JPS61178727A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability of the titled recording medium by incorporating more than a specified amt., based on ferromagnetic powder, of a fatty acid amide and a fatty acid ester into the recording layer. CONSTITUTION:The magnetic layer contains, based on the ferromagnetic fine particles, >=7wt% fatty acid amide and fatty acid ester as the lubricant. Namely, by using only >=7wt% lubricant, the troubles arising in the conventional videotape and audiotape can be eliminated, and the durability is improved. Ethyl stearate can be used as the fatty acid ester, and stearyl amide, etc. can be exemplified as the fatty acid amide.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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.

[Prior art]

In order to improve electromagnetic conversion characteristics in magnetic recording media, especially high-density recording (= magnetic disks and magnetic sheets that require suitable and strong durability), it is necessary to simultaneously improve surface smoothness and durability. However, the conventional methods are no longer able to meet the demands for higher densities in magnetic disks and the like.

In other words, in order to increase the density of magnetic disks, etc., it is important to smooth the surface of the magnetic layer so that the ferromagnetic particles exist in a uniformly dispersed state within the magnetic layer.
Sufficient durability of the magnetic layer cannot be obtained only by employing fine-grained magnetic material, strengthening the requirements for smoothing treatment such as calendering, and using techniques such as increasing the dispersibility of magnetic liquid. On the other hand, as the density increases, the thickness of the magnetic layer has to be made thinner than before.

Conventionally, it has been known to use fatty acids as a lubricant (Special Publication Show &?-J'94102) in order to increase durability. ) 4 or less.Also, it is known that α-olefin oxide is used as a lubricant, but it is known that the lubricant is used at 3 wt% or less with respect to the magnetic material ( (Japanese Patent Publication No. 71-'74010).The above case is an invention particularly used for video tapes, audio tapes, and memory tapes.

The reason why the amount of lubricant used was selected to be 7wt4 or less is that in video tapes, if more than 2 to 3wt% of lubricant is used, the magnetic layer becomes plasticized and weakens, causing dropouts. Furthermore, lubricants based on fatty acids or fatty acid esters tend to cause sticking to the magnetic head. Also, in audio tapes, if a lubricant of more than j-jWt* is used, the magnetic layer becomes plasticized, similar to video tapes.
This is due to problems such as "blanks" tend to appear due to the influence of temperature and humidity, the μ value of the magnetic layer decreases, which causes swelling and development during running, and the generation of white powder, which causes head stains. .

However, for magnetic recording media that require a high degree of durability, such as magnetic disks, which require durability over 1,000,000 cycles of continuous rotation for commercial value, the combination of binders and lubricants used in the past cannot be used. When less than 7 wt% of the ferromagnetic fine particles is used, there is a problem that no durability is obtained at all. Therefore, the inventors of the present invention conducted intensive studies regarding the type and amount of lubricant to be used, and as a result, discovered a relationship that could not be expected based on conventional common sense, and the present invention was achieved.

[Purpose of the invention]

An object of the present invention is to provide a magnetic recording medium with improved durability, particularly a magnetic recording medium with improved durability.

[Structure of the invention]

The present invention provides a magnetic recording medium in which a magnetic layer consisting of ferromagnetic fine particles and a binder is coated on a non-magnetic support, in which the magnetic layer contains fatty acid amide or fatty acid ester as a lubricant for the ferromagnetic fine particles in an amount of 7 wt. A magnetic recording medium characterized by containing % or more of

In other words, even if a lubricant of 7wt% or more is used, the present invention does not cause the various problems described above that occur with conventional audio tapes and video tapes, and can maintain the durability required for magnetic disks, etc., which is the object of the present invention. It was discovered that it is possible to improve the properties of

The lubricants used in the present invention include fatty acid esters and fatty acid amides, and other lubricants can also be used if necessary.

Examples of fatty acid esters include esters such as ethyl stearate, butyl stearate, amyl stearate, 9-butyl rumitate, hexyl laurate, butyl laurate, butyl myristate, and furthermore, butoxyethyl stearate and butoxybutyl stearate. , alkoxy esters such as ethoxyethyl stearate, ethoxybutyl stearate, butoxyethyl palmitate, etc. can be used. Examples of fatty acid amides include stearylamide, oleylamide, erucylamide, lumitylamide, myristylamide, and the like. Lubricants used as necessary include saturated or unsaturated fatty acids, fatty acid-modified silicones, α-olefin oxides, saturated hydrocarbons, and the like.

Durability can be further improved by adding abrasives, carbon black, etc. in addition to the above lubricants. As the abrasive, non-magnetic powder with a Mohs hardness or higher is effective for improving durability, and specific examples include alumina, Cr2O3, 5iC1 garnet, and the like. If the Mohs hardness is 4 or less, the durability deteriorates and it cannot be used.

The particle size of the non-magnetic powder is preferably /μ or less, particularly 0.
2μ to 007μ is preferred.

Carbon black used in the present invention: The second is the average particle size, and io-4tomμ is suitable.
Ketjen Black ECJ (manufactured by Lion Akzo), rXC-7JJ
(manufactured by Cabot) etc. are commercially available.

In order to further improve the surface properties of the magnetic recording medium, carbon black may be mixed with ferromagnetic powder, a binder and an organic solvent (two fronts). Also, the amount of auxiliary kneading of the magnetic powder and binder can be adjusted as necessary in the same way as with carbon black.Usually, for ferromagnetic powder, it is often better to pre-mix the entire amount. However, it is essential to carefully consider the type and amount of the binder and set the conditions for fronting.If the focus is only on the surface smoothness of the magnetic layer, it is preferable to use the entire amount of carbon black and perform frontlining. If the surface electrical resistance of the magnetic layer is required to be below a certain value, only a part of the surface is front-lined.
It is often best to use the remaining amount in a subsequent process.

As the front line method, it is preferable to use a three-roll mill, a pressure kneader, an open kneader, a Warner kneader, etc., but any method that can be used for the cross-line of ordinary pigments can be applied.

As the solvent for front printing, acetic esters such as ethyl acetate and butyl acetate, ketones such as MEK, MIBK and cyclohexanone, and other solvents commonly used in magnetic tapes can be used.

Ferromagnetic powders include r-Fe20a, FeaO4, Cr
Q2, cobalt-added r-Fe203, cobalt-added Fe
In addition to oxides such as Qx (x=/, jj ~/, j), Fe
Metal powders such as -Ni and Fe-Ni-Co can also be used.

As a binder, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, carboxyl group-containing vinyl chloride-vinyl acetate copolymer, vinyl alcohol-containing vinyl chloride-vinyl acetate copolymer, polyvinylidene chloride, vinylidene chloride-acrylonitrile copolymer, nitrocellulose Various other cellulose derivatives, acrylonitrile-butadiene rubber, styrene-butadiene rubber, polyester, epoxy resin, polyisocyanate, polyamide, and other ordinary magnetic recording media (= can be used. All can be used.

If necessary, plasticizers such as DBP (dibutyl phthalate) and TPP (triphenyl phosphate), and dispersants such as lecithin may be mixed into the magnetic layer.

As the non-magnetic support, ordinary magnetic recording media such as polyethylene terephthalate, triacetyl cellulose, polyethylene naphthalate, polyamide, polyimide, etc. (=all available materials can be used, and AI! vapor-deposited polyester film can also be used.

〔Example〕

Next I: The present invention will be explained in more detail in Examples and Comparative Examples (2). In the examples, all "parts" indicate parts by weight.

Example/Co-added FeQx 100 parts (X
±/, 4 with average particle size 0.3μxo, o3μ) PVC vinyl acetate copolymer 73 parts (product name, rUMcHJ manufactured by Nippon Carpide Co., Ltd.) Polyurethane part (product name [N-23o4t4 manufactured by Nippon Polyurethane ■) Poly Isocyanate 1 part (Product name [Urecoat B for Mylar ◆/Clear] manufactured by East Japan Paint ■) Cr2Q3 4 parts Carbon black Ri part ([Asahisu 10.
(Manufactured by J Asahi Carin ■) Ethoxybutyl stearate / part Ethoxybutyl normitate 2 parts Butyl stearate 2 parts Oleylamide
After removing the 3-part polyisocyanate, the above composition was coarsely dispersed using a stirrer, and then finely dispersed using a ball mill.Then, the polyisocyanate was added and stirred to obtain a viscosity of 6-t to 70 poise (0C). After adjusting the viscosity and filtering, it is 7! The above magnetic liquid was applied to a μ polyethylene terephthalate film by a reverse method, and the surface was smoothed using a super calender. This was processed into a J-, 2-inch flexible disk to obtain sample A/.

Example Sample A was obtained in the same manner as Sample A to Example Example 1, except that ethoxybutyl stearate, ethoxybutyl normitate, butyl stearate, and oleylamide in Example 1 were changed to those shown in Table 1.

Lubricant ethoxy-7-butyl stearate in Table Comparative Example/Example/
Sample A was prepared in the same manner as in Example except that the amounts of ethoxybutyl palmitate, butyl stearate, and oleylamide were changed as shown in Table 1. , I got the second one.

As a result of such studies, the sample shop/~g which is an example of the present invention has durability (at least 76 million times or more), and in comparison, it has a lubricant content of 7wt%. If it is below, the durability will be considerably inferior compared to the examples.

The evaluation method for the data shown in Table 3 is as follows.

Durability: 23°060%R using floppy disk drive
The number of rotations until the output of the floppy disk becomes less than !θ of the initial output when a durability test is performed by continuously rotating the disk under the condition of a pad pressure of 10 g is shown. , 70 million times or more is desirable as a product.

〔Effect of the invention〕

The magnetic recording medium according to the present invention has excellent durability against repeated use.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic layer coated on a non-magnetic support, characterized in that the magnetic layer contains fatty acid amide and fatty acid ester in an amount of 7% by weight or more based on ferromagnetic powder.