JPS60185224A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a magnetic metal layer and to expand the life of the magnetic metal layer by containing Cr, Al and Si and metal selected from alloys containing one or more said metals or their metal oxide into a ferromagnetic metallic thin film layer formed on a base body so as to be gradually reduced. CONSTITUTION:The base body 7 such as a polyester film is moved from a negative roll 8 along a cylindrical can 4 and wound around a winding roll 11, a magnetic material 14 such as Co and Co-Ni is set in an evaporation source 12 in a vacuum evaporation room 6 and Co-Cr alloy or individual metal 15 of Ar, Al and Si is set in an evaporation source 13 to evaporate these materials simultaneously in vacuum. Thus, a ferromagnetic material 14 is evaporated on the base body 7 at first, and then Cr, Al or Si is evaporated. Subsequently, O2 gas is supplied from a leading-in pipe by a glow discharge electrode 17 in a plasma treatment room 5 to oxidize the ferromagnetic metal thin film with plasma. Thus, a Co-rich cylindrical layer 20 consisting of Co or Co alloy is formed on the base body 7 and a corrosion-resistant alloy layer 21 containing much Co-Cr or the like and a layer 22 consisting of metal oxide and having high corrosion resistance are successively laminated on the layer 20 so that the density of these components is gradually reduced in the direction of the base board. Consequently, a magnetic recording medium having high durability can be obtained.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a magnetic recording medium having a ferromagnetic metal thin film layer as a recording layer, and more particularly relates to a magnetic recording medium having a ferromagnetic metal thin film layer containing a metal or an oxide thereof. Related to magnetic recording media.

[Background technology]

A magnetic recording medium having a ferromagnetic metal thin film layer as a recording layer is usually made by depositing metals or their alloys on a substrate such as a polyester film by vacuum deposition or the like.
Although it has characteristics suitable for high-density recording, it is easily oxidized by oxygen in the air, and this oxidation causes problems such as deterioration of magnetic properties such as maximum magnetic flux density.

For this reason, conventional efforts have been made to improve corrosion resistance by oxidizing the surface of the columnar crystals constituting the ferromagnetic metal thin film layer by vacuum evaporation in an oxygen gas atmosphere (Japanese Patent Laid-Open No. 56-23208). ) However, with the method of oxidizing the surface of the columnar crystals constituting the ferromagnetic metal thin film layer, the chemical stability of the ferromagnetic metal thin film layer is insufficient, and corrosion resistance cannot be sufficiently improved.

[Purpose of the invention]

This invention was made as a result of various studies to eliminate such drawbacks, and its purpose is to incorporate metals or their oxides with excellent corrosion resistance into the ferromagnetic metal thin film layer. It is an object of the present invention to provide the above-mentioned magnetic recording medium having excellent corrosion resistance.

[Summary of the invention]

In this invention, a metal selected from chromium, aluminum, silicon, and an alloy containing at least one of these metals, or an oxide thereof, is contained in a thin ferromagnetic metal layer so as to gradually decrease as it approaches a substrate. The chemical stability of the ferromagnetic metal thin film layer is improved and the magnetic properties are deteriorated by containing these metals or their oxides so that /41i decreases as it approaches the substrate. Corrosion resistance has been sufficiently improved without causing any damage.

In this invention, the formation of a ferromagnetic metal thin film layer containing a metal selected from chromium, aluminum, silicon, and alloys containing at least one of these or their oxides with a concentration gradient that gradually decreases as it approaches the substrate includes: This is carried out by binary vapor deposition of these metals or their oxides together with a ferromagnetic material, or by further oxidizing the binary vapor deposition by plasma oxidation or the like.

Figure 11 shows an example of a vacuum deposition apparatus used to form a ferromagnetic metal thin film layer containing the metals or their oxides with a concentration gradient that gradually decreases as it approaches the substrate. This figure shows a schematic cross-sectional view of the figure, and the following description will be made with reference to this figure.

In the figure, 1 is a vacuum chamber, and the inside of this vacuum chamber 1 is divided by partition walls 2 and 3, and a plasma processing chamber 5 is evacuated so that a cylindrical can 4 disposed in the center of the vacuum chamber 1 straddles it. It is formed separately from the vapor deposition chamber 6. A substrate 7 such as a polyester film moves along the circumferential side of the cylindrical can 4 from a raw roll 8 via a guide roll 9, and is wound onto a take-up roll 11 via a guide roll 10.

During this time, the base body 7 moves along the circumferential side of the cylindrical can 4.
In contrast, a ferromagnetic material 14 is produced by a ferromagnetic material evaporation source 12 and a metal evaporation source 13 arranged adjacent to the lower part of the vacuum deposition chamber 6.
Then, the metal such as chromium, aluminum, silicon, or an alloy 15 containing at least one of these metals is heated and evaporated, and the ferromagnetic material 14 and the metal or alloy 15 are simultaneously deposited. At this time, since the ferromagnetic material evaporation source 12 is disposed on the side where the substrate 7 is introduced, the ferromagnetic material is first deposited on the substrate 7, and then the metal or alloy mentioned above is deposited together with the ferromagnetic material. be done.

As a result, a ferromagnetic metal thin film layer containing the metal or alloy with a concentration gradient that gradually decreases as it approaches the substrate is formed. The ferromagnetic metal thin film layer thus formed is subsequently subjected to plasma oxidation in the adjacent plasma processing chamber 5 by introducing oxygen gas from the oxygen gas introduction tube 16 and by glow discharge from the glow discharge electrode 17. The metal or alloy contained in the ferromagnetic metal thin film layer is oxidized. As a result, a ferromagnetic metal thin I! containing the aforementioned metal or alloy with a concentration gradient that gradually decreases as it approaches the substrate! On top of the layer, a ferromagnetic metal thin film layer is further formed containing oxides of these metals or alloys with a concentration gradient that gradually decreases as it approaches the substrate. When such plasma oxidation is performed, the ferromagnetic material is also oxidized at the same time, so the oxide of the ferromagnetic material is similarly contained with a concentration gradient such that it gradually decreases as it approaches the substrate. . 1
8 and 19 are exhaust systems connected to the vacuum deposition chamber 6 and the plasma processing chamber 5, respectively, and these exhaust systems evacuate the vacuum deposition chamber 6 and the plasma processing chamber 5 to a predetermined degree of vacuum, respectively. In addition, in the above explanation, a case was explained in which a ferromagnetic metal thin film layer containing a metal or alloy with a concentration gradient that gradually decreases as it approaches the substrate is further oxidized. is obtained, so oxidation is not necessary.

The metals and alloys that are contained in the ferromagnetic metal thin film layer with a concentration gradient that gradually decreases as it approaches the substrate include metals with excellent corrosion resistance such as chromium, aluminum, and silicon, and alloys containing at least one of these metals. are preferably used, and alloys of these metals with excellent corrosion resistance and ferromagnetic metals, such as cobalt-chromium alloys, are also suitably used. When these highly corrosion-resistant metals such as chromium, aluminum, and silicon, and alloys containing these metals, are contained in a ferromagnetic metal thin film layer with a concentration gradient that gradually decreases as it approaches the substrate, The corrosion resistance of the ferromagnetic metal thin film layer is sufficiently improved by the metal having excellent corrosion resistance contained in a high concentration.

In addition, the ferromagnetic material in the ferromagnetic metal thin film layer has a concentration gradient that gradually decreases as it approaches the surface of the ferromagnetic metal thin film layer, contrary to the metals mentioned above, and because it is also present on the surface, the magnetic properties deteriorate. There's nothing to do.

In this way, even if a metal with excellent corrosion resistance is contained in a ferromagnetic metal thin film layer with a concentration gradient that gradually decreases as it approaches the substrate, corrosion resistance can be sufficiently improved without causing deterioration of magnetic properties. However, plasma oxidation selectively oxidizes these corrosion-resistant metals or alloys, making the oxides of these metals or alloys ferromagnetic. The corrosion resistance of the ferromagnetic metal thin film layer is further improved by the metal or alloy oxide with excellent corrosion resistance, which is contained in the metal thin film layer with a concentration gradient that gradually decreases as it approaches the substrate. When this plasma oxidation is performed, the ferromagnetic material is also oxidized at the same time, so the oxide of the ferromagnetic material is also contained in the ferromagnetic metal thin film layer at the same concentration as the oxide of the metal. , the corrosion resistance of the ferromagnetic metal thin film layer is further improved.The gas pressure of oxygen gas in the plasma processing chamber 5 during plasma oxidation is 3X10-').
- I No discharge occurs.

In this way, the content of the metal, alloy, or oxide thereof, which is contained in the ferromagnetic metal thin film layer with a concentration gradient that gradually decreases as it approaches the substrate, is
The average content is 1 to 20% by weight near the substrate, 1 to 70% by weight near the surface, based on the total amount with the ferromagnetic material.
It is preferable that the content is within the range of % by weight, and if the content near the surface is too small, corrosion resistance will not be sufficiently improved.
If the amount is too large, it may adversely affect magnetic properties.

As a ferromagnetic material, C02F e 1N iSCo-N
i alloy, Co-Cr alloy, Go-P alloy, C,.

-Ni-P alloys and other ferromagnetic materials commonly used in vacuum deposition may be used.

Further, as the substrate, a plastic film made of commonly used polymer moldings such as polyester, polyimide, polyamide, etc., and a metal film made of a nonmagnetic metal such as copper are used.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Using the vacuum evaporation apparatus shown in FIG.
The sheet was moved along the circumferential side of the cylindrical can 4 through the guide roll 10 and then wound onto the winding roll 11. At the same time, place 0014 into the ferromagnetic material evaporation source 12 in the vacuum evaporation chamber 6, and
A Co-Cr alloy (weight ratio 7:3) 15 was set in the chamber. Next, the vacuum deposition chamber 6 is heated to 1X using the exhaust systems 18 and 19.
At the same time, the plus/armor treatment chamber 5 is evacuated to lx10-6 Torr, and C014 in the ferromagnetic material evaporation source 12 and C014 in the metal evaporation source 13 are evacuated.
The o-Cr alloy 15 is heated and evaporated to form a 1,000-thick ferromagnetic metal thin film layer made of Go on the polyester film 7 and containing the co-Cr alloy so as to gradually decrease as it approaches the polyester film 7. Formed. Next, oxygen gas was introduced from the oxygen gas inlet pipe 16 in the plasma processing chamber 5, and plasma oxidation was performed at an oxygen gas pressure of 1×1 O −1 Torr and an applied voltage of the glow discharge electrode 17 of 550 μm. After that, they were cut into predetermined shapes to make magnetic tape. When the ferromagnetic metal thin film layer of the magnetic tape thus obtained was observed with an electron microscope, it was found that columnar crystals 20 containing a large amount of Co and a small amount of Co-Cr alloy were found in the center, as shown in FIG. A thin film layer 21 of co and Co-Cr alloy containing more Co-Cr alloy than the center is precipitated and formed on the circumferential surface.
A thin film 1'ti22 containing a large amount of o-Cr alloy oxide and a small amount of Co oxide was deposited to form a ferromagnetic metal thin film layer 23.

In addition, as a result of examining the concentration distribution of Co-'Cr alloy and oxygen in this ferromagnetic metal thin film layer using an Auger electron spectrometer, analysis in the thickness direction showed that the concentration distribution of Co-'Cr alloy and oxygen in this ferromagnetic metal thin film layer was up to 450 mm as shown in curve A in Figure 3. A concentration distribution in which Cr gradually decreases as it approaches the substrate 7 was detected, and as shown by curve B, a concentration distribution in which oxygen gradually decreases as it approaches the substrate 7 was detected in the analysis in the thickness direction up to a thickness of 400 mm. In addition, in FIG. 3, curve C is the concentration distribution of Co, and 7 is the polyester film.

Example 2 In Example 1, Co14 was added in the ferromagnetic material evaporation source 12.
Instead, a Co-Ni alloy (weight ratio 8:2) 14 is set, and Cr is set in place of the Co-Cr alloy 15 in the metal evaporation source 13.
A magnetic tape was produced in the same manner as in Example 1, except that the voltage applied to the glow discharge electrode attached to the plasma processing chamber 5 was changed from 550 V to 450 V. The concentration distribution of Cr and oxygen in the ferromagnetic metal thin film layer of the obtained magnetic tape was investigated using an Auger electron spectrometer. As a result of the analysis in the thickness direction, as shown by curve A in Fig. A concentration distribution in which Cr gradually decreased as it approached the substrate 7 was detected, and as shown by curve B, a concentration distribution in which oxygen gradually decreased as it approached the substrate 7 was detected in the analysis in the thickness direction up to a thickness of 300 mm. Furthermore, the fourth
In the figure, curve C is the concentration distribution of Co, and the curve is N
This is the concentration distribution of i. Further, 7 is a polyester film.

Example 3 In Example 1, A115 was set in place of the co-Cr alloy 15 in the metal evaporation source 13, and the voltage applied to the glow discharge electrode attached to the plasma processing chamber 5 was set at 550 V.
A magnetic tape was produced in the same manner as in Example 1, except that the magnetic tape was changed from 450 square meters to 450 square meters. The concentration distribution of Al and oxygen in the ferromagnetic metal thin film layer of the obtained magnetic tape was investigated using an Auger electron spectrometer. As shown in the curve in Figure 5, the analysis in the thickness direction showed that the concentration distribution of Al and oxygen in the ferromagnetic metal thin film layer was up to 500 mm. A concentration distribution that gradually decreased as AI approached the substrate 7 was detected, and as shown in curve B, a concentration distribution that gradually decreased as oxygen approached the substrate 7 was detected in the analysis in the thickness direction up to a thickness of 300. In addition, in FIG. 5, curve C is the concentration distribution of Co, and 7 is the polyester film.

Example 4 "In Example 1, 5i15 was set in place of the Co-Cr alloy 15 in the metal evaporation source 13, and the voltage applied to the glow discharge electrode attached to the plasma processing chamber 5 was set to 550.
A magnetic tape was produced in the same manner as in Example 1 except that V was changed to 450V. As a result of examining the concentration distribution of Si and oxygen in the ferromagnetic metal thin film layer of the obtained magnetic tape using an Auger electron spectrometer, analysis in the thickness direction showed that the thickness up to 800 mm was observed as shown in curve A in Figure 6. A concentration distribution that gradually decreases as Si approaches the substrate 7 is detected, and as shown in curve B, the thickness f71400 is determined by analysis in the thickness direction.
A concentration distribution was detected in which oxygen gradually decreased as it approached the base 7 up to the human body. In addition, in Fig. 6, the curve C is Co'
7 is a polyester film.

Example 5 A magnetic tape was produced in the same manner as in Example 1 except that the plasma oxidation treatment was omitted. When the ferromagnetic metal thin film layer of the magnetic tape thus obtained was observed with an electron microscope, it was found that Go
A columnar crystal 2o containing a large amount of Co-Cr alloy and a small amount of Co-Cr alloy is precipitated, and on its peripheral surface a thin film layer 21 of Co and co-Cr alloy containing a larger amount of Co-Cr alloy from the center.
The ferromagnetic metal thin film layer 24 was formed by precipitation. In addition, as a result of examining the concentration distribution of the Co-Cr alloy in the ferromagnetic metal S film layer of the obtained magnetic tape using an Auger electron spectrometer, it was found that the thickness A concentration distribution in which Cr gradually decreased as it approached the substrate 7 was detected up to 500 people. In addition, in FIG. 8, curve B is the concentration distribution of CO, and 7 is the polyester film.

Example 6 In Example 2, a magnetic tape was produced in the same manner as in Example 1 except that the plasma oxidation treatment was omitted. The concentration distribution of Cr in the ferromagnetic metal thin film layer of the obtained magnetic tape was investigated using an Auger electron spectrometer, and as shown by curve A in Figure 9, analysis in the thickness direction revealed that Cr up to a thickness of 800 mm was observed.
A concentration distribution was detected that gradually decreased as r approached the substrate 7.

In addition, in FIG. 9, curve B is the concentration distribution of CO,
Curve C is the concentration distribution of Ni. Further, 7 is a polyester film.

Example 7 In Example 3, a magnetic tape was produced in the same manner as in Example 1 except that the plasma oxidation treatment was omitted. As a result of examining the concentration distribution of AI in the ferromagnetic metal thin film layer of the obtained magnetic tape using an Auger electron spectrometer, curve A in Fig. 10 was obtained.
As shown in FIG. 2, analysis in the thickness direction detected a concentration distribution in which AI gradually decreased as it approached the substrate 7 up to a thickness of 900 layers. In addition, in FIG. 10, curve B is the concentration distribution of Co, and 7 is the polyester film.

Example 8 In Example 4, a magnetic tape was produced in the same manner as in Example 1 except that the plasma oxidation treatment was omitted. As a result of examining the Si concentration distribution in the ferromagnetic metal thin film layer of the obtained magnetic tape using an Auger electron spectrometer, curve A in FIG.
As shown in FIG. 2, analysis in the thickness direction detected a concentration distribution in which Si gradually decreased as it approached the substrate 7 up to a thickness of 900 mm. In addition, in FIG. 11, curve B is the concentration distribution of Co, and 7 is the polyester film.

Comparative Example 1 As shown in FIG.
6 is arranged, the substrate 7 is moved along the circumferential side of the cylindrical can 26 from the original fabric roll 27 via the guide roll 28, and is wound onto the take-up roll 30 via the guide roll 29, and A gas introduction pipe 3 is installed on the side wall of the vacuum chamber 25.
Using a vacuum evaporation apparatus equipped with C'o 3''3, C'o 3''3
At the same time, oxygen gas is introduced into the gas introduction pipes 31a and 31, and Co33 in the ferromagnetic material evaporation source 32 is heated and evaporated at an oxygen gas pressure of 1X10-5 tons to perform vacuum evaporation. A ferromagnetic metal thin film layer composed of columnar crystal grains with oxidized surfaces was formed. After that,
A magnetic tape was made by cutting it into 11 pieces.

Comparative example 2 In Example 1, C in the metal evaporation source 13.

A magnetic tape was produced in the same manner as in Example 1 except that the vacuum deposition of the -Cr alloy and the plasma oxidation treatment were omitted.

Comparative Example 3 A magnetic tape was produced in the same manner as in Example 2, except that the vacuum evaporation of Cr in the metal evaporation source 13 and the plasma oxidation treatment were omitted.

The magnetic tape obtained in each example and each comparative example was heated at 60°C.
, 90% RH, and the deterioration rate of the maximum magnetic flux density over time was measured, with the maximum magnetic flux density of the magnetic tape before being left as 100%, to examine corrosion resistance. 13th
The figure is a graph showing the change in the deterioration rate of the maximum magnetic flux density, where graph A is the magnetic tape obtained in Example 1, graph B is the magnetic tape obtained in Example 2, and graph C is the magnetic tape obtained in Example 2. Graph D is the magnetic tape obtained in Example 4. Graph E is the magnetic tape obtained in Example 5. Graph F is the magnetic tape obtained in Example 6. Graph G is the magnetic tape obtained in Example 6. Graph H shows the magnetic tape obtained in Example 7. Graph I shows the magnetic tape obtained in Comparative Example 1. Graph J shows the magnetic tape obtained in Comparative Example 2. shows the magnetic tape obtained in Comparative Example 3.

〔Effect of the invention〕

As is clear from the graph shown in FIG. 13, the deterioration rate of the magnetic tapes obtained in Comparative Examples 1 to 3 becomes extremely large with the passage of time, whereas the magnetic tapes obtained according to the present invention (implemented) In all of Examples 1 to 8), the deterioration rate increases over time, which indicates that the magnetic recording medium obtained by the present invention has excellent corrosion resistance.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of a vacuum evaporation apparatus used to manufacture the magnetic recording medium of the present invention, and FIGS. 2 and 7 are electron microscope observations of the magnetic tape obtained by the present invention. The enlarged cross-sectional explanatory views of the ferromagnetic metal thin film layer shown in FIGS. 3 to 6 show the ferromagnetic metal thin film II of the magnetic tape obtained according to the present invention! ii! Explanatory diagrams showing the results of examining the distribution state of ferromagnetic material, metal, and oxygen in the layer using an Auger electron spectrometer, Figures 8 to 11 are diagrams showing the results of examining the distribution state of the ferromagnetic material, metal, and oxygen in the layer in the ferromagnetic metal thin film layer of the magnetic tape obtained by the present invention. An explanatory diagram showing the results of examining the distribution state of ferromagnetic materials and metals using an Auger electron spectrometer, and FIG. 12 is a schematic cross-sectional view showing an example of a vacuum evaporation apparatus used to manufacture conventional magnetic recording media. , FIG. 13 is a diagram showing the relationship between the deterioration rate of the magnetic tape obtained by the present invention and the elapsed time. 7... Polyester film (substrate), 23.24.
...Ferromagnetic metal thin film layer patent applicant Hitachi Maxell Co., Ltd. Figure 12 Figure 15 Elapsed time

Claims (1)

[Claims] 1. In a magnetic recording medium in which a ferromagnetic metal thin film layer is provided on a substrate, a metal selected from chromium, aluminum, silicon, and an alloy containing at least one of these or an oxide thereof is contained in the ferromagnetic metal thin film layer. A magnetic recording medium characterized in that the content gradually decreases as it approaches the substrate.