JPH0580048B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a magnetic recording medium, and in particular, it is an object of the present invention to provide a magnetic recording medium that has excellent still (still image) durability and storage stability. [Prior Art] Magnetic recording media generally consist of a support made of polyethylene terephthalate or the like in the form of a tape or sheet, and a magnetic layer formed by coating the support with a magnetic paint containing magnetic powder and a binder as main components. It is formed from. The magnetic powder contained in the magnetic layer has the following characteristics in terms of magnetic properties such as squareness ratio, saturation magnetization, and coercive force.
Since metal magnetic powders containing Fe, Co, etc. as main components are superior to iron oxide magnetic powders, the use of these metal magnetic powders in magnetic recording media is attracting attention. [Problems to be solved by the invention] However, when conventional metal magnetic powders have a particle size of 1μ or less, which is used for magnetic recording, they not only have poor dispersibility, but also become susceptible to oxidation, rust, and saturation magnetization. deteriorates over time, reducing storage stability and still durability. Furthermore, in extreme cases, conventional metal magnetic powders have a tendency to ignite in the atmosphere, even at temperatures around room temperature. An object of the present invention is to provide a magnetic recording medium having excellent still durability and storage stability. [Means for Solving the Problems] In order to achieve the above object, the present invention provides a magnetic recording medium having a magnetic layer containing metal magnetic powder on a support, in which the metal magnetic powder completely occupies Al atoms. The content is in the range of 0.5 to 20 atomic weight % based on the atomic weight of the metal component, and the magnetic layer is further coated with a fatty acid having 8 to 18 carbon atoms (represented by R-COOH, where R is the number of carbon atoms). 7 to 17 saturated or unsaturated alkyl groups), a metal soap consisting of an alkali metal or alkaline earth metal of the fatty acid, lecithin, a higher alcohol having 12 or more carbon atoms, and a sulfuric ester. It is characterized by The present invention will be explained in detail below. The magnetic powder used in the magnetic layer of the magnetic recording medium of the present invention includes Fe, Fe-Ni-Co alloy, Fe-Mn
-Zn alloy, Fe-Co-Ni-P alloy, Fe-Ni-Zn
Alloy, Fe-Ni-Cr-P alloy, Fe-Co-Ni-Cr
Alloy, Fe-Co-P alloy, Fe-Ni alloy, Fe-Ni
- Metal magnetic powder in which the proportion of Al atoms in metal magnetic powder mainly composed of Fe such as Mn alloys and Fe-P alloys is 0.5 atomic weight % or more and 20 atomic weight % or less based on the atomic weight of all metal components. Examples include powder. The above-mentioned magnetic powder (hereinafter referred to as "magnetic powder according to the present invention") can be obtained, for example, by adding aluminum and/or this compound to the metal component of metal magnetic powder by a method such as inclusion or adhesion. . The metal components of metal magnetic powder mainly include carbon, which cannot be detected by an X-ray microanalyzer.
It means components other than hydrogen, oxygen, etc. The amount of Al and/or its compound added is determined based on the amount of Al atoms (e.g.,
If the additive is Al ₂ O ₃ , the proportion of Al ₂ ) is
The amount is in the range of 0.5 to 20 atomic weight %, particularly preferably 1 to 20 atomic weight %, based on the atomic weight of all metal components. If the Al atom content is less than 0.5 atomic weight %, the properties of the magnetic recording medium produced using the obtained metal magnetic powder, such as storage stability, reproduction output, and still durability, will be insufficient. Among the magnetic powders according to the present invention, those whose metal components essentially consist of Fe and Al are preferred. Here, "substantially" means that the third component other than Fe and Al is 1% or less. Also, among the magnetic powders according to the present invention, magnetic powders whose differential thermal curves do not change up to at least 80°C are preferred. A differential thermal curve is a method that measures the temperature difference that occurs between a metal magnetic powder and a reference material such as thermally stable animina or quartz when heated at a constant rate, and determines the energy state of both. Yes, and the measurement method is, for example, edited by the Chemical Society of Japan:
It is described in detail in ``New Experimental Chemistry Account 2, Basic Technology.'' The binder used in the magnetic layer of the magnetic recording medium of the present invention is preferably polyurethane or a combination of polyurethane and other binder components. Examples of the polyurethane include thermoplastic urethane elastomers, thermosetting urethane resins, and electron beam curable resins made of unsaturated prepolymers and polyfunctional monomers such as urethane acrylic types and polyurethane acrylic types. . Other binder components used in combination with polyurethane include thermoplastic resins such as vinyl chloride-vinyl acetate copolymers, thermosetting resins such as phenolic resins and epoxy resins, reactive resins such as polyester and polyisocyanate mixtures, Examples include electron beam irradiation-curable resins such as epoxy acrylic type and polyester acrylic type. In the present invention, urethane elastomers or combinations of urethane elastomers and other binder components (vinyl chloride-vinyl acetate, copolymers, etc.) are particularly preferably used. The mixing ratio of the magnetic material and the binder according to the present invention is 5 parts by weight of the binder per 100 parts by weight of the magnetic powder.
-400 parts by weight, preferably 10-200 parts by weight. If the amount of binder mixed is too large, the recording density of the magnetic recording medium will be reduced, and if it is too small, the strength of the magnetic layer will be weakened, resulting in undesirable situations such as decreased durability and powder falling off. Additionally, various hardening agents can be added within the magnetic layer to improve the durability of the magnetic recording medium. For example, polyisocyanate and the like can be contained. Examples of the polyisocyanate include an adduct of diisocyanate and a trivalent polyol, a pentamer of diisocyanate, and a decarboxylated product of 3 moles of diisocyanate and water. Specific examples of these include an adduct of 3 moles of tolylene diisocyanate and 1 mole of trimethylolpropane, an adduct of 3 moles of metaxylylene diisocyanate and 1 mole of trimethylolpropane, a pentamer of tolylene diisocyanate, and a tolylene diisocyanate 2 Hexamethylene diisocyanate, a pentamer consisting of moles 3
There are decarboxylated products obtained by reacting 1 mole of water with 1 mole of water, and these are easily obtained industrially. In addition to the magnetic powder, binder, and curing agent described above, additives such as a dispersant, an abrasive, and an antistatic agent may be added to the magnetic layer. Dispersants used include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid,
Fatty acids having 8 to 18 carbon atoms such as linoleic acid and linolenic acid (represented by R-COOH, where R is a saturated or unsaturated alkyl group having 7 to 17 carbon atoms): Alkali metals of the above fatty acids (Li, Na, K
etc.) or alkaline earth metals (Mg, Ca, Ba, etc.)
Metal soap consisting of: Lecithin etc. are used. In addition to these, higher alcohols having 12 or more carbon atoms, and in addition to these, sulfuric esters and the like can also be used. These dispersants may be used alone,
Alternatively, two or more types may be used in combination. These dispersants are added in an amount of 1 to 20 parts by weight per 100 parts by weight of the magnetic powder. Regarding these dispersants, please refer to Japanese Patent Publication No. 39-28369.
No. 44-17945, Publication No. 48-15001,
It is described in US Pat. No. 3,587,993, US Pat. No. 3,470,021, etc. Examples of lubricants include silicone oil, carbon black, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, monobasic fatty acids having 12 to 16 carbon atoms, and carbon Number of atoms is 21-23
It can also be used for fatty acid esters (so-called waxes) consisting of monohydric alcohols. These lubricants are added in an amount of 0.2/20 parts by weight per 100 parts by weight of the magnetic powder. Regarding these, special public relations
-23889, US Patent No. 43-81543, US Patent No. 3470021, US Patent No. 3492235, US Patent No. 3497411,
Same No. 3523086, Same No. 3625720, Same No. 3630772,
Specifications of No. 3634253, No. 3642539, No. 3687725, IBM Technical Disclosure Magazine Volume 9, No. 7, No.
779 pages (December 1966) (IBM Technical
Disclosure Bulletin Vol.9, No.7, Page779
(1966, December): Electronics Magazine No. 12
No. 380 (1961) (ELEKTRONIK, No. 12,
Page 380, 1961) etc. Materials commonly used as abrasives include fused alumina, silicon carbide, chromium oxide, corundum,
artificial corundum, artificial diamond, garnet,
Emery (main ingredients: corundum and magnetite) etc. are used. These abrasives have an average particle size of
A size of 0.05 to 5μ is used, preferably
It is 0.1~2μ. These abrasives are added in an amount of 2 to 20 parts by weight per 100 parts by weight of the magnetic powder. These abrasives are described in Japanese Patent Application Laid-Open No. 115510/1983, US Pat. No. 3007807, and US Pat. No. 3041196.
No. 3687725, British Patent No. 1145349, and West German Patent (DT-PS) No. 853211. If necessary, antistatic agents include conductive powders such as graphite, carbon black, tin oxide-antimony oxide compounds, tin oxide-titanium oxide-antimony oxide compounds, carbon black graft polymers, and natural interfaces such as saponin. Active agent: Nonionic surfactant such as alkylene oxide type, glycerin type, glycidol type etc. Cationic surfactant such as higher alkylamines, quaternary pinidine, other heterocycles, phosphonium or sulfonium type: Carboxylic acid, sulfone acid,
Alumine surfactants containing acidic groups such as phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups: Ampholytic surfactants such as amino acids, aminosulfonic acids, and sulfuric or phosphoric esters of amino alcohols are used. These surfactants that can be used as antistatic agents are US Pat. Nos. 2271623, 2240472,
No. 2288226, No. 2676924, No. 2676975, No. 2691566, No. 2727860, No. 2730498,
Same No. 2742379, Same No. 2739891, Same No. 3068101,
Same No. 3158484, Same No. 3201253, Same No. 3210191,
Same No. 3294540, Same No. 3415649, Same No. 3441413,
Same No. 3442654, Same No. 3475174, Same No. 3545974,
Including specifications such as West German Patent Publication (OLS) No. 1942655, British Patent No. 1077317, British Patent No. 1198450, etc., "Synthesis of Surfactants and Their Applications" by Ryohei Oda et al. (Maki Shoten 1964 edition): AW Peiri Author: “Surf S Active Agents” (Interscience Publications, Inc.)
1958 edition): TP Sisley, “Encyclopedia of Surf S Active Agents Volume 2” (Chemical Publishing Company, 1964 edition): “Surfactant Handbook”, 6th edition (Sangyo Tosho Co., Ltd., December 20, 1964) ) and other books. These surfactants may be added alone or in combination. Although these are used as antistatic agents, they are sometimes applied for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids. The magnetic recording medium according to the present invention is manufactured by kneading and dispersing the magnetic powder, binder, and other magnetic paint components in a solvent to prepare a magnetic paint, and then applying the obtained magnetic paint onto a support and drying it. Manufactured by In addition to the above-mentioned magnetic paint components, the magnetic paint may contain additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and the like, if necessary. Solvents for magnetic paint or solvents used when applying magnetic paint include acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK),
Ketones such as cyclohexanone: Alcohols such as methanol, ethanol, propanol, butanol: methyl acetate, ethyl acetate, butyl acetate,
Ester systems such as ethyl lactate, propyl acetate, and ethylene glycol monoacetate; Ether systems such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, and dioxane; Aromatic hydrocarbons such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, and Halogenated hydrocarbons such as carbon chloride, chloroform, and dichlorobenzene can be used. In addition, when kneading the magnetic paint components, the magnetic powder and other magnetic paint components are all fed into the kneader simultaneously or individually one after another. For example, first, the magnetic powder is added to a solution containing a dispersant and kneaded for a predetermined time, and then the remaining components are added and kneaded continuously to obtain a magnetic paint. Various kneaders are used for kneading and dispersing. For example, two roll mill, three roll mill, ball mill, pebble mill, sand grinder, Sjegvari attritor, high speed impeller disperser, high speed stone mill, high speed impact mill, disper kneader, high speed mixer, homogenizer,
Such as an ultrasonic dispersion machine. When the magnetic paint according to the present invention is kneaded and dispersed by these methods, the dispersion is extremely good, and the number of aggregates when observed with an electron microscope is extremely small compared to the case of conventional magnetic paints. . The techniques related to kneading and dispersion are described in ``Paint Flow and Pigment Dispersion'' by T.O.
Flow and Pigment Dispersion (1964.John
Willy and Son). It is also described in the specifications of US Pat. No. 2,581,414 and US Pat. No. 2,855,156. In addition, regarding the manufacturing method of magnetic paint,
No. 15, No. 39-26794, No. 43-186, No. 47-
No. 28043, No. 47-28045, No. 47-28046, No. 47
-28047, 47-31445, 48-11162, 47-31445, 48-11162,
It is described in detail in the specifications of the publications No. 48-21332 and No. 48-33683. In addition, materials for the support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate,
Plastics such as polycarbonate, Cu, Al,
Metals such as Zn, glass, and various ceramics such as so-called new ceramics are used. The support may be in any form such as a tape, sheet, card, disk, or drum, and various materials are selected as necessary depending on the form. The thickness of these supports is approximately 3 to 100μ in the case of a tape or sheet, preferably 5 to 50μ, approximately 30μ to 10mm in the case of a disk or card, and cylindrical in the case of a drum. The type is determined depending on the recorder used. The support may be coated with a so-called back coat on the side opposite to the side on which the magnetic layer is provided for purposes such as antistatic and transfer prevention. Regarding back coats, for example, U.S. Patent No.
No. 2804401, No. 3293066, No. 3617378, No. 3062676, No. 3734772, No. 3476596,
Same No. 2643084, Same No. 2803556, Same No. 2887462,
Same No. 2923642, Same No. 2997451, Same No. 3007892,
It is described in the specifications of the same No. 3041196, the same No. 3115420, the same No. 3166688, etc. In addition, in order to apply the magnetic paint onto a support to form a magnetic layer, gravure roll coating, Meyer bar coating, doctor blade coating, reverse roll coating,
Methods such as dip coating, air knife coating, calendar coating, skies coating, kiss coating, and fan coating can be used, and other methods are also possible. It is described in detail in ``Plastic Film - Processing and Its Applications'' (published by Gihodo in 1971). The magnetic layer coated on the support by such a method is optionally subjected to a treatment for orienting the magnetic powder according to the present invention in the layer, and then the coated magnetic layer is dried. Further, a magnetic recording medium is manufactured by performing surface smoothing processing and cutting into a desired shape if necessary. The orientation magnetic field for orienting the magnetic powder in the magnetic layer is alternating current or direct current, and is about 500 to 3500 Gauss, and the drying temperature is about 50 to 100°C.
The drying time is preferably about 3 to 10 minutes. The orientation direction of the magnetic powder can be determined, for example, according to U.S. Patent No.
No. 1949840, No. 2796359, No. 3001891, No. 3172776, No. 3416949, No. 3473960,
Specifications of the same No. 3681138, Special Publication No. 32-3427,
No. 39-28368, No. 40-23624, No. 40-23625,
It is described in the specifications of the respective publications such as No. 41-13181, No. 48-13043, and No. 48-39722. The method for orienting the metal magnetic powder contained in the magnetic layer of the magnetic recording medium according to the present invention is determined depending on its use. [Example] Hereinafter, the specific content of the present invention will be explained with reference to Examples and Comparative Examples. In the examples and comparative examples,
References to "parts" shall mean "parts by weight." Examples 1 to 6 Preparation of magnetic paint Add water-soluble aluminum salt to ferrous salt aqueous solution
_Aluminum The acicular α-Fe OOH particles containing aluminum are generated, and the acicular α-Fe OOH particles containing aluminum are heat-treated at a temperature range of 350 to 650°C in a non-reducing atmosphere to contain aluminum. After forming acicular α-Fe ₂ O ₃ particles, the particles were heat-treated in a reducing gas at a temperature range of 350 to 500° C. to produce Fe-based metal magnetic powder. The Al content produced in this way was 1.3, 3, and 3, respectively.
The following magnetic powder-containing compositions were prepared using QFe-based metal magnetic powders of 3.5, 4.2, 5.1, and 7.0 atomic weight % (Fe content is 60 atomic weight % or more). In addition,
Those with Al content of 1.3, 3, and 3.5 atomic weight %, respectively, have Si atomic weight % of 0.5% or less,
The 4.2% Si contained less than 1 atomic weight %.
The atomic weight percent of Al and Si was determined using an X-ray microanalyzer (Hitachi "X-556", KEVEX-
7000 model). Fe-based metal magnetic powder 100 parts VAGH (trade name: manufactured by Union Carbide Co., Ltd., vinyl chloride-vinyl acetate copolymer) 10 parts Estan 5701 (trade name: manufactured by Gutsudoritsu Co., Ltd., polyurethane resin) 10 parts Lecithin 3 parts MEK 70 parts Toluene 60 parts Cyclohexanone 5 parts However, in the above Fe-based metal magnetic powder, Al
The content is 1.3, 3, 3.5, 4.2, 5.1 and
For 7.0 atomic weight%, the differential thermal curve is
It has properties that do not change up to 83℃, 86℃, 88℃, 95℃, 97℃ and 130℃. Each of the above magnetic powder-containing compositions is thoroughly milled in a ball mill.
After mixing and dispersing, 5 parts of Coronate L (polyisocyanate solution manufactured by Nippon Polyurethane Co., Ltd.) was added and mixed uniformly to obtain six types of magnetic paints. For the six types of magnetic paints obtained, the Al content of the Fe-based metal magnetic powder contained was 1.3, 3, 3.5, 4.2, 5.1.
and 7.0 atomic weight %, magnetic paints 1, 2, 3, 4, 5 and 6 were used, respectively. Preparation of magnetic recording medium Next, magnetic paints 1, 2, 3, 4, 5, and 6 were coated on one side of five types of polyethylene terephthalate films with a thickness of 12μ, respectively.
The coating was applied to a dry film thickness of 5μ while applying a Gaussian magnetic field. Each of the obtained wide samples was subjected to supercalender treatment, and then slit into 12.65 mm width.
Six types of videotapes were made. For each of these videotapes, the applied magnetic paint-1, 2,
Example tapes 1, 2, 3, 4, 5, and 6 were prepared according to samples 3, 4, 5, and 6, respectively. Examples 7 and 8 100 parts of the Fe-based metal magnetic powder with an Al content of 0.8% and 1.3% was mixed with 0.2% by weight of the following Tomide #220.
(Product name: manufactured by Fuji Chemical Industry Co., Ltd.) H-[NH-(CH ₂ CH ₂ NH)- _n CH ₂ CH ₂ -NHCO-R
-CO]- _o -NH- (CH ₂ CH ₂ NH) - _o CH ₂ CH ₂ -NH ₂ However, R is

[C] Solution (methylene chloride/toluene = 70:30) 670
The resulting magnetic powder was redispersed in 300 ml of mineral oil (Isobar), and then a solution of 2 parts of toluylene diisocyanate/60 parts of Isopar was added, and this solution was heated at 50°C for 1 hour. After heating, it is filtered and the obtained magnetic powder is washed with n-hexane and then dried in a nitrogen atmosphere. Thus,
We obtained coated magnetic powders with stable differential thermal curves up to 120°C and 140°C, respectively. A videotape having a width of 12.65 mm was prepared by performing the same treatment as in Example 1 except that this coated magnetic powder was used. These videotapes were designated as Example Tapes 7 and 8. Example 9 Fe-based metal magnetic powder (Al content: 2 atomic weight %)
A videotape with a width of 12.65 mm was prepared in the same manner as in Example 1, except that a magnetic powder showing no change in the differential thermal curve up to 93° C. was used. This videotape was designated as Example Tape 9. Example 10 The surface of Fe-based metal magnetic powder (Al content: 3.5 atomic weight %) was treated with silicone oil to prevent rust, and the magnetic powder showed no change in the differential thermal curve up to 100°C. A videotape having a width of 12.65 mm was prepared by applying the same processing as in Example 1, and this videotape was designated as Example Tape 10. Examples 11 to 14 Oleic acid, sodium oleate, myristic acid and stearic acid (1:1), and sodium oleate and myristic acid (1:1) were used instead of lecithin used in Example 1. A videotape was prepared in the same manner as in Example 1,
These tapes were designated as Example tapes 11, 12, 13 and 14, respectively. Example 15 Example tape 15 was prepared in the same manner as in Example 3, except that 3 parts of dodecyl alcohol (C ₁₂ H ₂₅ OH) was used in place of 3 parts of lecithin. Example 16 Example tape 16 was prepared in the same manner as in Example 3, except that 3 parts of sodium dodecyl sulfate (C ₁₂ H ₂₅ OSO ₃ Na) was used in place of 3 parts of lecithin. Example 17 In Example-3, Fe-Ni-Co was used instead of Fe.
Example tape 17 was prepared in the same manner as in Example 3, except that 100 parts of metal magnetic powder of -Al alloy (Al content: 3.5 atomic weight %) was used. Example 18 In Example-3, Fe-Ni-Zn was used instead of Fe.
Example tape 18 was prepared in the same manner as in Example 3, except that 100 parts of metal magnetic powder of -Al alloy (Al content: 3.5 atomic weight %) was used. Comparative Example 1 The same treatment as in Example 1 was applied, except that Fe-based metal magnetic powder with the following composition (conventional Fe-based metal magnetic powder with a stable differential thermal curve up to 25°C) was used.
A videotape with a width of 12.65 mm was made. This videotape was designated as Comparative Example Tape 1. Comparative Example 2 The following examples were used, except that a silicone oil coating was formed on the surface of the metal magnetic powder having the composition below (the differential thermal curve easily changes at room temperature), and a magnetic powder whose differential thermal curve did not change up to 50°C was used. Adding the same processing as 1
A videotape with a width of 12.65 mm was made. This videotape was designated as Comparative Example Tape 2. Metal magnetic powder used in Comparative Example 1 and Comparative Example 2
The magnetic powder (before being coated with silicone oil) used in XMA (Hitachi "X-556")
When observed with a KEVEX-7000 model), the magnetic powder of Comparative Example 1 had Si content: 1.1 atomic weight %, Ni content: 6.8 atomic weight %, and Al: not detected. The magnetic powder of Comparative Example 2 had Si content: 3.0 atomic weight %, Ni content: 5.0 atomic weight %, and Al: not detected. It was hot. Comparative Example 3 The surface of the metal magnetic powder of Comparative Example 1 was slowly oxidized and heated to 73°C.
A videotape with a width of 12.65 mm was prepared by performing the same treatment as in Example 1, except that magnetic powder with no change in the differential thermal curve was used, and this videotape was designated as Comparative Example Tape 3. Comparative Example 4 A videotape was prepared in the same manner as in Example 1 except that the lecithin used in Example 1 was removed, and this was designated as Comparative Example Tape 4. Comparative Example 5 Fe-based metal magnetic powder (Al content: 22 atomic weight%)
A videotape was produced in the same manner as in Example 1, except that a videotape was used, and this was designated as Comparative Example Tape 5. Next, Examples 1 to 14 and Comparative Examples 1 to 5
In order to investigate the tape performance of Example Tapes 1 to 14 and Comparative Example Tapes 1 to 5 obtained in , still durability, saturation magnetization Bm, and storage stability were measured and the results are shown in Table 1. Comparative Examples 6 and 7 Examples 12 and 13 except that 100 parts of Fe-based metal magnetic powder containing no Al was used instead of Fe-based metal magnetic powder (Al content: 1.3 atomic weight %). Comparative Example Tapes 6 and 7 in the same manner as 13.
It was created. Comparative Example 8 Comparative Example Tape 8 was prepared in the same manner as in Example 1 except that 3 parts of fluorine-containing butyl stearate was used instead of 3 parts of lecithin. Comparative Example 9 Comparative Example Tape 9 was prepared in the same manner as in Example 1 except that 3 parts of stearamide was used instead of 3 parts of lecithin. Comparative Example 10 Comparative Example Tape 10 was prepared in the same manner as in Example 1, except that 3 parts of polyalkylene oxide alkyl phosphate (trade name: Gafac RE610) was used instead of 3 parts of lecithin. Comparative Example 11 Comparative Example Tape 11 was prepared in the same manner as in Example 1 except that 3 parts of trimethylpolyethyleneoxy quaternary ammonium salt was used in place of 3 parts of lecithin. Comparative Example 12 In Example 1, the Al content was 0.4 atomic weight%.
Comparative Example Tape 12 was prepared in the same manner except that Fe-based metal magnetic powder was used.

【table】

【table】

[Table] However, in Table 1, still durability, saturation magnetization,
The saturation magnetization and the residual rate of saturation magnetization after storage were expressed according to the following criteria. Still Endurance: Indicates the time in minutes until the playback output of still images decreases by 2 dB. Saturation magnetization: The saturation magnetization of the sample tape is shown in Gauss. Saturation magnetization after storage: The saturation magnetization after leaving the sample tape in an atmosphere of 50°C and 90RH% (relative temperature) for one week is shown in Gauss. Residual rate of saturation magnetization: Indicates the percentage of the saturation magnetization measured after leaving the sample tape in an atmosphere of 50℃ and 90RH% (relative temperature) for one week compared to the saturation magnetization measured before leaving it. Ta. From the results in Table 1, it is clear that the samples according to the present invention have dramatically improved still durability and excellent storage stability. [Effects of the Invention] Since the magnetic recording medium of the present invention uses metal magnetic powder with a specific composition and a specific dispersant in the magnetic layer, the electromagnetic conversion characteristics do not change even when the magnetic recording medium is repeatedly run. Does not decrease. Also, when recording or reproducing from a magnetic recording medium, the degree of heat generated by friction between the magnetic head and the magnetic recording medium (equilibrium temperature 60
~75℃), the magnetic powder does not change and has excellent still durability. Furthermore, the tape performance remains unchanged even when left under high temperature and high humidity conditions, and the tape has excellent storage stability.

Claims (1)

[Claims] 1. In a magnetic recording medium having a magnetic layer containing metal magnetic powder on a support, the metal magnetic powder has Al atoms in proportion to the atomic weight of all metal components.
The magnetic layer contains a fatty acid (R
-COOH, R is a saturated or unsaturated alkyl group having 7 to 17 carbon atoms), a metal soap consisting of an alkali metal or alkaline earth metal of the fatty acid, lecithin, a saturated or unsaturated alkyl group having 7 to 17 carbon atoms, A magnetic recording medium characterized by containing at least one selected from higher alcohols and sulfuric esters.