JPS6218629A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve a squareness ratio and to provide the higher output by uniformly coating a magnetic coating compd. prepd. by uniformly dispersing pulverous ferromagnetic particles into a resin binder on a non-magnetic substrate to a prescribed thickness and impressing a uniform magnetic field thereto right after the application of ultrasonic oscillation thereto prior to curing by drying thereby orienting the pulverous ferromagnetic particles. CONSTITUTION:The magnetic coating compd. prepd. by dispersing the pulverous ferromagnetic particles into the resin binder is uniformly coated on the non-magnetic substrate and the uniform magnetic field is impressed thereto to orient the ferromagnetic particles right after the ultrasonic oscillation is impressed thereto prior to curing by drying. More specifically, the ultrasonic oscillation of a suitable oscillation frequency and suitable mode is applied to the magnetic coating compd. through a deflective oscillation diaphragm 15 attached to the top end of an amplitude amplifying horn 14 of an ultrasonic oscillation generator 13 to apply a large shear to the magnetic coating compd. constituting the coating layer 11; in succession, of the magnetic particles are easily rotated and united in the magnetic field direction when the substrate is passed through the orientation magnetic field generated from repulsive opposed magnets 16 in succession thereof: The highly oriented state is thus created.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing a magnetic recording medium using a coating method, and in particular, the present invention relates to a method of manufacturing a magnetic recording medium using a coating method. Regarding the manufacturing method.

As is well known in the art, magnetic recording media such as audio tapes and video tapes are made by uniformly dispersing ferromagnetic particles in a resin binder while running a strip-shaped non-magnetic support in the longitudinal direction. After applying the magnetic paint uniformly to an appropriate thickness and passing it through a uniform magnetic field in the width direction of the non-magnetic support, it is heated and dried, and then heated and pressed between rolls with a smooth surface. It is made by cutting it to a specified width. At this time, the application of a uniform magnetic field before drying orients the axis of easy magnetization of the magnetic fine particles dispersed in the magnetic paint in the longitudinal direction of the non-magnetic support.

Problems to be Solved by the Invention In general, the magnetic particles constituting such magnetic paints are ferromagnetic single-domain particles, and unlike other paint pigments, they behave as magnetic dipoles, and due to the strong magnetic interaction between the dipoles. It is easy to attract each other to form structures such as chains, rings, and even three-dimensional networks, and as a magnetic paint, it has so-called strong tecntropic properties.

It has been reported that ferromagnetic particles with such magnetic dipole efficiency rotate on the order of several tens to several 1 oom, s when an external magnetic field is applied in a state where no interaction occurs. In reality, the above-mentioned interaction cannot be ignored in paints, and research and study has been conducted on ways to obtain a higher degree of orientation in the magnetic paint itself, as well as in the production method. In other words, in paint manufacturing, the composition of a material or In the construction method, efforts were made to ensure that the magnetic particles were sufficiently dispersed to the state of primary particles, and in addition, in the coating process, the magnetic particles aggregated during paint transport and supply, creating a structure. To prevent this formation, efforts have been made to routinely provide the paint with adequate agitation to maintain a good initial dispersion state.

However, when considering the physical properties and durability characteristics of the magnetic recording medium as the final product, there are significant restrictions on the selection of magnetic paint materials and compositions. While reaching the orientation magnetic field in a sheared state, structure formation had already occurred in some parts, inhibiting the free rotation of the magnetic particles and making it difficult to obtain high orientation.

The present invention eliminates these conventional manufacturing constraints, effectively performs magnetic field orientation, improves the squareness ratio, and provides a high-output magnetic recording medium.

Means for Solving the Problems In order to solve the above-mentioned problems, the method for manufacturing a magnetic recording medium of the present invention includes coating a non-magnetic support with a magnetic paint comprising fine ferromagnetic particles dispersed in a resin binder. Immediately after applying ultrasonic vibration before uniformly coating and drying and curing, a uniform magnetic field is applied to orient the ferromagnetic particles.

Effect 5 The present invention has the above configuration by applying ultrasonic waves to the magnetic paint coated on the τ non-magnetic support to apply shear within the paint, and after forming the coated layer and immediately before orientation. The structure is destroyed, and the rotational movement of the magnetic particles by the orienting magnetic field is facilitated, making them highly oriented.

By improving the squareness ratio, it is possible to improve the output characteristics of the magnetic recording medium.

EXAMPLES Hereinafter, the present invention will be described in further detail with reference to the accompanying drawings.

1 and 2 illustrate one embodiment of a method of carrying out the present invention. That is, the undried magnetic paint coating layer 11
to the non-magnetic support 12 provided with.

Through the flexible diaphragm 16 attached to the tip of the amplitude amplification horn 14 of the ultrasonic vibration generator 13.

Gives ultrasonic vibrations of appropriate frequency and appropriate posture.

When this applies a large amount of shear to the magnetic paint that constitutes the coating layer 11, and subsequently passes through the alignment magnetic field created by the repulsive opposing magnets 16, the magnetic particles easily rotate and align in the direction of the magnetic field, resulting in a high degree of shearing. Create an oriented state.

The frequency of the ultrasonic vibration applied to the flexible diaphragm 16 used here was selected to be relatively low, around several tens of KHz, which is generally said to be suitable for dispersing magnetic paint. Furthermore, various vibration modes of the flexible diaphragm 15 can be obtained depending on the dimensions, shape, material, etc. of the diaphragm 16 for one frequency, but the present invention is not particularly limited by these modes, and may vary depending on the orientation. You should choose effectively. However, if neatly knitted vibration nodal lines appear only in the longitudinal direction of the diaphragm 15 (striped patterns can be confirmed by the Claude method), the vibration effect will be uniformly distributed in the width direction of the non-magnetic support 12. As shown in FIG. 3, an appropriate angle ψ (ψ≦tan-1(λ
/4), λ: wavelength of vibration generated in the diaphragm 15, e: width of the diaphragm 16) It is necessary to take measures such as installing the diaphragm at an angle τ.

This is to eliminate unevenness in the shear imparting effect due to the position of the standing wave on the diaphragm 15.

In addition, in order to effectively transmit vibrations from the diaphragm 16, the diaphragm 15 is installed at a position where the non-magnetic support 11 has an appropriate entrance angle θ and exit angle θ' with respect to the diaphragm 16. 16
It is necessary to apply pressure to the surface of the non-magnetic support 12, and therefore, in order to avoid scratching the back surface of the non-magnetic support 11, the side of the longitudinal edge 17 of the diaphragm 15 in contact with the surface of the non-magnetic support 12 must be It is necessary to consider such things as giving it an appropriate roundness. It has been confirmed that the diaphragm 15 provided in this manner has no resistance at all to the contact movement of the support 11 during the application of ultrasonic vibration, and is no different from the conventional case in which the device of the present invention is not used. has been done.

Examples will be described in more detail below.

In addition, magnetic materials and additives used in the present invention.

There are no particular limitations on the solvent, coating composition, or non-magnetic support, and the coating method can be a knife coater, reverse coater, gui coater, gravure coater, etc., and the drying method can be a hot air method, an infrared method, or other commonly known methods. Any technique used in manufacturing magnetic recording media can be used in the present invention.

(Example-1) As magnetic particles, specific surface area 2 evl/gr (B K
T method), using HO3500e powder, mix and disperse the composition shown in Table 1 in a 100e ball mill for 20 hours, then add the composition and mix and disperse for 16 hours, then take it out to a tank and add a curing agent. (Coronate 59 Nippon Polyurethane) was added in an amount of 5 parts by weight based on the magnetic particles, and the mixture was stirred for 30 minutes to obtain a magnetic paint having a viscosity of 10 voids (B-type viscometer).

Using the thus obtained magnetic paint, a polyester film (thickness 11.6 μm, width 3
00), coating was performed using a gravure coater running at a coating speed of 80 m/win, adjusting the thickness of the dry-cured resulfuric layer to 6.6 μm, and applying ultrasonic vibration of 20 KH2. rear.

An orientation magnetic field of 2000 G was applied by the repulsive opposing magnet 16 to perform orientation treatment, and after drying and hardening in a drying oven, the length was 3.81 m.
I cut it into widths and made magnetic tape. Also, for comparison,
A conventional magnetic tape was also created by using the same paint and performing orientation with the ultrasonic diaphragm 15 removed. These results are summarized in Table 2.

Note that the ultrasonic diaphragm 15 used in this example is a duralumin plate (Mu2011TP-T3) with a thickness of 1 mm, a width of 1 mm, and a length of 350 mm.
A 0KH2π type ferrite vibrator was used, and 50 W was applied as a high frequency electrical input to the vibrator. In addition, a conical horn that can amplify the amplitude by five times was used as the amplitude amplification horn. In addition, the contact pressure of the diaphragm 15 to the non-magnetic support 12 is s gr /
It was set to cA.

(Example-2) As a magnetic particle, the specific surface area is 31yp? / gr, H
A magnetic paint having a viscosity of 17 points was obtained using powder of aa5ooe and the same formulation as in Example-1. Using the thus obtained coating material, it was applied in the same manner as in Example 1, dried and cured in a drying oven, and further cut into 3.8114 mm pieces to prepare a magnetic tape. For comparison, a conventional magnetic tape was prepared by performing orientation without the ultrasonic diaphragm. These results are summarized in the second garment.

(hereinafter referred to as gold and white) Table 1 Magnetic paint composition table Table 2 Characteristic evaluation results Effects of the invention As mentioned above, in the past, the effect of the orienting magnetic field was easily obtained from the structure formation due to aggregation between magnetic particles after the coating layer was formed. However, the method of the present invention not only greatly improved the squareness ratio compared to the conventional method, but also had a great effect on increasing the specific surface area.

We can expect great things from this in response to future trends toward high-density recording.

[Brief explanation of drawings]

FIG. 1 is a plan view illustrating an outline of a manufacturing apparatus for carrying out the present invention, and FIG. 2 is a side view of FIG. 1. FIG. 3 is an explanatory diagram of another example of a manufacturing apparatus for implementing the present invention. 11...Coating layer, 12...Nonmagnetic support, 13...Ultrasonic vibration generator, 15...
...Camera plate, 16... Repulsion opposing magnet. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2. Teacher's Strategy Figure 3.

Claims (1)

[Claims] Immediately after applying a magnetic paint consisting of ferromagnetic fine particles uniformly dispersed in a resin binder to a predetermined thickness on a non-magnetic support and applying ultrasonic vibrations before drying and curing. A method for manufacturing a magnetic recording medium, which comprises applying a uniform magnetic field to orient ferromagnetic particles.