JPS63268117A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve sliding durability with a magnetic head by forming a protective film consisting of a thin org. film contg. a specific fluorine lubricating agent on the surface of a thin film which is provided on a nonmagnetic substrate and contains a magnetic film. CONSTITUTION:The fluorine lubricating agent expressed by the formula Rf-X1-X2 (Rf is a perfluorinated polyoxyalkyl group; X1 is a direct bond or -O-, -CH2O-, -CO2-, -CONH-; X2 is an org. high polymer) is incorporated into the surface of the thin org. film 1.3 of a magnetic recording medium disposed with the thin org. film (magnetic coated film layer) 1 into which the magnetic layer is incorporated on the surface of the nonmagnetic substrate 2 or a magnetic recording medium formed with the thin continuous film (thin magnetic film layer) 4 of the magnetic material on the substrate 2 and coated with the protective film of the film 3 on the surface thereof. The X2 part of such fluorine lubricating agent has high compatibility with the thin org. film 1.3 and the Rf part has the poor compatibility therewith. The Rf group is, therefore, exposed and oriented on the surface of the film 1.3 and the X2 part is securely fixed on the medium surface when the film is cured as it is. The excellent lubricating effect is thereby maintained for a long period of time and the durability of a magnetic disk etc., is enhanced.

Description

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

[Conventional technology]

Magnetic disks are applied in many fields for large capacity information storage and playback devices. These include floppy disks as digital signal recording devices, and hard disks as peripheral storage devices for large computers.

All of these magnetic disks are expected to have an increased recording capacity, and at the same time are required to have reliability that can withstand long-term operation.

Information is written to and read from the magnetic disk while it slides against the bed. In some special cases, some devices are devised so that the magnetic disk 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 magnetic disk 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, magnetic disks with sufficient durability are not available.

Technologies currently being used to improve durability include:
This is a method to reduce friction and wear during sliding with the help of im lubricants.

One method is to impregnate the magnetic recording medium layer of a magnetic disk with a lubricant made of a long-chain fatty acid derivative such as oleic acid or stearic acid. This method is often used in magnetic recording media of the type in which magnetic powder is mixed with a binder and applied, but the lubricant scatters little by little from the surface, making it difficult to expect long-term lubricity.

As an improved method, fluorine-based lubricants with better lubricity (du Pont: Krytox 143,
A method of applying Montefluos Nihonpurin Y) to the surface of a magnetic disk (US Pat. No. 3,490,046).

No. 3778308). However, the method of applying the lubricant to the surface of the magnetic recording medium is very effective at the initial stage, but has the disadvantage that, after long-term use, the lubricant may fall off, reducing its effectiveness.

On the other hand, with a focus on preventing early drop-off of lubricant, a method has been proposed in which a fluorine-based surfactant with enhanced d-adsorption properties is applied to the surface of a magnetic recording medium. (Unexamined Japanese Patent Publication No. 59-116931
No. 58-41431, No. 58-29147.

No. 57-154619, No. 57-44226). The fluorine-based surfactant mentioned here is JP-A No. 58-29147.
The compound Cn having the following general formula described in the publication No.
F zn"x""X (wherein n = 4 to 13, or polar group
(Me is K or Na), -8O2F, -COON
H4゜-COOH, -S Oa I-I, -OH)
On the other hand, with a focus on preventing early drop-off of the lubricant, a US patent has been granted for a method for fixing fluorine-based lubricant to the surface of magnetic recording media.
No. 412O995, JP-A-54-36171.

No. 59-2O3239, No. 60-38730, No. 5
This method has been proposed in 9-172159 and 61-39919. This is a compound Rf -S i X a (wherein Rf is a perfluoroalkyl group, or a halogen, cyanide, or alkoxy group) having the following general formula, or JP-A-60-109028 and JP-A-60-101717.

There is a phosphoric acid type proposed in Publication No. 60-24602O. This is a compound Rf-P (○)-〇- (in the formula, R is a perfluoroalkyl group), which has the following general formula, and is a type of lubricant that reacts and adheres to the surface of metal films or oxide films. .

[Problem that the invention aims to solve]

In the method of applying a fluorine-based surfactant represented by the above general formula to the surface of a magnetic recording medium of a magnetic disk, the fluorine-based surfactant is not firmly fixed to the surface, so it scatters from the sliding surface during sliding. As a result, the durability of the magnetic disk cannot be sufficiently improved, nor can the durability of the storage device be improved.

U.S. Patent No. 412O995, JP 54-3617
No. 1.

No. 59-2O3239, No. 60-38730, No. 5
No. 9-172159.

The method described in publications such as No. 61-39919 fixes the lubricant on the surface of the magnetic recording medium through a chemical reaction, so it is difficult to detach from the sliding surface and is expected to significantly improve durability. It has the disadvantage that the reaction is fixed and it is difficult to obtain a homogeneous reaction film, so it is very difficult to apply in actual production lines. Furthermore, the chain length of the hook chain is too small, so the lubricating effect is not very good, and the durability of the magnetic recording medium is not sufficiently improved.

As described above, conventional fluorine-based surfactants and fluorine-based lubricants do not significantly improve the durability of magnetic disks, and
Chemically bonding lubricants to surfaces is impractical.

[Means for solving problems]

To summarize the present invention, the present invention relates to a magnetic recording medium and a storage device using the same, and the present invention is a magnetic recording medium in which a magnetic recording film containing a magnetic material is formed on the surface of a non-magnetic base material. It is characterized in that at least the surface layer of the thin film is formed of an organic polymer film containing a fluorine-containing group that is effective in improving sliding durability.

In order to achieve the above-mentioned object, the present invention has been developed as a result of studying a method for retaining components effective in improving the sliding durability of a magnetic recording medium and a head in a magnetic recording medium for a long period of time.
It has been reached.

In order to increase the sliding durability of magnetic recording media, it is necessary to interpose a lubricant on the surface that can reduce the friction coefficient and wear rate, and the reactive fluorine-based lubricants that have been proposed in the prior art are It has been considered an effective means. However, since the sliding durability is insufficient and the fixing method is extremely difficult, in the present invention, a fluorine-based compound in which a long-chain perfluorinated polyoxyalkyl group and a long-chain organic polymer chain are bonded is used. The major feature is that we devised a method that allows it to be fixed to the surface simply by mixing it with a coating material to create a magnetic recording medium. Moreover, it is characterized by the use of organic polymer chains that are highly compatible with the organic thin film of the magnetic disk. Specifically, this is achieved by forming an organic polymer film containing a fluorine-based compound having the above-mentioned long-chain perfluorinated polyoxyalkyl group on the sliding surface with the head.

[Effect]

An example of the perfluorinated polyoxyalkyl group referred to in the present invention is represented by the following general formula (% formula %), and the fluorine-based compound is 10-, -CHzO-, -COO- in the perfluorinated polyoxyalkyl group.

It is bonded to an organic polymer material through a bonding group such as -CON H-1 or by a direct bond. As the organic polymer material, the following general formula (wherein R1 is a direct bond or -CHx-CH(OH)
CH2, R2 are -CH-CHz-1 or -CH-C
2H4-5R3 is -CmH2m+x, -C(CHa)a
, or -CHz OHlm is an integer from 0 to 18, and n is
an integer of 1 or more), or a copolymer thereof, or the following general formula (wherein, R number is -G Hz -CH(○H)CHz-1
R6-CHa, -CxHs, -CIIH7, -CFat
may be the same or different) (n is an integer of 1 or more) or the molecular skeleton contains the following general formula (%). A specific example of the fluorine-based compound at this time is a compound having the following general formula in which a long chain perfluorinated polyoxyalkyl group is bonded to a vinylphenol copolymer represented by the above general formula as a basic skeleton. It is something.

Rf -CH-CHz□ (wherein, Rf is a perfluorinated polyoxyalkyl group, n
is an integer of 1 or more) When the above fluorine-based compound and organic thin film material are mixed to create a coating film, the fluorine-free vinylphenol group in the fluorine-based compound is highly compatible with the organic thin film, so it blends well with the organic thin film.
On the other hand, since perfluorinated polyoxyalkyl groups have very poor compatibility with organic thin films, perfluorinated polyoxyalkyl groups are oriented on the surface of the coating film, and vinylphenol groups that do not contain fluorine are oriented inside the coating film. By curing the coating film in this state, the perfluorinated polyoxyalkyl groups are exposed and oriented on the coating surface, and the fluorine-free vinylphenol groups are firmly fixed to the surface of the magnetic recording medium, providing a sufficient and excellent lubrication effect. The durability of the magnetic disk is sufficiently improved by being connected for a long time.

The organic polymer agent used in the present invention is not particularly limited, and may be polyester-based or polyamide-based.

Polyimide-based, polyurethane-based, polyacrylic-based.

Polyether amide type, polyvinyl butyral type.

Either phenol type or epoxy type may be used.

The present invention can be used in the following forms.

(A) Magnetic powder is mixed with a binder and mixed into a coated magnetic recording medium, and perfluorinated polyoxyalkyl groups are oriented on the magnetic coated surface.

(Structure shown in FIG. 1) (B) A continuous thin film of a magnetic material is formed, and perfluorinated polyoxyalkyl groups are oriented on the protective film formed on the surface of the continuous medium.

(Structure in FIG. 2) FIGS. 1 and 2 are cross-sectional views of the magnetic medium surface of coated type and continuous thin film type magnetic disks.

In each figure, numeral 1 means a magnetic coating film 5 (layer containing a fluorine compound), 2 means an aluminum substrate, 3 means an organic coating film (a layer containing a fluorine compound), and 4 means a magnetic thin film layer. In this case, the magnetic film may be of a coating type or a continuous medium. In the case of a coating type, the outermost layer may include a magnetic layer.

Figure 3 shows the results of measuring the concentration of fluorine compounds (Fl) on the surface and inside (50 depths) using xPS after creating a protective film containing the fluorine compound of the present invention on the surface of a continuous medium. It can be seen that the fluorine compound is oriented only on the extreme surface.

〔Example〕

Hereinafter, the effects of this research will be explained in detail in Examples, but the present invention is not limited to these Examples.

Example 1 22 g (0,
A mixed solution of CFs (in the formula n is 14 on average) and 100 g of trifluorotrichloroethane is sealed. Next, thionyl chloride (S OCQ z) Log
was sealed, heated at 80°C for 4 hours, and continued stirring. After the reaction is completed, unreacted S OCQ z, HF as a reaction byproduct, and 1-lifluorotrichloroethane as a solvent are removed by vacuum distillation to produce a reaction product (1).

On the other hand, 100 g of methyl ethyl ketone dehydrated with anhydrous magnesium sulfate was mixed with 2.5 g of P-vinylphenol copolymer (trade name Niresin M) manufactured by Cosmo Oil Co., Ltd.
A mixture of 30 g of trifluorotrichloroethane dehydrated with anhydrous magnesium sulfate and 0.6 g of triethylamine (EtsN) was introduced into a three-hole flask equipped with a reflux device containing reactant (1). ,
Continue the reaction at 60°C for 4 hours. After the reaction, methyl ethyl ketone, trifluorotrichloroethane and triethylamine are removed by vacuum distillation to obtain 20 g of a dark brown viscous reaction product (11) of the following formula.

Rf (wherein Rf is a perfluorinated polyoxyalkyl group, m
, n is a ratio of 1:1) 0.04 g of this reactant (II)
is dissolved in a mixed solution of 50 g of methyl ethyl ketone and log of trifluorotrichloroethane to prepare solution (1).

Next, 48 g of Resin M (Cosmo Oil Co., Ltd.) and trifunctional epoxy resin manufactured by DuPont (trade name: xD9053) ss
As a binder consisting of g and a curing accelerator, onium compound triethylammonium calibol salt (trade name: TEA-K) from Hokko Chemical Co., Ltd. was added to methyl ethyl ketone 2.
After dissolving in a mixed solution of O0g and 150g of cyclohexanone, 150g of magnetic iron oxide (Y-F ezoa)
and dispersed by ball mill kneading (n)
was prepared.

60 g of solution (I) is added to this solution (n), thoroughly kneaded in a ball mill, and then 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. Next, the magnetic disk was completed by thermosetting at 250°C.

The durability of the magnetic disk thus obtained was evaluated using a spherical sliding tester. That is, a load Log is applied to the sapphire spherical (R30) slider, the peripheral speed is 10 m/s, and the zero ambient temperature is 2.
The disk was rotated at 5° C., and the total number of rotations until the magnetic coating was damaged was evaluated.

As a comparative example, the solution [■] was dispersed by a ball mill, applied to an aluminum plate with a clean surface, the magnetic powder was oriented, and it was cured at 250°C to create a magnetic disk.
A fluorine-based lubricant, U.S.P.
A case in which Krytox 143 AC described in No. 3,490,946 was simply applied was used.

As a result, as shown in Table 1, the magnetic disk of the present invention was superior to the comparative example in that the total number of revolutions until the magnetic coating was damaged was larger.

Example 2 In a three-hole flask with a 500 mΩ reflux device, 4.5 g (0.02 mol) of trifunctional epoxy resin (trade name: XD9053) manufactured by Dow Chemicals Co., Ltd. was added to a mixed solution of 50 g of methyl ethyl ketone and 50 g of dimethylformamide. Seal the solution and heat the solution while stirring. Thereafter, 22 g (0.02 mol) of the following fluorine compound (prototype manufactured by Nippon Mectron Co., Ltd.) was dehydrated with anhydrous magnesium sulfate.

A mixed solution of 0.3 g of sodium hydride (NaH) and 50 g of methyl ethyl ketone was slowly added dropwise into the three-ring flask, and the reaction was continued at 80° C. for 5 hours. After the reaction, the reactant is repeatedly washed with water and then purified by vacuum distillation.
2Og of a dark brown viscous reaction product (I[I) of the following formula is obtained.

(In the formula, Rf is F(CF(CFa)-CFz 0-)
-■ CF(CFa)-, m is 7 on average, R6 is -Ca HI!
-1R7 is -○CHz -CH-CHz -, n is an integer from 1 to ■H ).

Next, a solution (n) was prepared in the same manner as in Example 1.

60 g of solution (m) is added to this solution (II), thoroughly kneaded in a ball mill, and then 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. Next, the magnetic disk was completed by thermosetting at 250°C.

The durability of the thus obtained magnetic disk was evaluated using a spherical sliding tester in the same manner as in Example 1.

As a result, as shown in Table 1, the magnetic disk of the present invention was superior to the comparative example shown in Example 1, with a higher total number of revolutions until the magnetic coating was damaged.

Example 3 A mixed solution of 50 g of methyl ethyl ketone dehydrated with anhydrous magnesium sulfate and 50 g of dimethyl formamide was placed in a 500 mQ three-hole flask with a reflux device, and then an epoxy resin (trade name: EP-1004) manufactured by DuPont Co., Ltd. (trade name: EP-1004) 48
g (0.02 mol) and dissolve while stirring at 80'C. Then, a fluorine compound of the following formula (Nippon Mectron Co., Ltd. l) 2 was dehydrated with anhydrous magnesium sulfate.
6g (0,024 mol).

F(CF(CFa)-CFz-0-), -CF(CF3
) -CI+2-0H (in the formula, 1 m is 7 on average) 0.3 g of sodium hydride (NaH), 30 g of trichlorotrifluoroethane, 50 g of methyl ethyl ketone
Slowly drop 80 g of the mixed solution while stirring.
Heated at ℃ for 4 hours. The reaction solution was returned to room temperature, thoroughly washed with water, and purified by vacuum distillation.

A light brown viscous reaction product (IV) having the following formula was obtained.

(In the formula, Rf is F(CF(CFs) -CFz-0-)
, -CF (CFa) This reactant (IV) 0.08 g
was dissolved in a mixed solution of 50 g of methyl ethyl ketone and 10 g of trifluoro-1-lichloroethane to form solution (IV).
Mix. Next, the epoxy resin Epicoat (E
P1004) 48 g (0.02 mol), and Heatanol 1501, a phenolic resin (Hitachi Chemical Co., Ltd.)
(manufactured by Hokuko Chemical Co., Ltd.) 8-8 g (0.02 mol) and 0.59 g of triethylammonium carbol salt (manufactured by Hokko Chemical Co., Ltd., part name: TEA-K), which is a curing accelerator, were mixed with 200 g of methyl ethyl ketone and 150 g of dimethyl formamide. Dissolve in a solvent to create solution (V). This solution (
A mixed solution (VI) of V) and solution (IV) is prepared.

Next, after alumite treatment was performed on the surface of the 5-inch aluminum alloy disk, this disk was installed in a vacuum evaporation device, and the 5-inch aluminum alloy disk was
The cobalt-chromium alloy was heated and evaporated under a vacuum of X10''1I Torr to form a 0.2 μm thick ferromagnetic thin film layer of the cobalt-chromium alloy on the disk. Solution (VI) was applied onto this disk and thermally cured at 250° C. to complete a magnetic disk.

The durability of the magnetic disk thus obtained was evaluated using a spherical sliding tester in the same manner as in Example 1.

As a comparative example, the surface of a 5-inch aluminum alloy disk was subjected to alumite treatment, and then this disk was installed in a vacuum evaporator to heat and evaporate the cobalt-chromium alloy under a vacuum of 5 x 10-5 Torr, resulting in a thick layer on the disk. A ferromagnetic thin film layer made of a cobalt-chromium alloy with a thickness of 0.2 μm was formed. A magnetic disk is prepared by coating the solution (V) on this disk and thermosetting it at 250°C.
A case where 3AC was simply applied was used.

As a result, as shown in Table 2, the magnetic disk of the present invention was superior to the comparative example in that the total number of rotations until the magnetic coating was damaged was larger.

Table 1 Table 2 [Effects of the Invention] As is clear from this example, the magnetic recording medium of the present invention and the storage device using the same have excellent sliding durability.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the surface of a magnetic medium according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the surface of a magnetic medium according to another embodiment, and FIG.
The figure is a diagram showing the spectral intensity when the protective film of the present invention is created. 1...Magnetic coating layer, 2...Aluminum substrate, 3...Organic coating film, bamboo 3 Nail a! (b)

Claims (1)

[Claims] 1. A magnetic recording medium in which an organic thin film containing a magnetic substance is formed on the surface of a non-magnetic base material, or a continuous thin film of a magnetic substance is formed on the surface of a non-magnetic base material, and In a magnetic recording medium whose surface is coated with a protective film of an organic thin film, the surface of the organic thin film has the following general formula Rf-X_1-X_2 (wherein Rf is a perfluorinated polyoxyalkyl group, X_
1 is a direct bond or -O-, -CH_2O-, -CO
A magnetic recording medium characterized in that O-, -CONH-, and X_2 are organic polymer materials) and contain a fluorine-based lubricant.