JPH0470690B2 - - 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 on a non-magnetic support, in which the magnetic layer has the following general formula (). {In the formula, R ₁ and R ₂ have a carbon number of 1 to 25 (however, R ₁ and
R ₂ has a straight or branched saturated alkyl group (the sum of carbon atoms is 22 to 34), R ₃ has 7 to 29 carbon atoms
It is a saturated or unsaturated alkyl group having a straight chain or a branch. } and the following general formula () {In the formula, R ₄ is an aliphatic hydrocarbon group having 1 to 29 carbon atoms, R ₅ is a linear or branched aliphatic hydrocarbon group having 1 to 23 carbon atoms, or a straight chain aliphatic group having 24 to 36 carbon atoms The present invention provides a magnetic recording medium characterized by containing an ester compound represented by a hydrocarbon group (the sum of the carbon numbers of R ₄ and R ₅ is 15 to 65). [Function] The magnetic recording medium of the present invention includes an ester compound represented by the general formula () {hereinafter abbreviated as ester compound ()} and a compound represented by the general formula () in the magnetic layer.
It contains an ester compound represented by {hereinafter abbreviated as ester compound ()}. When these specific ester compounds are used in combination, excellent lubricity is imparted, and as a result, the durability of the magnetic recording medium is greatly improved, but the reason why such excellent lubricity is imparted is not clear. The ester compound () can be obtained, for example, by an esterification reaction between a branched alcohol and a fatty acid. This branched alcohol is called Guerbet alcohol because of its synthesis method. In the ester compound (), _R4 is preferably an aliphatic hydrocarbon group having 7 to 23 carbon atoms. Further, this R ₄ is preferably a straight chain one or one branched from a low molecular weight group such as a methyl group or an ethyl group. Specific compound names include tridecyl stearate, isotridecyl stearate, oleyl stearate, tridecyl palmitate, isotridecyl palmitate, cetyl myristate, isocetyl stearate, isostearyl palmitate, iso Examples include stearyl oleate and eicosyl myristate. In addition, the total usage amount of the ester compound () and the ester compound () is usually 1 to 15% by weight based on the magnetic powder, and the usage ratio of the ester compound () and the ester compound () is usually 1 to 15% by weight based on the magnetic powder. ()/()=range of 10/90 to 90/10. 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 some 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. In order to stabilize iron metal powder, a thin oxide film may be formed on the surface in a weakly oxidizing atmosphere, and metal powder treated in this manner may 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. [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 5 Using ester compounds of the types and amounts shown in Table 1 as lubricants, 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 Polyurethane resin 1 ^*2 27 Polyurethane resin 2 ^*3 5 Carbon black 8 α-Al ₂ O ₃ 4 Toluene 67 Methyl ethyl ketone 67 Cyclohexanone 100 Note) *1 Product name manufactured by Union Carbide Company in the United States
VAGH *2 Product name manufactured by Nippon Polyurethane Industries Co., Ltd.
N2301 *3 Product name manufactured by Nippon Polyurethane Industries Co., Ltd.
N2304 Next, the above mixture is kneaded in a sand mill for 5 hours, then a lubricant is added and kneaded in a ball mill for 10 hours. Furthermore, a polyisocyanate compound (product name N3200 manufactured by Sumitomo Bayer Urethane) is added to this.
A total of 5 types of magnetic paints were prepared by adding 5.4 parts by weight of . These paints were then applied onto a 75μ thick polyethylene terephthalate film to achieve a dry film thickness of
It was applied to a thickness of 1.5μ, and after drying, it was calendered. Further, this was left at 60° C. for 4 days to undergo a hardening reaction, and then punched out into a disk shape and surface polished to produce a magnetic disk. The durability of each magnetic disk was determined by loading these disks into a floppy disk accelerated durability test drive and measuring the running time at 5℃ and 25℃ until the playback output reached 70% of the initial output. was determined. The results are shown in Table 1.

[Table] Comparative Examples 1 to 4 In place of the lubricant used in the example, the type and amount of lubricant shown in Table 2 was used, the other components and their amounts were the same as in the example, and the method of the example was carried out. A total of four types of magnetic paints were prepared according to the method. Magnetic disks were manufactured using these paints in the same manner as in the examples, and the durability of these disks was examined. The results are shown in Table 2.

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Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer on a non-magnetic support, wherein the magnetic layer has the following general formula (). {In the formula, R ₁ and R ₂ have a carbon number of 1 to 25 (however, R ₁ and
R ₂ has a straight or branched saturated alkyl group (the sum of carbon atoms is 22 to 34), R ₃ has 7 to 29 carbon atoms
It is a saturated or unsaturated alkyl group having a straight chain or a branch. } and the following general formula () {In the formula, R ₄ is an aliphatic hydrocarbon group having 1 to 29 carbon atoms, R ₅ is a linear or branched aliphatic hydrocarbon group having 1 to 23 carbon atoms, or a straight chain aliphatic group having 24 to 36 carbon atoms 1. A magnetic recording medium characterized by containing an ester compound represented by a hydrocarbon group (the sum of the carbon numbers of R ₄ and R ₅ is 15 to 65). 2. The magnetic recording medium according to claim 1, wherein _R4 is an aliphatic hydrocarbon group having 7 to 23 carbon atoms.