JPH0944846A - Production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a high quality magnetic tape with a high production yield by eliminating deformation such as wrinkles and loosening of a magnetic tape web to flatten the web so that a protective layer to be successively formed can be uniformly formed. SOLUTION: A magnetic tape web 6 produced by forming a metal thin film recording layer on a polymer film is subjected to heat treatment with hot air blow 11 along the longitudinal direction of the magnetic tape web 6. By this method, deformation such as wrinkles and loosening of the tape web 6 is eliminated and the web is flattened. Thereby, a protective layer to be successively formed can be uniformly formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal thin film type magnetic recording medium suitable for high density magnetic recording. More specifically, it relates to a method of manufacturing a thin metal thin film type magnetic recording medium which is most suitable for long-time recording.

[0002]

2. Description of the Related Art As a magnetic tape for video, a magnetic recording medium of a ferromagnetic metal thin film type, which is a so-called vapor deposition tape, in which a ferromagnetic metal thin film is formed on a non-magnetic support by a method such as electron beam vapor deposition or sputtering. However, it has been studied as a recording medium for high image quality and for digital use, and has already been partially commercialized.

In these magnetic tapes, friction and wear with the magnetic head and guide rollers are reduced to obtain good running performance and durability, and corrosion of the magnetic layer is prevented under high temperature and high humidity environment. However, in order to obtain good corrosion resistance, it has been conventionally practiced to provide a protective layer composed of a carbon film, a lubricant and an anticorrosive agent on the surface of the magnetic layer.

As a method of forming a protective layer composed of these carbon film, lubricant and rust preventive agent on the surface of the magnetic layer, generally, a carbon film is formed by a dry method such as a sputtering method or a plasma polymerization method. The rust preventive agent layer is formed by applying, drying and forming a coating solution containing a lubricant and a rust preventive agent by a general coating method such as a gravure method, an offset method, a reverse method, a die method. There is.

However, in a magnetic tape stock having a small thickness, the magnetic tape stock is deformed due to wrinkles, sagging, etc. due to uneven thickness of the polymer film and uneven heat load generated when the magnetic thin film layer is formed. Therefore, when forming a protective layer by a coating method, coating defects such as coating unevenness and coating streaks occur, and there is a problem that a sufficient protective film function cannot be exhibited. In addition, the carbon film is sputtered,
When forming by dry method such as plasma polymerization method,
Partial heat load increases due to poor adhesion to the can at deformed parts such as wrinkles and sags, and heat loss of the magnetic tape raw material occurs.In extreme cases, there is a hole in the magnetic tape raw material. There are problems such as.

Therefore, conventionally, mechanical wrinkles and sagging have been conventionally performed by an expander roll, a spiral roll or the like before the protective layer forming portion.

As a coating method for preventing uneven coating,
A dipping method (Japanese Patent Publication No. 4-353623) in which the entire magnetic tape stock is dipped in a coating solution has been proposed.

[0008]

However, according to the above-mentioned method, the effect is not sufficient for the magnetic tape stock having a thin film thickness of 7 μm or less, and the mechanical strength of the expander roll, the spiral roll, etc. By way of
When the action is strengthened, there is a problem that the surface of the original magnetic tape is scratched.

The present invention solves the above problems.
In a magnetic tape stock having a thin film thickness of 7 μm or less, it is possible to eliminate wrinkles and slack by heat treatment, which enables the subsequent formation of a protective layer to be uniform.
An object of the present invention is to provide a magnetic recording medium manufacturing method capable of manufacturing a high-quality magnetic recording medium with a high yield.

[0010]

In order to achieve this object, the present invention provides a magnetic tape stock having a magnetic recording layer made of a metal thin film formed on a polymer film substrate, in the longitudinal direction of the magnetic tape stock. The heat treatment is performed by applying hot air along with.

[0011]

With this structure, by applying hot air along the longitudinal direction of the magnetic tape original material, heat shrinkage of the polymer film is caused, and a flat surface free from wrinkles and sagging is realized, and the protective layer to be continuously applied. Can be uniformly formed.

[0012]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a magnetic tape used in an embodiment of the present invention. In FIG. 1, 1 is a polymer film, 2 is a magnetic recording layer made of a ferromagnetic metal thin film,
3 is a protective film layer made of a carbon layer, 4 is a lubricant layer, and 5 is a back coat layer.

The polymer film used in the magnetic recording medium of the present invention has a film thickness of 3 to 7 μm, and polyethylene terephthalate is often used. In addition to polyethylene naphthalate, a polyester film, a cellulose derivative such as cellulose acetate, a polyamide, a polyimide are used. It may be a plastic film such as.

As the ferromagnetic metal thin film, iron, cobalt, nickel or an alloy containing them as a main component formed by a vacuum deposition method, a sputtering method or an ion plating method, or a partial oxide or a partial nitride thereof is used. Can be used. As a magnetic tape, a thin film material is melted by an electron beam method and vapor-deposited on a polymer film along a can to form a magnetic layer.

The protective film composed of a carbon layer can be formed by plasma polymerization of a hydrocarbon gas or a mixed gas of hydrocarbon and argon, or sputtering of carbon or graphite.

When the hydrocarbon gas is formed by plasma polymerization, the hydrocarbon gas or a mixed gas of the hydrocarbon gas and the inert gas is introduced into a vacuum container, and 0.00
While maintaining a pressure of 1 to 1 Torr, discharge inside the vacuum container to generate plasma of hydrocarbon gas,
A carbon layer is formed on the surface of the raw magnetic tape. The discharge method may be either an external electrode method or an internal electrode method, and the discharge frequency can be experimentally determined. Further, by applying a voltage of 0 to -3 KV to the electrode on the original side of the magnetic tape, the hardness of the film and the adhesion can be improved.

As the hydrocarbon gas, methane, ethane,
Propane, butane, pentane, hexane, heptane, octane, benzene and the like can be used.

Further, in order to form a hard film, it is desirable to increase the discharge energy as much as possible. Also, it is desirable to raise the temperature of the magnetic tape stock as much as possible.

Fluorine-based lubricants are effective as the lubricant, and there are perfluorocarboxylic acid and its ester, and perfluoropolyether and its derivative, which can be used alone or in combination. The formation of the lubricant layer is performed by dissolving a fluorine-based lubricant in an organic solvent and coating and drying the solution by a usual method such as a gravure coating method, an offset coating method, a reverse roll coating method.

The heat treatment apparatus of the present invention is shown in FIG. In FIG. 2, reference numeral 6 is a magnetic tape raw material, and hot air flows out from a blowout port 7 of a hot air nozzle 9, flows along the longitudinal direction of the magnetic tape raw material, and is sucked from a suction port 8. Also,
A guide plate 10 is provided at the blow-out port, and hot air hits the magnetic tape original at an angle of 60 ° or more to prevent deformation due to wind pressure. A plurality of hot air nozzles 9 are installed, and they are installed on both the upper surface and the lower surface of the magnetic tape original fabric to improve efficiency.

It is appropriate that the tension during heat treatment is 100 kg / cm ² or less, and if it is more than 100 kg / cm ² , heat shrinkage does not sufficiently occur in the magnetic tape raw material during heat treatment, and wrinkles and slack cannot be eliminated. Further, even when heat-treated with hot air at 80 ° C. or less, heat shrinkage does not sufficiently occur, and it becomes impossible to eliminate wrinkles and slack.

The heat treatment can be carried out as a single step,
The effect can be further enhanced by installing the protective layer on the unwinding side in the forming step and performing continuous treatment. Further, as shown in FIG. 3, by adjusting the guide plate at the end of the hot air nozzle to deflect the hot air at the end of the magnetic tape roll to the outside,
Tension in the width direction can be applied to the magnetic tape raw material, and the flattening effect can be further enhanced.

A more specific embodiment will be described below. An electron beam was introduced while introducing oxygen onto a polyethylene terephthalate film having a thickness of 6.3 microns having wavy projections and granular projections composed of a modified silicone in which silica particles having a particle size of 120Å are dispersed on a smooth surface and a thickener. Was carried out continuously to form a Co—O film having a thickness of 1500 Å. Then, on the side opposite to the vapor-deposited layer, a coating liquid in which a mixture of carbon black and calcium carbonate in a ratio of 1: 1 by weight is dispersed in a resin component of polyurethane and nitrocellulose in a ratio of 3: 2 by weight is a reverse roll type coating machine. Apply with 1
It was dried at a temperature of 00 ° C. to form a back coat layer with a film thickness of 0.6 μm. Next, using the heat treatment apparatus of FIG.
The first heat treatment was performed. Further, a high-frequency (10 KHz) plasma of a mixed gas of methane and argon was applied to the vapor-deposited layer, and a DC voltage of -1.2 KV was applied to the magnetic tape raw material by using the electrode and the magnetic tape raw material as opposite electrodes. A discharge was performed to form a carbon film having a thickness of 200 Å. Further, the magnetic tape original fabric 1 is installed in front of the coater head of a reverse roll coater with the heat treatment apparatus shown in FIG. 2, and after the second heat treatment is carried out, the carbon film contains a fluorine-containing carboxylic acid continuously. An alcohol solution was applied and dried at a temperature of 70 ° C. to form a lubricant layer under the condition of 9 mg / m ² . Next, the raw magnetic tape was cut into a width of 8 mm with a slitter to obtain an 8 mm magnetic tape for VTR. Further, using the magnetic tape raw material 2 having a large wrinkle and slack, as shown in FIG.
A magnetic tape was produced in the same manner.

Then, the amount of lubricant on the tape surface was calculated from the intensity of fluorine atoms by photoelectron spectroscopy. For the measurement, 30 rolls in the width direction and 5 rolls in the longitudinal direction were measured, and the tape ratio within the predetermined lubricant amount range (90 to 110%) was calculated. The heat treatment conditions and the evaluation results are shown in (Table 1) and (Table 2).

[0026]

[Table 1]

[0027]

[Table 2]

As is clear from (Table 1), by performing the heat treatment 1, it is possible to prevent thermal damage in the carbon film forming step, and as shown in (Table 2), the lubricant coating is performed. By performing the heat treatment 2 before, a high yield can be achieved in forming the lubricant layer.

The magnetic tape produced in the above steps was subjected to still durability and storage characteristics measurement using a commercially available 8 mm VTR (EV-S900, manufactured by Sony) remodeling machine. Still durability is 2 samples in an environment of 5 ° C and 80% RH.
Was measured 5 times, and the time from the initial output to a decrease of 6 dB was measured, and the average value was taken as the still life of the tape. Regarding the storage characteristics, the sample was left in an environment of 40 ° C. and 80% RH for 1 month, the surface was observed with an optical microscope at a magnification of 100 times, and the dropout was measured. Dropout was recorded and played back for 10 minutes with 2 samples, the number of signal defects with output decrease of 3 μsec, 10 dB or more was calculated, and the average value for 1 minute was calculated. Was calculated. Table 3 shows the process conditions and evaluation results.

[0030]

[Table 3]

As is clear from Table 3, the magnetic tape having a predetermined amount of lubricant has good still durability, little increase in dropout after long-term storage, and no deterioration in corrosion resistance. . The heat treatment 1 can also be used by using the heat treatment apparatus of the present invention as a drying furnace for forming the back coat layer.

[0032]

INDUSTRIAL APPLICABILITY As described above, the present invention makes it possible to eliminate wrinkles and sagging of a magnetic tape raw material by heat treatment, and to improve the yield in the subsequent protective layer forming step, and to provide a high-quality metal thin film. Type magnetic tape has the excellent effect that it can be supplied with high yield.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a magnetic recording medium according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a heat treatment apparatus in the first embodiment of the present invention.

FIG. 3 is a conceptual diagram of a hot air nozzle according to the first embodiment of the present invention.

[Explanation of symbols]

 1 Polymer Film 2 Magnetic Recording Layer 3 Carbon Layer 4 Lubricant Layer 5 Back Coat Layer 6 Backing Layer of Magnetic Tape 7 Outlet 8 Intake 9 Hot Air Nozzle 10 Guide Plate 11 Hot Air

Claims (4)

[Claims] 1. A magnetic tape stock having a magnetic recording layer made of a metal thin film formed on a polymer film substrate, characterized in that heat treatment is performed by applying hot air along the longitudinal direction of the magnetic tape stock. Manufacturing method of magnetic recording medium. 2. The heat treatment applies hot air along the longitudinal direction of the magnetic tape raw fabric, and at the end of the magnetic tape raw fabric,
The hot air deflected to the outside is applied to the air.
The manufacturing method of the magnetic recording medium according to the above. 3. The method for producing a magnetic recording medium according to claim 1, wherein the magnetic tape stock is heat-treated with a hot air of 80 ° C. or higher with a tension of 100 kg / cm ² or lower. 4. A magnetic tape raw material having a magnetic recording layer made of a metal thin film formed on a polymer film substrate. After heat treatment of the magnetic tape raw material, the magnetic tape raw material surface is continuously provided with a protective layer. A method of manufacturing a magnetic recording medium, characterized in that