JP2000239849A - Continuous plasma cvd method and cvd device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a stable continuous thin film having low inside stress and high durability and free from secular deterioration on the surface of a wide and long flexible medium. SOLUTION: This is a method for continuously forming a thin film by exposing a wide and long flexible substrate 1 to the inside of plasma jointly using microwave plasma and RF plasma while it is run along a coating drum 5, microwaves are radiated from a linear array antenna 11 provided so as to be faced to the whole face of the width of the coating drum 5 via a wave-guide to make an introduced gas into plasma, and, as to the RF plasma, while a bias potential is applied by an RF generating source 12 connected to the drum 5 electrically insulated from a vacuum tank 2, an introduced gas is made into plasma, and, by exposing the flexible substrate 1 to the inside of these two kinds of plasma, a thin film can widely and continuously be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous plasma CVD method and a CVD apparatus capable of forming a film in a wide range at a high speed, and more particularly to a flexible magnetic tape having a magnetic recording layer of a ferromagnetic metal thin film. The present invention relates to a continuous plasma CVD method and a CVD apparatus capable of forming a surface protective layer having high durability and small internal stress of a film on a surface of a shaku original fabric at a high speed.

[0002]

2. Description of the Related Art A magnetic recording medium such as a magnetic tape having a magnetic recording layer made of a ferromagnetic metal layer made of a ferromagnetic metal or an alloy thereof has been developed with increasing recording density. How to reduce the track width of the head, increase the relative speed between the head and the medium and the number of heads,
Furthermore, such as improving the surface smoothness of the base film,
The load on the media surface is only increasing.

For example, a vapor deposition tape generally developed for Hi8 is coated with an oxide film formed by forcibly oxidizing the outermost surface during ferromagnetic layer deposition, and provided with a lubricant layer to provide a running durability. Maintain their sexuality. Although these surface treatment methods are effective in the current Hi8 VTR, they are very unlikely to be compatible with the next-generation VTR.

[0004] In order to solve this problem, various studies have been made to form a surface protective film on the magnetic recording layer. In particular, in recent years, researches on amorphous carbon films, diamond-like carbon films (DLC films), other organic films, and metal oxide inorganic protective films that can be formed by a sputtering method or a plasma CVD method have been actively conducted. Have been done. In particular, the DLC film literally has a property close to that of diamond, and has been spotlighted as a protective film having high hardness, excellent durability, and being dense and rich in corrosion resistance.

[0005]

The DLC film formed by the sputtering method is generally formed by using a graphite target with an argon gas or a sputtering gas obtained by mixing a hydrogen gas or a hydrocarbon gas with the argon gas. However, the DLC film formed by the sputtering method has a large change in the durability with respect to the film thickness, and the durability decreases as the film thickness decreases (for example, by Yamamoto; tribology of a carbon protective film for a disk; surface technology). Vol.44, No.1
0, 1993).

For this reason, if the thickness of the protective film is increased so as not to impair the durability, there is a problem that the spacing loss increases and the recording / reproducing characteristics deteriorate.

Further, a DL formed by a plasma CVD method is used.
The C film is generally formed by a CVD method using RF plasma (for example, Japanese Patent Publication No. 6-1549), and although a high-hardness and dense thin film can be formed in a wide width as described above, Since the internal stress of the film is extremely large, when the film is formed on the surface of a flexible medium, there arises a problem that the medium itself is deformed.

[0008] On the other hand, the price competition for recording media such as magnetic tapes is intensifying year by year, and it is an important point how the production cost can be reduced and stable supply can be achieved. For this purpose, it is indispensable to improve productivity, and it is a big problem to increase the film formation width, film formation length, and film formation speed.

In forming a protective film by a sputtering method, a slow film formation rate is a major problem. In the plasma CVD method, an RF plasma CVD method using an induction type CVD apparatus or an RF plasma CVD method using a counter electrode type CVD apparatus is used.

In the former, although the film forming range is wide and a relatively high film forming speed can be obtained, there is a problem in that the medium is deformed because the internal stress of the CVD film becomes large as described above. Therefore, as a CVD method for relaxing internal stress, a plasma CVD method using both microwave and RF bias has been studied (for example, A. Raveh et al.
Deposition and properties
of diamondlike carbon fi
lms produced in microwave
and radiofrequency plasma
a, J. et al. Vac. Sci. Technol. A10
(4), described in Jul / Aug 1992). However, in the CVD method using both microwaves and RF bias, a circular mode is generally used as a microwave propagation mode, so that the microwave emission range is small. This is extremely difficult and poses a problem when considering productivity.

According to the present invention, as described above, when the thickness is reduced as in a film formed by the sputtering method, the durability is deteriorated, and the internal stress is large as in a film formed by the RF plasma CVD method. It solves the problems of the conventional technology, such as the inability to form a film on a large area, which the technology using microwaves has until now. An object is to continuously form a CVD thin film having high durability and reduced internal stress of the film at a high film forming rate.

[0012]

As a method for achieving the above-mentioned object, there is provided a method of forming a thin film while continuously exposing a magnetic tape along a rotating drum to plasma using a combination of microwave plasma and RF plasma. In the above, microwaves generated by a microwave generation source provided outside the vacuum chamber are radiated through a waveguide from a linear antenna disposed so as to face a predetermined position in a drum width direction.

The gas introduced from the vicinity of the antenna is converted into plasma to generate microwave plasma, and while applying a bias potential by an RF generator connected to a rotating drum electrically insulated from the vacuum chamber body. In the plasma generated by converting the introduced gas into plasma, it is effective to cause the wide and long substrate to run along a rotating drum having a diameter of 300 mm or more, and to continuously transport the magnetic tape to the film forming chamber. This makes it possible to form a stable thin film having high durability and extremely small internal stress on the surface of the wide and long substrate.

The reason why the internal stress is smaller than that in the case of RF plasma alone is not completely clear and cannot be surmised. However, the ionization efficiency in the plasma is high, and the internal surface stress during the film formation is low. This is probably because the mobility of the arrived particles and ions is large, and the film grows in a stable state with small stress and distortion.

At this time, the diameter of the rotating drum is 300 mm
Below this, the internal stress of the film increases, and the diameter of the rotating drum is desirably 300 mm or more.

In this case, since it is technically difficult to uniformly emit microwaves in the width direction from one linear antenna, a plurality of linear antennas are required to obtain a uniform film thickness over a wide range. It is desirable to emit microwaves from the antenna.

In order to efficiently obtain a wide film forming area,
It is extremely effective that the linear antenna is a slot type linear array antenna having a ridge waveguide and a plasma converging magnet inside, or a loop antenna type linear array antenna. In addition, when increasing the deposition rate, it is possible to arrange a plurality of micro sources and linear antennas to increase the deposition area.

When the flexible substrate is made of a dielectric material, RF is applied to the take-up roll and the unwind roll when RF is applied to the rotating drum. Plasma is generated in the system chamber, and a source gas having a low ionization efficiency, which is not sufficiently decomposed by microwaves, adheres to the substrate surface, and it is difficult to form a film having high hardness.

Therefore, the degree of vacuum in the traveling system chamber needs to be higher than the degree of vacuum in the film forming chamber. In addition, in order to apply RF bias efficiently, it is effective to provide a shield plate along the drum surface to control the area exposed to plasma and to increase the bias voltage applied per unit area. It is. Further, by providing this shield plate, it is possible to suppress the diffusion of plasma to the ineffective portion. This shield plate is 1
It is desirable that the interval is not less than 10 mm and not more than 10 mm.

Further, as described above, self-bias is generated in the flexible substrate by RF, and when the unwinding, winding and guide rolls in the traveling chamber are electrically conductive, a current flows on the substrate surface. , Causing damage to the substrate.

For this reason, it is necessary to use an insulating material that electrically blocks high frequency for all components that come into contact with the substrate, such as unwinding, winding and guide rolls in the traveling room.

As described above, by utilizing microwave plasma using a linear antenna and plasma generated by applying an RF bias, a thin film having a long and wide substrate can be formed continuously and with very little internal stress. Therefore, it is particularly effective as a means for forming a surface protective layer such as a magnetic tape having a ferromagnetic metal layer made of a ferromagnetic metal or an alloy thereof as a magnetic recording layer on a wide flexible long base. Thus, it is possible to obtain a surface protective film having running durability comparable to that of the protective layer even when formed with a protective layer thickness capable of minimizing the spacing loss due to the gap, and not causing deformation due to internal stress.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION As an example of the present invention, a surface protective layer is formed on a surface of a vapor deposition source using a ferromagnetic metal layer as a magnetic recording layer by using a continuous plasma CVD apparatus shown in FIGS. An example in which is formed will be described. Figure 1 shows continuous CVD
FIG. 2 is a front view of the apparatus, and FIG.

First, using a continuous vacuum evaporation apparatus for forming another magnetic film, pure Co metal was introduced into a long polyethylene terephthalate film having a thickness of 6 μm, a width of 500 mm and a roughness of 2 nm Ra while introducing a predetermined amount of oxygen gas. Dissolve / evaporate, lower layer 80 nm thick, upper layer 80 nm thick, 490 mm
A 500 mm-wide vapor-deposited raw material having a magnetic recording layer made of Co-O having a two-layer structure having a width was prepared.

The raw material is used as a substrate 1 shown in FIG. 1 as an unwinding roll 3 made of ceramic material provided in a vacuum chamber 2 and a guide roll 4 and a cooled coating drum having a diameter of 300 mm or more. Drum) 5
Winding roll 6 made of surface and ceramic material
Was loaded to run.

Also, the degree of vacuum in the film forming chamber and the traveling system chamber can be independently adjusted by using the partition plate 7, and the area exposed to the plasma can be controlled at intervals of 1 mm or more and less than 10 mm from the rotating drum 5. Earth shield plate 8
Was provided.

Next, the microwave generated by the microwave generating source 9 is passed through a waveguide 10 and a flange provided with a ceramic window to a 200-mm-wide slot-type linear array antenna having a ridge waveguide therein. Three antennas 11 are arranged as shown in FIG. 1, and microwaves are radiated from each of them. A predetermined amount of methane gas, argon gas, and hydrogen gas are mixed into a film forming chamber from gas introduction nozzles installed near the antennas. And a plasma is generated while applying a bias by the RF generation source 12 connected to the rotating drum 5, and is 490 m thick with a thickness of 10 nm.
An m-width DLC film was formed to produce a raw magnetic tape.
At this time, the degree of vacuum in the traveling system chamber was set to a sufficiently high vacuum that plasma was not generated.

The raw magnetic tape was loaded into a coating machine, and F was diluted with FC-77 (3M), a fluorine-based solvent.
Omblin-Z-DOL (manufactured by Montedison) solution is applied / dried to form a lubricant layer, and a coating liquid in which carbon black is dispersed as a powder in a binder is applied / coated.
After drying to form a back coat layer, the tape was cut into a predetermined width to produce a magnetic tape A.

Further, a continuous plasma CVD shown in FIG. 1 is provided with a 550 mm-width loop antenna type linear array antenna having a ridge waveguide and a plasma focusing magnet as a linear antenna on the same vapor deposition source.
Using a device, a DLC film having a thickness of 10 nm and a width of 490 mm was formed, and a magnetic tape B was produced through the same coating process as that for the magnetic tape A.

Further, a magnetic tape A was placed on the same evaporation source.
Using the continuous plasma CVD apparatus shown in FIG. 1 used for the preparation of the above, a predetermined amount of silane gas, oxygen gas, and argon gas were mixed and introduced instead of methane gas, argon gas, and hydrogen gas, and silicon oxide having a thickness of 10 nm was introduced. A magnetic tape C was prepared in the same manner as the magnetic tape A except that a protective layer was formed.

In addition to the above, a 10 nm-thick DLC using the same deposition source and an existing RF plasma CVD apparatus.
A film was formed, and a magnetic tape E was manufactured through the same coating process, and a magnetic tape E was manufactured by omitting only the protective film forming process.

Next, for the magnetic tapes A, B, C, D and E, a high-speed still life test (head relative speed: 11.3)
m / sec, winding angle: 220 degrees, tape tension: 1
0gf, measure the time until the playback output starts to fluctuate rapidly)
Was done. The result is shown in FIG.

Each of the magnetic tapes on which the DLC protective film or the silicon oxide protective film was formed exhibited a still life of about 10 hours, indicating that the still durability was remarkably improved as compared with about 15 minutes without the protective film. .

FIG. 2 shows a steel ball sliding test (sliding speed: 2).
m / min, load: 5 g, slider: 1/4 inch diameter, S
UJ-2, the number of times until a part of the sliding portion starts to be peeled and damaged) is measured.

According to this measurement method, the magnetic tapes A and C exhibited stable running properties even after 1000-pass sliding, and maintained a low friction coefficient of about 0.2.

Although not shown in the figure, the magnetic tape B showed almost the same tendency.

On the other hand, although the magnetic tape C runs stably up to about 400 passes, the friction coefficient tends to gradually increase. When the sliding portion after sliding the magnetic tape C for 1000 passes was observed, many cracked streaks perpendicular to the sliding direction were observed with an optical microscope, although it could not be confirmed with the naked eye.

Next, the magnetic tapes A, B, C, and D are
A high-speed still life test is performed after standing in a high-temperature and high-humidity atmosphere at 90 ° C and a high humidity for 90% RH. The quality of the protective film changes due to the internal stress of the protective film, and the running durability deteriorates with time. FIG. 3 shows the results of evaluation as indices for causing.

The magnetic tapes A and C do not undergo any significant deterioration even after storage for 25 days and exhibit stable still durability (not shown, but the same results are obtained for the magnetic tape B), while the magnetic tape D does not. Still life tended to decrease as storage days increased.

Also in this case, cracked streaks perpendicular to the head scanning direction as observed in the sample after the steel ball sliding test were observed, indicating that the film quality was changed.

When a continuous plasma CVD apparatus using a microwave and RF plasma equipped with a linear antenna is used as described above, a film can be continuously formed on a long flexible substrate, and mass production efficiency can be greatly improved.

[0042]

As described above, continuous plasma CVD according to the present invention.
By using the method and the apparatus, it is possible to form a thin film with a wide range, high durability and extremely low internal stress on the surface of the long flexible substrate, and in particular, a ferromagnetic metal or an alloy thereof on a wide flexible long substrate. It is effective as a means for forming a surface protective layer such as a magnetic tape having a ferromagnetic metal layer as a magnetic recording layer, and is formed with a protective layer thickness capable of minimizing a spacing loss due to a gap between a head and a medium. Thus, it is possible to obtain a surface protective film having comparable running durability and extremely little deterioration over time.

[Brief description of the drawings]

FIG. 1 shows a continuous plasma CV according to an embodiment of the present invention.
It is a front view of D apparatus.

FIG. 2 is a side view of the same.

FIG. 3 is a diagram showing the results of a steel ball sliding test of magnetic tapes A, C, D and E.

FIG. 4 is a view showing still life test results of magnetic tapes A, C, and D after storage at high temperature and high humidity.

FIG. 5 is a table showing still life times of magnetic tapes A, B, C, D, and E;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Vacuum tank 3 Unwind roll 4 Guide roll 5 Coating drum 6 Take-up roll 7 Partition plate 8 Shield plate 9 Microwave generation source 10 Waveguide 11 Linear antenna 12 RF generation source 13 Vacuum exhaust system

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kichio Asano 1-88 Ushitora, Ibaraki City, Osaka Prefecture Inside Hitachi Maxell Co., Ltd. (72) Tetsuo Mizumura 1-188 Ushitora, Ibaraki City, Osaka Prefecture No. Hitachi Maxell Co., Ltd. (72) Inventor Ryo Yano 1-88 Ushitora, Ibaraki-shi, Osaka F-term in Hitachi Maxell Co., Ltd. 4K030 AA10 AA16 AA17 BA28 FA01 FA03 FA14 GA02 GA04 GA14 HA01 HA04 KA12 KA20 LA20 5D112 AA07 AA22 BC05 FA10 KK02

Claims (10)

[Claims] 1. A method in which a continuous flexible substrate is moved along a rotary drum disposed in a vacuum chamber, and a flexible substrate connected to a rotary drum electrically insulated from the vacuum chamber body.
A continuous plasma CVD method characterized in that a thin film is continuously formed by exposing to a plasma using a combination of RF plasma and microwave plasma by an F oscillator. 2. The vacuum chamber according to claim 1, wherein the vacuum chamber uses a partition plate to form a film forming chamber in which a thin film is formed by plasma using microwave plasma and RF plasma in combination, and an unwinding and winding roll. A continuous plasma CVD method, which is divided into provided traveling system chambers, and wherein the degree of vacuum in the film forming chamber and the traveling system chamber can be independently adjusted. 3. The device according to claim 1, wherein microwaves generated by a microwave oscillator provided close to the vacuum chamber are arranged to face the rotating drum via a waveguide. Or continuous plasma CVD characterized by radiating into a vacuum chamber from a plurality of linear antennas
Law. 4. The rotary drum according to claim 1, wherein a diameter of the rotary drum electrically insulated from the vacuum chamber main body is 300 mm.
A continuous plasma CVD method characterized by the above. 5. The method according to claim 2, wherein one or several guide rolls for feeding the unwinding roll and the flexible substrate provided in the traveling system chamber to the rotary drum, and one or several guide rolls for feeding the unwinding roll and the flexible substrate from the rotary drum to the take-up roll. A continuous plasma CVD method, wherein an electrically insulating material is used as a material for the guide roll and the take-up roll. 6. An R connected to a rotary drum electrically insulated from the vacuum tank body while running a continuous flexible substrate along a rotary drum disposed in the vacuum tank.
A continuous plasma CVD apparatus characterized in that a thin film is formed continuously by exposing to a plasma in which RF plasma and microwave plasma are used together by an F oscillator. 7. The vacuum chamber according to claim 6, wherein a partition plate is used as the vacuum chamber, and a film forming chamber in which a thin film is formed by plasma using microwave plasma and RF plasma together, and an unwinding and winding roll. A continuous plasma CVD apparatus, which is divided into a traveling system chamber provided, wherein the degree of vacuum in the film forming chamber and the traveling system chamber can be independently adjusted. 8. The device according to claim 6, wherein microwaves generated by a microwave oscillator provided near the vacuum chamber are arranged so as to face the rotating drum via a waveguide. Or continuous plasma CVD characterized by radiating into a vacuum chamber from a plurality of linear antennas
apparatus. 9. The rotary drum according to claim 6, wherein the diameter of the rotary drum electrically insulated from the vacuum chamber main body is 300 mm.
A continuous plasma CVD apparatus characterized by the above. 10. The unwinding roll provided in the traveling system chamber, one or several guide rolls for sending out a flexible substrate to a rotary drum, and 1 to 1 for sending out a flexible roll from a rotary drum to a take-up roll. A continuous plasma CVD apparatus characterized in that an electrically insulating material is used as a material for several guide rolls and a take-up roll.