JPS62262230A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a high orientation state by using permanent magnets for two pass rolls to support a magnetic recording medium right after orientation and drying the magnetic recording medium in a drying zone. CONSTITUTION:A nonmagnetic substrate 1 may be formed by using, for example, a PE terephthalate, etc., and a magnetic coating compd. 2 is coated on the nonmagnetic substrate and is then dried to form a magnetic layer. Two pieces of the pass rolls 4a, 4b consisting of the permanent magnets are installed on the side opposite from the magnetic layer and may be disposed as well in the drying zone 3 for the magnetic coated film. A magnetic field is acted in the orientation direction during the time when the coated film is dried after the orientation treatment. The deterioration in the orientation state in the drying process is thereby prevented and the high orientation state is obtd.

Description

Detailed Description of the Invention Field of the Invention The present invention relates to a method for manufacturing magnetic recording media such as audio tapes and video tapes, and more particularly to a method for manufacturing magnetic recording media that effectively performs magnetic field orientation treatment. It is.

BACKGROUND OF THE INVENTION It is well known that a magnetic recording medium is required to have a high residual magnetic flux density Br in order to improve its electromagnetic conversion characteristics such as sensitivity, output, and S/N.

For this reason, when manufacturing a coated magnetic recording medium, it is common to perform a magnetic field orientation treatment so that the axis of easy magnetization of the magnetic particles coincides with the direction of the recording track. At the time of orientation treatment, the magnetic coating film is in an undried state, and the magnetic powder is rotated in the desired orientation direction by the magnetic field.

Problems to be Solved by the Invention However, since the magnetic powder is aligned in one direction and the magnetic poles are aligned in the same direction, the state after the orientation operation is extremely unstable in terms of entropy and magnetic energy. It is. Also, the magnetic coating film is not dried.

It is in a state of Therefore, the magnetic powder gradually returns to an unoriented state, resulting in a problem in that the squareness ratio becomes lower than the highest value during the orientation process.

In view of the above-mentioned problems, the present invention provides a method for producing a magnetic recording medium that maintains the highest orientation state during orientation treatment until the coating film is solidified and dried, thereby obtaining a high orientation state.

Means for Solving the Problems In order to solve the above problems, the present invention uses permanent magnets in two pass rolls that support the magnetic recording medium immediately after orientation.
The magnetic recording medium is dried in a drying zone.

Function The present invention has the above-described structure, and by applying a magnetic field in the direction of orientation after the orientation treatment until the coating film dries, it is possible to prevent deterioration of the orientation state during the drying process and achieve a high degree of orientation. The state will be obtained.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the manufacturing process of the present invention.

In FIG. 1, numeral 1 indicates a nonmagnetic support, for example, polyethylene terephthalate or the like may be used. Reference numeral 2 denotes a magnetic paint 2, which is coated on a non-magnetic support and is later dried to form a magnetic layer. 3 indicates a magnetic field orientation device, for example, a permanent magnet, a solenoid magnet, etc. are used. 41L.

Reference numeral 4b denotes two pass rolls made of permanent magnets, which are placed on the opposite side from the magnetic layer. 5 indicates the drying zone of the magnetic coating film. Note that the pass rolls 4N and 4kl may be placed in the drying zone.

Next, an example using this manufacturing method will be shown.

Go coating - Fe2O2 100 parts by weight Polyurethane resin 10 parts by weight Vinyl chloride-vinyl acetate copolymer 10 parts by weight Oleic acid 2 parts by weight Lecithin
1 part by weight alumina
6 parts by weight carbon black
3 parts by weight MICK-toluene-cyclohexanone (weight ratio 5:3:2) 300 parts by weight The above composition was mixed and dispersed in a ball mill for 48 hours, taken out, 4 parts by weight of curing agent was added, and stirred for 30 minutes with a disper to make it magnetic. Get paint. This is coated onto polyethylene terephthalate at a coating speed of 1ooWL/min to a thickness of about 4 μm. The magnetic field orientation device used is one in which permanent magnets having a magnetic field strength of 20000e are repelled and opposed to each other.

FIG. 2 is a diagram showing the relationship between the presence or absence of magnetic poles of the pass rolls 41L and 4b, the direction of the magnetic field between the pass rolls, and the squareness ratio of the coating film. The magnetic field strength between the pass rolls is 5000a.

As is clear from Fig. 2, when the pass rolls are non-magnetic, the squareness ratio is 0.78, but when permanent magnets are used for the pass rolls, and the magnetic field generated between the pass rolls is When the direction of the magnetic field coincides with the direction of the magnetic field, the squareness improves to 0.82. In case B, when the magnetic field generated between the pass rolls is in the opposite direction, the squareness ratio is rather lowered to 0.76 because the alignment state is promoted to collapse.

FIG. 3 is a diagram showing the relationship between the magnetic field strength between pass rolls and the squareness ratio. The magnetic field between the pass rolls is in the same direction as the orientation direction. As the magnetic field strength increases, the squareness ratio improves, reaches saturation at about 4oooe, and conversely decreases at about 100006 or more.

Effects of the Invention As is clear from the Examples and the corresponding Comparative Examples, the present invention can obtain a high squareness ratio by using a permanent magnet in the Pascoal 5 and applying a magnetic field in the orientation direction.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a manufacturing apparatus for embodying a method for manufacturing a magnetic recording medium according to an embodiment of the present invention, and FIG. 2 shows the presence or absence of magnetic poles of the pass and roll, and the direction of the magnetic field between the pass rolls. FIG. 3 is a characteristic diagram showing the relationship between the magnetic field strength between pass rolls and the squareness ratio of the coating film. 1...Nonmagnetic support, 2...Magnetic paint, 3...Magnetic field orientation device, 41L, 4b...
...Pass roll, 5...Drying zone. Name of agent: Patent attorney Toshio Nakao and 1 other person 2
Illustration angle lN1IHI Sono Kasumi ro ■■ ro ■■

Claims (3)

[Claims] (1) Permanent magnets are used in the two pass rolls that support the magnetic recording medium immediately after it has been oriented by the main magnetic field orientation device,
A method for manufacturing a magnetic recording medium, comprising drying the magnetic recording medium in a drying zone. (2) The magnetic recording medium according to claim 1, characterized in that two pass rolls are present between the main magnetic field orientation device and between or within the drying zone of the coating film. Production method. (3) The method for manufacturing a magnetic recording medium according to claim 1, wherein the magnetic poles exposed on the surfaces of the two pass rolls are different from each other.