JP2826234B2 - Magnetic recording medium and method of manufacturing the same - Google Patents

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 particularly, to improving head wear and head contact of a VTR, maintaining a high output, and improving the performance of the VTR. 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) and the like, a magnetic layer in which ferromagnetic fine powder is dispersed in a binder (binder) is provided on a non-magnetic support. Is used. Conventionally, these magnetic recording media have used a magnetic layer containing a ferromagnetic fine powder, a binder, and an abrasive having a Mohs hardness of 8 or more. Of these, abrasives in particular have reduced head contamination on VTRs and have always provided the best image, sound and data recording. Various abrasives have been proposed for this purpose, and Japanese Patent Publication No. 49-39402,
JP-A-57-183628, U.S. Pat. No. 3,630,910
And JP-A-57-179945.
In recent years, these magnetic recording media have been required to have high density recording,
Higher output and lower noise in reproduction output / noise due to ultra-smoothness of the surface of the magnetic recording medium, finer ferromagnetic powder, finer metal powder, higher filling, and thinner magnetic recording medium are required. . In order to improve recording density and image quality, VTR
In this case, the writing speed and the calling speed to the magnetic recording medium are shortened, the recording method (from the analog method to the digital method) is changed, the recording width is reduced (5 to 20 nm), and the shortest recording wavelength is reduced (0.1 to 0. 9 μm), and a head cylinder speed of 5400 RP in a helical scan VTR
M or more, and the relative speed between the tape and the head is also 20m / s
ec. In order for a magnetic recording medium to have such high output and high-speed sliding suitability, it is essential that the magnetic recording medium has running stability in a running system, a head, and a cylinder system of a VTR. In addition, various lubricants such as carbon black and organic compounds are used in addition to the abrasives described above. A major problem with these magnetic recording media is their compatibility with VTR heads. It is extremely difficult to lower the coefficient of friction with respect to the head of a VTR when trying to achieve thinner and ultra-smoothness for high-density recording. The surface layer of the magnetic layer where the friction coefficient increases increases, and the head becomes dirty. For this reason, the above-described abrasive is added to the magnetic layer. However, if the abrasive is added in an amount sufficient to prevent head contamination, the wear of the head is significantly increased. As the head wear increases, it is proposed that the head material be made harder, so that the amount of abrasive in the magnetic layer must be increased again.

That is, in the prior art, a magnetic recording medium and a VTR
Effective means for increasing the coefficient of friction with the head have been the addition of an abrasive and the addition of a lubricant. As for the contamination of the head of the magnetic recording medium recording, adding an abrasive to the magnetic layer has an effect on the head contamination. When such an amount is added, the wear of the magnetic recording medium on the VTR head is significantly increased. As the head wear increases, it is proposed that the head material be made harder, so that the amount of abrasive in the magnetic layer must be increased again. As described above, the balance between head wear and head contamination sacrifices one of the characteristics. Also, in order to reduce the coefficient of friction of the VTR head with respect to the output that is lost when trying to achieve thinning and ultra-smoothness for high-density recording, that is, compatibility with the VTR head, a lubricant other than abrasives is used. An addition is made. The addition of a lubricant for lowering the friction coefficient results in plasticization of the magnetic layer, which causes a decrease in output and head fouling. It was also very difficult to balance the reduction in the coefficient of friction and the reduction in output.

There has also been a proposal to improve the durability by specifying the amount of abrasive present on the surface of the magnetic layer. For example, Japanese Unexamined Patent Publication (Kokai) No. 61-57036 discloses that abrasive particles having a Mohs hardness of 6 or more are mixed with magnetic powder 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 set to 0.25 / μm ² or more. Japanese Patent Application Laid-Open No. 60-9 / 1985
No. 3631 discloses a magnetic recording medium in which the number of nonmagnetic 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.

Japanese Patent Application Laid-Open No. 63-183619 discloses a magnetic layer in which a magnetic layer is coated, dried, calendered, hardened, and then has a blade made of sapphire or diamond and having a blade. Press against the surface,
Further, there is disclosed a method of manufacturing a magnetic recording medium in which a magnetic layer surface is polished with a cylindrical diamond grindstone having a particle size of 0.5 to 4 μm. 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 carbide blade. I have. However, satisfactory results were not obtained for all items of initial head wear, VTR compatible output difference, and low humidity output.

[0006]

SUMMARY OF THE INVENTION In other words, the present invention
It is an object of the present invention to provide a magnetic recording medium that is excellent in high output, high density recording and running durability. In particular, an object of the present invention is to provide a magnetic recording medium that is extremely excellent in running durability such as head wear characteristics and head contamination.

[0007]

The inventors of the present invention have conducted intensive studies focusing on the characteristics, shape, and the like of the abrasive present on the surface of the magnetic layer. The present inventors have found that the average projection height up to the upper end of the abrasive material greatly affects items such as initial head wear, VTR-compatible output difference, and low humidity output. That is, the object of the present invention is to provide a magnetic recording medium having 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. The average protrusion height up to the upper end of the abrasive existing above the center line of the magnetic layer and existing on the surface of the magnetic layer
This can be achieved by a magnetic recording medium characterized by being 13 nm or less from the center line of the surface roughness . Preferably, the magnetic recording medium is characterized in that the abrasive contained in the magnetic layer is at least one selected from alumina, chromium oxide and diamond. That is, the magnetic recording medium of the present invention is provided with 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. By making the average protrusion height up to the upper end of the abrasive present in the magnetic layer and the surface layer of the magnetic layer not more than 13 nm , a magnetic recording medium having little VTR head wear and excellent running durability was obtained. Preferably, when at least one of the abrasives contained in the magnetic layer is alumina, chromium oxide, or diamond and the surface roughness of the magnetic layer is from 0.1 nm to 6 nm, the magnetic recording medium has excellent durability between the VTR head and the magnetic recording medium. A recording medium is obtained. The number of abrasives present in the surface of the magnetic layer is 100 to 1000 per 100 μm ² , and the amount of abrasive contained in the magnetic layer is 5/100 parts of ferromagnetic fine powder.
When the metal powder is ２０20 parts by weight and the specific surface area of the ferromagnetic fine powder of the magnetic layer is 47 m ² / g or more, high output and appropriate polishing ability can be obtained. Further, by providing a back layer having a surface roughness of 2 nm to 15 nm on the back surface of the non-magnetic support provided with the magnetic layer, extremely excellent running durability can be obtained.

In the present invention, the average projection height up to the upper end of the abrasive existing above the center line of the magnetic layer surface roughness of the magnetic layer and existing in the surface layer of the magnetic layer can be measured as follows. AF
Observing the abrasive present on the surface of the magnetic layer by M (Atomic Force Microscope), finding the curve of the magnetic layer surface roughness and its center line, identifying the position of the abrasive present on the surface from the micrograph, Layer above the center line of the magnetic layer surface roughness and up to the upper end of the abrasive present in the magnetic layer surface layer
Measure the height of the protrusions at 20 different locations, and take the average
By doing so, the average projection height can be determined . In this case, when the magnetic layer has a multilayer structure, the average particle size of the abrasive present in the uppermost magnetic layer is suitably from 0.1 to 1 μm, and the thickness of the uppermost layer at this time is determined by the average particle size of the abrasive. The following may be used. When the magnetic layer has a single-layer structure, the abrasive has a mean particle size of 0.1 to 1 in the magnetic layer.
μm is appropriate, and the thickness of the single layer at this time is preferably not less than the average particle size of the abrasive. In the present invention, the amount of the abrasive added to the magnetic layer is preferably 5 to 20 parts by weight per 100 parts by weight of the ferromagnetic fine powder. When the amount of the abrasive added to the magnetic layer is less than 5 parts by weight 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 or less. Can be achieved, but it is difficult to obtain a sufficient cleaning effect due to the small amount of addition. 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. And the cleaning effect can be sufficiently obtained, but the wear of the head increases abnormally and is not suitable as a magnetic recording medium.

That is, the present invention relates to a magnetic recording medium comprising a nonmagnetic support and a magnetic layer containing a ferromagnetic fine powder, a binder and an abrasive having a Mohs hardness of 8 or more. Average protrusion height up to the upper end of the abrasive present above the center line of
By setting the thickness to 13 nm or less, a magnetic recording medium having a VTR with less head wear and excellent running durability can be obtained. The use of abrasives for magnetic recording media has been known for a long time, but the height of the abrasives cannot be controlled by the particle size and the amount of the abrasives conventionally known. Conventionally, an abrasive having a particle size of about 0.01 to 2 μm is used.
It is used in an amount of 0.1 to 20 parts by weight per g. As these shapes, spherical shapes, shapes approximating spherical shapes, shapes having corners, and the like have been used. The average protrusion height to the upper end of the abrasive existing above the center line of the magnetic layer surface roughness of the magnetic layer formed by the prior art and existing in the surface layer of the magnetic layer is calculated from the center line of the magnetic layer surface roughness. As a result, the wear of the VTR head was increased, and only a magnetic recording medium having poor running durability was obtained. As described above, when the projection height of the abrasive is high, the VTR head wear increases, and the head life of the VTR becomes short. It is an effective means to reduce the amount of abrasive added to reduce VTR head wear,
The cleaning effect of the magnetic recording medium on the VTR head is reduced, and as a result of clogging of the head, the output is reduced, resulting in no commercial value.

The projection 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-processing. That is, a magnetic layer containing a ferromagnetic fine powder, a binder, and an abrasive having a Mohs hardness of 8 or more is applied on a non-magnetic support, and then a transfer speed of 10 m / min to 900 m /
2 minutes or more at a molding temperature of 50 ° C. to 130 ° C., a super-calendering treatment with a multi-stage facing metal roll, followed by a burnishing treatment to obtain an average projection height up to the upper end of the abrasive present on the magnetic layer surface layer. It can be 13 nm or less. Details of the super calendar process and the burnish process will be described later. At this time, it is preferable that at least one of the abrasives contained in the magnetic layer uses alumina, chromium oxide, or diamond. The surface roughness of the magnetic layer was set to 0.1 nm to 6 nm by a calendar, and a magnetic recording medium having excellent durability of the VTR head and the magnetic recording medium was obtained. At this time, the abrasive present on the surface layer of the magnetic layer is reduced by 100%.
100 to 1000 particles per μm ^{2, and the} abrasive contained in the magnetic layer is 5 to ² particles per 100 parts by weight of the ferromagnetic fine powder.
0 parts by weight, and 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, a high output can be achieved due to the super smoothness of the magnetic material, the magnetic layer, and the back layer.
In addition, by controlling the height of the projections of the abrasive and the number of the abrasives, an appropriate polishing ability is obtained. The surface roughness of the back layer on the back surface of the non-magnetic support provided with the magnetic layer is 2.
When the thickness is in the range of 15 nm to 15 nm, extremely excellent running durability and high CN are obtained. Although the reason is not clear, if the height of the abrasive is controlled as in the present invention, it is easy to secure the output for different heads. In addition, 1 μsec. It has been found that dropout of about -2 db is also greatly improved.

The magnetic recording medium of the present invention has a basic structure in which a magnetic layer containing at least a 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 and 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 inhibitor, a fungicide,
It may contain an antistatic agent, a nonmagnetic powder, a dye, an organic magnetic compound, a dispersant, and the like, and may have a mixed layer of different or identical magnetic layers of ferromagnetic fine powder or a multilayer structure.

As the ferromagnetic fine powder of the present invention, γ-Fe
Γ-Fe2 containing 2 O3 and Co (deposition, metamorphosis, doping)
O3, Fe3 O4, Co-containing (deposition, metamorphosis, doping)
Containing Fe3 O4, .gamma.-FeOX and Co (deposition, metamorphosis,
.Gamma.-FeOX (X = 1.33 to 1.5)
0), CrO2, etc. can be used.
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-
A ferromagnetic metal fine powder such as an Fe alloy is preferable. The particle size of these ferromagnetic metal fine powders is about 0.005 to 1 micron in length, and the ratio of shaft length / shaft width is about 1/2 to 15/1. The specific surface area of these ferromagnetic metal powders is 4
7 to 80 m2 / g, more preferably 53 to 70 m2 / g,
The coercive force (Hc) is 1250 to 2500 Oe, the water content is 0.1 to 2.0% by weight, and the 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 inhibitor, a surface treatment agent, a dispersant, a lubricant, an antistatic agent, etc. in a solvent prior to dispersion for each purpose, and adsorbed. . 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. The metal content in the ferromagnetic alloy powder is 60% by weight or more, and 70% by weight of the metal content.
% Or more of at least one ferromagnetic metal or alloy (eg, Fe, Fe—Co, Fe—Co—Ni, Co,
Ni, Fe-Ni, Co-Ni, Co-Ni-Fe), and the metal content is 40% by weight or less, and more preferably 20% by weight or less.
The 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, and P), and iron nitride, iron carbide, and the like. In particular, in order to supplement the strength of metallic iron, it is preferable to provide Al, Si, and Cr alone or in combination on the surface layer. In addition, the ferromagnetic metal contains a small amount of hydroxide or oxide, an alkali metal element (Na, K, etc.), an 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, as an example of a method for producing a ferromagnetic alloy fine powder, the following method can be mentioned. (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 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) A method of evaporating a metal in a low-pressure inert gas to obtain a fine powder. In the case of using a ferromagnetic metal fine powder, there is no particular limitation on its shape, but usually a needle shape, a granular shape, a die shape, Rice grains and plate-like grains are used, and those having the needle-like ratio described above are particularly preferred. Further, σs of these ferromagnetic materials is preferably 100 to 210 emu / g. The crystallite size is preferably 100 to 300A. The dice are preferably cubic or hexahedral or octahedral. As a plate, the ratio of plate / thickness is
Those having a ratio of 3/1 to 30/1 are preferred. Examples of these ferromagnetic alloy fine powders are described in 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.
No. 61, U.S. Pat. No. 4,447,264, U.S. Pat.
No. 021 and U.S. Pat. No. 4,931,198.

As the binder used for the magnetic layer and the back layer of the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, electron beam-curable resins, ultraviolet-curable resins, and visible light-curable resins. Resins and mixtures thereof are used. As a thermoplastic resin, the softening temperature is 150 ° C or less,
Average molecular weight of 10,000-300000, degree of polymerization of 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 copolymer, vinyl acrylonitrile copolymer, acrylate acrylonitrile copolymer, acrylate Vinylidene chloride copolymer, acrylate styrene copolymer, methacrylate acrylonitrile copolymer, methacrylate vinylidene chloride copolymer, methacrylate styrene copolymer, urethane elastomer, nylon-silicon resin, nitrocellulose -Polyamide resin, polyfuccavinyl, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer,
Polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose stracetate, cellulose propionate, nitrocellulose, ethyl cellulose)
, Methylcellulose, propylcellulose, methylethylcellulose, carboxymethylcellulose, acetylcellulose, etc.), styrene butadiene copolymer, polyester resin, polycarbonate resin, chlorovinyl ether acrylate copolymer For example, coalesced resins, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof are used. Examples of these resins are described in JP-B-37-6877.
No., JP-B-39-12528, JP-B-39-1928
No. 2, JP-B-40-5349 JP-B-40-2090
7, JP-B-41-9463, JP-B-41-1405
No. 9, Japanese Patent Publication No. 41-16985 Japanese Patent Publication No. 42-642
No. 8, JP-B-42-11621, JP-B-43-462
No. 3, JP-B-43-15206 JP-B-44-288
9, JP-B-44-17947, JP-B-44-182
No. 32, JP-B-45-14020, JP-B-45-14
No. 500, JP-B-47-18573, JP-B-47-2
No. 2063, JP-B-47-2264 JP-B-47-264
22068, JP-B-47-22069, JP-B-47
-22070, JP-B-47-27886, JP-A-Showa
57-133351, JP-A-58-137133, JP-A-58-166533, JP-A-58-222433, JP-A-59-58642, and the like, U.S. Pat.
This is described in U.S. Pat. No. 4,752,530.

The thermosetting resin or the 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 a reaction such as condensation and addition by heating and humidifying after coating and drying. Becomes Among these resins, those which do not soften or melt before the resin is thermally decomposed are preferred. 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 resin, nitrocellulose melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of methacrylate copolymer and diisocyanate prepolymer, mixture of polyester polyol and polyisocyanate, urea formaldehyde resin , Low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate, polyamine resin, polyimine resin and mixtures thereof.
Examples of these resins are described in JP-B-39-8103, JP-B-40-9779, JP-B-41-7192, and JP-B-sho-4.
No. 1-8016 No. 41-14275, No. 4
No. 2-18179, JP-B-43-12081, JP-B-44-28023 JP-B-45-14501, JP-B-45-24902, JP-B-46-13103, JP-B-47-22265 and JP-B-47-22066 issue,
JP-B-47-22067 and JP-B-47-22072
No., JP-B-47-22073, JP-B-47-2804
No. 5, JP-B-47-28048, JP-B-47-289
No. 22, etc. These thermoplastic, thermosetting resins and reactive resins have carboxylic acid (COOM), sulfinic acid, sulfenic acid, sulfonic acid (SO ₃ M) and phosphoric acid (PO (PO) as functional groups other than the main functional groups of the resin. OM) (OM)), phosphonic acid, sulfuric acid (OSO)
₃ M) and acidic groups such as ester groups thereof (M is H,
Alkali metals, alkaline earth metals, hydrocarbon groups), amino acids; aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohol, amphoteric groups such as alkyl betaine type, amino group, imino group, imide group, amide Groups,
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 usually contains at least one kind of nitrile group, oxo group, acryl group and phosphine group, and preferably contains 1 × 10 −6 eq to 1 × 10 −2 eq per gram of resin. Among these resins, resins having at least one functional group of sulfonic acid, phosphoric acid, phosphonic acid, epoxy group and hydroxyl group are particularly preferable.

The polyisocyanate used for the magnetic layer and the back layer of the present invention includes tolylene diisocyanate,
4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate
G, naphthylene-1, 5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate
, Triphenylmethane triisocyanate, isophorone diisocyanate and other isocyanates, products of the isocyanates and polyalcohols, and condensation of isocyanates The polyisocyanate of the dimer or dimer prepared above, or the product of a polyisocyanate and a polyurethane having a terminal functional group of isocyanate can be used. The average molecular weight of these polyisocyanates is preferably 100 to 20,000.
Commercially available trade names of these polyisocyanates include Coronate L, Coronate HL, Coronate 20
30, Coronate 2031, Millionate MR, Millionate MTL (manufactured by Nippon Polyurethane Co., Ltd.), Takenate D
-102, Takenate D-110N, Takenate D-
200, Takenate D-202, Takenate 300S,
Takenate 500 (manufactured by Takeda Pharmaceutical Co., Ltd.), Sumidur T-
80, Sumidur 44S, Sumidur PF, Sumidur L, Sumidur N desmodul L, Desmodur IL, Desmodur N, Desmodur HL,
Desmodule T65, Desmodule 15, Desmodule R, Desmodule RF, Desmodule SL,
Desmodur Z4273 (manufactured by Sumitomo Bayer Ltd.) and the like can be used alone or in combination of two or more by utilizing the difference in curing reactivity. In addition, for the purpose of accelerating the curing reaction, hydroxyl groups (butanediol, hexanediol, having a molecular weight of 1,000 to
It is also possible to use a compound having an amino group (monomethylamine, dimethylamine, trimethylamine and the like), a metal oxide catalyst, and 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 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 disclosed in
Nos. 0-131622 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 in the range of 3 to 100 parts by weight of the binder per 100 parts by weight of the ferromagnetic fine powder. The mixing ratio of the fine powder and the binder in the back layer is in the range of 8 to 150 parts by weight of the binder with respect to 100 parts by weight of the fine powder. Additives include 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 furnace black for rubber, thermal black for rubber, black for coloring, acetylene black, or the like. 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,
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., according to the US ASTM standard D-176.
Those classified as 5-82a can be used. The average particle size of these carbon blacks used in the present invention is 5 to 1000 millimicrons (electron microscope), the specific surface area by the nitrogen adsorption method is 1 to 800 m 2 / g, PH
Are 4 to 11 (JIS K-6221-1982 method),
Dibutyl phthalate (DBP) oil absorption is 10-800m
1 / 100g (JIS K-6221-1982 method)
It is. The size of the carbon black used in the present invention is 5 to 100 in order to reduce the surface electric resistance of the coating film.
Millimicron carbon black is used, and carbon black of 50 to 1000 millimicrons is used to control the strength of the coating film. Fine particles of carbon black (less than 100 millimicrons) are used to smooth the surface for the purpose of controlling the surface roughness of the coating film, and coarse particles of carbon black are used for the purpose of roughening the surface to reduce the friction coefficient. (100
Millimeters or more). 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 surface-treated with a dispersant described later or grafted with a resin for use. In addition, a carbon black which is treated at a furnace temperature of 2000 ° C. or more to produce carbon black and a part of the surface of which is graphitized can also be used. Also, hollow carbon black can be used as a special carbon black. In the case of a magnetic layer, it is desirable to use 0.1 to 20 parts by weight based on 100 parts of the ferromagnetic fine powder. In the case of the back layer, 2 per 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 in the back layer can be referred to, for example, "Carbon Black Handbook", edited by Carbon Black Association (issued in 1971). Examples of these carbon blacks are described in U.S. Pat. No. 4,539,257 and U.S. Pat.
No. 4885, JP-A-61-92424, JP-A-61-924.
No. 99927, etc.

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, and is composed of 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 component: corundum and magnetite), garnet, silica, silicon nitride, boron nitride, molybdenum carbide, boron carbide , Tungsten carbide, titanium carbide, tripoly, diatomaceous earth, dolomite, etc., and it is preferable to use a material having a Mohs hardness of 6 or more in combination of 1 to 4 types. These abrasives have an average particle size of 0.005 to 5 microns, particularly preferably 0.01 to 2 microns. These abrasives are desirably used 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. It is desirable to use these abrasives in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the nonmagnetic powder of the back layer. Examples of these are AKP1, AKP1 manufactured by Sumitomo Chemical Co., Ltd.
5, AKP20, AKP30, AKP50, AKP8
0, Hit50, Hit100, and the like. These are described in JP-B-52-28642 and JP-B-49-3.
No. 9402, JP-A-63-98828, U.S. Pat.
No. 87725, U.S. Pat. No. 3,077,807, U.S. Pat.
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 1,145,349, West German Patent 853211 and the like.

The powdery lubricant used for the magnetic layer and / or the 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, etc., acrylic styrene resin fine powder, benzoguanamine resin fine powder, melamine resin fine powder, polyolefin resin fine powder, polyester Resin fine powder such as fine resin powder of polyamide resin, fine powder of polyamide resin, fine powder of polyimide resin, fine powder of polyethylene ethylene resin, and the like. Silicone oil (dialkyl polysiloxane, dialkoxy polysiloxane, phenyl polysiloxane,
Fluoroalkylpolysiloxane (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, perfluorofatty acid, perfluorofatty acid ester, perfluoroalkyl sulfate, Compounds in which fluorine or silicon is introduced, such as fluoroalkylsulfonic acid ester, perfluoroalkylbenzenesulfonic acid ester, perfluoroalkylphosphate ester (for example, Krytox), alkyl sulfate, alkylsulfonic acid ester, alkylphosphonic acid triester , Alkyl phosphonic acid monoester,
Organic acids and organic acid ester compounds such as alkyl phosphonic acid diesters, alkyl phosphate esters, and succinate esters, and heterogenous compounds containing nitrogen and sulfur such as triazaindolizine, tetraazaindene, benzotriazole, benzotriazine, benzodiazole, and EDTA. (Hetero) cyclic 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 esters comprising any one or more of the following: monobasic fatty acids having 10 or more carbon atoms and monovalent to hexavalent fatty acids having 11 to 70 carbon atoms in total with the carbon numbers of the fatty acids. Fatty acid esters composed of monovalent alcohols, fatty acids having 8 to 40 carbon atoms or fatty acid amides, fatty acid alkylamides, and aliphatic alcohols can also be used. These carbons may be branched at any place. As the location of the branch, iso or 2,3-position branch is preferable. 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 amide, alkyl stearic acid, butoxyethyl stearate, anhydrosorbitan monostearate, ann 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, a so-called lubricating oil additive can be used alone or in combination. Antioxidants (alkylphenol, benzotriazine, tetraazaindene, sulfamide) , Guanidine, nucleic acid, pyridine, amine, hydroquinone, metal chelating agents such as EDTA), rust inhibitors (naphthenic acid, alkenyl succinic acid, phosphoric acid, dilauryl phosphate, etc.), oily agents (rapeseed oil, lauryl alcohol) Extreme pressure agents (dibenzyl sulfide, tricresyl phosphate, tributyl phosphite, etc.),
There are cleaning dispersants, viscosity index improvers, pour point depressants, foaming agents and the like. These lubricants may be used in the form of a composite, or two or more of these characteristic groups may be introduced into one molecule. For example, a fluorine-containing fatty acid, a fluorine-containing fatty acid ester, a siloxane-containing fatty acid, a siloxane-containing fatty acid ester and the like can be mentioned. These lubricants are added in the range of 0.01 to 30 parts by weight based on 100 parts by weight of the binder for the magnetic layer and / or the back layer. These are described in JP-B-43-23889 and JP-B-48-24.
No. 041, JP-B-48-18482, JP-B-44-1
8221, JP-B-47-28043, JP-B-57-5
6132, JP-A-59-8136, JP-A-59-81
39, JP-A-61-85621, U.S. Pat.
No. 233, U.S. Pat.
No. 2235, U.S. Pat. No. 3,497,411, U.S. Pat.
No. 23086, U.S. Pat. No. 3,625,760, U.S. Pat.
No. 630772, US Pat. No. 3,634,253, US Pat. No. 3,642,539, US Pat. No. 3,687,725, US Pat. No. 4,350,311, US Pat. No. 4,497,864, US Pat. No. 4,552,794, IBM Technical Day
Scro-Ja Britain (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.

The dispersing agent and dispersing agent 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 stearoyl. -Fatty acids having 2 to 40 carbon atoms (R1 COOH, R1 is an alkyl group having 1 to 39 carbon atoms, phenyl group, aralkyl group) such as carboxylic acid, behenic acid, maleic acid, phthalic acid, etc .; Metal soap (copper oleate) composed of metal (Li, Na, K, NH4 +, etc.) or alkaline earth metal (Mg, Ca, Ba, etc.), Cu, Pb, etc., 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, cetyl alcohol, isocetyl alcohol) and their sulfates, sulfonic acids, Phenylsulfonic acid, alkylsulfonic 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, metal sulfosuccinate, sulfosuccinate and the like can also be used. One or more of these dispersants are usually used, and one kind of the dispersant is added in an amount of 0.005 to 20 parts by weight based on 100 parts by weight of the binder. How to use these dispersants
It may be applied in advance to the surface of a ferromagnetic fine powder or a non-magnetic fine powder, or may be added during dispersion. Such a structure is disclosed, for example, in JP-B-39-28369 and JP-B-44-1.
7945, JP-B-44-18221, JP-B-48-
7441, JP-B-48-15001, JP-B-48-
15002, JP-B-48-16363, JP-B-49
No. 39402, U.S. Pat.
No. 0021 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 shown in, for example, "Microbial Disaster and Prevention Technology", Engineering Books, 1972, "Chemistry and Industry", 32, 904 (1979). These fungicides are used in the range of 0.005 to 20 parts by weight based on 100 parts by weight of the binder.

As the antistatic agent other than carbon black used in the present invention, graphite, modified graphite, carbon black graft polymer, tin oxide-antimony oxide, tin oxide, titanium oxide-tin oxide-antimony oxide,
Nonionic surfactants such as alkylene oxide, glycerin, glycidol, polyhydric alcohols, polyhydric alcohol esters, alkylphenol EO adducts, etc. Agents; higher alkyl amines, cyclic amines, hydantoin derivatives, amidoamines, ester amides, quaternary ammonium salts, pyridine and other heterocycles, phosphoniums or sulfoniums, and other cationic surfactants; 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 acids, sulfuric acid or phosphate esters 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. 2,224,472, 2,288,226, 26
No. 76122, No. 2676924, No. 2676975
Nos. 2691566 and 2727860 and 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
No. 42654, No. 3475174, No. 3545974
No. 1, West German Patent Publication (OLS) 1942665, British Patent Nos. 1077317 and 1198450, and the like.
Ryohei Oda et al., "Synthesis of Surfactants and Their Applications" (Maki Shoten, 1972 Edition); W. T. Beili, "Surface Active Agents" (Interscience Publication Corporation, 1985);
P. By Shisley, "Encyclopedia of Surfactive Agents, Vol. 2," (Chemical Publishing Co., Ltd., 1964); "Surfactant Handbook," 6th printing (Sangyo Tosho Co., Ltd., December 1966. Month 20
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 these surfactants used in a magnetic recording medium depends on the ferromagnetic fine powder
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 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.

As the organic solvent used in the dispersion, kneading and coating of the present invention, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone and tetrahydrofuran in any ratio; methanol, ethanol Alcohols such as acetic acid, propanol, butanol, isobutyl alcohol, isopropyl alcohol and methylcyclohexanol; methyl acetate;
Ester systems such as ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, and glycol monoethyl ether; ethers such as diethyl ether, tetrahydrofuran, glycol dimethyl ether, glycol monoethyl ether, and dioxane Tar system (aromatic hydrocarbon) such as benzene, toluene, xylene, cresol, chlorobenzene, styrene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. Chlorinated hydrocarbons, N, N-dimethylformaldehyde, hexane and the like can be used. These solvents are generally used in two or more kinds at an arbitrary ratio. In addition, trace amounts of impurities (polymerization of the solvent itself, water,
Raw material components). 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 preferred solid content of the magnetic liquid is 5 to 40% by weight. The preferred solid content of the back solution is 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 combining the above-mentioned compositions and the like arbitrarily in an organic solvent alone or in combination and impregnating, dissolving, mixing, dispersing, kneading and diluting the coating solution in any order. Create, apply and dry on the support
Orient. When used as a tape or disk, the thickness of the support is preferably about 2.5 to 500 microns, preferably about 3 to 100 microns. The material is 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,
"Textile and Industry", vol. 31, p. 50-55, 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 according to the purpose.

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 divisional addition of the same raw material, the dispersion temperature (0 to 80 ° C.), the humidity, and the like can be appropriately set. For preparing the magnetic paint and the back layer paint, a conventional kneading machine 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, coneder, intensive mixer, Tumbler, blender, disperser, homogenizer, single-screw extruder, twin-screw extruder,
And an ultrasonic dispersing machine. 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 technique relating to kneading and dispersion, see T.S. C.
"Paint" by Patton (Tec. Patton)
Flow and Pigment Dispers
ion "(Paint Flo and Pigment Day Spurgeon) 1964 John Wiley &
Published by Sons, Inc. (John Willy and Sons) and Shinichi Tanaka, Industrial Materials, Vol. 25, 37 (197)
7) and the cited reference of the book. As an auxiliary material for the dispersion and kneading, a steel ball, a steel bead, a ceramic bead, a glass bead, and an organic polymer bead having an equivalent sphere diameter of 10 cmφ to 0.05 mmφ can be used in order to efficiently promote the dispersion and kneading. 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. Hardeners and some additives (fatty acids, phosphoric acids, phosphonic acids, sulfonic acids, and their esters, which are highly reactive with magnetic substances) are added to the coating solution using an adding machine such as a mixing valve immediately before coating. May be.

As a method for applying the above-mentioned coating solution for the magnetic recording layer, the coating solution for the back layer, and the undercoating solution on the support, the viscosity of the coating solution is preferably 1 to 20,000 centistokes (25
° C), air doctor coat, blade coater
Coat, air knife coat, squeeze coat, impregnation coat,
Reverse 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. These concrete explanations are described in “Coating Engineering” published by Asakura Shoten, pages 253 to 277 (published by Showa 46.3.20.).
Etc. are described in detail. The order of application of these coating solutions can be arbitrarily selected, and the undercoat layer may be applied continuously before the application of the desired solution. When it is desired to form the magnetic layer or the back layer with multiple layers, simultaneous multilayer coating, sequential multilayer coating, or the like may be performed. These are described in, for example,
JP-A-7-123532, JP-B-62-37451, JP-A-59-142741 and JP-A-59-1.
No. 65239, and the like.

By such a method, about 1 to about
The magnetic liquid applied to a thickness of about 100 μm (solid content: 0.1 to 50 g / m ² ) can be obtained by immediately drying the magnetic powder in the layer at 20 to 130 ° C. in multiple stages at 500 to 5
The desired direction (vertical, longitudinal, width, random,
After performing a treatment for oblique orientation, the formed magnetic layer is dried to a thickness of 0.1 to 10 μm. The conveying speed of the support at this time is usually 10 m / min to 900 m / min, and the drying temperature is set at 20 ° C. to 130 ° C. in a plurality of drying zones.
C. to control the amount of residual solvent in the coating film from 0.01 to 40 mg /
m2. In the present invention, after that, the magnetic recording medium is subjected to a super calendering process to perform a surface smoothing process, and the center line average surface roughness of the magnetic layer and the back layer is adjusted to a desired value.
Further, the magnetic recording medium of the present invention is manufactured by cutting into a desired shape. At this time, it is preferable to use a facing metal roll for the super calendering process. At this time, the magnetic recording medium is usually processed at a conveying speed of 10 m / min to 900 m / min, and is usually processed by two or more multi-stage metal rolls, preferably at a molding temperature of 50 ° C. to 130 ° C. . The remaining processing may use a combination of a metal roll, a super-hard plastic, and a super-hard plastic.

In these production 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 performed. It is desirable. These are described, for example, in JP-B-40-23625, JP-B-39-28368, JP-B-47-38802, and British Patent 119.
No. 1424, JP-B-48-11336, JP-A-Showa 4
JP-A-9-53631, JP-A-50-112005, JP-A-51-77303, JP-B-52-17404, JP-A-60-70532, JP-A-2-265672
No. 3,473,960, U.S. Pat.
569 and U.S. Pat. No. 4,746,542. On the other hand, the method disclosed in Japanese Patent Publication No. 41-13181 is considered to be a basic and important technique in this field.

After the magnetic recording medium thus produced is cut, it is 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 end face, base face) immediately before or before winding. Burnish uses a hard material such as a sapphire blade, a razor blade, a super hard material blade, a diamond blade, or a ceramic blade to flatten the magnetic recording medium to protrude the magnetic recording medium surface. The Mohs hardness of these materials is preferably 8 or more, but is not particularly limited as long as protrusions can be removed. The shape of these materials does not need to be a blade in particular, and shapes such as a square shape, a round shape, and a wheel (these materials may be provided around a rotating cylindrical shape) can be used. Cleaning of the magnetic recording medium is performed by removing the surface layer of the magnetic recording medium with a non-woven fabric or the like with a magnetic layer surface, a back layer surface,
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 manufactured by Nippon Vilene and Toraysee manufactured by Toray, Ecseine, Kimwipe (trade name), various types of polishing tapes manufactured by Fuji Photo Film, and nonwoven fabrics made of nonwoven fabric made of nylon, polyester, and rayon Tissue paper and the like such as acrylonitrile nonwoven fabric and blended nonwoven fabric can be used. These are described, for example, in JP-B-46-39309.
No., JP-B-58-46768, JP-A-56-9042.
9, JP-B-58-46767, JP-A-63-259
No. 830, JP-A-1-201824 and the like. In particular, in the present invention, it is necessary to treat with a rotary blade or a polishing tape made of a material having a Mohs' hardness of 9 or more. . When processing with a polishing tape, the contact surface needs to be 0.1 mm or more. At this time, the tension applied to the magnetic recording medium needs to be 200 g or more per 1/2 inch width, and the tension change before and after this processing apparatus is 200 g.
It is necessary to be above.

[0030]

EXAMPLES The present invention will be described more specifically with reference to the following examples. It will be readily understood by those skilled in the art that the components, ratios, operation sequences, 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 embodiments. In the examples, parts by weight indicate parts by weight.

Example 1 A magnetic coating material (1) having the composition shown below was kneaded with an open kneader, added with a composition (2), dispersed in a sand mill, added with (3) before application, adjusted and dried. 6. Thickness of the undercoat layer previously applied so that the thickness of the subsequent magnetic layer is 2.0 μm.
0 μm non-magnetic support polyethylene naphthalate (MD
The Young's modulus in the TD direction was 900 kg / mm ² and the Young's modulus in the TD direction was 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 (phenylsulfonic acid) 2 parts Iron oleate 0. 1 part Vinyl chloride copolymer resin 9 parts (Zeon Corporation: 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 part 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 ( Nippon Zeon: MR110) Methyl ethyl ketone 40 parts or more Dispersion cyclohexanone 60 parts

(3) Polyisocyanate (Nippon Polyurethane: Coronate 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 paint is subjected to a magnetic field orientation treatment and drying in a state where the magnetic paint is not dried, and then (2) is added to the following back paint (1) immediately before coating, and the thickness is dried. It was applied at 0.6 μm. After drying, metal calendering is performed at 100 ° C., at a linear pressure of 350 kg / cm, and at a speed of 2.
The process was performed 5 times at 00 m / min, and then slit to a 1/2 inch width. Continue to tape with 2% diamond (1μ
m) The magnetic layer is wrapped with a wrapping tape of -98% alumina (0.5 μm), the contact distance is 100 mm, and the tension is 400 g.
/ Hc1700 Oe, SQ 0.91, Ra
3 nm (cutoff value 0.25 mm, measurement length 0.25
mm) , gloss 260 (reflection at 45 degrees), back layer Ra7n
m (cutoff value 0.25 mm, measurement length 0.25 m
m) Video tape was prepared. Table 1 shows the list of the results.
It was shown to.

Back coating composition (1) Carbon black (Cabot BP800) 90 parts Carbon black (Cancarb MTCI) 10 parts α-alumina (Sumitomo Chemical HIT100) 0.2 parts Barium sulfate (Sakai Chemical BF1) 0.2 parts Stearic acid 2 parts ethylhexyl 0.5 parts copper oleate 0.1 parts vinyl chloride copolymer resin 40 parts (manufactured by Zeon Corporation: MR110) urethane resin 30 parts (Toyobo: UR8300) cyclohexanone 200 parts methyl ethyl ketone 300 parts (2) polyisocyanate (Nippon Polyurethane Co., Ltd .: Coronate 3040) 20 parts Methyl ethyl ketone 3500 parts Toluene 200 parts Silicone (Shin-Etsu Chemical KF69) 0.1 part

Table 1 Latching material Abrasive material Initial head VTR compatible Low humidity treatment Height Quantity Wear Output difference Output (tension) (nm) (q / 100 μm ² ) (μ / 100H) (dB) Decrease (dB) Available (400 g) 2 200 100-22 (350 g) 4 200 15 22-23 (300 g) 6 200 23 3-14 (250 g) 8 200 30 4-15 (200 g) 12 200 35 6-16 〃 (300 g) 8 400 30 3-17 〃 (300 g) 7 250 25 4-2 Comparative Example 1 Available (50 g) 14 200 80 12 -4 2 None 20 200 100 14 14-23 １６ 16 80 80 12 -6>

Note 1) In the sixth embodiment, the abrasive (Hit
55) The amount was 15 g. Note 2) In the seventh embodiment, the abrasive is 0.5 in the first embodiment.
It was chromium oxide of μm. Note 3) In Comparative Example 3, the abrasive (Hit
55) The amount was 4.5 g. Note 4) The initial head wear was converted to 100 hours by running two turns of a new product for 90 minutes 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 by another VTR. I asked. Note 6) Output drop in a low humidity environment is 23 ° C and 10% RH.
The vehicle was run for 90 minutes under the conditions described above, and a decrease in output under low humidity was observed.

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, the abrasive must be 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 make the height of the abrasive 13 nm or less.

[0040]

According to the magnetic recording medium of the present invention, a magnetic layer containing a ferromagnetic fine powder, a binder and an abrasive having a Mohs hardness of 8 or more is provided on a nonmagnetic support. By setting the average protrusion height to the upper end of the abrasive existing above the center line and in the surface layer of the magnetic layer to 13 nm or less, it is possible to obtain a magnetic recording medium having less VTR head wear and excellent running durability. 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 from 0.1 nm to 6 n.
At m, a magnetic recording medium having excellent durability between the VTR head and the magnetic recording medium was obtained. The surface layer of the magnetic layer contains 100 to 1000 abrasives per 100 μm ² , the magnetic layer contains 5 to 20 parts by weight of abrasives per 100 parts of ferromagnetic fine powder, and the magnetic layer contains When the powder was a metal powder having a specific surface area of 47 m ² / g or more, high output and appropriate polishing ability were obtained. The surface roughness of the back surface of the non-magnetic support on which the magnetic layer is coated is 2 nm to 1 nm.
By having a back layer of 5 nm, extremely excellent running durability was obtained.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-184708 (JP, A) JP-A-4-205817 (JP, A) (58) Fields investigated (Int.Cl. ⁶ , DB name) G11B 5/70 G11B 5/708 G11B 5/84

Claims (6)

(57) [Claims] In a magnetic recording medium having a magnetic layer containing a ferromagnetic fine powder, a binder and an abrasive having a Mohs hardness of 8 or more on a nonmagnetic support, a center line of the magnetic layer surface roughness of the magnetic layer is used. The average protrusion height up to the upper end of the abrasive present on the magnetic layer surface layer is the center line of the magnetic layer surface roughness.
A magnetic recording medium characterized in that the magnetic recording medium has a thickness of 13 nm or less. 2. The abrasive material contained in the magnetic layer is alumina,
2. The magnetic recording medium according to claim 1, wherein the medium is at least one selected from chromium oxide and diamond. 3. The magnetic layer has a surface roughness of 0.1 nm to 6 nm.
2. The magnetic recording medium according to claim 1, further comprising a back layer having a surface roughness of 2 nm to 15 nm on the back surface of the nonmagnetic support on which the magnetic layer is provided. 4. An abrasive material present on a surface layer of the magnetic layer, wherein
^2. The magnetic recording medium according to claim 1, wherein the amount of the abrasive is 100 to 1000 per 00 [mu] m < ² >, and the abrasive contained in the magnetic layer is 5 to 20 parts by weight per 100 parts by weight of the ferromagnetic fine powder. 5. The method according to claim 1, wherein the ferromagnetic fine powder has a specific surface area of 47 m ² / g.
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is the above metal powder. 6. A magnetic layer containing a ferromagnetic fine powder, a binder and an abrasive having a Mohs hardness of 8 or more is applied on a non-magnetic support, and then a conveying speed of 10 to 900 m / min and a molding temperature of 50 to 130.degree. Super calendering with a multi-stage counter metal roll at least twice at ℃, followed by burnishing , and present above the center line of the magnetic layer surface roughness of the magnetic layer
And the average of the abrasives present on the surface of the magnetic layer up to the upper end
A method for manufacturing a magnetic recording medium, wherein the protrusion height is 13 nm or less from the center line of the magnetic layer surface roughness .