Substrates for magnetic discs, magnetic discs and process for producing magnetic discs

• US 6,048,589 A
• Filed: 11/09/1998
• Issued: 04/11/2000
• Est. Priority Date: 06/21/1995
• Status: Expired due to Fees

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: Takeya, Fuminori, Abe, Masahiro, Suzuki, Tomio
• Primary Examiner(s): Resan, Stevan A.
• Application Number:
  US09/188,982
• Time in Patent Office: 519 Days
• Field of Search: 427/554, 427/555, 427/444, 427/301, 427/299, 427/275, 427/131, 427/129
• US Class Current: 427/554
• CPC Class Codes: C03C 10/0027 containing SiO2, Al2O3, Li2O as main constituents
• CPC Class Codes: C03C 21/001 in liquid phase, e.g. molten salts, solutions
• CPC Class Codes: C03C 21/005 to introduce in the glass such metals or metallic ions as Ag, Cu
• CPC Class Codes: G11B 5/73921 Glass or ceramic substrates
• CPC Class Codes: G11B 5/8404 manufacturing base layers
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]

Abstract

A magnetic disc substrate is provided, which includes a magnetic disc substrate body made of glass and is characterized in that a metal element capable of absorbing light in at least a surface portion of the magnetic disc substrate body, and a texture is formed on a surface of the magnetic disc substrate body. Ions of the metal element are dispersed in the surface portion of the magnetic disc substrate, or the metal element is contained in a composition of the glass constituting the magnetic disc substrate in the form of an oxide. The glass is preferably a crystallized glass a Li₂ O--Al₂ O₃ --SiO₂ based crystallized glass, which particularly preferably contains 65 to 85 wt % of SiO₂, 8 to 15 wt % of Li₂ O, 2 to 8 wt % of Al₂ O₃, 1 to 5 wt % of P₂ O₅ and 1 to 10 wt % of ZrO₂ and has lithium disilicate (Li₂ O.2SiO₂) as a main crystalline phase.

Claims

1. A process for producing a magnetic disc substrate, comprising the steps of:

polishing a surface of a glass magnetic disc substrate;

immersing the magnetic disc substrate into a melted salt of metal ions to incorporate a metallic element into at least the polished surface portion of the magnetic disc substrate, wherein said metallic element is capable of absorbing light having a wavelength of 1600 nm or less; and

irradiating high energy having a wavelength of 1600 nm or less upon the polished surface of the magnetic disc substrate, whereby said metallic element allows formation of a textured area on the surface of said magnetic disc substrate.

2. The process for producing the magnetic disc substrate set forth in claim 1, wherein the magnetic disc substrate comprises a reading/writing zone for recording the reproducing signals and a landing zone with which a magnetic head slider, the textured area having protuberances at heights of 50 to 200 Å

is formed by irradiating the high energy light having a wavelength of 1600 nm or less upon the landing zone after finely polishing the surface of the magnetic disc substrate such that an area of top portions of said protuberances amounts to 2 to 5% of a total area of the landing zone.

3. The process for producing the magnetic disc substrate set forth in claims 1, wherein a laser beam selected from the group consisting of a YAG laser beam and an argon laser beam is used as said high energy light having a wavelength of 1600 nm or less.

4. The process for producing the magnetic disc substrate set forth in claims 1, wherein each of the protuberances constituting said textured area has an arched planar shape extending in a circumferential direction.