensity can be increased.

Each raw material used in the mixing step can include one or more selected from the group consisting of a simple substance of a metal element contained in the composition of a phosphor and a metal compound containing the metal element. Examples of the metal compound include nitrides, hydrides, fluorides, oxides, carbonates, chlorides and the like. Of these, nitrides are preferably used as the metal compound containing M ¹ and M ² from the viewpoint of improving the emission intensity of the phosphor. Specifically, as a metal compound containing ^{_{_{_{M 1, Sr 3 N 2,}}}} SrN 2, etc. SrN the like. Examples of the metal compound containing M ² include Li ₃ N and Li N ₃ . Examples of the metal compound containing M ³ include Eu ₂ O ₃ , Eu N, and Eu F ₃ . Examples of the metal compound containing Al include AlN, AlH ₃ , AlF ₃ , LiAlH _{4 and the} like. If necessary, flux may be added. Examples of the flux include LiF, SrF ₂ , BaF ₂ , AlF _{3, and the} like.

(Baking process)
In the firing step, the above-mentioned mixture of raw materials is filled inside the firing container and fired. The firing container preferably has a structure capable of enhancing airtightness, and the inside of the firing container is preferably filled with an atmospheric gas of a non-oxidizing gas such as argon, helium, hydrogen, or nitrogen. The firing vessel is preferably made of a material that is stable under high temperature atmospheric gas and does not easily react with the mixture of raw materials and the reaction product thereof. For example, a vessel made of boron nitride or carbon, molybdenum or tantalum, or a container made of boron nitride or tantalum. It is preferable to use a container made of a refractory metal such as molybdenum or tungsten.

[Baking temperature]
The lower limit of the firing temperature in the firing step is preferably 900 ° C. or higher, more preferably 1000 ° C. or higher, and even more preferably 1100 ° C. or higher. On the other hand, the upper limit of the firing temperature is preferably 1500 ° C. or lower, more preferably 1400 ° C. or lower, and even more preferably 1300 ° C. or lower. By setting the firing temperature within the above range, the amount of unreacted raw material after the completion of the firing step can be reduced, and the decomposition of the main crystal phase can be suppressed.

[Type of firing atmosphere gas]
As the type of firing atmosphere gas in the firing step, for example, a gas containing nitrogen as an element can be preferably used. Specific examples include nitrogen and / or ammonia, with nitrogen being particularly preferred. 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 a mixed gas of a plurality of types of gases.

[Pressure of firing atmosphere gas]
The pressure of the firing atmosphere gas is selected according to the firing temperature, but 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, but considering industrial productivity, it is preferably 0.5 MPa · G or more and 1 MPa · G or less.

[Baking time]
As the firing time in the firing step, a time range is selected in which a large amount of unreacted substances are not present, the phosphor particles are insufficiently grown, or the productivity is not lowered. In the method for producing surface-coated phosphor particles according to the embodiment, the lower limit of the firing time is preferably 0.5 hours or more, more preferably 1 hour or more, still more preferably 2 hours or more. The upper limit of the firing time is preferably 48 hours or less, more preferably 36 hours or less, and even more preferably 24 hours or less.

The state of the fired product obtained by the firing process varies from powdery to lumpy depending on the raw material composition and firing conditions. A crushing / crushing step and / or a classification operation step of converting the obtained fired product into a powder having a predetermined size may be provided in preparation for actual use as surface-coated phosphor particles. The average particle size of the surface-coated fluorophore particles is the same as that of the surface-coated phosphor particles when used as the surface-coated phosphor particles for LEDs, from the viewpoint of obtaining excitation light absorption efficiency and sufficient emission efficiency. It is preferable to adjust so that the average particle size is 5 μm or more and 30 μm or less. Further, in the above-mentioned crushing / crushing step, in order to prevent impurities derived from the treatment from being mixed in, 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 described above in an acidic aqueous solution containing one or more of nitric acid, hydrochloric acid, acetic acid, sulfuric acid, formic acid and phosphoric acid, for example. A general method is to disperse the calcined product and stir for several minutes to several hours.
Specifically, the above-mentioned fired product can be dispersed in a mixed solution of an organic solvent and an acidic solution, stirred for several minutes to several hours, and then washed with an organic solvent. By the acid treatment, impurity elements contained in the raw material, impurity elements derived from the firing container, different phases generated in the firing step, and impurity elements mixed in the crushing step can be dissolved and removed. Since it is possible to remove fine powder at the same time, light scattering can be suppressed and the light absorption rate of the phosphor can be improved.
As the organic solvent, alcohols such as methanol, ethanol and 2-propanol and ketones such as acetone can be used. The acidic solution is one or more of nitric acid, hydrochloric acid, acetic acid, sulfuric acid, formic acid, and phosphoric acid. The mixing ratio of these solutions is, for example, adjusted so that the acidic solution has a concentration of 0.1% by volume or more and 3% by volume or less with respect to the organic solvent.

(Fluorine treatment process)
In the fluorine treatment step, a hydrofluoric acid aqueous solution is preferably used as a compound containing a fluorine element to be mixed with the fired product that has undergone the acid treatment step. The lower limit of the concentration of the hydrofluoric acid aqueous solution is preferably 25% or more, more preferably 27% or more, still more preferably 30% or more. On the other hand, the upper limit of the concentration of the hydrofluoric acid aqueous solution is preferably 38% or less, more preferably 36% or less, still more preferably 34% or less. By setting the concentration of the hydrofluoric acid aqueous solution to 25% or more, a 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 hydrofluoric acid aqueous solution to 38% or less, it is possible to prevent the reaction between the particles and hydrofluoric acid from becoming too violent.
The fired product that has undergone the acid treatment step and the hydrofluoric acid aqueous solution can be mixed by a stirring means such as a stirrer. The lower limit of the mixing time of the fired product and the aqueous solution of hydrofluoric acid is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 15 minutes or more. On the other hand, the upper limit of the mixing time of the fired product and the aqueous solution of hydrofluoric acid is preferably 30 minutes or less, more preferably 25 minutes or less, still more preferably 20 minutes or less. By setting the mixing time of the fired product and the aqueous solution of hydrofluoric acid within the above range, a coating portion containing (NH ₄ ) ₃ AlF ₆ is stably formed on at least a part of the outermost surface of the particles containing the phosphor. Can be done.

(Heating process)
When the product obtained by the fluorine treatment contains (NH ₄ ) ₃ AlF ₆ as a coating portion, a heating step may be carried out after the above steps. The lower limit of the heating temperature in the heating step is preferably 220 ° C. or higher, more preferably 250 ° C. or higher. On the other hand, the upper limit of the heating temperature is preferably 500 ° C. or lower, more preferably 450 ° C. or lower, and even more preferably 400 ° C. or lower.
By setting the heating temperature to 220 ° C. or higher and proceeding with the following reaction formula (1), (NH ₄ ) ₃ AlF ₆ can be changed to AlF ₃ .
(NH ₄ ) ₃ AlF ₆ → AlF ₃ + 3NH ₃ + 3HF ... (1)
On the other hand, by setting the heating temperature to 500 ° C. or lower, the crystal structure of the phosphor can be maintained well and the emission intensity can be increased.
The lower limit of the heating time is preferably 1 hour or more, more preferably 1.5 hours or more, still more preferably 2 hours or more. 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 even more preferably 5 hours or less. By setting the heating time within the above range, (NH ₄ ) ₃ AlF ₆ can be reliably changed to AlF ₃ having higher moisture resistance.
The heating step is preferably carried out in the air or in a nitrogen atmosphere. According to this, the target substance can be produced without the substance itself in the heating atmosphere hindering the above reaction formula (1).

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

(Light emitting device)
The light emitting device according to the embodiment includes the surface-coated phosphor particles of the above-described embodiment and a light emitting element.
As the light emitting element, an ultraviolet LED, a blue LED, a fluorescent lamp alone, or a combination thereof can be used. The light emitting element is preferably one that emits light having a wavelength of 250 nm or more and 550 nm or less, and particularly preferably a blue LED light emitting element of 420 nm or more and 500 nm or less.

As the phosphor particles used in the light emitting device, in addition to the surface-coated phosphor particles of the above-described embodiment, fluorescent particles having other emission colors can be used in combination. Examples of the phosphor particles having other emission colors include blue emission phosphor particles, green emission phosphor particles, yellow emission phosphor particles, orange emission phosphor particles, and red phosphor. 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 Examples thereof include Si ₆ N ₁₁ : Ce, α-SiAlON: Eu, Sr ₂ Si ₅ N ₈ : Eu and the like. The phosphor particles that can be used in combination with the surface-coated phosphor particles of the above-described embodiment are not particularly limited, and can be appropriately selected depending on the brightness, color rendering property, and the like required for the light emitting device. By mixing the surface-coated phosphor particles of the above-described embodiment with phosphor particles of other emission colors, it is possible to realize white color having various color temperatures such as neutral white color and light bulb color.
Light emitting devices include a lighting device, a backlight device, an image display device, and a signal device.

By adopting the surface-coated phosphor particles of the above-described embodiment, the light emitting device of this embodiment can improve reliability while realizing high light emitting intensity.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above can be adopted.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Example 1)
In order to obtain a phosphor having a composition represented by M ¹ _a M ² _b M ³ _c Al ₃ N _4-d _Od and satisfying M ¹ = Sr, M ² = Li, and M ³ = Eu. Sr ₃ N ₂ (manufactured by Pacific Cement), Li ₃ N (manufactured by Matterion), AlN (manufactured by Tokuyama), Eu ₂ O ₃ (manufactured by Shin-Etsu Chemical Industries) are used as raw materials, and LiF (Jun Wako) is used as the flux. Made by Yakusha) was used. When the molar ratio of Al was 3, the amount of Sr charged was 1.15, and the amount of Eu charged was 0.0115. 5% by mass of LiF was added to 100% by mass of the total amount of the raw material mixture and the flux. As described above, Eu has a molar ratio of 0.0115 when the molar ratio of Al is 3.
Hereinafter, the method for producing the surface-coated phosphor particles of Example 1 will be specifically described.
AlN, Eu ₂ O ₃ and LiF were weighed and mixed in the air, and then the agglomerates were crushed with a nylon sieve having a mesh size of 150 μm to obtain a premix.
The pre-mixture was moved into a glove box holding an inert atmosphere with water content of 1 ppm or less and oxygen of 1 ppm or less. Then, after weighing the above-mentioned Sr ₃ N ₂ and Li ₃ N 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 additional compounding and mixing, the agglomeration was crushed with a nylon sieve having an opening of 150 μm to obtain a raw material mixture of the phosphor. Since Sr and Li are likely to scatter during firing, they are blended in a larger amount than the theoretical value.
Next, the raw material mixture was filled in a cylindrical BN container with a lid (manufactured by Denka Corporation).
Next, after taking out the container filled with the raw material mixture of the phosphor from the glove box, it was set in an electric furnace (manufactured by Fuji Denpa Kogyo Co., Ltd.) equipped with a graphite heat insulating material and equipped with a carbon heater, and a firing step was carried out.
At the start of the firing step, the inside of the electric furnace was once degassed to a vacuum state, and then firing was started in a pressurized nitrogen atmosphere of 0.8 MPa · G from room temperature. 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 product was pulverized in a mortar, classified with a nylon sieve having an opening of 75 μm, and recovered.
As an acid treatment step, after adding the powder of the calcined product to a mixed solution of MeOH (99%) (manufactured by Kokusan Kagaku Co., Ltd.) and HNO ₃ (60%) (manufactured by Wako Pure Chemical Industries, Ltd.) and stirring for 3 hours. , Classified to obtain a phosphor powder.
The obtained fluorescent powder was added to a 30% aqueous hydrofluoric acid solution, and the mixture was stirred for 15 minutes to carry out a fluorine treatment step. After the fluorine treatment step, the solution is washed by decantation with MeOH until the solution becomes neutral, solid-liquid separation is performed by filtration, the solid content is dried, and the solid content is passed through a sieve having a mesh size of 45 μm. , The agglomeration was released to obtain the surface-coated phosphor particles of Example 1.

(Example 2)
The fluorescent powder, which had been subjected to fluorine treatment and then disaggregated by passing through a sieve having a mesh size of 45 μm, was heat-treated at 250 ° C. for 4 hours in an air atmosphere, except that it was heat-treated. The surface-coated phosphor particles of Example 2 were obtained by the same raw material charge amount and procedure as in Example 1.

(Example 3)
After being treated with fluorine, the fluorescent powder that had been disaggregated by passing through a sieve with a mesh size of 45 μm was heat-treated at 300 ° C. for 4 hours in an air atmosphere. The surface-coated phosphor particles of Example 3 were obtained by the same amount and procedure of charging raw materials as in Example 1.

(Example 4)
After being treated with fluorine, the fluorescent powder that had been disaggregated by passing through a sieve with a mesh size of 45 μm was heat-treated at 350 ° C. for 4 hours in an air atmosphere. The surface-coated phosphor particles of Example 4 were obtained by the same amount and procedure of charging raw materials as in Example 1.

(Example 5)
After being treated with fluorine, the fluorescent powder that had been disaggregated by passing through a sieve with a mesh size of 45 μm was heat-treated at 400 ° C. for 4 hours in an air atmosphere. , The surface-coated phosphor particles of Example 5 were obtained by the same raw material charge amount and procedure as in Example 1.

(Comparative Example 1)
The phosphor particles of Comparative Example 1 were obtained by the same raw material charge amount and procedure as in Example 1 except that the fluorine treatment was not performed.

(Comparative Example 2)
Fluorescent particles of Comparative Example 2 were obtained by the same raw material charge amount and procedure as in Example 1 except that a 10% hydrofluoric acid aqueous solution was used for the fluorine treatment.

(Comparative Example 3)
Fluorescent particles of Comparative Example 3 were obtained by the same raw material charge amount and procedure as in Example 1 except that a 20% hydrofluoric acid aqueous solution was used for the fluorine treatment.

For the surface-coated fluorescent particles of each example and the fluorescent particles of each comparative example, the total chemical composition of all crystal phases (that is, general formula: M ¹ _a M ² _b M ³ _c Al ₃ N _4-d _Od ), The subscripts a to d of each element were obtained.
In obtaining the above subscripts a to d, the obtained phosphor particles were analyzed by the following method. That is, analysis using an ICP emission spectroscopic analyzer (Spectro, CIROS-120) for Sr, Li, Al and Eu, and an oxygen-nitrogen analyzer (EMGA-920, HORIBA, Ltd.) for O and N. Calculated using the results. Table 1 shows the numerical values a to d for the phosphors of Examples and Comparative Examples.

(Analysis by X-ray diffraction method)
The crystal structures of the surface-coated fluorescent particles of each example and the fluorescent particles of each comparative example were confirmed by a powder X-ray diffraction pattern using CuKα rays using an X-ray diffractometer (Ultima IV manufactured by Rigaku Co., Ltd.). .. In Example 1, a peak corresponding to (NH ₄ ) ₃ AlF ₆ was confirmed in the range where 2θ was 16.5 ° or more and 17.5 ° or less. In Examples 2 to 5, a peak corresponding to AlF ₃ was confirmed in the range where 2θ was 14 ° or more and 15 ° or less. On the other hand, in Comparative Examples 1 and 2, neither the peak corresponding to (NH ₄ ) ₃ AlF ₆ nor the peak corresponding to AlF ₃ was observed. In Comparative Example 3, no peak corresponding to AlF ₃ was confirmed, and a small peak corresponding to (NH ₄ ) ₃ AlF ₆ was observed.

(Surface analysis by XPS)
The surface-coated fluorescent particles of each example and the fluorescent particles of each comparative example were subjected to surface analysis by XPS. Regarding 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. On the other hand, in Comparative Examples 1 and 2, it was not confirmed that Al and F were covalently bonded, and in Comparative Example 3, it was confirmed that Al and F were covalently bonded, albeit slightly.
According to the surface analysis result by XPS and the analysis by the X-ray diffractometry, in the surface-coated phosphor particles of Example 1, at least a part of the outermost surface of the phosphor particles is composed of (NH ₄ ) ₃ AlF ₆ . In the surface-coated phosphor particles of Examples 2 to 5, it can be said that AlF ₃ constitutes at least a part of the outermost surface of the phosphor particles.
Further, in Comparative Examples 1 and 2, (NH ₄ ) ₃ AlF ₆ and AlF ₃ were not present on the outermost surface of the phosphor particles, and in Comparative Example 3, AlF ₃ was not present and was slightly present. (NH ₄ ) ₃ AlF ₆ is considered to be present.

(Content rate of fluorine element)
The content of fluorine element in the entire surface-coated phosphor particles of each example and the content of fluorine element in the entire phosphor particles of each comparative example are determined by a sample combustion device (manufactured by Mitsubishi Chemical Analytech Co., Ltd., AQF-2100H) and ions. It was calculated using the analysis result using a chromatograph (ICS1500 manufactured by Nippon Dionex Co., Ltd.).

(Diffuse reflectance)
The diffuse reflectance was measured by attaching an integrating sphere device (ISV-469) to an ultraviolet-visible spectrophotometer (V-550) manufactured by JASCO Corporation. Baseline correction is 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 is attached, and the diffuse reflectance for light having a wavelength of 300 nm is determined. And the diffuse reflectance for light of peak wavelength was measured.

(Emission characteristics)
The chromaticity x was measured by a spectrophotometer (MCPD-7000 manufactured by Otsuka Electronics Co., Ltd.) and calculated by the following procedure.
The surface-coated fluorescent particles of each example or the fluorescent particles of each comparative example were filled so that the surface of the concave cell was smooth, and an integrating sphere was attached. Blue monochromatic light dispersed at a wavelength of 455 nm from a light source (Xe lamp) was introduced into the integrating sphere using an optical fiber. Using this monochromatic light as an excitation source, a phosphor sample was irradiated, and the fluorescence spectrum of the sample was measured.
The peak wavelength and the half width of the peak were obtained from the obtained fluorescence spectrum data.
Further, the chromaticity x is the CIE chromaticity coordinate x value in the XYZ color system defined by JIS Z 8781-3: 2016 according to JIS Z 8724: 2015 from the wavelength range data in the range of 465 nm to 780 nm of the fluorescence spectrum data. (Saturation x) was calculated.

(Ratio of emission intensity before and after high temperature and high humidity test)
For the surface-coated fluorescent particles of each example and the fluorescent particles of each comparative example, the emission intensity I ₀ was measured before starting the high temperature and high humidity test. Subsequently, using a thermo-hygrostat (manufactured by Yamato Scientific Co., Ltd., IW-222), the emission intensity I ₁ after the high-temperature and high-humidity test of placing in an environment of 60 ° C. and 90% RH for 50 hours was measured. The emission intensity ratio I ₁ / I ₀ (%) was calculated from the obtained measured values.
Further, it was placed in an environment of 60 ° C. and 90% RH for 100 hours, and the emission intensity I ₂ after the high temperature and high humidity test was measured. The emission intensity ratio I ₂ / I ₀ (%) was calculated from the obtained measured values.
Table 1 shows the results obtained for the emission intensity ratios I ₁ / I _{0 and} I ₂ / I ₀ .
The emission intensity was measured using a spectrofluorometer (F-7000, manufactured by Hitachi High-Technologies Corporation) corrected by Rhodamine B and a sub-standard light source. That is, the fluorescence spectrum at an excitation wavelength of 455 nm was measured using the solid sample holder attached to the photometer.
The peak wavelength of the fluorescence spectrum of the surface-coated phosphor particles of each example and the phosphor particles of Comparative Example 3 was 656 nm. The peak wavelength of the fluorescence spectrum of the phosphor particles of Comparative Examples 1 and 2 was 657 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 the phosphor particles.

As shown in Table 1, Examples 1 to 5 in which at least a part of the outermost surface of the phosphor particles was composed of a coating portion containing a fluorine-containing compound containing a fluorine element and an aluminum element, had high temperature and high humidity for 50 hours. The decrease in emission intensity after the test is remarkably suppressed, the emission intensity ratio I ₁ /I ₀ is significantly higher than that of Comparative Examples 1 to 3, and the moisture resistance is excellent. confirmed. Further, in Examples 2 to 4, the luminescence intensity ratio I ₂ /I ₀ after passing through the high temperature and high humidity test for 100 hours is almost the same as the luminescence intensity ratio I ₁ / I ₀ after passing through the high temperature and high humidity test for 50 hours. It was confirmed that there was no decrease and the moisture resistance was particularly excellent.
In Comparative Example 3, it is considered that sufficient moisture resistance could not be obtained because the amount of (NH ₄ ) ₃ AlF ₆ produced was insufficient.

This application claims priority based on Japanese Application Japanese Patent Application No. 2019-074459 filed on April 9, 2019, and incorporates all of its disclosures herein.

Claims

Particles containing phosphors and
A coating portion that covers the surface of the particles and
Surface-coated fluorophore particles containing
The phosphor is a general formula M 1 a M 2 b M 3 c Al 3 N 4-d Od (where M 1 is one or more elements selected from Sr, Mg, Ca and Ba, and M 2 Is one or more elements selected from Li and Na, and M 3 is one or more elements selected from Eu and Ce), and has a composition represented by (a, b, c). , And D satisfy the following equations,
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 coating portion comprises at least a part of the outermost surface of the particles and contains a fluorine-containing compound containing a fluorine element and an aluminum element.
Surface-coated phosphor particles having a fluorine element content of 15% by mass or more and 30% by mass or less with respect to the entire surface-coated phosphor particles.
The surface-coated phosphor particle according to claim 1, wherein the fluorine element and the aluminum element are directly covalently bonded in the fluorine-containing compound.
The surface-coated phosphor particles according to claim 1 or 2, wherein the fluorine-containing compound contains either one or both of (NH 4 ) 3 AlF 6 and AlF 3 .
The surface-coated phosphor particles 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.
The surface-coated fluorescence according to any one of claims 1 to 4, wherein the diffuse reflectance for light irradiation at a wavelength of 300 nm is 56% or more, and the diffuse reflectance for light irradiation at the peak wavelength of the fluorescence spectrum is 85% or more. Body particles.
The surface-coated phosphor particles according to any one of claims 1 to 5, wherein 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 when excited by blue light having a wavelength of 455 nm.
The invention according to any one of claims 1 to 6, wherein the color purity of the emitted color satisfies 0.680 ≦ x <0.735 in the CIE-xy chromaticity diagram when excited by blue light having a wavelength of 455 nm. Surface-coated phosphor particles.
The method for producing surface-coated phosphor particles according to any one of claims 1 to 7.
Mixing process to mix raw materials and
A firing step of firing the mixture obtained by the mixing step, and a firing step.
An acid treatment step of mixing the fired product obtained by the firing step with an acidic solution, and
A fluorine treatment step of mixing the fired product that has undergone the acid treatment step with a compound containing a fluorine element.
Including
A method for producing surface-coated phosphor particles in which the amount of M 1 charged in the mixing step when the molar ratio of Al is 3 is 1.10 or more and 1.20 or less in molar ratio.
The method for producing surface-coated phosphor particles according to claim 8, wherein a hydrofluoric acid aqueous solution having a fluorine concentration of 25% or more is used as the acidic solution in the acid treatment step.
The method for producing surface-coated phosphor particles according to claim 8 or 9, further comprising a heating step of heat-treating the result obtained by the fluorine treatment step.
A light emitting device having the surface-coated phosphor particles according to any one of claims 1 to 7 and a light emitting element.