JPS62185223A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To considerably decrease the coefft. of friction of a magnetic layer without deteriorating the electromagnetic conversion characteristic thereof by providing semispherical projections on the magnetic recording layer. CONSTITUTION:The coefft. of friction is decreased by the decrease of the true contact area or the generation of an air layer, etc. if the convex projections 1 are formed on the magnetic layer 2 on a nonmagnetic base 3. 'Waving' is generated on the magnetic surface by the transfer to the rear side during taking up of a magnetic tape and modulation noise is generated if the diameter of the projections is larger than 0.20mum or the height thereof is larger than 0.1mum. The decrease of the output is resulted if the number of the projections is >=20 pieces/mum<2>. The satisfactory effect of decreasing the coefft. of friction is not obtainable if the diameter of the projections is smaller than 0.05mum, if the height is smaller than 0.01mum or if the density of the projections is smaller than 0.2 piece/mum<2>. The recording medium having the excellent runnability and electromagnetic conversion characteristic are thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording media such as magnetic tapes and magnetic sheets used in audio equipment, video equipment, computers, and the like.

BACKGROUND OF THE INVENTION In recent years, each of these magnetic recording media has moved toward high-density recording, and the surface of the magnetic layer has become increasingly smooth in order to reduce spacing loss during high-frequency recording and reproduction.

As the surface of the magnetic layer becomes highly smooth, the coefficient of friction increases and the running properties of the magnetic recording medium deteriorate.

For this reason, various additives have been added to the magnetic layer to reduce the coefficient of friction.

Problems to be Solved by the Invention However, the addition of such additives is no longer sufficient to reduce the coefficient of friction of magnetic recording media, which are becoming increasingly smooth. Further, addition of an inorganic lubricant causes deterioration of electromagnetic conversion characteristics, and addition of an organic lubricant causes a temperature change in the coefficient of friction, making it impossible to obtain a sufficiently low coefficient of friction at low temperatures. The present invention is intended to solve these problems and to provide a magnetic recording medium that can maintain good surface properties of the magnetic layer and provide stable running durability.

Means for Solving the Problems In order to solve the above problems, the present invention provides a magnetic recording medium in which a magnetic recording layer is provided on a non-magnetic support, in which hemispherical protrusions are provided on the magnetic recording layer. It is something.

Effect: The above-described structure significantly reduces the coefficient of friction of the magnetic layer without deteriorating the electromagnetic conversion characteristics compared to the conventional structure.

Example Embodiments of the present invention will be described below with reference to the drawings.

As shown in the figure, a convex projection 1 is formed on a magnetic layer 2 on a nonmagnetic support 3. As a result, the coefficient of friction is reduced due to a reduction in the actual contact area or the generation of an air layer.

If the diameter of the protrusions is larger than 0.20 μm or the height is thicker than 0.1 μm, when the magnetic tape is wound, a set-off phenomenon will occur on the magnetic surface, causing undulations and modulation noise. If the number of doors is 20 or more, the output will decrease.

In addition, the diameter of the protrusion is smaller than 0.06 μm and the height is 0.
Lower than 0.01 μm or the density of protrusions is 0.2 pieces/μ
If the door width is too small, a sufficient friction coefficient reduction effect cannot be obtained.

The protrusions used in this example are: (1) A method of applying a thin layer of silicone resin, fluororesin, etc. on the above-mentioned stretched film to form island-like protrusions due to the difference in surface tension. good.

(2) A method in which an inorganic substance such as silica, carbon, molybdenum disulfide, etc. is deposited on the stretched film by vapor deposition, sputtering, or the like.

(3) A method of hydrolyzing and applying a silane coupling agent, a titanium coupling agent, etc. on the above-mentioned stretched film.

Established by etc.

Next, a method for manufacturing a magnetic recording medium will be explained using a magnetic tape as an example.

First, the magnetic layer is formed as follows.

Magnetic powder, abrasive material, inorganic pigments such as antistatic agents added as necessary, binder 1 dispersant, lubricant, etc. are thoroughly mixed and dispersed with an organic solvent in a mixer to obtain the desired component ratio. Create a magnetic coating solution.

Here, the magnetic powder used is magnetic iron oxide.

Either chromium dioxide or metal magnetic powder may be used. Examples of antistatic agents include carbon black and graphite particles. Alpha alumina is used as an abrasive.

Titanium oxide, red iron oxide, chromium oxide, SiC, etc. are used. Polyurethane resin is used as a binder.

Examples include vinyl chloride resin, epoxy resin, phenol resin, cellulose resin, polyester resin, etc., and these resins may be used alone or in combination of two or more. Examples of dispersants include higher fatty acids, higher alcohols, phosphoric acid esters, and chryseroline. Examples of lubricants include silicone resins and higher fatty acid esters. As a hardening agent,
Examples include incyanate, polyamine, polyamide, etc. Examples of organic solvents include methyl ethyl ketone, methyl isobutyl ketone, toluene, cyclohexanone, and ethyl acetate.

These compositions are thoroughly mixed and dispersed together with a solvent in a mixer to produce a magnetic paint having a desired component ratio. Mixing machines include ball mills, sand mills, desilver,
You can use an attritor, high-speed mixer, kneader, Henschel mill, Franetarium mixer, 3 rolls, etc.

The magnetic paint thus obtained is applied onto the non-magnetic support. As a coating method, a doctor blade method, a gravure method, a reverse roll method, etc. are used. Immediately after application,
In order to further improve the smoothness of the coating film, a smoother may be brought into contact with it. For this purpose, use a haha smoother, wire smoother, film smoother, etc.

Immediately before drying, an orientation treatment is performed using a magnetic field orientation device or a randomizer in order to bring the magnetic particles in the coated film into an appropriate orientation state. Thereafter, the coating film is dried to remove the solvent.

After coating and drying, the surface of the wide magnetic layer is processed using a super calender to further smooth the surface. Calendar conditions include temperature 5O-1000C2 pressure 5o-ao
oKy/cm and a speed of 50-400 m/min are desirable.

(Example 1) Water vapor was blown onto the magnetic surface of the magnetic recording medium obtained as described above to form hemispherical water droplets on the magnetic surface, and the medium was allowed to pass through silane coupling agent vapor. By hydrolyzing the silane coupling agent in water droplets on the magnetic surface,
Protrusion diameter 0.1 μm, height O, OS μm, protrusion density 1
0 protrusions/μiK were provided on the magnetic surface. The jumbo roll thus obtained was cut into inch-width pieces to make a videotape.

(Example 2) In Example 1, the diameter of the protrusion is 0.2μ and the height is 0.10μ.
A videotape was produced in the same manner as in Example 1.

(Example 3) In Example 1, the diameter of the protrusion is 0.02 μm and the height is 0.01 μm.
A protrusion density of 20/μ7 was produced in μm,
After that, a videotape was produced in the same manner as in Example 1.

(Comparative Example 1) In Example 1, the diameter of the protrusion is 0.02 μm and the height is 0.01 μm.
A videotape with a protrusion density of 60 μm/μm door was produced, and the rest was carried out in the same manner as in Example 1 to produce a videotape.

(Comparative Example 2) In Example 1, the diameter of the protrusion is 0.30 μm and the height is 0.16 μm.
A videotape with a protrusion density of 1 μm/μ7 was produced, and the rest was carried out in the same manner as in Example 1 to produce a videotape.

(Comparative Example 3) A videotape was produced in the same manner as in Example 1 except that no protrusions were provided in Example 1.

For each sample above, the friction coefficient of the magnetic layer and the color S
The N ratio was measured.

(Hereinafter referred to as margins) In the above table, (1) The diameter, height, and density of the protrusions were measured using a scanning electron microscope.

(2) The coefficient of friction was determined by making sure that the tape magnetic surface was in contact with an aluminum alloy drum with a diameter of 126fl over half the circumference, applying a tension of 36g on the entrance side to the drum, and setting a tape running speed of 3.3g.
The tension on the output side when set to an/second was measured, and the friction coefficient was determined from the following equation.

π λ side tension crab 36g (3) SN ratio is VH8 system VTFt NV6200
(manufactured by Matsushita Electric Co., Ltd.), input the reproduced output of the - color chroma signal to a 925C color video noise meter (Shibaku Co., Ltd.), and filter the temporary SN of 1 to 500KH2.
was measured and relative values are shown with Comparative Example 3 as OdB.

As is clear from the table above, the magnetic tape obtained as described above has excellent running properties and electromagnetic conversion characteristics compared to conventional products.

Although the above embodiments have been described with respect to magnetic tape, it goes without saying that the present invention can be applied not only to magnetic tapes but also to other magnetic recording media such as magnetic sheets and magnetic cards.

Effects of the Invention As detailed above, according to the present invention, a magnetic recording medium with excellent running properties and electromagnetic conversion characteristics can be obtained, and its practical value is considerable.

[Brief explanation of drawings]

The figure shows a cross-sectional structure of a magnetic tape according to an embodiment of the present invention. 1... Protrusion, 2... Magnetic layer, 3...
...Nonmagnetic support. Name of agent: Patent attorney Toshio Nakao and 1 other person! ~
--Menjo 2--Ikhada Ryusei J-Ichipaku ΔJ Gehata body

Claims (2)

[Claims] (1) A magnetic recording medium comprising a magnetic recording layer provided on a non-magnetic support, characterized in that hemispherical protrusions are provided on the magnetic recording layer. (2) The diameter of the protrusion is 0.05-0.20 μm, and the height is 0.
01-0.10μm and the density of protrusions is 0 per 1μm^2
．． The magnetic recording medium according to claim 1, characterized in that the number of magnetic recording media is 2 to 20.