JPH01165027A - Production for magnetic recording medium - Google Patents

Abstract

PURPOSE:To completely crush a bulky protrusion and to form a good magnetic recording medium by including processes for heating and rolling a member including a base film. CONSTITUTION:A member 3 is fed to rolling rollers 1 and 2 in order to respectively press the side (face) 4 and the back face 5 of the recording and reproducing face of the member 3 having the heat resistant base film. Thereby, the bulky protrusion present in the surface 4 can be crushed. When a polyimide film is used as the base film, in order that the height of the bulky protrusion is <=0.1mum the temperature of the rolling roller is brought to above 150 deg.C, pressure to about 30kg/mm<2>-60kg/mm<2>, namely, the pressure for plastically deforming the base film. Thereby, a load is concentrated to the bulky protrusion to crush.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a magnetic recording medium, and particularly to a method for manufacturing a metal thin film type magnetic recording medium using a heat-resistant base film.

[Conventional technology]

Recently, instead of coated magnetic recording media, metal thin film magnetic recording media having high coercive force and residual magnetic flux density have been attracting attention. In general, a metal thin film type magnetic recording medium has a magnetic layer of a metal thin film formed on a polymer base film by vacuum deposition or the like. The thickness of the magnetic layer can be made approximately 1710 mm thick compared to a coating type magnetic layer.

(Problems to be Solved by the Invention) As mentioned above, metal thin film magnetic recording media have excellent high frequency characteristics because of their thin thickness, but on the other hand, because the magnetic layer is thin, the surface roughness of the base film It has the disadvantage of being susceptible to In other words, the surface of the base film generally has coarse protrusions with a height of about 0.1 to 0.5 #IjI, and similarly the magnetic layer of the metal thin film formed on the base film has coarse protrusions on the surface with a height of 0.1 to 0.5 #IjI. It becomes about 0.5 scales. If the surface roughness of the magnetic layer is large, for example, in the case of a magnetic recording tape, it causes deterioration of high frequency characteristics due to spacing loss, dropouts, level fluctuations, etc.

Conventionally, in order to reduce the surface roughness of the magnetic layer as described above,
The magnetic layer formed on the base film is polished, or the base film is polished in advance and then the magnetic layer is formed on the polished surface. However, the former method has the disadvantage that the thickness of the magnetic layer becomes non-uniform, and the magnetic layer, which is more expensive than the base film, is scraped off, making it uneconomical and reducing manufacturing efficiency. Furthermore, the latter has the disadvantage that the strength of the base film decreases due to polishing, and that depending on the type of base film, polishing cannot be performed.

The present invention was made to solve these problems, and its purpose is to manufacture a magnetic recording medium that does not suffer from deterioration of frequency characteristics, dropouts, or level fluctuations even without polishing. The goal is to provide a method that can be used.

[Means for solving problems]

The above-mentioned object of the present invention is to manufacture a magnetic recording medium, characterized in that the method for manufacturing a magnetic recording medium includes the step of laminating a magnetic layer on a base film, the method comprising the step of hot rolling a member including the base film. This can be achieved by this method.

In the rolling step included in the method of the present invention, the member including the base film is heated to an appropriate level and passed through a rolling roller set at an appropriate pressure, so that the base film is plastically deformed and exists on the surface of the member. It is possible to crush the large protrusions to such an extent that they do not cause the various problems (occurrence of dropouts) mentioned above. Specifically, these various problems can be prevented by crushing the coarse protrusions to a height of 0.1 mm or less. Note that the member including the base film treated in the hot rolling step in the method of the present invention may include a base film alone, a base film with a magnetic layer laminated thereon, or other layers provided as necessary. This includes those who are present. Moreover, the hot rolling process includes not only carrying out with a rolling roller but also carrying out with a press machine or the like.

Hereinafter, the method of the present invention using a rolling roller will be explained in detail.

As mentioned above, the temperature and pressure of the rolling roller used in the method of the present invention are preferably such that the coarse protrusions can be crushed to a height of 0.1 μm or less. Therefore, these values may be appropriately selected depending on the structure and type of the member including the base film, the size of the coarse protrusions it has, and the like. Note that the temperature is preferably high. Specifically, for example, when a polyimide film is used as the base film, the temperature of the rolling roller is 150°C or higher, and the pressure is 30 kg/mm 2 to 60
If the pressure is about 12 kg/11ff12, that is, the base film is plastically deformed, the load will be concentrated on the coarse protrusions and they will collapse. However, the heating means in the method of the present invention is not limited to heating with a rolling roller; a heating means is provided separately from the rolling roller, and the heating means heats the medium while heating the rolling roller at about room temperature. It is also possible to pass through the medium. The surface roughness of the rolling roller used in the present invention may be such that it does not impede the control of the appropriate surface roughness required for a magnetic recording medium. In particular, the surface roughness of the rolling roller that comes into contact with the recording/reproducing surface of the medium, i.e., when the magnetic layer is laminated only on one side of the base film, the magnetic layer side, or the side on which the magnetic layer is to be laminated. degree is 0.5 S (maximum height 0
．． 5 μ or less), preferably 0.23 (maximum height 0
．． 2- or less) or more.

The above surface roughness was determined by Talystep manufactured by Taylor Bobson Co., Ltd. to be 0.1μ×2.5. Using g stylus, load 2
It was measured under the condition of 00g. As the rolling roller used in the present invention, any rolling roller having the above-mentioned surface roughness and pressing force may be used. The surface of the roller is, for example, Fc, Cr%Co, A
A metal such as I, Sus, etc. is preferable.

1 to 3 are schematic diagrams showing various embodiments of the present invention. In these embodiments, coarse protrusions existing on the surface 4 are crushed by rolling rollers 1 and 2 that press the recording/reproducing surface 4 and the back surface 5 of the member 3 having at least a heat-resistant base film, respectively. be. The embodiment shown in FIG. 1 is a method of feeding the member 3 horizontally to the rolling surface. The embodiment shown in FIG. 2 is a method in which the member 3 is fed perpendicularly to the rolling surface so that the surface 4 contacts half of the outer peripheral surface of the rolling roller 1. The embodiment shown in FIG. 3 is a method in which the member 3 is fed perpendicularly to the rolling surface so that the back surface 5 contacts half of the outer peripheral surface of the rolling roller 2. When heating the member 3 using a rolling roller as a heat source,
The embodiment shown in FIGS. 2 and 3 has the advantage of good thermal efficiency because the contact area between the roller and the medium is large.

It should be noted that the present invention is not limited to these methods, and may include a mode in which a large number of rolling rollers are installed as a production line for one medium and rolling is performed continuously, or a plurality of methods shown in FIGS. 1 to 3 are used. Various methods can be used, such as repeating the process several times.

In the present invention, the degree of collapse of the coarse protrusions can also be controlled by appropriately selecting the tension or feeding speed of the member 3 during rolling.

The process of flattening coarse protrusions using a rolling roller in the method of the present invention has been described above. By performing this step, the conventional burnishing step can be omitted. That is, the present invention can solve the above-mentioned problems associated with vanishing (such as exposure of the magnetic layer due to lack of the protective layer). As steps other than hot rolling in the method of the present invention, steps used in conventionally known methods for manufacturing magnetic recording media can be used as appropriate. Below, those steps will be explained.

FIG. 4 is a partial cross-sectional view showing an example of a magnetic recording medium. The base film 6 is a heat-resistant polymer film such as polyimide, polyamide, polyamideimide, polysulfone, etc., and its surface has an appropriate surface roughness for the purpose of improving slipperiness. Its roughness can be controlled by filling with filler,
This is carried out by a chemical etching method, a sandblasting method, etc., but coarse protrusions are often present due to the reasons mentioned above, and this support 6 may be subjected to the process using a rolling roller in the present invention alone. A magnetic thin film 7 is formed on this base film 6. The magnetic layer @7 is made of Fe, C
It is a single layer or multilayer of a ferromagnetic alloy film, a ferromagnetic oxide film, a ferromagnetic nitride, etc. whose main components are O, Ni, etc., and the film thickness is usually about 0.01 to 1.0 -. As the film forming method, vacuum evaporation, sputtering, physical vapor deposition such as ion blating, plating method, etc. are used. The support 6 on which the magnetic thin film 7 has been formed in this manner may be subjected to the step of using a rolling roller in the present invention. Also,
In the production of conventionally known magnetic recording media, AI, Ge%Cr, Ti, 5i0
A thin film such as No. 2 is provided between the support 6 and the magnetic thin film 7,
In some cases, a high magnetic permeability layer such as a Fe-Ni film or a Co-Zr film is provided as a backing layer for a perpendicular magnetization film, but the process of using a rolling roller in the present invention on a medium on which such a thin film or backing layer is formed may be applied.

Further, the hot rolling process of the present invention may be applied to a member in which a magnetic thin film is formed on both the front and back surfaces of a support for the purpose of alleviating curls occurring in the medium.

In addition, Al2O3, 5i02, Si3N4, etc. are added to the magnetic thin film for the purpose of improving corrosion resistance, wear resistance, lubricity, etc.
, Mo, an inorganic protective layer such as Ni, or a fluororesin,
An organic lubricating layer such as fatty acid ester or stearic acid may be provided, and a suitable back coat layer may also be provided.

〔Effect of the invention〕

As explained above, according to the present invention, coarse protrusions can be sufficiently crushed using rolling rollers, so there is no need to perform burnishing, and problems caused by burnishing can be solved.
That is, there are no problems such as a decrease in the strength of the base film, nonuniform thickness of the magnetic layer, or the need to scrape off an expensive magnetic layer.

Furthermore, since the coarse protrusions can be sufficiently crushed, problems caused by the coarse protrusions, such as deterioration of high frequency characteristics, dropouts, and level fluctuations, can be solved.
Good magnetic recording media can be manufactured.

(Example〕 Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 First, 12.0 mm has the surface roughness shown in FIG. A thick polyimide film was prepared. The surface roughness is 0.1 g x 2.5 using Talystep manufactured by Taylor Bobson.
Measurements were made using a P stylus and a load of 200 g.

The film was then passed through a set of rolling rollers made of Fe with a surface roughness of 0.28. The temperature of the roller at that time was 200° C. and the pressure of the roller was 50 kg/ml12.

The surface roughness of the film after the coarse protrusions were crushed as described above was measured under the same conditions as described above, and the results are shown in FIG. As is clear from comparing FIG. 5 and FIG. 6, it was confirmed that the process using a rolling roller in the present invention can crush coarse protrusions.

Next, on one side of the film with the coarse protrusions crushed,
The thickness was 0.4 using an electron beam heating continuous evaporation device.
p, Co-C with 79% by weight Co and 21% by weight Cr
An r perpendicular magnetization film was formed. The can temperature at that time was 150
℃, and the film formation rate was 20 scales/min.

When the surface roughness of the Co--Cr perpendicular magnetization film formed as described above was measured in the same manner under the above conditions, the maximum height of surface irregularities was 0.067 LII. In addition, its magnetic properties are 4πM s = 4800 Gauss, Hc”
= 12000 e, Hc' = 7000 e.

Next, a Co oxide film (protective layer) having a thickness of 120 mm was formed on the perpendicularly magnetized film by a reactive sputtering method.

Next, a back coat layer containing carbon particles in a polyester binder having a thickness of 0.5 μ+ was formed on the back surface.

Next, the film on which the back coat layer was formed was heated to 8
The magnetic tape according to the present invention was completed by cutting it into a width of III1.

Example 2 A Co--Cr perpendicular magnetization film was formed on a polyimide film in the same manner as in Example 1, except that the process of passing the polyimide film through a rolling roller was not performed on the polyimide film alone. Then,
The polyimide film on which the magnetized film was formed was passed through a rolling roller under the same conditions as in Example 1.

When the surface roughness of the Co--Cr perpendicular magnetization film of the medium obtained as described above was measured in the same manner as in Example 1, the maximum height of surface irregularities was 0.06-. Since this value is the same as the value in Example 1, the process of passing through the rolling roller in the present invention is the same regardless of whether it is performed on the support alone or on the support on which the magnetic thin film has been formed. It was confirmed that coarse protrusions could be crushed well.

Next, a protective layer and a back coat layer were formed on the medium in the same manner as in Example 1, and the medium was cut into a width of 8 mm to complete a magnetic tape according to the present invention.

Example 3 A magnetic tape according to the present invention was completed in the same manner as in Example 1 except that the pressure of the rolling roller was set to the roller's own weight. In this example, the maximum height of the unevenness on the surface of the magnetic thin film immediately after it was formed was 0.08 scale.

Comparative Example 1 A magnetic tape was completed in the same manner as in Example 1 except that the step of passing it through a rolling roller was not performed.

In addition, in this comparative example, the maximum height of the unevenness on the surface of the magnetic thin film immediately after deposition was 0.30 μm.

The brightness signal output and dropout of the magnetic tapes produced in Evaluation Examples 1 to 3s3 and Comparative Examples 1 to 2 were evaluated using a commercially available 8++ format video deck. The results and evaluation conditions are shown in Table-1.

As is clear from the results shown in Table 1, it was confirmed that the magnetic recording medium produced by the method of the present invention has excellent brightness signal output and less dropout.

[Brief explanation of the drawing]

1 to 3 are schematic diagrams showing various embodiments of the present invention, FIG. 4 is a diagram showing an example of a magnetic recording medium, and FIGS. 5 and 6 are diagrams showing the surface of the polyimide film in Example 1. It is a figure showing roughness. 1.2---One rolling roller, 3---------One medium, 4---Front side of the medium, 5---The back side of the medium, 6--- −−−−ψ−Base film, ? −−−−−−−−− Monomagnetic thin film.

Claims (2)

[Claims] (1) A method for manufacturing a magnetic recording medium that includes the step of laminating a magnetic layer on a base film, the method comprising the step of hot rolling a member including the base film. (2) Claim 1, wherein the magnetic layer is a metal thin film.
A method for manufacturing a magnetic recording medium according to paragraph 1.