JP2001312813A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a wear amount and friction of a head due to high speed sliding so as to be a effectively small amount,, while keeping high recording density and a high transfer rate of a multi-layer coating type magnetic recording medium, especially a magnetic disk and to enhance durability and reliability of the medium. SOLUTION: An upper layer (magnetic layer) 20 on the multi-layer coating type magnetic disk 3 contains the mixed three kinds of powders (a), (b) and (c). (a) metal powder which contains cobalt. (b) alumina powder. (c) titanium aluminum oxide powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, such as a magnetic (recording) disk, manufactured by multi-layer coating.

[0002]

2. Description of the Related Art At present, many magnetic recording media such as magnetic disks are manufactured by a coating method such as multi-layer coating. That is, first, a ferromagnetic powder, a binder, an additive, and the like are dispersed in an organic solvent to prepare a magnetic paint. Next, the magnetic paint is applied on a non-magnetic support, and the coating is dried to form a magnetic layer.

Recently, in order to increase the recording density of a magnetic recording medium, metal fine particles have been used as the ferromagnetic powder.

[0004] Magnetic recording media containing such metal fine particles in the magnetic layer have begun to be used not only in various formats for audio and video, but also in computer peripherals such as large-capacity floppy disks and backup data cartridges. .

[0005] Such a magnetic recording medium needs to have running durability. In particular, floppy disks, which have been increasingly installed in personal computers, are expected to be used in a variety of environments in the future. Has become.

On the other hand, with the increase in the capacity of magnetic recording media and the size of files, improvement in data transfer speed is also an essential element for magnetic recording media.

[0007] In a disk drive, the demand for the improvement of the transfer speed is met by increasing the rotation speed of the disk. For example, in a so-called large-capacity storage system, the design is shifted to a high-speed rotation of the disk.

[0008] The reliability and durability of the disk must also be designed to cope with such high-speed rotation of the disk. However, these have not been sufficiently developed today. At present, there are almost no design guidelines.

As one solution corresponding to high-speed rotation of a disk, there has been known an attempt to employ a so-called flying head. This flying head has been used widely in hard disks, and its research and development is ongoing today. (Eg B.Bhushan; "Tribology
and Mechanics of Magnetic Storage Devices "(Spring
en-Verlag, 1990)).

[0010] However, in the case of the combination with a flexible disk, there are only a few research reports [Y. Muratomi; "Numerical analysis for head-flex".
ibledisk interface under a mixed lubrication regim
e ", Adv. Info. Storage Syst., 6 (1995) 395 and K. Ono an
d T. Arisake; "Stability analysis of the head-disk i
nterface in flexible disk drive ", Adv. Info. Stora
Analytical studies such as ge Syst. 5 (1993) 451, K. Okamoto e
t.al,; "Development of high capacity floppy disk" H
An experimental report on iFD "]. At present, a method to ensure durability with this combination has not yet been established.

On the other hand, attempts have been made to improve the running durability of a magnetic disk with a sliding head, and the present applicant has previously proposed a contact type head slider having a contact pad in which a magnetic head is buried. 11-251815
issue). Hereinafter, the outline of the invention of the prior application will be described.

[0012]

In the head slider for a flexible magnetic disk of the prior invention, a pad in which a magnetic head is embedded is provided on a surface facing the flexible magnetic disk, and the pad has a relative speed with the magnetic head. Is 1.
In the state in which the magnetic head is in contact with the flexible magnetic disk of 9 m / s to 25.0 m / s, recording or reproduction of a signal with respect to the flexible magnetic disk by the magnetic head is performed. 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 in which a head slider 1 according to an embodiment is attached to a tip end. The HGA 2 is a radial extension of a flexible magnetic disk 3 (see FIG. 4). The head slider 1 is supported by the tip of the suspension beam 5. The head slider 1 is composed of a base plate 4 in the shape of a rectangular plate that is long in the direction and a suspension beam 5 stuck on the lower surface of the tip of the base plate 4 in an overlapping manner. Incidentally, two head sliders 1 and two HGAs 2 are arranged so as to face up and down, and as shown in FIG. 4, the flexible magnetic disk 3 is sandwiched from both sides.

The base plate 4 has a narrow portion formed at its base end on both left and right sides. The base end 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.

[0016] 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 is composed of 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 suspension beam 5 has a spring constant of 200 mgf / m consisting of three layers such as SUS / adhesive / SUS.
m and a very soft laminate material of about m.
/ Degree, pitch stiffness 0.04μN · m / deg
The flexibility of ree is secured. Although not described in detail, the suspension beam 5 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 described later. Thus, it also functions as a signal line.

The head slider 1 has a vertically long trapezoidal shape when viewed from a plane. A contact pad (magnetic pole pad) 14 having a magnetic head 13 buried in a tip portion thereof and a contact portion in contact with a corner portion on the opposite side. Pads 15, 15 are supported respectively. The head slider 1 is formed of a sputtered alumina body or the like by a thin film process and has a thickness of 50 μm.
Since it is extremely thin as follows, the rigidity is about eight digits softer than that of a picos slider having a thickness of about 300 μm used in 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 3 and, since it is extremely lightweight, the force generated with respect to the acceleration applied from the outside 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 a magnetic head 13 having a magnetic gap for recording / reproducing is embedded in the contact pad 14. The periphery of the magnetic core is surrounded by DLC or the like on the sliding surface. FIG.
Indicates the positional relationship between the contact pad 14 and the flexible magnetic disk 3 when performing recording / reproduction.

The hardness of the contact pads 14, 15, and 15 is required to be 700 or more Viccus hardness from the viewpoint of abrasion resistance.
The material is not limited to DLC as long as it gives 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 8 need to be obtuse angles of 90 degrees or more in order to suppress the abrasion of the medium. Preferably, it is 115 degrees or more. The sliding surface of the contact 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 in which the windings are parallel to the surface of the head slider 1 so that the structure can be accommodated inside such a thin head slider 1, but is not limited thereto. Absent. The 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 17 having a length substantially half the length thereof, and link pieces extending from the left and right ends of the distal end edge of the base portion 17 toward the distal ends and approaching each other. 18, 18 and a pressing piece 19 provided between the distal ends of the link pieces 18, 18 are integrally formed.

The link piece 18 of the pivot spring 16
Reference numeral 18 is bent between the base 17 and the distal end thereof, and the pressing piece 19 is bent between the link pieces 18 and 18 and biased downward toward the distal end. . A triangular pressing portion 19a is provided at the center of the tip side edge of the pressing piece 19 of the pivot spring 16.
The tip of the pressing portion 19a is formed at a position corresponding to the slider supporting portion 10 of the suspension beam 5. And the pivot spring 16
The base 17 of the suspension beam 5 is sandwiched between the front end of the base plate 4 and the base end of the suspension beam 5, whereby the suspension beam 5 is pressed downward by the pressing portion 19a of the pivot spring 16 when the slider supporting portion 10 is pressed. The flexible magnetic disk 3 is bent and an appropriate load is applied to the flexible magnetic disk 3. The pivot spring 16 is formed of an ultra-thin stainless steel having a spring constant of about 250 mgf / mm. Therefore, even if a load as low as 200 mgf is applied to the position of the center of gravity of the head slider 1 and run-out fluctuation of the flexible magnetic disk 3 occurs, The width of the load variation is as narrow as 100 to 800 mgf, and uniform contact pressure is applied to each of the contact pads 14, 15, 15. 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 of the invention of the prior application described above slides on a magnetic disk rotating at a high speed of, for example, 3000 rpm or more, and is designed to have a very small load load from the viewpoint of durability. And
It is possible to flexibly follow the surface shape of the magnetic disk.

[0025]

The technology for improving running durability with such a contact type magnetic head slider can be applied to a conventional technology of a disk system or a technology used in a streamer (tape data recording medium). Therefore, it is considered that maturity is high.

Some examples of the prior art are as follows.
(1) a method of reducing the coefficient of friction by adding a fatty acid,
There are known (2) a method of adding a fatty acid ester, and (3) a method of adding an ester having a specific molecular structure such as a branch.

However, even if these methods are applied, a technique for simultaneously satisfying the low wear and low friction of the (magnetic) head for a high-speed rotation system has not yet been established. That is, even if low friction can be achieved by appropriately selecting a lubricant, the amount of wear on the head is excessive, or conversely, if the amount of wear on the head is suppressed to an appropriate range, the friction increases. And inconveniences such as deposits are deposited on the head.

The present invention has been made in order to improve the situation described above, and has an object to be suitable for use in combination with the contact type magnetic head slider, while maintaining a high recording density and a high transfer rate. Another object of the present invention is to provide a magnetic recording medium capable of simultaneously achieving low wear and low friction of a head due to high-speed sliding.

[0029]

The magnetic recording medium of the present invention has a multilayer coating type magnetic recording medium in which a second layer is formed on a first layer by multilayer coating, and at least the second layer is formed as a magnetic layer. The recording medium is characterized in that the magnetic layer contains a cobalt-containing metal powder, an alumina powder, and a titanium aluminum oxide powder.

According to the study of the present inventors, the magnetic layer of the above-described multilayer coating type magnetic recording medium is provided with a cobalt-containing metal powder, an alumina powder, and titanium aluminum oxide (Al ₂ O _3).
When TiO ₅ or the like is blended, low wear and low friction of the head can be simultaneously achieved while maintaining high recording density and high transfer rate.

A magnetic recording medium in which the powder group specified as described above is blended in a magnetic layer, in particular, a magnetic disk,
In particular, a next-generation recording system using the contact-type head slider of the prior invention described above, that is, a magnetic disk is 30 minutes per minute.
When applied to a next-generation magnetic recording system using a head-disk interface that rotates at a high speed of 00 rotation or more and whose surface is protected by a so-called DLC (diamond-like carbon) film, the effect is remarkably exhibited. It is possible to make a great contribution to improving the performance of the system. Incidentally, even in a conventional low-speed rotating head-disk interface or a magnetic recording system in which the surface of the head is not DLC-coated, when the magnetic recording medium of the present invention is applied, the effect of the present invention is potentially reduced. Is considered to be exhibited.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically based on embodiments.

In the magnetic recording medium of the present invention, the first layer can be a magnetic layer, but it is usually preferable to form it as a non-magnetic layer. When the first layer is a non-magnetic layer as described above, the second layer laminated thereon can be effectively smoothed or made thin.

In the present invention, a cobalt-containing metal powder is used as the ferromagnetic powder contained in the second layer (magnetic layer). Specifically, Fe-Co, Fe-Co-Ni, F
e-Co-Al, Fe-Co-Ni-Al, Fe-Co
-Al-P, Fe-Co-Ni-Si-Al, Fe-C
o-Ni-Si-Al-Mn, Fe-Co-Mn-Z
n, Fe-Co-Ni-Zn, Fe-Co-Ni-C
r, Fe-Co-Ni-P, Fe-Co-B, Fe-C
alloy powders such as o-Cr-B and Fe-Co-V; Of course, an appropriate amount of a light metal element such as Al, Si, P, B, etc. is used for the purpose of preventing sintering during reduction or maintaining the shape.
The addition to the layer does not impair the effects of the present invention.
Most commonly, Al and / or Si powder is added to an alloy of Fe-Co and Fe-Co-Ni for the purpose of preventing sintering.

The Co content of the cobalt-containing metal powder is preferably 70% by weight based on the magnetic metal other than cobalt.
The following is desirable. By alloying Co, Fe
The magnetic properties are improved as compared with a single substance, and not only characteristics suitable for higher density recording are obtained, but also weather resistance is increased, and storage characteristics of the medium are improved.

The specific surface area of these metal powders is preferably from 20 to 90 m ² / g, and more preferably from 25 to 70 m ² / g.

When viewed from the average particle size, the major axis length is 0.0
It is 1 to 0.3 μm, preferably 0.1 to 0.2 μm.

When the specific surface area or the particle size is in the above range, the powder is finely divided, high-density recording becomes possible, and a magnetic recording medium having excellent noise characteristics can be obtained.

The needle ratio is 2 to 20, preferably 4 to 10. The saturation magnetization is 100 to 180 Am ² / kg, desirably 130 to 160 Am ² / kg, and the coercive force is 120
２４０240 kA / m, desirably 160 to 220 kA / m
It is. One kind of each of the above metal powders can be used, but two or more kinds may be used in combination.

The alumina powder (abrasive) used in the present invention has an average particle size of 0.01 to 0.5 μm, preferably 0.1 to 0.5 μm.
0.4 μm, and the pregelatinization rate is 50% or more, preferably 8%.
0% or more. The shape may be spherical, dice-like, needle-like, irregular, or anything, but it is preferable to have a uniform distribution of size and shape. The alumina powder may be added to the paint as it is, or may be added to the paint after being slurried with a binder or a solvent in advance. The addition amount is 1 to 15 parts by weight, preferably 2 to 5 parts by weight, based on 100 parts by weight of the cobalt-containing metal powder. If the amount is less than the lower limit, the polishing property is poor, and if the amount exceeds the upper limit, not only the magnetic properties are deteriorated, but also the wear of the head becomes remarkable, and the life of the system is significantly shortened. Absent.

As the alumina powder, those having the same particle size and / or shape can be used, or a plurality of different types can be used as a mixture. When the latter is used as a mixture, it is necessary to keep the total amount within the above-mentioned range.

In the present invention, it is necessary to use titanium aluminum oxide powder in addition to the cobalt-containing metal powder and the alumina powder as the powder to be contained in the second layer. Of these, alumina powder and titanium aluminum oxide are used as abrasives.

The particle size of the titanium aluminum oxide powder is also preferably about the same as that of the above-mentioned alumina powder, and the average particle size of the powder is 0.1.
The thickness is preferably from 01 to 0.5 μm, more preferably from 0.1 to 0.4 μm. Those having a uniform distribution of size and shape are preferred. Titanium aluminum oxide can also be added to the paint as it is.

Regarding the amount of the alumina powder and the titanium aluminum oxide powder to be added, first, the amount of the alumina powder added was 2 parts per 100 parts by weight of the cobalt-containing metal powder.
It is not less than 15 parts by weight, preferably not less than 3 parts by weight and not more than 8 parts by weight. The addition ratio of the alumina powder and the titanium aluminum oxide powder is not particularly limited as long as the addition amount of the titanium aluminum oxide powder is 2 parts by weight or more based on 100 parts by weight of the cobalt-containing metal powder. When the addition amount of the alumina powder is less than 2 parts by weight, the effect of removing head dirt is weak, but the head is liable to be clogged in some cases, although the wear amount of the head is reduced. On the other hand, when the alumina powder exceeds 15 weight, not only the amount of wear of the head is increased but also the friction is not reduced, which is not preferable. If the addition amount of the titanium aluminum oxide powder is less than 2 weight, low friction of the head is not realized.

Generally, when the magnetic powder is miniaturized, the voids between the particles are also miniaturized if the geometrical arrangement does not change. As a result, in order to wet the fine space between the particles and uniformly cover and disperse with the binder, a binder having strong affinity for the ferromagnetic powder and having excellent fluidity is used. A kneading step is required so that the binder can sufficiently exhibit an adsorption function.

As the binder used in the present invention, a thermoplastic resin, a thermosetting resin, a reactive resin and the like which are conventionally known for magnetic recording media can be used, and the number average molecular weight is 5
000 to 100,000 are preferred.

Examples of the thermoplastic resin include vinyl chloride, vinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, and 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, polyamide resin, polyvinyl butyral, cellulose Derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene-butadiene copolymer, polyurethane resin, polyester resin, amino resin, synthetic rubber, and the like.

Examples of the thermosetting resin or the reactive resin include a phenol resin, a polyamine resin, a urea formaldehyde resin and the like (refer to the revised edition "Plastic Handbook" (Asakura Shoten)).

The polar functional group contained in the binder is -S
_{O 3 M, -OSO 3 M,} -COOM, P = O (OM) 2.
(Where M is a hydrogen atom or an alkali metal such as lithium, potassium, sodium, etc.), -N
R ₁ R ₂ , -NR ₁ R ₂ R ₃ ⁺ X ⁻ side chain type having a terminal group, and> NR ₁ R ₂ ⁺ X ⁻ main chain type (here, in the formula, R ₁ , R ₂ and R ₃ are a hydrogen atom or a hydrocarbon group, and X ⁻ is a halogen element ion such as fluorine, chlorine, bromine or iodine or an inorganic or organic ion.). Further, a polar functional group such as —OH, —SH, —CN, or an epoxy group may be contained in the binder. The amount of these polar functional groups is 10 ^-1 to 10 ^-8 mol / g, preferably 10 ^-2 to 10 ^-6 mol / g. If the number of the functional groups is too small, the effect on the dispersion of the magnetic powder will not be exhibited. These binders can be used alone or in combination of two or more. The amount of the binder in the coating film is 1 to 200 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the ferromagnetic powder or nonmagnetic powder.

Specific examples of the binder that can be used in the present invention include VAGH, VYHH, VMCH, and VA.
GF, VAGD, VROH, VYES, VYNC, VM
CC, XYHL, XYSG, PKHH, PKHJ, PK
HC, PKFE (Union Carbide), MR
110, MR100, MR112, MR555 and MR
104 (manufactured by Zeon Corporation), Nipporan N230
1, N2302 and N2304 (manufactured by Nippon Polyurethane Industry Co., Ltd.), Byron UR8200, UR8300,
RV530 and RV280 (manufactured by Toyobo Co., Ltd.), Diferamine 4020, 9020, 9022, and 702
0 (manufactured by Dainichi Seika Co., Ltd.), Saran F310 and F21
0 (manufactured by Asahi Kasei Corporation).

In the case of forming the non-magnetic layer in the present invention,
What is used as the nonmagnetic powder is, for example, α-
Nonmagnetic iron oxide such as Fe ₂ O ₃ , carbon black, goethite, rutile type titanium oxide, anatase type titanium oxide,
Tin oxide, tungsten oxide, silicon oxide, zinc oxide, chromium oxide, cerium oxide, titanium carbide, BN, α-
Alumina, β-alumina, γ-alumina, calcium sulfate, barium sulfate, molybdenum disulfide, magnesium carbonate, calcium carbonate, barium carbonate, strontium carbonate, barium titanate, etc., and these powders can be used alone However, it is also possible to use a mixture of two or more.

These non-magnetic powders can be doped with an appropriate amount of impurities according to the purpose. For the purpose of improving dispersibility, imparting conductivity, improving color tone, etc., Al,
Surface treatment with a compound such as Si, Ti, Sn, Sb, or Zr is also possible.

The shape of these nonmagnetic powders is needle-like, spherical,
Any shape such as a dice shape may be used. The specific surface area of the nonmagnetic powder is 10 to 80 m ² / g, preferably 20 to 70 m ² / g.
m ² / g, and the size is preferably 0.5 μm or less.

Specific examples of the non-magnetic powder used for the non-magnetic layer include HIT-100, HIT-82 (manufactured by Sumitomo Chemical), DPN-250, DPN-250BX, and DPN.
-270BX, DPN-500BX, (made by Toda Kogyo),
TTO-51B, TTO-55A, TTO-55B, T
TO-55C, TTO-55S, TTO-55D, SN
-100, E270, E271, E300, E303
(Made by Ishihara Sangyo).

The non-magnetic powder has no magnetic cohesion and is easier to disperse than the ferromagnetic powder (except for carbon black). Difficulty dispersing the body. If the specific surface area is too small, surface smoothness that can withstand high-density recording cannot be secured.

In the present invention, a polyisocyanate can be used in combination for crosslinking and curing the binder. Examples of the polyisocyanate include tolylene diisocyanate, alkylene diisocyanate, 4,4'-diphenylmethane diimocyanate, and adducts thereof. Specific examples of these isocyanates include Coronate L, Coronate HL, Coronate 2030, and Coronate 2031 (Nippon Polyurethane Industry Co., Ltd.)
Manufactured), Takenate D-102, Takenate D-110
N, Takenate D-200 and Takenate D-202 (manufactured by Takeda Pharmaceutical Co., Ltd.).

The amount of the polyisocyanate to be added to the binder is 5 to 80 parts by weight, preferably 10 to 60 parts by weight, based on 100 parts by weight of the binder. These polyisocyanates can be used in both the magnetic layer and the non-magnetic layer, or can be used in only one layer. When used in both layers, the compounding amount can be contained in each layer in an equal amount, or can be changed at an arbitrary ratio.

In the present invention, a lubricant can be contained in the magnetic layer and the non-magnetic layer. As the lubricant, graphite, molybdenum disulfide, fine powder such as tungsten disulfide, fatty acids having 10 to 22 carbon atoms, and
A fatty acid ester composed of an alcohol having 2 to 26 carbon atoms, a silicone oil such as fluorocarbons, dialkylpolysiloxane and fluoroalkylpolysiloxane, and a first to third grade having at least one alkyl chain having 10 to 22 carbon atoms. Amines, amino alcohols and derivatives thereof.

These lubricants can be added only to the magnetic layer or to both the magnetic layer and the non-magnetic layer. Of these, fatty acid esters are generally preferred and widely used in coating-type displays. Specific examples of the fatty acid ester include butyl stearate, isopropyl stearate, butyl oleate, 2-ethylhexyl stearate, 2-hexyl decyl stearate, heptyl stearate, butyl palmitate, and 2-butyl stearate.
Examples include various ester compounds such as ethylhexyl myristate, a mixture of butyl stearate and butyl palmitate, oleyl oleate, butoxyethyl stearate, 2-butoxy-1-propyl stearate, diethylene glycol dioleate, and glycerin oleate. Can be.

When a lubricant is used for the purpose of reducing hydrolysis which is likely to occur when the magnetic disk is used under high humidity and preventing migration to another layer during the storage period, when a lubricant is used, the fatty acid or fatty acid used as the raw material is not used. It is preferable to appropriately select an isomer structure and a branch position such as alcohol branch / straight chain and cis / trans.

In the present invention, a dispersing agent can be added in order to disperse the raw material powder in the magnetic layer and / or the non-magnetic layer well. Specific examples of dispersants include nonionic surfactants such as polyoxyalkylene alkyl ethers and polyoxyalkylene phenol ethers; anionic surfactants such as polyoxyalkylene phosphates, sulfonic acids, and various fatty acids; There are cationic surfactants such as quaternary ammonium salts, and amphoteric surfactants. Various coupling agents such as a silane coupling agent, a titanium coupling agent, and an aluminum coupling agent can also be used as the dispersant.

These can be used in different types and amounts for each layer according to the purpose, or may be used for only one of the layers. The amount of the lubricant is preferably 0.5 to 20 parts by weight based on 100 parts by weight of the ferromagnetic or non-magnetic powder. Further, the lubricant can be applied after the calendering treatment in order to optimize the surface abundance of the lubricant. In this case, the lubricant is applied after being dissolved in an organic solvent, and the organic solvent is selected so as not to dissolve the binder.

Examples of the nonmagnetic support used in the present invention include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polypropylene; celluloses such as cellulose triacetate and cellulose diacetate; vinyl resins; Examples thereof include films and plates made of a polymer material represented by polyamides, polyimides, polyamideimide, polysulfone, polyaramid, and polycarbonates. The non-magnetic support can be previously subjected to heat treatment, corona discharge treatment, and plasma treatment for the purpose of easy adhesion treatment and deformation correction.

In the present invention, when forming the nonmagnetic layer and the magnetic layer, an undercoat layer may be provided between the nonmagnetic support and the nonmagnetic layer or the magnetic layer in order to improve the adhesion.
This thickness is preferably from 0.01 to 1 μm, and more preferably from 0.03 to 0.5 μm. In forming the undercoat layer, known ones conventionally used in magnetic tapes and magnetic recording disks can be used. The surface roughness of the non-magnetic support is 8 nm or less, preferably 5 nm or less in Ra measured by Maxim 3D5700 manufactured by ZYGO. Further, it is preferable that these supports have no coarse protrusions of 0.4 μm or more.
If there are coarse protrusions exceeding 0.4 μm on the non-magnetic support, even if a magnetic layer or a non-magnetic layer is applied, the shape of the magnetic layer or the non-magnetic layer extends to the surface, which causes deterioration of running durability and dropout. The surface roughness shape is controlled by the size and amount of the filler added to the support. Examples of these fillers include oxides and carbonates such as Ca, Si and Ti, and organic fine powders such as acryl.

In order to form a coating film on the non-magnetic support, both layers may be formed into a coating material, which may be coated and dried.
Solvents used in the preparation of this paint, acetone, methyl ethyl ketone, methyl isobutyl ketone, ketone solvents such as cyclohexanone, alcohol solvents such as methanol, ethanol, propanol, butanol, isobutyl alcohol, methyl acetate, ethyl acetate, butyl acetate,
Ester solvents such as propyl acetate, ethyl lactate and ethylene glycol acetate; ether solvents such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran and dioxane; aromatic hydrocarbon solvents such as benzene, toluene and xylene; methylene chloride; ethylene Halogenated hydrocarbon solvents such as chloride, carbon tetrachloride, chloroform and chlorobenzene are used. These organic solvents need not necessarily be of high purity, and may contain a small amount of impure components.

The coating is prepared by a kneading step, a dispersing step, and a mixing step provided before and after these steps as necessary. Raw materials such as ferromagnetic powder, non-magnetic powder, carbon black, binder, lubricant, and solvent used in the present invention may be added at the beginning or during any of the steps. Further, individual raw materials may be added in two or more steps in a divided manner.

For dispersion and kneading, conventionally known devices such as a roll mill, a ball mill, a sand mill, an agitator, a kneader, an extruder, a homogenizer, and an ultrasonic disperser are used.

The coating material thus produced is applied to the non-magnetic support by various known methods such as gravure coating, roll coating, blade coating, and die coating. In the production of a magnetic recording disk having a multilayer structure, a simultaneous multilayer coating method using a die coater is preferable. The lip configuration of the die coater is 2
A lip method, a three lip method, a four lip method, or the like is used.

FIG. 1 is a longitudinal sectional view showing an example of the magnetic disk of the present invention. This magnetic disk 3 can be formed, for example, with a multilayer coating solution shown in FIG. First, the film-shaped nonmagnetic support 22 unwound from the supply roll
Is sent to the extrusion-type extrusion coater 30 while sending in the direction of arrow A. Here, the respective coating materials for the lower layer (non-magnetic layer) 21 and the upper layer (magnetic layer) 20 are simultaneously applied on the non-magnetic support 22 in multiple layers. Extrusion coater 3
0 is provided with liquid reservoirs 25 and 26, each paint is supplied through slits 31 and 32, and is simultaneously superimposed on the nonmagnetic support 22 in a wet-on-wet manner.

The simultaneous multi-layer coating method using a wet-on-wet method is particularly preferable for the present invention from the viewpoints of uniformity of the coating film, adhesion between upper and lower interfaces, productivity, and the like. According to this method, the magnetic paint of the upper layer 20 is applied on the lower layer 21 in a wet state, so that the surface of the lower layer 21 (that is, the boundary surface with the upper layer 20) is smooth and the surface property of the upper layer 20 is good. And the adhesion between the two layers is also 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. Note that this multi-layer coating may be sequentially performed by multi-layer coating.

On the other hand, for example, Japanese Unexamined Patent Publication No.
In the case of the wet-on-dry method as in the case of No. 3, it is necessary to select a lower layer paint having sufficient solvent resistance to the upper layer paint.

A clear boundary substantially exists between the upper and lower layers formed by the wet-on-wet multi-layer coating method, and a boundary region where components of both layers are mixed with a certain thickness. May be present, but the upper or lower layer excluding such a boundary region may be a magnetic layer or a non-magnetic layer. Either case is included in the scope of the present invention.

After the coating step, a non-orientation treatment is generally performed while the magnetic layer is not dried. This is performed by passing through an AC magnetic field generator, and the AC magnetic field preferably has a frequency of 10 to 150 Hz and a magnetic field strength of 50 to 500 Oe. Further, if necessary, it may be passed through a magnetic field applied in the longitudinal direction before the non-alignment treatment. This makes the surface of the magnetic disk smoother. The orientation ratio (the ratio of the squareness ratio in the longitudinal direction to the squareness ratio in the direction perpendicular thereto) of the ferromagnetic powder by the non-orientation treatment is preferably 0.9 or more, and more preferably 0.95 or more. preferable.

After the coating step or the non-orientation treatment, the coating film on the non-support is dried in a drying step. After the drying step, a calendar process is performed. A well-known method conventionally used for a magnetic recording medium is applied to the calendar processing. That is, it is performed by passing the non-magnetic support after the formation of the coating film between the heated rolls while applying pressure. Generally, a heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimide amide is used for the roll, and a metal roll can also be used. The processing temperature is 70 ° C to 120 ° C (preferably 80 ° C to
110 ° C). Linear pressure is usually 200-450kg
/ Cm. The calendering machine is 30m / min ~ 50
It is preferable to use a roll having a processing speed of 0 m / min and 5 to 10 rolls.

After the calendering treatment, the non-magnetic support having the magnetic layer formed on one side is once wound on a roll, and then the above steps are repeated to form a magnetic layer on the opposite side of the non-magnetic support. Finally, a magnetic disk is obtained by punching to a predetermined size.

[0076]

EXAMPLES Hereinafter, specific examples and comparative examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

(Example 1) Based on the following composition, a magnetic powder or a non-magnetic powder, an abrasive, an additive and a solvent were first mixed and kneaded by a continuous kneader, and then the upper layer (magnetic layer) paint was coated. Was dispersed in a sand mill for 5 hours, and the lower layer (nonmagnetic layer) paint was dispersed in a sand mill for 3 hours.

<Composition of upper layer coating composition> FeCo alloy-based metal ferromagnetic powder (average major axis length = 0.2 μ, acicular ratio = 9, Co content 6%, saturation magnetization = 130 Am ² / kg, coercive force = 135 kA / m) 100 parts by weight Polyvinyl chloride resin (degree of polymerization 150, containing 5 × 10 ⁻⁵ mol / g of sodium oxysulfonate as a polar functional group) 14 parts by weight Polyester polyurethane resin (sulfone as a polar functional group) Sodium acid salt 1 × 10 ^-4 mol / g) 6 parts by weight Alumina powder (primary particle size 0.30 μm) 3 parts by weight Al ₂ TiO ₅ powder (primary particle size 0.25 μm) 2 parts by weight Stearic acid 1 Parts by weight heptyl stearate 1 part by weight methyl ethyl ketone 150 parts by weight cyclohexanone 150 parts by weight

<Lower layer coating composition> 100 parts by weight of carbon black (iron oxide / carbon black = 90/10) α iron oxide (average major axis length = 0.15 μ, needle ratio = 12, pH = 5.7) 11 parts by weight Polyvinyl chloride resin (degree of polymerization: 150, containing 5 × 10 ⁻⁵ mol / g of potassium sulfonate as a polar functional group) 17 parts by weight Stearic acid 1 part by weight Heptyl stearate 1 part by weight Methyl ethyl ketone 150 parts by weight Cyclohexanone 150 parts by weight

Next, 4 parts by weight of the polyisocyanate was added to the upper layer paint and 2 parts by weight to the lower layer paint, and the mixture was coated on a 62 μm-thick polyethylene terephthalate film (surface roughness Ra = 8 nm) using a 4-lip die coater. The layers were simultaneously coated and non-oriented by a solenoid coil, and then dried. After forming the same coating film on the back surface, a calender treatment was performed. Here, the coating thickness of each layer after drying is 0.20
μm, and the lower layer was 2.0 μm.

The amount of wear was measured as follows using a spin stand equipped with a head slider. That is, a sliding test was performed for 96 hours in a so-called seek mode in which a slider reciprocated within a predetermined range on a disk rotating at 3600 rpm, and the amount of head wear at that time was examined. The moving range of the slider was 10 to 20 mm from the center, and the range was reciprocated at 5 Hz.

As the head, a thin film head having a track width of 6 μm was used.
A slider covered with a C pad and equipped with this head was used.

The coefficient of abrasion was measured by a static gauge by a strain gauge method in a so-called still mode in which a slider was fixed and continuously slid using a spin stand equipped with a head slider. At this time, the solitary wave output was also observed at the same time, and the stage at which the output decreased by -3 dB from the initial value was defined as output attenuation. The above tests were all performed in a normal temperature and normal humidity environment.

Example 2 3 parts by weight of Al ₂ O ₃ powder, ZrO ₂
A disk was prepared and performance tested in the same manner as in Example 1, except that 1 part by weight of powder and 1 part by weight of Al ₂ TiO ₅ powder were used.

Example 3 A disk was manufactured in the same manner as in Example 1 except that the addition amount of the Al ₂ O ₃ powder was 5 parts by weight and the addition amount of the Al ₂ TiO ₅ powder was 3 parts by weight. The test was performed.

(Example 4) A disk was manufactured and a performance test was performed in the same manner as in Example 3 except that the amount of the Al ₂ O ₃ powder added was changed to 15 parts by weight.

(Example 5) A disk was manufactured in the same manner as in Example 1 except that the addition amount of the Al ₂ O ₃ powder was changed to 2 parts by weight.
A performance test was performed.

(Example 6) A disk was manufactured and a performance test was performed in the same manner as in Example 5 except that Al ₂ TiO ₅ powder was not used.

(Examples 7, 8, 9, and 10) The addition amounts of the Al ₂ O ₃ powder were 3 parts by weight, 5 parts by weight, 10 parts by weight and 15 parts by weight, respectively.
Example 6 except that parts by weight were used and no other abrasive was used.
A disk was manufactured in the same manner as described above, and a performance test was performed.

(Examples 11 and 12) Discs were manufactured in the same manner as in Example 1 except that ZrO ₂ powder alone was used as the abrasive (Al ₂ O ₃ was not used), and the addition amount was as shown in Table 1. A performance test was performed.

(Examples 13 and 14) Al ₂ Ti as an abrasive
O ₅ powder alone was used (Al ₂ O ₃ is not used), except that the addition amount shown in Table 1 to prepare a disk in the same manner as in Example 1 was subjected to performance tests.

Table 1 summarizes the above experimental results.

[0093]

[Table 1]

As can be seen from Table 1, Examples 1, 2, 3, 4,
In No. 5, cobalt-containing magnetic powder, alumina and Al
_It can be seen that, since the powder of 2TiO ₅ is added, both low wear of the head and low friction are achieved without the output decay. As described above, according to the present invention, reliability can be ensured even in a system employing a head-disk interface that slides at a high speed.

(Example 15) The magnetic powder used for the upper layer was FeC
o From an alloy-based metal ferromagnetic powder to a Fe-based metal powder (average major axis length = 0.2 µ, acicular ratio = 9.5, saturation magnetization = 115
(Am ² / kg, holding power = 120 kA / m), the solitary wave output decreased by about 10%.

[0096]

According to the present invention, since the cobalt-containing metal powder, the alumina powder and the titanium aluminum oxide powder are blended in the magnetic layer of the multilayer coating type magnetic recording medium, high recording density and high recording density can be obtained. While maintaining a high transfer rate, low wear and low friction of the head due to the magnetic recording medium that slides at high speed can be simultaneously achieved.

A magnetic recording medium having such features, especially a magnetic disk, is a next-generation magnetic recording system using a contact type head slider of the prior application, that is, a head in which the magnetic disk rotates at a high speed of 3000 rpm or more. -When applied to a next-generation recording system using a disk interface and a head whose surface is protected by a so-called DLC film, the effect can be remarkably exhibited, and greatly contributes to the improvement of the performance of the system. Is possible.

[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 is a perspective view of a flexible magnetic disk head slider attached to the tip of the HGA.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Head slider, 3 ... Flexible magnetic disk, 5 ... Suspension beam, 13 ... Magnetic head, 1
4 magnetic pad, 20 upper layer, 21 lower layer, 22 non-magnetic support

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 1/06 H01F 1/06 H (72) Inventor Takao Kudo 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo No. Sony Corporation (72) Inventor Kazuo Goto 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo F-term (reference) 4J038 EA011 GA03 GA07 GA08 GA12 GA13 GA14 GA16 HA026 HA066 HA216 HA286 HA356 HA376 KA08 KA12 KA20 MA07 NA20 PA18 PB11 5D006 BA01 BA08 BA10 EA01 5E040 AA02 AA05 AA14 AA19 BB01 BB04 BB05 CA06 NN01 NN04

Claims (7)

[Claims] 1. A multi-layered magnetic recording medium in which a second layer is formed on a first layer by a multi-layer coating, and at least the second layer is formed as a magnetic layer. A magnetic recording medium comprising: a powder; an alumina powder; and a titanium aluminum oxide powder. 2. The magnetic recording medium according to claim 1, wherein the cobalt content of the cobalt-containing metal powder is 70% by weight or less based on a magnetic metal other than cobalt. 3. The amount of the alumina powder is 2 parts by weight or more based on 100 parts by weight of the cobalt-containing metal powder.
2. The magnetic recording medium according to claim 1, wherein the amount is 5 parts by weight or less, and the blending amount of the titanium aluminum oxide powder is 2 parts by weight or more with respect to 100 parts by weight of the cobalt-containing metal powder. 4. The alumina powder and the titanium aluminum oxide each have an average particle size of 0.01 to 0.5 μm.
The magnetic recording medium according to claim 1, wherein 5. The magnetic recording medium according to claim 1, wherein the first layer is formed as a non-magnetic layer. 6. The magnetic recording medium according to claim 1, wherein the first layer and the second layer are formed on both main surfaces of the non-magnetic support. 7. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is configured as a magnetic disk.