JPS6386114A - Magnetic disk substrate - Google Patents

Abstract

PURPOSE:To form a surface layer which is highly strong and dense by laminating insert material layers consisting of copper or copper alloy, nickel, titanium, nickel alloy or titanium alloy layers and glass sheets successively on a core plate consisting of aluminum. CONSTITUTION:The nickel, titanium, nickel alloy or titanium alloy film 3 is formed by physical vapor deposition or plating to 0.5-20mum thickness on one face of the soda lime glass sheet or ceramic layer 2. A copper sheet 4 having 0.5-100mum thickness is sandwiched as an insert material between the film 3 and the surface of a substrate 1 consisting of aluminum or aluminum alloy and the film and sheet are press-welded at about 548-630 deg.C, by which the magnetic disk substrate is formed. The hard materials such as glass sheets or ceramic layers are used for the surface hardening layer in the above- mentioned manner, by which the thickness is adjusted as desired and the high strength as well as the heat resistance and denseness are obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a substrate for a magnetic disk used as a storage medium.

<Prior art> Substrates for thin-film magnetic disks for high-density recording must have sufficient strength for ease of handling, and when forming magnetic media by sputtering, they must be strong enough to withstand temperature rises. It is necessary to have high heat resistance, high surface precision, and sufficient hardness to enable high-density magnetic recording and to ensure the required wear resistance against sliding contact of the magnetic head.

Conventionally, as shown in Fig. 2, both surfaces of a thin aluminum alloy blank are polished, and the polished surfaces are electroless nickel plated or alumite coated to improve the surface @5. By polishing the surface of this surface layer, a magnetic film made of chromium, iron, nickel, cobalt, etc. is applied to the surface, formed by plating sputtering, etc., and a protective film is further formed on the surface. He was trying to complete the magnetic disk.

However, in order to form such a surface layer 5 well, it is necessary that the surface roughness of the aluminum core plate 1 has a high precision of about 0,0'15 μm, and in particular, it is necessary to prevent non-metallic inclusions. This requires an expensive aluminum alloy material that does not contain carbon dioxide, and since the aluminum alloy is relatively soft, it is difficult to process the surface of the aluminum alloy, which increases the cost of the magnetic disk substrate. Furthermore, since the electroless nickel plating layer has a thickness of about 10 to 20 μm, its strength is not necessarily sufficient, and magnetic transformation occurs at around 250°C, so when forming a magnetic film by sputtering, it is difficult to As the temperature rises on the surface, the magnetic properties may deteriorate, or a special sputtering process that suppresses the temperature rise is required, which causes the manufacturing process to take a long time. Furthermore, in the case of alumite treatment, if the thickness of the surface layer is made sufficiently large to obtain sufficient strength, defects such as bores are likely to occur on the surface.

Furthermore, since the polishing process is required twice, the manufacturing cost increases and a large amount of time is required for manufacturing.

Therefore, as disclosed in Japanese Patent Publication No. 53-37202, it has been proposed to form a hard surface layer by depositing fine powder of a ceramic material on the surface of a core plate made of aluminum by sputtering. However, when the surface layer is formed by sputtering or vapor deposition, it takes time to form the coating and heat is dissipated, making it difficult to make the coating thicker than about 1 μm.

If the hard coating is thin, the strength of the magnetic disk will be insufficient and handling problems may occur, such as opacity when it comes into contact with a magnetic head or damage if the magnetic disk is dropped, for example, on the floor. .

<Problems to be Solved by the Invention> In view of these problems of the prior art, the main object of the present invention is to provide an improved magnetic disk substrate having the strength, heat resistance, surface precision, and surface hardness necessary for the magnetic disk substrate. An object of the present invention is to provide a substrate for magnetic disks.

According to the present invention, such an object is to provide a magnetic disk substrate that includes a core plate made of aluminum or an aluminum alloy, an insert material layer, and a nickel, titanium, or nickel alloy. Alternatively, this can be achieved by providing a magnetic disk substrate characterized by laminating a titanium alloy layer and a glass or ceramic layer in this order.

Effect> By using a ceramic or glass layer as the hardened surface layer in this way, sufficient strength, heat resistance, density, and hardness can be obtained. In particular, nickel, titanium, or their alloys have good adhesion to glass-based materials, and the pressure welding process can be performed at a temperature higher than the eutectic temperature between the insert material and the core plate, but below the melting point of the core plate or the softening point of the surface layer. By performing the bonding at a temperature of , it is possible to ensure the bonding force between the core plate and the insert material.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view of a magnetic disk substrate according to the present invention. First, the core plate 1 is made of a relatively inexpensive aluminum alloy or pure aluminum, but unlike the case based on the conventional technology, its surface roughness is relatively not a problem. Next, the thickness is about 50 μm to A nickel film 3 is PVD deposited on one side of a glass thin plate 2 made of 500 μm soda lime glass.
(physical vapor deposition) or plating etc. to 0.5 μm to 2
A film is formed to a thickness of 0 μm. The thin plate 2 may be made of a ceramic material such as alumina, zirconia, silicon carbide, or silicon nitride, or a glass material such as quartz glass or borosilicate glass, and the nickel film 3 may be made of titanium, a nickel alloy, or a titanium alloy. It is okay to leave it as it consists of .

Next, there is a gap of 0.5 μm between the nickel film 3 and the surface of the core plate 10.
Thin copper plate 4 as insert material with a thickness of ~1100LL
are sandwiched and pressed together at a temperature of 548°C to 630°C.

The magnetic disk substrate thus obtained has a diameter of 350″
Even when the magnetic film is sputtered at a temperature of C, there is no adverse effect. Moreover, even after repeating the rapid cooling process of heating to 400'C and immersing it in water for 5 cycles, no abnormalities such as cracking or deformation occurred.

Furthermore, when the thin glass plate 2 was chamfered and dropped onto a vinyl chloride tile from a height of about 1 meter, no damage or cracks occurred. Furthermore, when a cracking test was conducted using such a sample, it was found that even if the glass layer cracked, the bonded surface did not peel off, and sufficient bonding strength was obtained.

Copper is suitable as the insert material, but copper has poor adhesion to glass. However, nickel, titanium, etc. have good adhesion to glass. If an insert material is not used, an Al2O2 film is formed on the surface of the aluminum core plate 1, and the bonding strength with the nickel film 3 becomes a problem. Since the pressure bonding is performed at a temperature above the eutectic temperature between copper and aluminum, sufficient bonding strength can be obtained.

<Effect of the invention> The effects of the present invention are as follows.

Since the surface layer is made of a non-magnetic and hard material and its thickness can be arbitrarily adjusted, a high-strength and dense surface layer can be obtained.

Since the properties of the 0 surface are obtained by the bonded hard layer,
The aluminum alloy used as the core plate is an inexpensive general material and can reduce costs.

■The surface roughness of the core plate before bonding has little effect, eliminating the need for surface polishing of the aluminum alloy, which is difficult to polish, and reducing costs as well.

■If the bonding method is a heat-resistant method of 300℃ or higher (brazing, diffusion bonding, etc.), the magnetic film can be efficiently formed by sputtering, improving magnetic properties and productivity. can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a magnetic disk substrate according to the present invention. FIG. 2 is a sectional view of a conventional magnetic disk substrate. 1...Core plate 2...Thin glass plate 3...
Nickel film 4... Copper thin plate 5... Surface layer

Claims (2)

[Claims] (1) A magnetic disk substrate, in which a core plate made of aluminum or aluminum alloy, an insert material layer, a nickel, titanium, nickel alloy or titanium alloy layer, and a glass or ceramic layer are laminated in this order. A magnetic disk substrate characterized by: (2) The magnetic disk substrate according to claim 1, wherein the insert material is made of copper or a copper alloy.