JPH0325848B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention aims at improving the corrosion resistance and runnability by modifying the surface of the magnetic layer of a metal thin film magnetic recording medium. In general, thin film magnetic recording media made by vacuum deposition or plating are said to have excellent high density properties. Particularly in recent years, applications have been expected for audio recording and video recording tapes, and thin films of cobalt-based alloys formed by vacuum deposition on plastic substrates have been put into practical use for small recording tapes. It has become commercially available. However, ferromagnetic metals are generally prone to corrosion, and in order to avoid this corrosion, methods such as alloying the magnetic material itself or forming a film of a polymer compound on the magnetic layer are employed. However, in these methods, when alloying the magnetic layer, it is common that alloys with good corrosion resistance do not necessarily have good properties from the viewpoint of magnetic properties. Furthermore, although it is effective to form a corrosion-resistant film on the surface of the magnetic layer, it is not desirable for the film thickness to be too large from the viewpoint of electromagnetic conversion characteristics. The permissible range of film layer thickness is at most 500Å.
The thickness is preferably about 200 Å. It is extremely difficult to stably form a corrosion-resistant film with such a thickness and with good mass production. Further, even if a film is formed, it is difficult to completely prevent moisture from entering with such a thickness. In the present invention, in order to avoid the conventional difficulties, sufficient corrosion resistance is obtained by applying a solution of a silane coupling agent and then drying it. The present invention will be explained below. A solution of a silane coupling agent is applied onto a magnetic recording thin film medium made of a ferromagnetic metal such as cobalt and made by vacuum evaporation, sputtering, electroplating, or the like. As the silane coupling agent, one having an alkoxy group such as a methoxy group or an ethoxy group as a reactive group and a long-chain alkyl group is used. In the case of halogen atoms such as Cl or Br, corrosive compounds are generated after hydrolysis, which adversely affects corrosion resistance. As the alkyl group, those having 8 to 22 carbon atoms are useful from the viewpoint of water repellency, lubricity, and solubility of the formed film.
Alkyl groups having 8 or fewer carbon atoms have insufficient water repellency and lubricity, while those having 22 or more carbon atoms are unsuitable from the viewpoint of dissolution. The silane coupling agent was dissolved in 0.001% to 10% by volume using ethanol as a solvent, applied to the magnetic thin film by dipping, brushing, spraying, etc., and dried in a hot air dryer. . Other solvents that can be used include alcohols such as methanol and isopropyl alcohol. The thinner the concentration of the silane coupling agent is, the thinner the film produced is, which is desirable from the viewpoint of electromagnetic conversion characteristics. However, if the concentration is too low, it will not be possible to form a uniform film on the metal thin film, and the metal thin film will be exposed as it is, making it impossible to obtain sufficient corrosion resistance. From the above viewpoint, the concentration of the silane coupling agent used is 10% to 0.001%, preferably 1% to 0.01%. The silane coupling agent reacts with the water on the metal thin film and is hydrolyzed, forming a film on the thin film in which long-chain alkyl groups exhibiting hydrophobicity are aligned. As a result, not only does moisture, which causes rust, decrease, but
The contact angle with water also increases, preventing the intrusion of water that causes rust, and improving corrosion resistance. Furthermore, since the long-chain alkyl group has a good lubricating effect, running properties are also improved. In the examples described later, as a ferromagnetic metal thin film.
Co-Ni film is used, but Co film, Co-Cr film,
Similar effects were obtained with Co-Ni-Cr films, Co-Fe films, etc. Next, examples will be specifically explained. Example 1 A solution having the following composition was applied to a magnetic layer of a ferromagnetic alloy thin film of cobalt (80%) and nickel (20%) prepared by vacuum evaporation on a polyester film. Silane coupling agent (triethoxystearylsilane: C ₁₈ H ₃₇ Si (OC ₂ H ₅ ) ₃ ) 1 ml ethyl alcohol 100 ml After coating, it was dried at 60° C. for about 15 minutes. The treated magnetic layer had improved water repellency compared to before treatment. Furthermore, when the frictional resistance was measured under a load of 10g on a mirror-finished SUS304 block, it was found to have decreased to about three-fourths of that before treatment. Table 1 shows the contact angle and environmental test results.

[Table] This effect was the same in magnetic layers containing 100% Co, 5% to 35% Ni compared to Co, or those in which Si, W, V, Cr, etc. were added to Co. Furthermore, it has been confirmed that there is little difference depending on the manufacturing conditions, and that it is effective even with plating and sputtering films. The above also applies to Examples 2 and 3, which will be described later. Example 2 A solution having the following composition was applied to the magnetic layer of a ferromagnetic alloy thin film of cobalt (80%) and nickel (20%) prepared by vacuum evaporation on a polyester film. Silane coupling agent (trimethoxycaprylic silane; C ₈ H ₁₇ Si (OCH ₃ ) ₃ ) 1 ml Ethyl alcohol 100 ml After the treatment, it was dried at 60° C. for about 15 minutes. The treated magnetic layer had improved water repellency compared to before treatment. Furthermore, when the frictional resistance was measured under a load of 10g on a mirror-finished SUS304 block, it was found to have decreased to about four-fifths compared to before treatment. Table 2 shows the contact angle and environmental test results.

[Table] Example 3 A solution having the following composition was applied to the magnetic layer of a ferromagnetic alloy thin film of cobalt (80%) and nickel (20%) prepared by vacuum evaporation on a polyester film. Silane coupling agent (triethoxybehenicsilane; C ₂₂ H ₄₅ Si (OC ₂ H ₅ ) ₃ ) 1 ml ethanol 100 ml After coating, it was dried at 60° C. for about 15 minutes. The treated magnetic layer had improved water repellency compared to before treatment. Furthermore, when the frictional resistance was measured under a load of 10g on a mirror-finished SUS304 block, it was found to have decreased to about two-thirds compared to before treatment. Table 3 shows the contact angle measurement results and the environmental test results.

[Table] Comparative Example 1 In the same manner as in Example 1, a solution having the following composition was applied and dried. Silane coupling agent (CH ₂ =CHSiCl ₃ ) 1 ml Ethyl alcohol 100 ml Comparative Example 2 In the same manner as in Example 1, a solution having the following composition was applied and dried. Silane coupling agent ( _{H2NC3H6Si ( OCH3} ) _{3 )}
1 ml Ethyl alcohol 100 ml The evaluation results of the samples obtained in Comparative Examples 1 and 2 are shown below.

[Table] * Before processing is set as 1
According to the present invention, as described above, the corrosion resistance and orientation of a metal thin film magnetic recording medium can be easily improved.

Claims (1)

[Claims] 1. A metal thin film type characterized in that a solution of a silane coupling agent having a reactive group consisting of an alkyl group having 8 to 22 carbon atoms and a methoxy group or an ethoxy group is applied to the surface of a magnetic layer made of a ferromagnetic metal thin film and dried. A method for manufacturing a magnetic recording medium.