JPH04328321A - Magnetic recording medium and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide the magnetic recording medium having excellent lubrication durability, traveling property and wear resistance as well as excellent self- lubricity by forming a chemical adsorption film chemically bonded with at least >=2 kinds of straight chain surfactants varying the number of carbon atoms via siloxane bonds on the surface of the magnetic recording medium. CONSTITUTION:At least 2 kinds of the straight chain surfactants varying in the number of carbon atoms are the straight chain surfactants having a chlorosilyl group at one end and a fluoroarbon group or methyl group at the remaining other terminal. A raw material liquid is prepd. by dissolving these surfactants into a nonaq. solvent. A hard disk 3 of the magnetic recording medium is brought into contact with this raw material liquid, by which the chemical adsorption film 6 chemically bonded with the chlorosilane straight chin surfactants having the methyl group or fluorocarbon group at the terminal via the siloxane bonds is formed on the surface 4 of the disk 3.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a high recording density magnetic recording medium used in the information industry, etc.
In particular, the present invention relates to a magnetic recording medium provided with a lubricating film having self-lubricating properties.

0002

[Prior Art] In recent years, in place of coated magnetic recording media such as magnetic tape, in which a magnetic material such as ferrite powder is applied to a polyester film together with a solvent, plating methods, sputtering methods, vacuum evaporation methods, and ion spraying methods have been used. 2. Description of the Related Art A magnetic recording medium in which a ferromagnetic metal thin film is provided on a nonmagnetic support by a method such as the tinging method is being researched as a high-density magnetic recording medium.

However, the magnetic recording medium using the ferromagnetic metal thin film produced by the method described above has problems in its wear resistance and running properties. That is, the magnetic recording medium is subjected to high-speed relative motion with the magnetic head during the process of recording and reproducing magnetic signals. At this time, the magnetic recording medium must run smoothly and stably. However, the ferromagnetic metal thin film produced by the above method cannot withstand the harsh conditions of magnetic recording and reproducing processes.
Running may become unstable due to friction from magnetic heads, etc.
When running for a long time, the output may drop significantly due to wear, breakage, or generation of abrasion powder. Therefore, it was necessary to form a lubricant on the surface of the magnetic recording medium. For reference, there is a description regarding lubricants in Tribology of Electrical Materials, page 185, published by Realize Co., Ltd.

0004

Conventional lubricants include solid lubricants and liquid lubricants. Solid lubricants are difficult to apply uniformly and are no longer used. Liquid lubricants form a lubricant film by spin coating or dipping, but the film thickness is at least 50 angstroms, and in order to achieve high density and high capacity, liquid lubricants are not suitable for bringing the magnetic head closer. There is a limit. In addition, since it is a liquid lubricant, the lubricant tends to accumulate in the concave portions of the fine irregularities imparted to the surface of the magnetic recording medium, and lubricates the convex portions where the lubricant film should reduce wear caused by contact between the head and the magnetic recording medium. There was almost no film. Also, with liquid lubricants, it is difficult to accurately control the supply amount.
There was a problem that if the supply amount was large, the liquid would scatter. Therefore, the requirements for a lubricating film were not met.

[0005] In order to solve the above-mentioned prior art, the present invention
A magnetic device with a lubricating film that forms a thin, uniform lubricating film with a thickness of about nanometers along the unevenness of a magnetic recording medium, and has excellent lubricity, durability, runnability, and abrasion resistance, as well as self-lubricating properties. The purpose is to provide a recording medium and a method for manufacturing the same.

[0006]

Means for Solving the Problems In order to achieve the above object, the magnetic recording medium of the present invention has a magnetic recording material formed on a base, in which at least one surface of the magnetic recording medium is provided. A chemisorption film is formed by bonding at least two types of linear molecules having different carbon numbers via siloxane bonds.

[0007] In the above structure, it is preferable that the at least two linear molecules having different numbers of carbon atoms are at least a molecule having a fluorinated carbon group at the end and a molecule having a methyl group at the end. Further, in the above structure, among at least two or more types of linear molecules having different numbers of carbon atoms, the molecule with a larger number of carbon atoms has a methyl group at the end, and at least one of the remaining molecules has a fluorinated carbon group at the end. It is preferable to have.

Further, in the above structure, the magnetic recording medium according to claim 1, wherein the difference in the number of carbon atoms between the at least two linear molecules having different numbers of carbon atoms is 1 or more and 15 or less. Next, the method for manufacturing a magnetic recording medium of the present invention is a manufacturing method in which a chemically adsorbed film is provided on a magnetic recording medium in which a magnetic recording material is formed on a base, and first, at least two types of chemically adsorbed films having different numbers of carbon atoms are formed. The method is characterized in that it is brought into contact with a solution in which a linear surfactant is dissolved in a non-aqueous organic solution, and then excess surfactant on the magnetic recording medium is removed using an organic solvent.

In the method of the present invention, at least two linear surfactants having different numbers of carbon atoms have a chlorosilyl group at one end, and a fluorocarbon group at the other end.
Alternatively, a surfactant having a methyl group is preferable.

0010

[Operation] According to the configuration of the present invention, a chemically adsorbed film chemically bonded via siloxane bonds is formed on at least one surface of the magnetic recording medium, so that the magnetic head and various other members that come into contact with it during running are formed on at least one surface of the magnetic recording medium. The chemical adsorption film is not scraped off by the friction of
A magnetic recording medium with excellent wear resistance can be obtained. Furthermore, since it is an extremely thin film with a thickness on the nanometer level, the original functions of the magnetic recording medium and magnetic recording device are not impaired.

Next, according to the production method of the present invention, since the linear surfactant has a chlorosilyl group at the end of the molecule, it is extremely active against moisture, but the reaction can be carried out under conditions where the moisture content is controlled to be extremely low. As a result, the hydroxyl group on the surface of the oxide film of the magnetic recording medium and the chlorosilyl group at the end of the molecule undergo a dehydrochlorination reaction, and a thin film with a thickness of one molecule is uniformly formed, which is chemically bonded to the surface of the metal oxide. Furthermore, by changing the molecular length, it is possible to reduce the contact area when a magnetic recording medium and a magnetic head come into contact, and it is possible to suppress friction and wear. Furthermore, by using a surfactant having a fluorocarbon group in a molecule with a small molecular length, it is possible to reduce frictional wear between the molecules and to impart water- and oil-repellent effects to the film.

0012

[Example] The magnetic recording medium of the present invention includes magnetic tape,
There are magneto-optical recording disks, hard disks, etc. Substrates that can be used for magnetic recording media include polyethylene terephthalate, polyethylene-2,6-naphthalate, polyphenylene sulfide, polyvinyl chloride, cellulose acetate, polyethylene, polypropylene, and polycarbonate. There are films, plates, etc. made of well-known materials such as polymer materials such as polyimide and polyamide, non-magnetic metal materials, and ceramic materials such as glass and porcelain. Further, as the magnetic recording material, any known material can be used, such as an alloy of one or more of iron, cobalt, and nickel, or an alloy of these and other metals such as manganese, chromium, titanium, phosphorus, yttrium, samarium, and bismuth. There are alloys that combine these metals, and there are also oxides of the above metals. The magnetic recording material can be formed on the substrate by any known method such as vacuum evaporation, sputtering, plating, or the like.

The chemisorption film of the present invention is composed of at least two types of linear surfactants having different carbon numbers, and is a chlorosilane linear surfactant having a methyl group or a fluorocarbon group at the end. be. For example, as shown below (
This is a group of compounds represented by chemical formula 1).

[0014]

[Chemical formula 1]

In the group of compounds represented by (Chemical Formula 1) above, it is preferable that (Chemical Formula 1) A has a larger number of linear carbon atoms than (Chemical Formula 1) B, and the difference in the number of carbon atoms is 1 or more and 15 or less. is preferred. Furthermore, the number of carbon atoms in l of (Chemical formula 1) B is from 0 to 1.
Preferably it is an integer up to 7. As long as these conditions are met, it is also possible to mix three or more types of surfactants. Further, a similar chemically adsorbed film can be formed using a lower alkyl group-substituted dichlorosilane type or a monochlorosilane type. Furthermore, similar effects can be obtained with halogenated silane surfactants other than the above-mentioned chlorosilane surfactants, and surfactants other than silicon such as titanium, ie, chlorotitanium surfactants.

The method for manufacturing a magnetic recording medium of the present invention includes the steps of: immersing the magnetic recording medium in a non-aqueous organic solution of a linear surfactant; and removing excess surfactant on the magnetic recording medium with an organic solvent. Consisting of In both processes, the chlorosilyl group in the surfactant is extremely active against moisture, so it is necessary to keep it as dry as possible using dry nitrogen gas, etc., and the process must be carried out in an atmosphere with a controlled humidity of 25% or less. is preferred. In the above step, if there are few exposed hydroxyl groups on the entire surface of the magnetic recording medium and it is difficult to uniformly cover the entire surface with a chemically adsorbed film made of a linear surfactant, a chemical adsorption film made of a linear surfactant is used. For example, SiCl4, SiHCl3, Si
H2Cl2, Cl-(SiCl2O)n-Si
Cl3 (where n is a natural number in the formula), SiClm (CH
3) 4-m, SiClm (C2 H5) 4-m
(However, in the formula, m is an integer of 1 to 3), HSiCl (
CH3)3-l, HSiCl(C2H5)
After a substance containing multiple chlorosilyl bonds such as 3-l (where l is 1 or 2 in the formula) is chemically adsorbed onto the surface of a magnetic recording medium, when it reacts with water, the chlorosilyl bonds on the surface become hydrophilic silanol bonds. The surface of the substrate becomes hydrophilic. Among these substances containing a plurality of chlorosilyl groups, tetrachlorosilane (SiCl4) is preferable because it has high reactivity and a small molecular weight, so that silanol bonds can be provided at a higher density. After making it hydrophilic in this way, it can be immersed in a linear surfactant to form a chemically adsorbed film.

The nonaqueous solvent used in the present invention may be any organic solvent that does not have active hydrogen that reacts with the chlorosilane surfactant. Examples include 1,1-dichloro, 1-
Fluoroethane, 1,1-dichloro,2,2,2-trifluoroethane, 1,1-dichloro,2,2,3,3,
3-pentafluoropropane, 1,3-dichloro,1,
Fluorine solvents such as 1,2,2,3-heptafluoropropane, hydrocarbon solvents such as hexane, octane, hexadecane, and cyclohexane, ether solvents such as dibutyl ether and dibenzyl ether, such as methyl acetate, acetic acid Any of ester solvents such as ethyl, isopropyl acetate, and amyl acetate is preferred.

Representative examples of the present invention are shown below. Example 1 Octadecyltrichlorosilane manufactured by Shin-Etsu Chemical Co., Ltd. and heptafluoroethyltrichlorosilane manufactured by Toshiba Silicon Corporation were used as surfactants. The above surfactant was dissolved at a molar ratio of 1:1 in a non-aqueous mixed solvent of hexadecane manufactured by Aldrich, chloroform and carbon tetrachloride manufactured by Kanto Kagaku Co., Ltd. (weight ratio 80:12:8) so that the concentration was 1 mmol/liter. , surfactant solution 2 was prepared. The solution was stored in a closed polytetrafluoroethylene container. Next, the humidity is reduced to 10% using dry nitrogen gas.
A petri dish 1 for immersing the substrate was placed in a glove bag kept in a dry state, and the surfactant solution 2 was placed in the petri dish 1. Using a hard disk 3 as a magnetic recording medium that has been processed and cleaned as a base material, 1
It was soaked for an hour (Figure 1). A film made of oxide is formed on the outermost surface of the hard disk, and many hydroxyl groups 5 are exposed on the surface of the oxide film 4 (FIG. 2). By immersion for 1 hour, the dehydrochloric acid reaction between the hydroxyl group 5 and the trichlorosilane group on the hard disk surface progresses sufficiently, and the siloxane bonds of (Chemical formula 2) and (Chemical formula 3) shown below are formed, and the siloxane bonds are formed by the chemical adsorption film 6. Therefore, it was uniformly covered.

[0019]

[Case 2]

[0020]

[Chemical formula 3]

At this time, it was confirmed that the ratio of surfactants constituting the thin film formed on the hard disk was approximately the same as the mixing ratio of surfactants used to prepare the immersion solution. Next, the humidity inside the glove bag is 1
A cleaning container 7 containing chloroform was placed in the cleaning container 7, and the hard disk 3 removed from the surfactant solution was placed in the cleaning container 7, and stirred and cleaned with a stirrer for 15 minutes, and the chloroform was changed twice. Figure 4). This operation removes the surfactant that is not chemically bonded but physically adsorbed onto the hard disk. Through this series of treatments, a film thickness of the surfactant consisting of octadecyltrichlorosilane and heptafluoroethyltrichlorosilane corresponding to the molecular length (in this case, approximately 2.0 mm) is formed on the hard disk.
A chemisorption film 6 was formed with a thickness of 5 nm). The dynamic friction coefficient of the hard disk on which this thin film was formed was 0.1 or less after 200 sliding movements under a load of 20 g, and it was confirmed that it could withstand practical use.

Example 2 Cobalt (90 wt%) - chromium (10 wt%) was deposited on a 20 μm thick polyimide film substrate by vacuum evaporation method.
) A ferromagnetic metal thin film with a thickness of 150 nm was prepared. 100mm× from the substrate on which this ferromagnetic metal thin film was formed.
Cut a piece of 100 mm in size, and add 1 portion of octadecyltrichlorosilane manufactured by Shin-Etsu Chemical Co., Ltd. and heptafluoroethyltrichlorosilane manufactured by Toshiba Silicon Co., Ltd.
: In a surfactant solution dissolved in a non-aqueous mixed solvent (weight ratio 80:12:8) of hexadecane manufactured by Aldrich, chloroform manufactured by Kanto Kagaku Co., and carbon tetrachloride (weight ratio 80:12:8) at a molar ratio of 1 mmol/liter. The sample was immersed for 1 hour in a glove bag kept in a dry state with a humidity of 10% using dry nitrogen gas, and subsequently, unreacted surfactant was washed away with chloroform. Surfactants consisting of octadecyltrichlorosilane and heptafluoroethyltrichlorosilane formed a chemically adsorbed film on the surface of the ferromagnetic metal thin film through siloxane bonds. A chemically adsorbed film is formed with a film thickness equal to the molecular length of the surfactant used (approximately 2.5 nanometers in this case), and the dynamic friction coefficient of the hard disk formed with this thin film is 200 when measured under a 20g load. After several times of sliding, it was 0.1 or less, confirming that it could withstand practical use.

[0023] In the above embodiments, hard disks and magnetic tapes were shown, but the magnetic recording medium of the present invention can also be applied to magnetic disks, magnetic cards, magneto-optical recording disks, etc. it is obvious. Further, for example, in the case of a magnetic tape, the chemical adsorption film of the present invention may be formed on the recording material layer side, or may be formed on the resin base layer side on the back side.

[0024]

As explained above, according to the present invention, there is provided a chemical adsorption film on at least one surface of the magnetic recording medium, in which at least two linear molecules having different numbers of carbon atoms are chemically bonded through siloxane bonds. By forming the chemically adsorbed film, the chemical adsorption film is not scraped off by friction with various members that come into contact with the magnetic recording medium such as the magnetic head and magnetic tape when it runs, and improves lubricity, durability, runnability, and durability. It has excellent abrasion resistance and can be maintained for a long period of time. This chemically adsorbed film is made of linear chlorosilane surfactants with different numbers of carbon atoms having a fluorocarbon group or a methyl group at the end, and by changing the molecular length of each surfactant, magnetic recording media can be The contact area when the magnetic head comes into contact with the magnetic head can be reduced, and frictional wear can be suppressed. Further, by using a surfactant having a fluorocarbon group in a molecule having a small molecular length, it is possible to reduce frictional wear between the molecules, and it is also possible to impart an oil-repellent effect to the film.

[Brief explanation of drawings]

FIG. 1 is a process conceptual diagram of a manufacturing method for forming a chemically adsorbed film on the surface of a magnetic recording medium according to the present invention.

FIG. 2 is a conceptual cross-sectional view of the magnetic recording medium surface before processing, enlarged to the molecular level, for explaining the first embodiment of the magnetic recording medium of the present invention.

FIG. 3 is a conceptual cross-sectional view of the magnetic recording medium surface after processing, enlarged to the molecular level, in order to explain the first embodiment of the magnetic recording medium of the present invention.

FIG. 4 is a conceptual diagram of a manufacturing method for cleaning excess surfactant after forming a chemically adsorbed film on the surface of a magnetic recording medium according to the present invention.

[Explanation of symbols]

1 Petri dish 2 Surfactant solution 3 Hard disk 4 Oxide film 5 Hydroxyl group 6 Chemical adsorption membrane 7. Cleaning container

Claims (6)

[Claims] 1. A magnetic recording medium comprising a magnetic recording material formed on a substrate, wherein at least one surface of the magnetic recording medium is provided with siloxane bonds of at least two or more linear molecules having different numbers of carbon atoms. 1. A magnetic recording medium characterized in that a chemically adsorbed film is formed by bonding via a chemically adsorbed film. 2. The magnetic recording medium according to claim 1, wherein the at least two linear molecules having different numbers of carbon atoms are at least a molecule having a fluorinated carbon group at the end and a molecule having a methyl group at the end. 3. Among at least two or more types of linear molecules having different numbers of carbon atoms, the molecule with a larger number of carbon atoms has a methyl group at its end, and at least one of the remaining molecules has a fluorinated carbon group at its end. The magnetic recording medium according to claim 1. Claim 4: Claim 1, wherein the difference in the number of carbon atoms between at least two or more linear molecules having different numbers of carbon atoms is 1 or more and 15 or less.
The magnetic recording medium described. 5. A manufacturing method for providing a chemically adsorbed film on a magnetic recording medium having a magnetic recording material formed on a substrate, the method comprising: first adding at least two types of linear surfactants having different numbers of carbon atoms; Contact with a solution dissolved in an aqueous organic solution,
A method for manufacturing a magnetic recording medium, characterized in that the excess surfactant on the magnetic recording medium is then removed using an organic solvent. 6. At least two linear surfactants having different numbers of carbon atoms are surfactants having a chlorosilyl group at one end and a fluorocarbon group or a methyl group at the other end. The method for manufacturing a magnetic recording medium according to claim 5.