JPH06139566A - Production of substrate for magnetic disk - Google Patents

Abstract

PURPOSE:To produce substrates for magnetic disks with excellent productivity in an enhanced yield. CONSTITUTION:When the layer of a vinyl chloride-vinyl acetate copolymer having a principal skeleton consisting of 80-92mol% vinyl chloride and 8-20mol% vinyl acetate is formed on a nonmagnetic substrate and a groove is formed in the copolymer layer with a grooved master, a stamper 211 held by a holding member 215 through a spring 213 whose one end comes into contact with the central part of the rear side of the groove forming face for transfer is used. By the elastic deformation of the spring 213, the stamper 211 is brought into contact with the copolymer layer from the central part of the groove forming face for transfer toward the peripheral part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing 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.

From the above, the applicant has previously
"The surface of a non-magnetic substrate is hydrophilized to reduce the contact angle to water, and the main skeleton of which vinyl chloride is 80 to 92 mol% and vinyl acetate is 8 to 20 mol% on the hydrophilized substrate. Is formed by forming a layer of a vinyl chloride-vinyl acetate copolymer having, and transferring the groove of the grooved master to the layer, and forming the groove ". Japanese Patent Application No. 4-196292).

However, it is confirmed that the groove of the grooved master is not entirely transferred, especially when a flexible substrate such as polyethylene terephthalate (PET) is used, though the above-mentioned drawbacks are solved by such a process. Was done. This is because when the grooved master is heated and brought into contact with the vinyl chloride-vinyl acetate copolymer layer as described above, the grooved master is set in a mold in a flat state. It is thought that this is due to some air entering between.

If the groove is not entirely transferred in this way, the yield is lowered and the productivity is deteriorated.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a magnetic disk substrate having an improved yield and excellent productivity.

[0010]

These objects are achieved by the present invention described in (1) to (8) below. (1) The vinyl chloride formed on the non-magnetic substrate is 80 to 92.
When forming a groove by pressing the grooved master to the groove of the grooved master to a layer of vinyl chloride-vinyl acetate copolymer having a main skeleton of 8 to 20 mol% of vinyl acetate in mol%, A method for producing a magnetic disk substrate, wherein the grooved master and the vinyl chloride-vinyl acetate copolymer layer are in contact with each other from a central portion of a transfer groove forming surface, and then gradually contact with a peripheral portion thereof. (2) The method for manufacturing a magnetic disk substrate according to (1), wherein the grooved master is a stamper, and the stamper is pressed while being deformed. (3) The method for manufacturing a magnetic disk substrate according to (1) or (2), wherein the stamper is held by a holding member via a spring having one end in contact with the center of the back surface of the surface on which the transfer groove is formed. . (4) The method for manufacturing a magnetic disk substrate according to any one of (1) to (3), wherein the groove formation is performed by heating. (5) The method for producing a magnetic disk substrate according to any one of the above (1) to (4), wherein at least the surface of the non-magnetic substrate on the vinyl chloride-vinyl acetate copolymer layer forming side is subjected to a hydrophilic treatment. (6) The method for producing a magnetic disk substrate according to any one of (1) to (5), wherein the dry film thickness of the vinyl chloride-vinyl acetate copolymer layer is 3 to 12 μm. (7) The method for manufacturing a magnetic disk substrate according to any one of (1) to (6), wherein the non-magnetic substrate is flexible. (8) The method for manufacturing a magnetic disk substrate according to any one of (1) to (7), which is used to obtain a magnetic disk having a continuous thin film magnetic layer formed on the groove formation surface.

[0011]

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

In the present invention, a vinyl chloride-vinyl acetate copolymer layer is formed on a non-magnetic substrate, and a grooved master (preferably a stamper) is used to form grooves on the copolymer layer.

FIG. 1 shows a structural example of a groove forming device used in this case.

The device 1 shown in the drawing has a PET as a non-magnetic substrate.
A substrate for a floppy disk using the above is manufactured.

The device 1 has a groove forming portion 2 for forming a groove having a predetermined shape, and a non-magnetic substrate 100 having a copolymer layer formed thereon.
Is provided in the form of a roll, and a substrate supply unit 3 for supplying the substrate 10 after the groove is formed, and a substrate storage unit 4 for storing the substrate 10 after the groove is formed.

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

The stamper portion 21 of FIG. 1 is the same as that of FIG. 2 and FIG.
It has the configuration shown in.

FIG. 2 is an enlarged partial sectional view showing the stamper portion 21 in an unused state, and FIG. 3 is a sectional view taken along the line AA of FIG.

As shown in these figures, the stamper portion 21 transfer has a stamper 211 having a transfer groove formed therein and a holding member 215 for holding the stamper 211. A mold 217 is installed in the holding member 215 so as to be vertically movable in the holding member 215. Also, the mold 217
As shown in the drawing, a spring 213 is installed at the center of the end surface of the stamper 211 on the side of the mold 2
The other end is in contact with the center of the back surface of the surface of the stamper 211 where the transfer groove is formed.

That is, the stamper 211 is held by the holding member 215 via the spring 213, and the die 217 is installed so as to be able to press the stamper 211 via the spring 213.

In FIG. 1, the lower mold 25 may be installed at room temperature or may be cooled.

In the structure shown in FIG. 1, the base 100 is sequentially fed out from the base supply unit 3, and the stamper unit 2 is formed in the groove forming unit 2.
1 presses under heating.

In this case, at the start of pressing with the non-magnetic substrate 100, as shown in FIG. 2, the center of the stamper 211 is pushed out by the spring 213 to form a convex shape. Therefore, only the central portion comes into contact with the nonmagnetic substrate 100. After that, gradually the mold 217 and the lower mold 2
When 5 moves, the spring 213 elastically deforms and the stamper 2
11 and the non-magnetic substrate 100 gradually come into contact with each other over the peripheral portion, and finally the pressing surface of the stamper 211 becomes flat as shown in FIG.
The entire surface of 11 comes into contact with the non-magnetic substrate 100.

After that, the state in which the non-magnetic substrate 100 is held by the stamper portion 21 and the lower die 25 is released, and one groove forming process is completed.

Then, the non-magnetic substrate 100 is extended and moved, and the same steps as those described above are sequentially repeated. In this way, it becomes possible to continuously form the grooves.

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

In the present invention, when the groove is formed, the stamper 211 and the non-magnetic substrate 100 gradually come into contact with each other from the central portion toward the peripheral portion as described above. The air between and can be pushed out. Therefore, the entire surface of the groove is reliably transferred, the yield is improved, and the effect of the present invention is realized. Further, when the stamper 211 is peeled off, the stamper 211 is peeled off from the periphery, so that the next process can be smoothly performed.

When a groove is formed by using a stamper set in a metal mold in a conventional flat state, there is a problem that a part of air is introduced between the stamper and the substrate and the whole surface is not transferred. The invention solves this. In particular, such problems are caused by polyethylene terephthalate (PET).
It was remarkable when a flexible substrate like the above was used and pressed under heating.

In the illustrated example, the stamper 2 is formed by a spring.
Although 11 is pressed, the present invention is not limited to this, and may be gradually pressed by a pressing member such as a spring in addition to a spring. In some cases, the stamper and the base may be separated from the center of the base. The base may be deformed by a pressing means such as a spring so that the base comes into contact with the stamper having a flat pressing surface.

In the present invention, the material of the stamper to be used is not particularly limited, but since it can be deformed by a spring or the like, it may be normally made of metal, among which availability and cost are particularly preferable. It may be made of Ni in terms of surface and plating.

The stamper may have any thickness as long as it can form a groove and can be deformed by a spring or the like, and is usually 0.3.
~ 1.0 mm.

However, in the embodiment in which the substrate is deformed, these are not limited, and any one may be used.

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

It is preferable to heat at the time of pressing, but the heating temperature is 140 to 250 ° C., preferably 170.
The temperature may be set to ˜200 ° C. By setting such a heating temperature, the polymer moves to an appropriate state, and the pressing becomes easy. On the other hand, if the temperature is too high, deformation is likely to occur, and if the temperature is too low, the groove cannot be transferred.

The pressing pressure may be 130 to 250 kg / cm ² , preferably 140 to 220 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. .

In the present invention, the vinyl chloride-vinyl acetate copolymer layer is formed by coating on a non-magnetic substrate using a coating solution of this copolymer.

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

The dimension 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.

In forming the above-mentioned copolymer layer using such a non-magnetic substrate, the surface of the non-magnetic substrate is preferably hydrophilized. The hydrophilic treatment is not particularly limited, and any treatment that reduces the contact angle of the substrate surface with water can be used.

By such 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.

For such hydrophilic treatment, plasma treatment,
Corona treatment etc.

Among 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.

When the corona treatment is used, the usual method may be used.

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. Also,
Good releasability from stamper.

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. Further, the life of the grooved master (stamper) used is extended, the groove can be reliably transferred from the stamper, and even an extremely narrow groove of about 1 μm can be formed accurately. it can.

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 coating solvent used in the present invention is not particularly limited as long as it dissolves such a copolymer and does not attack the non-magnetic substrate. Methyl ethyl ketone (MEK), acetone and the like have a low boiling point and a low solvent. A polar solvent can be used, and among them, methyl ethyl ketone or the like is preferably used.

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 a gravure roll coating method, a reverse roll coating method, a spin coating method and the like are preferable. 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, it may be 3 to 7 μm, preferably 4 to 6 μm. 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.

In the present invention, the substrate on which the groove is formed is
Used as a flexible 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.

An example of the structure of a floppy disk using the substrate thus obtained is shown in FIG.

As shown in FIG. 5, 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. 5, 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. 5, 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 the 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 flexible substrate for the floppy disk, which is preferably obtained in the present invention, has been described. In the present invention, a rigid substrate is used as the non-magnetic substrate to form a rigid substrate for a hard type magnetic disk. You can also do it.

When a hard type magnetic disk is used,
The copolymer layer is formed by a spin coating method using a disk-shaped non-magnetic substrate, the lower mold is placed on a belt conveyor, and the non-magnetic substrate having the copolymer layer formed thereon is placed on the lower mold (stamper part). It is preferable to form a groove by pressing when the substrate is located in the.

The press pressure in this case is 200 to 300 kg.
/ cm ² , preferably 230 to 250 kg / cm ² .

The dry film thickness of the copolymer layer is 3 to 10
The thickness may be set to μm, preferably 5 to 8 μm.

The non-magnetic substrate used as the rigid substrate for such a hard type magnetic disk may be any of glass, aluminum and resin. A substrate is rigid when the Young's modulus of the substrate is E and the thickness is t.
t ³ ≧ 1 × 10 ⁷ dyn · cm, more preferably E · t ³ ≧ 3
× 10 ^{7 It} means that it is dyn · cm.

Therefore, in this case, only the method of deforming the stamper is applied in the present invention.

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 the 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 dimension 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 the case of a hard type magnetic disk,
The layer configuration and the like are the same as those in FIG. 5, and only the point that a rigid substrate is used among them is largely different.

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.

An underlayer is provided between the substrate and the magnetic layer for the purpose of favorably performing epitaxial growth and improving magnetic characteristics, if necessary.

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 above-mentioned magnetic layer.
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 grooves on the substrate form irregularities 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 with other elements added in an amount of about 5% by weight or less, and the 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 and the like may be formed by dip coating, spray coating, spin coating or the like.

In the above, as shown in FIG. 5, the single-sided recording type magnetic disk has been described as an example, but the present invention is
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.

[0098]

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
A film was used and plasma-treated under the following conditions. The contact angle with water after the treatment was 10 °.

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

Then, a 20 wt% methyl ethyl ketone solution of a vinyl chloride (85 mol%)-vinyl acetate (15 mol%) copolymer was applied onto the non-magnetic substrate after this treatment, and 5
A coating film having a thickness of μm (dry film thickness) was formed. The application was by a gravure roll coating method.

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.

In FIG. 1, the stamper portion has the structure shown in FIGS. In this case, the stamper is made of Ni,
The thickness of the stamper was 0.5 mm. The groove has a width of 0.4
The grooves were formed in concentric circles with a groove spacing of 1.6 μm and a depth of 0.5 μm.

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

In this way, a substrate sample for a 3.5-inch floppy disk (FD) was prepared. This is method A.

A substrate sample was prepared in the same manner as in Method A, except that a conventional apparatus having no spring in the stamper portion was used. This is method B.

The yields of the methods A and B were examined as follows.

It was examined by the yield light reflection method whether the groove was transferred over one round. The substrate with the groove transferred is punched into a cookie shape. At that time, punch out with the center shifted. Put this thing on a reflectometer and rotate. Then, the incident light is detected by the detector each time it crosses the groove. Then,
As shown in FIG. 6, a sine wave appears when the entire circumferential groove is exposed [(a)], but is interrupted midway if there is no groove on the entire surface [(b)]. If there was a state of (b) even in part on the way, it was counted as out of yield. 100 sheets of each sample obtained by each of the method A and the method B were evaluated.

The yield thus obtained was 95% in Method A, but 20% in Method B.

Further, by using the substrate sample in the yield obtained by the method A, a Cr underlayer having a film thickness of 0.1 μm was formed, and further an underlayer film of a plasma polymerization film was formed, and then a film thickness of 0.05 μm was formed. The Co-Ni-Cr magnetic layer of 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 / (FM): 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 each formed by DC-magnetron sputtering.

The sputtering conditions for the underlayer and magnetic layer were such that the operating pressure was 1 Pa and the atmosphere was Ar.

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%).

The FD sample thus obtained was
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.

[0117]

According to the present invention, the yield is improved and the productivity is excellent.

[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 an enlarged partial cross-sectional view for explaining the stamper portion of FIG.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is an enlarged partial sectional view for explaining the stamper portion of FIG.

FIG. 5 is a partial cross-sectional view of a magnetic disk to which the present invention has been applied.

FIG. 6A and FIG. 6B are graphs for explaining the evaluation of groove transfer by the light reflection method.

[Explanation of symbols]

 1 Device 21 Stamper Part 211 Stamper 213 Spring 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 (8)

[Claims] 1. Vinyl chloride formed on a non-magnetic substrate is 8
A grooved master is pressed against a layer of vinyl chloride-vinyl acetate copolymer having a main skeleton of 0 to 92 mol% and vinyl acetate of 8 to 20 mol% to form a groove by transferring the groove of the grooved master. In this case, the method for producing a magnetic disk substrate, wherein the grooved master and the vinyl chloride-vinyl acetate copolymer layer are in contact with each other from the center of the transfer groove forming surface, and then gradually with the periphery. 2. The method for manufacturing a magnetic disk substrate according to claim 1, wherein the grooved master is a stamper, and the stamper is pressed while being deformed. 3. The method for manufacturing a magnetic disk substrate according to claim 1, wherein the stamper is held by a holding member via a spring whose one end is in contact with the center of the back surface of the surface on which the transfer groove is formed. 4. The method for manufacturing a magnetic disk substrate according to claim 1, wherein the groove formation is performed by heating. 5. The method for producing a magnetic disk substrate according to claim 1, wherein at least the surface of the non-magnetic substrate on the vinyl chloride-vinyl acetate copolymer layer forming side is subjected to a hydrophilic treatment. 6. The method for manufacturing a 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. 7. The non-magnetic substrate is flexible.
7. A method for manufacturing a magnetic disk substrate according to any one of 1 to 6. 8. A magnetic disk in which a continuous thin film magnetic layer is formed on the groove forming surface to obtain a magnetic disk.
1. A method for manufacturing a magnetic disk substrate according to any one of 1.