JPS5843813B2 - 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 made of a polymeric material such as a polyester base coated with a magnetic paint, which is a mixture of magnetic powder and a binder made of a polymeric material.

However, the base itself and the binder are insulating materials, and
The magnetic powder used is also a metal oxide with relatively high electrical resistance, such as γFe2O3, chromium oxide, cobalt-doped type, γFe2O3, etc., so the electrical resistance of the finished magnetic recording medium is high, which causes static electricity to build up. However, this caused dirt and dust to be absorbed.

Therefore, anionic, cationic, nonionic, and amphoteric surfactants have traditionally been used as antistatic agents. 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.

That is, the only means to prevent static electricity was to lower the electrical resistance of the tag 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,
Magnetic recording is achieved by keeping the amount of polyurethane resin at 40% by weight or less based on the total amount of binder, using an alkyl ether type surfactant, and applying a magnetic paint, which is a mixture of these and magnetic powder, to the substrate. It was previously discovered that the half-life of a medium, during which the amount of charge charged thereon is halved, is significantly shortened.

As a result of further research, the present inventor found that when a phosphate ester type surfactant is used together with the above alkyl ether type surfactant, the magnetic properties (orientation) are improved compared to the case of alkyl ether alone. Ta.

Furthermore, it has been found that the effect of decreasing the half-life does not change even if the ratio of these active agents is changed within a range where the total amount of both active agents is constant.

The effect of adding an alkyl ether type activator becomes sharply greater at 3 parts by weight or more (for a composition such as the formulation in the example below), but the same degree of decrease in half-life is about 50% for this activator. It can also be obtained by replacing it with a phosphate ester type surfactant.

Moreover, as mentioned above, the addition of a phosphate ester type surfactant improves the magnetic orientation, thereby providing an excellent magnetic recording medium.

The reason why the polyurethane resin content is about 40% by weight or less based on the total binder is that the half-life is significantly reduced in this range due to synergistic action with the surfactant.

If the amount of polyurethane resin exceeds about 40% by weight, the half-life will be undesirably large.

The present invention will be specifically described below with reference to Examples.

Example 1 γFe2O3 100 parts by weight Thermoplastic polyurethane resin 1.8 parts by weight C9H1oOH phosphoric acid varnish 1.2 chilled. However, x + y = 30 parts by weight constant, and X is 10, 20, 30, 40 and 50% (3 to 1
5 parts by weight).

Mixing the above five types of compositions in a ball mill,
A magnetic recording medium was fabricated by applying it to a polyester base according to a conventional method.

Its initial characteristics are shown in Table 1. Comparative Example In Example 1, five types of magnetic recording media were manufactured using 3 parts by weight of an alkyl ether type activator and without using a phosphate ester type activator.

The results are shown in Table 1.

The first thing that can be seen from Table 1 is that the polyurethane content is 40
% or less, the half-life becomes extremely short.

Therefore, in the present invention, a polyurethane content of 40% or less based on the total binder is used.

Next, there is almost no difference in electrical resistance between 3 parts by weight of alkyl ether type activator (comparative example) and when a part of it is replaced with 1.2 parts by weight of phosphate ester type activator. It can be seen that there is almost no difference.

Therefore, it can be understood that phosphate ester type surfactants also have the same half-life decreasing effect as alkyl ether type surfactants.

However, it will be explained later that there are limits to substitution.

Finally, it can be seen that in the case of the present invention, the magnetic orientation was considerably improved, and a magnetic recording medium superior to that of the comparative example could be provided.

Example 2 To see the effect of replacing a part of the alkyl ether type surfactant with a phosphate ester type surfactant, γFe2O3 100 parts by weight Thermoplastic polyurethane resin 12.0 (Nysten 5701) Vinyl chloride polymer Vinyl acetate co-18.0 Alkyl ether type surfactant (Neucol 1010 from Nippon Nyukazai Co., Ltd.) 3.0
Several types of mixtures of varnish phosphate having a weight part of C9H190H (+1=3.0 parts by weight) were prepared by changing 1, and magnetic recording media were manufactured in the same manner as in Example 1.

The half-life is shown in Figure 1. As can be seen from the figure, the alkyl ether type surfactant has a sufficiently short half-life (approximately 10 seconds or less) when present alone in 3 parts by weight;
．． It can be seen that even when replaced with up to 5 parts by weight of a phosphate ester type surfactant, the half-life is sufficiently short.

On the other hand, as shown in Example 1, the orientation can be improved by partial substitution.

Example 3 rrFe203 ioo parts by weight Thermoplastic polyurethane resin (Nysten 5701) 2 Vinyl chloride-vinyl acetate copolymer 8 Alkyl ether type surfactant (Neucol lolo from Nippon Nyukazai Co., Ltd.) C15H27→ζ=2)OH glue l t
Tonic acid ester A magnetic recording medium was produced using the above composition in the same manner as in Example 1.

The results are shown in Table 2. In addition, in Example 2 = 3
．． 0 (alkyl ether 3.0 parts by weight) was used as a comparative example.

The results in Table 2 show that substitution of the phosphate ester type activator improves orientation.

[Brief explanation of drawings]

FIG. 1 is a graph showing the effect of the addition of alkyl ether type and phosphate ester type surfactants on the half-life of the magnetic recording medium of the present invention.

Claims (1)

[Claims] 1 Contains vinyl chloride-vinyl acetate copolymer plasticized with polyurethane resin in an amount of 40% by weight or less based on the total binder amount, an alkyl ether type surfactant, a phosphate ester type surfactant, and magnetic powder. A magnetic recording medium in which a magnetic paint containing a phosphate ester type surfactant in an amount of 50% or less of the total amount of surfactants is coated on a substrate.