JPS61208620A - Magnetic disk - Google Patents

Abstract

PURPOSE:To decrease noise and to improve durability by forming a thin magnetic metallic film on a substrate and forming a carbon protective film on the thin magnetic metallic film then treating the surface with a liquid lubricating agent. CONSTITUTION:The thin magnetic metallic film 4 is formed on the substrate 1 and the carbon protective film 5 is formed on the thin magnetic metallic film and thereafter the surface thereof is treated with the liquid lubricating agent 6. The carbon protective film has excellent lubricity, corrosion resistance, etc. and is formed by a method such as vacuum deposition or sputtering. The surface thereof is further treated by the liquid lubricating agent. The liquid lubricating agent used for the surface treatment is exemplified by a freon soln. of perfluoropolyether, etc. Light alloys such as aluminum alloy and titanium alloy, thermoplastics such as polystyrene and ABS resin, ceramics such as alumina glass and single crystalline silicon, etc. are used for the blank material of the substrate. The magnetic disk having the remarkably improved durability, runnability, impact resistance and corrosion resistance, excellent mechanical strength and less noise is thus obtd.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic disk used as a storage medium of a magnetic storage device such as a magnetic disk device, and in particular, a protective film for improving durability etc. Regarding improvements.

[Conventional technology]

For example, as a storage medium for computers etc., LasoAlp
, MA/F Jp 1 礒 (Words 炸fr 田儒中＾三浒; 1吋力礒) (Widely used, among others, it has excellent responsiveness, large storage capacity, good storage stability, and reliability. Due to the high cost, magnetic disks whose substrates are made of hard materials such as A1 alloy plates, glass plates, plastic plates, etc., so-called hard disks, have come to be used as fixed disks, or external disks.

The hard disk has, for example, an A1 alloy substrate on which a magnetic layer involved in recording and reproduction is formed, and rotates at high speed to record and reproduce information on a large number of concentric tracks.

By the way, when performing recording and reproduction on the above-mentioned hard disk, after the magnetic head and the magnetic layer surface are mounted in contact with each other at the start of operation, the distance between the head and the magnetic layer surface is established by applying a predetermined rotation to the hard disk. The CSS method (which forms a minute air layer in the air and performs recording and playback in this state)
The contact start/stop method is generally used.

In such a C8S system, the magnetic head is in frictional contact with the magnetic layer surface at the beginning and end of an operation, and the frictional force generated between the head and the magnetic disk is the cause of wear on the magnetic head and magnetic disk. becomes. Or, if there is dust or peeling powder from the magnetic layer on the magnetic head,
Head crashes (falling of the magnetic head) may occur, and the magnetic head may suddenly come into contact with the magnetic disk during recording and playback due to head jumping, etc., which may cause a large impact to the magnetic disk. It also causes damage to magnetic disks and magnetic heads.

In particular, a method in which the magnetic layer is formed by thinning an alloy such as Co-N1 using a vacuum thin film forming technique such as vacuum evaporation or sputtering, or a method in which an alloy such as Co-N1-P is formed into a thin film by a wet method such as electroless plating. This tendency is remarkable in the case of a continuous thin film formed by et al.

[Problem that the invention seeks to solve]

Deterioration of durability caused by such sliding contact between the magnetic disk and the magnetic head is not desirable because it causes noise, and an impact on the magnetic disk can cause damage to the magnetic head or disk surface. This impedes good recording and playback.

Conventionally, therefore, it has been considered to improve the durability of the magnetic disk by forming a protective film on the surface of the magnetic disk. I haven't gotten what I want.

In view of this situation, an object of the present invention is to provide a protective film that has excellent mechanical strength and can provide good runnability, and to provide a magnetic disk that has low noise and excellent durability.

[Means for solving problems]

As a result of intensive research to achieve the above-mentioned objectives, the present inventors formed a carbon protective film on a metal magnetic thin film and further treated the surface with a liquid lubricant to improve the durability of the magnetic layer. The present invention has been completed by discovering that it is possible to synergistically increase the It is characterized by being treated with a lubricant.

That is, in the magnetic disk of the present invention, the protective film has a two-layer structure of a carbon protective film and a liquid lubricant layer, and the synergistic effect of these improves durability, impact resistance, runnability, corrosion resistance, etc.

The carbon protective film has excellent lubricity, corrosion resistance, etc., and is formed by a method such as threading, vacuum deposition, or sputtering. For example, in the case of vacuum evaporation, the pressure is 5 x 10-' Torr or less, the substrate temperature is 50
Any condition of ~250°C is sufficient, and heating methods include electron beam heating and resistance heating.

Techniques such as induction heating and arc discharge methods are used.

Here, if the substrate temperature is too high, problems such as crystallization of the N1-P plating layer formed as a base film on the substrate surface may occur. In addition, when using sputtering, use an inert vacuum such as Ar, and a substrate temperature of 50 to 50°C.
Under the condition of 250℃, using a carbon plate (thickness 1~4 degrees) as a target, RF power 1~10Kw or DCC power 5*0, the film thickness of the bond protective film is within the range of 100~800. It is preferable.

Meanwhile, the surface of the carbon protective film is further treated with a liquid lubricant. Examples of liquid lubricants used for surface treatment of this carbon protective film include perfluoropolyether Freon solutions. That is, in the magnetic disk of the present invention, a Freon solution of perfluoropolyether is immersed and spin-coated onto the carbon protective film.

It is applied by a method such as spray coating to form a liquid lubricant layer.

The perfluoropolyether used here includes, for example, F (CF (CF3)-CFz O), -C*F
Those having the structure shown by s (manufactured by DuPont, USA).

KRYTOXl 43AC, KRYTOXl 43AD
, KRYTOX143AX, KRYTOX143AB,
KRYTOX143AY, KRYTOX143AA, K
RYTOX143AZ, KRYTOX143CZ, etc.). These perfluoropolyethers include alcohols and glycols.

It is preferable to add an organic compound having a hydrophilic group such as glycerin, phenol, or carboxylic acid, or a fluorine-substituted product thereof to improve the wettability of the coating liquid and form a uniform liquid lubricant layer. In addition, perfluoroalkanes, perchloroperfluoroalkanes, etc. can be used as freons, which are solvents for perfluoropolyether, and trichlorotrifluoroethane, tetrachlorodifluoroethane,
Examples include trichloromonofluoromethane. Alternatively, as the liquid lubricant, silicone oil such as dialkylpolysiloxane, dialkoxypolysiloxane, monoalkylmonoalkoxypolysiloxane, phenylpolysiloxane, fluoroalkylpolysiloxane, or unsaturated aliphatic hydrocarbon (n - Compounds in which an olefinic double bond is bonded to the terminal carbon, carbon antagonists (20), fatty acid esters consisting of monobasic fatty acids with 12 to 20 carbon atoms and monohydric alcohols with 3 to 12 carbon atoms, etc. are used. It is also possible.

The magnetic disk to which the present invention is applied has a continuous film of ferromagnetic metal as a magnetic layer on a disk substrate, and the material of this disk substrate may be light alloys such as aluminum alloys and titanium alloys, polystyrene, etc. , thermoplastic resin such as ABS resin, ceramics such as alumina glass, single crystal silicon, etc. can be used.

Here, when a relatively soft material is used as the disk substrate, it is preferable to form a non-magnetic metal underlayer to harden the surface.The material of the non-magnetic metal underlayer is N1. -P alloy* Cu + Cr
* Z n + Stainless steel etc. are preferable, and these are coated on the substrate surface with a film thickness of about 4 to 20 μm by a method such as plating, sputtering, M adhesion, etc. For example, A1
When N1-P plating is applied to the surface of a 1-Mg alloy substrate, its hardness becomes approximately 400, and the magnetic layer formed on this substrate has excellent magnetic properties.

In addition, the above magnetic layer can be formed by plating or sputtering.

It is formed as a continuous film using techniques such as vacuum evaporation.

For example, a metal magnetic thin film is formed as a magnetic layer by plating with Go-P, Co-N1-p, etc.

Alternatively, a vacuum thin film forming technique such as a vacuum evaporation method, an ion blating method, or a sputtering method may be used.

In the vacuum evaporation method described above, a ferromagnetic metal material is evaporated by resistance heating, high frequency heating, electron beam heating, etc. under a vacuum of 10'' to 10-'' Torr, and the evaporated metal (ferromagnetic metal material) is deposited on a disk substrate. It is roughly divided into oblique evaporation method and vertical evaporation method. The above-mentioned oblique vapor deposition method includes a method in which the above-mentioned ferromagnetic metal material is vapor-deposited obliquely to a substrate in an elementary atmosphere in order to obtain a high coercive force. In the vertical evaporation method described above, Bi is pre-coated on the substrate in order to improve the evaporation efficiency and productivity and to obtain high coercive force.
, Sb, Pb, Sn, Ga, In, C, Go.

The ferromagnetic metal material is vertically deposited on a base metal layer such as St or T1.

The above ion blating method is also a type of vacuum deposition method, in which DC glow discharge and RF glow discharge are caused in an inert gas atmosphere of 10-4 to 10-'' Torr, and the ferromagnetic metal material above the disk is evaporated during discharge. It is to let them do so.

The above sputtering method uses 10"2 to 10" Torr.
A glow discharge is caused in an atmosphere mainly composed of argon gas, and the generated argon gas ions are used to knock out atoms on the target surface. method, or magnetron sputtering method using magnetron discharge.

In the case of this sputtering method, Cr or W is used.

U ”M /7'l Ding++h Ml!11- Tsuzuru J
, “7” k l,s ? i, ) r, s When forming a metal magnetic thin film using such a vacuum thin film forming technique, the ferromagnetic metal materials used include Fe, Co,
In addition to metals such as Ni, C.

-Ni alloy, Co-Pt alloy, Co-Ni-Pt alloy,
Fe-Co alloy, Fe-Ni gold alloy Fe-Co
-N1 alloy, Fe-Go-B alloy, Co-N1-Fe-
B alloy, Co-Cr alloy or these with Cr, lk
Examples include those containing metals such as , It, and the like. In particular, when a Co--Cr alloy is used, a perpendicularly magnetized film is formed.

The thickness of the magnetic layer formed by such a method is 0.
It is about 0.04 to 1 μm.

[Effect]

In this way, by forming a protective film consisting of a two-layer structure of a carbon protective film and a liquid lubricant layer on the surface of the magnetic layer, these two protective films act synergistically to improve wear resistance and impact resistance. , excellent effects on corrosion resistance, running properties, etc.

〔Example〕

Example 1 First, as shown in FIG. 1, an AN-
Mg alloy substrate (1) (thickness approximately 1.27 mm.

Prepare a plating layer (outer diameter: 95, inner diameter: 25), and apply this plating layer (2
) on pressure I x 10-'Torr, substrate temperature 150
A low melting point metal base film (3) having a thickness of 200 mm was formed by electron beam evaporation of Bl at .degree.

Next, a pressure of 1 x 10-
Co was deposited by electron beam under conditions of 5 Torr and substrate temperature of 150° C. to form a metal magnetic thin film (4) with a thickness of 1000 μm.

Furthermore, a carbon protective film (5) is formed on this metal magnetic thin film (4) by a vacuum evaporation method, and then a liquid lubricant layer made of perfluoropolyether is applied on this carbon protective film (5) by a spin cord method. (6) was formed.

The thickness of the carbon protective film (5) and liquid lubricant layer (6) was changed as shown in the table below, and CSS was determined by the generally known contact start-stop (C3S) test.
We investigated the characteristics. At the same time, we also investigated peeling of the protective film and noise. The results are shown in Table 1.

Table 1 Example 2 The N1-P plating layer (
On the AJI-Mg alloy substrate (1) on which 2) was formed, a low melting point metal base film (3), a metal magnetic thin film (4), and a carbon protective film (5) were sequentially formed. A 0.2% methyl ethyl ketone lubricant layer (6) of fatty acid ester was formed thereon.

The film thicknesses of the carbon protective film (5) and liquid lubricant layer (6) were changed as shown in the following table, and the CSS characteristics were examined by a contact start/stop (CSS) test.

At the same time, we also investigated peeling of the protective film and noise.
The results are shown in Table 2.

Table 2 These examples show that by forming a carbon protective film on a metal magnetic thin film and a liquid lubricant layer on its surface, CSS characteristics are greatly improved, noise is reduced, and protection is achieved. It can be seen that no peeling of the film was observed.

Although specific embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these embodiments.

〔Effect of the invention〕

As is clear from the above description, in the magnetic disk of the present invention, a carbon protective film is formed on the metal magnetic thin film, and the surface of this carbon protective film is treated with a liquid lubricant, so that the carbon protective film and the liquid lubricant are treated. Forms a protective film consisting of a two-layer structure of agent layer, which improves durability, runnability,
Significantly improved impact resistance and corrosion resistance, excellent mechanical strength,
It has little noise.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a main part showing an example of a magnetic disk to which the present invention is applied. 1...A1 alloy substrate 4...Metal magnetic thin film 5...Carbon protective film 6...Liquid lubricant layer Current review applicant Sony Corporation

Claims (1)

[Claims] 1. A magnetic disk characterized in that a metal magnetic thin film is formed on a substrate, a carbon protective film is formed on the metal magnetic thin film, and the surface thereof is treated with a liquid lubricant.