Patents by Inventor Yohichi Kitagawa

Yohichi Kitagawa has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20230280670
    Abstract: [Summary] An object of the present invention is to provide a toner that has both low-temperature fixability and heat-resistant storage stability, suppresses contamination of cleaning parts and photoconductors, and has excellent charging stability. [Tasks] A toner includes toner based particles containing a binder resin, a colorant, and a wax; and fine resin particles and an inorganic external additive that are present on a surface of the toner based particles, wherein a coverage of the fine resin particles is in a range from 30% to 70%, and wherein the inorganic external additive covers a surface of oxide of a metal element with hydroxide of a metal element.
    Type: Application
    Filed: February 28, 2023
    Publication date: September 7, 2023
    Applicant: Ricoh Company, Ltd.
    Inventors: Tsukiko TAKAHASHI, Mitsuaki Hirose, Yohichi Kitagawa, Suzuka Karato, Hiroshi Yamada
  • Publication number: 20230195005
    Abstract: Provided is a toner including toner particles. Each of the toner particles includes a toner base particle including a binder resin, resin particles covering the toner base particle, and zinc stearate particles serving as an external additive. In each of the toner particles, a coverage rate of the toner base particle with the resin particles is 30% or greater and 70% or less. The zinc stearate particles have a volume average particle diameter of 3 ?m or greater and 20 ?m or less.
    Type: Application
    Filed: December 20, 2022
    Publication date: June 22, 2023
    Inventors: Taishi YAMASHITA, Yohichi KITAGAWA, Tsukiko TAKAHASHI, Mitsuaki HIROSE, Daisuke INOUE
  • Publication number: 20230152724
    Abstract: A toner includes toner base particles each including a binder resin and a releasing agent, resin particles, and an external additive. Resin particles, from among the resin particles in the toner, and the external additive are deposited on a surface of each of the toner base particles. A standard deviation of a distance between resin particles next to one another on the surface is less than 600 nm, the resin particles next to one another being from among the resin particles deposited on the surface. The external additive includes primary particles each standing alone and non-spherical cohesive particles each including cohered primary particles. A proportion of the primary particles each standing alone per 1,000 particles of the external additive is 30% or less, the particles of the external additive in the per 1,000 particles being the primary particles each standing alone and the cohesive particles.
    Type: Application
    Filed: November 9, 2022
    Publication date: May 18, 2023
    Inventors: Suzuka KARATO, Mitsuaki HIROSE, Hiroshi YAMADA, Yohichi KITAGAWA, Tsukiko TAKAHASHI
  • Publication number: 20230040461
    Abstract: A toner includes: toner base particles including a binder resin, a colorant, an inorganic filler, and a release agent; and an external additive. An average circularity of the toner is 0.974 or more but 0.985 or less. A surface roughness parameter Sz of a surface of the toner is 200 nm or more but 500 nm or less, the surface roughness parameter Sz being measured with an atomic force microscope (AFM).
    Type: Application
    Filed: July 25, 2022
    Publication date: February 9, 2023
    Applicant: Ricoh Company, Ltd.
    Inventors: Daisuke Inoue, Mitsuaki Hirose, Yohichi Kitagawa, Tsukiko Takahashi, Kenji Komito, Akihiko Moki
  • Patent number: 11372363
    Abstract: An image forming apparatus is provided. The image forming apparatus includes an image bearer and a cleaning blade configured to remove toner particles remaining on the image bearer. The cleaning blade includes an elastic member in contact with a surface of the image bearer to remove the toner particles. The elastic member has a Martens hardness of from 3 to 8 N/mm2 when measured by a nanoindentation method with a load of 1 ?N. The toner particles comprise toner base particles and an external additive, and the external additive comprise silica particles. A liberation ratio (Xs) of the silica particles liberated from the toner particles is from 40% to 75% when measured by an ultrasonic vibration method. A proportion (R70) of the silica particles having a volume-based particle diameter of 70 nm or more in the silica particles liberated from the toner particles is from 70% to 90% by number.
    Type: Grant
    Filed: December 4, 2020
    Date of Patent: June 28, 2022
    Assignee: RICOH COMPANY, LTD.
    Inventors: Daisuke Inoue, Shinya Nakayama, Yohichi Kitagawa, Takaaki Tawada, Kenji Komito
  • Publication number: 20220155699
    Abstract: A toner is provided. The toner comprises toner particles each comprising a toner base particle and an external additive. The toner base particle comprises a binder resin and a colorant. The toner satisfies the following conditions (a) and (b): (a) an average surface roughness Ra [nm] of the toner particles, detected by a scanning probe microscope analyzer, satisfies the following formula (1): 10<Ra<200??Formula (1); and (b) the external additive comprises coalesced particles being non-spherical secondary particles in which primary particles are coalesced with each other, the coalesced particles having a number average particle diameter of 50 nm or more.
    Type: Application
    Filed: October 14, 2021
    Publication date: May 19, 2022
    Applicant: Ricoh Company, Ltd.
    Inventors: Yohichi KITAGAWA, Kenji Komito, Masayuki Ukigaya, Mitsuaki Hirose, Daisuke Inoue
  • Publication number: 20220057725
    Abstract: A toner is provided. The toner comprises toner base particles, resin particles adhered to surfaces of the toner base particles, and an external additive adhered to the surfaces of the toner base particles. The toner base particles each comprising a binder resin, a colorant, and a wax. The toner has a storage elastic modulus G? of 4.0×105 or less at 70° C. An embedment degree of the external additive is from 15% to 40%, as the embedment degree is measured by stirring 10 g of the toner and 20 g of a carrier in a 50-mL vial at 67 Hz for 60 minutes using a rocking mill.
    Type: Application
    Filed: August 16, 2021
    Publication date: February 24, 2022
    Applicant: Ricoh Company, Ltd.
    Inventors: Daisuke INOUE, Mitsuaki Hirose, Yohichi Kitagawa, Masayuki Ukigaya, Kenji Komito, Hiroshi Yamada
  • Patent number: 11054757
    Abstract: A toner including toner base particles each including a binder resin and a colorant, and external additive, wherein the toner satisfies conditions (a), (b), and (c) below: (a) storage elastic modulus G?(50) of the toner at 50° C. and storage elastic modulus G?(90) of the toner at 90° C. satisfy Formula (1); G?(50)/G?(90)?6.0×102??Formula (1) (b) a BET specific surface area Bt(m2/g) of the toner and a coverage Ct (%) of the toner base particles covered with the external additive satisfy Formula (2); and Bt?0.03×Ct?1.60??Formula (2) (c) the external additive includes at least cohered particles, the cohered particles are non-spherical secondary particles each formed through cohesion of primary particles, and a number average secondary particle diameter of the cohered particles is 130 nm or greater.
    Type: Grant
    Filed: September 26, 2019
    Date of Patent: July 6, 2021
    Assignee: Ricoh Company, Ltd.
    Inventors: Yohichi Kitagawa, Keiji Makabe, Yuka Mizoguchi, Tsuneyasu Nagatomo, Shinya Nakayama
  • Publication number: 20210173337
    Abstract: An image forming apparatus is provided. The image forming apparatus includes an image bearer and a cleaning blade configured to remove toner particles remaining on the image bearer. The cleaning blade includes an elastic member in contact with a surface of the image bearer to remove the toner particles. The elastic member has a Martens hardness of from 3 to 8 N/mm2 when measured by a nanoindentation method with a load of 1 ?N. The toner particles comprise toner base particles and an external additive, and the external additive comprise silica particles. A liberation ratio (Xs) of the silica particles liberated from the toner particles is from 40% to 75% when measured by an ultrasonic vibration method. A proportion (R70) of the silica particles having a volume-based particle diameter of 70 nm or more in the silica particles liberated from the toner particles is from 70% to 90% by number.
    Type: Application
    Filed: December 4, 2020
    Publication date: June 10, 2021
    Inventors: Daisuke INOUE, Shinya NAKAYAMA, Yohichi KITAGAWA, Takaaki TAWADA, Kenji KOMITO
  • Publication number: 20200103775
    Abstract: A toner including toner base particles each including a binder resin and a colorant, and external additive, wherein the toner satisfies conditions (a), (b), and (c) below: (a) storage elastic modulus G?(50) of the toner at 50° C. and storage elastic modulus G?(90) of the toner at 90° C. satisfy Formula (1); G?(50)/G?(90)?6.0×102??Formula (1) (b) a BET specific surface area Bt(m2/g) of the toner and a coverage Ct (%) of the toner base particles covered with the external additive satisfy Formula (2); and Bt?0.03×Ct?1.60??Formula (2) (c) the external additive includes at least cohered particles, the cohered particles are non-spherical secondary particles each formed through cohesion of primary particles, and a number average secondary particle diameter of the cohered particles is 130 nm or greater.
    Type: Application
    Filed: September 26, 2019
    Publication date: April 2, 2020
    Inventors: Yohichi Kitagawa, Keiji Makabe, Yuka Mizoguchi, Tsuneyasu Nagatomo, Shinya Nakayama