JPH0520663A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To greatly improve the corrosion resistance and durability of the magnetic recording medium by forming a substrate film of a plasma-polymerized film contg. Si and and a top coat film of a plasma-polymerized film contg. C and H. CONSTITUTION:This magnetic recording medium has the metallic substrate layer and a ferromagnetic metallic thin film on a nonmagnetic resin base body. The substrate film is the plasma-polymerized film contg. the Si and the top coat film is the plasma-polymerized film contg. the C and H. Further, the film thickness of the substrate film is 100 to 1000Angstrom and contains Si and O. The atom ratio of the O to the Si is 1.2 to 1.95 and the refractive index is 1.44 to 1.55. The top coat film has 10 to 50Angstrom film thickness and >=1.8 refractive index. The ferromagnetic metallic thin film consists essentially of Co and is formed by a diagonal vapor deposition method. The corrosion resistance and durability are greatly improved in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a ferromagnetic metal thin film.

[0002]

2. Description of the Related Art In recent years, magnetic tapes have become higher and higher in density. Among them, magnetic tapes using a ferromagnetic metal thin film containing Co as a main component and having Ni added thereto have a large saturation magnetic flux density and a high coercive force. Has been actively studied.

This type of magnetic tape is manufactured by various methods. As a particularly excellent method, a ferromagnetic metal thin film is formed as a single-layer film on a non-magnetic substrate by oblique vapor deposition, or two or more layers are formed. It has been proposed to stack them to form a multilayer structure.

As a non-magnetic substrate for magnetic tape,
A resin film such as polyethylene terephthalate is used.

When a magnetic layer is formed on such a resin film by vapor deposition, moisture or air penetrates through the resin film, corroding the magnetic layer and deteriorating electromagnetic conversion characteristics during recording / reproduction. Moreover, the durability is also insufficient.

Conventionally, it has been proposed to apply various plasma polymerized films as a base film formed between a resin film and a magnetic layer or a top coat film formed on the magnetic layer. However, such a conventional base film or top coat film is insufficient in blocking moisture and oxygen, and is insufficient in terms of corrosion resistance and durability. In particular, the problem of cupping in which the magnetic tape bends in the width direction due to the generation of rust is large, and if the cupping is large, the spacing between the tape and the magnetic head cannot be kept constant and output fluctuations occur.

[0007]

The main object of the present invention is to significantly improve the corrosion resistance and durability of a magnetic recording medium having a ferromagnetic metal thin film as a magnetic layer.

[0008]

Such an object is achieved by the following constitutions (1) to (5). (1) In a magnetic recording medium having a base film, a ferromagnetic metal thin film, and a top coat film on a non-magnetic resin substrate, the base film is a plasma-polymerized film containing Si, and the top coat film is C. A magnetic recording medium comprising a plasma-polymerized film containing H.

(2) The thickness of the base film is 100 to 100
The magnetic recording medium according to (1) above, wherein the underlayer contains Si and O, and the atomic ratio of O to Si, O / Si, is 1.2 to 1.95.

(3) The refractive index of the base film is 1.44 to
The magnetic recording medium as described in (1) or (2) above, which has a value of 1.55.

(4) The top coat film has a thickness of 10 to 10
The magnetic recording medium as described in any of (1) to (3) above, which has a refractive index of 50 A and is 1.8 or more.

(5) The magnetic recording medium according to any one of (1) to (4) above, wherein the ferromagnetic metal thin film contains Co as a main component and is formed by an oblique vapor deposition method.

[0013]

Specific Structure The specific structure of the present invention will be described in detail below. The magnetic recording medium of the present invention is specifically a magnetic tape.

<Non-Magnetic Substrate> The material of the non-magnetic substrate used in the present invention is not particularly limited, and various films that can withstand the heat of vapor deposition of a ferromagnetic metal thin film, such as polyethylene terephthalate, can be used. Also, JP-A-63-1031
Each material described in Japanese Patent Publication No. 5 can be used.

<Base Film> The base film in the present invention is made of Si.
It is a plasma polymerized film containing.

As a source material for forming such a plasma-polymerized film, various sources containing silicon, carbon, hydrogen and oxygen can be used. Specifically, it is a gas or a liquid at room temperature. Organosilicon compounds such as various silanes and siloxanes [eg tetramethoxysilane (T
MOS), tetraethoxysilane, trimethylmethoxysilane, trimethylchlorosilane] is used.

The plasma-polymerized film containing Si has a large effect of blocking moisture, is suitable as a base film, and is advantageous in obtaining a rust preventive effect.

The film thickness may be 100 to 1000 A, preferably 200 to 700 A.

The base film needs to have a certain thickness, and the effect of the present invention becomes extremely high by setting the thickness within the above range. If the film thickness is less than 100 A, the present invention is not effective, and if it exceeds 1000 A, it is disadvantageous in mass production. When the film thickness is increased, the effect is not improved, rather the base film is apt to be cracked and the ability to block water, oxygen and the like is deteriorated.

When a plasma-polymerized film is used, the organosilicon compound has a high film-forming rate, so that it is easy to obtain a film thickness within the above range. From this point as well, it is preferable to form the base film.

An ellipsometer or the like may be used to measure the film thickness. Such control of the film thickness may be achieved by limiting the reaction time at the time of forming the plasma polymerized film, the raw material gas flow rate, and the like.

The plasma polymerized film in the present invention contains Si.
In addition to C, H and O are preferably contained.

In this case, the content of C in the film is 5 at
% Or less, preferably 1 at% or less, and the H content is 5
At% or less, preferably 1 at% or less, and the O content is 70 at% or less, preferably 60 to 65 at%. In addition, N may be contained depending on the case.

The atomic ratio of O to Si is O / S.
It is preferable that i is 1.2 to 1.95, preferably 1.6 to 1.90.

As described above, the effects of the present invention are improved by controlling C, H, O, etc. in the film and setting O / Si within the above range.

In the plasma polymerized film, Si, O, C,
The analysis of the content of H and the like may be performed according to SIMS (secondary ion mass spectrometry), AES (Auger spectroscopic analysis), or the like.

In the present invention, in order to bring the film composition into the above-mentioned preferred range, particularly the O / Si ratio, etc., one or more kinds of the organic silicon compounds mentioned above are appropriately added with one or more kinds of the organic source gas, and the raw material is added. It is preferably used as a gas.

[0028] As such an organic raw material gas, as O _{source, O 2, O 3, H} 2 O, NO, N 2 O, NO X , such as NO _2, CO, CO ₂ and the like, also N Sources include N ₂ , NO _x , NH _{3 and the} like. Of these, O ₂ is preferably used as the O source.

The refractive index of the plasma polymerized film in the present invention is 1.44 to 1.55, preferably 1.45 to 1.50. By setting such a refractive index,
The composition of the film can be optimized, and the effect of the present invention is improved. An ellipsometer may be used to measure such a refractive index.

The plasma polymerized film is formed by bringing the above-mentioned discharge plasma of the source gas into contact with the substrate according to a known method. Electrode placement, applied current,
Processing time, operating pressure, etc. may be set under normal conditions.

As the carrier gas, Ar, N ₂ ,
He, H ₂ or the like may be used. As a plasma generation source, in addition to high frequency discharge, microwave discharge, direct current discharge,
Either AC discharge or the like can be used.

In the present invention, the plasma polymerized film as the underlayer is preferably formed on a substrate, particularly on a plasma-treated substrate. By plasma-treating the surface of the substrate, the adhesive force between the substrate and the plasma polymerized film is improved. The principle of the plasma treatment method for the surface of the substrate, the method and the forming conditions are basically the same as those of the plasma polymerization method described above.

However, as a general rule, the plasma treatment uses an inorganic gas as a treatment gas, and on the other hand, as a general rule, an organic gas (in some cases, an inorganic gas may be mixed even if an inorganic gas is mixed in) to form a plasma-polymerized film by the plasma polymerization method described above. Is used as a source gas. Further, the frequency of the plasma processing power source is not particularly limited, and may be DC, AC, microwave, or the like.

<Magnetic Layer> In the present invention, the magnetic layer is Co
Is a main component, and is preferably composed of one or two or more ferromagnetic metal thin films formed by the oblique deposition method. Then, the effect of the present invention is enhanced in such a magnetic layer.

In the oblique vapor deposition method, for example, a long film-shaped non-magnetic substrate fed from a supply roll is sent along with the surface of a rotating cooling drum to perform oblique vapor deposition from one or more stationary metal sources, It is to be wound up on a winding roll.

At this time, when the angle between the incident angle of the ferromagnetic metal component at the time of film formation and the normal to the substrate is θ, θ changes, and vapor deposition is carried out within the range from the initial θmax to the final θmin. . Further, θmax during the deposition of the ferromagnetic thin film is preferably 80 to 90 degrees, and θmin is preferably 10 to 60 degrees.

Each ferromagnetic metal thin film constituting the magnetic layer is N
A Co—Ni alloy containing i is preferable, and an alloy containing Co in an amount of about 80% or more and Ni in an amount of 20% or less is particularly preferable.

If necessary, Cr may be contained in an amount of 10% or less, and various metals described in JP-A-63-10315 and other metal components may be contained.

Further, if necessary, a small amount of oxygen may be contained in the surface layer of each layer, or a non-magnetic layer may be interposed therebetween to improve the corrosion resistance and the like.

The total thickness of the magnetic layer is 1200 to 3000.
It is preferably about A. At this time, the output can be made sufficiently large.

The incident angle of the vapor-deposited metal particles is θmax at the initial stage of vapor deposition.
To the final θ min, columnar crystal grains of ferromagnetic metal containing Co as a main component are grown in one direction in an arc shape and aligned on the surface of the non-magnetic substrate. When the magnetic layer has a multilayer structure, this step is repeated.

<Topcoat Film> A topcoat film is provided on such a magnetic layer. The top coat film is
It is a plasma polymerized film containing C and H.

As a raw material source for forming such a plasma-polymerized film, various sources containing carbon and hydrogen can be used, but since they are usually easy to operate,
At least one of methane, ethane, propane, butane, pentane, ethylene, propylene, butene, butadiene, acetylene, methylacetylene, and other saturated or unsaturated hydrocarbons that are gaseous at room temperature is used as the C and H sources. If necessary, hydrocarbons that are liquid at room temperature may be used as a raw material.

In such a plasma-polymerized film containing C and H, the source gas molecules are small and a dense film can be formed. Therefore, it is advantageous in covering the surface of the medium to block moisture, oxygen, and the like, is suitable as a topcoat film, and can effectively prevent rusting. Also, C
Since the HO-based plasma polymerized film can have low friction and high hardness, it is highly effective as a durable protective film.

The film thickness of the top coat film may be 10 to 50 A, preferably 20 to 30 A. The effect of the present invention is extremely high in a film thickness in this range, and if the film thickness exceeds 50 A, stress is strongly generated, and this effect is critically reduced, and the problem of spacing loss becomes more serious. Further, in order to increase the film thickness, the magnetic layer is exposed to plasma with high power or for a long time, which damages the magnetic layer. Further, if the film thickness is less than 10 A, the effect of the present invention is reduced.

Further, the polymer film containing C and H is suitable for the control of the process since it is in a range that easily corresponds to the speed at the time of vapor deposition of the magnetic layer.

As in the above case, an ellipsometer or the like may be used to measure the film thickness. Such control of the film thickness may be achieved by limiting the reaction time at the time of forming the plasma polymerized film, the raw material gas flow rate, and the like.

In the present invention, the total content of C and H in the film is 85 at% or more, preferably 95 at% or more, and it is preferable that the film contains substantially only C and H. .

The atomic ratio of H to C is such that H / C is 1.6 or less, preferably 0.7 or less, and the content of C in the film is 30 at% or more, preferably 60 to. 10
0 at%, on the other hand, the H content is 55 at% or less, preferably 3
It is recommended to be 5 at% or less. Also, in some cases,
In addition to C and H, O, N and the like may be contained at 15 at% or less. By regulating C, H, etc. in the film in this way, the effect of the present invention is improved.

The content of C, H and other elements in the plasma polymerized film may be analyzed by SIMS (secondary ion mass spectrometry), CHN coder or the like.

In the present invention, the refractive index of the plasma polymerized film is preferably 1.8 or more, more preferably 1.9 to 2.3.

An ellipsometer may be used for the measurement of the refractive index as described above.

By setting the refractive index in the above range, the density of the polymer film is increased, the magnetic recording medium is imparted with high rigidity, and the durability is improved. And when the refractive index is less than 1.8,
Such effects are critically reduced.

When other elements are contained, one or more of the above hydrocarbons may be added to O ₂ , O ₃ , H ₂ O, N ₂ and N.
NOx such as O, N ₂ O and NO ₂ , H ₂ , NH ₃ and C
O, may be used as a source gas plus at least one of such CO ₂ as N and O source.

A specific film forming method may be performed according to a known method as in the case of the base film.

The processing condition at this time is W / (FM) [where W is plasma input power (Joule / sec), and
Organic raw material gas flow rate, M is the unit of F · M the material gas molecular weight kg / sec] values 10 ⁸ Joule / kg or more, in particular 5 × 10 ⁸ is
It is preferably carried out at 1 × 10 ¹⁰ Joule / kg. If this value is less than 10 ⁸ Joule / kg, the refractive index will decrease,
The denseness of the plasma polymerized film becomes insufficient.

Such a top coat film is formed on the magnetic layer, but is preferably formed on the plasma-treated magnetic layer. By plasma-treating the surface of the magnetic layer, the adhesion between the magnetic layer and the magnetic layer is improved, and thus the adhesion between the magnetic layer and the plasma polymerized film is improved. Specifically,
The plasma treatment may be performed according to the case of the substrate.

In the present invention, as described above, the rust preventive effect is obtained by using the plasma-polymerized film containing C and H as the top coat film and the plasma-polymerized film containing Si as the base film, respectively. Such an effect is obtained only in such a combination, and cannot be obtained by making the film materials of the base film and the top coat film opposite to each other or by using either one of the materials.

Further, in the present invention, the difference in film forming rate between the two materials can be effectively utilized, which is preferable in terms of productivity.

In the present invention, various constitutions such as a back coat layer may be added.

[0061]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 A polyethylene terephthalate film having a thickness of 7 μm was unwound from a supply roll, moved along with the periphery of a rotating cylindrical cooling drum, and evacuated to a vacuum of 10 ⁻⁴ Pa.
A base film was formed as shown in Table 1.

As shown in Table 1, each polyethylene terephthalate film having a base film formed thereon was treated with 10 ⁻⁴ Pa.
In an Ar atmosphere of 20 at% by letting it out of the supply roll and moving it around the rotating cylindrical cooling drum.
A Ni—Co alloy was obliquely vapor-deposited to form a ferromagnetic metal thin film, which was wound on a winding roll.

Then, using this winding roll as a supply roll, a ferromagnetic metal is obliquely vapor-deposited in an incident direction crossing the incident direction at the time of oblique vapor deposition with the normal line direction of the PET film sandwiched therebetween, thereby forming a two-layer structure. Magnetic layer was formed.

Further, as shown in Table 1, on the magnetic layer,
A top coat film was formed.

Thus, magnetic tape sample No. 1
-No. 15 was produced.

[0066]

[Table 1]

Magnetic tape samples No. 2 to No. 1
The base film and the top coat film in No. 5 were formed under the plasma polymerization conditions shown in Table 2. Tetraethoxysilane is indicated by TEOS.

[0068]

[Table 2]

These magnetic tape sample Nos. 1 to No.
No. 15 was loaded on an 8 mm video deck (S900 manufactured by Sony Corporation) and the following evaluations were performed.

(1) Δφm Maximum magnetic flux density φ after storage for 1 week at 80 ° C. and 90% RH
m was measured and the increment with respect to the initial φm was determined. φm
Was measured by VSM.

(2) Output change The output after storage for 1 week at 60 ° C. and 90% RH was measured,
The reduction rate (%) with respect to the initial output was obtained.

(3) Running Durability Recording was carried out for 5 minutes, and the number of passes at which the output became 50% was measured and obtained.

(4) After being stored in the cupping atmosphere for one week, the tape was placed on a flat surface, and the sled height h of the tape width direction end portion was measured.

The results are shown in Table 1. The effects of the present invention are clear from the results shown in Table 1. Among them, the sample No. 9 in which the plasma polymerized film (CH film) containing C and H was used as the base film and the plasma polymerized film (Si film) containing Si was the top coat film was not only inferior in characteristics Since CH and CH films are inferior in mass productivity, it took a lot of effort to reach 500A.

C is applied to both the base film and the top coat film.
In sample No. 10 using the H film, labor is required to form the base film and the characteristics are not sufficient. Furthermore, sample No. 11 using Si film as both the base film and the top coat film
Then, not only the characteristics were poor, but it was difficult to control the film thickness of the top coat film.

Further, in Sample No. 7 in which the film thickness of the top coat film was increased, in addition to the problem of spacing loss in order to increase the film thickness, the time of exposure to plasma was prolonged, and the output There is a big problem in terms of characteristics.

Further, Sample No. 16 was prepared in the same manner as in Sample No. 2 except that the film thickness of the base film exceeded 1000 A. However, the effect of the present invention was not improved with this sample. However, it was found that not only mass productivity is poor because the film thickness is increased, but also cracks are easily generated in the base film, and the ability to block water and oxygen deteriorates.

[0078]

According to the present invention, corrosion resistance and durability are remarkably improved.

Claims (5)

[Claims] 1. A magnetic recording medium having a base film, a ferromagnetic metal thin film, and a top coat film on a non-magnetic resin substrate, wherein the base film is a plasma-polymerized film containing Si, and the top coat film is A magnetic recording medium comprising a plasma polymerized film containing C and H. 2. The thickness of the base film is 100 to 1000 A
The magnetic recording medium according to claim 1, wherein the underlayer contains Si and O, and the atomic ratio of O to Si, O / Si, is 1.2 to 1.95. 3. The base film has a refractive index of 1.44 to 1.5.
The magnetic recording medium according to claim 1 or 2, which is 5. 4. The top coat film has a thickness of 10 to 50.
A and a refractive index of 1.8 or more.
The magnetic recording medium according to any one of 1. 5. The magnetic recording medium according to claim 1, wherein the ferromagnetic metal thin film contains Co as a main component and is formed by an oblique deposition method.