JPH11102518A - Production method of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a magnetic recording medium having both improved mechanical characteristics and improved electromagnetic conversion characteristics. SOLUTION: Within a vacuum chamber 2, deposition is performed on a base film 1 to produce a magnetic recording medium. The base film 1 travels from the maximum incident angle side of vapor to be deposited toward the minimum incident angle side thereof. In the vicinity of the maximum incident angle, an ionized or heated gas 13 is supplied to the base film 1. The gas may be an oxidizing gas or an inert gas. In addition, the water vapor partial pressure of the gas under atmospheric pressure is preferably at 1×10<-2> Torr or less.

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 magnetic recording medium, and more particularly to a method for manufacturing a magnetic recording medium having improved electromagnetic conversion characteristics and / or mechanical characteristics.

[0002]

2. Description of the Related Art Conventionally, magnetic recording media such as video tapes have been manufactured by forming a magnetic layer by a coating method. However, in recent years, as the demand for high-density recording on a magnetic recording medium has increased, it has become difficult to respond to a magnetic layer formed by a coating method. Therefore, recently, a magnetic recording medium having a metal thin film type magnetic layer, which is filled with a magnetic material at a high density, has attracted attention. Above all, the vacuum deposition method is becoming mainstream as a method of forming such a metal thin film type magnetic layer because the apparatus is simpler and stable film formation is possible as compared with other methods.

In general, a magnetic recording medium of a vapor deposition type is manufactured by forming a magnetic layer by forming a thin metal film made of a ferromagnetic material in a vacuum atmosphere on a base film such as polyethylene terephthalate (PET). Is being done. When the magnetic layer is formed by vapor deposition, an oxidizing gas such as oxygen is introduced. In the magnetic recording medium obtained in this manner, the magnetic layer deposited on the base film is composed of a mass of magnetic particles grown in a column structure, and an oxide layer is formed between each column, thereby forming the magnetic layer. Of the coercive force and the saturation magnetic flux density are improved. At the same time, an oxide film is also formed on the surface of the magnetic layer, thereby protecting the inside of the magnetic layer and improving the corrosion resistance.

[0004]

By the way, even when the film is formed by supplying the oxidizing gas as described above, or when the oxidizing gas is not supplied, other impurities exist in the deposition region. It is important not to do so.
For example, when hydrogen and carbon are present as impurities, when they come into contact with a high-energy metal vapor stream, they easily penetrate into the deposited metal, causing the film to become embrittled, and oxygen in the metal over a long period of time. And adversely affect corrosion resistance. However, for example, the base film is generally transferred from the unwinding chamber having a lower degree of vacuum to the film forming chamber having a higher vacuum. In such a case, impurities adsorbed on the base film are released, or Impurities may be entrained by the base film from the unwinding chamber. In these cases, it is necessary to ensure that the deposition is not adversely affected. Therefore, a first object of the present invention is to make the deposition region as clean as possible, and to remove impurities that are entrained by the base film.
It is to provide a new method for vacuum deposition.

When the oxidizing gas is supplied as described above, the obtained magnetic layer may be excessively oxidized. That is, the oxidizing gas is supplied from the nozzle into the vacuum vessel. However, when the oxidizing gas is injected from the nozzle, the gas is instantaneously diffused by a pressure difference, so that it is difficult to perform delicate control thereof. However, in order to obtain excellent electromagnetic conversion characteristics, it is not desirable that the oxidation is performed excessively. In such a case, it would be highly desirable if diffusion of the oxidizing gas could be prevented and at the same time, the deposition region could be cleaned. Therefore, a second object of the present invention is to provide a novel method of manufacturing a magnetic recording medium by vacuum evaporation, which can meet such a demand.

[0006]

According to the present invention, there is provided a method for producing a magnetic recording medium by vapor deposition on a base film in a vacuum container, that is, a vacuum vapor deposition method. In this case, the base film travels from the maximum incident angle side of the vapor deposition to the minimum incident angle side. Therefore, for example, when the base film runs on the cooling can roll and the film is formed by oblique vapor deposition, the column grows from the maximum incident angle side to the minimum incident angle side, and the film formation proceeds.
According to the present invention, an ionized or heated gas is supplied to the base film near the maximum incident angle.

[0007] The ionization or heating of the gas is performed for the purpose of improving the chemical activity of the species constituting the gas. Therefore, the degree of ionization and heating is a matter to be determined in light of this purpose, but generally, as ionization, a degree of ionization such that a glow discharge current of about 100 to 1000 mA per 10 m of the base film width is preferable, Glow discharge and other known means can be used as the ionization means. Further, it is considered that at least the nozzle temperature is required to be about 100 to 200 ° C. when heating the nozzle and the piping connected thereto. The heating means may also be a known one, and can be realized, for example, by winding a ribbon heater around a gas nozzle. In some cases, ionization and heating may be performed simultaneously.

When the gas whose chemical activity is improved by ionization or heating is supplied to the base film near the maximum incident angle, that is, at the start of film formation, the gas is cleaned immediately before film formation. Act on.
In particular, the vicinity of the maximum incident angle is a deposition region where the base film accesses first from the unwinding chamber, and is most susceptible to the influence of impurities. By cleaning the base film and removing impurities in this part, it is possible to eliminate defects such as deterioration of mechanical properties due to the incorporation of impurities, and to increase the bonding strength between the layer to be formed and the base film. it can.

In particular, when the chemical activity is increased by ionization, it is possible to expect an effect of eliminating the charge of the base film immediately before film formation. It is very difficult to remove electricity without physical contact in a vacuum,
As a result, such a problem that wrinkles occur in the base film can be eliminated, and the yield can be improved. Generally, when ions are used in vacuum film formation, ions are accelerated by using an ion gun or the like. However, in the present invention, the reactivity and charge of ions are inexpensively and effectively used, such as vapor deposition in bombarding without accelerating ions.

As the gas, an inert gas or an oxidizing gas can be used. As the inert gas, nitrogen or argon can be used, and by ionizing or heating them and supplying them near the maximum incident angle, effects such as improvement of binding strength by the above-described cleaning and static elimination are obtained. Obtainable. The oxidizing gas is represented by oxygen. In this case, in addition to the above-described effects, an effect of efficiently oxidizing the magnetic layer to be formed can be achieved. That is, by increasing the chemical activity by ionization or heating, the oxidizing gas immediately reacts with the deposited metal in the vicinity of the supplied maximum deposition region, and immediately oxidizes only the target portion. Therefore, a situation in which excessive oxidation is performed by diffusion can be avoided, and the electromagnetic conversion characteristics can be appropriately controlled.

The partial pressure of water vapor at atmospheric pressure of the gas used is preferably 1 × 10 ⁻² Torr or less. When the partial pressure of water vapor exceeds this, the incorporation of hydrogen atoms into the film increases, which may be undesirable in terms of mechanical properties.

In the present invention, an oxidizing gas can be introduced in the vicinity of the minimum incident angle as in the conventional case. The flow rate in this case can be in a known range of, for example, about 30 SCCM.

The method for producing a magnetic recording medium of the present invention can be used mainly for forming a magnetic layer. This is performed, for example, by vacuum deposition using an electron beam. As the ferromagnetic metal material forming the magnetic layer, for example, a ferromagnetic metal such as Co, Ni, Fe, or Fe-Co, Fe-Ni, Co-Ni, Fe −Co
-Ni, Fe-Cu, Co-Cu, Co-Au, Co-Y, Co-La, Co-
Pr, Co-Gd, Co-Sm, Co-Pt, Ni-Cu, Mn-Bi, Mn-S
b, Mn-Al, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co-Cr, Ni
-Co-Cr and other ferromagnetic alloys. In particular, at least one selected from ferromagnetic alloys containing iron, cobalt, and nickel as main components and nitrides thereof is preferable. The magnetic layer is formed of one layer or two or more layers. To cope with high-frequency recording, it is advantageous to have many layers, but it is considered that 2 to 5 layers are appropriate as a practical range. .
The thickness of the magnetic layer is not particularly limited, but is preferably set to 50 to 500 nm, and particularly preferably 80 to 300 nm as a practical range.
It is preferred that

In the method for producing a magnetic recording medium of the present invention, a magnetic recording medium is generally obtained by forming a magnetic layer on a support.
Conventionally known ones can be used. For example, in the case of a plastic film, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonate; polyvinyl chloride; And aromatic polyamides. However, PET is preferred in terms of price. Such a support is usually wound in a roll and placed in a chamber adjacent to a vacuum vessel for vapor deposition, and introduced into the vacuum vessel through a slit provided in a wall separating the chamber and the vacuum vessel. In this case, it is preferable to perform a known treatment such as bombarding in the above-mentioned chamber so that the support does not carry impurities as much as possible.

The method for producing a magnetic recording medium of the present invention can also be used to form a back coat layer on the surface of the support opposite to the magnetic layer by vapor deposition. Such a back coat layer includes, for example, metals such as Cu, Ni, and Al, C and Si,
A semimetal such as Ge can be formed by e-beam evaporation and then oxidizing, nitriding or carbonizing. In this case, by supplying the ionized or heated gas from the vicinity of the maximum incident angle according to the present invention, the obtained back coat layer can have excellent corrosion resistance and mechanical properties. The thickness of the back coat layer is not particularly limited, and is appropriately determined depending on the material and the purpose of use. However, it is generally preferred that the thickness be 300 nm or less.

The magnetic recording medium manufactured according to the present invention may be provided with a protective layer or a lubricating layer, if necessary. For example, the protective layer can be formed by depositing a high-hardness substance such as diamond-like carbon on the magnetic layer and / or the back coat layer using a CVD method or the like. The lubricating layer can be formed by applying or spraying a fluorine-based lubricant represented by perfluoropolyether on the outermost layer of the magnetic recording medium.

[0017]

1 and 2 show an example of a vacuum deposition apparatus suitable for use in carrying out the manufacturing method of the present invention. This apparatus is configured as an apparatus for forming a magnetic layer by performing oblique evaporation, and includes a vacuum container connected to a vacuum exhaust device (not shown), that is, a vacuum chamber 2, and a canister provided in the vacuum chamber 2. A roll 5, an unwinding roll 6 in the unwinding chamber 3 for running the base film 1 on the can roll 5, and a winding roll 7 in the winding chamber 4 are appropriately arranged. Reference numerals 8a and 8b denote anti-adhesion plates, which are provided in order to limit the deposition region in an oblique direction as viewed from the crucible 10.

The base film 1 is introduced from the unwinding chamber 3 into the vacuum chamber 2 through a slit 9 provided in a partition wall between the unwinding chamber 3 and the vacuum chamber 2, and is wound through the can roll 5. It is run to the room 4. Crucible
A ferromagnetic metal 11 suitable for forming a magnetic layer is accommodated in 10, and heated and melted by an electron beam struck by an electron gun 12, and evaporated vapor is regulated by a maximum incident angle and a minimum incident angle. In the deposited region, the light enters the base film 1 and a magnetic layer is formed. In this case, the base film 1 runs from the maximum incident angle side of the vapor deposition to the minimum incident angle side. Reference numeral 17 denotes a nozzle for supplying an oxidizing gas, which can supply an oxidizing gas such as oxygen at the time of film formation at a flow rate of, for example, about 30 SCCM as conventionally known.

According to the present invention, a gas is supplied to the base film 1 from the vicinity of the maximum incident angle, and the gas is supplied to the base film 1 as shown in FIG.
In the example, the water is supplied from a supply source (not shown) via the ionization device 13 and the nozzle 14. The ionizer 13 is provided with a discharge tube in this example. The gas is, for example, an oxidizing gas such as oxygen or an inert gas such as nitrogen.
In the example of FIG. 2, a heater 16 is wound around the nozzle 15 so that the gas is heated.
By these means, the gas is chemically activated, and the base film is cleaned or neutralized at the vicinity of the maximum incident angle, that is, at the start of the vapor deposition, to remove impurities which are likely to flow into the vapor deposition region together with the base film 1, When an oxidizing gas is used, only the vicinity of the maximum incident angle is appropriately oxidized, and wasteful oxidation caused by diffusion can be minimized. Thus, it is possible to improve the binding strength between the magnetic layer and the base film, reduce the generation of wrinkles on the base film, and improve the magnetic and mechanical properties.

[0020]

【Example】

Examples 1 to 4 and Comparative Examples 1 to 6 <Production Method> A magnetic layer was formed by oblique evaporation using a vacuum evaporation apparatus as shown in FIG. 1 or FIG. A 4.5 μm thick polyamide film was used as the base film, and 99.9% pure metallic cobalt was used as the magnetic material. The maximum and minimum incident angles of the deposited atoms are respectively
90 ° and 60 °, deposition rate 100nm / sec, thickness of magnetic layer
It was 180 nm.

In forming the magnetic layer, as shown in Table 1, oxygen was used as an oxidizing gas, and nitrogen was used as an inert gas. The gas flow was 30 SCCM. In each case, heating was performed by energizing a ribbon heater wound around a nozzle, or gas was ionized by applying an ionization current to a glow discharge tube. Further, the partial pressure of water vapor in the atmosphere of each gas was as shown in Table 1. As for nitrogen, a water vapor partial pressure having a value shown in Table 1 was obtained by publishing ultra-high-purity nitrogen gas through water in a thermostat and mixing it with the original ultra-high-purity nitrogen gas. At the time of ionization, the extraction of ions was not accelerated.

After forming the magnetic layer as described above, a back coat layer and a lubricating layer were formed on the obtained raw material, and 6.35
It was slit to a width of mm and loaded on a DVC cassette to produce a magnetic recording medium.

[0023]

[Table 1]

<Evaluation> The samples obtained in Examples 1 to 4 and Comparative Examples 1 to 6 were evaluated for electromagnetic conversion characteristics, mechanical characteristics, and wrinkling. The measurement of the electromagnetic conversion characteristics was performed by measuring the output with an oscilloscope using a commercially available device modified from DVC.
The measurement frequencies were 5 MHz, 10 MHz and 20 MHz. Table 2 shows the results. The unit of the numerical value is dB, and the output of Comparative Example 1 is 0.
It is a relative value expressed as dB.

The mechanical properties were evaluated by performing a peel test and a scratch strength test. In the peeling test, a cellophane tape (CT-12 manufactured by Nichiban Co., Ltd.) was adhered to the magnetic layer, and then peeled off as vigorously as possible without tearing the base film, and the peeling degree of the magnetic layer from the base film was determined. In this case, the evaluation criteria were as follows: も の: no peeling of the magnetic layer due to adhesion of the cellophane tape; Δ: peeling of the magnetic layer was not mottled; and ×: peeling of the magnetic layer.

In the scratch test, a scanning stylus tester for thin film evaluation (SST-101, manufactured by Shimadzu Corporation) was used as a test device, and a diamond stylus having a tip diameter of 10 μm was used for an amplitude of 50.
The sample surface was run while micro-vibrating at μm, and the load was gradually increased. The minimum load at which the film was broken was taken as a measure of the mechanical strength of the film surface.

With respect to the frequency of occurrence of wrinkles, ○ indicates that no wrinkles occurred during the film formation for 20 minutes, Δ indicates that wrinkles occasionally occurred, and x indicates that wrinkles constantly occurred. Table 2 shows the above results.

[0028]

[Table 2]

[0029]

As is evident from the results of the examples and comparative examples, by improving the chemical activity by increasing the chemical activity by heating / ionizing using an oxidizing gas, the obtained magnetic layer has improved electromagnetic conversion characteristics. Can be seen. In the peeling test, the same improvement is observed, and an increase in the binding property between the base film and the magnetic layer is observed. When an inert gas such as nitrogen gas is used, the electromagnetic conversion characteristics are not significantly improved, but the mechanical characteristics are greatly improved. Regarding the generation of wrinkles, the effect in the case of ionization was large.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a vacuum deposition apparatus suitable for carrying out the method of the present invention.

FIG. 2 is a schematic view showing another example of a vacuum evaporation apparatus suitable for carrying out the method of the present invention.

[Description of Signs] 1 Base film 2 Vacuum chamber 3 Unwinding chamber 4 Take-up chamber 5 Can roll 6 Unwind roll 7 Take-up roll 8a, 8b Deposition plate 9 Slit 10 Crucible 11 Metal material 12 Electron gun 13 Ionizer 14 ， 15 gas nozzle 16 heater

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Hirohide Mizunoya 2606 Akabane, Kaimachi, Haga-gun, Tochigi Pref.

Claims (4)

[Claims] 1. A method for manufacturing a magnetic recording medium by performing vapor deposition on a base film in a vacuum vessel, wherein the base film travels from the maximum incident angle side of the vapor deposition to the minimum incident angle side. A method of manufacturing a magnetic recording medium, comprising supplying an ionized or heated gas to the base film near the maximum incident angle. 2. The method according to claim 1, wherein said gas is an oxidizing gas.
Manufacturing method. 3. The gas of claim 1, wherein said gas is an inert gas.
Manufacturing method. 4. The gas according to claim 1, wherein a partial pressure of water vapor at atmospheric pressure of the gas is 1 × 10 ⁻² Torr or less.
Manufacturing method.