JPH07169044A - Magnetic disc - Google Patents

Abstract

PURPOSE:To obtain the protective layer of a magnetic disc which has a large tenacity and low abrasion characteristics by forming the protective layer of the magnetic disc out of a polyorganosiloxane-containing layer which is formed by applying and curing solution having specific composition. CONSTITUTION:A foundation layer 3, a magnetic layer 4, a protective layer 5 and a lubrication layer 6 are formed on a glass board 2 in this order to form a magnetic disc 1. The protective layer 5 is composed of a polyorganosiloxane- containing layer which is formed by applying and curing solution which contains organic silicon compounds which are expressed by formula I and formula II wherein R<1> denotes hydroxyl group, epoxy group, mercapto group, amino group or organic which has 4th grade alcohol group on the end of its molecular chain, R<2> denotes an alkoxyl group, acyloxy group, alkoxyalkoyl group, isocyanate group or chlorine atom and (n) denotes one integer among 1, 2 and 3. As the protective layer 5 contains a polyorganosiloxane, the protective layer 5 has a large tenacity and low abrasion characteristics and cracking and flaws in the protective layer 5 can be eliminated, so that the magnetic layer 4 can be protected from damages.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk excellent in surface lubrication durability. In particular, the present invention relates to a magnetic disk having an excellent CSS characteristic in which the toughness of a protective layer is improved.

[0002]

2. Description of the Related Art As a magnetic disk used in a contact start / stop type magnetic disk device, there is known a magnetic disk in which a magnetic layer, a protective layer and a lubricating layer are sequentially formed on a non-magnetic substrate having an uneven surface. -126627. Here, the protective layer protects the magnetic layer from the external environment and prevents the magnetic layer from being damaged by direct contact with the magnetic head, while the lubricating layer plays a role of reducing wear of the protective layer. The protective layer is composed of inorganic materials such as metal oxides, metal nitrides and amorphous carbon from the viewpoint of good wear resistance, and the lubricating layer has chemical stability, low vapor pressure, low surface tension and boundary lubrication. A perfluoroalkylpolyether-based liquid lubricant having excellent properties and adhesion to the protective layer is used.

Further, in order to reduce the friction between the magnetic disk and the magnetic head, a magnetic disk having a protective layer made of a silicon dioxide film or a silicon dioxide film in which hard particles are dispersed is provided on the magnetic layer. 57-5873
No. 1 and Japanese Patent Laid-Open No. 61-732227.

[0004]

However, in the above-mentioned magnetic disk of the prior art, since the adhesion between the protective layer and the lubricating layer and the uniform coating property of the lubricant are insufficient, contact and sliding of the magnetic head are caused. There was a problem of high friction. In such a protective layer, the friction coefficient increases remarkably in the part where the lubricating layer has disappeared, and since the silicon dioxide film itself is fragile, when the wear of the protective layer progresses, the magnetic layer may sometimes be destroyed. It was The present invention has been made to solve the above problems, and an object of the present invention is to provide a magnetic disk having an improved protective layer.

[0005]

According to the present invention, in a magnetic disk in which a magnetic layer, a protective layer and a lubricating layer are sequentially formed on a non-magnetic substrate having an uneven surface, the protective layer is the following general A magnetic disk comprising a polyorganosiloxane-containing layer formed by applying a solution containing an organosilicon compound represented by the formulas (1) and (2) and curing the solution.

R ¹ _n Si (R ² ) _4-n (1) Si (R ² ) ₄ (2) Here, R ^{1 is a} hydroxyl group, an epoxy group, a mercapto group, an amino group, or a quaternary ammonium group. An organic group at the end of the molecular chain, R ² : an alkoxy group, an acyloxy group, an alkoxyalkoxy group, an isocyanate group or a chlorine element, and n: an integer of 1 to 3.

The protective layer according to the present invention comprises a solution containing at least one organic silicon compound represented by the general formulas (1) and (2), or an organic silicon compound represented by the general formulas (1) and (2). Obtained by applying a solution containing at least one partial hydrolyzate or a solution containing at least one polymer of the organosilicon compounds represented by the general formulas (1) and (2) onto the magnetic layer and curing it. To be It is also possible to use a solution containing at least one of the above organosilicon compound, a partial hydrolyzate thereof, and a condensation polymer thereof.

Examples of the organosilicon compound represented by the general formula (1) used in the present invention include γ-hydroxypropyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride,
γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl)-
γ-aminopropyltrimethoxysilane, 3- (N, N
-Diglycidyl) aminopropyltrimethoxysilane,
Typical examples thereof include γ-glycidoxypropylmethyldimethoxysilane and the like. As the silicon compound represented by the general formula (2), tetramethoxysilane,
Examples include tetraethoxysilane, tetraacetoxylan, and tetraisocyanatesilane.

The solution may be applied by a known dip coating method or spin coating method. The curing treatment of the protective layer by heating is preferably performed at 400 ° C. or lower, which is a temperature at which the magnetic properties of the magnetic layer do not affect recording and reproduction, and more preferably 300 ° C. or lower. Thereby, the organic group directly bonded to the silicon atom can be cured without being decomposed and scattered. Further, the protective layer can be cured by irradiating with ultraviolet rays, far ultraviolet rays, or the like.

The mixing ratio of the organosilicon compounds represented by the general formulas (1) and (2) to be contained in the solution is such that the R ¹ _n SiO _{(4-n) / 2} converted mol number and the SiO ₂ converted mol number are respectively. When expressed by, SiO ₂ / R ¹ _n SiO _{(4-n) / 2} (molar ratio)
It is preferable that the value of is not more than 1000. When the content of the organosilicon compound represented by the general formula (2), which becomes silicon dioxide by curing, is increased and the matrix of silicon dioxide in the protective layer is increased, the abrasion resistance of the protective layer is increased. When the above value exceeds 10 ³ , the properties of the layer consisting of the silicon dioxide component alone are approached, the protective layer becomes brittle, and the uniform coating property and adhesive force of the lubricating layer provided on the protective layer become insufficient. It is not preferable. That is, the friction with the magnetic head increases and the durability of the magnetic disk decreases, which is not preferable. From the practical viewpoint that the protective layer has both wear resistance and toughness, the above ratio is 1 to
The range of 1000 is preferable, and the range of 10 to 300 is more preferable. In the present invention, in order to improve the adhesion between the protective layer and the magnetic layer, it is preferable to provide a coating film containing Cr on the magnetic layer before forming the protective layer.

In the present invention, in order to increase the abrasion resistance of the protective layer, hard fine particles can be contained in the coating liquid. As the hard particles, metal oxide particles are used, and silicon dioxide particles and aluminum oxide particles are preferably used. Colloidal silica and colloidal alumina can be used as the source of these fine particles. As colloidal silica and colloidal alumina, particle diameters of 1 to 50n
A sol in which ultrafine particles of m of silica or alumina are dispersed in a water or alcohol dispersion medium, or a sol in which a dry powder obtained by removing the dispersion medium from this sol is dispersed again in an appropriate dispersion medium is preferable. These fine particles may be used to give unevenness to the surface of the magnetic disk. The particle diameter of the fine particles is preferably 30 nm or less, more preferably 20 nm or less, in relation to the thickness of the protective layer. The content of the metal oxide in the coating solution is the number of moles of the metal,
It is preferable not to exceed twice the number of moles of silicon in the metal silicon compound in the coating liquid. If it exceeds 2 times, the film-forming property and toughness of the protective layer deteriorate, which is not preferable.

The total amount of the organic silicon compound and the hard fine particles contained in the coating solution is represented by the general formulas (1) and (2).
Organosilicon compounds represented by R ¹ _n SiO
_When expressed in terms of _{(4-n) / 2} equivalent weight and SiO ₂ equivalent weight and the hard fine particles are represented by metal oxide weight, the value is 0.1 to
It is preferable to adjust the coating liquid so as to be 10% by weight. Methanol, ethanol, isopropyl alcohol, ethoxyethanol, propylene glycol monomethyl ether or the like can be used as a solvent for adjusting the concentration of the solution.

As the non-magnetic substrate having an uneven shape used in the present invention, a glass or ceramic plate is corroded into a predetermined shape with an etching solution such as hydrofluoric acid, or a metal plate such as aluminum is plated with nickel / phosphorus. ,
It is possible to use the plated layer having irregularities of a predetermined shape formed by abrasive grains. Further, it is also possible to use a heated glass substrate on which the low melting point metal such as aluminum is covered by sputtering or the like over the entire surface of the substrate or partially to form the unevenness. As the magnetic layer according to the present invention, a known magnetic layer such as a Co-based alloy magnetic layer coated by sputtering can be used. For the lubricating layer used in the present invention, a fluorinated lubricating oil such as perfluoroalkyl polyether is preferably used.

[0014]

Since the protective layer of the magnetic disk of the present invention is a layer containing polyorganosiloxane, its surface has greater toughness than the magnetic disk of the prior art. Therefore, even if the magnetic head lands on the surface of the magnetic disk so as to collide with the protective layer, the magnetic disk is prevented from being broken. Further, the protective layer of the present invention contains a polyorganosiloxane formed from an organosilicon compound having a functional group,
This functional group firmly bonds the lubricating layer and the protective layer applied on the protective layer through hydrogen bonds, so that the lubricating layer is prevented from moving on the surface of the protective layer, and the lubricating layer is thinly provided. In addition, the protective layer is prevented from being exposed during the operation of the magnetic disk, and the durability of lubricity of the magnetic disk is increased.

[0015]

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the gist.

Example 1 10 g of tetraethoxysilane, 1 g of γ-hydroxypropyltrimethoxysilane, 15 g of ethyl alcohol, 20 g of distilled water and 5 g of acetic acid were mixed and stirred at room temperature for 5 hours. After diluting 25 g of this solution with 150 g of ethyl alcohol, silicon dioxide particles having a particle size of about 10 nm are diluted with pure water to form 4 parts.
A coating solution for forming a protective layer was prepared by adding 1 g of a solution dispersed in weight%. Concavo-convex shape on the surface using an etching solution containing hydrofluoric acid (peak height; about 30 nm, peak pitch;
A Cr underlayer and a magnetic layer containing Co as a main component were sequentially coated on a glass substrate having a thickness of about 0.4 μm by sputtering. After applying the above coating solution by spin coating, 290
It heat-treated at 1 degreeC for 1 hour, it hardened | cured, and the protective layer was formed. The protective layer was confirmed to be polyorganosiloxane by X-ray photoelectron spectroscopy. When the fracture surface of the protective layer was observed with a scanning electron microscope, irregularities were confirmed on the surface of the magnetic layer. A perfluoropolyether having a hydroxyl group at the terminal was applied onto the protective layer by spin coating and dried at 100 ° C. for 30 minutes to form a lubricating layer having a thickness of about 2 nm to obtain a magnetic disk. Table 1 shows the results of measuring the static friction coefficient of the magnetic head and the in-plane dynamic friction coefficient of the magnetic disk after the CSS test was performed 20,000 times.

[0017]

[Table 1]

Example 2 100 g of tetraethoxysilane, 10 g of γ-glycidoxypropyltrimethoxysilane, 20 of ethyl alcohol
0 g, 35 g of distilled water and 3 g of acetic acid are mixed, and the temperature is about 50 ° C.
And stirred for 20 hours. 30 g of this solution was diluted with 200 g of ethyl alcohol to prepare a coating liquid for forming a protective layer. A Cr underlayer and an alloy magnetic layer containing Co as a main component are sequentially coated on a glass substrate having an irregular shape (peak height; about 50 nm, peak pitch; about 1 μm) on the surface thereof with an etching solution containing hydrofluoric acid. The coating solution was applied onto the magnetic layer by spin coating, and then heat-treated at 290 ° C. for 1 hour to cure and form a protective layer. This protective layer was confirmed to be polyorganosiloxane when analyzed by X-ray photoelectron spectroscopy. When the fracture surface of the protective layer was observed with a scanning electron microscope, irregularities were confirmed, and the thickness of the protective layer measured by an ellipsometer was about 25 nm. After coating the obtained protective layer with a perfluoropolyether having a hydroxyl group at the terminal by spin coating, 10
After drying at 0 ° C. for 30 minutes, a lubricating layer having a film thickness of about 2 nm was formed to obtain a target magnetic disk. Table 2 shows the results of a pin-disk wear test (pin shape: diameter about 2 mm, 10 gf, 300 rpm) performed on this magnetic disk. This test shows that the longer the time until the protective film is destroyed, the lower the friction and the toughness of the protective film.

[0019]

[Table 2]

Comparative Example 1 Tetraethoxysilane 11 g, ethyl alcohol 15
g, 20 g of distilled water and 5 g of acetic acid were mixed and stirred at room temperature for 5 hours. 25 g of this solution was added to 150 ml of ethyl alcohol.
After diluting with g, 1 g of a solution in which 4% by weight of silicon dioxide particles having a particle size of about 10 nm was dispersed in pure water was added to prepare a coating liquid for forming a protective layer. By etching with an etching solution containing hydrofluoric acid, the surface has an uneven shape (peak height: about 5
A Cr underlayer and a magnetic layer containing Co as a main component were sequentially coated on a glass substrate having a thickness of 0 nm and a peak pitch of about 1 μm by sputtering, and the coating solution was applied by spin coating, followed by heat treatment at 290 ° C. for 1 hour. Then, it was cured to form a protective layer. When the protective layer was analyzed by X-ray photoelectron analysis, it was confirmed to be silicon dioxide. When the fracture surface of the protective layer was observed with a scanning electron microscope, irregularities were confirmed, and the thickness of the protective layer measured by an ellipsometer was about 20n.
It was m. A perfluoropolyether having a hydroxyl group at the terminal was applied onto the obtained protective layer by spin coating, followed by drying at 100 ° C. for 30 minutes to form a lubricating layer having a film thickness of about 2 nm to form a magnetic disk. . Table 1 shows the results of measuring the static friction coefficient of the magnetic head and the in-plane dynamic friction coefficient of the magnetic disk after the CSS test was performed 20,000 times. As shown in Table 1, the magnetic disk of the present invention has a low absolute coefficient of friction with the magnetic head. Also, the in-plane variation of the dynamic friction coefficient is extremely small.

Comparative Example 2 Tetraethoxysilane 100 g, ethyl alcohol 17
5 g, distilled water 35 g and acetic acid 5 g were mixed and stirred for 5 hours at room temperature. 25 g of this solution was added to ethyl alcohol 20
It was diluted with 0 g to prepare a coating liquid for forming a protective layer. A magnetic disk was manufactured in the same manner as in Example 2 except that this coating solution was used. Table 2 shows the pin-disk wear test results of the obtained magnetic disks.

From the above Examples and Comparative Examples, the effect of using γ-hydroxypropyltrimethoxysilane as the organosilicon compound represented by the general formula (1) for forming the protective layer is clear. That is, it is presumed that the hydroxyl group of γ-hydroxypropyltrimethoxysilane improves the adhesive force between the protective layer and the lubricant and the uniform coating property of the lubricant, so that the protective layer and the magnetic head are not adsorbed through the lubricant. It

[0023]

Since the magnetic disk of the present invention contains polyorganosiloxane, it has greater toughness and lower frictional characteristics than the conventional protective layer composed of only inorganic oxide. Even if the magnetic head lands on the magnetic disk so as to collide with it, the protective layer can be prevented from cracking or chipping, and the magnetic layer can be protected without damage.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an embodiment of a magnetic disk of the present invention.

[Explanation of symbols]

1 ... Magnetic disk, 2 ... Glass plate, 3 ... Underlayer, 4 ... Magnetic layer, 5 ... Protective layer, 6 ... Lubrication layer

Claims (4)

[Claims] 1. A magnetic disk in which a magnetic layer, a protective layer and a lubricating layer are sequentially formed on a non-magnetic substrate having an uneven surface, and the protective layer has the following general formulas (1) and (2). A solution containing an organosilicon compound represented by
A magnetic disk comprising a polyorganosiloxane-containing layer formed by curing. R ¹ _n Si (R ² ) _4-n (1) Si (R ² ) ₄ (2) where R ^{1 is a} hydroxyl group, an epoxy group, a mercapto group, an amino group, or a quaternary ammonium group in the molecular chain. R ² is an organic group having a terminal, R ^{2 is an} alkoxy group, an acyloxy group, an alkoxyalkoxy group, an isocyanate group or a chlorine element, and n is an integer of 1 to 3. 2. At least one of R ^{1 in} the general formula (1) is that at least one of hydrogen is an organic group having 1 to 5 carbon atoms, which is substituted with a hydroxy group, an amino group or an epoxy group. The magnetic disk according to claim 1, wherein the magnetic disk is a magnetic disk. 3. An organosilicon compound represented by the general formula (1) or (2) contained in the solution is added to R ¹ _n SiO 2.
_{(4-n) / 2} when expressed in terms of number of moles and SiO ₂ in terms of number of moles, claims, characterized in that the SiO ₂ / R ¹ _n SiO 1~1000 a _{(4-n) / 2} ratio 1. The magnetic disk according to 1 or 2. 4. Fine particles of silicon dioxide having a diameter of 30 nm or less in the solution are expressed as a molar ratio in terms of elemental silicon with respect to the total amount of the organosilicon compounds represented by the general formulas (1) and (2). 4. The magnetic disk according to claim 1, wherein the magnetic disk is included in a range not exceeding twice.