JPH0737235A - Substrate of magnetic recording medium and magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a low-cost magnetic recording medium having a metallic magnetic thin film formed with satisfactory surface properties, excellent in running durability and electromagnetic transducing characteristics and not causing uneven wear of a magnetic head. CONSTITUTION:A masking layer 2 having <=10nm center line average roughness Ra, <=80nm ten-point average roughness Rz, <=150nm max. height Rmax and 0.5-4.0mum thickness is formed on a substrate 1 for a metallic thin film type magnetic recording medium having 5-20nm center line average roughness Ra, 30-450nm ten-point average roughness Rz and 30-450nm max. height Rmax.

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 support applied to a so-called metal thin film type magnetic recording medium in which a magnetic layer is formed by a vacuum thin film forming technique such as a vacuum deposition method and a sputtering method. The present invention relates to a magnetic recording medium.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a powder magnetic material such as an oxide magnetic powder or an alloy magnetic powder on a non-magnetic support is used as a vinyl chloride-vinyl acetate copolymer, polyester resin, urethane resin, polyurethane. A so-called coating type magnetic recording medium, which is prepared by coating and drying a magnetic coating material dispersed in an organic binder such as a resin, is widely used.

On the other hand, with the increasing demand for high-density recording, Co--Ni alloys, Co--Cr alloys, Co--
A so-called metal thin film type magnetic recording medium in which a metal magnetic material such as O is directly deposited on a non-magnetic support by plating or vacuum thin film forming means (vacuum evaporation method, sputtering method, ion plating method, etc.) is proposed. Has been attracting attention. This metal magnetic thin film type magnetic recording medium is not only excellent in coercive force and squareness ratio and excellent in electromagnetic conversion characteristics at short wavelengths, but also because the thickness of the magnetic layer can be made extremely thin, recording demagnetization and reproduction thickness It has a number of advantages such as a very small loss and the fact that it is not necessary to mix the binder, which is a non-magnetic material, in the magnetic layer, so that the packing density of the magnetic material can be increased.

By the way, in such a magnetic recording medium, the surface properties of the magnetic layer largely influence the electromagnetic conversion characteristics, the running property, the dropout occurrence frequency, and the like. For example, if the surface of the magnetic layer is too rough, the slidability with respect to a sliding member such as a guide roll or the magnetic head during recording / reproduction will be poor, the electromagnetic conversion characteristics and the running property will be deteriorated, and the frequency of dropout will increase. Durability and recording / reproducing characteristics become insufficient. When the magnetic head is a metal-in-gap type head in which a metal magnetic thin film is arranged particularly near the gap, the head is unevenly worn to induce output attenuation.

Therefore, in the magnetic recording medium, various methods are taken to control the surface property of the magnetic layer, and the film forming conditions of the nonmagnetic support are adjusted to improve the smoothness of the nonmagnetic support. , The filler is internally added to the non-magnetic support,
By controlling the size and density of the filler, it is possible to give an appropriate surface roughness.

That is, when a metal magnetic thin film having a film thickness of, for example, about 0.2 μm is formed on a non-magnetic support, the surface shape of the non-magnetic support is remarkably reflected on the surface of the metal magnetic thin film. Therefore, if the surface roughness of the non-magnetic support is optimized, the metal magnetic thin film formed thereon will also have good surface properties, and magnetic recording excellent in running durability and recording / reproducing characteristics will be achieved. The medium will be obtained.

For example, in a vapor-deposition type magnetic tape in which a metal magnetic thin film is formed by a vacuum vapor deposition method, a center line average roughness of 5 nm, a ten-point average roughness of 39 nm and a maximum height Rmax of 55 nm are obtained by such a control method. A non-magnetic support having a surface roughness lower than that used in a coating type magnetic recording medium, which is adjusted to a certain degree, is mainly used.

[0008]

However, the non-magnetic support having a low surface roughness as described above has a large friction coefficient due to a large contact area with the rolls in sliding contact in the manufacturing process, resulting in poor runnability. The rate of becoming Therefore, there are problems that the yield is low and the manufacturing cost is high.

Therefore, the present invention has been proposed in view of such conventional circumstances, and the surface on which the metal magnetic thin film is formed has a good surface property and the manufacturing cost is low.
An object of the present invention is to provide a support for a magnetic recording medium and a magnetic recording medium which are excellent in running durability and electromagnetic conversion characteristics and can realize an inexpensive magnetic recording medium.

[0010]

In order to achieve the above-mentioned object, the inventors of the present invention have conducted extensive studies, and as a result, controlled the surface roughness on the surface of the non-magnetic support on which the metal magnetic thin film is formed. It has been found that by forming a masking layer for this purpose, a metal magnetic thin film having good surface properties can be formed without using a nonmagnetic support whose surface roughness is so strictly controlled.

The present invention has been completed based on these findings. That is, in the magnetic recording medium support of the present invention, the center line average roughness Ra is 5 to 20 nm, the ten-point average roughness Rz is 30 to 450 nm, and the maximum height Rmax is 30.
Center line average roughness Ra on a non-magnetic support of ˜450.
Is 10 nm or less, the ten-point average roughness Rz is 80 nm or less, the maximum height Rmax is 150 nm or less, and the thickness is 0.5 to 4.
It is characterized in that a masking layer having a thickness of 0 μm is provided.

The masking layer has a particle size of 10 to 500.
It is a layer formed by dispersing a non-magnetic pigment of nm in a binder. Further, the magnetic recording medium of the present invention has a center line average roughness Ra of 5 to 20 nm, a ten-point average roughness Rz of 30 to 450 nm, and a maximum height Rmax of 30.
The center line average roughness Ra is 10 nm or less, the ten-point average roughness Rz is 80 nm or less, the maximum height Rmax is 150 nm or less, and the thickness is 0.5 on the non-magnetic support having a thickness of ˜450 nm.
It is characterized in that a metal magnetic thin film is formed on a magnetic recording medium support having a masking layer having a thickness of up to 4.0 μm.

Further, the masking layer has a particle size of 10 to 50.
It is a layer formed by dispersing a 0 nm non-magnetic pigment in a binder.

The centerline average roughness Ra, the ten-point average roughness Rz, and the maximum height Rmax are all three-dimensional centerline average roughness SRa, three-dimensional ten-point average roughness SRz, and three-dimensional maximum height. The value measured as SRmax.

The magnetic recording medium support of the present invention is applied to a so-called metal thin film type magnetic recording medium in which a magnetic layer is formed by directly depositing a metal magnetic material on the support by a vacuum thin film forming technique. It is what is done. This magnetic recording medium support is constructed by forming a masking layer for controlling the surface roughness on a non-magnetic support.

The masking layer formed to control the surface roughness is obtained by coating a non-magnetic support with a masking layer coating material obtained by dispersing and kneading non-magnetic fine particles and a binder in an organic solvent. It is what is formed.

The non-magnetic fine particles are preferably spherical particles such as colloidal silica and ultrafine metal particles.
Carbon (eg carbon black), hematite,
Mica, magnesium oxide, zinc sulfide, tungsten carbide, boron nitride, starch, zinc oxide, kaolin, talc, clay, lead sulfate, barium carbonate, calcium carbonate, magnesium carbonate, boehmite (γ-Al ₂ O ₃ · H)
₂ O), alumina, tungsten sulfide, titanium oxide, polytetrafluoroethylene powder, polyethylene powder, polyvinyl chloride powder and the like. These may be used alone or in combination of two or more. The non-magnetic fine particles have an average particle diameter of 10 to 500 nm, more preferably 60 to 400 nm.
In addition, it is desirable to use a material having a particle size slightly larger than that in the case where the surface roughness is controlled by internally adding to the non-magnetic support itself. However, when non-magnetic fine particles having a particle size exceeding 500 nm are used, the electromagnetic conversion characteristics of the magnetic recording medium may be deteriorated. Further, non-magnetic particles having a particle size of less than 10 nm are not suitable because it is difficult to produce them industrially stably.

As the binder for dispersing the non-magnetic particles, acrylic ester latex and synthetic rubber latex are preferable, and vinyl chloride-vinyl acetate copolymer,
Vinyl chloride-vinyl acetate-vinyl alcohol copolymer,
Vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic acid ester-styrene Copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, butadiene-acrylonitrile-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene- Butadiene copolymer, polyester resin, phenol resin, epoxy resin, thermosetting polyurethane resin, urea resin, melamine resin, alkyd resin, urea-formaldehyde resin or mixtures thereof And the like. Of these, polyurethane resins, polyester resins, and acrylonitrile-butadiene copolymers are preferable because they can impart flexibility.
Further, as the binder, those resins may be crosslinked with an isocyanate compound to improve durability, or those having an appropriate polar group introduced.

Examples of the organic solvent for the non-magnetic fine particles and the binder include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexane, methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ester and the like. Ester solvent, glycol dimethyl ether, glycol monoethyl ether,
Glycol ether solvent such as dioxane, benzene,
Examples thereof include aromatic hydrocarbon solvents such as toluene and xylene, and organic chlorine compound solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene.

On the other hand, as a non-magnetic support to which a coating material prepared by dispersing and kneading these non-magnetic fine particles and a binder in an organic solvent is applied, the center line average roughness Ra is 5 to 20 nm and the ten-point average roughness is Rz is 30 to 450 nm, maximum height Rmax
Of 30 to 450 nm, which has a higher surface roughness and a lower grade than those conventionally used in metal magnetic thin film type magnetic tapes. When the above-mentioned coating material for masking is applied to the surface of such a non-magnetic support on which the metal magnetic thin film is formed, the non-magnetic fine particles added internally to the masking layer impart an appropriate roughness to the surface of the non-magnetic support. The projections and irregularities called fish eyes are masked. The center line average roughness Ra is 10
nm or less, a ten-point average roughness Rz of 80 nm or less, and a maximum height Rmax of 150 nm or less are formed,
A support comparable to the non-magnetic support one grade above will be obtained.

Center line average roughness Ra, ten-point average roughness Rz,
When a non-magnetic support having a low surface roughness and a high grade such that the maximum height Rmax falls below the above range is used, the magnetic recording medium becomes expensive. In the case of a support in which a masking layer is formed on a low non-magnetic support, the non-magnetic support is less likely to cause poor running in the manufacturing process and the yield is good, and the formation of the masking layer hardly leads to an increase in manufacturing cost. Low. Therefore, by using such a support, an inexpensive magnetic recording medium having a good magnetic layer surface can be realized. A non-magnetic support having a surface roughness below the above range is expensive and at the same time has a too smooth surface, so that the masking layer is difficult to fix and is not suitable for controlling the surface roughness by the masking layer. On the other hand, a non-magnetic support whose surface roughness exceeds the above range is inexpensive,
The surface roughness is too rough, and even if a masking layer is formed, the roughness cannot be kept within a practical range, and the electromagnetic conversion characteristics of the magnetic recording medium are deteriorated. The non-magnetic support more preferably has a center line average roughness Ra of 5 to 10 nm and a ten-point average roughness Rz of 30 to 25.
It is desirable to use 0 nm and a maximum height Rmax of 30 to 250 nm.

In order to apply the above-mentioned coating material for the masking layer to such a non-magnetic support, a general continuous winding type gravure coater may be used. The masking layer is formed by applying a masking paint on the non-magnetic support with this continuous winding gravure coater and drying. At this time, in order to improve the surface property of the masking layer, it is preferable to set the molecular weight of the binder used in the masking layer and the glass transition point to be high. In addition, after the drying step, calendering may be performed to flatten the surface.

When forming a masking layer on such a non-magnetic support, the film thickness is 0.5 to 4.0.
μm, and more preferably 0.5 to 3.0 μm. If the thickness of the masking layer is less than 0.5 μm, the effect of controlling the surface roughness by the masking layer cannot be sufficiently obtained. When the film thickness of the masking layer exceeds 4 μm, the total thickness of the medium becomes too thick, which is disadvantageous in the case of thinning, and at the same time, unevenness in thickness occurs during coating to cause surface deterioration such as waviness and electromagnetic conversion characteristics. Will be insufficient.

The magnetic recording medium of the present invention is constructed by forming a metal magnetic thin film serving as a magnetic layer on the above support.

As the metal magnetic material used for the metal magnetic thin film, any of those usually used in metal magnetic thin film type magnetic recording media can be used. For example, ferromagnetic metals such as Fe, Co and Ni, Fe-Co,
Co-Ni, Fe-Co-Ni, Fe-Cu, Co-C
u, Co-Au, Co-Pt, Mn-Bi, Mn-A
1, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co
Examples include ferromagnetic alloys such as -Cr, Co-Ni-Cr, and Fe-Co-Ni-Cr.

These metal magnetic materials include a vacuum vapor deposition method of evaporating a ferromagnetic metal magnetic material under vacuum to deposit it on a support, an ion plating method of evaporating a ferromagnetic metal material in a discharge, and argon. A thin film is formed by a so-called PVD technique such as a sputtering method in which atoms on the target surface are knocked out by argon ions generated through a glow discharge in an atmosphere containing the main component. The magnetic layer may be either a single layer film or a multi-layer film of a metal magnetic thin film formed by these methods. In order to improve the adhesive force between layers and control the coercive force between the non-magnetic support and the metal magnetic thin film, and also between the metal magnetic thin films when the metal magnetic thin film is a multilayer film. A base layer and an intermediate layer may be provided. Further, the vicinity of the surface of these metal magnetic thin films may be an oxide layer for the purpose of improving corrosion resistance and the like.

When the metal magnetic material is deposited on the support provided with the masking layer by the above-described method, the metal magnetic thin film is formed with good surface property reflecting the surface shape of the support, which is inexpensive. And running durability,
It is possible to obtain a magnetic recording medium which has excellent electromagnetic conversion characteristics and which does not cause uneven wear of the magnetic head.

In the magnetic recording medium of the present invention, a protective film is formed on the magnetic layer, or a back coat layer is formed on the surface of the support opposite to the side on which the magnetic layer is formed. It may be.

As the protective film, the following materials are used for the P method such as the vacuum deposition method, the ion plating method and the sputtering method.
VD technology, plasma CVD method, ECR plasma CVD
Method, a thin film formed by a CVD method such as an arc jet plasma CVD method, or the like, is usually formed as a protective film formed in a magnetic recording medium of a metal magnetic thin film type. Materials of the protective film include carbon, CrO ₂ , Al ₂ O ₃ , BN,
Co oxide, MgO, SiO ₂ , Si ₃ O ₄ , Si
_{N x, SiC, SiN x -SiO} 2, ZrO 2, TiO
₂ , oxides such as TiC and ceramics, Cu, Cr, T
i, Zn, Pt, Au, Zr, Al, Sn, Ta, Cr
-Ti, Cr-Zr, Cr-Nb, Cr-Ta, Cr-
Al, Cr-Zr, Cu-Ni, Ni-Mo-Cr-F
Examples thereof include metals such as e and alloys. The protective film may be a single layer film, a composite film, or a composite film in which a plurality of materials are combined.

The back coat layer is also made of non-magnetic powder obtained by dispersing a non-magnetic powder such as carbon black, which is formed in a usual magnetic recording medium, having an antistatic effect and a friction reducing effect in a binder. Good in layers.

Further, in the above magnetic recording medium, an undercoat layer for forming fine projections may be formed on the masking layer, or a layer made of a lubricant, a rust preventive agent or the like may be formed on the top surface. . Any conventionally known material can be used for the materials used for these layers.

[0032]

The center line average roughness Ra is 5 to 20 nm, the ten-point average roughness Rz is 30 to 450 nm, and the maximum height Rmax is 30.
On the non-magnetic support having a relatively high surface roughness of ~ 450 nm, the center line average roughness Ra is 10 nm or less, the ten-point average roughness Rz is 80 nm or less, the maximum height Rmax is 150 nm or less, and the thickness is 0. In the magnetic recording medium support provided with a masking layer having a thickness of 5 to 4.0 μm, the non-magnetic support itself is less likely to cause defective running in the manufacturing process and has a good yield, and the formation of the masking layer also leads to an increase in cost. Manufacturing cost is low because it does not exist. Further, since the surface of the support is made to have a low roughness by a masking layer, when a metal magnetic material is deposited on the masking layer, the metal magnetic thin film reflects the surface shape of the support and has a good surface property. Formed with. Therefore, by using such a support for the magnetic recording medium of the metal magnetic thin film type, it is possible to obtain a magnetic recording medium which is inexpensive, has excellent running durability and electromagnetic conversion characteristics, and does not cause uneven wear of the magnetic head. It will be.

[0033]

EXAMPLES Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

Example 1 In this example, as shown in FIG. 1, a nonmagnetic support P was formed.
Masking layer 2, metal magnetic thin film 3, on ET film 1
A magnetic recording medium in which the protective film 4 was formed and the back coat layer 5 was formed on the surface opposite to the side on which these layers were formed was prepared as follows.

First, a coating material for a masking layer having the following composition was continuously wound on a polyethylene terephthalate (PET) film 1 having a thickness of 10 μm and a width of 150 mm, SRa of 6 nm, SRz of 56 nm and SRmax of 66 nm. It was applied with an arc coater.

Composition of coating material for masking layer Non-magnetic fine particles: 90 parts by weight of colloidal silica having an average particle diameter of 65 nm 10 parts by weight of colloidal silica having an average particle diameter of 250 nm Binder: 100 parts by weight of acrylic ester Organic solvent: coating thickness of ethanol Adjust according to

After drying, it was flattened by calendering to form a masking layer 2 having a film thickness of 0.8 μm to prepare a support. The surface roughness of the masking layer 2 formed at this time has SRa of 3 nm, SRz of 34 nm, and SRm.
ax is 46 nm.

Masking layer 2 thus formed
A metal magnetic thin film 3 having a thickness of 0.2 μm was formed on the above by a vacuum vapor deposition method using a Co ₉₅ —Ni ₅ alloy (subscripts represent% by weight) as a vapor deposition source. The structure of the vapor deposition apparatus used for forming the metal magnetic thin film 3 is shown in FIG.

In the above vapor deposition apparatus, the feed roll 13 and the take-up roll 14 are placed in the vacuum chamber 11 which is evacuated from the exhaust ports 25, 25 provided at the head and the bottom, respectively, and the inside of which is in a vacuum state. It is installed and these feed rolls 1
The tape-shaped support 12 is sequentially run from 3 to the winding roll 14.

A cooling can 15 having a diameter larger than that of each of the rolls 13 and 14 is provided at an intermediate portion where the support 12 runs from the feed roll 13 to the take-up roll 14 side.
Is provided. The cooling can 15 is provided so as to pull out the support 12 downward in the drawing. A cooling device (not shown) is provided inside the cooling can 15 so as to suppress deformation of the support 12 due to temperature rise.

The feed roll 13, the take-up roll 14 and the cooling can 15 are respectively provided in the support member 12.
It has a cylindrical shape having a length substantially the same as the width.

Therefore, the support 12 is sequentially fed from the feed roll 13, moved and run along the peripheral surface of the cooling can 15, and further wound around the winding roll 14 in sequence. ing. Further, between the feed roll 13 and the cooling can 15, and between the cooling can 15 and the take-up roll 14, guide rolls 16 and 17 having a smaller diameter than the rolls 13 and 14 are arranged, respectively. , The feed roll 13 to the cooling can 15, the cooling can 15 to the take-up roll 1
A predetermined tension is applied to the support 12 that travels for four times so that the support 12 can travel smoothly.

A crucible 18 is disposed in the vacuum chamber 11 below the cooling can 15.
A ferromagnetic metal material 19 is filled in the inside 8. The crucible 18 has a width substantially the same as the width of the cooling can 15.

On the other hand, an electron gun 20 for heating and evaporating the ferromagnetic metal material filled in the crucible 18 is attached to the side wall of the vacuum chamber 11. The electron gun 20 is arranged at a position such that the electron beam X emitted from the electron gun 20 irradiates the ferromagnetic metal material 19 in the crucible 18. Then, the ferromagnetic metal material 19 heated and evaporated by the electron gun 20 is vapor-deposited on the support 12 that runs at a constant speed on the peripheral surface of the cooling can 15, and a metal magnetic thin film that is a magnetic layer is formed. It is like this.

The cooling can 15 and the crucible 1 are also provided.
8 and a shutter 23 is provided near the cooling can 15. The shutter 23 is formed so as to cover a predetermined region of the support 12 that runs at a constant speed along the peripheral surface of the cooling can 15, and controls the incident direction of the ferromagnetic metal material 19 on the surface of the support 12. It is done like this. That is, in the evaporated ferromagnetic metal material 19, the minimum incident angle θ ₁ with respect to the surface of the support 12 is regulated by the end of the shutter 23 on the feed roll 13 side, and the predetermined angle range θ _{2 to} θ. ₁ is obliquely evaporated.

Further, during such vapor deposition, oxygen gas is supplied to the vicinity of the surface of the support 12 through an oxygen gas inlet (not shown) provided through the side wall of the vacuum chamber 11. Therefore, the magnetic properties, durability and weather resistance of the obtained metal magnetic thin film are improved.

In this vacuum deposition, the degree of vacuum in the vacuum chamber 1 is maintained at about 1 × 10 ⁻⁴ Torr, and oxygen gas is introduced into the vacuum chamber 1 through the oxygen gas inlet, for example, 2.5 × 10 4. ^-Perform while introducing at a rate of about ⁶ m ³ / sec. In this case, the incident angle of the ferromagnetic metal material 9 with respect to the support 2 is in the range of 45 to 90 °.

The film forming conditions for the metal magnetic thin film are as follows. Deposition conditions of metal magnetic thin film Deposition source: Co ₉₅ -Ni ₅ alloy Incident angle: 45 to 90 ° Tape speed: 0.17 m / sec Film thickness: 0.2 μm Oxygen introduction amount: 3.3 × 10 ^-6 m ³ / Sec Vacuum degree during vapor deposition: 7 × 10 ^-2 Pa

After forming the metal magnetic thin film, a protective film having a thickness of 10 nm was formed on the metal magnetic thin film by a DC magnetron sputtering method using carbon as a target. The conditions for forming the protective film are as follows. Film forming conditions Target protective film: Carbon Sputtering gas: Argon background vacuum degree: 4 × 10 ^- 3 Pa Degree of vacuum during deposition: 2 Pa tape speed: 0.15 m / sec thickness: 10 nm

Then, according to the following composition, each backcoat composition was put into a ball mill and dispersed and mixed for 24 hours, and then a crosslinking agent was added to prepare a backcoat paint. Composition of back coat paint Carbon black: 100 parts by weight Polyurethane resin: 100 parts by weight Then, the adjusted back coat paint is applied to the surface of the PET film opposite to the side where the metal magnetic thin film is formed, and the film thickness is 0. A back coat layer having a thickness of 0.6 μm was formed.

Further, perfluoropolyether was coated on the protective film to form a top coat layer, which was then slit into a width of 8 mm to prepare a magnetic tape.

Examples 2 to 8 PET having the surface roughness shown in Table 1 as a non-magnetic support.
A magnetic tape was produced in the same manner as in Example 1 except that the film was used and the thickness of the masking layer was changed as shown in Table 1. The surface roughness of the formed masking layer is as shown in Table 1.

Examples 9 to 11 As a non-magnetic support, the center line average roughness Ra is 6 nm, the ten-point average roughness Rz is 56 nm, and the maximum height Rmax is 66 nm.
The same as Example 1 except that the PET film was used, the fine particles of the type and particle size shown in Table 2 were used as the non-magnetic fine particles of the masking layer, and the thickness of the masking layer was changed as shown in Table 2. Then, a magnetic tape was produced. The surface roughness of the formed masking layer is as shown in Table 2.

Comparative Example 1 As a non-magnetic support, the center line average roughness Ra is 5 nm, the ten-point average roughness Rz is 39 nm, and the maximum height Rmax is 55 nm.
A magnetic tape was produced in the same manner as in Example 1 except that the PET film of No. 1 was used and no masking layer was formed on the PET film. The PET film used here is a PET film that has been conventionally used for vapor deposition type magnetic tapes.

Comparative Examples 2 and 3 PET having the surface roughness shown in Table 1 as a non-magnetic support.
A magnetic tape was produced in the same manner as in Example 1 except that the film was used and the film thickness of the masking layer was set outside the predetermined range as shown in Table 1. The surface roughness of the formed masking layer is as shown in Table 1.

Comparative Example 4 and Comparative Example 5 A PET film having a surface roughness outside a predetermined range as shown in Table 1 was used as the non-magnetic support, and the film thickness of the masking layer was changed as shown in Table 1. A magnetic tape was produced in the same manner as in Example 1. The surface roughness of the formed masking layer is as shown in Table 1.

Comparative Example 6 As a non-magnetic support, the center line average roughness Ra is 6 nm, the ten-point average roughness Rz is 56 nm, and the maximum height Rmax is 66 nm.
In addition to the above-mentioned PET film, fine particles of the type shown in Table 2 having a particle diameter outside the predetermined range were used as the non-magnetic fine particles of the masking layer, and the thickness of the masking layer was changed to Table 2.
A magnetic tape was produced in the same manner as in Example 1 except that the magnetic tape was changed as shown in FIG. The surface roughness of the formed masking layer is as shown in Table 2.

Comparative Example 7 As a non-magnetic support, the center line average roughness Ra is 6 nm, the ten-point average roughness Rz is 56 nm, and the maximum height Rmax is 66 nm.
In addition to using the PET film as described above, as the non-magnetic fine particles of the masking layer, fine particles having a particle size outside the predetermined range shown in Table 2 are used and the film thickness of the masking layer is also outside the predetermined range as shown in Table 2. A magnetic tape was produced in the same manner as in Example 1 except that the setting was made. The surface roughness of the formed masking layer is as shown in Table 2.

[0059]

[Table 1]

[0060]

[Table 2]

The surface roughness, shuttle durability, and electromagnetic conversion characteristics of the magnetic tapes manufactured as described above were measured.

The surface roughness is 500 at a magnification of 500 using a surface roughness measuring device manufactured by Kosaka Laboratory Ltd. under the trade name of SE-30H.
The measurement was performed under the conditions of 00 times, measurement length 1 mm, and cutoff value 0.08 mm. The shuttle durability is 100 by using a recording / reproducing apparatus (manufactured by Sony Corporation, trade name EV-S900 modified machine) to shuttle a magnetic tape of 2 hours long 100 times.
Measure the output level after running and set the initial output level to 0.
It was evaluated by converting relative values as dB.

The electromagnetic conversion characteristics were evaluated by measuring the output level of the wavelength 0.54 μm signal recorded on the magnetic tape using the recording / reproducing apparatus and converting the output value of Comparative Example 1 to 0 dB to convert it to a relative value. did. The results are shown in Table 3.

[0064]

[Table 3]

First, Examples 1 to 11 and Comparative Examples 2 to 2
When the surface roughness of the non-magnetic support and the surface roughness of the masking layer are compared for Comparative Example 7, the surface roughness of the masking layer is lower than the surface roughness of the non-magnetic support in each case. There is. From this, it is understood that forming the masking layer on the non-magnetic support is effective in masking the irregularities of the non-magnetic support to obtain a support having a small surface roughness.

However, when the thickness of the masking layer is too thin as in Comparative Examples 2, 3, and 7, or is too thick on the contrary, or nonmagnetic as in Comparative Examples 3 and 4. When the surface roughness of the support is too high, or when the particle diameter of the non-magnetic fine particles internally added to the masking layer is too large as 550 nm as in Comparative Examples 6 and 7, the surface roughness of the masking layer is Is not small enough. Therefore, in the magnetic tapes of Comparative Examples 1 to 7, the output value after the shuttle running and the electromagnetic conversion characteristics were the surface roughness of the non-magnetic support, the particle size of the non-magnetic fine particles internally added to the masking layer, The thickness of the masking layer is appropriate, and the masking layer is lower than the magnetic tapes of Examples 1 to 11 in which the masking layer is formed with a small surface roughness, and is below the lower limit of tolerance -3 dB. There is.

From the above, in order to obtain a magnetic tape having sufficient electromagnetic conversion characteristics and durability by forming a masking layer, the surface roughness of the non-magnetic support should be set as follows. The particle size of the non-magnetic particles internally added to the masking layer and the thickness of the masking layer are appropriate, and the masking layer is formed with a sufficiently small surface roughness, that is, the center line average roughness of the non-magnetic support. Ra of 5 to 20 nm and ten-point average roughness Rz of 3
0 to 450 nm, maximum height Rmax is 30 to 450 n
m, the particle size of the non-magnetic fine particles internally added to the masking layer is 10
~ 500 nm, the thickness of the masking layer is 0.5-4.0 n
m, the center line average roughness Ra of the masking layer is 10 nm or less, the ten-point average roughness Rz is 80 nm or less, and the maximum height Rma.
It was found that x needs to be 150 nm or less.

The magnetic tape of Comparative Example 1 was excellent in shuttle durability and electromagnetic conversion characteristics, but was lower in roughness than the magnetic tapes of Examples 1 to 11, and a PET film of high grade was used. Since it is used, manufacturing costs are high.

[0069]

As is apparent from the above description, in the present invention, the center line average roughness Ra of 5 to 20 nm and the ten-point average roughness Rz of 3 are used as the support of the metal thin film type magnetic recording medium.
0-450nm, maximum height Rmax is 30-450nm
On the non-magnetic support having a center line average roughness Ra of 10 n
m or less, ten-point average roughness Rz is 80 nm or less, maximum height R
Since a masking layer having a max of 150 nm or less and a thickness of 0.5 to 4.0 μm is provided,
It is possible to obtain a magnetic recording medium that is inexpensive and has a metal magnetic thin film formed with good surface properties, is excellent in running durability and electromagnetic conversion characteristics, and does not cause uneven wear of the magnetic head.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an essential part showing a structural example of a magnetic recording medium to which the present invention is applied.

FIG. 2 is a schematic diagram showing a vapor deposition device for forming a metal magnetic thin film on a support.

[Explanation of symbols]

 1 ... Support for magnetic recording medium 2 ... Masking layer 3 ... Metal magnetic thin film 4 ... Protective film 5 ... Back coat layer

Claims (4)

[Claims] 1. A center line average roughness Ra of 5 to 20 nm, a ten-point average roughness Rz of 30 to 450 nm, and a maximum height Rmax.
Of 30 to 450 nm on the non-magnetic support, center line average roughness Ra of 10 nm or less, and ten-point average roughness Rz of 80 n.
A support for a magnetic recording medium comprising a masking layer having a maximum height Rmax of 150 nm or less and a thickness of 0.5 to 4.0 μm. 2. The masking layer has a particle size of 10 to 500 nm.
The support for a magnetic recording medium according to claim 1, which is a layer in which the non-magnetic pigment of (1) is dispersed in a binder. 3. A magnetic recording medium comprising the magnetic recording medium support according to claim 1 and a metal magnetic thin film formed thereon. 4. A magnetic recording medium comprising a magnetic recording medium support according to claim 2 and a metal magnetic thin film formed on the support.