Glass substrate for magnetic disk and manufacturing method of the same
First Claim
Patent Images
1. A method of manufacturing a glass substrate for a magnetic disk,wherein the glass contains in expression of percent by mass:
- SiO2 57 to 75%;
Al2O3 5 to 20%;
(where the total amount of SiO2+Al2O3 is 74% or more)the total of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3, and TiO2 exceeding 0% to 6% or less;
Li2O exceeding 1% to 9% or less;
Na2O 5 to 18%;
(where the mass ratio Li2O/Na2O is 0.5 or less)K2O 0 to 6%;
MgO 0 to 4%;
CaO exceeding 0% to 5% or less;
(where the total amount of MgO and CaO is 5% or less, and the content of CaO is higher than the content of MgO) andSrO+BaO 0 to 3%,the method comprising the step of applying chemical reinforcement treatment to the glass substrate,wherein a glass composition of the glass substrate and conditions of the chemical reinforcement treatment are selected to perform the chemical reinforcement treatment on the selected conditions so that when the glass substrate for a magnetic disk is made by the chemical reinforcement treatment, a penetration length in an uppermost-portion stress layer on a main surface of the glass substrate for a magnetic disk is 49.1 μ
m or less, and that assuming that an angle between the main surface and compressive stress in a stress profile by a Babinet compensator method is θ
, the penetration length in the uppermost-portion stress layer is a value y of {12·
t·
ln(tan θ
)+(49.1/t)} or less,the penetration length in the uppermost-portion stress layer is a length of the longer diagonal in an indentation when a diamond quadrangular pyramid indenter of rhombic transverse section with vertex angles of 172°
30′ and
130°
is pressed against the main surface with a pressing force of 100 g, the tan θ
is a value {(L1+L2)/(P1+P2)} calculated from stress values and stress depths obtained by the Babinet compensator method, the t is a thickness of the substrate,P1 is a compressive stress value, P2 is a tensile stress value, L1 is a compressive stress depth, and L2 is a tensile stress depth.
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Abstract
A glass substrate for a magnetic disk of the invention is a disk-shaped glass substrate for a magnetic disk where the substrate has a main surface and end face and is subjected to chemical reinforcement treatment, and is characterized in that the penetration length in the uppermost-portion stress layer on the main surface is 49.1 μm or less, and that assuming that an angle between the main surface and compressive stress in the stress profile by a Babinet compensator method is θ, a value y of {12·t·ln(tan θ)+(49.1/t)} is the penetration length in the uppermost-portion stress layer or less.
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Citations
17 Claims
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1. A method of manufacturing a glass substrate for a magnetic disk,
wherein the glass contains in expression of percent by mass: -
SiO2 57 to 75%; Al2O3 5 to 20%; (where the total amount of SiO2+Al2O3 is 74% or more) the total of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3, and TiO2 exceeding 0% to 6% or less; Li2O exceeding 1% to 9% or less; Na2O 5 to 18%; (where the mass ratio Li2O/Na2O is 0.5 or less) K2O 0 to 6%; MgO 0 to 4%; CaO exceeding 0% to 5% or less; (where the total amount of MgO and CaO is 5% or less, and the content of CaO is higher than the content of MgO) and SrO+BaO 0 to 3%, the method comprising the step of applying chemical reinforcement treatment to the glass substrate, wherein a glass composition of the glass substrate and conditions of the chemical reinforcement treatment are selected to perform the chemical reinforcement treatment on the selected conditions so that when the glass substrate for a magnetic disk is made by the chemical reinforcement treatment, a penetration length in an uppermost-portion stress layer on a main surface of the glass substrate for a magnetic disk is 49.1 μ
m or less, and that assuming that an angle between the main surface and compressive stress in a stress profile by a Babinet compensator method is θ
, the penetration length in the uppermost-portion stress layer is a value y of {12·
t·
ln(tan θ
)+(49.1/t)} or less,the penetration length in the uppermost-portion stress layer is a length of the longer diagonal in an indentation when a diamond quadrangular pyramid indenter of rhombic transverse section with vertex angles of 172°
30′ and
130°
is pressed against the main surface with a pressing force of 100 g, the tan θ
is a value {(L1+L2)/(P1+P2)} calculated from stress values and stress depths obtained by the Babinet compensator method, the t is a thickness of the substrate,P1 is a compressive stress value, P2 is a tensile stress value, L1 is a compressive stress depth, and L2 is a tensile stress depth. - View Dependent Claims (2, 3, 13)
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4. A method of manufacturing a glass substrate for a magnetic disk, wherein the glass contains in expression of percent by mass:
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SiO2 57 to 75%; Al2O3 5 to 20%; (where the total amount of SiO2+Al2O3 is 74% or more) the total of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3, and TiO2 exceeding 0% to 6% or less; Li2O exceeding 1% to 9% or less; Na2O 5 to 18%; where the mass ratio Li2O/Na2O is 0.5 or less, K2O 0 to 6%; MgO 0 to 4%; CaO exceeding 0% to 5% or less; where the total amount of MgO and CaO is 5% or less, and the content of CaO is higher than the content of MgO, and SrO+BaO 0 to 3%, said method comprising; a chemical reinforcement treatment step of immersing a disk-shaped glass substrate, having a circular hole formed at a center portion thereof and made from said glass, in a chemical reinforcement treatment solution, causing ion exchange for replacing relatively small ions contained in a surface of the glass substrate made from said glass with relatively large ions contained in the chemical reinforcement treatment solution, and thereby creating a compressive stress layer in the surface of the glass substrate, wherein the chemical reinforcement treatment is performed so that a deformation amount of the circular hole formed at the center portion of the disk-shaped glass substrate is within 0.05% of the diameter of the circular hole, and that the transverse strength of the disk-shaped glass substrate is 98 N or more. - View Dependent Claims (9, 10, 11, 12, 14)
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5. A method of manufacturing a glass substrate for a magnetic disk, wherein the glass contains in expression of percent by mass:
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SiO2 57 to 75%; Al2O3 5 to 20%; (where the total amount of SiO2+Al2O3 is 74% or more) the total of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3, and TiO2 exceeding 0% to 6% or less; Li2O exceeding 1% to 9% or less; Na2O 5 to 18%; where the mass ratio Li2O/Na2O is 0.5 or less, K2O 0 to 6%; MgO 0 to 4%; CaO exceeding 0% to 5% or less; where the total amount of MgO and CaO is 5% or less, and the content of CaO is higher than the content of MgO, and SrO+BaO 0 to 3%, wherein the glass substrate is a doughnut-shaped glass substrate for a magnetic disk, and has a circular hole at a center portion thereof, and wherein when diameters of circular holes of 500 to 1000 glass substrates that are arbitrarily selected are measured, the diameter of the circular hole of each of the glass substrates is within the range of ±
5×
10−
4×
A relative to the average diameter A of the circular holes of the glass substrates, the transverse strength of each of the glass substrates is 98 N or more, and control is thus performed. - View Dependent Claims (6, 15)
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7. A method of manufacturing a glass substrate for a magnetic disk, wherein a glass material in said substrate contains in expression of percent by mass:
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SiO2 57 to 75%; Al2O3 5 to 20%; where the total amount of SiO2+Al2O3 is 74% or more, the total of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3, and TiO2 exceeding 0% to 6% or less; Li2O exceeding 1% to 9% or less; Na2O 5 to 18%; where the mass ratio Li2O/Na2O is 0.5 or less, K2O 0 to 6%; MgO 0 to 4%; CaO exceeding 0% to 5% or less; where the total amount of MgO and CaO is 5% or less, and the content of CaO is higher than the content of MgO, and SrO+BaO 0 to 3%, said method comprising; a chemical reinforcement treatment step of immersing a disk-shaped glass substrate with, having a circular hole formed at a center portion thereof and made from said glass material, in a chemical reinforcement treatment solution, causing ion exchange for replacing relatively small ions contained in a surface of the glass substrate made from said glass material with relatively large ions contained in the chemical reinforcement treatment solution, and thereby creating a compressive stress layer in the surface of the glass substrate, wherein the chemical reinforcement treatment is performed by selecting said glass material of the disk-shaped glass substrate and treatment conditions of the chemical reinforcement treatment so that a deformation amount of the circular hole formed at the center portion of the disk-shaped glass substrate is within 0.05% of the diameter of the circular hole, and that the transverse strength of the disk-shaped glass substrate is 98 N or more. - View Dependent Claims (16)
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8. A method of manufacturing a glass substrate for a magnetic disk, wherein a glass material in said substrate contains in expression of percent by mass:
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SiO2 57 to 75%; Al2O3 5 to 20%; where the total amount of SiO2+Al2O3 is 74% or more, the total of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3, and TiO2 exceeding 0% to 6% or less; Li2O exceeding 1% to 9% or less; Na2O 5 to 18%; where the mass ratio Li2O/Na2O is 0.5 or less, K2O 0 to 6%; MgO 0 to 4%; CaO exceeding 0% to 5% or less; where the total amount of MgO and CaO is 5% or less, and the content of CaO is higher than the content of MgO, and SrO+BaO 0 to 3%, said method comprising; a chemical reinforcement treatment step of immersing a disk-shaped glass substrate, having a circular hole formed at a center portion thereof and made from said glass material, in a chemical reinforcement treatment solution, causing ion exchange for replacing relatively small ions contained in a surface of the glass substrate made from said glass material with relatively large ions contained in the chemical reinforcement treatment solution, and thereby creating a compressive stress layer in the surface of the glass substrate, wherein a deformation amount due to the chemical reinforcement treatment of the circular hole formed at the center portion of the disk-shaped glass substrate is beforehand grasped for each glass, said glass material is selected so that the deformation amount is within 0.05% of the diameter of the circular hole, and that the transverse strength of the disk-shaped glass substrate due to the chemical reinforcement treatment is 98 N or more, the selected glass material is processed in disk form, while the circular hole is formed at the center portion, and the chemical reinforcement treatment is performed. - View Dependent Claims (17)
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Specification