JPH0481247B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a metal thin film magnetic recording medium used for short wavelength recording.

Conventional structure and problems Conventionally, magnetic recording media have been made using oxides such as γ-Fe ₂ O 3 or CrO ₂ doped with γ-Fe ₂ O ₃ or Co on a non _- magnetic support, mainly a polymer substrate. Widely used are coating types in which powdered magnetic materials such as magnetic powder or ferromagnetic alloy powders such as Co and Fe are dispersed in an organic binder such as vinyl chloride-vinyl acetate copolymer epoxy resin or polyurethane resin, coated, and dried. It has been used.

However, in recent years, so-called metal thin film magnetic recording media with a magnetic recording layer made of a ferromagnetic metal thin film, which has become known as a medium capable of high-density recording, have been used in computer hard disk memories using the plating method, audio microcassette tapes, etc. , some of which have been put into practical use, such as vapor-deposited tape for video,
A movement toward practical use of perpendicular magnetic recording media such as CoCr is beginning to gain momentum.

However, at present, although it is acknowledged that it has overwhelming superiority in terms of electromagnetic conversion characteristics, its practical reliability is questionable, and some are doubting its practical application.

Regardless of whether it is a coating type or a metal thin film type, short wavelength recording suffers from severe spacing loss, which naturally requires surface smoothness, which leads to unstable running and the rotating head. This idea originates from the idea that low durability against interactions with cylinders, especially still durability in video tapes, is fatal.

In order to solve this problem, various attempts have been made to apply a thin layer of lubricant onto the metal thin film.

As for the materials, fatty acids, fatty acid esters, fatty acid amides, silicone oils, animal and vegetable oils alone or as a mixture have been investigated and tested extensively, and manufacturing methods include various known wet coating methods, dry vacuum deposition, sputtering, Ion plating, plasma CVD methods, etc. are applied, but
The reality is that satisfactory results have not been achieved in a wide range of practical applications.

OBJECTS OF THE INVENTION An object of the present invention is to provide a metal thin film magnetic recording medium with improved durability and runnability under a wide range of practical environments.

Structure of the Invention The present invention provides a magnetic recording layer disposed on a polymer substrate, which is a ferromagnetic metal thin film, and pinholes penetrating the ferromagnetic metal thin film in the thickness direction are uniformly present over almost the entire area. A metal thin film magnetic recording medium characterized in that the sum of the areas of the holes is 0.5% or more and 5.0% or less of the total area of the magnetic recording medium.

Polymer substrates that can be used in the present invention include polyethylene terephthalate, polyethylene naphthalate, aromatic polyamide, polyimide, and the like.

Furthermore, it goes without saying that materials based on the above-mentioned materials that contain fine particles, and materials that have fine irregularities applied to one or both surfaces by a coating method or the like can also be used in the present invention.

Ferromagnetic metal thin films that can be used as magnetic recording layers are broadly divided into in-plane magnetization films and perpendicular magnetization films, and the materials include Co, Co-Ni, and Co.
-Fe, Co-P, Co-B, Co-V, Co-W, Co
−Mo, Co−Pd, Co−Sm, Co−Cu, Co−Cr,
Co-Ni-Cr, Co-Ni-W, Co-Ni-Mo, Co
−Ni−Cu, Co−Ni−Ti, Co−Ni−Si, Co−Ni
-Mn, Co-Ni-P, Co-Ni-O, Co-Cr-
Ferromagnetic metals such as O, Co-Ti-O, Co-Si-O,
They are ferromagnetic alloys, and the manufacturing methods that can be used to obtain these thin films include electron beam evaporation, induction heating evaporation, electric field evaporation, ion plating, electroplating, electroless plating, and sputtering.

Further, a non-magnetic metal layer and a soft magnetic underlayer may be disposed as the underlayer of the magnetic recording layer, and
It does not matter whether the magnetic recording layer is provided on only one surface or on both surfaces of the substrate.

However, when there are magnetic recording layers on both sides, the numerical limitations of the present invention are applied to the area fractions described below for each side.

Also, there is no question as to whether or not there is a back coating layer for running aid, a lubrication treatment layer, and a rust prevention treatment layer.

The ferromagnetic metal thin film layer of the present invention has a wavelength because it has pinholes penetrating in the thickness direction, and the pinholes are the same even if there is a nonmagnetic underlayer or a soft magnetic underlayer. The requirement is that it reaches the level of molecular substrates.

It is easy to make the pinhole shape circular, elliptical, or something close to it, but from the perspective of its operation, shape dependence is hardly a problem. Considering the trend of increasing recording density, it is of course necessary to take precautions to ensure that pinholes with a diameter of about 0.2 to 1 μm are uniformly scattered, and the total area of these pinholes is the total magnetic field. If the area fraction of the missing portion expressed as a ratio to the area of the layer, that is, the area of the tape or disk, is 0.5% or more, as shown in Figures 2 and 3, a wide range of still durability is achieved. It is something that is brought about.

The effect of pinholes is not clear, but it is better to use a highly hygroscopic polymer substrate.
Judging from the results, such as the improvement effect seen at a low area fraction and the good durability of the still after long-term storage in a high-temperature and humid environment, water vapor escapes from the polymer substrate through the missing parts during still operation. It is thought that this is due to the lubrication effect generated by the transfer of heat to the interface of the head tape.

On the other hand, the upper limit is, as expected, determined by the fact that a drop in high frequency output occurs due to a drop in the magnetic layer and a drop in the total flux amount.

At the same time, there are restrictions from the noise side, and in the end, from an output perspective, it is practical even if it is close to 5% to 10%, but from a noise perspective, 5% or less is preferable.

DESCRIPTION OF EXAMPLES The present invention will be specifically explained below using Examples, but the present invention is not limited to the Examples below.

The method for obtaining the medium of the present invention is that immediately after forming a ferromagnetic metal thin film on a polymer substrate moving along a cylindrical rotating can by electron beam evaporation, sputtering, or ion plating, Then, a method was adopted in which the ferromagnetic metal thin film was pressed with rubber and a portion was cut out to form a pinhole.

The size and area fraction of the pinholes were adjusted by changing the surface roughness of the rubber and the diameter and pressure of the rubber roller. The area fraction was measured by comparing the transparent area with the non-transparent area in a 150x optical microscope photograph and performing image processing. At that time, uniformity was confirmed by randomly selecting 10 sampling points and checking that the results were within ±15%.

Example 1 On top of polyethylene terephthalate 10.5 μm,
Co80%Ni20% is heated and evaporated by electron beam evaporation to give an atomic% of 9% to Co in an oxygen atmosphere.
A Co-Ni-O thin film of 0.1 μm was formed at an incident angle of 40° or more. A butyl rubber roller with a diameter of 9cm and a maximum roughness of 1μ (1S) was adjusted by linear pressure in the range of 0.2 to 3.6Kg/cm, and the diameter of the pinhole (expressed as a diameter since most are circular) was adjusted to 0.1 to 3.6Kg/cm. The total area occupied by the pinholes was adjusted by adjusting the diameter within a range of 2.7 μm. Behenic acid amide was formed on the surface of the magnetic layer to 30 Å by vacuum deposition, and the recording and reproducing characteristics were investigated using a tape with a width of 8 mm and a ferrite head with a gap length of 0.26 μm. The cylinder diameter was 40 mm and the scanning speed was 3.75 m/sec. In evaluating the reproduction C/N of a 4.5MHz carrier, a value of 4MHz was used for N.

Also, the dropout was 45μsec, -16dB was calculated by a counter, and relative comparison was made.

The results are shown in Figure 1.

Figure 2 shows the still characteristics at 30°C.
Measurements were discontinued for still life at 90% RH of 30 minutes or more.

Example 2 Co80%Cr20% on aromatic polyamide 8.5μm
After forming a perpendicularly magnetized film of 0.2 μm by high-frequency sputtering, pinholes were formed in the same manner as in Example 1, and the relationship between still characteristics and area fraction was investigated.

As high frequency sputtering conditions,
Adopted Ar0.02Torr 1500W, 13.56MHz glow discharge.

Figure 3 shows the still characteristics under each environment.

It should be noted that the characteristics are the same as in Example 1, in which a vapor-deposited layer of behenic acid amide was added to the surface.

It is understood from this figure that the still characteristics are improved if the ratio is 0.5% or more.

As in FIG. 1, the upper limit was 5% at most due to increased noise and increased dropout.

Example 3 After forming a Co-Ni-O thin film of 0.15 μm on a 10.6 μm aromatic polyamide by oblique evaporation at an angle of 40° or more, linear pressure was applied using a rubber roller made of silicone rubber with a diameter of 6 cm and a maximum roughness of 0.7 μm. 1.4, 2.1Kg/cm, form a pinhole with an average diameter of 0.25, 0.33μ,
Tapes having two types of pinholes with area fractions of 0.5% and 1.0% were manufactured. In the case of 80% Co and 20% Ni, O was 11% by atomic % relative to Co. As a comparative example, one with an area fraction of 0.1% or less (that is, one manufactured without nipping with rubber) was selected. This 3
A slippery layer was formed on the surface of the specimen by organic vapor deposition of stearyl stearate, and the still characteristics at 30°C, 20% RH were compared with the still characteristics of a specimen stored at 40°C, 80% HR for 4 weeks. The tape tension was compared at 1.8 times that of normal use.

The thickness of the organic deposited layer was examined in the range of 35 Å to 50 Å.

The products of the present invention showed a still life of 25 minutes or more regardless of the type of organic vapor source, whereas the comparative examples showed a still life of 15 minutes or less for the best product and 10 minutes or less for most products. Ta. After storage for 4 weeks at 40°C and 80% RH, the still characteristics of the tapes with an area fraction of 0.5% and 1.0% were 32 to 39 minutes and 45 to 51 minutes, respectively, whereas the comparative example It took 7-9 minutes.

The types of organic substances confirmed were natural paraffin microwax, myristic acid, palmitic acid stearic acid, behenic acid, linoleic acid, lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hardened semi-fatty amide, and stearin. There were 14 types of methyl acid and sodium myristate, but almost no material dependence was observed, and it was confirmed that the area fraction made a dominant contribution.

Effects of the Invention The magnetic recording medium of the present invention has significantly improved durability as seen in improved still life under a wide range of environmental conditions, making it ideal for video applications.

The product of the present invention has improved durability, with output reduction within 1 dB and dropout increase within a practically negligible range, and is useful for short wavelength recording.

[Brief explanation of the drawing]

Figure 1 shows the pinhole area fraction, C/N,
Figure 2 shows the influence of pinhole area fraction on still life. Figure 3 shows the influence of pinhole area fraction on still life depending on temperature and humidity conditions. It is a figure showing a difference.

Claims (1)

[Claims] 1 A magnetic recording layer placed directly on a polymer substrate is
A ferromagnetic metal thin film, in which pinholes penetrating the ferromagnetic metal thin film in the thickness direction are uniformly present over almost the entire area, and the sum of the areas of the pinholes is 0.5% or more and 5.0% or less of the total area of the magnetic recording medium. A metal thin film magnetic recording medium characterized by: