JPS63316314A - Glass substrate for magnetic disk - Google Patents

Abstract

PURPOSE:To prevent the deterioration of magnetic films at a peripheral margin by elution of an alkali by providing alkali insulating films on the surfaces of a glass substrate formed with uniform and very small ruggedness on the surfaces. CONSTITUTION:Both faces of a glass disk are lapped with an abrasive material by using a surface polishing machine to form the very small ruggedness on the surfaces. The alkali insulating layers prevent the deposition of the alkali component from the substrate glass to the substrate surfaces and prohibit the contact of the magnetic film 3 layers and the alkali component. The alkali insulating layers 2 prevent the elution of the alkali ions from the glass substrate by the reaction of the moisture in the air and the alkali component in the glass even if glass such as soda lime glass allowing easy elution of the alkali is used as the substrate glass. The alkali ions are thereby prevented from acting on the magnetic films 3, by which the corrosion of the magnetic films 3 and the deterioration in the magnetic performance are prevented.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a glass substrate for magnetic disks suitable for magnetic recording media with excellent durability.

[Conventional technology]

A magnetic recording medium (hereinafter referred to as "media") is a magnetic recording medium (hereinafter referred to as "media"), which is a magnetic recording medium (hereinafter referred to as "media"), which is used for magnetic disks and consists of a magnetic film and a protective film formed thereon by processes such as sputtering, plating, and vapor deposition.
It is called. A magnetic storage device consists of this media and a recording/reproducing magnetic head (
The head (hereinafter referred to as the head) is the main component, and after the head and the media are set in contact at the start of operation, by giving the media the required rotation, the air circumference is created between the head and the media surface. A space is created, and recording and reproducing operations are performed in this state. Further, at the end of the operation, the rotation of the media stops, and at this time, the head and the media return to the contact state as at the beginning of the operation. The contact friction force generated between the head and the media when starting and stopping the device wears out the head and media and causes deterioration of magnetic properties (this method is commonly known as contact start/stop C3S). ). Furthermore, if the media is left in a humid atmosphere and moisture is adsorbed on the surface of the media, moisture will enter between the head and the media, causing adhesion. therefore,
If it is started in this state, a large resistance force will be generated on the head and the media, which may cause damage to the head or destruction of the media.
(commonly known as Crash). In general, glass is attracting attention as a substrate for magnetic disks suitable for high density applications because it has excellent surface smoothness, is hard, has high deformation resistance, and has few surface defects (Japanese Patent Laid-Open No. 122707/1983). (Japanese Patent Publication No. 18002/1983)
. However, in terms of the above-mentioned C3S resistance and head stick property, because glass has excellent specularity, media using glass substrates have a higher head stick property than media using other substrates with poor smoothness. This is problematic because the contact area between the media and the media increases, leading to an increase in frictional resistance and adhesive force. In order to eliminate these drawbacks, Japanese Patent Application Laid-Open No. 123906/1983 discloses a method of reducing the frictional force and adhesive force generated between the head and the media by forming minute irregularities on the surface of the substrate by mechanical means. has been proposed. Further, a method of forming irregularities on the surface of a glass substrate by chemical etching has been proposed in Japanese Patent Laid-Open No. 138035/1983. In addition, when ordinary soda lime glass is used as a glass substrate, alkaline components in the glass elute to the surface, affecting the properties of the magnetic film, and depending on the type of magnetic film, durability such as corrosion may be affected. There were problems such as a decline in This corrosion problem was particularly noticeable in those that had minute irregularities mechanically imparted to them in order to improve their head-stick resistance. In addition, with glass that has been given minute irregularities by other methods, or even with flat glass that does not have minute irregularities, the glass component is easily eluted with alkali, such as soda lime glass, which may cause corrosion around the magnetic film, causing problems. Ta. [Problem to be Solved by the Invention 1] The present invention solves the above-mentioned C resistance of the glass substrate for magnetic disks.
The purpose of this invention is to simultaneously solve problems such as 8S characteristics and head stick property, as well as deterioration of magnetic film characteristics and durability due to glass easily eluted with alkali such as soda lime glass. With the conventional method of forming unevenness using mechanical methods, when using a brittle material such as glass as a substrate, cracks may occur on the glass surface, which may impair handling and reduce the strength of the glass substrate surface. Problems caused by the cracks, such as the possibility of causing cracks, could not be denied. In addition, gaps caused by sharp recesses and cracks are not sufficiently cleaned and dried, leaving dirt and other residue behind, which causes deterioration of magnetic properties over time. Furthermore, when the magnetic head collides with the C8S, the convex portion of the glass may break off, causing a head crash. Furthermore,
In order to minimize the occurrence of these problems, there is a method of forming recesses using small-diameter abrasive grains and a light load, but this requires a long working time and results in the use of a large amount of tape material and abrasive grains. It became. Furthermore, in the chemical method proposed in JP-A-60-138035, a metal layer is formed on a glass substrate in advance,
It also required heat treatment. In addition, a test to check the durability of a magnetic disk is to leave it in a hot and humid environment for a certain period of time to check for any deterioration of its magnetic properties. Depending on the type of glass, some substrates deteriorate in a short period of time in this test. This deterioration was particularly noticeable in soda lime glass, which is commonly used as sheet glass. In addition, with such glass, there is a problem in that alkali is eluted from areas where the magnetic film is not coated on the inner or outer periphery of the glass substrate, degrading the magnetic film on the periphery. E Means for Solving Problem 1 The present invention has been made to solve the above-mentioned problems, and provides a glass substrate for a magnetic disk on which a magnetic film is formed by a method such as sputtering, plating, or vapor deposition. The present invention provides a glass substrate for a magnetic disk, characterized in that an alkali insulating layer is provided on the surface of the glass substrate on which uniform minute irregularities are formed without impairing flatness. Further, in the present invention, the surface of the alkali insulating layer has a height of 50 mm.
The present invention provides a glass substrate for a magnetic disk characterized in that it is provided with unevenness in which the peaks are in the range of 700 to 700 people and are formed at a pitch in the range of 0.1 to IO μm. The shape of this unevenness and the pitch of the peaks can be determined by using a surface roughness meter with a stylus with a sufficiently small radius at the tip under a sufficiently light load, or by using a non-contact method using an optical or electron beam with sufficient resolution. By using a type roughness meter,
Measurements shall be made at a sufficiently slow scanning speed. FIG. 1 is a plan view of a magnetic disk substrate manufactured according to the present invention, in which polar coordinates (r, θ) are taken with the center of the circle forming the substrate disk as the origin, and the substrate is made of ordinary soda lime silicate. Glass, low alkali glass, non-alkali glass, borosilicate glass, quartz glass, physically strengthened glass by wind cooling or liquid cooling, chemically strengthened glass, crystalline glass, crystallized glass, etc. can be used. The alkali insulating layer of the present invention covers a wider area than the magnetic film on the surface of the glass substrate having the above-mentioned irregularities, and the magnetic film does not come into direct contact with the glass substrate at any part, not to mention the peripheral area of the magnetic film. The glass substrate is provided on the surface of the glass substrate so that there are no scratches. Figure 2 shows a magnetic disk (
They are a) a plan view and (b) a sectional view. The figure shows that the alkali insulating layer covers a wider area of the glass substrate at the periphery than the magnetic film. It is preferable that the alkali insulating layer covers the entire surface of the glass substrate, and the alkali insulating layer may be present on the end surface of the glass substrate as long as it does not cause any practical problems as a magnetic disk substrate. FIG. 3 is a schematic diagram illustrating the present invention, which is characterized in that the unevenness is formed on the surface of a base glass substrate, and an alkali insulating layer is provided on the unevenness on the surface of the glass substrate. A glass substrate for magnetic disks is shown. The structure and form of the unevenness on the surface of the glass substrate for a magnetic disk of the present invention shown in FIG. 3 are too small to be shown in FIGS. 1 and 2, and therefore are not shown in these figures. Figure 4 (a), (b) and Figure 5 (c), (d)
is perpendicular to the main surface of the substrate obtained as an example of the present invention.
FIG. 2 is an explanatory diagram showing the shape of unevenness in a cross section in the direction and a cross section in the θ direction. In the cross-sectional views of FIGS. 4(a) and 4(b), the surface irregularities of the substrate have similar profiles in the r and θ directions. Similarly, the cross-sectional views in Figures 5(c) and 5(d) have concentric circles or spiral patterns, and as shown in (C) and ld), the profiles are different and exhibit anisotropy. FIG. 6 is an enlarged explanatory view of the surface of the substrate on which unevenness is formed. Hereinafter, "height of r mountains" refers to the head difference H between the peaks and valleys, and "pitch of mountains" refers to the distance W between the tips of adjacent peaks. The appropriate shape of the unevenness is C, which reduces friction between the head and the media without significantly affecting playback noise.
The height of the mountain is 50-700 because it can improve the 8S characteristics.
It is appropriate that the range is between 50 and 200 people, but especially between 50 and 200 people.
The pitch of the mountain, which should be within the human range, is 0.1-
It is desirable that the thickness be in the range of 10 μm. In addition, it is desirable that the height of all the piles does not exceed 700 people over the entire surface of the board, but the height of the above-mentioned i4
There may be a mountain with a height of more than 700 people as long as there is no problem in achieving improvement in the css characteristics and head stick property. In the present invention, the alkali insulating layer may be formed by dissolving the alkoxide of the metal element as the main component in a solvent, forming a film with the liquid on the surface of the glass substrate on which the unevenness is formed, and performing hydrolytic condensation. Although Si is used as the main component metal element, Ti or Zr may also be used. Moreover, a plurality of these elements can also be used. When forming an alkaline insulating layer made of SiO Among them, tetraethoxysilane or a partial hydrolyzate of tetraethoxysilane is representative because of its ease of use, storage stability, and availability. The coating may be formed by immersing the glass substrate with the unevenness in the above alkoxide solution and then lifting it above the liquid level at a constant speed and drying it to obtain a coating. Alternatively, the glass substrate may be rotated at high speed. Spin code coating method The thickness of the alkaline insulating layer of the present invention is 500 to 3,600 layers, particularly preferably 1,000 to 1,600 layers. If the film thickness is less than 500, the anti-alkali effect is low and pinholes are likely to form, so the anti-corrosion effect is low. Also 3
If the thickness is thicker than 600, cracks are likely to occur, which is problematic as a substrate for magnetic disks. It is particularly preferable that the alkaline insulating layer has a thickness of 1,000 to 1,600 people since it has a sufficient anticorrosive effect and does not cause cracking. [Function] In the present invention, the alkali insulating layer prevents precipitation of alkali components from the substrate glass onto the substrate surface, and blocks contact between the magnetic film layer and the alkali components. In the alkali insulating layer of the present invention, even when glass from which alkali is easily eluted, such as soda lime glass, is used as the substrate glass, alkali ions are eluted from the glass substrate due to the reaction between moisture in the air and alkali components in the glass. This prevents alkali ions from acting on the magnetic film, thereby preventing corrosion of the magnetic film and deterioration of magnetic performance. The mechanism of action of alkaline components in promoting corrosion is not necessarily clear, but upon contact with water vapor, alkali ions on the glass surface move to the glass surface, which promotes the condensation of water vapor and electrochemically damages surrounding metals. It is thought that the corrosion occurs due to battery action. Therefore, it is considered that the alkali insulating layer should have a composition and structure (such as tightness and absence of cracks) that blocks the movement of alkali components. [Examples] Example 1 A glass disk as shown in FIG. 1 was lapped on both sides with an abrasive material using a plane polisher to form minute irregularities on the surface. Next, this disk was immersed in an ethyl silicate solution and then slowly pulled up to coat the entire surface with a film. After drying this disk for 1 hour, it is cured (fired) at 300-500℃ for 5 hours in a dust-free clean state.
did. A base layer of C is applied to the surface by sputtering.
A magnetic disk was prototyped by forming a magnetic film containing o-Ni as a main component and further providing a protective film containing C as a main component thereon. At this time, the thickness of the magnetic film is 600, and the thickness of the protective film is 3.
There were 00 people. Furthermore, a lubricant made of perfluoropolyether was coated over the protective film by a dipping method. This disk was subjected to a humidity resistance test under the conditions of temperature: 80°C, humidity: 90%. Appearance inspection and certifier test were conducted as evaluation methods. Comparative Example 1 A glass disk as shown in Fig. 1 ``'iF!: Using a surface polishing machine, both surfaces were lapped with abrasive grains to form microscopic irregularities.After this was thoroughly cleaned, the surface was polished by sputtering. A magnetic disk was fabricated by forming an underlayer of Cr and a magnetic film mainly composed of Co-Ni, and further providing a protective film mainly composed of C on top of the magnetic film.The film thickness at this time was as shown in the example. Furthermore, as in Example 1, a lubricant made of perfluoropolyether was coated on the protective film by a dipping method.This disk was heated under the same conditions as in Example 1 at a temperature of 80°C and a humidity of 90°C. A moisture resistance test was conducted at %RH.The evaluation method was also the same as Example 1.
It is similar to The evaluation results of Example 1 and Comparative Example 1 are shown in Table 1. In addition, this Example, Comparative Example, and the Examples and Comparative Examples described below.
In both comparative examples, glass having a soda lime composition was used. Table 1 evaluation results! When the number of defects increased to 10, the measurement using Sardifier was stopped. The coating thickness is the average thickness of the coating layer shown in FIG. Example 2 A glass disk as shown in FIG. 1 was immersed in a solution consisting of hydrofluoric acid and potassium fluoride to form minute irregularities. Next, an alkali insulating layer was formed in the same manner as in Example 1, a magnetic film and a protective film were formed, and a lubricant was further coated thereon to produce a magnetic disk. A moisture resistance test was conducted on this disk under the same conditions as in Example 1 to evaluate the moisture resistance performance. Comparative Example 2 After forming minute irregularities in the same manner as in Example 2, a magnetic disk was prototyped by sputtering in the same manner as in Comparative Example 1. A moisture resistance test was conducted on this disk under the same conditions as in Example 1 to evaluate the moisture resistance performance. The evaluation results of Example 2 and Comparative Example 2 are shown in Table 2. Table 2 Price Results 2 The increase in the number of defects is IK! Measurement using the Certafire was stopped when the temperature reached i. *Ne Coat film thickness is the average film thickness of the coating layer shown in Figure 3. [Effects] A magnetic disk using the glass substrate for a magnetic disk of the present invention has excellent corrosion resistance, so it can be used in a high temperature and humid environment. Furthermore, even when placed in a humid environment as a magnetic disk drive, the head and magnetic disk do not stick together, and the drive operates smoothly (no staking phenomenon occurs). It also has excellent corrosion resistance, ensuring long-term durability. Therefore, a magnetic disk storage device using the disk of the present invention has increased reliability and a wide range of uses. Since a glass substrate with better flatness than an aluminum substrate can be used, the recording density is improved and the recording capacity is increased even with drives of the same size. As the glass substrate can be made of soda lime glass, which is inexpensive and easily available, and has good flatness, the polishing process is relatively simple and can be completed in a short time, resulting in economical effects such as improved productivity. is large. Furthermore, in the glass substrate of the present invention, cleaning of the peripheral edge of the glass and removal of cullet may be insufficient6, but by covering the peripheral edge with the alkaline insulating layer, cleaning residues and cullet are released from the peripheral edge. It has the effect of preventing various problems caused by this over a long period of time. Furthermore, since the alkali insulating layer of the present invention covers a wider area of the glass substrate surface than the outer periphery of the magnetic film, there is an effect that corrosion of the periphery of the magnetic film is less likely to occur.

[Brief explanation of drawings]

FIG. 1 is a plan view of a glass substrate for a magnetic disk according to the present invention. FIG. 2(a) is a plan view of a magnetic disk using the glass substrate for magnetic disks of the present invention, (bl is also a sectional view. FIG. 3 is a plan view of a magnetic disk using the glass substrate for magnetic disks of the present invention. FIG. 4(a) is a partially enlarged view of a cross section.
1 is an enlarged view of an r-direction cut surface of an example of a glass substrate for a magnetic disk according to the present invention, and FIG. FIG. 5 (al is an enlarged cross-sectional view in the r direction of another example of the glass substrate for a magnetic disk of the present invention, and FIG. 5 (b) is an enlarged cross-sectional view in the θ direction. FIG. 6 is a schematic diagram of unevenness; [1 represents the height of the mountain, and W represents the pitch of the mountain. 1...Glass substrate 2...Alkali insulating layer 3...Magnetic film 4...・Protective film multi-20

Claims (4)

[Claims] (1) A glass substrate for magnetic disks on which a magnetic film is formed by a method such as sputtering, plating, or vapor deposition. A glass substrate for magnetic disks characterized by having an alkali insulating layer provided on the surface. (2) The surface of the alkali insulating layer has a height of 50 to 70 mm.
2. The glass substrate for a magnetic disk according to claim 1, wherein the glass substrate is provided with unevenness in which peaks in the range of 0 Å are formed at a pitch in the range of 0.1 to 10 μm. (3) The glass substrate for a magnetic disk according to claim 1, wherein the alkali insulating layer is made of SiO_3. (4) After the alkali insulating layer coats the surface of the glass substrate with a film forming solution made of metal alkoxide,
The glass substrate for a magnetic disk according to claim 1, characterized in that it is formed by curing this coating layer.