JPH0836750A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a magnetic recording medium which can realize a satisfactory corrosion resistance and durability under hard conditions. CONSTITUTION:When a protective film is formed by sputtering a metal magnetic thin film which is formed as a magnetic layer by vacuum evaporation on a non-magnetic supporting body 102, the flow rate Lin (sccm) of argon gas introduced into a vacuum tank 101 at the time of sputtering, an exhaust flow rate Lout (sccm) and the capacity V(cc) of the vacuum tank are set to Lout/V 0.3(min<-1>), and 2.0X10<-4=Lin/Lout<=2.0X10<-3>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic recording medium having a magnetic metal thin film as a magnetic layer, and more particularly to a method of manufacturing a magnetic recording medium having excellent rust resistance.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, a powder magnetic material such as an oxide magnetic powder or an alloy magnetic powder is provided on a non-magnetic support, a vinyl chloride-vinyl acetate copolymer, a polyester resin, a urethane resin, A so-called coating type magnetic recording medium, which is manufactured by coating and drying a magnetic coating material dispersed in an organic binder such as a polyurethane resin, is widely used.

On the other hand, with the increasing demand for high-density magnetic recording, Co--Ni alloys, Co--Cr alloys, Co
A metal magnetic material made of an alloy such as -O alloy is plated on a non-magnetic support made of a polyester film, a polyamide film, a polyimide film, etc. by a vacuum thin film forming technique (vacuum deposition method, sputtering method, ion plating method, etc.). A so-called metal magnetic thin film type magnetic recording medium in which a magnetic layer is formed by direct deposition is proposed and attracts attention.

This metal magnetic thin film type magnetic recording medium is excellent not only in coercive force and squareness ratio but also in electromagnetic conversion characteristics in a short wavelength range, and since the magnetic layer can be extremely thin, recording demagnetization and reproduction are possible. There are many advantages such as a significantly small thickness loss at the time, and the fact that it is not necessary to mix a binder, which is a non-magnetic material, in the magnetic layer, so that the packing density of the magnetic material can be increased.

In such a metal magnetic thin film type magnetic recording medium, in order to improve electromagnetic conversion characteristics and obtain a larger output, the metal magnetic layer is formed when the magnetic layer of the magnetic recording medium is formed. A so-called oblique vapor deposition method is adopted in which vapor of a material is vapor-deposited obliquely on the surface of the non-magnetic support. The magnetic recording medium in which the magnetic layer is formed by the oblique evaporation method has the excellent characteristics that the recording can be easily performed by the ring head due to the structure of the magnetic layer and the recording demagnetization is small.

However, in the above-mentioned magnetic recording medium, since the magnetic layer is made of a metal material, it is said that there is a problem in rust resistance. Thus far, coating lubricants and rust preventives have been used. Of organic materials and so-called undercoating technique of coating fine particles on a non-magnetic support in advance before forming a magnetic layer have been studied.

However, the above-mentioned method can obtain sufficiently satisfactory characteristics for a magnetic recording medium used in a system with harsh specifications such as use in a special environment or business use. Instead, as a new method, a surface protection film by a vacuum thin film forming means is being studied.

[0008]

Generally, in vacuum thin film forming means such as sputtering, the film forming conditions such as the background vacuum degree and the amount of argon gas introduced have a great influence on the film quality, and the background vacuum degree is possible. It is desirable that the amount is as low as possible, and it is known that the amount of argon gas introduced is optimum depending on the purpose.

In the protective film, the film quality is durability,
It affects practical properties such as rust resistance, and it is important that the structure does not contain impurities and has a dense structure.

However, these conditions depend on the performance of the sputtering apparatus, such as the capacity of the vacuum chamber, the performance of the exhaust pump, and the type of conductance adjustment method, and it depends on which apparatus is selected. A certain range is decided.

Therefore, it is important to optimize the amount of argon gas introduced and the amount of argon gas exhausted within the capacity range of the apparatus used, but these effective ranges are quantified including the capacity of the vacuum chamber. I haven't.

Therefore, the present invention has been proposed for the purpose of solving this problem, and provides a magnetic recording medium capable of achieving satisfactory rust resistance and durability even under severe specifications. It is intended to provide a manufacturing method.

[0013]

A method of manufacturing a magnetic recording medium according to the present invention is proposed to achieve the above-mentioned object.

That is, the present invention is a method of manufacturing a magnetic recording medium, in which a metal magnetic thin film is formed on a non-magnetic support by vacuum vapor deposition, and then a protective film is formed by sputtering. Argon gas flow rate L _in (sccm) and exhaust flow rate L _out
(Sccm) and the capacity V (cc) of the vacuum chamber are L _out /V≧0.3 (min ⁻¹ ) and 2.0 × 10 ⁻⁴ ≦ L _in /
It is characterized in that L _out ≦ 2.0 × 10 ⁻³ .

In the method for manufacturing a magnetic recording medium of the present invention, a metal magnetic thin film made of a ferromagnetic metal material is formed as a magnetic layer on a non-magnetic support, and then a protective film is formed on the metal magnetic thin film by sputtering. It is a thing.

A metal magnetic thin film is formed as a magnetic layer by directly depositing a ferromagnetic metal material on the non-magnetic support, and the ferromagnetic metal material used here is a usual ferromagnetic metal material. Any material may be used as long as it is used for a vapor deposition tape.

For example, ferromagnetic metals such as Fe, Co and Ni, Fe-Cu, Co-Cu, Fe-Co and Co.
-Ni, Co-Ni-Pt, Fe-Co-Ni, Co-
Au, Co-Pt, Mn-Bi, Mn-Al, Fe-C
r, Ni-Cr, Fe-Co-Cr, Fe-Ni-B,
Fe-Co-B, Co-Ni-Cr, Fe-Co-Ni
-Cr, Fe-Co-Ni-B, in-plane magnetization recording ferromagnetic alloys, Co-Cr, Co-Ta, Co-Cr-Ta,
Perpendicular magnetic recording ferromagnetic alloys such as Co—Cr—V and Co—O are listed.

In particular, when the in-plane magnetization recording ferromagnetic alloy is used, Bi, Sb, Pb, S are previously formed on the non-magnetic support.
A base film made of a low melting point non-magnetic material such as n, Ga, In, Si, or Ti is formed in advance, and the ferromagnetic metal material is vapor-deposited or sputtered from the vertical direction to form a low melting point magnetic material in the metal magnetic thin film. The material may be diffused to eliminate the orientation to secure the in-plane isotropic property and improve the coercive force.

As a method for forming such a metal magnetic thin film, a vacuum vapor deposition method of heating and evaporating a disk ferromagnetic metal material under vacuum to deposit it on a non-magnetic support, or a glow discharge in an atmosphere containing argon as a main component. The so-called vacuum thin film forming technology such as a sputtering method in which atoms on the target surface are knocked out by the generated argon ions and an ion plating method in which the evaporation of the ferromagnetic metal material is performed in a discharge can be used, but is not limited to this. Not something.

The magnetic layer may be a single layer film of a metal magnetic thin film made of these ferromagnetic metal materials or a multi-layer film. Further, an underlayer or an intermediate layer may be provided between the non-magnetic support and the metal magnetic thin film, or in the case of a multi-layer film, to improve the adhesive force between the layers and control the coercive force. Further, for example, the vicinity of the surface of the magnetic layer may be an oxide for improving the corrosion resistance.

A protective film is formed on the magnetic layer by the sputtering method.

When performing this sputtering, the flow rate of the argon gas L _in (sccm) introduced into the vacuum chamber, the flow rate of the exhaust gas L _out (sccm) and the capacity V (cc) of the vacuum chamber are expressed by the following equations (1), ( The relationship shown in 2) should be satisfied.

L _out /V≧0.3 (min ⁻¹ ) (1) and 2.0 × 10 ⁻⁴ ≦ L _in / L _out ≦ 2.0 × 10 ⁻³ (2) As a result, the impurity content is A protective film having a low density and a dense structure is obtained, and the rust resistance is significantly improved.

However, when the inside of the vacuum chamber is divided into a plurality of film forming chambers and each has an exhaust pump, the exhaust flow rate L _out and the capacity V of the vacuum chamber are values for each film forming chamber. And

Here, as a constituent material of the protective film,
Any protective film material that is usually used in this type of magnetic recording medium can be used and is not particularly limited. For example, carbon, Al ₂ O ₃ , CrO ₂ , SiO ₂ , S
_{i 3 N 4, SiN x,} SiN x -SiO 2, BN, Zr
O ₂ , TiO ₂ , MoS ₂ , SiC, TiC, TiN,
Examples thereof include Co oxide and MgO.

The protective film may be a single layer film or a multilayer film.

The structure of the magnetic recording medium as described above is not limited to this, and may be changed without departing from the scope of the present invention, for example, a back coat layer may be formed or a non-magnetic layer may be formed if necessary. It does not matter at all whether an undercoat layer is formed on the surface of the support or various functional layers such as a lubricant layer and a rust preventive layer are formed. In this case, as the material contained in the non-magnetic pigment, the resin binder, or the lubricant layer or the rust preventive layer contained in the back coat layer, any conventionally known material can be used.

The non-magnetic support is not particularly limited as long as it is a material usually used in this kind of magnetic recording medium, and if specifically exemplified, polyesters,
Polyolefins, cellulose derivatives, vinyl resins,
Any polymer support formed of a polymer material represented by polyimides, polyamides, polycarbonates and the like can be used.

[0029]

When a protective film is formed on a magnetic layer made of a metal magnetic thin film formed on a non-magnetic support by sputtering, the amount of introduced argon gas and the amount of exhausted argon gas are determined in relation to the capacity of the vacuum chamber. By optimizing so as to satisfy the conditions, a protective film containing no impurities and having a dense structure can be obtained. As a result, the rust resistance is significantly improved.

[0030]

EXAMPLES Specific examples to which the present invention is applied will be described in detail below with reference to the drawings and experimental results.

In the present embodiment, when a vapor deposition tape suitable for digital VTR is produced, a magnetic layer made of a metal magnetic thin film is formed by an ordinary oblique vapor deposition method, and then the introduction amount and the exhaust amount of argon gas are adjusted to a vacuum chamber. This is an example in which the protective film is formed by performing sputtering while controlling it under a predetermined condition in relation to the capacity of.

First, as shown below, a non-magnetic support made of polyethylene terephthalate (PET), which was previously undercoated, was subjected to the following conditions in an oxygen atmosphere using a vacuum deposition apparatus as shown in FIG. Co was obliquely vapor-deposited, and a metal magnetic thin film having a thickness of 0.2 μm was deposited as a magnetic layer.

<Used non-magnetic support> Material: Polyethylene terephthalate (PET) Undercoat: Water-soluble latex containing acrylic ester as a main component (density 10 million pieces / mm ² ) <Deposition conditions> Ingot: Co ₁₀₀ ( Incident angle: 45 to 90 ° Tape speed: 25 m / min Film thickness of magnetic layer: 0.2 μm Oxygen introduction amount: 600 sccm Vacuum degree during vapor deposition: 2.0 × 10 ^-2 Pa where In the vacuum vapor deposition apparatus used, as shown in FIG. 1, the inside of the vacuum chamber 81 is evacuated from the exhaust ports 95 provided at the head and the bottom, respectively, and the inside is in a vacuum state.
A feed roll 83 that rotates at a constant speed in the counterclockwise direction in the drawing and a winding roll 84 that rotates at a constant speed in the clockwise direction in the drawing are provided.
4, a tape-shaped non-magnetic support 82 is sequentially run.

From the feed roll 83 to the take-up roll 84
A cooling can 85 having a diameter larger than that of each of the rolls 83 and 84 is provided in the middle of the traveling side of the non-magnetic support 82.

The cooling can 85 is provided so as to draw the non-magnetic support member 82 downward in the drawing, and is configured to rotate at a constant speed in the clockwise direction in the drawing.

The feed roll 83, the take-up roll 84, and the cooling can 85 each have a cylindrical shape having a length substantially the same as the width of the non-magnetic support member 82. A cooling device (not shown) is provided inside so that deformation of the non-magnetic support member 82 due to temperature rise can be suppressed.

Therefore, the non-magnetic support 82 is sequentially fed from the feed roll 83, and the cooling can 85 is fed.
After passing through the peripheral surface of the above, it is further taken up by the take-up roll 84.

Guide rolls 86 and 87 are provided between the feed roll 83 and the cooling can 85 and between the cooling can 85 and the take-up roll 84, respectively. A predetermined tension is applied to the cooling can 85 and the non-magnetic support 82 traveling from the cooling can 85 to the winding roll 84 so that the non-magnetic support 82 smoothly travels.

A crucible 88 is provided in the vacuum chamber 81 below the cooling can 85.
8 is filled with a magnetic metal material 89.

The crucible 88 has a width substantially the same as the width of the cooling can 85 in the longitudinal direction.

On the other hand, an electron gun 90 for heating and evaporating the metallic magnetic material 89 filled in the crucible 88 is attached to the side wall of the vacuum chamber 81. The electron gun 90 is arranged at a position such that the electron beam X emitted from the electron gun 90 irradiates the metallic magnetic material 89 in the crucible 88.

Then, the metallic magnetic material 90 evaporated by the electron gun 90 is deposited and formed as a magnetic layer on the non-magnetic support 82 which runs at a constant speed on the peripheral surface of the cooling can 85. .

The cooling can 85 and the crucible 8 are also provided.
8, a shutter 93 is arranged near the cooling can 85. The shutter 93 is the non-magnetic support 8 that runs at a constant speed on the peripheral surface of the cooling can 85.
2 is formed so as to cover a predetermined region, and the metal magnetic material 89 evaporated by the shutter 93 is obliquely deposited on the non-magnetic support member 82 within a predetermined angle range.

Further, in the case of such vapor deposition, an oxygen gas introducing port 94 is provided which penetrates the side wall of the vacuum chamber 81.
Oxygen gas is supplied to the surface of the non-magnetic support 82 via the magnetic recording medium to improve the magnetic properties, durability and weather resistance.

Therefore, in the vacuum vapor deposition apparatus having such a structure, the non-magnetic support 82 fed from the feed roll 83 is made to run along the peripheral surface of the cooling can 85, and the metallic magnetic material is used. By heating and evaporating 88 by the electron beam X from the electron gun 90, a metal magnetic thin film is deposited on the non-magnetic support 82.

Although Co ₁₀₀ (numerical values indicate composition ratio) is used as the metallic magnetic material 88 here, the present invention is not limited to this.

Immediately after completion of the vapor deposition, sputtering is performed under the following conditions using the sputtering apparatus shown in FIG. 2 to form a protective film on the magnetic layer, followed by backcoating and topcoating. Then, the tape was cut into a predetermined tape width (slit width: 8 mm width) to prepare a sample tape.

<Sputtering conditions> Method: DC magnetron sputtering method Target material: Carbon Input power: 1.4 W / cm ² Working gas: Ar gas Background vacuum degree: 5.0 × 10 ⁻³ Pa Tape speed: 4 0.0 m / min Protective film thickness: 0.012 μm <Backcoat condition> Constituent material: A mixture of carbon and urethane binder Coating thickness: 0.6 μm <Topcoat condition> Constituent material: Perfluoropolyether The structure of the sputtering apparatus used for forming the protective film will be described.

That is, as shown in FIG. 2, this sputtering apparatus is installed in a vacuum chamber 101 in which the inside is evacuated by being exhausted from exhaust ports 115 provided at the head and the bottom, respectively. Feed roll 1 that rotates at a constant speed in the clockwise direction
03 and a take-up roll 104 that rotates at a constant speed in the clockwise direction in the figure, and a tape-shaped non-magnetic support 102 is sequentially run from the feed roll 103 to the take-up roll 104.

From the feed roll 103 to the take-up roll 1
A cylindrical can 105 having a diameter larger than that of each of the rolls 103 and 104 is provided on the 04 side in the middle of travel of the non-magnetic support 102.

The cylindrical can 105 is provided so as to draw the non-magnetic support member 102 downward in the figure, and is configured to rotate at a constant speed in the clockwise direction in the figure.

The feed roll 103, the take-up roll 104, and the cylindrical can 105 each have a cylindrical shape having a length substantially the same as the width of the non-magnetic support member 102. A cooling device (not shown) is provided inside so that deformation of the non-magnetic support member 102 due to temperature rise can be suppressed.

Therefore, the non-magnetic support member 102 is sequentially fed from the feed roll 103, passes through the peripheral surface of the cylindrical can 105, and is further taken up by the take-up roll 104.
It is designed to be wound up in.

The guide roll 10 is provided between the feed roll 103 and the cylindrical can 105 and between the cylindrical can 105 and the take-up roll 104, respectively.
6, 107 are provided, and the non-magnetic support 10 runs from the feed roll 103 to the cylindrical can 105 and from the cylindrical can 105 to the take-up roll 104.
By applying a predetermined tension to the nonmagnetic support 102, the nonmagnetic support 102 can smoothly run.

A cathode target 108 is provided below the cylindrical can 105 in the vacuum chamber 81, and the protective film material 1 is provided on the surface of the cathode target 108.
09 is glued.

The cathode target 108 has substantially the same width as the longitudinal width of the cylindrical can 105.

In this embodiment, the cylindrical can 10 is used.
Although 5 is cooled, it may be appropriately heated to improve the adhesive strength between the protective film and the magnetic layer.

The flow rate of argon gas introduced during sputtering is controlled by the mass flow controller 117, and the exhaust flow rate is controlled by the conductance valve 118.

Therefore, the sputtering conditions at the time of forming the protective film were changed, and the stillness and rust resistance of the obtained sample tape were evaluated.

The still durability was evaluated by measuring the time from the initial output level to the attenuation of 3 dB by using a video tape recorder (VTR), EV-S900 modified machine (trade name) manufactured by Sony Corporation. The value obtained was used.

The rust resistance was measured by using a gas corrosion tester with SO ₂
The deterioration amount Δφs of the total magnetic flux amount from the initial value after being stored for 24 hours in an atmosphere containing a gas of 0.3 ppm at a temperature of 30 ° C. and a relative humidity of 90% was determined and calculated by the following mathematical formula 1.

[0062]

[Equation 1]

It is practically desirable that the still durability is 24 hours or more, and it is desirable that the rust resistance is 5% or less.

Further, the stability of plasma during sputtering was also examined, and a three-stage evaluation was performed in order from the highest stability, as ◯, Δ, and ×.

The results are shown in Table 1 below.

The volume V of the vacuum chamber in Table 1 is as shown in FIG.
In the capacity of the bottom of the vacuum chamber (film forming chamber) 101 shown in FIG.
5 × 10 ⁶ (cc), and the parameters L _out / V and L _in / L _out are the argon introduction flow rate L _in and the vacuum chamber 1 described above.
The exhaust flow rate L _out on the bottom side of 01 was controlled respectively.

[0067]

[Table 1]

As a result, as shown in Table 1, L _out / V
= 0.2 (Comparative Examples 1 to 3), plasma stability was good regardless of the values of L _in / L _out , but still durability and rust resistance were at practical levels. Did not meet. It is considered that this is because the exhaust flow rate is insufficient and is affected by the residual gas in the vacuum chamber. Therefore, in order to avoid the influence of the residual gas, L _out / V is set to 0.2.
It has been found that a larger value than that is necessary.

In Comparative Example 4, L _out /V=0.3
Although both the still durability and the rust resistance were slightly improved as compared with Comparative Examples 1 to 3, they were still below the practical level and the plasma stability was poor. This is because the argon introduction flow rate L _in is smaller than the exhaust flow rate L _out , and in order to stabilize the plasma, L _in
It has been found that it is necessary to make / L _out larger than 1.3 × 10 ⁻⁴ .

On the other hand, L _in / L _out is 2.7 × 1
In Example 1 in which 0 ^-3 was set, the plasma was somewhat unstable, but still durability and rust resistance were good, and practicability could be secured.

In Comparative Example 5, L _in / L _out = 2.7.
In the case of × 10 ^-3 , the rust resistance deteriorated as compared with Examples 1-5. It is considered that this is because the film structure becomes sparse as the argon introduction flow rate L _in increases. From this, _in order to obtain good rust resistance, L _in / L _out
It has been found that it is necessary to make the value smaller than 2.7 × 10 ⁻³ .

On the other hand, L _in / L _out = 2.0 × 1
In Example 5 in which 0 ^-3 was set, good still durability and plasma stability were obtained, and it can be judged that this is sufficiently effective.

From the above results, the argon gas flow rate L _in (scc) introduced at the time of sputtering when forming the protective film
m), exhaust flow rate L _out (sccm) and vacuum chamber capacity V
Let (cc) be L _out /V≧0.3 and 2.0 × 10 ⁻⁴ ≦
It was found that good durability and rust resistance can be obtained by setting L _in / L _out ≦ 2.0 × 10 ⁻³ . In particular, L
_out / V = 0.3, L _in / L _out = 4.3 × 10 ⁻⁴
In the range of 9.3 × 10 ^-4 , the best durability,
It was possible to secure rust resistance.

[0074]

As is clear from the above description, in the present invention, when a protective film is formed on a magnetic layer made of a metal magnetic thin film provided on a non-magnetic support by sputtering, it is introduced at the time of sputtering. Since the flow rate of argon gas, the flow rate of exhaust gas, and the capacity of the vacuum chamber are optimized, a good protective film can be formed, and durability and rust resistance can be significantly improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of a vacuum vapor deposition apparatus used when forming a magnetic layer in the present invention.

FIG. 2 is a schematic diagram showing a configuration example of a sputtering apparatus used when forming a protective film in the present invention.

[Explanation of symbols]

 101 Vacuum Tank 102 Non-Magnetic Support 103 Feed Roll 104 Winding Roll 105 Cylindrical Can 108 Cathode Target 109 Protective Film Material 117 Mass Flow Controller 118 Conductance Valve

Claims (1)

[Claims] 1. A method for producing a magnetic recording medium, comprising forming a metal magnetic thin film on a non-magnetic support by vacuum vapor deposition and then forming a protective film by sputtering. When performing the sputtering, the magnetic recording medium is introduced into a vacuum chamber. Argon gas flow rate L _in (sccm), exhaust gas flow rate L _out (sc
cm) and the capacity V (cc) of the vacuum chamber are L _out /V≧0.3 (min ⁻¹ ) and 2.0 × 10 ⁻⁴ ≦ L _in /
A method for manufacturing a magnetic recording medium, wherein L _out ≦ 2.0 × 10 ⁻³ .