JPH06274847A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic conversion characteristics by essentially forming ferromagnetic powder of ferromagnetic hexagonal system ferrite and specifying the thickness thereof and the relations between the coercive forces in longitudinal, perpendicular and transverse directions at the time of providing a magnetic layer consisting of ferromagnetic powder and a binder on the nonmagnetic base. CONSTITUTION:The thickness of the magnetic layer is confined to <=1mum. Further, the relations between the coercive force in the longitudinal direction, designated as Hc1, the coercive force in the perpendicular direction as Hc2 and the coercive force in the transverse direction as Hc3 are specified to Hc1>Hc2>Hc3. The magnetic layer is formed of two layers by providing a nonmagnetic layer consisting essentially of nonmagnetic powder and a binder between the magnetic layer and a nonmagnetic base and providing the first magnetic layer consisting essentially of the acicular ferromagnetic powder and a binder under the magnetic layer. High outputs are obtd. even in a wide recording wavelength region from a low to a high-region if the recording medium is formed in such a manner. The recording in the longitudinal direction is made easy in the lower part of the magnetic layer and the recording in the perpendicular direction in the upper part by the influence of the magnetic field distribution of the head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high density recording having a thin magnetic layer mainly composed of ferromagnetic hexagonal ferrite in which ferromagnetic powder is magnetically oriented in the in-plane direction of the magnetic layer. It relates to a magnetic medium.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium such as a video tape, an audio tape, a magnetic disk, etc., ferromagnetic iron oxide, ferromagnetic Co-modified iron oxide, CrO ₂ , ferromagnetic alloy powder and the like are contained in a binder. A non-magnetic support coated with a dispersed magnetic layer has been widely used. However, since these magnetic powders are generally needle-shaped and magnetized in the longitudinal direction, there is a problem that self-demagnetization becomes large and sufficient output cannot be obtained in short wavelength recording which is required today.

In JP-A-61-217936 and JP-A-61-273735, a ferromagnetic hexagonal ferrite having a plate-like particle shape and an easy axis of magnetization in a direction perpendicular to the plate surface is used. Another magnetic recording medium has been proposed. However, since the ferromagnetic hexagonal ferrite is inferior in dispersibility, the surface is roughened as it is and the space loss becomes large, so that a sufficient output cannot be obtained.

Further, it is possible to further reduce the self-demagnetization by orienting the ferromagnetic hexagonal ferrite in a direction perpendicular to the magnetic layer surface, as disclosed in JP-A-4-12312 and JP-A-62-208415. It is described in the official gazette. However, this method does not provide sufficient short-wavelength output, and since ferromagnetic hexagonal ferrite has a small saturation magnetization, there is a problem in that long-wavelength output is low particularly when vertically oriented.

On the other hand, many attempts have been made in the past to provide two or more magnetic layers to obtain signals with different recording wavelengths at high outputs. For example, Japanese Patent Publication Sho 37-2
I have no time to list 218 bulletins. This is Hc in the upper and lower layers,
In many cases, magnetic materials having different Bm, particle morphology, and particle size are arranged for the purpose of high output and high C / N. In a magnetic recording medium having two or more magnetic layers, an example in which a ferromagnetic hexagonal ferrite is used as an upper layer is disclosed in JP-A-60-22301.
Japanese Patent Laid-Open Publication No. Sho 60-86, as an example in which the easy axis of magnetization of the upper ferromagnetic hexagonal ferrite is oriented in the in-plane vertical direction.
-212817, Japanese Patent Application Laid-Open No. 1-251427, Japanese Patent Application Laid-Open No. 1-251424, Japanese Patent Application Laid-Open No. 1-251
426, JP-A-59-129935, JP-A-64-79930, JP-A-64-55732, and JP-A-59-77628. However, since a magnetic material is used for the lower layer, it does not have a good surface property, and the surface is rough and the thickness of the lower layer is large. There wasn't.

It has been attempted to reduce the thickness of the magnetic layer by paying attention to the fact that if the thickness of the magnetic layer is large, the problems of self-demagnetization loss during recording and thickness loss during reproduction are increased. When the layer is thinned to about 2 μm or less, the influence of the nonmagnetic support is likely to appear on the surface of the magnetic layer, and the electromagnetic conversion characteristics are deteriorated. For this reason, it is known that a nonmagnetic thick undercoat layer is provided on the surface of a support and then the magnetic layer is provided as an upper layer.
No. 536 and Japanese Patent Application Laid-Open No. 63-191315, the thin coating of the magnetic layer causes coating defects, resulting in poor yield. As a method for solving this, JP-A-63
As described in JP-A-191315 and JP-A-63-187418, there is a method of providing a non-magnetic layer as a lower layer by using a simultaneous multilayer coating method. However, the characteristics are not sufficient for today's high density recording media.

On the other hand, a method has been proposed which pays attention to the direction dependence of the magnetic characteristics of the magnetic layer containing the ferromagnetic hexagonal ferrite. For example, in Japanese Unexamined Patent Publication No. Sho 62-1113, the squareness ratio in the in-plane direction and in the direction perpendicular to that in Japanese Unexamined Patent Publication No. Sho 64-79927 are used.
In Japanese Patent Application Laid-Open No. 4-109425, the difference between the vertical coercive force and in-plane coercive force, in the directionality of the residual magnetic flux density, and in Japanese Patent Application Laid-Open No. 58-6525, the squareness ratio in the vertical direction. Japanese Patent Application Laid-Open No. 62-109226 discloses a magnetic recording medium focused on the squareness ratio and the coercive force in the vertical direction.

However, although these examples have the effect of improving the signal output of a specific recording wavelength, they have no effect of improving the output over the entire frequency range. On the other hand, Japanese Patent Application Laid-Open No. 3-280215 discloses a technique focusing on the residual magnetic flux density in the longitudinal direction, the vertical direction, and the width direction in order to improve the output over the entire frequency range. However, even with these methods, 0.5 μ will be required in the future.
Sufficient characteristics could not be obtained in the recording wavelength region of m or less.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium having a good electromagnetic conversion characteristic and having a high characteristic in a wide recording wavelength range from a short wavelength signal to a long wavelength signal.

[0010]

DISCLOSURE OF THE INVENTION As a result of study by the present inventors by paying attention to the layer structure having good electromagnetic conversion characteristics, the physical characteristics of a magnetic substance contained therein, and the physical characteristics of a magnetic layer, It came to do.

That is, the above object of the present invention is to provide a magnetic recording medium in which a magnetic layer mainly containing a ferromagnetic powder and a binder is provided on a non-magnetic support, the ferromagnetic powder being a ferromagnetic hexagonal ferrite. The magnetic layer has a thickness of 1 μm or less, and the coercive force in the longitudinal direction of the magnetic layer is Hc ₁ , the coercive force in the vertical direction is Hc ₂ , and the coercive force in the width direction is Hc.
When c ₃ is set, the coercive force relationship is Hc ₁ > Hc ₂ > Hc
It is achieved by a magnetic recording medium, which is a _3.

In order to achieve the above object of the present invention more effectively, a non-magnetic layer containing a non-magnetic powder and a binder as a main component is provided between the magnetic layer and the non-magnetic support, and a comparison is made. A magnetic recording medium having at least two layers in which a non-magnetic layer is provided under a relatively thin magnetic layer, and a first magnetic layer mainly containing acicular ferromagnetic powder and a binder is provided under the magnetic layer. A magnetic recording medium comprising at least two magnetic layers provided, and a magnetic recording medium further comprising a non-magnetic layer below the first magnetic layer, at least two layers of the non-magnetic layer and the magnetic layer Is preferably a magnetic recording medium formed by a wet-on-wet coating method.

The magnetic recording medium of the present invention is a magnetic layer in which hexagonal ferrite is used as a ferromagnetic powder, and the ferromagnetic powder is magnetically oriented in the in-plane direction of the magnetic layer, and The main feature is that the relationship of the coercive force in the three directions of the direction, the vertical direction, and the width direction is specified as described above, and at the same time, the magnetic layer has a thin thickness of 1 μm. The longitudinal direction as used herein means the direction in which the medium runs, the vertical direction means the direction perpendicular to the magnetic layer surface, and the width direction means the running direction of the medium. It is a direction in the plane of the magnetic layer that is perpendicular.

With the above structure, the magnetic recording medium of the present invention can obtain a high output in a wide recording wavelength range from a low range to a high range. The reason why the magnetic recording medium of the present invention exhibits excellent electromagnetic conversion characteristics is not clear, but it is considered as follows. When a signal is recorded on a magnetic recording medium by a ring head, the lower part of the magnetic layer is easily recorded in the longitudinal direction and the upper part of the magnetic layer is easily recorded in the vertical direction due to the influence of the head magnetic field distribution. Therefore, in the magnetization inside the magnetic layer, both the longitudinal magnetization component and the perpendicular magnetization component contribute to the reproduction output. However, since the ring head has a greater effect on the reproduction output of the longitudinal magnetization component, the reproduction output is improved when the residual magnetic flux density in the longitudinal direction is higher than the residual magnetic flux density in the vertical direction as disclosed in Japanese Patent Laid-Open No. 3-280215. Is predicted. However, when the recording signal has a short wavelength, the output is significantly reduced. As a result of examining the cause, it was found that the directionality of the coercive force has a greater influence than the directionality of the residual magnetic flux of the magnetic layer. When a short-wavelength signal is recorded, a strong demagnetizing field acts in the longitudinal direction, which becomes more prominent as the residual magnetic flux is larger, and it is considered that the reproduction output is significantly reduced. On the other hand, since the demagnetizing field in the vertical direction is relatively weak, it is not necessary to increase the coercive force. Rather, since the head magnetic field strength in the vertical direction is weak, if the coercive force is set too high, recording by the head tends to be insufficient. Since the magnetization component in the width direction does not contribute to the reproduction output at all, it is necessary to minimize it.

In the present invention, when viewed from three directions with respect to the magnetic layer.
The coercive force of the
The relationship between the residual magnetic flux density (Br) and
Degree Br₁, The residual magnetic flux density in the vertical direction Br₂, Widthwise residual
Magnetic flux density Br₃Is Br₁> Br ₂> Br₃To have a relationship
Is desirable. Where Br₂Is the value after diamagnetic field correction
It

The relationship of the coercive force of the magnetic layer mainly composed of hexagonal ferrite in the magnetic recording medium of the present invention is H
c ₁ > Hc ₂ > Hc ₃ . This relationship is, for example, Hc ₁
If it breaks, such as> Hc ₃ > Hc ₂ , it is not preferable because the decrease in output at the recording wavelength near 0.5 μm becomes large. Further, the desirable range of the coercive force is Hc ₁ is 1
000-4000 Oe, Hc ₂ is 800-3200
Oe, and Hc ₃ is 500 to 2000 Oe.

In the magnetic recording medium of the present invention, there are various methods for setting the coercive force relationship of the magnetic layer mainly composed of hexagonal ferrite as described above. For example, 1) crystal anisotropy Use a strong magnetic material. 2) Use a magnetic material having a weak shape anisotropy. 3) Use a magnetic material having a small plate ratio. 4) After being oriented in the vertical direction, it is oriented in the longitudinal direction with a stronger magnetic field. 5) Determine the amount and temperature of the drying air inside the magnet so that the coating film will dry near the exit of the longitudinally oriented magnet zone. That is, the coercive force is adjusted by using the above methods alone or in combination.

Specifically, in the above method 1),
The crystallinity is improved by reducing the amount of impurities and substitutional elements contained in the ferromagnetic powder particles, and by the method of 2) above, the shape anisotropy is reduced by shortening the length in the easy magnetization axis direction. can do. A large amount of coercive force can be obtained due to the large crystal anisotropy, and a weak magnetization component distributed in the width direction can be suppressed by weakening the shape anisotropy. In the method of 3) above, it becomes easier to arrange in the longitudinal direction than in the vertical direction in terms of shape, and in the method of 4) above, 1
The coercive force relationship of the present invention is obtained by vertically orienting with a heteropolar opposing magnet having a relatively weak magnetic field of 000 to 2000 G (Gauss) and then longitudinally orienting with a strong homopolar opposing magnet or solenoid of 5000 G or more. Can be formed. 5) above
In the above method, Hc ₁ can be increased and Hc ₃ can be decreased by passing a dry air of 60 ° C. or higher through the magnet zone for longitudinal orientation and allowing it to stay therein for 1 second or longer. A magnetic recording medium can be obtained. In order to achieve the object of the present invention, it is desirable to employ at least two means of the above method. In particular, the method 4) is most preferable from the viewpoint that the arrangement of the ferromagnetic powder particles in the width direction is prevented and the arrangement of the ferromagnetic powder particles in the longitudinal direction is highly effective.

The thickness of the magnetic layer containing ferromagnetic hexagonal ferrite in the magnetic recording medium of the present invention is 1 μm or less, preferably 0.01 μm or more,
It is 0.5 μm or less. If the thickness of the magnetic layer is too large, the surface property of the magnetic layer deteriorates, which is a problem. Also,
If the thickness of the magnetic layer becomes too thin, defects will occur in the coating film, so be careful, but regarding the lower limit of the thickness of the magnetic layer,
It cannot be decided unconditionally because it varies greatly depending on the coating method.

Further, in the magnetic recording medium of the present invention, by providing the first magnetic layer mainly composed of acicular ferromagnetic powder under the second magnetic layer mainly composed of hexagonal ferrite, a long wavelength region is provided. Output is improved, and the object of the present invention can be achieved more effectively. Furthermore, by providing a non-magnetic layer between the magnetic layer and the non-magnetic support in the magnetic recording medium of the present invention, furthermore, between the magnetic layer and the non-magnetic support in the magnetic recording medium of the present invention. By providing the non-magnetic layer, the surface property of the magnetic layer can be improved, which is even more preferable. As described above, in the magnetic recording medium of the present invention, the main constituent element is the coercive force of the magnetic layer mainly composed of the hexagonal ferrite and having a thickness of 1 μm or less. The coating method for further coating the magnetic layer on the non-magnetic layer or the first magnetic layer is a so-called wet-on-wet method in which the upper coating solution is applied while the lower coating layer is still in a wet state. Is preferred. By forming each layer by this coating method, a magnetic layer having a uniform structure with few defects as a coating film can be formed, so that the object of the present invention can be achieved more effectively.

In the magnetic layer mainly composed of ferromagnetic hexagonal ferrite in the magnetic recording medium of the present invention, it is preferable that at least 50% by weight of the ferromagnetic powder is ferromagnetic hexagonal ferrite. If the amount of the ferromagnetic hexagonal ferrite is less than 50% by weight, the number of ferromagnetic powder particles arranged in the width direction increases, and the object of the present invention cannot be sufficiently achieved.

As the ferromagnetic hexagonal ferrite in the magnetic recording medium of the present invention, hexagonal Co powders such as barium ferrite, strontium ferrite, lead ferrite, calcium ferrite substitutes, and Co substitutes can be used. Specific examples include magnetoplumbite-type barium ferrite and strontium ferrite, and further magnetoplumbite-type barium ferrite and strontium ferrite containing a part of a spinel phase. In addition to other predetermined atoms, Al, Si, S, Sc, T
i, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, S
n, Sb, Te, Ba, Ta, W, Re, Au, Hg,
Pb, Bi, La, Ce, Pr, Nd, P, Co, M
Atoms such as n, Zn, Ni, Sr, B, Ge and Nb may be included. Generally, Co-Ti, Co-Ti-
Zr, Co-Ti-Zn, Ni-Ti-Zn, Ir-Z
It is possible to use those to which an element such as n is added,
Particularly desirable are Co substitution products of barium ferrite and strontium ferrite. When the SFD of the uppermost layer in the longitudinal direction is 0.3 or less, the distribution of coercive force becomes small, which is preferable. In order to control the coercive force, the particle diameter and particle thickness are made uniform, the thickness of the spinel phase of the ferromagnetic hexagonal ferrite is made constant, the amount of substitution elements of the spinel phase is made constant, the spinel phase There is a method such as making the place of the replacement site constant. The ferromagnetic hexagonal ferrite used in the present invention is usually hexagonal plate-like particles, and the particle diameter means the plate width of the hexagonal plate-like particles and is measured by using an electron microscope. In the present invention, the particle diameter (plate diameter) is 0.01
To 0.2 μm, particularly preferably 0.03 to 0.1 μm. The average thickness (plate thickness) of the fine particles is 0.001 to 0.2 μm, but especially 0.0
03-0.05 μm is desirable. Furthermore, the plate ratio (particle size /
The plate thickness) is 1 to 15, and preferably 3 to 7. The specific surface area (SBET) of these ferromagnetic hexagonal ferrite fine powders by the BET method is 25 to 100 m2 / g, 40
~ 70 m2 / g is desirable. When it is 25 m ² / g or less, noise becomes high, and when it is 100 m ² / g or more, the surface property is difficult to obtain, which is not desirable. The coercive force of magnetic material is 1000 Oe or more, 400
It is preferably 0 Oe or less, more preferably 1200 Oe or more 3
It is less than 000 Oe. When it is 1000 Oe or less, the short wavelength output is lowered, and when it is 4000 Oe or more, recording by the head is difficult and it is not preferable. σs is 50 emu / g or more, preferably 60 emu / g or more. Tap density is 0.5g /
It is preferably cc or more, more preferably 0.8 g / cc or more. The Br of the layer containing the ferromagnetic hexagonal ferrite is preferably 1000 G (Gauss) or more and 2500 G or less in the longitudinal direction, 500 G or more and 2000 G or less in the vertical direction after demagnetizing field correction, and 1000 G or less in the width direction. The squareness ratio is 0.6 or more and 0.95 or less in the longitudinal direction, 0.2 or more and 0.6 or less in the value obtained by demagnetizing field correction in the vertical direction, and 0.4 in the width direction.
The following is desirable.

In the magnetic recording medium of the present invention, when the first magnetic layer mainly composed of needle-like ferromagnetic powder is provided below the magnetic layer mainly composed of ferromagnetic hexagonal ferrite, the needle-like ferromagnetic The powder is preferably metallic ferromagnetic fine powder or cobalt-modified iron oxide. The acicular ratio of the acicular ferromagnetic powder is 2 to 20, preferably 4 to 12, and more preferably 6 to 12.

The acicular ferromagnetic powder used in the first magnetic layer of the magnetic recording medium of the present invention is γ-FeOx.
(X = 1.33 to 1.5), Co-modified γ-FeOx (x
= 1.33 to 1.5), a known ferromagnetic powder such as a ferromagnetic alloy fine powder containing Fe, Ni or Co as a main component (75% or more), acicular barium ferrite, etc. and having an acicular ratio of 2 to
Although those having a content of 20 can be used, a ferromagnetic alloy powder containing α-Fe as a main component or Co-modified γ-FeOx is preferable, and the acicular ratio is preferably 4 to 12. In addition to predetermined atoms, these ferromagnetic powders include Al, Si, S, Sc, Ti,
V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn,
Sb, Te, Ba, Ta, W, Re, Au, Hg, P
b, Bi, La, Ce, Pr, Nd, P, Co, Mn,
It may contain atoms such as Zn, Ni, Sr, B, Ge and Nb. These ferromagnetic fine powders may be previously treated with a dispersant, a lubricant, a surfactant, an antistatic agent, etc., which will be described later, before dispersion. In particular,
Japanese Patent Publication No. 44-14090, Japanese Patent Publication No. 45-1837
No. 2, JP-B-47-22062, JP-B-47
-22513, Japanese Patent Publication No. 46-28466,
Japanese Patent Publication No. 46-38755, Japanese Patent Publication No. 47-4286
Publication, Japanese Patent Publication No. 47-12422, Japanese Patent Publication No. 47-42
17284, Japanese Patent Publication No. 47-18509, Japanese Patent Publication No. 47-18573, and Japanese Patent Publication No. 39-10307.
Japanese Patent Publication No. 48-39639, US Patent No. 30
No. 26215, No. 3031341, and No. 310.
No. 0194, No. 3242005, No. 3389
No. 014 publication and the like.

The ferromagnetic alloy fine powder exemplified above may contain a small amount of hydroxide or oxide. What was obtained by the well-known manufacturing method of a ferromagnetic alloy fine powder can be used, and the following method can be mentioned. A method of reducing a complex organic acid salt (mainly oxalate) and a reducing gas such as hydrogen, a method of reducing iron oxide with a reducing gas such as hydrogen to obtain Fe or Fe—Co particles, a metal carbonyl compound Pyrolysis method, reduction method by adding reducing agent such as sodium borohydride, hypophosphite or hydrazine to an aqueous solution of ferromagnetic metal, evaporation of metal in a low pressure inert gas to form fine powder. How to get it. The ferromagnetic alloy powder thus obtained is subjected to a known gradual oxidation treatment, that is, a method of immersing it in an organic solvent and then drying it, and after dipping it in an organic solvent and feeding an oxygen-containing gas to form an oxide film on the surface. How to dry,
Any of the methods of adjusting the partial pressures of oxygen gas and inert gas to form an oxide film on the surface without using an organic solvent can be used. When the magnetic particles of the first magnetic layer of the present invention are represented by the specific surface area by the BET method, they are 25 to 80 m ^2.
/ G, and preferably 40 to 70 m ² / g. Two
When it is 5 m ² / g or less, noise becomes high, and when it is 80 m ² / g or more, it is difficult to obtain the surface property, which is not desirable. Σ of iron oxide magnetic powder
s is 50 emu / g or more, preferably 70 emu / g or more, and 100 emu / g in the case of ferromagnetic metal fine powder.
g or more is desirable, more preferably 110 emu / g
~ 170 emu / g. Coercive force is 500 Oe or more, 2
It is preferably 500 Oe or less, and more preferably 800 Oe or more and 2000 Oe or less. The tap density of γ iron oxide is 0.5
It is preferably g / cc or more, more preferably 0.8 g / cc or more. In the case of alloy powder, 0.2 to 0.8 g / cc is desirable, and if it is used in an amount of 0.8 g / cc or more, oxidation easily proceeds in the compaction process of the magnetic material, and it becomes difficult to obtain sufficient σ S. If it is 0.2 cc / g or less, the dispersion tends to be insufficient. When using gamma iron oxide, the ratio of divalent iron to trivalent iron is preferably 0 to 20%, more preferably 5 to 10%. The amount of cobalt atoms to iron atoms is 0 to 15%, preferably 2 to 8%.

The other desirable characteristics of the magnetic particles contained in the first magnetic layer and the second magnetic layer of the present invention are as follows. The crystallite size is 450 to 50 angstroms, preferably 350 to 100 angstroms.
It is. It is desirable that r1500 of the magnetic material be 1.5 or less. More preferably, r1500 is 1.0 or less. The r1500 indicates the percentage of the amount of magnetization remaining without being reversed when a magnetic field of 1500 Oe is applied in the opposite direction after saturation magnetization of the magnetic recording medium. The water content of the magnetic material is preferably 0.01 to 2%. It is desirable to optimize the water content of the magnetic material depending on the type of binder. It is desirable to optimize the pH of the magnetic substance depending on the combination with the binder used. The range is 4-12,
It is preferably 6 to 10. A magnetic material can be
The surface treatment may be performed with l, Si, P or an oxide thereof. Desirably Al ₂ O ₃ or SiO ₂
It is desirable to change the amount and ratio depending on the binder used. The amount thereof is 0.1 to 10% with respect to the magnetic substance, and when the surface treatment is performed, the adsorption of the lubricant such as fatty acid becomes 100 mg / m ² or less, which is desirable. The magnetic substance may contain soluble inorganic ions such as Na, Ca, Fe, Ni, and Sr, but if it is 500 ppm or less, the characteristics are not particularly affected. The magnetic material used in the present invention preferably has a small number of voids, and the value thereof is 20% by volume or less, more preferably 5% by volume or less.

In the magnetic recording medium of the present invention, the first magnetic layer preferably has a longitudinal orientation higher than a vertical orientation. Longitudinal coercive force is 500 Oe or more, 2
500 Oe or less, squareness ratio 0.6 or more, 0.95 or less,
Br is 1000 G or more and 4000 G or less, and SFD is 0.
It is preferably 6 or less. The coercive force in the vertical direction is 300 Oe or more and 2000 Oe or less, the squareness ratio is 0.6 or less, and Br is 1
500 G or less, and SFD is preferably 3 or less.

The non-magnetic layer formed below the magnetic layer in the magnetic recording medium of the present invention is mainly composed of non-magnetic powder and a binder. As the non-magnetic powder, various kinds of inorganic non-magnetic powder particles and organic powder particles can be used. Above all, it is desirable that the non-magnetic powder is at least one selected from titanium dioxide, barium sulfate, zinc oxide, and α-iron oxide as described in detail below. The thickness of the non-magnetic layer is not particularly limited, but from the viewpoint of masking irregularities on the surface of the underlying non-magnetic support to improve surface properties, it is 0.2 to 5 μm, preferably 1 μm. ~ 3μ
m.

The non-magnetic powder can be selected from inorganic compounds such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides and metal sulfides.
Examples of the inorganic compound include α-alumina, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide having an α-conversion rate of 90% or more. Silicon dioxide, tin oxide, magnesium oxide, tank oxide, strontium oxide, silicon oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate,
Barium sulfate, molybdenum sulfide and the like are used alone or in combination. Particularly preferred are titanium dioxide, zinc oxide, iron oxide and barium sulfate, and more preferred is titanium dioxide. The particle size of these non-magnetic powders is preferably 0.005 to 2 μm, but if necessary, non-magnetic powders having different particle sizes may be combined, or a single non-magnetic powder may be used to broaden the particle size distribution to achieve the same effect. You can also Especially desirable is 0.01 μm to 0.2
μm. The tap density is 0.05 to 2 g / cc, preferably 0.2 to 1.5 g / cc. Water content is 0.1-5%
Desirably 0.2 to 3%. pH is 2 to 11, but 6
The range between 9 and 9 is particularly desirable. Specific surface area is 1 to 100 m ² /
g, preferably 5 to 50 m ² / g, more preferably 7 to
It is 40 m ² / g. Crystallite size is 0.01 μm to 2 μm
m is desirable. The oil absorption using DBP is 5-100 ml /
100g, preferably 10-80ml / 100g, more preferably 2
It is 0 to 60 ml / 100 g. The specific gravity is 1 to 12, preferably 3 to 6. The shape may be needle-like, spherical, polyhedral or plate-like. The loss on ignition is preferably 20% or less. The inorganic powder used in the present invention has a Mohs hardness of 4
The above is desirable. The roughness factor of the surface of these powders is preferably 0.8 to 1.5, more preferably 0.9 to 1.2. SA adsorption amount is 1 to 20 μm
ol / m ² , more preferably ² to 15 μmol / m ² . The heat of wetting of non-magnetic powder in water at 25 ° C is 20.
The range of 0 erg / cm ^{2 to} 600 erg / cm ² is desirable. In addition, a solvent having a heat of wetting in this range can be used. The amount of water molecules on the surface at 100 to 400 ° C. is appropriately 1 to 10 / 100A. The pH of the isoelectric point in water is preferably between 3 and 6. The surfaces of these powders are Al ₂ O ₃ , SiO ₂ , TiO ₂ , Zr.
Surface treatment with O ₂ , SnO ₂ , Sb ₂ O ₃ , and ZnO is desirable. Al ₂ O ₃ and SiO are particularly desirable for dispersibility.
₂ , TiO ₂ and ZrO ₂ , more preferably A
L ₂ O ₃ , SiO ₂ , and ZrO ₂ . These may be used in combination, or may be used alone. Depending on the purpose, a co-precipitated surface treatment layer may be used, or a structure in which the surface layer is first treated with alumina and then the surface layer is treated with silica, or the reverse structure may be employed. Also,
The surface treatment layer may be a porous layer depending on the purpose, but it is generally desirable that the surface treatment layer be homogeneous and dense.

Specific examples of the non-magnetic powder used in the present invention
For example, Showa Denko UA5600, UA5
605, Nanotight, Sumitomo Chemical AKP-20, AKP
-30, AKP-50, HIT-55, HIT-10
0, ZA-G1, manufactured by Nippon Kagaku Kogyo Co., Ltd., G5, G7, S-
1, Toda Kogyo Co., Ltd., TF-100, TF-120, TF
-140, R516, DPN250, Ishihara Sangyo TTO
-51B, TTO-55A, TTO-55B, TTO-
55C, TTO-55S, TTO-55D, FT-10
00, FT-2000, FTL-100, FTL-20
0, M-1, S-1, SN-100, R-820, R-
830, R-930, R-550, CR-50, CR-
80, R-680, TY-50, Titanium Industry ECT-
52, STT-4D, STT-30D, STT-30,
STT-65C, Mitsubishi Materials T-1, Nippon Shokubai N
SO, NS-3Y, NS-8Y, TAYCA MT-10
0S, MT-100T, MT-150W, MT-500
B, MT-600B, MT-100F. FINAL made by Sakai Chemical
EX-25, BF-1, BF-10, BF-20, BF
-1L, BF-10P, Dowa Mining DEFIC-Y, D
EFIC-R. Titanium industry Y-LOP and firing it
The most preferable non-magnetic powder is titanium dioxide.
Therefore, the production method will be described in detail by taking titanium dioxide as an example. these
Titanium oxide is mainly produced by a sulfuric acid method and a chlorine method. Sulfuric acid method
Is a source of Illuminite ore that is digested with sulfuric acid,
Extract throat as sulfate. Iron sulfate is removed by crystallization and separation.
Then, the remaining titanyl sulfate solution is purified by filtration and then hydrolyzed.
Is carried out to precipitate the hydrous titanium oxide. Filter this
After washing, remove impurities by washing and add a particle size regulator etc.
After adding, if it is fired at 80 to 1000 ° C, crude titanium oxide
Becomes Rutile type and anatase type are added during hydrolysis
It depends on the type of nucleating agent used. This crude titanium oxide
It is created by crushing, sizing, and surface treatment. Chlorine method
Natural or synthetic rutile is used as the raw ore. ore
Is chlorinated under reduced temperature at high temperature and Ti is TiCl _FourTo Fe
Becomes FeCl2, and the iron oxide solidified by cooling is
Liquid TiCl_FourAnd separated. Obtained crude TiCl_FourIs
After purification by rectification, a nucleating agent is added, and the temperature is 1000 ° C or higher.
Instantly react with oxygen at the above temperature to obtain crude titanium oxide
It The crude titanium oxide produced in this oxidative decomposition step is pigmentary
The finishing method for imparting properties is the same as the sulfuric acid method.
Surface treatment is dry pulverization of the above titanium oxide material, then dispersion with water.
Addition of agents, wet grinding, centrifugation to perform coarse particle classification
Be done. After that, the fine-grained slurry is transferred to the surface treatment tank and
Here, the surface coating of the metal hydroxide is carried out. First, the predetermined
Of Al, Si, Ti, Zr, Sb, Sn, Zn, etc.
Add an aqueous salt solution to neutralize the acid or alkali
In addition, the surface of the titanium oxide particles is cleaned with the hydrous oxide produced.
To cover. Water-soluble salts produced as by-products are decanted and filtered.
And remove it by washing and finally adjust the slurry pH.
Filtered and washed with pure water. Washed cake is sp
It is dried with a ray dryer or band dryer.
Finally, this dried product is crushed with a jet mill and made into a product.
It In addition to water-based titanium oxide powder, AlCl
₃, SiCl_FourAfter that, steam is introduced through the steam of
It is also possible to apply a surface treatment of 1, Si. Other faces
For the manufacturing method of the ingredients, please refer to "Characterizatatio
no of Powder Surfaces "Acad
You can refer to the empress.

Further, by mixing carbon black with non-magnetic powder, Rs, which is a known effect, can be lowered.
For this purpose, a furnace for rubber, a thermal for rubber, a black for color, acetylene black, etc. can be used. The specific surface area is 100 to 500 m ² / g, desirably 150~400m ² / g, DBP oil absorption amount from 20 to 40
0ml / 100g, preferably 30-200ml / 100g
Is. Particle size is 5 to 80 mμ, preferably 10 to 5
It is 0 mμ, and more preferably 10 to 40 mμ. pH
Is preferably 2 to 10, the water content is 0.1 to 10%, and the tap density is 0.1 to 1 g / CC. As a specific example of the carbon black used in the present invention, manufactured by Cabot Corporation,
BLACKPEARLS 2000, 1300, 100
0, 900, 800, 880, 700, VULCAN
XC-72, Mitsubishi Kasei Co., Ltd., # 3050B, 315
0B, 3250B, # 3750B, # 3950B, # 9
50, # 650B, # 970B, # 850B, MA-6
00, manufactured by Conlon Bia Carbon Co., Ltd., CONDUCTEX
SC, RAVEN 8800,8000,7000,
5750, 5250, 3500, 2100, 2000,
1800, 1500, 1255, 1250, Ketjen Black EC manufactured by Akzo and the like. Carbon black may be surface-treated with a dispersant or the like, may be grafted with a resin, or may be graphitized on a part of the surface. Further, the carbon black may be dispersed with a binder in advance before being added to the paint. The content of these carbon blacks is within the range of not more than 50% by weight based on the above inorganic powder, and 40% of the total weight of the non-magnetic layer.
It can be used within the range not exceeding. These carbon blacks can be used alone or in combination. The carbon black that can be used in the present invention can be referred to, for example, "Carbon Black Handbook" edited by Carbon Black Association.

Organic powder can be used as the non-magnetic powder, and examples thereof include acrylic styrene resin powder, benzoguanamine resin powder, melamine resin powder, and phthalocyanine pigment, and polyolefin resin powder and polyester resin powder. , Polyamide resin powder,
Polyimide resin powder and polyfluorinated ethylene resin are used. As the manufacturing method, those described in JP-A-62-18564 and JP-A-60-255827 can be used.

In the conventional magnetic recording medium, an undercoat layer is provided on the surface of the non-magnetic support, which is provided to improve the adhesive force between the non-magnetic support and the magnetic layer. The thickness is 0.5 μm or less, which is different from the non-magnetic layer in the magnetic recording medium of the present invention. Also in the present invention, it is desirable to provide this undercoat layer in order to improve the adhesion between the non-magnetic layer and the non-magnetic support.

A binder, a lubricant, a dispersant for the non-magnetic layer,
As for the additive, solvent, dispersion method and the like, those of the magnetic layer can be applied. In particular, with respect to the amount and type of binder, the amount and type of additive and dispersant added, known techniques for the magnetic layer can be applied.

The non-magnetic layer in the present invention, even if it contains a small amount of ferromagnetic powder within the range in which the effects of the present invention are exhibited, belongs to the category of the non-magnetic layer of the present invention. is there. The small amount of ferromagnetic powder is 20% by weight or less based on the non-magnetic powder. If it exceeds 20% by weight, the effect of the present invention is lost.

In the magnetic recording medium of the present invention, the non-magnetic layer and the first magnetic layer preferably have a center line average surface roughness of 0.006 μm or less when coated alone.

As the binder used in the magnetic layer or non-magnetic layer in the magnetic recording medium of the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins and mixtures thereof are used. Whether it is a magnetic layer or a non-magnetic layer, there is no particular difference in the conditions required for the binder resin.
The ratio of the ferromagnetic powder or non-magnetic powder to the binder is not particularly limited, but is usually 5 to 50% by weight, preferably 10 to 30% by weight.

The thermoplastic resin has a glass transition temperature of −100 to 150 ° C. and a number average molecular weight of 1000 to 200.
000, preferably 10,000 to 100,000, and the degree of polymerization is about 50 to 1,000. Such examples include vinyl chloride, vinyl acetate, vinyl alcohol,
Polymers or copolymers containing maleic acid, acrylic acid, acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, vinyl ether, etc. as constituent units. There are polymers, polyurethane resins, and various rubber resins. Further, as the thermosetting resin or the reaction type resin, a phenol resin, an epoxy resin, a polyurethane curing type resin, a urea resin, a melamine resin, an alkyd resin, an acrylic reaction resin, a formaldehyde resin, a silicone resin, an epoxy-polyamide. Resin, a mixture of polyester resin and isocyanate prepolymer, a mixture of polyester polyol and polyisocyanate, a mixture of polyurethane and polyisocyanate, and the like. These resins are described in detail in "Plastic Handbook" published by Asakura Shoten. It is also possible to use a known electron beam curable resin for each layer. These examples and their manufacturing method are described in detail in JP-A-62-256219. The above resins can be used alone or in combination, but as preferable ones, vinyl chloride resin, vinyl chloride vinyl acetate resin, vinyl chloride vinyl acetate vinyl alcohol resin,
Vinyl chloride vinyl acetate maleic anhydride copolymer, a combination of at least one selected from the above and a polyurethane resin,
Alternatively, a combination of these with polyisocyanate can be used.

As the structure of the polyurethane resin, known ones such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate carbonate polyurethane, polyester polycarbonate carbonate polyurethane, and polycaprolactone polyurethane can be used. For all of the binders listed here, COO may be added as necessary to obtain better dispersibility and durability.
_{M, SO 3 M, OSO 3} M, P = O (OM) 2, O-P
═O (OM) ₂ , (at least one of which is a hydrogen atom or an alkali metal base), OH, NR ² , N ⁺ R ³ (R is a hydrocarbon group) epoxy group, SH, CN, and the like. It is desirable to use the above-mentioned polar group introduced by copolymerization or addition reaction. The amount of such a polar group is 10 ^-1 to 10 ^-8 mol / g, preferably 10 ^-2 to 10 ^-6 mol / g.

Specific examples of these binders used in the present invention include VAGH and VY manufactured by Union Carbite.
HH, VMCH, VAGF, VAGD, VROH, VY
ES, VYNC, VMCC, XYHL, XYSG, PK
HH, PKHJ, PKHC, PKFE, manufactured by Nisshin Chemical Industry Co., Ltd., MPR-TA, MPR-TA5, MPR-TAL,
MPR-TSN, MPR-TMF, MPR-TS, MP
R-TM, MPR-TAO, 1000W manufactured by Denki Kagaku,
DX80, DX81, DX82, DX83, 100F
D, ZEON Corporation MR-105, MR110, MR1
00, 400X-110A, Nippon Polyurethane Co., Ltd. Nipporan N2301, N2302, N2304, Dainippon Ink and Chemicals Pandex T-5105, T-R3080,
T-5201, Barnock D-400, D-210-8
0, Crisbon 6109, 7209, Toyobo Co., Ltd. Byron UR8200, UR8300, UR-8600, UR
-5500, UR-4300, RV530, RV28
0, manufactured by Dainichiseika, Daiferamine 4020, 502
0,5100,5300,9020,9022,702
0, Mitsubishi Kasei Co., MX5004, Sanyo Kasei Co., Ltd. Sampren SP-150, TIM-3003, TIM-300
5, Asahi Kasei Corp. Saran F310, F210 and the like.

The binder used in the non-magnetic layer, the first magnetic layer and the second magnetic layer in the magnetic recording medium of the present invention is preferably in the range of 5 to 50% with respect to the non-magnetic powder or magnetic material. Is used in the range of 10 to 30%. It is desirable to use a combination of these in the range of 5 to 30% when using a vinyl chloride resin, 2 to 20% when using a polyurethane resin, and 2 to 20% of polyisocyanate. In the present invention, when polyurethane is used, the glass transition temperature is −50 to 100 ° C. and the elongation at break is 10
0 to 2000%, breaking stress 0.05 to 10 kg / cm
² , and the yield point is preferably 0.05 to 10 kg / cm ² .

The magnetic recording medium of the present invention comprises two or more layers. Therefore, the amount of binder, the amount of vinyl chloride resin, polyurethane resin, polyisocyanate, or other resin in the binder, the molecular weight of each resin forming the magnetic layer, the amount of polar group, or the amount described above. It is of course possible to change the physical properties of the resin between the non-magnetic layer, the first magnetic layer, and the second magnetic layer, if necessary, and known techniques for multilayer magnetic layers can be applied. For example, when changing the amount of binder in each layer, it is effective to increase the amount of binder in the second magnetic layer in order to reduce scratches on the surface of the magnetic layer. This is achieved by increasing the amount of binder in the two magnetic layers or the non-magnetic layer to give flexibility.

The polyisocyanate used in the present invention includes tolylene diisocyanate, 4-4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate and naphthylene.
Isocyanates such as 1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate and triphenylmethane triisocyanate, and also
Products of these isocyanates and polyalcohols, polyisocyanates produced by condensation of isocyanates, and the like can be used. Commercially available trade names of these isocyanates are Coronate L, Coronet HL, manufactured by Nippon Polyurethane Co., Ltd.
Coronate 2030, Coronet 2031, Millionaire
To MR Millionate MTL, Takeda Pharmaceutical Co., Ltd., Takenet D-102, Takenet D-110N, Takenet D-
200, Takenet D-202, Sumitomo Bayer Co., Ltd., Desmodule L, Desmodule IL, Desmodule N Desmodule HL, etc., and these are used alone or by utilizing the difference in curing reactivity. Each layer can be used in one or more combinations.

The carbon black used in the magnetic layer of the present invention may be a furnace for rubber, thermal for rubber, black for color or acetylene black. Specific surface area is 5-500 m ² / g, DBP oil absorption is 1
0-400ml / 100g, particle size 5mμ-300m
It is desirable that μ, pH is 2 to 10, water content is 0.1 to 10%, and tap density is 0.1 to 1 g / CC. Specific examples of the carbon black used in the present invention include BLACKPEARLS 2000, 1300 manufactured by Cabot Corporation.
1000, 900, 800, 700, VULCAN X
C-72, Asahi Carbon Co., Ltd., # 80, # 60, # 55,
# 50, # 35, Mitsubishi Kasei Co., Ltd., # 2400B, #
2300, # 900, # 1000 # 30, # 40, # 1
0B, manufactured by Conlon Bia Carbon Co., Ltd., CONDUCTEX
SC, RAVEN 150, 50, 40, 15 and the like. Carbon black may be surface-treated with a dispersant or the like, may be grafted with a resin, or may be graphitized on a part of the surface. Further, the carbon black may be dispersed with a binder in advance before being added to the magnetic paint. These carbon blacks can be used alone or in combination. When carbon black is used, it is preferably used in an amount of 0.1 to 30% of the amount of the magnetic material. Carbon black has the functions of preventing static charge of the magnetic layer, reducing the friction coefficient, imparting light-shielding properties, improving the film strength, etc. These differ depending on the carbon black used. Therefore, these carbon blacks used in the present invention have different characteristics, such as particle size, oil absorption, electric conductivity, pH, etc., in the upper magnetic layer and the lower non-magnetic layer by changing the kind, amount and combination thereof. Of course, it is possible to use them properly according to the purpose. Carbon black which can be used in the magnetic layer of the present invention includes, for example, "carbon black".
You can refer to the “Bon Black Handbook” edited by the Carbon Black Association.

The abrasives used in the magnetic layer of the magnetic recording medium of the present invention include α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, which have an α-conversion rate of 90% or more. Artificial diamond, silicon nitride, silicon carbide titanium carbide, titanium oxide, silicon dioxide, boron nitride, etc. are mainly used as a material of 6 or more, alone or in combination. A composite of these abrasives (abrasive surface-treated with another abrasive) may be used. These abrasives may contain compounds or elements other than the main component, but if the main component is 90% or more, the effect remains the same. The particle size of these abrasives is preferably 0.01 to 2 μm,
If necessary, abrasives having different particle sizes may be combined, or a single abrasive may be used to broaden the particle size distribution to obtain the same effect. Tap density is 0.3-2g / c
c, the water content is 0.1 to 5%, the pH is 2 to 11, and the specific surface area is preferably ¹ to 30 m ² / g. The shape of the abrasive used in the present invention may be needle-like, spherical, or dice-like, but those having a corner in part of the shape are preferable because of high abradability. Specific examples of the polishing agent used in the present invention include AKP-20AKP-30 and AKP manufactured by Sumitomo Chemical Co., Ltd.
-50, HIT-50, HIT-100, Nippon Kagaku Kogyo KK, G5, G7, S-1, Toda Kogyo TF-10
0, TF-140 and the like. The abrasives used in the present invention can be of different types, amounts and combinations in the first magnetic layer, the second magnetic layer and the intermediate layer, and can be used properly according to the purpose. These abrasives may be dispersed in a binder in advance and then added to the magnetic paint. The number of abrasives present on the surface of the magnetic layer and the end face of the magnetic layer of the magnetic recording medium of the present invention is preferably 5 pieces / 100 μm ² or more.

As the additives used in the present invention, those having a lubricating effect, an antistatic effect, a dispersing effect, a plasticizing effect, etc. are used. Molybdenum disulfide, tungsten disulfide graphite, boron nitride, graphite fluoride, silicon
Oil, polar group-containing silicone, fatty acid-modified silicone, fluorine-containing silicone, fluorine-containing alcohol,
Fluorine-containing ester, polyolefin, polyglycol
, Alkyl phosphates and their alkali metal salts, alkyl sulfates and their alkali metal salts, polyphenyl ethers, fluorine-containing alkyl sulfates and their alkali metal salts, monobasic fatty acids having 10 to 24 carbon atoms (unsaturated bonds May be included or may be branched), and these metal salts (Li,
Na, K, Cu, etc.), or monovalent, divalent, trivalent, tetravalent, pentavalent, hexavalent alcohol having 12 to 22 carbon atoms (including an unsaturated bond or branched). It doesn't matter),
Alkoxy alcohol having 12 to 22 carbon atoms, 10 carbon atoms
-24 monobasic fatty acids (which may contain unsaturated bonds or may be branched) and monovalent C2-12,
A mono-fatty acid ester or a di-fatty acid ester consisting of any one of divalent, trivalent, tetravalent, pentavalent, and hexavalent alcohols (which may contain an unsaturated bond or may be branched) or Tri-fatty acid ester, monoalkyl ether fatty acid ester of alkylene oxide polymer, fatty acid amide having 8 to 22 carbon atoms, aliphatic amine having 8 to 22 carbon atoms, and the like can be used. Specific examples of these include lauric acid, myristic acid, palmitic acid, stearic acid,
Behenic acid, butyl stearate, oleic acid, linoleic acid, linolenic acid, elaidic acid, octyl stearate, amyl stearate, isooctyl stearate,
Octyl myristate, butoxyethyl stearate,
Anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate, oleyl alcohol, lauryl alcohol
Le is given. Further, nonionic surfactants such as alkylene oxide type, glycerin type, glycidyl type, alkylphenol ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, phosphonium. Or a cationic surfactant such as sulfonium, carboxylic acid,
Amphoteric amphiphiles such as anionic surfactants containing acidic groups such as sulfonic acid, phosphoric acid, sulfuric acid ester group, phosphoric acid ester group, amino acid, aminosulfonic acid, sulfuric acid or phosphoric acid ester of amino alcohol, alkylbedine type, etc. Surfactants and the like can also be used. These surfactants are described in detail in "Surfactant Handbook" (published by Sangyo Tosho Co., Ltd.). These lubricants, antistatic agents, etc. are not necessarily 100% pure, and in addition to the main components, isomers,
Impurities such as unreacted substances, by-products, decomposition products, and oxides may be included. These impurities are preferably 30% or less, more preferably 10% or less. These lubricants and surfactants used in the present invention are nonmagnetic layers,
The type and amount of the magnetic layer can be properly used according to need. For example, fatty acids having different melting points in the non-magnetic layer and magnetic layer are used to control bleeding to the surface, esters having different boiling points and polarities are used to control bleeding to the surface, and the amount of surfactant is adjusted. Therefore, it is considered that the stability of coating is improved, the amount of the lubricant added is increased in the intermediate layer, and the lubricating effect is improved. Needless to say, the examples are not limited to those shown here.

Further, all or a part of the additives used in the present invention may be added at any step in the production of the coating material for the magnetic layer and the non-magnetic layer, for example, mixed with the magnetic material before the kneading step. In this case, the magnetic substance, the binder, and the solvent may be added in the kneading step, the dispersing step, the dispersing step, the adding step immediately before coating, and the like. In some cases, the purpose may be achieved by applying a part or all of the additives simultaneously or sequentially after applying the magnetic layer according to the purpose. Depending on the purpose, a lubricant may be applied to the surface of the magnetic layer after calendering or after slitting. Examples of products of these lubricants used in the present invention include NOF Corporation,
NAA-102, NAA-415, NAA-312, N
AA-160, NAA-180, NAA-174, NA
A-175, NAA-222, NAA-34, NAA-
35, NAA-171, NAA-122, NAA-14
2, NAA-160, NAA-173K, castor hardened fatty acid, NAA-42, NAA-44, cation SA, cation MA, cation AB, cation BB, nymine L-201, nymine L-202, nymi- S-2
02, nonion E-208, nonion P-208, nonion S-207, nonion K-204, nonion NS-
202, Nonion NS-210, Nonion HS-20
6, nonion L-2, nonion S-2, nonion S-
4, nonion O-2, nonion LP-20R, nonion PP-40R, nonion SP-60R, nonion OP-
80R, Nonion OP-85R, Nonion LT-22
1, nonion ST-221, nonion OT-221, monogly MB, nonion DS-60, anon BF, anon LG, butyl stearate, butyl laurate, erucic acid, Kanto Chemical Co., oleic acid, Takemoto Yushi Co., Ltd., FAL
-205, FAL-123, New Nippon Rika Co., Ltd., Engerb LO, Enjorb IPM, Sansosizer-E40
30, manufactured by Shin-Etsu Chemical Co., Ltd., TA-3, KF-96, KF-
96L, KF96H, KF410, KF420, KF9
65, KF54, KF50, KF56, KF907, K
F851, X-22-819, X-22-822, KF
905, KF700, KF393, KF-857, KF
-860, KF-865, X-22-980, KF-1
01, KF-102, KF-103, X-22-371
0, X-22-3715, KF-910, KF-393
5, Lion Armor Co., Amid P, Armide C, Amoslip CP, Lion Oil & Fat Co., Deuomin TDO, Nisshin Oil Co., BA-41G, Sanyo Kasei Co., Profan 2012E , Newport PE61, Ionet MS-400, Ionet MO-200, Ionet DL-200, Ionet DS-300, Ionet DS-1000 Ionet DO-200.

The organic solvent used in the present invention may be any ratio of ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, tetrahydrofuran, etc., and methano- ketone.
Alcohols such as alcohol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, methylcyclohexanol, etc., methyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycoacetate -Esters such as glycol, dimethyl ether, glycol monoethyl ether, glycol ethers such as dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, cresol, chlorobenzene, methylene chloride, ethylene chloride, etc. Chlorinated hydrocarbons such as carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, N,
Those such as N-dimethylformamide and hexane can be used. These organic solvents are not necessarily 100% pure, and may contain impurities such as isomers, unreacted substances, by-products, decomposition products, oxides, and water in addition to the main components. These impurities are preferably 30% or less, more preferably 10% or less. The organic solvent used in the present invention is preferably the same type in the magnetic layer and the non-magnetic layer. The addition amount may be changed. Solvents with high surface tension in the non-magnetic layer (cyclohexanone, dioxane, etc.)
It is important that the stability of coating is increased by using, specifically, the arithmetic average value of the solvent composition of the upper layer does not fall below the arithmetic average value of the solvent composition of the lower layer. In order to improve the dispersibility, it is desirable that the polarity is strong to some extent, and the dielectric constant of the solvent composition is 1
It is desirable that 50% or more of 5 or more solvents is contained. Further, the dissolution parameter is preferably 8-11.

The thickness of the magnetic recording medium of the present invention is such that the non-magnetic support has a thickness of 1 to 100 μm, preferably 4 to 20 μm. The total thickness of the magnetic layer and the non-magnetic layer is 1/100 to 2 times the thickness of the non-magnetic support. Further, an undercoat layer for improving adhesion may be provided between the nonmagnetic support and the nonmagnetic layer or between the magnetic layers. The thickness of the undercoat layer is 0.01 to 2 μm, preferably 0.02 to 0.5 μm.
Is. In addition, a backcoat layer may be provided on the side opposite to the side of the nonmagnetic support magnetic layer. This thickness is 0.1
˜2 μm, preferably 0.3 to 1.0 μm. Known layers can be used as the undercoat layer and the backcoat layer. The non-magnetic support used in the present invention includes polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins, and cellulose triacetate.
Well-known films such as polyester, polycarbonate, polyamide, polyimide, polyamideimide, polysulfone, aramid, aromatic polyamide, and polobenzoxazole can be used, but particularly when a thin support of 10 μm or less is used. It is desirable to use a high-strength support such as polyethylene naphthalate or polyamide. Further, in order to change the surface roughness of the magnetic surface and the base surface, if necessary, the method disclosed in Japanese Patent Laid-Open No.
It is also possible to use a laminated type support as shown in Japanese Patent Publication No. 224127. These supports may be previously subjected to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, and the like. To achieve the object of the present invention, the non-magnetic support has a center line average surface roughness of 0.03 μm or less at a cutoff of 0.08 mm, preferably 0.01 μm or less, and more preferably 0.00
It is necessary to use one having a thickness of 5 μm or less. It is desirable that these non-magnetic supports not only have a small center line average surface roughness, but also that they do not have large protrusions of 1 μm or more. Further, the surface roughness shape can be freely controlled depending on the size and amount of the filler added to the support, if necessary. As an example of these fillers, Ca,
In addition to oxides and carbonates such as Si and Ti, organic fine powders such as acrylics can be used. Maximum height of support SRma
x is 1 μm or less, ten-point average roughness SRz is 0.5 μm or less, center plane peak height SRp is 0.5 μm or less, center plane valley depth SRv is 0.5 μm or less, and center plane area ratio SSr is 1.
0% or more and 90% or less, the average wavelength Sλa is 5 μm or more,
It is preferably 300 μm or less. The surface protrusions of these supports can be controlled by a filler in the range of 0.01 to 1 μm and 0 to 2000 per 0.1 mm ² .

The F-5 value in the tape running direction of the non-magnetic support used in the present invention is preferably 5 to 50 Kg / m.
m ^2, Te - F-5 value of the flop width direction is desirably 3~30K
g / mm ² , and the F-5 value in the long taper direction is the tape
It is generally higher than the F-5 value in the width direction, but this is not the case when it is necessary to particularly increase the strength in the width direction. In addition, the tape in the tape running direction and the width direction of the support 10
The heat shrinkage at 0 ° C. for 30 minutes is preferably 3% or less, more preferably 1.5% or less, and the heat shrinkage at 80 ° C. for 30 minutes is preferably 1% or less, more preferably 0.5% or less. is there. Breaking strength is 5 to 100 kg / mm ^{2 in} both directions,
The elastic modulus is preferably 100 to 2000 Kg / mm ² .

The step of producing the magnetic coating material for the magnetic recording medium of the present invention comprises at least a kneading step, a dispersing step, and a mixing step provided before and after these steps, if necessary. Each process may be divided into two or more stages. All raw materials such as magnetic materials, non-magnetic powders, binders, carbon blacks, abrasives, antistatic agents, lubricants and solvents used in the present invention may be added at the beginning or in the middle of any step. . In addition, individual raw materials may be divided and added in two or more steps. For example, polyurethane may be divided and added in the kneading step, the dispersing step, and the mixing step for adjusting the viscosity after dispersion. In order to achieve the object of the present invention, it is needless to say that the conventionally known manufacturing technique can be used as a part of the steps, but in the kneading step, a strong force such as a continuous kneader or a pressure kneader is used. It is desirable to use one having kneading power. When a continuous kneader or a pressure kneader is used, all or part of the magnetic substance or non-magnetic powder and the binder (however, 3
0% or more) and 15 to 500 parts by weight per 100 parts by weight of the magnetic material. Details of these kneading treatments are described in JP-A-1-106338 and JP-A-1-79274. Further, when adjusting the non-magnetic layer liquid, it is desirable to use a dispersion medium having a high specific gravity, and zirconia beads are suitable.

The following constitution can be proposed as an example of an apparatus and method for coating a magnetic recording medium having a multilayer constitution as in the present invention. 1. A lower layer is first coated by a gravure coating, a roll coating, a blade coating, an extrusion coating device or the like which is generally used for coating a magnetic coating material, and the lower layer is in a wet state. 60
The upper layer is applied by a support pressure type extrusion coating apparatus disclosed in Japanese Patent Application Laid-Open No. 238179 and Japanese Patent Application Laid-Open No. 2-265672. 2. JP-A-63-88080, JP-A-2-179
No. 71, JP-A-2-265672, the upper and lower layers are coated almost simultaneously by one coating head having two slits for passing the coating liquid. 3. The upper and lower layers are coated almost at the same time by an extrusion coating device with a backup roll disclosed in JP-A-2-174965. In order to prevent the deterioration of the electromagnetic conversion characteristics of the magnetic recording medium due to the agglomeration of the magnetic particles, the inside of the coating head is formed by the method disclosed in JP-A-62-95174 and JP-A-1-236968. It is desirable to apply shear to the coating solution of. Further, the viscosity of the coating liquid needs to satisfy the numerical range disclosed in Japanese Patent Application No. 1-312659.

The above method is desirable for providing two magnetic layers or non-magnetic layers in the magnetic recording medium of the present invention. Even when two magnetic layers and one non-magnetic layer are provided, the above method can be easily applied to three layers. However, a method in which a nonmagnetic layer is applied and dried, and then a first magnetic layer and a second magnetic layer are simultaneously provided thereon, and a nonmagnetic layer and a first magnetic layer are simultaneously provided and dried, and then a second magnetic layer is provided thereon. It is also possible to use a method of providing.

A known orienting device can be used, but a vertical orientation uses a heteropolar anticobalt magnet of 1000 G to 3000 G, a longitudinal orientation uses a homopolar anticobalt magnet of 5000 G or more, or a solenoid of 5000 G or more. Is desirable. When a solenoid is used, it is desirable to install a repulsive magnet in order to eliminate the bending of the magnetic field near the outlet because the magnetization component in the width direction is reduced. In order to dry the coating film near the exit of the longitudinally oriented magnet zone, it is desirable to carry out an appropriate preliminary drying.

As the calendering roll, a heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimideamide is used. Further, it is also possible to treat with metal rolls. The processing temperature is preferably 7
The temperature is 0 ° C or higher, and more preferably 80 ° C or higher. The linear pressure is preferably 200 Kg / cm, more preferably 30
It is 0 Kg / cm or more.

The magnetic layer surface and its surface of the magnetic recording medium of the present invention
The friction coefficient of SUS420J on the opposite side is -1
In the range of 0 ℃ to 40 ℃ and humidity of 0% to 95%
0.5 or less, preferably 0.3 or less, desired surface resistivity
More preferably 10 on both the magnetic and back surfaces. ^Four-10¹²Ohm / s
q, it is desirable that the charge potential is within -500V to + 500V.
Yes. Elastic modulus at 0.5% elongation of magnetic layer is running direction and width direction
It is desirable to be 100-2000Kg / mm², Rupture
The strength is preferably 1 to 30 kg / cm², Magnetic recording media
The elastic modulus of is preferably 100 to 100 in both the running direction and the long direction.
1500 Kg / mm², The residual spread is preferably 0.5%
Below, heat shrinkage at any temperature below 100 ° C is desired
It is preferably 1% or less, more preferably 0.5% or less.
Both are preferably 0.1% or less. Glass layer of magnetic layer
Transfer temperature (loss of dynamic viscoelasticity measured at 110 Hz
It is desirable that the maximum point of the sex ratio is 50 ° C or higher and 120 ° C or lower,
The lower nonmagnetic layer preferably has a temperature of 0 ° C to 100 ° C. loss
Elasticity is 1 × 10⁸~ 8 × 10⁹dyne / cm²Range of
The loss tangent should be 0.2 or less.
And is desirable. If the loss tangent is too large, adhesive failure will occur
Yes. The residual solvent contained in the magnetic layer is preferably 100 m
g / m²Below, more desirably 10 mg / m²Below
The residual solvent contained in the second magnetic layer is contained in the first magnetic layer.
It is desirable that the residual solvent is less than the residual solvent. Has a magnetic layer
The porosity is preferably 30% by volume for both the non-magnetic layer and the magnetic layer.
Hereafter, it is more preferably 20% by volume or less. Porosity
Is preferable to achieve high output, but the purpose is
Depending on the case, it may be better to secure a certain value. example
For example, magnetic recording media for data recording, where repeated use is important
It is preferable that running durability is higher for the body with a higher porosity
Many.

The center line surface roughness Ra of the magnetic layer in the magnetic recording medium of the present invention is 0.008 μm or less, preferably 0.004 μm or less, but the RMS surface roughness RRMS obtained by evaluation by AFM is 2 nm to 15 nm. It is desirable to be in the range of. The maximum height SRmax of the magnetic layer is 0.
5 μm or less, ten-point average roughness SRz is 0.3 μm or less, center plane crest height SRp is 0.3 μm or less, center plane valley depth SR
v is 0.3 μm or less, center plane area ratio SSr is 20% or more and 80% or less, average wavelength Sλa is 5 μm or more, 300
μm or less is desirable. The surface protrusion of the magnetic layer is 0.01 μm
The size is from 0 to 2000 in the range of 1 to 1 μm. These can be easily controlled by a surface control by a filler of the support or a roll surface shape of calendar treatment.

In the magnetic recording medium of the present invention, it is easily estimated that the physical properties of the non-magnetic layer and the magnetic layer can be changed according to the purpose. For example, the elastic modulus of the magnetic layer is increased to improve running durability, and at the same time, the elastic modulus of the non-magnetic layer is made lower than that of the magnetic layer to improve the contact of the magnetic recording medium with the head.

[0059]

Examples <Non-magnetic layer coating material X> Non-magnetic powder TiO ₂ crystalline rutile 80 parts by weight (average primary particle diameter: 0.035 μm, specific surface area by BET method: 40 m ² / g, pH: 7, TiO 2 ₂ content 90% or more, DBP oil absorption: 27 to 38 g / 100 g, surface treatment agent Al ₂ O ₃ : 8% by weight) Carbon black 20 parts by weight (average primary particle diameter: 16 mμ, DBP oil absorption: 80 ml / 100 g) , PH: 8.0, specific surface area by ET method: 250 m ² / g, volatile matter: 1.5% by weight) Vinyl chloride copolymer 12 parts by weight (-SO ₃ Na content: 1 × 10 ^-4 eq) / G, degree of polymerization: 300) Polyester polyurethane resin 5 parts by weight (neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1 (molar ratio), —SO ₃ Na group: 1 × -4 eq / g Contains) Butyl Teareto 1 part by weight 1 part by weight Methyl ethyl ketone 100 parts Cyclohexanone 50 parts Toluene 50 parts by weight of stearic acid

<First Magnetic Layer Coating Material Y> Ferromagnetic metal fine powder (composition: Fe / Zn / Ni = 92/4/4) 100 parts by weight (Hc: 1600 Oe, BET specific surface area: 61 m ² / g) , Crystallite size: 195 Å, surface treatment agent: Al ₂ O ₃ 5% by weight, SiO ₂ 2% by weight, particle size (major axis diameter): 0.12 μm, acicular ratio: 10, σs: 130 emu / g) vinyl copolymer 12 parts by weight chloride (-SO ₃ Na ^{content: 1 × 10 -4 eq / g} , polymerization degree: 300) 3 parts by weight of the polyester polyurethane resin (neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1, —SO ₃ Na group: 1 × 10 ⁻⁴ eq / g) α-alumina (particle size 0.3 μm) 2 parts by weight carbon black (particle size 0.10 μm) 0.5 parts by weight Butyl stearate 1 part by weight Stearic acid 5 parts by weight Methyl ethyl ketone 90 parts by weight Cyclohexanone 30 parts by weight Toluene 60 parts by weight

<Second Magnetic Layer Coating Z> 100 parts by weight of hexagonal barium ferrite (Hc: 1500 Oe, specific surface area by BET method: 40 m ² / g, average particle diameter (plate diameter): 0.05 μm, average plate thickness : 0.01 μm, σs: 60 emu / g, surface treatment agent; Al ₂ O ₃ : 5% by weight, SiO ₂ : 2% by weight) Vinyl chloride copolymer 12 parts by weight (-SO ₃ Na content: 1 × 10 ⁻⁴ eq / g, degree of polymerization: 300) 3 parts by weight of polyester polyurethane resin (neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1, —SO ₃ Na group: 1 × 10 ⁻⁴ eq. Α-alumina (particle size 0.3 μm) 2 parts by weight Carbon black (particle size 0.015 μm) 5 parts by weight Butyl stearate 1 part by weight Stearic acid 2 parts by weight Methyl ethyl keto 90 parts by weight Cyclohexanone 30 parts by weight Toluene 60 parts by weight

The components of each of the above three paints were kneaded with a continuous kneader and then dispersed using a sand mill. 1 part by weight of the coating liquid composition X for the non-magnetic layer, 3 parts by weight of the coating liquid composition Y for the second magnetic layer, and 3 parts of the coating liquid composition Z for the first magnetic layer in the obtained dispersion liquid. Parts, and then 40 parts by weight of a mixed solvent of methyl ethyl ketone and cyclohexanone, and filtered using a filter having an average pore diameter of 1 μm to adjust the nonmagnetic layer coating material X, the magnetic layer forming coating materials Y and Z, respectively. did.

Example 1 The thickness of the magnetic layer after drying the magnetic coating material Z was 0.5 μm, and the center line surface roughness Ra was 0.002 μm (cutoff value 0.08) with a thickness of 7 μm.
(mm) polyethylene naphthalate support was applied at a coating speed of 200 m / min and vertically aligned with a heteropolar anti-cobalt magnet having a magnetic force of 2000 G.
Longitudinal orientation was carried out by passing it through a 5000 G homopolar anti-cobalt magnet zone in which a dry air of .degree. After that, processing was performed at a temperature of 90 ° C. with a 7-stage calender consisting of only metal rolls, slitting to a width of 8 mm, and an 8 mm video tape.
Manufactured. The obtained sample is shown in Table 1 A-1. The longitudinal Br of A-1 was 1700 G, the vertical Br was 700 G, and the transverse Br was 600 G.

Next, a sample obtained in the same manner as in A-1 except that the temperature of the dry air in the longitudinally oriented magnet zone was 100 ° C. was A-2, and in the longitudinally oriented magnet zone. A sample obtained in the same manner as in A-1 except that the temperature of the drying air was 100 ° C. and immediately after that was longitudinally oriented by a 1500 G solenoid magnet was designated as A-3. The longitudinal Br of A-2 is 1800 G (Gauss), the vertical Br is 550 G, the lateral Br is 550 G, and the longitudinal Br is 19 Br.
00G, vertical Br is 400G, widthwise Br is 5
It was 00G.

Next, samples obtained in the same manner as A-1 except that the coercive force of the ferromagnetic hexagonal ferrite was 1200 Oe and 2000 Oe were designated as A-4 and A-5, respectively. Next, samples obtained in the same manner as A-1 except that the thicknesses of the layers containing ferromagnetic hexagonal ferrite were 0.3 μm and 1.0 μm were designated as A-6 and A-7, respectively.

Comparative Example 1 5000 was performed without vertical alignment.
A sample obtained in the same manner as in A-1 except that the magnet was oriented only with the homopolar pair anti-magnet of G and the dry air in the magnet zone was not passed was designated as B-1.

(Example 2) The thickness of the non-magnetic coating material X after drying was 2.0 μm, and immediately after that, the thickness of the magnetic layer after drying magnetic coating material Z was 0.5 μm. So that the thickness is 7 μm and the centerline surface roughness is 0.002 μm.
Samples obtained in the same manner as in A-1 to A-7 except that the simultaneous multilayer coating was performed on the polyethylene naphthalate support in Table 2 were designated as Samples A-8 to A-14 in Table 2. Next, as the non-magnetic coating material, instead of TiO ₂ , a particle length of 0.1 μm, an acicular ratio of 8, a specific surface area of 55 m ² / g, Si
Α _{2 with} O ₂ surface treatment weight%, pH 6, tap density 1.0
A sample obtained in the same manner as in A-8 except that iron oxide was used was designated as A-15.

(Comparative Example 2) 5000 was obtained without vertical alignment.
A sample obtained in the same manner as in A-8 except that it was oriented only by the anti-magnet of G of the same pole pair and the dry air in the magnet zone was not passed was designated as B-2.

(Example 3) The magnetic paint Y was dried so that the thickness after drying was 1.5 μm, and immediately after that, the magnetic paint Z was formed.
Was applied on the polyethylene naphthalate support having a thickness of 7 μm and a center line surface roughness of 0.002 μm so that the thickness of the magnetic layer after drying was 0.1 μm. Samples obtained in the same manner as in A-1 to A-7 except for the above are designated as Table 3 samples A-16 to A-22, respectively. However, in A-21, the thickness of the uppermost layer is 0.02μ.
m and A-22 were 0.3 μm. Next, instead of the ferromagnetic metal powder of the magnetic paint Y, Hc 800 Oe, BE
Specific surface area by T method 45 m ² / g Crystallite size 20
0, surface treatment agents Al ₂ O ₃ , SiO ₂ , particle size (major axis diameter) 0.19 μm, acicular ratio 7, σs: 80 emu /
A-23 was a sample obtained in the same manner as in A-16 except that cobalt-modified iron oxide having g, pH 6, and tap density of 0.9 was used.

(Comparative Example 3) 5000 was obtained without vertical alignment.
A sample obtained in the same manner as in A-16 except that it was oriented only by the G antipolar magnet of the same pole and the dry air in the magnet zone was not passed, was designated as B-3.

(Example 4) A non-magnetic coating material X was applied between the magnetic coating material Y of Example 3 and a support using a simultaneous multi-layer coating method so that the thickness after drying was 2.0 μm. The sample obtained in the same manner as in Example 3 except that
~ A-31.

(Comparative Example 4) 5000 was performed without vertical alignment.
A sample obtained in the same manner as in A-24 except that it was oriented only by the antipolar magnet of G and the dry air in the magnet zone was not passed was designated as B-4.

<Evaluation Method> (Hc, Br) A vibrating sample type magnetometer (manufactured by Toei Industry Co., Ltd.) was used to measure at H _m 5 kOe. The magnetic characteristics of each magnetic layer can be obtained by any of the following methods. 1. Each magnetic layer is individually coated to a thickness of 3 μm and the magnetic properties of each are measured. 2. The second magnetic layer is removed with a polishing tape and the hysteresis of the first magnetic layer is measured. Next, from the difference between the hysteresis curves of all layers and the second magnetic layer, the magnetic characteristics of the second magnetic layer are calculated.
Seeking sex. The thickness of each layer was obtained from an electron micrograph of the cross section of the medium. (Center line average surface roughness Ra) Cut-off 0.08 mm using a stylus-type three-dimensional surface roughness meter (manufactured by Kosaka Laboratory)
It was measured at. (Electromagnetic conversion characteristics) 7 MHz, 2 MHz output A FUJIX8 8 mm video deck manufactured by Fuji Photo Film Co., Ltd. was used to record a 7 MHz signal, and the 7 MHz and 2 MHz signal reproduction outputs when the signal was reproduced were measured with an oscilloscope. The reference is 8 mm tape SAGP6-120 manufactured by Fuji Photo Film Co., Ltd.

Table 1 shows the evaluation results obtained as described above.
~ Shown in Table 2.

[0075]

[Table 1]

[0076]

[Table 2]

[0077]

[Table 3]

[0078]

[Table 4]

[0079]

The ferromagnetic powder is mainly composed of ferromagnetic hexagonal ferrite, and the thickness of the magnetic layer is 1 μm or less. It was found that the magnetic recording medium exhibiting high output in a wide range from low to high can be obtained by specifying.

[Procedure amendment]

[Submission date] April 28, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

Specific examples of the non-magnetic powder used in the present invention
As an example, UA5600 manufactured by Showa Denko KK,
UA5605, Nanotight, AKP- manufactured by Sumitomo Chemical Co., Ltd.
20, AKP-30, AKP-50, HIT-55, H
IT-100, ZA-G1, manufactured by Nippon Chemical Industry Co., Ltd., G
5, G7, S-1, Toda Industry Co., Ltd., TF-100,
TF-120, TF-140, R516, DPN25
0, Ishihara Sangyo Co., Ltd. TTO-51B, TTO-55
A, TTO-55B, TTO-55C, TTO-55
S, TTO-55D, FT-1000, FT-200
0, FTL-100, FTL-200, M-1, S-
1, SN-100, R-820, R-830, R-93
0, R-550, CR-50, CR-80, R-68
0, TY-50, ECT-52, S manufactured by Titanium Industry Co., Ltd.
TT-4D, STT-30D, STT-30, STT-
65C, T-1 manufactured by Mitsubishi Materials Corporation, Nippon Shokubai
NS-O, NS-3Y, NS-8Y, TAYCA
MT-100S, MT-100T, MT-15 manufactured by Co., Ltd.
0W, MT-500B, MT-600B, MT-100
F, Sakai Chemical Co., Ltd. FINEX-25, BF-1, BF
-10, BF-20, BF-1L, BF-10P, Dowa
DEFIC-Y, DEFIC-R manufactured by Mining Co., Ltd. Titanium
Y-LOP manufactured by Kogyo Co., Ltd. and a product obtained by firing it, especially
The preferred non-magnetic powder is titanium dioxide, so
The production method will be described in detail using titanium as an example. Of these titanium oxide
The manufacturing method mainly includes a sulfuric acid method and a chlorine method. The sulfuric acid method is Illuminai
Source ore of Toto is digested with sulfuric acid, and Ti, Fe, etc. are converted to sulfate.
And extract. Iron sulfate is removed by crystallization and the remaining sulfuric acid is removed.
The titanyl solution is purified by filtration and then thermally hydrolyzed to
Precipitate the titanium hydroxide. After filtering and washing this,
After washing away the pure substance and adding a particle size regulator etc.,
Crude titanium oxide is obtained by firing at ~ 1000 ° C. Rutile
Type and anatase type are nucleating agent species added during hydrolysis
Divided by type. This crude titanium oxide is crushed, sized,
Created by applying surface treatment. Chlorine method is natural ore
Rutile or synthetic rutile is used. High temperature reduction state of ore
Chlorinated with Ti is TiCl _FourFe is FeCl₂Tona
And iron oxide that became solid by cooling is liquid TiCl_Four
And separated. Obtained crude TiCl_FourPurified by rectification
After that, add a nucleating agent, and add oxygen at a temperature of 1000 ° C or higher.
And reacts momentarily with to obtain crude titanium oxide. This oxidation
To give pigmentary properties to the crude titanium oxide produced in the solution process
The finishing method is the same as the sulfuric acid method. Surface treatment is as above
After dry grinding the titanium oxide material, add water and dispersant, then wet
Coarse-grain classification is carried out by pulverization and centrifugation. afterwards,
The fine-grained slurry is transferred to the surface treatment tank, where metal hydroxide is added.
The surface coating of the object is performed. First, a certain amount of Al, S
An aqueous solution of salt such as i, Ti, Zr, Sb, Sn, Zn
In addition, add acid or alkali to neutralize
The surface of titanium oxide particles is coated with the hydrous oxide formed. Vice
The water-soluble salts that form are decanted, filtered and washed.
And finally adjust the slurry pH and filter to
Wash with water. The washed cake is a spray dryer
-Or dried with a band dryer. Finally this dry
The dried product is crushed with a jet mill to obtain a product. Also water
Not only the system but also titanium oxide powder AlCl₃, SiCl_Four
Then, steam is introduced through the steam of Al and Si surface treatment.
It is also possible to give reason. For other pigment manufacturing methods
"Characterization of Po"
wder Surfaces "Academic Pr
You can refer to ess.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0059

[Correction method] Change

[Correction content]

[0059]

Examples <Non-magnetic layer coating material X> Non-magnetic powder TiO ₂ crystalline rutile 80 parts by weight (average primary particle diameter: 0.035 μm, specific surface area by BET method: 40 m ² / g, pH: 7, TiO 2 ₂ content 90% or more, DBP oil absorption: 27 to 38 g / 100 g, surface treatment agent Al ₂ O ₃ : 8% by weight) Carbon black 20 parts by weight (average primary particle size: 16 mμ, DBP oil absorption: 80 ml / 100 g) , PH: 8.0, specific surface area by ET method: 250 m ² / g, volatile matter: 1.5% by weight) Vinyl chloride copolymer 12 parts by weight (-SO ₃ Na content: 1 × 10 ^-4 eq / G, degree of polymerization: 300) Polyester polyurethane resin 5 parts by weight (neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1 (molar ratio), —SO ₃ Na group: 1 × 10 ⁻⁴ eq. / G included ) Butyl stearate 1 part by weight 1 part by weight Methyl ethyl ketone 100 parts Cyclohexanone 50 parts Toluene 50 parts by weight of stearic acid

Claims (6)

[Claims] 1. A magnetic recording medium having a magnetic layer mainly composed of a ferromagnetic powder and a binder on a non-magnetic support, wherein the ferromagnetic powder mainly comprises a ferromagnetic hexagonal ferrite. , The thickness of the magnetic layer is 1 μm or less, and the coercive force in the longitudinal direction is Hc ₁ and the coercive force in the vertical direction is Hc ₁ .
A magnetic recording medium characterized in that the coercive force relationships are as follows when c ₂ and coercive force in the width direction are Hc ₃ . Hc ₁ > Hc ₂ > Hc ₃ 2. The magnetic recording medium according to claim 1, wherein a nonmagnetic layer containing a nonmagnetic powder and a binder as a main component is provided between the magnetic layer and the nonmagnetic support. 3. A first magnetic layer mainly composed of acicular ferromagnetic powder and a binder on a non-magnetic support, and a second magnetic layer mainly composed of ferromagnetic hexagonal ferrite and a binder thereon. In a magnetic recording medium provided with a magnetic layer, the thickness of the second magnetic layer is 1.0 μm or less, and the coercive force in the longitudinal direction is H
c ₁ , the coercive force in the vertical direction is Hc ₂ , the coercive force in the width direction is Hc
A magnetic recording medium characterized in that the coercive forces have the following relationships when set to ₃ : Hc ₁ > Hc ₂ > Hc ₃ 4. The magnetic recording medium according to claim 3, wherein a nonmagnetic layer containing a nonmagnetic powder and a binder as a main component is provided between the nonmagnetic support and the first magnetic layer. 5. A residual magnetic flux density B in the longitudinal direction of a magnetic layer mainly composed of said ferromagnetic hexagonal ferrite and a binder.
r _1, the magnetic recording medium according to any one of claims 1 to 4, the residual magnetic flux density Br ₂ in the vertical direction, the residual magnetic flux density Br ₃ in the width direction, characterized in that the following relationship. Br ₁ > Br ₂ > Br ₃ 6. The magnetic recording medium according to claim 2, wherein at least two layers of the non-magnetic layer and the magnetic layer are formed by a wet-on-wet coating method.