JPH1021530A - Disk type magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a disk type magnetic recording medium in which electromagnetic transduction characteristics, especially high-density recording characteristics are significantly improved and excellent characteristics can be shown in any size of the medium. SOLUTION: This medium is produced by successively forming a base layer which is substantially nonmagnetic and a magnetic layer having dispersion of a ferromagnetic fine powder or a ferromagnetic hexagonal ferrite fine powder in a binder on a nonmagnetic base body. The nonmagnetic base body is composed of a polyethylene naphthalate having <=10nm center face average surface roughness SRa. The thickness dμm of the nonmagnetic base body and the outer diameter Dmm of the recording region satisfy the relation of 1.00<=D/d<=2.00.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk-shaped magnetic recording medium for high-density recording, which has a magnetic layer and a non-magnetic layer, and contains a ferromagnetic metal fine powder or a hexagonal ferrite fine powder in the uppermost layer. .

[0002]

2. Description of the Related Art In the field of magnetic disks, 2 MB MF-2HD floppy disks using Co-modified iron oxide have been standardly mounted on personal computers. However, in today's rapidly increasing data capacity, the capacity cannot be said to be sufficient, and it has been desired to increase the capacity of floppy disks.

Conventionally, a magnetic recording medium has a magnetic layer obtained by dispersing iron oxide, Co-modified iron oxide, CrO ₂ , ferromagnetic metal powder, and hexagonal ferrite powder in a binder on a non-magnetic support. Is widely used. Among them, ferromagnetic metal fine powder and hexagonal ferrite fine powder are known to have excellent high density recording characteristics. As a large-capacity disk using a ferromagnetic metal fine powder having excellent high-density recording characteristics, 10
4 MB as a large capacity disk using MB MF-2TD, 21 MB MF-2SD or hexagonal ferrite
MF-2ED, 21 MB floptical, etc., but were not sufficient in capacity and performance. Under such circumstances, many attempts have been made to improve the high-density recording characteristics.

On the other hand, a disk-shaped magnetic recording medium comprising a thin magnetic layer and a functional non-magnetic layer has recently been developed.
0MB class floppy disks have appeared. Japanese Patent Application Laid-Open No. 5-109061 shows these features.
Japanese Patent Application Laid-Open No. Hei 5-197946 discloses a configuration having a magnetic layer having a Hc of 1400 Oe or more and a thickness of 0.5 μm or less and a nonmagnetic layer containing conductive particles. The magnetic layer thickness is 0.5
μm or less, the thickness variation of the magnetic layer thickness should be within ± 15%,
Japanese Patent Laid-Open No. 6-68453 discloses a configuration in which the surface electric resistance is specified.
Has proposed a configuration in which two types of abrasives having different particle sizes are included, and the amount of the abrasive on the surface is regulated.

However, with the rapid increase in density of disk-shaped magnetic recording media, it has become difficult to obtain satisfactory characteristics even with such a technique. Investigation of the cause revealed that as the recording density was increased, the instability of the contact state between the head and the medium, that is, the deterioration of the head contact and the deformation of the medium significantly deteriorated the characteristics. In particular, when the disk is rotated at a high speed to increase the transfer speed, the entire disk vibrates or flutters (plane runout), and a spacing is generated between the head and the medium to obtain satisfactory characteristics. I found that I could not do it.

Further, high-density disks having various diameters are being devised in order to cope with various uses. However, in the case of such disk media having different diameters, the above-described influences are different, so that a solution is required. It turned out to be complicated.

[0007]

SUMMARY OF THE INVENTION The present invention provides a disk-shaped magnetic recording medium in which the electromagnetic conversion characteristics, especially the high-density recording characteristics, are remarkably improved, and exhibit excellent characteristics in all sizes. It is intended to be.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above-mentioned problems, and as a result, it has been found that the conventional disk medium is caused by the use of polyethylene terephthalate as a support, and furthermore, the rigidity is higher. The use of supports has also been proposed, but they have found that the balance between thickness and outer diameter is poor, and conversely, the properties are degraded. As a result of further study, it has been found that the object of the present invention is achieved by using the following medium, and the present invention has been achieved.

That is, the present invention provides a non-magnetic support comprising a substantially non-magnetic underlayer and a ferromagnetic metal fine powder or a ferromagnetic hexagonal ferrite fine powder dispersed in a binder. The non-magnetic support is a polyethylene naphthalate having a center plane average surface roughness SRa of 10 nm or less, and a relational expression (1) is provided between the thickness d μm of the non-magnetic support and the outermost diameter Dmm of the recording area. : 1.00 ≦ D / d ≦
It is a disk-shaped magnetic recording medium characterized by satisfying the relationship of 2.00, and has been found to be capable of obtaining excellent electromagnetic conversion characteristics in any environment and size that could not be obtained by the conventional technology. It was.

In the present invention, relational expression (1): 1.0
0 ≦ D / d ≦ 2.00 is preferably in the range of 1.3 ≦ D / d ≦ 1.7. [Relationship between constituent features and effects] The reason why the present invention brings about such effects is not clear, but is considered as follows. When performing high-density recording on a disk, it is necessary to control the contact between the head and the medium appropriately and uniformly. But,
It is considered that the following phenomenon occurs when the rotation speed of the disk is increased. The high-speed rotation makes it easier for the head to float, and the deformation and fluctuation of the high-speed rotating flexible disk medium, such as vibration and surface runout, also increase, making it difficult to maintain a stable positional relationship between the head and the medium, which reduces the output. Will be invited. In particular, it was found that this phenomenon was remarkable in the outer peripheral portion of a disk having a high peripheral speed. It is estimated that the flying height of the head is related not only to the peripheral speed but also to the surface property of the medium, and it is estimated that deformation and fluctuation are related to the rigidity of the medium.

In addition, in the case of a flexible disk medium, the flexibility of the medium varies depending on the distance from the center of the disk or the end of the hole in the center of the disk to the pressure of the head. It is necessary to control the stiffness, and for the same reason, depending on the disk size, it may be necessary to change the stiffness of the medium to change the flexibility.

On the other hand, in the case of a flexible disk medium, the medium is considered to play a role of maintaining a constant contact state with the head by deforming the medium around the head so as to follow the head shape. It is estimated that the rigidity and surface properties of the medium are related. The above phenomenon is
It is difficult to predict accurately because of the complex operation.

The disk medium using the polyethylene naphthalate (PEN) as a support according to the present invention has a stable head contact with a large fluctuation and deformation of the disk and a high peripheral speed, especially in high-density recording at high speed rotation. It has been experimentally confirmed that, in the outer peripheral portion of the disk where it is difficult to obtain a state, the characteristics which are far superior to the conventionally used polyethylene terephthalate (PET), that is, the surface runout is suppressed and the head contact is improved. Things.

This is presumed to be because polyethylene naphthalate having a rigidity different from that of polyethylene terephthalate has a configuration as in the present invention, so that the above-mentioned complicated phenomena of the head and the medium can be balanced. [Description on Support] The non-magnetic support used in the present invention is made of polyethylene naphthalate. The thickness d of the nonmagnetic support is a thickness that satisfies the relational expression (1) of the present invention, but refers to an average thickness in the present invention, and specifically,
The average value of measured values of 10 or more points is obtained by using a digital thickness meter MINICON manufactured by Tokyo Seimitsu Co., Ltd. The range of d is 1.00 ≦ D / d ≦
If 2.00 is modified, it can be determined from 0.5D ≦ d ≦ D. For example, when D is 35 mm, 17.
5 μm ≦ d ≦ 35 μm, and when D is 140 mm, 70 μm ≦ d ≦ 140 μm.

In the present invention, a laminated type support may be used to change the surface roughness of the surface on the magnetic layer side and the surface (base surface) on the opposite side, if necessary. These supports may be subjected to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, or the like in advance. In order to achieve the object of the present invention, it is necessary to use WYKO as a non-magnetic support.
The center plane average surface roughness SRa measured by the Mirau method of TOPO-3D manufactured by KK is 10 nm or less, preferably 5 nm or less.
It is necessary to use the one of nm or less. These nonmagnetic supports not only have a small center plane average surface roughness, but also
It is preferable that there is no coarse projection of 0.5 μm or more. The surface roughness shape can be freely controlled by the size and amount of the filler added to the support as needed. Examples of these fillers include Ca,
In addition to oxides and carbonates such as Si and Ti, organic fine powders such as acryl-based can be used. Maximum support height SRmax
Is 1 μm or less, ten-point average roughness SRz is 0.5 μm or less,
The center plane peak height SRp is 0.5 μm or less, the center plane valley depth SRv is 0.5 μm or less, and the center plane area ratio SSr is 10%.
Not less than 90%, and the average wavelength Sλa is not less than 5 μm and not more than 30%.
It is preferably 0 μm or less. In order to obtain desired electromagnetic conversion characteristics and durability, the surface projection distribution of these supports can be arbitrarily controlled by a filler.
Can be controlled in the range of 0 to 2000 pieces per 0.1 mm ² .

F-5 of the non-magnetic support used in the present invention
The value is preferably 10 to 40 kg / mm^TwoAnd 10 of the support
The heat shrinkage at 5 ° C. for 30 minutes is preferably 0.5% or less.
More preferably 0.3% or less at 80 ° C. for 30 minutes.
Has a heat shrinkage of preferably 0.3% or less, more preferably
Is 0.2% or less. The elastic modulus is 500 ~ 1400Kg / m
m^TwoIs preferably 600 to 1000 kg / mm^TwoIn
You. Thermal expansion coefficient is 10 ^-Four-10^-8/ ° C, preferred
H10^-Five-10^-6/ ° C. Humidity expansion coefficient is 10^-Four
/ RH% or less, preferably 10^-Five/ RH% or less. This
Their thermal, dimensional and mechanical strength properties are within the plane of the support.
Approximately equal, preferably within 10% difference for each direction
New

In order to obtain a polyethylene naphthalate support having such characteristics, it is preferable to control the degree of stretching in the vertical and horizontal directions at the time of film formation so that no characteristic difference occurs in the in-plane direction. [Description of Shape and Layer Structure] The shape of the disk-shaped magnetic recording medium of the present invention is not particularly limited. In the present invention,
The outermost diameter D of the recording area must satisfy the relational expression (1). FIG. 1 is a plan view showing an example of a disk-shaped magnetic recording medium according to the present invention.
Is defined as equivalent to the outermost diameter of the recording area.

D is not particularly limited, but is preferably in the range of 70 mm or more and 140 mm or less particularly for the purpose of increasing the capacity, and in the range of 35 mm or more and less than 70 mm for the purpose of miniaturization. is there. The former shows a greater effect on recording and reproduction when the peripheral speed at the outermost periphery e of the recording area is 10 m / s or more, and the latter shows the outermost periphery e of the recording area.
When the peripheral speed is 5 m / s or more, a great effect is exhibited by recording and reproducing.

The peripheral speed V of the outermost periphery of the recording area and the disk rotation speed α (rpm) are calculated as follows: V = α · πD / 60000 =
There is a relationship of 5.23 × 10 ⁻⁵ α · D (m / s) (α = rpm), and V can be obtained from D and the value of the rotation speed. The disk rotation speed α is generally 600 rpm or more, 8
2,000 rpm or less, preferably 2,000 rpm or more,
5000 rpm or less.

The center hole diameter a of the disk is generally 10 mm
Above, it is 50 mm or less. The inner peripheral portion of the recording area has a low peripheral speed and a small surface runout, but the rigidity of the medium is higher than that of the outer peripheral portion. The distance is set to the optimum distance from the center of the disk or the end of the center hole of the disk. Distance f between the outermost circumference of the center hole and the innermost circumference of the recording area
Is usually in the range of 1 to 40 mm, preferably 3 to 20 mm. If the distance is too small, the rigidity becomes too strong, which is not preferable. If the distance is too large, the recording area becomes narrow, which is not preferable.

The distance c between the outer periphery of the disk and the outermost periphery of the recording area is generally 0.2 to 10 mm, preferably 0.1 mm.
It is in the range of 5 to 3.0 mm. In the thickness configuration of the magnetic recording medium of the present invention, the non-magnetic support is the outermost diameter D of the recording area.
It is necessary to have a predetermined ratio to An undercoat layer for improving adhesion may be provided between the nonmagnetic support and the nonmagnetic layer or the magnetic layer. The thickness of the undercoat layer is 0.01
.About.2 .mu.m, preferably 0.02 to 0.5 .mu.m. Although the present application is a double-sided magnetic layer disk-shaped medium in which a nonmagnetic layer and a magnetic layer are usually provided on both sides of the support, it may be provided on only one side. In this case, a back coat layer may be provided on the side opposite to the non-magnetic layer and the magnetic layer in order to provide effects such as antistatic and curl correction. This thickness is 0.1 ~ 4μ
m, preferably 0.3 to 2.0 μm. Known undercoat layers and backcoat layers can be used.

The thickness of the magnetic layer of the medium of the present invention is optimized according to the saturation magnetization of the head used, the head gap length, and the band of the recording signal.
It is at least 1.0 μm and at most 0.05 μm and at most 0.5 μm, more preferably at most 0.4 μm. The magnetic layer may be separated into two or more layers having different magnetic properties, and a known configuration relating to a multilayer magnetic layer can be applied.

The thickness of the nonmagnetic layer which is the underlayer of the medium according to the present invention is 0.2 μm or more and 5.0 μm or less, preferably 0.5 μm or more and 3.0 μm or less, and more preferably 1.
0 μm or more and 2.5 μm or less. The underlayer of the medium of the present application exerts its effect as long as it is substantially a non-magnetic layer.For example, even if a small amount of a magnetic substance is included as an impurity or intentionally, the effect of the present invention is exhibited. It goes without saying that the configuration can be regarded as substantially the same as that of the present application. Substantially a non-magnetic layer means that the underlayer has a residual magnetic flux density of 100 G or less or a coercive force of 100 Oe or less, and preferably has no residual magnetic flux density and no coercive force. [Description on Ferromagnetic Metal Fine Powder] As the ferromagnetic metal fine powder used in the magnetic layer of the present invention, a ferromagnetic alloy powder containing α-Fe as a main component is preferable. These ferromagnetic metal fine powders include Al, Si, S, Sc, C
a, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, A
g, Sn, Sb, Te, Ba, Ta, W, Re, Au,
Hg, Pb, Bi, La, Ce, Pr, Nd, P, C
It may contain atoms such as o, Mn, Zn, Ni, Sr, and B. In particular, Al, Si, Ca, Y, Ba, L
a, Nd, Co, Ni, at least one of B and α-Fe
It is preferable to include at least one of Co, Y, and Al. Co content is F
It is preferably from 0 to 40 at%, more preferably from 15 to 35 at%, and even more preferably from 20 to 35 at%. The content of Y is preferably from 1.5 to 12 at%, more preferably from 3 to 10 at%, and still more preferably from 4 to 9 at%. Al is preferably 1.5 atomic% or more and 12 atomic% or less, and more preferably 3 atomic% or less.
It is at least 10 at% and more preferably at least 4 at% and at most 9 at%. These ferromagnetic metal fine powders may be preliminarily treated with a dispersant, a lubricant, a surfactant, an antistatic agent, or the like before dispersion before dispersion.

The ferromagnetic metal fine powder may contain a small amount of hydroxide or oxide. A ferromagnetic metal fine powder obtained by a known production method can be used, and the following method can be used. A method of reducing a complex organic acid salt (mainly oxalate) with 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, Thermal decomposition method, reduction method by adding reducing agent such as sodium borohydride, hypophosphite or hydrazine to aqueous solution of ferromagnetic metal, reduction of fine powder by evaporating metal in low pressure inert gas And how to get it. The ferromagnetic alloy powder thus obtained is subjected to a known slow oxidation treatment, that is, a method of immersing the powder in an organic solvent and then drying it.
A method of immersing in an organic solvent, sending an oxygen-containing gas to form an oxide film on the surface, and then drying, and a method of forming an oxide film on the surface by adjusting the partial pressure of oxygen gas and inert gas without using an organic solvent Any of these can be used.

The ferromagnetic metal fine powder of the magnetic layer of the present invention is
When expressed in terms of the specific surface area by the T method, it is 45 to 80 m ² / g,
Preferably it is 50 to 70 m ² / g. If it is less than 40 m ² / g, noise increases, and if it is more than 80 m ² / g, it is difficult to obtain surface properties, which is not preferable. The crystallite size of the ferromagnetic metal fine powder of the magnetic layer of the present invention is 350 to 80 °, preferably 250 to 80 °.
100 °, more preferably 200 to 140 °. The major axis diameter of the ferromagnetic metal fine powder is 0.02 μm or more and 0.25 μm
m, preferably 0.05 μm or more and 0.15 μm
m, and more preferably 0.06 μm or more.
It is 1 μm or less. The needle ratio of the ferromagnetic metal fine powder is preferably 3 or more and 15 or less, and more preferably 5 or more and 12 or less. The? S of the ferromagnetic metal fine powder is from 100 to 180 emu / g, preferably from 110 emu / g to 170 emu / g, more preferably from 125 to 160 emu / g. The coercive force of the ferromagnetic metal fine powder is preferably from 1400 Oe to 3500 Oe, more preferably from 1,800 Oe to 3000 Oe.

The water content of the ferromagnetic metal fine powder is 0.01 to 2
% Is preferable. It is preferable to optimize the water content of the ferromagnetic metal fine powder depending on the type of the binder. It is preferable that the pH of the ferromagnetic metal powder be optimized by a combination with the binder used. Its range is from 4 to 12, preferably from 6 to 10. The ferromagnetic metal fine powder may be subjected to a surface treatment with Al, Si, P or an oxide thereof, if necessary. The amount is 0.1 to 10% with respect to the ferromagnetic metal fine powder, and the surface treatment is preferable because the adsorption of a lubricant such as a fatty acid becomes 100 mg / m ² or less. Soluble Na, Ca, Fe,
It may contain inorganic ions such as Ni and Sr. It is preferable that these are essentially absent, but if they are 200 ppm or less, there is little influence on the characteristics. The ferromagnetic metal fine powder used in the present invention preferably has a small number of vacancies, and the value is preferably 20% by volume or less, more preferably 5% by volume or less.
% By volume or less. The shape may be any of a needle shape, a rice grain shape, and a spindle shape as long as the characteristics of the particle size described above are satisfied. The SFD of the ferromagnetic metal fine powder itself is preferably small, and is preferably 0.8 or less.
It is necessary to reduce the distribution of Hc in the ferromagnetic metal fine powder. When the SFD is 0.8 or less, the electromagnetic conversion characteristics are good, the output is high, and the magnetization reversal is sharp and the peak shift is small, which is suitable for high-density digital magnetic recording. In order to reduce the distribution of Hc, there are methods of improving the particle size distribution of goethite in ferromagnetic metal fine powder, preventing sintering, and the like. [Description of Hexagonal Ferrite Fine Powder] As the hexagonal ferrite contained in the uppermost layer of the present invention, there are barium ferrite, strontium ferrite, lead ferrite, calcium ferrite substitution products, Co substitution products and the like. Specific examples include magnetoplumbite-type barium ferrite and strontium ferrite, magnetoplumbite-type ferrite whose particle surface is coated with spinel, and magnetoplumbite-type barium ferrite and strontium ferrite further containing a part of spinel phase. , Other than 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
It may contain atoms such as n, Zn, Ni, Sr, B, Ge, and Nb. Generally, Co-Ti, Co-Ti-
Zr, Co-Ti-Zn, Ni-Ti-Zn, Nb-Z
A substance to which an element such as n-Co, Sb-Zn-Co, or Nb-Zn is added can be used. Some raw materials and production methods contain specific impurities.

The particle size is 10 to 200 nm in hexagonal plate diameter,
Preferably it is 20 to 100 nm. When reproducing with a magnetoresistive head, it is necessary to reduce noise, and the plate diameter is 40
nm or less is preferable, but if it is 10 nm or less, stable magnetization cannot be expected due to thermal fluctuation. Above 200nm the noise is high,
Neither is suitable for high-density magnetic recording. Plate ratio (plate diameter /
1 to 15 is desirable. Preferably it is 2-7. When the plate ratio is small, the filling property in the magnetic layer is increased, which is preferable, but sufficient orientation cannot be obtained. If it is larger than 15, noise increases due to stacking between particles. The specific surface area of the particle size range by the BET method is 10 to 20.
0 m ² / g. The specific surface area substantially coincides with an arithmetic calculation value from the particle plate diameter and the plate thickness. Crystallite size is 50-450
{, Preferably 100 to 350}. The distribution of particle plate diameter and plate thickness is generally preferably as narrow as possible. Although it is difficult to make a numerical value, it can be compared by randomly measuring 500 particles from a particle TEM photograph. The distribution is often not normal,
When calculated and expressed as a standard deviation with respect to the average size, σ / average size = 0.1 to 2.0. In order to sharpen the particle size distribution, the particle generation reaction system is made as uniform as possible, and the generated particles are subjected to a distribution improving treatment. For example, a method of selectively dissolving ultrafine particles in an acid solution is also known. The coercive force Hc measured on the magnetic material can be made up to about 500 Oe to 5000 Oe. H
A higher c is advantageous for high-density recording, but is limited by the capability of the recording head. Usually, it is about 800 Oe to 4000 Oe, but is preferably 1500 Oe or more and 3500 Oe or less. When the saturation magnetization of the head exceeds 1.4 Tesler, it is preferable that the saturation magnetization be 2000 Oe or more. Hc can be controlled by particle size (plate diameter / plate thickness), kind and amount of contained element, substitution site of element, particle generation reaction condition and the like. The saturation magnetization as is 40 emu / g to 80 emu / g. The higher the value of σs, the better, but the smaller the fine particles, the lower the tendency. It is well known to combine spinel ferrite with magnetoplumbite ferrite to improve σs, and to select the type of element contained and the amount to be added. It is also possible to use W-type hexagonal ferrite. When dispersing the magnetic substance, the surface of the magnetic substance particles is treated with a substance suitable for the dispersion medium and the binder. Surface treatment materials are inorganic compounds,
Organic compounds are used. The main compounds are Si and A
Representative examples include oxides or hydroxides of l, P, etc., various silane coupling agents, and various titanium coupling agents.
The amount is 0.1 to 10% based on the magnetic material. P of magnetic material
H is also important for dispersion. Usually, the optimum value is about 4 to 12, depending on the dispersion medium and the binder, but about 6 to 10 is selected from the chemical stability and storage stability of the medium. Water contained in the magnetic material also affects dispersion. There is an optimum value depending on the dispersion medium and the binder, but usually 0.01 to 2.0% is selected. Hexagonal ferrite is produced by mixing barium oxide, iron oxide, and a metal oxide that replaces iron with boron oxide as a glass-forming substance to obtain the desired ferrite composition, then melting, quenching, and then crystallization. After the body and then reheat treatment,
A glass crystallization method of obtaining barium ferrite crystal powder by washing and pulverization, neutralizing a barium ferrite composition metal salt solution with an alkali, removing by-products, heating the liquid phase at 100 ° C. or higher, and then washing, drying, A hydrothermal reaction method in which a barium ferrite crystal powder is obtained by pulverization, a barium ferrite composition metal salt solution is neutralized with an alkali, by-products are removed, dried and treated at 1100 ° C. or lower, and pulverized to obtain a barium ferrite crystal. There is a coprecipitation method for obtaining a powder, etc., but the present invention does not select a production method. [Description of Underlayer] Next, when an underlayer (hereinafter, also referred to as a lower layer or a non-magnetic layer) is used, a detailed description thereof will be given. The inorganic powder used for the underlayer of the present invention is a non-magnetic powder and is selected from, for example, inorganic compounds such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides, and the like. be able to. Examples of the inorganic compound include α-alumina, β-alumina, γ-alumina, θ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, goethite, corundum, silicon nitride, and titanium having an α conversion of 90% or more. Carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide,
Tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide and the like are used alone or in combination. Particularly preferred are titanium dioxide, zinc oxide, iron oxide and barium sulfate because of their small particle size distribution and many means for imparting functions, and more preferred are titanium dioxide and α-iron oxide. The particle size of these non-magnetic powders is preferably from 0.005 to 2 μm, but if necessary, non-magnetic powders having different particle sizes may be combined, or even a single non-magnetic powder may have the same effect by widening the particle size distribution. You can also. Particularly preferably, the particle size of the nonmagnetic powder is from 0.01 μm to 0.2 μm. In particular, when the non-magnetic powder is a granular metal oxide, the average particle size is not more than 0.1.
08 μm or less, and in the case of an acicular metal oxide, the major axis length is preferably 0.3 μm or less. The tap density is 0.05-2 g / ml, preferably 0.2-1.5 g / ml. The water content of the non-magnetic powder is 0.1 to 5% by weight, preferably 0.2 to 3% by weight, more preferably 0.3 to 1.5% by weight. The pH of the nonmagnetic powder is 2 to 11, but p
H is particularly preferably between 5.5 and 10. The specific surface area of the nonmagnetic powder is 1 to 100 m ² / g, preferably 5 to 80 m ² / g, more preferably 10 to 70 m ² / g. The crystallite size of the nonmagnetic powder is preferably from 0.004 μm to 1 μm,
It is more preferably from 4 μm to 0.1 μm. Oil absorption using DBP (dibutyl phthalate) is 5 to 100 ml / 100 g, preferably 10 to 80 ml / 100 g, and more preferably 20 to 6 ml.
It is 0ml / 100g. Specific gravity is 1 to 12, preferably 3 to 6
It is. The shape may be any of a needle shape, a spherical shape, a polyhedral shape, and a plate shape. The Mohs' hardness is preferably 4 or more and 10 or less. Non-magnetic powder has a SA (stearic acid) adsorption amount of 1 to 2
It is 0 μmol / m ² , preferably ² to 15 μmol / m ² , more preferably 3 to 8 μmol / m ² . Preferably, the pH is between 3 and 6. The surface of these nonmagnetic powders has Al
₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , S
It is preferable to perform a surface treatment with b ₂ O ₃ , ZnO, and Y ₂ O ₃ . Particularly preferable for dispersibility are Al ₂ O ₃ and SiO _2.
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.
Further, a co-precipitated surface treatment layer may be used according to the purpose, or a method of first treating with alumina and then treating the surface layer with silica, or vice versa, may be employed. Although the surface treatment layer may be a porous layer depending on the purpose, it is generally preferable that the surface treatment layer be homogeneous and dense. Needless to say, these surface treatment amounts should be optimized depending on the binder used, dispersion conditions, and the like.

Specific examples of the non-magnetic powder used in the lower layer of the present invention include Nanotite manufactured by Showa Denko, HIT-100, ZA-G1 manufactured by Sumitomo Chemical, and α-hematite DPN-250 and DPN-250BX manufactured by Toda Kogyo. , DPN-24
5, DPN-270BX, DBN-SA1, DBN-S
A3, Titanium oxide TTO-51B, TTO- manufactured by Ishihara Sangyo
55A, TTO-55B, TTO-55C, TTO-5
5S, TTO-55D, SN-100, α hematite E
270, E271, E300, E303, Titanium Oxide STT-4D, STT-30D, STT-3
0, STT-65C, α-hematite α-40, MT-100S, MT-100T, MT-150W, M manufactured by Teika
T-500B, MT-600B, MT-100F, MT
-500HD, Sakai Chemical FINEX-25, BF-1,
BF-10, BF-20, ST-M, DEF manufactured by Dowa Mining
IC-Y, DEFIC-R, AS2B made by Nippon Aerosil
M, TiO2P25, Ube Industries 100A, 500A,
And baked products thereof. Particularly preferred non-magnetic powders are titanium dioxide and α-iron oxide.

By mixing carbon black in the lower layer, it is possible to lower the surface electrical resistance Rs, which is a known effect, to reduce the light transmittance, and to obtain a desired micro Vickers hardness. In addition, it is possible to bring about the effect of storing the lubricant by including carbon black in the lower layer. As the type of carbon black, furnace for rubber, thermal for rubber, black for color, acetylene black, and the like can be used. The following characteristics of the carbon black in the lower layer should be optimized depending on the desired effect, and the combined effect may provide more effects.

The specific surface area of the carbon black in the lower layer is 10
0 to 500 m ² / g, preferably 150 to 400 m ² / g,
DBP oil absorption is 20-400ml / 100g, preferably 30
~ 200ml / 100g. The particle size of the carbon black is 5 μm to 80 μm, preferably 10 to 50 μm, more preferably 10 to 40 μm. Carbon black p
H is preferably 2 to 10, the water content is preferably 0.1 to 10%, and the tap density is preferably 0.1 to 1 g / ml. Specific examples of the carbon black used in the present invention include B.C.
LACKPEARLS 2000, 1300, 100
0,900,800,880,700, VULCAN
XC-72, manufactured by Mitsubishi Kasei Kogyo Co., Ltd. # 3050B, # 31
50B, # 3250B, # 3750B, # 3950B,
# 950, # 650B, # 970B, # 850B, MA
-600, MA-230, # 4000, # 4010, CONDUCTEX SC manufactured by Konlon Via Carbon,
Raven 8800,8000,7000,575
0,5250,3500,2100,2000,180
0, 1500, 1255, 1250, and Ketjen Black EC manufactured by Akzo Corporation. Carbon black may be used after being surface-treated with a dispersant or the like or grafted with a resin, or may be used in which a part of the surface is graphitized. Further, the carbon black may be dispersed in a binder before adding it to the paint. These carbon blacks can be used in an amount not exceeding 50% by weight and not exceeding 40% of the total weight of the nonmagnetic layer based on the inorganic powder. 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).

In the lower layer, an organic powder is used according to the purpose.
It can also be added. For example, acrylic styrene-based resin powder, benzoguanamine resin powder, melamine-based resin powder, phthalocyanine-based pigments, but also polyolefin-based resin powder, polyester-based resin powder, polyamide-based resin powder, polyimide-based resin powder, and polyfluoroethylene resin Can be used. The manufacturing method is disclosed in
No. 18,564, and those described in JP-A-60-255827 can be used.

The binder resin, lubricant, dispersant, additive, solvent, dispersing method, etc. of the lower layer can be the same as those of the magnetic layer described below. In particular, binder resin amount, type, additives,
Known techniques for the magnetic layer can be applied to the amount and type of the dispersant. [Description of Binder] As the binder used in the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins and mixtures thereof are used. As the thermoplastic resin, the glass transition temperature is −100 to 150 ° C., the number average molecular weight is 1,000 to 200,000, preferably 10,000 to
100,000 and a degree of polymerization of about 50 to 1,000.

Such examples include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid,
Acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene,
There are polymers or copolymers containing butadiene, ethylene, vinyl butyral, vinyl acetal, vinyl ether, and the like as constituent units, polyurethane resins, and various rubber resins. In addition, as a thermosetting resin or a reactive resin, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic-based reactive resin, formaldehyde resin, silicone resin,
Examples include epoxy-polyamide resin, a mixture of polyester resin and isocyanate prepolymer, a mixture of polyester polyol and polyisocyanate, and a mixture of polyurethane and polyisocyanate. These resins are described in detail in "Plastic Handbook" published by Asakura Shoten. In addition, a known electron beam-curable resin can be used for each layer. These examples and the production method thereof are described in detail in JP-A-62-256219. The above resins can be used alone or in combination, but preferred are vinyl chloride resins,
A combination of at least one selected from vinyl chloride vinyl acetate copolymer, vinyl chloride vinyl acetate vinyl alcohol copolymer, vinyl chloride vinyl acetate maleic anhydride copolymer and a polyurethane resin, or a combination of these with a polyisocyanate Is raised.

As the structure of the polyurethane resin, known materials such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. For all of the binders shown here, COO is required to obtain better dispersibility and durability.
M, SO ₃ M, OSO ₃ M, P = O (OM) ₂ , O−
P = O (OM) ₂ , wherein M is a hydrogen atom or an alkali metal base, OH, NR ₂ , N ⁺ R ₃ (R is a hydrocarbon group), an epoxy group, SH, CN, or the like. It is preferable to use one obtained by introducing one or more polar groups 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 Carbide.
HH, VMCH, VAGF, VAGD, VROH, VY
ES, VYNC, VMCC, XYHL, XYSG, PK
HH, PKHJ, PKHC, PKFE, manufactured by Nissin Chemical 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-104, MR-105, MR
110, MR100, MR555, 400X-110
A, Nipporan N2301, N2 manufactured by Nippon Polyurethanes
302, N2304, Pandex T manufactured by Dainippon Ink and Chemicals, Inc.
-5105, T-R3080, T-5201, Burnock D-400, D-210-80, Crisbon 610
9,7209, Toyobo Byron UR8200, UR
8300, UR-8700, RV530, RV280,
Daiferamine 4020, 5020, 5 manufactured by Dainichi Seika
100, 5300, 9020, 9022, 7020, manufactured by Mitsubishi Kasei Co., Ltd., MX5004, Samprene S manufactured by Sanyo Kasei Co., Ltd.
P-150 and Saran F310, F210 manufactured by Asahi Kasei Corporation.

The binder used in the non-magnetic layer and the magnetic layer of the present invention is in the range of 5 to 50% by weight, preferably 10 to 50% by weight, based on the non-magnetic powder (excluding carbon black) or the magnetic material.
It is used in the range of 30% by weight. 5 to 30% by weight when using a vinyl chloride resin, 2 to 20% by weight when using a polyurethane resin, 2 to 20% by weight of polyisocyanate
It is preferable to use these in combination in the range of weight%. For example, when head corrosion occurs due to a slight amount of dechlorination, it is also possible to use only polyurethane or only polyurethane and isocyanate. In the present invention, when polyurethane is used, the glass transition temperature is -50 to 150C, preferably 0C to 100C, the breaking elongation is 100 to 2000%, and the breaking stress is 0.05 to 10 kg.
/ mm ² , and the yield point is preferably 0.05 to 10 kg / mm ² .

The magnetic recording medium of the present invention comprises two or more layers. Therefore, the amount of the binder, the amount of the vinyl chloride resin, the polyurethane resin, the polyisocyanate or the other resin in the binder, the molecular weight of each resin forming the magnetic layer, the amount of the polar group, or the resin described above. It is of course possible to change the physical characteristics of the non-magnetic layer and the magnetic layer as needed, and rather, it should be optimized for each layer, and a known technique for a multilayer magnetic layer 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 magnetic layer in order to reduce scratches on the surface of the magnetic layer. Can be made flexible by increasing the amount of binder.

Examples of the polyisocyanate used in the present invention include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and naphthylene-isocyanate.
1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, isocyanates such as triphenylmethane triisocyanate,
Products of these isocyanates and polyalcohols, and polyisocyanates formed by condensation of isocyanates can be used. Commercially available trade names of these isocyanates include Nippon Polyurethane Co., Ltd., Coronate L, Coronate HL,
Coronate 2030, Coronate 2031, Millionate MR, Millionate MTL, Takenate D-102, Takenate D-110N, Takenate D
-200, Takenate D-202, manufactured by Sumitomo Bayer,
There are Death Module L, Death Module IL, Death Module N, Death Module HL, etc. These can be used alone or in combination of two or more layers by utilizing the difference in curing reactivity. [Description of Carbon Black and Abrasive] As the carbon black used in the magnetic layer of the present invention, furnace for rubber, thermal for rubber, black for color, acetylene black and the like can be used. Specific surface area is 5-50
0 m ² / g, DBP oil absorption 10-400 ml / 100
g, particle size is 5 nm to 300 nm, pH is 2 to 10, water content is 0.1 to 10%, tap density is 0.1 to 1 g / c.
c is preferred. Specific examples of carbon black used in the present invention include BLACKPE manufactured by Cabot Corporation.
ARLS 2000, 1300, 1000, 900, 9
05, 800, 700, VULCAN XC-72, manufactured by Asahi Carbon Co., Ltd., # 80, # 60, # 55, # 50, # 3
5. # 2400B, # 2300, #, manufactured by Mitsubishi Kasei Kogyo Co., Ltd.
900, # 1000 # 30, # 40, # 10B, manufactured by Columbian Carbon Co., Ltd., CONDUCTEX SC, RA
VEN 150, 50, 40, 15, RAVEN-MT
-P, manufactured by EC Japan, Ketjen Black EC, and the like. Carbon black may be used after being surface-treated with a dispersant or the like or grafted with a resin, or may be used in which a part of the surface is graphitized. Before adding the carbon black to the magnetic paint, the carbon black may be dispersed in a binder in advance. These carbon blacks can be used alone or in combination. When carbon black is used, it is preferable to use 0.1 to 30% of the amount based on the magnetic material. Carbon black has functions such as antistaticity of the magnetic layer, reduction of friction coefficient, provision of light-shielding properties, and improvement of film strength, and these differ depending on the carbon black used. Therefore, these carbon blacks used in the present invention, the upper layer, the type in the lower layer,
Change the amount and combination, particle size, oil absorption, conductivity, pH
It is, of course, possible to selectively use them according to the purpose based on the above-mentioned various characteristics, but rather, it should be optimized in each layer. The carbon black that can be used in the magnetic layer of the present invention can be referred to, for example, "Carbon Black Handbook" edited by Carbon Black Association. Examples of the abrasive used in the present invention include α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, artificial diamond, silicon nitride, and silicon carbide titanium carbide having an α conversion of 90% or more. Known materials mainly having a Mohs hardness of 6 or more, such as a bite, titanium oxide, silicon dioxide, and boron nitride, are used alone or in combination. Further, a composite of these abrasives (abrasive whose surface is treated with another abrasive) may be used. These abrasives may contain compounds or elements other than the main component, but the effect remains unchanged if the main component is 90% or more. The particle size of these abrasives is preferably from 0.01 to 2 μm,
In particular, in order to enhance the electromagnetic conversion characteristics, it is preferable that the particle size distribution is narrow. Further, in order to improve the durability, it is possible to combine abrasives having different particle sizes as needed, or to achieve the same effect by widening the particle size distribution even with a single abrasive. Tap density: 0.3-2 g / cc, water content: 0.1-5%, pH: 2-11, specific surface area: 1-3
0 m ² / g is preferred. The shape of the abrasive used in the present invention may be any of a needle shape, a spherical shape, and a dice shape, but a shape having a part of a corner is preferable because of high abrasiveness. Specifically, AKP-12, AKP-15, and AK manufactured by Sumitomo Chemical Co., Ltd.
P-20, AKP-30, AKP-50, HIT20,
HIT-30, HIT-55, HIT60, HIT7
0, HIT80, HIT100, Reynolds, ER
C-DBM, HP-DBM, HPS-DBM, Fujimi Abrasives, WA10000, Uemura Industries, UB20,
Nihon Kagaku Kogyo Co., Ltd., G-5, Chromex U2, Chromex U1, Toda Kogyo Co., Ltd., TF100, TF140,
Examples include IBIDEN's Beta Random Ultra Fine, Showa Mining's B-3, and the like. These abrasives can be added to the nonmagnetic layer as needed. By adding to the non-magnetic layer, the surface shape can be controlled, and the projected state of the abrasive can be controlled. The particle size and amount of the abrasive added to the magnetic layer and the non-magnetic layer should of course be set to optimal values. [Description of Additives] As the additives used in the magnetic layer and the nonmagnetic layer of the present invention, those having a lubricating effect, an antistatic effect, a dispersing effect, a plasticizing effect and the like are used. Molybdenum disulfide, tungsten graphite disulfide, boron nitride, graphite fluoride, silicone oil, silicone with polar groups, fatty acid-modified silicone, fluorine-containing silicone, fluorine-containing alcohol, fluorine-containing ester, polyolefin, polyglycol, alkyl phosphate and Alkali metal salts thereof, alkyl sulfates and alkali metal salts thereof, polyphenyl ether, phenylphosphonic acid, aminoquinones, various silane coupling agents, titanium coupling agents, fluorine-containing alkyl sulfates and alkali metal salts thereof, having 10 carbon atoms ~ 24
Monobasic fatty acids (which may contain unsaturated bonds or may be branched), and metal salts thereof (L
i, Na, K, Cu, etc.) or a monovalent, divalent, trivalent, tetravalent, pentavalent, hexavalent alcohol having 12 to 22 carbon atoms (including an unsaturated bond or branched. C12 to C22 alkoxy alcohols, C10 to C24 monobasic fatty acids (which may contain unsaturated bonds or may be branched) and C2 to C12
Mono-fatty acid esters or di-fatty acids comprising any one of monohydric, divalent, trivalent, tetravalent, pentavalent, and hexavalent alcohols (which may contain an unsaturated bond or may be branched) Esters or trifatty acid esters, fatty acid esters of monoalkyl ethers of alkylene oxide polymers, fatty acid amides having 8 to 22 carbon atoms, and aliphatic amines having 8 to 22 carbon atoms can be used.

Specific examples of these fatty acids include capric acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid and isostearic acid. No. Esters include butyl stearate, octyl stearate, amyl stearate, isooctyl stearate, butyl myristate, octyl myristate, butoxyethyl stearate, butoxydiethyl stearate, 2-ethylhexyl stearate, and 2-octyldodecyl palmitate. 2-hexyldecyl palmitate, isohexadecyl stearate, oleyl oleate, dodecyl stearate, tridecyl stearate, oleyl erucate, neopentyl glycol didecanate, alcohols such as oleyl alcohol, stearyl alcohol, lauryl alcohol, And so on. Also, nonionic surfactants such as alkylene oxides, glycerin, glycidol, alkylphenol ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, phosphonium or sulfoniums, etc. Cationic surfactants, carboxylic acids, sulfonic acids, phosphoric acids, sulfate groups, phosphate groups, anionic surfactants containing acidic groups such as amino acids, aminosulfonic acids, sulfuric acid or phosphates of amino alcohols, An amphoteric surfactant such as an alkylbedine type can also be used. About these surfactants, "Handbook of Surfactants" (published by Sangyo Tosho Co., Ltd.)
In more detail. These lubricants, antistatic agents, and the like are not necessarily 100% pure, and may contain impurities such as isomers, unreacted materials, by-products, decomposed products, oxides, and the like in addition to the main components. These impurities are preferably 30% or less, more preferably 10% or less.

Each of these lubricants and surfactants used in the present invention has a different physical action.
The type, amount, and combination ratio of the lubricant that produces a synergistic effect should be optimally determined according to the purpose.
To control bleeding to the surface by using fatty acids with different melting points in the non-magnetic layer and magnetic layer, to control bleeding to the surface by using esters with different boiling points, melting points and polarities, and to adjust the amount of surfactant It can be considered to improve the stability of coating and to improve the lubricating effect by increasing the amount of the lubricant added in the intermediate layer, and it is needless to say that the present invention is not limited to the examples shown here. Generally, the total amount of the lubricant is from 0.1% to 50%, preferably from 2% to 2%, based on the magnetic substance or the non-magnetic powder.
It is selected in the range of 5%.

All or a part of the additives used in the present invention may be added at any step in the production of magnetic and non-magnetic paints. There are a case where it is added in a kneading step using a body, a binder and a solvent, a case where it is added in a dispersion step, a case where it is added after dispersion, and a case where it is added just before coating. In some cases, the purpose may be achieved by applying a part or all of the additive 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 the slit is completed. Known organic solvents can be used in the present invention.
The solvent described in 453 can be used. [Description of Production Method] The step of producing the magnetic coating material of 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 as necessary. Each step may be divided into two or more steps. Magnetic material used in the present invention, non-magnetic powder, binder, carbon black, abrasive, antistatic agent,
All raw materials such as a lubricant and a solvent may be added at the beginning or during any step. Further, individual raw materials may be added in two or more steps in a divided manner. For example,
Polyurethane may be added separately 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, a conventionally known manufacturing technique can be used as a part of the steps. In the kneading step, it is preferable to use one having a strong kneading force, such as an open kneader, a continuous kneader, a pressure kneader, and an extruder. When a kneader is used, the magnetic material or the nonmagnetic powder and all or a part of the binder (however, preferably 30% or more of the total binder) and the magnetic material are kneaded in the range of 15 to 500 parts with respect to 100 parts. . Details of these kneading processes are described in Japanese Patent Application Nos. 62-264722 and 62-236.
872. Glass beads can be used to disperse the magnetic layer solution and the non-magnetic layer solution, but zirconia beads, titania beads, and steel beads, which are high-density dispersion media, are preferable. The particle size and the filling rate of these dispersion media are optimized and used. A well-known disperser can be used.

When applying a magnetic recording medium having a multilayer structure in the present invention, it is preferable to use the following method. First, a gravure coating, a roll coating, a blade coating, an extrusion coating device, etc., which are generally used in the application of a magnetic paint, are used to apply a base layer first. JP-A-60-2
38179, a method of applying an upper layer by a support pressure type extrusion coating apparatus disclosed in JP-A-2-265672. Second, upper and lower layers are coated almost simultaneously by one coating head having two built-in coating liquid passage slits as disclosed in JP-A-63-88080 and JP-A-2-17971. Method. A third method is to apply the upper and lower layers almost simultaneously using an extrusion coating apparatus with a backup roll disclosed in Japanese Patent Application Laid-Open No. 2-174965. Incidentally, in order to prevent the electromagnetic conversion characteristics of the magnetic recording medium from deteriorating due to agglomeration of magnetic particles, Japanese Patent Application Laid-Open Nos. 62-95174 and 1-2369.
It is desirable to apply shear to the coating liquid inside the coating head by a method as disclosed in No. 68. further,
The viscosity of the coating solution must satisfy the numerical range disclosed in Japanese Patent Application No. 1-312659. In order to realize the constitution of the present invention, it is of course possible to use a sequential multi-layer coating in which a magnetic layer is provided thereon after coating and drying a base layer, and the effect of the present invention is not lost. However, in order to reduce coating defects and improve quality such as dropout, it is preferable to use the above-described simultaneous multilayer coating.

In some cases, sufficient isotropic orientation can be obtained even without orientation, without using an orientation device. However, a known random orientation device such as alternately arranging cobalt magnets diagonally or applying an alternating magnetic field with a solenoid. It is preferable to use In the case of ferromagnetic metal fine powder, isotropic orientation is generally preferable to be in-plane two-dimensional random, but it is preferable to add three-dimensional
It can be dimensionally random. In the case of hexagonal ferrite, three-dimensional randomness in the in-plane and vertical directions generally tends to occur, but in-plane two-dimensional randomness is also possible. In addition, isotropic magnetic characteristics can be imparted in the circumferential direction by using a known method such as a different polarity opposed magnet and making the magnets vertically oriented. In particular, when performing high-density recording, vertical alignment is preferable. It is preferable that the drying position of the coating film can be controlled by controlling the temperature of the drying air, the amount of air, and the application speed. The application speed is preferably 20 m / min to 1000 m / min, and the temperature of the drying air is preferably 60 ° C. or higher. It is also possible to carry out a moderate predrying before entering the magnet zone.

A calendering roll is treated with a heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimideamide or a metal roll.
In particular, in the case of forming a double-sided magnetic layer, it is preferable to perform the treatment with metal rolls. The processing temperature is preferably 50 ° C. or higher,
More preferably, the temperature is 100 ° C. or higher. The linear pressure is preferably 200 kg / cm or more, more preferably 300 kg / cm.
That is all. [Description of Physical Properties] The saturation magnetic flux density of the magnetic layer of the magnetic recording medium according to the present invention is 2,000 G (Gauss) or more and 5,000 G or less when ferromagnetic metal fine powder is used, and 800 G or more and 3000 G or less when hexagonal ferrite is used. It is. Coercive force Hc and Hr are 1000 Oe or more and 50
00 Oe or less, preferably 1500 Oe or more,
It is 3000 Oe or less. The distribution of coercive force is preferably narrow, and SFD and SFDr are preferably 0.6 or less.
The squareness ratio is 0.55 or more and 0.67 for two-dimensional randomness.
Or less, preferably 0.58 or more and 0.64 or less; It is preferably 45 or more and 0.55 or less. In the case of vertical alignment, it is 0.6 or more, preferably 0.7 or more in the vertical direction, and when demagnetizing field correction is performed, it is 0.7 or more, preferably 0.8 or more. The orientation ratio is preferably 0.8 or more for both two-dimensional random and three-dimensional random. For two-dimensional random, vertical squareness ratio, Br, Hc and H
r is preferably within 0.1 to 0.5 times the in-plane direction.

The coefficient of friction of the magnetic recording medium of the present invention with respect to the head is -10 ° C. to 40 ° C. and humidity is 0% to 95%.
0.5 or less, preferably 0.3 or less, and the surface resistivity is preferably 10 ⁴ to 10 ¹² ohm / s.
q, the charge potential is preferably within the range of -500V to + 500V. Preferably 100 to 2,000 kg / mm ² in elastic modulus plane directions at 0.5% elongation of the magnetic layer, the breaking strength is preferably 10 to 70 kg / mm ^2, the modulus of elasticity of the magnetic recording medium is plane directions in preferably 100 to 1,500 / mm ^2, the residual elongation is preferably 0.5% or less, the thermal shrinkage rate at all temperatures 100 ° C. or less, preferably 1% or less, more preferably 0.5% or less, most preferably Is 0.1% or less. The glass transition temperature of the magnetic layer (the maximum point of loss elastic modulus in dynamic viscoelasticity measurement measured at 110 Hz) is 50 ° C or more and 120 ° C or more.
° C or less, and that of the lower nonmagnetic layer is 0 ° C to 100 ° C.
C is preferred. Loss modulus is 1 × 10 ⁸ to 8 × 10 ⁹ dyn
e / cm ² , the loss tangent is 0.2
The following is preferred. If the loss tangent is too large, adhesion failure is likely to occur. It is preferable that these thermal characteristics and mechanical characteristics are substantially equal within 10% in each direction in the plane of the medium. The residual solvent contained in the coating layer is preferably 100 mg
/ m ² or less, more preferably 10 mg / m ² or less. The porosity of the coating layer is preferably 30% by volume or less, more preferably 20% by volume or less, for both the nonmagnetic layer and the magnetic layer. The porosity is preferably small in order to achieve high output, but it may be better to secure a certain value depending on the purpose. For example, in a disk medium in which repeated use is emphasized, a larger porosity is often preferable in running durability.

The center layer surface roughness SRa of the magnetic layer measured by the Mirau method of TOPO-3D is 10 nm or less, preferably 5 nm or less, more preferably 3 nm or less. The maximum height SRmax of the magnetic layer is 0.5 μm or less, and the ten-point average roughness S
Rz is 0.3 μm or less, and peak height SRp is 0.3 μm.
m, the center plane valley depth SRv is 0.3 μm or less, the center plane area ratio SSr is 20% or more, 80% or less, and the average wavelength Sλ.
a is preferably 5 μm or more and 300 μm or less. The surface protrusions of the magnetic layer should be 0.01 μm to 1 μm in size.
It is preferable to arbitrarily set the friction coefficient in the range of 2,000 to 2,000 to optimize the friction coefficient. These can be easily controlled by controlling the surface properties by the filler of the support, the particle size and amount of the powder added to the magnetic layer, the roll surface shape of the calendering treatment, and the like. The curl is preferably within ± 3 mm.

When the magnetic recording medium of the present invention has a nonmagnetic layer and a magnetic layer, it is easily presumed that the physical properties of the nonmagnetic 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.

[0048]

【Example】

<Preparation of paint> Magnetic paint X Ferromagnetic metal fine powder 100 parts Composition: 70% Fe, 30% Co, Hc2300 Oe, specific surface area 55 m ² / g, σs 140 emu / g Crystallite size 155 nm, major axis length 0.065 μm, needle shape The ratio 5 sintering inhibitor Al compound (Al / Fe atomic ratio 8%) Y compound (Y / Fe atomic ratio of 6%) vinyl chloride copolymers (-SO ₃ K content) 12 parts MR 110 (made by Nippon Zeon Co., Ltd.) polyurethane (Containing -SO ₃ Na): UR8200 (manufactured by Toyobo Co., Ltd.) 3 parts α-alumina (average particle size: 0.2 μm): HIT55 (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts # 50 (manufactured by Asahi Carbon Co., Ltd.) 5 parts Butyl stearate 10 parts of butoxyethyl stearate 5 parts isohexadecyl stearate 3 parts stearic acid 2 parts Methyl ethyl ketone 180 parts cyclohexanone 180 parts magnetic paint Y Bali Beam ferrite magnetic powder 100 parts-to Ba molar ratio composition: Fe9.10, Co0.20, Zn0.77 Hc2500Oe, a specific surface area of ^{50m 2 / g, σs 58emu /} g plate size 30 nm, plate ratio 3.5 MR 110 (Nippon Zeon 12 parts UR8200 (manufactured by Toyobo) 3 parts HIT55 (manufactured by Sumitomo Chemical) 10 parts # 50 (manufactured by Asahi Carbon) 5 parts butyl stearate 10 parts butoxyethyl stearate 5 parts isohexadecyl stearate 3 parts Stearic acid 2 parts Methyl ethyl ketone 125 parts Cyclohexanone 125 parts Non-magnetic paint Z non-magnetic powder TiO ₂ crystalline rutile 80 parts Average primary particle diameter 0.035 μm, Specific surface area by BET method 40 m ² / g pH 7 TiO ₂ content 90% or more DBP oil absorption 27-38 g / 100 g, surface treatment agent Al ₂ O ₃ 8 wt% Conductex SC -U (manufactured by Columbian Carbon Co.) 20 parts MR110 12 parts UR8200 5 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 Parts [Description of Examples and Comparative Examples] For each of the above three paints, each component was kneaded with a kneader and then dispersed using a sand mill. To the resulting dispersion was added 10 parts of a polyisocyanate for the coating solution for the non-magnetic layer and 10 parts for the coating solution for the magnetic layer.
0 parts were added, and the mixture was filtered using a filter having an average pore diameter of 1 μm to prepare a coating solution for forming a nonmagnetic layer and a coating solution for forming a magnetic layer, respectively.

The non-magnetic layer coating solution Z was dried to a thickness of 1.5 μm, and immediately thereafter, the magnetic layer coating material X was dried thereon to a thickness of 0.2 μm. As a result, simultaneous multilayer coating was performed on a polyethylene naphthalate support having a thickness of 58 μm and a surface roughness of 5 nm. While both layers are still wet, they are passed through an AC magnetic field generator with a frequency of 50 Hz and a magnetic field strength of 250 Gauss or a frequency of 50 Hz and 120 Gauss and subjected to random orientation treatment and dried. Temperature 90 ° C, linear pressure 30
The disk was treated at 0 kg / cm 2, punched out to a disk outer diameter b of 94 mm as shown in FIG. 1, and subjected to a surface polishing treatment to obtain a disk A as a sample A-6.

Subsequently, the disk is rotated at 3000 rpm, and a signal having a recording density of 90 kfci is recorded / reproduced at a position where the outermost diameter D of the recording area is 90 mm. The relationship between the change and the change was examined. A maximum output value and a penetration window, which is a range of the position of the head at which an output of 80% or more of the maximum output value is obtained, were obtained. The larger the penetration window, the more stable the output will be. The maximum output of Sample A-6 was set to 0 dB.

Next, discs having different outer diameters were prepared by changing the diameter of the puncher of the punching machine, and samples in which the outermost diameter D of the recording area was changed were A-1 to A-5, A-7 and A-.
8, B-1 to B-8, and the same measurement was performed. The recording frequency of the recording signal was changed according to the outermost diameter D of the area to be measured so that the recording density was 90 kfci. Next, samples obtained by changing the surface roughness of the support and the thickness of the magnetic layer were A-9 to
The same measurement was performed for A-12 and B-9.

Next, a sample using polyethylene terephthalate (PET) as a support was subjected to B-10 to B-13.
And the same measurement was performed. Next, a sample obtained in the same manner as in Sample A-6 except for using the magnetic layer coating material Y was designated as A-13, and the same measurement was performed. Table 2 shows the measurement results of these samples.

Next, the samples shown in Table 1 or 2 (B-1 to 13 (Comparative Example), A-1 to 13 (Example))
The same measurement was carried out at a rotation speed of 720 rpm for some of the samples, and the results were shown in Samples A-14 to 17 in Table 2.
(Examples) and B-14 to 16 (Comparative Examples).

[0054]

[Table 1]

[0055]

[Table 2]

[Comparison between Example and Comparative Example] It can be seen that the disk-shaped medium of the present invention not only has a high maximum output, but also has a wide head penetration window and stable output. Sample B using conventional PET
From -10 to B-17, not only the output is low but also the penetration window is narrow. In particular, the medium of the present invention using polyethylene naphthalate at the time of high-speed rotation and using the relationship between the outermost diameter D of the recording area and the thickness d of the non-magnetic support according to the present invention as compared with a conventional medium using PET. It can be seen that the penetration window is significantly widened. [Description of Measurement Method] The center surface average surface roughness SRa of the support and the magnetic layer (described as “surface roughness” in the table) is WYK.
Approximately 250 by MIRAU method using TOPO3D manufactured by Company O
SRa of an area of × 250 nm was measured and determined. Spherical correction and cylindrical correction are added at a measurement wavelength of about 650 nm. This method is a non-contact surface roughness meter that measures by light interference.

For the thickness of the magnetic layer, a section sample of the layer was prepared and a scanning electron microscope (S-700, manufactured by Hitachi, Ltd.) was used.
Was obtained from the cross-sectional photograph taken. The thickness d of the nonmagnetic support is an average value of 10 or more measured values using a digital thickness gauge MINICON manufactured by Tokyo Seimitsu Co., Ltd.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a disk-shaped magnetic recording medium according to the present invention.

[Explanation of symbols]

 a center hole diameter b disk outer diameter e outermost circumference of recording area D outermost diameter of recording area

Claims (3)

[Claims] 1. A non-magnetic support comprising a substantially non-magnetic underlayer and a magnetic layer comprising a ferromagnetic metal fine powder or a ferromagnetic hexagonal ferrite fine powder dispersed in a binder in this order. And the nonmagnetic support has a center plane average surface roughness SRa1
0 nm or less polyethylene naphthalate, between the thickness dμm of the non-magnetic support and the outermost diameter Dmm of the recording area,
Relational expression (1): A disk-shaped magnetic recording medium characterized by satisfying a relationship of 1.00 ≦ D / d ≦ 2.00. 2. An outermost diameter of the recording area is not less than 35 mm
mm and the outermost circumference of the recording area has a peripheral speed of 5 m / s
2. The disk-shaped magnetic recording medium according to claim 1, wherein recording / reproducing is performed at the rotation speed described above. 3. The magnetic disk according to claim 1, wherein the outermost periphery of the recording area is recorded / reproduced at a rotational speed of not less than a peripheral speed of 10 m / s, and the center surface average surface roughness SRa of the magnetic layer is not more than 5 nm. 3. The disk-shaped magnetic recording medium according to 2.