JPS62197918A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide excellent durability and good lubricating effect for a long period of time and to improve the reliability of a coating type magnetic disk by forming a titled medium into construction in which a specific fluorine compd. exists stably on the medium surface for a long period. CONSTITUTION:At least the surface layer of the thin film of the magnetic recording medium constituted by forming the thin film contg. a magnetic material on the surface of a magnetic base material is formed of an org. polymer contg. the fluorine-contg. group expressed by the formula. The org. high polymer contg. the fluorine-contg. group expressed by the formula is not particularly limited but is preferably a material which is highly resistant to heat and is resistant to wear. A polyamide acid which is the deriv. of a polyimide is a preferable example, and a polyamide acid soln. is mixed with the acid chloride or the fluorine-contg. compd. at an adequate ratio and is brought into reaction therewith. The mixture is mixed with a magnetic coating compd. and after the mixture is coated on a disk, the coating is subjected to a heating treatment to form the polyimide contg. a perfluorpolyether group and to fix the same in the coated film. The perfluorpolymer band group is thereby partly exposed on the medium surface to act as a lubricating agent by which the lubricity for a long period of time is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium having an organic coating film as a sliding surface, and particularly to a magnetic recording medium with excellent durability.

[Prior art]

[Known example closest to the invention; JP-A-50-1265861
Magnetic recording media are used in many fields as media for large-capacity information recording and reproducing devices. audio.

These include magnetic tape as a recording medium for communications, floppy disks as digital signal recording devices, and hard disk media as peripheral storage devices for large computers. All of these recording media are expected to have increased recording capacity, and at the same time are required to have reliability that can withstand long-term operation.

In the case of magnetic recording media, information is written and read in most cases while performing a sliding operation with a head. In some special cases, some devices are devised so that the medium and head do not slide, and information is written and read while maintaining a constant, very narrow gap. It is recognized that in this case as well, the head and the medium come into contact and slide with a certain probability.

An increase in storage capacity inevitably leads to harsher sliding conditions, and improved durability is an essential element. At present, a medium with sufficient durability has not been obtained.

Technologies currently being used to improve durability include:
This method uses lubricants to reduce friction and wear during sliding.

One method is to impregnate the magnetic recording medium layer with a lubricant made of a long-chain fatty acid derivative such as oleic acid or stearic acid. This method is often used for media that mixes magnetic powder with a binder and coats it (!! It is difficult to expect sex.

As an improved method, fluorine-based lubricants with better lubricity (du Pont: Krytx 143,
Method of applying Montefluos (Honbri Y) to the desk surface (US P 3490946.377)
8308).

However, the method of applying the lubricant to the surface of the magnetic layer has the disadvantage that although it is very effective in the initial stage, the lubricant tends to fall off when used for a long period of time, reducing its effectiveness.

On the other hand, with a focus on preventing early drop-off of the lubricant, a method has been proposed in which a fluorine-based surfactant with enhanced adsorption properties is applied to the surface of the medium. (Japanese Patent Application Laid-Open No. 59-116931.

58-41431.58-29147.57-1546
19.57-44226).

The fluorine-based surfactant mentioned here is JP-A No. 58-29147.
The compound Cn Fzn has the following general formula as stated in
+z-X (where n = 4 to 13, or -3OzMe (M
e is K or Na), -8OzF, -COONH4
y-COOH, -8OaH, -○H) or the compound CnFzn+x-0-CHzO-(RO)m-H (in the formula, n is 5 to 131m is An integer of 1 or more, R has 3 to 4 carbon atoms
It is a compound that has an adsorbent functional group at the end, such as (alkylene group).

[Problem that the invention seeks to solve]

In the method of coating the surface of the magnetic layer with a fluorine-based surfactant represented by the above general formula, the molecular weight of the fluorine-based surfactant is too small, so the lubricating effect is not very good, and the durability of the magnetic layer is insufficient. Not improved.

On the other hand, a method in which a perfluoropolyether-based fluorine-based lubricant having a fluorine-containing carbon number of approximately 21 to 65 is applied to the magnetic layer surface exhibits a good lubricating effect because the fluorine-containing alkyl group has a large number of carbon atoms. However, the adhesion to the surface of the magnetic layer is not very good, and simply applying it to the surface of the magnetic layer will not work.
The durability of the magnetic layer cannot be sufficiently improved.However, in the method of coating the magnetic layer with perfluoropolyether carboxylic acid having -COOH at the terminal, the coefficient of friction is small immediately after coating on the surface of the magnetic layer, and the durability of the magnetic layer is considerably improved. However, when used for a long time, the lubricant disappears and good durability cannot be obtained.

In this way, simply fixing the fluorine-based surfactant and fluorine-based lubricant to the surface using interfacial energy does not provide much durability because the fluorine-based surfactant and fluorine-based lubricant tend to detach from the magnetic layer at an early stage. Since the sliding conditions with the magnetic head are particularly severe for magnetic disks, sufficient effects cannot be obtained even if these conventional fluorine-based lubricants and fluorine-based surfactants are applied to the surface of the magnetic layer. .

[Means for solving problems]

In order to achieve this object, the present invention has devised a method for retaining components effective in improving the sliding durability between the medium and the head in a magnetic recording medium for a long period of time.

In order to increase the sliding durability of a medium, it is necessary to interpose a lubricant on the surface that can reduce the friction coefficient and wear rate, and the fluorine-based lubricants and surfactants that have been proposed in the prior art are It has been considered an effective means. Therefore, when we consider their active ingredients, we find that they have a common structure of long-chain perfluoroalkyl groups or perfluoropolyether groups. As long as such a fluorine-based compound exists on the surface, sliding durability will be maintained.

Therefore, a major feature of the present invention is that it has a structure that allows the above-mentioned fluorine-based compound to stably exist on the surface of the medium for a long period of time. Specifically, this is achieved by forming an organic polymer film containing the above-mentioned active ingredient as a bonding group on the sliding surface of the head.

The active ingredient referred to in the present invention is a perfluoropolyether group represented by the following formula.

OC(CzFaO)x-(CFzO)y CFzC
O- (wherein, X is 6 to 32 and y is 10 to 52) There are several methods for introducing these bonding groups into a polymer, but the simplest method is as follows. What is necessary is to prepare an acid chloride having the above-mentioned structure, mix it with a reactive polymeric material having an active group capable of reacting with the acid chloride, and complete the reaction.

An acid chloride having the structure described above can be synthesized as follows. That is, after reacting Honpurin Z-DIAC (manufactured by Nteflos) and thionyl chloride at around 100°C,
When unreacted thionyl chloride and generated SOz gas and HCQ gas are removed by vacuum distillation, the desired acid chloride is obtained.

Examples of active groups that can react with acid chlorides include hydroxyl groups and amino groups, and any polymeric material in which these groups exist at the terminal or side chain can be used in the present invention.

However, as a polymer material, it is desirable to have high heat resistance and wear resistance, and polyimide is a suitable example.
Other effective polymeric materials include polyetheramide polymers, phenolic polymers, epoxy polymers, and the like.

[Effect]

The organic polymer containing a fluorine-containing group mentioned below in the present invention is not particularly limited, but it is preferably a material that has high heat resistance and is resistant to wear.

100-Rf-CO- (In the formula, Rf is a fluorine-containing polyoxyalkyl group.) Polyamic acid, which is a derivative of polyimide, is a preferred example, and a polyamic acid solution is mixed with an appropriate amount of the acid chloride of the fluorine-containing compound mentioned above. and react. This is mixed into a magnetic paint and applied onto a disk, followed by heat treatment to form a polyimide containing perfluoropolyether groups, which is fixed within the paint film.

By doing so, a portion of the perfluoropolyether bonding group is exposed to the surface of the medium and acts as a lubricant. With such a structure, no lubricant components are transferred to the head, and long-term lubricity can be achieved.

The present invention can be used in the following forms.

(A) It is mixed into the binder component of the coating type medium to contain the active ingredient in the magnetic coating film.

(B) Forming a polymer film containing an active ingredient on the surface of a magnetic medium.

In this case, the magnetic film may be of a coating type or a continuous medium.

In the case of a coating medium, the outermost layer may be a film containing magnetic powder.

Hereinafter, the effects of the present invention will be explained in detail using Examples.

[Example 1] 57 g of sufficiently dehydrated p-phenylenediamine (0,5
25 mol) in 1000 g of N-methyl-2-pyrodrine, 147 g (0.50 mol) of 3.3',4.4'-bisphenyltetracarboxylic dianhydride are added. These mixtures are sufficiently stirred to prepare a polyamic acid solution Cll of the following formula.

After that, an acid chloride type fluorine-based compound CjlOC-(CaF22)x-(CFzO)y-CF of the following formula was added to the polyamic acid solution [11].
z-COCQ (in the formula, X is 10, y is 14) is 0.02
A solution (It) is prepared by adding 5 molar amount and stirring homogeneously. As a result, the terminal functional group of the acid chloride-type fluorine-based compound reacts with the amino group in the polyamic acid solution, and the rainer becomes -CON.
II- is connected. Thereafter, the solution (II) is vacuum distilled to remove the generated HCfi gas.

Next, a 0.2 μm thick vapor-deposited thin film of an alloy with a Co/Ni weight ratio of 4 was created on the surface of the aluminum plate in advance.
The above solution [111] is applied to a thickness of 0.1 μm on this magnetic thin film and then thermally cured at 300° C. to form a lubricating layer.

The durability of the magnetic thin film thus obtained was evaluated using a spherical sliding tester. In other words, the load Log on the sapphire spherical slider
and rotate the disk at a circumferential speed of 10 m/s,
The results are shown in Table 1. As a comparative example, the fluorine-containing lubricant Honprin Z-DIAC (Montefros II) was simply applied onto the magnetic thin film. I used a case.

As a result, the lubricating layer of the present invention was superior in that the total number of rotations until the magnetic thin film was damaged was larger than that of the comparative example.

[Example 2] A binder consisting of 45 g of bisphenol type epoxy resin, 40 g of resol type phenol resin, and 15 g of polyvinyl butyral resin was mixed with 40 g of cyclohexanone resin.
In a solution dissolved in 0 g.

A solution [ml] was prepared by dispersing 150 g of magnetic iron oxide (7FaxOa) using a ball mill.

Next, the above resol type phenol resin and the following acid chloride type fluorine compound are mixed in equimolar amounts to prepare 50 g of a mixture.

CQOC-(CiFiO)x-(CFzO)y-CFz
-COCQ (wherein, X is 10 and y is 14) Next, 5 parts of the mixture is dissolved in 100 g of cyclohexanone and reacted by heating. After that, vacuum distillation is performed, and the generated HCO
Remove the gas and create a solution [IV]. This solution [IV
] was added to 5 g of solution [mllOO] to prepare solution (V).

Furthermore, solution [VI] was prepared by dispersing solution [V] by ball mill kneading.

Next, the above solution [VI] is applied to an aluminum plate whose surface has been cleaned in advance. The magnetic powder in this coating film is oriented by a well-known method and then thermally cured at 300°C.

The durability of the magnetic coating film thus obtained was evaluated using a spherical sliding tester. In other words, the load Lo on the sapphire spherical slider
The results are shown in Table 1, but as a comparative example, Honprin Z-DIA
A case was used in which a magnetic coating film was created after C (manufactured by Monteflos) was simply mixed into the solution [■]. As a result, the magnetic coating film of the present invention was superior in that the total number of rotations until the magnetic coating film was damaged was larger than that of the comparative example.

[Example 3] Magnetic oxide film (Y-F ezoa) 68 g, VA
GH (vinyl chloride-vinyl acetate-vinyl alcohol copolymer manufactured by U, C, C, USA) 26 g, N1482J (acrylonitrile-butadiene copolymer manufactured by Nippon Zeon Co., Ltd.) 5 g, Coronate L (polyisocyanate manufactured by Nippon Polyurethane Co., Ltd.) 2g, carbon black 7g, toluene 7g
5 g of methyl isobutyl ketone and 75 g of methyl isobutyl ketone were mixed and dispersed in a ball mill to prepare a solution [■].

On the other hand, 2,2-bis(4(4-aminophenoxy)phenyl)propane and the following acid chloride type fluorine-based lubricant CQOC-(CzFtO)x (CFzO)y-CF
A 5% solution of a molar reactant such as z-COCA (wherein is 10 and y is 14) in N-methyl-2-pyrrolidone [■] is prepared. Add 30 g of this solution [■] into a ball mill and thoroughly disperse and mix to prepare solution [1].

The solution [1X] was applied to a disc-shaped polyester film with a thickness of 75 μm so that the dry thickness was 3 μm.

It was dried to form a magnetic coating.

The durability of the magnetic coating film thus obtained was evaluated using a spherical sliding tester. In other words, the load Log on the sapphire spherical slider
The results are shown in Table 1, where the disk was rotated at a circumferential speed of 10 n/s and evaluated based on the total number of rotations until the magnetic coating was damaged. A comparative example shows a case in which a magnetic coating film was formed on a disc-shaped polyester film with a thickness of 75 μm to a dry thickness of 3 μm using a solution [■], and Honprin Z-DIAC (manufactured by Monteflos) was applied. Ta. As a result, the magnetic coating film of the present invention was superior in that the total number of rotations until the magnetic coating film was damaged was larger than that of the comparative example.

〔Effect of the invention〕

As is clear from this example, the magnetic coating film of the present invention has excellent durability, exhibits a good lubrication effect over a long period of time, and can improve the reliability of coated magnetic disks.

Claims (1)

[Claims] 1. In a magnetic recording medium in which a thin film containing a magnetic substance is formed on the surface of a magnetic base material, at least the surface layer of the thin film is made of an organic polymer containing a fluorine-containing group represented by the following general formula. A magnetic recording medium made of molecules. -OC-Rf-CO- (In the formula, Rf is a fluorine-containing polyoxyalkyl group.) 2. A patent in which the thin film containing a magnetic material is a coating film in which the binder contains a fluorine-containing organic polymer and magnetic powder is dispersed. Claim 1
Magnetic recording medium described in Section 1. 3. The magnetic recording medium according to claim 1, wherein the thin film containing the magnetic material is a continuous film of the magnetic material formed by vapor deposition, sputtering, or the like.