JPH0760517B2 - Magnetic recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to a magnetic recording medium. Specifically, it relates to a magnetic recording medium having excellent durability.

[Conventional technology and problems]

A magnetic recording medium is generally made by coating a base material such as a polyester film with a magnetic paint comprising a magnetic powder, a binder resin, an organic solvent and other necessary components. Since the magnetic layer is liable to wear due to a strong sliding contact with the head, jacket liner, etc., a magnetic layer with less wear and excellent durability is required.

Therefore, various lubricants have been mixed in the magnetic layer as one measure for improving the wear resistance of the magnetic layer.

Conventionally, various compounds have been proposed as lubricants.
They are various fatty acids, fatty acid esters, fatty acid amides,
Liquid paraffin, waxes and the like. However, it is extremely difficult for these lubricants, especially when used alone, to obtain satisfactory results in terms of performance. Even if it is effective in improving the durability, it is often incompatible with the resin binder and easily bleeds from the surface of the magnetic layer, or bleeding does not occur on the contrary, but it is often insufficient in terms of improving the durability.

Therefore, some of the above compounds may be used in combination for practical use, but in the present situation, it cannot be said that a sufficiently satisfactory lubricant system has been obtained. Particularly, recently, a device equipped with a magnetic recording medium such as a floppy disk is increasingly used outdoors, and a magnetic recording medium having excellent durability is required together with the device even under various environmental changes. .

[Means for solving problems]

The present inventors have arrived at the present invention as a result of earnest research to obtain a magnetic recording medium that is imparted with good lubricity and has significantly improved durability even in a wide range of use environments.

That is, the present invention provides a magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a resin binder, wherein the magnetic layer is (a) the following formula (1): (In the formula, R represents a branched alkyl group having 13 carbon atoms.) A magnetic recording medium comprising an ester compound represented by: (b) butyl stearate and (c) butoxyethyl stearate. It is provided.

The lubricant system according to the invention is composed of a very limited combination of ester compounds.

The ester compound represented by the above formula (1) is tridecyl stearate, and it is necessary to use a compound in which an alcohol-derived alkyl chain is branched. Although it may be partially substituted with unbranched tridecyl stearate, the total amount of branched tridecyl stearate is 60% by weight or more, more preferably 90% by weight or more.

Further, the compounding ratio of the ester compound (a) represented by the formula (1), butyl stearate (b), and butoxyethyl stearate (c) is 100 parts by weight, and (a) is 2
0 to 70 parts by weight, (b) 10 to 40 parts by weight, (c) 20 to 70 parts by weight
Parts by weight are preferred.

This lubricant system may be used by adding it to the magnetic paint,
You may melt | dissolve in a suitable solvent and spray it on a magnetic coating film.
This lubricant system is usually used in an amount of 1 to 15% by weight based on the magnetic powder.

The magnetic powder according to the present invention is acicular fine γ-Fe ₂ O.
Metal oxides such as ₃ , Fe ₃ O ₄ , and CrO ₂ , and Co-deposited γ-Fe
₂ O ₃ , γ-Fe which has been processed such as Co-doped γ-Fe ₂ O ₃
Fe ₂ O ₃ , iron metal powder, barium ferrite in the form of microplates, and magnetic powder in which some of the Fe atoms are replaced with one or more of Ti, Co, Zn, V, Nb, Co, Fe Examples include ultrafine powder of metal or alloy such as —Co and Fe—Ni. Of these, iron metal powders have particularly poor chemical stability, so nickel, cobalt, titanium, silicon, aluminum, etc. may be added in small amounts in the form of metal atoms, salts and oxides or surface-treated for improvement. However, these can also be used. The iron metal powder may form a thin oxide film on the surface in a weak oxidizing atmosphere for its stabilization, but the metal powder treated in this way can also be used.

Examples of the resin binder that can be used in the present invention, polyurethane, polyester, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, polyacrylonitrile, nitrile rubber, epoxy resin, alkyd resin,
Polyamide, polyacrylic acid ester, polymethacrylic acid ester, polyvinyl acetate, polyvinyl butyral,
Examples thereof include vinylidene chloride, vinylidene chloride copolymer, nitrification cotton, maleic acid-modified vinyl chloride / vinyl acetate copolymer, ethyl cellulose and the like. These may be used alone, but are usually used as a mixture of two or more kinds. In addition, a plasticizer or a curing agent may be added to adjust the hardness of the resin.

Further, the compounding amount of the resin binder is generally 15 to 60 parts by weight with respect to 100 parts by weight of the magnetic powder. Even if the resin binder has the largest binding force, if it is less than 15 parts by weight, the strength of the magnetic coating film becomes weak and the adhesive force between the substrate and the magnetic coating film becomes insufficient. On the other hand, if the amount is more than 60 parts by weight, the magnetic powder concentration in the magnetic coating film becomes small and the reproduction output is lowered, which is disadvantageous. In addition, the coating film characteristics may deteriorate.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 The following mixture was kneaded in a sand mill for about 15 hours.

As the above-mentioned tridecyl stearate having 95% by weight or more of branching, Exepearl TDS (trade name) manufactured by Kao Corporation was used.
It is to be noted that this is a mixture of n-butene and isobutene, which is subjected to a trimerization reaction to obtain a branched olefin having 12 carbon atoms, and further oxo-reacted this olefin to give a branched tridecyl alcohol (about 140 kinds of A mixture) was obtained, and this alcohol was obtained by esterifying stearic acid.

Thereafter, 7 parts by weight of a polyisocyanate compound (trimethylolpropane triisocyanate) was added to prepare a magnetic paint.

Next, this coating material was applied onto a polyethylene terephthalate film having a thickness of 75 μm so that the dry film thickness would be 1.5 μm, and calendering was performed after drying. Furthermore, this
After leaving it to stand at 60 ° C. for 4 days to carry out a curing reaction, it was punched into a disk shape, surface-polished, and enclosed in a jacket to manufacture a floppy disk.

This disk is loaded into a floppy disk accelerated durability test drive under the following test conditions, and a durability test is performed, and the running time until the playback output reaches 70% of the initial value is measured. The durability was evaluated.

The results are shown in Table 1.

<Test conditions> First, hold at a temperature of 5 ° C and a humidity of 30% RH for 8 hours.

Gradually raise temperature and humidity, and 40 ° C, 80% after 4 hours
Try to be RH.

Hold at 40 ℃, 80% RH for 8 hours. Gradually reduce temperature and humidity, and after 4 hours, 5 ℃, 30%
Try to be RH.

 This is repeated below.

Example 2 In Example 1, tridecyl stearate (branching 95%
(Part by weight or more) 2.7 parts by weight, butyl stearate 2.5 parts by weight, and butoxyethyl stearate 2.7 parts by weight. A floppy disk was manufactured in the same manner as in Example 1 and its durability test was conducted.

The results are shown in Table 1.

Example 3 A floppy disk was manufactured in the same manner as in Example 1 except that 30 parts by weight of vinyl chloride / vinyl acetate copolymer resin was used and 15 parts by weight of nitrile butadiene rubber was used in place of the polyurethane resin. A durability test was conducted.

The results are shown in Table 1.

Comparative Examples 1 to 6 A floppy disk was produced in the same manner as in Example 1 except that the lubricant shown below was used instead of the lubricant consisting of tridecyl stearate, butyl stearate, and butoxyethyl stearate. Then, the durability test was performed.

The results are shown in Table 1.

Lubricant Comparative Example 1 olein oleate 8 parts by weight Comparative Example 2 tridecyl stearate (branching 95% by weight or more) 8 parts by weight Comparative Example 3 tridecyl stearate (branching 95% by weight or more) / isocetyl Stearate = 4 parts by weight / 4 parts by weight Comparative Example 4 ... Tridecyl stearate (95% by weight or more of branching) / isocetyl stearate / oleic acid = 3 parts by weight
/ 2 parts by weight / 3 parts by weight Comparative Example 5 ... Butoxyethyl stearate 8 parts by weight Comparative Example 6 ... Butyl stearate / Butoxyethyl stearate = 2.5 parts by weight / 5.5 parts by weight

Claims (1)

[Claims] 1. In a magnetic recording medium having a magnetic layer containing magnetic powder and a resin binder as main components, the magnetic layer comprises (a) the following formula (1): (In the formula, R represents a branched alkyl group having 13 carbon atoms.) A magnetic recording medium comprising an ester compound represented by: (b) butyl stearate and (c) butoxyethyl stearate.