JPS62270018A - Magnetic disk medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk medium maintains the long-period high reliability of a contact start stop operation and head crash resistance by fixing an org. silicon functional group by a chemical bond to the surface of a thin inorg. compd. film formed on a magnetic film to form a lubricating layer, thereby maintaining high lubricity for a long period of time even at and under a high temp. and high humidity. CONSTITUTION:The lubricating layer is formed on the surface of the thin inorg. compd. film consisting of silicon dioxide or the like formed on the magnetic film by chemically bonding the org. silicon functional group thereto by a silylation reaction. The org. silicon functional group expressed by the formula is used. In the formula, R1-R3 are an alkyl group or phenyl group. The org. silicon functional group formed by the silylation reaction forms a thin modified film to prevent the adsorption as the hydrogen atoms of the metallic hydroxide, etc., on the surface of the thin inorg. compd. film or the magnetic film exist only in the modified form. The silylation reaction is carried out by bringing the magnetic disk into contact with a silylating agent and holding the same for the prescribed time at a specified temp.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention <Field of Application in Industry 1> The present invention is a method of chemically adding organosilicon functional groups to the surface of a magnetic film or the surface of an inorganic compound thin film formed on a magnetic film. The present invention relates to a magnetic disk medium having a lubricating layer that achieves high long-term stability and low head flying height by being fixed by bonding.

<Conventional technology> Conventionally, the lubricant layer of magnetic disk media has been formed by applying a lubricant to a thin inorganic compound film formed on the surface of a magnetic film, and over time, the liquid lubricant used has changed to hydrocarbons. These oils have been improved through the use of lubricants based on lubricants, such as silicone-based oils, and fluorine-based synthetic lubricants such as perfluoropolyethers. By the way, in the process of manufacturing a lubricating layer for such magnetic disk media,
It is necessary to control the lubricant solution at 4 degrees Celsius and to optimize the application method in order to obtain an optimal lubricant film, and manufacturers are making great efforts to achieve this goal. Therefore, a lot of research has been carried out on improving lubricants or lubricant application methods. However, no research has been conducted to date on improving the inorganic compound thin film itself, called a top coat, represented by silicon dioxide (SiO□). Therefore, in conventional magnetic disk media, a method has been adopted in which a lubricant is simply applied onto the inorganic compound layer that has been formed on the surface of the magnetic film by sputtering or spin coding.

<Problems to be solved by the invention> However, in the inorganic compound thin j1 (as described above), the adsorption h1 of contaminants such as hydrocarbons, carbon dioxide, other dust, and adsorbed water varies depending on the storage conditions, and It changes from moment to moment depending on the atmosphere.

For this reason, the lubrication performance of the surface of the inorganic compound thin film changes over time and has positional differences.

In addition, the head slider, which is responsible for one of the PJjM coefficients, is made of ferrite such as 1An4n, AI! Mixed ceramics of 203 and TiC, and oxides such as sapphire are often used, but these all have a great affinity with inorganic compound thin films mainly composed of SiO, as well as surface hydroxyl groups and adsorbed water. At the same time, the coefficient of friction also increases.

Therefore, even if the above-mentioned lubricating layer is formed on the inorganic compound thin film, which has a large coefficient of friction, tends to cause head adsorption, and has different lubricating performance depending on the location, the magnetic disk and the head/slider will not be able to adhere properly. There was a problem in that the lubrication performance deteriorated in a short period of time.

In view of these problems, the present invention has been developed to eliminate adhesion for a long period of time even under high temperature and high humidity atmospheres, maintain high lubricity for one fl, and improve contact start/stop (C85) operation and head crush resistance. The objective is to provide a magnetic disk medium with long-term quality reliability.

<Means for Solving the Problems> The structure of the present invention for achieving the above object is a magnetic disk medium in which an inorganic compound thin film is formed on the surface of a magnetic film.
A lubricating layer is formed by fixing an organic silicon functional group to the surface of the inorganic compound thin film through chemical bonds,
It is also characterized in that a lubricating layer is formed by fixing organic silicon functional groups on the surface of the material by chemical bonding.

As described above, the magnetic disk medium according to the present invention is directly fixed to the surface of the inorganic compound thin film of the magnetic film or the surface of the magnetic film by chemical bonding, and the organosilicon functional groups are fixed to the surface of the magnetic film. A lubricating layer having lubricity and water repellency is formed.

A preferred method for fixing organosilicon functional groups through chemical bonds is a method in which hydroxyl groups on the surface of an inorganic compound thin film or magnetic film are modified into organosilicon functional groups by a silylation reaction. This silylation reaction is represented by the following formula.

113 Here, as the organosilicon functional group, those represented by can be used, which can be classified into the following four types, and any one of them may be used in the present invention.

■ R,, R2, R, are both methyl groups (Clh) 2
S i - n,, R2 is a methyl group, R3 is a phenyl group Ph (
CI+3)2Si- (llh represents a phenyl group) ■ R,, R2 is a methyl group, n is a tertiary butyl group t-
Bu(CI+,)2Si- (t-no represents a tertiary butyl group) ■ R,, R2 is a methyl group, R1 is a pentafluorophenyl group 1:6F5(C1l,)2Si- Through such a silylation reaction, The organosilicon functional groups that are formed exist only in the form of modified hydrogen atoms such as metal hydroxides on the inorganic compound thin film or on the surface of the magnetic film, forming a very thin modified layer of several angstroms, and are adsorbed. It works to prevent In addition, hydrocarbons and hydroxyl groups in adsorbed water, which are contaminants on the inorganic compound thin film, are not modified into organosilicon functional groups at all by the silylation reaction, and these hydrocarbons and adsorbed water undergo the silylation reaction. Before the start of the reaction and as the reaction progresses, 1 decomposition, substitution,
Removed by evaporation etc. Therefore, the surface of the inorganic thin film or magnetic film after the silylation reaction is covered with organosilicon functional groups that suppress the adsorption phenomenon, and becomes an extremely clean surface free of contaminating hydrocarbons and adsorbed water.
It has much superior fJI slipperiness and water repellency compared to the surface of an inorganic thin film that does not have the organosilicon functional group.

Furthermore, as can be seen from the above formula, this organic silicon functional layer is formed only as a monomolecular film and not as a multilayer film, and therefore is formed as a very thin film of several angstroms. Therefore, this organosilicon functional layer hardly causes an increase in spacing loss between the head slider and the magnetic disk. Therefore, by forming a lubricating layer using such organosilicon functional groups, it becomes possible to realize a magnetic disk device with higher density recording than before.

The silylation reaction is carried out by bringing the magnetic disk into contact with a silylation agent and holding the magnetic disk at a constant temperature for a predetermined period of time. Contact methods include methods such as contacting in a bulk silylating agent, contacting with vapor of silyl and other agents, and methods and methods of contacting in a solution of silyl and other agents, but the most suitable method is adopted depending on the silylating agent used. This allows the reaction to proceed efficiently.

Here, the silylating agent used in the present invention may be one having an organosilicon functional group as described above, but those having a trimethylsilyl group in the above category (1) can be used at the lowest cost. These silylating agents having trimethylsilyl groups are shown in Table 1.

Table 1. Organosilicon functionality by such silylation reaction7. H
The degree to which the inorganic compound thin Iq or magnetic film of the magnetic disk) depends on the reaction time and reaction temperature of the silylation reaction,
Alternatively, by adjusting the concentration of the silylating agent used, a desired degree of surface hydroxyl group reactivity can be achieved. Furthermore, the organosilicon functional group thus formed can maintain the same lubricity and water repellency as the initial state without deteriorating for a long period of time even in a humid atmosphere at a high temperature of 100 to 150°C.

The lubricating layer of the magnetic disk medium according to the present invention may be formed by adding a conventionally used lubricant to 9Iσ on the f-functional silicon functional layer. In other words, the organosilicon functional layer consists of conventionally known perfluoropolyether carboxylic acids and other carboxyls,! ! Even if any lubricant, such as a liquid lubricant such as fluorinated polyether containing fluorinated polyether or a solid lubricant such as 1TIO3, is further applied, it may react with each other and cause deterioration, or the lubricity or water repellency of both may change. There is no. On the contrary, a lubricant applied on the organosilicon functional group layer is expected to exhibit superior lubricating performance than conventional ones due to the moisture release and water repellency of the organosilicon functional layer.

The lubricating layer according to the present invention as described above is superior to conventional ones, as it does not increase the coefficient of friction between the head and the slider for a long period of time and does not cause adhesion even in accelerated tests under high temperature and high humidity. Shows C3S characteristics and head crush resistance.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(Working example) This example shows an example in which a lubricating layer is formed by chemically bonding trimethylsilyl groups on a thin film of an inorganic compound made of silicon dioxide on a magnetic film. An explanatory diagram showing the orientation state of molecules on the surface of the inorganic compound thin film layer made of silicon dioxide formed on the magnetic l1llllI of the disk. Figure 1 (b) shows the orientation of molecules when trimethylsilyl groups are chemically bonded to the surface. It is an explanatory diagram showing a state. As shown in both figures, the magnetic disk SiO□Inorganic Thin II! ;The surface of lil contains Si that reacts with the silylating agent.
There are many hydroxyl groups bonded to atoms, and by holding this magnetic disk in hexamethylsilazane for 30 minutes or more at around 126°C, which is the boiling point of hexamethyldisilane, trimethylsilyl groups form on the 5in2 inorganic thin film 1-H. A lubricating layer 2 was formed.

This magnetic disk medium was heated to 80% at 50°C using a Winchester type Herad slider (material: mixed ceramics of AJ!20. and 'l' iC: load logF).
R) When the friction coefficient was measured under the conditions of i, it was 0.25.
(↓) Even if we measure the change over time, it is 10
No increase was observed after 0 days. In addition, Si
The friction coefficient of the surface of the O□ inorganic thin film is about 0.6 to 10.

Furthermore, the adsorbed moisture content of the magnetic disk medium of Example 5 is reduced to about A compared to the SiO□ inorganic thin model in the relative humidity range of IO to 95%, and the surface becomes aqueous. It has been proven that Furthermore, when we measured the adsorption phenomenon using the above head, we found that the total temperature i up to 1.00℃
No adsorption phenomenon was observed throughout the area. Also, 100
Even when looking at changes over time, no increase in the amount of adsorbed water, no increase in the amount of adsorbed water in the head, or any adsorption phenomenon in the head were observed.

Furthermore, floating 1ii O, I
0μm, load! , Ogf's low flying height, high load 412
0. ,Constant start-stop (CSS) testing was conducted using a slider made of Tie mixed ceramics. The magnetic disk medium according to the present invention has 50
"C5S was tested 100,000 times even under 60% RH, and no abnormality was observed in the magnetic disk or magnetic head.The number of C5S tests for lubricating layers other than those of the present invention was 20.
It was 00-3000. By using a magnetic disk medium with eight grains and a floating amount of 0.12 μm, the magnetic disk device can be operated stably for five years.

The method of bringing the silylating agent hexamethyldisilazane into contact with the surface of the magnetic disk is not only by heating it in a liquid of hexamethyldisilazane, but also by placing the magnetic disk in the heated vapor of hexamethyldisilazane. Using this method, we were able to form an extremely thin organosilicon functional layer of several angstroms, similar to a monolayer, and were able to provide exactly the same excellent effects to magnetic disks. In addition to hexamethyldisilazane, trimethylchlorosilane, trimethylmethoxysilane, dimethylaminotrimethylsilane, and bis(trimethylacetamide) listed in Table 1 are also available.
, trimethylsilyldiphenylurea, bistrimethylsilylurea, and trimethylsilylimidazole were used in the silylation reaction to provide magnetic disks with excellent lubricity and water repellency similar to those of hexamethyldisilazane.

(Actual hh Example 2) A continuous thin film magnetic layer containing γ-Fe 203 as a main component is formed by sputtering on a mirror-polished aluminum magnetic disk substrate with an alumite layer. The magnetic layer of the magnetic disk is trimethylsilylated under the same reaction conditions as in Example 1. FIG. 2(a) shows the orientation state of molecules containing hydroxyl groups on the surface of the magnetic film 4 on the alumite layer 3, and FIG.
) is a magnetic layer 3 whose surface hydroxyl groups are trimethylsilylated.
and the orientation state of molecules in the lubricating layer 4. The main component of the magnetic film 4 is γ-Fe20. ．． However, since a large number of iron hydroxides exist on the magnetic surface, organosilicon functional groups such as trimethylsilyl groups can be easily fixed by chemical bonding by silylation reaction. In an experiment to measure the spacing coefficient of the magnetic disk prepared in this way, the head before the silylation reaction had a lot of adsorption and the friction coefficient was approximately 0.8, but after the reaction, there was no adsorption phenomenon at all and the friction coefficient decreased. It had fallen to about O0:. Further 50℃, 8
The change over time in the friction coefficient between 100L1 was investigated in an atmosphere of 0% RH, but no change was observed.

When a carboxyl group-containing fluorinated polyether lubricant such as barfluoroboryether lubricant is further applied on this magnetic disk, a load of 10 gf is applied.
In a C8S test using a Mn-Ze ferrite head, the head passed a 100,000 direction test even at 50° C. and 80% RH, and no abnormalities were observed in the magnetic disk or head slider. In addition, the C3S number of the above-mentioned magnetic disk without applying lubricant was 50,000 times, and the C551 number of a conventional magnetic disk having no chemically bonded organic silicon functional group was very small at about 1000 times.

Note that in this example, as in Example 1, all the silylating agents listed in Table 1 can be used. Furthermore, when organic silicon functional groups such as phenyldimethylsilyl and t-butyldimethylsilyl groups, which are bulkier than trimethylsilyl groups, are bonded to the magnetic disk, the number of C5S increases from 50,000 times to approximately 80,000 times. did.

A lubricating layer was formed by applying a perfluoropolyether lubricant on the magnetic disk having a layer of organosilicon functional groups according to this example, and a Winchester type A
J! 203. When a C5S test was conducted with a flying height of 0.10 μm using a head slider made of a TiC mixed ceramic material (load: 8 gf), it passed 100,000 cycles, and no abnormality was observed in the magnetic disk or head slider. As described above, by forming a lubricating layer based on organic silicon functional groups fixed by chemical bonds according to the present invention, it was possible to achieve high recording density in a magnetic disk device by reducing spacing loss.

<Effects of the Invention> As specifically explained with the six fruitful examples, the magnetic disk medium of the present invention has magnetic I+! ! By fixing the organosilicon functional group to the inorganic compound thin film or magnetic llI2 with chemical bonds, the surface of the inorganic compound thin film or magnetic film has excellent lubricity and water repellency, so it can be adsorbed even under high temperature and high humidity. The moisture content is low, and over a long period of time, there is no increase in the H friction coefficient, no fluctuation in the amount of adsorbed moisture, and no adsorption by the head. Therefore, by using the warm-up disk medium of the present invention, it is possible to perform constant rotation-stop rotation operations of a magnetic disk in high-temperature, high-humidity environments over a long period of time using a head slider with a lower float and higher load than in the past. It can be repeated in a highly reliable and stable state.

For this reason, the present invention provides an important technique for achieving high-density recording in magnetic disk devices.

[Brief explanation of the drawing]

1(a) and (b) are explanatory diagrams of a first embodiment of the present invention, and FIGS. 2(a) and (b) are explanatory diagrams of a second embodiment of the present invention. In the drawing, 1 is a 5in2 inorganic thin film, 2 is d',! 4 is a magnetic film, and 5 is a lubricating layer.

Claims (1)

[Scope of Claims] 1) In a magnetic disk medium in which an inorganic compound thin film is formed on the surface of a magnetic film, an organic silicon functional group is fixed to the surface of the inorganic compound thin film by chemical bonding to form a lubricating layer. Features of magnetic disk media. 2) The magnetic disk medium according to claim 1, wherein the chemical bond between the inorganic compound thin film and the organosilicon functional group is formed by a silylation reaction. 3) The magnetic disk medium according to claim 1 or 2, wherein the inorganic compound thin film is a silicon dioxide thin film. 4) The magnetic disk medium according to claim 1, 2 or 3, characterized in that a lubricant is further applied on the layer of organosilicon functional groups to form a lubricant layer. 5) The magnetic disk medium according to claim 4, wherein the lubricant is a carboxyl group-containing fluorinated polyether lubricant. 6) A magnetic disk medium characterized in that a lubricating layer is formed by fixing organic silicon functional groups on the surface of a magnetic film through chemical bonds. 7) The magnetic disk medium according to claim 6, wherein the chemical bond between the magnetic film and the organosilicon functional group is formed by a silylation reaction. 8) The magnetic disk medium according to claim 6 or 7, characterized in that a lubricant is further applied on the layer of organosilicon functional groups to form a lubricant layer. 9) The magnetic disk medium according to claim 8, wherein the lubricant is a carboxyl group-containing fluorinated polyether lubricant.