JPH08255332A - Support for magnetic recording medium and magnetic recording medium - Google Patents

Abstract

(57) [Summary] [Structure] The center line average roughness Ra1 is 5 to 20 nm and the ten-point average roughness Rz is used as a support for a magnetic recording medium of a metal thin film type.
1 is 30 to 450 nm, maximum height Rmax1 is 30 to 4
On the non-magnetic support 1 having a thickness of 50 nm, the center line average roughness R
a2 is 10 nm or less, ten-point average roughness Rz2 is 80 nm or less, maximum height Rmax2 is 150 nm or less, and thickness is 10
The masking layer 2 having a thickness of 400 nm and formed by a die coating method is used. [Effect] In addition to being inexpensive, the metal magnetic thin film is formed with a good surface property, which is excellent in running durability and electromagnetic conversion characteristics, while suppressing fluctuations in hitting during running and color unevenness in reproduced images. It is possible to obtain a magnetic recording medium that does not cause uneven wear of the head.

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 having a metal magnetic thin film formed by a vacuum vapor deposition method, the center line average roughness Ra is 5 nm, the ten-point average roughness Rz is 39 nm, and the maximum height is high by such 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 have a Rmax of about 55 nm, 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.

In order to solve this, the applicant of the present invention, as disclosed in Japanese Patent Application Laid-Open No. 7-37235, has a surface roughness of 0.5 to 4.0 μm on a non-magnetic support. A proposal has been made for a magnetic recording medium support and a magnetic recording medium provided with a masking layer having a thickness. If a masking layer for controlling the surface roughness is formed on the surface of the non-magnetic support on which the metal magnetic thin film is formed, it is possible to use a non-magnetic support whose surface roughness is not so strictly controlled. A metal magnetic thin film having good surface properties can be formed.

However, the thickness of the masking layer is 0.5 to
The thickness of 4.0 μm is suitable when it is formed by, for example, a gravure coating method, but it is not always suitable when other methods are used. Further, in the gravure coating method, the shape of the gravure roll is likely to affect the surface state of the formed masking layer.

Therefore, the present invention has been proposed in view of the above conventional circumstances, and by forming the masking layer by a die coating method, the surface on which the metal magnetic thin film is formed has a good surface property. It is an object of the present invention to provide a magnetic recording medium support and a magnetic recording medium that can realize an inexpensive magnetic recording medium that is low in manufacturing cost, excellent in running durability, and electromagnetic conversion characteristics.

[0012]

The present invention has been proposed in order to achieve the above-mentioned object, and the magnetic recording medium support according to the present invention has a center line average roughness Ra1 of 5 to 20 n.
m, the ten-point average roughness Rz1 is 30 to 450 nm, the maximum height Rmax1 is 30 to 450 nm, the center line average roughness Ra2 is 10 nm or less, the ten-point average roughness Rz2 is 80 nm or less, Maximum height Rmax2 is 150
A masking layer having a thickness of 0.01 nm or less and a thickness of 0.01 to 0.4 μm is provided.

The centerline average roughness Ra2 on the surface of the masking layer is less than the centerline average roughness Ra1 on the surface of the non-magnetic support, and the ten-point average roughness Rz1 on the surface of the masking layer is nonmagnetic. The ten-point average roughness Rz2 on the surface of the support is less than or equal to, and the maximum height Rmax1 on the surface of the masking layer is less than or equal to the maximum height Rmax2 on the surface of the non-magnetic support.

In the magnetic recording medium support of the present invention, the masking layer is preferably a layer in which a non-magnetic pigment having a particle diameter of 10 to 400 nm is dispersed in a binder.

The masking layer can be obtained by applying a coating material prepared by dispersing and kneading a nonmagnetic pigment and a binder in an organic solvent onto the surface of the nonmagnetic support.

As the non-magnetic pigment, spherical particles such as colloidal silica and ultrafine metal particles are preferable. In addition to these, carbon (for example, 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 Etc. These may be used alone or in combination of two or more.

These non-magnetic pigments have an average particle size of 10 to 400 nm, more preferably 60 to 300 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 a non-magnetic pigment having a particle size of more than 400 nm is used, the particle size is larger than the thickness of the masking layer and the surface property of the masking layer is deteriorated, which may deteriorate the electromagnetic conversion characteristics of the magnetic recording medium. There is. Further, the electromagnetic conversion characteristics are also deteriorated when the height of the protrusions becomes too large due to the relationship between the thickness of the masking layer and the particle size. On the other hand, non-magnetic pigments 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 above non-magnetic pigment, 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 obtained by crosslinking these resins with an isocyanate compound to improve durability or introducing an appropriate polar group may be used.

Examples of the organic solvent include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexane, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ester, glycol dimethyl ether and glycol. Glycol ether solvents such as monoethyl ether and dioxane, aromatic hydrocarbon solvents such as benzene, toluene and xylene, organochlorine compounds such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene. Examples include system solvents.

On the other hand, the non-magnetic support coated with the above-mentioned coating material comprising the non-magnetic pigment, the binder and the organic solvent has the center line average roughness Ra1 of 5 to 20 as described above.
nm, the ten-point average roughness Rz1 is 30 to 450 nm, and the maximum height Rmax1 is 30 to 450 nm. The surface roughness is higher than that of the non-magnetic support conventionally used in the metal magnetic thin film type magnetic tape. It has a low grade. When the above coating material is applied to the surface of such a non-magnetic support on which the metal magnetic thin film is formed to form a masking layer,
While the non-magnetic pigment added internally to the masking layer imparts an appropriate degree of roughness, the projections and irregularities called fish eyes on the surface of the non-magnetic support are masked. Then, on the masking layer surface, the center line average roughness Ra
2 is 10 nm or less, the ten-point average roughness Rz2 is 80 nm or less, and the maximum height Rmax2 is 150 nm or less, so that a support comparable to a non-magnetic support one grade above can be obtained.

Centerline average roughness Ra1, ten-point average roughness Rz
1. If a non-magnetic support having a low surface roughness and a high grade such that the maximum height Rmax1 falls below the above range is used, the magnetic recording medium becomes expensive, but the surface roughness is relatively low. In the case of a support with a masking layer formed on a highly non-magnetic support, the non-magnetic support is less likely to cause defective running in the manufacturing process, yield is good, and formation of the masking layer does not lead to an increase in cost. The cost is 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, but the surface roughness is too rough, and even if a masking layer is formed, the roughness cannot be kept within the practical range, and the magnetic It is also unsuitable because it deteriorates the electromagnetic conversion characteristics of the recording medium. As the non-magnetic support, more preferably, the centerline average roughness Ra1 is 5 to 10 nm, the ten-point average roughness Rz1 is 30 to 250 nm, and the maximum height Rmax1 is 30 to 250.
It is desirable to use nm.

By the way, a gravure coating method can also be applied in order to apply the above-mentioned coating material comprising a non-magnetic pigment, a binder and an organic solvent for forming a masking layer onto a non-magnetic support. It is preferable to apply the die coating method, which can obtain a coating film that is not affected by the shape of the gravure roll.

The masking layer is formed by applying a coating material and then drying it. 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.

Here, the coating material for the masking layer has a film thickness of 10 after drying or calendering.
It is suitable to be applied so as to have a thickness of up to 400 nm, more preferably 100 to 400 nm. If the thickness of the masking layer is less than 10 nm, the effect of controlling the surface roughness by the masking layer cannot be sufficiently obtained. Further, the unevenness of the coating thickness affects the characteristics of the magnetic recording medium. On the other hand, when the film thickness of the masking layer exceeds 400 nm, it becomes difficult to control the coating thickness by the die coating method, and the selection of the binder to be used and the solid content concentration in the coating material are restricted.

The magnetic recording medium according to the present invention is constructed by forming a metal magnetic thin film 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 a metal magnetic thin film type magnetic recording medium 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 method, the metal magnetic thin film is formed with a 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.

The material of the protective film is carbon or CrO.
₂ , Al ₂ O ₃ , BN, Co oxide, MgO, Si
_{O 2, Si 3 O 4,} SiN x, SiC, SiN x -Si
O _2, ZrO _2, oxides or ceramic TiO _2, TiC or the like, Cu, Cr, Ti, Zn , Pt, Au, Zr,
Al, Sn, Ta, Cr-Ti, Cr-Zr, Cr-N
b, Cr-Ta, Cr-Al, Cr-Zr, Cu-N
Metals or alloys such as i and Ni-Mo-Cr-Fe may be mentioned. 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 non-magnetic powder such as carbon black having an antistatic effect and a friction reducing effect, which is formed in a usual magnetic recording medium, in a binder. Good in layers.

Further, in the above magnetic recording medium, an undercoat layer for forming fine protrusions 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.

[0034]

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 10 nm or less. A magnetic recording medium support provided with a masking layer having a thickness of 400 nm is manufactured because the non-magnetic support itself does not easily cause defective running in the manufacturing process and the yield is high, and the formation of the masking layer does not increase the cost so much. The cost is low. 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.

For this reason, the magnetic recording medium constituted by such a support is inexpensive, has excellent running durability and electromagnetic conversion characteristics, and does not cause uneven wear of the magnetic head slidingly contacting the magnetic recording medium. It becomes a medium.

When the masking layer is formed by the die coating method, the shape of the gravure roll does not affect the surface state of the masking layer, unlike the case where the masking layer is formed by the gravure coating method.

Therefore, when the magnetic recording medium having such a masking layer formed thereon is mounted on a video tape recorder as a magnetic tape and played back for reproduction, the variation in hitting is small and the S / N ratio is excellent. Becomes

[0038]

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 masking layer 2, a metal magnetic thin film 3 and a protective film 4 were formed on a non-magnetic support 1 made of a PET film, and these layers were formed. A magnetic recording medium having a back coat layer 5 formed on the surface opposite to the side was prepared as follows.

First, the thickness is 10 μm and the width is 150 mm, SRa1 is 6 nm, SRz1 is 60 nm, and SRma is
Polyethylene terephthalate (PE with x1 of 66 nm)
T) A coating material for a masking layer having the following composition was applied on Film 1 by a die coating method.

Composition of coating material for masking layer Non-magnetic pigment: 90 parts by weight of colloidal silica having an average particle size of 40 nm 10 parts by weight of colloidal silica having an average particle size of 180 nm Binder: 100 parts by weight of acrylic ester Organic solvent: ethanol After that, flatten by drying and calendering,
A masking layer 2 having a film thickness of 400 nm was formed to prepare a support. The surface roughness of the masking layer 2 formed at this time has SRa2 of 5 nm, SRz2 of 39 nm, and SRma.
x2 is 46 nm.

The above-mentioned surface roughness values were measured under the conditions of a magnification of 50,000 times, a measurement length of 1 mm, and a cutoff value of 0.08 mm using a surface roughness measuring device manufactured by Kosaka Laboratory Ltd. under the trade name of SE-30H. It was measured in.

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, a feed roll 13 and a take-up roll 14 are arranged in a vacuum chamber 11 which is evacuated from exhaust ports 25 provided at the head and the bottom, respectively, so that the inside is in a vacuum state. The tape-shaped support 12 is sequentially run from the feed roll 13 toward the winding roll 14.

A cooling can 15 having a diameter larger than that of each of the rolls 13 and 14 is provided in the middle of the traveling of the support 12 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 on 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, respectively, are provided. A predetermined tension is applied to the support 12 which is disposed and runs from the feed roll 13 to the cooling can 15 and from the cooling can 15 to the take-up roll 14 so that the support 12 runs smoothly. Has been done.

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 the metal magnetic thin film 3 that is a magnetic layer is formed. It has become so.

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 characteristics, durability and weather resistance of the obtained metal magnetic thin film 3 are improved.

In this vacuum deposition, the degree of vacuum in the vacuum chamber 1 is maintained at about 1 × 10 ⁻⁴ Torr, and the oxygen gas is introduced into the vacuum chamber 1 from the oxygen gas inlet, for example, 2.5 × 10 5. ^-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 3 are as follows.

Film-forming conditions of magnetic metal 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 3, a protective film 4 having a thickness of 10 nm was formed on the metal magnetic thin film 3 by DC magnetron sputtering using carbon as a target. Was deposited. The conditions for forming the protective film 4 are as follows.

Deposition conditions of protective film Target: Carbon Sputtering gas: Argon Background vacuum degree: 4 × 10 ⁻³ Pa Vacuum degree during film formation: 2 Pa Tape speed: 0.15 m / sec Film thickness: 10 nm In accordance with the composition, each back coat composition was put into a ball mill, dispersed and mixed for 24 hours, and then a cross-linking agent was added to prepare a back coat paint.

Composition of Backcoat Paint Carbon black: 100 parts by weight Polyurethane resin: 100 parts by weight Then, the prepared backcoat paint was applied to the non-magnetic support 1
Was coated on the surface opposite to the side on which the metal magnetic thin film 3 was formed to form a back coat layer 5 having a film thickness of 0.6 μm.

Further, after coating the protective film 4 with perfluoropolyether to form a top coat layer, 8 mm
A magnetic tape was produced by slitting the width. This is the sample tape of Example 1.

The surface roughness (SRa1, SRz1) of the non-magnetic support 1 in the sample tape of Example 1 was measured.
, SRmax1), the thickness of the masking layer 2 and the surface roughness (SRa2, SRz2, SRmax2) are summarized in Table 1.

[0061]

[Table 1]

Examples 2 to 8 PE having the surface roughness shown in Table 1 as the non-magnetic support 1.
Magnetic tapes were produced in the same manner as in Example 1 except that the T film was used and the film thickness of the masking layer 2 was changed as shown in Table 1 to obtain sample tapes of Examples 2 to 8.

The surface roughness of the masking layer 2 in each sample tape is shown in Table 1.

Examples 9 to 11 Other than changing the kind and particle size of the non-magnetic pigment of the masking layer 2 as shown in Table 2 and changing the film thickness of the masking layer 2 as shown in Table 1. A magnetic tape was produced in the same manner as in Example 1 to obtain the sample tapes of Examples 9 to 11.

[0065]

[Table 2]

The surface roughness of the masking layer 2 in each sample tape is shown in Table 1.

Comparative Example 1 A magnetic tape was prepared in the same manner as in Example 1 except that the surface roughness of the non-magnetic support 1 was as shown in Table 1 and the masking layer 2 was not formed. A sample tape of 1 was obtained.

The non-magnetic support 1 used here is a PET film which has been conventionally used for a vapor deposition type magnetic tape.

Comparative Examples 2 and 3 As in Example 1 except that the surface roughness of the non-magnetic support 1 is shown in Table 1 and the thickness of the masking layer 2 was changed as shown in Table 1. Magnetic tapes were produced in the same manner, and sample tapes of Comparative Examples 2 and 3 were obtained.

The surface roughness of the masking layer 2 in each sample tape is shown in Table 1.

Comparative Examples 4 and 5 Other than changing the kind and particle size of the non-magnetic pigment of the masking layer 2 as shown in Table 2 and changing the film thickness of the masking layer 2 as shown in Table 1. A magnetic tape was produced in the same manner as in Example 1 to obtain sample tapes of Comparative Examples 4 and 5.

The surface roughness of the masking layer 2 in the sample tape of Comparative Example 4 is as shown in Table 1. In the sample tape of Comparative Example 5, after the masking layer 2 was formed, carbon particles were severely detached from the masking layer 2, and it was difficult to measure the surface roughness.

Comparative Examples 6 to 9 By coating the non-magnetic support 1 whose surface roughness is shown in Table 1 with the masking layer coating composition having the composition of Example 1 by the gravure coating method, A magnetic tape was produced in the same manner as in Example 1 except that the masking layer 2 was formed to have the film thickness shown in Table 1. Thereby, the sample tapes of Comparative Examples 6 to 9 were obtained.

The surface roughness of the masking layer 2 in each sample tape is as shown in Table 1.

Evaluation of Characteristics With respect to each of the sample tapes manufactured as described above, shuttle durability, electromagnetic conversion characteristics, fluctuation in hitting during running, and color unevenness of reproduced images were evaluated.

Here, the shuttle durability is the output after 100 times of shuttle running a magnetic tape of 2 hours 100 times using a recording / reproducing apparatus (manufactured by Sony Corporation, trade name EV-S900 modified machine). The level was measured and evaluated by converting the initial output level to 0 dB and converting it into a relative value.

The electromagnetic conversion characteristics were obtained by measuring the output level of the 0.54 μm wavelength signal recorded on each sample tape using the recording / reproducing apparatus and converting the output value of Comparative Example 1 to 0 dB to convert it into a relative value. evaluated.

The variation in hitting during running and the color unevenness of the reproduced image are recorded on each of the above sample tapes by a color bar,
While the RF waveform output while running was observed with an oscilloscope, it was confirmed whether or not color unevenness occurred on the monitor screen. The RF waveform and color unevenness described above are
O was evaluated as a level without any problem, Δ is a visually acceptable level, and X was a level with a visually problem. The results of these evaluations are shown in Table 3.

[0079]

[Table 3]

Here, the above-mentioned evaluation results will be considered in light of the surface roughness of the non-magnetic support 1 and the surface roughness of the masking layer 2 of each sample tape.

First, Examples 1 to 11 and Comparative Examples 2 to
Comparing the surface roughness of the non-magnetic support 1 and the surface roughness of the masking layer 2 in Comparative Example 9, the surface roughness of the masking layer 2 is lower in all cases except Comparative Examples 4 to 6. It is lower than the surface roughness of the magnetic support 1. From this, it is understood that forming the masking layer 2 on the non-magnetic support 1 is effective in masking the irregularities of the non-magnetic support 1 to obtain a support having a small surface roughness.

However, as in Comparative Example 6, the masking layer 2
If the thickness is too thin, the effect of lowering the surface roughness cannot be obtained, and even if the particle size of the non-magnetic pigment contained in the masking layer 2 is too large as in Comparative Example 4, the surface roughness is Does not become small enough. That is, these sample tapes were not such that the shuttle durability and electromagnetic conversion characteristics could be measured, and even when they were regenerated and run, they had many dropouts and were not practically usable.

Furthermore, when the particle size of the non-magnetic pigment is too large and the thickness of the masking layer 2 is thin as in Comparative Example 5,
Not only is it difficult to measure the surface roughness of the masking layer 2 because the non-magnetic pigment is severely removed,
The non-magnetic pigment that has fallen off during the metal magnetic thin film deposition process,
Since it adheres to the guide rolls 16 and 17 and the cooling can 15 of the vapor deposition device and causes scratches and heat loss to the metal magnetic thin film,
It was also impossible to evaluate the shuttle durability, the electromagnetic conversion characteristics, the variation in hitting during traveling, and the color unevenness of the reproduced image as described above.

If the masking layer 2 is too thick as in Comparative Example 2, it becomes difficult to control the coating thickness by the die coating method, and the surface condition of the masking layer 2 deteriorates. The hit variation and the color unevenness of the reproduced image are deteriorated.

When the surface roughness of the non-magnetic support 1 itself is too large as in Comparative Examples 3 and 7, even if the masking layer 2 is provided, the surface roughness of the masking layer 2 is reduced. The shuttle characteristics and electromagnetic conversion characteristics are remarkably deteriorated because they are not sufficiently reduced.

Further, when the masking layer 2 was formed by the gravure coating method as in Comparative Examples 6 to 9, variations in hitting during running were confirmed and color unevenness of reproduced images caused by this was also generated. are doing.

On the other hand, the sample tapes of Examples 1 to 11 have sufficient shuttle durability and electromagnetic conversion characteristics, and are free from fluctuations during hitting and deterioration of color unevenness of reproduced images.

From the above results, in order to obtain sufficient shuttle durability and electromagnetic conversion characteristics by forming the masking layer 2 and to prevent hit variation during running and color unevenness of reproduced images, non-magnetic support The surface roughness of the body 1, the particle size of the non-magnetic pigment internally added to the masking layer 2 and the thickness of the masking layer 2 are appropriate, and the masking layer 2 must be formed with a sufficiently small surface roughness. I found out.

That is, the center line average roughness R of the non-magnetic support 1
a1 is 5 to 20 nm and ten-point average roughness Rz1 is 30 to 45
0 nm, the maximum height Rmax1 is 30 to 450 nm, and the particle size of the non-magnetic pigment internally added to the masking layer 2 is 10 to 400.
nm, the thickness of the masking layer 2 is 10 to 400 nm, the center line average roughness Ra2 of the masking layer 2 is 10 nm or less, the ten-point average roughness Rz2 is 80 nm or less, and the maximum height Rmax2.
Has to be 150 nm or less, and it has been found that the masking layer 2 is preferably formed by a die coating method.

The magnetic tape of Comparative Example 1 is excellent in shuttle durability and electromagnetic conversion characteristics, and is free from fluctuations in hitting during running and deterioration of color unevenness of reproduced images. Since a high-grade PET film having a lower surface roughness than that of a magnetic tape is used, the manufacturing cost is high.

[0091]

As is apparent from the above description, in the present invention, the center line average roughness Ra1 is 5 to 20 nm and the ten-point average roughness Rz is used as the support of the metal thin film type magnetic recording medium.
1 is 30 to 450 nm, maximum height Rmax1 is 30 to 4
Center line average roughness Ra on a non-magnetic support having a thickness of 50 nm.
2 is 10 nm or less, ten-point average roughness Rz2 is 80 nm or less, maximum height Rmax2 is 150 nm or less, and thickness is 10 nm.
Since a masking layer having a thickness of up to 400 nm is used, it is inexpensive and the metal magnetic thin film is formed with a good surface property, which is excellent in running durability and electromagnetic conversion characteristics and causes uneven wear of the magnetic head. It is possible to obtain a magnetic recording medium without any problems.

Further, by forming the masking layer by the die coating method, it is possible to suppress variation in hitting and color unevenness during reproduction, so that it is possible to provide a magnetic recording medium of higher quality.

[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 non-magnetic support 2 masking layer 3 metal magnetic thin film 4 protective film 5 back coat layer

Claims (8)

[Claims] 1. A center line average roughness Ra1 of 5 to 20 nm,
Ten-point average roughness Rz1 is 30 to 450 nm, maximum height Rm
On a non-magnetic support having ax1 of 30 to 450 nm, center line average roughness Ra2 is 10 nm or less and ten-point average roughness Rz.
2. A support for a magnetic recording medium, comprising a masking layer having 2 of 80 nm or less, a maximum height Rmax2 of 150 nm or less, and a thickness of 10 to 400 nm. 2. The centerline average roughness Ra2 on the surface of the masking layer is less than or equal to the centerline average roughness Ra1 on the surface of the non-magnetic support, and the ten-point average roughness Rz1 on the surface of the masking layer is non-magnetic support. 2. The magnetic recording according to claim 1, wherein the ten-point average roughness Rz2 on the surface of the body is less than or equal to Rz2, and the maximum height Rmax1 on the surface of the masking layer is less than or equal to the maximum height Rmax2 on the surface of the non-magnetic support. Media support. 3. The masking layer has a particle size of 10 to 400 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. 4. The support for a magnetic recording medium according to claim 1, wherein the masking layer is formed by a die coating method. 5. The center line average roughness Ra1 is 5 to 20 nm,
Ten-point average roughness Rz1 is 30 to 450 nm, maximum height Rm
On a non-magnetic support having ax1 of 30 to 450 nm, center line average roughness Ra2 is 10 nm or less and ten-point average roughness Rz.
2 is 80 nm or less, maximum height Rmax2 is 150 nm or less, and thickness is 10 to 400 nm. A metal magnetic thin film is formed on a magnetic recording medium support provided with a masking layer. Magnetic recording medium. 6. The centerline average roughness Ra2 on the masking layer surface is not more than the centerline average roughness Ra1 on the non-magnetic support surface, and the ten-point average roughness Rz1 on the masking layer surface is nonmagnetic support. 6. The magnetic recording according to claim 5, wherein the ten-point average roughness Rz2 on the surface of the body is not more than Rz2, and the maximum height Rmax1 on the surface of the masking layer is not more than Rmax2 on the surface of the non-magnetic support. Medium. 7. The masking layer has a particle size of 10 to 400 nm.
6. The magnetic recording medium according to claim 5, which is a layer formed by dispersing the non-magnetic pigment of claim 1 in a binder. 8. The magnetic recording medium according to claim 5, wherein the masking layer is formed by a die coating method.