JP2016028170A - Method for producing coated phosphor, coated phosphor, and white light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated phosphor which has good fluorescent characteristics and is capable of maintaining light-emitting characteristics over a long period of time.SOLUTION: A method for producing the coated phosphor includes a mixing step of mixing a phosphor and a metal alkoxide in a solvent to coat the phosphor with an aluminum oxide formed from an aluminum alkoxide. The phosphor contains group 2 elements (M), europium (Eu), silicon (Si), and oxygen (O) in an atomic ratio of compositional formula (1): [(M)Eu]SiOwhere a, b, c, and x satisfy relations of 1.8<a<3.3, 0.9<b<1.1, 3.6<c<5.5, and 0<x<0.09.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a coated phosphor in which a phosphor is coated with a coating material, a coated phosphor and a white light source.

As a study of performing metal coating on a phosphor having low water resistance, for example, Patent Document 1 discloses a technique (sol-gel method) based on a hydrolysis reaction of a metal alkoxide in which a coating material is SiO ₂ . In the example of Patent Document 1, the phosphor is dispersed and mixed as a suspension in a reaction solution and processed by a sol-gel reaction for 8 hours, and the conductivity in the solution due to impurity elution becomes 100 μS / cm or less. After repeating the cleaning, drying and baking are performed to obtain a coated light emitter.

An example of coating phosphor particles with various metal oxides is described in Patent Document 2 and the like. Specifically, the metal alkoxide is added at a rate of 0.2 mol / hour or less with respect to 100 parts by weight of the target phosphor (sulfide), and at the same time, 0.01 to 5.0 mol of 1 mol of the added metal source. The coating material is adhered by adding H ₂ O as an initiator at a ratio, and performing drying and baking treatment.

  In Patent Document 2, the coated phosphor is evaluated by evaluating UV degradation, burning, Cu contamination, conductivity, hydrophilicity, and dispersibility of the target phosphor.

_{Incidentally, ((Ba 1-y,} Sr y) 1-x Eu x) a Si b O oxide represented by _c phosphor has an emission peak at a wavelength 600～610Nm, the characteristics of the phosphor good. However, this oxide phosphor has not been put into practical use because the phosphor itself is vulnerable to moisture and has a problem in long-term reliability. Therefore, measures against water resistance are taken against this problem.

  However, it cannot be said that sufficient characteristics can be imparted, for example, for backlights and LED lighting applications that require a long life. Specifically, the acceleration test environment in the white LED package (PKG) is generally performed at 85 ° C. and 85% RH. Therefore, the phosphor itself dispersed in the resin on the white LED package must also have a performance that can withstand this environment.

  With respect to this required performance (required specification), Patent Document 2 in which the target phosphor is a sulfide has no description of the test itself under high temperature and humidity.

In addition, when the sol-gel method is carried out, the hydrolysis reaction process of the metal alkoxide is inevitably included, so that addition of H ₂ O into the system is inevitable. For example, when TEOS (tetraethoxysilane) having a low reaction rate is used as a film source, a large excess of H ₂ O is required. This contributes to promoting the deterioration of the phosphor itself during the surface treatment process.

  Patent Document 1 describes that the reliability can be improved by increasing the number of coatings. However, as described above, in the coating process when TEOS having a slow reaction rate is used, particles are used. There is a limit to the film thickness growth on the surface, and it is questionable whether the required performance can be reached.

JP 2007-23221 A Japanese Patent Laid-Open No. 04-279893

  The present invention has been proposed in view of such circumstances, and a method for producing a coated phosphor, which has good fluorescence characteristics and can maintain light emission characteristics over a long period of time, a coated phosphor and a white light source The purpose is to provide.

The method for producing a coated phosphor according to the present invention includes a mixing step in which a phosphor and an aluminum alkoxide are mixed in a solvent, and the phosphor is coated with an aluminum oxide formed from the aluminum alkoxide. The body contains a group 2 element (M), europium (Eu), silicon (Si) and oxygen (O) in an atomic ratio of the following composition formula (1).
[(M) _1-x Eu _x ] _a Si _b O _c composition formula (1)
However, in the composition formula (1), a, b, c, and x are 1.8 <a <3.3, 0.9 <b <1.1, 3.6 <c <5.5, 0 < The relationship x <0.09 is satisfied.

The coated phosphor according to the present invention is obtained by coating a phosphor with an aluminum oxide, and the phosphor contains a group 2 element (M), europium (Eu), silicon (Si), and oxygen (O) as follows: It is contained in the atomic ratio of composition formula (1).
[(M) _1-x Eu _x ] _a Si _b O _c composition formula (1)
However, in the composition formula (1), a, b, c, and x are 1.8 <a <3.3, 0.9 <b <1.1, 3.6 <c <5.5, 0 < The relationship x <0.09 is satisfied.

A white light source according to the present invention includes a blue light emitting diode formed on an element substrate, a kneaded material that is disposed on the blue light emitting diode and kneaded a red phosphor and a green phosphor or a yellow phosphor in a transparent resin, The red phosphor is coated with an aluminum oxide, and the phosphor contains a group 2 element (M), europium (Eu), silicon (Si), and oxygen (O), It contains by the atomic ratio of the following composition formula (1).
[(M) _1-x Eu _x ] _a Si _b O _c composition formula (1)
However, in the composition formula (1), a, b, c, and x are 1.8 <a <3.3, 0.9 <b <1.1, 3.6 <c <5.5, 0 < The relationship x <0.09 is satisfied.

  According to the present invention, it is possible to obtain a coated phosphor that has good fluorescence characteristics and can maintain light emission characteristics over a long period of time.

It is a schematic sectional drawing which shows the white light source which concerns on one embodiment of this invention. It is a schematic plan view which shows the illuminating device which concerns on one embodiment of this invention. It is a schematic sectional drawing which shows the illuminating device which concerns on one embodiment of this invention. It is the graph which compared the characteristic of the fluorescent substance before and behind a coating process. It is a graph which shows the specific surface area change by Al / (Sr + Ba) element abundance ratio. It is a figure which shows the electron micrograph of the evaluation sample obtained in Example 1- Example 5, Comparative Example 3, and Comparative Example 4. FIG. It is a graph which shows a high temperature, high humidity environment test result. It is a graph which shows the reliability change by the surface treatment reaction time in a mixing process. It is a graph which shows the reliability change by the reaction temperature in a mixing process. It is a graph which shows the peak intensity and reliability change by Al / (Sr + Ba) element abundance ratio. 6 is a graph showing a change in conductivity of an evaluation sample obtained in Example 6.

Hereinafter, embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail in the following order with reference to the drawings.
1. 1. Manufacturing method of coated phosphor Application example of coated phosphor 2-1. White light source 2-2. 2. Illumination device Example

<1. Method for producing coated phosphor>
The method for producing a coated phosphor according to the present embodiment includes a mixing step in which the phosphor and aluminum alkoxide are mixed in a solvent. Next, the method for manufacturing the coated phosphor according to the present embodiment includes a separation step of separating the mixed solution into a solid phase and a liquid phase.

(Mixing process)
In the mixing step, the phosphor and aluminum alkoxide are mixed in a solvent, and the phosphor is covered with an aluminum oxide formed from the aluminum alkoxide. Here, coating the phosphor with aluminum oxide formed from aluminum alkoxide is not limited to, for example, uniformly attaching aluminum oxide to the surface of the phosphor, and aluminum oxide is applied to the surface of the phosphor. In a case where the aluminum oxide is non-uniformly deposited, and a case where a portion where the aluminum oxide is not deposited is included in part of the surface of the phosphor. In the mixing step, the phosphor and aluminum alkoxide are mixed in a solvent to hydrolyze the aluminum alkoxide in the mixed solution to start the sol-gel reaction, and the phosphor is covered with the aluminum oxide formed from the aluminum alkoxide. A coated phosphor is obtained. That is, a mixed solution in which a phosphor is coated with aluminum oxide is prepared using a sol-gel method.

  For example, in the mixing step, a first solution prepared from a phosphor and a solvent and a second solution prepared from an aluminum alkoxide and a solvent are prepared. In the reaction apparatus, the second solution is added to the first solution, or the first solution is added to the second solution to mix a phosphor and aluminum alkoxide in a solvent. obtain.

As the phosphor, an oxide phosphor containing a group 2 element (M), europium (Eu), silicon (Si) and oxygen (O) in an atomic ratio of the following composition formula (1) (hereinafter simply referred to as “ Called "phosphor"). This phosphor is a silicate phosphor having a light emission peak at a wavelength of 600 to 610 nm, and has good characteristics (fluorescence characteristics, etc.) as the phosphor.
[(M) _1-x Eu _x ] _a Si _b O _c composition formula (1)
In the composition formula (1), M represents a group 2 element, and a, b, c, and x are 1.8 <a <3.3, 0.9 <b <1.1, 3.6 <c <. 5.5, 0 <x <0.09 is satisfied.

For example, when strontium (Sr) or barium (Ba) is contained as a group 2 element, strontium (Sr), barium (Ba), europium (Eu), silicon (Si), and oxygen (O) have the following composition: A phosphor containing the atomic ratio of formula (2) can be used.
_{[(Ba 1-y Sr y} ) 1-x Eu x] a Si b O c compositional formula (2)
In the composition formula (2), a, b, c, x, and y are 1.8 <a <3.3, 0.9 <b <1.1, 3.6 <c <5.5, 0 < The relations x <0.09 and 0.25 <y <0.75 are satisfied.

Aluminum alkoxide is formed by hydrolysis (sol-gel method) to form an aluminum coat consisting of an aluminum oxide covering the phosphor, that is, aluminum oxide, aluminum oxide hydrate (alumina hydrate), aluminum hydroxide or a mixture thereof. Is to do. Among metal alkoxides, by using aluminum alkoxide, the above-mentioned phosphor that is brittle to moisture is covered with aluminum oxide having good water resistance, so that the water resistance of the phosphor is improved, and the light emission characteristics of the phosphor Can be maintained over a long period of time. Further, since the aluminum alkoxide has a steep reaction rate, it does not require a large excess of H ₂ O, and can prevent the deterioration of the phosphor during the hydrolysis reaction.

  Examples of the aluminum alkoxide include those selected from ethoxide, methoxide, isopropoxide, butoxide, etc., specifically, aluminum isopropoxide, aluminum tert-butoxide, aluminum triethoxide, aluminum tri-n-propoxide. , Aluminum isopropoxide, aluminum tri-n-butoxide, aluminum triisobutoxide, sec-butoxyaluminum diisopropoxide, aluminum tri-sec-butoxide, aluminum-tert-tributoxide and the like. As the aluminum alkoxide, a coupling agent having an alkyl group, an amino group, a mercapto group, or the like that does not contribute to the sol-gel reaction, such as an alkylalkoxyaluminum, may be used. Among these aluminum alkoxides, it is preferable to use aluminum isopropoxide from the viewpoint of improving the water resistance of the phosphor.

  In the mixing step, the atomic weight ratio of aluminum in the aluminum oxide to the group 2 element in the phosphor (atom weight of aluminum / group 2 element), that is, the element abundance ratio of (Al / 2 group element) is 0.10. It is preferable to set it as the above, and it is more preferable to set it as 0.10-0.29. By setting (atomic weight of aluminum / atomic weight of group 2 element) to 0.10 to 0.29, the surface of the phosphor is almost entirely covered with aluminum oxide having good water resistance. The water resistance of the phosphor is further improved, and the light emission characteristics of the phosphor can be maintained for a longer period of time.

  In addition, it is more preferable to set (atomic weight of aluminum / atomic weight of group 2 element) to 0.10 to 0.20. By setting (atomic weight of aluminum / atomic weight of group 2 element) to 0.10 to 0.20, aggregation of the coated phosphor can be reduced. Thereby, for example, when potting a resin composition containing a coated phosphor and a resin component on a resin filling portion of a case (package) provided with LED light emitting elements, handling of a device for potting the resin composition It can prevent that property falls.

  The solvent is not particularly limited as long as it can be uniformly dispersed, and for example, water, an organic solvent, or the like can be used. As the organic solvent, alcohol, ether, ketone, polyhydric alcohol and the like can be used. Examples of the alcohol include methanol, ethanol, propanol, and pentanol. Examples of the polyhydric alcohols include ethylene glycol, propylene glycol, and diethylene glycol. Moreover, you may use the solvent individually or in combination of 2 or more types.

  The above-described aluminum alkoxide generally has a high reaction rate and is easily hydrolyzed with a small amount of water. Therefore, when aluminum alkoxide is used as the metal alkoxide, the reaction of covering the phosphor with the aluminum oxide formed from the above-described aluminum alkoxide can proceed without using a catalyst. In the reaction step, a catalyst may be used. As the catalyst, both a basic catalyst and an acidic catalyst can be used, but it is desirable to use a basic catalyst in consideration of deterioration of the light emitter.

  As a reaction apparatus for mixing the phosphor and the aluminum alkoxide in a solvent, for example, a glass or polyethylene (PE) container, a magnetic stirrer, or a stirring blade can be used. In order to suppress sticking and uneven distribution of particles during processing, it is preferable to use a reactor having a flat bottom and a stirrer (stirring blade) having a size that does not allow a gap on the bottom of the container.

  In the mixing step, the temperature at which the phosphor and the aluminum alkoxide are mixed in the solvent is preferably 30 to 50 ° C, and more preferably 35 to 45 ° C. Thus, by mixing the phosphor and the aluminum alkoxide in a solvent at 30 to 50 ° C., the phosphor is sufficiently covered with the aluminum oxide formed by the hydrolysis of the aluminum alkoxide, and the fluorescence due to moisture. Deterioration of the body can be effectively prevented. Thereby, the light emission characteristics of the phosphor can be maintained over a longer period.

  In the mixing step, the time for mixing the phosphor and the aluminum alkoxide in the solvent is preferably 30 to 90 minutes, and more preferably 45 to 75 minutes. As described above, the phosphor and the aluminum alkoxide are mixed in the solvent for 30 minutes or more to sufficiently cover the phosphor with the aluminum oxide formed by hydrolysis of the aluminum alkoxide, and the phosphor is deteriorated by moisture. Can be effectively prevented. In addition, by setting the time for mixing the phosphor and aluminum alkoxide in the solvent to 90 minutes or less, the aluminum oxide coated on the phosphor is prevented from peeling off, and the phosphor is deteriorated by moisture. It can be effectively prevented. Therefore, by setting the time for mixing the phosphor and the aluminum alkoxide in the solvent to 30 to 90 minutes, the emission characteristics of the phosphor can be maintained for a longer period.

(Separation process)
In the separation step, the coated phosphor, which is a solid phase, is separated from the mixed solution by separating the mixed solution in which the phosphor and the aluminum alkoxide are mixed in a solvent into a solid phase and a liquid phase in the mixing step described above. obtain.

  For example, in the separation step, a mixed solution is separated into a solid phase and a liquid phase using a suction filter, the separated solid phase is dried, a sample obtained by drying is crushed, and subjected to a firing treatment. Do. As a result, a coated phosphor in which the phosphor is coated with aluminum oxide can be obtained.

When the mixed solution is separated into a solid phase and a liquid phase, the aluminum alkoxide is affected by H ₂ O contained in the atmosphere, and therefore, the inside of the test system is preferably replaced with dry N ₂ gas.

  The drying temperature of the separated solid phase can be changed depending on the solvent used, but is preferably 80 to 110 ° C. The time for drying the separated solid phase is preferably 2 hours or longer.

  As a method of crushing the sample obtained by drying, for example, a method of crushing with an agate mortar is preferable in order to reduce particle aggregation.

  The temperature for firing the crushed sample is preferably 150 to 350 ° C, more preferably 150 to 250 ° C. The time for firing the crushed sample is preferably 8 hours or longer.

  The coated phosphor obtained by the above-described method for manufacturing a coated phosphor according to the present embodiment is obtained by coating the phosphor with aluminum oxide, and the phosphor is a group 2 element (M) or europium (Eu). Silicon (Si) and oxygen (O) are contained in the atomic ratio of the composition formula (1). Such a coated phosphor has good fluorescence characteristics, and the phosphor is coated with an aluminum oxide having good water resistance, so that the water resistance of the phosphor is improved, and the phosphor emission characteristics are prolonged. Can be maintained over a period of time.

  In the above description, a method of coating the phosphor only once with the aluminum oxide when manufacturing the coated phosphor, that is, a method of coating the phosphor with only one layer of aluminum oxide has been described. However, it is not limited to this example. For example, the phosphor oxide may be repeatedly coated to coat the phosphor with two or more layers of aluminum oxide. In the method for manufacturing a coated phosphor according to the present embodiment, when the phosphor is coated with a multilayer aluminum oxide, the peak intensity of the phosphor is reduced and the particles are aggregated. The number of times is preferably 2 to 3 times.

<2. Application example of coated phosphor>
The coated phosphor obtained by the above-described coated phosphor manufacturing method can be applied to, for example, a white light source or a lighting device.

<2-1. White light source>
First, the white light source according to the present embodiment will be described using the schematic cross-sectional view shown in FIG. As shown in FIG. 1, the white light source 1 has a blue light emitting diode 13 on a pad portion 12 formed on an element substrate 11. Electrodes 14 and 15 for supplying electric power for driving the blue light-emitting diode 13 are formed on the element substrate 11 while maintaining insulation, and the electrodes 14 and 15 are, for example, blue light-emitting diodes by lead wires 16 and 17 13 is connected.

  Further, for example, a resin layer 18 is provided around the blue light emitting diode 13, and an opening 19 that opens on the blue light emitting diode 13 is formed in the resin layer 18. The opening 19 is formed on an inclined surface whose opening area is widened in the light emitting direction of the blue light emitting diode 13, and a reflective film 20 is formed on the inclined surface. That is, the resin layer 18 having the mortar-shaped opening 19 is covered with the wall reflecting film 20 of the opening 19 and the blue light emitting diode 13 is disposed on the bottom surface of the opening 19. And the kneaded material 21 which mixed the red fluorescent substance and the green fluorescent substance in the transparent resin in the opening part 19 is embedded in the state which covers the blue light emitting diode 13, and the white light source 1 is comprised.

  As the red phosphor, the coated phosphor represented by the above-described composition formulas (1) and (2) is used. This red phosphor has a peak emission wavelength in the red wavelength band, a high emission intensity, and a high luminance. Therefore, it is possible to obtain bright white light having a wide color gamut by three primary colors including blue light of the blue LED, green light by the green phosphor, and red light by the red phosphor.

<2-2. Lighting device>
Next, the lighting device according to the present embodiment will be described with reference to the schematic plan view of FIG. As shown in FIG. 2, in the lighting device 2, a plurality of white light sources 1 described with reference to FIG. The arrangement example may be, for example, a square lattice arrangement as shown in FIG. 2 (A), or an arrangement shifted by ½ pitch every other row as shown in FIG. 2 (B), for example. Good. Further, the shifting pitch is not limited to 1/2, and may be 1/3 pitch or 1/4 pitch. Furthermore, you may shift every 1 line or every several lines (for example, 2 lines).

  Further, although not shown in the figure, the arrangement may be shifted every other column, for example, by 1/2 pitch. The shifting pitch is not limited to 1/2, and may be 1/3 pitch or 1/4 pitch. Further, it may be shifted every line or every plural lines (for example, 2 lines). That is, how to shift the white light source 1 is not limited.

  The white light source 1 has the same configuration as that described with reference to FIG. That is, the white light source 1 has a kneaded material 21 in which a red phosphor and a green phosphor are kneaded with a transparent resin on a blue light emitting diode 13. As the red phosphor, the red phosphor represented by the composition formula (1) described above is used.

  Further, the illumination device 2 is equivalent to surface light emission because a plurality of white light sources 1 substantially equivalent to point light emission are arranged vertically and horizontally on the illumination substrate 22, and thus, for example, used as a backlight of a liquid crystal display device. be able to. Moreover, the illuminating device 2 can be used for various illuminating devices such as a normal illuminating device, a photographing illuminating device, and a construction site illuminating device.

  Since the illuminating device 2 uses the white light source 1, it can obtain bright white light with a wide color gamut. For example, when used for a backlight of a liquid crystal display device, pure white with high luminance can be obtained on the display screen, and the quality of the display screen can be improved.

  The coated phosphor according to the present embodiment can be applied to a phosphor sheet in a lighting device, for example. For example, as shown in FIG. 3, the lighting device 3 includes a light emitting structure 23 in which a blue light emitting element is covered with a convex surface-shaped transparent resin, a substrate 24 on which the light emitting structure 23 is two-dimensionally arranged, A diffuser plate 25 that diffuses blue light of the light emitting element, a phosphor sheet 26 that is disposed apart from the substrate 24 and contains powdered phosphor that obtains white light from the blue light of the blue light emitting element, and an optical film 27 With.

  The board | substrate 24 and the fluorescent substance sheet 26 are arrange | positioned at about 10-50 mm apart, and the illuminating device 3 comprises what is called a remote fluorescent substance structure. The gap between the substrate 24 and the phosphor sheet 26 is held by a plurality of support columns and reflectors, and is provided so that the support columns and reflectors surround the space formed by the substrate 24 and the phosphor sheet 26 in all directions. .

  The light emitting structure 23 constitutes a so-called LED package having, for example, an InGaN-based blue LED (Light Emitting Diode) chip as a blue light emitting element.

  The board | substrate 24 which comprises an illuminating device is comprised from the glass cloth base material using resin, such as a phenol, an epoxy, a polyimide, polyester, a bismaleimide triazine, an allylated polyphenylene oxide. On the substrate 24, the light emitting structures 23 are two-dimensionally arranged corresponding to the entire surface of the phosphor sheet 26 at equal intervals with a predetermined pitch. Moreover, you may perform a reflection process to the mounting surface of the light emission structure 23 on the board | substrate 24 as needed.

  The diffusion plate 25 diffuses the radiated light from the light emitting structure 23 over a wide range to such an extent that the shape of the light source becomes invisible. As the diffusing plate 25, one having a total light transmittance of 20% or more and 80% or less is used.

  The phosphor sheet 26 contains a powdery phosphor that obtains white light from the blue light of the blue light emitting element. As the phosphor, for example, a sulfide phosphor, an oxide phosphor or a mixed phosphor thereof is used. As the oxide phosphor, the above-described coated phosphor is used. The phosphor powder having an average particle size of several μm to several tens of μm is used. Thereby, the light scattering effect of the phosphor sheet 26 can be improved.

  The optical film 27 is composed of, for example, a reflective polarizing film, a lens film, a diffusion film, etc. for improving the visibility of the liquid crystal display device. Here, the lens film is an optical film in which minute lenses are arrayed on one surface, and is for increasing the directivity of diffused light in the front direction and increasing the luminance.

  Examples of the present invention will be described below. In this example, coated phosphors were produced in Examples 1 to 6 and Comparative Examples 1 to 4, and the produced phosphors were evaluated for light emission characteristics, particle diameter / specific surface area measurement, high temperature and high humidity environment test. And element elution test was conducted. The present invention is not limited to these examples.

Example 1
Phosphor [(Ba, Sr) _0.97 Eu _0.03 ] ₃ SiO _{5 5} g, ethanol 40 g, and pure water (H ₂ O) 0.375 g were weighed in predetermined amounts to prepare a first solution. . Next, a second solution was prepared by dissolving 0.75 g of aluminum isopropoxide and toluene in an arbitrary ratio. The first solution dispersed and mixed by ultrasonic stirring was adjusted to 40 ° C. in a thermostatic bath, and then the reaction was started by adding the second solution. After adding the second solution, the reaction vessel was taken out of the thermostat 60 minutes later, and after the particles settled, the supernatant was removed from the reaction vessel, followed by vacuum filtration. Thereafter, the sample was dried in an oven at 85 ° C. for 2 hours, and the sample was crushed in an agate mortar, followed by baking at 200 ° C. for 8 hours to obtain an evaluation sample (sample). In Example 1, the atomic weight ratio of aluminum in the aluminum alkoxide to the total of group 2 elements in the phosphor (Sr + Ba) (atom weight of aluminum / (atomic weight of strontium + atomic weight of barium)), that is, Al / (Sr + Ba) element The abundance ratio was set to 0.1161.

(Example 2)
In Example 2, an evaluation sample was obtained in the same manner as in Example 1 except that the Al / (Sr + Ba) element abundance ratio was 0.1603.

(Example 3)
In Example 3, an evaluation sample was obtained in the same manner as in Example 1 except that the Al / (Sr + Ba) element abundance ratio was 0.2279.

Example 4
In Example 4, an evaluation sample was obtained in the same manner as in Example 1 except that the Al / (Sr + Ba) element abundance ratio was 0.2834.

(Example 5)
In Example 5, an evaluation sample was obtained in the same manner as in Example 1 except that the Al / (Sr + Ba) element abundance ratio was 0.3081.

(Example 6)
In Example 6, [(Ba, Sr) _0.94 Eu _0.06 ] ₂ SiO ₄ was used instead of the phosphor [(Ba, Sr) _0.97 Eu _0.03 ] ₃ SiO ₅ . An evaluation sample was obtained in the same manner as in Example 1 except that the Al / (Sr + Ba) element abundance ratio was 0.1901.

(Comparative Example 1)
In Comparative Example 1, an evaluation sample was obtained in the same manner as in Example 1 except that aluminum isopropoxide was not used.

(Comparative Example 2)
In Comparative Example 2, a second solution was prepared using 5 g of TEOS, which is a metal alkoxide of silicon dioxide (SiO ₂ ), instead of aluminum isopropoxide, except that 7 g of aqueous ammonia was used as a catalyst. An evaluation sample was obtained in the same manner as in Example 1.

(Comparative Example 3)
In Comparative Example 3, an evaluation sample was obtained in the same manner as in Example 1 except that aluminum isopropoxide was not used.

(Comparative Example 4)
In Comparative Example 4, an evaluation sample was obtained in the same manner as in Example 1 except that the Al / (Sr + Ba) element abundance ratio was 0.0479.

  Table 1 summarizes the results regarding the evaluation samples obtained in Examples 1 to 5 and Comparative Examples 1 to 4.

<Emission characteristic evaluation>
The light emission characteristics of the evaluation samples obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were measured using FP6500 (manufactured by JASCO Corporation). “Sample absorptance” in Table 1 is the ratio of incident light that is reduced by the sample of excitation light. The “internal quantum efficiency” in Table 1 is a value obtained by dividing the number of photons of excitation light absorbed by the sample from the number of photons of fluorescence emitted from the sample. The “external quantum efficiency” in Table 1 is (sample absorption rate) × (internal quantum efficiency). Table 1 shows the results of the evaluation of the light emission characteristics.

  In FIG. 4, the light emission characteristic before and behind the coating process of the evaluation sample obtained in Example 1 is shown. As shown in FIG. 4, although the sample absorption rate slightly decreased before and after the coating treatment, it was confirmed that the internal quantum efficiency was improved and as a result, the external quantum efficiency was improved. This is considered to be because light is easily incident from the outside to the inside of the coated phosphor due to the lens effect of the aluminum oxide, and light is easily emitted from the inside to the outside of the coated phosphor.

<Particle diameter / specific surface area measurement>
The particle diameters (D ₁₀ , D ₅₀ , D ₉₀ ) of the evaluation samples obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were measured using Multisizer 4 (manufactured by Beckman Coulter, Inc.). did. The specific surface area was determined by performing particle size distribution measurement using LA-500 (manufactured by Horiba, Ltd.). Table 1 shows the results of the particle diameter / specific surface area measurement.

  FIG. 5 shows specific surface areas of the evaluation samples obtained in Examples 1 to 3, Example 5, Comparative Example 3, and Comparative Example 4 with respect to the Al / (Sr + Ba) element abundance ratio. The Al / (Sr + Ba) element abundance ratio was calculated by performing an ICP emission spectroscopic analyzer (ICP-AES) or fluorescent X-ray analysis (XRF) on each of the obtained evaluation samples. It can be seen that the specific surface area of the evaluation sample decreases as the abundance of the aluminum element increases. This is considered to suggest that the aggregation of the evaluation sample occurs as the abundance of the aluminum element increases. It was confirmed that when the Al / (Sr + Ba) element abundance ratio was 0.20 or more, the specific surface area of the evaluation sample was reduced to about 60% compared to the case where the Al / (Sr + Ba) element abundance ratio was 0. .

  FIG. 6 shows electron micrographs of the evaluation samples obtained in Comparative Example 3, Comparative Example 4, and Examples 1 to 5. 6A is Comparative Example 3, B of FIG. 6 is Comparative Example 4, C of FIG. 6 is Example 1, D of FIG. 6 is Example 2, E of FIG. 6 is Example 3, and F of FIG. Example 4 and G in FIG. 6 show electron micrographs of the respective evaluation samples obtained in Example 5. From these results, as described above, it was confirmed that aggregation of the evaluation sample occurred as the abundance of the aluminum element increased.

<High temperature and high humidity change test>
In the high-temperature and high-humidity environment change test, the evaluation samples obtained in Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to a high-temperature and high-humidity test at 60 ° C. and 90% RH or 85 ° C. and 85% RH. Changes from the initial light emission intensity and the like until 500 hours after the end of the test were confirmed. A spectrophotometer FP-6500 (manufactured by JASCO Corporation) was used for measuring the emission intensity. The result of the high temperature and high humidity environment change test is shown in FIG. In FIG. 7, the symbol (Δ) indicates the result of the evaluation sample obtained in Example 1. The symbol (■) shows the result of the evaluation sample obtained in Comparative Example 2. The symbol (♦) indicates the result of the evaluation sample obtained in Comparative Example 3.

  The evaluation sample without the coating treatment (Comparative Example 3) rapidly deteriorated in 3 hours in the test environment. Further, in the evaluation sample (Comparative Example 2) in which the phosphor was coated with TEOS, a significant reduction in luminance was observed after 24 hours. On the other hand, it was found that the evaluation sample produced in Example 1 maintained about 90% of the initial light emission even after nearly 100 hours after the test. As a result, the evaluation sample (Comparative Example 2) in which the phosphor is coated with TEOS rapidly whitens in 20 hours, whereas the evaluation sample (Example 1) in which the phosphor is coated with aluminum oxide is moisture resistant. It was confirmed that there was a significant improvement. This is presumably because the water resistance of the phosphor was improved by coating the phosphor with aluminum oxide, and the light emission characteristics of the phosphor could be maintained for a long time.

  8 and 9 show changes in reliability in the surface treatment reaction time and reaction temperature environment. From the results shown in FIG. 8 and FIG. 9, when phosphor and aluminum alkoxide are reacted in a solvent for 60 minutes, when phosphor and aluminum alkoxide are mixed in a solvent at 40 ° C., high reliability is obtained. It was confirmed that

  FIG. 10 shows the peak intensity (symbol (♦)) and the high temperature and high humidity test at 85 ° C. and 85% RH for the evaluation samples obtained in Examples 1 to 5, Comparative Example 3, and Comparative Example 4. The result (symbol (■)) of confirming the change from the initial emission intensity to 96 hours after the end of the test is shown. As shown in FIG. 9, the evaluation samples obtained in Examples 1 to 4, that is, the Al / (Sr + Ba) element abundance ratio (aluminum atomic weight / (strontium atomic weight + barium atomic weight)) is 0.10. It was confirmed that the evaluation sample of ˜0.29 has good fluorescence characteristics and can maintain the light emission characteristics over a long period of time.

  In addition, from the results of the specific surface area shown in FIG. 5 described above, it was confirmed that the evaluation samples (Example 1 and Example 2) having an Al / (Sr + Ba) element abundance ratio of 0.10 to 0.20 had little aggregation. did it. Therefore, in the range where the Al / (Sr + Ba) element abundance ratio is in the range of 0.10 to 0.20, it is possible to obtain a coated phosphor that has good fluorescence characteristics, little aggregation, and can maintain the light emission characteristics over a long period of time. I found out that

<Element dissolution test>
In order to confirm the reliability of the evaluation sample obtained in Example 6, an element elution test was performed. In the element elution test, 1 g of the evaluation sample obtained in Example 6 or the evaluation sample without coating treatment was added to 100 ml of ion-exchanged water heated to 55 ° C., and the change in conductivity at that time was 0, 1, 5, Recording was performed at times of 10, 30, and 60 min, respectively.

In FIG. 11, (a) shows the result of the change in conductivity of the phosphor not coated with aluminum oxide, and (b) shows the result of the change in conductivity of the phosphor coated with aluminum oxide. From the results shown in FIG. 11, it was found that the phosphor coated with aluminum oxide can suppress the increase in conductivity smaller than the phosphor not coated with aluminum oxide. This is because when a silicate phosphor is added to water, the group 2 element is eluted and the conductivity changes, but by covering the phosphor with aluminum oxide, the element elution on the phosphor surface is suppressed. Suggests that Therefore, phosphors other than the phosphors used in Examples 1 to 5 ([(Ba, Sr) _0.97 Eu _0.03 ] ₃ SiO ₅ ) are coated with aluminum oxide. It is considered that the light emission characteristics can be maintained for a long time.

  DESCRIPTION OF SYMBOLS 1 White light source, 2, 3 Illumination device, 11 Element board | substrate, 12 Pad part, 13 Blue light emitting diode, 14, 15 Electrode, 16, 17 Lead wire, 18 Resin layer, 19 Opening part, 20 Wall reflecting film, 21 Kneaded material , 22 Illumination substrate, 23 Light emitting structure, 24 substrate, 25 Diffuser plate, 26 Phosphor sheet, 27 Optical film

Table 1 summarizes the results regarding the evaluation samples obtained in Examples 1 to 5 and Comparative Examples 1 to 4. Examples 3 to 5 are reference examples.

Claims (8)

Mixing a phosphor and an aluminum alkoxide in a solvent, and coating the phosphor with an aluminum oxide formed from the aluminum alkoxide;
The phosphor is a method for producing a coated phosphor containing a group 2 element (M), europium (Eu), silicon (Si), and oxygen (O) in an atomic ratio of the following composition formula (1).
[(M) _1-x Eu _x ] _a Si _b O _c composition formula (1)
However, in the composition formula (1), a, b, c, and x are 1.8 <a <3.3, 0.9 <b <1.1, 3.6 <c <5.5, 0 < The relationship x <0.09 is satisfied.   The phosphor and the aluminum so that the atomic weight ratio of aluminum in the aluminum oxide to the group 2 element in the phosphor (atomic weight of aluminum / atomic weight of group 2 element) is 0.10 to 0.29. The method for producing a coated phosphor according to claim 1, wherein the alkoxide is mixed in a solvent.   The method for producing a coated phosphor according to claim 2, wherein in the mixing step, the phosphor and the aluminum alkoxide are mixed in the solvent at 30 to 50 ° C.   The method for producing a coated phosphor according to claim 2, wherein in the mixing step, the phosphor and the aluminum alkoxide are reacted in the solvent for 30 to 90 minutes. When the phosphor contains strontium (Sr) and barium (Ba) as the group 2 element (M), strontium (Sr), barium (Ba), europium (Eu), silicon (Si) and The method for producing a coated phosphor according to any one of claims 2 to 4, comprising oxygen (O) in an atomic ratio of the following composition formula (2).
_{[(Ba 1-y Sr y} ) 1-x Eu x] a Si b O c compositional formula (2)
However, in the composition formula (2), a, b, c, x, and y are 1.8 <a <3.3, 0.9 <b <1.1, 3.6 <c <5.5, The relations 0 <x <0.09 and 0.25 <y <0.75 are satisfied. The phosphor is coated with aluminum oxide,
The phosphor is a coated phosphor containing a group 2 element (M), europium (Eu), silicon (Si) and oxygen (O) in an atomic ratio of the following composition formula (1).
[(M) _1-x Eu _x ] _a Si _b O _c composition formula (1)
However, in the composition formula (1), a, b, c, and x are 1.8 <a <3.3, 0.9 <b <1.1, 3.6 <c <5.5, 0 < The relationship x <0.09 is satisfied.   The coated phosphor according to claim 6, wherein the atomic weight ratio of aluminum in the aluminum oxide to the group 2 element in the phosphor (atom weight of aluminum / atom weight of group 2 element) is 0.10 to 0.29. A blue light emitting diode formed on the element substrate;
It is disposed on the blue light emitting diode, and has a kneaded product obtained by kneading a red phosphor and a green phosphor or a yellow phosphor in a transparent resin,
The red phosphor is coated with an aluminum oxide phosphor,
The phosphor is a white light source containing a group 2 element (M), europium (Eu), silicon (Si) and oxygen (O) in an atomic ratio of the following composition formula (1).
[(M) _1-x Eu _x ] _a Si _b O _c composition formula (1)
However, in the composition formula (1), a, b, c, and x are 1.8 <a <3.3, 0.9 <b <1.1, 3.6 <c <5.5, 0 < The relationship x <0.09 is satisfied.