JPH11102515A - Glass substrate for recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a glass substrate for magnetic disk producible at a low cost with less deformation while ensuring sufficient mechanical strength. SOLUTION: This ring-shaped glass substrate 2 for magnetic disk having a center hole 4 at the center portion thereof is subjected to a strengthening process for improving mechanical strength of the glass substrate 2 only in the inner peripheral region 6 thereof. As the above-mentioned strengthening process, a process for forming a compressing stress on the surface of the glass substrate 2, or a process for removing minute scratches existing on the surface of the glass substrate 2, can be employed. Furthermore, an outer edge 6a of the inner peripheral region 6 is preferably positioned at a prescribed position which is more inside in a diameter direction than the middle position between an inner periphery 2a and an outer periphery 2b. Furthermore, after performing such a strengthening process for the inner peripheral region, a protection film is preferably formed by metal plating or UV resin on the whole surface of the glass substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an annular glass substrate for a disk-shaped recording medium having a central hole formed in the center.

[0002]

2. Description of the Related Art Generally, the theoretical strength of glass is about 3500.
Although it is said to be kg / mm ² , the practical strength is only about several tenths to several hundredths of the theoretical strength, and the gap between the practical strength and the theoretical strength has been proved by Griffith theory.

[0003] As a method of bringing the practical strength closer to the theoretical strength, a method of removing micro scratches such as micro cracks which cause deterioration of the strength or a method of forming a compressive stress on a glass surface in response to a tensile force which causes a crack. A method for imparting strength is known.

[0004] For example, an annular glass substrate having a center hole formed in the center is used for a magnetic disk which is a kind of disk type recording medium. After the mirror polishing, a reinforcing treatment for forming a compressive stress on the surface of the glass substrate is performed to improve the strength and suppress the occurrence of breakage such as a crack. This reinforcing treatment is performed on the entire surface of the glass substrate, and a chemical strengthening method is used as a method for generating a compressive stress.

As the chemical strengthening method, an ion exchange method,
Examples include a dealkalization method and a surface crystallization method. In particular, 1
By dipping the glass in a molten salt at a temperature lower than the annealing temperature of the glass, called a low-temperature ion exchange method, which has been implemented since about 962, the alkali ions in the glass are converted into an alkali having a larger ionic radius in the molten salt. A method has been put to practical use in which ions are replaced with ions to generate a compressive stress on the glass surface.

[0006]

However, the method of forming a compressive stress on the entire surface of a glass substrate by immersing the glass substrate in a molten salt as described above tends to cause deformation such as warpage in the case of a thin glass substrate. There's a problem. In addition, performing the reinforcement process on the entire surface of the glass substrate requires time and costs for the process, and as a result, there is a problem that the glass substrate is expensive.
Therefore, an annular glass substrate for a recording medium, which has a small deformation and can be reinforced at low cost, is desired.

In addition, in the case of an annular glass substrate for a recording medium which has been subjected to a reinforcing treatment, various treatments such as film formation (for example, formation of a magnetic recording layer) are performed on the glass substrate after the reinforcement treatment. There is a possibility that a new flaw or the like may be generated during handling or the like before reaching the point of time, and it is practically difficult to prevent the generation of such a flaw or the like by, for example, strict management. Therefore, it is desirable to take some measures on the glass substrate after the reinforcement processing to prevent the occurrence of scratches and the like due to the handling and the like.

In view of the above circumstances, an object of the present invention is to provide an annular glass substrate for a recording medium that can be subjected to reinforcement processing with little deformation and at low cost.

In view of the above, an object of the present invention is to provide
An object of the present invention is to provide an annular glass substrate for a recording medium which has been subjected to the above-mentioned reinforcing treatment and which can prevent the occurrence of scratches or the like due to subsequent handling or the like.

[0010]

In order to achieve the above object, a glass substrate for a recording medium according to the present invention is an annular glass substrate for a recording medium having a central hole formed in a central portion, wherein The reinforcement processing for improving the strength of the substrate is performed only on the inner peripheral portion.

As the above-mentioned reinforcing treatment, a treatment for forming a compressive stress on the surface of the glass substrate or a treatment for removing minute scratches present on the surface of the glass substrate can be used.

[0012] The inner peripheral portion may be a region from the inner edge to a predetermined position radially inward of a center position between the inner edge and the outer edge.

On a glass substrate whose inner peripheral portion is reinforced only, a metal plating film for protecting the glass substrate is provided on the surface of the glass substrate, or a UV resin (ultraviolet curing resin) film is provided. be able to.

Not only the glass substrate in which only the inner peripheral portion has been subjected to the reinforcing treatment, but also the glass substrate to which the above-mentioned reinforcing treatment has been applied, that is, the outer peripheral portion, has been subjected to the above-described supplementary processing or the entire surface has been subjected to the reinforcing treatment. The treated glass substrate may also be provided with a metal plating film for protecting the glass substrate on the surface of the glass substrate, or a UV resin (ultraviolet curable resin) film.

The recording medium glass substrate may be any type of recording medium glass substrate as long as it is an annular disk type recording medium glass substrate. Glass substrates for optical magnetic disks or optical disks.

The concept of performing the reinforcement processing only on the inner peripheral portion includes a case where the reinforcement processing is performed only on the inner peripheral side surface portion of the glass substrate.

[0017]

As a result of various studies on the reinforcement of the glass substrate, the present inventor has determined that the glass substrate for an annular disk-type recording medium whose purpose of use is determined and in which the direction in which stress acts can be determined is not necessarily glass. It has been found that necessary strength can be ensured without performing a reinforcing treatment on the entire surface of the substrate.

That is, the portion of the glass substrate for an annular disk type recording medium which is most stressed is the inner peripheral side surface portion, and is generally 3.5 inches in diameter and 0.635 in thickness.
The maximum stress in practical use is the stress at the time of rotation of 10,000 rpm on a glass substrate of 1 mm, and the stress value in that case is 2.04 k
g / mm ² . Therefore, if a basic reinforcement treatment is applied to the inner peripheral portion where the stress is applied most, it is possible to sufficiently secure the strength necessary for practical use, and it is not necessary to perform the reinforcement treatment on the entire surface.

The present invention has been made on the basis of the above-described findings, and the reinforcing process is performed only on the inner peripheral portion of the annular disk-shaped glass substrate for a recording medium as described above.
While it is possible to secure the strength necessary for practical use, and because the entire surface is not reinforced, for example, when the method of immersing in a molten salt as described above to form a compressive stress on the entire glass substrate surface is used. Also, there is no possibility that the problem of deformation such as warpage of the glass substrate may occur, and even when the reinforcing treatment is performed by other methods, the processing area can be small, so that the time and cost required for the treatment can be reduced. Thus, an annular glass substrate for a recording medium can be manufactured at low cost.

Further, according to the present invention, a protective film made of a metal plating film or a UV resin film is provided on the surface of the glass substrate which has been subjected to the reinforcing treatment as described above. Thus, the glass substrate is protected, and it is possible to prevent the glass substrate from being damaged by handling until the subsequent processing such as film formation is performed.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a glass substrate for a magnetic disk according to an embodiment of the present invention, and FIG.
It is a line sectional view.

The illustrated glass substrate 2 for a magnetic disk has a diameter of 3.5 inches and a thickness of 0.635 mm, and has an annular shape with a center hole 4 formed in the center. Is subjected to a reinforcing treatment (dots in the figure indicate portions subjected to the reinforcing treatment).

The inner peripheral portion 6 to be subjected to the reinforcing treatment is a region from the inner edge 2a of the glass substrate to a predetermined position radially inward of the outer edge 2b, and this predetermined position (the outer peripheral position 6a of the inner peripheral portion).
Can be arbitrarily set within a range radially inward of the outer edge 2b, but is desirably set in a range further radially inward than the center position 2c between the inner edge 2a and the outer edge 2b. In the present embodiment, the outer peripheral position 6a of the inner peripheral portion is set to the center position 2c between the inner edge 2a and the outer edge 2b, that is, the inner edge 2a
A region (a region including the inner peripheral side surface portion 2d) between the inner peripheral portion 2a and the center position 2c between the inner edge 2a and the outer edge 2b is set as the inner peripheral portion 6, and the region is subjected to reinforcement processing.

It is desirable that the outer peripheral position 6a of the inner peripheral portion 6 is located radially inward of the center position 2c between the inner edge 2a and the outer edge 2b as described above. Width (length from the inner edge 2a to the outer peripheral position 6a of the inner peripheral portion) W
Is preferably not more than L / 2, where L is the length from the inner edge 2a to the outer edge 2b, but may be set to be larger than L / 2 if necessary. However, if this W is too large, a sufficient cost reduction effect cannot be obtained, so it is desirable that the W be 0.8 L or less, preferably 0.6 L or less. In addition, W can be set to 0, that is, only the inner peripheral side surface portion 2d can be set as the inner peripheral portion 6. However, from the viewpoint of obtaining a sufficient reinforcing effect, the value of 0.
It is desirably 2 L or more, and more preferably 0.3 L or more.

The reinforcement treatment may be any treatment as long as it can improve the strength of the glass substrate 2, for example, a treatment for forming a compressive stress on the surface of the glass substrate 2, or the treatment described above. A process for removing micro scratches such as micro cracks present on the surface of the glass substrate 6 can be used.

The treatment for forming a compressive stress on the surface of the glass substrate 2 includes various methods such as the above-described ion exchange method (including low-temperature ion exchange method), dealkalization method, and chemical strengthening method such as surface crystallization method. Can be used. Specifically, for example, the following method can be used.

1) A method in which potassium nitrate is screen-printed on the inner peripheral surface of a glass substrate, and then ion exchange is performed at a temperature lower than the annealing temperature to form a stress layer.

2) A method in which potassium ions are implanted into the inner peripheral surface of a glass substrate by sputtering.

3) A method of strengthening air-cooling in which a glass substrate is heated to a predetermined temperature, and then cold air is blown onto the surface to cool and shrink only the surface. However, this air-cooling strengthening method requires a large temperature difference between the central part in the glass thickness direction and the surface. Conventionally, it is said that it is extremely difficult to use a sheet thickness of 3 mm or less. It is considered that it cannot be applied to a single substrate. Therefore, for example, a plurality of glass substrates are stacked, or a holding material is brought into contact with one or a plurality of stacked glass substrates so that the total thickness becomes 3 mm or more. Heat and blow cold air to the inner peripheral side. By doing so, it is possible to form a compressive stress by the air-cooling strengthening method on the inner peripheral side surface 2d of each glass substrate. Therefore,
This method can be applied to the case where reinforcement processing is performed only on the inner peripheral side surface 2d. Note that such a method of strengthening the air-cooling of a glass substrate is based on the idea of generating a stress distribution by considering the radial direction of the glass substrate as the plate thickness.

As a process for removing the scratches present on the surface of the glass substrate 6, for example, the surface of the glass substrate is heated and melted by microwave irradiation, laser irradiation, fire polish, halogen lamp or the like, so that microcracks are removed. A method of removing (healing) from the surface of the glass substrate can be used.

As the reinforcement treatment applied to the inner peripheral portion 6 of the glass substrate 2, various treatments other than the above-mentioned treatments, for example, an acid etching treatment for etching the surface of the glass substrate, a plating treatment and a film formation treatment, and the like. For example, a process of embedding a predetermined material inside the micro crack may be used.

After the inner peripheral portion 6 of the glass substrate 2 is reinforced as described above, a film forming process for forming a magnetic recording layer, for example, is performed. There is a possibility that the glass substrate 2 may be damaged by handling during this time. Therefore, in order to prevent the glass substrate 2 from being damaged, the surface of the glass substrate 2 which has been subjected to the above-described inner peripheral portion reinforcement processing is made of a metal plating film or a UV resin (ultraviolet curing resin) film. A protective film can be provided.

FIG. 3 is a sectional view showing a glass substrate provided with such a protective film. The illustrated glass substrate 2 has the inner peripheral portion 6 subjected to the above-described reinforcing treatment, and then has a protective film 10
Is provided. The protective film 10 is basically preferably provided on the entire surface of the glass substrate 2, but is not necessarily provided on the entire surface, and prevents the glass substrate 2 from being damaged mainly by the hand link up to the film forming step. Therefore, for example, it may be provided only in a portion that is likely to be damaged or only in a portion that is not easily damaged. It should be noted that the dotted portions in the figure are portions subjected to reinforcement processing, and the same applies to FIG. 4 described later.

In the case where a metal plating film is provided as the protective film, it may be provided by applying metal plating to the glass substrate 2. Specifically, for example, a Ni-P plating film can be provided. In the case of a Ni-P plating film, the Ni-P plating may be usually performed by electroless plating. The thickness of the metal plating film is preferably about 5 μm to 15 μm. or,
When a metal plating film is provided, the surface of the glass substrate (the surface on which the metal plating film is provided) is provided to facilitate plating and to prevent the plating film from peeling off from the glass substrate.
The surface roughness is optimally 50 to several hundreds of degrees, but may be about 1000 to 2000 degrees.

When a UV resin film is provided as the protective film, the glass substrate 2 may be coated with U
What is necessary is just to provide by applying V resin. As the UV resin, for example, a UV acrylate resin can be used. When a UV resin film is provided, its film thickness is several tens.
It is better to be uniform at about μ. When a UV resin film is provided, the roughness of the surface of the glass substrate (the surface on which the UV resin film is provided) may be 10 ° or less.

As a specific example of the case where such a protective film is formed, a non-alkali glass substrate is used as the glass substrate 2, and for example, only the inner peripheral side surface portion 2 d of the glass substrate 2 is subjected to the inner peripheral portion reinforcement processing. Fine polishing is applied to the entire surface in the circumferential direction of 2d, and the surface of the glass substrate 2 has a surface roughness of 1000 ° or less, preferably 100 to 500 °.
The glass substrate 2 is managed so as to be as follows.
Of which the above-mentioned metal plating treatment or UV resin coating is applied to the entire surface. In this case, in the inner peripheral portion reinforcing treatment, acid (fluorinated) etching may be performed instead of the fine polish. The strength of the inner peripheral portion is strengthened by 2 to 3 as compared with the case where the process is not performed.
Can be improved twice. In addition, the above-mentioned metal plating treatment or metal plating film by UV resin coating or UV
After the resin films are provided, for example, a magnetic recording layer is formed on those films in a film forming step.

In the above-described embodiment, the protective film 10 is formed on the glass substrate 2 in which only the inner peripheral portion is subjected to the reinforcing treatment. However, the protective film 10 is not limited to the inner peripheral portion, and furthermore. Can be performed on the glass substrate 2 which has been subjected to the reinforcing treatment in the range of, for example, the glass substrate 2 which has been subjected to the reinforcing treatment on the entire surface. FIG. 4 is a cross-sectional view of an example in which the protective film 10 is formed on the glass substrate 2 on which the entire surface has been subjected to reinforcement processing. The protective film 10 in this case may be formed in the same manner as the protective film 10 in the embodiment shown in FIG.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a glass substrate for a magnetic disk of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view similar to FIG. 2 of another embodiment.

FIG. 4 is a sectional view similar to FIG. 2 of still another embodiment.

[Explanation of symbols]

 2 Glass substrate for magnetic disk 2a Inner edge 2b Outer edge 2d Inner peripheral side surface 2c Intermediate position 4 Center hole 6 Inner peripheral portion 6a Outer peripheral position of inner peripheral portion 10 Protective film

Claims (8)

[Claims] 1. An annular disk-shaped recording medium glass substrate having a central hole formed in a central portion, wherein a reinforcing treatment for improving the strength of the glass substrate is performed only on an inner peripheral portion. Characteristic glass substrate for recording medium. 2. The glass substrate for a recording medium according to claim 1, wherein said reinforcing treatment is a treatment for forming a compressive stress on a surface of said glass substrate. 3. The glass substrate for a recording medium according to claim 1, wherein said reinforcing treatment is a treatment for removing minute scratches present on the surface of said glass substrate. 4. The recording according to claim 1, wherein the inner peripheral portion is a region from the inner edge to a predetermined position radially inward of a center position between the inner edge and the outer edge. Glass substrate for media. 5. The glass substrate according to claim 1, wherein a metal plating film for protecting the glass substrate is provided on a surface of the glass substrate having a reinforcing treatment applied only to the inner peripheral portion. 2. The glass substrate for a recording medium according to claim 1. 6. A UV resin film for protecting the glass substrate provided on a surface of the glass substrate having a reinforcing treatment applied only to the inner peripheral portion thereof. 2. The glass substrate for a recording medium according to claim 1. 7. An annular glass substrate for a disk-type recording medium having a central hole formed in a central portion, wherein the glass substrate is subjected to a reinforcing treatment for improving the strength of the glass substrate, and A glass substrate for a recording medium, wherein a metal plating film for protecting the glass substrate is provided on a surface of the glass substrate subjected to the reinforcing treatment. 8. An annular glass substrate for a disk-type recording medium having a central hole formed in a central portion, wherein the glass substrate is subjected to a reinforcing treatment for improving the strength of the glass substrate, and A glass substrate for a recording medium, wherein a UV resin film for protecting the glass substrate is provided on a surface of the glass substrate subjected to the reinforcing treatment.