JPH05225559A - Substrate for magnetic disk and magnetic disk - Google Patents

Abstract

PURPOSE:To obtain the substrate for a magnetic disk which assures the shape transfer from a stamper and is secure in the adhesion of a photopolymer and a nonmagnetic base body by subjecting the surface on the groove forming side of the nonmagnetic base body to a plasma treatment. CONSTITUTION:The surface 11 on the groove 31 forming side of the nonmagnetic base body 1 is subjected to the plasma treatment at the time of adopting a photopolymer method for the substrate for the magnetic disk formed with the photopolymer layer 3 on the base body 1 and the grooves 31 on the layer 3. The secure adhesion of the base body 1 and the layer 3 is attained by such plasma treatment and the shape transfer from the stamper 2 is assured. The magnetic disk constituted by using this substrate, therefore, has excellent durability and the high coercive force in the circumferential direction of the disk, prevents the modulation of the reproduced output and has a large recording capacity. The film thickness of the photopolymer layer is preferably 15 to 40mum.

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 and a magnetic disk using the same.

[0002]

2. Description of the Related Art For example, in a magnetic disk drive used in a computer or the like, a hard type magnetic disk having a magnetic layer formed on a rigid substrate and a floating magnetic head are used.

Conventionally, a coating type magnetic disk has been used in such a magnetic disk drive, but since the magnetic disk has a large capacity, it is advantageous in terms of magnetic characteristics, recording density, etc. A thin film magnetic disk having a continuous thin film type magnetic layer formed by a vapor phase film forming method such as a method has been used.

As the thin film magnetic disk, a Ni-P underlayer is formed by plating on an Al-based disk-shaped metal plate, or the surface of this metal plate is oxidized to form alumite. Cr layer, Co-
A metal magnetic layer of Ni or the like and a protective lubricating film of C or the like are generally formed sequentially by a sputtering method. However, high-speed rotation and driving for improving transfer rate and recording density are required. There is a great demand for downsizing of the device, and there is a strong demand for weight reduction and further cost reduction of the magnetic disk.

For this reason, a magnetic disk using a rigid substrate made of resin, which is lighter than a metal substrate and is low in cost, is drawing attention.

However, when a continuous thin metal magnetic layer is formed on a substrate having a smooth surface, the coercive force of the magnetic layer in the disk circumferential direction becomes insufficient.

Then, modulation occurs in the reproduced output waveform.

Such a problem similarly occurs in a floppy disk having a continuous thin metal magnetic layer formed on a flexible substrate.

By the way, as a magnetic disk substrate,
For example, sheet-shaped resin films typified by polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and molded products such as polyetherimide (PEI) are mainly used.

However, in such a resin substrate, Al
Since the dimensional stability against heat is inferior to that of a metal substrate, such as a glass or ceramic substrate as described above, accurate tracking cannot be performed when a magnetic layer is formed on a smooth surface, and the track density can be improved as it is. I can't. Therefore, for example, with a 3.5-inch disc, 20
In order to achieve a high recording density with a recording capacity of 0 Mbytes or more, it is necessary to cover the poor dimensional stability. Then, in order to cover this poor dimensional stability, it is effective to form a groove on the surface of the resin substrate to perform tracking. Therefore, in such a resin substrate,
Grooves are formed on the side surface of the magnetic layer (substrate surface) by an injection molding method or a photopolymer method (2P method). Among them, the 2P method is widely used because of the high precision of groove formation.

However, if the groove is formed directly on these substrates by the 2P method, the photopolymer (2P resin) remains on the stamper side and is not transferred to the substrate side.

Further, there is a problem that the adhesiveness between the photopolymer and the substrate is not sufficient.

Therefore, when applying the 2P method, a method of coupling the surface of a resin substrate has been proposed. However, in the case of a resin, the functional group to be bonded does not always exist, and the effect cannot be uniformly obtained for all resins.

Also, a method of modifying the resin surface by ultraviolet (UV) treatment has been proposed, but it is not sufficient.

If the grooves are not formed reliably, the C-axis direction of the crystal grains in the magnetic layer provided on the substrate cannot be sufficiently aligned with the disk circumferential direction. For this reason, the coercive force of the magnetic layer in the disk circumferential direction becomes insufficient, and the modulation of the reproduction output cannot be sufficiently prevented.

[0016]

SUMMARY OF THE INVENTION The first object of the present invention is to ensure the shape transfer from the stamper when the groove is formed by using the photopolymer method (2P method), and to provide the photopolymer and the non-magnetic substrate. It is to provide a substrate for a magnetic disk having strong adhesion.

A second object of the present invention is to provide a magnetic disk which is excellent in durability, has a high coercive force in the disk circumferential direction, can prevent the modulation of the reproduction output, and can improve the track density. is there.

[0018]

These objects are achieved by the present invention described in (1) to (7) below.

(1) In a magnetic disk substrate in which a photopolymer layer is formed on a nonmagnetic substrate and grooves are formed in the photopolymer layer, at least the surface of the nonmagnetic substrate on which the groove is formed is subjected to plasma treatment. Characteristic magnetic disk substrate.

(2) The thickness of the photopolymer layer is 15
The magnetic disk substrate according to (1) above having a thickness of -40 μm.

(3) The magnetic disk substrate according to (1) or (2), wherein the non-magnetic substrate is made of resin.

(4) The processing gas used for the plasma processing is a gas containing at least one of oxygen and nitrogen or a gas of a compound containing at least one of oxygen and nitrogen (1) to (3). The magnetic disk substrate according to any one of 1.

(5) The magnetic disk substrate according to any one of the above (1) to (4), wherein the contact angle of water on the plasma-treated surface of the non-magnetic substrate is 30 degrees or less.

(6) In the groove, the opening width is larger than the bottom width, the opening width and the cross-sectional shape are substantially uniform, and the grooves are formed in the circumferential direction of the substrate (1) to (5). The magnetic disk substrate according to any one of 1.

(7) A magnetic disk having a continuous thin film magnetic layer on the groove forming surface of the magnetic disk substrate according to any one of the above (1) to (6).

[0026]

In the present invention, since the groove is formed by the photopolymer method (2P method) after plasma-treating the surface of the non-magnetic substrate, the shape transfer from the stamper is ensured, and an opening such as a V-shape is formed. It is possible to reliably form a groove having a width larger than the bottom width and having a substantially uniform opening width and sectional shape in the substrate circumferential direction.

Therefore, when a continuous thin film type magnetic layer is formed on such a substrate, the C-axis direction of the crystal grains is constrained to be in-plane and in the groove direction, that is, the circumferential direction, so that uniform epitaxial growth is performed. In particular, the direction of epitaxial growth can be restricted even inside the groove, and the C axis can be aligned in the disk circumferential direction.

Therefore, the direction of the easy axis of magnetization of the magnetic layer is aligned with the disk circumferential direction, the magnetic anisotropy is increased, the coercive force in the circumferential direction and the squareness ratio are improved, and in addition, the modulation of the reproduction output is prevented. it can.

Further, the plasma treatment strengthens the adhesion between the non-magnetic substrate and the photopolymer and improves the durability.

Further, by forming the groove, the track density is improved, the orientation in the disk circumferential direction is improved, and the adhesiveness with the magnetic layer is improved.

Further, in the present invention, since the film thickness of the photopolymer layer is further set to 15 to 40 μm, the amount of the polymerization initiator in the film becomes sufficient, and the curing by the ultraviolet irradiation sufficiently proceeds. Also, the adhesion between the non-magnetic substrate and the photopolymer layer becomes strong.

As a result of the strong adhesion between the non-magnetic substrate and the photopolymer layer, the durability of the magnetic disk becomes sufficient. Therefore, there are no errors, etc.
It has excellent disc characteristics.

[0033]

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

The magnetic disk substrate of the present invention comprises a photopolymer method (2P) layer formed on a non-magnetic substrate, and a groove formed in the photopolymer layer. That is, the groove is formed by the photopolymer (2P) method.

In the 2P method, for example, as shown in FIG. 1, a non-magnetic substrate 1 and a stamper 2 are combined to form a non-magnetic substrate 1.
Then, a photopolymer that is cured by ultraviolet irradiation is injected to form a photopolymer layer 3, and ultraviolet UV is irradiated from the nonmagnetic substrate 1 side to cure the photopolymer layer 3 and then the stamper 2 is peeled off. This is a molding method in which the shape is transferred from the stamper 2.
Thus, the magnetic disk substrate 10 on which 1 is formed is obtained.

In the present invention, when the 2P method is adopted, the surface 11 of the nonmagnetic substrate 1 on the side where the groove 31 is formed is subjected to plasma treatment. The plasma treatment improves the adhesiveness between the non-magnetic substrate 1 and the photopolymer layer 3 and ensures reliable transfer. Further, the durability of a magnetic disk using such a substrate is improved, and the track density is improved.

Such an effect is obtained only by performing the plasma treatment, and is not obtained by the ultraviolet irradiation treatment (UV treatment) or the coupling treatment.

Further, in the present invention, the thickness of the photopolymer layer 3 is set to 15 to 40 μm, further 20
The thickness is preferably about 40 to 40 μm, and particularly preferably 25 to 35 μm. The film thickness in this case includes the thickness of the groove 31, and is after curing.

With such a film thickness, the amount of the polymerization initiator in the layer becomes sufficient and the curing by ultraviolet irradiation sufficiently proceeds, so that the adhesion between the non-magnetic substrate 1 and the photopolymer layer 3 is improved. It is preferable in improving. As a result, the durability of the magnetic disk is improved and the occurrence of errors is reduced.

When the film thickness of the photopolymer layer 3 becomes small, the amount of the polymerization initiator is insufficient when irradiated with ultraviolet rays, so that the curing does not proceed sufficiently and the adhesive strength is extremely lowered. Even if a magnetic layer is provided on the magnetic disk, durability cannot be obtained, and the magnetic layer peels off, causing an error or damaging the magnetic layer.

On the other hand, when the thickness of the photopolymer layer 3 is increased, the effect is not improved in terms of adhesiveness,
It is disadvantageous in terms of productivity and cost. In addition, due to shrinkage during curing, the warp becomes rather large, and when used as a magnetic disk, the characteristics deteriorate in terms of durability and error occurrence.

The film thickness can be measured with a step gauge.

The plasma treatment in the present invention is preferably performed using a gas containing at least one of oxygen and nitrogen as a treatment gas. Specifically, it may be oxygen gas, nitrogen gas, or a mixed gas thereof. Further, it may be a gas of a compound containing at least one of oxygen and nitrogen, and examples of such a gas include N ₂ O, NO ₂ and NH ₃ . Further, a gas obtained by mixing these gases with another gas may be used, but it is preferable that these gases are contained in an amount of 30 vol% or more.
By treating with such a gas, the adhesiveness between the non-magnetic substrate 1 and the photopolymer layer 3 is further improved.

This improvement in adhesiveness is due to the non-magnetic substrate surface 11
Is considered to be hydrophilic by the plasma treatment.

At this time, the contact angle of the nonmagnetic substrate surface 11 with water is preferably 30 degrees or less, more preferably 10 degrees or less. From the viewpoint of hydrophilicity, the smaller the contact angle, the more preferable, and the lower limit value at this time is almost 0 degree.

Such an effect is particularly remarkable when the above processing gas is used, and is significantly decreased when other processing gas (for example, hydrogen gas alone) is used.

The plasma processing conditions at this time are not particularly limited, and the electrode arrangement, the applied current, the processing time, the operating pressure, etc. may be the same as the 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.

Further, the photopolymer or its precursor used in the present invention is not particularly limited and can be selected from various radiation-curable compounds used in the usual 2P method.

Monomers to be used are preferably monofunctional, bifunctional, trifunctional or polyfunctional ester acrylates, urethane acrylates, epoxy acrylates and the like, and at least one of them may be used.

Further, one kind or two or more kinds of oligomers may be used together instead of the monomer or in addition to the monomer.

Suitable oligomers are oligoester acrylates and the like.

In addition to the monomers and oligomers, a photopolymerization initiator may be usually added, and the addition amount thereof is preferably 1 to 10% by weight, particularly 3 to 5% by weight.

The non-magnetic substrate 1 is usually ultraviolet UV
In many of these materials, it is preferable to irradiate ultraviolet rays UV from the side of the non-magnetic substrate 1 as shown in FIG. However, in some cases, the stamper 2 may be made of a material such as glass that transmits ultraviolet UV, and the ultraviolet UV may be irradiated from the stamper 2 side. The irradiation from the stamper 2 side is particularly effective when applied to the non-magnetic substrate 1 made of a material that does not transmit ultraviolet rays UV.

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

The rigid substrate may be made of glass, but is preferably made of 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.

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, polyethersulfone, polyetherketone, polyetheretherketone, polyphenylenesulfide, polyphenyleneether, polyphenyleneoxide, polyketonesulfide, 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.
It has a diameter of about 9 mm and a diameter of about 60 to 130 mm.

On the other hand, 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, such as polyethylene terephthalate (PET) and polyethylene naphthalate. Polyester such as (PEN) and polyether ether ketone (PEEK) 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.

As described above, the magnetic disk substrate of the present invention has a groove formed by the 2P method. The groove has an opening width wider than the bottom width on one main surface or both main surfaces. Moreover, it is preferable that the opening width and the cross-sectional shape are substantially uniform.

In this case, if the groove is formed in the circumferential direction of the substrate, its pattern is not particularly limited, but it is preferably concentric or spiral, and the groove pattern may be slightly deformed or eccentric.

When the substrate has grooves on both main surfaces, the shapes, dimensions, patterns, etc. of the grooves may be the same or different.

A preferred example of the magnetic disk substrate having such a groove is shown in FIG.

As shown in FIG. 2, the magnetic disk substrate 1
At 0, a groove 31 having a trapezoidal cross section and having a substantially uniform cross sectional shape and opening width a is formed in the substrate circumferential direction.

In FIG. 2, only the groove 31 having the same cross-sectional shape as the opening width a is formed, but the present invention is not limited to the case where the groove 31 has exactly the same shape, and the opening width a of each groove 31 is not limited thereto. May differ slightly. The cross-sectional shape of the groove 31 may include a similar shape or a slightly deformed shape.

Quantitatively, the opening width a and the groove 3
When the area of the cross section of No. 1 was measured in the diameter direction of the substrate, the variation coefficient of the area of the opening width a and the cross section of the groove 31 was 50%.
It is preferably below 20%, more preferably below 20%.

Among these, in order to make the cross-sectional area of the groove 31 as described above, one of the depth h of the groove 31, the gap b between the grooves 31 and the bottom width c of the groove 31 is the same as above. It is preferable that the definition is uniform using the coefficient of variation, and it is particularly preferable that h is uniform. Further, it is preferable that b, particularly h and b are uniform.

The radial spacing of the grooves 31 (the same as the above-mentioned spacing b) may change irregularly in some cases, but the As described above, it is preferable that the variation coefficients are preferably 50% or less, particularly 20% or less, at equal intervals, and are substantially regularly arranged in the radial direction of the substrate.

The size of the groove 31 is such that the ratio c / a of the bottom width c and the opening width a is 9/10 or less, particularly 5/10.
The following is preferable.

The opening width a of the groove 31 is 0.0.
It is preferably 5 to 10 μm, more preferably 0.05 to 5 μm, and particularly preferably 0.05 to 1 μm.

The depth h of the groove 31 is 0.01 to 0.5.
μm, more preferably 0.01 to 0.3 μm, particularly preferably 0.01 to 0.15 μm.

Further, the gap b between the grooves 31 may be appropriately determined according to the capacity of the magnetic disk.

Here, the opening width a of the groove 31 is
The distance between the highest points of the substrate 10 and the bottom width c are the groove 3
The distance between the lowest points of the substrate 10 within 1 and the groove gap b is the distance between the highest points of the substrate 10 between a pair of adjacent grooves, and the depth h is
The distance between the highest and lowest points.

Further, the dimensions a, b, c and h of the groove 31 are 2 beam scanning electron microscope (SE
M) or a scanning tunneling electron microscope (STM) profile may be used within the range of resolution.

In FIG. 2, the gap b between the grooves 31 is
May be zero, that is, the trapezoidal groove 31 may be continuously formed.

When the continuous thin film type magnetic layer is formed by regulating the shape of the groove 31 as described above, the C-axis direction of the crystal grains is constrained in-plane and in the groove direction, that is, in the circumferential direction to be uniform. Epitaxial growth is performed. In particular, the direction of epitaxial growth can be restricted even inside the groove, and the C axis can be aligned in the disk circumferential direction.

Therefore, the direction of the easy axis of magnetization of the magnetic layer is aligned with the disk circumferential direction, the magnetic anisotropy is increased, the coercive force in the circumferential direction and the squareness ratio are improved, and in addition, the modulation of the reproduction output is prevented. it can.

The groove 31 may have various shapes other than the trapezoidal shape shown in FIG. 2, but may have a V shape and / or a U shape, and such a shape is preferable.

For example, a V-shaped groove 31 as shown in FIG. 3 may be used. In addition to the symmetrical V-shape, an asymmetric V-shape as shown in FIG.
As shown in FIG. 5, the wall surface of the groove 31 may be slightly deformed, such as one having a curvature.

Further, as shown in FIG. 6, a vertical straight line portion having an inclination different from V, for example, may be provided, and the wall surface of the groove 31 may have a polygonal line shape. As shown in FIG. The wall may have steps or shoulders.

Further, as shown in FIG. 8, one groove 31 may have two or more V-shapes, and the two or more V-shapes may have different depths.

Further, the U-shaped groove 3 as shown in FIG.
The number may be 1, and in this case as well, various modifications similar to the V-shaped groove 31 are possible.

Further, the present invention is not limited to the illustrated example, and V-shaped or U-shaped grooves may be continuously formed, and the substrate surface may have a cycloidal shape, a sine wave shape or the like.

The groove 31 is preferably one kind on the same substrate in terms of the orientation in the substrate circumferential direction, the coercive force, and the modulation of the reproduction output, but if necessary, two or more kinds thereof are preferable. Are in a predetermined arrangement with each other,
Both may be provided regularly.

The substrate surface may be smooth or may be finished to have a predetermined surface roughness.

Even in the case of forming the groove which is preferable in the present invention as described above, when the 2P method is adopted, in the present invention, the surface of the non-magnetic substrate is subjected to plasma treatment, and preferably the photopolymer layer is formed as described above. Since the thickness is set to, the transfer from the stamper is sure and the adhesion between the photopolymer and the non-magnetic substrate is good.

The magnetic disk substrate 10 of the present invention is preferably used for a magnetic disk, particularly a magnetic disk having a continuous thin film type magnetic layer.

When the squareness ratio of such a magnetic layer in the disk circumferential direction is S ₁ and the squareness ratio in the disk radial direction is S ₂ ,
In the present invention, the ratio S ₁ / S ₂ of S ₁ and S ₂ are realized 1.10 or more disks.

As described above, as described above,
Specific examples include hard type magnetic disks and floppy disks.

FIG. 10 shows a preferred example of a hard type magnetic disk. In this case, a rigid substrate is used among the substrates.

The magnetic disk 5 has a magnetic layer 14 on a substrate 10.

If necessary, the underlayer 13 is provided between the substrate 10 and the magnetic layer 14, and the protective layer 15 and the like are provided on the magnetic layer 14.

In this case, the substrate 10 having the V-shaped groove 31 is used, but the shape of the groove 31 is not limited to this.

The magnetic layer 14 is not particularly limited as long as it is a continuous thin film type, and may be formed of, for example, a continuous thin film containing at least one selected from Fe, Co and Ni, particularly a Co-based continuous thin film.

Specific examples of the composition of the magnetic layer 14 include Co
-Ni alloy, Co-Ni-Cr alloy, Co-V alloy, C
o-Ni-P alloy, Co-P alloy, Co-Zn-P alloy, Co-Ni-Pt alloy, Co-Pt alloy, Co-N
Examples thereof include i-Mn-Re-P alloy.

An underlayer 13 is provided between the substrate 10 and the magnetic layer 14 for the purpose of favorably performing epitaxial growth and improving magnetic characteristics, if necessary.

The underlayer 13 may be composed of, for example, a continuous thin film containing at least one selected from Cr, Mo and W. In this case, the metal used may be a simple substance or an alloy. The thickness of the underlayer 13 is preferably 0.05 to 0.5 μm for the purpose of improving the orientation and crystallinity of the magnetic layer 14.

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 film thickness of the magnetic layer 14 is 0.03 to 0.
2 μm is preferred.

The magnetic layer 14 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 is cured, a gas atmosphere containing O ₂ may be used.

The underlayer 13 is formed by vapor deposition, sputtering, ion plating, C as in the magnetic layer 14 described above.
The film may be formed by various vapor phase film forming methods such as VD, and it is particularly preferable to form the film by sputtering.

On the magnetic layer 14, a protective layer 15 and an organic lubricant film (not shown) may be further provided, if necessary.

In this case, the groove 31 on the substrate forms unevenness on the uppermost surface of the disk, further improving the lubricity between the magnetic disk and the magnetic head.
SS durability is improved.

The protective layer 15 is usually composed of carbon or carbon to which another element is added in an amount of about 5% by weight or less, and its film thickness may be set to about 0.03 to 0.1 μm.

The lubricating film is usually made of a fluorine-based liquid lubricant or the like, and the film thickness may be about 5 to 20A.

The protective layer 15 and the like are formed by various vapor deposition methods,
In particular, the film may be formed by sputtering.

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

On the other hand, in the case of a floppy disk, the layer structure and the like are the same as those in FIG. 10, and the only difference is that a flexible substrate is used among the above substrates.

When an underlayer is provided, a plasma polymerized film containing C, H or Si or SiOx.
It is preferable to use an oxide vapor deposition film such as (1 ≦ x ≦ 2). The thickness of the base film is about 50 to 200A.

Each ferromagnetic metal thin film forming the magnetic layer is N
A Co-Ni alloy containing i is preferable, and an alloy containing about 80% Co and about 20% Ni in molar ratio is particularly preferable.

If necessary, Cr may be contained in an amount of 10% or less, and various metals described in JP-A-63-10315 and other metal components may be contained. In principle, the hard disk type may be the same as the hard type magnetic disk, and the manufacturing method may be the same.

Furthermore, 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 is preferably about 0.03 to 0.2 μm. At this time, the output can be made sufficiently large.

Further, it is preferable that the top coat film is provided on the magnetic layer, if necessary, and the plasma polymerization film is used. At this time, the thickness of the top coat film is preferably 10 to 50 A from the viewpoint of spacing loss. In addition, a lubrication protective film may be separately provided.

Further, similar to the hard type magnetic disk described above, unevenness is formed on the uppermost surface of the disk. Due to this unevenness, the track density is improved by groove tracking,
The contact area with the head is reduced, so that effects such as improvement in durability can be obtained.

Although the single-sided recording type magnetic disk has been described above as an example as shown in FIG. 10, the present invention may be a double-sided recording type magnetic disk.

[0121]

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

Example 1 A non-magnetic base made of polyetherimide having an outer diameter of 3.5 inches and a thickness of 1.2 mm was manufactured by injection molding, and one main surface of the substrate was processed by the 2P method (see FIG. 1). An attempt was made to form a groove having a V-shaped cross section in a concentric circular shape in the circumferential direction.

The photopolymer used was a mixture of two kinds of UV-curable monomers and two kinds of photopolymerization initiators in the following proportions.

Trimethylolpropane triacrylate: 150 parts by weight Hydroxipivalic acid neopentyl glycol diacrylate: 50 parts by weight 2,2-dimethoxy-2-phenylacetophenone: 4
Parts by weight 2-methyl- [4- (methylthio) phenyl] -2-morpholino-1-propanone: 4 parts by weight

A high pressure mercury lamp was used for curing the photopolymer, and the curing conditions were as follows. Ultraviolet irradiation dose: 1 Joule / cm ² Maximum radiant flux: 0.1 Watt / cm ² Atmosphere: In N ₂ gas

This is designated as HD substrate sample No. 1. In this substrate sample No. 1, the adhesiveness with the photopolymer layer was not obtained, and the photopolymer layer could not be practically formed.

In this HD substrate sample No. 1, 2
When the groove is formed by the P method, H is similarly applied to the surface of the non-magnetic substrate as shown in Table 1 except that plasma treatment is performed.
D substrate samples No. 2 to No. 4, No. 7 and No. 8 were produced. The processing gas flow rate at this time is 50 SCCM.
And In addition, the HD substrate sample No. is performed in the same manner except that the non-magnetic substrate surface is subjected to UV treatment and coupling treatment.
No. 5 and No. 6 were produced. In this case, the film thickness of each photopolymer layer was 25 μm.

The film thickness of the photopolymer layer was measured by a step gauge.

These HD substrate samples No. 1 to No. 8
For, the adhesive strength and the transfer area were measured as follows. The results are shown in Table 1. In addition, Table 1 also shows the contact angle to water.

(1) Adhesive Strength (Peel Test) The sample was cut into 1/2 inch, and an adhesive tape was attached and pulled apart. The weight at that time was measured with a load cell.

(2) Transfer Area After the substrate was peeled from the stamper, the transfer area on the substrate side was measured.

[0132]

[Table 1]

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

Among these, HD substrate sample No. 2,
For No. 3, No. 7, and No. 8, the groove opening width a, the groove bottom width c, the groove depth h, and the inter-groove gap b were measured in the substrate radial direction. The average value and the coefficient of variation were calculated as follows. Each dimension was determined by STM.

Opening width a: 0.2 μm, coefficient of variation 13% Bottom width c: 0 μm, coefficient of variation 0% Depth h: 0.1 μm, coefficient of variation 15% Gap between grooves b: 0.2 μm, coefficient of variation 13 %

Then, the above-mentioned HD substrate sample No. 2,
No. 3, No. 7, and No. 8 were used, and the film thickness was 0.1 μm.
After forming the Cr underlayer of
A Ni-Cr magnetic layer was formed.

Then, after forming a C protective layer having a film thickness of 0.04 μm, perfluoropolyether is applied and 10 A is applied.
HD sample No. 2, No. 3, N
o.7 and No.8 were obtained.

In this case, the underlayer and the magnetic layer are formed by
Each was performed by DC-magnetron sputtering, and the protective layer was formed by RF-magnetron sputtering.

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

The targets are Cr and Co ₇₀ , respectively.
Ni ₂₀ Cr ₁₀ (at%) and C were used.

When the composition of the magnetic layer was determined by ICP emission analysis, it was Co ₇₀ Ni ₂₀ Cr ₁₀ (at%).

These HD samples No. 2, No. 3, N
For No. 7 and No. 8, the coercive force Hc of the magnetic layer in the disk circumferential direction and the radial direction was applied by VSM to obtain a magnetic field strength of 10
It was measured at kOe.

As a result, it was found that Hc was particularly high in the circumferential direction and had a sufficient Hc.

[0144] In order to evaluate the disk circumferential direction of the orientation, the a and the measurement in the same manner, the squareness ratio S ₁ of the disk circumferential direction, the radial direction of the disk squareness ratio S _2, S ₁ and S ₂
When the ratio S ₁ / S _{2 of the above} was calculated, it was 1.10 or more.

By X-ray diffraction, sample No. 2,
In No. 3, No. 7 and No. 8, it was confirmed that the C-axes of the crystal grains of the magnetic layer were oriented in the disk circumferential direction.

Next, for each sample, the modulation MODi of the reproduction output at the innermost circumference of the disc, the intermediate circumference of the inner circumference and the outer circumference, and the outermost circumference of the disk are calculated as follows, and the average value MOD is obtained to obtain the modulation value MOD. An evaluation was done.

MODi: A signal having a single wavelength of 3.3 MHz is recorded on the disc, and the maximum value of the output PP (peak to peak) value is A and the minimum value is the minimum value from the output waveform envelope for one round. B was calculated from the following formula. MOD _i = (AB) / (A + B) × 100 (%)

As a result, it was found that the MOD was less than 5%, which was a satisfactory level.

Example 2 In the HD substrate sample Nos. 1 to 6 of Example 1,
A substrate sample for a floppy disk was prepared in the same manner except that polyethylene terephthalate (PET) was used as the nonmagnetic substrate instead of polyetherimide (PEI).

The FD substrate samples No. 21 to No. 26 are made to correspond to the HD substrate samples No. 1 to No. 6 (Table 2).

FD substrate sample No. 21 is H of Example 1
Similar to the D substrate sample No. 1, it was practically difficult to form the photopolymer layer. The film thickness of the photopolymer layer was all 25 μm.

Also, the FD substrate sample Nos. 27 to N were changed by changing the plasma processing conditions and the non-magnetic substrate material as shown in Table 2.
o.29 was prepared.

However, the resin film thickness of these non-magnetic substrates was set to about 75 μm. In addition, the non-magnetic substrate material is P
When it was EN, the stamper was made of glass, and ultraviolet rays (UV) were irradiated from the stamper side.

The flow rate of the processing gas in the plasma processing was 100 SCCM.

FD substrate sample Nos. 21 to No.
For No. 29, the adhesive strength and the transfer area were measured in the same manner as in Example 1. The results are shown in Table 2.

Next, these FD substrate sample No. 21
~ No. 29, HD sample No. 2, N of Example 1
o.3, No. 7 and No. 8 magnetic layer is formed and FD
Samples No. 21 to No. 29 were produced.

However, in these, the undercoat film and the top coat film were plasma polymerized films, and the film thicknesses thereof were 20 respectively.
It was set to 0A and 50A. The plasma polymerization conditions at this time 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 Above FD sample No. 21 to No. 29 of 3.
It was incorporated into a 5-inch floppy disk drive and allowed to run at room temperature, and the number of passes until the FD sample was scratched was measured to examine the durability. However, the upper limit was set to 10 million passes.

Table 2 shows the above measurement results. Table 2
In addition, the contact angle with water is also shown.

[0160]

[Table 2]

From Table 2, the effects of the present invention are clear.

FD sample Nos. 22, 23, 27
~ 29, in the same manner as in Example 1, Hc, S ₁ /
When S ₂ and MOD were determined, good results were obtained as in Example 1.

The same applies to the measurement results of X-ray diffraction,
It was found that the C axis of the crystal grains of the magnetic layer was oriented in the disc circumferential direction.

FD substrate sample Nos. 22, 23,
The grooves in Nos. 27 to 29 were similar to the HD substrate sample No. 2, No. 3, No. 7, and No. 8 of Example 1.

Example 3 As in Example 2, the outer diameter was 3.5 inches and the thickness was 75 μm.
A non-magnetic substrate made of a polyethylene terephthalate (PET) film was manufactured by a 2P method (see FIG. 1) on one main surface of the non-magnetic substrate to form a group having a V-shaped cross section in a concentric pattern in the circumferential direction of the substrate.

The same photopolymer as in Examples 1 and 2 was used, and when forming the groove, the surface of the non-magnetic substrate was plasma-treated under the following conditions, and the thickness of the photopolymer layer after curing is shown in Table 3. FD substrate sample Nos. 32 to No. 32 are similarly provided, except that a photopolymer layer is provided instead.
37 was produced. The film thickness was determined by changing the injection amount of photopolymer.

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

Next, using FD substrate sample Nos. 32 to 37, FD sample Nos. 32 to N were obtained in the same manner as in Example 2.
o. 37 was prepared. FD sample No. 32 to No. 37 according to the substrate sample No. 32 to 37.

FD substrate sample No. 32 to No. 3 above
For 7, the adhesive strength was measured in the same manner as in Example 1. For FD sample No. 32 to No. 37,
The durability of the disk was examined in the same manner as in Example 2. In addition, error measurement was performed as follows. The results are shown in Table 3. Table 3 also shows the contact angle of the substrate with water.

Error measurement This shows the number of recording / reproducing output ratios when 100 samples were put into a 1 MB certifier.

[0171]

[Table 3]

From Table 3, the effects of the present invention are clear.

FD sample No. 34, No. 35,
Regarding No. 36, in the same manner as in Example 1, Hc, S ₁
When / S ₂ and MOD were obtained, Hc, S ₁ / S ₂ and MOD were obtained in the same manner as in Example 1, and good results were obtained as in Example 1.

The same applies to the measurement results of X-ray diffraction,
It was found that the C axis of the magnetic tank was oriented in the disk circumferential direction.

FD substrate samples No. 34 and No. 3
The grooves in No. 5 and No. 36 are similar to the grooves in HD substrate sample Nos. 2, 3, 7, 8 of Example 1 and FD substrate sample Nos. 22, 23, 27 to 29 of Example 2. It was

Example 4 In the FD substrate samples No. 32 to No. 37 of Example 3, polyethylene terephthalate (P
Polyethylene naphthalate (PEN) instead of ET)
A substrate sample for a floppy disk was prepared in the same manner except that was used. At this time, the stamper was made of glass and irradiated with ultraviolet rays (UV) from the stamper side.

FD substrate sample Nos. 42 to 47 are made to correspond to FD substrate sample Nos. 32 to 37.

These substrate samples No. 42 to No. 47
In the same manner as in Example 3, corresponding to these substrate samples, and FD sample Nos. 42 to No. 4, respectively.
47 was produced.

In the same manner as in Example 3, the substrate sample No.
The adhesive strength of Nos. 42 to No. 47 was measured, and the durability of FD sample Nos. 42 to No. 47 was examined, and the error was measured. The results are shown in Table 4. Table 4 also shows the contact angle of the substrate with water.

[0180]

[Table 4]

From Table 4, the effect of the present invention is clear.

FD sample No. 44, No. 45,
Regarding No. 46, in the same manner as in Example 1, Hc, S ₁
When / S ₂ and MOD were determined, good results were obtained as in Example 1.

The same applies to the measurement results of X-ray diffraction,
It was found that the C axis of the crystal grains of the magnetic layer was oriented in the disc circumferential direction.

FD substrate sample No. 44, No. 4
The grooves in No. 5 and No. 46 were the same as those in FD substrate samples No. 34, No. 35, and No. 36 of Example 3.

Example 5 In the FD substrate samples No. 32 to No. 37 of Example 3, the non-magnetic substrate had an outer diameter of 3.5 inches and a thickness of 1.2.
A hard disk substrate sample was prepared in the same manner except that a non-magnetic substrate made of polyetherimide having a size of mm was used.

The HD substrate samples No. 52 to No. 57 are made to correspond to the FD substrate sample Nos. 32 to 37.

[0187] These HD substrate samples No. 52 to No.
For 57, the adhesive strength was measured in the same manner as in Example 3. The results are shown in Table 5. In Table 5, the contact angle with water is also shown.

Next, the above HD substrate sample No. 5
HD samples were prepared in the same manner as in Example 1 using No. 4, No. 55 and No. 56. Substrate sample No. 54,
HD sample No. 5 corresponding to No. 55 and No. 56
No. 4, No. 55, and No. 56.

HD substrate sample No. 54, No. 5
5, No. 56, in the same manner as in Example 1, Hc,
When S ₁ / S ₂ and MOD were determined, good results were obtained as in Example 1.

The same applies to the measurement results of X-ray diffraction,
It was found that the C axis of the crystal grains of the magnetic layer was oriented in the disc circumferential direction.

In addition, HD substrate sample No. 54, No. 5
The grooves in No. 5 and No. 56 were the same as those in FD substrate samples No. 34, No. 35 and No. 36 of Example 3.

Also, HD substrate sample No. 52, No. 5
HD Sample Nos. 52, 53, and 57 were prepared in the same manner as described above for No. 3 and No. 57.

HD sample Nos. 52 to 57 including these
For, the durability and error rate of the disk were examined as follows. The results are shown in Table 5.

Durability The HD sample was incorporated in a hard disk drive, run at room temperature, the number of passes until the HD sample was scratched was measured, and the durability was examined. However, the upper limit was set to 10 million passes.

Error rate Recording frequency was 3.3 MHz, track feed pitch was 15 μm, and certification was performed on the entire surface of the disk, and the total number of missing pulse errors and extra pulse errors was evaluated as the number of signal defects.

The missing pulse error is an error when a signal is recorded on a disk and the output of the reproduced signal is reduced to 65% or less of the average output of the entire circumference.

The extra pulse error is an error when the signal is written on the disk and then the DC signal is erased, and the remaining signal becomes 25% or more of the average output of the entire circumference.

[0198]

[Table 5]

From Table 5, the effects of the present invention are clear.

[0200]

According to the present invention, when the groove is formed by the 2P method, the shape transfer from the stamper is surely performed, and the bond between the photopolymer and the non-magnetic substrate is strong, and the magnetic disk substrate is strong. Therefore, the magnetic disk using this is excellent in durability, has a high coercive force in the circumferential direction of the disk by regulating the shape of the groove, and prevents the modulation of the reproduction output. Also, the track density is improved and the errors are reduced.

[Brief description of drawings]

FIG. 1 is a process diagram schematically illustrating a photopolymer method.

FIG. 2 is a partial sectional view showing an example of a magnetic disk substrate of the present invention.

FIG. 3 is a partial cross-sectional view showing an example of a magnetic disk substrate of the present invention.

FIG. 4 is a partial cross-sectional view showing an example of a magnetic disk substrate of the present invention.

FIG. 5 is a partial cross-sectional view showing an example of a magnetic disk substrate of the present invention.

FIG. 6 is a partial cross-sectional view showing an example of a magnetic disk substrate of the present invention.

FIG. 7 is a partial cross-sectional view showing an example of a magnetic disk substrate of the present invention.

FIG. 8 is a partial cross-sectional view showing an example of a magnetic disk substrate of the present invention.

FIG. 9 is a partial sectional view showing an example of a magnetic disk substrate of the present invention.

FIG. 10 is a partial cross-sectional view showing an example of a magnetic disk of the present invention.

[Explanation of symbols]

 1 Non-Magnetic Substrate 2 Stamper 3 Photopolymer Layer 31 Groove 10 Substrate for Magnetic Disk 5 Magnetic Disk 14 Magnetic Layer

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

Claims (7)

[Claims] 1. A magnetic disk substrate having a photopolymer layer formed on a non-magnetic substrate and grooves formed in the photopolymer layer, wherein at least a surface of the non-magnetic substrate on the side where the groove is formed is subjected to plasma treatment. Substrate for magnetic disk. 2. The thickness of the photopolymer layer is 15 to 4
The magnetic disk substrate according to claim 1, which has a thickness of 0 μm. 3. The non-magnetic substrate is made of resin.
Alternatively, the magnetic disk substrate described in 2. 4. The processing gas used for the plasma processing is
4. The magnetic disk substrate according to claim 1, which is a gas containing at least one of oxygen and nitrogen or a gas of a compound containing at least one of oxygen and nitrogen. 5. The magnetic disk substrate according to claim 1, wherein the plasma-treated surface of the non-magnetic substrate has a contact angle with water of 30 degrees or less. 6. The groove according to claim 1, wherein the groove has an opening width larger than a bottom width, the opening width and the cross-sectional shape are substantially uniform, and the groove is formed in the substrate circumferential direction. A magnetic disk substrate as described above. 7. A magnetic disk having a continuous thin film magnetic layer on the groove forming surface of the magnetic disk substrate according to claim 1. Description: