JPH079698B2 - Magnetic recording medium - Google Patents

Description

The present invention relates to a magnetic recording medium such as a magnetic disk having a magnetic layer provided on at least one surface of a base.

[Conventional technology]

Generally, in a magnetic recording medium in which a magnetic layer comprising a magnetic powder, a binder and other necessary components is formed on a base such as a polyester film, the magnetic layer is used as a magnetic head or a magnetic pad or the like when recording / reproducing. Since it is in sliding contact at high speed, it is required that the magnetic layer has excellent wear resistance. By incorporating a lubricant such as higher fatty acid ester or higher fatty acid into the magnetic layer than before, the wear resistance of the magnetic layer is improved. Have been improved (literature unknown).

However, in the above-mentioned conventional lubricants, for example, those having a high boiling point and being hard to volatilize solidify at a low temperature to become a solid or thicken, so that a sufficient lubricating effect is not exhibited in use at a low temperature. In the case of a low viscosity liquid at low temperature, it has a low boiling point and volatilizes easily, and at high temperature the viscosity decreases too much, so the lubricant excessively exudes on the surface of the magnetic layer due to sliding contact with the contact object, Even when stored underneath, the lubricant was exuded to the surface of the magnetic layer, so that it was inferior in use and storage stability at high temperature. Therefore, the conventional lubricant has a problem that it is difficult to improve the wear resistance of the magnetic layer over a wide operating temperature range from low temperature to high temperature.

[Problems to be solved by the invention]

Therefore, the present invention solves the problem that the conventional general-purpose lubricant is difficult to satisfy both the lubricity under the use environment of low temperature to high temperature, and not only under the normal condition but also under the use environment of low temperature and high temperature. The object of the present invention is to provide a magnetic recording medium that exhibits excellent lubricity and good storage stability at high temperatures, and that has a large effect of improving wear resistance and excellent durability.

[Means for solving problems]

As a result of diligent studies from the above viewpoints, the present inventors have shown that when a specific fatty acid ester is used as a lubricant, good lubricity is exhibited in a wide operating temperature range from low temperature to high temperature, and high temperature storage stability is good. The inventors have found that a magnetic layer having a great effect of improving wear resistance and excellent durability can be formed, and have completed the present invention.

That is, according to the present invention, at least one fatty acid ester selected from 2-ethylhexyl oleate and n-octyl oleate is contained as a lubricant in the magnetic layer provided on at least one surface of the base. The present invention relates to a magnetic recording medium.

[Constitution / Operation of Invention]

The fatty acid ester used as a lubricant in the present invention has a carbon-carbon double bond in the molecule of a higher unsaturated fatty acid, and thus generally gives a fatty acid ester having a low cooling cloud point, while a carbon atom is used as an alcohol component. Number is 8
2-ethylhexanol or n-octanol is used, and since the unsaturated fatty acid consists of oleic acid having 18 carbon atoms, it has a high boiling point and is difficult to volatilize, and the viscosity may be too low even at high temperatures. Absent. That is, the lubricant of the present invention has the features that it has a high boiling point and low volatility, but has a low cooling cloud point and that its viscosity does not drop too much even at high temperatures. For this reason, the magnetic layer containing this can not only exhibit excellent lubrication effect in use environment from low temperature to high temperature, but also has good storage stability at high temperature, thus improving wear resistance and excellent durability. It is supposed to be.

Such a fatty acid ester generally has a boiling point of 200 ° C (10 m
mHg) or higher, preferably 230 ° C. (10 mmHg) or higher, and the cooling cloud point is usually 10 ° C. or lower, preferably 0 ° C. or lower.

The amount of the lubricant used is 100% of the magnetic powder in the magnetic layer.
About 1 to 30 parts by weight is preferable with respect to parts by weight. If the amount used is too small, the effect of improving wear resistance is not sufficiently exerted. On the contrary, if the amount is too large, it exudes the surface of the magnetic layer and contaminates a contact object such as a magnetic head.

To obtain the magnetic recording medium of the present invention, a lubricant is added to a magnetic coating material containing magnetic powder and a binder, and this is applied to one side or both sides of a base such as polyester film and dried to form a magnetic layer. Then, it can be obtained by subjecting it to a surface treatment such as calendering by a conventional method and then subjecting it to slitting or punching. As another method of incorporating a lubricant into the magnetic layer, a magnetic coating material containing no lubricant is prepared, a magnetic layer is formed in the same manner as above, and then a solution containing a lubricant is applied to the surface of the magnetic layer. Alternatively, it may be contained by immersing it in this solution.

In the present invention, organic lubricants such as higher fatty acids, higher fatty acid esters, hydrocarbons, polyethers, etc., which are different from the above-mentioned lubricants of the present invention which are conventionally used as lubricants for magnetic layers together with the above-mentioned lubricants, An inorganic lubricant such as silicon oil or fluorine oil may be used.

Magnetic powders used in the present invention include γ-Fe ₂ O ₃ , Fe ₃
O ₄ , an intermediate oxide between γ-Fe ₂ O ₃ and Fe ₃ O ₄ , Co-containing γ-Fe ₂
In addition to oxide-based magnetic powders such as O ₃ , Co-containing Fe ₃ O ₄ and CrO ₂ , there are metallic magnetic powders such as Fe powder and alloy powders. Further, as the binder, vinyl chloride-vinyl acetate copolymer, fibrin resin, polyvinyl butyral resin, polyurethane resin, polyester resin, epoxy resin, polyether resin, isocyanate compound, etc. Various known binder components are used. Further, the magnetic layer may appropriately contain other additive components such as a surfactant, a dispersant, an antistatic agent, an abrasive and a pigment.

〔The invention's effect〕

The magnetic recording medium according to the present invention, by including the specific fatty acid ester as a lubricant in the magnetic layer, can exhibit excellent lubricity not only under normal conditions but also under operating conditions from low temperature to high temperature, and Since it is also excellent in high-temperature storability, it has improved wear resistance and excellent durability.

〔Example〕

The present invention will be specifically described below based on examples. In the following, "parts" means "parts by weight".

Example 1 Co-containing γ-Fe ₂ O ₃ powder 100 parts Nitrocellulose resin 19 parts Polyurethane resin 12 parts Trifunctional low molecular weight isocyanate compound 8 parts 2-Ethylhexyl oleate 10 parts Cyclohexanone 150 parts Toluene 150 parts A magnetic paint was prepared by kneading in a ball mill No. 3 for 96 hours, and this magnetic paint was applied to both sides of a polyester film having a thickness of 75 μm so that the thickness after drying was 1.1 μm, and dried to form a magnetic layer. . Then, it was calendered and punched into a disk shape to prepare a magnetic disk.

Example 2 A magnetic disk was produced in the same manner as in Example 1 except that n-octyl oleate was used in the same amount instead of 2-ethylhexyl oleate in Example 1.

Comparative Example 1 A magnetic disk was produced in the same manner as in Example 1 except that n-butyl oleate was used in the same amount instead of 2-ethylhexyl oleate in Example 1.

Comparative Example 2 A magnetic disk was produced in the same manner as in Example 1 except that the same amount of stearyl stearate was used instead of 2-ethylhexyl oleate in Example 1.

With respect to the magnetic disks obtained in the above Examples and Comparative Examples, a durability test was conducted and the results are shown in the following table. The durability test was carried out at low temperature (5 ° C) and high temperature (40 ° C) for each of the magnetic disks immediately after preparation (initial) and those stored at 60 ° C for 4 weeks (high temperature storage).
I went under the conditions.

While this is brought into sliding contact with a magnetic head in the pad pressure 30 g / cm ² was loaded to <Durability Test> Each magnetic disk recording and reproducing apparatus, durability running time until the reproduction output becomes 70% of the initial output It was time.

As is clear from the above table, the magnetic disk of the present invention not only has good wear resistance of the magnetic layer under the use environment from low temperature to high temperature, but also has an initial state after being stored at high temperature for a long time. It can be seen that it is well maintained and has good results in storage stability at high temperatures, and that it has even more excellent durability.

Claims (1)

[Claims] 1. A magnetic layer provided on at least one surface of a base contains, as a lubricant, at least one fatty acid ester selected from 2-ethylhexyl oleate and n-octyl oleate. Magnetic recording medium.