JPS6194236A - Manufacture of magnetic disk - Google Patents

Abstract

PURPOSE:To improve the specular property and to enhance the capacity by allowing a liq. synthetic resin contg. magnetic particles to exist on the substrate surface, superposing a mold consisting of a specular plate on the substrate surface on which the synthetic resin is present, and curing the resin under said conditions. CONSTITUTION:The surface of a nonmagnetic substrate 1 is roughed, and an undercoat layer 2 is provided. Then a resin 3 contg. sufficiently defoamed magnetic particles is coated on the substrate by coating, etc., and the substrate 1 is placed between the upper and the lower mold 5 and 6 with a spacer 4 having specified size in between. A specular plate whose lower surface is specular is used as the upper mold 5. The assembly is placed in a magnetic field, and heated or heated under pressure to cure the resin 3 contg. magnetic particles. The molds are then removed, and a specular magnetic disk on which the specular surface of the upper mold is transferred is obtained. Since molding pressure can be exerted directly on the resin contg. magnetic particles on the substrate, the specular property can be obtained, and the recording sensitivity can be enhanced. Since the thickness of the disk can be controlled, the capacity can be enhanced by thinning the disk.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a magnetic disk, particularly a rigid magnetic disk with excellent surface smoothness.

[Prior Art] Rigid magnetic disks are seen as promising as computer backup memories in terms of cost and capacity, and are being put into practical use.

Rigid magnetic disks are manufactured by forming an anisotropic magnetic film on a mirror plate such as an AI plate, but in order to increase the capacity, the Il! ll
It is necessary to narrow the gap, which is usually said to be 3 μm, but there are also requests for 1 to 2 μm. The constraints on this interval from the disk side are the surface condition and accuracy (warpage, deformation).Generally, in magnetic disks, the surface roughness R-
It is said that axO of 02μ or less, flatness of 25μ or less, and thickness accuracy of ±20μ or less are required.

Methods for forming magnetic films include (I) coating, (I)
I) Electroless plating, (III) Sputtering,
Coatings are currently common. Electroless plating has problems with reproducibility, and sputtering has problems with uniformity of film quality.

Coating does not provide a mirror-like surface, which is an obstacle to increasing capacity.

[Objective of the Invention J] The present invention provides a fourth method that eliminates these drawbacks and can fully meet the requirements for a rigid magnetic disk.

[Structure I & of the Invention] The present invention involves making a liquid synthetic resin containing magnetic particles exist on a substrate surface, superimposing a template made of a mirror plate on the substrate surface where the synthetic resin is present, and curing the resin in this state. This is a method of manufacturing a magnetic disk characterized by the following.

Below, typical steps of the present invention are shown in Figures 1 and 2.
This will be explained using figures.

First, ultrafine magnetic particles and liquid synthetic resin as a binder are thoroughly mixed.

On the other hand, a non-magnetic substrate (1) processed into required dimensions is prepared.

This substrate usually has an undercoat layer (2) after the surface is roughened.
will be established.

The surface roughening may be carried out by a normal method, and the roughness level is Rmax 6.5 to 10. The undercoat agent is preferably a flexible curable resin, especially an epoxy resin or a urethane resin, and the thickness of the undercoat layer is from several tens to
Appropriately, the thickness is about several hundred μm.

Next, the sufficiently degassed magnetic particle-containing resin (3) is made to exist on the substrate by coating, etc., and as shown in FIG.
The substrate (1) is placed between the upper and lower mold plates (5) and (6) with
). The upper mold (5) uses a mirror plate whose lower surface is a mirror surface. In this state, the magnetic particle-containing resin (magnetic film) (3) is heated or heated and pressurized in a magnetic field to impart anisotropy.
harden.

Thereafter, the template is removed to obtain a mirror-like magnetic disk on which the mirror surface of the upper mold is transferred.

In most cases, magnetic disks have magnetic films on both sides, but in this case, as shown in Figure 2, a normal substrate (one
), an undercoat layer (2) is applied, magnetic particle-containing resin (3) is present on both sides, and the upper and lower templates (
5) and (6), a mirror plate is used and a spacer (4) is interposed, and the process is performed in a magnetic field.

[Effects of the Invention] The method of the present invention has the following features compared to other methods.

(1) Since the specularity of the disk surface is obtained by transferring the specular surface of the template, no surface processing of the substrate is required, and the cost of the substrate can be significantly reduced.

(2) The thickness of the magnetic film may range from several μm to several tens of micrometers, as necessary.
It can be changed up to 0 μm.

(3) Since molding pressure is applied directly to the liquid resin containing magnetic particles on the substrate, specularity can be obtained even if the mixing ratio of the magnetic material is increased, and recording sensitivity can be increased.

(4) Since the thickness of the disk can be controlled by molding using spacers, the thickness accuracy is extremely good.

[Example 1 As a substrate, an AI board (thickness 1.7 mm, outer diameter 13 (hm
, inner diameter 40 mm), the surface was roughened by dry blasting to a surface roughness Rmax 8 of about 0 μm, and a urethane resin undercoat agent was applied to a thickness of 50 μm.

As a magnetic material, γ-F is needle-shaped and has a length of 0.2 to 0.4 μm.
An acid anhydride-cured liquid epoxy resin containing 30% by weight of e20 was applied to both sides of the substrate.

This substrate was placed on a lower mold made of a blue glass plate with a size of 150 x 150 m+, and a thickness of 1.9 m was placed on the lower mold around the substrate.
A Teflon spacer of 8 mra in thickness was placed on the substrate and the spacer, and an upper mold made of a blue glass plate with a thickness of 8 mra and a size of 150 x 150+ m was placed on the substrate and the spacer. The molding surface of the blue glass plate is a mirror surface with a surface roughness RmaxO of 01 to 0.02 μm.

In this state, it was pressurized to 5 kg/cm 2 and heat-molded at 100° C. for 5 hours in a magnetic field of 2000 Gauss.

20 made of Sio2 by a conventional method on the molded disk
A protective layer of 00A was provided.

The obtained magnetic disk had the following characteristics.

Thickness: 1.9mm Thickness accuracy ±10μm Magnetic film thickness 50±1μm Surface skin 5-10μm Coercive force 4000e

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing one step in a typical example of the present invention. 1 2 Substrate 2: Undercoat layer 3: Magnetic particle-containing resin layer 4: Spacer 5: Template (upper mold) 6: Template (lower mold)

Claims (1)

[Claims] A method for producing a magnetic disk, which comprises making a liquid synthetic resin containing magnetic particles exist on a substrate surface, overlaying a template made of a mirror plate on the substrate surface on which the synthetic resin is present, and curing the resin in this state.