JPH077501B2 - 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 used lubricants include fatty acids, oleyl oleate, butoxides stearates, fatty acid amides, liquid paraffin and waxes. However, at present, it is difficult to say that these lubricants are satisfactory in terms of performance. For example, oleyl oleate,
Stearic acid butoxide is insufficient for improving the durability of the medium, and fatty acids such as stearic acid and oleic acid and hydrocarbon-based lubricants such as liquid paraffin are effective for improving the durability, but are binders. It has poor compatibility with, and when used in a large amount, it has a drawback that it easily bleeds from the surface of the magnetic layer and stains the head.

[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 on a non-magnetic support, wherein the magnetic layer has the following general formula (I): {Wherein R ₁ and R ₂ are saturated alkyl groups having ₁ to 25 carbon atoms (however, the sum of the carbon numbers of R ₁ and R ₂ is 16 to 34) having a straight chain or a branch, and R ₃ is the carbon number. It is a saturated or unsaturated alkyl group having 7 to 29 straight or branched chains. } And a branched ester compound represented by the following general formula (II) (In the formula, R ₄ is a linear or branched saturated alkyl group having 5 to 29 carbon atoms.), And a general formula (III). {In the formula, R ₅ is an aliphatic hydrocarbon group having 1 to 29 carbon atoms, R ₆ is an aliphatic hydrocarbon group having a linear or branched chain having 1 to 17 carbon atoms,
Alternatively, it is a linear aliphatic hydrocarbon group having 18 to 36 carbon atoms (however, the sum of the carbon numbers of R ₅ and R ₆ is 15 to 65). } The present invention provides a magnetic recording medium containing an ester compound represented by: and one or more aliphatic compounds selected from the group consisting of fatty acids having 8 to 30 carbon atoms. .

[Operation] In the magnetic recording medium of the present invention, in the magnetic layer, the branched ester compound represented by the general formula (I), the cyclic ester compound represented by the general formula (II), and the general formula ( III) and one or more aliphatic compounds selected from the group consisting of fatty acids having 8 to 30 carbon atoms. When these compounds are contained in the magnetic layer, excellent lubricity is imparted, and as a result, durability is improved. It is not clear why the durability of the magnetic recording medium is improved when these compounds are used.

The branched ester compound represented by the general formula (I) can be obtained, for example, by an esterification reaction of a branched alcohol and a fatty acid. This branched alcohol is called Guerbet alcohol because of its synthetic method.

A suitable method for obtaining the cyclic ester compound represented by the general formula (II) is as follows. Is an esterification reaction of a cyclodecanol represented by and a fatty acid having a linear or branched saturated alkyl group having 6 to 30 carbon atoms.

In the present invention, the branched ester compound, the cyclic ester compound and the aliphatic compound are used in combination, and it is considered that the combined use system of these functions as a lubricant. In these combined systems, among the branched ester compounds, the sum of carbon numbers of R ₁ and R ₂ is preferably 22 to 34, and among the cyclic ester compounds, R ₄
Having 6 to 18 carbon atoms is preferable. Further, in this compound, the degree of branching is preferably low molecular weight such as methyl group or ethyl group.

Further, among the ester compounds represented by the general formula (III), R ₅ is an aliphatic hydrocarbon group having 7 to 23 carbon atoms, and R ₆ is a straight or branched aliphatic compound having 1 to 17 carbon atoms. A group hydrocarbon group is preferable, and also in R ₅ , the degree of branching is preferably a low molecular weight group such as a methyl group or an ethyl group.

Further, among the above-mentioned aliphatic compounds, it is preferable to use fatty acids.

The total amount of each compound used in the present invention is usually 1 to 15% by weight based on the magnetic powder. The preferred amount of each of the branched ester compound, the cyclic ester compound and the aliphatic compound is 15 to 55% by weight of the branched ester compound, 25 to 75% by weight of the cyclic ester compound and 1 to 30 of the aliphatic compound, with the total of these being 100. % By weight.

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 Fe atoms thereof are replaced by one or more of Ti, Co, Zn, V, Nb, Co, Fe -Ultra fine powder of metal or alloy such as -Co, Fe-Ni, etc. may be mentioned. Of these, iron metal powder has poor chemical stability, so nickel for this improvement,
Cobalt, titanium, silicon, aluminum and the like may be added in a small amount in the form of metal atoms, salts and oxides or may be surface-treated, but these can also be used. Iron metal powder sometimes forms a thin oxide film on the surface in a weak oxidizing atmosphere for its stabilization, but such treated metal powder 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 / 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.

The amount of the binder compounded is generally 15 to 60 parts by weight with respect to 100 parts by weight of the magnetic powder. Even if the 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.

Examples 1 to 5 Using the types and amounts of lubricants shown in Table 1, mixtures having the compositions shown below were prepared.

Co deposition 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 VAGH manufactured by Union Carbide Co., USA * 2 Product name N2301 manufactured by Nippon Polyurethane Industry Co., Ltd. * 3 Product name N2304 manufactured by Nippon Polyurethane Industry Co., Ltd. Then, the above mixture is kneaded in a sand mill for 5 hours, and then a lubricant is added. And knead in a ball mill for 10 hours. Further, 5.4 parts by weight of a polyisocyanate compound (trade name N3200 manufactured by Sumitomo Bayer Urethane Co., Ltd.) was added to this to prepare a total of 5 types of magnetic paints. Then these paints are
It was coated on a 75 μm polyethylene terephthalate film so that the dry film thickness would be 1.5 μm, and calendered after drying. Further, this was left standing at 60 ° C. for 4 days to carry out a curing reaction, then punched into a disk shape and surface-polished to manufacture a magnetic disk.

By loading these disks into a floppy disk accelerated durability test drive Note and measuring the running time until the playback output reaches 70% of the initial output at 5 ° C and 25 ° C, the durability of each magnetic disk is measured. It was judged. The results are shown in Table 1.

Comparative Examples 1 to 4 Instead of the lubricant used in the examples, the types and amounts of lubricants shown in Table 2 were used, the other components and the amounts thereof were the same as those of the examples, and the method of the examples was used. A total of four types of magnetic paint were prepared. Using these paints, magnetic disks were manufactured by the same method as in the example, and the durability of these disks was examined. The results are shown in Table 2.

Claims (4)

[Claims] 1. A magnetic recording medium having a magnetic layer on a non-magnetic support, wherein the magnetic layer has the following general formula (I): {Wherein R ₁ and R ₂ are saturated alkyl groups having ₁ to 25 carbon atoms (however, the sum of the carbon numbers of R ₁ and R ₂ is 16 to 34) having a straight chain or a branch, and R ₃ is the carbon number. It is a saturated or unsaturated alkyl group having 7 to 29 straight or branched chains. } A branched ester compound represented by the following general formula (II) (In the formula, R ₄ is a straight-chain or branched saturated alkyl group having 5 to 29 carbon atoms.), And the following general formula (III) {In the formula, R ₅ is an aliphatic hydrocarbon group having 1 to 29 carbon atoms, R ₆ is an aliphatic hydrocarbon group having a linear or branched chain having 1 to 17 carbon atoms,
Alternatively, it is a linear aliphatic hydrocarbon group having 18 to 36 carbon atoms (however, the sum of the carbon numbers of R ₅ and R ₆ is 15 to 65). } The magnetic recording medium containing the ester compound represented by these, and 1 type (s) or 2 or more types of aliphatic compounds selected from the group which consists of C8-C30 fatty acid. 2. The magnetic recording medium according to claim 1, wherein the sum of the carbon numbers of R ₁ and R ₂ of the branched ester compound represented by the general formula (I) is 22 to 34. 3. The cyclic ester compound represented by the general formula (II), wherein R ₄ is a linear or branched saturated alkyl group having 6 to 18 carbon atoms. Magnetic recording medium. 4. An ester compound represented by the general formula (III), wherein R ₆ is a linear or branched aliphatic hydrocarbon group having 1 to 17 carbon atoms. Alternatively, the magnetic recording medium according to item 3.