JP5613222B2 - Surface-coated strontium silicate phosphor particles and light-emitting diodes comprising the phosphor particles - Google Patents

Description

  The present invention relates to alkaline earth silicate phosphor particles, and more particularly, to surface-coated strontium silicate phosphor particles with significantly improved water resistance, a method for producing the same, and a light-emitting diode including the phosphor particles.

2. Description of the Related Art Conventionally, alkaline earth silicate phosphors, particularly phosphors made of strontium silicates such as (Sr, Ba, Ca) ₂ SiO ₄ : Eu ²⁺ are known as materials for light-emitting elements used for various light sources. In recent years, various phosphors that emit yellow or orange light when excited with blue or ultraviolet LEDs have been provided for LED light sources that emit white light.

For example, among phosphors made of alkaline earth silicates, Sr ₂ SiO ₄ : Eu ²⁺ mainly containing Sr, Sr ₃ SiO ₅ : Eu ²⁺ , (Sr, Ba) ₃ SiO ₅ : Eu ²⁺ , (Sr , Ba, Ca) ₂ SiO ₄ : Eu ^{2+ and} other strontium silicate phosphors (see Patent Documents 1 and 2), when excited with a blue LED, have a brightness equivalent to or higher than that of existing YAG: Ce ³⁺ phosphors Flashes yellow or orange.

  The strontium silicate phosphor having such characteristics is useful as a yellow or orange light source in combination with a blue LED. Further, it is also useful as a phosphor for white LED that converts a part of blue light emission from blue LED to yellow and produces white by combining with blue. Moreover, it is also possible to produce a white LED with good color rendering properties by using it mixed with a blue or red phosphor.

  However, it is known that the surface of the phosphor made of the above-mentioned alkaline earth silicate or strontium silicate is decomposed and deteriorated (formation of hydrate) by water vapor or water in the air. For this reason, a long-term use in the atmosphere and a temperature increase due to excitation light tend to cause a decrease in luminance and a change in color tone, and there has been a significant problem in water resistance or chemical stability as a phosphor.

Therefore, the phosphor particles made of these alkaline earth silicates or strontium silicates are coated with a coating layer having moisture resistance. Examples of the material used for the coating layer include inorganic materials such as metal oxides such as MgO and Al ₂ O ₃ , and organic materials such as latex and polyorganosiloxane.

For example, a phosphor particle made of (Sr, Ba) ₂ SiO ₄ : Eu ²⁺ is coated with a coating layer made of MgO is known (see Patent Document 3). The phosphor particles are prepared, for example, by dispersing the phosphor particles in an aqueous solution obtained by dissolving a water-soluble magnesium salt such as nitrate, acetate, citrate, etc. After obtaining phosphor particles coated with a coating layer made of hydroxide, it can be produced by filtering the dispersion and firing the separated phosphor particles.

  However, in the method for producing the phosphor particles having the MgO coating layer described above, when the phosphor particles made of alkaline earth silicate or strontium silicate are dispersed in an aqueous solution and the dispersion liquid is adjusted, the fluorescent particles are dispersed in the dispersion liquid. There was a problem that body particles were hydrolyzed.

JP 2006-036943 A JP 2007-131843 A JP 2002-223008 A

  In view of such a conventional problem, the present invention can prevent surface degradation due to water vapor or water in the air, and does not cause a decrease in luminance or a change in color tone even when used for a long time or when the temperature rises. Another object of the present invention is to provide phosphor particles comprising an alkaline earth silicate or strontium silicate excellent in water resistance or chemical stability, and a light emitting diode comprising the phosphor particles.

  As a result of intensive studies to achieve the above object, the present inventors have found that alkaline earth silicate phosphor particles dispersed in an organic solvent, particularly strontium silicate phosphor particles, have an aluminum-based surface. The phosphor particles are coated with a zirconium compound while adsorbing the organometallic compound to keep the phosphor particles in a highly dispersed state, and then the phosphor particles are separated from the organic solvent to heat the aluminum-based organometallic compound. By heating and firing at a decomposition temperature or higher, the surface of each phosphor particle can be uniformly and sufficiently coated, and the particle surface is coated with an amorphous zirconium compound by this surface coating treatment. The inventors have found that strontium silicate phosphor particles having excellent water resistance and chemical stability can be obtained, and have completed the present invention.

  That is, the method for producing surface-coated strontium silicate phosphor particles in the present invention includes the following first to third steps. The method of the present invention can be widely applied not only to strontium silicate phosphor particles but also to alkaline earth silicate phosphor particles.

(1) First step: An aluminum-based organic metal compound containing aluminum as a constituent element is added to and mixed with a dispersion of strontium silicate phosphor particles in which strontium silicate phosphor particles are dispersed in an organic solvent. The compound is adsorbed on the surface of the strontium silicate phosphor particles.

(2) Second step: A hydrolyzable zirconium compound and water are added to and mixed with the dispersion of the strontium silicate phosphor particles adsorbed with the aluminum-based organometallic compound, and the hydrolyzable zirconium compound is hydrolyzed and polymerized. The produced zirconium compound is coated on the surface of the strontium silicate phosphor particles adsorbed with the aluminum-based organometallic compound.

(3) Third step: After separating and recovering the strontium silicate phosphor particles coated with the zirconium compound from the dispersion, the strontium silicate phosphor is heated and fired at a temperature equal to or higher than the thermal decomposition temperature of the aluminum-based organometallic compound. The surface of the particles is coated with an amorphous zirconium compound.

  In the method for producing surface-coated strontium silicate phosphor particles of the present invention, the aluminum-based organometallic compound is at least one selected from aluminum alcoholate and its polymer, cyclic aluminum oligomer, and alkoxy group-containing aluminum chelate. It is preferable. Moreover, it is preferable that the addition amount of the said aluminum type organometallic compound is the range of 10-300 weight part with respect to 100 weight part of strontium silicate fluorescent substance particles.

  In the method for producing surface-coated strontium silicate phosphor particles according to the present invention, the hydrolyzable zirconium compound includes zirconium tetra-n-butoxide, tetranormal propoxyzirconium, zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, It is preferably at least one selected from zirconium monobutoxyacetylacetonate bis (ethylacetoacetate), zirconium dibutoxybis (ethylacetoacetate), zirconium tetraethylacetoacetate, and partial hydrolysis products thereof. Moreover, it is preferable that the addition amount of the said hydrolyzable zirconium compound is the range of 400-1500 weight part with respect to 100 weight part of strontium silicate fluorescent substance particles.

  In the method for producing surface-coated strontium silicate phosphor particles according to the present invention, in the second step, a hydrolyzable zirconium compound and water are added and mixed to a dispersion of strontium silicate phosphor particles adsorbed with an aluminum-based organometallic compound. After stirring for 4 to 8 hours while maintaining the liquid temperature at 10 to 15 ° C, it is preferable to continue stirring at a liquid temperature of 20 to 28 ° C for 4 to 24 hours.

  In the method for producing the surface-coated strontium silicate phosphor particles of the present invention, in the third step, after separating and recovering the strontium silicate phosphor particles coated with the amorphous zirconium compound from the dispersion, the aluminum-based organometallic compound It is preferable that the firing temperature for heating and firing at a temperature equal to or higher than the thermal decomposition temperature of 300 to 400 ° C. in an oxidizing atmosphere or 300 to 600 ° C. in a non-oxidizing atmosphere.

In the method for producing surface-coated strontium silicate phosphor particles of the present invention, the organic solvent is preferably at least one alcohol solvent selected from methanol, ethanol, isopropanol, and butanol. The strontium silicate phosphor particles include Sr ₃ SiO ₅ : Eu ²⁺ , (Sr, Ba) ₃ SiO ₅ : Eu ²⁺ , Sr ₂ SiO ₄ : Eu ²⁺ , (Sr, Ba, Ca) ₂ SiO ₄ : Eu. One or more strontium silicates selected from ²⁺ are preferable.

  Further, the surface-coated strontium silicate phosphor particles provided by the present invention are obtained by the above-described method of the present invention, and the strontium silicate phosphor particles and the non-coated strontium silicate phosphor particles having a thickness of 100 to 800 nm covering the phosphor particles. It comprises a coating layer of a crystalline zirconium compound, and has a density in the range of 85 to 95% when the density of the phosphor particles alone is 100%.

  The surface-coated strontium silicate phosphor particles of the present invention can have excellent moisture resistance by having a coating layer made of an amorphous zirconium compound and having a thickness of 100 to 800 nm on the surface of the phosphor particles. The thickness of the coating layer of the surface-coated strontium silicate phosphor particles is preferably in the range of 200 to 600 nm, and more preferably in the range of 360 to 600 nm.

  By controlling the thickness of the coating layer of the surface-coated strontium silicate phosphor particles in the range of 100 to 800 nm, the external quantum efficiency can be improved, and the fluorescence emitted from the phosphor under high temperature and high humidity can be improved. A decrease in chromaticity can be suppressed. Further, when the thickness of the coating layer is in the range of 200 to 600 nm, more preferably in the range of 360 to 600 nm, the external quantum efficiency can be further improved, and at the same time, it is emitted from the phosphor under high temperature and high humidity. A decrease in chromaticity of fluorescence can be reliably suppressed.

  In addition, when the thickness of the coating layer of the surface-coated strontium silicate phosphor particles is less than 100 nm, the chromaticity of the fluorescence emitted from the phosphor is likely to decrease greatly under high temperature and high humidity. On the other hand, when the thickness of the coating layer exceeds 800 nm, the external quantum efficiency may be greatly reduced, and formation of the coating layer becomes difficult, which is disadvantageous for production.

  The surface-coated strontium silicate phosphor particles of the present invention have a density in the range of 85 to 95% when the density of the phosphor particles alone is 100%. When the phosphor particles and a resin having thermosetting properties and fluidity at room temperature are mixed, the phosphor particles can be uniformly dispersed in the resin. Therefore, the arrangement of the phosphor particles in the resin can be easily controlled, and as a result, a good light emitting diode with little variation in emission intensity from the phosphor can be obtained.

  In the surface-coated strontium silicate phosphor particles, when the density is less than 85% with respect to the density of the phosphor particles alone, it is difficult to uniformly disperse the phosphor particles in the resin. On the other hand, when the density of the surface-coated strontium silicate phosphor particles exceeds 95% of the density of the phosphor particles alone, the phosphor particles are likely to settle in the resin when the phosphor particles and the resin are mixed. . Therefore, in either case, it is difficult to control the arrangement of the phosphor particles in the resin, and as a result, it may be difficult to obtain a light emitting diode with small variation in emission intensity from the phosphor.

In the surface-coated strontium silicate phosphor particles of the present invention, the strontium silicate is Sr ₃ SiO ₅ : Eu ²⁺ , (Sr, Ba) ₃ SiO ₅ : Eu ²⁺ , Sr ₂ SiO ₄ : Eu ²⁺ , (Sr, Ba, Ca) ₂ SiO ₄ : It is preferably composed of one or more strontium silicates selected from Eu ²⁺ . The strontium silicate preferably contains 0.1 to 10% of Eu.

  Furthermore, the present invention comprises the surface-coated strontium silicate phosphor particles described above, and absorbs light having a wavelength in the range of 420 to 480 nm and emits light having a wavelength exceeding 480 nm and not more than 800 nm. A diode (LED) is provided. The light-emitting diode of the present invention can be used as various light sources such as lamps, indoor lighting fixtures, outdoor lighting fixtures, in-vehicle lighting fixtures, and liquid crystal backlight sources.

  According to the present invention, surface degradation of surface strontium silicate with excellent water resistance can be achieved by eliminating degradation and deterioration of the surface due to water vapor or water in the air, and suppressing changes in luminance and chromaticity even with prolonged use and temperature rise. Phosphor particles can be provided. Therefore, the surface-coated strontium silicate phosphor particles having excellent water resistance according to the present invention are extremely useful industrially as phosphors for light sources such as LEDs.

It is a schematic sectional drawing for demonstrating the surface covering strontium silicate fluorescent substance particle of this invention. 4 is a TEM cross-sectional photograph of surface-coated strontium silicate phosphor particles of Sample 11 obtained in Example 3. FIG. 4 is a TEM cross-sectional photograph of surface-coated strontium silicate phosphor particles of Sample 13 obtained in Example 3. FIG. It is a graph which shows the electrical conductivity change of the water by the surface covering strontium silicate fluorescent substance particle of this invention, and the strontium silicate fluorescent substance particle of a comparative example. It is a graph which shows the chromaticity change of the fluorescence by the light emitting diode provided with the surface covering strontium silicate fluorescent substance particle of this invention, and the strontium silicate fluorescent substance particle of a comparative example.

The phosphor targeted by the present invention may be any alkaline earth silicate phosphor containing an alkaline earth element such as strontium and silicon oxide as main components, and a typical one is a strontium silicate phosphor. . For example, one kind selected from Sr ₃ SiO ₅ : Eu ²⁺ , (Sr, Ba) ₃ SiO ₅ : Eu ²⁺ , Sr ₂ SiO ₄ : Eu ²⁺ , (Sr, Ba, Ca) ₂ SiO ₄ : Eu ²⁺ Two or more kinds of phosphors are preferred. These strontium silicate phosphors can contain 0.1 to 10% of Eu. In general, a phosphor indicates a collection of a plurality of phosphor particles. That is, the “surface-coated strontium silicate phosphor” in the present invention is a collection of a plurality of surface-coated strontium silicate phosphor particles, and the “strontium silicate phosphor” is a collection of a plurality of strontium silicate phosphor particles. is there.

  Next, the method for producing the surface-coated strontium silicate phosphor particles according to the present invention includes (1) a first step of adsorbing an aluminum-based organometallic compound on the surface of the strontium silicate phosphor particles, and (2) the surface of the strontium silicate phosphor particles. The process is divided into a second process for coating the zirconium compound, and (3) a third process for coating the amorphous strontium silicate phosphor particles by heating and firing, and each process will be described below.

  (1) In the first step, an aluminum-based organometallic compound containing aluminum is added to and mixed with a dispersion of strontium silicate phosphor particles in which strontium silicate phosphor particles are dispersed in an organic solvent, and the aluminum-based organometallic compound is mixed with strontium. Adsorbed on the surface of the silicate phosphor particles.

  In this first step, the aluminum-based organometallic compound having an excellent dispersion function is adsorbed on the surface of the strontium silicate phosphor particles, so that the dispersion of the strontium silicate phosphor particles in the organic solvent by the dispersing action of the organometallic compound. Thus, it becomes possible to keep the high concentration strontium silicate phosphor particles in a monodispersed state.

  In general, the strontium silicate phosphor particles have poor reactivity with the hydrolyzable zirconium compound added in the second step, and the zirconium compound adheres to the surface of the particle because the zirconium compound produced by the hydrolysis is weak. However, it is easy to detach when a certain amount of shearing force is applied. However, by previously adsorbing the aluminum-based organometallic compound on the surface of the strontium silicate phosphor particles, the affinity with the zirconium compound is improved, and the zirconium compound can be more strongly adsorbed on the strontium silicate phosphor particles.

  Although it does not specifically limit as an aluminum type organometallic compound to be used, it is compatible with an organic solvent, has high affinity and adsorption power with the surface of strontium silicate phosphor particles, and has an excellent function of dispersing phosphor particles. And what is excellent in the function which accelerates | stimulates superposition | polymerization of a hydrolyzable zirconium compound in the 2nd process mentioned later is preferable. From such a viewpoint, at least one selected from aluminum alcoholate and a polymer thereof, a cyclic aluminum oligomer, and an alkoxy group-containing aluminum chelate compound can be preferably used.

  Specifically, as a preferable aluminum-based organometallic compound, aluminum alcoholate is aluminum alcoholate such as aluminum ethylate, aluminum isopropylate, aluminum sec-butylate, mono-sec-butoxyaluminum diisopropylate, or a polymer thereof. Can be mentioned. Moreover, in a cyclic | annular aluminum oligomer, a cyclic | annular aluminum oxide octylate etc. can be mentioned.

  The above alkoxy group-containing aluminum chelate compounds include ethyl acetoacetate aluminum diisopropylate, aluminum tris (ethyl acetoacetate), octyl acetoacetate aluminum diisopropylate, stearyl acetoaluminum diisopropylate, aluminum monoacetylacetonate bis (ethyl Aluminum alcoholates such as acetoacetate) and aluminum tris (acetylacetonate) are dissolved in aprotic solvents, petroleum solvents, hydrocarbon solvents, ester solvents, ketone solvents, ether solvents, amide solvents, etc. Then, β-diketone, β-ketoester, mono- or polyhydric alcohol, fatty acid, etc. are added to this solution and heated to reflux to obtain a ligand substitution reaction. .

  These aluminum-based organometallic compounds have high reactivity with inorganic surfaces and are easily adsorbed on the surface of strontium silicate phosphor particles. Moreover, the dispersibility of the strontium silicate phosphor particles in the organic solvent can be significantly improved by orienting the organic chains in the molecules to the outside of the particle surface. Also, hydrolysis and polycondensation reactions are faster than those of hydrolyzable zirconium compounds, and the organometallic compound itself acts as a crosslinking agent for the zirconium monomer or oligomer, and the hydrolyzable zirconium compound added in the next second step. Since it has a function of accelerating polymerization, it does not hinder the formation of a coating layer unlike a surfactant or a polymer dispersant.

  As a method of adsorbing the aluminum-based organometallic compound to the strontium silicate phosphor particles, the aluminum-based organometallic compound is added to the dispersion liquid in which the strontium silicate phosphor particles are dispersed in the organic solvent as described above, and the mixture is stirred and mixed. A wet method can be employed. When performing this wet method, agglomerates of strontium silicate phosphor particles are previously crushed in an organic solvent using a ball mill, a sand mill, an ultrasonic homogenizer, etc., and an aluminum-based organic substance is dispersed in a uniformly dispersed slurry. A method in which a metal compound is added to act on the particle surface or an aluminum-based organometallic compound is added simultaneously during the crushing treatment is further preferred.

  The amount of the aluminum-based organometallic compound added is preferably 10 to 300 parts by weight, more preferably 80 to 150 parts by weight, based on 100 parts by weight of the strontium silicate phosphor particles. When the aluminum-based organometallic compound is less than 10 parts by weight, the effect of covering the surface is small, and the effect of improving dispersibility and water resistance may not be sufficient. Even if the amount exceeds 300 parts by weight, if the adsorbed amount on the strontium silicate phosphor particles exceeds a certain level, the dispersion effect in the treatment liquid becomes saturated and the cost is disadvantageous. In addition, when there is too much addition amount of an aluminum type organometallic compound, when removing a solvent at the 3rd process mentioned later, since it will become easy to granulate particles, from an industrial viewpoint, 200 weight part is made an upper limit. It is particularly preferred.

  The organic solvent in the first step is not particularly limited as long as it does not dissolve the strontium silicate phosphor particles and dissolves the hydrolyzable zirconium compound and its partial hydrolysis product added in the next second step, and water. There is no limit. For example, alcohols, cellosolves, ketones, ethers and the like can be used. Among them, alcohols are preferable, and methanol, ethanol, isopropanol, and butanol are particularly preferable. Depending on the number of carbon atoms in the alcohol, the hydrolysis rate of the aluminum-based organometallic compound or the hydrolyzable zirconium compound varies, so it is desirable to conveniently select the type of alcohol according to the target coating amount.

  (2) In the second step, a hydrolyzable zirconium compound and water are added and mixed to the dispersion of the strontium silicate phosphor particles to which the aluminum-based organometallic compound is adsorbed in the first step. A zirconium compound is produced by hydrolysis and polymerization, and the surface of the strontium silicate phosphor particles on which the aluminum-based organometallic compound is adsorbed is coated with the zirconium compound.

  In this second step, the aluminum-based organometallic compound adsorbed on the surface of the phosphor particles is hydrolyzed, and the hydrolysis and polymerization reaction of the added hydrolyzable zirconium compound proceeds. The zirconium compound produced by this reaction grows with the strontium silicate phosphor particles in a monodispersed state adsorbed by the aluminum-based organometallic compound as a nucleus, and uniformly coats the particle surface.

  The hydrolysis reaction can be performed under any pressure of reduced pressure, normal pressure, or increased pressure, but is preferably performed at a temperature not higher than the boiling point of the reaction mixture and with sufficient stirring. Specifically, in order to form a dense layer by slowly reacting on the surface of the strontium silicate phosphor particles, a hydrolyzable zirconium compound is added, and then the liquid temperature is kept at 10 to 15 ° C. After stirring for 8 hours, stirring is preferably continued for about 4 to 24 hours at a liquid temperature of 20 to 28 ° C.

  The amount of strontium silicate phosphor particles in the second step is preferably 1 to 50% by weight of the mixed solution to which the hydrolyzable zirconium compound is added. If the amount of strontium silicate phosphor particles in the mixed solution is less than 1% by weight, it is industrially disadvantageous because of the cost for concentration and solvent removal, and if it exceeds 50% by weight, strontium silicate phosphor particles are aggregated. This is not preferable because it is difficult to disperse in the solvent.

  Further, the amount of water used in the second step may be more than the amount by which the hydrolysis of the aluminum-based organometallic compound and the hydrolyzable zirconium compound proceeds, preferably the hydrolyzable zirconium compound or its partial hydrolysis. It is in the range of 0.5 to 15 equivalents relative to the number of moles of alkoxy groups in the product.

  The hydrolyzable zirconium compound to be used is not particularly limited. For example, zirconium tetra-n-butoxide, tetranormal propoxyzirconium, zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium monobutoxyacetylacetonate bis (ethyl At least one selected from acetoacetate), zirconium dibutoxybis (ethyl acetoacetate), zirconium tetraethyl acetoacetate and partial hydrolysis products thereof is preferred.

  The addition amount of the hydrolyzable zirconium compound is preferably in the range of 400 to 1500 parts by weight with respect to 100 parts by weight of the strontium silicate phosphor particles. If the amount of the hydrolyzable zirconium compound added is less than 400 parts by weight, the effect of coating the surface of the strontium silicate phosphor particles is small, and therefore a sufficient effect of improving water resistance cannot be obtained. On the other hand, when the amount exceeds 1500 parts by weight, moisture in the atmosphere is absorbed and a gelation reaction occurs in the entire liquid, making it impossible to recover the strontium silicate phosphor particles.

  In addition, in order to suppress excessive reactivity and polycondensation of hydrolyzable zirconium compounds and to control them appropriately, a liquid mixture containing acid, cellosolve, aminoalcohol, acetylacetone, alkylamine, formamide, etc. is hydrolysable. It can also be used as a zirconium compound solution.

  In addition, when adding water and a hydrolyzable zirconium compound in the second step, it may be added by dissolving in an organic solvent, but it is not always necessary to use an organic solvent, and the organic solvent in the first step is used instead. can do.

  In the case of using an organic solvent in the second step, there is no particular limitation as long as it dissolves a hydrolyzable zirconium compound or a partial hydrolysis product thereof and water, and alcohols, cellosolves, ketones, ethers Among them, alcohols are preferable. As alcohols, methanol, ethanol, isopropanol, and butanol are particularly preferable. However, as in the case of the first step, the hydrolysis rate of the hydrolyzable zirconium compound varies depending on the number of carbon atoms of the alcohol, so it is desirable to conveniently select the type of alcohol according to the target coating amount. .

  (3) In the third step, the strontium silicate phosphor particles coated with the zirconium compound are separated and recovered from the dispersion, and then heated and fired at a temperature equal to or higher than the thermal decomposition temperature of the aluminum-based organometallic compound so that the surface is non-coated. Strontium silicate phosphor particles coated with a crystalline zirconium compound are obtained. The amorphous zirconium compound contains zirconium oxide as a main component and contains carbon in addition to zirconium and oxygen.

  In this third step, the strontium silicate phosphor particles coated with the zirconium compound are heated and fired at a temperature equal to or higher than the decomposition temperature of the aluminum organometallic compound, whereby the aluminum organometallic compound is thermally decomposed, The film of the amorphous zirconium compound formed on the surface of the strontium silicate phosphor particles is densified, and it becomes possible to more effectively suppress the transmission of moisture.

  As a specific process, first, strontium silicate phosphor particles coated with a zirconium compound are separated and recovered from the dispersion by removing the solvent. As a method for removing the solvent, well-known methods such as a filter press method, a ultrafiltration method, and a centrifugal separation method can be used in addition to the evaporation method, but the method is not limited to these methods. After removing the solvent and recovering, the strontium silicate phosphor particles coated with the zirconium compound are at a temperature above the boiling point of the remaining organic solvent, preferably at a temperature of 60 to 150 ° C. for 1 hour or more. It is preferable to perform drying by heating.

  Next, the strontium silicate phosphor particles coated with the zirconium compound separated and recovered and dried as necessary are heat-treated. The heat treatment temperature may be equal to or higher than the thermal decomposition temperature of the aluminum-based organometallic compound, but the heat resistant temperature of the strontium silicate phosphor and the heating atmosphere must be taken into consideration.

  For example, in an oxidizing atmosphere where oxygen is present, particularly in the air, if the temperature exceeds 500 ° C., Eu in the strontium silicate phosphor is oxidized and changes from divalent to trivalent, so that the thermal decomposition of the aluminum-based organometallic compound A heat treatment temperature that is not lower than the temperature and not higher than 500 ° C. is preferable, and a range of 300 to 400 ° C. is more preferable. If the firing temperature is less than 300 ° C., the aluminum-based organometallic compound may not be sufficiently removed, and an amorphous zirconium compound coating layer may not be formed. On the other hand, when the firing temperature exceeds 400 ° C., the phosphor particles may be deteriorated, and the external quantum efficiency of the obtained phosphor may be lowered.

In the case of a non-oxidizing atmosphere that does not contain oxygen such as nitrogen or argon, the organic solvent is difficult to decompose during firing at a temperature lower than 300 ° C., and therefore a range of 300 ° C. to 600 ° C. is preferable. Baking at a temperature higher than 600 ° C. is not preferable because CO or CO ₂ generated from the organic solvent reacts with Sr or the like to form strontium carbonate or the like on the surface of the phosphor particles. In addition, when heat treatment is performed at a temperature higher than 600 ° C., zirconium oxide grows and grain boundaries are generated in the coating layer, and moisture may diffuse through the grain boundaries, so that good moisture resistance cannot be obtained. There is.

By the third step, as shown in FIG. 1, the surface-coated strontium silicate phosphor particle 1 of the present invention in which the coating layer 3 made of an amorphous zirconium compound is formed on the surface of the strontium silicate phosphor particle 2 is obtained. be able to. The coating layer 3 does not need to be zirconium oxide (ZrO ₂ ), and may contain an organic substance or an element such as carbon constituting the hydrolyzable zirconium compound. Further, the coating layer 3 may be a single layer or a plurality of layers as long as it is a layer made of an amorphous zirconium compound. Furthermore, the coating layer 3 is continuous, and it is preferable that the unevenness and the boundary due to the crystal grain boundary or the like do not exist because they cause diffusion of moisture and the like.

  The amorphous zirconium compound coating layer 3 formed on the surface of the strontium silicate phosphor particles 2 has a thickness of 100 to 800 nm, preferably 200 to 600 nm, more preferably 360 to 600 nm. By the coating layer 3 of this amorphous zirconium compound, the surface-coated strontium silicate phosphor particles 1 can have excellent water resistance. The surface-coated strontium silicate phosphor particles have a density in the range of 85 to 95% when the density of the phosphor particles alone is 100%.

The density of the amorphous zirconium compound coating layer itself is usually 1.0 to 5.0 g / cm ³ , preferably 1.0 to 2.0 g / cm ³ . When the density of the coating layer is high, the thickness of the coating layer is reduced. For example, the density is 1.0 to 5.0 g / cm ³ , the thickness is in the range of 100 to 800 nm, and the density is 1.0 g to 2.0 g / cm ³ . The thickness is in the range of 360-600 nm. In any range of the coating layer density, the density of the entire surface-coated strontium silicate phosphor particles can be 85 to 95% with respect to the density of the phosphor particles alone.

  The above-mentioned surface-coated strontium silicate phosphor particles of the present invention are excellent in water resistance, have little surface degradation due to water vapor or water in the air, and can change luminance and decrease chromaticity even when used for a long time or when the temperature rises. Can be suppressed. Therefore, the surface-coated strontium silicate phosphor particles having excellent water resistance according to the present invention are extremely useful as phosphors for light sources such as light-emitting diodes (LEDs). For example, they absorb light in the wavelength range of 420 to 480 nm. It can be used for a light emitting diode that emits light having a wavelength of more than 480 nm and less than 800 nm.

  The light emitting diode provided with the surface-coated strontium silicate phosphor particles of the present invention can be manufactured, for example, as follows. First, 30-50 mass% of surface-coated strontium silicate phosphor particles are mixed with a resin having thermosetting properties and fluidity at room temperature to prepare a slurry. Examples of the resin having thermosetting properties and fluidity at room temperature include silicone resins (specifically, product name: JCR6175 manufactured by Toray Dow Corning Co., Ltd.).

  Next, 3 to 4 μL of the slurry is injected into a top view type package on which a blue LED chip having a peak wavelength at 460 nm is mounted. The top view type package into which this slurry has been injected is heated at a temperature in the range of 140 to 160 ° C. for 2 to 2.5 hours to cure the slurry. In this manner, a light emitting diode that absorbs light in the wavelength range of 420 to 480 nm and emits light having a wavelength of more than 480 nm and not more than 800 nm can be manufactured.

  At this time, the surface-coated strontium silicate phosphor particles preferably have a density in the range of 85 to 95% with respect to the density of the phosphor particles alone. Surface-coated strontium silicate phosphor particles having a density in this range can be uniformly dispersed in the silicone resin by mixing. Thereby, since arrangement | positioning of the fluorescent substance particle in a silicone resin can be controlled easily, as a result, the favorable light emitting diode with small dispersion | variation in emitted light intensity can be obtained.

[Example 1]
In the first step, 700 g of isopropyl alcohol (IPA) is mixed with 10 g of ethyl acetoacetate aluminum diisopropylate (produced by Kawaken Fine Chemical Co., Ltd., trade name: aluminum chelate ALCH) as an aluminum-based organometallic compound, and further strontium silicate fluorescence. Sr ₃ SiO ₅ : Eu ²⁺ (manufactured by Lumitec, SSE) (10 g) was added as body particles, and the mixture was stirred and mixed with an ultrasonic cleaner for 10 minutes to prepare a strontium silicate phosphor particle dispersion.

  In the second step, 56 g of zirconium tetra-n-butoxide (manufactured by Kanto Chemical Co., Ltd.) and 104 g of butanol are mixed as a hydrolyzable zirconium compound, and 16 g of acetylacetone (manufactured by Kanto Chemical Co., Ltd.) is further added, and 1 at room temperature is added. A hydrolyzable zirconium compound solution was prepared by stirring for a period of time. Further, 32 g of water was mixed with 32 g of isopropyl alcohol (IPA) to prepare water for hydrolysis.

  While the strontium silicate phosphor particle dispersion obtained in the first step is cooled to 12 ° C. with cooling water and stirred, the hydrolyzable zirconium compound solution is added, and then the hydrolysis water is added. The mixture was held at 12 ° C. for 5 hours with stirring, and then aged by holding at 24 ° C. for 12 hours with further stirring.

  Thereafter, in the third step, the dispersion obtained in the second step is vacuum-dried to evaporate the solvent, and the obtained strontium silicate phosphor particles are heated and dried at 110 ° C. for 1 hour, and further 350 ° C. in the air. Was fired for 1 hour to obtain strontium silicate phosphor particles whose surface was coated with an amorphous zirconium compound.

  The surface-coated strontium silicate phosphor particles obtained in the first step, the second step, and the third step were used as Sample 1. It was found that an amorphous zirconium compound film having a thickness of about 300 nm was formed on the entire surface of the strontium silicate phosphor particles by cutting the phosphor particles of Sample 1 and analyzing the cross-sectional TEM image. It was.

[Example 2]
As other examples of the present invention, surface-coated strontium silicate phosphor particles of Samples 2 to 5 below were prepared. That is, the surface-coated strontium silicate phosphor particles of Sample 2 were prepared in the same manner as in Sample 1 except that the amount of the hydrolyzable zirconium compound added in Step 2 was doubled.

  Further, except that 73.3 g (0.15 mol) of zirconium dibutoxybis (ethylacetoacetate) (manufactured by Matsumoto Fine Chemical Co., Ltd., ORGATIZ ZC-580) was added as the hydrolyzable zirconium compound. Similarly, the surface-coated strontium silicate phosphor particles of Sample 3 were produced.

  As the above hydrolyzable zirconium compound, a sample was obtained in the same manner as in Sample 1 except that 61.5 g (0.15 mol) of zirconium tributoxyacetylacetonate (manufactured by Matsumoto Fine Chemical Co., Ltd., ORGATIZ ZC-540) was added. 4 surface-coated strontium silicate phosphor particles were prepared.

  Furthermore, surface-coated strontium silicate phosphor particles of Sample 5 were produced in the same manner as Sample 1 except that the amount of the aluminum-based organometallic compound added was doubled.

[Comparative Example 1]
As comparative examples, coated strontium silicate phosphor particles of Samples 6 to 9 below were produced. That is, sample 6 is the same as sample 1 except that the amount of the hydrolyzable zirconium compound added is halved. In sample 7, the amount of the hydrolyzable zirconium compound added is ¼. Except that, amorphous zirconium compound-coated strontium silicate phosphor particles were produced in the same manner as in the case of Sample 1 above.

  Sample 8 was the same as Sample 1 except that the amount of the hydrolyzable zirconium compound added was quadrupled. However, since the solution gelled during stirring at room temperature, the operation was stopped, and strontium silicate phosphor particles whose surface was coated with an amorphous zirconium compound were not obtained. In Sample 9, surface-coated strontium silicate phosphor particles were prepared in the same manner as in Sample 1 except that no aluminum-based organometallic compound was added.

<Evaluation of fluorescence intensity of phosphor particles>
The surface-coated strontium silicate phosphor particles of Samples 1 to 5 of the present invention obtained in Example 1 above, and Samples 6 to 9 obtained in Comparative Example 1 (except for Sample 8 whose operation was stopped halfway) For the surface-coated strontium silicate phosphor particles, the initial fluorescence intensity and the fluorescence intensity after the environmental resistance test were measured, respectively.

  The fluorescence intensity (arbitrary unit) is a result of measuring the fluorescence intensity at a wavelength of 570 nm at an excitation wavelength of 380 nm using a spectrofluorometer (manufactured by Jusco, FP-6500ST). In addition, the environmental resistance test was performed by holding the surface-coated strontium silicate phosphor particles in an atmosphere of 85 ° C. and 85% humidity for 500 hours.

  Furthermore, in order to evaluate the water resistance of the surface-coated strontium silicate phosphor particles, the change rate of the initial fluorescence intensity and the fluorescence intensity after the environmental resistance test were calculated. As the evaluation of water resistance, it was judged that the change rate of the fluorescence intensity was 10% or less as compared with the conventional example, the 10-30% or less was normal, and the case where the change rate exceeded 30% was poor.

  For the surface-coated strontium silicate phosphor particles of Samples 1 to 9, the addition amount of hydrolyzable zirconium compound and aluminum-based organometallic compound, the fluorescence intensity after the initial and environmental resistance tests, and the rate of change thereof are shown in Table 1 below. Show. Moreover, the phosphor intensity | strength and change rate which measured similarly about the said strontium silicate fluorescent substance particle | grains (unprocessed) which do not have a surface coating are shown as the sample 10. FIG.

  As can be seen from the above results, the surface-coated strontium silicate phosphor particles of Samples 1 to 5 which are examples of the present invention have a change rate of fluorescence intensity of 10% or less, and have good water resistance and chemical properties. Stability. On the other hand, the surface-coated strontium silicate phosphor particles of Samples 6, 7, and 9, which are comparative examples, have a rate of change in fluorescence intensity that is about the same as that of the untreated sample 10 or exceeds 10%. It was inferior in stability.

[Example 3]
After using 10 g of strontium silicate phosphor particles made of (Sr, Ba) ₃ SiO ₅ : Eu ²⁺ and having a particle size in the range of 6 to 40 μm, and adding the hydrolyzable zirconium compound in the second step, then at 12 ° C. A surface-coated strontium silicate phosphor particle of Sample 11 coated with an amorphous zirconium compound was produced in the same manner as in Sample 1 of Example 1 except that the mixture was stirred for 5 hours and further stirred at 24 ° C. for 7 hours. did.

  After embedding the surface-coated strontium silicate phosphor particles of Sample 11 in an epoxy resin, a protective film is formed by W deposition, and using FIB (focused ion beam processing apparatus, manufactured by Hitachi High-Tech, FB-2100). A thin piece with a phosphor cross section was produced. A cross-sectional image of this thin piece was taken using a transmission electron microscope (TEM, manufactured by Hitachi High-Tech, HF-2200), and the thickness of the surface coating layer was measured.

  A TEM cross-sectional photograph of the surface-coated strontium silicate phosphor particles of Sample 11 is shown in FIG. As is apparent from FIG. 2, it can be seen that the coating layer of the amorphous zirconium compound is formed on the entire surface of the strontium silicate phosphor particles with a substantially constant thickness. As a result of measurement from FIG. 2, the thickness of the coating layer in the surface-coated strontium silicate phosphor particles of Sample 11 was 200 nm.

  As another example, surface-coated strontium silicate phosphor particles of Samples 12 to 14 below were produced. That is, in Sample 12, the surface coating was performed in the same manner as in Sample 11 except that after adding the hydrolyzable zirconium compound in the second step, the mixture was stirred at 12 ° C. for 5 hours and further stirred at 24 ° C. for 12 hours. Strontium silicate phosphor particles were prepared. The thickness of the coating layer of the surface-coated strontium silicate phosphor particles of this sample 12 was 360 nm as measured in the same manner as described above.

  Sample 13 was the same as Sample 11 except that the hydrolyzable zirconium compound was added in the second step, and then the coating treatment was performed twice at 12 ° C. for 5 hours and then at 24 ° C. for 12 hours. Thus, surface-coated strontium silicate phosphor particles were produced. A TEM photograph of the surface-coated strontium silicate phosphor particles of Sample 13 is shown in FIG. Further, the thickness of the coating layer of the surface-coated strontium silicate phosphor particles of Sample 13 was 590 nm.

  In Sample 14, the surface-coated strontium silicate was added in the same manner as in Sample 11 except that the hydrolyzable zirconium compound was added in the second step, followed by stirring at 12 ° C. for 5 hours and further stirring at 24 ° C. for 4 hours. Phosphor particles were prepared. The thickness of the coating layer of the surface-coated strontium silicate phosphor particles of Sample 14 was 100 nm as measured in the same manner as described above.

Next, as a sample 15 of the comparative example, strontium silicate phosphor particles made of (Sr, Ba) ₃ SiO ₅ : Eu ²⁺ and having a particle size in the range of 6 to 40 μm were prepared. As a result of measuring the thickness of the coating layer from the cross-sectional image obtained by TEM in the same manner as in the case of Sample 11, it was clear that the thickness of the coating layer was 0 nm and no coating layer was provided.

<Evaluation of moisture resistance of phosphor particles>
About the surface-coated strontium silicate phosphor particles of the samples 11 to 14 and the strontium silicate phosphor particles of the sample 15 as a comparative example, utilizing the fact that the conductivity of water changes when the phosphor particles are dissolved in water, The moisture resistance was evaluated. That is, 0.2 g of surface-coated strontium silicate phosphor particles were added to 300 mL of pure water to prepare a dispersion, and the conductivity of the obtained dispersion was measured for 1500 seconds. The obtained results are shown in FIG.

  As can be seen from FIG. 4, the change in water conductivity in the surface-coated strontium silicate phosphor particles is 43 mS / m for sample 11 for 1500 seconds, 26 mS / m for sample 12 for 1500 seconds, and 1500 seconds for sample 13 for 1500 seconds. 17 mS / m, and Sample 14 was 105 mS / m in 1500 seconds. On the other hand, in the case of the sample 15 not provided with the coating layer of the comparative example, the water conductivity change was 175 mS / m in 1500 seconds.

  Moreover, with respect to the change in water conductivity (1500 seconds) in the strontium silicate phosphor particles of the sample 15 which is not provided with the coating layer as a comparative example, the surface-coated strontium silicate phosphor particles of the samples 11 to 14 The rate of change in the electrical conductivity of water (1500 seconds) was 24% for sample 11, 9.7% for sample 12, 14.8% for sample 13, and 59.7% for sample 14.

<Evaluation of density of phosphor particles>
About each surface covering strontium silicate fluorescent substance particle of above-mentioned samples 11-14, and a strontium silicate fluorescent substance particle of sample 15 which is a comparative example, using a dry automatic densimeter (the Shimadzu Corporation make, brand name: Accuvic 1330). The respective densities were measured.

  The density of the surface-coated strontium silicate phosphor particles of Samples 11 to 14 is 97% when the density of the strontium silicate phosphor particles of Sample 15 that does not have a coating layer as a comparative example is 100%. 12 was 91%, Sample 13 was 86%, and Sample 14 was 99%.

Further, when the density of the coating layer of the surface-coated strontium silicate phosphor particles was determined from the density of these phosphor particles and the thickness of the coating layer, the sample 11 was 3.23 g / cm ³ and the sample 12 was 1. 50 g / cm ^3, the sample 13 is 1.67 g / cm ^3, and sample 14 was 4.31 g / cm ^3.

<Evaluation of external quantum efficiency>
The external quantum efficiencies of the surface-coated strontium silicate phosphor particles of Samples 11, 12, and 14 and the strontium silicate phosphor particle of Sample 15 as a comparative example were measured.

  In the measurement of external quantum efficiency, a quantum efficiency measurement system (manufactured by Otsuka Electronics Co., Ltd., trade name: instantaneous multi-photometry system MCPD-7000) equipped with a Xe lamp and a spectroscope is used, and the phosphor is irradiated with light having a wavelength of 460 nm. The ratio of the number of photons emitted and emitted by the phosphor divided by the number of irradiated light (number of photons emitted from the phosphor / photon irradiated to the phosphor) Of the number of) was determined as the external quantum efficiency.

  When the external quantum efficiency of the strontium silicate phosphor particles of the sample 15 as a comparative example is 100%, the external quantum efficiencies of the surface-coated strontium silicate phosphor particles of the samples 11 to 14 are 103% for the sample 11 and 12 Was 103% and Sample 14 was 105%. In addition, about the sample 13, the measurement of external quantum efficiency is not performed.

[Example 4]
Using the surface-coated strontium silicate phosphor particles of Samples 11 to 14 obtained in Example 3 and the strontium silicate phosphor particle of Sample 15 that does not have a coating layer as a comparative example, light-emitting diodes were produced.

  That is, 50% by mass of each phosphor particle of Samples 11 to 15 is added to a silicone resin having thermosetting properties and fluidity at room temperature (trade name: JCR6175, manufactured by Toray Dow Corning Co., Ltd.). The mixture was stirred and mixed to prepare a slurry. Next, after injecting 3.4 μL of the slurry into two top view type packages on which blue LED chips having a peak at a wavelength of 460 nm are mounted, the slurry is cured by heating at 150 ° C. for 2 hours. It was.

  In this way, the surface-coated strontium silicate phosphor particles of the samples 11 to 14 are provided, or the sample 15 strontium silicate phosphor particles not provided with the coating layer as a comparative example are provided, and the wavelength is in the range of 420 to 480 nm. A light-emitting diode that absorbs the light and emits light in the range of more than 480 nm and less than 800 nm was manufactured.

<Evaluation of initial luminous flux of light emitting diode>
About each light emitting diode of the samples 11-14 produced in the said Example 4, and the light emitting diode of the sample 15 which is a comparative example, an initial light beam is measured, respectively, using LED measurement apparatus (Instrument System company make, brand name: CAS140B). did.

  As a result, the initial luminous flux of the light emitting diodes including the surface-coated strontium silicate phosphor particles of the samples 11 to 14 is the initial luminous flux of the light emitting diode including the strontium silicate phosphor particles of the sample 15 that does not have the surface coating layer of the comparative example. In contrast, Sample 11 was 108%, Sample 12 was 119%, Sample 13 was 116%, and Sample 14 was 122%.

<Evaluation of chromaticity of light emitting diode>
Next, the chromaticity change was measured for each of the light emitting diodes of Samples 11 to 13 manufactured in Example 4 and the light emitting diode of Sample 15 as a comparative example. The chromaticity change is measured by leaving the light emitting diode at a high temperature and high humidity of 85 ° C. and 85% humidity for a predetermined time, and then using the LED measuring device, the chromaticity of the fluorescence emitted from the light emitting diode. Changes were measured.

  FIG. 5 shows changes in chromaticity of the obtained light emitting diodes of Samples 11 to 13 and the light emitting diode of Sample 15 as a comparative example. FIG. 5 shows a change in CIEEx in the CIExy chromaticity diagram as a change in chromaticity of fluorescence by the light emitting diode.

  For the surface-coated strontium silicate phosphor particles and light-emitting diodes of Samples 11 to 14 prepared in Example 3 above, and for the strontium silicate phosphor particles and light-emitting diodes of Sample 15 that do not have a coating layer as a comparative example, the above-described surface coating Table 2 below summarizes the layer thickness, phosphor density and coating layer density, conductivity change, external quantum efficiency, and initial luminous flux of the light emitting diode.

  As can be seen from Table 2 and FIG. 4 described above, the surface-coated strontium silicate phosphor particles of the samples 11 to 14 having the coating layer made of an amorphous zirconium compound are the strontium silicate fluorescence of the sample 15 having no coating layer. It is clear that the change in conductivity is small compared to the body particles and has excellent moisture resistance. Further, according to the surface-coated strontium silicate phosphor particles of Samples 11 to 14, the external quantum efficiency can be increased as compared with the phosphor particles of Sample 15 that do not include the coating layer, and the coating layer is provided. It can also be seen that the external quantum efficiency does not decrease.

  Moreover, from the said Table 2, according to the surface covering strontium silicate fluorescent substance particle of samples 11-14, it is clear that a density is small compared with the fluorescent substance of the sample 15 which is not provided with the coating layer. Therefore, when manufacturing the light emitting diode, the surface-coated strontium silicate phosphor particles can be uniformly dispersed in the silicone resin, and the arrangement of the phosphor particles in the silicone resin can be easily controlled. A good light emitting diode with small variation in intensity can be obtained.

  From Table 2 above, according to the light-emitting diode using the surface-coated strontium silicate phosphor particles of Samples 11 to 14, as compared with the light-emitting diode using the phosphor particles of Sample 15 that does not have the coating layer of the comparative example. It is apparent that the initial luminous flux can be increased and the initial luminous flux does not decrease even if the coating layer is provided.

  Furthermore, from FIG. 5, the light emitting diode using the surface-coated strontium silicate phosphor particles of Samples 11 to 14 is compared with the light emitting diode using the phosphor particles of Sample 15 that does not have the coating layer of the comparative example. Thus, it is clear that a decrease in chromaticity of fluorescence emitted under high temperature and high humidity can be suppressed.

[Example 5]
In the third step, the dispersion obtained in the second step was vacuum-dried to evaporate the solvent, and the obtained strontium silicate phosphor particles were heated to 110 ° C. The surface-coated strontium silicate phosphor particles of Sample 16 were prepared by heating and drying at 380 ° C. for 1 hour and further firing in the atmosphere at 380 ° C. for 1 hour.

  In Sample 17, in the third step, the dispersion obtained in the second step was vacuum dried to evaporate the solvent, and the obtained strontium silicate phosphor particles were dried by heating at 110 ° C. for 1 hour, and further in the atmosphere. The surface-coated strontium silicate phosphor particles of Sample 17 were produced in the same manner as in Sample 16 except that baking was performed at 420 ° C. for 1 hour.

  Further, in Sample 18, in the third step, the dispersion obtained in the second step was vacuum dried to evaporate the solvent, and the obtained strontium silicate phosphor particles were dried by heating at 110 ° C. for 1 hour, and further in the atmosphere. The surface-coated strontium silicate phosphor particles of Sample 18 were produced in the same manner as in Sample 16 except that baking was performed at 450 ° C. for 1 hour.

  With respect to the surface-coated strontium silicate phosphor particles of Samples 16 to 18 thus obtained, the light excited and emitted by the light having a wavelength of 460 nm was measured in the same manner as in Example 3 above. We asked for efficiency. The obtained results are shown in Table 3 below. In Table 3, the external quantum efficiency of the surface-coated strontium silicate phosphor particles of Sample 12 in Example 3 is also shown.

  From the results of Table 3, in the third step, the higher the firing temperature in the atmosphere of the strontium silicate phosphor particles, the lower the external quantum efficiency of the obtained surface-coated strontium silicate phosphor particles, exceeding 400 ° C. The external quantum efficiency of the surface-coated strontium silicate phosphor particles of samples 17 to 18 fired at a temperature may be lower than the external quantum efficiency of 100% of the strontium silicate phosphor particles (sample 15) that do not have a coating layer. I understand.

1 Surface-coated strontium silicate phosphor particles 2 Strontium silicate phosphor particles 3 Coating layer

Claims (6)

Sr ₃ SiO ₅ : Eu ²⁺ or (Sr, Ba) ₃ SiO ₅ : Eu ²⁺ phosphor particles composed of strontium silicate, and non-contained main component is zirconium oxide having a thickness of 100 to 800 nm covering the phosphor particles. When the density of the amorphous zirconium compound coating layer is 1.0 to 5.0 g / cm ³ and the density of the phosphor particles is 100%, Surface-coated strontium silicate phosphor particles characterized by having a density in the range of ~ 95%. The coating layer adsorbs an aluminum-based organometallic compound on the surface of a strontium silicate phosphor particle, coats the surface of the strontium silicate phosphor particle with a zirconium compound, and then heats the aluminum-based organometallic compound at a temperature equal to or higher than the thermal decomposition temperature of the aluminum-based organometallic compound. 2. The surface-coated strontium silicate phosphor particles according to claim 1, wherein the particles are formed by firing . The surface-coated strontium silicate phosphor particles according to claim 1 or 2 , wherein the thickness of the coating layer is in the range of 200 to 600 nm . The surface-coated strontium silicate phosphor particles according to claim 3 , wherein the thickness of the coating layer is in the range of 360 to 600 nm. The strontium silicate is characterized in that it comprises 0.1% to 10% of the Eu Sr, surface coating strontium silicate phosphor particles according to any one of claims 1 to 4.   The surface-coated strontium silicate phosphor particles according to any one of claims 1 to 5, comprising light having a wavelength in the range of 420 to 480 nm, and emitting light having a wavelength of more than 480 nm and not more than 800 nm. A light emitting diode characterized.