JP2655379C - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001]     [Industrial applications]   The present invention relates to a magnetic recording disk for high density recording, and more particularly to a magnetic recording disk for data recording.
It is about a disk. [0002]     [Prior art]   Magnetic recording technology allows the medium to be used repeatedly, and makes it easy to digitize signals
And that a system can be constructed in combination with peripheral electronic devices.
Excellent features not found in other recording methods, such as easy modification of signals
, Video, audio, computer applications, etc.
It has been widely used. In addition, miniaturization of equipment, high quality of recording / reproduction signals,
In order to respond to demands such as longer time and increased recording capacity,
Further improvements in density have always been desired. And a coating type magnetic recording disk
In, the particle size of the ferromagnetic powder was reduced or its dispersibility was improved.
Various measures have been proposed to increase the degree of filling in the magnetic layer. As an effective means, use ferromagnetic metal powder or hexagonal ferrite with excellent magnetic properties.
That is also being done. [0003]   In addition, mini-computers as OA equipment and external storage media have become
Use of magnetic recording disks is remarkable, and the frequency of use of magnetic recording disks is increasing.
Is used and stored under a wide range of environmental conditions with regard to temperature and humidity.
It has been used in many places. In particular, large recording capacity and miniaturization
There is a strong demand for an increase in recording density in order to achieve this.
To obtain a magnetic recording disk suitable for high-density recording using powder,
The maximum dimension must be sufficiently smaller than the recording wavelength or the recording bit length.
At present, needle-like ferromagnetic powder having a size of about 0.3 μm has already been put into practical use.
Thus, the shortest recording wavelength of about 1 μm or less is possible. [0004]   In order to obtain a medium capable of higher density recording in the future, the size of the acicular ferromagnetic powder must be reduced.
It needs to be even smaller. But in such a small acicular ferromagnetic powder
Has a very small thickness of 100 mm or less and a particle volume of 10^-17cm^ThreeLess than
Magnetic properties are degraded due to thermal disturbance and surface effects,
However, there is a problem that a sufficient orientation cannot be obtained even when a magnetic field is applied to the conductive coating film. [0005]   Ferromagnetic metal powders have been studied as ferromagnetic powders for high-density recording.
Hexagonal systems with a flat plate shape and an axis of easy magnetization in the direction perpendicular to the plate surface in recent years
Magnetic recording media using ferrite particles as ferromagnetic powder have been developed (for example,
JP-A Nos. 58-6525 and 58-6526. By these, ferromagnetic powder
The average particle diameter of the powder became 0.05 μm or less, and high-density recording became possible. [0006]   Further, a significantly narrow track width is required for high-density recording. these
Strong magnets that can be expected to have high output and high recording density even on magnetic disks to meet requirements
The use of conductive metal powders and ferromagnetic hexagonal ferrite powders has been studied.
In order to respond to the demand for miniaturization and improvement of the recording density of the medium, keen development and practical application are being studied. ing. In particular, the magnetic layer is used for high recording density and improvement of overwrite electromagnetic conversion characteristics.
Thinning and high output are desired.
You. [0007]   That is, usually, a magnetic recording disk for computer use such as a floppy disk
Requires overwriting of recording signals with different magnetic wavelengths.
However, conventionally, two types of signals, 1f and 2f signals, which are twice as related in frequency, are used.
It would have been nice if overwriting could be done, but recently 10 Mbytes or more
For the high-capacity magnetic recording disk above, not only the recording wavelength became shorter, but also
Of a plurality of signals in a wider band with a frequency ratio of 3: 8, such as an RLL signal, etc.
Site has been requested. Use a signal with a short recording wavelength and a large difference in recording frequency.
Overwriting a signal with a short recording wavelength on a signal with a long recording wavelength (overlap
In order to carry out the process successfully, it is necessary to use Japanese Patent Application Laid-Open (JP-A) No. 58-122623 and
As disclosed in, for example, Japanese Patent No. 74137, the magnetic property of the magnetic layer is simply improved.
There was a limit to just running. [0008]   That is, in the conventional magnetic layer having a thickness of 1.0 μm or more, the information is previously recorded.
Magnetic field lines are magnetic even when a shorter recording signal is overwritten on a longer wavelength recording signal
Longer wavelength signal previously recorded is erased because it does not go deeper into the layer
You can't.   Further, the gap of the recording head is becoming narrower with the improvement of the recording density.
. Along with this, it has become difficult to perform sufficient recording in the thickness direction of the medium. [0009]   Therefore, when the magnetic layer is thinned to 1 μm or less in order to solve the above problem, the magnetic layer becomes
It is easy to peel off and it is not possible to ensure running durability such as causing dropout,
There was a problem of reduced reliability.   Therefore, in order to provide a magnetic recording disk capable of coping with the high density recording described above,
Is particularly effective in improving reproduction output, securing overwrite characteristics, and running durability.
Has become a problem. [0010]   In addition, the electrification during running of the magnetic recording disk causes dropout due to the adhesion of dust.
The number has increased, and the error rate has become a fatal defect. This charge
To add an additive to prevent electrification in the magnetic layer in order to improve the problem of
Is usually taken, and among them, the method of adding carbon black is the most effective.
, Has been widely adopted. However, the magnetic recording disk for high density recording described above
In, the addition of carbon black lowers the magnetic material filling degree and lowers the output
Therefore, the addition amount is limited, and sufficient measures for preventing static electricity cannot be taken. [0011]   In particular, the ferromagnetic hexagonal ferrite powder is made of Co-Fe_TwoO_ThreeFerromagnetic powder,
Compared to ferromagnetic metal powder, etc., the saturation magnetization is low and it is difficult to obtain high output, so high output
To provide high power magnetic recording disks, the packing density must be increased,
And its hexagonal shape, its dispersibility is lower than that of conventional ferromagnetic powders.
It is basically difficult to secure antistatic properties and high reproduction output. [0012]   Various proposals have been made to satisfy the above-mentioned prevention of electrification, high output and improvement of durability.
It is shown. (Japanese Patent Application Laid-Open Nos. 55-55431, 55-55432,
JP-A-55-55433, JP-A-55-55434, JP-A-60-164926
JP-A-55-55436, JP-A-62-38523, JP-A-62-15
No. 9337)   That is, an intermediate layer is provided between the magnetic layer and the support.
Apply black and binder resin, and then try to form a magnetic layer on it
It is. [0013]   However, although this method was effective for improving running durability,
It is a magnetic recording disk for density recording, while ensuring sufficient running durability, and
Satisfies excellent electromagnetic characteristics, that is, high reproduction output and overwrite characteristics.
And could not.   As a further complication, the magnetic layer must be extremely If the edge is thinned, for example, to 0.5 μm or less, the current coating technology is as follows.
Problems have arisen. (1) It is difficult to apply a uniform thickness directly on the non-magnetic support. Also, the magnetic layer
Are easily peeled off. (2) The intermediate layer (non-magnetic layer) may be used as a lower layer and applied thereon.
If it is applied, adhesion is a problem, and the magnetic layer peels off and may cause dropout.
Or become. [0014]   Therefore, as a result of the examination, a so-called multi-layer coating is performed while the non-magnetic layer and the magnetic layer are in a wet state.
Adopting a wet-on-wet coating method solves the above problem.
Proved to be effective.   However, simply applying this wet-on-wet coating method requires
The above problem could not be solved. [0015]   When providing a non-magnetic layer, the dispersion solvent for the magnetic layer is important, and
When the same type of solvent as the solvent, the magnetic layer coating solvent is applied when the magnetic layer is coated on the non-magnetic layer.
Dissolves the non-magnetic layer and disturbs the boundary between the non-magnetic layer and the magnetic layer.
The taste causes a large variation in film thickness. Also, dissolve the magnetic layer solvent into the non-magnetic layer.
When using a solvent that does not understand, the binder resin used for the magnetic layer is very limited,
When coated with such a solvent, the adhesion between the nonmagnetic layer and the magnetic layer described above is significantly lower.
And the durability is extremely reduced. [0016]   That is, the coating solution for the non-magnetic layer and the coating solution for the magnetic layer are in a liquid state with each other.
Because it is applied on top, the interface between the nonmagnetic layer and the magnetic layer is disturbed, and the thickness of the magnetic layer fluctuates.
Became easy to occur. If there is a thickly fluctuating part in the magnetic layer,
Good write characteristics cannot be achieved, and previously written signals cannot be erased.
However, there is a problem that reproduction may not be possible. Also, the thickness variation of the magnetic layer is suppressed.
There was also a problem that it was difficult to secure durability when trying to control. [0017]   Therefore, the magnetic layer should be made as thin as possible to improve the overwrite characteristics.
According to the current coating technology, the average thickness of the magnetic recording disk can be reduced.
Taste fluctuations increase and overwrites all tracks suitable for digital recording.
Magnetic recording with a thin magnetic layer with good running characteristics and excellent running durability with high reproduction output
It was difficult to get a recording disc. [0018]   And no effective way to address this problem has yet been proposed. [0019]     [Problems to be solved by the invention]   The present invention has been made in view of the above-mentioned problems of the related art, and has an
The magnetic recording characteristics are good over all tracks of the magnetic recording disk, and the electromagnetic characteristics including output are good.
To provide a high-density magnetic recording disk with good exchange characteristics and excellent running durability
It is an object. [0020]     [Means for Solving the Problems]   The present invention provides a non-magnetic layer mainly composed of a non-magnetic powder and a binder resin on a non-magnetic support.
Also, a magnetic layer mainly composed of ferromagnetic powder and a binder resin should not be formed in this order.
In the magnetic recording disk described above, the magnetic layer is formed such that the coating layer of the non-magnetic layer coating liquid is wet.
Formed by applying the magnetic layer coating solution on the
The average thickness of the magnetic layer is 0.5 μm or less, and the maximum thickness is
The minimum thickness is within ± 15% of the average thickness.And the non-magnetic powder is a carbon bra.
The magnetic recording disk contains a magnetic recording medium and a non-magnetic inorganic powder.
5 × 10 ⁹ Ω / sq or lessA magnetic recording disk, characterized in that
Can solve the above problem. [0021]   The present invention provides a magnetic recording system comprising a nonmagnetic layer and a magnetic layer provided on a nonmagnetic support in this order.
The disk has an average thickness of 0.5 μm or less and a maximum thickness of the magnetic layer.
Taste (T_max) And minimum thickness (T_min) Was controlled within ± 15% of the average thickness.
Is the biggest feature.   That is, the present invention provides that the thickness of the magnetic layer and its variation are at least within the above range.
For example, the electromagnetic conversion characteristics such as overwrite characteristics and reproduction output
It has been found that it can be provided stably and favorably on a truck. [0022]   Average thickness of magnetic layer (T₀) Is a value calculated as follows.   The magnetic recording disk is placed on an ultramicrotome using a diamond cutter.
And cut it out to a thickness of about 0.1 μm, and cut the cross section with a transmission electron microscope.
Take a photograph of the piece at 5,000 to 10,000 times and use a 8.7 cm x 10.7 cm
Lint size, and then the interface between the nonmagnetic layer and the magnetic layer is
Judgment is made visually by paying attention to the shape difference, etc., and the magnetic layer surface is similarly blackened.
The distance between the lines that have been trimmed by the Zeiss image processing device IBAS2.
The length (distance) was measured. The measurement site is a magnetic layer with a length of 20 μm (actual length) and a non-magnetic layer.
(T) between the top of the magnetic layer and the surface of the magnetic layer formed by the outlined interface of the magnetic layer.₁
) And the distance between the bottom of the valley formed by the interface and the surface of the magnetic layer (T_Two) For 5 places each
The average value of the sum of the above is defined as the average thickness. [0023]   In the present invention, the maximum thickness (T_max) Is the T_TwoMeans the largest measured value of
, Similarly, the minimum thickness (T_min) Is the T₁Means the smallest measured value.   That is, in the present invention, the thickness of the magnetic layer is controlled so that all of the following expressions are satisfied.
.   ΔT_max= 100 × (T_max-T₀) / T₀≦ 15 (%) (a)   ΔT_min= 100 × (T_min-T₀) / T₀≧ −15 (%) (b)   ΔT_max−ΔT_min= 100 × (T_max-T_min) / T₀≦ 30 (%) (c)   That is, in formula (a), it exceeds 15%, or in formula (b), it exceeds -15%.
If it is small, or if it exceeds 30% in (c), overwrite characteristics
Electromagnetic conversion characteristics such as reproduction output cannot be satisfied. [0024]   In the present invention, the trimming curve forming the interface ideally has a magnetic layer thickness.
It is most preferable that the straight line is constant (in the above (a), (b) and (c)). And the left side = 0%), but in reality, T₀With small amplitude
Since a curve similar to a clear sine curve is formed, the above equations (a) and (c)
This is true, and the variation in thickness is suppressed as much as possible. [0025]   In equation (a), ΔT_maxIs preferably 0 ≦ ΔT_max≦ 12, especially preferred
Or 0 ≦ ΔT_max≦ 8, ΔT_minIs preferably −12 ≦ Δ
T_min≦ 0, particularly preferably −8 ≦ ΔT_minIt is controlled in the range of ≦ 0.   In the present invention, the border line at the interface is long if the interval between the peak and the valley is long.
It is more preferable. It is desirable that the distance between the hills and the valleys is equal. [0026]   The present invention provides a reproduction output, an overwrite characteristic, etc.
Can significantly improve the stability of the electromagnetic conversion characteristics.   Further, the present invention provides a wet coating method for forming a magnetic layer and a non-magnetic layer.
The to-on-wet coating method prevents peeling of the magnetic layer, etc.
Was found to be effective for obtaining discs. [0027]   A non-magnetic layer is provided on a support by a conventional blade coating method, a gravure coating method, or the like,
If the magnetic layer is further provided after drying, the adhesion between the non-magnetic layer and the magnetic layer is sufficient.
Rather, the ultra-thin magnetic layer as in the present invention has inferior durability and is difficult to be put to practical use.
there were.   The present invention employs at least a wet-on-wet coating method.
Therefore, the above formula can be satisfied, and the nonmagnetic layer and the magnetic layer have the same characteristics as an integrated layer.
Thus, the adhesion between the nonmagnetic layer and the magnetic layer can be increased. [0028]   Specific examples of the wet-on-wet coating method include the following.
It is. 1. Gravure coating, roll coating, and blade commonly used for applying magnetic paint
First, a non-magnetic layer is applied using a coating or extrusion coating device.
While in a wet state, for example, Japanese Patent Publication No. 179 and JP-A-2-265672.
A method of applying a magnetic layer using a pressure-type extrusion coating device. 2. JP-A-63-88080, JP-A-2-17971, JP-A-2-2656
No. 72, the head having two built-in slits
A method of applying a coating solution for a non-magnetic layer and a coating solution for a magnetic layer almost simultaneously. 3. Japanese Patent Application Laid-Open No. 174965/1990 discloses a device with a backup roll.
The coating solution for non-magnetic layer and the coating solution for magnetic layer are applied almost simultaneously
How to cloth. [0029]   The manufacturing method of the present invention is a method for forming a magnetic layer in a wet-on-wet coating method.
The purpose of the present invention is to provide a method for suppressing taste fluctuation and improving the accuracy of thick taste.
Examples of the method include the first to fifth methods below.   First, select the solvent used for the coating solution for the non-magnetic layer and the coating solution for the magnetic layer.
The selection criteria are that the boiling point of the solvent used for the non-magnetic layer
Above the boiling point of the solvent used. [0030]   Briefly, the effect of evaporation of the solvent from the previously applied non-magnetic layer is
It suppresses dimensional deformation of the surface of the non-magnetic layer and suppresses the viscoelastic properties of the coating liquid.
The turbulence of the liquid at the interface is suppressed even when the magnetic layer coating liquid having different
Making the thickness of the magnetic layer formed on the magnetic layer more uniform, that is,
That is, it can be suppressed small. [0031]   The solvent used for the non-magnetic layer has a boiling point of 90 ° C or higher, preferably 100 ° C or higher.
The solvent used for the magnetic layer preferably has a boiling point of 100 ° C. or lower, particularly preferably 80 ° C.
It is below ° C. The difference in boiling point is preferably 40 ° C. or higher, more preferably 50 ° C. or lower.
The upper limit of the difference between the boiling points is set at 100 ° C. so that the thickness of the magnetic layer falls within the range of the present invention.
can do.   The boiling point of the solvent used in the non-magnetic layer coating solution used in the present invention is 90 ° C. or higher.
As the solvent, cyclohexanone (boiling point: 156 ° C.), methyl isobutyl ketone ( Ketones such as diisobutyl ketone (168 ° C.) and isophorone (boiling point 116 ° C.)
Boiling point 215 ° C), butanol (boiling point 118 ° C), isobutyl alcohol (boiling point 1
08 ° C), 2-methylcyclohexanol (boiling point 173 ° C), etc.
And a single or mixed solvent can be used. Non-magnetic layer coating solution
With the binder resin of the non-magnetic layer such as cyclohexanone and the added lubricant
It is desirable that the compound has excellent compatibility. [0032]   The boiling point of the solvent of the magnetic layer coating liquid applied on the nonmagnetic layer is determined by the nonmagnetic layer coating liquid.
Lower than the boiling point of the solvent, for example, methyl ethyl ketone (boiling point 79 ° C.)
), THF (boiling point 66 ° C), acetone (boiling point 56 ° C), propanol (boiling point 97).
° C), methyl acetate (boiling point 58 ° C), benzene (boiling point 80 ° C), hexane (boiling point 6 ° C).
9 ° C), carbon tetrachloride (boiling point 77 ° C), etc.
Wear. When used as a mixed solvent, its boiling point is calculated from the weight usage ratio of each solvent.
The calculated boiling point can be used as a guide. [0033]   Second, after the coating on the non-magnetic support by the wet-on-wet coating method,
It is to specify a drying method in the drying step. That is, the non-magnetic layer and the magnetic layer
After the support is provided on a porous support, orientation is performed as necessary, and then a drying step is performed.
By gradually raising the temperature from room temperature to the drying process of the non-magnetic layer and the magnetic layer.
Thickness fluctuation of the magnetic layer can be suppressed. [0034]   For example, the coated magnetic recording disk is heated from room temperature to a high temperature, preferably 20 to 15 minutes.
0 ° C., particularly preferably at an ambient temperature varying from 25 to 120 ° C.
Drying method may be mentioned. The method of changing the ambient temperature is arbitrary and continuous.
May also be intermittent. Also, the temperature rise rate can be controlled to 0.6 to 4 ° C / sec.
preferable. [0035]   Specifically, do not transport the web after wet-on-wet application at a constant speed.
However, it is necessary to pass through a drying chamber where the ambient temperature is set intermittently high in the direction of travel. To do more. For example, let the web transfer speed be 50 to 300 m / min.
120 ° C for 4 to 24 seconds each at 25 ° C, 40 ° C, 60 ° C, 80 ° C, and 100 ° C.
Drying for 1.5 to 9 seconds. [0036]   Third, in the wet-on-wet coating method, the non-magnetic layer
It is preferable that the viscoelastic properties of the coating liquid for the hydrophilic layer be matched as much as possible. Non-magnetic layer wets
Since the magnetic layer is provided at the time of the state, if the viscoelastic properties are significantly different,
As a result, the respective liquids are disturbed, and the thickness of the magnetic layer fluctuates greatly.   As a means for adjusting the viscoelastic properties, the following methods may be used.
Can be. [0037]   Each coating solution has thixotropic properties and a shear rate of 10^Foursec^-1Shear stress at
A10^FourAnd shearing speed 10 sec^-1Stress A10 ratio to A10 A10^Four/ A10
100 ≧ A10^Four/ A10 ≧ 3, preferably 90 ≧ A10^Four/ A10 ≧ 30
Adjustment.   Specific means for adjusting such viscoelastic properties include, for example, the following factors:
Choosing a child. [0038]   The factors include, for example, non-magnetic powder or ferromagnetic powder to be dispersed.
Are (1) particle size (specific surface area, average primary particle size, etc.), (2) structure (oil absorption,
(3) Properties of powder surface (pH, loss on heating, etc.), (4) Aggregation of particles
Force (σ_sFor example, the binding agent (e.g., (1) molecular weight, (2) the type of functional group, etc.)
For the agent, (1) type (polarity etc.), (2) binder solubility, (3) solvent formulation amount, etc.
, Water content and the like. [0039]   The liquid viscosity of both non-magnetic layer coating liquid and magnetic layer coating liquid is a single cylindrical rotational viscometer.
0.5 to 300 centipoise is suitable, and preferably 3 to 200 centipoise.
It is. The viscosity difference between the non-magnetic layer coating solution and the magnetic layer coating solution is 100 centipoise or less.
Is suitable, and preferably not more than 50 centipoise.   Fourth, the raw material particles used for each coating solution for the non-magnetic layer and the magnetic layer should be at least dried.
A size smaller than the thickness of the subsequent nonmagnetic layer and magnetic layer is desirable. In other words, the strong magnet to use
Powders, carbon black particles, abrasive particles, and non-magnetic particles are used in magnetic layers.
In this case, at least 0.5 μm or less is desirable. For non-magnetic layers, the thickness is regulated.
Because it is not restricted, it is possible to increase the film thickness depending on the particle size used
. [0040]   Fifth, the size of various powders contained in the magnetic layer coating liquid and / or the non-magnetic layer coating liquid
The mixed region does not occur at the interface between the magnetic layer and the non-magnetic layer
Can be controlled as follows.   For example, when needle-shaped nonmagnetic powder is used, if these are aligned,
A strong coating film is formed even in a dry state, and even if the ferromagnetic powder of the magnetic layer rotates,
Mixing hardly occurs. In addition, if flaky non-magnetic powder is used for the non-magnetic layer,
When the ferromagnetic powder of the magnetic layer rotates, mixing occurs at the interface
It becomes difficult. [0041]   Since the present invention is a thin layer having an average magnetic layer thickness of 0.5 μm or less, digital recording
The characteristic overwrite characteristics can be greatly improved. High linear recording density
As the recording wavelength becomes shorter, the effect of the thickness of the magnetic layer becomes more significant.
You. In particular, when the recording wavelength is 1.4 μm or less, the thickness of the magnetic layer must be 0.5 μm or less.
Therefore, the definition of the thickness variation of the present invention in the above formulas (a) to (c) is
Not only is it important in ensuring the stability of the light characteristics,
This is effective in reducing the difference between the minimum values and increasing the average reproduction output value. [0042]   The present invention not only improves the above-mentioned electromagnetic conversion characteristics, but also provides a wet-on-
Adhesion between the non-magnetic layer and the magnetic layer is ensured by using
It also has the effect that it can be secured.   The non-magnetic layer of the magnetic recording disk of the present invention mainly comprises a non-magnetic powder and a binder resin.
Is what you do. Non-magnetic powder isContains carbon black and non-magnetic inorganic powder Can include organic powders. Carbon black Adjusts the viscoelastic properties of the coating liquid
, Effective for controlling the surface electrical resistance of the magnetic layer surface, and for ensuring running durability
Used for. [0043]   The content of carbon black in the nonmagnetic layer depends on the amount of nonmagnetic powder contained in the nonmagnetic layer.
The content is preferably 3 to 20% by weight, particularly 5 to 15% by weight. Triple
When the amount is less than 20% by weight, the surface resistivity cannot be sufficiently reduced.
Surface resistivity can be reduced, but a sufficiently smooth surface property of the magnetic layer can be obtained.
Can not. Specific surface area is 5-1200m^Two/ G, more preferably 5
0-1000m^Two/ G, and the DBP oil absorption is 10 to 1500 mL (min.
L) / 100g, preferably 20-600mL / 100g, average particle size
, 5-500 mμ, preferably 10-300 mμ, pH 2-10, more preferably
2.5 to 9.5, the water content is 0.1 to 10% by weight, more preferably 0.3 to 10% by weight.
3.0% by weight, tap density: 0.1 to 1 g / cc, more preferably 0.12 to 0
. 80 g / cc is preferred. [0044]   This makes it possible to reduce the amount of carbon black added in the magnetic layer.
Packing density of the conductive powder can be secured.   The carbon black has a low surface electrical resistance to form a structure.
I can do it. For this reason, the surface specific electric resistance value of the magnetic layer can also be suppressed low,
The occurrence of dropouts in running durability can be reduced. [0045]   In the present invention, the surface specific electric resistance of the magnetic layer is set to 5 × 10⁹Ω / sq or less
, Preferably 5 × 10⁸It is desirable to adjust to Ω / sq or less. Also non-magnetic
Layer / magnetic layer has a smooth surface and reduces the spacing loss with the recording / reproducing head.
High reproduction output can be obtained. Furthermore, DBP oil absorption is 200mL / 100g
The above carbon black is easy to form a structure, resulting in low surface voltage.
Air resistance can be obtained, and dropouts in running durability are particularly reduced
It is preferable. The DBP oil absorption of carbon black is calculated as Add dibutyl phthalate little by little, knead and knead the carbon black
Observing the point, finding a point that forms one lump from the dispersed state,
The amount (mL) of butyl phthalate added was defined as the DBP oil absorption. [0046]   Carbon black imparts conductivity to magnetic recording disks and
Is effective to prevent electrostatic charging and adjusts the physical strength of the magnetic layer and non-magnetic layer
It is also used as a material for In addition, carbon black is applied to the non-magnetic layer
It also has the function of adjusting the viscoelastic properties of the liquid. In addition, carbon black has a coefficient of friction
It is a very useful material that has various functions such as adjustment of light transmittance and imparting light-shielding properties. Therefore, on
For the same purpose as described above, carbon black can be included in the magnetic layer. This place
In this case, it is preferable to use the ferromagnetic powder at 0.1 to 30% by weight. [0047]   Further, the present invention provides a carbon brass that can be used for a non-magnetic layer or a magnetic layer.
As the hook, those manufactured by any method can be used. For example, furnace black
, Thermal black, acetylene black, channel black, lamp black
Can be used. As a specific example, BLACK manufactured by Cabot Corporation
PEARLS 2000, 1300, 1000, 900, 800, 700, VU
LCAN XC-72, manufactured by Asahi Carbon Co .; # 80, # 60, # 55, # 50, #
35, manufactured by Mitsubishi Chemical Corporation; # 3950B, # 2400, # 2300, # 900,
# 1000, # 30, # 40, # 10B, manufactured by Columbia Carbon; CONDU
CTEX SC, RAVEN 150, 50, 40, 15 manufactured by Lion Akzo
Ketchen Black EC, Ketchen Black ECDJ-500, Ketchen
Black ECDJ-600 and the like. [0048]   Use carbon black after surface treatment with dispersant or grafting with resin
Alternatively, a material in which a part of the surface is graphitized may be used. Also the car
Before adding Bon Black to the coating solution for the non-magnetic layer or the coating solution for the magnetic layer,
It may be dispersed with a binder. These carbon blacks can be used alone or in pairs.
Can be used in combination. [0049]   As described above, carbon black prevents the magnetic layer from charging, reduces the coefficient of friction, and imparts light-shielding properties.
, Works to improve film strength, etc., and these differ depending on the carbon black used.
. Therefore, these carbon blacks used in the present invention are used in the non-magnetic layer and the magnetic layer.
Change the type, amount and combination of the particle size, oil absorption, conductivity, pH, etc.
Of course, it is possible to use them properly according to the purpose based on the various characteristics. In the present invention
Usable carbon black is, for example, "Carbon Black Handbook" (Carbon Black
Eds. Association). [0050]   In the magnetic recording disk of the present invention, the ferromagnetic powder contained in the magnetic layer is iron oxide.
Ferromagnetic powder, ferromagnetic metal powder or ferromagnetic hexagonal ferrite powder
Ferromagnetic metal powder or ferromagnetic hexagonal ferrite powder is preferred.
No. If the ferromagnetic powder is a ferromagnetic metal powder, its particle size should preferably be a ratio table.
The area is 30-60m^Two/ G, more preferably 40-60 m^Two/ G and X-ray times
The crystallite size determined from the folding method is 100 to 300 °, more preferably 100 to 300 °.
And the axial ratio (major axis length / minor axis length) is 5 or more, more preferably 6 or more.
Above. [0051]   If the specific surface area is too small, it will not be possible to cope with high-density recording, and it will be too large.
However, dispersion was not sufficiently performed, and a magnetic layer having a smooth surface could not be formed.
It is not preferable because it cannot respond. Here, the crystallite size is a half value of the diffraction lines of the (1,1,0) plane and the (2,2,0) plane.
It is required from the width. [0052]   When the ferromagnetic powder is a ferromagnetic hexagonal ferrite powder, the specific surface area is 25 to 50 m.
^Two/ G, more preferably 40-60 m^Two/ G, and the plate ratio (plate diameter / plate thickness) is
2 to 6, more preferably 2.5 to 5.5, and a plate diameter of 0.02 to 1.0 μm, more preferably
More preferably, it is 0.03 to 0.08 μm.   If the particle size is too large or too small for the same reason as ferromagnetic metal powder, Density recording becomes difficult. [0053]   The ferromagnetic metal powder is preferably a powder containing at least Fe,
Physically, gold mainly composed of Fe, Fe—Co, Fe—Ni, or Fe—Ni—Co
There is a simple substance or an alloy. To increase the recording density of the magnetic recording disk of the present invention
In addition, it is preferable that the particle size is small as described above, and at the same time, the magnetic characteristics are
, Saturation magnetization (σ_s) Is at least 110 emu / g or more, preferably 120 emu / g
u / g or more. The coercive force is 800 Oe (Oersted) or more,
More preferably, it is 900 Oe or more. [0054]   In order to further improve the characteristics, non-metals such as B, C, Al, Si, and P are added to the composition.
May be added. Usually, the particle surface of the metal powder is chemically stabilized.
For this purpose, an oxide layer is formed.   As a method of forming the oxide, a known slow oxidation treatment, that is, immersion in an organic solvent
After drying, immerse in an organic solvent and then send oxygen-containing gas to the surface.
Drying after forming oxide film, oxygen gas and inert gas without using organic solvent
Method of forming an oxide film on the surface by adjusting the partial pressure of
Can also be used. [0055]   As the ferromagnetic hexagonal ferrite powder, a flat plate-shaped
Ferromagnetic powder with an easy axis of magnetization in the direction of barium ferrite, strontium
Ferrite, lead ferrite, calcium ferrite or their cobalt
Substituents, among them, especially cobalt substituted of barium ferrite, strontium
Preference is given to cobalt substitutes of um ferrite. Further improve its properties as needed
For this purpose, elements such as In, Zn, Ge, Nb, and V may be added. [0056]   To increase the recording density of the magnetic recording disk of the present invention, the hexagonal ferrite is used.
It is preferable to reduce the particle size in the magnetic layer of the powder as described above.
At the same time, as the magnetic characteristics, the saturation magnetization (σ_s) Is at least 50 emu / g or more , Desirably 53 emu / g or more. The coercive force is 500 Oe or more,
In particular, it is desirable to be 600 Oe or more. [0057]   In the magnetic recording disk of the present invention, the output in the circumferential direction is uniform and does not fluctuate.
It is necessary that the in-plane orientation ratio be as high as possible.
The orientation ratio of the magnetic powder is preferably 0.85 or more. 0.85 or more orientation ratio
In order to achieve this, the magnetic layer is in an undried state.
As described in the report, a random orientation method using a permanent magnet or JP-A-63-148417
And Japanese Patent Application Laid-Open Nos. Hei 1-300427 and Hei 1-300428.
A method of applying a flowing magnetic field can be used. [0058]   In the present invention, when ferromagnetic metal powder and hexagonal ferrite powder are used, zero
. An orientation ratio as high as 9 or more can be realized.   Here, the orientation degree ratio is a value obtained by dividing the minimum squareness ratio in the circumferential direction by the maximum squareness ratio.
.   The magnetic properties of the ferromagnetic powder, such as the saturation magnetization and the coercive force, were measured using a vibrating sample magnetometer
(Manufactured by British Industry Co., Ltd.) at a maximum applied magnetic field of 5 kOe. The measurement of specific surface area
BET method using Canter Soap (Cantar Chrome, USA)
You. After dehydration in a nitrogen atmosphere at 250 ° C for 30 minutes, measured by the BET single point method (partial pressure 0.30)
This is the specified value. [0059]   The water content of these ferromagnetic powders is preferably 0.01 to 2% by weight.
. The moisture content is preferably optimized depending on the type of the binder resin. P of ferromagnetic powder
Preferably, H is also optimized by a combination with the binder resin used. Its range
Is from 4 to 12, preferably from 5 to 10.   The ferromagnetic powder may be surface-treated with Al, Si, P or their oxides if necessary.
May be applied. The amount is 0.1 to 10% based on the ferromagnetic powder,
When treated, adsorption of lubricants such as fatty acids is 100mg / m^TwoLess preferred
. The ferromagnetic powder contains soluble inorganic ions such as Na, Ca, Fe, Ni, and Sr. However, if the content is 500 ppm or less, the characteristics are not particularly affected. [0060]   As the ferromagnetic powder, an iron oxide ferromagnetic powder may be used if desired.
25-80m in terms of specific surface area^Two/ G, preferably 35-60.
m^Two/ G. 25m^Two/ G or less, the noise is high and 80 m^Two/ G or more
It is difficult to obtain surface properties, which is not preferable. The crystallite size measured by the X-ray diffraction method is 4
50-100 Å, preferably 350-100 Å
It is a theme. σ_sIs at least 50 emu / g, preferably at least 70 emu / g
. [0061]   These ferromagnetic powders contain dispersants, lubricants, surfactants, antistatic
Before dispersing with an agent or the like, treatment may be performed in advance. To be more specific,
No. 4-14090.   Non-magnetic inorganic powder among the non-magnetic powder that can be used for the non-magnetic layer of the present invention, for example,
Metal, metal oxide, metal carbonate, metal sulfate, metal nitride, metal carbide, metal
Sulfide and the like. Specifically, TiO_Two(Rutile, anatase), TiO_x(
x is less than 2 or 3 to 5), cerium oxide, tin oxide, tungsten oxide, Z
nO, ZrO_Two, SiO_Two, Cr_TwoO_Three, Α-alumina, β-Al with 90% or more pregelatinization ratio
Mina, γ-alumina, α-iron oxide, goethite, corundum, silicon nitride, titanium car
Bite, magnesium oxide, boron nitride, molybdenum disulfide, copper oxide, MgCO_Three
, CaCO_Three, BaCO_Three, SrCO_Three, BaSO_Four, CaSO_Four, Silicon carbide, etc.
Used alone or in combination. The shape and size of these inorganic powders are acicular,
They may be spherical, dice-shaped, etc., and these may be combined with different inorganic powders as necessary.
The particle size distribution and the like can be selected by combining them or using a single nonmagnetic powder. particle
The size is preferably 0.01 to 2 μm. The following are non-magnetic powders
Is preferred. [0062]   Tap density is 0.3-2 g / cc, water content is 0.1-5%, pH is 2-11,
Specific surface area is 1-30m^Two/ G is preferred. Oil absorption using DBP is 5-100m L / 100 g, preferably 10-80 mL / 100 g, more preferably 20-6
It is 0 mL / 100 g. The above non-magnetic powder must be 100% pure
However, depending on the purpose, the surface may be coated with another compound such as Al, Si, Ti, Zr, S
Treatment with each compound such as n, Sb, Zn and the like may form an oxide thereof on the surface.
. At this time, if the purity is 70% or more, the effect is not reduced. Ignition loss
Is preferably 20% or less. [0063]   Specific examples of the non-magnetic powder used in the present invention include AKP- manufactured by Sumitomo Chemical Co., Ltd.
20, AKP-30, AKP-50, G5, G7, S-1, manufactured by Nippon Chemical Industry Co., Ltd.
TF-100, TF-120, TF-140, manufactured by Tadashi Kogyo, TT05, manufactured by Ishihara Sangyo
5 series, ET300W, STT30 manufactured by Titanium Industries, and the like. [0064]   The non-magnetic organic powder used in the present invention includes acrylic styrene resin powder, benzene
Zoguanamine resin powder, melamine resin powder, phthalocyanine pigment
But polyolefin resin powder, polyester resin powder, polyamide resin
Powder, polyimide resin powder, and polyfluoroethylene resin powder are used. That
The production method is described in JP-A-62-18564 and JP-A-60-255827.
You can use something like [0065]   As the binder used for the magnetic layer and the non-magnetic layer of the present invention, a conventionally known thermoplastic resin is used.
Fats, thermosetting resins, reactive resins and mixtures thereof are used.   As a thermoplastic resin, the glass transition temperature is -100 to 150 ° C, the number average molecular weight
Is from 1000 to 200,000, preferably from 10,000 to 100,000, and the degree of polymerization is about
It is about 50 to 1000. Such examples include vinyl chloride and vinyl acetate.
Nyl, vinyl alcohol, maleic acid, acrylic acid, acrylate, chloride
Vinylidene, acrylonitrile, methacrylic acid, methacrylate, styrene
, Butadiene, ethylene, vinyl butyral, vinyl acetal, vinyl acetate
Polymers or copolymers containing ter, etc. as constituent units, polyurethane resins, various types
There is a rubber-based resin. [0066]   In addition, as thermosetting resin or reactive resin, phenol resin, epoxy resin
, Polyurethane curing resin, urea resin, melamine resin, alkyd resin, acrylic
Resin, formaldehyde resin, silicone resin, epoxy-polyamide resin
Fat, polyester resin and isocyanate prepolymer mixture, polyester resin
Mixture of riol and polyisocyanate, polyurethane and polyisocyanate
And mixtures thereof. [0067]   For details on these resins, see "Plastic Handbook" published by Asakura Shoten.
It is described in. In addition, a known electron beam-curable resin is applied to a non-magnetic layer or a magnetic layer.
It is also possible to use. These examples and the production method thereof are described in
No. 256219. These resins are used alone or in combination
But preferably vinyl chloride resin, vinyl chloride vinyl acetate resin, salt
Vinyl acetate vinyl acetate vinyl alcohol resin, vinyl chloride vinyl acetate anhydrous maleic
Polyurethane with at least one selected from the group consisting of acid copolymers and nitrocellulose
Resin combinations or combinations of these with polyisocyanates
. [0068]   Polyurethane resin structure is polyester polyurethane, polyetherpolyuree
Tan, polyether polyester polyurethane, polycarbonate polyurethane
, Polyester polycarbonate polyurethane, polycaprolactone polyurethane
A known material such as a resin can be used. For all of the binders shown here,
In order to obtain excellent dispersibility and durability, COOM, SO_ThreeM, OSO_ThreeM
, P = O (OM)_Two, OP = O (OM)_Two, (Where M is a hydrogen atom, or
Alkali metal), OH, NR_Two, N⁺R_Three, (R is a hydrocarbon group), epoxy group, S
At least one polar group selected from H, CN, etc.
It is preferable to use those introduced in the reaction. The amount of such polar groups is 10^-1~ 1
0^-8Mol / g, preferably 10^-2-10^-6Mol / g. [0069]   Specific examples of these binders used in the present invention include Union Carbide
Company: VAGH, VYHH, VMCH, VAGF, VAGD, VROH, VYE
S, VYNC, VMCC, XYHL, XYSG, PKHH, PKHJ, PKHC
, PKFE, manufactured by Nissin Chemical Industries: MPR-TA, MPR-TA5, MPR-TA
L, MPR-TSN, MPR-TMF, MPR-TS, MPR-TM, MPR-
TAO, manufactured by Denki Kagaku: 1000 W, DX80, DX81, DX82, DX83
, 100FD, manufactured by Zeon Corporation: MR105, MR110, MR100, 400
X110A, manufactured by Nippon Polyurethane Industries: Nipporan N2301, N2302, N2
304, manufactured by Dainippon Ink Co., Ltd .: Pandex T-5105, T-R3080, T-
5201, Burnock D-400, D-210-80, Crisbon 6109, 7
209, manufactured by Toyobo: Byron UR8200, UR8300, UR8600, U
R5500, UR4300, RV530, RV280, manufactured by Dainichi Seika: Daifue
Lamin 4020, 5020, 5100, 5300, 9020, 9022, 702
0, manufactured by Mitsubishi Kasei: MX5004, manufactured by Sanyo Kasei: Samprene SP-150, Asahi
Karan Corporation: Saran F310, F210 and the like. [0070]   The binder used in the magnetic layer of the present invention is used for the ferromagnetic powder and for the non-magnetic layer.
The binder obtained is in the range of 5 to 50% by weight, preferably 10 to 3% by weight, based on the nonmagnetic powder.
It is used in the range of 0% by weight. When using a vinyl chloride resin, 5 to 100
%, 2 to 50% by weight when using a polyurethane resin, polyisocyanate
It is preferable to use these in combination in the range of 2 to 100% by weight. [0071]   In the present invention, when a polyurethane resin is used, the glass transition temperature is -50 to
100 ° C, elongation at break 100-2000%, stress at break 0.05-10 kg / c
m^Two, Yield point is 0.05 to 10 kg / cm^TwoIs preferred.   Although the magnetic recording disk of the present invention basically comprises two layers of a non-magnetic layer and a magnetic layer,
The non-magnetic layer and the upper layer may each be formed of a plurality of layers. Here, the coating liquid for each layer
The composition may be the same or different, and the type, size, etc. of the powder can be variously selected. This The application method of each layer coating solution by wet-on-wet coating method is basically
The method described above may be applied mutatis mutandis. [0072]   Therefore, the amount of binder, vinyl chloride resin in the binder, polyurethane resin,
The amount of polyisocyanate or other resin, the amount of each resin forming the magnetic layer
The molecular weight, polar group content, or the physical properties of the resin described above may be applied to each layer as necessary.
It is of course possible to change with a cloth solution.   As the polyisocyanate used in the present invention, tolylene diisocyanate, 4
-4'-diphenylmethane diisocyanate, hexamethylene diisocyanate
, Xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-
Toluidine isocyanate, isophorone diisocyanate, triphenylmethane
Isocyanates such as triisocyanate, and these isocyanates
Products with polyalcohols and polyisocyanates
Liisocyanate and the like can be used. Commercialization of these isocyanates
Trade names include those manufactured by Nippon Polyurethane Corporation: Coronate L, Coronate
HL, Coronate 2030, Coronate 2031, Millionate MR, Millione
MTL, manufactured by Takeda Pharmaceutical Co., Ltd .: Takenate D-102, Takenate D-110N,
Takenate D-200, Takenate D-202, manufactured by Sumitomo Bayer: Desmodu
L, death module IL, death module N, death module HL, etc.
, These alone or in combination of two or more utilizing the difference in curing reactivity
Can be used for each layer. [0073]   The abrasive used in the magnetic layer or the non-magnetic layer of the present invention may have an α conversion of 90%.
The above α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide,
α-iron oxide, corundum, artificial corundum, emery (main component: corundum and magnetic
Iron ore), artificial diamond, silicon nitride, silicon carbide, titanium carbide, titanium oxide
Known materials mainly having a Mohs hardness of 5 or more such as silicon, silicon dioxide, boron nitride, etc.
Used alone or in combination. In addition, a composite of these abrasives (abrasives
Surface-treated with another abrasive) may be used. The main component of these abrasives In some cases, compounds or elements other than the above may be contained.
There is no difference. [0074]   These abrasives having an average particle size of 0.05 to 2 μm are effective.
More preferably, it is 0.2 to 1.0 μm. Especially when used for magnetic layerIs 0. 5 μmLess than
underIs preferred. If necessary, combine abrasives with different particle sizes or use a single abrasive.
A similar effect can be obtained by broadening the particle size distribution even with an abrasive. Tap density is
0.3-2 g / cc, water content 0.1-5%, pH 2-11, specific surface area 1
30m^Two/ G is preferred. The abrasive used in the present invention may have a needle-like shape, a spherical shape, or a spherical shape.
It may be in the shape of a dice. [0075]   These abrasives are 100 times of non-magnetic powder of non-magnetic layer or ferromagnetic powder of magnetic layer.
It is added in an amount of 3 to 20 parts by weight based on parts by weight.   If the amount is less than 3 parts by weight, sufficient durability cannot be obtained.
The degree of filling decreases, and sufficient output cannot be obtained.   These abrasives, in the non-magnetic layer, the amount, type,
In the layer, the combination is changed according to the amount and type of the upper and lower ferromagnetic powders,
Of course, it is possible to use them properly according to the purpose. For example, the durability of the magnetic layer surface
In order to improve the durability, increase the amount of abrasive in the non-magnetic layer and improve the durability of the end face of the magnetic layer.
In order to improve the quality, it is possible to take measures such as increasing the amount of abrasive in the magnetic layer.
These abrasives are pre-dispersed with a binder and then used in magnetic and non-magnetic paints.
May be added. Magnetic layer surface and magnetic layer of magnetic recording disk of the present invention
5 abrasives / 100 μm on the end face^TwoThe above is preferred. [0076]   Specific examples of the abrasive used in the present invention include AKP-2 manufactured by Sumitomo Chemical Co., Ltd.
0, AKP-30, AKP-50, HIT-50, manufactured by Nippon Chemical Industry: G5, G
7, S-1, manufactured by Toda Kogyo: TF-100, TF-140, 100ED, 140
ED and the like.   As the dispersant (pigment wetting agent) used in the present invention, caprylic acid, capric acid, Lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, olein
Acids, elaidic acid, linoleic acid, linolenic acid, stearic acid, etc.
18 fatty acids (R₁COOH, R₁Is an alkyl or alk having 11 to 17 carbon atoms
A kenyl group); an alkali metal (Li, Na, K, etc.) or an alkali of the above fatty acid
Metal soaps composed of earth metals (Mg, Ca, Ba); fluorine of the above fatty acid esters
Amides of the above fatty acids; polyalkylene oxide alkyl
Acid ester; lecithin; trialkylpolyolefinoxy quaternary ammonium
Salt (alkyl has 1 to 5 carbon atoms, olefin is ethylene, propylene, etc.); etc.
Is used. In addition, higher alcohols having 12 or more carbon atoms, and sulfur
Acid esters and the like can also be used. These dispersants are based on 100 parts by weight of the condensing agent resin.
Then, it is added in the range of 0.5 to 20 parts by weight. [0077]   As a lubricant, dialkyl polysiloxane (alkyl has 1 to 5 carbon atoms),
Dialkoxypolysiloxane (alkoxy group has 1 to 4 carbon atoms), monoalkyl
Monoalkoxypolysiloxane (alkyl is 1 to 5 carbon atoms, alkoxy group is carbon
Phenylpolysiloxane, fluoroalkylpolysiloxane (A
(The alkyl group has 1 to 5 carbon atoms.) Silicon oil; conductive fine particles such as graphite
Powders; inorganic powders such as molybdenum disulfide, tungsten disulfide, etc .;
Propylene, polyethylene vinyl chloride copolymer, polytetrafluoroethylene
Α-olefin polymer; unsaturated aliphatic carbon liquid at room temperature
Hydrogen (a compound in which an n-olefin double bond is bonded to a terminal carbon, having about 20 carbon atoms
); A monobasic fatty acid having 12 to 20 carbon atoms and a monovalent alcohol having 3 to 12 carbon atoms.
Fatty acid esters, fluorocarbons and the like can be used. [0078]   Among them, fatty acid esters are most preferred.   Examples of alcohols used as raw materials for fatty acid esters include ethanol, butanol,
Phenol, benzyl alcohol, 2-methylbutyl alcohol, 2-hexyl
Decyl alcohol, propylene glycol monobutyl ether, ethylene glyco
Monobutyl ether, dipropylene glycol monobutyl ether, diethyl Monoalcohols such as lenglycol monobutyl ether and s-butyl alcohol
, Ethylene glycol, diethylene glycol, neopentyl glycol,
Examples include polyhydric alcohols such as lyserin and sorbitan derivatives. [0079]   Similarly, fatty acids include acetic acid, propionic acid, octanoic acid and 2-ethylhexa.
Acid, lauric acid, myristic acid, stearic acid, palmitic acid, behenic acid,
Laquinic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, palmitole
An aliphatic carboxylic acid such as an acid or a mixture thereof is exemplified.   Specific examples of the fatty acid ester include butyl stearate and s-butyl stearate.
Salt, isopropyl stearate, butyl oleate, amyl stearate, 3
-Methylbutyl stearate, 2-ethylhexyl stearate, 2-hexyl
Decyl stearate, butyl palmitate, 2-ethylhexyl myristate,
Butoxyethyl stearate, a mixture of butyl stearate and butyl palmitate
G, 2-butoxy-1-propyl stearate, dipropylene glycol monobu
Acetyl ether acylated with stearic acid, diethylene glycol dipal
Amitate, hexamethylenediol is acylated with myristic acid to form a diester.
And various ester compounds such as glycerin oleate.
Wear. [0080]   Furthermore, when a magnetic recording disk is used under high humidity, fatty acid
In order to reduce the hydrolysis of stell, the branched / straight chain of fatty acids and alcohols as raw materials,
Isomeric structures such as cis / trans and branch positions are selected.   The following compounds can also be used as the lubricant. That is, silicon
Oil, graphite, molybdenum disulfide, boron nitride, graphite fluoride, fluorine fluoride
Alcohol, polyolefin, polyglycol, alkyl phosphate, disulfide
Ngusten and the like. [0081]   These lubricants may be used as non-magnetic powder of the non-magnetic layer or ferromagnetic powder of the magnetic layer.
It is added in the range of 0.2 to 20 parts by weight with respect to 0 parts by weight. Used in the present invention These lubricants are used in the magnetic layer and the non-magnetic layer according to the type and amount as needed.
be able to. For example, bleeding to the surface using fatty acids with different melting points in each layer
Control, bleeding to the surface using esters with different boiling points and polarities
It is conceivable to increase the amount of lubricant added to the non-magnetic layer to improve the lubrication effect,
Of course, it is not limited to only the examples shown here. [0082]   All or some of the additives used in the present invention may be used in the production of magnetic paints.
May be added in the step of, for example, mixing with ferromagnetic powder before the kneading step.
When adding in the kneading process using ferromagnetic powder, binder and solvent,
In some cases, it is added after dispersion, or it is added just before coating.   Examples of commercial products of these lubricants used in the present invention include NAA- manufactured by NOF Corporation.
102, NAA-415, NAA-312, NAA-160, NAA-180,
NAA-174, NAA-175, NAA-222, NAA-34, NAA-3
5, NAA-171, NAA-122, NAA-142, NAA-160, NA
A-173K, castor hardened fatty acid, NAA-42, NAA-44, cationic SA
, Cation MA, Cation AB, Cation BB, Nymeen L-201, Nymi
L-202, Nymeen S-202, Nonion E-208, Nonion P-2
08, nonionic S-207, nonionic K-204, nonionic NS-202, nonionic
On 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, Nonion OP-85R,
Neon LT-221, Nonion ST-221, Nonion OT-221, Monogri
MB, Nonion DS-60, Anone BF, Anone LG, Butyl stearate,
Cyllaurate, erucic acid, manufactured by Kanto Chemical Co .: Oleic acid, manufactured by Takemoto Yushi: FAL
-205, FAL-123, manufactured by Nippon Rika Co., Ltd.
IPM, Sansocizer E4030, manufactured by Shin-Etsu Chemical Co., Ltd .: TA-3, KF-96, K
F-96L, KF-96H, KF410, KF420, KF965, KF54,
KF50, KF56, KF-907, KF-851, X-22-819, X-2
2-822, KF-905, KF-700, KF-393, KF-857, KF -860, KF-865, X-22-980, KF-101, KF-102, K
F-103, X-22-3710, X-22-3715, KF-910, KF-
3935, manufactured by Lion Armor, Inc .: Armid P, Armid C, Armoslip
CP, manufactured by Lion Yushi Co., Ltd .: Duomin TDO, manufactured by Nisshin Oil Co., Ltd .: BA-41G,
Sanyo Kasei Co., Ltd .: ProFan 2012E, New Pole PE61, Ionet MS
-400, IONET MO-200, IONET DL-200, IONET DS
-300, IONET DS-1000, IONET DO-200, etc.
You. [0083]   The non-magnetic support used in the present invention is preferably a flexible and balanced type support.
Polystyrene such as polyethylene terephthalate, polyethylene naphthalate, etc.
Ters, polyolefins, cellulose triacetate, polycarbonate, polycarbonate
Lamide, polyimide, polyamideimide, polysulfone, polyethersulfo
, Aramid, aromatic polyamide, syndiotactic polystyrene, etc.
Film can be used. Generally, polyethylene terephthalate is preferred.
The thickness of the nonmagnetic support varies depending on the Young's modulus, but generally 10 to 100 μm.
It is suitable, preferably 30 to 80 μm, and more preferably 50 to 80 μm for high recording density.
７５75 μm. These supports are subjected to corona discharge treatment and plasma treatment in advance.
Treatment, easy adhesion treatment, heat treatment, dust removal treatment, and the like. Object of the present invention
Is achieved by using a non-magnetic support having a center line average surface roughness (Ra) (cutoff
Value 0.25 mm) is 0.03 μm or less, preferably 0.02 μm or less,
It is preferable to use one having a size of 0.01 μm or less. Also, these non-
The magnetic support not only has a small center line average surface roughness, but also has a coarseness of 1 μm or more.
Preferably, there are no protrusions. The surface roughness profile can be added to the support if necessary.
It is freely controlled by the size and amount of the filler added. This
Examples of these fillers include oxides and carbonates such as Ca, Si, and Ti.
In addition, an organic fine powder such as an acrylic resin may be used. [0084]   The F-5 value of the non-magnetic support used in the present invention in the web running direction (longitudinal direction) is Preferably 5 to 50 kg / mm^Two, The F-5 value in the web width direction is preferably 3 to 3
0Kg / mm^TwoAnd the F-5 value in the web longitudinal direction is different from the F-5 value in the web width direction.
Is generally higher, especially when it is necessary to increase the strength in the width direction.
Not limited. [0085]   The thickness of the magnetic recording disk is preferably non-magnetic, preferably 30 to 8 mm.
0 μm, the non-magnetic layer has a thickness of 0.5 to 10 μm, and the magnetic layer has a thickness of 0.01 to 0.5 μm.
It is also possible to provide an undercoat layer between the nonmagnetic support and the nonmagnetic layer to improve adhesion.
I don't know. The thickness is 0.01 to 2 μm, preferably 0.05 to 0.5 μm.
You. Further, a back coat layer may be provided on the side of the non-magnetic support opposite to the side of the magnetic layer.
Absent. This thickness is 0.1 to 2 μm, preferably 0.3 to 1.0 μm. this
Known undercoat layers and backcoat layers can be used. The magnetic recording disk of the present invention
The disk may be provided with a magnetic layer on both sides or one side. Also, on the surface of the magnetic layer
A layer of a resin and / or a lubricant may be provided as a protective layer. [0086]   Further, heat collection at 100 ° C. for 30 minutes in the web running direction and the width direction of the non-magnetic support.
The shrinkage ratio is preferably 3% or less, more preferably 1.5% or less, at 80 ° C. for 30 minutes.
The heat shrinkage is preferably 1% or less, more preferably 0.5% or less. Breaking strength
The degree is 5 to 100 kg / mm in both directions.^Two, Elastic modulus is 100-2000Kg / mm^Two
Is preferred. [0087]   The step of producing the magnetic layer coating solution of the magnetic recording disk of the present invention, the non-magnetic layer coating solution
At least in the kneading step, the dispersing step, and before or after these steps as necessary.
It consists of a digit mixing step. Each process can be divided into two or more stages.
I don't know. Ferromagnetic powder, non-magnetic powder, binder, carbon black used in the present invention
All raw materials such as abrasives, antistatic agents, lubricants, solvents, etc.
It may be added on the way. In addition, each raw material is divided and added in two or more processes.
You can add it. For example, polyurethane is kneaded, dispersed, and dispersed
It may be divided and supplied in a mixing step for adjusting the degree. [0088]   In kneading and dispersing each coating solution, various kneading machines are used. For example, two
Roll mill, three roll mill, ball mill, pebble mill, tron mill, sanding
Rinder, Szegvari, Attritor, High-speed impeller
Dispersion, high-speed stone mill, high-speed impact mill, disperser, kneader, high-speed mixer
, A homogenizer, an ultrasonic disperser or the like can be used. [0089]   In order to achieve the object of the present invention, a conventionally known manufacturing technique is used as a part of the steps.
Of course, it can be used, but in the kneading process, a continuous kneader or a pressure kneader is used.
Magnetic recording disk of the present invention
Br can be obtained. Strong when using a continuous or pressure kneader
All or part of the magnetic powder and the binder (however, more than 30% by weight of the total binder
(Preferably) and 15 to 500 parts by mass with respect to 100 parts of the ferromagnetic powder.
It is. Details of these kneading processes are described in JP-A-1-106338 and JP-A-6-106338.
4-79274. When preparing a coating solution for the non-magnetic layer,
It is desirable to use a dispersion medium having a high specific gravity, such as zirconia beads and metal beads.
Is preferred. [0090]   In the present invention, a simultaneous multilayer coating method as disclosed in JP-A-62-212933 is used.
By using, it is possible to produce more efficiently.   A non-magnetic layer coated on the non-magnetic support by wet-on-wet coating;
The magnetic layer is preferably subjected to a calendering process after an orientation process and a drying process.
Epoxy, polyimide, polyamide, polyimide
Use a heat-resistant plastic roll such as metal. In addition, processing with metal rolls
Can also be managed. The processing temperature is preferably 70 ° C. or higher, more preferably 8 ° C.
0 ° C. or higher. The linear pressure is preferably 200 kg / cm, more preferably 30 kg / cm.
0 kg / cm or more. [0091]   The elastic modulus of the magnetic layer at 0.5% elongation is preferably 100 to 100 in both the running direction and the width direction. 2000Kg / mm^Two, Breaking strength is preferably 1 to 30 kg / cm^Two, Magnetic recording
The elastic modulus of the disk is preferably 100 to 1500 kg / mm in both the running direction and the width direction.
^Two, The residual elongation is preferably 0.5% or less, heat recovery at any temperature of 100 ° C or less.
The shrinkage ratio is preferably 1% or less, more preferably 0.5% or less, and most preferably.
Is 0.1% or less. [0092]   The residual solvent contained in the magnetic layer is preferably 100 mg / m^TwoLess preferred
Or 10mg / m^TwoBelow, the residual solvent contained in the magnetic layer is contained in the non-magnetic layer
It is preferably smaller than the residual solvent to be obtained.   Both the magnetic layer and the non-magnetic layer preferably have a porosity of 30% by volume or less.
Is preferably 10% by volume or less. The porosity of the non-magnetic layer is larger than the porosity of the magnetic layer
It is preferable that the porosity of the nonmagnetic layer be as small as 5% or more.
Absent. [0093]   The magnetic recording disk of the present invention has a plurality of layers.
It is easily estimated that the physical properties can be changed. For example, non-magnetic
The elastic modulus of the magnetic layer is higher than that of the magnetic layer,
Improve head contact, increase the elastic modulus of both non-magnetic and magnetic layers
The effect of improving running durability can be easily predicted. [0094]   The magnetic layer coated on the support by the wet-on-wet coating method
After performing a process for orienting the ferromagnetic powder in the layer as necessary, the formed magnetic layer is
dry. If necessary, the surface may be smoothed or cut into a desired shape.
Thus, the magnetic recording medium of the present invention is manufactured.   The magnetic recording disk of the present invention is capable of high-density magnetic recording.
Important for digital data storage media used to store and read data
Electromagnetic conversion characteristics such as writing characteristics and reproduction output are, for example, the shortest recording wavelength is 1.5 μm
Even if the recording density is as follows, it does not decrease and can be obtained stably.
There is an advantage that the row durability does not decrease. [0095]   Not only when the recording wavelength is shortened but also when the track density is increased.
In this case, the use of the magnetic recording disk of the present invention also reduces signal crosstalk.
It is possible to perform recording with a small amount of peak shift and excellent separability. Therefore, the recording track
When the width is 50 μm or less and the track density is 14 tracks / mm or more, the shortest recording wave
Excellent overwriting suitability and good running durability even when recording with a length of 1.5 μm or less.
Recording and playback are possible. [0096]     【Example】   Hereinafter, the present invention will be described more specifically with reference to examples. Components, proportions,
The operation order and the like can be changed without departing from the spirit of the present invention.
That is easy to understand for those in the industry.   Therefore, the present invention should not be limited to the following examples. In addition, there is "part"
Means "parts by weight". [0097]   Example 1   A coating solution for the nonmagnetic layer and a coating solution for the magnetic layer were prepared according to the following formulation. Non-magnetic layer paint   Non-magnetic inorganic powder 80 parts     Granular TiO_Two (TY50 manufactured by Ishihara Sangyo Co., Ltd.)       Average particle size 0.34μm       Specific surface area by BET method 5.9 m^Two/ G       pH 5.9   20 parts of carbon black     Average particle size 16mμ     DBP oil absorption 80mL / 100g       pH 8.0     Specific surface area by BET method 250m^Two/ G     Volatile content 1.5% by weight   14 parts of vinyl chloride-vinyl acetate-vinyl alcohol copolymer     -N (CH_Three)_Three ⁺Cl^-Base 5 × 10^-6eq / g content     Composition ratio 86: 13: 1 Degree of polymerization 400   5 parts of polyester polyurethane resin     Neopentyl glycol / caprolactone polyol / MDI     = 0.9 / 2.6 / 1     -SO_ThreeNa group 1 × 10^-Foureq / g content   sec-butyl stearate 4 parts   2-butoxy-1-ethyl stearate 3 parts   Oleic acid 1 part   Cyclohexanone 400 parts Magnetic layer paint   100 parts of ferromagnetic metal powder     Composition Fe / Ni = 96/4     Hc 1600 Oe, BET specific surface area 58m^Two/ G     Crystallite size 195Å     Average particle size (major axis length) 0.20 μm, needle ratio 10     Saturation magnetization (σ_s) 130 emu / g   14 parts of vinyl chloride copolymer     -SO_ThreeNa group 1 × 10^-Foureq / g content Degree of polymerization: 300   Polyester polyurethane resin 3 parts     Neopentyl glycol / caprolactone polyol / MDI     = 0.9 / 2.6 / 1     -SO_ThreeNa group 1 × 10^-Foureq / g content   α-alumina (average particle size 0.2 μm, maximum 0.42 μm) 2 parts   0.5 parts of carbon black   (Average particle size 0.10 μm, maximum 0.25 μm)   Isohexadecyl stearate 6 parts   Oleic acid 1 part   300 parts of methyl ethyl ketone   After kneading each component with a continuous kneader for each of the above two paints,
It was dispersed using a sand mill. Add the polyisocyanate ("Colour
Nate L ") is added to the non-magnetic layer paint by 10 parts and the magnetic layer paint by 12 parts.
40 parts of butyl acetate were added to each, and a filter having an average pore size of 1 μm was used.
And filtered to prepare a coating solution for the non-magnetic layer and a coating solution for the magnetic layer. The viscosity of the two liquids is not
The magnetic layer coating solution was 150 centipoise and the magnetic layer coating solution was 185 centipoise.
(Measured with a rotational viscometer). [0098]   Immediately after that, the obtained non-magnetic layer coating solution is dried so as to have a thickness of 2 μm.
The center average surface is 62 μm thick so that the thickness of the magnetic layer is 0.45 μm
Speed of 150 m / min on a polyethylene terephthalate support having a roughness of 0.01 μm
Wet-on-wet simultaneous wet multi-layer coating
While the layer is still wet, the frequency is 50 Hz, the magnetic field strength is 200 Gauss or
Passing through two alternating magnetic field generators of several 50 Hz, 120 gauss,
Perform random orientation treatment, 25 ° C, 40 ° C, 60 ° C, 80 ° C, 100 ° C for 8 seconds
After drying at 120 ° C for 3 seconds, the temperature is 90 ° C and the linear pressure is 300K with a 7-stage calender.
g / cm, and punched into 3.5-inch size and subjected to surface polishing.
Later, the liner is placed in a 3.5 inch cartridge with the inside installed, and the diameter is 29
The center core with a diameter of mm is used.
A floppy disk was obtained. [0099]   Example 2   The coating composition of the magnetic layer of Example 1 was changed to the following composition, and a 3.5-inch
I got a ppypy disk. Magnetic layer paint   Ferromagnetic hexagonal ferrite powder 100 parts     Hc 1400Oe, BET specific surface area 45m^Two/ G     Average particle size (plate diameter) 0.06 μm, plate ratio 5.2     Saturation magnetization (σ_s) 65 emu / g   12 parts of vinyl chloride copolymer     -SO_ThreeNa group 1 × 10^-Foureq / g content   Polyester polyurethane resin 3 parts     Neopentyl glycol / caprolactone polyol / MDI     = 0.9 / 2.6 / 1     -SO_ThreeNa group 1 × 10^-Foureq / g content   0.5 parts of carbon black     Average particle size 0.10μm, maximum 0.25μm   α-alumina 10 parts     Average particle size 0.2 μm, maximum 0.42 μm,     Specific surface area 7.5m^Two/ G   Isohexadecyl stearate 6 parts   Oleic acid 2 parts   400 parts of methyl ethyl ketone   For each of the two paints of the non-magnetic layer paint and the magnetic layer paint of Example 1,
After kneading the components with a continuous kneader, they were dispersed using a sand mill. Obtained
10 parts of polyisocyanate ("Coronate L") in the non-magnetic layer paint
, 9 parts to the magnetic layer paint, and 40 parts of butyl acetate to each,
m, filtered using a filter having an average pore size of m.
Fabric liquors were each prepared. At this time, the viscosity of the magnetic layer coating solution was 200 centipoise.
Was. [0100]   Immediately after that, the obtained non-magnetic layer coating solution is dried so as to have a thickness of 2 μm.
The center average surface is 62 μm thick so that the thickness of the magnetic layer is 0.45 μm
Speed of 150 m / min on a polyethylene terephthalate support having a roughness of 0.01 μm
Wet-on-wet simultaneous wet multi-layer coating
While the layer is still wet, 3000 G on the vertical in a direction perpendicular to the coating surface
Permanent magnets are set up and down so that After drying at 40 ° C, 40 ° C, 60 ° C, 80 ° C, 100 ° C for 8 seconds and 120 ° C for 3 seconds, 7
2. Perform processing at a temperature of 90 ° C. and a linear pressure of 300 Kg / cm using a calendar device in a stage.
Punched 5 inch size, surface polished, liner installed inside
Into a 3.5 inch cartridge and use a center core with a diameter of 29 mm.
The other mechanical parts were added to obtain a 3.5-inch floppy disk.
. [0101]   Comparative Example 1   20 parts of carbon black of the coating solution for the non-magnetic layer of Example 1 was added to 5 parts of cyclohexano
3.5 inch floppy disk under the same conditions as in Example 1 except that 400 parts were replaced with 350 parts.
Created a disc.   Comparative Example 2   10 parts of carbon black of the coating solution for the non-magnetic layer in Example 1 was mixed with 5 parts of cyclohexano
3.5 inch floppy disk under the same conditions as in Example 2 except that 400 parts were replaced with 350 parts.
Created a disc. [0102]   Comparative example3   Except that the drying conditions in Example 1 were changed to 100 ° C., 40 seconds, 120 ° C., and 3 seconds.
A 3.5-inch floppy disk was prepared under the same conditions as in Example 1.   Comparative example4   Except that the drying conditions in Example 2 were changed to 100 ° C., 40 seconds, 120 ° C., and 3 seconds.
A 3.5-inch floppy disk was prepared under the same conditions as in Example 2. [0103]   Comparative example5   Cyclohexanone in the non-magnetic layer coating solution of Example 1 was changed to methyl ethyl ketone
A 3.5-inch floppy disk was prepared under the same conditions as in Example 1 except for the above.   Comparative example6   Cyclohexanone in the non-magnetic layer coating solution of Example 2 was changed to methyl ethyl ketone
A 3.5 inch floppy disk was prepared under the same conditions as in Example 2 except for the above. [0104]   Comparative example7   400 parts of cyclohexanone of the coating solution for the non-magnetic layer in Example 1 was changed to 750 parts.
At this time, the viscosity was 10 centipoise. Otherwise, under the same conditions as in Example 1.
A 3.5 inch floppy disk was made.   Comparative example8   400 parts of methyl ethyl ketone of the magnetic layer coating solution of Example 2 was changed to 750 parts.
At this time, the viscosity was 25 centipoise. Otherwise under the same conditions as in Example 2.
A 3.5 inch floppy disk was made. [0105]   Comparative example9   Α-Alumina (average particle size 0.2 μm, maximum 0.42 μm) in the magnetic layer coating solution of Example 1
μm) 2 parts replaced with 2 parts of α-alumina (average particle size 0.4 μm, maximum 0.9 μm)
A 3.5 inch floppy disk was prepared under the same conditions as in Example 1 except for the above.   Comparative example10 Comparative Example 1Using the non-magnetic layer composition of Comparative Example3And other conditions
Produced a 3.5-inch floppy disk under the same conditions as in Example 1. [0106]   Comparative example11   The same conditions as in Example 1 were used except that the average thickness of the magnetic layer in Example 1 was 0.9 μm.
A 3.5 inch floppy disk was made.   Comparative example12   The same conditions as in Example 2 were used except that the average thickness of the magnetic layer in Example 2 was 0.9 μm.
A 3.5 inch floppy disk was made. [0107]   Each sample of the floppy disk thus obtained was measured by the following evaluation method.
Specified.   1. Orientation ratio: Hm10KOe using a vibrating sample magnetometer (manufactured by Toei Kogyo)
Apply a magnetic field and rotate the magnetic field from 0 degree to 360 degrees every 10 degrees to measure the sample. The mold ratio was determined, and a value obtained by dividing the minimum value of the square shape ratio by the maximum value was calculated and defined as the degree of orientation. [0108]   2. Measurement of playback output: Measurement of playback output
Metal gap head with a gap length of 0.45 μm using a test device SK606B
At a recording frequency of 625 kHz and a radius of 24.6 mm.
After recording, the playback output of the head amplifier is output to a Tektronix oscilloscope.
It was measured with Model 7633. The average value, maximum value and minimum value of the reproduction output are based on JIS-X6
221 was calculated. The reproduction output is Comparative Example 1, Comparative Example3, Comparative example5, Comparison
An example7, Comparative example9, Comparative example10, Comparative example11Now, let the playback output of the first embodiment be 100
And described as relative values. Comparative example2, Comparative example4, Comparative example6, Comparative example8,ratio
Comparative example12Is described as a relative value with the reproduction output of Example 2 being 100. [0109]   3. Overwrite: Overwriting characteristics are advanable to the above test equipment.
Using the tester TR4171 spectrum analyzer with gate option
And each window obtained by dividing one cycle into 72 is provided.
The reproduction signal at each location obtained by dividing the measurement track on the medium corresponding to
The spectrum can be measured. At a position of 39.5 mm using this measuring device,
Record 312.5 kHz on AC degaussed sample and place in each window
The output of the 312.5 kHz component is measured from 01-1 (dB) to 01-72 (dB).
Immediately after that, 1 MHz is overwritten, and each window at that time is overwritten.
From the output 02-1 (dB) of the 312.5 kHz component, 01-72 (dB) is measured.
After that, overwriting of each place 02-J-01-J (dB) (J is 1 to 72)
I asked. The maximum, minimum, and average of these 72 points of overwriting were determined. This value is
Usually, -30 dB or less is a practical range. [0110]   4. Magnetic layer surface electric resistance (Ω / sq): manufactured by Takeda Riken, TR-8611A (
Digital super insulation resistance meter) and described in JISX61019.4.
It was measured by the method.   5. Running durability: FD1331 type floppy disk drive manufactured by NEC After recording on all 240 tracks at a recording frequency of 625 kHz,
At a position of 37.25 mm from the thermocycle flow described in Table 1 for one cycle.
Thermocycle test was conducted. Under the thermo conditions, the number of passes
Running durability was evaluated based on the running state when the vehicle was driven up to 12 million times.
. [0111]   6. Magnetic layer thickness: 21 mm radius of 3.5 inch floppy disk sample
10 mm in the circumferential direction according to the above-mentioned measuring method, and the average thickness T
₀, Maximum thickness T_maxAnd minimum thickness T_minI asked. Also. Formulas (a) and (b)
) To T₀Thickness variation ΔT_maxAnd ΔT_minI asked.   The viscosities of the coating solution for the non-magnetic layer and the coating solution for the magnetic layer were measured using a single cylindrical rotational viscometer (Shiba
It was measured under the conditions of 23 ° C. and 50% RH by Ura System VH-H1). [0112] [Table 1] [0113]   The evaluation results of the respective characteristic values of the examples and comparative examples obtained by the above evaluation methods are shown in the table.
2 is shown. [0114] [Table 2] [0115]   Example 1 of the present invention2Means that the average thickness of the magnetic layer is 0.5 μm or less and ΔT_max
And ΔT_minIs stable because the thickness variation represented by is within 15% in absolute value
Shows reproduction output, overwrite characteristics, and electromagnetic conversion characteristics of orientation ratio,Also run
Excellent line durabilityHowever, Comparative Examples 1 and 2 show the same electromagnetic conversion characteristics as those of the above-described embodiment.
However, running durability is poor.   On the other hand, a comparative example3-10The average thickness of any of the magnetic layers is 0.5 μm or less,
ΔT_maxAnd ΔT_minMagnetic layer because the thickness variation represented by the formula exceeds 15% in absolute value
The stability of reproduction output and overwrite characteristics is inferior due to large fluctuation in thickness. [0116]   Comparative example3, 4as well as10Is in the drying process after wet-on-wet application
Therefore, unlike the example, drying was not performed from room temperature, but was performed at a high temperature from the beginning.
Therefore, the thickness variation of the magnetic layer is large.   Comparative example5as well as6Is a solvent having a high boiling point in the coating solution for the non-magnetic layer (e.g., cyclohexanone,
156 ° C.) was changed to a solvent with a low boiling point (methyl ethyl ketone, boiling point 79 ° C.)
This is an example, and the thickness variation of the magnetic layer is also large. [0117]   Comparative example7as well as8Means that the viscosity difference between the non-magnetic layer coating solution and the magnetic layer coating solution is -140 poise.
Therefore, the interface fluctuation between the non-magnetic layer and the magnetic layer is large due to the large size, -125 poise.   Comparative example9Is an example in which the size of α-alumina in the magnetic layer composition is increased.   Comparative example10and12Sets the average thickness of the magnetic layer to 0.91 μm and 0.89 μm
In this case, the overwrite characteristics are extremely poor. [0118]     【The invention's effect】   The present invention preferably has a non-magnetic powder dispersed in a binder on a non-magnetic support.
While the non-magnetic layer and the non-magnetic layer are in a wet state, a ferromagnetic powder is added thereto in a binder.
A magnetic recording disk provided with a dispersed magnetic layer, wherein the non-magnetic layer is a non-magnetic powder
ageCarbon black and non-magnetic inorganic powderAnd the average thickness of the magnetic layer is 0.1.
A magnetic recording medium having a thickness of 5 μm or less and a maximum and minimum thickness of the magnetic layer within ± 15% of the average thickness. This makes it possible to achieve high overwrite characteristics and stable output.
A durable medium can be obtained.

Claims (1)

1. A non-magnetic layer mainly composed of a non-magnetic powder and a binder resin and a magnetic layer mainly composed of a ferromagnetic powder and a binder resin are arranged on a non-magnetic support in this order. In the magnetic recording disk formed, the magnetic layer is formed by applying a magnetic layer coating solution thereon while the coating layer of the nonmagnetic layer coating solution is in a wet state. the thickness of the layer is an in average thickness is 0.5μm or less, the maximum thickness and the minimum thickness is Ri near within ± 15% of the average thickness, the non-magnetic powder is carbon
The magnetic recording disk contains black and non-magnetic inorganic powder, and has a surface electric resistance
A magnetic recording disk having a resistance of 5 × 10 ⁹ Ω / sq or less . 2. The magnetic recording disk according to claim 1, wherein the ferromagnetic powder is a ferromagnetic metal powder or a hexagonal ferrite powder.