JPH10320744A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which is improved in electromagnetic conversion characteristics, particularly in bulk density recording characteristics, is excellently made larger in capacity and density and has durability as well and more particularly a disk-shaped magnetic recording medium. SOLUTION: This recording medium is constituted by providing the surface of a base with a substantially nonmagnetic lower layer and providing the surface of this lower layer with a magnetic layer contg. ferromagnetic metallic powder or ferromagnetic powder which is ferromagnetic hexagonal ferrite powder in a binder. In such a case, the magnetic recording medium is a magnetic recording medium for recording signals of 0.17 to 2 Gbit/inch<2> in surface recording density, for which the following magnetic recording medium is used: The dry thickness of the magnetic layer described above is 0.005 to 0.30 μm and the coercive force of the magnetic layer is 1800 oersted. At least the lower layer described above contains fatty acid ester and the C/Fe peak ratio when the surface of the magnetic layer is measured by Auger electron spectroscopy is 5 to 120.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coating type magnetic recording medium having a high recording density. In particular, the present invention relates to a magnetic recording medium for high-density recording, which has a magnetic layer and a substantially non-magnetic lower layer, and includes a ferromagnetic metal powder or a hexagonal ferrite powder as an uppermost layer.

[0002]

2. Description of the Related Art In the field of magnetic disks, 2 MB MF-2HD floppy disks using Co-modified iron oxide have been standardly mounted on personal computers. However, in today's rapidly increasing data capacity, the capacity cannot be said to be sufficient, and it has been desired to increase the capacity of floppy disks.

In the field of magnetic tapes, in recent years, with the spread of office computers such as minicomputers, personal computers, and workstations, magnetic tapes for recording computer data as external storage media (so-called backup tapes).
Research is being actively conducted. In practical use of magnetic tapes for such applications, especially with the downsizing of computers and the increase in information processing capacity, the increase in recording capacity,
In order to achieve miniaturization, improvement in recording capacity is strongly required.

[0004] Conventionally, magnetic recording media have widely been prepared by coating a support with a magnetic layer in which iron oxide, Co-modified iron oxide, CrO ₂ , ferromagnetic metal powder, and hexagonal ferrite powder are dispersed in a binder. Used. Among them, ferromagnetic metal powders and hexagonal ferrite powders are known to be excellent in high density recording characteristics. In the case of a disk, a large-capacity disk using a ferromagnetic metal powder excellent in high-density recording characteristics is 4 MB as a large-capacity disk using 10 MB MF-2TD, 21 MB MF-2SD or hexagonal ferrite.
There are MF-2ED of MB, 21MB floptical, etc., but it was not sufficient in capacity and performance. Under such circumstances, many attempts have been made to improve the high-density recording characteristics. An example is shown below.

In order to improve the characteristics of a disk-shaped magnetic recording medium, Japanese Patent Application Laid-Open No. 64-84418 proposes to use a vinyl chloride resin having an acidic group, an epoxy group and a hydroxyl group. It has been proposed to use a metal powder having a Hc of 1000 Oe (Oe) or more and a specific surface area of 25 to 70 m ² / g. Proposed.

In order to improve the durability of a disk-shaped magnetic recording medium, Japanese Patent Publication No. 7-85304 proposes to use a fatty acid ester having an unsaturated bond with an unsaturated fatty acid ester. It has been proposed to use a fatty acid ester having a fatty acid ester and an ether bond, and JP-A-54-124716 proposes to include a non-magnetic powder having a Mohs hardness of 6 or more and a higher fatty acid ester. Has a volume and surface roughness of 0.005 to 0.025
μm is proposed in Japanese Patent Application Laid-Open No. 61-294637.
It is proposed to use a low melting point and a high melting point fatty acid ester in JP-B-7-36216.
It has been proposed to use an abrasive having a particle size of ４ to ／ and a fatty acid ester having a low melting point, and JP-A-3-203018 proposes to use a ferromagnetic metal powder containing Al and chromium oxide.

As a configuration of a disk-shaped magnetic recording medium having a nonmagnetic lower layer and an intermediate layer, JP-A-3-120613 proposes a configuration having a conductive layer and a magnetic layer containing metal powder, and JP-A-6-290446. Has proposed a structure having a magnetic layer and a non-magnetic layer of 1 μm or less.
337 proposes a configuration including a carbon intermediate layer and a magnetic layer containing a lubricant, and JP-A-5-290358 proposes a configuration having a nonmagnetic layer having a defined carbon size.

On the other hand, a disk-shaped magnetic recording medium comprising a thin magnetic layer and a functional non-magnetic layer has recently been developed.
0MB class floppy disks have appeared. Japanese Patent Application Laid-Open No. 5-109061 shows these features.
Has an Hc of 1400 Oe or more and a thickness of 0.5 μm
A configuration having the following magnetic layer and a non-magnetic layer containing conductive particles has been proposed. Japanese Patent Application Laid-Open No. 5-197946 has proposed a configuration containing an abrasive larger than the magnetic layer thickness.
Japanese Patent Application Laid-Open No. Hei 6-68453 discloses a configuration in which the thickness of the magnetic layer is 0.5 μm or less, the thickness variation of the magnetic layer is within ± 15%, and the surface electric resistance is specified. There has been proposed a configuration in which an abrasive is included and the amount of abrasive on the surface is regulated.

[0009] In recent years, with the spread of office computers such as minicomputers and personal computers, magnetic tapes (so-called backup tapes) for recording computer data as external storage media have been developed for tape-shaped magnetic recording media. Research is being actively conducted. When a magnetic tape for such a purpose is put to practical use, especially in connection with the miniaturization of computers and the increase in information processing capacity, an increase in recording capacity is strongly demanded in order to achieve large-capacity recording and miniaturization. In addition, the use environment of magnetic tapes is widespread, so it can be used under a wide range of environmental conditions (especially in the circumstance where temperature and humidity fluctuates rapidly). Reliability for performance such as recording and reading is required more than before.

Conventionally, a magnetic tape used in a digital signal recording system is determined for each system, and a so-called DLT type, 3480, 3490, 3590,
Magnetic tapes compatible with QIC, D8 type, or DDS type are known. And in any system, the magnetic tape used has a film thickness of 2.
A magnetic layer containing a ferromagnetic powder, a binder and an abrasive having a relatively thick single layer structure of 0 to 3.0 μm is provided. In order to maintain the condition, a back coat layer is provided. However, in the magnetic layer having a relatively thick single-layer structure as described above, there is a problem of a loss in thickness that the output is reduced.

It is known that the magnetic layer is made thinner in order to improve the decrease in reproduction output due to the thickness loss of the magnetic layer. Comprising a lower nonmagnetic layer dispersed in a binder and an upper magnetic layer having a thickness of 1.0 μm or less formed by dispersing ferromagnetic powder in the binder while the nonmagnetic layer is in a wet state. A recording medium is disclosed.

However, with the rapid increase in capacity and density of magnetic recording media in the form of disks or tapes, it has become difficult to obtain satisfactory characteristics even with such techniques. In particular, it has become difficult to achieve both high capacity, high density, and durability. Conventionally, mineral oils, silicone oils, higher alcohols, higher fatty acids, fatty acid esters, animal oils such as tallow, whale oil, and shark oils and vegetable oils have been used as lubricants, but all have poor durability. In order to improve durability, monoesters of saturated and unsaturated fatty acids and alcohols are widely used, as is well known, including Japanese Patent Publication No. 51-39081. However, in the case of a magnetic recording medium for high-density recording with an ultra-smooth magnetic surface, it was not sufficient to achieve high capacity, high density and durability at the same time with monoester. In addition, fatty acid esters of polyhydric alcohols are disclosed in JP-B-41-18063 (ester of carboxylic acid and dihydric alcohol), JP-B-58-31655 (glyceride oleate triester), and JP-A-54-21806. Fatty acid esters of alcohols containing three or more unsaturated bonds), and JP-A-61-198422 (esters of polyhydric alcohols and fatty acids). There was no one that was compatible with durability.

As the fatty acid monoester having an unsaturated bond, oleyl oleate described in Japanese Patent Publication No. 4917/1992 can be cited. It is not enough to balance the properties. Japanese Patent Application Laid-Open No. 61-280025 discloses a method in which a part of OH of polyglycerin is esterified with a fatty acid. This is because the OH group remains, and the compatibility of the lubricant with the binder resin is too large, so that the lubricant dissolves in the magnetic layer and does not easily leach onto the surface of the magnetic layer, thus exhibiting the function as a lubricant. It is presumed that it is difficult. It is also considered that the polyisocyanate contained in the binder resin as the curing agent reacts with the OH group, so that the reaction between the curing agent and the binder resin is inhibited.

Japanese Patent Publication No. 47-12950 discloses fatty acid esters of unsaturated alcohols, for example, vinyl stearate, and JP-A-55-139637 discloses fatty acids. Combinations of esters, fatty acid amides and fatty acids are disclosed. JP-A-58-164025 discloses unsaturated fatty acid esters, and JP-A-59-148131 discloses a combination of unsaturated fatty acid esters and hydrocarbons. Disclose unsaturated fatty acid esters of branched alcohols, but none of them has achieved sufficient capacity, high density and durability.

In the conventional magnetic recording medium described above, if the amount used is increased to enhance the lubricating effect, the mechanical strength of the magnetic coating film becomes weaker, the magnetic layer is easily shaved, and the shaved powder may contaminate the traveling path. Or, sufficient durability could not be obtained. In particular, these disclosed examples have a drawback that the durability is insufficient when the vehicle is run in a high temperature or high humidity environment, dropouts occur frequently, and errors frequently occur. Further, there is room for further improvement in terms of durability at a high speed of 1800 rpm or more and a low temperature.

Therefore, Japanese Unexamined Patent Publication (Kokai) No. 8-167137 discloses a diester of an unsaturated fatty acid in order to achieve both durability and electromagnetic conversion characteristics. However, JP-A-8-16
In Japanese Patent No. 7137, evaluation is performed using a drive having a relatively low rotation speed. In a drive having a high rotation speed aiming at a high transfer rate, sufficient capacity, high density and durability can be ensured. Did not. Further, in order to achieve both electromagnetic conversion characteristics and durability, Japanese Patent Laid-Open No. 4-117614,
JP-A-6-215360 uses a ferromagnetic metal powder containing an Al element. However, in these inventions, butyl stearate, which is a relatively low molecular weight and monoester, is used as the lubricant, and sufficient capacity, high density and durability cannot be obtained. Further, in Japanese Patent Application Laid-Open No. 4-117614, since a non-magnetic layer is not provided as a lower layer, the supply of the lubricant is insufficient, and in this respect, sufficient capacity, high density and durability can be obtained. Could not. Japanese Patent Application Laid-Open No. 6-215360 has confirmed the effect in 100-time repetition running durability evaluation using an 8 mm video, but a severe evaluation using a high-speed rotating magnetic disk system according to the present invention has a sufficiently large capacity. However, there is a problem that high density and durability cannot be secured. Japanese Patent Application Laid-Open No. 8-194939 discloses a magnetic recording medium using a saturated fatty acid having a melting point of 50 ° C. or more, an unsaturated fatty acid having a melting point of less than 50 ° C. and a fatty acid ester.
A drive with a high rotation speed aiming at a high transfer rate could not secure sufficient capacity, high density and durability.

[0017]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium in which the electromagnetic conversion characteristics, especially the high-density recording characteristics, are remarkably improved, and which have both high capacity, high density and durability. And Especially the recording capacity is 0.17
２2 Gbit / inch ² , preferably 0.2-2 Gbit / inch ² ,
It is an object of the present invention to provide a magnetic recording medium having a large capacity of preferably 0.35 to ² Gbit / inch ² , particularly a disk-shaped magnetic recording medium.

According to the present invention, the electromagnetic conversion characteristics, especially the high-density recording characteristics are remarkably improved, and the running performance, the repetitive running durability, the storage stability under high temperature and high humidity, the liner wear is good, and the starting torque It is an object of the present invention to provide a disk-shaped magnetic recording medium having a low density.

[0019]

Means for Solving the Problems The present inventors have increased the capacity,
As a result of intensive studies to obtain a magnetic recording medium with remarkably high density and excellent durability, the following media are used to achieve excellent high-density recording characteristics and excellent durability. Are obtained, and the present invention has been achieved.

That is, the present invention provides a substantially non-woven fabric on a support.
A magnetic lower layer is provided, and a ferromagnetic metal powder or
Magnetic layer containing ferromagnetic hexagonal ferrite powder in binder
In the magnetic recording medium provided, the magnetic recording medium
Recording density is 0.17-2Gbit / inch^TwoMagnetic signal recording signal
Air recording medium, wherein the dry thickness of the magnetic layer is 0.05 to
0.30 μm, and the coercive force of the magnetic layer is 1800
Rusted or higher, and at least the lower layer
And a surface of the magnetic layer containing Auger electrons.
When the C / Fe peak ratio as measured by the optical method is 5 to 120,
Can be achieved by a magnetic recording medium characterized by
You. Preferred embodiments of the present invention are as follows. (1) φm of the magnetic layer is 10.0 × 10^-3~ 1.0 ×
10^-3emu / cm^TwoAnd the coercive force of the magnetic layer is 2100
Magnetic recording medium characterized by being at least Oersted
body. (2) The dry thickness of the magnetic layer is 0.05 to 0.25 μm
And the surface of the magnetic layer is subjected to Auger electron spectroscopy.
The C / Fe peak ratio when measured is 5-100.
And a magnetic recording medium. (3) At least the lower layer contains a fatty acid and a fatty acid ester.
Wherein the fatty acid comprises at least a saturated fatty acid;
The fatty acid ester is at least a saturated fatty acid ester or
Magnetic recording medium containing a saturated fatty acid ester
body. (4) The fatty acid ester is a monoester or a diester.
A magnetic recording medium comprising: (5) The fatty acid ester is a saturated fatty acid ester and an unsaturated fatty acid ester.
Magnetic recording medium containing a saturated fatty acid ester
body. (6) The surface of the magnetic layer is measured by Auger electron spectroscopy.
C / Fe peak ratio of 5 to 100, preferably 5
-80, a magnetic recording medium characterized by the above-mentioned. (7) 100 parts by weight of the ferromagnetic powder or contained in the lower layer
100 parts by weight of the non-magnetic powder to
5 to 30 parts by weight of each of the magnetic layer and the non-magnetic layer, preferably
8 to 30 parts by weight, more preferably 10 to 30 parts by weight
And the magnetic recording medium has a disk shape.
A magnetic recording medium characterized by the above-mentioned. (8) The fatty acid ester is R1-COO-R2-OC
O-R3, R4-COO- (R5-O) m-R6 (formula
Wherein m is an integer of 1 to 10), or R7-COO-R8
Characterized in that it is at least one of the following:
recoding media. (Wherein R2 and R5 are each independently-(C
H_Two) N-or-(CH_Two) N- (n is 1 to 12)
2) which may contain an unsaturated bond derived from
A valence group, or-[CH_TwoCH (CH_Three)]-
Iha-[CH_TwoC (CH_Three) _TwoCH_Two]-, R1
 , R3, R4 and R7 each independently have 12 to 3 carbon atoms.
0 chain saturated or unsaturated hydrocarbon groups,
May be different. R6 and R8 are a chain having 1 to 26 carbon atoms.
Or the same as a branched, saturated or unsaturated hydrocarbon group
But it may be different. (9) The dry thickness of the magnetic layer is 0.05 to 0.20 μm
And the average particle diameter in the magnetic layer is 0.4 μm or less.
A magnetic recording medium comprising the following abrasive. (10) The magnetic recording medium has a surface recording density of 0.20.
~ 2Gbit / inch^TwoMagnetic recording medium for recording signals
And the lower layer contains an inorganic powder having a Mohs hardness of 4 or more.
A magnetic recording medium characterized by the above-mentioned. (11) The ferromagnetic metal powder is mainly composed of Fe and has an average length.
The axial length is 0.12 μm or less, and the crystallite size is 80 to 18
2. The magnetic recording medium according to claim 1, wherein 0.degree.
body. (12) Al / Fe of the ferromagnetic metal powder is 5 atomic% or more.
A magnetic recording medium characterized by being 30 atomic%. (13) The magnetic recording medium has a rotation speed of 1800 rpm or more.
For disk-shaped magnetic recording media for recording and playback systems
A magnetic recording medium characterized in that:

According to the present invention, the use of such a magnetic recording medium has both excellent high-density characteristics and excellent durability, which cannot be obtained by the prior art, and particularly, the running durability is remarkably improved. It has been found that a magnetic recording medium can be obtained.

The lower layer which is substantially non-magnetic means that it may have magnetic properties to such an extent that it does not participate in recording, and is hereinafter simply referred to as a lower layer, a non-magnetic layer or a lower non-magnetic layer. The surface recording density is obtained by multiplying the linear recording density by the track density.

Φm is defined by using a vibration sample type magnetometer (VSM: manufactured by Toei Kogyo Co., Ltd.) from the magnetic layer per unit area on one side,
Hm is the magnetic moment amount (emu / cm ² ) directly measurable with 10 k Oe, and the magnetic flux density Bm (unit G = 4πemu / cm ³ ) determined by the VSM has a thickness (c
m). Therefore, the unit of φm is emu
/ Cm ² or G · cm.

The linear recording density is the number of bits of a signal to be recorded per inch in the recording direction. These linear recording density, track density, and areal recording density are values determined by the system. That is, in the present invention, in order to improve the areal recording density, the magnetic layer thickness, the magnetic layer Hc, and the center plane average surface roughness were improved in terms of linear recording density, and φm was optimized in terms of track density. Things. In the present invention, the magnetic layer is an upper layer,
Also referred to as upper magnetic layer.

According to the present invention, the excellent areal recording density is 0.1
7 to ² Gbit / inch ² , preferably 0.2 to ² Gbit / inch
^{2. In} addition, a magnetic recording medium having both a high density characteristic and excellent durability, which has not been achieved by a coating type magnetic recording medium, which has been achieved by products known in the world, with a surface recording density of 0.35 to ² Gbit / inch ^2. It is quite unexpected that practical characteristics were obtained when applied to a medium, especially a disk-shaped magnetic recording medium. The magnetic recording medium of the present invention organically combines and combines the following points, and is the first coating-type magnetic recording medium to be described later that is comparable to or higher than a hard disk or MO. A magnetic recording medium of high density and large capacity can be obtained.

The points of the present invention are high Hc, super smoothness,
Improved durability by improving composite lubricants, highly durable binders and ferromagnetic powders, ultra-thin magnetic layers and reduced fluctuations at the interface with the lower layer, high filling of powders (ferromagnetic powders and non-magnetic powders) ,
Ultra fine particles of powder (ferromagnetic powder, non-magnetic powder), stabilization of head touch, dimensional stability and servo, improvement of thermal shrinkage of magnetic layer and support, action of lubricant at high and low temperature, etc. These were combined, and as a result of the synthesis, the present invention was achieved.

[0027] In the field of personal computers, which are becoming increasingly multi-media, attention has been paid to large-capacity recording media replacing conventional floppy disks, and they have been sold as ZIP disks by IOMEGA (Iomega), USA. This is an ATOMM (Advanced S) developed by the present applicant.
upper Thin Layer & High Ou
input Metal Media Technology
gy), a recording medium having a lower layer and a thin magnetic layer, and a product having a recording capacity of 3.7 inches and a recording capacity of 100 MB or more is sold. 100-120MB capacity is MO
(3.5 inches), and one newspaper article can fit in July or August. The transfer rate indicating data (information) write / read time is 2 MB or more per second, which is comparable to that of a hard disk.
20 times faster than MO and more than twice as fast as MO. Further, this recording medium having a lower layer and a thin magnetic layer can be mass-produced with the same coating type medium as that of the current FD, and has the advantage of being lower in price than MOs and hard disks.

The present inventors have conducted intensive studies based on the knowledge of such a medium, and as a result, have found that the ZIP disk and the MO
(3.5 inches), the areal recording density which is much larger than the recording capacity is 0.17 to ² Gbit / inch ^{2 and} preferably 0.2 to ² Gb.
it / inch ^{2 and} surface recording density of 0.35 to ² Gbit / inch
⁽²⁾ A magnetic recording medium that has both high density characteristics and excellent durability that have never been achieved with products known to the world, and especially improved error rate especially in high density recording area, especially disk-shaped magnetic recording A medium has been obtained, which is an invention which can also be applied to magnetic tapes such as computer tapes.

The magnetic recording medium of the present invention comprises an ultra-thin magnetic layer containing ultra-fine ferromagnetic powder having high output and high dispersibility, and a lower layer containing a spherical or acicular inorganic powder. By reducing the thickness of the magnetic layer, the offset of the magnetic force in the magnetic layer is reduced, the output in the high frequency range is greatly increased, and the overwriting characteristics are also improved. By improving the magnetic head, the effect of the ultra-thin magnetic layer can be further exhibited in combination with the narrow gap head, and the digital recording characteristics can be improved.

The thickness of the upper magnetic layer is 0.05 to 0.30 μm, and preferably 0.05 to 0.3 μm, so as to match the magnetic recording system for high density recording and the performance required from the magnetic head.
It is selected for a thin layer of 25 μm. Such an ultrathin magnetic layer, which is uniform and thin, has a high degree of packing by highly dispersing fine ferromagnetic powder and nonmagnetic powder using a combination of a dispersant and a binder having high dispersibility. Was. The ferromagnetic powder used is a ferromagnetic powder excellent in high output, high dispersibility, and high randomization in order to maximize the suitability of a large-capacity FD or computer tape. That is, by using a ferromagnetic metal powder or a ferromagnetic hexagonal ferrite powder which is very fine and can achieve a high output, particularly, the average major axis length is 0.1 μm or less, and the crystallite size is 80 ° to 1 mm.
When the angle is 80 °, high output and high durability can be achieved by further containing Co, and by containing Al and Y as a sintering inhibitor. In order to achieve a high transfer rate, a three-dimensional network binder system suitable for an ultra-thin magnetic layer is used to ensure running stability and durability during high-speed rotation. Also, use a composite lubricant that can maintain its effectiveness even when used under a wide range of temperature and humidity conditions or when used at high speeds.
Layer, and the lower layer also serves as a lubricant tank, so that an appropriate amount of lubricant can always be supplied to the upper magnetic layer, increasing the durability of the upper magnetic layer and improving reliability. I have. Further, the cushion effect of the lower layer can provide good head touch and stable running performance.

In a large-capacity recording system, a high transfer rate is required. For example, the transfer speed of Zip is 1.4 MB / sec, and the transfer speed of HiFD is 3.6 MB / sec at maximum. For this purpose, it is necessary to increase the number of rotations of the magnetic disk by one digit or more compared to the conventional FD system. Specifically, the rotation speed is preferably 1800 rpm or more, more preferably 3000 rpm or more. As the capacity and density of magnetic recording increase, the recording track density increases. In general, a servo recording area is provided on a medium to ensure traceability of a magnetic head with respect to a recording track. In the magnetic recording medium of the present invention, it is preferable to use a base having enhanced isotropic dimensional stability as a support base, so that traceability can be further stabilized. By using an ultra-smooth base, the smoothness of the magnetic layer can be further improved.

To increase the density of magnetic recording in the form of a disk,
It is necessary to improve the linear recording density and the track density. Of these, the characteristics of the support are important for improving the track density. In the medium of the present invention, the dimensional stability of the support base, particularly the isotropy, is considered. Servo recording is an indispensable technique in recording / reproducing at a high track density, but this improvement can be achieved from the medium side by making the support base as isotropic as possible.

The advantages of the present invention in which the magnetic layer is changed from a single layer to an ATOMM structure are considered as follows. (1) Improvement of electromagnetic conversion characteristics by thinning the magnetic layer, (2) Improvement of durability by stable supply of lubricant (3) High output by smoothing the upper magnetic layer (4) Separation of functions of the magnetic layer These functions cannot be achieved simply by layering the magnetic layers. In order to configure a multilayer structure, a “sequential multilayer system” in which layers are sequentially configured is generally used. In this method, first, a lower layer is applied, cured or dried, and then an upper magnetic layer is similarly applied, cured, and surface-treated. The FD differs from the magnetic tape in that the same processing is performed on both sides. After the coating process, it is completed as a final product through a slitting process, a punching process, a shell assembling process, and a certifying process.

By forming a thin magnetic layer, the following electromagnetic conversion characteristics can be greatly improved. (1) Improvement of output in high frequency region by improvement of recording demagnetization characteristics (2) Improvement of overwrite (overwrite) characteristics (3) Ensuring window margin Durability is an important factor for magnetic disks. Particularly, in order to achieve a high transfer rate, it is necessary to increase the number of rotations of the magnetic disk by one digit or more compared to the conventional FD system, and the medium durability when the medium in the magnetic head / cartridge and the medium slide at high speed. Is an important issue.
As means for improving the durability of the medium, there are a binder formulation for increasing the film strength of the disk itself and a lubricant formulation for maintaining the slipperiness with the magnetic head. The media of the present invention improves upon the 3D network binder system proven in current FD systems for binder formulations.

In the present invention, the lubricant contains a plurality of lubricants, each exhibiting an excellent effect under various temperature and humidity environments used, specifically, at least a fatty acid and / or a lubricant in the lower layer and / or the magnetic layer. A combination of at least three types of fatty acid esters is used, and a wide range of temperatures (low temperature, room temperature,
Even under high temperature) and humidity (low humidity, high humidity) environments, each lubricant exerts its function, and can maintain a comprehensively stable lubrication effect.

By utilizing the structure of the upper and lower two layers and providing the lower layer with a lubricant tank effect, an appropriate amount of lubricant is always supplied to the upper magnetic layer, and the durability of the upper magnetic layer can be improved. It is like that. There is a limit to the amount of lubricant that can be included in the ultra-thin magnetic layer, and simply thinning the magnetic layer reduces the absolute amount of lubricant, leading to deterioration in running durability. In this case, it was difficult to obtain a balance between the two. The upper and lower layers are provided with different functions and complement each other to achieve both improved electromagnetic conversion characteristics and improved durability. This functional differentiation was particularly effective in a system in which a magnetic head and a medium slide at high speed.

The lower layer can have a function of controlling the surface electric resistance in addition to the function of holding the lubricant. Generally, for controlling the electric resistance, a solid conductive material such as carbon black is often added to the magnetic layer. These not only limit the packing density of the ferromagnetic powder but also affect the surface roughness as the magnetic layer becomes thinner. These disadvantages can be eliminated by adding a conductive material to the lower layer.

With the multi-media society, the need for image recording is increasing not only in the industrial world but also in homes. The large-capacity magnetic recording medium of the present invention is not limited to data such as characters and numerals, but is used for image recording. It has the ability to sufficiently meet the demands for function / cost as a medium. The large-capacity medium of the present invention is based on a coated magnetic recording medium with a proven track record, and has excellent long-term reliability and excellent cost performance.

The present invention is achieved for the first time by accumulating various factors as described above, acting synergistically and organically, and also by combining and synthesizing all the techniques described above. The magnetic recording medium is, for example, a HiFD jointly developed by Sony Corporation and Fuji Film Corporation.
With the ability to apply to HiFD is the rapid development of the processing capacity of personal computers in recent years,
With a large increase in the amount of information to be handled, there is a demand for a new high-performance data recording system having a large capacity and a high data transfer rate, while a current 3.5-inch floppy disk is required.
Discs are widely used as easy-to-use recording media around the world. These discs have been developed as a new system that can continue to use these discs and read out and reuse a huge amount of accumulated data. 3.5 inch floppy disk "HiFD" has a large capacity of 200MB and 3.6MB.
This is a next-generation large-capacity floppy disk system that realizes backward compatibility with a current 3.5-inch floppy disk with a high transfer rate of / sec. By adopting a newly developed ultra-thin layer coated metal disk and a dual discrete gap head with both a narrow gap for high-density recording and a wide gap for the current 3.5-inch floppy disk A large capacity of 200 MB can be realized, and a large capacity data file such as an image and a sound can be easily handled. Also, due to the high linear recording density and the high-speed disk rotation of 3600 rpm, the conventional 3.5-inch floppy disk (2H
While the transfer rate of D) is about 0.06 MB / sec, a high-speed transfer rate of 3.6 MB / sec at maximum is realized. This enables about 60 times faster processing than in the past. Also, the dual discrete gap head floats due to the rotation of a disk similar to a hard disk, so that the head does not contact during recording / reproducing, so that the floating type has a long life and high reliability. By using a linear type voice coil motor for driving, high speed random access can be performed three to four times faster than a conventional 3.5 inch floppy disk drive. Further, the dual discrete gap head realizes backward compatibility enabling recording and reproduction with the current 3.5-inch floppy disk. Further, by incorporating a new mechanism for performing head loading in a software manner, the wear of the disk can be reduced, and high reliability is ensured by mounting an error correction function. Such a large capacity of 200MB,
The magnetic recording medium of the present invention is a next-generation large-capacity floppy disk system that realizes backward compatibility capable of recording / reproducing with a current 3.5-inch floppy disk with a high transfer rate of 3.6 MB / sec. It has been developed to be applicable.

In order to realize a large capacity and a high transfer rate, it is an important requirement to enhance the lubricating ability of the magnetic recording medium.
The basic concept for increasing the lubricating ability is as follows. (1) A plurality of lubricants having different functions and performances are used in combination. (2) A plurality of lubricants having similar functions and performances are used in combination.

According to the above (1), a wide range of functions and performances can be achieved under a wide range of conditions. Further, the affinity and compatibility between the lubricants are secured by the above (2), and a smooth lubrication function can be exhibited. An example of a combination of a plurality of lubricants having different functions and performances of the above (1) is as follows.

1) A lubricant having a fluid lubrication function and a lubricant having a boundary lubrication function are used in combination. 2) A polar lubricant and a non-polar lubricant are used in combination. 3) Use a combination of a liquid lubricant and a solid lubricant. 4) Lubricants having different polarities, particularly fatty acids and / or fatty acid esters are used in combination. For example, a monoester and a diester of a fatty acid ester are used in combination.

5) Lubricants having different melting points and boiling points, particularly fatty acids and / or fatty acid esters are used in combination. 6) Lubricants having different carbon numbers, especially fatty acids and / or fatty acid esters, are used in combination. 7) Linear and branched lubricants, especially fatty acids and / or fatty acid esters are used in combination. For example, a linear fatty acid ester and a branched fatty acid ester are used in combination.

8) Saturated and unsaturated carbon chain lubricants, especially fatty acids and / or fatty acid esters are used in combination. For example, a saturated fatty acid ester and an unsaturated fatty acid ester are used in combination. 9) Use a combination of lubricants having different affinities with the binder. 10) A lubricant having a different affinity for the inorganic powder is used in combination.

By combining the lubricants of the above (1), a wide range of functions and functions can be obtained under a wide range of conditions.
Performance can be achieved. An example of a combination of a plurality of lubricants having similar functions and performances in the above (2) is as follows. 1) The fatty acid residues of the fatty acid and the fatty acid ester are made identical.

2) The fatty acid residues of the fatty acid ester and / or the alcohol residue are used in combination with the same fatty acid ester. 3) Two or more kinds of saturated fatty acids are used in combination. 4) Saturated fatty acids are used in the fatty acid residue portion of the fatty acid and the fatty acid ester. 5) Unsaturated fatty acids are used in the fatty acid residue portion of the fatty acid and the fatty acid ester.

6) Only three or more fatty acid esters are used in combination. 7) Make the fatty acid portions of the fatty acid and the fatty acid amide identical. By the combination of the lubricant (2), the affinity and compatibility between the lubricants are secured, and a smooth lubrication function can be exhibited. The lubricant of (1) and the lubricant of (2) are not applied independently, and the lubricant of (1) and the lubricant of (2) may be used in combination or the lubricant of (1) By combining them with each other or by using the lubricants of (2) together, it is possible to achieve a wide range of functions and performance under a wide range of conditions, as well as to ensure the compatibility and compatibility of the lubricants with each other. The lubrication function can be exhibited.

As the lubricant used for the magnetic layer and the non-magnetic layer of the present invention, the following can be used. Lubricants are one type of additives for magnetic recording media, and additives that have lubricating, antistatic, dispersing, and plasticizing effects are used. I can do it. As a material exhibiting a lubricating effect, a lubricant is used which exerts a remarkable effect on the adhesion which occurs during friction between the surfaces of the substances. There are two types of lubricants.
Although it is not possible to determine whether a lubricant used in a magnetic recording medium is completely fluid lubrication or boundary lubrication, if it is classified according to the general concept, higher fatty acid esters, liquid paraffin, silicon derivatives, etc. that indicate fluid lubrication and boundary lubrication. It is classified into lubricating long-chain fatty acids, fluorinated surfactants, fluorinated polymers and the like. In the coating type medium, the lubricant is dissolved in the binder or partially exists in a state of being adsorbed on the surface of the ferromagnetic powder, and the lubricant is transferred to the surface of the magnetic layer.
The transfer speed is determined by the compatibility between the binder and the lubricant. When the compatibility between the binder and the lubricant is high, the migration speed is low, and when the compatibility is low, the migration speed is high. One approach to compatibility is to determine the solubility parameters of the two.
There is a comparison of tar. A non-polar lubricant is effective for fluid lubrication, and a polar lubricant is effective for boundary lubrication. In the present invention, large capacity, high density, and high durability can be exhibited by combining at least three kinds of higher fatty acid esters exhibiting fluid lubrication having different properties and long chain fatty acids exhibiting boundary lubrication. It is. Solid lubricants can also be used in combination with these.

As the solid lubricant, for example, molybdenum disulfide, tungsten graphite disulfide, boron nitride, graphite fluoride and the like are used. As long-chain fatty acids exhibiting boundary lubrication, monobasic fatty acids having 10 to 24 carbon atoms (which may contain unsaturated bonds or may be branched), and metal salts thereof (Li, Na, K) , Cu, etc.). Fluorinated surfactants, fluorine-containing silicones as fluorine-containing polymers, fluorine-containing alcohol,
Examples thereof include a fluorine-containing ester, a fluorine-containing alkyl sulfate, and an alkali metal salt thereof. As higher fatty acid esters showing fluid lubrication, those having 10 to 24 carbon atoms
A monobasic fatty acid (which may contain an unsaturated bond or may be branched) and a monovalent, divalent, 2 to 12 carbon atom,
One of trihydric, tetrahydric, pentahydric, and hexahydric alcohols (may contain unsaturated bonds or be branched)
And fatty acid esters of monoalkyl ethers of alkylene oxide polymers. Liquid paraffin, and dialkyl polysiloxane (alkyl has 1 to 5 carbon atoms) as a silicon derivative
), Dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms, alkoxy has 1 to 4 carbon atoms), phenylpolysiloxane, fluoroalkyl Examples include silicone oils such as polysiloxane (alkyl has 1 to 5 carbon atoms), silicone having a polar group, fatty acid-modified silicone, and fluorine-containing silicone.

As other lubricants, monovalent, divalent, trivalent, tetravalent, pentavalent, hexavalent alcohols having 12 to 22 carbon atoms (which may contain unsaturated bonds or may be branched),
Alkoxy alcohols having 12 to 22 carbon atoms (which may contain unsaturated bonds or may be branched), alcohols such as fluorine-containing alcohols, polyolefins such as polyethylene wax and polypropylene, and polyolefins such as ethylene glycol and polyethylene oxide wax Glycols, alkyl phosphates and their alkali metal salts, alkyl sulfates and their alkali metal salts, polyphenyl ethers, fatty acid amides having 8 to 22 carbon atoms, aliphatic amines having 8 to 22 carbon atoms and the like can be mentioned.

Phenylphosphonic acid, specifically α-naphthylphosphoric acid, phenylphosphoric acid, diphenylphosphoric acid, p-ethylbenzene, etc. exhibiting an antistatic effect, a dispersing effect, a plasticizing effect and the like. Phosphonic acid, phenylphosphinic acid, aminoquinones, various silane coupling agents, titanium coupling agents, fluorine-containing alkyl sulfates and alkali metal salts thereof can be used.

The lubricant used in the present invention is particularly preferably a fatty acid and a fatty acid ester, and in addition to these, different lubricants and additives can be used in combination. Specific examples of these are given below. First, for fatty acids, caprylic acid (C ₇ H ₁₅ COOH,
Melting point 16 ° C.), pelargonic acid (C ₈ H ₁₇ COOH, melting point 15 ° C.), capric acid (C ₉ H ₁₉ COOH, melting point 31.
5 ° C.), undecylic acid (C ₁₀ H ₂₁ COOH, melting point 28.
6 ° C.), lauric acid (C ₁₁ H ₂₃ COOH, melting point 44 ° C.)
Specifically, tridecylic acid (C ₁₂ H ₂₅ COOH, melting point 45.5) such as “NAA-122” manufactured by NOF Corporation
° C.), myristic acid (C ₁₃ H ₂₇ COOH, melting point 58 ° C.)
Etc. Specifically NOF Corporation's "NAA-142", pentadecyl acid (C ₁₄ H ₂₉ COOH, melting point 53-5
4 ° C.), palmitic acid (C ₁₅ H ₃₁ COOH, melting point 63-
64 ° C.) Specifically, “NAA-16” manufactured by NOF Corporation
0 ”and other heptadecylic acids (C ₁₆ H ₃₃ COOH, melting point 6
0-61 ° C.), stearic acid (C ₁₇ H ₃₅ COOH, melting point 71.5-72 ° C.) Specifically, “N” manufactured by NOF Corporation
AA-173K ”and other nonadecanoic acids (C ₁₈ H ₃₇ COO
H, melting point 68.7 ° C.), arachidic acid (C ₁₉ H ₃₉ COO)
H, melting point 77 ° C.), behenic acid (C ₂₁ H ₄₃ COOH, melting point 81-82 ° C.) and the like. Oleic acid as an unsaturated fatty acid (C ₁₇ H ₃₃ COOH (cis), melting point 16 ° C.)
Specifically, elaidic acid (C ₁₇ H ₃₃ COOH (trans), melting point 44) such as “oleic acid” manufactured by Kanto Chemical Co., Ltd.
-45 ° C.) Specifically, such as “elaidic acid” manufactured by Wako Pure Chemical Industries, Ltd., such as setreic acid (C ₂₁ H ₄₁ COOH, melting point 3)
3.7 ° C.), erucic acid (C ₂₁ H ₄₁ COOH, melting point 33.
4 to 34 ° C.) Specifically, brassic acid (C ₂₁ H ₄₁ COOH (trans), melting point 61.5 ° C.), linoleic acid (C ₁₇ H ₃₁ COO) such as “erucic acid” manufactured by NOF Corporation
H, boiling point 228 ° C. (14 mm)), linolenic acid (C ₁₇ H
₂₉ COOH, boiling point: 197 ° C. (4 mm)). As branched saturated fatty acids, isostearic acid (CH _{3
CH (CH 3) (CH 2} ) 14 COOH, melting point 67.6 to 6
8.1 ° C.).

As esters, lauric acid esters
Isocetyl laurate (C₁₁H_{twenty three}COOCH_TwoCH (C₆
H₁₃) C₈H₁₇), Oleyl laurate (C₁₁H_{twenty three}CO
OC_{1 8}H₃₅), Stearyl laurate (C₁₁H_{twenty three}COO
C₁₈H₃₇), Isopropyl as myristate
Millistate (C₁₃H₂₇COOCH (CH_Three)_Two)concrete
Nippon Rika Co., Ltd.'s “Engelbu IPM”
Butyl myristate (C₁₃H₂₇COOC_FourH₉),I
Sobutyl myristate (C₁₃H₂₇COOiso-C_FourH₉)
Specifically, Nippon Rika Co., Ltd.'s “Engelbu IB
M ”and other heptyl myristates (C₁₃H₂₇COOC₇
H_Fifteen), Octyl myristate (C₁₃H₂₇COOC₈H
₁₇), Isooctyl myristate (C₁₃H₂₇COOCH
_TwoCH (C_TwoH_Five) C_FourH₉), Isocetyl myristate
(C₁₃H₂₇COOCH_TwoCH (C₆H₁₃) C ₈H₁₇)Such
Is mentioned.

Isooctyl palmitate (C ₁₅ H ₃₁ COOCH ₂ CH (C ₁₅ H ₃₁ COOC ₈ H ₁₇ ), decyl palmitate (C ₁₅ H ₃₁ COOC ₁₀ H ₂₁ ), etc. ₂ H ₅₎ C ₄ H
₉ ), isocetyl palmitate (C ₁₅ H ₃₁ COOCH ₂ C
H (C ₆ H ₁₃ ) C ₈ H ₁₇ ) and the like, 2-octyldodecyl palmitate (C ₁₅ H ₃₁ COOCH ₂ CH (C ₈ H ₁₇ ) C ₁₂
H _25), 2-hexyl-dodecyl palmitate (C ₁₅ H ₃₁
COOCH ₂ CH (C ₆ H ₁₃ ) C ₁₂ H ₂₅ ) and oleyl palmitate (C ₁₅ H ₃₁ COOC ₁₈ H ₃₅ ).

Propyl stearate as a stearic acid ester
Allate (C₁₇H₃₅COOC_ThreeH₇), Isopropyl
Allate (C₁₇H₃₅COOCH (CH_Three)_Two), Butils
Tearate (C₁₇H₃₅COOC_FourH₉) Specifically, Nippon Oil
Such as "butyl stearate" from Yasu Co., Ltd.
Rustearate (C₁₇H₃₅COOCH (CH_Three) C
_TwoH_Five), Tert-butyl stearate (C₁₇H₃₅COOC
(CH_Three)_Three), Amyl stearate (C₁₇H₃₅COOC
_FiveH₁₁) Such as isoamyl stearate (C₁₇H₃₅CO
OCH_TwoCH_TwoCH (CH_Three)_Two), Hexyl stearate
(C₁₇H₃₅COOC₆H₁₃), Heptyl stearate
(C₁₇H₃₅COOC₇H_Fifteen) Octyl steerer
To (C₁₇H₃₅COOC₈H₁₇) Specifically, Nippon Oil & Fat
Such as "N-octyl stearate"
Cutyl stearate (C₁₇H₃₅COOisoC₈H ₁₇), De
Silstearate (C₁₇H₃₅COOC_TenH_{twenty one})
Sodecyl stearate (C₁₇H₃₅COOiso-C
_TenH_{twenty one}), Dodecyl stearate (C₁₇H₃₅COOC₁₂
H_{twenty five}), Isotridecyl stearate (C₁₇H₃₅COO
iso-C₁₃H₂₇), 2-ethylhexyl stearate
(C₁₇H₃₅COOCH_TwoCH (C_TwoH_Five) C_FourH₉), Iso
Hexadecyl stearate or isocetyl stearate
To (C₁₇H_{Three Five}COOisoC₁₆H₃₃Specifically, New Japan Rika
Isosteari, Inc., Inc. “Engelbud HDS”
Rustearate (C₁₇H₃₅COOisoC₁₈H₃₇),me
Il stearate (C₁₇H₃₅COOC₁₈H₃₅)
I can do it.

Isotetracosyl behenate (C ₂₁ H ₄₃ COOCH ₂ CH (C ₆ H ₁₃ ) C ₁₂ as a behenate ester
H _25), etc. More specifically, New Japan Chemical Co., of "Enujerubu DTB"), and the like. Butoxyethyl stearate (C ₁₇ H ₃₅ CO
OCH ₂ CH ₂ OC ₄ H ₉ ), butoxyethyl oleate (C ₁₇ H ₃₃ COOCH ₂ CH ₂ OC ₄ H ₉ ), diethylene glycol monobutyl ether terstearate or butoxyethoxyethyl stearate (C ₁₇ H ₃₅ COO ( CH
₂ CH ₂ O) ₂ C ₄ H ₉ ), tetraethylene glycol monobutyl ether stearate (C ₁₇ H ₃₅ COO (CH ₂
CH ₂ O) ₄ C ₄ H ₉ ), diethylene glycol monophenyl ether terstearate (C ₁₇ H ₃₅ COO (CH ₂ CH ₂₎
O) ₂ C ₆ H ₆ ), diethylene glycol mono 2-ethylhexyl ether terstearate (C ₁₇ H ₃₅ COO (CH
_{2 CH 2 O) 2 CH 2} CH (C 2 H 5) C 4 H 9), such as JP 59-227030, the esters described in JP-A-59-65931 can be used.

Isocetyl isostearate (isoC ₁₇ H ₃₅ COOCH ₂ CH)
(C ₆ H ₁₃ ) C ₈ H ₁₇ ) Specifically, oleyl isostearate (isoC ₁₇ H ₃₅ COOC ₁₈ H ₃₅ ), stearyl isostearate (such as “ICIS” of Higher Alcohol Company) isoC ₁₇ H ₃₅ COOC ₁₈ H ₃₇ ), isostearyl isostearate (isoC ₁₇ H ₃₅ COOiso-C ₁₈ H)
₃₇ ), eicosenyl isostearate (isoC ₁₇ H ₃₅ C
OOC ₂₂ H ₄₃ ).

Oleyl oleate (C ₁₇ ) such as butyl oleate (C ₁₇ H ₃₃ COOC ₄ H ₉ ) as an oleic acid ester, and “Engelbu BO” manufactured by Nippon Rika Co., Ltd.
H ₃₃ COOC ₁₈ H _35), ethylene glycol dioleyl _{(C 17 H 33 COOCH 2 CH} 2 OCOC 17 H 33) , and the like. Oleyl erucate (C ₂₁ H ₄₁ COOC ₁₈ H ₃₅ ) is mentioned as an erucate.

Dioleyl maleate as diester
(C₁₈H₃₅OCOCH = CHCOOC ₁₈H₃₅), Neope
Ethylene glycol didecanoate (C_TenH_{twenty one}COOCH
_TwoC (CH_Three)_TwoCH_TwoOCOC_TenH_{twenty one}), Ethylene glyco
Lujlaurate (C₁₁H_{twenty three}COOCH_TwoCH_TwoOCOC
₁₁H_{twenty three}), Ethylene glycol dioleyl (C₁₇H₃₃C
OOCH_TwoCH_TwoOCOC₁₇H₃₃) 1,4-butanegio
Rugistearate (C₁₇H₃₅COO (CH_Two)_FourOCO
C₁₇H₃₅) 1,4-butanediol dibehenate (C
_{twenty one}H₄₃COO (CH_Two)_FourOCOC_{twenty one}H₄₃) 1,10-
Decanediol dioleyl (C₁₇H₃₃COO (CH_Two)
_TenOCOC₁₇H₃₃), 2-butene-1,4-diolset
Rail (C_{twenty one}H₄₁COOCH_TwoCH = CHCH_TwoOCOC
_{twenty one}H₄₁).

Triglyceryl caprylate as a triester
Ride (C₇H_FifteenCOOCH_TwoCH (OCOC₇H_Fifteen) C
H_TwoOCOC₇H_Fifteen). These fatty acid esthetics
Oleyl alcohol for alcohols in addition to alcohol and fatty acids
(C ₁₈H₃₅OH), stearyl alcohol (C₁₈H₃₇O
H), lauryl alcohol (C₁₂H_{twenty five}OH)
Can be

As the fatty acid amide, lauric amide (C
₁₁ H ₂₃ CONH ₂ ) Specifically, myristic acid amide (C ₁₃ H ₂₇ ) such as “lauric amide” of Tokyo Chemical Industry Co., Ltd.
CONH ₂ ), palmitic amide (C ₁₅ H ₃₁ CON
H ₂ ), oleic acid amide (cis-C ₈ H ₁₇ CHＣＨCH
(CH ₂ ) ₇ CONH ₂ ) Specifically, erucamide (cis-C ₈ H ₁₇ CH = CH (CH ₂ ) ₁₁ CON, such as “Armoslip CP-P” manufactured by Lion Akzo Co., Ltd.
H ₂ ) Specifically, stearamide (C ₁₇ H ₃₅ CON) such as “Armoslip E” of Lion Akzo Co., Ltd.
H ₂ ) Specific examples include “Armide HT” manufactured by Lion Akzo Co., Ltd. Shin-Etsu Chemical Co., Ltd. “TAV-3630”, “TA-3”,
"KF-69" can be mentioned.

Nonionic surfactants such as alkylene oxides, glycerins, glycidols, alkylphenol ethylene oxide adducts, etc., cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, phosphonium or sulfonium Anionic surfactants containing acidic groups such as carboxylic acids, sulfonic acids, phosphoric acids, sulfate groups, phosphate groups, etc., amino acids, aminosulfonic acids, and sulfuric acid or phosphate esters of amino alcohols , An amphoteric surfactant such as an alkylbedine type or the like can also be used. These surfactants are described in detail in "Surfactant Handbook" (published by Sangyo Tosho Co., Ltd.). These lubricants, antistatic agents, etc.
Not pure, but isomers, unreacted materials,
Impurities such as by-products, decomposition products, and oxides may be included. These impurities are preferably 30% or less, more preferably 10% or less.

Each of these lubricants and surfactants used in the present invention has a different physical action.
The type, amount, and combination ratio of the lubricant that produces a synergistic effect should be optimally determined according to the purpose.
To control leaching to the surface using fatty acids having different melting points in the non-magnetic layer and magnetic layer, to control leaching to the surface using esters having different boiling points, melting points and polarities, and to adjust the amount of surfactant It can be considered to improve the stability of coating and to improve the lubricating effect by increasing the amount of the lubricant added in the intermediate layer, and it is needless to say that the present invention is not limited to the examples shown here. Generally, the total amount of the lubricant is selected in the range of 0.1% by weight to 50% by weight, preferably 2% by weight to 25% by weight based on the ferromagnetic powder or nonmagnetic powder.

All or a part of the additives used in the present invention may be added in any step of producing magnetic and non-magnetic paints. For example, when the additives are mixed with the ferromagnetic powder before the kneading step, There are 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. In some cases, the purpose may be achieved by applying a part or all of the additive simultaneously or sequentially after applying the magnetic layer according to the purpose. Depending on the purpose, a lubricant may be applied to the surface of the magnetic layer after calendering or after slitting.

In the present invention, particularly preferable results are obtained when a monoester and a diester are used in combination as the fatty acid ester as described in Example 34. This will be described in detail below.

That is, the present invention provides a high-density, large-capacity magnetic recording medium requiring an ultra-smooth magnetic layer,
It is a magnetic recording medium that provides stable running durability even after running. Conventionally, lubricants such as monoesters and diesters have been used. The present inventors diligently studied the properties of these lubricants and focused on the ester groups, and as a result of carefully examining the behavior in the lower layer and the magnetic layer, the monoester lubricant has a polar ester group as a molecular group. Since there is only one of them, the affinity with the binder is not so high, it has the property that it is easy to appear on the surface of the magnetic layer without staying in the layer, and the diester lubricant has a polar ester group such as an ester group. Since there are two in the molecule, it has a high affinity for the binder and tends to remain in the layer, so that it has a property that it does not come out on the surface of the magnetic layer. Therefore, it is considered that a very good running durability can be obtained because the lubricant of the monoester contributes in the early stage of running and the lubricant of the diester contributes after the running. Also, diester lubricants have extremely good low-temperature durability, and when used in combination with monoester lubricants, which have good high-temperature durability,
Extremely excellent running durability from low to high temperatures can be obtained. These effects have a so-called synergistic effect that is more than the effect obtained by simply adding the effect of the monoester lubricant and the effect of the diester lubricant.

In the fatty acid ester used in the present invention, the diester lubricant is preferably a compound represented by the following formula (1). R 1 -COO-R 2 -OCO-R 3 (1) (wherein R 2 is-(CH ₂ ) n-or-(C
H ₂ ) n represents a divalent group which may contain an unsaturated bond derived from-(n is an integer of 1 to 12), or-[CH
₂ CH (CH ₃ )]-or-[CH ₂ C (C
H _{3) 2} CH _2] - indicates, R1 and R3 represent a linear, saturated or unsaturated hydrocarbon group having 12 to 30 carbon atoms each independently may be the same or different from each other. The chain of the chain hydrocarbon group may be linear or branched, but it is preferred that both R1 and R3 are linear unsaturated, in which case the structures of R1 and R3 are the same. Are particularly preferred. Further, as the unsaturated bond, any of a double bond and a triple bond may be used, but a double bond is preferable, and the number of unsaturated bonds may be one or more, and two or three. The double bond may be either cis or trans.

Each of R 1 and R 3 has 12 to 3 carbon atoms.
0, preferably 14 to 26, more preferably 14 to 2
0. When the number of carbon atoms is less than 12, volatility is high, so that it tends to volatilize from the surface of the magnetic layer during traveling and stop traveling. If the number of carbon atoms is more than 30, the mobility of the molecules will be low, so that the lubricant will not easily leach out to the surface of the magnetic layer, and the durability tends to be poor.

Also, the C / Fe peak ratio described later is 5 to 80.
In order to achieve the above conditions, it is preferable that R1 and R3 satisfy the following conditions. That is, R1 and R3 are alkyl or alkenyl groups, which may be branched or straight chain;
A group containing an unsaturated bond which can be represented by is preferred. It is more preferable that both have the same structure. R1 and R3 have 5 to 21, preferably 7 carbon atoms.
To 17, more preferably 9 to 13. R1,
If the length of the carbon chain of R3 is too short, it is not preferable.
If it is too short, it tends to evaporate. If it becomes easy to volatilize, when the magnetic layer becomes high temperature due to frictional heat generated with the magnetic head, it will volatilize, reducing the surface amount of the lubricant in the magnetic layer and reducing the durability. Because it becomes. If the length of the carbon chain is too long, the viscosity is increased, and the fluid lubrication performance may be reduced, and the durability may be reduced.

R 2 is preferably a straight-chain dihydric alcohol residue having OH at both terminals, and n is preferably 3 to 12. n
When the value is too small, the running durability is poor. When the value is too large, the viscosity tends to be high, which makes it difficult to use and the durability tends to be poor. Specifically, residues such as ethylene glycol, neopentyl glycol, propanediol, propylene glycol, and butanediol are preferable.

The compound represented by the general formula (1) of the present invention comprises a diol represented by HO-R2-OH and R1-CO
Diesters of OH and R3 -COOH, preferably with unsaturated fatty acids.

The unsaturated fatty acids include 4-dodecenoic acid, 5-dodecenoic acid, 11-dodecenoic acid, cis-9-
Tridecenoic acid, myristoleic acid, 5-myristoleic acid, 6-pentadecenoic acid, 7-palmitoleic acid, ci
s-9-palmitoleic acid, 7-heptadecenoic acid, oleic acid, ellagic acid, cis-6-octadecenoic acid, t
ran-11-octadecenoic acid, cis-11-eicosenoic acid, cis-13-docosenoic acid, 15-tetracosenoic acid, 17-hexacosenic acid, cis-9, cis-
12-octadienoic acid, trans-9, trans-
12-octadienoic acid, cis-9, trans-1
1, trans-13-octadecatrienoic acid, cis
Linear unsaturated fatty acids such as -9, cis-12, cis-15-octadecatrienoic acid and stearolic acid, 5-methyl-2-tridecenoic acid, 2-methyl-9-octadecenoic acid, 2-methyl-2 -Branched unsaturated fatty acids such as eicosenoic acid and 2,2-dimethyl-11-eicosenoic acid.

Examples of the diol include ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-pentanediol, 1,8-octanediol, Linear saturated both terminal diols such as 1,9-nonanediol and 1,10-decanediol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 2,4-pentanediol, 2,2- Dimethyl-1,3-propanediol, 2,5-hexanediol, 2-ethyl-1,3-hexanediol, 3-methyl-1,6-hexanediol, 1-methyl-1,7-
Branched saturated diols such as pentanediol, 2,6-dimethyl-1,7-pentanediol, 1-methyl-1,8-nonanediol, 2-butene-1,4-diol,
2,4-hexadiene-1,6-dienediol, 3-
Linear unsaturated diols such as pentene-1,7-diol, 2-methyl-2-butene-1,4-diol,
2,3-dimethyl-2-butene-1,4-diol,
Examples include branched unsaturated diols such as 2,6-dimethyl-3-hexene-1,6-diol.

Of these, particularly preferred compounds of the present invention are esters of linear unsaturated fatty acids. Specifically, myristoleic acid, 5-myristoleic acid, 7-palmitoleic acid, cis-9-palmitoleic acid, oleic acid, elaidic acid, cis-6-octadecenoic acid (petroceric acid), trans-6-octadecenoic acid (Petrosaelaidic acid), trans-11-octadecenoic acid (basenic acid), cis-11-eicosenoic acid, ci
s-13-docosenoic acid (erucic acid), cis-9, ci
Linear unsaturated fatty acids such as s-12-octadienoic acid (linoleic acid) and diethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-pentane Esters of diol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol and the like are preferable, and more preferably, the linear unsaturated fatty acid and 1,1
4-butanediol, 1,5-pentanediol, 1,
6-hexanediol, 1,7-pentanediol,
1,8-octanediol, 1,9-nonanediol,
An ester with 1,10-decanediol or the like. Specific examples include neopentyl glycol didecanoate, ethylene glycol dioleyl and the like and diesters described later. Examples of diesters are as follows.

L-a1 C ₁₇ H ₃₅ COO (CH ₂ ) ₄ OCOC ₁₇ H ₃₅ L-a 2 C ₁₁ H ₂₁ COO (CH ₂ ) ₄ OCOC ₁₁ H ₂₁ L-a 3 C ₁₇ H ₃₃ COO (CH ₂ ) _{2 OCOC 17 H 33 L-a4 C} 11 H 23 COO (CH 2) 4 OCOC 11 H 23 L-a5 C 27 H 53 COO (CH 2) 4 OCOC 27 H 53 L-a6 C 11 H 21 COO (CH 2) _{4 OCOC 17 H 33 L-a7} C 17 H 33 COO (CH 2) 11 OCOC 17 H 33 L-a8 C 17 H 33 COOCH 2 CH = CHCH 2 OCOC 17 H 33 L-a9 C 14 H 27 COOCH 2 CH = _{CHCH 2 OCOC 14 H 27 L-} a10 C 17 H 33 COO (CH 2) 8 OCOC 14 H 27 Further, as the fatty acid ester used in the present invention, a dicarboxylic acid, also diester of chain unsaturated alcohol use Can .

Examples of the dicarboxylic acid include saturated acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, methylmalonic acid, ethylmalonic acid, propylmalonic acid and butylmalonic acid. Specific examples include unsaturated dicarboxylic acids such as dicarboxylic acid, maleic acid, fumaric acid, glutaconic acid, itaconic acid, and muconic acid.

As the chain unsaturated alcohol, cis-
9-octadecene-1-ol (oleyl alcohol), trns-9-octadecene-1-ol (elaidyl alcohol), 9,10-octadecediene-1
-All (linoleyl alcohol), 9, 12, 15-
Octadecetrien-1-ol (linolenyl alcohol), cis-9-trns-11,13-octadecetrien-1-ol (eleostearyl alcohol), 2-pentadecene-1-ol, 2- Hexadecene-1-ol, 2-heptadecen-1-ol, 2-
Octadecene-1-ol, 15-hexadecene-1-
Oars and the like are specific examples.

Of these, particularly preferred compounds of the present invention are esters of a linear unsaturated alcohol and a saturated dicarboxylic acid. Specifically, as the alcohol component,
Oleyl alcohol, elaidyl alcohol, linoleyl alcohol, linolenyl alcohol, eleostearyl alcohol, etc., as the dicarboxylic acid component, malonic acid, succinic acid, glutaric acid, adipic acid, methyl malonic acid, ethyl malonic acid, Propylmalonic acid, butylmalonic acid and the like, and diesters between them. More preferably, it is a diester between malonic acid and succinic acid and oleyl alcohol, elaidyl alcohol, linoleyl alcohol, and linolenyl alcohol.

The C / Fe peak ratio described later is 5 to 120,
Preferably attain 5 to 100, particularly preferably at least 5 to 80
Examples of preferred diesters include the following:
Can be mentioned. That is, neopentyl glycol geo
Rate (L-a11), ethylene glycoldiolate (L-a
3), neopentyl glycol didecanoate (L-a1
2), propanediol dimyristate (L-a13)
Can be mentioned. Other examples include:
be able to. C_FiveH₁₁COOCH_TwoC (CH_Three)_TwoCH_TwoOCOC_FiveH₁₁ C₇H_FifteenCOOCH_TwoC (CH_Three)_TwoCH_TwoOCOC₇H_Fifteen C₉H₁₉COOCH_TwoC (CH_Three)_TwoCH_TwoOCOC₉H₁₉ C₁₁H_{twenty three}COOCH_TwoC (CH_Three)_TwoCH_TwoOCOC₁₁H_{twenty three} C₁₃H₂₇COOCH_TwoC (CH_Three)_TwoCH_TwoOCOC₁₃H₂₇ C₁₇H₃₅COOCH_TwoC (CH_Three)_TwoCH_TwoOCOC₁₇H₃₅ C_{twenty one}H₄₃COOCH_TwoC (CH_Three)_TwoCH_TwoOCOC_{twenty one}H₄₃ C_FourH₇COOCH_TwoC (CH_Three)_TwoCH_TwoOCOC_FourH₇ C_{twenty two}H₄₅COOCH_TwoC (CH_Three)_TwoCH_TwoOCOC_{twenty two}H₄₅ C₁₇H₃₅COOCH_TwoC (CH_Three)_TwoCH_TwoOCOC₁₃H₂₇ In the fatty acid ester used in the present invention, monoester
The following general formulas (2) and (3) are preferable examples of the lubricant.
It is mentioned. R4-COO- (R5-O) m-R6 (2) R7-COO-R8 (3) (wherein m is an integer of 1 to 10, and R5 is-(CH_Two) N −
Or-(CH_Two) N- (n is an integer of 1 to 12)
Shows a divalent group that may contain an induced unsaturated bond
Or-[CH_TwoCH (CH_Three)]-Or-[C
H_TwoC (CH_Three) _TwoCH_TwoWherein R4 and R7 are each
A chain saturated or unsaturated carbon having 12 to 30 carbon atoms each independently
Represents a hydride group and may be the same or different from each other. R6
And R8 are each independently a chain or branched chain having 1 to 26 carbon atoms.
Represents a branched, saturated or unsaturated hydrocarbon group,
May also be different. ) In addition, monobasic fatty acids having 10 to 24 carbon atoms (unsaturated bonds
May be included or branched) and carbon number 2
~ 24 monohydric alcohols (including unsaturated bonds,
Mono-fatty acid ester consisting of
Tell can be used.

Specific examples thereof include butyl stearate, octyl stearate, amyl stearate, isooctyl stearate, butyl myristate, octyl myristate, butoxyethyl stearate, butoxydiethyl stearate, 2-ethylhexyl stearate, 2-octyldodecyl palmitate, 2-hexyldodecyl palmitate, isohexadecyl stearate, oleyl oleate, dodecyl stearate, tridecyl stearate, oleyl erucate and the like are preferred.

In addition, monoesters of saturated and unsaturated fatty acids and alcohols and fatty acid monoesters having an unsaturated bond, as well known in Japanese Patent Publication No. 51-39081, and Japanese Patent Publication No. 4-4917, are well known. Oleyl oleate described in Japanese Patent Application Laid-Open Publication No. H11-209, etc. can also be used. Specific examples of the monoester are as follows. _{L-b1 C 17 H 35 COOC} 17 H 35 L-b2 C 17 H 35 COOC 4 H 9 L-b3 C 17 H 35 COOCH 2 CH 2 OC 4 H 9 L-b4 C 17 H 35 COO (CH 2 CH 2 O) ₂ C ₄ H ₉ The amount of the monoester-based lubricant of the present invention used is 1 part by weight or more, preferably 3 parts by weight or more, and more preferably 100 parts by weight of the upper layer ferromagnetic powder. 5 parts by weight or more, and in the lower layer, 1 part by weight or more, preferably 3 parts by weight or more, more preferably 5 parts by weight or more based on 100 parts by weight of the nonmagnetic powder, and it is preferable to add both the upper layer and the lower layer. . The upper limit of each layer is 20% by weight. If the amount is too large, the surface of the magnetic layer becomes rough and the magnetic properties are deteriorated. If the amount is too small, the durability becomes poor. The diester-based lubricant and the monoester-based lubricant are used for the ferromagnetic powder 1 contained in the magnetic layer.
The amount is preferably 8 to 30 parts by weight, more preferably 10 to 20 parts by weight, per 100 parts by weight of the nonmagnetic powder contained in the lower layer or 100 parts by weight. The diester compound and the monoester compound may be used as a mixture. In this case, the amount of the diester compound is preferably 30% or more based on the total amount of the diester and the monoester. Here, the non-magnetic powder refers to an inorganic powder other than carbon black.

The present invention also relates to a magnetic recording medium comprising a substantially nonmagnetic lower layer provided on a support, and a magnetic layer containing a ferromagnetic powder in a binder provided on the lower layer. Each of the lower layers is formed of the ferromagnetic metal powder 100, respectively.
The fatty acid ester is preferably contained in an amount of 8 to 30 parts by weight with respect to 100 parts by weight of the nonmagnetic powder contained in the lower layer, or the C / Fe peak ratio when the surface of the magnetic layer is measured by Auger electron spectroscopy. It is preferably 5 to 100, more preferably 5 to 80, and the magnetic recording medium is preferably in the form of a disk. Such a magnetic recording medium has substantially the same fatty acid ester content in the magnetic layer and the lower layer as compared with the conventional floppy disk,
Since the lubricant present on the surface of the magnetic layer was suppressed to a low value, extremely high durability was achieved, the hardness of the surface of the magnetic layer was kept high, and high scratch resistance was provided. In particular, when the rotation speed is 1800 rpm or more (such as ZIP),
In particular, it has been found that outstanding durability can be achieved with a recording system (for example, HiFD) having a high-speed rotation of 3000 rpm or more.

The C / Fe peak ratio by Auger electron spectroscopy on the surface of the magnetic layer according to the present invention is an index indicating the amount of the lubricant present on the surface of the magnetic layer. This is based on the principle of irradiating a sample with an electron beam to determine the type of element from the kinetic energy of Auger electrons emitted from the sample and measuring the amount of the element from the Auger electron dose.

When the surface of the magnetic layer is analyzed by Auger spectroscopy, a peak of iron atoms derived from ferromagnetic powder and a peak of carbon derived from a binder and a lubricant appear. However, most of the carbon peaks are from lubricants. The basis is that when the magnetic disk of the present invention is subjected to hexane treatment and the surface of the magnetic layer is measured by Auger electron spectroscopy except for the lubricant according to the present invention, the Fe peak is strong, but the C peak contributed by the binder is weak, Conversely, if the hexane treatment is not performed, the C peak is strong. That is, when the surface of the magnetic layer is analyzed by Auger spectroscopy, peaks of iron atoms derived from the ferromagnetic powder and carbon peaks derived from the binder and the lubricant appear, but most of the carbon peaks are derived from the lubricant derived from the lubricant according to the present invention. Because they can be considered.

In the present invention, the measurement of C / Fe by Auger electron spectroscopy indicates a value obtained as follows. Apparatus: PHI-660 manufactured by Φ Company Measurement conditions: Primary electron beam Acceleration voltage 3 kV Sample current 130 nA Magnification 250 times Tilt angle 30 ° Under the above conditions, kinetic energy (Kinetic Energy) 130 eV
To 730 eV three times, the intensity of the KLL peak of carbon and the intensity of the LMM peak of iron are obtained in a differential form, and the ratio of C / Fe is obtained.

The C / Fe peak ratio of the surface of the magnetic layer of the magnetic recording medium of the present invention determined by Auger electron spectroscopy is 5 to 12%.
0, preferably 5 to 100, more preferably 5 to 80
However, this indicates that it is preferable that the surface of the magnetic layer has a relatively small amount. In other words, it is possible to secure good lubrication characteristics for a long time even when durability is extremely required, such as a floppy disk, while reducing the amount of lubricant on the magnetic layer surface to prevent sticking. This is a feature of the invention.

As described above, the amount of the lubricant contained in each of the magnetic layer and the lower layer of the magnetic recording medium of the present invention is preferably 5 to 100 parts by weight of the ferromagnetic powder or the nonmagnetic powder.
30 parts by weight, more preferably 10 to 30 parts by weight.
This is almost equivalent to the amount contained in a conventional floppy disk or the like. Therefore, although the amount of lubricant contained in the magnetic layer and the lower layer of the magnetic recording medium of the present invention is almost the same as that of a conventional floppy disk or the like, the amount of lubricant present on the surface of the magnetic layer is smaller than that of the conventional floppy disk. It is preferable that the number is significantly smaller than that of a disk or the like.

As a disadvantage of the conventional floppy disk,
If the amount of the lubricant is increased in order to improve the durability, the amount of the lubricant is increased on the surface, and as a result, the magnetic layer surface sticks to the magnetic head at rest, and there is a disadvantage that the torque at the time of startup increases. Also, to lower the starting torque,
When the amount of the lubricant is reduced, the friction coefficient increases and the durability deteriorates. These disadvantages become more pronounced when high-speed rotation is performed by high-density recording or the like.

In the magnetic recording medium of the present invention, the amount of the fatty acid ester in the magnetic layer and the lower layer is almost equal to that of the conventional floppy disk, but the lubricant present on the surface of the magnetic layer is suppressed to a low value. As a result, extremely high durability was achieved, the hardness of the surface of the magnetic layer was kept high, and high scratch resistance was imparted. Especially when the rotation speed is 700
It has been found that excellent durability can be achieved with a high-speed recording system (such as HiFD) at a speed of 1 rpm or more, further 1800 rpm or more (such as ZIP), especially 3000 rpm or more.

Further, it was found that the magnetic layer and the lower layer contained a large amount of lubricant and gradually emerged from the surface to exert a lubricating function, so that they had excellent long-term storage properties. The lubricant according to the present invention has a large amount of lubricant in the magnetic layer and the lower layer, and a suitable amount of the lubricant (mainly from the detected amount of C atoms of the lubricant and Fe atoms of the ferromagnetic powder in the Auger electron spectroscopy). As means for realizing the presence of the obtained C / Fe value, which is preferably 5 to 100, particularly preferably 5 to 80), there is the following method.

The lubricant is a fatty acid ester of a monoester or a diester. In particular, a diester compound and a monoester compound having an unsaturated C ＝ C are preferable because they have an affinity for the binder and the surface of the nonmagnetic powder. The addition amount in the coating layer is preferably 8 to 30 parts by weight for each of the magnetic layer and the lower layer based on 100 parts by weight of the ferromagnetic powder or the nonmagnetic powder. The amount of the binder in the magnetic layer is adjusted to 10
It is desirable to increase the amount of the binder in the lower layer to 10 to 25 parts by weight based on 0 part by weight and the amount of the binder in the lower layer to 25 to 40 parts by weight based on 100 parts by weight of the nonmagnetic powder.

Particularly, the binder for the lower layer preferably has a strong polar group such as SO ₃ Na and a structure containing a large number of aromatic rings in the skeleton. As a result, the affinity between the lubricant and the lower binder is further increased, and the lubricant can be more and stably present in the lower layer. If the affinity between the lubricant and the binder is too high and the binder and the lubricant become completely compatible at the molecular level, the lubricant cannot move to the upper layer, which is not preferable.

The surface of the magnetic recording medium of the present invention has a smaller amount of lubricant than the conventional one, but the fatty acid ester is necessary and sufficient, and the temperature rises due to frictional heat between the disk and the head rotating at high speed. Even though, it is difficult to volatilize due to strong intermolecular interaction, and stable fluid lubrication can be maintained without causing breakage of the lubricating film. In the present invention, Al / F
When e is 5 atomic% to 30 atomic%, the storage stability at high temperature and high humidity can be improved. This is because fatty acid esters originally have a high hydrophilicity and easily absorb moisture, and thus have a property of being easily hydrolyzed. This problem is further enhanced by the catalytic activity of the surface of the ferromagnetic powder, and the fatty acid ester is more easily decomposed when stored at high temperature and high humidity. Al / F
In the case of a ferromagnetic metal powder in which e is 5 at% to 30 at%, it was found that this effect was small, and it was difficult to decompose. As a result, even after storage under high temperature and high humidity, the characteristics of the disk before storage can be exhibited with almost no decrease in durability.

[0094]

BEST MODE FOR CARRYING OUT THE INVENTION

[Magnetic Layer] In the magnetic recording medium of the present invention, the lower layer and the ultrathin magnetic layer may be provided on only one side or both sides of the support. After applying the lower layer, the upper and lower layers are in a wet state (W / W),
Even after the lower layer is dried (W / D), the upper magnetic layer can be provided on the lower layer. From the viewpoint of production yield, simultaneous or sequential wet coating is preferable, but in the case of a disk, coating after drying can be used sufficiently. The upper layer / lower layer can be formed simultaneously by simultaneous or sequential wet coating (W / W) with the multilayer structure of the present invention, so that a surface treatment step such as a calendering step can be effectively utilized, and even an ultra-thin layer can be used for the surface of the upper magnetic layer. Roughness can be improved. The coercive force Hc of the magnetic layer needs to be 1800 Oe or more.
100-5000G, 100 for barium ferrite powder
It is necessary to be 0-3000G.

[Ferromagnetic Metal Powder] The ferromagnetic metal powder used in the upper magnetic layer of the present invention is preferably a ferromagnetic alloy powder containing α-Fe as a main component. These ferromagnetic metal powders include Al, Si, S, Sc, Ca,
Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag,
Sn, Sb, Te, Ba, Ta, W, Re, Au, H
g, Pb, Bi, La, Ce, Pr, Nd, P, Co,
It may contain atoms such as Mn, Zn, Ni, Sr, and B. In particular, Al, Si, Ca, Y, Ba, La, N
Preferably, at least one of d, Co, Ni, and B is contained other than α-Fe, and more preferably, at least one of Co, Y, and Al is contained. The content of Co is preferably at least 0 at% and at most 40 at% with respect to Fe, more preferably at least 15 at% and at most 35 at%, more preferably 2 at% to 35 at%.
It is 0 atomic% or more and 35 atomic% or less. The content of Y is 1.
The content is preferably from 5 at% to 12 at%, more preferably from 3 at% to 10 at%, more preferably from 4 at% to 9 at%. Al is preferably 1.5 atomic% or more and 12 atomic% or less, more preferably 3 atomic%.
It is at least 10 at% and more preferably at least 4 at% and at most 9 at%. These ferromagnetic metal powders may be preliminarily treated with a dispersant, a lubricant, a surfactant, an antistatic agent or the like before dispersion before the dispersion. Specifically, Japanese Patent Publication No. 44-14090, Japanese Patent Publication No. 45-1837
No. 2, JP-B-47-22062, JP-B-47-225
No. 13, JP-B-46-28466, JP-B-46-38
No. 755, JP-B-47-4286, JP-B-47-12
No. 422, JP-B-47-17284, JP-B-47-1
8509, JP-B-47-18573, JP-B-39-
No. 10307, JP-B-46-39639, U.S. Pat. Nos. 3,026,215, 3,303,341 and 31,001.
No. 94, No. 3242005, and No. 3389014.

The ferromagnetic alloy powder may contain a small amount of hydroxide or oxide. A ferromagnetic alloy powder obtained by a known production method can be used, and the following method can be used. A method of reducing a complex organic acid salt (mainly oxalate) with a reducing gas such as hydrogen, reducing iron oxide with a reducing gas such as hydrogen to reduce Fe or F
a method of obtaining e-Co particles or the like, a method of thermally decomposing a metal carbonyl compound, a method of reducing by adding a reducing agent such as sodium borohydride, hypophosphite or hydrazine to an aqueous solution of a ferromagnetic metal; A method of evaporating in a low-pressure inert gas to obtain a powder. The ferromagnetic alloy powder thus obtained is subjected to a known slow oxidation treatment, that is, a method of immersing in an organic solvent and then drying, and immersing in an organic solvent and then feeding an oxygen-containing gas to form an oxide film on the surface and drying. Any of the methods of forming an oxide film on the surface by adjusting the partial pressure of oxygen gas and inert gas without using an organic solvent can be used.

The ferromagnetic metal powder of the magnetic layer of the present invention was
When expressed in terms of specific surface area by the method, it is 40 to 80 m ² / g,
Preferably it is 45-70 m < ² > / g. If it is less than 40 m ² / g, noise increases, and if it is more than 80 m ² / g, surface properties tend to be difficult to obtain, which is not preferable. The crystallite size of the ferromagnetic powder of the magnetic layer of the present invention is preferably 80 to
180 °, more preferably 100 to 180 °, particularly preferably 110 to 175 °. The average major axis length of the ferromagnetic metal powder is usually 0.01 μm or more and 0.25 μm or less, preferably 0.03 μm or more and 0.15 μm or less, and more preferably 0.03 μm or more and 0.12 μm or less. The needle ratio of the ferromagnetic metal powder is preferably 3 or more and 15 or less, and more preferably 3 or more and 12 or less. The saturation magnetization s of the ferromagnetic metal powder is usually 100 to 180 emu / g.
, Preferably from 110 emu / g to 170 emu / g, more preferably from 125 to 160 emu / g. The coercive force of the metal powder is preferably from 1700 Oe to 3500 Oe, and more preferably from 1,800 Oe to 3000 Oe.

The water content of the ferromagnetic metal powder is 0.01 to 2%.
It is preferred that It is preferable to optimize the water content of the ferromagnetic metal powder depending on the type of the binder. It is preferable that the pH of the ferromagnetic metal powder be optimized depending on the combination with the binder used. Its range is from 4 to 12, preferably from 6 to 10. Ferromagnetic metal powder can be
Surface treatment may be performed with l, Si, P, or an oxide thereof. The amount thereof is 0.1 to 10% based on the ferromagnetic metal powder, and it is preferable that the surface treatment is performed so that the adsorption of a lubricant such as a fatty acid becomes 100 mg / m ² or less. Soluble Na, Ca, Fe, Ni, S
It may contain an inorganic ion such as r. It is preferable that these inorganic ions are essentially absent, but if they are 200 ppm or less, they do not particularly affect the properties. The ferromagnetic metal powder used in the present invention preferably has a small number of vacancies, and its value is preferably 20% by volume or less, more preferably 5% by volume or less.
% By volume or less. Needle shape, rice grain shape,
Any spindle shape is acceptable. The SFD of the ferromagnetic metal powder itself is preferably small, and is preferably 0.8 or less.
It is necessary to reduce the distribution of Hc in the ferromagnetic metal powder.
When the SFD is 0.8 or less, the electromagnetic conversion characteristics are good, the output is high, and the magnetization reversal is sharp and the peak shift is small, which is suitable for high-density digital magnetic recording. In order to reduce the distribution of Hc, there are methods for improving the particle size distribution of goethite and preventing sintering in ferromagnetic metal powder.

[Ferromagnetic Hexagonal Ferrite Powder] As the ferromagnetic hexagonal ferrite contained in the magnetic layer of the present invention, there are barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, and substituted Co. Specifically, magnetoplumbite-type barium ferrite and strontium ferrite, magnetoplumbite-type ferrite whose particle surface is coated with spinel,
Furthermore, magnetoplumbite-type barium ferrite and strontium ferrite containing a part of spinel phase are mentioned.
Sc, Ti, V, Cr, Cu, Y, Mo, Rh, Pd,
Ag, Sn, Sb, Te, Ba, Ta, W, Re, A
u, Hg, Pb, Bi, La, Ce, Pr, Nd, P,
It may contain atoms such as Co, Mn, Zn, Ni, Sr, B, Ge, and Nb. Generally, Co-Zn, Co
-Ti, Co-Ti-Zr, Co-Ti-Zn, Ni-
Ti-Zn, Nb-Zn-Co, Sb-Zn-Co, N
A substance to which an element such as b-Zn is added can be used. Some raw materials and production methods contain specific impurities.

The size of the ferromagnetic hexagonal ferrite powder is usually 10 to 200 nm, preferably 10 to 100 nm, as an average of the maximum major axis of the hexagonal plate (hereinafter referred to as “average plate diameter”).
nm, and particularly preferably 10 to 80 nm.

In particular, when reproducing with a magnetoresistive head in order to increase the track density, it is necessary to reduce the noise. The plate diameter is preferably 40 nm or less, but if it is 10 nm or less, stable magnetization cannot be expected due to thermal fluctuation. Above 200 nm, noise is high and none of them are suitable for high-density magnetic recording. The plate ratio (average plate diameter / average plate thickness) is desirably 1 to 15. Preferably it is 1-7. When the plate ratio is small, the filling property in the magnetic layer is increased, which is preferable, but sufficient orientation cannot be obtained. 1
If it is larger than 5, noise increases due to stacking between particles. The specific surface area by the BET method in this particle size range usually shows 10 to ²⁰⁰ m ² / g. The specific surface area generally corresponds to an arithmetic calculation value from the particle plate diameter and the plate thickness. The distribution of particle plate diameter and plate thickness is generally preferably as narrow as possible. Although it is difficult to make a numerical value, it can be compared by randomly measuring 500 particles from a particle TEM photograph. In many cases, the distribution is not a normal distribution, but when calculated and expressed as a standard deviation with respect to the average size (average plate diameter and average plate thickness), σ / average size = 0.1 to 2.
0. In order to sharpen the particle size distribution, the particle generation reaction system is made as uniform as possible, and the generated particles are subjected to a distribution improving treatment. For example, a method of selectively dissolving ultrafine particles in an acid solution is also known. The coercive force Hc measured with the ferromagnetic powder can be made up to about 500 Oersted to 5000 Oersted. A higher Hc is advantageous for high-density recording, but is limited by the capability of the recording head. In the present invention, Hc is about 1700 Oersted to 4000 Oersted, but is preferably 1800 Oersted or more and 3500 Oersted or less. When the saturation magnetization of the head exceeds 1.4 Tesla, it is preferable that the saturation magnetization be 2000 Oe or more. Hc can be controlled by particle size (plate diameter / plate thickness), kind and amount of contained element, substitution site of element, particle generation reaction condition and the like. The saturation magnetization s is 40 emu / g to 80 emu / g. The higher the value of σs, the better, but the smaller the fine particles, the lower the tendency. It is well known to combine spinel ferrite with magnetoplumbite ferrite to improve σs, and to select the type of element contained and the amount to be added. It is also possible to use W-type hexagonal ferrite. When dispersing the ferromagnetic powder, the surface of the ferromagnetic powder particles is sometimes treated with a substance suitable for the dispersion solvent and the polymer. As the surface treatment material, an inorganic compound or an organic compound is used. Typical examples of the main compound include oxides or hydroxides of Si, Al, P, etc., various silane coupling agents, and various titanium coupling agents. The amount of the surface treatment material is 0.1 to 10% by weight based on the ferromagnetic powder. The pH of the ferromagnetic powder is also important for dispersion. Normally, the pH is about 4 to 12, and there is an optimum value depending on the dispersion solvent and the polymer.
The moisture contained in the ferromagnetic powder also affects the dispersion, the dispersion solvent,
Although there is an optimum value depending on the polymer, usually, the water content is selected from 0.01 to 2.0% by weight based on the ferromagnetic powder. Hexagonal ferrite is produced by mixing barium oxide, iron oxide, and a metal oxide that replaces iron with boron oxide as a glass-forming substance to obtain the desired ferrite composition, then melting, quenching, and then crystallization. And then reheated, washed and pulverized to obtain a barium ferrite crystal powder, a glass crystallization method, a barium ferrite composition metal salt solution is neutralized with an alkali, and by-products are removed. Liquid phase heating, washing, drying and grinding to obtain barium ferrite crystal powder, hydrothermal reaction method, barium ferrite composition metal salt solution is neutralized with alkali, by-products are removed and then dried and dried at 1100 ° C or less , And pulverization to obtain a barium ferrite crystal powder, but the present invention is not limited to a production method.

[Non-Magnetic Layer] Next, detailed contents regarding the lower layer
Will be described. Inorganic powder used for the lower layer of the present invention
Is a non-magnetic powder, for example, metal oxide, metal carbonate
Salt, metal sulfate, metal nitride, metal carbide, metal sulfide
And other inorganic compounds. Mineralization
As the compound, for example, α-alumina having an α conversion of 90% or more,
β-alumina, γ-alumina, θ-alumina, silicon carbide
Element, chromium oxide, cerium oxide, α-iron oxide, hemata
Site, goethite, corundum, silicon nitride, titanium car
Bites, titanium oxide, silicon dioxide, tin oxide, mug oxide
Nesium, tungsten oxide, zirconium oxide, nitride
Boron, zinc oxide, calcium carbonate, calcium sulfate,
Barium sulfate, molybdenum disulfide, etc. alone or in combination
Used by Particularly preferred is a small particle size distribution.
Now, titanium dioxide,
Zinc oxide, iron oxide and barium sulfate are more preferable.
Are titanium dioxide and α-iron oxide. These inorganic powders
The average particle size is preferably 0.005 to 2 μm,
Depending on the combination of inorganic powder with different particle size,
Even with a single inorganic powder, the same effect can be achieved by broadening the particle size distribution.
It can be added. Particularly preferred are inorganic powders.
The average particle size is from 0.01 μm to 0.2 μm. In particular, nothing
When the machine powder is a granular metal oxide, the average particle size is 0.1 mm.
08 μm or less is preferable, and when it is an acicular metal oxide
The average major axis length is preferably 0.3 μm or less, 0.2 μm
The following are more preferred. Tap density is 0.05-2g / m
l, preferably 0.2-1.5 g / ml. Of inorganic powder
Water content is 0.1 to 5% by weight, preferably 0.2 to 3% by weight
%, More preferably 0.3 to 1.5% by weight. inorganic
The pH of the powder is 2-11, but the pH is 5.5-10.
Particularly preferred is between. Specific surface area of inorganic powder is 1-100m
^Two/ g, preferably 5 to 80 m^Two/ g, more preferably 10
~ 70m^Two/ g. The crystallite size of the inorganic powder is 0.0
04 μm to 1 μm is preferable, and 0.04 μm to 0.1 μm is preferable.
More preferred. Using DBP (dibutyl phthalate)
Oil absorption is 5-100ml / 100g, preferably 10-80ml /
100 g, more preferably 20 to 60 ml / 100 g. specific gravity
Is 1 to 12, preferably 3 to 6. Needle-shaped, spherical
Shape, polyhedral shape, or plate shape. Mohs hardness is 4
The number is preferably 10 or less. SA of inorganic powder
(Tearic acid) adsorption amount is 1 to 20 μmol / m^Two,Preferably
2 to 15 μmol / m^Two, More preferably 3 to 8 μmol / m^Two
It is. Preferably, the pH is between 3 and 6. this
The surface of these inorganic powders is subjected to a surface treatment,_TwoO
_Three, SiO_Two, TiO_Two, ZrO_Two, SnO_Two, Sb_Two
O_Three, ZnO, Y_TwoO_ThreePreferably there is
No. Particularly preferred for dispersibility is Al_TwoO _Three, SiO_Two,
TiO_Two, ZrO_TwoHowever, more preferred is Al_Two
O_Three, SiO_Two, ZrO_TwoIt is. These are combinations
Or may be used alone. Ma
Further, a surface treatment layer coprecipitated according to the purpose may be used.
First, after the presence of alumina, silica is added to the surface layer.
You can take the method of making it exist, or vice versa.
You. The surface treatment layer may be a porous layer depending on the purpose.
Although it does not matter, it is generally preferred that the material be homogeneous and dense.

Specific examples of the inorganic powder used for the lower layer of the present invention include Nanotite manufactured by Showa Denko and H
IT-100, ZA-G1, α hematite DPN-250, DPN-250BX, DPN-24 manufactured by Toda Kogyo Co., Ltd.
5, DPN-270BX, DPN-500BX, DBN
-SA1, DBN-SA3, titanium oxide TT manufactured by Ishihara Sangyo
O-51B, TTO-55A, TTO-55B, TTO
-55C, TTO-55S, TTO-55D, SN-1
00, α hematite E270, E271, E300, E
303, titanium industrial titanium oxide STT-4D, STT
-30D, STT-30, STT-65C, α hematite α-40, MT-100S, MT-100 manufactured by Teika
T, MT-150W, MT-500B, MT-600
B, MT-100F, MT-500HD, FI made by Sakai Chemical
NEX-25, BF-1, BF-10, BF-20, S
TM, Dowa Mining DEFIC-Y, DEFIC-R,
Examples include AS2BM and TiO ₂ P25 manufactured by Nippon Aerosil, 100A and 500A manufactured by Ube Industries, and fired products thereof. Particularly preferred inorganic powders are titanium dioxide and α-
It is iron oxide.

The α-iron oxide (hematite) is carried out under the following conditions. That is, α-F in the present invention
The production of e ₂ O ₃ particles uses acicular goethite particles as precursor particles. Acicular goethite particles can be produced, for example, by the following method.

An aqueous solution of an alkali hydroxide in an amount equal to or more than an equal amount is added to the aqueous ferrous solution, and a pH 11 containing colloid of ferrous hydroxide is added.
A method in which the above suspension is prepared, and an oxygen-containing gas is passed through the suspension at a temperature of 80 ° C. or lower to cause an oxidation reaction of ferrous ions to generate needle-like goethite particles. Reacting an aqueous ferrous salt solution with an aqueous alkali carbonate solution,
A method in which an oxygen-containing gas is passed through the obtained suspension containing FeCO ₃ to cause oxidation reaction of iron ions to generate spindle-like needle-like goethite particles.

An aqueous solution of an alkali hydroxide or an aqueous solution of an alkali carbonate having less than an equal amount is added to the aqueous ferrous salt solution, and an oxygen-containing gas is passed through the aqueous ferrous salt solution containing ferrous hydroxide colloid to obtain an iron ion solution. Is subjected to an oxidation reaction to produce acicular goethite core particles. Next, to the ferrous salt aqueous solution containing the acicular goethite core particles, an aqueous solution of an alkali hydroxide having an amount equal to or more than Fe ²⁺ in the ferrous salt aqueous solution is added, and then an oxygen-containing gas is passed. Growing the needle-like goethite nucleus particles.

An aqueous ferrous salt solution containing a ferrous hydroxide colloid is prepared by adding less than an equal amount of an aqueous alkali hydroxide or alkali carbonate solution to an aqueous ferrous solution, and an oxygen-containing gas is passed through the obtained aqueous solution. To cause the iron ions to undergo an oxidation reaction, thereby generating acicular goethite core particles,
Next, a method of growing the acicular goethite core particles in an acidic to neutral region.

It is to be noted that Ni, Zn, and the like which are usually added during the reaction for forming goethite particles to improve the characteristics of the particle powder, etc.
There is no problem even if different elements such as P and Si are added.
Needle-like goethite particles, which are precursor particles, are prepared at 200-500.
Dehydrate in the temperature range of ℃, or if necessary, add
Annealing is performed by heat treatment in a temperature range of -800 ° C to obtain acicular α-Fe ₂ O ₃ particles. Note that P, Si, B, Z are added to the surface of the acicular goethite particles to be dehydrated or annealed.
There is no problem even if sintering inhibitors such as r and Sb are attached.
Annealing by heat treatment in a temperature range of 350 to 800 ° C. is performed by annealing pores formed on the particle surface of the acicular α-Fe ₂ O ₃ particles obtained by dehydration, so that the extreme surface of the particles is formed. This is because it is preferable that the pores are closed by melting to form a smooth surface.

The α-Fe used in the present invention_TwoO_Three
The particle powder is a needle obtained by the dehydration or annealing.
Α-Fe_TwoO_ThreeIt is manufactured from the particles as follows. needle
Α-Fe_TwoO_ThreeThe particles are dispersed in an aqueous solution to obtain a suspension.
You. An Al compound is added to the obtained suspension, and p of the suspension is added.
H and α-Fe_TwoO_ThreeOn the surface of the particles
Coated with Al compound, then filtered, washed with water, dried, powdered
Crushing and, if necessary, further deaeration / consolidation treatment. Used
Aluminum compounds, aluminum acetate, aluminum sulfate,
Aluminum such as aluminum chloride and aluminum nitrate
Uses salts and alkali aluminates such as sodium aluminate
can do. In this case, the added amount of the Al compound is α-
Fe_TwoO_Three0.01 to 50 in terms of Al based on the particle powder
% By weight. If it is less than 0.01% by weight,
Insufficient dispersion in mixture resin, 50% by weight
If it exceeds, the Al compounds floating on the particle surface
It is not preferable because of interaction. The lower layer in the present invention
In inorganic powders, Si compounds are used together with Al compounds.
First, P, Ti, Mn, Ni, Zn, Zr, S
using one or more compounds selected from n and Sb
Can also be coated. Use with Al compound
The amount of each of these compounds is α-Fe_TwoO _Threeparticle
It is in the range of 0.01 to 50% by weight based on the powder. 0.
When the content is less than 01% by weight, the dispersibility is improved by the addition.
If there is almost no effect and exceeds 50% by weight,
It is preferred because compounds floating on surfaces other than
Not good.

The method for producing titanium dioxide is as follows. The methods for producing these titanium oxides are mainly a sulfuric acid method and a chlorine method. In the sulfuric acid method, raw ore of illuminite is digested with sulfuric acid, and Ti, Fe, etc. are extracted as sulfates. Iron sulfate is removed by crystallization separation, and the remaining titanyl sulfate solution is filtered and purified, and then thermally hydrolyzed to precipitate hydrous titanium oxide. After filtration and washing, impurities are washed and removed, a particle size regulator and the like are added, and the mixture is calcined at 80 to 1000 ° C. to obtain crude titanium oxide. Rutile type and anatase type are classified according to the type of nucleating agent added at the time of hydrolysis. The crude titanium oxide is prepared by pulverizing, sizing and surface treatment. Natural or synthetic rutile is used as the raw ore in the chlorine method. Ore is chlorinated in high-temperature reduction state, Ti
Fe becomes FeCl _{2 in} iCl ₄ , and iron oxide which has become solid by cooling is separated from liquid TiCl ₄ . After the obtained crude TiCl ₄ is purified by rectification, a nucleating agent is added and reacted with oxygen instantaneously at a temperature of 1000 ° C. or more to obtain crude titanium oxide. The finishing method for imparting pigmentary properties to the crude titanium oxide produced in this oxidative decomposition step is the same as the sulfuric acid method.

In the surface treatment, after the above-mentioned titanium oxide material is dry-pulverized, water and a dispersant are added thereto, and wet-pulverization and centrifugal separation are performed to classify coarse particles. Thereafter, the fine slurry is transferred to a surface treatment tank, where the metal hydroxide is coated on the surface. First, a predetermined amount of Al, Si, Ti, Zr, Sb, S
an aqueous solution of a salt such as n or Zn, and an acid for neutralizing the solution;
Alternatively, the surface of the titanium oxide particles is coated with a hydrated oxide by adding an alkali. Water-soluble salts produced as by-products are removed by decantation, filtration and washing, and finally the slurry is adjusted in pH and filtered, and washed with pure water. The washed cake is dried with a spray drier or a band drier. Finally, the dried product is pulverized by a jet mill into a product.

It is also possible to apply Al and Si surface treatment by passing steam of AlCl ₃ and SiCl ₄ into the titanium oxide powder as well as the water-based powder and then flowing the steam.

By mixing carbon black in the lower layer, the surface electric resistance Rs, which is a known effect, can be reduced, the light transmittance can be reduced, and a desired micro Vickers hardness can be obtained. In addition, it is possible to bring about the effect of storing the lubricant by including carbon black in the lower layer. Examples of carbon black include furnace black for rubber, thermal black for rubber, black for color, acetylene black, and the like. The following characteristics of the carbon black in the lower layer should be optimized depending on the desired effect, and the combined effect may provide more effects.

The specific surface area of the lower carbon black is 10
0~500m ² / g, preferably 150~400m ² /
g, DBP oil absorption is 20 to 400 ml / 100 g, preferably 30 to 400 ml / 100 g. The average particle size of the carbon black is 5 nm to 80 nm, preferably 10 to 50 nm,
More preferably, it is 10 to 40 nm. PH of carbon black is 2 to 10, water content is 0.1 to 10% by weight,
The tap density is preferably from 0.1 to 1 g / ml. Specific examples of the carbon black used in the present invention include BLACKPEARLS 2000, 130 manufactured by Cabot Corporation.
0, 1000, 900, 800, 880, 700, VU
LCAN XC-72, # 3050 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.
B, # 3150B, # 3250B, # 3750B, # 3
950B, # 950, # 650B, # 970B, # 85
0B, MA-600, MA-230, # 4000, # 4
010, CONDUCTE manufactured by Columbian Carbon Co., Ltd.
XSC, RAVEN 8800,8000,7000,
5750, 5250, 3500, 2100, 2000,
1800, 1500, 1255, 1250, Ketjen Black EC manufactured by Akzo Corporation, and the like. Carbon black may be used after being surface-treated with a dispersant or the like or grafted with a resin, or may be used in which a part of the surface is graphitized. Further, the carbon black may be dispersed in a binder before adding it to the paint. These carbon blacks are contained in an amount not exceeding 50% by weight based on the weight of the inorganic powder, that is, 4% of the total weight of the nonmagnetic layer.
It can be used within a range not exceeding 0% by weight. These carbon blacks can be used alone or in combination. 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).

The lower layer may contain an organic powder according to the purpose.
It can also be added. For example, acrylic styrene-based resin powder, benzoguanamine resin powder, melamine-based resin powder, phthalocyanine-based pigments, but also polyolefin-based resin powder, polyester-based resin powder, polyamide-based resin powder, polyimide-based resin powder, and polyfluoroethylene resin Can be used. The manufacturing method is disclosed in
No. 18,564, and those described in JP-A-60-255827 can be used.

[Binder] The binder resin, lubricant, dispersant, additive, solvent, dispersing method, etc. of the lower layer can be the same as those of the magnetic layer described below. In particular, with respect to the amount and type of the binder resin, the amount of the additive and the type of the dispersant, and the type thereof, a known technique for the magnetic layer can be applied.

As the binder used in the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins and mixtures thereof are used. As a thermoplastic resin, the glass transition temperature is −100 to 150 ° C., and the number average molecular weight is 1.0.
00 to 200,000, preferably 10,000 to 10
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,
Acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene,
There are polymers or copolymers containing butadiene, ethylene, vinyl butyral, vinyl acetal, vinyl ether, and the like as constituent units, polyurethane resins, and various rubber resins. In addition, as a thermosetting resin or a reactive resin, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic-based reactive resin, formaldehyde resin, silicone resin,
Examples include epoxy-polyamide resin, a mixture of polyester resin and isocyanate prepolymer, a mixture of polyester polyol and polyisocyanate, and a mixture of polyurethane and polyisocyanate. These resins are described in detail in "Plastic Handbook" published by Asakura Shoten. In addition, a known electron beam-curable resin can be used for each layer. These examples and the production method thereof are described in detail in JP-A-62-256219. The above resins can be used alone or in combination, but preferred are vinyl chloride resins,
A combination of at least one selected from vinyl chloride vinyl acetate copolymer, vinyl chloride vinyl acetate vinyl alcohol copolymer, vinyl chloride vinyl acetate maleic anhydride copolymer and a polyurethane resin, or a combination of these with a polyisocyanate Is raised.

As the structure of the polyurethane resin, known ones 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 = O (OM) ₂ , where M is a hydrogen atom,
Or an alkali metal base), OH, NR ₂ , N ⁺ R
Preferably, at least one polar group selected from ₃ (R is a hydrocarbon group), an epoxy group, SH, CN, or the like is introduced by a copolymerization or addition reaction.
The amount of such a polar group is 10 ^-1 to 10 ^-8 mol / g,
Preferably it is 10 ^-2 to 10 ^-6 mol / g.

Specific examples of these binders used in the present invention include VAGH and VY manufactured by Union Carbide.
HH, VMCH, VAGF, VAGD, VROH, VY
ES, VYNC, VMCC, XYHL, XYSG, PK
HH, PKHJ, PKHC, PKFE, manufactured by Nissin Chemical Co., Ltd., MPR-TA, MPR-TA5, MPR-TAL,
MPR-TSN, MPR-TMF, MPR-TS, MP
R-TM, MPR-TAO, 1000W manufactured by Denki Kagaku,
DX80, DX81, DX82, DX83, 100F
D, ZEON Corporation MR-104, MR-105, MR
110, MR100, MR555, 400X-110
A, Nipporan N2301, N2 manufactured by Nippon Polyurethanes
302, N2304, Pandex T manufactured by Dainippon Ink and Chemicals, Inc.
-5105, T-R3080, T-5201, Burnock D-400, D-210-80, Crisbon 610
9,7209, Toyobo Byron UR8200, UR
8300, UR-8700, RV530, RV280,
Daiferamine 4020, 5020, 5 manufactured by Dainichi Seika
100, 5300, 9020, 9022, 7020, manufactured by Mitsubishi Kasei Co., Ltd., MX5004, Samprene S manufactured by Sanyo Kasei Co., Ltd.
P-150 and Saran F310, F210 manufactured by Asahi Kasei Corporation.

The binder used in the nonmagnetic layer and the magnetic layer of the present invention is used in an amount of 5 to 50% by weight, preferably 10 to 30% by weight, based on the nonmagnetic powder or the ferromagnetic powder. It is preferable to use 5 to 30% by weight when a vinyl chloride resin is used, 2 to 20% by weight when a polyurethane resin is used, and 2 to 20% by weight of a polyisocyanate in combination. If head corrosion occurs due to a small amount of dechlorination, it is also possible to use only polyurethane or only polyurethane and isocyanate. In the present invention, when using polyurethane, the glass transition temperature is −50 to 150 ° C.,
Preferably 0 ° C to 100 ° C, elongation at break is 100 to 200
0%, the breaking stress is preferably 0.05 to 10 kg / mm ² , and the yield point is preferably 0.05 to 10 kg / mm ² .

The magnetic recording medium of the present invention comprises two or more layers. Therefore, the amount of the binder, the amount of the vinyl chloride resin, the polyurethane resin, the polyisocyanate or the other resin in the binder, the molecular weight of each resin forming the magnetic layer, the amount of the polar group, or the resin described above. It is of course possible to change the physical characteristics of the non-magnetic layer and the magnetic layer as needed, and rather, it should be optimized for each layer, and a known technique for a multilayer magnetic layer can be applied. For example, when changing the amount of the binder in each layer, it is effective to increase the amount of the binder in the magnetic layer in order to reduce abrasion on the surface of the magnetic layer,
In order to improve the head touch with the head, the amount of the binder in the nonmagnetic layer can be increased to provide flexibility.

The polyisocyanate used in the present invention includes tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,
Use of isocyanates such as 5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, 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., Ltd., Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate M
R, Millionate MTL, Takeda Yakuhin, Takenate D
-102, Takenate D-110N, Takenate D-2
00, Takenate D-202, manufactured by Sumitomo Bayer Co., Ltd., 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.

[Carbon Black, Abrasive] As the carbon black used in the magnetic layer of the present invention, furnace black for rubber, thermal black for rubber, black for color, acetylene black and the like can be used. Specific surface area is 5-50
0 m ² / g, DBP oil absorption 10-400 ml / 100
g, average particle size is 5 nm to 300 nm, pH is 2-1.
0, water content is 0.1-10% by weight, tap density is 0.1
１1 g / cc is preferred. Specific examples of the carbon black used in the present invention include BLA manufactured by Cabot Corporation.
CKPEARLS 2000, 1300, 1000, 9
00, 905, 800, 700, VULCAN XC-
72, manufactured by Asahi Carbon Co., Ltd., # 80, # 60, # 55, # 5
0, # 35, manufactured by Mitsubishi Chemical Corporation, # 2400B, # 23
00, # 900, # 1000 # 30, # 40, # 10
B, manufactured by Columbian Bonn, CONDUCTEX
SC, RAVE150, 50, 40, 15, RAVE
N-MT-P, manufactured by EC Japan, Ketjen Black E
C, and the like. Even if carbon black is surface-treated with a dispersant or grafted with resin,
A part of the surface may be graphitized. Before adding the carbon black to the magnetic paint, the carbon black may be dispersed in a binder in advance. These carbon blacks can be used alone or in combination. When carbon black is used, it is preferably used in an amount of 0.1 to 30% by weight based on the ferromagnetic powder. Carbon black has functions such as antistaticity of the magnetic layer, reduction of friction coefficient, provision of light-shielding properties, and improvement of film strength, and these differ depending on the carbon black used. Therefore, these carbon blacks used in the present invention are magnetic layers,
It is of course possible to change the type, amount, and combination in the lower layer, and use them according to the purpose based on the above-mentioned characteristics such as particle size, oil absorption, conductivity, and pH. Should be. The carbon black that can be used in the magnetic layer of the present invention can be referred to, for example, "Carbon Black Handbook" edited by Carbon Black Association.

The abrasive used in the present invention includes α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, artificial diamond, silicon nitride, carbonized carbon having an α conversion of 90% or more. Known materials mainly having a Mohs hardness of 6 or more, such as silicon, titanium carbide, titanium oxide, silicon dioxide, and boron nitride, are 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 preferably from 0.01 to 2 μm, and in particular, in order to enhance the electromagnetic conversion characteristics, it is preferable that the particle size distribution is narrow. Further, in order to improve the durability, it is possible to combine abrasives having different average particle diameters as needed, or to use a single abrasive to broaden the particle diameter distribution to have the same effect. Tap density is 0.3-2g / cc, water content is 0.1-5% by weight,
The pH 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 dice shape, but a shape having a part of a corner is preferable because of high abrasiveness. Specifically, AKP-12, AKP-15, AKP-20, and AKP manufactured by Sumitomo Chemical Co., Ltd.
-30, AKP-50, HIT20, HIT-30, H
IT-55, HIT60, HIT70, HIT80, H
IT100, manufactured by Reynolds, ERC-DBM, HP-
DBM, HPS-DBM, manufactured by Fujimi Abrasives, WA10
000, Uemura Industry Co., Ltd., UB20, Nippon Chemical Industry Co., Ltd.,
G-5, Chromex U2, Chromex U1, Toda Kogyo Co., Ltd., TF100, TF140, Ibiden Co., Ltd., Beta Random Ultra Fine, Showa Mining Co., Ltd., B-3, and the like. These abrasives can be added to the nonmagnetic layer as needed. By adding to the non-magnetic layer, the surface shape can be controlled, and the projected state of the abrasive can be controlled. The particle size and amount of the abrasive added to the magnetic layer and the non-magnetic layer should of course be set to optimal values.

[Additives] As additives used in the magnetic layer and the nonmagnetic layer of the present invention, those having a lubricating effect, an antistatic effect, a dispersing effect, a plasticizing effect, and the like are used. Molybdenum disulfide, tungsten graphite disulfide, boron nitride, graphite fluoride, silicone oil, silicone with polar groups, fatty acid-modified silicone, fluorine-containing silicone, fluorine-containing alcohol, fluorine-containing ester, polyolefin, polyglycol, alkyl phosphate and Alkali metal salts, alkyl sulfates and alkali metal salts thereof, polyphenyl ether, phenylphosphonic acid, α-naphthylphosphoric acid, phenylphosphoric acid, diphenylphosphoric acid, p-ethylbenzenephosphonic acid, phenylphosphinic acid, aminoquinones, various silane coupling agents , A titanium coupling agent, a fluorine-containing alkyl sulfate and an alkali metal salt thereof, a monobasic fatty acid having 10 to 24 carbon atoms (whether an unsaturated bond may be contained or branched. There), and, these metal salts (Li,
Na, K, Cu, etc.) or monovalent, divalent, trivalent, tetravalent, pentavalent, hexavalent alcohols having 12 to 22 carbon atoms (including unsaturated bonds and may be branched) An alkoxy alcohol having 12 to 22 carbon atoms (which may contain an unsaturated bond or may be branched), and having 8 carbon atoms
And fatty acid amides having 8 to 22 carbon atoms and aliphatic amines having 8 to 22 carbon atoms can be used in combination with the fatty acid ester of the present invention.

Specific examples of these fatty acids include capric acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid and isostearic acid. No. For alcohols, oleyl alcohol, stearyl alcohol, lauryl alcohol,
And so on. Also, nonionic surfactants such as alkylene oxides, glycerin, glycidol, alkylphenol ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, phosphoniums or sulfoniums, etc. Cationic surfactants, carboxylic acids,
Anionic surfactants containing acidic groups such as sulfonic acid, phosphoric acid, sulfate groups, phosphate groups, etc., amphoteric surfactants such as amino acids, aminosulfonic acids, sulfuric acid or phosphate esters of amino alcohols, alkylbedine types, etc. Agents and the like can also be used. These surfactants are described in detail in "Surfactant Handbook" (published by Sangyo Tosho Co., Ltd.). These lubricants, antistatic agents, etc. are not necessarily 100% pure,
Impurities such as unreacted products, by-products, decomposition products, and oxides may be contained. These impurities are preferably 30% or less, more preferably 10% or less.

These lubricants and surfactants used in the present invention each have a different physical action.
The type, amount, and combination ratio of the lubricant that produces a synergistic effect should be optimally determined according to the purpose.
To control bleeding to the surface by using fatty acids with different melting points in the non-magnetic layer and magnetic layer, to control bleeding to the surface by using esters with different boiling points, melting points and polarities, and to adjust the amount of surfactant It can be considered to improve the stability of coating and to improve the lubricating effect by increasing the amount of the lubricant added in the intermediate layer, and it is needless to say that the present invention is not limited to the examples shown here. Generally, the total amount of the lubricant is selected in the range of 0.1% by weight to 50% by weight, preferably 2% by weight to 25% by weight based on the ferromagnetic powder or nonmagnetic powder.

All or a part of the additives used in the present invention may be added at any step in the production of magnetic and non-magnetic paints. There are 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. In some cases, the purpose may be achieved by applying a part or all of the additive simultaneously or sequentially after applying the magnetic layer according to the purpose. Depending on the purpose, a lubricant may be applied to the surface of the magnetic layer after calendering or after slitting.

As the organic solvent used in the present invention, known solvents can be used, and for example, solvents described in JP-A-6-68453 can be used. [Layer Structure] The thickness structure of the magnetic recording medium of the present invention is such that the support has a thickness of 2 to 100 μm, preferably 2 to 80 μm. The support of the computer tape is 3.0 to 6.5 μm (preferably 3.0 to 6.0 μm, more preferably 4.0.
厚 5.5 μm).

An undercoat layer for improving adhesion may be provided between the support and the nonmagnetic layer or the magnetic layer. The thickness of the undercoat layer is 0.01 to 0.5 μm, preferably 0.02 to
0.5 μm. The present invention may be a double-sided magnetic layer disk-shaped medium in which a nonmagnetic layer and a magnetic layer are provided on both sides of a support, or may be provided on only one side. In this case, a non-magnetic layer,
A back coat layer may be provided on the side opposite to the magnetic layer side. This thickness is 0.1 to 4 μm, preferably 0.3 to
2.0 μm. Known undercoat layers and backcoat layers can be used.

The thickness of the magnetic layer of the magnetic recording medium of the present invention is optimized according to the saturation magnetization of the head used, the head gap length, and the band of the recording signal. The magnetic layer may be separated into two or more layers having different magnetic properties, and a known configuration relating to a multilayer magnetic layer can be applied. In that case, the dry thickness of the magnetic layer indicates the total of those magnetic layers.

The thickness of the non-magnetic layer as the lower layer of the medium according to the present invention is 0.2 μm or more and 5.0 μm or less, preferably 0.3 μm or less.
It is not less than μm and not more than 3.0 μm, more preferably not less than 1.0 μm and not more than 2.5 μm. The lower layer of the medium of the present invention exerts its effect if it is substantially non-magnetic,
For example, even if a small amount of ferromagnetic powder is included as an impurity or intentionally, the effect of the present invention is exhibited, and it goes without saying that the structure can be regarded as substantially the same as that of the present invention. Substantially non-magnetic means that the lower layer has a residual magnetic flux density of 100 G (Gauss) or less or a coercive force of 100 Oersted or less, and preferably has no residual magnetic flux density and coercive force.

[Backcoat Layer] In general, magnetic tapes for recording computer data are required to have higher repetitive running properties than video tapes and audio tapes. In order to maintain such high running durability, the back coat layer preferably contains carbon black and inorganic powder.

The carbon black is preferably used in combination of two kinds having different average particle diameters.
In this case, it is preferable to use a combination of fine-particle carbon black having an average particle diameter of 10 to 20 nm and coarse-particle carbon black having an average particle diameter of 230 to 300 nm. In general, the surface electric resistance of the back coat layer can be set low and the light transmittance can be set low by the addition of the fine carbon black as described above. Some magnetic recording devices use the light transmittance of the tape and use it as an operation signal. In such a case, the addition of fine carbon black is particularly effective. In addition, fine carbon black is generally excellent in holding power of a liquid lubricant, and contributes to reduction of a friction coefficient when used in combination with a lubricant. On the other hand, coarse-grained carbon black having an average particle diameter of 230 to 300 nm has a function as a solid lubricant, and also forms fine projections on the surface of the back layer to reduce the contact area, thereby reducing the friction coefficient. Contributes to the reduction of However, coarse-grained carbon black is used in severe driving systems.
The sliding of the tape easily causes the tape to fall off from the back coat layer, which has a drawback of increasing the error ratio.

Specific products of the particulate carbon black include the following. RAVE
N2000B (18 nm), RAVEN 1500B (1
7 nm) (all manufactured by Columbia Carbon Co., Ltd.), BP80
0 (17 nm) (Cabot), PRINTENTEX
90 (14 nm), PRINTEX 95 (15 nm),
PRINTEX85 (16 nm), PRINTEX75
(17 nm) (all manufactured by Degussa), # 3950 (16
nm) (manufactured by Mitsubishi Chemical Corporation).

Specific examples of commercial products of coarse particle carbon black include thermal black (270 nm) (manufactured by Khancarb) and RAVEN MTP (275 nm).
(Made by Columbia Carbon Co., Ltd.).

In the case of using two types having different average particle diameters in the back coat layer, the content ratio (weight ratio) of the fine particle carbon black of 10 to 20 nm and the coarse particle carbon black of 230 to 300 nm is the former. : The latter is preferably in the range of 98: 2 to 75:25, more preferably in the range of 95: 5 to 85:15.

The content of carbon black in the back coat layer (when two types are used, the total amount thereof) is usually in the range of 30 to 80 parts by weight with respect to 100 parts by weight of the binder. Preferably, it is in the range of 45 to 65 parts by weight.

It is preferable to use two kinds of inorganic powders having different hardnesses in combination. Specifically, Mohs hardness 3 ~
It is preferable to use a 4.5 soft inorganic powder and a 5 to 9 Mohs hardness hard inorganic powder. Mohs hardness is 3-4.
By adding the soft inorganic powder of No. 5, the friction coefficient can be stabilized by repeated running. Further, with the hardness in this range, the sliding guide pole is not cut off. The average particle diameter of the inorganic powder is 30 to 50 nm.
Is preferably within the range.

Examples of the soft inorganic powder having a Mohs hardness of 3 to 4.5 include calcium sulfate, calcium carbonate, calcium silicate, barium sulfate, magnesium carbonate, zinc carbonate, and zinc oxide. They are,
They can be used alone or in combination of two or more. Among these, calcium carbonate is particularly preferred.

[0142] The content of the soft inorganic powder in the back coat layer is 10 to 14 parts by weight per 100 parts by weight of carbon black.
It is preferably in the range of 0 parts by weight, more preferably 35 to 100 parts by weight.

By adding a hard inorganic powder having a Mohs hardness of 5 to 9, the strength of the back coat layer is enhanced and the running durability is improved. When these inorganic powders are used together with carbon black or the above-mentioned soft inorganic powders, they are less deteriorated even in repeated sliding and form a strong backcoat layer. In addition, the addition of the inorganic powder provides an appropriate polishing force, and reduces the adhesion of shavings to the tape guide pole and the like. In particular, when used in combination with a soft inorganic powder (among others, calcium carbonate), the sliding characteristics with respect to a guide pole having a rough surface are improved, and the friction coefficient of the back coat layer can be stabilized.

The hard inorganic powder has an average particle diameter of 80 to
It is preferably in the range of 250 nm (more preferably, 100 to 210 nm).

Examples of the hard inorganic powder having a Mohs hardness of 5 to 9 include α-iron oxide, α-alumina, and chromium oxide (Cr ₂ O ₃ ). These powders may be used alone or in combination. Of these, α-iron oxide or α-alumina is preferred. The content of the hard inorganic powder is usually 3 to 30 parts by weight based on 100 parts by weight of carbon black,
Preferably, it is 3 to 20 parts by weight.

When the soft inorganic powder and the hard inorganic powder are used together in the back coat layer, the difference in hardness between the soft inorganic powder and the hard inorganic powder is 2 or more (more preferably 2.5 or more, particularly It is preferable to select and use a soft inorganic powder and a hard inorganic powder as in (3).

It is preferable that the back coat layer contains the above-mentioned two types of inorganic powders having different specific Mohs hardnesses and the above-mentioned two types of carbon black having different average particle sizes. In particular, in this combination, it is preferable that calcium carbonate is contained as the soft inorganic powder.

The back coat layer may contain a lubricant. The lubricant can be appropriately selected from the above-mentioned lubricants that can be used for the nonmagnetic layer or the magnetic layer. In the back coat layer, the lubricant is usually added in a range of 1 to 5 parts by weight based on 100 parts by weight of the binder. [Support] The support used in the present invention includes polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins, and cellulose triacetate.
And known films such as polycarbonate, polyamide, polyimide, polyamide imide, polysulfone, polyaramid, aromatic polyamide, and polybenzoxazole. It is preferable to use a high-strength support such as polyethylene naphthalate or polyamide. If necessary, a laminated type support as disclosed in JP-A-3-224127 can be used to change the surface roughness of the magnetic surface and the base surface. 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 addition, an aluminum or glass substrate can be used as the support of the present invention.

In order to achieve the object of the present invention, the center surface average surface roughness SRa measured by the Mirau method of TOPO-3D manufactured by WYKO as a support is usually 8.0 nm or less, preferably 4.0 nm or less. More preferably, it is necessary to use one having a thickness of 2.0 nm or less. It is preferable that these supports not only have a small center plane average surface roughness but also have no coarse protrusions of 0.5 μm or more. The surface roughness can be freely controlled by the size and amount of the filler added to the support as required. Examples of these fillers include oxides and carbonates such as Ca, Si and Ti, and organic powders such as acryl. The maximum height SRmax of the support is 1 μm or less, the ten-point average roughness SRz is 0.5 μm or less, and the height of the center plane peak is SR.
Preferably, p is 0.5 μm or less, center plane valley depth SRv is 0.5 μm or less, center plane area ratio SSr is 10% or more and 90% or less, and average wavelength Sλa is 5 μm or more and 300 μm or less.
In order to obtain the desired electromagnetic conversion characteristics and durability, the surface projection distribution of these supports can be arbitrarily controlled by a filler. Each of the particles having a size of 0.01 μm to 1 μm is reduced from 0 particles per 0.1 mm ^2. It can be controlled in the range of 2000.

The F-5 value of the support used in the present invention is preferably 5 to 50 kg / mm ² ,
The heat shrinkage at 0 minute is preferably 3% or less, 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 is 5-100 kg / mm ² , elastic modulus is 100-20
00 kg / mm ² is preferred. The coefficient of thermal expansion is 10 ^-4 to 10
⁻⁸ / ° C., preferably 10 ⁻⁵ to 10 ⁻⁶ / ° C.
The coefficient of humidity expansion is 10 ⁻⁴ / RH% or less, preferably 10
^-5 / RH% or less. It is preferable that these thermal characteristics, dimensional characteristics, and mechanical strength characteristics are substantially equal to each other in the in-plane direction of the support with a difference of 10% or less.

[Production Method] The step of producing the magnetic paint and the lower layer 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,
All raw materials such as an abrasive, 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. In order to manufacture the magnetic recording medium of the present invention,
Conventionally known manufacturing techniques can be used as some of the steps. In the kneading step, it is preferable to use one having a strong kneading force, such as an open kneader, a continuous kneader, a pressure kneader, and an extruder. When a kneader is used, the ferromagnetic powder or the non-magnetic powder and all or part of the binder (preferably at least 30% by weight of the total binder) and 15 to 500 parts of kneading are mixed with 100 parts of ferromagnetic powder. It is processed. The details of these kneading processes are described in JP-A-1-106338 and JP-A-1-79274. Glass beads can be used to disperse the magnetic layer solution and the non-magnetic layer solution, but zirconia beads, titania beads, and steel beads, which are high-density dispersion media, are preferable. The particle size and the filling rate of these dispersion media are optimized and used. A well-known disperser can be used.

When a magnetic recording medium having a multilayer structure is applied in the present invention, it is preferable to use the following method. First, a lower layer is first 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. Showa 60-238
179, Japanese Patent Application Laid-Open No. 2-265672, a method of applying an upper layer by a support pressure type extrusion coating apparatus.
No. 17971, Japanese Patent Application Laid-Open No. 2-265672, a method of applying upper and lower layers almost simultaneously by one coating head having two built-in slits, and a third method disclosed in Japanese Patent Application Laid-Open No. 2-174965. This is a method in which the upper and lower layers are applied almost simultaneously by an extrusion coating device with a backup roll. Incidentally, in order to prevent the electromagnetic conversion characteristics and the like of the magnetic recording medium from deteriorating due to the aggregation of the magnetic particles, JP-A-62-95174 and JP-A-1-236968 have been proposed.
It is desirable to apply shear to the coating liquid inside the coating head by a method as disclosed in US Pat. Further, the viscosity of the coating liquid must satisfy the numerical range disclosed in Japanese Patent Application No. 1-312659. In order to realize the structure of the present invention, it is of course possible to use a sequential multi-layer coating in which a lower layer is applied and dried, and then a magnetic layer is provided thereon, and the effect of the present invention is not lost. However, in order to reduce coating defects and improve quality such as dropout, it is preferable to use the above-described simultaneous multilayer coating.

In the case of a disk, sufficient isotropic orientation may be obtained even without orientation, without using an orientation device. It is preferable to use a known random alignment device. In the case of ferromagnetic metal powder, isotropic orientation is generally preferably in-plane two-dimensional random, but may be three-dimensional random with a vertical component.
In the case of hexagonal ferrite, three-dimensional randomness in the in-plane and vertical directions generally tends to occur, but in-plane two-dimensional randomness is also possible. In addition, isotropic magnetic characteristics can be imparted in the circumferential direction by using a known method such as a different polarity opposed magnet and making the magnets vertically oriented. In particular, when performing high-density recording, vertical alignment is preferable. In addition, circumferential orientation may be performed using spin coating.

In the case of a magnetic tape, it is oriented in the longitudinal direction using a cobalt magnet or a solenoid. It is preferable that the drying position of the coating film can be controlled by controlling the temperature of the drying air, the amount of air, and the coating speed.
The temperature of the drying air is preferably 60 ° C. or more at 000 m / min, and an appropriate preliminary drying can be carried out before entering the magnet zone.

As a calendering roll, treatment is performed with a heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimideamide or a metal roll.
In particular, in the case of forming a double-sided magnetic layer, it is preferable to perform the treatment with metal rolls. The processing temperature is preferably 50 ° C. or higher,
More preferably, the temperature is 100 ° C. or higher. The linear pressure is preferably at least 200 kg / cm, more preferably at least 300 kg / cm.

[Physical Characteristics] The saturation magnetic flux density of the magnetic layer of the magnetic recording medium according to the present invention is 2 when a ferromagnetic metal powder is used.
When the hexagonal ferrite is used, it is 1000G or more and 3000G or less. The coercive forces Hc and Hr are from 1500 Oersteds to 5000 Oersteds, preferably from 1700 Oersteds to 3000 Oersteds. The distribution of coercive force is preferably narrow.
It is preferably 6 or less. The squareness ratio is 0.55 or more and 0.67 or less in the case of two-dimensional random, preferably 0.58 or more and 0.64 or less. In the case of three-dimensional random, it is preferably 0.45 or more and 0.55 or less. The orientation is 0.6 or more, preferably 0.7 or more in the vertical direction, and 0.7 or more, preferably 0.8 or more when demagnetizing field correction is performed. 2
The orientation ratio is preferably 0.8 or more in both the three-dimensional random and the three-dimensional random. In the case of two-dimensional randomness, the squareness ratio in the vertical direction, Br, Hc and Hr are 0.1 to 0.5 in the in-plane direction.
It is preferable to set it within twice.

In the case of a magnetic tape, the squareness ratio is 0.7 or more,
Preferably it is 0.8 or more. The magnetic recording medium of the present invention
The coefficient of friction for the head is from -10 ° C to 40 ° C,
0.5 or less in the range of 0% to 95%, preferably
Is 0.3 or less, and the surface resistivity is preferably 10^Four
-10¹²Ohm / sq, charged potential is from -500V to + 500V
Is preferably within. The elastic modulus at 0.5% elongation of the magnetic layer is
100 to 2000 kg / mm in each direction^Two, Breaking strength
The degree is preferably 10 to 70 kg / mm^TwoBullets on magnetic recording media
The modulus is preferably 100 to 1500 kg / mm in each direction in the plane.
^Two, Residual growth is preferably 0.5% or less, 100 ° C or less
The heat shrinkage at all temperatures is preferably 1% or less.
More preferably 0.5% or less, most preferably 0.1%.
1% or less. Glass transition temperature of magnetic layer (at 110Hz
The maximum point of the loss elastic modulus in the measured dynamic viscoelasticity measurement) is 50.
C. to 120.degree. C. is preferred, and that of the lower non-magnetic layer is
0 ° C to 100 ° C is preferred. Loss modulus is 1 × 10⁶~
8 × 10⁹dyne / cm^Two Preferably in the range of
The tangent is preferably 0.2 or less. Large loss tangent
If it is too hard, an adhesive failure is likely to occur. These thermal properties
Mechanical properties are almost equal within 10% in each direction in the plane of the medium
Is preferred. The residual solvent contained in the magnetic layer is preferable.
100mg / m^TwoBelow, more preferably 10 mg / m^TwoLess than
Below. The porosity of the coating layer is non-magnetic lower layer, magnetic layer
Preferably 30% by volume or less, more preferably 20% by volume or less.
% By volume or less. Porosity is small to achieve high output
Is preferable, but a certain value is secured depending on the purpose.
Sometimes it is better. For example, repetitive applications are important
In the case of disk media, the higher the porosity, the better the running durability.
Often good.

The surface of the magnetic layer was formed by using Mira of TOPO-3D.
The center plane surface roughness Ra measured by the u method is preferably 4.0.
nm or less, more preferably 3.8 nm or less, particularly preferably 3.5 nm or less. The maximum height SRmax of the magnetic layer is 0.
5 μm or less, ten-point average roughness SRz is 0.3 μm or less, center plane peak height SRp is 0.3 μm or less, center plane trough depth SRv is 0.3 μm or less, center plane area ratio SSr is 20% or more, 80
% Or less, and the average wavelength Sλa is preferably 5 μm or more and 300 μm or less. The surface protrusions of the magnetic layer can be arbitrarily set in a range of 0 to 2000 with a size of 0.01 μm to 1 μm, and it is preferable to optimize the electromagnetic conversion characteristics and the friction coefficient. . These can be easily controlled by controlling the surface properties by the filler of the support, the particle size and amount of the powder to be added to the magnetic layer, the roll surface shape of the calendar treatment, and the like. Curl is ± 3mm
It is preferable to be within.

In the present invention, it is easily presumed that the physical properties of the nonmagnetic layer and the magnetic layer can be changed according to the purpose. For example, the elastic modulus of the magnetic layer is increased to improve running durability, and at the same time, the elastic modulus of the non-magnetic layer is made lower than that of the magnetic layer to improve the contact of the magnetic recording medium with the head.

[0160]

Hereinafter, specific examples of the present invention will be described.
The present invention is not limited to this. In addition,
In the examples, "parts" indicates "parts by weight" unless otherwise specified. <Preparation of paint> Magnetic paint ML-1 (using needle-like ferromagnetic powder) Ferromagnetic metal powder: 100 parts of M-1 Composition: Co / Fe (atomic ratio) 30% Hc 2550 Oersted, specific surface area 55 m ² / g, σs 140 emu / g Crystallite size 120 °, average major axis length 0.048 μm, acicular ratio 4 Al compound (Al / Fe atomic ratio 8%) Y compound (Y / Fe atomic ratio 6%) Vinyl chloride copolymer MR110 (Nihon Zeon) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo) 3 parts α-alumina HIT55 (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co.) 5 parts 3 parts phenylphosphonic acid 10 parts butyl stearate 10 parts butoxyethyl Stearate 5 parts Isohexadecyl stearate 3 parts Stearic acid 2 parts Methyl ethyl ketone 180 parts Cyclohexanone 1 80 parts Magnetic paint ML-2 (using needle-like ferromagnetic powder) Ferromagnetic metal powder: M-2 100 parts Composition: Co / Fe (atomic ratio) 30% Hc2360 Oersted, specific surface area 49 m ² / g, σs 146 emu / g crystal Particle size 170 °, average major axis length 0.100 μm, needle ratio 6, SFD 0.51 Al compound (Al / Fe atomic ratio 5%) Y compound (Y / Fe atomic ratio 5%) pH 9.4 Polymer MR110 (manufactured by Zeon Corporation) 10 parts Polyurethane resin UR5500 (manufactured by Toyobo) 4 parts α-alumina HIT70 (manufactured by Sumitomo Chemical) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co.) 1 part Phenylphosphonic acid 3 parts olein Acid 1 part Stearic acid 0.6 part Ethylene glycol dioleyl 12 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint ML-3 (using acicular ferromagnetic powder: comparative example) Ferromagnetic metal powder: M-3 composition / Fe: Ni = 96: 4 100 parts Hc1600 oersted, specific surface area 45 m ² / g Crystallite size 220 °, σs135 emu / g Average major axis length 0.20 μm, needle ratio 9 Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR-8600 (manufactured by Toyobo) 5 parts α-alumina (particle diameter 0.65 μm) 2 parts Oxidation Chromium (average particle diameter: 0.35 μm) 15 parts Carbon black (average particle diameter: 0.03 μm) 2 parts Carbon black (average particle diameter: 0.3 μm) 9 parts Isohexadecyl stearate 4 parts n-butyl stearate 4 parts Butoxyethyl stearate 4 parts Oleic acid 1 part Stearic acid 1 part Methyl ethyl ketone 300 parts Magnetic paint ML-4 (plate ferromagnetic 100 parts Barium ferrite powder: M-4 to Ba molar ratio composition: Fe 9.10, Co 0.20, Zn 0.77 Hc 2500 Oersted, specific surface area 50 m ² / g, σs 58 emu / g Average plate diameter 35 nm, plate shape Ratio 4 Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo) 3 parts α-alumina HIT55 (manufactured by Sumitomo Chemical) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co.) 5 parts Phenyl Phosphonic acid 3 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 3 parts Stearic acid 2 parts Methyl ethyl ketone 125 parts Cyclohexanone 125 parts Magnetic paint ML-5 (using plate-like ferromagnetic powder) Barium ferrite powder: M -5 100 parts: molar ratio to Ba composition: Fe 9.10, Co 0.20, Zn 0.77 Hc 2500 Oersted, specific surface area 50 m ² / g, σs 58 emu / g average plate diameter 35 nm, plate ratio 2.5 vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 10 parts Polyurethane resin UR5500 (manufactured by Toyobo Co., Ltd.) 4 parts α-alumina HIT55 (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co., Ltd.) 1 part Phenylphosphonic acid 3 parts Oleic acid 1 part Stearic acid 0.6 part Ethylene Glycoldioleyl 16 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint ML-6 (using needle-shaped ferromagnetic powder) Ferromagnetic metal powder: M-2 100 parts Composition: Co / Fe (atomic ratio) 30% Hc2360 Oersted, specific surface area 49m ² / g, σs146emu / g crystallite size 170 Å, an average major axis length 0.10 μm, needle ratio 6, SFD 0.51 Al compound (Al / Fe atomic ratio 5%) Y compound (Y / Fe atomic ratio 5%) pH 9.4 Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 10 Part Polyurethane resin UR5500 (manufactured by Toyobo) 4 parts α-alumina HIT70 (manufactured by Sumitomo Chemical) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co.) 1 part Phenylphosphonic acid 3 parts Myristinic acid 1 part Stearic acid 0.6 part Stearin Butyl acid 4 parts Cetyl palmitate 4 parts Oleyl oleate 4 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint ML-7 (using needle-like ferromagnetic powder) Ferromagnetic metal powder: M-2 100 parts Composition: Co / Fe (atomic Ratio) 30% Hc2360 Oersted, specific surface area 49 m ² / g, σs 146 emu / g, crystallite size 170Å , Average major axis length 0.100 μm, needle ratio 6, SFD 0.51 Al compound (Al / Fe atomic ratio 5%) Y compound (Y / Fe atomic ratio 5%) pH 9.4 vinyl chloride copolymer MR110 (Manufactured by Zeon Corporation) 10 parts Polyurethane resin UR5500 (manufactured by Toyobo) 4 parts α-alumina HIT70 (manufactured by Sumitomo Chemical) 10 parts carbon black # 50 (manufactured by Asahi Carbon Co.) 1 part phenylphosphonic acid 3 parts amyl stearate 4 Part Butoxyethyl stearate 6 parts Oleyl oleate 4 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Nonmagnetic paint NU-1 (using spherical inorganic powder) Inorganic powder TiO ₂ crystal rutile 80 parts Average particle diameter 0.035 μm, ratio by BET method Surface area 40 m ² / g pH 7 TiO ₂ content 90% or more, DBP oil absorption 27-38 ml / 100 g, 8% by weight of Al ₂ O _{3 on the} surface of the whole particles on the surface Carbon black Conductex SC-U (manufactured by Columbian Carbon Co., Ltd.) 20 parts Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (Manufactured by Toyobo Co., Ltd.) 5 parts Phenylphosphonic acid 4 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Nonmagnetic paint NU -2 (using spherical inorganic powder) Inorganic powder TiO ₂ crystalline rutile 100 parts Average primary particle diameter 0.035 μm, specific surface area by BET method 40 m ² / g pH 7 TiO ₂ content 90% or more, DBP oil absorption 27 to 38 ml / 100g, Al ₂ O ₃ on the surface, SiO ₂ is present Ketjen black EC (AKUZO NOBEL Co.) 13 parts Average particle size: 30 nm DBP oil absorption: 350 ml / 100 g pH: 9.5 BET specific surface area: 950 meters ² / g Volatile content: 1.0% Vinyl chloride copolymer MR 110 ( Zeon Corporation) 16 parts Polyurethane resin UR8200 (Toyobo) 6 parts Phenylphosphonic acid 4 parts Ethylene glycol dioleyl 16 parts Oleic acid 1 part Stearic acid 0.8 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Non-magnetic paint NU-3 (using spherical inorganic powder powder) Inorganic powder TiO ₂ crystalline rutile 75 parts Average particle diameter 0.035 μm, specific surface area 40 m ² / g pH 7 TiO ₂ content 90% or more, DBP oil absorption 27 to 38g / 100g, Al ₂ O ₃ and SiO ₂ present on the surface Carbon black Ketchumbra EC 10 parts α-alumina AKP-15 (Sumitomo Chemical Co., Ltd.) Average particle diameter: 0.65 μm 15 parts Vinyl chloride copolymer MR110 (Nippon Zeon) 12 parts Polyurethane resin UR8600 (Toyobo) 5 parts Isohexadecyl stearate 4 parts n-butyl stearate 4 parts butoxyethyl stearate 4 parts oleic acid 1 part stearic acid 1 part methyl ethyl ketone 300 parts Nonmagnetic paint NU-4 (using needle-like inorganic powder) inorganic powder α-Fe ₂ O ₃ hematite 80 parts average major axis length 0.15 [mu] m, BET method specific surface area by 50m ² / g pH 9 surface to Al ₂ O ₃ carbon black Con existence 8 wt% relative to total particle Conductex Tex SC-U (Columbian carbon 20 parts Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane Resin UR8200 (Toyobo) 5 parts Phenylphosphonic acid 4 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Nonmagnetic Paint NU-5 (using acicular inorganic powder) Inorganic powder α-Fe ₂ O ₃ hematite 100 parts Average major axis length 0.15 μm, BET specific surface area 50 m ² / g pH 9, Al ₂ O ₃ particles on surface 8% by weight based on the whole Carbon black # 3250B (Mitsubishi Kasei) 18 parts Vinyl chloride copolymer MR104 (Nippon Zeon) 15 parts Polyurethane resin UR5500 (Toyobo) 7 parts Phenylphosphonic acid 4 parts Ethylene glycol Dioleyl 16 parts Oleic acid 1.3 parts Stearic acid 0.8 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Non-magnetic paint NU-6 (using needle-like inorganic powder) Inorganic powder α-Fe ₂ O ₃ hematite 100 parts Average major axis length 0.15 μm, BET specific surface area 50 m ² / g pH 9, Al ₂ O _{3 on the} surface 8% by weight based on the whole particles Carbon black # 3250B (manufactured by Mitsubishi Kasei) 18 parts Vinyl chloride copolymer MR104 (manufactured by Zeon Corporation) 15 parts Polyurethane resin UR5500 (Manufactured by Toyobo) 7 parts Phenylphosphonic acid 4 parts Butyl stearate 3 parts Cetyl palmitate 3 parts Oleyl oleate 10 parts Myristinic acid 1.3 parts Stearic acid 0.8 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 part nonmagnetic coating NU-7 (needle-like inorganic powder used) inorganic powder α-Fe ₂ O ₃ f Tight 100 parts Average major axis length 0.15 [mu] m, specific surface area by the BET method: ^{50m 2 / g pH 9, Al} 2 O 3 is present 8 wt% with respect to the entire particles to the surface of carbon black # 3250B (manufactured by Mitsubishi Chemical Industries, Ltd.) 18 parts Vinyl chloride copolymer MR104 (manufactured by Zeon Corporation) 15 parts Polyurethane resin UR5500 (manufactured by Toyobo Co., Ltd.) 7 parts Phenylphosphonic acid 4 parts Amyl stearate 6 parts Butoxyethyl stearate 6 parts Oleyl oleate 6 parts Methyl ethyl ketone / cyclohexanone (8 / 2 mixed solvent) 250 parts Production method 1 (disk: W / W) For each of the above 14 paints, each component was kneaded with a kneader, and then dispersed using a sand mill. To the resulting dispersion, add 10 parts of polyisocyanate to the coating liquid for the nonmagnetic layer and 10 parts to the coating liquid for the magnetic layer, and further add 40 parts of cyclohexanone to each, and use a filter having an average pore diameter of 1 μm. And filtered to prepare coating solutions for forming a nonmagnetic layer and a magnetic layer, respectively.

The obtained non-magnetic layer coating solution was applied to a thickness of 62 μm so that the thickness after drying became 1.5 μm and immediately thereafter, the thickness of the magnetic layer became 0.15 μm thereon. In this method, simultaneous multi-layer coating is performed on a polyethylene terephthalate support having a center plane average surface roughness of 3 nm. After passing through an AC magnetic field generator and performing random orientation treatment and drying, the temperature is 90 ° C. and the linear pressure is 300 with a 7-stage calendar.
After 3.7 inch punching and surface polishing, a 3.7 inch cartridge (zip-disk manufactured by Iomega, USA) with a liner installed inside
Cartridge) and add predetermined mechanical parts.
A 7-inch floppy disk was obtained. Further, some of the samples were subjected to longitudinal orientation using a 4000 G same-polarity opposed Co magnet before randomizing orientation treatment.

In this case, it is preferable to increase the frequency and the magnetic field strength of the AC magnetic field generator so that sufficient randomization is finally performed.
The above can be obtained. When a barium ferrite magnetic material is used, vertical alignment can be performed in addition to the above-described alignment method. Also, if necessary, after punching into a disk shape, a high-temperature thermotreatment (usually 50 ° C to 90 ° C)
C.) to accelerate the curing treatment of the coating layer, perform a burnishing treatment with a polishing tape, and perform a post-treatment such as shaving projections on the surface. Production method 2 (computer tape: W / W) After kneading each component with a kneader,
It was dispersed using a sand mill. A polyisocyanate is added to the resulting dispersion, 2.5 parts for the coating solution for the non-magnetic layer, 3 parts for the coating solution for the magnetic layer, and 40 parts of cyclohexanone. Then, a coating solution for forming a nonmagnetic layer and a coating solution for forming a magnetic layer were prepared.

The obtained non-magnetic layer coating liquid was applied to a thickness of 4 μm so that the thickness after drying was 1.7 μm, and immediately thereafter, the thickness of the magnetic layer was 0.15 μm thereon. .4μ
m and an aramid support (trade name: MICRON) having a center plane average surface roughness of 2 nm. Orientation was carried out by the holding solenoid. After drying, 200 m / min. / Min.
Then, a 0.5 μm-thick back layer (carbon black average particle diameter: 17 nm 100 parts, calcium carbonate average particle diameter: 40 nm 80 parts, α-alumina average particle diameter: 200 nm 5 parts is nitrocellulose resin, polyurethane resin , Dispersed in polyisocyanate). Slit to a width of 3.8 mm, attach the non-woven fabric and razor blade to a device having a slit product feeding and winding device so that the non-woven fabric and razor blade are pressed against the magnetic surface.
The surface of the magnetic layer was cleaned with a precleaning apparatus, and the obtained magnetic tape was incorporated into a DDS cartridge. Production Method 3 (Disc: W / D) For each of the above 10 paints, each component was kneaded with a kneader, and then dispersed using a sand mill. Polyisocyanate was added to the obtained dispersion and 1 to the coating liquid for the nonmagnetic layer.
0 parts, 10 parts of the coating solution for the magnetic layer, and 40 parts of cyclohexanone were added to each, and the mixture was filtered using a filter having an average pore size of 1 μm. Was prepared respectively.

The obtained coating solution for the non-magnetic layer was applied on a polyethylene terephthalate support having a thickness of 62 μm and an average surface roughness of 3 nm so that the thickness after drying would be 1.5 μm, and dried once. After performing a calendar process, a magnetic layer is further applied thereon by a blade method so that the thickness of the magnetic layer becomes 0.15 μm, and a frequency of 50 Hz, a magnetic field strength of 250 Gauss and a frequency of 50 Hz and 120 Gauss are used. After passing through a high-intensity alternating magnetic field generator, random orientation treatment was performed. Further, a method in which the calendering of the non-magnetic layer is not performed may be adopted. Production method 4 (computer tape: W / D) The above-mentioned paint was kneaded with a kneader, and then dispersed using a sand mill. A polyisocyanate is added to the resulting dispersion, 2.5 parts for the coating solution for the non-magnetic layer, 3 parts for the coating solution for the magnetic layer, and 40 parts of cyclohexanone. Then, a coating solution for forming a nonmagnetic layer and a coating solution for forming a magnetic layer were prepared.

An aramid support having a thickness of 4.4 μm and a center plane average surface roughness of 2 nm (trade name: MICRON) was prepared so that the obtained nonmagnetic layer coating solution had a thickness of 1.7 μm after drying. After coating and drying once, and performing a calendaring process, a magnetic layer is further coated thereon by a blade method so that the magnetic layer has a thickness of 0.15 μm. It was oriented by a solenoid having magnetic force. The subsequent steps were performed in the same manner as in Production Method 2. Further, a method in which the calendering of the non-magnetic layer is not performed may be adopted. Production Method 5 (Disc: Spin Coating) Each of the above 14 paints was kneaded with a kneader, and then dispersed using a sand mill. Polyisocyanate was added to the obtained dispersion and 1 to the coating liquid for the nonmagnetic layer.
0 parts, 10 parts of the coating solution for the magnetic layer, and 40 parts of cyclohexanone were added to each, and the mixture was filtered using a filter having an average pore size of 1 μm. Was prepared respectively.

The obtained non-magnetic layer coating solution was spin-coated on a polyethylene terephthalate support having a thickness of 62 μm and a center plane average surface roughness of 3 nm so that the thickness after drying became 1.5 μm. After drying, a magnetic layer was further applied thereon by spin coating so that the thickness of the magnetic layer was 0.15 μm, and an orientation treatment was performed in the circumferential direction with a 6000 G same-opposing Co magnet. This was subjected to a batch-type rolling treatment capable of obtaining the same pressure as in Production Method 1 to smooth the surface. The subsequent steps were performed in the same manner as in Production Method 1. Alternatively, a method of spin-coating a non-magnetic layer and spin-coating a magnetic layer on the non-magnetic layer while the non-magnetic layer is not dried may be used. The use of the spin coating method not only increases the amount of residual magnetization in the recording direction, but also reduces the perpendicular magnetization component of barium ferrite and ferromagnetic metal powder having a short needle ratio, thereby improving the symmetry of the reproduced waveform. it can. Support B-1 Polyethylene terephthalate Thickness: 62 μm, F-5 value: MD 114 MPa, TD 107 MPa Breaking strength: MD 276 MPa, TD 281 MPa Breaking elongation: MD 174 MPa, TD 139 MPa Heat shrinkage (80 ° C., 30 minutes): MD 0.04%, TD 0.05% Heat shrinkage (100 ° C., 30 minutes): MD 0.2%, TD 0.3% Thermal expansion coefficient: major axis 15 × 10 ⁻⁵ / ° C., minor axis 18 × 10 ⁻⁵ / ° C. Center plane average surface roughness 3 nm Support B-2 Polyethylene naphthalate Thickness: 55 μ, Center plane average surface roughness 1.8 nm Thermal shrinkage (80 ° C., 30 minutes): MD 0.007 %, TD 0.007% Heat shrinkage (100 ° C., 30 minutes): MD 0.02%, TD 0.02% Thermal expansion coefficient: major axis 10 × 10 ⁻⁵ / ° C., minor axis 11 × 10 ⁻⁵ / ℃ Body B-3 Polyethylene terephthalate thickness: 62 .mu.m, a central plane average surface roughness 9nm support B-4 Aramid thickness 4.4μm central plane average surface roughness 2nm orientation O-1 randomized orientation performed.

After orientation in the longitudinal direction with an O-2Co magnet, randomized orientation is performed. After orienting in the longitudinal direction with an O-3Co magnet, orienting in the longitudinal direction with a solenoid. Perform vertical orientation with O-4Co magnet. Circumferential orientation is performed with an O-5 Co magnet. Back layer paint BL-1 Fine carbon black powder 100 parts [(Cabot, BP-800, average particle diameter: 17 nm)] Coarse particle carbon black powder 10 parts [(Kahncarb, thermal black, average particle diameter) : 270 nm)] Calcium carbonate (soft inorganic powder) 80 parts [(Shiraishi Kogyo Co., Ltd., white luster O, average particle diameter: 40 nm, Mohs hardness: 3)] α-alumina (hard inorganic powder) 5 parts [(average Particle size: 200 nm, Mohs hardness: 9)] Nitrocellulose resin 140 parts Polyurethane resin 15 parts Polyisocyanate 40 parts Polyester resin 5 parts Dispersant: Copper oleate 5 parts Copper phthalocyanine 5 parts Barium sulfate 5 parts Methyl ethyl ketone 2200 parts Butyl acetate 300 Parts toluene 600 parts

The components forming the back coat layer were kneaded with a continuous kneader, and then dispersed using a sand mill. The obtained dispersion was filtered using a filter having an average pore diameter of 1 μm to prepare a coating liquid for forming a backcoat layer. Magnetic properties, center plane average roughness, areal recording density, etc. were measured for samples obtained by appropriately combining the above methods as shown in Tables 1 to 4. (1) Magnetic properties (Hc): Measured using a vibration sample type magnetometer (manufactured by Toei Kogyo Co., Ltd.) with an Hm of 10 kOe. (2) Center plane average surface roughness (Ra): 3D-MIRAU
Surface roughness (Ra): Ra of an area of about 250 μm × 250 μm was measured by MIRAU method using TOPO3D manufactured by WYKO. Spherical correction at a measurement wavelength of about 650 nm,
Cylinder correction is added. This method is a non-contact surface roughness meter that measures by light interference. (3) The areal recording density is obtained by multiplying the linear recording density by the track density. (4) The linear recording density is the number of bits of a signal recorded per inch in the recording direction. (5) Track density is the number of tracks per inch. (6) φm is the amount of magnetization per unit area of the magnetic recording medium. Bm (Gauss) multiplied by the thickness, using a vibrating sample magnetometer (Toei Kogyo Co., Ltd.)
It is a value that can be measured directly at a Hm of 10 kOe. (7) The error rate of the tape is obtained by recording the signal of the above linear recording density on the tape by the 8-10 conversion PR1 equalization method, and
It measured using the S drive. (8) The error rate of the disk was measured by recording the signal of the above linear recording density on the disk by the (2,7) RLL modulation method. (9) The dry thickness of the magnetic layer is determined by cutting out the magnetic recording medium to a thickness of about 0.1 μm with a diamond cutter over the longitudinal direction and using a transmission electron microscope to magnify 10,000 to 100 times.
Observation was performed at a magnification of 000 times, preferably 20,000 times to 50,000 times, and the photograph was taken. The print size of the photograph is A4 to A5. Thereafter, the interface was visually judged by paying attention to the shape difference between the ferromagnetic powder and the nonmagnetic powder of the magnetic layer and the lower nonmagnetic layer, and the surface of the magnetic layer was similarly blackened. After that, Zeiss image processing device IBAS2
The length of the edged line was measured at. When the length of the sample photograph was 21 cm, the measurement was performed 85 to 300 times. The average value of the measured values at that time was defined as the dry thickness of the magnetic layer.

[0169]

[Table 1]

[0170]

[Table 2]

In Examples 18 to 20 and Reference Example 1, the error rate was measured by using the disk of Example 13 while changing the linear recording density and the track density.

[0172]

[Table 3]

[0173]

[Table 4]

As described above, the error rate was measured using a DDS drive after recording the signal of the linear recording density on a tape by the 8-10 conversion PR1 equalization method. Examples 32 and 3
3. In Reference Example 2, the error rate was similarly measured using the tape of Example 26 while changing the linear recording density and the track density.

From the results shown in the above table, it can be seen that the magnetic recording medium of the present invention is much better than the conventional disk-shaped medium, especially when the error rate in a high-density recording area is 10 ^-5 or less. It can also be seen that the error rate is remarkably good when the error rate is 10 ^-5 or less. Example 34 <Preparation of paint> Magnetic paint mL-1 (using acicular ferromagnetic powder) Ferromagnetic metal powder: m-1 100 parts Composition: Co / Fe (atomic ratio) 30%, Hc 2550 Oersted, specific surface area 55 m ² / g, σs140 emu / g Crystallite size 120 °, average major axis length 0.048 μm, acicular ratio 4 Al compound (Al / Fe atomic ratio 8%) Y compound (Y / Fe atomic ratio 6%) Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.) 3 parts α-alumina HIT55 (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co., Ltd.) 5 parts Phenylphosphonic acid 3 parts Lubricant ( Fatty acid esters: Tables 9 to 11) Stearic acid 2 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint mL-2 (needle-shaped ferromagnetic powder) Use) ferromagnetic metal powder: m-2 100 parts Composition: Co / Fe (atomic ratio) 30%, Hc2360 Oersted, a specific surface area of 49m ² / g, σs146emu / g Crystallite size 170 Å, an average major axis length 0.100 .mu.m, Needle ratio 6, SFD 0.51 Al compound (Al / Fe atomic ratio 5%) Y compound (Y / Fe atomic ratio 5%) pH 9.4 Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 10 parts Polyurethane Resin UR5500 (manufactured by Toyobo) 4 parts α-alumina HIT70 (manufactured by Sumitomo Chemical) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co.) 1 part Phenylphosphonic acid 3 parts Lubricant (fatty acid esters: Tables 9 to 11) Oleic acid 1 part Stearic acid 0.6 part Ethylene glycol dioleil 12 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint L-3 (acicular ferromagnetic powder used: Comparative Example) ferromagnetic metal powder: m-3 Composition / Fe: Ni = 96: 4 100 parts Hc1600 Oe, a specific surface area of 45 m ² / g Crystallite size 220Å, σs135emu / g Average major axis length 0.20 μm, needle ratio 9 Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR-8600 (manufactured by Toyobo) 5 parts α-alumina (particle diameter 0.65 μm) 2 parts Oxidation Chromium (average particle diameter: 0.35 μm) 15 parts Carbon black (average particle diameter: 0.03 μm) 2 parts Carbon black (average particle diameter: 0.3 μm) 9 parts Lubricant (fatty acid esters: Tables 9 to 11) Olein Acid 1 part Stearic acid 1 part Methyl ethyl ketone 300 parts Magnetic paint mL-4 (using plate-like ferromagnetic powder) 100 parts Barium ferrite powder: m-4 to Ba Molar ratio composition: Fe 9.10, Co 0.20, Zn 0.77 Hc 2500 Oersted, specific surface area 50 m ² / g, σs 58 emu / g average plate diameter 35 nm, plate ratio 4 vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo) 3 parts α-alumina HIT55 (manufactured by Sumitomo Chemical) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co.) 5 parts Phenylphosphonic acid 3 parts Lubricant (fatty acid esters: Tables 9 to 11) Stearic acid 2 parts Methyl ethyl ketone 125 parts Cyclohexanone 125 parts Magnetic paint mL-5 (using plate-like ferromagnetic powder) Barium ferrite powder: m-5 100 parts Molar ratio to Ba composition: Fe 9.10, Co 0.20, Zn 0.77 Hc2500 Oe, a specific surface area of ^{50m 2 / g, σs 58emu /} g average plate diameter 35 nm, Shape ratio 2.5 Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 10 parts Polyurethane resin UR5500 (manufactured by Toyobo Co., Ltd.) 4 parts α-alumina HIT55 (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co., Ltd.) 1 part Phenylphosphonic acid 3 parts Lubricant (fatty acid esters: Tables 9 to 11) Oleic acid 1 part Stearic acid 0.6 part Ethylene glycol dioleyl 16 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Nonmagnetic paint nU-1 (spherical inorganic) Powder) inorganic powder TiO ₂ crystalline rutile 80 parts Average particle size 0.035 μm, specific surface area by BET method 40 m ² / g pH 7 TiO ₂ content 90% or more, DBP oil absorption 27-38 g / 100 g, Al on the surface 8% by weight of ₂ O _{3 based} on the whole particles Carbon black Conductex SC- U (manufactured by Columbian Carbon Co., Ltd.) 20 parts Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.) 5 parts Phenylphosphonic acid 4 parts Lubricants (fatty acid esters: Tables 9 to 11) Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Non-magnetic paint nU-2 (using spherical inorganic powder) Inorganic powder TiO ₂ crystalline rutile 100 parts Average particle diameter 0.035 μm, BET specific surface area 40 m ² / g pH 7 TiO ₂ content 90% or more, DBP oil absorption 27-38 g / 100 g, Al ₂ O ₃ and SiO ₂ present on the surface Ketjen Black EC (manufactured by AKUZO NOBEL) 13 parts Average particle diameter: 30 nm DBP oil absorption amount: 350ml / 100g pH: 9.5 BET specific surface area: 950 meters ² g Volatile content: 1.0% Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 16 parts Polyurethane resin UR8200 (manufactured by Toyobo) 6 parts Phenylphosphonic acid 4 parts Lubricant (fatty acid esters: Tables 9 to 11) Oleic acid 1 part Stearic acid 0.8 part Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Nonmagnetic paint nU-3 (using spherical inorganic powder) Inorganic powder TiO ₂ crystalline rutile 75 parts Average particle diameter 0.035 μm, specific surface area 40 m ² / g pH 7 TiO ₂ content 90% or more, DBP oil absorption 27-38 g / 100 g, Al ₂ O ₃ and SiO _{2 on} the surface Carbon black Ketjen black EC 10 parts α-alumina AKP-15 (Sumitomo Chemical Average particle size: 0.65 μm 15 parts Vinyl chloride copolymer MR110 (Nippon Zeon) 12 parts Po Urethane resin UR8600 (Toyobo Co., Ltd.) 5 parts Lubricant (fatty acid esters: Tables 9 to 11) Oleic acid 1 part Stearic acid 1 part Methyl ethyl ketone 300 parts Nonmagnetic paint nU-4 (using needle-shaped inorganic powder) Inorganic powder α-Fe 80 parts of ₂ O ₃ hematite Average long axis length 0.15 μm, specific surface area by BET method 50 m ² / g pH 9 Al ₂ O ₃ is present on the surface at 8% by weight based on the whole particles Carbon black Conductex SC-U (Columbian Carbon Co.) 20 parts Vinyl chloride copolymer MR110 (vinyl chloride copolymer) 12 parts Polyurethane resin UR8200 (Toyobo) 5 parts Phenylphosphonic acid 4 parts Lubricants (fatty acid esters: Tables 9 to 11) Stearic acid 3 Part: methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts: non-magnetic paint nU- (Needle-like inorganic powder used) inorganic powder α-Fe ₂ O ₃ hematite 100 parts Average major axis length 0.15 [mu] m, specific surface area by the BET method: ^{50m 2 / g pH 9, Al} 2 O 3 on the surface with respect to the entire particles 8 % By weight Carbon black # 3250B (Mitsubishi Kasei) 18 parts Vinyl chloride copolymer MR104 (Nippon Zeon) 15 parts Polyurethane resin UR5500 (Toyobo) 7 parts Phenylphosphonic acid 4 parts Lubricant (fatty acid ester: Tables 9 to 11) Oleic acid 1.3 parts Stearic acid 0.8 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Production method 1 (disc: W / W) For each of the above 10 paints, each component was kneaded. And then dispersed using a sand mill. To the resulting dispersion, add 10 parts of polyisocyanate to the coating liquid for the nonmagnetic layer and 10 parts to the coating liquid for the magnetic layer, and further add 40 parts of cyclohexanone to each, and use a filter having an average pore diameter of 1 μm. And filtered to prepare coating solutions for forming a nonmagnetic layer and a magnetic layer, respectively.

The obtained non-magnetic layer coating solution was applied to a thickness of 62 μm so that the thickness after drying was 1.5 μm, and immediately thereafter, the thickness of the magnetic layer was 0.15 μm thereon. In the above, simultaneous multi-layer coating is performed on a polyethylene terephthalate support having a center plane average surface roughness of 3 nm, and while both layers are still in a wet state, two magnetic field strengths of a frequency of 50 Hz and a magnetic field strength of 250 Gauss or a frequency of 50 Hz and 120 Gauss are used. After passing through an AC magnetic field generator and performing random orientation treatment and drying, the temperature is 90 ° C. and the linear pressure is 300 with a 7-stage calendar.
After processing at 3.7 kg / cm and punching to 3.7 inches and subjecting to surface polishing, it was placed in a 3.7-inch cartridge (zip-disk cartridge manufactured by Iomega, USA) with a liner installed inside, 3.7 additional mechanical parts
An inch floppy disk was obtained. Further, some of the samples were subjected to longitudinal orientation using a 4000 G same-polarity opposed Co magnet before randomizing orientation treatment.

In this case, it is preferable to increase the frequency and the magnetic field strength of the AC magnetic field generator so that sufficient randomization is finally performed, whereby an orientation ratio of 98% or more can be obtained. When a barium ferrite magnetic material is used, vertical alignment can be performed in addition to the above-described alignment method. Also, if necessary, after punching into a disk shape, heat treatment at high temperature (normally 50 ° C to 90 ° C)
May be performed to accelerate the curing treatment of the coating layer, to perform burnishing treatment with a polishing tape, and to perform post-treatment such as shaving projections on the surface. Production method 2 (computer tape: W / W) After kneading each component with a kneader,
It was dispersed using a sand mill. A polyisocyanate is added to the resulting dispersion, 2.5 parts for the coating solution for the non-magnetic layer, 3 parts for the coating solution for the magnetic layer, and 40 parts of cyclohexanone, respectively, and a filter having an average pore size of 1 μm. Then, a coating solution for forming a nonmagnetic layer and a coating solution for forming a magnetic layer were prepared.

The obtained coating solution for the nonmagnetic layer was applied to a thickness of 4 μm so that the thickness after drying became 1.7 μm, and immediately thereafter, the thickness of the magnetic layer became 0.15 μm. 0.4 μm
Coating on an aramid support (trade name: MICRON) having a center plane average surface roughness of 2 nm at the same time. Oriented by solenoid. After drying, 200 m / min. / Min.
Then, a 0.5 μm-thick back layer (carbon black average particle diameter: 17 nm 100 parts, calcium carbonate average particle diameter: 40 nm 80 parts, α-alumina average particle diameter: 200 nm 5 parts is nitrocellulose resin, polyurethane resin , Dispersed in polyisocyanate). Slit to a width of 3.8 mm, attach the non-woven fabric and razor blade to a device having a slit product feeding and winding device so that the non-woven fabric and razor blade are pressed against the magnetic surface.
The surface of the magnetic layer was cleaned with a precleaning apparatus, and the obtained magnetic tape was incorporated into a DDS cartridge. Production Method 3 (Disc: W / D) For each of the above 10 paints, each component was kneaded with a kneader, and then dispersed using a sand mill. To the resulting dispersion, add 10 parts of polyisocyanate to the coating liquid for the nonmagnetic layer and 10 parts to the coating liquid for the magnetic layer, and further add 40 parts of cyclohexanone to each, and use a filter having an average pore diameter of 1 μm. And filtered to prepare coating solutions for forming a nonmagnetic layer and a magnetic layer, respectively.

The obtained coating solution for the non-magnetic layer was applied on a polyethylene terephthalate support having a thickness of 62 μm and an average surface roughness of 3 nm so that the thickness after drying would be 1.5 μm, and dried once. After performing a calendaring process, a magnetic layer is further applied thereon by a blade method so that the thickness of the magnetic layer becomes 0.15 μm, and a frequency of 50 Hz, a magnetic field strength of 250 Gauss and a frequency of 50 Hz and 120 Gauss After passing through a high-intensity alternating magnetic field generator, random orientation treatment was performed. Further, a method in which the calendering of the non-magnetic layer is not performed may be adopted. Production method 4 (computer tape: W / D) After kneading each component with a kneader,
It was dispersed using a sand mill. A polyisocyanate is added to the resulting dispersion, 2.5 parts for the coating solution for the non-magnetic layer, 3 parts for the coating solution for the magnetic layer, and 40 parts of cyclohexanone, respectively, and a filter having an average pore size of 1 μm. Then, a coating solution for forming a nonmagnetic layer and a coating solution for forming a magnetic layer were prepared.

The obtained non-magnetic layer coating solution was coated with an aramid support having a thickness of 4.4 μm and an average surface roughness of 2 nm (trade name: MICRON) so that the thickness after drying was 1.7 μm. After coating and drying once and calendering, a magnetic layer is further applied thereon by a blade method so that the magnetic layer has a thickness of 0.15 μm, and a cobalt magnet having a magnetic force of 6000 G and a 6000 G magnetic layer. It was oriented by a solenoid having magnetic force. The subsequent steps were performed in the same manner as in Production Method 2. Further, a method in which the calendering of the non-magnetic layer is not performed may be adopted. Production method 5 (disk: spin coating) For each of the above 10 paints, each component was kneaded with a kneader, and then dispersed using a sand mill. To the resulting dispersion, add 10 parts of polyisocyanate to the coating liquid for the nonmagnetic layer and 10 parts to the coating liquid for the magnetic layer, and further add 40 parts of cyclohexanone to each, and use a filter having an average pore diameter of 1 μm. And filtered to prepare coating solutions for forming a nonmagnetic layer and a magnetic layer, respectively.

The obtained nonmagnetic layer coating liquid was spin-coated on a polyethylene terephthalate support having a thickness of 62 μm and a center plane average surface roughness of 3 nm so that the thickness after drying became 1.5 μm. After drying, a magnetic layer was further applied thereon by spin coating so that the thickness of the magnetic layer was 0.15 μm, and an orientation treatment was performed in the circumferential direction with a 6000 G same-opposing Co magnet. This is manufacturing method 1.
The surface was smoothed by performing a batch-type rolling treatment capable of obtaining the same pressure as described above. The subsequent steps were performed in the same manner as in Production Method 1. Alternatively, a method of spin-coating a non-magnetic layer and spin-coating a magnetic layer on the non-magnetic layer while the non-magnetic layer is not dried may be used. The use of the spin coating method not only increases the amount of residual magnetization in the recording direction, but also reduces the perpendicular magnetization component of barium ferrite and ferromagnetic metal powder having a short needle ratio, thereby improving the symmetry of the reproduced waveform. it can. Lubricants: fatty acid esters diester _{L-a1 C 17 H 35 COO} (CH 2) 4 OCOC 17 H 35 L-a2 C 11 H 21 COO (CH 2) 4 OCOC 11 H 21 L-a3 C 17 H 33 COO (CH _{2) 2 OCOC 17 H 33 L} -a4 C 11 H 23 COO (CH 2) 4 OCOC 11 H 23 L-a5 C 27 H 53 COO (CH 2) 4 OCOC 27 H 53 L-a6 C 11 H 21 COO ( _{CH 2) 4 OCOC 17 H 33} L-a7 C 17 H 33 COO (CH 2) 11 OCOC 17 H 33 L-a8 C 17 H 33 COOCH 2 CH = CHCH 2 OCOC 17 H 33 L-a9 C 14 H 27 COOCH _{2 CH = CHCH 2 OCOC 14 H} 27 L-a10 C 17 H 33 COO (CH 2) 8 OCOC 14 H 27 monoesters _{L-b1 C 17 H 35 COOC} 17 H 35 L-b2 C 17 H 35 COOC 4 H 9 L-b3 C ₁₇ H ₃₅ C _{OOCH 2 CH 2 OC 4 H 9} L-b4 C 17 H 35 COO (CH 2 CH 2 O) 2 C 4 H 9 support b-1 Polyethylene terephthalate thickness: 62μm, F-5 value: MD 114MPa, TD 107MPa Breaking strength: MD 276 MPa, TD 281 MPa Breaking elongation: MD 174 MPa, TD 139 MPa Heat shrinkage (80 ° C., 30 minutes): MD 0.04%, TD 0.05% Heat shrinkage (100 ° C., 30 minutes): MD 0.2%, TD 0.3% Thermal expansion coefficient: long axis 15 × 10 ⁻⁵ / ° C., short axis 18 × 10 ⁻⁵ / ° C. center plane average surface roughness 3 nm support b-2 polyethylene naphthalate thickness Thickness: 55 μ, center plane average surface roughness 1.8 nm Heat shrinkage (80 ° C., 30 minutes): MD 0.007%, TD 0.007% Heat shrinkage (100 ° C., 30 minutes): MD 0.02 %, TD 0.02% Thermal expansion coefficient: major axis 10 × 10 ⁻⁵ / ° C., minor axis 11 × 10 ⁻⁵ / ° C. Support b-3 Polyethylene terephthalate Thickness: 62 μm, center plane average surface roughness 9 nm Support b -4 Aramid thickness 4.4 μm Center plane average surface roughness 2 nm Orientation o-1 Randomize orientation is performed.

After orientation in the longitudinal direction with the o-2 Co magnet, random orientation is performed. After being orientated in the longitudinal direction by an o-3 Co magnet, it is orientated in the longitudinal direction by a solenoid. Perform vertical orientation with an o-4 Co magnet. Circumferential orientation is performed with an o-5 Co magnet. Back layer paint bL-1 Fine carbon black powder 100 parts [(Cabot, BP-800, average particle diameter: 17 nm)] Coarse particle carbon black powder 10 parts [(Kahncarb, thermal black, average particle diameter) : 270 nm)] Calcium carbonate (soft inorganic powder) 80 parts [(Shiraishi Kogyo Co., Ltd., white luster O, average particle diameter: 40 nm, Mohs hardness: 3)] α-alumina (hard inorganic powder) 5 parts [(average Particle size: 200 nm, Mohs hardness: 9)] Nitrocellulose resin 140 parts Polyurethane resin 15 parts Polyisocyanate 40 parts Polyester resin 5 parts Dispersant: Copper oleate 5 parts Copper phthalocyanine 5 parts Barium sulfate 5 parts Methyl ethyl ketone 2200 parts Butyl acetate 300 Parts toluene 600 parts

The components forming the back coat layer were kneaded with a continuous kneader, and then dispersed using a sand mill. The obtained dispersion was filtered using a filter having an average pore diameter of 1 μm to prepare a coating liquid for forming a backcoat layer. The magnetic characteristics and the magnetic properties of the samples obtained by appropriately combining the above methods as shown in Table 5 or Table 7
The center plane average roughness, surface recording density and the like were measured and are shown in Table 6 or Table 8. (1) Magnetic properties (Hc): Measured with a vibration sample type magnetometer (manufactured by Toei Kogyo Co., Ltd.) at Hm 10 kOe. (2) Center plane average surface roughness (Ra): 3D-MIRAU
Surface roughness (Ra): Ra value of an area of about 250 μm × 250 μm was measured by MIRAU method using TOPO3D manufactured by WYKO. Spherical correction and cylindrical correction are added at a measurement wavelength of about 650 nm. This method is a non-contact surface roughness meter that measures by light interference. (3) The linear recording density is the number of bits of a signal recorded per inch in the recording direction. (4) The track density is the number of tracks per inch. (5) The areal recording density is obtained by multiplying the linear recording density by the track density. (6) φm is the amount of magnetization per unit area of the magnetic recording medium. Bm (Gauss) multiplied by the thickness, using a vibrating sample magnetometer (Toei Kogyo Co., Ltd.)
It is a value that can be measured directly at a Hm of 10 kOe.

The linear recording density, track density, and areal recording density are values determined by the system. (7) The error rate of the disk was measured by recording the signal of the above linear recording density on the disk by the (2,7) RLL modulation method. (8) The error rate of the tape is obtained by recording the signal of the above linear recording density on a tape by the 8-10 conversion PR1 equalization method,
It measured using the S drive. (9) The dry thickness of the magnetic layer is determined by cutting out the magnetic recording medium to a thickness of about 0.1 μm with a diamond cutter over the longitudinal direction and using a transmission electron microscope to magnify 10,000 to 100 times.
Observation was performed at a magnification of 000 times, preferably 20,000 times to 50,000 times, and the photograph was taken. The print size of the photograph is A4 to A5. Thereafter, the interface was visually judged by paying attention to the shape difference between the ferromagnetic powder and the nonmagnetic powder of the magnetic layer and the lower nonmagnetic layer, and the surface of the magnetic layer was similarly blackened. After that, Zeiss image processing device IBAS2
The length of the edged line was measured at. When the length of the sample photograph was 21 cm, the measurement was performed 85 to 300 times. The average value of the measured values at that time was defined as the dry thickness of the magnetic layer. (10) Running durability: floppy disk drive (US
Iomega ZIP100: 2968 rpm
m), the head is fixed at a position with a radius of 38 mm, recording is performed at a recording density of 34 kfci, and the signal is reproduced.
00%. Thereafter, the vehicle was run for 1500 hours in a thermocycle environment in which the following flow was defined as one cycle. The output was monitored every 24 hours of running, and the point where the output became 70% or less of the initial value was regarded as NG. (Thermocycle flow) 25 ° C, 50% RH 1 hour → (Temperature rise 2 hours) → 60
℃, 20% RH 7 hours → (Temperature drop 2 hours) → 25 ° C,
50% RH 1 hour → (Temperature drop 2 hours) → 5 ° C, 50%
RH 7 hours → (Temperature rise 2 hours) → <Repeat this> (11) Evaluation of liner wear In a head-off state, the sample is run for 1000 hours in the same environment as the running durability, and after the finished sample is run, the cartridge case is removed. The magnetic layer surface of the open magnetic disk was visually observed and evaluated. ：: No defect on the magnetic layer surface △: Fine scratches on a part of the magnetic layer surface ×: Fine scratches on the entire magnetic layer surface (12) Evaluation of liner adhesion Head-off state In the same environment as the running durability, the sample was run for 1000 hours. After running the completed sample, the cartridge case was opened and the magnetic layer surface of the magnetic disk was visually observed and evaluated. ○: No liner adhered to the magnetic layer surface △: Liner adhered to a part of the magnetic layer surface ×: Liner adhered to the entire magnetic layer surface (13) Starting torque evaluation Using a torque gauge Model 300ATG, a start-up torque at the time of head-on in an LS-120 drive manufactured by Imation was measured (unit: g · c).
m).

[0185]

[Table 5]

[0186]

[Table 6]

In sample Nos. 18 to 20, sample no.
Using the 13 disks, the error rate was similarly measured while changing the linear recording density and the track density.

[0188]

[Table 7]

[0189]

[Table 8]

As described above, the error rate was measured using a DDS drive by recording the above-mentioned signal of the linear recording density on a tape by the 8-10 conversion PR1 equalization method. Sample No3
For Nos. 0 and 31, the error rate was measured similarly using the tape of Sample No. 24 while changing the linear recording density and the track density.

[0191]

[Table 9]

[0192]

[Table 10]

[0193]

[Table 11]

As is clear from the results of Tables 9 to 11, when the monoester and diester lubricants were used in combination as the fatty acid ester of the present invention, the running durability, liner wear, liner adhesion, and starting torque were remarkably improved. And exhibited a good effect. Although the experimental results are not specified, when the above-mentioned monoester and diester lubricants are used in combination, even when applied to a computer tape, a good 100%
It was found that a low friction coefficient was obtained even after the pass and after the 1,000 pass, and that a magnetic recording medium with less clogging and excellent abrasion resistance was obtained as the durability, which was preferable. Examples 35 to 40 A magnetic liquid for the upper layer and a non-magnetic liquid for the lower layer were prepared and applied to the surface of a polyethylene terephthalate support to produce a magnetic recording medium of the present invention.

[Preparation of magnetic liquid for upper layer] Ferromagnetic alloy powder A
(Composition: Co 20%, Al 9
%, Y6%, Hc2000 Oersted, crystallite size
15nm, BET specific surface area 59m^Two/ g, average major axis length 0.09
μm, needle ratio 7, s140emu / g) 100 parts open
Grind for 10 minutes in a kneader, then vinyl chloride / acetic acid
Vinyl / glycidyl methacrylate / 2-hydroxyp
To propyl allyl ether = 86/5/5/4 copolymer
Add hydroxyethyl sulfonate sodium salt
Compound (SO _ThreeNa group = 6 × 10^-Fiveeq / g content, Epoki
Si group = 10^-3eq / g, Mw = 30,000) at 7.5
Part and polyurethane resin (SO_ThreeNa group = 7 × 10^-Fiveeq /
g, terminal OH group, Mw = 40,000, Tg =
5 parts (solid content) of 90 ° C. polyester polyurethane)
And 60 parts of cyclohexanone and kneaded for 60 minutes
And then

Abrasive (Al ₂ O ₃ average particle diameter 0.2 μm) 2 parts Carbon black (average particle diameter 40 nm) 2 parts Methyl ethyl ketone / toluene = 1/1 200 parts were added and dispersed by a sand mill for 120 minutes. 5 parts of polyisocyanate (Coronate 3041 manufactured by Nippon Polyurethane Co., Ltd.) (solid content) 1 part of stearic acid of Table 12 1 part of oleic acid 50 parts of methyl ethyl ketone were added, and the mixture was further stirred and mixed for 20 minutes to have an average pore diameter of 1 μm. The mixture was filtered using a filter to prepare a magnetic paint.

[0197]

[Table 12]

[Preparation of Nonmagnetic Liquid for Lower Layer] Titanium oxide (mean particle size 0.035 μm, crystalline rutile, TiO ₂ content 90% or more, surface treatment layer: alumina, BET specific surface area 3
5 to 42 m ² / g, true specific gravity 4.1, pH 6.5 to 8.0) 8
5 parts were ground in an open kneader for 10 minutes, then vinyl chloride / vinyl acetate / glycidyl methacrylate = 86
/ 9/5 copolymer to which hydroxyethyl sulfonate sodium salt is added (SO ₃ Na group = 6 × 1
0 ^-5 eq / g containing, epoxy group = 10 ^-3 eq / g containing, Mw = 3
000) (vinyl chloride-based binder) and 17 parts of sulfonic acid-containing polyurethane resin UR8700 manufactured by Toyobo
(Polyurethane) 6 parts (solid content) and 60 parts of cyclohexanone were added and kneaded for 60 minutes.

200 parts of methyl ethyl ketone / cyclohexanone = 6/4 was added and dispersed by a sand mill for 120 minutes. Table 1
Lubricant 3 and polyisocyanate: curing agent (Coronate 3041 manufactured by Nippon Polyurethane) 13 parts (solid content) Stearic acid 1 part Oleic acid 1 part Methyl ethyl ketone 50 parts was added, and further stirred and mixed for 20 minutes. The mixture was filtered using a filter having the same to prepare a non-magnetic paint.

[0200]

[Table 13]

The obtained non-magnetic paint was coated simultaneously on the surface of a polyethylene terephthalate support having a thickness of 62 μm so that the obtained non-magnetic paint had a thickness of 1.5 μm and immediately thereafter the magnetic paint had a thickness of 0.2 μm after drying. did. 50 Hz, 250 Gauss, 50 H frequency with both layers wet
z, passing through an AC magnetic field generator having two magnetic field strengths of 120 gauss to perform random orientation treatment, and after drying, metal roll-metal roll-metal roll-metal roll-metal roll-metal roll-metal roll Calendar processing by combination (speed 100m / min, linear pressure 300kg /
cm, temperature 90 ° C.). After punching a 3.7-inch disc and subjecting it to a surface polishing treatment, a Zip-Disk manufactured by Iomega Corporation of the United States with a liner installed inside
A floppy disk sample was obtained by inserting the cartridge into a cartridge and adding predetermined mechanical parts.

[Measurement Experiments] Examples 35 to 40 and Comparative Example 5
Was measured by the following method. Measurement of C / Fe The C / Fe value was measured using a PHI-660 type Auger electron spectrometer manufactured by Φ Company. The measurement conditions were as follows.

[0203] Primary electron beam acceleration voltage 3 kV, sample current 1
30 nA, magnification 250 times, inclination angle 30 degrees. Kinetic energy range from 130 eV to 730 eV
The intensity of the KLL peak of carbon and the intensity of LMN peak of iron were obtained in a differential form, and the ratio of C / Fe was obtained.

Electromagnetic Conversion Characteristics Measurement Test RWA1001 type disk evaluation device manufactured by GUZIK, USA and spinstand LS-9 manufactured by Kyodo Electronic System Co., Ltd.
At 0, using a metal-in-gap head with a gap length of 0.3 μm, the reproduction output (TAA) at a linear recording density of 60 kfci and the noise level after DC erase were measured at a radius of 24.6 mm, and the S / N ratio was measured. The value was determined. In addition, the relative S / N when the S / N of Example 40 was set to zero dB was evaluated.

Running Durability Measurement Test Floppy Disk Drive (ZI manufactured by Iomega, USA)
(P100: rotation speed 2968 rpm) The head was fixed at a position of a radius of 38 mm using a recording density of 34 kfci, and the signal was reproduced to make it 100%. Then follow the flow 1
The vehicle was run for 1500 hours in a thermocycle environment.

The output was monitored every 24 hours of running, and when it became 70% or less of the initial value, it was regarded as NG and the time was indicated. 25 ° C, 50% RH for 1 hour → Temperature rise for 2 hours → 60 ° C, 20%
RH 7 hours → Temperature drop 2 hours → 25 ° C 50% RH 1 hour → Temperature drop 2 hours → 5 ° C 10% RH 7 hours → Temperature rise 2 hours

Running Durability Test after Storage at High Temperature and High Humidity After the disk samples were stored at 60 ° C. in a 90% RH atmosphere for 8 weeks, the running durability was evaluated in the same manner as described above. Starting Torque Test Using a torque gauge model 300 ATG manufactured by Tohnichi Seisakusho, the starting torque of the LS-120 drive manufactured by Imation Corporation when the head was turned on was measured.

Liner Wear Test The sample was run for 1000 hours in the same environment as the running durability with the head off. After running, the cartridge case of the sample was opened and the surface of the magnetic layer of the magnetic disk was visually observed, and evaluated according to the following criteria. ○: No defect on the surface of the magnetic layer △: Fine scratches on a part of the surface of the magnetic layer ×: Fine scratches on the entire surface of the magnetic layer The method for measuring the particle size of the ferromagnetic powder used was as follows.

The ferromagnetic powder particles of the sample were observed with a transmission electron microscope, and each particle of the printed photograph was measured with an image analyzer to determine the particle size distribution. 1. Sample Preparation Almost one cup of powder particles was put into a weighing bottle containing about 10 ml of water, subjected to ultrasonic dispersion for 10 minutes, and then dried with a copper mesh covered with a collodion film. It was reinforced by carbon deposition to obtain an observation sample. 2. Observation of particles and photo printing Observation: Apparatus: transmission electron microscope Photographing magnification: 60,000 times Photo printing: total magnification: 200,000 times The total magnification was corrected from the diffraction grating image of simultaneous observation. 3. Particle size measurement device: KONTRON image analyzer KS400 Method: Trace the outer shape of the photographed particle on a digitizer with a slice pen, measure the long axis length and short axis length of the ferromagnetic metal powder, The average is defined as the average major axis length and average minor axis length, and their ratio (average major axis length / average minor axis length) is defined as the acicular ratio. For ferromagnetic hexagonal ferrite powder, the plate diameter and thickness are measured. The average thereof was defined as an average plate diameter and an average plate thickness, and their ratio (average plate diameter / average plate thickness) was defined as a plate ratio.

Number of particles to be measured: 500

[0211]

[Table 14]

The following results were found from the above results. The present Examples 35 to 40 are excellent in running durability such that even after running for a long time, there is no problem in running thereafter. It is also excellent in preservability that it does not hinder use even when stored for a long time under high temperature and high humidity. It is also excellent in running durability after storage, in which even after running for a long time after storage under high temperature and high humidity, there is no trouble in running. No abnormality occurs in the magnetic layer of the magnetic disk even after running for a long time. That is, the liner wear is improved and the starting torque is low.

[0213]

According to the present invention, there is provided a magnetic material comprising a substantially non-magnetic lower layer provided on a support, and a magnetic layer containing a ferromagnetic metal powder or a ferromagnetic hexagonal ferrite powder in a binder on the lower layer. In the recording medium, the magnetic recording medium is a magnetic recording medium for recording a signal having an areal recording density of 0.17 to ² Gbit / inch ² , and the magnetic layer has a dry thickness of 0.05 to 0.30.
μm, the coercive force of the magnetic layer is 1800 Oe or more, at least the lower layer contains at least a fatty acid ester, and the C / Fe peak ratio when the surface of the magnetic layer is measured by Auger electron spectroscopy is 5 μm. ~ 120
A magnetic recording medium characterized by the fact that the magnetic recording medium has a large capacity, excellent high-density characteristics and excellent durability that cannot be obtained by the conventional technology, and has particularly excellent running durability. Medium can be obtained.

According to the present invention, the areal recording density of the magnetic recording medium is 0.17 to ² Gbit / inch ² , preferably 0.2
２2 Gbit / inch ² , and the dry thickness of the magnetic layer is 0.
05 to 0.30 μm, preferably 0.05 to 0.25 μm
m, preferably φm is 8.0 × 10 ^{−3 to} 1.0 ×
10 ⁻³ emu / cm ² , more preferably φm is 10.0 × 1
Practical characteristics of running durability can be imparted to a magnetic recording medium of 0 ^{-3 to} 1.0 × 10 ^-3 emu / cm ^2, which is an excellent property that cannot be obtained by the conventional coating type magnetic recording medium technology. It is possible to obtain a magnetic recording medium having both high-density recording characteristics and excellent durability and significantly improved running durability.

Continued on the front page (72) Inventor Nobuo Yamazaki 2-12-1, Ogimachi, Odawara City, Kanagawa Prefecture Inside Fuji Photo Film Co., Ltd. (72) Inventor Hiroshi Hashimoto 2-12-1, Ogimachi, Odawara City, Kanagawa Prefecture Fuji Photo Inside Film Co., Ltd.

Claims (14)

[Claims] 1. A substantially nonmagnetic lower layer is provided on a support, and a magnetic layer containing a ferromagnetic powder, which is a ferromagnetic metal powder or a ferromagnetic hexagonal ferrite powder, in a binder is provided on the lower layer. In the magnetic recording medium, the magnetic recording medium is a magnetic recording medium for recording a signal having an areal recording density of 0.17 to ² Gbit / inch ² , and the dry thickness of the magnetic layer is 0.05.
0.30 μm, and the coercive force of the magnetic layer is 1800
Oersted or more, at least the lower layer contains a fatty acid ester, and has a C / Fe peak ratio of 5 to 120 when the surface of the magnetic layer is measured by Auger electron spectroscopy.
A magnetic recording medium characterized by the following. 2. The magnetic layer according to claim 1, wherein φm is 10.0 × 10^-3~
1.0 × 10^-3emu / cm ^TwoAnd the coercive force of the magnetic layer is
Claim 2100 Oersted or more
Item 7. The magnetic recording medium according to Item 1. 3. The dry thickness of the magnetic layer is 0.05 to 0.5.
25 μm and a C / Fe peak ratio of 5 to 100 when the surface of the magnetic layer is measured by Auger electron spectroscopy.
The magnetic recording medium according to claim 1, wherein 4. The method according to claim 1, wherein at least the lower layer contains a fatty acid and a fatty acid ester, the fatty acid contains at least a saturated fatty acid, and the fatty acid ester contains at least a saturated fatty acid ester or an unsaturated fatty acid ester. Magnetic recording medium. 5. The magnetic recording medium according to claim 1, wherein the fatty acid ester includes a monoester and a diester. 6. The magnetic recording medium according to claim 1, wherein the fatty acid ester includes a saturated fatty acid ester and an unsaturated fatty acid ester. 7. The magnetic recording medium according to claim 1, wherein the C / Fe peak ratio when the surface of the magnetic layer is measured by Auger electron spectroscopy is 5 to 80. 8. The magnetic recording medium according to claim 1, wherein the fatty acid ester is contained in the magnetic layer and the non-magnetic layer in an amount of 8 to 30 parts by weight based on 100 parts by weight of the ferromagnetic powder or 100 parts by weight of the non-magnetic powder contained in the lower layer. 7. The magnetic recording medium according to claim 6, wherein the medium has a disk shape. 9. The method according to claim 8, wherein the fatty acid ester is R1 -COO-R.
2-OCO-R3, R4-COO- (R5-O) m-R
6 (where m is an integer of 1 to 10), or R 7 —COO
-At least one of R8
The magnetic recording medium according to claim 1. (Wherein R2 and R5
Are each independently-(CH_Two) N-or-(CH_Two)
an unsaturated bond derived from n- (n is an integer of 1 to 12)
Or a divalent group which may contain-[CH_TwoCH
(CH_Three)]-Or-[CH_TwoC (CH_Three) _TwoC
H_TwoWherein R1, R3, R4 and R7 are each independently
A chain saturated or unsaturated hydrocarbon having 12 to 30 carbon atoms
The groups may be the same or different. R6 and R8 are each
Each independently having 1 to 26 carbon atoms in a chain or branched, saturated or
Are unsaturated hydrocarbon groups which may be the same or different
No. ) 10. The magnetic layer having a dry thickness of 0.05 to 0.05.
2. The magnetic recording medium according to claim 1, wherein the magnetic layer contains an abrasive having an average particle diameter of 0.4 [mu] m or less. 11. The magnetic recording medium is a magnetic recording medium for recording a signal having a surface recording density of 0.20 to ² Gbit / inch ² , and includes an inorganic powder having a Mohs hardness of 4 or more in the lower layer. The magnetic recording medium according to claim 1, wherein 12. The ferromagnetic metal powder mainly composed of Fe, having an average major axis length of 0.12 μm or less and a crystallite size of 8
2. The magnetic recording medium according to claim 1, wherein the angle is 0 ° to 180 °. 13. The ferromagnetic metal powder wherein Al / Fe is 5
13. An atomic% to 30 atomic%.
The magnetic recording medium according to the above. 14. The rotation speed of the magnetic recording medium is 1800 rp.
2. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a disk-shaped magnetic recording medium for a recording / reproducing system of m or more.