Hoya Corporation

Xuelu Zou

Mikio Ikenishi

Yasuhiro Fujiwara

Yoshiko Kasuga

Tomoaki Negishi

Kazutaka Hayashi

Yoichi Hachitani

Kazuo Tachiwana

Hiroshi Kawazoe

Kinobu Osakabe

Hisayoshi Toratani

Hiromasa Tawarayama

Kouji Azegami

Atsuko Morita

Yoshio Nojima

Kazuaki Hashimoto

Junichi Horikawa

Hiroki Takazawa

Yunoshin Kanayama

Kenji Yamanaka

Masahiro Yoshida

Hiroshi Kouno

Katsuaki Uchida

Yoshikane Shinkuma

Youichi Hachitani

Kohichiro Shiraishi

Kouichiroh Shiraishi

Rie Yamane

Hiroshi Kohno

According to one aspect of the present invention, provided is glass for use in substrate for information recording medium, which comprises, denoted as molar percentages, a total of 70 to 85 percent of SiOand AlO, where SiOcontent is equal to or greater than 50 percent and AlOcontent is equal to or greater than 3 percent; a total of equal to or greater than 10 percent of LiO, NaO and KO; a total of 1 to 6 percent of CaO and MgO, where CaO content is greater than MgO content; a total of greater than 0 percent but equal to or lower than 4 percent of ZrO, HfO, NbO, TaO, LaOYOand TiO; with the molar ratio of the total content of LiO, NaO and KO to the total content of SiO, AlO, ZrO, HfO, NbO, TaO, LaO, YOand TiO((LiO+NaO+KO)/(SiO+AlO+ZrO+HfO+NbO+TaO+LaO+YO+TiO)) being equal to or less than 0.28. Further provided are the substrate for information recording medium, information recording medium and their manufacturing methods according to the present invention.

Glass for use as substrate for information recording medium, substrate for information recording medium and information recording medium, and their production methods

A glass for use in chemical reinforcement for use in a substrate of an information recording medium, having a composition comprising, denoted as mol %: and the total content of the above-stated components is greater than or equal to 95%. A glass for use in chemical reinforcement for use in the substrate of an information recording medium employed in a perpendicular magnetic recording system, in which the glass exhibits the glass transition temperature is greater than or equal to 600&#xb0; C. A substrate for use in an information recording medium consisting of the above glass and being chemically reinforced. A substrate for an information recording medium consisting of a chemically reinforced glass having a glass transition temperature of greater than or equal to 600&#xb0; C. and exhibiting a bending strength following heating for two hours at 570&#xb0; C. of greater than or equal to 15 kgf/mm. An information recording medium comprising an information recording layer on the above substrate for an information recording medium. The present invention provides glass having both high thermal resistance and high strength, a substrate for use in information recording media comprised of this glass, and an information recording medium employing such a substrate.

Glass for chemical strengthening, substrate for information recording media and information recording media

A method for manufacturing an optical glass element, comprising: annealing a press-molded product obtained by press molding into a lens shape a glass material comprised of a core portion comprised of an optical glass (first glass) with a transition temperature of 550&#xb0; C. or higher and a covering portion comprised of a second glass covering the surface of said core portion; and then removing the covering layer from the surface of the press-molded product to obtain an optical glass element. To provide a method for manufacturing high-optical-performance mold-pressed lenses in which the defective external appearance of optical elements comprised of high-temperature glass materials with a Tg of 550&#xb0; C. or higher is prevented.

Method for manufacturing optical glass element

Optical glass

An optical glass having high-refractivity and low-dispersion properties and containing, by mol %, 0.1 to 40% of SiO, 10 to 50% of BO, wherein the mass ratio of the content of SiOto the content of BO, SiO/BO, is 1 or less, 0.5 to 22% of ZnO, 5 to 50% of LaO, and optionally other ingredients. The optical glass has a refractive index nd of 1.86 to 1.95 and an Abbe's number &#x3bd;d of (2.36&#x2212;nd)/0.014 or more but less than 38, and a glass transition temperature of equal to or greater than 640&#xb0; C.

A high-refractivity low-dispersion optical glass that can be stably supplied and has excellent glass stability and that has coloring reduced, composed of in mass %, 5 to 32% of total of SiOand BO, 45 to 65% of total of LaO, GdOand YO, 0.5 to 10% of ZnO, 1 to 20% of total of TiOand NbO, and optionally other components. The optical glass has a refractive index nd of 1.89 to 2.0, an Abbe's number &#x3bd;d of 32 to 38 and a coloring degree &#x3bb;70 of 430 nm or less.

An optical glass that is an oxide glass having a very high refractive index in spite of its low-dispersion property, having excellent glass stability and having less susceptibility to coloring.

A glass material for mold pressing, comprised of a core portion and a covering portion. In one embodiment, the core portion comprises a multicomponent optical glass containing at least one readily reducible component selected from among W, Ti, Bi, and Nb and the covering portion comprises a multicomponent glass containing none or a lower quantity of the readily reducible component than is contained in the core portion. In another embodiment, the core portion comprises a fluorine-containing multicomponent optical glass, and the covering portion comprises a multicomponent glass containing none or a lower quantity of fluorine than is contained in the core portion. A method for manufacturing an optical glass element employing the above glass material that comprises heat softening a glass material that has been preformed into a prescribed shape, and conducting press molding with a pressing mold.

Glass material for mold pressing, method for manufacturing same, and method for manufacturing optical glass element

Disclosed are a glass substrate for an information recording medium, having excellent scratch resistance and a light weight and having high fracture toughness, the glass substrate having a fragility index value, measured in water, of 12 &#x3bc;mor less or having a fragility index value, measured in an atmosphere having a dew point of &#x2212;5&#xb0; C. or lower, of 7 &#x3bc;mor less, or the glass substrate comprising, by mol %, 40 to 75% of SiO, 2 to 45% of BOand/or AlOand 0 to 40% of R'O in which R&#x2032; is at least one member selected from the group consisting of Li, Na and K), wherein the total content of SiO, BO, AlOand R&#x2032;O is at least 90 mol %, and a magnetic information recording medium comprising a magnetic recording layer formed on the glass substrate.

Glass substrate for information recording medium and magnetic information recording medium to which the glass substrate is applied

A method for manufacturing a disklike glass material comprising the successive molding of multiple pieces of disklike glass material from glass melt. Being suppressed variation over time in the concentration of infrared radiation-absorbing ions contained in the glass melt being molded into the pieces of disklike glass material so that the variation in the sheet thickness of the multiple pieces of disklike glass material falls within a range of &#xb1;15 percent of a reference value. The reference value being the median between the maximum value and the minimum value of the sheet thickness of 1,000 pieces of the glass material. In the course of molding multiple pieces of disklike glass material comprised of glass containing 0.1 to 100 ppm of infrared radiation-absorbing ions, vaiiation over time in the concentration of the infrared radiation-absorbing contained in the glass melt is suppressed to suppress variation in the sheet thickness of the multiple pieces of sheet like glass material.

Material for information recording medium substrate, information recording medium substrate, information recording medium, and method for manufacturing them

Disclosed is a glass material for press forming providing an optical element having a sufficient optical performance without surface cracks, cloudiness, scratches, and the like even when the glass material contains a highly reactive component. Also disclosed are an optical element having a sufficient optical performance without surface cracks, cloudiness, scratches, and the like and a method for manufacturing the same. Specifically disclosed is a glass material for press forming which comprises a core portion composed of multicomponent optical glass and a surface glass layer covering at least a region serving as an optical functional surface of the core portion. The surface glass layer contains more than 90 mass % of SiO, and the thickness of the layer is less than five nanometers. Also specifically disclosed is a method for manufacturing a glass optical element by heating the glass material and by press forming the softened glass material using a forming die. Yet also specifically disclosed is a press formed glass optical element having a core portion composed of multicomponent optical glass and a surface glass layer covering at least an optical functional surface of the core portion. The surface glass layer contains more than 90 mass % of SiO, and the thickness of the layer is less than five nanometers.

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Tokyo, Japan

Xuelu Zou