JP2670941B2 - Manufacturing method of magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic recording medium comprising a magnetic layer and a non-magnetic support, and more specifically, it improves head wear and contact of a VTR, maintains a high output, The present invention relates to a method for manufacturing a magnetic recording medium having a magnetic layer that suppresses head contamination and has excellent running stability.

[0002]

2. Description of the Related Art Generally, as a magnetic recording medium for audio, video, computer (disk, memory tape), etc., a magnetic layer in which ferromagnetic fine powder is dispersed in a binder is placed on a non-magnetic support. Is used for the magnetic recording medium. In recent years, high density recording is required for these magnetic recording media, and high signal / noise and low noise have been achieved by making fine particles of ferromagnetic fine powder, high packing, and super smoothing of magnetic recording media. ing. Further, in order to perform high-density recording in the same time, it is necessary to reduce the writing speed and the calling speed to the magnetic recording medium, and high-speed transportation of the magnetic recording medium is required. Because of the suitability for high-speed conveyance, runnability, charging characteristics, and head cleaning characteristics are indispensable. For this purpose, carbon black and non-magnetic particles called abrasives having a Mohs hardness of 8 or more are used. In the US
P3630910, USP38333412, USP
4614685, USP 4539257, JP-A-5
No. 9-193533 and the like.

On the surface of the magnetic layer of the magnetic recording medium thus manufactured, powder components (for example, ferromagnetic fine powder, non-magnetic particles such as abrasives) are generally firmly fixed to the magnetic layer film, Considered to be very smooth. However, studies by the present inventors have revealed that the surface of the magnetic layer contains fine protrusions and powder components that are not sufficiently fixed.
These are fine ferromagnetic particles and hard non-magnetic particles such as alumina and chromium oxide added to the magnetic coating material to improve the head cleaning property and having a Mohs hardness of 8 or more are difficult to disperse because they are fine particles or are dispersed. Even if it is left unattended, it tends to reaggregate. When such a magnetic coating that easily agglomerates is applied to a non-magnetic support, a magnetic layer on the surface of which fine protrusions with high Mohs hardness and insufficiently fixed powder components are present is formed. The head wears and deteriorates in a short time.
In addition, such fine protrusions and poorly fixed powder components
It may be detached during traveling and adhere to the magnetic head, causing clogging of the magnetic head and dropout. In addition, minute projections that are detached during running and powder components that are not properly fixed cause detachment of ferromagnetic fine powder on the magnetic layer surface, and the amount of ferromagnetic fine powder near the magnetic layer surface gradually decreases. Therefore, there is also a problem that the electromagnetic conversion characteristics are reduced (output is reduced) by repeating traveling.

In the field of magnetic disks, it is known to perform a burnishing treatment for surface smoothing. For example, a surface smoothing device for a magnetic disk substrate, in which an abrasive tape is continuously supplied to the head slider surface ( Japanese Patent Sho 58-
46768) or a substrate for a magnetic disk, and a varnish head having a rough surface portion formed of an abrasive grain layer containing hard particles on the slider surface is reciprocated in a contact state on the substrate. The surface smoothing method (Japanese Patent Publication No. 58-46767) is also known.

As a method for preventing the occurrence of such clogging and dropout and reducing the output reduction due to repeated running, it is disclosed in, for example, Japanese Patent Laid-Open Nos. 62-172532 and 63-98834. To
A method of manufacturing a magnetic recording medium has been proposed in which powder components that are insufficiently fixed on the surface of the magnetic layer are ground. That is, by varnishing the surface of the calendered magnetic layer with a high hardness grinding tool such as a diamond wheel, a fixed blade or a rotating blade, fine protrusions present on the surface of the magnetic layer and insufficiently fixed powder. It removes body components, deposits, etc., and suppresses clogging, dropout, and output reduction due to long-time running. However, even with the above technique, it has not been possible to sufficiently improve the running durability associated with high-speed transport of the tape, particularly head wear, and VTR compatible output difference and reduction in RF output due to large wear.

[0006]

SUMMARY OF THE INVENTION The present invention reduces head wear, especially head wear at the beginning of tape running, to reduce VTR.
It is an object of the present invention to provide a method of manufacturing a magnetic recording medium having a small compatible output difference and excellent RF output.

[0007]

The above object of the present invention is to provide a magnetic layer containing a ferromagnetic powder, a binder, an additive and an abrasive having a Mohs hardness of 8 or more on a non-magnetic support, and then a polishing tape. In the method of manufacturing a magnetic recording medium for burnishing the surface of a magnetic layer by means of burnishing the surface of a magnetic layer with a polishing tape containing at least one abrasive having a Mohs hardness higher than that of the abrasive contained in the magnetic layer. Can be solved by

That is, the present inventors provided a magnetic layer containing a ferromagnetic powder, a binder, an additive, and an abrasive having a Mohs hardness of 8 or more on a non-magnetic support, and then applied a magnetic tape to the surface of the magnetic layer with an abrasive tape. In a method for producing a magnetic recording medium to be subjected to a nish treatment, head wear is caused by burnishing the surface of the magnetic layer with a polishing tape containing at least one abrasive having a Mohs hardness higher than that of the abrasive contained in the magnetic layer. Head wear at the beginning of running is reduced and V
It was found to be excellent in TR compatible output difference and RF output,
The present invention has been accomplished. In other words, burnishing the surface of the magnetic layer with a polishing tape containing at least one abrasive having a Mohs hardness higher than that of the abrasive contained in the magnetic layer makes it possible to top-cut the abrasive that appears on the surface of the magnetic layer. Further, the binder on the surface of the magnetic layer, which is an effect peculiar to the polishing tape, can be removed, and a remarkable effect of reducing the output is exhibited. With the conventional polishing tape treatment, it was possible to lightly remove those that adhered to the surface of the magnetic layer, but it was not possible to top-cut the abrasive material that was firmly embedded inside and was exposed. As a result, head wear, particularly head wear at the beginning of tape running, could not be reduced. Further, a grinding tool such as a diamond wheel was able to top-cut the abrasive material, but could not remove the binder on the surface of the magnetic layer and could not prevent the output from decreasing. The present invention solves such problems at once.

The magnetic recording medium of the present invention comprises a non-magnetic support, a magnetic layer provided on the support, and a back layer provided on the opposite side of the magnetic layer, if necessary. The magnetic layer is composed of a ferromagnetic fine powder, powdery components such as carbon black, an abrasive, and a powdery lubricant, if necessary, and a binder in which the powdery components are dispersed. The binder is composed of a resin component and a curing agent further blended as required.

The non-magnetic support used in the present invention has a support thickness of 2.5 when used as a tape.
˜100 μm, preferably 3˜70 μm. In the case of a disk or card, the thickness is about 0.03 to 10 mm, and in the case of a drum, it can be used in a cylindrical shape. Materials include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, cellulose triacetate, cellulose diacetate and the like.
In addition to resin derivatives, vinyl resins such as polyvinyl chloride, plastics such as polycarbonate, polyimide, polyamide and polysulfone, metals such as aluminum and copper and ceramics such as glass can be used. Prior to coating, these supports may be subjected to corona discharge treatment, plasma treatment, undercoating treatment, heat treatment, dust removal treatment, metal dusting treatment, and alkali treatment. Regarding these supports, see, for example, West German Patent 3,338,854A, JP-A-59-1169.
26, JP 61-129731 A, U.S. Pat. No. 438.
No. 8368; Yukio Mitsuishi, Textile and Industry, vol. 31, p5
0-55, 1975 and the like. In the case of a video tape or the like, the center line average surface roughness of these supports is 0.
001-0.5 micron (cutoff value 0.25mm)
Is preferred. The Young's modulus (F5 value) of these supports is 2 to 30 kg / m in both the width direction and the longitudinal direction depending on the purpose.
m ² can be selected.

The ferromagnetic fine powder used in the present invention includes γ-Fe2 O3 and Co (deposition, metamorphism, doping).
Γ-Fe2O3, Fe3O4, Co-containing (deposition, metamorphism, dope) Fe3O4, γ-FeOX, Co-containing (deposition, metamorphism, dope) γ-FeOX (X = 1.33 to 1) .5
0), CrO2, Fe-Co alloy, Co-Ni-P alloy, Co-Ni-Fe-B alloy, Fe-Ni-Zn alloy, Ni-Co alloy, Co-Ni-Fe alloy, etc. Powder can be used, specifically, Japanese Patent Publication No.44-14
090, Japanese Patent Publication No. 45-18372, Japanese Patent Publication No. 47-2
2062, Japanese Patent Publication No. 47-22513, Japanese Patent Publication No. 46-
28466, Japanese Patent Publication No. 46-38755, Japanese Patent Publication No. 47
-4286, JP47-12422, JP47
-17284, Japanese Patent Publication No. 47-18509, Japanese Patent Publication No. 4
7-18573, Japanese Patent Publication No. 39-10307, Japanese Patent Publication No. 48-29280, Japanese Patent Publication No. 48-39639, Japanese Patent Publication No. 58-29605, Japanese Patent Publication No. 60-44254, Japanese Unexamined Patent Publication No.
9-126605, U.S. Pat.
No. 31341, No. 3100194, No. 3242005
And No. 3389014. The particle size of these ferromagnetic fine powders is about 0.005 to 1 micron, and the ratio of axial length / axial width is about 1/1 to 50/1. The specific surface area of these ferromagnetic fine powders is 1 to 8
0m more preferably ² / g ^{20~70m 2} / g, coercive force (Hc) can be controlled 250～3000Oe, water content 0.1
2.0% by weight, PH 3 to 11 (5 g magnetic material / 100 g
Water). The surface treatment agent, dispersant, lubricant, antistatic agent, etc., which will be described later, may be impregnated in a solvent and adsorbed on the surface of each of these ferromagnetic fine powders for each purpose. The magnetic recording medium of the present invention has a magnetic layer in which these ferromagnetic fine powders are dispersed in a binder on a non-magnetic support. In addition, elements other than those described in amounts of 10000 ppm or less (Sr, Pb, Mn, Cd, Al,
Si, Na, Ca, K, Ti, Cu, Zn, S, etc.) for improving magnetic properties or as an impurity. In particular, the metal ferromagnetic fine powder contains Al and Si compounds as sintering inhibitors on the surface of the particles, and the amount thereof is 1 to 10% by weight of the metal component.

As the ferromagnetic fine powder used in the present invention, plate-like hexagonal barium ferrite, modified barium ferrite, modified strontium ferrite and the like can be used. The particle size of barium ferrite is about 0.
The diameter is 001 to 1 micron and the thickness is 1/2 to 1/1 of the diameter.
Twenty. The specific gravity of barium ferrite is 4-6g / c
In c, a specific surface area of 1m ² / g~70m ² / g. These barium ferrites may contain rare earth elements in an amount of 10 if necessary.
It is contained in an amount of not more than wt% and contains other alkali metals and alkaline earth metals for improving magnetic properties or as impurities. The surface of these ferromagnetic fine powders may be impregnated with a dispersant, a lubricant, an antistatic agent and the like described below in a solvent prior to dispersion and adsorbed for each purpose.

The present invention is particularly effective when a ferromagnetic alloy powder containing iron, cobalt or nickel is used. Its specific surface area is 40 m ² / g or more and its coercive force is 8
00-3000 Oe, more preferably 1300-180
It is preferable to use a ferromagnetic alloy powder of 0 Oe or more as the ferromagnetic powder. As a detailed example of this ferromagnetic alloy powder, the metal content in the ferromagnetic alloy powder is 60% by weight or more, and 70% by weight or more of the metal content is at least one kind of ferromagnetic metal or alloy (eg Fe , Co, Ni, F
e-Co, Fe-Ni, Co-Ni, Co-Ni-F
e), and other components (eg, Al, Si, 40% by weight or less, more preferably 20% by weight) of the metal content.
S, Sc, Ti, V, Cr, Mn, Cu, Zn, Y, M
o, Rh, Pd, Ag, Sn, Sb, Te, Ba, T
a, W, Re, Au, Hg, Pb, Bi, La, Ce,
Pr, Nd, B, P) may be included in the alloy, iron nitride, iron carbide, and the like. Further, the above-mentioned ferromagnetic metal is a small amount of water, hydroxide or oxide, alkali metal element (Na, K, etc.), alkaline earth metal element (Mg, C).
a, Sr). Methods for producing these ferromagnetic metal powders are already known, and ferromagnetic alloy powders, which are typical examples of the ferromagnetic powder used in the present invention, can be produced according to these known methods.

That is, the following method can be given as an example of the method for producing the ferromagnetic alloy fine powder. (A) a method of reducing a complex organic acid salt (mainly oxalate) with a reducing gas such as hydrogen; and (b) reducing iron oxide with a reducing gas such as hydrogen to obtain Fe or Fe—Co particles. (C) a method of thermally decomposing a metal carbonyl compound, (d) a method of reducing by adding a reducing agent such as sodium borohydride, hypophosphite or hydrazine to an aqueous solution of a ferromagnetic metal, and (e). A method for separating ferromagnetic metal powder from mercury after electrolytic fermentation using a mercury cathode,
(F) Method for obtaining fine powder by evaporating metal in a low pressure inert gas

When the ferromagnetic fine powder is used, its shape is not particularly limited, but is usually needle-like, granular, dice-like,
Rice granules and plates are used. The specific surface area (S-bet) of this ferromagnetic alloy powder is preferably 40 m ² / g or more, and more preferably 45 m ² / g or more. Further, σs of these ferromagnetic materials is preferably 100 to 200 emu / g. The crystallite size is preferably 150 to 300A. Examples of these ferromagnetic alloy fine powders are described in JP-A-53-70397 and JP-A-5-70397.
8-119609, JP-A-58-130435, JP-A-59-80901, JP-A-59-16903,
JP-A-59-41453, JP-B-61-37761.
No. 4,447,264, US Pat.
No. 1 and U.S. Pat. No. 4,931,198.

The resin component of the binder used in the magnetic layer and the back layer of the present invention is a conventionally known thermoplastic resin, thermosetting resin, reactive resin, electron beam curable resin, ultraviolet curable resin, visible resin. Light curable resins and mixtures of these are used. The thermoplastic resin has a softening temperature of 150 ° C. or lower, an average molecular weight of 10,000 to 300,000, and a polymerization degree of about 50 to 2000, and more preferably 200 to
It is about 600, for example, vinyl chloride vinyl acetate copolymer, vinyl chloride copolymer, vinyl chloride vinyl acetate vinyl alcohol copolymer, vinyl chloride vinyl alcohol copolymer, vinyl chloride vinylidene chloride copolymer, vinyl acrylonitrile copolymer. Polymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer Polymers, urethane elastomers, nylon-silicone resins, nitrocellulosic-polyamide resins, polyvinyl chloride, vinylidene chloride acrylonitrile copolymers, butadiene acrylonitrile copolymers, polyamide resins Polyvinyl butyral - le, cellulose -
Derivatives (cellulosic acetate butyrate, cellulose
Sudiaceteate, cellulose acetate, cellulose propionate, nitrocellulose, ethyl cellulose, methyl cellulose, propyl cellulose, methyl ethyl cellulose, carboxymethyl cellulose, acetyl cellulose, etc. ), Styrene-butadiene copolymer, polyester resin, polycarbonate resin, chlorovinyl ether acrylate copolymer, amino resin, various synthetic rubber thermoplastic resins, and mixtures thereof. Examples of these resins are JP-B-37-687.
No. 7, JP-B 39-12528, JP-B 39-192
82, Japanese Patent Publication No. 40-5349, Japanese Patent Publication No. 40-209
07, Japanese Patent Publication No. 41-9463, Japanese Patent Publication No. 41-140
No. 59, Japanese Patent Publication No. 41-16985, Japanese Patent Publication No. 42-64
No. 28, Japanese Patent Publication No. 42-11621, Japanese Patent Publication No. 43-46
No. 23, JP-B-43-15206, JP-B-44-28
No. 89, Japanese Patent Publication No. 44-17947, Japanese Patent Publication No. 44-18
No. 232, Japanese Patent Publication No. 45-14020, Japanese Patent Publication No. 45-1
No. 4500, Japanese Patent Publication No. 47-18573, Japanese Patent Publication No. 47-
22063, Japanese Patent Publication No. 47-22064, Japanese Patent Publication No. 47
-22068, Japanese Patent Publication No. 47-22069, Japanese Patent Publication No. 4
7-22070, JP-B-47-27886, JP-A-57-133521, JP-A-58-137133, JP-A-58-166533, JP-A-58-222433, JP-A-59-58642, etc. No. 4571364,
This is described in U.S. Pat. No. 4,752,530.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating solution, and by heating and humidifying after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. . Further, among these resins, those which are not softened or melted before the resin is thermally decomposed are preferable. Specifically, for example, phenol resin, phenoxy resin, epoxy resin, polyurethane resin, polyester resin, polyurethane polycarbonate resin, urea resin, melamine resin, alkyd resin,
Silicon resin, acrylic reaction resin (electron beam curable resin), epoxy-polyamide resin, nitrocellulose-melamine resin, high molecular weight polyester resin and isocyanate
A mixture of a toppolymer, a mixture of a methacrylate copolymer and a diisocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, a urea formaldehyde resin, a low molecular weight glycol / high molecular weight geo-polymer.
/ Triphenylmethane triisocyanate mixture,
And polyamine resins, polyimine resins, and mixtures thereof. Examples of these resins are described in JP-B-39-8103.
No., JP-B-40-9779, JP-B-41-7192
No., JP-B-41-8016, JP-B-41-14275
No., JP-B-42-18179, JP-B-43-1208
No. 1, JP-B-44-28023, JP-B-45-145
No. 01, JP-B-45-24902, JP-B-46-13
103, JP-B-47-2265, JP-B-47-2
2066, Japanese Patent Publication No. 47-22067, Japanese Patent Publication No. 47-
22072, JP-B-47-22073, JP-B-47
-28045, JP-B-47-28048, JP-B-4
It is described in publications such as 7-28922. These thermoplastic resins, thermosetting resins, and reactive resins include carboxylic acid (COOM), sulfinic acid, sulfenic acid, sulfonic acid (SO ₃ M), and phosphoric acid (PO (OM)) as functional groups other than the main functional groups. (OM)), phosphonic acid, sulfuric acid (OS
O ₃ M) and acidic groups such as ester groups thereof (M is H, an alkali metal, an alkaline earth metal, a hydrocarbon group),
Amino acids; aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohol, amphoteric groups such as alkyl betaine type, amino groups, imino groups, imide groups, amide groups, etc .; hydroxyl groups, alkoxyl groups, thiol groups , An alkylthio group, a halogen group (F, Cl, Br, I), a silyl group,
It usually contains at least one type of siloxane group, epoxy group, isocyanato group, cyano group, nitrile group, oxo group, acryl group, and phosphine group.
It is preferable to contain 1 × 10 ⁻⁶ eq to 1 × 10 ⁻² eq per g.

As the curing agent, a polyisocyanate compound is usually used. Examples of the polyisocyanate compound used in the magnetic layer and / or the back layer of the present invention include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate. Isocyanates such as naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate and isophorone diisocyanate; Further, a product of the isocyanate and the polyalcohol, a polyisocyanate of 2 to 10 mer formed by the condensation of the isocyanate, and a product of the triisocyanate and the polyurethane, which have a terminal functional group. Is an isocyanate. The average molecular weight of these polyisocyanates is 100 to 20.
000 are preferred. Commercially available trade names of these polyisocyanates are Coronet L, Coronet HL, Coronet 2030, and Coronet 203.
1, Millionate MR, Millionate MTL (manufactured by Nippon Polyurethane Co., Ltd.), Takenet D-102, Takenet D
-110N, Takenet D-200, Takenet D-2
02, Takenate 300S, Takenate 500 (manufactured by Takeda Pharmaceutical Co., Ltd.), Sumidur T-80, Sumidur 44
S, Sumidur PF, Sumidur L, Sumidur N, Desmodur L, Desmodur IL, Desmodur N, Desmodur HL, Desmodur T6
5, Desmodule 15, Desmodule R, Desmodule RF, Desmodule SL, Desmodule Z4
273 (manufactured by Sumitomo Bayer Co., Ltd.) and the like, and these can be used alone or in combination of two or more by utilizing the difference in curing reactivity. Compounds having a hydroxyl group (butanediol, hexanediol, polyurethane having a molecular weight of 1,000 to 10,000, water, etc.), an amino group (monomethylamine, dimethylamine, trimethylamine, etc.) and metal oxides for the purpose of accelerating the curing reaction. A catalyst such as a product catalyst or a catalyst such as iron acetylacetonate can be used in combination. It is desirable that these compounds having a hydroxyl group or an amino group are polyfunctional. These polyisocyanates are preferably used in an amount of 2 to 70 parts by weight, more preferably 5 to 50 parts by weight, per 100 parts by weight of the total amount of the binder resin and the polyisocyanate for both the magnetic layer and the back layer. These examples are described in JP-A-60-131622.
And JP-A-61-74138.

These binders may be used alone or in combination, and other additives may be added. The mixing ratio of the ferromagnetic fine powder and the binder in the magnetic layer is 5 to 300 parts by weight based on 100 parts by weight of the ferromagnetic fine powder. The mixing ratio of the fine powder and the binder in the back layer is 8 to 400 parts by weight with respect to 100 parts by weight of the fine powder.
Used in parts by weight. Additives include carbon black, abrasives, lubricants, dispersants / dispersion aids, fungicides,
Antistatic agents, solvents, etc. are added.

The carbon black used in the magnetic layer and the back layer of the present invention is a furnace for rubber, a thermal for rubber,
Color black, acetylene black and the like can be used. These carbon blacks are used for the purpose of improving the durability of the tape, such as an antistatic agent, a light shielding agent, a friction coefficient adjusting agent, and the like. Specific examples of abbreviations of carbon black in the United States include SAF, ISAF and IISA.
F, T, HAF, SPF, FF, FEF, HMF, GP
F, APF, SRF, MPF, ECF, SCF, CF,
FT, MT, HCC, HCF, MCF, LFF, RCF
And the like, and the US ASTM standard D-1765-82a
Can be used. The carbon black used in the present invention has an average particle size of 5 to 1000 millimicrons (electron microscope), a nitrogen adsorption specific surface area of 1 to 800 m ² / g, and a PH of 4 to 11 (J.
IS standard K-6221-1982 method), dibutyl phthalate (DBP) oil absorption is 10 to 800 ml / 100 g
(JIS standard K-6221-1982 method). The size of the carbon black used in the present invention is 5 to 100 nm for the purpose of lowering the surface electric resistance of the coating film, and 50 when controlling the strength of the coating film.
It uses carbon black of ~ 1000 nm. Further, for the purpose of controlling the surface roughness of the coating film, carbon black of fine particles (less than 100 nm) is smoothed to reduce the spacing loss and roughened to reduce the friction coefficient by roughening. -Bon black (100 nm or more) is used. As described above, the type and amount of carbon black are properly used depending on the purpose required for the magnetic recording medium. Further, these carbon blacks may be used after being surface-treated with a dispersant described later or grafted with a resin. Further, it is also possible to use one in which a part of the surface is graphitized by treating the furnace temperature at the time of producing carbon black at 2000 ° C. or higher. Also, hollow carbon black can be used as a special carbon black. These carbon blacks are preferably used in the magnetic layer in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the ferromagnetic fine powder. In the case of the back layer, resin 10 described later
It is desirable to use 20 to 400 parts by weight with respect to 0 parts by weight. Carbon black that can be used in the present invention can be referred to, for example, "Carbon Black Handbook", edited by Carbon Black Association (issued in 1971). Examples of these carbon blacks are US Pat. No. 4,539,257,
U.S. Pat. No. 4,614,685, JP-A-61-92424.
And JP-A-61-99927.

The abrasive used in the magnetic layer and the back layer of the present invention is used to improve the durability of the magnetic recording medium and the head cleaning effect of the VTR, and is generally a material having a polishing action or a polishing action. -Alumina,
γ-alumina, α, γ-alumina Fused alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, diamond, α-iron oxide, garnet, emery (main components: corundum and magnetite), garnet ,
Silica, silicon nitride, boron nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, tripoly,
Materials such as diatomaceous earth and dolomite having a Mohs hardness of 6 or more, preferably a Mohs hardness of 8 or more, are used in combinations of 1 to 4 types. As these abrasives, those having an average particle size of 0.005 to 5 μm are used, and particularly preferably 0.01 to 2 μm. In the case of the magnetic layer, these abrasives are added in the range of 0.01 to 20 parts by weight with respect to 100 parts by weight of the ferromagnetic fine powder. Further, in the case of the back layer, it is 0.
It is preferably used in an amount of 01 to 5 parts by weight. Specific examples of these include AKP1 and AKP15 manufactured by Sumitomo Chemical Co., Ltd.
AKP20, AKP30, AKP50, AKP80, H
It50, Hit100, etc. are mentioned. Regarding these, Japanese Patent Publication No. 52-28642 and Japanese Patent Publication No. 49-3940.
No. 2, JP-A-63-98828, US Pat. No. 36877.
25, US Pat. No. 3,078,807, US Pat. No. 3041
196, U.S. Pat. No. 3,293,066, U.S. Pat.
0910, U.S. Pat. No. 3,833,412, U.S. Pat. No. 41
17190, British Patent 1145349, West German Patent 8
No. 53211, etc.

As the powdery lubricant used in the magnetic layer and the back layer of the present invention, graphite, molybdenum disulfide, boron nitride, graphite fluoride, calcium carbonate, barium sulfate, silicon oxide, titanium oxide, zinc oxide, Inorganic fine powder of tin oxide, tungsten disulfide, etc., acrylic styrene resin fine powder, benzoguanamine resin fine powder, melamine resin fine powder, polyolefin resin fine powder, polyester resin fine powder, polyamide resin fine powder, polyimide Resin fine powders such as fine resin powder and polyhooker ethylene resin fine powder. As the organic compound-based lubricant, silicone oil (dialkyl polysiloxane, dialkoxy polysiloxane, phenyl polysiloxane, fluoroalkyl polysiloxane (KF96, KF69 manufactured by Shin-Etsu Chemical Co., Ltd.)
Etc.)), fatty acid modified silicone oil, fluorine alcohol
, Polyolefin (polyethylene wax, polypropylene, etc.), polyglycol (ethylene glycol, polyethylene oxide wax, etc.), tetrafluoroethylene oxide wax, polytetrafluoroglycol
Perfluoroalkyl ether, perfluoro fatty acid, perfluoro fatty acid ester, perfluoroalkyl sulfate, perfluoroalkyl sulfonate, perfluoroalkyl benzene sulfonate, perfluoroalkyl phosphate, etc. And compounds containing silicon, alkyl sulfate, alkyl sulfonate, alkyl phosphonate triester,
Organic acids and organic acid ester compounds such as alkylphosphonic acid monoester, alkylphosphonic acid diester, alkylphosphoric acid ester, and succinic acid ester, triazaindolizine, tetraazaindene, benzotriazole, benzotriazine, benzodiazole, EDTA, etc. Heterocyclic compounds containing nitrogen and sulfur, C10-4
0 monobasic fatty acid and any of monohydric alcohols having 2 to 40 carbon atoms, dihydric alcohols, trivalent alcohols, tetravalent alcohols, and hexavalent alcohols Fatty acid esters composed of at least one or two or more carbon atoms having 10 carbon atoms
Or more monobasic fatty acid and fatty acid ester consisting of monovalent to hexavalent alcohol having 11 to 70 carbon atoms in total with the carbon number of the fatty acid, fatty acid having 8 to 40 carbon atoms or fatty acid Amides, fatty acid alkylamides, and aliphatic alcohols can also be used. Specific examples of these compounds include butyl caprylate, octyl caprylate, ethyl laurate, butyl laurate, octyl laurate, ethyl myristate, butyl myristate, octyl myristate, 2-ethylhexyl myristate, ethyl palmitate. , Butyl palmitate, octyl palmitate, 2-ethylhexyl palmitate, ethyl stearate, butyl stearate, isobutyl stearate,
Octyl stearate, 2-ethylhexyl stearate, amyl stearate, isoamyl stearate, 2-ethyl pentyl stearate, 2-hexyl decyl stearate, isotridecyl stearate, stearic acid amide, alkyl stearate, butoxyethyl stearate, anhydrosorbitan. Monostearate,
Anhydrosorbitan distearate, anhydrosorbitan tristearate, anhydrosorbitan tetrastearate, oleyl oleate, oleyl alcohol
, Lauryl alcohol, montan wax, carnauba wax, etc., which can be used alone or in combination.

As the lubricant used in the present invention, a so-called lubricating oil additive can be used alone or in combination.
Antioxidants known as rust preventives (alkylphenol, benzotriazine, tetraazaindene, sulfamide, guanidine, nucleic acid, pyridine, amine, hydroquinone, metal chelating agents such as EDTA), rust-stopping agent (naphthene) Acid, alkenyl succinic acid, phosphoric acid, dilauryl phosphate, etc.), oiliness agent (rapeseed oil, lauryl alcohol, etc.), extreme pressure agent (dibenzyl sulfide, tricresyl phosphate, tributyl phosphite, etc.) ), Cleaning dispersants, viscosity index improvers, pour point depressants, foaming agents and the like. These lubricants are added in the range of 0.01 to 30 parts by weight based on 100 parts by weight of the binder. About these, Japanese Patent Publication No. 23889/43 and Japanese Patent Publication No.
No. 041, JP-B-48-18482, JP-B-44-1
No. 8221, Japanese Patent Publication No. 47-28043, Japanese Patent Publication No. 57-
56132, JP-A-59-8136, JP-A-59-8
139, JP-A-61-85621, US Pat. No. 342.
3233, U.S. Pat. No. 3470021, U.S. Pat.
92235, U.S. Pat. No. 3,497,411, U.S. Pat.
523086, U.S. Pat. No. 3,625,760, U.S. Pat. No. 3,630,772, U.S. Pat. No. 3,634,253, U.S. Pat. Bulletin (IBM Technical)
Disclosure Bulletin) Vol.
9, No7, p779 (December 1966), ELEKTRONIK 1961 No12,
p380, Handbook of Chemistry, Advanced Edition, p954-967, 19
It is described in 1980 Maruzen Issuance.

Examples of the dispersant and dispersion aid used in the present invention include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid and stearoic acid. -C2-C40 fatty acids such as acid, behenic acid, maleic acid and phthalic acid (R1COOH, R1 is a C1-C3 alkyl group, phenyl group, aralkyl group), alkali metal of the above fatty acids (Li, Na, K, NH ^4+, etc.) or alkaline earth metal (Mg, Ca, Ba, etc.), metal soap composed of Cu, Pb, etc. (copper oleate), fatty acid amide; lecithin (soybean oil lecithin), etc. Is used. In addition, higher alcohols having 4 to 40 carbon atoms (butanol, octyl alcohol, myristyl alcohol, stearyl alcohol) and their sulfates, sulfonic acids, phenylsulfonic acids, and alkylsulfonic acids. Sulfonic acid ester, phosphoric acid monoester, phosphoric acid diester, phosphoric acid triester, alkylphosphonic acid, phenylphosphonic acid, amine compound and the like can also be used. Further, polyethylene glycol, polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid metal salt, sulfosuccinic acid ester and the like can also be used. One or more of these dispersants are usually used, and one dispersant is used in an amount of 0.005 to 100 parts by weight of the binder.
It is added in the range of ２０20 parts by weight. Regarding the method of using these dispersing agents, the dispersing agent may be applied in advance to the surface of the ferromagnetic fine powder or the non-magnetic fine powder, or may be added during the dispersion. Such a compound is disclosed, for example, in JP-B-39-28369, JP-B-44-17945, JP-B-44-18221, JP-B-48-7441, JP-B-48-15001, and JP-B-48-15002. JP-B-48-16363, JP-B-49-39402, US Pat. No. 3,387,993,
No. 3470021 and the like.

The antifungal agent used in the present invention is 2- (4-
Thiazolyl) -benzimidazole, N- (fluorodichloromethylthio) -phthalimide, 10,10'-oxybisphenoxalcin, 2,4,5,6 tetrachloroisophthalonitrile, P-tolyldiiodomethylsulfone, triiodo Examples include allyl alcohol, dihydroacetoacid, mercury phenyloleate, bis (tributyltin oxide), and saltylanilide. Such a substance is described in, for example, "Microbial Disaster and Prevention Technology", Engineering Books, 1972, "Chemistry and Industry", 32, 904 (1979).

Antistatic agents other than carbon black used in the present invention include graphite, modified graphite, carbon black graft polymer, tin oxide-antimony oxide, tin oxide, titanium oxide-tin oxide-antimony oxide,
Nonionic surface activity such as alkylene oxide, glycerin, glycidol, polyhydric alcohol, polyhydric alcohol ester, alkylphenol EO adduct, etc. Agents; higher alkyl amines, cyclic amines, hydantoin derivatives, amidoamines, ester amides, quaternary ammonium salts, pyridine and other heterocycles, cationic surfactants such as phosphoniums or sulfoniums; carboxylic acids, sulfonic acids, phosphonic acids Surfactants containing acidic groups such as carboxylic acid, phosphoric acid, sulfate group, phosphonate ester, phosphate group; amino acids; amphoteric interface such as aminosulfonic acid, sulfuric acid or phosphate ester of amino alcohol, alkyl betaine type, etc. Activators and the like are used. Some examples of surfactant compounds that can be used as an antistatic agent are described in JP-A-60-28025 and U.S. Pat. No. 2,271,623.
No. 2, No. 2240472, No. 2288226, No. 26
No. 76122, No. 2676924, No. 2676975
No. 2691566, No. 2727860, No. 27
No. 30498, No. 2742379, No. 2739891
No. 3068101, No. 3158484, No. 32
No. 01253, No. 3210191, No. 3294540
No. 3415649, No. 3441413, No. 34
42654, 3475174, and 3545974.
, West German Patent Publication (OLS) 1942665, British Patents 1077317 and 1198450, etc.
Ryohei Oda et al., "Synthesis of Surfactants and Their Applications" (Maki Shoten, 1972 Edition); W. Bailey's "Surface Active Agents" (Interscience Publications Coporated 1985 edition);
P. Sisley's "Encyclopedia of Surfactive Agents, Volume 2" (Chemical Publishing Company, 1964 edition); "Surfactant Handbook", 6th edition (Sangyo Tosho Co., Ltd., Dec. 1941) 20 a month
Sun); written by Hideo Marumo, "Antistatic Agent", written books such as Koshobo (1968). These surfactants may be added alone or as a mixture. The amount of the surfactant used in the magnetic recording medium is 0.01 to 10 parts by weight per 100 parts by weight of the ferromagnetic fine powder. The amount used in the back layer is 0.01 to 30 parts by weight per 100 parts by weight of the binder. These are used as antistatic agents, but are sometimes applied for other purposes, such as dispersion, improved magnetic properties, improved lubricity, coating aids, wetting agents, curing accelerators, and dispersion accelerators. In some cases.

The magnetic layer can be formed according to a usual method. For example, the ferromagnetic fine powder and the resin component, and the magnetic layer forming components such as an abrasive and a curing agent, which are blended as necessary, are mixed and dispersed together with a solvent to prepare a magnetic paint, and the magnetic paint is supported by a non-magnetic material. A method of applying it on the body can be used. As the organic solvent used in the dispersion, kneading, and coating of the present invention, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, a ketone system such as tetrahydrofuran, etc. in any ratio; methanol, ethanol, propanol Le, butano
, Isobutyl alcohol, isopropyl alcohol,
Alcohol such as methylcyclohexanol; ester such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate monoethyl ether; diethyl ether, tetrahydrofuran, glycol dimethyl ether -Ether, glycol monoethyl ether, dioxane and other ethers; benzene, toluene, xylene, cresol, chlorobenzene, styrene and other tars (aromatic hydrocarbons); methylene chloride, ethylene chloride, Carbon tetrachloride,
Chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin and dichlorobenzene, N, N-dimethylformaldehyde, hexane and the like can be used. Further, these solvents are usually used in two or more kinds at an arbitrary ratio. 1% by weight
The following amount may contain a trace amount of impurities (polymer of the solvent itself, moisture, raw material components, etc.). These solvents are used in an amount of 100 to 20000 parts by weight based on 100 parts by weight of the total solid content of the magnetic liquid, the back liquid and the undercoat liquid.
The preferred solid content of the magnetic liquid is 10 to 40% by weight.
The solid content of the back liquid is preferably 5 to 20% by weight. Aqueous solvent (water, alcohol,
Acetone etc.) can also be used.

The method of dispersion and kneading is not particularly limited, and the order of addition of each component (resin, powder, lubricant, solvent, etc.),
The addition position during dispersion / kneading, the dispersion temperature (0 to 80 ° C.), and the like can be appropriately set. For preparing magnetic paints and back layer paints, conventional kneaders such as two roll mills, three roll mills, ball mills, pebble mills, tron mills, sand grinders, and Zegva burs (Szegva) are used.
ri) Attritor, high-speed impeller, disperser, high-speed stone mill, high-speed impact mill, disperser, kneader,
High-speed mixer, ribbon blender, coneder, intensive mixer, tumbler, blender, disperser
A screw, a homogenizer, a single-screw extruder, a twin-screw extruder, and an ultrasonic disperser can be used. Usually, a plurality of these dispersing and kneading machines are provided for dispersing and kneading, and the treatment is continuously performed. For details of the kneading and dispersing technique, see C. PATTON (Paint Flow and Pi) "Paint Flow and Pi"
gment Dispersion "(Paint Flow and Pigment Day Spurgeon) 196
4 years, published by John Wiley & Sons (John Willy & Sons), and Shinichi Tanaka, "Industrial Materials," Vol. 25, 37 (1977), and other references cited therein. In order to efficiently promote dispersion and kneading as an auxiliary material for these dispersion and kneading, the equivalent spherical diameter is 10 cm.
Steel balls, steel beads, ceramic beads, glass beads, and organic polymer beads having a diameter of φ to 0.05 mmφ can be used. These materials are not limited to spherical shapes. It is also described in specifications such as U.S. Patent Nos. 2,581,414 and 2,855,156. Also in the present invention, the magnetic coating material and the back layer coating material can be prepared by kneading and dispersing according to the method described in the above-mentioned book or the cited document of the book.

As a method for coating the above-mentioned magnetic recording layer coating liquid and back layer coating liquid on a support, the viscosity of the coating liquid is adjusted to 1 to 20000 centistokes (25 ° C.), and an air doctor is used. Coat, blade coat, air knife coat, squeeze coat, impregnation coat, river roll coat, transfer roll coat, gravure coat, kiss coat, cast coat To, spray-
, Rod coat, forward rotation roll coat, carten coat
, An extrusion coat, a bar coat, etc. can be used, and other methods are also possible, and a detailed explanation of these can be found in "Coating Engineering", pages 253 to 277 (Showa 46.
3.20. Issuance). The order of application of these coating liquids can be arbitrarily selected, and a corona discharge treatment or the like may be performed before application of a desired liquid to improve adhesion to an undercoat layer or a support. Also, if you want to configure the magnetic layer or back layer in multiple layers, simultaneous multilayer coating,
You may perform multilayer coating sequentially. These are described, for example, in JP-A-57-123532 and JP-B-62-3745.
1, JP-A-59-142741, JP-A-5
This is described in the specification of 9-165239.

By such a method, about 1 to 1 is formed on the support.
If necessary, the magnetic liquid applied in a thickness of about 200 μm may be dried in a multi-step manner at 20 to 130 ° C. to immediately dry the magnetic powder in the layer in about 500 to 5000 G in a desired direction (vertical, longitudinal,
Width, random, oblique, etc.), that is, a magnetic field orientation process is performed, and then the formed magnetic layer is formed in an amount of 0.1 to 30.
Dry to a thickness of μm. The transport speed of the support at this time is
Usually, it is performed at 10 m / min to 900 m / min, the drying temperature is controlled at 20 ° C. to 130 ° C. in a plurality of drying zones, and the residual solvent amount of the coating film is 0.1 to 40 mg / m ² .

After drying in this way, the coating layer is optionally subjected to calendering so that the center line average surface roughness of the magnetic layer or the back layer is 0.001 to 0.3 micron (cutoff 0.25 mm). ). For the calendar process, for example, a spar calendar roll is used. By performing the calendering process, the voids generated by the removal of the solvent during drying are reduced and the filling rate of the ferromagnetic fine powder in the magnetic layer is improved, so that a magnetic recording medium with high electromagnetic conversion characteristics can be obtained. .

In the calendering step, when a curing agent is used as a binder-forming component, 90% by weight or more of the curing agent contained in the magnetic layer is usually contained in the magnetic layer in an unreacted state. Therefore, at least 50% by weight (particularly preferably 8%) of the curing agent is subjected to a curing treatment.
It is desirable to carry out the subsequent treatment after the reaction of 0% by weight or more). The curing treatment includes a heat curing treatment and an electron beam curing treatment, and any method can be used in the present invention. The unreacted curing agent contained in the magnetic layer calendered by this curing reaction reacts with a resin component such as a vinyl chloride copolymer and a polyurethane resin to form a three-dimensional network crosslinked structure. To do. The heat treatment process itself is already known, and the heat treatment can be performed according to these methods also in the present invention. For example, the heat treatment is usually performed by setting the heating time to 40 ° C. or higher (preferably within the range of 50 to 80 ° C.) and the heating time to usually 20 hours or longer (preferably 24 hours to 7 days). Further, the process itself of the curing treatment by electron beam irradiation is already known, and the curing treatment can be carried out according to these methods also in the present invention.

The magnetic recording medium thus prepared is cut into a desired shape and then wound on a plastic or metal reel. The cutting can be performed under normal conditions using a normal cutting machine such as a slitter. In the production method of the present invention, the surface of the magnetic layer thus formed, or the surface of the magnetic layer and the surface of the back layer are magnetic recording media (magnetic layer, back layer,
The edge end surface and the base surface) are burnished with a polishing tape. Here, the burnishing process is roughly classified into a polishing process and a grinding process. The polishing treatment is a treatment for polishing the surface of the magnetic layer using a polishing tape or the like to reduce powdery components such as ferromagnetic fine powder easily detached from the surface of the magnetic layer. By grinding the surface of the magnetic layer with a high-hardness grinding tool such as a blade, a diamond wheel, and a rotary blade, the powdery components that are easily desorbed or the deposits on the surface of the magnetic layer are removed, and the magnetic layer This is a treatment for reducing the amount of desorbed substances from the surface.

Normally, the burnishing treatment with a polishing tape is carried out in the lengthwise direction of the laminate of 50 to 200 g / (1/2 inch).
The tension within the range of 60 to 1200 m /
The surface of the magnetic layer is burnished by contacting while traveling at a speed within the range of minutes. At this time, the polishing tape is fed at a speed of 1 to 3 cm / min in the direction opposite to the feeding direction of the laminate. Further, at this time, the burnishing treatment is most advantageously performed by pressing the polishing surface of the polishing tape against the laminated body from the back surface of the polishing tape with the pad and setting the contact angle between the polishing tape and the magnetic layer within the range of 30 to 120 degrees. It can be carried out.

FIG. 1 is a schematic view showing an example of burnishing and wiping steps used in the present invention. As shown in FIG. 1, the laminate is delivered from the delivery roll 1 and polished by the polishing tape 2, and the fixed blade 3
And then wiped with the wiping material 4, and further wound with the winding roll 5 to complete the process. Reference numeral 10 denotes a feed roll that smoothly feeds the laminate. The polishing tape 3 is moved at a speed of 1 to 3 cm / min in a direction opposite to the direction of feeding the laminated body by the rotating roll 8, the polishing tape 3 is pressed by the pad 6 and comes into contact with the magnetic layer surface for burnishing. .

In FIG. 1, there may be two or more polishing points with the polishing tape. When the burnishing is performed not only on the surface of the magnetic layer but also on the surface of the back layer, the same polishing tape is also provided on the opposite side.
The fixed blade 3 for burnishing does not have to be used, and a diamond wheel or a rotating blade can be used instead of the fixed blade. Further, a fixed blade, a diamond wheel, and a rotating blade may be used in combination as needed. Further, when the surface of the backing layer as well as the surface of the magnetic layer is subjected to burnishing treatment, a fixed blade and / or a diamond wheel and a rotating blade are provided on the opposite side.

The wiping member 4 is moved at a speed of 0.5 to 10 cm / min in the direction opposite to the feed direction of the laminate by the rotating roll 9, and the pad 7 holds the wiping member 4 in contact with the surface of the magnetic layer. Perform wiping process. Further, there may be two or more places to be wiped by the wiping material, and when the surface of the backing layer as well as the surface of the magnetic layer is to be wiped off, the same wiping portion as the wiping material is provided on the opposite side. An example of the burnishing treatment is described in JP-A-63-259830.

The hardness of the abrasive material of the polishing tape used in the present invention is such that the Mohs hardness is in the range of 5 to 10, and for example, α-Al ₂ O ₃ , SiO ₂ , Cr ₂ O ₃ and α-Fe _{2 are used.} O ₃ ,
It contains at least one or more abrasives selected from the group consisting of diamond, ZnO ₂ and TiO ₂ . Particularly, in the present invention, it is necessary to include at least one abrasive having a Mohs hardness higher than that of the abrasive contained in the magnetic layer. When the abrasive having a Mohs hardness higher than that of the abrasive contained in the magnetic layer is not included, the burnishing effect is insufficient for the magnetic layer.

The average particle size of the abrasive used in the present invention is usually in the range of 0.05 to 10 μm, preferably 0.1 to 5 μm. To be If it is less than 0.05 μm, polishing may not be effectively performed, while if the average particle size is more than 10 μm, the surface of the magnetic layer may be scratched. Further, the proportion of the abrasive having a hardness higher than that of the abrasive contained in the magnetic layer and used in the present invention with respect to the whole abrasive contained in the polishing tape is in the range of 0.5% by weight to 100% by weight.
If it is less than 0.5% by weight, the polishing may not be effectively performed.

Polyethylene terephthalate (PET) is used as the material for the support of the polishing tape used in the present invention.
Or the like, a film or sheet made of a polyester such as polypropylene, a polyolefin such as polypropylene, a cellulose derivative, a synthetic resin such as a vinyl resin, a polycarbonate, or a polyamide; a nonmagnetic metal foil such as aluminum or copper; a paper or a ceramic sheet. Further, the surface roughness (center line average roughness) Ra of the polishing tape used in the present invention is preferably in the range of 0.07 to 0.9 μm.
The measurement conditions of the surface roughness (center line average roughness) Ra of the polishing tape are as follows. Using the Safcom 400B, 403B, and 404B systems of the centerline average roughness measuring machine, the cutoff value is 0.8 mm, the moving speed is 0.3 mm, and the stylus pressure is 0.
It was measured under the conditions of 07 g, needle diameter 2 μR and range 20K / 0.5.

The polishing tape used in the present invention is manufactured, for example, as follows. The above abrasive is dispersed in a binder, coated on a support, dried and then cut into a predetermined size. As the binder, a thermoplastic resin, a thermosetting resin and a reactive resin are used alone or in combination. The mixing ratio of the abrasive and the binder is within the range of 10 to 200 parts by weight of the binder with respect to 100 parts by weight of the abrasive. Regarding the burnishing method, for example, JP-A-62-172532 and JP-A-63-98834.
No. 5, for example. That is, examples of the grinding tools used include fixed blades, diamond wheels,
And rotating blades.

Here, the fixed blade is a blade whose portion in contact with the surface of the magnetic layer or the back layer to be burnished is made of a substance of high hardness. The Mohs hardness of the blade is preferably 9 or more, but is not particularly limited as long as the protrusion can be removed. Usually, sapphire, alumina, cermet, zirconia (zirconium oxide),
It is made of a material such as silicon nitride, silicon carbide, diamond, or cemented carbide, and has an effect of smoothing and smoothing the protrusions on the surface of the magnetic recording medium. Usually, the contact angle between the fixed blade and the magnetic layer is usually set in the range of 30 to 120 degrees, and 50 to 160 g / (1
/ 2 inch) with a tension within the range of 60 to 12
The surface of the magnetic layer is burnished by contact while traveling at a speed within the range of 00 m / min.

The diamond wheel is a rotating cylindrical grinding tool in which diamond is sintered around the diamond wheel. A diamond wheel usually has a surface grain size of 1
Those within the range of 200 to 5000 are used. If the particle size is lower than 1200, the surface of the magnetic layer may be scratched, while if it is higher than 5000, burnishing may not be effectively performed. Usually, the diamond wheel and the magnetic layer have a peripheral speed of 50 to 1 of the diamond wheel.
In the range of 500 m / min, the contact angle is set in the range of 30 degrees to 270 degrees, and 50 to 160 in the length direction of the laminate.
Giving a tension within the range of g / (1/2 inch) to make the laminated body 6
The surface of the magnetic layer is burnished by contacting while traveling at a speed within the range of 0 to 1200 m / min. Usually, it is preferable to rotate the diamond wheel in a direction opposite to the running direction of the laminate. By rotating in this manner, burnishing can be most advantageously performed.

Further, the rotary blade is a grinding tool composed of a rotary body and at least one blade provided on the outer peripheral portion of the rotary body along the rotation axis of the rotary body. Usually, the rotating blade and the magnetic layer are set such that the rotating speed of the rotating blade is in the range of 300 to 6000 rotations / minute, the contact angle is in the range of 30 degrees to 270 degrees, and 50 in the length direction of the laminate. The surface of the magnetic layer is burnished by applying a tension within the range of 160 g / (1/2 inch) and bringing the laminate into contact while running at a speed within the range of 60 to 1200 m / min. Generally, it is preferable to rotate the rotary blade in a direction opposite to the traveling direction of the laminate. By rotating in this manner, burnishing can be most advantageously performed.

The magnetic layer is brought into contact with the fixed blade, the diamond wheel or the rotating blade at least once. In particular, by adopting a method in which 2 to 5 fixed blades, diamond wheels or rotating blades are arranged and brought into continuous contact with each other, it is possible to manufacture a magnetic recording medium with extremely improved running durability. Furthermore, continuous contact can be achieved by a combination of fixed blades, diamond wheels or rotating blades.

By the burnishing treatment using the above-mentioned polishing tape and the burnishing treatment using a grinding tool such as a fixed blade, a diamond wheel or a rotating blade, the ferromagnetic powder or the abrasive material protruding from the surface of the magnetic layer is removed. Such powdery components, as well as unreacted hardener present on the surface of the magnetic layer, surface deposits (for example, dust in the air adhered to the surface when manufacturing a magnetic recording medium), etc. The surface of the magnetic layer is smoothed by being scraped off together with the binder in the vicinity of the surface (generally, height of 0.01 to 5 μm). When the back layer is also burnished, the desorption of powdery components such as non-magnetic powder is reduced by burnishing the back layer. For example, a magnetic recording medium cut into a tape is wound. Even when used in the state, the powdery component desorbed from the surface of the back layer is less likely to adhere to the surface of the magnetic layer and cause dropout or clogging.

In the wiping treatment of the magnetic recording medium, the surface layer of the magnetic recording medium is made of a non-woven fabric or the like for the purpose of removing dirt and excess lubricant on the surface of the magnetic recording medium.
This is performed by wiping the edge end surface and the base surface on the back side. Examples of such wiping materials include various types of virgin made by Japan Vilene, Toraysee made by Toray, Kuraray WRP series made by Ecseine and Kuraray, and nonwoven fabric made of nylon, nonwoven fabric made of polyester, nonwoven fabric made of rayon, nonwoven fabric made of acrylonitrile, mixed spinning Non-woven fabrics can also be used. In addition, tissue paper, Kimwipe, and the like can be used. These are described, for example, in JP-B-46-39309, JP-B-58-46768, JP-A-56-90429, JP-B-58-46767, JP-A-63-259830, JP-A-1-201824 and the like. Have been. By this wiping treatment, deposits and organic substances on the magnetic layer and / or the back layer are completely removed, and the frequency of dropout or clogging is reduced.

By using the above treatments together,
The effect of the burnishing treatment with the polishing tape can be further enhanced. In particular, it is desirable that the surface burnished with an abrasive tape be burnished with a grinding tool such as a blade and then wiped with a wiping material. However, the order of performing the burnishing process and the wiping process is not limited to the above order.

In the above description, the surface of the magnetic layer or the surface of the magnetic layer and the surface of the back layer are mainly described after cutting the cured laminate, but the present invention is not limited to this order. For example, a method of performing burnishing while cutting or a method of performing burnishing before cutting can be used. Further, since the curing reaction gradually progresses even without performing the curing treatment, the surface of the magnetic layer or the surface of the magnetic layer and the back layer can be subjected to the burnishing treatment with an abrasive tape without performing the curing treatment after the calender treatment. .

These manufacturing methods include the steps of pretreatment / surface treatment of powder, kneading / dispersion, coating / orientation / drying, calender treatment, curing treatment (heat treatment, EB treatment), burnishing treatment, cutting and winding. It is desirable to carry out continuously. These are disclosed, for example, in Japanese Patent Publication No. 40-23625, Japanese Patent Publication No. 39-28368, and Japanese Patent Publication No. 47-38.
No. 802, British Patent No. 1191424, Japanese Patent Publication No. 48
-11336, JP-A-49-53631, JP-A-50-112005, JP-A-51-77303,
JP-B-52-17404, JP-A-60-70532, JP-A-2-265672, and U.S. Pat. No. 3,473.
960, US Pat. No. 4,728,569, US Pat.
No. 46542, and the like. The method disclosed in Japanese Patent Publication No. 41-13181 is considered to be a basic and important technique in this field.

Ferromagnetic fine powder or non-magnetic powder used in the present invention, binder, additive (lubricant, dispersant, antistatic agent, surface treatment agent, carbon black, abrasive, light-shielding agent,
An antioxidant, an antifungal agent, etc., a solvent and a support (which may have an undercoat layer, a back layer, a back undercoat) or a method for producing a magnetic recording medium are described in JP-B-56-26890. You can also refer to what is present.

In the above description, the method of cutting the calendered laminate and then burnishing the surface of the magnetic layer or the surfaces of the magnetic layer and the back layer with a polishing tape was mainly described. The present invention is not limited to this order, and, for example, a method of burnishing while cutting or a method of burnishing before cutting can be used.

Further, since the curing reaction proceeds gradually even if the curing treatment is not carried out, the surface of the magnetic layer or the surface of the magnetic layer and the back layer is burnished with a polishing tape after the calendering treatment without particularly performing the curing treatment. Processing can be performed.

[0054]

EXAMPLES The present invention will be described more specifically with reference to the following examples. It will be readily understood by those who are involved in the art that the components, proportions, order of operation and the like shown herein can be changed without departing from the spirit of the present invention. Therefore, the present invention should not be limited to the following examples. The parts in the examples are parts by weight.

Example 1 (1) of the following magnetic layer composition was placed in a kneader and sufficiently kneaded, then (2) was additionally charged and sufficiently kneaded, and (3) and then (4) were added and mixed before coating. A magnetic paint was prepared by dispersion. After adjusting the viscosity of the obtained magnetic paint, thickness 1
A dry film thickness of 2 μm was applied onto polyethylene terephthalate (Young's modulus in MD direction: 900 kg / mm ² , Young's modulus in TD direction: 700 kg / mm ² ) as a non-magnetic support having a thickness of 0 μm.

Magnetic coating composition (1) Ferromagnetic alloy powder 100 parts (Fe metal powder, Al 5% by weight, specific surface area (S-BET): 55 m ² / g) Phosphoric acid ester (phenyl sulfonic acid) 2 parts Oleic acid 0 1 part Vinyl chloride copolymer resin 8 parts (Nippon Zeon Co., Ltd .: MR110) Polyurethane resin 2 parts (Toyobo Co., Ltd .: UR8600) 2 ethylhexyl palmitate 0.6 parts Cyclohexanone 60 parts Methyl ethyl ketone 80 parts

(2) Carbon black 1 part (Cabot Corporation: Conductex SC) Polyurethane resin 1 part (Toyobo Co., Ltd .: UR8600) Methyl ethyl ketone 10 parts or more Dispersion Abrasive material 13 parts (Sumitomo Chemical Co., Ltd .: HIT55 [ α-Al ₂ O ₃ ]) Vinyl chloride copolymer resin 1 part (manufactured by Nippon Zeon Co., Ltd .: MR110) Cyclohexanone 60 parts Methyl ethyl ketone 40 parts Dispersion above

(3) Polyisocyanate 2 parts (Nippon Polyurethane Co., Ltd .: Coronate 3040) Stearic acid dibutylamide 0.5 part Palmitic acid 0.5 part Butoxyethyl stearate 0.5 part Methyl ethyl ketone 50 parts Toluene 30 Department

The non-magnetic support coated with the magnetic coating is subjected to magnetic field orientation treatment and drying in a state where the magnetic coating is not dried, and then (2) is added to the following back coating composition (1) immediately before coating. The back side of the support coated with magnetic paint has a thickness of 0.6.
It was applied to have a thickness of μm.

Back coating composition (1) Carbon black 97 parts (Cabot: BP800) Carbon black 3 parts (Cancarb: MTCI) α-Al ₂ O ₃ 0.1 part (Sumitomo Chemical Co., Ltd .: HIT55) Barium sulfate 0.1 part (Sumitomo Chemical Co., Ltd .: HIT55) 2-Ethylhexyl stearate 0.5 part Copper oleate 0.1 part Vinyl chloride copolymer resin 50 parts (Nippon Zeon Co., Ltd .: MR110) ) Polyurethane resin 40 parts (manufactured by Toyobo Co., Ltd .: UR8300) Cyclohexanone 200 parts Methyl ethyl ketone 300 parts

(2) Polyisocyanate 20 parts (Nippon Polyurethane Co., Ltd .: Coronate 3040) Methyl ethyl ketone 3500 parts Toluene 200 parts Silicone compound 0.1 parts (Shin-Etsu Chemical Co., Ltd .: KF69)

Further, after drying, calendering is continued at a temperature of 90 ° C., a linear pressure of 350 Kg / cm, and a speed of 200 m /.
This was performed five times at a minimum to produce a laminate comprising a nonmagnetic support, a magnetic layer and a back layer. This laminate is 2 at 60 ℃
After heat treatment for 4 hours to cure the polyisocyanate compound contained in the layered product, slitting into 1/2 inch width, an average particle diameter of 0.1 μm as an abrasive, and 2. to all abrasives. The surface of the magnetic layer was burnished with an abrasive tape (abrasive material: diamond / Cr2O3 / red iron oxide) containing 0% by weight of diamond (Mohs hardness of 10) as follows, and then a wiping material (WRP73 manufactured by Kuraray Co., Ltd.).
A 6 inch video tape was prepared by wiping with 6).

Polishing tape treatment conditions: The polishing tape and the magnetic layer were set at a contact angle of 80 degrees and brought into contact with each other at a tension of 800 g / (1/2 inch) to make the laminated body 60.
The surface of the contact magnetic layer was burnished while traveling at a speed within the range of up to 1200 m / min. The polishing tape is
By the rotating roll, 1.
The polishing tape was moved at a speed of 5 cm / min and pressed from the back surface of the polishing tape by a pad.

Example 2 In Example 1, an abrasive having an average particle size of 0.5 μm,
Abrasive tape containing 2.0% by weight of diamond (Mohs hardness 10) based on the total abrasive (abrasive: diamond /
A 1/2 inch video tape was manufactured in the same manner as in Example 1 except that the burnishing treatment was performed with Cr2O3 / red iron oxide.

Example 3 In Example 1, as an abrasive, an average particle size of 1.0 μm,
Abrasive tape containing 2.0% by weight of diamond (Mohs hardness: 10) based on all abrasives (trade name: MA20000)
[Abrasive material: diamond / Cr2O3 / red iron oxide] A 1/2 inch video tape was produced in the same manner as in Example 1 except that the burnishing treatment was performed using Fuji Photo Film Co., Ltd.

Example 4 In Example 1, an abrasive having an average particle size of 2.0 μm,
Abrasive tape containing 2.0% by weight of diamond (Mohs hardness 10) based on the total abrasive (abrasive: diamond /
A 1/2 inch video tape was manufactured in the same manner as in Example 1 except that the burnishing treatment was performed with Cr2O3 / red iron oxide.

Example 5 In Example 1, as an abrasive, an average particle size of 5.0 μm,
Abrasive tape containing 2.0% by weight of diamond (Mohs hardness 10) based on the total abrasive (abrasive: diamond /
A 1/2 inch video tape was manufactured in the same manner as in Example 1 except that the burnishing treatment was performed with Cr2O3 / red iron oxide.

Example 6 In Example 1, as an abrasive, an average particle size of 5.0 μm,
Abrasive tape containing 0.5% by weight of diamond (Mohs hardness 10) based on the total abrasive (abrasive: diamond /
A 1/2 inch video tape was manufactured in the same manner as in Example 1 except that the burnishing treatment was performed with Cr2O3 / red iron oxide.

Example 7 In Example 1, as an abrasive, an average particle size of 1.0 μm,
Abrasive tape containing 1.0% by weight of diamond (Mohs hardness 10) with respect to the total abrasive (abrasive: diamond /
A 1/2 inch video tape was manufactured in the same manner as in Example 1 except that the burnishing treatment was performed with Cr2O3 / red iron oxide.

Example 8 In Example 1, as an abrasive, an average particle size of 1.0 μm,
Abrasive tape containing 4.0% by weight of diamond (Mohs hardness 10) based on the total abrasive (abrasive: diamond /
A 1/2 inch video tape was manufactured in the same manner as in Example 1 except that the burnishing treatment was performed with Cr2O3 / red iron oxide.

Example 9 In Example 1, an abrasive having an average particle size of 1.0 μm,
1 in the same manner as in Example 1 except that the burnishing treatment was performed with a polishing tape (abrasive: diamond / Cr2O3 / red iron oxide) containing 10.0% by weight of diamond (Mohs hardness 10) with respect to all the abrasives. / 2 inch video tape was manufactured.

Example 10 In Example 1, as an abrasive, an average particle size of 1.0 μm,
1 in the same manner as in Example 1 except that the burnishing treatment was performed using a polishing tape (abrasive: diamond / Cr2O3 / red iron oxide) containing 50.0% by weight of diamond (Mohs hardness 10) with respect to all the abrasives. / 2 inch video tape was manufactured.

Example 11 In Example 1, as an abrasive, an average particle size of 1.0 μm,
1 in the same manner as in Example 1 except that the burnishing treatment was performed using a polishing tape (abrasive: diamond / Cr2O3 / red iron oxide) containing 100.0% by weight of diamond (Mohs hardness 10) with respect to all the abrasives. / 2 inch video tape was manufactured.

Example 12 In Example 3, the abrasive had an average particle size of 1.0 μm,
Abrasive tape containing 2.0% by weight of diamond (Mohs hardness: 10) based on all abrasives (trade name: MA20000)
Abrasive material: Diamond / Cr2O3 / Bengala After burnishing with Fuji Photo Film Co., Ltd.,
A 1 / 2-inch video tape was manufactured in the same manner as in Example 1 except that the surface of the magnetic layer was burnished with a sapphire blade by the following method.

Sapphire blade treatment A sapphire blade made of sapphire and having a tip angle of 60 degrees (width 5 mm, length 35 mm: Kyocera Corp.)
Manufactured) and the magnetic layer with a contact angle of 80 degrees and a tension of 80 g / (1 /
The magnetic layer was burnished by making contact with each other at a width of 2 inches. The contact between the magnetic layer and the sapphire blade was performed once with a set of four sapphire blades.

Example 13 In Example 3, as an abrasive, the average particle size was 1.0 μm,
Abrasive tape containing 2.0% by weight of diamond (Mohs hardness: 10) based on all abrasives (trade name: MA20000)
Abrasive material: Diamond / Cr2O3 / Bengala After burnishing with Fuji Photo Film Co., Ltd.,
A 1 / 2-inch video tape was manufactured in the same manner as in Example 1 except that the surface of the magnetic layer was burnished with a diamond wheel by the following method.

Diamond Wheel Treatment A diamond wheel (diameter 70 mm, grain size 30) obtained by sintering diamond to a thickness of 2 mm around an iron core material.
No. 00, manufactured by Oriental Diamond Co., Ltd., was rotated at 2000 rpm in the direction opposite to the running direction of the magnetic layer, and the tape was contacted at a contact angle of 180 degrees and a tension of 80 g / (1/2 inch width). The surface of the magnetic layer was burnished. The contact between the magnetic layer and the diamond wheel was performed once.

Example 14 In Example 3, the abrasive had an average particle size of 1.0 μm,
Abrasive tape containing 2.0% by weight of diamond (Mohs hardness: 10) based on all abrasives (trade name: MA20000)
Abrasive material: Diamond / Cr2O3 / Bengala After burnishing with Fuji Photo Film Co., Ltd.,
½ in the same manner as in Example 1 except that the surface of the magnetic layer was burnished with a rotating blade by the following method.
Produced inch video tape.

Rotating blade treatment Sapphire having the shape of an equilateral triangular prism having a length of 35 mm and a cross section of 5 mm on a side around a cylindrical metal (length: 35 mm, diameter: 20 mm, cavity inner diameter: 12 mm). A rotating blade body (blade installation angle θ: 65 degrees) equipped with one blade is rotated at a speed of 1000 revolutions / minute in the direction opposite to the running direction of the magnetic layer to make the tape contact angle 12
The surface of the magnetic layer was burnished by contacting it at 0 degree and a tension of 80 g / (1/2 inch).

Example 15 In Example 3, an abrasive having an average particle size of 1.0 μm,
Abrasive tape containing 2.0% by weight of diamond (Mohs hardness: 10) based on all abrasives (trade name: MA20000)
Abrasive material: Diamond / Cr2O3 / Bengala After burnishing with Fuji Photo Film Co., Ltd.,
A 1/2 inch video tape was manufactured in the same manner as in Example 1 except that the surface of the magnetic layer was subjected to the burnishing treatment with the diamond wheel and the sapphire blade according to the method described below.

Example 16 In Example 1, the abrasive has an average particle size of 1.0 μm,
Abrasive tape containing 2.0% by weight of diamond (Mohs hardness 10) based on the total abrasive (abrasive: diamond /
After the burnishing treatment with Cr2O3), the magnetic layer surface was subjected to the following method in the same manner as in Example 1 except that the magnetic layer surface was subjected to the burnishing treatment with a diamond wheel and a sapphire blade. 1/2
Produced inch video tape.

Comparative Examples 11 to 15 In Examples 11 to 15, abrasive tapes (commodity name: MS20000 Abrasive material: Cr2) made of Cr ₂ O ₃ (Mohs hardness 8) and Al ₂ O ₃ (Mohs hardness 9) were used as the abrasives.
Tapes were produced in the same manner as in Examples 11 to 15 except that the burnishing treatment was performed using O3 / Bengala Fuji Photo Film Co., Ltd.

(Evaluation Method) Initial Head Wear Characteristics The obtained tape was run under a humid condition (25 ° C., 70% RH) with a M2VTR manufactured by Matsushita Electric Industrial Co., Ltd. for 2 rolls of 90 minutes long to measure the wear amount of the VTR head. It was calculated and converted per 100 hours.

VTR compatible output difference The obtained tape was prepared under a humidified condition (25 ° C., 70% RH) by a M2 VTR manufactured by Matsushita Electric Industrial Co., Ltd., and VTRs having different head mounting angles were prepared and recorded and reproduced by one unit. And the output difference when the tape was reproduced on another VTR.

Output Reduction The obtained tape was recorded on a M2VTR manufactured by Matsushita Electric Industrial under low humidity conditions (25 ° C., 10% RH) and then run for 90 minutes to measure the reduction in reproduction RF output.

Table 1 Dyamont Dyamond Initial head VTR compatible Output reduction Polishing tape Abrasive material composition Average particle size Addition amount Abrasion output difference μm wt% μm / 100H dB dB Example 1 Dyamont / Cr ₂ O ₃ / Bengal 0.1 2. 0 7 2 0 2 Diagonal / Cr ₂ O ₃ / Bengal 0.5 0.5 2.0 6 1 1 3 Diagonal / Cr ₂ O ₃ / Bengal 1.0 2.0 5 5 1 1 4 Diagonal / Cr ₂ O ₃ / Bengal 2 0.0 2.0 4 1 1 5 Dirty / Cr ₂ O ₃ / Bengal 5.0 5.0 2.0 4 1 1 6 Dir / Cr ₂ O ₃ / Bengal 1.0 0.5 9 2 0 7 Dir / Cr ₂ O ₃ / Bengal 1.0 1.0 7 1 10 8 Diagonal / Cr ₂ O ₃ / Bengal 1.0 2.0 5 5 1 1 9 Diagonal / Cr ₂ O ₃ / Benka Error 1.0 5.0 4 1 1 10 Diagonal / Cr ₂ O ₃ / Bengal 1.0 1.0 4 4 1 1 11 Diagonal / Cr ₂ O ₃ / Bengal 1.0 1.0 3 3 1 1 12 Diagonal / Cr ₂ O ₃ / Bengal 1.0 1.0 1.0 4 0 1 13 Diagonal / Cr ₂ O ₃ / Bengal 1.0 1.0 4 40 1 14 Diagonal / Cr ₂ O ₃ / Bengal 1.0 1.0 1.0 40 1 15 Dyamont / Cr ₂ O ₃ / Bengala 1.0 1.0 5 5 1 1 16 Diyamont / Cr ₂ O ₃ 1.0 2.0 5 5 1 1 Comparative Example 1 Cr ₂ O ₃ / Bengala − 0 30 <6 − 6 <2 Cr ₂ O ₃ / Bengal − 0 30 <5 − 6 <3 Cr ₂ O ₃ / Bengal − 0 30 <7 − 6 <4 Cr ₂ O ₃ / Bengal − 0 30 <8 − 6 <5 Cr ₂ O ₃ / Bengal 0-30 <5-6 <

The magnetic recording medium of the present invention has reduced head wear, especially head wear at the beginning of tape running, has a small VTR compatible output difference, and exhibits excellent RF output characteristics, as is apparent from the examples of Table 1. ing. In particular, when the burnishing treatment is performed using a polishing tape containing an abrasive having a hardness higher than that of the abrasive contained in the magnetic layer, the head wear can be effectively reduced and the life of the head can be extended. At this time, the VTR compatibility is good and the output is not lowered, so that the present invention has a remarkable effect as compared with the conventional method.

[0088]

As described above, according to the present invention, a magnetic layer containing a ferromagnetic powder, a binder, an additive and an abrasive having a Mohs hardness of 8 or more is provided on a non-magnetic support, and then the magnetic layer is formed by using a polishing tape. In the method of manufacturing a magnetic recording medium in which the surface is burnished, the surface of the magnetic layer is burnished by a polishing tape containing at least one abrasive having a Mohs hardness higher than that of the abrasive contained in the magnetic layer.
It is possible to provide the characteristics of a method for manufacturing a magnetic recording medium that reduces head wear, especially head wear at the beginning of tape running, has a small VTR compatible output difference, and has excellent RF output.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of steps of a polishing process, a grinding process and a wiping process according to the present invention.

[Explanation of symbols]

 1 Feeding roll 2 Polishing tape 3 Fixed blade 4 Wiping material 5 Winding roll 6 Pad (for polishing tape) 7 Pad (for wiping material) 8 Rotating roll (polishing tape) 9) Roll (for wiping material) 10 Feed roll

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Claims (5)

(57) [Claims] 1. A ferromagnetic powder, a binder, and
In a method for producing a magnetic recording medium, wherein a magnetic layer containing an additive and an abrasive having a Mohs hardness of 8 or more is provided, and then the surface of the magnetic layer is burnished by an abrasive tape, the Mohs hardness is higher than that of the abrasive contained in the magnetic layer. A method for producing a magnetic recording medium, characterized in that the surface of the magnetic layer is burnished with an abrasive tape containing at least one or more high abrasives. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the abrasive particles contained in the polishing tape have an average particle diameter in the range of 0.05 to 10 μm. 3. A ratio of the abrasive having a Mohs hardness higher than that of the abrasive contained in the magnetic layer to the entire abrasive contained in the polishing tape is 0.5% by weight or more and 100% by weight or less. A method of manufacturing a magnetic recording medium according to claim 1. 4. The magnetic material according to claim 1, wherein at least one abrasive having a Mohs hardness higher than that of the abrasive contained in the magnetic layer is diamond, and one abrasive is diamond. Recording medium manufacturing method. 5. The surface of the magnetic layer is burnished with an abrasive tape, and then burnished with a fixed blade, a diamond wheel or a rotary blade, and then the magnetic layer is wiped with a wiping material. The method of manufacturing a magnetic recording medium according to claim 1, wherein the method is performed.