JP2571350B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention
Regarding recording media. [0002] 2. Description of the Related Art Magnetic recording media include a recording tape, a video,
Widely used as tape, computer tape, disk, etc.
Commonly used. The density of magnetic recording media is increasing year by year.
The recording wavelength is shorter and the recording method is analog.
In addition, digital systems are being studied. This high density
Magnetic recording medium using a metal thin film for the magnetic layer
Body has been proposed, but practical reliability such as productivity and corrosion
Disperse the ferromagnetic powder in the binder at the point and apply it on the support
A so-called coated magnetic recording medium is excellent. But
On the other hand, the coating type medium has a magnetic material filling degree against the metal thin film.
Since it is low, the electromagnetic conversion characteristics are inferior. Coated magnetic recording media
Are ferromagnetic iron oxide, Co-modified ferromagnetic iron oxide, Cr
O_TwoA magnetic layer in which a ferromagnetic alloy powder or the like is dispersed in a binder.
Those coated on a non-magnetic support are widely used. Improvement of electromagnetic conversion characteristics of coating type magnetic recording medium
Include improving the magnetic properties of ferromagnetic powder, smoothing the surface, etc.
Although various methods have been proposed,
Is not enough. Also, in recent years,
Recording wavelength tends to be shorter, and the thickness of the magnetic layer is thicker
Output decreases, self-demagnetization loss during recording, and thickness during reproduction
The problem of losses is growing. For this reason, magnetic layers have been made thinner.
However, if the thickness of the magnetic layer is reduced to about 2 μm or less,
The effect of the non-magnetic support is likely to appear on the surface,
The characteristics and DO tend to deteriorate. For this reason, Japanese Unexamined Patent Publication
As described in JP-A-7-198536, non-magnetic
Providing a thick undercoat layer and then a magnetic layer as the upper layer
The effect of the surface roughness of the support is eliminated
But the head wear and durability are not improved
There was a problem. It is conventionally thermoset as a non-magnetic underlayer
Since the base resin is used as a binder, the lower layer is cured,
Non-buffering of friction between magnetic layer and head and contact with other members
Magnetic recording with such an underlayer
This is thought to be due to the medium's lack of flexibility.
available. To solve this, use a non-curing resin in the lower layer.
Can be used as a binder, but the conventional method
In the case where the lower layer is applied and dried, and then the magnetic layer is
If the lower layer swells with the organic solvent of the upper layer coating solution,
Surface of the magnetic layer, which may cause turbulence in the coating liquid
Problems such as poor surface properties and poor electromagnetic conversion characteristics
I will. Also, to reduce the thickness of the magnetic layer, reduce the amount of coating.
Or add a large amount of solvent to the magnetic coating solution
To reduce the concentration. When taking the former,
If the amount of coating is reduced, sufficient leveling time will not be
The coating defects, such as streaks and
The problem that the pattern of the mark remains, and the yield is
It always gets worse. When the latter method is used, the magnetic coating solution
If the concentration is low, the resulting coating film has many voids,
Insufficient magnetic material filling properties cannot be obtained, and
Various problems such as insufficient strength of the coating
Cause harm. Invention of Japanese Patent Application Laid-Open No. 62-154225
Then, such a low yield is a big problem.
Was. [0005] When the coercive force is low, the magnetic layer has a self-demagnetization loss.
Loss, and is not suitable for short wavelength recording.
It is necessary to have Can be used for such a purpose
As means, 0.5 to 5.0 between the nonmagnetic support and the magnetic layer.
An undercoat layer containing only a binder of μm was provided, and the Hc of the magnetic layer was reduced to 10 μm.
It has been proposed to make it 00 Oe (JP-A-57-1).
No. 98536). In order to further improve electromagnetic conversion characteristics,
In addition, the self-demagnetization loss is reduced by increasing the
Reduction of magnetism is also needed. To achieve this goal,
With increasing Hc, the perpendicular magnetization component received during short wavelength recording
It is necessary to reduce the demagnetization loss due to this. Therefore, Hc
Magnetic layer with strong in-plane orientation of highly ferromagnetic powder
It turns out that the residual coercivity in the normal direction should be increased.
Was. [0007] However, in the conventionally known technique,
There are the following problems to achieve the goal. The above-mentioned Japanese patent
The technology disclosed in Japanese Patent Application Laid-Open No.
Next, a method of applying an upper layer and a lower layer is disclosed.
However, when simultaneous upper layer and lower layer coating is performed, the upper layer and lower layer
Mixing of layers causes not only poor surface properties but also misalignment
You. In addition, technology to improve orientation in simultaneous multilayer coating
Japanese Patent Application Laid-Open No. 3-49032 discloses carbon black.
Discloses that multi-stage alignment is performed by using a layer dispersed with
It has a low true specific gravity like carbon black.
Filler is a rotating Brownian motion of ferromagnetic powder during orientation
Interface between the upper and lower layers during simultaneous multilayer coating
Although the squareness ratio measured in the in-plane direction is high, the magnetic layer normal
The problem is that the improvement of the residual coercivity in
You. Further, the lower non-magnetic layer as described above and
Electromagnetic conversion characteristics of a magnetic recording medium with an upper magnetic layer
To improve self-reduction by reducing the self-demagnetization loss by increasing Hc
At the same time, it is necessary to reduce the recording demagnetization. Achieve this purpose
In order to achieve this, it is required to perform the above-described high Hc and at the time of short wavelength recording.
It is necessary to reduce demagnetization loss. This demagnetization loss is
Low coercive force in the longitudinal direction and width direction of the magnetic layer
It becomes big. In particular, if the coercive force in the width direction is low,
(The demagnetization due to the magnetic field of the adjacent track) increases,
RF output decreases, BER (block error rate)
There is a problem of rising. For such a multilayer coating type magnetic recording medium,
As a lower non-magnetic layer described above as a known technique,
Or upper layer magnetic using binder or carbon black
An example of sequential layering using short needle-like ferromagnetic powder as the layer
JP-A-57-198536 and JP-A-62-1115.
Is disclosed. However, they overlap simultaneously
In the coating or orientation process,
Mixing between the lower and upper magnetic layers, or the two-layer boundary due to turbulence
Causes surface irregularities. Such mixing and turbulence between the two layers
Extremely lowers the orientation of the ferromagnetic powder in the magnetic layer. Furthermore, short needle-like ferromagnetic powder, that is, a long axis length is short.
Ferromagnetic powder with low acicular ratio is difficult to flow orient
Therefore, the orientation of the ferromagnetic powder is further reduced and sufficient electromagnetic
There has been a problem that conversion characteristics cannot be obtained. [0011] SUMMARY OF THE INVENTION In the present invention, the RF output is
Excellent power with high dropout and reduced BER
Magnetic recording medium with magnetic conversion characteristics and excellent productivity
The purpose is to provide. [0012] That is, the above object of the present invention.
Under the condition that the inorganic powder is dispersed in the binder on the non-magnetic support
A non-magnetic layer, andToDisperse ferromagnetic powder in binder
The magnetic recording medium provided with the upper magnetic layer formed as above,
The dry thickness of the layer magnetic layer is 1.0 μm or less, and
The upper magnetic layer has a major axis length of 0.25 μm or less and a needle ratio of 1
Two or less ferromagnetic alloy powders, the longitudinal length of the upper magnetic layer
Direction coercive force (Hc) is 1500 Oe or more, width direction coercive force
Magnetic force (Hc) is 1000 Oe or moreThe lower non-magnetic
Powder containing 3 or more true specific gravities in the conductive layer
IsCan be achieved by a magnetic recording medium characterized by that
You. [0013] The present invention relates to a method of forming an upper magnetic layer and a lower nonmagnetic layer.
By suppressing fluctuation or turbulence at the interface,
Dry thickness is 1μm or less by preventing orientation disorder
Of the magnetic layer of a magnetic recording medium having a thin magnetic layer of
That the coercive force in each of the
Improves electromagnetic conversion characteristics especially in short wavelength recording
It was done. In the present invention, the dry film thickness is 1 μm
The following upper magnetic layer (hereinafter simply referred to as the magnetic layer or upper layer)
U. ) To the lower non-magnetic layer (hereinafter simply referred to as the non-magnetic layer or
Also called a layer. ) Under coating to provide no coating defects
Use a liquid that contains inorganic powder and use a non-magnetic support
First, applying the upper layer while the lower layer is wet.
Obtained by That is, the present invention provides a
Extremely thin magnetic layer with excellent mass productivity with reduced coating defects
Magnetic recording media with performance comparable to ferromagnetic metal thin films
It provides the body. In the present invention, in the longitudinal direction (longitudinal direction) of the magnetic layer,
The direction refers to the direction parallel to the coating orientation and parallel to the plane.
Hc for magnetic recording medium sump in VSM
A magnetic field of 10 kOe was applied in the in-plane direction of the upper magnetic layer.
Later, the upper magnetic layer necessary to cancel the residual magnetic field of the sample
The external magnetic field applied in the longitudinal direction parallel to the
means. Similarly, in the width direction (the width direction is
Hc for the direction perpendicular to the cloth orientation direction) is VS
At M, parallel to the upper magnetic layer plane of the magnetic recording medium sample
After applying a magnetic field of 10 kOe in the width direction,
For the upper magnetic layer surface necessary to cancel the residual magnetic field of the pull
It means an external magnetic field applied in parallel and in the width direction. According to the present invention, there is provided a magnetic layer having a thickness of 1 μm or less.
Hc in the direction of 1500 Oe or more, preferably 1600 Oe
e or more and Hc in the width direction of 1000 Oe or more, preferably
Is defined as 1100 Oe or more,
Performance, especially reproduction output, and suppress crosstalk.
And BER can be reduced. The present invention
Hc in the longitudinal direction of the active layer is 1500 Oe or more,
By setting c to be more than 1000 Oe,
Demagnetization loss can be effectively suppressed and high output
Can be maintained. This is because both Hc are ferromagnetic powderLongitudinal direction,
Width directionIt is thought to be for the magnetization component, especially for short wavelength
In the record thisMagnetization componentOf coercive force increases
Therefore, in the present invention, both Hc are set large.
AndLongitudinal direction, width directionIt is thought that recording demagnetization is suppressed.
available. In order to ensure the performance of the magnetic layer,
Means for ensuring productivity, which has been an issue in the prior art
Was solved by using inorganic powder for the lower layer
However, the embodiment is not particularly limited, but in the present invention,
Specify the inorganic powder contained in the lower layer and the thickness of the lower layer
Is preferred. In the present invention, both Hc are secured.
The major axis length is 0.25 μm or less, preferably 0.2 μm
Or less, and the needle ratio is 12 or less, preferably 7 to 11.
A needle-shaped ferromagnetic alloy powder is used.In addition, here
"Long axis length" is the average long axis length based on common general technical knowledge.
It is. The acicular ferromagnetic alloy powder may be a single metal powder.
The needle ratio (major axis length / minor axis length) is 12 or less.
Below, preferably, the range of 5 to 12 is desirable. This needle
As a specific example of the ferromagnetic alloy powder, a combination of Fe and Co
Mainly metal or alloys such as gold or Co
Component (75% or more)
In addition to atoms, Al, Si, S, Sc, Ti, V, Cr, C
u, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te,
Ba, Ta, W, Re, Au, Hg, Pb, Bi, L
a, Ce, Pr, Nd, P, Co, Mn, Zn, Ni,
It may contain atoms such as Sr and B. Fe and C
The alloy with o preferably contains Co at 5% or more,
Those containing up to about 20% are preferred. In the present invention,
If desired, ferromagnetic powders other than those described above, for example, magnetic
Iron oxide FeOx (x = 1.33-1.5), Co-modified F
eOx (x = 1.33-1.5) etc.
Can be used together with powder. Also, as an inorganic powder used for the lower layer,
Is preferably a true specific gravity of 3 or more, particularly preferably 4 to 8
And the average particle size is 0.2 μm or less, preferably 0.005
~ 0.08 μm granular particles or major axis length of 0.05
~ 1.0 μm, preferably 0.05-0.5 μm and needle
Examples are needle-like particles having a shape ratio of 5 to 20, preferably 5 to 15.
It is. Specific inorganic powders are the inorganic powders shown below.
You can choose from. True specific gravity is synonymous with true density.
Substantially only density excluding pores of inorganic powder, voids between powders, etc.
Means Examples of the inorganic powder include, for example, metal
(Cu, Cr, Ag, Al, Ti, W, etc.), metal oxidation
Material, metal carbonate, metal sulfate, metal nitride, metal carbide
And metal sulfides. Specifically, TiO
_Two(Rutile, anatase), TiO_X, Cerium oxide,
Tin oxide, tungsten oxide, ZnO, ZrO_Two, Si
O_Two, Cr_TwoO_Three, Α-alumina with α-rate of 90% or more, β
Alumina, gamma alumina, alpha iron oxide, goethite, corane
Dam, silicon nitride, titanium carbide, magnesium oxide
, Boron nitride, molybdenum disulfide, copper oxide, MgC
O_Three, CaCO_Three, BaCO_Three, SrCO_Three, BaSO
_Four, Silicon carbide, titanium carbide, etc., alone or in combination
Used. The shape and size of these inorganic powders are optional.
These are combined with different inorganic powders as needed.
Combine or select particle size distribution etc. even for a single non-magnetic powder
You can also. The following inorganic powders can be used:
Are preferred. Tap density is 0.05-2g
/ Cc, preferably 0.2 to 1.5 g / cc. The water content is
0.1-5%, preferably 0.2-3%. pH 2-1
One. Oil absorption using DBP is 5-100ml / 100
g, preferably 10-80 ml / 100 g, more preferably
Or 20 to 60 ml / 100 g. The above non-magnetic powder
The powder does not have to be 100% pure,
The surface can be treated with another compound such as Al, Si, Ti, Z
treated with each compound such as r, Sn, Sb, Zn, etc.
An oxide may be formed on the surface. At that time, the purity is 70%
If it is above, the effect will not be reduced. Ignition loss
Is preferably 20% or less. Specific examples of the inorganic powder used in the present invention
Examples are UA5600 and UA560 manufactured by Showa Denko KK
5. AKP-20, AKP-30, AKP manufactured by Sumitomo Chemical Co., Ltd.
-50, HIT-55, HIT-100, ZA-G1,
G5, G7, S-1 manufactured by Nippon Chemical Industry Co., Ltd., T manufactured by Toda Industry Co., Ltd.
F-100, TF-120, TF-140, R516,
Ishihara Sangyo TTO-51B, TTO-55A, TTO
-55B, TTO-55C, TTO-55S, TTO-
55S, TTO-55D, FT-1000, FT-20
00, FTL-100, FTL-200, M-1, S-
1, SN-100, R-820, R-830, R-93
0, R-550, CR-50, CR-80, R-68
0, TY-50, ECT-52, STT manufactured by Titanium Industry Co., Ltd.
-4D, STT-30D, STT-30, STT-65
C, T-1 manufactured by Mitsubishi Materials, NS- manufactured by Nippon Shokubai
O, NS-3Y, NS-8Y, MT-100 manufactured by Teika
S, MT-100T, MT-150W, MT-500
B, MT-600B, MT-100E, FI manufactured by Sakai Chemical Co.
NEX-25, BF-1, BF-10, BF-20, B
F-1L, BF-10P, DEFIC- manufactured by Dowa Kogyo
Y, DEFIC-R, Y-LOP and its
This is a fired product. The non-magnetic inorganic powder used in the present invention
In particular, titanium oxide (particularly titanium dioxide) is preferred.
No. Hereinafter, the method for producing the titanium oxide will be described in detail. Oxidation
There are mainly two methods for producing tongue: the sulfuric acid method and the chlorine method. The sulfuric acid method
Dilute raw ore of luminite with sulfuric acid to remove Ti, Fe, etc.
Extract as sulfate. The iron sulfate is removed by crystallization separation, and the remaining
After filtration and purification of the titanyl sulfate solution, thermal hydrolysis was performed.
To precipitate the hydrous titanium oxide. After filtering and washing this,
After washing and removing contaminants and adding a particle size regulator, etc.,
If calcined at 80 to 1000 ° C., it becomes crude titanium oxide. Le
Chill type and anatase type are core materials added during hydrolysis.
It is divided by the type. This crude titanium oxide is pulverized and adjusted.
It is made by applying grain, surface treatment, etc. Chlorine method is raw ore heaven
Naturally, rutile or synthetic rutile is used. Ore is reduced at high temperature
Chlorinated in the state, Ti is TiCl_FourFe is FeCl_Two
And the iron oxide solidified by cooling becomes liquid TiC
l_FourAnd separated. The obtained crude TiCl_FourIs rectified
After purification, add a nucleating agent and heat to a temperature above 1000 ° C.
And react instantaneously with oxygen to obtain crude titanium oxide. this
Giving pigment-like properties to crude titanium oxide produced in the oxidative decomposition process
The finishing method for obtaining is the same as the sulfuric acid method. In the present invention, the lower layer may be made of a material other than the inorganic powder.
Can use carbon black for well-known effects
R that is_S(Surface electrical resistance) and the like can also be reduced.
Furnace for rubber, rubber
Thermal, black for color, acetylene black,
Etc. can be used. Specific surface area is 100-500m
^Two/ G, DBP oil absorption is 20-400ml / 100g,
Particle size is 5mμ ~ 30mμ, pH is 2 ~ 10 Water content is
0.1 to 10%, tap density preferably 0.1 to 1 g / cc
Good. Carbon black ingredients used in the present invention
As a specific example, BLACKPEAR manufactured by Cabot Corporation
LS 2000, 1300, 1000, 900, 80
0, 880, 700, VULCAN XC-72, Mitsubishi
# 3050, # 3150, # 3250, # made by Kasei Kogyo
3750, # 3950, # 2400B, # 2300, #
1000, # 970, # 950, # 900, # 85
0, # 650, # 40, MA40, MA-600, roller
CONDUCTEX SC, RA
VEN 8800, 8000, 7000, 5750,
5250, 3500, 2100, 2000, 1800,
1500, 1255, 1250, Akzo Ketche
Black EC and the like. Carbon black
Surface-treated with dispersant or grafted with resin
Use a part of the surface that has been graphitized
It does not matter. Addition of carbon black to paint
Before dispersing with a binder. this
These carbon blacks are used alone or in combination
can do. Examples of the carbon black usable in the present invention are as follows.
For example, "Carbon Black Handbook"
Association) can be referred to. In addition, the present invention
Use non-magnetic organic powder as required in addition to inorganic powder
Acrylic styrene resin
Powder, benzoguanamine resin powder, melamine resin powder
Powders include phthalocyanine pigments.
Resin powder, polyester resin powder, polyamide
Resin powder, polyimide resin powder, polyfluoroethylene
Resin powder and the like. The manufacturing method is disclosed in
Nos. 18564 and 60-255827
Anything that has been used can be used. Non-magnetic powders such as inorganic powders are generally used.
Normally, the weight ratio is 20 to 0.1 with respect to the binder, and the volume ratio
It is used in the range of 10 to 0.1 at a rate. In addition, general magnetic
It has been practiced to provide an undercoat layer in a gas recording medium.
However, this improves the adhesion between the support and the magnetic layer.
And the thickness is less than 0.5μm
This is different from the lower non-magnetic layer of the present invention. In the present invention
To improve the adhesion between the lower layer and the support.
It is preferable to provide a coating layer. The multi-step orientation method of the upper magnetic layer in the present invention
Then, a conventionally known method can be used, and specifically,
3000 gau while the layers (upper and lower layers) are still wet
After orientation with a cobalt magnet having magnetic force of
A method of orienting with a solenoid having a magnetic force of 0 Gauss
No. The dry thickness of the lower layer is 0.5 μm or less.
Above, preferably 0.5 to 5.0 μm is desirable. 0.5
If it is less than μm, productivity will decrease and calendar
Moldability deteriorates and sufficient electromagnetic conversion characteristics are obtainedNo,
Even if it is about 0.3 μm, depending on the application, a practical electromagnetic
Exchange characteristics are obtained.The present invention provides an upper magnetic layer and a lower non-magnetic layer.
Suppresses the disorder of the orientation of the ferromagnetic powder at the interface with the layer,
Has a function to suppress disturbance or vertical fluctuation of the interface itself.
In the present invention, these interfaces are controlled.
Various factors relating to control can be appropriately selected. This
Factors such as the magnetic paint of the magnetic layer and the non-magnetic lower layer
Adjusting the viscosity properties of each dispersion of the layer, for example, the upper layer
Thixotropy of coating solution for magnetic layer and coating solution for lower non-magnetic layer
Control so that the characteristics are close to each other.
You. As a specific method, each coating solution is applied at a shearing speed.
Degree 10^Foursec^-1Stress A10 at^FourAnd shear rate 1
0 sec^-1Stress A10 ratio to A10 A10^Four/ A
10 is 100 ≧ A10^Four/ A10 ≧ 3 can be adjusted
No. And the factors involved in this adjustment include
For example, regarding the inorganic powder or magnetic powder to be dispersed
Means (1) particle size (specific surface area, average primary particle size)
Etc.), (2) Structure (oil absorption, particle form, etc.), (3) Powder
Surface properties (pH, loss on heating, etc.), (4) Suction force of particles
(Σ_SFor the binder, (1) molecular weight,
(2) Regarding the solvent, such as the type of functional group,
Properties, etc.), (2) binder solubility, (3) solvent formulation, etc.
Water rate and the like. Further, the magnetic recording medium of the present invention has an interface
Fluctuation (that is, fluctuation in the thickness direction of the interface)
Width Δd is １ ／ of the dry thickness average value d of the magnetic layer.
Is preferable, and the standard deviation of the magnetic layer thickness is preferred.
The difference 3σ is 0.6 μm, preferably σ is 0.2 μm or less.
It is. That is, if 3σ is 0.6 μm or less, each segment
It is sufficient that 97% of
Means Further, it is preferable that 3σ ≦ 6d / 10.
New These d, Δd, and σ are obtained as follows.
It is. Diamond on magnetic recording media
Cut out to a thickness of about 0.1 μm with a cutter,
A magnification of 10,000 to 100,000 times with a microscope, preferably
Observe at 20,000 to 50,000 times and take a photo
(The print size of the photograph is A4 to A5). That
After that, ferromagnetic powder and inorganic powder of upper magnetic layer and lower non-magnetic layer
Visually determine the interface, paying attention to the difference in
Also, the surface of the magnetic layer is similarly blackened. First, Δ
A method for obtaining d will be described. Upper magnetic layer with the above border
The distance between the peak or valley at the interface between the conductive layer and the lower non-magnetic layer is Δd.
I do. The standard deviation σ is determined by
And then using the Zeiss image processing device IBAS2
Measure the length of the interval between the bordered lines. Measurement of magnetic layer thickness
Divides 21-cm intervals into 100-300 segments
Then, the operation was performed for the number of times to obtain d. The standard deviation σ is
X_iThen, it is expressed by the following equation 1. [0032] (Equation 1) The aforementioned Δd focuses only on the fluctuation at the interface.
However, the standard deviation σ of the average thickness d is
Upper layer magnetism including both surface roughness factors and interface variations.
It means a variation in the thickness of the layer. The variation of this interface is 3σ
It is preferably 0.6 μm or less. This allows the magnetic
The uniformity of the thickness of the conductive layer and the surface roughness Ra.
≦ λ / 50, that is, λ / Ra is 50 or more, preferably 75
Above, more preferably 100 or more
You. Here, Ra was measured using an optical interference roughness meter.
It refers to the value obtained by measuring the core wire average roughness. Further, for the shortest recording wavelength λ, λ / 4 ≦ d
≦ 3λ, preferably λ / 4 ≦ d ≦ 2λ (ie, 0.2
5 ≦ d / λ ≦ 2) and the surface roughness Ra of the magnetic layer is Ra ≦ λ
/ 50 is preferable. This allows playback
To prevent power fluctuations and amplitude modulation noise, to achieve high playback output and high C /
N can be realized. In the present invention, the shortest recording wavelength λ is
Although it varies depending on the type of recording medium, for example, an 8 mm
0.7 μm for digital video and 0.2 μm for digital video.
5μm, 0.67μm for digital audio
It is. The thickness of the magnetic layer is obtained by actual measurement as described above.
Indicate the elements that are specifically contained in the magnetic layer by fluorescent X-rays.
Measure a magnetic layer sample of known thickness and create a calibration curve
Then, the thickness of the sample of the unknown material was
It can also be determined from degrees. The present invention also relates to a scanning tunnel on the surface of the magnetic layer.
Mean Roughness R by Microscope (STM) Method_rmsBefore
30 ≦ d / R between the dry thickness average value d of the magnetic layer_rms
It is preferable that the relationship Magnetic layer thickness becomes thin
Should reduce self-demagnetization loss and improve output.
However, the pressing margin is reduced due to the reduction in thickness of the magnetic layer.
This leads to poor calender moldability and large surface roughness.
You. To improve output by reducing self-demagnetization loss
Surface roughness by STM that satisfies the relationship of the expression is preferable. R by AFM_rmsIs preferably 10 nm or less.
Good. Light interference surface roughness R measured by 3d-MIRAU
a is 1 to 4 nm, R_rmsIs 1.3 to 6 nm, PV value
(Peak-Valley) value is 80 nm or less
Is preferred. The glossiness of the magnetic layer surface is determined by a calendar process.
250-400% is preferred after processing. Such surface properties
In order to achieve, for example, within the conditions of the present invention, the following further
This can be achieved by satisfying the four conditions. (1) The non-magnetic powder contained in the lower non-magnetic layer has Mohs hardness
Strong magnetism containing three or more inorganic powders and contained in the upper magnetic layer
The conductive powder is a needle-shaped ferromagnetic powder, and
The average particle size is 1/2 to 4 of the crystallite size of the acicular ferromagnetic powder.
Being double. (2) Non-magnetic powder contained in lower non-magnetic layer has Mohs hardness
Strong magnetism containing three or more inorganic powders and contained in the upper magnetic layer
The conductive powder is a needle-shaped ferromagnetic powder, and
The average particle size is 1/3 or less of the major axis length of the acicular ferromagnetic powder
thing. (3) The ferromagnetic powder contained in the upper magnetic layer has an axis of easy magnetization.
Is a hexagonal plate-shaped ferromagnetic powder in the vertical direction of the flat plate,
And the non-magnetic powder contained in the lower non-magnetic layer is an inorganic powder.
Ferromagnetic material whose average particle size is contained in the upper magnetic layer
It must be less than the diameter of the powder. (4) The inorganic powder contained in the lower non-magnetic layer is inorganic oxide
Containing inorganic non-magnetic powder having a surface layer coated with an object
thing. (1)-(3) are the ferromagnetic powder of the upper magnetic layer and the lower layer.
Limit the size and shape of the inorganic powder in the non-magnetic layer to the lower layer
The surface properties of the non-magnetic layer are ensured and the inorganic powder is ferromagnetic.
The size is such that the powder is mechanically and stably aligned.
is there. Further, the volume in the lower layer of the inorganic powder
The filling factor is preferably 20-60%, more preferably 25%.
It is desirable to be in the range of 55%. Also, inorganic powder
Powder must contain at least 60% by weight of non-magnetic powder
Preferably, the inorganic powder includes metal oxides,
It is preferably an earth metal salt or the like. Also carbon
Known effects (for example, table
Surface electrical resistance) can be expected.
Although it is preferable to use in combination with powder,
Black has very poor dispersibility, so carbon black
Can not secure sufficient electromagnetic conversion characteristics by itself.
No. 60% or more by weight to obtain good dispersibility
Is selected from metal oxides, metals and alkaline earth metal salts
There is a need. Inorganic powder is 60% by weight of non-magnetic powder.
%, Carbon black is more than 40% of non-magnetic powder
If there is, dispersibility becomes insufficient and desired electromagnetic conversion characteristics are obtained
You will not be able to do it. When the thickness of the magnetic layer is less than 5 times the major axis length,
If there is, the improvement of the filling degree by the calendar is remarkable, more
A magnetic recording medium having excellent electromagnetic conversion characteristics can be obtained. next
(4) will be described. Inorganic contained in lower non-magnetic layer
Inorganic oxide coated on the surface of porous powder
Or Al_TwoO_Three, SiO_Two, TiO_Two, ZrO_Two, S
nO_Two, Sb_TwoO_Three, ZnO, etc. are preferred, and more preferred
Ino is Al_TwoO_Three, SiO_Two, ZrO_TwoIt is. these
May be used in combination or alone
Can also. Also, use a surface treatment tank that is coprecipitated according to the purpose.
After treating with alumina, the surface layer
Silica-treated structure and vice versa
You. The surface treatment layer may be a porous layer according to the purpose.
Although it does not matter, it is generally preferred that the material be homogeneous and dense. The following are general items that can be selected in the present invention.
Described in the section. Ferromagnetic powder used in the magnetic layer of the present invention
Finally, dispersants, lubricants, surfactants, and charging
It may be treated in advance before dispersing with an inhibitor, etc.
Absent. Specifically, Japanese Patent Publication No. 44-14090,
No. 45-18372, No. 47-22062, No.
No. 47-22513, No. 46-28466, No.
JP 46-38755, JP 47-4286, JP
No. 47-12422, No. 47-17284,
JP-B-47-18509, JP-B-47-18573
No., JP-B-39-10307, JP-B-48-3963
9, U.S. Pat. Nos. 3,026,215 and 3,303,341
Nos. 3,100,194, 3,242,005, and 33
No. 89014 and the like. Among the above ferromagnetic powders, ferromagnetic alloy powders
And may contain a small amount of hydroxide or oxide.
Ferromagnetic alloy powder obtained by a known manufacturing method
The following methods can be used.
Complex organic acid salt (mainly oxalate) and reduction of hydrogen etc.
To reduce iron oxide with reducing gas such as hydrogen
To obtain Fe or Fe-Co particles by reduction
Method, thermal decomposition method of metal carbonyl compound, ferromagnetic gold
Sodium borohydride, hypophosphite, etc.
Or reduction by adding a reducing agent such as hydrazine
Method, metal is evaporated in low pressure inert gas to obtain fine powder
And so on. Ferromagnetic alloy obtained in this way
The powder was immersed in a known slow oxidation treatment, that is, an organic solvent.
After drying method, containing oxygen after immersion in organic solvent
Send gas to form an oxide film on the surface and then dry
Method, partial pressure of oxygen gas and inert gas without using organic solvent
Any of the methods of forming an oxide film on the surface by adjusting
It can also be used. The ferromagnetic powder of the upper magnetic layer of the present invention was
25-80m in terms of specific surface area^Two/ G,
Preferably 40 to 70 m^Two/ G. 25m^Two/ G or less
The noise is high below 80m^Two/ G or more, surface properties
Is difficult to obtain. R1500 of ferromagnetic powder is
It is preferably 1.5 or less. More preferably, r
1500 is 1.0 or less. r1500 is magnetic recording
After the medium is saturated, the magnetic flux of 1500 Oe is
Indicates the percentage of the amount of magnetization remaining without being reversed when a field is applied
Things. The water content of the ferromagnetic powder is 0.01 to 2%.
Preferably. Including ferromagnetic powder depending on the type of binder
The water content is preferably optimized. For alloy powder,
0.2 to 0.8 g / cc is preferable, and 0.8 g / cc or less
When used above, oxidation proceeds easily during the compaction process of ferromagnetic powder
Sufficient saturation magnetization (σ_S) Is difficult to obtain.
At 0.2 cc / g or less, dispersion tends to be insufficient. The amount of cobalt atoms relative to iron atoms is 0.
-15%, preferably 2-8%. P of ferromagnetic powder
It is preferred that H be optimized in combination with the binder used.
Good. The range is from 4 to 12, preferably from 6 to
It is 10. The ferromagnetic powder can be made of Al, Si, P
Alternatively, surface treatment with these oxides, etc.
Absent. The amount is 0.1 to 10% based on the ferromagnetic powder.
Adsorption of lubricants such as fatty acids is 100m after surface treatment
g / m^TwoThe following is preferred. Soluble in ferromagnetic powder
Including inorganic ions such as Na, Ca, Fe, Ni, Sr
In some cases, if the concentration is 500 ppm or less, the characteristics are particularly affected.
Does not affect. The ferromagnetic powder used in the present invention is empty.
The smaller the number of pores, the better, the value is 20% by volume or less.
More preferably, the content is 5% by volume or less. The lower non-magnetic layer of the present invention
Conventionally known binders used for the magnetic layer and the upper magnetic layer
Thermoplastic resins, thermosetting resins, reactive resins and
A mixture is used. As a thermoplastic resin, glass
Transfer temperature of -100 to 150 ° C, number average molecular weight of 1000
２００200,000, preferably 10,000 to 10,000
0, having a degree of polymerization of about 50 to 1,000. this
Examples include vinyl chloride, vinyl acetate, vinyl alcohol
Alcohol, maleic acid, acrylic acid, acrylic acid ester
, Vinylidene chloride, acrylonitrile, methacryl
Acid, methacrylate, styrene, butadiene,
Tylene, vinyl butyral, vinyl acetal, vinyl
Polymer or copolymer containing ether, etc. as constituent units
Body, polyurethane resin and various rubber resins. Also,
Phenol tree as thermosetting resin or reactive resin
Fat, epoxy resin, polyurethane curable resin, urea tree
Fat, melamine resin, alkyd resin, acrylic reaction tree
Fat, formaldehyde resin, silicone resin, epoxy
-Polyamide resin, polyester resin and isocyanate
Prepolymer mixture, polyester polyol and poly
Mixtures of isocyanates, polyurethane and polyisocyan
And the like. These resins are published by Asakura Shoten
See the Plastic Handbook for details
You. In addition, a known electron beam-curable resin is used as a lower layer or an upper layer.
It is also possible to use it. Examples of these and how to make them
The method is described in detail in JP-A-62-256219.
Have been. The above resins can be used alone or in combination.
But preferred are vinyl chloride resin and vinyl chloride.
Vinyl acetate resin, vinyl chloride vinyl acetate vinyl alcohol
Resin, vinyl chloride vinyl acetate maleic anhydride copolymer
At least one selected from the group of
Combination, or combination of these with polyisocyanate
There are things. The structure of the polyurethane resin is a polyester resin.
Polyurethane, polyether polyurethane, polyether
Polyester polyurethane, polycarbonate polyurethane
Tan, polyester polycarbonate polyurethane,
Known products such as licaprolactone polyurethane can be used.
Wear. Better for all binders shown here
In order to obtain high dispersibility and durability, -COO
M, -SO_ThreeM, -OSO_ThreeM, -P = O (OM₁)
(OM_Two), -OP = O (OM₁) (OM_Two), -NR
_FourX (where M, M₁, M_TwoAre H, Li, Na,
K, -NR_Four, -NHR_ThreeAnd R is an alkyl group
X represents a halogen atom. ), OH, N
R^Two, N⁺R^Three, (R is a hydrocarbon group), epoxy group, S
At least one polar group selected from H, CN, etc.
Can be used by copolymerization or addition reaction
preferable. The amount of such polar groups is 10^-1-10^-8Mole
/ G, preferably 10^-2-10^-6Mol / g
You. The vinyl chloride copolymer is preferably
Is an epoxy group-containing vinyl chloride copolymer,
A vinyl chloride repeating unit and a repeating unit having an epoxy group
And optionally -SO_ThreeM, -OSO_ThreeM, -COO
M and -PO (OM)_Two(M is a hydrogen atom,
Or a repeating unit having a polar group such as
And vinyl chloride-based copolymers containing Epoxy group
When used in combination with a repeating unit having_ThreeHas Na
Epoxy-Containing Vinyl Chloride Copolymer Containing Repeating Units
The body is preferred. In a copolymer of a repeating unit having a polar group,
Content is usually 0.01 to 5.0 mol% (preferably
Or 0.5 to 3.0 mol%). Epoki
Content of the repeating unit having a thio group in the copolymer
Is usually 1.0 to 30 mol% (preferably 1 to 20 mol%
%). And the vinyl chloride polymer is
Usually 0.01 to 1 mol of vinyl chloride repeating unit
0.5 mole (preferably 0.01-0.3 mole) of epo
It contains a repeating unit having a xy group. The content of the repeating unit having an epoxy group is
Less than 1 mol% or 1 vinyl chloride repeating unit
The amount of the repeating unit having an epoxy group per mole is 0.
If less than 01 mol, hydrochloric acid from vinyl chloride copolymer
Outgassing may not be effectively prevented.
On the other hand, higher than 30 mol% or vinyl chloride
Repeating unit having epoxy group per mole of repeating unit
When the amount of the position is more than 0.5 mol, the vinyl chloride copolymer
Hardness may be low, and if this is used,
The running durability of the layer may decrease. Further, the repeating unit having a specific polar group
If the content is less than 0.01 mol%, the ferromagnetic powder is dispersed.
Properties may be insufficient, and if it is more than 5.0 mol%,
The copolymer becomes hygroscopic and the weather resistance decreases.
Sometimes. Usually, such a vinyl chloride copolymer is used.
The number average molecular weight is in the range of 15,000 to 60,000. Having such an epoxy group and a specific polar group
Vinyl chloride copolymer to be, for example, as follows
Can be manufactured. For example, an epoxy group and a polar group
And -SO_ThreeVinyl chloride copolymer with Na introduced
When producing a union, a reactive double bond and a polar group
And -SO_Three2- (meth) acrylamide containing Na
Sodium do-2-methylpropanesulfonate (reactivity
Monomer having a double bond and a polar group) and diglycidide
Mix the acrylate at low temperature and mix it with vinyl chloride
By polymerizing at a temperature of 100 ° C or less under pressure
Can be manufactured. It is used for introducing a polar group by the above method.
Examples of monomers having a reactive double bond and a polar group
Is 2- (meth) acrylamide-2-methyl
2- (meth) acryl outside of sodium lopansulfonate
Luamido-2-methylpropanesulfonic acid, vinyl sulf
Fonic acid and its sodium or potassium salts,
T) Ethyl acrylate-2-ethyl sulfonate and sodium
Or potassium salts, (anhydrous) maleic acid and
(T) acrylic acid, (meth) acrylic acid-2-phosphate
Tell can be mentioned. The introduction of the epoxy group may be carried out by a reactive double bond.
Generally, glycidyl is used as a monomer having a bond and an epoxy group.
Jill (meth) acrylate is used. Note that the above manufacturing
Outside the law, for example, vinyl chloride and vinyl alcohol
Having polyfunctional OH by polymerization reaction with
A copolymer was prepared, and the copolymer
Reaction with a compound containing a reactive group and a chlorine atom (dehydrochlorination
Reaction) to introduce a polar group into the copolymer.
Can be ClCH_TwoCH_TwoSO_ThreeM, ClCH_TwoC
H_TwoOSO_ThreeM, ClCH_TwoCOOM, ClCH_TwoPO
(OM)_Two In addition, for the introduction of an epoxy group using this dehydrochlorination reaction,
Usually, epichlorohydrin is used. Incidentally, the vinyl chloride copolymer is made of another simple substance.
It may contain a monomer. Examples of other monomers
Is a vinyl ether (eg, methyl vinyl ether,
Butyl vinyl ether, lauryl vinyl ether), α
-Monoolefins (eg, ethylene, propylene),
Lylic acid esters (eg, methyl (meth) acrylate,
Contains functional groups such as roxyethyl (meth) acrylate
(Meth) acrylate), unsaturated nitrile
(Eg, (meth) acrylonitrile), aromatic vinyl
(Eg, styrene, α-methylstyrene), vinyl ester
(Eg, vinyl acetate, vinyl propionate, etc.)
It is. Specific examples of these binders used in the present invention
A typical example is VAGH, V manufactured by Union Carbide.
YHH, VMCH, VAGF, VAGD, VROH, V
YES, VYNC, VMCC, XYHL, XYSG, P
KHH, PKHJ, PKHC, PKFE, Nissin Chemical
Company: MPR-TA, MPR-TA5, MPR-TA
L, MPR-TSN, MPR-TMF, MPR-TS,
MPR-TM, MPR-TAO, manufactured by Denki Kagaku: 100
0W, DX80, DX81, DX82, DX83, 10
0FD, manufactured by Zeon Corporation: MR105, MR110, M
R100, 400X110A, manufactured by Nippon Polyurethane Co .:
Nipporan N2301, N2302, N2304, Dainichi
Manufactured by the Ink Company: Pandex T-5105, T-R30
80, T-5201, Barnock D-400, D-21
0-80, Chris Bon 6109, 7209, Toyobo
Made: Byron UR8200, UR8300, UR860
0, UR5500, UR4300, RV530, RV2
80, manufactured by Dainichi Seika Co., Ltd .: Daifelamin 4020, 502
0, 5100, 5300, 9020, 9022, 702
0, manufactured by Mitsubishi Chemical: MX5004, manufactured by Sanyo Chemical: Sun
Plain SP-150, manufactured by Asahi Kasei Corporation: Saran F310, F
210 and the like. The binder used in the upper magnetic layer of the present invention is
5 to 50% by weight based on the ferromagnetic powder, preferably
It is used in the range of 10 to 35% by weight. Vinyl chloride tree
When using fat, 5 to 30% by weight, polyurethane resin
When 2 to 20% by weight of polyisocyanate is used
It is preferable to use these in combination in the range of 2 to 20% by weight.
Good. Binder used in lower non-magnetic layer of the present invention
Is in the range of 5 to 50% by weight in total with respect to the nonmagnetic powder;
Preferably, it is used in the range of 10 to 35% by weight. Ma
When using a vinyl chloride resin, 3 to 30 weight
%, When a polyurethane resin is used, 3 to 30% by weight,
Polyisocyanates are used in the range of 0 to 20% by weight.
It is preferable to use them in combination. Further, in the present invention, an ether having a molecular weight of 30,000 or more is used.
3 to 30% by weight of non-magnetic powder is used
When using, non-magnetic resin other than epoxy group-containing resin
3 to 30% by weight based on powder, polyurethane resin
When using, 3 to 30% by weight of polyisocyanate
Can be used in an amount of 0 to 20% by weight.
4 × 10 based on the total weight (including the curing agent)^-Five~ 16 × 1
0^-FourIt is preferable to be contained in the range of eq / g. In the present invention, a polyurethane resin is used
If the glass transition temperature is -50 ~ 100 ℃, elongation at break
Is 100 to 2000%, and the breaking stress is 0.05 to 10 kg.
/ Cm^Two, Yield point is 0.05 to 10 kg / cm^TwoIs preferred
New The magnetic recording medium of the present invention basically consists of two layers
However, three or more layers may be used. As a configuration of three or more layers
Means that the upper magnetic layer is composed of two or more magnetic layers.
You. In this case, the relationship between the uppermost magnetic layer and the lower magnetic layer is
The usual concept of a plurality of magnetic layers can be applied. For example,
The upper magnetic layer has a higher coercive force than the lower magnetic layer,
Use ferromagnetic powder with small average major axis length and crystallite size
Such a concept can be applied. In addition, the lower non-magnetic layer
It may be formed of a non-magnetic layer. However, broadly classified
In this case, the upper magnetic layer and the lower nonmagnetic layer are configured. Accordingly, the amount of the binder and the amount of chloride in the binder
Vinyl resin, polyurethane resin, polyisocyanate
Or the amount of other resin, each forming the magnetic layer
The molecular weight of the resin, the amount of the polar group, or the resin described above
The physical characteristics etc. can be changed between the lower and upper magnetic layers as necessary.
Of course it is possible. Polyisocyanate used in the present invention
As tonates, tolylene diisocyanate, 4-4 '
-Diphenylmethane diisocyanate, hexamethylene
Diisocyanate, xylylene diisocyanate, naph
Tylene-1,5-diisocyanate, o-toluidine
Socyanate, isophorone diisocyanate, triffe
Isocyanates such as nylmethane triisocyanate,
In addition, these isocyanates and polyalcohols
Product, also formed by condensation of isocyanates
Polyisocyanate and the like can be used. this
As commercially available trade names of these isocyanates
Is manufactured by Nippon Polyurethane Co .: Coronate L, Coronate
HL, Coronate 2030, Coronate 2031, Millimeter
Onate MR, Millionate MTL, manufactured by Takeda Pharmaceutical Company: TA
Takenate D-102, Takenate D-110N, Takene
D-200, Takenate D-202, Sumitomo Bayer
Company: Desmodur L, Desmodur IL, Desmo
Joule N, Death Module HL, etc.
Germany or two or more utilizing the difference in curing reactivity
Use the lower non-magnetic layer and the upper magnetic layer in the above combination.
Can be. The carbon used in the upper magnetic layer of the present invention
Black is rubber furnace, rubber thermal, color
Black, acetylene black, etc.
Wear. Specific surface area is 5-500m^Two/ G, DBP oil absorption
10-400 ml / 100 g, particle size 5 mμ-300
mμ, pH 2-10, water content 0.1-10%,
The packing density is preferably from 0.1 to 1 g / cc. Used in the present invention
A specific example of carbon black
Tokusha: BLACKPEARLS 2000, 130
0, 1000, 900, 800, 700, VULCAN
  XC-72, manufactured by Asahi Carbon Co .: $ 80, $ 60, $ 5
5, $ 50, $ 35, manufactured by Mitsubishi Kasei Industries: $ 2400
B, $ 2300, $ 900, $ 1000, $ 30, $ 4
0, $ 10B, manufactured by Konlon Via Carbon: CONDU
CTEX SC, RAVEN 150, 50, 40, 1
5 and the like. Carbon black with dispersant
Even if surface treated or grafted with resin,
You may use a part of the surface graphitized.
Absent. Before adding carbon black to magnetic paint
May be dispersed in advance with a binder. these
Use carbon black alone or in combination
Can be. Ferromagnetic powder when using carbon black
0.1 to 30% of the amount of the powder
No. Carbon black has antistatic property of magnetic layer and low friction coefficient
It has the functions of reducing, providing light-shielding properties, and improving film strength.
Depends on the carbon black used. Therefore, the present invention
These carbon blacks used in the lower and upper layers
Change the type, amount, and combination to determine the particle size, oil absorption,
According to the purpose, based on the characteristics shown above, such as conductivity and pH
It is of course possible to use them properly. Upper layer of the present invention
Carbon black that can be used in
Reference manual (edited by the Carbon Black Association)
Can be. The abrasive used in the upper magnetic layer of the present invention
Α-alumina, β-aluminum with α conversion of 90% or more
Na, silicon carbide, chromium oxide, cerium oxide, α-oxidation
Iron, corundum, artificial diamond, silicon nitride, silicon carbide
Element, titanium carbide, titanium oxide, silicon dioxide, nitride
Known materials with a Mohs hardness of 6 or more, such as boron,
Used alone or in combination. Also, these abrasives
A composite of two (abrasives that have been surface treated with another abrasive)
May be used. Other than the main components in these abrasives
May be included, but the main component is 9
If it is 0% or more, the effect is not changed. Of these abrasives
The particle size is preferably from 0.01 to 2 μm.
Abrasives with different particle sizes,
Broadening the particle size distribution for abrasives to achieve the same effect
Can also. Tap density is 0.3-2g / cc, water content is
0.1-5%, pH 2-11, specific surface area 1-30m
^Two/ G is preferred. Shape of abrasive used in the present invention
May be needle-like, spherical or dice-like,
It is preferable that some of them have corners because of high abrasiveness. Specific examples of the abrasive used in the present invention include
AKP-20, AKP-30, manufactured by Sumitomo Chemical Co., Ltd.
AKP-50, HIT-50, manufactured by Nippon Chemical Industries: G
5, G7, S-1, manufactured by Toda Kogyo: TF-100, TF
-140, 100ED, 140ED and the like.
The abrasive used in the present invention is of a type, amount and quantity in the lower layer and the upper layer.
It is easy to change the combination and use it according to the purpose
Is possible. These abrasives are pre-divided with a binder.
After dispersion treatment, it may be added to the magnetic paint. The additive used in the present invention is lubrication.
Has effects, antistatic effect, dispersing effect, plasticizing effect, etc.
Things are used. Molybdenum disulfide, Tungsten disulfide
Ten, graphite, boron nitride, graphite fluoride, silicon
Oil, polar group silicone, fatty acid modified silicone
Corn, fluorine-containing silicone, fluorine-containing alcohol
, Fluorine-containing ester, polyolefin, polyglyco
, Alkyl phosphates and their alkali metals
Salts, alkyl sulfates and alkali metal salts thereof,
Polyphenyl ether, fluorine-containing alkyl sulfate ester
And its alkali metal salts, monosalts having 10 to 24 carbon atoms
Basic fatty acids (including unsaturated bonds,
And metal salts thereof (Li, N
a, K, Cu etc.) or monovalent having 12 to 22 carbon atoms,
Divalent, trivalent, tetravalent, pentavalent, hexavalent alcohol (unsaturated bond
, Or may be branched), carbon number
12 to 22 alkoxy alcohols, 10 to 24 carbon atoms
Monobasic fatty acids (including unsaturated bonds, also branched
And C2-12 monovalent, divalent,
Any one of trihydric, tetrahydric, pentahydric, and hexahydric alcohols (not
(It may contain a saturated bond or be branched)
Mono- or di-fatty acid esters consisting of
Or trifatty acid ester, alkylene oxide polymer
Fatty acid esters of monoalkyl ethers of 8 to
22 fatty acid amides, aliphatic amines having 8 to 22 carbon atoms,
Etc. can be used. Examples of these are laurine
Acid, myristic acid, palmitic acid, stearic acid,
Acid, butyl stearate, oleic acid, linoleic acid,
Linolenic acid, elaidic acid, octyl stearate,
Amyl stearate, isooctyl stearate, myris
Octyl phosphate, butoxyethyl stearate,
Drosorbitan monostearate, anhydrosorbitan
Distearate, anhydrosorbitan tristeale
Or oleyl alcohol or lauryl alcohol
I can do it. Also, alkylene oxides, glycerides
System, glycidol system, alkylphenol ethylene oxide
Nonionic surfactants such as oxide adducts, cyclic amines
, Ester amides, quaternary ammonium salts, hidan
Toin derivatives, heterocycles, phosphoniums or sulfonis
Cations, carboxylic acids, sulfonates
Fonic acid, phosphoric acid, sulfate group, phosphate group,
Which acidic groups contain anionic surfactants, amino acids,
Minosulfonic acid, sulfuric acid or phosphoric acid of amino alcohol
Amphoteric surfactants such as esters and alkylbedynes
Etc. can also be used. For more information on these surfactants, see
Surfactant Handbook "(published by Sangyo Tosho Co., Ltd.)
Have been. These lubricants, antistatic agents, etc. are not necessarily
Not 100% pure, isomer other than main component, unreacted
Impurities, by-products, decomposition products, oxides, etc.
It doesn't matter. These impurities are preferably less than 30%
And more preferably 10% or less. These lubricants and interface used in the present invention
The type and amount of activator are required for the lower non-magnetic layer and the upper magnetic layer.
You can use them as needed. For example, the lower non-magnetic
Layer and upper magnetic layer using fatty acids with different melting points on the surface
Esters with different boiling points and polarities to control oozing
Adjust the amount of surfactant to control bleeding to the surface
Addition of lubricant to improve application stability by reducing
Increasing the amount in the lower non-magnetic layer to improve the lubrication effect, etc.
Of course, and is of course limited to only the examples shown here.
There is no. Further, all of the additives used in the present invention are described.
Or some of them can be added at any stage of the production of magnetic paints.
It does not matter, for example, mixing with ferromagnetic powder before the kneading process
The ferromagnetic powder, binder and solvent during the kneading process.
When adding in the dispersion step, add after the dispersion.
May be added immediately before coating. In the present invention
Examples of these lubricants that are used include Nippon Oil & Fats Co., Ltd.
Made: NAA-102, NAA-415, NAA-31
2, NAA-180, NAA-174, NAA-17
5, NAA-222, NAA-34, NAA-35, N
AA-171, NAA-122, NAA-142, NA
A-160, NAA-173K, castor hardened fatty acid, N
AA-42, NAA-44, Cation SA, Cation M
A, Cation AB, Cation BB, Nymeen L-20
1, Nimeen L-202, Nimeen S-202, No
Nonion E-208, Nonion P-208, Nonion S-
207, Nonion K-204, Nonion NS-202,
Nonion NS-210, Nonion HS-206, Nonion
L-2, Nonion S-2, Nonion S-4, Nonion
O-2, Nonion LP-20R, Nonion PP-40
R, Nonion SP-60R, Nonion OP-80R, No
Neon OP-85R, Nonion LT-221, Nonion
ST-221, Nonion OT-221, Monogly MB,
Nonion DS-60, Anon BF, Anon LG, butyl
Stearate, butyl laurate, erucic acid, Kanto Chemical
Company: Oleic acid, Takemoto Yushi Company: FAL-205, F
AL-123, manufactured by Shin Nippon Rika Co., Ltd.
Nujorube IPM, Sansocizer E4030, Shin-Etsu
Gakusha: TA-3, KF-96, KF-96L, KF-
96H, KF410, KF420, KF965, KF5
4, KF50, KF56, KF-907, KF-85
1, X-22-819, X-22-822, KF-90
5, KF-700, KF-393, KF-857, KF
-860, KF-865, X-22-980, KF-1
01, KF-102, KF-103, X-22-371
0, X-22-3715, KF-910, KF-393
5. Lion Armor Co .: Armid P, Armid
C, Armoslip CP, manufactured by Lion Yushi Co., Ltd .: Duomi
TDO, manufactured by Nisshin Oil Co., Ltd .: BA-41G, Sanyo Chemical Industries, Ltd.
Made: PROFAN 2012E, New Pole PE61, A
Onet MS-400, Ionet MO-200, Ionet
Net DL-200, Ionnet DS-300, Ione
DS-1000, Ionnet DO-200, etc.
I can do it. The organic solvent used in the present invention may be in any ratio
With acetone, methyl ethyl ketone, methyl isobutyl ketone
Ton, diisobutyl ketone, cyclohexanone, isophor
Ketones such as rone, tetrahydrofuran, etc., methanol
, Ethanol, propanol, butanol, isobutyl
Alcohol, isopropyl alcohol, methylcyclo
Alcohols such as hexanol, methyl acetate, acetic acid
Butyl, isobutyl acetate, isopropyl acetate, lactate
, Glycols and other esters, glycol dimethyl
Ether, glycol monoethyl ether, dioxa
Glycol ethers such as benzene, benzene, toluene
, Xylene, cresol, chlorobenzene, etc.
Aromatic hydrocarbons, methylene chloride, ethylene chloride
Id, carbon tetrachloride, chloroform, ethylene chlorohydrate
Chlorinated hydrocarbons such as phosphorus and dichlorobenzene, N,
Uses N-dimethylformamide, hexane, etc.
Wear. These organic solvents are not necessarily 100% pure.
Isomers, unreacted materials, by-products, decomposition
It does not matter if impurities such as substances, oxides, and moisture are included.
No. These impurities are preferably 30% by weight or less.
It is preferably at most 10% by weight. Yes used in the present invention
If necessary, the solvent type is the same in the upper layer and the lower layer
Is preferred. The amount added may be changed. under
Solvents with high surface tension (cyclohexanone, dioxa
Etc.) to increase the stability of the coating, specifically the upper layer
The arithmetic mean value of the solvent composition is lower than the arithmetic mean value of the lower solvent composition.
It is important not to turn. To improve dispersibility
It is preferable that the polarity is somewhat strong.
Solvent used for the coating solution for the magnetic layer
Has a dielectric constant of 15 or more at 20 ° C.
It is preferable that the solvent is contained in 15% or more. The thickness of the magnetic recording medium of the present invention is non-magnetic.
The support is 1 to 100 μm, preferably 4 to 80 μm, below
The layer is 0.5 to 10 μm, preferably 1 to 5 μm, and the upper layer is
0.05 μm or more and 1.0 μm or less, preferably 0.05
μm or more and 0.6 μm or less, more preferably 0.05 μm
m or more and 0.3 μm or less. Combined upper and lower layers
The thickness should be 1/100 to 2 times the thickness of the non-magnetic support.
Used. In addition, the adhesiveness between the non-magnetic support and the lower layer is improved.
An undercoat layer for top may be provided. These thickness
Only 0.01 to 2 μm, preferably 0.05 to 0.5 μm
m. Also, a non-magnetic support is provided on the side opposite to the magnetic layer side.
A back coat layer may be provided. This thickness is 0.1
２2 μm, preferably 0.3-1.0 μm. this
The undercoat layer and the back coat layer can be any of known ones.
You. The nonmagnetic support used in the present invention is a polymagnetic support.
Tylene terephthalate, polyethylene naphthalate, etc.
Polyesters, polyolefins, cellulose tris
Acetate, polycarbonate, polyamide, polyamide
, Polyamideimide, polysulfone, aramid,
A known film such as an aromatic polyamide can be used. This
Corona discharge treatment, plasma
Processing, easy adhesion processing, heat treatment, dust removal processing, etc.
May be. To achieve the object of the present invention, a non-magnetic support
The center line average surface roughness is preferably 0.03 μm or less.
0.02 μm or less, more preferably 0.01 μm
You need to use: Also, these non-magnetic
Supports are not merely low centerline average surface roughness.
In addition, it is preferable that there is no coarse projection of 1 μ or more. Also,
The shape of the surface roughness can be adjusted by adding the filler to the support as needed.
Can be freely controlled by the size and amount of the
It is. Examples of these fillers include C
a, Si, Ti and other oxides and carbonates, acrylic
And other organic fine powders. Further, F of the non-magnetic support in the tape running direction is
The -5 value is preferably 5 to 50 kg / mm.^Two, Tape width
The F-5 value in the direction is preferably 3 to 30 kg / mm.^Twoso
Yes, F-5 value in the tape longitudinal direction is F-value in the tape width direction.
It is generally higher than 5 values, but especially in the width direction
This is not the case when it is necessary to raise it. Also, non
100 ° C.3 in the tape running direction and width direction of the magnetic support
The heat shrinkage at 0 minutes is preferably 3% or less, more preferably.
1.5% or less, heat shrinkage at 80 ° C for 30 minutes is preferred
At most 1%, more preferably at most 0.5%.
The breaking strength is 5 to 100 kg / mm in both directions.^Two, Elastic modulus
Is 100 to 2000 kg / mm^TwoIs preferred. The magnetic paint for the magnetic recording medium of the present invention is produced.
The kneading step, the dispersing step, and the
The mixing process, which is provided before and after these processes as necessary
You. Even if each process is divided into two or more stages
I don't care. The ferromagnetic powder, binder, and powder used in the present invention
Carbon black, abrasives, antistatic agents, lubricants, solvents
Add all ingredients at the beginning or during any process
It doesn't matter. In addition, individual raw materials are separated in two or more processes.
It may be divided and added. For example, polyurethane
Kneading process, dispersing process, mixing process for adjusting viscosity after dispersion
It may be divided and introduced in the process. In order to achieve the object of the present invention, a conventional
Known manufacturing techniques can be used as some steps
Of course, in the kneading process,
By using a material with strong kneading power such as pressure kneader
High Br of the magnetic recording medium of the present invention can be obtained.
You. Ferromagnetic when using a continuous or pressure kneader
All or part of the powder and binder (but not all binders)
Is preferably 30% by weight or more) and ferromagnetic powder 100
The kneading treatment is performed in a range of 15 to 500 parts per part. this
For details of the kneading process, see JP-A-1-106338.
And JP-A-64-79274. Ma
Also, when preparing the lower non-magnetic layer liquid, use a high specific gravity dispersion medium.
Zirconia beads, gold
Genus beads are preferred. According to the present invention, Japanese Patent Application Laid-Open No.
By using the simultaneous multilayer coating method as shown in
And can be produced more efficiently. As in the present invention
Apparatus and method for applying a magnetic recording medium having a multilayer structure
Then, the following configuration can be proposed. 1. Gravure coating commonly used for applying magnetic paint
Cloth, roll coating, blade coating, extrusion coating
Apply the lower layer first with a cloth device, etc.
Among them, Japanese Patent Publication No. 46186/1994 and Japanese Patent Laid-Open No. 60-23 / 1985
8179 and JP-A-2-265672.
Upper layer by pressurized extrusion coating equipment
Is applied. 2. JP-A-63-88080, JP-A-2-17921
As disclosed in JP-A-2-265672.
One coating head with two built-in coating liquid passage slits
The upper and lower layers are applied almost simultaneously. 3. Japanese Patent Application Laid-Open No. 2-174965 discloses a bag.
Up by the extrusion coating device with up roll
The layer and the lower layer are applied almost simultaneously. The electromagnetic conversion of the magnetic recording medium by the aggregation of the ferromagnetic powder
In order to prevent the deterioration of the characteristics and the like, see JP-A-62-95174.
And Japanese Patent Application Laid-Open No. 1-236968.
Method to apply shear to the coating liquid inside the coating head.
Is desirable. Furthermore, regarding the viscosity of the coating solution, refer to
Satisfies the numerical range disclosed in Hei 1-312659
Is preferred. In the present invention, the coating solution for the lower layer is wetted.
So-called wet-on-wet
It is provided on a non-magnetic support by a coating method. In the present invention
Wet-on-wet used to provide lower and upper layers
Coating method means that after first coating one layer,
A so-called sequential coating method in which the next layer is applied quickly and quickly.
Method and multi-layer simultaneous extrusion coating method
And the like. As a wet-on-wet coating method
Is a magnetic recording disclosed in JP-A-61-139929.
Medium application methods can be used. To obtain the medium of the present invention
Need strong alignment. 1000G (Gauss)
The above solenoid and cobalt magnet of 2000G or more
Preferably, the orientation after drying is the most
It is necessary to provide an appropriate drying step before orientation so that the
Is preferred. In addition, the present invention is suitable for a disk medium.
When using, it is rather an orientation that randomizes the orientation
Law is needed. Further, as a calendar processing roll, Epoxy
, Polyimide, polyamide, polyimideamide
Use a hot plastic roll. Also metal
It can also be processed by rolls. Processing temperature is preferred
70 ° C or higher, more preferably 80 ° C or higher.
You. The linear pressure is preferably 200 kg / cm, more preferably
Or more than 300kg / cm, the speed is 20m / min ~
The range is 700 m / min. The effect of the present invention is 80 ° C or more
More effect with a linear pressure of 300 kg / cm or more at a temperature of
Can be raised. The upper layer of the magnetic recording medium of the present invention and its upper layer
The coefficient of friction for the facing SUS420J is preferably
0.5 or less, further 0.3 or less, the magnetic layer surface resistivity is
10^Four-10¹¹Ohm / sq, if the lower layer is applied alone
Surface specific resistance is 10^Four-10⁸Ohm / sq,
The surface electric resistance of the black layer is 10^Three-10⁹Ohm / sq
preferable. The elastic modulus at 0.5% elongation of the upper layer
300-2000 Kg / mm in both the width and width directions
^Two, Breaking strength is preferably 2 to 30 kg / cm^Two, Magnetic
The elastic modulus of the recording medium is preferably 1 in both the running direction and the width direction.
00 ~ 1500Kg / mm^Two, The residual growth is preferably
Heat shrink at any temperature below 0.5% and below 100 ° C
The rate is preferably 1% or less, more preferably 0.5% or less.
Below, most preferably 0.1% or less. The porosity of the upper and lower layers is preferably both
30% by volume or less, more preferably 20% by volume or less
Below. The smaller the porosity, the higher the output
It is preferable, but it is better to secure a certain value depending on the purpose
There are cases. For example, data where repeated use is important
In magnetic recording media for recording, the higher the porosity, the longer the running durability
Is often preferred. These values are appropriate for the purpose
It can be easily implemented to set it in a proper range. The magnetic characteristics of the magnetic recording medium of the present invention are as follows.
When measured by KOe, the squareness ratio in the tape running direction is 0.1.
70 or more, preferably 0.80 or more
Or 0.90 or more. Two perpendicular to the tape running direction
Is 80% or less of the squareness in the running direction.
Is preferred. The SFD of the magnetic layer should be 0.6 or less.
Is preferred. The magnetic recording medium of the present invention has a lower layer and an upper layer.
However, the physical properties of the lower and upper layers change depending on the purpose.
What can be obtained is easily estimated. An example
For example, increase the elastic modulus of the magnetic layer to improve running durability
At the same time, the elastic modulus of the non-magnetic layer
For example, the head of the recording medium can be easily hit. Departure
The bright magnetic recording medium preferably has the following physical property values. A tensile tester for a magnetic recording medium according to the present invention.
Young's modulus measured at 400-5000Kg / mm^Two,
Preferably, 700 to 4000 Kg / mm^TwoAnd before
The magnetic layer has a Young's modulus of 400 to 5000 kg / mm.^Two,
Preferably 700 to 4000 Kg / mm^Two, The yield stress is
3-20kg / mm^Two, Preferably 3 to 15 kg / mm
^TwoThe yield elongation is 0.2-8%, 0.4-5%
Is desirable. This is made up of ferromagnetic powder, binder, carbon
Durable because rack, inorganic powder and support are involved
Affects gender. Also, the bending rigidity of the magnetic recording medium of the present invention.
(Annular stiffness) has a total thickness of more than 11.5 μm
In this case, it is preferable that the total thickness of 40 to 300 mg is 10.5 ± 1.
In the case of μm, preferably 20 to 90 mg and the total thickness is 9.5 μm
When it is thinner, it is preferably 10 to 70 mg. This is mainly related to the support.
It is important for ensuring durability. In addition, the magnetic recording of the present invention
Crack generation elongation of the recording medium measured at 23 ° C and 70% RH
The degree is preferably 20% or less. In addition, the present invention
The air recording medium was measured using an X-ray photoelectron spectrometer.
The Cl / Fe spectrum α on the surface of the magnetic layer is preferably 0.
3 to 0.6, the N / Fe spectrum β is preferably 0.0
3 to 0.12. This is based on ferromagnetic powder, inorganic powder and binding
It is important in obtaining durability in connection with the agent. In addition,
Bright magnetic recording media were measured using a dynamic viscoelasticity measuring device
The glass transition temperature Tg of the magnetic layer (measured at 110 Hz)
(The maximum point of the loss elastic modulus in the dynamic viscoelasticity measurement)
40 to 120 ° C., and the storage elastic modulus E ′ (50 ° C.) is good.
Preferably 0.8 × 10¹¹~ 11 × 10¹¹dyne / cm
^TwoAnd the loss modulus E ″ (50 ° C.) is preferably
0.5 × 10¹¹~ 8 × 10¹¹dyne / cm^TwoIs
Is desirable. Loss tangent should be 0.2 or less
Is preferred. If the loss tangent is too large, adhesive failures are likely to occur.
No. These include binders, carbon black, and solvents
And an important property related to durability. Further, the non-magnetic support and the magnetic layer
180 ° adhesion of 8mm wide tape at 23 ° C and 70% RH
The strength is preferably 10 g or more. Ma
In addition, the wear of a steel ball of 23 ° C. and 70% RH on the surface of the upper magnetic layer
Preferably 0.7 × 10^-7~ 5 × 10^-7m^ThreeBeing
Is desirable. This is because the wear of the magnetic layer surface is directly observed.
Therefore, it is a measure of durability primarily related to ferromagnetic powders. Further, the magnetic recording medium of the present invention was used for SEM (electron microscopy).
The magnetic layer surface photographed with a microscope at a magnification of 50,000 times
The number of polishing agents on the surface is preferably 0.1 / μm.^Two
It is desirable that this is the case. Also, the magnetic recording medium of the present invention
5 abrasives / 100 μm on the end face of the upper magnetic layer
^TwoThe above is preferred. These are the abrasive and binder for the magnetic layer
Is a scale that is affected by
You. Further, the magnetic recording medium of the present invention is used for gas chromatography.
Residual Dissolution of the Magnetic Recording Medium Measured Using Chromatography
The agent is preferably 50 mg / m^TwoShould be
No. The residual solvent contained in the upper layer is preferably 50 m
g / m^TwoOr less, more preferably 10 mg / m^TwoBelow
Yes, the residual solvent contained in the upper layer is
It is preferable that the amount is smaller than the medium. Further, the magnetic recording medium of the present invention
Layer of soluble solids extracted from body using THF
The sol fraction, which is the ratio to the weight, is 15% or less.
Is desirable. This is affected by ferromagnetic powder and binder
And a measure of durability. [0093] Hereinafter, specific examples of the present invention will be described.
The present invention is not limited to this. In the examples
"Parts" refers to "parts by weight" unless otherwise specified. Thickness of magnetic layer: Elements specifically contained in the magnetic layer by X-ray fluorescence
Measure a known thickness magnetic layer sample for
Create. Next, the thickness of the unknown sample is determined by the fluorescent X-ray intensity.
Derived from degrees. Embodiment 1 Magnetic coating solution for upper magnetic layer and lower non-magnetic with the following formulation
A coating solution for a layer was prepared. Magnetic coating solution for upper magnetic layer   100 parts of ferromagnetic powder     Fe alloy powder (Co added 5%)     Hc 1600 Oe, saturation magnetization (σ_S) 130 emu / g     Long axis length 0.18μm, needle ratio 8   Vinyl chloride copolymer 10 parts     -SO_ThreeContains Na and epoxy group   5 parts of polyurethane resin     -SO_ThreeNa content, molecular weight 45000   α-alumina (average particle size 0.2μm) 5 parts   Cyclohexanone 100 parts   200 parts of methyl ethyl ketone After mixing and dispersing in the above composition sand mill for 6 hours,
5 parts of isocyanate (Coronate L) and stearin
5 parts of acid and 10 parts of butyl stearate are added to form an upper magnetic layer
A magnetic coating solution was obtained. [0095] Coating solution for lower non-magnetic layer   Granular TiO_Two(Average particle size 0.04 μm) 100 parts   5 parts of carbon black (average particle size 20mμ)   8 parts of vinyl chloride copolymer     -SO_ThreeContains Na and epoxy group   5 parts of polyurethane resin     -SO_ThreeContains Na group, molecular weight 45,000   α-alumina (average particle size 0.2μm) 5 parts   Cyclohexanone 150 parts   Methyl ethyl ketone 50 parts After mixing and dispersing the above composition in a sand mill for 4 hours,
5 parts of stearic acid, 10 parts of butyl stearate, polyiso
Lower non-magnetic layer by adding 5 parts of cyanate (Coronate L)
An application liquid was obtained. The above-mentioned coating solution was applied to two dopes having different caps.
Using a permanent magnet after applying in a wet state
After the orientation treatment, it was dried. The support is 5.5 μm polyoxy.
Using a polyethylene naphthalate film, the magnetic properties of the support
On the opposite side of the layer, a back layer containing carbon black
Provided. Thereafter, a super calendar process was performed. Paint
The thickness of the cloth is 0.5 μm for the magnetic layer and 2.5 μm for the lower non-magnetic layer.
there were. The raw material obtained in this way has a width of 3.81 mm
Cut and create digital audio tape (DAT)
Was. Other Examples 2 to 5, Comparative Example1, 3-5
And reference examplesChanged the factors shown in Tables 1-2 for Example 1.
And made a tape. These tapes should be the same as above
The results were shown in Tables 1 and 2. Hc: Toei Kogyo
With Hm10KOe using a vibrating sample type magnetometer
Was. C / N: Reduce noise spectrum when measuring playback output
From the playback output and the center recording frequency (4.7 MHz)
Find C / N from the ratio of noise level separated by 0.1MHz
Was. Spectrum analyzer uses HP-3585A
0 dB with respect to the single-layer magnetic layer tape of Comparative Example 1.
And BER (block error rate): BER
Is the number of error flags in 10,000 tracks
And is expressed by the following equation. BER = error flag / 10000 × 128 blocks The DAT signal configuration encodes an analog signal, and one code is
8 bits, 1 block is 32 symbols × 8 bits = 25
Since it is 6 bits, one track is composed of 128 blocks.
Is done. 2 tracks, ie 128 × 2 blocks of signal
Signal into memory, shuffle, and detect errors
do. Counter using Sony DAT deck
Hewlett-Packard HP5328A
Used and connected to a personal computer for measurement. Dropout: 4.7MHz single frequency signal input
Force, length at threshold level (-10dB)
It was measured with a 0.5 μs dropout counter. [0099] [Table 1] [0100] [Table 2]As is clear from the above table, the examples of the present invention
Has high Rf output and reduces dropout and BER
It shows excellent electromagnetic conversion characteristics. Comparative Example 1
This is an example of only a magnetic layer without a lower nonmagnetic layer.Reference example
Is a sequential layering method in which the lower layer is dried and then the upper layer is applied thereon.
This is an example of creating a magnetic recording medium by BER and DO.
Bad dropout. Comparative Example 3 was performed in place of the inorganic powder.
This is an example using carbon black, BER,
I am not satisfied with my power. Comparative Example 4 has a strength larger than a predetermined size.
Since magnetic alloy powder is used, H in the width direction and the longitudinal direction
Since c is lower than the present invention, a high reproduction output cannot be obtained,
The BER is also high. Comparative Example 5 is a ferromagnetic material having a large needle ratio.
This is an example in which powder is used, and Hc in the width direction is larger than that of the present invention.
Low reproduction output cannot be obtained because of low, and BER is also improved.
RenaNo. [0102] According to the present invention, a thin layer having a dry thickness of 1 μm or less is provided.
Longitudinal direction and width of magnetic layer of magnetic recording medium having magnetic layer
By setting each holding force in the direction to a specific value or more,
Improvement of reproduction output and dropout especially in short wavelength recording
And BER are reduced and have improved electromagnetic characteristics.
A magnetic recording medium can be obtained. Also, the present invention
A magnetic layer having a uniform thickness and 1 μm or less is used as a lower non-magnetic layer.
Large with no coating defects and reduced pinholes and streaks
Extremely thin ferromagnetic metal thin film of magnetic layer with excellent mass productivity
To provide magnetic recording media with performance comparable to
is there.

Claims (1)

(57) [Claims 1] provided the lower non-magnetic layer dispersed in a binder of inorganic powder on a non-magnetic support, the upper magnetic layer dispersed in a binder a ferromagnetic powder thereon Wherein the dry thickness of the upper magnetic layer is 1.0 μm or less, and the major axis length of the upper magnetic layer is 0.25 μm or less,
The upper magnetic layer has a coercive force (Hc) in the longitudinal direction of 1500 Oe or more and a coercive force (Hc) in the width direction of 1000 Oe or more.
The inorganic powder contained in the lower non-magnetic layer has a true specific gravity of 3
A magnetic recording medium comprising the above inorganic powder . 2. An inorganic powder contained in the lower nonmagnetic layer
But flat Hitoshitsubu diameter 0.2μm or less granular particles or magnetic according to claim 1, wherein the long axis length is equal to or is less acicular particles 0.05~1.0μm and acicular ratio 20, recoding media. 3. The magnetic recording medium according to claim 1, wherein the ferromagnetic alloy powder is an alloy of Fe and Co or a ferromagnetic alloy powder containing Co metal as a main component. 4. The ferromagnetic alloy powder contains 75% or more of the ferromagnetic alloy as a main component, and further contains Al, Si, S, S
c, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, A
g, Sn, Sb, Te, Ba, Ta, W, Re, Au,
Hg, Pb, Bi, La, Ce, Pr, Nd, P, M
The magnetic recording medium according to claim 1, further comprising an atom selected from n, Zn, Ni, Sr, and B. 5. An abrasive particle contained in the upper magnetic layer.
The size is 0.01 to 2 μm.
Item 5. The magnetic recording medium according to any one of Items 1 to 4. 6. An inorganic powder contained in the lower nonmagnetic layer
But TiO ₂ (rutile, anatase), TiO _x , oxidation
Cerium, tin oxide, tungsten oxide, ZnO, ZrO
₂ , Cr ₂ O ₃ , alumina with α conversion of 90% or more, β-Al
Mina, gamma alumina, alpha iron oxide, goethite, colander
System, silicon nitride, titanium carbide, magnesium oxide,
Molybdenum disulfide, copper oxide, BaCO ₃ , SrCO ₃ ,
At least one selected from BaSO ₄ , silicon carbide and titanium carbide
6. The method as claimed in claim 1, wherein one of said two is contained.
The magnetic recording medium according to claim 1. 7. The magnetic recording medium is for digital sound recording.
Tapes, video tapes, computer tapes, discs
7. The method according to claim 1, wherein
The magnetic recording medium according to the above. 8. An inorganic material having a true specific gravity of 3 or more on a nonmagnetic support.
Coating solution and ferromagnetic powder for lower non-magnetic layer containing powder and binder
And preparing an upper layer magnetic layer coating solution containing a binder, respectively.
On the non-magnetic support, the coating solution for the lower non-magnetic layer and the magnetic material for the upper layer
Of magnetic recording media by applying a coating solution for the conductive layer
The ferromagnetic powder has a coercive force (Hc) of 150
0 Oe or more, major axis length 0.25 μm or less, and needle ratio 1
2 or less ferromagnetic alloy powder, and said non-magnetic support
The lower layer non-magnetic layer coating solution is coated on the upper layer to obtain the lower layer.
While the nonmagnetic layer is in a wet state, the lower nonmagnetic layer is coated.
Simultaneously or sequentially with the application of the liquid, the dry thickness of the magnetic layer is 1
Apply the upper magnetic layer coating solution to a thickness of
, The coercive force (H) in the longitudinal direction of the upper magnetic layer
c) is 1500 Oe or more and the coercive force (Hc) in the width direction is 1
Manufacturing magnetic recording media of 000 Oe or more.
A method for manufacturing a magnetic recording medium. 9. The non-magnetic layer contained in the lower non-magnetic layer coating solution.
The powdery material has an average particle diameter of 0.2 μm or less,
Or the major axis length is 0.05 to 1.0 μm and the needle ratio is 5 to 2.
The particles according to claim 8, wherein the particles are zero needle particles.
A method for manufacturing a magnetic recording medium.