JPS59207021A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability, wear resistance, surface state and traveling performance by incorporating an aliphatic isocyanate and an aromatic isocyanate as a curing agent. CONSTITUTION:Magnetic powder, a binder and additives are dispersed in an org. solvent, and an aromatic isocyanate and an aliphatic isocyanate are added to prepare a coating liq. This coating liq. is coated on a support to manufacture a magnetic recording medium. Tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), the adduct of TDI or MDI to an active hydrogen compound or the like is used as the aromatic isocyanate, and the preferred average mol. wt. is 100-3,000. Hexamethylene diisocyanate (HMDI), lysine isocyanate, the adduct of HMDI or lysine isocyanate to an active hydrogen compound or the like is used as the aliphatic isocyanate, and the preferred mol.wt. is 100-3,000. The amount of the isocyanates added is 1-100wt% of the amount of the binder, and aromatic isocyanate accounts for 20-80% of the amount of the isocyanates.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium having a magnetic layer containing magnetic powder and a binder component on the upper surface of a support. The objective is to provide a magnetic recording medium that has a high magnetic flux and is free from particles, dropouts, and the like.

[B] Prior art: Magnetic recording medium 11 is usually obtained by kneading magnetic powder into a binder. The magnetic filler was coated on the surface of the support and dried to form a 3% magnetic filler. Generally, the magnetic powder used is ferromagnetic powder, which has a large magnetic moment, and therefore tends to cause interaction between particles, resulting in particle aggregation and cannot be uniformly dispersed in the binder.

As a result, the obtained magnetic recording medium not only has significantly inferior magnetic properties such as squareness ratio, but also has inferior properties such as surface properties, runnability, and abrasion resistance, and has problems such as powder falling and dropouts. occurs, leading to a decrease in playback output and still characteristics.

Special Publication No. 57-44967 for the purpose of eliminating such defects
In No. 18, magnetic powder contains polyvinyl butyral resin and a polyfunctional incyanate compound as a binder component.
It is proposed to use adhesive paint.

In addition, in Japanese Patent Publication No. 57-56128, a binder for the magnetic layer (a vinyl chloride-vinyl acetate-vinyl alcohol copolymer with a molecular weight distribution of 1.80 to 2.40 and a urethane polymer are used as soil components, It is proposed that a low molecular weight polyinsyanate be added to this.

However, the dispersibility of the magnetic paint applied by methods ① and ① above is not necessarily sufficient, and the viscosity is high, and the durability and abrasion resistance of the coating film (magnetic layer) are low. It is not possible to reduce the occurrence of head clogging, dropouts, etc. due to dropping.

In view of these circumstances, the present inventors conducted a study and found that aromatic incyanates and aliphatic incyanates (which may also be cycloaliphatic incyanates) are compatible with each other. It has the property of reacting with and curing the magnetic paint containing magnetic powder and binder components, and the reaction of aromatic isocyanate in one layer of the magnetic paint is fast-acting, but the reaction of aliphatic incyanate is fast-acting. Since it is slow-acting, it is believed that if both are mixed in an appropriate ratio and added to the magnetic coating material, a magnetic layer with an appropriate 6Il degree and no viscosity can be formed. , arrived at the present invention.

[Objective of the invention C1: The object of the present invention is to provide a magnetic recording medium that has high durability and abrasion resistance, has excellent surface properties and runnability, and does not suffer from flaking, dropouts, etc. °D] Structure of the invention: This object is achieved by providing a magnetic layer containing magnetic powder, a binder component, and an aliphatic incyanate and an aromatic incyanate as a hardening agent. .

Aromatic incyanates used in the present invention include, for example, tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDIl), xylylene diisocyanate (XDll), metaxylylene diisocyanate (MXDII) and active hydrogen There are adducts with compounds, etc., and those having an average molecular weight in the range of jloO to 3,000 are suitable.

Specifically, the parts names manufactured by GE and Sumitomo Bayer Urethane ■ are Sumidur T80, Sumidur 44S1 PF, Desmodur L1 T65, Sumidur 15, R1 RF, and Sumidur IL.

SL: 300S manufactured by Takeda Pharmaceutical Co., Ltd.
Same 500: Mitsui Nippon Urethane Co., Ltd. product rNDIJ, rT
Nippon Polyurethane Co., Ltd. JJ 1 product desmodule in ODI
rloO, Millionate Kite, MT, Coronate L; Products manufactured by Kasei Upjohn Co., Ltd. PAPI-135, TDI65
, 80, Zoo, Isoi, -to 125M, 143
Examples include L.

On the other hand, as aliphatic incyanate, hexamethylene diisocyanate (HMDII, lysine incyanate, trimethylhexamethylene diisocyanate + TMD
I), and additives of these insea aggregates and active hydrogen compounds.

Among these aliphatic incyanates and adducts of these incyanates and active hydrogen compounds, those having a molecular weight in the range of 100 to 3,000 are preferred.

On the other hand, among the aliphatic isocyanates, non-alicyclic isocyanates and adducts of these compounds with active hydrogen compounds are preferred.

For example, Sumidur N1 Desmodur Z4273 manufactured by Sumitomo Bayer Urethane, Duranate 50M1 24A-100, 24 manufactured by Asahi Kasei, etc.
A-900X, product Coronate manufactured by Nippu Polyurethane ■
products such as TNIDI manufactured by Hüls.

Examples of the alicyclic incyanate include 4,4'-methylenebis(cyclohexyl incyanate) inphorone diisocyanate and its adduct of an active hydrogen compound.

Specific [This is a product manufactured by Huls Chemical Co., Ltd. rIPDIJ, I
'PDI-T1890, PDI-H2921, PDI-B10
65, etc. The magnetic recording medium of the present invention, for example, can be prepared by preparing a magnetic coating material by mixing and dispersing magnetic powder, an inder, and various additives in an organic solvent, and adding the above-mentioned aromatic incyanate and aliphatic isocyanate. Afterwards, this is coated onto a support (for example, a polyester film), and dried if necessary, to produce the film.

The amount of incyanate (both aromatic isocyanate and aliphatic incyanate is simply referred to as incyanate) is added as a binder (1 to 100% by weight is added. Less than 1%) The hardening of the magnetic layer tends to be insufficient, and if it exceeds 100φ, the magnetic layer tends to become "sticky" even after hardening/coating.To obtain a more preferable magnetic layer,
fj (1 piece, preferably 5 pieces for each binder)
~30 years old.

The ratio of aromatic incyanate in the total weight of aromatic incyanate (weight of aromatic incyanate [weight of aromatic incyanate + weight of aliphatic incyanate]) is 2.
The desired value is 0 to 80%. (See attached drawing) If it is less than 20%, the stiffness reaction may be too slow;
If it exceeds so%, the curing reaction may be too fast. The surface condition of the magnetic layer may also become unfavorable in the case of "stickiness" or the surface becomes rough.For example, the luminance C/N of the magnetic recording medium may become unfavorable.
The magnetic cocoon of the magnetic recording medium of the present invention (1-Fe2O3, 1-Fe2O3,
CO-containing -Fe203, COO-attached 1-Fe20a,
Fe3O4, cog Fe3O4, etc. (7) Acid (IZ iron magnetic powder; Fe s N1% Co, Fe-Ni -C
o alloy, Fe-Mn Zn alloy, Fe-Ni-Z
n alloy, Fe-Co-Ni Cr alloy, Fe-Co
-Ni-P alloy, c.

Examples include various ferromagnetic powders such as F''e such as -Ni alloys, metal magnetic powders containing Ni, and Co as main components.

Magnetism of the magnetic recording medium of the present invention)
Examples of ingu include thermoplastic resins, heat-resistant resins, reactive resins, or electron-beam terimishiki-type mgetsuji,
The thermoplastic resin to be used is a mixture of soft and hard materials with a soft temperature of 1150'O or less, an average molecular weight of io, ooo to 200,000, and a degree of polymerization (about 200 to 2.000). Eg.
J ronito 1-nor copolymer, acrylic acid ester-ac I
Jronito 1-nor copolymer, acrylic free ester-salt f-hibini-1-nodene copolymer, acrylic free ester-styrene copolymer, methacrylic acid ester-acrylonitrile copolymer, methacrylic acid ester-vinyl chloride y copolymer combination, methacrylic acid ester-styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile-butadiene copolymer, polyamide resin, polyvinyl fluoride,
Cellulose derivatives (cellulose acetate butyrate,
cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.),
Styrene-butadiene copolymer, BoIJ ester resin,
Chlorovinyl needle-gamma acrylic acid ester copolymer,
Amine resins, various composite comb-based thermoplastic resins, and mixtures thereof are used.
19282-@, No. 40-5349, No. 40-209
No. 07, No. 41-9'463, No. 41-14059, No. 41-16985, No. 42-6428, No. 42
-LL621, 43-4623, concave 43-152
No. 06, No. 44-2889, No. 44-1-7947, No. 44-18232, No. 45-14020, No. 4
5-t4soO No. 47-18573, No. 47-2
No. 2063, No. 47-22064, No. 47-2206
No. 8, No. 47-22069, No. 47-22070,
Publication No. 48-27886, U.S. Patent No. 3.144,3
No. 52, No. 3,419,420, No. 3,499.789, and No. 3,713.887.

As a thermosetting resin or a reactive resin, it has a molecular weight of 200,000 or less in the state of a coating liquid, and after coating and drying, it undergoes reactions such as &go condensation and addition (this results in an infinite molecular weight). 1. Among these resins, those that do not soften or melt in the bath until the resin is thermally decomposed are preferred.
Specifically, examples include phenol resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reaction resins, mixtures of high molecular weight polyester resins and insium polymers, and methacrylates. Blends of polymers and diincyanate prepolymers@9 Of course, mixtures of polyester polyols and polyincyanates, urea formaldehyde resins, low molecular weight glycols/carrying diols/triphenylmethane triisocyanates? These include conglomerate proboscis, polyamine tree proboscis, and mixtures thereof.

These resins (Go, Japanese Patent Publication No. 39-8 IQ3, No. 40-9779, No. 41-7192, No. 41-8016)
No. 41-14275, No. 42-18179, No. 43-12081, No. 44-28023, No. 45-
No. 14501, No. 45-24902, No. 46-131
No. 03, No. 47-22067, No. 47-22072, No. 47-22073, No. 47-28045, No. 4
No. 7-28048, No. 47-28922, U.S. Patent No. 3,144,353, U.S. Pat. No. 3,320,090
No. 3,437,510, No. 3゜597, 2
No. 73, No. 3,781,210, No. 3, 7.8
1, No. 211, 71.

Examples of electron beam irradiation-curable resins include unsaturated oroble polymers, such as maleic anhydride type, urethane acrylic type, epoxy acrylic type, polyester acrylic type, polyether acrylic type, polyurethane acrylic type, polyamide acrylic type, etc. Examples of the polyfunctional monomer include ether acrylic type 1, urethane acrylic type, epoxy acrylic type, phosphorous ester acrylic type, and aryl tights-1L\hydrocarbon type.

These binders may be used alone or in combination, and other additives may be added as required.

The mixing ratio of magnetic powder and binder is
1 to 400 parts by weight of the binder, preferably 5 to 100 parts by weight, more preferably 5 to 50 parts by weight, based on the weight of M.
Used within the scope of the section. If the amount of binder is too large, the recording density will decrease when used as a magnetic recording medium, and if it is too small, the strength of the magnetic layer will be poor, resulting in undesirable situations such as decreased durability and powder falling off.

In addition to the magnetic powder, binder, and hardening agent, the magnetic layer may contain additives such as a dispersant, a lubricant, an abrasive, and an antistatic agent.

The dispersant C is a fatty acid having 8 to 18 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, valmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, and lylunic acid (R-COOJ). (represented by
R is a saturated or unsaturated alkyl group having 7 to 17 carbon atoms): an alkali metal of the above fatty acid (Li, Na,
etc.) Also, Goalkali earth gold M I Mg , Ca
+ Ba, etc.): lecithin is used. In addition, sieve alcohols having 12 or more carbon atoms and other sulfuric acid esters are also useful. These dispersants may be used alone or in combination of two or more. These dispersants are added in an amount of 0.1 to 2 oni parts per 100 M parts of magnetic powder. Publication, U.S. Pat. No. 3.587,993, U.S. Pat. No. 43,470
, 021 specification, etc.

As a lubricant, liquid oil, carbon black,
Graphite, carbon black graft polymer ~, two L1 hismolybdenum, tungsten disulfide, monobasic fatty acid with 12 to 16 carbon atoms, and the total number of carbon atoms in the fatty acid is 21 to 23 Fatty acid esters (so-called waxes) consisting of monohydric alcohols can also be used.

These lubricants should be added to the binder 100 violet part (for this, 0
．． It is added in an amount of 2 to 20 parts by weight. Regarding these problems, see Japanese Patent Publications No. 43-23889 and No. 43-815.
Publications such as U.S. Pat. No. 43, U.S. Pat. No. 3,470,021, U.S. Pat.
No. 60, No. 3,630,772, No. 3.634,
No. 253, No. 3,642,539, No. 3. '68
7゜725, IBM Technica
l I)isclosureBulletin Vo
l, 9, A 7. page 779 (196
December 6): ELEKTRONIK 1961
, %12, page 380, etc.

The abrasives used include general materials such as fused alumina, silicon carbide chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main ingredients: corundum and magnetite). These abrasives have an average particle size of 0.05~
A size of 5μ is used, particularly preferably O,i
These abrasives are added in an amount of 0.5 to 20 parts by weight per ioo parts by weight of the magnetic powder.

These abrasives are disclosed in Japanese Unexamined Patent Application Publication No. 115510/1983,
U.S. Patent No. 3.007.807, U.S. Patent No. 3,041.
No. 196, No. 3,687゜725, British Patent No. 1
, 145, No. 349, West German Patent (DT-PS)
No. 853,211.

As an antistatic agent (・graphite, carbon black, tin oxide-[depleted antimony compound, tin oxide-depleted titanium-depleted antimony compound, carbon black graft polymer, dielectric powder such as Nizabonin, natural surfactant : Nonionic surfactants such as alkylene oxide type, glycerin type, cricidol type, etc. Cationic surface-boosting activators such as secondary alkylamines, quaternary ammonium salts, pyridine, other heterocycles, phosphoniums or sulfoniums : Anionic surfactants containing acidic groups such as carboxylic acids, sulfonic acids, phosphoric acids, sulfur ester groups, phosphoric ester groups, amino acids, amino sulfonic acids, 4iR of amino alcohols (fl or phosphoric esters, etc.) agents etc. are used.

These surfactants that can be used as direct spinning agents are disclosed in U.S. Pat. Nos. 2,271,623 and 2,240,472.
No. 2,288,226, No. 2,676.12
No. 2, No. 2,676.924, No. 2,676.9
No. 75, No. 2,691,566, No. 2,727,
No. 860, No. 2,730,498, No. 2.74
2.379, 2.739.891, 3.0
No. 68,104, No. 3,158°4841, No. 3,201,258, No. 3,210,191, No. 3,294, 540, No. 3,415,649
No. 3,441, 413, No. 3,442.6
No. 54, No. 3,475,174, No. 3,545,
No. 974, West German Patent Publication (OLSll, 942,6
No. 65, British Patent No. 1.077, British Patent No. 317, British Patent No. 1.
198,450, etc., by Q Yujime and Ryohei Oda, "Synthesis of Surfactants and Their Applications" +aui: Store 1964
R+J-Fasactive Agents by A. W. Bayley (Interscience Publications Inc. 1958 M): T.
"Encyclopedia of Surface Active Agents Volume 2" by P. Sisley (Chemical Bubbles Company, 1964 edition +:, I'
6th edition of "W Surface Active Agent Handbook" (Sangyo Tosho Co., Ltd., December 20, 1920).

These surfactants may be added alone or as a mixture.These surfactants are used as anti-electrification agents or are sometimes used for other purposes, such as dispersion, dispersion, etc.
In some cases, it can be applied to improve air properties, improve lubricity, and as a coating aid.

Ketone-based solvents such as Qma, acetone, methyl ethyl ketone, methyl isopnal ketone, and cyclohexanone are used as solvents for magnetic paints or for removing magnetic paint coatings.
Ester systems such as μ-methyl, ethyl acetate, butyl acetate, ethyl lactate, ethylene glycol monoacetate monoethyl ether: ethylene glycol dimethyl ether,
Ethers such as diethylene glycol monoethyl ether, dioxane, and tetrahydrofuran; Aromatic hydrocarbons such as benzene, toluene, and cylene; Halogenated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and dichlorobenzene. can be used.

In addition, as materials for the support, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, polycarboy, etc. Plastics, metals such as Cu, AL, Zn, glass, and so-called new ceramics are used.

Thickness of stiff support material Qc For tape, sorted type (
・It is about 3 to 8 degrees, preferably 5 to 50 μ, and in the case of disks and cards, it is about 30 to 10 degrees, and in the case of drums, it is cylindrical, and the shape depends on the recorder used. The surface of the support opposite to the side on which the magnetic layer is provided for the purpose of preventing static electricity, preventing transfer, etc. is coated with a so-called
Regarding bank coats (1, e.g., U.S. Pat. Nos. 2.804,401, 3.293.066, 3.617,378)
No. 3,062.676, No. 3.734, 7
No. 72, No. 3.476.596, No. 2.643.
No. 048, No. 2,803.556, No. 2.887
, No. 462, No. 2.923,642, No. 2.99
No. 7,451-, No. 3,007,892, No. 3.
No. 041,196, No. 3,115.420, No. 3
．． 166.688 and other specifications, the support may be in any form, such as sheets, cards, disks, drums, etc., and various materials may be used as necessary depending on the form. selected.

Magnetic powder, binder, dispersant, lubricant, abrasive, antistatic agent, solvent, etc. are kneaded to form a magnetic paint.

For crosstalk, the magnetic powder and each of the components are added to the mixer simultaneously or individually.For example, the magnetic powder is first added to a bath solution containing a dispersant. One method is to knead the mixture for a sufficient amount of time, then add the remaining ingredients and continue mixing to form a magnetic paint.

Mixing machines in each building are used for mixing and dispersing. For example, two roll mill, three roll mill, ball mill, pebble mill, sand grinder, Szegvari
There are Attritor, Sosoku 1 Impeller Disperser, High Speed Stone Mill, High Speed Hon Mill, Disper Kneader 1 High Speed Mixer, Homogenizer, Ultrasonic Disperser, etc.

Techniques related to crosstalk fractions & written by Go, T, O, PATTON P
a1nt Flow and Pigment Dis
persion (1964 John Willey
& 5ons Publishing]. Also, U.S. Patent Nos. 2,581,414 and 2,855.15
It is also mentioned in each specification of No. 6.

As a coating method for coating the magnetic coating material onto a support to form a magnetic layer (coating, gravure roll coating,
Mayer barcoding, doctor blade coating, reverse roll coating, dip coating, air knife coating, calendar coating, Skies Coach ink, Kiss Coach ink, Fantine coating, etc. are available, and other methods are also possible, and these specific methods may be used. The explanation is in "Coating Engineering" published by Hatsubon Shoten (published by Hatsubon Shoten; published in March 1971, 2
5 pages] and “Plastic Films – Processing and Applications”
(published by Gihodo; published in July 1972) in detail.

The magnetic powder coated on the support by such a method is, if necessary, subjected to a treatment to orient the akip powder in the layer, and then the formed magnetic powder is dried if necessary. 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.

In this case, the orientation magnet @ is approximately 500 to 35
00 Gauss and the drying temperature is about 50-100'
It is preferable that the drying time is approximately 3 to 10 minutes.

The method for orienting the magnetic powder according to the present invention may be the method described in the following patents. For example, US Pat. No. 1,949,840, US Pat.
No. 796,359, No. 3.001.891, No. 3
．． Specifications of No. 172.776, No. 3,416,949, No. 3.473.960, No. 3.681.138, Japanese Patent Publication No. 32-3427M, No. 39-28368
No. 40-23624, No. 40-23625, No. 41-13181, No. 448-13043, No. 48-
39722, etc.

Further, the orientation direction of the magnetic powder is determined depending on its use.

[E] Effect When forming a magnetic layer, aromatic incyanates tend to have a fast curing reaction, while aliphatic incyanates tend to have a slow curing reaction. The hardening and formation of the magnetic layer can proceed at an appropriate speed, and the surface state of the formed magnetic layer can be made suitable for use as a magnetic recording medium.

For example, the running stability and recording and reproducing performance of the medium are improved. Also, among the aromatic insyanates, for example, methylene diincyanate (OCNQCN 2QN)
The aliphatic part of COl (Yu).

(e.g. methylene group), adducts of aromatic isocyanates and active hydrogen compounds (e.g. ]) can control the curing reaction, make the surface condition of the formed magnetic layer more preferable as a magnetic recording medium, and make the recording medium more porous.

On the other hand, when the magnetic paint is used, the change in viscosity of the paint over time is smaller than that of conventional paints, so the performance of the formed magnetic layer is stable and superior to conventionally known magnetic recording media. .

[F) Examples: Hereinafter, the content of the present invention will be specifically explained with reference to Examples and comparative examples. In Examples and Comparative Examples, the term "parts" means "parts by weight."

Examples 1 to 5 ■Magnetic paint Magnetic powder-containing composition components include magnetic powder, VAGH (manufactured by Union Carbide Co., Ltd., partially hydrolyzed vinyl chloride-vinyl acetate copolymer, trade name), PKHHI, manufactured by Union Carbide Co., Ltd. Phenoxy resin, trade name), R82/1 (manufactured by Daicel Chemical Co., Ltd., nitrocellulose, trade name), Niboran N-3022 (manufactured by Nippon Polyurethane Co., Ltd., polyurethane, trade name), lecithin, AKP-20 (manufactured by Sumitomo Chemical Co., Ltd., Alumina, product name J, MEK (mef ethyl ketone), toluene, and cyclohexanone, respectively, coating-'1
．． After thoroughly mixing and dispersing the compositions mixed at the compounding ratios shown in columns 42 to 6 in a ball mill, an incyanate compound was added to form magnetic paints -1, -2, -3, -4 and -5, respectively. Created.

Below is a margin (2). Polyethylene terephthalate films A, B, C, and I with a film thickness of 2μ were prepared separately.
) and E while applying a magnetic field, the dry film thickness was 3μ
It was painted to look like this.

The thus-obtained valley sample was subjected to supercalender treatment and then cut to a width of 12.65 mm to produce five types of videotapes. These videotapes
Depending on whether the applied magnetic paints -1, -2, -3, -4 and -5 are applied, the Example Tape L,
2, 3.4 and 5.

Comparative Examples 1 to 3 Same as Examples j to 5 (magnetic powder, VAGH, Niboran N- mixed at the distribution ratio shown in Table 1, columns 7 to 9)
ao22, lecithin, AKP-20, MEK.

After thoroughly mixing and dispersing the magnetic powder-containing composition consisting of toluene and cyclohexanone in a ball mill, an iso-a-but compound was added thereto to prepare comparative magnetic paints-i and -, respectively.
2g and -3 were produced.

Next, a videotape was produced from a terephthalate film having a film thickness of 2μ by adding the same process as in Examples 1 to 5. Depending on whether or not the comparative magnetic pigment applied was 1 to 3,
Comparative Example Tapes 1.2 and 3 were used.

Examples 6 to 8 ■Magnetic paint As magnetic powder, CO was used instead of Fe-N1-Co alloy.
Adhesion - A composition in which the same magnetic powder-containing composition components as in Examples 1 to 5 were mixed at the mixing ratios shown in the hole table = 2 and the second to fourth columns, except that Fe203 powder was used. After thoroughly mixing and dispersing the materials using a ball mill, an isocyanate compound was added to prepare magnetic paints-6, -7, and -8.

The following margin is ■Magnetic recording medium The obtained magnetic paints -6, -7, and -8 were separately prepared on one side of polyethylene terentalate films F, G, and H with a film thickness of 12μ (ζ, and a magnetic field was applied. The coating was carried out so that the dry film thickness was 3 μm.

Each of the wide samples obtained was subjected to supercalender treatment to produce videotapes cut to a width of 12.65 square meters. The obtained video tape number, the type of applied magnetic paint -6, -7 and -8 (according to ζ, respectively) 8 Similarly, prepare a magnetic paint by mixing and dispersing the magnetic powder-containing composition components listed in the first column of Table 2 at the mixing ratio in the fifth bucket, using a ball mill.
The magnetic obstetrics was used as a comparative magnetic paint-4.

Thereafter, a videotape was produced using the same method and treatment 8 as in Examples 6-8. This videotape was designated as Comparative Example Tape 4.

In addition, Examples 1 to 8:8 and Comparative Examples 1 to 4 of MiJ
Tape performance of Example tapes 11 to 8 and Comparative example tapes 1 to 4 prepared by
Show K.

Tape performance was evaluated for luminance Cβ, dropout, still time, dust, viscosity, and tack.

However, ■Luminance C/N: In the example tapes 5 to 5 and the comparative examples 1 to 3, a single signal of 5.0 MHz was recorded at the optimal current value with the tape at a relative speed of 4.0 m to 7 m. Regenerate and pass through a frequency analyzer to 5.0 & 1j (z regeneration output and 4.0 Ml
-1z tape noise and the comparison example tape 1.
The value of 0 is expressed as a relative value (dll) with respect to the standard (month). For example tapes 6 to 8, comparative example tape ↓ (go, relative velocity 5.3 Hl / formula 4.0 Mf (z 4. Record and reproduce the single signal at the optimum recording current and pass it through a frequency analyzer.
It was measured as the difference between the playback output of 0 MHz and the tape noise of 3.0 + VI Hz, and was expressed as the value idJ versus the eye when the value of Comparative Example Tape 4 was taken as the reference (0).

■Dropout: 5μ type, -2Q db It is shown by how many db output drops occur per minute.

■Still durability: Displayed as the time required for RFP+raw output to drop.

■Powder falling: Judgment was made by the dirt on the head when a 5 m long tape was run at a speed of 7 m/air against a simulated head.

Dirt 21. Severe stains are marked with an X, those with some stains are marked with a Δ, those with almost no stains are marked with an ○, and those with no stains are marked with a Q mark.

■Viscous expansion: Immediately after addition of inso-art compound/70 and 6 hours after addition, the magnetic viscosity was measured using a B-type viscometer (till f). Displayed as a value.

■Visibility: The tape was left on a 60'0, 80RH% (relative flaw) for 24 hours, and then 23'0.55
Leave it in an atmosphere of Rf (%) for 24 hours. After that, it was judged by the degree of stickiness when the tape was unraveled.Table-
3. In the 8th column, ○ marks indicate that no sticking occurs, Δ
Mark f1. Indicates that the material is slightly sticky.

From the results shown in Margin Table 3 below, 8 cavities of a conventional monolinear paint containing only aromatic incyanate or aliphatic incyanate as the incyanate compound were added to the magnetic powder-containing composition. A magnetic recording medium having a magnetic layer (Comparative Example Tapes 1 to 4) was compared to a magnetic recording medium having a magnetic layer containing a mixture of aliphatic inanate and aromatic isocyanate (Examples 1 to 8). Luminance C,
It was confirmed that it has excellent performance in terms of dropout, still durability, powder resistance, viscosity, and adhesive properties.

In addition, the viscosity IL of the magnetic paint 6 hours after the addition of the isocyanate compound to the isocyanate compound containing composition t The results of measurement with different ratios are shown in the characteristic curve attached to the specification.From this characteristic curve C, the blending ratio of aromatic incyanate and aliphatic incyanate is 80/20 to 20/
When it is within the range of 80 parts, it is stable at about 100%, but when the blending ratio of aromatic isocyanates exceeds 80 parts, the viscosity increases rapidly. When the blending ratio of the group incyanate is 80 parts or more, the viscosity decreases rapidly.

[G] Effect: As mentioned above, the uninvented 4'fi magnetic recording medium (G) is superior not only in terms of durability and abrasion resistance but also in surface properties and runnability compared to conventional magnetic recording media. It is clear that

Furthermore, the pot life of the magnetic paints 1 to 8 used in the present invention is longer than that of the conventionally used magnetic paints (comparative magnetic paints 1 to 8).
4), and the retention of the prepared magnetic paint is extremely inferior to that of 0.

[Brief explanation of the drawing]

The figure is a characteristic curve diagram showing the viscosity 6 hours after the preparation of the magnetic paint used in the present invention, which is a mixture of aromatic isocyanate "Coronate L) and aliphatic isocyanate [IPDI] in various proportions. 4,000 To 11 Districts (RPvB Procedures Sleeve Masahui Spontaneous) September 30, 1981 Patent Application No. 7904354 Relationship with Kui Patent Applicant (1) Specification 1, page 3, line 1, `` ...Abrasion resistance..."
is defined as "...abrasion resistance...". (2) "...polyvinyl butyral..." on page 9, line 7 of Meiwa J. Co., Ltd. is changed to "...polyvinyl butyral...". ``...methylene diisocyanate <0CN-'' on the first line of the page
...Diphenylmethane-4,4'-diincyanate (4) Specification; Page 14, line 5, "...Binder 1
00..." is replaced with "...Ferromagnetic powder 100..."
・Use it as a phrase. that's all

Claims (1)

[Claims] A magnetic recording medium having, on the upper surface of a support, a magnetic layer containing magnetic powder, a binder component, and an aliphatic isocyanate and an aromatic insyanate as a hardening agent.