JP2002008910A - Magnetic powder and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize recording of density which is higher than conventional cases, enhancing magnetic power in dispersion properties to improve a magnetic layer in surface smoothness. SOLUTION: A magnetic recording medium 1 is equipped with a magnetic layer 3, formed by the application of a magnetic paint containing magnetic powder, that contains Fe and a nonmagnetic support 2. The magnetic powder 2 contains 1.0 to 20 wt.% Al in a ratio of Al to Fe and one out of nonmagnetic metal elements, having trivalent ionization energy range of 30 to 45 eV in an amount of 1.0 to 40 wt.% for the ratio of the element Fe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a magnetic layer formed by applying a magnetic paint, and is particularly suitable for use in a helical scan magnetic recording system using a magnetoresistive read head. The present invention relates to a magnetic recording medium.

[0002]

2. Description of the Related Art Recording media used in audio devices, video devices, computer devices, etc. include magnetic powders,
There is known a so-called coating type magnetic recording medium in which a magnetic coating prepared by kneading / dispersing a binder and various additives in an organic solvent is coated on a non-magnetic support to form a magnetic layer. . This coating type magnetic recording medium is predominant as the above-mentioned recording medium because of its excellent productivity and versatility.

A magnetic recording medium is recorded / reproduced by a recording / reproducing apparatus having a magnetic head such as an inductive head. In recent years, this recording / reproducing apparatus has been reduced in size and weight, improved in image quality, and extended in time. Accordingly, high-density recording is also strongly required in the above-mentioned coating type magnetic recording medium.

In a coating type magnetic recording medium, in order to realize high-density recording, the magnetic layer is made thinner to suppress output loss due to recording demagnetization, and the surface of the magnetic layer is smoothed to minimize spacing loss. Attempts have been made to limit this.

Further, in this type of magnetic recording medium, by using a magnetic powder having a large saturation magnetic flux density, it is intended to achieve high-density recording in a recording / reproducing system using an inductive head. As such a magnetic powder, a metal magnetic powder mainly composed of iron, a plate-like magnetic powder such as barium ferrite, or the like is used in place of a conventionally used iron oxide-based magnetic powder.

For example, metal magnetic powder mainly composed of iron is
The saturation magnetic flux density is higher than that of iron oxide-based magnetic powder, and it has a higher saturation magnetic flux density by adding cobalt. And a recording / reproducing system using an inductive head is adapted to high-density recording.

Further, in this type of magnetic recording medium,
The aim is to achieve high-density recording by reducing noise and improving S / N by using micronized magnetic powder.

[0008]

However, when the magnetic powder is made finer, the dispersibility of the magnetic powder tends to decrease. For this reason, the magnetic layer containing the finely divided magnetic powder had poor surface smoothness. As a result, there has been a problem that the magnetic recording medium cannot obtain desired electromagnetic conversion characteristics and cannot achieve high-density recording.

The present invention has been proposed in view of such circumstances, and it is an object of the present invention to provide a magnetic powder which is excellent in dispersibility even if it is finely divided. Another object of the present invention is to provide a magnetic recording medium having excellent electromagnetic conversion characteristics by containing the magnetic powder and realizing unprecedented high-density recording.

[0010]

In order to achieve the above-mentioned object, a magnetic powder according to the present invention is characterized in that in a magnetic powder containing Fe, Al is contained in an Fe ratio of 1.0% by weight or more and 20% by weight or less. And at least one kind of non-magnetic metal element having a trivalent ionization energy of 30 eV or more and 45 eV or less is contained at a Fe ratio of 1.0% or more.
It is characterized in that it is contained at a ratio of not less than 40% by weight and not more than 40% by weight.

The magnetic powder according to the present invention configured as described above is highly dispersed in, for example, a magnetic layer.

Further, the magnetic powder according to the present invention contains at least one kind of nonmagnetic metal element in the magnetic powder containing Fe, and the average value of the trivalent ionization energy of the nonmagnetic metal element is 30 ev. As described above, the range is 40 eV or less.

The magnetic powder according to the present invention configured as described above is highly dispersed in, for example, a magnetic layer.

Further, the magnetic powder according to the present invention is characterized in that
The magnetic powder containing e has an isoelectric point in the range of 7 or more and 11 or less in zeta potential measurement.

The magnetic powder according to the present invention configured as described above is highly dispersed in, for example, a magnetic layer.

The magnetic recording medium according to the present invention has an F
In a magnetic recording medium comprising a magnetic layer coated with a magnetic paint containing a magnetic powder containing e and a non-magnetic support, the magnetic powder contains Al in an amount of 1.0% by weight or more and 20% by weight in terms of Fe ratio. % Or less, and at least one or more of the non-magnetic metal elements having a trivalent ionization energy of 30 eV or more and 45 eV or less,
It is characterized in that it is contained in a ratio of not less than 1.0% by weight and not more than 40% by weight.

In the magnetic recording medium according to the present invention configured as described above, since the magnetic layer contains a magnetic powder having excellent dispersibility, it has excellent surface smoothness.

Further, the magnetic recording medium according to the present invention is characterized in that
In a magnetic recording medium comprising a magnetic layer coated with a magnetic paint containing a magnetic powder containing: and a nonmagnetic support, the magnetic powder comprises at least one of the nonmagnetic metal elements
And the average value of the trivalent ionization energies of the non-magnetic metal elements is in the range of 30 eV or more and 40 eV or less.

In the magnetic recording medium according to the present invention configured as described above, since the magnetic layer contains a magnetic powder having excellent dispersibility, it has excellent surface smoothness.

Further, the magnetic recording medium according to the present invention is characterized in that
In a magnetic recording medium comprising a magnetic layer coated with a magnetic paint containing a magnetic powder containing: and a non-magnetic support, the magnetic powder has an isoelectric point of 7 or more and 11 or less in zeta potential measurement. It is characterized by being a range.

In the magnetic recording medium according to the present invention configured as described above, since the magnetic layer contains magnetic powder having excellent dispersibility, it has excellent surface smoothness.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of a magnetic recording medium according to the present invention will be described in detail with reference to the drawings.

The magnetic recording medium 1 to which the present invention has been applied has the structure shown in FIG.
As shown in FIG. 1, a nonmagnetic support 2 and a magnetic layer 3 formed by applying a magnetic paint containing a magnetic powder and a binder on the nonmagnetic support 2 are provided.

Here, the magnetic powder used for the magnetic layer 3 is a magnetic powder containing Fe, specifically, a metal magnetic powder mainly composed of Fe (Fe-based acicular magnetic powder, Fe—C
o alloy-based needle-like magnetic powder), plate-like magnetic powder such as barium ferrite, and iron nitride.

The major axis length of these magnetic powders (in the case of a plate-like magnetic powder such as barium ferrite, the plate length is 2) is 2
μm or less. The major axis length of the magnetic powder is 0.12μ.
m, preferably 0.10 μm or less, and most preferably 0.085 μm or less. The smaller the major axis length of the magnetic powder, the better the surface smoothness of the magnetic layer containing the magnetic powder.

In particular, the average major axis length of the metal magnetic powder, which is a magnetic powder mainly composed of Fe, is 0.01 μm to 0.15 μm.
It is preferable to be within the range. Average long axis length is 0.01μ
If it is less than m, the metal magnetic powder becomes superparamagnetic, and the electromagnetic conversion characteristics of the magnetic recording medium 1 may be significantly reduced. On the other hand, if the average major axis length exceeds 0.15 μm, noise components may increase in short wavelength recording.

Further, the crystallite size of the metal magnetic powder determined by the X-ray diffraction method, that is, the X-ray crystal grain size Dx is 50 °-
Preferably it is in the range of 200 °. If Dx is too small, the metal magnetic powder becomes superparamagnetic, and the electromagnetic conversion characteristics of the magnetic recording medium 1 may be significantly reduced. On the other hand, D
If x is too large, the noise component may increase to deteriorate the electromagnetic conversion characteristics.

Further, the saturation magnetization (saturation magnetic flux density) (δs) of the metal magnetic powder is preferably from 80 to 150 emu / g. If the saturation magnetization is less than 80 emu / g, a sufficient reproduction output may not be obtained. On the other hand, if the saturation magnetization exceeds 150 emu / g, agglomeration of the metal magnetic powder occurs in the magnetic layer 3 and the surface properties of the magnetic layer 3 may be deteriorated.

Incidentally, the magnetic properties of the magnetic recording medium are affected by the dispersibility of the magnetic powder contained in the magnetic layer. Therefore, the squareness ratio R, which is an index of magnetic properties, is used to determine the dispersibility of magnetic powder.
The relationship between the dispersibility and the volume of the magnetic powder is shown in FIG. 2 by evaluating using s. FIG. 2 shows that the smaller the volume of the magnetic powder, the smaller the squareness ratio Rs. That is, it can be said that the dispersibility of the magnetic powder decreases as the particle size becomes smaller.

The present inventors have attempted to modify the surface of a magnetic powder by adding a non-magnetic metal element to a conventional magnetic powder in order to improve the dispersibility of the magnetic powder. Here, the non-magnetic metal element is a metal element other than a ferromagnetic metal element (for example, Fe, Co, Ni, etc.), specifically, Si, Zn,
Sr and the like.

When a non-magnetic metal element Y having a trivalent ionization energy of less than 30 eV is added, Rs decreases as shown by a point A in FIG. That is, it is understood that the dispersibility of the magnetic powder deteriorates. On the other hand, when a nonmagnetic metal element Si having a trivalent ionization energy exceeding 30 eV is added, Rs is improved as shown by a point B in FIG. That is, it was confirmed that the dispersibility of the magnetic powder was improved.

Therefore, the composition is defined so that the finely divided magnetic powder has a high degree of dispersibility. Specifically, as a first rule, in a magnetic powder containing Fe, Al is contained at a ratio of 1.0% by weight or more and 20% by weight or less in Fe ratio, and trivalent ionization energy is 30%.
At least one kind of nonmagnetic metal element having a range of eV or more and 45 eV or less is contained in an Fe ratio of 1.0% by weight or more and 40% by weight or less.

The magnetic powder thus defined has excellent dispersibility, and is highly dispersed in, for example, the magnetic layer 3. Therefore, the magnetic layer 3 containing this magnetic powder has excellent surface smoothness.

Alternatively, as a second rule, in the magnetic powder containing Fe, at least one of the nonmagnetic metal elements may be used.
Or more, and the average value of the trivalent ionization energies of the nonmagnetic metal elements is in the range of 30 eV to 40 eV.

The magnetic powder thus defined has excellent dispersibility, and is highly dispersed in, for example, the magnetic layer 3. Therefore, the magnetic layer 3 containing this magnetic powder has excellent surface smoothness.

The present inventors measured the zeta potential of a magnetic powder to which a nonmagnetic metal element was added in an aqueous system. As a result, the trivalent ionization energy is 30 eV
It has been confirmed that the isoelectric point decreases when a non-magnetic metal element Si exceeding 3% is added, and the isoelectric point increases when a non-magnetic metal element Y having a trivalent ionization energy of less than 30 eV is added.

Therefore, the isoelectric point is defined so that the finely divided magnetic powder has a high degree of dispersibility. Specifically, as a third rule, the magnetic powder has an isoelectric point in the range of 7 or more and 11 or less in zeta potential measurement.

The magnetic powder thus defined has excellent dispersibility, and is highly dispersed in, for example, the magnetic layer 3. Therefore, the magnetic layer 3 containing this magnetic powder has excellent surface smoothness.

The following models are considered as these operations. On the surface of the magnetic powder, a non-magnetic metal element exists as an oxide, for example, in the form of Al ₂ O ₃ . In addition, a myriad of hydroxyl groups (OH
Group) is present. It is considered that the magnetic powder is dispersed in the magnetic layer by bonding the hydroxyl group and the polar group of the resin contained as the binder.

Incidentally, the non-magnetic metal element present on the surface of the magnetic powder has an action of attracting electrons of the oxygen atom of the hydroxyl group. In particular, a nonmagnetic metal element having a large ionization energy has a strong power to attract electrons of an oxygen atom, and thus causes a strong polarity to a hydroxyl group. As a result, the dispersibility of the magnetic powder is improved.

As the binder used for the magnetic layer 3, any resin conventionally used as a binder in this type of magnetic recording medium can be used. For example, a vinyl chloride-vinyl acetate copolymer Vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinylidene chloride copolymer, methacryl Acid ester-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, polyacetal, cellulose Conductor, styrene - butadiene copolymer, polyester resin, phenol resin, epoxy resin, polyurethane resin, urea resin, melamine resin, alkyd resin, urea - formaldehyde resins. One of these binders may be used alone, or two or more thereof may be used in combination.

As the binder, it is preferable to use a resin having a hydrophilic polar group introduced. Thereby, the dispersibility of the pigment such as the magnetic powder contained in the magnetic layer 3 is improved, and the coating strength of the magnetic layer 3 is improved. As the hydrophilic polar group that can be introduced into the resin described above, a sulfonic acid group,
Examples thereof include a sulfate group, a carboxylic acid group and a salt thereof, a tertiary amine group, a quaternary ammonium base, a phosphate group, and a phosphate group. Among these hydrophilic polar groups, it is particularly preferable to use an alkali metal salt of a sulfonic acid group or a sulfate group, or a quaternary ammonium base.

The durability of the magnetic layer 3 is further improved by containing a crosslinking agent (curing agent). Examples of the crosslinking agent include a trifunctional isocyanate compound (specifically, a reaction product of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate), isocyanurate which is a cycloaddition polymerization compound of 3 mol of diisocyanate, and the like. .

Further, the magnetic layer 3 may contain an abrasive, an antistatic agent and the like in addition to the magnetic powder and the binder described above.

In the magnetic recording medium 1, the magnetic layer 3 controls the type of magnetic powder used, the mixing ratio of the magnetic powder and the binder, and the type and mixing ratio of other additives used. By doing so, the output is regulated so that the maximum output is obtained without saturating the magnetoresistive read head (hereinafter referred to as the MR read head) and without distortion. Specifically, the value of the product Mr · δ of the residual magnetization amount Mr and the film thickness δ of the magnetic layer 3 is 0.8 to 6.5 memu / c.
m ² .

The value of the product Mr · δ is 0.8 memu / c
If it is less than m ² , sufficient reproduction output cannot be obtained. On the other hand, when it exceeds 6.5 memu / cm ² , the MR reproducing head is saturated, and distortion occurs.

Within the above range, the film thickness δ and the amount of residual magnetization Mr
Can be set arbitrarily, but if the film thickness δ or the residual magnetization amount Mr is too small, it is difficult to secure the value of the product Mr · δ of 0.8 memu / cm ² or more. Conversely, if the film thickness δ or the residual magnetization Mr is too large, distortion becomes a problem.

The coercive force in the in-plane direction of the magnetic layer 3 is as follows:
In order to realize low noise and high resolution, 1400 Oe
It is preferable to keep the above. However, if the coercive force is too large, sufficient recording cannot be performed, and the reproduction output decreases.

As the solvent used for the magnetic paint, those usually used in the production of magnetic recording media, for example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, methyl acetate, acetic acid Esters such as ethyl, butyl acetate, ethyl lactate, and glycol monoethyl ether, ethers such as ethyl ether, glycol dimethyl ether, glycol monoethyl ether, dioxane, and tetrahydrofuran; aromatic hydrocarbons such as benzene, toluene, and xylene; and methylene Chloride, ethylene chloride,
Carbon tetrachloride, chloroform, ethylene chlorohydrin,
And chlorinated hydrocarbons such as dichlorobenzene.
This solvent may be used alone or as a mixture of two or more.

Examples of the nonmagnetic support 2 include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate, polycarbonate, polyimide, polyamideimide and the like. And plastics on which a metal such as aluminum is deposited.

The shape of the nonmagnetic support 2 may be any of a film shape, a tape shape, and a sheet shape. The non-magnetic support 2 corresponds to each shape.
Is appropriately selected.

This magnetic recording medium 1 has a magnetic layer 3 formed by applying a magnetic paint on a non-magnetic support 2. This magnetic paint is prepared, for example, by kneading and dispersing a magnetic powder together with a binder or the like in an organic solvent.

On the other hand, when preparing a magnetic coating material from the above-mentioned raw materials, a kneader or a dilution disperser can be used. This kneader is used in a kneading step of dispersing a magnetic powder having a relatively high solid content in a mixture containing a binder at a high shear. Further, the diluting and dispersing machine is used in a diluting and dispersing step of dispersing a magnetic powder having a relatively low solid content in a mixture containing a binder by impact force of beads or the like.

As these kneaders and dilution / dispersion machines, conventionally known kneaders and dilution / dispersion machines can be used. Specifically,
Examples of the kneader include a continuous twin-screw kneader (extruder), a co-kneader, and a pressure kneader. Examples of the dilution / dispersion machine include a vertical sand mill, a horizontal sand mill, a spike mill, a pearl mill, and a double cylinder pearl mill.

The prepared magnetic paint is applied on the non-magnetic support 2 and then dried to form the magnetic layer 3. Examples of a coating device for coating the magnetic paint on the non-magnetic support 2 include a reverse roll, a gravure roll, an air doctor coater, a blade coater, an air knife coater, a squeeze coater, an impregnation coater, a transfer roll coater, a kiss coater, a cast coater, A spray coater or the like is used.

In the above description, the magnetic recording medium 1 having the magnetic layer 3 formed by applying a magnetic paint on the non-magnetic support 2 has been described, but the present invention is not limited to this. . That is, the magnetic recording medium according to the present invention may have a configuration in which a magnetic layer is formed on both surfaces of a nonmagnetic support, and a nonmagnetic paint and a magnetic paint are simultaneously coated on the nonmagnetic support by multi-layer coating. Thereafter, the non-magnetic paint and the magnetic paint are dried, and the non-magnetic layer and the magnetic layer may be laminated on the non-magnetic support in this order.

A back coat layer (not shown) may be provided on the other main surface of the non-magnetic support 2 opposite to the main surface on which the magnetic layer 3 is formed. By providing the back coat layer, the running property of the magnetic recording medium 1 is improved, and interlayer adhesion is prevented.

The magnetic recording medium 1 configured as described above
Is provided with a magnetic layer 3 having excellent surface smoothness by containing a magnetic powder that satisfies at least one of the above-described first, second, and third rules. Has conversion characteristics.

The magnetic powder contained in the magnetic layer 3 may satisfy all of the first to third rules, and may satisfy the first and third rules or the second or third rule. It may satisfy the regulation and the third regulation.

The magnetic recording medium 1 is suitable as a magnetic tape for a helical scan magnetic recording system using an MR reproducing head.

In this case, the MR reproducing head is an MR reproducing head.
A recording / reproducing apparatus is configured by using a shield type MR head in which an element is sandwiched between shields and mounted on a rotating drum.

By combining the helical scan magnetic recording system using the MR head and the magnetic recording medium 1 according to the present invention, an unprecedented high-density recording system can be constructed.

The magnetic recording / reproducing device of the helical scan magnetic recording system is a helical scan type magnetic recording / reproducing device for performing recording / reproducing using a rotating drum, and an MR head is used as a reproducing magnetic head mounted on the rotating drum. Use

FIGS. 3 and 4 show an example of the configuration of a rotary drum device mounted on the magnetic recording / reproducing apparatus. Note that FIG.
4 is a perspective view schematically showing the rotary drum device 11, and FIG.
FIG. 3 is a plan view schematically showing a magnetic tape feed mechanism 20 including the rotary drum device 11.

As shown in FIG. 3, the rotating drum device 11
Are cylindrical fixed drum 12 and cylindrical rotary drum 1
3, a motor 14 for rotating and driving the rotary drum 13, a pair of inductive magnetic heads 15 a and 15 b mounted on the rotary drum 13, and a pair of MR heads 16 a and 16 b mounted on the rotary drum 13.

The fixed drum 12 is a drum that is held without rotating. On the side surface of the fixed drum 12, a lead guide portion 18 is formed along a running direction of a magnetic tape 17 formed by slitting the magnetic recording medium 1 having the above-described configuration to an appropriate width. As will be described later, the magnetic tape 17 runs along the read guide portion 18 during recording and reproduction. The rotating drum 13 is disposed so that the center axis of the fixed drum 12 coincides with that of the fixed drum 12.

The rotary drum 13 is a drum that is driven to rotate at a predetermined rotation speed by a motor 14 during recording and reproduction on the magnetic tape 17. This rotating drum 13
It is formed in a cylindrical shape having substantially the same diameter as the fixed drum 12, and is arranged so that the center axis of the fixed drum 12 coincides with the center axis.
A pair of inductive magnetic heads 15a, 15a,
15b and a pair of MR heads 16a and 16b are mounted.

Inductive magnetic heads 15a, 15
Reference numeral b denotes 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 17. . These inductive magnetic heads 15a and 15b are mounted on the rotating drum 13 such that the angle formed between them with respect to the center of the rotating drum 13 is 180 °, and their magnetic gaps protrude from the outer periphery of the rotating drum 13. Have been. The inductive magnetic heads 15a and 15b are set so that the azimuth angles are opposite to each other so that azimuth recording is performed on the magnetic tape 17.

On the other hand, the MR heads 16a and 16b are reproducing magnetic heads having an MR element as a magnetic sensing element for detecting a signal from the magnetic tape 17, and are used when reproducing a signal from the magnetic tape 17. . And these M
The R heads 16a and 16b are mounted on the rotating drum 13 so that the angle formed between them with respect to the center of the rotating drum 13 is 180 °, and the magnetic gap portion protrudes from the outer periphery of the rotating drum. Note that these MR heads 16
A and 16b are set such that the azimuth angles are opposite to each other so that signals recorded in azimuth on the magnetic tape 17 can be reproduced.

The magnetic recording / reproducing apparatus records a signal on the magnetic tape 17 and reproduces a signal from the magnetic tape 17 by sliding the magnetic tape 17 on the rotating drum device 11.

That is, at the time of recording and reproduction,
As shown in FIG. 4, the recording medium is sent from a supply reel 21 through guide rollers 22 and 23 so as to be wound around a rotary drum device 11, and recording and reproduction are performed by the rotary drum device 11. The magnetic tape 17 recorded and reproduced by the rotating drum device 11 is sent to a take-up roll 28 via guide rollers 24 and 25, a capstan 26, and a guide roller 27. That is, the magnetic tape 17 is fed at a predetermined tension and speed by a capstan 26 rotated and driven by a capstan motor 29, and is wound on a winding roll 28 via a guide roller 27.

At this time, the rotary drum 13 is driven to rotate by the motor 14 as shown by the arrow A in FIG. On the other hand, the magnetic tape 17 is sent along the lead guide portion 18 of the fixed drum 12 so as to slide obliquely with respect to the fixed drum 12 and the rotating drum 13. That is, the magnetic tape 17 moves along the tape running direction as shown in FIG.
As shown by the middle arrow B, the fixed drum 12
And the lead guide portion 1 so as to be in sliding contact with the rotating drum 13.
8 and then to the tape exit side as shown by arrow C in FIG.

Next, the internal structure of the rotary drum device 11 will be described with reference to FIG.

As shown in FIG. 5, a rotating shaft 31 is inserted through the center of the fixed drum 12 and the rotating drum 13. The fixed drum 12, the rotating drum 13, and the rotating shaft 31 are made of a conductive material, are electrically connected, and the fixed drum 12 is grounded.

Further, two bearings 32 and 33 are provided inside the sleeve of the fixed drum 12, whereby the rotating shaft 31 is rotatably supported with respect to the fixed drum 12. That is, the rotating shaft 31 is
2, 33, it is rotatably supported with respect to the fixed drum 12. On the other hand, the rotating drum 13 has a flange 34 formed on the inner peripheral portion thereof, and the flange 34 is fixed to the upper end of the rotating shaft 31. Thus, the rotating drum 13 rotates with the rotation of the rotating shaft 31.

A rotary transformer 35, which is a non-contact type signal transmission device, is disposed inside the rotary drum device 11 for transmitting signals between the fixed drum 12 and the rotary drum 13. . This rotary transformer 35
The stator core 36 attached to the fixed drum 12
And a rotor core 37 attached to the rotating drum 13.

The stator core 36 and the rotor core 37 are
A magnetic material such as ferrite is formed in an annular shape around the rotation shaft 31. Also, the stator core 36
Have a pair of inductive magnetic heads 15a and 15a.
b, a pair of signal transmission rings 36a and 36b corresponding to b
A signal transmission ring 36c corresponding to the pair of MR heads 16a and 16b, and a pair of MR heads 16a and 16b.
And a power transmission ring 36d for supplying electric power necessary for driving the power supply are arranged concentrically. Similarly, the rotor core 37 has a pair of inductive magnetic heads 1.
A pair of signal transmission rings 37 corresponding to 5a and 15b
a, 37b; a signal transmission ring 37c corresponding to the pair of MR heads 16a, 16b;
a and a power transmission ring 37d for supplying power required for driving the 16a and 16b are arranged concentrically.

The rings 36a, 36b, 36c,
36d, 37a, 37b, 37c, and 37d are rotating shafts 3
1, each of the rings 36a, 36b, 36c, 3 of the stator core 36.
6d, each ring 37a, 37b, 3 of the rotor core 37.
7c and 37d are arranged to face each other. The rotary transformer 35 includes the rings 36a, 36b, 36c, 36d of the stator core 36,
Each ring 37a, 37b, 37c, 3 of the rotor core 37
Signals and electric power are transmitted in a non-contact manner with 7d.

The rotating drum device 11 is provided with a motor 14 for driving the rotating drum 13 to rotate. The motor 14 includes a rotor 38 as a rotating part,
And a stator 39 which is a fixed portion. Rotor 3
8 is attached to the lower end of the rotating shaft 31 and includes a driving magnet 40. On the other hand, the stator 39
Is attached to the lower end of the fixed drum 12 and has a driving coil 41. And the driving coil 4
By supplying a current to the rotor 1, the rotor 38 is rotationally driven. Accordingly, the rotating shaft 31 attached to the rotor 38 rotates, and accordingly, the rotating drum 13 fixed to the rotating shaft 31 is driven to rotate.

Next, the rotary drum device 11 as described above
Will be described with reference to FIG. 6, which shows a schematic circuit configuration of the rotary drum device 11 and its peripheral circuits.

When recording a signal on the magnetic tape 17 using the rotary drum device 11, first, a current is supplied to the drive coil 41 of the motor 14, whereby the rotary drum 13 is driven to rotate. Then, while the rotating drum 13 is rotating, as shown in FIG.
Is supplied to the recording amplifier 51.

The recording amplifier 51 amplifies a recording signal from the external circuit 50, and when the signal is recorded by one of the inductive magnetic heads 15a, the signal transmission of the stator core 36 corresponding to the inductive magnetic head 15a is performed. Supply the recording signal to the use ring 36a,
At the time of recording a signal by the other inductive magnetic head 15b, a recording signal is supplied to the signal transmission ring 36b of the stator core 36 corresponding to the inductive magnetic head 15b.

Here, as described above, the pair of inductive magnetic heads 15a and 15b
Are arranged so that the angle between them becomes 180 ° with respect to the center of the magnetic recording medium. These inductive magnetic heads 15a and 15b alternately record with a phase difference of 180 °. That is, the recording amplifier 51
The timing at which the recording signal is supplied to one inductive magnetic head 15a and the timing at which the recording signal is supplied to the other inductive magnetic head 15b are 18
Switching is performed alternately with a phase difference of 0 °.

The recording signal supplied to the signal transmission ring 36a of the stator core 36 corresponding to the one inductive magnetic head 15a is transmitted to the signal transmission ring 37a of the rotor core 37 without contact. The recording signal transmitted to the signal transmission ring 37a of the rotor core 37 is supplied to the inductive magnetic head 15a, and the inductive magnetic head 15a records a signal on the magnetic tape 17.

Similarly, the recording signal supplied to the signal transmission ring 36b of the stator core 36 corresponding to the other inductive magnetic head 15b is transmitted to the signal transmission ring 37b of the rotor core 37 without contact. The recording signal transmitted to the signal transmission ring 37b of the rotor core 37 is supplied to the inductive magnetic head 15b, and the inductive magnetic head 15b records a signal on the magnetic tape 17.

When reproducing a signal from the magnetic tape 17 using the rotary drum device 11, first, a current is supplied to the drive coil 41 of the motor 14, whereby the rotary drum 13 is driven to rotate. You. Then, in a state where the rotating drum 13 is rotating, as shown in FIG.
High frequency current is supplied from the oscillator 52 to the power drive 53.
Supplied to

The high-frequency current from the oscillator 52 is converted into a predetermined alternating current by the power drive 53 and then supplied to the power transmission ring 36 d of the stator core 36. The alternating current supplied to the power transmission ring 36d of the stator core 36 is transmitted to the power transmission ring 37d of the rotor core 37 in a non-contact manner. The AC current transmitted to the power transmission ring 37d of the rotor core 37 is rectified by the rectifier 54 to become a DC current, which is supplied to the regulator 55. The DC current is set to a predetermined voltage by the regulator 55.

The current set to a predetermined voltage by the regulator 55 is applied to the pair of MR heads 16a, 1
6b is supplied as a sense current. Note that a pair of MRs
The heads 16a, 16b include the MR heads 16a, 1
A reproduction amplifier 56 for detecting a signal from 6b is connected, and a current from the regulator 55 is also supplied to the reproduction amplifier 56.

Here, each of the MR heads 16a and 16b includes an MR element whose resistance value changes according to the magnitude of an external magnetic field. In the MR heads 16a and 16b, the resistance value of the MR element changes due to the signal magnetic field from the magnetic tape 17, whereby a voltage change appears in the sense current.

The reproducing amplifier 56 detects this voltage change and outputs a signal corresponding to the voltage change as a reproduced signal. The reproducing amplifier 56 outputs a reproduced signal detected by the MR head 16a at the timing of reproducing a signal by one MR head 16a, and outputs the reproduced signal by the other MR head 16b at the timing of reproducing the signal. And outputs a reproduction signal detected by the MR head 16b.

Here, a pair of MR heads 16a, 16b
Are arranged so that the angle between them with respect to the center of the rotating drum 13 is 180 °, as described above, these MR heads 16a and 16b are alternately provided with a phase difference of 180 °. Will be played. That is,
The reproduction amplifier 56 is configured to output a reproduction signal from one of the MR heads 16a and output the reproduction signal from the other MR head 16a.
The timing at which the reproduced signal from b is output is 180 °
Alternately with a phase difference of

The reproduction signal from the reproduction amplifier 56 is supplied to the signal transmission ring 37c of the rotor core 37, and the reproduction signal is transmitted to the signal transmission ring 36c of the stator core 36 without contact. Stator core 36
The reproduction signal transmitted to the signal transmission ring 36c is amplified by the reproduction amplifier 57 and then corrected by the correction circuit 58.
Supplied to Then, the reproduction signal is subjected to predetermined correction processing by the correction circuit 58, and then output to the external circuit 50.

When the circuit configuration is as shown in FIG. 6, a pair of inductive magnetic heads 15a and 15
b, a pair of MR heads 16a and 16b, a rectifier 54, a regulator 55, and a reproducing amplifier 56
3 and rotates together with the rotating drum 13. on the other hand,
Recording amplifier 51, oscillator 52, power drive 5
3. The reproduction amplifier 57 and the correction circuit 58 are disposed on a fixed portion of the rotary drum device 11 or are external circuits configured separately from the rotary drum device 11.

Next, the MR heads 16a and 16b mounted on the rotary drum 13 will be described in detail with reference to FIG. The MR head 16a and the MR head 16b 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 16a and 16b are collectively referred to as the MR head 16.

The MR head 16 is mounted on the rotating drum 13 and is a read-only magnetic head for detecting a signal from the magnetic tape 17 by a helical scan method using a magnetoresistance effect. As shown in FIG. 7, the MR head 16 has a pair of magnetic shields 61 and 62 made of a soft magnetic material such as Ni-Zn polycrystalline ferrite and a pair of magnetic shields 61 and 62 with an insulator 63 interposed therebetween. And a substantially rectangular MR element portion 64 sandwiched between the MR element portions 64. In addition, a pair of terminals is led out from both ends of the MR element section 64, and a sense current can be supplied to the MR element section 64 via these terminals.

The MR element section 64 includes an MR element having a magnetoresistance effect, a SAL (Soft Adjacent Layer) film,
An insulator film disposed between the R element and the SAL film is laminated. MR element has anisotropic magnetoresistance effect (AMR)
, The resistance value of which varies with the magnitude of the external magnetic field
It is made of a soft magnetic material such as i-Fe. SAL membrane is
This 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 is used to insulate the MR element and the SAL film from each other and to prevent electrical shunt loss, and is made of an insulating material such as Ta.

The MR element portion 64 is formed in a substantially rectangular shape, and the pair of magnetic shields 61 and 62 forms an insulator 6 such that one side surface is exposed to the magnetic tape sliding surface 65.
3. Specifically, the MR element portion 64 has a pair of magnetic shields such that the short axis direction is substantially perpendicular to the magnetic tape sliding surface 65 and the long axis direction is substantially orthogonal to the magnetic tape sliding direction. It is sandwiched between insulators 61 and 62 via an insulator 63.

The magnetic tape sliding surface 6 of the MR head 16
5 is cylindrically polished along the sliding direction of the magnetic tape 17 so that one side surface of the MR element portion 64 is exposed on the sliding surface 65 of the magnetic tape, and Cylindrically polished along the direction perpendicular to the direction. As a result, the MR head 16
4 or its vicinity is made to protrude most. In this manner, by making the MR element portion 64 or the vicinity thereof most protrude, the contact characteristics of the MR element portion 64 with the magnetic tape 17 can be improved.

When reproducing a signal from the magnetic tape 17 using the MR head 16 as described above, the magnetic tape 17 is slid on the MR element section 64 as shown in FIG. The arrows in FIG. 8 schematically show how the magnetic tape 17 is magnetized.

Then, the magnetic tape 17 is
While sliding on the element section 64, a sense current is supplied to the MR element section 64 via terminals 64a and 64b connected to both ends of the MR element section 64, and a voltage change of the sense current is detected. Specifically, a predetermined voltage Vc is applied from a terminal 64a connected to one end of the MR element section 64, and a terminal 64b connected to the other end of the MR element section 64.
Is connected to the rotating drum 13. Here, the rotating drum 13 is electrically connected to the fixed drum 12 via the rotating shaft 31, and the fixed drum 12 is grounded. Therefore, one terminal 64 b connected to the MR element section 64 is grounded via the rotating drum 13, the rotating shaft 31 and the fixed drum 12.

When a sense current is supplied to the MR element section 64 while the magnetic tape 17 is slid, the resistance value of the MR element formed on the MR element section 64 changes according to the magnetic field from the magnetic tape 17. Change, resulting in a voltage change in the sense current. Therefore, by detecting the voltage change of the sense current, the signal magnetic field from the magnetic tape 17 is detected, and the signal recorded on the magnetic tape 17 is reproduced.

In the MR head 16 used, M
The MR element formed in the R element section 64 may be any element exhibiting a magnetoresistance effect. For example, a so-called giant magnetoresistance in which a larger magnetoresistance effect is obtained by laminating a plurality of thin films. An effect element (GMR element) can also be used. The method of applying a bias 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, a split element method, Various methods such as a servo bias method can be applied. The giant magnetoresistive effect and various bias methods are described in detail in, for example, "Magnetoresistance Head-Basic and Application Translated by Kazuhiko Hayashi" published by Maruzen Co., Ltd.

[0103]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments to which the present invention is applied will be described in detail based on experimental results.

First, the F used as the magnetic powder in this example was used.
Tables 1 to 5 show the composition, magnetic properties, ionization energy, and the like of the metal magnetic powder containing e. The average ionization energy in the table is the average of the trivalent ionization energies of the nonmagnetic metal elements contained in the magnetic powder.

[0105]

[Table 1]

[0106]

[Table 2]

[0107]

[Table 3]

[0108]

[Table 4]

[0109]

[Table 5]

In the following samples 1 to 41, magnetic tapes were prepared using these various magnetic powders 1 to 41.

Sample 1 First, a magnetic coating material was prepared by weighing, kneading and dispersing each composition according to the following composition.

<Magnetic coating composition> 100 parts by weight of magnetic powder (magnetic powder 1) Binder: 10 parts by weight of polyvinyl chloride resin: 10 parts by weight of polyester polyurethane resin Abrasive: α-Al ₂ O ₃ (average particle size: 0.1%) 3 μm) 5 parts by weight Stearic acid 1 part by weight Methyl ethyl ketone 150 parts by weight Cyclohexanone 150 parts by weight

The polyvinyl chloride resin used was MR-110 manufactured by Zeon Corporation, and the polyester polyurethane used was UR-8200 manufactured by Toyobo.

Next, the magnetic paint prepared as described above was applied on a polyethylene terephthalate film having a thickness of 60 μm using a die coater, subjected to an orientation treatment, and dried to form a magnetic layer. . Furthermore,
Forming a back coat layer on the surface opposite to the surface on which the magnetic layer of the polyethylene terephthalate film is formed,
After a calendering treatment, a hardening treatment was performed, and the resultant was cut into a width of 8 mm to produce a magnetic tape.

Samples 2 to 41 Magnetic tapes were prepared in the same manner as in Sample 1 except that Magnetic Powders 2 to 41 shown in Tables 1 to 5 were used as the magnetic powders.

After assembling the magnetic tape manufactured as described above into a cassette, the magnetic properties of the magnetic recording medium were examined to evaluate the dispersibility of the magnetic powder in the magnetic layer.

The magnetic properties were evaluated by measuring the squareness ratio Rs with a sample vibration magnetometer (manufactured by Toei Kogyo Co., Ltd.), and the dispersibility of the magnetic powder in the magnetic layer was evaluated using the squareness ratio Rs as an index. did.

In order to examine the electromagnetic conversion characteristics of the magnetic recording medium, the relative speed between the magnetic tape and the magnetic head was set to 3.
7.6 MHz at a recording wavelength of 0.5 μm as 8 m / s
After recording the single frequency signal, the reproduction output was measured by the inductive head. Then, the electromagnetic conversion characteristics were evaluated by obtaining a relative value when the reproduction output of the magnetic tape of Sample 1 was set to 0 dB. In addition, 7.6M
The noise ratio of Hz ± 1.0 MHz was evaluated as S / N.

[0119] Also, as described above, 7.
After recording a 6 MHz single frequency signal, the shield type M
The error rate was measured using an R head. In addition,
The element of the MR head used for reproduction was FeNi-AMR.
(Anisotropic magnetoresistance effect element), and the saturation magnetization is 800
emu / cc, film thickness is 40 nm, shielding material is NiZ
n, the distance between the shields is 0.17 μm. The track width is 18 μm and the azimuth angle is 25 °.

First, the magnetic powders 1 to 3 in which the addition amounts of various nonmagnetic metal elements having different trivalent ionization energies were changed.
Regarding Sample 1 to Sample 17 using the magnetic powder 17, the magnetic properties were examined to evaluate the dispersibility of the magnetic powder,
In addition, the electromagnetic conversion characteristics were evaluated. Table 6 shows the above results.

[0121]

[Table 6]

When the magnetic powder 7 containing no Al is used like the sample 7, the desired electromagnetic conversion characteristics cannot be obtained. Further, as in Sample 11, Al was added at an Fe ratio of 20%.
When the magnetic powder 11 containing more than 10% by weight is used, a sufficient reproduction output cannot be obtained.

Further, when a magnetic powder 16 containing K which is a non-magnetic metal element having a trivalent ionization energy exceeding 45 eV as in sample 16 is used, the dispersibility of the magnetic powder is poor, so that a desired electromagnetic conversion is obtained. Characteristics cannot be obtained, and resolution tends to decrease. When a magnetic powder 17 containing V, which is a non-magnetic metal element having a trivalent ionization energy of less than 30 eV, is used as in Sample 17, the desired electromagnetic conversion characteristics are obtained because the magnetic powder has poor dispersibility. It cannot be obtained, and the resolution tends to decrease.

Further, when magnetic powder 1 containing no non-magnetic metal element having a trivalent ionization energy of 30 eV or more and 45 eV or less as in sample 1,
The desired dispersibility of the magnetic powder is so poor that the desired electromagnetic conversion characteristics cannot be obtained. When the magnetic powder 5 and the magnetic powder 13 containing more than 40% by weight of a non-magnetic metal element having a trivalent ionization energy of 30 eV or more and 45 eV or less are used as in Samples 5 and 13. However, a sufficient reproduction output cannot be obtained, and the resolution tends to decrease.

From the above results, it was found that the Fe-containing metal magnetic powder contained Al in an amount of 1.0 wt% or more and 20 wt%
By containing a non-magnetic metal element having a trivalent ionization energy of 30 eV or more and 45 eV or less in an Fe ratio of 1.0 wt% or more and 40 wt% or less, Highly dispersed in the magnetic layer. As a result, the magnetic recording medium has excellent electromagnetic conversion characteristics.

Next, the magnetic powders 18 to 23 obtained by changing the average value of the trivalent ionization energy of the nonmagnetic metal element
For Samples 18 to 23 using the above, the magnetic characteristics were evaluated in order to evaluate the dispersibility of the metal magnetic powder in the same manner as described above, and the electromagnetic conversion characteristics were evaluated. Table 7 shows the above results.

[0127]

[Table 7]

When the magnetic powder 18 having an average value of the trivalent ionization energy of the non-magnetic metal element of less than 30 ev is used as in the sample 18, the dispersibility of the magnetic powder is poor.
Desired electromagnetic conversion characteristics cannot be obtained. Sample 23
As described above, when the magnetic powder 23 having an average value of the trivalent ionization energy of the non-magnetic metal element exceeding 40 eV is used, a sufficient reproduction output cannot be obtained and the resolution tends to decrease.

From the above results, the magnetic powder is highly dispersed in the magnetic layer because the average value of the trivalent ionization energy of the nonmagnetic metal element is in the range of 30 eV to 40 eV. As a result, the magnetic recording medium has excellent electromagnetic conversion characteristics.

Further, by changing the amount of the nonmagnetic metal element added, the magnetic powders 24 to
With respect to Samples 24 to 29 using the magnetic powder 29, the magnetic characteristics were examined in order to evaluate the dispersibility of the metal magnetic powder in the same manner as described above, and the electromagnetic conversion characteristics were evaluated.
Table 8 shows the above results.

[0131]

[Table 8]

When the magnetic powder 24 having a large isoelectric point is used as in the sample 24, the dispersibility of the magnetic powder is poor.
Also, the resolution tends to decrease. Sample 29
As described above, when the magnetic powder 29 having a small isoelectric point is used, a sufficient reproduction output cannot be obtained.

From the above results, the magnetic powder is highly dispersed in the magnetic layer when the isoelectric point in zeta potential measurement is in the range of 7 or more and 11 or less. As a result, the magnetic recording medium has excellent electromagnetic conversion characteristics.

Further, the residual magnetization Mr of the magnetic layer and the film thickness δ
For samples 30 to 33 in which the value of the product Mr · δ was changed, the magnetic characteristics were examined in the same manner as described above, and the electromagnetic conversion characteristics were evaluated. Table 9 shows the above results. As the magnetic powder, magnetic powders 30 to 33 were used.

[0135]

[Table 9]

When Mr · δ is small as in the sample 32, there is a possibility that a sufficient reproduction output cannot be obtained. On the other hand, when Mr · δ is large as in the sample 33, the MR element is saturated, the reproduced waveform is distorted, and the error rate is deteriorated.
Therefore, Mr · δ is 0.8 to 6.5 memu /
It is preferably in the range of cm ² .

The samples 34 to 41 using the magnetic powders 34 to 41 in which the X-ray crystal particle diameter Dx, the major axis length, and the saturation magnetization (σs) of the magnetic powders are changed are as follows.
In the same manner as described above, the magnetic properties were examined to evaluate the dispersibility of the magnetic powder, and the electromagnetic conversion properties were evaluated. Table 10 shows the above results.

[0138]

[Table 10]

As in Sample 37, the saturation magnetization is 80
In the case where the magnetic powder 37 of less than emu / g is used, a sufficient reproduction output cannot be obtained.

When a magnetic powder 38 having an X-ray crystal grain size Dx of more than 200 ° is used as in the case of the sample 38, noise increases and electromagnetic conversion characteristics deteriorate. On the other hand, when a magnetic powder 39 having an X-ray crystal grain size Dx of less than 50 ° is used as in the case of the sample 39, the electromagnetic conversion characteristics are deteriorated. Therefore, the X-ray crystal grain size Dx of the metal magnetic powder is 50 ° to 20 °.
It is preferable that the angle is in the range of 0 °.

Further, when a magnetic powder 40 having a major axis length of more than 0.15 μm is used as in the case of the sample 40, noise increases and electromagnetic conversion characteristics deteriorate. On the other hand, when the magnetic powder 41 having a major axis length of less than 0.01 μm is used as in the case of the sample 41, the electromagnetic conversion characteristics are significantly deteriorated.
Therefore, the major axis length of the metal magnetic powder is 0.01 μm to 0.1 μm.
It is preferable that the thickness be in the range of 15 μm.

As a method of controlling the isoelectric point in the zeta potential measurement of the metal magnetic powder, other than a method of changing the amount of the non-magnetic metal element added, a method of adjusting the reduction temperature at the time of preparing the magnetic powder is used. In addition, a method of changing the crystallinity of the surface of the magnetic powder may be used. Here, the magnetic powder 42 to the magnetic powder 46 in which the reduction temperature was changed when producing the magnetic powder was used.
Table 11 shows the composition, magnetic properties, ionization energy, and the like of No.

[0143]

[Table 11]

As is clear from Table 11, when the reduction temperature was changed while the composition of the magnetic powder was the same, it was found that the higher the reduction temperature, the higher the isoelectric point in the zeta potential measurement.

Samples 42 to 46 Magnetic tapes were prepared in the same manner as in Sample 1, except that the magnetic powders 42 to 46 shown in Table 11 were used as the magnetic powders.

With respect to 42 to 46, the magnetic characteristics were evaluated in order to evaluate the dispersibility of the magnetic powder in the same manner as described above, and the electromagnetic conversion characteristics were evaluated. Table 1 shows the above results.
It is shown in FIG.

[0147]

[Table 12]

Even if the reduction temperature at the time of preparing the metal magnetic powder was changed, samples 43 to 46 using magnetic powders 43 to 46 having an isoelectric point in the range of 7 to 11 in zeta potential measurement were used. No. 46 was found to be excellent in electromagnetic conversion characteristics.

On the other hand, in the sample 42 using the magnetic powder 42 in which the average value of the trivalent ionization energy of the non-magnetic metal element is less than 30 ev, the dispersibility of the magnetic powder is poor, and the desired electromagnetic conversion characteristics cannot be obtained. .

[0150]

As is clear from the above description, the magnetic powder according to the present invention contains Fe, and Al is contained in a ratio of 1: 1.
0% by weight or more and 20% by weight or less;
Since at least one kind of nonmagnetic metal elements having a valence ionization energy of 30 eV or more and 45 eV or less is contained at a Fe ratio of 1.0% by weight or more and 40% by weight or less, the magnetic layer Excellent dispersibility.

Accordingly, the magnetic recording medium containing this magnetic powder has improved surface smoothness of the magnetic layer and excellent electromagnetic conversion characteristics. In particular, an unprecedented high-density recording system can be constructed by using it as a magnetic recording medium of a helical scan magnetic recording system using a shield type MR reproducing head.

The magnetic powder according to the present invention contains Fe, contains at least one kind of nonmagnetic metal element, and has an average trivalent ionization energy of the nonmagnetic metal element of 30 eV or more and 40 eV or less. Is excellent in dispersibility in the magnetic layer.

Therefore, the magnetic recording medium containing this magnetic powder has improved surface smoothness of the magnetic layer and excellent electromagnetic conversion characteristics. In particular, an unprecedented high-density recording system can be constructed by using it as a magnetic recording medium of a helical scan magnetic recording system using a shield type MR reproducing head.

Furthermore, the magnetic powder according to the present invention contains Fe, and has an isoelectric point in the range of 7 or more and 11 or less in zeta potential measurement, so that the magnetic layer is excellent in dispersibility.

Therefore, the magnetic recording medium containing this magnetic powder has improved surface smoothness of the magnetic layer and excellent electromagnetic conversion characteristics. In particular, an unprecedented high-density recording system can be constructed by using it as a magnetic recording medium of a helical scan magnetic recording system using a shield type MR reproducing head.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing one configuration example of a magnetic recording medium.

FIG. 2 is a characteristic diagram showing a relationship between dispersibility and volume of a magnetic powder.

FIG. 3 shows a configuration example of a rotating drum device mounted on a magnetic recording / reproducing device of a helical scan magnetic recording system.
It is a perspective view showing the outline.

FIG. 4 is a plan view schematically showing a configuration example of a magnetic tape feed mechanism including the rotary drum device.

FIG. 5 is a sectional view showing an internal structure of the rotary drum device.

FIG. 6 is a circuit diagram schematically showing a circuit configuration of the rotary drum device and its peripheral circuits.

FIG. 7 is a perspective view, partially cut away, of an example of an MR head mounted on the rotary drum.

FIG. 8 is a schematic diagram schematically showing how a signal from a magnetic tape is reproduced using an MR head.

[Explanation of symbols]

 1 magnetic recording medium, 2 non-magnetic support, 3 magnetic layer

Claims (17)

[Claims] 1. A magnetic powder containing Fe, wherein Al is contained at a ratio of not less than 1.0% by weight and not more than 20% by weight in terms of Fe ratio, and trivalent ionization energy is 30 eV.
As described above, at least one kind of the non-magnetic metal elements having a range of 45 eV or less is not less than 1.0% by weight in Fe ratio,
A magnetic powder, which is contained in a proportion of 40% by weight or less. 2. The Fe-containing magnetic powder contains at least one or more non-magnetic metal elements, and the non-magnetic metal element has an average trivalent ionization energy of 3
A magnetic powder having a range of 0 ev or more and 40 eV or less. 3. A magnetic powder containing Fe, wherein an isoelectric point in zeta potential measurement is in a range of 7 or more and 11 or less. 4. A magnetic recording medium comprising a magnetic layer coated with a magnetic paint containing Fe-containing magnetic powder and a non-magnetic support, wherein the magnetic powder contains Al in an Fe ratio of 1.0%. Weight% or more, 2
0% by weight or less, and at least one non-magnetic metal element having a trivalent ionization energy of 30 eV or more and 45 eV or less is contained in an Fe ratio of 1.0% by weight or more and 40% by weight or less. % Of the magnetic recording medium. 5. The magnetic recording medium according to claim 4, wherein a value of a product Mr · δ of the residual magnetization amount Mr and the film thickness δ of the magnetic layer is 0.8 to 6.5 memu / cm ^2. . 6. The magnetic recording medium according to claim 4, wherein the coercive force in the in-plane direction is 1400 Oe or more. 7. The magnetic recording medium according to claim 4, wherein the magnetic recording medium is used in a helical scan magnetic recording system using a magnetoresistive read head. 8. The magnetic recording medium according to claim 4, wherein the magnetic powder has an isoelectric point in the range of 7 to 11 in zeta potential measurement. 9. A magnetic recording medium comprising a magnetic layer coated with a magnetic paint containing Fe-containing magnetic powder, and a non-magnetic support, wherein the magnetic powder comprises at least one of non-magnetic metal elements. A magnetic recording medium containing at least three types of nonmagnetic metal elements, wherein the average value of the trivalent ionization energies of the nonmagnetic metal element is in the range of 30 eV to 40 eV. 10. The residual magnetization Mr and the film thickness δ of the magnetic layer.
10. The magnetic recording medium according to claim 9, wherein the value of the product Mr · δ is 0.8 to 6.5 memu / cm ² . 11. The magnetic recording medium according to claim 9, wherein the coercive force in the in-plane direction is 1400 Oe or more. 12. The magnetic recording medium according to claim 9, wherein the magnetic recording medium is used in a helical scan magnetic recording system using a magnetoresistive read head. 13. The magnetic recording medium according to claim 9, wherein said magnetic powder has an isoelectric point in the range of 7 to 11 in zeta potential measurement. 14. A magnetic recording medium comprising a magnetic layer coated with a magnetic paint containing Fe-containing magnetic powder and a non-magnetic support, wherein the magnetic powder has an isoelectric point in zeta potential measurement. Is 7 or more,
A magnetic recording medium having a range of 11 or less. 15. A remanent magnetization Mr and a film thickness δ of the magnetic layer.
15. The magnetic recording medium according to claim 14, wherein the value of the product Mr · δ is 0.8 to 6.5 memu / cm ² . 16. The magnetic recording medium according to claim 14, wherein a coercive force in an in-plane direction is 1400 Oe or more. 17. The magnetic recording medium according to claim 14, wherein the magnetic recording medium is used for a helical scan magnetic recording system using a magnetoresistive read head.