JP2001325712A - Discoid magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress the wear of a multilayer coating type discoid magnetic recording medium, particularly a magnetic disk and a magnetic head due to high-speed sliding while maintaining the high recoding density and high transfer rate of the magnetic disk and to enhance durability and reliability. SOLUTION: The discoid magnetic recording medium contains at least one amino-ester of formula (I) (where R1 is a <=24C hydrocarbon group; R2 is a <=12C hydrocarbon group; and R3 and R4 are the same <=24C hydrocarbon group or mutually different <=24C hydrocarbon groups) in each magnetic layer 20 containing a magnetic powder dispersed in a binder and/or on the surface of the disk 3. The number of revolutions of the magnetic recording medium is >=2,400 r.p.m. and a magnetic head 13 is brought into contact sliding relatively to the medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk-shaped magnetic recording medium, for example, a high-density-coated magnetic disk, and more particularly to a magnetic disk provided for a contact-type recording system.

[0002]

2. Description of the Related Art A magnetic disk is used as a portable magnetic recording medium for a computer or a word processor. Conventionally used magnetic disks are floppy (registered trademark) disks called 2HD, which have a recording capacity of 1.44 MB (megabytes). However, in recent years, not only characters,
With the background of handling audio data and image data and the advancement of application software, there is no doubt that the conventional recording capacity is in short supply, and there is an increasing demand for higher capacity.

Further, with the increase in data capacity, a higher data transfer rate is required. This is because it is necessary to prevent as much as possible the deterioration of workability due to the increase in capacity. For that purpose, it is necessary to increase the disk rotation speed.

In a conventional floppy disk drive system, a head slider contacts and slides on a disk.
This is a so-called contact system. However, if the number of rotations of the disk is increased with the increase in capacity, the head slider flies, and the flying amount (spacing) at this time lowers the efficiency at the time of recording and reproduction. Therefore, if a contact recording magnetic head slider is used instead of a floating magnetic head slider, the flying height will be zero,
Further densification is achieved.

[0005]

However, at present, such a high-speed rotating and contact sliding type floppy disk drive system has not been realized.

Conventionally, a method of adding a fatty acid ester to a magnetic layer (JP-A-50-22603, JP-A-50-153905)
JP, JP-A-55-139637, JP-B-39-28367, JP-B-41-18065, JP-B-47-12950),
A method of adding a fatty acid or a hydrocarbon, and a method of adding a fatty acid ester having a high molecular weight and having a branched hydrocarbon group or an unsaturated hydrocarbon group to the magnetic layer are disclosed in
-12950, JP-A-58-160425, JP-A-58-2180
No. 38, JP-A-60-205827, JP-A-61-294637, and JP-A-62-125529. However, even with these conventional methods, there is a problem in that running durability deteriorates due to contact sliding under high-speed rotation, head wear increases above all, and head characteristics cannot be guaranteed. Will happen. That is, the conventional technology has a limit in dealing with the above problem.

The present invention provides a high-density coated disk-shaped magnetic recording medium suitable for use in a contact recording system,
It is an object of the present invention to provide a disk-shaped magnetic recording medium such as a magnetic disk having excellent head wear characteristics and running durability under a wide range of environmental conditions.

[0008]

That is, the present invention is configured so that the number of rotations is 2400 or more per minute and the magnetic head relatively slides in contact, and the magnetic powder is dispersed in the binder. The magnetic layer thus formed and / or the medium surface contain at least one kind of nitrogen-containing ester represented by the following general formula (I) (hereinafter referred to as amino-containing ester of the present invention). The present invention relates to a disk-shaped magnetic recording medium (hereinafter, a magnetic disk will be described as a representative example).

Embedded image (However, in the general formula (I), R ¹ has 24 carbon atoms.
The following (especially 8 to 24) hydrocarbon groups, R ² has 12 carbon atoms
The following hydrocarbon groups, R ³ and R ⁴ , are the same or different hydrocarbon groups having 24 or less carbon atoms. )

The inventor of the present invention has reported that the disk rotation speed is 2 minutes per minute.
As a result of studying to realize a recording system in which the magnetic head slider slides in contact with the magnetic head slider at a high speed of 400 rotations or more, the output of the magnetic disk during high-speed sliding is reduced while the head wear is reduced. It is recognized that the deterioration of the head characteristics due to is the biggest problem. Moreover, it has been recognized that the sliding speed is increased by one digit or more by sliding while seeking, as compared with when sliding the same track.

Therefore, as a result of intensive studies to reduce the head wear during the seek, the amino-containing ester of the present invention, which is present at least on the surface of the magnetic disk, is compared with the conventional lubricants such as fatty acid esters and fatty acids. ,
The present inventors have found that there is an effect of reducing the head wear rate by one digit or more, and have reached the present invention. Further, the contact surface pressure has a great effect on the wear rate of the head. It can be considered that the head wear speed is almost proportional to the contact surface pressure. If the contact surface pressure is too large, the head wear speed increases, and even if the amino ester-containing (lubricant) of the present invention is used, a practical wear level is achieved. Cannot be obtained. On the other hand, if the contact surface pressure is too small, stable contact sliding cannot be performed, and the head slider jumps or floats.

The structure of the amino-containing ester of the present invention is represented by the above-mentioned general formula (I), and the structure of R ^{1 to} R ⁴ in the amino-containing ester represented by the above general formula is only linear. In addition, it is possible to freely select a branched structure, an unsaturated bond, the presence or absence of an aromatic ring, the type of isomer, and the alicyclic structure. However, the carbon number of R ¹ , R ³ , and R ⁴ is preferably 24 or less, and R ² is preferably 12 or less. If it is larger than this, it becomes difficult to manufacture and lacks practicality. Further, R ¹ preferably has 8 or more carbon atoms. If it is smaller than this, running durability, in particular, still durability is not excellent, which is not preferable.

As a method for incorporating the amino-containing ester of the present invention in the magnetic layer and / or on the surface of the magnetic disk, there are roughly two types of methods. One is to add it to the magnetic paint during magnetic disk production and / or to the lower non-magnetic paint. The other is to dissolve the amino-containing ester alone or in a solvent and apply air doctor coating to the surface of the magnetic disk. , Gravure coat, spray coat, spin coat or dip coat. Further, these two types of methods may be used in combination. The method of adding only in the lower non-magnetic layer is known to be supplied to the surface through holes in the magnetic layer, and also can avoid dispersion deterioration and the like by directly adding to the magnetic paint, This is one of the effective means for incorporating the amino-containing ester in the magnetic layer and / or on the surface of the magnetic disk.

In the present invention, it is preferable that a second layer is formed on the first layer by multi-layer coating, and at least the second layer is formed as the magnetic layer. Preferably, a substantially non-magnetic lower non-magnetic layer is provided as the first layer between the magnetic layer and the non-magnetic support. The lower non-magnetic layer which is substantially non-magnetic means that it may have a magnetic property to such an extent that it does not participate in recording, and is hereinafter simply referred to as a lower non-magnetic layer.

The apparatus using the magnetic disk according to the present invention has a rotation speed of 2400 rpm or more, preferably 2400 to 8000 rpm. The head is preferably of a type mounted on a slider such as used in a hard disk, and a contact-type magnetic head slider that stably contacts and slides without floating even at a rotation speed of 2400 rpm or more. By being sandwiched from above and below, the vehicle can run stably. The material of the slider contact surface (contact pad) is diamond-like carbon (DLC), amorphous carbon, Al ₂ O ₃ .Ti
C, Al ₂ O ₃ , Si, SiC, BN and the like are suitable, but not limited thereto. Further, in addition to the conventional inductive head, an MR head, a GMR head, and a TMR head can be used.

The contact surface pressure (pressing load / total contact area) is preferably 1 to 40 gf / mm ² . If the contact surface pressure is too high, the head wear rate will increase, and even if the lubricant of the present invention is used, it is difficult to obtain a practical wear rate. On the other hand, if the contact surface pressure is too small, stable contact sliding cannot be performed, and the head slider easily jumps or floats.

A magnetic head suitably used for a magnetic disk according to the present invention has been proposed by the present applicant,
This is a contact type head slider having a contact pad in which a magnetic head is embedded (Japanese Patent Application No. 11-251815). Hereinafter, the outline of the invention of the prior application will be described.

In the head slider for a flexible magnetic disk of the prior application, a pad in which the magnetic head is embedded is provided on the opposite surface of the flexible magnetic disk, and the relative speed between the pad and the magnetic head is 1. 3m /
In the state where the magnetic head is in contact with the flexible magnetic disk at a speed of s to 25.0 m / s, the magnetic head records or reproduces signals on the flexible magnetic disk. According to the prior application, there is no floating mechanism having a taper flat or a negative pressure mechanism like a conventional head slider for a hard disk, and recording / reproducing by a magnetic head is performed from a low speed in a state of being in contact with the surface of a flexible magnetic disk. The operation can be performed stably over a wide range up to a high speed for a long time, the density of the flexible magnetic disk can be increased, the transfer rate can be increased, and the power consumption can be reduced.

FIG. 3 shows an HGA (head slider suspension) 2 having a head slider 1 according to an embodiment attached to the tip thereof. The HGA 2 is a rectangular plate elongated in the radial direction of the flexible magnetic disk 3. A magnetic head slider 1 is supported by the tip of the suspension beam 5, comprising a base plate 4 in a shape of a circle and a suspension beam 5 stuck on the lower surface of the tip of the base plate 4 in an overlapping manner. Note that two head sliders 1 and two HGAs 2 are arranged so as to face up and down.
As shown in FIG. 3, the magnetic layer 20 (upper layer) and the non-magnetic layer 21
(Lower layer) sandwiches the flexible magnetic disk 3 laminated on both main surfaces of the nonmagnetic support 22 from both sides thereof.

The base plate 4 has a narrow portion formed at its base end on both left and right sides. The base portion of the base plate 4 is held by a carriage of a linear motor (not shown). A cantilever arm 7 protruding laterally is integrally formed on one of the side portions.

Although not shown, when the cantilever arm 7 is relatively lifted by the lifter due to the movement of the linear motor in the front-rear direction, the base plate 4 tends to bend mainly at the narrow portion, and the one side of the base plate 4 is bent. Despite the edge being lifted, the tip is pushed upwards while remaining substantially horizontal without twisting.

[0021] Incidentally, a front-rear direction of "D ₁ direction" is a linear motor shown in FIG., A seek direction for recording or reproducing by the magnetic head. The “D ₂ direction” indicates the traveling direction (rotation direction) of the flexible magnetic disk 3.
Running direction (D ₃ ) of the flexible magnetic disk 3
May be reversed. A linear motor (not shown) moves parallel to the radial direction of the flexible magnetic disk 3, and the base plate 4 moves in the radial direction of the flexible magnetic disk 3 by driving the linear motor. .

The suspension beam 5 includes an adhered portion 8 attached to the lower surface of the distal end portion of the base plate 4 via a pivot spring, a suspension portion 9 which becomes narrower toward the distal end, and a distal end portion of the suspension portion 9. A slider supporting portion 10 for supporting the head slider 1. The suspension part 9 has several holes 11, 11,
.. Are formed so that appropriate elasticity is imparted. In particular, a U-shaped link portion 12 having an opening at the tip is formed at the tip of the suspension portion 9, and a substantially rectangular slider support portion 10 is formed between the tips of the link portion 12.

The material of the suspension beam 5 is as follows.
Spring constant 20 consisting of three layers such as SUS / adhesive / SUS
It is made of a very soft laminate material of about 0 mgf / mm, and the link portion 12 at the tip end has a roll rigidity of 0.2 μN · m / degree and a pitch rigidity of 0.04 μm.
The flexibility of N · m / degree is secured.
Although the details are omitted, the suspension beam 5 is
It is mechanically connected to the back surface of the head slider 1 and is also electrically connected to a lead terminal extending from a magnetic head embedded in the center of a magnetic pole pad, which will be described later, and also functions as a signal line.

As shown in FIG. 5, the magnetic head slider 1 has a vertically long trapezoidal shape when viewed from the top, and a contact pad (magnetic pole pad) 14 having a magnetic head 13 buried at a tip end thereof. , Contact pad 1 on the opposite corner
5 and 15 are respectively supported. The magnetic head slider 1 is formed of a sputtered alumina body or the like by a thin film process, and is extremely thin at 50 μm or less, so that its rigidity is about eight digits softer than a pico slider having a thickness of about 300 μm used for a hard disk. And its own weight is as light as 500 μg or less. As a result, it is possible to smoothly follow the surface of the flexible magnetic disk 9 and, since it is extremely lightweight, a force generated with respect to an externally applied acceleration is very weak. Excellent impact resistance.

The contact pads 14, 15, 15 are formed of diamond-like carbon (hereinafter abbreviated as DLC) or the like, and the magnetic pole pad 14 is embedded with a magnetic head 13 having a magnetic gap for recording / reproducing. The periphery of the magnetic core is surrounded by DLC or the like on the sliding surface. FIG.
Shows the positional relationship between the magnetic pole pad 14 and the flexible magnetic disk 3 when recording / reproducing.

The hardness of the contact pads 14, 15, 15 needs to be Vickers hardness 700 or more from the viewpoint of abrasion resistance.
The material is not limited to DLC as long as it provides such characteristics. Contact pad 1
The angles α of the corners of the sides 4, 15, and 15 that come into contact with the flexible magnetic disk 3 are required to be an obtuse angle of 90 degrees or more in order to suppress the abrasion of the medium. Preferably, it is 115 degrees or more. The sliding surface shape of the magnetic pole pad 14 is elliptical, and the contact pad 1
Although the sliding surfaces 5 and 15 are formed in a perfect circle, the shape is not limited to this, and may be any of a rectangle, a square, and a triangle. The magnetic head 13 employs a so-called planar type thin-film inductive head whose windings are parallel to the surface of the magnetic head slider 1 so that the structure can be accommodated inside such a thin head slider 1, but is not limited thereto. is not. The magnetic head slider 1 is attached to the lower surface of the slider support 10 at the tip of the suspension beam 5.

The pivot spring 16 has a base portion having a length substantially half the length thereof, and link pieces 18 extending from the left and right ends of the distal end edge of the base portion so as to further extend toward the distal end and approach each other. And the link pieces 18, 1
A pressing piece 19 erected between the distal ends of 8 is integrally formed.

The link piece 18 of the pivot spring 16
Reference numeral 18 is bent between the base and the base, and is deflected downward toward the tip.
It is bent between 8 and 18 and is biased downward toward the tip. Pressing piece 1 of pivot spring 16
A triangular pressing portion 19a is formed at the center of the tip side edge of 9, and the tip of the pressing portion 19a is formed at a position corresponding to the slider supporting portion 10 of the suspension beam 5. The base of the pivot spring 16 is sandwiched between the distal end of the base plate 4 and the base end of the suspension beam 5, whereby the suspension support 5 is pressed by the pressing portion 19 a of the pivot spring 16. The flexible magnetic disk 3 is flexed downward to apply an appropriate load to the flexible magnetic disk 3. The pivot spring 16 is formed of an ultra-thin stainless steel material having a spring constant of about 250 mgf / mm. Therefore, a low load load of 200 mgf is applied to the position of the center of gravity of the head slider 1,
Even when the run-out fluctuation of the flexible magnetic disk 3 occurs, the width of the load fluctuation is as narrow as 100 to 800 mgf, and the contact pads 14, 15, 15 are given uniform contact pressure. As a result, steady and unsteady run-out fluctuations of the flexible magnetic disk 3 are tracked very well, and stable recording / reproduction is realized.

The contact type magnetic head slider according to the invention of the prior application described above has a speed of 2400 rpm or more, for example, 3000 rpm.
It slides at a relatively high speed relative to a magnetic disk that rotates at a high speed of at least rpm, and is designed to have a very small load load from the viewpoint of durability, and can flexibly follow the surface shape of the magnetic disk. .

Hereinafter, the constituent materials of the magnetic disk according to the present invention and the manufacturing method thereof will be described in detail. <Magnetic Layer> First, constituent materials of the magnetic layer will be described.

The ferromagnetic material contained in the magnetic layer is not particularly limited. For example, ferromagnetic alloy powder, ferromagnetic hexagonal ferrite powder, ferromagnetic iron oxide particles, ferromagnetic Cr
O ₂ , ferromagnetic cobalt ferrite (CoO-Fe
Fine particles such as ₂ O ₃ ), cobalt-adsorbed oxide, and iron nitride.

As the ferromagnetic alloy powder, Fe alloy powder,
Co alloy powder, Ni alloy powder, and Fe-Co, F
e-Ni, Fe-Co-Ni, Co-Ni, Fe-Co
-B, Fe-Co-B, Mn-Bi, Mn-Al, Fe
An alloy powder such as -Co-V or an alloy powder which is a compound of these alloys and other elements can be used.
In order to further improve the properties, Al, Si, P,
Non-metals such as B and C may be added. Usually, an oxide layer is formed on the particle surface of the metal powder in order to stabilize it chemically. As a method of forming an oxide, a known slow oxidation treatment, that is, a method of drying after immersion in an organic solvent, a method of drying after immersion in an organic solvent and forming an oxide film on the surface by feeding an oxygen-containing gas, A method of forming an oxide film on the surface by adjusting the partial pressure of an oxygen gas and an inert gas without using an organic solvent, and the like can be used.

The ferromagnetic hexagonal ferrite powder is a flat ferromagnetic powder having an easy axis of magnetization in a direction perpendicular to the plane of the ferrite powder, such as barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, or the like. There are such cobalt-substituted products and the like, and among them, a cobalt-substituted product of barium ferrite and a cobalt-substituted product of strontium ferrite are particularly preferable. If necessary, In, Zn, Ge, N
Elements such as b and V may be added. The output of hexagonal ferrite powder is lower in proportion to other magnetic particles in the case of long wavelength recording, but the recording wavelength in the high frequency band is 1.5 μm.
m or less, preferably 1.0 μm or less, has the characteristic that high output can be expected rather than other magnetic particles.

The shape of the ferromagnetic material is not particularly limited, and examples thereof include a needle shape, a granular shape, a dice shape, a rice grain shape, and a plate shape. In the case of a needle, the needle ratio is 3
/ 1 to about 30/1, and more preferably 4/1 or more. The specific surface area of the ferromagnetic material is preferably 40 m ² / g or more in terms of electromagnetic conversion characteristics, and more preferably 45 m ² / g or more.

As the binder in the magnetic layer, conventionally known thermoplastic resins, thermosetting resins, radiation-crosslinkable resins using an electron beam or the like, and mixtures thereof can be used.

The thermoplastic resin preferably has a softening point of 150 ° C. or lower, an average molecular weight of 5,000 to 50,000, and a degree of polymerization of about 50 to 500. For example, vinyl chloride, vinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer,
Vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinylidene chloride Copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-vinyl chloride copolymer, methacrylate-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-allylonitrile copolymer, acrylonitrile-butadiene copolymer Polymers, polyamide resins, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrose) Loin), styrene-butadiene copolymer, polyurethane resin, polyester resin, amino resin, synthetic rubber, and mixtures thereof.

Examples of the thermosetting resin include phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, silicone resin, polyamine resin, and urea formaldehyde resin.

Further, the resin used as the binder
-SO in the molecule_ThreeH, -OSO_ThreeH, -PO_ThreeH, -OP
O_ThreeH_Two, -COOH or the like or a salt thereof, or
Polar groups such as hydroxyl group, epoxy group, amino group, etc.
Has better dispersibility and coating durability.
-SO_ThreeNa, -COOH, -OPO_ThreeN
a _Two, -NH_TwoThose having a group are preferred.

The magnetic layer of the magnetic recording medium of the present invention preferably further contains inorganic particles having a Mohs hardness of 5 or more.

The inorganic particles used have a Mohs hardness of 5
There is no particular limitation as long as it is above. Examples of the inorganic particles having a Mohs hardness of 5 or more include Al ₂ O ₃ (Mohs hardness of 9), T
iO (6), TiO ₂ (6.5), SiO ₂ (7), SnO ₂ (6.5), Cr ₂ O ₃ (9) and α
—Fe ₂ O ₃ (5.5), and these can be used alone or in combination. Particularly preferred are inorganic particles having a Mohs hardness of 8 or more.
When relatively soft inorganic particles having a Mohs hardness of less than 5 are used, the inorganic particles easily fall off the magnetic layer, and there is almost no polishing effect, so head clogging is likely to occur, and running durability is also high. Also become scarce.

The content of such inorganic particles is usually
It is in the range of 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the ferromagnetic material.

In preparing the coating material for the magnetic layer, an antistatic agent may be used in addition to the above components. Examples of antistatic agents include conductive fine powders such as carbon black and carbon black graft polymer; natural surfactants such as saponin; nonionic surfactants such as alkylene oxide, glycerin and glycidol; higher alkylamines , Quaternary ammonium salts, salts of pyridine and other heterocyclic compounds,
Cationic surfactants such as phosphoniums or sulfoniums; Anionic surfactants containing acidic groups such as carboxylic acid, phosphoric acid, sulfate group, phosphate group, etc .; Sulfuric acid or phosphoric acid of amino acids, aminosulfonic acids and aminoesters Examples include amphoteric surfactants such as esters.

Further, as a lubricant internally added to the magnetic layer,
In addition to the amino-containing esters described above, the following can be used in combination. As the lubricant that can be used in combination, a fatty acid ester, a fatty acid having 8 to 22 carbon atoms or a fatty acid amide, an aliphatic alcohol, or the like can be used. In addition, silicone oil, graphite, molybdenum disulfide, boron nitride, fluorinated graphite, fluoroalcohol, polyolefin (polyethylene wax, etc.), polyglycol (polyethylene oxide wax, etc.), alkyl phosphate, thiophosphite, Polyphenyl ether and tungsten disulfide can also be used.

Specific examples of the lubricant comprising these organic compounds include capric acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and fatty acids.
Behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, isostearic acid, and the like. Esters 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 and alcohols include oleyl alcohol, stearyl alcohol, lauryl alcohol and the like.

<Lower Nonmagnetic Layer> Next, the constituent materials of the lower nonmagnetic layer according to the present invention will be described.

The non-magnetic pigment contained in the lower non-magnetic layer includes, for example, α-Fe ₂ O ₃ , TiO ₂ , carbon black, graphite, barium sulfate, ZnS, MgC
O ₃ , CaCO ₃ , ZnO, CaO, tungsten disulfide, molybdenum disulfide, boron nitride, MgO, Sn
O ₂ , Cr ₂ O ₃ , α-Al ₂ O ₃ , α-FeOOH, Si
C, cerium oxide, corundum, artificial diamond, α
-Iron oxide, garnet, garnet, silica, silicon nitride, boron nitride, silicon carbide, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, triboli, diatomaceous earth, dolomite, and the like.
Among them, preferred are α-Fe ₂ O ₃ , TiO ₂ , carbon black, CaCO ₃ , barium sulfate, α-Al ₂
Examples include inorganic powders such as O ₃ , α-FeOOH and Cr ₂ O ₃ and polymer powders such as polyethylene.

As the binder in the lower non-magnetic layer, it is necessary to consider firstly that the surface properties of the lower layer, that is, the dispersibility of the lower pigment and the uniformity of the interface between the upper and lower layers are satisfied. As the binder satisfying these, similarly to the binder in the upper layer, a conventionally known thermoplastic resin, thermosetting resin, radiation-crosslinkable resin using an electron beam or the like, and a mixture thereof can be used.

As the lubricant internally added to the lower non-magnetic layer, the following may be used in addition to the above-mentioned amino-containing ester. As the lubricant that can be used in combination, fatty acid esters, fatty acids having 8 to 22 carbon atoms, fatty acid amides, aliphatic alcohols, and the like can be used. Also, silicone oil,
Graphite, molybdenum disulfide, boron nitride, fluorinated graphite, fluoroalcohol, polyolefin (polyethylene wax, etc.), polyglycol (polyethylene oxide wax, etc.), alkyl phosphate, thiophosphite, polyphenyl ether, Tungsten sulfide can also be used.

Specific examples of the lubricant comprising these organic compounds include fatty acids such as capric acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid,
Behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, isostearic acid, and the like. Esters 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 and alcohols include oleyl alcohol, stearyl alcohol, lauryl alcohol and the like.

In preparing the coating for the nonmagnetic layer, it is preferable to use an antistatic agent in addition to the above-mentioned components. Examples of antistatic agents include conductive fine powders such as carbon black and carbon black graft polymer; natural surfactants such as saponin; nonionic surfactants such as alkylene oxide, glycerin and glycidol; higher alkylamines Kind, first
Quaternary ammonium salts, salts of pyridine and other heterocyclic compounds, cationic surfactants such as phosphonium or sulfonium; carboxylic acid, phosphoric acid, sulfate group,
Anionic surfactants containing an acidic group such as a phosphate group; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric acid or phosphate esters of amino-containing esters;

When the above conductive fine powder is used as an antistatic agent, for example, 100 parts by weight of the nonmagnetic pigment
It is used in the range of 1 to 15 parts by weight, and similarly when the surfactant is used, it is used in the range of 1 to 15 parts by weight.

Further, similarly to the upper magnetic layer, inorganic particles having a Mohs hardness of 5 or more may be contained.

The inorganic particles having a Mohs hardness of 5 or more include:
Al ₂ O ₃ (Mohs hardness 9), TiO (6), TiO ₂
(6.5), SiO ₂ (7), SnO ₂ (6.
5), Cr ₂ O ₃ (9) and α-Fe ₂ O ₃ (5.5)
These can be used alone or in combination.

<Production of Magnetic Recording Medium> Next, an example of a method for producing the magnetic recording medium of the present invention will be described.

The above-mentioned ferromagnetic material, binder, and, if necessary, other fillers and additives are kneaded with a solvent to prepare a magnetic coating material.

Solvents used for kneading include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, alcohol solvents such as methanol, ethanol and propanol, methyl acetate, ethyl acetate, butyl acetate and propyl acetate. , Ethyl lactate, ester solvents such as ethylene glycol acetate, diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, ether solvents such as dioxane, benzene, toluene, aromatic hydrocarbon solvents such as xylene, methylene chloride, ethylene chloride, Examples thereof include halogenated hydrocarbon solvents such as carbon tetrachloride, chloroform, and chlorobenzene. These solvents may be appropriately mixed and used.

The method of kneading is not particularly limited, and the order of addition of each component can be appropriately set. For the preparation of the magnetic paint, a usual kneading machine, for example, sand mill, dyno mill, double cylinder pearl mill, two-roll mill, three-roll mill, ball mill, high-speed impeller disperser, high-speed stone mill, high-speed impact mill, extruder Examples include a ruder, a disperser, a high-speed mixer, a homogenizer, and an ultrasonic disperser.

The thickness of the non-magnetic support to be used may be appropriately determined according to the purpose of use of the medium, and is often 10 to 120 μm, more preferably 30 to 100 μm.

The constituent materials of the nonmagnetic support include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and vinyl resins such as polyvinyl chloride. In addition to plastics such as polycarbonate, polyamide, and polysulfone, metals such as aluminum and copper, and ceramics such as glass can also be used. Prior to coating, these supports are subjected to corona discharge treatment, plasma treatment, priming treatment, heat treatment, dust removal treatment, metal deposition treatment,
An alkali treatment may be performed.

The coating can be performed directly on the nonmagnetic support, but can also be performed on the nonmagnetic support via an adhesive layer or the like. Examples of the coating method on the non-magnetic support include air doctor coat, blade coat, rod coat, extrusion coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, gravure coat,
Kiss coat, cast coat, spray coat, spin coat method and the like can be mentioned. In particular, using a so-called wet-on-wet coating method in which a non-magnetic paint for the lower layer and a magnetic paint for the upper layer are applied in a superposed state in a wet state. Is also good.

FIG. 2 shows an example of a wet-on-wet coating method. In this manufacturing method, FIG.
In manufacturing the disc shown in FIG. 1, first, the film-like support 22 unwound from the supply roll is fed in the direction of arrow A by the extrusion-type extruder coater 30 so that the paints 21 ′ and 2 for the lower layer and the magnetic layer are formed.
0 ′ is simultaneously applied in multiple layers. Extrusion coater 30 is provided with liquid pools 25 and 26, and each paint 20 ',
21 'is supplied through the slits 31 and 32, and is simultaneously overlapped in a wet-on-wet manner.

In the simultaneous multi-layer coating method in such a wet-on-wet method, the lower layer is in a wet state.
Since the magnetic paint 20 'of the upper layer is applied as it is at 1', the surface of the lower layer (that is, the boundary surface with the upper layer) becomes smooth, the surface properties of the upper layer are improved, and the adhesion between the upper and lower layers is improved. As a result, the performance required for a magnetic recording medium that requires high output and low noise, particularly for high-density recording, is satisfied, film peeling is eliminated, and film strength is improved. In addition, dropout can be reduced, and reliability is improved.

In the magnetic disk according to the present invention, it is possible to obtain a sufficiently isotropic orientation even in the non-oriented state without using an orientation device. It is preferable to use a known random alignment device such as applying a magnetic field. Generally, in-plane two-dimensional random is preferable as the isotropic orientation,
Three-dimensional randomness can be obtained by adding a vertical component. In addition, by using a known method such as a different-magnet opposed magnet and performing vertical alignment, it is possible to impart isotropic magnetic characteristics in the circumferential direction. In particular, when performing high-density recording, vertical alignment is preferable. In addition, circumferential orientation may be performed using spin coating.

The orientation is preferably controlled by controlling the temperature of the drying air, the amount of air, and the coating speed so that the drying position of the coating film can be controlled. The coating speed is from 20 m / min to 100 m / min.
0 m / min, the temperature of the drying air is preferably 60 ° C. or more. Also, an appropriate preliminary drying can be performed before entering the magnet zone.

In the calendar processing, epoxy is used as a roll,
The treatment is performed with a heat-resistant plastic roll such as polyimide, polyamide, or polyimide amide or a metal roll. In the case of a double-sided magnetic layer, the treatment is preferably performed between metal rolls. Processing temperature is preferably 50 ° C
The temperature is more preferably 100 ° C. or more. The linear pressure is preferably at least 200 kg / cm, more preferably at least 300 kg / cm.

[0066]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. It will be readily understood by those skilled in the art that the components, ratios, operation orders, and the like shown herein can be changed without departing from the spirit of the present invention. Therefore, the present invention should not be limited to the following examples.

Example 1 In this example, a magnetic disk having a lower non-magnetic layer and an upper magnetic layer formed on a non-magnetic support was prepared as a sample. First, a magnetic paint for forming a magnetic layer and a non-magnetic paint for forming a non-magnetic layer were manufactured. The production of each paint shall be carried out in accordance with a normal production method. In both cases, first, a pigment (ferromagnetic powder or non-magnetic powder), a binder, an additive, a solvent, and the like are mixed, and then the non-volatile components at the time of kneading are mixed. The mixture was kneaded with a kneader so as to be 85% by weight. Then, after that, the magnetic paint was dispersed in a sand mill for 5 hours, and the non-magnetic paint was dispersed in a sand mill for 3 hours to obtain each paint. The composition of each paint is shown below.

<Magnetic paint formulation> Fe-based metal ferromagnetic powder (coercive force = 170 kA / m, saturation magnetization 100 parts by weight = 150 Am ² / kg, major axis length = 0.1 μm) Binder: polyvinyl chloride resin (functional Group [-OSO ₃ K] = 6 × 10 ⁻⁵ mol / g) 15 parts by weight Inorganic particles: α-Al ₂ O ₃ (average particle size = 0.3 μm, Mohs hardness 9) 5 parts by weight Solvent: 150 parts by weight methyl ethyl ketone Solvent: cyclohexanone 150 parts by weight

<Non-magnetic paint formulation> Non-magnetic pigment: 100 parts by weight of acicular α-iron oxide (specific surface area = 53 m ² / g, major axis length = 0.15 μm, acicular ratio = 11) Binder: polyvinyl chloride Resin (functional group [-OSO ₃ K] = 6 × 10 ⁻⁵ mol / g) 25 parts by weight Antistatic agent: carbon black (Ketjen Black EC manufactured by Lion Aguzo) 15 parts by weight Solvent: 150 parts by weight methyl ethyl ketone Solvent: cyclohexanone 150 Parts by weight

Then, 5 parts by weight of the compound (1) shown in the following Table 1 as an amino-containing ester was added to the non-magnetic paint obtained as described above, and the mixture was stirred for 30 minutes. As a curing agent, 3.5 parts by weight of polyisocyanate (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) was added to complete a magnetic paint and a non-magnetic paint.

Using a die coater as shown in FIG. 2, the magnetic paint and the non-magnetic paint were applied on a 60 μm-thick polyethylene terephthalate film as a non-magnetic support, with the non-magnetic paint as the lower layer and the magnetic paint as the upper layer. Coating is applied simultaneously so that the AC magnetic field is 150
e, Non-orientation treatment was performed under the conditions of a frequency of 60 Hz. After drying, 90 ° C, 200k using a 5-stage metal roll calender
A smoothing treatment was performed under the condition of g / cm.

At this time, the thickness of the dried magnetic layer was 0.2
μm, and the thickness after drying of the nonmagnetic layer was set to 2.0 μm. Thereafter, the disk was punched out into a 3.5-inch floppy disk, placed in a constant temperature layer at 60 ° C. for 48 hours, annealed, and formed into a magnetic disk. This magnetic disk sample is referred to as a magnetic disk-1.

Examples 2 to 10 Samples were prepared in the same manner as for the magnetic disk 1 except that 5 parts by weight of each of the compounds (2) to (10) were added instead of the compound (1) in Table 1 below as amino-esters containing the same. Then, magnetic disks -2 to 10 were obtained.

Example 11 For the magnetic paint, the following amino acid-containing ester was used as shown in Table 1 below.
A sample was prepared in the same manner as for the magnetic disk-1 except that 2 parts by weight of the compound (1) was added to obtain a magnetic disk-11.

Example 12 The same procedure as in the case of the magnetic disk-1 was performed except that 5 parts by weight of the compound (1) shown in the following Table 1 was not added to the non-magnetic paint as an amino-containing ester. In the magnetic layer, the following Table 1 was used as an amino-containing ester.
A sample was prepared in the same manner as the magnetic disk-1 except that a 0.3% by weight n-hexane solution of the compound (1) was applied (top-coated) so that the coating amount was 100 mg / m ^2. -12.

Example 13 A magnetic disk-13 was prepared in the same manner as the magnetic disk-1 except that 2 parts by weight of isohexadecyl stearate was added to the nonmagnetic paint as a lubricant.

Example 14 A magnetic paint was prepared in the same manner as in the magnetic disk 1 except that 5 parts by weight of the compound (1) shown in Table 1 below was added as an amino-containing ester to the magnetic paint, and dried using a gravure coater. A magnetic disk-14 was prepared in the same manner as the magnetic disk-1 except that only the magnetic paint was applied so that the thickness became 3.0 μm.

Example 15 Using only a magnetic coating material, a gravure coater was used to apply a coating so that the thickness after drying became 3.0 μm, and the process was repeated until calendering. Then, a 0.3% by weight n-hexane solution of the compound (1) shown in Table 1 below as an amino-containing ester was applied to both magnetic layers of the above sample in an amount of 100 m.
A magnetic disk-15 was prepared in the same manner as the magnetic disk-1 except that the coating (top coating) was performed so as to give a g / m ² .

Comparative Example 1 Magnetic disk-1 except that 5 parts by weight of isohexadecyl stearate was added instead of compound (1) in Table 1 below.
A sample was prepared in the same manner as in Comparative Example 1 and used as Comparative Disk-1.

Comparative Example 2 A sample was prepared in the same manner as the magnetic disk-1 except that 5 parts by weight of butyl stearate was added instead of the compound (1) in Table 1 below, and the sample was used as a comparative disk-2.

Comparative Example 3 A sample was prepared in the same manner as the magnetic disk-1 except that 5 parts by weight of myristic acid was added in place of the compound (1) in Table 1 below, and a comparative disk-3 was obtained.

Each magnetic disk produced by the above method was evaluated in combination with the magnetic head sliders shown in Tables 2 and 3 below as shown in Table 4 below.

Magnetic Head Slider: The magnetic head slider portion shown in FIG. 5 has contact pads I, II, and III arranged in a disk shape and is located at a position corresponding to each vertex of an isosceles triangle on the surface of the magnetic head slider. Is provided. Each contact pad has a flat surface (tip surface) at a portion that comes into contact with the magnetic disk. The area of the contact pad I having the magnetic head (recording / reproducing element) 13 is set to be larger than the areas of the other two contact pads II and III. These contact pads I, II and III are formed by an etching method, and the total area is as shown in Tables 2 and 3 below. The pressing loads of the slider are also shown in Tables 2 and 3 below. Diamond-like carbon was used as the material of the contact pad.

Examples 1 to 15 and 16 prepared as described above
To 27 and Comparative Examples 1 to 3 were evaluated by the following methods. The evaluation results are shown in Table 4 below.

Head Wear Test (Seek Mode): FIG.
The magnetic head slider is mounted on both sides of the magnetic disk so that the contact pads are in contact with the disk surface, the disk rotation speed is kept constant at 3600 rpm, and the slider is set in a range of 18 mm to 38 mm from the center of the disk.
It was slid repeatedly at Hz. This operation was continuously performed for 48 hours. The height of the pad before and after the test was measured using a non-contact general-purpose three-dimensional surface structure analyzer (NewView5020, manufactured by Zygo), and the difference was defined as the pad wear height. Pad I-II
Find the sum of I wear height multiplied by each pad area,
It was the abrasion volume. The wear volume was divided by the total area of the pads I to III to obtain the amount of wear, and further divided by the sliding time of 48 hours to obtain a head wear rate (nm / h). (Average of 5 measurements)

Running durability test (still mode): Similar to the head wear test, a magnetic head slider was mounted on both sides of the magnetic disk, and the disk rotation speed was set to 3600 rpm.
And keep the slider position at 35 from the disc center.
A sliding test was performed in a so-called still mode in which the track was fixed at a distance of 0.1 mm and continuously slid, and the time required for the output of the track 35 mm from the center to drop to 80% of the initial value was measured. (Average of 5 measurements)

Electromagnetic conversion characteristics: The electromagnetic conversion characteristics
Through a commercially available recording and playback evaluation device (Guz
ik1601 + PRML), digital storage oscilloscope
(Lecroy9345), spectrum analyzer (Advantes)
Analyzed / evaluated using t). Motor speed 360
0 rpm, the measurement position is 20 mm from the center of the disk
And The head is a thin film head with a track width of 6 μm.
Using. Slider equipped with this pad is used for magnetic recording
A disk with a 10 μm wavelength isolated reproduction waveform.
Amplitude from slope (= GND) to peak: IS TAA and I
Pulse width at half the level of STAA: PW₅₀Measure
did. Generally, IS TAA is used as an indicator of S / N, and PW
₅₀Is the distance between the head and the medium, so-called magnetic spacing.
Because it is very sensitive, it is used as an indicator of contact status.
You. IS TAA and PW₅₀Are 0 dB, 1
It was represented by a relative value as 00%.

[0088]

Table 1 Table 1 Amino-containing esters of general formula (I) (However, Ph represents a benzene ring.)

[0089]

[Table 2] Table 2 Magnetic head slider

[0090]

[Table 3] Table 3 Magnetic head slider

[0091]

[Table 4A]

[0092]

[Table 4B]

As is clear from the results shown in Table 4,
In Examples 1 to 21 according to the present invention, when the magnetic layer or / and / or the surface of the magnetic disk contain at least one kind of amino-containing ester represented by the general formula (I), the disk rotation speed is 2400 or more per minute. Even when used in a recording system in which a magnetic head slider slides in contact, even in a seek mode under a wide range of environmental conditions, it has excellent head wear characteristics of 3 nm / h or less and running durability. A magnetic disk is obtained. In any environment, the running durability time is 100
h, which is a good result.

On the other hand, in Comparative Examples 1 and 2 using fatty acid esters and fatty acids, which are widely used in coating type media,
Excellent running durability, but head wear speed is 20n
m / h. In Comparative Example 3 using fatty acids as in Comparative Examples 1 and 2, the head wear rate was 30 nm.
/ H or more, and the durability time was 1 h, which was not good. Therefore, by using the amino-containing ester of the present invention, it is possible to suppress the head wear rate by about one digit.

In Examples 22 and 23, both the head abrasion characteristics and the running durability were very good, but the PW _{50 of} the reproduction signal was increased, and it was found that the contact recording / reproduction was insufficient. It is considered that this is because the head slider jumps due to the low contact surface pressure, and it is difficult to obtain stable contact sliding (PW ₅₀ is a half-value width of an isolated reproduction waveform, and generally PW ₅₀ Is the distance between the head and the medium,
Because it is very sensitive to so-called magnetic spacing, it is used as an indicator of the contact state. ).

In Examples 24 to 27 using a magnetic head slider having a contact surface pressure as high as 45 gf / mm ² , the running durability time was short, and the head wear rate did not become 3 nm / h or less under all environmental conditions. Therefore, it is not very practical.

[0097]

The disk-shaped magnetic recording medium according to the present invention can be used in a recording system in which the number of rotations of the disk is 2400 or more per minute and the magnetic head slider slides in contact with the magnetic recording medium under a wide range of environmental conditions. It shows excellent head wear characteristics and running durability.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a magnetic disk according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a multilayer coating apparatus used for manufacturing a magnetic disk.

FIG. 3 shows a head slider suspension (HG
FIG. 2A is a perspective view of a head slider for a flexible magnetic disk attached to the tip of FIG.

FIG. 4 is a cross-sectional view showing a contact state between a magnetic head attached to a slider and a flexible magnetic disk.

FIG. 5 is a perspective view of the slider.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic head slider, 3 ... Flexible magnetic disk, 5 ... Suspension beam, 13 ... Magnetic head,
14, 15 ... contact pad, 20 ... upper layer, 20 '...
Upper layer paint, 21 ... Lower layer, 21 '... Lower layer paint, 22 ... Nonmagnetic support

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C10N 30:06 C10N 30:06 40:18 40:18 F term (reference) 4H104 BE02A LA03 LA20 PA16 4J038 BA021 CA001 CA041 CA071 CD021 CD081 CD101 CE071 CF031 CF041 CG141 CG161 CJ011 CJ061 CJ131 DA061 DA14 DA16 DB001 DD001 DG00 DG001 DH001 DL00 HA066 HA166 JB03 KA08 NA11 NA22 PB11 PC08 5D006 BA09 DA02 EA01

Claims (4)

[Claims] 1. A magnetic layer or / and a medium in which the number of revolutions is 2400 revolutions per minute or more and a magnetic head is relatively slid in contact, and a magnetic powder is dispersed in a binder. A disk-shaped magnetic recording medium comprising at least one type of nitrogen-containing ester represented by the following general formula (I) on the surface. Embedded image (However, in the general formula (I), R ¹ has 24 carbon atoms.
The following hydrocarbon groups, R ² is a hydrocarbon group having 12 or less carbon atoms, and R ³ and R ⁴ are the same or different carbon atoms 2
4 or less hydrocarbon groups. ) 2. The disk-shaped magnetic recording medium according to claim 1, wherein a second layer is formed on the first layer by multi-layer coating, and at least the second layer is formed as the magnetic layer. 3. The disk-shaped magnetic recording medium according to claim 2, wherein said first layer is formed as a non-magnetic layer. 4. Contact pressure (pressing load / total contact area)
There is used in combination with the magnetic head slider is 1~40gf / mm ^2, a disc-like magnetic recording medium as claimed in any one of claims 1 to 3.