JP2006099945A - Glass substrate for magnetic recording medium, and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium which can reduce errors, even when the distance is made further smaller between the head and the disk for higher density recording, and to provide a glass substrate suitable to this medium. <P>SOLUTION: This is a glass substrate, having chamfered surface (rounded surface corners) between the surface for forming films which includes a magnetic layer (data surface) and the outer end surface (straight surface). Further, a rounded surface of a curvature 0.013-0.080 mm is provided between the data surface and the chamfered surface of this glass substrate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic recording medium that can be widely used as a recording medium in various electronic devices (such as computers), and a glass substrate that can be suitably used as a substrate for forming the magnetic recording medium.

  Conventionally, aluminum substrates have been widely used as substrates for magnetic recording media including magnetic disks (for example, hard disks). On the other hand, in recent years, with the widespread use of various electrical appliances including small personal computers, portable audio / video recording / playback devices, etc. With respect to magnetic recording media, which are one of the important parts of the product, demands in various usage environments are increasing more and more.

  In order to meet such severe demands, glass substrates having high impact resistance, rigidity / hardness, and high chemical durability have been widely used in recent years. When this glass substrate is used for a magnetic recording medium in the form of a hard disk (HD), the flatness suitable for lowering the head on the magnetic recording surface, which is extremely important for increasing the density of the magnetic recording surface. There is also a general advantage that can be easily obtained.

  More specifically, in the field of magnetic disk substrates, mechanical properties such as thinness accompanying weight reduction and high rigidity capable of withstanding disk undulation during high-speed rotation are required, and higher recording density is required. The demand is very high. In order to achieve high recording density, the flying height of the magnetic head with respect to the magnetic disk substrate is becoming extremely small. To achieve this, the magnetic disk substrate has a flat surface such as a mirror surface and a small surface roughness. It is required that the surface is free from defects such as micro scratches and micro pits.

  On the other hand, it is well known that various errors (for example, recording / reading errors during recording / reproduction and head crashes) may occur in recording / reproduction using the hard disk.

  In order to reduce such various errors, various shapes of glass substrates have been defined in order to reduce particles (particulate matter) that may occur on the disc ( Patent Documents 1 and 2).

  However, when the distance between the head and the disk is further reduced to increase the recording density (for example, about 10 μm or less), such an error tends to further increase.

JP 2002-100031 A JP 2002-342915 A

  An object of the present invention is to provide a magnetic recording medium capable of eliminating the above-described drawbacks of the prior art and a glass substrate that can be suitably used for the medium.

  Another object of the present invention is to provide a magnetic recording medium capable of reducing errors even when the distance between the head and the disk is further reduced for higher density, and a glass substrate that can be suitably used for the medium. It is to provide.

  As a result of diligent research, the present inventor has found that it is extremely effective to achieve the above object to provide an “R surface” having a specific curvature between the data surface and chamfer surface of a glass substrate. I found it.

  The glass substrate for a magnetic recording medium of the present invention is based on the above knowledge, and more specifically, between a surface (data surface) for forming a film including a magnetic layer and an outer peripheral end surface (straight surface), A glass substrate having a chamfer (chamfered) surface; characterized in that it has an R surface with a curvature of 0.013 to 0.080 mm between the data surface and the chamfer surface of the glass substrate. is there.

According to the present invention, there is further provided a magnetic recording medium comprising the glass substrate and a magnetic recording layer disposed on the data surface of the glass substrate.
The present invention includes, for example, the following aspects.
(1) A glass substrate having a chamfer (chamfered) surface between a surface (data surface) for forming a film including a magnetic layer and an outer peripheral end surface (straight surface), the data of the glass substrate A glass substrate for a magnetic recording medium, comprising an R surface having a curvature of 0.013 to 0.080 mm between the surface and the chamfer surface.
(2) A magnetic recording medium comprising the glass substrate according to item 1 and a magnetic recording layer disposed on the data surface of the glass substrate.

  The reason why the error reduction effect is obtained when the glass substrate for magnetic recording medium or the magnetic recording medium of the present invention having the above-described configuration is obtained is estimated as follows according to the knowledge of the present inventor.

  That is, in various manufacturing stages where a glass substrate for a magnetic recording medium is to be manufactured, a large number of the substrate materials are often placed in a predetermined cassette (usually made of resin) for transportation and storage. However, when a substrate material is taken in and out of such a cassette, if an acute shape remains between the “data surface → the chamfer surface” of the substrate material, particles are rubbed against the cassette. It is estimated that the particles adhere to the HD formed from the substrate and cause various errors.

  On the other hand, according to the experiment by the present inventors, in the present invention, when the “R surface” having the specific curvature as described above is provided between the data surface and the chamfer surface of the glass substrate. It is estimated that such “rubbing” is reduced or eliminated, and various errors in HD are also reduced.

  As described above, according to the present invention, a magnetic recording medium capable of reducing errors even when the distance between the head and the disk is further reduced for higher density, and glass that can be suitably used for the medium. A substrate is provided.

  Hereinafter, the present invention will be described more specifically with reference to the drawings as necessary. In the following description, “parts” and “%” representing the quantity ratio are based on mass unless otherwise specified.

(Glass substrate)
The glass substrate of the present invention has a chamfer (chamfered) surface between a surface (data surface) for forming a film including a magnetic layer and an outer peripheral end surface (straight surface), and the glass substrate. Between the data surface and the chamfer surface, there is an R surface with a curvature of 0.013 to 0.080 mm.

(Basic aspect)
FIG. 1 is a schematic perspective view (a) and a schematic cross-sectional view (b) showing a basic embodiment of the glass substrate of the present invention. FIG. 2 is an enlarged cross-sectional view of such an embodiment.

  With reference to FIGS. 1 and 2, in the glass substrate of this embodiment of the present invention, an R surface 12 having a specific curvature is provided between a data surface 10 and a chamfer surface 11. In FIG. 2, the R surfaces 12 and 22 are provided on both the outer peripheral surface and the inner peripheral surface, but according to the experiments by the present inventors, the effect of the R surface 12 on the outer peripheral surface is great. Therefore, in the present invention, it is sufficient that at least the outer peripheral surface R surface 12 is provided (of course, it is preferable that both the R surfaces 12 and 22 are provided).

(R side)
In the present invention, the “R surface” refers to a boundary surface between a data (recording) surface and a chamfer surface. The size (length along the cross section) of the R surface is preferably about 0.06 to 0.100 mm.

(curvature)
In the present invention, the curvature of the R surface 12 described above is 0.013 to 0.080 mm (more preferably 0.03 to 0.07 mm). This curvature can be suitably measured by the method shown in Test Example 1 described later.

  If the curvature is less than 0.013 mm, the effect of making the “R surface” is insufficient. On the other hand, if the curvature exceeds 0.080 mm, the end shape such as dub off is deteriorated (here In addition, “dub-off” is also referred to as edge sagging and can be referred to, for example, the document WO 01/23485).

(Glass material)
Glass substrates for magnetic disks are attracting attention as substrates that take advantage of advantages such as high rigidity and low profile, and high impact resistance. The glass materials for these substrates are chemically strengthened glass and crystallized glass. It is divided roughly. All of these materials have been subjected to a tempering treatment or a crystallization treatment in order to overcome the disadvantage of glass that is inherently brittle.

Usually, since the presence of scratches on the glass surface greatly impairs the mechanical strength, chemical strengthening treatment by ion exchange is performed from the viewpoint of improving disk reliability. In other words, a glass substrate (original plate) is immersed in an alkali molten salt, and by replacing alkali ions on the glass surface with larger ions in the molten salt, a compressive stress-strained layer is formed on the surface layer of the glass. The strength is greatly increased. In such a chemically strengthened glass substrate, alkali elution from the inside of the glass is suppressed. Examples of the HD glass substrate preferably used include an aluminosilicate glass substrate containing Li ⁺ and Na ⁺ , a soda lime glass substrate containing K ⁺ and Na ^+, and crystallized glass.

(Suitable glass material)
The glass material that can be suitably used in the present invention is not particularly limited as long as it can form an R-plane having the specific curvature described above.

  The present invention can be suitably used for both crystallized glass and tempered glass regardless of the type of glass. For example, the glass material includes a series of materials referred to as so-called “glass ceramics”, and the commercially available product includes, for example, glass ceramics (trade name: TS-10X) manufactured by OHARA.

(Glass substrate manufacturing method)
The manufacturing method of the glass substrate which can be used in the present invention is not particularly limited as long as the R surface having the specific curvature described above can be formed.

(Magnetic recording medium)
The magnetic recording medium of the present invention has a magnetic recording layer disposed on the data surface of the glass substrate of the present invention described above. The method for forming the magnetic recording layer is not particularly limited as long as the effect of the glass substrate of the present invention having the R surface having the specific curvature described above is not substantially inhibited.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Test example 1
(Measurement of curvature)
The curvature was measured using a commercially available measuring device “Contracer” (trade name: Contracer CP400, manufactured by Mitutoyo Corporation). The measurement conditions used at this time were as follows.

<Measurement conditions>
Speed: 0.06mm / s
Pitch: 0.0010nm
Mode: X axis fixed

<Measurement method>
As shown in the schematic cross-sectional view of FIG. 3, an extension line of the recording surface (data surface) of the glass substrate is drawn, and the position where the shape curve of the R surface is separated from the extension line by the curvature based on the R surface of the glass substrate. Let it be point A. Circles passing through these points A, B, and C are obtained by setting a position 10 μm away from the point A as points B and C, respectively, and the radius of the circle is defined as “curvature”.

Example 1
The glass surface having an R surface with a curvature of 0.038 mm was obtained by polishing between the data surface and the chamfer surface. The characteristics of each glass substrate were measured as follows.
Test Method 1: As shown in FIG. 4 (a), hold the glass substrate sample to be used for the test in the hand and put it on the top cover of a commercially available cassette (made of resin, product name: S800-65TSJ). Pressed lightly.

  Test Method 2: As shown in FIG. 4B, the substrate is put in the cassette, the upper and lower lids are closed, the glass substrate sample is reciprocated 10 times along the vertical direction, and the glass substrate sample is put into the cassette. Rubbed.

  Test Method 3: As shown in FIG. 4 (c), the glass substrate sample was placed in the cassette receiving groove.

Contamination of each sample tested as described above was measured by the following method.
<Measurement method of contamination>
The chamfer part and the outermost peripheral part of the data surface were observed with an optical microscope 400 times, and the actual number of particles was counted.

The glass substrate which was not polished in Example 1 was used as a comparative example.
Example 2
A glass substrate (45 degrees straight between the data surface and the chamfer surface) and a glass substrate of Example 1 (R surface having a curvature of 0.038 mm between the data surface and the chamfer surface) were scanned with SEM (Hitachi). The cross section was observed with an electron microscope trade name: S4700 (magnification 500 times), and the contamination measurement results obtained in Example 1 were summarized.

  From the comparison result of FIG. 5, almost no contamination occurs in the glass substrate of the present invention having a specific R-plane.

It is the model perspective view and schematic sectional drawing which show the basic aspect of the glass substrate of this invention. It is an expansion schematic cross section of the basic aspect of the glass substrate of FIG. It is a schematic cross section which shows the measuring method of the curvature of the corner R in this invention. It is a SEM photograph which shows the test method used in the Example. It is a SEM photograph and data which show the test result obtained in the Example.

Claims (2)

A glass substrate having a chamfer (chamfered) surface between a surface (data surface) for forming a film including a magnetic layer and an outer peripheral end surface (straight surface),
A glass substrate for a magnetic recording medium, comprising an R surface having a curvature of 0.013 to 0.080 mm between a data surface and a chamfer surface of the glass substrate.   A magnetic recording medium comprising the glass substrate according to claim 1 and a magnetic recording layer disposed on a data surface of the glass substrate.