JPS605421A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium for a magnetic disc and magnetic sheet having excellent surface smoothness of the magnetic layer and considerably improved durability by incorporating a specific lubricating material and non-magnetic powder into the magnetic layer at a specific ratio to ferromagnetic fine particles. CONSTITUTION:The magnetic layer of a magnetic recording medium formed by coating a magnetic layer contg. ferromagnetic fine particles on a non-magnetic base is so constituted as to contain at least one kind of fatty acid, fatty acid ester, fatty acid-modified silicone and alpha-olefin oxide as a lubricating material at >=10wt% by the weight of the ferromagnetic fine particles and to contain nonmagnetic powder having >=6Mohs hardness at >=6wt% satd. and unsatd. fatty acids are usable as the fatty acid. The silicone expressed by the general formulas I , II is usable as the fatty acid-modified silicone. The non-magnetic powder having >=6Mohs hardness is effective particularly for the durability of the magnetic layer and, for example, Cr2O3, alumina, SiC, MgO, etc. which are usually known as an abrasive may be used. The particle size is preferably <=1mu.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium for magnetic disks and magnetic sheets, and particularly to a magnetic recording medium with improved durability.

Magnetic recording media, especially magnetic disks and magnetic sheets that are suitable for high-density recording2 and require strong durability, require improvements in surface smoothness and durability at the same time to improve electromagnetic conversion characteristics. be done.

However, for some reason, the conventional methods have not been able to adequately meet the demands for higher density disks, etc.

That is, in order to further increase the density of magnetic disks, etc., the magnetic layer surface 1
The important factor is that the ferromagnetic fine particles exist in a uniformly dispersed state in the magnetic layer, but the adoption of fine magnetic particles, strengthening of smoothing treatment conditions such as calendering, and improving the dispersibility of magnetic liquids are important factors. If only technique 1 is used, sufficient durability of the magnetic layer cannot be obtained. On the other hand, with the increase in magnetic density, the thickness of the magnetic layer is becoming thinner than before, and the situation is such that there is no overwriting.

Conventionally, it has been known to use fatty acids as a lubricant to improve durability (Special Publication No. 9-39+02), or the usable amount of lubricant is 1.7 wt% or less based on the magnetic material. Are known.

It is also known to use α-olefin oxide 1 as a lubricant, but it is a lubricant f j w t for magnetic materials.
It is known that less than % is used (% Kosho 5ii--
AO No. 10). The above case is an invention that can be used particularly for video tapes, audio tapes, and memory tapes.

In this way, the reason why the amount of lubricant used was selected to be 7 wt. This is because dry, fatty acid, or fatty acid ester type @erasing will cause stickiness to the magnetic head. Also on the audio tape j~Aw
If more than 1% lubricant is used, the magnetic layer will become plasticized, similar to videotape, and "6" will easily occur due to the influence of temperature and humidity.
This is because the .mu. value of the magnetic layer decreases, leading to problems such as the phenomenon of heaviness and swelling occurring during running, and the generation of white powder, which causes head stains.

However, in magnetic recording media that require a high degree of durability, such as magnetic disks, which have no commercial value unless they are durable for 10 million or more continuous rotations, conventional binder binding and lubrication are required. agent to ferromagnetic fine particles to 1.1
If less than 0 wt% was used, there was a problem that no durability could be obtained. Therefore, the present inventors developed a lubricant,
As a result of intensive study on the type and amount of non-magnetic powder to be used, we discovered a relationship that could not be expected based on conventional common sense, leading to the present invention.

An object of the present invention is to provide a magnetic recording medium for magnetic disks and magnetic sheets that has improved durability and has sufficient electromagnetic conversion characteristics.

The object of the present invention is to provide a magnetic recording medium in which a magnetic layer consisting of ferromagnetic fine particles and a binder is entirely coated on a non-magnetic support, in which the magnetic layer is coated with (1) a fatty acid, a fatty acid esteno t1 as a lubricant; Fatty acid-modified silicone IJ contains at least 10 wt% of α-olefin oxide to the -alk ferromagnetic particles, and (2) non-magnetic powder on Mohs hard grade tJA is added to the ferromagnetic particles by 6w1.
This is achieved by a magnetic recording medium having a characteristic of t% or more.

As the fatty acids used in the present invention, both saturated and unsaturated fatty acids can be used. Specific examples of the acid include phosphoric acid, panopetic acid, myristic acid, stearic acid, behenic acid, phosphoric acid, erucic acid, oleic acid, etc., and of course these should be mixed and used at the required Vc. You can also do that.

Examples of fatty acid esters include ethyl styrene, phthyl stearate, diamyl stearate, alkyl remitate, hexyl laurate, butyl laurate, butyl myristate, and the like.

As fatty acid-modified silicones, general formulas [1] and [11
) can be used.

Di = 0 1 2 In the above general formula [1], R1, R21-r carbon number 7
~21 saturated or unsaturated hydrocarbon groups, IN
, 3 o t)) is an integer. In the general formula [1], R3,1 (4, R5 is a saturated or unsaturated hydrocarbon group m having 7 to .2 carbon atoms, and 11 is an integer from θ to 0). Specific examples of silicones shown include capric acid-modified silicone (R□, where R is '7H15 and l is ko), myristic acid-modified silicone (where RR is -C□3),
II27, l 2 is λ), behenic acid-modified silicon (R1, R2 are -
2 □H43, If)-, oleic acid modified silicon (Itn is -7H381% 2, l is 2, etc.) are opened.

A specific example of silicon represented by the general formula (1) is oleic acid-transferable silicon [R3, R4 are -, H11 or -
(17”33 with nl or 10.n31 5 is male), myristic acid modified silicone (R3, R4
, where R5 is 1'13I-127, m is 73, and n is 25), and the α-olefin oxide has the following general formula [
The compound sounds shown in [l ] can be used.

[Otori]

In the above general formula [1], R6 has a carbon number i.

~30 alkyl groups.

The non-magnetic powder with a Mohs hardness of 6 or more used in the present invention is particularly effective for the durability of the magnetic layer.
203, alumina, Sit, M, 90, etc., which are usually called abrasives, can be used. Morse fil! When the degree is 6 or more, the effect on durability is significantly deteriorated.

The particle size of non-magnetic powder with a Mohs hardness of 6 or more is 1
μ or less is preferable, especially KO, 2 μ to 0.7 μ is good. The amount used is preferably 3 wt% or more, particularly preferably 4 wt% to /jwt%, based on the ferromagnetic fine particles.

As the non-magnetic support, any material that can be used for ordinary magnetic recording materials such as polyethylene terephthalate, triacetylcellulose, polyethylene naphthalate, polyamide, polyimide, etc. can be used, and AA-deposited polyester film gold can be used.

As the carbon black used in the present invention, a carbon black having an average particle size of io-1 lomμ is suitable, and is referred to as "Contactexta JO" [Contactexta JJl'-Conductex S to j [Conductexta 00J ( Manufactured by Columbia Carhon Co.)
, "Ketjenblack Eshi" (manufactured by Lion Akzo), "rX-(-'-7ko" (manufactured by Cabot), etc. are commercially available.

In order to further improve the surface properties of the magnetic recording medium, carbon black may be front-heated together with ferromagnetic fine particles, a binder, and an organic solvent. In this case, even if the entire amount of carbon black is front-heated, only a portion of the carbon black may be front-heated. Furthermore, the amount of ferromagnetic fine particles and binder can be adjusted as necessary in the same manner as carbon black. Tsutomi ferromagnetic fine particles often give favorable results even if the total amount of ferromagnetic particles is reduced, but it is essential to carefully consider the type and fk of the binder and set the front resistance conditions. If only the surface smoothness of the magnetic layer is the focus, use the entire amount of carbon black.Is it preferable to use carbon black in the front?If the electric resistance of the magnetic layer surface is required to be below a certain value, then add some of the carbon black. only on the front line,
It is often best to use the remaining amount in a subsequent process.

As the front sheeting method, it is preferable to use a three-roll mill, a pressure kneader, an oven kneader, a Warner kneader, etc., but almost any method that can be used for mixing ordinary pigments can be applied.

As the solvent for front printing, most of the acetate esters such as ethyl acetate and butyl acetate, ketones such as MEKXMIBK and cyclohexanone, and other bath agents commonly used in magnetic tapes can be used.

As a magnetic material, urke 303, Fe3O4, (-
In addition to (7) oxides such as r 02, cobalt-added r F'e203, Kono (rut-added FeOx, (X=/, 33~/-6), etc., metal powders such as Fe-N1X Fe-N1-L:o) can also be used.

As a binder, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, carboxyl-based salt vinyl acetate copolymer,
Vinyl alcohol-containing salt vinyl acetate copolymer, polyvinylidene chloride, vinylidene chloride-acrylonitrile copolymer, nitrocellulose and other cellulose derivatives, acrylonitrile-butadiene rubber, styrene-butadiene rubber, polyester, epoxy resin, polyisocyanate,
Any material that can be used for ordinary magnetic recording materials, such as polyimide, can be used.

If necessary, a plasticizer such as DBP (dibutyl phthalate, TPP ()riphenyl phosphate) may be added to the magnetic layer.
Dispersants such as lecithin and tenguchi may be mixed.

The magnetic recording medium of the present invention obtained in this way has excellent surface smoothness of the magnetic layer and has significantly improved durability.

Hereinafter, the present invention will be specifically explained in more detail with reference to Examples. Hereinafter, [parts Jti, ``ii, parts r] will be shown.

Example 1 0-added FeOx "' parts (X=/, average particle size,: 0.3 μ x 0.03 μ) PVC vinyl chloride acetate copolymer 13 parts (trade name, jUMUHJ, manufactured by Manion Carbide Co., Ltd.) Polyurethane, μ part (Product name 1-N-230 Hiromu) Nippon Polyurethane @ Polyisocyanate 3 parts (Product name) URECORD product #11 clear for mylar Made by Higashi Nippon Toyo ■) Cr203 19 Carbon black 7 parts (Asahi @ IOJ Asahi Carbon (manufactured by Hep) Oleic acid j
Part No. 2 Eboxytetradecane 5 parts Myristic acid 3 parts Except for the polyisocyanate, the above composition was finely dispersed using a stirrer and then subjected to fine dispersion treatment using a ball mill.

After that, polyincyanate was added and stirred until the viscosity was 6J~
The viscosity was adjusted to 70 voids, and after passing through a p-pass, it was coated on a 74μ polyethylene terephthalate film using the above-mentioned magnetic liquid coating method using the reverse method. Super calendar missing circle,
Flat surface? 11 chemical treatment was carried out. Is this an inch flexible disk, Kanji 7, and Zanburu Al? ]l-
Obtained.

Example 2 Oleic acid/2epoxytetradecane of Example x
Myristin 1iBL - Change the sample AK shown below, and add icL to Zamble A2-161 as in Example 1.
``I got L.

l@/Table Comparative Example 1 The amounts of palmitic acid, butyl stearate, and oleic acid-modified silicon in the sample No. % 2 of Example 2 were changed, and the same procedure as in Example 1 was carried out, but in the sample version 6~&J',
Obtained.

/ Example 3 The polishing agent and ti shown below were changed to Cr2O3 of Example 1, and samples A~16. / Moss Obtained in the same manner as in Example 1.

Table 3 Comparative Example 2 Sample A was obtained in the same manner as in Example 1 by changing the 111I of r203 of Example 1.

Table Comparative Example 3 Example 1 (r 203 quantity changed)
A/7 Obtained in the same manner as in Example 1.

Table 5 Samples A, /~A/ of the Examples and Comparative Examples mentioned above
7, the durability was compared using a t-inch floppy disk drive. The results are shown in Table 6.

Based on the above study results, JL, which is an embodiment of the present invention,
al-J%' % A 9-□& / -Z tl'l
Durable BK oil, which lasts at least io'oθ ten thousand times or more, as shown in Comparative Example 1.3, A6 to A;
Regarding A/'1 to A/7, even if the lubricant (fatty acid, fatty acid ester, fat IFli silicon, α-olefin oxide) is 70w1% or less, or if it is an abrasive or Awt% scent. , the durability is inferior compared to the examples.

As shown in Example A/7, when the amount of r20:I is jMshabu, the durability is j0 million times and the commercial value is indicated, but the durability of the magnetic disk is 10 million times in terms of commercial value.
Considering that it is necessary, it can be seen that the abrasive (non-magnetic powder) having a Mohs hardness of 6 or more specified in the present invention is necessary in an amount of Awt% or more. The amount of lubricant shown in Sample A6 ~ Boiled is several wt%! The durability of iA is quite poor.

The evaluation method of the takes shown in Table 1 is as follows.

Durability: Floppy drive mail! Old -23° (-60%RH
In )ξrad out 10n'! fl'F, ; A durability test was carried out by rotating the floppy disk, and the number of revolutions was increased until the output of the floppy disk became J'0% or less of the initial output, and this number of revolutions was Igo, 10 million. As a product more than once, I'm hopeful.

Claims (1)

[Claims] A magnetic recording medium comprising a magnetic scale coated with ferromagnetic fine particles on a non-magnetic support, the magnetic layer comprising (1) a lubricant of fatty acid, fatty acid ester, fatty acid-modified silicon, Containing at least 10wt% of at least one type of α-olefin oxide in ferromagnetic fine particles and containing 10wt% or more in ferromagnetic fine particles (non-magnetic powder with a Mohs hardness of 6 or more) recoding media.