Patents by Inventor Kiyokazu Tohma

Kiyokazu Tohma 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: 20020101669
    Abstract: A master information carrier comprises a substrate whose surface has an embossed pattern corresponding to an information signal. At least a surface of the protruding portion of the embossed pattern is made of a ferromagnetic material. A method for writing an information signal into a sheet or disk magnetic record medium with a ferromagnetic thin film or coating is performed by putting the surface of-the magnetic record medium into contact with the master information carrier so as to write a magnetized pattern corresponding to the embossed pattern of the master information carrier into the magnetic record medium.
    Type: Application
    Filed: March 26, 2002
    Publication date: August 1, 2002
    Applicant: Matsushita Electric Industrial Co., Ltd.
    Inventors: Tatsuaki Ishida, Ryuji Sugita, Kiyokazu Tohma, Keizou Miyata, Hiroshi Ryonai
  • Publication number: 20020101670
    Abstract: A master information carrier comprises a substrate whose surface has an embossed pattern corresponding to an information signal. At least a surface of the protruding portion of the embossed pattern is made of a ferromagnetic material. A method for writing an information signal into a sheet or disk magnetic record medium with a ferromagnetic thin film or coating is performed by putting the surface of the magnetic record medium into contact with the master information carrier so as to write a magnetized pattern corresponding to the embossed pattern of the master information carrier into the magnetic record medium.
    Type: Application
    Filed: March 26, 2002
    Publication date: August 1, 2002
    Applicant: Matsushita Electric Industrial Co., Ltd.
    Inventors: Tatsuaki Ishida, Ryuji Sugita, Kiyokazu Tohma, Keizou Miyata, Hiroshi Ryonai
  • Publication number: 20020089768
    Abstract: A master information carrier comprises a substrate whose surface has an embossed pattern corresponding to an information signal. At least a surface of the protruding portion of the embossed pattern is made of a ferromagnetic material. A method for writing an information signal into a sheet or disk magnetic record medium with a ferromagnetic thin film or coating is performed by putting the surface of the magnetic record medium into contact with the master information carrier so as to write a magnetized pattern corresponding to the embossed pattern of the master information carrier into the magnetic record medium.
    Type: Application
    Filed: February 26, 2002
    Publication date: July 11, 2002
    Applicant: Matsushita Electric Industrial Co., Ltd.
    Inventors: Tatsuaki Ishida, Ryuji Sugita, Kiyokazu Tohma, Kazunari Yoshimoto, Keizou Miyata, Hiroshi Ryonai
  • Publication number: 20020089769
    Abstract: A master information carrier comprises a substrate whose surface has an embossed pattern corresponding to an information signal. At least a surface of the protruding portion of the embossed pattern is made of a ferromagnetic material. A method for writing an information signal into a sheet or disk magnetic record medium with a ferromagnetic thin film or coating is performed by putting the surface of the magnetic record medium into contact with the master information carrier so as to write a magnetized pattern corresponding to the embossed pattern of the master information carrier into the magnetic record medium.
    Type: Application
    Filed: February 26, 2002
    Publication date: July 11, 2002
    Applicant: Matsushita Electric Industrial Co., Ltd.
    Inventors: Tatsuaki Ishida, Ryuji Sugita, Kiyokazu Tohma, Kazunari Yoshimoto, Keizou Miyata, Hiroshi Ryonai
  • Publication number: 20020075583
    Abstract: A master information carrier comprises a substrate whose surface has an embossed pattern corresponding to an information signal. At least a surface of the protruding portion of the embossed pattern is made of a ferromagnetic material. A method for writing an information signal into a sheet or disk magnetic record medium with a ferromagnetic thin film or coating is performed by putting the surface of the magnetic record medium into contact with the master information carrier so as to write a magnetized pattern corresponding to the embossed pattern of the master information carrier into the magnetic record medium.
    Type: Application
    Filed: December 21, 2001
    Publication date: June 20, 2002
    Applicant: Matsushita Electric Industrial Co., Ltd.
    Inventors: Tatsuaki Ishida, Ryuji Sugita, Kiyokazu Tohma, Kazunari Yoshimoto, Keizou Miyata, Hiroshi Ryonai
  • Patent number: 6347016
    Abstract: A master information carrier comprises a substrate whose surface has an embossed pattern corresponding to an information signal. At least a surface of the protruding portion of the embossed pattern is made of a ferromagnetic material. A method for writing an information signal into a sheet or disk magnetic record medium with a ferromagnetic thin film or coating is performed by putting the surface of the magnetic record medium into contact with the master information carrier so as to write a magnetized pattern corresponding to the embossed pattern of the master information carrier into the magnetic record medium.
    Type: Grant
    Filed: July 13, 1998
    Date of Patent: February 12, 2002
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Tatsuaki Ishida, Ryuji Sugita, Kiyokazu Tohma, Keizou Miyata, Hiroshi Ryonai
  • Patent number: 6242085
    Abstract: An underlying layer is formed of Cr or the like on a glass substrate, and a magnetic layer is formed on the underlying layer by simultaneously sputtering a magnetic substance and a non-magnetic substance that does not form a solid solution with the magnetic substance in an atmosphere having a pressure of 30 mTorr to 75 mTorr. The magnetic recording medium comprises clusters, each of which is formed of aggregated magnetic grains, and a non-magnetic substance between the clusters. Each magnetic grain has a grain diameter of 5 nm to 20 nm. An average gap between the clusters is 1.5 nm to 5 nm. Thus, the present invention can provide a magnetic recording medium having a high S/N ratio that is suitable for high density recording.
    Type: Grant
    Filed: September 15, 1998
    Date of Patent: June 5, 2001
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Hiroshi Ryonai, Tatsuaki Ishida, Kiyokazu Tohma, Keizou Miyata, Taizou Hamada
  • Patent number: 5851660
    Abstract: The objective of the present invention is to provide a method of fabricating a thin film magnetic recording medium where excellent read/write characteristics and high productivity are obtained and also to provide the thin film magnetic recording medium. The present invention is a method of fabricating a thin film magnetic recording medium where vapor evaporation is given by a vacuum evaporation device onto a traveling substrate to form a magnetic layer. The temperature of a reevaporation member, disposed so as to be opposed to the substrate on the downstream side of a magnetic layer formation start portion where the magnetic layer begins to form, is raised to higher than the melting point of an evaporation material. Atoms, which are evaporated from an evaporation source and reach said reevaporation member for forming said magnetic layer, are reevaporated by the raised temperature of the reevaporation member.
    Type: Grant
    Filed: November 5, 1996
    Date of Patent: December 22, 1998
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Kiyokazu Tohma, Kazunari Yoshimoto, Ryuji Sugita
  • Patent number: 5679410
    Abstract: A thin film magnetic recording medium is manufactured with vacuum deposition or sputtering technique. One or more reflectors are provided between the substrate and an evaporation source around a path through which evaporated atoms travel onto a substrate. When a thin film is deposited on a substrate, the one or more reflectors are heated above a melting point of an evaporation material to reflect evaporated atoms arriving them. Thus, atoms reflected by the one or more reflectors also contribute to deposition of a thin film as well as evaporated atoms arriving directly from the evaporation source, and deposition efficiency is improved. Such a reflector is also used to limit a boundary or the path through which evaporated atoms travel onto a substrate. Then, a range of incident angles of evaporated atoms onto the substrate is kept the same for a long time on deposition, and characteristics of the thin film are stable.
    Type: Grant
    Filed: June 5, 1995
    Date of Patent: October 21, 1997
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Ryuji Sugita, Kiyokazu Tohma, Tatsuaki Ishida, Kazunari Yoshimoto
  • Patent number: 5665460
    Abstract: A magnetic recording medium having a first magnetic layer positioned on a substrate and a second magnetic layer positioned on the first magnetic layer, wherein the first magnetic layer is a film of a partial oxide based on Co in which a growth direction of crystalline grain is substantially normal to the film plane and the easy magnetization axis is in a direction of the film plane or direction substantially normal to the film plane, and the second magnetic layer is a film of a partial oxide based on Co in which the growth direction of crystalline grain is diagonally inclined to the line normal to the film plane and the easy magnetization axis is diagonally inclined to the line normal to the film plane.
    Type: Grant
    Filed: October 26, 1995
    Date of Patent: September 9, 1997
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Ryuji Sugita, Kiyokazu Tohma, Tatsuaki Ishida, Kazunari Yoshimoto
  • Patent number: 5554440
    Abstract: A magnetic tape having a polymer substrate and a magnetic layer which is formed directly on a surface of the substrate or on a primer layer formed on the substrate and contains cobalt, oxygen and optionally nickel, in which a coercive force is at least 120 kA/m and a squareness ratio is at least 0.
    Type: Grant
    Filed: September 9, 1993
    Date of Patent: September 10, 1996
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Tatsuaki Ishida, Ryuji Sugita, Kiyokazu Tohma, Yasuaki Ban
  • Patent number: 5549936
    Abstract: In a manufacturing method of a magnetic recording medium with a vacuum deposition, two shielding members are provided above a substrate for defining an aperture. An evaporation source is located at a position wherein evaporated atoms from an evaporation material can adhere to a moving substrate through the aperture. The substrate is moved while a material in the evaporation source is irradiated at two evaporation portions with two electron beams along a moving direction of the substrate to form a magnetic layer. Thus, curving of columnar gains formed in the magnetic layer is suppressed or crystal orientation is enhanced, and magnetic read/write characteristics are improved. Further, a productivity is improved because the aperture can be enlarged than previously by using the two evaporation portions.
    Type: Grant
    Filed: October 18, 1994
    Date of Patent: August 27, 1996
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Kiyokazu Tohma, Kazunari Yoshimoto, Ryuji Sugita, Tatsuaki Ishida
  • Patent number: 5534324
    Abstract: A magnetic recording medium has a cobalt-based first magnetic layer and a cobalt-based second magnetic layer which are formed on a substrate of high polymer by vacuum evaporation. In order to have a high reproducing output and a high S/N ratio, the first magnetic layer has high oxygen density area which is arranged at a vicinity of the second magnetic layer, and the second magnetic layer has high oxygen density area which is arranged at a vicinity of the first magnetic layer.
    Type: Grant
    Filed: November 10, 1993
    Date of Patent: July 9, 1996
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Ryuji Sugita, Kiyokazu Tohma, Tatsuaki Ishida, Yasuaki Ban
  • Patent number: 5472506
    Abstract: A magnetic recording medium having good high density recording characteristics is produced by forming a magnetic layer on a substrate which is traveling around a peripheral surface of a cylindrical can by an oblique vapor deposition method to form a magnetic layer comprising cobalt, an axis of easy magnetization of which inclined from a line normal to the layer plane. A residual gas pressure in an initial region of the formation of the magnetic layer is kept as low as possible, in particular, the residual gas pressure in the initial region of the formation of the magnetic layer is lower than in the other part of the production apparatus.
    Type: Grant
    Filed: January 3, 1995
    Date of Patent: December 5, 1995
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Kiyokazu Tohma, Ryuji Sugita, Tatsuaki Ishida, Yasuaki Ban
  • Patent number: 5458914
    Abstract: A magnetic recording medium having good high density recording characteristics is produced by forming a magnetic layer on a substrate which is traveling around a peripheral surface of a cylindrical can by an oblique vapor deposition method to form a magnetic layer comprising cobalt, an axis of easy magnetization of which inclined from a line normal to the layer plane. A residual gas pressure in an initial region of the formation of the magnetic layer is kept as low as possible, in particular, the residual gas pressure in the initial region of the formation of the magnetic layer is lower than in the other part of the production apparatus.
    Type: Grant
    Filed: January 3, 1995
    Date of Patent: October 17, 1995
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Kiyokazu Tohma, Ryuji Sugita, Tatsuaki Ishida, Yasuaki Ban
  • Patent number: 5433999
    Abstract: In a magnetic recording medium with a back coat layer including polyurethane having a Tg (glass-transition temperature) below room temperature, isocyanate hardener, carbon powder and inorganic abrasive pigment are formed on a face of a non-magnetic substrate opposite a face covered by a magnetic recording film. Using this back coat layer, improved post contact characteristics and the like are obtained and smooth running conditions under small tensions are realized. Further, the magnetic recording medium causes only a small amount of head wear, and the medium has improved wear resistance.
    Type: Grant
    Filed: September 29, 1993
    Date of Patent: July 18, 1995
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Yoshiki Goto, Yukihiro Shimasaki, Kazuyoshi Honda, Tatsuaki Ishida, Kiyokazu Tohma, Ryuji Sugita, Yasuhiro Kawawake
  • Patent number: 5427869
    Abstract: A magnetic recording medium includes a nonmagnetic substrate and a magnetic layer which is formed on a surface of the substrate and which has an axis of easy magnetization inclined from a direction to normal plane of the layer. An angular dependency of coercive force, of the medium which is measured by changing an application angle of a magnetic field in a range relative to -90.degree. to +90.degree. from the plane of the layer with a plane normal to the layer and including the axis of easy magnetization, has two local maximum values and two local minimum values. A ratio of the local maximum value closer to a plane direction to the minimum value closer of the layer to the local plane direction of the layer is from 1.6 to 2.4, and the local maximum value closer to the plane direction of the layer is larger than the local maximum value closer to the line normal to of the plane of the layer. The medium has a high S/N ratio.
    Type: Grant
    Filed: August 10, 1993
    Date of Patent: June 27, 1995
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Ryuji Sugita, Kiyokazu Tohma, Tatsuaki Ishida, Yasuaki Ban
  • Patent number: 5418059
    Abstract: A magnetic recording medium having a nonmagnetic substrate, a first magnetic layer which is formed on a surface of the substrate, has an axis of easy magnetization slanting from a normal line of a layer plane, contains cobalt and oxygen in an amount of not more than 40 atomic % and has a thickness of not larger than 0.15 .mu.m, and a second magnetic layer which is formed on a surface of the first magnetic layer, contains cobalt, has an axis of easy magnetization slanting from a normal line of a layer plane, contains oxygen in an amount of not larger than 37 atomic % and from 61 % to 99 % of the oxygen concentration in the first layer, and has a thickness of not larger than 0.15 .mu.m, which medium has a large S/N ratio.
    Type: Grant
    Filed: June 4, 1993
    Date of Patent: May 23, 1995
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Ryuji Sugita, Kiyokazu Tohma, Tatsuaki Ishida, Yasuaki Ban
  • Patent number: 5298282
    Abstract: A method for producing a magnetic recording medium having a magnetic layer having a two-layered structure positioned on a substrate, which includes forming the magnetic layer on the substrate by a vacuum deposition process during the travel of the substrate on a cylindrical can, wherein a first evaporation source and a second evaporation source are positioned on the same side of a vertical line passing across a longitudinal axis of the cylindrical can while confronting the cylindrical can, a shield plate having a first opening and a second opening is positioned between the cylindrical can and the first and second evaporation sources, each of vapors evaporated from the first and second evaporation sources passes through the first and second openings, respectively, a distance between the vertical line passing across the longitudinal axis of the cylindrical can and a center of an evaporation part of the first evaporation source is longer than a radius of the cylindrical can, and a distance between the vertical l
    Type: Grant
    Filed: July 20, 1993
    Date of Patent: March 29, 1994
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Ryuji Sugita, Kiyokazu Tohma, Tatsuaki Ishida
  • Patent number: 5202149
    Abstract: In the method for making the magnetic recording wherein a first magnetic layer is formed on a substrate and a second magnetic layer is formed on the first magnetic layer, before forming the second magnetic layer, accelerated ions are irradiated onto a surface of the first magnetic layer. Thereby, naturally formed oxidized layer and adhered impurity on the first magnetic layer are removed from the surface of the first magnetic layer by ion etching action by the irradiation of ions, and hence a preferable condition of an interface between the first magnetic layer and subsequently formed second magnetic layer is obtained.
    Type: Grant
    Filed: June 2, 1992
    Date of Patent: April 13, 1993
    Assignee: Matsushita Electric Industrial Co., Ltd.
    Inventors: Tatsuaki Ishida, Ryuji Sugita, Kiyokazu Tohma, Kazuyoshi Honda, Yasuhiro Kawawake, Yoshiki Goto