JPH03237618A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To uniformly apply fine particles in a good dispersion state on a polymer substrate and to form a uniformly rugged surface of a metal alloy thin film magnetic layer by subjecting the polymer film to surface treatment to obtain <=70 deg. contact angle of the surface, dispersing the fine particles thereon, and then forming the alloy thin film magnetic layer thereon. CONSTITUTION:The polymer film 1 is subjected to surface treatment so that the contact angle of the film 1 becomes <=70 deg., on which fine particles 2 are dispersed, and further an alloy thin film magnetic layer 3 is formed on the film 1. Then an oxide layer or carbon protective film is formed on the alloy thin film magnetic layer 3, and a fluorinated lubricant is applied thereon to form a protective layer 4. Thereby, wettability of a solvent for fine particles is improved to give good dispersion state of the particles, and shapes of the fine particles remain on the surface of the magnetic layer to give a uniform rough pattern to the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium such as an alloy thin film type having excellent durability and running properties and high reproduction output, and a method for manufacturing the same.

BACKGROUND ART Magnetic recording and reproducing devices are becoming denser every year, and there is a demand for magnetic recording media with excellent short wavelength recording and reproducing characteristics. Currently, coated magnetic recording media in which magnetic powder is coated on a non-magnetic substrate are mainly used, and although characteristics have been improved to meet the above requirements, the recording density is almost reaching its limit.

Alloy thin film magnetic recording media are currently being developed to overcome this limit. Alloy thin film magnetic recording media are produced by vacuum evaporation, sputtering, plating, etc., and have excellent short wavelength recording and reproducing characteristics. The magnetic layer in the alloy thin film magnetic recording medium includes Co, Co-Ni
, Co-N1-P, Fe-○, etc. thin film for in-plane recording;
Co-Cr, Co-0, Co-Ni-Cr, Co-Cr
Mo, Co-Cr-W, Co-Cr-Nb, C.

Perpendicular recording thin films made of Co-based alloys such as Cr-Ta, Co-V, and Co-Cr-A1 are promising.

Problems to be Solved by the Invention Although such alloy thin film magnetic recording media have excellent short-wavelength recording and reproducing characteristics, they are easily scratched when recording and reproducing by bringing the magnetic head into contact with the medium, resulting in poor durability. However, there were problems with poor performance and running performance.

In order to solve this problem, it has been considered to provide the surface of the thin film magnetic layer with an appropriate surface roughness.

One of the methods is to deposit SiO2, Al2O. There is a method of dispersing and coating fine particles such as, for example, forming a magnetic layer thereon, and forming irregularities on the surface of the thin Ill magnetic layer. With this method, it is possible to form irregularities on the surface of the magnetic layer while maintaining the magnetic properties of the magnetic layer.
It is not easy to coat the polymer film uniformly, and especially when the particle size of the particles is about 50 nm or less, the particles tend to aggregate on the polymer film, which may actually reduce the durability of the medium. This may cause deterioration or increase the spacing loss between the head and the magnetic layer during recording and reproduction, resulting in a decrease in recording and reproduction output.

Means for Solving the Problems The present invention was invented in view of the above-mentioned problems, and involves dispersing fine particles on a polymer film whose surface has been treated so that the contact angle of the surface is 70 degrees or less. A magnetic recording medium and a method for manufacturing the same are characterized in that they are more powerful than a structure in which an alloy thin film magnetic layer is formed thereon.

According to the present invention, the surface of the polymer film is modified to lower the contact angle and improve the solvent applicability, thereby improving the dispersion state of the particles. Furthermore, when an alloy thin film magnetic layer is formed on a film in which these fine particles are uniformly dispersed, the shape of the fine particles is preserved on the surface of the magnetic layer.
--like unevenness is formed on the surface. When a magnetic head is brought into contact with this medium for recording and reproduction, the actual contact area between the medium and the head is reduced, and the coefficient of friction is reduced. As a result, the medium is less likely to be scratched, and compared to a thin magnetic layer formed without applying fine particles to the film, running properties are improved and durability is greatly improved. Compared to coating microparticles on a polymer film with a contact angle of 70' or more, spacing is reduced due to reduced agglomeration of microparticles.
While high reproduction output is obtained, the occurrence of scratches on the medium caused by aggregates of fine particles is reduced, and the durability of the medium is also improved.

Example The present invention will be described below based on a specific example.

Example 1 FIG. 1(a) schematically shows the structure of a magnetic recording medium according to an example of the present invention. In Fig. 1(a), 1 is a polymer film whose surface has been treated so that the contact angle on the film surface is 70' or less, 2 is a fine particle coated on the polymer film, and 3 is a polymer film further formed on the polymer film. This is an alloy VIT magnetic layer. Usually, a protective layer 4 is formed by forming an oxide layer or a carbon protective film on the surface of the alloy thin film magnetic layer, and then applying a fluorine-based lubricant.

Next, a case where the surface of the substrate is treated using acid treatment will be explained. As a polymer substrate, the thickness is 10 μm and the width is 150 m.
A polyimide film was continuously treated by immersing it in a chromic acid solution having a concentration of 10 pp-. When the contact angle of the polyimide substrate was measured before and after treatment, it was over 90 degrees before treatment, but it decreased to a minimum of 30 degrees after treatment with chromic acid. Hydrochloric acid, sulfuric acid, nitric acid, and polyphosphoric acid were used in place of chromic acid as surface-treating acids, and the effects were almost the same as those of chromic acid.

Next, the polymer film treated with acid as described above was
While traveling at a running speed of 0 m/+in, Sin particles with a particle size of about 15 nm dispersed in a solvent containing IPA (isopropyl alcohol) as the main solvent were applied onto a polymer substrate. At this time, the size of the fine particles is 5nIll to 50nm.
is appropriate. If the particle size is less than 5 nm, it will have little effect on improving the durability of the medium.On the other hand, if the particle size exceeds 50 nm, the spacing loss between the head and the medium will increase during recording and playback, resulting in a significant drop in output. .

Next, on the polyimide substrate coated with 5iOz, a film thickness of 25
A 0na+ Co--Cr perpendicular magnetic anisotropic film was formed by vacuum evaporation. Thereafter, the Co--Cr perpendicular magnetic anisotropy film was run along the circumferential surface of the cylindrical can at 300° C. in the atmosphere to form an oxide layer on the surface.

The medium produced as described above was slit into a width of 8W and was evaluated by placing it on a commercially available 811Ili VTR deck.

The resulting contact angle dependence is shown in FIGS. 2 and 3. FIG. 2 shows the contact angle dependence of still durability time. The still durability time is evaluated by the time it takes for the playback output to become half of the time at the start of measurement. However, this measurement was completed in a maximum of 60 minutes.

It was found that media with a polymer film contact angle of 90" or more had a still life of about 5 minutes, while media with a contact angle of 70° or less had a still life of more than 60 minutes, indicating improved durability. FIG. 3 shows the contact angle dependence of the reproduction output.

According to this, it was found that when the contact angle is 70° or less, there is almost no difference in reproduction output, but when the contact angle is 70° or more, the output decreases as the contact angle increases.

From the above, the contact angle can be increased to 70 by film surface treatment.
When using a polymer film l whose temperature is below 100°C, the dispersibility of the fine particles 2 is significantly improved, the unevenness of the surface of the magnetic recording medium becomes uniform, and the spacing loss between the head and the medium is greatly reduced. It is thought that the durability has been significantly improved.

In the above, Sin was used as the fine particles, but AIzO
The present invention is also effective for fine particles such as i. In addition, IPA was used as a solvent for dispersing the fine particles, but ethanol, acetone, MEK (methyl ethyl ketone), MIB
K (methyl isobutyl ketone), and as a polymer substrate, the present invention is effective not only for polyimide films but also for polyamide films, polyetherimide films, polyethylene naphthalate films, and polyethylene terephthalate films.

In addition, although the case where the contact angle of a polymer film is lowered by acid treatment has been explained above, ultraviolet treatment using ultraviolet rays generated from an ultraviolet lamp in the atmosphere, oxygen,
UV treatment in ozone atmosphere, corona treatment in air, RF in vacuum.

A similar effect can be obtained by lowering the contact angle of the polymer film using a method such as glow discharge treatment using DC glow.

Embodiment 2 FIG. 4 is a diagram showing an example of a substrate processing apparatus using an ion gun. The polymer substrate 11 is unwound from the supply roll 13, moves in the direction of arrow A along the circumferential surface of the cylindrical can 12, and is taken up by the take-up roll 14. During this time, the surface of the polymer substrate 11 is treated on the circumferential surface of the cylindrical can 12 by the ion beam 16 emitted from the ion gun 15 . The ion gun 15 is the same as one normally used in ion beam sputtering, ion milling, and the like. In this apparatus, the reason why the substrate ion treatment is performed on the surface of the cylindrical can is to prevent the substrate from being thermally damaged by dissipating the heat generated on the substrate by the ion beam to the cylindrical can.

A polyimide film with a thickness of 10 μm was used as the polymer film, and the substrate was subjected to ion treatment at a speed of 10 m/Iin. The ion gun used was a Kaufmann type, the acceleration voltage of the ion gun was 300 V, and the ion current density was 0.2 m A/ail.
, the gas introduced into the ion gun is Ar, and the amount introduced is 20cc/s.
It was set as in. At this time, the accelerating voltage of the ion gun is 100v
Although there is no sufficient effect of substrate modification below, 1500 V
In this case, the substrate is thermally damaged and deteriorates. Also, for the same reason, the current density of the ion gun is 0.
．． 1 mA/cm2 to 1.5 mA/cffl is suitable.

The contact angle of the polymer film treated in this way was 60
It was °. This film was subjected to a surface oxidation treatment in the air after dispersing fine particles and depositing a Co-Cr perpendicular magnetic anisotropic film in the same manner as in Example 1, resulting in the results shown in Figures 2 and 3. Similarly, the still durability time increased by more than 10 times and the reproduction output increased by 5 dB compared to the one without ion treatment.

Example 3 A polyimide film having a thickness of 10 μm and a width of 150 m+ was continuously treated using the solutions shown in Table 1.

When the contact angle of this polyimide film was measured, the contact angle was around 65° for all samples.

m of the magnetic recording medium produced using this polymer film
s is shown in FIG. 1 (b). In FIG. 1 (g), 5 is a polymer film, 6 is a treated layer containing a compound that reduces the contact angle of the polymer film, and 2.3.4 is a first
They are the same as in Figure (a) and consist of fine particles, an alloy thin film magnetic layer, and a protective layer, respectively.

When a Co-Cr perpendicular magnetic recording medium is formed in exactly the same manner as in Example 1 using a polymer film coated with the above compound layer, the medium coated with a compound layer with a low contact angle in exactly the same manner as in Example 1 is It showed excellent durability and high playback output.

Effects of the Invention According to the method for manufacturing a magnetic recording medium of the present invention, fine particles can be uniformly coated on a polymer substrate with good dispersion. As a result, it becomes possible to form -like unevenness on the surface of the alloy thin film magnetic layer. This medium maintains high reproduction output and at the same time exhibits excellent durability and runnability.

[Brief explanation of drawings]

FIG. 1(a) is a cross-sectional view of a magnetic recording medium manufactured by the manufacturing method of the present invention, FIG. 1(b) is a cross-sectional view having a treated layer of the present invention, and FIGS. FIG. 4 is an explanatory diagram showing an example of a manufacturing apparatus for carrying out the present invention. 1...Surface treated polymer film, 2...
...Fine particles, 3...Alloy thin film magnetic layer, 4.
...Protective layer, 5...Polymer film, 6
...Processing layer, 11 ... Polymer film, 12 ... Cylindrical can, 13 ... Supply 0-ru, 14 ... Winding roll, 15...
...Ion gun, 16...Ion beam.

Claims (1)

Scope of Claims: (1) A first step of reducing the contact angle of the polymer film surface to 70° or less by surface treatment of the polymer film, and a second step of applying fine particles on the polymer film. and a third step of forming an alloy thin film magnetic layer on the polymer film. (2) The method for manufacturing a magnetic recording medium according to claim (1), wherein the surface treatment is performed by acid treatment. (3) The method for manufacturing a magnetic recording medium according to claim (1), wherein the surface treatment is performed by ultraviolet treatment. (4) The method for manufacturing a magnetic recording medium according to claim (1), wherein the surface treatment is performed using ultraviolet rays in an atmosphere containing oxygen, ozone, or both. (5) The method for manufacturing a magnetic recording medium according to claim (1), wherein the surface treatment is performed by corona treatment. (6) The method for manufacturing a magnetic recording medium according to claim (1), wherein the surface treatment is performed by glow treatment. (7) The method for manufacturing a magnetic recording medium according to claim (1), wherein the surface treatment is performed using ions emitted from an ion gun. (8) Set the ion gun acceleration voltage to 100 to 1500.
8. The method for manufacturing a magnetic recording medium according to claim 7, wherein the surface treatment is performed at a current density of 0.1 to 1.5 mA/cm^2. (9) In the step in which the surface treatment is performed using ions emitted from an ion gun, the polymer film is placed along the circumferential surface of the cylindrical can, and the surface of the polymer film is continuously treated. The method for manufacturing a magnetic recording medium according to any one of claims (1), (7), and (8). (10) A compound having a hydrophilic group at the end and a silane group at the end is placed on a polymer film, fine particles are further dispersed thereon, and then an alloy thin film magnetic layer is formed. A magnetic recording medium characterized by: (11) The magnetic recording medium according to claim (10), wherein the hydrophilic group at the end of the polymer film is a vinyl group, a halogen group, a hydroxyl group, a carboxyl group, or a thiol group. (12) The magnetic recording medium according to any one of claims (10) and (11), wherein the compound is a monomolecular layer. (13) The magnetic recording medium according to claim (10), wherein the particle size of the fine particles is 5 to 50 nm. (14) Claim (10) or (13) characterized in that the fine particles are SiO_2 or Al_2O_3.
The magnetic recording medium according to any one of.