Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K11/00—Luminescent materials, e.g. electroluminescent or chemiluminescent
  • C09K11/08—Luminescent materials, e.g. electroluminescent or chemiluminescent containing inorganic luminescent materials
  • C09K11/62—Luminescent materials, e.g. electroluminescent or chemiluminescent containing inorganic luminescent materials containing gallium, indium or thallium
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10H—INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
  • H10H20/00—Individual inorganic light-emitting semiconductor devices having potential barriers, e.g. light-emitting diodes [LED]
  • H10H20/80—Constructional details
  • H10H20/85—Packages
  • H10H20/852—Encapsulations
  • H10H20/854—Encapsulations characterised by their material, e.g. epoxy or silicone resins

Definitions

• the present invention relates to phosphor powders, phosphor resin compositions, phosphors, light-emitting elements, light-emitting devices, and display devices.
• Light-emitting devices that use light-emitting diodes (LEDs) that emit near-ultraviolet or blue light as a light source (excitation source) and combine this with phosphors are widely used in light-emitting devices such as lighting and backlights for mobile devices, as well as display devices such as displays.
• LEDs light-emitting diodes
• excitation source emission source
• the phosphor absorbs the light emitted by the LED (radiated light) and emits light of a different wavelength from the absorbed light. This makes it possible to obtain light emission of a different color tone from the LED emitted light. For example, by combining a blue-emitting LED (blue LED) with a green phosphor and/or red phosphor, it is possible to obtain green light, red light, or white light.
• Patent Document 1 which discloses applications of phosphors for LEDs, discloses a white light-emitting device that includes a light-emitting diode that emits blue light, a thiogallate-based green phosphor that emits green light, and an alkaline earth metal sulfide-based red phosphor that emits red light, and that emits white light by mixing the green light and the red light with a portion of the blue light (claim 3 of Patent Document 1).
• the white light-emitting device is used as a backlight source for lighting, notebook computers, etc. ([0002] of Patent Document 1).
• ⁇ LED displays have each of the sub-pixels R (red), G (green), and B (blue) made up of independent LEDs, and compared to LCD panels, they have the advantage of being able to produce images with higher brightness and a higher contrast ratio, with faster response speeds and lower power consumption. Also, compared to OLED displays, they have the advantage of being able to display images with higher brightness and no burn-in caused by deterioration.
• Patent Document 2 discloses a green phosphor in which element M (where element M is an element such as Mn) and element A (where element A is one or more metal elements other than element M and Al) are dissolved in a host crystal having the same crystal structure as a cubic spinel type AlON crystal (claim 1 of Patent Document 2).
• This green phosphor is applied to light-emitting elements such as white LEDs, and light-emitting devices such as lighting devices, backlight devices, image display devices, and signal devices that use these light-emitting elements ([0009] of Patent Document 2).
• Patent Document 3 discloses a phosphor that satisfies formula [1] : M1aM2bM3cOd (wherein M1 is an element such as Cr, M2 is mainly a divalent metal element, M3 is mainly a trivalent metal element, 0.0001 ⁇ a ⁇ 0.2, 0.8 ⁇ b ⁇ 1.2, 1.6 ⁇ c ⁇ 2.4, 3.2 ⁇ d ⁇ 4.8) and contains at least two elements selected from the group consisting of Li and the like (claim 1 of Patent Document 3).
• the phosphor is applied to various light-emitting devices such as the light-emitting section of an image display device and a lighting device (paragraphs [0185] and [0186] of Patent Document 3).
• Phosphor powders are usually made by pulverizing a compound that has been synthesized using the solid-phase method. During this process, the pulverization is carried out so that the particles that make up the phosphor powder have a high degree of sphericity. This is because particles with a high degree of sphericity have a higher packing ability.
• Patent Document 2 describes that for a green phosphor, the percentage of particles with a circularity of 0.6 or more is 50% or more of the total particles on a number basis (Patent Document 2, [0018]).
• Patent Document 3 describes that for Phosphor A, the percentage of particles with a circularity of less than 85% is usually less than 10% by number, and that the particle shape is close to spherical, so that it has appropriate dispersibility and packing density in actual use and can emit light with high brightness (Patent Document 3, [0075]).
• the luminous efficiency (external quantum efficiency, internal quantum efficiency) is particularly low in external quantum efficiency.
• the absorptivity (Abs) is the proportion of light absorbed by the phosphor out of the irradiated light.
• the external quantum efficiency (EQE) is the efficiency at which light irradiated to the phosphor is converted into light of a different color
• the internal quantum efficiency (IQE) is the efficiency at which light absorbed by the phosphor is converted into light of a different color.
• Phosphor powders with low absorptivity and luminous efficiency not only emit inferior light, but also cannot efficiently convert the color of the LED light. This results in low luminous intensity.
• the present invention was completed based on these findings, and aims to provide a phosphor powder with high absorption rate and luminous efficiency.
• Another aim of the present invention is to provide a phosphor resin composition, phosphor, light-emitting element, light-emitting device, and display device that contain the phosphor powder.
• the present invention encompasses the following aspects (1) to (12).
• the expression “to” includes both ends of the expression.
• "X to Y” is synonymous with "X or more and Y or less.”
• any combination of suitable aspects may be adopted as long as technical consistency can be achieved.
• one of the suitable numerical ranges may be combined with the other in any combination.
• a phosphor powder containing phosphor particles having a circularity of 0.6 or less, as determined by scanning electron microscope (SEM) observation using the formula: circularity 4 ⁇ S/ L2 (where S is the particle area and L is the circumferential length of the particle), at a content of 30 volume% or more.
• a phosphor powder containing phosphor particles having a circularity of 0.4 or less, as determined by scanning electron microscope (SEM) observation using the formula: circularity 4 ⁇ S/ L2 (where S is the particle area and L is the circumferential length of the particle), at a content of 10 volume% or more.
• the phosphor powder is any one of the phosphor powders (1) to (5) above, which includes a host crystal containing at least one metal element selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca), gallium (Ga) and sulfur (S), and a host crystal containing at least one metal element selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca) and sulfur (S), and a luminescent center element.
• a phosphor resin composition comprising any one of the phosphor powders (1) to (6) above and a resin.
• a phosphor comprising the phosphor resin composition of (7) above.
• a light-emitting element comprising the phosphor of (8) above and an excitation source.
• the present invention provides a phosphor powder having high absorptivity and luminous efficiency.
• the present invention also provides a phosphor resin composition, a phosphor, a light-emitting element, a light-emitting device, and a display device, each of which contains the phosphor powder.
• Example 1 shows an SEM image of phosphor powder (Example 1). 1 shows an SEM image of a phosphor powder (Comparative Example 1).
• present embodiment A specific embodiment of the present invention (hereinafter referred to as the "present embodiment") will be described. Note that the present invention is not limited to the following embodiment, and various modifications are possible without departing from the gist of the present invention.
• Phosphor powder>> This embodiment is directed to phosphor powder.
• the powder refers to a material that is composed of a plurality of particles and exhibits overall fluidity in a powder state. Even if some particles are bonded or bound to each other, it is called a powder as long as it exhibits overall fluidity.
• the phosphor powder of this embodiment includes a plurality of phosphor particles. It can also be called an aggregate of a plurality of phosphor particles.
• the phosphor powder of this embodiment contains a high percentage of particles with small circularity (sphericity).
• content of phosphor particles having a circularity of x or less will be expressed as "content (circularity ⁇ x)".
• circularity is an index of the circularity (sphericity) of a particle; the greater the circularity, the closer the particle shape is to a perfect sphere, and the smaller the circularity, the further away the particle shape is from a perfect sphere.
• a spherical particle has a circularity of 1. Also, SEM observations provide a two-dimensional image. For this reason, the sphericality of a particle is expressed as "circularity.”
• phosphor powders are synthesized by the solid-phase method. That is, raw material powders are fired and the fired product obtained is pulverized to produce the product.
• the fired product is in a polycrystalline state in which multiple crystallites, which are unit crystals of the phosphor, are joined to each other via cleavage planes (crystal grain boundaries).
• cleavage planes crystal grain boundaries
• phosphor powders are milled to increase the sphericity (roundness) of the phosphor particles in order to increase the packing density.
• milling is performed by attrition, which is dominated by surface milling.
• Attrition is a mode of milling in which shear force and friction force are applied to the particles, causing the milling to proceed frictionally.
• the phosphor powder of this embodiment which is composed of particles with low sphericity, is thought to cause less damage to the crystals than conventional phosphor powders composed of particles with high sphericity, and therefore has a higher absorption rate and luminous efficiency.
• the phosphor powder of this embodiment is characterized by high absorptivity and luminous efficiency due to the high ratio of particles with low circularity (sphericity), i.e., the high content (circularity ⁇ 0.6) or content (circularity ⁇ 0.4).
• the phosphor powder of the second embodiment in which the content (circularity ⁇ 0.4) is limited to 10 volume % or more, contains a small amount (10 volume % or more) of particles with particularly low circularity, and is therefore considered to have high luminous efficiency.
• the phosphor powder of the first embodiment in which the content (circularity ⁇ 0.6) is limited to 30 volume % or more, contains a considerable amount (30 volume % or more) of particles with a moderately low circularity.
• the content (circularity ⁇ 0.6) is preferably 40 vol.% or more, more preferably 50 vol.% or more, even more preferably 60 vol.% or more, and particularly preferably 70 vol.% or more.
• phosphor powder with an excessively high content (circularity ⁇ 0.6) may result in increased manufacturing costs.
• the content (circularity ⁇ 0.6) is typically 90 vol.% or less, or 80 vol.% or less.
• the content is preferably 30 vol.% or more and 90 vol.% or less, more preferably 40 vol.% or more and 90 vol.% or less, even more preferably 50 vol.% or more and 90 vol.% or less, particularly preferably 60 vol.% or more and 80 vol.% or less, and most preferably 70 vol.% or more and 80 vol.% or less.
• the content (circularity ⁇ 0.4) is preferably 20 vol.% or more, more preferably 30 vol.% or more, even more preferably 40 vol.% or more, and particularly preferably 50 vol.% or more.
• phosphor powder with an excessively high content (circularity ⁇ 0.4) may result in increased manufacturing costs.
• the content (circularity ⁇ 0.4) is typically 70 vol.% or less, or 60 vol.% or less.
• the content is preferably 10 vol.% or more and 70 vol.% or less, more preferably 20 vol.% or more and 70 vol.% or less, even more preferably 30 vol.% or more and 70 vol.% or less, particularly preferably 40 vol.% or more and 60 vol.% or less, and most preferably 50 vol.% or more and 60 vol.% or less.
• a higher content (circularity ⁇ 0.4) is desirable.
• the content (circularity ⁇ 0.4) is preferably 10 vol% to 70 vol%, more preferably 20 vol% to 70 vol%, even more preferably 30 vol% to 70 vol%, particularly preferably 40 vol% to 60 vol%, and most preferably 50 vol% to 60 vol%.
• a higher content (circularity ⁇ 0.6) is desirable.
• the content (circularity ⁇ 0.6) is preferably 30 vol.% to 90 vol.%, more preferably 40 vol.% to 90 vol.%, even more preferably 50 vol.% to 90 vol.%, particularly preferably 60 vol.% to 80 vol.%, and most preferably 70 vol.% to 80 vol.%.
• the phosphor powder of this embodiment preferably contains phosphor particles with a circularity of 0.8 or less at a content of 75% by volume or more.
• the content of phosphor particles with a circularity of 0.8 or less is 75% by volume or more.
• the content of particles with a circularity of more than 0.8 is less than 25% by volume. Since the proportion of spherical particles is reduced, it is possible to further increase the absorptivity and luminous efficiency.
• the content (circularity ⁇ 0.8) is more preferably 85% by volume or more, and even more preferably 95% by volume or more.
• the content (circularity ⁇ 0.8) is typically 100% by volume or less.
• SEM scanning electron microscope
• a frequency distribution graph is obtained with particle circularity on the horizontal axis and particle volume (V) on the vertical axis.
• a cumulative frequency distribution graph is also obtained with circularity on the horizontal axis and cumulative volume accumulated from the smallest particle volume on the vertical axis.
• the vertical axis is normalized so that the total particle volume (V) is 100 volume %.
• the cumulative volume of particles with a circularity of x or less is determined as the content (circularity ⁇ x). For example, the content of particles with a circularity of 0.6 or less is determined as the content (circularity ⁇ 0.6).
• the phosphor powder of this embodiment preferably has a cumulative 50% diameter (D50) in the volume particle size distribution of 15.0 ⁇ m or less.
• D50 is preferably 14.0 ⁇ m or less, and more preferably 13.0 ⁇ m or less.
• D50 is preferably 5 ⁇ m or more, and more preferably 7 ⁇ m or more.
• Phosphor powders having such particle sizes are particularly suitable for, but not limited to, mini LED display applications. Note that D50 is determined by calculating a cumulative distribution curve based on the volume (mass) of the phosphor powder, and is calculated as the 50% diameter in this cumulative distribution curve. The method for measuring D50 will be described later.
• the phosphor powder of this embodiment preferably has a cumulative 50% diameter (D50) in the volume particle size distribution of 10.0 ⁇ m or less.
• D50 is preferably 9 ⁇ m or less, more preferably 8 ⁇ m or less, and even more preferably 7 ⁇ m or less.
• D50 is preferably 0.5 ⁇ m or more, more preferably 1 ⁇ m or more, and even more preferably 2 ⁇ m or more. Phosphor powders having such particle sizes are particularly suitable for use in ⁇ LED displays, although this is not limited thereto.
• the phosphor powder of this embodiment is not limited in its material composition as long as it exhibits fluorescence.
• Fluorescent materials are composed of a host crystal and a luminescent center (activator), and in many cases the luminescent center is dissolved in an appropriate host crystal at a level of about several mol %.
• Known fluorescent materials include oxide-based, sulfide-based, oxysulfide-based, nitride-based, and oxynitride-based materials, and any of these may be used.
• oxide-based fluorescent materials (Y, Gd, Lu) 3 (Al, Ga) 5 O 12 : Ce 3+ , (Ba, Sr, Ca) 2 SiO 4 : Eu 2+ , (Ba, Sr, Ca) 3 MgSi 2 O 8 : Eu 2+ , CaAl 12 O 19 : Mn 4+ , Ca 3 Sc 2 Si 3 O 12 : Ce 3+ , CaSc 2 O 4 : Ce 3+ , (Ba, Sr) 3 SiO 5 : Eu 2+ , Li 2 SrSiO 4 : Eu 2+ , Ba 9 Sc 2 Si 6 O 24 :Eu 2+ , Ca 3 Si 2 O 7 : Eu 2+ , LiSrPO 4 : Eu 2+ , CaLa 4 Si 3 O 13 : Eu 3+ , Ba 2 Gd 3 Li 3 Mo 8 O 32 : Eu 3+ and BaMgAl 10 O 17 : Eu 2+ , Mn 2+ and the like.
• Examples of sulfide- based fluorescent materials include (Ba, Sr, Ca) Ga2S4 :Eu2 + , (Ba, Sr, Ca) Ga2S4 :Ce3 + , (Sr, Ca) S :Eu2 + , (Sr, Cd)S:Eu2 + , and ZnS:Cu.
• Examples of oxysulfide fluorescent materials include (La,Y) 2O2S :Eu3 + , La (Ca,Sr ) Ga3S6O :Eu2 + , and La2O3S :Eu3 + .
• nitride- based fluorescent materials include ( Ba,Sr,Ca) 2Si5N8 : Eu2 + , (Ba,Ca,Sr) AlSiN3 :Eu2+, La3Si6N11 :Ce3 + , (Ba, Sr ,Ca) LiAl3N4 :Eu2 + , Sr( Mg3SiN4 ): Eu2 + and (Ba, Sr)2Si5N8 : Eu2 + .
• Examples of oxynitride-based fluorescent materials include Eu-containing ⁇ -type sialon, Eu -containing ⁇ - type sialon , Ba9Sc3Si6O21N3 :Eu2 + , Ba3Si6O12N2 :Eu2 + , BaSi2O2N2 : Eu2+ , and (Ba,Sr,Ca ) AlSi ( ON ) 3 : Eu2 + .
• fluorescent materials include, for example, Sr10 ( PO4 ) 6C12 : Eu2 + and K2 (Si,Ge,Ti) F6 :Mn4 + .
• the phosphor powder contains a host crystal containing at least one metal element selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca), gallium (Ga) and sulfur (S), as well as a host crystal containing at least one metal element selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca) and sulfur (S), as well as a luminescent center element, as in the compositions listed for the sulfide phosphor material described above.
• a host crystal containing at least one metal element selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca) and sulfur (S), as well as a luminescent center element, as in the compositions listed for the sulfide phosphor material described above.
• the luminescent center contains at least one element selected from the group consisting of europium (Eu), cerium (Ce), manganese (Mn), and samarium (Sm).
• Eu europium
• Ce cerium
• Mn manganese
• Sm samarium
• the luminescent center preferably contains Eu, more preferably contains a divalent ion of Eu (Eu 2+ ), and even more preferably contains only Eu 2+ .
• the phosphor powder contains a crystal represented by the general formula: MGa 2 S 4 :Eu 2+ (wherein M is at least one element selected from the group consisting of Ba, Sr, and Ca).
• the phosphor powder having such a composition emits green light when excited by excitation light having a wavelength (approximately 300 nm to 510 nm) in the near ultraviolet region to the blue region.
• the phosphor powder contains a host crystal containing a metal element selected from Ba, Sr, and Ca and S, and a luminescent center element
• the phosphor powder contains at least one element selected from the group consisting of europium (Eu), cerium (Ce), manganese (Mn), and samarium (Sm) as the luminescent center.
• the phosphor powder contains a crystal represented by the general formula: MS:Eu 2+ (wherein M is at least one element selected from the group consisting of Ba, Sr, and Ca).
• the phosphor powder having such a composition emits red light when excited by an excitation light having a wavelength in the ultraviolet to visible light range (approximately 250 nm to 610 nm).
• the ratio of the molar amount XA of the luminescence center element A to the sum (XM+XA) of the molar amount XM of the alkaline earth metal element M contained in the phosphor powder and the molar amount XA of the luminescence center element A is preferably 0.05 or more, more preferably 0.07 or more, and even more preferably 0.10 or more.
• XA/(XM+XA) is preferably 0.30 or less, more preferably 0.25 or less, and even more preferably 0.20 or less.
• the phosphor powder has a composition represented by ( BaxSr1 -x- yCay ) 1- zGatS4 - ⁇ : Euz , where 0 ⁇ x ⁇ 0.5, 0 ⁇ y ⁇ 0.5, 0.01 ⁇ z ⁇ 0.3, 1.5 ⁇ t ⁇ 2.5, and ⁇ is a positive integer satisfying the charge neutrality condition. It is more preferred that x, y, z, and t satisfy the relationships 0 ⁇ x ⁇ 0.4, 0 ⁇ y ⁇ 0.4, 0.05 ⁇ z ⁇ 0.20, and 1.8 ⁇ t ⁇ 2.2.
• the phosphor powder may or may not have a surface coating layer.
• durability such as moisture resistance can be improved.
• the coating layer is preferably made of one or more inorganic compounds such as oxides containing silicon dioxide (SiO 2 ), zinc oxide (ZnO), aluminum oxide (Al 2 O 3 ), titanium oxide (TiO 2 ), and/or boron (B) or metal sulfates such as barium sulfate (BaSO 4 ).
• the phosphor powder of this embodiment is not limited in its manufacturing method as long as it satisfies the above-mentioned requirements.
• the phosphor powder is synthesized from raw materials, and the phosphor powder is subjected to particle size adjustment processing such as pulverization and classification.
• particle size adjustment processing such as pulverization and classification.
• An example of a suitable manufacturing method for the phosphor powder is described below.
• At least one of a strontium (Sr) raw material, a barium (Ba) raw material, and a calcium (Ca) raw material, a gallium (Ga) raw material, a sulfur (S) raw material, and a europium (Eu) raw material are weighed and mixed to obtain a raw material mixture.
• a strontium (Sr) raw material the barium (Ba) raw material, and the calcium (Ca) raw material
• oxides, double oxides, and/or carbonates of each element can be used.
• oxides (Ga 2 O 3 , GaO) can be used as the gallium (Ga) raw material.
• S strontium sulfide
• BaS barium sulfide
• CaS calcium sulfide
• sulfur (S) silicon sulfide
• SiS 2 silicon sulfide
• Ce 2 S 3 cerium sulfide
• hydrogen sulfide (H 2 S) gas etc.
• europium (Eu) raw material europium compounds such as europium fluoride (EuF 3 ), europium oxide (Eu 2 O 3 ), and europium chloride (EuCl 3 ) can be used.
• rare earth elements such as praseodymium (Pr) and samarium (Sm) may be added to the raw material.
• at least one element selected from rare earth elements such as scandium (Sc), lanthanum (La), gadolinium (Gd), and lutetium (Lu) may be added to the raw material as a sensitizer.
• the amount of each of these elements is 5 mol% or less relative to strontium (Sr).
• alkali metal elements monovalent cationic metals such as silver ions (Ag + ), and halogen ions such as chlorine (Cl), fluorine (F), and iodine (I) may be added to the raw material as a charge compensation agent.
• halogen ions such as chlorine (Cl), fluorine (F), and iodine (I)
• the amount of addition is approximately equal to the content of the aluminum group and rare earth elements.
• the method of mixing the raw materials is not limited. Either dry or wet mixing may be used.
• dry mixing the raw materials may be mixed in a mixer such as a paint shaker or ball mill using zirconia balls as media, and dried as necessary to produce a raw material mixture.
• wet mixing a solvent such as water may be added to the raw materials to form a suspension, which may then be mixed in a mixer such as a paint shaker or ball mill using zirconia balls as media, after which the media may be separated using a sieve or the like, and the solvent may be removed from the suspension by a drying method such as reduced pressure drying or vacuum drying.
• the resulting raw material mixture is fired to produce a fired product.
• the raw material mixture may or may not be crushed, classified, and/or dried as necessary.
• the firing it is preferable to perform the firing at a temperature of 1000°C or higher. At 1000°C or higher, sufficient and uniform firing can be performed.
• the upper limit of the firing temperature cannot be determined in general because it is determined by the endurance temperature of the firing furnace and the production temperature. However, it is preferable to perform the firing at a temperature of 1000°C or higher and 1200°C or lower.
• the firing time is determined in relation to the firing temperature. However, it is preferable for it to be around 2 hours or higher and 24 hours or lower.
• the firing atmosphere may be an inert gas or a reducing gas.
• examples include an argon atmosphere, a nitrogen atmosphere, a sulfur atmosphere, an argon atmosphere containing hydrogen gas, a nitrogen atmosphere containing hydrogen gas, and a hydrogen sulfide atmosphere. Of these, firing in a hydrogen sulfide atmosphere is preferred.
• the fired product is then pulverized (crushed) into powder to produce phosphor powder.
• the pulverization can be performed using a known pulverizer such as a ball mill, stamp mill, jet mill, crusher, and/or paint shaker. If necessary, the pulverized product obtained by pulverization can be classified. The classification can be performed using known methods such as a sieve or air classifier.
• pulverization is performed so that the resulting phosphor powder contains a high proportion of particles with low circularity.
• pulverization is performed using a method that allows sufficient crushing, dominated by volumetric crushing, rather than frictional grinding. Particle destruction occurs along the cleavage planes (grain boundaries), so damage to the crystals is minimal. As a result, phosphor powder with high absorptivity and luminous efficiency can be obtained.
• the pulverization method and pulverization conditions are adjusted. Taking the case of pulverization using a stamp mill as an example, the sintered material is pulverized by the stamp mill for a predetermined time so as not to be excessively pulverized, and then sieved for a predetermined time. If sintered material remains on the sieve, pulverization by the stamp mill and sieving may be carried out again for a predetermined time as necessary. Next, pulverization by the stamp mill and sieving may be repeated for the sintered material below the sieve in the same manner as above as necessary. In this way, a sintered material with a predetermined degree of circularity can be obtained.
• the phosphor resin composition of the present embodiment contains the above-mentioned phosphor powder and a resin.
• the phosphor resin composition is a phosphor paste that is a precursor of a phosphor.
• the phosphor is produced by applying or molding the phosphor resin composition.
• thermoplastic resins for example, one or more types selected from thermoplastic resins, thermosetting resins, ionizing radiation curable resins, and two-part mixed curable resins can be used.
• thermoplastic resins include polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonate resins; polyacrylic acid resins such as polyacrylic acid or its esters, polymethacrylic acid or its esters; polyvinyl resins such as polystyrene and polyvinyl chloride; cellulose resins such as triacetyl cellulose; and urethane resins such as polyurethane.
• thermosetting resins include silicone resins, phenolic resins, epoxy resins, melamine resins, urea resins, unsaturated polyester resins, alkyd resins, polyurethane resins, and polyimide resins.
• ionizing radiation curable resins include acrylic resins, urethane resins, vinyl ester resins, and polyester alkyd resins. Not only polymers but also oligomers and monomers can be used for these resins.
• An example of a two-part mixed curable resin is epoxy resin.
• the phosphor resin composition may contain an organic solvent, additives, etc.
• the viscosity of the phosphor resin composition (phosphor paste) can be adjusted by adding an organic solvent.
• the organic solvent may be any known solvent that dissolves resin.
• an inorganic filler such as glass particles or metal oxide particles, or a flow adjuster made of an organic component can be used.
• the phosphor resin composition is produced by mixing and kneading phosphor powder, resin, and, if necessary, organic solvents and additives. Mixing and kneading can be performed using known means, such as a three-roll mill, kneader, single-axis or double-axis kneader, revolution-type stirring and degassing device, and/or a planetary mill. The resulting phosphor resin composition is used as a phosphor paste for producing phosphors.
• the phosphor of this embodiment is made of the phosphor resin composition described above. In other words, it is a molded body of the phosphor resin composition.
• the molded body is a concept that includes coatings and fillers obtained from the composition.
• the phosphor resin composition (phosphor paste) is applied, filled or molded, and further dried and/or cured as necessary to produce a phosphor.
• the phosphor has phosphor powder (particles) dispersed in a resin matrix.
• the light-emitting element of this embodiment includes the above-mentioned phosphor and excitation source.
• the excitation source has a function of emitting light toward the phosphor to excite the phosphor.
• an LED with a central wavelength of 250 nm to 510 nm, particularly a blue LED with a central wavelength of 450 nm to 460 nm is suitable.
• the arrangement of the phosphor and the excitation source is not limited. However, it is preferable to arrange the phosphor directly above the excitation source. This allows the phosphor to more efficiently absorb the light emitted from the excitation source and convert the color.
• the light-emitting element when the light-emitting element is applied to a ⁇ LED display, it is preferable to arrange an LED as an excitation source at the bottom and arrange a phosphor above it in each package rib of the display.
• quantum dots can also be used as a component of the light-emitting element instead of phosphors, but quantum dots often contain environmentally regulated substances. In addition, since they have poor durability, phosphors are more advantageous.
• the light emitting device of the present embodiment includes the light emitting element described above.
• the light emitting device is not particularly limited as long as it includes a phosphor light emitting element. Examples of the light emitting device include a lighting device, a backlight device, and a signal device.
• the display device of this embodiment includes the above-mentioned light-emitting element.
• a display device there is no particular limitation as long as it includes a phosphor light-emitting element.
• the display device of this embodiment has a phosphor that has a high absorption rate and a high luminous efficiency, and therefore has the characteristics of high luminous intensity and excellent luminous color.
• the display device of this embodiment is particularly suitable for a miniLED display or a ⁇ LED display.
• Example 1 Barium sulfide (BaS), strontium sulfide (SrS), europium sulfide (EuS), and gallium sulfide (Ga 2 S 3 ) were prepared and weighed so that the molar ratio was Ba 0.22, Sr 0.65, Eu 0.13, and Ga 2.00. The weighed materials were then mixed with a paint shaker using a zirconia ball having a diameter of 3 mm for 100 minutes to obtain a raw material composition. The raw material composition was then fired under a hydrogen sulfide (H 2 S) atmosphere at a heating rate of 5° C./min, a firing temperature of 1100° C., and a firing time of 6 hours to obtain a fired product.
• H 2 S hydrogen sulfide
• 100 g of the obtained fired product was ground in a stamp mill for 10 minutes, and then sieved using a sieve with a mesh size of 250 ⁇ m for 30 minutes.
• the sieved ground material was subjected to stamp mill processing and sieving operations repeatedly until no more material remained on the sieve.
• the obtained ground material below the sieve was then ground again in a stamp mill for 10 minutes, and then sieved using a sieve with a mesh size of 53 ⁇ m for 30 minutes.
• the sieved ground material was subjected to stamp mill processing and sieving operations repeatedly until no more material remained on the sieve.
• the obtained ground material below the sieve was then ground again in a stamp mill for 10 minutes, and then sieved using a sieve with a mesh size of 25 ⁇ m for 30 minutes.
• the sieved ground material was subjected to stamp mill processing and sieving operations repeatedly until no more material remained on the sieve.
• the ground material below the sieve was then collected to obtain a phosphor powder.
• the composition of the obtained phosphor powder is shown in Table 1 below.
• Example 2 A phosphor powder was obtained in the same manner as in Example 1, except that the stamp mill pulverization time was changed to 15 minutes in all cases.
• the composition of the obtained phosphor powder is shown in Table 1 below.
• Example 3 A fired product was obtained in the same manner as in Example 1. Next, 100 g of the fired product was crushed in a stamp mill for 15 minutes, and then sieved using a sieve with a mesh size of 250 ⁇ m for 30 minutes. The crushed product on the sieve was subjected to stamp mill processing and sieving operations repeatedly until no more residue remained on the sieve. Then, the crushed product below the sieve was crushed again in a stamp mill for 15 minutes, and then sieved using a sieve with a mesh size of 106 ⁇ m for 30 minutes. The crushed product above the sieve was subjected to stamp mill processing and sieving operations repeatedly until no more residue remained on the sieve.
• the crushed product below the sieve was crushed again in a stamp mill for 15 minutes, and then sieved using a sieve with a mesh size of 25 ⁇ m for 30 minutes.
• the crushed product above the sieve was subjected to stamp mill processing and sieving operations repeatedly until no more residue remained on the sieve.
• the crushed product below the sieve was then collected to obtain a phosphor powder.
• the composition of the resulting phosphor powder is shown in Table 1 below.
• Example 4 Strontium sulfide (SrS), calcium sulfide (CaS), europium sulfide (EuS), and gallium sulfide ( Ga2S3 ) were prepared, and the raw materials were weighed so as to obtain a phosphor powder having the composition shown in the following Table 1. Otherwise, the phosphor powder was obtained in the same manner as in Example 1.
• Example 5 Strontium sulfide (SrS), europium sulfide (EuS), and gallium sulfide (Ga 2 S 3 ) were prepared, and the raw materials were weighed so as to obtain a phosphor powder having the composition shown in the following Table 1. Otherwise, the phosphor powder was obtained in the same manner as in Example 1.
• Example 1 A fired product was obtained in the same manner as in Example 1. The fired product was then crushed and pulverized using a jet mill (Dec Group, MC DecJet (registered trademark) 30) to obtain a phosphor powder. The gas pressure was 0.1 MPa, and the supply gas was nitrogen ( N2 ). The composition of the obtained phosphor powder is shown in Table 1 below.
• the circularity and content of the phosphor powder were determined by SEM observation. Specifically, the phosphor powder was dispersed on a carbon tape at a vacuum of 0.8 to 0.9 bar using a disperser (Thermo Scientific, NEBULA) so that the particles contained therein do not overlap as much as possible. This was observed using an SEM (Thermo Scientific, Phenom XL G2). The observation was performed under conditions of a magnification of 10,000 times and an accelerating voltage of 10.0 kV, and a backscattered electron image was obtained.
• the obtained backscattered electron image was binarized using image processing software (Thermo Scientific, Phenom SmartScan).
• the binarization was performed under the following conditions: histogram adjustment Min: 132, Max: 140, and Gamma: 54.
• the particle shape was determined using the ParticleMetric function of the image analysis software (Thermo Scientific, Particle ProSuite), and the perimeter (L) and particle area (S) of each particle were obtained.
• Particle detection in the image analysis was performed under the following conditions: Min contrast 0.90, Merge shared borders 0.70, Ignore covered particles disabled, Exclude edge particles enabled, Conductance 0.30, Min detection size 0.10%.
• the circularity of each particle was calculated using the obtained perimeter (L) and particle area (S) according to the following formula (1).
• a frequency distribution graph was obtained with the particle circularity on the horizontal axis and the particle volume (V) on the vertical axis.
• a cumulative frequency distribution graph was also obtained with the circularity on the horizontal axis and the cumulative volume accumulated from the smallest particle volume on the vertical axis.
• the vertical axis was normalized so that the total particle volume (V) was 100 volume %.
• ⁇ Particle size distribution> The particle size distribution of the phosphor powder was measured using a laser diffraction particle size distribution analyzer (Microtrac Bell, MT3300EXII). First, the inside of the circulation system of the device was filled with a 99.5% ethanol solution, and the sample (phosphor powder) was added so that the transmittance was 95-60%. When adding, the sample was subjected to a dispersion treatment such as ultrasonic dispersion (40 W, 180 seconds). Next, the particle size was measured while circulating the particles in the solvent in the measurement cell. From the measurement, a frequency particle size distribution curve and a cumulative particle size distribution curve on a volume basis were obtained, and the cumulative 50% diameter (D50) was calculated from these. The particle size measurement was performed under the following conditions.
• P 1 ( ⁇ ) be the standard white board spectrum
• P 2 ( ⁇ ) be the sample spectrum
• P 3 ( ⁇ ) be the indirectly excited sample spectrum.
• the area L 1 (see formula (i) below) of the spectrum P 1 ( ⁇ ) surrounded by the excitation wavelength range of 461 nm to 481 nm is defined as the excitation intensity.
• the area L 2 (see formula (ii) below) of spectrum P 2 ( ⁇ ) surrounded by the excitation wavelength range of 461 nm to 481 nm is defined as the sample scattering intensity.
• the area E 2 (see formula (iii) below) of spectrum P 2 ( ⁇ ) surrounded by the excitation wavelength range of 482 nm to 648.5 nm is defined as the fluorescence intensity of the sample.
• the area L 3 (see formula (iv) below) of spectrum P 3 ( ⁇ ) surrounded by the excitation wavelength range of 461 nm to 481 nm is defined as the indirect scattering intensity.
• the area E 3 (see formula (v) below) of spectrum P 3 ( ⁇ ) surrounded by the excitation wavelength range of 482 nm to 648.5 nm is defined as the indirect fluorescence intensity.
• the absorptance (Abs) is the ratio of the excitation light reduced by the sample to the incident light, as shown in the following formula (vi).
• the external quantum efficiency (EQE) is calculated by dividing the number of photons N em of the fluorescence emitted from the sample by the number of photons N ex of the excitation light irradiated onto the sample, as shown in the following formula (vii).
• the internal quantum efficiency (IQE) is, as shown in the following formula (viii), the number of photons of the fluorescence emitted from the sample, N em , divided by the number of photons of the excitation light absorbed by the sample, N abs .
• the phosphor powders of Examples 1 to 5 have a relatively large proportion of particles with low circularity.
• Example 1 has a high frequency of particles with a circularity of 0.2 to 0.3
• Examples 2 and 3 have a high frequency of particles with a circularity of 0.4 to 0.5.
• the phosphor powder of Comparative Example 1 has a large proportion of particles with high circularity.
• the frequency of particles with a circularity of 0 to 0.6 is relatively low, and instead the frequency of particles with a circularity of 0.6 to 0.7 is the highest.
• the frequency of particles with a circularity of 0.8 to 0.9 is also relatively high.
• this embodiment provides phosphor powder with high absorption rate and luminous efficiency.

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  • 2024-12-11 WO PCT/JP2024/043745 patent/WO2025134882A1/ja active Pending
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