JPS63153721A - Magnetic disk - Google Patents

Abstract

PURPOSE:To improve durability and running performance by forming a magnetic coated film contg. 2-20pts.wt. aliphat. dibasic acid diester and 2-10pts.wt. graphited carbon having 20-200mum average grain size per 100pts.wt. magnetic powder on a base. CONSTITUTION:The magnetic disk having the magnetic layer in which 2-10pts. wt. aliphat. dibasic acid diester and 2-10pts.wt. graphited carbon having 20-200mum average grain size per 100pts.wt. magnetic powder are made to co-exist on the base has the excellent durability and running performance. The reasons are as follows: The aliphat. dibasic acid diester has a relatively low visconsity and does not considerably deteriorate the mechanical strength of a binder even if said ester is incorporated into the magnetic layer. In addition, the aliphat. dibasic acid diester strongly adsorbed to the graphited carbon used in conjunction acts an internal lubriating effect. The magnetic coated film formed by using both in conjunction has the sufficiently high lubrication sustaining effect and can exhibit the excellent durability even in wide environmental conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Use The present invention relates to a magnetic disk used in floppy disks and the like, and particularly to a magnetic disk with improved durability and runnability.

BACKGROUND ART Magnetic disks are required to have excellent durability with little wear on the magnetic layer, as well as to have a low coefficient of friction and excellent running properties, since they come into vigorous sliding contact with a magnetic head during recording and reproduction.

Therefore, the selection of the lubricant added to the magnetic layer is extremely important. Conventionally used lubricants include:
Fatty acid ester, fluorine oil, problems to be solved by the invention However, with the above configuration, durability and runnability cannot be fully satisfied.

In particular, when a magnetic disk and a magnetic head are ejected for a long period of time in a stationary state, the lubricant layer present on the surface of the magnetic layer adheres the two, and this adsorption causes the magnetic disk to move in a low 1 drive torque drive. There is a problem that rotation and driving are difficult. Further, even if such a problem does not occur, the above-mentioned adsorption phenomenon may cause instability in running properties and a decrease in electromagnetic conversion characteristics.

For example, the present inventors have already demonstrated that the use of higher fatty acids and dioleyl adipate in combination in the magnetic layer improves durability compared to conventional magnetic layers. However, although the wear resistance has been improved, the coefficient of friction has not been improved at all, and the running performance in particular is not fully satisfactory.

In view of the above problems, the present invention provides a magnetic disk with greatly improved durability and running performance.

Means for Solving the Problems In order to solve the above problems, the magnetic disk of the present invention contains 2 to 10 parts by weight of aliphatic dibasic acid diester and an average particle diameter of 20 to 200 mμ per 100 parts by weight of magnetic powder. So 2-1
A magnetic layer containing 0 parts by weight of graphitized carbon is formed on a support.

Effect As a result of intensive study on the lubricant to be added into the magnetic layer, the inventors found that aliphatic dibasic acid diester and an average particle size of 20 to 2
It has been found that a magnetic disk having a magnetic layer in which graphitized carbon of 00 mμ coexists has excellent durability and runnability.

The reason for this is that the aliphatic dibasic acid diester has a relatively low viscosity and does not significantly deteriorate the mechanical strength of the binder even if it is contained in the mother layer. In addition, the aliphatic dibasic acid diester is strongly adsorbed to the graphitized carbon particles used in combination, which acts as an internal lubricant, and the magnetic coating film using both of them has a sufficient long-lasting lubrication effect and can be used in a wide range of environmental conditions. Excellent durability can also be obtained.

In addition, a small amount of graphitized carbon exists as fine solid particles on the surface of the magnetic layer, and when it comes into sliding contact with the magnetic head, the sliding is very good, resulting in good running properties. It is thought that this property also plays a major role in preventing adsorption phenomena.

Note that normal graphite particles have a particle size of 0.5 to 2 μm.
This is extremely large and reduces the surface smoothness of the magnetic coating.

On the other hand, if carbon black is used as a raw material and graphitized, it is possible to obtain graphitized carbon having approximately the same particle size as the raw material. As a result, it was found that the effects of graphite can be exhibited without reducing surface smoothness.

The aliphatic dibasic acid diester used in the present invention is a diester consisting of a saturated or unsaturated alcohol having 18 or less carbon atoms and an aliphatic dibasic acid having 10 or less carbon atoms, which is liquid at room temperature. Preferably, specific examples thereof include dioleyl malate, dioleyl adipate,
Examples include dioleyl sebacate, diisodecyl lumarate, diindecyl succinate, diisotyladipate, diisotyladipate, diisostearyl adipate, and the like.

In addition, the amount of aliphatic dibasic acid diester added is as follows: magnetic powder 1
The amount is preferably within the range of 2 to 10 parts by weight per 00 parts by weight.

Next, the average particle size of the graphitized carbon used in the present invention is suitably 20 to 200 mm.The amount of graphitized carbon added is in the range of 2 to 10 parts by weight per 100 parts by weight of magnetic powder. It is preferable to keep it within 1 ha.

If the amount of the aliphatic dibasic acid diester added is less than 2 parts by weight, the lubricating effect cannot be sufficiently exerted, and if it is more than 10 parts by weight, protrusions may occur on the surface of the magnetic layer and contaminate the magnetic head. This may reduce the output and generate missing pulses or extra pulses.

Furthermore, if the amount of graphitized carbon added is less than 21 parts by weight, the above-mentioned slipping effect cannot be sufficiently exhibited, and conversely, if it is more than 10 parts by weight, the appropriate viscoelasticity of the binder is impaired. The mechanical strength of the magnetic layer deteriorates, and the wear resistance cannot be improved.

Example EXAMPLES Below, examples of the present invention will be described and specifically explained.

In addition, all parts below indicate parts by weight.

(Example 1) Cobalt magnetized iron oxide 100 parts Nitrified cotton (manufactured by Asahi Kasei Industries, Ltd.; product name 5L-1) 1a part Polyurethane resin 14 parts (manufactured by Nippon Polyurethane Co., Ltd.: @Product name N-2304) Alumina powder
4 part wrench 7
1 part oleic acid
1 part dioleyl adipate 3 parts graphitized carbon (average particle size SOWμ) 5 parts (manufactured by Mitsubishi Chemical Industries, Ltd.: trade name + 4010BS) toluene
100 parts methyl ethyl ketone
100 parts cyclohexanone
After thoroughly mixing and dispersing 100 parts of the above composition in a ball mill, 4 parts of a polyinsyanate compound (manufactured by Nippon Polyurethane Co., Ltd., trade name: Coronet L) was added, and the resulting magnetic paint was coated on both sides of a 76 μm thick polyester film. , the thickness of the dry coating is 1.3
After coating and drying to a thickness of .mu.m, the surface was treated with a super calendar roll, cured by heating at 60.degree. C. for 24 hours, and punched out into a disk shape to produce a magnetic sheet.

(Example 2) A magnetic sheet was made using the same composition as in Example 1 except that 6 parts of dioleyl malate was used instead of dioleyl adipate. (Example 3) Example A magnetic sheet was prepared under the same conditions as in Example 1 except that the graphitized carbon used was replaced with one having an average particle size of 20 mμ (however, some graphitized carbon).

(Comparative Example 1) A magnetic sheet was produced in the same manner as in Example 1 except that dioleyl adipate was used.

(Comparative Example 2) A magnetic sheet was made in the same manner as in Example 1, except that graphitized carbon was used. (Comparative Example 3) In the composition of Example 1, instead of dioleyl adipate, A magnetic 7-sheet was made under the same conditions except that liquid paraffin was used.

(Comparative Example 4) A magnetic sheet was prepared using the same composition as in Example 1 except that carbon black was used instead of the graphitized carbon used. The magnetic sheets of each of the above samples were surface-polished. It was later assembled into a 3-inch compact floppy disk. Load this disc into a recording/playback device, set the temperature at -6°C and 4 parts at 80°C.
While running on the same track in an environment of %RH, the magnetic head was brought into contact with a head pressure of 7cm2 and slid at a circumferential speed of 2m/sec, and the reproduction output was 70% of the initial value.
Acceleration durability was investigated by measuring the running time until .

In addition, the above disc was tested 3 times in an environment of 40°C and 80%RH.
The starting torque (Ts) of the same truck was examined after it was installed in an inch compact floppy disk drive and stopped for 6 hours after running on the same truck for 24 hours. Furthermore, the static friction coefficient (μS) of the magnetic layer was measured using a cursor-type static friction coefficient measuring device (manufactured by Kyowa Kagaku Co., Ltd.) in an environment of 23°C and 55,000 RH. After being left in an environment of 40'(:, Bo%RH) for 30 days, visual observation was performed using a microscope.

Table 1 summarizes the results.

(Margins below) Table 1 As is clear from the results in Table 1, the magnetic disks obtained in the examples had better durability, starting torque, and palm friction coefficient than the comparative examples, and moreover, the surface of the magnetic layer It can be seen that the lubricant does not bulge out, indicating a good balance between wear resistance and running performance.

Effects of the Invention As described above, according to the present invention, by forming on a support a magnetic layer containing an aliphatic dibasic acid diester and graphitized carbon having an average particle size of 20 to 200 mμ,
A highly reliable magnetic disk with stable durability and running performance under a wide range of environmental conditions can be obtained. Therefore, it has practical value as a dog.

Claims (1)

[Claims] 2 to 10 parts by weight of aliphatic dibasic acid diester per 100 parts by weight of magnetic powder and 2 to 10 parts by weight with an average particle size of 20 to 200 mμ
A magnetic disk characterized in that a magnetic coating film containing a weight part of graphitized carbon is formed on a support.