JPH08194942A - Plasma CVD film forming method and magnetic recording medium produced thereby - Google Patents

Abstract

(57) [Summary] [Object] The present invention provides a remote plasma CVD film forming method in which a plasma generation source and a film forming route are improved, and a metal thin film type magnetic film having a carbon film having an improved wear resistance applied to the method. The purpose is to realize a recording medium. A carbon film having an increased ion ratio by inserting a filter 9 into a plasma generation source 6 by a remote plasma CVD film forming method to trap unnecessary decomposed gas molecules to prevent mixing in the film formation. By achieving the film formation of the above, and by curving the migration path of radical species so as not to directly damage the target surface of the recording medium surface by the ultraviolet light, a carbon film with improved film quality was realized, which was used for metal thin film magnetic recording. Provided is a metal thin film type magnetic recording medium having improved wear resistance when applied to a medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD film forming method for decomposing and polymerizing gaseous molecules in a plasma generating source and a metal thin film type magnetic recording medium to which the same is applied.

[0002]

2. Description of the Related Art Conventionally, with respect to the CVD method, many technical approaches have been made for semiconductors, functional materials, protective materials, etc., and many features have been proposed. For example, JP-A-6-45877, JP-A-6-45896, and JP-A-6-45877
Although disclosed in Japanese Patent No. 45897, these have insufficient points such that continuous film formation is impossible or the film quality is non-uniform. When a thin carbon layer is formed on a thin film by the continuous film forming method as in the present invention, it is the current state that it is hardly seen in the conventional publicly known documents.

On the other hand, a metal thin film type magnetic recording medium is a metal thin film in which a metal magnetic recording layer is formed on a non-magnetic substrate by a direct plating method, a sputtering method, a vacuum deposition method, an ion plating method or the like for the purpose of high density recording. A type recording medium is being developed. However, this type of medium causes microscopic wear due to slight contact with the head when running on the deck, the head surface wears away members near the recording gap, and the tape metal surface is mechanically scratched by protrusions and mechanically. There is a problem that deformation occurs, which causes recording, reproduction, and deterioration of characteristics. Therefore, conventionally, JP-A-5-12661 and JP-A-51261
Although many proposals for improvement have been made based on the contents described in Japanese Patent Publication No. -20680 and Japanese Patent Laid-Open No. 4-349216, control of the initial output decreases and recording / playback characteristics in repetitive operation are required. It was difficult and inadequate.

[0004]

SUMMARY OF THE INVENTION The present invention is a plasma C
It is intended for the homogeneity of the carbon film formed by the VD film forming method. However, according to the conventional plasma CVD film forming method, the film quality is generally formed by mixing various decomposition gases, and it has been an important subject to realize a homogeneous polymerized film. Especially when applied to a metal thin film type magnetic recording medium, it is necessary to realize wear resistance with a thickness of about 10 nm or less, to consider adhesiveness with a metal magnetic layer, or to prevent damage by ultraviolet rays. There are many problems related to the invention, such as the strength not being given or the strength having to be determined in relation to the sliding metal composition.

Therefore, the approach proposed in the conventional plasma CVD film forming method is inadequate in that more than necessary atsushi is laminated to obtain abrasion resistance, or peeling is not considered at all. It often affects the characteristics of the signal such as increase in signal defects (dropout) in the generation of wear particles due to deterioration or scraping of the reproduction signal and roughening of the end of the signal envelope. There were many.

[0006]

When a carbon protective layer is provided, a remote plasma CVD method is used to obtain a high quality film by selective control of plasma gas species. Further, a carbon film having more abrasion resistance is formed on the magnetic layer by mixing the inert gas species. Then, in consideration of the interface between the magnetic recording layer and the carbon layer, an organic molecule is inserted between the magnetic recording layer and the carbon layer, or a treatment with a plasma gas is performed to provide a carbon layer having higher homogeneity.

[0007]

[Function] By using the remote plasma method in which various gas species such as ions, radicals and undecomposed molecules generated from the plasma generation source are selectively controlled by inserting a filter, unnecessary gas species can be removed. When the mixing is controlled and the selective permeation film formation with an increased ionic species ratio can be arbitrarily controlled, the abrasion resistance can be improved and the uniformity can be exerted. In addition, it is also an advantage of remote plasma that bending the gas species movement path does not damage the metal surface with ultraviolet rays generated by the plasma generation source. In terms of the relationship with the magnetic layer, interposing organic molecules at the interface improves the adhesiveness and creates a better wear film, and by selecting the type of gas used, it is possible to create a wear film with the strength suitable for the sliding partner. Become.

Since the carbon thin film obtained by the above-mentioned measures is homogeneous and has improved scratch resistance for practical use, the metal thin film type magnetic tape to which this is applied has a uniform contact with the head and a surface lubricating layer. It is provided as a magnetic recording medium which is effectively reflected in ensuring the uniformity of the magnetic recording medium and has excellent running properties.

[0009]

EXAMPLE FIG. 1 shows a model diagram of the plasma CVD film forming method of the present invention. In FIG. 1, 1 is a vacuum tank, 2 is a vacuum pump, 3 is a winding side roller, 4 is a winding side roller, Reference numeral 5 is a conveyance roller. Further, 6 is a plasma generation source, 7 is a plasma gas moving path, 8 is a discharge electrode, 9 is a filter of the present invention, 10 is a gas introduction tube, 11 is a power source, 12 is a metal thin film type magnetic recording applied. It is a medium. The structure of the metal thin film magnetic recording medium produced is shown in FIG. 2, 13 is a non-magnetic substrate, 14 is a metal thin film magnetic recording layer, 15 is a plasma CVD carbon protective layer of the present invention, and 16 is a lubricating layer. , 17 are back coat layers.

The configuration of FIG. 2 to which the present invention is applied is not directly related to the present invention, and only a brief description will be given here.

The non-magnetic substrate 13 is a polymer film of polyamide, polyimide, polyethylene, polyethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, vinyl chloride. The metal thin-film magnetic recording layer 14 is a ferromagnetic metal containing at least one selected from Fe, Co, and Ni, or Mn, Cr, Ti, P, Y, and S of these.
There are m, Bi and the like or alloys in which these oxides are combined, and in particular, at least one element selected from Co, Cr and Ni. The lubricating layer 15 is a low molecular weight lubricant developed in consideration of the bondability with the protective layer. Back coat layer 17
Is a resin of a mixture paint mainly containing carbon, an abrasive and the like. The plasma CVD carbon layer 15 described in the present invention forms a carbon layer on the surface of a magnetic medium by introducing hydrocarbons such as methane and ethane under plasma conditions.
At this time, the carbon layer is formed in various states depending on the process conditions, but considering the scratch resistance, the treatment of the lubricating layer and the like, the amorphous state is preferable as the film structure.

Although the thickness depends on the other member, it is preferably -10 nm in consideration of the retention of wear resistance and the thickness loss. During this manufacturing process, the applied magnetic recording medium has an extremely smooth surface roughness of 15 to 25 nm and a thickness of 7 μm.
In the following extremely thin cases, wear resistance is required especially in the thin layer region.

Therefore, in order to realize these, the present invention has reached the present invention by considering the following points. In the plasma CVD film formation method, when gas molecules are decomposed, generally, various kinds such as ions, radicals and undecomposed substances are generated. If these are mixed and incorporated into one film formation as in the past, the required performance cannot be controlled arbitrarily. Therefore, there is a remote plasma method as a method of selecting them and forming them with the same kind of material as in the present invention. This is accomplished by inserting an insulating filter within the plasma source. When a mesh-shaped sieve of an insulating material is attached near the substrate (here, the surface of the magnetic medium) where the generated plasma gas species are deposited and permeated, only the ionic species can be selectively permeated, and other gas species are insulated materials. Captured on the sieve. The filter is shown in FIG. 3, and the insulating material is not particularly limited as long as it can withstand the plasma heat in the generation source, but a polymer plate may be used as long as it is heat resistant, glass,
An inorganic material such as ceramic may be used. The thickness is not particularly limited within the range of workability as long as it is 1 mm or more in consideration of supporting strength and the like. If the mesh of the sieve has a porosity of 5 to 30 mesh, it is considered that it is possible to form a film that does not interfere with radical deposition other than ionicity or gas flow rectification of radical flow.
By doing so, a more uniform film is possible and wear resistance is improved.

Further, since it is considered that the surface of the magnetic medium is damaged by the effect of the generated ultraviolet rays, it is also an improvement to bend the moving path of the gas species as shown in FIG. 4 to form a film.

When the strength is adjusted in consideration of the mating material, the structural composition is changed by selecting the gas species to form the film. For example, like the present invention, hydrocarbons and nitrogen,
If a gas containing a combination of gas species such as argon is used to form a film containing a C—N bond, the change of the crystal structure or the bond with the lubricating layer on the surface is promoted. As for the ratio of these gas species, if the hydrocarbon / (nitrogen + argon) ratio is 5 or more, a high voltage is required due to a decrease in plasma discharge, or if the nitrogen / argon ratio is 2 or more, arc discharge becomes excessive. The ratio of hydrocarbon: nitrogen: argon is preferably about 3 to 5: 1 to 2: 1.

If the gas used at this time is introduced at a purity close to 100%, or if a desiccant is inserted during the introduction of the gas to prevent mixing of water, which would inhibit polymerization, the film quality will be considerably improved. Good things can be realized.

When applied to the magnetic layer, the adhesion is improved by further interposing organic molecules at the interface. The thickness may be about a single molecule. For example, a triazine compound has a substituent bonded to a metal surface and a carbon coating or the like on the opposite side. Adhering such a material by ordinary coating or vacuum deposition is relatively easy to achieve and its effect is great. Further, since the magnetic layer is made of metal, surface deterioration is likely to occur depending on the history. For this reason, it is also possible to improve the formation of a new metal surface by cleaning the surface with argon gas in advance or reducing unnecessary oxygen on the surface with hydrogen radicals.

As described above, the plasma C made in the present invention
The VD film can realize a carbon film that is of good quality, does not peel off from the magnetic surface, and takes into consideration the adhesion to the lubricating layer. The metal thin film magnetic recording medium obtained by this is easy to wear and run. The characteristics that are achieved are achieved. Less than,
Examples will be described in detail.

Example 1 A non-magnetic substrate film having a thickness of 6.3 μm and a width of 200 mm was used, and the material was polyethylene naphthalate (PEN). Under the example of vapor deposition conditions shown in (Table 1), CoO was formed into a metal thin film type magnetic layer with a thickness of 0.16 μm in each laminated state, and a resin back coat was applied.

[0020]

[Table 1]

Plasma CVD is performed by using methane as a raw material gas at a DC voltage of 500 V and a DC current of 500 mA at a tape speed of 10 / min.
In mixing ratio by introducing an argon gas simultaneously CH _4: Ar = 0.2:
The film thickness was 0.05 (Torr ratio), the degree of vacuum was 1 × 10 ^-4 Torr, and the substrate temperature was room temperature. At this time, a filter was inserted in the plasma generation source, and the materials, thicknesses and meshes shown in (Table 2) were used to prepare (specimen Nos. 1 and 2). Then, for comparison, a sample without a filter was prepared (Sample No. 3).

[0022]

[Table 2]

Then, commercially available polyether was applied to these to prepare a magnetic recording medium having a lubricating layer, which was then slit to a width of 8 mm and evaluated with a tape length of 30 min. The evaluation was made by improving the commercially available 8 mm deck and using these at 5 ° C and 8
The tape was repeatedly run in an environment room of 0% RH, and changes in the output signal and the tape and head surface after running were observed and compared. The decrease of the output signal was evaluated by comparing the reproduced signal recorded for 30 seconds and the reproduced signal after the test.

Then, the sample No.
In the case of No. 3, a decrease of -5 dB was observed from around 85 pass, and many adherent substances were observed on the head surface. The tape surface had two or three abrasions in the helical direction, and abrasion was recognized with the naked eye.

On the other hand, the sample No. 130 pass for 1
Even in the vicinity, it is constant with a decrease of -3 dB. Two
The signal drop was -1.5 dB. Observing each of these, the former had no helical scratches, but the depth of damage was no. Not as clear as 3 400
Only observed under a microscope at a magnification of 2.times. In No. 2, there was almost no wear and almost no wear was observed. From this, it was found that the sample formed by the remote plasma method described in the present invention has a thinner layer and improved wear resistance, even though the sample is thinner than before. Also, when observing the inside of the plasma generation source after film formation, a trace of alteration was seen on one surface of the inserted filter and on the part of the lattice, but it was not on the glass plate at all. From this fact, it is considered that a better quality protective film is realized because the carbon film having an improved ionic species ratio is selectively permeated among the gas species during film formation.

From the above, when the carbon layer is provided on the metal thin film type magnetic recording medium, the abrasion property of the magnetic recording medium is improved when the carbon layer is coated by the remote plasma CVD film forming method as described in the present invention. Can be said.

(Example 2) A recording medium having a magnetic recording layer in which one layer of CoO was vapor-deposited with a total thickness of 0.1 µm on a PET film having a thickness of 6.3 µm was prepared to obtain a magnetic recording medium having a surface roughness of 10 to 20 nm. A recording medium was obtained.

These samples are referred to as sample No. 1 of Example 1. As in No. 1, the carbon layer was provided by the remote plasma method. In the method, a glass plate filter having a thickness of 3 mm and 25 mesh and having comb-shaped holes in the vertical and horizontal directions was used, and the plasma conditions were the same. At this time, in order to prevent damage due to ultraviolet irradiation, the moving path of the plasma gas species was bent to form a film as shown in FIG. 4 of the present invention (Sample No.
4). Other than that, the sample No. 1 of Example 1 was used. It was produced in the same manner as in 1.

Then, the non-uniformity due to the thermal expansion in the central portion as in the case of the conventional method disappears, and the uniformity in the width direction is obtained, and the uniform optical reflectance before and after the film formation also contributes to the film formation. It was confirmed inside. It is considered that this is effective when the non-magnetic substrate constituting the magnetic recording medium is relatively affected by a slight difference in physical properties.

Therefore, as described in the present invention, when it is applied to a magnetic recording medium which is damaged when it is manufactured by the remote plasma method, the movement path of the plasma gas is bent so that the film is uniform in the width direction and of good quality. Is possible.

(Example 3) Next, the film quality was compared by changing only the type of introduced gas. The gas species is a mixture of ethane, nitrogen, and argon, and the partial pressure ratio is 4: 1: 1 (Torr ratio).
The sample No. of Example 1 was used. The same as that of Sample 1 (Sample No. 5). The purity of ethane at this time is 99.99.
%. For comparison of purity, when 99% (Sample N
o. A sample was also prepared in 6). When introducing the gas, when the dry zeolite is filled in the introduction pipe passage (Sample No.
7) was also produced. And, comparing these with the output decrease of 100pass deck running in the environment room of 5 ℃ and 80% RH,
The still durability was compared in an environment room of 23 ° C., 10% RH and 5 ° C., 80% RH. This is shown in (Table 3).

[0032]

[Table 3]

According to (Table 3), it can be seen that all of these samples have an improved signal drop value during deck running and are improved. This is probably because the C—N bond was contained in the film, so that it was optimized with respect to the magnetic head metal surface of the counterpart material. Further, since the surface is also composed of N component, it is considered that the holding power of the lubricating layer is improved and the still durability is improved.

Further, in detail, the sample No. prepared by the purity comparison In No. 6, the decrease is in the sample No. Although it did not change from 5, the still durability at low temperature was improved. It is considered that this is due to a slight improvement in film quality. In addition, the sample No. In No. 7, it is considered that since there is no mixing of water that inhibits the polymerization, the homogeneity of the polymerized film and the retention of the lubricating layer due to the N composition on the surface are improved, and the wear resistance is dramatically improved.

(Example 4) Then, in order to improve the interface with the magnetic layer, introduction by adhesion of organic molecules and surface plasma treatment were carried out. Plasma conditions are DC voltage 300V,
The sample No. 1 of Example 1 was used except that the direct current was 50 mA. The same as 1.

Among the triazine compounds of the invention, 6-dichloroamine-1,3,5-triazine-2,4-dithiol was coated on a magnetic layer prepared by dissolving 1000 ppm in isopropyl alcohol. As a method, a sample having a thickness of about 50 A was prepared at a drying temperature of 100 ° C. at a coater machine of 10 / min (sample No. 8). In addition, for a sample in which the magnetic recording medium was left for 180 days immediately after the recording layer was formed, plasma treatment was performed with argon gas after being provided with a triazine compound (sample No. 9) or after hydrogen gas was introduced and plasma treatment was performed. Then (Sample No. 10), a sample having a carbon film was prepared.

These are decks equipped with MIG type dummy heads, load 30 gf, 5 ° C., 80% RH
In the above environment, the still durability was checked for 60 min and the peeled state was observed.

Then, the sample No. In Nos. 8 to 9, when the surface after the measurement was observed, only the head biting marks of the dummy head were slightly seen, and the film was not peeled off. It can be said that this is a much improved bond at the interface, considering the phenomenon in which peeling occurs within a few minutes in the past, considering the load conditions. Sample No. No. 8 is the sample No. It can be seen that the surface is less damaged than in Sample No. 9 and Sample No. 10, and the film quality is stabilized. Therefore, when examining the envelope during the deck running test, the flatness of the envelope is lost after 50 passes due to slight wear and peeling, as shown in Figs. 5 (a) and (b). It has been found that the magnetic recording medium of the present invention is a magnetic recording medium capable of obtaining a completely flat signal because of improved peeling during running and good film growth.

It can be said that the present invention realizes an appropriate process in view of the tendency of flattening the surface roughness and thinning the thickness, which will be required from the future demand for high C / N.

Further, since the plasma CVD method described in Embodiments 1 to 4 of the present invention is a manufacturing method including a conveying roller, there is no heat loss of the magnetic tape during film formation. It can be said that this is a manufacturing method which is superior in mass productivity and can be industrialized as compared with a method not containing it.

[0041]

According to the present invention, a plasma CVD film forming method having the following effects is proposed, and a metal thin film type magnetic recording medium produced by applying the method has a constant running property and a constant output signal. It is possible to provide high C / N characteristics. 1) A polymerized film can be achieved by arbitrarily controlling the decomposition gas species,
It is possible to form a film with high homogeneity. 2) Abrasion resistance due to a polymer film with a large ionic species ratio,
A carbon film with improved hardness can be formed. 3) The protective effect by the remote plasma method of the present invention is, for example, in the metal thin film type magnetic recording medium, envelope flatness,
A magnetic recording medium having excellent sliding characteristics can be provided.

[Brief description of drawings]

FIG. 1 Model diagram of remote plasma CVD film forming method

FIG. 2 is a sectional view of a metal thin film type magnetic recording medium provided with a carbon film by a plasma CVD film forming method.

FIG. 3 is a diagram showing a filter of the present invention.

FIG. 4 is a bending diagram of a plasma gas species moving path performed by a remote plasma CVD film forming method.

FIG. 5A is a diagram showing an envelope of the magnetic recording medium of the present invention carried out in Example 4 during deck running. FIG. 5B is a diagram of a conventional magnetic recording medium carried out in Example 4 during deck running. Illustration showing the envelope

[Explanation of symbols]

 1 Vacuum Tank 2 Vacuum Pump 3 Rolling Side Roller 4 Rolling Side Roller 5 Conveying Roller 6 Plasma Generation Source 7 Plasma Gas Moving Path 8 Discharge Electrode 9 Filter 10 Gas Introducing Tube 11 Power Supply 12 Metal Thin Film Magnetic Recording Medium 13 Nonmagnetic Substrate 14 metal thin film type magnetic recording layer 15 plasma CVD carbon layer 16 lubricating layer 17 back coat layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Oda Kiri 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (11)

[Claims] 1. A plasma source, a plasma gas moving path,
Plasma CVD composed of a magnetic recording medium for film formation
In the film forming method, a plasma is characterized in that a carbon film is formed by inserting an insulating filter on the side closer to the magnetic recording medium surface, apart from the plasma discharge part due to electrode discharge in the plasma gas moving path. CVD film forming method. 2. The plasma CVD film forming method according to claim 1, wherein the filter has a porous mesh surface and is made of a heat resistant polymer material or a heat resistant inorganic material. 3. The plasma CVD film forming method according to claim 1, wherein the filter is made of at least one material selected from the group consisting of polyamide, polyimide, polyaramid, silicone, mica, ceramic and glass. 4. The plasma CVD film forming method according to claim 1, wherein the filter has a thickness of 1 mm or more and a porosity of 5 to 30 mesh. 5. The plasma CVD film forming method according to claim 1, wherein the gas path extending from the plasma generation source to the surface of the magnetic recording medium is bent to form the film. 6. The introduction gas is hydrocarbon, nitrogen, or argon, and the introduction partial pressure ratio (Torr ratio) is 3 to 5: 1 to 2: 1.
Plasma CV characterized by forming a carbon film by
D film forming method. 7. A protective layer made of a carbon film produced by a plasma CVD film forming method in which a filter made of an insulator is inserted on the side closer to the surface of the magnetic recording medium and apart from the plasma discharge portion due to electrode discharge in the plasma gas moving path. A metal thin film type magnetic recording medium having the above-mentioned. 8. The metal thin film type magnetic recording medium according to claim 7, wherein the carbon film is formed after organic molecules are provided on the surface of the metal thin film in a thickness of about a monomolecular layer. 9. The magnetic recording medium according to claim 7, wherein the organic molecule is a triazine compound. 10. A metal thin film type magnetic recording medium according to claim 7, wherein a carbon film is produced after plasma treatment with an argon gas after providing the organic molecules. 11. The metal thin film type magnetic recording medium according to claim 7, wherein a carbon film is produced after the surface of the metal thin film is previously treated with hydrogen radicals.