JPS62222436A - Production of magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a disk which is improved in the dispersibility of magnetic powder, is decreased in the fracture thereof, and has decreased noise and degree of orientation by using a magnetic coating compd. prepd. by kneading the magnetic powder, resin, solvent and beads having a prescribed value of the specific weight at the time of forming a magnetic film on a nonmagnetic substrate. CONSTITUTION:The magnetic coating compd. to be used at the time of forming the magnetic film on the nonmagnetic substrate is prepd. dividedly in two stages; an acrylic resin and solvent are added to the magnetic powder and the beads having <=3 specific gravity are added thereto and are kneaded, by which the uniform dispersion is executed and the magnetic coating compd. having the decreased tendency to the fracture of the magnetic powder is prepd. in the 1st stage. The other resin and magnetic powder are added to such coating compd. and are kneaded by using the beads having >=3.5 specific gravity to prepare the magnetic coating compd. in the 2nd stage. Such magnetic coating compd. is coated on the nonmagnetic substrate and is subjected to a baking treatment, by which the magnetic disk having the decreased noise and excellent orientability is manufactured.

Description

[Detailed Description of the Invention] [Summary] As a method for forming a magnetic film with low orientation and low noise, the formation of a magnetic paint is divided into two steps. First, an acrylic resin and a solvent are added to magnetic powder. After kneading, other resins and solvents are added and kneaded to create a paint, which is then used to form a magnetic coating film.

[Industrial application field]

The present invention relates to a method for manufacturing a magnetic disk with a high critical recording density (and low noise).

A magnetic disk has a recording layer formed by forming a thin film of a magnetic recording medium on a disc made of a non-magnetic metal such as an aluminum (AN) alloy using methods such as spin coding, vacuum evaporation, and sputtering. .

That is, the spin code method is used for recording media made of oxides such as iron oxide powder (γ-Fe2O3) and barium ferrite (BaO-Fe20.l), while the Ni・
For those using magnetic alloy films such as Co-P) and cobalt-chromium (Co-Cr), vacuum evaporation and sputtering methods are used.

Both have their own characteristics, however.

The former is generally used because it is superior in terms of durability such as contact start-stop (CSS) characteristics.

The present invention relates to the former method of forming a magnetic film formed by the Spinco-1 method.

[Conventional technology]

Conventional magnetic paints are formed by adding resin and solvent that act as a binder to magnetic powder, and kneading the mixture using a sand grinder or the like.

Table 1 shows the conventional configuration.

Table 1 shows that in the past, magnetic powder, resin, and solvent were put into a sand grinder, and low-wear beads with a diameter of 1 to 2 mm and made of glass, zirconia, titania, etc. were added.
It was formed by kneading for ~8 hours.

However, the magnetic powder thus formed did not have sufficient dispersibility and there was room for improvement.

[Problem that the invention seeks to solve]

As mentioned above, the magnetic film formed by the spin code method is made using a magnetic coating material that is sufficiently mixed with magnetic powder, resin, and solvent, but the dispersibility of the magnetic powder may not be sufficient. That's a problem.

[Means for solving problems]

The above problem occurs when a magnetic coating is applied to a uniform thickness on a non-magnetic substrate and then baked to form a magnetic film.
After adding acrylic resin and a solvent to magnetic powder and kneading them using beads with a specific gravity of 3 or less to make a paint, add other resins and a solvent to the paint and kneading with beads with a specific gravity of 365 or more to make a magnetic powder. This problem can be solved by a method of manufacturing a magnetic disk by making a paint and using the paint.

[Effect]

The present invention was made as a result of research into the relationship between the degree of orientation and dispersibility of magnetic powder.

That is, a magnetic film formed using only acrylic resin as a binder has good dispersibility of magnetic powder and low noise, but the film has low strength and has poor mechanical strength and characteristics, such as CS.
Poor S characteristics.

Therefore, if an epoxy resin or the like is added to improve the film strength, the mechanical strength will improve, but the magnetic properties will decrease.

As a result of research into the cause of this, the inventors found that the cause was a decrease in the degree of dispersion of the magnetic powder and breakage of the magnetic powder.

Here, the reason why magnetic powder has good dispersibility when acrylic resin is used as a binder is that magnetic powder has adsorbed water, and acrylic resin has moisture permeability, so it is compatible with moisture.

Moreover, the breakage of the magnetic powder is due to collision with beads.

Therefore, the present invention divides the formation of the paint into two stages, using only acrylic resin as a binder in the initial primary kneading, and since the viscosity of the paint formed in this case is not very high, beads added to the sand grinder are used. used one with low specific gravity.

As a result, breakage of the magnetic powder is prevented and force is uniformly distributed.

Next, in the secondary kneading process, other resins and solvents are added to the beads, and the beads are replaced with ones of high specific gravity, and the beads are kneaded to maintain uniform dispersion while preventing breakage. By using a paint, a magnetic film with good magnetic properties and mechanical performance can be obtained.

〔Example〕

Table 2 shows the composition of the primary and secondary kneaded paints in which the present invention was implemented.

Table 2 Figure 1 shows that the primary mixing materials shown in Table 2 were kneaded for 3 hours with different specific gravity of the beads, and then mixed using glass beads with a specific gravity of 2.5. Indicates the degree of orientation characteristics of a coating film formed using paints kneaded over time,
This figure shows that when the specific gravity of the beads is high during primary kneading, breakage of the magnetic powder occurs.

Next, Figure 2 shows that the primary mixing material shown in Table 2 was kneaded for 3 hours using beads with a specific gravity of 2.5, and then kneaded for 3 hours using beads of various specific gravity. It shows the degree of orientation characteristics of the coating film formed using the kneaded paint, and shows that the higher the specific gravity of the beads in the secondary kneading, the less noise there is, and the higher the degree of orientation, the better the dispersibility.

Based on the above results, as an example of the present invention, materials having the primary kneading composition shown in Table 2 were first kneaded for 3 hours using beads with a specific gravity of 2.5, and then beads with a specific gravity of 6.4 were mixed. In place of the zirconia beads, materials of the secondary kneading composition were added and kneaded for 3 hours to produce a magnetic paint.

The thus-prepared magnetic paint was spin-coded onto a substrate to form a coating film, and then conventional treatments such as baking and polishing were performed to form a magnetic disk.

Next, as a comparative example, the materials shown in Table 2 were mixed at the same time, and kneaded for 6 hours as in the conventional method using zirconia beads with a specific gravity of 6.4. From then on, a magnetic disk was prepared in the same manner as in the example. Formed.

Table 3 shows the measurement results of the degree of orientation and noise for both.

Table 3 Note that the medium noise is DC noise in the IOMH band.

As described above, by carrying out the present invention, the degree of orientation can be improved and noise can be reduced.

In addition, as a result of the improved orientation of the magnetic film, the critical recording density (O
S. ) was approximately 15,000 [IPI] in the conventional method, but was able to be improved to approximately 200,008 PI.

〔Effect of the invention〕

As described above, by carrying out the present invention, it is possible to improve the dispersibility of magnetic powder and reduce breakage, thereby making it possible to put into practical use magnetic disks with excellent orientation and low noise.

[Brief explanation of drawings]

Figure 1 shows the relationship between the bead specific gravity and the degree of orientation of the coating film in the primary mixing, and Figure 2 shows the relationship between the bead specific gravity and the degree of orientation of the coating film in the secondary kneading.

Claims (1)

[Claims] After applying magnetic paint to a uniform thickness on a non-magnetic substrate, when performing a baking process to form a magnetic film, magnetic powder is mixed with acrylic resin and a solvent using beads with a specific gravity of 3 or less. A magnetic coating characterized in that the magnetic coating is formed by adding other resins and a solvent to the coating and kneading the coating using beads with a specific gravity of 3.5 or more to produce a magnetic coating. Disc manufacturing method.