JP2017095568A - Phosphor, light emitting device, illumination device and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide KSF phosphors that does not tend to clog nozzles, and light emitting devices comprising the KSF phosphors and high-quality illumination devices and image display devices.SOLUTION: A phosphor comprises a crystal grain having a composition represented by the following formula [1], a non-light-emitting fine particle provided on the surface of the crystal grain. In the formula [1]: MnKSiF, m, a, b, c independently represent values satisfying the following formulas: 0<m≤0.2, 1.6≤a≤2.4, m+b=1, 4.8≤c≤7.2).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a phosphor, a light emitting device, a lighting device, and an image display device.

  A light-emitting device that emits white light (hereinafter referred to as “LED” as appropriate) by using a phosphor together with an excitation light source that emits light in the near-ultraviolet or short-wavelength visible range has become common and has been put to practical use in image display devices and illumination devices. ing. In particular, a phosphor that emits red fluorescence (hereinafter referred to as “red phosphor” as appropriate) is used in a light-emitting device for an image display device or a lighting device, and its light emission characteristics are variously improved. Among these, in order to achieve both efficiency and color rendering properties, development of a phosphor having a narrow half-value width in a specific wavelength band is regarded as important.

In order to realize both high efficiency and color rendering properties of the image display device and the lighting device, for example, the emission peak wavelength of the emission spectrum is 590 nm or more and less than 780 nm, and the half width of the emission spectrum is 1 nm or more and 130 nm or less. It is effective to use a red phosphor. Therefore, red phosphors having the above-mentioned light emission characteristics have been developed.
As such a phosphor, for example, Patent Document 1 discloses a Mn ⁴⁺ activated fluoride phosphor such as a fluorogermanate phosphor and K ₂ SiF ₆ : Mn ⁴⁺ (KSF phosphor).
Further developments have been made with respect to the KSF phosphor. For example, Patent Document 2 discloses a KSF phosphor in which the phosphor surface is coated with a matrix that does not contain an activator.

US Pat. No. 3,576,756 Special table 2014-514388 gazette

When manufacturing a light-emitting device, there is a method in which a liquid in which a phosphor is dispersed in a resin (phosphor dispersion liquid) is selectively applied by a dispenser.
If an attempt is made to apply the phosphor dispersion liquid using a dispenser having a large nozzle diameter, application accuracy may be reduced, and application to an unnecessary site may occur. Therefore, from the viewpoint of coating accuracy, it is conceivable to use a dispenser having a small nozzle diameter. However, when the phosphors described in Patent Documents 1 and 2 are used, there may be a problem that the nozzle is clogged.
An object of the present invention is to provide a KSF phosphor that is less likely to be clogged with nozzles.
Another object of the present invention is to provide a light emitting device including the KSF phosphor, a high quality lighting device, and an image display device.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have presumed as follows why nozzle clogging may become a problem when using a KSF phosphor.
In particular, when the KSF phosphor is synthesized in a liquid, the phosphors tend to aggregate due to the charge balance. On the other hand, the KSF phosphor has low mechanical strength. For this reason, when a generally used mechanical dispersion process is applied, the light emission characteristics may be affected. Therefore, it is very difficult to suppress nozzle clogging without deteriorating the light emission characteristics of the phosphor.
As a result of intensive studies, the present inventors have found that the crystal grains of the KSF phosphor have non-light-emitting fine particles on the surface thereof, and have reached the present invention.
That is, the present invention is as follows.
<1>
A phosphor comprising crystal grains having a composition represented by the following formula [1], wherein the phosphor has non-light emitting fine particles on the surface of the crystal grains.
Mn ⁴⁺ _m K _a Si _b F _c [1]
(In the above formula [1], m, a, b and c are values satisfying the following formula independently.
0 <m ≦ 0.2
1.6 ≦ a ≦ 2.4
m + b = 1
4.8 ≦ c ≦ 7.2)
<2>
<1> The phosphor according to <1>, wherein an average particle diameter of the non-light-emitting fine particles is 1/10 or less of an average particle diameter of the phosphor.
<3>
The phosphor according to <1> or <2>, wherein the non-light-emitting fine particles are crystal grains having a composition represented by the following formula [2].
K _{a ′} SiF _{b ′} [2]
(In the above formula [2], a ′ and b ′ each independently satisfy the following formula.
1.6 ≦ a ′ ≦ 2.4
4.8 ≦ b ′ ≦ 7.2)
<4>
A first illuminant, and a second illuminant that emits visible light when irradiated with light from the first illuminant, wherein the second illuminant is the fluorescence according to <1> or <2>. A light-emitting device comprising a body.
<5>
An illumination device comprising the light-emitting device according to <4> as a light source.
<6>
An image display device comprising the light-emitting device according to <4> as a light source.

The present invention can provide a KSF phosphor that is less susceptible to nozzle clogging.
In addition, since the phosphors are easily dispersed, it is possible to provide a high-quality light-emitting device, a high-quality illumination device, and an image display device in which color variation is suppressed.

The change of the discharge amount using the phosphor obtained in Examples 1 to 3 and Comparative Example 1 was measured. The vertical axis is the relative discharge amount, and the horizontal axis is the discharge time. It is an image by the scanning electron microscope of the fluorescent substance of Example 1 (a), Comparative example 1 (b), and Comparative example 2 (c) (drawing substitute photograph).

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.

In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In the composition formulas of the phosphors in this specification, each composition formula is delimited by a punctuation mark (,). In addition, when a plurality of elements are listed separated by commas (,), one or two or more of the listed elements may be included in any combination and composition.
For example, the composition formula “(Ca, Sr, Ba) Al ₂ O ₄ : Eu” has “CaAl ₂ O ₄ : Eu”, “SrAl ₂ O ₄ : Eu”, and “BaAl ₂ O ₄ : Eu”. “Ca _1−x Sr _x Al ₂ O ₄ : Eu”, “Sr _1−x Ba _x Al ₂ O ₄ : Eu”, “Ca _1−x Ba _x Al ₂ O ₄ : Eu”, _{"Ca 1-x-y Sr x} Ba y Al 2 O 4: Eu " and all assumed to generically indicated (in the above formula, 0 <x <1,0 <y <1,0 <X + y <1).
In the present specification, “Mn ⁴⁺ ” and “tetravalent manganese” are synonymous.

  The present invention includes the phosphor according to the first embodiment, the light emitting device according to the second embodiment, the illumination device according to the third embodiment, and the image display device according to the fourth embodiment.

<1. First Embodiment: Phosphor>
The phosphor according to the first embodiment of the present invention is a phosphor including crystal grains having a composition represented by the following formula [1], and has non-light emitting fine particles on the surface of the crystal grains. And a phosphor.

[Regarding Formula [1]]
Mn ⁴⁺ _m K _a Si _b F _c [1]
(In the above formula [1], m, a, b and c are values satisfying the following formula independently.
0 <m ≦ 0.2
1.6 ≦ a ≦ 2.4
m + b = 1
4.8 ≦ c ≦ 7.2)

In formula [1], Mn represents manganese. Unless the effect of the present embodiment is impaired, Mn is another activator element, such as europium (Eu), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), terbium (Tb). , Dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm) and ytterbium (Yb) may be partially substituted with one or more.
In the formula [1], K represents potassium. K is partially substituted with other elements of Group 1 of the periodic table, for example, alkali metals such as lithium (Li), sodium (Na), rubidium (Rb), cesium (Cs), and francium (Fr). May be.
In formula [1], Si represents silicon. Si may be partially substituted with other tetravalent elements such as germanium (Ge), tin (Sn), titanium (Ti), and zirconium (Zr).
In formula [1], F represents fluorine. F may be partially substituted with other halogen elements such as Cl (chlorine), Br (bromine), I (iodine), and oxygen.

m represents the content of Mn, the range is usually 0 <m ≦ 0.2, the lower limit is preferably 0.01, more preferably 0.02, and the upper limit is preferably 0. .15, more preferably 0.1.
Within the above range, concentration quenching is unlikely to occur, and a different phase showing a chemical composition other than the phosphor of the present embodiment is unlikely to occur, which is preferable in terms of good emission characteristics.
a represents the content of K, the range is usually 1.6 ≦ a ≦ 2.4, the lower limit is preferably 1.8, more preferably 1.85, and the upper limit is preferably Is 2.2, more preferably 2.15.
b represents the silicon content.
The relationship between m and b is usually
m + b = 1
Satisfied.
c represents the content of fluorine, the range is usually 4.8 ≦ c ≦ 7.2, the lower limit is preferably 5.2, more preferably 5.6, and the upper limit is preferably Is 6.8, more preferably 6.4.

[Average phosphor particle size]
The phosphor particles of this embodiment have a volume-based average particle size of usually 5 μm or more, preferably 15 μm or more, more preferably 25 μm or more. Moreover, it is 75 micrometers or less normally, Preferably it is 65 micrometers or less, More preferably, it is 55 micrometers or less. The volume-based average particle diameter of the phosphor particles is a value measured by a laser particle size meter.
Here, the volume-based average particle size is a volume-based relative particle when a sample is measured using a particle size distribution measuring apparatus based on the laser diffraction / scattering method to obtain a particle size distribution (cumulative distribution). It is defined as the particle diameter (d ₅₀ ) at which the amount is 50%.

[About non-luminous fine particles]
The phosphor of this embodiment has non-light emitting fine particles on the surface of crystal grains.
The non-light emission in this embodiment means that light is not absorbed or does not emit light in the excitation band of the phosphor and the emission spectrum band of the phosphor.

[Average particle size of non-light-emitting fine particles]
The non-light-emitting fine particles of the present embodiment have a volume-based average particle size of usually 0.3 μm or more, preferably 1 μm or more, more preferably 2 μm or more. Moreover, it is 7 micrometers or less normally, Preferably it is 6 micrometers or less, More preferably, it is 5 micrometers or less, and is 1/10 or less normally with respect to the average particle diameter of fluorescent substance. The volume-based average particle size of the non-light-emitting fine particles is a value measured by a laser particle size meter. The definition of the volume-based average particle diameter is the same as described above.

[Amount of non-light emitting fine particles attached]
The weight of the non-light-emitting fine particles adhering to the phosphor of this embodiment is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 3% by weight or more, and usually 50% by weight with respect to the weight of the phosphor. % By weight or less, preferably 10% by weight or less.
Within the above range, the effect of this embodiment can be obtained satisfactorily and the amount of phosphor used in the light emitting device does not increase, which is preferable.

[Regarding Formula [2]]
Further, the non-light-emitting fine particles may have a composition other than KSF as long as the effects of the present embodiment are not impaired, but KSF is preferable because of its high affinity with the KSF phosphor.
More specifically, the non-light emitting fine particles are preferably crystal grains having a composition represented by the following formula [2].
K _{a ′} SiF _{b ′} [2]
(In said formula [2], a 'and b' are values which satisfy the following formula each independently.
1.6 ≦ a ′ ≦ 2.4
4.8 ≦ b ′ ≦ 7.2)

a ′ represents the content of K, and its range is usually 1.6 ≦ a ′ ≦ 2.4, and the lower limit is preferably 1.8, more preferably 1.85, and the upper limit is , Preferably 2.2, more preferably 2.15.
b ′ represents the fluorine content, and the range is usually 4.8 ≦ b ′ ≦ 7.2, the lower limit is preferably 5.2, more preferably 5.6, and the upper limit is , Preferably 6.8, more preferably 6.4.

[Characteristics of phosphor]
(Emission spectrum)
The phosphor of this embodiment preferably has the following characteristics when the emission spectrum is measured by excitation with light having a peak wavelength of 455 nm.
The peak wavelength λp (nm) in the above-mentioned emission spectrum is usually 600 nm or more, particularly 610 nm or more, more preferably 620 nm or more, and usually 650 nm or less.
Within the above range, it is preferable in that it has a suitable orange or red light emission.

In the phosphor of this embodiment, the half-value width of the emission peak in the above-described emission spectrum is usually less than 50 nm, preferably 40 nm or less, more preferably 20 nm or less, particularly preferably 10 nm or less, and usually in the range of 1 nm or more. If this half width is too wide, the color purity may decrease, and if it is too narrow, the emission intensity may decrease.
For example, a xenon light source can be used to excite the phosphor with light having a peak wavelength. Moreover, the measurement of the emission spectrum of the phosphor of this embodiment can be performed using, for example, a fluorescence spectrophotometer F-4500 (manufactured by Hitachi, Ltd.). The emission peak wavelength and the half width of the emission peak can be calculated from the obtained emission spectrum.

[Phosphor production method]
The KSF phosphor of this embodiment is manufactured by dissolving each phosphor raw material in HF and mixing the obtained phosphor raw material solution in HF so that the composition of the formula [1] is obtained. Is possible.
As the phosphor material, a metal compound, a metal, or the like is used. For example, when manufacturing a phosphor having the composition represented by the above formula [1], a raw material of K element (hereinafter referred to as “K source” as appropriate), a raw material of Si element (hereinafter referred to as “Si source” as appropriate), Mn element Required combinations (hereinafter referred to as “Mn sources”) and F element sources (hereinafter referred to as “F sources”) are dissolved in HF (dissolution step), and the resulting raw material solutions are mixed in HF. Reaction to produce a phosphor-containing slurry (precipitation step), and the obtained phosphor slurry is washed (washing step) or dispersed / classified (dispersion / classification step) as necessary, and further fine particles are phosphorized It can be manufactured by adhering to the surface (particulate adhesion step).
Although an example of the manufacturing method of the KSF fluorescent substance of this embodiment is shown below, this embodiment is not limited to these.

(Phosphor raw material)
As the phosphor material used in the production of the KSF phosphor of this embodiment, a known material can be used.
Specific examples of the K source include potassium hydrogen fluoride (KHF ₂ ), potassium fluoride (KF), potassium carbonate (K ₂ CO ₃ ), potassium hydrogen carbonate (KHCO ₃ ), potassium oxalate monohydrate (K ₂ C ₂ O ₄ .H ₂ O), potassium chloride (KCl), and the like. Of these, potassium hydrogen fluoride (KHF ₂ ) is preferable.
Specific examples of the Si source include hexafluorosilicate (H ₂ SiF ₆ ), potassium hexafluorosilicate (K ₂ SiF ₆ ), silicon oxide (SiO ₂ ), and silicon (Si).
Examples of the Mn source include potassium permanganate (KMnO ₇ ), manganese dioxide (MnO ₂ ), manganese carbonate (MnCO ₃ ), potassium tetrafluoromanganate (K ₂ MnF ₆ ), manganese chloride (MnCl ₂ ) and the like. It is done.

Specific examples of the F source include hydrofluoric acid (HF), potassium hydrogen fluoride (KHF ₂ ), potassium fluoride (KF), hexafluorosilicic acid (H ₂ SiF ₆ ), potassium tetrafluoromanganate (K ₂ MnF ₆ ), potassium hexafluorosilicate (K ₂ SiF ₆ ), fluorine (F ₂ ) and the like.
Furthermore, any of these carbonates, oxides, oxalates, metals, chlorides, and the like that can be converted into fluorides after being dissolved in HF can be used as raw materials.
Note that the F source (fluorine) in the formula [1] may be supplied from a K source, a Si source, or a Mn source, or may be supplied from HF as a reaction solution. Each raw material may contain inevitable impurities.

(Dissolution process)
In the production of the phosphor of this embodiment, the phosphor raw materials are usually sufficiently dissolved in HF using a stirrer or the like in a necessary combination so as to obtain the target composition to obtain a phosphor raw material solution (dissolution step) ).
Phosphor raw materials that are dissolved in combination include HF and K sources, HF and Si sources, HF and Mn sources, and three types of phosphor raw material solutions, including HF and K sources, HF, Si sources, and Mn sources. Even if two kinds of phosphor raw material solutions are combined, or two kinds of phosphor raw material solutions are combined by combining HF, K source and Si source, and HF, K source and Mn source, the combination of raw materials is insoluble in HF. The raw materials may be dissolved in any combination as long as it does not produce a salt.
The hydrofluoric acid (HF) used for dissolving the raw material can be used as a raw material as long as the concentration of the hydrofluoric acid (HF) dissolves the raw material and can be converted into a fluoride after being dissolved. Preferably, when the concentration of hydrofluoric acid is low, the possibility of the formation of compounds other than fluorides such as hydroxide is increased. Therefore, the concentration of hydrofluoric acid is preferably high, but the concentration of hydrofluoric acid is Since the danger increases in the handling when it becomes high, the concentration of hydrofluoric acid is preferably about 40 to 55%.

(Precipitation process)
In manufacturing the phosphor of this embodiment, the obtained raw material solution is mixed in HF and reacted to produce a phosphor-containing slurry (precipitation step).
The method of producing a phosphor-containing slurry by mixing and reacting the raw material solution includes, for example, a raw material solution comprising HF and K sources, a raw material solution comprising HF and Si sources, and a raw material comprising HF and Mn sources. A solution is added to the HF solution and reacted to produce a phosphor-containing slurry, or a raw material solution consisting of HF, K source and Mn source is added to a raw material solution consisting of HF, K source and Si source. The reaction may be carried out by any method as long as the phosphor-containing slurry is produced by reacting after mixing, such as a method of producing a phosphor-containing slurry to be reacted, or a method of changing the opposite.

The concentration of hydrofluoric acid (HF) used when mixing the raw material reaction liquid to produce the phosphor-containing slurry is such that the concentration of the raw material solution reacts and the precipitate obtained after the reaction becomes a fluoride. If you can, you can use it. Preferably, the lower the concentration of hydrofluoric acid, the higher the possibility of formation of compounds other than fluorides such as hydroxides. Therefore, the higher the concentration of hydrofluoric acid, the higher the concentration of hydrofluoric acid. In this case, the handling is increased in danger and the solubility of the KSF phosphor in HF is increased and the yield is lowered. Therefore, the concentration of hydrofluoric acid is preferably about 30 to 55%.
There is no restriction | limiting in particular in the speed | rate which adds a raw material solution, For example, 1 L per minute or 1 L per hour may be sufficient. This is because the production speed of the KSF phosphor is fast. Also, the reaction temperature is not particularly limited, but a lower liquid temperature is preferable because the solubility of the KSF phosphor is low and the yield is increased.

(Washing process)
After producing the phosphor slurry, it is preferable to have a step (washing step) of washing the phosphor produced by precipitation before separating the phosphor by filtration.
Impurities and raw materials mainly composed of unreacted residues such as HF, K source, Si source, Mn source, fluoride generated when dissolved in HF, etc. There is a tendency that unreacted components remain in the phosphor, and side-reacted components are generated in the phosphor slurry.
In order to improve the characteristics, it is necessary to remove as much as possible the residue of the raw material and impurities generated during dissolution. In this embodiment, the cleaning method is not particularly limited as long as impurities can be removed. For example, the phosphor produced is a compound other than fluoride such as hydroxide, such as hydrofluoric acid, a mixed liquid of potassium hydrogen fluoride and hydrofluoric acid, or a mixed liquid of hexafluorosilicic acid and hydrofluoric acid. If not, it can be washed with any liquid.

In consideration of removing unreacted Mn, Si, and K in particular, it is preferable to clean with hydrofluoric acid. When the concentration of the hydrofluoric acid is low, the possibility of generating a compound other than a fluoride such as a hydroxide is increased, and the emission characteristics are deteriorated. When the concentration of hydrofluoric acid is increased, the handling thereof is more dangerous, and the solubility of the KSF phosphor in HF is increased and the yield is lowered. Therefore, the concentration of hydrofluoric acid is about 40 to 50%. preferable.
The weight of “hydrofluoric acid” when the phosphor is washed is usually 1 time or more, preferably 3 times or more, more preferably 5 times or more, usually 100 times or less, preferably 50 times or less of the weight of the phosphor. It is.

Here, while it is immersed, it may be allowed to stand, but from the viewpoint of work efficiency, it is preferable to stir to such an extent that the cleaning time can be shortened. Moreover, although it normally works at room temperature, you may heat aqueous solution as needed. It may be further added an oxidizing agent and a reducing agent such as hydrogen peroxide (H 2 _{O 2).}
The time for immersing the phosphor in hydrofluoric acid is usually 10 minutes or longer, preferably 1 hour or longer, and usually 72 hours or shorter, preferably 60 hours or shorter, although it varies depending on the stirring conditions. Moreover, you may wash | clean several times and may change the kind and density | concentration of the liquid to wash | clean.
In the washing step, it is preferable to perform filtration while substituting the precipitation reaction solution with ethanol, acetone, methanol, or the like after performing the operation of immersing the phosphor in the washing solution.

(Dispersion / classification process)
The obtained phosphor is granular or massive. When this is dispersed using a general disperser such as a ball mill, a vibration mill, or a jet mill, the light emission characteristics of the phosphor deteriorate. This is because the KSF phosphor is weak against mechanical force and pulverized by the above general dispersion method having strong dispersion strength.
Therefore, it is preferable to disperse and classify the obtained phosphor with a sieve having different openings without passing through a dispersion process, and to pass the powder that has passed through the sieve or the powder remaining on the sieve to the next process.

(Non-emission fine particle adhesion process)
There is no particular limitation on the method of attaching the non-luminescent particles to the phosphor surface in this embodiment, but the non-luminescent particles are synthesized as a slurry different from the phosphor slurry and added to the phosphor surface in addition to the phosphor slurry. And a method of generating non-emitting fine particles in the phosphor slurry and attaching them to the phosphor surface. In any method, the effect of this embodiment can be obtained as long as non-luminescent particles are adhered to the phosphor surface.

[Method for producing non-luminescent fine particles]
The method for producing the non-light emitting fine particles of this embodiment is not particularly limited, but a solution containing a K source, a Si source and hydrofluoric acid, for example, in a similar manner as described in [Phosphor production method] A plurality of can be mixed and manufactured.
The non-light-emitting fine particles of this embodiment are produced by dissolving each non-light-emitting fine particle raw material in HF so as to have the composition of the formula [2], and mixing the obtained non-light-emitting fine particle raw material solution in HF. Is possible.
As the non-light emitting fine particle raw material, a metal compound, a metal, or the like is used. For example, when producing non-luminescent particles having the composition represented by the above formula [2], a raw material of K element (hereinafter referred to as “K source” as appropriate), a raw material of Si element (hereinafter referred to as “Si source” as appropriate), F Elemental raw materials (hereinafter referred to as “F
The required combination is dissolved in HF (dissolution step), and the resulting raw material solution is mixed in HF and reacted to produce a slurry containing non-luminescent particles (precipitation step). The luminescent fine particle slurry can be produced by washing (washing step) as necessary.
Hereinafter, an example of a method for producing the non-light-emitting fine particles adhering to the surface of the KSF phosphor according to this embodiment will be described, but this embodiment is not limited thereto.

(Non-luminescent fine particle material)
As the non-light-emitting fine particle material used in the production of the non-light-emitting fine particles attached to the surface of the KSF phosphor of this embodiment, known materials can be used.
Specific examples of the K source include potassium hydrogen fluoride (KHF ₂ ), potassium fluoride (KF), potassium carbonate (K ₂ CO ₃ ), potassium hydrogen carbonate (KHCO ₃ ), potassium oxalate monohydrate (K ₂ C ₂ O ₄ .H ₂ O), potassium chloride (KCl), and the like. Of these, potassium hydrogen fluoride (KHF ₂ ) is preferable.
Specific examples of the Si source include hexafluorosilicate (H ₂ SiF ₆ ), potassium hexafluorosilicate (K ₂ SiF ₆ ), silicon oxide (SiO ₂ ), and silicon (Si).
Specific examples of the F source include hydrofluoric acid (HF), potassium hydrogen fluoride (KHF ₂ ), potassium fluoride (KF), hexafluorosilicic acid (H ₂ SiF ₆ ), and potassium hexafluorosilicate (K _2). SiF _6), fluorine _{(F 2),} and the like.

Furthermore, any of these carbonates, oxides, oxalates, metals, chlorides, and the like that can be converted into fluorides after being dissolved in HF can be used as raw materials.
Note that the F source (fluorine) in the formula [2] may be supplied from a K source or a Si source, or may be supplied from HF as a reaction solution. Each raw material may contain inevitable impurities.

(Dissolution process)
In the production of non-luminous fine particles adhering to the surface of the KSF phosphor of this embodiment, the non-luminous fine particle raw materials are usually sufficiently dissolved in HF using a stirrer or the like in a necessary combination so as to obtain the target composition. A non-light emitting fine particle raw material solution is obtained (dissolution step).
Non-luminescent particulate raw materials that are dissolved in combination include HF and K sources, HF and Si sources in combination as non-luminescent particulate raw material solutions, HF and K sources and Si sources, and HF and Si sources in combination with non-luminescent particulate raw materials As a solution, or a combination of HF and K source and Si source, or a combination of HF and K source as a non-luminous fine particle raw material solution, any combination is possible as long as the combination of raw materials does not produce an insoluble salt in HF. The raw materials may be dissolved in combination.

  The hydrofluoric acid (HF) used for dissolving the raw material can be used as a raw material as long as the concentration of the hydrofluoric acid (HF) dissolves the raw material and can be converted into a fluoride after being dissolved. Preferably, when the concentration of hydrofluoric acid is low, the possibility of the formation of compounds other than fluorides such as hydroxide is increased. Therefore, the concentration of hydrofluoric acid is preferably high, but the concentration of hydrofluoric acid is Since the danger increases in the handling when it becomes high, the concentration of hydrofluoric acid is preferably about 40 to 55%.

(Precipitation process)
In the production of non-luminescent particles adhering to the surface of the KSF phosphor of this embodiment, the obtained raw material solution is mixed and reacted in HF to produce a non-luminescent particle-containing slurry (precipitation step).
A method for producing a slurry containing non-luminous fine particles by mixing and reacting a raw material solution is, for example, adding a raw material solution composed of HF and K source and a raw material solution composed of HF and Si source to the HF solution and reacting them. A method for producing a slurry containing non-light emitting fine particles, a method for producing a non-light emitting fine particle slurry in which a raw material solution comprising HF and K source is added to and reacted with a raw material solution comprising HF, K source and Si source, or vice versa. As long as it reacts after mixing and produces | generates a non-light-emitting fine particle containing slurry, it may be made to react by arbitrary methods.

Hydrofluoric acid (HF) used when mixing the raw material reaction liquid to produce a slurry containing non-luminescent particles, the concentration of the raw material solution reacts, and the precipitate obtained after the reaction can become a fluoride. If you can, you can use it. Preferably, the lower the concentration of hydrofluoric acid, the higher the possibility of formation of compounds other than fluorides such as hydroxides. Therefore, the higher the concentration of hydrofluoric acid, the higher the concentration of hydrofluoric acid. In this case, the handling is increased in danger, and the solubility of non-luminescent particles in HF is increased and the yield is lowered. Therefore, the concentration of hydrofluoric acid is preferably about 20 to 40%.
There is no restriction | limiting in particular in the speed | rate which adds a raw material solution, For example, 1 L per minute or 1 L per hour may be sufficient. This is because the generation speed of the non-light emitting fine particles is high. The reaction temperature is not particularly limited, but a lower liquid temperature is preferable because the yield of the non-light-emitting fine particles is low and the yield is high.

(Washing process)
It is preferable to have a step (cleaning step) of washing the non-light-emitting fine particles precipitated after the non-light-emitting fine particle slurry is produced.
Non-light-emitting impurities and raw material unreacted mainly from unreacted residues in HF, K source, Si source, or fluoride generated when dissolved in HF It tends to remain in the fine particles or to generate side reaction components in the non-light emitting fine particle slurry.
In order to improve the characteristics, it is necessary to remove as much as possible the residue of the raw material and impurities generated during dissolution. In this embodiment, the cleaning method is not particularly limited as long as impurities can be removed. For example, compounds other than fluoride such as hydroxide, such as hydrofluoric acid, mixed liquid of potassium hydrogen fluoride and hydrofluoric acid, or mixed liquid of hexafluorosilicic acid and hydrofluoric acid. If not, it can be washed with any liquid.

Considering removal of unreacted Si and K in particular, it is preferable to clean with hydrofluoric acid. When the concentration of the hydrofluoric acid is low, the possibility of generating a compound other than a fluoride such as a hydroxide is increased, and the emission characteristics are deteriorated. When the concentration of hydrofluoric acid increases, the handling becomes more dangerous, the solubility of non-luminescent particles in HF increases, and the yield decreases, so the concentration of hydrofluoric acid is about 40-50%. preferable.
The weight of “hydrofluoric acid” when washing the non-light emitting fine particles is usually 1 or more times, preferably 3 times or more, more preferably 5 times or more, usually 100 times or less, preferably 50 times the weight of the non-light emitting fine particles. Is less than double.

Here, while it is immersed, it may be allowed to stand, but from the viewpoint of work efficiency, it is preferable to stir to such an extent that the cleaning time can be shortened. Moreover, although it normally works at room temperature, you may heat aqueous solution as needed. It may be further added an oxidizing agent and a reducing agent such as hydrogen peroxide (H 2 _{O 2).}
The time for immersing the non-luminous fine particles in hydrofluoric acid varies depending on the stirring conditions and the like, but is usually 10 minutes or longer, preferably 1 hour or longer, and usually 24 hours or shorter, preferably 12 hours or shorter. . Moreover, you may wash | clean several times and may change the kind and density | concentration of the liquid to wash | clean.
In the KSF phosphor of this embodiment, when the non-light emitting fine particles are attached to the phosphor surface, the non-light emitting fine particles may be used after filtration while replacing the precipitation reaction solution with ethanol, acetone, methanol or the like. It is more preferable to use the non-light emitting fine particle slurry as it is because the work is easy and there is no aggregation occurring during filtration.

<Phosphor-containing composition>
The phosphor according to the first embodiment of the present invention can be used by mixing with a liquid medium. In particular, when the phosphor according to the first embodiment of the present invention is used for a light emitting device or the like, it is preferable to use the phosphor in a form dispersed in a liquid medium. The phosphor according to the first embodiment of the present invention dispersed in a liquid medium is appropriately referred to as “phosphor-containing composition according to one embodiment of the present invention” or the like.

[Phosphor]
There is no restriction | limiting in the kind of fluorescent substance which concerns on the 1st embodiment of this invention contained in the fluorescent substance containing composition of this embodiment, It can select arbitrarily from what was mentioned above. Further, the phosphor according to the first embodiment of the present invention to be contained in the phosphor-containing composition of the present embodiment may be only one type, or two or more types may be used in combination in any combination and ratio. Also good. Furthermore, the phosphor-containing composition of the present embodiment may contain a phosphor other than the phosphor according to the first embodiment of the present invention as long as the effects of the present embodiment are not significantly impaired.

[Liquid medium]
The liquid medium used in the phosphor-containing composition of the present embodiment is not particularly limited as long as the performance of the phosphor is not impaired within the intended range. For example, any inorganic material and any material can be used as long as it exhibits liquid properties under the desired use conditions, suitably disperses the phosphor according to the first embodiment of the present invention, and does not cause an undesirable reaction. An organic material can be used, and examples thereof include a silicone resin, an epoxy resin, and a polyimide silicone resin.

[Content of liquid medium and phosphor]
The phosphor and the liquid medium content in the phosphor-containing composition of the present embodiment are arbitrary as long as the effects of the present embodiment are not significantly impaired, but for the liquid medium, the phosphor-containing composition of the present embodiment. The amount is usually 20% by weight or more, preferably 40% by weight or more, and usually 99% by weight or less, preferably 95% by weight or less.

[Other ingredients]
In addition, you may make the fluorescent substance containing composition of this embodiment contain other components other than a fluorescent substance and a liquid medium, unless the effect of this embodiment is impaired remarkably. Moreover, only 1 type may be used for another component and it may use 2 or more types together by arbitrary combinations and a ratio.

<2. Second Embodiment: Light Emitting Device>
A second embodiment of the present invention is a light-emitting device including a first light emitter (excitation light source) and a second light emitter that emits visible light when irradiated with light from the first light emitter. The second luminous body contains the phosphor according to the first embodiment of the present invention. Here, any one of the phosphors according to the first embodiment of the present invention may be used alone, or two or more thereof may be used in any combination and ratio.

As the phosphor in the light emitting device of this embodiment, for example, a phosphor that emits fluorescence in the orange or red region under irradiation of light from an excitation light source is used. Specifically, when a light-emitting device is configured, the orange to red phosphor has a wavelength range of 600 nm to 650 nm.
As the excitation source, one having an emission peak in a wavelength range of less than 455 nm may be used.

Hereinafter, when the phosphor according to the first embodiment of the present invention has a light emission peak in the wavelength range of 600 nm or more and 650 nm or less, and the first light emitter has a light emission peak in the wavelength range of 455 nm. Although the embodiment of the light emitting device is described, this embodiment is not limited thereto.

In the above case, the light-emitting device of this embodiment can be set to the following embodiment (A) or (B), for example.
(A) As the first phosphor, one having an emission peak at 455 nm is used, and as the first phosphor of the second phosphor, at least one kind of fluorescence having an emission peak in a wavelength range of 560 nm to less than 600 nm The aspect which uses the fluorescent substance which concerns on 1st embodiment of this invention as a 2nd fluorescent substance of a body (yellow fluorescent substance) and a 2nd light-emitting body.
(B) As the first illuminant, one having an emission peak at 455 nm is used, and as the first phosphor of the second illuminant, at least one kind of fluorescence having an emission peak in a wavelength range of 500 nm to less than 560 nm. The aspect which uses the fluorescent substance which concerns on 1st embodiment of this invention as a 2nd fluorescent substance of a body (green fluorescent substance) and a 2nd light-emitting body.

(Yellow phosphor)
For example, the following phosphors are preferably used as the yellow phosphor.
Examples of the garnet phosphor include (Y, Gd, Lu, Tb, La) ₃ (Al, Ga) ₅ O ₁₂ : (Ce, Eu, Nd),
Examples of the orthosilicate include (Ba, Sr, Ca, Mg) ₂ SiO ₄ : (Eu, Ce),
Examples of (acid) nitride phosphors include (Ba, Ca, Mg) Si ₂ O ₂ N ₂ : Eu (SION phosphor), (Li, Ca) ₂ (Si, Al) ₁₂ (O, N ₁₆ : (Ce, Eu) (α-sialon phosphor), (Ca, Sr) AlSi ₄ (O, N) ₇ : (Ce, Eu) (1147 phosphor)
Etc.
The phosphor is preferably a garnet phosphor, and most preferably a YAG phosphor represented by Y ₃ Al ₅ O ₁₂ : Ce.

(Green phosphor)
For example, the following phosphors are preferably used as the green phosphor.
Examples of the garnet phosphor include (Y, Gd, Lu, Tb, La) ₃ (Al, Ga) ₅ O ₁₂ : (Ce, Eu, Nd), Ca ₃ (Sc, Mg) ₂ Si ₃ O _12. : (Ce, Eu) (CSMS phosphor),
Examples of the silicate phosphor include (Ba, Sr, Ca, Mg) ₃ SiO ₁₀ : (Eu, Ce), (Ba, Sr, Ca, Mg) ₂ SiO ₄ : (Ce, Eu) (BSS phosphor). ),
As the oxide phosphor, for example, (Ca, Sr, Ba, Mg) (Sc, Zn) ₂ O ₄ : (Ce, Eu) (CASO phosphor),
Examples of (acid) nitride phosphors include (Ba, Sr, Ca, Mg) Si ₂ O ₂ N ₂ : (Eu, Ce), Si _6-z Al _z O _z N _8−z : (Eu, Ce) (β-sialon phosphor) (0 <z ≦ 1), (Ba, Sr, Ca, Mg, La) ₃ (Si, Al) ₆ O ₁₂ N ₂ : (Eu, Ce) (BSON phosphor) ,
As the aluminate phosphor, for example, (Ba, Sr, Ca, Mg) ₂ Al ₁₀ O ₁₇ : (Eu, Mn) (GBAM phosphor)
Etc.

(Red phosphor)
In the light emitting device of this embodiment, other red phosphors may be used in combination with the phosphor according to the first embodiment of the present invention. As other red phosphors, for example, the following phosphors are preferably used.
Examples of sulfide phosphors include (Sr, Ca) S: Eu (CAS phosphor), La ₂ O.
₂ S: Eu (LOS phosphor),
Examples of the garnet phosphor include (Y, Lu, Gd, Tb) ₃ Mg ₂ AlSi ₂ O ₁₂ : Ce,
Examples of nanoparticles include CdSe,
Examples of the nitride or oxynitride phosphor include (Sr, Ca) AlSiN ₃ : Eu (S / CASN phosphor), (CaAlSiN ₃ ) _1-x · (SiO ₂ N ₂ ) _x : Eu (CASON fluorescence). Body), (La, Ca) ₃ (Al, Si) ₆ N ₁₁ : Eu (LSN phosphor), (Ca, Sr, Ba) ₂ Si ₅ (N, O) ₈ : Eu (258 phosphor), ( _{Sr, Ca) Al 1 + x} Si 4-x O x N 7-x: Eu (1147 _{phosphors), M x (Si, Al} ) 12 (O, N) 16: Eu (M is, Ca, Sr, etc.) ( α sialon phosphor), Li (Sr, Ba) Al ₃ N ₄ : Eu (wherein x is 0 <x <1).

[Configuration of light emitting device]
The light emitting device of this embodiment has a first light emitter (excitation light source) and uses at least the phosphor according to the first embodiment of the present invention as the second light emitter, The configuration is not limited, and a known device configuration can be arbitrarily employed.
Examples of the device configuration and the light emitting device include those described in Japanese Patent Application Laid-Open No. 2007-291352.
In addition, examples of the form of the light emitting device include a shell type, a cup type, a chip on board, a remote phosphor, and the like.

  The application of the light-emitting device of this embodiment is not particularly limited, and can be used in various fields in which ordinary light-emitting devices are used. However, since the color reproduction range is wide and color rendering is high, It is particularly preferably used as a light source for an illumination device or an image display device.

<3. Third Embodiment: Lighting Device>
A third embodiment of the present invention is an illumination device including the light emitting device according to the second embodiment of the present invention as a light source.
When the light-emitting device according to the second embodiment of the present invention is applied to a lighting device, the light-emitting device as described above may be appropriately incorporated into a known lighting device. For example, a surface emitting illumination device in which a large number of light emitting devices are arranged on the bottom surface of the holding case can be used.

<4. Fourth Embodiment: Image Display Device>
According to a fourth embodiment of the present invention, there is provided an image display device comprising the light emitting device according to the second embodiment of the present invention as a light source.
When the light emitting device according to the second embodiment of the present invention is used as a light source of an image display device, the specific configuration of the image display device is not limited, but it is preferably used with a color filter. For example, when the image display device is a color image display device using color liquid crystal display elements, the light emitting device is used as a backlight, a light shutter using liquid crystal, and a color filter having red, green, and blue pixels; By combining these, an image display device can be formed.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples without departing from the gist thereof.

<Measurement method>
[Evaluation method of nozzle clogging]
The discharge test of the phosphor paste was performed using an air dispenser, and nozzle clogging was evaluated from the change over time of the discharge amount of the phosphor paste.
The dispenser is ML-808FXcom (manufactured by Musashi Engineering Co., Ltd.), and the nozzle with an inner diameter of 0.2 mm is moved in the X, Y, and Z directions, and discharged onto the slide glass at regular intervals (500 kPa × 3 seconds / shot). The discharge weight of the phosphor paste was measured.

The discharge weight was obtained by measuring the weight of the phosphor paste discharged for 10 minutes from a certain time. FIG. 1 is a diagram showing the change over time in the discharge weight of the phosphor paste normalized by the discharge weight of the phosphor paste from the start of discharge to time 10 minutes, for example, a plot of time 15 minutes in FIG. The discharge start is time 0, and the weight of the phosphor paste discharged for 10 minutes from time 15 to time 25 minutes is divided by the discharge weight of the phosphor paste from discharge start (time 0) to time 10 minutes. It is shown as a relative value.
The phosphor paste is composed of LED sealing material KER-2500 (manufactured by Shin-Etsu Chemical Co., Ltd.), KSF phosphor and β-SiALON phosphor BG-601 / E (manufactured by Mitsubishi Chemical Corporation), and sealing material: KSF fluorescent material. Body: β-SiALON phosphor = 1: 1: 0.3.

[Luminescent characteristics]
Samples are packed in a copper sample holder, the emission spectrum is measured using a fluorescence measuring device (manufactured by JASCO Corporation) equipped with a 150 W xenon lamp as an excitation light source and a multichannel CCD detector C7041 (manufactured by Hamamatsu Photonics) as a spectrum measuring device. It was measured.

[Average phosphor particle size]
The average particle size of the phosphor in the first embodiment of the present invention is a volume-based average particle size, the phosphor is dispersed in ethanol, the volume distribution and the number distribution are evaluated using a laser scattering diffraction method, and the particle size The average particle diameter of the phosphor was determined as the particle diameter d ₅₀ (μm) corresponding to 50% of the cumulative distribution from the smaller particle diameter in the volume distribution. A particle size meter Model 1064 (manufactured by CILAS) or the like was used as a particle size distribution measuring apparatus.

Example 1
<About the production of non-luminescent particles>
The non-light emitting fine particle slurry was synthesized by the following method.
Solution B obtained by dissolving KHF ₂ weighed in a solution A obtained by mixing H ₂ SiF ₆ in 47% HF so that the molar ratio of Si: K is 1: ₂ in 35% HF Were mixed to obtain a slurry containing non-light emitting fine particles K ₂ SiF ₆ .

<Synthesis of phosphor>
Next, the phosphor of Example 1 was synthesized by the following method.
In a liquid A obtained by mixing H ₂ SiF ₆ and K ₂ MnF ₆ weighed so that the molar ratio of Si: Mn is 0.95: 0.05 in 47% HF, the molar ratio of Si + Mn: K The B liquid obtained by dissolving KHF ₂ weighed so as to be 1: 2 in 47% HF was mixed to obtain a phosphor-containing slurry containing K ₂ SiF ₆ : Mn ⁴⁺ . Next, while stirring the phosphor-containing slurry containing K ₂ SiF ₆ : Mn ⁴⁺ , the phosphor-containing slurry is mixed with the slurry containing the non-light-emitting fine particles K ₂ SiF ₆ and the weight of the non-light-emitting fine particles is that of the phosphor. The phosphor was added to 3% by weight, filtered, washed with ethanol, and dried at 100 ° C. for 15 hours to obtain the phosphor of Example 1.
The obtained phosphor had an emission peak peak wavelength of 631 nm and a main emission peak half width of 6 nm. Moreover, the image by the scanning electron microscope of the obtained fluorescent substance was shown to Fig.2 (a).

(Example 2)
Example 1 is the same as Example 1 except that the addition amount of the non-emitting fine particles is changed to 1% of the weight of the phosphor.
A phosphor was prepared in the same manner as described above to obtain the phosphor of Example 2.

(Example 3)
A phosphor was produced in the same manner as in Example 1 except that the amount of non-emitting fine particles added was changed to 0.5% of the weight of the phosphor in Example 1, and the phosphor of Example 3 was obtained.

(Comparative Example 1)
In a liquid A obtained by mixing H ₂ SiF ₆ and K ₂ MnF ₆ weighed so that the molar ratio of Si: Mn is 0.95: 0.05 in 47% HF, the molar ratio of Si + Mn: K The B liquid obtained by dissolving KHF ₂ weighed so as to be 1: 2 in 47% HF was mixed to obtain a phosphor-containing slurry containing K ₂ SiF ₆ : Mn ⁴⁺ . The phosphor-containing slurry was filtered, washed with ethanol, and dried at 100 ° C. for 15 hours to obtain the phosphor of Comparative Example 1.
The obtained phosphor had an emission peak peak wavelength of 631 nm and a main emission peak half width of 6 nm. Moreover, the image by the scanning electron microscope of the obtained fluorescent substance was shown in FIG.2 (b).

(Comparative Example 2)
The compound was synthesized according to the method described in JP-T-2014-514388. More specifically, it is as follows.
In a liquid A obtained by mixing H ₂ SiF ₆ and K ₂ MnF ₆ weighed so that the molar ratio of Si: Mn is 0.95: 0.05 in 47% HF, the molar ratio of Si + Mn: K The B liquid obtained by dissolving KHF ₂ weighed so as to be 1: 2 in 47% HF was mixed to obtain a phosphor-containing slurry containing K ₂ SiF ₆ : Mn ⁴⁺ . Next, in the phosphor-containing slurry containing K ₂ SiF ₆ : Mn ⁴⁺ obtained by adding H ₂ SiF ₆ to the liquid A and stirring, the molar ratio of Si: K to Si of H ₂ SiF ₆ added is 1 : A phosphor-containing slurry containing K ₂ SiF ₆ : Mn ⁴⁺ coated with K ₂ SiF ₆ by mixing C liquid obtained by dissolving KHF ₂ weighed so as to be ₂ in 47% HF Obtained. The phosphor-containing slurry was filtered, washed with ethanol, and dried at 100 ° C. for 15 hours to obtain a phosphor of Comparative Example 2.
The obtained phosphor had an emission peak peak wavelength of 631 nm and a main emission peak half width of 6 nm. Moreover, the image by the scanning electron microscope of the obtained fluorescent substance was shown in FIG.2 (c).

For the phosphors obtained in Examples 1 to 3 and the phosphors obtained in Comparative Examples 1 and 2, the measurement results of the light emission characteristics and the average particle diameter are shown in Table 1. D _x represents the particle size (μm) when the cumulative value accumulated from the smaller particle size is x% of the whole, and d _max represents the largest particle among the particles detected during the particle size distribution measurement. Represents the particle size (μm).

As shown in Table 1, all of the phosphors according to the first embodiment of the present invention have a smaller _dmax than the phosphors of Comparative Examples 1 and 2. For this reason, it turns out that the fluorescent substance which concerns on 1st embodiment of this invention does not aggregate easily.
The dispenser discharge amount was measured and the results are shown in FIG. As shown in FIG. 1, the discharge amount of the phosphor of Comparative Example 1 has changed by 20% at time 30 minutes, but the phosphor according to the first embodiment of the present invention does not exceed 180 minutes. There is almost no change in the discharge amount and it is stable.
More specifically, in Example 3 where 0.5% by weight of the non-light emitting fine particles adhered, the discharge amount slightly changes after 30 minutes. Further, in Example 2 in which 1.0% by weight of the non-light emitting fine particles adhered, the discharge amount slightly changes after the time of 90 minutes. Further, in Example 1 in which non-light emitting fine particles adhered to 3.0% by weight, there was almost no change in the discharge amount even after the time of 180 minutes.
In Comparative Example 2, as shown in FIG. 2C, it was found that K ₂ SiF ₆ covered phosphor particles as a thin film, not as fine particles. The film thickness was 2 μm.

Further, the average particle diameter (d ₅₀ ) of the phosphors of the respective examples was as shown in Table 1. In each case, the particle size of the non-light-emitting fine particles was measured with a scanning electron microscope. In each case, only a particle having a particle size of 1/10 or less of the average particle size of the phosphor could be confirmed. That is, it has been found that the average particle size of the non-light-emitting fine particles is 1/10 of the average particle size of the phosphor at most and 1/10 or less of the average particle size of the phosphor. As described above, the non-light-emitting fine particles of this embodiment have a high probability of being 1/10 or less of the average particle diameter of the phosphor as described above.

(Examples 4 to 6: LED test)
A mixture obtained by mixing the phosphors of Examples 1 to 3 and BG-601 / E (manufactured by Mitsubishi Chemical Corporation) (green phosphor), which is a β-SiALON phosphor, at a predetermined mixing ratio is used as a thickener. A phosphor-containing composition is prepared by adding and dispersing in a silicone resin KER-2500 containing 5% of RX200 (manufactured by Shin-Etsu Chemical Co., Ltd.), and one 810 μm square InGaN-based blue LED chip is mounted on a 5050 SMD ceramic package Then, a white LED containing the phosphor of Example 1 was obtained by sealing with a silicone resin (phosphor-containing composition) in which each phosphor was dispersed.

The emission peak wavelength of the blue LED chip in the produced white LED was 452.5 to 455 nm, and a white LED was applied with a current of 350 mA to emit light.
The white LED has a mixture ratio of the phosphor of Example 1 and the β-SiALON phosphor, and phosphor so that the emission chromaticity (x, y) becomes x = 0.276 and y = 0.263. It was prepared according to the sealing amount of the silicone resin dispersed.
The characteristics of each LED are summarized in Table 2.

  As shown in Table 2, the light emitting device obtained using the phosphor according to the first embodiment of the present invention has high luminous efficiency.

Claims (6)

A phosphor comprising crystal grains having a composition represented by the following formula [1], wherein the phosphor has non-light emitting fine particles on the surface of the crystal grains.
Mn ⁴⁺ _m K _a Si _b F _c [1]
(In the above formula [1], m, a, b and c are values satisfying the following formula independently.
0 <m ≦ 0.2
1.6 ≦ a ≦ 2.4
m + b = 1
4.8 ≦ c ≦ 7.2)   2. The phosphor according to claim 1, wherein an average particle diameter of the non-light-emitting fine particles is 1/10 or less of an average particle diameter of the phosphor. The phosphor according to claim 1 or 2, wherein the non-light-emitting fine particles are crystal grains having a composition represented by the following formula [2].
K _{a ′} SiF _{b ′} [2]
(In the above formula [2], a ′ and b ′ each independently satisfy the following formula.
1.6 ≦ a ′ ≦ 2.4
4.8 ≦ b ′ ≦ 7.2)   A first illuminant and a second illuminant that emits visible light when irradiated with light from the first illuminant, wherein the second illuminant comprises the phosphor according to claim 1 or 2. A light-emitting device comprising:   An illumination device comprising the light-emitting device according to claim 4 as a light source.   An image display device comprising the light-emitting device according to claim 4 as a light source.