JPS62188021A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To keep the excellent lubricating effect of the titled medium for a long time and to improve the durability by dispersing fine activated carbon powder wherein a lubricant is adsorbed and occluded in the magnetic layer. CONSTITUTION:Fine activated carbon powder wherein a lubricant is adsorbed and occluded is dispersed in the magnetic layer on a nonmagnetic carrier. The particle diameter of the fine activated carbon powder is preferably controlled to 0.1-1.0mum. A long-chain fatty acid, a fatty acid ester, a silicon derivative, a fluorine-contg. compd., etc., are preferably used as the lubricant. An excellent lubricating effect can be obtained by this constitution, the effect can be kept for a long time, and hence the durability is improved.

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, technology for imparting good durability and running stability to magnetic recording media continues to become 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, in a coated magnetic recording medium obtained by coating a magnetic paint in which magnetic powder, binder resin, and various additives are dispersed in an organic solvent on a non-magnetic support and drying,
A commonly used method is to add a lubricant to a magnetic paint to form a magnetic layer to provide lubricity.

Known examples of such lubricants include long-chain fatty acids, fatty acid esters, liquid paraffin, silicone derivatives, and fluorine-containing compounds.

Problems to be Solved by the Invention In the above lubrication method, the added lubricant exhibits the desired characteristics only after it migrates to the surface of the magnetic layer, but this migration phenomenon greatly affects the compatibility with the binder resin, etc. affected. That is,
If the compatibility is high, the migration of the lubricant to the surface of the magnetic layer will be reduced, resulting in a decrease in the lubricating effect, plasticization of the magnetic layer, etc.
Deterioration of physical properties of the coating film, such as a decrease in glass transition temperature, occurs.

On the other hand, if the compatibility is low, the deterioration of the physical properties of the coating film will be less, but the lubricant will be more likely to float to the surface of the magnetic layer.
There are disadvantages such as deterioration of electromagnetic conversion characteristics and surface properties, and shortening of the duration of the lubricating effect.

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

Means for Solving the Problems In order to solve the above problems, the magnetic recording medium of the present invention comprises:
A magnetic layer in which magnetic powder is dispersed in a binder resin is provided on a non-magnetic support, and activated carbon fine powder adsorbing and occluding a lubricant is dispersed in the magnetic layer.

Function The present invention focuses on the ability of activated carbon to adsorb and store lubricants. That is, a lubricant conventionally used in coated magnetic recording media is adsorbed and occluded in the pores on the surface of the activated carbon fine powder, and then dispersed in the magnetic paint to form a magnetic layer. With the above structure, the lubricant moves from the surface of the activated carbon 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. In addition, as the lubricant gradually leaches into the magnetic layer from the surface of the activated carbon fine powder as it slides against the magnetic head, the lubricant has a greater lubrication effect than when the lubricant is dispersed alone in the magnetic layer. Even if the lubricant persists for a long time and the compatibility between the lubricant and the binder resin is high, the lubricating effect may decrease, the physical properties of the coating may deteriorate (1, plasticization of the layer, a decrease in the glass transition temperature, etc.). It becomes less likely to occur.

Furthermore, if the lubricant is dispersed in the magnetic paint to form a magnetic layer, even if the lubricant is unusable because it bulges out onto the surface of the magnetic layer due to its low compatibility, it will be adsorbed and occluded by fine activated carbon powder and then dispersed in the magnetic paint to form the magnetic layer. When formed, an excellent lubrication effect can be obtained without protruding onto the surface of the magnetic layer.

The particle size of the activated carbon fine powder applicable to the present invention is 0.1 μm
to 1.0 μm, preferably 0.2 μm to 0
．． It is 5 μm. Further, the pore diameter on the surface of the activated carbon fine powder is preferably from 11111 to 10 mm. If the particle size of the activated carbon fine powder is smaller than 0.1 .mu.m or larger than 1.0 .mu.m, the dispersibility in the magnetic paint deteriorates, which adversely affects the surface properties of the magnetic layer. Furthermore, if the pore diameter on the surface of the activated carbon fine powder is smaller than 11 m, it becomes difficult to adsorb and occlude lubricant. On the other hand, if it is larger than 1 OnIn, the lubricant is likely to be detached and the sustainability of the lubricating effect is reduced. Furthermore, if the number of pores on the surface of the activated carbon fine powder is about 500 m''/f to 1000 m''/f in terms of surface area, the lubricant can be adsorbed and occluded well, giving good results.

In the present invention, the lubricant adsorbed and occluded by the activated carbon fine powder may be long-chain fatty acids, fatty acid esters, fatty acid amines, liquid paraffin, silicon derivatives, fluorine-containing compounds, etc., which have been conventionally used in coated magnetic recording media. .

The method for adsorbing and occluding lubricant into the activated carbon fine powder is as follows:
Conventionally known methods such as vacuum impregnation method and gas phase adsorption method can be applied.

Regarding the magnetic powder, binder resin, abrasive, antistatic agent, dispersant, plasticizer, hardening agent, substrate (base film), etc. that constitute the magnetic recording medium in the present invention, conventionally known ones can be used. . Furthermore, conventionally known solvents can be used for preparing the magnetic paint. Furthermore, lubricants other than those adsorbed and occluded in the activated carbon fine powder can be added as needed.

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

Activated carbon fine powder is pulverized in a ball mill to a particle size of 0.
Pieces with a size ranging from 1 μm to 0.6 μm were obtained by various classification methods. The BET specific surface area of this activated carbon fine powder is 7oor
It was d/f. Three types of fatty acid ester lubricants, oleyl oleate, stearyl stearate, and glycerin triolate, were adsorbed and occluded into this activated carbon fine powder using a vacuum impregnation method to obtain three types of lubricant-occluding activated carbon: human, B, and C. Ta. The adsorption amount of each lubricant is as shown below.

o, eoyi (activated carbon fine powder 12) B: stearyl stearet) o, ssf/
(Activated carbon fine powder 12) C: Glycerin triolate o
, 4sr/(activated carbon fine powder 1f) Example 1 Next, a magnetic paint was prepared with the following composition.

Co-adhered - Fe205 magnetic powder 100 parts Vinyl chloride-vinyl acetate copolymer resin 10 parts by weight Urethane resin 10 parts by weight Alumina 6 parts by weight Carbon black 3 parts by weight Oleic acid
2 parts by weight hardener
6 parts by weight lubricant storage activated carbon
10.6 parts by weight methyl ethyl ketone
150 parts by weight toluene
160 parts by weight cyclohexanone
76 parts by weight The magnetic paint prepared with the above composition was coated with a thickness of 76 parts by weight.
It was coated onto a 5-μm polyethylene terephthalate film to a final thickness of 4 μm, and after drying, surface smoothing, and curing, it was punched out into a 6-inch disk to obtain a floppy disk.

Example 2 In Example 1, 11 parts by weight of lubricant-storing activated carbon B was added instead of lubricant-storing activated carbon B to form a paint.
I obtained a floppy disk in the same way.

Example 3 In Example 1, 13 parts by weight of lubricant-storing activated carbon C was added instead of lubricant-storing activated carbon C to form a paint.
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 6.6 parts by weight of activated carbon that does not store lubricant were added instead of the lubricant-storing activated carbon to form a paint, 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 7 parts by weight of activated carbon that does not store lubricant were added in place of lubricant-storing activated carbon B to form a paint, and a floppy disk was prepared in the same manner as in Example 1. I got it.

Comparative Example 3 In the composition of Example 3, 4 parts by weight of glycerin triolate and 9 parts by weight of activated carbon that does not store lubricant were added in place of lubricant-storing activated carbon C to form a paint, and a floppy disk was prepared in the same manner as in Example 1. Obtained.

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. The durability was measured using a commercially available 5-inch floppy disk device under the following conditions. The durability of the floppy disks was compared by rotating the same track at a head pressure of 409 and using the number of passes in which the output level became 80% or less of the initial value. The temperature and humidity conditions of the measurement environment are 6℃, 104RH: 25℃, 60%
RH: 50°C.

This was done at 86chi RH.

In Comparative Example 2, the lubricant was visible on the surface of the magnetic layer, and the durability could not be measured properly. Example 1 and Comparative Example 1.
In Example 2 and Comparative Example 2, and in Example 3 and Comparative Example 3, the same fatty acid ester lubricant and the same amount of activated carbon fine powder were added. Table 2 shows that when a lubricant is adsorbed and occluded in activated carbon fine powder, durability is clearly improved under various environments compared to when a lubricant is added alone to the magnetic layer. Furthermore, as shown in Example 2 and Comparative Example 2, even if the lubricant is unusable because it bulges out onto the surface of the magnetic layer due to low compatibility between the lubricant and the binder resin, it can be adsorbed and occluded by fine activated carbon powder. When dispersed in a magnetic paint to form a magnetic layer, an excellent lubricating effect can be obtained without protruding onto the surface of the magnetic layer.

Further, from Table 1, it is not observed that the magnetic properties and surface properties of the magnetic layer are particularly deteriorated by the method of the present invention.

Effects of the Invention As described above, according to the present invention, a magnetic recording medium with excellent durability can be provided by dispersing fine activated carbon powder in which a lubricant is adsorbed and occluded in a magnetic layer.

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 fine activated carbon powder adsorbing and occludes a lubricant is dispersed in the magnetic layer. .