JPH11195216A - Glass composition for magnetic disk and glass disk substrate for magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve the low floating of a magnetic disk and to provide the rotation stability of a disk substrate. SOLUTION: This vitreous compsn. essentially consists of silica, magnesia and alumina, contains at least one kind of potassium oxide, sodium oxide and lithium oxide as an alkali component by 3.0 to 20.0 wt.% and further, contains zirconia, calcia zinc oxide or boron oxide by at least >=5 wt.%. Moreover, nitrogen is added by 0.1 to 10.0 wt.% to the compsn. More preferably, oxides of scandium, yttrium, lanthanum, samarium, cerium, neodymium, europium, erbium are added by the range of 0.1 to 10.0 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass composition used for a disk substrate for a magnetic recording medium and a glass disk substrate formed from the composition.

[0002]

2. Description of the Related Art Conventionally, disk substrates for magnetic recording media have been provided by aluminum substrates, carbon substrates, polycarbonate substrates, and the like. In recent years, with the increase in storage capacity of hard disks, surface smoothness has been improved. Therefore, a glass substrate has been attracting attention because it has a possibility of meeting this demand and can be expected to have low cost. This is because with the development of the polishing technique, the surface smoothness of the glass substrate can be theoretically reduced as much as possible because the crystal grain boundaries do not exist. That is, unevenness on the disk substrate is reduced, and the distance between the magnetic recording medium portion and the read head (referred to as flying height) can be reduced. As a result, the recording density increases and the recording capacity increases. . However, in order to further increase the storage capacity, it is conceivable that the disk substrate is rotated at a higher speed and the flying height is reduced more than the current level. It was possible.
This is because the head is pushed up due to the vibration of the disk substrate during rotation, and a reading error occurs. Therefore, it has been demanded to be able to further reduce the flying height of the magnetic head and to avoid this reading error without impairing the advantage of the glass substrate for the current disk. In general, magnetic recording media are specially disclosed.
As disclosed in Japanese Patent No. 52130, after a substrate surface is polished, an ion exchange treatment is performed to strengthen the glass, and a magnetic film is formed thereon. By improving the composition, sufficient rigidity can be obtained, and as a result, sufficient strength can be maintained without performing ion exchange treatment.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and achieves a low flying height of a magnetic head by improving a glass composition used for a disk substrate for a magnetic recording medium. At the same time, it provides the rotation stability of the disk substrate. Further, the strength can be sufficiently maintained without performing the ion exchange treatment.

[0004]

Means for Solving the Problems The glass composition for a glass substrate for a magnetic disk of the present invention, which has been made to solve the above-mentioned problems, comprises silica, magnesia and alumina as main components and potassium oxide as an alkali component. , Sodium oxide and lysium oxide in at least one kind of 3-20.
A glassy composition containing at least 5% by weight of zirconia, calcia, zinc oxide and boron oxide. And nitrogen added to the glassy composition at 0.1 to 10.0% by weight. More preferably, at least one oxide selected from scandium, yttrium, lanthanum, samarium, cerium, neodymium, eurobium, and erbium is used in an amount of 0.1 to 10.0.
It is added in% by weight. If their Young's modulus is 95
It is even better if it is at least 00 kg / mm ² . The glass disk substrate for a magnetic recording medium of the present invention is formed from the above glass compositions.

[0005] Increasing the Young's modulus increases the fracture toughness value of the glass. In addition, the crack depth generated by polishing, handling and the like also becomes smaller. Therefore, the breaking strength is increased and no reinforcement is required.

[0006]

DETAILED DESCRIPTION OF THE INVENTION In forming vitreous, silica,
Magnesia and alumina must be the main components. Potassium oxide, sodium oxide,
At least one kind of lithium oxide is contained in an amount of 3 to 20% by weight. The reason for limiting the alkali component is 5% by weight or less.
This is because the meltability is poor and the bubble elimination is poor, and if it is 15% by weight or more, the chemical resistance is deteriorated. Further, a vitreous composition containing at least 5% by weight or more of zirconia, calcia, zinc oxide, and boron oxide. It is preferable that nitrogen is added to the glassy composition at 0.1 to 10.0% by weight. If the content is less than 0.1% by weight, the rotation stability of the disk substrate, which is the object of the present invention, cannot be sufficiently achieved, and the Young's modulus is low. If the content is 10.0% by weight or more, it is practically impossible to introduce the molten raw material by starting the nitride, and the ion implantation may increase the processing time and change the surface state (roughness change). . Scandium, yttrium, lanthanum, samarium, cerium,
It is advantageous to add at least one oxide of neodymium, eurobium and erbium, but it is necessary to add the oxide in the range of 0.1 to 10.0% by weight. If the content is 0.1% by weight or less, the effect of increasing the rigidity is small, and if it is 10% by weight or more, vitrification is difficult, and the cost increases. It is further preferable that the Young's modulus of these compositions is 9500 kg / mm ² or more. This is to further prevent the possibility that a rotational deflection occurs at the time of rotation of the disk, the head collides with the substrate, and a reading error occurs. The most preferable composition range for the amorphous composition is SiO ₂ : 40.0 to 80.
0% by weight, Al ₂ O ₃ : 5.0 to 30.0% by weight, Mg
O: 5.0 to 25.0 wt%, ZrO _2: 3.0~1
0.0% by weight, CaO: 5.0 to 15.0% by weight, Zn
O: 5.0-20.0 wt%, B ₂ O _3: 5.0~1
0.0 wt%, (wherein, the alkali _{component, K 2 O, Na 2 O} , comprising. At least one or more of Li ₂ O) alkaline component sum of 3.0 to 20.0 wt% It is. Other components such as scandium, yttrium,
It is preferable to add at least one oxide of lanthanum, samarium, cerium, neodymium, eurobium, and erbium at 0.1 to 10.0% by weight. Also,
(Al ₂ O ₃ /MgO)≧0.5 or (SiO ₂ / (A
l ₂ O ₃ + MgO)) ≧ 1.0 is even better. This glass composition forms a glass disk substrate for a magnetic recording medium.

(Example 1) Glass raw materials were mixed with powder at a predetermined composition ratio (in each case expressed by weight%) as shown in Table 1. The raw materials are silica, alumina, magnesia, zirconia, sodium carbonate, zinc white, borax,
Potassium carbonate, lithium carbonate, and oxides of scandium, yttrium, samarium, lanthanum, cerium, neodymium, eurobium, and erbium were used. Nitrogen of silicon, magnesium, aluminum, boron and zirconium was used as a nitrogen source. In addition, nitrogen was introduced into the glass substrate after polishing was completed by ion implantation to form a glass composition on the disk surface. For each composition, (Al ₂ O ₃ / MgO) and (SiO ₂
/ (Al ₂ O ₃ + MgO)). Other components used were yttrium and lanthanum. These were melted and vitrified to measure the Young's modulus. The results are also shown in Table 1.

[0008]

[Table 1]

Example 2 Sample D used in Example 1
Hv (Vickers hardness) was examined using ~ U. The results are shown in Table 2, and the correlation between Young's modulus and Hv is shown as a graph.

[0010]

[Table 2]

As a result, Hv changes as the Young's modulus increases. Therefore, σ _max increases, and damage during handling can be avoided.

[0012]

As described above, the glass substrate for a magnetic disk of the present invention achieves the low flying height of the magnetic head and provides the rotation stability of the disk substrate. Further, the strength can be sufficiently maintained without performing the ion exchange treatment. Therefore, the present invention is of great significance as a glass substrate for a magnetic disk that has eliminated the conventional problems.

[Brief description of the drawings]

FIG. 1 is a graph showing a correlation between Young's modulus and Hv in Example 2.

Claims (5)

[Claims] 1. A composition comprising silica, magnesia, and alumina as main components and at least one kind of potassium oxide, sodium oxide, and lithium oxide as an alkali component.
A glass composition for a magnetic disk, comprising 0% by weight and at least 5% by weight of zirconia, calcia, zinc oxide and boron oxide. 2. The glass composition for a magnetic disk substrate according to claim 1, wherein nitrogen is added at 0.1 to 10.0% by weight. 3. The method according to claim 1, wherein at least one oxide selected from the group consisting of scandium, yttrium, lanthanum, samarium, cerium, neodymium, eurobium, and erbium is added in an amount of 0.1 to 10.0% by weight. Glass composition for magnetic disk substrates. 4. The glass composition for a magnetic disk substrate according to claim 1, wherein the Young's modulus is 9500 kg / mm ² or more. 5. A glass disk substrate for a magnetic recording medium comprising the glass composition according to claim 1.