JPS63166012A - 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 which is formed by adding a heat stabilizer to a binder contg. a metal or alloy magnetic material of >=7.5 pH value and chlorine atom on a nonmagnetic base. CONSTITUTION:The magnetic layer which is formed by adding the heat stabilizer to the binder contg. the metal or alloy magnetic material of >=7.5 pH value and chlorine atom is formed on the nonmagnetic base. The increase in the drop-out (D.O.) and the generation of the cylinder blocking arise from the dehydrochloration generated from the binder contg. the chlorine atom by preservation, as the magnetic powder is of alkalinity of >=7.5 pH. An inorg. acid salt, metal soap, etc., are used as the heat stabilizer and the amt. of said stabilizer to be added is adequately 0.1-5wt.%. The increase in the D.O. and the cylinder blocking are thereby prevented and the durability is improved.

Description

[Detailed description of the invention] Industrial applications The present invention relates to audio tapes and video tapes.

The present invention relates to magnetic recording media that can be used for magnetic cards, magnetic disks, etc., and particularly relates to magnetic recording media made of metal powder with improved weather resistance.

BACKGROUND OF THE INVENTION In recent years, research and development of magnetic materials has progressed from conventional iron oxide to metal/alloy systems, particularly in the field of video tapes, in order to achieve 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 has become possible to stably manufacture products with a ratio of 2/f or higher. 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 structure caused problems in weathering 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 includes a metal or alloy magnetic material having a pH value of 7.5 or more and a binder containing chlorine atoms, and a heat stabilizer added to the binder. The magnetic layer is formed on a non-magnetic support.

Effect: This configuration ensures that 0.
0 increase, it is possible to prevent cylinder prosking 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 being left in an environment of 90% RH for 10 days. The inventor p, 0. We have worked diligently to clarify the phenomenon of cylinder blocking and the increase in the number of binders, and have discovered that many of the phenomena are caused by the decomposition of the binder, leading to the present invention. That is, vinyl chloride resin is often used as a binder due to its excellent properties, but the above-mentioned phenomenon occurs due to dehydrochlorination, and this phenomenon can be suppressed by adding a heat stabilizer.

The metal or alloy magnetic material used in the present invention is F
e, Fe-Co, Fe-Hl, Co-N
i, Fe-co-N3, etc.

Those having a pH value of 7.5 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.

Binding agents include those containing chlorine atoms, such as vinyl chloride resin,
vinyl chloride-vinyl acetate-vinyl alcohol copolymer,
Vinyl chloride derivatives with large hydrophilic groups, etc. can be used.

Lecithin, oleic acid, etc. are used as the dispersant.

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 C can also be added to Kettin black. Furthermore, graphitized carbon black can also be used.

Various types of dispersion machines are used to disperse crosstalk in magnetic paint. For example, three-roll, pressure kneader, double planetary mixer, ball mill Henschel mixer, vibration mill, disper mill, pebble mill, agitator mill attritor, sand grinder, coball mill, combi mix, line mill, line flow, bottle mill, etc. Used alone or in combination.

As the heat stabilizer for the vinyl chloride resin used in the present invention, inorganic acid salts, metal soaps, organic tin compounds, epoxy compounds, amine compounds, etc. are used. The appropriate amount to be added is 0.1 to 6 parts by weight based on the resin.

Example Examples of the present invention will be specifically described below.

Example 1 Ferromagnetic metal iron powder (PH: 8.7) Lecithin 1 part by weight Polyurethane resin having sodium sulfonate group 10 parts by weight Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 10 parts by weight α-alumina (
Average particle size 0.3μm) 5 parts by weight stearic acid
2 parts by weight n-butyl stearate
1 part by weight dibutyltin dilaure) 0
．． 2 parts by weight MKK-toluene-cyclohexanone (2:2:1) 200 parts by weight The above composition was firstly dispersed using a Henschel mixer and then secondarily dispersed using a sand grinder to obtain a magnetic coating material. 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 A magnetic tape was obtained in the same manner as in Example 1 except that dibutyltin dilaurate was omitted.

Example 2 In Example 1, the ferromagnetic metal iron powder was Fe-G.

A magnetic tape was obtained in the same manner except that the -Ni alloy was used.

Comparative Example 2 A magnetic tape was obtained in the same manner as in Example 2 except that dibutyltin dilaurate was omitted. Each of the obtained magnetic tapes was cut into inch pieces, rolled into a cassette, and subjected to a durability test. The environment was 60'C, 90% RH, and after leaving the tape for 10 days, it became 0. was measured. Cylinder blocking was performed by wrapping a tape around a cylinder in an environment of 6°C and 90% RH, and observing the cylinder surface 10 days later.

The VTR used was a VHS video tape recorder (Ny-saoo manufactured by Kishita Denki Sangyo Co., Ltd.), and the recording/playback head was changed to a Sendust alloy.

The results are shown below.

As is clear from the Examples and the corresponding Comparative Examples, the system beam without adding a heat stabilizer, the 0. is 160-230 after weathering test
It has increased about twice as much. Further observation of the cylinder revealed corrosion caused by hydrochloric acid.

This is thought to be due to the fact that since the magnetic powder has a pH of 7.5 or more and is alkaline, dehydrochlorination occurred from the binder containing chlorine atoms by storage at 60° C. and 90% RH for 10 days. The present invention has succeeded in obtaining a magnetic recording medium that satisfies the weather resistance test even under the above conditions by adding a vinyl chloride resin heat stabilizer.

Effects of the Invention As described above, according to the present invention, dehydrochlorination of the 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 formed on a non-magnetic support by adding a heat stabilizer to a binder containing a metal or alloy magnetic material having a pH value of 7.5 or more and a chlorine atom.