JPH0516090B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method for producing a perpendicular magnetic recording medium having an axis of easy magnetization perpendicular to a magnetic recording surface on a molded polymer substrate. [Prior Art] Conventionally, thin film manufacturing techniques such as vapor deposition and sputtering have been used as a method for manufacturing perpendicular magnetic recording media on polymer molded substrates. When manufacturing a perpendicular magnetic recording medium by vapor deposition or sputtering, a perpendicular magnetic recording medium with good magnetic properties can be obtained by making the substrate temperature as high as possible, and the adhesion strength of the magnetic film can be improved. However, these vapor deposition and sputtering methods
Because the magnetic film is formed by bombarding the substrate with high-energy metal atoms in a vacuum, the substrate becomes even hotter. In other words, in the case of polymer molded substrates that have melting, sublimation, or decomposition temperatures, the substrate temperature cannot be increased indefinitely, and the upper limit is usually about 100° C. lower than these melting, sublimation, or decomposition temperatures. However, since polymer molded substrates always contain unreacted monomers and polymers with a low degree of polymerization (hereinafter referred to as oligomers), when held at high temperatures, these oligomers is deposited on the substrate surface, and a soft magnetic film (permalloy, CoTi,
CoTa, CoZrNb, etc.) and perpendicular magnetization films (CoCr,
CoW, CaMo, CoV, etc.), the adverse effect of oligomers on the substrate surface, that is, the unevenness causes unevenness in the film itself, resulting in poor head contact between the medium and the head, resulting in a deterioration of the reproduction output. Furthermore, due to these irregularities, the soft magnetic film is subjected to domain wall pinning, resulting in deterioration of magnetic properties. Furthermore, the protrusions on the medium create areas that collide with the head, causing scratches on the medium and flaking of the film, resulting in a significant deterioration in durability. The instability of the head touch due to this unevenness can lead to significant deterioration of the envelope characteristics.
The deterioration of recording density characteristics _D50 , etc. had a significant negative effect. Note that this oligomer is not only unavoidable in the manufacturing process for producing a polymer molded substrate, but is also intentionally included to provide stretchability when processing into a film. Conventionally, in order to eliminate the unevenness caused by oligomers after film formation, the protrusions were buffed to improve the smoothness, but this only impaired the continuity of the film and caused further damage to the film surface due to abrasion particles. It had drawbacks. [Purpose] In view of the above points, the present invention removes oligomers that have an adverse effect on all aspects before film formation, and improves smoothness, magnetic properties, durability, playback output, and The purpose is to obtain a perpendicular magnetic recording medium with excellent envelope characteristics, recording density characteristics, etc. [Summary] The present invention provides a perpendicular magnetic recording medium in which a molded polymer substrate of the medium is heat-treated at a temperature below the melting, sublimation, or decomposition temperature of the substrate;
After cleaning the oligomer deposited on the substrate with a solvent, a magnetic layer is formed to create a magnetic recording medium with very little unevenness. [Examples] Examples of the present invention will be described below with reference to figures and tables. In this example, the polymer molded substrate is PET.
(polyethylene terephthalate) and acetone was used as the solvent. This solvent may also be trichlene or xylene. FIG. 1 is a flowchart of the process for creating the media of the present invention. First, PET
The PET was placed in a constant temperature bath at 180°C for 1 hour, and the PET with the oligomer precipitated thereon was immersed in acetone. next
Soak the PET in alcohol to remove any remaining acetone evaporation. Afterwards, the alcohol remaining on the PET is blown off with nitrogen, the PET is set in the sputtering device, and a soft magnetic film is formed on top of it.
CoTi, CoCr film as perpendicular magnetization film at substrate temperature 150
It sputtered at ℃. Figure 2a shows a perpendicular magnetic recording medium made according to the present invention; 1 is PET treated with acetone after oligomer precipitation; 2 is PET treated with acetone;
CoTi soft magnetic film 0.5μm, 3 is CoCr perpendicular magnetization film
It is 0.5 μm. FIG. 2b is a conventional medium. In other words, PET was directly placed in a sputtering device and sputtered at a substrate temperature of 150°C.
4 is PET, 2 is a CoTi film, 3 is a CoCr film, and 5 is a precipitated oligomer. Table 1 shows the surface roughness of the above media.

[Table] As is clear from FIG. 2 and Table 1, the surface properties of the media according to the present invention are extremely smooth compared to those of the conventional method. Table 2 also shows the magnetic properties.

[Table] As can be seen, the medium according to the present invention shows good characteristics as a perpendicularly magnetized film. Next, Figures 3 and 4 show the reproduction output, recording density characteristics, and envelope. These are all media rotation speeds
Measurements were taken at 300 rpm and a linear velocity of 2 m/s with a head main pole film thickness of 0.5 μm. Figure 3 shows recording density characteristics (a)
(b) is the medium according to the present invention, and (b) is the medium according to the conventional method. The data in FIG. 3 are summarized in Table 3.

〔effect〕

As described above, the perpendicular magnetic recording medium according to the present invention has various effects compared to the conventional method. The effects are summarized below. ◎Improved playback output ◎Improved recording density characteristics ◎Improved envelope characteristics ◎Reduced media defects ◎Improved magnetic characteristics ◎Improved durability Furthermore, before setting the PET in the vacuum chamber,
Since oligomers are processed, the degree of vacuum can be improved, and the time required to reach a predetermined degree of vacuum can be shortened, leading to cost reductions. It also has the effect of drastically reducing dirt inside the vacuum chamber. In this example, as a polymer molded substrate,
Although PET was used, the present invention is also effective in the case of a heat-resistant polymer molded substrate such as aramid or polyimide. Further, although the solvents used in this example are acetone, trichlene, xylene, etc., the present invention is effective even if these are diluted with alcohols. Furthermore, even greater effects can be obtained by using the above-mentioned solvent in the form of steam. In addition, this example is used as a soft magnetic film.
CoTr film was used as CoTi/perpendicular magnetization film, but
Soft magnetic films other than these (permalloy, CoTa,
The present invention is also effective for perpendicularly magnetized films (CoZrNb, etc.) and perpendicularly magnetized films (CoW, CoV). Furthermore, in addition to two-layer film media,
A single OoCr layer is also effective, and a Ba-Ferrite coated perpendicular magnetic recording medium is also effective. In addition, this example was created as a floppy disk medium, but the 16 mm
It has the same effect as VTR tape, 8mm VTR tape, and audio tape. In this example, PET was held at 180°C for 1 hour in a constant temperature bath, but the temperature may be any number of times as long as it is below the melting, sublimation, and decomposition temperatures, and the time may vary depending on the holding temperature and
It cannot be generalized as it varies depending on the type of PET and the thickness of PET. Furthermore, in this example, oligomers are precipitated by heat-treating PET in a constant temperature bath, but heat-treating in a vacuum will shorten the oligomer precipitation time. Further, in this example, a solvent is used to remove the precipitated oligomer, but oxidation by ultrasonic waves, ultraviolet irradiation, charged particle irradiation, and ozone are also effective.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram for producing a perpendicular magnetic recording medium according to the present invention. FIGS. 2a and 2b are cross-sectional views of the medium of the present invention and the conventional medium, respectively.
FIG. 3 shows the recording density characteristics, and FIG. 4 shows the envelope. 1...PET treated with acetone after oligomer precipitation, 2...CoTi spatter film, 3...CoCr
Spattered film, 4...PET (untreated), 5...Oligomer, a...Medium according to the present invention, b...Medium according to conventional method.

Claims (1)

[Claims] 1. In a perpendicular magnetic recording medium having an axis of easy magnetization perpendicular to the magnetic recording surface, the polymer molded substrate of the medium is heat-treated at a temperature below any one of melting, sublimation, or decomposition temperature of the substrate, and A method for producing a magnetic recording medium, which comprises removing precipitates on the surface of a substrate, and then forming a magnetic layer on the polymer molded substrate from which the precipitates have been removed.