JPS59191136A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium consisting of a Co alloy having an excellent high density recording characteristics and excellent resistance to wear with a head by forming a protective lubricating layer consisting of a thin alloy film composed essentially of Co contg. In on a magnetic recording layer. CONSTITUTION:A thin magnetic film of a Co alloy has the problem in that the hardness is high and that the m.p. is high, but the thin film of the Co alloy added with a metal of low melting point, i.e., In, is considerably improved in wear resistance and the magnetic characteristic thereof is not so much deteriorated as compared with the case in which In is not incorporated in said alloy. The protective lubricating layer is formed by a known PVD method such as vacuum deposition method, sputtering method, etc. like with the magnetic recording layer and the distribution of the concn. of In in the film thickness direction is easily controlled if said film is formed by an opposed target type sputtering method. The content of In in the protective lubricating layer is preferably 0.5-20at% (atomic per cent).

Description

[Detailed Description of the Invention] [Field of Application] The present invention relates to a magnetic recording medium having a magnetic recording layer made of a magnetic thin film mainly composed of Co (cobalt), which is suitable for high-density recording, and more specifically relates to the magnetic recording medium. The present invention relates to a technology for improving the durability of perpendicular magnetic recording media, and in particular to a technology suitable for improving the durability of perpendicular magnetic recording media, which has been actively researched for practical use in recent years.

[Prior art]

Magnetic thin films used for perpendicular magnetic recording include Co-Cr (chromium) alloys, Co-Cr-Ta (tantalum) alloys, and Co-Cr-Re (rhenium), which have an axis of easy magnetization perpendicular to the film surface. alloy.

Co-Cr-W (tungsten) alloy, Co-C
r-M.

(molybdenum) alloy, Co-V (vanadium)
Co-based alloys such as alloys have been proposed. In addition, Co-Ni is currently used as a magnetic thin film for in-plane recording.
(=Tsukeru) alloy, Co-Pt (platinum) alloy, Co
-P(')N) and other Co-based alloys have been proposed.

Although the Co-based alloy containing Co as a main component has magnetic properties suitable for high-density recording, the following problems remain unsolved from a practical standpoint.

In other words, the most stable and large electrical signal can be obtained by bringing the magnetic head into close contact with the surface of the magnetic recording layer during magnetic recording/reproduction, but in this way the Co-based alloy magnetic thin film will peel off from the substrate in a short time.・It is missing and has poor durability.

〔the purpose〕

The present invention provides a magnetic recording medium made of a Co-based alloy that has excellent high-density recording characteristics and excellent abrasion resistance with a head.

[Composition/effect]

The present invention provides a magnetic recording medium having a magnetic recording layer made of a magnetic thin film mainly composed of Co on a non-magnetic substrate, wherein the magnetic recording layer is made of an alloy thin film mainly composed of Co containing In on the magnetic recording layer. A magnetic recording medium characterized by forming a protective lubricating layer.

The above-mentioned present invention considers that magnetic thin films of Co-based alloys have problems in that they have high hardness and high melting points, and as a result of various studies focusing on In, a low-melting point metal, a thin film of Co-based alloys containing In has been developed. It was discovered that the wear resistance was significantly improved, and the magnetic properties did not deteriorate much compared to the case where In was not included.

As mentioned above, the protective lubricant layer of the present invention has C
Since it is an o-based alloy, it has good compatibility at the interface with the magnetic recording layer, and high adhesion strength can be expected. Furthermore, in this case, unlike conventional protective layers, the protective lubricant layer has magnetic properties similar to those of the magnetic recording layer, so that the loss of recording and reproducing characteristics due to the provision of the protective layer is significantly reduced. From this point,
The Co-based alloy of the protective lubricating layer is preferably an alloy having the same composition as the Co-based alloy of the magnetic recording layer to which In is added.

In particular, when the magnetic recording layer is a perpendicularly magnetized film made of a Co-Cn alloy film or the like having an axis of easy magnetization perpendicular to the film surface, in this configuration the protective lubricant layer also becomes a perpendicularly magnetized film, which is extremely advantageous for high-density recording. becomes.

In addition, from the above point, the In content of the protective lubricating layer is 0.
5 to 20 at% (atomic percent) is preferred. In view of the lubricating effect of the In film surface, etc., even if the In content is the same, it is preferable that the In content be distributed such that it is higher on the cylinder surface side and gradually decreases on the magnetic recording layer side. Further, the thickness of the protective lubricating layer is usually selected from several X to several μm, with the thicker the better from the viewpoint of durability and the thinner the better from the viewpoint of electromagnetic conversion.

By the way, the protective lubricant layer of the present invention, like the magnetic recording layer,
Well-known vacuum evaporation method and sputtering method.

Although it is formed by a PVD (physical vapor deposition) method such as an ion blasting method, according to the second invention of the present invention, which is formed by a facing target sputtering method, the In concentration distribution in the film thickness direction can be easily controlled. There is.

Further, if the magnetic recording layer is similarly formed by the facing target sputtering method, a substrate of an inexpensive polymer film such as a polyester film can be obtained, and continuous production using the same apparatus is possible.

In addition, the above-mentioned facing target sputtering method uses 1%
It is publicly known from Publication No. 7-158380 and the like.

A sputtering method in which a substrate is placed on the sides of a pair of facing targets, and a vertical magnetic field for plasma trapping is applied between the targets to perform sputtering to form a film on the substrate.

〔Example〕

Hereinafter, 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, this device has the same structure as that known in the above-mentioned Japanese Patent Laid-Open No. 57-158380, etc., except for the holding means for the substrate 40.

That is, in Figure 1, 10 is a vacuum chamber, and 20 is a vacuum chamber 10.
30 is a gas introduction system that introduces a predetermined gas 1-4 into the vacuum chamber 10 and sets the pressure inside the vacuum chamber 10 to a predetermined gas pressure of about 10 to 10 Torr. It is.

Inside the vacuum chamber 10, a pair of targets T3. T2 is its sputtered surface 'r, sl T
2B are arranged so as to face each other in parallel across a space. The target TI+ T2 and its corresponding target holder 15.
Target TI + T2 by cooling water through 161
, the permanent magnets 152, 162 are cooled. magnet 152
．． T62 is provided so that its north and south poles face each other via target TI+T2, so the magnetic field is
, , 72 and only between the targets. Incidentally, reference numerals 17 and 18 are cooled members for protecting the insulating members 13 and 14 and the target holder 15 and 16 from plasma particles during stumbling and for preventing abnormal discharge on parts other than the target surface.

Further, the substrate holding means 41 holding the substrate 40 on which the magnetic thin film is formed is connected to the target TI r T in the vacuum chamber 10 .
It is provided on the side of 2. The substrate holding means 41 includes a feed roll 41a and a support roll 4, which are rotatably supported by supporting brackets (not shown) and parallel to each other's axes.
It consists of three rolls, 1b1 and 41c, and is arranged so as to hold the substrate 40 in a direction substantially perpendicular to the sputtering surface so as to face the space between T, , and Ti. It is. Therefore, the substrate 40 is sputtered on the sputtering surface Tl5I7 by the take-up roll 41c.
It is movable in a direction perpendicular to 211.

On the other hand, the power supply means 50, which is a DC power supply that supplies sputtering power, has its positive side connected to the ground, and its negative side connected to the targets "l+T2K".Therefore, the power supplied from the power supply means 50 is connected to the ground. 7 nodes, with targets T, , and T2 as cathodes, and are supplied between the anode and cathode.

Note that in order to protect the substrate 40 during pre-sputtering, the substrate 4
A shutter (not shown) is provided between T+ and T2.

Since the above structure is basically the same as that of the above-mentioned Japanese Patent Laid-Open No. 57-158380, high-speed low-temperature sputtering is possible as is known. Therefore, target T, ,
In the space between T2, sputtering gas ions, γ electrons emitted by the vines, etc. are bound by the action of the magnetic field, and a high-density plasma is formed. Therefore, target T, ,
The sputtering of T is promoted, the amount of precipitation increases in the space, the deposition rate on the substrate 40 is increased, high-speed sputtering is possible, and since the substrate 40 is on the side of the targets T, , T2, low-temperature snow Ivy can also grow.

Note that the facing target type Snotsuta method of the present invention is not limited to the above-mentioned apparatus, but as mentioned above, a substrate is placed on the side of a pair of facing targets, and a vertical magnetic field is applied between the targets. This is a sputtering method that applies sputtering to form a film on a substrate. Therefore, the magnetic field generating means may also be an electromagnet instead of a permanent magnet. 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 example of a perpendicular magnetic recording medium according to the present invention, which was 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 diffractometer manufactured by Rigaku Denki, and the vertical orientation was determined by the hexagonal close-packed structure and the rocking curve of the (002) plane peak using the X-ray diffractometer. It was evaluated using its 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) (manufactured by Atlas Electric Devices (USA), model CM-1) in the following manner.

As shown in FIG. 2, the samples 202 and 203 to be compared are fixed side by side on a slide glass 201 with 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 to form a surface of the samples 202 and 203. The deterioration status was observed. The contact area of the contact member 204 is 1 cd, the contact pressure is 900 g, the speed is 3 F/sec, and the repetition frequency is 30
The test was carried out by adhering a polyethylene tele-7 (PET) film and a permalloy thin film (78% Ni, 22% Fe) to the contact surface of the lower surface of the contact member 204 under conditions of rotations per minute.

Furthermore, in order to measure the actual wear characteristics, as shown in FIG.
were brought into contact with each other and moved up and down repeatedly at a speed of 3.3 C:In/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 1 and the outlet tension T2 of the fixing pin 3010, and using the known formula below.

In the above formula, θ is the contact angle, which was set to θ−180°.

Example 1 A perpendicular magnetic recording medium made of the above-mentioned known CoCr alloy film was prepared and compared under the following conditions using the facing target-type Sino (Ivy) apparatus shown in FIG. 1. In this example, the substrate 40 was in a stopped state.

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

A Equipment conditions a Target TI + T2 material: Co 83 wt
%, Cr17wt% alloy target b Substrate 40° Kagton (manufactured by DuPont) film 7
5μm C target TI + T2 interval: 7s rrL/
md Magnetic field on the sputtering surface: 100 to 200 Gauss e Target TI r Shape of T2: 110 mtφ circular f Distance between substrate 40 and target section T, , T2 end: 30 m/m B Operating procedure Film formation is performed using the following steps. I did it.

a After installing the substrate, the degree of vacuum reached in the vacuum chamber 10 is I
Exhaust at a pressure of 10 Torr or less.

b Introduce argon (Ar) gas to a predetermined pressure, and
~ Do a 5 minute press bank.

The shutter was opened and a film was formed on the substrate.

Note that the Ar gas pressure during sputtering was 4×10 Tcrr.

C sputtering was performed at an input power of Fi1 kW to form a thin film with a thickness of about 1 μm.

C Results (Sample Properties) Table 1 shows the composition and magnetic properties of the CoCrIn alloy film containing In 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, 0.5n was obtained by repeating 2 x 103 times.
A missing portion of the Co Cr layer of φ was generated, and as the number of repetitions was increased, the missing portion of the Co Cr layer expanded. On the other hand, in I-1, no missing portions of the CoCr layer occurred even after repeating 4×10' times.

I-2 was similar to I-1.

2) When the contact member of the crockmeter is made of permalloy In I-3, a Co Cr layer missing portion occurred after 600 repetitions. In I-2, Co Cr is repeated 5ooo times.
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 CoCr 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. It is clear that there are.

The reason for this improved durability can be explained as follows from the nature of metal wear.

That is, the contact member and Co Cr alloy or Co Cr
When sliding between In alloys.

Frictional heat is generated locally. CoCr alloy has a melting point of 15
If it slides against a PET film with a melting point of 300°C or lower, not only will the surface of the PET film soften, but some of it will accumulate on the surface of the CoCr alloy, causing smudges between the PET films. In this case, the bonding force between the Kapton film surface and the CoCr layer is stronger.

PET and P4. Co
A missing portion of the Cr layer occurs.

However, in a CoCr alloy containing In, the heat generated during sliding softens the In and causes plastic flow at the surface, so even if a small amount of In is included, shear force is always generated only on the bottom surface. There is. This is useless, Co Cr I
It seems that wear of the n-alloy is less likely to occur.

3) CoCr with magnetic properties of electromagnetic conversion test samples I-1, 2, and 3
The electromagnetic characteristics of the alloy and the CoCrIn alloy were investigated.

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

10 KFRPI (910,000 magnetic flux reversals per i inch)
In the following cases, the output changed in proportion to the perpendicular coercive force, but in the recording/reproducing region of 50KFR1 or more, the results were almost uniform for samples I-1, I-2, and I-3. 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, the addition of In
．． It can be seen that there is no practical problem in the range of 5 to 20 atX.

Example 2 Different from Example 1, a perpendicularly magnetized film made of a CoCr alloy film was used as a magnetic recording layer under the following conditions while operating the substrate holding means 41 to transfer the substrate 40 in the direction of the arrow. A perpendicular magnetic recording medium having a protective lubricant layer made of a CoCrIn alloy provided thereon was fabricated and evaluated.

A Apparatus conditions a Target TI * T2 material: When creating the magnetic recording layer - "I + T2 both Co 80 wt%,
When creating a protective lubricant layer for an alloy target with 20 wt% Cr-T
, , T2 is an alloy target of Co82vrt% and Cr18wt%, and a small piece of In is placed on T1b Substrate 40: 50 μm thick PET film C target TI r Spacing between T2: x6 om/md Magnetic field on sputtering surface: 100 to 150 Gauss e Target TI, T2 shape: 180 m/mW
Rectangle f of Xtaom/mL Distance between substrate and Targetera F TI + T2 end = 3
0 m/m B Operation procedure Film formation was performed according to the following procedure.

a After installing the substrate, the degree of vacuum reached in the vacuum chamber 10 is lX1
Evacuate to 0 Torr or less.

b Argon (Ar) gas is introduced to a predetermined pressure, and the substrate is sputtered while being transferred from the target T2 side to the T, side. The Ar gas pressure was 4×10 −3 Torr.

The power input during C sputtering was lkw.

d) After the CoCr alloy film is formed, the CoCrIn alloy film as the protective lubricating layer is formed on the CoCr alloy film of the magnetic recording layer.
After replacing T2, perform the above operation fr procedure (a, b, c
).

Example Table 2 shows the film thickness and magnetic properties of the perpendicular magnetic recording medium having only a magnetic recording layer made of a CoCr alloy film and the obtained perpendicular magnetic recording medium having a protective lubricating layer made of a CoCrIn alloy film.

Incidentally, the composition distribution in the film thickness direction (In T7 of:o Cr In) is shown in FIG. In the figure, the vertical axis represents the In concentration normalized to 100CX with an average In concentration of 19 at%, and the horizontal axis represents the thickness δ from the surface of the magnetic recording layer, normalized to the CoCrIn film thickness of 0.13 μm as 100%.
shows.

D. Evaluation Results a Wear Characteristics Table 3 shows the results of evaluating the friction coefficient μ of sample ■-1° If-2 using the method shown in FIG.

Table 3 Note that for I-1, the friction coefficient became too large after 200 cycles, so the test was discontinued.

Sample IT-2 according to the present invention is based on the prior art If-IK
In comparison, the degree of increase in the coefficient of friction μ is small, and the durability is 5.
It can be improved by ~10 times.

b For electromagnetic conversion characteristic samples ll-1 and Tl-2, disk 1 with a diameter of 5α (cut out, Sankyo Seiki floppy driver (FMC
-100), the electromagnetic conversion characteristics were investigated using a modified test device. The results are shown in Table 4. The numerical values in the table represent the percentage of the output, with the envelope value of the output at the start being taken as 100%, and were evaluated in correspondence to the number of repetitions.

As shown in Table 4, in sample h-t, that is, one with only a conventional CoCr alloy magnetic recording layer, the reduction in reproduction output increases from about 50,000 busses, and decreases to 60% at 500,000 busses, whereas Sample 1bTI-2 i.e. CoC
r In the case of the present invention with a protective lubricating layer of In alloy, 6
It took 1.5 million passes for it to drop to 0%, which can be said to be an improvement in 3x diameter durability compared to the conventional technology. Note that ll-1 had a large output reduction rate of 5×10 5 ha, so further experiments were discontinued.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a facing target type sputtering apparatus in which the present invention is not implemented, and FIG. 2 is an explanatory diagram of a durability evaluation method.
Figure 3 is an explanatory diagram of the friction characteristics measurement method, Figure 4 is Example 2
In of the protective lubricant layer of sample Naff-1 in the film thickness direction
It is a distribution map of concentration. 10: Vacuum chamber, 20: Exhaust system. 30: Gas introduction system, 40: Substrate. 50・Power supply means + T1 + T2' target. 201 Niss Ride Glass. 204: Contact member, 301° fixing pin Patent applicant Teijin Ltd. agent Patent attorney Mae 1) 0 −′τ〜゛゛゛1
,ku,i',,,,l i-':,,j-1,+ 3 figure 1 concentration (Rio+ figure

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic recording layer made of a magnetic thin film mainly composed of Co on a non-magnetic substrate, wherein the magnetic recording layer contains In and C. A magnetic recording medium characterized in that a protective lubricant layer is formed from an alloy thin film mainly composed of. 2. The magnetic thin film of the magnetic recording layer is made of Cr, Co,
W, V. 2. The magnetic recording medium according to claim 1, which is a perpendicularly magnetized film having an axis of easy magnetization perpendicular to the film surface, which is made of an alloy of Co and at least -fIIi of Re, Ta, and Ni. 3. The magnetic recording medium according to claim 1 or 2, wherein the alloy thin film of the protective lubricating layer is made of an alloy with In added to an alloy having the same composition as the magnetic thin film of the magnetic recording layer. 4. The In content in the direction perpendicular to the film surface of the protective lubricant layer is
The magnetic recording medium according to claim 1, 2, or 3, wherein the magnetic recording layer is smaller on the magnetic recording layer side than on the surface side. 5. Magnetic device having a magnetic recording layer made of a magnetic thin film mainly composed of K Co on a non-magnetic substrate, and a protective lubricating layer formed on the magnetic recording layer made of an alloy thin film containing In and mainly composed of Co. A method for manufacturing a magnetic recording medium, characterized in that, in manufacturing the recording medium, the protective lubricant layer is formed by a facing target sputtering method. 6. A method for manufacturing a magnetic recording medium according to claim 5, in which the protective lubricant layer is formed while the substrate is being transferred, using a facing target sputtering method in which only the downstream target in the substrate transfer direction contains In. .