JPH01253823A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling durability without impairing other characteristics by incorporating a carbon black having a prescribed average particle with an specific compd. into a magnetic layer. CONSTITUTION:The carbon black having 15-150mmu average particle size and the ester compd. of tridecyl alcohol and stearic acid and/or palmitic acid are incorporated into the magnetic layer formed on a nonmagnetic base. The content of the carbon black is 1-10pts.wt., more preferably 2-7pts.wt. per 100pts.wt. ferromagnetic metal powder. The mixing ratios of the ester compd. of the tridecyl alcohol and stearic acid and the ester compd. of the tridecyl alcohol and palmitic acid are 80-20mol% of 20-80mol% in the case of using a mixture composed of said compds. The content of the ester compd. in the magnetic layer is 5-20pts.wt., per 100pts.wt. ferromagnetic metal powder.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a magnetic recording medium, and particularly to improving the running durability of a magnetic recording medium using ferromagnetic metal powder.

[Prior art and its problems]

In recent years, there has been an increasing demand for magnetic recording media suitable for high-density recording. Among them, a magnetic recording medium (hereinafter referred to as a metal powder-based magnetic recording medium) consisting of a ferromagnetic metal powder and a binder.

) has excellent magnetic properties such as coercive force (Hc) and saturation magnetization fi (Bm), and is expected to be a magnetic recording medium suitable for high-density recording. It is already in practical use as a magnetic recording medium for 8mm videos and video floppies.

However, in the metal powder-based magnetic recording medium, the surface of the magnetic layer is smooth in order to support high-density recording, so the friction coefficient of the contact between the magnetic layer and the device system increases while the magnetic recording medium is running. As a result, there were problems with running durability such as a decrease in output, damage to the magnetic layer, head clogging, and peeling of the magnetic layer.

Various attempts have been made to solve these problems and improve the running durability of the metal powder-based magnetic recording medium.

For example, methods of adding a lubricant into the magnetic layer include a method of adding polyethylene glycol ester (Japanese Patent Application Laid-Open No. 57-3225), a method of adding a ketone compound (Japanese Patent Application Laid-Open No. 57-158026), Method of adding glycerin ester of fatty acid and sorbitan ester of fatty acid (JP-A-57-158027), method of adding fatty acid and fatty acid ester (JP-A-5F+-130435, JP-A-60-5420) Fatty acids Al; method of adding toluester and fatty acid alkoxy ester (
JP-A-61-229234, JP-A-61-230
624 Publication) etc. However, in these methods, it is difficult to adjust the amount of lubricant added, and if the lubricant is added to the extent that it becomes effective, the magnetic layer will become weaker, which may actually reduce its durability or cause it to stick to the head. Something happened.

Another method is to add an abrasive to the magnetic layer. For example, a method of adding α-type ferric oxide (Japanese Unexamined Patent Publication No. 58-159227), a method of adding Al2O,3 (Japanese Unexamined Patent Publication No. 58-171721), 0.2μ
There is a method of adding particles having a Mohs hardness of 6 or more and a hardness of 6 or more (Japanese Unexamined Patent Publication No. 61-289528). However, when added in an amount sufficient to improve running durability, the wear of the magnetic head was accelerated, the surface properties of the magnetic layer deteriorated, and the electromagnetic conversion characteristics deteriorated.

Still other methods have been proposed, such as a method of using an abrasive and a fatty acid ester in combination (Japanese Unexamined Patent Publication No. 58-189826) and a method of using a combination of carbon black and silicone oil (Japanese Unexamined Patent Publication No. 62-195730). ing.

However, in either method, other properties may be degraded, and although the running durability of the metal powder-based magnetic recording medium can be improved to some extent, it is not sufficient. especially,
When the head is repeatedly turned on and off in relation to the magnetic layer, as in the case of floppy disks, ferromagnetic metal powder may fall off from the magnetic layer, which may cause the head to become clogged. It was very difficult to improve.

[Purpose of the invention]

The present invention has been made to improve the problems of the prior art described above.8 The purpose of the present invention is to provide a metal powder-based magnetic recording medium that has good running durability without impairing other characteristics. be.

[Means for solving problems]

The object of the present invention is to provide a magnetic recording medium comprising a magnetic layer made of ferromagnetic metal powder and a binder on a non-magnetic support, which contains carbon black with an average particle diameter of 15 to 150 mμ, and This is achieved by a magnetic recording medium characterized by containing an esterified product of tridecyl alcohol and stearic acid and/or palmitic acid.

The tridecyl alcohol has a branched structure, and therefore the esterified product used in the present invention has a low melting point relative to its molecular weight and is liquid at room temperature. Therefore, in a relatively low temperature region, it exhibits a lubricating effect by liquid lubrication, and on the other hand, even in a relatively high temperature region, it acts as a lubricant without volatilizing from the surface of the magnetic layer. 1. Furthermore, in the present invention, by containing the carbon black having a specific average particle size in the magnetic layer together with the esterified product,
By constantly absorbing an appropriate amount of the esterified product on its surface,
The amount of the esterified product on the surface of the magnetic layer should be neither excessive nor insufficient.

As described above, in the present invention, due to the characteristics of the esterified product and the action of the carbon black, the lubricant can be used under a wide range of environmental conditions without causing running abnormalities due to precipitation of the lubricant on the surface of the magnetic layer or the presence of an excessive amount of the lubricant. This made it possible to improve the running durability of metal powder-based magnetic recording media.

In the present invention, the average particle diameter of the carbon black contained in the magnetic layer is 15 to 150 mμ, preferably 20 to 100 mμ. If the average particle diameter becomes too small, the dispersibility of the magnetic coating liquid will be poor and the surface properties of the magnetic layer will be reduced, and the surface electrical resistance of the magnetic layer will also increase, making it easier for deposits to form that cause dropouts. Become. On the other hand, if the average particle diameter becomes too large, the lubricant retaining performance deteriorates and the friction coefficient of the magnetic layer increases, making head vibration and stick-slip more likely to occur.

The amount of carbon black added is 100% of the ferromagnetic metal powder.
The amount is 1 to 10 parts by weight, preferably 2 to 7 parts by weight.

The carbon black used in the present invention can be produced by any method. For example, furnace blanks, thermal blacks, acetylene blanks, channel blanks, etc. can be used.

In the present invention, the esterified product contained in the magnetic layer may be an esterified product of tridecyl alcohol and stearic acid, an esterified product of tridecyl alcohol and palmitic acid alone, or a mixture of both esterified products. In addition, tridecyl alcohol, which is a raw material, is usually synthesized by the oxo method, and the resulting product is a mixture of several isomers, so the esterified product is also a mixture of several isomers. obtained as. When using a mixture of the esterified product of tridecyl alcohol and stearic acid 1 and the esterified product of tridecyl alcohol and palmitic acid, the mixing ratio is 80 to 20 mol% to 20 to 80 mol%. , preferably 60 to 40 mol % to 40 to 60 mol % of the esterified product contained in the magnetic layer is 5 to 20 parts by weight, preferably 9 to 15 parts by weight per 100 parts by weight of ferromagnetic metal powder. It is.

The ferromagnetic metal powder in the present invention contains at least Fe.
specifically, Fe, Fe-C
It is a metal unit or alloy mainly composed of o, Fe-Ni or Fe-Co-Ni.

B, C, AI, Si to improve its properties.

Non-metals such as P may be added. Usually, an oxide layer is formed on the particle surface of the ferromagnetic metal powder to stabilize it. The particle size is 40rd/specific surface area.
It is desirable that the crystallite size is 400A or less, the axial ratio is 5 or more, and the saturation magnetization is 110 parts mu/
g or more, and the coercive force is preferably 8000 parts or more.

The binder used in the present invention is a conventionally known thermoplastic resin,
Thermosetting resins, reactive resins, and mixtures thereof, such as vinyl chloride-vinyl acetate copolymers, other vinyl chloride copolymers, acrylic ester copolymers,
These include methacrylic acid ester copolymers, urethane elastomers, cellulose derivatives, and epoxy-polyamide resins, and various polyisocyanates are also used as curing agents. The amount of the binder used is 1 1 of the ferromagnetic metal powder.
The amount is preferably 5 to 300 parts by weight per 00 parts by weight, and an appropriate amount of functional groups such as carboxyl groups, sulfonic acid groups, hydroxyl groups, amino groups, and eboxy groups are introduced into the molecule to improve dispersibility. This is desirable.

Examples of the nonmagnetic support used in the present invention include various synthetic resin films such as polyethylene terephthalate, polycarbonate, polyamide, and polyimide, and metal foils such as aluminum foil and stainless steel foil.

A magnetic coating solution is prepared by adding an organic solvent to the ferromagnetic metal powder, the binder, the carbon planer, and the esterified product for cross-dispersion, and coating the solution on the non-magnetic support, orienting it, and drying it. , a surface smoothing treatment is performed to produce a metal powder-based magnetic recording medium. Also, if necessary, a back layer is applied on the opposite side to the magnetic layer.

As the organic solvent, various solvents such as methyl ethyl ketone, cyclohexanone, isobutyl alcohol, butyl acetate, and toluene can be used alone or in a mixture.

In addition, in the cross-mixing dispersion, the above-mentioned materials are simultaneously or individually sequentially fed into a kneading machine and subjected to cross-crossing fraction processing.

The thickness of the magnetic layer in the present invention is usually 0.5 to 12 μm.
It is m.

In addition, for the purpose of improving the characteristics of the metal powder-based magnetic recording medium, an abrasive, a lubricant other than the esterified product, a dispersant, an antistatic agent, etc. are added as needed.

Highly hard fine powder of alumina, chromium oxide, silicon carbide, etc. is used as the abrasive.

As lubricants other than the above-mentioned esterified products, there are various types of fats.
fm, silicone oil, ester, etc. are used.

The following Examples and Comparative Examples will further clarify the novel effects of the present invention. In addition, all references to "1 part" refer to "parts by weight J."

[Example-1] Ferromagnetic metal powder (Fe 99%, Ni 1% specific surface area
51 bo/g, coercive force (Hc) 15800e, saturation magnetization CaS) 125 emu/g) 300 parts Vinyl chloride/vinyl acetate/maleic anhydride copolymer (manufactured by Nippon Zeon Co., Ltd. 400X110A) 30 parts chromium oxide (CrgOs) Average particle size 0.5μm)
30 parts carbon black (manufactured by Lion Akuzu Co., Ltd. Ketchen Bra, Ri E, C, average particle size 30 μm) 15
Part toluene 4. 36 parts Methyl ethyl ketone 36 parts After kneading the above composition in a Nigu for about 1 hour, the following composition is further added.

Polyester polyurethane (UR830 manufactured by Toyobo Co., Ltd.)
0 sulfonic acid group 150''!U!/10'g Contains weight average molecule l 70,000) 20 parts methyl ethyl ketone 250 parts toluene
250 parts of the above composition was then subjected to a cross-cutting treatment using a sand grinder at 2000 revolutions for about 2 hours. Furthermore, the following composition was added and cross-dispersion treatment was performed again using a sand grinder to obtain a uniformly dispersed magnetic paint.

A l:l mixture of an ester of tridecyl alcohol and stearic acid (TDS) and an ester of tridecyl alcohol and palmitic acid (TDP) (INOLE)
X B109) 30 parts polyisocyanate (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) 25 parts or more The magnetic paint obtained as described above was applied to a width of 300 m+,
It was coated on both sides of a 75 μm thick polyethylene terephthalate film using a gravure roll so that each had a dry film thickness of 3 μm, and calendered to obtain a metal powder diameter magnetic recording medium.

[Example-2] Ketchen Black E in Example-1.

In place of C0, NEOSPECTRAMA RK + v manufactured by Columbia Carbon Co., Ltd. was used as a carbon blank.
(average particle size 16 mμ) was used. Other conditions were the same as in Example-1 to obtain a metal powder-based magnetic recording medium.

[Example-3] Ketchen Black E and C in Example-1.

Instead, 15 parts of Carbop Rack Asahi #50 (average particle diameter 80 mμ) manufactured by Asahi Carbon Co., Ltd. was used as a carbon blank.

Other conditions were the same as in Example-1 to obtain a metal powder-based magnetic recording medium.

[Example-4] Ketchen Black E and C in Example-1.

Instead, 15 parts of Asahi #20 (average particle diameter 118 mμ) manufactured by Chubu Ichibon Co., Ltd. was used as a carbon blank.

Other conditions were the same as in Example-1 to obtain a metal powder-based magnetic recording medium.

[Comparative example-1] Ketchen blanks E and C in Example-1.

ROYAL 5PECTRA manufactured by Columbia Carbon Co., Ltd. (average particle size 10 m) was used instead of carbon black.
15 parts of μ) were used.

Other conditions were the same as in Example-1 to obtain a metal powder-based magnetic recording medium.

[Comparative example-2] Ketchen blanks E and C in Example-1.

Stc manufactured by CABOT as carbon black instead of
15 parts of rling FT (average particle size 180 mμ) were used.

Other conditions were the same as in Example-1 to obtain a metal powder-based magnetic recording medium.

[Comparative Example-3] A metal powder-based magnetic recording medium was obtained under the same conditions as in Example-1, except that 1N0LEX B109 was not added.

[Comparative Example-4] A metal powder-based magnetic recording medium was obtained under the same conditions as in Example-1 except that carbon black was not added.

(Example-5) In Example-i, the esterified product of tridecyl alcohol and stearic acid (TDS) and the esterified product of tridecyl alcohol and palmitic acid (TDP)]:
1 part compound (INOLEX8109) was replaced with 30 parts.
A metal powder-based magnetic recording medium was obtained under the same conditions as in Example-1 except that 5 parts were used.

[Example-6] In Example-1, 1 of the esterified product of tridecyl alcohol and stearic acid (TDS) and the esterified product of tridecyl alcohol and palmitic acid (TDP)
A metal powder-based magnetic recording medium was obtained under the same conditions as in Example-1 except that 60 parts of the 1-part compound (INOLEX B109) was used instead of 30 parts.

[Example-7] In Example-1, carbon black (Ketchen Black E manufactured by Lion Akzo Co., Ltd.) was used.

A metal powder-based magnetic recording medium was obtained under the same conditions as in Example-1 except that 3 parts were used instead of 15 parts (C2 average particle diameter 30 mμ).

[Example-8] In Example-1, carbon black (Ketchen Black E manufactured by Lion Akzo Co., Ltd.) was used.

A metal powder-based magnetic recording medium was obtained under the same conditions as in Example-1 except that 30 parts were used instead of 15 parts (C2 average particle diameter 30 μm).

[Comparative Example-5] In Example-1, 1 to 1 of the esterified product of tridecyl alcohol and stearic acid (TDS) and the esterified product of tridecyl alcohol and palmitic acid (TDP)
Example-1 except that 30 parts of INOLEX B109 was changed to 30 parts of INOLEX B109.
A metal powder-based magnetic recording medium was obtained under the same conditions as in Example 1.

[Comparative Example-6] In Example-1, 1 of the esterified product of tridecyl alcohol and stearic acid (TDS) and the esterified product of tridecyl alcohol and palmitic acid (TDP):
A metal powder-based magnetic recording medium was obtained under the same conditions as in Example 1, except that 30 parts of the l mixture (INOLEX B109) was replaced with 30 parts of butyl laurate.

[Comparative Example-7] In Example-1, the esterified product of tridecyl alcohol and stearic acid (TDS) and the esterified product of tridecyl alcohol and palmitic acid (TDP):
1 (IN OI-E XB109) at 30
Example except that 9 parts of the esterified product was added instead of 1 part.
A metal powder-based magnetic recording medium was obtained under the same conditions as in Example 1.

(Comparative Example-8) In Example-1, 1 of the esterified product of tridecyl alcohol and stearic acid (TDS) and the esterified product of tridecyl alcohol and palmitic acid (TDP);
A metal powder-based magnetic recording medium was obtained under the same conditions as in Example 1, except that 75 parts of the esterified product was added instead of 30 parts of the 1-part compound (INOLEX B109).

The metal powder-based magnetic recording media obtained in Examples -1 to -8 and Comparative Examples -1 to -8 were processed into 3.5-inch floppy disk samples.

Next, transfer each sample to a floppy disk drive rFD.
-1135-DJ (manufactured by NEC Corporation),
A 24-hour thermocycle test was conducted under environmental conditions ranging from 5°C/10% relative humidity to 50'C/30% relative humidity.

As a result, the results shown in Table 1 were obtained regarding the running durability and tUt conversion characteristics of each sample.

Note that running durability was evaluated by running each sample under the above-mentioned conditions by repeatedly running the bus a maximum of 25 million times. Moreover, the electric-Mi conversion characteristic was 100% for the sample of Example-1.

The value of the initial 2F output was evaluated.

Examples 1 to 4, in which the carbon blank has an average particle diameter in the range of 15 to 150 mμ, show good results in both running durability and output. Comparative Example-1 where the particle size of the carbon blank is outside the above range (10 mμ
) and Comparative Example-2 (180 mμ), both caused running abnormalities midway through, and in Comparative Example-1, although the output was good, the bus stuck to the head after 20 million cycles, making it impossible to run. became. On the other hand, in Comparative Example 2 as well, the output decreased, probably due to the large particle size of carbon black, and the magnetic layer was scratched after 1.5 million baths.
Running stopped.

In Comparative Example 3, which was completely esterified by removing the esterified product from Example 1, the output was good, but scratching occurred after 500,000 baths were run at a constant rate of about 24 hours. . In addition, in Example-1, when isocetyl stearate or butyl laurate was used as the esterified product, as is clear from the results of Comparative Example-5 and Comparative Example-6, in both cases, the magnetic layer was 1N0LE, which is a 1:1 mixture of TDS and TDP,
In the case of Example=1 using X B109, the running durability was not as good.

Furthermore, in Comparative Example 4 in which no carbon black was added, the output was considerably high, but the magnetic layer was scratched after 20 million passes. Even when 1 part by weight of carbon black was added per 100 parts by weight of ferromagnetic metal powder (Example-7) and when 10 parts by weight was added (Example-8), the output of Example-〇 decreased slightly. Both had good running durability. Furthermore, both the output and running durability were good when 5 parts by weight (Example 5) and 20 parts by weight (Example 6) of the esterified product were added per 100 parts by weight of the ferromagnetic metal powder. Ta.

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer made of ferromagnetic metal powder and a binder is provided on a non-magnetic support, carbon black with an average particle size of 15 to 150 mμ, tridecyl alcohol, stearic acid and/or palmitic acid are used. A magnetic recording medium characterized by containing an esterified product of.