JPH0419609B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic storage medium used in a magnetic storage device (such as a magnetic disk or magnetic drum), and particularly to a continuous thin film magnetic storage medium. The surface of a continuous thin film magnetic memory is finished to be extremely smooth in order to allow the magnetic head to move as close as possible to recording and reproducing information in order to perform high-density recording. Using such a magnetic memory, the magnetic head and the surface of the magnetic memory are set in contact at the start of operation, and by applying the required rotation to the magnetic memory, the distance between the magnetic head and the surface of the magnetic memory is created. It has become clear that the following problems occur when using the so-called contact start-stop method, in which an air space is created in the recording medium and recording and playback is performed in this state. . When the magnetic storage body is stopped, the magnetic head is in contact with the surface of the magnetic storage body, but at this time, the close contact between the magnetic head and the magnetic storage body is strong, and an excessive force is applied to the magnetic head when the operation starts. Accidents may occur in which the magnetic head is destroyed by the magnetic head, or the magnetic head bounces on the surface of the magnetic storage medium and damages the magnetic storage medium. Also, during operation, the magnetic head may collide with the magnetic storage body, or the flying becomes unstable, especially immediately after the start of rotation or just before stopping when the levitation force of the magnetic head becomes weak, causing the magnetic head to collide with the magnetic storage body. Accidents may occur. Furthermore, during operation, discharge occurs between the magnetic head and the magnetic storage body, which may generate noise and cause malfunctions during recording and reproduction. This phenomenon is noticeable in continuous thin-film magnetic storage materials that use magnetic metals or ferrite as storage media, but is less of a problem in so-called coated disks, in which magnetic powder is dispersed and coated in a binder. . This is considered to be due to the fact that in the former case, the surface of the magnetic storage body is extremely smooth and the distance between the magnetic head and the magnetic storage body is small. The present invention aims to solve the above-mentioned problems in a continuous thin-film magnetic memory, especially in a magnetic memory using magnetic metal as a storage medium, and the present invention aims to solve the above-mentioned problems in a magnetic memory using a magnetic metal as a storage medium. This magnetic memory is characterized by containing an antistatic agent in the protective film. The protective film used in the present invention is a silicon compound or a nonmagnetic metal oxide. Further, the antistatic agent of the present invention is an ionized amine surfactant. Examples of the main surfactants are shown in the table below.
In the chemical structural formula in the table, R represents an alkyl group, and m and n represent integers.

[Table] Conductive powders or fibers such as carbon powder, metal powder, or metal fibers are also effective in preventing static electricity, but if they are included in the protective film, they will impair the surface smoothness of the protective film. This is not desirable as an antistatic agent in the present invention. The continuous thin film magnetic storage body that is the object of the present invention is
A base layer 2 with a thickness of several tens of μm is provided on a substrate 1 as shown in FIG.
A structure in which a metal magnetic medium layer 3 with a thickness of m is coated and a protective film 4 with a thickness of 0.01 to 0.3 μm is further coated thereon, or between a metal magnetic medium layer 3 and a protective film 4 as shown in FIG. It has a structure in which a non-magnetic alloy layer 5 with a thickness of about 0.02 μm is further provided. The substrate 1 is made of titanium alloy or aluminum alloy, which is light and easy to work with, and has a surface roughness of 50 μm in the circumferential direction.
Hereinafter, it is used after being machined by lathe processing and thermal straightening to a thickness of 100 μm or less in the radial direction. The base layer 2 is provided to obtain a smooth surface, and is coated with Ni-P alloy or the like by plating, and is mechanically polished to a maximum surface roughness of about 0.03 μm. . The metal magnetic medium layer 3 is an alloy containing Co, No or Fe, typically Co-Ni-P or Co-Mn.
-P, Co-W-P, Co-Cr, etc., and these are formed by a plating method, a vapor deposition method, a sputtering method, or an ion blating method. As the protective film 4, silicic acid polymer (polysilicic acid),
Silicon compounds such as glass and other silicon oxides or silicon nitrides, non-magnetic metals with high hardness and corrosion resistance such as Rn or Cr, or alloys thereof, or Al, Co, Ni, Cr, Ti, Zr or Ce or their An alloy oxide formed by a coating method, a vapor deposition method, or a sputtering method is used. Further, the nonmagnetic alloy layer 5 is provided to improve the adhesion between the metal magnetic medium layer 3 and the protective film 4 thereon, and is preferably made of Ni-P. In order to incorporate the antistatic agent into the protective film, a suitable method can be selected depending on the type of the protective film. For example, in the case of a protective film formed by a coating method such as a silicic acid polymer, a desired amount of antistatic agent is dissolved in a solution for forming the protective film, and the solution is applied to or on the metal magnetic medium layer. A protective film containing an antistatic agent can be obtained by coating the provided nonmagnetic alloy layer by spin coating, drying, and baking if necessary. In addition, in the case of a protective film formed by a vapor deposition method or a sputtering method such as glass, alloy, or metal oxide, the magnetic memory body coated with such a protective film is placed in an antistatic agent or an antistatic agent. A protective film containing an antistatic film can be obtained by immersing the protective film in a solution in which the antistatic agent is dissolved. The higher the content of the antistatic agent, the more remarkable the antistatic effect will be, but on the other hand, if it is too large, the abrasion resistance of the protective film will be reduced. Therefore, it is preferable to limit the amount to about 50% by weight at most, and practically a few weight% can sufficiently exhibit the antistatic effect. The antistatic agent contained in the protective film reduces the electrical resistance of the protective film and reduces the load generated on the surface of the protective film due to relative movement between the magnetic head and the magnetic storage body during operation of the storage device. Discharge occurs via the metal part, thereby stabilizing the flying of the magnetic head and preventing collision with the magnetic storage body.
It also acts to prevent the generation of noise due to discharge between them. Furthermore, by preventing charging, the adhesion strength between the magnetic head and the magnetic storage body is weakened when the magnetic storage body is stopped, thereby reducing accidents at the start of operation. In particular, in the present invention, an excellent antistatic effect can be obtained by using a silicon compound or a nonmagnetic metal oxide as the protective film material and using an ionized amine surfactant as the antistatic agent. That is, the basic amine surfactant has a good affinity with acidic silicon compounds and nonmagnetic metal oxides, and is characterized by being easily adsorbed onto the surface of the protective film. Furthermore, since the molecules adsorbed on the surface of the protective film are ionized, it has good conductivity and can efficiently discharge charges generated on the surface of the protective film. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 Surface roughness is 50 μm or less in the circumferential direction and radial direction.
On a disk-shaped substrate made of aluminum alloy processed to a thickness of 10 μm or less, a Ni-P alloy is plated as a base layer to a thickness of about 50 μm, and this is coated to a thickness such that the maximum surface roughness is 0.02 μm. Mirror polished to 30μm. On top of that is Co-co as a metal magnetic medium layer.
Ni-P alloy is plated to a thickness of 0.05 μm, and the following solution containing an antistatic agent is applied by spin coating to form a protective film on top of the Ni-P alloy. After drying, The material was baked at 200℃ for 5 hours to create a magnetic disk. Note that the protective film in this case is polysilicic acid. Tetrahydroxysilane 2% n-butyl alcohol solution 99.9g Tetramethylammonium chloride 0.1g Example 2 In the same manner as in Example 1, except that the following solution was used as a solution for forming a protective film containing an antistatic agent. I made a magnetic disk. Tetrahydroxysilane 2% n-propyl alcohol solution 99.9g Methylpetaine 0.1g Example 3 A magnetic disk was prepared in the same manner as in Example 1, except that the following solution containing an antistatic agent was used to form a protective film. I made it. Tetrahydroxysilane 2% ethyl alcohol solution 99.9g N,N-bis(2-hydroxyethyl)methylamine 0.1g Example 4 A Ni-P alloy layer was formed on the substrate in the same manner as in Example 1.
Furthermore, a Co-Ni-P alloy layer is formed on top of the Co-Ni-P alloy layer, but the protective film is made of Co-Ni-P instead of polysilicate.
The surface of the alloy magnetic medium layer was oxidized and the oxide was used as a protective film. This was immersed in an ethyl alcohol solution containing 9% by weight of sodium tetramethylammonium for 15 hours to produce a magnetic disk containing an antistatic agent in a metal alloy oxide protective film. Example 5 A magnetic disk was manufactured in the same manner as in Example 1, except that the following solution containing an antistatic agent was used as a solution for forming a protective film. Tetrahydroxysilane 2% n-butyl alcohol solution 99.5g Trimethylbenzylammonium chloride
0.5g Example 6 A magnetic disk was prepared in the same manner as in Example 1, except that the following solution containing an antistatic agent was used as a solution for forming a protective film. Tetrahydroxysilane 2% n-propyl alcohol solution 99.5g Lausol imidasone derivative

[Formula] 0.5g Comparative Examples 1 to 4 In Examples 1 to 4, magnetic disks were prepared without containing an antistatic agent in the protective film, and these were prepared in Comparative Examples 1 to 4 corresponding to Examples 1 to 4, respectively. shall be. When an experiment was conducted using the magnetic disks prepared in Examples 1 to 6 and Comparative Examples 1 to 3 by repeatedly recording and reproducing in an environment with a humidity of 30% using the contact start-stop method, it was found that the magnetic disks of Comparative Examples In this case, collisions between the magnetic head and the surface of the magnetic disk occurred at a rate of about 1% at the start of operation, but this collision almost never occurred with the magnetic disk of the example. Comparing the playback output, the playback output of the magnetic disk of the comparative example fluctuates by 5 to 10% due to the instability of flying the magnetic head, but in the case of the magnetic disk of the example, the playback output fluctuates by 5 to 10%. The fluctuation was reduced to 2-3%. Furthermore, in the examples, no discharge noise was observed during recording or reproduction.

[Brief explanation of drawings]

1 and 2 are partial cross-sectional views showing the present invention, respectively. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Underlayer, 3...Metal magnetic medium layer, 4...Protective film, 5...Nonmagnetic alloy layer.

Claims (1)

[Claims] 1. A metal magnetic medium layer is coated on a mirror-polished base layer on a substrate, and a protective film is further coated on the metal magnetic medium layer directly or via a non-magnetic alloy layer. 1. A magnetic memory, wherein the protective film is made of a silicon compound or a nonmagnetic metal oxide, and contains an antistatic agent made of an ionized amine surfactant. 2. The magnetic memory according to claim 1, wherein the silicon compound is polysilicic acid. 3. The magnetic memory according to claim 1, wherein the silicon compound is _SiO2 . 4. The magnetic memory according to claim 1, wherein the nonmagnetic metal oxide is an oxide of Ni-Co. 5. The magnetic memory according to claim 1, wherein the nonmagnetic metal oxide is a Ni oxide.