JPS6356816A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability without deteriorating magnetic characteristics and surface characteristic by dispersing fine activated aluminum powder adsorbed and occluded with a lubricating agent into a magnetic layer. CONSTITUTION:The lubricating agent is adsorbed and occluded into the pores on the surface of the fine activated aluminum powder and is disposed into the magnetic layer. The lubricating agent is thereby migrated from the surface of the fine activated aluminum powder further into the magnetic layer and to the surface of the magnetic layer, by which the coefft. of friction on the surface of the magnetic layer is decreased and the excellent lubricity is obtd. The lubricating agent leaches gradually into the magnetic layer from the surface of the fine activated aluminum powder as the medium slides a magnetic head; therefore, the lubricating effect is sustended for the longer time than in the case of dispersing the lubricating agent alone into the magnetic layer. The degradation in the a lubricating effect and the deterioration in the properties of the coated film hardly arise even in the case of high compatibility between the lubricating agent and binder resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording medium used as a magnetic tape or a floppy disk, and particularly to a magnetic recording medium with improved durability.

BACKGROUND OF THE INVENTION In recent years, magnetic recording media are required to have even higher recording densities, and the environments in which they are used are expanding from low temperature and low humidity to high temperature and high humidity. For this reason, magnetic recording media with good durability and running stability have been developed, and the technology thereof is becoming more and more sophisticated. In order to improve this durability and running stability, it is necessary to impart good lubricity to the magnetic recording medium. By the way, magnetic powder, binder rotten fat.

In coated magnetic recording media, which are obtained by coating a magnetic paint in which various additives are dispersed in an organic solvent on a non-magnetic support and drying it, a lubricant is added to the magnetic paint to form a magnetic layer. A commonly used method is to impart lubricity by applying this method. Known lubricants include long-chain fatty acids, fatty acid esters, liquid paraffin, licon derivatives, and fluorine-containing compounds (see, for example, Japanese Patent Publication No. 18065/1983).

JP-A-56-80829, Kagaku to Kogyo, Vol. 35, No. 9 (19B2), P2S5).

Problems to be Solved by the Invention In the conventional lubrication method as described above, the desired effect is obtained only after the added lubricant migrates to the surface of the magnetic layer, but this migration phenomenon is caused by the interaction with the binder resin, etc. It is greatly influenced by compatibility. In other words, when the compatibility is high, the lubricant migration to the surface of the magnetic layer is reduced, the lubricant effect is reduced, and the physical properties of the coating film are deteriorated, such as plasticization of the magnetic layer and a decrease in the glass transition temperature. Occur. On the other hand, if the compatibility is low, the physical properties of the coating film will be less affected, but the lubricant will tend to bulge out onto the surface of the magnetic layer, deteriorating the electromagnetic characteristics and surface properties, and further increasing the duration of the lubricating effect. There are disadvantages such as shortening of the length.

In view of the above-mentioned problems, the present invention has been developed to provide a durable lubricant that provides an excellent lubricating effect regardless of the compatibility between the lubricant in the magnetic layer and the binder resin, and that the effect lasts for a long time under various environments. The present invention provides a complete magnetic recording medium comprising a magnetic layer with excellent properties.

Means for solving all the problems In order to solve all the above problems, the magnetic recording medium of the present invention has the following steps:
A magnetic layer in which magnetic powder 1 is dispersed in a binder resin is provided on a non-magnetic support, and activated alumina imitation powder in which a lubricant is adsorbed and occluded is completely dispersed in the magnetic layer.

The present invention focuses on the ability of activated alumina to adsorb and absorb lubricants. Is activated alumina a non-crystalline alumina with strong adsorption ability? It has many pores on its surface. The lubricant conventionally sprayed on coated magnetic recording media is absorbed into the pores on the surface of activated alumina fine powder.
and dispersed in the magnetic layer. The grooves g allow the lubricant to migrate from the surface of the activated alumina fine powder into the magnetic layer and further to the surface of the magnetic layer, thereby reducing the coefficient of friction on the surface of the magnetic layer and providing excellent lubricity. As the lubricant gradually leaches into the magnetic layer from the surface of the activated alumina imitation powder as it slides against the magnetic head, the lubricant is more lubricated than when the lubricant is dispersed in the magnetic layer entirely. Even if the effect lasts for a long time and the compatibility between the lubricant and binder resin is high, the lubricating effect may decrease and the physical properties of the coating film may deteriorate (plasticization of the magnetic layer, decrease in glass transition temperature, etc.) becomes less likely to occur.

Furthermore, if it is directly dispersed in the magnetic coating phase and formed into a magnetic layer,
Even a lubricant that cannot be sprayed because of its low compatibility because it floats onto the surface of the magnetic layer will float onto the surface of the mother layer if it is adsorbed and occluded in activated alumina fine powder and then dispersed in magnetic paint to form a magnetic layer. Excellent lubrication effect can be obtained without any lubrication.

The particle size of the activated alumina fine powder applicable to the present invention is 0.
In the range of 1 μm to 1.0 μm, preferably 0.2 μm
0.6 μm. Further, a pore diameter of 1 nm to 1 Q nm on the surface of the activated alumina fine powder gives preferable results. Particle size of activated alumina fine powder is 0.1μm
If the diameter is smaller or larger than 1.0 μm, the dispersibility in the magnetic coating material will deteriorate, and the surface properties of the magnetic layer will be adversely affected. Furthermore, if the pore diameter on the surface of the activated alumina fine powder is smaller than 1 nm, it becomes difficult to adsorb and store the lubricant. .

On the other hand, if it is larger than 10 nm, the lubricant is likely to be detached, and the sustainability of the lubricating effect will be reduced. Furthermore, the number of pores on the surface of the activated alumina fine powder is 100 m1/g in terms of surface area.
About 300rn'zl adsorbs and occludes lubricant well and gives good results.

In the present invention, the lubricant to be adsorbed and occluded in the activated alumina imitation powder includes long-chain fatty acids, fatty acid esters, fatty acid amides, liquid paraffin, silicon derivatives, fluorine-containing compounds, etc., which are conventionally used in coated magnetic recording media. It is possible to use it.

As a method for adsorbing and occluding the lubricant into the activated alumina fine powder, conventionally known methods such as a vacuum impregnation method and a gas phase adsorption method are used.

Magnetic powder that constitutes the entire magnetic recording medium in the present invention.

As the binder resin, abrasive, antistatic agent, 1-minute adhesion agent, plasticizer, hardening agent, base material (base film, film), etc., conventionally known materials can be used. In addition, conventionally known solvents can be used for preparing magnetic materials. Furthermore, lubricants other than those adsorbed and occluded by the activated alumina fine powder can be added as necessary.

EXAMPLES Hereinafter, examples of the present invention will be explained while comparing them with comparative examples.

Example 1 Activated alumina fine powder was pulverized in a ball mill to obtain particles with particle diameters ranging from 0.2 μm to 0.5 μm using a virtual invactor. The amount of activated alumina is 0
The BET specific surface area was 150 mI/night. This activated alumina fine powder was adsorbed and occluded with oleyl oleate as a fatty acid ester lubricant by a vacuum impregnation method to obtain a lubricant occluded activated alumina powder. The adsorption amount of the lubricant oleyl oleate is o, tso [g (1 g of activated alumina fine powder)].

Next, a magnetic paint was prepared with the following composition.

Co fracture adhesion - Fe205 magnetic powder 100 parts by weight Vinyl chloride-vinyl acetate copolymer resin 10 parts by weight Urethane resin 10 parts by weight α-alumina
5 parts by weight carbon black
3 parts by weight oleic acid 2
Parts by weight Curing agent 6 parts by weight Lubricant Storage active alumina 12 parts by weight Methyl ethyl ketone 150 parts by weight Toluene
150 parts by weight cyclohexanone
75 parts by weight The magnetic paint prepared with the above composition was applied onto a polyethylene terephthalate film with a thickness of 75 μm to a final film thickness of 4 μm, and after passing through the steps of drying, surface smoothing, and curing, A floppy disk was obtained by punching out an inch disk.

Example 2 Instead of the lubricant-occluding active alumina of Example 1, stearyl stearate was adsorbed and occluded in the same activated alumina fine powder as in Example 1 by vacuum impregnation, with an adsorption amount of o, 4.
A floppy disk was obtained in the same manner as in Example 1 by adding 14 parts by weight of lubricant-occluding activated alumina B'i of o9/(1 g of activated alumina fine powder) to form a coating.

Example 3 Instead of the lubricant occluding activated alumina of Example 1, glycerin triole 11a - the same activated alumina fine powder as in Example 1 was adsorbed and occluded by the vacuum impregnation method, and the adsorption amount o
, 4 og/(1 g of activated alumina fine powder) was added in parts by weight of lubricant-storing activated alumina C1114 to form a paint, Example 1
I obtained a floppy disk in the same way.

Comparative Example 1 In the composition of Example 1, 4 parts by weight of oleyl oleate and 8 parts by weight of activated alumina that does not store lubricant were added in place of lubricant-storing activated alumina A, and a floppy disk was prepared in the same manner as in Example 1. I got it.

Comparative Example 2 In the composition of Example 2, 4 parts by weight of stearyl stearate and 10 parts by weight of activated alumina that does not store lubricant were added in place of lubricant-storing activated alumina B, and a floppy film was prepared in the same manner as in Example 1. Got the disc.

Comparative Example 3 In the composition of Example 3, 4 parts by weight of glycerin triolate and 10 parts by weight of activated alumina that does not store lubricant were added in place of lubricant-storing activated alumina C to form a paint, and a floppy film was prepared in the same manner as in Example 1. Got the disc.

Regarding the floppy disks of Examples and Comparative Examples prepared as described above, the measurement results of magnetic properties and surface glossiness (surface properties) are shown in Table 1, and the measurement results of durability are shown in Table 2.
Shown in the table. The durability was measured using a commercially available 5-inch floppy disk drive under the following conditions. The durability of the floppy disks was compared based on the number of passes in which the same track was rotated with a head pressure of 40 g and the output level became 8Q% or less of the initial value. The temperature and humidity conditions of the measurement environment are 6°C, 11o%RH.
i 26°C, 60% RHi 50°C, 85% RH.

In Comparative Example 2 of Table 1 and Table 2, the lubricant was protruding from the surface of the magnetic layer, and the durability could not be measured properly. Example 1 and Comparative Example 1.
Example 2 and Comparative Example 2. In Example 3 and Comparative Example 3, the same fatty acid ester lubricant and the same amount of activated alumina fine powder were added.

From Table 1, no particular deterioration in the magnetic properties and surface properties of the magnetic layer is observed by the method of the present invention.

Table 2 shows that when a lubricant is adsorbed and occluded in fully activated alumina fine powder, a clear i (improvement in durability is observed under each environment) compared to when the lubricant is added alone as a magnetic layer. In addition, as shown in Example 2 and Comparative Example 2,
Even if the lubricant is not compatible with the binder resin, etc. and cannot be used legally because it floats to the surface of the magnetic layer, it can be adsorbed and occluded by activated alumina fine powder and then dispersed in the magnetic paint to form the magnetic layer. Excellent lubrication effect can be obtained without protrusion on the surface of the magnetic layer.

Effects of the Invention As described above, according to the present invention, by dispersing the activated alumina fine powder in which the lubricant is totally adsorbed and occluded in the entire magnetic layer,
A magnetic recording medium with excellent durability can be provided without deteriorating magnetic properties or surface properties.

Claims (1)

[Claims] A magnetic recording medium characterized in that a magnetic layer in which magnetic powder is dispersed in a binder resin is provided on a non-magnetic support, and activated alumina in which a lubricant is adsorbed and occluded is dispersed in the magnetic layer.