JPS6132218A - Manufacture of magnetic disk - Google Patents

Abstract

PURPOSE:To incorporate stably a lubricant in large amts. by providing fine pores to a magnetic disk, impregnating the pores with a lubricant having a reactive group, and fixing the lubricant by the reaction with a resin. CONSTITUTION:A thermophastic resin which is not involved in the curing reaction of a resin is previously added into a magnetic paint, and the thermoplastic resin is solved out by using a solvent to form fine pores having <1mum diameter, after the magnetic film is formed. The pore is impregnated with a lubricant having a reactive group, and the lubricant is fixed by baking. Concretely, both thersetting resin and thermoplastic resin are used as the resin constituting the magnetic paint, and the primary baking is carried out at a temp. at which the curing reaction of the thermosetting resin proceeds to the extent of 60-70%. The reaction is stopped at this stage, and the thermoplastic resin is solved out and replaced with a lubricating oil. Then the thermosetting resin is heated to a temp. at which the curing reaction proceeds to the extent of 100%, and succeedingly baked. Consequently, the reactive group in the lubricating oil is allowed to reat with the resin, and the resin is cured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a magnetic disk having a surface layer in which a lubricant is reliably impregnated and fixed.

A magnetic disk uses a nonmagnetic metal plate, such as an aluminum alloy plate, as a substrate, and a magnetic film is formed thereon by thinning it using a method such as a spin code method or a vacuum evaporation method.

In other words, the spin code method is mainly used for magnetic films formed mainly of oxides such as iron sesquioxide (T-Fe203), while the spin code method is mainly used for magnetic films formed using oxides such as iron sesquioxide (T-Fe203). -P) or a magnetic alloy such as cobalt chromium (CO.Cr), the film is formed using a vacuum evaporation method, a sputtering method, or the like.

Here, information is recorded and reproduced by a magnetic head that levitates over a magnetic disk that rotates at high speed at a distance of about 0.5 μm. In this case, if there is dust or recording medium powder attached to the magnetic head, the magnetic head will drop and collide, or head crash will occur, and in devices with a C3S (contact start/stop) configuration, the magnetic disk When the magnetic head starts and stops rotating, there is friction because the magnetic head is in contact with the magnetic film, and there is also an impact caused by the jumping of the magnetic head.

For these reasons, it is necessary for magnetic films to have excellent mechanical strength, and in particular, magnetic disks used in external recording devices for computers have a rotational speed of several tens of meters per second, which is more than an order of magnitude faster than that for acoustic use. Therefore, it is necessary to have better mechanical strength, and a magnetic film mainly composed of oxide magnetic powder such as r-Fe 203 is often used.

The present invention relates to a method for manufacturing a magnetic disk in which the wear resistance of such a magnetic film is further improved.

[Conventional technology]

In a magnetic disk having a C8S configuration, a lubricant is applied to the surface to increase wear resistance and reduce contact resistance, and fluorinated carbon oil is generally used.

However, since this lubricant is oil, when the magnetic disk rotates at high speed and the temperature inside the device rises to 60 to 70 degrees Celsius, centrifugal force tends to bias the lubricant toward the outer periphery of the magnetic disk. There is a problem in that the mechanical strength of the inner peripheral portion is not improved much.

Therefore, a method has been used in which a fluorinated carbon oil having a reactive group, such as a carboxyl group, is used as a lubricant, applied to the magnetic film, and reacted with the resin constituting the magnetic film to fix the lubricant.

Representative structural formulas for both are shown below.

Fluorinated carbon oil CF CF 20+-n Cz F sCF3 Fluorinated carbon oil with reactive groups CF3, CF3 In this way, the fluorinated carbon oil is fixed at the reactive group, so the mechanical strength is improved to a certain degree. What is done＼
However, because the oil was thin, it was insufficient for the purpose.

[Problem that the invention seeks to solve]

As explained above, for magnetic disks, especially magnetic disks using the CSS method, it is necessary for the magnetic film to have wear resistance, and for this reason, it is necessary to fix the lubricating oil to a considerable thickness. .

However, a method for stably fixing it has not yet been found.

[Means for solving problems]

The above problem is solved by kneading magnetic powder, thermosetting resin, and thermoplastic resin using a solvent to make a magnetic paint, applying the paint onto the disk substrate, and then heating the substrate to make the above-mentioned thermosetting resin. The resin is baked under conditions to reach a reaction rate of 60 to 70%, then the baking dissolves the thermoplastic resin contained in the coating film using a solvent, and then a lubricant having a reactive group is applied to the coating film. This problem can be solved by a method for manufacturing a magnetic disk in which the thermosetting resin in the coating film is baked under conditions such that the reaction rate reaches 100% to react with the reactive groups of the lubricant.

[Effect]

In the present invention, even if fluorinated carbon oil having a reactive group is applied to a magnetic film and reacted to fix it, the film thickness is too thin to achieve sufficient effect. By forming pores and impregnating and fixing fluorinated carbon oil having a reactive group into the micropores, a magnetic disk with excellent mechanical strength can be obtained.

That is, in the present invention, a thermoplastic resin that does not participate in the curing reaction of the resin is added to the magnetic paint, and after the magnetic film is formed, this thermoplastic resin is dissolved and extracted using a solvent to form micropores of less than 1 μm. The pores are then impregnated with a lubricant having a reactive group, and the pores are fixed by baking.

〔Example〕

In the present invention, both a thermosetting resin and a thermoplastic resin are used as the resin constituting the magnetic paint, and the primary baking temperature is set at a temperature at which the curing reaction of the thermosetting resin progresses by 60 to 70%. The reaction is stopped, the thermoplastic resin is extracted with a solvent, and the lubricating oil is substituted in its place.Then, secondary baking, which is a temperature condition in which the curing reaction of the thermosetting resin proceeds 100%, is performed by heating the thermoplastic resin at a temperature to replace the lubricating oil. This reaction group is reacted with the resin and the resin is cured.

The figure shows, as a specific example, the relationship between the reaction rate of epoxy resin and baking temperature.
When heated for a period of time, the reaction of the epoxy ring proceeds by about 70%.

Therefore, this temperature condition is selected as the temperature for the primary baking, and then 21
When heated at 0° C. for 1 hour, the curing reaction of the epoxy resin ends and the epoxy ring disappears, so this temperature condition is selected as the temperature for the secondary baking.

The present invention will be explained below with reference to Examples.

The table shows the materials and composition ratios that make up the magnetic paint, including rFe2O3 as the magnetic powder, epoxy resin, phenol resin, and acrylic resin as the thermosetting resin, and polyvinyl methyletherene and cellosolve acetate as the thermoplastic resin. Three types are used.

A magnetic paint was prepared by kneading the constituent materials shown in the above table using a ball mill, and the magnetic coating was coated on an aluminum alloy substrate by a spin cord method to form a magnetic film.

After primary baking of this magnetic film was performed at a temperature of 140°C for 1 hour, the magnetic film was immersed in ethyl alcohol for 30 minutes to dissolve the polyvinyl methyl ether, and after drying, the above-mentioned fluorinated carbon oil having carboxyl groups was added. was coated, and then treated at a secondary baking temperature of 210° C. for 1 hour, and the surface was polished to complete a magnetic disk.

In this example, polyvinyl methyl ether is used as the thermoplastic resin, but polyvinylethyl ether, polyvinyl butyl ether, polyethylene glycol, etc. may be used instead, and ethyl alcohol can be used as a solvent to selectively dissolve it. was used, but methyl alcohol or cellosolve may also be used.

Next, as an effect of implementing the present invention, a forced CSS durability test was conducted by applying a load to the magnetic head, and the results showed that the conventional magnetic disk failed at approximately 50,000 rotations, whereas the present invention was implemented. The magnetic disk has a lifespan of up to 150,000 cycles.
It was clear that the durability was improved.

〔Effect of the invention〕

As described above, the present invention provides a magnetic disk with minute holes, impregnates the holes with a lubricant having a reactive group, and reacts with the resin to fix the lubricant in a large amount and stably. This makes it possible to extend the life of the magnetic disk.

[Brief explanation of drawings]

The figure shows the relationship between temperature and reaction rate for epoxy resin baking.

Claims (1)

[Claims] A magnetic paint is made by kneading magnetic powder, a thermosetting resin, and a thermoplastic resin using a solvent, and the paint is applied onto a disk substrate.The substrate is then heated to increase the reaction rate of the thermosetting resin to 60. Baking is performed under conditions that reach 70% to The reaction rate of thermosetting resin in the coating film is 100%.
A method for manufacturing a magnetic disk, characterized in that baking is performed under conditions that reach the following conditions to react with the reactive groups of the lubricant.