Patents by Inventor Yoshimichi Ishikawa
Yoshimichi Ishikawa 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).
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Patent number: 11106150Abstract: A carrier for forming an electrophotographic image is provided. The carrier includes a core particle comprising a manganese-based ferrite particle having an apparent density of from 2.0 to 2.2 g/cm3 and a magnetization of from 44 to 52 emu/g in a magnetic field of 500 Oe; and a coating layer coating a surface of the core particle. The coating layer contains a carbon black, an inorganic particle A, and an inorganic particle B. The inorganic particle A and the carbon black each have a concentration gradient in a thickness direction of the coating layer. A concentration of the inorganic particle A increases toward a surface of the coating layer, and a concentration of the carbon black decreases toward the surface of the coating layer.Type: GrantFiled: November 14, 2019Date of Patent: August 31, 2021Assignee: RICOH COMPANY, LTD.Inventors: Masashi Nagayama, Hiroyuki Kishida, Masahiro Seki, Yoshimichi Ishikawa, Saori Yamada
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Publication number: 20200166867Abstract: A carrier for forming an electrophotographic image is provided. The carrier includes a core particle comprising a manganese-based ferrite particle having an apparent density of from 2.0 to 2.2 g/cm3 and a magnetization of from 44 to 52 emu/g in a magnetic field of 500 Oe; and a coating layer coating a surface of the core particle. The coating layer contains a carbon black, an inorganic particle A, and an inorganic particle B. The inorganic particle A and the carbon black each have a concentration gradient in a thickness direction of the coating layer. A concentration of the inorganic particle A increases toward a surface of the coating layer, and a concentration of the carbon black decreases toward the surface of the coating layer.Type: ApplicationFiled: November 14, 2019Publication date: May 28, 2020Inventors: Masashi NAGAYAMA, Hiroyuki KISHIDA, Masahiro SEKI, Yoshimichi ISHIKAWA, Saori YAMADA
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Patent number: 9971260Abstract: A toner is provided. The toner includes toner particles each including a binder resin and a release agent. From 20% to 80% by number of the toner particles satisfy the following formula (1) and (2): 2/3?T/Dv?1.5??(1) 1/3?R/Dv?1.0??(2) wherein Dv represents a volume average particle diameter of the toner particles; and T and R represent the longest cross-sectional diameters of each toner particle and the release agent contained therein, respectively, measured by observing cross-sections of the toner particles with scanning transmission electron microscope.Type: GrantFiled: September 20, 2016Date of Patent: May 15, 2018Assignee: Ricoh Company, Ltd.Inventors: Tsuyoshi Nozaki, Yoshimichi Ishikawa, Tomoharu Miki, Yuta Takeuchi
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Publication number: 20170248896Abstract: Image forming apparatus, including: image bearer; charging unit for electrically charging image bearer surface; developing unit for developing with toner, electrostatic latent image formed over image bearer by exposure unit for performing light exposure; transfer unit for transferring developed toner to receiving member; and cleaning unit for cleaning toner remaining over image bearer without being transferred, wherein the toner contains: external additives; and base particles made of at least binder resin and colorant, external additive content of the toner is from 4 to 7 parts by mass relative to 100 parts by mass of base particles, primary particles of at least one external additive have a number average particle diameter of 0.01 to 0.05 ?m, cleaning unit includes an elastic-body blade having surface elastic modulus of from 15 to 25 N/mm2 and surface friction coefficient of from 0.5 to 0.7 at an abutment part thereof abutting on image bearer.Type: ApplicationFiled: July 17, 2015Publication date: August 31, 2017Inventors: Naoki NAKATAKE, Takeshi YAMASHITA, Tetsushi SAKUMA, Mitsutoshi KICHISE, Tsuyoshi NOZAKI, Yoshihiro MIKURIYA, Yoshimichi ISHIKAWA, Atsushi YAMAMOTO, Kazuoki FUWA, Tomohiro FUKAO, Tomoharu MIKI
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Patent number: 9709912Abstract: A toner is provided. The toner includes a crystalline resin and a non-crystalline resin, and has a thermal property such that when the toner is heated after being firstly heated to 60° C. followed by cooling in differential scanning calorimetry (DSC), the toner has a clear peak specific to melting of the crystalline resin at a temperature T1, and when the toner is heated after being firstly heated to 80° C. followed by cooling in the differential scanning calorimetry (DSC), the toner does not have a clear peak specific to melting of the crystalline resin at a temperature not higher than the temperature T1.Type: GrantFiled: October 1, 2013Date of Patent: July 18, 2017Assignee: Ricoh Company, Ltd.Inventors: Kazuoki Fuwa, Takuya Kadota, Yoshihiro Mikuriya, Tsuyoshi Nozaki, Yoshimichi Ishikawa, Yuta Takeuchi, Tomohiro Fukao, Tomoharu Miki, Takayuki Nakamura
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Patent number: 9563140Abstract: A toner is prepared by wet granulation methods, including a monoester wax having carbon atoms of from 36 to 46 on average as a release agent. The toner has a DSC endothermic energy amount (?H1) originating from the wax of from 10 to 12 mJ/mg and a DSC endothermic energy amount (?H2) originating from the wax of from 0.6 to 0.9 times as much as ?H1 after a part of the wax is separated by hexane extraction from the toner. The hexane extraction includes mixing 1 g of the toner in 7 ml of n-hexane to prepare a mixture; stirring the mixture at 120 rpm for 1 min by a pot mill to prepare a dispersion; and subjecting the dispersion to suction filtration.Type: GrantFiled: October 23, 2013Date of Patent: February 7, 2017Assignee: Ricoh Company, Ltd.Inventors: Tsuyoshi Nozaki, Takuya Kadota, Yoshihiro Mikuriya, Yoshimichi Ishikawa, Kazuoki Fuwa, Tomohiro Fukao, Tomoharu Miki
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Publication number: 20170010548Abstract: A toner is provided. The toner includes toner particles each including a binder resin and a release agent. From 20% to 80% by number of the toner particles satisfy the following formulae (1) and (2): 2/3?T/Dv?1.5 ??(1) 1/3?R/Dv?1.0 ??(2) wherein Dv represents a volume average particle diameter of the toner particles; and T and R represent the longest cross-sectional diameters of each toner particle and the release agent contained therein, respectively, measured by observing cross-sections of the toner particles with scanning transmission electron microscope.Type: ApplicationFiled: September 20, 2016Publication date: January 12, 2017Inventors: Tsuyoshi Nozaki, Yoshimichi Ishikawa, Tomoharu Miki, Yuta Takeuchi
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Patent number: 9417541Abstract: A toner including: toner particles each including a toner base particle and an external additive attached thereon, where the toner base particle includes a binder resin and a colorant, wherein the toner base particles each have protrusions on a surface thereof, an average of lengths of long sides of the protrusions is 0.10 ?m or more but less than 0.50 ?m, a standard deviation of the lengths of the long sides of the protrusions is 0.2 or less, a coverage rate of the protrusions on the surface of the toner base particle is 10% to 90%, and the external additive includes fine inorganic particles whose surfaces have been treated with an amino group-containing silane coupling agent.Type: GrantFiled: April 25, 2012Date of Patent: August 16, 2016Assignee: Ricoh Company, Ltd.Inventors: Yoshimichi Ishikawa, Takuya Kadota, Yoshihiro Mikuriya, Tsuyoshi Nozaki, Kazuoki Fuwa, Tomohiro Fukao, Tomoharu Miki
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Patent number: 9360824Abstract: An image forming apparatus is provided which includes an image bearer, a charger, an irradiator, a developing device to develop an electrostatic latent image on the image bearer with a toner to form a toner image, a transfer device to transfer the toner image onto a transfer medium, and a cleaner to remove toner particles remaining on the image bearer without being transferred. The toner includes a mother particle including a binder resin and a colorant and one or more external additives. At least one of the external additives includes primary particles having a number average particle diameter in the range of 0.05 to 0.30 ?m. The cleaner includes an elastic body blade having a contact part with the image bearer. The contact part has a surface elastic modulus in the range of 15 to 25 N/mm2 and a surface friction coefficient in the range of 0.5 to 0.7.Type: GrantFiled: July 6, 2015Date of Patent: June 7, 2016Assignee: Ricoh Company, Ltd.Inventors: Tomohiro Fukao, Tsuyoshi Nozaki, Yoshihiro Mikuriya, Yoshimichi Ishikawa, Atsushi Yamamoto, Kazuoki Fuwa, Tomoharu Miki, Naoki Nakatake, Takeshi Yamashita, Tetsushi Sakuma
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Patent number: 9285695Abstract: A toner including: a core particle containing at least a binder resin, a colorant and a releasing agent; and a shell on a surface of the core particle, wherein the toner gives a supernatant having a transmittance of 50% to 95% with respect to light having a wavelength of 800 nm, where the supernatant is formed after 3 g of the toner is added to 40 g of ion-exchange water containing 0.5% by mass of sodium dodecyl sulfate, followed by stirring for 90 min and by irradiating with ultrasonic waves of 20 kHz and 80 W for 5 min, and a liquid containing the toner dispersed therein is centrifugated at 3,000 rpm for 5 min.Type: GrantFiled: September 12, 2012Date of Patent: March 15, 2016Assignee: Ricoh Company, Ltd.Inventors: Tomoharu Miki, Takuya Kadota, Yoshihiro Mikuriya, Tsuyoshi Nozaki, Yoshimichi Ishikawa, Kazuoki Fuwa, Tomohiro Fukao
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Patent number: 9268244Abstract: An electrostatic image developing toner including: toner base particles each including a binder resin and a colorant; and an external additive, wherein the toner base particles each have protrusions on a surface thereof, an average of lengths of long sides of the protrusions is 0.1 ?m or more but less than 0.5 ?m, a standard deviation of the lengths of the long sides of the protrusions is 0.2 or less, a coverage rate of the protrusions on the surface of each toner base particle is 10% to 90%, and the external additive includes an external additive (A) which is fine inorganic particles each containing silicone oil.Type: GrantFiled: April 25, 2012Date of Patent: February 23, 2016Assignee: Ricoh Company, Ltd.Inventors: Tomohiro Fukao, Takuya Kadota, Yoshihiro Mikuriya, Tsuyoshi Nozaki, Yoshimichi Ishikawa, Kazuoki Fuwa, Tomoharu Miki
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Publication number: 20160033924Abstract: An image forming apparatus is provided which includes an image bearer, a charger, an irradiator, a developing device to develop an electrostatic latent image on the image bearer with a toner to form a toner image, a transfer device to transfer the toner image onto a transfer medium, and a cleaner to remove toner particles remaining on the image bearer without being transferred. The toner includes a mother particle including a binder resin and a colorant and one or more external additives. At least one of the external additives includes primary particles having a number average particle diameter in the range of 0.05 to 0.30 ?m. The cleaner includes an elastic body blade having a contact part with the image bearer. The contact part has a surface elastic modulus in the range of 15 to 25 N/mm2 and a surface friction coefficient in the range of 0.5 to 0.7.Type: ApplicationFiled: July 6, 2015Publication date: February 4, 2016Inventors: Tomohiro FUKAO, Tsuyoshi NOZAKI, Yoshihiro MIKURIYA, Yoshimichi ISHIKAWA, Atsushi YAMAMOTO, Kazuoki FUWA, Tomoharu MIKI, Naoki NAKATAKE, Takeshi YAMASHITA, Tetsushi SAKUMA
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Patent number: 9182688Abstract: An image forming apparatus, including: an electrostatic latent image bearing member; an electrostatic latent image forming unit configured to form an electrostatic latent image on the electrostatic latent image bearing member; and a developing unit containing a toner and configured to develop the electrostatic latent image with the toner to thereby form a visible image, wherein the developing unit is a contact type one-component developing unit which includes a toner bearing member being in contact with the electrostatic latent image bearing member, wherein a contact pressure between the electrostatic latent image bearing member and the toner bearing member is 2.0×104 N/m2 to 7.5×104 N/m2, wherein the toner contains a binder resin and a releasing agent, and wherein an extracted amount of the releasing agent extracted with hexane from the toner is 10 mg/g to 25 mg/g.Type: GrantFiled: November 25, 2013Date of Patent: November 10, 2015Assignee: Ricoh Company, Ltd.Inventors: Takuya Kadota, Yoshihiro Mikuriya, Tsuyoshi Nozaki, Yoshimichi Ishikawa, Kazuoki Fuwa, Tomohiro Fukao, Yuta Takeuchi, Tomoharu Miki, Takayuki Nakamura, Naoki Nakatake, Yasuhide Matsuno
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Patent number: 9098013Abstract: A developing roller, including: a shaft containing a metal; an elastic layer on a circumference of the shaft; and a surface layer on a circumferential surface of the elastic layer, wherein the surface layer contains: a polyurethane which is a reaction product between a fluoroethylene vinyl ether copolymer and an isocyanurate form of an isocyanate; and particles having an average primary particle diameter of 5 nm to 30 nm, and wherein the polyurethane has a peak intensity ratio of a NCO group to a hydroxyl group of 5.6 to 8.8 in an infrared absorption spectrum obtained by an attenuated total reflection method.Type: GrantFiled: April 23, 2014Date of Patent: August 4, 2015Assignee: RICOH COMPANY, LTD.Inventors: Hideaki Yasunaga, Keiichiro Juri, Yuta Takeuchi, Tsuyoshi Nozaki, Yoshimichi Ishikawa, Tomoharu Miki
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Publication number: 20150198901Abstract: A toner is provided. The toner includes toner particles each including a binder resin and a release agent. From 20% to 80% by number of the toner particles satisfy the following formulae (1) and (2): ??T/Dv?1.5 ??(1) ??R/Dv?1.0 ??(2) wherein Dv represents a volume average particle diameter of the toner particles; and T and R represent the longest cross-sectional diameters of each toner particle and the release agent contained therein, respectively, measured by observing cross-sections of the toner particles with scanning transmission electron microscope.Type: ApplicationFiled: December 17, 2014Publication date: July 16, 2015Inventors: Tsuyoshi NOZAKI, Yoshimichi ISHIKAWA, Tomoharu MIKI, Yuta TAKEUCHI
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Publication number: 20150078790Abstract: Provided is a developing device, including: a toner having an average circularity of from 0.880 to 0.960; and a developing roller configured to rotate while carrying the toner, wherein the developing roller has on a surface thereof, a plurality of streaky grooves each formed in a circumferential direction, and a plurality of steps each formed in a direction of a rotation axis.Type: ApplicationFiled: September 12, 2014Publication date: March 19, 2015Inventors: Yoshimichi ISHIKAWA, Tsuyoshi NOZAKI, Tomoharu MIKI, Yuta TAKEUCHI, Hideaki YASUNAGA, Keiichiro JURI
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Publication number: 20140356774Abstract: A toner including: a core particle containing at least a binder resin, a colorant and a releasing agent; and a shell on a surface of the core particle, wherein the toner gives a supernatant having a transmittance of 50% to 95% with respect to light having a wavelength of 800 nm, where the supernatant is formed after 3 g of the toner is added to 40 g of ion-exchange water containing 0.5% by mass of sodium dodecyl sulfate, followed by stirring for 90 min and by irradiating with ultrasonic waves of 20 kHz and 80 W for 5 min, and a liquid containing the toner dispersed therein is centrifugated at 3,000 rpm for 5 min.Type: ApplicationFiled: September 12, 2012Publication date: December 4, 2014Inventors: Tomoharu Miki, Takuya Kadota, Yoshihiro Mikuriya, Tsuyoshi Nozaki, Yoshimichi Ishikawa, Kazuoki Fuwa, Tomohiro Fukao
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Publication number: 20140321888Abstract: A developing roller, including: a shaft containing a metal; an elastic layer on a circumference of the shaft; and a surface layer on a circumferential surface of the elastic layer, wherein the surface layer contains: a polyurethane which is a reaction product between a fluoroethylene vinyl ether copolymer and an isocyanurate form of an isocyanate; and particles having an average primary particle diameter of 5 nm to 30 nm, and wherein the polyurethane has a peak intensity ratio of a NCO group to a hydroxyl group of 5.6 to 8.8 in an infrared absorption spectrum obtained by an attenuated total reflection method.Type: ApplicationFiled: April 23, 2014Publication date: October 30, 2014Applicant: RICOH COMPANY, LTD.Inventors: Hideaki Yasunaga, Keiichiro Juri, Yuta Takeuchi, Tsuyoshi Nozaki, Yoshimichi Ishikawa, Tomoharu Miki
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Patent number: 8871417Abstract: To provide a toner comprising: a binder resin, a colorant, and a releasing agent, wherein the toner has a core shell structure, and wherein the core contains at least one resin selected from the group consisting of a hybrid resin and a polyester resin, where the hybrid resin is a resin in which a polyester resin and a vinyl resin are chemically bonded to each other, and the shell contains a resin prepared by polymerizing at least a styrene monomer and an ester monomer represented by the following General Formula (1): where, ‘n’ is 2 or 3, ‘X’ is any of 0 to 9, R1 is a hydrogen atom, or an alkyl group, and R2 is a hydrogen atom, an alkyl group, or a phenyl group.Type: GrantFiled: August 27, 2010Date of Patent: October 28, 2014Assignee: Ricoh Company, Ltd.Inventors: Tomoharu Miki, Takuya Kadota, Yoshihiro Mikuriya, Tsuyoshi Nozaki, Atsushi Yamamoto, Yoshimichi Ishikawa, Tomohiro Fukao
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Publication number: 20140147784Abstract: An image forming apparatus, including: an electrostatic latent image bearing member; an electrostatic latent image forming unit configured to form an electrostatic latent image on the electrostatic latent image bearing member; and a developing unit containing a toner and configured to develop the electrostatic latent image with the toner to thereby form a visible image, wherein the developing unit is a contact type one-component developing unit which includes a toner bearing member being in contact with the electrostatic latent image bearing member, wherein a contact pressure between the electrostatic latent image bearing member and the toner bearing member is 2.0×104 N/m2 to 7.5×104 N/m2, wherein the toner contains a binder resin and a releasing agent, and wherein an extracted amount of the releasing agent extracted with hexane from the toner is 10 mg/g to 25 mg/g.Type: ApplicationFiled: November 25, 2013Publication date: May 29, 2014Inventors: Takuya Kadota, Yoshihiro Mikuriya, Tsuyoshi Nozaki, Yoshimichi Ishikawa, Kazuoki Fuwa, Tomohiro Fukao, Yuta Takeuchi, Tomoharu Miki, Takayuki Nakamura, Naoki Nakatake, Yasuhide Matsuno