JPH02252121A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the magnetic characteristics, more particularly aspect ratio of the magnetic recording medium by impressing a magnetic field to the magnetic coating applied on a base film in the thickness direction of the coated film before the coating compd. is not dry yet, then impressing the magnetic field thereto in the longitudinal direction of the base film and drying the coating film to solidify in this state. CONSTITUTION:The film 1 coated with the magnetic coating is inserted between two magnets 2 and the magnetic field in the thickness direction of the coated film (the magnetic field in the direction perpendicular to the longitudinal direction of the film 1) is impressed to the coating in the undried state. The magnetic field in the longitudinal direction of the film 1 is thereafter impressed to the film 1 by a solenoid 3 disposed in the traveling direction of the film 1. The film 1 is put into a drying furnace 4 while the acicular particles of the magnetic coating are oriented in the longitudinal direction of the film 1. The film is thus dried in the state of impressing the magnetic field in the longitudinal direction of the film by an auxiliary solenoid 5 to maintain the acicular state oriented in the longitudinal direction of the film 1 in this state. The problem that the aspect ratio to be a measure for orientation of the acicular particles is poor is solved in this way.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method of manufacturing a magnetic recording medium.

(Prior Art) In a magnetic tape, the axis of easy magnetization of magnetic particles is generally oriented along the longitudinal direction (running direction) of the base film.

To this end, as shown in Figure 2, a base film b having an undried magnetic coating is inserted between two magnets a with the same poles facing each other (or a base film b is passed through a base film b with a undried magnetic coating). By inserting the base film b into the solenoid), the axis of easy magnetization of the magnetic particles is oriented along the running direction of the base film b. Drying oven C until the paint dries and solidifies.
A current is applied to a solenoid d disposed inside the base film b, so that the orientation of the magnetic particles is maintained by a magnetic field in the longitudinal direction of the base film b.

(Problems to be Solved by the Invention) The magnetic paint used in magnetic recording media is in the form of a slurry in which acicular magnetic particles, an organic binder, and other additives are mixed and dispersed.

This paint contains acicular magnetic particles (hereinafter simply referred to as acicular particles) oriented in random directions. Magnetic paint is manufactured in such a way that the needle-like particles are sufficiently dispersed, but not all of the needle-like particles in the paint are dispersed into a single particle, and multiple needle-like particles intersect with each other. Some remain as they are.

When such a paint is applied to a base film and a magnetic field is applied in the longitudinal direction of the base film using a coil or magnet, the acicular particles in the paint form magnetic poles at both ends of the particles in the longitudinal direction, which is the axis of easy magnetization. is formed, and the axes of the acicular particles are aligned in the direction of the magnetic field.

In a magnetic paint in which needle-like particles are sufficiently dispersed, the needle-like particles easily align in the direction of the magnetic field, but needle-like particles that intersect with each other have their rotation blocked by other needle-like particles and are not easily aligned with the magnetic field. There are some that are not parallel to each other and are tilted at a certain angle to the longitudinal direction of the base film.

Therefore, conventional magnetic recording media have a problem in that the squareness ratio, which is used as a guideline for the orientation of acicular particles, is poor. The present invention aims to solve this problem.

(Means for Solving the Problems) In order to achieve the above object, the present invention applies a magnetic paint onto a base film, and applies a magnetic field to the undried magnetic paint in a direction different from the longitudinal direction of the base film. is applied to orient the axis of easy magnetization of the magnetic particles in the direction, and then a magnetic field is applied in the longitudinal direction of the base film to orient the axis of easy magnetization of the magnetic particles in the direction of the magnetic field. The magnetic paint is dried and solidified while its orientation is maintained by a magnetic field.

The magnetic field in the specific direction is preferably a magnetic field in the thickness direction of the magnetic paint coating.

(Function) When the magnetic paint coated on the base film is in an undried state, for example, when a magnetic field is applied in the thickness direction of the paint film, the acicular particles dispersed in single particles The plurality of acicular particles that are oriented in the direction and intersect with each other are partially uncrossed by the magnetic field and are oriented in the thickness direction of the coating film. However, there are some cases in which the intersection is not canceled even by the magnetic field in the thickness direction of the coating film.

After that, when a new magnetic field is applied in the longitudinal direction of the base film, each of the dispersed acicular particles easily orients in the direction of the new magnetic field, and the acicular particles that remain crossed are oriented in a different direction from the previous one. Since a magnetic field is applied, some of the intersections are canceled and most of the needle-like particles in the magnetic paint are oriented in the longitudinal direction of the base film. Since a magnetic field is applied to the oriented acicular particles in the longitudinal direction of the base film until the magnetic paint is dried and solidified, disturbance of the orientation of the acicular particles is prevented.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

100 parts by weight of acicular Co・γ-Pe2 o3 powder, 9 parts by weight of vinyl chloride resin, 9 parts by weight of polyurethane resin, 2 parts by weight of bifunctional isocyanate compound, 2 parts by weight of abrasive, 100 parts by weight of methyl ethyl ketone, 50 parts by weight of toluene. A magnetic paint prepared by mixing and dispersing a composition consisting of 1 part and 50 parts by weight of cyclohexanone in a ball mill for 40 hours was applied onto a polyethylene terephthalate film with a thickness of +21 Lm, and this film 1 was coated as shown in FIG. 2
The magnets 2 are inserted between two magnets 2 to apply a magnetic field in the thickness direction of the paint film (magnetic field perpendicular to the longitudinal direction of the film) to the undried paint, and then placed in the running direction of the film 1. A magnetic field in the longitudinal direction of the film 1 is applied by the solenoid 3. Thus, the acicular particles in the magnetic paint are first oriented in the thickness direction of the coating film and then in the longitudinal direction of the film. With the acicular particles oriented in the longitudinal direction of the film 1, the film 1 enters the drying oven 4, where it is dried. Until it is dried, a magnetic field in the longitudinal direction of the film 1 is applied to the magnetic coating material by the auxiliary solenoid 5 to maintain the acicular particles oriented in the longitudinal direction of the film 1 in that state.

The table below shows that the strength of the vertical magnetic field is varied from 1000 to 3000 oersteds, and the longitudinal magnetic field of film 1 by solenoid 3 and auxiliary solenoid 5 is varied from 2000 oersted to 3000 oersteds.
The squareness ratio (residual magnetic flux density/saturation magnetic flux density) of magnetic properties when changed to 00 oersted is shown.

As is clear from the table, the squareness ratio of the magnetic tape becomes 0.88 or more by setting the perpendicular magnetic field to 2000 or more and the longitudinal magnetic field to 3000 or more. The magnetic properties are significantly improved compared to the conventional one that applied a magnetic field.

In the above embodiment, the solenoid 3 is placed outside the drying oven 4, but it may be placed inside the drying oven.

Further, one solenoid that serves both the solenoid 3 and the auxiliary solenoid 5 may be arranged in the drying oven 4.

(Effects of the Invention) Since the present invention is configured as described above, it has the effect of improving the magnetic properties of the magnetic recording medium, particularly its squareness ratio.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a manufacturing apparatus used to carry out the method of the present invention, and FIG. 2 is a diagram showing the configuration of a manufacturing apparatus used to carry out the conventional method. 1... Film 2... Magnet 3... Solenoid 4... Drying oven 5... Solenoid

Claims (1)

[Claims] 1. Magnetic paint is applied onto a base film, and a magnetic field is applied to the undried magnetic paint in a direction different from the longitudinal direction of the base film to facilitate magnetization of magnetic particles in that direction. After that, a magnetic field is applied in the longitudinal direction of the base film to orient the axis of easy magnetization of the magnetic particles in the direction of the magnetic field, and the magnetic paint is kept oriented in the direction of the magnetic field by the magnetic field. A method for manufacturing a magnetic recording medium, characterized in that it is dried and solidified. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the magnetic fields in different directions are magnetic fields in the thickness direction of the magnetic paint coating.