JPS61246921A - Magnetic disk - Google Patents

Abstract

PURPOSE:To reduce the off-track quantity and to improve the reliability of the titled magnetic disk by providing a ceramic substrate having >=0.05cal/cm/ sec/ deg.C heat conductivity and a magnetic film formed on the substrate and having >=300Oe coercive force to the disk. CONSTITUTION:For example, 1pt.wt. cellulose and 4pts.wt. tungsten powder are added to 100pts.wt. mixture composed of 70wt% silicon carbide powder and 30wt% carbon powder and wax is added to the obtained material. The material is pelletized, molded in the form of a disk under 1,000kg/cm<2> pressure and calcined in vacuum at 700 deg.C. On the calcined body, 15g silicon powder is placed. The body is heated under 0.1Torr reduced pressure to 1,500 deg.C in 1hr, kept at that temp. for 3hr and sintered. The thermal conductivity of the sintered body is 0.14cal/cm/sec/ deg.C. Since a ceramic having such high thermal conductivity is used, the difference in temp. between magnetic disks is reduced, the off-track quantity can be correspondingly decreased and high track density can be obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a magnetic disk used in a magnetic disk device. In addition to A/alloys, ceramic substrates mainly made of glass or aluminum oxide are used as substrate materials. There have also been reports of laboratory use of
However, none of them exceeds the Aj alloy substrate in terms of thermal conductivity.

HP alloy substrates have been used in all of these rounded commercial products. The reason for this is that in magnetic disk drives, the servo surface that stores servo information and the data surface that stores data information are generally separated, so if there is a temperature difference between the two, a finite amount of off-track will occur due to thermal expansion. This is because the lower the thermal conductivity, the greater the temperature difference between the center and the outer periphery of the magnetic disk, or when using a large magnetic disk that uses multiple magnetic disks. In a capacity magnetic disk device, the temperature difference becomes large for each magnetic disk, and as a result, the off-track amount becomes large due to the difference in thermal expansion, and it becomes impossible to increase the off-track amount fx and the sit-track density.

On the other hand, the H1 alloy base itself is too soft to withstand wear with the magnetic head, and has the drawback of lacking reliability. An object of the present invention is to provide a highly reliable magnetic disk that reduces the amount of off-track caused by temperature distribution within a magnetic disk device by employing this material as a substrate material. The thermal conductivity of magnetic disks is 0.05 cal/c.
rtt/sec/℃ or higher ceramic substrate;
It is characterized by having a magnetic film formed thereon having a coercive force of 300 Oe or more.

(Detailed explanation of configuration) Hereinafter, the present invention will be explained using the drawings.

Fig. 1 shows the configuration of the present invention, and the figure (!I) shows a coercive force on a ceramic substrate 1 having a thermal conductivity of 0.05 c a l /l:n4/sec/°C or more. is 3
The same figure (b
) shows a magnetic disk in which a protective film 3 is formed on the magnetic film 2, and (c) in the same figure shows a magnetic disk in which a lubricating film 4 is further formed on this protective film 3. Figure 2 shows a magnetic disk in which a lubricating film 4 is formed on a magnetic film 2 having the configuration shown in (a). Figure 2 shows another configuration of the present invention.
Figure (b) shows a magnetic disk in which a base film 5 is provided between a ceramic substrate 1 having a thermal conductivity of 0.05 cal/+1/sec/ or more and a magnetic film 2 having a coercive force of 300 Oe or more. Figure (a) shows a magnetic disk in which a protective film 3 is provided on a magnetic film 2, and figure (C) shows a magnetic disk in which a protective film 4 is provided on a protective film 3 in the configuration shown in figure (b). A magnetic disk is shown in FIG. 2(d) with a lubricating film 4 on the magnetic film 2 in the configuration shown in FIG.
Each of the magnetic disks shown in FIG.

Here, the necessary requirements for the constituent elements of the present invention and an example of substitute materials are shown below as the ceramics substrate 1. The thermal conductivity is o,
7/crry's e c/℃ or higher, hardness of Vickers value of 600 or higher, surface roughness of 0.05 μm or lower, and pore diameter of 0.5 μm or lower.0 Especially for thermal conductivity, For example, in a magnetic disk device consisting of 8 disks with radius l, if the bottom layer (first disk) is a servo disk, the outermost track will be off-track due to the temperature difference ΔT with the center layer (4th to 5th disks). Amount Δl! Let α be the coefficient of thermal expansion of the disk substrate.

ΔT=α・ΔT−J, and in fact, the thermal conductivity of conventional aluminum alloys is approximately 0.2 calhVsec/l (F)! = 10 cm, it became ΔT'al'C. Using α=25 x 10”6/℃ as the thermal expansion coefficient of aluminum alloy, Δ
2 = 2.5μm, and the track density is approximately 1000TPI
(Tracks Per Inch X makes it difficult to pass.

On the other hand, when a ceramic substrate of 0.05 cal10n7 sec/°C was used, the temperature difference ΔT' was about 5°C. The temperature can be adjusted by adjusting the α composition of the ceramic substrate, and can usually be kept at 5 x 107°C or less.

1252.5μm, which can be lower than that of conventional aluminum alloys.In order to further reduce Δl, it is necessary to increase the thermal conductivity and reduce the temperature difference ΔT.
This is an important point in terms of making the temperature of the entire magnetic disk device uniform. Another means of reducing Δl is to reduce the coefficient of thermal expansion α, but even if α becomes zero, as long as the temperature difference ΔT is finite, a difference in thermal expansion will occur in the arm that supports the magnetic head. Undesirable. Therefore, it is fundamental to increase the thermal conductivity and reduce the temperature difference. If Δ is reduced in this way, it is possible to increase the track density by that amount.As for hardness, a Vickers hardness of 600 or higher is required to withstand contact wear with the magnetic head. (Conventional aluminum alloys are in the 100-200 range). Defining the surface roughness and pore diameter is an essential condition for making the characteristics of the magnetic film uniform and ensuring mechanical durability.

Ceramic substrates tend to have holes due to the manufacturing process.
In order to reduce or eliminate the pore diameter, a base film 5 may be provided. There are only a limited number of materials that simultaneously satisfy the above conditions as a ceramic substrate, but ceramics containing silicon carbide as the main part are suitable, and contain 5 to 10% by weight of silicon and 1.3 to 13% by weight of tungsten silicide. Silicon carbide ceramics containing 5 to 12% by weight of erbium oxide, at least one metal element (light metal element, transition metal element, or rare earth metal element) itself or its compound (oxide, nitride, or boride). Silicon carbide-based ceramics containing 1 to 5% by weight of silicon are particularly suitable.In addition, in the former silicon carbide-based ceramics and clays containing silicon-tungsten silicide, dense ceramics cannot be obtained if the silicon content is less than 5% by weight. Moreover, if the weight exceeds 10, the corrosion resistance (9) mechanical strength and the surface roughness of the polished surface will deteriorate, making it unsuitable.

If the content of tungsten silicide is less than 1.3% by weight, there is a problem with oxidation resistance, and if it exceeds 13% by weight, the difference in thermal expansion coefficient with silicon carbide becomes noticeable and the oxidation resistance deteriorates. I am considering it. Furthermore, in the latter type of silicon carbide ceramics containing erbium oxide-metallic elements (or their compounds), dense ceramics could not be obtained when the content of erbium oxide was less than 5% by weight.
When the content of metal elements or their compounds exceeds 1% by weight, no significant improvement in thermal conductivity was observed, and when the content exceeds 5% by weight, the transverse rupture strength and impact value decrease. The reduction in rupture strength and impact value is taken into consideration.◎ The base film 5 can be formed by vapor deposition, sputtering or plasma CV.
Oxides or nitrides such as aluminum oxide, silicon nitride, silicon nitride, and aluminum nitride formed by the D method, Cr
, Ti, Mo, We, or other non-magnetic metals or alloys containing these metals as main components, or by spin coating and firing. An oxide film mainly composed of silicon oxide or aluminum oxide, or a thin film formed by hardening an organic material such as resist, polyimide, or epoxy is suitable.

The magnetic film 2 has a long diameter of 0.5 μm formed by a coating method.
The following needle-like or grain-like γ-Fe203. Co-deposited r-Fe, 0. , Co-doped'-Fe101v
Or a thin film with a thickness of several microns or less made of magnetic powder such as plate-shaped Ba-7 Elai with a major axis of 0.5 μm or less and hardened with resin together with non-magnetic particles such as sio, hl, O, etc.
Co-P alloy, Co-N1-P alloy, Co-Ni-M=-P alloy, Co-Ni- formed by plating method
A thin film containing Co such as Mn-Re-P alloy 1 with a thickness of 1.0 μm or less, γ-F formed by vapor deposition or sputtering method
e20. + rFe2 containing oxides such as c, Cu, etc.
O3, Coo-Co mixture, Co, Fe nitride, C
o-Ni alloy, Co-Pt alloy, Co-Cr alloy.

Co-P alloy, Co-Re alloy, Co-rare earth alloy, or mixtures of these alloys, as well as other tertiary alloys.
, a thin film containing fLCo to contain the fourth element, 'FeN
A thin film with a thickness of 1.0 μm or less made of an alloy containing Fe such as d is suitable.◎ As the protective film 3, a thin film with a thickness of 0.1 μm or less made of silicon oxide, aluminum oxide, etc. formed by a spin coating method is suitable. Oxide film, oxide film or nitride film with a thickness of 0.1 μm or less mainly composed of silicon oxide, aluminum oxide, silicon nitride, aluminum nitride, etc. formed by vapor deposition/sputtering or plasma CVD method, or C, Cr, Mo, W,
A thin film having a thickness of 0.1 μm or less made of a single substance or an alloy containing a non-magnetic metal such as Rh as a main component is suitable.

As the lubricant film 4, well-known lubricants KRYTOX and VYD are used.
A fluorocarbon thin film typified by AX (all trade names of Depon Co., Ltd., USA) is suitable.

Next, specific embodiments of this invention will be described.

(Example 1) For 100% of silicon carbide powder and 30% of carbon powder by weight, cellulose 1. Select I'7/Sten powder in a weight ratio of 4, add wax, granulate it, and make it into granules with an outer diameter of 210 mm and an inner diameter of 5 at a pressure of 1000 K17 cm2.
Shaped into a disc with a thickness of 0mm and 2m 5 and then placed in a vacuum 7
Temporary firing was performed at 00°C. Silicon powder 15 is added to this pre-fired body.
1 g at a temperature of 1500°C under a reduced pressure of 0.1 Torr.
The temperature was raised over time and then held for 3 hours to perform reaction sintering. The composition of the reaction sintered body thus obtained was 6% by weight of silicon.

5% by weight of tungsten silicide, balance silicon carbide.

Thermal conductivity is 0.14 cal/CM7'sec/℃, thermal expansion coefficient 43X10/l? :, Vickers hardness 1,
800, and the pore diameter was 0.5 μm or less. The surface of this sintered body was polished with fine diamond particles of 0.1 μm to obtain a finished disk substrate with a surface roughness of 0.05 μm or less.

Next, as a typical coating method, T-FelO3 acicular particles with a major diameter of 0.2 μm and Al2O fine particles with a diameter of 0.2 μm were mixed with a dispersant and an epoxy resin, and then applied by spin coating. A magnetic film with a thickness of 067 μm was formed to obtain a magnetic disk. Coercive force Hc of magnetic film after coating
was 350 Oe. (Example 2) A disk substrate was produced in the same manner as in Example 1. However, the substrate material was changed as follows. Silicon carbide powder 90% by weight Aluminum oxide powder as an oxide of metal element 3
By weight, cellulose and wax are added to a product consisting of erbium oxide powder (7 by weight) and granulated, and 100
Outer diameter 210 mm and inner diameter 50 m at a pressure of 0 h/1 m
Shaped into a disk shape with a thickness of 2 mm and then heated in a vacuum for 70 minutes.
This calcined body was calcined at 0°C, and then the temperature was raised to 1500°C over 1 hour under a reduced pressure of 1 Torr, and then held as it was for 3 hours to perform sintering. The composition of the sintered body is 3% by weight of aluminum oxide, 7% by weight of erbium oxide, and the balance is silicon carbide, and the thermal conductivity is 0.28 cal/'cHv'sec/
C, thermal expansion coefficient is 4.4. X 10-6/l t The Vickers hardness was 2000, and the pore generation rate was 0.5 μm or less. The surface of this sintered body was polished with 0.1 μm diamond fine particles to reduce the surface roughness to 0.05 μm or less. Finished with a disc substrate.

Next, as a representative coating method, Co-coated Fe101 acicular particles with a major diameter of 0.2 μm and 0.2 μm were coated onto this disk substrate.
AJ with μm diameter! ,0. The fine particles are mixed with a dispersant and an epoxy resin, a magnetic film with a thickness of 0.7 μm is formed by spin coating, and KRYTQX is coated on the surface of this film as a lubricant. Had made. The coercive force of this magnetic film was 600 Oe. (Example 3) The disk substrate used in Example 1 was used. However, A using sputtering method as a base film before the new calendar using diamond fine particles.
I! ,0. A film of 10 .mu.m was formed on the sintered body, which was then polished with 0.1 .mu.m diamond grains.

As a result, a disk substrate with excellent surface roughness was obtained, with a surface roughness of approximately 0-OX μm. A Fe104 film as a representative thin film magnetic material was formed thereon by a 0.15 .mu.n1 sputtering method, and then gradually oxidized in the atmosphere at 300.degree. C. to convert it into an r-Fezes film, thereby forming a magnetic film to form a magnetic disk. 3.0% by weight and 1.0% by weight of Cu and Co, respectively.
By adding 8% by weight, the coercive force of this magnetic film is 60%.
0 Oe (Example 4) A magnetic film was formed using the same manufacturing process as in Example 3, and 0.05 μm of 810@ was formed as a protective film by sputtering on this to form a magnetic disk. .

(Example 5) A protective film was formed using the same manufacturing process as in Example 4, and KRYTOX was applied thereon as a lubricant to prepare a magnetic disk.

(Example 6) The magnetic film was formed using the same manufacturing process as in Example 3, and KRXTOX was applied thereon as a lubricant to create a magnetic disk (Example 7) Used in Example 2 However, using a disk substrate.

Before polishing with fine diamond particles, a W film of 5 μm thickness was formed on the sintered body as a base film by sputtering, and then a 0.1 μm
As a result of polishing with .mu.m fine diamond particles, a disk substrate with excellent surface roughness was obtained with a surface roughness of about 0.02 .mu.m. This substrate was immersed in a plating bath consisting of cobalt sulfate, nickel sulfate, sodium hypophosphite, sodium malate, sodium succinate, sodium malonate, and ammonium sulfate, and a magnetic film made of Co-N1-P alloy was coated with a thickness of 0.05 μm. It was formed by electroless plating.

A 5iO1 film having a thickness of 0.1 μm was formed thereon by spin coating, and then IIYTOX was applied as a lubricant to form a magnetic disk. The coercive force of this magnetic film was 600 Oe (Example 8) The disk substrate used in Example 7 was used, and Ni
A 0.5 μm thick Fe alloy (Pg 1 8% by weight) was then formed by a 0.2 μm sputtering method using a CoCr alloy (Cr 20 weight 1 layer) to form a magnetic film to form a magnetic disk.

The coercive force of the CoCr film in the direction perpendicular to the disk surface is 300O.
It was e.

(Example 9) A magnetic film was formed using the same manufacturing process as in Example 8, and a protective film of 5i02 with a thickness of 0.05 μm was formed thereon by sputtering to form a magnetic disk. (Example 10) A protective film was formed using the same manufacturing process as in Example 9, and a magnetic disk was made by applying α as a lubricant (Example 11) Using the same manufacturing process as in Example 8 A magnetic film was formed, and a lubricant, Shukan α, was applied to create a magnetic disk.

(Comparative example) AI! - Mg alloy 5086 with an outer diameter of 210 mm and an inner diameter of 5
It was processed into a disk shape with a length of 0 m and a thickness of 1.9 mm, and finished with a diamond lathe to a surface roughness of about 0.0 μm to obtain a disk substrate. A magnetic film similar to that in Example 1 was formed thereon by the same procedure, and KRYTOX was further applied as a lubricant to form a magnetic disk. The coercive force of the magnetic film was 350 Oe as in Example 1.

Eight magnetic disks each from Examples 1 to 11 and Comparative Example were selected, mounted on a magnetic disk device, and placed in the bottom layer (
When a servo pattern was written on the disk in the center layer (4th to 5th disks) and the positional deviation amount Δl was measured immediately after turning on the power and after a 30-minute seek test, it was found that the magnetic fields of Examples 1 to 11 were When using a disk, Δtl, 1μ
m, whereas in the comparative example it was Δ/'': 1.5 μm, and in the contact start/stop test, the former example of the present invention had no accidents even after 30,000 passes. On the other hand, in the latter comparative example, a crush accident occurred after 5000 cycles.

(Effect of the invention) As shown in the above examples of the present invention and comparative examples.

Compared to conventional magnetic disks, the present invention has (11
Since the temperature difference between the rounded magnetic disks using ceramics with high thermal conductivity is small, the amount of off-track can be reduced and high track density can be achieved.

(2) Since ceramics, which are much harder than conventional ones, is used as the substrate material, it has high durability in contact start/stop tests, and therefore has high long-term reliability.

It has extremely useful features in practice.

Note that such effects of the present invention are not limited to the above-mentioned materials or embodiments using one example thereof, but can be achieved by any magnetic disk that satisfies the conditions set forth in the claims. It is clear that it can be done.

[Brief explanation of the drawing]

Fig. 1 (a) Substrate 2...Magnetic film 3...Protective film 4...Lubricating film 5...Underlying film/-゛ Enjoy 1 Figure (a) 2 Port (d)

Claims (6)

[Claims] (1) A ceramic substrate with a thermal conductivity of 0.05 cal/cm/sec/°C or higher and a coercive force of 3
A magnetic disk characterized by having a magnetic film of 00 Oe or more. (2) The magnetic disk according to claim 1, wherein a base film is formed between the ceramic substrate and the magnetic film. (3) The magnetic disk according to claim 1, further comprising a protective film on the magnetic film. (4) The magnetic disk according to claim 1, which has a lubricating film on at least its surface. (5) The composition of the ceramic substrate is 5 to 10% by weight of silicon,
Claim 1, characterized in that 1.3 to 13% by weight of tungsten silicide, with the remainder mainly consisting of silicon carbide.
A magnetic disk according to items 4 to 4. (6) The composition of the ceramic substrate is erbium oxide 5~
12% by weight, 1 to 5% by weight of at least one metal element (light metal element, transition metal element, or rare earth metal element) itself or its compound (oxide, nitride, or boride);
5. The magnetic disk according to claim 1, wherein the remaining main portion is made of silicon carbide.