JPS628325A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a vapor deposition tape having stable characteristics by providing a thin magnetic metallic film layer on a high-polymer substrate having fine projections and providing org. molybdenum or a mixture composed of the org. molybdenum and higher fatty acid on the surface of the thin magnetic metallic film layer. CONSTITUTION:The surface layer of a high-polymer substrate 1 has the fine projections having about 500Angstrom diameter and 200Angstrom height. Co or CoNi alloy is used for the material to be formed on the winding 1 surface of the layer 2. Since the thin film of such magnetic layer is formed on the surface of the winding 1, the film has the shape proportional to the fine projections on the surface. The thickness of the org. molybdenum lubricating layer 3 is 100-200Angstrom . The org. molybdenum contains S in the molecular structure and the resultant product of decomposition by sliding is the compd. of Mo and S. The lubricating effect approximate to the lubricating effect of MoS2 which is a solid lubricating agent is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high density magnetic recording medium that can be used in the field of magnetic recording.

Background of the Invention In recent years, high-density magnetic recording media have been developed due to the demand for high-density recording in video tape recorders, floppy disks, etc.
Technological progress has been remarkable.

There are two trends in technological progress; one is the extension of the conventional coating-type magnetic layer, which was achieved by changing the magnetic powder from iron oxide to a single or alloy powder of iron or cobalt, which has a high energy density. The other method attempts to achieve high-density recording by forming the coated magnetic layer into a thin metal film with high energy density.

When a magnetic material is made into a metal, it is possible to increase the residual magnetic flux density, and as the residual magnetic flux density increases, more information can be recorded in a smaller area.Using this principle, high-density recording is possible. Efforts are being made to achieve this.

Among coated magnetic layers and metal thin film magnetic layers, the metal thin film type, which is a 100% metal magnetic layer, is advantageous for high-density recording.

An example of the conventional high-density magnetic recording medium mentioned above will be described below with reference to the drawings.

FIG. 5 shows a cross-sectional view of a magnetic tape constructed as a conventional vapor-deposited tape. In FIG. 5, 21 is a polymer substrate having minute protrusions on its surface. 22 is a metal thin film magnetic layer, and 23 is a lubricating layer of higher fatty acid coated on the surface of the magnetic layer. 24 is a back coat layer formed on the back surface.

When a vapor-deposited tape is used as a videotape, the tape runs while sliding on a guide post, a cylinder, and a head. At this time, frictional resistance occurs in the sliding portion, and if the resistance is large, running problems occur and the characteristics of the tape deteriorate, so a lubricant is applied to the sliding surface of the tape.

Higher fatty acids are used as lubricants, such as myristic acid, stearic acid, and valmitic acid, either singly or as a mixture, to improve running performance.

Problems to be Solved by the Invention However, when the lubricant configured as described above is used in a high temperature and low humidity environment of about 40'010%, the lubricant on the surface is lost and the frictional resistance increases. I had a problem.

In view of the above-mentioned problems, the present invention uses organic molybdenum as the surface lubricant to obtain a vapor-deposited tape that provides a good lubricating effect in all environments in which it is used and has stable characteristics. The present invention provides a high-density magnetic recording medium.

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention comprises:
It has a structure in which a metal thin film magnetic layer is provided on a polymer substrate having minute protrusions, and organic molybdenum or a mixture of organic molybdenum and higher fatty acid is provided on the surface of the metal thin film magnetic layer.

Effect of the present invention Due to the above-described structure, when the magnetic tape runs, the organic molybdenum coated on the sliding part decomposes and the decomposition product that becomes an inorganic substance acts as a lubricant, so that the lubricant does not run out even in a running environment of high temperature and low humidity. This results in a vapor-deposited tape with stable characteristics without any increase in frictional resistance.

EXAMPLES Below, magnetic recording media according to examples of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional view of a first embodiment of the invention. In FIG. 1, reference numeral 1 denotes a polymer substrate, for example, a polyethylene terephthalate substrate having a thickness of about 2 to 7 μm is used. The surface layer has a diameter of 5008 and a height of 2
Approximately 00 people have 0 minute projections. The purpose of having such protrusions is to reduce the contact area at the sliding portion when the tape runs, thereby reducing frictional resistance. The formation of such microprotrusions is caused by calcium carbonate, SiO,, Fe, O,
It can be obtained by applying fine powder such as.

2 is a metal thin film magnetic layer, and the material formed on the surface of the substrate 10 is an alloy of co and coNi, and in the case of an alloy, the content is 6%.
~30% is used.

The magnetic thin film is formed using the vacuum evaporation method to a thickness of 1,000 to 20
Form a film of 00 people. In order to obtain magnetic properties as a magnetic tape, oblique vapor deposition and a trace amount of oxygen are introduced during vapor deposition.

Since the magnetic thin film is formed on the surface of the substrate 1, it has a shape proportional to the fine protrusions on the surface.

3 is an organic molybdenum lubricating layer with a thickness of 10 to 80 mm.
It is 00 people thick. The organic molybdenum layer C is obtained by coating, for example, molybdenum dialkyl diphosphate or molybdenum dialkyl dithiocarbamate diluted with ketones or alcohols.

The characteristic of organic molybdenum is that it contains S in its molecular structure, and the decomposition product due to sliding is a compound of Mo and S, which has a lubricating effect similar to that of the solid lubricant UOS2 (molybdenum disulfide). can get.

4 is a back coat layer, and in order to improve running performance, a back coat layer with a thickness of 2 to 3 μm is provided.

The material of the back coat layer is a fine powder of Tancal carbon dispersed in a resin such as acetyl cellulose or 1/tan. The back coat layer is formed by coating using gravure or a reverse roller.

FIG. 2 is a graph showing the difference in performance between the magnetic recording medium of the present invention shown in FIG. 1 and the conventional example shown in FIG. The horizontal axis of the graph is the number of sliding movements between the tape and the test post. The vertical axis is the coefficient of friction between the tape and the test post. Part A shows the number of times of sliding and changes in the coefficient of friction of a magnetic recording medium with a conventional configuration, and part B shows the characteristics of a magnetic recording medium with a configuration of the present invention. The characteristics shown in FIG. 2 were measured in a high temperature, low humidity environment of 40°C and 10%.

FIG. 3 is a side view of the apparatus for measuring friction characteristics shown in FIG. 2. Reference numeral 11 is a test post having a diameter of 1 oφ, a surface roughness of Q, 18 or less, a material of 5US4Ω0, and rotating at 100 revolutions per minute in the direction of the arrow.

Reference numeral 12 denotes a test tape, which has a width of 8 ff and is set with its magnetic surface in contact with the test post.

13 is a weight, add 30g. 14 is a strain gauge, one end of the test tape is fixed to the weight measurement part,
The coefficient of friction is measured by measuring the tension of the tape, which is the sum of the tension of the weight and the frictional force.

The operation of the magnetic recording medium of this embodiment configured as described above will be explained below with reference to FIGS. 1, 2, and 3.

Figure 2 is a diagram showing the number of times of sliding and changes in friction coefficient at high temperature and low humidity for the magnetic recording medium of the present invention and a conventional magnetic recording medium. This is an example of coating, and in the present invention example, molybdenum dialkyl phosphate was coated by 150 people. In the conventional configuration, the coefficient of friction gradually increases after 100 rotations of sliding with the test post, reaching 0.4 or more at 1000 rotations.

This change is due to the fact that the lubricant in the sliding parts breaks down due to high temperature and low humidity, causing magnetic powder to adhere to the test post.

On the other hand, in the configuration of the present invention, no increase in the friction coefficient is observed even when sliding is performed for 100 rotations or more.

This effect is thought to be due to the fact that organic molybdenum decomposes at the sliding parts of the tape and the test post, forming a compound of MO and S as a decomposition product, which acts as a lubricant.

Organomolybdenum is less effective in lowering the coefficient of friction as a lubricant than palmitic acid, so by adding minute protrusions to the surface of the magnetic surface to reduce the actual contact area, the coefficient of friction can be reduced without causing any problems during running. can be obtained. In FIG. 2, the reason why the coefficient of friction of Conventional Example 3 is low is considered to be that when palmitic acid is applied to the surface of the same protrusions, it has the effect of lowering the coefficient of friction, which is lower than that of organic molybdenum.

As described above, according to this embodiment, the organic molybdenum layer is provided on the surface of the metal thin film magnetic layer having minute protrusions, so that the friction coefficient is low, and even when running at high temperature and low humidity, the lubricating layer does not break and the friction coefficient remains low. It is possible to provide a vapor-deposited tape with stable performance that does not increase.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a sectional view of a magnetic recording medium according to a second embodiment of the present invention.

In the figure, 1 is a polymer substrate having minute protrusions, 2 is a metal thin film magnetic layer, and 3' is a lubricating layer containing a mixture of higher fatty acids and organic molybdenum.

4 is a back coat layer. This embodiment differs from the structure shown in FIG. 1 in that the lubricating layer 3' is made of a mixture of higher fatty acids and organic molybdenum.

The operation of the magnetic recording medium configured as described above will be described below.

When a mixture of higher fatty acids and organic molybdenum is used as a lubricant, the initial coefficient of friction is lower than when organic molybdenum alone is used, but the durability cannot exceed that of organic molybdenum alone.

As described above, by using a mixture of organic molybdenum and higher fatty acids as a lubricant, it is possible to lower the initial coefficient of friction and provide a magnetic recording medium having a durable coefficient of friction.

In the lubricant, the organic molybdenum 3 in the first embodiment is molybdenum dialkyl diphosphate, but molybdenum dialkyl dithiocarbamate may also be used.

1. In the second embodiment, the organic molybdenum of the lubricant may be molybdenum dialkyl diphosphate or molybdenum dialkyl dithiocarbamate, and the higher fatty acids are lauric acid, myristic acid, palmitic acid, stearic acid, eicosanoic acid, Behenic acid may be used alone or as a mixture.

Effects of the Invention As described above, according to the present invention, excellent effects such as a low initial coefficient of friction, a stable friction coefficient and no deterioration of running performance during endurance running in a high temperature, low humidity environment can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a magnetic recording medium according to a first embodiment of the present invention, and FIG. 2 is a characteristic diagram showing durability sliding test data at high temperature and low humidity for the magnetic recording medium of the present invention and a conventional magnetic recording medium. , FIG. 3 is a side view of the measuring device for the durability sliding test data shown in FIG. 2, FIG. 4 is a sectional view of the magnetic recording medium of the second embodiment of the present invention, and FIG. 5 is a conventional magnetic recording medium. FIG. 1... Polymer substrate having minute protrusions, 2...
...Metal thin film magnetic layer, 3...Organic molybdenum layer, 3'...Mixture of higher fatty acid and organic molybdenum, 4...Back coat layer. Name of agent: Patent attorney Toshio Nakao and one other person
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Claims (1)

[Claims] A magnetic recording medium characterized in that a metal thin film magnetic layer is provided on a polymer substrate having minute protrusions, and organic molybdenum or a mixture of organic molybdenum and higher fatty acid is provided on the surface of the metal thin film magnetic layer.