JPH09204632A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability and head-touch of a magnetic recording medium, particularly the magnetic recording medium with a magnetic layer containing iron, nitrogen and oxygen. SOLUTION: In a magnetic recording medium with at least two layers of magnetic layers formed on a supporter, both the first magnetic layer farthest from the supporter and the second magnetic layer adjacent to the first magnetic layer in all magnetic layers are formed in an Fe-N-O magnetic layer, and nitrogen concentration in the first magnetic layer is made higher than that in the second magnetic layer. Coercive force (Hc) is set at 1000Oe or more.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a magnetic recording medium. More specifically, the present invention relates to a metal thin film type magnetic recording medium having a magnetic layer containing iron, nitrogen and oxygen.

[0002]

2. Description of the Related Art Magnetic recording media, such as magnetic tape,
The binder is completely coated by using a coating tape made by coating a magnetic paint in which a magnetic powder is dispersed in a binder on a film that is a non-magnetic support, and a vacuum deposition method that deposits a magnetic metal in a vacuum on the film. There is a metal thin film type tape in which a magnetic layer of a metal thin film which is not included is attached on a non-magnetic support.
And, magnetic recording in recent years is in the direction of high density recording,
The metal thin film type tape is considered to be promising for high density recording because the density of the magnetic material can be increased because the magnetic layer does not contain a binder.

By the way, as a magnetic material for a magnetic layer formed on a non-magnetic support by a vacuum deposition method, Co type, Co--Ni type and Co--Cr type ferromagnetic alloys are conventionally used. There is. However, Co, Ni and Cr are all expensive and have pollution problems. In this respect, Fe (metallic iron) is inexpensive and has no problem in terms of pollution safety, but it has the drawbacks of low coercive force, which is essential for high recording density, and low corrosion resistance. , Co—Cr based materials and magnetic layer materials replacing Fe are desired. In addition, in order to increase the recording density, the relative contact speed between the tape and the head tends to increase. However, at present, satisfactory durability is not obtained for the metal thin film type magnetic layer.

Under these circumstances, Fe is used as a main component of the magnetic layer, which is inexpensive and does not cause environmental pollution, and oxygen, nitrogen, etc. are deposited during deposition of Fe in order to form a magnetic layer having corrosion resistance. By irradiating with gas of these and mixed gas of these, so-called ion-assisted deposition method,
Attempts have been made to form Fe-N based and Fe-N-O based magnetic films. On the other hand, it has also been attempted to improve the S / N and reduce the error rate by making the Fe-based magnetic layer a multilayer structure.

[0005]

However, in particular, Fe
In the -N-O-based magnetic layer, durability and head touch may not always be sufficient depending on the existence state (concentration) of each element in the magnetic layer. At present, it has not been sufficiently examined whether or not these three elements should be present in the magnetic layer in proportion. In particular, in a magnetic recording medium having a multi-layer structure having a plurality of Fe-N-O based magnetic layers, the influence of the element concentration in each magnetic layer on durability and head touch has hardly been studied. Therefore, the object of the present invention is to provide Fe-N
In a magnetic recording medium having a plurality of -O based magnetic layers, the present invention aims to provide a magnetic recording medium having a magnetic layer having higher durability and good head touch, paying attention to the abundance of three elements, particularly nitrogen. .

[0006]

In order to obtain a magnetic recording medium having an Fe—N—O type magnetic layer which is more durable and has a good head touch in view of the above situation, As a result of earnest research, the magnetic layer farthest from the support (the outermost magnetic layer) and the magnetic layer adjacent to the magnetic layer were both Fe-N-O based magnetic layers and the outermost magnetic layer. The inventors have found that the above object can be achieved by increasing the nitrogen concentration in the lower Fe—N—O 2 -based magnetic layer to achieve the present invention.

That is, the present invention is a magnetic recording medium having a support and at least two magnetic layers formed on the support, and a first magnetic layer farthest from the support among all magnetic layers. The second magnetic layer adjacent to this is a magnetic layer containing iron, nitrogen and oxygen as main components (hereinafter referred to as Fe—N—O based magnetic layer), and the nitrogen concentration (N ₁ ) Is higher than the nitrogen concentration (N ₂ ) in the second magnetic layer, there is provided a magnetic recording medium.

The term "mainly composed of iron, nitrogen and oxygen" as used herein means that even if other elements are contained, the amount thereof is minute and the concentration is such that the intended effect of the present invention is not affected. Means that.

The magnetic recording medium of the present invention has at least two magnetic layers, and the first magnetic layer farthest from the support and the second magnetic layer adjacent to the first magnetic layer are both Fe--N. -O type magnetic layer. The nitrogen concentration (N ₁ ) in the first magnetic layer is higher than the nitrogen concentration (N ₂ ) in the second magnetic layer (N ₁ > N ₂ ). As long as this relationship is satisfied, the type and formation position of the other magnetic layer does not matter. Here, the nitrogen concentration in the Fe-N-O-based magnetic layer refers to the total nitrogen content in each magnetic layer.

In the magnetic recording medium of the present invention, each Fe--N
The nitrogen concentration distribution in the —O 2 magnetic layer may have a concentration variation of about several percent in the depth direction of each magnetic layer. Here, the depth direction of the magnetic layer means a direction perpendicular to the support from the surface of the magnetic layer.

In the magnetic recording medium of the present invention, the total nitrogen concentration (N ₁ ) in the first magnetic layer is preferably 10-30 atom%. The total nitrogen concentration (N ₂ ) in the second magnetic layer is preferably 5 to 20 atom%. Furthermore, the difference between N ₁ of N ₁ and N ₂
It is desirable that -N ₂ is 5 atomic% or more.

The magnetic recording medium of the present invention has at least two Fe--N--O magnetic layers, but iron (Fe), nitrogen (N) and oxygen (O) in the total of all Fe--N--O magnetic layers. ) Is the atomic ratio (%) of Fe: N: O = 60〜 in terms of durability.
The range of 88: 7 to 25: 5 to 35 is preferable.

In the magnetic recording medium of the present invention, it is considered that since the nitrogen concentration in the first magnetic layer is higher, the hardness of the surface layer is higher, the durability is improved, and the head touch is improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the magnetic recording medium of the present invention,
The Fe-N-O-based magnetic layer is formed by a so-called ion-assisted vapor deposition method in which nitrogen ions and oxygen ions are supplied while iron is vapor-deposited. The ion-assisted deposition method for forming the magnetic layer can be performed by a conventionally known method. However, as described above, in the present invention, it is necessary to adjust the supply amount of nitrogen ions so that the nitrogen concentration N ₁ in the first magnetic layer becomes higher than the nitrogen concentration N ₂ in the second magnetic layer.

The relationship between the oxygen concentration and the iron concentration in the first magnetic layer and the second magnetic layer is not limited, but when N ₁ > N ₂ ,
The oxygen concentration (O ₁ ) in the first magnetic layer can be made lower than the oxygen concentration (O ₂ ) in the second magnetic layer (O ₁ <O ₂ ) by adjusting the supply amount of oxygen ions. . N ₁ + O ₁ may be almost the same as N ₂ + O ₂ . Further iron concentration (Fe ₁₎ and the iron concentration in the second magnetic layer of the first magnetic layer (Fe ₂₎ and may be substantially the same. In the present invention, "substantially the same"
The concentration does not mean that they are exactly the same concentration, and there may be a difference in concentration of several% within the range that does not impair the effects of the present invention, but the difference in concentration is less than 5%.

The element concentration in the magnetic layer can be measured by Auger electron spectroscopy. However, in the surface layer of the magnetic recording medium and in the vicinity of the interface between the support and the magnetic layer, the shape of the Auger profile must be accurately determined due to the influence of foreign matter (contamination), lubricant, protective layer, support, etc. Is difficult, and in the present invention, the change in element concentration in these portions is not considered.

In the present invention, the magnetic layer formed on the support may be three or more layers of Fe--N--O type magnetic layer. In that case, as described above, the outermost surface layer of all magnetic layers. The nitrogen concentration, the oxygen concentration, and the iron concentration of the other layers are not limited as long as the nitrogen concentration of the first magnetic layer and the nitrogen concentration of the second magnetic layer adjacent thereto are satisfied and satisfy the relationship defined in the present invention. Also,
A magnetic layer made of another metal material, such as Co or Co—Ni, may be formed below the second magnetic layer. Further, a non-magnetic intermediate layer may be formed between the support and the second magnetic layer or between the first magnetic layer and the second magnetic layer.

The coercive force (Hc) of the magnetic recording medium of the present invention is preferably 1000 (Oe) or more, more preferably 1200 (Oe) or more.

In the present invention, the thickness of the Fe--N--O system magnetic layer is not limited, but usually, the thickness of the first magnetic layer and the second magnetic layer is 500 to 2000 Å, and when other magnetic layers are formed, the thickness thereof is not limited. It is about 500-2000Å.

Materials for the support of the magnetic recording medium of the present invention include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonates; polychlorination. Vinyl; polyimide; plastics such as aromatic polyamide are used. The thickness of these base materials is about 3 to 50 μm.

On the magnetic layer, a protective layer having a thickness of about 10 to 200 Å, especially a carbon thin film such as diamond-like carbon and graphite, a silicon-containing thin film such as silicon oxide and silicon carbide, a zirconium oxide thin film, etc. It is desirable to provide a protective layer. Moreover, a thickness of 2 to 50 is formed on the protective layer.
It is preferable to form a lubricating layer of about Å, especially a lubricating layer made of a fluorine-based lubricant such as perfluoropolyether,
On the surface opposite to the surface on which the magnetic layer is formed, a back coat layer containing carbon black as a main component and having a thickness of about 0.1 to 1.0 μm may be further provided. As a raw material for forming these layers, conventionally known materials can be appropriately used. Further, the back coat layer may be formed by depositing a metal such as Cu-Al alloy.

FIG. 1 shows an example of a vacuum vapor deposition apparatus for oblique vapor deposition used for manufacturing the magnetic recording medium of the present invention. FIG.
In, the inside of the vacuum container 1 is maintained in a vacuum state by a vacuum system (not shown). The vacuum container 1 is defined by a plurality of chambers, and this apparatus has a chamber A for forming a second magnetic layer (lower layer) and a chamber B for forming a first magnetic layer (upper layer). An unwind roll 2 and a take-up roll 3 are provided in the vacuum container, and PET (polyethylene terephthalate), polyimide, aramid, or the like is fed between the unwind roll 2 and the take-up roll 3 while being unwound. The film 4 as a support manufactured in
It travels and moves on the can roll 5 ′ in the chamber B via the cylindrical can roll 5 installed therein. Each can roll has a cooling mechanism inside. Below each can roll, MgO-made crucibles 6 and 6'are placed, and iron (for example, 99.95% pure Fe) 7 and 7'is put in the crucibles 6 and 6 '. An electron beam is emitted from the electron beam guns 8 and 8 ′ obliquely above the surface. As a result, Fe is heated and vaporized. At the time of vapor deposition of Fe, the ion guns 9 and 9 ′ are arranged so that the ions are irradiated in the direction perpendicular to the vapor deposition surface of the film 4, and nitrogen gas is supplied to the ion guns 9 and 9 ′ to generate nitrogen ions. Then, while depositing Fe on the film 4 and ventilating the oxygen gas from the oxygen gas introducing pipes 10 and 10 ', Fe-N-O of the lower layer
The system magnetic layer and the outermost Fe-N-O system magnetic layer are formed. The ion guns 9 and 9'can change the irradiation direction of nitrogen ions. It is also possible to supply a mixed gas of nitrogen gas and oxygen gas to the ion guns 9 and 9'to generate nitrogen ions and oxygen ions, and irradiate the vapor deposition surface of the film with nitrogen ions and oxygen ions. In FIG. 1, 11 and 11 'are film 4
It is a shielding plate for controlling the vapor deposition range on the substrate. Further, it is of course possible to form the Fe—N—O 2 -based magnetic layers as the lower and upper layers in a batch process by using an apparatus having one chamber as shown in FIG.

[0023]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 (1) Manufacture of magnetic recording medium A magnetic film was manufactured by forming two Fe—N—O based magnetic layers on a PET film, further forming a lubricating layer and a back coat layer. did. The conditions for forming each layer are as follows. The ion-assisted oblique deposition apparatus shown in Fig. 1 has a thickness of 6.3.
The PET film 4 of μm is set, the electron gun 8 is operated in the chamber A (output 15 kW) while running at the speed of 2.4 m / min, the iron 7 in the crucible 6 is evaporated, and the PET film 4 is placed on the PET film 4. While vapor-depositing iron particles, nitrogen gas was supplied to the Kauffman type ion gun 9 (flow rate 10 SCCM) to generate nitrogen ions, which were irradiated with nitrogen ions toward the iron vapor deposition surface of the PET film 4, and the oxygen gas introduction pipe 10 The second magnetic layer (lower layer) was formed by further ventilating oxygen gas (flow rate 28 SCCM). Subsequently, the first magnetic layer (upper layer) was similarly formed on the second magnetic layer in the chamber B. In addition, chamber B
The output of the electron gun 8'is 15 kW, the amount of nitrogen gas permeated to the Kauffman type ion gun 9'is 30 SCCM, and the amount of oxygen gas permeated is 10 SCCM.

After that, perfluoropolyether (FOMBL
IN Z DOL, made by Ausimont Co., Ltd., as a fluorine-based inert liquid (Fluorinert FC-77, made by Sumitomo 3M Limited)
The coating composition diluted and dispersed to 0.05% by weight was applied onto the first magnetic layer by a die coating method so that the dry film thickness was 20Å, and dried at 105 ° C to form a lubricating layer. Also, on the side of the PET film opposite to the magnetic layer side,
A back coat paint consisting of carbon black with an average particle size of 10 to 20 nm dispersed in a binder resin of urethane prepolymer and vinyl chloride resin is applied by a die coating method to a dry film thickness of 0.5 μm. And dried to form a back coat layer. By the above, the film on which the upper and lower Fe-N-O based magnetic layers are formed is
Cut to a width of 8 mm and load in a cassette case for 8 mm VTR
I got a mm videotape.

Table 1 shows the nitrogen concentrations in the upper and lower Fe--N--O system magnetic layers obtained as described above. Further, FIG. 2 shows the result of analysis of the element distribution in the entire magnetic layer of the magnetic tape by Auger electron spectroscopy. The measurement conditions of Auger electron spectroscopy at this time are as follows: electron gun condition: acceleration voltage: 10 kV, emission current: 10 nA, magnification: 2000 times, etching condition: etching gas: argon gas, acceleration voltage: 3 kV, The ion current was 300 nA, and etching was performed every 30 seconds under this condition for analysis.
As a result of Auger electron spectroscopy analysis, it is found that the nitrogen concentration in the upper Fe—N—O system magnetic layer is higher than the nitrogen concentration in the lower Fe—N—O system magnetic layer. The carbon atom at the start of the Auger profile is the effect of the lubricant.

The element ratio of the entire magnetic layer of the 8 mm tape obtained in Example 1 was Fe: N: O = 65: 16: 19 (atomic%).

(2) Performance Evaluation With respect to the 8 mm video tape obtained above, the envelope was evaluated by the following method as an index of its durability and head touch. Table 1 shows the results. Durability Durability is 7MHz by modifying a commercially available high band 8mm VTR.
A sine wave signal was input at and the reproduction output after still for 5 hours was measured using a spectrum analyzer to measure the decrease in output. The unit of output is dB. Envelope Envelope is the maximum value of the output waveform (envelope) obtained under the conditions of RBW = 10kHz, VBW = 30kHz, frequency span = 0MHz, sleep time = 40ms, mileage = 16 using Advantest TR4171 type spectrum analyzer. The ratio of the minimum value a to b was represented by% (see FIG. 5). When this ratio (envelope holding ratio) is 100%, the output waveform is the cleanest and the head touch is good, and the lower this ratio is, the worse the head touch is.

Example 2 The film forming conditions for the magnetic layer in Example 1 were the electron guns 8 and 8 '.
Output of 12 kW, the flow rate of nitrogen gas to the Kauffman type ion gun 9 in the chamber A is 15 SCCM, and the oxygen gas introduction pipe 10
The flow rate of oxygen gas to the chamber is 20SCCM, and the flow rate of nitrogen gas to the Kaufman type ion gun 9'of chamber B is 25SCC.
M, the flow rate of oxygen gas to the oxygen gas introduction tube 10 'is 10SCCM, to form the upper and lower Fe-N-O-based magnetic layers, except for the same as in Example 1 to produce a magnetic film,
The same evaluation as in Example 1 was performed. Table 1 shows the results.

The distribution of elements in the entire magnetic layer of the magnetic tape was analyzed by Auger electron spectroscopy under the same conditions as in Example 1, and the results are shown in FIG. As a result of Auger electron spectroscopy analysis, it is found that the nitrogen concentration in the upper Fe—N—O based magnetic layer is higher than the nitrogen concentration in the lower Fe—N—O based magnetic layer as in Example 1. The carbon atom at the start of the Auger profile is the effect of the lubricant. The element ratio of the entire magnetic layer of the 8 mm tape obtained in Example 2 was Fe: N: O 2 = 75: 13: 12 (atomic%).

Example 3 As the film forming conditions of the magnetic layer in Example 1, the flow rate of nitrogen gas to the Kauffman type ion gun 9 was 7 SCCM, and the oxygen gas introduction tube was used.
The flow rate of oxygen gas to 10 is 30 SCCM, the flow rate of nitrogen gas to the Kaufman type ion gun 9'is 35 SCCM, and the flow rate of oxygen gas to the oxygen gas introducing pipe 10 'is 6 SCCM. A magnetic film was produced in the same manner as in Example 1 except that the N—O based magnetic layer was formed, and the same evaluation as in Example 1 was performed. Table 1 shows the results.

Comparative Example 1 In Example 1, the output of the electron gun 8 in the chamber A was set to 13 k.
W, flow rate of nitrogen gas to Kaufman type ion gun 9 is 25SCC
M, the flow rate of oxygen gas to the oxygen gas introduction tube 10 is 12 SCCM, the output of the electron gun 8'in the chamber B is 11 kW, the flow rate of nitrogen gas to the Kaufman type ion gun 9'is 26 SCCM, the oxygen gas introduction tube 10 The flow rate of oxygen gas to the magnetic field was 13 SCCM, the upper and lower Fe—N—O based magnetic layers were formed, and a magnetic film was produced in the same manner as in Example 1 except for the above, and the same evaluation as in Example 1 was performed. Was done. Table 1 shows the results. In addition,
FIG. 4 shows the result of analyzing the distribution of elements in the entire magnetic layer of the magnetic tape by Auger electron spectroscopy under the same conditions as in Example 1. The element ratio of the entire magnetic layer of the 8 mm tape obtained in Comparative Example 1 was Fe: N 3: O 2 = 71: 15: 14 (atomic%).

[0033]

[Table 1]

[0034]

According to the present invention, the durability and head touch (envelope) of a magnetic recording medium having an iron-nitrogen-oxygen type magnetic layer are significantly improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for manufacturing a magnetic recording medium of the present invention.

FIG. 2 is a chart of Auger electron spectroscopy analysis of the magnetic layer formed in Example 1.

FIG. 3 is a chart of Auger electron spectroscopy analysis of the magnetic layer formed in Example 2.

FIG. 4 is a chart of Auger electron spectroscopy analysis of the magnetic layer formed in Comparative Example 1.

FIG. 5 is a schematic diagram showing a method for measuring envelope retention rate.

[Explanation of symbols]

 1 vacuum container 4 support 8,8 'electron beam gun 9,9' ion gun 10,10 'oxygen gas introduction tube

Continued on the front page (72) Inventor Katsumi Endo 2606 Akabane, Kakaicho, Haga-gun, Tochigi Pref.

Claims (7)

[Claims] 1. A magnetic recording medium comprising a support and at least two magnetic layers formed on the support, wherein a first magnetic layer farthest from the support among all magnetic layers and an adjacent thereto. The second magnetic layer is a magnetic layer containing iron, nitrogen and oxygen as main components, and the nitrogen concentration (N ₁ ) in the first magnetic layer is greater than the nitrogen concentration (N ₂ ) in the second magnetic layer. A magnetic recording medium characterized by high cost. 2. A magnetic recording medium according to claim 1, wherein the difference between N ₁ -N ₂ of N ₁ and N ₂ is 5 atomic% or more. 3. The magnetic recording medium according to claim 1, wherein the oxygen concentration (O ₁ ) in the first magnetic layer is lower than the oxygen concentration (O ₂ ) in the second magnetic layer. 4. The iron concentration (Fe ₁ ) in the _first magnetic layer and the iron concentration (Fe ₂ ) in the second magnetic layer are substantially the same.
4. The magnetic recording medium according to any one of 3 to 3. 5. The magnetic recording medium according to claim 1, wherein N ₁ + O ₁ is substantially the same as N ₂ + O ₂ . 6. The nitrogen concentration distribution in the first magnetic layer and the nitrogen concentration distribution in the second magnetic layer are each constant in the depth direction of the magnetic layer. Magnetic recording medium. 7. The magnetic recording medium according to claim 1, which has a coercive force (Hc) of 1000 (Oe) or more.