JP2946257B2 - Magnetic recording disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic recording disk for high-density recording, and more particularly to a magnetic disk for recording data.

[0002]

2. Description of the Related Art Magnetic recording technology is capable of repeatedly using a medium, is easy to digitize a signal, enables a system to be constructed in combination with peripheral electronic devices, and easily modifies a signal. Because it has excellent features not available in other recording methods such as what can be done, computers,
It has been widely used in various fields including video and audio applications. Further, in order to respond to demands such as miniaturization of equipment, higher quality of recording / reproducing signals, longer recording time, increase of recording capacity, etc., it is always desired to further improve recording density of recording media. It has been rare. For coating-type magnetic recording disks, various measures have been proposed for reducing the particle size of the ferromagnetic powder, improving its dispersibility, and increasing the degree of filling in the magnetic layer. As an effective means, use of ferromagnetic metal powder or hexagonal ferrite having excellent magnetic properties has been performed.

[0003] Further, with the spread of minicomputers as OA equipment and personal computers, magnetic recording disks as external storage media have become remarkably widespread, the frequency of use of magnetic recording disks has increased, and temperature-humidity use and storage in a wide range of environmental conditions have been achieved. In addition, it has come to be used in places where the use environment is very dusty. In particular, there is a strong demand for an increase in recording density in order to achieve large recording capacity and miniaturization, but to obtain a magnetic recording disk suitable for high-density recording using conventional needle-like ferromagnetic powder. It is necessary to make the maximum dimension of the acicular ferromagnetic powder sufficiently smaller than the recording wavelength or the recording bit length. Currently, 0.3 μm as acicular ferromagnetic powder
Those having a size of the order have already been put to practical use, and the shortest recording wavelength of about 1 μm or less is possible.

In order to obtain a medium capable of recording at a higher density in the future, it is necessary to further reduce the size of the acicular ferromagnetic powder. However, such a small acicular ferromagnetic powder has a very small thickness of 100 mm or less and a very small particle volume of 10 ^-17 cm ³ or less. However, there is a problem that a sufficient orientation cannot be obtained even when a magnetic field is applied to the magnetic coating film.

As a ferromagnetic powder corresponding to high density recording,
Ferromagnetic metal powders have been studied so far, and recently, magnetic recording media using hexagonal ferrite particles having a flat plate shape and having an easy axis of magnetization in a direction perpendicular to the plate surface as a ferromagnetic powder have been developed (for example, JP-A-58-6525,
No. 58-6526, etc.). As a result, the average particle size of the ferromagnetic powder can be 0.05 μm or less, and high-density recording can be achieved.

Further, for high-density recording, a significantly narrow track width is required. To meet these demands, the use of ferromagnetic metal powder and ferromagnetic hexagonal ferrite powder, which can be expected to have high output and high recording density even on magnetic disks, is being studied. In order to respond to the demands of, development and practical application are being studied. In particular, it is desired to reduce the thickness of the magnetic layer and increase the output in order to improve the high recording density and the overwrite electromagnetic conversion characteristics.

That is, in a magnetic recording disk for a computer such as a floppy disk, it is usually necessary to overwrite recording signals having different magnetic wavelengths (overwriting). It would have been good if the two types of signals, 1f and 2f signals, could be overwritten. However, for a magnetic recording disk having a high capacity of 10 Mbytes or more, which has recently been strongly demanded, not only the recording wavelength has been shortened, but also the RLL. Frequency ratio of signal 3:
There is a need for overwriting a plurality of signals over a wider bandwidth of eight. When a signal having a short recording wavelength and a large difference in recording frequency is used, a signal having a short recording wavelength is overwritten on a signal having a long recording wavelength (overwriting). As disclosed in JP-A-61-74137 and the like,
There is a limit to simply improving the magnetic properties of the magnetic layer.

That is, in the conventional magnetic layer having a thickness of 1.0 μm or more, even if a shorter recording signal is overwritten on a previously recorded recording signal of a longer wavelength, the magnetic field lines are deeper in the magnetic layer. Because it does not reach that point, the previously recorded longer wavelength signal cannot be erased. Also,
As the recording density is improved, the gap of the recording head is becoming narrower. Along with this, it has become difficult to perform sufficient recording in the thickness direction of the medium.

Therefore, if the thickness of the magnetic layer is reduced to 1 μm or less in order to solve the above-mentioned problem, the magnetic layer is apt to be peeled off. A problem has occurred. Therefore,
In order to provide a magnetic recording disk capable of coping with the above-mentioned high-density recording, it has become a serious problem to improve reproduction output, secure overwrite characteristics, and run durability.

In addition, the electrification of the magnetic recording disk during running causes an increase in the number of dropouts due to the adhesion of dust,
The resulting error rate was a fatal flaw. In order to improve this charging problem, a method of adding an additive to prevent charging in the magnetic layer is usually employed, and among them, a method of adding carbon black is most effective and widely used. . However, in the magnetic recording disk for high-density recording described above, the addition of carbon black lowers the filling degree of the magnetic substance and lowers the output, so that the amount of addition is limited, and sufficient for antistatic. Could not cope.

In particular, the ferromagnetic hexagonal ferrite powder has a low saturation magnetization and is difficult to obtain a high output as compared with Co—Fe ₂ O ₃ ferromagnetic powder, ferromagnetic metal powder, etc. In order to provide a magnetic recording disk of the type described above, the packing density must be increased. However, because of the fine particles and the hexagonal shape, the dispersibility is inferior to that of conventional ferromagnetic powder, and the antistatic property and the antistatic property are high. It is basically difficult to ensure a reproduction output.

Various proposals have been disclosed for satisfying the above-described prevention of electrification, high output and improved durability. (JP-A-55-55431, JP-A-55-55432,
JP-A-55-55433, JP-A-55-55434
JP-A-60-164926, JP-A-55-554
No. 36, JP-A-62-38523, JP-A-62-15
That is, an intermediate layer is provided between the magnetic layer and the support. Carbon black and a binder resin are applied to the intermediate layer,
Thereafter, a magnetic layer is to be formed thereon.

However, this method has been effective for improving running durability, but it is a magnetic recording disk of high-density recording, and has a sufficient electromagnetic resistance while ensuring sufficient running durability. Characteristics such as high reproduction output and overwrite characteristics could not be satisfied. As a further complication, if the magnetic layer is made extremely thin, for example, 0.5 μm or less in order to improve the overwrite characteristics, the following problems occur with the current coating technology. (1) It is difficult to apply a uniform thickness directly on the non-magnetic support. Further, the magnetic layer is easily peeled. (2) An intermediate layer (non-magnetic layer) can be used as a lower layer and applied on the lower layer. However, if the application is performed sequentially, adhesion is a problem, and the magnetic layer may peel off and cause dropout. I do.

Therefore, as a result of the study, it has been found that adopting a so-called wet-on-wet coating method in which the coating layers of the respective coating liquids of the non-magnetic layer and the magnetic layer are coated in a wet state, is used. It was found to be effective to eliminate it. However, simply applying the wet-on-wet coating method could not solve the following problems.

That is, in a magnetic recording disk having a structure in which the lower layer is a non-magnetic layer and the upper layer is a thin magnetic layer, the temperature is higher (50 ° C. or higher) and lower (5 ° C.) than the conventional single-layer magnetic layer. C), the magnetic layer is damaged, and the magnetic head is likely to be stuck to the magnetic layer. On the other hand, in a conventional magnetic recording disk having a single magnetic layer, various lubricants have been selected in order to cope with the above problem.

For example, JP-A-2-33724 discloses a magnetic recording medium using a fatty acid ester having a limited number of carbon atoms having a branched structure of an alcohol residue (10 to 32 carbon atoms) as a lubricant. JP-A-53220 discloses a magnetic recording medium using as a lubricant a fatty acid ester having a carbon number-limited structure in which an alcohol residue (having 10 to 32 carbon atoms) has a methyl-branched structure. Group (having 16 or more carbon atoms) has a branched structure (limited to carbon atoms)
JP-A-62-231417 discloses a magnetic recording medium having a multilayer structure of a lubricant-containing non-magnetic layer and a magnetic layer. JP-A-63-44312 discloses a magnetic recording medium using butoxyethyl stearate and an ester of an alcohol residue having 13 carbon atoms and stearic acid (tridecyl stearate) in combination.

In Japanese Patent Application Laid-Open No. Hei 4-87021,
A magnetic recording medium containing a branched aliphatic alcohol and a higher fatty acid ester obtained from a linear higher fatty acid is disclosed. Specifically, the branched alcohol has 7 to 13 carbon atoms, As the fatty acid, a fatty acid ester having 9 or more carbon atoms is disclosed. However, even when the above lubricant is simply applied to a magnetic recording disk having a nonmagnetic layer / magnetic layer, sufficient running durability cannot be ensured under a wide range of environmental conditions from low to high temperatures.

That is, at low temperatures, the magnetic head sticks to the surface of the magnetic layer, and at high temperatures, the magnetic layer surface is damaged by the magnetic head. Could not find the means of.

[0019]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has excellent running durability under a wide range of environmental conditions from a low temperature to a high temperature. It is an object of the present invention to provide a high-density, large-capacity magnetic recording disk having good electromagnetic conversion characteristics such as modulation.

[0020]

According to the present invention, a non-magnetic layer mainly comprising a non-magnetic powder and a binder resin and a magnetic layer mainly comprising a ferromagnetic powder and a binder resin are provided on a non-magnetic support.
In the magnetic recording disk formed in this order, the orientation ratio of the particles of the ferromagnetic powder in the magnetic layer is 0.85.
As described above, the magnetic layer and the non-magnetic layer further contain a compound represented by Structural Formula (1) and a compound represented by Structural Formula (2) described in Chemical Formula 3, and Wherein the content of the compound represented by the formula is at least 30% by weight or more of the total amount of the compound represented by the structural formula (1) and the compound represented by the structural formula (2). This is a disk, which can solve the above problem.

[0021]

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In the magnetic recording disk of the present invention, the fatty acid ester consisting of the above-mentioned structural formulas (1) and (2) is used as a lubricant in each of the magnetic layer and the non-magnetic layer, and the structural formula (1) It is necessary that the lubricant of the above) contains at least 30% by weight or more of the lubricant content. In other words, the present invention was the first to find out the lubricant composition of each layer in a coating type magnetic recording disk in which a lower layer provided on a nonmagnetic support has a nonmagnetic layer and an upper layer has a magnetic layer.

In the present invention, if the above lubricant composition is used, the detailed function of solving the above-mentioned problems is not clear, but fatty acid esters having different basic structures of structural formulas (1) and (2) are selected. And, by specifying the mixing ratio, the behavior of each fatty acid ester in the magnetic layer and the non-magnetic layer is appropriately controlled, and the amount of the lubricant on the magnetic layer surface is appropriately and permanently secured. Conceivable.

For example, conventionally, in order to increase the capacity of a magnetic recording disk and improve its overwrite characteristics, it has been required to make the magnetic layer thinner. As the thickness of the magnetic layer is reduced, the amount of lubricant that can be impregnated into the magnetic layer decreases, and in running durability, the lubricant is gradually removed by sliding with the recording / reproducing head. There was a phenomenon that abrasion stop and the like occurred.

However, in the present invention, even if the thickness of the magnetic layer is reduced, by satisfying the above conditions, the insufficient lubricant on the surface of the magnetic layer is replenished from the lower layer to the upper layer, so that the amount of the lubricant can always be compensated. It is thought that running durability can be ensured. The lubricant used for the magnetic layer and the non-magnetic layer is
A mixture of the fatty acid esters of the above structural formulas (1) and (2), wherein R1 is a branched hydrocarbon having 6 to 9 carbon atoms, preferably a branched alkyl group, and R2 and R3 are 2 carbon atoms.
R6 is a linear or branched hydrocarbon group having 12 to 21 carbon atoms, preferably a linear or branched alkyl or alkenyl group having 12 to 21 carbon atoms. .

The number of carbon atoms of R1 is 6 to 9, preferably 7 to 8, and more preferably 7. R2 and R3 have 2 to 6, preferably 3 to 5, more preferably 4 carbon atoms.
It is. R4 has 12 to 21, preferably 14 carbon atoms.
To 19, more preferably 17. Further, in the structural formula (1), particularly preferably, R1 is a group (A) or a group (B) represented by the following formula (4).

[0027]

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The fatty acids used as raw materials for the fatty acid esters of the structural formulas (1) and (2) include acetic acid, propionic acid,
Aliphatic carboxylic acids such as octanoic acid, 2-ethylhexanoic acid, lauric acid, myristic acid, stearic acid, palmitic acid, behenic acid, arachinic acid, oleic acid, linoleic acid, linoleic acid, elaidic acid, palmitoleic acid, and the like Mixtures are mentioned.

As the fatty acid ester of the structural formula (1),
Isoheptyl stearate is preferred. Preferred examples of the fatty acid ester of the structural formula (2) include butoxyethyl stearate, s-butoxyethyl stearate, butoxyethyl oleate, butoxyethyl palmitate,
s-butoxyethyl palmitate, butoxypropyl stearate, s-butoxypropyl stearate, butoxypropyl oleate, butoxypropyl palmitate, s-butoxypropyl palmitate, butoxyheptyl stearate, butoxyoctyl stearate, butoxyheptyl palmitate And various ester compounds such as butoxyoctyl palmitate.

Furthermore, in order to reduce the hydrolysis of fatty acid esters which often occur when a magnetic recording disk is used under high humidity, the fatty acid and alcohol used as raw materials should have different isomer structures such as branched / straight chain, cis / trans and the like, and branch positions. You can choose. More preferred fatty acid esters include butoxyethyl stearate or s-butoxyethyl stearate, butoxypropyl stearate, s
-Butoxyethyl palmitate, butoxypropyl palmitate.

Since these lubricants have an appropriate molecular weight, they have an advantage that they can easily move in the layer, have a high replenishing effect, and are difficult to evaporate. Here, the lubricant of the structural formula (1) is at least 30% by weight or more, preferably 35 to 70% by weight, particularly preferably 40% by weight, of the total content of the lubricants of the structural formulas (1) and (2). ６０60% by weight.

If the lubricant content is less than 30% by weight,
On the other hand, if the content is more than 70% by weight, a sufficient replenishing effect cannot be obtained, and no effect is obtained in running durability. These lubricants are used in an amount of 3 to 20 parts by weight, preferably 5 to 15 parts by weight, more preferably 8 to 12 parts by weight based on 100 parts by weight of the ferromagnetic powder and the nonmagnetic powder contained in the magnetic layer and the nonmagnetic layer. Parts. If the amount is less than 3 parts by weight, a sufficient replenishing effect cannot be obtained. On the other hand, if the amount is more than 20 parts by weight, the replenishing effect is too large, the amount of the lubricant present on the surface of the magnetic layer becomes excessive, the head sticks easily in running durability, and the adhesion between the magnetic layer and the non-magnetic layer decreases. I will.

Furthermore, a lubricant other than the fatty acid esters of the structural formulas (1) and (2) may be included. Also,
By using a so-called wet-on-wet coating method in which the upper layer is provided while the lower layer is in a wet state, the adhesion between the upper layer and the lower layer is improved, and excellent running durability is obtained. The solvent contained in the upper layer does not dissolve the dried and solidified surface of the non-magnetic layer, and the smooth surface property of the magnetic layer can be obtained as described above, and a high reproduction output can be achieved.

According to the present invention, the thickness of the magnetic layer can be controlled to be as thin as 0.5 μm or less, and the overwrite characteristics unique to digital recording can be greatly improved. The higher the linear recording density, that is, the shorter the recording wavelength, the more the effect of the magnetic layer thickness is exerted. In particular, the wavelength is 1.4.
If the thickness is less than μm, the thickness of the magnetic layer must be 0.5 μm or less.

As described above, ferromagnetic metal powder or ferromagnetic hexagonal ferrite powder is suitable as the ferromagnetic powder in such a high recording density thin magnetic layer magnetic recording disk. It is necessary to obtain a uniform and stable reproduction output. For this purpose, a circularly uniform reproduction output is achieved by obtaining an orientation ratio of at least 0.85 or more. In order to achieve an orientation degree of 0.85 or more, a random orientation method using a permanent magnet or a method disclosed in Japanese Patent Application Laid-Open No. Sho 62-92132 is disclosed in Japanese Patent Publication No. 3-41895 where the upper magnetic layer is in an undried state. As described in JP-A-63-148417, JP-A-1-304247 and JP-A-1-304288, a method of applying an alternating magnetic field can be used.

As described above, in a preferred embodiment of the present invention, the lower layer in which the nonmagnetic powder is dispersed in the binder on the nonmagnetic support and the ferromagnetic powder are added while the lower layer is in a wet state. A magnetic recording disk comprising an upper layer dispersed therein, wherein the orientation ratio of the upper layer is 0.85 or more, and isoheptyl is used as a lubricant with respect to the upper and lower ferromagnetic powders and nonmagnetic powders. The ester comprising stearate and butoxyalkyl alcohol and a fatty acid in the above-mentioned mixing ratio is 100 parts by weight of the ferromagnetic powder (in the case of the upper magnetic layer) or 100 parts by weight of the nonmagnetic powder (in the case of the lower nonmagnetic layer). A high-density recording magnetic recording medium having a high recording density, a large capacity, good electromagnetic conversion characteristics, and excellent running durability is provided by a magnetic recording disk preferably containing 3% by weight to 20% by weight with respect to parts by weight. It is possible to obtain a disk.

As described above, the wet-on-wet coating method for forming the magnetic layer and the nonmagnetic layer is effective for obtaining a highly durable magnetic recording disk.
If the nonmagnetic layer is provided on the support by a conventional blade coating method, a gravure coating method, or the like, and the magnetic layer is further provided after drying, the adhesion between the nonmagnetic layer and the magnetic layer is not sufficient, as in the present invention. Such an ultra-thin magnetic layer had poor durability and was difficult to put into practical use.

According to the present invention, by adopting the wet-on-wet coating method, the nonmagnetic layer and the magnetic layer have characteristics like an integrated layer, and the adhesion between the nonmagnetic layer and the magnetic layer can be increased. Specific examples of the wet-on-wet coating method include the following. 1. First, a non-magnetic layer is applied by a gravure coating, a roll coating, a blade coating, an extrusion coating device, etc., which are generally used in the application of a magnetic paint, and while the layer is in a wet state, for example, 46186, JP-A-60-238179, JP-A-2-265672
A method of applying a magnetic layer using a non-magnetic support pressurized extrusion coating apparatus disclosed in each of the above publications. 2. JP-A-63-88080, JP-A-2-17971
And a method of applying a coating solution for a non-magnetic layer and a coating solution for a magnetic layer almost simultaneously using a head having two built-in coating solution passage slits as disclosed in JP-A-2-265672. 3. A method of applying a coating solution for a non-magnetic layer and a coating solution for a magnetic layer almost simultaneously using an extrusion coating device with a backup roll disclosed in JP-A-2-174965.

In the wet-on-wet coating method, the thickness variation of the magnetic layer can be suppressed and the thickness accuracy can be improved.
And the like. The first is to select a solvent used for the non-magnetic layer coating solution and the magnetic layer coating solution.

Second, a drying method is selected in a drying step after coating on a non-magnetic support by a wet-on-wet coating method. That is, after providing the non-magnetic layer and the magnetic layer on the non-magnetic support, after performing the orientation as needed,
The drying step is performed. By gradually increasing the temperature from room temperature to the drying step, the thickness variation of the magnetic layer in the drying step of the non-magnetic layer and the magnetic layer can be suppressed.

Third, in the wet-on-wet coating method, it is preferable that the viscoelastic properties of the non-magnetic layer coating solution and the magnetic layer coating solution be matched as much as possible. Since the magnetic layer is provided when the non-magnetic layer is in a wet state, if the viscoelastic properties are significantly different, the liquids are disturbed at the interface, and the magnetic layer thickness fluctuates greatly. Means for adjusting the viscoelastic properties include selecting the following factors.

As the factors, for example, regarding the non-magnetic powder or ferromagnetic powder to be dispersed, (1) particle size (specific surface area, average primary particle diameter, etc.), (2) structure (oil absorption, particle morphology, etc.) ), (3) Properties of powder surface (pH, loss on heating, etc.), (4) Attraction force of particles (σ _S, etc.), etc. For binders, (1) molecular weight, (2) type of functional group, etc. Examples of the solvent include (1) the type (polarity, etc.), (2) the solubility of the binder, (3) the amount of the solvent, the water content, and the like.

Fourth, it is desirable that the raw material particles used in each coating solution for the nonmagnetic layer and the magnetic layer have a size smaller than at least the thickness of the dried nonmagnetic layer and the magnetic layer. That is, when the ferromagnetic powder, carbon black particles, abrasive particles, and non-magnetic particles used are used in the magnetic layer, at least a maximum of 0.1% is used.
5 μm or less is desirable. In the case of the non-magnetic layer, the thickness is not regulated, so that the film thickness can be increased depending on the particle size used.

Fifth, the size and shape of various powders contained in the magnetic layer coating solution and / or the non-magnetic layer coating solution are specified so that a mixed region is not mechanically generated at the interface between the magnetic layer and the non-magnetic layer. Can be controlled as follows. For example, when needle-shaped non-magnetic powders are used, if they are aligned, they form a strong coating even in an undried state, and even when the ferromagnetic powder of the magnetic layer rotates, mixing occurs at the interface. It becomes difficult. or,
When flake-like non-magnetic powder is used for the non-magnetic layer, the flakes are laid in a so-called tile-like manner, so that even when the ferromagnetic powder of the magnetic layer rotates, mixing at the interface hardly occurs.

In the magnetic recording disk of the present invention, the ferromagnetic powder contained in the magnetic layer may be an iron oxide-based ferromagnetic powder, a ferromagnetic metal powder, or a ferromagnetic hexagonal ferrite powder. Powder or ferromagnetic hexagonal ferrite powder is preferred. When the ferromagnetic powder is a ferromagnetic metal powder, the particle size is preferably such that the specific surface area is 30 to 60 m ² / g, the crystallite size determined by X-ray diffraction is 100 to 300 °, The ratio (long axis length / short axis length) is 5 or more.

If the specific surface area is too small, it is impossible to sufficiently cope with high-density recording, and if it is too large, dispersion cannot be sufficiently performed, so that a magnetic layer having a smooth surface cannot be formed, and it is impossible to cope with high-density recording. It is not preferable. Here, the crystallite size is determined from the spread of the half value width of the diffraction lines on the (1,1,0) plane and the (2,2,0) plane. When the ferromagnetic powder is a ferromagnetic hexagonal ferrite powder, the specific surface area is 25 to
50 m ² / g, and the plate ratio (plate diameter / plate thickness) is 2 to 2.
6. The plate diameter is 0.02 to 1.0 μm.

For the same reason as the ferromagnetic metal powder, if the particle size is too large or too small, high density recording becomes difficult. The ferromagnetic metal powder preferably comprises at least Fe
And specifically, Fe, Fe—C
o, a simple metal or an alloy mainly composed of Fe-Ni or Fe-Ni-Co. In order to increase the recording density of the magnetic recording disk of the present invention, it is preferable that the particle size is small as described above, and at the same time, as the magnetic characteristics, the saturation magnetization (σ _S ) is at least 110 emu / g or more, preferably 120 emu / g or more. g or more. The coercive force is 800 Oe (Oersted) or more, preferably 90 Oe.
0 Oe or more.

To further improve the properties, B,
Non-metals such as C, Al, Si, and P may be added. Usually, an oxide layer is formed on the particle surface of the metal powder for chemical stability. As a method for forming an oxide, a known slow oxidation treatment, that is, a method of immersing in an organic solvent and then drying, a method of immersing in an organic solvent and then feeding an oxygen-containing gas to form an oxide film on the surface and then drying, A method of forming an oxide film on the surface by adjusting the partial pressure of an oxygen gas and an inert gas without using a solvent, and the like, may be used.

The ferromagnetic hexagonal ferrite powder is a ferromagnetic powder having a tabular shape and having an easy axis of magnetization in a direction perpendicular to the plane of the ferrite, such as barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, or the like. Of these, a cobalt-substituted product of barium ferrite and a cobalt-substituted product of strontium ferrite are particularly preferable. In order to further improve the characteristics as necessary, In, Zn, Ge, N
Elements such as b and V may be added.

In order to increase the recording density of the magnetic recording disk of the present invention, it is preferable to reduce the particle size of the magnetic layer of the hexagonal ferrite powder as described above. (σ _S ) is at least 50 emu / g or more, desirably 53 emu / g
g or more. The coercive force is desirably 500 Oe or more, particularly preferably 600 Oe or more.

In the present invention, when a ferromagnetic metal powder or a hexagonal ferrite powder is used, a high orientation ratio as high as 0.9 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, VSM-PI (manufactured by Toei Kogyo Co., Ltd.) at a maximum applied magnetic field of 10 kOe. The measurement of the specific surface area is based on the BET method using Canter Soap (manufactured by Canter Chrome, USA). This is a value measured by the BET one-point method (partial pressure 0.30) after dehydration in a nitrogen atmosphere at 250 ° C. for 30 minutes.

The water content of these ferromagnetic powders is set at 0.1.
It is preferable that the content be 01 to 2% by weight. The moisture content is preferably optimized depending on the type of the binder resin. Preferably, the pH of the ferromagnetic powder is also optimized by a combination with the binder resin used. The range is from 4 to 12, but preferably from 5 to 10. A ferromagnetic powder can be used if necessary.
Surface treatment may be performed with l, Si, P, or an oxide thereof. The amount is 0.1 to
When the surface treatment is performed, the adsorption of a lubricant such as a fatty acid becomes 100 mg / m ² or less, which is preferable. The ferromagnetic powder may contain inorganic ions such as soluble Na, Ca, Fe, Ni, and Sr, but if it is 500 ppm or less, the characteristics are not particularly affected.

The ferromagnetic powder usable in the magnetic recording disk of the present invention has a specific surface area of 25 to 80 m by the BET method.
² / g, and preferably 35 to 60 m ² / g.
At 25 m ² / g or less, the noise increases, and 80 m ² / g
Above is difficult to obtain surface properties, which is not preferable. The crystallite size as measured by X-ray diffraction is between 450 and 100 Angstroms, preferably between 350 and 100 Angstroms. σ _S is 50 emu / g or more, preferably 70 emu / g or more.

These ferromagnetic powders may be preliminarily treated with a dispersant, a lubricant, a surfactant, an antistatic agent or the like before dispersion before dispersion. Specifically, it is described in JP-B-44-14090 or the like. The thickness of the magnetic recording disk is such that the nonmagnetic support is
0 μm, preferably 20 to 85 μm, and the non-magnetic layer
10 μm, the magnetic layer being 0.8 μm or less, preferably 0.1 μm or less.
5 μm or less. Further, an undercoat layer for improving adhesion may be provided between the nonmagnetic support and the nonmagnetic layer.
This thickness is 0.01 to 2 μm, preferably 0.05 to
0.5 μm. Further, a back coat layer may be provided on the non-magnetic support on the side opposite to the magnetic layer side. This thickness is 0.1 to 2 μm, preferably 0.3 to 1.0 μm. Known undercoating layers and backcoat layers can be used. The magnetic recording disk of the present invention may have a magnetic layer on both sides or one side. Further, a resin and / or lubricant layer may be provided as a protective layer on the surface of the magnetic layer.

The non-magnetic powder that can be used in the non-magnetic layer of the present invention may be an inorganic powder or an organic powder, and may be carbon black. Examples of the nonmagnetic inorganic powder include metals, metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, metal sulfides, and the like. Specifically, TiO ₂ (rutile, anatase), TiO _X , cerium oxide, tin oxide, tungsten oxide, ZnO, Z
rO ₂ , SiO ₂ , Cr ₂ O ₃ , α-alumina, β-alumina, γ-alumina having α conversion of 90% or more, α-iron oxide, goethite, corundum, silicon nitride, titanium carbide, magnesium oxide, boron nitride, 2 Molybdenum sulfide, copper oxide, MgCO ₃ , CaCO ₃ , BaCO ₃ , SrC
O ₃ , BaSO ₄ , CaSO ₄ , silicon carbide and the like are used alone or in combination. The shape and size of these inorganic powders are arbitrary, such as needle-like, spherical, dice-like,
These can be combined with different inorganic powders as needed, or the particle size distribution and the like can be selected even with a single non-magnetic powder. The particle size is preferably from 0.01 to 2 μm. The following are preferred as the nonmagnetic powder.

The tap density is 0.3 to 2 g / cc, the water content is 0.1 to 5%, the pH is 2 to 11, and the specific surface area is 1 to 30.
m ² / g is preferred. The above non-magnetic powder is not necessarily 10
It need not be 0% pure and the surface may be coated with another compound, such as Al, Si, Ti, Zr, Sn, Sb, depending on the purpose.
The oxide may be formed on the surface by treatment with each compound such as Zn. At this time, if the purity is 70% or more, the effect is not reduced. The ignition loss is preferably 20% or less.

Specific examples of the nonmagnetic powder used in the present invention include AKP-20 and AKP-3 manufactured by Sumitomo Chemical Co., Ltd.
0, AKP-50, HIT-50, G manufactured by Nippon Chemical Industry Co., Ltd.
5, G7, S-1, TF-100, TF- manufactured by Toda Kogyo
120, TF-140, TT055 series manufactured by Ishihara Sangyo Co., Ltd., ET300W, STT30 manufactured by Titanium Industry Co., Ltd., and the like.

The non-magnetic organic powder used in the present invention comprises:
Acrylic styrene resin powder, benzoguanamine resin powder, melamine resin powder, and phthalocyanine pigment are listed, but polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, and polyfluoroethylene resin powder are used. Is done. Its production method is described in JP-A-62-18564 and JP-A-60-25558.
No. 7 can be used.

Examples of the abrasive used for the magnetic layer or non-magnetic layer of the present invention include α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum having an α conversion of 90% or more. , Artificial corundum, emery (main components: corundum and magnetite), artificial diamond, garnet, silicon nitride, silicon carbide, titanium carbide, titanium oxide, silicon dioxide, boron nitride, and other known materials mainly having a Mohs hardness of 5 or more. Used alone or in combination. Further, a composite of these abrasives (abrasive whose surface is treated with another abrasive) may be used. These abrasives may contain compounds or elements other than the main component, but the effect remains unchanged if the main component is 90% or more.

The average particle size of these abrasives is 0.05 to 2 μm.
Those having a size of m are effective, preferably from 0.2 to
1.0 μm. In particular, when it is used for a magnetic layer, it is preferably at least 0.5 μm. If necessary, abrasives having different particle sizes may be combined, or even a single abrasive may have the same effect by broadening the particle size distribution. Tap density 0.3-2g / cc, water content 0.1-5%, p
H is preferably ^{2 to} 11, and the specific surface area is preferably 1 to 30 m ² / g. The shape of the abrasive used in the present invention may be any of a needle shape, a spherical shape, and a die shape.

These abrasives are added in an amount of 3 to 20 parts by weight based on 100 parts by weight of the nonmagnetic layer, the nonmagnetic powder of the magnetic layer, and the ferromagnetic powder. If the amount is less than 3 parts by weight, sufficient durability cannot be obtained, and if it is more than 20 parts by weight, the filling degree decreases, and a sufficient output cannot be obtained. These abrasives, in the non-magnetic layer, the amount and type of the non-magnetic powder contained, in the magnetic layer, the amount and type of the ferromagnetic powder in the magnetic layer, the combination thereof is changed according to the purpose, and, of course, can be properly used depending on the purpose. It is possible. For example, to improve the durability of the magnetic layer surface, increase the amount of the abrasive in the nonmagnetic layer, and to improve the durability of the end surface of the magnetic layer, increase the amount of the abrasive in the magnetic layer. be able to. These abrasives may be dispersed in a binder in advance and then added to a magnetic paint or a non-magnetic paint. The abrasive present on the surface of the magnetic layer and the end face of the magnetic layer of the magnetic recording disk of the present invention is 5/1.
It is preferably at least 00 μm ² .

Specific examples of the polishing agent used in the present invention include AKP-20, AKP-30, and 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 magnetic layer and non-magnetic layer of the magnetic recording disk of the present invention may contain conductive particles in addition to the ferromagnetic powder, non-magnetic powder and abrasive. In particular, it is preferable to use carbon black for the nonmagnetic layer as the conductive powder from the viewpoint of preventing static charge.

In the present invention, as the carbon black which can be used for the non-magnetic layer or the magnetic layer, those of any production method can be used. For example, furnace black,
Thermal black, acetylene black, channel black, lamp black and the like can be used. Specific surface area is 5 to 500 m ² / g, DBP oil absorption is 10
１1500 mL (milliliter) / 100 g, average particle size is 5 to 300 mμ, pH is 2 to 10, and water content is 0.1 to 0.1 mL.
The tap density is preferably 0.1 to 1 g / cc. The DBP oil absorption of carbon black is determined by adding dibutyl phthalate to the carbon black powder little by little, observing the state of the carbon black while kneading, and finding the point where the dispersed state forms a single lump from the dispersed state. The amount (mL) was taken as the DBP oil absorption.

As a specific example, BL manufactured by Cabot Corporation;
ACKPEARLS 2000, 1300, 1000,
900, 800, 700, VULCAN XC-72,
Asahi Carbon Co .; # 80, # 60, # 55, # 50, #
35, manufactured by Mitsubishi Kasei Kogyo; # 3950B, # 2400
B, # 2300, # 900, # 1000, # 30, # 4
0, # 10B, manufactured by Columbia Carbon Co .; CONDUC
TEX SC, RAVEN 150, 50, 40, 1
5, manufactured by Lion Akzo; Ketjen Black EC, Ketjen Black ECDJ-500, Ketjen Black ECDJ-600, and the like.

The carbon black may be subjected to a surface treatment with a dispersant or the like, or may be grafted with a resin, or may be a carbon black obtained by partially graphitizing the surface. Also,
Before adding the carbon black to the coating solution for the non-magnetic layer or the coating solution for the magnetic layer, the carbon black may be dispersed with a binder in advance. These carbon blacks can be used alone or in combination.

The content of carbon black in the nonmagnetic layer is preferably 3 to 20% by weight of the total amount of nonmagnetic powder contained in the nonmagnetic layer. As a result, the amount of carbon black added in the magnetic layer can be reduced, and the packing density of the ferromagnetic powder can be secured. Since the carbon black forms a structure, a low surface electric resistance can be obtained.
For this reason, the surface specific electric resistance of the magnetic layer can also be kept low, and the occurrence of dropout in running durability can be reduced.

In the present invention, the magnetic layer has a surface specific electric resistance of 5 × 10 ⁹ Ω / cm ² or less, preferably 5 × 10 ⁹ Ω / cm ² or less.
It is desirable to adjust to 10 ⁸ Ω / cm ² or less. Further, a smooth surface property of the non-magnetic layer / magnetic layer can be obtained, a spacing loss with the recording / reproducing head can be reduced, and a high reproducing output can be obtained. DBP oil absorption is 200mL / 10
Carbon black of 0 g or more can easily form a structure, and as a result, can obtain a low surface electric resistance,
The occurrence of dropout in running durability can be particularly reduced, which is preferable.

Further, carbon black can be contained in the magnetic layer. In this case, the ferromagnetic powder may be used in an amount of 0.1.
It is preferable to use 1 to 30% by weight. When carbon black is used in the magnetic layer, the amount of the carbon black is preferably 0.1 to 30% by weight based on the ferromagnetic powder. Carbon black has functions such as antistaticity of the magnetic layer and non-magnetic layer, reduction of the coefficient of friction, provision of light-shielding properties, improvement of film strength, and the like, which differ depending on the carbon black used. Therefore, these carbon blacks used in the present invention are different in type, amount and combination in the non-magnetic layer and the magnetic layer, and are based on the above-mentioned properties such as particle size, oil absorption, conductivity, and pH. Of course, it is possible to use them properly according to the purpose. The carbon black that can be used in the present invention can be referred to, for example, “Carbon Black Handbook” (edited by Carbon Black Association).

As the binder used for the magnetic layer and the non-magnetic layer of the present invention, conventionally known thermoplastic resins, thermosetting resins,
Reactive resins and mixtures thereof are used. As the thermoplastic resin, the glass transition temperature is -100 to 150C, the number average molecular weight is 1,000 to 200,000, preferably 10
000 to 100,000 and a degree of polymerization of about 50 to 1,000. Such examples include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylates, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic esters, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, There are polymers or copolymers containing vinyl ether, etc. as constituent units, polyurethane resins, and various rubber resins.

Examples of the thermosetting resin or the reactive resin include phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic reaction resin, formaldehyde resin, silicone resin, and epoxy-polyamide resin. , A mixture of a polyester resin and an isocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, and a mixture of a polyurethane and a polyisocyanate.

These resins are described in detail in "Plastic Handbook" published by Asakura Shoten. Further, a known electron beam-curable resin can be used for the non-magnetic layer or the magnetic layer. These examples and the method for producing them are described in detail in JP-A-62-256219. The above resins can be used alone or in combination, but are preferably selected from the group consisting of vinyl chloride resin, vinyl chloride vinyl acetate resin, vinyl chloride vinyl acetate vinyl alcohol resin, vinyl chloride vinyl acetate maleic anhydride copolymer, and nitrocellulose. And a combination of at least one of these and a polyurethane resin, or a combination of these with a polyisocyanate.

As the structure of the polyurethane resin, known materials such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. For all of the binders shown here, COO is required to obtain better dispersibility and durability.
M, SO ₃ M, OSO ₃ M, P = O (OM) ₂ , OP
ＯO (OM) ₂ , where M is a hydrogen atom or an alkali metal, OH, NR ₂ , N ⁺ R ₃ , (R is a hydrocarbon group), epoxy group, SH, CN, etc. It is preferable to use one obtained by introducing one or more polar groups by copolymerization or addition reaction. The amount of such a polar group is from 10 ^-1 to 10 ^-8 mol / g, preferably from 10 ^-1 to 10 ^-8 mol / g.
^-2 to 10 ^-6 mol / g.

Specific examples of these binders used in the present invention include those manufactured by Union Carbide: VAGH, V
YHH, VMCH, VAGF, VAGD, VROH, V
YES, VYNC, VMCC, XYHL, XYSG, P
KHH, 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: 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, manufactured by Dainippon Ink Co., Ltd .: Pandex T-5105, T-R30
80, T-5201, Barnock D-400, D-21
0-80, Chris Bon 6109, 7209, manufactured by Toyobo: 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 Kasei: MX5004, manufactured by Sanyo Kasei: Samprene SP-150, manufactured by Asahi Kasei: Saran F310, F
210 and the like.

The binder used in the magnetic layer of the present invention is in the range of 5 to 50% by weight, preferably 10 to 50% by weight, based on the ferromagnetic powder, and the binder used in the non-magnetic layer is based on the non-magnetic powder.
It is used in the range of ３０30% by weight. 5 to 100% by weight when using a vinyl chloride resin, 2 to 50% by weight when using a polyurethane resin,
It is preferable to use these in combination in the range of １００100% by weight.

In the present invention, when a polyurethane resin is used, the glass transition temperature is −50 to 100 ° C., the breaking elongation is 100 to 2000%, and the breaking stress is 0.05 to 10 kg.
/ Cm ² , and the yield point is preferably 0.05 to 10 kg / cm ² . 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 by a plurality of layers. Here, the composition of the coating liquid for each layer may be the same or different, and the type, size, etc. of the powder can be variously selected. As a method of applying these layer coating solutions by a wet-on-wet coating method, the above-described method may be basically applied.

Therefore, the type of powder, its amount, amount of binder,
The amount of vinyl chloride resin, polyurethane resin, polyisocyanate or other resin in the binder, the molecular weight of each resin forming the magnetic layer, the amount of polar group, or the physical properties of the resin described above, the present invention Of course, it is possible to change the lubricant composition and the like in each layer coating solution as required.

The polyisocyanates used in the present invention include tolylene diisocyanate, 4-4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,
Use of isocyanates such as 5-diisocyanate, o-toluidine isocyanate, isophorone diisocyanate, and triphenylmethane triisocyanate, products of these isocyanates and polyalcohols, and polyisocyanates formed by condensation of isocyanates can do. Commercially available trade names of these isocyanates include Nippon Polyurethane Co .: Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate M
R, Millionate MTL, Takeda Pharmaceutical: Takenate D
-102, Takenate D-110N, Takenate D-2
00, Takenate D-202, manufactured by Sumitomo Bayer: Desmodur L, Desmodur IL, Desmodur N, Desmodur HL, etc. These are used alone or in combination of two or more using the difference in curing reactivity. Each layer can be used in combination.

The dispersants (pigment wetting agents) used in the present invention include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid and linolenic acid. , A fatty acid having 12 to 18 carbon atoms such as stearic acid (R ₁ CO
OH and R ₁ are alkyl or alkenyl groups having 11 to 17 carbon atoms); alkali metals (Li, N
a, K, etc.) or alkaline earth metals (Mg, Ca, B)
a) a fluorine-containing compound of the above-mentioned fatty acid ester; an amide of the above-mentioned fatty acid; a polyalkylene oxide alkyl phosphate; a lecithin; a trialkylpolyolefinoxy quaternary ammonium salt (alkyl having 1 to 1 carbon atoms) 5, olefins such as ethylene and propylene); and the like. In addition, higher alcohols having 12 or more carbon atoms, and sulfate esters and the like can also be used. These dispersants may be ferromagnetic powder (for a magnetic layer) or non-magnetic powder (for a non-magnetic layer) 100
It is added in the range of 0.5 to 20 parts by weight based on parts by weight.

As the lubricant, the following compounds can be used in addition to the above-mentioned fatty acid esters. That is, fatty acids, fatty acid esters other than those described above, silicone oil, graphite, molybdenum disulfide, boron nitride, fluorinated graphite, fluorinated alcohol, polyolefin, polyglycol, alkyl phosphate, tungsten disulfide and the like.

All or a part of the additives used in the present invention may be added in any step of producing a magnetic paint or a non-magnetic paint. For example, when the additives are mixed with a ferromagnetic powder before the kneading step. There is a case where it is added in a kneading step using a ferromagnetic powder, a binder and a solvent, a case where it is added in a dispersion step, a case where it is added after dispersion, and a case where it is added just before coating.

The non-magnetic support used in the present invention is preferably a flexible and balanced type support. Polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate, polycarbonate And films of various synthetic resins such as polyamide, polyimide, polyamideimide, polysulfone, polyethersulfone, aramid, aromatic polyamide, and syndiotactic polystyrene, and metal foils such as aluminum foil and stainless steel foil. Generally, polyethylene terephthalate is preferred. The thickness of the nonmagnetic support varies depending on the Young's modulus, but generally ranges from 1 to 100.
μm is suitable, and preferably 25 to 85 μm. These supports may be subjected to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, or the like in advance.

In order to achieve the object of the present invention, the non-magnetic support has a center line average surface roughness (Ra) (cutoff value).
0.25 mm) is 0.03 μm or less, preferably 0.03 μm or less.
It is desirable to use one having a size of 2 μm or less, more preferably 0.01 μm or less. Further, these non-magnetic supports not only have a small center line average surface roughness but also have a
It is preferable that there are no coarse protrusions of m or more. The surface roughness shape can be freely controlled by the size and amount of the filler added to the support as needed. Examples of these fillers include Ca, S
In addition to oxides and carbonates such as i and Ti, organic fine powders such as acryl-based are exemplified.

The organic solvent used in the present invention may be any ratio of ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, tetrahydrofuran, methanol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol. Alcohols such as methylcyclohexanol, esters such as methyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, and glycol acetate; glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, and dioxane; benzene; Aromatic hydrocarbons such as toluene, xylene, cresol, chlorobenzene, methylene chloride, ethylene chloride, carbon tetrachloride, Chloroform, ethylene chlorohydrin, dichlorobenzene, chlorinated hydrocarbons and the like, N,
N-dimethylformamide, hexane and the like can be used. These organic solvents are not necessarily 100% pure, and may contain impurities such as isomers, unreacted products, by-products, decomposed products, oxides, and moisture in addition to the main components. These impurities are preferably 30% by weight or less, more preferably 10% by weight or less.

The kind and amount of the organic solvent used in the present invention may be changed between the nonmagnetic layer and the magnetic layer if necessary. Use a highly volatile solvent for the magnetic layer to improve surface properties, use a solvent with a high surface tension (cyclohexanone, dioxane, etc.) for the non-magnetic layer to increase coating stability, and use a solvent with a high solubility parameter for the magnetic layer. Examples include raising the filling degree used, but it is a matter of course that the present invention is not limited to these examples.

The step of producing the magnetic paint and the non-magnetic paint of the magnetic recording medium of the present invention comprises at least a kneading step, a dispersing step, and a mixing step provided before and after these steps as necessary. Each step may be divided into two or more steps. Ferromagnetic powder used in the present invention, non-magnetic powder, binder, carbon black, abrasive,
All raw materials such as an antistatic agent, a lubricant, and a solvent may be added at the beginning or during any step. Further, individual raw materials may be added in two or more steps in a divided manner. For example, polyurethane may be divided and supplied in a kneading step, a dispersing step, and a mixing step for adjusting the viscosity after dispersion.

Various kneaders are used for kneading and dispersing the paints. For example, two-roll mill, three-roll mill, ball mill, pebble mill, tron mill, sand grinder, Segvari, attritor, high-speed impeller disperser, high-speed stone mill, high-speed impact mill, disper, kneader, high-speed mixer, homogenizer, ultra A sound disperser or the like can be used.

In order to achieve the object of the present invention, it is a matter of course that a conventional known manufacturing technique can be used as a part of the process. However, in the kneading step, a strong kneading force such as a continuous kneader or a pressure kneader is used. By using the magnetic recording medium, it is possible to obtain a high Br of the magnetic recording medium of the present invention. When a continuous kneader or a pressure kneader is used, all or a part of the ferromagnetic powder and the binder (however, preferably 30% by weight or more of the total binder) and the ferromagnetic powder 100 are used.
The kneading treatment is performed in a range of 15 to 500 parts per part. The details of these kneading processes are described in JP-A-1-106338.
And JP-A-64-79274. Further, in the present invention, efficient production can be achieved by using a simultaneous multilayer coating method as disclosed in JP-A-62-212933.

Further, a heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimide amide is used as the calendering roll. Further, the treatment can be performed between metal rolls. The processing temperature is preferably 70 ° C. or higher, more preferably 80 ° C. or higher. The linear pressure is preferably 200 kg / cm, more preferably 300 kg / cm or more.

The residual solvent contained in the magnetic layer is preferably 100 mg / m ² or less, more preferably 10 mg / m 2.
² or less, and it is preferable that the residual solvent contained in the magnetic layer be smaller than the residual solvent contained in the nonmagnetic layer. Magnetic layer,
The porosity of the nonmagnetic layer is preferably 30% by volume or less, more preferably 10% by volume or less. The porosity of the nonmagnetic layer is preferably larger than the porosity of the magnetic layer, but may be small as long as the porosity of the nonmagnetic layer is 5% or more.

Although the magnetic recording disk of the present invention has a plurality of layers, it is easily presumed that the physical characteristics of each layer can be changed according to the purpose. For example,
The elastic modulus of the non-magnetic layer is made higher than that of the magnetic layer to improve the contact of the magnetic head with the magnetic recording disk, and the elastic modulus of both the non-magnetic layer and the magnetic layer is increased,
Effects such as improvement in running durability can be easily predicted.

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 ² , and the F-5 value in the web width direction is preferably 3
Was 30 kg / mm ^2, the F-5 value in the web lengthwise direction is higher than F-5 value in the web width direction, but is common, when it is necessary to particularly increase the strength in the width direction thereof Not limited.

The heat shrinkage of the non-magnetic support in the web running direction and the width direction at 100 ° C. for 30 minutes is preferably 3%.
%, More preferably 1.5% or less, and the heat shrinkage at 80 ° C. for 30 minutes is preferably 1% or less, more preferably 0.5% or less. Breaking strength 5-100 in both directions
Kg / mm ² , elastic modulus is 100-2000 Kg / mm ²
Is preferred.

The elastic modulus of the magnetic layer at 0.5% elongation is preferably 100 to 2000 kg / mm in both the running direction and the width direction.
^{2. The} breaking strength is preferably 1 to 30 kg / cm ² , the elastic modulus of the magnetic recording disk is preferably 100 to 1500 kg / mm ^{2 in} the running direction and the width direction, and the residual elongation is preferably 0.5% or less, 100 ° C. or less. Is preferably 1% or less, more preferably 0.5% at all temperatures.
Or less, most preferably 0.1% or less.

According to such a method, the magnetic layer coated on the support is subjected to a treatment for orienting the ferromagnetic powder in the layer if necessary, and then the formed magnetic layer is dried. or,
If necessary, the surface is smoothed or cut into a desired shape to manufacture the magnetic recording disk of the present invention.
The magnetic recording disk of the present invention is most suitable for information recording using a digital recording system where dropout of a signal due to the occurrence of dropout is fatal. However, even in an analog recording system, the advantages can be fully utilized. Of course.

Further, the magnetic recording disk of the present invention is capable of high-density magnetic recording. In particular, the magnetic recording disk has an overwriting characteristic and a reproduction output essential for a digital data recording medium used for storing and reading computer information. The conversion characteristic is
For example, there is an advantage that even if high-density recording in which the shortest recording wavelength is 1.5 μm or less, the recording is not reduced and can be obtained stably, and the running durability does not decrease.

In addition to the case where the recording wavelength is shortened as well as the case where the track density is increased, the use of the magnetic recording disk of the present invention reduces the signal crosstalk and the separability of the peak shift. Excellent recording is possible. Therefore, under the condition that the recording track width is 50 μm or less and the track density is 14 tracks / mm or more, even if the shortest recording wavelength is 1.5 μm or less, the overwriting suitability is excellent.
Recording / reproduction with good running durability is possible.

[0097]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. It is easily understood by those skilled in the art that the components, ratios, operation orders, and the like shown here can be changed without departing from the spirit of the present invention. Therefore, the present invention should not be limited to the following examples. It is to be noted that all “parts” are “parts by weight”.

Example 1 A coating solution for a non-magnetic layer and a coating solution for a magnetic layer were prepared according to the following formulations. Non-magnetic layer paint Non-magnetic inorganic powder 90 parts TiO ₂ (TY50 manufactured by Ishihara Sangyo Co., Ltd.) Average particle diameter 0.34 μm Specific surface area by BET method 5.9 m ² / g pH 5.9 Carbon black 10 parts (Lion Agzo Co., Ltd. Chain Black EC) Average particle size 30 mμ DBP oil absorption 350 mL / 100 g Specific surface area by BET method 950 m ² / g Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 14 parts -N (CH ₃ ) ₃ ⁺ Cl ^- group 5 × 10 ^-6 eq / g content Composition ratio 86: 13: 1 Polymerization degree 400 Polyester polyurethane resin 5 parts Neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1-SO ₃ Na group 1 × 10 ^-4 eq / g-containing isoheptyl stearate [compound of structural formula (1)] 5 parts butoxyethyl stearate [structure Compound of formula (2)] 2 parts Butoxyethyl palmitate [Compound of structural formula (2)] 3 parts Methyl ethyl ketone 200 parts Magnetic layer paint Ferromagnetic metal powder 100 parts Composition Fe / Ni = 96/4 Hc 1600 Oe by BET method Specific surface area 58 m ² / g Crystallite size 195 ° Saturation magnetization (σ _S ) 130 emu / g Average particle size (long axis length) 0.20 μm, needle ratio 10 Vinyl chloride copolymer 14 parts —SO ₃ Na group 1 × ^10-4 eq / g-containing polyester polyurethane resin 3 parts neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1-SO ₃ Na group 1 × 10 ^-4 eq / g-containing α-alumina (average particle Diameter 0.3 μm) 4 parts Carbon black (average particle size 0.10 μm) 2 parts Isoheptyl stearate [compound of structural formula (1)] 5 parts Toxylethyl stearate [compound of structural formula (2)] 2 parts Butoxyethyl palmitate [compound of structural formula (2)] 3 parts Methyl ethyl ketone 200 parts For each of the above two paints, after kneading each component with a continuous kneader Using a sand mill.
A polyisocyanate ("Coronate L" (manufactured by Nippon Polyurethane Co., Ltd.)) was added to the obtained dispersion to prepare a non-magnetic layer paint.
0 parts, 9 parts to the magnetic layer paint, and further 40 parts of butyl acetate were added to each, and the mixture was filtered using a filter having an average pore diameter of 1 μm to prepare a nonmagnetic layer coating solution and a magnetic layer coating solution, respectively. .

The obtained non-magnetic layer coating solution was dried to a thickness of 2 μm, and immediately thereafter, the thickness of the magnetic layer was set to 62 μm so that the thickness of the magnetic layer became 0.45 μm. Simultaneous multi-layer coating is performed on a polyethylene terephthalate support having a surface roughness of 0.01 μm. After passing through the generator, and performing random orientation treatment and drying, the temperature is 90 ° C and the linear pressure is 3 with a 7-stage calender.
After processing at 00 kg / cm and punching into a 3.5-inch size and subjecting to surface polishing, the product was placed in a 3.5-inch cartridge with a liner installed inside, and predetermined mechanical components were added. An inch floppy disk was obtained.

Example 2 A sample was prepared in the same manner as in Example 1 except that butoxyethyl stearate and butoxyethyl palmitate used for the nonmagnetic layer in Example 1 were changed as follows. Butoxypropyl stearate 2 parts Butoxypropyl palmitate 3 parts Example 3 Same as Example 1 except that butoxyethyl stearate and butoxyethyl palmitate used for the nonmagnetic layer in Example 1 were changed as follows. To make a sample.

Butoxyethyl oleate 5 parts Example 4 The non-magnetic layer coating solution in Example 1 was dried to a thickness of 2
Example 1 except that the magnetic layer was dried so as to have a dry thickness of 0.3 μm.
A sample was prepared in the same manner as described above.

Comparative Example 1 A sample was prepared in the same manner as in Example 1 except that the amount of isoheptyl stearate used for the magnetic layer and the nonmagnetic layer was changed from 5 parts to 1 part. Comparative Example 2 A sample was prepared in the same manner as in Example 1 except that the power of the AC magnetic field alignment device was turned off and random alignment treatment was not performed.

Example 5 The procedure of Example 1 was repeated except that the amounts of isoheptyl stearate, butoxyethyl stearate and butoxyethyl palmitate used in the nonmagnetic layer in Example 1 were changed as follows. To make a sample. Isoheptyl stearate 12 parts Butoxyethyl stearate 6 parts Butoxyethyl palmitate 6 parts Comparative Example 3 Isoheptyl stearate, butoxyethyl stearate and butoxyethyl palmitate used for the nonmagnetic layer in Example 1 were not added. Other than the above, a sample was prepared in the same manner as in Example 1.

Comparative Example 4 The lubricants used for the non-magnetic layer and the magnetic layer in Example 1 (isoheptyl stearate, butoxyethyl stearate,
A sample was prepared in the same manner as in Example 1 except that (butoxyethyl palmitate) was changed to the following fatty acids. Oleic acid 9 parts Stearic acid 2 parts Example 6 The non-magnetic layer coating solution in Example 1 was dried to a thickness of 2
A sample was prepared in the same manner as in Example 1, except that the thickness of the magnetic layer was 0.9 μm on the magnetic layer immediately after that, and then the thickness was set to 0.9 μm.

Comparative Example 5 The same magnetic layer formulation as in Example 1 was applied to the same polyethylene terephthalate support as in Example 1 after drying so as to have a thickness of 0.45 μm. Under the same conditions as above, random orientation, drying and calendering were performed to prepare a sample (no nonmagnetic layer was provided).

Comparative Example 6 In Example 1, 10 parts of isoheptyl stearate was used instead of 5 parts of isoheptyl stearate, 2 parts of butoxyethyl stearate and 3 parts of butoxyethyl palmitate in the nonmagnetic layer and the magnetic layer. A 3.5-inch floppy disk was obtained under the same conditions as in Example 1 except for the above.

Comparative Example 7 In Example 1, 10 parts of butoxyethyl stearate were used instead of 5 parts of isoheptyl stearate, 2 parts of butoxyethyl stearate, and 3 parts of butoxyethyl palmitate in the nonmagnetic layer and the magnetic layer. A 3.5-inch floppy disk was obtained under the same conditions as in Example 1 except for the above.

Comparative Example 8 In Example 1, 5 parts of isotridecyl stearate was used instead of 5 parts of isoheptyl stearate, 2 parts of butoxyethyl stearate and 3 parts of butoxyethyl palmitate in the nonmagnetic layer and the magnetic layer. A 3.5-inch floppy disk was obtained under the same conditions as in Example 1 except that butoxyethyl stearate was changed to 2 parts and butoxyethyl palmitate was changed to 3 parts.

Comparative Example 9 The procedure of Example 1 was repeated, except that 5 parts of isoheptyl stearate, 2 parts of butoxyethyl stearate, and 3 parts of butoxyethyl palmitate in the nonmagnetic layer and the magnetic layer were replaced with 5 parts of isopropyl stearate and butoxy. A 3.5-inch floppy disk was obtained under the same conditions as in Example 1, except that 2 parts of ethyl stearate and 3 parts of butoxyethyl palmitate were used.

Example 7 A coating solution for a non-magnetic layer and a coating solution for a magnetic layer were prepared according to the following formulations. Non-magnetic layer paint Non-magnetic inorganic powder 90 parts TiO ₂ (TY50 manufactured by Ishihara Sangyo Co., Ltd.) Average particle diameter 0.34 μm Specific surface area by BET method 5.9 m ² / g pH 5.9 Carbon black 10 parts (Lion Agzo Co., Ltd. Chen black EC) average particle size 30Emumyu DBP oil absorption of 350 mL / 100 g BET method by a specific surface area of 950 meters ² / g vinyl chloride - vinyl acetate - vinyl alcohol copolymer 14 parts ^{_{-N (CH 3) 3 + Cl}} - group 5 × 10 ^-6 eq / g content Composition ratio 86: 13: 1 Degree of polymerization 400 Polyester polyurethane resin 5 parts Neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1-SO ₃ Na group 1 × 10 ^-4 eq / g-containing isoheptyl stearate [compound of structural formula (1)] 5 parts butoxyethyl stearate [structure Compound of formula (2)] 2 parts Butoxyethyl palmitate [Compound of structural formula (2)] 3 parts Methyl ethyl ketone 200 parts Magnetic layer paint Ferromagnetic hexagonal ferrite powder 100 parts Hexagonal barium ferrite powder Hc 1400 Oe by BET method Specific surface area 45 m ² / g Saturation magnetization (σ _S ) 65 emu / g Average particle size (plate diameter) 0.06 μm, plate ratio 5.2 Vinyl chloride copolymer 12 parts —SO ₃ Na group 1 × 10 ^-4 eq / g-containing polyester polyurethane resin 3 parts neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1-SO ₃ Na group 1 × 10 ^-4 eq / g-containing α-alumina (AKP manufactured by Sumitomo Chemical Co., Ltd.) -30) 10 parts average particle size 0.2 [mu] m, a specific surface area of 7.5 m ² / g of carbon black (average particle size 0.10 .mu.m) 2 parts Isohepu Rustearate [compound of structural formula (1)] 5 parts Butoxyethyl stearate [compound of structural formula (2)] 2 parts Butoxyethyl palmitate [compound of structural formula (2)] 3 parts Methyl ethyl ketone 200 parts For each of the paints, each component was kneaded with a continuous kneader and then dispersed using a sand mill.
To the resulting dispersion was added 10 parts of polyisocyanate ("Coronate L") for the non-magnetic layer coating, 9 parts for the magnetic layer coating, and 40 parts of butyl acetate each.
The solution was filtered using a filter having an average pore size of μm to prepare a coating solution for the non-magnetic layer and a coating solution for the magnetic layer.

The non-magnetic layer coating solution was dried to a thickness of 2 μm, and immediately after that, the thickness of the magnetic layer was set to 62 μm so that the thickness of the magnetic layer became 0.45 μm. Simultaneous multi-layer coating is performed on a polyethylene terephthalate support having a surface roughness of 0.01 μm, and while both layers are still in a wet state, 3
The permanent magnet was arranged at the upper limit so as to reach 000 G, and was passed between them to perform vertical orientation. After drying, the plate is treated at a temperature of 90 ° C. and a linear pressure of 300 kg / cm with a 7-stage calender, punched into a 3.5-inch size and subjected to surface polishing, and then a 3.5-inch liner is installed inside. The cartridge was placed in a cartridge, and predetermined mechanical components were added thereto to obtain a 3.5-inch floppy disk.

Example 8 A sample was prepared in the same manner as in Example 7 except that butoxyethyl stearate and butoxyethyl palmitate used for the nonmagnetic layer in Example 7 were changed as follows. Butoxypropyl stearate 2 parts Butoxypropyl palmitate 3 parts Example 9 Same as Example 7 except that butoxyethyl stearate and butoxyethyl palmitate used for the nonmagnetic layer in Example 7 were changed as follows. To make a sample.

Butoxyethyl oleate 5 parts Example 10 The non-magnetic layer coating solution in Example 7 was dried to a thickness of 2
Example 7 except that the magnetic layer was immediately coated thereon so as to have a dry thickness of 0.3 μm.
A sample was prepared in the same manner as described above.

Example 11 The procedure of Example 7 was repeated, except that the amounts of isoheptyl stearate, butoxyethyl stearate, and butoxyethyl palmitate used for the nonmagnetic layer in Example 7 were changed as follows. To make a sample. Isoheptyl stearate 12 parts Butoxyethyl stearate 6 parts Butoxyethyl palmitate 6 parts Comparative Example 10 Isoheptyl stearate, butoxyethyl stearate and butoxyethyl palmitate used for the nonmagnetic layer in Example 7 were not added. Other than the above, a sample was prepared in the same manner as in Example 1.

Comparative Example 11 The lubricants (isoheptyl stearate, butoxyethyl stearate,
A sample was prepared in the same manner as in Example 7, except that (butoxyethyl palmitate) was changed to the following fatty acids. 9 parts of oleic acid 2 parts of stearic acid Example 12 The non-magnetic layer coating solution in Example 7 was dried to a thickness of 2
A sample was prepared in the same manner as in Example 7, except that the thickness of the magnetic layer was set to 0.9 μm on the magnetic layer immediately after that, and the thickness was set to 0.9 μm.

Comparative Example 12 The same magnetic layer formulation as in Example 7 was applied to the same polyethylene terephthalate support as in Example 7 after drying so as to have a thickness of 0.45 μm. The sample was prepared by performing vertical alignment, drying, and calendering treatment under the same conditions as described above (no nonmagnetic layer was provided).

Each sample of the floppy disk thus obtained was measured by the following evaluation method. 1. Orientation degree ratio: Using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.), applying a magnetic field of Hm10KOe to measure 10
The magnetic field was rotated from 0 to 360 degrees at every degree to determine the squareness ratio, and a value obtained by dividing the minimum value of the squareness ratio by the maximum value was calculated to be the degree of orientation. 2. Measurement of reproduction output: The reproduction output was measured using a disk tester SK606B manufactured by Tokyo Engineering, using a metal in gap head having a gap length of 0.45 μm, a recording frequency of 625 kHz, and a radius of 24.6.
After recording at the position of mm, the reproduction output of the head amplifier was measured with an oscilloscope type 7633 manufactured by Tektronix. The reproduction output is described as a relative value with the reproduction output of Example 1 being 100. 3. Modulation (Mo): Determined by the following equation from the maximum value Vmax and the minimum value Vmin in one round of the reproduction waveform using the same conditions and apparatus as in the measurement of the reproduction output.

Mo = (Vmax−Vmin) / (Vma
x + Vmin) 4. Overwriting (overwriting): The overwriting characteristics were recorded at 39.5 mm using the above-described test apparatus, at 312.5 kHz on an AC demagnetized sample, and measured using an ADVANTEST TR4171 type spectrum analyzer at 312.5 kHz.
Immediately after measuring the output 01 (dB) of the kHz component, 1
MHz was overwritten, and overwriting 02-01 (dB) was obtained from the output 02 (dB) of the 312.5 kHz component at that time. 5. Running durability: After recording on all 240 tracks at a recording frequency of 625 kHz using a floppy disk drive FD1331 manufactured by NEC Corporation, the radius is 37.
At a position of 25 mm, a thermocycle test in which the thermocycle flow described in Table 1 was one cycle was performed. Under these thermo-conditions, running durability was evaluated based on the running state when the vehicle was run up to 12 million times in the number of passes.

[0119]

[Table 1]

6. Center line average surface roughness (Ra): Cutoff 0.25 using a three-dimensional surface roughness meter (manufactured by Kosaka Laboratories)
mm. Table 2 below shows the evaluation results of the characteristic values of the examples and comparative examples obtained by the above evaluation methods.

[0121]

[Table 2]

Examples 1 to 4 and Examples 7-1 of the present invention
0 indicates excellent characteristics in each of the electromagnetic conversion characteristics of reproduction output, modulation, and overwriting, and shows stable results in cycle durability. On the other hand, in Comparative Example 2 in which a ferromagnetic metal powder not subjected to random orientation treatment was used, the degree of orientation decreased and the modulation was poor.

When the amount of fatty acid ester added to the non-magnetic layer was large, the head was stuck in a short time in cycle durability and stopped, and when the amount was not added, the magnetic layer was scraped in short time in cycle durability. Occurred (Examples 5 and 11, Comparative Examples 3 and 10). Furthermore, Comparative Examples-4 and 11 in which a fatty acid was added instead of the fatty acid ester, and Comparative Examples 5 and 12 in which the nonmagnetic layer was not provided, were stopped by scraping due to cycle durability.

Comparative Example 6 is an example in which the compound of the structural formula (2) was not used, Comparative Example 7 was an example in which the compound of the structural formula (1) was not used, and Comparative Example 8 was an example in which the compound of the structural formula (1) was not used. (1)
Is an example in which R1 has a carbon number larger than that of the present invention, and Comparative Example 9 shows that R1 in the structural formula (1)
Is an example using a carbon number smaller than the present invention,
In any case, running durability is inferior.

When the magnetic layer was dried and thick after drying, sufficient overwrite characteristics were not obtained (Examples 6 and 1).
2). In general, a digital recording medium requires an overwrite characteristic of -30 dB or less.

[0126]

According to the present invention, 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 formed on a non-magnetic support in this order. In the magnetic recording disk, the orientation ratio of the particles of the ferromagnetic powder in the magnetic layer is 0.85 or more, and the magnetic layer and the non-magnetic layer have a lubricant represented by the structural formula (1) as a lubricant. It contains a fatty acid ester compound represented by the formula (2) and a fatty acid ester compound of an alkoxyalkyl alcohol represented by the structural formula (2), and the content of the compound represented by the structural formula (1) is represented by the structural formula (1). At least 30 of the total amount of the compound represented by the formula (2) and the compound represented by the structural formula (2).
% By weight and preferably by applying a wet-on-wet coating method to provide a magnetic layer having a uniform thickness and an extremely thin magnetic layer, excellent running durability, and suitable for high-density recording. A large-capacity magnetic recording disk having excellent conversion characteristics and running stability can be obtained with high productivity.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) G11B 5/71 C10M 105/34 C10N 40:18 WPI / L (QUESTEL)

Claims (6)

(57) [Claims] A magnetic recording comprising 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 formed on a non-magnetic support in this order. In the disk, the orientation ratio of the particles of the ferromagnetic powder in the magnetic layer is 0.85 or more, and the magnetic layer and the nonmagnetic layer are represented by the structural formula (1) shown in Chemical Formula 1. It contains the compound represented by the structural formula (1) and the compound represented by the structural formula (1), and contains the compound represented by the structural formula (1) and the compound represented by the structural formula (2). A magnetic recording disk comprising at least 30% by weight or more of the total amount of the compound. Embedded image 2. The magnetic recording disk according to claim 1, wherein the R1 in the structural formula (1) is a branched alkyl group having 7 carbon atoms. 3. The magnetic recording disk according to claim 1, wherein the R1 in the structural formula (1) is a group (A) or a group (B) according to Chemical Formula 2. Embedded image 4. The magnetic recording disk according to claim 1, wherein the ferromagnetic powder is a ferromagnetic metal powder or a hexagonal ferrite powder. Alternatively, the magnetic recording disk according to claim 2. 5. The magnetic recording medium according to claim 1, wherein said magnetic layer has a thickness of 0.
The magnetic recording disk according to claim 1, wherein the thickness of the magnetic recording disk is 5 μm or less. 6. The magnetic layer, wherein the coating layer for the non-magnetic layer coated on the non-magnetic support is in a wet state,
6. The magnetic recording disk according to claim 1, wherein the magnetic recording disk is formed by applying a coating solution for a magnetic layer onto the coating layer for a nonmagnetic layer.