Method of producing phosphor powder

Abstract

To provide a method of producing phosphor powder excellent in light-emitting characteristics.SOLUTION: The method of producing phosphor powder of the present invention is a method of producing phosphor powder including a phosphor whose main crystal phase has the same crystal structure as CaAlSiN3 expressed by a general formula (Ca1-x-ySrxEuy)AlSiN3 provided that 0≤x<1, 0<y<1, and 1-x-y>0 including: a mixing process of mixing raw material powder to obtain raw material mixed powder; and a calcination process of calcining the obtained raw material mixed powder in a calcination space, where the calcination process includes temperature raising treatment of introducing inert gas in a temperature range of 300°C or higher and 700°C or lower into the calcination space in a temperature raising process under a vacuum environment.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a phosphor powder. [Background technology]

[0002] In order to manufacture white LEDs, research has been conducted into red phosphors that convert blue light from a blue LED chip into red light. Known red phosphors include CASN phosphors such as CASN phosphor and SCASN phosphor (for example, Patent Document 1, etc.). These CASN phosphors are generally synthesized by heating raw material powders that include europium oxide or europium nitride, calcium nitride, silicon nitride, and aluminum nitride. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2005 / 052087 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it was found that the method for producing the SCASN phosphor described in Patent Document 1 above leaves room for improvement in terms of the light emitting properties of the phosphor powder. [Means for solving the problem]

[0005] After further investigation, the inventors discovered that a method for producing phosphor powder in which an inert gas is introduced at a predetermined gas introduction temperature during the temperature rise process in a vacuum environment can improve the total luminous flux when the resulting phosphor powder is molded into a sheet, thereby completing the present invention.

[0006] According to one aspect of the present invention, there is provided the following method for producing a phosphor powder.

[0007] 1. The main crystal phase has the same crystal structure as CaAlSiN3 and has the general formula (Ca 1-x-y Sr x EU y )AlSiN3(where 0≦x<1, 0 <y<1、1-x-y> 0), a method for producing a phosphor powder comprising the phosphor represented by the formula: a mixing step of mixing the raw material powders to obtain a raw material mixed powder; A firing step of firing the obtained raw material mixed powder in a firing space, The firing step is a method for producing a phosphor powder, the method comprising a temperature rise treatment in which an inert gas is introduced into the firing space, which is in a vacuum environment and is in a temperature range of 300°C or more and 700°C or less, during the temperature rise process. 2. A method for producing the phosphor powder according to 1., comprising the steps of: The method for producing a phosphor powder, wherein the inert gas includes nitrogen gas and / or a rare gas. 3. A method for producing a phosphor powder according to 1. or 2., The method for producing a phosphor powder, wherein the temperature increasing process in the firing step is performed by increasing the temperature of the firing space from room temperature in a vacuum environment until the temperature reaches a temperature at which the inert gas is introduced. 4. A method for producing a phosphor powder according to any one of 1. to 3., The firing step includes a heat treatment at 1500° C. or more and 2100° C. or less after the temperature increase treatment. 5. A method for producing a phosphor powder according to any one of 1. to 4., The method for producing a phosphor powder, wherein the firing step includes a heat treatment for 0.5 hours to 30 hours after the temperature increase treatment. 6. A method for producing a phosphor powder according to any one of 1. to 5., The firing step includes a heat treatment in an inert gas atmosphere of 10 MPa or less after the temperature increase treatment. 7. A method for producing a phosphor powder according to any one of 1. to 6., A method for producing a phosphor powder, wherein the median diameter of the resulting phosphor powder is 5 μm or less. Effect of the Invention

[0008] According to the present invention, there is provided a method for producing phosphor powder having excellent luminescence characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The method for producing the phosphor powder of this embodiment will be outlined below.

[0010] The manufacturing method of phosphor powder containing the phosphor of this embodiment includes a mixing step of mixing raw material powders to obtain a raw material mixed powder, and a firing step of firing the obtained raw material mixed powder in a firing space. The firing step includes a temperature rise treatment in which an inert gas is introduced into the firing space, which is in a vacuum environment and is in the process of heating, within a temperature range of 300°C or more and 700°C or less. The phosphor powder obtained by this method has a main crystal phase having the same crystal structure as CaAlSiN3 and has the general formula (Ca 1-x-y Sr x EU y )AlSiN3(where 0≦x<1, 0 <y<1、1-x-y> 0) is included.

[0011] According to the inventor's findings, it has been found that by producing phosphor powder by introducing an inert gas at a predetermined gas introduction temperature during the heating process in a vacuum environment, the total luminous flux can be improved when the obtained phosphor powder is mixed with resin and molded into a sheet. Although the detailed mechanism is unclear, it is speculated that during vacuum heating, moisture within the system (from adhering to the raw materials, etc.) evaporates, and some of this water reacts with raw materials (strontium nitride, calcium nitride) that react easily with water, causing the raw materials to decompose. However, the higher the temperature of the vacuum atmosphere, the more the raw materials decompose, and the worse the phosphor properties after firing. Therefore, it is believed that by lowering the gas introduction temperature below the heating temperature, the decomposition of the raw materials can be reduced, improving the luminescence properties of the phosphor powder. On the other hand, if the inert gas is introduced under conditions where the gas introduction temperature is too low, it becomes difficult for the moisture adhering to the raw materials to be discharged outside the system. In such an environment, a reaction occurs in which the raw materials produce a phosphor in the presence of water, and it is presumed that this leads to a deterioration in the crystallinity of the phosphor, i.e., its optical properties. In other words, by making the gas introduction temperature relatively high, the water in the firing space can be volatilized and discharged outside the system, which is thought to suppress the deterioration of the luminescence properties of the phosphor powder.

[0012] The phosphor powder obtained by the manufacturing method of this embodiment has good luminescence characteristics both when in powder form and when mixed with a resin to form a sheet, and is therefore suitable for a variety of uses. One example of the application is an LED package, in which the phosphor powder of the present invention is used as a wavelength conversion material for converting blue light emitted from a blue LED into white light. Another example application could be in self-emissive displays such as mini-LEDs and micro-LEDs.

[0013] Each step of the method for producing the phosphor powder of this embodiment will be described in detail below.

[0014] The method for producing the phosphor powder of this embodiment preferably includes the following steps. A mixing process in which the starting materials are mixed to obtain a raw material powder mixture. A firing process in which the raw material powder obtained in the mixing process is fired to obtain a fired product.

[0015] Incidentally, in this embodiment, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes as long as the purpose of the process is achieved.

[0016] ·Mixing process In the mixing step, the starting materials (raw material powders) are mixed to obtain a raw material mixed powder. Examples of the starting material include raw material powder containing Al, raw material powder containing Si, raw material powder containing Sr (when x≠0), raw material powder containing Ca, and raw material powder containing Eu. The above starting materials are preferably in the form of powder.

[0017] As the raw material powder containing Al, an aluminum compound such as aluminum nitride can be used. As the raw material powder containing Si, silicon nitride such as α-type silicon nitride can be used. As the raw material powder containing Sr, a strontium compound such as strontium nitride can be used. As the Ca-containing raw material powder, a calcium compound such as calcium nitride can be used. As the raw material powder containing Eu, a europium compound can be used. The starting material is not limited to these, and nitrides or oxides containing the elements that constitute the phosphor can be used.

[0018] Examples of europium compounds include oxides containing europium, hydroxides containing europium, nitrides containing europium, oxynitrides containing europium, and halides containing europium. These can be used alone or in combination of two or more. Among these, it is preferable to use europium oxide, europium nitride, and europium fluoride alone, and it is more preferable to use europium oxide alone.

[0019] In the mixing step, the raw material mixed powder can be obtained, for example, by a method of dry mixing the starting materials, or a method of wet mixing in an inert solvent that does not substantially react with each starting material, followed by removing the solvent. As a mixing device, for example, a small mill mixer, a V-type mixer, a rocking mixer, a ball mill, a vibration mill, etc. can be used. After mixing using the device, the raw material mixed powder can be obtained by removing aggregates using a sieve as necessary. In order to prevent deterioration of the starting materials and unintended inclusion of oxygen, the mixing step is preferably carried out in a nitrogen atmosphere and in an environment with as little moisture (humidity) as possible.

[0020] · Firing process In the firing step, the raw material powder mixture obtained in the mixing step is fired in a firing space to obtain a fired product.

[0021] As a firing method, for example, a method can be adopted in which the mixture is filled in a container made of a material (such as tungsten) that does not react with the raw material mixed powder during firing, and heated in a nitrogen atmosphere. The firing space means a space in which the temperature and pressure can be controlled during firing, and is, for example, the internal space of a furnace that houses a container filled with a raw material powder mixture.

[0022] The firing step may include a temperature-raising process in which the temperature in the firing space is raised from room temperature to a predetermined heating temperature, and a heat treatment in which the firing space is heated to the predetermined heating temperature after the temperature-raising process. However, the temperature rise time, temperature rise rate, heating retention time and pressure in the firing step are not particularly limited and may be appropriately adjusted depending on the raw materials used.

[0023] The temperature increase process is carried out by increasing the temperature of the firing space in a vacuum environment from room temperature, for example, 23° C. to 30° C., until it reaches a temperature at which an inert gas is introduced. The vacuum environment can be achieved by adjusting the degree of vacuum and pressure based on known means. The pressure in the vacuum environment may be, for example, 0.001 Pa to 100 Pa.

[0024] Next, in the temperature rise process, an inert gas is introduced into the firing space in a vacuum environment in the temperature range of 300° C. to 700° C. This produces phosphor powder with excellent luminescence properties.

[0025] In this embodiment, the gas introduction temperature at the start of the inert gas introduction may be within the temperature range of 300°C or higher and 700°C or lower, and the temperature at the end of the inert gas introduction may exceed 700°C, but is preferably 700°C or lower. Furthermore, the temperature within the firing space during the introduction of the inert gas need only be kept within the range of 300°C or higher and 700°C or lower, and may be kept constant during the introduction process or may be raised during at least part of the introduction process.

[0026] Examples of inert gases include nitrogen gas and rare gases, and nitrogen gas is preferred. These gases may be used alone or in combination of two or more kinds as inert gases. However, unavoidable gas components (e.g., water vapor, etc.) contained in the inert gas are permitted. The concentration of nitrogen gas in the inert gas is, for example, 80 vol % or more, preferably 90 vol % or more, and more preferably 99 vol % or more.

[0027] Subsequently, the temperature is increased by increasing the temperature of the firing space into which the inert gas has been introduced until the temperature reaches a predetermined heating temperature. The predetermined heating temperature is not particularly limited, but is preferably 1500°C or higher and 2100°C or lower, and more preferably 1550°C or higher and 2000°C or lower.

[0028] After the temperature increase process, the heating process heats the firing space within a predetermined heating temperature range. By setting the heating temperature to the above lower limit, the grain growth of the phosphor particles proceeds more effectively, and therefore the light absorptance, internal quantum efficiency, and external quantum efficiency can be further improved. By setting the heating temperature to the above upper limit or less, decomposition of the phosphor particles can be further suppressed, and therefore the light absorptance, internal quantum efficiency, and external quantum efficiency can be further improved.

[0029] The heating and holding time in the heat treatment is typically preferably 0.5 hours or more and 30 hours or less. The pressure in the heat treatment is typically preferably 0.1 MPa or more and 10 MPa or less. Moreover, the heat treatment is preferably performed in an inert gas atmosphere such as a nitrogen gas atmosphere from the viewpoint of controlling the oxygen concentration, etc. As a specific example, the heat treatment is preferably performed in a nitrogen gas atmosphere with a pressure of 0.1 MPa or more and 10 MPa or less.

[0030] The fired product obtained through the firing step is usually a granular or lumpy sintered body. The fired product can be powdered once by using a process such as crushing, grinding, or classification, either alone or in combination. A specific processing method includes, for example, pulverizing the sintered body to a predetermined particle size using a general pulverizer such as a ball mill, a vibration mill, a jet mill, etc. However, it should be noted that excessive pulverization may generate fine particles that easily scatter light or may cause crystal defects on the particle surface, resulting in a decrease in luminous efficiency.

[0031] In addition to the above-mentioned mixing and firing steps, the method for producing the phosphor powder of this embodiment may, if necessary, include one or more steps selected from the group consisting of a low-temperature firing step, a grinding step, a decantation step, a filtration / drying step, and an acid treatment step.

[0032] Low-temperature firing process (annealing process) The method for producing the phosphor powder of this embodiment may include a low-temperature firing step (annealing step) after the firing step, if necessary. In the low-temperature firing step, the fired product is heated at a temperature lower than the firing temperature in the firing step. The fired product used in the low-temperature firing step may be from any step, for example, immediately after the firing step or immediately after the crushing step.

[0033] The low-temperature firing step (annealing step) is preferably carried out in a non-oxidizing atmosphere other than pure nitrogen, such as an inert gas such as a rare gas or nitrogen gas, a reducing gas such as hydrogen gas, carbon monoxide gas, hydrocarbon gas, or ammonia gas, or a mixture of these gases, or in a vacuum, etc. It is particularly preferably carried out in a hydrogen gas atmosphere or an argon atmosphere.

[0034] The low-temperature firing step (annealing step) may be performed under atmospheric pressure or under pressure. The heat treatment temperature in the low-temperature firing step (annealing step) is not particularly limited, but is preferably 1200° C. to 1700° C., more preferably 1300° C. to 1600° C. The time for the low-temperature firing step (annealing step) is not particularly limited, but is preferably 3 hours to 12 hours, more preferably 5 hours to 10 hours. By performing a low-temperature firing process (annealing process), the luminous efficiency of the phosphor particles can be sufficiently improved. In addition, the rearrangement of elements removes distortions and defects, which improves transparency.

[0035] Crushing process The method for producing the phosphor powder of this embodiment may include a pulverization step after the firing step, if necessary. In the pulverization step, the fired product is pulverized to obtain fine powder. The fired product used in the pulverization step may be from any step, for example, immediately after the firing step or immediately after the low-temperature firing step.

[0036] The pulverization step is preferably carried out using a ball mill. It is preferable to carry out the treatment using the method shown below. If the treatment is carried out outside the range of conditions, the performance of the phosphor particles cannot be maintained. If the pulverization force is too strong, defects will be generated in the phosphor particles, degrading the optical properties. If the pulverization force is too weak, the desired fineness cannot be achieved.

[0037] In the pulverization step, a ball mill is preferably used as a pulverizer, and the pulverization step is desirably performed by ball mill pulverization in a wet manner in the presence of an aqueous solution such as ion-exchanged water.

[0038] The aqueous solution may contain components other than ion-exchanged water, such as organic solvents, such as lower alcohols and acetone, and dispersants, such as sodium hexametaphosphate, sodium pyrophosphate (Napp), trisodium phosphate (TSP), and surfactants.

[0039] The lower limit of the amount of the aqueous solution may be, for example, 0.1% by volume or more, 0.3% by volume or more, 0.5% by volume or more, or 1.0% by volume or more based on the total volume of the annealed product. By setting the lower limit of the amount of the aqueous solution within the above range, the annealed product can be pulverized under milder conditions, and the deterioration of the optical properties as a phosphor can be further suppressed. The upper limit of the amount of the aqueous solution may be, for example, 60% by volume or less, 50% by volume or less, 45% by volume or less, or 40% by volume or less based on the total volume of the annealed product. By setting the upper limit of the amount of the aqueous solution within the above range, the force applied to the pulverization of the annealed product by the ball can be improved. The amount of the aqueous solution may be adjusted within the above range, and may be, for example, 1.0 to 45% by volume based on the total volume of the annealed product.

[0040] Zirconia balls can be used as balls for use in the ball mill. The diameter of the balls may be, for example, 0.2 to 20.0 mm, or 0.5 to 10.0 mm. Outside these conditions, it is difficult to keep the average circularity and the standard deviation of the circularity within the specified range, and it is difficult for the resulting phosphor powder to exhibit the desired color reproducibility.

[0041] The lower limit of the time of the pulverization treatment (pulverization time) in the pulverization step may be, for example, 1 hour or more, 2 hours or more, 3 hours or more, 4 hours or more, 5 hours or more, 6 hours or more, 7 hours or more, 8 hours or more, 9 hours or more, 10 hours or more, or 12 hours or more. By setting the lower limit of the pulverization time within the above range, a sufficiently fine pulverized product can be obtained, and the efficiency of the acid treatment in the subsequent acid treatment step can be further improved. The upper limit of the time of the pulverization treatment may be, for example, 80 hours or less, 70 hours or less, 60 hours or less, or 40 hours or less. By setting the upper limit of the pulverization time within the above range, it is possible to more sufficiently suppress the occurrence of scratches and cracks on the surface of the phosphor particles, and the occurrence of defects inside the phosphor particles, caused by excessive pulverization of the annealed product. The pulverization time may be adjusted within the above range, and may be, for example, 1 to 60 hours, or 4 to 40 hours.

[0042] Decantation process The method for producing the phosphor powder of this embodiment may include a decantation step, if necessary. In the decantation step, ultrafine powder contained in the fired product is removed. The fired product used in the pulverization step may be from any step, for example, immediately after the firing step, immediately after the low-temperature firing step, or immediately after the pulverization step.

[0043] In the decantation step, the powdered fired product (phosphor particles) is put into an appropriate dispersion medium and dispersed. The dispersion medium may be, for example, an aqueous solution containing sodium hexametaphosphate, sodium pyrophosphate (Napp), trisodium phosphate (TSP), lower alcohol, acetone, a surfactant, etc. In this case, the weight ratio of the phosphor particles to the dispersion medium is preferably 2% or more and 40% or less, more preferably 3% or more and 20% or less, and even more preferably 4% or more and 10% or less. Next, after the dispersion treatment, the dispersion medium containing the phosphor particles is left to stand or centrifuged to allow the particles to settle. Subsequently, the particles are allowed to settle, and the supernatant is removed. This makes it possible to remove fine particles (ultrafine powder) contained in the supernatant that may adversely affect optical properties. In addition, aggregation due to ultrafine powder is reduced. The particle diameter of the fine particles (ultrafine powder) is, for example, less than 0.4 μm.

[0044] · Filtration and drying process The method for producing the phosphor powder of this embodiment may include a filtering and drying step after the firing step, if necessary. The calcined product used in the filtration and drying step may be, for example, the product immediately after the calcination step, or the product immediately after any step carried out after the calcination step. Specifically, the precipitate obtained in the decantation step may be filtered and dried. After the filtering and drying process, coarse particles may be removed using a sieve if necessary. This reduces fine particles (ultrafine powder) and allows the desired phosphor particles to be obtained. For drying, a tray dryer, freeze drying, supercritical drying, vacuum drying, fluidized bed dryer, far-infrared dryer, microwave dryer, spray dryer, etc. may be used. In addition, a dispersant or the like may be added to suppress aggregation before drying.

[0045] Acid treatment process The method for producing the phosphor powder of this embodiment may include an acid treatment step after the firing step, if necessary. In the acid treatment step, the calcined product is treated with acid. The calcined product used in the acid treatment step may be, for example, a product immediately after the calcination step, or a product immediately after any step carried out after the calcination step. By treating the fired product with an acid, it is possible to remove at least a portion of the impurities that do not contribute to light emission. Incidentally, it is presumed that the impurities that do not contribute to light emission are generated during the firing process or the low-temperature firing process (annealing process).

[0046] The acid may be an aqueous solution containing one or more acids selected from hydrofluoric acid, sulfuric acid, phosphoric acid, hydrochloric acid, and nitric acid. In particular, hydrofluoric acid, nitric acid, and a mixed acid of hydrofluoric acid and nitric acid are preferred. The acid treatment can be carried out by dispersing the low-temperature calcined powder in an aqueous solution containing the above-mentioned acid. The stirring time is, for example, from 10 minutes to 6 hours, preferably from 30 minutes to 3 hours. The stirring temperature can be, for example, from 40°C to 90°C, preferably from 50°C to 70°C. After the acid treatment step, it is preferable to separate substances other than the phosphor particles by filtration and to wash the substances adhering to the phosphor particles with water.

[0047] (About phosphors) The phosphor contained in the phosphor powder obtained by the method for producing phosphor powder of this embodiment may include a CASN phosphor and / or a SCASN phosphor. Each of the CASN phosphor and the SCASN phosphor has a crystal structure in which the main crystal phase is CaAlSiN3, and has the general formula (Ca 1-x-y Sr x EU y )AlSiN3(where 0≦x<1, 0 <y<1、1-x-y> It has the composition: A representative phosphor that approximates the above general formula is CaAlSiN3, where the Ca site occupancy is 100% and Si / Al=1. 2+ A part of Eu acts as a luminescence center. 2+ When substituted with , it becomes a red-emitting phosphor. Such phosphors are often called "CASN", an acronym for the elements. Another phosphor is (Sr,Ca)AlSiN3, in which Sr is substituted for Ca and dissolved in solid solution. 2+ A part of Eu acts as a luminescence center. 2+ When substituted with , it becomes a red-emitting phosphor. Such phosphors are often referred to as "SCASN", an acronym for the elements.

[0048] The median diameter (cumulative 50% value in the volume-based particle size distribution curve: D 50 ) is preferably 5 μm or less, more preferably 4.8 μm or less, and further preferably 4.5 μm or less.50 is preferably 0.1 μm or more, more preferably 0.3 μm or more. D 50 Since the diameter is not too large or too small, for example, the phosphor powder can be favorably applied to mini LEDs or micro LEDs.

[0049] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of the present invention are included in the present invention. EXAMPLES

[0050] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0051] <Method of manufacturing phosphor powder> Example 1 In a glove box maintained under a nitrogen atmosphere, 25.5 parts by mass of α-type silicon nitride (Si3N4, manufactured by Ube Industries, Ltd., SN-E10 grade), 22.4 parts by mass of aluminum nitride (AlN, manufactured by Tokuyama Corporation, E grade), 2.4 parts by mass of calcium nitride (Ca3N2, manufactured by Materion), 43.9 parts by mass of strontium nitride (Sr3N2, purity 2N, manufactured by Kojundo Chemical Laboratory Co., Ltd.), and 5.8 parts by mass of europium oxide (Eu2O3, manufactured by Shin-Etsu Chemical Co., Ltd., RU grade) were weighed out and placed in a container and dry-mixed to obtain a raw material powder (mixed powder).

[0052] The raw material powder was filled into a tungsten container with a lid in a glove box. The container with the lid was removed from the glove box and placed in an electric furnace equipped with a carbon heater, and then the electric furnace was evacuated sufficiently until the pressure in the furnace became 10 Pa or less.

[0053] While continuing the vacuum evacuation, the temperature inside the electric furnace was raised to 300°C. After reaching 300°C, nitrogen gas was introduced into the electric furnace and the pressure inside the electric furnace was adjusted to 0.125MPa. After that, in a nitrogen gas atmosphere, the temperature inside the electric furnace was raised to 1650°C (heating treatment). After reaching 1650°C, heat treatment was carried out for 4 hours while maintaining that temperature. After that, the heating was stopped and the mixture was cooled to room temperature. After cooling to room temperature, the lumps were collected from the container. The collected lumps were crushed and pulverized to obtain a fired powder.

[0054] The obtained fired powder was placed in a ball mill and subjected to wet grinding treatment for 4 hours to prepare a ground product (grinding step). Zirconia balls with a diameter of 3 mm were used as the balls. A red phosphor powder was obtained as the ground product.

[0055] Example 2 A phosphor powder was obtained in the same manner as in Example 1, except that the temperature at which nitrogen gas was introduced during firing was 400°C.

[0056] Example 3 A phosphor powder was obtained in the same manner as in Example 1, except that the temperature at which nitrogen gas was introduced during firing was 700°C.

[0057] Comparative Example 1 A phosphor powder was obtained in the same manner as in Example 1, except that the temperature at which nitrogen gas was introduced during firing was 850°C.

[0058] Comparative Example 2 A phosphor powder was obtained in the same manner as in Example 1, except that the temperature at which nitrogen gas was introduced during firing was 1000°C.

[0059] Comparative Example 3 A phosphor powder was obtained in the same manner as in Example 1, except that the temperature at which nitrogen gas was introduced during firing was 250°C.

[0060] <Confirmation of crystal structure> The crystal structure of the phosphor powders obtained in each of the Examples and Comparative Examples was confirmed by the powder X-ray diffraction pattern using Cu-Kα radiation using an X-ray diffractometer (Ultima IV manufactured by Rigaku Corporation). As a result, the powder X-ray diffraction pattern of the phosphor powders obtained in each of the Examples and Comparative Examples was confirmed to have the same diffraction pattern as CaAlSiN3 crystals. In other words, it was confirmed that the phosphor particles contained in the phosphor powders of each of the Examples and Comparative Examples have the same crystal structure as CaAlSiN3 in the main crystal phase.

[0061] [Table 1]

[0062] The phosphor powder obtained above was evaluated for the following items.

[0063] <Measurements of internal quantum efficiency, external quantum efficiency, and peak emission wavelength for 455 nm light> The internal quantum efficiency and external quantum efficiency of each of the phosphor powders obtained in Examples 1 to 3 and Comparative Examples 1 and 2 when irradiated with excitation light having a wavelength of 455 nm were calculated by the following procedure. The results are shown in Table 1.

[0064] First, the phosphor powder to be measured was filled into a concave cell so that the surface was smooth, and the cell was attached to the opening of the integrating sphere. Monochromatic light with a wavelength of 455 nm was split from a Xe lamp, which was a light source, and introduced into the integrating sphere using an optical fiber as excitation light for the phosphor. The phosphor powder to be measured was irradiated with this monochromatic excitation light, and the fluorescence spectrum was measured. A spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., product name: MCPD-7000) was used for the measurement.

[0065] From the obtained fluorescence spectrum data, the number of reflected excitation light photons (Qref) and the number of fluorescent photons (Qem) were calculated. The number of reflected excitation light photons was calculated in the same wavelength range as the number of excitation light photons, and the number of fluorescent photons was calculated in the range of 465 to 800 nm. In addition, using the same device, a standard reflector with a reflectance of 99% (Spectralon (registered trademark) manufactured by Labsphere) was attached to the opening of the integrating sphere to measure the spectrum of excitation light with a wavelength of 455 nm. At that time, the number of excitation light photons (Qex) was calculated from the spectrum in the wavelength range of 450 to 465 nm.

[0066] From the above calculation results, the absorptance of the 455 nm excitation light and the internal quantum efficiency of the phosphor powder to be measured were calculated based on the following formulas. Absorption rate of 455 nm excitation light = ((Qex-Qref) / Qex) x 100 Internal quantum efficiency = (Qem / (Qex-Qref)) x 100 External quantum efficiency = (Qem / Qex) x 100 From the above formula, the relationship between the external quantum efficiency, the absorptance of 455 nm excitation light, and the internal quantum efficiency can be expressed as follows: External quantum efficiency = 455 nm light absorptance × internal quantum efficiency

[0067] The emission peak wavelength of the phosphor powder was determined to be the wavelength that showed the highest intensity in the wavelength range of 465 to 800 nm in the spectrum data obtained by attaching the phosphor powder to the opening of the integrating sphere.

[0068] <Particle size measurement> The particle size distribution of the phosphor powder was measured using the following procedure using a particle size measuring device, Microtrac MT3300EXII (Microtrac Bell Co., Ltd.), which uses the laser diffraction and scattering method. From the particle size distribution obtained, the particle size D50 (μm) corresponding to the cumulative 50% in the volume-based integrated fraction was calculated. The ultrasonic homogenizer used was "US-150E" (manufactured by Nippon Seiki Co., Ltd.). (Processing) 30 mg of phosphor powder was uniformly dispersed in 100 ml of 0.2% sodium hexametaphosphate aqueous solution, and the resulting dispersion was placed in a cylindrical container with an inner diameter of 5.5 cm at the bottom. Next, the transducer (cylindrical tip with an outer diameter of 20 mm) of an ultrasonic homogenizer was inserted from above the dispersion, and with the transducer immersed to a depth of 1.0 cm or more, ultrasonic waves were irradiated to the dispersion for 3 minutes at a frequency of 19.5 kHz and an output of 150 W.

[0069] <Measurement of total luminous flux for a cured resin sheet with phosphor powder dispersed in it> [Preparation of cured resin sheet (measurement sample)] First, 40 parts by mass of the phosphor powder to be measured and 60 parts by mass of silicone resin (manufactured by Toray Dow Corning Co., Ltd., product name: OE-6630) were mixed and degassed using a rotation / revolution mixer to obtain a uniform mixture (liquid). Next, the mixture was dropped onto a transparent first fluororesin film, and a transparent second fluororesin film was further layered on top of the dropped matter to obtain a sheet-like laminate. The sheet-like laminate was then formed into an uncured sheet by adjusting the thickness of the layer of the dropped matter using a roller with a gap of 50 μm added to the total thickness of the first fluororesin film and the second fluororesin film.

[0070] The uncured sheet was heat-treated at 150° C. for 60 minutes. After the heat treatment, the first fluororesin film and the second fluororesin film were peeled off to obtain a cured resin sheet having a thickness of 50±5 μm and having the phosphor dispersed therein.

[0071] [Total luminous flux measurement] A blue light emitting diode (blue LED) having a peak wavelength in the range of 450 to 460 nm was prepared. The blue light emitted from the blue LED was irradiated onto one main surface of the resin cured sheet, and the emission spectrum of the light emitted from the other main surface of the resin cured sheet was measured. The total luminous flux was calculated from the spectral data in the wavelength range of 500 to 800 nm of the emission spectrum. The evaluation results were relative evaluations in which the total luminous flux produced using the phosphor of Comparative Example 1 was taken as 100%. The results are shown in Table 1.

[0072] The blue light emitting diode used in the measurement had a peak wavelength of 450 to 460 nm, a chromaticity X of 0.145 to 0.165, and a chromaticity Y of 0.023 to 0.037 (product number: SMT type, PLCC-6, 0.2 W, SMD 5050 LED).

[0073] The phosphor powders of Examples 1 to 3 showed higher total luminous flux values ​​when used as a sheet than those of Comparative Examples 1 to 3. The phosphor powders of such examples are preferably applicable to mini LEDs or micro LEDs.

Claims

1. The main crystal phase is CaAlSiN ３ and has the same crystal structure as that of the general formula (Ca １－ｘ－ｙ Sr ｘ EU ｙ ) AlSiN ３ (wherein 0≦x<1, 0<y<1, 1-x-y>0), a mixing step of mixing the raw material powders to obtain a raw material mixed powder; A firing step of firing the obtained raw material mixed powder in a firing space, The firing step includes a temperature rise treatment in which an inert gas is introduced into the firing space in a vacuum environment, the temperature of which is in the range of 300° C. to 700° C.

2. A method for producing the phosphor powder according to claim 1, The method for producing a phosphor powder, wherein the inert gas includes nitrogen gas and / or a rare gas.

3. A method for producing a phosphor powder according to claim 1 or 2, comprising the steps of: The method for producing a phosphor powder, wherein the temperature increasing process in the firing step is performed by increasing the temperature of the firing space from room temperature in a vacuum environment until the temperature reaches a temperature at which the inert gas is introduced.

4. A method for producing a phosphor powder according to claim 1 or 2, comprising the steps of: The firing step includes a heat treatment at 1500° C. or more and 2100° C. or less after the temperature increase treatment.

5. A method for producing a phosphor powder according to claim 1 or 2, comprising the steps of: The method for producing a phosphor powder, wherein the firing step includes a heat treatment for 0.5 hours to 30 hours after the temperature increase treatment.

6. A method for producing a phosphor powder according to claim 1 or 2, comprising the steps of: The firing step includes a heat treatment in an inert gas atmosphere of 10 MPa or less after the temperature increase treatment.

7. A method for producing a phosphor powder according to claim 1 or 2, comprising the steps of: A method for producing a phosphor powder, wherein the median diameter of the resulting phosphor powder is 5 μm or less.

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