JPH0620266A - Board for magnetic disc - Google Patents

Abstract

PURPOSE:To obtain a board for magnetic disc which is excellent in productivity and groove forming accuracy. CONSTITUTION:When a flexible board 10 for floppy disc is produced, a nonmagnetic basic material 100 of PET, for example, having surface subjected to hydrophilic treatment, onto which a vinyl chloride-vinyl acetate copolymer layer having main skeleton of 80-92mol% vinyl chloride and 8-20mol% vinlyl sequentially. A stamper 21 is then pressed while heating to transfer the grooves therefrom to the copolymer layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk substrate.

[0002]

2. Description of the Related Art In the case of a magnetic disk having a groove, since the distance from the magnetic head in the groove increases and demagnetization due to separation loss increases, adjacent recording tracks can be separated by the groove and the track recording density can be increased. It is possible to prevent crosstalk even when it is high.

Such a magnetic disk is obtained by using a substrate having grooves formed therein and forming a magnetic layer on the substrate.

In a magnetic disk substrate having such a groove, as a method for mechanically forming the groove, as disclosed in, for example, Japanese Patent Laid-Open No. 54-12806, a racker plate is formed by a non-modulation cutter. There is a method in which overcutting is performed, a stamper having the same shape as this racker plate is formed using this racker plate, and a magnetic disk substrate is produced by this stamper.

However, with such a method, it is impossible to form a groove having a super narrow width of about 1 μm. Moreover, since the substrates to be produced are of the single-wafer type, the production efficiency cannot be rapidly improved. Further, such a method can be applied to a hard disk such as a floppy disk from a relatively thin substrate having a thickness of 100 μm or less.
It has a drawback that even a relatively rigid substrate of about 2 mm cannot be obtained by the same method.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic disk substrate having excellent productivity and good groove processing accuracy.

[0007]

These objects are achieved by the present invention described in (1) to (5) below.

(1) The surface of a non-magnetic substrate is hydrophilized to reduce the contact angle to water, and vinyl chloride is contained in an amount of 80 to 92 mol% and vinyl acetate is contained in an amount of 8 to 20 on the hydrophilized substrate. A substrate for a magnetic disk, which is obtained by forming a layer of a vinyl chloride-vinyl acetate copolymer having a main skeleton of mol%, transferring a groove of a grooved master to the layer, and forming the groove.

(2) The magnetic disk substrate according to (1) above, wherein the dry film thickness of the vinyl chloride-vinyl acetate copolymer layer is 3 to 12 μm.

(3) The magnetic disk substrate according to the above (1) or (2), wherein the contact angle of water on the surface of the non-magnetic substrate becomes 40 degrees or less by the hydrophilic treatment.

(4) The magnetic disk substrate according to any one of the above (1) to (3), which is used for obtaining a magnetic disk having a continuous thin film magnetic layer formed on the groove forming surface.

(5) The magnetic disk substrate according to the above (4), wherein a plasma polymerized film is provided on the vinyl chloride-vinyl acetate copolymer layer after forming the groove when forming the continuous thin film magnetic layer.

[0013]

Specific Structure The specific structure of the present invention will be described in detail below.

To obtain the magnetic disk substrate of the present invention,
First, a vinyl chloride-vinyl acetate copolymer layer is formed on a non-magnetic substrate.

In this case, the surface of the non-magnetic substrate on which the vinyl chloride-vinyl acetate copolymer layer is formed is hydrophilized.

After forming a copolymer layer on such a non-magnetic substrate, a grooved magnetic recording disk substrate having predetermined grooves is obtained.

A predetermined groove can be formed by passing through such steps. That is, it is possible to form a groove having an ultra narrow width of about 1 μm. Further, the non-magnetic base material on which the copolymer layer is formed can be continuously conveyed to continuously form the grooves on the master plate, which enables mass production.

Further, by the same method as described above, it is possible to form a groove on any substrate from a relatively thin substrate such as a floppy disk to a relatively rigid substrate such as a hard disk. Extensive.

The vinyl chloride-vinyl acetate copolymer used in the present invention has a vinyl chloride content of 80 to 92 mol%, preferably 85 to 90 mol%, and a vinyl acetate content of 8 to 20 mol%.
It preferably has a main skeleton of 10 to 15 mol%.

This product has a wide selection of coating solvents, is easy to coat on a non-magnetic substrate, and is preferable in manufacturing.

Further, by using the copolymer having such a component constitution, the adhesion between the non-magnetic substrate and the copolymer layer becomes strong, which is preferable for forming a grooved substrate. Furthermore, the life of the grooved master (stamper) used is extended, and the grooves can be reliably transferred from the stamper.

The above copolymer may be partially modified as long as it has the above main skeleton.

Further, in addition to the above components, a third component different from the above may be contained, and examples of the third component include those derived from vinyl alcohol, butadiene, urethane and the like, When the total of vinyl chloride and vinyl acetate is 100 mol%, 1 to 10
It is good to set it as the ratio of mol%. Further, polymers such as polyvinyl alcohol, polybutadiene and polyurethane may be mixed in such a ratio.

The magnetic disk substrate of the present invention is used as a flexible substrate for a floppy disk or a rigid substrate for a hard type magnetic disk.

The material of the non-magnetic substrate used for the flexible substrate for the floppy disk is not particularly limited, and various films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) can withstand the heat of forming the ferromagnetic metal thin film. ) And other polyesters, polyether ether ketone (PEEK), and the like can be used. Further, each material described in JP-A-63-10315 can be used.

The size of the resinous non-magnetic substrate at this time may be selected according to the purpose, but normally the thickness is 30 to 100.
The diameter is about μm and the diameter is about 60 to 130 mm.

On the other hand, when a rigid substrate for a hard type magnetic disk is used, it may be made of glass, aluminum or resin. A substrate is rigid when E · t ³ ≧ 1 × 10 ⁷ where E is the Young's modulus and t is the thickness of the substrate.
dyn · cm, more preferably E · t ³ ≧ 3 × 10 ⁷ dyn · cm.

The resin used at this time is not particularly limited,
Any resin such as a thermoplastic resin, a thermosetting resin, or a radiation curable resin may be used.

In this case, when the non-magnetic substrate is molded by the casting method, for example, polyurethane, epoxy resin, acrylic resin, polystyrene, polyamide, silicone resin, polyester and modified products thereof can be used.

In the case of molding by injection method, for example, polyethylene, polypropylene, vinyl chloride resin, vinylidene chloride resin, vinylidene fluoride resin, polystyrene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylic resin , Polyamide, polycarbonate, polyacetal, polyester, polysulfone, polyoxybenzylene, polyether sulfone, polyether ketone, polyether ether ketone, polyphenylene sulfide, polyphenylene ether, polyphenylene oxide, polyketone sulfide, polyimide, polyamideimide, polyacrylic Use of imide, polyetherimide, polyolefin, amorphous polyolefin and modified products of these Kill.

The size of the resinous non-magnetic substrate at this time may be selected according to the purpose, but normally the thickness is 0.8-1.
The diameter is about 9 mm and the diameter is about 60 to 130 mm.

In forming the above-mentioned copolymer layer using such a non-magnetic substrate, the surface of the non-magnetic substrate is hydrophilized, but the hydrophilization treatment is not particularly limited, and the contact angle of water on the substrate surface is not limited. Any of the treatments that reduce the can be used.

By such a treatment, the adhesiveness between the non-magnetic substrate and the copolymer layer is improved and the transfer of the groove is ensured.

In this case, the contact angle of the surface of the substrate with water is preferably 40 degrees or less, more preferably 30 degrees or less. From the viewpoint of hydrophilicity, the smaller the contact angle, the more preferable.

Plasma treatment is used for such hydrophilic treatment.
Corona treatment etc.

Of these, in the case of plasma treatment, an inorganic gas such as oxygen or nitrogen may be used as a treatment gas. The plasma processing conditions are not particularly limited, and the electrode arrangement, applied current, processing time, operating pressure and the like may be the same as those under normal plasma processing conditions. Usually, the operating pressure is about 0.01 to 1 Torr. Further, the flow rate of the processing gas may be 5 to 100 SCCM.

The frequency of the plasma processing power source is not particularly limited and may be any of direct current to microwave.

Also, when the corona treatment is used, a usual method may be used.

The copolymer layer is formed by using the above coating solution of vinyl chloride-vinyl acetate copolymer.

The coating solvent at this time is not particularly limited as long as it dissolves such a copolymer and does not attack the non-magnetic substrate, and it has a low boiling point and low polarity such as methyl ethyl ketone (MEK) and acetone. The solvent can be used, and it is preferable to use methyl ethyl ketone or the like.

The concentration of the coating solution is 10 to 30 wt%,
Preferably, it should be about 15 to 25 wt%.

The coating method is not particularly limited, and any known method may be used, and preferably, a gravure roll coating method, a reverse roll coating method, a spin coating method, or the like. The coating conditions and the like in this case may also be according to known methods.

The film thickness of the copolymer layer thus formed is 3 to 12 μm as a dry film thickness. In the case of a flexible substrate for a floppy disk, the thickness is 3 to 7 μm, preferably 4 to 6 μm, and in the case of a rigid substrate for a hard type magnetic disk, 3 to 10 μm, preferably 5 to 8 μm.
You can use m. By setting the film thickness in such a range, it is possible to reliably transfer the groove. On the other hand, if the film thickness is too large, peeling or the like may occur during pressing, which is not preferable in manufacturing, and if the film thickness is too small, groove transfer cannot be performed.

The film thickness may be measured with a micrometer or the like, and is usually calculated by subtracting the thickness of the nonmagnetic substrate from the total thickness of the nonmagnetic substrate and the copolymer layer.

Next, a grooved master disk (stamper) is used to press the grooved master disk on the copolymer layer to form grooves on the non-magnetic substrate on which the copolymer layer has been formed.

The material of the master plate at this time is not particularly limited, but it may be usually made of metal, and among them, it is made of Ni in view of availability, cost, and plating capability. And it is sufficient.

Further, it is preferable to heat during pressing.

The pressing pressure is 130 to 250 kg / cm ² , preferably 140 in the case of a flexible substrate for a floppy disk.
~220kg / cm ^2, when the rigid substrate 200~300kg / cm ² for a hard type of magnetic disk, preferably 230 to
It should be 250 kg / cm ² .

By using such a pressing pressure, the groove can be transferred reliably and accurately. If the pressure becomes too large, it becomes necessary to upsize the press machine, which is expensive and inferior in terms of accuracy, which is not preferable. If the pressure becomes too small, groove transfer cannot be performed reliably. .

The heating temperature may be 140 to 250 ° C, preferably 170 to 200 ° C. By setting such a heating temperature, the polymer moves to an appropriate state, and the pressing becomes easy.

If the temperature is too high, deformation is likely to occur, and if the temperature is too low, the groove cannot be transferred.

The shape of the groove can be made predetermined by selecting the shape of the groove of the stamper.

Usually, the grooves are formed in a concentric shape, a spiral shape, etc., and the groove width, depth, groove pitch, etc. may be appropriately selected according to the recording density and the recording material.

In the present invention, even a groove having an ultra-narrow width of about 1 μm can be accurately formed, and both the groove width and the depth are less than ± 10% as compared with the groove of the stamper. Therefore, the number of defective products is reduced, and the yield is improved.

In the present invention, an example of the constitution of an apparatus for forming a groove in a non-magnetic substrate on which a copolymer layer is formed is shown in FIG.
Is shown in.

The illustrated apparatus 1 has a PET as a non-magnetic substrate.
A substrate for a floppy disk using the above is manufactured.

The apparatus 1 has a stamper portion 2 for forming a groove having a predetermined shape, and a non-magnetic substrate 10 having a copolymer layer formed thereon.
It has a substrate supply part 3 for storing 0 in a roll shape and sequentially feeding the same, and a substrate storage part 4 for storing the substrate 10 after the groove is formed.

The stamper portion 2 includes a stamper 21 having a groove of a predetermined shape and a heating portion 23 for heating the stamper 21 to a predetermined temperature. Below the stamper 21, a pair of the stamper 21 is formed at the time of forming the groove. A lower mold 25 that holds the base 100 is installed.

The lower mold 25 may be installed at room temperature or may be cooled.

In the structure shown in FIG. 1, the substrate 100 is sequentially fed out from the substrate supply section 3, and the stamper section 2 stamps the stamper.
21. Pressing with heating. This makes it possible to continuously form the grooves.

Substrate 1 after the grooves are formed in this way
0 is wound up and stored in the substrate storage unit 4.

The substrate 10 having the groove formed in this way
Is used as a plastic substrate for floppy disks. In this case, the substrate may be punched into a disc shape and then the magnetic layer may be formed. Alternatively, the magnetic layer and the like may be formed and all layers may be formed and then punched.

When the punching method is adopted at the same time as the former press, the magnetic layers can be simultaneously formed on both surfaces by using a single-wafer sputtering apparatus, and the labor for aligning the punching can be omitted.

When the latter method of punching after forming all the layers is adopted, an alignment guide groove is formed in the stamper 21 in advance, and recording of the magnetic layer forming area of the substrate 10 is performed as shown in FIG. -It is preferable to form the alignment guide groove 105 corresponding to the stamper 21 in the area 10B outside the reproducing portion 10A. That is, such a groove 105 is
As shown in the figure, it is preferable to provide the disk-shaped object at three positions at 120 ° intervals. This method is advantageous because it is possible to continuously form the groove and the magnetic layer.

An example of the structure of a floppy disk obtained by such a method is shown in FIG.

As shown in FIG. 3, the floppy disk 5
Has the magnetic layer 15 on the substrate 10 in which the groove 31 is formed as described above, with the underlying film 13 and the underlying layer 14 interposed therebetween. The top coat film 16 is formed on the magnetic layer 15.
Is provided.

If necessary, as the material of the underlayer 14 provided as shown in FIG. 3, a metal, a metal compound, or an alloy in which the easy axis of magnetization is oriented in the in-plane and perpendicular directions is selected according to the magnetic layer 15. And use it. Specifically, Cr, M
o, permalloy, etc., which are the same as the underlayer of the hard type magnetic disk described later. Underlayer 1
The film thickness of 4 is 500-10000A (0.05-1μm)
The degree.

Further, such a metal underlayer 14 and the substrate 1
It is preferable to provide a base film 13 of a plasma polymerized film between 0 and 0. Underlayer film 13 of such a plasma-polymerized film
By providing, the adhesion between the magnetic layer 15 and the underlayer 14 and the substrate 10 is improved, and the durability is improved. Further, when the underlayer 14 and the magnetic layer 15 are formed by, for example, sputtering, there is an advantage that the shape of the groove is not thermally deformed.

The base film 13 of the plasma polymerized film has a thickness of 50.
Approximately 300A.

The magnetic layer 15 is not particularly limited as long as it is a continuous thin film type, and each ferromagnetic metal thin film forming the magnetic layer 15 is
For example, a continuous thin film containing one or more selected from Fe, Co and Ni, particularly a Co-based continuous thin film, may be used.

A specific example of the composition of the magnetic layer is Co--N.
i alloy, Co-Ni-Cr alloy, Co-V alloy, Co-
Ni-P alloy, Co-P alloy, Co-Zn-P alloy, C
o-Ni-Pt alloy, Co-Pt alloy, Co-Ni-M
An n-Re-P alloy etc. are mentioned.

Further, if necessary, a small amount of oxygen may be contained in the surface layer of each layer, or a non-magnetic layer may be interposed therebetween to improve the corrosion resistance and the like.

The thickness of the magnetic layer 15 is 0.03 to 0.2 μm.
It is preferably about m 2. At this time, the output can be made sufficiently large.

The magnetic layer 15 may be formed by various vapor phase film forming methods such as vapor deposition, sputtering, ion plating and CVD, but it is particularly preferable to form it by sputtering.

When the film is formed by sputtering, there are no particular restrictions on the sputtering method, apparatus, etc., and the various conditions may be appropriately determined according to the sputtering method and the like.

For example, in the case of DC-magnetron sputtering, the operating pressure may be about 0.1 to 10 Pa and it may be performed in an atmosphere of an inert gas such as Ar. When the surface of the magnetic layer 15 is hardened, a gas atmosphere containing O ₂ may be used.

Further, as shown in FIG. 3, a top coat film 16 is provided on the magnetic layer 15 if necessary.
It is preferably a plasma polymerized film. At this time, the thickness of the top coat film 16 is 10 from the viewpoint of spacing loss.
~ 200A is recommended. In addition, a lubrication protective film may be separately provided.

In this case, the groove 31 on the substrate 10 forms unevenness on the uppermost surface of the disk. Due to the unevenness, the track density is improved by groove tracking and the contact area with the head is reduced, so that the durability is improved. It is possible to obtain effects such as improvement of

In the above, the present invention has been described for the case where it is preferably used as a flexible substrate for a floppy disk, but it can be used for a rigid substrate of a hard type magnetic disk.

In this case, the copolymer layer is formed by a spin coating method using a disk-shaped non-magnetic substrate, the lower mold is placed on the belt conveyor, and the non-magnetic substrate having the copolymer layer formed thereon is placed on the upper mold. It is preferable to form a groove by pressing, for example, when the base body is located under.

When a hard type magnetic disk is used,
The layer structure and the like are the same as those in FIG. 3, and the only difference is that a rigid substrate is used among the above.

The magnetic layer is not particularly limited as long as it is a continuous thin film type. In this case, the magnetic layer may be basically the same as that of the floppy disk, and the manufacturing method may be the same.

The thickness of the magnetic layer is preferably 0.03 to 0.2 μm from the viewpoint of reproduction output and coercive force.

If necessary, an underlayer is provided between the substrate and the magnetic layer for the purpose of favoring epitaxial growth and improving magnetic characteristics.

The underlayer may be composed of a continuous thin film containing at least one selected from Cr, Mo and W, like the underlayer of a floppy disk. In this case, the metal used may be a simple substance or an alloy. The thickness of the underlayer is set to 0. to improve the orientation and crystallinity of the magnetic layer.
05-0.5 μm is preferred.

If necessary, these alloys may contain O,
Other elements such as N, Si, Al, Mn, Ar, B and C are 2
You may contain about 0 weight% or less.

The underlayer is formed by vapor deposition, like the magnetic layer described above.
The film may be formed by various vapor phase film forming methods such as sputtering, ion plating, and CVD, and it is particularly preferable to form the film by sputtering.

On the magnetic layer, a protective layer, an organic lubricant film (not shown) or the like may be further provided, if necessary. Also,
Similar to the floppy disk, a plasma polymerized film may be interposed between the substrate and the underlayer or magnetic layer, and the same effect can be obtained.

In this case, the groove on the substrate forms unevenness on the uppermost surface of the disk, which further improves the lubricity between the magnetic disk and the magnetic head.
S durability is improved. Also, the track density is improved.

The protective layer is usually composed of carbon or carbon containing another element in an amount of about 5% by weight or less, and the film thickness thereof may be about 0.03 to 0.1 μm.

The lubricating film is usually composed of a fluorinated liquid lubricant or the like, and the film thickness may be about 5 to 20A.

The protective layer and the like may be formed by various vapor phase film forming methods, particularly sputtering.

The lubricating film or the like may be formed by dip coating, spray coating, spin coating or the like.

In the above, as shown in FIG. 3, a single-sided recording type magnetic disk has been described as an example.
It can also be applied to a double-sided recording type magnetic disk.

In this case, in the flexible substrate for the floppy disk, the groove may be formed on one surface as described above, and then the same operation may be repeated to form the groove on the other surface.

On the other hand, in a rigid substrate for a hard type magnetic disk, grooves can be formed on each surface in the same manner as this.

[0097]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

Example 1 Polyethylene terephthalate (PET) having a thickness of 75 μm
Using a film, polyvinyl chloride or a vinyl chloride-vinyl acetate copolymer having the composition shown in Table 1 was used, and a 20 wt% methyl ethyl ketone solution of this polymer was applied, and the film thickness (dry film thickness) shown in Table 1 was applied. A film was formed. The application was by a gravure roll coating method.

In addition, when forming the polymer layer,
As shown in, a non-treated non-magnetic substrate and a plasma-treated non-magnetic substrate under the following conditions were used.

Plasma processing conditions Gas used: oxygen Flow rate: 100 SCCM RF: 50 W Pressure: 0.05 Torr

The film thickness of the polymer layer was measured by a micrometer and calculated by subtracting the thickness of the PET film from the total thickness of the PET film and the polymer layer.

Next, the PET film having the coating film formed thereon was housed in a roll form, and grooves were formed using the apparatus shown in FIG.

The stamper is made of Ni, and the groove at this time is
The width is 0.4 μm and the depth is 0.5 μm, and the gap between the grooves is 1.6.
μm, and formed in concentric circles. Further, as shown in FIG. 2, alignment guide grooves were also formed.

The pressing pressure for forming the groove is 15
The heating temperature was 0 kg / cm ² , and the heating temperature was 180 ° C.

For each of the thus obtained substrate samples, the adhesive strength between PET and the polymer layer, the stamper life and the yield were examined as follows.

(1) Adhesive Strength A scotch tape (manufactured by 3M) was attached to a substrate sample cut into a width of 1/2 inch, and the force (g) required for peeling the polymer layer from the PET film was determined. .

(2) Life of Stamper The evaluation was made by the number of substrate samples until the entire transfer from the stamper to the polymer layer was stopped.

(3) Yield With respect to 1000 substrate samples, the groove width and depth of the groove were measured by a scanning tunneling microscope (STM),
If the deviation from the groove of the stamper by ± 10% or more in either one of the groove width and the depth was judged to be outside the yield, the ratio of those both less than ± 10% was calculated as the yield (%).

The results are shown in Table 1. Table 1 also shows the contact angle of water on the surface of the non-magnetic substrate.

[0110]

[Table 1]

The effect of the present invention is clear from Table 1.

The above substrate samples No. 3, No. 5, No. 7
Was used to form a Cr underlayer having a thickness of 0.1 μm, and a plasma polymerized underlayer was further formed.
A 05 μm Co-Ni-Cr magnetic layer was formed. Further, a top coat film of a plasma polymerized film was formed on the magnetic layer. The film thicknesses of the underlayer and the top coat film were 200 A and 50 A, respectively, and the plasma polymerization conditions were as follows.

Plasma polymerization conditions W / (F · M): 1.05 × 10 ⁹ Joule / kg CH ₄ flow rate: 40 SCCM Operating pressure: 0.1 Torr Plasma output: 500 W Plasma frequency: 13.56 MHz

The underlayer and the magnetic layer were formed by DC-magnetron sputtering.

The sputtering conditions for the underlayer and the magnetic layer were an operating pressure of 1 Pa and an Ar atmosphere.

The targets are Cr and C, respectively.
o _62.5 Ni ₃₀ Cr _7.5 (at%) was used.

When the composition of the magnetic layer was determined by ICP emission analysis, it was Co _62.5 Ni ₃₀ Cr _7.5 (at%).

After that, a 3.5 inch floppy disk (F
D) A sample was obtained. FD depending on the substrate sample used
Sample No. 3, No. 5, and No. 7

FD sample No. 3, No. 5, No. 7
Built in 3.5 inch floppy disk drive,
When the durability was examined, the durability was sufficient. Also,
The electromagnetic conversion characteristics were also at a satisfactory level.

Further, a cross section of the above FD sample was taken by TEM.
The full width at half maximum (W _G ) of the groove was determined by observing with, and compared with the full width at half maximum (W _S ) of the stamper, W _G / W _S was almost 1, and the transfer of the groove was reliable and spattering etc. It was confirmed that the shape of the groove was maintained well without being subjected to thermal deformation or the like.

In the FD sample described above, an F film having the same structure except that the base film of the plasma-polymerized film was not formed.
When the D sample was obtained and compared with the above FD sample, it was found that the FD sample having the underlayer film of the plasma polymerized film was superior in durability. It is considered that this is because the plasma polymerized film increased the adhesiveness between the magnetic layer or the underlayer and the substrate.

Further, when the cross section of the FD sample was observed by a TEM, it was found that the one having the underlayer film of the plasma polymerized film was excellent in maintaining the shape of the groove. However, even if it did not have the underlayer film of the plasma polymerized film, it was at a level where practically no problem occurred. It is considered that this is because the base film of the plasma-polymerized film alleviates the deformation of the groove due to the sputtering heat when forming the base layer and the magnetic layer.

[0123]

According to the present invention, the productivity is excellent and the groove processing accuracy is good.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for forming a groove used in the present invention.

FIG. 2 is a schematic diagram for explaining a guide groove for alignment.

FIG. 3 is a partial cross-sectional view of a magnetic disk to which the present invention has been applied.

[Explanation of symbols]

 1 Device 2 Stamper Section 10 Substrate 5 Magnetic Disk 15 Magnetic Layer 31 Groove

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Tokuoka 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC Corporation

Claims (5)

[Claims] 1. A surface of a non-magnetic substrate is hydrophilized to reduce the contact angle to water, and 80 to 92 mol% vinyl chloride and 8 vinyl acetate are added to the hydrophilized substrate.
A substrate for a magnetic disk obtained by forming a layer of a vinyl chloride-vinyl acetate copolymer having a main skeleton of ˜20 mol%, transferring the groove of a grooved master to this layer, and forming the groove. 2. The magnetic disk substrate according to claim 1, wherein the dry film thickness of the vinyl chloride-vinyl acetate copolymer layer is 3 to 12 μm. 3. The contact angle of water on the surface of the non-magnetic substrate to 40 degrees or less by the hydrophilic treatment.
The magnetic disk substrate as described in. 4. A magnetic disk having a continuous thin film magnetic layer formed on the groove formation surface.
The magnetic disk substrate according to any one of 1. 5. The magnetic disk substrate according to claim 4, wherein a plasma polymerized film is provided on the vinyl chloride-vinyl acetate copolymer layer after forming the groove when forming the continuous thin film magnetic layer.