JPS583135A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a ferromagnetic metallic thin film type magnetic recording medium excellent in antiblocking property and corrospion resistant effect by providing a coating film consisting of an antistatic agent, a water-repelling agent, a lubricant, and thermoplastic polyester on the back side of a nonmagnetic substance base. CONSTITUTION:A ferromagnetic metallic thin film is formed on a nonmagnetic substance base with vacuum deposition, and a coating film consisting of a solid an antistatic agent such as carbon black or graphite, a water-repelling agnet such as higher fatty acid, higher fatty acid ester, higher fatty acid metallic salt, higher fatty acid amide, and higher fatty alcohol, or lubricant, and a thermoplastic polyester, and, as required, nitrocellulose, is provided on the back side of the nonmagnetic substance base.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a ferromagnetic metal thin film type magnetic recording material, particularly a magnetic tape, in which a coating film mainly composed of a resin material is provided on the opposite surface of the base film to the magnetic layer, thereby preventing the running of the magnetic tape. The purpose is to improve corrosion resistance, antistatic properties, corrosion resistance under high temperature and high humidity environmental conditions, and blocking resistance.

Gold cormorant obtained by forming a ferromagnetic thin film mainly composed of iron, cobalt, nickel, or an alloy thereof on a polymer film support such as polyester or polyimide by vacuum evaporation, sputtering, ion blating, etc. Thin film magnetic tape is ideal for high density recording such as video signal recording. However, metal thin films generally have a problem of poor corrosion resistance under high temperature and high humidity environments, and are especially susceptible to rapid temperature changes when wound up in tape form on reels, hubs, etc. under high humidity conditions. In this case, condensation is likely to occur between the opposing magnetic surfaces and the back surface in the rolled-up state, and the water droplets that form once condensed are difficult to evaporate due to the narrow gap between the magnetic surface and the back surface, so the magnetic surface cannot be left on the magnetic surface for a long time. It has become clear that even when wet, corrosion tends to occur in that area, and when the corroded area dries, the magnetic surface and the back surface tend to come into contact with each other (blocking) through corrosion products.

If the surface properties of the magnetic surface are improved in order to increase the recording density, the gap between the magnetic surface and the back surface in the rolled-up state will become smaller, and the above phenomenon will become even more noticeable.

3 pages The back side of metal thin film magnetic tape is slippery.

In addition to satisfying the general characteristics of magnetic tapes, such as prevention of rust and antistatic properties, it is necessary to deal with rust and the blocking phenomenon caused by rust, as described above.

From this point of view, as a result of examining various materials, we have found a material with excellent blocking resistance and rust prevention effect.

The basic constituent material of the present invention is an antistatic agent.

Consists of water repellent, lubricant, and binding resin.

As the antistatic agent in the present invention, a solid antistatic agent such as carbon black or particulate graphite is used.

Conventionally, organic surfactants such as anionic surfactants, cationic surfactants, and nonionic surfactants that have been used in coated magnetic tapes have good affinity with water, so they prevent the formation of rust. It was unsuitable from a rust prevention point of view because it easily caused corrosion.

In addition, water repellent agents include higher fatty acids such as stearile acid, palmitic acid, myristic acid, lauric acid, and oleic acid, their alcohol esters, higher fatty acid esters such as polyhydric alcohol esters, their sodium salts, potassium salts, and lithium salts. salt, calcium salt, barium salt, zinc salt.

Higher fatty acid metal salts such as magnesium salts, aluminum salts, lead salts, chromium salts, cobalt salts, nickel salts, copper salts, iron salts, tin salts, mercury salts, and higher fatty acid metal salts such as lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, etc. Fatty alcohols and higher fatty acid amides such as lauric acid amide, myristic acid amide, and valmitic acid amide are used.

Graphite, higher fatty acids, higher fatty acid esters, higher fatty acid metal salts, higher fatty alcohols.

Higher fatty acid amides have excellent lubricity, but the lubricity can be further improved by adding a solid lubricant such as molybdenum disulfide or carbon fluoride.

A small amount of other resin may be mixed with the thermoplastic polyester which has excellent compatibility with antistatic agents, lubricants, and water repellents and excellent dispersibility of solid particles.

By incorporating nitrocellulose, blocking resistance and solvent removal properties during coating are improved.

Stearic acid and graphite are added to thermoplastic polyester, a solvent is added, and a dispersion process is performed using a ball mill.
A paint solution was prepared. The coating material was applied to the back side of a metal thin film type magnetic tape on which a cobalt alloy was vapor-deposited on a polyethylene terephthalate film. No rust or blocking was observed with this tape even under high temperature and high humidity conditions. When I ran it using a Ushita video tape recorder, it ran stably and there was no noise due to charging.

The present invention will be specifically explained in detail below.

Example 1 The following composition was charged into a ball mill and stirred for 40 hours to perform a dispersion treatment.

The obtained paint was applied to the back side of a ferromagnetic alloy thin film containing 80% Kobal and 20% nickel, which was prepared by vacuum deposition on a polyester film using a vasita.

After drying, it was cut to an appropriate width to create a magnetic tape. The coating film thickness was 3.0μ. Let this be the sample.

Example 2 The following composition was charged into a ball mill, stirred for 40 hours,
Performed distributed processing.

Cobalt 80% nickel 20% was created by vacuum evaporation method on polyester film using a bar coater to coat the resulting 7-base paint.
was applied to the back side of the ferromagnetic alloy thin film. After drying, it was cut to an appropriate width to create a magnetic tape. Coating film thickness is 5゜Q
It was μ. This is designated as sample B.

Example 3 The following composition was charged into a ball mill, stirred for 40 hours,
Performed distributed processing.

The resulting paint was coated with 80% cobalt and 20% nickel on a polyester film using a vacuum evaporation method using a bar coater.
was applied to the back side of the ferromagnetic alloy thin film. After drying, it was cut to an appropriate width to create a magnetic tape. Coating film thickness is 4.2
It was μ. This is designated as sample C.

Example 4 The following composition was charged into a ball mill, stirred for 48 hours,
Performed distributed processing.

Page 9 Cobalt 80% nickel 20% Cobalt 80% Nickel 20% Cobalt 80% Nickel 20% Cobalt 80% Nickel
was applied to the back side of the ferromagnetic alloy thin film. After drying, it was cut to an appropriate width to create a magnetic tape. Coating film thickness is 3.8
It was μ. Use this as a sample.

Example 6 The following composition was charged into a ball mill, stirred for 4 hours,
Performed distributed processing.

Cobalt 80% nickel 20% was created by vacuum evaporation method on a polyester film using a bar coater with the obtained 10 main paint.
was applied to the back side of the ferromagnetic alloy thin film. After drying, it was cut into appropriate pieces to create magnetic tape. The coating film thickness is 3. o
It was μ. This is designated as sample E.

Samples A, B, and C prepared in Examples 1 to 5 above
.

With D, E and the applied sample wound on a reel,
An environmental test was conducted by leaving the product under conditions of a temperature of 60'C and a humidity of 9o%. In addition, the contact angle of the coating film with water was determined by δ11, and the water repellency was investigated. The results are shown in Table I below.

As is clear from Table 1 on page 11, the magnetic thin film according to the present invention is water repellent, which prevents moisture from entering, and improves the corrosion resistance of the magnetic thin film.

Furthermore, a running test was conducted using a test machine having the same functions as a commercially available VTR. With the sample whose back side was not coated, the running was unstable and noise, which was thought to be caused by triboelectric charging, was occasionally observed, but sample 4. B.C.

In D and E, the running was stable, and no noise that could be caused by frictional charging was observed.

In addition, 10% on a stainless steel block with a mirror finish.
Frictional resistance was measured using g load. The frictional resistance of the uncoated sample on the back side is 1. Table 3 shows the frictional resistance of each sample when oO.

As is clear from Table (2), the material according to the present invention has low frictional resistance and excellent lubricity.

As described above, according to the present invention, corrosion resistance and blocking resistance can be easily improved.

Claims (1)

[Claims] A magnetic recording medium comprising a ferromagnetic metal thin film formed on a non-magnetic substrate, containing the ferromagnetic metal thin film and at least one member selected from the group consisting of anti-higher fatty acid amides and higher aliphatic alcohols. A magnetic recording medium characterized by forming a coating film made of thermoplastic polyester.