Manufacturing method of glass substrate for magnetic disk, manufacturing method of glass blank, glass substrate for magnetic disk, and glass blank
AssigneeHoya Corporation
InventorsShinji Eda, Hideki Isono
Life of this patent
Estimating the term…
Abstract
There are provided, a method for efficiently manufacturing a glass substrate for magnetic disk in which the degree of surface irregularity of the principal surface is suppressed, and the glass substrate for magnetic disk. When manufacturing a glass substrate for magnetic disk including a pair of principal surfaces, a glass blank is formed by pressing molten glass or softened glass with planar press forming surfaces of dies in such a way that the molten glass or the softened glass is sandwiched from the both sides. Temperature condition is equalized around the pair of principal surfaces of the glass blank during the pressing.
Claims19
A manufacturing method of a glass substrate for a magnetic disk including a pair of principal surfaces, the method comprising:
- forming a glass blank by performing press forming to molten glass or softened glass with planar press forming inner surfaces of a pair of dies in such a way that the molten glass or the softened glass is sandwiched between the inner surfaces from both sides in a horizontal direction while maintaining a temperature difference between the inner surfaces of the pair of dies at or below 5 degrees Celsius to equalize a temperature condition around the pair of principal surfaces of the glass blank and creating a heat flow in the inner surfaces of the pair of dies during the press forming to form the pair of principal surfaces of the glass blank with concave shapes such that a section thickness of the glass blank decreases from the outer circumference of the glass blank toward the center of the glass blank;
- and
- polishing the glass blank.
A manufacturing method of a glass blank for a magnetic disk including a pair of principal surfaces, the method comprising:
- causing a lump of molten glass or softened glass to fall, and
- forming a glass blank by pressing the lump with planar press forming inner surfaces of a pair of dies in such a way that the lump is sandwiched between the inner surfaces from both sides in a horizontal direction during the fall of the lump while maintaining a temperature difference between the inner surfaces of the pair of dies at or below 5 degrees Celsius to equalize a temperature condition around the pair of principal surfaces of the glass blank and creating a heat flow in the inner surfaces of the pair of dies during the press forming to form the pair of principal surfaces of the glass blank with concave shapes such that a section thickness of the glass blank decreases from the outer circumference of the glass blank toward the center of the glass blank.
A manufacturing method of a glass substrate for a magnetic disk including a pair of principal surfaces, the method comprising:
- causing a lump of molten glass or softened glass to fall, and
- forming a disk-shaped glass blank by pressing with planar press forming inner surfaces of a pair of dies the falling lump from both sides in directions orthogonal to a falling direction of the falling lump, such that the lump is pressed during the forming of the glass blank from the start of the pressing with the dies until a temperature of the lump drops to a strain point in such a way that temperatures of portions of the planar press forming inner surfaces of the dies contacting the lump are equalized such that a temperature difference between the inner surfaces of the pair of dies is maintained at 5 degrees Celsius or less to make a flatness of the glass blank into a target flatness provided for the glass substrate for the magnetic disk and to form the pair of principal surfaces of the glass blank with concave shapes by creating heat flow in the inner surfaces of the pair of dies during the pressing, such that a section thickness of the glass blank decreases from the outer circumference of the glass blank toward the center of the glass blank.
A manufacturing method of a glass substrate for a magnetic disk including a pair of principal surfaces, the method comprising:
- causing a lump of molten glass or softened glass to fall;
- forming a disk-shaped glass blank by pressing with inner surfaces of a pair of dies the falling lump from both sides in directions orthogonal to a falling direction of the falling lump while maintaining a temperature difference between the inner surfaces of the dies at or below 5degrees Celsius, the glass blank being pressed with the inner surfaces of the dies until a temperature of the pressed glass blank drops to a strain point in such a way that temperatures of portions of the inner surfaces of the dies contacting the glass blank are equalized to make a flatness of the glass blank into a target flatness provided for the glass substrate for a magnetic disk and to form the pair of principal surfaces of the glass blank with concave shapes by creating heat flow in the inner surfaces of the pair of dies during the pressing, such that a section thickness of the glass blank decreases from the outer circumference side to the central side;
- and grinding with fixed abrasive grains the pair of principal surfaces at the both sides of the glass blank.
Dependencies are inferred from the claim text.