JPH0636263A - Substrate for magnetic disc - Google Patents

Abstract

PURPOSE:To achieve higher yields by forming a photopolymer layer of a substrate for a magnetic disc on a non-magnetic substrate through a ground film to ensure the transferring of a groove from a stamper. CONSTITUTION:A floppy disc 5 has a magnetic layer 14 on a substrate 10 on which a groove 31 is formed through a ground layer 13 and a top coated layer 15 is provided on the layer 14. The layer 13 employs a plasma polymerized film containing C, H, Si and the like. The layer 13 undergoes a plasma treatment in the formation of a photopolymer layer to improve adhesiveness of the photopolymer layer on the layer 13. The layer 13 thus arranged prevents infiltration of water and oxygen into the layer 14. Ferromagnetic metal thin films composing the layer 14 employ Co-Ni alloys containing Ni. With the groove 31 on the substrate 10, a protrusion and a recess are formed on the uppermost surface of the disc. The formation of the protrusion and recess achieves improvements in the density of a track with a groove tracking and in the endurance with a decrease in the contact surface with a head.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In the case of a magnetic disk having a groove, since the distance from the magnetic head in the groove increases and demagnetization due to separation loss increases, adjacent recording tracks can be separated by the groove and the track recording density is high. Even at times, crosstalk can be prevented.

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

Resin is often used as the substrate material.

Therefore, in such a resin substrate, a groove is formed on the side surface of the magnetic layer (substrate surface) by an injection molding method or a photopolymer method (2P method). Above all, the 2P method is widely used because of high precision of groove formation.

However, if a groove is formed directly on these substrates by using the 2P method, the photopolymer (2P resin) has too high hardness, and when the substrate is peeled from the stamper, cracks or defects are formed in the photopolymer layer. Has occurred,
There is a problem that the yield becomes poor.

[0007]

The object of the present invention is to ensure the shape transfer from the stamper when the groove is formed by using the photopolymer (2P method), and to prevent the photopolymer layer from cracking when peeled from the stamper. No defects occur,
An object is to provide a magnetic disk substrate having a high yield.

[0008]

The above objects are achieved by the present invention described in (1) to (10) below.

(1) In a magnetic disk substrate in which a photopolymer layer is formed on a non-magnetic substrate and grooves are formed in the photopolymer layer, the photopolymer layer is formed on the non-magnetic substrate via an underlayer film. Magnetic disk substrate.

(2) The magnetic disk substrate of (1), which is a flexible substrate.

(3) The underlying film has a glass transition temperature of 30.
The magnetic disk substrate according to the above (1) or (2), which is a resin film of at least one kind of thermosetting resin, ultraviolet ray curable resin and electron beam curable resin having a temperature of not higher than 0 ° C.

(4) The magnetic disk substrate according to (3), wherein the resin film has a thickness of 2 to 10 μm.

(5) The magnetic disk substrate according to (1) or (2), wherein the underlayer film is a plasma polymerized film.

(6) The plasma polymerized film has a refractive index of 1.
The magnetic disk substrate of (5) above, which is 7 or less.

(7) The magnetic disk substrate according to the above (5) or (6), wherein the plasma-polymerized film contains C and H.

(8) The plasma polymerized film has a thickness of 50 to
The magnetic disk substrate according to any one of (5) to (7), which has a thickness of 300 μm.

(9) The thickness of the photopolymer layer is 15
The magnetic disk substrate according to any one of (1) to (8) above, which has a thickness of -40 μm.

(10) The above (1) used for obtaining a magnetic disk having a continuous thin film magnetic layer formed on the groove forming surface.
A magnetic disk substrate according to any one of (9) to (9).

[0019]

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

The magnetic disk substrate of the present invention has grooves formed by the photopolymer (2P) method. That is, a photopolymer layer is formed on a nonmagnetic substrate, and grooves are formed in this photopolymer layer.

In this case, in the present invention, the photopolymer layer is formed on the non-magnetic substrate via the underlayer.

Then, the 2P method is carried out by using the non-magnetic substrate having the underlying film thus formed, for example, as shown in FIG.

As shown in FIG. 1, a non-magnetic substrate 1 on which a base film 11 is formed and a stamper 2 are combined, and a photopolymer which is cured by ultraviolet irradiation is injected onto the non-magnetic substrate 1 to form a photopolymer layer. 3 is formed.

After forming the photopolymer layer 3 in this way, preferably, when bubbles are introduced from the base film 11 and the photopolymer layer 3, the bubbles are removed.

After that, ultraviolet rays U are applied from the nonmagnetic substrate 1 side.
After irradiating V to cure the photopolymer layer 3, the stamper 2 is peeled off.

As a result, the shape transfer from the stamper 2 can be performed, and the magnetic disk substrate 10 in which the groove 31 is formed can be obtained.

The non-magnetic substrate 1 is usually ultraviolet UV
In many of these materials, the ultraviolet ray UV is preferably irradiated from the non-magnetic substrate 1 side, 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 undercoating film in the above has a glass transition temperature (Tg) of 30 ° C. or lower, preferably 25 ° C. or lower, and is at least one resin selected from thermosetting resins, ultraviolet curable resins and electron beam curable resins. It is a film or a plasma polymerized film. The Tg of the resin is preferably low, and the lower limit is not particularly limited, but the lower limit is usually −
It is about 60 ° C. The Tg is obtained by differential scanning calorimetry (DSC) after the resin film is formed on the substrate by curing and then peeled off from the substrate.

By forming such a base film, the base film plays a role of a buffer layer and acts to relieve the tensile stress when the 2P method is carried out. Therefore, the groove is surely transferred from the stamper, and it is possible to prevent the photopolymer layer 3 from being cracked or defective at the time of peeling.
Yield is improved.

Such an effect can be obtained only by using the above-mentioned resin film or plasma-polymerized film having Tg of 30 ° C. or less as the base film.

Therefore, for example, a base film using a resin having a Tg of more than 30 ° C. does not have a sufficient effect of relaxing the tensile stress, and the effect of the present invention cannot be obtained. Further, when it is used for the floppy disk which is a preferred embodiment of the present invention, the flexibility of the substrate cannot be maintained and it is difficult to hit the head.

First, a thermosetting resin having Tg of 30 ° C. or lower,
The case of using an ultraviolet curable resin or an electron beam curable resin will be described.

The thermosetting resin has a tensile elongation of 200 to 200.
It is preferably 1000%.

Here, the tensile elongation means the length (L) and the original length when cut by applying a force up to cutting to a resin sample having a width of 1/2 inch and a length of 100 mm and a thickness of 25 μm. (L
_O) and from the obtained refers to _{(L O / L) × 100} (%).

The tensile strength at this time is 200 to 4
It is about 00 kg / cm ² . Here, the tensile strength is 1/2
1 inch resin sample with a width of 100 mm and a length of 25 μm
It is the force until cutting when pulled at a pulling speed of 00 mm / min.

Examples of the thermosetting resin include urethane resins of diisocyanate / adipate / diol type and modified products thereof, and commercially available products can be used as they are.

Examples of such commercially available products include the above-mentioned diisocyanate, adipate, and diol-based urethane resins under the trade names N-2304 and N-2301 [manufactured by Nippon Polyurethane Industry Co., Ltd.].

In order to form the base film using such a thermosetting resin, a coating film may be formed using a coating liquid of the thermosetting resin. The solvent for preparing the coating solution is not particularly limited as long as the above resin is soluble, but methyl ethyl ketone (MEK), acetone, toluene, cyclohexanone, methyl isobutyl ketone (MIBK), etc., or a mixed solvent thereof. Etc. may be used.

The resin content in the coating liquid is 1
It may be about 0 to 35 wt%.

The coating method is not particularly limited, and any known method may be used, including spin coating, gravure coating, spray coating, reverse roll coating, dipping and the like.

To cure the coating film, heating may be performed.
Heat at a temperature of ~ 70 ° C for about 20-40 hours.

The thickness of the base film thus formed may be 2 to 10 μm, preferably 4 to 7 μm.

Further, the ultraviolet curable resin is preferably one having a tensile elongation of 50 to 300% with the same definition as above. The tensile strength is about ² to 10 kg / cm ² .

As such an ultraviolet curable resin, 2
Among the P resins, those having Tg of 30 ° C. or less can be used.

In this case, it is preferable to polymerize using a precursor such as a monomer or an oligomer which is polymerized by irradiation with ultraviolet rays.

Specifically, it is preferable to use a monofunctional ester acrylate or the like as a monomer and to cure it with ultraviolet rays.

Examples of such a monomer include CH ₂ ═C
_{HCO (OC 2 H 4) 4} -O-C 6 H 4 those represented by -R can be mentioned, trade name _{M-111 (R = -C 4} H
_{9), M-117 (R} = -C 9 H 19) [ manufactured by Nippon Kayaku Co.,
Commercially available ”can be used as it is.

In addition to these, modified products thereof can also be used.

In order to form a base film using such an ultraviolet curable resin, a coating film may be formed using a coating liquid containing the above-mentioned monomer and the like and ultraviolet cured. In this case, it is preferable to add a photopolymerization sensitizer or an initiator to the coating film, and the addition amount thereof may be the same as that of the 2P resin used when the photopolymer method described later is carried out.

The coating method, coating solvent, etc. may be the same as those described above. Further, the ultraviolet irradiation condition is that the ultraviolet intensity is 50 to
The irradiation amount may be about 200 mW / cm ² and the irradiation amount may be about 500 to 1000 mJ / cm ² . A mercury lamp or the like may be used as the ultraviolet ray source.

The thickness of the base film thus formed may be 2 to 10 μm, preferably 4 to 7 μm.

Further, the electron beam curable resin is preferably one having a tensile elongation of 200 to 1000% with the same definition as above.

As the electron beam curable resin, Japanese Patent Laid-Open No. 56-
No. 122802, No. 56-124119, etc. are mentioned. Specifically, it is an electron beam cured compound using an electron beam curable compound as a monomer.

Examples of such a monomer include urethane compounds and modified products thereof. For example, as the urethane monomer, there is a commercially available product under the trade name YH8009 (manufactured by Toyobo Co., Ltd.).

In order to form a base film using such an electron beam curable resin, a coating film may be formed using a coating solution containing the above-mentioned monomer and the like and electron beam irradiation may be performed. The electron beam irradiation condition may be 3 to 10 Mrad, and particularly 4 to 7 Mrad.

The thickness of the base film thus formed may be 2 to 10 μm, preferably 4 to 7 μm.

The thickness of the base film, which is a resin film, can be determined by a step gauge or the like.

The plasma-polymerized film used as the underlayer preferably has a refractive index of 1.7 or less, more preferably 1.5 or less. It is preferable that the refractive index is small, but the lower limit is usually about 1.40.

An ellipsometer may be used to measure such a refractive index.

The plasma polymerized film preferably contains C and H, and the total content of C and H in the film should be 85 at% or more, preferably 95 at% or more. It is preferable to contain only H and H.

The atomic ratio of H to C is such that H / C is 1.0 or less, preferably 1.3 or more, and the content of C in the film is 50 at% or less, preferably 40 at%. On the other hand, the content of H is 50 at% or more, preferably 60 at
It should be at least%. In some cases, C, H
In addition to O, N and the like may be contained at 15 at% or less.

Thus, the refractive index of the film and C, H in the film are
The effect of the present invention is improved by controlling the above.

The content of C, H and other elements in the plasma polymerized film may be analyzed by SIMS (secondary ion mass spectrometry), CHN coder or the like.

When SIMS is used, C, H, etc. may be counted and calculated on the surface of the plasma polymerized film. Alternatively, while performing ion etching with Ar or the like, C, H
Alternatively, the profile may be measured and calculated. SIMS
For the measurement of, see Surface Science Basic Course, Volume 3 (198
4) Basics and Applications of Surface Analysis (P70) "SIMS and LAMMA" may be followed.

As a raw material source for forming such a plasma-polymerized film, various sources containing carbon and hydrogen can be used, but since they are usually easy to operate,
At least one of methane, ethane, propane, butane, pentane, ethylene, propylene, butene, butadiene, acetylene, methylacetylene, and other saturated or unsaturated hydrocarbons that are gaseous at room temperature is used as the C and H sources. If necessary, hydrocarbons that are liquid at room temperature may be used as a raw material.

When other elements are contained, one or more of the above hydrocarbons may be added to O ₂ , O ₃ , H ₂ O, N ₂ and N.
NOx such as O, N ₂ O and NO ₂ , H ₂ , NH ₃ and C
O, may be used as a source gas plus at least one of such CO ₂ as N and O source.

The plasma polymerized film is formed by bringing the above-mentioned discharge plasma of the source gas into contact with the substrate or the magnetic layer according to a known method. The electrode arrangement, applied current, processing time, operating pressure, etc. may be set under normal conditions.

Although the processing conditions vary depending on the processing apparatus used, for example, W / (F · M) [where W is plasma input power (Joule / sec), F is an organic source gas flow rate, and M is It is preferable that the value is 5 × 10 ⁷ Joule / kg or less, particularly 1 × 10 ⁷ Joule / kg or less, in terms of the raw material gas molecular weight and the unit of F · M is kg / sec. The smaller the W / (FM) value, the better, but the lower limit is usually 1 × 10 ⁶ Joul.
It is about e / kg. When this value becomes large, the refractive index becomes large, the plasma polymerized film becomes too dense, and the effect of relaxing the tensile stress when carrying out the 2P method becomes insufficient. On the other hand, when this value becomes small, the quality of the plasma polymerized film becomes poor.

The actual conditions may be appropriately set so as to satisfy the above range of the refractive index and the like depending on the processing apparatus used. Therefore, if the raw material gas flow rate becomes larger than a suitable value under a certain condition, or the plasma output becomes small, the effect of the present invention decreases.

As the carrier gas, Ar, N ₂ ,
He, H ₂ or the like may be used. As a plasma generation source, in addition to high frequency discharge, microwave discharge, direct current discharge,
Either AC discharge or the like can be used.

The thickness of the base film thus formed may be 50 to 300 nm, preferably 100 to 200 nm.

An ellipsometer or the like may be used to measure the film thickness. Such control of the film thickness may be achieved by limiting the reaction time at the time of forming the plasma polymerized film, the raw material gas flow rate, and the like.

In the present invention, the photopolymer or the precursor thereof used for forming the photopolymer layer is not particularly limited, and can be selected from various radiation (particularly ultraviolet) 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 in combination in place 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 preferably 3 to 5% by weight.

The thickness of the photopolymer layer is 15 to 4
0 μm, further 20 to 40 μm, especially 25 to 35 μm
It is preferably m. Note that the film thickness in this case includes the thickness corresponding to the groove and is after curing.

With such a film thickness, the amount of the polymerization initiator in the layer is sufficient and the curing by ultraviolet irradiation is sufficiently advanced, so that the adhesion between the non-magnetic substrate and the photopolymer layer is improved. It is preferable for the purpose. 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 becomes smaller,
When irradiated with ultraviolet rays, the amount of the polymerization initiator is not sufficient, so that the curing does not proceed sufficiently and the adhesive strength is extremely reduced.
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 film thickness of the photopolymer layer is large, the effect is not improved in terms of adhesiveness and the like, which is disadvantageous in terms of productivity and cost. In addition, due to shrinkage during curing, warpage 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 magnetic disk substrate of the present invention is preferably used as a flexible substrate for a floppy disk.

There is no particular limitation on the material of the non-magnetic substrate used for the flexible substrate for the floppy disk, and various films such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) can withstand the heat of forming the ferromagnetic metal thin film. ) And other polyesters, polyether ether ketone (PEEK), and the like can be used. Further, each material described in JP-A-63-10315 can be used.

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

In forming a base film of a resin film or a plasma polymerized film using such a non-magnetic substrate, it is preferable to subject the surface of the non-magnetic substrate to plasma treatment.

The plasma treatment can improve the adhesion between the non-magnetic substrate and the base film. Plasma treatment is particularly effective in forming a plasma polymerized film.

In the plasma processing, an inorganic gas such as oxygen or nitrogen may be used as a processing 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.

Further, such plasma treatment may be performed on the base film when forming the photopolymer layer.

This improves the adhesiveness between the base film and the photopolymer layer.

The groove shape in the present invention can be set to a predetermined shape by selecting the groove shape of the stamper.

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

An example of the structure of a floppy disk to which the magnetic disk substrate of the present invention is applied is shown in FIG.

As shown in FIG. 2, the floppy disk 5
Has the magnetic layer 14 on the substrate 10 in which the groove 31 is formed as described above via the underlayer 13. And
A top coat film 15 is provided on the magnetic layer 14.

If necessary, the underlayer 13 provided as shown in FIG. 2 is preferably a plasma polymerized film containing C, H or Si. By providing such an underlayer, it is possible to prevent water and oxygen from entering the magnetic layer. The underlying layer is SiOx (1 ≦ x ≦ 2)
An oxide vapor deposition film such as

The thickness of the underlayer 13 is about 50 to 300A.

The magnetic layer 14 is not particularly limited as long as it is a continuous thin film type, and each ferromagnetic metal thin film forming the magnetic layer 14 is
A Co-Ni alloy containing Ni is preferable,
Particularly, an alloy containing about 80% Co and about 20% Ni in molar ratio is 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.

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 14 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 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 14 is hardened, a gas atmosphere containing O ₂ may be used.

Further, as shown in FIG. 2, a top coat film 15 is provided on the magnetic layer 14 if necessary.
It is preferably a plasma polymerized film. The thickness of the top coat film 15 at this time is 10 from the viewpoint of spacing loss.
It is better to set it to ~ 100A. In addition, a lubrication protective film may be separately provided.

In this case, the grooves 31 on the substrate 10 form irregularities on the uppermost surface of the disk. These irregularities improve the track density by the groove tracking and reduce the contact area with the head, thus improving the durability. It is possible to obtain effects such as improvement of

The magnetic disk substrate of the present invention can be used as a rigid substrate of a hard type magnetic disk. However, glass or rigid resin is used for the non-magnetic substrate in this case, and it is preferable that the non-magnetic substrate is made of resin. The substrate is rigid when the Young's modulus of the substrate is E and the thickness is t,
E · t ³ ≧ 1 × 10 ⁷ dyn · cm, more preferably E · t ³
It means ≧ 3 × 10 ⁷ dyn · cm.

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

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

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

When a hard type magnetic disk is used,
The layer structure and the like are the same as those in FIG. 2 except that a rigid substrate as described above is used.

In the hard type magnetic disk, the magnetic layer is not particularly limited as long as it is a continuous thin film type.
A continuous thin film containing at least one 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. In this case, the magnetic layer may be basically the same as 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 holding power.

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

The underlayer may be formed 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 is preferably 0.05 to 0.5 μm for the purpose of improving the orientation and crystallinity of the magnetic layer.

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

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

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

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, thereby improving the CSS durability. Also, the track density is improved.

The protective layer is usually made of carbon or carbon to which other elements are added in an amount of about 5% by weight or less, and the film thickness thereof may be about 0.03 to 0.1 μm.

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

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

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

In the above, as shown in FIG. 2, 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.

[0126]

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

Example 1 A non-magnetic substrate made of polyethylene terephthalate (PET) having an outer diameter of 3.5 inches and a thickness of 75 μm was provided on one main surface with 2
By the P method (see FIG. 1), concentrically in the circumferential direction of the substrate,
An attempt was made to form a groove having a shape as shown in FIG.

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

UV-Curable Monomer Product name M309; Nippon Kayaku Co., Ltd .; CH ₃ CH ₂ C (CH ₂ OCOCH = C H ₂ ) ₃ : 50 parts by weight Product name MANDA; Nippon Kayaku Co., Ltd .: 50 parts by weight Photopolymerization initiator; trade name Irgacure-651; manufactured by Ciba Geigy: 4 parts by weight Product name Irgacure 907; manufactured by Ciba Geigy: 4 parts by weight

After the above composition was dropped on the stamper,
The non-magnetic substrate was placed, bubbles were removed, and ultraviolet rays were irradiated.

A high pressure mercury lamp was used for curing the photopolymer, and the curing conditions were as follows. Ultraviolet irradiation amount: 700 mJ / cm ² Maximum radiant flux: 0.1 Watt / cm ² Atmosphere: in N ₂ gas After curing in this way, the film was peeled from the stamper.

This is designated as FD substrate sample No. 1. In this substrate sample No. 1, the adhesiveness between the non-magnetic substrate and the photopolymer layer was not obtained, and the photopolymer layer could not be practically formed.

In this FD substrate sample No. 1, 2
When the groove is formed by the P method,
FD substrate sample No. 2 was prepared in the same manner except that a coating film of a mixture of an ultraviolet curable monomer and a photopolymerization initiator was formed and cured to form a base film, which was cured.

UV curable monomer; trade name M-30
9; manufactured by Nippon Kayaku Co., Ltd .; CH ₃ CH ₂ C (CH ₂ OCOCH = CH ₂ ) ₃ : 92
Parts by weight Photopolymerization initiator; trade name Irgacure-651; manufactured by Ciba Geigy: 4
Weight part Product name Irgacure-907; Ciba-Geigy: 4
Parts by weight

The curing conditions were the same as those for the photopolymer, and the thickness of the underlying film after curing was 5 μm. The thickness of the photopolymer layer was 25 μm. The film thickness of the base film and the photopolymer layer was measured by a step gauge.

In the FD substrate sample No. 2, as the UV-curable monomer, the trade name M-111 [Nippon Kayaku Co., Ltd .; CH ₂ = CHCO (OC ₂ H ₄ ) ₄ -O-C] was used.
FD substrate sample No. 3 was prepared in the same manner except that [ ₆ H ₄ -C ₄ H ₉ ] was used.

As the UV-curable monomer, trade name M-117 [manufactured by Nippon Kayaku Co., Ltd .; CH ₂ = CHCO
(OC ₂ H ₄ ) ₄ —O—C ₆ H ₄ —C ₉ H ₁₉ ],
Similarly, FD substrate sample No. 4 was prepared.

The stamper used was concentrically formed with grooves having a groove width of 0.4 μm, a depth of 0.1 μm, and an interval between grooves of 1.6 μm.

The yields of FD substrate samples No. 1 to No. 4 were examined as follows. Further, the tensile elongation and tensile strength of the ultraviolet curable resins forming the underlayer films of FD substrate samples No. 2 to No. 4 were examined as follows. The results are shown in Table 1. Table 1 also shows the Tg of the UV curable resin used in FD substrate samples No. 2 to No. 4 and the film thickness of the base film after curing.
The Tg is determined by DSC after the resin film is formed on the substrate by curing and then peeled from the substrate.

(1) Yield With respect to 1000 substrate samples, the groove width and depth of the groove were measured by a scanning tunneling microscope (STM),
If either the groove width or the depth is deviated from the stamper groove by ± 10% or more, it is judged to be outside the yield,
Yield (%) of the ratio of both less than ± 10%
Sought as. In addition, even if the formed 2P layer had cracks or defects, it was excluded from the yield.

(2) Tensile elongation (%) A resin sample having a width of 1/2 inch and a length of 100 mm and a thickness of 25 μm is applied with a force until the cutting, and the length (L) at the time of cutting is measured. determined, since the L and the original length and (L _O), (L
It is indicated by _O / L) × 100 (%).

(3) Tensile strength (kg / cm ² ) With a force up to cutting when a resin sample having a width of 1/2 inch and a length of 100 mm and a thickness of 25 μm is pulled at a pulling speed of 100 mm / min. Shows.

[0143]

[Table 1]

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

Using the above FD substrate samples No. 3 and No. 4, after forming an underlayer of a plasma polymerized film, the film thickness of 0.
A 05 μm Co-Ni-Cr magnetic layer was formed. Further, a top coat film of a plasma polymerized film was formed on the magnetic layer. The film thicknesses of the underlayer and the top coat film were 200 A and 50 A, respectively, and the plasma polymerization conditions were as follows.

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

In this way, FD sample Nos. 3 and 4 were obtained according to the FD substrate sample used.

When FD samples No. 3 and No. 4 were incorporated in a 3.5-inch floppy disk drive and the characteristics of the disk such as electromagnetic conversion characteristics and disk durability were examined, good results were shown.

Example 2 An FD substrate sample was prepared in the same manner as in FD substrate sample No. 2 of Example 1 except that a thermosetting resin was used as the material of the base film instead of the ultraviolet curing resin.

As the thermosetting resin, the trade name VAGH is used.
[Nippon Polyurethane Industry Co., Ltd .: vinyl chloride-vinyl acetate copolymer], trade name N-2304 [Nippon Polyurethane Industry Co., Ltd .: diisocyanate adipate.
Diol-based urethane resin], product name N-2301 [Nippon Polyurethane Industry Co., Ltd .: diisocyanate / adipate / diol-based urethane resin: modified product of N-2304], and methyl ethyl ketone (MEK) as a coating solvent. A 30 wt% resin solution was prepared by using it, and a resin coating film was formed by a gravure coating method and dried to obtain a base film.

FD substrate samples No. 21, No. 22, and No. 23 are prepared in the above order according to the thermosetting resin used.

These FD substrate sample Nos. 21 to No.
For 23, the yield (%) was obtained in the same manner as in Example 1. The same evaluation was performed for each resin.

The results are shown in Table 2.

[0154]

[Table 2]

The effects of the present invention are clear from Table 2.

FD substrate sample No. 22 and No. 2
FD sample No. 2 in the same manner as in Example 1
No. 2, No. 23 was prepared and the characteristics of the disk were evaluated. As a result, good results were shown.

Example 3 An FD substrate sample was prepared in the same manner as in FD substrate sample No. 2 of Example 1 except that electron beam curable resin was used as the material of the base film instead of UV curable resin. .

As electron beam curable monomers, trade name PVC49 [UCC Co., Ltd .: vinyl chloride type],
Product name YH8009 [Toyobo Co., Ltd .: urethane type]
Was used to form a coating film by a gravure coating method, which was dried and then irradiated with an electron beam to be cured to form a base film.

FD substrate samples No. 31 and No. 32 are prepared in the above order according to the electron beam curable monomer used.

These FD substrate samples No. 31, No.
For 32, the yield (%) was determined in the same manner as in Example 1. The same evaluation as in Example 1 was performed for each resin.

The results are shown in Table 3.

[0162]

[Table 3]

From Table 3, the effect of the present invention is clear.

Also, FD substrate sample No. 31, No. 3
FD sample No. 3 in the same manner as in Example 1
No. 1, No. 32 was prepared and the characteristics of the disk were evaluated. As a result, good results were shown.

Example 4 An FD substrate sample was prepared in the same manner as in FD substrate sample No. 2 of Example 1 except that the base film was made of a plasma-polymerized film instead of the ultraviolet curable resin material.

The plasma-polymerized film was formed under the conditions shown in Table 4, and FD substrate samples No. 41 to No. 46 were selected according to the film forming conditions.

These FD substrate sample Nos. 41 to No.
For 46, the yield (%) was determined in the same manner as in Example 1. Further, the plasma polymerized film and the refractive index (n) were measured by an ellipsometer.

The results are shown in Table 4 together with the FD substrate sample No. 1 of Example 1.

[0169]

[Table 4]

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

Also, FD substrate samples No. 41 to No. 4
FD sample No. 41 in the same manner as in Example 1
~ No. 46 was prepared and the disk characteristics were evaluated.
It showed good results.

Example 5 FD substrate samples No. 41 to No. 46 of Example 4 were used in the same manner as in Example 4 except that the surface of the non-magnetic PET substrate was plasma-treated under the following conditions when the underlayer was formed. Was produced. FD board sample No. 41-N
FD board sample No. 51-No. 56 according to o.
And

Plasma processing conditions Gas used: Oxygen Flow rate: 100 SCCM AF (100 kHz): 50 W Pressure: 0.05 Torr Processing time: 10 minutes

These FD substrate sample Nos. 51 to No.
The yield (%) of No. 56 was examined, and it was found that the FD substrate samples No. 41 to No.
The yields were improved by 1 to 4%, respectively.

[0175]

According to the present invention, the yield is improved in the 2P method.

[Brief description of drawings]

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

FIG. 2 is a partial cross-sectional view of a magnetic disk to which the present invention has been applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-magnetic substrate 11 Base film 2 Stamper 3 Photopolymer layer 31 Groove 10 Magnetic disk substrate 5 Magnetic disk 14 Magnetic layer

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

Claims (10)

[Claims] 1. A magnetic disk substrate having a photopolymer layer formed on a non-magnetic substrate and grooves formed in the photopolymer layer, wherein the photopolymer layer is formed on the non-magnetic substrate with an underlying film interposed therebetween. Substrate for magnetic disk. 2. The magnetic disk substrate according to claim 1, which is a flexible substrate. 3. The undercoat film is a resin film of at least one selected from thermosetting resins, ultraviolet curable resins, and electron beam curable resins having a glass transition temperature of 30 ° C. or lower. Substrates for magnetic disks. 4. The magnetic disk substrate according to claim 3, wherein the resin film has a thickness of 2 to 10 μm. 5. The magnetic disk substrate according to claim 1, wherein the base film is a plasma polymerized film. 6. The magnetic disk substrate according to claim 5, wherein the plasma-polymerized film has a refractive index of 1.7 or less. 7. The magnetic disk substrate according to claim 5, wherein the plasma-polymerized film contains C and H. 8. The thickness of the plasma polymerized film is 50 to 30.
The magnetic disk substrate according to claim 5, which has a thickness of 0 μm. 9. The photopolymer layer has a thickness of 15 to 4
The magnetic disk substrate according to claim 1, which has a thickness of 0 μm. 10. The magnetic disk substrate according to claim 1, which is used to obtain a magnetic disk having a continuous thin film magnetic layer formed on the groove forming surface.