JPH0652541A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which can perform high-output high-packing density recording and has an extremely excellent head wear characteristic and running durability against head contamination, etc. CONSTITUTION:In the magnetic recording medium which has a magnetic layer containing ferromagnetic fine particles, a binder, and abrasive powder of >=8 in Moh's hardness formed on a nonmagnetic substrate, the average projecting height of the abrasive powder in the surface layer of the magnetic layer above the center line of the surface roughness of the magnetic layer to the upper ends of the powder is controlled to <=15nm by performing super-calender treatment by using faced metallic rolls. After the calender treatment, the recording medium is subjected to burnishing treatment.

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 comprising a magnetic layer and a non-magnetic support, and more specifically, it improves head wear and contact of a VTR, maintains high output, The present invention relates to 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 formed on a non-magnetic support. Is used for the magnetic recording medium. Conventionally, these magnetic recording media have been used as a magnetic layer containing ferromagnetic fine powder, a binder, and an abrasive having a Mohs hardness of 8 or more. Of these, the abrasives in particular have suppressed head contamination on the VTR and have always provided the best image, sound and data recording. Various abrasives have been proposed for this purpose, including Japanese Patent Publication No. Sho 39-39402,
JP 57-183628 A, U.S. Pat. No. 3,630,910.
And JP-A-57-179945.
In recent years, high density recording is required for these magnetic recording media,
There are demands for higher reproduction output / noise, lower noise, finer ferromagnetic fine powder, metal powder, higher packing, and thinner magnetic recording media due to ultra-smoothing of the magnetic recording medium surface. . In order to improve recording density and image quality, VTR
In the magnetic recording medium, the writing speed to the magnetic recording medium is shortened, the recording method (analog method to digital method) is changed, the recording width is decreased (5 to 20 nm), and the recording shortest wavelength is decreased (0.1 to 0. 9 μm) is required, and the head cylinder speed is 5400 RP in the helical scan VTR.
M or more, and the relative speed between the tape and the head is 20 m / s
ec is going to be far exceeded. In order to provide the magnetic recording medium with such high output and high-speed sliding suitability, it is essential to secure traveling stability in the VTR traveling system, head and cylinder system. In addition to the abrasives described above, various lubricants such as carbon black and organic compounds are used. A major problem with these magnetic recording media is compatibility with VTR heads. When attempting to achieve thinning and ultra-smoothness for high-density recording, it is extremely difficult to reduce the friction coefficient of the VTR head. The surface layer of the magnetic layer where the coefficient of friction rises is scraped off and the head becomes dirty. For this reason, the abrasive as described above is added to the magnetic layer, but if it is added in an amount that is sufficiently effective against head contamination, head wear increases significantly. When head wear increases, it is proposed to make the head material harder, so that the amount of abrasive in the magnetic layer must be increased again.

That is, in the conventional technique, a magnetic recording medium and a VTR are used.
Effective means for increasing the coefficient of friction with the head has been the addition of abrasives and lubricants. As for the stain on the head of the magnetic recording medium, adding an abrasive to the magnetic layer is effective for the stain on the head. When such an amount is added, the wear of the magnetic recording medium on the VTR head is significantly increased. When head wear increases, it is proposed to make the head material harder, so that the amount of abrasive in the magnetic layer must be increased again. As described above, conventionally, the balance between head wear and head contamination sacrifices either characteristic. Also, in order to reduce the friction coefficient of the VTR head with respect to the output which is lost when trying to achieve thinness and ultra-smoothness for compatibility with the VTR head, that is, high density recording, a lubricant other than the abrasive is used. The addition is done. Addition of a lubricant for reducing the coefficient of friction causes plasticization of the magnetic layer which causes a reduction in output and head contamination. It was also extremely difficult to balance the reduction of friction coefficient and the reduction of output.

Further, it has been proposed to limit the amount of the abrasive present on the surface of the magnetic layer to improve the durability. For example, in Japanese Patent Laid-Open No. 61-57036, abrasive particles having a mohs hardness of 6 or more are contained in an amount of 3 to 15 wt.
%, And the average number of particles per unit area on the surface of the magnetic layer is 0.25 / μm ² or more. In addition, JP-A-60-9
Japanese Patent No. 3631 discloses a magnetic recording medium in which the number of non-magnetic abrasive particles having a mohs hardness of 7 or more is set to 20 or more per 100 μm ² of the magnetic layer surface. However, satisfactory results were not obtained for all items of initial head wear, VTR compatible output difference, and low humidity output.

Further, in Japanese Patent Laid-Open No. 63-183619, a magnetic layer is formed by applying a magnetic layer, drying it, calendering it, and curing it, and then braiding it with edges made of sapphire or diamond. Press on the surface,
Further, a method of manufacturing a magnetic recording medium is disclosed in which the surface of the magnetic layer is polished with a cylindrical diamond grindstone having a particle size of 0.5 to 4 μm. Further, JP-A-3-162717 discloses a method for producing a magnetic recording medium in which a magnetic layer is coated, dried, calendered, and the surface of the obtained magnetic layer is burnished with a cemented carbide blade. There is. However, satisfactory results were not obtained for all items of initial head wear, VTR compatible output difference, and low humidity output.

[0006]

That is, the present invention is
It is an object of the present invention to provide a magnetic recording medium having high output / high density recording and extremely excellent running durability. In particular, it is an object of the present invention to provide a magnetic recording medium having extremely excellent running durability such as head wear characteristics and head dirt.

[0007]

Therefore, the present inventors
Diligently paying attention to the characteristics and shape of the abrasives present on the surface layer
As a result of the examination, the magnetic layer was measured by AFM (atomic force microscope).
The average protrusion height up to the top edge of the abrasive present on the surface is
Major items such as head wear, VTR compatible output difference, low humidity output, etc.
The present invention has been found out that it has a great influence. Sunahachi
The above object of the present invention is to provide a ferromagnetic fine powder on a non-magnetic support.
Magnetic including binder and abrasive with Mohs hardness of 8 or more
In the recording of a magnetic recording medium provided with a layer, the magnetic property of the magnetic layer
It exists above the center line of the layer surface roughness and exists on the surface layer of the magnetic layer.
The average protrusion height to the upper end of the existing abrasive is 15 nm or less.
Achieved by a magnetic recording medium characterized by
Wear. Further, preferably, the abrasive contained in the magnetic layer is
Less selected from Lumina, Chromium oxide, Diamond
According to the magnetic recording medium characterized in that
Can be achieved. That is, the magnetic recording medium of the present invention is non-magnetic.
Ferromagnetic fine powder and binder on the support, Mohs hardness of 8 or more
A magnetic layer containing an abrasive is provided on the surface of the magnetic layer.
Exists above the centerline of roughness and on the surface of the magnetic layer
The average protrusion height up to the upper end of the polishing material should be 15 nm or less.
As a result, VTR head wear is minimal and running durability
A magnetic recording medium excellent in Preferably magnetic
At least one of the abrasives contained in the conductive layer is alumina,
Chromium oxide and diamond with a surface roughness of the magnetic layer of 0.
When 1 nm to 6 nm, VTR head and magnetic recording medium
A magnetic recording medium having excellent body durability can be obtained. Also magnetic
Abrasive present on the surface of the layer is 100 μm ²Around 100
~ 1000 pieces, the abrasive contained in the magnetic layer is ferromagnetic
5 to 20 parts by weight per 100 parts of fine powder, and of the magnetic layer
Specific surface area of ferromagnetic fine powder is 47m ²/ G or more metal powder
Therefore, high output and appropriate polishing ability can be obtained.
In addition, the surface of the non-magnetic support formed by coating the magnetic layer has a rough surface.
By having a back layer having a size of 2 nm to 15 nm.
Excellent running durability is obtained.

The average height of protrusions up to the upper end of the abrasive present in the surface of the magnetic layer above the center line of the surface roughness of the magnetic layer of the magnetic layer of the present invention can be measured as follows. AF
While observing the abrasive present on the surface of the magnetic layer by M (atomic force microscope), the curve of the surface roughness of the magnetic layer and its center line were obtained, and the curve was found above the center line of the surface roughness of the magnetic layer. Moreover, after measuring the average protrusion height to the upper end of the abrasive present on the surface of the magnetic layer and identifying the position of the abrasive present on the surface by a micrograph, the height above the center line of the magnetic layer surface roughness of the magnetic layer Can be confirmed by measuring the average height of protrusions up to the upper end of the abrasive present in the surface layer of the magnetic layer at n = 20. In this case, when the magnetic layer has a multi-layered structure, the average particle size of the abrasive present in the uppermost magnetic layer is suitably 0.1 to 1 μm, and the thickness of the uppermost layer at this time is the average particle size of the abrasive. It may be the following. When the magnetic layer has a single-layer structure, the average particle size of the abrasive present in the magnetic layer is suitably 0.1 to 1 μm, and the thickness of the single layer at this time is not less than the average particle size of the abrasive. preferable. In the present invention, the amount of abrasive added to the magnetic layer is ferromagnetic fine powder 1.
It is preferably 5 to 20 parts by weight per 00 parts by weight. The amount of the abrasive added to the magnetic layer is ferromagnetic fine powder 100.
When the amount is less than 5 parts by weight per part by weight, the average protrusion height of the abrasive existing above the center line of the magnetic layer surface roughness of the magnetic layer is 1
Although it may be possible to achieve 5 nm or less, it is difficult to obtain a sufficient cleaning effect because the addition amount is small. When the amount of the abrasive added to the magnetic layer is 20 parts by weight or more per 100 parts by weight of the ferromagnetic fine powder, the average protrusion height of the abrasive existing above the center line of the magnetic layer surface roughness of the magnetic layer is 15 nm. Over that, a sufficient cleaning effect can be obtained, but the head wear is abnormally increased and it is not suitable as a magnetic recording medium.

That is, the present invention provides a magnetic recording medium comprising a non-magnetic support and a magnetic layer containing ferromagnetic fine powder, a binder and an abrasive having a Mohs hardness of 8 or more. Of the abrasive present above the center line of the magnetic layer and on the surface of the magnetic layer to an average protrusion height of 15 nm or less, a magnetic recording medium with less wear of the VTR head and excellent running durability is obtained. That is what I got. Although it has been known for a long time to use an abrasive for a magnetic recording medium, the height of the abrasive cannot be controlled by the particle size and the addition amount of the conventionally known abrasive. Conventionally, an abrasive having a particle size of about 0.01 to 2 μm is used, and the addition amount is 100 μg of ferromagnetic fine powder.
It is used in an amount of 0.1 to 20 parts by weight per g. As these shapes, a spherical shape, a shape close to a spherical shape, a shape having a corner, and the like have been used. The average protrusion height from the center line of the magnetic layer surface roughness to the upper end of the abrasive present above the center line of the magnetic layer surface roughness of the magnetic layer prepared by the conventional technique and present on the surface layer of the magnetic layer is Since it exceeds 15 nm, wear of the VTR head increases and only a magnetic recording medium having poor running durability can be obtained. If the protrusion height of the abrasive material is high as described above, the VTR head wear increases, and the VTR head life becomes short. Although it is an effective means to reduce the amount of abrasive added in order to reduce the wear of the VTR head,
The cleaning effect on the VTR head of the magnetic recording medium is reduced, and as a result of clogging of the head, the output is reduced and the product has no commercial value.

The protrusion height of the abrasive can be achieved by first using a metal roll as a calender, making the surface of the magnetic layer as smooth as possible (6 nm or less), and then controlling the height of the abrasive by post-treatment. That is, after applying a magnetic layer containing a ferromagnetic fine powder, a binder and an abrasive having a Mohs hardness of 8 or more on a non-magnetic support, a conveying speed is 10 m / min to 900 m /
Min., At a molding temperature of 50 ° C to 130 ° C twice or more, super calendering is performed by a multi-stage opposed metal roll, and then a bar treatment is performed.
The average height of protrusions up to the upper end of the abrasive present on the surface of the magnetic layer can be reduced to 15 nm or less by performing the nishing treatment. Details of the super calendar processing and burnish processing will be described later. At this time, it is preferable that at least one of the abrasives contained in the magnetic layer is alumina, chromium oxide, or diamond. The surface roughness of the magnetic layer was 0.1 nm to 6 nm on a calendar, and a magnetic recording medium excellent in durability of the VTR head and the magnetic recording medium was obtained. At this time, 100% of the abrasive present on the surface of the magnetic layer is removed.
The abrasive contained in the magnetic layer is present in an amount of 5 to ² per 100 parts by weight of the ferromagnetic fine powder.
The specific surface area of the ferromagnetic fine powder of the magnetic layer is 47 parts by weight.
By using a metal powder of m ² / g or more, high output can be achieved due to the super smoothness of the magnetic material, the magnetic layer and the back layer,
Moreover, an appropriate polishing ability is obtained by controlling the projection height of the abrasive and the number of abrasives. The surface roughness of the back layer on the back surface of the non-magnetic support having a magnetic layer is 2
When the thickness is 15 nm to 15 nm, excellent running durability and high CN are obtained. Although the reason is not clear, controlling the height of the abrasive material as in the present invention makes it easy to secure output for different heads. It was also found that the dropout of about 1 μsec and −2 db, which causes a drop in the output, is significantly improved.

The magnetic recording medium of the present invention has a basic structure in which a magnetic layer containing at least ferromagnetic fine powder, a binder and an abrasive is coated on a non-magnetic support. In the magnetic recording medium of the present invention, various solid or liquid lubricants may be contained in the magnetic layer, and a non-magnetic powder (carbon black) is provided on the opposite surface of the non-magnetic support provided with the magnetic layer. , An inorganic powder, an abrasive, a solid lubricant, etc.) and a binder. Furthermore, in the magnetic recording medium of the present invention, in addition to the lubricant in the magnetic layer, a rust preventive, a fungicide,
It may contain an antistatic agent, a non-magnetic powder, a dye, an organic magnetic compound, a dispersant, etc., and may have a mixed layer or a multi-layer structure composed of different or the same magnetic layer of ferromagnetic fine powder.

The ferromagnetic fine powder of the present invention includes γ-Fe
2 O3, Co-containing (deposition, metamorphism, doping) γ-Fe2
O3, Fe3 O4, Co content (deposition, metamorphism, doping)
Fe3 O4, γ-FeOX, Co containing (deposition, metamorphism,
Γ-FeOX (X = 1.33 to 1.5)
0), CrO2, etc. can also be used, but especially α-Fe, C
o, Ni, Fe-Co alloy, Fe-Co-Ni alloy, F
e-Co-Ni-P alloy, Fe-Co-Ni-B alloy,
Fe-Ni-Zn alloy, Ni-Co alloy, Co-Ni-
Ferromagnetic metal fine powders such as Fe alloys are preferred. The particle size of these ferromagnetic metal fine powders is about 0.005 to 1 micron, and the ratio of axial length / axial width is about 1/2 to 15/1. Moreover, the specific surface area of these ferromagnetic metal fine powders is 4
7-80 m2 / g, more preferably 53-70 m2 / g,
Coercive force (Hc) is 1250 to 2500 Oe, water content is 0.1 to 2.0% by weight, PH is 3 to 11 (5 g magnetic material /
100 g water) is preferred. The surface of these ferromagnetic fine powders may be impregnated with a rust preventive agent, a surface treating agent, a dispersant, a lubricant, an antistatic agent, etc. in a solvent prior to dispersion for each purpose and may be adsorbed. . The magnetic recording medium of the present invention has a magnetic layer in which these ferromagnetic fine powders are dispersed in a binder, provided on a non-magnetic support. The metal content in the ferromagnetic alloy powder is 60% by weight or more, and the metal content is 70%.
Weight% or more is at least one ferromagnetic metal or alloy (eg, Fe, Fe-Co, Fe-Co-Ni, Co,
Ni, Fe-Ni, Co-Ni, Co-Ni-Fe), and 40% by weight or less of the metal content, more preferably 20
Other components (eg, Al, Si, S,
Sc, Ti, V, Cr, Mn, Cu, Zn, Y, Mo,
Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta,
W, Re, Au, Hg, Pb, Bi, La, Ce, P
r, Nd, B, P) may be included in the alloy, iron nitride, iron carbide, and the like. In particular, in order to supplement the strength of metallic iron among them, it is preferable to provide Al, Si, and Cr individually or in a mixture on the surface layer. Further, the above-mentioned ferromagnetic metals are small amounts of hydroxides or oxides, alkali metal elements (Na, K, etc.), alkaline earth metal elements (Mg, C).
a, Sr) may be included. The method for producing these ferromagnetic metal powders is already known, and the ferromagnetic alloy powder, which is a typical example of the ferromagnetic powder used in the present invention, can also be produced according to these known methods.

That is, the following method can be given as an example of a 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. A method, (c) a method of thermally decomposing a metal carbonyl compound, (d) a method of adding a reducing agent such as sodium borohydride, hypophosphite or hydrazine to an aqueous solution of a ferromagnetic metal for reduction, (e) A method of electrolyzing ferromagnetic metal powder using a mercury cathode and then separating it from mercury,
(F) A method of evaporating a metal in a low pressure inert gas to obtain a fine powder, and when using a ferromagnetic metal fine powder, the shape thereof is not particularly limited, but is usually needle-like, granular, dice-like, Rice granules and plates are used, and the acicular ratio described above is particularly preferable. Further, σs of these ferromagnetic materials is preferably 100 to 210 emu / g. The crystallite size is preferably 100 to 300A. The dice-shaped one is preferably cubic or hexahedral or octahedral. For the plate-shaped one, the plate-shaped / thickness ratio is
It is preferably 3/1 to 30/1. Examples of these ferromagnetic alloy fine powders are JP-A-53-70397, JP-A-58-119609, and JP-A-58-130435.
JP-A-59-80901, JP-A-59-1690
3, JP-A-59-41453, JP-B-61-377.
61, U.S. Pat. No. 4,447,264, U.S. Pat.
No. 021 and US Pat. No. 4,931,198.

As the binder used in the magnetic layer or back layer of the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, electron beam curable resins, ultraviolet curable resins, visible light curable resins are used. Resins and mixtures of these are used. As a thermoplastic resin, the softening temperature is 150 ° C or lower,
Average molecular weight 10,000 to 300,000, degree of polymerization about 5
About 0 to 2000, more preferably 200 to 60
0, 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 chloride acrylonitrile copolymer, acrylic ester acrylonitrile copolymer, acrylic ester Vinylidene chloride copolymer, acrylic ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, nylon-silicone resin, nitrocellulose -Su-polyamide resin, poly (vinyl fluoride), vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer,
Polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, 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 Combined materials, amino resins, various synthetic rubber thermoplastic resins, and mixtures thereof are used. Examples of these resins include Japanese Patent Publication No. 37-6877.
Issue, Japanese Examined Patent Publication No. 39-12528, Japanese Examined Patent Publication No. 39-1928
No. 2, JP-B-40-5349 JP-B-40-2090
No. 7, Japanese Patent Publication No. 41-9463, Japanese Patent Publication No. 41-1405
No. 9, Japanese Patent Publication No. 41-16985 Japanese Patent Publication No. 42-642
No. 8, Japanese Patent Publication No. 42-11621, Japanese Patent Publication No. 43-462
No. 3, JP-B-43-15206, JP-B-44-288
No. 9, JP-B-44-17947, JP-B-44-182
No. 32, Japanese Patent Publication No. 45-14020, Japanese Patent Publication No. 45-14
No. 500, Japanese Patent Publication No. 47-18573, Japanese Patent Publication No. 47-2
2063, Japanese Patent Publication No. 47-22064 Japanese Patent Publication No. 47-
22068, Japanese Patent Publication No. 47-22069, Japanese Patent Publication No. 47
-22070, Japanese Patent Publication No. 47-27886, Japanese Patent Laid-Open No.
57-133521, JP-A-58-137133, JP-A-58-166533, JP-A-58-222433, JP-A-59-58642, etc., US Pat. No. 4,571,364,
It is described in US Pat. No. 4,752,530.

A thermosetting resin or a reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and has an infinite molecular weight due to reactions such as condensation and addition by heating and humidifying after coating and drying. Becomes Further, among these resins, those that do not soften or melt before the resin thermally decomposes are preferable. Specifically, for example, phenol resin, phenoxy resin, epoxy resin, polyurethane resin, polyester resin, polyurethane polycarbonate resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin (electron beam curing resin), epoxy -Polyamide resins, nitrocellulosmelamine resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins , Low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate mixtures, polyamine resins, polyimine resins and mixtures thereof.
Examples of these resins include Japanese Patent Publication Nos. 39-8103, 40-9779, 41-7192 and 41-4.
1-8016 Japanese Patent Publication No. 41-14275, Japanese Patent Publication No. 4
2-18179, Japanese Patent Publication No. 43-12081, Japanese Patent Publication No. 44-28023, Japanese Patent Publication No. 45-14501, Japanese Patent Publication No. 45-24902, Japanese Patent Publication No. 46-13103, Japanese Patent Publication No. 47-22065, Japanese Patent Publication No. 47-22066. issue,
Japanese Patent Publication No. 47-22067, Japanese Patent Publication No. 47-22072
No. 47-20743
No. 5, Japanese Patent Publication No. 47-28048, Japanese Patent Publication No. 47-289
22 and other publications. These thermoplastic, thermosetting resins, and reactive resins have carboxylic acid (COOM), sulfinic acid, sulfenic acid, sulfonic acid (SO ₃ M), phosphoric acid (PO (PO ( OM) (OM)), phosphonic acid, sulfuric acid (OSO)
₃ M) and acidic groups such as ester groups (M is H,
Alkali metals, alkaline earth metals, hydrocarbon groups), amino acids; aminosulfonic acids, aminosulfuric acid or phosphoric acid esters, amphoteric groups such as alkylbetaine type, amino groups, imino groups, imide groups, amides Base, etc.
Hydroxyl group, alkoxyl group, thiol group, alkylthio group, halogen group (F, Cl, Br, I), silyl group, siloxane group, epoxy group, isocyanato group, cyano group,
It is preferable that the nitrile group, the oxo group, the acryl group, and the phosphine group are usually contained in one kind or more and six kinds or less, and each functional group is contained in 1 × 10 −6 eq to 1 × 10 −2 eq per 1 g of the resin. Among these resins, a resin having at least one functional group of sulfonic acid, phosphoric acid, phosphonic acid, epoxy group and hydroxyl group is particularly preferable.

The polyisocyanate used in the magnetic layer or back layer of the present invention is tolylene diisocyanate,
4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate
, Naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate
, Triphenylmethane triisocyanate, isophorone diisocyanate, and other isocyanates, the products of the isocyanates with polyalcohol, and the condensation of the isocyanates. It is possible to use the above-mentioned 2- to 10-mer polyisocyanate, or the product of a polyisocyanate and polyurethane in which the terminal functional group is isocyanate. The average molecular weight of these polyisocyanates is preferably 100 to 20,000.
Commercially available trade names of these polyisocyanates are Coronet L, Coronet HL, and Coronet 20.
30, Coronet 2031, Millionate MR, Millionate MTL (Nippon Polyurethane Co., Ltd.), Takenet D
-102, Takenet D-110N, Takenet D-
200, Takenet D-202, Takenet 300S,
Takenet 500 (manufactured by Takeda Pharmaceutical Co., Ltd.), Sumire T-
80, Sumidule 44S, Sumidule PF, Sumidule L, Sumidule N Desmodule L, Desmodule IL, Desmodule N, Desmodule HL,
Death module T65, Death module 15, Death module R, Death module RF, Death module SL,
There is Desmodule Z4273 (manufactured by Sumitomo Bayer Co., Ltd.) and the like, and these can be used alone or in combination of two or more utilizing the difference in curing reactivity. In addition, for the purpose of promoting the curing reaction, hydroxyl groups (butanediol, hexanediol, molecular weight of 1000-
It is also possible to use 10000 polyurethane, water, etc.), a compound having an amino group (monomethylamine, dimethylamine, trimethylamine, etc.), a metal oxide catalyst or a catalyst such as iron acetylacetonate. It is desirable that these compounds having a hydroxyl group or an amino group are polyfunctional.
These polyisocyanates are preferably used in both the magnetic layer and the back layer in an amount of 2 to 70 parts by weight, and more preferably 5 to 50 parts by weight, per 100 parts by weight of the total amount of the binder resin and the polyisocyanate. Examples of these are JP-A-6
Nos. 0-131622 and 61-74138. These binders are used alone or in combination, and other additives are added.
The mixing ratio of the ferromagnetic fine powder and the binder in the magnetic layer is 3 to 100 parts by weight of the binder with respect to 100 parts by weight of the ferromagnetic fine powder. The mixing ratio of the fine powder and the binder in the back layer is such that the binder is 8 to 150 parts by weight based on 100 parts by weight of the fine powder. As additives, dispersants, lubricants, abrasives, antistatic agents, antioxidants,
A solvent or the like is added.

The carbon black used in the magnetic layer and / or the back layer of the present invention may be a furnace for rubber, thermal for rubber, black for color, acetylene black or the like. These carbon blacks are used as an antistatic agent, a light-shielding agent, a friction coefficient adjusting agent, and a durability improving tape. Specific examples of these carbon black abbreviations in the US are SAF, ISAF,
IISAF, T, HAF, SPF, FF, FEF, HM
F, GPF, APF, SRF, MPF, ECF, SC
F, CF, FT, MT, HCC, HCF, MCF, LF
F, RCF, etc., American ASTM standard D-176
Those classified as 5-82a can be used. These carbon blacks used in the present invention have 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.
Is 4 to 11 (JIS standard K-6221-1982 method),
Dibutyl phthalate (DBP) oil absorption is 10-800m
1 / 100g (JIS standard K-6221-1982 method)
Is. The size of the carbon black used in the present invention is 5-100 for the purpose of lowering the surface electric resistance of the coating film.
Millimicron carbon black is used, and 50 to 1000 millimicron carbon black is used to control the strength of the coating film. Further, for the purpose of controlling the surface roughness of the coating film, fine carbon black (less than 100 mm) is used for smoothing the surface, and for the purpose of roughening the carbon black to reduce the friction coefficient. (100
More than a millimicron). As described above, the type and the amount of carbon black added are properly selected according to 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 part of the surface is graphitized by treating the temperature of the furnace at the time of producing carbon black at 2000 ° C. or higher. Hollow carbon black can also be used as a special carbon black. In the case of the magnetic layer, it is desirable to use 0.1 to 20 parts by weight with respect to 100 parts of the ferromagnetic fine powder. In the case of the back layer, it is 2 with respect to 100 parts by weight of the binder.
It is desirable to use 0 to 400 parts by weight. The carbon black that can be used for the back layer can be referred to, for example, "Carbon Black Handbook", edited by Carbon Black Association (published in 1972). Examples of these carbon blacks are US Pat. No. 4,539,257 and US Pat. No. 461.
4685, JP-A-61-92424, JP-A-61-
It is described in Japanese Patent Publication No. 99927.

The abrasive used in the magnetic layer or the back layer of the present invention is used for improving the durability of the magnetic tape, and is generally a material having an abrasive action or a polishing action, which is α-alumina, γ-alumina, α, γ-alumina It is preferable to use at least one of fused alumina, chromium oxide, and diamond. Other abrasives include silicon carbide, cerium oxide, corundum, α-iron oxide, garnet, emery (main components: corundum and magnetite), garnet, silica stone, silicon nitride, boron nitride, molybdenum carbide, boron carbide , Tungsten carbide, titanium carbide, tripoly, diatomaceous earth, dolomite, etc., and it is preferable to use mainly materials having a Mohs hardness of 6 or more in a combination of 1 to 4 kinds. 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. It is desirable to use these abrasives in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the ferromagnetic fine powder of the magnetic layer. Further, these abrasives are preferably used in an amount of 0.01 to 5 parts by weight with respect to 100 parts by weight of the non-magnetic powder in the back layer. Specific examples of these are AKP1 and AKP1 manufactured by Sumitomo Chemical Co., Ltd.
5, AKP20, AKP30, AKP50, AKP8
0, Hit50, Hit100 and the like. Regarding these, Japanese Patent Publication No. 52-28642 and Japanese Patent Publication No. 49-3
9402, JP-A-63-98828, and US Pat.
87725, US Patent 3007807, US Patent 3
No. 041196, U.S. Pat. No. 3,293,066, U.S. Pat. No. 3,630,910, U.S. Pat. No. 3,833,412, U.S. Pat. No. 4,117,190, British Patent No. 1145349, West German Patent No. 853211 and the like.

The powdery lubricant used in the magnetic layer and / or back layer of the present invention includes graphite, molybdenum disulfide, boron nitride, graphite fluoride, calcium carbonate,
Inorganic fine powder such as barium sulfate, silicon oxide, titanium oxide, zinc oxide, tin oxide, tungsten disulfide, 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 powder, resin fine powder such as polyfuccoethylene ethylene resin fine powder, and the like. As the organic compound-based lubricant, silicon oil (dialkyl polysiloxane, dialkoxy polysiloxane, phenyl polysiloxane,
Fluoroalkyl polysiloxane (KF9 manufactured by Shin-Etsu Chemical)
6, KF69, etc.)), fatty acid-modified silicone oil, fluorine alcohol, alkane (liquid paraffin), 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 ester, per Fluoroalkylsulfonic acid ester, perfluoroalkylbenzenesulfonic acid ester, perfluoroalkylphosphoric acid ester (for example, Krytox, etc.) containing fluorine or silicon, alkyl sulfuric acid ester, alkylsulfonic acid ester, alkylphosphonic acid triester , Alkylphosphonic acid monoester,
Organic acids and organic acid ester compounds such as alkylphosphonic acid diesters, alkylphosphoric acid esters, and succinic acid esters, nitrogen-sulfur-containing complexes such as triazaindolizine, tetraazaindene, benzotriazole, benzotriazine, benzodiazole, and EDTA (Hetero) ring compound, monobasic fatty acid having 10 to 40 carbon atoms and 2 to 2 carbon atoms
40 monovalent or divalent alcohols,
Trivalent alcohol, tetravalent alcohol, hexavalent alcohol
Fatty acid ester consisting of any one or two or more of the above, monobasic fatty acids having 10 or more carbon atoms, and monovalent to six carbon atoms having a total of 11 to 70 carbon atoms. It is also possible to use fatty acid esters consisting of valence alcohols, fatty acids having 8 to 40 carbon atoms or fatty acid amides, fatty acid alkylamides, and aliphatic alcohols. These carbons may be branched at any place. The location of branching is preferably iso or 2- or 3-position branching. 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, stearic acid 2
Ethylhexyl, amyl stearate, isoamyl stearate, 2-ethylpentyl stearate, 2-hexyldecyl stearate, isotridecyl stearate, stearic acid amide, stearic acid alkylamide, butoxyethyl stearate, anhydrosorbitan monostearate, an Hydrosorbitan distearate, anhydrosorbitan tristearate, anhydrosorbitan tetrastearate, oleyl oleate, oleyl alcohol, lauryl alcohol, montan wax, carnauba wax, etc. alone or Can be used in combination. As the lubricant used in the present invention, so-called lubricating oil additives can be used alone or in combination, and antioxidants (alkylphenol, benzotriazine, tetraazaindene, sulfamide) which are known as rust preventives are used. , Metal chelators such as guanidine, nucleic acid, pyridine, amine, hydroquinone, and EDTA), rust suppressant (naphthenic acid, alkenyl succinic acid, phosphoric acid, dilauryl phosphate, etc.), oiliness agent (rapeseed oil, lauryl alcohol) , Etc.), extreme pressure agents (dibenzyl sulfide, tricresyl phosphate, tributyl phosphite, etc.),
Detergent dispersants, viscosity index improvers, pour point depressants, foam depressants, etc. These lubricants may be used in the form of a composite, or one having two or more of these characteristic groups introduced into one molecule. Examples thereof include a fluorine group-introduced fatty acid, a fluorine group-introduced fatty acid ester, a siloxane-introduced fatty acid, and a siloxane-introduced fatty acid ester. These lubricants are added in the range of 0.01 to 30 parts by weight with respect to 100 parts by weight of the binder of the magnetic layer and / or the back layer. About these, Japanese Patent Publication No. 43-23889 and Japanese Patent Publication No. 48-24
041, Japanese Patent Publication No. 48-18482, Japanese Patent Publication No. 44-1
8221, Japanese Patent Publication No. 47-28043, Japanese Patent Publication No. 57-5
6132, JP-A-59-8136, JP-A-59-81
39, JP-A-61-85621, U.S. Pat. No. 3,423.
233, US Pat. No. 3470021, US Pat.
2235, US Pat. No. 3,497,411, US Patent 35
23086, US Patent 3,625,760, US Patent 3
630772, U.S. Pat. No. 3,634,253, U.S. Pat. No. 3,642,539, U.S. Pat. No. 3,687,725, U.S. Pat. No. 4135031, U.S. Pat. No. 4,497,864, U.S. Pat. No. 4,552,794, IBM Technical Day.
Sukuroja Britain (IBM Technical)
Disclosure Bulletin) Vol.
9, No7, p779 (December 1966), Electronic (ELEKTRONIK) 1961 No12,
p380, Handbook of Chemistry, Advanced Edition, p954-967, 19
It is described in the issue of Maruzen Co., Ltd. in 1980.

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, stearoic acid. -Fatty acids such as acid, behenic acid, maleic acid, phthalic acid, etc., having 2 to 40 carbon atoms (R1 COOH, R1 is alkyl group having 1 to 39 carbon atoms, phenyl group, aralkyl group), alkali of the above fatty acids Metal soaps (copper oleate) composed of metals (Li, Na, K, NH4 + etc.) or alkaline earth metals (Mg, Ca, Ba etc.), Cu, Pb etc., fatty acid amides; lecithin (soy oil lecithin) etc. Is used. In addition to these, higher alcohols having 4 to 40 carbon atoms (butanol, octyl alcohol, myristyl alcohol, stearyl alcohol, cetyl alcohol, isocetyl alcohol) and their sulfates, sulfonic acids, Phenyl sulfonic acid, alkyl sulfonic acid, 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. Also, polyethylene glycol,
Polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid metal salt, sulfosuccinic acid ester and the like can also be used. These dispersants are usually used in one or more kinds, and one kind of the dispersant is added in the range of 0.005 to 20 parts by weight with respect to 100 parts by weight of the binder. The usage of these dispersants is
It may be deposited on the surface of the ferromagnetic fine powder or the non-magnetic fine powder in advance, or may be added during the dispersion. Such a material is disclosed, for example, in Japanese Patent Publication No. 39-28369 and Japanese Patent Publication No. 44-1.
7945, Japanese Patent Publication No. 44-18221, Japanese Patent Publication No. 48-
7441, Japanese Patent Publication 48-15001, Japanese Patent Publication 48-
15002, Japanese Patent Publication No. 48-16363, Japanese Patent Publication No. 49
-39402, U.S. Pat. Nos. 3,387,993 and 347.
No. 0021 and the like.

The antifungal agent used in the present invention is 2- (4-
Thiazolyl) -benzimidazole, N- (fluorodichloromethylthio) -phthalimide, 10,10'-oxybisphenoxarcin, 2,4,5,6 tetrachloroisophthalonitrile, P-tolyldiiodomethylsulfone, triiodo Examples include allyl alcohol, dihydroacetate, mercury phenyloleate, bis (tributyltin) oxide, and saltylanilide. Such a thing is shown, for example, in "Microbial Hazard and Prevention Technology", 1972 Engineering Book, "Chemistry and Industry" 32,904 (1979), and the like. These antifungal agents are used in the range of 0.005 to 20 parts by weight based on 100 parts by weight of the binder.

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,
Conductive powders such as saponin; Natural surfactants such as saponin; Nonionic surface active agents such as alkylene oxide type, glycerin type, glycidyl type, polyhydric alcohol, polyhydric alcohol ester, and alkylphenol EO adduct Agents; higher alkyl amines, cyclic amines, hydantoin derivatives, amido amines, ester amides, quaternary ammonium salts, pyridine and other heterocycles, cationic surfactants such as phosphonium or sulfoniums; carboxylic acids, sulfonic acids, phosphonic acids , Anionic surfactants containing acidic groups such as phosphoric acid, sulfuric acid ester groups, phosphonic acid ester groups, phosphoric acid ester groups, etc .; amino acids; aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, amphoteric interfaces such as alkyl betaine type Activators and the like are used. Some examples of surfactant compounds that can be used as these antistatic agents are disclosed in JP-A-60-28025 and US Pat.
No. 2, No. 2240472, No. 2288226, No. 26
No. 76122, No. 2676924, No. 2676975
Nos. 2,691,566, 2727860, 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, 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., 1241) 20 a month
Sun); Hideo Marumoshi, "Antistatic Agent," written in Koshobo (1968). These surfactants may be added alone or as a mixture. The amount of these surfactants used in the magnetic recording medium is 10
It is 0.01 to 10 parts by weight per 0 parts by weight. The amount used in the back layer is 0.01 to 100 parts by weight of the binder.
30 parts by weight. These are used as antistatic agents, but sometimes they are used for other purposes such as dispersion, improvement of magnetic properties, improvement of lubricity, coating aid, wetting agent, curing accelerator, dispersion accelerator. In some cases.

As the organic solvent used in the dispersion, kneading and coating of the present invention, ketones such as acetone, methylethylketone, methylisobutylketone, cyclohexanone, isophorone, tetrahydrofuran and the like in any ratio; methanol, ethanol , Propanol, butanol, isobutyl alcohol, isopropyl alcohol, methylcyclohexanol, and other alcohols; methyl acetate,
Ester systems such as ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate monoethyl ether; ethers such as diethyl ether, tetrahydrofuran, glycol dimethyl ether, glycol monoethyl ether, dioxane System: benzene, toluene, xylene, cresol, chlorobenzene, styrene and other tar systems (aromatic hydrocarbons); methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. Chlorinated hydrocarbons, 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. In addition, a trace amount of impurities (polymer of the solvent itself, water,
Raw material components, etc.) may be included. These solvents are used in an amount of 100 to 200,000 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 solid content of the magnetic liquid is preferably 5 to 40% by weight. The solid content of the backing liquid is preferably 5 to 30% by weight. An aqueous solvent (water, alcohol, acetone, etc.) can be used instead of the organic solvent.

The magnetic recording layer and the back layer are formed by arbitrarily combining the above-mentioned compositions and the like or individually or in combination with an organic solvent, and impregnating, dissolving, mixing, dispersing, kneading and diluting them in any order to form a coating solution. Create and apply / dry /
Orient. When used as a tape or disk, the thickness of the support is preferably about 2.5 to 500 μm, more preferably about 3 to 100 μm. As materials, polyethylene naphthalate, polyethylene terephthalate,
Plastics such as polyimide and polyamide are preferred.
Regarding these supports, for example, West German Patent 333885
4A, JP-A-59-116926, JP-A-61-12
9731, U.S. Pat. No. 4,388,368; Yukio Mitsuishi,
"Fiber and Industry", Vol. 31, p50-55, 1975. In the case of a video tape or the like, the center line average surface roughness of these supports is 0.1 to 30 nanometers (n
m) (cutoff value 0.25 mm) is preferred. The Young's modulus (F5 value) of these supports can be selected from 2 to 100 kg / mm @ 2 in both the width direction and the longitudinal direction depending on the purpose.

The method of dispersion and kneading is not particularly limited, and the addition order of each component (resin, powder, lubricant, solvent, etc.),
The addition position during dispersion / kneading, the divided addition of the same raw material, the dispersion temperature (0 to 80 ° C.), the humidity and the like can be appropriately set. For preparing magnetic paints and back layer paints, conventional kneading machines such as a two-roll mill, a three-roll mill, a ball mill, a pebble mill, a tron mill, a sand grinder,
Szegvari Attritor, High Speed Impeller, Disperser, High Speed Stone Mill, High Speed Impact Mill, Disperser, Kneader, High Speed Mixer, Ribbon Blender, Conveyor, Intensive Mixer, Tumbler, blender, disperser, homogenizer, single-screw extruder, twin-screw extruder,
Also, an ultrasonic disperser or the like can be used. Usually, a plurality of these dispersing / kneading machines are provided for the dispersing / kneading, and the treatment is continuously performed. For details of the technique regarding kneading and dispersion, see T.W. C.
PATTON (T-C-Patton) "Paint
Flow and Pigment Dispersers
Ion ”(Paint Flow and Pigment Day Spar John) 1964 John Wiley &
Published by Sons (John Willy and Sons) and Shinichi Tanaka, "Industrial Materials," Vol. 25, 37 (197).
7) etc. and the references cited in the book. As an auxiliary material for the dispersion and kneading, in order to efficiently carry out the dispersion and kneading, steel balls, steel beads, ceramic beads, glass beads, and organic polymer beads having a sphere equivalent diameter of 10 cmφ to 0.05 mmφ can be used. Also, these materials are not limited to spherical shapes. It is also described in the specifications such as US Pat. 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 in accordance with the method described in the above-mentioned book or the references cited in the book. Hardeners and some additives (fatty acids, phosphoric acid, phosphonic acid, sulfonic acids, and their esters, which have high reactivity with magnetic materials) are added to the coating liquid just before coating using an mixing machine such as a mixing valve. You may.

The magnetic recording layer coating solution, the back layer coating solution, and the undercoating solution may be coated on the support by varying the viscosity of the coating solution from 1 to 20000 centistokes (25
° C) and adjust the air doctor coat and blade coat
, Air knife coat, squeeze coat, impregnation coat,
Liver roll coat, transfer roll coat,
Gravure coat, kiss coat, cast coat, spray coat, rod coat, forward rotation roll coat, carten coat, extrusion coat, bar coat, extrusion coat, etc. Can be used, and other methods are also available, and detailed explanations of these can be found in "Coating Engineering", pages 253 to 277 (published by Showa 4.3.20, published by Asakura Shoten).
Etc. in detail. The order of applying these coating liquids can be arbitrarily selected, and the undercoat layer may be continuously applied before the desired liquid is applied. When it is desired to form the magnetic layer or the back layer in multiple layers, simultaneous multilayer coating, sequential multilayer coating and the like may be performed. These are, for example, Japanese Patent Laid-Open No.
7-123532, JP-B-62-37451, JP-A-59-142741, JP-A-59-1.
This is described in the specification of Japanese Patent No. 65239.

By such a method, about 1 to about 1 is formed on the support.
The magnetic liquid applied to have a thickness of 100 μm (solid content: 0.1 to 50 g / m ² ) is required to be 500 to 5 while immediately drying the magnetic powder in the layer at 20 to 130 ° C. in multiple stages.
About 000G in the desired direction (vertical, longitudinal, width, random,
After performing a treatment for orienting the film (obliquely), the formed magnetic layer is dried to a thickness of 0.1 to 10 μm. The transport speed of the support at this time is usually 10 m / min to 900 m / min, and the drying temperature is 20 ° C. to 130 ° C. in a plurality of drying zones.
The residual solvent amount of the coating film is controlled to 0.01 to 40 mg /
m2. In the present invention, the magnetic recording medium is then subjected to a super calendering treatment for surface smoothing to adjust the center line average surface roughness of the magnetic layer and the back layer to a desired value.
Further, the magnetic recording material of the present invention is manufactured by cutting it into a desired shape. At this time, it is preferable to use an opposing metal roll for the super calendar treatment. At this time, the carrying speed of the magnetic recording medium is usually 10 m / min to 900 m / min. Usually, the magnetic recording medium is processed with a multi-stage metal roll at least twice, and the molding temperature is preferably 50 ° C. to 130 ° C. . For the other treatment, a combination of a metal roll, superhard plastic, and superhard plastic may be used.

In these manufacturing methods, the steps of powder pretreatment / surface treatment, kneading / dispersion, coating / orientation / drying, smoothing treatment, heat treatment, EB treatment, surface polishing treatment, cutting and winding are continuously carried out. Is desirable. These are disclosed, for example, in Japanese Patent Publication No. 40-23625, Japanese Patent Publication No. 39-28368, Japanese Patent Publication No. 47-38802, and British Patent 119.
1424, JP-B-48-11336, JP-A-4
9-53631, JP-A-50-112005, JP-A-51-77303, JP-B-52-17404, JP-A-60-70532, JP-A-2-265672.
U.S. Pat. No. 3,473,960, U.S. Pat. No. 4,728.
569, U.S. Pat. No. 4,746,542 and the like. Moreover, the method described in Japanese Patent Publication No. 41-13181 is considered to be a basic and important technique in this field.

The magnetic recording medium thus prepared is cut and then wound on a desired plastic or metal reel.
It is desirable to burnish and / or clean the magnetic recording medium (magnetic layer, back layer, edge surface, base surface) immediately before or before winding. The burnish specifically smoothes the magnetic recording medium by cutting off the protrusions on the surface of the magnetic recording medium with a hard material such as a sapphire blade, a razor blade, a super hard material blade, a diamond blade, and a ceramics blade. The Mohs hardness of these materials is preferably 8 or more, but there is no particular limitation as long as the protrusions can be removed. The shape of these materials does not have to be a blade in particular, and a shape such as a square shape, a round shape, or a wheel (these materials may be provided around a rotating cylindrical shape) can also be used. Further, the cleaning of the magnetic recording medium is carried out by using a non-woven fabric or the like as the magnetic recording layer surface, the back layer surface, the surface of the magnetic recording medium for the purpose of removing dirt and excess lubricant on the surface of the magnetic recording medium.
This is done by wiping the edge end surface and the back side base surface. Examples of such wiping materials include various types of Vilene made by Japan Vilene and Toray made by Toray, Excene, trade name Kimwipe, various polishing tapes made by Fuji Photo Film, and non-woven fabric made of nylon, non-woven fabric of polyester, non-woven fabric of rayon, Tissue paper such as acrylonitrile non-woven fabric, blended non-woven fabric, etc. can be used. These are, for example, Japanese Patent Publication No. 46-39309.
Japanese Patent Publication No. 58-46768, Japanese Patent Laid-Open No. 56-9042.
9, JP-B-58-46767, JP-A-63-259.
830, JP-A-1-201824 and the like. Particularly, in the present invention, it is necessary to process with a rotary blade or a polishing tape made of a material having a Mohs hardness of 9 or more. In the case of a rotary blade, it is preferable to process with a winding angle of 180 degrees or more and a rotary blade of 900 rotations or more. . When processing with a polishing tape, the contact surface must be 0.1 mm or more. The tension applied to the magnetic recording medium at this time must be 200 g or more per 1/2 inch width, and the change in tension before and after the processing device is 200 g.
It is necessary to be above.

[0030]

EXAMPLES The present invention will be described more specifically below with reference to examples. It will be easily understood by those skilled in the art that the components, ratios, operation sequences, etc. shown here can be changed without departing from the spirit of the present invention. Therefore, the present invention should not be limited to the following examples. In the examples, the parts are parts by weight.

Example 1 A magnetic coating composition (1) having the composition shown below was kneaded with an open kneader, added with the composition (2), dispersed in a sand mill, and added with (3) before coating to prepare and dry. 7. A thickness of an undercoat layer previously applied so that the thickness of the subsequent magnetic layer will be 2.0 μm.
0 μm non-magnetic support polyethylene naphthalate (MD
Direction Young's modulus of 900 Kg / mm ² and TD direction Young's modulus of 700 Kg / mm ² ).

Magnetic coating composition (1) Ferromagnetic alloy powder 100 parts (Fe metal powder, Si 5% by weight, specific surface area [S-BET]: 60 m 2 / g) Phosphate ester (phenyl sulfonic acid) 2 parts Iron oleate 0. 1 part Vinyl chloride copolymer resin 9 parts (Nippon Zeon Co., Ltd .: MR110) Urethane resin 3 parts (Toyobo: UR8600) 2 ethylhexyl palmitate 0.5 part Cyclohexanone 30 parts Methyl ethyl ketone 20 parts

(2) Carbon black (Conductex SC) 0.4 parts Urethane resin 1 part (Toyobo: UR8600) Methyl ethyl ketone 10 parts or more Dispersion Abrasive (Sumitomo Chemical: Hit55) 10 parts Vinyl chloride resin 1 part ( Zeon Corporation: MR110) Methyl ethyl ketone 40 parts or more Dispersion cyclohexanone 60 parts

(3) Polyisocyanate (Nippon Polyurethane: Coronet 3040) 3 parts Methyl ethyl ketone 50 parts Toluene 30 parts Stearic acid dibutylamide 0.5 parts Myristic acid 0.3 parts Butoxyethyl stearate 0.5 parts

The non-magnetic support coated with the magnetic coating is subjected to a magnetic field orientation treatment and drying in a state where the magnetic coating is not dried, and then (2) is added to the back coating (1) shown below immediately before coating to obtain a thickness after drying. It was applied at 0.6 μm. After further drying, the metal calender treatment is 100 ° C., linear pressure is 350 Kg / cm, speed 2
It was performed 5 times at 00 m / min, and then slit into a 1/2 inch width. Continue to tape 2% diamond (1μ
m) -98% alumina (0.5 μm) wrapping tape with magnetic layer at contact distance 100 mm, tension 400 g
/ Width processed, Hc1700Oe, SQ0.91, Ra
3 nm, gloss 260 (45 degree reflection), back layer Ra7n
m videotape was created. A list of the results is shown in Table 1.

Back coating composition (1) Carbon black (Cabot BP800) 90 parts Carbon black (Kancarb MTCI) 10 parts α-alumina (Sumitomo Chemical HIT100) 0.2 parts Barium sulfate (Sakai Chemical BF1) 0.2 parts Stearic acid 2 Ethylhexyl 0.5 part Copper oleate 0.1 part Vinyl chloride copolymer resin 40 parts (Nippon Zeon Co., Ltd .: MR110) Urethane resin 30 parts (Toyobo: UR8300) Cyclohexanone 200 parts Methyl ethyl ketone 300 parts (2) Polyisocyanate (Nippon Polyurethane Co., Ltd .: Colonate 3040) 20 parts Methyl ethyl ketone 3500 parts Toluene 200 parts Silicone (Shin-Etsu Chemical KF69) 0.1 parts

Table 1 Lapping abrasive Abrasive Initial head VTR compatible Low humidity treatment Height Number Wear output difference Output (tension) (nm) (ke / 100 μm ² ) (μ / 100H) (dB) Decrease (dB) Example 1 Yes (400g) 2 200 10 0 -2 2 〃 (350g) 4 200 15 2 -2 3 〃 (300g) 6 200 23 3 -1 4 〃 (250g) 8 200 30 4-1 -5 〃 (200g) 12 200 35 6 -1 6 〃 (300g) 8 400 30 3 -1 7 〃 (300g) 7 250 25 4 -2 Comparative Example 1 Yes (50g) 14 200 80 12 12 -4 2 None 20 200 100 14 -2 3 3 〃 16 80 80 12 -6>

Note 1) In Example 6, the abrasive material (Hit
55) The amount was 15 g. Note 2) In Example 7, 0.5% of abrasive was used in Example 1.
It was chromium oxide of μm. Note 3) In Comparative Example 3, the abrasive material (Hit
55) The amount was 4.5 g. Note 4) Initial head wear was converted to 100 hours by running a new 90 minute long 2 rolls with an M2VTR. Note 5) The VTR compatibility difference is the difference between the output at that time and the maximum output difference when the tape is played back on another VTR, with three VTRs with different mounting angles of the M2VTR head prepared. I asked. Note 6) Output drop in low humidity environment is 23 ℃, 10% RH
It was run for 90 minutes under the above conditions and a decrease in output was observed under low humidity.

From the examples, it can be seen that controlling the height of the abrasive is very excellent in initial head wear, VTR compatible output difference, and low humidity output reduction. At this time, it is necessary that the amount of the abrasive is 5 parts or more per 100 parts by weight of the ferromagnetic fine powder contained in the magnetic layer, and it is very effective to set the height of the abrasive to 15 nm or less.

[0040]

The magnetic recording medium of the present invention is provided with a magnetic layer containing ferromagnetic fine powder, a binder, and an abrasive having a Mohs hardness of 8 or more on a non-magnetic support, and the magnetic layer surface roughness of the magnetic layer is adjusted. By setting the average protrusion height to the upper end of the abrasive existing above the center line and on the surface of the magnetic layer to 15 nm or less, a magnetic recording medium with less wear of the VTR head and excellent running durability can be obtained. It was Particularly, the abrasive contained in the magnetic layer is at least one of alumina, chromium oxide, and diamond, and the surface roughness of the magnetic layer is 0.1 nm to 6 n.
When it was m, a magnetic recording medium excellent in durability of the VTR head and the magnetic recording medium was obtained. The number of abrasives present in the surface layer of the magnetic layer is 100 to 1000 per 100 μm ² , the amount of the abrasive contained in the magnetic layer is 5 to 20 parts by weight per 100 parts of ferromagnetic fine powder, and the amount of ferromagnetic fine particles in the magnetic layer is 100. The metal powder having a specific surface area of 47 m ² / g or more provided high output and appropriate polishing ability. In addition, the back surface of the non-magnetic support provided with a magnetic layer has a surface roughness of 2 nm to 1
By having a back layer of 5 nm, excellent running durability was obtained.

Claims (6)

[Claims] 1. A magnetic recording medium recording comprising a magnetic layer containing a ferromagnetic fine powder, a binder and an abrasive having a Mohs hardness of 8 or more on a non-magnetic support, and a center line of the magnetic layer surface roughness of the magnetic layer. A magnetic recording medium, characterized in that the average protrusion height up to the upper end of the abrasive existing above and above the magnetic layer is 15 nm or less. 2. The magnetic recording medium according to claim 1, wherein the abrasive contained in the magnetic layer is at least one selected from alumina, chromium oxide, and diamond. 3. The magnetic layer has a surface roughness of 0.1 nm to 6 nm, and a back layer having a surface roughness of 2 nm to 15 nm is provided on the back surface of a non-magnetic support on which the magnetic layer is coated. The magnetic recording medium according to claim 1, wherein: 4. The surface layer of the magnetic layer has 100 to 1000 abrasives per 100 μm ² , and the abrasive contained in the magnetic layer is 5 to 20 parts by weight per 100 parts by weight of ferromagnetic fine powder. The magnetic recording medium according to claim 1, wherein 5. The ferromagnetic fine powder has a specific surface area of 47 m ² /
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a metal powder of g or more. 6. A non-magnetic support is coated with a magnetic layer containing ferromagnetic fine powder, a binder and an abrasive having a Mohs hardness of 8 or more, and then the conveying speed is 10 m / min to 900 m / min and the molding temperature is 50 ° C. to 130 ° C. Super calendering is performed by using a multi-stage counter metal roll at least twice at a temperature of ℃, and then burnishing is performed to obtain an average protrusion height of 15 nm up to the upper end of the abrasive present on the magnetic layer surface layer. A method of manufacturing a magnetic recording medium characterized by the following.