# US 11,112,716 B2 · Carrier core material for electrophotographic developer and method for producing the same, and carrier for electrophotographic developer and developer containing said carrier core material > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,112,716 B2 - Document ID: US11112716B2 - Status: Granted - Kind: B2 - Application number: 16/751,031 - Filed: 2020-01-23 - Published: 2020-07-30 - Granted: 2021-09-07 - Earliest claimed: 2019-01-25 - Assignees: Powdertech Co., Ltd. - Applicants: Powdertech Co., Ltd. - Inventors: Hiroki Sawamoto; Atsushi Nil; Yuji Ito; Hajime Akiba; Shinya Hanyu - Web page: https://patentgrep.com/patent/US11112716B2 ## CPC - G03G 9/1085: {with non-ferrous metal oxide, e.g. MgO-Fe2O3} - G03G 9/0808: {by dry mixing the toner components in solid or softened state} - G03G 9/0902: {Inorganic compounds} - G03G 9/0926: {characterised by physical or chemical properties} - G03G 9/107: having magnetic components - G03G 9/1075: {Structural characteristics of the carrier particles, e.g. shape or crystallographic structure} - G03G 9/113: having coatings applied thereto - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract The present invention relates to a carrier core material for electrophotographic developer, having a ferrite composition and having a supernatant transmittance of 85.0% or more, a method for producing the carrier core material, a carrier for electrophotographic developer, containing the carrier core material, and a developer containing the carrier. ## Claims ### Claim 1 A carrier core material for an electrophotographic developer, comprising a ferrite composition having a transition metal oxide as a main component, wherein an amount of an ultrafine powder contaminant adhering to a surface of the carrier core material is attenuated by determining the transmittance with a spectrophotometer of a supernatant separated from the ultrafine powder. ### Claim 2 (depends on 1) The carrier core material according to claim 1, having an apparent density of from 1.5 to 2.5 g/cm3. ### Claim 3 (depends on 1) The carrier core material according to claim 1, having a volume average particle diameter D50 of from 20 to 50 μm. ### Claim 4 (depends on 1) The carrier core material according to claim 1, having a shape factor SF-1 of from 105 to 150. ### Claim 5 (depends on 1) The carrier core material according to claim 1, having a BET specific surface area of from 0.05 to 0.55 m2/g. ### Claim 6 (depends on 1) The carrier core material according to claim 1, having an average equivalent circle diameter of from 20 to 50 μm. ### Claim 7 (depends on 1) The carrier core material according to claim 1, wherein the ferrite composition is represented by formula (1): (MO)x(Fe2O3)y, wherein, x+y is 100% by mole, y is 30 to 95% by mole, and M is at least one element selected from the group consisting of Fe, Mn, Mg, Sr, Ca, Ti, Li, Al, Si, Zr, and Bi. ### Claim 8 (depends on 1) A method for producing the carrier core material as described in claim 1, comprising: mixing and pulverizing raw materials of the carrier core material to form a raw material mixture; calcining the raw material mixture to form a calcined product; pulverizing and granulating the calcined product to form a granulated product; sintering the granulated product to form a sintered product; and removing ultrafine powder from the sintered product. ### Claim 9 (depends on 8) The method according to claim 8, wherein in the step of removing ultrafine powder, the sintered product is mixed to and dispersed in a solvent to from a slurry, the slurry is allowed to stand to separate into a precipitate and a supernatant liquid, and after removing the supernatant liquid, the precipitate is recovered and dried. ### Claim 10 (depends on 1) A carrier for electrophotographic developer, comprising the carrier core material as described in claim 1. ### Claim 11 (depends on 10) The carrier according to claim 10, further comprising a resin coating layer provided on a surface of the carrier core material. ### Claim 12 (depends on 10) The carrier according to claim 10, wherein the carrier core material is composed of porous ferrite particles having pores, and the carrier further comprises a resin filled in the pores. ### Claim 13 (depends on 1) A developer comprising the carrier core material as described in claim 1 and a toner. ### Claim 14 (depends on 13) The developer according to claim 13, wherein the toner is a white toner or a clear toner. ### Claim 15 (depends on 1) The carrier core material according to claim 1, wherein the transition metal oxide is iron oxide (Fe2O3) or manganese oxide (MnO). ### Claim 16 (depends on 1) The carrier core material according to claim 1, wherein the ultrafine powder migrates to a toner and results in toner color contamination. ### Claim 17 (depends on 16) The carrier core material according to claim 16, wherein the toner is a white color toner or a clear toner. ### Claim 18 (depends on 16) The carrier core material according to claim 16, wherein migration of the ferrite ultrafine powder to a toner can be suppressed by restricting the supernatant transmittance of the carrier core material to a predetermined range. ### Claim 19 (depends on 1) The carrier core material according to claim 1, wherein the supernatant has a transmittance of 85.0% or more. ### Claim 20 A method for attenuating toner color contamination, comprising: separating a ferrite ultrafine powder contaminant adhering to a sintered ferrite carrier core product by means of a supernatant; and determining the transmittance of the supernatant with a spectrophotometer. ### Claim 21 (depends on 20) The method of claim 20, wherein the attenuating is preventing, reducing, suppressing, or controlling toner color contamination.