JPH07105037B2 - Method and apparatus for forming protective film of metallic magnetic medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to the formation of, for example, a diamond-like carbon film (hereinafter abbreviated as DLC film) on the surface of a film-shaped metal magnetic medium having a ferromagnetic metal thin film as a recording layer. The present invention relates to a thin film forming method and apparatus for synthesizing such a protective film having excellent durability and slipperiness with high mass productivity.

Conventional technology Metal magnetic media is a new medium suitable for high density recording.
Many reports have been made from the past. The recording layer made of a ferromagnetic metal has a nonmagnetic portion such as an oxide of a nonmagnetic metal such as Cr or Ni or an oxide of a ferromagnetic metal such as CoO for the purpose of improving characteristics such as noise reduction. However, even in those cases, the basic magnetic characteristics are due to the ferromagnetic metal, and henceforth, in the present description, the recording layer including the ferromagnetic metal is collectively referred to as all of them. However, since the recording layer of these metal magnetic media is made of metal, friction with sliding against the magnetic head or the like is large, and there is a problem in stability and reliability. Therefore, various protective films for the purpose of protecting the recording layer have been studied mainly for organic thin films.

We clarified that a diamond-like carbon film (hereinafter abbreviated as DLC film), which is hard and has good slidability, is effective as this protective film (Japanese Patent Application No. 60-50031: magnetic recording medium), and metal magnetic We have developed a new film formation method suitable for thin protective film synthesis (Japanese Patent Application No. 59-2252: plasma injection CVD equipment, Japanese Patent Application No. 59-258038: high hardness carbon film formation method). This is a method for synthesizing a DLC film by spraying a plasma of a hydrocarbon gas containing hydrogen, which we call the plasma injection CVD method (PI-CVD method). FIG. 6 shows an outline of the PI-CVD apparatus. The metal magnetic thin film 15 is carried by a drive system composed of an unwinding roller 4, a winding roller 6, and rotating rollers 7a to 7e in the vacuum chamber 3. The tip of the plasma tube 1 is narrowed into a nozzle shape, the nozzle 1a is installed so as to face the can roller 6, and an excitation coil 8 is wound around the outer circumference. A mesh-shaped anode electrode is installed inside the plasma tube 1,
A potential difference is generated between the metal magnetic thin film 15 and the recording layer. The recording layer is normally at ground potential, but the can roller 6 is used for the purpose of preventing wrinkles, curls, and heat damage to the substrate.
In order to enhance the close contact between the metal magnetic thin film 15 and the recording layer, a potential difference may be set between the recording layer and the can roller 6. The hydrocarbon gas 13 and the argon gas 14 introduced into the plasma tube 1 are turned into plasma by the high frequency power applied from the high frequency power supply 11 to the excitation coil through the matching device 10. The ions in the plasma are accelerated in the direction of the metal magnetic medium 15 by the potential difference between the anode electrode 16 and the recording layer, and a current is generated in the recording layer. The plasma is sprayed onto the recording layer together with the ions accelerated by the pressure difference between the plasma tube 1 and the vacuum chamber 3 to synthesize the DLC film.

In the case of the PI-CVD method, the tip of the plasma tube 1 is squeezed into a nozzle shape, and the conductance of the nozzle 1a causes the plasma tube 1
And a pressure difference between the vacuum chamber 3 and the vacuum chamber 3. Neutral species in plasma such as radicals are efficiently sprayed to the recording layer due to this pressure difference, and form a DLC film together with accelerated ions. Thus, in the PI-CVD method, ions and neutral species in plasma are efficiently used by utilizing the pressure difference,
It is possible to synthesize DLC film at high speed. PI
-According to the CVD method, the film formation rate is 3000 Å / min or more.
The LC film can be synthesized and can be applied as a protective film for metal magnetic media that requires mass productivity.

As another method for forming a film on the surface of a continuously running film-shaped metal magnetic medium, the CVD method as shown in Patent Publication No. 60-38727 or 60-69825 (see FIG. 7) is reported. Has been done. In this, plasma excited by a plasma generation unit 19 installed in a part of the vacuum chamber 17 flows out to the surface of the metal magnetic medium 18 that continuously runs in the vacuum chamber 17, and a film is synthesized.

Problems to be Solved by the Invention However, when a DLC film is formed on the surface of a film-shaped metallic magnetic medium that continuously runs by a conventional CVD method including the PI-CVD method, the film formation area and film formation speed are increased to improve mass productivity. In order to improve, the following problems had to be solved.

First, in the PI-CVD apparatus, in order to efficiently blow the neutral species in the plasma onto the metallic magnetic medium 15, the plasma blowout portion is squeezed into a nozzle shape, and the pressure difference between the plasma tube 1 and the vacuum chamber 3 is reduced. Must be provided. For this reason, it was extremely difficult to increase the diameter of the nozzle 1a to expand the film formation area and cope with mass production.

Further, in the conventional CVD method shown in FIG. 7, it is difficult to control the film quality because the pressure is unlikely to be uniform in the film formation region 21. Further, since the flow of plasma and the film forming region 21 change depending on the flow rate, gas pressure, etc., control of the film thickness becomes difficult. Further, if the film formation rate is increased (plasma density is increased), the heat of plasma is accumulated in the metallic magnetic medium, and the metal magnetic medium is easily damaged by heat and deformed.
Further, when a bias is applied to the surface of the metal magnetic medium 18 or the anode electrode installed in the vacuum chamber / plasma generating unit for the purpose of accelerating the ions, the pressure difference between the plasma generating unit 19 and the vacuum chamber 17 is small, and thus high. When the gas pressure of the plasma generating part 19 is increased in order to form a film, spark discharge is likely to occur everywhere. Therefore, the vacuum chamber should be at least 0.
It is necessary to keep the pressure below 1Pa.

Secondly, when using ions such as the PI-CVD method, a current is generated in the recording layer during film formation. When trying to increase the deposition rate in order to support mass production (when synthesizing a DLC film by the PI-CVD method, in order to increase the deposition rate, the pressure inside the plasma tube, the potential difference between the anode electrode and the recording layer Is increased), the current flowing through the recording layer increases. When a current flows, Joule heat is generated according to the resistance, and the recording layer generates heat.
Increasing the deposition rate increases the amount of heat generated by the recording layer, causing deterioration of the recording layer, peeling of the DLC film, and sometimes the substrate (base film).
-Problems such as heat damage to the recording layer occur. This problem will be specifically described by taking the PI-CVD method shown in FIG. 6 as an example.

When a plasma containing accelerated ions is sprayed from the nozzle 1a onto the metal magnetic medium 15, the nozzle 1a rotates the roller.
An electric current is generated over 7c. In the case of this example, a potential difference is set between the can roller 6 and the metal magnetic medium 15 in order to enhance the close contact therebetween. The unwinding roller 4, the winding roller 5, and the rotating rollers 7a to 7d are installed in a potentialless state, and the recording layer potential on the surface of the metal magnetic medium 15 is set from the rotating roller 7e. Therefore, the current flows from the nozzle 1a to the surface of the metal magnetic medium 15 on the rotating roller 7e, and heat is generated in the recording layer. When the flowing current is large, the amount of heat generated inevitably increases, and the magnetic characteristics of the recording layer change or the adhesive force between the recording layer and the DLC film deteriorates. The damage due to heat generation is most severe between the rotating rollers 7c and 7e. This is because there is no place for heat to escape. In comparison with this, heat is radiated to the can roller at a portion in close contact with the can roller 6, so that damage due to heat generation is small. However, thermal damage occurs where the metal magnetic medium 15 is deformed or the like and adhesion is insufficient. Such heat damage and alteration of the recording layer significantly deteriorate the characteristics of the metal magnetic medium and reduce the reliability.

In view of the above points, the present invention is a homogeneous and easy-to-control DLC over a continuously running film-shaped metal magnetic medium surface.
It is an object of the present invention to provide a method for forming a protective film for a metal magnetic medium suitable for mass production capable of synthesizing a film and an apparatus therefor.

Means for Solving Problems In the present invention, as a means for solving these problems, a plasma tube is installed so that the gap between the plasma outlet and the film-forming roller is uniform, and this gap is By controlling the pressure difference between the plasma tube and the first vacuum chamber while synthesizing the DLC film, one or more potential rollers are formed on the film-forming roller and in the vicinity of the recording layer of the metal magnetic medium. The Joule heat generated by the electric current is efficiently radiated to the film-forming roller by preventing the damage and the characteristic deterioration due to the heat.

Action The feature of the present invention is that the conductance is adjusted by controlling the gap between the plasma outlet of the plasma tube and the film forming roller, and the pressure difference is set between the plasma tube and the first vacuum chamber. . Here, conductance is the reciprocal of resistance when gas flows (generally called exhaust resistance), and represents the ease of gas flow. The gas introduced into the plasma tube flows out into the main vacuum chamber through the plasma outlet. At this time, if the gap between the plasma outlet and the film forming roller is made small, the exhaust resistance becomes large (that is, the conductance becomes small), and it becomes difficult for gas to flow out, and a pressure difference occurs between the plasma tube and the main vacuum chamber. . Even if the size and shape of the plasma outlet are changed, the conductance can be kept constant by appropriately controlling this gap. Therefore, the pressure in the plasma tube can be increased while keeping the pressure in the vacuum chamber at 0.1 Pa or less, and the plasma outlet can be further increased.In addition, the pressures in the plasma tube and the plasma outlet can be made almost uniform at this time. Since it is maintained, the DLC is uniformly and well controlled over a wide range.
Membranes can be synthesized.

Also, since the pressure in the main vacuum chamber is kept at least one digit lower than the pressure in the plasma tube, even if a bias is applied to the anode electrode installed in the plasma tube to accelerate the ions, The spark discharge at is less likely to occur. Therefore, the pressure inside the plasma tube and the bias applied to the anode electrode can be increased to increase the deposition rate of the DLC film. Further, in the present invention, the film-shaped metal magnetic medium is wound around the film-forming roller, and if necessary, a potential difference is provided between the film-forming roller and the recording layer to increase the sticking force so that the film is run. The heat is quickly dissipated to the film forming roller to prevent heat damage and heat deformation of the metal magnetic medium.

When the plasma containing ions is blown onto the medium, a current is generated between the anode electrode and the potential roller through the plasma and the recording layer of the medium. In order to run the medium wound around the film forming roller, a regulating roller is required near the film forming roller at the beginning and end of winding (hereinafter, the former is referred to as a winding start proximity roller, and the latter is referred to as a winding end proximity roller). . If a potential roller is installed between the plasma outlet and the proximity roller, current flows from the anode electrode to the potential roller through the plasma and recording layer. The Joule heat generated in the recording layer due to the electric current is quickly radiated to the film-forming roller around which the magnetic metal medium is wound, so the heat deteriorates or damages the recording layer and the adhesion between the recording layer and the DLC film deteriorates. Can be prevented. If a potential difference is provided between the recording layer and the film-forming roller to increase the adhesion between the film-forming roller and the metal magnetic medium, the heat dissipation will be even quicker, which is more effective. By providing a plurality of potential rollers and installing appropriately selected resistors in series, the current can be separated into a plurality of currents. If the potential rollers are set so that the current systems do not overlap each other, the Joule heat is separated, which is effective for preventing the characteristic deterioration due to heat and improving the film formation rate.

Embodiment 1 FIG. 1 shows a first embodiment of the present invention. The film-shaped metal magnetic medium 34 (hereinafter abbreviated as medium) is wound around the film-forming roller 27 from the unwinding roller 23 via the rotating rollers 25a and 25b, and is wound on the winding roller 26 via the rotating rollers 25c, d and e. It is wound up. In the recording layer on the surface of the medium 34, a potential is set by the potential roller 24 so that a potential difference is formed between the medium 34 and the film forming roller 27, and the medium 34 is firmly attached to the film forming roller 27 by this potential difference.

The main vacuum tank 22 and plasma tube 28 are vacuum pumped to 10 ^-2 Pa
After setting the pressure below, the pressure in the plasma tube 28 becomes 0.5P.
Introduce hydrocarbon gas and argon gas so that the pressure is a or higher. The introduced gas flows out to the main vacuum tank 22 through the plasma outlet 36, at this time, the film forming roller 27 and the plasma outlet 36 so that the pressure in the main vacuum tank 22 is 0.1 Pa or less. The gap between them is set by the Z-axis moving table 29. Due to the low conductance due to the gap between the deposition roller 27 and the plasma outlet 36, the plasma outlet
Even when 36 is larger than the cross section of the plasma generating portion 37, the pressure in the plasma tube 28 is kept substantially uniform. The gas in the plasma tube 28 is turned into plasma by the high-frequency power applied to the excitation coil 31, and the ions in the plasma are accelerated toward the medium 34 by the potential difference between the anode electrode 30 and the recording layer.
Ions are accelerated along the line of electric force between the anode electrode 30 and the recording layer, and even if the plasma outlet 36 is larger than the plasma generator 37, the line of electric force is substantially uniform, and the ions are evenly distributed near the plasma outlet 36. Be accelerated. Also the plasma outlet
The plasma density around 36 is almost uniform because the pressure is constant. As described above, in the vicinity of the plasma outlet 36, the plasma density and the acceleration of ions are both uniform, and a uniform DLC film having uniform film quality and film thickness over a wide range can be synthesized with good control. At this time, the vacuum chamber holds a pressure of 10 ^-1 Pa or less, and since the high frequency power is shielded by the sub vacuum chamber 35 and does not leak into the main vacuum chamber 22, the main vacuum chamber 22
Glow discharge inside does not occur. Further, even if the potential applied to the recording layer and the anode electrode 30 is increased, spark discharge is less likely to occur in the main vacuum chamber 22.

When the ions reach the recording layer, a current is generated between the anode electrode 30 and the potential roller 24 through the plasma and the recording layer. The Joule heat in the recording layer generated by the current quickly moves to the film forming roller to which the medium 34 is firmly attached, so problems such as heat damage to the medium 34 due to heat and peeling of the CLD film are unlikely to occur. . Moreover, since the pressure in the main vacuum chamber is kept lower than the pressure in the plasma tube by one digit or more,
Even when a bias is applied to the anode electrode installed in the plasma tube to accelerate the ions, spark discharge is less likely to occur in the main vacuum chamber. Therefore, the pressure inside the plasma tube and the bias applied to the anode electrode can be increased to increase the deposition rate of the DLC film. Further, in the present invention, the film-shaped metal magnetic medium is wound around the film-forming roller, and if necessary, a potential difference is provided between the film-forming roller and the recording layer to increase the sticking force so that the film is run. The heat is quickly dissipated to the film forming roller to prevent heat damage and heat deformation of the metal magnetic medium. In this embodiment, a potential difference is provided between the recording layer and the film-forming roller 24 to strengthen the sticking. However, if no thermal damage occurs, the potential difference may be set to 0 and only the sticking due to the tension of the medium 34 may be used. Absent.

The outer circumference of the plasma tube 28 including the plasma generation unit 37 in which the excitation coil 31 is installed is held by the sub-vacuum tank 35 to a vacuum level similar to that of the main vacuum tank 22. This is to prevent the plasma 28 from being damaged by atmospheric pressure when the plasma tube 28 is enlarged with the expansion of the film formation area, and the plasma tube 28 is pushed into the main vacuum chamber 22 due to the pressure difference between the atmosphere and the plasma tube 28 and the plasma The set gap between the outlet 36 and the film forming roller 27 is prevented from changing. Further, the high frequency power applied to the excitation coil 31 is prevented from leaking to the main vacuum chamber 22, and the gas flowing out from the plasma outlet 36 is prevented from flowing into the vicinity of the excitation coil 31. Therefore, when high-frequency power is applied to the excitation coil 31, other than inside the plasma tube 28, for example, the main vacuum chamber 22
Glow discharge does not occur in the sub-vacuum tank 35, and modulation of the traveling system due to high-frequency power is prevented. In the present embodiment, in adjusting the gap between the plasma outlet 36 and the film forming roller 27, the entire plasma tube 28 was moved using the Z-axis moving table 29. However, as shown in FIG. Department
38 and the plasma generating tube 39 may be divided and joined by the bellows tube 41, and the gap adjusting jig 40 may be used to move and adjust the plasma outlet port 38.

The gap between the plasma outlet 38 and the film forming roller 27 varies depending on the size and shape of the plasma outlet 38, the required pressure difference, etc., but when using a 300 mm × 120 mm plasma outlet, it is efficient. A gap of 1 mm or less was required to form the DLC film. In addition, when the relationship between the pressure in the plasma tube and the DLC film formation rate was examined in this example, see Table 1, D
In order to synthesize an LC film efficiently, the pressure inside the plasma tube should be
It is necessary to make it 0.5 Pa or more, more preferably 10 Pa or more.

FIG. 3 shows a second embodiment of the present invention. The plasma tube 46 has three plasma generators 43 and one large plasma outlet.
It consists of 42 and. When the plasma outlet 42 is made large in consideration of mass productivity, a plurality of plasma generators 43 may be provided. Plasma outlet 42 and film forming roller 4
Since the conductance due to the gap between the plasma tube and the tube is small, the pressure in the plasma tube 46 is constant, and if the high-frequency power and DC bias applied to the excitation coil and the anode electrode 47 installed in each plasma generator are the same, the plasma flow Exit 4
The plasma density of 2 and the ion acceleration state are almost constant. Therefore, it becomes possible to synthesize a uniform DLC film in a wider range.

FIG. 4 shows a third embodiment of the present invention. The basic structure is almost the same as that of the first embodiment, but the feature of this embodiment is that the plasma outlet 53 and the winding start proximity roller 49a and the potential roller between the plasma outlet 53 and the winding end proximity roller 49b, respectively. 50a, b installed, each potential roller 50a, b and DC
The variable resistors 51a and 51b are provided in series with the power sources 52a and 52b. In the case of the present embodiment, the current flowing from the anode electrode 54 to the potential roller is the anode electrode 54-plasma-recording layer-
The electric current is divided into two systems of potential roller 50a-variable resistor 51a-DC power source 52a and anode electrode 54-plasma-recording layer-potential roller 50b-variable resistor 51b-DC power source 52b. (The current flowing in the former is referred to as Ia and the latter is referred to as Ib.) The currents Ia and Ib in each system are deteriorated and deteriorated in characteristics of the recording layer due to Joule heat, and the adhesive force between the recording layer and the DLC film is deteriorated. Since it is possible to increase the maximum current (hereinafter abbreviated as "allowable current") without any problem, the current flows between the anode electrode and the potential roller as compared with the conventional example in which the allowable current value of one current system is limited. The current I (I = Ia + Ib) can be increased. Therefore, the film forming rate can be increased, and a medium excellent in mass productivity can be obtained. The ratio of currents Ia and Ib is variable resistor 5
It can be set arbitrarily by selecting the ratio of 1a and b (by Kirchoff's law), and by Joule heat
When forming a film on the surface of a recording layer (for example, when the thermal expansion coefficient of the recording layer and the DLC film differ greatly) that deteriorates the adhesion with the DLC film, adjust the variable resistance to increase Ia and decrease Ib. By setting the ratio of the values 51a and b, it is possible to prevent deterioration of the adhesive force due to heat after film formation. In the case of this embodiment,
Although the potential rollers 50a and 50b are provided so as to contact the recording layer of the medium 48 wound around the film forming roller, the winding start roller 49a and the winding end roller 49b may be used as the potential rollers depending on the magnitude of the current.

FIG. 5 shows a fourth embodiment of the present invention. In order to improve mass productivity, a plurality of plasma tubes may be installed on one film forming roller. Here, the case where there are two plasma tubes as shown in FIG. 5 will be described. A potential roller is installed between the first plasma outlet 59a and the second plasma outlet 59b, and together with the potential rollers 56a and 56b installed on the winding start side and the winding end side of the film forming roller 58, the recording layer. Apply a potential to. Potential roller 59a and potential roller 59c
The electric current flowing in the recording layer between the variable resistances 57a and 57c is "the recording layer between the first anode electrode 61a-plasma-the first plasma outlet 59a and the potential roller 56a-the potential roller 56a". First Anode Electrode 61a-Plasma-
The recording layer between the first plasma outlet 59a and the potential roller 56c to the potential roller 56c "is separated into two systems. Similarly second
When synthesizing the DLC film with the plasma tube 60b of "2nd anode electrode 61b-plasma-recording layer between second plasma outlet 59b and potential roller 56c-potential roller 56c" and "second
Anode Electrode 61b ~ Plasma ~ Second Plasma Outlet 5
An electric current flows through two systems, that is, the recording layer between 9b and the potential roller 56b to the potential roller 56b ". Since the current systems do not overlap each other, the Joule heat is quickly radiated to the film forming roller 58. Therefore, even if there are two plasma tubes, there is no heat damage or characteristic deterioration of the medium 55 due to heat, and mass productivity is excellent.
The same applies when the number of plasma tubes increases. If the potential rollers of the same potential are installed between the start and end of the film formation roller and each plasma outlet, the current from each plasma tube can be separated without duplication. According to the present invention, the medium can be synthesized with good mass productivity.

EFFECT OF THE INVENTION The present invention provides a method for forming a protective film for a metal magnetic medium capable of continuously and rapidly synthesizing a diamond-like carbon film on the recording layer surface of a metal magnetic medium on a film having a ferromagnetic metal thin film as a recording layer, and The apparatus is provided, and a metal magnetic medium having excellent durability and reliability can be obtained with good mass productivity, and the effect is very large.

[Brief description of drawings]

FIG. 1 is a principle view of a thin film forming apparatus according to the first embodiment of the present invention, FIG. 2 is a partially enlarged view of a part of the apparatus, and FIG. 3 is a thin film forming apparatus according to the second embodiment of the present invention. FIG. 4 is a principle diagram of an apparatus, FIG. 4 is a principle diagram of a thin film forming apparatus in a third embodiment of the present invention, FIG. 5 is a principle diagram of a thin film forming apparatus in a fifth embodiment of the present invention, and FIG. PI-CVD
FIG. 7 is a principle diagram of the apparatus, and FIG. 7 is a principle diagram of a conventional plasma CVD apparatus. 24 …… Potential roller, 27 …… Film forming roller, 28 …… Plasma tube, 36 …… Plasma outlet.

Claims (11)

[Claims] 1. A surface of a film-shaped metal magnetic medium having a recording layer made of a ferromagnetic metal that continuously wraps around a film-forming roller in a pressure of 0.1 Pa or less, and 0.5 Pa or more containing accelerated ions. A method of forming a protective film for a metal magnetic medium, which comprises bringing a plasma of a hydrocarbon gas held at a pressure of 1 to contact with the recording layer to synthesize a diamond-like carbon film. 2. A running system in which a film-shaped metal magnetic medium having a recording layer made of a ferromagnetic metal is wound around a film-forming roller to run, and a main vacuum chamber in which the running system is installed.
A plasma generating unit having a plasma generating unit for converting hydrocarbon gas into plasma and a plasma outlet having a plasma outlet for discharging the plasma; an accelerating unit for accelerating ions in the plasma in the direction of the metal magnetic medium; An apparatus for forming a protective film for a metal magnetic medium, which is composed of an internal sub-vacuum tank. 3. The protective film forming apparatus for a metal magnetic medium according to claim 2, wherein the plasma tube is installed so that a gap between the film forming roller and the plasma outlet is uniform. 4. The protective film forming apparatus for a metal magnetic medium according to claim 3, wherein the gap between the film forming roller and the plasma outlet is 1.0 mm or less. 5. The protective film forming apparatus for a metal magnetic medium according to claim 3, wherein the cross-sectional area of the plasma outlet is larger than that of the plasma generating portion. 6. A protective film forming apparatus for a metal magnetic medium according to claim 3, wherein the plasma tube is composed of a plurality of plasma generating sections. 7. The protective film forming apparatus for a metal magnetic medium according to claim 2, wherein at least one roller constituting the running system is a potential roller for setting the potential of the recording layer. 8. The protective film forming apparatus for a metal magnetic medium according to claim 7, wherein the potential roller has a potential different from that of the film forming roller. 9. The protective film forming apparatus for a metal magnetic medium according to claim 8, wherein the potential roller is installed so as to come into contact with the recording layer on the surface of the metal magnetic medium wound around the film forming roller. 10. The protective film forming apparatus for a metal magnetic medium according to claim 8, wherein the potential roller is installed so as to come into contact with the recording layer on the surface of which the diamond-like carbon film is not yet synthesized. 11. The protective film forming apparatus for a metal magnetic medium according to claim 2, wherein the accelerating means uses a potential difference between the anode electrode and the recording layer installed in the plasma tube.