JPS63166010A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent increase in D.O. (drop-out) and generation of cylinder blocking by forming a magnetic layer contg. a vinyl chloride resin having a metal or alloy magnetic material of >=7.5 pH value and epoxy group on a nonmagnetic base. CONSTITUTION:The magnetic layer contg. the vinyl chloride resin having the metal or alloy magnetic material of >=7.5 pH value and the epoxy group is formed on the nonmagnetic base. The increase of the D.O. and the cylinder blocking often arise from the decomposition of a binder, which decomposition is generated by the dehydrochloration of the vinyl chloride resin. The dehydrochloration is liable to arise from the binder if the magnetic powder is of alkalinity of >=7.5 pH, but the epoxy group is effective as a stabilizer even under such conditions. The increase in the D.O. and the cylinder blocking are thereby prevented and the durability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording medium that can be used for audio tapes, video tapes, magnetic cards, magnetic disks, etc., and particularly relates to a metal powder with improved weather resistance. The present invention relates to magnetic recording media according to the present invention.

BACKGROUND OF THE INVENTION In recent years, research and development of magnetic materials has progressed from the conventional iron oxide to metal/alloy systems, particularly in the field of videotapes, with the aim of achieving high-density recording. Among these, improvements have been made to the composition and manufacturing conditions of metal/alloy magnetic materials in order to achieve uniform particle size, and the BET specific surface area has increased to 60 m2.
It is now possible to stably produce products weighing more than 27g. Furthermore, as a measure against moisture resistance, which is a problem unique to metal/alloy magnetic materials, metal/alloy magnetic materials with a pH value of 7.6 or more are being considered, as disclosed in Japanese Patent Laid-Open No. 60-32123.

Problems to be Solved by the Invention However, the conventional configurations caused problems in weather resistance tests depending on the type of binder.

The present invention is a magnetic recording medium using a metal or alloy magnetic material with a pH value of 7.6 or more, and has a pH value of O, (
The object of the present invention is to provide a magnetic recording medium that solves the problems of increased dropout and cylinder blocking.

Means for Solving the Problem In order to solve this problem, the magnetic recording medium according to the present invention has a magnetic layer containing a metal or alloy magnetic material having a pH value of 7.6 or more and a vinyl chloride resin having an epoxy group. is formed on a non-magnetic support.

Function: With this configuration, lubrication, O,
This makes it possible to prevent cylinder blocking and improve durability.

In the durability test of magnetic recording media, the weather resistance test was 60%.
It is required that no increase in D, 0. or cylinder blocking occurs after leaving the product in an environment of 90% RH for 10 days. It was discovered that a considerable number of substances are generated from the decomposition of the binder, and this led to the present invention.

In other words, vinyl chloride resin is often used as a binder due to its excellent properties, but this phenomenon occurs due to dehydrochlorination, and the epoxy group acts as a stabilizer to suppress this dehydrochlorination phenomenon. This is what I discovered.

The vinyl chloride resin having an epoxy group used in the present invention can be synthesized easily by adding glycidyl methacrylate during vinyl chloride polymerization.

The metal or alloy magnetic material used in the present invention is F
e1Fe-Co, Fe-Ni, Co-Ni, Fe-G
o-Ni.

etc.

Those having a pH value of 7.6 or more can be easily obtained through a dry oxidation process during the production of metal or alloy magnetic materials. This is thought to be due to the precipitation of alkaline roots on the surface of the magnetic powder due to dry oxidation.

As the dispersant, lecithin, oleic acid, etc. are used.

Higher fatty acids such as myristic acid, palmitic acid, stearic acid, and behenic acid can be used as lubricants.

Alumina, red iron oxide, chromium oxide, titanium oxide, etc. are used as the abrasive.

As an antistatic agent, conductive carbon such as Ketchinplak E, C, etc. can also be added.

Furthermore, graphitized carbon black can also be used.

Various types of dispersion machines are used to disperse crosstalk in magnetic paint.

For example, triple roll, pressure kneader, double planetary mixer, ball mill, Henschel mixer? -11 Vibration mill, Disper mill, Pebble mill, Agitator mill,
Attritor, sand grinder, cobal mill, combimix, line mill, line flow, bottle mill, etc. are used alone or in combination.

Example The present invention will be further explained in detail below.

Example 1 Ferromagnetic metallic iron powder (PH: 8.5) 100 parts by weight Lecithin 1 part by weight Polyurethane resin having sodium sulfonate groups
Vinyl chloride-vinyl acetate-vinyl alcohol copolymer having 10 parts by weight of epoxy groups
10 parts by weight α-alumina average diameter, 3 μm) 5 parts by weight Stearic acid
2 parts by weight n-butyl stearate
1 part by weight carbon black
3 parts by weight MEK-) luene-cyclohexanone (2:
2:1) After primary dispersion of 100 parts by weight of the above composition using a Henschel mixer, M
EK-) luene-cyclohexanone (2:2:1) in 1
00 parts by weight was added and secondary dispersed using a sand grinder to obtain a magnetic paint.

After adding 4 parts by weight of Coronate L (polyisocyanate made by Nippon Polyurethane) and mixing and dispersing with a disper, it was filtered through a filter with an average pore size of 1 μm, coated on a 10 μm thick polyethylene terephthalate film, oriented, dried, mirror-finished, and then cured. Furthermore, a back coat layer containing carbon black as a main component was provided on the polyethylene terephthalate film on the side opposite to the magnetic layer to obtain a magnetic tape.

Comparative Example 1 In Example 1, vinyl chloride, vinyl acetate, and vinyl alcohol each having an epoxy group! A magnetic tape was obtained in the same manner except that a vinyl chloride-vinyl acetate-vinyl alcohol copolymer containing no epoxy groups was used.

Example 2 In Example 1, the ferromagnetic metal iron powder was replaced with Fe-Co-Ni
A magnetic tape was obtained in the same manner except that the alloy was used.

Comparative Example 2 A magnetic tape was obtained in the same manner as in Example 2, except that the vinyl chloride-vinyl acetate-vinyl alcohol copolymer having an epoxy group was replaced with a vinyl chloride-vinyl alcohol-maleic acid copolymer.

Each magnetic tape obtained was cut into % inch pieces, and cassettes and
・Durability test was conducted by winding up at -7. The environment is 60'C
, 9041H, and after leaving the tape for 10 days, 0.
was measured. Cylinder blocking is 60”C, 90%
A tape was wrapped around a cylinder in an RH environment, and the entire surface of the cylinder was observed 10 days later.

The VTR used was a VHS video tape recorder (Kekishita Denki Sangyo ■l!! NV-SSOO), and the recording/playback head was changed to Sendust alloy.

The results are shown below.

As is clear from the Examples and the corresponding Comparative Examples, O increases by about 62 to 114 times after the weathering test in the magnetic tapes whose binder is vinyl chloride resin that does not contain epoxy groups. Further observation of the cylinder revealed corrosion caused by hydrochloric acid.

This is because the magnetic powder has a pH of 7.6 or more and is alkaline, so it is thought that dehydrochlorination occurred from the binder containing chlorine atoms by storing it at 60'0 90% RH for 10 days. The present invention recognized that the epoxy group is effective as a stabilizer for vinyl chloride resin even under the above conditions, and succeeded in obtaining a magnetic recording medium that satisfies the weather resistance test by introducing the epoxy group into the molecule. This is what I did.

Effects of the Invention As described above, according to the present invention, dehydrochlorination of the vinyl chloride resin binder is prevented, and the weather resistance of the recording medium is improved.

In addition, in the above embodiment, a magnetic tape was explained, but
It goes without saying that the present invention is applicable not only to magnetic tapes but also to magnetic recording media such as magnetic disks and magnetic cards.

Claims (1)

[Claims] A magnetic recording medium comprising a magnetic layer containing a metal or alloy magnetic material having a pH value of 7.5 or more and a vinyl chloride resin having an epoxy group, formed on a non-magnetic support.