JPH0434205B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a magnetic recording medium in which a ferromagnetic thin film is provided as a magnetic recording layer on a substrate.
In particular, it relates to a method of manufacturing a metal thin film magnetic recording medium with excellent magnetic properties. [Prior art] Conventional magnetic recording media include γ-Fe ₂ O ₃ , Co-doped γ-Fe ₂ O ₃ , Fe ₃ O ₄ ,
Co-doped Fe ₃ O ₄ , γ-Fe ₂ O ₃ and Fe ₃ O ₄ bertolide compounds, magnetic powders such as CrO ₂ or ferromagnetic alloy powders, etc. are used as powder magnetic materials such as vinyl chloride.
Coating type materials have been widely used, in which a material dispersed in an organic binder such as vinyl acetate copolymer, styrene-butadiene copolymer, epoxy resin, or polyurethane resin is coated and dried. In recent years, with the increasing demand for high-density recording, vacuum deposition,
A so-called non-binder type magnetic recording medium that does not use a binder has a magnetic recording layer that is a ferromagnetic metal thin film formed by a paper deposition method such as sputtering or ion plating, or a plating method such as electroplating or electroless plating. It is attracting attention and various efforts are being made to put it into practical use. Conventional coating-type magnetic recording media mainly use metal oxides, which have lower saturation magnetization than ferromagnetic metals, as magnetic materials, so the thinning of the magnetic layer required for high-density recording results in a reduction in signal output. It has reached its limit, and its manufacturing process is complicated, and it has the drawback of requiring large auxiliary equipment for solvent recovery and pollution prevention. In non-binder type magnetic recording media, a ferromagnetic metal having a saturation magnetization higher than that of the above-mentioned oxides is formed as a thin film without containing a non-magnetic substance such as a binder, so it can be made into an ultra-thin layer for high-density recording. This has the advantage that the manufacturing process is further simplified. As one of the requirements for magnetic recording media for high-density recording, high coercive force and thinness have been proposed both theoretically and experimentally. There are great expectations for non-binder type magnetic recording media that can be easily made into small and thin layers and have a high saturation magnetic flux density. In particular, the vacuum deposition method is very advantageous because it does not require drainage treatment as is the case with plating, the manufacturing process is simple, and the deposition rate of the film can be increased. As a method for manufacturing a magnetic film having coercive force and squareness desirable for magnetic recording media by vacuum deposition, the oblique deposition method described in US Pat. Nos. 3,342,632 and 3,342,633 is known. In practice, when manufacturing a magnetic recording medium by forming a ferromagnetic metal thin film on a tape-shaped substrate by oblique vapor deposition, the tape-shaped substrate is conveyed along a cooling can, and the vapor of the magnetic metal material evaporated from an evaporation source flows. is deposited obliquely onto a moving tape-like substrate. At this time, a magnetic thin film with a high coercive force can be obtained as the incident angle of the vapor flow that is incident on the substrate is large, but a large incident angle tends to lower the vapor deposition efficiency, which is not preferable in terms of manufacturing. A method of introducing oxygen gas during oblique deposition has been proposed as a method for forming a magnetic thin film with high coercive force at a relatively low incident angle.
For example, Japanese Patent Application Laid-open No. 58-41443 discloses that a tape-shaped moving base is arranged so that the incident angle (θ) of the vapor flow on the base changes continuously from a high incidence angle (θmax) to a low incidence angle (θmin). A method is disclosed in which the oxidizing gas is introduced into the vicinity of a low incident angle (θmin). According to this method, a film with high coercive force can be obtained, but it has the disadvantage that the squareness deteriorates. [Object of the Invention] An object of the present invention is to provide a method for manufacturing a magnetic recording medium having a high coercive force and a high squareness ratio suitable for high-density recording. [Structure of the Invention] The present invention provides a method for manufacturing a magnetic recording medium in which a ferromagnetic metal thin film is formed on a non-magnetic substrate by an oblique evaporation method. A method for manufacturing a magnetic recording medium by blowing an air current mainly composed of O ₂ gas onto the surface of the ferromagnetic metal thin film while heating the thin film, or by blowing an air current mainly composed of heated O ₂ gas. Regarding. Here, as the substrate, plastic bases such as polyethylene terephthalate, polyimide, polyvinyl chloride, cellulose triacetate, polycarbonate, polyethylene naphthalate, etc., Al, Ti, stainless steel, etc. can be used. In addition, ferromagnetic metals and alloys that can be used as magnetic layer materials include ferromagnetic metals such as Fe, Co, and Ni, and Fe-
Co, Fe−Ni, Co−Ni, Fe−Co−Ni, Fe−Rh,
Fe-Cu, Co-Cu, Co-Au, Co-Y, Co-La,
Co-Pr, Co-Gd, Co-Sm, Co-Pt, Ni-Cu,
Mn-Bi, Mn-Sb, Mn-Al, Fe-Cr, Co-
Cr, Ni−Cr, Fe−Co−Ni, Fe−Co−Cr, Ni−
Examples include ferromagnetic alloys such as Co-Cr. Among these, Co or
It is an alloy containing 50% by weight or more of Co. O ₂ gas, N ₂ gas, etc. may be introduced into the vapor flow of the ferromagnetic metal during vapor deposition. In the present invention, the oblique evaporation method refers to the U.S. patent
This is a vapor deposition method disclosed in No. 3342632, No. 3342633, etc. Furthermore, in the present invention, "within the same vacuum system" means that the ferromagnetic metal thin film formed by the oblique evaporation method in vacuum is subjected to air flow blowing in the same vacuum system as that used during evaporation without returning it to the atmosphere. It is. Although it is preferable to perform the air flow blowing in the same vacuum chamber as the deposition vacuum chamber, it may be performed in a separate vacuum chamber separated from the deposition vacuum chamber. At this time, the degree of vacuum in the vacuum chamber for airflow blowing can be 10 ^-2 to ^{10 2} times that in the vapor deposition vacuum chamber. An example of the manufacturing apparatus used in the present invention is shown in FIG. A rotary can 2 and an evaporation source 3 are provided inside the vacuum chamber 1, and the vapor flow from the evaporation source 3 is designed so that only desired vapor flow components reach the rotary can 2 through a mask 4. . A nozzle 5 is provided in the vacuum chamber 1 for blowing an air flow onto the surface of the ferromagnetic metal thin film. A heater 6 is wound around the nozzle 5. The substrate 8 fed from the delivery roll 7 travels along the rotating can 2 and is wound up on a take-up roll 9. During this travel, the ferromagnetic metal/alloy in the evaporation source 3 is vacuum-deposited onto the base 8, and subsequently a gas stream heated by the heater 5 is blown onto the surface of the ferromagnetic thin film on the base 8 by the nozzle 5. When forming a ferromagnetic metal thin film, a coolant is circulated inside the rotating can 1 to coat the surface of the rotating can.
It is preferable to maintain the temperature at 15°C or lower. FIG. 2 shows another example of the manufacturing apparatus used in the present invention. Rotary cans 22 and 23 are provided inside the vacuum chamber 21, and the substrate 24 is conveyed from a delivery roll 25 along the rotary cans 22 and 23, and then wound onto a take-up roll 26. Rotating can 22
An evaporation source 27 is disposed below the evaporation source 27, and the vapor flow from the evaporation source 27 is masked by a mask 28 so that only desired vapor flow components reach the surface of the substrate 24 on the rotary can 22. Vacuum chamber 21 is exhaust port 2
9, while the gas supply pipe 30
A gas whose main component is O ₂ gas is now supplied. A nozzle 31 is provided at the tip of the gas supply pipe 30 and sprays a gas containing O ₂ gas as a main component onto the surface of the deposited magnetic metal thin film formed on the substrate 24 moving along the rotating can 23 . A mechanism is provided in which a coolant is circulated inside the rotary can 22 to maintain the surface of the rotary can at 15° C. or less, and a hot medium is circulated inside the rotary can 23 to heat the deposited magnetic metal thin film. A method for preventing wrinkles by spraying O ₂ gas, N ₂ gas, etc. after forming a ferromagnetic metal thin film (Japanese Patent Laid-Open No.
55-14569), a method for improving corrosion resistance by exposing a magnetic film to an oxidizing atmosphere after forming a ferromagnetic metal thin film (Japanese Patent Application Laid-open No. 57-198543), exposing a magnetic film to an oxidizing atmosphere after forming a ferromagnetic metal thin film A method for improving corrosion resistance by exposing to a glow discharge atmosphere using
17544), and a method of forming a ferromagnetic metal thin film and then exposing the magnetic film to an ozone atmosphere in a heated state to improve its durability under repeated running and high temperature and high humidity conditions (Japanese Unexamined Patent Publication No. 1759- 63031), etc., but in the present invention, after forming a ferromagnetic metal thin film by an oblique evaporation method, a gas mainly composed of O ₂ gas is applied to the surface of the magnetic metal thin film while the magnetic metal thin film is heated. A magnetic recording medium having extremely good magnetic properties is obtained by spraying
The present invention relates to a method for manufacturing a novel magnetic recording medium that cannot be predicted using the above-mentioned known techniques. Furthermore, in the present invention, after forming a ferromagnetic metal thin film by oblique vapor deposition, a magnetic recording medium having extremely good magnetic properties can be obtained by blowing an air current mainly composed of heated O ₂ gas onto the surface of the magnetic metal thin film. This is a new technology that could not be predicted using conventional technology. When manufacturing a tape-shaped magnetic recording medium according to the present invention, it is preferable to blow a gas flow mainly composed of O ₂ onto the surface of a ferromagnetic metal thin film while conveying the tape-shaped substrate along a rotating can. Moreover, in this case, the gas blowing section should be arranged so that the ratio R/r of the distance (R) from the center of the rotation can to the gas introduction section and the radius (r) of the rotation can is in the range of 1.01 to 1.20. preferable. The present invention will be explained below based on Examples. This example does not limit the scope of application of the present invention. Example 1 Using the manufacturing equipment shown in Figure 1, a film with a thickness of 1500 mm was deposited on a 12.5 μm thick polyethylene terephthalate film.
A magnetic tape was fabricated by forming a cobalt-deposited magnetic thin film with a thickness of 1.5 Å using an oblique evaporation method while introducing O ₂ gas. The magnetic properties of the obtained magnetic tape were measured using a vibrating magnetometer (VSM). The results are shown in the table below.

[Table] As can be seen from the table, the squareness ratio SQ is larger in Samples D and E, in which the O ₂ gas stream is directed while heating the magnetic film immediately after oblique evaporation, compared to Sample A produced by the conventional manufacturing method. Widespread improvement was observed. It should be noted here that no change in magnetic properties appears when simply blowing an air current (B) or when simply heating the magnetic film (C). In the above case, when ozone gas was used instead of O ₂ gas after forming the deposited film, no improvement in magnetic properties could be obtained. Example 2 A film with a thickness of 1300 Å was deposited on a 9.5 μm thick polyethylene terephthalate film using the manufacturing equipment shown in Figure 2.
A CoNi alloy (Ni 25% by weight) vapor-deposited magnetic thin film was formed by oblique vapor deposition while introducing O ₂ gas to create a magnetic tape. The magnetic properties of the obtained magnetic tape were as follows. In the table below, sample F, sample G and sample H
By comparing Sample I and Sample I, the following can be found. When the temperature of the rotating can is low, no improvement in the squareness ratio is observed even if O ₂ gas is sprayed onto the surface of the ferromagnetic metal thin film, and the surface of the ferromagnetic thin film is heated so that the rotating can reaches 75°C. However, when O ₂ gas is blown onto the surface of a ferromagnetic thin film, an improvement in the squareness ratio is observed. Furthermore, good results were also obtained for sample J in which the temperature of the rotating can was 85°C.

[Table] As is clear from the table, the magnetic tape manufactured according to the present invention has excellent squareness. Example 3 In Example 1, a cobalt evaporated magnetic thin film with a film thickness of 1300 A was formed on a 9.5 μm thick polyethylene terephthalate film, and O ₂ gas was blown onto the surface of the ferromagnetic thin film by changing the position of the O ₂ gas inlet. . The location of the O ₂ gas inlet is determined by the distance from the center of the rotation can (R) and the radius of the rotation can (r).
The ratio R/r was changed so that it was in the range of 1.015 to 1.25. The properties of the magnetic tape obtained were as shown in the table below.

〔Effect of the invention〕

As described above, according to the present invention, a magnetic recording medium having extremely good magnetic properties suitable for high-density recording can be obtained through a simple process.

[Brief explanation of drawings]

FIG. 1 shows a schematic diagram of a manufacturing apparatus used in the present invention. DESCRIPTION OF SYMBOLS 1... Vacuum chamber, 2... Rotating can, 3... Evaporation source, 4... Mask, 5... Gas stream blowing nozzle, 6... Heater, 7... Delivery roll, 8... Substrate, 9... Winding roll. FIG. 2 shows another example of the manufacturing apparatus according to the present invention. 21... Vacuum chamber, 22, 23... Rotating can,
24...base body, 25...feeding roll, 26...
... Winding roll, 27 ... Evaporation source, 28 ... Mask, 29 ... Exhaust hole, 30 ... Gas supply pipe, 31
...Gas airflow spray nozzle.

Claims (1)

[Claims] 1. In a method for manufacturing a magnetic recording medium by forming a ferromagnetic metal thin film on a non-magnetic support by an oblique evaporation method, after forming the ferromagnetic metal thin film by an oblique evaporation method, The ferromagnetic metal thin film is heated in the system so that the temperature of the rotating can becomes 75°C or higher, and an air flow containing O ₂ gas as a main component is applied to the surface of the ferromagnetic metal thin film from the center of the rotating can. The ratio R/r between the distance (R) and the radius (r) of the rotating can is
A method for manufacturing a magnetic recording medium, characterized in that the gas is sprayed from a gas spraying section arranged so that the gas is in the range of 1.01 to 1.20. 2. After forming a ferromagnetic metal thin film on a non-magnetic support by oblique vapor deposition, an air flow mainly composed of heated O ₂ gas is applied to the surface of the ferromagnetic metal thin film in the same vacuum system from the center of the rotating can. distance (R)
A method for manufacturing a magnetic recording medium, characterized in that the gas is sprayed from a gas spraying section arranged such that the ratio R/r of the radius (r) of the magnetic recording medium and the radius (r) of the rotating can is in the range of 1.01 to 1.20.