JPS6032886B2 - 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 rFe203, chromium oxide, cobalt-doped rFe203, etc., so the electrical resistance of the finished magnetic recording medium is high, which causes static electricity to be charged. This caused dirt and dust to be absorbed. 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 static electricity in magnetic recording media has been to lower the electrical resistance of the magnetic recording media in order to completely discharge the static electricity.

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 inventor of the present invention revised the conventional concept of preventing static electricity - reducing electrical resistance, and realized that the point is that the static electricity that has been charged should be eliminated quickly. Rather than focusing on the idea of electrical resistance, we considered how to quickly reduce static electricity itself. As a result, when using vinyl chloride-vinyl acetate copolymer plasticized with polyurethane resin as a binder, the amount of polyurethane resin is 4% relative to the total amount of binder.
% by weight or less, and further uses an alkyl ether-type surfactant, and a magnetic coating that is a mixture of these and magnetic powder is coated on the substrate.A magnetic recording medium has a half-life when the amount of electric charge is halved. We have previously found that the value becomes significantly smaller.

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

Furthermore, it has been found that the effect of decreasing the half-life does not change even if the window amounts of both active agents are kept constant and the proportions of these active agents are varied within a certain range. For example, the effect of containing 3 parts by weight of an alkyl ether type surfactant (for a composition such as the formulation in the example below) is that approximately 50% of this active agent is replaced by a phosphate ester type surfactant. You can also get it.
Moreover, as mentioned above, the addition of a phosphate ester type surfactant improves the magnetic orientation, thereby providing an excellent magnetic recording medium. However, since the addition of alkyl ether type and phosphate ester type surfactants is carried out by simply kneading the magnetic powder and the binder, the strength between the binders deteriorates to some extent, and the peeling powder of the magnetic film is removed from the head. Head'
This sticks.

Therefore, in the present invention, magnetic powder is treated in advance with an alkyl ether type and phosphate ester type surfactant (the ratio of phosphate ester type to the total amount of surfactants is 50% or less) to cover the surface of the magnetic powder, thereby increasing the strength between the binders. It is possible to achieve a significant improvement in half-life without affecting the magnetic field, at the same time avoid the problem of head adhesion, and desirably have good orientation in terms of magnetic properties, thereby providing an excellent magnetic recording medium.

The reason why the polyurethane resin is used in an amount of 4% by weight or less based on the total amount of the binder is that a synergistic half-life reduction effect with the surfactant can be achieved within this range. Beyond this range, the half-life increases rapidly. The invention will be specifically described below with reference to Examples.

Example 1 rFe203 10 wt% alkyl ether type activator 1.8
(Neucol lolo manufactured by Nippon Nyukazai) C9th, 9th
0 day phosphate 1.2 water
A composition of 1000% or more was thoroughly mixed, a surfactant was adsorbed onto the surface of magnetic powder, and then the mixture was heated and dried.

The ferromagnetic powder treated with antistatic treatment in this way is [1]
rFe203 10 parts by weight Thermoplastic polyurethane resin 4.5 (Goodrich Esten 5701) Vinyl chloride-vinyl acetate copolymer 25.5 and ■ rFe208
10 parts by weight Thermoplastic polyurethane resin 12 (Goodrich Esten 5701) Vinyl chloride-vinyl acetate copolymer 18
The magnetic paint was dispersed with a binder and a solvent using a dispersing machine, and the resulting magnetic paint was applied to a polyester base.

The measurement results of various characteristics were as shown in the attached table. Example
2 rFe203 Cloud cover of 10 Alkyl ether type surfactant 2 Phosphate ester of (Ne skin oilolo of Nippon Nyukaza ■) 1 M old K IO
Mix well OO〃, perform surface treatment of magnetic powder, and apply this to '1} rFe203 10
Part by weight of thermoplastic polyurethane resin 4.5″
(Goodrich Esten 5701) Vinyl chloride-pinyl acetate copolymer 25.5 and '2} rFe2
03 10 parts by weight Thermoplastic polyurethane resin la parts by weight Goodrich Esten 5701) Vinyl chloride-vinyl acetate copolymer
18 was dispersed with a binder and a solvent using a dispersing machine, and the magnetic paint was applied to a polyester base.

The various characteristics were as shown in the attached table. Comparative Example 1 For comparison, a magnetic paint was produced by direct mixing without pre-treating the magnetic powder.

Untreated ferromagnetic powder [1] rFe203
10 parts by weight Alkyl ether type surfactant 1.8 (Neucollo from Nippon Nyukazai ■)
lo) C 9 days, 90 days phosphate 1.
2 Thermoplastic polyurethane resin 4.5 (Goodrich Esten 5701) Vinyl chloride-vinyl acetate copolymer 25.5 and [2] rFe203
10 parts by weight Alkyl ether type surfactant 1.8 C9-day, 90-day phosphate ester 1.2 Thermoplastic polyurethane resin 12 parts by weight (Goodrich Esten 5
701) Vinyl chloride-pinyl acetate copolymer 18
A magnetic paint was made by kneading two different formulations and was applied to the base.

Characteristics are shown in the attached table. This comparative example is compared to Example 1. Comparative Example 2 Instead of pre-treating the magnetic powder in Example 2, this surfactant was directly mixed.

That is, (1'rFe203
10 parts by weight of alkyl ether type surfactant 2
Phosphate ester of (Neucol lolo) 1″ *Thermoplastic polyurethane resin 4.5 (Esten 5701) Pinychloride-pinyl acetate copolymer 2
5.5″ and [21 rFe203
10 parts by weight alkyl ether type surfactant
A blend of phosphoric acid ester of 2 (Ne skin ol1010) 1 thermoplastic polyurethane resin IZ parts by weight vinyl chloride-vinyl acetate copolymer 18 was kneaded and applied to the base.

The characteristics are shown in the table below. Note: Head adhesion was evaluated visually using a 5-point method for adhesion of magnetic film peeling powder to the head.
As can be seen from the table above, when the magnetic recording medium of the present invention was compared with the additive magnetic recording medium of the comparative example, the electrical resistance was almost unchanged, but the head adhesion was improved and the strength of the coating film was improved. . Furthermore, the magnetic composition is clearly improved and the electrical properties are improved. The half-life was also slightly improved. Example 3 In Example 1 and Comparative Example 1, instead of 1.8 parts by weight of the alkyl ether type surfactant, k parts by weight and C9 days, 9
1 part by weight (instead of 1.2 parts by weight of phosphate ester on day 0)
However, magnetic recording media were manufactured by varying k and 1 (k11=3).

Example 3 corresponds to Example 1, Comparative Example 3 corresponds to Comparative Example 1, and their half-lives are shown in FIG. 1 (solid line - Example, dotted line - Comparative example). From FIG. 1, it can be seen that even if about 50% of the alkyl ether type activator is replaced with a phosphate ester type, the half-life remains unchanged. This, when compared to the table above, shows that film strength and formulation can be improved without reducing half-life. Furthermore, when Comparative Example 3 is compared with this example, it can be seen that the present invention is slightly more advantageous in terms of half-life.

[Brief explanation of drawings]

FIG. 1 is a graph showing the effect of a surfactant on the half-life in the magnetic recording medium of the present invention.

Claims (1)

[Claims] 1 A vinyl chloride-vinyl acetate copolymer plasticized with a polyurethane resin that accounts for 40% by weight or less of the total binder, and an alkyl ether type and phosphate ester type surfactant, in which phosphate ester accounts for 50% of the total active agent. A magnetic recording medium made by kneading ferromagnetic powder whose surface is preliminarily coated with ferromagnetic powder and coating it on a substrate.