JPH03183020A - Method for manufacturing magnetic recording media - Google Patents

Abstract

PURPOSE:To prevent the cracking of the magnetic recording medium by forming a Co oxide layer directly or via an underlying layer on a high-polymer substrate, then forming a Co-based magnetic thin film layer thereon by a vacuum vapor deposition method. CONSTITUTION:The Co oxide layer 2 which has <=500Angstrom layer thickness and has the NaCl type structure of about 1:1 atomic compsn. of Co and O is formed on the high-polymer substrate 1. The Co-based magnetic thin film layer 3 is thereafter formed by the vacuum vapor deposition method on the Co oxide layer 2. Thus, the cracking of the Co-based magnetic thin film layer 3 is prevented.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for manufacturing a magnetic recording medium in which a magnetic layer containing Co as a main component is formed on a polymer substrate by vacuum evaporation, and in particular to prevent the occurrence of cracks. The present invention relates to a manufacturing method for preventing.

(Prior Art) Currently, magnetic recording and reproducing devices are trending toward smaller size and higher density, and thin film media are attracting attention as a device that exceeds the limits of high density of conventional coated media.

In particular, Co-Cr film (or Co-Cr-Ni film)
Co-based magnetic thin films such as Co-Ni-O[II and Co-Ni-0[II] are being developed and put into practical use as promising candidates for thin-film media. For a method of manufacturing thin film type media.

There are methods such as plating method, sputtering method, vacuum evaporation method, etc.
In terms of mass production, the vacuum evaporation method is the best. In order to form a thin film type medium stably with good productivity using the vacuum evaporation method, for example, as shown in FIG. Vapor deposition may be performed while moving in the direction. In addition, 7.8
are a supply roller and a take-up roll for the polymer substrate 1, respectively, and 11 is an evaporation source.

(Problems to be Solved by the Invention) However, one of the problems when forming a magnetic layer on a polymer substrate by vacuum evaporation is the occurrence of cracks. If cracks exist in the magnetic layer, not only will proper recording and reproduction not be performed, but it will also have an adverse effect such as damaging the magnetic head, making it no longer usable as a magnetic recording medium. For this reason, various restrictions arise from the viewpoint of preventing the occurrence of cracks, and various conditions during vapor deposition are restricted, preventing optimization of the magnetic properties and recording/reproducing characteristics of the magnetic layer, or reducing costs during mass production. It can also be a cause of hindrance.

The present invention solves the above problems, and aims to provide a manufacturing method that prevents the occurrence of cracks in magnetic recording media.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention is directed to a polymer substrate having a layer thickness of 500λ or less and an atomic composition of Go and O. After forming a Co oxide layer having an NaC'' type structure with a ratio of approximately 1:1, a Co-based magnetic thin film layer is formed by vacuum evaporation.

(Function) In general, the factors that influence the presence or absence of cracks when forming a Go-based magnetic thin film on a polymer substrate by the vacuum evaporation method include chamber atmospheric pressure, substrate temperature, thinness,
There are film composition and film deposition rate. According to our experimental data, cracks tend to occur more easily as the atmospheric pressure P in the chamber is higher, as the substrate temperature T sub is lower, or as the film thickness δ is thicker. However, the influence of the film composition varies depending on the material composing the magnetic layer, and -
No internal discussion is possible. Furthermore, changing the deposition rate also relatively changes the atmospheric pressure inside the chamber, and the same effect as when actually changing the atmospheric pressure inside the chamber is added.

It is difficult to remove the above effects and discuss the effects of film deposition rate alone. Therefore, under the conditions that the film composition and film deposition rate are constant, the atmospheric pressure P in the chamber and the substrate temperature Tsub.

We will focus on the influence of three factors on the film thickness δ.

According to the present invention, as shown in FIG.
(Figure 1(b)) The atomic composition of Co and O is approximately 1.
:1 Co oxide layer 2 is formed in advance, and a Co-based magnetic thin film layer 3 is formed on the layer by vacuum evaporation, so that the atmospheric pressure P in the chamber, the substrate temperature Tsub, and the film thickness can be controlled such that no cracks occur. The range of δ can be made wider than in the case of a conventional film structure in which a Co-based magnetic thin film layer is formed directly without a Co oxide layer or via only an underlayer.

That is, the atmospheric pressure P in the chamber is higher than that of the conventional example.
It is possible to prevent the occurrence of cracks even in the range of lower substrate temperature Tsub and thicker film thickness δ. Cracks occur due to internal stress remaining within the magnetic thin film, and the mechanical mismatch between the magnetic thin film, polymer substrate, and underlying layer greatly influences the magnitude of this internal stress. considered to be a thing. In the case of the film structure in the present invention, Co is formed between the polymer substrate 1 and the Co-based magnetic thin film layer 3.
Plays the role of the oxide layer 2 and forms a Co-based magnetic thin film layer 3
This is thought to reduce the internal stress remaining within the structure. In addition, within the scope of our experiments described below, the above-mentioned crack prevention effect was obtained when the Co oxide layer 2 was mainly composed of Co; , O, etc., the rack prevention effect described above cannot be observed.

Therefore, in the manufacturing method of the present invention, it is necessary that the atomic composition of Go and O in the Co oxide layer 2 be approximately 1:1. It is sufficient that the thickness of the Co oxide layer 2 is several hundred A or less,
On the other hand, if the layer thickness is several hundred λ or more, the magnetic properties of the Co-based magnetic thin film layer 3 may be affected.

Therefore, it is desirable that the thickness of the Co oxide layer 2 be made as thin as possible within a range that provides the effect of preventing crack generation. Furthermore, as shown in FIG. 2, there is an intermediate layer between the Co oxide layer 2 and the Co-based magnetic thin film layer 3 made of other elements! 45, the role of the buffer layer of the Co oxide layer 2 is maintained when the layer thickness of the intermediate layer 5 is 500λ or less,
As in the case of the film structure shown in FIG. 1, the Co-based magnetic thin film layer 3
It has the effect of preventing the occurrence of cracks in.

(Example) An example of the present invention will be described below with reference to the Go-based magnetic thin film layer 3.
A case where the film is made of a Co--Cr film will be explained.

A Go--Cr perpendicular magnetic recording medium having the film structure shown in FIG. 1(a) was fabricated using a continuous vapor deposition apparatus having the system shown in FIG. In this continuous vapor deposition apparatus, by replacing the evaporation source 11 with the crucible 12 and repeating continuous vapor deposition, a long magnetic recording medium having the film structure shown in FIG. 1 or 2 can be easily produced. In this embodiment, a polyimide film with a thickness of 10 mm is used as the polymer substrate 1.

First, the Co oxide layer 2 is formed by using Co as the evaporation source 11 and evaporating it while introducing oxygen into the vicinity of the evaporation source. Next, the evaporation source 11 is made of Co with an appropriate composition ratio.

and Cr alloy on the Co oxide layer.
A film was formed. The film deposition rate of Co oxide layer 2 is approximately 200
The layer thickness was about 100 μm at 0 people/sec, the amount of oxygen introduced during vapor deposition was about 3 liters per minute, and the atmospheric pressure in the chamber was about 3×10−4 Torr. Further, the substrate temperature during the formation of the Co oxide layer was approximately 150°C. Measurements using X-ray photoelectron spectroscopy (XPS) confirmed that this Co oxide layer was mainly composed of Coo.
When producing the Co-Cr layer, among the factors that affect the presence or absence of cracks mentioned above, the film composition and film deposition rate are kept constant, and the chamber internal ambient pressure P, substrate temperature Tsub, and layer thickness δ are varied. I let it happen. C produced in this example
All o-Cr layers have a Cr composition of about 20% by weight,
By carrying out evaporation while continuously supplying an appropriate amount of granular Cr to the evaporation source 11 in order to keep the film composition constant, a film with almost no change or variation in composition in the longitudinal direction was obtained.

The film deposition rate of the Co--Cr layer was approximately 8000 people/sec. The atmospheric pressure P in the chamber during Go-Cr layer deposition is:
Controlled by varying the conductance of the exhaust pump, from 5 X 10-'Torr to 1XlO'-4Torr
It was varied within the range of rr. The substrate temperature Tsub was controlled by heating and cooling the circumferential side of the cylindrical roller 6 from the inside, and was varied in the range of 230°C to 300°C.
The layer thickness δ of the o-Cr layer was controlled by changing the transport speed of the polymer substrate 1, and was varied in the range of 100 OA to 6000 OA. By the manufacturing method described above, the substrate temperature T
sub is constant at 260°C, and the chamber internal ambient pressure P2
Magnetic recording media in which a Go-Cr layer was formed by varying the layer thickness δ were prepared, and the presence or absence of cracks was examined under the same conditions.
A comparison is shown in FIG. 3 with an example of a conventional medium in which a Go--Cr film is directly formed on a polymer substrate without an O-oxide layer. O in the figure represents that no cracks were generated, and . represents that cracks were generated. According to FIG. 3, in the case of the magnetic recording medium manufactured in this example (FIG. 3(b)), the area where cracks occur is the same as in the conventional example (FIG. 3(a)).
)) than the value of chamber atmospheric pressure P and Co-C
The value of the r layer thickness δ has shifted to the larger side, and the range in which no cracks occur has expanded. Also, according to Figure 3,
As shown by the broken line in the figure, a rough boundary line between the area where cracks occur and the area where no cracks occur can be obtained. Therefore, the substrate temperature T sub is set to 230°C and 300°C,
Co-C by changing the chamber atmospheric pressure P and layer thickness δ
The above boundary line was similarly determined for the magnetic recording medium in which the r layer was formed. The above boundary lines at each substrate temperature Tsub are shown in FIG. 4 in comparison with an example of a conventional medium in which a Go--Cr film was directly formed on a polymer substrate without a Co oxide layer under the same conditions. Atmospheric pressure inside the chamber P from the boundary line in the diagram
Cracks occur on the side where the value of or the value of the Go-Cr layer thickness δ is larger. In the case of the magnetic recording medium manufactured in this example (FIG. 4(b)), at which substrate temperature Ts
In the case of UB, the boundary line has shifted to the side where the value of the chamber atmospheric pressure P and the value of the Go-Cr layer thickness δ are larger than in the conventional example (Fig. 4 (a)), and the range in which no cranking occurs has expanded. There is. According to FIG. 4, the layer thickness δ of the Co-Cr layer
is 5000 Å or less, the boundary line of the substrate temperature Tsub = 300°C in the conventional example (Fig. 4(a)) and the substrate temperature Tsub = 230°C in the present example (Fig. 4(b)).
When forming a Co-Cr layer under conditions near this boundary line, in the conventional example, the substrate temperature T
While it is impossible to prevent cracks from occurring unless the substrate temperature Tsub is raised to 300℃ or higher, in this example
If the temperature is raised to 230°C or higher, cracks can be prevented from occurring. That is, in the case of the magnetic recording medium manufactured in this example, the chamber atmospheric pressure P and Co
-Cr layer If the layer thickness is constant, the range of the substrate temperature Tsub in which cracks do not occur is also expanded to the side where the value of the substrate temperature Tsub is smaller than in the conventional example. In the case of a magnetic recording medium using a Co-Cr film as a magnetic layer, the Co-Cr film must have a clear columnar structure in order to obtain high reproduction output, but this columnar structure depends on the substrate temperature Tsub. The higher the price, the more you get.

According to our experiments, a columnar structure is generally not obtained when the substrate temperature Tsub exceeds 270°C. Therefore, it is more difficult to obtain a Go--Cr magnetic recording medium that is free from cracks and has a clear columnar structure, the more the atmospheric pressure P in the chamber or the Co--Cr layer thickness value is increased. In view of the above, the manufacturing method of the present invention in this example has the effect of significantly relaxing the restrictive conditions during vapor deposition to obtain a Co-Cr magnetic recording medium that is free of cracks and has a clear columnar structure. It can be said. In addition, when a Go-Cr layer is deposited at a high substrate temperature Tsub to prevent the occurrence of cracks, strong curls generally occur in the resulting magnetic recording medium due to thermal expansion of the polymer substrate, and it is not used as a magnetic recording tape. This causes problems such as adverse effects on running performance, winding performance, and magnetic rad touch. Furthermore, the higher the substrate temperature Tsub is used for vapor deposition, the higher the temperature resistance of the polymer substrate used is required. Therefore, from the standpoint of thermal expansion coefficient and heat resistance, there is very little room for selection of polymer substrates that can be used in conventional manufacturing methods, but the manufacturing method of the present invention in this example According to , the range of selection of polymer substrates to be used can be greatly expanded from the viewpoint of thermal expansion coefficient and heat resistance.

Furthermore, even if a Co-based magnetic thin film layer with sufficient properties for use as a magnetic recording medium can be formed without cracking by conventional manufacturing methods,
By the manufacturing method of the present invention, it is possible to relax the conditions required for various performances of the vacuum evaporation apparatus, such as the chamber pumping speed, the vacuum level achieved in the chamber, and the upper limit of the substrate heating temperature. The effects of the present invention, such as expanding the selection range of polymer substrates and relaxing the conditions required for various performances of the vacuum evaporation apparatus, as described above, can sufficiently lead to cost reduction during mass production.

Here, an example in which the Co oxide layer 2 is mainly composed of a Co oxide other than Co 2 O will be described. Using the continuous evaporation apparatus used in the above example, a high-frequency electrode is arranged between the cylindrical roller 6 and the evaporation source 11, and a mixed gas of oxygen and argon is supplied near the electrode so that the atmospheric pressure in the chamber is approximately lXl0- A Co oxide layer having a thickness of about 100 mm was formed by the ion blating method.

According to measurements using X-ray photoelectron spectroscopy (XPS), the obtained Co oxide layer has a partial pressure ratio of oxygen in the introduced gas of about 3.
When it is 0%, it is mainly composed of Co:IOl, and when the partial pressure ratio of oxygen in the introduced gas is about 60%, it is mainly composed of Coo. Hereinafter, when a Co--Cr layer was formed according to the above-mentioned example and a similar study was conducted, it was found that, for example, Co--
Atmospheric pressure inside the chamber when forming the Cr layer P = 5 X
Under the conditions of 10''5 Torr and substrate temperature T sub =260°C, when the Co oxide layer is mainly composed of Coo, the thickness δ of the Go-Cr layer is approximately 500°C.
While cracks occurred at 0 A or higher, Co
When the oxide layer was mainly composed of Go and O, cracks occurred when the thickness δ of the Go-Cr layer was about 3000 Å or more. Comparing this result with the result shown in FIG. 3, it is found that when the Co oxide layer is mainly composed of Co, the effect of preventing crack generation is remarkable as in the previous example, but The Co oxide layer is mainly Co, 04
There is almost no difference between the film structure and the conventional film structure in which a Go-Cr layer is directly formed without a Co oxide layer, and no significant racking prevention effect is obtained. I understand that. Therefore, in the manufacturing method of the present invention, it is necessary to form the Co oxide layer 2 so that the atomic composition of Co and O is approximately 1:1. on the other hand,
Even when some of the Co atoms in the Co oxide layer are replaced with Ni or Fe or both up to a maximum of 20%, if the composition of these metal atoms and O is approximately 1:1, the Co made of Co It was possible to obtain the same crack prevention effect as when using an oxide layer.

Now, when we conducted a similar study in accordance with the above, we found that when the composition of Cr in Co-CrJil as the Co-based magnetic thin film layer 3 was varied in the range of 10 to 30% by weight, Ni
When using a Go-Cr-Ni film containing 10 to 30% by weight of Cr and 0 to 20% by weight of N5, the polymer substrate 1 has a thickness of 7.5,17111.151 An,
Similar results were obtained in all cases where No. 204 was used. In addition, as shown in FIG. 1(b), an underlayer 4 such as permalloy with a thickness of about 2000λ or A (1-Cu) with a thickness of about 100 is provided on the substrate, and a Co oxide layer 2 is formed on it. , Go as the Co-based magnetic thin film layer 3
Results similar to those described above were also obtained with a magnetic layer formed of a -Cr film or a Go-Cr-Ni film.

Furthermore, as shown in FIGS. 2(a) and (b), G.

After forming the oxide layer 2, carbon is applied through the intermediate layer 5 made of Ti, Ge, etc.
A Co-Cr film or a Co-
In the case where the magnetic layer of Cr--Ni film was formed, the same results as above were obtained when the layer thickness of the intermediate layer 5 was 500 Å or less. Further, as the Co-based magnetic thin film layer 3, G o
Similar results were obtained when the -N i-0 film was used as in the case where the Go-Cr film was used.

For reference, we also investigated a case where a single Co film was used as the Co-based magnetic thin film layer 3, although it was not practical as a magnetic recording medium, and the same results as above were obtained.

Note that even when any of the above-mentioned magnetic thin films is used as the Co-based magnetic thin film layer 3, when the layer thickness of the Go oxide MI2 is increased to 500λ or more, significant deterioration of the magnetic properties is observed. Therefore, it is desirable that the thickness of the Co oxide layer be extremely thin within the range in which the effects of the present invention can be obtained, but in this example, the thickness of the Co oxide layer is uniform at the value of 100 While a film with excellent crack prevention properties can be obtained, and the effect of preventing cracks is sufficiently recognized, it is also sufficiently effective to be comparable to conventional thin film media in which a Co-based magnetic thin film is formed directly without a Co@ride layer or only through an underlayer. It also has good magnetic properties.

(Effects of the Invention) As described above, according to the method of the present invention, when a Co-based thin film magnetic recording medium is formed on a polymer substrate by vacuum evaporation, the atmospheric pressure P in the chamber is such that no cracks occur.
The range of substrate temperature T sub and film thickness δ can be made wider than in conventional manufacturing methods. As a result, various conditions during vapor deposition, which were limited in conventional manufacturing methods from the viewpoint of preventing the occurrence of cracks, are relaxed, and it becomes easier to optimize the magnetic properties and recording/reproducing properties of the magnetic layer.

At the same time, the method according to the present invention expands the selection range of polymer substrates in terms of heat resistance and coefficient of thermal expansion, and also eases the requirements for various performances of vacuum evaporation equipment. also leads to cost reduction. As described above, according to the method of the present invention,
The present invention has the effect that it is possible to provide a method for manufacturing at a lower cost a Go-based thin film magnetic recording medium that is free from cracks and has excellent magnetic properties, recording and reproducing properties, and running and winding properties as a magnetic tape.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing the film structure of a magnetic recording medium according to the present invention, and FIG. 3 is a view showing the presence or absence of cracks in magnetic recording media produced under different conditions in Examples of the present invention. FIG. 4 is a diagram showing the approximate boundary line between the crack-producing and non-cracking regions of magnetic recording media produced under different conditions in the examples of the present invention, and FIG. FIG. 2 is a diagram showing a cylindrical roller system used when forming a thin film magnetic recording medium. 1...Polymer substrate, 2...Co oxide layer, 3
... Go-based magnetic thin film layer, 4 ... Underlayer, 5
... intermediate layer, 6 ... cylindrical roller, 7 ... supply roll, 8 ... take-up roll, 9 ...
Guide roller, 10... mask, 11... evaporation source,
12... Crucible.

Claims (2)

[Claims] (1) Directly or via a base layer on the polymer substrate,
After forming a Co oxide layer having a NaCl type structure with a layer thickness of 500 Å or less and an atomic composition of Co and O of approximately 1:1, a Co-based magnetic thin film layer is formed by a vacuum evaporation method. A method for manufacturing a magnetic recording medium. (2) The method for manufacturing a magnetic recording medium according to claim (1), wherein after forming the Co oxide layer, the Co-based magnetic thin film layer is formed via an intermediate layer having a thickness of 500 Å or less.