JPS59116927A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To prevent the wear and dropout of the head itself and the thin metallic film itself and to enable a considerable improvement in the durability thereof by incorporating a low-melting metal in a thin metallic film consisting of a Co contg. alloy as a magnetic recording layer. CONSTITUTION:Any low-melting metal which is plastically made fluidify by locally generated friction heat is acceptable. The temp. of the friction point by such friction heat is known to be about 1,000 deg.C and the metal applicable in practicability includes Ga, In, Pb, Sn, Hg, Zn, Wood's metal, etc. If the content of the low-melting metal to be incorporated in a thin metallic film is too low, the effect thereof is not obtainable and if the content is too high, the magnetic characteristic necessary as a recording layer cannot be maintained and therefore said content needs be selected in a suitable range. A magnetic recording medium that can be satisfied in a wide range of 0.5-20at% is obtd. with In. The low-melting point is preferably higher in the content thereof on the outside surface side of the thin metallic film that contacts with a head than on the inside surface inside.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium made of a Co (cobalt) alloy metal thin film capable of high-density recording, and a method for manufacturing the same.
More specifically, the present invention relates to a magnetic recording medium suitable for perpendicular magnetic recording, which has been actively researched for practical use in recent years.

In recent years, due to the demand for high-density recording, magnetic recording media whose recording layer is a ferromagnetic metal thin film formed by PVD methods such as vacuum evaporation and sputtering, or plating methods have attracted attention.
There are many suggestions.

Among these, the metal thin film of the above-mentioned co-based alloy is attracting attention because it has magnetic properties suitable for high-density recording, and as a recording layer used for perpendicular magnetic recording, which is expected to achieve even higher densities. Co has magnetic anisotropy perpendicular to
-0r (chromium) alloy, Co-0r-Ta (tantalum) alloy, co-Or-Mo (molybdenum) alloy,
Co-0r-W (yu/gesten) alloy, Co-0r
OCOCo alloy thin films such as -Re (rhenium) alloy and Co-V (vanadium) alloy have been proposed;
The recording layer for the current method of longitudinal recording is Co-Ni (metal), Oo-Pt (platinum), Co-P (phosphorous), etc.
Metal thin films made of o-based alloys have been proposed.

However, the above-mentioned Co-based alloy film has the following problems from a practical standpoint. In other words, in order to obtain stable recording and reproduction characteristics with a good 87N ratio, it is optimal to bring the magnetic head into contact with the recording layer during recording and reproduction, but with this contact method, the Co-based alloy film suffers from abrasion, etc. There is a major problem with poor durability. This problem is particularly important in those that use a polymer film for the substrate.

The present invention was made in view of the current situation, and provides a magnetic recording medium whose recording layer is a highly durable Co-based alloy film, and a method for manufacturing the same.

That is, the present invention provides a magnetic recording medium having a metal thin film made of a Co-based alloy as a magnetic recording layer, in which the metal thin film contains a low melting point metal. A second invention provides a method for manufacturing a magnetic recording medium, characterized in that a metal thin film of the magnetic recording medium is formed by a facing target sputtering method.

By the way, the above-mentioned first invention focuses on the fact that the contact between the magnetic head and the Co-based alloy metal thin film during recording/reproducing can be regarded as friction between solid objects.

Co-based ferromagnetic metals such as Co-Or gold alloys form intermetallic compounds, have extremely high hardness, and have a high melting point. In addition, since the head material is made of semi-chemicals, permalloy, sendust, etc., it has high hardness similar to ferromagnetic metals.
It also has a high melting point. Therefore, when there is repeated friction between the two,
Particularly when the contact area between the two is large, they abrade each other, so that, for example, if the adhesion between the metal thin film of the recording medium and the substrate is weak, the metal thin film will peel off. Furthermore, both the medium and the head are scratched, and the metal or ceramic fine particles that caused the scratches act as an abrasive. Due to these reasons, it is thought that magnetic recording media made of thin metal films have poor durability.

On the other hand, when the metal thin film contains a low melting point metal, the durability is greatly improved as shown in the example below due to the effect of the low melting point metal.

In other words, when the metal thin film and the head rub against each other,
Frictional heat is generated locally at the contact area, and this frictional heat softens the low-melting point metal, causing plastic flow between the head and the metal surface, and the shear force that causes wear and tear to become plastic flow. Occurs on the side of the face. Therefore, abrasion and chipping of the head itself and the metal thin film itself are effectively prevented, and their durability is greatly increased.

From the above, the low melting point metal in the present invention may be any metal that can be plastically fluidized by locally generated frictional heat. The temperature at the friction point due to such frictional heat is said to be around 1000°C, and therefore metals having a melting point of 1000°C or less can be specifically used. Such metals include Ga (gallium) and In (
indium), Pb (lead), 8n (tin), Hg (mercury)
, Zn (zinc), wood metal, etc.

By the way, if the content of the low melting point metal contained in the metal thin film is too low, the effect will not be exhibited, and if it is too high, the magnetic properties necessary for the recording layer cannot be maintained, so it is necessary to select it within an appropriate range. be. IP, 0.5-2
A magnetic recording medium that was satisfactory over a wide range of 0 at% was obtained. Further, from the above point, it is preferable that the content of the low melting point metal is higher on the outer surface of the thin metal film that contacts the head than on the inner surface.

Note that the present invention is a KPVD method on a nonmagnetic substrate.

The object is a metal thin film type magnetic recording medium in which a metal thin film of a Co-based alloy is formed as a recording layer by a plating method or the like. Here, the Co-based alloy is a general term for ferromagnetic alloys containing cobalt as a main component. The metal thin film may be a multilayer film, and in this case, a low melting point metal may be included in the outermost metal thin film that contacts the head.

Furthermore, the present invention is particularly effective for magnetic recording media using a polymer film such as a polyester film as a substrate, which requires contact recording/reproduction.

In addition, JP-A-54-51804 and JP-A-54-51804 contain a large amount of Or, which is said to be difficult to lubricate with lubricants.
The present invention is particularly effective for magnetic recording media for perpendicular magnetic recording made of 000r alloy films such as those disclosed in S7-10O627.

In this case, the CoOr alloy film is required to have magnetic anisotropy that facilitates magnetization in the direction perpendicular to the film surface, but this requirement can be met without any problem if the content of the low melting point metal is selected within an appropriate range. Ru.

The above-described magnetic recording medium of the first invention can be manufactured by a PVD method such as vacuum evaporation or sputtering using an alloy containing a predetermined content of a low melting point metal as an evaporation substance and a target.

In particular, the second invention, which is manufactured by the facing target sputtering method in which a film is formed by placing a substrate on the sides of a pair of targets placed opposite each other, described in JP-A-S7-158380, etc., uses inexpensive polyester. In addition to being able to form a continuous film on a substrate such as a film at high speed, the concentration distribution of the low melting point metal in the film thickness direction can be controlled simply by appropriately selecting the content of each low melting point metal in the target. It is an excellent manufacturing method.

Hereinafter, the details of the above-mentioned present invention will be explained based on examples.

FIG. 1 is a block diagram of a facing target type sputtering apparatus used in carrying out the present invention.

As is clear from the figure, the present apparatus has the same structure as that of the above-mentioned Japanese Patent Application Laid-open No. 57-158380, except for the means for holding the substrate 40.

That is, in the figure, 10 is a vacuum container, 20 is an evacuation system consisting of a vacuum pump etc. that evacuates the vacuum container 10, and 30 is a predetermined gas introduced into the vacuum container 10 to increase the pressure in the vacuum container 10 by 10-1 to 10-1. This is a gas introduction system that is set to a predetermined gas pressure of about 10 to 4 Torr.

In the vacuum container IO, there is a vacuum container 10 as shown in the figure.
A pair of targets T, , T2 are fixed to the side plates 11, 12 of the target holder 15, 16 through insulating members 13, 14 on their sputtered surfaces T+s,
The T2S are arranged so as to face each other in parallel across a space. The targets 'r, ,'r2 and the corresponding target holders 15 and 16 are connected to the water cooling pipe 151.
Cooling water is supplied through ゜161.
T2, permanent magnets 152, 162 are cooled. magnet 15
2.162 is the N pole via target T,, T2.

The south poles are arranged to face each other, so that a magnetic field is formed only in the direction perpendicular to the targets TI*T2 and between the targets. Note that 17.18 is the insulating member 13.
14 and target holders 15 and 16 from plasma particles during sputtering and to prevent abnormal discharge in areas other than the target surface.

Further, the substrate holding means 41 that holds the substrate 4o on which the magnetic thin film is formed is connected to the targets Tl and T2 in the vacuum container 10.
It is installed on the side of the The substrate holding means 41 includes a feed roll 41a and a support roll 41b, which are rotatably supported by support brackets (not shown) and parallel to each other's axes.
The three rolls of the nine-winding roll 41c hold the substrate 4° in a direction substantially perpendicular to the sputtering surfaces 'r, s, and T2S so as to face the space between the targets T, , and T2. It is arranged. Therefore, the substrate 4o is sputtered on the sputtering surfaces 'r, s, 'r2s' by the winding roll 41c.
It is movable in a direction perpendicular to .

On the other hand, a power supply means 50 consisting of a DC power source for supplying sputtering power has its glass side connected to the ground, and its negative side connected to the targets T, T2, respectively.

Therefore, the sputtering power from the power supply means 50 is supplied between the anode and the cathode, with the ground as the anode and the target TI+T2 as the cathode.

Note that in order to protect the substrate 4o during pre-sputtering,
A shutter (not shown) that goes in and out between TI+T2 and TI+T2 is provided.

As described above, since the configuration is basically the same as that of the above-mentioned Japanese Patent Application Laid-Open No. 57-158380, it is possible to perform the well-known high-speed low-temperature sputtering. That is, targets T, , T
In the space between the two, due to the action of the magnetic field, locust gas ions,
Gamma electrons etc. emitted by sputtering are bound and a high-density plasma is formed. Therefore, the target 'r,,'r
The sputtering of No. 2 is promoted, the amount of deposition in the space increases, the deposition rate on the substrate 40 increases, high-speed sputtering is possible, and since the substrate 40 is on the side of the targets TI and T2, low-temperature sputtering is also possible.

Note that the facing target sputtering method of the present invention is not limited to the above-mentioned apparatus, and sputtering is performed by placing a substrate on the side of a pair of facing targets and applying a perpendicular magnetic field between the targets. This refers to a sputtering method that forms a film on a substrate. Therefore, the magnetic field generating means is not a permanent magnet,
An electromagnet may also be used. Further, the magnetic field may be one that confines γ electrons and the like in the space between the targets, and therefore includes the case where it is generated not over the entire surface of the target but only around the target.

Next, an embodiment of a perpendicular magnetic recording medium according to the present invention, which is implemented using the above-mentioned facing target type sputtering apparatus, will be described.

The crystal structure of the obtained alloy film was identified using a counting X-ray diffraction device manufactured by Rigaku Corporation, and the vertical orientation was determined using a hexagonal close-packed structure and the rocking curve of the (002) plane peak using the X-ray diffraction device. It was calculated using the half width Δθ50.

The film thickness and composition were determined from a curve calibrated in advance using a fluorescent X-ray device manufactured by Rigaku Denki.

Durability is evaluated using a Crockmeter.
er ) (Atlas Electric Devices Co., Ltd. (USA)
The test was carried out as follows using a model CMT-1 (manufactured by Manufacturer Co., Ltd.).

As shown in FIG. 2, samples 202 and 203 to be compared are fixed side by side on a slide glass 201 using double-sided adhesive tape, and the contact member 204 is moved back and forth from side to side as shown by arrow A in the figure. The state of surface deterioration was observed. The contact area of the contact member 204 is l-1, the contact pressure is 900 f, the speed is 3 cr++/sec, and the repetition frequency is 30 times/min. A polyethylene terephthalate (PET) film and a Vermalon thin films (Ni 78%, Fe 22%) were adhered to each other.

Furthermore, in order to measure the actual wear characteristics, as shown in FIG.
were brought into contact with each other and repeatedly moved up and down at a speed of 3.3 crn/sec, and the durability was examined from the change in friction coefficient μ and the occurrence of scratches.

The friction coefficient μ was determined by measuring the inlet tension T1 and the outlet tension T2 k of the fixed bottle 301, and using the well-known formula below.

2 μ=7′. No In the above equation, θ is the contact angle and was set to θ-1800.

Example 1 Using the above-mentioned facing target type sputtering apparatus shown in FIG. 1, a perpendicular magnetic recording medium made of the above-mentioned known CoOr alloy film was prepared under the following conditions and compared. Note that in this example, the substrate 4o was in a stopped state.

A Co Or alloy film containing a low melting point metal was created under the same conditions by using In as the low melting point metal and arranging small pieces of In on the target T1 so that the area ratio became a predetermined content rate.

A Equipment conditions a Target TI+T2 material: CO83/CR17 alloy target b Substrate 4o: Kapton (manufactured by DuPont) film 7
5 μm C target T1. T2 interval: 75 m/.

d Magnetic field on sputtering surface: lθ0 to 200 Gauss e Shape of target TI+T2: 110. Circular f of φ Distance between substrate 40 and target T, T2 end = 30
m/m B Operation procedure Film formation was carried out using the following procedure.

a After installing the substrate, the degree of vacuum reached within the vacuum container 10 is I.
X 1 (Exhaust to below 1' Torr.

b Introduce argon (Ar) gas to a specified pressure,
Press the button for 3 to 5 minutes, open the shutter,
A film was formed on the substrate.

The Ar gas pressure during sputtering was 4X10-3 Torr.
And so.

The power input during C sputtering was 1 kW, and the film thickness was approximately 1 kW.
A thin film of μm was formed.

C Results (Sample Properties) Table 1 shows the composition and magnetic properties of the Co Or In alloy film obtained and the In-containing Co Or In alloy film of the present invention.

Table 1 D Evaluation results 1) When the contact member of the crockmeter is a polyethylene terephthalate film In the comparative example I-3, 0.5 u was obtained by repeating 2x103 times.
A missing portion of the 0oOr layer of φ occurred, and as the number of repetitions increased, the missing portion of the CoCr layer expanded. On the other hand, in I-1, even if the number of repetitions is 4 × 10', C
! No missing portions of the oor layer occurred.

I-2 was the same as I-1.

2) When the contact member of the crockmeter is made of permalloy In I-3, a CoOr layer missing portion occurred after 600 repetitions. In I-2, Co Or
A missing portion of the In layer occurred.

In other words, a CoCr alloy thin film containing In has significantly improved wear resistance compared to a 0oOr alloy thin film, regardless of whether the contact member is an organic material such as a PET film or a metal thin film such as permalloy. That is clear.

The reason for this improved durability can be explained from the above-mentioned properties of metal wear. That is, when the contact member and the Co Or gold alloy slide against the Oc + Or In alloy, frictional heat is locally generated. Co Or-alloy has a high melting point of 1500°C or higher, so PET with a melting point of 300°C or lower
When sliding with the film, not only the surface of the PET film softens (but some of it accumulates on the surface of the CoOr alloy, and sliding between PK'1' also occurs.In this case, the surface of the Kapton film and the CoCr layer The bonding strength of PET
Since the bonding force between the film and the PET is weaker, the shear force is concentrated on the Kapton film and the OoOr layer, resulting in a missing portion of the C00r layer. However, CoOr gold alloy containing In,
The heat generated during sliding softens In and sometimes causes plastic flow on the surface, so even if a small amount of In is included, shear force is always generated only on the sliding surface.

For this reason, it is thought that wear of the CoCrIn alloy is less likely to occur.

3) CoOr with magnetic properties of electromagnetic conversion test samples I-1, 2, and 3
The electromagnetic characteristics of gold alloy and Co Or In alloy were investigated.

Recording was performed with a single-pole vertical magnetic head and reproduction was performed with a ring head, and the recording density characteristics were investigated using the NRZI recording method and all signals (square wave writing).

, In the case of 10KFRPI (10,000 magnetic flux reversals per inch) or less, the neutral force changed in proportion to the perpendicular coercive force, but in the recording/reproducing area of 50KF or more, samples I-1, 2, In all three cases, the results of K were uniform. That is, samples I-1, I-2, and I-3 were all suitable media for high-density magnetic recording. Therefore, although the addition of In appears to reduce the magnetic properties in Table 1, it is understood that there is no problem in practical use when the content is in the range of 0.5 to 20 at%, including the examples described below.

Example 2 Unlike Example 1, a perpendicular magnetic recording medium was fabricated continuously in the same manner as in Example 1 while operating the substrate holding means 41 to transport the substrate 40 in the direction of the arrow.

A Equipment conditions a Target T,, T2 material: 0o83 0r17 alloy target) (In case of In addition, place a small piece of In metal on T1s as in Example 1) b Substrate 40: Kapton (manufactured by DuPont) film 2
5μm C target T1 + T2 spacing: 120 m/md
Shape of target T, T2: 150. Distance between the substrate 40 and the ends of the targets T, , and T2.

3　0　　m/m B. Operating procedure Film formation was performed using the following procedure.

a The degree of vacuum achieved inside the vacuum container 1o is I x 10-6T
Exhaust to below orr.

b Fluorine (KR) gas was introduced to a predetermined pressure, and a film was formed on the substrate while the substrate was running.

Note that the Ar gas pressure during sputtering was 4 x 10-3To
It was set as rr.

The power input during C sputtering was 1 kW, and the film thickness was adjusted by changing the running speed of the substrate.

Example Table 1 shows the composition and magnetic properties of the O, ocr alloy film obtained.

Table D Evaluation Results The durability of the magnetic recording medium was evaluated using the measurement method shown in FIG.

Figure 4 shows the evaluation results. The horizontal axis shows the number of repetitions N, and the vertical axis shows the behavior of the friction coefficient μ.

As shown in the figure, it can be seen that in the conventional sample 11-3, the friction coefficient suddenly rises after 10 repetitions, and the friction coefficient becomes extremely large at higher repetitions. However, in the samples [-1 and 2 related to the present invention, there is no sudden rise, and although a slight increase is observed with respect to the number of repetitions up to 100 times, the change is almost flat. Recognize.

In addition, when we observed and compared the samples after the test, we found that sample 11-3 had deep scratches due to friction and numerous scratches, and as a result, the sample had completely lost its metallic luster. Regarding samples dn-1 and dn-2, although scratches were observed, their number was small and the metallic luster remained sufficiently maintained. Furthermore, when the surface was observed using a differential interference microscope with a magnification of ×50 to ×100, the sample
-3 has numerous scratches with a very short pitch, and it is recognized that the CoCr layer is severely worn, but sample 11
In case of -2, the pitch of the scratches is large and the number of scratches is small, and the surface condition is smooth and beautiful. No wear was observed.

Therefore, it was confirmed that Samples I+-1 and 2 had significantly better durability than Sample 2-3.

From the above, it can be seen that by containing the CoOr gold alloy In, the lubricity and wear resistance (durability) can be significantly improved.

E Film thickness dependence of In content Tls 0oOr fabricated by placing small pieces of In metal on soil
The average In content of the In alloy thin film is shown in Table 2, and the In content increases closer to the surface in the film thickness direction. As described above, in the facing target sputtering method in which a large amount of stone as a lubricant is present at the interface, the target layer (T+) on the downstream side in the traveling direction of the substrate 40 can be effectively formed simply by increasing the In concentration.

FIG. 5 shows the relationship between the obtained film thickness (δ) and In concentration.

Regardless of the size of the film thickness (δ), the total thickness io.

The distribution of the In concentration for the average concentration has the characteristics shown in FIG. 5 for the average concentration of 100.

That is, even if the In concentration in the region adjacent to the interface is a small average concentration, it can contribute to improving the lubrication performance.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the facing target type sputtering equipment, Figure 2
Figure 3 is an explanatory diagram of the durability test, Figure 4 is a graph showing changes in the friction coefficient in the example, and Figure 5 is a graph showing the change in the friction coefficient in the film thickness direction.
# This is a grab showing the degree distribution. 10゛Vacuum container, 20: Exhaust system, 30: Gas introduction system, 4
0 substrate, 50: power supply means, T1. T2: Target spear 2 Figure + 3 Figure + 2 5 10 20 S
D I”N (number of gB) 4 figures, 5 figures

Claims (1)

[Claims] 1. A magnetic recording medium having a metal thin film made of a cobalt-based alloy as a magnetic recording layer, wherein the metal thin film contains a low melting point metal. 2. The magnetic recording medium according to claim 1, wherein the concentration of the low melting point metal is higher on the outer surface side of the metal thin film than on the inner surface side. & Claim 1 or 2, wherein the metal thin film is a perpendicularly magnetized film having an axis of easy magnetization perpendicular to the film surface.
Magnetic recording medium described in Section 1. A method for manufacturing a magnetic recording medium having a metal thin film made of a cobalt-based alloy containing a low melting point metal as a magnetic recording layer, characterized in that the metal thin film is multi-formed by a facing target sputtering method. manufacturing method. 5. Making one of the targets have a higher content of a low melting point metal than the other, and continuously transferring the substrate of the magnetic recording medium from the target with a lower content of the low melting point metal to the target with a higher content of the low melting point metal. 5. The method of manufacturing a magnetic recording medium according to claim 4, wherein the metal thin film is formed while forming the metal thin film.