JPS5921090B2 - Method for manufacturing magnetic recording media - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a magnetic recording medium.

Generally, a magnetic recording medium is a substrate such as a polyester base coated with a magnetic paint, which is a mixture of magnetic powder and a binder. However, since the substrate itself and the binder are insulators, and the magnetic powder used is also a metal oxide with relatively high electrical resistance, such as γ-Fe2O3, the electrical resistance of the resulting magnetic recording medium itself becomes high. As a result, static electricity is charged, which causes dirt and dust to be attracted. Therefore, anionic, cationic, nonionic, and amphoteric surfactants have traditionally been used as antistatic agents, but conventionally, these antistatic agents were only added to the mixture of magnetic powder and binder. It was then applied to the substrate.

The conventional approach to preventing charging of magnetic recording media has been to lower the electrical resistance of the magnetic recording media in order to immediately discharge the static electricity that has been charged.

In other words, the only means to prevent static electricity was to lower the electrical resistance of the material itself. Therefore, it was not possible to achieve a sufficiently satisfactory antistatic effect. Therefore, the inventor of the present invention first revised the conventional idea of preventing static electricity by reducing electrical resistance, and instead of focusing on the concept of electrical resistance, since the point is that the static electricity that has been charged should disappear quickly, the inventors of the present invention focused on how to reduce the static electricity itself as quickly as possible. I thought about this. As a result, the surface was coated with at least one of alkyl sulfate salts, alkyl sulfonate salts, alkyl phosphate salts, quaternary ammonium salts, amine salts, alkyl ether type, alkyl ester type, sorbitan derivatives, betaine type and imidazoline type surfactants. We have found that a magnetic recording medium coated with a mixture of magnetic powder and binder on a substrate has a significantly shorter half-life, in which the electric charge on the medium is halved. Based on this knowledge, the previously invented magnetic recording medium will first be described based on examples. Example 1 100 parts by weight of γ-Fe2O3 2.5 parts by weight of alkyl sulfate salt surfactant (PMX-3007 manufactured by Yoshimura Yuka Co., Ltd.) A composition containing 1000 parts by weight or more of water was thoroughly mixed, and the surfactant was applied to the surface of magnetic powder. After absorption, it was heated and dried.

The ferromagnetic powder thus antistatically treated was dispersed in a ball mill together with a binder and a solvent, and the resulting magnetic paint was applied to a polyester base to obtain a magnetic recording medium. The sample was designated as 1-A, and the sample prepared by directly dispersing the surfactant together with magnetic powder in a binder was designated as 1-B. Table 1 shows the characteristics of both. Samples 2-A and 2-B were prepared in the same manner as in Example 1 with the compositions above.
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The results are shown in Table 2. Samples 3-A and 3-B were prepared in the same manner as in Example 1 with the compositions above.
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The results are shown in Table 3. Samples 4-A and 4-B were prepared in the same manner as in Example 1 with the compositions above.
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The results are shown in Table 4. Samples 5-A and 5-B were prepared in the same manner as in Example 1 with the compositions above.
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The results are shown in Table 5. Example Vjtsu 1, J1I 卜1- With the above composition, samples 6-A and 6-B were prepared in the same manner as in Example 1.
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The results are shown in Table 6. Samples 7-A and 7-B were prepared in the same manner as in Example 1 with the compositions above.
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The results are shown in Table 7. Samples 8-A and 8-B similar to Example 1 with the compositions above.
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The results are shown in Table 8. Samples 9-A and 9-B were prepared in the same manner as in Example 1 with the compositions above.
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The results are shown in Table 9. Sample 101A, lO as in Example 1 with the composition above.
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The results are shown in Table 10. Samples 11-A and 11-B were prepared in the same manner as in Example 1 using the compositions described above.

The results are shown in Table 11. Samples 12-A and 12-B were prepared in the same manner as in Example 1 using the compositions described above.

The results are shown in Table 12. As is clear from the above results, although the electric resistance itself of the magnetic recording medium according to the earlier invention has not been reduced that much, the half-life has been significantly shortened, so there is significantly less adhesion of dirt, dust, etc. 0 As described above, the previous invention made it possible to obtain a magnetic recording medium with significantly less adhesion of dirt, dust, etc., but as a result of further research, the inventors discovered that the surfactant was divided into two parts. In other words, if you first coat the surface of the magnetic powder with a surfactant and then add the surfactant again when kneading the magnetic powder with the binder and solvent, a small amount of surfactant will be sufficient. I found out that it is possible to increase the

The present invention is based on this knowledge, and comparative examples and examples will be shown below. Comparison/Example 1 The sample of Example 4 was referred to as (1), and the sample (1Y) was prepared by adding 2 parts by weight of the surfactant to sample (1).

Then, using this test scale 1Y, a magnetic paint is made by kneading it with a binder and a solvent. At this time, a surfactant was further added and the magnetic paint was applied to a polyester base film to produce a magnetic recording medium. Table 13 shows the type and brand name of the surfactant added to the binder, the amount added, and the sample corrosion of the magnetic recording medium prepared using the surfactant. The above results are shown in Table 14.

Note that elasticity is the limit at which a sample breaks when a load is applied.

Also, for sample (1) a', the amount of surfactant added was changed,
Changes in half-life were determined.

The results are shown in FIG. From this figure, sample 716 (1)
It can be seen that if the half-life is the same as , the addition amount is only about 0.75 days. Comparison/Example 2 Sample (2) was obtained by changing the surfactant to 2.5 parts by weight of alkyl sulfate salt (PMX-3007 of Yoshimura Yuka Co., Ltd.) in (1) of Comparison/Example. Test 2Y using 1 part by weight of surfactant as compared to 2).
shall be.

Table 15 shows samples prepared by adding a surfactant later in the same manner as in Comparative Example 1. The above results are shown in Table 16.

Comparison/Example 3 The sample of Example 10 above was designated as (3), and 0.5 part by weight of the surfactant sorbitan derivative surfactant and 1 part by weight of the amine salt surfactant were added to sample (3). Let's call it Trial 3Y.

Table 17 shows samples prepared by adding a surfactant later in the same manner as in Comparative Example 1. The above results are shown in Table 18.

Also other surfactants, namely alkyl sulfonate salts (C),
Examples of the alkyl phosphonate salt (D), amine salt (E), alkyl ether salt (F), alkyl ester type (G), and betaine type 11 imidazoline type (1) are shown below.

Note that the pretreatment examples correspond to the previously proposed examples, and the additions correspond to Examples 1 to 3 of the present application. Also, electrical resistance is [Ω/Cd], half-life is [SeO], elasticity is [Kg/C
d]. Table 19 shows the orientation of representative samples selected from these examples.

Furthermore, Table 21 shows the orientation of representative samples selected from Example C-1.

As described above, since the magnetic recording medium manufactured according to the present invention has less charging phenomenon, it is free from dust. Does not attract dust, etc., and has good electromagnetic properties. It has excellent physical properties.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram of the magnetic recording medium according to the present invention.

Claims (1)

[Claims] 1. Surface is treated with at least one of alkyl sulfate salts, alkyl sulfonate salts, alkyl phosphonate salts, quaternary ammonium salts, amine salts, alkyl ether type, alkyl ester type, sorbitan derivatives, betaine type and imidazoline type surfactants. 1. A method for manufacturing a magnetic recording medium, which comprises applying a magnetic paint obtained by kneading magnetic powder, a binder containing the surfactant, and a solvent onto a substrate.