JP2843136B2 - CoCr perpendicular magnetic recording tape and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a CoCr perpendicular magnetic recording tape and a method for manufacturing the same, and in particular, effectively improves the crystal orientation of a soft magnetic backing layer and a magnetic recording layer, This is for the purpose of advantageously improving magnetic properties as a magnetic recording medium.

(Prior Art) Since the perpendicular magnetic recording system was proposed as a next-generation high-density magnetic recording system, much research has been conducted on perpendicular magnetic recording media. As a result, it has been found that a CoCr film is most promising as a perpendicular magnetic recording medium, and various researches and developments are currently being made on the film formation method. There are various media such as a hard disk, a floppy disk, and a tape, and the manufacturing method differs according to the medium. In particular, in the case of a tape medium, it is necessary to continuously form a CoCr film having good crystallinity without thermally damaging the substrate tape, and thus there are many technical problems.

(Problems to be Solved by the Invention) Here, the details of the above technical problems will be described as follows.

(1) As the substrate tape, it is preferable to use a thermoplastic plastic tape such as polyethylene naphthalate (PEN) or polyethylene terephthalate (PET),
Since such tapes generally have poor heat resistance, thermal damage to such tapes must be avoided as much as possible.

(2) Since the recording / reproducing output is proportional to the saturation magnetization of the magnetic recording layer, it is preferable to use CoCr exhibiting high saturation magnetization as much as possible, but it is generally difficult to form CoCr having high saturation magnetization with good crystallinity. .

(3) In order to obtain perpendicular magnetic anisotropy, it is necessary to orient the c-axis of the hcp crystal structure of CoCr perpendicular to the tape surface. Therefore, when a film is formed on a moving tape, the c-axis is inclined. It is necessary to form a film so as to prevent the occurrence of filming.

(4) The interface between the permalloy layer, which is the soft magnetic underlayer, and the high saturation magnetization CoCr layer, which is the magnetic recording layer, is improved, and the half angle width Δθ ₅₀ of the c-axis of the high saturation magnetization CoCr magnetic recording layer is reduced.
Make a film with good orientation of 10mm or less.

(5) The above process is continuously performed without lowering the film forming speed.

In addition, as a film forming method, a vacuum evaporation method, a three-electrode sputtering method, a DC two-electrode sputtering method, an RF two-electrode sputtering method, a magnetron sputtering method, and the like are mentioned, but a manufacturing method that has overcome all of the above problems has not yet been developed. .

The object of the present invention is to effectively solve the above-mentioned problems,
A CoCr perpendicular magnetic recording tape having excellent magnetization characteristics is proposed together with its advantageous manufacturing method.

(Means for Solving the Problems) The present inventors have earnestly conducted studies in order to achieve the above object, and have obtained the following findings.

i) The magnetic recording tape is desirably provided with a permalloy soft magnetic backing layer as an underlayer for recording and reproduction, but permalloy originally has poor crystallinity, and therefore the CoCr magnetic recording layer formed thereon has a poor crystallinity. Crystallinity is also deteriorated. According to the study by the inventors, hcp (00
The 2) plane and the fcc (111) plane of Permalloy have a heteroepitaxial effect. Therefore, if a CoCr thin film with good crystallinity is formed before the permalloy layer is formed, good crystal orientation can be obtained. A permalloy layer, and thus a CoCr magnetic recording layer with good crystal orientation, can be obtained.

ii) When the facing target sputtering method is used, a film can be formed without damaging the film or the substrate tape being deposited by plasma.

 The present invention is based on the above findings.

 That is, the gist configuration of the present invention is as follows.

1. On the flexible tape substrate, Cr content: Low saturation magnetization CoCr of 20at% or more,
Axis dispersion angle half width Δθ ₅₀ ≦ 10 °, thickness: _{50 to} 200 °, orientation degree control layer, Ni content: epitaxially grown on this thin film, Ni content: 7
Thickness of permalloy of 5 to 85 at%: soft magnetic backing layer of 100 mm or more and less than critical thickness, and high saturation magnetization CoCr with a Co content of 80 at% or more, further epitaxially grown on this soft magnetic backing layer CoCr perpendicular magnetic recording tape (first invention), comprising: a magnetic recording layer having a thickness of 400 to 3000 mm.

2. A flexible tape, which is a substrate, is continuously supplied to a film forming zone divided into three, and while passing through the film forming zone, an orientation control layer and a soft magnetic backing are sequentially formed on one surface of the substrate by a sputtering method. In forming the layer and the magnetic recording layer, it is assumed that an oriented target type sputtering method is used as a means for forming each layer. First, in the first film formation zone, under the use of a narrow slit for suppressing oblique incidence on the substrate, Sputter Ar gas thickness: 1
At a low pressure of less than mTorr, a low saturation magnetization CoCr layer with a Cr content of 20 at% or more is formed to a film thickness of 50 to 200 mm, and a wide slit is used in the second film formation zone to allow oblique incidence. Under the above, a permalloy layer having a Ni content of 75 to 85 at% under a sputtering Ar gas pressure of 5 mTorr or less and a thickness of 100 mm
Above, the critical film thickness is formed below, and in the third film forming zone, the sputtering Ar gas pressure is 5 mT under the use of a wide slit which also allows oblique incidence.
A method for producing a CoCr perpendicular magnetic recording tape comprising forming a highly saturated magnetized CoCr layer having a Co content of 80 at% or more with a thickness of 400 to 3000 ° or less (second invention).

 Hereinafter, the present invention will be described specifically.

FIG. 1 schematically shows the procedure for manufacturing a perpendicular magnetic recording tape according to the present invention, and FIGS. 2a to 2d schematically show the state of film formation on the tape after each film forming process.

In the figure, number 1 is a flexible tape, 2-1, 2-2 and 2-3 are can rolls, and 3-1 and 3-2.
And 3-3 are facing target type sputtering apparatuses for producing an orientation control layer, a soft magnetic backing layer and a magnetic recording layer, respectively. As shown in FIG. 1,2-2 and 2-3
During the transport in synchronization with the rotation of the substrate, the orientation control layer 4 (the second layer) is formed on the flexible tape 1 (FIG. 2a) by using the facing target type sputtering apparatus 3-1, 3-2 and 3-3.
The perpendicular magnetic recording tape is manufactured by sequentially applying the soft magnetic underlayer 5 (FIG. 2c) and the magnetic recording layer 6 (FIG. 2d) in FIG.

In FIG. 3, the facing target type sputtering apparatus 3 is shown in a perspective view. In the drawing, reference numerals 7-1 and 7-2 indicate targets which are opposed to each other, and reference numerals 8-1 and 8-2 indicate a back side of each target. A magnetic pole 9 made of a permanent magnet, 9 is a mask, and 10 is a slit provided in the mask 9.

In the facing target type sputtering apparatus 3, two targets 7-1 and 7-2 of, for example, 10 × 10 cm ² are opposed to each other with a distance of about 10 cm as a sputtering source, and a magnetic pole 8 provided behind each target is provided. According to -1,8-2, a magnetic field runs perpendicular to each target surface between the targets,
By applying negative DC to both targets 7-1 and 7-2, sputter particles are supplied to the tape substrate 1 while confining the plasma between the two targets. Here, a slit 10 is provided between the sputter source and the substrate 1 to control the amount of sputter particles flying from the target. At this time, the substrate surface is set at a distance of 3 to 10 cm from the ends of the two targets, perpendicular to the target surfaces and at the center between the targets. Here, a film is continuously formed on the tape surface while the tape surface wound on the can roll is passed along with the rotation of the roll at the position of the substrate surface. According to this facing target type sputtering method, the object to be processed can be formed in a plasma-free state without being exposed to plasma, so that it does not damage even an object which is relatively easily damaged by heat, such as a plastic thin film. It can be coated on.

(Operation) Now, in the first zone, when the sputter is performed by widening the slit width (for example, 10 cm),
Of the sputtered particles flying from the target source, those that pass through the center of the slit reach the roll curved surface by perpendicular incidence, while those that pass through the end of the slit reach the roll curved surface by oblique incidence, and a film is formed. At this time, the film formed by the oblique incidence has a c-axis canting, and its magnetic characteristics deteriorate.

As a measure for preventing such canting, oblique incidence may be prevented by reducing the slit width as much as possible (eg, about 2 cm). It is difficult to deposit thousands of square meters of film. However, a very thin film of, for example, about 10 to 200 ° can be formed in a short time even with a narrow slit, so that high-speed film formation is possible.

Therefore, in the present invention, in the first zone, the film thickness is reduced to 20 by using a narrow slit for suppressing oblique incidence on the substrate.
An orientation control layer serving as an underlayer of 0 ° or less is formed. What is important here is that the sputtering is performed at a very low gas pressure of Ar gas pressure P _Ar of 1 mTorr or less, preferably 0.5 mTorr or less. This is because when P _Ar exceeds 1 mTorr, the crystallinity is deteriorated. In this respect, the facing target sputtering method has an extremely excellent feature that it can stably discharge even at a low gas pressure of 1 mTorr or less as compared with other sputtering methods. For this reason, the mean free path of the sputtered particles becomes large, reaches the substrate tape with a large kinetic energy, sufficiently migrates on the tape, and since it is plasma-free sputtering, 50 to 100
A CoCr film with good crystallinity can be formed from a very thin film thickness of Å, and this has been confirmed from electron beam diffraction and X-ray diffraction.

Note in the present invention, crystal orientation is assumed to be evaluated by the dispersion angle half width [Delta] [theta] ₅₀ of the c-axis of the CoCr layer, this value is can be said good crystal orientation if 10 ° or less.

Here, as the orientation control layer, low saturation magnetization CoCr having a Cr content of 20 at% or more (preferably 40 at% or less), particularly Co
₇₉ Cr ₂₁ is preferred. The thickness of the CoCr underlayer is
Must be 50-200Å. If the film thickness is less than ₅₀ °, the canting becomes large, and the c-axis dispersion angle half-width Δθ50, which is an index of crystal orientation, exceeds 10 ° and functions as an orientation control layer. Not get, 200Å
This is because, if it exceeds, the canting also increases, and when a permalloy soft magnetic underlayer is formed thereon, the soft magnetism deteriorates.

In other sputtering methods, for example, magnetron sputtering, stable discharge is difficult at a low pressure of 1 mTorr or less, and the substrate is exposed to plasma.
With a 0 ° thin film, an initial layer with microcrystallinity and poor crystallinity is formed.

Next, in the second zone, the slit is fully opened, and permalloy as a soft magnetic backing layer is formed on the orientation control layer while feeding a substrate tape. At this time, not only the normal incidence but also the oblique incidence is included, but on the orientation control layer which is a special underlayer as described above, the permalloy fc is placed on the (002) plane of the underlying hcp structure.
The (111) plane of the c structure grows epitaxially, Δθ ₅₀ is about 8 °, and a permalloy layer with good crystallinity without (111) axis canting can be obtained at a high film forming rate. On the other hand, when the film is formed without the orientation control layer, the Δ
θ ₅₀ becomes 20 ° or more, and (111) axis canting occurs. As the permalloy, those having a Ni content of 75 to 85 at%, particularly Ni ₈₁ Fe ₁₉ are preferable. At this time, P _Ar is 5mTor
It must be less than r. This is because if it exceeds 5 mTorr, scattering between sputtered particles and Ar gas increases, which causes a decrease in crystallinity. Further, the film thickness must be not less than 100 ° and not more than the critical film thickness. This is because if the thickness is less than 100 mm, the function as a soft magnetic underlayer cannot be sufficiently exhibited, while if the thickness exceeds the critical thickness, the soft magnetic properties are deteriorated. Here, the critical film thickness is a film thickness where a strong magnetic field is applied and a phenomenon (rotatable anisotropy) in which the direction of the axis of easy magnetization of the permalloy layer instantaneously rotates in the direction of the applied magnetic field starts to occur. Although it varies by minutes, it is usually about 3000 mm.

It was confirmed that the soft magnetic characteristics of Permalloy were not adversely affected when the thickness of the CoCr orientation control layer was 200 ° or less.

Next, in the third zone, open the slit fully
A Cr magnetic recording layer is formed on the permalloy layer while feeding the tape. Since the recording / reproducing output is proportional to the saturation magnetization of the magnetic recording layer, it is preferable to use CoCr with high saturation magnetization as much as possible for the CoCr magnetic recording layer.However, it is generally impossible to form CoCr with high saturation magnetization with good crystallinity. difficult. However, despite the inclusion of normal and obliquely incident particles, the (002) plane of CoCr epitaxially grows on the (111) plane of permalloy on the special permalloy layer with good crystal orientation described above. , Δθ ₅₀ is about 8 °, and a CoCr magnetic recording layer having excellent crystal orientation without c-axis canting is formed at a high film forming rate.

Here, for the CoCr magnetic recording layer, a high saturation magnetization CoCr having a Co content of 80 at% or more (preferably 90 at% or less) is obtained.
₈₃ Cr ₁₇ is preferred. Also, if P _Ar is too high, the crystallinity decreases due to the scattering of sputtered particles and Ar gas, so 5 m
Must be less than Torr. Furthermore, if the film thickness is less than 400 mm, the film becomes an in-plane magnetized film, while if it exceeds 3000 mm, the flexibility is reduced.
Limited to the range of 0Å.

The coating obtained as described above has a dense structure and excellent flexibility.

In this way, (CoCr magnetic recording layer / Permalloy soft magnetic underlayer / CoCr orientation control layer) can be formed on the tape substrate. At this time, polyethylene naphthalate tape (PEN) and polyethylene terephthalate tape (PET) are used as the substrate tape. And a polyimide tape are preferable, and the thickness is preferably about 5 to 50 μm.

The magnetic recording medium is required to have corrosion resistance in terms of long-term storage of recording, and wear resistance in terms of high-speed contact between the medium surface and the sensor during use.
Therefore, in a magnetic recording tape in which a magnetic recording medium is formed on a plastic substrate, a top coat is applied to the surface for the purpose of protecting the surface of the magnetic recording medium, and static electricity is prevented, a friction coefficient of the tape surface is reduced, and slip between the tapes is improved. From the viewpoint, it is preferable to apply a bark coat on the back surface, and any of conventionally known protective films are suitable as such a protective film.

(Example) FIG. 4 schematically shows a magnetic recording tape manufacturing apparatus suitable for use in the implementation of the initial eradication. Since the outline of the structure is the same as that shown in FIG. 1, common numbers are given to them, and numbers 2-4 and 3-4 in the figure are respectively a can roll for forming a protective film and a facing target type sputtering. The apparatus, 11 is a vacuum chamber, and 12 and 13 are a take-up roll and a take-up roll of the substrate tape, respectively.

As shown in the figure, this manufacturing apparatus has four film forming zones in a vacuum chamber 11, and a facing zone type sputtering source and a tape transfer can roll are installed in a corner zone. The opposing target type sputtering source has two targets of about 10 × 10 cm ² placed face to face and separated by 10 cm, and a permanent magnet is installed on the back side of each target.
250 (G
auss) magnetic field and a negative DC (about 2k)
W) is applied to supply sputtered particles to the substrate tape.
A slit is provided between the sputter source and the substrate tape to control the amount of sputter particles flying from the target. At this time, the substrate surface is set at a distance of 10 cm from the ends of the two targets, perpendicular to the target surfaces and at the center between the targets. Here, a polyethylene naphthalate tape surface of 12 μm thickness wrapped around a can roll surface with a diameter of 15 cm comes to the position of the substrate surface, and a film is continuously formed on the tape surface while moving in synchronization with the roll rotation. It is a mechanism.

The target composition is such that the first zone is Co ₇₉ Cr ₂₁ , the second zone is Ni ₈₁ Fe ₁₉ , the third zone is Co ₈₃ Cr ₁₇ , and the fourth zone is carbon for the protective film.

The Ar gas pressure P _Ar in the first zone is 0.25 mTor.
r, the second, third and fourth zones were all 1 mTorr. Furthermore, the slit width is 2cm in the first zone and 10cm in the second, third and fourth zones.
And

Under the above conditions, first, the film thickness in the first zone is 0,100,20.
CoCr underlayer of 0,300 mm, thickness in the second zone: 1550,200
A permalloy soft magnetic underlayer having a thickness of 0 ° was formed, a CoCr magnetic recording layer having a thickness of 1300 ° was formed in the third zone, and a protective film having a thickness of 200 ° was formed in the fourth zone.

FIG. 5 shows the results of a study on the relationship between the thickness of the underlayer of the (permalloy layer / orientation control underlayer) two-layer film and the in-plane coercive force of the permalloy layer.

As is clear from the drawing, the coercive force hardly increases when the thickness of the underlayer is 200 ° or less, and no adverse effect of the underlayer on the soft magnetism of the permalloy layer is observed.

Then in Figure 6, shows the results of examining the relationship between the base film thickness and canting of (Co ₈₃ Cr ₁₇ layers / permalloy layer / orientation control underlying layer) three-layered film.

As is clear from the figure, the canting was extremely large when there was no underlayer, whereas
By forming a Co ₇₉ Cr ₂₁ thin film of about 50 to 200 mm,
Canting has been greatly improved.

Next, FIG. 7 shows the same (Co ₈₃ Cr ₁₇ layer / permalloy layer /
Underlayer for controlling the degree of orientation) Underlayer thickness and X-ray diffraction intensity of a three-layer film
The relationship between I _P and Δθ ₅₀ is shown.

The first I _P, when no underlying layer is not a peak appears from permalloy layer and do not exhibit only very weak peaks from Co ₈₃ Cr ₁₇ layers. The reason for this is that the crystallinity of the permalloy layer is very poor when there is no underlayer,
It is considered that the crystallinity of the ₈₃ Cr ₁₇ layer also became poor.

On the other hand, a special Co ₇₉ Cr ₂₁
The base layer only forms the, appeared intense peak with Ni ₈₁ Fe ₁₉ layer and Co ₈₃ Cr ₁₇ layer, the crystallinity of the two layers is seen to have been greatly improved.

This is clear from the change in [Delta] [theta] _50, [Delta] [theta] ₅₀ is Co ₇₉
It has been greatly reduced by the crystallinity orientation effect of the Cr ₂₁ underlayer, confirming the improvement in the crystal orientation of both layers.

(Effects of the Invention) Thus, according to the first invention, in a CoCr perpendicular magnetic recording medium having a permalloy backing layer, a permalloy soft magnetic backing is formed by forming an orientation control layer composed of a low saturation magnetization CoCr thin film as a base layer. The crystal orientation of the layer and the CoCr magnetic recording layer can be remarkably improved, and the magnetic properties as a perpendicular magnetic recording medium can be greatly improved.

According to the second aspect of the present invention, since a film can be formed in a plasma-free condition in which the object to be processed is not exposed to plasma, it is possible to damage even a tape substrate such as a plastic tape which is relatively easily damaged by heat. Without, each layer can be coated. Moreover, since the orientation control layer formed by the narrow slit for removing the c-axis canting may be extremely thin, the film can be formed in a short time, and continuous high-speed film formation can be performed as a whole process.

[Brief description of the drawings]

FIG. 1 is a diagram showing a procedure for manufacturing a perpendicular magnetic recording tape according to the present invention, FIGS. 2a to 2d are schematic diagrams showing a film formation state on the tape after each film forming process, and FIG. FIG. 4 is a schematic view of an apparatus for manufacturing a perpendicular magnetic recording tape suitable for use in the present invention, and FIG. 5 is (permalloy layer / underlayer for controlling the degree of orientation). graph showing the relationship between the in-plane coercivity of the base film thickness and permalloy layer of two-layer film, FIG. 6, under the (Co ₈₃ Cr ₁₇ layers / permalloy layer / orientation control underlying layer) three-layer film FIG. 7 is a graph showing the relationship between the underlayer thickness and the canting. FIG. 7 shows the underlayer thickness and X-ray diffraction intensity I of the same three-layer film (Co ₈₃ Cr ₁₇ layer / permalloy layer / orientation degree control underlayer). it is a graph showing the relationship between _P and [Delta] [theta] _50. 1. Flexible Tape 2-1,2-2,2-3,2-4 Can Roll 3-1,3-2,3-3,3-4 Opposite Target Type Sputtering Apparatus 4. Orientation Degree control layer, 5 ... Soft magnetic underlayer 6 ... Magnetic recording layer, 7-1,7-2 ... Target 8-1,8-2 ... Magnetic pole, 9 ... Mask 10 ... Slit, 11 ... ... Vacuum chamber 12 ... Unwind roll, 13 ... Rewind roll

Continuation of front page (72) Inventor Makoto Sumide 1-8-8 Maison Axia 205, Sagamihara, Sagamihara City, Kanagawa Prefecture (56) References JP-A-63-201913 (JP, A) (58) Fields investigated (Int .Cl. ⁶ , DB name) G11B 5/66 G11B 5/85

Claims (2)

(57) [Claims] 1. An orientation control layer made of low saturation magnetization CoCr having a Cr content of 20 at% or more, a c-axis half angle width Δθ ₅₀ ≦ 10 °, and a thickness: _{50 to} 200 ° on a substrate of a flexible tape. Ni content: 75-85at% of permalloy epitaxially grown on this thin film.
Above, a soft magnetic underlayer having a critical thickness or less, and a high saturation magnetization CoCr layer having a Co content of 80 at% or more, which is further epitaxially grown on the soft magnetic underlayer. A CoCr perpendicular magnetic recording tape, comprising: 2. A flexible tape as a substrate is continuously supplied to three divided film forming zones, and an orientation control layer is sequentially formed on one side of the substrate by a sputtering method while passing through the film forming zone. In forming the soft magnetic backing layer and the magnetic recording layer, a facing target sputtering method is used as a means for forming each layer. First, in the first film forming zone, use of a narrow slit for suppressing oblique incidence on the substrate is used. Below, sputter Ar gas pressure: 1mT
At low pressure of orr or less, Cr content: low saturation magnetization of 20at% or more
A CoCr layer is formed to a thickness of 50 to 200 mm. Then, in the second film forming zone, under a sputter Ar gas pressure of 5 mTorr or less and a Ni content of 75 using a wide slit that allows oblique incidence. ~ 85at% permalloy layer thickness: 100mm
Above, the film thickness is formed below the critical film thickness. Subsequently, in the third film forming zone, the sputtering Ar gas pressure: 5 mTor under the use of the wide slit similarly allowing the oblique incidence.
A method for producing a CoCr perpendicular magnetic recording tape, comprising: forming a highly saturated magnetized CoCr layer having a Co content of 80 at% or more and a thickness of 400 to 3000 mm.