JPS585456B2 - magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic recording media, and more particularly to antistatic magnetic recording media.

In magnetic recording tape, if the coating film is highly charged,
It easily attracts dust, etc., which may lead to dropouts or a drop in level.

Conventionally, as a countermeasure to this problem, it has been considered to add various antistatic agents, carbon black, and even metal powder to the magnetic coating film in order to increase the conductivity of the coating film.

However, each of these has drawbacks, such as blooming (oozing) when using antistatic agents.
The addition of carbon black or metal powder causes problems such as a decrease in sensitivity and accelerated deterioration of the coating film.

As a result of research into how to reduce this static charge, the present inventors discovered that among various antistatic agents, a betaine-type amphoteric antistatic agent has particularly excellent antistatic effects. Ta.

However, the antistatic effect of the betaine type amphoteric antistatic agent can be lowered from the resistance of 1013 to 1014Ω when no additive is added to about 1011Ω with the addition of a considerable amount (the definition of resistance will be described later), but it is still a countermeasure for preventing static electricity in magnetic recording media. It couldn't be said to be perfect.

In the present invention, by adding a betaine-type amphoteric antistatic agent and metal powder to magnetic paint, it was possible to create a magnetic recording tape with much lower chargeability than when both were used alone. It is something.

According to this method in which both are used in combination, the amount of each of the metal powder and the antistatic agent used can be kept to a small amount, and the above-mentioned drawbacks that occur with the use of the metal powder and the antistatic agent can be kept to a minimum. The electrical resistance, which is one measure of chargeability, can be lowered to a value of 10 9 to 10 10 Ω, which is sufficient for magnetic recording tapes.

Examples will be described below.

Example 1 γ-Fe203 powder 100 parts Vinyl chloride vinyl acetate copolymer 20 NBR (acrylonitrile 5 butadiene rubber) Dispersant (lecithin) 2 Solvent 200 Fe powder (particle size approx. Similarly, Anon BF (manufactured by NOF Corporation) was added in an amount of 0 to 1% as a betaine type antistatic agent to the magnetic powder in an amount of 0 to 5%, and a dispersion treatment was performed for 2 hours.

The resulting paint was applied onto a polyester film, and after drying, it was cut into a 6.3 mm width and the electrical resistance at a length of 5 cm was measured.

FIG. 1 shows the change in electrical resistance with the addition of Fe powder and antistatic agent.

When Fe powder and antistatic agent are used alone, Fe powder is 5%
, Anon BF can be reduced to the order of ×10 11 Ω by adding 1%, but this value is still not perfect.

However, when the two are combined, the electrical resistance decreases considerably, and even with pe of 1%, it is possible to reduce it to a no-problem range of ×10 10 Ω.

Furthermore, by increasing the amounts of both added, the electrical resistance can be further lowered.

In this way, by skillfully adjusting the amount of each addition, it is possible to efficiently lower the electrical resistance with a small amount.

Example 2 Cu and AI powders were respectively added as metals other than Fe to the same basic composition as in Example 1, and the synergistic effect with the betaine type antistatic agent was investigated.

Table 1 shows the electrical resistance values with and without the addition of betaine antistatic agent (Anon BF).

As seen in the table, the value is about half an order of magnitude lower when an antistatic agent is used in combination.

This shows that the combination with a betaine type antistatic agent is effective for metals other than Fe as well.

Comparative Example 1 Antistatic agents commonly used for PvC were investigated to see if the synergistic effect with metal powder as shown in Examples 1 and 2 also holds true for antistatic agents other than betaine type.

For comparison, ■TS-2 (non-ionic type, Kao Sekitsuken), ■New Nilegan A (cationic type, NOF),
■ There are three types: Resistat 141 (non-ionic type, Daiichi Kogyo Seiyaku).

Table 2 shows the electrical resistance values when 2% of the resin was added to the basic composition of Example 1, and 1% of Fe powder was added as metal powder to the magnetic powder.

As shown in Table 2, the values when the three types of antistatic agents mentioned above are added are all on the order of ×1012Ω, and the electrical resistance value when betaine antistatic agent is used under the same conditions is ×1010Ω. There is a difference of about 2 orders of magnitude.

Therefore, it can be said that these antistatic agents have no synergistic effect with metal powder.

As described above, by simultaneously adding metal powder and a betaine type amphoteric antistatic agent to a magnetic coating material, the electrical resistance can be efficiently lowered with a small amount, and the influence of charging can be eliminated.

The metal powder used may be any type of powder, but the antistatic agent is specific to the betaine type.

[Brief explanation of drawings]

FIG. 1 is a graph showing the effect of reducing the electrical resistance of a magnetic recording medium (antistatic effect) by adding a betaine type amphoteric antistatic agent and iron powder.

Claims (1)

[Scope of Claims] 1. A magnetic recording medium comprising a magnetic coating coated on a substrate with a magnetic paint containing at least 0.5% by weight of metal powder and at least 0.05% by weight of a betaine type antistatic agent based on the magnetic powder. . 2. The magnetic recording medium according to claim 1, which contains 0.5-5.0% by weight of metal powder and 0.05-1.0O1 of betaine type antistatic agent.