JPH01320124A - Manufacture of magnetic disc board - Google Patents

Abstract

PURPOSE:To reduce surface defect by a method wherein a photo-setting resin layer is formed by 2P forming method with a stamper having high surface smoothness on a light transmissible resin board, which is produced by injection- molding thermoplastic resin. CONSTITUTION:Resist is applied onto a master such as glass with flat surface or the like. Next, a first metal layer made of Ni or the like is formed on the surface of the master coated with the resist. After that, a second metal layer made of Ni or the like is formed on the first metal layer. After the formation of the second metal layer, a backing material such as glass or the like is bonded on the second metal layer and then a stamper consisting of the backing material, the second metal layer and the first metal layer is separated from the master. By using the stamper prepared as mentioned above, a photo-setting resin layer is formed by 2P forming method on a thermoplastic resin board. As the transparent thermoplastic resin board, polyacrylate resin, polysulfone resin, polyether imide resin or the like is exampled. Further, as the photo-setting resin, polyurethane methacrylate, polyester methacrylate or the like is used. Thus, a disc, which has a few surface defects and is excellent in surface smoothness, can be produced.

Description

[Detailed Description of the Invention] The present invention relates to a method for manufacturing a substrate for a magnetic disk, and more specifically to a method for producing a magnetic recording layer having excellent electromagnetic conversion characteristics using a thin film type in which a magnetic recording layer having excellent electromagnetic conversion characteristics is formed by a vapor deposition method or a plating method. The present invention relates to a method for manufacturing a substrate used in a magnetic disk medium.

The 'self' amount of the day and the IJ title.

Conventionally, magnetic disk IJX bodies (coating type magnetic disk media) have been used as magnetic disk media, in which a recording layer is formed by coating an AI substrate with a magnetic paint in which magnetic powder is dispersed in an organic binder such as polyurethane. ) is used. However, since such a magnetic disk body requires the use of an organic binder to hold the magnetic powder on the AJ substrate, it is becoming difficult to cope with the recent trend toward higher density recording.

Therefore, a layer (metallic magnetic layer) in which a magnetic material is deposited in a thin film form on a substrate using a vacuum evaporation method or a plating method is used.
A magnetic disk medium (thin-film magnetic disk medium) with
is attracting attention. Such a thin film type magnetic disk medium is suitable for high-density recording because the recording layer does not contain an organic binder.

In general, it is preferable for a magnetic disk to have a smooth surface in consideration of characteristics such as running performance and electromagnetic conversion characteristics. , the surface properties of the substrate surface directly become the surface state of the magnetic recording layer.

However, 1. When attempting to manufacture a substrate with a highly smooth surface for thin-film magnetic disk media using L, strict process control such as dust prevention measures is required, and the manufacturing process is complicated. In other words, the manufacturing process of the "A" board includes casting,
The process is complex, consisting of homogenization of the ingot, hot rolling, cold rolling, circle punching, straightening softening, precision cutting, precision polishing, etc., and all of these processes are subject to dust-proofing measures and rigorous Process control requires a huge investment in equipment, and furthermore, process control becomes complicated.

Therefore, as mentioned above, A1, which requires complex process management,
Instead, organic polymers are used as substrate forming materials,
A method of molding a substrate by injection molding and a resin substrate for a thin film type magnetic disk medium made of an organic polymer have been proposed.

However, a magnetic disk substrate made of an organic polymer molded by injection molding has many surface defects, and the surface of the magnetic recording layer of a magnetic disk manufactured using this resin substrate is There is a problem in that head crashes and errors occur because there are defects corresponding to the surface defects that exist above. In other words, martensitic stainless steel used as a mold material for injection molding (for example, Arasab Starbucks) has a large number of "s", so no matter how much you improve the polishing accuracy of the mold surface, On the surface of the mold, a large number of convex surface defects are produced on the surface of a magnetic disk substrate obtained by injection molding using this mold.

In addition to the surface defects caused by the mold as mentioned above,
The resin used for injection molding contains impurities such as Fe and N.
There is also a problem in that the presence of I, Si, etc. causes concave surface defects on the surface of the resin substrate for magnetic disks.

In order to solve these problems, the mold surface is coated with Ni
- coated with P alloy etc. and present on the surface.
Then, the surface of the formed coating layer is precisely polished using abrasive grains such as synthetic quartz or diamond.
There have been attempts to obtain a resin substrate for magnetic disks with fewer surface defects by smoothing the surface of the mold.

The present inventors have also proposed a method of manufacturing a resin substrate for a magnetic disk with few surface defects by attaching a stamper with a smooth surface to the inner surface of a mold and performing injection molding.

However, in the above method of providing a coating layer on the mold surface, the mold metal and the coated metal have different linear expansion coefficients under high temperatures during injection molding, so delamination occurs between the mold metal and the coating layer. There was a problem that injection molding could not be carried out stably over a long period of time.

In addition, by adopting the method of providing a coating layer and the method of using a stamper, the convex surface defects that are formed on the surface of the magnetic disk substrate due to the "s" present on the mold surface are reduced. However, Fe, Ni,
There is a problem in that it is not possible to reduce concave surface defects formed by impurities such as Si serving as nuclei.

The present invention aims to solve the problems associated with the prior art as described above, and provides a method for manufacturing a magnetic disk substrate with few surface defects and excellent surface smoothness. is intended to provide.

Good comic! The method for producing a magnetic disk substrate according to the present invention is to form a photocurable resin layer on a light-transmissive resin substrate made of an injection molded thermoplastic resin by a 2P molding method using a stamper having a high surface smoothness. It is characterized by the formation of

In the method for manufacturing a magnetic disk according to the present invention, a photocurable resin layer is formed on a magnetic disk substrate by employing a 2P molding method using a stamper having high surface properties as described above. A magnetic disk substrate having a photocurable resin layer on the surface having a high surface smoothness corresponding to the surface smoothness of - is obtained.

Rinho! 11. A method for manufacturing a magnetic disk substrate according to the present invention will now be described in detail.

In the present invention, a magnetic disk substrate is manufactured by forming a photocurable resin layer on a transparent thermoplastic resin substrate using a 2P molding method.

[Thermoplastic resin] In the present invention, a resin substrate is manufactured using a thermoplastic resin by an injection molding method.

In the present invention, when curing the photocurable resin using the 2P molding method, curing energy rays are irradiated from the thermoplastic resin substrate side, so at least the resin substrate obtained by injection molding is not irradiated. must be transparent to energy radiation.

In addition, in order to prevent thermal deformation of the substrate when forming a recording layer made of ferromagnetic metal or the like on a resin substrate, the temperature of the substrate forming resin is 150°C or higher, preferably 150 to 450°C.
It is desirable that the glass transition temperature is .

Further, the resin for forming the substrate preferably has a tensile strength of 700 ht/cd or more in consideration of the durability of the resulting magnetic disk.

Examples of resins having such characteristics include polyarylate resins, polysulfone resins, polyetherimide resins, polyethersulfone resins, polyphenylene sulfide resins, and polyetherethergetone resins.

Among these, preferred are polyarylate resins, polysulfone resins, polyetherimide resins, and polyethersulfone resins, which have good processing properties such as melt flowability.

By a normal method using a thermoplastic resin as described above,
The diameter, thickness, etc. of the injection molded article thus obtained can be appropriately set so as to comply with, for example, standards for magnetic disks.

[Stambar] The stub bar with a highly smooth surface used in the present invention can be produced, for example, by the method described below.

That is, a resist is applied to a thickness of 500 to 5000 Å on a master with excellent surface smoothness, such as a glass master with a smooth surface. By applying the resist in this manner, the surface roughness (Ra) of the master can be reduced to 0.1 Å or less.

In the present invention, the surface roughness of the master can be reduced by coating the resist on the master as described above, so there is a direct relationship between the surface roughness of the master and the surface roughness of the stamper to be manufactured. It is not necessary to have a corresponding relationship, however, if the surface quality of the master is significantly reduced, it will be impossible to manufacture a stamper with sufficient smoothness even when resist is applied, so normally the surface Roughness (Ra
) is preferably 5 Å or less.
As a resist that can be used here, for example, novolak resin (manufactured by Hoechst Javan Co., Ltd., trade name:
AZ 1350 J).

As a method for applying such a resist to the master disc, a wide variety of conventionally known methods can be used, and specifically, a method such as a spin code can be used.

The coating thickness of the above-mentioned resist should be J7 enough to fill at least four parts on the master surface, and is preferably 0.06 to 20 μm.

N
A first metal layer made of i metal or the like is formed.

Such a first metal layer can be formed by, for example, a vapor deposition method. Moreover, this first metal layer usually has a thickness of 50
It has a film thickness of 0 to 3000 people.

After forming the first metal layer in this manner, a second metal layer is formed on the first metal layer. This second metal layer can be formed by a plating method or the like, preferably using the same metal as that forming the first metal layer. Further, the thickness of this second metal layer is usually 200 to 40 mm.
It is 0 μm.

Note that by increasing the thickness of the first metal layer, it is also possible to omit the provision of the second metal layer.

After forming the second metal layer in this manner, a backing material is bonded onto the second metal layer. The backing material used here is preferably a material with a high surface smoothness; for example, a suitable backing material is glass. Furthermore, various adhesives such as epoxy adhesives can be used to bond such backing material.

After the backing material is attached as described above, the stamper consisting of the backing material, the second metal layer, and the first metal layer is peeled off from the master. Then, from the master to the stand bar like this,
By peeling off the resist coated on the master,
Most of them adhere to the master disc and remain on the master disc. Note that the resist that has adhered to the first metal layer can be removed by electrolytic cleaning.

The thus obtained stamper has a surface to which the high smoothness of the resist surface is transferred, and usually has a surface roughness (Ra) of 0.1 Å or less and has few surface defects.

[2P molding method] In the present invention, the stambar prepared as described above
2P photocuring resin layer on thermoplastic resin substrate using
Formed by a molding method.

That is, a photocurable resin liquid is dropped or applied onto a thermoplastic resin substrate, and then a stand bar is brought into contact with the photocurable resin to form a photocurable resin layer between the thermoplastic resin substrate and the stand bar. By irradiating the photocurable resin layer with energy rays from the thermoplastic resin substrate side, the photocurable resin can be cured to form a photocurable resin layer.

Examples of the photocurable resin used in the present invention include polyurethane methacrylate and polyester methacrylate.

Further, the thickness of the photocurable resin layer as described above is usually 20 to 20 mm.
It is 200 μm.

Specifically, the energy rays used to cure such photocurable resins have a main wavelength of 3.
Examples include ultraviolet rays that are in the vicinity of 65n11 and have an intensity of 80 to 160 W/■.

For curing a photocurable resin using energy rays as described above, for example, when irradiating the above-mentioned ultraviolet rays, the irradiation intensity is 50 m W / d to I W / cl, and the irradiation time is 2 to 30 seconds. It is preferable.

Since the stamper has two metal layers and is opaque, the energy beam is irradiated from the light-transmissive thermoplastic resin substrate side.

By irradiating the energy beam in this manner, the photocurable resin between the resin substrate and the stamper is cured. After the photocurable resin is cured in this manner, the stamper is removed.

By curing the photocurable resin in this way,
Since the surface of the photocurable resin layer that is in contact with the stamper is directly transferred to the surface of the stamper, for example, when using a stamper with a surface roughness (Ra) of 0.1 Å or less, The surface roughness (Ra) of the photocurable resin layer is 0.1
It will be less than Å.

It is also possible to manufacture a magnetic disk by directly vapor depositing a ferromagnetic metal or the like on the photocurable resin layer of a resin substrate having a photocurable resin layer on the surface obtained in this way, to form a recording layer. Depending on the case, it is also possible to further provide another layer such as a hard metal layer on the surface of this photocurable resin, and form a recording layer thereon. Examples of such a layer include a nonmagnetic metal layer, a nonmagnetic inorganic layer, and an organic polymer layer.

Non-magnetic metals that can be used in this case include:
Titanium, chromium, tungsten, molybdenum, etc. can be mentioned, and non-magnetic inorganic materials include titanium nitride,
Examples include titanium carbide and diamond-like carbon. Furthermore, examples of organic polymers include acetal resins, acrylate resins, vinyl chloride-vinyl acetate copolymer resins, and epoxy resins.

The thickness of such a nonmagnetic metal thin film, nonmagnetic inorganic thin film, or organic polymer thin film is usually within the range of 200A to 20 μm.

A thin-film magnetic disk can be obtained by depositing a recording layer of magnetic metal or the like on the thus obtained magnetic disk substrate by vapor deposition or plating.

By using the resin substrate manufactured in this way, a magnetic disk with fewer surface defects can be manufactured. Here, a surface defect is a convex shape with a diameter of 5 to 20 μm and a height of 10 OA or more, and a surface defect with a diameter of 5 to 20 μm.
This type of surface defect can be confirmed by surface observation using an optical microscope Ia with a magnification of 400 times, for example.

It is most preferable that the magnetic disk has no surface defects such as those described above. Considering the C8S characteristics, etc., it is preferable that a generally used magnetic disk substrate with a diameter of 130 mm has 10 or less surface defects, and a magnetic disk substrate with a diameter of 90 mm should have 10 or less defects. It is preferable that the number is 4 or less.

According to the manufacturing method of the present invention, the number of surface defects can be reduced to 10 or less in a magnetic disk substrate with a diameter of 130 sq.
In the related magnetic disk substrate, the number of stampers can be reduced to four or less, and by using a stamper with a highly smooth surface, a magnetic disk substrate with particularly few surface defects can be manufactured.

According to the method for manufacturing a magnetic disk substrate according to the present invention, a magnetic disk substrate with significantly fewer surface defects can be manufactured.

Further, by using the magnetic disk substrate obtained by the manufacturing method according to the present invention, it is possible to obtain a magnetic disk that is less prone to head crashes and does not cause errors. Furthermore, the substrate obtained by the manufacturing method of the present invention is
Since thermoplastic resin is used, the weight of the magnetic disk itself including the substrate can be reduced, making it possible to downsize the motor and/or
Alternatively, it is possible to reduce the size of the hard disk drive.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples.

Injection molding was performed using polyetherimide resin (manufactured by General Electric Co., product name Ultem 1ooo) as a thermoplastic resin, and the diameter was 1301t1 and the thickness was 1.9mm.
A disc-shaped thermoplastic resin molded body of 1.5 mm was obtained.

Injection molding was performed using an injection molding machine (Dynamelter, H-14OL/D=26) manufactured by Meiya Seisakusho ■ at a resin temperature of 43.
The test was carried out at 0°C and a cycle time of 40 seconds.

On the other hand, a stamper was manufactured by the method described below.

That is, a resist (manufactured by Hoechst Japan Co., Ltd., trade name: A2 1350 J) was coated onto a blue glass (Ra 5 Å or less) having a diameter of 200 mm and a thickness of 10 m to a thickness of 1000 m using a spin code method. The surface roughness (Ra) of the coating layer was 0.1 Å or less.

On the resist surface, a Ni metal layer is deposited with a thickness of 10
It is formed to a thickness of 0.00 mm, and then N is formed on top of it by electroforming.
One plating layer was formed to a thickness of 300 μm. After applying a two-component type epoxy adhesive as thinly as possible on the surface of the plating layer, a piece of blue glass with a diameter of 200 mm and a thickness of 5111111 is adhered on top of the adhesive, and a backing material is applied. Established.

After the adhesive hardens, the resist layer and the deposited N1 layer are peeled off,
The resist remaining on the Ni metal layer was removed by electrolytic cleaning. The surface roughness (Ra) of the thus obtained stamper surface was 0.1 Å or less.

A photocurable resin made of polyurethane methacrylate was dropped onto the stamper obtained above, and the disk-shaped thermoplastic resin molding obtained above was further brought into contact with the stamper, followed by a high-pressure mercury lamp with a light source intensity of 100 W/■. A photocuring resin layer was formed to a thickness of 25 μm by irradiating a curing light beam from the thermoplastic resin side at an irradiation intensity of 0.5 W/− for 10 seconds. The stamper and the thermoplastic resin molded body on which the photocurable resin layer was formed were peeled off, and the outer periphery was processed to a diameter of 130 mm.
After forming a circle, a hard metal layer made of Ti metal was further formed on the photocurable resin layer to a thickness of 4,500 mm to obtain a magnetic disk substrate.

Five magnetic disk substrates were manufactured as described above.

With respect to the thus obtained magnetic disk substrate, surface defects before and after the formation of the photocurable resin layer were observed using an optical microscope at a magnification of 400 times, and the number thereof was counted.

The observation results for the five substrates are shown in Table 1. On the obtained substrates, a Co-Ni alloy layer was formed as a magnetic layer by sputtering, and stearic acid was further applied as a lubricant layer on top of the Co-Ni alloy layer. And a magnetic disk? A left behind.

The C8S characteristics of this magnetic disk were measured 1,000,000 times.

An L-plate plate with a diameter of 130 am and a thickness of 1.9++ un was formed by injection molding in the same manner as in Example 1, except that the photocurable resin layer was not formed.
A magnetic disk substrate was obtained. In the same manner as in Example 1, r
The number of surface defects observed was equivalent to the number of surface defects of the thermoplastic resin molded articles shown in Table 1.

Next, a Ti hard metal layer was formed on the obtained thermoplastic resin molded body and a magnetic disk was manufactured in the same manner as in Example 1. When the C8S characteristics were measured using this magnetic disk, it was found that 3,000 times. Met.

Agent: Patent Attorney: Shunbetsu Suzuki

Claims (1)

[Claims] 1) Using a stamper with high surface smoothness, 2.
A method for manufacturing a magnetic disk substrate, characterized by forming a photocurable resin layer by a P molding method.