JPH0556566B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to magnetic recording media. Specifically, the present invention relates to a magnetic recording medium with excellent durability. [Prior Art and Problems] Magnetic recording media are generally made by applying a magnetic paint consisting of magnetic powder, binder resin, organic solvent, and other necessary components onto a substrate such as a polyester film. Since floppy disks come into violent sliding contact with magnetic heads, jacket liners, etc. during recording and reproduction, the magnetic layer is likely to be abraded, so a magnetic layer that is less abrasive and has excellent durability is required. Therefore, as a measure to improve the wear resistance of the magnetic layer, various lubricants are mixed into the magnetic layer. Conventionally used lubricants include fatty acids, oleyl oleate, butoxide stearate, fatty acid amides, liquid paraffin, wax, and the like. However, it is currently difficult to say that these lubricants are satisfactory in terms of performance. For example, oleyl oleate, butoxide stearate, etc. are insufficient for improving the durability of media, while fatty acids such as stearic acid and oleic acid, and hydrocarbon-based lubricants such as liquid paraffin are effective in improving durability. Although effective, it has poor compatibility with the binder, and when used in large quantities, it bleeds from the surface of the magnetic layer and tends to stain the head. [Means for Solving the Problems] The present inventors have developed the present invention as a result of intensive research in order to obtain a magnetic recording medium that is endowed with good lubricity and has significantly improved durability even under a wide range of usage environments. reached. That is, the present invention provides a magnetic recording medium having a magnetic layer containing magnetic powder and a binder as main components, wherein the magnetic layer contains an ester compound represented by the following general formula (1). It provides a recording medium. {In the formula, R ₁ and R ₂ each have 1 to 25 carbon atoms (however, R ₁
and R ₂ have a total number of carbon atoms of 21 to 32), a linear or branched saturated alkyl group, and R ₃ is an oleyl group. } [Function] The ester compound represented by the general formula (1) according to the present invention is a certain limited compound, and the part derived from alcohol is a branched alcohol having 23 to 34 carbon atoms, and the resin acid The moiety derived from must be oleic acid. It is not clear why the lubricity of magnetic recording media is greatly improved when such specific ester compounds are used as lubricants. According to the studies conducted by the present inventors, ester-based lubricants are optimal in terms of compatibility with binders, and lubricants with relatively large molecular weights are more effective in improving lubricity. . However, many ordinary esters with large molecular weights have high melting points and have good lubricity at relatively high temperatures, but have poor fluidity and permeability at temperatures as low as 5°C, and at low temperatures. It was not possible to impart good durability to the media. Inferred from the above, the synergistic effect of the branched alcohol and unsaturated fatty acid lowers the melting point of the ester compound according to the present invention, thereby imparting good lubricity to the magnetic recording medium and increasing its durability. It is assumed that the performance will improve. The ester compound according to the present invention has 23 to 34 carbon atoms.
It can be obtained by an esterification reaction using a branched alcohol and oleic acid. The branched alcohol used here is called Guerbet alcohol because of its synthesis method. The ester compound of the present invention may be used by being added to a magnetic coating, or may be dissolved in a suitable agent and sprayed onto a magnetic coating. Furthermore, a conventional lubricant may be added to the ester compound of the present invention. The magnetic powder according to the present invention includes fine needle-shaped metal oxides such as γ-Fe ₂ O ₃ , Fe ₃ O ₄ , and CrO ₂ ,
In addition, γ-Fe ₂ O ₃ treated with Co-coated γ-Fe ₂ O ₃ , Co-doped γ-Fe ₂ O ₃ , iron metal powder,
Microplate-like barium ferrite and magnetic powder in which part of its Fe atoms are replaced with one or more of Ti, Co, Zn, V, Nb, etc., Co, Fe-Co, Fe-
Examples include ultrafine powder of metals such as Ni or alloys.
Among these, iron metal powder has particularly poor chemical stability, so to improve this, small amounts of nickel, cobalt, titanium, silicon, aluminum, etc. are added in the form of metal atoms, salts, and oxides, or the surface is treated. However, these can also be used. Iron metal powder may also form a thin oxide film on its surface in a weakly oxidizing atmosphere to stabilize it.
Metal powder treated in this way can also be used. Examples of binders that can be used in the present invention include 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, vinylidene chloride, vinylidene chloride copolymer, nitrified cotton, maleic acid-modified vinyl chloride/acetic acid Examples include vinyl copolymers and ethyl cellulose. Although these may be used alone, two or more types are usually used in combination. Furthermore, a plasticizer or a hardening agent may be added to adjust the hardness of the resin. In addition, the amount of binder blended is generally 100% magnetic powder.
It is 15 to 60 parts by weight. Even if the binder has the highest binding strength, if it is less than 15 parts by weight, the strength of the magnetic coating will be weak and the adhesive strength between the substrate and the magnetic coating will be insufficient. On the other hand, when the amount is more than 60 parts by weight, the concentration of magnetic powder in the magnetic coating film decreases, which is disadvantageous because the reproduction output decreases. Furthermore, the properties of the coating film may deteriorate. Further, the ester compound represented by the general formula (1) is usually contained in an amount of 1 to 15% by weight based on the magnetic powder. [Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. Examples 1 to 3 Using the lubricants shown in Table 1, mixtures having the compositions shown below were prepared. Co-adhered γ-Fe ₂ O ₃ 100 parts by weight PVC/vinyl acetate copolymer ^*1 30 Nitrile butadiene rubber ^*2 15 Carbon black 7 Aluminum oxide 6 Toluene 150 Methyl ethyl ketone 150 Lecithin 1 Lubricant 6 (Note) *1 Manufactured by UCC, USA Product name VAGH *2 Product name 1432J manufactured by Nippon Zeon Co., Ltd. Next, the above mixture was kneaded in a sand mill for 15 hours, and then 7 parts by weight of a polyisocyanate compound (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) was added to make a total of 11 types. A magnetic paint was prepared. Next, these paints were applied onto a polyethylene terephthalate film having a thickness of 75μ so that the dry film thickness was 1.5μ, and after drying, a calender treatment was performed. Furthermore, after leaving this at 60℃ for 4 days to perform a curing reaction,
A magnetic disk was manufactured by punching it into a disk shape and polishing the surface. The durability of each magnetic disk was determined by loading these disks into a floppy disk acceleration durability test drive and measuring the running time at 5°C until the playback output reached 70% of the initial output. . The results are shown in Table 1.

[Table] Comparative Examples 1 to 6 In place of the lubricant used in the example, 6 parts by weight of the various lubricants shown in Table 2 were used, and the other components and their amounts were the same as in Example 1. A total of six types of magnetic paints were prepared according to the method. Magnetic disks were manufactured using these paints in the same manner as in Example 1, and the durability of these disks was examined. The results are shown in Table 2.

【table】

Claims (1)

[Scope of Claims] 1. A magnetic storage medium having a magnetic layer mainly composed of magnetic powder and a binder, characterized in that the magnetic layer contains an ester compound represented by the following general formula (1). magnetic recording medium. {In the formula, R ₁ and R ₂ each have 1 to 25 carbon atoms (however, R ₁
and R ₂ have a total number of carbon atoms of 21 to 32), a linear or branched saturated alkyl group, and R ₃ is an oleyl group. }