JPH0419814A - Floppy disk - Google Patents

Abstract

PURPOSE:To improve durability and adsorption characteristic by specifying the glass transition point of the binder incorporated into a magnetic coating material and incorporating carbon blacks having specific two particle size distribution centers into the binder. CONSTITUTION:The glass transition point of the binder resin 3 is specified to <=65 deg.C and further, contains the carbon blacks 4, 5 having the centers of the particle size distributions at the two points 150 to 250mum and 10 to 50mum. The effective contact area of a head and a medium is controlled and the head attraction is lessened by the introduction of the coarse carbon particles 4 having >=150mum grain size in this way. The adoption of the soft resin is allowed by the introduction of the carbons 4, 5 and, therefore, the magnetic coated film which is resistant to flawing is obtd. without impairing electromagnetic conversion characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a flow-nobby disk in which a magnetic layer is formed by coating a magnetic paint on a substrate such as a polyester film.

BACKGROUND OF THE INVENTION Floppy disks have been widely used as external storage devices for personal computers and the like. This floppy disk is manufactured by coating a base material such as polyester with magnetic paint, subjecting it to surface treatment, curing it, punching it into a disk shape, polishing the surface, and placing it in a predetermined case.

Problems to be Solved by the Invention In floppy disks, the head and the medium are often left in contact with each other, resulting in a phenomenon in which the two stick together. In order to avoid phenomena such as head adsorption, a urethane resin having a high glass transition point and a high Young's modulus is used as the binder.

However, although these resins have sufficient hardness, they tend to be brittle, and if a part of the coating surface is damaged by sliding contact with the head, the abrasion particles will accelerate the coating and reduce its durability. However, there was a problem with the problem of a decline in performance.

Means for Solving the Problems In order to solve the above problems, the floppy disk of the present invention has a binder resin with a glass transition point of 65° C. or lower, and a particle size distribution with a center of 150 mμ or more.
It is constructed by containing carbon black in two locations: 50 mμ or less and 10 mμ or more and 50 mμ or less.

According to the present invention, with the above configuration, by introducing coarse carbon particles having a particle size of 150 mμ or more, it is possible to control the effective contact area between the head and the medium and improve head adsorption. Furthermore, since the introduction of carbon makes it possible to use a resin that is more flexible than before, it is possible to obtain a magnetic coating film that is less susceptible to scratches without impairing the electromagnetic conversion characteristics.

EXAMPLE Hereinafter, an example of the present invention will be described in comparison with a conventional example with reference to the drawings.

After activating the surface of a polyester film with a thickness of 75 μm by corona discharge, etc., a magnetic paint having the composition shown in the examples in Table 1 was applied, dried, and calendered to harden the paint film. , punched out into a disk shape, polished the surface, and then placed in a designated case.

Next, as a comparative example, a floppy disk was prepared in the same manner as in the example except that the paint was prepared with the composition shown in Comparative Examples 1 to 4 in Table 1, and compared with the example.

In the Examples and Comparative Examples, two types of carbon black were blended so that the center of the particle size distribution of the carbon black was 150 mμ or more and 50 mμ or less.

When the particle size of carbon becomes larger than 250 mμ, the surface properties of the coating deteriorate and the electromagnetic conversion characteristics become unsatisfactory.
If it is smaller than 0 mμ, not only will the viscosity increase, causing problems with the properties of the paint, but it will also no longer be able to play the role played by small particle size carbon, which is to reduce the electrical resistance of the paint film.

(Hereinafter referred to as a margin) (Hereinafter referred to as a margin) In the Examples in Table 1, a coating film was obtained that had a low surface electrical resistance, good non-adsorption property and was resistant to scratches caused by a head. A schematic cross-section of the coating film of the floppy disk according to the example is shown in FIG. Carbon black with a particle size of 150 mμ or more is considered to have a greater possibility of protruding onto the coating surface than one with a particle size of 50 mμ.

Comparative Example 1 and Comparative Example 2 have conventional coating compositions, and the glass transition point of the binder is 70° C. or higher, making them more likely to be scratched by a head than in the Examples. This is thought to be because the paint film itself is hard and brittle, so the abrasion powder generated by the sliding contact of the head further damages the paint film.Furthermore, as in Comparative Examples 1 and 4, the particle size If carbon black of 150 mμ or more is not contained, characteristics such as ``head adsorption'', in which adsorption force is generated between the head and the media when they are left in stationary contact for a long period of time, will deteriorate and become a practical problem. .

A schematic cross-sectional view of the coating film on the floppy disk at this time is shown in the second figure.
As shown in the figure. When the glass transition temperature of the binder is low, head adsorption becomes even greater. In Comparative Examples 3 and 4, the binder was the same as in the examples of the present invention, and carbon black was either one with a particle size of 150 mμ or more (Comparative Example 3) or one with a particle size of 50 mμ or less (Comparative Example 4). This is the case when used. Comparative Example 3 and Comparative Example 4 have improved resistance to scratching by the head as in the Examples, but in Comparative Example 3, the surface electrical resistance is high, and the electrostatic charge of the paint film makes it easy for dust to adhere to the paint film surface. This will cause an out. In Comparative Example 4, the head adsorption deteriorated.

This is because carbon black with a diameter of 50 mμ or less has the effect of lowering the surface electrical resistance of the magnetic coating film, and carbon black with a diameter of 150 mμ or more partially protrudes from the coating surface to prevent direct contact between the binder, which has a low glass transition point, and the head. It is speculated that this is due to the effect of It is also speculated that the improvement in scratch resistance is due to the flexible binder absorbing the impact of contact between the carbon black and the head.

As described in detail, according to the present invention, scratches caused by the sliding contact between the magnetic coating film and the head will not spread further, and a floppy disk with excellent durability and adsorption properties can be produced. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of the coating film structure of a floppy disk according to the present invention, and Fig. 2 is a schematic cross-sectional view of the coating film structure of floppy disks of Comparative Examples 1 and 4 using only carbon black with a particle size of 50 mμ or less. It is a diagram. l... Base film, 2... Magnetic powder, 3... Binder resin, 4... Particle size 15
Carbon black of 0 mμ or more, 5...Particle size 5
Carbon black of 0 mμ or less, 6...... To magnetic throat. Name of agent: Patent attorney Shigetaka Awano Hk 1-Ho/Frasoku IL Ra (he/7 F)

Claims (1)

[Claims] A floppy disk in which a magnetic layer is provided by coating a magnetic paint on a substrate such as a polyester film, the glass transition point of the binder contained in the magnetic paint is 65°C or less, and the particle size distribution on one side is The center of is 1
A floppy disk containing carbon black having two particle diameter distribution centers, one of which is 50 mμ to 250 mμ, and the other particle diameter distribution center is 10 mμ to 50 mμ.