JP2002343617A - Magnetic powder and magnetic recording medium using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium, for which the thermal stability and magnetic characteristics of ferromagnetic hexagonal system Ba ferrite powder are suited and a magnetic layer containing the powder is formed on a non-magnetic support body, to prevent deteriorated output of the magnetic recording medium or burning phenomenon. SOLUTION: The weight percentage of Ba atoms to Fe atoms of hexagonal system Ba ferrite is set to 0.15-0.21, and the integrated intensity ratio (surface Ba/surface Fe) of Ba3d5/2 spectrum to Fe2p3/2 spectrum obtained by ESCA measurement of the surface of the hexagonal system Ba ferrite powder is set to 0.45-0.70. Then, a magnetic layer, containing the hexagonal system Ba ferrite magnetic powder, is formed on a non-magnetic support body for making a magnetic recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic powder comprising hexagonal Ba ferrite and a magnetic recording medium using the magnetic powder.

[0002]

2. Description of the Related Art Magnetic tapes have been used and developed as magnetic recording media in a wide range of fields such as tape recorders, video recording systems, and computer recording systems. A magnetic tape as a magnetic recording medium is classified into a coating type and a vapor deposition type depending on a difference in a manufacturing method. In particular, the coating type is widely used for general audio and video. In this coating type magnetic tape, a magnetic recording layer (magnetic layer) made of a binder (binder) and ferromagnetic magnetic powder is formed and provided on a non-magnetic support made of resin (plastic, etc.) by a coating method. I have. When the magnetic tape is operated a number of times, output deterioration and burning may occur, which has been an important problem. In particular, as the recording density increases, the size (particle size) of the magnetic powder needs to be reduced, and as a method for coping with this, a ferromagnetic hexagonal barium ferrite (hereinafter referred to as a hexagonal Ba ferrite) is used. Omitted) Powder is promising.

[0003] Such a hexagonal Ba ferrite can be miniaturized as a magnetic powder by a manufacturing method thereof.
It is a promising material for future high recording density magnetic recording media. Further, since hexagonal Ba ferrite is a thermally stable compound, it has been considered that the output deterioration of the head and the seizure phenomenon during many runs can be eliminated.

However, it has been found that when a magnetic tape is manufactured using hexagonal Ba ferrite, output deterioration and seizure may occur. As a result of analyzing the hexagonal Ba ferrite powder particles, the reason for the output deterioration and the seizure phenomenon is that the Fe oxide having a thermally unstable spinel structure exists on the surface of the hexagonal Ba ferrite powder, It is considered that the Fe-based compound is formed by the transition, lattice defect, intrusion of the substitution element, introduction of the substitution element, and the like, so that the proportion of the Ba · 6 (Fe ₂ O ₃ ) composition decreases accordingly. If an Fe-based compound is present on the surface of the hexagonal Ba ferrite powder, it is considered that the Fe-based compound is thermally unstable and causes a seizure phenomenon.

A conventional hexagonal Ba ferrite powder (Ba · 6 (Fe ₂ O ₃ )) is used to improve the magnetic properties.
Part of the composition of a.6 (Fe ₂ O ₃ ) was converted to a spinel compound (F
(e-based oxide) in some cases, but the spinel compound lacked stability and sometimes caused seizure.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to improve the thermal stability of hexagonal Ba ferrite powder as a ferromagnetic magnetic powder. It is an object of the present invention to provide a magnetic recording medium in which output characteristics and image sticking are reduced by optimizing magnetic properties and providing a magnetic layer containing the same on a nonmagnetic support.

[0007]

[MEANS FOR SOLVING THE PROBLEMS]
The magnetic powder according to the present invention is a hexagonal Ba ferrite.
Powder, wherein the ratio of Ba atoms / Fe atoms is 0.15 by weight.
-0.21 and said hexagonal Ba ferrite powder
Ba3d measured by ESCA on the surface_5/2 Spect
(Surface Ba) and Fe2p_3/2Spectrum (surface Fe)
Of the surface Ba / surface Fe = 0.45-0.
70. The magnetic recording of the present invention
The medium includes a magnetic layer containing a magnetic powder on a non-magnetic support.
In the magnetic recording medium provided with, the magnetic powder,
Hexagonal Ba ferrite powder comprising Ba atom / Fe
The atoms are 0.15 to 0.21 by weight and
Measured by ESCA on the surface of amorphous Ba ferrite powder
Ba3d_5/2 Spectrum (surface Ba) and Fe2p_3/2S
The integrated intensity ratio with the spectrum (surface Fe) is expressed as surface Ba / table
It is characterized in that the surface Fe = 0.45 to 0.70.

[0008]

Embodiments of the present invention will be described below. The Ba atom / Fe atom of the hexagonal Ba ferrite, which is the ferromagnetic magnetic powder in the present invention, may have a weight ratio of 0.15 to 0.21. When the ratio by weight of Ba atoms / Fe atoms is less than 0.15, Fe is contained more than Ba.6 (Fe ₂ O ₃ ), which is a stoichiometric composition. Since an unstable Fe-based compound is generated, seizure occurs. When the weight ratio of Ba atoms / Fe atoms exceeds 0.21, Ba becomes excessive, and non-magnetic compounds such as BaO are formed in addition to Ba · 6 (Fe ₂ O ₃ ), resulting in saturation magnetization. And a sufficient output cannot be obtained as a magnetic recording medium.

The magnetic powder of the present invention, hexagonal B
aBa measured by ESCA on the surface of ferrite powder
The integral intensity ratio (surface Ba / surface Fe) between the 3d _5/2 spectrum and the Fe2p _3/2 spectrum may be 0.45 to 0.70. When the integrated intensity ratio (surface Ba / surface Fe) is 0.
If it is less than 45, the stoichiometric composition of Ba · 6 (Fe
Fe is more contained on the surface than ₂ O ₃ ),
As a result, a thermally unstable Fe-based compound is formed, and seizure occurs. When the integrated intensity ratio (surface Ba / surface Fe) exceeds 0.70,
Ba becomes excessive on the surface, and BaO, which is a non-magnetic compound, is formed in addition to Ba · 6 (Fe ₂ O ₃ ), thereby decreasing the saturation magnetization and obtaining a sufficient output as a magnetic recording medium. become unable.

In the present invention, the integrated intensity ratio between the Ba3d _5/2 spectrum and the Fe2p _3/2 spectrum (surface Ba / surface Fe: A) of the hexagonal Ba ferrite powder surface measured by ESCA, The ratio (A / B) of the integrated intensity ratio (center Ba / center Fe: B) between the Ba3d _5/2 spectrum and the Fe2p _3/2 spectrum measured by ESCA at the center of the Ba ferrite powder is A / B = 0.
It may be 8 to 1.2. If A / B is less than 0.8, Ba on the surface of the hexagonal Ba ferrite powder will
a, the surface of the hexagonal Ba ferrite powder has Ba · 6 (Fe ₂ O ₃ ) and Ba · 6 (Fe
_{Ba · 6 (Fe 2 O 3} ) Fe -based compounds other than compounds which are substituted product ₂ O ₃₎ is present and seizure occurs. Also, A
When / B exceeds 1.2, Ba becomes excessive on the surface of the hexagonal Ba ferrite powder, and BaO, which is a nonmagnetic compound, is formed in addition to Ba · 6 (Fe ₂ O ₃ ). The saturation magnetization decreases, and a sufficient output as a magnetic recording medium cannot be obtained.

The hexagonal Ba of the ferromagnetic powder in the present invention
The size (particle size) of the ferrite powder particles may be a hexagonal plate-like particle diameter of 10 to 60 nm. If the particle size is smaller than 10 nm, the particles become superparamagnetic, cannot maintain stable magnetization, and deteriorate in S / N. Also,
When the particle size is larger than 60 nm, when a magnetic recording layer (magnetic layer) of a magnetic recording medium is applied and formed using the particle size, the surface smoothness of the magnetic layer coating film is impaired and noise increases. It will not match the record. Further, the plate ratio (plate diameter / film thickness) of the hexagonal Ba ferrite powder is 1 to
It is preferably 10. Particularly preferably, it is 2-7. When the tabular ratio is less than 1, when the composition is dispersed in a binder and applied on a non-magnetic support, the orientation as a magnetic layer deteriorates and noise increases. On the other hand, when the plate ratio is larger than 10, stacking is strong, dispersibility is deteriorated, and S / N is deteriorated.

The hexagonal Ba ferrite, which is a ferromagnetic powder in the present invention, may be one in which a part of Ba is replaced by Sr (strontium), Pb (lead), Ca (calcium), Co (cobalt) or the like. Including. In this case, each numerical value defined in the claims is a value when each of the above atoms is replaced with Ba.

Other than the above atoms, S, Sc, Ti,
V, Cr, Cu, Mo, Rh, Pd, Ag, Sn, S
b, Te, Ba, Ta, W, Re, Au, Hg, Bi,
It may contain atoms such as Ce, P, Mn, Zn, Ni, B, Ge, Zr, and Nb. Generally, Co-Zn, Co
-Ti, Co-Ti-Zr, Co-Ti-Zn, Ni-
Ti-Zn, Nb-Zn-Co, Sb-Zn-Co, N
b-Zn or the like can be used.

The method for producing the hexagonal Ba ferrite powder is as follows: (1) Barium oxide, iron oxide, a metal oxide to be replaced by iron if necessary, and boron oxide or the like as a glass-forming substance to obtain a desired ferrite composition. A glass crystallization method of dissolving after mixing, quenching this to form an amorphous body, then reheating, washing and pulverizing to obtain a Ba ferrite crystal powder, (2) a Ba ferrite composition metal salt solution After neutralization with an alkali to remove by-products, liquid phase heating at 100 ° C. or higher, and then washing, drying and pulverization to obtain a Ba ferrite crystal powder by a hydrothermal reaction method, or (3) B
a The ferrite composition metal salt solution is neutralized with an alkali to remove by-products, dried, treated at 1100 ° C. or less and pulverized to obtain a Ba ferrite crystal powder by a coprecipitation method. The method for producing the hexagonal Ba ferrite powder of the present invention may be any of these methods, and the production method is not limited.

Methods for controlling the amounts of Ba and Fe atoms in the hexagonal Ba ferrite powder, which is a ferromagnetic powder, and the amounts of Ba and Fe atoms at the powder surface and the center of the powder have been known. The method is applicable. For example, in the above glass crystallization method, hydrothermal synthesis method, coprecipitation method, etc., a method of adjusting and controlling Ba ions and Fe ions mixed as raw materials, a glass crystallization method, a hydrothermal synthesis method, a coprecipitation method Ba ions are applied to the hexagonal Ba ferrite powder produced by the above method, and the Fe-based compound formed on the surface of the powder is subjected to a heat reaction treatment to form Ba · 6 (Fe ₂ O ₃ ) or Ba · 6.
(Fe ₂ O ₃ ) compounds.

The ferromagnetic hexagonal Ba ferrite powder obtained as described above is used, for example, in a magnetic layer formed on a non-magnetic support such as a magnetic tape which serves as a base film. This magnetic layer has a composition mainly composed of a hexagonal Ba ferrite powder and a binder, and to which various additives (abrasive, lubricant, antistatic agent, dispersant, matting agent, etc.) are added as required. When the magnetic layer is formed by a coating method, the components for forming the magnetic layer are mixed with a solvent to form a paint (magnetic paint), which is applied on a non-magnetic support.

As described above, in the magnetic recording medium formed by using the ferromagnetic powder of hexagonal Ba ferrite of the present invention, the magnetic layer mainly composed of the ferromagnetic powder and an organic binder has a non-magnetic property. This is a so-called coating type magnetic recording medium having a structure formed on a magnetic support. The configuration of the magnetic layer may be a single layer or a multilayer of two or more layers.

In the case of the magnetic recording medium of the present invention, for example, a magnetic tape, the surface roughness (surface roughness) Ra is 7.0 n.
m or less. If Ra exceeds 7.0 nm, a sufficient output cannot be obtained because there is a loss (spacing loss) that the distance between the magnetic head and the magnetic tape is increased and the signal strength is reduced. The surface roughness (surface roughness) Rz of the magnetic recording medium may be 90 nm or less. Rz is 90n
If it exceeds m, the spacing loss increases and a sufficient output cannot be obtained. In order to control Ra and Rz, the size, shape, amount, etc. of the ferromagnetic powder, non-magnetic powder, and various additives to be used are made appropriate, and the resin described below used as a binder is used. When the degree of polymerization and the polar group are adjusted, or when two or more kinds of resins are mixed and used, various methods such as changing the mixing ratio may be employed. In addition, for example, control can be performed by adjusting conditions such as temperature and pressure of calendering in the process of manufacturing the magnetic tape.

The coercive force Hc of the magnetic recording medium of the present invention is 8
It is preferable to be 0 kA / m or more and 235 kA / m or less. Thereby, low noise and high resolution can be realized. If the coercive force Hc exceeds 235 kA / m, sufficient recording cannot be performed, and the reproduction output tends to decrease.

The binder used for the magnetic layer is not particularly limited, and a conventionally known thermoplastic resin, thermosetting resin, curable resin of an ultraviolet or electron beam crosslinking reaction type, or a mixture thereof is used. As the thermoplastic resin, for example, vinyl chloride resin, vinyl acetate resin, vinyl fluoride resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer , Vinyl chloride-acrylonitrile copolymer, vinylidene chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinyl chloride-vinylidene chloride copolymer, methacrylate-vinyl chloride copolymer, methacryl Acid ester-vinylidene chloride copolymer,
Methacrylic acid ester-ethylene copolymer, acrylonitrile-butadiene copolymer, styrene-butadiene copolymer, polyester resin, polyurethane resin, polyester polyurethane resin, polycarbonate resin, polycarbonate polyurethane resin, polyamide resin, polyvinyl butyral resin, cellulose derivative (Cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), amino resins, and various synthetic rubbers. These resins and copolymers usually have a softening temperature of about 150 ° C and an average molecular weight of about 10,000 to 20.
The molecular weight is about 000 and the degree of polymerization is about 150 to 2,000, but is not limited thereto.

On the other hand, thermosetting resins or curable resins include phenol resins, epoxy resins, urea formaldehyde resins, melamine resins, alkyd resins, silicone resins, polyamine resins, polyurethane curable resins, high molecular weight polyester resins and isocyanate resins. Examples thereof include a mixed composition of a prepolymer, a low molecular weight glycol, a mixed composition of a high molecular weight diol and an isocyanate, and a mixed composition of these resins.

In the case of the above-mentioned curable resin, for example, a polyisocyanate or the like can be added as a curing agent. As a polyisocyanate, an adduct of trimethylolpropane and 2,4-tolylene diisocyanate (TDI) (for example, trade name: Coronate L50) is generally known, but 4,4′-diphenylmethane diisocyanate (MDI) ) Or hexane diisocyanate (H
An adduct of an alkylene diisocyanate such as DI) may be used. In addition, polyglycidylamine compounds such as tetraglycidyl metaxylenediamine, tetraglycidyl-1,3-bisaminomethylcyclohexane, tetraglycidylaminodiphenylmethane, triglycidyl-p-aminophenol, and 2-dibutylamino-4,6
-Polythiol compounds such as dimercapto-substituted triazines, epoxy compounds such as triglycidyl isocyanurate, mixtures of epoxy compounds and isocyanate compounds,
Any of the conventionally known compounds such as a mixture of an epoxy compound and an oxazoline compound, a mixture of an imidazole compound and an isocyanate compound, and methylnadic anhydride can be used.

The mixing ratio of these curing agents to the resin is 5 to 80 parts by weight, preferably 1 to 100 parts by weight of the curing agent.
0 to 50 parts by weight.

Of the above thermoplastic resins and thermosetting resins,
It is preferable to use a polyurethane resin, a polycarbonate resin, a polyester resin, an acrylonitrile-butadiene copolymer or the like which is considered to be imparted with flexibility. In these resins and copolymers, -SO ₃ M and -OS are used in order to easily disperse the ferromagnetic powder as acicular iron oxide hydroxide fine particles.
It may contain a polar functional group such as O ₃ M, —COOM, or —PO (OM ′) ₂ (where M is H or an alkali metal such as Li, K, Na, or M ′). Represents H, or an alkali metal such as Li, K, or Na, or an alkyl group).

Further, as a polar functional group, -N (R
^{1 R 2), - N +} (R 1 R 2 R 3) X - and those having a side chain of the resin as a terminal group and the ^{like, = N + (R 1 R} 2) X -
(Where R ¹ , R ² , and R ³ are H or a hydrocarbon group, and X ⁻
Represents a halogen atom ion such as fluorine, chlorine, bromine and iodine). In addition, as a polar functional group, -OH, -SH,
—CN, an epoxy group and the like.

The content of the polar functional group is 10 ^-1 to 10 ^-8 m
ol / g, preferably 10 ⁻² to 10 ⁻⁶ m
ol / g. The amount of the binder in the magnetic layer is
The amount is 1 to 200 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the magnetic powder.

Acetone, methyl ethyl ketone, methyl isobutyl ketone and the like are used as solvents for preparing various paints such as a magnetic paint used for forming a magnetic layer of a magnetic recording medium and a non-magnetic paint used for forming a non-magnetic layer. , Ketones such as cyclohexanone, alcohols such as methanol, ethanol, propanol, butanol,
Methyl acetate, ethyl acetate, propyl acetate, butyl acetate,
Ethyl lactate, esters such as ethylene glycol monoacetate, diethylene glycol dimethyl ether, glycol monoethyl ether, dioxane, ethers such as tetrahydrofuran, benzene, toluene, aromatic hydrocarbons such as xylene, methylene chloride, ethylene chloride, carbon tetrachloride, Halogenated hydrocarbons such as chloroform and dichlorobenzene are used.

Nonmagnetic supports used in the case of a magnetic tape as a magnetic recording medium include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate, cellulose diacetate and the like. Cellulose derivatives, vinyl resins such as polyvinyl chloride, vinylidene resins such as polyvinylidene chloride, other polycarbonate resins, polyamideimide resins, and polyimide resins.

As a non-magnetic support used in the case of a hard disk as a magnetic recording medium, that is, as a substrate, a rigid substrate such as an Al-based metal, ceramics, plastic, or glass can be used. In these rigid substrates, in order to further increase the surface hardness, an oxide film may be formed by alumite treatment or the like, or a Ni or P film may be formed.

As described above, as an additive to the magnetic paint,
Abrasives, lubricants, antistatic agents, dispersants and the like are added. These additives will be described below.

The abrasive used in the present invention includes, for example, α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, artificial diamond, silicon nitride, titanium nitride having an α conversion of 90% or more. Examples include carbide, titanium oxide, silicon dioxide, and boron nitride. Such a material having a Mohs hardness of 6 or more alone,
Alternatively, they are used in combination. These abrasives may contain compounds or elements other than the main component,
Generally, there is no difference in the effect if the main component is 90% or more.

The size (particle size) of the abrasive particles is
0.01 to 2 μm is preferable, and 0.05 to 1.0 μm is more preferable.
μm is preferred. In particular, it is preferable that the particle size distribution is narrow in order to enhance the electromagnetic conversion characteristics. Further, in order to improve the durability, it is also possible to combine abrasives having different particle sizes as needed, or to broaden the particle size distribution of a single abrasive within a necessary and appropriate range, and to have the same effect. . The tap density of the abrasive particles is 0.3 to 2 g / cc, and the water content is 0.1.
５5%, pH 2-11, specific surface area 1-30 m ² / g
Is preferred. The shape of the abrasive may be any of a needle shape, a spherical shape, and a dice shape.

Lubricants are used to lower the coefficient of friction of the magnetic recording medium to improve running properties. Examples of the lubricant include graphite, molybdenum disulfide, silicone oil, fatty acids having 10 to 22 carbon atoms, fatty acid esters of these fatty acids and alcohols having 2 to 26 carbon atoms, terpene compounds, and the like. Oligomers and the like.

The antistatic agent used in the present invention includes
Examples thereof include carbon black, graphite, and other metal particles.

Examples of the carbon black include those manufactured by any method, and examples thereof include furnace black, thermal black, acetylene black, channel black, and lamp black. Also,
Carbon black may be subjected to a surface treatment with a dispersant or the like, grafted with a resin, or a part of the surface of which is graphitized. These carbon blacks can be used alone or in combination.

When particles such as magnetic powder and the like are mixed with a binder to form a coating, a surfactant is used as a dispersant to improve the dispersibility of the particles. An example of this is
Nonionic (nonionic) surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants and the like can be mentioned.

If necessary, on the magnetic layer of the magnetic recording medium
May be provided with a protective layer. As the material used for the protective layer,
Carbon, diamond-like carbon, SiO_Two, S
i_ThreeN _Four, SiON, SiC, Al_TwoO_Three, AlN, TiO
_Two, Cr_TwoO_Three, TiN, TiC, ZrO_Two, MgO, B
N, CoO, or a non-magnetic metal is used. This
They can be used alone or as a composite membrane
Alternatively, they may be used as a single layer or as a laminate. These protections
The method for forming the protective layer is not particularly limited.
Method, vacuum evaporation method, or CVD (Chemical
From the gas phase such as the Vapor Deposition method
It is preferable to use a thin film forming technique in terms of uniformity and film quality.

Further, a top coat layer may be formed on the surface of the protective layer to enhance lubricity. This top coat layer can be formed, for example, by dissolving a lubricant in a solvent such as alcohol or toluene in advance, and applying and drying this solution on the protective layer. As the lubricant, any conventionally known lubricants such as fluorocarbons, alkylamines, alkylesters, and silicones can be used.

When used under severe environmental conditions, the extreme pressure agent is added to the lubricant or the lubricant composition in a weight ratio of (lubricant or lubricant composition) / (extreme pressure agent) =
You may mix and use it in the ratio of about 30 / 70-70 / 30. Extreme pressure agent is a compound that acts to prevent friction and wear by forming a reaction product film by reacting with the metal surface due to the frictional heat that accompanies partial metal contact in the boundary lubrication region. Consists of For example, conventionally known phosphorus-based extreme pressure agents, sulfur-based extreme pressure agents, halogen-based extreme pressure agents, organometallic extreme pressure agents, and composite extreme pressure agents thereof can be used.

In order to form a magnetic layer, a magnetic paint in which a magnetic powder and additives are dispersed in a binder may be directly coated on a non-magnetic support, or a non-magnetic lower layer may be provided on the non-magnetic support. May be applied thereon. Further, a non-magnetic lower layer and a magnetic layer may be simultaneously coated on a non-magnetic support. The magnetic layer can be composed of a single layer or a laminate. In the case of a laminated structure, a non-magnetic intermediate layer may be interposed.

Whether a magnetic layer is provided directly on a nonmagnetic support or
Alternatively, there is no limitation on the method of providing a non-magnetic lower layer on a non-magnetic support and applying a magnetic paint for providing a magnetic layer thereon. Such coating methods include, for example, air doctor coat, blade coat, air knife coat, squeeze coat, impregnated coat, reverse roll coat, transfer roll coat, gravure coat, kiss coat, cast coat, extrusion coat, die coat, spin coat Any of the conventionally known methods can be adopted. In the case of a coating type magnetic recording medium, a die coater having a plurality of lips is adopted, and a non-magnetic lower layer,
And the magnetic layer are desirably applied simultaneously. After the non-magnetic lower layer is coated on the non-magnetic support, it is dried with heated air or the like to remove the organic solvent, and if necessary, may be subjected to a curing treatment, and then the magnetic layer may be formed thereon by coating.

When the magnetic recording medium is a magnetic tape, a back coat layer (coating type back coat layer) is generally formed on the other surface of the nonmagnetic support by a coating method. The configuration of the back coat layer is not particularly limited. The coating type back coat layer is formed by dispersing non-magnetic particles in an organic binder, and controls surface roughness and conductivity. Non-magnetic particles include, for example, various aluminas such as hematite, boehmite, fused alumina, α, β, γ alumina, mica, kaolin, talc, clay, silica, magnesium oxide, titanium oxide (rutile and anatase), zinc oxide Inorganic compounds such as zinc sulfide, calcium carbonate, magnesium carbonate, barium carbonate, lead sulfate, and tungsten sulfate; polymer resins such as polyethylene, polyvinyl chloride, polyimide, and polytetrafluoroethylene; starch; and nonmagnetic metals and carbon Is exemplified.

The non-magnetic particles have an average particle size of 0.05 to
1 μm, preferably 0.1 to 0.7 μm is used, and is usually added in the range of 1 to 20 parts by weight based on 100 parts by weight of the organic binder. Further, the particles preferably have an isotropic shape such as a substantially spherical shape and a substantially regular polyhedron from the viewpoints of paint suitability and durability. In addition, all of a thermoplastic resin, a thermosetting resin, a curable resin, and the like used for the back coat layer can be used. It is preferable that the thermoplastic resin is used in combination with a thermosetting resin or a curable resin.

The magnetic recording medium obtained as described above is suitable as a magnetic tape for a magnetic recording system using a magnetoresistive read head (MR read head).
As the MR reproducing head, a shield type MR head having an MR element sandwiched between shields is used, and this is mounted on a rotating drum to constitute a recording / reproducing apparatus. By combining a magnetic recording system using an MR reproducing head with the magnetic recording medium of the present invention, an unprecedented high-density recording system can be constructed. The case of a helical scan magnetic recording system using an MR reproducing head will be described below, but the effect of the present invention is effective in all magnetic recording systems using an MR reproducing head.

The magnetic recording / reproducing apparatus of the helical scan magnetic recording system is a helical scan type magnetic recording / reproducing apparatus which performs recording / reproducing using a rotating drum, and uses an MR head as a reproducing magnetic head mounted on the rotating drum. I do.

FIGS. 1 and 2 show an example of the configuration of a rotary drum device mounted on this magnetic recording / reproducing apparatus. In addition,
FIG. 1 is a perspective view schematically showing the rotary drum device 1, and FIG. 2 is a plan view schematically showing a magnetic tape feed mechanism 10 including the rotary drum device 1.

As shown in FIG. 1, the rotary drum device 1
A cylindrical fixed drum 2, a cylindrical rotary drum 3, a motor 4 for rotating the rotary drum 3, and a pair of inductive magnetic heads 5a, 5a mounted on the rotary drum 3;
b and a pair of MR heads 6 mounted on the rotating drum 3
a, 6b.

The fixed drum 2 is a drum that is held without rotating. On the side of this fixed drum 2,
A lead guide portion 8 is formed along the running direction of the magnetic tape 7. The magnetic tape 7 is attached to the lead guide portion 8.
Follow along. The rotating drum 3 is arranged so that the center axis of the fixed drum 2 coincides with that of the fixed drum 2.

The rotary drum 3 is a drum that is driven to rotate at a predetermined rotation speed by the motor 4 during recording and reproduction on the magnetic tape 7. The rotating drum 3 is formed in a cylindrical shape having substantially the same diameter as the fixed drum 2.
And the central axes are aligned. A pair of inductive magnetic heads 5a and 5b and a pair of MR heads 6a and 6b are mounted on a side of the rotary drum 3 facing the fixed drum 2.

Inductive magnetic heads 5a, 5b
Is a recording magnetic head in which a pair of magnetic cores are joined via a magnetic gap and a coil is wound around the magnetic core, and is used when recording a signal on the magnetic tape 7. The inductive magnetic heads 5a and 5b are mounted on the rotating drum 3 so that the angle formed therebetween with respect to the center of the rotating drum 3 is 180 °, and their magnetic gaps protrude from the outer periphery of the rotating drum 3. Have been. The inductive magnetic heads 5a and 5b are set so that the azimuth angles are opposite to each other so that azimuth recording is performed on the magnetic tape 7.

On the other hand, the MR heads 6a and 6b are reproducing magnetic heads having an MR element as a magnetic sensing element for detecting a signal from the magnetic tape 7, and are used when reproducing a signal from the magnetic tape 7. . These MR heads 6a and 6b are mounted on the rotating drum 3 such that the angle formed therebetween with respect to the center of the rotating drum 3 is 180 °, and their magnetic gap portions protrude from the outer periphery of the rotating drum 3. I have. These MR heads 6a and 6b are set so that the azimuth angles are opposite to each other so that signals recorded azimuthally on the magnetic tape 7 can be reproduced.

The magnetic recording / reproducing apparatus records a signal on the magnetic tape 7 and reproduces a signal from the magnetic tape 7 by sliding the magnetic tape 7 on the rotating drum device 1. That is, at the time of recording / reproduction, the magnetic tape 7
As shown in FIG. 2, is supplied from a supply reel 11 of a magnetic tape feed mechanism 10 through guide rollers 12 and 13 so as to be wound around the rotary drum device 1, and recording and reproduction are performed by the rotary drum device 1. . And the rotary drum device 1
The magnetic tape 7 recorded and played back by the guide roller 1
The paper is sent to a take-up roll 18 through the cap rollers 4 and 15, the capstan 16 and the guide roller 17. That is, the magnetic tape 7 is fed at a predetermined tension and speed by the capstan 16 rotated and driven by the capstan motor 19, and is wound on the winding roll 18 via the guide roller 17.

At this time, the rotary drum 3 is driven to rotate by a motor 4 as shown by an arrow A in FIG. On the other hand, the magnetic tape 7 is attached to the lead guide 8 of the fixed drum 2.
Along the fixed drum 2 and the rotating drum 3 so as to slide obliquely. That is, the magnetic tape 7
1 is fed along the tape running direction from the tape entrance side along the lead guide portion 8 so as to slidably contact the fixed drum 2 and the rotating drum 3 as shown by an arrow B in FIG. As shown by arrow C, the tape is sent to the tape exit side.

Next, the internal structure of the rotary drum device 1 will be described with reference to FIG. As shown in FIG.
In the center of the fixed drum 2 and the rotating drum 3, a rotating shaft 21
Is inserted. The fixed drum 2 and the rotating drum 3
The rotating shaft 21 is made of a conductive material, these are electrically conductive, and the fixed drum 2 is grounded.

[0055] Two bearings 22 and 23 are provided inside the sleeve of the fixed drum 2, whereby the rotating shaft 21 is rotatably supported with respect to the fixed drum 2. That is, the rotating shaft 21 is
By 23, it is rotatably supported by the fixed drum 2. On the other hand, the rotary drum 3 has a flange 24 formed on the inner peripheral portion thereof.
1 is fixed to the upper end. Thereby, the rotating drum 3 is configured to rotate with the rotation of the rotating shaft 21.

In order to transmit signals between the fixed drum 2 and the rotating drum 3, a rotary transformer 2, which is a non-contact type signal transmission device, is provided inside the rotating drum device 1.
5 are arranged. The rotary transformer 25 has a stator core 26 attached to the fixed drum 2 and a rotor core 27 attached to the rotating drum 3.

The stator core 26 and the rotor core 27
A magnetic material such as ferrite is formed in an annular shape around the rotation shaft 21. The stator core 26 has a pair of signal transmission rings 26a, 26b corresponding to the pair of inductive magnetic heads 5a, 5b and a pair of signal transmission rings 2 corresponding to the pair of MR heads 6a, 6b.
6c and a power transmission ring 26d for supplying power required for driving the pair of MR heads 6a and 6b are arranged concentrically. Similarly, the rotor core 27 also has
A pair of signal transmission rings 27a and 27b corresponding to a pair of inductive magnetic heads 5a and 5b, and a pair of M
Signal transmission ring 27c corresponding to R heads 6a and 6b
And a power transmission ring 27d for supplying power required for driving the pair of MR heads 6a and 6b are arranged concentrically.

These rings 26a, 26b, 26c,
26d, 27a, 27b, 27c, and 27d are rotating shafts 2
1 and each of the rings 26a, 26b, 26c, 2
6d and each ring 27a, 27b, 27 of the rotor core 27
c and 27d are arranged to face each other.
The rotary transformer 25 is connected to the stator core 2
Signals and electric power are transmitted in a non-contact manner between the respective rings 26a, 26b, 26c, 26d of No. 6 and the respective rings 27a, 27b, 27c, 27d of the rotor core 27.

The rotary drum device 1 is provided with a motor 4 for rotating and rotating the rotary drum 3. This motor 4 has a rotor 28 as a rotating part and a stator 29 as a fixed part. The rotor 28 is attached to the lower end of the rotating shaft 21 and includes a driving magnet 30. On the other hand, the stator 29 is attached to the fixed drum 2 and has a driving coil 31. By supplying a current to the driving coil 31, the rotating shaft 21 attached to the rotor 28 is supplied.
Rotates, and accordingly, the rotating drum 3 fixed to the rotating shaft 21 is rotationally driven.

Next, recording and reproduction by the above-described rotary drum device 1 will be described with reference to FIG. 4 which shows a schematic circuit configuration of the rotary drum device 1 and its peripheral circuits.

When a signal is recorded on the magnetic tape 7 using the rotary drum device 1, first, a current is supplied to the drive coil 31 of the motor 4, whereby the rotary drum 3 is driven to rotate. Then, while the rotary drum 3 is rotating, a recording signal from the external circuit 40 is supplied to the recording amplifier 41 as shown in FIG.

The recording amplifier 41 amplifies the recording signal from the external circuit 40, and when the signal is recorded by one of the inductive magnetic heads 5a, the signal transmission of the stator core 26 corresponding to the inductive magnetic head 5a is performed. The recording signal is supplied to the inductive magnetic head 5b and the recording signal is supplied to the signal transmission ring 26b of the stator core 26 corresponding to the inductive magnetic head 5b at the timing when the signal is recorded by the other inductive magnetic head 5b. I do.

Here, as described above, the pair of inductive magnetic heads 5a and 5b are arranged so that the angle formed between them with respect to the center of the rotary drum 3 is 180 °. Head 5a,
5b is recorded alternately with a phase difference of 180 °. That is, the recording amplifier 41 alternates the timing of supplying a recording signal to one inductive magnetic head 5a and the timing of supplying a recording signal to the other inductive magnetic head 5b with a phase difference of 180 °. Switch to.

The recording signal supplied to the signal transmission ring 26a of the stator core 26 corresponding to the one inductive magnetic head 5a is transmitted to the signal transmission ring 27a of the rotor core 27 in a non-contact manner. And
The recording signal transmitted to the signal transmission ring 27a of the rotor core 27 is supplied to the inductive magnetic head 5a, and a signal is recorded on the magnetic tape 7 by the inductive magnetic head 5a.

Similarly, the recording signal supplied to the signal transmission ring 26b of the stator core 26 corresponding to the other inductive magnetic head 5b is transmitted to the signal transmission ring 27b of the rotor core 27 in a non-contact manner. And
The recording signal transmitted to the signal transmission ring 27b of the rotor core 27 is supplied to the inductive magnetic head 5b, and a signal is recorded on the magnetic tape 7 by the inductive magnetic head 5b.

When reproducing a signal from the magnetic tape 7 using the rotary drum device 1, first, a current is supplied to the drive coil 31 of the motor 4 so that the rotary drum 3
Is driven to rotate. Then, while the rotating drum 3 is rotating, a high-frequency current from the oscillator 42 is supplied to the power drive 43 as shown in FIG.

The high-frequency current from the oscillator 42 is converted into a predetermined alternating current by the power drive 43 and then supplied to the power transmission ring 26 d of the stator core 26. Then, the alternating current supplied to the power transmission ring 26d of the stator core 26 is transmitted to the power transmission ring 27d of the rotor core 27 in a non-contact manner. The AC current transmitted to the power transmission ring 27d of the rotor core 27 is rectified by the rectifier 44 to become a DC current, and is supplied to the regulator 45. The DC current is set to a predetermined voltage by the regulator 45.

The current set to a predetermined voltage by the regulator 45 is applied to the pair of MR heads 6a and 6b.
Is supplied as a sense current. A reproducing amplifier 46 for detecting signals from the MR heads 6a and 6b is connected to the pair of MR heads 6a and 6b, and the current from the regulator 45 is also supplied to the reproducing amplifier 46. You.

Here, each of the MR heads 6a and 6b includes an MR element whose resistance value changes depending on the magnitude of an external magnetic field. The MR heads 6a and 6b are
The resistance value of the MR element changes due to the signal magnetic field from the sensor element, thereby causing a voltage change in the sense current.

The reproducing amplifier 46 detects this voltage change and outputs a signal corresponding to the voltage change as a reproduced signal. The reproducing amplifier 46 outputs a signal detected by the MR head 6a at the time of reproducing a signal by one MR head 6a, and outputs a signal at the timing of reproducing a signal by the other MR head 6b. The reproduced signal detected by the MR head 6b is output.

Here, the pair of MR heads 6a and 6b
As described above, the MR heads 6a and 6b are alternately reproduced with a phase difference of 180 ° since they are arranged so that the angle between them with respect to the center of the rotary drum 3 is 180 °. Will be. That is, the reproduction amplifier 46 alternately switches the timing of outputting the reproduction signal from one MR head 6a and the timing of outputting the reproduction signal from the other MR head 6b with a phase difference of 180 °. . The reproduction signal from the reproduction amplifier 46 is transmitted to the signal transmission ring 27 c of the rotor core 27.
The reproduced signal is transmitted to the signal transmission ring 26c of the stator core 26 in a non-contact manner. The reproduction signal transmitted to the signal transmission ring 26c of the stator core 26 is amplified by a reproduction amplifier 47 and then supplied to a correction circuit 48. Then, after the reproduction signal is subjected to a predetermined correction process by the correction circuit 48, the external circuit 40
Is output to.

In the case of the circuit configuration shown in FIG. 4, a pair of inductive magnetic heads 5a, 5b,
The pair of MR heads 6a and 6b, the rectifier 44, the regulator 45, and the reproducing amplifier 46 are mounted on the rotating drum 3 and rotate together with the rotating drum 3. On the other hand, the recording amplifier 41, the oscillator 42, the power drive 43, the reproducing amplifier 47, and the correction circuit 48 are provided in a fixed portion of the rotary drum device 1 or are provided separately from the rotary drum device 1. Circuit.

Next, the MR mounted on the rotary drum 3
The heads 6a and 6b will be described in detail with reference to FIG. The MR head 6a and the MR head 6b
Have the same configuration except that the azimuth angles are set to be opposite to each other. Therefore, in the following description, these MR heads 6a and 6b are collectively referred to as the MR head 6.

The MR head 6 is mounted on the rotating drum 3,
This is a read-only magnetic head that detects a signal from the magnetic tape 7 using the magnetoresistance effect by the helical scan method. Generally, MR heads are more inductive than magnetic heads that perform recording and reproduction using electromagnetic induction.
Because of its high sensitivity and high reproduction output, it is suitable for high-density recording. Therefore, by using the MR head 6 as the reproducing magnetic head, higher density recording can be achieved.

As shown in FIG. 5, the MR head 6 has a pair of magnetic shields 51 and 52 made of a soft magnetic material such as Ni—Zn polycrystalline ferrite, and a pair of magnetic shields 51 with an insulator 53 interposed therebetween. A substantially rectangular MR element portion 54 sandwiched between the magnetic shields 51 and 52 is provided. In addition,
A pair of terminals is led out from both ends of the MR element section 54, and a sense current can be supplied to the MR element section 54 through these terminals.

The MR element section 54 includes an MR element having a magnetoresistive effect and a SAL (Soft Adjustable).
ayer) film and an insulator film disposed between the MR element and the SAL film. The MR element is made of a soft magnetic material, such as Ni-Fe, whose resistance changes according to the magnitude of an external magnetic field due to the anisotropic magnetoresistance effect (AMR). The SAL film is for applying a bias magnetic field to the MR element by a so-called SAL bias method, and is made of a magnetic material having a low coercive force and a high magnetic permeability such as permalloy. The insulator film insulates between the MR element and the SAL film and prevents electronic shunt loss.
And the like.

The MR element portion 54 is formed in a substantially rectangular shape, and a pair of magnetic shields 51 and 52 is provided so that one side surface is exposed to the magnetic tape sliding surface 55.
3. More specifically, the MR element 54 has a pair of magnetic shields such that the short axis direction is substantially perpendicular to the magnetic tape sliding surface 55 and the long axis direction is substantially perpendicular to the magnetic tape sliding direction. It is sandwiched between insulators 51 and 52 via an insulator 53.

The magnetic tape sliding surface 55 of the MR head 6
Is cylindrically polished along the sliding direction of the magnetic tape 7 so that one side surface of the MR element 54 is exposed on the sliding surface 55 of the magnetic tape. Polished along the orthogonal direction. Thus, the MR head 6 is configured such that the MR element portion 54 or a portion near the MR element portion protrudes the most, so that the
The contact characteristics of the element portion 54 to the magnetic tape 7 can be improved.

When reproducing the signal from the magnetic tape 7 using the MR head 6 as described above, as shown in FIG.
The magnetic tape 7 is slid on the MR element 54. The arrows in FIG. 6 schematically show how the magnetic tape 7 is magnetized.

Then, with the magnetic tape 7 slid on the MR element section 54, the MR element section 5 is connected via the terminals 54a and 54b connected to both ends of the MR element section 54.
4 is supplied with a sense current, and a voltage change of the sense current is detected. Specifically, a predetermined voltage Vc is applied from a terminal 54a connected to one end of the MR element 54, and a terminal 54b connected to the other end of the MR element 54 is
It is connected to the rotating drum 3. Here, the rotating drum 3 is electrically connected to the fixed drum 2 via the rotating shaft 21, and the fixed drum 2 is grounded. Therefore, M
One terminal 54 b connected to the R element 54 is grounded via the rotating drum 3, the rotating shaft 21 and the fixed drum 2.

Then, when a sense current is supplied to the MR element 54 while the magnetic tape 7 is slid, the M formed on the MR element 54 in response to the magnetic field from the magnetic tape 7.
The resistance value of the R element changes, and as a result, a voltage change occurs in the sense current. Therefore, by detecting the voltage change of the sense current, the signal magnetic field from the magnetic tape 7 is detected, and the signal recorded on the magnetic tape 7 is reproduced.

In the MR head 6 to be used, the MR head
The MR element formed in the element section 54 may be any element that exhibits a magnetoresistance effect. For example, a so-called giant magnetoresistance effect is obtained by stacking a plurality of thin films so as to obtain a greater magnetoresistance effect. An element (GMR element) can also be used. The method of applying a magnetic field to the MR element may not be the SAL bias method, for example, a permanent magnet bias method, a shunt current bias method, a self-bias method, an exchange bias method, a barber pole method,
Various methods such as a split element method and a servo bias method can be applied. The giant magnetoresistance effect and various bias methods are described in detail in, for example, "Magnetoresistance Head Basics and Applications Translated by Kazuhiko Hayashi" by Maruzen Co., Ltd.

[0083]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Examples 1 to 19 and Comparative Examples 1 and 2 Hexagonal Ba ferrite powders of Examples 1 to 19 and Comparative Examples 1 and 2 were obtained by a glass crystallization method. That is, barium oxide as a raw material, iron oxide, a metal oxide to replace iron if necessary, and a glass forming substance boron oxide,
After mixing such that the weight ratio of Ba atoms to Fe atoms of the hexagonal Ba ferrite powder conforms to the ratio shown in Table 1,
It was melted and then quenched to obtain an amorphous body. Next, after the reheating treatment, the powder was washed and pulverized to obtain hexagonal Ba ferrite powders of Examples 1 to 19 and Comparative Examples 1 and 2.
In this production, the Ba atom / Fe atomic ratio of the powder was controlled by the ratio of barium oxide and iron oxide to be mixed. Further, the ratio of surface Ba atoms to surface Fe atoms (surface Ba / surface Fe: A), (hereinafter, surface Ba / Fe (A)
), The ratio of the center Ba atom to the center Fe atom (center Ba / center Fe: B), (hereinafter, center Ba / Fe
(Abbreviated as (B)) was adjusted by controlling the time and temperature of the reheating treatment after forming the amorphous body, or the time and temperature during melting. The particle size of the hexagonal Ba ferrite powder was adjusted to a predetermined value by controlling the rate of amorphization during the quenching process.

The Ba atom / Fe atom ratio of the hexagonal Ba ferrite powder thus obtained was measured and evaluated by X-ray fluorescence analysis.

On the other hand, the ratio of the surface Ba atoms to the surface Fe atoms on the surface of the hexagonal Ba ferrite powder (surface Ba / Fe
(A)) was determined by measuring with ESCA (ESCA-300 manufactured by ULVAC-PHI). In this case, surface B
a atom is Ba3d _5/2 spectrum, surface Fe atom is Fe
The 2p _3/2 spectrum was measured, the integrated intensity ratio determined the background by Shirley's plot, and the integrated intensity ratio of the hexagonal Ba ferrite powder surface (surface Ba / Fe (A)) was determined by the area value. Calculated. Further, the integrated intensity ratio of the center of the hexagonal Ba ferrite powder (center Ba / F
e (B)), after etching the hexagonal Ba ferrite powder by argon sputtering, the center of the exposed powder is subjected to ESCA to obtain Ba3d in the same manner as the surface.
_It was determined by measuring the _5/2 spectrum and the Fe2p _3/2 spectrum.

Regarding the integrated intensity evaluation, the specification of C1s
Torr to 284.5 eV and Ba3d_5/2Spect
And Fe2p_3/2After correcting the spectrum, Ba
3d_5/2 776.5 to 783.5 for the spectrum
In eV, Fe2p_3/2703.5 for spectrum
Determine the area value at eV to 718.5 eV and integrate
The intensity was calculated.

As described above, the hexagonal Ba ferrite powder evaluated for each of Examples 1 to 19 and Comparative Examples 1 and 2 had a Ba atom / Fe atomic ratio (Ba / Fe) and a surface integral intensity ratio (surface Table 1 shows Ba / Fe (A)), the center integrated intensity ratio (center Ba / Fe (B)), and the ratio (A / B) between the surface integrated intensity ratio and the center integrated intensity ratio.
Hexagonal plate diameter (particle size) of hexagonal Ba ferrite powder
Are shown in Table 1. The plate ratio (plate diameter / plate thickness) of Example 1
Is 3.

[0088]

[Table 1]

Hexagonal B obtained by the above glass crystallization method
Using a ferrite powder, a magnetic tape was prepared in which a magnetic layer consisting of a lower non-magnetic layer and an upper magnetic layer was provided on a non-magnetic support. Iron oxide, a binder resin, a lubricant, and a solvent were blended in the composition shown in Table 2 as a lower non-magnetic layer coating composition to obtain a lower non-magnetic coating composition. As the paint for the upper magnetic layer, each hexagonal Ba ferrite powder obtained by the above-mentioned glass crystallization method is used, and this is uniformly mixed with a binder resin, an abrasive, an antistatic agent, a lubricant and the like by a solvent. The mixture was mixed to obtain an upper layer magnetic paint. Table 3 shows the composition of the upper layer magnetic paint.

[0090]

[Table 2]

[0091]

[Table 3]

The lower non-magnetic coating prepared as described above was first applied on a non-magnetic support made of a polyethylene terephthalate (PET) film to form a lower non-magnetic layer having a thickness of 1.5 μm. Next, an upper magnetic layer is applied on the lower non-magnetic layer to form an upper magnetic layer having a thickness of 0.3 μm, and a two-layer structure is formed. Tape).

The surface roughness Ra and the surface roughness Rz of each magnetic tape were adjusted by controlling the mixing ratio of the magnetic powder and the binder, the amount of the solvent, the dispersant, and the dispersion state of the composition. The coercive force Hc was controlled by controlling the thickness of the applied magnetic layer, the mixing ratio of the magnetic powder and the binder, the state of filling of the particles, and the like to obtain a predetermined magnetic tape.

The electromagnetic conversion characteristics of each magnetic tape produced by the coating method as described above were measured. Using a modified 8mm VTR, the recording wavelength is 0.5μm
After recording the information signal, the reproduction output, the noise level, the error rate, and the output deterioration were measured by the shield type MR head. The error rate indicates a symbol error rate. The MR head element used for reproduction was FeNi-A
MR (anisotropic magnetoresistive element) with saturation magnetization of 8
00 emu / cc, film thickness 40 nm, shielding material is Ni
Zn and the shield interval are 0.17 μm. The track width is 18 μm and the azimuth angle is 25 degrees. Regarding the output deterioration of each sample tape, the output deterioration after 20 passes was measured based on the initial output by running an 8 mm VTR modified deck in an environment of a temperature of 40 ° C. and a relative humidity of 20%.

The surface roughness Ra and the surface roughness R of each magnetic tape
Table 4 shows the results of evaluating z, coercive force Hc, and the results of evaluating output, noise, S / N, error rate, and output degradation.

[0096]

[Table 4]

As shown in Comparative Examples 1 and 2 in Table 4, Ba atom / F of hexagonal Ba ferrite powder which is a ferromagnetic powder was used.
If the weight ratio of e-atoms (Ba / Fe) is less than 0.15, a large amount of Fe is contained, so that the reproduction output becomes large. This shows that sufficient electromagnetic conversion characteristics cannot be obtained. On the other hand, in the range of 0.15 to 0.21, the output degradation is small and good values are obtained, and sufficient electromagnetic conversion characteristics as a magnetic recording medium can be obtained.

Further, from Table 4, the integrated intensity ratio of the Ba3d _5/2 spectrum and the Fe2p _3/2 spectrum measured by ESCA on the surface of the hexagonal Ba ferrite powder (surface Ba)
If (/ Fe (A)) is less than 0.45, burn-in occurs due to running of the deck as described above, and the output deterioration is increased. As a result, sufficient electromagnetic conversion characteristics cannot be obtained.
On the other hand, in the range of 0.45 to 0.70, the output degradation is small and good values are obtained in all cases, and sufficient electromagnetic conversion characteristics as a magnetic recording medium can be obtained.

Similarly, from Table 4, the integrated intensity ratio (A) of the Ba3d _5/2 spectrum and the Fe2p _3/2 spectrum measured by ESCA on the surface of the hexagonal Ba ferrite powder.
And the ratio (A / B) between the integrated intensity ratio (B) of the Ba3d _5/2 spectrum and the Fe2p _3/2 spectrum measured by ESCA at the center of the hexagonal Ba ferrite powder and Burning occurs due to the running of the deck, and output deterioration is increased. As a result, sufficient electromagnetic conversion characteristics cannot be obtained. On the other hand, in the range of 0.8 to 1.2, the output degradation is small and good values are obtained, and a sufficient electromagnetic conversion characteristic as a magnetic recording medium can be obtained.

Further, as shown in Table 4, regarding the influence of the particle size of the hexagonal Ba ferrite powder, if the particle size is less than 10 nm, noise increases. This means that the particle size is 10n
If it is less than m, it becomes superparamagnetic, and stable magnetization cannot be maintained. On the other hand, if it exceeds 60 nm, the surface smoothness of the coating layer will be impaired, and noise will also increase. On the other hand, in the range of 10 to 60 nm, noise is small, and characteristics such as good output and S / N are obtained.

Table 4 shows that the magnetic tape has a surface roughness Ra.
Exceeds 7.0 nm, and the surface roughness Rz is 90
If it exceeds nm, spacing loss will occur and noise will increase. On the other hand, when the surface roughness Ra is equal to or less than 7.0 nm and the surface roughness Rz is equal to or less than 90 nm, there is no problem of the spacing loss and the noise is small.

The coercive force Hc of the magnetic tape is shown in Table 4
If it is less than kA / m, or if it exceeds 235 kA / m, noise is generated so that sufficient recording cannot be performed. On the other hand, 80 kA / m to 235 kA / m
Within this range, noise is low and sufficient recording can be performed.

[0103]

According to the first aspect of the present invention, hexagonal Ba is used.
The ratio of Ba atoms / Fe atoms in the ferrite powder is 0.1 by weight.
₅ to 0.21, and the integrated intensity ratio between the Ba3d _5/2 spectrum and the Fe2p _3/2 spectrum measured by ESCA on the surface of the hexagonal Ba ferrite powder is surface Ba / surface Fe = 0.45. By setting it to 0.70, a magnetic powder free from burning and output deterioration is provided.

According to the second aspect of the present invention, Ba3d measured on a hexagonal Ba ferrite powder surface by ESCA.
The integrated intensity ratio between the _5/2 spectrum and the Fe2p _3/2 spectrum (Surface Ba / Surface Fe: A) and Ba3d measured by ESCA at the center of hexagonal Ba ferrite powder
The ratio (A / B) of the integrated intensity ratio (center Ba / center Fe: B) between the _5/2 spectrum and the Fe2p _3/2 spectrum is A / B
By setting B = 0.8 to 1.2, it is possible to prevent a decrease in saturation magnetization, and to provide a magnetic powder free from seizure and output deterioration.

In the invention according to claim 3, the hexagonal B
a Ferrite powder has a hexagonal plate diameter of 10
By setting the thickness to ｎｍ60 nm, a superparamagnetic and magnetic powder in which noise is prevented is provided.

According to a fourth aspect of the present invention, in a magnetic recording medium comprising a magnetic layer containing a magnetic powder provided on a non-magnetic support, the magnetic powder comprises a Ba atom / Fe of hexagonal Ba ferrite powder. Atoms are 0.15 to 0.2 by weight
1 and the E of the surface of the hexagonal Ba ferrite powder.
Ba3d _5/2 spectrum measured by SCA and F
By setting the integrated intensity ratio with the e2p _3/2 spectrum to be surface Ba / surface Fe = 0.45 to 0.70, a magnetic recording medium free from image sticking and output deterioration is provided.

In the invention according to claim 5, the magnetic powder has an integral intensity ratio of the Ba3d _5/2 spectrum and the Fe2p _3/2 spectrum measured by ESCA on the surface of the hexagonal Ba ferrite powder (surface Ba / surface Ba). Fe: A);
The ratio of the integrated intensity ratio (center Ba / center Fe: B) between the Ba3d _5/2 spectrum and the Fe2p _3/2 spectrum measured by ESCA at the center of the hexagonal Ba ferrite powder (A
/ B) is A / B = 0.8 to 1.2,
Provided is a magnetic recording medium that prevents a decrease in saturation magnetization and is free from burn-in and output deterioration.

According to the sixth aspect of the present invention, there is provided a magnetic recording medium in which supermagnetic properties and noise are prevented by making the magnetic powder a hexagonal Ba ferrite powder having a hexagonal plate diameter of 10 to 60 nm. Is done.

According to the seventh aspect of the present invention, by setting the surface roughness Ra to 7.0 nm or less and the surface roughness Rz to 90 nm or less, there is no spacing loss and no reduction in signal strength. Is provided.

In the invention according to claim 8, the coercive force Hc is set to 8
By setting it to 0 to 235 kA / m, a low-noise, high-resolution magnetic recording medium is provided.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an example of a rotary drum device mounted on a helical scan type magnetic recording / reproducing apparatus.

FIG. 2 is a plan view schematically showing an example of a magnetic tape feeding mechanism including the rotary drum device of FIG.

FIG. 3 is a sectional view showing an internal structure of the rotary drum device of FIG.

FIG. 4 is a block diagram showing a circuit configuration of the rotary drum device of FIG. 1 and its peripheral circuits.

FIG. 5 is a perspective view schematically showing an MR head mounted on the rotary drum device of FIG. 1;

FIG. 6 is a schematic diagram showing how a signal from a magnetic tape is reproduced using an MR head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotary drum apparatus, 2 ... Fixed drum, 3 ... Rotary drum, 4 ... Motor, 5a ... Inductive type magnetic head,
5b: inductive magnetic head, 6a: MR head, 6b: MR head, 7: magnetic tape, 8: lead guide, 10: magnetic tape feed mechanism, 11: supply reel,
12-15: Guide roller, 16: Capstan, 17
... Guide roller, 18 ... Take-up roll, 19 ... Capstan motor, 21 ... Rotating shaft, 22 ... Bearing, 23 ... Bearing, 24 ... Flange, 25 ... Rotary transformer, 26 ...
Stator core, 26a ... signal transmission ring, 26b ... signal transmission ring, 26c ... signal transmission ring, 26d ...
Power transmission ring, 27: rotor core, 27a: signal transmission ring, 27b: signal transmission ring, 27c: signal transmission ring, 27d: power transmission ring, 28: rotor, 29: stator, 30: driving magnet , 31 ...
Drive coil, 40: external circuit, 41: recording amplifier,
42 ... Oscillator, 43 ... Power drive, 44 ... Rectifier, 45 ... Regulator, 46 ... Reproduction amplifier, 47 ...
Reproduction amplifier, 48: correction circuit, 51: magnetic shield,
52: magnetic shield, 53: insulator, 54: MR element part, 54a: terminal, 54b: terminal, 55: magnetic tape sliding surface

Claims (10)

[Claims] 1. A hexagonal Ba ferrite powder,
The weight ratio of Ba atoms / Fe atoms is 0.15 to 0.21, and the ESCA of the surface of the hexagonal Ba ferrite powder is
_5/2 spectrum (surface B
magnetic powder, wherein the integrated intensity ratio of a) and Fe2p _3/2 spectrum (surface Fe) is a surface Ba / surface Fe = 0.45 to 0.70. 2. ES on the surface of hexagonal Ba ferrite powder
Ba3d _5/2 spectrum measured by CA and Fe
2p _3/2 integrated intensity ratio (surface Ba / surface F
e: A) and the ES of the center of the hexagonal Ba ferrite powder.
Ba3d _5/2 spectrum measured by CA and Fe
2p _3/2 spectrum integrated intensity ratio (center Ba / center F
e: B), the ratio (A / B) is A / B = 0.8 to 1.2.
The magnetic powder according to claim 1, wherein 3. The magnetic powder according to claim 1, wherein the hexagonal Ba ferrite powder has a hexagonal plate diameter of 10 to 60 nm. 4. A magnetic recording medium in which a magnetic layer containing a magnetic powder is provided on a non-magnetic support, wherein the magnetic powder is hexagonal Ba ferrite powder, and Ba atoms / Fe atoms are in weight. 0.15 to 0.21 in ratio
And the ES of the surface of the hexagonal Ba ferrite powder
And wherein the integrated intensity ratio of Ba3d _5/2 spectrum measured (surface Ba) and Fe2p _3/2 spectrum (surface Fe) by CA is a surface Ba / surface Fe = 0.45 to 0.70 Magnetic recording medium. 5. The magnetic powder according to claim 3, wherein the surface of the hexagonal Ba ferrite powder is Ba3d _5/2 measured by ESCA.
Integrated intensity ratio between surface spectrum and Fe2p3 _{/ 2} spectrum (surface Ba / surface Fe: A), and integrated intensity of Ba3d5 _{/ 2} spectrum and Fe2p3 _{/ 2} spectrum measured by ESCA at the center of the hexagonal Ba ferrite powder. The ratio (A / B) to the ratio (center Ba / center Fe: B) is A / B =
5. The magnetic recording medium according to claim 4, wherein the ratio is 0.8 to 1.2. 6. The magnetic recording medium according to claim 4, wherein the magnetic powder is a hexagonal Ba ferrite powder having a hexagonal plate diameter of 10 to 60 nm. 7. A surface roughness Ra of not more than 7.0 nm,
5. The magnetic recording medium according to claim 4, wherein the surface roughness Rz is 90 nm or less. 8. The magnetic recording medium according to claim 4, wherein the coercive force Hc is 80 to 235 kA / m. 9. The magnetic recording medium according to claim 4, wherein the magnetic recording medium is used in a magnetic recording system including a magnetoresistive read head. 10. The magnetic recording system according to claim 9, wherein said magnetic recording system is a helical scan magnetic recording system.
The magnetic recording medium according to the above.