JPH0487021A - Magnetic coating material and magnetic recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] Does the present invention impart lubricity to the magnetic layer? The present invention relates to a magnetic paint with improved lubricant and a magnetic recording medium using the same.

BACKGROUND OF THE INVENTION Magnetic recording media such as magnetic tapes and magnetic disks are widely used in the video field, audio field, computer field, and the like. Coating-type magnetic recording media, in which a magnetic coating consisting of magnetic powder, resin, solvent, dispersant, and other additives is applied to a support and dried to form a magnetic coating, are also used as such magnetic recording media. ing.

In recent years, magnetic recording media have been required to have higher recording densities as well as higher reliability, and for this reason, magnetic layers have been formed by fine-graining magnetic powder and filling it with high density. Efforts have been made to make the magnetic layer thinner and to improve the running properties of the magnetic layer.

In particular, for example, a magnetic tape is repeatedly recorded and reproduced by being rubbed by a magnetic head, a guide roller, a rotating cylinder, etc. while the tape is running. Furthermore, in the case of a videotape, a still image is sometimes viewed during playback, and in this case, the same location of the magnetic layer is repeatedly rubbed by a magnetic head. Therefore, magnetic tapes are required to have no damage to the magnetic layer even when used for long periods of time in these cases, but in order to achieve this and improve recording and playback, it is necessary to improve the lubricity and durability of the magnetic layer. It is also required to have good running stability. Specifically, it is required to reduce the coefficient of friction, improve wear resistance, and prevent magnetic powder from falling off.

[Problem to be solved by the invention]

A conventional method for improving the lubricity of the magnetic layer is to add a solid lubricant such as molybdenum disulfide, wax, or graphite to the magnetic paint.

However, although the magnetic layer to which these solid lubricants are added has an effect on lubricity, it may impair the durability of the magnetic layer.

-7. Use higher fatty acids, zero-type higher fatty acid esters obtained using normal aliphatic alcohols, paraffinic hydrocarbons, silicone oil (e.g. dimethyl silicone oil, diphenyl silicone oil), etc. as a lubricant. However, magnetic layers using these lubricants not only do not exhibit sufficient lubricity and durability, but also cause the so-called blooming phenomenon in which these lubricants seep onto the surface of the magnetic layer. When this blooming occurs, problems arise in that the magnetic layer sticks to the rotating cylinder or the like with which it comes in contact, a so-called sticking phenomenon, and that the surface of the rotating cylinder gets dirty and this dirt accumulates, impairing its function.

An object of the present invention is to provide a magnetic recording medium that does not impair the durability of the magnetic layer, does not cause the blooming phenomenon, and has excellent lubricity, and a magnetic coating therefor.

[Means to solve the problem]

In order to solve the above problems, the present invention is characterized in that a magnetic paint for forming a magnetic layer on a support contains a higher fatty acid ester obtained from a branched aliphatic alcohol and a linear higher fatty acid. We provide magnetic paints that can be used as

In this case, the branched aliphatic alcohol is an alcohol with a carbon number larger than 7 and smaller than 13, and the straight chain higher fatty acid is an alcohol with a carbon number of 9 or more, and it is particularly preferable that the carbon number is 14 to 22. is 1.0 to 5 for magnetic powder
．． It is also preferable that the content is 0% by weight.

The present invention also provides a magnetic recording medium using the above coating material.

Next, the present invention will be explained in detail.

In the present invention, a higher fatty acid ester consisting of a branched aliphatic alcohol and a straight chain higher fatty acid is used.
Branched aliphatic alcohols are so-called isoalcohols, and linear higher fatty acids are normal aliphatic fatty acids. n-C4・Hl)1't+
When expressed as C0OH, N = 8 = 8 or more, that is, the number of carbon atoms in the straight chain higher fatty acid is preferably 9 or more, particularly 14 to 14 carbon atoms.
22 is preferred. From these, higher fatty acid ester n-
Cv'H2B'+I C01so-Ck/hv+l is preferably N+N'=15 or more; if it is smaller than this, the effect of preventing powder falling off of the magnetic layer and durability such as steel durability may not be improved; , if this is too large, the durability of the steel may not be improved.

In addition, if it is too small or too large, the effect of improving the dynamic friction coefficient of the magnetic layer may be small.
'=15-34 is preferable.

The above-mentioned higher fatty acid ester is preferably 1.0 to 5.0 parts by weight, particularly 1.5 to 4.0 parts by weight, based on 100 M parts of magnetic powder.
It is preferably 0; if it is too small, the lubricity effect of the magnetic layer will be small, and if it is too large, blooming or the like may occur.

Examples of the binder resin used in the magnetic recording medium of the present invention include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer-vinyl alcohol copolymer,
Vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-pinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic acid Ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer , polyamide resins, polyvinyl butyral, cellulose derivatives, styrene-butadiene copolymers, polyester resins, synthetic rubbers such as polybutadiene, and other resins.

Thermosetting resins are also used, such as phenolic resins, epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, silicone resins, acrylic reaction resins, epoxy-polyamide resins, Nitrocellulose-melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of polyester polyol and polyisocyanate, urea formaldehyde resin, mixture of low molecular weight glycol/high molecular weight diol/triphenylmethane triisocyanate, polyamine resin and these Among these, it is preferable to use a combination of those that have good dispersibility for strong powders.

In addition, as magnetic powder, r-Fe203, r-Fe2J
and Fe3O4 crystals, CrO2, and cobalt-coated r-
Examples include Fe205 or Fe3O4. In addition, non-oxide magnetic powders such as metal magnetic powders, metal nitride magnetic powders, and metal carbide magnetic powders can also be used, and both can also be used in combination.

In addition to the above-mentioned binder resin and magnetic powder, the magnetic paint also contains an organic solvent, and the magnetic paint further contains dispersants, abrasives, fillers, antistatic agents, rust preventives, fungicides, etc. as necessary. Each component is appropriately selected and mixed. A known method is used as the manufacturing method.

This magnetic paint is applied to a support such as a polyethylene terephthalate film (PET film) using a known coating method such as a doctor blade, reverse roll, gravure roll, or spinner coat, and the magnetic powder is oriented and dried depending on the application. A magnetic recording medium is obtained by surface smoothing treatment.

[Effect]

If the above-mentioned higher fatty acid ester is contained in the magnetic layer, it becomes excessively compatible with the binder of the magnetic layer and excessively floats on the surface of the magnetic layer (though it is thought that the details are not clear).

〔Example〕 Next, the present invention will be explained in detail.

Example 1 Co-containing r-Fe2J 100 parts by weight (average particle size 0.2μ-1Hc=8500e) A/2
03 (average particle size 0.2 μm) 5 parts by weight Vinyl chloride vinyl acetate copolymer resin 11 parts by weight Polyurethane resin 11 parts by weight 1so-C5J90H
Higher fatty acid ester consisting of and n-C+5H27COOH (equimolar) 1. si amount county carbon black
5 parts by weight (νalcan manufactured by Kabonoto Co., Ltd.
72) A mixture of 130 parts by weight of methyl ethyl ketone and 130 parts by weight of toluene was mixed in a sand mill for 5 hours, and 3 parts by weight of a curing agent (isocyanate compound) was added to the resulting dispersion to obtain a magnetic paint.

This magnetic paint was applied onto a 14 μm thick PET film (polyethylene terephthalate film) using a gravure coater so that the film thickness after drying was 4 to 6 μm.
dry.

Thereafter, the magnetic layer was subjected to a calender treatment to give a mirror finish, and slits were made into 1/2 inch widths, and the slits were kept at 50° C. for sufficient hardening.

Table 1 shows the results of the dynamic friction coefficient, powder drop, running test in VTR equipment, and steel durability test using the sample magnetic tape obtained in this way. G) ) and squareness ratio Or/
Table 1 shows the results of measuring Bs using a sample vibrating magnetometer (manufactured by Riken Denshi Co., Ltd.).

To measure the coefficient of dynamic friction, one end of a magnetic tape wound on a reel is pulled out, wrapped around a cylinder parallel to the reel axis and separated from the reel for about half a turn, then folded back and taken up on a powered take-up reel. A tape tension detector on the drawer side is installed between the drawer reel and the cylinder, and the magnetic tape is moved at a speed of 3.3 (Im/sec). When the tape tension on the take-off side shows a stable value, the former is T1 and the latter is 12, and the contact angle θ at which the tape is wound around the cylinder is expressed in radians,
It was calculated using the following Euler's formula.

A video signal was recorded on the magnetic tape of each sample using a stick, a still image was reproduced, and the time until the reproduced image lost its sharpness was taken as a measured value as the still time.

To remove powder, a piece of magnetic tape of about 20 C1l is stretched and tightly attached to a mirror-surfaced stainless steel plate with the magnetic layer side facing up so that no sagging occurs, and both ends are fixed to the stainless steel plate with adhesive tape. Then, a sheet of Silpon paper was wrapped around the tip, and a metal rod designed to apply a load of 100 g was slid on the tape. After repeating this 500 times, the presence or absence of magnetic powder adhering to the Silpon paper was visually observed. The evaluation is as follows.

○... No powder falling △... Some powder falling X... Powder falling Example 2 In Example I, higher fatty acid ester was used as iso-Cg.
)11gOH and n-C+7H35Coo)I A magnetic tape was prepared in the same manner except that a higher fatty acid ester consisting of n-C+7H35Coo)I was used. Table 1 shows the results of measurements made in the same manner as in Example 1.

Example 3 In Example 1, the higher fatty acid ester was 1so-C9
A magnetic tape was prepared in the same manner except that a higher fatty acid ester consisting of H+90H and n-Cz+H45C0OH was used instead. Table 1 shows the results of measurements made in the same manner as in Example I.

Example 4 In Example I, higher fatty acid ester was
It is used in place of higher fatty acid ester consisting of old 90H and n-Cg H,9cootl, and the amount used is 1
Magnetic tapes were prepared in the same manner except that the parts by weight shown in the respective columns of Table 2 were used for 00 parts by weight, and these were also measured in the same manner as in Example 1. Table 2 shows the results. Table 1 also shows the case where the same amount as in Example 1 was used.

Comparative Example 1 A magnetic tape was prepared in the same manner as in Example 1 except that 1.5 parts by weight of a conventional solid lubricant was used instead of the higher fatty acid ester, and these were also measured in the same manner as in Example 1. are shown in Table 1.

Comparative Example 2 In Example 1, a higher fatty acid ester in which a conventional n-alcohol was used instead of a higher fatty acid ester was changed to 1.
A magnetic tape was prepared in the same manner except that 5 parts by weight was used,
Table 1 shows the results of measuring these in the same manner as in Example 1.
Shown below. Note that blooming was observed on the surface of the magnetic layer.

Comparative Example 3 A magnetic tape was prepared in the same manner as in Example 1 except that t and S weight parts of conventional silicone oil were used instead of the higher fatty acid ester, and these were also prepared in the same manner as in Example 1.
Table 1 shows the results measured in the same manner as above.

Comparative Example 4 A magnetic tape was prepared in the same manner as in Example 4, except that the higher fatty acid ester was not used, and the results of measurement were also shown in Table 2 in the same manner as in Example 1.

(Margins below this page) Table ■ We can provide magnetic paints containing esters and magnetic recording media using them. It is possible to provide a recording medium, and in particular, it is possible to further improve the performance of a high-density recording type magnetic recording medium.

July 31, 1990 From the results in the table above, it can be seen that the examples are better than the comparative examples.

〔Effect of the invention〕

Claims (5)

[Claims] (1) A magnetic paint for forming a magnetic layer on a support, characterized by containing a higher fatty acid ester obtained from a branched aliphatic alcohol and a linear higher fatty acid. (2) The magnetic paint according to claim 1, wherein the branched aliphatic alcohol is an alcohol having more than 7 carbon atoms and less than 13 carbon atoms, and the linear higher fatty acid has carbon atoms of 9 or more. (3) The magnetic paint according to claim 1 or 2, wherein the linear higher fatty acid has 14 to 22 carbon atoms. (4) Higher fatty acid ester obtained from branched aliphatic alcohol and straight chain higher fatty acid at 1.0% relative to magnetic powder.
The magnetic paint according to any one of claims 1 to 3, containing ~5% by weight. (5) A magnetic recording medium obtained using the magnetic coating material according to any one of claims 1 to 4.