JPH0935231A - Magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive thin film magnetic recording medium and a flexible disk having a large recording capacity by using each specified material for a magnetic layer and a nonmagnetic substrate. SOLUTION: This magnetic recording medium is produced by using a polycarbonate injection-molded substrate as a nonmagnetic substrate 11 and forming a Ni-P film as a nonmagnetic metal base layer 12 by electroless plating, then forming a Cr base layer 2 and a CoSm alloy magnetic layer 3 by sputtering, and further forming a protective layer 4 and a lubricating layer 5. The texture (rough surface) T of the polycarbonate injection-molded base body is formed by using a die. A Ni electroformed die 93 having the texture is produced by the following method. (a) A silicone mother die 91 is processed to form the texture T with a diamond abrasive slurry. (b) Then Ni is electroformed to form an electroformed layer 92 having proper thickness. (c) Then the silicone mother die 91 is chemically dissolved and removed to obtain the Ni- electroformed die 93.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium used in a storage device utilizing magnetic recording such as a fixed magnetic disk device.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing the structure of a typical magnetic recording medium. Nonmagnetic substrate 11 such as Al or glass
On the base 1 on which the non-magnetic metal underlayer 12 such as Ni-P or Al is formed, the non-magnetic metal underlayer 2,
A single magnetic layer 3 (for example, CoCrTa or CoCrPtTa) having a coercive force (Hc) of 1600 Oe or more and C
The protective layer 4 mainly composed of is formed, and further on it,
A lubricating layer 5 made of a liquid lubricant is formed. Such a magnetic recording medium (hereinafter referred to as a medium) is formed of, for example, Al.
A non-magnetic metal underlayer 12 made of a Ni-P or Al layer is formed on the surface of a non-magnetic substrate 11 made of an alloy or a glass material by a wet film forming process such as electroless plating or a dry process such as sputtering or vapor deposition. Non-magnetic substrate 1
(Hereinafter, referred to as a base). After that, the flatness and the surface roughness may be finished by machining again. Further, if necessary, unevenness (texture) having a Ra of about 10 nm is formed on the surface to improve the magnetic characteristics and the sliding characteristics with the recording head.

This substrate 1 was heated to about 300 ° C., and DC bias-350 V was applied to the substrate while Cr was applied to the surface.
A nonmagnetic metal underlayer 2 having a thickness of 100 nm, a magnetic layer 3 having a thickness of 30 nm such as CoCrPtTa containing Co as a main component, and a protective layer 4 having a thickness of 10 nm containing C as a main component. The medium is prepared by applying a fluorocarbon-based liquid lubricant to a thickness of 2 nm to form the liquid lubrication layer 5.

The medium manufactured in this manner has good mechanical properties such as strength and dimensional accuracy without any practical problems, magnetic properties have a non-coercive force of about 2000 Oe, and the product of residual magnetic flux density and film thickness (Br).・ Δ) is as good as about 100 G ・ μm. In recent years, miniaturization and large capacity of hard disk devices have been rapidly advanced, and further higher coercive force is desired. Recently,
As disclosed in Japanese Unexamined Patent Publication No. 3-23513, CoSm alloy has been attracting attention as a material having a coercive force of 3000 Oe or more. CoSm alloy is a C such as conventional CoCrTa.
A higher coercive force than that of the o alloy magnetic layer can be obtained, and a low temperature process is possible.

Further, the characteristics of the CoSm alloy change depending on the composition ratio of Co and Sm, but since the coercive force and the saturation magnetic flux density have a trade-off relationship, the read / write characteristics (R /
However, there is a problem that the W characteristic) deteriorates.
As disclosed in Japanese Patent No. 0328, it is improved by adding Fe to CoSm.

[0006]

However, the non-magnetic substrate made of Al alloy or glass material used in the above medium needs to be subjected to a texture treatment step for each substrate, and the material cost is relatively high. Since the cost is high, the cost is high, which has been a bottleneck in the cost of the thin film magnetic recording medium.

Regarding flexible disks,
A recording medium having a recording capacity of 2 MB is used as a standard product, and a recording medium having a high recording capacity (100 MB) is beginning to be released. An oxide magnetic material is applied to these materials and used, but further increase in recording capacity cannot be expected. The present invention has been made in view of the above problems, and an object of the present invention is to provide a thin film magnetic recording medium and a flexible disk having a large recording capacity, which are highly mass-producible and inexpensive.

[0008]

To achieve the above object, in a magnetic recording medium in which at least a nonmagnetic metal underlayer and a magnetic layer are sequentially laminated on a nonmagnetic substrate, the magnetic layer is CoSm. The non-magnetic substrate is made of plastic and is made of plastic. The plastic is assumed to be molded by injection molding or extrusion molding.

It is assumed that the plastic has a sheet shape.

[0010]

According to the present invention, in the magnetic recording medium, the non-magnetic substrate is made of plastic and the magnetic layer is made of CoSm type alloy. The establishment of this constitution is based on the following actions. In a conventional thin film magnetic recording medium, a Co alloy having high crystallinity is used for the magnetic layer 3. When forming this layer, it is necessary to heat the substrate 1 to about 300 ° C. as described above, and the non-magnetic substrate 11 is used. As a result, heat resistance above this temperature was required. On the other hand, the magnetic layer 3 made of a CoSm-based alloy can obtain sufficient magnetic characteristics even if an amorphous or fine crystalline thin film is formed at room temperature. Focusing on this point, the present invention suppresses the temperature in the manufacturing process of the recording medium by using the CoSm-based alloy as the magnetic layer 3, and the non-magnetic substrate 11
As a result, the cost can be suppressed by using a plastic material.

When a method such as injection molding or extrusion molding is used as the method for producing the plastic substrate, the molding die is textured in advance so that it is transferred to the molded plastic substrate. The texture processing step can be omitted, and since the textures of the substrates manufactured by the same mold are all the same, the magnetic characteristics can be stabilized.

As another form of the plastic substrate, if it is in the form of a sheet, a low temperature sputtered film made of a CoSm type alloy can be used as a magnetic layer, and a high recording density of a magnetic recording medium such as a tape or a flexible disk can be obtained. Can be achieved.

[0013]

[Examples] Plastic materials are required to have moldability, weather resistance, water resistance, and the like. Specific examples include polyester,
Amorphous thermoplastic resins containing polyester carbonate, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether sulfone, polyarylate, polyetherimide, and their modified products and copolymers can be mentioned. Further, as a method for producing the plastic substrate, there are injection molding, extrusion molding and the like.
Another method for producing a plastic substrate is a general sheet forming method such as calendar forming. The sheet-like substrate is flexible in its own right, for example, a tape,
It is used for magnetic recording media such as flexible disks. Example 1 A magnetic recording medium of an example according to the present invention comprises a non-magnetic substrate 1
1, an injection-molded substrate of polycarbonate is used, and Ni-P is formed by electroless plating as the nonmagnetic metal underlayer 12.
A Cr underlayer and a CoSm alloy magnetic layer are formed by sputtering, and a protective layer and a lubricating layer are further laminated.

The non-magnetic substrate 1 is precisely cleaned, set in a holder, and then sent to a preparation chamber of an in-line type magnetron sputtering apparatus. And this preparation room is 5 × 1
Evacuate to a vacuum below 0 ^-6 Torr. Subsequently, the holder on which the substrate is set is conveyed to the film forming chamber, and the film forming chamber is placed in an Ar gas atmosphere with a pressure of 3 Pa. Next, in this film forming chamber, an underlayer made of Cr and having a film thickness of 100 nm, and subsequently a magnetic layer having a film thickness of 30 nm and made of CoSm alloy and having a thickness of 10 nm and D
The LC protective layer is sequentially formed by the DC magnetron sputtering method. The composition of the CoSm alloy is Co: 79 at%, Sm:
It was 21 at%. After all of these film formations are completed, the holder is transported to the removal chamber, and the substrate on which the film has been formed is removed from the holder under atmospheric pressure. Then, a fluorocarbon liquid lubricant is applied to the surface of the protective layer to form a film having a thickness of 1 to 1.
A 2 nm lubricating layer is formed to obtain a magnetic recording medium.

The coercive force (H
c) and product of saturation magnetic flux density (Br) and film thickness (δ) Br
.Delta. Was 2900 Oe and 83 G. .mu.m, respectively, and these values were the same as when the conventional Al alloy was used as the substrate. Example 2 In this example, a substrate mold is described. In general,
The metal mold for plastics is manufactured by heat-resistant steel material, electroforming of Ni, or the like, but the metal mold for plastic substrate of the magnetic recording medium could be similarly manufactured.

When a steel material is used, after the portion corresponding to the outer shape of the plastic substrate is processed, the portion corresponding to the surface of the medium is textured by polishing with diamond abrasive grains. In the texturing, it is also possible to grind while rotating the die for the substrate to form a concentric texture. 2A and 2B are schematic diagrams of a process for producing a textured Ni electroformed mold according to the present invention, in which FIG. 2A is a silicon master mold having a texture, and FIG. 2B is Ni electroformed on the silicon master mold ( c) is electroformed Ni from which the silicon matrix has been removed. After the texture T is processed on the silicon master die 91 with a slurry of diamond abrasive grains, Ni is electroformed on the texture T to form an electroformed layer 92 having an appropriate thickness, and then the silicon master die 91 is chemically dissolved. When removed, an electroformed Ni mold 93 having a texture T formed on its inner surface
Can be produced.

A plastic substrate was molded using this electroformed Ni mold 93, and the texture T was transferred to the plastic substrate. A non-magnetic layer, a magnetic layer, a protective layer and a lubricating layer were formed on the plastic substrate thus produced in the same manner as in Example 1 to obtain a magnetic recording medium. Example 3 In this example, a flexible polyester sheet material was used as the non-magnetic substrate and Ni was sputter-deposited as the non-magnetic metal under layer, and a Cr under layer, C
A method of manufacturing a magnetic recording medium in which an oSm alloy magnetic layer is formed, and a protective layer and a lubricating layer are further laminated will be described.

FIG. 2 is a schematic view of a method of manufacturing a magnetic recording medium according to the present invention. The polyester sheet material 13 as a non-magnetic flexible substrate is precisely cleaned, wound on a winding roller 71, and then mounted in a preparation chamber 61 of an inline type magnetron sputtering apparatus. The leading edge of the sheet material passes through the sputter film forming chamber 62 and another take-out chamber 6
It is fixed to the take-up roller 72 set to 3. Then, after the entire film forming apparatus including the charging chamber 61, the film forming chamber 62, and the take-out chamber 63 is evacuated to a vacuum degree of 5 × 10 ⁻⁶ Torr or less, the film forming chamber 62 is placed in an Ar gas atmosphere with a pressure of 3 Pa. Star The sheet material 13 was continuously run at a constant speed through the guide 74 so as not to loosen from the winding roller 71 to the winding roller 73. In this film forming chamber 62, a nonmagnetic metal underlayer made of Ni and having a thickness of 200 nm, an underlayer made of Cr and having a thickness of 10 nm, and then Co
A magnetic layer of Sm alloy having a thickness of 30 nm and a protective layer of diamond-like carbon having a thickness of 10 nm were sequentially formed by DC magnetron sputtering. In order to achieve both the formation of a layer having a predetermined film thickness different for each material on a sheet material running at a constant speed and the fact that the predetermined magnetic characteristics can be obtained only by a constant input power, the target sheet material The length in the running direction was adjusted.

The composition of the CoSm alloy is 80 at% Co and S
m was 20 at%. After all these film formations are completed,
The take-up roller 63 is taken out from the take-out chamber, and under atmospheric pressure, a fluorocarbon liquid lubricant is applied to the surface of the protective layer to form a lubricating layer having a film thickness of 15Å, which is used as a magnetic recording medium. The product Br · δ of the coercive force (Hc) and the saturation magnetic flux density (Br) and the film thickness (δ) of the medium thus obtained are 2800 Oe and 85 G · μm, respectively. It was equivalent to the case of using an Al alloy.

[0020]

According to the present invention, in the magnetic recording medium, the nonmagnetic substrate is plastic and the magnetic layer is CoSm.
Since it is made of a system alloy, the magnetic layer 3 made of a CoSm system alloy can obtain sufficient magnetic characteristics even if an amorphous or fine crystalline thin film is formed at room temperature. By suppressing the temperature of the recording medium manufacturing process and using a plastic material as the non-magnetic substrate 11, the cost can be suppressed.

Further, by applying a texture to the molding die in advance, it is transferred to the molded plastic substrate, the conventional texture treatment step can be omitted, and the molding die is manufactured by the same die. Since all the textures of the substrate are the same, the magnetic characteristics can be stabilized. Further, the texture processing step can be omitted, and the cost can be reduced.

If a sheet-shaped substrate is used, a low temperature sputtered film made of a CoSm-based alloy can be used as a magnetic layer, and a high recording density of a magnetic recording medium such as a tape or a flexible disk can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a manufacturing process of a textured Ni electroforming mold according to the present invention.

FIG. 2 is a schematic diagram of a method of manufacturing a magnetic recording medium according to the present invention.

FIG. 3 is a sectional view showing the structure of a magnetic recording medium.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 non-magnetic base material 11 non-magnetic base material 12 non-magnetic metal layer 13 sheet material 2 non-magnetic metal underlayer 3 magnetic layer 4 protective layer 5 lubricating layer 61 preparation chamber 62 deposition chamber 63 take-out chamber 71 take-up roller 73 take-up roller 74 Guide 80 Counter electrode 81 Ni target 82 Cr target 83 CoSm target 84 C target 91 Si master 92 Electroformed Ni layer 93 Electroformed Ni mold T Texture

Claims (4)

[Claims] 1. A magnetic recording medium in which at least a non-magnetic metal underlayer and a magnetic layer are sequentially laminated on a non-magnetic substrate, wherein the magnetic layer is made of a CoSm-based alloy and the non-magnetic substrate is made of plastic. A magnetic recording medium characterized by: 2. The magnetic recording medium according to claim 1,
A method of manufacturing a magnetic recording medium, wherein the plastic is molded by injection molding or extrusion molding. 3. The method of manufacturing a magnetic recording medium according to claim 2, wherein the texture of the plastic substrate is formed through a mold. 4. The magnetic recording medium according to claim 1, wherein
A magnetic recording medium, wherein the plastic is sheet-shaped.