Kao Corporation

Shigeo Fujii

Toshiya Hagihara

Hiroaki Kitayama

Yoshiaki Oshima

Koichi Naito

Hiroyuki Yoshida

Kenichi Suenaga

Koji Taira

A method for manufacturing a substrate for a magnetic disk, including the steps of (a) polishing a substrate with a polishing composition A containing alumina abrasives having an average particle size of from 0.05 to 0.5 &#x3bc;m, and an oxidizing agent, and (b) polishing the substrate with a polishing composition B containing silica particles having an average particle size of from 0.005 to 0.1 &#x3bc;m; a substrate for a magnetic disk, obtainable by the method for manufacturing a substrate for a magnetic disk; and a substrate for a magnetic disk having the following surface properties of a long-wavelength waviness of 0.05 nm or more and 0.3 nm or less, and an AFM surface roughness of 0.03 nm or more and 0.2 nm or less. The substrate for a magnetic disk may be suitably used in the manufacture of a hard disk having a high recording density. Especially, a hard disk having a recording density of 50 G bits or more per square inch may be industrially manufactured.

Substrate for magnetic disk

To provide a polishing composition capable of increasing polishing rate and reducing surface roughness, without causing surface defects on a surface of an object to be polished; and a polishing process for a substrate to be polished. [1] a polishing composition comprising water, an abrasive, an intermediate alumina, and a polycarboxylic acid having 4 or more carbon atoms with no OH groups or a salt thereof, wherein a content of the intermediate alumina is from 1 to 90 parts by weight, based on 100 parts by weight of the abrasive; and [2] a polishing process for a substrate to be polished, comprising polishing a substrate to be polished under conditions that a composition of a polishing liquid during polishing is the composition as defined in item [1] above.

Polishing fluid composition

The present invention preferably provides a polishing composition for a hard disk substrate, containing aluminum oxide particles and water, wherein secondary particles of the aluminum oxide particles have a volume-median particle size of from 0.1 to 0.7 &#x3bc;m, and particles having particle sizes of 1 &#x3bc;m or more of the aluminum oxide particles are contained in an amount of 0.2% by weight or less of the polishing composition; and a method for manufacturing a hard disk substrate using the polishing composition. By using the polishing composition and the method for manufacturing a substrate of the present invention, for example, a hard disk substrate suitable for high recording density can be provided in high productivity.

Polishing composition for hard disk substrate

A polishing composition comprising an abrasive and water, wherein the polishing composition has an index of degree of sedimentation of 80 or more and 100 or less; a process for producing a substrate comprising polishing a substrate to be polished using the above-mentioned composition; a process for preventing clogging of a polishing pad comprising applying the above-mentioned composition; a process for preventing clogging of a polishing pad comprising applying the above-mentioned composition to polishing with a polishing pad for a nickel-containing object to be polished; and a process for preventing clogging of a polishing pad comprising applying a composition comprising a hydrophilic polymer having two or more hydrophilic groups in its molecule and a molecular weight of 300 or more, or a compound capable of dissolving nickel hydroxide at a pH of 8.0, and water to polishing with a polishing pad for a nickel-containing object to be polished.

Polishing composition

A microwaviness reducing agent for polishing a substrate for a precision part, containing either a surfactant having two or more ionic hydrophilic groups, or a polycarboxylic acid compound having 2 to 15 total carbon atoms and having either OH group or groups or SH group or groups, or a salt thereof; a polishing composition for a substrate for a precision part, containing the microwaviness reducing agent, an abrasive and water; a polishing composition comprising water, an abrasive, an organic acid or a salt thereof, and a surfactant, wherein the organic acid is a polycarboxylic acid compound having 2 to 15 total carbon atoms and having either OH group or groups or SH group or groups, and wherein the surfactant has two or more ionic hydrophilic groups in its molecule and has a molecular weight of 300 or more; a method of reducing microwaviness of a substrate for a precision part; and a method for manufacturing a substrate for a precision part.

A roll-off reducing agent comprising one or more compounds selected from the group consisting of carboxylic acids having 2 to 20 carbon atoms having either OH group or groups or SH group or groups, monocarboxylic acids having 1 to 20 carbon atoms, and dicarboxylic acids having 2 to 3 carbon atoms, and salts thereof; and a roll-off reducing agent composition comprising a roll off-reducing agent comprising one or more compounds selected from the group consisting of carboxylic acids having 2 to 20 carbon atoms having either OH group or groups or SH group or groups, monocarboxylic acids having 1 to 20 carbon atoms, and dicarboxylic acids having 2 to 3 carbon atoms, and salts thereof; an abrasive; and water.

Roll-off reducing agent

A polishing composition comprising 0.03 to 0.5% by weight of an organic acid or a salt thereof, an abrasive and water, wherein the abrasive has a surface potential of from &#x2212;140 to 200 mV; a roll-off reducing agent comprising an inorganic compound having a property of controlling a surface potential of an abrasive in a polishing composition, wherein a surface potential of the abrasive in a standard polishing composition is controlled to &#x2212;110 to 250 mV by the presence of the inorganic compound, wherein the standard polishing composition is prepared which comprises 20 parts by weight of an abrasive, the abrasive being high-purity alumina having AlOpurity of 98.0% by weight or more composed of &#x3b1;-type corundum crystal, 1 part by weight of citric acid, 78 parts by weight of water and 1 part by weight of an inorganic compound. The polishing composition or the roll-off reducing agent composition can be favorably used in polishing the substrate for precision parts.

A polishing composition comprising an abrasive, an acid and/or a salt thereof, and water, wherein copper (Cu) is contained in an amount of 1 mg or less per kg of the polishing composition; a process for reducing a surface defect of a substrate comprising applying to a substrate or a polishing pad a polishing composition comprising an abrasive, an acid and/or a salt thereof, and water, wherein copper (Cu) is contained in an amount of 1 mg or less per kg of the polishing composition fed to the substrate or the polishing pad; and a process for manufacturing a substrate comprising a polishing step comprising applying to a substrate or a polishing pad the above polishing composition. The polishing composition of the present invention is used for polishing a substrate for precision parts such as substrates for magnetic recording media such as magnetic disks, optical disks, opto-magnetic disks, and the like; photomask substrates, optical lenses, optical mirrors, optical prisms and semiconductor substrates, concretely polishing a substrate for memory hard disks, and especially finish polishing.

A polishing composition comprising an abrasive, water and an organic acid or a salt thereof, wherein the composition has a specified viscosity of from 1.0 to 2.0 mPa&#xb7;s at a shearing rate of 1500 sand 25&#xb0; C.; a roll-off reducing agent comprising a Br&#xf6;nsted acid or a salt thereof, having an action of lowering viscosity so that the amount of viscosity lowered is 0.01 mPa&#xb7;s or more, wherein the amount of viscosity lowered is expressed by the following equation:(Amount of Viscosity Lowered)=(Viscosity of Standard Polishing Composition)&#x2212;(Viscosity of Roll-Off Reducing Agent-Containing Polishing Composition),wherein the standard polishing composition is prepared which comprises 20 parts by weight of an abrasive, said abrasive being high-purity alumina having AlOpurity of 98.0% by weight or more composed of &#x3b1;-type co-random crystal, 1 part by weight of citric acid, and 79 parts by weight of water; the roll-off reducing agent-containing polishing composition is prepared which comprises 20 parts by weight of an abrasive, said abrasive being high-purity alumina having AlOpurity of 98.0% by weight or more composed of &#x3b1;-type co-random crystal, 1 part by weight of citric acid, 78.9 parts by weight of water and 0.1 parts by weight of a roll-off reducing agent; and the viscosity is a viscosity at a shearing rate of 1500 sand 25&#xb0; C. The polishing composition can be favorably used in polishing the substrate for precision parts.

A polishing composition comprising a chelating compound or a salt thereof; a partially esterified product and/or partially etherified product of a polyhydric alcohol compound; and water; a polishing composition comprising water, an abrasive, an intermediate alumina, and a chelating compound or a salt thereof, wherein the content of the intermediate alumina is from 1 to 50 parts by weight, based on 100 parts by weight of the abrasive; and a polishing composition comprising water, an abrasive, an intermediate alumina, a chelating compound or a salt thereof, and a partially esterified product and/or partially etherified product of a polyhydric alcohol compound, wherein the content of the intermediate alumina is from 1 to 50 parts by weight, based on 100 parts by weight of the abrasive. By using the polishing composition, the polishing rate can be increased, and the surface roughness can be lowered, without causing defects such as scratches and pits on the surface of an object to be polished.

Abrasive fluid compositions

A polishing composition comprising silica particles, water, and Fe salt and/or Al salt of a polyaminocarboxylic acid; a polishing process comprising applying the polishing composition; a process for manufacturing a magnetic disk substrate, comprising the step of polishing a substrate with the polishing composition; a magnetic disk substrate manufactured by applying the polishing composition.

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Wakayama, Japan

Shigeo Fujii