JPH0470689B2 - - 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 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. } Ester compound represented by the following general formula () {In the formula, R ₄ is a linear or branched aliphatic hydrocarbon group having 1 to 29 carbon atoms, and R ₅ is a linear or branched aliphatic hydrocarbon group having 1 to 23 carbon atoms, or an aliphatic hydrocarbon group having 24 to 23 carbon atoms. 36 straight-chain aliphatic hydrocarbon groups (but
The sum of the carbon numbers of R ₄ and R ₅ is 16 to 65)} and a magnetic recording medium characterized by containing a fatty acid () having 10 to 30 carbon atoms It is. [Function] The magnetic recording medium of the present invention includes, in the magnetic layer, an ester compound represented by the general formula () {hereinafter abbreviated as ester compound ()}, an ester compound represented by general formula () {hereinafter referred to as ester Compound()
} and fatty acids (). When these three types of compounds are included in the magnetic layer, excellent lubricity is imparted, resulting in significantly improved durability. It is not clear why the durability of the magnetic recording medium is greatly improved when these three types of compounds are used. 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 (), the aliphatic hydrocarbon group represented by R ₄ is preferably a linear one or one branched from a low molecular weight group such as a methyl group or an ethyl group. Specific compounds include tridecyl stearate, isotridecyl stearate, tridecyl palmitate, isotridecyl palmitate, isocetyl palmitate,
Cetyl myristate, isocetyl stearate,
Examples include isostearyl oleate, eicosyl myristate, and seryl laurate. Further, as the fatty acid (), a straight chain fatty acid having 12 to 22 carbon atoms or a branched fatty acid having a low molecular weight group such as a methyl group or an ethyl group is preferable. Specific compounds include oleic acid, palmitic acid, stearic acid, isostearic acid, isopalmitic acid,
Examples include arachidic acid, behenic acid, and erucic acid. In addition, the total usage amount of the ester compound (), ester compound () and fatty acid () is:
It is usually 1 to 15% by weight based on the magnetic powder. In addition, the ester compound (), the ester compound (),
The preferred usage amount of each fatty acid () is the sum of these 100, and the amount of ester compound ()
is 1 to 40% by weight, and ester compound () is 10 to 80% by weight.
% by weight, fatty acid () is 1 to 40% by weight, more preferably 5 to 35% by weight of ester compound (), 15 to 70% by weight of ester compound (), and 5 to 35% by weight of fatty acid (). It is. 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-shaped 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. [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 9 Using the types and amounts of 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 Polyurethane resin 1 ^*2 27 Polyurethane resin 2 ^*3 5 Carbon black 8 α-Al ₂ O ₃ 4 Toluene 67 parts by weight Methyl ethyl ketone 67 Cyclohexanone 100 Note) *1 Product name manufactured by Union Carbide Corporation 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 nine types of magnetic paints were prepared by adding 5.4 parts by weight of . These paints were then applied onto a 75μ thick polyethylene phthalate film to a dry film thickness of 1.5μ.
After drying, calender treatment was performed. 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】

[Table] Comparative Examples 1 to 5 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 five 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.

【table】

【table】

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. } Ester compound represented by the following general formula () {In the formula, R ₄ is a linear or branched aliphatic hydrocarbon group having 1 to 29 carbon atoms, and R ₅ is a linear or branched aliphatic hydrocarbon group having 1 to 23 carbon atoms, or an aliphatic hydrocarbon group having 24 to 23 carbon atoms. 36 straight-chain aliphatic hydrocarbon groups (but
The sum of the carbon numbers of R ₄ and R ₅ is 16 to 65)} A magnetic recording medium characterized by containing an ester compound represented by the following formula and a fatty acid having 10 to 30 carbon atoms ().