JPS62121928A - Magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk having good flatness at a high temp. and good shelf stability by providing flexible disks to at least one side of a substrate, sticking the disks to the substrate via the spacings provided between the rear surface of the disks and the substrate and providing at least one air holes communicating with the atm. to said spacings. CONSTITUTION:The flexible disks 2 each consisting of a base 4 and magnetic layer 5 are stuck via the spacings 3 to one or both faces of the substrate 1 to constitute the magnetic disk. The air holes 8 are provided to the substrate to play the role of maintaining the internal pressure of the spacings 3 always equal to the atm. pressure. The spacing 3 are provided to improve durability by dispersing the frictional force in the stage when a head and the magnetic layer 5 contact and to permit the adequate contact of the magnetic layer 5 with the head as well as to permit high density recording by the extremely narrowed spacing. The influence of the dust sticking to the magnetic layer 6 is small if the spacings 3 are provided.

Description

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

[Conventional technology]

Conventionally, a rigid magnetic disk has been used as one type of magnetic disk9, and a rigid material with little flexibility is used as the base of this magnetic disk.

Usually, an aluminum disk (for example, JIS kjO♂6) is used as the base of a rigid magnetic disk.

Such rigid magnetic disks are generally made by cutting aluminum using a lathe, drilling the spacing between the head and the disk, polishing the disk surface to enable high-density recording, and then using vapor deposition, spin coating, etc. It is made by providing a magnetic layer. In this case, for high-density recording and reproduction, the smoother the surface roughness of the disk, the better, but it is difficult to obtain a surface with a center line average roughness Ra of less than 0.1 μm with conventional aluminum-based disks. there were. Furthermore, since the base lacks flexibility, the magnetic layer? When installing it, it was extremely difficult to handle due to restrictions such as the wedge path. Furthermore, since the influence of dust adhering to the surface is significant for high-density recording, it is necessary to manufacture discs to prevent dust from adhering to them, which is more troublesome and complicated than the already time-consuming process, and requires a huge amount of capital investment. I was making it a thing.

On the other hand, conventional substrates, such as those made of aluminum, are rigid and have little flexibility, making it extremely difficult for the head to remain narrow as the head traces the magnetic layer of the disk. , signal errors often occurred.

On the other hand, when tracing with narrow spacing, since the base is rigid, the sliding friction force tends to concentrate on the surface where the head and magnetic layer are in contact, causing surface damage and shortening the life of the disk. .

Furthermore, the polished aluminum substrate itself is expensive.

On the other hand, recently, as shown in Figure 1, floppy disks or flexible disks (hereinafter referred to as flexible disks) that have concave overcoats on both sides of a disk substrate and a magnetic layer on the negative side have been developed with a magnetic layer on the entire surface. A magnetic disk has been proposed in which the flexible disk 2 is laminated on both sides of the substrate 1 and three gaps are provided between the back surface of the flexible disk 2 and the substrate 1.

This type of magnetic disk is attracting attention as it can overcome the drawbacks of conventional rigid magnetic disks because the technology of flexible disks can be applied as is, and the magnetic layer has a smooth surface and is durable, and is used as the magnetic layer for magnetic disks. It's wandering.

[Problem that the invention seeks to solve]

As a result of studying this type of magnetic disk, the inventors of the present invention found that there were still major problems.

Furthermore, if the film is simply pasted onto a substrate, the volume will double according to the Boyle-Charles law if the storage environment has a temperature difference of 10°C.

Depending on the temperature, the surface becomes uneven, which is not desirable.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic disk of the above-mentioned type in which the base does not become uneven even when there is a temperature difference.

Another object of the present invention is to easily and inexpensively provide a magnetic disk that allows high-density recording, does not cause signal errors, and has good durability.

[Means for solving problems]

As a result of intensive research into the cause of the above, the present inventors found that
Will changes in the unevenness of the base due to temperature differences be eliminated if at least one pinhole-shaped air hole is provided between the gap 3 shown in Figure 1 and the atmosphere? I found it. In this case, if pinholes are provided in the flexible disk, they tend to grow into scratches, which is undesirable in terms of the life of the disk.

That is, the present invention provides a magnetic disk attached to a flexible disk such that a gap is provided between the back surface of the flexible disk and the substrate on at least one side of the substrate, and the gap is open to the atmosphere so that air can be removed. A magnetic disk characterized by having at least one hole.

Hereinafter, the non-invention will be explained in detail.

The magnetic disk targeted by the present invention has a substrate lO7 or both sides (
In the illustrated example, a flexible disk 2 is completely pasted on both sides with a gap 3 between the support and the magnetic layer.

The air hole j is provided in the base and serves to always keep the internal pressure of the gap 3 equal to atmospheric pressure. Note that 7 is a center hole into which a rotating shaft for completely rotating the disk is inserted.

As the flexible disk 2 used in the present invention, materials used for so-called floppy disks can be used. As the support for the flexible disk, a plastic film such as polyethylene terephthalate is used, and λ-axis oriented polyethylene terephthalate film (PET) is preferred.

Furthermore, as a support for a flexible disk, Ra (center roughness) of at least the side on which the magnetic layer is provided is Q, 1 μm.
m or less, and by using such a support, the recording density of the final product, the magnetic disk, can be increased.

In the case of flexible disks, in general, if both sides of the support are made smooth, the friction will be less thick, the disk will easily stick, and it will be difficult to handle in the process, and such a support will also be expensive.

If the surface of the support is rough, the spacing will generally become large when a magnetic layer is provided, making it unsuitable for high-density recording. Therefore, it is preferable to coat the magnetic layer on the smooth surface of a support that is smooth on one side and rough on the other.

The magnetic layer j provided on the support may be formed not only by applying magnetic iron oxide or ferromagnetic alloy powder together with a binder, but also by paper deposition methods such as vacuum evaporation, sputtering, and ion blasting, and plating methods. But that's fine.

As the disk substrate used in the present invention, for example, one having a cross-sectional shape illustrated in FIGS. 1 and 2 is used.

Is gap 3 sufficient for durability because the frictional force is fully dispersed when the head and magnetic layer j come into contact? It is provided for two purposes: to strengthen the magnetic layer, and to allow the magnetic layer j to properly contact the head and to have an extremely narrow spacing, thereby enabling high-density recording. For this purpose, the depth d of the gap 3 is at least 0. In or more is required. In addition, if there is a gap 3, the influence of dust attached to the magnetic layer B seems to be less, although the cause is not clear.

The air holes t are used to maintain the air pressure to prevent unevenness from appearing on the flexible disk due to expansion or contraction of air when the temperature changes. Further, when sliding with the head, the force between the head and the flexible disk is dispersed to other parts, thereby preventing the entire gap from being pressurized.

The air hole fl may be a pinhole, but preferably has a diameter of 0,
711 or more, and at least l or more gaps are provided for each l gap.

The position and shape of the air hole may be arbitrary.

Although FIGS. 1 and 2 show the case where the inner and outer peripheral portions are horizontal, they may be inclined.

Further, the inner diameter and outer diameter of the base and the size of the peripheral portion B can be arbitrarily selected depending on the purpose of use.

Regarding the requirements for the material of the disk substrate, in the present invention, for example, even if it is used for an aluminum substrate, which is a typical metal, the magnetic layer is not affected by the surface roughness of the substrate, as can be seen from Figure 1. Polishing accuracy is not required so much, and the cost required for polishing etc. can be significantly reduced.

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

Furthermore, it is preferable that it is not deformed by heat, and is made of a crystalline polymer and has heat resistance, or has a glass transition point of /2.
Non-grade polymers of 00C or higher are preferred. Specific examples of the material include polycarbonate, polysulfide polyimide, polysulfone, polyacrylate, polyethersulfone, polyetherimide, polyetheretherketone, and the like.

In addition, in order to reduce the value of the expansion coefficient of the substrate, TiO
Metal oxides such as 2+ S t O2 and B a S 0
4 + Glass fiber or the like may be mixed in an amount of 5 to 35% by weight.

The thickness of the base in the present invention is / "'-' -t m,
The thickness of the flexible 7 pull disc to be pasted is 10~100
Since the dimensional stability of the magnetic disk is generally determined by that of the substrate, it is preferable to select a substrate with good dimensional stability.

Aluminum is usually used as the material for the arm of the magnetic head, so the thermal expansion coefficient of the base is the value of aluminum (2,
≠×10-57'C) and the smaller the hygroscopic expansion coefficient, the better.

The flexible disk t[]e is attached to the above-mentioned base, and as the adhesive, a thermosetting adhesive, a radiation curing type such as an electron beam, an ultraviolet ray, etc. can be used.

During bonding, one or both of the surfaces to be bonded may be coated with a polymer such as polyester or polycarbonate, or physically treated with corona discharge, glow discharge, flame treatment, etc. to facilitate bonding. It is better to perform a complete surface treatment.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the scope of the present invention is not limited.

Example [Preparation of flexible disk] A magnetic liquid having the following composition 1 was coated on one side of a 71 μm thick co-axis oriented polyethylene terephthalate film support so that the thickness of the magnetic layer after complete drying and calendering was 1 μm. After drying and calendering, the entire magnetic layer was formed and a doughnut-shaped sheet was punched out to produce a flexible sheet.

Magnetic liquid l γ-F 6203 (0, JxO0OJμm) 300 parts by weight PVC
-AC (vinyl chloride-vinyl acetate copolymer) (VYHHUCC [) aoz Kubu Epoxy Resin Picoat/00/manufactured by Shell Chemical Co., Ltd.] Hiro O parts by weight Polyamide (Persamide//J-GM Shashi) 20 parts by weight Methyl isobutyl ketone/kijirole (-2//) too heavy part [adjustment of base] On the other hand, a base containing 30 pieces of glass fiber in polyetherimide was formed by total injection molding.

The shape of the base was as shown in FIG. 1, and the outer diameter and inner diameter of the disk base were 211 blades, respectively. The thickness of the base plate was -2fi, the depth d of the gap 3 was 0.25u1, and the air hole t had a diameter of 0.2-1 mI and was moss provided in the gap. A flexible sheet punched out from the doughnut-shaped sheet was attached to a substrate with or without air holes using a thermosetting adhesive epoxy tm, and cured at room temperature for 2≠ hours.

The results are shown in Table 2.

Table 1: Adhesion of a flexible sheet without air holes Table 1: Storage stability of a magnetic disk attached to a flexible sheet [Effects of the invention] and has good storage stability.

[Brief explanation of drawings]

1 is a sectional view showing an example of a magnetic disk of the type to which the present invention is applied, and FIG. 2 is a partially enlarged sectional view of the magnetic disk shown in FIG. /...Base 2...Flexible disk 3...Gap Reference...Support j
...Magnetic layer 7 ... Center hole Fig. 1 Fig. 2

Claims (2)

[Claims] (1) In a magnetic disk in which a flexible disk is attached to at least one side of a base with a gap provided between the back surface of the disk and the base, the gap has at least one air hole communicating with the atmosphere. A magnetic disk characterized by having two (2) The magnetic disk according to claim (1), wherein the base is made of metal, glass, a polymer that does not undergo thermal deformation up to at least 120°C, or a combination thereof.