JPS5942638A - Metallic thin film type magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a thin metallic film type magnetic recording medium having a coefft. of friction which is hardly affected by speed, superior traveling stability and favorable enveloping characteristics, by forming a part contributing to traveling on the surface of a magnetic layer with gathered fine protrusions of a specified average diameter produced by diagonal vapor deposition in an oxygen atmosphere. CONSTITUTION:A magnetic layer is formed on a nonmagnetic substrate made of a polyester film, a polyimide type film such as a polyester imide film or a polyimide film, an aromatic polyamide film or the like. A part contributing to traveling on the surface of the magnetic layer is formed with gathered fine protrusions of 20-300Angstrom average diameter produced by diagonal vapor deposition in an oxygen atmosphere. The resulting magnetic recording medium has a coefft. of friction which is hardly affected by speed, high traveling stability and favorable enveloping characteristics, and the head cleaning effect of the gathered fine protrusions can be expected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks.

Configuration of conventional example and its problems Iron, Kobal 1-. Polyester film is produced using vacuum deposition methods such as vacuum evaporation, sputtering, and ion blasting, using thin films of nickel, nickel, or alloys containing them as main components, or oxides thereof.

Ferromagnetic thin-film magnetic recording media formed on polymer film substrates such as polyimide films can dramatically improve recording density compared to conventional coated magnetic recording media. In order to achieve this, it is necessary to smooth the surface of the magnetic recording medium to reduce spacing loss as much as possible.

However, if the surface is made too flat, it will cause problems in head touch and running surface. In order to further improve the magnetic tape recording density in rotating head video tape recorder systems that have become popular in the general market in recent years, it is necessary to apply ferromagnetic thin film magnetic recording media. Practical performance requirements for magnetic recording media include good head touch, good wear resistance, and resistance to head clogging, and cylinders for rotating heads, tape guide bosses, fixed heads for audio, etc. The aim is to achieve stable running performance (low friction, good wear resistance) at the contact area with the The surface properties of ferromagnetic thin-film magnetic recording media are such that the magnetic layer thickness is 0.1 to
Since it is very small, about 0.6 μm, it almost entirely depends on the surface shape of the plastic film that is the substrate. Therefore, many proposals have been made regarding the surface properties of films. An example is JP-A-63-116115
Publication No. 128683/1983, Japanese Patent Application Laid-open No. 1983-128683
-94674 publication, JP-A-56-10456 publication,
It is described in JP-A-56-16937 and the like. In all of these examples, the surface shape is relatively finely and uniformly roughened, for example, wrinkle-like protrusions are formed or waves are formed.

By forming earthworm-like or granular protrusions,
The aim is to improve head touch and running performance all at once. However, the video rotary head has a narrow contact width of several hundred microns or less, and the relative speed with the magnetic tape is as fast as several meters and seven seconds, whereas the friction of the magnetic tape running system is slow (several centimeters). 7 seconds) Since it is a large-area contact, it is necessary to provide the same running performance to both partners (that is, the friction coefficient speed dependence is small), but in general, the above-mentioned ones on each side are The speed dependence of the coefficient of friction is relatively large, which causes problems such as noise and unstable envelope characteristics during actual driving.

OBJECTS OF THE INVENTION An object of the present invention is to provide a metal thin film type magnetic recording medium that has a small speed dependence of the coefficient of friction, excellent running stability, and good envelope characteristics.

Composition of the Invention In the metal thin film magnetic recording medium according to the present invention, at least the portion of the surface of the magnetic layer that contributes to running is composed of an aggregate of microprotrusions with an average diameter of 20 to 300, developed by oblique vapor deposition in an oxygen atmosphere. It is characterized by the presence of

DESCRIPTION OF EMBODIMENTS FIGS. 1 to 3 are cross-sectional views in the thickness direction of a magnetic recording medium that is an embodiment of the present invention. In the figure, 1゜1', 1'' is a non-magnetic substrate, 2.2', 2'' is a non-magnetic underlayer having fine irregularities on the surface formed on the non-magnetic substrate, 3.3
', 3'' is a ferromagnetic metal thin film formed on the non-magnetic underlayer by oblique vapor deposition in an oxygen atmosphere. In the diagram,
Q1 to Q3 are the main incident angles of oblique evaporation, the arrows are the incident directions, and d
~d3 indicates the diameter in the planar direction of the microprotrusions formed on the surface of the ferromagnetic metal thin film. Note that this diameter can be measured by observation using a scanning electron microscope. Figure 1 shows a case in which microprotrusion aggregates 3 are formed on the entire surface of a smooth non-magnetic substrate 1''2, and Figure 2 shows a non-magnetic substrate 1 with a finely roughened surface.
When microprotrusion aggregates 3' are formed on the entire surface of the substrate 1', FIG. This is the case when microprotrusion aggregates 3' are formed. In the example shown in this figure, it is the 3'' portion that contributes to actual running.

Figure 4 shows a method for forming a ferromagnetic metal thin film on a long non-magnetic substrate by continuous oblique deposition.
1 is a vacuum container, 5 is a non-magnetic substrate, 6 is a port exit portion thereof, 7 is a winding portion, 8 is a drum rotating in the direction, 9 is an evaporation container, 1
0 is an evaporation source made of a ferromagnetic metal melt, and 8 is a mask that regulates the lower limit of the incident angle of the evaporated vapor onto the non-magnetic substrate. θ represents the general angle of incidence, and θmin represents the minimum angle of incidence, that is, the principal angle of incidence.

When a ferromagnetic metal thin film is formed on a substrate by vacuum evaporation, the ferromagnetic metal vapor ejects from the evaporation source and adheres to the substrate, then moves on the substrate and becomes fixed at an appropriate location. As a result, ferromagnetic metal crystals are formed.

When oxygen gas is present in a vacuum, a portion of the ferromagnetic metal vapor adhering to the substrate reacts with oxygen early in the process of moving over the substrate, so that its movement is significantly restricted. Therefore, in oblique vapor deposition in an oxygen atmosphere, it is expected that a vapor deposited film will be formed having a surface in which the fine unevenness of the substrate surface is emphasized. As a result of the studies conducted by the present inventors, the above-mentioned expected effect appears when the spacing between the unevenness on the substrate surface is very small, that is, about 3008 or less, and the surface shape obtained by this effect is It has been revealed that this significantly contributes to the running performance of the vehicle. 1 to 3 schematically illustrate this effect. It should be noted that if the interval between the unevenness on the substrate surface is 300 Å or more, a slight disturbance will occur in the envelope of the signal reproduction output.

The nonmagnetic substrate used in the present invention is polyethylene terephthalate or a copolymer or mixture thereof.

Polyethylene naphthalate or its copolymer.

Suitable materials include polyester films made of mixtures, polyimide films such as polyesterimide and polyimide, and aromatic polyamide films that have excellent surface smoothness. Taking polyester film as an example, it has good smoothness with almost no microprotrusions made of nail residue, or the height of microprotrusions is less than a few hundred, and it has the wrinkles and earthworms mentioned above. These include those on which uniform fine protrusions, such as two-grain shapes, are formed on the surface, and the surface roughness is several hundred angstroms or less. Although a non-magnetic underlayer, which will be described later, is formed on the surface of these materials, uniform fine protrusions such as wrinkle-like or earthworm-like grains as described above are formed on the surface without forming a separate underlayer. In this case, by adding a large number of ultrafine particles with a diameter of 100 Å or less to the surface forming material, the fine protrusions themselves may have the properties of a non-magnetic underlayer, which will be described later.

The feature of the present invention is that the surface is composed of aggregates of microprotrusions with an average diameter of 20 to 300, which are formed by oblique evaporation in an oxygen atmosphere. This is obtained when the shapes have a loosely similar shape. Even if you try to examine this type of shape in advance before vapor deposition, it is difficult to confirm it with a scanning electron microscope with a normal magnification of 100,000 or more, and it is difficult to see it with a high-resolution electron microscope. It is only to the extent that it becomes clear. Moreover, even if the normal incidence angle is close to 90', a microprotrusion aggregate that is effective in the present invention cannot be obtained on a surface of such a shape, and simply diagonal deposition in a high vacuum In vapor deposition, it is not possible to obtain the remarkable unevenness enlarging effect that can be obtained by oblique vapor deposition in an oxygen atmosphere.

This is clear, for example, from the results of measuring the coefficient of dynamic friction of the magnetic surface, which will be described later.

The non-magnetic underlayer is a thin layer of resin (with a thickness of 100 Å or less) containing 5% or more, more preferably 10 to 60% by weight of ultrafine particles with a diameter of 100 Å or less, more preferably 10 to 90 particles.
0QQÅ or less, more preferably 10 to 500 people), for example, a resin solution in which ultrafine particles are dispersed (
It can be obtained by applying a resin concentration of 1 to voop per million on the surface of a substrate that is smooth or has wrinkles, worm-like, or granular projections. Examples of ultrafine particles with a diameter of 100 Å or less include hydrolysis of organometallic compounds and hydrolysis of metal halides.

Decomposition with acid-alkali, reduction of salt solution, evaporation method in gas,
Aluminum is obtained by aggregation, crystallization, etc. of organic compounds, polymer compounds, etc.

Oxides of silicon, magnesium, titanium, zinc, iron, etc.
Fine metal particles such as hydroxide, gold, silver, copper, nickel, iron, etc.
Alternatively, fine particles of organic compounds/polymer compounds, etc. can be used. Incidentally, when fine particles with an average diameter of 100 particles are used, the average diameter of the small protrusions in the plane direction of the surface of the base layer obtained is about 200 to 300 particles due to secondary aggregation of the particles.

The nonmagnetic underlayer may be provided over the entire surface of the substrate as shown in FIGS. 1 and 2, or may be provided partially as shown in FIG. In the latter case, it is desirable that the underlayer regions exist over 10% or more of the entire surface at intervals of at least 2 0 μm or less. Such a state can be obtained, for example, by adding a small amount of silicone oil to the coating liquid when forming the base layer. In any case,
It is necessary that the microprotrusion aggregates exist in the protruding portions of the magnetic layer, that is, in the portions that contribute to travel.

Regarding vacuum evaporation in an oxygen atmosphere, Japanese Patent Publication No. 66-2
3208. Tokuko Showa 67-2393-1. Special Public Service 1977-2
9770. JP-A-66-16014° JP-A-67-37
719, etc., the effects of the present invention are such that the main incident angle is 2σ or more, preferably 30° or more, the obtained film thickness is 400 Å or more, and the oxygen content (relative to ferromagnetic metals) is 400 Å or more. (atomic ratio of oxygen) 3% or more ◇In addition, when implementing the present invention, it is also possible to provide various lubricant-containing layers, rust preventive agent-containing layers, etc. on the surface of the magnetic layer or the back surface of the non-magnetic substrate. .

Next, a more specific example will be explained.

Surface roughness Rmax - approx. 250 people with a thickness of 12 μm,
A solution containing 10 ppm of silica colloid (a hydrolyzed product of alkoxysilane) with an average particle size of 8 µm and 30 ppm of a copolymerized polyester resin was applied to the surface of a long polyester film having wavy projections with an interval of about 2 μm and dried.

Place this along the circumferential surface of the cylindrical drum, and
Oxygen gas was introduced at a flow rate of 0.3 n/min at a vacuum degree of
An oxygen-containing coNi ferromagnetic thin film was formed on the film. At this time, by changing the position of the incident angle limiting mask, the main incident angle can be set to 30°, 20', or 100°.
．． Four types of samples of Oo were obtained. These samples were designated as A, B, C, and D, respectively. For comparison, the original film without silica colloid treatment also had a principal incidence angle of 300.
The same vapor deposition as above was carried out. This product was designated as sample E. Furthermore, an experiment was also conducted in the case where oxygen was not introduced under the sample manufacturing conditions, and this sample was designated as F. The average amount of oxygen in the films of samples A-F is CoN1E+1o%, F
<It was 1%. By scanning electron microscopy, samples A and B
It was confirmed that microprotrusion aggregates with an average diameter of 200A were formed on the entire surface. However, sample 0. D,F
In sample E, only traces of roots of microprotrusion aggregates were observed, and in sample E, no traces of such roots were observed. These samples were cut into predetermined widths to make magnetic tapes, and the envelope characteristics were observed on a prototype deck, and the tapes were wrapped around a 6#Iffφ stainless steel round bar 1800 times and run to measure the speed dependence of the friction coefficient. The envelopes were good in the following order.

Best A-B)F, -C-F)D Furthermore, FIG. 6 shows the speed dependence of the friction coefficient.

Effects of the Invention The magnetic recording medium of the present invention has a small speed dependence of the coefficient of friction, excellent running stability, and good envelope characteristics.
Furthermore, since a head cleaning effect is expected due to the aggregate of fine protrusions, its practical value is extremely high.

[Brief explanation of drawings]

1, 2, and 3 are sectional views of a magnetic recording medium according to an embodiment of the present invention, FIG. 4 is a sectional view of a continuous oblique evaporation apparatus, and FIG. 5 is a sectional view of a magnetic recording medium according to an embodiment of the present invention. FIG. 3 is a diagram showing the speed dependence of the friction coefficient of a recording medium. 1...Nonmagnetic substrate, 2...Underlayer, 3
...Ferromagnetic metal thin film. Name of agent Toshi Nakao, Physician, 1 person Figure 1 Figure 82 Figure 4 Figure 5 i! Pickled) U, Ji

Claims (1)

[Claims] A metal thin film type magnetic recording medium characterized in that at least a portion of the surface of the magnetic layer of the magnetic recording medium that contributes to running is composed of aggregates of microprotrusions with an average diameter of 20 to 300 A developed by oblique vapor deposition in an oxygen atmosphere. .