JP2003242624A - Magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium containing ferromagnetic metallic powder having a good carrier to noise ratio and excellent weatherability in high-density recording. <P>SOLUTION: A particle volume is ≥800 to <3,000 nm<SP>3</SP>; the ratio of the volume of a metallic section to the particle volume is 5 to 45%; the thickness of a magnetic layer is 0.020 to 0.18 μm; the coercive force of the magnetic layer is ≥127.3 kA/m, by which the magnetic recording medium having small magnetic clusters and the good carrier to noise ratio is obtained. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to a coating type high recording density magnetic field.
Relates to a recording medium. Especially ultrafine ferromagnetic metal powder
Relates to a magnetic recording medium for high density recording including
The [0002] 2. Description of the Related Art In magnetic recording technology, repeated use of a medium is possible.
Peripheral devices that are possible
It is possible to construct a system by combining with
Other recording methods such as easy signal correction
Video, audio,
Wide range in various fields including computer applications
Have been used. And downsizing of equipment, quality of recording / reproducing signal
Demands such as improved recording, longer recording time, and increased recording capacity
In order to cope with the recording medium, the recording density, reliability
It has always been desired to improve the durability and durability.
It was. In recent years, with the spread of office computers
Record computer data as an external storage medium
For magnetic tape (so-called backup tape)
Has been actively conducted. Of magnetic tape for such applications
In practical use, in particular, downsizing of computers and information processing
Increased capacity and downsizing of recordings, combined with increased capacity
Therefore, there is a strong demand for improvement in recording capacity. Magnetic
A wide range of environmental conditions due to the expansion of the usage environment
(Especially under highly fluctuating temperature and humidity conditions)
Reliability for data storage and for repeated use at high speed
Stable recording and reading of data in multiple runs
However, the reliability of the performance such as
The Conventionally, in a digital signal recording system.
The magnetic tape used is determined by the system.
So-called DLT type, 3480, 3490, 3590,
Magnetic for QIC, D8, LT0, or DDS
Tape is known. And in any system
Also, the magnetic tape used is one of the nonmagnetic supports
On the side, a relatively thick multilayer structure with a film thickness of 0.2 to 3.0 μm
Or a ferromagnetic powder with a single layer structure, a binder, and an abrasive.
A magnetic layer is provided, and the other side has a winding
To prevent turbulence and maintain good running durability,
A gate layer is provided. But generally the ratio as above
In a magnetic layer with a relatively thick single layer structure, the output decreases.
There is a problem of thickness loss. In recent years, computer data has been recorded and reproduced.
Thin film magnetic head for magnetic recording and reproducing system for
A system that incorporates is put into practical use. Thin film magnetic
The head is easy to process into a compact and multi-track head.
Therefore, especially in systems using magnetic tape as the recording medium,
Many use of thin-film magnetic head multi-track fixed head
Has been. Miniaturization by using thin film magnetic head
This makes it possible to improve track density and recording efficiency.
Multi-track as well as high-density recording
It becomes possible to improve the data transfer speed. Thin film magnetism
Qi head is an inductive head that responds to changes in magnetic flux over time
And magnetic resistance using the magnetoresistive effect that responds to the magnitude of the magnetic flux.
It can be roughly divided into a gas resistance type head (MR head). Electromagnetic induction
Is used for magnetic head (inductive magnetic head)
It is popular. However, it is used in higher density recording / playback areas.
The limits are starting to appear. That is, a big re
To obtain raw output, increase the number of coil turns in the playback head.
It is necessary to increase the inductance but resistance at high frequency
As a result, there is a problem that the reproduction output decreases.
In recent years, read heads based on MR (magnetoresistance) operating principle have been proposed.
It is proposed and used in hard disks. MR Head
Can produce a playback output several times that of an inductive magnetic head.
And no induction coil is used.
Equipment noise such as noise is greatly reduced, and magnetic recording media
It is possible to obtain a large signal-to-noise ratio by reducing noise
It has become. The inductive head is
It is difficult to increase the magnetomotive force due to a small number of windings
Therefore, there is a problem that sufficient reproduction output cannot be obtained.
is there. For this reason, it is easy to obtain a high reproduction output for reproduction.
An MR head is used, while an inductive head is used for recording.
Is used. These magnetic heads are usually integrated
Built into the system as a mold. Such magnetic
The recording system can achieve faster data transfer speeds.
A linear recording method is used. On the other hand, a large capacity magnet using a small cassette
To realize tape recording at high transfer speeds of information,
Rotating drum applied to a laser scanning tape recorder
Development of an on-board MR head is underway. Also, Oh
For audio and video applications, improve sound quality and image quality.
Practical use of digital recording system to be realized, Hi-Vision T
In order to cope with the development of the recording system corresponding to V
Is it possible to record and play back shorter wavelength signals than the system?
Even if the relative speed of the head and medium increases,
Magnetic recording media with high durability have been required.
ing. High density recording of a coating type magnetic recording medium
For this reason, it replaces the conventionally used magnetic iron oxide powder.
Use of iron or alloy magnetic powder mainly composed of iron and magnetic powder
Improvement of magnetic materials such as miniaturization of particles or their filling properties and orientation
To improve the magnetic properties of the magnetic layer
Improving the dispersibility of the ferromagnetic powder, and
Various methods from the viewpoint of enhancing the surface properties of the adhesive layer
Has been studied and proposed. For example, ferromagnetic powder to enhance magnetic properties
Use ferromagnetic metal powder or hexagonal ferrite powder as the powder.
Japanese Patent Application Laid-Open No. 58-122623, Japanese Patent Application Laid-Open No.
61-74137, JP-B 62-49656
, Japanese Patent Publication No. 60-50323, US462965
No. 3, US 4666770, US 4543198
It is disclosed in. Japanese Patent Laid-Open No. 1-189661 discloses a major axis diameter.
0.05 to 0.2 μm, metal magnetic powder with an axial ratio of 4 to 8,
Specific surface area of 30-55m²/ G, coercive force is 1300 L
Stead or higher, saturation magnetization is 120 emu / g or higher
Disclose magnetic powder and provide fine metal powder with small specific surface area
It is supposed to. Also, Japanese Patent Laid-Open No. 60-11300
JP-A-60-21307 discloses ferromagnetic powders,
Fine α-iron oxyhydroxide especially suitable for ferromagnetic metal powder
A method for producing acicular crystals is disclosed, the latter having a major axis length of 0.12
From goethite with ~ 0.25μm, axial ratio of 6 ~ 8 to Hc14
50-1600 oersted, σs142-155em
discloses that u / g ferromagnetic metal powder can be produced.
The In Japanese Patent Laid-Open No. 9-91684, the average major axis is 0.
Ferromagnetic metal grains of 05 μm to 0.12 μm and acicular ratio of 8 or more
Whether the child is 5.0% or less of the entire ferromagnetic metal particle, or
Is a ferromagnetism whose acicular ratio of the crystallites constituting the particles is 4 or more
The metal particles are 17.0% or less of the entire ferromagnetic metal particles
It has been proposed to use ferromagnetic metal particles
High-Hc ferromagnetic powder is obtained when particles with small shape ratio are mixed
S / N and overwriting are also insufficient. Further, JP-A-6-340426 and
JP-A-7-109122 discloses a hematite nucleus.
Monodisperse spindle type hemata using crystal, iron hydroxide and specific ions
And particles obtained by reducing the hematite particles
A very small ferromagnetic powder is disclosed. In order to improve the dispersibility of the ferromagnetic powder
In addition, various surfactants (for example, JP-A-52-15660).
6, JP 53-15803, JP 53
-116114 etc.)
Various reactive coupling agents (for example, JP-A-4)
No. 9-59608, JP-A 56-58135
Published in Japanese Patent Publication No. 62-28489.
Is proposed. Japanese Patent Laid-Open No. 1-239819 discloses
Boron compound, aluminum on the surface of magnetic iron oxide particles
Compound or aluminum compound and silicon compound sequentially
Deposited magnetic powder is disclosed, magnetic properties and dispersibility
Is going to be improved. Furthermore, JP-A-7-22224
In the Gazette, the content of Group 1a element of the periodic rate table is 0.05.
% By mass or less, based on the total amount of metal elements as required
0.1 to 30 atomic% of aluminum and further metal elements
Contains 0.1 to 10 atomic percent of rare earth elements with respect to the total amount of
In addition, the residual amount of the group 2a element in the periodic table is 0.1 mass.
% Or less ferromagnetic metal powder, storage stability and magnetism
It is said that a high-density magnetic recording medium with good gas characteristics can be obtained.
The Furthermore, in order to improve the surface properties of the magnetic layer,
How to improve the surface formation method of the magnetic layer after coating and drying
Law (for example, disclosed in Japanese Patent Publication No. 60-44725)
Have been proposed). On the other hand, a high recording density of the magnetic recording medium is achieved.
Therefore, the shortening of the wavelength of the signal to be used has been strongly promoted.
Yes. However, the length of the area where the signal is recorded is used
When the size is comparable to the size of the magnetic material
Since it is not possible to create a magnetization transition state,
It becomes impossible to record. For this reason, the minimum wavelength used is
It is necessary to develop a magnetic material with a small particle size.
The fine particles of sex bodies have been directed for many years. In the metal powder for magnetic recording, the particle shape is a needle shape.
To give shape anisotropy and obtain the desired coercive force.
The For high-density recording, the ferromagnetic metal powder is made finer.
It is necessary to reduce the surface roughness of the obtained media
Is well known to those skilled in the art. However magnetic
When the metal powder for recording is made finer, acicular
The ratio is lowered and the desired coercive force cannot be obtained. Recently
A DVC system that digitizes and records video signals
A high performance metal evaporated tape for its application
(ME tape) and metal powder (coating) tape (MP
Tape) is used. MP tape used for DVC
Has a coercive force of 159.2 kA / m (2000 Elstre
D) Because of the above, the coercive force is large and fine, and the particle size distribution
There is a need for excellent ferromagnetic metal powders. Also practical form
Many of them are over-recorded because the recording method overwrites magnetic signals.
It is desired that the write characteristics are good. The applicant has previously proposed a strength suitable for a DVC system.
Proposed magnetic metal powder and magnetic recording medium using it
(JP-A-7-326035). This invention is magnetic
Layer, coercive force 2000-3000 oersted, thickness
0.05-0.3 μm, surface roughness controlled to 1-3 nm,
In addition, a magnetic recording medium that specifies a specific reversal magnetization component ratio is proposed.
It is something to offer. Further, a magnet with a built-in thin film magnetic head.
Non-magnetic as a magnetic recording medium used in recording systems
The inorganic nonmagnetic powder is dispersed on the support in a binder.
A non-magnetic layer and a ferromagnetic metal powder bonded on the non-magnetic layer
A magnetic recording medium provided with an upper magnetic layer dispersed in an agent is provided.
Has been proposed (Japanese Patent Laid-Open No. 8-227517). the above
By thinning the upper magnetic layer like
Output reduction is suppressed and high recording density can be achieved.
Therefore, compared with a magnetic recording medium having a single layer magnetic layer
Larger amounts of data can be stored. And here
The upper magnetic layer has a thickness of 0.05 to 1.0 μm, preferably
Preferably, there is a description of 0.05 to 0.8 μm.
More specifically, a polyethylene telemeter having a thickness of 10 μm.
On one side of the phthalate support, a 2.7 μm thick non-
Strong magnetic layer and coercive force Hc of 1800 oersted
A 0.3 μm thick magnetic layer containing magnetic metal powder
Provided magnetic recording medium for computer data recording
Has been described. Magnetic recording system incorporating an MR head
Used in this system with this MR head
The following problems are associated with adaptability with magnetic recording media.
is there. Relatively thick (0.3 μm) as a magnetic recording medium
When a magnetic layer is used, the magnetic flux of the magnetic layer
As a result, the reproduction output becomes too high and the MR head becomes tired.
And the playback waveform is distorted, resulting in a sufficiently high S / N value.
The error rate is likely to increase,
In general, to achieve high recording density, recording and playback waveforms
(Isolated playback inverted waveform) is sharper (the half-width of the waveform is
Small), but the magnetic layer is relatively thick
In magnetic recording media, the half-value width of the recording / reproducing waveform is large.
Thus, it has been found that a sufficiently high recording density cannot be obtained. one
On the other hand, those having a very thin (0.02 μm) magnetic layer
If used, the recording / playback waveform will be distorted,
As a result, similarly, a high S / N value cannot be obtained, and the reproduction output itself
It became clear that it became easy to fall. Fast data transfer
MR magnetic head capable of high-density recording at high speed
Magnets suitable for use in built-in magnetic recording / reproducing systems
Air recording media require extremely fine ferromagnetic powders.
However, as it becomes finer, electromagnetic conversion characteristics and storage stability
It is difficult to produce ferromagnetic powder that satisfies both (weather resistance)
It has become to. [0020] The present invention is directed to high density recording.
The output is high and noisy at a recording wavelength of less than 0.5 μm
Includes ferromagnetic metal powder with low resistance and excellent weather resistance
An object is to provide a magnetic recording medium. [0021] The present inventor is particularly interested in high density recording.
To obtain a magnetic recording medium with good electromagnetic characteristics in the recording area
As a result of diligent examination, the following medium is used:
The excellent high density recording characteristics that are the object of the present invention can be obtained.
Thus, the present invention has been achieved. The present invention
Magnetic layer mainly composed of ferromagnetic metal powder and binder on a support
In the magnetic recording medium provided with
Child volume is 800nm^ThreeMore than 3000nm^ThreeMagnetism that is less than
Metal powder, the ferromagnetic metal powder with respect to the particle volume
The volume ratio of the metal part is 5 to 45%, and the magnetic layer is
The thickness of the magnetic layer is 0.020 to 0.18 μm, and the magnetic layer
The coercive force of the active layer is 127.3 kA / m or more.
This is a magnetic recording medium. The preferred embodiments of the present invention are as follows. 1) The ferromagnetic metal powder has a particle volume of 1000 nm.^ThreeAfter
Top 3000nm^ThreeMagnetism using ferromagnetic metal powder that is less than
Care recording medium. 2) The ferromagnetic metal powder is a metal part body with respect to the particle volume.
A magnetic recording medium having a product ratio of 10 to 45%. 3) The magnetic layer has a coercive force of 143.2 kA / m or more.
Magnetic recording media. 4) The average major axis length of the ferromagnetic metal powder is less than 45 nm.
The coefficient of variation is 25% or less, and the needle ratio is 2.5 or more.
Magnetic recording media. 5) The average major axis length of the metal part of the ferromagnetic metal powder is 25 n
m and less than 42 nm, and its coefficient of variation is 25% or less,
A magnetic recording medium having an average needle ratio of 3.5 or more. 6) The average major axis length of the ferromagnetic metal powder is less than 40 nm.
The coefficient of variation is 25% or less, and the needle ratio is 2.5 or more.
Magnetic recording media. 7) The average major axis length of the metal part of the ferromagnetic metal powder is 25 n
m or more and less than 37 nm, and its coefficient of variation is 25% or less,
A magnetic recording medium having an acicular ratio of 3.5 or more. 8) The average minor axis length of the ferromagnetic metal powder is the crystallite size
Magnetic recording medium using smaller ferromagnetic metal powder. 9) The magnetic recording medium has a residual magnetic flux (Φr) = residual magnetic flux.
Density (Br) × magnetic layer thickness (δ) is 5 to 75 mT · μm
A magnetic recording medium. 10) The magnetic recording medium comprises the support and the magnetic layer.
A nonmagnetic layer mainly composed of nonmagnetic powder and binder resin is placed between them.
And the surface roughness of the magnetic layer is an average surface of the center plane.
A magnetic recording medium having a roughness of 3.0 nm or less. 11) Volume content of ferromagnetic metal powder contained in the magnetic layer
A magnetic recording medium having a rate of 35% or more. [0023] DESCRIPTION OF THE PREFERRED EMBODIMENTS First, ferromagnetic metals used in the present invention.
Let's start with powder. The ferromagnetic metal powder used in the present invention is
Size of ferromagnetic metal powder with high resolution transmission electron microscope
(That is, average major axis length, average minor axis length and average major axis of metal part
Cylinder model (average major axis length X section)
Product (πr²): R = 1/2 of average minor axis length)
The product and the volume of the metal part are specified, and the density is high.
Improved electromagnetic conversion characteristics in recording (λ = less than 0.5μm)
To provide a magnetic recording medium having good weather resistance
You can. The ferromagnetic metal powder used in the present invention is X-ray diffraction
Thus, an α-Fe peak is present. particle
The average major axis length is preferably 25 nm or more and less than 45 nm,
More preferably, it is 25-40 nm. Long axis length variation
The number is preferably 25% or less, more preferably 20% or less.
Yes. Also, the average needle ratio {average of (major axis length / minor axis length)} is
2.5-6 are preferable. Average needle ratio is less than 2.5
Sometimes the coercive force Hc based on shape anisotropy is small.
This is disadvantageous for high-density recording. Average needle of ferromagnetic metal powder
When the shape ratio is 2.5 to 6, the larger the average needle ratio, the more
The force Hc increases. Long axis length and needle of ferromagnetic metal powder
It is preferable that the coefficient of variation of each state ratio is 25% or less and is small
That's right. When the coefficient of variation of the long axis length and needle ratio is small, H
c distribution is small, especially high Hc component (magnetic field 320 kA /
The ratio of the component that reverses magnetization at m or more) decreases.
-It is preferable in terms of barite characteristics. Average powder size is constant
If the average major axis length and needle ratio variation coefficient is small,
High Hc and small Hc distribution, low high coercive force component,
SFD (switching-field distr
ibt), SFDr tends to decrease
It was. It turns out that the contribution of the needle ratio of the metal part is particularly large
It was. Particle volume of ferromagnetic metal powder used in the present invention
And the particle size for determining the metal (core) part volume is
The value measured by the following. High resolution transmission electron microscope
Observe the lattice image of the ferromagnetic metal powder with a microscopic mirror.
Whole powder (oxide layer (oxide film) around the metal part)
The length of the inside (core part) of the ferromagnetic metal powder (long)
(Axis length or minor axis length). Specific description will be given below. Ahead
First, place the particles dispersed ultrasonically in water on the mesh
Granules using a transmission electron microscope H-9000, manufactured by Tatetsu Seisakusho
The child was photographed (300kV) and the total magnification was 500,000 times and 300
Get 10,000 times more photos. Ferromagnetic metal powder with 500,000 times magnification
Body (including oxide layer (oxide film) around the metal part)
Particle length (major axis length or minor axis length). 30
Measure 0 particles and determine the average particle length and standard deviation. grain
The variation rate of the child length is obtained by dividing the standard deviation of the particle length by the average particle length.
Ask. Next, the thickness of the oxide film is obtained with a 3 million times photograph.
I will. In the photograph, the metal part in the center is black.
The film portion is observed in a whitish state than the center portion. Money
Use a scanner to capture the lines on the genus and coating surface,
The interval is adjusted by the image analysis device KS-400 manufactured by Kontron.
Dynamic measurement to determine the average oxide film thickness. The number of measurements is one
Measure 150 points with particles, 15 particles (total 2250 particles)
) And determine the average oxide thickness and standard deviation. Oxidation
The variation rate of the film thickness is the standard deviation of the oxide film thickness (oxide layer).
Obtained by dividing by the uniform oxide film thickness. Average major axis length of the whole particle and
From the average minor axis length, the average oxide film thickness
Average of the metal part (core part) by subtracting the uniform oxide film thickness X2)
The major axis length and the average minor axis length were used. Based on the values obtained above, a cylindrical model
Calculate the particle volume and metal part volume of ferromagnetic metal powder
The Particle volume is 800nm^ThreeLess than the average needle shape of the particles
Ratio (axial ratio) is less than 2.5 and Hc is extremely high
It becomes small and the problem of thermal fluctuation occurs, which is preferable
Yes. 3000nm^ThreeAbove, compatible metal thin film media
Noise against the body (ME tape: for example, microMV)
Is unfavorable because it increases. The crystallite size of the ferromagnetic metal powder is
Each of the 110- and 220-side surfaces of α-Fe by folding
Value obtained by dividing the sum of the peak (half width) by 2
Means larger than the average minor axis length of the ferromagnetic metal powder particles
It is preferable. 80-130cm, preferably 80-
125 ?, more preferably 85? 120 ?. crystal
If the child size is smaller than 80mm, Hc will be small.
In addition, the weather resistance is inferior, which is not preferable. From 130cm
If it is large, the noise becomes extremely large, which is inappropriate. The σs of the ferromagnetic metal powder used in the present invention is 7
5-130A ・ m²/ Kg, preferably 80-125A
・ M²/ Kg, more preferably 85 to 120 A · m²/ K
g. Strengthen gradual oxidation and thicken oxide film to reduce σs
SFD increases, especially the average major axis length is 65n
The increase in SFD is remarkable at m or less. Average long axis length is 65
The increase in SFD is noticeable when the particle size is below nm.
It has a distribution, and when the average major axis length becomes smaller
The fine particle component increases in the region where the thermal fluctuation increases. You
In other words, it is thought that the content of superparamagnetic components increases.
It is. Furthermore, by gradually oxidizing to lower σs,
This is probably because the magnetic component increases. Lower SFD
In order to achieve this, it is necessary to control the gradual oxidation conditions to make the surface oxide layer dense.
And making it as thin as possible is effective. So book
The average oxide film of the ferromagnetic metal powder of the invention is 1.5 to 3.5.
It is preferably controlled to nm. The thickness of the oxide film
As a preferable method for reducing σs within the range, strong
Magnetic metal powder is strong by reducing oxides of ferromagnetic metal elements
Use magnetic metal powder and gradually oxidize to 120 to 15
0A ・ m²/ Kg, then at least Al in water,
A small amount selected from Y, lanthanoid, Zr and W
After depositing at least one element, heat treatment,
Slow oxidation treatment is very effective. σs is 75A
・ M²If it is lower than / kg, SFD will only deteriorate significantly
In addition, Hc is also reduced, which is disadvantageous for high-density recording.
On the other hand, σs is 130A ・ m²/ Kg exceeds Br (remaining
Even if the magnetic layer thickness is reduced.
The residual magnetic flux (Φr) of the body becomes high and the MR head
Saturate the waveform, causing waveform distortion and pulse asymmetry
Adverse effects. Further, the change rate ΔHc of Hc of the medium
It was observed that the absolute value increased. The higher σs, the more magnetic
The durability of the adhesive layer becomes weaker, and the lower the σs, the better the durability.
I found out. In addition, the residual magnetic flux density
The unit is reduced by reducing the thickness of the magnetic layer.
The abundance of ferromagnetic metal powder per area is reduced.
The necessary S / N cannot be obtained. Magnetic layer
Volume content of ferromagnetic metal powder contained in (100 × ferromagnetic)
The volume of the conductive metal powder / the volume of the magnetic layer) is preferably 35% or more.
More preferably, it is 40% or more. Per unit recording area
To increase the amount of ferromagnetic metal powder present,
Make the saturation magnetization σs of magnetic metal powder as small as possible.
Is important, and the durability of the magnetic layer when used as a medium
It is also effective for improving the property and weather resistance. The coercive force Hc of the ferromagnetic metal powder is preferably
111.4 to 320 kA / m, more preferably 127.
3 to 280 kA / m, particularly preferably 143.2 to 23
0 kA / m. As mentioned earlier, the ferromagnetic metal powder
Defines the volume ratio of the metal part to the particle volume.
The magnetic layer thickness is as thin as 0.02 to 0.18 μm
Of overwriting characteristics with low Hc distribution.
It is estimated that an excellent magnetic recording medium was obtained. Σ
The smaller s is, the more Hc of the magnetic recording medium is
It tends to be a large value with respect to Hc. The ferromagnetic metal powder used in the present invention is Fe or less.
It is preferable that Co is contained in an amount of 20 to 45% by mass with respect to Fe.
Good. The ferromagnetic metal powder used in the present invention is Fe
In addition to Co and Al at a mass ratio of 20% by mass or less,
Si, S, Ti, V, Cr, Cu, Y, Mo, Rh, P
d, Ag, Sn, Sb, Te, Ba, Sr, W, Au,
Pb, Bi, La, Ce, Pr, Nd, P, Mg, M
It is preferable to contain atoms such as n, Zn, Sr, B, and Ca.
That's right. In particular, Al is in the range of 5 to 15 atomic% in Al / Fe
The rare earth elements are the sum of the rare earth elements / Fe of 10 elements
It is preferable to contain more than%. This rare earth element is Y
And lanthanoid elements, specifically Y, La,
Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
y, Ho, Er, Tm, Yb, Lu, but Y, L
Particularly preferred are a, Ce, Nd, Sm, Gd and the like. these
In addition to controlling the shape of the starting material, these elements prevent sintering between particles.
Acceleration of reduction and shape and particles of reduced ferromagnetic metal powder
Effective for controlling surface irregularities. In the present invention, the size and form of the starting material
In particular, the one with a small coefficient of variation of the long axis length and needle ratio is used.
The size and variation of ferromagnetic metal powder particles
While reducing the coefficient, from the conventional polycrystalline state
As many particles as possible with a single crystal structure
Is preferred. The ferromagnetic metal powder used in the present invention is monodispersed.
Starting from goethite or monodisperse hematite
In order to reduce to metal finally,
Reduce with hydrogen. In the middle of the process, αFe₂O_ThreeA
Neal treatment is useful for increasing crystallinity
It is. ΑFe₂O_ThreeFe_ThreeO_FourReduced to FeO
Use various reducing gases instead of pure hydrogen.
Can do. It is known that moisture is related to sintering during reduction.
Therefore, the generation of nuclei is suppressed as much as possible,
In order to increase the crystallinity, the water generated by the reduction is reduced for a short time.
Water generated during removal or reduction in the meantime
It is preferable to control the amount. Such water control
Controls the partial pressure of the reducing gas or controls the amount of reducing gas
Can be done. Giving the average oxide thickness
The surface oxide layer is formed by a known oxidation method after forming the metal portion,
For example, it is formed around the metal part by the slow oxidation treatment or the like.
Can be made. In gas used for slow oxidation treatment
If carbon dioxide is contained in the ferromagnetic metal powder surface,
Since it adsorbs to the basic point, such carbon dioxide is included.
It may be. Surface oxidation of ferromagnetic metal powder used in the present invention
As the oxide that constitutes the physical layer, even a magnetic oxide is non-magnetic
It may be an oxide. A small amount of metal elements such as Al,
Mg, Si, Y, lanthanoid, Ca, Ba, Sr, N
A metal such as i may be dissolved. As magnetic oxide
Preferably has a saturation magnetization of 50 to 90 A · m.²/ Kg
Some are listed. For example, magnetic iron oxide
As Co_xFe (1-x) O_y(E.g. CoFe
₂O_FourCoFe_ThreeO_FourEtc.), FeO_x(However, x is 1.3.
3 ≦ x ≦ 2, for example, γFe₂O_Three, Fe_ThreeO_Four, Verdola
Id compound). Also as non-magnetic oxide
Crystalline and amorphous metal oxides and oxyhydroxide
Alone or in combination, including products, hydroxides and hydrated oxides
Is included. This non-magnetic oxide is mainly a sintering inhibitor.
When adding elements and ferromagnetic metal powder raw materials
Derived from elements added to The surface oxide layer is, for example, a magnetic oxide.
Single, nonmagnetic oxide alone, or a combination of both
The structure is not particularly limited. Surface acid
When the oxide layer is composed of a combination of both, the magnetic oxide
And non-magnetic oxides are mixed with each other
Independent layers may be formed. Ferromagnetic metal particles
When oxide layers independent from each other are provided on the surface portion, each layer
Metal phase, magnetic oxide phase, and magnetic oxide phase at the interface between
And the nonmagnetic oxide phase may be mixed. Metal parts
Magnetic oxide layer, non-magnetic oxidation toward the particle surface, sequentially around
A physical layer may be formed. The ferromagnetic metal powder used in the present invention will be described later.
Dispersed with dispersants, lubricants, surfactants, antistatic agents, etc.
Processing can be performed in advance. In particular,
Japanese Examined Patent Publication No. 44-14090, Japanese Examined Publication No. 45-1837
No. 2, Japanese Patent Publication No. 47-22062, Japanese Patent Publication No. 47
-22513, JP-B-46-28466,
Japanese Patent Publication No. 46-38755, Japanese Patent Publication No. 47-4286
No. 47, Japanese Patent Publication No. 47-12422, Japanese Patent Publication No. 47-
No. 17284, JP-B 47-18509, JP
Japanese Patent Publication No. 47-18573, Japanese Patent Publication No. 39-10307
Gazette, JP-B 48-39639, and US patent
3026215, 3031341, 31001
94, 324005, 3338914, etc.
It is described in each gazette. The water content of the ferromagnetic metal powder is 0.01-2.
It is desirable to use the amount%. However, the type of binder described below
It is hoped that the moisture content will be optimized between the above ranges depending on the type
Good. The tap density of the ferromagnetic metal powder is 0.2 to
0.8 g / ml is desirable. Greater than 0.8g / ml
And when the powder is gradually oxidized,
It was difficult to handle the powder safely.
The magnetization of the obtained magnetic recording medium decreases with time.
There is a tendency to. Tap density is less than 0.2g / ml
It becomes bulky and difficult to handle, and it is dispersed
Tends to be insufficient. Next, a ferromagnetic metal powder used in the present invention is manufactured.
How to do is described. How to obtain the above ferromagnetic metal powder
The method is not particularly limited, and any method can be used.
However, the following method is preferably exemplified. Long axis length and needle shape
Sintered into starting materials with good ratio and particle size
Metal oxide (e.g. Fe
Ox: 1 ≦ x ≦ 1.5, for example Fe₂O_Three, Fe_ThreeO_FourOr
It is possible to control the acicular ratio of the metal (eg, Fe).
The starting material is a simple particle size distribution with no branching.
Dispersed goethite or monodisperse hematite
The In the starting material, the average major axis length is 30 to
It is preferable that the average needle ratio is 70 to 70 nm.
Yes. Adjust the starting material shape, major axis length, minor axis length, and needle ratio.
It is important to rub. Average long axis length is less than 30nm
When using raw materials, make Hc and Bm within the desired range.
I can't. Raw material whose average long axis length is larger than 70 nm
If the material is used, high density recording (λ = less than 0.5μm)
As a magnetic recording medium, the surface roughness becomes rough.
In addition, when noise increases and excellent S / N cannot be obtained
There is a match. If the needle ratio is greater than 10, the particle size distribution is wide.
As the magnetic layer thickness is reduced as in the present invention,
Manufacturing becomes difficult, and the degree of filling of the magnetic recording medium
Unevenness easily occurs. In addition, the high coercive force component increases,
Bar light properties tend to be inferior. Needle ratio is less than 4
The coercive force when it is made a ferromagnetic metal powder is small, SFD
Used for magnetic recording media for high-density recording.
Can be difficult. Further, as a means for controlling the ferromagnetic metal powder.
Examples of the method include the following.   Identifying elemental composition mainly inside ferromagnetic metal powder
about. In particular, the metal part is mainly composed of Fe or Fe-Co.
Ferromagnetic metal powder that contains trace elements that interact with Fe
Identify. The trace elements include Ca, Mn, Ni, C
r, Mg and the like are preferable. This trace element is
Addition and / or after creation of matite
It is preferable to add by surface treatment. Also prevents sintering
Doping and / or depositing sintering inhibitor to stop
That is an important factor. As the sintering inhibitor, Si,
Al, Y, lanthanoids and the like are effective.   Ferromagnetic metal powder by reducing oxides of ferromagnetic metal elements
In the end-to-end method, pretreatment before reduction, for example, game
Dehydration conditions such as tightness, annealing conditions (for example, temperature, atmosphere
Ambient, processing time, temperature difference between initial and second half)
The reduction conditions, such as temperature, reducing gas, reduction treatment time, etc.
Select. In particular, the major axis length and minor axis of ferromagnetic metal powder
Keep the length size uniform and the needle ratio in the range of 2.5-7
In order to maintain it, the reduction treatment and the slow oxidation treatment are repeated step by step.
Processing, shape control, crystallinity control, and oxide layer
It is very important to control the thickness and the crystallinity of the oxide layer.
It is important. Specifically, the trace element content obtained above is contained.
The conditions for processing goethite are as follows:
The The dehydration condition is a static or rotary electric furnace.
Under a nitrogen atmosphere, usually 250 to 400 ° C., preferably 3
0.5 to 2 hours at 00 to 400 ° C., preferably 0.5 to
One hour may be mentioned. As annealing conditions,
In a static reducing furnace, usually in a nitrogen atmosphere, 500 to 800
℃, preferably at 550-700 ℃ for 1-5 hours
Or for 2 to 3 hours. After dehydration,
Hematite obtained by dehydration before water treatment
Even if a process of washing and removing soluble alkali metals is provided
Good. For example, low dehydration and annealing treatment and slow oxidation treatment
From warm to gradually higher, preferably 25 at the beginning of the dehydration process
0-300 ° C, then 300-350 ° C, and further 350-
400 ° C. and annealing conditions first 500-550
At 550 ° C, then 550-650 ° C, then 600-800 ° C
Process, perform stepwise temperature rise and repeat process
Shape control, crystallinity control, oxide layer thickness and oxide layer
It is effective to control the crystallinity. As a reduction condition, hydrogen is used in a stationary reduction furnace.
Under atmosphere, usually 350 to 600 ° C., preferably 425
˜530 ° C., usually 0.25 to 2 hours, preferably 0.
Reduction treatment for 25 to 1.5 hours, and then the atmosphere is changed to nitrogen
After substitution, usually 450-650 ° C., preferably 50
0 to 600 ° C., usually 0.5 to 4 hours, preferably 1 to
Heat for 3 hours, then switch to pure hydrogen at the temperature 3
Reduction treatment for ˜5 hours can be mentioned. Example of reduction treatment
For example, from the low temperature to the high temperature, preferably the initial reduction is 3
50-470 ° C., then 370-620 ° C., further 450
~ 620 ° C (and increase the temperature by 10 ° C or more at each stage)
Etc., step by step and repeated processing of the metal part
Increasing shape control and crystallinity is very effective. At the end of the reduction, the water content in the drainage system gas is dew point.
Determine by measuring with a meter. In the manufacturing method of the above ferromagnetic metal powder
Known methods, for example, JP-A-7-109122.
And Japanese Patent Application Laid-Open No. 6-340426
The law can be applied. Metal part of ferromagnetic metal powder
As the ferromagnetic metal element, Fe or Fe-Co is mainly used.
It is preferable to use as a component. Here, the main component is metal
Means 75% by mass or more with respect to the total mass of the part.
Taste. Co increases σs and creates a dense and thin oxide film
Since it can form, it is especially preferable. Ferromagnetic metal powder
The Co content in the powder is compared to the Fe contained in the ferromagnetic metal powder.
15 to 45 atomic% is preferable, more preferably 20 to
42% by weight. The Co content of the ferromagnetic metal powder is 15
If it is less than atomic%, σs and coercive force become small,
It is difficult to keep the fluctuation rate of the oxide film thickness low.
Furthermore, demagnetization is suppressed to within 10% with the magnetic recording medium configuration of the present invention.
It becomes difficult to obtain. Moreover, when it exceeds 45 atomic%,
It is difficult to align the degree distribution. In addition, the reduction rate control
Which makes it difficult to break down and cause particle breakage and sintering between particles.
Mae. The means for including Co in the ferromagnetic metal powder is as described above.
Dope part of the sea urchin into raw materials such as goethite, then the remaining amount
Is applied to the surface of the raw material by anti-sintering treatment and reduced.
It is preferable to form an alloy. Applied to the raw material surface
The amount of Co is 10 with respect to Fe contained in the ferromagnetic metal powder.
It is preferable that it becomes -45 atomic%, Furthermore, 15-40
It is preferable to be atomic%. After the reduction of the oxide, the metallized powder
Is subjected to a gradual oxidation treatment. The atmosphere of gradual oxidation treatment is acid
It is an inert gas atmosphere containing element. Inert gas atmosphere
As nitrogen gas, helium gas, argon gas, etc.
Nitrogen gas is particularly preferable. The oxygen content is
0.1-5 vol% is preferred, oxygen gradually up to a predetermined amount
It is preferred to increase the amount. Also, inert gas atmosphere
As the gas, water vapor may be contained. Contains water vapor
Spindle-shaped alloy magnetic particle powder with high coercive force
The end is easy to get. The slow oxidation temperature is preferably 40 to 200 ° C.
More preferably, it is 40-180 degreeC. 40
If it is less than ℃, form a surface oxide layer with sufficient thickness.
Difficult to achieve, and the magnetic properties are reduced by washing with water.
Become prominent. If the temperature exceeds 200 ° C, the shape of the particles
In particular, because of the large amount of oxides produced,
In some cases, it is easy to destroy
It ’s not good. After the slow oxidation treatment, heat treatment and reduction treatment
And surface oxidation treatment (slow oxidation treatment)
May be. By repeating these processes
A finer ferromagnetic metal powder can be easily obtained. Ma
After washing with ferromagnetic metal powder, it is
Removing water-soluble salts present on the surface of metal powder
It can be processed if necessary. Furthermore, Japanese Patent Application 2001
-Slow oxidation treatment method proposed in No. 315366
It is also effective to use. Next, the magnetic recording medium of the present invention will be described.
The The magnetic recording medium of the present invention has a weather resistance of the magnetic layer, that is,
Demagnetization after storage for 1 week at 60 ° C and 90% RH is less than 10%
By suppressing the storage stability of magnetic recording media is a problem.
Level. However, the lower the demagnetization, the better
That's right. To keep demagnetization (△ Φm) below 10%,
The ratio of the volume of the metal part to the particle volume is 5
It is important to be in the range of ~ 45%. Magnetic layer demagnetization
ΔΦm (%) means the value obtained by the following measurement method.
Taste. ΔΦm (%) = 100 × (Φm before storage−Φm after storage) /
Φm before storage Φm: Maximum magnetic flux Measurement is performed using a vibrating sample magnetometer VSM-5 (manufactured by Toei Kogyo Co., Ltd.)
Used, time constant 0.1 seconds, sweep speed 3 minutes
/ 10 kOe {Oe = (1 / 4π) kA / m}, measured magnetism
Measure at a field of 10 kOe. Also, the change rate Hc of Hc
The absolute value of (%) is preferably within 2.5%. ΔHc
(%) Means the value obtained by the following measurement method.
The ΔHc (%) = 100 × (Hc before storage−Hc after storage) /
Hc before storage The measurement is the same as ΔΦm. ΔHc (%) is −2.5
Less than 10%, the increase in high Hc component occurs
If + 2.5% is exceeded, an increase in low Hc content occurs
Therefore, it is not preferable. The residual magnetic flux (Φr) of the magnetic layer of the present invention {residual
Magnetic flux density (Br) × magnetic layer thickness (δ)} is 5 to 75 m.
T · μm is preferable, more preferably 10 to 70 mT ·
It is μm, particularly preferably 15 to 60 mT · μm.
The residual magnetic flux (Φr) of the magnetic layer is the highest depending on the performance of the MR head.
It is desirable to set an appropriate value so that the MR head is not saturated.
It is preferable to select a higher value within the range. In the present invention, Hc of the magnetic layer is 127.
3 kA / m to 320 kA / m is preferable and more preferable
143.2 to 300 kA / m, particularly preferred
Is 159.2 to 240 kA / m. Hc is 127.
If it is less than 3 kA / m, the output is insufficient, and the low Hc component
The abundance increases and the problem of thermal fluctuation occurs. 3
If it exceeds 20 kA / m, it is preferable in terms of overwrite characteristics
Absent. Also, the recording current is insufficient or the head is saturated.
As a result, distortion occurs and output becomes insufficient.
This tendency is particularly high for a highly sensitive head such as a magnetoresistive type (M
R) This is remarkable in a system using a head. Hc, Br, Φ
If r is smaller than the lower limit, sufficient short wavelength output can be obtained.
In some cases, and they are larger than the upper limit.
If the recording head is saturated, the output will be saturated.
May not be secured. The layer structure of the magnetic recording medium of the present invention is basically
At least the ferromagnetic metal powder used in the present invention on the support
A magnetic layer containing powder, and the magnetic layer
If it is provided on either side or both sides, there is no particular limitation.
Yes. Also, the magnetic layer is composed of two or more layers even if it is a single layer.
In the latter case, the positional relationship between these layers
Even if they are adjacent to each other, a layer other than the magnetic layer is interposed between them.
A known layer structure can be adopted. In addition, this departure
In the light, the thickness of the magnetic layer is the thickness of the top layer in the case of multiple layers.
The dry thickness of the magnetic layer. The thickness of the magnetic layer is 0.020
To 0.18 μm, preferably 0.03 to 0.18 μm,
More preferably, it is 0.03-0.15 micrometer. 0.0
If it is less than 2 μm, there are only two ferromagnetic metal powder layers.
Therefore, the thickness variation becomes large. Also, per unit area
The number of particles becomes small and is not suitable for high density recording.
The magnetic recording medium of the present invention is preferably a support, a magnetic layer,
A nonmagnetic layer mainly composed of nonmagnetic powder and binder is provided between
It is done. In this case, the surface roughness of the magnetic layer is a center plane average table.
The surface roughness (Ra) is preferably 3.0 nm or less, more preferably
It is preferably 0.6 to 2.8 nm. The dispersibility of the magnetic layer is
This is important because it affects noise. Magnetic cluster
-You can measure the size to see the dispersibility of the magnetic layer
The Smaller magnetic cluster size in the present invention
Is desirable, 13000 nm^ThreeBelow, preferably 110
00nm^ThreeIt is as follows. The magnetic layer can be composed of multiple layers.
Is possible. Examples include ferromagnetic iron oxide, ferromagnetic cobalt
Modified iron oxide, CrO₂Powder, hexagonal ferrite powder
And ferromagnetic powder selected from various ferromagnetic metal powders
For example, a combination of magnetic layers dispersed in a binder
It is. In this case, even in the same kind of ferromagnetic powder, the element
Magnetic layer containing ferromagnetic powder with different composition, powder size, etc.
Can also be combined. In the present invention, a ferromagnetic metal powder is included.
Magnetic recording medium having nonmagnetic layer provided between magnetic layer and support
Is preferred. The positional relationship of the layers with such a layer structure
The magnetic layer is also referred to as the upper layer, and the nonmagnetic layer is also referred to as the lower layer. Next lower layer
The detailed contents of will be described. The lower layer is substantially
Is non-magnetic and includes a non-magnetic powder and a binder.
However, it should not be particularly limited.
Magnetic powder is also used as long as the lower layer is substantially non-magnetic.
To get. The lower layer is substantially non-magnetic
The lower layer is within a range that does not substantially deteriorate the electromagnetic conversion characteristics of the layer.
It means that it has magnetism. Nonmagnetic powders include, for example, metal oxidation
Mineralization of metal, metal carbonate, metal nitride, metal carbide, etc.
You can choose from compounds. Examples of inorganic compounds
For example, α-alumina, β-alumina having an α conversion rate of 90% or more,
γ-alumina, θ-alumina, silicon carbide, black oxide
, Cerium oxide, α-iron oxide, goethite, silicon nitride
Elemental, titanium dioxide, silicon dioxide, tin oxide, magnesia oxide
Sium, zirconium oxide, zinc oxide, barium sulfate,
Etc. are used alone or in combination. Especially preferred
Has a small particle size distribution and a lot of functions
From titanium dioxide, zinc oxide, α-iron oxide, sulfuric acid
Barium, more preferably titanium dioxide, α-
It is iron oxide. α-Iron oxide is a magnet with a uniform particle size.
Heat-dehydrated iron oxide raw material for the production of functional iron oxide and metal powder
Neal processing to reduce voids and surface treatment if necessary
Are preferred. Usually, titanium dioxide has photocatalytic properties.
Therefore, when light strikes, radicals are generated and the binder
-There is a concern of reacting with lubricants. Therefore, in the present invention
The titanium dioxide used is 1-10% of Al, Fe, etc.
It is necessary to make a solid solution and to reduce photocatalytic properties.
Furthermore, the surface is treated with Al and Si compounds to reduce the catalytic action.
It is also preferable to lower. The particle size of these non-magnetic powders
0.005 to 1 μm is preferable, but if necessary
Combination of non-magnetic powders with different particle sizes or single
Even non-magnetic powders have the same effect by widening the particle size distribution
It can also be made. Particularly preferred non-magnetic powder particle size
Is 0.01 μm to 0.5 μm. Especially non-magnetic powder
When the powder is a granular metal oxide, the average equivalent circle diameter is 0.
It is preferably less than or equal to 08 μm.
In some cases, the average major axis is preferably 0.3 μm or less.
More preferably, it is 0.2 μm or less.
Tap density is usually 0.3 to 1.5 g / ml, preferably
Is 0.4 to 1.3 g / ml. Moisture content of non-magnetic powder
Is usually 0.2 to 5 mass%, preferably 0.3 to 3 mass%
%, More preferably 0.3 to 1.5% by mass. Non-magnetic
The pH of the conductive powder is usually 2 to 12, but 5.5 to 11
It is particularly preferred that BET method of non-magnetic powder
Specific surface area (S_BET) Is usually 1-100m²/ G,
Preferably 5-80m²/ G, more preferably 10-8
0m²/ G. The crystallite size of non-magnetic powder is 40 ~
1000? Is preferred, 40-800? Is more preferred
Yes. Oil absorption using DBP (dibutyl phthalate)
Usually 5-100 ml / 100 g, preferably 10-80
ml / 100 g, more preferably 20-60 ml / 10
0 g. The specific gravity is usually 1.5-7, preferably 3-
6. The shape is any of acicular, spherical, polyhedral, and plate
But it ’s okay. SA (stearic acid) adsorption amount of non-magnetic powder is
1-20 μmol / m², Preferably 2-15 μmol
/ M²More preferably, 3 to 8 μmol / m²It is.
When using non-magnetic powder with a large amount of stearic acid adsorption,
The surface of the magnetic recording medium is modified with an organic substance that strongly adsorbs to the surface.
It is preferable to create. The surface of these nonmagnetic powders has Al, M
g, Si, Ti, Zr, Sn, Sb, Zn, Y, etc.
Surface treatment with a compound containing element is preferable. This table
As an oxide formed on the surface by surface treatment, especially
Preferred for dispersibility is Al₂O_Three, SiO₂TiO₂, Z
rO₂MgO and their hydrated oxides.
Preferred for Al₂O_Three, SiO₂, ZrO₂And this
These are hydrous oxides. Use these in combination
It can also be used alone. Depending on the purpose,
The surface treatment layer co-precipitated may be used.
A method of forming silica on the surface layer after forming the mina,
Or the reverse method can also be taken. In addition, surface treatment
The physical layer may be a porous layer depending on the purpose, but it is homogeneous.
And dense are generally preferred. Specific examples of nonmagnetic powder used for the lower layer
, Showa Denko Nano Tight, Sumitomo Chemical HIT-
100, HIT-82, Toda Kogyo α-iron oxide DPN-
250BX, DPN-245, DPN-270BX, D
PN-550BX, DPN-550RX, DPN-01
10RX, DBN-650RX, DAN-855RX,
DAN-890RX, titanium oxide TTO-5 made by Ishihara Sangyo
1B, TTO-55A, TTO-55B, TTO-55
C, TTO-55S, TTO-55D, SN-100,
Titanium Industrial Titanium Oxide STT-4D, STT-30
D, STT-30, STT-65C, α-iron oxide α-4
0, Teica titanium oxide MT-100S, MT-100
T, MT-150W, MT-500B, MT-600
B, MT-100F, MT-500HD, Sakai Chemicals FI
NEX-25, BF-1, BF-10, BF-20, S
T-M, Dowa Mining Iron Oxide DEFIC-Y, DEFIC
-R, AS2BM manufactured by Nippon Aerosil, TiO2P25,
Ube Industries 100A, 500A, and those fired
Can be mentioned. Mixing carbon black in the lower layer
As is well known, the surface electrical resistance Rs is
Lowering, reducing light transmittance, desired microphone
Robickers hardness can be obtained. In the present invention,
The carbon black used for the lower layer is the above non-magnetic powder
It may be included as a powder. Also, carbon black in the lower layer
It is also possible to bring about the effect of storing lubricant by including
Noh. Suitable types of carbon black include gold
Furnace black for rubber and various thermals for rubber
Black, carbon black for color, conductive carbon
Black, acetylene black, etc. can be used
The The underlying carbon black depends on the desired effect,
The following characteristics should be optimized and used together
May be more effective. By the BET method of the lower carbon black
The measured specific surface area is usually 50 to 500 m.²/ G, preferred
Or 70-400m²/ G, DBP oil absorption is usually 2
0-400ml / 100g, preferably 30-400m
1/100 g. The average particle size of carbon black is
Usually 5 to 80 nm, preferably 10 to 50 nm,
The thickness is preferably 10 to 40 nm. Carbon black
PH is 2 to 10, moisture content is 0.1 to 10% by mass, tap.
The density is preferably 0.1 to 1 g / ml. Used in the present invention
Specific examples of carbon black
BLACKPEARLS 2000, 1300, manufactured by To
1000, 900, 800, 880, 700, VULC
AN XC-72, Mitsubishi Chemical # 3050B, # 31
50B, # 3750B, # 3950B, # 950, # 6
50B, # 970B, # 850B, MA-600, MA
-230, # 4000, # 4010, Colombian car
BON CONDUCTEX SC, RAVEN 88
00, 8000, 7000, 5750, 5250, 35
00, 2100, 2000, 1800, 1500, 12
55, 1250, Akzo Ketchen Black EC
Etc. Display carbon black as a dispersant.
Even if the surface treatment or grafting with resin is used, the surface
It is acceptable to use a graphitized part of
Yes. Also, before adding carbon black to the paint,
It may be dispersed with a caulking binder. These carbos
Black exceeds 50% by mass with respect to the non-magnetic powder.
Used in a range not exceeding 40% by mass of the total mass of the lower layer.
Can be used. These carbon blacks can be used alone or in combination.
Can be used together. Cars that can be used in the present invention
Bon Black is an example of “Carbon Black Handbook” (Car
You can refer to the Bon Black Association). In the lower layer, an organic powder is added according to the purpose.
It can also be added. As a preferable organic powder,
For example, acrylic styrene resin powder, benzoguanami
Resin powder, melamine resin powder, phthalocyanine face
Include polyolefin resin powder, polyester
Steal resin powder, polyamide resin powder, polyimide
Resin powder and polyfluorinated ethylene resin can also be used
it can. The production method thereof is, for example, JP-A-62-18564.
No., JP-A-60-255827, etc.
You can use what you have. Lower layer binder (type and amount), lubricant / dispersion
For the amount, type, solvent, and dispersion method of additives and additives
A known technique can be applied. The magnetic layer in the magnetic recording medium of the present invention
Alternatively, the binder used for the nonmagnetic layer is a conventionally known binder.
Thermoplastic resins, thermosetting resins, reactive resins and their mixtures
Compound can be used. As a thermoplastic resin, glass transition
Temperature is −100 to 150 ° C., number average molecular weight is 1000 to
200000, preferably 10000-100000,
Those having a degree of polymerization of about 50 to 1000 are preferably used.
It is. Such binders include vinyl chloride,
Vinyl acetate, vinyl alcohol, maleic acid, acrylic
Acid, acrylic acid ester, vinylidene chloride, acryloni
Tolyl, methacrylic acid, methacrylic acid ester, styrene
, Butadiene, ethylene, vinyl butyral, vinyl
Contains acetal, vinyl ether, etc. as structural units
Polymer or copolymer, polyurethane resin, various rubbers
There is a resin. In addition, a thermosetting resin or a reactive resin is used.
Phenolic resin, epoxy resin, polyurethane curing
Mold resin, urea resin, melamine resin, alkyd resin, active resin
Ryl reaction resin, formaldehyde resin, silicone resin
Fat, epoxy-polyamide resin, polyester resin and
Mixture of socyanate prepolymer, polyester poly
A mixture of all and polyisocyanate, polyurethane and
Examples thereof include mixtures of polyisocyanates. In the above binder, a superior ferromagnetic powder
To obtain the dispersion effect and durability of the magnetic layer, if necessary
-COOM, -SO_ThreeM, -OSO_ThreeM, -P = O (O
M) ₂, -OP = O (OM)₂(M in each group is hydrogen
Atom or alkali metal), -OH, -NR₂, -N⁺
R_Three(R is a hydrocarbon group), epoxy group, SH, CN, NA
Copolymerize at least one polar group selected from
Or it is preferable to use the one introduced by addition reaction.
Yes. The amount of such polar groups is 10 with respect to the amount of binder.
^-1-10^-8Mol / g, preferably 10^-2-10^-6
Mol / g. Binder used in the magnetic recording medium of the present invention
Is preferably in the range of 5 to 50 mass% with respect to the ferromagnetic powder.
Or 10 to 30% by mass. Vinyl chloride
5 to 100% by mass when polyurethane resin is used, polyurethane
0 to 100% by mass when using resin, polyisocyanate
The combination of these in the range of 2 to 100% by mass
It is preferable to use it. Polyurethane as a binder
It is possible to use the resin alone. Examples of the polyurethane resin include diols.
And reaction products made mainly from organic diisocyanate
Made of a certain polyurethane resin, as a diol component
Is a short-chain diol unit having a cyclic structure and an ether group.
It preferably contains a long-chain diol unit. So
This polyurethane resin is a short chain dihydrate having a cyclic structure.
Containing 17-40% by weight of all units in polyurethane resin
And ether groups on the entire polyurethane resin
Long chain diol units containing 1.0-5.0 mmol / g
A binder containing 10 to 50% by weight in a polyurethane resin
It is preferable. Short chain diol having a cyclic structure is saturated
Or having an unsaturated cyclic structure and a molecular weight of less than 500
Means diol. Short chain diols having a cyclic structure are usually
It is selected from those having a molecular weight of 50 or more and less than 500. Ma
Along with the short-chain diol having the cyclic structure, usually
Other diols with a molecular weight of less than 500 can be used in combination
The Specifically, ethylene glycol, 1,3-propylene
Rangeall, 1,2-propylene glycol, 1,4
-Butanediol, 1,5-pentanediol, 1,6
-Hexanediol, 2,2-dimethylpropanediol
1,8-octanediol, 1,9-nonanedio
Of diethylene glycol, N-diethanolamine
Such as ethylene oxide or propylene oxide adduct
Mention may be made of linear or branched diols. By using these, a ring structure is formed.
A coating film with higher strength and higher Tg and higher durability was obtained.
It is. Further branch CH_ThreeTo improve solubility in solvents
Since it is excellent, high dispersibility is obtained. In polyurethane resin
The content of short-chain diol units is preferably 17 to 40% by weight.
More preferably, it is 20 to 30% by weight. The long chain diol has a molecular weight of 500.
It means the above diol, specifically, bisphenol
A, hydrogenated bisphenol A, bisphenol S or bi
Sphenol P, ethylene oxide, propyleneoxy
Or a combination of both, polypropylene
Glycol, polyethylene glycol, polytetramethyl
Len glycol is preferred. Long chain diol weight average molecular weight (Mw)
Is usually 500 to 5000, preferably 700
It is suitable to be selected from the range of ~ 3000. A
The content of long-chain diol units containing a tellurium group is
It is preferably 10 to 50% by weight in the resin.
It is suitable that it is preferably 30 to 40% by weight.
The The ether group content of the long-chain diol unit is
This is 1.0 to 5.0 mmol / g in the urethane resin.
And more preferably 2.0 to 4.0 mmol
/ G is appropriate. Number average molecular weight (Mn) of polyurethane resin
Is preferably 18000-56000, more preferably
Or 23,000 to 34000, weight average molecular weight
(Mw) is preferably 30,000 to 100,000,
More preferably, it is suitable from 40,000 to 60,000.
It is right. The above polyurethane resin is vinyl chloride.
Synthetic resins such as resin may be used together, but urethane resin
The higher the ratio, the lower the surface tension of the magnetic liquid.
Therefore, the magnetic layer thickness unevenness and thickness fluctuations during coating and drying are suppressed.
You can control. The polyurethane resin is non-
It is also preferable to blend in the magnetic layer. In the present invention, a place where polyurethane is used.
The glass transition temperature is −50 to 100 ° C. and the elongation at break is 1
00-2000%, breaking stress is usually 0.05-10K
g / mm²(≈0.49 to 98 MPa), yield point is 0.
05-10Kg / mm²(≈0.49 to 98 MPa)
preferable. As the polyisocyanate used in the present invention,
Is tolylene diisocyanate, 4,4'-diphenyl
Methane diisocyanate (MDI), hexamethylene di
Isocyanate, xylylene diisocyanate, naphthi
Len-1,5-diisocyanate, o-toluidine dii
Socyanate, isophorone diisocyanate, trifer
Isocyanates such as nylmethane triisocyanate
These isocyanates and polyalcohols
Products produced by condensation of isocyanates
Polyisocyanate made can be used
The Commercial name of these isocyanates
As a product of Nippon Polyurethane, Coronate L, Coro
Nate HL, Coronate 2030, Coronate 203
1. Millionate MR, Millionate MTL, Takeda
Manufactured by Takenate D-102, Takenate D-110
N, Takenate D-200, Takenate D-202, residence
Made by Tomo Bayer, Death Module L, Death Module I
L, Death Module N, Death Module HL, etc.
These can be used either alone or by utilizing the difference in curing reactivity.
Or more combinations. The magnetic layer of the magnetic recording medium of the present invention and / or
In the nonmagnetic layer, usually lubricant, abrasive, dispersant, charging
Various machines such as anti-oxidants, plasticizers, anti-mold agents, etc.
Can be added depending on the purpose.
Yes. As the lubricant, dialkylpolysiloxa
(Alkyl is 1 to 5 carbon atoms), dialkoxy policy
Loxane (alkoxy has 1 to 4 carbon atoms), monoalkyl
Rumonoalkoxypolysiloxane (alkyl has 1 carbon atom)
~ 5, alkoxy has 1 to 4 carbon atoms), phenyl poly
Siloxane, fluoroalkylpolysiloxane (alkyl)
Is silicon oil such as 1 to 5 carbon atoms;
Conductive fine powder such as molybdenum disulfide, tantalum disulfide
Inorganic powder such as gusten; polyethylene, polypropylene
, Polyethylene vinyl chloride copolymer, polytetrafur
Fine plastic powder such as oloethylene; α-Olephy
Saturated fatty acid solid at room temperature (10 to 2 carbon atoms)
2); unsaturated aliphatic hydrocarbons (n-olefins) that are liquid at room temperature
A compound in which a double bond is bonded to the terminal carbon, about carbon number
20); monobasic fatty acid having 12 to 20 carbon atoms and carbon number
Fatty acid ester consisting of 3-12 monohydric alcohols
And fluorocarbons can be used. Among the above, saturated fatty acids and fatty acid esters
It is preferable to use both in combination. Saturation
Fatty acids include lauric acid, myristic acid, steari
Acid, palmitic acid, behenic acid, arachidic acid
The As alcohol used as a raw material for fatty acid esters,
Ethanol, butanol, phenol, benzyl alcohol
, 2-methylbutyl alcohol, 2-hexyldecyl
Alcohol, propylene glycol monobutyl ether
, Ethylene glycol monobutyl ether, dipropy
Lenglycol monobutyl ether, diethyleneglycol
Such as monobutyl ether and s-butyl alcohol
Monoalcohols, ethylene glycol, diethylene glycol
Recall, neopentyl glycol, glycerin, sol
And polyhydric alcohols such as bitane derivatives. the same
Examples of fatty acids used as raw materials for esters include acetic acid and propylene.
On acid, octanoic acid, 2-ethylhexanoic acid, laurin
Acid, myristic acid, stearic acid, palmitic acid, behe
Acid, arachidic acid, oleic acid, linoleic acid, linolene
Aliphatic calcium such as acid, elaidic acid, palmitoleic acid
Examples include boric acid or a mixture thereof. Specific examples of fatty acid esters include butyl
Stearate, s-butyl stearate, isopropyl
Stearate, butyl oleate, amyl stearate
, 3-methylbutyl stearate, 2-ethylhexyl
Rustearate, 2-hexyldecyl stearate,
Til palmitate, 2-ethylhexyl myristate,
A mixture of butyl stearate and butyl palmitate,
Toxiethyl stearate, 2-butoxy-1-propi
Rustearate, dipropylene glycol monobutyl ether
Ether esterified with stearic acid, diethyl
Glycol dipalmitate, hexamethylene diol
Esterified with myristic acid to form a diester
Various ester compounds such as oleate of glycerin
You can list things. Furthermore, the magnetic recording medium is used under high humidity.
Reduces the hydrolysis of fatty acid esters that often occur
Branching / straightening of raw fatty acids and alcohols
Select chain, cis / trans isomeric structure, branch position
It is also preferable. These lubricants are 100 masses of binder.
It is added in the range of 0.2 to 20 parts by mass with respect to parts. The following compounds are further used as lubricants:
You can also That is, silicon oil, graphi
Molybdenum disulfide, boron nitride, graphite fluoride, fluorine
Alcohol, polyolefin, polyglycol, alkyl
Such as ruphosphoric acid ester and tungsten disulfide. As an abrasive used in the magnetic layer of the present invention
Are commonly used materials such as α alumina, γ alumina,
Fused alumina, corundum, artificial corundum, silicon carbide
Element, chromium oxide (Cr₂O_Three), Diamond, artificial die
Almond, garnet, emery (main component: corundum and
Magnetite), αFe₂O_ThreeEtc. are used. Polishing these
The agent has a Mohs hardness of 6 or more. A specific example is residence
AKP-10, AKP-12, AKP-1 manufactured by Tomo Chemical Co., Ltd.
5, AKP-20, AKP-30, AKP-50, AK
P-1520, AKP-1500, HIT-50, HI
T60A, HIT70, HIT80, HIT-100,
Nippon Chemical Industry Co., Ltd., G5, G7, S-1, chromium oxide
K, Uemura Kogyo UB40B, Fujimi Abrasive WA8
000, WA10000, TF100, T made by Toda Kogyo Co., Ltd.
F140, TF180, etc. are raised. Average powder size
A size of 0.05 to 3 μm is effective and good
The thickness is preferably 0.05 to 1.0 μm. The total amount of these abrasives is 100% magnetic material.
1 to 20 parts by weight, preferably 1 to 15 parts by weight with respect to parts by weight
In a range of parts. Less than 1 part by mass is sufficient
There is a tendency not to be permanent, and it is more than 20 parts by mass.
And surface property and filling degree tend to deteriorate. These abrasives
Is pre-dispersed with a binder and then in the magnetic paint.
It may be added. In the magnetic layer of the magnetic recording medium of the present invention,
Contains conductive particles as an antistatic agent in addition to non-magnetic powders
It can also be made. Non-magnetic layer between support and magnetic layer
The provided magnetic recording medium maximizes the saturation flux density of the upper layer.
Add as little as possible to the upper layer to increase
And it is preferable to add to coating layers other than an upper layer. Antistatic
Carbon black should be added as a stopper.
Is preferable in terms of reducing the surface electrical resistance of the entire medium. Book
Carbon black that can be used in the invention is a variety of rubber
-Ness black, various thermal black for rubber, color
-Carbon black, conductive carbon black, AS
Tylene black or the like can be used. S_BETIs 5
~ 500m²/ G, DBP oil absorption is 10 to 1500 m
1/100 g, average particle size is 5 to 300 nm, pH is 2
-10, moisture content is 0.1-10% by mass, tap density is
0.1-1 g / ml is preferred. Used in the present invention
A specific example of carbon black is Cabot
Made by BLACKPEARLS 2000, 1300, 1
000, 900, 800, 700, VULCAN XC
-72, Asahi Carbon Co., # 80, # 60, # 55, #
50, # 35, manufactured by Mitsubishi Chemical Corporation, # 3950B, # 270
0, # 2650, # 2600, # 2400B, # 230
0, # 900, # 1000, # 95, # 30, # 40,
# 10B, MA230, MA220, MA77, colon
Via Carbon, CONDUCTEX SC, RAV
EN150, 50, 40, 15, K made by Lion Aguso
Kutchen Black EC, Ketjen Black ECDJ-
500, Ketjen Black ECDJ-600, etc.
I can get lost. Surface treatment of carbon black with a dispersant
Or carbon black is oxidized
Even if it is used in the form of a glass, part of the surface is graphitized.
You can use the same one. Carbon black
Before adding it to the magnetic paint, disperse it with a binder.
It doesn't matter. Use carbon black for the magnetic layer
In this case, the amount of the magnetic material is 0.1 to 30% by mass.
It is preferable. The nonmagnetic layer contains inorganic nonmagnetic powder (just
(Nonmagnetic powder does not contain carbon black)
It is preferable to make it contain 3-20 mass%. Generally, carbon black is an antistatic agent.
As well as reducing friction coefficient, providing light shielding, film strength
There are functions such as improvement, and these are suitable properties
Carbon black with is selected. Therefore, in the present invention
These carbon blacks used are of the type
Change amount, combination, powder size, oil absorption, conductivity, pH
Use properly according to the purpose based on the above-mentioned characteristics.
Of course it is possible. Available carbon bra
For example, the carbon black handbook carbon black
You can refer to the Kyushu Association. As a magnetic recording medium of the present invention, on a support.
When two or more coating layers are formed, the formation
As a means, sequential application method (wet-on-dry)
Method) and simultaneous application method (wet-on-wet method)
The latter creates an ultra-thin magnetic layer
It is particularly good because it can. Its simultaneous application method,
In other words, a specific method of wet-on-wet method
The (1) Gradus commonly used in magnetic paints
Via coating, roll coating, blade coating, extrusion
First, apply the lower layer using the application device, and the layer is still wet.
While in the state of hydration, for example, Tokuhoku 1-446186
Japanese Laid-Open Patent Publication No. 60-238179 and Japanese Patent Laid-Open No. 2-238179.
No. 265672 gazette disclosed in Japanese Patent No. 265672
A method of applying an upper layer by means of a stretch application device; (2) Japanese Patent Laid-Open No. 63-88080, Special
Japanese Laid-Open Patent Application No. 2-17971 and Japanese Laid-Open Patent Application No. 2-265672.
Two slits for coating liquid passage as disclosed in Japanese Patent Publication No.
With a built-in coating head, the lower coating liquid and the upper coating liquid
A method of applying the coating liquid almost simultaneously, (3) Opened in Japanese Patent Laid-Open No. 2-174965
Extrusion with backup roll shown
Apply the upper layer and lower layer almost simultaneously with the coating device.
Method, etc. Apply by wet-on-wet method
The flow characteristics of the magnetic layer coating solution and the non-magnetic layer coating solution are
The closest possible field is the boundary between the coated magnetic and nonmagnetic layers.
A magnetic layer with uniform surface thickness and little thickness fluctuation.
Can be obtained. The fluidity of the coating solution is determined by the powder in the coating solution.
Especially depending on the combination of body and binder,
It is important to pay attention to the choice of non-magnetic powder used for the magnetic layer.
It is important. The thickness of the support of this magnetic recording medium is usually
1-100μm, desirable when used in tape form
3 to 20 μm, used as a flexible disk
In the case, 40 to 80 μm is preferable, and it is not provided on the support.
The magnetic layer is usually 0.5 to 10 μm, preferably 0.5 to
3 μm. Further, other than the magnetic layer and the nonmagnetic layer,
Other layers can be formed depending on the purpose. For example,
An undercoat layer is provided between the support and the lower layer to improve adhesion
It doesn't matter. This thickness is usually 0.01-2 μm,
Preferably it is 0.05-0.5 micrometer. Also support
A back layer may be provided on the side opposite to the magnetic layer side.
This thickness is usually 0.1 to 2 μm, preferably 0.3 to
1.0 μm. These undercoat layers and back layers are known.
Can be used. Single-sided for disk-shaped magnetic recording media
Or the layer of the said structure can be provided in both surfaces. There are no particular restrictions on the support used in the present invention.
However, a commonly used one can be used.
Examples of materials that form the support include polyethylene
Phthalate, polyethylene, polypropylene, polycar
Bonate, polyethylene naphthalate, polyamide, polyester
Riamideimide, polyimide, polysulfone, polyether
Various synthetic resin films such as telsulfone, and
Name metal foils such as luminium foil and stainless steel foil
Can do. In order to effectively achieve the object of the present invention, support is provided.
The surface roughness of the body is the center plane average surface roughness (Ra) (cut
0.03 μm or less at an off value of 0.25 mm), desirably
0.02 μm or less, more desirably 0.01 μm or less
is there. Also, these supports are simply the center plane average surface.
Not only the roughness is small, but there is no coarse protrusion of 1μm or more.
It is preferable. Also, the surface roughness shape can be
Freely depending on the size and amount of filler added to the support
It is to be controlled. One of these fillers
Examples include oxides and carbonates such as Ca, Si, and Ti.
Other examples include fine organic resin powders such as acrylic. Book
The F-5 value in the web running direction of the support used in the invention is
Preferably 5-50Kg / mm²(≒ 49-490MP
a) The F-5 value in the web width direction is preferably 3 to 30K.
g / mm²(≈29.4 to 294 MPa)
The F-5 value in the longitudinal direction of the web is higher than the F-5 value in the web width direction.
Generally, it is necessary to increase the strength in the width direction.
This is not the case when there is a need. Also, the web running direction and width direction of the support
The heat shrinkage rate for 30 minutes at 100 ° C is preferably 3%
Or less, more desirably 1.5% or less, and at 80 ° C.
The heat shrinkage rate for 30 minutes is preferably 1% or less, further desired
Preferably, it is 0.5% or less. Breaking strength is 5-100K
g / mm²(≈49-980 MPa), elastic modulus is 100
~ 2000Kg / mm²(≒ 0.98 ~ 19.6GP
a) is preferred. The organic solvent used in the present invention can have any ratio.
With acetone, methyl ethyl ketone, methyl isobutyl ketone
, Diisobutyl ketone, cyclohexanone, isophor
Ketones such as Ron and tetrahydrofuran, methanol
Ethanol, propanol, butanol, isobuty
Alcohol, isopropyl alcohol, methylcyclo
Alcohols such as hexanol, methyl acetate,
Chill, isobutyl acetate, isopropyl acetate, ethyl lactate
, Esters such as glycol acetate, glycol dimethyl ester
Chill ether, glycol monoethyl ether, dioxane
Glycol ethers such as sun, benzene, and trout
Fragrances such as ethylene, xylene, cresol, chlorobenzene
Group hydrocarbons, methylene chloride, ethylene chloride
Carbon tetrachloride, chloroform, ethylene chlorohydride
, Chlorinated hydrocarbons such as dichlorobenzene, N, N
-Mix dimethylformamide, hexane, etc.
Or it can be used as a single solvent. These organic solvents
Not necessarily 100% pure, isomers in addition to the main component,
Impurities such as unreacted materials, by-products, decomposition products, oxides, moisture
Minutes may be included. These impurities are 30
% Or less, more preferably 10% or less
The If necessary, the organic solvent used in the present invention is a magnetic layer and a nonmagnetic layer.
The type and amount of the sex layer may be changed. For example, non
Improve surface properties by using a highly volatile solvent for the magnetic layer
Solvent with high surface tension (cyclohexano
, Dioxane, etc.)
Or, use a solvent with a high solubility parameter for the magnetic layer.
An example of this is to increase the filling degree.
Of course, it is not limited to these examples. The magnetic recording medium of the present invention comprises a nonmagnetic powder or
Along with ferromagnetic powder and binder, and other additives if necessary
Kneading and dispersing using organic solvent, non-magnetic paint and magnetic paint
Is applied on the support, and oriented and dried as necessary.
It is. A magnetic coating material for the magnetic recording medium of the present invention is produced.
At least a kneading step, a dispersing step, and this
From the mixing process provided as needed before and after these processes.
The Even if each process is divided into two or more stages
It doesn't matter. Nonmagnetic powder and ferromagnetic powder used in the present invention
Powder, binder, carbon black, abrasive, antistatic agent,
All raw materials such as lubricants, solvents, etc.
It may be added in the middle. Also, two individual raw materials
You may divide | segment and add in the above process. For example,
Polyurethane kneading process, dispersion process, viscosity adjustment after dispersion
It may be divided and added in the mixing step. When kneading and dispersing non-magnetic paints and magnetic paints
Various kneaders are used. For example, two rolls
Le, three roll mill, ball mill, pebble mill, TRON
Mill, Sand Grinder, Segbar
i) Attritor, high speed impeller disperser, high speed striker
Mill, high speed impact mill, disper, kneader, high speed
Use a mixer, homogenizer, ultrasonic disperser, etc.
be able to. In order to achieve the object of the present invention,
Known manufacturing techniques can be used as part of the process
Of course, in the kneading process, continuous kneader and processing
It is preferable to use a material with a strong kneading force such as a pressure kneader.
Good. When using a continuous or pressure kneader,
All or part of the ferromagnetic powder and binder (but not all
30% by mass or more of binder) and ferromagnetic powder
Solvents in the range of 15 to 500 parts by mass with respect to 100 parts by mass
It is kneaded with other additive components. These kneading processes
For details of JP-A-1-106338, JP-A-1-106338
This is described in Japanese Patent Application Laid-Open No. 64-79274. In the present invention
Is a simultaneous weight as disclosed in JP-A-62-212933.
Produce more efficiently by using layer coating method
I can do it. Included in the magnetic layer of the magnetic recording medium of the present invention.
The residual solvent is preferably 100 mg / m²The following
Preferably 10 mg / m²Is included in the magnetic layer
Less residual solvent than non-magnetic layer
Is preferred. The porosity is preferably 30 volumes for both the lower layer and the upper layer.
The amount is not more than%, more preferably not more than 10% by volume. Non
It is preferable that the porosity of the magnetic layer is larger than the porosity of the magnetic layer.
However, it is small if the porosity of the nonmagnetic layer is 5% by volume or more.
You don't mind. The magnetic recording medium of the present invention has a lower layer and an upper layer.
Depending on the purpose.
The physical properties can be changed. For example, the elastic modulus of the upper layer
To improve running durability and at the same time lower layer elastic modulus
Lower than the magnetic layer so that the magnetic recording medium hits the head.
It can be improved. By such a method, it is applied onto the support.
If necessary, the magnetic layer orients the ferromagnetic powder in the layer.
After the treatment, the formed magnetic layer is dried. Must
Surface smoothing is performed if necessary, or cut into a desired shape
Thus, the magnetic recording medium of the present invention is manufactured. The elastic modulus at 0.5% elongation of the magnetic layer is the web.
Desirably 100 to 2000 kg in both coating direction and width direction
/ Mm²(≒ 980 ~ 19600N / mm²),Breaking strength
Is preferably 10-70 kg / mm²(≒ 98 ~ 686
N / mm²) The elastic modulus of the magnetic recording medium is favorable in each in-plane direction.
Preferably 100-1500Kg / mm²(≒ 980-1
4700 N / mm²) Residual spread is preferably 0.5%
Below, the thermal shrinkage at any temperature below 100 ° C is preferred
1% or less, more preferably 0.5% or less.
Both are preferably 0.1% or less. The magnetic recording medium of the present invention is used for video and audio.
Even for tapes for audio applications, etc.
Floppy (registered trademark) disk or magnetic disk
However, the loss of signal due to the occurrence of dropout
This is especially true for deadly digital recording media.
It is effective. Furthermore, the lower layer is a nonmagnetic layer, and the magnetic layer on the lower layer
By making the thickness of 0.25 μm or less, electromagnetic conversion
High characteristics, excellent overwrite characteristics and high density
A large-capacity magnetic recording medium can be obtained. EXAMPLES The novel features of the present invention are concretely shown in the following examples.
However, the present invention is not limited to this.
Yes. Production of ferromagnetic metal powder (Sample 1) Production process of sample A (goethite) 1.7 mol / l in a 150 liter tank with a stirrer
35 liters of ammonium carbonate and 2.0 mol / l
Bubbling a mixed solution of 15 liters of aqueous ammonia with nitrogen
The liquid temperature is set to 20 ° C. while nitrogen is bubbled in another tank.
Ferrous sulfate and sulfuric acid at a liquid temperature of 22 ° C dissolved while
Aqueous solution containing cobalt and aluminum sulfate (Fe
²⁺Concentration is 1.35 mol / l, Co concentration is 0.33 mo
l / l, Al concentration is 0.06 mol / l) 45 liters
Was added and mixed. After stirring for 10 minutes, the temperature of the suspension
Was 28 ° C., and a precipitate containing ferrous iron as a main component was produced.
Nitrogen was bubbled and the precipitate was aged for 90 minutes. Nitrogen
Air is introduced and the precipitate is oxidized to form goethite nuclei.
I let you. Fe in suspension²⁺Concentration is 0.75 mol / l
When it becomes, the air oxidation is interrupted and replaced with nitrogen.
After heating to 40 ° C and holding for 2 hours, nitrogen is aired
A spindle shape with a solid solution of Al by proceeding with the oxidation reaction
The goethite (sample A) was produced. Gain
The resulting particles were filtered and washed with water. Partially dried and transmissive electron
When the micrograph was taken to determine the powder size, the average major axis
The length was 60 nm and the average needle ratio was 6. Also in nitrogen
When the specific surface area was measured after dehydration by heating at 120 ° C. for 30 minutes, 16
5m²/ G. Manufacturing process of sample A subjected to sintering prevention treatment 2% slurry of goethite (sample A) in water
-Cobalt sulfate aqueous solution (Co equivalent 20
Parts: The number of moles when the number of moles of iron in goethite is 100 parts.
The manganese number (in terms of Mn, 0.
5 parts: When the number of moles of iron in goethite is 100 parts
The number of moles is expressed in parts) and neutralized with aqueous ammonia.
Depositing baltic and manganese compounds on the particle surface
It was. The slurry is washed with filtered water and made into 2% water slurry again.
Aqueous acid aluminum solution (Al equivalent 8.0 parts: Goethite
The number of moles is expressed in parts when the number of moles of iron is 100 parts.
And ferric sulfate aqueous solution (Fe³⁺Conversion 3.2 parts: Gator
The number of moles when the total number of moles of iron in the site is 100 parts
In parts) was added. After stirring for 20 minutes,
The ammonia was added to neutralize the slurry. Washed with excess water
After that, a 2% slurry was prepared and an aqueous yttrium nitrate solution (Y conversion 1
2.0 parts: 100 moles of iron in goethite
The number of moles in hours) is added, and the pH is adjusted with aqueous ammonia.
Was set to 8.5. Wash with filtered water to make 5% water slurry 150
Heated at 0 ° C. for 1 hour. Then, the case was obtained by washing with filtered water.
Spindle shape that has been processed through a molding machine and dried to prevent sintering
A goethite exhibiting Reduction processing step Put the obtained spindle-type goethite in a stationary baking furnace and add nitrogen.
And heated at 300 ° C. for 30 minutes, heated to 360 ° C. and further 30
Heat for minutes and dehydrate, then heat at 550 ° C for 1 hour
Heating at 650 ° C. for 2 hours increased the crystallinity of hematite.
The temperature is set to 400 ° C., and the gas is changed from nitrogen to hydrogen: nitrogen = 20:
Switch to 80 gases and reduce for 0.5 hour. Replace with nitrogen
After that, it was switched to pure hydrogen and further reduced for 5 hours. Hydrogen
Cool while flowing, switch to nitrogen at 250 ° C and cool to room temperature
did. Slow oxidation treatment step Move to a gradual oxidizer and change the mixing ratio of air and nitrogen
The temperature is 0.2%, the dew point of gas is -45 ° C, and the temperature of the metal powder.
Slow oxidation at 40 ° C or lower for 3 hours while monitoring the temperature, generating heat
When the stagnation subsided, the oxygen concentration was adjusted to 1% and the oxidation was carried out for 10 hours.
At this time, the temperature of the slow oxidation apparatus is maintained at 45 ° C.
Slow oxidation was performed so that the temperature of the powder did not exceed 45 ° C. metal
While evaporating distilled water so that the moisture is 1% of the powder
Ferromagnetic metal transported with air, conditioned and stabilized
A powder (Sample 1) was obtained. [Samples 2 to 9]
And changing the conditions in each process, the strength of samples 2-9
A magnetic metal powder was obtained. The magnetic properties of the obtained ferromagnetic metal powder are vibrated.
Measured with a sample-type magnetometer (Toei Kogyo Co., Ltd.) with an external magnetic field of 10 kOe
Set. High resolution transmission electron in the obtained ferromagnetic metal powder
The average major axis length and variation of ferromagnetic metal powder by taking micrograph
Number (standard deviation / average major axis length), average minor axis length and average oxide film
The thickness was determined, and the average major axis length and average minor axis length of the metal part were determined.
From this value, the particle volume and metal part volume can be calculated by a cylindrical model.
Asked. A crystallite support is obtained by the following method using an X-ray diffractometer.
Asked for Izu. Powder X-ray diffraction method (50kV-300m
A: Using CuKβ radiation), corresponding to α-Fe (11
It is obtained from the expansion of the half-value width of the diffraction lines of the (0) plane and the (220) plane.
I tried. Magnetic property measurement is a vibration sample type magnetometer VSM-5 (East
Time constant 0.1 seconds,
-Measured at a speed of 3 minutes / 10 KOe and a measurement magnetic field of 10 kOe.
did. Table 1 shows the powder characteristics of ferromagnetic metal powder samples 1-9.
Shown in [0109] [Table 1] Production of magnetic recording medium “Synthesis of polyurethane resin A”
Hydrogenated bisphenol in a container that has been previously purged with nitrogen
A, propylene oxide adduct of bisphenol A (min
Molecular weight 40), polypropylene glycol (molecular weight 40)
0) and bis (2-hydroxyethyl) sulfoisophthalate
Rate sodium salt in a molar ratio of 24: 14: 1 each
0: 2 and 5 cyclohexanone and dimethylacetamide
Dissolved in a mixed solvent containing a weight ratio of 0:50, under nitrogen stream
At 60 ° C. Di-n-dibutyls as catalyst
Zuji laurate, 60p based on the total amount of raw materials used
pm was added. Next, MDI (4,4-diphenylmethane
Diisocyanate) is added in an equimolar amount to the sum of the diols, and 9
Heat reaction at 0 ° C. for 6 hours to convert the ether group to 4.0 nmo
containing 1 / g and -SO_ThreeNa group is 8 × 10^-Five/ G guidance
Polyureta with Mw 45000 and Mn 25000
Resin A was obtained. [Examples 1-3, 7-11, Comparative Examples 1-
5] Multilayer magnetic table using the above ferromagnetic metal powder.
The following magnetic layer composition, non-magnetic for lower layer
A layer composition and a back layer composition were prepared. (Composition of magnetic layer) 100 parts of ferromagnetic metal powder (samples 1-9) Binder resin   13 parts of vinyl chloride copolymer     (-SO_ThreeNa group 1 × 10^-Foureq / g, polymerization degree 300)   Polyester polyurethane resin 7 parts     (Neopentyl glycol / Caprolactone polyol / MDI         = 0.9 / 2.6 / 1, -SO_ThreeNa group: 1 × 10^-Foureq / g) α-alumina (average particle size 0.13 μm) 5 parts Carbon black (average particle size 50nm) 1 part Phenylphosphonic acid 3 parts Butyl stearate 3 parts Stearic acid 3 parts 360 parts mixed solvent of methyl ethyl ketone and cyclohexanone 1: 1 [0112] (Composition of the nonmagnetic layer for the lower layer) 80 parts of acicular hematite   (Specific surface area 55m by BET method²/ G, average long axis length 0.10 μm,     Average needle ratio 7, pH 8.8, aluminum treated Al₂O_ThreeAs 1% by mass) 20 parts of carbon black   (Average primary particle size: 17 nm, DBP oil absorption: 80 ml / 100 g,     Surface area by BET method: 240m²/ G, pH 7.5) Binder resin     12 parts of vinyl chloride copolymer       (-SO_ThreeNa group 1 × 10^-Foureq / g content, degree of polymerization: 300)     Polyester polyurethane resin 5 parts       (Neopentyl glycol / Caprolactone polyol / MDI         = 0.9 / 2.6 / 1, -SO_ThreeNa group: 1 × 10^-Foureq / g) Phenylphosphonic acid 3 parts Butyl stearate 3 parts Stearic acid 3 parts 280 parts of 1: 1 mixed solvent of methyl ethyl ketone and cyclohexanone [0113] (Back layer composition)   100 parts of fine carbon black powder     [(Manufactured by Cabot, BP-800, average particle size: 17 nm)]   Coarse particulate carbon black powder 3 parts     [(Chan Calve, thermal black, average particle size: 270 nm)]   α-alumina (hard inorganic powder) 0.5 part     (However, HIT55 / MR110 / MEK = 5 parts / 1 part / 4 parts dispersed product Used, 0.5 part of α-alumina (HIT55) of the dispersion product)   108 parts of nitrocellulose resin   15 parts of polyurethane resin   40 parts of polyisocyanate   5 parts of polyester resin   Dispersant: 4 parts of copper oleate           4 parts copper phthalocyanine           5 parts of barium sulfate   Methyl ethyl ketone 2200 parts   300 parts of butyl acetate   600 parts of toluene [Examples 4 to 6] Ferromagnetic metal powder (Samp
5), and the composition of the magnetic layer in Examples 1 to 3
Change the binder resin of the prescription to the polyurethane resin A,
And the same as in Examples 1 to 3 except that the addition amount was changed,
The composition of the nonmagnetic layer for the lower layer and the composition of the back layer are the same.
Created something. The center surface average surface roughness is 2 with a thickness of 3.7 μm.
Non-magnetic on nm aramid support (trade name: Mictron)
The thickness of the lower layer after drying the coating liquid for forming the adhesive layer (for the lower layer)
Apply to 1.05-1.29 μm,
On top of that, the magnetic layer has a predetermined thickness so that the magnetic layer has a predetermined thickness.
4 while the wet layer is applied.
A cobalt magnet having a magnetic force of 77.5 kA / m;
Oriented by a solenoid with magnetic force of 5 kA / m and dried
The coating film was set by. Non-magnetic and magnetic layers after drying
The thickness was adjusted to a desired thickness. After drying, metal roll and plastic roll
A 7-stage calendar consisting of
Degree 200 m / min. Processing is performed at a linear pressure of 2940 N / cm
Then, use the backcoat layer forming coating solution
A 0.5 μm back layer was applied. Desired width (8mm,
1 / 4mm, 1 / 2mm or 3.8mm)
Not suitable for devices with a slitting device
Install so that the woven fabric and polishing tape are pressed against the magnetic surface.
And cleaning the surface of the magnetic layer with a tape cleaning device.
And tape samples were obtained. The obtained sample was measured with a vibrating sample magnetometer.
Defined magnetic properties and demagnetization, surface roughness, magnetic clusters
-Measure surface state observation and electromagnetic conversion characteristics with SEM
did. The results are shown in Table 2. The measurement method of electromagnetic conversion characteristics is as follows.
According to the method. 8mm deck for data recording to MIG
(Head gap 0.2 μm, track width 17 μm)
m, saturation magnetic flux density 1.5T, azimuth angle 20 °)
MR head (SAL bias, MR element is Fe-N
i, track width 6μm, gap length 0.2μm, ajma
S angle 20 °). Using the MIG head,
The relative speed of the head and head is 10.2 m / sec, 1 / 2T
b (λ = 0.5μm) The optimum recording current from the input / output characteristics
The signal was recorded with this current and reproduced by the MR head.
C / N is from the peak of the regenerative carrier to the demagnetization noise.
The resolution bandwidth of the spectrum analyzer is 100
It was set to kHz. Properties for tape using Example 1
It was expressed as The magnetic characteristics were measured with a vibrating sample magnetometer (Toei Industry Co., Ltd.).
Parallel to the orientation direction with an external magnetic field of 796 kA / m
Measured. The magnetic layer thickness is measured by measuring the length of the magnetic recording medium.
About 0.1μm thick with a diamond cutter across the direction
Cut out and observed with a transmission electron microscope at a magnification of 30,000 times
I took a picture of it. Photo print size is A
It is 4th edition. After that, magnetic powder, non-magnetic layer ferromagnetic powder
Focus on the shape difference of the non-magnetic powder to make the interface visually judged black
The edge of the magnetic layer and the surface of the magnetic layer are blackened in the same way.
With an image analyzer (manufactured by Carl Zeiss: KS4000)
The distance between the edged lines was measured. The length of the sample photo is 21
Measurement points were measured over a range of cm. That
The thickness of the magnetic layer by dividing the simple average of the measured values by the magnification
It was. The center plane average surface roughness (Ra) is WYKO.
Optical interference three-dimensional roughness meter "HD-" manufactured by Arizona (USA)
2000 ”, the surface of the magnetic layer (about 184 μm × 24
Ra of 2 μm area) is measured. Objective lens 50 times,
Inclination correction and cylinder correction are added at 0.5x intermediate lens
The This method is a non-contact surface roughness meter that measures by optical interference.
The Weather resistance of magnetic layer ΔΦm (%), ΔHc
(%) Was according to the above method. Magnetic cluster size measurement is performed using a sample,
10 KOe using a vibrating sample magnetometer (Toei Kogyo Co., Ltd.)
After applying the magnetic field of
I did it. Digital instruments after erasure
Rumens Nanoscope III magnetic force microscope mode
Use to measure a range of 5 × 5 μm at a lift height of 40 nm.
And a magnetic force image was obtained. Standard deviation of magnetic force distribution (rm
s) 70% of the value is set as the threshold value, and the image is binarized.
Only the portion having a magnetic force of 70% or more was displayed. This
The image is introduced into the image analyzer (KS400) and noise
After removing and filling holes, the average area (nm²)
I put it out. For SEM observation, put the sample in the sputtering device,
FE type SE manufactured by Hitachi, Ltd. with platinum coating on the surface of the magnetic layer
M (model number S-800), inclination angle 30 °, acceleration
10 field observations at a voltage of 20 kV and a magnification of 5,000 times
It was. In the observation of the surface state by SEM, ○ indicates a missing magnetic layer
, X indicates that the magnetic layer is missing
Indicates what was observed. [0123] [Table 2][0124] From Tables 1 and 2, the particle volume is 800 nm.^Three
More than 3000nm^ThreeLess than, metal to particle volume
The volume ratio of the part is 5 to 45%, and the magnetic layer is the magnetic layer
The thickness is 0.020 to 0.18 μm, and the magnetic layer has anti-magnetism
When the force is 127.3 kA / m or more,
It can be seen that the raster is small and the C / N is good,
A magnetoresistive (MR) head mounted as a playback head
Can provide magnetic recording media suitable for existing systems.
Yes.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kiyomi Ejiri             2-1-12 Ogimachi, Odawara-shi, Kanagawa Prefecture             Shishi Photo Film Co., Ltd. F-term (reference) 5D006 BA02 BA04 BA08 BA10 BA19

Claims (1)

What is claimed is: 1. A magnetic recording medium in which a magnetic layer mainly comprising a ferromagnetic metal powder and a binder is provided on a support. The ferromagnetic metal powder has a particle volume of 800 nm ³ or more and 3000 nm ^3. The ferromagnetic metal powder has a ratio of the volume of the metal part to the particle volume of 5 to 45%, and the magnetic layer has a thickness of the magnetic layer of 0.020 to 0.18 μm.
m, and the magnetic layer has a coercive force of 127.3 kA / m or more.