Coated phosphor particles, phosphor resin composition, wavelength conversion member, light source, and display

Abstract

Provided are coated phosphor particles which are capable of maintaining high light-emitting characteristics even in a severe high-temperature and high-humidity environment, and which exhibit little characteristic deterioration even when combined with a matrix resin. Each of these coated phosphor particles comprises a phosphor particle and a coating layer provided on the surface of the phosphor particle. The coating layer contains an inorganic filler and a film-forming resin. In the coating layer, the film-forming resin and the inorganic filler are present in a mixed state.

Description

Coated phosphor particles, phosphor resin composition, wavelength conversion member, light source, and display

[0001] The present invention relates to coated phosphor particles, a phosphor resin composition, a wavelength conversion member, a light source, and a display.

[0002] In addition to conventional liquid crystal displays, next-generation displays such as micro LEDs have attracted attention in recent years. In these displays, a light source combining the three primary colors of pixels, red, green, and blue, specifically a blue LED functioning as a backlight, and a wavelength conversion member that converts the emitted light of the blue LED into green light or red light, are used.

[0003] As a material for a wavelength conversion member (wavelength conversion material), a material that can perform color conversion of emitted light with high efficiency is required, and phosphors are regarded as promising materials that meet such requirements. Among them, sulfide phosphors have high color purity and can cover a wide color gamut. Therefore, they are expected to have high applicability for use as wavelength conversion materials for displays. The wavelength conversion member is produced by mixing particulate phosphor (phosphor particles) with a resin and molding the obtained mixture (phosphor resin composition).

[0004] A technique for forming coated phosphor particles in which a coating layer is provided on the surface of particulate phosphor (phosphor particles) is also known. For example, Patent Document 1 discloses a phosphor in which particles containing a crystalline metal borate are present on the surface of a sulfur-containing phosphor (Claim 1 of Patent Document 1). It is also described that the phosphor can effectively suppress corrosion of metal members caused by sulfur-based gas and maintain high brightness of the phosphor itself (

[0010] of Patent Document 1).

[0005] Patent Document 2 discloses a coated phosphor including inorganic phosphor particles and a silicon oxide coating that coats the inorganic phosphor particles (Claim 1 of Patent Document 2). It is also described that the coated phosphor has excellent stability under high temperature and high humidity conditions when the LED is in a lit state (

[0009] of Patent Document 2).

[0006] Patent Document 3 discloses an inorganic phosphor powder having inorganic oxide particles such as silica or alumina adhered to the surface (claims 1 and 2 of Patent Document 3). It also describes that, despite having a simple structure, the inorganic phosphor powder can improve the wavelength conversion efficiency of light emitted from an optical semiconductor element (

[0015] of Patent Document 3).

[0007] Patent Document 4 discloses a composition MSe １－ｘ S ｘ : a coated phosphor comprising Eu, phosphor particles having an average particle diameter D50 of 5 μm to 25 μm, and an alumina coating (claim 1 of Patent Document 4). It also describes that, for the coated phosphor, the decrease in photoluminescence intensity at the peak emission wavelength is about 15% or less after an aging treatment at about 85° C. and a relative humidity of about 85% for 1,000 hours, and the change in chromaticity coordinates after the aging treatment is about 10×10 －３ or less (claim 1 of Patent Document 4).

[0008] Patent Document 5 discloses a phosphor sheet comprising: a coated phosphor coated with a silicon dioxide film; a phosphor layer formed from a phosphor-containing resin composition containing a polymerizable compound and a polymerization initiator; and a pair of transparent substrates (claim 1 of Patent Document 5). It also describes that, with respect to the phosphor sheet, chromaticity shift and corrosion accompanying deterioration of a sulfide phosphor can be suppressed (

[0017] of Patent Document 5).

[0009] International Publication No. 2015 / 146231, Japanese Unexamined Patent Application Publication No. 2021-192103, Japanese Unexamined Patent Application Publication No. 2015-089898, Japanese Unexamined Patent Application Publication No. 2020-183541, Japanese Unexamined Patent Application Publication No. 2014-024918

[0010] As mentioned above, conventional methods have been proposed to create coated phosphor particles by applying a coating layer to the surface of phosphor particles, or to fabricate wavelength conversion components for displays using phosphor resin compositions obtained by mixing phosphor particles with resin. On the other hand, the required level of durability for display materials has been increasing in recent years, and there is a demand for materials that do not degrade in properties even under harsh humid and hot environments (high temperature and high humidity environments), that is, materials with high humid and hot durability. In particular, not only the durability of the phosphor particles themselves but also the durability of the wavelength conversion components containing a composite of phosphor particles and resin is required. However, conventional technologies have been insufficient to meet these demands.

[0011] For example, Patent Document 1 shows that a mixture of phosphor and silicone resin exhibits high resistance to water vapor. However, the effect on resins other than silicone resin has not been clarified. In particular, acrylic UV-curable resins are frequently used in display applications, but there is no specific disclosure regarding the effect when mixed with this resin.

[0012] Patent Document 2 shows that the moisture and heat resistance of inorganic phosphor particles can be improved by a silicon oxide coating, but high-temperature firing is required to form the silicon oxide coating. Therefore, there is a problem that this will lead to an increase in the manufacturing cost of the phosphor. Patent Document 3 states that the light extraction efficiency can be improved when inorganic phosphor particles are mixed with various resins including silicone and acrylic. However, Patent Document 3 does not disclose any moisture and heat resistance required for the light conversion member.

[0013] Patent Document 4 describes mixing a phosphor with a resin such as acrylic to create a wavelength conversion member, but it does not specifically disclose the effects when mixed with an ultraviolet-curable resin used for display applications. Patent Document 5 mentions the moisture heat durability of a phosphor sheet in a 60°C-90% RH environment, but it does not specifically disclose durability under even harsher conditions. In recent years, wavelength conversion members for displays have been required to withstand moisture heat under harsh conditions, and the technology described in Patent Document 5 is insufficient to meet this requirement.

[0014] In light of these problems, the inventors conducted thorough research. As a result, they found that coated phosphor particles can be obtained that maintain high luminescence characteristics even under harsh high-temperature and high-humidity environments by providing a coating layer containing an inorganic filler and a film-forming resin on the surface of the phosphor particles and controlling the arrangement of the inorganic filler and film-forming resin in this coating layer. Furthermore, they found that these coated phosphor particles exhibit little degradation in properties even when compounded with a matrix resin such as an acrylic UV-curable resin.

[0015] The present invention was completed based on such findings, and aims to provide coated phosphor particles that can maintain high luminescence characteristics even in harsh high-temperature and high-humidity environments, and that exhibit little degradation of properties even when compounded with a matrix resin. The present invention also aims to provide a phosphor resin composition comprising the coated phosphor particles, a wavelength conversion member, a light source, and a display.

[0016] The present invention encompasses the following embodiments (1) to (13). In this specification, the expression "~" includes the numerical values ​​at both ends. That is, "X~Y" is synonymous with "X or more and Y or less".

[0017] (1) Coated phosphor particles comprising phosphor particles and a coating layer provided on the surface of the phosphor particles, wherein the coating layer contains an inorganic filler and a film-forming resin, and the inorganic filler and the film-forming resin are present in a mixed state in the coating layer.

[0018] (2) The coated phosphor particles of (1) above, wherein the inorganic filler comprises an oxide having one or more elements selected from the group consisting of silicon (Si), aluminum (Al), zinc (Zn), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and boron (B).

[0019] (3) The coated phosphor particles according to (1) or (2) above, wherein the film-forming resin is a resin containing at least one constituent unit selected from the group consisting of olefin units and silicone units.

[0020] (4) The coating resin contains olefin units as constituent units, and the weight-average molecular weight of the coating resin is 300 or more, wherein the coated phosphor particles are any of (1) to (3) above.

[0021] (5) The coating resin contains olefin units as constituent units and has a softening point of 100°C or higher as measured by ASTM D6090, and is any of the coated phosphor particles described in (1) to (4) above.

[0022] (6) Coated phosphor particles according to any of (1) to (5) above, wherein the proportion of the inorganic filler in the coating layer is 50% by mass or more and 95% by mass or less, and the proportion of the film-forming resin is 5% by mass or more and 50% by mass or less.

[0023] (7) The phosphor particles are coated phosphor particles of any of (1) to (6) above, the phosphor particles mainly comprising a sulfide fluorescent material.

[0024] (8) The coated phosphor particles of any of (1) to (7) above, wherein the average particle size of the coated phosphor particles is 0.3 μm or more and 30 μm or less.

[0025] (9) A phosphor resin composition comprising coated phosphor particles according to any of (1) to (8) above and a matrix resin, wherein the coated phosphor particles are dispersed in the matrix resin.

[0026] (10) The phosphor resin composition according to (9), wherein the matrix resin comprises at least a (meth)acrylic polyfunctional oligomer and a photopolymerization initiator.

[0027] (11) A wavelength conversion member which is a molded body of the phosphor resin composition of (10) above.

[0028] (12) A light source comprising the wavelength conversion member and excitation source described in (11) above.

[0029] (13) A display equipped with the light source described in (12) above.

[0030] According to the present invention, coated phosphor particles are provided that can maintain high luminescence characteristics even under harsh high-temperature and high-humidity environments, and that exhibit little degradation of properties even when compounded with a matrix resin. Furthermore, according to the present invention, a phosphor resin composition comprising the coated phosphor particles, a wavelength conversion member, a light source, and a display are provided.

[0031] This is a schematic cross-sectional view of coated phosphor particles. It is a diagram used to explain the phosphor resin composition.

[0032] Specific embodiments of the present invention (hereinafter referred to as "these embodiments") are described below. However, the present invention is not limited to the following embodiments, and various modifications are possible without altering the essence of the invention. Furthermore, in this specification, any combination of preferred embodiments can be adopted as long as technical consistency can be maintained. For example, one of the preferred numerical ranges can be arbitrarily combined with the other.

[0033] <<1. Coated Phosphor Particles>> A schematic cross-sectional view of the coated phosphor particles of this embodiment is shown in Figure 1. The coated phosphor particles (10) comprise phosphor particles (2) and a coating layer (4) provided on the surface of the phosphor particles. The coating layer (4) contains an inorganic filler (6) and a film-forming resin (8). The film-forming resin (8) and inorganic filler (6) contained in the coating layer (4) exist in a mixed state. Such coated phosphor particles can maintain high luminescence characteristics even under harsh high temperature and high humidity environments. They also have the advantage of exhibiting little degradation in properties even when compounded with a matrix resin.

[0034] [1] Phosphorescent particles Phosphorescent particles are particles that have fluorescence properties. Here, fluorescence properties refer to the property of absorbing high-energy, short-wavelength light (excitation light), and when the electrons excited by this absorption return to the ground state, they emit low-energy, long-wavelength light. Also, phosphorescent particles are inorganic particles. That is, they are composed of inorganic materials. As long as they are inorganic particles with fluorescence properties, the material and dimensions of phosphorescent particles are not particularly limited. Although not limited, examples of materials for phosphorescent particles include oxides, nitrides, oxynitrides, sulfides, oxysulfides, oxyfluorides, halides, aluminates, and / or halophosphate chlorides.

[0035] Preferably, the phosphor particles contain, as a main component, a material (phosphor material) having an excitation band in a wavelength range of 300 to 500 nm and an emission peak in a wavelength range of 500 to 780 nm, for example, a material that emits red, yellow or green light. Specifically, as a material that absorbs blue excitation light and emits red fluorescence (red phosphor material), CaS:Eu, SrS:Eu, CaAlSiN ３ :Eu, CaSiN ３ :Eu, (Ca, Sr) ２ Si ５ N ８ :Eu, and the like. As a material that absorbs blue light and emits yellow fluorescence (yellow phosphor material), (Sr, Ba, Ca) ２ SiO ４ :Eu, (Y, Gd) ３ (Al, Ga) ５ O １２ :Ce, CaGa ２ S ４ :Eu, La ３ Si ６ N １１ :Ce, and the like. As a material that absorbs blue excitation light and emits green fluorescence (green phosphor material), SrAl ２ O ４ :Eu, SrGa ２ S ４ :Eu, SrBaSiO ４ :Eu, Ba ３ Si ６ O １２ N ２ :Eu, Si ２ Al ４ O ４ N ４ :Eu, Sr ３ Si １３ Al ３ O ２ N ２１ :Eu, Ca ３ Sc ２ Si ３ O １２ :Ce, CaSc ２ O ４ :Ce, and the like.

[0036] Particularly preferably, the phosphor particles contain a sulfide fluorescent material as the main component. Sulfide fluorescent materials are fluorescent materials composed of sulfides and have the characteristics of high luminescence efficiency and a narrow-band emission peak shape. Therefore, they are suitable as materials for high-resolution display components such as displays. As red sulfide fluorescent materials, (Ca,Sr)S:Eu, (Zn,Cd)(S,Se):Ag,Ba ２ ZnS ３ Examples include Mn. Alternatively, materials may be used with calcium sulfide (CaS) as the base, containing Eu as the luminescent center (activator), and further containing sensitizers (co-activators) such as Mn, Li, Cl, Ce and / or Gd. Examples of green sulfide fluorescent materials include (Ca, Sr, Ba)(Al, Ga, In). ２ S ４ Examples include sulfide thiogallate materials represented by Eu. Examples of blue sulfide fluorescent materials include SrS:Ce, (Sr,Ca)Ga ２ S ４ : Ce, BaAl ２ S ４ : Eu, Ba ２ SiS ４ Examples include Ce.

[0037] From the viewpoint of increasing the luminescence efficiency of the molded body (wavelength conversion member) and achieving uniform emission, the average particle size of the coated phosphor particles is preferably 0.3 μm to 30 μm, and more preferably 0.5 μm to 15 μm. The average particle size of the coated phosphor particles can be determined by measuring the particle size distribution using a laser diffraction / scattering particle size distribution analyzer (for example, MT3300EXII manufactured by Microtrac-Bell Co., Ltd.) in accordance with JIS Z 8825:2013, and then determining the cumulative 50% diameter by volume from the obtained particle size distribution. Furthermore, if the coated phosphor is incorporated into the molded body, the average particle size can also be determined by cutting out a cross-section of the molded body and observing the cross-section with a scanning electron microscope (SEM), as described later.

[0038] [2] Coating layer The coating layer is provided on part or all of the surface of the phosphor particles. The coating layer contains an inorganic filler and a film-forming resin, such that the inorganic filler and the film-forming resin are present in a mixed state. If the amount of film-forming resin is large, it can be said that the inorganic filler is present in a dispersed state within the film-forming resin. In either case, the inorganic filler and the film-forming resin do not form separate layers, but are present on the particle surface in a mixed and integrated state. By providing such a coating layer on the surface of the phosphor particles, the moisture heat resistance of the phosphor particles is significantly improved, and the degradation of properties when compounded with the matrix resin is suppressed.

[0039] From the viewpoint of facilitating particle size control of the coated phosphor particles and improving moisture heat resistance, the proportion of inorganic filler in the coating layer is preferably 30% to 99% by mass, and more preferably 50% to 95% by mass. Similarly, the proportion of film-forming resin in the coating layer is preferably 1% to 70% by mass, and more preferably 5% to 50% by mass.

[0040] Furthermore, the average thickness of the coating layer is preferably 0.05 μm or more and 10 μm or less, and more preferably 0.07 μm or more and 1.0 μm or less. By setting the average thickness of the coating layer to 0.05 μm or more, it is possible to fully exhibit the function of protecting the phosphor particles from moisture and other factors that cause phosphor degradation, and as a result, the effect of improving the resistance to humid heat when used as a display material can be made even more pronounced. By setting the average thickness of the coating layer to 10 μm or less, it is possible to suppress the decrease in luminescence intensity due to an increase in the proportion of non-luminescent coating layer.

[0041] The average thickness of the coating layer is determined by scanning electron microscopy (SEM) observation of the cross-section of the coated phosphor particle. Specifically, if the phosphor particle is spherical, the thickness of the coating layer is measured by SEM observation at 20 points, with 0° being the 12 o'clock position from the center, at 0° + 18° × n (n = 1 to 20), and the average thickness is calculated. On the other hand, if the phosphor particle is non-spherical, the average thickness is calculated similarly from SEM observation, centered on the intersection of the longest major axis from both ends of the particle interface and the minor axis perpendicular to it. When observing the particles, since the measurement sample contains many particles, one particle is chosen to focus on. In this case, when observing multiple particles, there may be a mixture of particles that fall within the average thickness range and those that do not. In such cases, if there is one or more coated phosphor particles that fall within the average thickness range, it can be understood that these are coated phosphor particles obtained by the present invention. In other words, even if there are some differences in quality, if there is one or more particles that fall within the range, it is highly probable that a coated phosphor exhibiting the desired properties has been obtained as an overall trend. Naturally, it is preferable that the proportion of particles that fall within the average thickness range is greater than the total number of particles that do not fall within the average thickness range. Specifically, during SEM observation, a field of view is determined that contains 20 phosphor particles with a coating layer in the same field of view, and each particle is observed within that field of view by high-magnification observation. It is preferable that at least one out of 20 particles falls within the average thickness range, it is even more preferable that five or more out of 20 particles fall within the average thickness range, and it is particularly preferable that ten or more out of 20 particles fall within the average thickness range.

[0042] It is preferable that, per 100 parts by mass of phosphor particles, the amount of inorganic filler contained in the coating layer is 0.5 parts by mass or more and 50 parts by mass or less, and the amount of film-forming resin is 0.01 parts by mass or more and 20 parts by mass or less. Furthermore, it is more preferable that, per 100 parts by mass of phosphor particles, the amount of inorganic filler contained in the coating layer is 5 parts by mass or more and 30 parts by mass or less, and the amount of film-forming resin is 0.05 parts by mass or more and 5 parts by mass or less.

[0043] The coating layer may contain only inorganic fillers and film-forming resins, or it may contain other components. Other components include dispersants, heat stabilizers, processing aids, light diffusers, light stabilizers, ultraviolet absorbers, antioxidants, antifungal agents, flame retardants, fillers, strengtheners, crosslinking agents, reinforcing agents, lubricants, lightweight fillers, and colorants. However, if the content of other components is excessively high, the effects based on the inorganic fillers and film-forming resins may be insufficient. The total content of inorganic fillers and film-forming resins in the coating layer is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more. The coating layer may be a single layer or a laminate of multiple layers. However, a single layer is preferred.

[0044] (A) Inorganic filler The inorganic filler contained in the coating layer has the effect of improving the moisture heat resistance of the coated phosphor particles. As the material to be contained in the inorganic filler, it is preferable to use a material that has the effect of suppressing the reaction between the phosphor particles and moisture. Furthermore, it is preferable to use a material that absorbs outgassing from the phosphor particles, and it is desirable to use a material that does not impair the light absorption and light emission characteristics of the phosphor particles as much as possible. From the viewpoint of satisfying these requirements, it is preferable that the inorganic filler contains an oxide having one or more elements selected from the group consisting of silicon (Si), aluminum (Al), zinc (Zn), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and boron (B). Examples of such oxides include silicon oxide, aluminum oxide, zinc oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, and boron oxide. Among these oxides, silicon oxide (silica) and / or aluminum oxide (alumina) are preferred from the viewpoint of further improving the moisture resistance of the phosphor. Among these, colloidal silica dispersed in a solvent is more preferred, and fine colloidal silica with an average particle size (D50) of 30 nm or less is particularly preferred. This is because fine colloidal silica can uniformly improve moisture resistance. The D50 of colloidal silica is measured by dynamic light scattering. Furthermore, the inorganic filler may contain only one type of oxide, or it may contain multiple types of oxides.

[0045] The inorganic filler may be composed of a composite oxide containing multiple types of the above-mentioned elements (Si to B). For example, barium borate (Ba ｘ B ｙ O ｚ Examples of compounds represented by ) (where x is 1 or more and 3 or less, y is 2 or more and 4 or less, and z is 4 or more and 7 or less) include the following: In this case, the molar ratio of Ba to O, z / x, is preferably 1.3 or more and 7.0 or less. The molar ratio of Ba to B, y / x, is preferably 0.5 or more and 4.0 or less. The molar ratio of B to O, z / y, is preferably 1.3 or more and 3.5 or less. Ba ｘ B ｙ O ｚ It is preferable that the material is a crystalline compound. Phosphor particles containing sulfide phosphors as the main component may release sulfur-based gases as outgassing during use. Since sulfur-based gases can corrode metal components, it is preferable to suppress their release. In this regard, crystalline barium borate has the function of trapping sulfur-based gases between the crystal lattice and forming a composite compound containing metal and sulfur. Therefore, using crystalline barium borate as an inorganic filler material makes it possible to suppress the release of sulfur-based gases and corrosion of metal components.

[0046] From the viewpoint of forming a uniform coating layer with few voids and improving the moist heat durability of the coated phosphor, the average particle size of the inorganic filler is preferably 0.005 μm to 20 μm, and more preferably 0.01 μm to 5 μm. The average particle size can be determined by measuring and analyzing it using a method in accordance with JIS Z 8825:2013, i.e., a laser diffraction / scattering particle size distribution analyzer (e.g., MT3300EXII manufactured by Microtrac-Bell Co., Ltd.), or a method in accordance with ISO 22412:2017, i.e., a dynamic light scattering particle size distribution analyzer (e.g., a nanoparticle size analyzer NANOTRAC FLEX manufactured by Microtrac-Bell Co., Ltd.). The appropriate method should be selected according to the detectable particle size range.

[0047] (B) Film-forming resin The film-forming resin has the function of filling the voids in the inorganic filler and making the coating layer dense. It is desirable that the film-forming resin be chemically stable, that is, inert to acidic substances, basic substances, oxidizing substances, and reducing substances. As mentioned above, sulfurous gases (outgassing) may be generated from the phosphor particles. In this case, if the activity of the film-forming resin is high, the properties of the film-forming resin may deteriorate due to reaction with the sulfurous gas. Also, when manufacturing a wavelength conversion component from coated phosphor particles and a matrix resin, if the activity of the film-forming resin is excessively high, the reaction between the film-forming resin and highly reactive components such as acidic functional groups and photoradical polymerizers contained in the matrix resin will proceed, and the long-term durability of the wavelength conversion component may be impaired. By using a chemically stable film-forming resin, the occurrence of such problems can be suppressed.

[0048] Furthermore, it is desirable that the film-forming resin has low compatibility with the matrix resin and low solubility in organic solvents. That is, when preparing a wavelength conversion component from a mixture of matrix resin and coated phosphor particles (phosphor resin composition), if the film-forming resin and the matrix resin are easily compatible, the coating layer of the coated phosphor particles may dissolve, potentially impairing the protective function of the coating layer. Also, organic solvents may be added to adjust the viscosity of the phosphor resin composition. In this case, if the film-forming resin is easily soluble in the organic solvent, the coating layer may dissolve, potentially impairing its protective function. Solubility (compatibility) of the film-forming resin is important to avoid such problems. In addition, when alkali-soluble resins, which will be discussed later, are used, the polymers constituting the alkali-soluble resin have acidic groups. If the coating-forming resin dissolves or decomposes due to these acidic groups, the protective function of the coating layer may also be impaired. From these viewpoints, it is desirable that the film-forming resin is insoluble in concentrated hydrochloric acid and / or propylene glycol monomethyl ether. Here, insolubility of the coating resin means that the amount of coating resin that dissolves in 100 mL of solvent at 25°C is 0.1 g or less, or that no chemical change involving decomposition proceeds at room temperature.

[0049] Furthermore, it is desirable that the film-forming resin has a high light transmittance. By using a film-forming resin with high light transmittance, the decrease in the absorption and emission characteristics of the phosphor particles placed beneath the coating layer is suppressed. Specifically, a resin with a total light transmittance of 50% or more, more preferably 80% or more, is desirable. Note that the total light transmittance is the value measured for a resin sheet with a film thickness of 1 μm.

[0050] As a film-forming resin that satisfies the above requirements, while not limited to the above, a resin containing at least one constituent unit selected from the group consisting of olefin units, silicone units, alkylene oxide units, amide units, and urethane units is preferred. Among these, a resin containing at least one selected from the group consisting of olefin units, silicone units, and alkylene oxide units, which have particularly high light transmittance, is more preferred. Furthermore, from the viewpoint of light transmittance and resistance to photodegradation, a resin containing an aliphatic parent structure that does not contain aromatics is even more preferred. Note that a unit is a constituent unit of the film-forming resin, that is, an element derived from the monomer structure. Monomers can be of the addition type or condensation type. When an addition type monomer is used, an addition polymer is obtained in which repeating unit structures are linked by bond cleavage of unsaturated groups. When a condensation type monomer is used, a condensation polymer is obtained by sequentially carrying out a reaction in which reactive functional groups condense with the elimination of low molecular weight molecules.

[0051] When the film-forming resin contains olefin units, examples of olefin units include at least one unit selected from the group consisting of ethylene, propylene, 1-butene, 1,3-butadiene, isobutylene, isoprene, 4-methyl-1-pentene, cyclopentene, cyclopentadiene, cyclohexene, norbornene, dicyclopentadiene, and structures obtained by adding hydrogen to these. From the viewpoint of improving the chemical and optical stability of the coating layer, the bromine value of the film-forming resin containing olefin units is preferably 20 g or less, and more preferably 5 g or less. Here, the bromine value is the amount of halogen that reacts with 100 g of the substance, converted to grams of bromine.

[0052] When the film-forming resin contains silicone units, the average composition formula is: [R １ SiO３／２ ] ｍ [R ２ SiO] ｎ (R １ , R ２ Each of these is a monovalent organic group having 1 to 20 carbon atoms, either identical or different, with m+n being 1.0. It is preferable that the silicone unit represented by ( ) is included. The coating layer obtained by condensing the silanol residues has excellent film strength.

[0053] Regardless of which units are included, from the viewpoint of film strength and thermal stability of the coating layer, the weight-average molecular weight of the film-forming resin is preferably 300 or more, and more preferably 500 or more. Furthermore, the softening point of the film-forming resin, as measured by ASTM D6090, is preferably 100°C or higher, and more preferably 120°C or higher. For example, the film-forming resin may contain olefin units as constituent units, and the weight-average molecular weight of the film-forming resin may be 300 or more. Also, the film-forming resin may contain olefin units as constituent units, and the softening point, as measured by ASTM D6090, may be 100°C or higher.

[0054] <<2. Manufacturing of Coated Phosphor Particles>> The manufacturing method of the coated phosphor particles in this embodiment is not limited as long as it satisfies the requirements described above. However, a preferred method for manufacturing coated phosphor particles includes the steps of: dissolving a film-forming resin in a good solvent, and further adding and mixing phosphor particles and an inorganic filler to prepare a raw material solution (raw material solution preparation step); adding a poor solvent to this raw material solution to precipitate the film-forming resin (precipitation step); and removing the good solvent and the poor solvent from the raw material solution from which the coating liquid resin has precipitated to obtain coated phosphor particles (solvent removal step). Each step will be described below.

[0055] <Preparation of Raw Material Solution> In the preparation of the raw material solution, the film-forming resin is dissolved in a good solvent. In addition, phosphor particles and inorganic fillers are added to the good solvent and mixed to prepare the raw material solution. The resulting raw material solution is a slurry-like liquid containing the dissolved film-forming resin, as well as dispersed phosphor particles and inorganic fillers. As the good solvent, a solvent is used that has high solubility for the film-forming resin and does not cause aggregation of the inorganic filler. Specifically, a solvent is used that has higher solubility for the film-forming resin and higher inorganic filler dispersibility than the poor solvent described later. Here, high solubility for the film-forming resin means that the amount of solubility of the film-forming resin in 100 mL of solvent at 25°C is 1 g or more. The types of solvents that can be used vary depending on the film-forming resin and inorganic filler, so it is difficult to determine this uniquely. For example, if the film-forming resin consists of olefin units and the inorganic filler is colloidal silica (TOL-ST manufactured by Nissan Chemical Corporation) dispersed in toluene solvent, a suitable good solvent is methylcyclohexane. Furthermore, as long as the desired raw material solution is obtained, the order in which the raw materials (film-forming resin, phosphor particles, inorganic filler) are added is not restricted. The film-forming resin may be dissolved in a good solvent, and then the phosphor particles and inorganic filler may be added, or vice versa.

[0056] <Precipitation Process> In the precipitation process, a poor solvent is added to the raw material solution. Upon addition of the poor solvent, the film-forming resin dissolved in the raw material solution begins to precipitate, and at the same time, the inorganic filler aggregates and precipitates. The precipitated film-forming resin adheres to the surface of the phosphor particles, incorporating the inorganic filler, and there it forms a coating layer. As the poor solvent, a solvent with low solubility for the film-forming resin and low dispersibility of inorganic fillers is used. Here, low solubility for the film-forming resin means that the amount of coating-forming resin dissolved in 100 mL of solvent at 25°C is 0.1 g or less. The types of solvents that can be used vary depending on the film-forming resin and inorganic filler, so it is difficult to determine this uniquely. For example, if the coating-forming resin consists of olefin units and the inorganic filler is colloidal silica (TOL-ST manufactured by Nissan Chemical Corporation) dispersed in toluene solvent, isopropyl alcohol is a suitable poor solvent.

[0057] <Solvent Removal Process> In the solvent removal process, solvents (good solvents and poor solvents) are removed from the raw material liquid from which the film-forming resin and inorganic filler have been precipitated. The method of solvent removal is not particularly limited. For example, the solvent can be removed by operations such as distillation or centrifugation. Alternatively, the solvent may be removed by volatilization of the raw material liquid by heat treatment. In this case, it is preferable to perform the heat treatment at a low temperature, for example, 300°C or lower, in order to prevent deterioration of the film-forming resin.

[0058] <Other Processes> If necessary, other processing steps may be included. For example, a step may be included to wash the processed material (coated phosphor particles) obtained after solvent removal, or a particle size adjustment step may be included to classify the processed material.

[0059] In this way, coated phosphor particles of this embodiment can be obtained. With this manufacturing method, the loss of inorganic fillers and film-forming resins used as raw materials during manufacturing is minimized, so coated phosphor particles can be obtained with a good material balance. Furthermore, the obtained coated phosphor particles have a homogeneous coating layer and therefore exhibit excellent properties.

[0060] <<3. Phosphor Resin Composition>> The phosphor resin composition of this embodiment will be described with reference to Figure 2. The phosphor resin composition (20) includes the coated phosphor particles (10) and the matrix resin (12) described above. The phosphor resin composition (20) is made by mixing the coated phosphor particles (10) and the matrix resin (12). The phosphor resin composition (20) is also a precursor of the wavelength conversion member. That is, a molded body obtained by molding the phosphor resin composition (20) can be used as a wavelength conversion member. In the phosphor resin composition (20) and its molded body (wavelength conversion member), the coated phosphor particles (10) are contained in a dispersed state in the matrix resin (12).

[0061] [1] Coated Phosphor Particles The details of the coated phosphor particles are as described above. Specifically, the coated phosphor particles comprise phosphor particles and a coating layer provided on the surface of the phosphor particles. The coating layer contains an inorganic filler and a film-forming resin, and the inorganic filler and the film-forming resin exist in a mixed state.

[0062] [2] Matrix Resin The matrix resin acts as a binder that binds the coated phosphor particles in the phosphor resin composition. It is desirable to select a matrix resin material that can uniformly disperse the coated phosphor particles and can be applied to various molding processes. Such materials are not limited to, but include resins that exhibit chemical reactivity such as UV curability and alkali solubility.

[0063] The matrix resin may include an ultraviolet-curable resin. Using an ultraviolet-curable resin makes it possible to produce molded articles by ultraviolet irradiation. The ultraviolet-curable resin is an ultraviolet-curable monomer, oligomer, and / or polymer having one or more double bonds. These resins harden by ultraviolet irradiation to form molded articles with sufficient mechanical strength. In this specification, monomer means a compound that does not contain a repeating unit structure, oligomer means a compound that has a structure with repeating units of monomer as a main chain and has an average number of repeating units of 2 or more and less than 100, and polymer means a compound that has a structure with repeating units of monomer as a main chain and has an average number of repeating units equal to or greater than the average number of repeating units of oligomer. Note that one type of material may be used alone as a monomer, oligomer, or polymer, or multiple types of materials may be used in combination.

[0064] As the UV-curable resin used in the matrix resin, (meth)acrylic monomers, oligomers, and / or polymers are preferred. These resins have the advantage of being easy to design materials with high transparency and desired flexibility. Among these, (meth)acrylic polyfunctional oligomers are particularly preferred. This is because they have viscosity characteristics suitable for molding, and the resulting molded articles have a high crosslink density and excellent thermal and mechanical durability. Here, (meth)acrylic monomers, oligomers, and / or polymers refer to compounds having an acryloyl group or a methacryloyl group, i.e., a (meth)acryloyl group. Furthermore, if there is one (meth)acryloyl group, it is described as monofunctional, and if there are two or more (meth)acryloyl groups, it is described as polyfunctional. Examples of (meth)acrylic oligomers include urethane (meth)acrylate with a polybutadiene skeleton, urethane (meth)acrylate with a hydrogenated polybutadiene skeleton, urethane (meth)acrylate with a polycarbonate skeleton, urethane (meth)acrylate with a polyether skeleton, urethane (meth)acrylate with a polyester skeleton, urethane (meth)acrylate with a castor oil skeleton, isoprene-based (meth)acrylate, hydrogenated isoprene-based (meth)acrylate, and epoxy (meth)acrylate. Examples of (meth)acrylic polymers include those obtained by copolymerizing acrylic acid to an acrylic polymer to which glycidyl methacrylate has been added.

[0065] If the matrix resin contains an ultraviolet-curable resin, the matrix resin may further contain a photopolymerization initiator. The photopolymerization initiator promotes the polymerization reaction of the resin and the resulting curing reaction by ultraviolet irradiation. Examples of photopolymerization initiators include acylphosphine oxide-based photopolymerization initiators such as ethyl-2,4,6-trimethylbenzylphenylphosphine and (2,4,6-trimethylbenzoyl)-phenylphosphine oxide; α-ketol compounds such as 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and 1-hydroxycyclohexylphenylketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropan-1-one; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether; and benzyldimethyl ketone. Examples include ketal compounds such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketones; acylphosphonates; and α-hydroxyacetophenones such as 2-hydroxy-1-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl-2-methylpropan-1-one. Preferably, 2,2-dimethoxy-2-phenylacetophenone or 2-hydroxy-1-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl-2-methylpropan-1-one can be used.As a photopolymerization initiator, one material may be used alone, or a combination of multiple materials may be used. Preferably, the matrix resin comprises at least a (meth)acrylic polyfunctional oligomer and a photopolymerization initiator.

[0066] The photopolymerization initiator is used in any appropriate amount. The amount of the photopolymerization initiator is preferably 0.1 parts by mass to 10 parts by mass, and more preferably 0.5 parts by mass to 5 parts by mass, per 100 parts by mass of the base resin (UV-curable resin). If the amount of photopolymerization initiator is 0.1 parts by mass or more, the curing of the base resin can be sufficiently advanced when UV irradiation is performed. If the amount of photopolymerization initiator is 10 parts by mass or less, yellowing of the cured film (coating layer) and a decrease in the storage stability of the phosphor resin composition can be suppressed.

[0067] The matrix resin may contain an alkali-soluble resin. Using an alkali-soluble resin enables molding (patterning) using an alkaline developer. Various polymers conventionally used in photosensitive resin compositions can be used as the alkali-soluble resin. Examples of such polymers include (meth)acrylic acid copolymers, itaconic acid copolymers, crotonic acid copolymers, maleic acid copolymers, partially esterified maleic acid copolymers, phenol novolac resins, cresol novolac resins, polyimide precursors containing polyamic acid, and polyimide resins having carboxyl groups or hydroxyl groups in their side chains, which are organic polymer polymers soluble in alkaline developers. Note that (meth)acrylic acid copolymer refers to both acrylic acid copolymers and methacrylic acid copolymers. Among these, polyamic acid, polyimide, epoxy resins, (meth)acrylic resins, and phenolic resins are more preferred. These polymers may be used individually as the alkali-soluble resin, or multiple polymers may be used in combination.

[0068] The alkali-soluble resin is preferably one whose weight-average molecular weight is 5,000 or more and 50,000 or less, and whose acid value is 50 mg KOH / g or more and 300 mg KOH / g or less. Furthermore, from the viewpoint of facilitating control of alkali development characteristics, it is preferable to use (meth)acrylic monomers, oligomers and / or polymers in combination.

[0069] As the matrix resin, a (meth)acrylic polymer possessing both UV-curable and alkali-soluble properties may be used. Specifically, such a polymer may be obtained by copolymerizing acrylic acid and adding glycidyl methacrylate, with an appropriate amount of carboxyl derived from acrylic acid remaining.

[0070] The matrix resin is not limited to UV-curable resins or alkali-soluble resins; it may also be a non-reactive resin. For example, it may be polystyrene resin, acrylic resin, methacrylic resin, epoxy resin, polyurethane resin, polyester resin, alkyd resin, polycarbonate resin, polyarylate resin, polysulfone resin, and / or polyamide resin. Alternatively, a UV-curable resin / alkali-soluble resin may be used in combination with a non-reactive resin.

[0071] The proportion of matrix resin in the phosphor resin composition is not particularly limited. However, the amount of matrix resin per 100 parts by mass of coated phosphor particles is preferably 10 parts by mass or more and 5000 parts by mass or less, and more preferably 30 parts by mass or more and 1000 parts by mass or less.

[0072] [3] Other Components The phosphor resin composition may consist only of coated phosphor particles and matrix resin, or it may contain other components. Other components include additives that may be added as needed. Specifically, these include waxes, metal soaps, lubricants, heat stabilizers, plasticizers, processing aids, light diffusers, light stabilizers, ultraviolet absorbers, antioxidants, antifungal agents, flame retardants, fillers, strengtheners, crosslinking agents, reinforcing agents, lubricants, antifogging agents, antistatic agents, conductive materials, foaming agents, lightweight fillers, and colorants.

[0073] <<4. Wavelength Conversion Member>> The wavelength conversion member of this embodiment is a molded body of the phosphor resin composition described above. Specific examples of the wavelength conversion member, though not limited to these, include a wavelength conversion sheet comprising a transparent substrate film and a cured product (molded body) of the phosphor resin composition in contact with the transparent substrate film, and a wavelength conversion panel comprising a glass substrate and a cured product (molded body) of the phosphor resin composition in contact with the glass substrate.

[0074] The transparent substrate film used in the wavelength conversion sheet is selected from materials having the shape of a thin plate, sheet, or film to which a molded body of a phosphor resin composition can be bonded, and plastic materials are examples of such materials. Here, when used for applications that transmit light from the substrate, it is preferable to use a substrate with high light transmittance, such as a plastic material with high light transmittance or a substrate made of glass. Among these, from the viewpoint of use in wavelength conversion sheets for flat panel displays, it is more preferable to use a plastic film that is flexible and plastic and has high light transmittance. Examples of such plastic films include those made of polyester such as polycarbonate, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), poly(meth)acrylate such as polymethyl methacrylate (PMMA), polycarbonate, cyclic polyolefin (COP) or cyclic olefin copolymer (COC), polystyrene, hydrogenated styrene polymer, or hydrogenated styrene copolymer. In particular, from the viewpoint of transparency and heat resistance, it is especially preferable to use PET, PEN, COP, COC, or PMMA.

[0075] As transparent substrate films or glass substrates, those that have been surface-treated before the application of the phosphor resin composition may be used to improve surface polarity, more specifically, wettability and chemical affinity to the phosphor resin composition. Examples of surface treatments include corona treatment, primer treatment, flame treatment, fluorination, or plasma treatment. As transparent substrate films, those having a barrier function for the purpose of reducing the permeability of gases such as water vapor and oxygen may be used.

[0076] The thickness of the transparent substrate film is set appropriately according to its application. For example, from the viewpoint of use as a wavelength conversion sheet, it is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 25 μm or more. Furthermore, this thickness is preferably 5000 μm or less, more preferably 2500 μm or less, and even more preferably 1000 μm or less.

[0077] The thickness of the resin layer (molded body) formed from the phosphor resin composition is appropriately selected according to its application. For example, from the viewpoint of obtaining high color conversion efficiency and light extraction efficiency, the resin layer thickness is preferably 5 μm or more, more preferably 10 μm or more. Alternatively, the resin layer thickness is preferably 300 μm or less, more preferably 150 μm or less.

[0078] The method for molding the phosphor resin composition is not particularly limited and may be any known method. Examples include wire bar coating, roll coating, knife coating, blade coating, die coating (slit coating), gravure coating, dip coating, spray coating, spin coating, screen printing, extrusion, injection molding, and / or casting.

[0079] <<5. Light Source>> The light source of this embodiment comprises the wavelength conversion member and excitation source described above. In this light source, the light emitted from the excitation source is irradiated onto the wavelength conversion member. As a result, the phosphor contained in the wavelength conversion member is excited and emits light having a different wavelength from the light from the excitation source. A blue light-emitting LED with a wavelength of 420 nm to 500 nm is preferred as the excitation source. As long as the light from the excitation source is incident on the wavelength conversion member, the arrangement of the excitation source and the wavelength conversion member is not limited. Also, the color tone of the light emitted by the wavelength conversion member differs depending on the type of phosphor. The light source is, for example, a white light source.

[0080] <<6. Display>> The display (display device) of this embodiment is equipped with the light source described above. The display may be a known display such as a liquid crystal display, a mini LED display, or a μLED display.

[0081] The present invention will be described in more detail using the following examples and comparative examples. However, the present invention is not limited to the following examples.

[0082] (1) Preparation of coated phosphor particles [Example 1] In Example 1, Sr ０．８７ Eu ０．１３ Ga ２ S ４ Composition of SrGaS ４ Coated phosphor particles were prepared using EU particles (phosphor particles), petroleum resin (film-forming resin), colloidal silica (inorganic filler), methylcyclohexane (good solvent), and isopropyl alcohol (poor solvent). The specific preparation procedure was as follows.

[0083] A magnetic stirrer was placed inside a three-neck separable flask (capacity 500 mL) equipped with a thermometer, a nitrogen gas introduction line, and an atmospheric vent. Then, 0.1 g of petroleum resin (OP501, manufactured by ENEOS Material Co., Ltd., softening point: 140°C, weight-average molecular weight: 610) and 15.0 g of methylcyclohexane were added to the flask, and the contents of the flask were stirred using the stirrer at room temperature for 1 hour to obtain a solution. Next, 5.0 g of phosphor matrix particles (phosphor particles) were added to the obtained solution and stirred at room temperature for 1 hour to obtain a slurry.

[0084] Furthermore, colloidal silica (TOL-ST, manufactured by Nissan Chemical Corporation): 2.6 g (SiO ２ Mass equivalent amount: 1.0 g), barium tetraborate BaB ４ O ７0.1 g by mass was added to the slurry and stirred at room temperature for 1 hour, then 250 g of isopropyl alcohol was added and stirred at room temperature for 1 hour. Barium tetraborate was prepared by mixing reagent (manufactured by Kanto Chemical Co., Ltd.) with ethanol in a magnetic pot to a solid content of 3 wt%, adding 0.3 mm zirconia balls at 2000 wt% to the slurry, and performing a ball milling process at a rotation speed of 300 rpm for 24 hours. After that, the zirconia balls were removed from the slurry and the resulting mixture was used. Then, nitrogen was introduced into the flask at a flow rate of 2 L / min, and the flask was heated using a water bath. The solvent was removed when the thermometer placed inside the flask showed 75°C. After that, the powder obtained by drying was collected and placed in a vacuum heat dryer, and dried for 24 hours under conditions of a vacuum of 10 Pa or less and a set temperature of 60°C to obtain coated phosphor particles.

[0085] [Examples 2 to 15] The types and amounts of phosphor particles, inorganic fillers, and coating resins were changed as shown in Table 1 below. Otherwise, coated phosphor particles were prepared using the same procedure as in Example 1.

[0086]

[0087] (2) Phosphor resin composition A was prepared using the coated phosphor particles from Examples 1 to 6 and Examples 12 to 15, and urethane acrylate as the matrix resin. The specific preparation procedure was as follows.

[0088] First, 0.15 g of coated phosphor particles were placed in a plastic cup (capacity 10 mL). Then, 1.00 g of urethane acrylate (EBECRYL 8413, manufactured by Daicel Ornex Co., Ltd.), 0.83 g of 2-methoxyethyl methacrylate (MEMA), and 0.02 g of 2,4,6-trimethylbenzoyl-diphenyl phosphorine oxide (TPO) were added to the cup. Next, the contents of the cup were mixed using a stirring and defoaming device (SK-300S2, manufactured by Shashin Kagaku Co., Ltd.) at a rotation speed of 1000 rpm for 30 minutes, and then defoamed at a rotation speed of 2000 rpm for 5 minutes. In this way, phosphor resin compositions A of Examples 1 to 6 and Examples 12 to 15 were prepared. The material amounts used in the production of phosphor resin composition A are shown in Table 2 below.

[0089] (3) Wavelength conversion members A were fabricated using the phosphor resin compositions A of Examples 1 to 6 and 12 to 15. The specific fabrication procedure was as follows.

[0090] A 100 μm thick polyethylene terephthalate (PET) film (Lumirror T60, manufactured by Toray Industries, Inc.) was prepared as a base material, and phosphor resin composition A was applied onto this PET film. At this time, an applicator was used to apply the film under conditions that the cured film thickness would be 100 μm. Subsequently, a PET film (Lumirror T60) was placed on top of the coated film and attached using a rubber roller to create a laminate with PET films attached to both sides. This laminate was placed in a handy-type UV curing device (manufactured by Live Terrace Technologies Co., Ltd.), and further irradiated with ultraviolet light obtained from a metal halide lamp (Fe) for 120 seconds. In this way, wavelength conversion members A of Examples 1 to 15 were manufactured.

[0091] (4) Preparation of phosphor resin composition B Phosphor resin composition B was prepared using the coated phosphor particles from Example 1 and Examples 7 to 15, and using an alkali-soluble resin (alkali-soluble resin 1) as the matrix resin. The specific preparation procedure was as follows.

[0092] In preparing phosphor resin composition B, an alkali-soluble resin was first prepared. First, 10 g of methacrylic acid, 20 g of methyl methacrylate, 70 g of isobornyl methacrylate, 100 g of propylene glycol monomethyl ether acetate, and 2 g of n-dodecyl mercaptan were added to a four-neck separable flask (capacity 500 mL) equipped with a thermometer, nitrogen gas introduction line, Liebig condenser, and mechanical stirrer. Then, nitrogen gas was introduced into the flask at a flow rate of 0.5 L / min, and the contents of the flask were stirred for 15 minutes. Next, while stirring, the temperature of the contents of the flask was raised to 65°C using a water bath, and 0.5 g of an azo initiator (V-601, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and stirred for 2 hours. After that, the temperature of the contents was raised to 75°C, and another 0.5 g of V-601 was added and stirred for 2 hours. While maintaining the temperature at 75°C, 0.5 g of V-601 was added and the mixture was stirred for 2 hours. After that, the temperature of the contents was lowered to 50°C, the gas introduction line was switched, and air was introduced at a flow rate of 0.5 L / min. To this, 2 g of glycidyl methacrylate and 0.05 g of 4-methoxyphenol were added and the mixture was stirred for 24 hours. The resulting solution was cooled to room temperature to obtain alkali-soluble resin 1.

[0093] Next, alkali-soluble resin 1 (0.4 g by solid weight) was placed into a plastic cup (capacity 10 mL), and then coated phosphor particles: 0.5 g, trimethylolpropane triacrylate (TMPTA): 0.08 g, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (Omnirad 907): 0.02 g were added to the cup. Then, using a stirring and degassing device (SK-300SII, manufactured by Shashin Kagaku Co., Ltd.), the contents of the cup were mixed at a rotation speed of 1000 rpm for 30 minutes, and then degassed at a rotation speed of 2000 rpm for 5 minutes. In this way, phosphor resin compositions B of Examples 1 and 7-15 were prepared. The material amounts used in the production of phosphor resin composition B are shown in Table 2 below.

[0094] (5) Wavelength conversion member B was fabricated using each of the phosphor resin compositions B of Examples 1 and 7 to 15. The specific fabrication procedure was as follows.

[0095] A 10 cm x 10 cm alkali-free glass substrate (CORNING XG-□100-0.5) was prepared as the base material, and phosphor resin composition B was applied to this glass substrate. At this time, an applicator was used to apply the coating under conditions that the dry film thickness was 15 μm, thereby obtaining a coated film. Next, the coated film on the glass substrate was placed on a hot plate heated to 110°C and dried for 10 minutes. The dried coated film on the glass substrate was placed in a handy-type UV curing device (Live Terrace Technologies Co., Ltd.), and further irradiated with ultraviolet light obtained from a metal halide lamp (Fe) for 120 seconds. Wavelength conversion members B of Examples 1 and 7-15 were produced by curing the phosphor resin composition made of acrylic ultraviolet-curable resin in this way.

[0096]

[0097] (6) The coated phosphor particles and wavelength conversion members obtained in Evaluation Examples 1 to 15 were evaluated for various properties as follows.

[0098] <Particle Size Distribution> The particle size distribution of coated phosphor particles was determined using a laser diffraction / scattering particle size distribution analyzer (MT3300EXII, Microtrac-Bell Co., Ltd.) in accordance with JIS Z 8825:2013. Specifically, the sample (coated phosphor particles) was subjected to ultrasonic treatment at an output of 40W for 3 minutes, and then the particle size distribution was measured to determine the average diameter (D50) based on volume.

[0099] <Luminous Efficiency> The luminous efficiency (external quantum efficiency; EQE) of coated phosphor particles was measured using a spectrofluorometer (FP-8500, JASCO Corporation). The measurement was performed under conditions of an excitation wavelength of 450 nm.

[0100] <SEM Observation> Cross-sectional observation of molded products of phosphor resin compositions was performed using a scanning electron microscope (SEM) to evaluate the average thickness of the coating layer of coated phosphor particles. Specifically, molded products were processed using a cross-section polisher (JEOL IB-19520CCP) to prepare cross-sectional samples. Rough processing was performed at 6kV for 1 hour, followed by finishing processing at 3kV for 30 minutes. Next, the sample cross-sections were observed using a scanning electron microscope (Hitachi High-Tech SU7000; SEM). SEM images were taken at magnifications of 30,000 to 200,000x with automatic contrast adjustment.

[0101] <Brightness Maintenance Rate> Films of wavelength conversion members A and B were cut to a size of 2.5 cm x 2.5 cm and subjected to relative humidity tests: one for 500 hours in a LightSpec constant temperature and humidity chamber (SH-262, manufactured by ESPEC Corporation) at 85°C / 85%, and another for 100 hours at 85°C / 85%. The initial luminescence intensity (peak intensity of the phosphor's maximum emission wavelength) before the test and the luminescence intensity after the test were measured, and the ratio of the luminescence intensity after the test to the initial luminescence intensity was evaluated as the brightness maintenance rate (%). An integrating sphere-based optical measurement system (illumia plus2, manufactured by Labsphere Corporation) was used to measure the luminescence intensity.

[0102] (7) Evaluation results The evaluation results obtained for Examples 1 to 15 are summarized in Table 3 below.

[0103] Inorganic filler (SiO ２ A coating layer containing both phosphor particles (SrGa) and a film-forming resin (OP501, etc.) ２ S ４ In the example samples (Examples 1 to 11) provided on a surface of Eu or SrS:Eu, the external quantum efficiency (EQE) and EQE maintenance rate of the coated phosphor particles were relatively high (EQE 27-58%, EQE maintenance rate 87-100%). In addition, the brightness maintenance rate of the wavelength conversion member was also relatively high (brightness maintenance rate 34-97%).

[0104] In contrast, a coating layer containing only a film-forming resin (such as OP501) contains phosphor particles (SrGa ２ S ４In comparative examples (Examples 12 and 15) provided on a surface of Eu or SrS:Eu, the brightness maintenance rate of the wavelength conversion member was significantly low (brightness maintenance rate 0-3%). Also, inorganic filler (SiO ２ A coating layer containing only phosphor particles (SrGa) ２ S ４ In comparative examples (Examples 13 and 14) provided on the surface of the Eu (Luminance maintenance rate was relatively low, ranging from 0% to 7%).

[0105]

[0106] From the above results, it is understood that this embodiment provides coated phosphor particles that can maintain high luminescence characteristics even under harsh high-temperature and high-humidity environments, and that exhibit little degradation in properties even when compounded with a matrix resin.

[0107] 2. Phosphor particles 4. Coating layer 6. Inorganic filler 8. Film-forming resin 10. Coated phosphor particles 12. Matrix resin 20. Phosphor resin composition

Claims

1. Coated phosphor particles comprising phosphor particles and a coating layer provided on the surface of the phosphor particles, wherein the coating layer contains an inorganic filler and a film-forming resin, and the film-forming resin and the inorganic filler are present in a mixed state within the coating layer.

2. The coated phosphor particle according to claim 1, wherein the inorganic filler comprises an oxide having one or more elements selected from the group consisting of silicon (Si), aluminum (Al), zinc (Zn), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and boron (B).

3. The coated phosphor particle according to claim 1, wherein the film-forming resin is a resin comprising at least one constituent unit selected from the group consisting of olefin units and silicone units.

4. The coated phosphor particle according to claim 1, wherein the film-forming resin contains olefin units as constituent units, and the weight-average molecular weight of the film-forming resin is 300 or more.

5. The coated phosphor particles according to claim 1, wherein the film-forming resin contains olefin units as constituent units and has a softening point of 100°C or higher as measured by ASTM D6090.

6. The coated phosphor particle according to claim 1, wherein the proportion of the inorganic filler in the coating layer is 50% by mass or more and 95% by mass or less, and the proportion of the film-forming resin is 5% by mass or more and 50% by mass or less.

7. The coated phosphor particles according to claim 1, wherein the phosphor particles mainly consist of a sulfide fluorescent material.

8. The coated phosphor particles according to claim 1, wherein the average particle size of the coated phosphor particles is 0.3 μm or more and 30 μm or less.

9. A phosphor resin composition comprising coated phosphor particles and a matrix resin according to any one of claims 1 to 8, wherein the coated phosphor particles are dispersed in the matrix resin.

10. The phosphor resin composition according to claim 9, wherein the matrix resin comprises at least a (meth)acrylic polyfunctional oligomer and a photopolymerization initiator.

11. A wavelength conversion member which is a molded article of the phosphor resin composition according to claim 10.

12. A light source comprising the wavelength conversion member and excitation source described in claim 11.

13. A display comprising the light source described in claim 12.

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