JPH0466046B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks. Construction of conventional examples and their problems A thin film of cobalt, nickel, iron, alloys containing these as main components, or their oxides is deposited on a polyester film substrate using vacuum film forming methods such as vacuum evaporation, sputtering, and ion plating. The ferromagnetic metal thin film magnetic recording medium formed on the
It is possible to dramatically improve the recording density compared to conventional coating-type magnetic recording media, but in order to achieve this high density, the surface of the magnetic recording medium must be smoothed to reduce spacing loss as much as possible. It is necessary to force it. However, if the surface is made too flat, it will cause problems in head touching and running surface. In particular, when trying to further improve the magnetic tape recording density in a rotating head type video tape recorder system, the practical performance of the magnetic recording medium required is to have good head touch and head abrasion resistance, and to prevent head clogging. The objective is to be able to achieve stable running performance (low friction and good wear resistance) at the contact points with rotary head cylinders, tape guide posts, audio fixed heads, etc. The surface properties of ferromagnetic metal thin film magnetic recording media depend almost entirely on the surface shape of the polyester film substrate, since the thickness of the magnetic layer is very small, about 0.04 to 0.5 μm. Therefore, various proposals have been made regarding the surface properties of films. Among them, JP-A-56-
When a polyester film having earthworm-like microprotrusions on the surface as typified by Publication No. 10455 is used as a substrate, it is possible to obtain a magnetic recording medium with good head touch and head running properties at room temperature and humidity. However, the product obtained in this way has a relatively high coefficient of friction against the guide post, and is capable of suppressing noise in the cylinder part of the rotating head in high humidity at 30°C and 80% to 90% R.H. It has the disadvantage of being easy to occur. The present inventors have already performed a glow discharge treatment on a polyester film having the above-mentioned earthworm-like microprotrusions, and then applied a resin liquid containing inorganic colloid fine particles to the surface of the polyester film, thereby creating even finer protrusions on the protrusions of the earthworm-like protrusions. It has been found that the above problem can be solved by additionally forming . However, in industrial production, it is not always easy to obtain earthworm-like protrusions with a uniform height over the entire surface of a polyester film, and to form fine protrusions with a uniform height thereon. In the lamination method, non-uniformity of protrusion height can sometimes be promoted, and in such a case, the output of the obtained magnetic recording medium may vary in the length direction or width direction. I don't feel well. Purpose of the Invention With the above points in mind, the present inventors have discovered that even if there is a slight change in the height of the protrusion in industrial production, it is difficult to increase the output, and that the surface has better running performance than a surface with only earthworm-like protrusions. The present invention was discovered by conducting research on a method for manufacturing a magnetic recording medium having an improved surface. Structure of the Invention The present invention involves forming a metal thin film on a polyester film having a worm-shaped film structure mainly composed of at least one water-soluble polymer such as silicone or styrene-butadiene rubber, and then forming a metal thin film on the surface of the polyester film. The method relates to a method for producing a magnetic recording medium, characterized by coating the surface of the magnetic recording medium with a resin liquid containing ferromagnetic metal, and then forming a ferromagnetic metal thin film thereon. Microscopic protrusions with a core of
The main objective is to improve running performance by forming the recesses (between the protrusions) of the earthworm-like protrusions, and at the same time to allow variations in the protrusion height to some extent in terms of industrial production. The above-mentioned polyester film basically includes all the films described in Japanese Patent Application Laid-Open No. 10455/1982, and refers to those having earthworm-like protrusions on the surface. Particularly preferable conditions for the earthworm-like projections include a long diameter of 0.5 to 15 μm, a short shape of 0.01 to 0.1 μm,
It has a structure with a density of 1 × 10 ⁶ to 10 ⁹ pieces/cm ² ,
The material should not contain large amounts of low-molecular organic compounds that easily turn into vapor when heated in a vacuum, such as natural wax. The formation of metal thin films on vapor films is performed by vapor deposition,
It can be performed using vacuum film forming methods such as sputtering and ion plating, and the metals used include magnetic metals such as Fe, Co, and Ni, Al, Ti, Si,
Non-magnetic metals such as Su, Zn, Cr, Cu, Ag, and Au, or their alloys are suitable, and the film thickness is 10
~1000 Å, more preferably 50 to 500 Å is appropriate, and the film may be in a discontinuous film (island structure). After forming a vapor metal thin film, when a resin solution containing inorganic colloid fine particles is applied to the surface, it is clear that the inorganic colloid particles adhere mainly to the recesses of the earthworm-like protrusions on the surface and form minute secondary protrusions there. Summer. The inorganic colloid fine particles used in the present invention are suitably monodisperse particles with a diameter of 50 to 500 Å, more preferably 100 to 500 Å, and materials include various oxides such as alumina, silica, titanium oxide, lead oxide, and iron oxide. or their hydrates, carbonates and sulfates of calcium, barium, strontium, etc. are suitable. If the diameter is less than 50 Å, it is difficult to obtain a squeal prevention effect in high humidity, and if it is more than 500 Å, the envelope is likely to be disturbed. In order to firmly adhere inorganic colloid fine particles onto a polyester film, these fine particles are dispersed in a resin liquid and adhered with the resin. Suitable resins include polyester,
polyamide, polystyrene, polycarbonate,
polyarylate, polysulfone, polyethersulfone, polyacrylate, polyvinyl chloride,
Polyvinylidene chloride, polyvinyl butyral,
Single substances, mixtures, or copolymers of various resins such as polyphelene oxide and phenoxy resins can be used, and crosslinkable resins such as epoxy resins, urethane resins, silicone resins, and phenolic resins can also be used. These resins are dissolved in various solvents such as ester-based, ether-based, alcohol-based, ketone-based, aromatic hydrocarbon-based, etc., or mixed solvents thereof to obtain a resin liquid, and inorganic colloid fine particles are mixed and dispersed therein. The solution is coated on the polyester film. The average thickness of the applied and dried coating film is suitably 10 to 300 Å, more preferably 10 to 100 Å. If it is less than 10 Å, the adhesion strength between the inorganic colloid fine particles and the film will be poor;
If it is more than Å, the earthworm-like protrusions will be smoothed, which is undesirable. The density of microprojections on earthworm-like projections with inorganic colloid microparticles as the core is 1×10 ⁶
Ke/cm ² to 1× ¹⁰ Ke/cm ² , more preferably 2.5
×10 ⁶ to 1 × 10 ⁹ pieces/cm ² is suitable. The ferromagnetic metal thin film is formed by diagonal deposition in vacuum, vertical deposition, sputtering, etc.
Metals whose main components are Ni, Fe, etc.; metals whose main components are alloys thereof (e.g., CoNi alloy, CoCr
In these cases, a small amount of oxygen gas is introduced into the vacuum in order to improve the corrosion resistance, abrasion resistance, adhesion strength to the substrate, etc. of the resulting thin film. It is desirable to form a film while In addition, prior to forming a ferromagnetic metal thin film, metal thin films such as Ti, Cr, Ni, Al ₂ O ₃ , SiO ₂
A base layer made of a thin oxide film such as oxide may be formed as necessary. The thickness of the ferromagnetic metal film is
A suitable range is 0.04 to 0.5 μm, more preferably 0.04 to 0.20 μm. Below 0.04 μm, the still life rapidly decreases. Further, when the thickness is 0.5 μm or more, flexibility becomes a problem. After forming a ferromagnetic metal thin film, by attaching various lubricants to its surface, it is possible to further enhance the running performance improvement effect obtained from the earthworm-like protrusions and the fine protrusions formed on them, with the inorganic colloid fine particles as the core. It is. This makes it possible to more completely prevent squealing in high humidity environments.
In addition to coating or vapor-depositing these lubricants directly on the ferromagnetic metal thin film, there are also methods for coating or vapor-depositing them on the back side of the magnetic recording medium and applying them during stacking (winding) of the magnetic recording medium. A method of transferring it onto the surface of a ferromagnetic metal thin film is also possible. As lubricants used for these, various fatty acids, fatty acid esters, fatty acid amides, metal soaps, aliphatic alcohols, paraffins, silicones, fluorine surfactants, inorganic lubricants, etc. can be used, and the lubricants firmly adhere to the surface. A resin binder or the like may also be used in combination to increase the strength. The amount of lubricant present on the surface of the ferromagnetic metal thin film is suitably 0.5 to 500 mg, more preferably 5 to 200 g ^per square meter of surface. Description of Examples (Example) Using polyethylene terephthalate, which contains almost no internal particles due to polymerization catalyst residue, etc., during stretching film formation, airgelion containing epoxidized polydimethylsiloxane and methylcellulose as main components was applied and dried on both surfaces. The average protrusion height was 150 Å and the average protrusion density was 1×10 ⁷ pieces/cm ² on the entire surface obtained.
An aluminum evaporated film with a thickness of 100 Å was formed on one side of a polyester film (thickness 12 μm) having earthworm-like projections, and then the following composition was applied to that surface in a wet state to a thickness of 10 μm. Microprotrusions with silica colloid fine particles as cores are formed around the concavities of dried earthworm-like protrusions (average protrusion height approx.
A surface with an average protrusion density of 250 Å (1×10 ⁷ /cm ² ) was obtained. Organosilica sol A...0.1 part by weight Methyl ethyl ketone...1000 parts by weight Toluene...500 parts by weight Saturated polyester resin (Byron 200 manufactured by Toyobo Co., Ltd.)...0.1 part by weight The above organosilica sol A has a silica particle size of 250 Å. It is obtained by heating aqueous colloidal silica with isopropyl alcohol after ion exchange and distilling off excess water, and is an isopropyl alcohol solution with a silica content of 30% by weight. In addition, as a comparative example, one side of the above polyester film with earthworm-like protrusions formed on the surface was
between SUS electrodes in oxygen at a vacuum level of 1×10 ^-2 Torr.
After performing a glow discharge treatment by passing through a glow discharge generated by applying a 60Hz alternating current of 500 Vp-p, organosilica sol A is applied to the surface with the above liquid composition and organosilica sol B (same method as organosilica sol A) is applied. By applying a modified version of the silica sol (silica sol with a particle size of 150 Å) obtained in step 1 in the same manner, microprotrusions (average protrusion height approximately 150 Å, average protrusion density 5) were applied to the protrusions of the earthworm-like protrusions.
A surface with 10 × 10 ⁷ pieces/cm ² ) was obtained. Using the above polyester film having two types of surfaces, an oxygen-containing CoNi ferromagnetic metal thin film (Ni = 20% by weight, thin film 1200 Å) was formed on the surface by continuous vacuum oblique evaporation while introducing a trace amount of oxygen gas. Ta. The oxygen content of the magnetic layer was 5% in terms of atomic ratio to the metal. Next, a toluene solution of stearic acid with a concentration of 100 ppm was applied to these surfaces, and then the tapes were cut into specified widths to make magnetic tapes each 4,000 m in length.These tapes were numbered sequentially in 50 m increments from the outside of the roll. I put it in a bucket and connected it to a prototype video recorder to sequentially measure the brightness output and envelope state. The results are shown in the table below. The outputs in the table are shown as relative values with the highest value of each output being 0dB, and the envelope is ○...
Indicated as good, △...slightly poor.

[Table] Effects of the Invention As is clear from the above, the method of the present invention can reduce variations in characteristics such as output and envelope in the longitudinal direction and width direction when magnetic recording media are manufactured using long films. It can be reduced.

Claims (1)

[Claims] 1. A thin metal film is formed on a polyester film having a worm-like film structure mainly composed of at least one of silicone and styrene-butadiene rubber and a water-soluble polymer, and then a resin liquid containing inorganic colloid fine particles is poured onto the polyester film. 1. A method of manufacturing a magnetic recording medium, comprising coating the surface and then forming a ferromagnetic metal thin film thereon.