JPS583288B2 - magnetic recording medium - Google Patents

Description

[Detailed description of the invention] The present invention relates to magnetic recording media.

Generally, a magnetic recording medium is a substrate such as a polyester base coated with a magnetic paint, which is a mixture of magnetic powder and a binder.

However, the base itself and the binder are insulating materials, and
The magnetic powder used is a metal oxide with relatively high electrical resistance, such as γ-Fe2O3, so the electrical resistance of the finished magnetic recording medium itself is high, which causes it to be charged with static electricity, which attracts dirt and dust. It was causing this.

Therefore, anionic, cationic, nonionic, and amphoteric surfactants have traditionally been used as antistatic agents, but conventionally, these antistatic agents were only added to the mixture of magnetic powder and binder. It was then applied to the substrate.

The conventional approach to preventing charging of magnetic recording media has been to lower the electrical resistance of the magnetic recording media in order to immediately discharge the static electricity that has been charged.

In other words, the only way to prevent static electricity was to lower the electrical resistance of the material itself.

For this reason, it was not possible to achieve a sufficiently satisfactory antistatic effect, but the inventors of the present invention have developed a conventional antistatic effect.
We changed the idea of reducing electrical resistance, and instead of focusing on the concept of electrical resistance, since the point is that the static electricity that has been charged should disappear as quickly as possible, we considered how to reduce the static electricity itself as quickly as possible.

As a result, when using vinyl chloride-vinyl acetate copolymer plasticized with polyurethane resin as a binder,
A magnetic recording medium in which the amount of polyurethane resin is 40% by weight or less based on the total amount of binder, an alkyl ether type surfactant is further used, and a magnetic paint, which is a mixture of these and magnetic powder, is applied to the substrate. found that the half-life, during which the amount of electrical charge is halved, becomes significantly shorter.

The present invention has been made based on this knowledge, and will be explained below using Examples and Comparative Examples.

Example 1 γ-Fe2O3 100 parts by weight Thermoplastic polyurethane resin 4.5 parts by weight (Goodrich Esten 5701) Vinyl chloride-vinyl acetate copolymer 25.5 parts by weight Alkyl ether walking surfactant 3 parts by weight ( The above compositions (Neurol 1010) manufactured by Nippon Nyukazai Co., Ltd. were mixed in a ball mill and coated on a polyester base to prepare a magnetic recording medium.

Example 2 A magnetic recording medium was prepared using the same method as in Example 1 except that the thermoplastic polyurethane resin was 12 parts by weight, and the vinyl chloride-vinyl acetate copolymer was 25.5 parts by weight.

Comparative Example A magnetic recording medium was prepared in Example 1 except that the surfactant was replaced with an alkyl phosphate salt.

The above results are shown in the table.

From this, it can be seen that although the electrical resistance of the example is not so small, the half-life is significantly short.

The figure also shows the change in half-life when the content of polyurethane resin is changed relative to the total amount of binder.

It can be seen from the figure that a polyurethane content of 40% by weight or less has a significant effect.

As described above, since the magnetic recording medium according to the present invention has a significantly short half-life, there is no adhesion of dirt, dust, etc.

[Brief explanation of drawings]

The figure is a graph showing values of polyurethane content and half-life.

Claims (1)

[Claims] 1. Magnetic recording made by coating a substrate with a magnetic paint containing a vinyl chloride-vinyl acetate copolymer plasticized with polyurethane resin in an amount of 40% by weight or less based on the total amount of binder, an alkyl ether type surfactant, and magnetic powder. Medium.