Patents by Inventor Katsuhiro Imai

Katsuhiro Imai 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).

  • Patent number: 8241422
    Abstract: It is provided a method of growing gallium nitride single crystal of good quality with a high productivity, in the growth of gallium nitride single crystal by Na-flux method. Gallium nitride single crystal is grown using flux 8 containing at least sodium metal. Gallium nitride single crystal is grown in atmosphere composed of gases mixture “B” containing nitrogen gas at a pressure of 300 atms or higher and 2000 atms or lower. Preferably, the nitrogen partial pressure in the atmosphere is 100 atms or higher and 2000 atms or lower. Preferably, the growth temperature is 1000° C. or higher and 1500° C. or lower.
    Type: Grant
    Filed: March 30, 2005
    Date of Patent: August 14, 2012
    Assignee: NGK Insulators, Ltd.
    Inventors: Makoto Iwai, Katsuhiro Imai, Minoru Imaeda
  • Publication number: 20120175740
    Abstract: Regarding a base substrate, a plurality of steps are formed stepwise on the principal surface (c-face). Each step has a height difference of 10 to 40 ?m, and an edge is formed parallel to an a-face of a hexagonal crystal of GaN. Meanwhile, the terrace width of each step is set at a predetermined width. The predetermined width is set in such a way that after a GaN crystal is grown on the principal surface of the base substrate, the principal surface is covered up with grain boundaries when the grown GaN crystal is observed from the surface side. The plurality of steps can be formed through, for example, dry etching, sand blasting, lasing, and dicing.
    Type: Application
    Filed: October 15, 2010
    Publication date: July 12, 2012
    Inventors: Takayuki Hirao, Takanao Shimodaira, Katsuhiro Imai
  • Patent number: 8216365
    Abstract: Objects of the invention are to further enhance crystallinity and crystallinity uniformity of a semiconductor crystal produced through the flux method, and to effectively enhance the production yield of the semiconductor crystal. The c-axis of a seed crystal including a GaN single-crystal layer is aligned in a horizontal direction (y-axis direction), one a-axis of the seed crystal is aligned in the vertical direction, and one m-axis is aligned in the x-axis direction. Thus, three contact points at which a supporting tool contacts the seed crystal are present on m-plane. The supporting tool has two supporting members, which extend in the vertical direction. One supporting member has an end part, which is inclined at 30° with respect to the horizontal plane ?. The reasons for supporting a seed crystal at m-plane thereof are that m-plane exhibits a crystal growth rate, which is lower than that of a-plane, and that desired crystal growth on c-plane is not inhibited.
    Type: Grant
    Filed: February 29, 2008
    Date of Patent: July 10, 2012
    Assignee: Toyoda Gosei Co., Ltd.
    Inventors: Seiji Nagai, Shiro Yamazaki, Takayuki Sato, Katsuhiro Imai, Makoto Iwai, Takatomo Sasaki, Yusuke Mori, Fumio Kawamura
  • Publication number: 20120111264
    Abstract: A plurality of seed crystal films of a single crystal of a nitride of a metal belonging to group III are formed on a substrate, while a non-growth surface not covered with the seed crystal films is formed on the substrate. A single crystal of a nitride of a metal belonging to group III is grown on the seed crystal film. A plurality of the seed crystal films are separated by the non-growth surface and arranged in at least two directions X and Y. The maximum inscribed circle diameter “A” of the seed crystal film is 50 ?m or more and 6 mm or less, a circumscribed circle diameter “B” of the seed crystal film is 50 ?m or more and 10 mm or less, and the maximum inscribed circle diameter “C” of the non-growth surface 1b is 100 ?m or more and 1 mm or less.
    Type: Application
    Filed: January 6, 2012
    Publication date: May 10, 2012
    Inventors: Takanao Shimodaira, Katsuhiro Imai, Makoto Iwai
  • Patent number: 8154675
    Abstract: A lateral electric field liquid crystal display panel is provided which includes a pair of substrates, a liquid crystal enclosed between the pair of substrates, liquid crystal-drive electrodes provided on one of the pair of substrates, a translucent electrostatic shielding layer provided on an exterior surface of at least one of the pair of substrates, and a polarizer disposed on the translucent electrostatic shielding layer, and in this liquid crystal display panel, the translucent electrostatic shielding layer has properties not to disappear by a chemical reaction with a material forming the polarizer.
    Type: Grant
    Filed: April 28, 2009
    Date of Patent: April 10, 2012
    Assignee: Sony Corporation
    Inventors: Katsuhiro Imai, Kanechika Kiyose, Kennosuke Kakehi, Satoshi Taguchi
  • Publication number: 20120012984
    Abstract: To grow a gallium nitride crystal, a seed-crystal substrate is first immersed in a melt mixture containing gallium and sodium. Then, a gallium nitride crystal is grown on the seed-crystal substrate under heating the melt mixture in a pressurized atmosphere containing nitrogen gas and not containing oxygen. At this time, the gallium nitride crystal is grown on the seed-crystal substrate under a first stirring condition of stirring the melt mixture, the first stirring condition being set for providing a rough growth surface, and the gallium nitride crystal is subsequently grown on the seed-crystal substrate under a second stirring condition of stirring the melt mixture, the second stirring condition being set for providing a smooth growth surface.
    Type: Application
    Filed: August 12, 2011
    Publication date: January 19, 2012
    Applicant: NGK Insulators, Ltd.
    Inventors: Takanao SHIMODAIRA, Takayuki Hirao, Katsuhiro Imai
  • Patent number: 8084281
    Abstract: The present invention provides a method for producing a semiconductor substrate, the method including reacting nitrogen (N) with gallium (Ga), aluminum (Al), or indium (In), which are group III elements, in a flux mixture containing a plurality of metal elements selected from among alkali metals and alkaline earth metals, to thereby grow a group III nitride based compound semiconductor crystal. The group III nitride based compound semiconductor crystal is grown while the flux mixture and the group III element are mixed under stirring. At least a portion of a base substrate on which the group III nitride based compound semiconductor crystal is grown is formed of a flux-soluble material, and the flux-soluble material is dissolved in the flux mixture, at a temperature near the growth temperature of the group III nitride based compound semiconductor crystal, during the course of growth of the semiconductor crystal.
    Type: Grant
    Filed: March 15, 2007
    Date of Patent: December 27, 2011
    Assignees: Toyoda Gosei Co., Ltd., NGK Insulators, Ltd., Osaka University
    Inventors: Naoki Shibata, Koji Hirata, Shiro Yamazaki, Katsuhiro Imai, Makoto Iwai, Takatomo Sasaki, Yusuke Mori, Fumio Kawamura
  • Patent number: 8068202
    Abstract: A liquid crystal device includes a first substrate and a second substrate opposite each other with a liquid crystal layer interposed therebetween, wherein the first substrate includes a signal line, a switching element electrically connected to the signal line, a first electrode electrically connected to the switching element, a wiring line, a dielectric film covering the first electrode, the switching element, and the wiring line, and a second electrode disposed on the dielectric film so as to be opposite the first electrode, and wherein the second electrode is drawn from the dielectric film toward an area where the dielectric film does not exist and is electrically connected to the wiring line through the area where the dielectric film does not exist.
    Type: Grant
    Filed: November 19, 2007
    Date of Patent: November 29, 2011
    Assignee: Sony Corporation
    Inventors: Norihito Harada, Katsuhiro Imai
  • Publication number: 20110287222
    Abstract: A sapphire substrate on a surface of which a thin film of gallium nitride is formed is prepared as a seed-crystal substrate and placed in a growth vessel. Gallium and sodium metals are weighed to achieve a molar ratio of 25 to 32:68 to 75 and added into the vessel. The vessel is put into a reaction vessel. An inlet pipe is connected to the reaction vessel. Nitrogen gas is introduced from a nitrogen tank through a pressure controller to fill the reaction vessel. While the internal pressure of the reaction vessel is controlled to be a predetermined nitrogen gas pressure and target temperatures are set such that the temperature of a lower heater is higher than the temperature of an upper heater, a gallium nitride crystal is grown. As a result, a group 13 nitride crystal having a large grain size and a low dislocation density is provided.
    Type: Application
    Filed: July 21, 2011
    Publication date: November 24, 2011
    Applicant: NGK Insulators, Ltd.
    Inventors: Takayuki Hirao, Makoto Iwai, Katsuhiro Imai
  • Publication number: 20110274609
    Abstract: A group 13 nitride crystal substrate according to the present invention is produced by growing a group 13 nitride crystal on a seed-crystal substrate by a flux method, wherein a content of inclusions in the group 13 nitride crystal grown in a region of the seed-crystal substrate except for a circumferential portion of the seed-crystal substrate, the region having an area fraction of 70% relative to an entire area of the seed-crystal substrate, is 10% or less, preferably 2% or less.
    Type: Application
    Filed: July 15, 2011
    Publication date: November 10, 2011
    Applicant: NGK Insulators, Ltd.
    Inventors: Takanao Shimodaira, Katsuhiro Imai, Makoto Iwai, Takayuki Hirao
  • Patent number: 8025728
    Abstract: A seed crystal is immersed in a melt containing a flux and a single crystal material in a growth vessel to produce a nitride single crystal on the seed crystal. A difference (TS-TB) of temperatures at a gas-liquid interface of the melt (TS) and at the lowermost part of the melt (TB) is set to 1° C. or larger and 8° C. or lower. Preferably, the substrate of seed crystal is vertically placed.
    Type: Grant
    Filed: September 22, 2008
    Date of Patent: September 27, 2011
    Assignees: NGK Insulators, Ltd., Osaka University
    Inventors: Mikiya Ichimura, Katsuhiro Imai, Chikashi Ihara, Takatomo Sasaki, Yusuke Mori, Fumio Kawamura
  • Patent number: 7988784
    Abstract: It is used a substrate main body 1 having a side face 1b and a pair of main faces 1a and an underlying film 2 of a single crystal of a nitride of a metal belonging to the group III formed at least on one main face of the substrate main body 1. A single crystal 3 of a nitride of a metal belonging to the group III is grown on the main face 1a of the substrate main body 1 by a liquid phase process. The underlying film 2 has a shape of a convex figure in a plan view. A surface 4 without the underlying film thereon surrounds the entire circumference of the underlying film 2. The single crystal 3 of a nitride of a metal belonging to the group III grown on the underlying film 2 is not brought into contact with a single crystal of a nitride of a metal belonging to group III formed on another underlying film.
    Type: Grant
    Filed: July 23, 2010
    Date of Patent: August 2, 2011
    Assignee: NGK Insulators, Ltd.
    Inventors: Takayuki Hirao, Katsuhiro Imai, Mikiya Ichimura
  • Publication number: 20100307404
    Abstract: It is used a substrate main body 1 having a side face 1b and a pair of main faces 1a and an underlying film 2 of a single crystal of a nitride of a metal belonging to the group III formed at least on one main face of the substrate main body 1. A single crystal 3 of a nitride of a metal belonging to the group III is grown on the main face 1a of the substrate main body 1 by a liquid phase process. The underlying film 2 has a shape of a convex figure in a plan view. A surface 4 without the underlying film thereon surrounds the entire circumference of the underlying film 2 The single crystal 3 of a nitride of a metal belonging to the group III grown on the underlying film 2 is not brought into contact with a single crystal of a nitride of a metal belonging to group III formed on another underlying film.
    Type: Application
    Filed: July 23, 2010
    Publication date: December 9, 2010
    Applicant: NGK Insulators, Ltd.
    Inventors: Takayuki Hirao, Katsuhiro Imai, Mikiya Ichimura
  • Publication number: 20100301358
    Abstract: The present invention provides a method for producing a semiconductor substrate, the method including reacting nitrogen (N) with gallium (Ga), aluminum (Al), or indium (In), which are group III elements, in a flux mixture containing a plurality of metal elements selected from among alkali metals and alkaline earth metals, to thereby grow a group III nitride based compound semiconductor crystal. The group III nitride based compound semiconductor crystal is grown while the flux mixture and the group III element are mixed under stirring. At least a portion of a base substrate on which the group III nitride based compound semiconductor crystal is grown is formed of a flux-soluble material, and the flux-soluble material is dissolved in the flux mixture, at a temperature near the growth temperature of the group III nitride based compound semiconductor crystal, during the course of growth of the semiconductor crystal.
    Type: Application
    Filed: March 15, 2007
    Publication date: December 2, 2010
    Inventors: Naoki Shibata, Koji Hirata, Shiro Yamazaki, Katsuhiro Imai, Makoto Iwai, Takatomo Sasaki, Yusuke Mori, Fumio Kawamura
  • Patent number: 7839471
    Abstract: A liquid crystal device has a plurality of pixels arranged. The liquid crystal device includes a first substrate, a second substrate opposing the first substrate, liquid crystal provided between the first substrate and the second substrate, wires formed on the first substrate, and a reflective layer formed on the first substrate. Each pixel has a reflective display region formed by the reflective layer and a transparent display region without the reflective layer, and each wire is routed between two pixels in the transparent display region and in the reflective display region.
    Type: Grant
    Filed: March 14, 2007
    Date of Patent: November 23, 2010
    Assignee: Epson Imaging Devices Corporation
    Inventors: Mutsumi Matsuo, Katsuhiro Imai, Tomohiko Kojima, Yoshio Yamaguchi
  • Patent number: 7815733
    Abstract: A method of growing hexagonal boron nitride single crystal is provided. Hexagonal boron nitride single crystal is grown in calcium nitride flux by heating, or heating and then slowly cooling, boron nitride and a calcium series material in an atmosphere containing nitrogen. Bulk hexagonal boron nitride single crystal can thereby successfully be grown.
    Type: Grant
    Filed: August 13, 2007
    Date of Patent: October 19, 2010
    Assignees: NGK Insulators, Ltd.
    Inventors: Makoto Iwai, Katsuhiro Imai, Takatomo Sasaki, Fumio Kawamura, Minoru Kawahara, Hiroaki Isobe
  • Patent number: 7708833
    Abstract: An object of the invention is to carry out the flux method with improved work efficiency while maintaining the purity of flux at high level and saving flux material cost. The sodium-purifying apparatus includes a sodium-holding-and-management apparatus for maintaining purified sodium (Na) in a liquid state. Liquid sodium is supplied into a sodium-holding-and-management apparatus through a liquid-sodium supply piping maintained at 100° C. to 200° C. The sodium-holding-and-management apparatus further has an argon-gas-purifying apparatus for controlling the condition of argon (Ar) gas that fills the internal space thereof. Thus, by opening and closing a faucet at desired timing, purified liquid sodium (Na) supplied from the sodium-purifying apparatus can be introduced into a crucible as appropriate via the liquid-sodium supply piping, the sodium-holding-and-management apparatus, and the piping.
    Type: Grant
    Filed: March 11, 2008
    Date of Patent: May 4, 2010
    Assignees: Toyoda Gosei Co., Ltd., NGK Insulators, Ltd.
    Inventors: Shiro Yamazaki, Koji Hirata, Takayuki Sato, Seiji Nagai, Katsuhiro Imai, Makoto Iwai, Shuhei Higashihara, Takatomo Sasaki, Yusuke Mori, Fumio Kawamura
  • Patent number: 7670430
    Abstract: It is provided a method for gently and safely recovering only sodium metal from a flux containing sodium metal in a short time and in a reusable form. Flux 23 is heated in a medium 19 unreactive with sodium metal 22 at a temperature equal to or higher than the melting point of sodium metal to separate and recover the sodium metal 22 from the flux 23. The medium is a hydrocarbon, for example.
    Type: Grant
    Filed: August 5, 2008
    Date of Patent: March 2, 2010
    Assignee: NGK Insulators, Ltd.
    Inventors: Mikiya Ichimura, Katsuhiro Imai
  • Publication number: 20100012020
    Abstract: A nitride single crystal is produced on a seed crystal substrate 5 in a melt containing a flux and a raw material of the single crystal in a growing vessel 1. The melt 2 in the growing vessel 1 has temperature gradient in a horizontal direction. In growing a nitride single crystal by flux method, adhesion of inferior crystals onto the single crystal is prevented and the film thickness of the single crystal is made constant.
    Type: Application
    Filed: September 9, 2009
    Publication date: January 21, 2010
    Applicant: NGK Insulators, Ltd.
    Inventors: Mikiya Ichimura, Katsuhiro Imai, Makoto Iwai, Takatomo Sasaki, Yusuke Mori, Fumio Kawamura, Yasuo Kitaoka
  • Publication number: 20090294909
    Abstract: An object of the present invention is to realize, by the flux process, the production of a high-quality n-type semiconductor crystal having high concentration of electrons. The method of the invention for producing an n-type Group III nitride-based compound semiconductor by the flux process, the method including preparing a melt by melting at least a Group III element by use of a flux; supplying a nitrogen-containing gas to the melt; and growing an n-type Group III nitride-based compound semiconductor crystal on a seed crystal from the melt. In the method, carbon and germanium are dissolved in the melt, and germanium is incorporated as a donor into the semiconductor crystal, to thereby produce an n-type semiconductor crystal. The mole percentage of germanium to gallium in the melt is 0.05 mol % to 0.5 mol %, and the mole percentage of carbon to sodium is 0.1 mol % to 3.0 mol %.
    Type: Application
    Filed: May 20, 2009
    Publication date: December 3, 2009
    Applicant: OSAKA UNIVERSITY
    Inventors: Seiji Nagai, Shiro Yamazaki, Yasuhide Yakushi, Takayuki Sato, Makoto Iwai, Katsuhiro Imai, Yusuke Mori, Yasuo Kitaoka