JPS61214217A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide good lubricity to a magnetic layer formed of magnetic powder and binder as essential components and to improve the durability thereof by incorporating specified triglyceride into the magnetic layer. CONSTITUTION:The magnetic layer of a magnetic recording medium is formed essentially of the magnetic powder and binder. The magnetic layer is formed by contg. the specified triglyceride and contg. further the compd. selected from a fatty acid, fatty ester and liquid paraffin. In the formula, any one among R1, R2, R3 is the unsatd. alkyl group of 17-21C derived from an olefinic acid and the other both are both a satd. alkyl group of 17-31C derived for a behenic acid. The good lubricity is provided to the magnetic recording medium in the above-mentioned manner and the durability of the medium is improved. The bleeding from the magnetic layer is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media. Specifically, the present invention relates to a magnetic recording medium with excellent durability.

[Conventional technology and problems]

Magnetic recording media are generally made by applying magnetic paint consisting of magnetic powder, binder resin, organic solvent, and other necessary components onto a substrate such as polyester film. Since the magnetic layer is easily abraded due to violent sliding contact with the head, jacket liner, etc., there is a need for a magnetic layer that is less abrasive and has excellent durability.

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,
At present, these lubricants cannot be said to be 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 Problem C] The present inventors have developed the present invention as a result of intensive research 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 mainly composed of magnetic powder and a binder, wherein the magnetic layer contains a triglyceride represented by the following general formula (1). It provides a medium.

(In the formula, one of R+, Rz, and R1 has a carbon number of 17 to
21 unsaturated alkyl groups, the other two have 17 to 31 carbon atoms
is a saturated alkyl group. ) [Action] The triglyceride represented by the general formula (1) according to the present invention is very limited, and its molecule contains:
One unsaturated alkyl group and two saturated alkyl groups must be included. For example, trioleic acid glyceride, in which R3, R, and R1 are all unsaturated alkyl groups, is a liquid substance with a relatively low melting point and exhibits good lubricity, but is susceptible to bleeding from the magnetic layer.

Also, for example, tribehenic acid glyceride, where R+, Rz and R3 are all saturated alkyl groups, is a crystalline solid and does not provide good lubricity. The above general formula (1)
Only in the case of triglycerides represented by the above, good lubricity is imparted to magnetic recording media, thereby increasing the durability of such media, and also not causing bleeding onto the coating film.

The triglyceride used in the present invention is obtained by an esterification reaction of glycerin and a monobasic fatty acid. - Among the basic fatty acids, behenic acid and oleic acid are particularly preferred, and stearic acid is also in the preferred category. The bonding position of the unsaturated fatty acid residue in the triglyceride may be either α or β, but a mixture thereof is preferred. In addition, such triglycerides can be added to oleic acid, linoleic acid, erucic acid,
Bleeding tends to be further suppressed when mixed with fatty acids such as lauric acid, fatty acid esters such as oleyl oleate, butoxyethyl stearate, stearyl laurate, stearyl butyrate, or liquid paraffin.

As the magnetic powder according to the present invention, fine needle-shaped r-F
Metal oxides such as ew(1+, Fe, 0., Cro□, and Co-coated r-Fe, 0., Co-doped r-
γ-FezO* processed like Fe203,
Iron metal powder, platelet barium ferrite and its F
Magnetic powder in which a part of e atoms are substituted with one or more of TI+CO+Zn, V+Nb, etc., Go, Fe-Co,
Examples include ultrafine powder of metal or alloy such as Fe-Ni. Among these, iron metals have particularly poor chemical stability, so to improve this, small amounts of nickel, cobalt, titanium, silicon, aluminum, etc. in the form of metal atoms, salts, and oxides are added or surface 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/vinyl acetate copolymer, ethyl cellulose, and the like.

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.

Further, the amount of the binder blended is generally 15 to 60 parts by weight per 100 parts by weight of the magnetic powder. Even if the binder has the highest binding strength, if the amount 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, if the amount is more than 60 parts by weight, the concentration of magnetic powder in the magnetic coating film becomes small, which is disadvantageous because the reproduction output decreases. Furthermore, the properties of the coating film may deteriorate.

Further, the triglyceride represented by the general formula (1) is usually used in an amount of 1 to 15% by weight based on the magnetic powder.

〔Example〕

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 4 Using the lubricants shown in Table 1, mixtures having the compositions shown below were prepared.

Co-adhered γ-Fezes 100 parts by weight Lecithin 1 PVC/acetic acid picopolymer 30 Nitrile butadiene rubber *! 15 Carbon black 7 Aluminum oxide 6 Toluene 150 parts by weight Methyl ethyl ketone 150 Lubricant 12 Note) Feeding US t1.c, c. Product name: VAG)!*
2 (trade name: 1432J, manufactured by Nippon Zeon Co., Ltd.) Next, the above mixture was mixed and dispersed in a sand mill for 15 hours, and then 7 parts by weight of a polyisocyanate compound (Coronate (manufactured by Nippon Polyurethane)) was added thereto to prepare a magnetic paint.

Next, this was applied onto a polyethylene terephthalate film having a thickness of 75 μm so that the dry film thickness was 1.5 μm, and after drying, a calender treatment was performed. Furthermore, this is 60
The material was left to cure for 4 days at a temperature of .degree. C., and then punched out into a disk shape and the surface polished to produce a magnetic disk.

These disks were loaded into a floppy disk accelerated durability test drive, and the running time until the playback output reached 70% of the initial output was measured at 5° C. to determine the durability of each sample.

The results are shown in Table 1.

Table 1 Comparative Examples 1 to 5 In place of the lubricants used in the Examples, 12 parts by weight of the various lubricants shown in Table 2 were used, magnetic paints were prepared according to the method of the Examples, and magnetic disks were manufactured. A durability test was conducted on these disks in the same manner as in the examples.

The results are shown in Table 2.

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a binder, characterized in that the magnetic layer contains a triglyceride represented by the following general formula (1). magnetic recording medium. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(1) (In the formula, one of R_1, R_2, and R_3 is an unsaturated alkyl group with 17 to 21 carbon atoms, and the other two are unsaturated alkyl groups with 17 carbon atoms.
~31 saturated alkyl groups. ) 2. The magnetism according to claim 1, wherein one of R_1, R_2, and R_3 is an unsaturated alkyl group derived from oleic acid, and the other two are both saturated alkyl groups derived from behenic acid. recoding media. 3. The magnetic recording medium according to claim 1, wherein the magnetic layer further contains at least one compound selected from fatty acids, fatty acid esters, and liquid paraffin.