JPH01277323A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide the recording medium which is excellent in high-density recording, S/N and durability by using magnetic metallic powder having a specific surface area and specifying the contents of the respective constituting elements of the magnetic metallic powder and the existence ratios of the respective constituting elements in the surface area of the magnetic powder. CONSTITUTION:The specific surface area of the magnetic metallic powder incorporated into the magnetic layer is >=45m<2>/g and the magnetic layer is so formed that either of iron atoms and nickel atoms, aluminum atoms and silicon atoms, as well as zinc atoms and manganese atoms are incorporated therein. The contents of the respective atoms are specified to >=90atomic% iron, >=1atomic% and <10atomic% nickel, >=0.1atomic% and <5atomic% aluminum, >=0.1atomic% and <5atomic% silicon, and >=0.1atomic% and <=5atomic% zinc and/or manganese. The existence ratios of the respective atoms existing in the surface area of the magnetic metallic powder are specified, by number of carbon atoms, to 100 iron: <=4 nickel: 10-60 aluminum: 10-70 silicon: 20-80 zinc/or manganese. The magnetic recording medium which allows the high- density recording and has the excellent S/N and durability is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks.

・ In recent years, the density of magnetic recording media such as magnetic tape has increased, ・
With the increase in S/N, magnetic powder with smaller particle size
It is now being used.

) In general, it is said that the S/N ratio of a magnetic recording medium is proportional to the square root of the number of particles of magnetic powder in the recording material involved in recording and reproduction. The use of magnetic powder with a smaller diameter is more advantageous in improving the S/N. Further, by making the magnetic powder into fine particles and increasing its BET value, the surface of the magnetic layer becomes smoother and spacing loss is reduced, which is advantageous in obtaining high electromagnetic conversion characteristics. If metal magnetic powder is used, even higher density recording is possible and performance is further improved.

In other words, this metal magnetic powder has large saturation magnetization and coercive force,
It has excellent properties as a high-density recording material. However, due to its high surface activity, it has the following two main problems: Oxidation resistance stability of metal magnetic powder in air If metal magnetic powder is left in the air, oxidation progresses. As a result, magnetic properties gradually deteriorate.

■Dispersibility in binders When dispersing metal magnetic powder in a binder, it has poor dispersibility due to its high surface activity, making it difficult to disperse, and in extreme cases, the binder resin may gel in the paint.

In particular, the uses of video tapes in recent years have been wide-ranging as they have become portable, and the conditions for their use have varied. Therefore, video tapes are required to have high corrosion resistance.

The purpose of the present invention is to enable high-density recording, have excellent electromagnetic conversion characteristics such as S/N ratio, have good dispersibility of magnetic powder, corrosion resistance, squareness ratio, etc., and have excellent durability. It is an object of the present invention to provide a magnetic recording medium with a magnetic recording medium.

28 Structure of the invention and its effects The present invention provides a magnetic recording medium in which a magnetic layer contains a binder and metal magnetic powder dispersed in the binder, (a) The specific surface area is 45 rrr/g or more, (b) the metal magnetic powder contains iron atoms, nickel atoms, aluminum atoms, and silicon atoms, and (C) the content of the iron atoms is 90 at % or more. , the content of the nickel atoms is 1 atom % or more and less than 10 atom % (more preferably 3 atom % or more and 9 atom % or less), the content of the aluminum atoms is 0.1 atom % or more and less than 5 atom % (more preferably 0.5 atom % or more and 4 atom % or less), the content of silicon atoms is 0.1 atom % or more and less than 5 atom % (more preferably 0.5 atom % or more and 4 atom %) below), the content of the zinc atoms and/or the content of the manganese atoms (
However, when containing both zinc atoms and manganese atoms, the total amount) is 0.1 atomic % or more and 5 atomic % or less (more preferably 0.5 atomic % or more and 4 atomic % or less), (d) Abundance ratio of iron atoms, nickel atoms, aluminum atoms, silicon atoms, zinc atoms and/or manganese atoms present in the surface area of the metal magnetic powder (iron atoms: nickel atoms, aluminum atoms: silicon atoms: Zinc atoms and/or manganese atoms) have an atomic ratio of 100: (4 or less): (10-60) = (10-70): (20-
80) (more preferably 100: (2 or less)
: (20-50):(20-60):(30-7
0)).

According to the present invention, since metal magnetic powder having a specific surface area of 45 ho/g or more is used as the magnetic powder, high-density recording is possible and a medium with excellent S/N ratio etc. can be provided. The specific surface area of the metal magnetic powder is 50rrf/g or more and 70nf/g
The following is preferable: - layer.

Here, it is important to specify both the content ratio of each metal element contained in the metal magnetic powder and the abundance ratio of each metal element in the magnetic powder surface area.

That is, since the iron atom content is 90 atomic % or more and the Ni content is set to the above ratio, the electromagnetic conversion characteristics are good. Furthermore, since silicon atoms are contained in the above ratio, sintering of the magnetic powder can be prevented. Furthermore, since aluminum atoms are contained in the above ratio, the corrosion resistance of the magnetic powder is improved. Furthermore, by containing zinc atoms and manganese atoms in the above ranges, the crystal growth of the magnetic powder is improved. That is,
The inclusion of zinc atoms promotes the needle-like growth of crystals, and the inclusion of manganese atoms makes the crystals thicker and shorter to improve the squareness ratio.

In addition, since the abundance ratio of iron atoms to nickel atoms in the surface area of the metal magnetic powder is set to 100: (4 or less), the nickel atoms, which are prone to rust, are not exposed to the surface area, which improves the rust resistance of the magnetic powder. Corrosion resistance is improved, and the high electromagnetic conversion characteristics inherent to Fe-Ni metal magnetic powder can be enjoyed. In addition, since the abundance ratio of iron atoms and other aluminum atoms, silicon atoms, zinc atoms and/or manganese atoms in the surface area of the metal magnetic powder is limited to the above range, the content ratio in the entire metal magnetic powder is The abundance ratio of iron atoms in the above surface region can be significantly reduced compared to the above. Therefore, since the corrosion resistance of aluminum atoms and the like can be sufficiently exhibited, oxidation of the magnetic powder can be suppressed and the dispersibility of the particles can also be improved.

In this way, by improving the oxidation resistance and dispersibility of the metal magnetic powder, the durability of the medium can be improved while demonstrating the high electromagnetic conversion characteristics of the highly finely divided metal magnetic powder with a specific surface area of 45 rrf/g or more. can be improved.

The metal magnetic powder of the present invention can be produced, for example, as follows.

That is, iron hydrates such as a-FeOOH, 1-FeOOH, crFexOx, 7-FexO,,
Iron oxides such as Fe5Oa may be reduced with Hl or the like at high temperatures.

For example, ferrous salt compounds (e.g. FeSO4, FeC1z
etc.) with an alkaline component (e.g. NaOH, etc.) to generate α-FeOOH, and this α-FeOOH
is reduced at high temperature (e.g. by Hz) or α
Metal magnetic powder can be produced by converting -Fe00B into α-Fe, O, and then reducing it at high temperatures (for example, with H2). At these various stages, A2 compounds, Ni compounds, It can be manufactured by adding a Si compound. Furthermore, in the same way, a small amount of a zinc compound or a magnesium compound (either one of them can be added).

The same applies to compounds of other elements other than Fe.

In the present invention, the above-mentioned "surface area" refers to the "surface area of magnetic powder (ESCA)".
ctroscopy for che+5ical a
analysis depth (specifically, about 100 Å or less from the surface to the inside). Examples of metal magnetic powder include those produced by a dry reduction method in which iron oxide is reduced with hydrogen or the like.

Note that the above specific surface area is expressed as a BET value, which refers to the surface area per unit weight, and is a physical quantity that is completely different from the average particle size.For example, even if the average particle size is the same, the specific surface area is larger. , some have small specific surface areas.

To measure the specific surface area, for example, first, the powder is heat-treated at around 250 ° C for 30 to 60 minutes and degassed to remove what is adsorbed to the powder, and then introduced into a measuring device. The initial pressure of nitrogen is set to 0.5 kg/n, and the adsorption measurement is performed using nitrogen at a liquid nitrogen temperature (-195°C) (a specific surface area measurement method generally referred to as the B, E, T method). For details, J, ^me, chen+, soc, 60
309 (193B)). This specific surface area (BET
The measuring device used for the measurement of the value of the
soap)" can be used. For a general explanation of the specific surface area and its measurement method, see "Measurement of Granules"
(J, M, DALLAVALLE, CLYDEORRJ
r co-authored, translated by others, published by Sangyo Toshosha), and is also described in detail in ``Chemistry Handbook'' (Application Edition, 1170).
~1171 pages, edited by the Chemical Society of Japan, Maruzen ■ April 3, 1966
It is also listed in the above-mentioned "Chemical Handbook"
Although the specific surface area is simply described as surface area (rrf/gr), it is the same as the specific surface area in this specification. ).

The binder that can be used in the present invention has an average molecular weight of about 1
0000 to 200,000, such as urethane resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral , cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, various synthetic rubbers,
Phenolic resin, epoxy resin, urea resin, melamine resin, phenoxy resin, silicone resin, acrylic reactive resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of polyester polyol and polyisocyanate, urea formaldehyde resin, low molecular weight glycol/ Examples include mixtures of high molecular weight diols/isocyanates and mixtures thereof.

The resins mentioned above are -5O,M, -COOM.

PO(OM')t (M is hydrogen or lithium,
Alkali metals such as potassium and sodium, M' is hydrogen,
It is preferable that the resin contains a hydrophilic polar group such as an alkali metal such as lithium, potassium, or sodium or a hydrocarbon residue. In other words, the polar groups in the molecules of these resins improve the compatibility with the metal magnetic powder, which further improves the dispersibility of the magnetic powder and prevents agglomeration of the metal magnetic powder, further improving the stability of the coating liquid. The durability of the medium can also be improved.

The binder used, especially the vinyl chloride copolymer, can be obtained by copolymerizing a vinyl chloride monomer, a copolymerizable monomer containing an alkali salt of sulfonic acid or phosphoric acid, and other copolymerizable monomers as necessary. I can do it.

Since this copolymer is based on vinyl synthesis, it is easy to synthesize, and various copolymer components can be selected, so that the properties of the copolymer can be optimally adjusted.

The metal of the above-mentioned sulfonic acid or phosphoric acid salt is an alkali metal (especially sodium, potassium, lithium), and potassium is particularly preferable in terms of solubility, reactivity, yield, etc.

The above copolymerizable monomer containing a sulfonate salt is CH,=CH3O,M CH! = CHCHz S 03 MCHt =C(
CH3) CH2SOs MCHz = CHCHt O
COCH (CHz COOR)osM CHt = C) (CHz OCHz CH(OH)C
H, So, M cHz = c (CH3) coocg H, 30,
MCHz =CHC00C,H,So,MCHz
=CHC0NHC(CH3)z CHz SO3M
can be mentioned.

In addition, as a phosphate, CH2=CHCHg octt, CH(O)()CHg
-0-PO,MYI CHt -CHCoNHC(CH3)z CHz-0-
PO3MY” PO,MX' CI(,=CHCHg O(c)lz CHz O)m
PO, MX” In the above, M is an alkali metal and R is a carbon atom number of 1 to 2.
0 alkyl groups, Yl is H, M or CH! = C
HCHz OCHz CH, (OH) CHz-1Y2
is H, M or CHg =CHC0NHC(CH3)t CH, -1X
l is 0H or OM, X” is C)i z = CHCHz O(C1(z C
Hz O) m-1OH or OM. Also, n is 1
-100, m is a positive number from 1 to 100.

Copolymerizable polymers to be copolymerized as necessary include known polymerizable monomers, such as various vinyl esters, vinylidene chloride, acrylonitrile, methacrylonitrile, styrene, acrylic acid, methacrylic acid, and various acrylic monomers. Examples include acid ester, methacrylic ester, ethylene, propylene, isobutyne, butadiene, isoprene, vinyl ether, aryl ether, aryl ester, acrylamide, methacrylamide, maleic acid, and maleic ester.

The binder used in the present invention is polymerized by a polymerization method such as emulsion polymerization, solution polymerization, suspension polymerization, or bulk polymerization. In either method, known techniques such as divisional addition or continuous addition of molecular weight regulators, polymerization initiators, and monomers can be applied as necessary.

The amount of the acidic group salt-containing monomer in the binder used in the present invention is preferably 0.01 to 30 mol%. If the amount of the salt-containing monomer is too large, the solubility in solvents will be poor and gelation will likely occur. Furthermore, if the amount of salt-containing monomer is too small, desired characteristics cannot be obtained.

Preferably, the vinyl chloride copolymer further contains an epoxy group or a hydroxyl group. By the way, conventional vinyl chloride copolymers (for example, U, C1C).

VAGH) manufactured by Co., Ltd. consisted of the following copolymerized components.

OH: indicates a copolymerization unit.

However, the CH and Co-0- groups here do not contribute to the crosslinking reaction with the curing agent, etc. Therefore,
It is preferable to contain an epoxy group such as the following instead of CH3CO. For example, a copolymer having the following units may be mentioned.

(X: Monomer unit portion containing an alkali metal salt of a sulfo group or a phospho group) In particular, it is preferable to use at least a urethane resin, and furthermore a vinyl chloride copolymer, an epoxy resin (especially a phenoxy resin), a polyester resin. Or, it is better to use nitrocellulose resin (hereinafter referred to as other resin) in combination.
In this case, the blending ratio of the urethane resin and the other resin is 90 to 10 parts by weight, more preferably 80 to 10 parts by weight.
It is desirable that the amount is 20 parts by weight; if the above-mentioned blending ratio exceeds 90 parts by weight, the coating film becomes too brittle, the durability of the coating film is significantly deteriorated, and the adhesion to the support becomes poor. Moreover, if the above-mentioned blending ratio is less than 10 parts by weight, the magnetic powder tends to fall off.

Incorporating carbon black in the magnetic layer is further advantageous in terms of improving runnability and electromagnetic conversion characteristics, and also slightly improves dispersibility and reduces the amount of residual solvent in the magnetic layer.

If a light shielding carbon black is used as such carbon black, the degree of light shielding can be increased.

As the light-shielding carbon black, for example, Raben 2000 manufactured by Columbia Carbon Co., Ltd. (specific surface area 190 bo/g) is used.
, particle size 1Bmμ), 2100.1170.1000,
Mitsubishi Kasei #100, #75, #40, #35,
#30 etc. can be used.

Further, as the conductive carbon black, for example, Conductex (Columbia Carbon Co., Ltd.) is used.
x ) 975 (BET value (hereinafter abbreviated as BET) 25
0bo/g, DBP oil absorption (hereinafter abbreviated as DBP) 170ml
/100gr, particle size 24mμ), Conductex 90
0 (BET125 rf/g, particle size 27 mμ), Conductex 40-220 (particle size 20 mμ),
Conductex SC (BET220 m/gr, D
BP115 ml/100gr, particle size 20mμ), Cabot Vulcan
X C-72 (specific surface area 254rrr/g, particle size 30m
tI), Palkan P (BET143m2/gr,,D
B P 118 ml /100gr, particle size 20m
μ), Raven 1040.420, Black Pearls 2000 (particle size 15 mμ), #44 manufactured by Mitsubishi Kasei ■, etc.

Other carbon blacks that can be used in the present invention include Conductex (manufactured by Columbia Carbon) (
Conductex ) -3C, (BET220rr
f/g, DBP115 ml/100 g, particle size 20
mμ), Vulcan manufactured by Cabot
9 (BE T140 nf/g,,DB P114
ml/100 g, particle size 19 mμ), #80 manufactured by Asahi Carbon Co., Ltd. (BET117 if/g).

DB P113 ml/100 g, particle size 23m, cr
), H3100 manufactured by Denki Kagaku Co., Ltd. (BET32rrf/g
, DBP180m1! /100g, particle size 53mμ),
#22B manufactured by Mitsubishi Kasei (BET55rrf/g,
DB P131 mff1/100 g.

particle size 40mμ), #20B (BET56rrr/gS
DBP115ml/100g, particle size 40m
u), #3500 (BET47nf/g,
D B P 187 ml /100 g, particle size 4
0mμ), and in addition, CF-9 manufactured by Mitsubishi Chemical Co., Ltd.
, #4000, MA-600, Cabot Black Pearls L% Monarch 800, Black Pearls 700, Black Burls 1000, Black Pearls
Pearls 880, Black Pearls 900, Black Burls 1300, Black Burls 2000, Sterling v1 Columbia Carbon Raven 410, Seaven 3200. Examples include Raben 430, Raben 450, Raben 825, Raben 1255, Raben 1035, Raben 1000, Raben 5000, and Ketschen Black FC.

Furthermore, in the present invention, durability can be improved by further adding a polyisocyanate curing agent to the magnetic paint containing a binder.

Examples of such polyisocyanate curing agents include bifunctional isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and hexane diisocyanate, as well as coronate and Nippon Polyurethane Industries.
Trifunctional isocyanates such as Desmodur L (manufactured by Bayer AG), or urethane prepolymers containing isocyanate groups at both ends, which have been conventionally used as curing agents, can also be used as curing agents. Any polyisocyanate can be used. The polyisocyanate curing agent is used in an amount of 5 to 80 parts by weight based on the total amount of binder.

The magnetic recording medium of the present invention has, for example, as shown in FIG.
It has a magnetic layer 2 on a non-magnetic support 1 such as polyethylene terephthalate, and if necessary, a BCC 50 is provided on the opposite side of the magnetic layer 2. Also,
As shown in FIG. 2, an overcoat N (QC layer) 4 may be provided on the magnetic layer 2 of the magnetic recording medium shown in FIG.
.

Further, the magnetic recording media shown in FIGS. 1 and 2 may be provided with an undercoat layer (not shown) between the magnetic layer 2 and the support 1, or may be provided with no undercoat layer. Alternatively, the support may be subjected to corona discharge treatment.

In addition to the metal magnetic powder and binder described above, the magnetic layer 2 also contains:
Fatty acids and/or fatty acid esters can be contained as lubricants. This allows us to bring out the strengths of both while offsetting the defects that would occur when used alone.
Improves lubrication effect, still image durability, running stability, S
/N ratio etc. can be increased. In this case, the amount of fatty acid added is preferably 0.2 to 10 parts by weight, and even more preferably 0.5 to 8.0 parts by weight, per 100 parts by weight of the magnetic powder. If the fatty acid content falls outside of this range, the dispersibility of the magnetic powder will decrease, and the runnability of the medium will tend to decrease. The amount is 0.00 parts by weight per 100 parts by weight of magnetic powder.
1 to 10 parts by weight is good, and 0.2 to 8.5 parts by weight is even better. If the amount of ester is outside this range and the amount of ester decreases, the effect of improving running performance will be poor, and if the amount increases, the ester will easily seep out and the output will decrease.

In addition, in order to better achieve the above effects, the weight ratio of fatty acids and fatty acid esters should be set as fatty acid/fatty acid ester =
10/90 to 90/10 is preferred. Note that fatty acids also have a dispersing effect, and it is thought that by using fatty acids, the amount of other low molecular weight dispersants used can be reduced, and the Young's modulus of the magnetic recording medium can be improved by that amount.

Fatty acids may be monobasic or dibasic,
Fatty acids having 6 to 30 carbon atoms, more preferably 12 to 22 carbon atoms, are exemplified as follows.

(1) Caproic acid (2) Caprylic acid (3) Capric acid (4) Lauric acid (5) Myristic acid (6) Palmitic acid (7) Stearic acid (8) Isostearic acid (9) Rilunic acid (10) Linoleic acid (11) Oleic acid (12) Elaidic acid (13) Behenic acid (14) Malonic acid (15) Succinic acid (16) Maleic acid (17) Glutaric acid (18) Adipic acid (19) Pimelic acid (20) Azelaic acid (21) Sebacic acid (22) 1,12-dodecanedicarboxylic acid (23)
Octane dicarboxylic acid Examples of the above fatty acid esters are as follows.

(1) Oleyl oleate (2) Oleyl stearate (3) Isocetyl stearate (4) Dioleyl maleate (5) Butyl stearate (6) Butyl palmitate (7) Butyl myristate (8) Octyl myristate ( 9) Octyl palmitate (10) Amyl stearate (11) Amyl palmitate (12) Isobutyl oleate (13) Stearyl stearate (14) Lauryl oleate (15) Octyl oleate (16) Isobutyl oleate (17) Ethyl oleate ( 18) Isotridecyl oleate (19) 2-ethylhexyl stearate (20)
2-ethylhexyl myristate (21) ethyl stearate (22) 2-ethylhexyl palmitate (23) isopropyl palmitate (24) isopropyl myristate (25) butyl laurate (26) cetyl-2-ethyl hexalate ( 27) Dioleyl adipate (28) Diethyl adipate (29) Diisobutyl adipate (30) Diisodecyl adipate In addition to the above-mentioned fatty acids and fatty acid esters, other lubricants (such as silicone oil, carboxylic acid-modified, ester-modified Graphite, carbon fluoride, molybdenum disulfide, tungsten disulfide, fatty acid amide, α-olefin oxide, etc.) may be added to the magnetic layer.

Non-magnetic abrasive particles can also be added to the magnetic layer. For example, α-alumina, chromium oxide, titanium oxide, α-iron oxide, silicon oxide, silicon nitride, silicon carbide, zirconium oxide, zinc oxide, cerium oxide, magnesium oxide, boron nitride, etc. are used. The average particle size of this abrasive is preferably 0.6 μm or less, and even more preferably 0.3 μm or less.

Moreover, it is preferable that the Mohs hardness is 5 or more.

In addition, the magnetic layer further contains an antistatic agent such as graphite.
A dispersing agent such as powdered lecithin or phosphate ester can be added. Furthermore, carbon black can also be used in combination.

In addition, the non-magnetic particles contained in the back coat layer are
It is more preferable that the average particle size is within the range of 10 mμ to 1000 mμ, because within the above range, the nonmagnetic particles are fine (not too fine) and the addition effect is good.

Non-magnetic particles include silicon oxide, titanium oxide, aluminum oxide, chromium oxide, silicon carbide, calcium carbide,
Zinc oxide, α-FetO, talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, molybdenum dioxide,
Examples include those made of calcium carbide, barium sulfate, etc. In addition, organic powders such as benzoguanamine resins, melamine resins, phthalocyanine pigments, etc. can also be used, and organic powders and the above-mentioned inorganic powders can also be used in combination.

Furthermore, it is more preferable to use carbon black together with the above-mentioned non-magnetic particles. This further stabilizes the running properties of the medium, and in combination with the effect of the non-magnetic particles described above, it is possible to further improve the durability of the medium.

E, Example The present invention will be explained in detail below.

The components, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention. In addition, in the following examples, all "r parts" are parts by weight.

<Preparation of Videotape> First, a magnetic layer was formed on a polyethylene terephthalate base film having a thickness of 10 μm as a support in the following manner.

That is, after dispersing each component shown in FIG. 3 using a predetermined alloy metal magnetic powder, the magnetic paint was filtered through a 1 μm filter, 5 parts of polyfunctional isocyanate was added, and 2. Apply to 5 μm and apply super calendar.
Magnetic layers having various compositions shown in FIG. 3 were prepared.

Thereafter, a paint for the BC layer having the following composition was applied to the opposite surface of the magnetic layer to a dry thickness of 0.4 μm.

Carbon black 40 parts Barium sulfate 10 parts Nitrocellulose 25 parts N-230
1 (manufactured by Nippon Polyurethane) 25 parts Coronate L ('')
10 parts Cyclohexanone 400 parts Methyl ethyl ketone 250 parts Toluene 250 parts A wide magnetic film having a magnetic layer and a BC layer of a predetermined thickness was thus obtained and wound up.

This film was cut into a width of 8 m to form each videotape shown in FIG. 3 (corresponding to the numbers of each example).

However, in Figure 3, No. 21Ill! The following "parts" represent parts by weight.

However, in FIG. 3, for the indicators marked as "variable", characteristic experiments were conducted for each example by changing the numerical values as described below.

However, in FIGS. 4 to 10, the content ratio of each constituent element in the metal magnetic powder was measured by X-ray elemental analysis. In addition, the abundance ratio of each constituent element in the surface area of the magnetic powder is ESC
A was measured at an analysis depth of about 100 Å or less from the surface to the inside.

The specific surface area of the metallic magnetic powder was changed as shown in Figure 4,
The Lumi S/N value of the videotape was measured. Rumi S/N
The changes in the value of are shown in FIG.

Lumi S/N: Color video noise meter r Shibasoku 9
25, measured by D/IJ. The bypass filter was set to 10 kHz, and the low pass filter was set to 4.2 μm. The VTR used was an 8ffIII video deck.

1 ship ± 1 The content of iron atoms was varied as shown in FIG. 5, and the Lumi S/N of the videotape was measured. The results are shown in FIG.

1旌I1. ■ The content of nickel atoms in the metal magnetic powder (Example ■) and the abundance ratio of nickel atoms on the surface area of the magnetic powder (Example ■) were varied as shown in Figure 6, and the Lumi S/N of the videotape was The value of was measured. The results are shown in FIG.

Further, when powder falling and clogging of the magnetic head were measured for samples a, b, c, and d shown in FIG. 6, the following results were obtained.

Powder falling and magnetic head clogging: The sample tape was run continuously on a video deck at 40° C. and 80% temperature for 200 hours, and powder falling and magnetic head clogging were measured.

◎ Very good O Good Δ Fairly good・・・・× 1 ship■ヱ■ Content of aluminum atoms in metal magnetic powder (Example■)
The abundance ratio of aluminum atoms in the surface area of the magnetic powder (Example 2) was varied as shown in FIG. 7, and the residual rate of saturation magnetization after storage was measured.

The results are shown in FIG.

Residual rate of saturation magnetization: The saturation magnetization measured after leaving the sample tape in an atmosphere of 60° C. and 180% RH for one week corresponds to what percentage of the saturation magnetization measured before leaving it.

Example 1: The content of silicon atoms in the metal magnetic powder and the abundance ratio of silicon atoms in the surface area of the magnetic powder were varied as shown in Figure 8, and the squareness ratio and Lumi S/H were measured. .

The results are shown in FIG.

Squareness ratio; Hm5KOe using a vibrating sample magnetometer (manufactured by Toei Kogyo)
Br/Bm was calculated.

The content of zinc atoms in the metal magnetic powder and the abundance ratio of zinc atoms in the surface area of the magnetic powder were varied as shown in FIG. 9, and the squareness ratio was measured. The results are shown in FIG.

Further, when samples a, b, c, and d shown in Fig. σ were measured for powder falling and clogging of the magnetic head, the following results were obtained.

Powder falling and magnetic head clogging: The sample tape was run continuously on a video deck at 40° C. and 80% temperature for 200 hours, and powder falling and magnetic head clogging were measured.

◎ Very good 0 Good ∆ Fairly good ...× The squareness ratio was measured by changing the back coating distance, the content of manganese atoms in the X-treated metal magnetic powder, and the abundance ratio of manganese atoms in the surface area of the magnetic powder as shown in FIG.

The results are shown in FIG.

<Conclusion> From the results shown above, it can be seen that by constructing a magnetic tape based on the present invention, tape performance is significantly improved. That is, it is important to use metal magnetic powder with a BET value of 45rrf/g or more, to limit the content of each constituent element in the metal magnetic powder, and to limit the abundance ratio of each constituent element in the surface area of the magnetic powder. be.

[Brief explanation of the drawing]

FIGS. 1 and 2 are partially enlarged sectional views showing examples of magnetic recording media. FIG. 3 is a diagram showing changes in the composition of the magnetic layer. Figure 4 shows the specific surface area of metal magnetic powder and Lumi S of videotape.
It is a graph showing the correlation with /N. FIG. 5 is a graph showing the correlation between the iron atom content in the magnetic powder and the Lumi S/N. FIG. 6 is a graph showing the correlation between the content of nickel atoms in the metal magnetic powder, the abundance ratio in the surface area, and the Lumi S/N. FIG. 7 is a graph showing the correlation between the amount of aluminum atoms in the metal magnetic powder and the presence in the surface area and the saturation magnetization residual rate after storage. FIG. 8 is a graph showing the correlation between the content of silicon atoms in the metal magnetic powder, the abundance ratio in the surface area, the squareness ratio, and the lumi S/N. FIG. 9 is a graph showing the correlation between the content of zinc atoms in the metal magnetic powder, the abundance ratio in the surface area, and the squareness ratio. FIG. 10 is a graph showing the correlation between the content of manganese atoms in the metal magnetic powder, the abundance ratio in the surface area, and the squareness ratio. In addition, in the symbols shown in the drawings, 1...Nonmagnetic support 2...Magnetic layer 3...Back coat layer (BC layer) )4...
...... Overcoat layer (00 layer).

Claims (1)

[Scope of Claims] 1. A magnetic recording medium in which a magnetic layer contains a binder and metal magnetic powder dispersed in the binder, (a) the metal magnetic powder has a specific surface area of 45 m^ 2/g or more, and (b) iron atoms, nickel atoms, aluminum atoms, and silicon atoms are contained in the metal magnetic powder, and further, at least one of zinc atoms and manganese atoms is contained in the metal magnetic powder. (c), the content of the iron atoms is 90 atomic % or more, the content of the nickel atoms is 1 atomic % or more and less than 10 atomic %,
The aluminum atom content is 0.1 at% or more, 5
less than atomic%, the content of silicon atoms is 0.1 atomic% or more and less than 5 atomic%, the content of zinc atoms and/or the content of manganese atoms (however, the content of both zinc atoms and manganese atoms is If contained, this total amount) is 0.1 atomic%
(d) Abundance ratio of iron atoms, nickel atoms, aluminum atoms, silicon atoms, zinc atoms and/or manganese atoms present in the surface area of the metal magnetic powder (iron atoms: Nickel atom: Aluminum atom: Silicon atom: Zinc atom and/or manganese atom) in an atomic ratio of 100: (4 or less): (1
0-60):(10-70):(20-80).