JPH031318A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve Young's modulus of a magnetic layer and/or a back layer and durability of the medium by extremely reducing the amt. of water contained in a coating liquid so that polyisocyanate can be effectively used for crosslinking reaction with all components of a binder without reaction with water in the coating liquid. CONSTITUTION:The water content in the coating liquid for a magnetic layer is specified to 0.000 - 0.200 wt.%, and preferably, the water content of the coating liquid for a back layer is 0.000 - 0.20 wt.%. More preferably, cyanoacrylate or methacryloil isocyanate is incorporated into the coating liquid for the magnetic and/or back layer. thereby, the water content in the coating liquid can be controlled, and thus, Youn's modulus of the magnetic recording medium can be increased. Traveling durability of the medium can be also improve.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a magnetic recording medium comprising a nonmagnetic support, a magnetic layer, and a back layer, and particularly to a magnetic recording medium with improved running durability.

(Prior Art) Generally, as a magnetic recording medium for audio, video, computer use (disks, memory tapes), etc., a magnetic layer in which fine ferromagnetic powder is dispersed in a binder is placed on a non-magnetic support. A magnetic recording medium is used.

In recent years, these magnetic recording media are required to have high density recording.
Higher signal/noise and lower noise have been achieved by making fine ferromagnetic powders, alloy powders, higher filling, ultra-smooth surfaces of magnetic recording media, etc. Furthermore, in order to perform high-density recording in the same amount of time, it is necessary to shorten the writing speed and reading speed to the magnetic recording medium, and high-speed conveyance of the magnetic recording medium is required.

Running properties, charging properties, and head cleaning properties are essential for this high-speed conveyance suitability, and for this purpose fillers called carbon black and abrasives with a Mohs hardness of 8 or higher are used. USP3630910, USP3B33412, USP4614685,
It is disclosed in US Pat.

However, even with these techniques, it has been extremely difficult to sufficiently satisfy the running durability associated with high-speed tape conveyance. The reason for this is that the Young's modulus of the magnetic recording medium is large (it is difficult to do so.The reason for this is that the magnetic recording medium is made by coating a magnetic liquid and/or backing liquid on a non-magnetic support. This is because among the binders, polyisocyanate and/or isocyanate reacts with the moisture in the prepared coating liquid and cannot effectively contribute to the crosslinking reaction with the binder and resin.If the moisture in this coating liquid is reduced, Although an effective cross-linking reaction can be carried out, most of the moisture in the coating solution comes from the raw material powder, resin, and organic solvent, and moisture also enters from the atmosphere during the coating solution manufacturing process2. It was extremely difficult to control the water content of the liquid.

In other words, the magnetic layer conventionally obtained without adjusting the moisture content is 0.
．． It contained 25 to 0.3% by weight of moisture, but attempts have been made to add even more moisture than this.

For example, in JP-A No. 59-5424, an attempt was made to improve the dispersion stability of paint by using magnetic powder with a moisture content of 0.5 to 1.5%, and to obtain a product with high density and high durability. In JP-A No. 59-77623, the water content of the magnetic layer is 0.35% by weight or more, and this is achieved by reacting polyisocyanate with water to form appropriate amounts of urea bonds and biuret bonds. This is a proposal that will give you sex. Furthermore, JP-A-63-306524 attempts to improve antistatic properties and durability by using a magnetic recording medium containing 200 to 2000 ppm of water in the magnetic layer. Attempts have been made to improve the various properties of ferromagnetic powder by adding more water to the untreated powder.It is true that the dispersibility of ferromagnetic powder has been improved, and the dispersibility of ferromagnetic powder has been improved. Although the reaction progressed, it was too early to find a fundamental solution to improving running durability.

The present inventors have discovered that controlling the moisture content of the magnetic coating liquid is a fundamental factor in running durability, and have further established a method for controlling the moisture content of this coating liquid, and have also attempted to increase the Young's modulus of the magnetic recording medium. The present invention has been devised by establishing this technology and dramatically improving running durability.

(Object of the invention) The object of the present invention is to obtain ferromagnetic fine powder constituting a magnetic recording medium,
binders, additives, carbon black, abrasives,
High reliability is achieved in magnetic recording media in which a magnetic layer containing a lubricant etc. is provided on a non-magnetic support, and a back layer containing a binder and carbon black is provided on the non-magnetic support on the opposite side of the magnetic layer. This provides a certain degree of running durability.

(Structure of the Invention) That is, the above object of the present invention is to coat a non-magnetic support with ferromagnetic fine powder 1. In a magnetic recording medium having a magnetic layer coated with a coating solution containing a binder and additives, and a back layer coated with a coating solution containing a binder and carbon black on the other side, the moisture content of the coating solution for the magnetic layer. ga o, ooo
A magnetic recording medium characterized in that the moisture content of the coating liquid of the back layer is preferably o, ooo to 0.200% by weight. This can be achieved by a recording medium, and more preferably by a magnetic recording medium characterized in that the coating liquid for the magnetic layer and/or back layer contains cyanoacrylate or methacryloyl isocyanate.

The magnetic recording medium of the present invention has a magnetic layer containing ferromagnetic fine powder, a binder, an additive, carbon black, an abrasive, a lubricant, etc. on a non-magnetic support, and a non-magnetic support provided with a magnetic layer. It has a basic structure in which a magnetic layer or a back layer containing non-magnetic powder and a binder is provided on the opposite side of the body.

The magnetic recording medium of the present invention contains polyisocyanate and/or isocyanate in the binder of the magnetic liquid for forming the magnetic layer and/or the backing liquid for forming the back layer, and contains a thermosetting resin (as a base material containing both). It has a structure.

The present inventors have made extensive studies regarding magnetic recording media that are excellent in running durability and signal/noise. As a result, (1) a magnetic layer containing ferromagnetic fine powder, a binder, and additives (carbon black, abrasive, lubricant, etc.) is provided on a non-magnetic support, and the back layer containing the binder and carbon black is made magnetic. In a magnetic recording medium provided on a non-magnetic support on the opposite side of the layer, the water content of the coating liquid for the magnetic layer is set to 0.
By controlling the content to 0.000 to 0.200% by weight, the Young's modulus of the magnetic layer coating film is increased. When the binder of the magnetic coating liquid for forming the magnetic layer contains polyisocyanate and/or isocyanate and also contains a thermosetting resin, the water content in the magnetic layer coating liquid is
, ooo to 0.200% by weight, otherwise the polyisocyanate and/or isocyanate will react with moisture in the coating solution and will not contribute to an effective crosslinking and curing reaction, resulting in a decrease in Young's modulus. Furthermore, when the polyisocyanate and/or isocyanate reacts with moisture in the coating solution, carbon dioxide gas is generated and pinhole defects occur in the coating film, which is undesirable.
The sources of moisture in this coating liquid are mainly raw materials constituting the coating liquid and moisture from the atmosphere during manufacturing of the coating liquid. In particular, the raw materials that make up the coating solution, such as ferromagnetic fine powder, binder, carbon black, and abrasives, usually contain no moisture.
Contains 2 to 5% by weight and controls moisture in the coating solution. 1
It was extremely difficult to do so. Also, (2) the water content of the coating liquid for the back layer is o, oo for the reasons mentioned above.
It is preferable to control it to 0 to 0.200% by weight (3
) A specific means for reducing the water content of the coating solution for these magnetic layers is to add cyanoacrylate to the coating solution and react the moisture with the cyanoacrylate in advance.
After reducing the amount to 200% by weight, an effective crosslinking and curing reaction can be achieved by adding polyisocyanate and/or isocyanate, stirring, and coating on a non-magnetic support. Regarding (4) specific means for reducing the water content of the coating solution for the back layer, similarly, by adding cyanoacrylate prior to the addition of polyisocyanate and/or isocyanate, the water content in the coating solution can be reduced to o, oo.
The content is controlled to 0 to 0.200% by weight. (5) Another specific means for reducing the water content of the coating solution for the magnetic layer and/or back layer is to add methacryloyl isocyanate to the coating solution to reduce the water content in the coating solution to 0.00.
A magnetic recording medium characterized in that an effective crosslinking and curing reaction is carried out by adding polyisocyanate and/or isocyanate after reducing it to 0 to 0.200% by weight, stirring, and coating it on a non-magnetic support. #Moisture in the coating liquid can be reduced by the method described above, and moisture entering from the atmosphere can be achieved by sealing the manufacturing process to block moisture from the atmosphere. Furthermore, if the manufacturing process cannot be sealed, moisture in the atmosphere can be blocked by purging the inside of the equipment for the manufacturing process with dry gas (air, nitrogen, etc.).

The cyanoacrylate used in the present invention is as follows:
).

N CH□-C General formula N) 0OR (R= CHs , -CHz C) (s , CH
g CHx CHs , CH(CHs )t
, CHg CHg CHt CHs ,
- Straight chain or branched alkyl group having 1 to 8 carbon atoms such as -〇H1-CH(CH3)8) Regarding the synthesis method of these compounds, please refer to U.S. Pat.
No. 1,858, the same patent No. 3,463,804, etc. can be referred to.

The methacryloyl isocyanate used in the present invention has the following pattern (If).

C (=0) NCO (R= CHs , CHi CHs , CH
g CHt CHs , CH(CHs ) *
, CHx CHg CHt CHs ,
The cyanoacrylate or methacryloyl isocyanate used in the present invention is preferably added in an amount of 2% by weight or less of the total amount of the binder. The timing of adding the cyanoacrylate or methacryloyl isocyanate used in the present invention may be before or after preparing the coating solution, but it is preferable to add the cyanoacrylate or methacryloyl isocyanate before adding the polyisocyanate and/or isocyanate in order to remove excess water. Acrylate or methacryloyl isocyanate may be used in combination.

The ferromagnetic fine powder used in the present invention is y -Fe2
O,, Co-containing (adhered, modified, doped) r-Fe,
Os, Fes Oa, Co-containing (adhered, modified, doped) Fe s Oa, Fe Ox −, Co-containing (adhered, modified, doped) FeOx (X=1°33
~1,50), CrOt, Rn, Te, Sb.

CrQ, Fe%Co, Ni containing at least one of Sr, Fe, TI, V, Mn5Cr=ol.

Fe-Co alloy, Fe-Ni alloy, Fe-Co-Ni alloy, Co-N1-P alloy, Co-N1-Fe-B alloy,
Fe-Ni-Zn alloy, Ni-Co alloy, Co-Ni-
Fe alloy, Fe-N alloy, Fe-Co-Cr alloy, Mn
-B1 alloy and other known ferromagnetic fine powders can be used;
No. 8372, Special Publication No. 1972-22062, Special Publication No. 1972-
No. 22513, Special Publication No. 1977-28466, Special Publication No. 1973
-28466, Special Publication No. 46-38755, Special Publication No. 46
No. 7-4286, Special Publication No. 47-12422, Special Publication No. 4
No. 7-17284, Equity No. 47-18509, Special Publication No. 47-18573, Special Publication No. 10307 of 1977,
Special Publication No. 4B-29280, Special Publication No. 48-39639, Special Publication No. 58-29605, Special Publication No. 60-44254
No., JP 59-126605, U.S. Patent No. 30262
No. 15, No. 3031341, No. 3100194, No. 3242005, No. 3389014, etc. The particle size of these ferromagnetic fine powders is approximately 0.00
The length is 5 to 1 micron, and the ratio of axial length/width is 1/1 to 1.
It is about 50/1. Further, the specific surface area of these ferromagnetic fine powders is about lnf/g to 70 po/g. The moisture content of these ferromagnetic fine powders is 0.2 to 2.0 wt%. When these ferromagnetic fine powders are used, the water content of the coating liquid is 0.00 to 2.00 wt%. The surface of these ferromagnetic fine powders may be impregnated with a dispersant, lubricant, antistatic agent, etc., which will be described later, in a solvent for each purpose prior to dispersion, and then adsorbed. The fine powder is
Sr, Pb, Mn, Ni, Cd5Cr5 within 1wt%
It is preferable that heavy metals such as Al, 5i1Ti, Cu, and Zn are included.

Alumina or the like may be applied and melted onto these ferromagnetic fine powders.

Further, as the ferromagnetic fine powder used in the present invention, plate-shaped hexagonal barium ferrite can also be used.

The particle size of barium ferrite is about 0.001 to 1 micron in diameter and the thickness is 1/2 to 1/20 of the diameter.

Barium ferrite has a specific gravity of 4 to 6 g/cc and a specific surface area of lnf/g to 70 rrf/g. The surface of these ferromagnetic fine powders may be impregnated with a dispersant, a lubricant, an antistatic agent, etc., which will be described later, in a solvent for each purpose prior to dispersion, and then stuck thereto.

Further, the alloy powder used as the ferromagnetic fine powder of the present invention is a ferromagnetic alloy powder containing iron, cobalt, or nickel, and when the ferromagnetic alloy powder whose specific surface area is 35 rtf/g or more is used as the ferromagnetic powder, The effect is noticeable.

An example of this ferromagnetic alloy powder is one in which the metal content in the ferromagnetic alloy powder is 75% or more, and the metal content is 8%.
0% by weight or more of ferromagnetic metals or alloys of at least fil (e.g., Fe, Co%Ni1Fe-Co%Fe-N
i, Co-Ni, Co-N1-Fe), and other components (e.g., A I,
S i % S SS c, Ti, V, CrSMn, C
u, Zn, Y, Mo.

Rh, Pd%Ag, Sn, Sb, Te%Ba.

T a SW s Re % A u 1Hg %P
d, B 1 s L a sCe5Pr, Nd, B,
Examples include alloys that may contain P), iron nitride, and the like. Further, the ferromagnetic metal may contain a small amount of water, hydroxide, or oxide, and methods for producing these ferromagnetic metal powders are already known. Ferromagnetic alloy powder, which is a typical example, can also be manufactured according to these known methods.

That is, examples of the method for producing ferromagnetic alloy powder include the following method.

(a) Method of reducing complex organic acid salts (mainly oxalates) with a reducing gas such as hydrogen: (b) Obtaining Fe or Fe-Co particles by reducing iron oxide with a reducing gas such as hydrogen Method: (c) Method of thermally decomposing a metal carbonyl compound: (d) Method of reducing an aqueous solution of a ferromagnetic metal by adding a reducing agent such as sodium borohydride, hypophosphite or hydrazine: (e) Method for electrolytically depositing ferromagnetic metal powder using a mercury cathode and then separating it from mercury: (f) Method for obtaining fine powder by evaporating the metal in a low-pressure inert gas: Magnetic layer and back layer of the present invention As the binder used for this purpose, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 300,000, and a degree of polymerization of about 50.
~2,000, such as vinyl chloride vinyl acetate copolymer, vinyl chloride polymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer,
Acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer Combined, urethane elastomer, nylon-silicon resin,
nitrocellulose polyamide resin, polyfukkavinyl,
Vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (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 copolymers, polyester resins, chlorovinyl ether acrylate copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof. Ru.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferable, such as phenol resins, phenoxy resins, epoxy resins, polyurethane curable resins, urea resins, and melamine resins. , alkyd resins, silicone resins, acrylic reactive resins, epoxy-polyamide resins, nitrocellulose melamine resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, polyester polyols and polyesters. mixtures with isocyanates,
These include urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanate, polyamine resins, polyimine resins, and mixtures thereof.

These thermoplastic resins, thermosetting resins, and reactive resins are
In addition to the main functional groups, acidic groups such as carboxylic acid, sulfinic acid, sulfenic acid, sulfonic acid, phosphoric acid, sulfuric acid, phosphonic acid, phosphine, boric acid, sulfuric ester group, phosphoric ester group, and their alkyl ester groups ( These acidic groups may be in the form of Na salts, etc.), amino acids; amino sulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, amphoteric groups such as alkyl betaine types, amino groups, imino groups, imido groups, amide groups. , epoxy group,
In addition, it usually contains 1 to 6 types of hydroxyl groups, alkosyl groups, thiol groups, halogen groups, silyl groups, and siloxane groups, and each functional group contains 1xlO-'eq (
It is preferable to contain 1X10-''eq (equivalent amount).

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 5 to 300 parts by weight based on 100 parts by weight of the ferromagnetic fine powder. The mixing ratio of the fine powder and the binder in the back layer is in the range of 11,130 to 300 parts by weight of the binder per 100 parts by weight of the fine powder. Additives include dispersants, lubricants, abrasives, antistatic agents, antioxidants, solvents, and the like.

Examples of the polyisocyanate used in the present invention include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-)luidine diisocyanate, isophorone diisocyanate, and triphenyl diisocyanate. Isocyanates such as methane triisocyanate and isophorone diisocyanate, or products of equivalent incyanates and polyalcohols, or 2 produced by condensation of isocyanates.
~15-mer polyisocyanate, etc. can be used. The average molecular weight of these polyisocyanates is 1
00 to 20,000 is suitable. Commercially available trade names of these polyisocyanates include Coronate HL5 Coronate 2030. Coronate 2031, Millione) MR, Millionate MTL (manufactured by Nippon Polyurethane), Takenate D-102, Takenate D-II
ON, Takenate D-200, Takenate D-202,
Takene) 3003. Takenate 500 (manufactured by Takeda Pharmaceutical ■), Sumijel T-80, Sumifer 44S, Sumijel PF, Sumijel, Sumijel N1 Desmodille L1 Desmosier IL, Desmosier N
, Desmosier HL, Desmosier T65, Desmosier 15, Desmodur R1 Desmosier RF,
There are Desmodier SL, Desmodur Z4273 (manufactured by Sumitomo Bayer), and these can be used alone or in combination of two or more by taking advantage of the difference in curing reactivity. In addition, for the purpose of promoting the curing reaction, hydroxyl groups (butanediol, hexanediol, polyurethane with a molecular weight of 1000 to 1000, water
etc.), amino groups (monomethylamine, dimethylamine,
It is also possible to use a compound containing trimethylamine (such as trimethylamine) or a metal oxide catalyst. It is desirable that these compounds having hydroxyl groups or amino groups are polyfunctional, and these polyisocyanates are preferably used in an amount of 5 to 40 wt% of the total amount of the binder.

Dispersants used in the present invention include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, lylunic acid, stearolic acid, etc. 10-2
6 fatty acids (R+C0OH%R1 is an alkyl group having 9 to 25 carbon atoms), alkali metals (L i
Metal soaps made of alkaline earth metals (Mg, Ca, Ba, etc.), Cu, Pb, etc., fatty acid amides of the above fatty acids; lecithin, etc. are used. Higher alcohol with number 4 or more, (
butanol, octyl alcohol, myristyl alcohol, stearyl alcohol) and their sulfuric acid esters, phosphoric acid esters, amine compounds, etc. can also be used. Further, polyalkylene oxides and their sulfuric acid esters, phosphoric acid esters, amine compounds, etc., sulfosuccinic acid, sulfosuccinic acid esters, etc. can also be used. 'It is also possible to introduce a 5tSF substituent into these compounds in order to change their compatibility with the binder and their properties. These dispersants are usually used in one or more types, and one type of dispersant is added in an amount of o, oos to 20 parts by weight per 100 parts by weight of the binder.

These dispersants can be used by applying them to the surface of the ferromagnetic fine powder or non-magnetic fine powder in advance (or adding them during the dispersion process, for example). 2
No. 8369, Special Publication No. 23889, Special Publication No. 1977-
No. 17945, Special Publication No. 18221, Special Publication No. 18221, Special Publication No. 1977-
39402, Japanese Patent Publication No. 48-15001, U.S. Patent No. 33
No. 87993, No. 3470021, etc.

In addition, preferred compounds as dispersants include surfactants such as carboxylic acids and phosphoric esters, and fluorosurfactants such as Florard FC95, FCl29, Fe230, and FCl29.
e231 can be used.

Examples of lubricants and antioxidants used in the magnetic layer and back layer of the present invention include molybdenum disulfide, boron nitride, graphite fluoride, calcium carbonate, barium sulfate, cane oxide, titanium oxide, zinc oxide, tin oxide, Fine inorganic powder such as tungsten disulfide, fine acrylic styrene resin powder, fine benzoguanamine resin powder, fine melamine resin powder, fine polyolefin resin powder, fine polyester resin powder, fine polyamide resin powder, fine polyimide resin powder. Powder, fine resin powder such as polyfluoroethylene resin fine powder, silicone oil, fatty acid-modified silicone oil, graphite, fluorine alcohol, polyolefin (polyethylene wax, etc.), polyglycol (polyethylene oxide wax, etc.), tetrafluoroethylene oxide wax, poly Tetrafluoroglycol, perfluoro fatty acid, perfluoro fatty acid ester, perfluoroalkyl sulfate, perfluoroalkyl phosphate, alkyl phosphate, polyphenyl ether, carbon number 10-20
From a monobasic fatty acid and one or more of m alcohols having 3 to 12 carbon atoms, dihydric alcohols, trihydric alcohols, tetrahydric alcohols, hexahydric alcohols Fatty acid esters consisting of 10 carbon atoms
Organic compound lubricants such as fatty acid esters made of monobasic fatty acids and monovalent to hexavalent alcohols having a total of 11 to 28 carbon atoms can be used. Furthermore, fatty acids or fatty acid amides and aliphatic alcohols having 8 to 22 carbon atoms can also be used. Specific examples of these organic compound lubricants include butyl caprylate, octyl caprylate, ethyl laurate, butyl laurate,
Octyl laurate, ethyl myristate, butyl myristate, octyl myristate, ethyl palmitate, butyl palmitate, octyl palmitate, ethyl stearate, butyl stearate, octyl stearate, amyl stearate, anhydrosorbitan monostearate , anhydrosorbitan distearate,
Anhydrosorbitan tristearate, anhydrosorbitan tetrastearate, anhydrosorbitan ethylene oxide monostearate, oleyl oleate,
Oleyl alcohol, lauryl alcohol, etc. are available and can be used alone or in combination. In addition, as the lubricant used in the present invention, so-called lubricating oil additives can be used alone or in combination, such as antioxidants (alkylphenols, etc.), rust inhibitors (naphthenic acid, alkenylsuccinic acid, dilauryl phosphate, etc.). ), oil agents (rapeseed oil, lauryl alcohol, etc.), extreme pressure agents (dibenzyl sulfide, tricresyl phosphate, tributyl phosphite, etc.), etc.

The antistatic agents used in the present invention include graphite, carbon black, carbon black graft polymer, tin oxide-antimony oxide, tin oxide, titanium oxide-tin oxide-
Conductive powders such as antimony oxide; natural surfactants such as saponin; nonionic surfactants such as alkylene oxides, glycerin, glycidol, polyhydric alcohols, polyhydric alcohol esters, and alkylphenol EO adducts; higher alkyl amines Cationic surfactants such as cyclic amines, hydantoin derivatives, amidoamines, ester amides, quaternary ammonium salts, pyridine and other heterocycles, phosphoniums or sulfoniums; carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups , anionic surfactants containing acidic groups such as phosphate ester groups;
Amino acids; aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, amphoteric surfactants such as alkyl betaines, etc. are used. These surfactants may be added alone or in combination, and these surfactants may be overcoated on the surface of the magnetic recording medium from 1 g/I to 5501 g/I. I can put it on,
The amount of these surfactants used is 0.01 to 10 parts by weight per 100 parts by weight of the ferromagnetic fine powder. Although these are used as antistatic agents, they are sometimes used for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

As the carbon black used in the present invention, furnace black for rubber, thermal black for rubber, black for color, acetylene black, etc. can be used. Specific examples of carbon black abbreviations in the United States include SAF, l5A
F%I15AF%T.

HAF%5PFSFF%FEF, HMFSGPF.

APF, SRF%MPFSECF, SCF, CF.

FT, MT, HCC,I(CF%MCF,,RCF
etc., and the US ASTM standard D-1765-82a
The average particle size of these carbon blacks used in the present invention is 5 to 1000 millimicrons (electron microscope), and the specific surface area by nitrogen adsorption method is 1 to 1500 nf/g%. pH is 2-13
(JIS standard -6221-1982 method), dibutyl phthalate (DBP) oil absorption is 5 to 2000 m/100
g (JIS standard -6221-1982 method).

The water content of these carbon blacks used in the present invention is 0.00 to 20 wt%. The size of the carbon black used in the present invention is 5 to 100 mm for the purpose of lowering the surface electrical resistance of the coating film. Micron carbon black, and 50 to 100 micron carbon black when controlling the strength of the coating film.
Uses 0 millimicron carbon black. In addition, in order to control the surface roughness of the coating film, finer particles of carbon black (100 mm or less) are used for smoothing to reduce spacing loss, and coarser particles of carbon are used to roughen the surface and lower the friction coefficient. Use black (50 mm or more). In this way, the type and amount of carbon black to be added can be selected depending on the purpose required for the magnetic recording medium.

In addition, these carbon blacks may be used after being surface-treated with a dispersant or grafted with a resin.
It is also possible to use a material whose surface is partially graphitized by treatment at 0° C. or higher. It is also possible to use airborne carbon black as a special carbon black.

In the case of a magnetic layer, these carbon blacks are desirably used in an amount of 0.1 to 20 parts by weight per 100 parts by weight of ferromagnetic fine powder. Black Handbook 1, Carbon Black Association Line, (published in 1972)
can be used as a reference.

The abrasive for the magnetic layer and back layer used in the present invention is a commonly used material with an abrasive or polishing effect.
α-alumina, T-alumina, α-T-alumina, fused alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, α-iron oxide, garnet,
Emery (main components: corundum and magnetite), garnet, silica, silicon nitride, boron nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, quartz, tripoli, diatomaceous earth, dolomite, etc., mainly with a Mohs hardness of 6 or higher. Preferably, one to four materials having a Mohs hardness of 8 or more are used in combination. These abrasives have an average particle size of 0,000 to 5 microns, particularly preferably 0 to 5 microns. .01-2 microns. These abrasives are added in an amount of 0.01 to 20 parts by weight per 100 parts by weight of the binder.

The organic solvents used in the dispersion, crosstalk, and coating of the present invention include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran; methanol, ethanol, propatool, butanol, and isobutyl; Alcohols such as alcohol, isopropyl alcohol, methylcyclohexanol; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate monoethyl ether; diethyl ether, tetrahydrofuran, glycol dimethyl ether, glycols monoethyl ether,
Ethers such as dioxane; tars (aromatic hydrocarbons) such as benzene, toluene, xylene, cresol, chlorobenzene, and styrene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. chlorinated hydrocarbons, N,N,-dimethylformaldehyde, hexane, and the like can be used.

There are no particular restrictions on the dispersion/kneading method, and the order of addition of each component can be set as appropriate.

For preparing magnetic paints and back layer paints, ordinary kneading machines,
For example, two-roll mill, three-roll mill, ball mill, pebble mill, thoron mill, sand grinder, Szegvari, attritor, high-speed impeller, dispersion machine, high-speed stone mill, high-speed impact mill, disper, nygu, high-speed mixer, ribbon. blender, coney goo, intensive mixer, tumbler
, a blender disperser, a homogenizer, a single screw extruder, a two-wheel screw extruder, an ultrasonic disperser, and the like can be used. For details on crosstalk dispersion techniques, see T. C. FATTON (Chi.
Sea Balaton) “Pa1nt Flow and P
igmentDisρ-version (Paint
Flow and Pigment Disversion) 19
Published by John 1+1iley & 5ons in 1964 (
It is described in the literature cited in the book, such as Digon Willey & Sons), Makoto Tanaka, Industrial Materials J25, Vol. 37 (1977), and for continuous processing, these crosstalk dispersion machines are appropriately combined to feed and apply the liquid. . In addition, it is also described in specifications such as U.S. Pat. and back layer paints can be prepared.

To form the magnetic layer, the above-mentioned compositions are arbitrarily combined and dissolved in an organic solvent, and a coating solution is coated on the support and dried. When used as a tape, the thickness of the support is 2.5
The thickness is about ~100 microns, preferably about 3 to 70 microns, and the thickness is 0 if it is in the form of a disk or card.
．． It is about 0.03 to 10.0 mm, and in the case of a drum, it can also be used in a cylindrical shape. Materials include polyesters such as polyethylene terephthalate and polyethylene naphthalate,
Polyolefins such as polypropylene and polyethylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, plastics such as polycarbonate, polyamide, and polysulfone, as well as metals such as aluminum and copper, Ceramics such as glass can also be used.

Prior to coating, these supports may be subjected to corona discharge treatment, plasma treatment, undercoating treatment, heat treatment, dust removal treatment, metal vapor deposition treatment, and alkali treatment.

Methods for coating the magnetic layer and back layer on the support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, clavier coating, kiss coating, cast coating, and spray coating. Coating, barcode, etc. can be used, and other methods are also possible, and detailed explanations of these can be found in "R Coating Engineering" published by Shokusen Shoten, pages 253 to 277 (published March 20, 1977). Are listed.

By such a method, the magnetic layer coated on the support is subjected to a treatment to orient the ferromagnetic fine powder in the layer in a desired direction while immediately drying, if necessary, and then the formed magnetic layer is dried. The conveying speed of the support at this time is usually 1
The drying speed is 0 m/min to 1000 m/min, and the drying temperature is 2.
The temperature is controlled between 0°C and 130°. Further, the magnetic recording medium of the present invention is manufactured by subjecting it to surface smoothing processing and cutting it into a desired shape, if necessary. In these manufacturing methods, it is preferable to perform the steps of surface treatment, kneading/dispersion, coating, heat treatment, calendering, EB treatment, surface polishing treatment, and cutting of the filler continuously, or the steps may be divided into several steps as necessary. I can do things.

In these processes, temperature and humidity are controlled, and the temperature is 10℃ to 130'', and the humidity is expressed as the amount of moisture in the air.
5■/ITr to 20■/I. These are, for example,
Special Publication No. 40-23625, Special Publication No. 39-2836
No. 8, US Pat. No. 3,473,960, and the like. Furthermore, the method disclosed in Japanese Patent Publication No. 41-13181 is considered to be a fundamental and important technique in this field.

(Effects of the Invention) The magnetic recording medium of the present invention includes a ferromagnetic fine powder, a binder,
A magnetic layer containing additives (carbon blank, abrasive, lubricant, etc.) is provided on a non-magnetic support, and a back layer containing a binder and carbon black is placed on the non-magnetic support on the opposite side from the magnetic layer. In the magnetic recording medium provided, the water content of the coating liquid for forming the magnetic layer and/or back layer is made to be 0.000 to 0.200% by weight, and the curing reaction by the isocyanate of the binder of the magnetic layer and/or back layer is caused. This allows for efficient progress, increases the Young's modulus of the magnetic recording medium, and significantly improves the durability.

That is, in the magnetic recording medium of the present invention, by greatly reducing the water content of the coating solution, the polyisocyanate does not react with the moisture in the coating solution, and all of the polyisocyanate is effectively used for the crosslinking reaction with the binder. Alternatively, the Young's modulus of the back layer increased and the durability was improved.

(Examples) The present invention will be explained in more detail below using examples. It will be readily understood by those skilled in the art that the components, proportions, order of operations, etc. herein may be modified without departing from the spirit of the invention.

Therefore, the present invention should not be limited to the following examples; in the examples, "part" means "part by weight".

(Example 1) After putting (1) of the following example composition into a kneader and thoroughly kneading, (II) was added and kneaded thoroughly, and before application, [■
], then (fV) was added and mixed and dispersed to prepare a magnetic paint.

■YuI Azoko (1) Co-containing 1-Fe, 0. 300 parts of powder (nitrogen adsorption specific surface area: 35nf/g.

Fe''-4ats% Powder Hc Near 000e) Vinyl chloride Vinyl acetate resin 33 parts (COOH,
400X100A.

Nippon Zeon Co., Ltd.) Polyurethane resin 15 parts (Crispon 7209, Dainippon Ink Co., Ltd.) Carbon black 12 parts (Condagtex S01 Colombifufu Co., Ltd., average particle size 20 m
, u) Abrasive: α-AItos 24 parts (Sumitomo Chemical Co., Ltd., HIT5G Oleic acid 3 parts Cyclohexanone 150 parts (II) Polyurethane resin 8 parts Tuboran N2304, Nippon Polyurethane Co., Ltd.) Butyl acetate 850 parts Tert-butyl stearate 3 Part (III) Ethyl 2-cyanoacrylate Part Coated on polyethylene terephthalate with a dry film thickness of 5.0 μm, and
After magnetic field orientation using a magnet of 000 gauss, the film was dried and then calendered to form a magnetic layer. Subsequently, on the back side of the non-magnetic support on which the magnetic layer was provided, the following backing composition (1) was mixed and dispersed using a ball mill.
I) was mixed and stirred to prepare a backing solution, which was coated to a dry film thickness of 2.0 μm to form a backing layer.

, Beyuno JIJ Friendship (1) Carbon black 50 parts (Leben MTP+ Nitrogen adsorption specific surface area: 1027g Average particle size 250mμ Cabot Corporation) Carbon black 50 parts (Palcan X
C? 2 Nitrogen adsorption specific surface area: 160 i/g Average particle size 30 mμ (manufactured by Cabot) Polyurethane polycarbonate resin 33 parts (FJ2,
Dainichiseika Chemical Co., Ltd.) Phenoxy resin - 15 parts (PKHH.

Union Carbide) Oleic acid 1 0.1 parts Methyl ethyl ketone 700 parts Cyclohexanone
300 parts (n) Ethyl 2-cyanoacrylate Part Y (11) Polyisocyanate
8 parts (Coronet 2061, manufactured by Nippon Polyurethane Co., Ltd.) Lubricant 0.1 part (Silicone, KF69, manufactured by Shin-Etsu Chemical Co., Ltd.) Lubricant
1 part (oleic acid) 100 parts methyl ethyl ketone This was then slit into 1 inch width to produce a video tape.

(Example, Comparative Example) In Example 1, the addition amount of ethyl 2-cyanoacrylate, X part, Y part was changed as shown in Tables 1 and 2 to create a tape, and the rest was the same as Example 1. A sample was created.

(Evaluation method) Durability (D, O,) At room temperature (23°C, 50% RH), Sony's BV
After measuring the dropout (initial value) with the H2180 VTR, it was repeatedly run 100 passes, and the video tape was stored at 40°C and 80% RH (relative humidity) for one week, then returned to the room and dropped again.・Measure out (value over time),
Dropout value over time and dropout per minute
The number of out differences from the initial value was calculated.

Single-person driving (still image) At room temperature (23℃, 60% RH), playback in still image mode with double the driving weight on an Ampex VTR3 VTR until the output was -16 dP. I checked the time.

As is clear from the examples shown in Tables 1 and 2, the magnetic recording medium of the present invention exhibits excellent performance in terms of drop-out and still image characteristics. In the case of Comparative Examples 1 to 9, it is thought that the water content in the coating solution was excessive and the effective crosslinking of the curing agent was inhibited, and the Young's modulus of the coating film was extremely low, making it unsuitable for use as a magnetic recording medium. It is recognized that

Patent Applicant: Fuji Photo Film Co., Ltd. Procedural Amendment 4. Subject of amendment: "Detailed description of the invention" column of the specification 5. Contents of amendment Display of incidents Heisei Japanese Patent Application No. 131174 name of invention magnetic recording medium person who makes corrections Relationship with the incident

Claims (3)

[Claims] (1) A magnetic layer coated with a coating liquid containing ferromagnetic fine powder, a binder, and additives on one side of a nonmagnetic support, and a back layer coated with a coating liquid containing a binder and carbon black on the other side. A magnetic recording medium provided therein, wherein the coating liquid for the magnetic layer has a moisture content of 0.000 to 0.200% by weight. (2) The water content of the coating liquid for the back layer is 0.000 to 0.
．． 2. The magnetic recording medium according to claim 1, wherein the content is 200% by weight. (3) A magnetic recording medium characterized in that the coating liquid for the magnetic layer and/or back layer contains cyanoacrylate or methacryloyl isocyanate.