Rare earth phosphate powder, its manufacturing method, and light scattering components

Abstract

The rare earth phosphate powder of the present invention comprises rare earth phosphate particles containing LnPO4 (where Ln represents at least one element selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu). The rare earth phosphate powder comprises rare earth phosphate particles having internal voids. The proportion of the aforementioned rare earth phosphate particles having voids with a maximum length of 3.0 nm or more relative to the total number of rare earth phosphate particles is 10% or more. The objective of the present invention is to provide a light-scattering powder that is closer to white.

Description

Technical Field

[0001] This invention relates to rare earth phosphate powders and methods for manufacturing the same. Additionally, this invention relates to light scattering components containing rare earth phosphate powders. Background Technology

[0002] Light-scattering sheets, made by containing light-scattering particles in transparent resin, are used in various optical devices such as backlight modules for LCD displays in televisions and smartphones, screens for image display devices such as projection televisions, transparent screens for head-up displays and projectors, LED and μLED elements used as sealing materials, and lighting fixtures used as covers. For such light-scattering sheets, excellent light-scattering properties are required while ensuring transparency. Furthermore, a wide viewing angle is also required. Therefore, titanium dioxide, silicon dioxide, zirconium oxide, barium titanate, zinc oxide, and resin particles are used as light-scattering particles.

[0003] In addition, the applicant previously proposed rare earth phosphate particles as particles used in light scattering sheets formed by dispersing light scattering particles in resin (see Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: US2019 / 0353828A1 Summary of the Invention

[0007] If light-scattering particles themselves are colored, the color of the reflected light will change when illuminated. From this perspective, it is desirable for light-scattering particles to be as close to white as possible.

[0008] Therefore, the objective of this invention is to provide a light-scattering powder that is closer to white.

[0009] To address the aforementioned issues, the inventors conducted in-depth research and discovered that if voids are created within the rare earth phosphate particles, the whiteness of the rare earth phosphate powder containing these particles is improved.

[0010] The present invention is based on the above-mentioned insights and solves the above-mentioned problems by providing a rare earth phosphate powder, which is a rare earth phosphate powder containing rare earth phosphate particles containing LnPO4 (where Ln represents at least one element selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu).

[0011] The aforementioned rare earth phosphate powder contains rare earth phosphate particles with internal pores.

[0012] The proportion of rare earth phosphate particles having the above-mentioned voids with a maximum length of 3.0 nm or more, relative to the total number of rare earth phosphate particles, is more than 10%.

[0013] In addition, the present invention provides a method for manufacturing rare earth phosphate powder, wherein an aqueous solution containing phosphate or its salt and an alkaline substance is added to an aqueous solution containing rare earth elements to generate a precipitate containing rare earth elements and phosphorus.

[0014] The above precipitate is calcined to obtain rare earth phosphate powder containing rare earth phosphate particles with internal pores. Attached Figure Description

[0015] Figure 1 This is a transmission electron microscope image of the yttrium phosphate powder obtained in Example 1.

[0016] Figure 2 This is a transmission electron microscope image of the yttrium phosphate powder obtained in Example 2.

[0017] Figure 3 This is a transmission electron microscope image of the yttrium phosphate powder obtained in Comparative Example 4. Detailed Implementation

[0018] The present invention will now be described based on its preferred embodiments. The present invention relates to rare earth phosphate powders. Rare earth phosphate powders are aggregates of rare earth phosphate particles. The term "phosphate" as used in this specification refers to orthophosphate. Known orthophosphates include normal salts, hydrogen phosphates, and dihydrogen phosphates; the rare earth phosphates used in this invention are normal salts of orthophosphate. Rare earth phosphates are represented by LnPO4. In the formula, Ln represents at least one element selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu. These elements may be used alone or in combination of two or more.

[0019] The rare earth phosphate powder of the present invention may consist solely of the aforementioned rare earth phosphate particles, or it may contain other particles in addition to the aforementioned rare earth phosphate particles. The presence of these other particles in the rare earth phosphate powder is permitted without impairing the effects of the present invention.

[0020] Rare earth phosphates are materials with high refractive indices. Therefore, when light is irradiated onto the rare earth phosphate powder of the present invention, the light is significantly scattered. Furthermore, rare earth phosphates generally have high Abbe numbers and low wavelength dependence of their refractive index. That is, rare earth phosphates are substances with small deviations in the degree of refraction when light of various wavelengths is incident. As a result, by using the rare earth phosphate powder of the present invention, scattered light with strong contrast can be obtained. From these viewpoints, the rare earth element Ln in the rare earth phosphate represented by LnPO4 is preferably selected from at least one of Y, La, Gd, Yb, and Lu, and particularly preferably Y.

[0021] Rare earth phosphate particles can be crystalline or amorphous (non-crystalline). Generally, if rare earth phosphate particles are manufactured using the method described later, crystalline rare earth phosphate powder can be obtained. When the rare earth phosphate powder is crystalline, it is preferable from the perspective of increasing refractive index.

[0022] The rare earth phosphate particles contained in the rare earth phosphate powder of the present invention preferably have voids inside the particles. That is, it is preferable that the rare earth phosphate particles have spaces inside them. This space can be referred to as a void portion. One or more void portions may exist in a single rare earth phosphate particle. The inventors' research results show that by making the rare earth phosphate particles have void portions, the whiteness of the rare earth phosphate powder of the present invention is improved.

[0023] The rare earth phosphate powder of the present invention may be composed entirely of rare earth phosphate particles that are porous, or it may be a mixture of rare earth phosphate particles with and without porous structures. In the latter case, from the viewpoint of improving whiteness, a higher proportion of rare earth phosphate particles with porous structures relative to all rare earth phosphate particles is preferred.

[0024] There are no particular restrictions on the shape of the gap. For example, the gap can be spherical, ellipsoidal, cuboid, cuboid with rounded edges, cuboid with rounded corners, prism, cylinder, or elliptical cylinder, or a combination thereof.

[0025] From the viewpoint of improving the whiteness of rare earth phosphate powder, it is preferable that the voids in the porous rare earth phosphate particles have a predetermined size. From this viewpoint, it is preferable that the rare earth phosphate powder contains voids with a maximum length of 3.0 nm or more within the interior of the rare earth phosphate particles constituting it. More preferably, the maximum length of the voids is 10.0 nm or more, and even more preferably 20.0 nm or more. The upper limit of the maximum length of the voids is determined by the particle size of the rare earth phosphate particles; the closer the maximum length of the voids is to the particle size of the rare earth phosphate particles, the higher the whiteness of the rare earth phosphate powder tends to be.

[0026] The maximum length of the void can be determined by observing rare earth phosphate particles using a transmission electron microscope (TEM). The length of the longest line segment observed across the void within the rare earth phosphate particle is defined as the maximum length of the void.

[0027] In the rare earth phosphate powder of the present invention, the higher the proportion of rare earth phosphate particles having pores with a maximum length of 3.0 nm or more, the higher the whiteness of the rare earth phosphate powder. From this perspective, in the present invention, the proportion of rare earth phosphate particles having pores with a maximum length of 3.0 nm or more relative to the total number of rare earth phosphate particles is preferably 10% or more, more preferably 35% or more, further preferably 40% or more, and even more preferably 50% or more. In this specification, "total rare earth phosphate particles" refers to both rare earth phosphate particles with pores and rare earth phosphate particles without pores present in the TEM image within the field of view.

[0028] In the following explanation, for simplicity, the proportion of rare earth phosphate particles with a maximum length of 3.0 nm or more will be referred to as the "void particle content".

[0029] Rare earth phosphate powder having the above-mentioned void particle content can be appropriately manufactured, for example, by the method described later.

[0030] Regarding the maximum length of the voids in the rare earth phosphate particles, from the viewpoint of improving the whiteness of the rare earth phosphate powder, the average value of the maximum length of the voids is preferably 1 nm or more, more preferably 8 nm or more, further preferably 10 nm or more, and even more preferably 20 nm or more.

[0031] Furthermore, from the viewpoint of ensuring the strength of rare earth phosphate particles, the average value of the maximum length of the voids is preferably 100 nm or less, more preferably 75 nm or less, even more preferably 60 nm or less, even more preferably 50 nm or less, and even more preferably 38 nm or less.

[0032] In the following explanation, for the sake of simplicity, the average value of the maximum length of the gap will also be referred to as the "average maximum length of the gap".

[0033] The average maximum pore length refers to the arithmetic mean of the maximum pore lengths measured from more than 100 rare earth phosphate particles containing pores. When there are two or more pores in a particle, the maximum length refers to the arithmetic mean of the maximum lengths of each pore. For example, if a rare earth phosphate particle contains pores A and B, the maximum length of pore A is L. A The maximum length of gap B is L. BAt that time, the maximum length of the voids in the rare earth phosphate particles is (L A +L B ) / 2.

[0034] In this invention, from the viewpoint of further improving the whiteness of rare earth phosphate powder, based on the total number of rare earth phosphate particles, the number of voids in each particle is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.3 or more, and even more preferably 2.5 or more.

[0035] Furthermore, from the viewpoint of ensuring the strength of rare earth phosphate particles, based on the total number of rare earth phosphate particles, the number of voids in each particle is preferably 100 or less per particle, more preferably 50 or less per particle, further preferably 40 or less per particle, and even more preferably 10 or less per particle.

[0036] In the following explanation, for simplicity, the ratio of the number of voids in each rare earth phosphate particle to the total number of particles will be referred to as "porosity".

[0037] Rare earth phosphate powder having the above-mentioned porosity can be appropriately manufactured, for example, by the method described later.

[0038] From the viewpoint of suppressing the increase in viscosity of the coating liquid containing rare earth phosphate particles, the average particle size D of the rare earth phosphate particles is preferably 10 nm or more, more preferably 80 nm or more, and even more preferably 100 nm or more.

[0039] Furthermore, from the viewpoint of improving the dispersibility of rare earth phosphate particles in a coating solution containing rare earth phosphate particles, the average particle size D of the rare earth phosphate particles is preferably 250 nm or less, more preferably 200 nm or less, even more preferably 170 nm or less, and even more preferably 150 nm or less.

[0040] The average particle size D of rare earth phosphate particles can be determined by TEM observation. The length of the longest segment in a cross-section of a rare earth phosphate particle is defined as the particle size. The arithmetic mean of the particle sizes of more than 100 rare earth phosphate particles is defined as the average particle size D.

[0041] From the viewpoint of obtaining a rare earth phosphate powder that is closer to white, it is preferable that the whiteness of the rare earth phosphate powder of the present invention is expressed as a whiteness index value of 0.01 particles / particle or more, as defined below. From this viewpoint, a whiteness index value of 0.1 particles / particle or more is further preferred, and even more preferably 0.2 particles / particle or more is preferred.

[0042] The whiteness index is defined as porosity (porosity / particle) × average maximum porosity length (nm) / average particle size D (nm) of rare earth phosphate particles.

[0043] Related to the aforementioned whiteness index value, from the perspective of preventing the resin molded article containing rare earth phosphate powder and resin from being easily colored, the whiteness L of the rare earth phosphate powder of the present invention is preferred. High value and redness a Value and yellowness b The value is low.

[0044] Specifically, whiteness L The value is preferably 98.50 or higher and 100 or lower, more preferably 99.00 or higher and 100 or lower, and even more preferably 99.20 or higher and 100 or lower.

[0045] Redness a The value is preferably -0.10 or higher and 0.1 or lower, more preferably -0.04 or higher and 0.04 or lower, and even more preferably -0.02 or higher and 0.02 or lower.

[0046] In addition, yellowness b The value is preferably 0 or higher and 0.6 or lower, more preferably 0 or higher and 0.5 or lower, and even more preferably 0.1 or higher and 0.4 or lower.

[0047] Whiteness L Value, redness a Value, yellowness b The method for determining the value is described in the examples described later.

[0048] To ensure good dispersibility of the rare earth phosphate powder of the present invention in the resin molded article described later, without impairing the effects of the present invention, the surface of the rare earth phosphate particles may be subjected to an oleophilic treatment. Examples of oleophilic treatments include treatments using various coupling agents. Examples of coupling agents include organometallic compounds. Specifically, silane coupling agents, zirconium coupling agents, titanium coupling agents, aluminum coupling agents, etc., may be used.

[0049] The various coupling agents described above can be used individually or in combination of two or more. When using a silane coupling agent, the surface of the rare earth phosphate particles is coated with a silane compound. This silane compound preferably has a lipophilic group, such as an alkyl or substituted alkyl group. The alkyl group can be straight-chain or branched. In either case, from the perspective of good affinity with the resin, it is preferred that the alkyl group has 1 to 20 carbon atoms. When the alkyl group is substituted, amino, vinyl, epoxy, styryl, methacryl, acryloyl, urea, mercapto, thioether, isocyanate, etc., can be used as substituents. From the perspective of improving affinity with the resin, it is preferred that the amount of silane compound covering the surface of the rare earth phosphate particles is 0.01 to 200% by mass, particularly 0.1 to 100% by mass, relative to the mass of the rare earth phosphate particles.

[0050] Next, a preferred method for manufacturing the rare earth phosphate powder of the present invention will be described.

[0051] To manufacture the rare earth phosphate powder of the present invention, an aqueous solution containing one or more rare earth element sources (hereinafter also referred to as "first solution") is first prepared. At the same time, an aqueous solution containing phosphate or its salt and an alkaline substance (hereinafter also referred to as "second solution") is prepared.

[0052] The first solution can be prepared, for example, by dissolving rare earth element oxides in an aqueous solution of an inorganic acid (e.g., an aqueous solution of nitric acid). The concentration of rare earth elements in the first solution can be, for example, set to be 0.3 mol / L or more and 1.0 mol / L or less.

[0053] The second solution can be prepared, for example, by dissolving orthophosphate or its salt in water with an alkaline substance. The concentration of phosphate ions in the second solution can be set, for example, to be 0.3 mol / L or more and 3.0 mol / L or less. The concentration of the alkaline substance in the second solution can be set such that the pH of the second solution is preferably 2 or more and 6 or less, and more preferably 2 or more and 4 or less. By adjusting the pH of the second solution by including an alkaline substance, porous rare earth phosphate particles can be successfully generated. When the second solution does not contain an alkaline substance and the pH of the solution is not adjusted, as shown in Comparative Examples 1-3 described later, pores cannot be formed in the rare earth phosphate particles.

[0054] Examples of alkaline substances contained in the second solution include: alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, ammonia, ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, sodium carbonate, ethylamine, and propylamine. Ammonia is particularly preferred because it facilitates the formation of voids within the rare earth phosphate particles.

[0055] Next, the first liquid and the second liquid are mixed. The mixing of the two liquids is achieved by adding the second liquid to the first liquid. When both the first and second liquids are added simultaneously, as shown in Comparative Example 4 described later, voids cannot be formed in the rare earth phosphate particles.

[0056] In the mixing of the two liquids, the first liquid and / or the second liquid can be heated. From the viewpoint of smoothly forming voids in the rare earth phosphate particles, it is preferable to add the second liquid sequentially or continuously to the heated first liquid. In this case, from the perspective of void formation, it is preferable that the heating temperature of the first liquid is 80°C or higher and 98°C or lower.

[0057] Regarding the usage of the first and second solutions, the ratio of the number of moles of phosphate ions to the number of moles of rare earth elements is PO4. 3- / Ln is preferably 1.2 or more and 3.0 or less, and more preferably 1.5 or more and 2.0 or less.

[0058] By mixing two liquids, a precipitate containing rare earth elements and phosphorus is generated in the liquid. After mixing, the mixture is allowed to stand for a specified time to mature, thereby allowing the nuclei to form and grow in the precipitate. After obtaining the precipitate, the mixture is subjected to solid-liquid separation to recover the precipitate.

[0059] The recovered precipitate is then subjected to washing, drying, crushing, and grading processes before being fed into the calcination process. From the viewpoint of successfully obtaining the target phosphate particles, the calcination of the precipitate is preferably carried out at temperatures above 600°C and below 1500°C, particularly above 700°C and below 1500°C, further above 800°C and below 1200°C, and especially above 1000°C and below 1200°C. Setting the calcination temperature too high tends to result in the coalescence of small voids and the formation of larger voids.

[0060] The firing time is preferably 1 hour or more and 4 hours or less, and more preferably 2 hours or more and 4 hours or less, provided that the firing temperature is within the above-mentioned range.

[0061] The firing atmosphere can be set to an oxygen-containing atmosphere such as the atmosphere, or an inactive atmosphere such as nitrogen and argon.

[0062] Through the above processes, porous rare earth phosphate particles are obtained. The resulting rare earth phosphate powder has high whiteness because the rare earth phosphate particles that make it up have porosity.

[0063] The rare earth phosphate powder obtained in this way can be used, for example, as a light scattering component to improve the light scattering properties of a resin composition by dispersing it in a resin. The form of the resin composition is not particularly limited; examples include sheets (films), membranes, powders, granules (masterbatches), and dispersions (coating solutions). If it is in sheet form, it can be easily applied to light scattering sheets, which is advantageous. The type of resin to which the rare earth phosphate powder of the present invention is added is not particularly limited; thermoplastic resins and thermosetting resins that can be molded can be used. In particular, thermoplastic resins are preferred from the perspective of ease of molding into sheets. Examples of thermoplastic resins include homopolymers of olefins such as polyethylene and polypropylene; copolymers of polyethylene and polypropylene with other α-olefins; polyesters such as polyethylene terephthalate and polybutylene terephthalate; homopolymers and copolymers of acrylic monomers such as acrylic acid, acrylates, methacrylic acid, and methacrylates; homopolymers and copolymers of vinyl monomers such as styrene; homopolymers and copolymers of chlorine-containing monomers such as vinyl chloride and vinylidene chloride; polycarbonate; and cellulose resins such as triacetyl cellulose. These thermoplastic resins can be used alone or in combination of two or more.

[0064] When a light scattering component is made by dispersing the rare earth phosphate particles of the present invention in a resin, considering the balance between transmittance and light scattering, the proportion of rare earth phosphate powder contained in the light scattering component relative to the total mass of the light scattering component is preferably 0.05% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 0.1% by mass or more and 5% by mass or less.

[0065] To obtain a light-scattering component made of a resin composition comprising the rare earth phosphate powder and resin of the present invention, for example, the rare earth phosphate powder of the present invention is incorporated into the resin in a molten state and then formed by a known sheet forming method such as blow molding, T-die molding, solution casting, and calendering.

[0066] Furthermore, by applying the rare earth phosphate powder of the present invention to the surface of a resin molded body, the scattering properties of the resin molded body can also be improved. A method for applying the rare earth phosphate powder of the present invention to the surface of a resin molded body is, for example, to prepare a coating liquid by mixing a composition comprising the rare earth phosphate powder of the present invention, an organic solvent, and a binder resin, and then applying or spraying the coating liquid onto the surface of the resin molded body using a roller, spray gun, or the like. In this case, a light-scattering member formed by a coating of a resin composition comprising the rare earth phosphate powder of the present invention and a resin can be obtained on the surface of the resin molded body. Alternatively, as another method for applying the rare earth phosphate powder of the present invention to the surface of a resin molded body, sputtering or the like can be used to directly apply the rare earth phosphate powder of the present invention to the surface of the resin molded body without using a binder such as a resin.

[0067] As described above, when a light scattering component with a coating is provided on the surface of a resin molded body, considering the balance between transmittance and light scattering, the proportion of rare earth phosphate powder contained in the coating is preferably 0.01% by mass or more and 90% by mass or less, and more preferably 0.1% by mass or more and 65% by mass or less, relative to the total mass of the coating.

[0068] The light-scattering components obtained through this method can be appropriately manufactured as components for displays, lighting, windows, electrical decorations, light guide plates, projector screens, transparent screens used in head-up displays, and agricultural materials such as plastic greenhouses. They can also be assembled into optical devices. Examples of such optical devices include mobile devices such as LCD TVs, personal computers, tablets, and smartphones.

[0069] Regarding the above embodiments, the following rare earth phosphate powder, its manufacturing method, and light scattering components are further disclosed. [1]

[0071] A rare earth phosphate powder comprising rare earth phosphate particles containing LnPO4 (where Ln represents at least one element selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu).

[0072] The aforementioned rare earth phosphate powder contains rare earth phosphate particles with internal pores.

[0073] The proportion of rare earth phosphate particles having the above-mentioned voids with a maximum length of 3.0 nm or more, relative to the total number of rare earth phosphate particles, is more than 10%. [2]

[0075] According to the rare earth phosphate powder described in [1], the number of voids in each particle is more than 0.1 voids per particle and less than 100 voids per particle, based on the total number of rare earth phosphate particles. [3]

[0077] According to the rare earth phosphate powder described in [1] or [2], the average value of the maximum length of the above-mentioned voids is more than 1 nm and less than 100 nm. [4]

[0079] The rare earth phosphate powder according to any one of [1] to [3], wherein the average particle size of the rare earth phosphate particles is 10 nm or more and 150 nm or less. [5]

[0081] Rare earth phosphate powder according to any one of [1] to [4], wherein Ln is Y. [6]

[0083] A light scattering component is formed by dispersing any one of the rare earth phosphate powders described in [1] to [5] in a resin. [7]

[0085] A light scattering component is formed by disposing of any one of the rare earth phosphate powders described in [1] to [5] on the surface of a resin molded body. [8]

[0087] A method for manufacturing rare earth phosphate powder, wherein an aqueous solution containing phosphate or its salt and an alkaline substance is added to an aqueous solution containing rare earth elements to generate a precipitate containing rare earth elements and phosphorus.

[0088] The above precipitate is calcined to obtain rare earth phosphate powder containing rare earth phosphate particles with internal pores. [9]

[0090] According to the manufacturing method described in [8], the alkaline substance is ammonia.

[0091] The present invention will now be described in more detail through examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" refers to "mass %".

[0092] [Example 1]

[0093] In this embodiment, a powder containing yttrium phosphate particles was manufactured. The manufacturing steps are described below.

[0094] 3600g of water was measured into a glass container, and 880g of 67.5% nitric acid and 290g of yttrium oxide were added. The mixture was heated to 60℃ to dissolve the yttrium oxide, yielding the first solution. The concentration of yttrium in the first solution was 0.6 mol / L.

[0095] Add 3900g of water, 600g of 85% phosphoric acid, and 320g of 25% ammonia solution to another glass container to obtain the second solution. The concentration of phosphate ions in the second solution is 1.1 mol / L. The pH of the second solution is 3.

[0096] Heat the first solution to 90°C, and add the second solution dropwise while stirring. At the end of the addition, the PO4... - The molar ratio of Y / Y is 1.8. A precipitate is formed in the liquid by mixing the two liquids. After aging for 3 hours, the precipitate is decanted and washed. After washing, solid-liquid separation is performed by vacuum filtration, the precipitate is recovered, dried in the atmosphere, and then pulverized. The pulverized material is calcined in the atmosphere at 1200°C for 3 hours. This yields yttrium phosphate powder containing porous yttrium phosphate particles.

[0097] [Examples 2 to 6]

[0098] In Example 1, calcination was carried out at the temperatures shown in Table 1 below, otherwise yttrium phosphate powder was obtained in the same manner as in Example 1.

[0099] [Comparative Example 1]

[0100] 600g of water was measured into a glass container, and 61.7g of 60% nitric acid and 18.8g of yttrium oxide were added. The mixture was heated to 60℃ to dissolve the yttrium oxide, yielding the first solution. The concentration of yttrium in the first solution was 0.26mol / L.

[0101] Add 600g of water and 18.8g of 85% phosphoric acid to another glass container to obtain the second solution. The concentration of phosphate ions in the second solution is 0.27mol / L. The pH of the second solution is 1.

[0102] Heat the first solution to 80°C, and add the second solution dropwise while stirring. At the end of the addition, the PO4... - The molar ratio of Y / Y is 1.0. A precipitate is formed in the liquid by mixing the two liquids. After aging for 1 hour, the precipitate is decanted and washed. After washing, solid-liquid separation is performed by vacuum filtration, the precipitate is recovered, dried in the atmosphere, and then pulverized. The pulverized material is calcined in the atmosphere at 800°C for 3 hours. This yields yttrium phosphate powder.

[0103] [Compare Examples 2 and 3]

[0104] In Comparative Example 1, calcination was carried out at the temperatures shown in Table 1 below, and yttrium phosphate powder was obtained in the same manner as in Comparative Example 1.

[0105] [Comparative Example 4]

[0106] 370g of water was measured into a glass container, and 14.4g of 85% nitric acid and 4.2g of yttrium oxide were added. The mixture was heated to 60℃ to dissolve the yttrium oxide, yielding the first solution. The concentration of yttrium in the first solution was 0.1mol / L.

[0107] Add 390g of water, 5.3g of 25% phosphoric acid, and 9.3g of 25% ammonia solution to another glass container to obtain the second solution. The concentration of phosphate ions in the second solution is 0.03mol / L. The pH of the second solution is 7.

[0108] The first and second solutions were simultaneously added dropwise to the container at 25°C, while the mixture was stirred at high speed using a homogenizer. The PO4 at the end of the addition... - The molar ratio of Y / Y is 0.3. A precipitate is formed in the liquid by mixing the two liquids. After aging for 1 hour, the precipitate is decanted and washed. After washing, solid-liquid separation is performed by vacuum filtration, the precipitate is recovered, dried in the atmosphere, and then pulverized. The pulverized material is calcined in the atmosphere at 800°C for 5 hours. This yields yttrium phosphate powder.

[0109] [evaluate]

[0110] For the yttrium phosphate powders obtained in the examples and comparative examples, the average particle size, average maximum pore length, pore particle content, porosity, and whiteness index were determined using the methods described above. Additionally, L was determined using the following methods. a b L in the color system value, a value and b The value of the color difference ΔE is calculated from the obtained results using the following method. Furthermore, the total transmittance and diffuse transmittance were determined using the following methods. These results are shown in Table 2 below.

[0111] Furthermore, TEM images of the yttrium phosphate powders obtained in Examples 1 and 2 and Comparative Example 4 are shown below. Figures 1-3 .

[0112] [L a b L in the color system value, a value and b value]

[0113] A spectrophotometer (Konica Minolta, CM-2600d) was used, in accordance with JIS Z 8729 "Based on U V W The method of representing the color of objects in a system was measured.

[0114] [Color difference ΔE] [Calculation]

[0115] The L measured by the above method is calculated based on the following formula. value, a value and b Value and white (ΔL) =100、Δa =0、Δb Color difference ΔE (=0) .

[0116] ΔE =((ΔL ) 2 +(Δa ) 2 +(Δb ) 2 ) 1 / 2

[0117] Color difference ΔE The smaller the value, the closer the object being measured is to white.

[0118] [Determination of total transmittance and diffuse transmittance]

[0119] The acrylic resin (manufactured by Mitsubishi Chemical Corporation, trade name: Diana LR-167) was mixed with yttrium phosphate powder from the examples and comparative examples, diluted with toluene solvent to a volume concentration of 10%, and mixed with a paint mixer to prepare a coating solution.

[0120] Next, the coating liquid was applied to a PET film (manufactured by Toray Industries, thickness: 0.1 mm) using a bar coater (#3), and dried at 80°C for 5 minutes to obtain a light scattering component consisting of a light scattering layer and a PET film substrate layer.

[0121] The total transmittance and diffuse transmittance of the light scattering component were measured using a haze meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., trade name: NDH4000).

[0122] [Table 1]

[0123]

[0124] [Table 2]

[0125]

[0126] As shown in Table 2, the color difference ΔE of the powder containing yttrium phosphate particles obtained in each embodiment is... A small value indicates high whiteness.

[0127] Furthermore, a comparison of Examples 1 to 6 shows that as the firing temperature increases, the maximum length of the voids increases.

[0128] Industrial availability

[0129] According to the present invention, a rare earth phosphate powder having high whiteness and usable as a light scattering component is provided.

Claims

1. A rare earth phosphate powder comprising rare earth phosphate particles containing LnPO4, wherein Ln represents at least one element selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb and Lu. The rare earth phosphate powder contains rare earth phosphate particles with internal pores. The proportion of rare earth phosphate particles having a maximum length of 3.0 nm or more of the voids relative to the total number of rare earth phosphate particles is 10% or more.

2. The rare earth phosphate powder according to claim 1, wherein, Based on the total number of rare earth phosphate particles, the number of voids in each particle is more than 0.1 voids per particle and less than 100 voids per particle.

3. The rare earth phosphate powder according to claim 1, wherein, The average maximum length of the gap is greater than 1 nm and less than 100 nm.

4. The rare earth phosphate powder according to claim 1, wherein, The average particle size of the rare earth phosphate particles is greater than 10 nm and less than 150 nm.

5. The rare earth phosphate powder according to claim 1, wherein, Ln is Y.

6. A light scattering component, which is formed by dispersing the rare earth phosphate powder according to any one of claims 1 to 5 in a resin.

7. A light scattering component, which is formed by disposing the rare earth phosphate powder of any one of claims 1 to 5 on the surface of a resin molded body.

8. A method for manufacturing rare earth phosphate powder, wherein, Adding an aqueous solution containing phosphate or its salt and an alkaline substance to an aqueous solution containing rare earth elements produces a precipitate containing rare earth elements and phosphorus. The precipitate is calcined to obtain rare earth phosphate powder containing rare earth phosphate particles with internal pores.

9. The manufacturing method according to claim 8, wherein, The alkaline substance is ammonia.

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