JPH0562183A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To manufacture a magnetic recording medium in which the thickness of a magnetic coating film is uniform. CONSTITUTION:When a coating liquid is fed to an extrusion-type coating head, a stepped part is eliminated in the inner wall part of a pipe to which a pipe is connected in a pipe system used to feed the liquid after the liquid has been filtered by means of a final filter. Thereby, it is possible to obtain a uniform coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic recording medium.

[0002]

2. Description of the Related Art In manufacturing a magnetic recording medium,
In the final step, the dispersed coating material and curing agent are mixed and filtered, and then the mixed coating material is sent to a coating head and coated to obtain a magnetic recording medium such as a tape or a disk. Recently, as the media have been made narrower and the time has become longer or the densities have been made higher, the size of the defective dispersion remaining after the media has become smaller or the size of the dropout due to re-aggregation tends to become much finer. At the time of sending the liquid to the coating head, in order to remove the above-mentioned poor dispersion and reaggregation, filtration treatment is performed several times, but for the paint in which the curing agent is mixed at the final stage, The local retention in the liquid feeding system to the coating head becomes a problem rather than the reaggregation of the dispersion itself. That is, if there is a joint in the liquid supply system pipe and there is a step in the inner wall portion, there is a portion where the paint mixed with the curing agent does not flow, that is, a portion where the paint stagnates at that point. In such a place, it becomes a dead point where the flow of the coating is stagnant, and since it is after the curing agent is mixed, it becomes an agglomerate due to the curing of the coating itself.

[0003]

Although various types of coating methods are used for coating, in the case of coating by a method using an extrusion type coating head, the coating head itself, especially its agglomerates (aggregated lumps) is used. ), The agglomerates tend to get caught in the slits, which causes streaks, which not only causes dropouts, but also affects the yield of the original fabric.

[0004]

[Means for Solving the Problems] Such a phenomenon is caused by the stagnation of the paint in the step portion of the inner wall existing in the piping system, especially in the piping system after the final filtering treatment after mixing the curing agent. If such a portion is present, the agglomerates due to the hardening increase with time and the influence becomes large. Moreover, peeling or desorption occurs at the same time as the accumulation, and a dropout or a streak when using an extrusion type coating head may occur if the pipe has a step in the final liquid feeding system to the coating head. I found it not suitable. Therefore, in order to avoid such a phenomenon, when the piping after the final filter to the coating head is dealt with by a stepless construction method, dropout is reduced and streaks when using an extrusion type coating head are reduced. There was found. Specifically, conventionally, a screw-in type joint is used at the connecting portion of the pipe, and as shown in FIG. 1, there is a stagnation point of the paint at the connecting portion of the screwing portion. In the present invention, all of the joints shown in FIG. 2 have no stagnation point. That is, in FIG. 2, 1 is a tube, 2 is a butt flange, 3 is packing, and 4 is a clamp.

[0005]

Description of Examples Examples and comparative examples will be described.

(Example 1) An experiment was conducted by preparing a magnetic coating material with the following compounding ratio and applying it with an extrusion type coating head. Weight part Magnetic powder 100 Average major axis: 0.2 μm Average axial ratio: 8 Hc: 1500 Oe σ _s : 130 emu / g Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 10 (UCGH VAGH) Polyurethane resin (Nippon Polyurethane) N-2304) 10 Abrasives: Alumina 10 Stearic acid 0.2 Lecithin 0.5 Toluene 50 Methyl ethyl ketone 50 Methyl isobutyl ketone 50 After circulating and filtering this paint, low molecular weight polyisocyanate (Coronate L made by Nippon Polyurethane) as a curing agent. Was mixed with 5 parts by weight of the magnetic powder and liquid was fed to the coating head. At this time, the piping system used was one having no step on the inner wall portion of the present invention.

(Comparative Example 1) Coating was carried out in the same manner as in Example 1 except that the conventional screw-in type joint was used for the liquid feeding piping system to the coating head. In both cases of Example 1 and Comparative Example 1, the liquid feeding piping system to the coating head was thoroughly washed before the experiment, and there were no deposits, aggregates, etc. inside at the initial stage. I did an experiment. The results are shown in Table 1 showing the time from the start of liquid feeding, the number of dropouts, and the presence or absence of streaks. (The upper row shows the number of dropouts,
(The bottom row shows the occurrence of streaks)

[0008]

[Table 1] Regarding the dropout, the number of pieces per minute measured at a dropout level of -12 dB and 15 µs after cutting the sample into a width of 8 mm, incorporating the sample in an 8 mm cassette.

In the case of Example 1, the number of dropouts did not change with the passage of time, and good coating could be performed without the occurrence of coating stripes. In the case of Comparative Example 1, however, Initially it was good, but over time, hardened agglomerates were generated and accumulated in the pipe, the number of dropouts increased and streaks were observed.After the experiment was completed, the extrusion coating head was disassembled and at the entrance of the slit. The hardened agglomerates of the paint were caught.

[0010]

As described above, by using the liquid supply pipe for the coating head of the present invention, good coating can be performed without the generation or accumulation of aggregates due to the curing of the coating material. It is also clear that cleaning is easy because there are no stagnation points inside the piping system. In addition, the coating method using the extrusion coating head used in Example 1 and Comparative Example 1 is particularly advantageous because the influence of agglomerates at the slit entrance is likely to occur.

[Brief description of drawings]

FIG. 1 shows a conventional piping joint.

FIG. 2 shows a joint of a magnetic paint pipe of the present invention.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kazuo Katai 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation

Claims (1)

[Claims] 1. A method of feeding a coating solution to an extrusion type coating head, wherein after a filtering process with a final filter, in the piping system used for feeding the solution, there is no step in the inner wall portion of the tube connecting the piping. Manufacturing method of magnetic recording medium.