JPH0754575B2 - Magnetic recording medium - Google Patents

Description

The present invention relates to a magnetic recording medium, in particular, a magnetic film in which a specific metal element is contained in a Co—Ni-based metal film so as not to impair magnetic properties and to improve corrosion resistance. The present invention relates to a recording medium.

[Conventional technology]

A magnetic recording medium has been conventionally used in which a kneaded material obtained by kneading a magnetic powder such as γ-Fe ₂ O ₃ or Fe and a synthetic resin binder is coated on a non-magnetic substrate.

A magnetic recording medium capable of high-density recording has been developed in which a metal magnetic thin film is formed on a substrate for this type of coating type magnetic recording medium.

As a method for forming this metal thin film type magnetic recording medium, (a) a chemical plating method as a wet method, (b) a sputtering method as a dry method, an ion plating method, a vacuum deposition method, etc. are adopted. .

Generally, in comparison with the wet method of (a), the dry method of (b) provides a better magnetic recording medium in terms of the surface treatment applied to the substrate and the homogeneity of the magnetic layer in the longitudinal and width directions. It is believed to be obtained.

However, the metal thin film type magnetic recording medium formed by this dry method has extremely low thermodynamic stability as compared with the oxide magnetic powder and has a large number of pores, so that it corrodes in the air and deteriorates the performance. Easy to invite.

Conventionally, attempts have been made to improve the corrosion resistance of a magnetic recording medium without deteriorating its magnetic properties. For example, JP-A-55-105302 and JP-A-56-1501.
No.4, No.57-170505, No.57-170506, adding an additive metal, directing a mixed gas of ozone and oxygen to the magnetic layer forming part, or setting the number of oxygen atoms quantitatively. Then, it is disclosed that the corrosion resistance of the magnetic recording medium is improved.

However, in each of these, the corrosion resistance is slightly improved, but it is not sufficient, and in some cases, the saturation magnetization and the residual magnetization are decreased, and the reproduction output of the magnetic recording medium may be decreased.

[Problems to be solved by the invention]

The present invention solves the above-mentioned drawbacks in the conventional magnetic recording medium and improves the corrosion resistance without impairing the magnetic characteristics by adding a specific metal element to the Co-Ni-based metal thin film type magnetic recording medium. The purpose is to provide the above.

[Means for solving problems]

In the present invention, a magnetic layer comprising Co, Ni, Cu, element M ₁ or element M ₁ and element M ₂ and oxygen is formed on a non-magnetic substrate,
Element M ₁ is B 1 or 2 types of B and P, element M ₂ is Ti, V, C
The magnetic layer is composed of one or more of r, Zr, Nb, Sn, Ta, and Si. The composition of this magnetic layer is Ni 8 to 20% by weight, Cu 0.5 to 5%, and the element M ₁
0.05 to 3% or element M ₁ 0.01 to 2.5% and element M ₂ 0.5 to 6
%, Oxygen 3 to 13%, and the balance Co.

[Action]

 Hereinafter, the present invention will be described in more detail.

First, the reasons for limiting the composition of the magnetic layer formed on the non-magnetic substrate will be described.

Ni basically has a tendency to reduce the remanent magnetization of the magnetic recording medium, but it is necessary for improving the corrosion resistance of the magnetic layer of a metal mainly containing Co. If it is less than 8% by weight, the above effect is not sufficiently exhibited, while if it exceeds 20% by weight, the remanent magnetization of the magnetic layer is significantly reduced and the reproduction output is reduced.

Cu is added in order to improve the corrosion resistance of the magnetic layer of a Co-Ni-based metal. If it is less than 0.5% by weight, the above effect is not sufficient, while if it exceeds 5% by weight, the effect of corrosion resistance is not improved and the saturation magnetization Ms is lowered.

Element M ₁ consisting of B 1 or two kinds of B and P and Ti, V,
Element M consisting of one or more of Cr, Zr, Nb, Sn, Ta, Si
₂ is added in order to improve the corrosion resistance without impairing the magnetic characteristics of the Co-Ni based metal magnetic layer. An element M ₁ without adding an element M ₂ is added, or the amount of M ₁ is less than 0.05 wt%, with the addition of the element M ₁ and the element M _2, the amount of M ₁ 0.01 wt%
And less than, or the amount of M ₂ is either less than 0.5 wt%, is not sufficient improving corrosion resistance. On the other hand, without adding an element M ₂ added element M _1, or the amount of M ₁ is more than 3 wt%, by adding the element M ₁ and the element M _2, the amount of M ₁ is 2.5 wt%
And / or the amount of M ₂ exceeds 6% by weight, the magnetic properties deteriorate.

For the purpose of improving the coercive force of the magnetic recording medium, oxygen partially combines with the metal to form an oxide metal film, and the other part is adsorbed in the magnetic layer of the magnetic recording medium and contained in the magnetic recording medium. To be done. If it is less than 3% by weight, the effect of the addition of oxygen is not recognized, the coercive force of the magnetic recording medium is not improved, and the corrosion resistance is deteriorated. On the other hand, if the content is more than 13% by weight, the effect of oxidation is greatly exerted, the ratio of the metal oxide is increased, sufficient corrosion resistance cannot be obtained, and the saturation magnetization Ms is lowered.

The thickness of the magnetic layer of the composition of the present invention as described above is from 0.1 μm
About 1.0 μm is desirable. If the thickness is less than 0.1 μm, a sufficient reproduction output cannot be obtained, and if the thickness exceeds 1 μm, the flexibility of the substrate decreases and it becomes difficult to increase the recording density.

As a non-magnetic substrate on which such a magnetic layer is formed, a plastic such as polyester, acetate, polycarbonate, or polyimide having a thickness of 5 to 25 μm, which has appropriate flexibility and tensile strength and heat resistance during vapor deposition. the film,
Alternatively, a glass substrate or a metal substrate such as Al is used as the disc-shaped substrate.

Next, a method for producing the magnetic recording medium of the present invention will be described. In this case, due to the demand for high-density recording, it is required that the magnetic layer to be formed have high coercive force and high saturation magnetic flux density. Therefore, such as sputtering method, ion plating method, vacuum deposition method, etc. It is desirable to use the dry method.

In the dry method, in order to improve the coercive force, it is possible to improve the coercive force by obliquely injecting composition atoms into the substrate to form a metal thin film,
In this respect, the coating type has a feature that a magnetic recording medium having a large coercive force can be obtained. When the constituent atoms are obliquely incident on the substrate, the acicular metal thin film structure grows with the crystal orientation direction oblique to the substrate. In such a state, the crystal orientation and shape anisotropy cause the magnetic anisotropy characteristic, and the coercive force of the magnetic recording medium is improved by increasing the magnetic anisotropy. In addition, the dry method is excellent in reproducibility of the magnetic characteristics of the magnetic layer, and has a manufacturing feature that it is easy to manufacture a magnetic layer that is uniform in the longitudinal direction and the width direction.

It is desirable that the non-magnetic substrate be subjected to a base treatment such as a corona discharge treatment or a primer treatment in order to improve the adhesion with the magnetic layer.

〔Example〕

Hereinafter, the magnetic recording medium of the present invention will be described in detail according to its manufacturing method with reference to the drawings for its embodiments.

FIG. 1 shows a cross-sectional structure of a manufacturing apparatus of an embodiment of a magnetic recording medium of the present invention, in which a substantially bell-shaped vacuum vapor deposition tank 11 is formed. A vacuum pump 12 is connected to the vacuum vapor deposition tank 11, and by driving the vacuum pump 12, the inside of the vacuum vapor deposition tank 11 can be set to a predetermined degree of vacuum.

An electron beam evaporation source 14 is provided on the bottom plate 13 of the vacuum evaporation tank 11, and a ferromagnetic metal 15 is arranged in the electron beam evaporation source 14. The ferromagnetic metal 15 is an element M ₁ consisting of Co, Ni, Cu and B 1 or B and P, or an element M ₁ and Ti, V, Cr, Z.
The metal element M ₂ is made of at least one of r, Nb, Sn, Ta, and Si, and its composition ratio is set to a predetermined film composition.

On the other hand, an introduction pipe 18 is led out from the oxygen cylinder 16 via a variable leak valve 17, and an end portion of the introduction pipe 18 penetrates the bottom plate 13 and is inserted into the vacuum vapor deposition tank 11. Vacuum deposition tank 11
A feed roll 21 and a take-up roll 22 are rotatably provided inside the feed roll 21 and the take-up roll 22.
A can 23 is rotatably provided between them.

A shutter 25 is provided between the electron beam evaporation source 14 and the can 23. This shutter 25 is rotatable and is opened only during film formation. The blocking pieces 26, 27 allow adjustment of the maximum incident angle θ ₂ and the minimum incident angle θ ₁ of the evaporated material with respect to the substrate.

The non-magnetic substrate 30 is wound around the delivery roll 21, the end portion of the non-magnetic substrate 30 is pulled out, and the non-magnetic substrate 30 is wound around the winding roll 22 via the can 23. As the non-magnetic substrate 30, a 12 μm-thick polyester film was used.

The delivery roll 21 and the winding roll 22 are driven, and the non-magnetic substrate 30 is in contact with the peripheral surface of the can 23, for example, 15 m / min.
It is transported at the speed of. The vacuum pump 12 is driven to evacuate the inside of the vacuum vapor deposition tank 11 to 5 × 10 ⁻⁶ torr or less to evaporate the ferromagnetic metal 15 in the electron beam evaporation source 14 at a constant speed. At the same time, the opening / closing cock 17 is opened to release the oxygen gas from the introduction pipe 18 into the vacuum vapor deposition tank 11. The supply of oxygen gas into the vacuum vapor deposition tank 11 is also set so that the oxygen composition of the film becomes a predetermined value.

Of the ferromagnetic metal 15 emitted from the electron beam evaporation source 14 when the shutter 25 is opened, only the one that is obliquely incident on the non-magnetic substrate 30 within a predetermined angle range passes through the blocking pieces 26 and 27 and is non-magnetic. Reach substrate 30.

That is, the ferromagnetic metal 15 emitted from the electron beam evaporation source 14
Among them, only those in the angle range from the minimum angle θ ₁ to the maximum angle θ _{2 with} respect to the normal line of the plate surface of the non-magnetic substrate 30 pass through the shutter 25 and the non-magnetic substrate 30. It is obliquely incident on 30. Thus, a magnetic layer having a thickness of 0.2 μm was formed.

The obtained magnetic recording medium was cut, and a part of the magnetic recording medium was evaluated for magnetic properties, and the other was evaluated for corrosion resistance.

The magnetic characteristics were measured by a sample vibrating magnetometer. Also,
The corrosion resistance was evaluated by the linear polarization resistance method among the electrochemical measurement methods. The polarization resistance Rp is given by the following equation.

Here, i is the current, ΔE is the voltage, ba and bc are the anode and cathode Tafel slopes, respectively, and icorr is the measured corrosion current density of the sample. The larger this value, the lower the corrosion resistance. When the external current i required to change the potential of the thin film sample which is freely corroded in the liquid by ΔE = 10 to 20 mV is measured by the potentiostat, Rp is obtained from the inclination. Since Rp is proportional to 1 / icorr, icorr can be calculated from the above equation by assuming a Tafel slope, and corrosion resistance can be evaluated. Even assuming ba = bc = 0.1, the error that occurs at voltage ΔE = 20 mV is about 0.8 mV.

Table 1 shows the composition of the thin film sample used for the measurement, the measured magnetic properties, and the corrosion current obtained in a 3 wt% NaCl solution and a 3 wt% Na ₂ SO ₃ solution at a potential scanning rate of 1 mV / sec. Density i
Indicates corr. The composition analysis of the thin film sample was performed using both EPMA analysis and chemical analysis.

The following can be seen from Table 1. That is, the conventional example No. 1 is an additive element other than oxygen in the thin film composition, the comparative example No. 10 is oxygen, the same No. 12 is Cu, the same No. 14 is an additive element M ₂ , and the same No. .15 indicates that M ₁ is out of the composition range of the present invention and is inferior in magnetic properties and / or corrosion resistance. On the other hand, Example No. 2, 4, 5, 7 ~ 9
Indicates that the magnetic properties are not impaired and the corrosion resistance is excellent.

〔The invention's effect〕

As is clear from the above, the present invention can provide a magnetic recording medium having excellent corrosion resistance without impairing the magnetic characteristics as compared with the conventional Co-Ni magnetic recording medium.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of the main part of a magnetic recording medium manufacturing apparatus according to the present invention. 11: Vacuum deposition tank, 12: Vacuum pump, 14: Electron beam evaporation source, 15: Ferromagnetic metal, 16: Oxygen cylinder, 21: Roll, 22: Winding roll, 23: Can, 25: Shutter, 30: Non Magnetic substrate.

Claims (2)

[Claims] 1. A composition formed by weight on a non-magnetic substrate.
Ni 8-20%, Cu 0.5-5%, B 1 type or B, P 2
A magnetic recording medium characterized by being comprised of seeds 0.05 to 3%, oxygen 3 to 13%, and the balance Co. 2. Formed on a non-magnetic substrate, the composition by weight
Ni 8-20%, Cu 0.5-5%, B 1 type or B, P 2
0.01 to 2.5% of species, 0.5 to 6% of Ti, V, Cr, Zr, Nb, Sn, Ta and Si, 3 to 13% of oxygen, and the balance Co. Magnetic recording medium.