JPH08263828A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium suitable for use as a magnetic recording disk for a high capacity floppy disk or a still video floppy, a high capacity data tape or a tape for digital VTR. CONSTITUTION: A nonmagnetic layer and a magnetic layer are successively formed on a substrate. The dry film thickness of the magnetic layer is 0.05-0.3μm. The average major axis size (A) of ferromagnetic metal powder contained in the magnetic layer is 30-110nm and magnetic powder having a major axis size within a range of <=0.9A(nm) accounts for <=20% of the total number of the magnetic powder in the magnetic layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more specifically, it is preferably used as a magnetic recording disk for a large-capacity floppy disk, a still video floppy disk, a large-capacity data tape, or a tape for a digital VTR. Regarding

[0002]

2. Description of the Related Art In Japanese Patent Laid-Open No. 2-254623,
There is disclosed a magnetic recording medium having good electromagnetic conversion characteristics and excellent running durability by setting the SFD of the lower layer within an appropriate range. However, in this case, since the magnetic layer is provided as the lower layer, sufficient output in the high frequency region necessary for a large capacity data tape or a high capacity floppy disk could not be obtained. In addition, in order to cope with the higher capacity of floppy disks and the higher density of data tapes, it is necessary to improve the overwrite characteristics, error rate, and dropout characteristics as well as the higher density than before. However, the above-mentioned technique is not sufficient for solving the problem.

[0003]

The problems of the present invention are: 1) excellent durability for a long time even under a wide range of environmental conditions from high temperature to low temperature, and 2) no error occurs in a wide range of temperature conditions. The object is to provide a magnetic recording medium which has a small dropout under a wide range of temperature conditions, a high reproduction output, and a good overwrite property.

[0004]

[Means for Solving the Problems]

Invention 1: A non-magnetic layer and a magnetic layer are formed on a support in this order to form a magnetic layer having a dry film thickness of 0.05 to 0.3 μm, and the average length of the ferromagnetic metal powder contained in the magnetic layer. When the axial length is A (nm), 30 ≦ A ≦ 110, and the ratio of the magnetic powder having a major axis length in the range of 0.9 Anm or less is 20% or less of the total number of magnetic powders. Magnetic recording medium.

Invention 2: A non-magnetic layer and a magnetic layer are formed on a support in this order to form a magnetic layer having a dry film thickness of 0.05 to 0.3 μm, and a ferromagnetic metal powder contained in the magnetic layer. When the crystallite size of is B (nm), 8 ≦ B ≦
18. The magnetic recording medium according to claim 18, wherein the magnetic layer has an SFD of 0.5 or less.

[0006]

The present inventor has conducted research to solve the above technical problems, and as a result, in order to increase the density, it is essential to reduce the thickness of the upper magnetic layer. To solve the above problems, 1) the average major axis length A (nm) of the ferromagnetic metal powder contained in the magnetic layer is 30 ≦ A ≦ 110.
And the distribution of the major axis length of the magnetic powder is sharp,
For example, when a metal powder having a large particle size distribution is used, or the long axis length caused by the particles breaking during dispersion is 0.9 An
The ratio of magnetic powders having a major axis length of m or less is 20 of the total number of magnetic powders.
% Or less, 2) When the crystallite size of the ferromagnetic metal powder contained in the magnetic layer is B (nm), 8 ≦ B ≦ 1
It was found that the problem can be solved by setting the SFD of the magnetic layer to 8 or less. In order to set the SFD of the magnetic layer to 0.5 or less, 1) use a magnetic powder having a small SFD, 2) perform multi-stage dry orientation in a magnetic field with a combination of electromagnets, and 3) use a pressure kneader or a continuous kneader. The kneading may be carried out with a high shear, and 4) a known method such as adding shear to the coating material by ultrasonic treatment immediately before coating may be appropriately combined.

Here, the film thickness of the upper magnetic layer in the inventions 1 and 2 is preferably 0.08 to 0.2 μm, and 0.0
More preferably, it is 8 to 0.15 μm. The ratio of the magnetic powder having the major axis length in the range of 0.9 Anm or less in Invention 1 is preferably 15% or less of the total number of the magnetic powder.
% Or less is more preferable. In the invention 2, the crystallite size B is preferably 10 ≦ B ≦ 16, and 10 ≦ B ≦ 16.
It is more preferable that B ≦ 14. The SFD of the magnetic layer is preferably 0.20 to 0.45, more preferably 0.25 to 0.40.

Then, specifically, they have found that the problems of the present invention can be solved by the following constitution. Hereinafter, the present invention will be described in detail. (Layer Structure) The magnetic recording medium of the present invention basically comprises a nonmagnetic support and a nonmagnetic layer formed on the nonmagnetic support. In addition, on the surface (back surface) on which the above-mentioned magnetic layer is not provided on the non-magnetic support, improvement in running property and durability of the magnetic recording medium,
It is preferable to provide a back coat layer, a writing layer or a print recording layer, or an anti-counterfeiting layer for the purpose of preventing electrification and transfer, and between the non-magnetic layer and the non-magnetic support. It is also possible to provide an undercoat layer. In addition, an overcoat layer may be provided on the uppermost magnetic layer, if necessary.

(Non-magnetic support) As a material for forming the non-magnetic support, for example, polyesters such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose triacetate, cellulose diacetate, etc. Examples of the cellulose derivative include plastics such as polyamide and polycarbonate.

The form of the non-magnetic support is not particularly limited, and is mainly tape-like, film-like, sheet-like, card-like,
There are disc shape and drum shape.

The thickness of the non-magnetic support is not particularly limited, but usually 3 to 1 in the case of a film or sheet.
00 μm, preferably 5 to 50 μm, about 30 μm to 10 mm in the case of a disk or card, and appropriately selected depending on the recorder etc. in the case of a drum.

The non-magnetic support may have a single structure or a multi-layer structure. Further, the non-magnetic support may be subjected to surface treatment such as corona discharge treatment. A back coat layer may be provided on the surface (front surface) of the non-magnetic support on which the magnetic layer is not provided, for the purpose of improving the running property of the magnetic recording medium, preventing electrification and preventing transfer, and the like. As described above, it is preferable to provide a writing layer or a print recording layer, and an undercoat layer can be provided between the magnetic layer and the non-magnetic support.

(Magnetic Layer) In the present invention, the magnetic layer is
Basically, magnetic powder is dispersed in a binder resin. In the present invention, the magnetic condition of the laminated magnetic layer is S
FD (Switching Field Distribution: Switching Field Distributor)
b)).

Next, SFD will be described with reference to the drawings. The magnetization curve and hysteresis curve of the magnetic material are shown in FIG. The relationship between the magnetic flux density (B) and the magnetic field (H) is represented by B = μdμoH. μo is the magnetic permeability in vacuum, and μd is the relative magnetic permeability in the medium.

From the above equation, the differential coefficient of the magnetic flux density with respect to the magnetic field is

[0016]

[Equation 1] In this case, μd is called differential permeability. On the other hand, the differential curve along the hysteresis curve forms a loop having the extreme value shown in FIG.

If the half-value width related to this extreme value is ΔH, then S
The FD is defined by SFD = ΔH / Hc (2)

The above equations (1) and (2) relate the magnetic permeability to the SFD and further the magnetic field by the differential curve and the full width at half maximum at its extreme value, and Hc and ΔH, which are easy to measure,
That is, the magnetic permeability is grasped from the SFD, and when magnetic particles are used as a medium of the magnetic permeability, the composition of the magnetic material, Hc fluctuation due to crystal defects such as voids in the magnetic material, and focusing on the magnetic layer, It is linked to Hc fluctuations that control magnetic conditions such as packing ratio of magnetic particles, particle number density, and dispersity.
It is regarded as a parameter indicating the fluctuation of c.

As is clear from the definition formula of SFD, SFD
And Hc are reciprocal to each other, but the reciprocity is not always guaranteed depending on the behavior of ΔH. However, there is no finding that the reciprocity is unfavorable experimentally or from the conventionally known hysteresis curve. Is smaller, the SFD is larger.

According to experimental knowledge, magnetic particles having a large BET value give a large SFD. Further, when the SFD is large, the noise component in magnetic recording is reduced, and when the SFD is small, the packing rate of particles is increased. Also, the HiFi voice is H
Recording to a small layer with a large cFD gives good results.

This magnetic layer contains a ferromagnetic metal powder. The thickness of the magnetic layer is usually 0.05 to 0.3 μm, preferably 0.08 to 0.2 μm, and more preferably 0.08 to 0.15 μm.

Ferromagnetic metal powders used in the magnetic layer include Fe, Co, Fe-Al system, and Fe-Al-.
Ni-based, Fe-Al-Zn-based, Fe-Al-Co-based, F
e-Al-Ca system, Fe-Ni system, Fe-Ni-Al
System, Fe-Ni-Co system, Fe-Ni-Si-Al-M
n-based, Fe-Ni-Si-Al-Zn-based, Fe-Al-
Si-based, Fe-Ni-Zn-based, Fe-Ni-Mn-based, F
e-Ni-Si system, Fe-Mn-Zn system, Fe-Co-
Ferromagnetic powders such as Ni-P-based, Ni-Co-based, metal magnetic powders containing Fe, Ni, Co, etc. as main components are exemplified. Among them, Fe-based metal powder has excellent electrical characteristics.

On the other hand, from the viewpoint of corrosion resistance and dispersibility, Fe-Al type, Fe-Al-Ca type, Fe-Al-type.
Ni-based, Fe-Al-Zn-based, Fe-Al-Co-based, F
e-Ni-Si-Al-Zn system, Fe-Ni-Si-A
Fe-Al-based metal powder such as 1-Mn-based is preferable.

Particularly preferred ferromagnetic metal powder for the purpose of the present invention is a metal magnetic powder containing iron as a main component, and Al or Al and Ca, and Al in a weight ratio of Fe:
Al = 100: 0.5 to 100: 20, and Ca is preferably contained in a weight ratio of Fe: Ca = 100: 0.1 to 100: 10.

By setting the ratio of Fe: Al in such a range, the corrosion resistance is remarkably improved, and by setting the ratio of Fe: Ca in such a range, electromagnetic conversion characteristics are improved and dropout is reduced. Can be made. The reason why the electromagnetic conversion characteristics are improved and the dropout is reduced is not clear, but it is considered that the coercive force is increased and the agglomerates are decreased due to the improved dispersibility.

The preferred ferromagnetic metal powder used in the present invention has an average major axis length A (nm) observed by a transmission electron microscope of 30 ≦ A ≦ 110, preferably 50 ≦ A.
≦ 100, more preferably 50 ≦ A ≦ 90, and the X-ray particle size (crystallite size B (nm)) is 8 ≦ B ≦ 18, preferably 10 ≦ B ≦ 16, more preferably 10 ≦ B ≦ 14.
Is. The axial ratio (average major axis length / average minor axis length) is 12 or less, preferably 10 or less, and more preferably 4 to 9. When the average major axis length, the crystal size, and the axial ratio of the ferromagnetic metal powder are within the above ranges, the high frequency characteristics, especially the output of the perpendicular recording component can be enhanced.

The average major axis length (in the case of needle-like particles) and number average particle diameter (in the case of spherical particles) of the magnetic powder and non-magnetic powder used in the present invention are ferromagnetic powder or It is an average value obtained by measuring 500 major axis lengths or diameters (in the case of spherical particles) of the non-magnetic powder. The crystallite size was measured by the Scherrer method using Si powder as a reference, using the integral width of the (110) diffraction line of Fe with an X-ray diffractometer. Regarding the method of obtaining, the method described in the X-ray diffraction guide (Rigaku Denki Co., Ltd.) was used, and the correction of the spread due to double lines was performed by the correction by A: Jones (integral width) described on page 77. The axial ratio was determined as (average major axis length / average minor axis length) by measuring the average major axis length and the average minor axis length of 500 particles on an electron micrograph.

The ferromagnetic metal powder used in the present invention usually has a coercive force (Hc) of 1500 to 3000.
It is preferably in the range of Oe, and is preferably 1800 to 2500.
It is more preferably in the range of Oe.

The ferromagnetic powder preferably has a saturation magnetization amount (σs), which is a magnetic property, of usually 120 emu / g or more, and particularly preferably 130 to 170 emu / g. Further, according to the present invention, the specific surface area by the BET method is 30 m ^{2 as the} recording density is increased.
/ G or more, especially 45 m ² / g or more of a ferromagnetic metal powder is preferably used.

The specific surface area and its measuring method are described in "Measurement of powder" (JM Dallavelle,
Clyeorr Jr. Co-authored by Muta et al. (Translated by Sangyo Tosho Publishing Co., Ltd.)
170-1171 (Edited by Chemical Society of Japan: Maruzen Co., Ltd., Showa 41)
(Published April 30, 2013). To measure the specific surface area, for example, the powder is deaerated while being heated at about 105 ° C. for 13 minutes to remove what is adsorbed on the powder, and then the powder is introduced into a measuring device to reduce the initial pressure of nitrogen to 0. The pressure is set to 0.5 kg / m ² and measurement is performed with nitrogen at a liquid nitrogen temperature (−105 ° C.) for 10 minutes. As the measuring device, for example, a counter soap (manufactured by Yuasa Ionics Co., Ltd.) is used.

The ferromagnetic metal powder contains at least one of Fe, Al, and a rare earth element as its constituent elements. That is, it is preferable to contain at least one rare earth element selected from the group consisting of Sm, Nd, Y, Pr and La.

The ferromagnetic metal powder preferably used in the present invention is Fe, Al and
The abundance ratio of one or more rare earth elements selected from the group consisting of Sm, Nd, Y, Pr and La is 1 to 20 parts by weight of Al atoms relative to 100 parts by weight of Fe atoms, The amount of one or more rare earth elements selected from the group consisting of Sm, Nd, Y, Pr and La) is 1 to 16 parts by weight. Further, the existence ratio of Fe and Al (preferably one or more kinds selected from the group consisting of Sm, Nd, Y, Pr and La) on the surface thereof is 10 Fe atom number.
With respect to 0, the number of Al atoms is preferably 70 to 300, and the number of rare earth element atoms is preferably 0.5 to 100.

More preferably, the ferromagnetic metal powder further contains Na and Ca as its constituent elements, and the weight ratio of the elements in the entire ferromagnetic metal powder is Na with respect to 100 parts by weight of Fe atoms. Atoms are less than 0.1 parts by weight, Ca atoms are 0.1 to 2 parts by weight, Al atoms are 2 to 10 parts by weight, rare earth elements are 1 to 8 parts by weight, and The average abundance ratio of elements forming the surface of the magnetic metal powder is 2 to 30 for Na atoms, 5 to 30 for Ca atoms, and 5 to 30 for Ca atoms with respect to 100 Fe atoms.
The number of atoms is 70 to 200, and the number of atoms of rare earth elements is 0.5 to 30.

Further, preferably, the ferromagnetic metal powder contains at least one element selected from Co, Ni and Si as its constituent elements, and the weight ratio of the elements in the entire ferromagnetic metal powder is 100 parts by weight of Fe atoms. Against C
o atom is 2 to 40 parts by weight, Ni atom is 2 to 20 parts by weight, Si atom is 0.3 to 5 parts by weight, and Na is
Atoms are less than 0.1 parts by weight and Ca atoms are 0.1-2.
Parts by weight, Al atoms are 1 to 20 parts by weight, atoms of rare earth elements are 1 to 16 parts by weight, and the average abundance of elements forming the surface of the ferromagnetic metal powder is the number of Fe atoms. The number of Co atoms is less than 0.1 with respect to 100,
The number of Ni atoms is less than 0.1 and the number of Si atoms is 20 to 1
30, the number of Na atoms is 2 to 30, the number of Ca atoms is 5 to 30, the number of Al atoms is 70 to 300,
The number of atoms of the rare earth element is 0.5 to 100.

(Nonmagnetic Layer) A known nonmagnetic powder can be appropriately selected and used for the lower nonmagnetic layer in the present invention. As the non-magnetic powder, it is preferable to appropriately select and use from among various known non-magnetic powders used in this kind of magnetic recording medium, those excellent as a colored layer.
Examples of the non-magnetic powder include carbon black, graphite, titanium oxide, barium sulfate, ZnS and MgC.
o ₃ , CaCo ₃ , ZnO, CaO, tungsten disulfide, molybdenum disulfide, boric acid nitride, MgO, Sn
_{O 2, SiO 2, Cr 2} O 3, α-Al 2 O 3, α-F
e ₂ O ₃ , α-FeOOH, SiC, cerium oxide, corundum, artificial diamond, α-iron oxide, garnet,
Examples thereof include garnet, silica stone, silicon nitride, boron nitride, silicon carbide, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, tripoly, diatomaceous earth, dolomite, and polymer powder such as polyethylene.

Of these, preferred are carbon black, CaCO ₃ , titanium oxide, barium sulfate and α-.
Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, Cr ₂
Inorganic powders such as O ₃ and polymer powders such as polyethylene are used, among which α-Fe ₂ O ₃ and α-FeOOH are preferable, and α-Fe ₂ O ₃ is particularly preferable. In the present invention, a non-magnetic powder having a needle-like powder shape can be preferably used. By using the acicular non-magnetic powder, the smoothness of the surface of the non-magnetic layer can be improved, and the smoothness of the surface of the uppermost layer composed of the magnetic layer laminated thereon can also be improved.

The term "nonmagnetic layer" as used herein means a layer which is substantially nonmagnetic (saturation magnetic flux density Bm is 0) and a layer which is substantially nonmagnetic (slightly magnetic layer). so,
Bm of 0.01 to 100 Gauss) is also included. In particular, when acicular α-Fe ₂ O ₃ is used as the lower layer filler, the Bm of the layer is usually about 0.01 to 100 Gauss, but in this case also, it is called the nonmagnetic layer in the present invention. I will.

The thickness of the non-magnetic layer is usually 0.2 to
It is 2.5 μm, preferably 0.5 to 2.0 μm. When the thickness is 2.5 μm or less, the surface roughness of the upper layer surface after layering, that is, so-called layer surface roughness is less likely to occur, and preferable electromagnetic conversion characteristics can be obtained.
When it is 2 μm or more, high smoothness can be obtained at the time of calendering, and electromagnetic conversion characteristics are improved.

In order to control the shape and axial ratio of the non-magnetic powder, it is necessary to combine known methods such as selection of a starting material as a starting material, selection of oxidation-reduction conditions, and selection of a sintering inhibitor. You can

The major axis diameter of the acicular nonmagnetic powder used in the lower layer of the present invention or the number average particle diameter of nonacicular nonmagnetic powder is preferably 10 nm or more and 250 nm or less, and particularly preferably 200 nm or less. Is.

The minor axis diameter of the needle-shaped nonmagnetic powder and magnetic powder is usually 10 nm or more and 100 nm or less, preferably 80 nm or less, particularly preferably 6 nm.
It is 0 nm or less.

The axial ratio of the acicular non-magnetic powder and the magnetic powder is usually 2 to 20, preferably 5 to 15, and particularly preferably 5 to 10. The axial ratio referred to here is the ratio of the major axis diameter to the minor axis diameter (major axis diameter / minor axis diameter).

The specific surface area of the non-magnetic powder or magnetic powder is usually 10 to 250 m ² / g, preferably 20 to 150 m ² / g, particularly preferably 30 to 1
It is 00 m ² / g.

When the non-magnetic powder or the magnetic powder having the major axis diameter, the minor axis diameter, the axial ratio and the specific surface area within the above ranges is used, the surface property of the non-magnetic layer or the magnetic layer can be improved and the magnetic property can be improved. It is preferable in that the surface property of the uppermost layer, which is a layer, can be in a good state.

In the present invention, it is preferable that the non-magnetic powder or magnetic powder is surface-treated with a Si compound and / or an Al compound. When the non-magnetic powder subjected to such surface treatment is used, the surface condition of the uppermost layer which is the magnetic layer can be improved. The content of Si and / or Al is preferably 0.1 to 10% by weight of Si and 0.1 to 10% by weight of Al with respect to the non-magnetic powder or the magnetic powder, and more preferably Is 0.1
~ 5 wt%, Al is 0.1-5 wt%, especially Si
Is preferably 0.1 to 2% by weight and Al is 0.1 to 2% by weight. In the case of non-magnetic powder, the weight ratio of Si and Al is preferably Si <Al. In the case of magnetic powder, S
The weight ratio of i and Al is preferably Si / Al ≧ 3. The surface treatment can be performed by the method described in JP-A-2-83219.

The content of the nonmagnetic powder or magnetic powder in the lower layer is usually 50 to 99% by weight, preferably 60 to 99% by weight, based on the total of all components constituting the lower layer.
It is 95% by weight, particularly preferably 70 to 95% by weight. When the content of the non-magnetic powder or the magnetic powder is within the above range, the surface condition of the uppermost layer and the lower layer, which are magnetic layers, can be improved.

(Carbon) DBP oil absorption preferably 110 ml / 100 g to 500 ml contained in the magnetic layer
As the carbon black B of / 100 g, for example, Asahi # 80 (23 nm, 113 ml manufactured by Asahi Carbon Black Co., Ltd.
/ 100 g), Conductex SC (17 nm, 115 ml / 100 g) manufactured by Colombian Carbon Co., Ltd., Conductex 975 (20 nm, 183 ml / 100)
g), Cabot Monarch 1300 (13 nm, 1
21 ml / 100 g), Vulcan XC-72 (30 n
m, 178 ml / 100 g), Vulcan P (20 nm,
116 ml / 100 g), Vulcan 9 (19 nm, 11
4ml / 100g), Black Pearls 2000 (15
nm, 330 ml / 100 g) and the like.

DB preferably contained in the non-magnetic layer
Examples of the carbon black A having a P oil absorption of 20 ml / 100 g to 110 ml / 100 g include Raven 5000 (12 nm, 95 ml /
100 g), Raven 1255 (23 nm, 58 ml)
/ 100g), Raven1035 (27nm, 60m
1/100 g), Raven2000 (18 nm, 70
ml / 100g), Cabot Black Pearl 14
00 (13 nm, 80 ml / 100 g), Black Pearl 1300 (13 nm, 91 ml / 100 g), Black Pearl 1100 (14 nm, 50 ml / 100 g),
Black Pearl 900 (15nm, 64ml / 100
g), Black Pearl L (24 nm, 55 ml / 100)
g), Regal 400 (25 nm, 70 ml / 100)
g) etc.

The carbon black B contained in the magnetic layer preferably has a number average particle size of 10 to 40 nm, more preferably 10 to 30 nm for the purpose of smoothing the surface of the magnetic layer and obtaining high output. is there.

As for the carbon black A contained in the non-magnetic layer, the surface property of the upper magnetic layer greatly depends on the surface property of the lower layer as the thickness of the upper magnetic layer becomes thinner. Therefore, the characteristics of the carbon black A contained in the lower non-magnetic layer are extremely important, and the number average particle diameter is 10 to 40 nm.
And oil absorption is DBP value of 20 ml / 100 g
It is preferable to select 100 ml / 100 g of carbon black in order to improve the dispersibility of the non-magnetic layer and obtain good surface properties.

The number average particle diameter of carbon black A is preferably 10 to 40 nm, more preferably 10 to 30 nm. The oil absorption of carbon black A is preferably 30 to 90 ml / 100 g, more preferably 40 to 80 ml / 100 g in terms of DBP value.

The weight of carbon black B contained in the magnetic layer is preferably 0.1 to 5.0% by weight, and more preferably 0.2 to 2.0% by weight, based on the magnetic powder. The weight of carbon black A contained in the nonmagnetic layer is preferably 5.0 to 30% by weight, more preferably 7.0 to 20% by weight, based on the nonmagnetic powder.

The oil absorption of carbon black B is preferably 130 to 350 ml / 100 g in terms of DBP value.
More preferably, it is 50 to 250 ml / 100 g.

The method of adding carbon black can be variously changed. For example, fine particles and coarse particles of carbon black may be charged into a disperser at the same time and mixed, or only a part thereof may be added first, and the remaining amount may be added when the dispersion has progressed to some extent. When importance is placed on the dispersion of carbon black, it is also possible to knead carbon black together with a magnetic material or filler and a binder by a three-roll mill, Banbury mixer or the like, and then disperse with a disperser to obtain a coating material. When importance is attached to conductivity like layers other than the magnetic layer, the carbon black structure structure is less likely to be broken by adding carbon black in the latter half of the dispersion step and the liquid preparation step as much as possible.

A so-called "carbon masterbatch" in which carbon black is kneaded in advance with a binder may be used.

Here, the particle size of the above carbon black is directly measured visually by an electron microscope. That is, a magnetic recording medium, for example, a tape is cut in the longitudinal direction to a thickness of about 700Å, and the obtained cross section is observed with a transmission electron microscope (applied voltage 200 KV, magnification = 60,000). In this case, measure the diameter of each particle of carbon black,
The average of N = 100 pieces is defined as "number average particle diameter".

Regarding the above-mentioned "oil absorption (DBP method)", 100 g of pigment powder is added to DBP (Dibutylph).
The state of the pigment is observed while kneading, and the number of ml of DBP when the point of forming one lump from the dispersed state is found is the DBP oil absorption.

(Binder) Typical binders used for forming the magnetic layer and the non-magnetic layer are, for example, polyurethane, polyester, vinyl chloride copolymers, and the like. SO ₃ M, -OS
_{O 3 M, -COOM, -PO (} OM 1) 2 and -OPO
It is preferable to include a unit having at least one polar group selected from (OM ¹ ) ₂ . However, in the above polar group, M represents a hydrogen atom or an alkali metal such as Na, K and Li, and M ¹ represents a hydrogen atom, Na, K and L.
It represents an alkali atom such as i or an alkyl group.

The polar group has the function of improving the dispersibility of the ferromagnetic powder, and the content in each resin is 0.1 to 8.0 mol%, preferably 0.5 to 6.0 mol%. . When the content is less than 0.1 mol%, the dispersibility of the ferromagnetic powder is lowered, and when the content is more than 8.0 mol%, the magnetic coating tends to gel. The weight average molecular weight of each resin is preferably in the range of 15,000 to 50,000.

The content of the binder in the magnetic layer is usually 10 to 100 parts by weight of the ferromagnetic powder.
It is 40 parts by weight, preferably 15 to 30 parts by weight. The binder (binder) is not limited to one kind alone, and two or more kinds can be used in combination. In this case, the ratio of the polyurethane and / or polyester to the vinyl chloride resin is usually 90:10 by weight. 10:90,
It is preferably in the range of 70:30 to 30:70.

The polar group-containing vinyl chloride copolymer used as a binder in the present invention is a compound having a hydroxyl group and the following polar group and chlorine atom, such as a vinyl chloride-vinyl alcohol copolymer. It can be synthesized by addition reaction with.

Cl-CH ₂ CH ₂ SO ₃ M, Cl-CH ₂ CH ₂ OSO ₃ M, Cl-CH ₂ COOM, Cl-CH ₂ -P (= 0) (OM ¹ ) _{2 From} these compounds, Cl- Taking CH ₂ CH ₂ SO ₃ Na as an example, the above reaction will be described below. _{-CH 2 C (OH) H- +} ClCH 2 CH 2 SO 3 Na → -CH 2 C (OCH 2 CH 2 SO 3 Na) H-.

For the polar group-containing vinyl chloride copolymer, a predetermined amount of a reactive monomer having an unsaturated bond into which a repeating unit containing a polar group is introduced is charged into a reaction vessel such as an autoclave to start a general polymerization. Agents, eg BPO
(Benzoyl peroxide), AIBN (azobisisobutyronitrile) and other radical polymerization initiators, redox polymerization initiators, cationic polymerization initiators and the like can be obtained by carrying out a polymerization reaction.

Specific examples of the reactive monomer for introducing the sulfonic acid or its salt include unsaturated hydrocarbon sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, methacryl sulfonic acid, p-styrene sulfonic acid, and the like. Mention may be made of salt.

When introducing a carboxylic acid or a salt thereof, for example, (meth) acrylic acid or maleic acid is used,
When phosphoric acid or a salt thereof is introduced, for example, (meth) acrylic acid-2-phosphate ester may be used.

It is preferable that an epoxy group is introduced into the vinyl chloride copolymer. This is because the thermal stability of the polymer is improved by doing so.

When an epoxy group is introduced, the content of the repeating unit having an epoxy group in the copolymer is 1
-30 mol% is preferable, and 1-20 mol% is more preferable. As the monomer for introducing an epoxy group, for example, chrysidyl acrylate is preferable.

Regarding the technique for introducing a polar group into a vinyl chloride-based copolymer, JP-A-57-44227 and JP-A-57-42727 are cited.
8-108052, 59-8127, 60-1
No. 01161, No. 60-235814, No. 60-23
No. 8306, No. 60-238371, No. 62-121
No. 923, No. 62-146432, No. 62-1464.
No. 33 and the like are described, and these can be used in the present invention.

Next, the synthesis of polyester and polyurethane used in the present invention will be described. Generally, polyesters are obtained by reacting polyols with polybasic acids. By using this known method, a polyester (polyol) having a polar group can be synthesized from a polyol and a polybasic acid partially having a polar group.

Examples of polybasic acids having polar groups include 5
-Sulfoisophthalic acid, 2-sulfoisophthalic acid, 4-
Examples thereof include sulfoisophthalic acid, 3-sulfophthalic acid, dialkyl 5-sulfoisophthalate, dialkyl 2-sulfoisophthalate, dialkyl 4-sulfoisophthalate, dialkyl 3-sulfoisophthalate, and their sodium salts and potassium salts.

Examples of polyols include trimethylolpropane, hexanetriol, glycerin, trimethylolethane, neopentyl glycol, pentaerythritol, ethylene glycol, propylene glycol, 1.3-butanediol, 1.4-butanediol, 1 6-hexanediol, diethylene glycol, cyclohexanedimethanol and the like can be mentioned. Note that other polar group-introduced polyesters can also be synthesized by a known method.

Next, the polyurethane will be described. It results from the reaction of polyols with polyisocyanates. As the polyol, a polyester polyol obtained by reacting a polyol with a polybasic acid is generally used. Therefore, if a polyester polyol having a polar group is used as a raw material, a polyurethane having a polar group can be synthesized.

In the present invention, it is preferable to use an aromatic polyester polyurethane prepared by using a polyester polyol having an aromatic ring and / or a polyester polyol containing a cyclic hydrocarbon residue in order to achieve the object of the present invention.

Examples of polyisocyanates include diphenylmethane-4-4'-diisocyanate (MDI),
Hexamethylene diisocyanate (HMDI), tolylene diisocyanate (TDI), 1.5-naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), lysine isocyanate methyl ester (LDI) and the like can be mentioned.

Further, as another method for synthesizing a polyurethane having a polar group, an addition reaction between a polyurethane having a hydroxyl group and the following compound having a polar group and a chlorine atom is also effective. _{Cl-CH 2 CH 2 SO 3} M, Cl-CH 2 CH 2 OSO 2 M, Cl-CH 2 C OOM, Cl-CH 2 -P (= O) (OM 1) 2 The polarity group introduced into the polyurethane As a technique relating to the above, Japanese Patent Publication No. 58-41565 and Japanese Patent Application Laid-Open No. 57-9242.
No. 2, No. 57-92423, No. 59-8127, No. 59-5423, No. 59-5424, No. 62-12.
It is described in the publications such as 1923, and these can be used in the present invention.

In the present invention, the following resins can be used together as a binder in an amount of 20% by weight or less based on the total amount of the binder. The resin has a weight average molecular weight of 1
Vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose Derivatives (nitrocellulose etc.), styrene-butadiene copolymers, phenol resins, epoxy resins, urea resins, melamine resins, phenoxy resins, silicone resins, acrylic resins, urea formamide resins, various synthetic rubber resins, etc. .

(Other Components) In the present invention, it is desirable to contain polyisocyanate in order to improve the durability of the magnetic layer and other layers.

Examples of the polyisocyanate include aromatic polyisocyanates such as adducts of tolylene diisocyanate (TDI) and active hydrogen compounds, and fats such as adducts of hexamethylene diisocyanate (HMDI) and active hydrogen compounds. There are group polyisocyanates. The weight average molecular weight of the polyisocyanate is 100 to
It is preferably in the range of 3,000.

In the present invention, the magnetic layer and other layers may contain additives such as a dispersant, a lubricant, an abrasive, an antistatic agent and a filler, if necessary. First,
Examples of the dispersant include those described in paragraph No. 0093 of JP-A-4-214218. These dispersants are usually added to the ferromagnetic powder at 0.5.
Used in the range of up to 5% by weight.

Next, as the lubricant, a fatty acid and / or a fatty acid ester can be used. In this case, the amount of the fatty acid added is preferably 0.2 to 10% by weight, based on the ferromagnetic powder or nonmagnetic powder that is mainly used, and 0.5 to
5% by weight is more preferred. If the addition amount is less than 0.2% by weight, the running property tends to be lowered, and if the addition amount is more than 10% by weight, the fatty acid is likely to seep out to the surface of the magnetic layer or the output is likely to be lowered.

The amount of the fatty acid ester added is preferably 0.2 to 10% by weight, more preferably 0.5 to 5% by weight, based on the ferromagnetic powder or nonmagnetic powder that is mainly used. If the addition amount is less than 0.2% by weight, the still durability is likely to deteriorate, and if it exceeds 10% by weight, the fatty acid ester is likely to seep out to the surface of the magnetic layer or the output is likely to decrease.

When it is desired to use a fatty acid and a fatty acid ester together to enhance the lubricating effect, the weight ratio of the fatty acid and the fatty acid ester is preferably 10:90 to 90:10. The fatty acid may be a monobasic acid or a dibasic acid,
6-30 are preferable and, as for carbon number, the range of 12-22 is more preferable.

Specific examples of the fatty acid include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, linolenic acid, oleic acid, elaidic acid, behenic acid, malonic acid, succinic acid. Acid, maleic acid, glutaric acid, adipic acid,
Examples thereof include pimelic acid, azelaic acid, sebacic acid, 1.12-dodecanedicarboxylic acid and octanedicarboxylic acid.

Specific examples of the fatty acid ester include oleyl oleate, isocetyl stearate, dioleyl malate, butyl stearate, butyl palmitate, butyl myristate, octyl myristate, octyl palmitate, pentyl stearate, pentyl palmitate. Tate, isobutyl oleate, stearyl stearate,
Lauryl oleate, octyl oleate, isobutyl oleate, ethyl oleate, isotridecyl oleate, 2-ethylhexyl stearate, 2-ethylhexyl palmitate, isopropyl palmitate, isopropyl myristate, butyl laurate, cetyl-2.
-Ethyl hexalate, dioleyl adipate, diethyl adipate, diisobutyl adipate, diisodecyl adipate, oleyl stearate, 2-ethylhexyl myristate, isopentyl palmitate, isopentyl stearate, diethylene glycol mono-butyl ether palmitate, diethylene glycol mono- Butyl ether palmitate and the like.

As the lubricant other than the above fatty acids and fatty acid esters, for example, silicone oil, graphite, carbon fluoride, molybdenum disulfide, tungsten disulfide, fatty acid amide, α-olefin oxide and the like can be used. Next, specific examples of the abrasive include α-alumina, fused alumina, chromium oxide, titanium oxide, α-iron oxide, silicon oxide, silicon nitride, tungsten carbide, molybdenum carbide, boron carbide, corundum,
Examples thereof include zinc oxide, cerium oxide, magnesium oxide and boron nitride. The number average particle size of the abrasive is 0.05
˜0.6 μm is preferable, and 0.1 to 0.3 μm is more preferable. The weight of the abrasive used in the magnetic layer is usually 1 to 20% by weight, preferably 1 to 10% by weight, more preferably 2 to 6% by weight, based on the magnetic powder. In the non-magnetic layer, it is generally 1 to 20% by weight, preferably 1 to 10% by weight, more preferably 2 to
6% by weight.

Next, as the antistatic agent, conductive powder such as carbon black and graphite; cationic surfactant such as quaternary amine; acid such as sulfonic acid, sulfuric acid, phosphoric acid, phosphoric acid ester and carboxylic acid. Examples thereof include anionic surfactants containing a group; amphoteric surfactants such as aminosulfonic acid; and natural surfactants such as saponin. The above-mentioned antistatic agent is usually added in the range of 0.01 to 40% by weight with respect to the binder.

(Production of Magnetic Recording Medium) In the magnetic recording medium of the present invention, it is preferable that the upper layer is laminated by a so-called wet-on-wet method which is performed when the lower layer is in a wet state. As the wet-on-wet system, a known method used for manufacturing a multilayer structure type magnetic recording medium can be appropriately adopted.

In the present invention, Wet-on-wet.
The production method is not particularly limited except that the coating method is preferably used, and the production can be performed according to a known method used for producing a multilayer structure type magnetic recording medium. For example, generally, magnetic powder, binder, dispersant, lubricant, abrasive, antistatic agent, etc. are kneaded and dispersed in a solvent to prepare a magnetic paint, and then this magnetic paint is applied to a non-magnetic support. Apply to the surface of.

Examples of the solvent include, for example, JP-A-4-21.
The thing etc. which are described in paragraph number 0119 of 4218 can be used.

Various kneading and dispersing machines can be used for kneading and dispersing the components for forming the magnetic layer and other layers. As this kneading disperser, for example, Japanese Patent Laid-Open No. 4-2142
No. 18, Paragraph No. 0112 and the like can be mentioned. Among the above kneading dispersers, kneading dispersers capable of providing a power consumption load of 0.05 to 0.5 KW (per 1 Kg of magnetic powder) include a pressure kneader, an open kneader,
It is a continuous kneader, a two-roll mill, and a three-roll mill.

In order to coat the magnetic layer and other layers on the non-magnetic support, in the production of the magnetic recording medium of the present invention, simultaneous multi-layer coating by the wet-on-wet multi-layer coating method is particularly effective. It is preferable to carry out.

Specifically, as shown in FIG. 1, first, the film-shaped support 1 fed from the supply roll 32 is applied to the coating materials for the magnetic layer and other layers by the extrusion type extrusion coaters 10 and 11. Is applied in multiple layers by the wet-on-wet method, and then passes through the orienting magnet or the vertically orienting magnet 33, is introduced into the dryer 34, and hot air is blown from the nozzles arranged above and below to dry it.
Next, the dried support 1 with each coating layer is combined with a calender roll 38 to form a super calender device 37.
And after performing a calendar process here, it is wound up on a winding roll 39. The magnetic film thus obtained can be cut into a tape or disk having a desired width to produce, for example, a magnetic recording tape for an 8 mm video camera or a 3.5 inch floppy disk medium.

In the above method, each paint was extruded through an in-line mixer (not shown), the coater 10,
11 may be supplied. In the figure, arrow D indicates the transport direction of the non-magnetic base film. Extrusion coater 1
0 and 11 are provided with liquid reservoirs 13 and 14, respectively,
Overlay the paint from each coater in a wet-on-wet fashion. That is, the upper layer coating material is applied in multiple layers immediately after the lower magnetic layer coating material is applied (when it is in an undried state). The coater head shown in FIG. 2 (c) is preferable in the present invention.

As the wet-on-wet multilayer coating method, a combination of a reverse roll and an extrusion coater, a combination of a gravure roll and an extrusion coater, and the like can be used. Further, an air doctor coater, blade coater, air knife coater, squeeze coater, impregnation coater, transfer roll coater, kiss coater, cast coater, spray coater and the like can be combined.

In the multi-layer coating by the wet-on-wet method, the upper layer is coated while the lower layer is in a wet state, so that the surface of the lower layer (that is, the boundary surface with the upper layer).
And the surface property of the upper layer is improved, and the contact property between the upper and lower layers is also improved. As a result, the high performance and low noise required for high density recording are satisfied, for example, the performance required as a magnetic disk is satisfied, and film durability is also required for film peeling. It is eliminated, the film strength is improved, and the durability is sufficient. Further, the wet-on-wet multi-layer coating method can also reduce dropout and improve reliability.

As the solvent to be added to the above paint or a diluent solvent for applying this paint, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone: alcohols such as methanol, ethanol, propanol and butanol: methyl acetate , Esters such as ethyl acetate, butyl acetate, ethyl lactate, ethylene glycol cenoacetate: ethers such as glycol dimethyl ether, glycol monoethyl ether, dioxane, tetrahydrofuran: aromatic hydrocarbons such as benzene, toluene, xylene: methylene chloride, Ethylene chloride, carbon tetrachloride, chloroform,
Halogenated hydrocarbons such as dichlorobenzene can be used. These various solvents may be used alone or in combination of two or more. The magnetic field in the orienting magnet or the vertically orienting magnet is about 20 to 10,000 gauss, the drying temperature by the dryer is about 30 to 120 ° C., and the drying time is about 0.1 to 10 minutes.

Surface Smoothing Next, a surface smoothing process is performed by calendering. After that, if necessary, burnishing or blade processing is performed and slitting is performed. On this occasion,
The surface smoothing treatment is effective in achieving the object of the present invention.

In the surface smoothing treatment, temperature, linear pressure, C / S (coating speed) and the like can be mentioned as calendering conditions. To achieve the object of the present invention, the temperature is usually 50 to 140 ° C., the linear pressure is 50 to 400 kg / cm, and the C / S is 20 to 100.
It is preferable to keep it at 0 m / min.

[0099]

According to the present invention, the durability is excellent for a long time under any environmental condition, and no error occurs, the dropout is small, the reproduction output is high, and the overwrite characteristic is high under a wide range of temperature conditions. A good magnetic recording medium can be obtained.

[0100]

Embodiments of the present invention will be described below. The components, ratios, and operation order shown below can be variously changed without departing from the scope of the present invention. In the following examples, all "parts" are parts by weight. (Examples 1 to 20,
Comparative Examples 1 to 10 First, a magnetic layer coating material and a non-magnetic layer coating material having the following compositional formulations were kneaded and dispersed using a kneader and a sand mill, and each of the obtained coating materials was polyisocyanate (Coronate L, Nippon Polyurethane Industry Co., Ltd.). After adding 5 parts, the thickness is 75μ by the wet-on-wet method.
After coating the samples of Examples 1 to 20 and Comparative Examples (1 to 10) on the polyethylene terephthalate film of m in the combination shown in Table 1, a non-orientation treatment was performed while the coating film was not dried, and After drying, a surface smoothing treatment is performed with a calendar to prepare a raw sheet composed of a layer containing a nonmagnetic powder having a thickness of 2.0 μm and a magnetic layer having a thickness of 0.1 μm (the film thickness is described in Tables 1 to 4). Created. The magnetic film thus obtained was punched into a disk shape having a diameter of 86 mm and housed in a cassette to obtain a 3.5 inch floppy disk.
(Examples 1 to 11 and Comparative Examples 1 to 5) Also, by using the same coating material, the combination shown in the table on the polyethylene naphthalate film having a thickness of 5.5 μm by the wet-on-wet method was used. Example 6
After applying the samples of Nos. 10 to 10, magnetic field orientation treatment is performed while the coating film is undried, followed by drying, and then surface smoothing treatment with a calendar to obtain a layer containing a nonmagnetic powder having a thickness of 2.0 μm. And a magnetic layer having a thickness (described in Tables 3 and 4). The original fabric obtained in this way is 8 mm
The tape width was slit to obtain an 8 mm video tape.
(Examples 12 to 20, Comparative Examples 6 to 10)

Magnetic Layer Coating Formulation: (Coating A1) Fe-Al based ferromagnetic metal powder (average major axis length and crystallite size were changed as shown in Tables 1 to 4) (Fe: Co: Al: Y = 100: 10: 8: 5 (weight ratio), average major axis length: 65 nm, axial ratio: 5, Hc: 2200 Oe, σs: 135 e mu / g, crystallite size: 12 nm) 100 parts Sulfonic acid Metal salt-containing vinyl chloride resin [manufactured by Nippon Zeon Co., Ltd., MR-110] 10 parts Aromatic polyester polyurethane resin containing sulfonic acid metal salt [Toyobo Co., Ltd., UR-8200] 10 parts Alumina (α-Al ₂ O _3, a number average particle diameter: 0.1 [mu] m) 5 parts carbon black (number average particle diameter: 20 nm, oil absorption (DBP value: 220ml / 100g)) 0.8 parts 1 part 1 part butyl myristate stearate Teareto 2 parts oleyl oleate 5 parts Cyclohexanone 100 parts Methyl ethyl ketone 100 parts 100 parts toluene

(Coating A2) Fe-Al in the coating A1
Fe: Co: Al: Ni: S as the base ferromagnetic metal powder
Same as A1 except that i: Nd = 100: 10: 8: 5: 3: 5 (weight ratio) was used. (Average major axis length: 65 nm, axial ratio: 5, Hc: 2200 Oe, σs: 135 emu /
g)

Non-magnetic layer paint formulation: (Paint a: non-magnetic layer) α-Fe ₂ O ₃ (average major axis length: 160 nm, average minor axis length: 20 nm, acicular ratio: 8, Si to α-Fe ₂ O ₃ In contrast, 0.2% by weight and 1.0% Al by weight relative to α-Fe2O3) 100 parts Carbon black (number average particle size: 23 nm, oil absorption (DBP value: 60 ml / 100 g) ) 15 parts Vinyl chloride resin containing sulfonic acid metal salt [Nippon Zeon Co., Ltd., MR-110] 6 parts Aromatic polyester polyurethane resin containing sulfonic acid metal salt [Toyobo Co., Ltd., UR-8300] 3 parts α -Al ₂ O ₃ (number average particle size: 0.2 μm) 6 parts Myristic acid 1 part Butyl stearate 2 parts Oleyloylate 5 parts Cyclohexanone 100 parts Methyl ethyl ketone 100 parts Toluene 100 Department

(Paint b) In sample a, α-Fe ₂ O ₃
Instead of 100 parts titanium oxide. (Number average particle size 30n
m, Si is 0.2% by weight ratio to TiO ₂ , and Al is T
Only 1.0% by weight ratio to iO ₂ was used).

The characteristics of this floppy disk were measured according to the following items. The measurement results are shown in Tables 1, 2, and 3.

(1) Playback output Using the following commercially available drive, 25 signals (500 KH)
Recording was performed with the sine wave signal of z), and the reproduction output was measured.

Drive: PD made by TOSHIBA Co., Ltd.
-211 Measurement track: 79 tracks The measured reproduction output is shown as a relative value when the floppy disk manufactured in Example 1 is 100%. The larger the reproduction output, the better the magnetic disk.

(2) Durability A magnetic head mounted on a recording / reproducing device was manufactured by Toshiba Corp. 4
While making sliding contact with the MB drive PD-211 at a clamping pressure of 50 g / cm ² and rotating at a disk rotation speed of 1000 rpm, the running time until the reproduction output reaches 70% of the initial output is set as the durability time, and the temperature and humidity are set. It changed and measured. (0
Cycle between ℃ and 60 ℃ in 24 hours)

<Dropout> (Disc) Using 100 3.5-inch floppy disc samples, the number of discs in which dropout occurred after applying vibration for 1 hour was determined as reliability.

<Overwrite characteristics> A signal of 315 KHz was recorded on the demagnetized sample and the reproduction output was measured (Ad
After B), the signal of 1 MHz was overwritten, and the overwrite characteristic B-A (dB) was obtained from the output (B dB) of 315 KHz at that time.

<Electrical characteristics (db) CN ratio> Sony Corporation
It was measured by an 8 mm video camera CCDV-900 manufactured by KK. The CN ratio is the output difference (dB) between 7MHz and 6MHz.
Was measured.

<Running Durability> Running durability at 100 ° C. and 80% humidity and 100 ° C. and 20% humidity was evaluated as follows. A: No hindrance B: Scratch on the back surface C: Running, but frequent occurrence of D / O = 50 or more D: Running, but electrical characteristics degraded by 2 dB or more E: Running That stopped.

<Dropout characteristic> (tape) Dropout counter VD manufactured by Victor Company of Japan, Ltd.
Using -5M, with the output that is longer than 15 μsec or longer and 20 dB or more lower than the output of the RF envelope as one dropout, measure the entire length of each tape, and find the average value (units / minute) per minute. It was

<Overall composition>: Fe, Co, Nd, Si, Al, Y, Pr in the overall composition of the ferromagnetic metal powder,
Regarding the abundance ratio of each element of Sm and La, after measuring the fluorescent X-ray intensity of each element in the sample using a wavelength dispersive X-ray fluorescence analyzer (WDX), the fundamental parameter method (hereinafter referred to as FP method and It is calculated and calculated in accordance with

The FP method will be described below. For measuring fluorescent X-rays, WDX system 308 manufactured by Rigaku Denki Co., Ltd.
0 was used under the following conditions. X-ray tube: Rhodium tube output: 50 KV, 50 mA Spectroscopic crystal: LiF (Fe, Co, Ni, Nd, Y, P
r, Sm, La), PET (for Al),
RX-4 (for Si) Absorber: 1/1 (Fe only 1/10) Slit: COARSE Filter: OUT PHA: 15-30 (for Al, Si), 10
~ 30 (Fe, Co, Ni, Nd, Y, Pr, Sm, L
(For a) Counting time: peak = 40 seconds, background = 40
Second (Measure two points before and after the peak) The measurement of the fluorescent X-ray is not limited to the above-mentioned device, and various devices can be used.

The following eight kinds of metal compounds were used as standard samples. Standard sample 1 is Analytical R
effort Materials Intern
alloy SRM1219 (C is 0.1
5 wt%, Mn 0.42 wt%, P 0.03 wt%, Si 0.55 wt%, Cu 0.16 wt%, N
i is 2.16% by weight, Cr is 15.64% by weight, Mo is 0.16% by weight, and V is 0.06% by weight. ).

Standard sample 2 is Analytical R
effort Materials Intern
alloy SRM1250 (Ni 3
7.78 wt%, Cr 0.08 wt%, Mo 0.0
1% by weight, 16.10% by weight of Co, and 0.99% by weight of Al are contained. ).

The standard sample 3 is magnetic iron oxide powder (Mn 0.14 wt%, P 0.15 wt%, S 0.19 wt%, Si 0.36 wt%, Co 3.19). weight%,
It contains 1.26% by weight of Zn, 0.07% by weight of Ca, and 0.02% by weight of Na. ).

The standard sample 4 is a ferromagnetic metal powder (containing 2.73% by weight of Nd). The standard sample 5 is a ferromagnetic metal powder (containing 0.97% by weight of Sr). The standard sample 6 is a ferromagnetic metal powder (containing 1.40% by weight of Ba and 0.40% by weight of Ca). The standard sample 7 is a ferromagnetic metal powder (containing 2.69% by weight of La). The standard sample 8 is a ferromagnetic metal powder (Y is 1.
Contains 98% by weight. ).

The weight% of the elements in the standard samples 1 and 2 are the values on the data sheet provided by the manufacturer, and the weight% of the elements in the standard samples 3 to 8 are the values analyzed by the ICP emission spectrometer. This value was input as the elemental composition value of the standard sample in the calculation of the FP method below.

For the calculation of the FP method, the fundamental parameter software Version2.1 manufactured by Technos is used.
Was calculated under the following conditions. Sample model: Bulk sample Balance component sample: Fe Input component: Measured X-ray intensity (KCPS) Analytical unit: wt% The calculated abundance ratio of each element (wt%) is Fe atom 1
It is a quantitative value by converting it as the weight% of other elements with respect to 00 weight%.

[0122]

[Table 1]

[0123]

[Table 2]

[0124]

[Table 3]

[0125]

[Table 4]

[Brief description of drawings]

FIG. 1 is a diagram for explaining simultaneous multi-layer coating of magnetic layers by a wet-on-wet coating method.

FIG. 2 is a diagram of a coater head for applying a magnetic layer paint.

FIG. 3 is a diagram showing a magnetization curve, a hysteresis curve and a differential curve for explaining the definition of SFD.

Claims (2)

[Claims] 1. A non-magnetic layer and a magnetic layer are formed on a support in this order to form a magnetic layer having a dry film thickness of 0.05 to 0.3 μm, the ferromagnetic metal powder being contained in the magnetic layer. When the average major axis length is A (nm), 30 ≦ A ≦ 110, and the ratio of the magnetic powder having the major axis length in the range of 0.9 Anm or less is 20% or less of the total number of magnetic powders. Characteristic magnetic recording medium. 2. A non-magnetic layer and a magnetic layer are formed on a support in this order to form a magnetic layer having a dry film thickness of 0.05 to 0.3 μm. When the crystallite size is B (nm), 8 ≦ B ≦ 18 and the SFD of the magnetic layer is 0.5 or less.