Glass for magnetic recording media substrates, magnetic recording media substrates, magnetic recording media and method for preparation thereof

A method for manufacturing a glass for a magnetic recording medium substrate comprised of an oxide glass, characterized by:

• preparing a glass starting material to which Sn, and optionally Ce, are added, comprising, denoted as mass percentages:
• Si 20 to 40 percent,
• Al 0.1 to 10 percent,
• Li 0.1 to 5 percent,
• Na 0.1 to 10 percent,
• K 0 to 5 percent
• (wherein the total content of Li, Na, and K is 15 percent or lower),
• Sn 0.005 to 0.6 percent,
• Ce 0 to 1.2 percent, and
• so as to permit obtaining a glass comprising 0 to 0.1 percent of Sb and no As or F;
• melting the glass starting material;
• clarifying the resulting glass melt;
• and
• then molding the resulting glass melt.

A glass for a magnetic recording medium substrate comprised of oxide glass, characterized:

• by comprising, as converted based on the oxide, denoted as molar percentages:
• SiO2 60 to 75 percent,
• Al2O3 1 to 15 percent,
• Li2O 0.1 to 20 percent,
• Na2O 0.1 to 15 percent, and
• K2O 0 to 5 percent
• (where the total content of Li2O, Na2O, and K2O is 25 percent or lower);
• in that, based on the total amount of the glass components, 0.01 to 0.7 mass percent of Sn oxide and 0 to 1.4 mass percent of Ce oxide are added;
• in that the content of Sb oxide is 0 to 0.1 mass percent;
• and
• by not comprising As or F.

A method for manufacturing a glass for a magnetic recording medium substrate comprised of an oxide glass, characterized by:

• preparing a glass starting material to which Sn, and optionally Ce, are added, comprising, as converted based on the oxides, denoted as molar percentages:
• SiO2 60 to 75 percent,
• Al2O3 1 to 15 percent,
• Li2O 0.1 to 20 percent,
• Na2O 0.1 to 15 percent, and
• K2O 0 to 5 percent
• (wherein the total content of Li2O, Na2O, and K2O is 25 percent or lower);
• so as to permit obtaining a glass comprising 0 to 0.1 percent of Sb, no As or F, and, based on the total amount of the glass components, 0.01 to 0.7 mass percent of Sn oxide and 0 to 1.4 mass percent of Ce oxide;
• melting the glass starting material;
• clarifying the resulting glass melt;
• and
• molding the resulting glass melt.

A glass for a magnetic recording medium substrate comprised of oxide glass, characterized:

• by comprising, converted based on the oxide, denoted as molar percentages:
• SiO2 60 to 75 percent,
• Al2O3 1 to 15 percent,
• Li2O 0.1 to 20 percent,
• Na2O 0.1 to 15 percent,
• K2O 0 to 5 percent
• (where the total content of Li2O, Na2O, and K2O is 25 percent or less);
• by comprising a 0.1 to 3.5 mass percent of total content of Sn oxide and Ce oxide, based on the total amount of the glass components;
• in that the ratio of the Sn oxide content to the total content of Sn oxide and Ce oxide (Sn oxide content/(Sn oxide content+Ce oxide content)) is 0.01 to 0.99;
• in that the Sb oxide content is 0 to 0.1 percent;
• and
• by comprising no As or F.

A method for manufacturing a glass for a magnetic recording medium substrate comprised of an oxide glass, characterized by:

• preparing a glass starting material to which Sn and Ce are added, comprising, as converted based on the oxide, denoted as molar percentages:
• SiO2 60 to 75 percent,
• Al2O3 1 to 15 percent,
• Li2O 0.1 to 20 percent,
• Na2O 0.1 to 15 percent, and
• K2O 0 to 5 percent
• (wherein the total content of Li2O, Na2O, and K2O is 25 percent or lower);
• and, so as to permit obtaining a glass containing a total quantity of Sn oxide and Ce oxide of 0.1 to 3.5 mass percent based on the total amount of the glass components, wherein the ratio of the content of Sn oxide to the total content Sn oxide and Ce oxide (content of Sn oxide/(content of Sn oxide+content of Ce oxide)) is 0.01 to 0.99, having an Sb oxide content of 0 to 0.1 percent, and comprising no As or F;
• melting the glass starting material;
• clarifying the resulting glass melt;
• and
• molding the resulting glass melt.

A glass for a magnetic recording medium substrate comprised of oxide glass, characterized:

• by comprising, denoted as mass percentages:
• Si 20 to 40 percent,
• Al 0.1 to 10 percent,
• Li 0.1 to 5 percent,
• Na 0.1 to 10 percent,
• K 0 to 5 percent
• (where the total content of Li, Na, and K is 15 percent or less),
• Sn 0.005 to 0.6 percent, and
• Ce 0 to 1.2 percent;
• in that the Sb content is 0 to 0.1 percent;
• by not comprising As or F;
• and
• by having a λ(lambda)80 of 320 nm or greater.

A glass for a magnetic recording medium substrate comprised of oxide glass, characterized:

• by comprising, as converted based on the oxides, denoted as molar percentages:
• SiO2 60 to 75 percent,
• Al2O3 1 to 15 percent,
• Li2O 0.1 to 20 percent,
• Na2O 0.1 to 15 percent, and
• K2O 0 to 5 percent
• (where the total content of Li2O, Na2O, and K2O is 25 percent or lower);
• in that, based on the total amount of the glass components, 0.01 to 0.7 mass percent of Sn oxide and 0 to 1.4 mass percent of Ce oxide are added;
• in that the content of Sb oxide is 0 to 0.1 mass percent;
• by not comprising As or F;
• and
• by having a λ(lambda)80 of 320 nm or greater.

A glass for a magnetic recording medium substrate comprised of oxide glass, characterized:

• by comprising, converted based on the oxide, denoted as molar percentages:
• SiO2 60 to 75 percent,
• Al2O3 1 to 15 percent,
• Li2O 0.1 to 20 percent,
• Na2O 0.1 to 15 percent, and
• K2O 0 to 5 percent
• (where the total content of Li2O, Na2O, and K2O is 25 percent or less);
• by comprising a 0.1 to 3.5 mass percent of the total content of Sn oxide and Ce oxide, based on the total amount of the glass components;
• in that the ratio of the Sn oxide content to the total content of Sn oxide and Ce oxide (Sn oxide content/(Sn oxide content+Ce oxide content)) is 0.01 to 0.99;
• in that the Sb oxide content is 0 to 0.1 percent;
• by comprising no As or F;
• and
• by having a λ(lambda)80 of 320 nm or greater.