JP2003181890A - Method and apparatus for manufacturing substrate for magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a magnetic recording medium excellent in the floating characteristics of a head, and the magnetic recording medium. <P>SOLUTION: In the method for manufacturing the substrate for the magnetic recording medium by injecting a thermoplastic resin in a mold to mold the same, carbon coating is applied to the molding surface of the region at least corresponding to the recording region of the substrate in the mold and the thickness of the carbon coating layer is set to 0.01-9 μm and the surface roughness of the carbon coating layer is set to 0.2-2.0 nm. The mold is used to perform injection molding. <P>COPYRIGHT: (C)2003,JPO

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 mounted in various magnetic recording devices such as an external storage device of a computer, a method of manufacturing the same, and a magnetic recording device using the magnetic recording medium.

[0002]

2. Description of the Related Art When a conventional non-magnetic metal substrate (aluminum or the like) is used as a magnetic disk substrate for a magnetic recording medium which requires a high degree of surface precision, a high degree of precision processing is required. The nonmagnetic metal substrate is manufactured, for example, as follows.

First, a heat-melted metal material is rolled and heat-annealed, and then a blank material having a prescribed size is manufactured, and then the inner and outer diameters are processed. Furthermore, after lapping is performed to improve the surface accuracy, the Ni-P plating layer is 13 μm for the purpose of improving the surface hardness.
The surface roughness is R
Polish to a = 1.0 nm (10 Å) or less, and perform final lapping (texturing) using diamond slurry. After that, in the CSS (contact start / stop) zone, for example, the bump bite is 19.0 nm (190 Å) and 30μ
A general magnetic disk substrate for a hard disk is obtained by performing laser zone texture processing so that the density of one bump per m square and then performing precision cleaning.

On the magnetic disk substrate obtained as described above, a Cr underlayer 50 nm (500 Å, CoCrTa magnetic layer (Co: Cr: Ta = 82: 14: 4) 30 nm (3
00Å), and carbon protective layer 8.0 nm (80Å)
Are sequentially formed by the DC sputtering method, and tape burnishing is further performed on the surface after the sputtering. Finally, the fluorine-based lubricating layer by dip coating or spin coating 2.
By forming 0 nm (20 Å), a magnetic recording medium for hard disk can be obtained. However, the manufacturing method and configuration of the disk substrate and various recording media are not limited to the above.

The conventional methods for manufacturing the magnetic disk substrate and the magnetic recording medium as described above have become more and more complicated with the recent increase in recording density. On the other hand, there is a demand for a magnetic disk substrate and a magnetic recording medium that are cheaper than before while maintaining high performance. As a new magnetic disk substrate satisfying these contradictory requirements, a magnetic disk substrate and a magnetic recording medium using a thermoplastic resin (plastic) have been proposed.

[0006]

However, when a magnetic disk substrate, which is required to have a high degree of shape stability and surface accuracy, is manufactured by injection molding of plastic, it is different from the case of manufacturing it from a metal, glass or ceramic substrate. In comparison, since the mechanical strength is low, finish polishing (lapping, polishing, vanishing, etc.) cannot be performed. Therefore, it is necessary to adjust the surface accuracy (straightness, waviness, roughness, etc.) of a level required for the magnetic disk substrate at the end of injection molding. However, in resin molding, if the surface of the stamper is made to be a mirror surface, the adhesion between the stamper and the substrate becomes high, so the substrate itself may be deformed at the time of release from the stamper, and the flatness is lowered. there were.

In a recording medium that requires very high surface accuracy, such as a hard disk in which a magnetic head floats and moves a height of several tens of nm on a substrate to improve recording density, low flatness (poor) If a substrate having a surface accuracy) is used, a predetermined distance between the magnetic head and the recording medium cannot be maintained, and in the worst case, the magnetic head does not float and actual reading / writing cannot be performed. Causes the problem.

The present invention has been made in view of such a conventional situation, and realizes high flatness by controlling the adhesiveness when releasing a plastic substrate from a stamper,
An object of the present invention is to provide a magnetic recording medium substrate and a magnetic recording medium having excellent head flying characteristics.

[0009]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the surface roughness of the protective film on the stamper surface used in the mold is 0.2 nm to 2.0 nm.
Within the range of nm, the mold releasability from the stamper during injection molding is improved, the substrate shape is significantly improved, and the minimum flying height of the magnetic head can be stably lowered to 5 nm or less. Found.

The thickness of the protective film is 0.01 μm.
The thickness is preferably in the range of m to 9 μm, and when the manufacturing cost and the like are taken into consideration, the thickness of the protective film is further 0.01 μm.
It is preferably in the range of ˜5 μm.

The method for producing a substrate for a magnetic recording medium of the present invention is a method for producing a substrate for a magnetic recording medium in which a thermoplastic resin is injected into a molding die for molding, in which at least the substrate recording area in the molding die is used. A carbon coating is applied to the molding surface of the corresponding region, and the thickness of the layer of the carbon coating is within a range of 0.01 μm to 9 μm,
The surface roughness of the layer is in the range of 0.2 nm to 2.0 nm, and injection molding is performed using the molding die.

The method for producing a substrate for a magnetic recording medium of the present invention is further characterized in that the thickness of the carbon-coated layer is within the range of 0.01 μm to 5 μm.

A magnetic recording medium substrate manufacturing apparatus according to the present invention is a magnetic recording medium substrate manufacturing apparatus in which a thermoplastic resin is injected into a molding die for molding. A carbon coating is applied to the molding surface of the corresponding region, the layer thickness of the carbon coating is in the range of 0.01 μm to 9 μm, and the surface roughness of the layer is in the range of 0.2 nm to 2.0 nm. It is characterized by being inside.

In the apparatus for manufacturing a magnetic recording medium substrate of the present invention, the carbon coating layer has a thickness of 0.0.
It is characterized in that it is in the range of 1 μm to 5 μm.

Further, the magnetic recording medium substrate manufacturing apparatus of the present invention is characterized in that the molding surface is formed as a stamper.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a film forming apparatus for a stamper surface protective film of the present invention, a DC sputtering apparatus or a plasma CVD processing apparatus can be used, and this apparatus is used to form a carbon protective film on a stamper. While performing, the surface roughness can be controlled by the protective film thickness and the film forming conditions, and the surface roughness [Ra] at that time is 0.2 nm to
Range of 2.0 nm, preferably 0.2 nm to 1.0 nm
Can be As a method of controlling the surface roughness of the protective film, other than the above, as an adhesion layer below the protective film, for example, Ti, Cr, Mn, Fe, Co, Ni, C is used.
By forming a film of u, Zn, Mo, etc. by the DC sputtering method, it becomes possible to more easily control the required surface roughness.

In the present specification, the "flatness" is the maximum displacement of the entire surface of the disk substrate in the direction perpendicular to the substrate surface.

Further, the "minimum flying height of the magnetic head" means that the magnetic head (generally, a piezo actuator) is a magnetic head which is levitated on the surface of a substrate which is rotated at a certain rotational speed or more, by gradually reducing the rotational speed of the substrate. (The head is used) is the height calculated from the rotation speed (speed) of the substrate when the electrical signal when it contacts the substrate reaches 1 V or higher. The lower the height, the better the substrate. Means there is.

A magnetic disk substrate manufactured using the stamper of the present invention has a flatness of 10 μm or less and a minimum flying height of the magnetic head of 5 nm or less.

The magnetic disk substrate manufactured in the present invention may have a disk shape having a circular hole in the center. The central circular hole is used for mounting a spindle motor when a magnetic recording medium using the magnetic disk substrate is set in a magnetic recording device. Here, the diameters of the central circular hole and the circular plate depend on the design of the magnetic recording device.

The injection molding used in the present invention can use an injection molding apparatus known in the art. It is preferable to use a screw type injection molding apparatus in order to improve the homogeneity of the resin. Although it is possible to use a screw to melt and measure the resin and a plunger to inject the resin, use an in-line screw injection molding machine that integrates the functions of melting, measuring, and injection. Is preferred.

A schematic sectional view of an in-line screw type injection molding apparatus which can be used in the present invention is shown in FIG.
This in-line screw type injection molding apparatus has a heating cylinder 13 having a heating means 14 and an injection port 16 for a mold, and a resin inside the heating cylinder 13 for melting a resin,
(Movable) screw 11 for metering and injection
And a supply means 1 for supplying resin to the screw 11.
5 (such as a hopper) and screw driving means 12 for driving the screw 11 for weighing and injection.
As the mold, a mold composed of two separable parts (a fixed part 17 and a movable part 18) is used, and a driving means 1 for driving the movable part 18 by further applying a mold clamping pressure to the mold.
It is preferable to include 9 but is not limited thereto. Inside the mold, stampers 24 and 25 that are mirror-finished or have a protective film having a pattern formed thereon are set.

The stamper may be provided on either the fixed side or the movable side depending on the application of the molded substrate. Further, a protective film having a pattern may be directly provided on the mold surface corresponding to the recording area molding surface.

A schematic sectional view of a mold that can be used in the present invention is shown in FIG. FIG. 2 shows a mold at the time of resin filling. The mold is composed of a movable mold 18 and a fixed mold 17 which face each other, and the movable stamper 25 and the fixed stamper are respectively formed on the surfaces of the movable mold 18 and the fixed mold 17 on which resin is molded. And 26 are provided.

The mold has a space corresponding to the shape of the substrate to be manufactured (hereinafter referred to as the substrate cavity 22) and a space connecting the substrate cavity and the injection port 16 (hereinafter referred to as the sprue portion 21). Have. Further, a gate 23 is arranged between the substrate cavity 22 and the sprue portion 21, and a gate cutting means 24 for separating (gate cutting) the resin with which the substrate cavity 22 is filled and the resin of the sprue portion 21 is provided. Has been.

When manufacturing the magnetic disk substrate of the present invention, the resin melted and measured by using the injection device having the screw 11 is injected into the mold through the injection port 16, and the sprue portion 21 and the substrate are injected. The cavity 22 is filled with resin. After that, the filled molten resin is cooled and hardened in the mold. During cooling and curing, the punch 24, which is a gate cutting means, is moved forward to separate the resin in the sprue portion 21 and the substrate cavity portion 22, and further cooled and cured,
A magnetic disk substrate can be obtained.

The magnetic disk substrate of the present invention is ejected by using a die in which a stamper having a carbon protective film having an appropriate film thickness and an appropriate surface roughness is formed inside the die is set. It is molded.

One of the reasons why the flatness is not improved in injection molding is that the degree of deformation is different depending on the ease of peeling when a substrate is peeled from a stamper by applying a physical force. When it is difficult to peel off, the substrate is more deformed, and when it is easy to peel off, a stable shape is obtained. The present inventors have improved the releasability by using carbon having higher lubricity for the protective film on the stamper surface,
It was also found that the mold releasability can be further improved by stabilizing the shape and not making the surface roughness of the protective film on the stamper surface more than necessary. By doing so, the releasability is improved, and the variation in the releasability is reduced, so that the deformation of the entire substrate can be suppressed.

The protective film thickness of the stamper surface when the magnetic disk substrate of the present invention is manufactured is from 0.01 μm to 5 μm.
The surface roughness of the protective film is from 0.2 nm to
It is set to 2.0 nm. When a stamper satisfying this condition is used for molding, it is possible to suppress the deformation when the substrate is released from the mold, and it is possible to significantly improve the flatness of the substrate.

The magnetic disk substrate manufactured by using the stamper as described above has a flatness of 10 μm or less, more preferably 5 μm or less. Further, the surface roughness has Ra of 0.2 to 2.0 nm.

Further, it is preferable that the magnetic disk substrate manufactured as described above is annealed to relax the stress remaining in the substrate. The annealing treatment is performed at a temperature of (Tg−70) ° C. or higher of the material used (Tg−15) ° C. or lower (Tg means the glass transition temperature of the resin) for 0.5 hours to 4 hours.
It is preferably carried out for 8 hours. The annealing temperature is preferably as high as possible provided that it does not cause deterioration of the resin and local shape change of the substrate. The annealing treatment can be performed in an air atmosphere or a low oxygen atmosphere. Further, in order to prevent the occurrence of bending due to the weight of the substrate during the annealing process, it is preferable that the substrate is vertically placed and the annealing process is performed. It is possible to reduce the residual stress by performing sufficient annealing, minimize the shape change due to the release of the residual stress with time, and prevent the occurrence of local deformation.

The thermoplastic resin used in the present invention contains a polyolefin resin in addition to the polycarbonate resin and polymethylmethacrylate resin generally used for magneto-optical disk substrates. In particular, it is preferable to use a rigid structure polyolefin-based resin having high heat resistance and low hygroscopicity, for example, norbornene-based polycycloolefin resin. The Tg derived from the resin structure is in the range of 135 ° C to 190 ° C, and the higher the Tg within this range, the more preferable.

When a magnetic recording medium is manufactured using the magnetic disk substrate manufactured as described above, at least a magnetic recording layer is laminated on the substrate. Further, a base layer, a protective layer, a lubricating layer and the like can be provided as needed. further,
Depending on the application, the layers as described above can be provided on one side or both sides of the magnetic disk substrate to obtain a single-sided and double-sided magnetic recording medium, respectively.

When a magnetic recording medium of a horizontal recording system which has been generally used in a hard disk drive or the like is manufactured, it is preferable to provide an underlayer, a magnetic recording layer, a protective layer and a lubricating layer in this order. An intermediate layer may be provided between the underlayer and the magnetic recording layer for the purpose of improving the performance of the magnetic recording layer. Further, when manufacturing a perpendicular recording type magnetic recording medium, which has been attracting attention in recent years due to the possibility of improving the recording density, etc., an underlayer, a soft magnetic backing layer, a magnetic recording layer, a protective layer, and a lubricating layer are arranged in this order. It is preferable to provide. Also in this case, an intermediate layer may be provided between the underlayer and the soft magnetic backing layer and / or between the soft magnetic backing layer and the magnetic recording layer for the purpose of improving recording characteristics and the like.

Each of the above layers can be made from any material known in the art. For example, the underlayer can be made of a non-magnetic metal material of Cr or an alloy mainly containing Cr, and the magnetic recording layer can be made of Co and Cr.
Can be made of a magnetic material such as an alloy mainly containing, and the protective layer can be made of carbon (especially diamond-like carbon) or the like. Further, the lubricating layer can be made of a liquid lubricant such as fluorinated polyether, and the soft magnetic backing layer can be made of a non-quality Co alloy, NiFe alloy, or sendust (FeSiAl) alloy. it can. A material such as Ti or TiCr alloy may be used as the intermediate layer.

Each of the above layers except the lubricating layer is formed by the sputtering method,
It can be laminated on the magnetic disk substrate by a conventionally known method such as a vapor deposition method or a CVD method. In particular, it is preferable to use the sputtering method. Moreover, the lubricating layer can be formed by a method such as dip coating, spin coating, or spraying.

By using a high heat resistant thermoplastic resin and performing injection molding satisfying the conditions of the present invention, the flatness of the substrate is significantly improved, and thereby a magnetic disk substrate with improved magnetic head flying property is manufactured. be able to. Further, by using the magnetic disk substrate, it is possible to provide a magnetic recording medium having excellent head flying characteristics.

[Embodiment] An embodiment to which the present invention is applied will be described below in detail with reference to the drawings.

Example 1 A mold having a fixed stamper was mounted on a commercially available injection molding apparatus having a maximum injection molding pressure of 70 t. DLC (diamond-like carbon) is formed as a protective film on the stamper surface, and the film thickness at this time is 0.5 μm, and the surface roughness [Ra] measured by an AFM (atomic force microscope) is used. ] Of 0.5 nm was used. However, in this case, in order to keep the surface roughness constant, a Cr layer having a thickness of 3 μm was provided under the carbon protective film. A norbornene-based polyolefin resin (Tg = 138 ° C.) is used as the resin, the resin temperature is 320 ° C., the injection speed is 120 mm / s, and the mold clamping pressure is 120 kg / cm.
² (about 11.8 MPa), mold temperature (fixed side / movable side)
Injection molding was performed under the conditions of 110 ° C./110° C. and a gate cut timing of 0.2 seconds after completion of resin filling.
Within one hour, annealing is performed at 90 ° C. for 10 hours in a state where the substrate is held vertically in an air atmosphere, and a central circular hole having a diameter of 25 mm is formed, a diameter of 95 mm, and a thickness of 1.27 mm. A disk-shaped disk substrate having the dimensions of was obtained.

(Example 2) The thickness of the carbon protective film was set to 0.
A disk substrate was obtained in the same manner as in Example 1 except that the thickness was 01 μm.

(Example 3) The thickness of the carbon protective film was set to 0.
A disk substrate was obtained in the same manner as in Example 1 except that the thickness was 05 μm.

(Embodiment 4) The thickness of the carbon protective film is set to 0.
A disk substrate was obtained in the same manner as in Example 1 except that the thickness was 1 μm.

(Embodiment 5) The thickness of the carbon protective film is set to 1 μm.
A disk substrate was obtained in the same manner as in Example 1 except that m was set.

(Embodiment 6) The thickness of the carbon protective film is 3 μm.
A disk substrate was obtained in the same manner as in Example 1 except that m was set.

(Embodiment 7) The thickness of the carbon protective film is 5 μm.
A disk substrate was obtained in the same manner as in Example 1 except that m was set.

(Embodiment 8) The thickness of the carbon protective film is set to 7 μm.
A disk substrate was obtained in the same manner as in Example 1 except that m was set.

(Embodiment 9) The thickness of the carbon protective film is set to 9 μm.
A disk substrate was obtained in the same manner as in Example 1 except that m was set.

(Comparative Example 1) The thickness of the carbon protective film was set to 0.
A disk substrate was obtained in the same manner as in Example 1 except that the thickness was 001 μm.

(Comparative Example 2) The thickness of the carbon protective film was set to 0.
A disk substrate was obtained in the same manner as in Example 1 except that the thickness was 003 μm.

(Comparative Example 3) The thickness of the carbon protective film was set to 0.
A disk substrate was obtained in the same manner as in Example 1 except that the thickness was 005 μm.

Example 10 A mold having a fixed stamper was mounted on a commercially available injection molding apparatus having a maximum injection molding pressure of 70 t. DLC (diamond like carbon) is formed as a protective film on the stamper surface, and the film thickness at this time is 5 μm, and the surface roughness [Ra] measured using an AFM (atomic force microscope) is The one in the state of 0.5 nm was used. A norbornene-based polyolefin resin (Tg = 138 ° C.) is used as the resin, the resin temperature is 320 ° C., the injection speed is 120 mm / s, and the mold clamping pressure is 120.
Injection molding was carried out under the conditions of kg / cm ² (about 11.8 MPa), mold temperature (fixed side / movable side) 110 ° C./110° C., and gate cutting timing 0.2 seconds after completion of resin filling. Within 1 hour, 90 ° C for 10 hours with the substrate held vertically in the atmosphere.
Annealing was performed to obtain a disk-shaped disk substrate having a central circular hole with a diameter of 25 mm, a diameter of 95 mm, and a thickness of 1.27 mm.

(Example 11) A disk substrate was obtained in the same manner as in Example 10 except that the surface roughness of the carbon protective film was 0.2 nm.

(Example 12) A disk substrate was obtained in the same manner as in Example 10 except that the surface roughness of the carbon protective film was 0.8 nm.

(Example 13) A disk substrate was obtained in the same manner as in Example 10 except that the surface roughness of the carbon protective film was 1 nm.

(Example 14) A disk substrate was obtained in the same manner as in Example 10 except that the surface roughness of the carbon protective film was 1.5 nm.

(Example 15) A disk substrate was obtained in the same manner as in Example 10 except that the surface roughness of the carbon protective film was 2 nm.

Comparative Example 4 The surface roughness of the carbon protective film was
A disk substrate was obtained in the same manner as in Example 10 except that the thickness was 0.1 nm.

Comparative Example 5 A disk substrate was obtained in the same manner as in Example 10 except that the surface roughness of the carbon protective film was 3 nm.

(Comparative Example 6) A disk substrate was obtained in the same manner as in Example 10 except that the surface roughness of the carbon protective film was 5 nm.

(Evaluation method) Flatness of the substrate surface [Flat
Ness] for Flatness T made by Nidec
The amount of displacement was derived by measuring with esterFT-12. Five sheets were measured for each condition, and the average value was defined as the flatness at that time. Atomic force microscope [AM
F] to measure Ra (center line average roughness). Regarding the surface roughness, one substrate surface was measured at four 90 ° intervals, and the average value was taken as the roughness of the substrate surface.

(Evaluation Results) FIG. 3 shows the relationship between the stamper protective film thickness, the magnetic head flying property (Take off Height), and the flatness, and the stamper protective film surface roughness and the magnetic head flying property (Take off Heig).
FIG. 4 shows the relationship between ht) and flatness.

As is clear from FIG. 3, the thicker the stamper protective film, the better the flying characteristics of the magnetic head and the improved flatness.

Further, as is clear from FIG. 4, when the surface roughness of the stamper protective film was in the range of 0.2 nm to 2 nm, the magnetic head flying characteristics and flatness were good.

It is well known that the flatness and surface roughness of the substrate have a great influence on the flying characteristics of the head. According to the present invention, a magnetic disk substrate excellent in the flying characteristics of the head or the substrate is used. It is possible to manufacture the conventional magnetic recording medium.

[0065]

As is apparent from the above description, the disk substrate according to the present invention is manufactured by injection molding using a stamper having a carbon protective film formed thereon, and the carbon protective film thickness is 0.01 μm or more. , And the surface roughness is 0.2
By setting the thickness in the range of nm to 2.0 nm, the flatness of the substrate can be set to 10 μm or less and the magnetic head flying characteristic can be set to 5 nm or less. Therefore, according to the present invention, it becomes possible to manufacture a magnetic disk substrate having excellent head flying characteristics and a magnetic recording medium using the substrate.

Further, according to the method of the present invention, it becomes possible to mass-produce a plastic magnetic disk substrate excellent in shape characteristics at a low cost, and thus a magnetic recording medium and a magnetic recording / reproducing apparatus using the plastic magnetic disk substrate. Makes it possible to manufacture in large quantities and at low cost.

As described above, according to the present invention, by forming a carbon film on the stamper surface and controlling the film thickness and the surface roughness, the shape of the molded substrate and the shape of the substrate after annealing can be controlled. It is possible to stabilize the levitation of the magnetic head to the same level as conventional aluminum substrates.

[Brief description of drawings]

FIG. 1 is a conceptual cross-sectional view showing an example of an injection molding apparatus that can be used for producing a magnetic disk substrate of the present invention.

FIG. 2 is a conceptual cross-sectional view showing an example of a mold that can be used for producing the magnetic disk substrate of the present invention.

FIG. 3 is a graph showing the relationship between the levitation characteristics and the carbon protective film thickness and the relationship between the flatness and the carbon protective film thickness of the magnetic disk substrates manufactured in each example and comparative example.

FIG. 4 is a graph showing the relationship between the levitation characteristics and the surface roughness of the carbon protective film and the relationship between the flatness and the surface roughness of the carbon protective film of the magnetic disk substrates manufactured in the respective examples and comparative examples.

[Explanation of symbols]

11 screw 12 Screw drive means 13 Heating cylinder 14 Heating means 15 Supplying means 16 Exit 17 Mold fixing part 18 Movable part of mold 19 Movable part driving means 21 Sprue 22 Substrate cavity 23 gates 24 punch 25 Moving part stamper 26 Fixed part stamper

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsunori Suzuki             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. (72) Inventor Isao Sekiguchi             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. F-term (reference) 4F202 AF01 AG19 AH38 AJ01 AJ09                       AJ11 AR12 AR13 CA11 CB01                       CK03 CK11                 5D006 CB01 DA03 FA00                 5D112 AA02 BA01 BA10

Claims (10)

[Claims] 1. A method for manufacturing a substrate for a magnetic recording medium, comprising molding a thermoplastic resin by injecting it into a molding die, wherein a carbon coating is applied to at least a molding surface of the molding die in a region corresponding to a substrate recording region. The thickness of the carbon coating layer is in the range of 0.01 μm to 9 μm, and the surface roughness of the layer is 0.2 nm to 2.0 μm.
The method for producing a substrate for a magnetic recording medium is characterized in that it is within a range of nm and injection molding is performed using the molding die. 2. The method for manufacturing a substrate for a magnetic recording medium according to claim 1, wherein the thickness of the layer coated with carbon is in the range of 0.01 μm to 5 μm. 3. The method of manufacturing a substrate for a magnetic recording medium according to claim 1, wherein the molding surface is formed on a stamper. 4. A substrate for a magnetic recording medium, which is formed by the method according to any one of claims 1 to 3. 5. A magnetic recording medium comprising the substrate according to claim 4. 6. A magnetic recording medium substrate manufacturing apparatus for injecting and molding a thermoplastic resin into a molding die, wherein a carbon coating is applied to a molding surface of at least a region corresponding to the substrate recording region in the molding die. The carbon coating layer has a thickness of 0.01 μm to 9 μm.
And the surface roughness of the layer is 0.2 nm to 2.
An apparatus for manufacturing a substrate for a magnetic recording medium, which is in the range of 0 nm. 7. The thickness of the carbon coating layer is
The apparatus for manufacturing a substrate for a magnetic recording medium according to claim 6, wherein the thickness is in the range of 0.01 μm to 5 μm. 8. The apparatus for manufacturing a magnetic recording medium substrate according to claim 6, wherein the molding surface is formed on a stamper. 9. A substrate for a magnetic recording medium, which is molded by the apparatus according to any one of claims 6 to 8. 10. A magnetic recording medium comprising the substrate according to claim 9.