JPH02132631A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent deterioration of electromagnetic conversion characteristics of a magnetic recording medium after used many times by incorporating such metal magnetic powder having a specific compsn. and a specific dispersing agent into the magnetic layer. CONSTITUTION:The metal magnetic powder contains Al atoms at the amt. of 0.5-20 atomic wt.% of the total atomic weight of the metal components. The magnetic layer contains at least one compd. selected among fatty acids with 8-18 carbons (represented by R-COOH, wherein R is satd. or unsatd. alkyl groups with 7-17 carbons), metal soaps comprising alkali metal or alkaline-earth metal and fatty acids, lecithin, higher alcohol with 12 or more carbons and sulfates. The still (still picture) durability and storage stability of the medium are thereby improved.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to magnetic recording media, particularly still images.
[Prior art] In general, I4I recording media are made of polyethylene terephthalate 1, etc. in a tape form or a sheet. It is formed from a support molded into the shape of 1. and a magnetic layer formed by coating the support with a magnetic paint containing magnetic powder and a binder as main components. Regarding the magnetic powder contained in the magnetic layer, metal magnetic powder containing Fe, Go, etc. as the main components is better in terms of magnetic properties such as squareness ratio, saturation magnetization, and antimagnetic properties. Because of their excellent properties, the use of these metal magnetic powders in magnetic recording media is attracting attention. [Problems to be Solved by the Invention] However, when the conventional metal magnetic powder has a particle size of 1 μm or less, which is used for magnetic recording, it not only has poor dispersibility but also becomes 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 properties of methyl durability and storage stability. [Means for Solving the Problems] In order to achieve the above object, the present invention provides a magnetic recording medium in which a magnetic layer containing metal magnetic powder is disposed on a support, in which the metal magnetic powder is Affi atoms are contained in the range of 0.5 to 20 atomic weight percent based on the atomic weight of all metal components, and the magnetic layer further contains fatty acids having 8 to 18 carbon atoms (R-Coo and 1). represented, R has 7 carbon atoms
~17 saturated or unsaturated alkyl groups), metal soaps consisting of alkali metals or alkaline earth metals of the fatty acids, lecithin, higher alcohols having 12 or more carbon atoms; and sulfuric esters. It is characterized by containing one kind of 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 (Fc1Fe-Ni-co alloy, FC-
Mn-/n alloy, FO -Co -N+ -P alloy, F
O-N+-711 alloy, Fe-Ni-Cr 1P alloy, lTe-Co-Ni-cr alloy, Fe-co
-p alloy, Fc-Ni alloy, Fe -N+ -lyln
The proportion of △2 atoms in metal magnetic powder mainly composed of 1"e, such as alloys and Fe-P alloys, is the same as the atoms ff of all metal components.
Examples include metal magnetic powder having a content of 0.5 atomic weight % or more and 20 atomic weight % or less. The above magnetic powder (hereinafter referred to as "magnetic powder according to the present invention") is
For example, aluminum and/or a compound thereof can be added to the metal component of the metal magnetic powder by a method such as inclusion or deposition. Note that the metal magnetic powder component mainly refers to components other than carbon, hydrogen, oxygen, etc. that are not detected by an X-ray microanalyzer. A Q The addition m of J3 and/or its compound is such that the ratio of Affi atoms (for example, All 2 if the additive is Affi20a) in the gold-flexing component of the metal magnetic powder is such that the proportion of atoms in the total gold-flexing component is 0.5 to 2 for ffiffi
The range is 0 atomic mω%, particularly preferably 1 to 2
It is in the range of 0 atomic It'd%. △! When the number of atoms becomes less than 0.5 atom EQ (71% J), the properties of a magnetic recording medium produced using the metal magnetic powder, such as storage stability, reproduction output, and stickiness durability, become insufficient. Among the magnetic powders according to the present invention, those whose metal components essentially consist of Fe and 8L are preferred. Here, substantially means 1:
c, indicates that the third component other than Affi is 1% or less. Moreover, among the magnetic powders according to the present invention, at least 80°C
It is preferable to use magnetic powder that shows no change in the differential thermal curve. The differential thermal curve shows thermally stable E3 materials such as alumina and quartz.
11! When metal magnetic powder is heated with a substance at a constant rate, the temperature difference that occurs between the two is measured and the energy state of the two is determined. New Experimental Chemistry SF+ 11^
2.Basic technology”W is described in detail. The binder used in the I4l1'i layer of the magnetic recording medium of Wood's invention is preferably polyurethane or a combination of polyurethane and other binder components. Examples of the polyurethane include thermoplastic urethane entomers, thermosetting urethane resins, and electron beam curable resins made of unsaturated brevolimers 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 mixtures of polyester and polyisocyanate, and epoxy resins. Examples include electron beam irradiation-curable resins such as acrylic type and polyester acrylic type. In the present invention, urethane elastomer or
A combination of urethane elastomer and other binder components (vinyl chloride-vinyl acetate-co-m combination, etc.) is particularly preferably used. The mixing ratio of the magnetic powder and the binder according to the present invention is 5 to 4 m parts of the binder to 100 ffl m parts of the magnetic powder.
00 parts by weight, preferably 10 to 200 parts by weight. If the amount of binder mixed is too large, the recording density of the magnetic recording medium will decrease, 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. Furthermore, various hardening agents can be added to the magnetic layer in order to improve the durability of the magnetic recording medium. for example,
Polyisocyanate-1 and the like can be contained. Polyisocyanate and C1 diisocyanate and 3
Examples include an adduct with f+)j polyol, a 5m form of diisocyanate, and a 1:2 carbonate of 3 moles of diisocyanate and water. Specific examples of these include adducts of 3 moles of 1.lylene diisocyanate and 1 mole of trimedylolpropane, and 1.3 moles of metaxylylene diisocyanate.
mol and 1-trimethylolpropane 1 mole, a pentapod of tolylene diisocyanate, 1 mole of tolylene diisocyanate, a pentapod consisting of 2 moles of lylene diisocyanate, hex 1, 3 moles of namelene diisocyanate and 1 mole of water. There are decarboxylated products that can be reacted to yield 1q, and these can be easily obtained industrially. In addition to the magnetic powder, binder, and curing agent described above, additives such as a dispersant, abrasive, and an antistatic agent may be added to the magnetic layer. Dispersants used include fatty acids having 8 to 18 carbon atoms (R -Cool-1
R is a saturated or unsaturated alkyl group having 7 to 171 carbon atoms, and R is an alkali metal (Li, Na, K, etc.) or alkaline earth metal (M,
Resin resin, etc., made of resin (CaSBa, etc.) is 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 or in combination with two or more. F may be used in combination. These dispersants have magnetic 1
5) It is added in an amount of 1 to 20 parts by weight per 100 parts by weight. These dispersants are described in Japanese Patent Publications No. 39-28369, No. 44-17945, No. 48-15001, Illll., and U.S. Patent Publication No. 3. 5137. 993
No. 3,470,021 Specification 4 etc. For lubricants, silicone oil, carbon black,
Graphite, carbon black graph 1-bolimer,
Molybdenum disulfide, tungsten disulfide, 1 carbon atom
It can also be used for fatty acid esters (so-called waxes) consisting of 2 to 16 monobasic fatty acids and monohydric alcohols having a total number of carbon atoms of 21 to 23 carbon atoms. These lubricants are 0.2 parts per 100fil part of magnetic powder.
・~2 0 1 ffl. It is added within the range of 100%. These people (Yo Special Publication No. 11?
T No. 3.47+1,021, T No. 3,492,235
No. 3,497,411, No. 3,523,
No. 08G, No. 3, (i25.720, No. 3,63
No. 0, 772, No. 3, (i34,253, No. 3)
．． 642, 539, 3, 687, 725, IBM Technica JRe Desk Exit - Jabultan Magazine Volume 9, No. 7, Page 719 (19
(December, G6) (IBM Techni)
cal Disclosure Bulletin
Vol. 9, No. 7, Page 779 (
196G, December): Electronics Magazine No. 12, page 380 (19 (31) (EL
E KTRON I K, No. 12,Page
380, 1'l61), etc. As an abrasive, commonly used abrasives include fused alumina,
Carbonization

[Used are nitrogen, chromium oxide, corundum, artificial corundum, human diamond, garnet, emery (main ingredients: corundum and magnetite), etc. these? i
l) The polishing agent used has an average particle size of 0.05 to 5μ, preferably 0.1 to 2μ. These abrasives are added in an amount of 2 to 20 parts by weight per 100 parts by weight of the magnetic powder. Regarding these rtll polishing materials, please refer to Japanese Patent Application Laid-open No. 115510/1983. tJ Akira $11l
m, U.S. Patent No. 3,007,807, U.S. Patent No. 3,0
41,196, 3,687,725, British Patent No. 1,145,349, West German Patent (D
T1PS) No. 853,211M. If necessary, as an antistatic agent, use conductive powders such as graphite, carbon black, tin oxide, antimony monoxide compounds, tin oxide, titanium monoxide, andymonium monoxide compounds, carbon black graft polymers, etc., and natural substances such as bonin. Surfactant: alkylene oxide type,
Nonionic surfactants such as glycerin and glycidol: higher alkyl amines, quaternary pyridine, other heterocycles, cationic surfactants such as small bosium or sulfonium: carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid Anionic surfactants containing acidic groups such as ester groups and esder phosphate groups; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric acid or phosphoric acid esters of amino alcohols. These surfactants that can be used as antistatic agents are disclosed in U.S. Patent No. 2,271,623, U.S. Pat. No. 2,240,472, U.S. Pat.
No. 2,67G,975, III1 No. 2, G91
, No. 566, No. 2,727,860, No. 2,73
No. 0,/198, No. 2,742,379, No. 2,
No. 739,891, No. 3,068,101, No. 3
, No. 158,484, No. 3,201,253, No. 3,210,191, No. 3,294,540, No. 3,415,649, No. 3,441,413
No. 3,442,654@, No. 3,475,17
No. 4, No. 3.545,974, West German Patent Publication (
O L S ) 1,942.1355, British Patent No. 1,077,317, British Patent No. 1,198,45
0 and others, "Synthesis of Surfactants and Their Applications" by Ryohei Oda et al. (Maki Shoten 1964 edition): A.
W. Written by Bayley [Surf S Active Agents]
(Interscience Publication in] Voleteide 1958 Edition): T. P. Cicely Mei "Enzyme Bread of Surf S-Active Agents Volume 2" (Chemical Bubbles Company 1964 edition): "Surfactant Handbook" 6th edition (
It is described in adult rocks such as Sangyo Zuuchi Co., Ltd. (December 20, 1966). These surfactants may be added alone or in combination.
:stomach. Although these are used as antistatic agents, they are sometimes used for other purposes, such as dispersion, magnetic properties, etc.
It may also be used to improve lubricity, improve lubricity, and serve as a coating aid. The magnetic recording medium according to the present invention is manufactured by kneading and dispersing magnetic paint components such as the magnetic powder and binder in a solvent to prepare a magnetic coating, applying the obtained magnetic coating onto a support, and drying it. Manufactured by V. The magnetic coating R3+ may contain additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and the like, if necessary, in addition to the magnetic coating components described above. Solvents for magnetic paint or solvents used when applying magnetic paint include acetone, methyl ethyl ketone (MEK),
Ketones such as methyl isobutyl ketone (MIBK) and cyclohexyrinone; Al-1-ols such as methanol, ethanol, propanol, butanol; [■Pills, ester-based drugs such as ethylene glycol and noashdate:
2-
Ethers such as ethyl-hydrofuran, dioxane, etc.; aromatic hydrocarbons such as benzene, toluene, and xylene; Halogenated hydrocarbons and the like can be used. In addition, regarding cross-wires of magnetic paint components, please refer to l) "1...
The magnetic powder and other magnetic coating components are fed into the mixer either all at the same time or individually sequentially. For example, first, the magnetic powder is added to a solution containing a dispersant and kneaded for a predetermined period of time, and then the remaining components are added and the kneading is continued to form a magnetic paint. Various types of crosstalk machines are used for distributing the nine techniques. For example, Niki roll mill, three-mouth roll mill, ball mill, pebble mill, sand grinder, 3 jcgvari
No. 21-lighter, high-speed inveler disintegrating machine, high-speed stone mill, high-speed impact mill, disver kneader, high-speed millimeter, ho-sevenizer ultrasonic dispersion rPI machine, etc. When the magnetic paint according to the present invention is mixed and dispersed by these methods, it is extremely well dispersed and is suitable for electron microscopy.
The number of aggregates when observed with a mirror was much smaller than in the case of conventional magnetic coatings. Techniques related to crosstalk and dispersion are described in the book by T. O. Paine [Pain 1 Flow and Pigment Disversion (1964, published by John Wiley and Son), JT. O. PΔTTON( P aint F
low and pigment dispe
rsion (1964. John Willey a.
nd 3on)). Also, U.S. Patent Nos. 2,581,414 and 2,855,156
It is stated in each specification of the issue. Ma1= For the manufacturing method of S magnetic coating, please refer to Special Publication No. 35-1
No. 5, No. 39-2G794, No. 43-186, No. 4
No. 7-28043, May 47-2804, No. 47-2
No. 8046, No. 47-28047, No. 47-3144
No. 5, No. 48-11162, No. 48-21332,
It is described in detail in the specifications of each publication of No. 48-33683. In addition, materials for the support include polyesters such as polyethylene terephthalate 1 to polyethylene 2.6-naphthalate 1, polyolefins such as polypropylene, cellulose triacetate, relulose diacetate, and cellulose LiS. Plastics such as polycarbonate, metals such as Cl, /L, and Zn'j, glass, and various ceramics such as so-called neuroramic are used. Support forms include dave, sheet, card, disc,
For drums, etc., various materials are selected as necessary depending on the form. The thickness of these supports is approximately 3 mm in the case of tape or sheet form.
It is about 100μ, preferably 5 to 50μ, and in the case of a disk or card, it is about 30μ·-10ml, and in the case of a drum, it is cylindrical, and its shape is determined depending on the recorder used. The support has a so-called back coat (3 a
ck coat). Regarding the back coat, for example, U.S. Pat.
No. 04, 401, No. 3,293,066, No. 3
, 61 7. No. 378, No. 3, OG2. 67
No. G, No. 3, 734, 772, No. 3, 47
No. 6, 596, No. 2.6/13,084, No. 2
, No. 803,556, No. 2,887,462, No. 2,923,642@, No. 2,997,451,
3,007,892, 3,041,1
No. 96, No. 3, 115, 420, No. 3,
It is described in each specification such as No. 166, 688. In addition, in order to form a magnetic layer by coating the magnetic paint on the support, gravure coat coating, My V-bar coating, doctor blade coating, reverse roll coating, dip coating, air knife coating, calendar coating can be applied. Methods such as , squeeze coating, kiss coating, and fluorine coating can be used, as well as other methods. Specific explanations of these methods can be found in [Coating Engineering (March 1970, published by Asakura Shoten)] , p. 258 et seq.)A
'), [Plastic film processing and its applications-J
(IIIWa 46, published by Gihodo) is described in detail. The magnetic layer coated on the support by such a method is
After performing a treatment to orient the magnetic powder according to the present invention in the layer as necessary, the applied magnetic layer is dried. Further, if necessary, the magnetic recording medium is manufactured by subjecting it to surface smoothing and cutting it into a desired shape. The orientation magnetic lift for orienting the magnetic powder in the magnetic layer is approximately 500 to 3,500 Gauss using alternating current or direct current, the drying temperature is approximately 50 to 100°C, and the drying time is approximately 500 to 3,500 Gauss. is preferably about 3 to 10 minutes. The direction in which the magnetic powder is arranged can be determined, for example, according to U.S. Pat. No. 1,94
9,840, 2,796,359, 3,001,891, 3,172,776, 3,416,949, 3,473,9
No. 60, No. 3,681,138, Special Publication No. 32-37127, No. 39-28368, No. 40-
No. 23624, No. 40-23625, No. 41-131
81, No. 48-13043, No. 48-39722, and the like. 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 the intended use. [Example] Hereinafter, the main content of the present invention will be explained with reference to Examples and Comparative Examples. In Examples and Comparative Examples, the description "Part U" means "Part by weight J." Examples 1 to 6 ■ Preparation of magnetic paint Adding water-soluble aluminum salt to FO in ferrous salt aqueous solution FQ (0t))2 containing p obtained by reacting a solution containing 0.5 to 20 atomic weight percent with an alkaline aqueous solution
By passing an oxygen-containing gas through a suspension of li 1 or more to oxidize it, a needle-like article containing aluminum α-
FeOOl-1 particles are generated, and the aluminum-containing pin-shaped α-FeOOl-1 particles are heated in a non-reducing atmosphere.
Heat treatment in the temperature range of 50-650℃ J! I! After forming acicular α-F0203 particles containing aluminum, the particles were heat-treated in a reducing gas at a temperature of 350 to 500° C. to produce Fe-based metal powder. thus! 'J 31 A! Including right m is 1.3 respectively.
, 3, 3, 5, 42, 5.1, and 7.0 atomic weight % Fe-based metal magnetic powders (Fe-containing G of 60 atomic weight % or more) were used to prepare the following magnetic powder-containing compositions. was prepared. After the J3 and Δy-containing right hemispheres are 1.3, 3, and 3.5 atomic weight%, respectively, the S1 atomic weight% is less than 0.5%, and the 4.2% one has 3i. It was less than 1 atomic weight percent. Note that the atomic weight percent of Ax, s+ was measured using an X-ray microanalyzer (rX-556 J manufactured by Hitachi, KEVE
X-7000 model) was measured. Fe-based metal magnetic powder 100 parts VAG
I-1 (Product name: Union 7J-manufactured by Byte Co., Ltd., vinyl chloride-vinyl citrate co-coordination) 10 parts Estane 5701 (
Product name: Gutdrich, polyurethane resin)
io part resin
Part 3 M E K
70 parts l-luene
60 parts cyclohexanone
5 parts However, in the above Fe-based metal magnetic powder, Al
Contains right ffl caso tLF ray 1.3, 3. 3.5,
4.2, 5.1 J: and 7.0 atomic weight%,
Differential thermal curves are 83℃, 86℃, 88℃, and 95℃, respectively.
．． It has the property of not changing from 97℃ to 130℃. After thoroughly mixing and dispersing each of the above magnetic powder-containing compositions using a ball mill, 5 parts of coronate (polyisocyanate solution manufactured by Nippon Polyurethane Co., Ltd.) was added and mixed uniformly.
Six types of magnetic paints {q. The six types of magnetic coating tits obtained
Regarding the /l content of Fe-based metal magnetic powder contained in
．． 3, 3, 3.5, 4.2, 5.1, and 7.0 magnetic coatings were designated as 1, 2, 3, 4, 5, and 6, respectively, depending on the atomic weight percentage. ■ Preparation of magnetic recording media Next, a magnetic field of 2000 gauss was applied to one side of five types of polyethylene terephthalate films with a thickness of 12μ, prepared separately from magnetic paints 1, 2, 3, 4, 5, and 6. J: The sea urchin was coated with a dry film thickness of 5 μm. Each of the obtained wide samples was subjected to supercalender treatment, and then slit to 12.65 mm rl.
A video Dave of B was created. For each of these Video Dave, the Example Table 1, 2, 3, 1,
5J3 and 6. Example 7 J3 and 8 100 parts of the above Δ2 'fiff! ．． is 0.8%, 1,
3% Fa-based metal If powder was mixed with 0.2t1!1% of the following 1-mide #220 (trade name: manufactured by Fuji Kasei Kogyo Co., Ltd.) H-ENH-ecI-12-CI-1. N.H.
+-cH. cH. -NHCO-R-Co71n -NH-fCH. -CI-1. Nl-CH. CH. -N
H, however, R is a solution (jmethylene pentachloride/toluene = 70:30) 67
After dispersing in 0 parts, it is separated by Ura-separation, and the resulting magnetic powder is mixed with mineral oil (
Isobar) I lost again to 300d, and to the selection 1, Isobar 1.2 s++ y Isobar 60
Then, after heating the solution at 50 DEG C. for 1 hour, it was filtered, and the magnetic ladle was washed with 11-hexane and then dried in a nitrogen atmosphere. As a result, coated magnetic powders with stable differential thermal curves up to 120°C and 140°C were obtained. A videotape with a diameter of 12.65 mm I was prepared in the same manner as in Example 1, except that this powder was used. This bidet A table was designated as Example Tables 7 and 8. Actual 771 Example 9 1: Example 1 except that e-based metal magnetic powder (/l content m: 2 atomic weight %) was slowly oxidized and a magnetic powder that showed no change in differential thermal curve up to 93°C was used. Adding the same processing as 1
I made a 2.65mm R11 videotape. This video was designated as Example Video 9. Example 10 Fe-based metal magnetic powder (Δl content m: 3.5 atomic weight ω%)
The surface is treated with silicone oil to prevent rust.
12. The same treatment as in Example 1 was added, except that magnetic powder that showed no change in the differential thermal curve up to ℃ was used. A 65 mm wide video tape was prepared, and this tape was used as Example y-7.
It was set as 10. Examples 11 to 14 Instead of lecithin used in Example 1, oleic acid, 1 ml of sodium oleate, myristic acid and stearin M (
A videotape was prepared in the same manner as in Example 1 except that sodium oleate and myristic acid (1:1) and sodium oleate and myristic acid (1:1) were used, respectively, and Example Tape 11.1 was used.
2.13 and 14 happened. Comparative Example 1 The same treatment as in Example 1 was applied except that 1=e-based metal magnetic powder (conventional l"e-based metal magnetic powder with stable differential thermal curve up to 25°C) having the following composition was used. , 12.65mm
+p videotapes were made. This video tape was designated as Comparative Example Table 1. Comparative Example 2 A silicone oil coating was formed on the surface of the metal magnetic powder having the composition below (the differential thermal curve tends to change at room temperature), and the powder was heated at 50°C.
Uses magnetic powder with no change in differential thermal curve! Other than that, the same process as in Example 1 was added to create a total of 12.65m+n rl.
I created a video of Dave. This videotape was used as Comparative Example Tape 2. The metal magnetic powder used in Comparative Example 1 and the magnetic powder used in Comparative Example 2 (1) coated with silicone oil) were mixed with
When observed using a VEX-7000 model, the magnetic powder of Comparative Example 1 had the following: Si content: 1.1 atomic weight %, Ni content: 26.8 atomic weight σ%, Al: not detected. The magnetic powder of Comparative Example 2 had S i -containing ffi: 3. O atomic weight ffl%, N
1-containing ffi: 5.0 atomic weight%, Af: not detected. Met. Comparative Example 3 The same process as in Example 1 was carried out except that the surface of the metal magnetic powder of Comparative Example 1 was slowly oxidized and the magnetic powder with no change in differential thermal curve up to 73°C was used, and a 12.65 ml video tape was prepared. This videotape was used as Comparison/Example Tape 3. Comparative Example 4 A video tape was prepared in the same manner as in Example 1 except that the lecithin used in Example 1 was removed, and this was used as Comparative Example Table 14.
And so. Comparative Example 5 1: E-based metal positive powder (A-containing matrix = 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, in order to examine the tape performance of Example Tapes 1 to 14 and Comparative Example Tapes 1 to 5 obtained in Examples 1 to 14 and Comparative Examples 1 to 5, Sujiru durability, saturation magnetization BII and The results of storage stability measurements are shown in Table 1. However, in Table 1, methyl durability, saturation magnetization, saturation magnetization after storage, and residual rate of saturation magnetization are expressed according to the following group 11. ■ Sujiru durability: Indicates the time in minutes until the playback output of a still image decreases by 2 dB. ■ Saturation magnetization: The saturation magnetization of the sample tape is shown in Gauss. (2) Saturation magnetization after storage: The saturation magnetization after leaving the sample tape in an atmosphere of 50° C. and 90 RH% (relative temperature) for one week is shown in Gauss. ■ Residual rate of saturation magnetization: What percentage of the saturation magnetization measured after leaving the sample tape for 1 g in an atmosphere of 50°C and 90 RH% (relative temperature) corresponds to the saturation magnetization measured before leaving it? It was shown as follows. From the results in Table 1, it is clear that the samples according to the present invention have dramatically improved sujiru durability and are also excellent in storage stability. [Effects of the invention] This invention 1! Since IJ's magnetic recording medium uses metal magnetic powder with a specific composition and a specific dispersant in the magnetic layer, the electromagnetic conversion characteristics do not deteriorate even if the magnetic recording medium is repeatedly run. In addition, when recording or reproducing from a magnetic recording medium, the magnetic powder does not change at the level of heat generated due to friction between the magnetic head and the magnetic recording medium (equilibrium temperature 60 to 75°C), and the still durability Excellent. Furthermore, the Dave performance does not change even if left under high temperature and high humidity, and it has excellent storage stability (3).

Claims (1)

[Claims] In a magnetic recording medium having a magnetic layer containing metal magnetic powder on a support, the metal magnetic powder contains Al atoms in an amount of 0.5 to 20 atomic weight % based on the atomic weight of all metal components.
Furthermore, the magnetic layer contains a fatty acid having 8 to 18 carbon atoms (represented by R-COOH, where R is a saturated or unsaturated alkyl group having 7 to 17 carbon atoms).
, a metal soap made 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.