JPH0749617Y2 - Magnetic disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic disk used for in-plane or perpendicular magnetic recording.

[Prior Art] Conventionally, a rigid magnetic disk has been used as one of magnetic disks, and a rigid material having little flexibility is used as a base of the magnetic disk.

Usually, an aluminum disc (for example, JIS A5086) is used as the base of the rigid magnetic disc.

In such a rigid magnetic disk, generally, aluminum is machined by a lathe to reduce the spacing between the head and the disk, and the disk surface is polished so that high density recording can be performed, and then vapor deposition, spin coating, etc. Therefore, it is made by providing a magnetic layer. In this case, it is preferable that the surface roughness of the disk is smooth for high-density recording / reproduction, but it is difficult to obtain a surface having a center line average roughness Ra of 0.1 μm or less with a conventional aluminum-based disk. It was Further, since the substrate lacks flexibility, it was extremely troublesome to handle when the magnetic layer was provided, because it was not possible to apply it continuously due to restrictions of the web path and the like. Furthermore, since the influence of dust adhering to the surface is great for high-density recording, the disk must be made so that dust does not adhere,
It made the otherwise tedious process more tedious, complicated, and requires huge capital investment.

In addition, since the conventional substrate, which is represented by aluminum, is rigid, it is not flexible, and the head must be in non-contact when tracing on the magnetic layer of the disk, and this spacing remains constant and narrow. It is difficult to connect them, and signal errors often occur, and it has been extremely difficult to further reduce the space between the head and the disk surface in order to further increase the recording density in the future. On the other hand, if the head traces while the spacing is narrow and it happens that the head comes into contact with the disk surface, the base is rigid, so a large impact force tends to concentrate on the contact surface between the head and the magnetic layer, resulting in surface destruction. Occurred, and the life of the disk was shortened.

Further, there is a drawback that the polished aluminum substrate itself is expensive.

On the other hand, recently, a floppy disk or a flexible disk (hereinafter collectively referred to as a "flexible disk sheet") having a wide and annular recess on both sides of a disk base and having a magnetic layer on one surface has a magnetic layer as a surface. A magnetic disk has been proposed in which a flexible disk sheet is attached to both surfaces of the board to leave a gap between the back surface of the flexible disk sheet and the board.

Since the magnetic recording surface of this type of magnetic disk has flexibility, even if the head happens to come in contact with the magnetic recording surface, the head and magnetic recording surface may be brought into contact with each other to perform recording at a higher recording density. Moreover, unlike the case of the rigid disk, the magnetic layer is less likely to be destroyed. Therefore, the technique of the flexible disk can be applied as it is, and since the magnetic layer having a smooth surface and durability is used as the magnetic layer for the magnetic disk, it has been noted that the drawbacks of the conventional rigid magnetic disk can be solved. .

[Problems to be solved by the invention]

As a result of studying this type of magnetic disk, the inventors have found that there is still a big problem. That is, when the flexible disk sheet is attached to the substrate with an adhesive, if the amount of the adhesive is too small, the sheet may peel off, or if the amount is too large, wrinkles may easily occur on the sheet, There was a problem such as the agent protruding from the adhered part.

[Purpose of device]

Therefore, an object of the present invention is to solve the above-mentioned drawbacks, and to provide an improved magnetic disk so that the flexible disk sheet can be easily and surely attached.

[Means for solving problems]

The above object of the present invention is to provide a flexible disk sheet on the upper and lower sides of a base so as to have a gap between the base and the magnetic disk, and to attach the sheet to the outer peripheral edge and the inner peripheral edge of the base. Is provided with a plurality of grooves along the radial direction of the base, and the grooves are configured to communicate with the gap, and the groove depth becomes deeper toward the gap side. This can be achieved by the characteristic magnetic disk.

Hereinafter, one embodiment of the present invention illustrated in the drawings will be described in detail.

The magnetic disk shown in FIG. 1 is formed by attaching flexible disk sheets 2 on both upper and lower sides of a base 1. The base 1 has a central hole 7 in the center thereof into which a rotary shaft for rotating a disk is inserted, and an inner peripheral edge portion 6 near the central hole 7 and an outer peripheral edge portion 6 of the base are formed thicker than other portions. ing. In addition, the upper and lower surfaces of both peripheral edge portions 6, that is,
A plurality of grooves 8 are formed in the sheet radial direction on the sheet attaching surface to which the flexible disc sheet 2 is attached. The groove 8 formed on the outer peripheral edge portion 6 is configured so that the groove depth becomes deeper toward the inside of the base,
On the contrary, the one formed on the inner peripheral edge portion 6 is configured so that the groove depth becomes deeper toward the outside of the base. Further, as shown in FIG. 2, the depth l ₁ , the maximum width l ₂ , and the groove interval l ₃ of the groove 8 are not particularly limited, but for example, the depth l ₁ is 0.1 to 1.0 mm and the width is _1.
L ₂ can be 0.5 to 3.0 mm, and the interval l ₃ can be 1.0 to 3.0 mm.

The inner diameter and outer diameter of the base 1 and the size of the peripheral portion 6 can be arbitrarily selected according to the purpose of use.

The first requirement for the material of the substrate 1 is that thermal deformation does not occur in the heat treatment process.

For that purpose, as the material of the base 1, a metal such as aluminum or an aluminum alloy, glass, or at least a polymer that is not thermally deformed in the heat treatment step, or a combination thereof is used.

The next requirement is cheapness. In the present invention, even if aluminum, which is a typical metal, is used for the substrate 1, the magnetic layer is not affected by the surface roughness of the substrate 1 due to the gap 3 as shown in FIG. Precision is not so required, and the cost required for polishing etc. does not have to be large.

Polymer substrates are generally inexpensive because they can be manufactured in large quantities by injection molding.

As the flexible disc sheet 2 used in the present invention, a material used as a so-called floppy disc can be used. As the support for providing the magnetic layer of the flexible disk sheet 2, a plastic film such as polyethylene terephthalate is used. For example, a biaxially oriented polyethylene terephthalate film (PE
T) is good.

Further, as the support of the flexible disk sheet 2, at least Ra (center roughness) of the surface on which the magnetic layer is provided is set.
Is preferably 0.1 μm or less, and by using such a support, the recording density of the magnetic disk as the final product can be increased.

In the flexible disc sheet 2, generally, when both surfaces of the support are smoothed, friction is increased, sticking easily occurs, handling in a process becomes difficult, and such a support becomes expensive. However, if the surface of the support is rough, the spacing is generally large when the magnetic layer is provided, which is not suitable for high-density recording. Therefore, it is preferable to provide the magnetic layer on the smooth surface of the support, one of which is smooth and the other of which is rough.

The magnetic layer provided on the support is formed not only by coating magnetic iron oxide or ferromagnetic alloy powder with a binder or the like, but also by vapor deposition method such as vacuum deposition, sputtering, ion plating, or plating method. It may be one.

The gap 3 disperses the frictional force and enhances durability when the head and the magnetic layer on the surface of the flexible disk sheet 2 come into contact with each other, and the magnetic layer can appropriately come into contact with the head, resulting in extremely narrow spacing and high density. It is provided for the dual purpose of enabling recording. Therefore, the depth d of the gap 3 should be at least 0.15 in consideration of the usage condition of the magnetic disk.
mm or more is desirable.

Generally, the thickness of the base 1 in the present invention is 1 to 5 mm, and the thickness of the flexible disk sheet 2 to be attached is 10 to 100 μm, and the dimensional stability of the magnetic disk is controlled by that of the base 1. It is preferable to select a material having good dimensional stability.

The above-mentioned base 1 and flexible disk sheet 2 are adhered to each other. The peripheral edge portion 6 is slightly overcoated with an adhesive agent, and the flexible disk sheet 2 is attached to the inner and outer peripheral edge portions by appropriately pulling tension. . At this time, excess adhesive enters the groove 8. Furthermore, since the groove 8 is inclined toward the gap 3, the adhesive that does not fit in the groove 8 can easily enter the gap 3. Therefore, the degree of adhesion between the sheet sticking surface and the flexible disk sheet 2 becomes extremely good.

Examples of the adhesive include acrylic rosin-based resin, terpene-based resin, and the like mixed with methacrylic acid, butyl acrylate, triethylene glycol diacrylate, or the like, or a urethane elastomer having an acryloyl group or a methacryloyl group, Etc.,
Further, rubber-based resins such as polybutadiene and acrylonitrile-butadiene copolymer, polyester resins, and compositions obtained by adding tackifiers such as petroleum resins to these, heat-curable types, hot-melt types, electron beam, radiation-curable types such as ultraviolet rays. Etc. can be used. In addition, at the time of adhesion, one or both of the surfaces to be adhered may be subjected to undercoating treatment using a polymer such as polyester or polycarbonate, or corona discharge, glow discharge, flame treatment, etc. It is better to perform physical surface treatment.

In the above-described embodiment, the cross-sectional shape of the groove 8 is triangular, but the present invention is not limited to this shape, and various modifications such as a semicircle can be made.

[Effect of device]

As described above, since the groove 8 is provided on the base sheet attaching surface, excess adhesive is extruded into the groove 8 to improve the adhesion between the sheet attaching surface and the flexible disk sheet. The adhesive effect is enhanced, and the adhesive can be applied in a large amount and the adhesive can be prevented from protruding, so that the adhesive can be reliably attached. Therefore, according to the present invention, it is possible to provide a high-quality magnetic disk in which the flexible disk sheet is extremely well adhered, and sheet loosening, wrinkles, and the like that occur when the sheet attachment is poor are prevented.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an embodiment of the present invention, FIG. 2 is an enlarged perspective view of an essential part of the present invention, and FIG. 3 is an enlarged view of the AA cross section of FIG. 1 ... Base, 2 ... Flexible disk sheet, 3 ...
… Gap, 6 …… periphery, 7 …… center hole, 8 …… groove.

Claims (1)

[Scope of utility model registration request] 1. A magnetic disk in which flexible disk sheets are attached to the upper and lower sides of a base so as to have a gap with the base, and the base is attached to each of the outer peripheral edge portion and the inner peripheral edge portion of the base. A plurality of grooves are provided along the radial direction, the grooves communicate with the gap, and the groove depth increases as it approaches the gap side. Magnetic disk.